Research Journal of Aleppo University - جامعة حلب ... · Dr. Ibrahim Raheb Dr. Gassan Daood...
Transcript of Research Journal of Aleppo University - جامعة حلب ... · Dr. Ibrahim Raheb Dr. Gassan Daood...
Research Journal
of
Aleppo University
Basic Science Series
A Periodical Issued by University of Aleppo
Vol. 98 - 2014
ISSN 2227-9210
All rights reserved .No part of this publication may be
reproduced,stored in a retrieval system or transmitted in any
form without the prior written permission of the publisher .
Basic Science Series
Chairman of the Editorial Prof. Dr. Kamal Khoudary
Vice president for scientific research and high studies affairs
Editor in Chief Prof. Dr. Nawar Kadan
Editorial Board
Dr. Hesham Bawadekji Dr. Saad Antakli
Dr. Samer Bashmaf Dr. Mahmoud Amin
Dr Walid Al said Dr Ahmed Kumary
Dr. Zakria Nout
PRODUCTION Eng.Rama Mulki
The view expressed in this issue are those of the authors and do not necessarily
reflect the views of the Editorial Board or the Policies of the University of Aleppo
proof reading Aisha Moussa (Engish) Bakry Eko (Arabic)
5
Contents Dr. Ibrahim Raheb
Dr. Gassan Daood
Hussam Alrekad
Catalytic Cracking of Plastic Wastes
over Sulfated Syrian Natural Zeolite
7
Dr. Fatima Srouji
Sami Orfali
Poling Process Impact on the
Pyroelectric Properties of PZT
19
Dr. Fatima Srouji
Farouk Al Jasem
Optical Properties of CdTe QDs
Synthesized by Chemical Method and
Enhanced by Microwave Irradiation
31
Dr. Walied Hawaleh
Dr. Salah Al Haj Omar
M. Yahia Masri
Studying the Effect of Fineness on the
Thermal Treatment of Syrian
Petroleum Coke to Reduce the Sulfur
Content
47
Dr. Nizar Essa
Dr. Faiza Al atrash
Waleed Mlook
Screening, Identification and Partial
Characterization of Pullulanase
Enzyme from Local Bacterial Strain
49
Dr. Sabah Blaj
Dr. Leka Hoppo
Dr. Abeer Alyosef
Eman Almosa
A Study of Immunological and
Hematological Findings in Systemic
Lupus Erythematosus (SLE) Patients in
Aleppo
51
Dr. Abdel Aleem Bello Dr. Zaher S. Tahan Dr. Firas Haj Zein Yasmin Alshihabi
Antibacterial Activity of Salvia
officinalis against Some Pathogenic
Bacteria Isolated from Tonsillitis and
Pharyngitis Patients
53
Dr. Saleh El-Kadri
Dr. Ani Tersakian
Ahmad Alabboud
Synhesis of Some Push-Pull Alkenes
Containing Two Carbonyl Groups:
Ketene Dimethyl Dithio Acetal Type
55
Dr. Saja Abou Ghaloon A Comparative Study of the Structure
of Pancreas in the Two Species Clarias
gariepinus (syriacus) and Clarias salurus
Living in the Orontes and Euphrates
Rivers
57
Dr. Said Sabbagh
Murhaf Al-Sayed Ali A Comparative Study of Ball Point Pens
Writing Ink Using Techniques of XRF,
UV-VIS, FT-IR
59
Dr. M. Karman
N. Al Ghanom
Studies of XRD, FT-IR and Surface
Areas of Pure MoO3, WO3 and the
Mixed Oxide System Mo-W-O
61
Dr. Emad Asad
Dr. Farouk Kandil
M. Hasan Derbas
Synthesis and Characterization of
Nd:YAG Nanopowder via Polymer
DTPA Metal Chelated Complexes
63
Dr. Said Abdul Nour
Mouna Kurma
Study of the Structural Properties in
Polyacrylonitrile - anionic Surfactant
Systems
65
6
Dr. Anwar Batal
H. Aldeen KASSIR
Linear Waves Propagation in a Dusty
Plasma for Tails of Halley's Comet
67
Dr. M. Hasan
Dr. M. Saleh Hammami
Layla Al Sharif
A Study of the Effect of Adding Zinc
Metal on Physical Properties of Lead-
free Solders Ternary (Sn88 Sb10 Cu2)
Prepared in Rapid Solidification
69
Dr. Nehad Yosef
Faten Kang
Isolating and Identifying of Lactic Acid
Bacteria (LAB) from Fermented Milk
Products (Yoghurt and Traditional
White Cheese)
71
Dr. Said SABBAGH Analysis of Al khalas Date Bio-Physical
and Chemical Characteristics
Sterilized by Irradiation to Substitute
Fumigation Gases and Thermal
Treatments
73
Dr. Hala Wattar Global Optical Potential for Deuteron
Scattering at Energies from 10 to 180
MeV
75
Dr. Walid Al Said
Dr. Abdel Aleem Bello
Oula Darwish
Study of Leaf Epidermis and
Palynology in Two Varieties Related to
Silybum marianum (Asteraceae) in
North Aleppo
77
Dr. Adel Hamo
Dr. Hala Wattar
Eyman Al-hamdan
Advanced Study of Neutrino
Oscillation Phenomenon in Vacuum in
Quantum Fields Theory Framework
79
Dr. Mahmoud Karrom
Dr. Fadia Nashed
M. Salim Alibrahim
A Taxonomical Study on Species of
Helicidae (Gastropoda: Mollusca) in
Aleppo & Edlib Governorates
81
Dr. Adel Hamo A Study of the Time-dependent
Oscillation Systems Using the Creation
and Annihilation Operators
83
Dr. Walid Hawale
Shaghik Taghlian
The Study of Some of the Physical
Properties of the Glazed Layer
Prepared from Local Raw Materials
85
Dr. Tariq Zarouri
Hadeel Fakas Albeed
Studying of Some Thermal and
Electrical Properties of the Lead
Compounds PbS and PbTe
Precipitated in Chemical Solution
Method
87
Dr Ahmed Kumary
Dr. Hachem Alhussein
Omama Alloush
Studying the Effect of the Pomegranates
(Juice, Arils) on HbA1c Level, Serum
Fasting Glucose and Liver Enzymes in
Type II Diabetes Patients
89
R.J.of Aleppo Univ. Basic Science Series No.98 2014
6
Catalytic Cracking of Plastic Wastes over Sulfated
Syrian Natural Zeolite Ibrahim Raheb*, Gassan Daood
**, Hussam Alrekad
***
*Dept. of Chemistry, Faculty of Science, Tishreen University
**Doctor in Banias Refinery
** * Postgraduate Student (PhD). , Dept. of Chemistry, Faculty of Science, Tishreen
University
Abstract
In this paper, catalytic cracking of plastic wastes (PW) over
sulfated and non-sulfated natural zeolite in a batch reactor at 475,500
and 525oC was carried out. Thermal pyrolysis was also performed on
the same conditions. The best results were obtained at 475oC and
500oC for catalytic cracking. Non-sulfated zeolite showed high acidity
and the presence of sulfate ions led to higher acidity.
Catalytic process showed high conversion of PW, low content
of solid residues and direct effect on the reaction time in comparison
with thermal pyrolysis. On the other hand, sulfate ions affected the
content of the products, where the liquid product decreased and the gas
product increased.
Distribution of the liquid fraction showed a low content of light
hydrocarbons for a thermal pyrolysis, while the catalytic pyrolysis
showed a higher content of light hydrocarbons; that made it more
valuable especially when sulfated zeolite was used.
Keywords; catalytic cracking, plastic waste, natural zeolite, polymer
pyrolysis, super acid, impregnation.
Received 25 / 5 /2014
Accepted 14 / 9 /2014
Dr. Raheb Dr. Daood & Rekad
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1. Introduction Polymers are used in almost all fields of both economy and
daily life. Every year their worldwide production grows together with
the increase in their consumption and the amount of waste. Plastic
waste management policies are based on energy recovery of
elimination processes. A major amount of annually produced plastic is
land filled or incinerated [1,2]. Mechanical recycling aims at the
recovery and reuse of the plastic material contained in the waste,
although it is strongly limited by the low quality of the recycled
plastics due to the presence of different polymers additives and
impurities. Thermal degradation requires high temperatures and
usually leads to wide product distribution with poor economic value
[3].
Chemical recycling has emerged in the last years as a
potentially interesting alternative for the management of plastic wastes
and conversion into a variety of useful products mainly as raw
chemicals or as fuels. In contrast, catalytic degradation allows the
plastic cracking to be performed at lower temperature, while the
product distribution can be controlled by a right selection of the
catalyst type being used. In the case of the HDPE (High density
polyethylene) catalytic cracking, a number of acid porous solids, such
as amorphous silica-alumina, zeolites and ordered mesoporous
materials, Al-MCM-41, have been used as catalysts. ZSM-5 zeolite
directs the catalytic cracking towards light products [4,5,6]. Many
kinds of sulfate supported-materials have a strong acidity and attract
much attention because of their ability to catalyze many reactions such
as cracking, alkylation and isomerization. Sulphated zirconia
incorporating Fe and Mn has been shown to be highly active for butane
isomerization [7].
On the other hand, many metal sulfates generate fairly large
amounts of acid sites of moderate or strong strength on their surfaces
when they are calcined at 400-700 oC. The acidic property of metal
sulfate often gives high selectivity of diversified reaction such as
hydration, polymerization, alkylation, cracking and isomerization [8].
2. Experimental 2-1. Catalyst Preparation
Syrian natural zeolite from Om'ozon area was used. Zeolite was
crushed and sieved into many fractions. We used the fraction which
has (0.1-0.37 mm). The sample was washed with distilled water,
R.J.of Aleppo Univ. Basic Science Series No.98 2014
8
filtrated and dried at 110oC for 24h and named (Z). The catalysts
containing various sulfate ions were prepared by adding an aqueous
solution of ammonium sulfate (NH4)2SO4 to the sample Z powder by
impregnation method, at room temperature for 24h, then dried at 110
oC and calcined at 600
oC for 8h in air. These series of catalysts are
denoted by their weight percentage of 2
4
SO for example
ZSOx /2
4
indicates the catalyst containing x.wt% of 2
4
SO , where
x = 5,10,15 and 20.
2-2.Characterization The amount of acidic sites and the distribution of these sites
were determined by NH3-temperatue programmed desorption (TPD).
Measurements were carried out on a labsys instrument (TG-DTA
,France). Prior to TPD studies the sample was outgassed at 200oC for
2h; after outgassing, the sample was saturated with ammonia gas at
25oC for 24h and subsequently flushed with N2 at 100
oC for 1h to
remove the physisorbed ammonia. The total acidity of the samples was
determined by desorption of NH3 as a function of temperature, by
increasing the temperature up to 500oC with a heating rate of
15oC/min.
2-3. Activity Studies
The pyrolytic reactor and its accessories used in the present
study were manufactured locally. Thermal and catalytic cracking
experiments were accomplished at atmospheric pressure in a batch
type reactor as shown in Fig.1. The reactor consists of pyrix glass tube
(leng. 20cm, and diam.2 cm), and is provided with glass tube which
has allowed the exit of the products. The reactor was placed in the
vertical furnace and the heating process was achieved by controlled
temperature unit. The plastic waste (PW) used in this study is the
plastic waste bags of polyethylene LDPE (Low density poly ethylene),
HDPE and polypropylene. PW was shredded to 2×3 mm size. The
mixture of plastic and catalyst (with ratio P/C =3) was charged in the
bottom of the reactor. The furnace was heated to the reaction
temperature (475, 500 and 525oC) with heating rate of 30
oC/min.
Dr. Raheb Dr. Daood & Rekad
01
Fig.1. Schematic experimental setup
After the temperature reached the reaction temperature, the
reactor (containing PW and catalyst) was placed in the furnace and
maintained 4h for thermal pyrolysis and 2.30h for catalytic pyrolysis.
The liquid products were condensed and accumulated in ice trap. The
amount of solids (product in the reactor after cracking) and liquids
obtained in each experiment was weighed and the pyrolysis yield was
calculated. The results of the pyrolysis yields which are presented in
this paper are the mean value of at least three pyrolysis runs carried out
in the same conditions. The mass of all products (gas, liquid, solid
residues) was measured in grams and then converted into mass in
percentage. The relation between product yield with different
(temperature, and amount of 2
4
SO ) was also studied. The yield of
liquid product was calculated as the mass of the collected liquid
divided by the mass of the initial amount of polymer and then the
fraction of original polymer converted to liquid products. The solid
residues (coke) yield was calculated by dividing the mass of coke by
original mass of polymer. Gas yield was calculated by the difference
[(100-(yield of liquid + yield of solid)]. The selectivity to liquid
products was calculated as the mass of liquid divided by the mass of
reacted polymer. The boiling point distribution of each liquid fraction
was used to represent the liquid product distribution.
R.J.of Aleppo Univ. Basic Science Series No.98 2014
00
2. Results and Discussion The characterization of prepared samples (surface area, XRD,
FTIR, TG-DTA) was presented in a previous paper [9].
3-1. Acidic Properties
It is an established fact in the literature of surface acid studies that
ammonia is an excellent probe molecule for testing the acidic
properties of solid catalysts. The small size of NH3 molecule and its
basic property allow us to detect the acidic sites which are located in
the narrow pores of the solids [10]. The ammonia –TPD profiles of Z
and ZSOx /2
4
samples are shown in Fig.2 and the corresponding
total acidity results are presented in Table 1. Table 1. Total acidity of the prepared samples
Catalyst Total acidity, µmol/g
Z 108.8
5-SO42-
/Z 149.3
10-SO42-
/Z 162.9
15-SO42-
/Z 212.6
20-SO42-
/Z 251.6
As can be noted from TPD profiles in all samples, the acid
sites are distributed in three temperature regions. Desorption peaks
were observed at 150-250oC, 250-350
oC and 350-450
oC and the
maxima were located at 150oC, 300
oC and 400
oC respectively. These
peaks are normally attributed to NH3 chemisorbed on weak, moderate
and strong acid sites, respectively [11]. Among all prepared catalysts,
the sample Z without SO42-
ions has the lowest amount of acid sites. It
is observed that the weaker acid sites (maximum ~ 150oC) are
increased with increasing of SO42-
content, while the amount of
moderate and strong acid sites is increased slightly.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 100 200 300 400 500
T ,0C
Lo
s m
as
(NH
3)%
Z
5-SO4/Z
10-SO4/Z
15-SO42-/Z
20-SO42-/Z
5-SO42-/ Z
10-SO42-/Z
15-SO42-/Z
20-SO42-/Z
Fig.2. Ammonia TPD analysis of the prepared catalysts
Dr. Raheb Dr. Daood & Rekad
01
The NH3-TPD profile of the samples indicates that sulfate
groups can enhance the total acidity, when adsorbed on the zeolite tuff.
In addition, sulfate species themselves are Lewis acid sites, or they
generate Lewis acid sites on the oxide surface by attracting electrons
[12,13].
These Lewis acid sites increase the Bronsted acid strength of
the surface hydroxyl groups present on the surface. Furthermore, the
chemical states of the sulfate groups sometimes determine the acidity
of the oxide surface. The strong ability of the sulphate complex to
accommodate electrons from a basic molecule such as ammonia is a
driving force to generate super acidic properties [7]. Calcination at
higher temperature leads to change the ionic to covalent character with
S=O bond order close to 1,5, which is responsible for generating strong
acidic active centres on the oxide structures. The position of ammonia
desorption peak corresponding to the super-acidic sites is influenced
by the nature of the mixed oxides [14].
3-2. Catalytic Activity
It is interesting to examine how the catalytic activity of
prepared acid catalysts depends on the acidic properties. The catalytic
activities for cracking plastic waste were measured and the results
were illustrated as a function of the reaction temperature and content of
sulfate, using the mass ratio of polymer/catalyst (P/C=3). The pyrolysis
yields obtained in the thermal and catalytic experiments at different
temperatures were shown in Table 2 and Fig.3. The liquid fraction was
the main product in all cases, reaching almost 93 wt% when catalyst Z
was used, followed by gases. The effects of temperature were studied
without catalyst addition (thermal pyrolysis). The reaction was carried
out at 475,500, and 525oC Tabl.2 and Fig.3.
The results show that the products of pyrolysis were liquid, gas,
and solid residue. At 475oC the yield of liquid was 64.1 wt%, the
average yield of gas was 7.1 wt% and the average yield of solid
residue was 28.8 wt%. When temperature was increased to 500oC, the
yield of liquid, gas and solid residue was 76, 7.3, and 16.7 wt%,
respectively. At 525oC, the yield of liquid, gas and solid residue was
78, 10.4 and 11.6 wt%, respectively.
The use of prepared catalysts (zeolite and sulfated zeolite) in
the cracking process of PW leads to changes in the yield of products.
The results show that the yield of the liquid gases was increased and
the solid residue decreased strongly. At 475oC the amount of liquid
and gas was 93, and 5.3 wt% in the presence of non sulfated zeolite Z,
R.J.of Aleppo Univ. Basic Science Series No.98 2014
02
while in the case of the sulfated zeolite, the yield of the liquid
decreased from 90.1 wt% to 86.8 wt% when the loaded sulphate
increased from 5 to 20 wt%. On the contrary the yield of the gases
increased from 5.8 to 13 wt%, Table.2 and Fig.3.
At 500oC, the similar behaviour was noticed. At 525
oC the yields of
the liquid were 93.2 to 90.9 wt %, i.e higher than the yield at 475oC
and 500oC, whereas the yield of the gas was less, i.e 4.9-7.7 wt %. The
catalytic cracking of PW by sulphated Z leads to a decrease in the
amount of solid residue to minimum values.
The reaction time varied. For thermal pyrolysis the reaction time was
215, 95 and 63 min at 475, 500 and 525oC respectively. At 475
oC the
reaction time of catalytic pyrolysis decreased from 147 min when non
sulfated zeolite was used to 80 min in the case of 20-SO42-
/Z. This
trend was observed for catalytic cracking at 500oC and 525
oC.
However, the reaction time was decreased with raising the reaction
temperature, see Table.2. Table 2. Product yield of PW degradation, and reaction time
at different temperatures
thermal Z 5-SO42-
/Z 10-SO42-
/Z 15-SO42-
/Z 20-SO42-
/Z
475oC
liquid wt% 64.1 93 90.1 86.9 87 86.8
gas wt% 7.1 5.3 9.3 12.7 12.1 13
Solid wt% 28.8 1.7 0.6 0.4 0.9 0.2
react time, min 215 147 134 122 85 80
500oC
liquid wt% 76 91.2 89.5 89 84.2 83.5
gas wt% 7.3 6.3 10 10.7 15.6 16.5
solid wt% 16.7 2.5 0.3 0.3 0.2 0.1
react time, min 95 81 77 65 58 48
525oC
Liquid wt% 78 93.2 93 92.6 90.9 91.4
gas wt% 10.4 4.9 6.2 6.9 6.8 7.7
solid wt% 11.6 1.8 0.8 0.5 0.5 0.9
react time, min 63 50 46 45 43 40
Dr. Raheb Dr. Daood & Rekad
03
Fig.3. Product yield of PW degradation at different temperatures
R.J.of Aleppo Univ. Basic Science Series No.98 2014
04
The obtained results in certain condition in this work show a
low total yield of products (liquid + gas) in the case of thermal
pyrolysis of PW and high solid residues and long reaction time. While
the catalytic cracking of the same PW using sulfated and non sulfated
zeolite leads to high yield of products (liquid + gas), low solid residues
and short reaction time. The sample Z contains high acidity and this
acidity increased with an increase of sulfate ions Table 1. This is in
agreement with literature, as loading the metal oxides with sulfate ions
was found to enhance the acidic properties of the oxides. [12, 13].
On the other hand, the presence of sulfate ions stabilizes the
structure of the oxides, and the sulfated samples display a smaller
crystalline size and increase the amounts of tetragonal phase in
contrast with the corresponding non-sulfated samples [12].
As a consequence, higher conversion of PW was obtained with
catalysts than in the thermal pyrolysis. This is a well known effect
which has been reported before by other researcher groups [2,15]. The
higher conversion is attributed to both the textural properties of the
zeolite and the presence of Bronsted and Lewis acid sites in this
catalysts. In order to obtain more information about the liquid
products, we compared the liquid products at 475,500 and 525oC in the
thermal and catalytic pyrolysis, for non-sulfate Z and 20-SO42-
/Z were
used. Liquid products, received as a result of pyrolysis process, have
been distilled in the average of temperatures to 4 fractions according to
the boiling point. The distribution of the liquid fractions after
distillation was presented in Table.3. and Fig.4.
At 475oC the thermal pyrolysis gives a liquid product that
consists of light fraction 4.8 wt% on the average of temperature up to
130oC and the medium fraction ~20 wt% on the range of temperature
130-220oC and 220-340
oC, and the heavy fraction was 72.5 wt% at
temperature >340oC. While in the catalytic process by non-sulfated
zeolite, we found that the light, medium and heavy fractions were 16,
40.8, and 43.2 wt% respectively. When the sulfated zeolite (20-SO42-
/Z) was used, the order of the light, medium and heavy fractions was
30.2, 41.8 and 28wt%. These results showed that the presence of
catalyst in pyrolysis process leads to high content of light and medium
liquid fractions and low content of heavy fraction in comparison with
thermal pyrolysis.
At 500oC for thermal pyrolysis the light and medium fractions
were increased but the heavy fractions were decreased, while for
catalytic pyrolysis the main difference was in the case of the (20-SO42-
Dr. Raheb Dr. Daood & Rekad
05
/Z) where the medium fraction was increased and heavy fraction was
decreased in comparison with the results at 474oC. At 525
oC the
picture was different especially in the case of catalytic process, where
the heavy fraction was increased. This can be attributed to the short
connecting time between PW and catalyst due to the high speed of the
vaporous PW at 525oC.
Table.3. Liquid fraction distribution (v/v)% produced
after cracking of PW
475oC 500
oC 525
oC
thermal Z
20-SO
42- /Z
thermal Z
20-SO
42- /Z
thermal Z
20-SO
42- /Z
<130oC 4.8 16 30 6.9 16.2 30.1 7.9 15.5 20
130-220oC 9 19.2 21.5 11.9 19.8 24 13.6 18.3 18.1
220-340oC 13.7 21.6 20.5 17.8 22.1 23.5 20 20.6 19.6
>340oC 72.5 43.2 28 63.4 41.9 22.6 58.5 58.5 42.3
Fig.4. Liquid fraction distribution (v/v)% produced
after cracking of PW
4. Conclusion
A new solid super acid catalyst was prepared x-SO42-
/Z.
Catalysts were prepared by impregnating of Syrian natural zeolite,
with ammonium sulfate solutions. Sulfation of natural zeolite resulted
into significant change in the acidic properties. The ammonia TPD
experiments showed that sulfation of catalyst (natural zeolite) can lead
to the formation of more super-acidic sites in the catalyst than in
unprompted zeolite.
R.J.of Aleppo Univ. Basic Science Series No.98 2014
06
Prepared catalyst showed better results in the pyrolysis of plastic
wastes since high conversion of the samples can be obtained compared
with thermal pyrolysis. When the catalyst is used the conversion is
higher than 99 wt%, and the liquid fractions are the main product,
higher than 83 wt%. The increasing of sulfate ions leads to a decrease
in the content of liquid and to an increase of gas products. The
composition of liquid fraction resulting from thermal and pyrolysis of
PW was different. Presence of sulfate ions leads to higher light fraction
~30 wt% and lower heavy fraction at 475oC and 500
oC. The liquid
fraction can be used as an alternative to fossil fuel or as a source of
valuable chemicals, while the gaseous fraction could be used for power
generation for the process itself. Solid residues are lower than 1 wt% in
the catalytic process.
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R.J.of Aleppo Univ. Basic Science Series No. 98 2014
19
Poling Process Impact on the Pyroelectric Properties of
PZT Fatima Srouji, Sami Orfali
*
Dept. of Physics, Faculty of Science, Aleppo University
*Postgraduate Student (MSc.)
Abstract Crystalline nanostructured (PZT) with atomic ratio of the
Pb:Zr:Ti of 1:0.53:0.47 was synthesized by a chemical method starting
from Lead, Titanium and Zirconium salts and using low temperature
synthesis path which is supposed to compose a nanostructured PZT.
Using XRF, a qualitative analysis had been carried out to investigate
that the samples contain Lead, Titanium and Zirconium. The samples
were pressed as pellets then sintered at 11000C. Using a high voltage
generator, a poling process was achieved at (0.5 - 1.5) KV/mm at room
temperature. Using AC measurements, a relative permittivity including
real and imaginary parts in a function of frequency in the range (20
Hz-3 kHz) for unpoled samples at room temperature was measured in
order to investigate the polarization processes. The relative permittivity
and loss factor for poled samples were studied in a function of fre-
quency where the poling process results in increasing the relative per-
mittivity and decreasing the loss factor. The relative permittivity and
loss factor were also studied in a function of temperature at fixed fre-
quency. It is noticed that the relative permittivity increases with tem-
perature up to many thousands times. Hysteresis loop was plot to show
the ferroelectric property of the material. Pyroelectric current was
measured in order to calculate the pyroelectric coefficient of the mate-
rial which exhibits high increasing with temperature after 4000C.
Received 4/8/2014
Accepted 21/9/2014
Dr. Srouji. Orfali
20
1. Introduction Lead Zirconate Titanate, Pb (ZrxTi1-x)O3 (PZT) ceramics are an
important class of piezoelectric, pyroelectric and ferroelectric materi-
als.[1] Due to their excellent dielectric, piezoelectric and electro- optic
properties, they find a variety of applications in high energy capacitors,
non-volatile memories (FRAM), ultrasonic sensors, infrared detectors
and electro optic devices[2-4]. PZT alloys belong to the family of ce-
ramics, which are alloys of lead oxide, zirconium oxide, and titanium
oxide (PbO, ZrO2, and TiO2). The familiar Perovskite structure appears
in PZT alloys because there are equal numbers of divalent (Pb2+
) and
tetravalent (Zr4+
and Ti4+
) cations. PZT alloys are in fact the alloys of
two components: PbZrO3 and PbTiO3. Thus, by controlling the compo-
sition and microstructure of the PZT alloys, it is possible to adapt their
properties to suit particular applications [5]. The general chemical
formula of our samples is PbZr1-xTixO3, with x=0.47, due to the peculi-
arities of PZT; in the transition zone in between the two structures (x=
0.53), it is called morphotropic phase boundary (MPB), which has high
relative and piezoelectric coefficients [6]. Polycrystalline ferroelectric
materials (ceramics) may be brought into a polar state by applying a
strong electric field (10-100 kV/cm), usually at elevated temperatures.
This process, called poling, can reorient domains within individual
grains along those directions that are permissible by the crystal sym-
metry and that lie as close as possible to the direction of the field. A
poled polycrystalline ferroelectric exhibits piezoelectric and pyroelec-
tric properties, even if many domain walls are still present. After the
removal of the poling field, a ferroelectric material possesses macro-
scopic polarization, called spontaneous polarization PS [7,8]. In this
paper, chemical method is used to synthesize PZT at low sintering
temperature. XRF is used to detect the composition. High voltage
source was used to pole the samples. AC electrical measurements were
used to study the electrical properties and DC measurements were cur-
ried out to study the pyroelectric properties. Hysteresis loop was plot
of the material using high voltage supplier.
2. Materials
Lead Nitrate (PbNO3), Titanium tetrachloride (TiCl4), Zirconi-
um oxychloride octahydrate (ZrOCl2.8H2O), analytical grade, ammo-
nia, ethylene glycol, distilled water, and Nitric acid were used for
chemical preparation.
R.J.of Aleppo Univ. Basic Science Series No. 98 2014
21
3. Experimental 3.1. Preparation of PZT
The Low-Temperature Synthesis path followed by auto-
combustion process was adapted in this paper [2]. Lead Nitrate
(PbNO3), Titanium tetrachloride (TiCl4), Zirconium oxychloride oc-
tahydrate (ZrOCl2.8H2O), and analytical grade were used as starting
materials. Titanium tetrachloride (TiCl4) and Zirconium oxychloride
octahydrate (ZrOCl2.8H2O) were solved in distilled water at low tem-
perature (about 20C) then a stoichiometric amount of ammonia was
added to form a Precipitate of TiO (OH)2 and ZrO(OH)2. Nitric acid
was added to the two solutions until the complete solution yielded
TiO(NO3)2 and ZrO(NO3)2 solutions, then they were added to the
Pb(NO3)2 solution with an appropriate amount of ethylene glycol
which plays two roles, one as a chelating agent and the other is to pro-
vide the fuel for the auto combustion process. The atomic ratio of the
Pb:Zr:Ti of solution which was 1:0.53:0.47 with 2% excess of lead was
introduced to compensate the evaporated amount during sintering pro-
cess. After PZT, precursor sol was obtained; the mixture was heated
under 1000C until the gel formation. Then the gel was calcinated at
5000C. The formed powder was milled by a ceramic mortar, pressed
under 5 ton/cm2 as disks of 10mm diameter and 1mm thickness. The
sintering was at 11000C for 4h with temperature changes rate of
5oC/min. Then an XRF test was carried on the samples to investigate
the compositional characterization. The disks were polished and
washed by alcohol. In addition, an air-dry silver paste was applied to
the samples surfaces as electrodes, to ensure a good electrical contact
and introduce them for further characterization.
4. Results and Discussion 4.1. Qualitative Analysis
Using XRF device, Unisantis® type Si-PIN with molybdenum
(Mo) target operated at 50kV and 1mA, XRF spectrum was taken for
the samples. Fig. 1 reveals the existence of the three elements (Lead,
Zirconium and Titanium). Oxygen element was unable to be detected
because it is out of the resolution of the device.
Dr. Srouji. Orfali
22
Fig.1. XRF spectrum for PZT sample
This method gives a formation of the major tetragonal Perov-
skite phase [2].
4.2.Electrical Measurements
4.2.1 Electrical Characterization for Unpoled Samples
The real and the imaginary parts of the relative permittivity and
the loss factor tgδ were measured using LCR meter from MICRO-
TEST type 6379 in the range of frequency (20Hz-3 kHz) at room tem-
perature. As shown in fig. 2, the real part of dielectric permittivity de-
creases sharply with increased frequency at range (20Hz-100Hz), then
it decreases slightly at higher frequency.
Fig.2 Real part of relative permittivity in a function of frequency in the range of
(a: 20-210 Hz, b: 20-3000 Hz) at room temperature.
R.J.of Aleppo Univ. Basic Science Series No. 98 2014
23
Fig.3 The imaginary part of the relative permittivity in a function of frequency
at room temperature.
Theoretically, this manner can be explained as follows: at fre-
quencies below 1 KHz, the four polarization mechanisms (electronic,
ionic, orientational and space charge polarization) act. These polariza-
tions involving the movements of charges either by orientation (i.e.,
orientational polarization) or through the migration of charge carriers
(i.e., hopping or space charge polarization) belong to the relaxation
regime, because during the polarization or depolarization processes, a
relaxation phenomenon occurs due to the time required for the charge
carriers to overcome the inertia arising from the surrounding medium
in order to proceed in their movement. Whereas at frequencies increas-
es above 1 KHz, the only active polarization mechanisms are associat-
ed with vibrations of electrons (i.e., electronic or optical polarization)
or with vibrations of atoms or ions (i.e., atomic or ionic polarization).
This behavior belongs to the resonance regime, because at certain fre-
quencies a resonance will occur when the frequency of the excitation
field is close to the natural frequency of the vibration or oscillation
system, where the real part of relative permittivity is theoretically giv-
en by Debye equation [9]:
Where and
are the low- and high–frequency values of ,
respectively. is the relaxation time. Fig. 3 shows the imaginary part
of relative permittivity εr'' in function of frequency measured by LCR
meter. It is similar to the relative permittivity variation with frequency.
The values of εr'' decrease hundreds times before 1 KHz. That
can explained by Koop’s model which states that at low frequency,
grain boundaries are responsible for the high resistivity, and charges
0.00E+00
2.00E+00
4.00E+00
6.00E+00
8.00E+00
1.00E+01
0 1000 2000 3000 4000
ε r''
f(Hz)
Dr. Srouji. Orfali
24
need relatively high energy to hop between grains whereas at high fre-
quency, grains are the responsible areas for conductivity and its resis-
tivity is low [10]. So considering the hopping conductivity, the loss
factor can be theoretically given by the following equation [9]:
(
) ( )
(
)
Where ζ is the conductivity.
Figure 4. shows relative permittivity at different temperatures.
It is clear that the curves have the same shapes at higher degrees which
indicates that the same polarization process occurs at temperatures be-
low Curie point.
Fig.4 Relative permittivity in a function of frequency at different temperature
(25, 350, 550)0C
4.2.2 Poling the Sample
For optimal poling, an electric field is slightly higher than EC
(coercive field). The field should be applied at least for the switching
time of the domains at room temperature [8]. A poled polycrystalline
ferroelectric exhibits piezoelectric and pyroelectric properties, even if
many domain walls are still present. After the removal of the poling
field, a ferroelectric material possesses macroscopic polarization,
called spontaneous polarization PS. A small chamber was made to con-
tain the sample. The chamber was made of Teflon and provided with
terminals and thermocouple, as shown schematically in fig. 5.
R.J.of Aleppo Univ. Basic Science Series No. 98 2014
25
Fig 5. Schematic diagram for designed chamber.
Samples were submitted to an electrical field (1500V/mm,
1000V/mm and 500V/mm) under atmospheric conditions for half an
hour.
3.2.2 Electrical Characterization for Poled Samples
After poling process application, relative permittivity and die-
lectric loss were measured. Fig. (6,7) represent the dielectric constant
and dielectric loss factor as a function of frequency after poling with
different poling electric fields.
Fig.6 Relative permittivity variations with frequency at different poling field.
To illustrate the poling process effect on relative permittivity of
material, a vertical line is drawn at 1500Hz frequency. Table 1. lists
the values of intersections points. Table 1.
Poling
field(KV/mm)
0 0.5 1 1.5
Relative per-
mittivity
54 81 108 162
Poled samples show significant enhancement of the relative
permittivity with increasing the strength of the poling electric field.
Dr. Srouji. Orfali
26
Contrarily, the dielectric loss slightly decreased with increasing poling
field especially at low frequencies. Table 2. lists the intersection points
of the vertical line drawn at 1000 Hz frequency. This can be interpret-
ed by the formation of domains walls due to the poling process which
limits the conductivity resulting in the decrease of the dielectric loss
[16].
Fig.7 Dielectric loss factor as a function of frequency after poling with different
poling electric fields.
Table 2.
Poling
field(KV/mm)
0.5 1 1.5
Dielectric loss 0.596 0.513 0.394
3.2.3 Hysteresis Loop
As the pyroelectrics are a subgroup of the ferroelectrics, pyroe-
lectric materials exhibit ferroelectric properties. The most important
characteristic of ferroelectricity is the polarization reversal (switching)
with an electric field. One consequence of this switching is the occur-
rence of the ferroelectric hysteresis loop. The hysteresis loop can be
observed experimentally by using different techniques. We used the
Sawyer-Tower setup [17].
A home-made Sawyer-Tower circuit, as schematically repre-
sented in Figure 8, with manually changed electric field with frequency
of about 0.5Hz and an electric field amplitude of 500V/mm was used.
R.J.of Aleppo Univ. Basic Science Series No. 98 2014
27
Fig.8 schematic diagram of Sawyer-Tower circuit, where C is the sample capaci-
tance and C0=1µF>>C the reference capacitance.
Figure 9 shows the hysteresis loop of the material. It is clear that
there is a delay between the applied voltage and reference capacitor
voltage, and that is due to the time required for the domains wall to
move according to the electric field.
Fig 9. Hysteresis loop of prepared material.
3.3 Pyroelectric Measurements
By changing the samples temperatures gradually up to 550°C
at about 5°C/min rate, the temperature dependence of the dielectric pa-
rameters at 1 kHz for the 1.5 kV/mm poled sample and the non-poled
sample was measured. Fig 10 shows the relative permittivity changing
with temperature. It exhibits relatively constant value up to 300°C at
which the dipoles begin to align each other. The poling field shows
significant increase of the dielectric constant, where many domains are
already formed by mean of the poling field. As the relative permittivity
does not decrease within the used temperature range, Curie tempera-
ture of the material is not less than 550°C.
-200
-100
0
100
200
-400 -200 0 200 400
v o(v
olt
)
V (volt)
hysteresis loop
Dr. Srouji. Orfali
28
Fig 10. The relative permittivity variation in function of temperature for un-
poled sample and 1.5kV/mm poled sample.
The pyroelectric current was measured using KEITHLEY
6517B electrometer then the pyroelectric coefficient p was calculated
using the following relation [9,11]:
(
)
Where A is the sample area, IPyro pyroelectic current, and
(
) is the heating rate with time. Fig.11 shows the pyroe-
lectric coefficient p changing with temperature; it shows nonlinear var-
iation with temperature. As shown, the pyroelectric coefficient exhibits
low increasing with T in range of (200-400°C) and high increasing af-
ter T=400°C.
Fig 11. Pyroelectric coefficient variation in function of temperature.
4. Conclusions
Dielectric constant values decrease sharply with increased fre-
quency in the range of (20Hz-100KHz), then the dielectric con-
stant decreases slightly in the range of (1KHz-3KHz).
The same polarization process occurs at temperature below Tc.
0
5000
10000
0 200 400 600ε r
T0C
Unpoled sample
1.5 kV/mm poled sample
0
100
200
300
400
500
600
700
0 200 400 600pyr
oel
ectr
ic c
oef
fici
ien
t (μ
C/c
m2 .
0 C)
T0C
R.J.of Aleppo Univ. Basic Science Series No. 98 2014
29
Ferroelectric property of PZT material includes a hysteresis
loop.
Poling process increases the relative permittivity of the sam-
ples.
Poling process decreases the dielectric loss of the material es-
pecially at frequencies below 1 KHz.
The pyroelectric coefficient exhibits high increasing with tem-
perature after 4000C.
References [1] Haertling, G. H. 1999 - Ferroelectric ceramic. History and tech-
nology. J. Am. Ceram. Soc. 82, 797–818.
[2] Gajbhiye N. S.; Pandey P. K.; Smitha P. 2007 - “Low-
Temperature Synthesis of Nanostructured PZT for Dielectric
Studies” Synthesis and Reactivity in Inorganic, Metal-Organic, and
Nano-Metal Chemistry, 37:431–435.
[3]Kim, K.; Lee, S. 2006 - Integration of lead zirconium titanate
thin films for high density ferroelectric random access memory.
J. Appl. Phys. 100, 51604–51611.
[4] Yamashita, K.; Chansomphou, L.; Murakami, H.; Okuyama, M.
2004 - Ultrasonic micro array sensors using piezoelectric thin
films and resonant frequency tuning. Sensors Actuators. 114,
147–153.
[5] Jaffe B.; Cook W.R.; Jaffe H. 1971 - Piezoelectric Ceramics, (Ac-
ademic Press, New York).
[6] Noheda B.; Cox D. E.; Shirane G.; Gonzalo J. A.; Cross L. E.; Park
S-E. 1999 - A monoclinic ferroelectric phase in the Pb(Zr1-xTix)
O3 solid solution, Appl. Phys. Lett. 74, 2059.
[7] Dragan Damjanovic. 2006 - Hysteresis in Piezoelectric and Fer-
roelectric Materials. The Science of Hysteresis, Volume 3; I.
Mayergoyz and G.Bertotti (Eds.); Elsevier.
[8] Kamel T. M. “Poling and switching of pzt ceramics” doctorate of
philosophy essay 2007.
[9] Kwan Chi Kao. 2004 - Dielectric phenomena in solids, book,
ISBN 0-12-396561-6, Elsevier Academic Press, pp.-86-98.
[10] Koops C. G. 1951 - Phys. Rev. 83 (121).
[11] IRE standards on piezoelectric crystals, 1949, Proc. IRE,
37,PP.1378-1395, 1949.
Dr. Srouji. Orfali
30
[12] IRE strandards on piezoelectric crystals-the piezoelectric vi-
brator: definitions and methods of measurement, 1957”, Proc.
IRE, 45, PP. 353-358, 1957.
[13]Shining Zhu, Bei Jiang .; Wenwu Cao. Characterization of pie-
zoelectric materials using ultrasonic and resonant Techniques” SP1E Vol. 3341
[14] Mason W. P. 1950 - Piezoelectric Crystals and Their Applica-
tion to Ultrasonics. New York: Van Nostrand.
[15] Kuwata J.; Uchino K.; Nomura S. 1982 - Jpn. J. Appl. Phys. 21,
1298. [IEEE Standard on piezoelectricity. ANSI/IEEE Std. 176-
1987.
[16] J.Wu and C.Chen, J.Mater.Sci, 23, 4157, (1988).
[17] C. B. Sawyer and C. H. Tower, “Rochelle salt as a dielectric”
Physical Review, vol. 35, pp. 269–275, February 1930
R.J.of Aleppo Univ. Basic Science Series No.98 2014
13
Optical Properties of CdTe QDs Synthesized by
Chemical Method and Enhanced by Microwave
Irradiation
Fatima Srouji, Farouk Al Jasem*
Dept. of Physics, Faculty of Science, Aleppo University
*Postgraduate Student (MSc.)
Abstract CdTe quantum dots in aqueous phase were prepared by
chemical method enhanced by microwave irradiations. The influence
of capping with Thiol component (3- Mercaptopropionic acid) and
organic component (Polyvinylpyrrolidone) on the stability of the
quantum dots, absorption and Photoluminescence (PL) spectra, was
studied. The influence of microwave irradiations on the quantum dots
stability and reducing of surface defect was also studied. The
preparation parameters (synthesis temperature, PH value of CdTe
precursor solution and the Cd+2
/Te-2
ratio) were studied. It was found
that CdTe Quantum dots in the aqueous phase capped with thiol
(MPA) have high stability and photoluminescence compared with
quantum dots in the aqueous phase capped with PVP (organic). Using
microwaves leads to accelerating the growth of quantum dots; it results
in reducing the interaction energy and detracting the surface defects.
Received 30/6/2014
Accepted 23/10/2014
Dr. Srouji & Al jasem
13
1. Introduction Colloidal semiconductor nanocrystals (also known as quantum
dots, QDs) are generally known as II–VI and III–V semiconductors,
which strongly exhibit size dependent on optical and electrical
properties [1]. Bulk CdTe is transparent in the infrared wavelength,
from its bandgap energy, which is approximately 1.44eV at 300K (i.e.
860 nm) to its wavelength, greater than 20 μm, which is already in the
infrared region. It has been presented that if the size of the bulk CdTe
material shrinks to nanometer scale, normally 2 to 5 nm, the bandgap
energy of the material will increase, due to quantum confinement
effect, which means that the fluorescence peak will shift towards the
infrared region or visible range. This will open a wide gate of
application for this magical semiconductor material to be used in
several areas. CdTe quantum dots are also highly luminescent
nanoparticles with quantum yield up to 80% if the parameters through
the synthesis process are carefully manipulated [1-3]. The synthesis in
aqueous phase is an alternative method for preparation of QDs. A
series of thiol-stabilized QDs, such as CdS [2], CdSe [3] and CdTe [4–
5] could be prepared in aqueous solution. Compared with organic
phase synthesis, aqueous synthesis exhibits good reproducibility, low
toxicity, and low price; the products have especially excellent water-
solubility, stability and biological compatibility [5]. Using microwave
electromagnetic irradiation to synthesize QDs is recently widely used
because it can provide rate and yield enhancements [6]. These benefits
can be explained by dielectric heating in which polar materials are
heated preferentially because they absorb microwaves more strongly.
Depending on the relative polarity difference between the solvent and
precursor molecules, one can rapidly grows QDs by heating precursors
directly or by heating the solvent to form a traditional thermal bath.
Furthermore, dielectric heating differs from convective heating in that
the entire volume is heated uniformly, thereby reducing thermal
gradient effects and hence providing more control over the size
distribution (i.e., optical properties) of the QDs [6]. Therefore, with
careful selection of the reaction system (precursors, passivating
ligands, solvent, etc.) and microwave parameters (temperature, time,
power, etc.), one can potentially achieve superior control of the
nucleation and growth processes to generate high-quality QDs [7].
R.J.of Aleppo Univ. Basic Science Series No.98 2014
11
2. Experimental and Result 2.1 Materials
Cadmium chloride monohydrate (CdCl2.H2O, 98%,
HIMEDIA), Sodium tellurrite (Na2TeO3, 98%, BDH), Tri-sodium
citrate dehydrate (C6H5O7Na3.2H2O, 98%, HIMEDIA), 3-
Mercaptopropionic acid (C3H6O2S, 98%, IT USA), Sodium
borohydride powder (NaBH4, Scharlau), Polyvinylpyrrolidone (PVP)
and a modified domestic MW oven (900 Watt, 2.45 GHz).
UV-vis absorption spectra were obtained using a V630 UV-vis
spectrophotometer (Jasco). Photoluminescence (PL) spectra were
recorded with an F-2700 fluorescence spectrophotometer (Hitachi).
2.2. Synthesis of CdTe QDs
2.2.1 Synthesis of CdTe QDs Capped with MPA (Thiol) 4 mL of cadmium chloride solution (CdCl2, 0.04 mol/L) were
diluted to 42 mL with deionized water, and then trisodium citrate
dihydrate (100 mg), Na2TeO3 (0.01 mol/L, 4 mL), MPA (119 mg), and
NaBH4 (50 mg) were added successively under magnetic stirring. The
molar ratio of Cd2+
/MPA/Te-2
was 1:7:0.25. The resulting CdTe
precursor was put into a flask (250 mL). CdTe QDs were prepared at
temperature (120 °C) under microwave irradiation (900 W) for 10 min.
The mixture was allowed to cool to lower than 50 °C, then samples
were stored in the dark at low temperature.
Figures (1 and 2) show absorption and fluorescence spectra of
CdTe QDs aqueous in water capped with MPA (thiol) measured during
different times after preparation. It is clear from figs. (1 and 2) that
CdTe QDs synthesized by irradiation microwave have high stability
and photoluminescence (PL) in aqueous phase. The band gap of CdTe
QDs was determind to be (2.64 ev) and the radius of CdTe QDs
prepared in aqueous phase was 1.75 nm, which was calculated using
Barus equation [8]:
(
)
Where of CdTe is 1.49 eV, of CdTe is 0.098 ,
of CdTe is 0.11 and is 10.3 (
, are the effective
masses of electron and hole, respectively. is free electron mass and
is vacuum dielectric constant). By inserting these values into the
above equation it becomes:
Dr. Srouji & Al jasem
13
√
Where D (nm): is the diameter of CdTe QD , λ (nm) is
wavelength according to a peak absorption of QD
Fig.1: Absorption spectra of CdTe QDs aqueous in water capped with MPA
(thiol) after different aging intervals, where (a) is immediately after
preparation, (b) after one day, (c) after 4 days, (d) after one week.
Fig.2: fluorescence spectra of CdTe QDs aqueous in water capped with MPA
(thiol), where the excitation wavelength =461nm and the emission wavelength
=503nm.
2.3.2. Synthesis of CdTe QDs Capped with PVP
4 mL of cadmium chloride solution (CdCl2, 0.04 mol/L) were
diluted to 42 mL with deionized water, and then trisodium citrate
dihydrate (100 mg), Na2TeO3 (0.01 mol/L, 4 mL), PVP (100 mg), and
NaBH4 (50 mg) were added successively under magnetic stirring to
the first solution. The molar ratio of Cd2+
/PVP/Te-2
was 1:7:0.25. The
resulting CdTe precursor was divided into two parts:
Measurements were conducted on the first one without
exposing it to microwave irradiation; the second was put into a flask
with a volume of 250 mL. These series of CdTe QDs were irradiated in
R.J.of Aleppo Univ. Basic Science Series No.98 2014
13
microwaves at power (900W) until their temperature reached 1200C
for 5min. Then the mixture was allowed to cool lower 500C.
Figure (3) shows absorption spectrum of the prepared CdTe
QDs capped with PVP in the precursor solution after different aging
intervals, where (a) is immediately after preparation, (b) after half an
hour, (c) after 4 days, (e) after one week.
Fig.3 Absorption spectra of CdTe QDs capped with PVP after different aging
intervals, where (a) is immediately after preparation, (b) after half an hour, (c)
after 1.5h, (d) after 14.5 h, (e) after 24h.
The figure shows that the quantum dots capped with PVP in the
precursor solution are unstable and change with the time, and indicates
that the peak of absorption shifts toward the red, which means that the
prepared quantum dots have unstable size. Figure (4) shows the photoluminescence spectrum (PL) of the
prepared CdTe QDs, where the PL of this sample is very poor due to
the presence of large surface defects that lead to poor QY.
Fig.4 Photoluminescence spectrum of CdTe QDs capped with PVP immediately
after preparation, where the excitation wavelength λ=400 nm and the emission
wavelength λ=565nm.
Dr. Srouji & Al jasem
13
Figures (5 and 6) represent the relationship between QDs radii
and aging time; the same for energy gaps.
Fig.5 QDs radius variations with time.
Fig.6 Band gap of QDs variations with time.
It is clear from figures 5 and 6 that a large increase in the radii
of quantum dots for these samples takes place within the first 24 hours.
Then it becomes almost stable. Whereas the ∆Eg decreases largely
within the first 24 hours and then becomes stable. This can be
explained by the following: after the microwave irradiation for 5min
and at 1200C temperature, the CdTe QDs become more stable in size
but the photoluminescence stays low. This is because the
electromagnetic waves result in increasing the molecules polarization
and this, in turn, increases the coupling force between the PVP
molecules and the CdTe QDs, hence increasing the stability of CdTe
QDs size. The electromagnetic waves also work in reducing the
reaction energy of Cd2+
and Te2-
ions which accelerates the occurrence
of reactions and changes CdTe QDs size with time.
1.62
1.64
1.66
1.68
1.7
1.72
1.74
1.76
0 50 100 150 200
Rad
ius
(nm
)
Time (Hour)
1.1
1.15
1.2
1.25
1.3
1.35
0 50 100 150 200
∆E
g (
ev)
Time (Hour)
R.J.of Aleppo Univ. Basic Science Series No.98 2014
13
Table (1) Aging times, wavelength peak of absorption spectra, energy gaps and
radius of CdTe QDs.
Time (hour)
Wavelength
peak of
absorption
spectra (nm)
Eg nano (ev)
∆Eg (ev) R (nm)
0 444 2.792 1.302 1.63
0.5 450 2.755 1.265 1.66
1.5 458 2.707 1.217 1.69
14.5 468 2.649 1.159 1.74
24 470 2.638 1.148 1.75
168 471 2.632 1.142 1.75
After Irradiation of CdTe QDs using microwave for 5 min at
120ᵒC temperature, CdTe QDs become more stable in size but still
have poor photoluminescence (PL), as shown in figures (7 and 8).
Fig.7 Absorption spectra of CdTe QDs capped with PVP after aging for (a=0,
b=13, c=23) hours.
Fig.8 Florescence spectra of CdTe QDs capped with PVP, where excitation
wavelength (400nm) and emission wavelength (465nm).
Dr. Srouji & Al jasem
13
Fig.9 Variation of QDs radii with aging time.
Fig.10 Variation of QDs band gaps with aging time.
Figures (9,10) show the variation of the radius and the energy
gap with time, where the radius increases with time due to increased
growth of quantum dots and the corresponding change in the band gap,
and these changes are very small. Table (2) shows the aging time of the samples, the length of wave crest
absorption, energy gap, variety of band gap with time, and radius of CdTe QDs.
R (nm)
∆Eg (ev)
Egnano (ev)
Wavelength
peak of
absorption
spectra (nm)
Time (hour)
2.006 0.885 2.375 522 0
2.018 0.876 2.366 524 13
2.029 0.867 2.357 526 23
2.3.3 Influence of Some Parameters on the Properties of CdTe QDs
Capped with MPA 1.2.2 Temperatures
CdTe QDs prepared by the method mentioned in section )2.3.1)
were irradiated under (900 W) microwave irradiation for (5 min) and at
2.005
2.01
2.015
2.02
2.025
2.03
2.035
0 5 10 15 20 25
Rad
ius
(nm
)
Time (Hour)
0.865
0.87
0.875
0.88
0.885
0.89
0 5 10 15 20 25
∆E
g (
ev)
Time (Hour)
R.J.of Aleppo Univ. Basic Science Series No.98 2014
13
temperatures (A = 60, B = 80, C = 100 ᵒC). The last sample was heated
from room temperature to 120 ᵒC (line D).
Figures (11 and 12) show the absorption and photoluminescence
spectra of the samples prepared at different temperatures. As shown in
Figure (11), absorption peaks shift toward the red because of the
increase of the QDs size; this is due to the increase in the growth rate
of these dots with temperature. These figures also show an increase in
the intensity of the optical absorption and luminescence with
temperature. That is due to the reduction of surface defects in the
prepared QDs. While the quantum dots prepared at low temperatures
exhibit low intensity absorption and luminescence caused by the large
number of defects on the surface, generated owing to the slow growth
of QDs. The sample (D) showed the best result for the intensity of the
optical absorption and luminescence, so we can say that the
temperatures between 100ᵒC and 120ᵒC are the ideal temperatures to
achieve optimal synthesis of quantum dots.
Fig.11 Absorption spectra of CdTe QDs capped with MPA at different reaction
temperature (A=60 ᵒC, B=80 ᵒC, C=100 ᵒC, D=120 ᵒC).
Fig.12 luminescence spectra of CdTe QDs capped with MPA at different
reaction temperature.
Figures (13 and 14) represent quantum dots radii and the band
gap variations with preparation temperature. They reveal that the
0
200
400
600
800
450 500 550 600 650
Inte
nsi
ty
Wavelength (nm)
60 C 80 C 100 C 120 C
Dr. Srouji & Al jasem
34
radius of the quantum dots increases almost linearly for temperatures
between 60 ᵒC and 100 ᵒC, then becomes quasi-steady for temperatures
between 100 ᵒC and 102 ᵒC. Similarly, the band gap changes contrary
to radii.
Fig.13: Variation of QDs radii with aging time.
Fig14: Variation of QDs band gaps with aging time.
Table (3): Temperature synthesis, the wavelength of absorption peaks, the
energy gap, the gap energy change, and radii quantum dots.
R(nm) ∆Eg (ev) Enano(ev)
Wavelength peak of
absorption spectra
(nm)
t C
1.52 1.498 2.988 415 60
1.63 1.315 2.805 442 80
1.71 1.194 2.684 462 100
1.69 1.217 2.707 458 120
1.2.3. PH
Following the method of preparation in section (2.3.1) and
before adding Sodium borohydride (NaBH4) to the result solution, the
value of pH was controlled by adding sodium hydroxide (NaOH 0.1
mol/L) in different pH values.
1.5
1.55
1.6
1.65
1.7
1.75
50 70 90 110 130
Rad
ius
(nm
)
t ˚C
1
1.1
1.2
1.3
1.4
1.5
1.6
50 70 90 110 130
∆E
g (
ev)
t ͦ C
R.J.of Aleppo Univ. Basic Science Series No.98 2014
33
It was found that the samples with pH values (a: PH=4.52, b:
PH=5.12, c: PH=5.28, d: PH=6.8, e: PH=9.3) give better absorption
values as shown in Figure (15).
Fig.15 Absorption spectra of CdTe QDs synthesized at different PH values of
solution (a: PH=4.52, b: PH=5.12, c: PH=5.28, d: PH=6.8, e: PH=9.3).
Figures (15 and 16) show that the intensities of the optical
absorption and luminescence reach the highest values for pH= 6.8 (line
d). Thus, fluorescence intensity and the highest emission peak of the
CdTe QDs were strongly influenced by the pH value of the precursor
solution.
Fig.16 Fluorescence spectra of CdTe QDs synthesized at different PH values of
solution (a: PH=4.52, b: PH=5.12, c: PH=5.28, d: PH=6.8).
0
10
20
30
40
50
60
425 475 525 575 625 675
Inte
nsi
ty
Wavelength (nm)
a b c d
Dr. Srouji & Al jasem
33
Fig.17 radius of QDs with time.
Fig18 band gap variations of QDs with time.
Table (4) temperature synthesis, wavelength peaks of absorption, energy gap
and radii quantum dots.
PH
Wavelength
peak of
absorption
spectra (nm)
Enano (ev) ∆Eg (ev) R (nm)
3.1 575 2.156 0.667 2.35
4.52 451 2.749 1.259 1.66
5.12 433 2.863 1.373 1.59
5.28 431 2.877 1.387 1.58
5.58 441 2.811 1.321 1.62
6.8 480 2.583 1.093 1.79
Figures (17 and 18) represent quantum dots radii and the band
gap variations with PH. These curves show that the energy gap
increases with the pH value increase until the value 5.5. After returning
to decrease, they become almost stable for pH values between 7 and 9.
From the above behavior, it is noticed that the pH values have a
significant influence on the properties of quantum dots (radii,
wavelength and intensities of absorption and luminescence).
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2 4 6 8 10
Rad
ius
(nm
)
PH
0.4
0.6
0.8
1
1.2
1.4
1.6
0 2 4 6 8 10
∆E
g (
ev)
PH
R.J.of Aleppo Univ. Basic Science Series No.98 2014
31
1.2.4 Ratio of Cd+2
/Te-2
CdTe QDs prepared by the method mentioned in section )2.3.1)
were irradiated under (900 W) for 5 min and sample temperatures were
allowed to rise from room temperature to 120 ᵒC. The ratio of Cd+2
/
MPA/ Te-2
have been changed as follows: Table (5) The ratio of Cd
+2/Te
-2 in the prepared samples
sample a b c d e f g
Ratio of
Cd+2
/MPA/ Te-2
0.25/7/
0.25
0.5/7/
0.25
0.75/7/
0.25
1/7/
0.25
1/7/
0.0625
1/7/
0.125
1/7/
0.1875
Figures (9, 10) show the peaks of absorption and fluorescence
spectra of samples synthesized with different ratios of Cd+2
and Te-2
.
The figures show the effect of the cadmium ratio on surface defects of
the QDs synthesized in the solution, where the increasing in ratio of
Cd+2
results in an enhancement of the surface of QDs and a decrease in
the surface defects. These defects are less than that in the samples of
the ratio Cd+2
/MPA/Te-2
: 1/7/0.25.
Fig.19 Absorption spectra of CdTe QDs synthesized at different ratio Cd
+2/Te
-2
of solution.
It is obvious from the figure (19) that the intensity of the
photoluminescence is the largest for this ratio.
Fig.20 Photoluminescence spectra of CdTe QDs synthesized at different ratio
Cd+2/Te-2 of solution.
Dr. Srouji & Al jasem
33
Figures 21, 22 show radii and band gap variations of the QDs
for ratio of Cd+2
/Te-2
. From these curves it is noted that the best
samples are corresponding to a ratio of Cd+2
/Te-2
that equals (2:4:8).
Fig.21 Radii of QDs variations with time.
Fig.22 Band gap variations of QDs with time.
Table (6) Temperature synthesis, wavelength peaks of absorption, energy gap,
the gap energy change and radii quantum dots.
Cd+2
/Te-2
Wavelength
peak of
absorption
spectra (nm)
Enano(ev) ∆Eg (ev) R (nm)
1 469 2.661 1.171 1.74
2 404 2.719 1.229 1.48
3 441 2.737 1.247 1.62
4 431 2.877 1.387 1.58
5.33 453 2.644 1.154 1.67
8 456 3.069 1.579 1.68
16 466 2.811 1.321 1.73
Conclusion
A chemical method for CdTe Quantum dots enhanced with
microwave irradiation is a fast, easy, and cheap way for CdTe
1.45
1.5
1.55
1.6
1.65
1.7
1.75
1.8
0 5 10 15 20
Rad
ius
(nm
)
ratio of Cd+2/Te-2
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
0 5 10 15 20
∆Eg
(e
v)
ratio of Cd+2/Te-2
R.J.of Aleppo Univ. Basic Science Series No.98 2014
33
Quantum dots preparation and gives Quantum dots with different sizes
and good structure.
CdTe Quantum dots in the aqueous phase capped with thiol
(MPA) have high stability and photoluminescence compared with
quantum dots in the aqueous phase capped with PVP (organic). Using
microwave in the preparation of quantum dots increases the stability of
the quantum dots and improves the optical character, absorption and
photoluminescence. In addition, CdTe Quantum dots in the aqueous
phase capped with (PVP) have more stability than those prepared
without microwave irradiations. Using the microwaves leads to
accelerating the growth of quantum dots; it results in reducing the
interaction energy and detracting the surface defects.
The various parameters of preparation (temperature, pH and
ratio of Cd+2
/Te-2
) have strong influences on the physical properties of
QDs; therefore, these parameters can be adjusted during the synthesis
process, according to required applications of prepared quantum dots.
References [1] L.E. Brus, Electronic wave functions in semiconductor clusters:
experiment and theory, J. Phys. Chem., 1986, 90 (12), pp 2555–
2560
[2] T. Vossmeyer, L. Katsikas, M. Giersig, I.G. Popovic, K. Diesner,
A. Chemseddine, A. Eychmu¨ ller, H. Weller, CdS Nanoclusters:
Synthesis, Characterization, Size Dependent Oscillator
Strength, Temperature Shift of the Excitonic Transition
Energy, and Reversible Absorbance Shift, J. Phys. Chem.
1994,98, 7665-7673
[3] A.L. Rogach, A. Kornowski, M.Y. Gao, A. Eychmu¨ller, H.
Weller, Synthesis and Characterization of a Size Series of.
Extremely Small thiol-stabilized CdSe Nanocrystals, J. Phys. Chem. 1999; 103:3065–3069
[4] A.L. Rogach, L. Katsikas, A. Kornowski, D. Su, A. Eychmu¨ller,
H. Weller, Ber. Bunsen-Ges. Synthesis and Characterization of
Thiol-Stabilized CdTe Nanocrystals Phys. Chem. 100 (1996)
1772.
[5] N. Gaponik, D.V. Talapin, A.L. Rogach, K. Hoppe, E.V.
Shevchenko, A. Kornowski, A. Eychmu¨ller, H. Weller, Thiol-
Capping of CdTe Nanocrystals: An Alternative to
Organometallic Synthetic Routes, J. Phys. Chem.
B, 2002, 106 (29), pp 7177–7185
Dr. Srouji & Al jasem
33
[6] Gerbec, J. A.; Magana, D.; Washington, A.; Strouse, G. R. J. Am.
Direct Synthesis of Aqueous CdSe/ZnS-Based Quantum Dots
Using Microwave Irradiation, Chem. Soc. 2005, 127, 15791.
[7] William Schumacher, Amber Nagy, W. James Waldman, and
Prabir K. Dutta, Direct Synthesis of Aqueous CdSe/ZnS-Based
Quantum Dots Using Microwave Irradiation, Chemistry and
Pathology. 2009
[8]: A.El Moussaouy, D. Bria, A. Nougaoui. 2006. Thermal effect on
bound exciton inCdTe/Cd1-xZnxTe cylindrical quantum dots.
Solar Energy Materials & Solar Cells 90: 1403–1412.
Res. J of Aleppo Univ. Basic Science Series No.98 2014
74
Studying the Effect of Fineness on the Thermal
Treatment of Syrian Petroleum Coke to Reduce the
Sulfur Content
Walied Hawaleh*, Salah Al Haj Omar**, Mohammad Yahia Masri
***
*Dept. of Chemistry, Faculty of Science, University of Aleppo
**Dept. of Basic Science, Faculty of Mechanical Engineering, University of Aleppo
***Postgraduate Student (PhD), Dept. of Chemistry, Faculty of Science, University
of Aleppo
Abstract
In this research we studied the effect of fineness on the thermal
treatment of Syrian petroleum coke in order to define the favorable
fineness to reduce the sulfur content in lower temperature and time.
The samples of petroleum coke were crushed to different granular size,
from less than 90µm to more than 5mm, then we made physical and
chemical analysis for each sample to know the distribution of sulfur in
each sample. We found that the amount of sulfur is increased by the
increase of fineness. We measured the moisture, ash and volatile
content as well as the caloric value for each sample.
It was concluded that the ability of sulfur removing from
petroleum coke is by increasing treatment temperature up to 1200°C
and time of treatment to 2 hours. The best sulfur removal was with the
granular size between (710-1250µm). This sample is fit with ash and
volatile matter content within the allowed value according to ASTM
specifications.
Keywords: Syrian petroleum coke, Thermal treatment, Fineness effect, sulfur
content.
Received 15/6/2014
Accepted 25/8/2014
R.J. of Aleppo Univ. Basic Science Series No. 98 2014
49
Screening, Identification and Partial Characterization
of Pullulanase Enzyme from Local Bacterial Strain
Nizar Essa, Faiza Al atrash, Waleed Mlook* Dept. of Botany, Faculty of Science, Damascus University
* Postgraduate Student (MSc.)
Abstract
Fifty bacterial isolates, isolated from various local soils (19),
baking wastes (14) and food wastes (19) were screened to detect
pullulanase, by using pullulan as a sole carbon source according to
solid plate assay. Results showed that 17 strains (34 %) had the
ability to produce pullulanase in assay plate as evidenced by clear
hydrolization zones formed around the colonies. Seven strains
which presented considerable pullulytic activity with degradation
efficiency more than 1.5 were chosen, and the pullulanase activity
in poor broth was studied for each one. P8 isolate which had the
biggest degradation efficiency (2.88) showed high activity of the
enzyme (0.549 unit/ml) in broth medium. Based on morphological
and biochemical characteristics, P8 strain was identified as Bacillus
cereus. This isolate showed high activity to produce pullulanase at
50°C and pH 6.0. It was concluded that there is an ability to
produce locally pullulanase which can be used for some
manufacturing purposes. Keywords: Pullulanase, Pullulan, Bacillus.
Received 6/7/4104
Accepted 45/8/ 4104
Res. J. of Aleppo Univ. Basic Science Series No.98 2014
51
A Study of Immunological and Hematological Findings
in Systemic Lupus Erythematosus (SLE) Patients in
Aleppo Sabah Blaj*, Leka Hoppo*, Abeer Alyosef**, Eman Almosa***
* Dept. of Zoology, Faculty of Science, University of Aleppo
**Dept. of Laboratory Medicine, Faculty of Medicine, University of Aleppo ***Postgraduate Student (MSc.) Dept. of Zoology, Faculty of Science, University of
Aleppo
Abstract
The research aimed to study some Immunological and
Hematological findings in SLE patients in Aleppo. The recent study
examined 27 blood samples from Systemic lupus Erythematosus (SLE)
patients of both sexes, who fulfilled four or more of the classification
criteria of American College of Rheumatology (ACR, 1997). We
investigated the presence of Anti-nuclear antibodies (ANA) and double
stranded DNA antibodies (anti-ds-DNA). The positive was %85.18,
and %70.37, respectively. Elevated C-reactive protein (CRP), Low
complement C3, and Elevated immunoglobulin IgG in SLE patients
were found in 40.74%, 48.04%, and 37.04%, respectively. Blood tests
had been done for patients; the most common feature is Anemia, with
66.66%, Leucopenia and Thrombocytopenia were found in 11.11%,
and 18.5% , respectively.
Key words: Systemic lupus erythematosus (SLE), American College
of Rheumatology (ACR), antinuclear antibody (ANA), double stranded
DNA (dsDNA), Complement C3, C-reactive protein (CRP),
immunoglobulin G (IgG).
Received 20/7/2014
Accepted 25/8/2014
Res. J. of Aleppo Uni. Basic Science Series. No. 98 2014
35
Antibacterial Activity of Salvia officinalis against Some
Pathogenic Bacteria Isolated from Tonsillitis and
Pharyngitis Patients
Abdel Aleem Bello٭, Zaher Samman Tahan٭, Firas Haj Zein٭٭, Yasmin Alshihabi٭٭٭
Dept. of Botany, Faculty of Science ٭
Dept. of Otolaryngology, Faculty of Medicine٭٭
Postgraduate Student (MSc.) Dept. of Botany, Faculty of Science, University of ٭٭٭
Aleppo
Abstract
Salvia officinalis has a valuable medicinal importance; it is
used in traditional medicine for the treatment of Pharyngitis and
Tonsillitis. Leaves and aerial parts of Salvia officinalis were extracted
with Petroleum ether, chloroform, ethanol and water. The yield of
extracts was determined. The activity of extracts against bacteria
isolated from tonsillitis and pharyngitis patients was determined by
using Agar Well Diffusion Method, then the Minimal Inhibitory
Concentration (MIC) was determined.
The results showed that most of the examined extracts have
antibacterial activity. The most active extract against Gram positive
bacteria was chloroform extract of aerial parts, where zone of
Inhibition was 34.67 mm for Staphylococcus hominis. The most active
extract against Gram negative bacteria was Petroleum ether extract of
aerial parts, where zone of Inhibition was 19.67 mm for Klebsiella
pneumoniae. Gram positive bacteria were more sensitive to plant
extracts than Gram negative bacteria.
The results showed that plant extracts with examined
concentrations were more active than some standard therapeutic
antibiotics.
Keywords: Antibacterial activity, Plant extracts, Salvia officinalis,
Pharyngitis, Tonsillitis.
Received 14 /7/2014
Accepted 26 /8/2014
Res. J. of Aleppo Univ. Basic Sciences Series No.98 1024
55
Synhesis of Some Push-Pull Alkenes Containing Two
Carbonyl Groups: Ketene Dimethyl Dithio Acetal Type
Saleh El-Kadri, Ani Tersakian, Ahmad Alabboud* Dept. of Chemistry, Faculty of Science, University of Aleppo
*Postgraduate Student (MSc.)
Abstract
Starting from compounds containing acidic hydrogens which
are: Acetyl acetone, methyl aceto acetate, dimethyl malonate and ethyl
aceto acetate, we have synthesized some ketene dimethyl dithioacetal
compounds which belong to push – pull alkenes family according to
dithiocarboxylation general reaction in the presence of carbon disulfide
in two alkaline systems K2CO3/DMF and KOH/CH3CN. The
synthesized compounds structures have been approved by infrared
spectroscopy (IR) and mass spectrometry (GC/MS).
Keywords: push-pull alkenes, ketene dithio acetal, active methylene compounds.
Received 08/04/2014
Accepted 28/08/2014
R . J . of .Aleppo Univ. Basic Sciences Series No. 89 2041
75
A Comparative Study of the Structure of Pancreas in the
Two Species Clarias gariepinus (syriacus) and Clarias
salurus Living in the Orontes and Euphrates Rivers
Saja Abou Ghaloon
Dept. of Zoology, Faculty of Science, University of Aleppo
Abstract The research showed a difference in the prevalence,
correlation and thickness of the pancreas in the two Species, Clarias gariepinus (syriacus) and Clarias salurus especially with liver and
great portal vein. The researcher observed an overlap between the
pancreas and liver tissue in Clarias gariepinus (syriacus) without a
barrier of connective tissue between them, constituting pancreatic
liver, unlike the Clarias salurus where a connective capsule separating
the pancreas and liver was observed. The histological structure of
Pancreas in Clarias gariepinus (conjoined with follicle biliary, bile
ducts and blood vessels) interfered with serosa, and the situs exocrine
cells took the shape of sling cells. Also the cell takes Pear shape and is
linked with a thin layer of connective tissue; its tip top is free in
cavities connected with each other. While it takes the alveolar shape in
the Clarias salurus surrounded by connective tissue. The islets of
Langerhans are spread in both species in the central part of the gland
while they are absent in the areas of overlap with other organs. They
take in Clarias gariepinus (syriacus) the form of large vesicles with
irregular boundaries surrounded by thin connective capsule, but in the
Clarias salurus, they are smaller with regular borders surrounded by
thick connective capsule. Two different types of cells in the islets of
Langerhans in both species were distinguished, pyramid-shaped acidic
cells with basic nucleus positioning, and a basic cell with unclear
membrane and central nucleus positioning.
Keywords: Clarias gariepinus (syriacus), Clarias salurus, Pancreas,
islets of Langerhans. Received 6 /7/2014
Accepted 2 /9/2014
Res. J. of Aleppo Univ. Basic Sciences Series No.98 2014
95
A Comparative Study of Ball Point Pens Writing Ink
Using Techniques of XRF, UV-VIS, FT-IR
Said Sabbagh, Murhaf Al-Sayed Ali * Dept. of Physics, Faculty of Science, University of Aleppo
*Postgraduate Student (MSc)
Abstract
The purpose of this study was to evaluate, for legal
examinations, the possibility to discriminate among many samples of
ball point pen inks, provided from various manufacturers by using non-
destructive analysis techniques, such as: Fourier Transform Infrared
Spectroscopy (FT-IR), Ultra Violet – Visible (UV-VIS) Spectroscopy,
and Fluorescence X-ray Spectroscopy (XRF). It also aimed to examine
the ability of each technique to develop the devices of physics.
For analysis of UV-VIS spectra, two ways were used:
complementary color analysis, and color analysis using CIE L* a
* b
*
program. XRF and CIE L* a
* b
* program were successful in
discriminating ballpoint pen inks of different bands, while FT-IR
analysis revealed that each brand could be discriminated by looking
for the pattern of each spectrum.
This work suggests carrying out multiple analyses of unknown
and complex components of writing inks.
Keywords: Ball Point Pens, FT-IR Spectroscopy, UV-VIS Spectroscopy,
XRF Spectroscopy, Complementary Color, CIE L* a
* b
* Program, Writing
Inks.
Received 20/7 /2014
Accepted 2/9 /2014
Res. J. of .Aleppo Univ. Basic Science Series No. 89 2014
16
Studies of XRD, FT-IR and Surface Areas of Pure MoO3,
WO3 and the Mixed Oxide System Mo-W-O
M. Karman, N. Al Ghanom
*
Dept. of Chemistry, Faculty of Science, University of Aleppo
* Postgraduate Student (PhD)
Abstract
Pure MoO3, WO3 and a mixed oxide system Mo-W-O were
prepared by mechanical mixing method, then calcined at 500oC and
600oC. The XRD pattern of the pure MoO3 and mixed oxides system
shows peaks only due to MoO3 with an orthorhombic structure. On the
other hand, the pattern of the catalysts contains 15, 35 wt%. WO3
shows new peaks which can be assigned to formation of a new phase.
The FT- IR spectra of all the prepared samples show characteristic
bands referring to presence of MoO3 and not showing any bands
referring to presence of WO3. The surface areas of all the prepared
samples were determined by adsorption of MB from organic solution
and were found (0.84 - 4.45 m2/g) in case of catalysts calcined at 500
oC and (1.49– 3.47 m
2/g) in case of catalysts calcined at 600
oC.
Keywords: MoO3 - WO3 - surface area.
Received 66/9/4162
Accepted / 4/8/4162
Res. J. of .Aleppo Univ. Basic Science Series No. 98 2014
63
Synthesis and Characterization of Nd:YAG Nanopowder
via Polymer DTPA Metal Chelated Complexes
Emad Asad*، Farouk Kandil** ،Mohammad Hasan Derbas *** *Dept. of Chemistry and Institute for Laser Research and Applications, Damascus
University
**Institute for Laser Research and Applications, Damascus University
***Postgraduate Student (PhD.) Dept. of Chemistry, Faculty of Science, Damascus
University
Abstract
High transparency ceramic was prepared from Neodymium,
Aluminum and yttrium Nd: YAG nanopowder. This procedure
included preparation of diethylentriaminepentaacetic (DTPA) followed
by polymerization with ethylene glycol. The produced polymer was
used in forming chelated complexes with elements of YAG. The
formed complexes were calcinated at 600, 700 and 950oC and sintering
followed by product under vacuum. The prepared powder was
characterized by SEM, ZETA potential, XRD and DTA to make sure
of distribution homogeneity of YAG elements (components)
(Y2O3.Al2O3) in crystalline net. The studies showed that the prepared
polymer produced from DTPA with ethylene glycol can bond with
Al3+
,Y3+
, Nd3+
along its chains by chelating, which gives good
homogenous powder. The results showed possibility of development of
proposed method to give good homogeneity and to graft YAG crystal
by Nd with concentration more than 5%.
Keywords: NdYAG, nano-powders, DTPA, DTPA/metal.
Received 6/7/4104
Accepted 7/9/4104
Res. J. of Aleppo Univ. Basic Science Series No. 4104 89
56
Study of the Structural Properties in Polyacrylonitrile -
anionic Surfactant Systems
Said Abdul Nour, Mouna Kurma*
Dept. of Chemistry, Faculty of Science, University of Aleppo
*Postgraduate Student (MSc.)
Abstract
Viscosity and specific electrical conductivity are studied in N,
and N- dimetheylformamide (DMF) medium in the presence and
absence of anionic surfactant of Sodium Dodecylbenzene Sulfonate
(SDBS). Critical Micelle Concentration (CMC) of SDBS is determined
in DMF. We find that the leading force for the process of micelle
formation is the decrease of Enthalpy. Thermal and structural
properties of PAN are studied by differential thermal analysis and
scanning electron microscopy, respectively.
Keywords: Polyacrylonitrile, Fiber, mechanical properties, surfactants.
Received 4/9/4104
Accepted 9/8/4104
Res. J. of Aleppo Univ. Basic Science Series No. 98 2014
76
Linear Waves Propagation in a Dusty Plasma for Tails of
Halley's Comet Anwar Batal, Houssam Aldeen KASSIR
*
Dept. of Physics, Faculty of Science, University of Aleppo
*Postgraduate Student (PhD)
Abstract
The oblique propagation of the dust-acoustic and the dust-
cyclotron waves in a warm magnetized collisionless (dust-ion) plasma
which is present in some space environments is studied. A linear
dispersion relation which takes into account the effects of dust
streaming and the effects of warm dust grains is derived. It is observed
that the presence of dust streaming causes frequency shift known as the
Doppler frequency shift, and assuming that the dust grain is warm (i.e.
non-zero pressure) leads to generalizing the thermal speed of the dust
(the modified dust-acoustic speed). The implications of these results to
the dust regions (tails) of Halley's comet are applied and discussed.
Keywords: Dusty Plasma, Complex plasma, magnetized (dust-ion)
plasmas, oblique propagation, dust-acoustic wave, dust-cyclotron
wave.
Received 4/8/2014
Accepted 8/9/2014
Res. J. of .Aleppo Univ. Basic Sciences Series No 98 2014
69
A Study of the Effect of Adding Zinc Metal on Physical
Properties of Lead-free Solders Ternary (Sn88 Sb10 Cu2)
Prepared in Rapid Solidification
M. Hasan, M. Saleh Hammami, Layla Al Sharif * Dept. of Physics, Faculty of Science, University of Aleppo
* Postgraduate Student (MSc.)
Abstract
The objective of the work is to prepare ternary alloys (Sn88 Sb10
Cu2) using the technique of rapid cooling, and study the impact of
addition of zinc for improving their characteristics. The addition was in
a ratio of 2% from the weight of formation of Quaternary alloys. The
research also aimed to study the physical and mechanical changes by
this addition on ternary alloys, in order to use them as welding
mixtures in electronic devices for their physical and industrial
properties which are better than solder alloys containing lead.
The results showed that the exact composition of ternary alloys
(Sn88Sb10 Cu2) is characterized by intermetallic compounds (SbSn),
(Cu3Sn(, which are small particles of microns. In the case of
Quaternary alloys (Sn86 Sb10 Cu2 Zn2), additional components of the
intermetallic compounds (Cu6Sn5) appeared and attention was
attracted to the role of the intermetallic compounds and their influence
on the apparent properties of the prepared alloys.
Received 21 /7/2014
Accepted 9 /9 /2014
Res. J. of Aleppo Univ. Basic Science Series. No. 98 2014
17
Isolating and Identifying of Lactic Acid Bacteria (LAB)
from Fermented Milk Products
(Yoghurt and Traditional White Cheese) Nehad Yosef, Faten Kang ٭
Dept. of Botany, Faculty of Science, University of Aleppo
Postgraduate Student (PhD) ٭
Abstract
A total of (109) isolates of lactic acid bacteria (LAB) were isolated
from (16) samples of yoghurt and (14) samples of Traditional White
Cheese, collected from different small workshops of Aleppo city. Two
culture media were used: MRS and M17 following Spreader Plates
method. By studying the Morphological Biochemical and
physiological characteristics of these displayed isolates, (56) isolates
isolated from Cheese, were identified as Enterococcus (48.2%),
Lactobacillus (17.86%), Streptococcus (16.1%), Lactococcus (8.92%),
and Leuconostoc (8.92%). While the isolates of yogurt (53 isolates)
were identified as Enterococcus (49.06%), Lactobacillus (35.85%),
Streptococcus (9.43 %), and Leuconostoc (5.66 %). Enterococcus spp.
was the Dominant genus in both samples.
Keywords: Lactic Acid Bacteria, Yoghurt, Traditional White Cheese.
Received 13 /8/2014
Accepted 9/9 / 2014
Res. J. of .Aleppo Univ. Basic Science Series No 98 2014
37
Analysis of Al khalas Date Bio-Physical and Chemical
Characteristics Sterilized by Irradiation to Substitute
Fumigation Gases and Thermal Treatments Said SABBAGH
Dept. of Physics, Faculty of Science, Aleppo University
Abstract Al-khalas Date products, treated with gamma radiation, have
been examined to get rid of the most important bio-pollutants in stored
products. Date-products have been exposed to gamma radiation (0.5-
1.5) kGy. The irradiation effect on physical and chemical
characteristics like color, taste, moisture, protein, sugars and ascorbic
acid has been studied.
The safe dose for international marketing and export sterilized
Date products was suggested to be 1.5 kGy because there are different
types of micro-organisms and different sensitivity to radiation. The
suggested dose necessary to eliminate them all (or most resistant to
radiation) was 1.5 kGy. This result agrees with the results of previous
researches that recommended the dose of 1 kGy and allowed an upper
dose of 0.5 kGy addition.
Keywords: Date Irradiation, Food Irradiation, Food Safety, bio Characteristics,
Sterilization.
Received 1/7/2014
Accepted 14/9/2014
R.J. of Aleppo Univ. Basic Science Series No.98 2014
57
Global Optical Potential for Deuteron Scattering at
Energies from 10 to 180 MeV Hala Wattar
Dept. of Physics, Faculty of Science, University of Aleppo
Abstract
The Phenomenological optical potential (potential calculated
avec semiemirical formula) was used to describe the interaction
between two nuclei (scattering reaction and absorbtion reaction). This
potential depends on the energy of the project nucleus and mass, and
charge of the target nucleus.
In this article, we calculated the optical model potential and
geometry parameters for elastic deuteron scattering on nuclei 232
Th,208
Pb, 186
W,140
Ce, 116
Sn , 90
Zr , 70
Ge, 50
V, 32
S, 16
O
with energy10 180E MeV and Wood-Saxon form being used.
From the values of these optical potentials, we calculated the
differential cross sections of the elastic scattering of deuteron, which
agree with the experimental differential cross sections, that affirm the
success of potential formula used in this work in describing the
nuclear reactions. Keywords: Phenomenological Optical potential; Deuteron-nucleus nucleaire
potential; Saxon-Wood potentials; differential cross sections; reaction cross
sections.
Received 2/7/2014
Accepted 17/9/2014
Res. J. of .Aleppo Univ. Basic Sciences Series No.98 . 2014
77
Study of Leaf Epidermis and Palynology in Two
Varieties Related to Silybum marianum (Asteraceae)
in North Aleppo
Walid Al Said, Abdel Aleem Bello, Oula Darwish* Dept. of Botany, Faculty of Science, University of Aleppo
* Postgraduate Student (MSc.)
Abstract
Silybum marianum (L.) Gaertn is the only Species distributed
in north Aleppo. It includes two varieties: Silybum marianum var.
marianum with violet flowers, and Silybum marianum var. albiflora with white flowers.
Stomata and trichomes were presented on the adaxial and
abaxial of leaf surface in both varieties. Stomatal types are Anisocytic
and Anomocytic. Trichomes type is non-glandular branched
multicellular uniseriate.
The shape of pollen grains in both varieties is Spheroidal
because of the ratio of polar axis (P) /equatorial diameter (E) =1.
Aperture type of pollen grains is Tricolporate, where they have three
colpi with a pore in each of them. Sculpturing is Echinate in both
varieties. Key words: Silybum marianum, Anisocytic, Anomocytic, Spheroidal, Tricolporate,
Echinate.
Received 25 /06/2014
Accepted 18/09/2014
Res. J. of Aleppo Univ. Basic Sciences Series No.98 2014
97
Advanced Study of Neutrino Oscillation Phenomenon in
Vacuum in Quantum Fields Theory Framework Adel Hamo, Hala Wattar, Eyman Al-hamdan* Dept. of Physics, Faculty of Science, University of Aleppo
*Postgraduate Student (MSc)
Abstract
In this study a developed way to study neutrino oscillation
phenomenon in vacuum in quantum fields theory framework was
presented. The probability of neutrino oscillation was calculated
depending on Feynman diagrams which describe the processes of
production, propagation and detection as single process where the
interaction particles in source and detector are represented by external
wave packets, as the dispersion effect was inserted onto wave
functions associated with the propagated neutrinos from source to
detector by using asymptotic expansion method.
Keywords: Neutrino oscillation, Feynman diagrams, external wave packets,
dispersion, asymptotic expansion.
Received 26 /6/2014
Accepted 21 /9/2014
Basic Science Series No. 98 2014 R. J. of Aleppo Univ.
18
A Taxonomical Study on Species of Helicidae
(Gastropoda: Mollusca) in Aleppo & Edlib Governorates Mahmoud Karrom, Fadia Nashed
Mohammad Salim Alibrahim* Dept. of Zoology, Faculty of Science, University of Aleppo
* Postgraduate Student (MSc.)
Abstract Terrestrial snail species occupies an important position in
Helicidae mollusks. Terrestrial snails however have not received the
attention and study, which took place on the peers of aquatic snails.
Based on this, we aimed to study the biodiversity of some species in
the Syrian environment under two objectives: first, to start directing
the spotlight on this group, and second, to contribute to the building
map of livestock biodiversity and the environment in Syria. Samples were collected from the northern region in Syria
between 2012-2013, and lines were set for taxonomic study, returning
to the following global taxonomic keys: Bofill & Haas, 1921; Kerny &
Cameron, 1979; Godan, 1983; Dindal, 1990.
Samples followed subfamily Helicinae, with six genera, each with one
or more species as follows:
The genus Helix with two species H. pomatia L. and H.
Engaddensis (Bourguigant).
The genus Cepaea with one species C. hortensis Muller.
The genus Eobania with one species E. vermiculata Muller.
The genus Theba with one species T. pisana Muller.
The genus Levantina with one species L. spiriplana (Oliver).
The genus Monacha with three species M. cantiana (Montagu), M.
cartusiana Muller and M. syriaca (Ehrenberg). Received 21/7/2014
Accepted 28/9/2014
Res. J. of Aleppo Univ. Basic Science Series No.98 / 2014
38
A Study of the Time-dependent Oscillation Systems
Using the Creation and Annihilation Operators Adel Hamo
Dept. of Physics, Faculty of Science, Aleppo University
Abstract
Different possibilities for the treatment of Time-dependent
Oscillation Systems (harmonic oscillators) were discussed. Then an
electrical LC circuit connected on sequence with a variable with time
voltage generator as a time dependent harmonic oscillator was studied
mechanically. The annihilation and creation operators to define the
wave function that describes the system were used, and their energy
matrix was calculated.
Considering that this oscillator is incitement (transference of
squeezing), a system with two coupled oscillators was studied using
special transformations by decoupling the system as uncoupled system.
Keywords: Harmonic Oscillator, Time Dependent Hamiltonian,
Annihilation Operators, Creation Operators, Coupled Systems.
Accepted 27/8/2014
Received 28/9/2014
Res. J. of Aleppo Univ. Basic Sciences Series No. 98 2014
58
The Study of Some of the Physical Properties of the
Glazed Layer Prepared from Local Raw Materials
Walid Hawale, Shaghik Taghlian*
Dept of Chemistry, Faculty of Science , University of Aleppo
*Postgraduate Student (MSc.)
Abstract
The glazed layer is the most important layer in a ceramic,
which is considered one of the most common industrial products due to
its wide usage. It can also be used in various products, such as
abrasives, thermoceramics, tiles, ceramic walls etc.
The glazed layer consists of Silica as the main material and
Alumina as an adjuvant (auxiliary material) to form the glazed layer,
which is obtained from fusing the raw materials (quartz- kaoline-
feldspar- dolomite..), and due to the high melting temperature of silica
some flux materials are added to lower it, such as sodium carbonate
and potassium carbonate.
Since Syria is rich in mineral ores and different types of clay,
we suggested using the raw materials in manufacturing the glazed
layer as a substitute for the imported material, thus we would invest
our raw materials in local industries and save the importing expenses.
Received 7/9/2014
Accepted 12/10/2014
Res. J. of Aleppo Uni. Basic Science Series. No. 98 2014
78
Studying of Some Thermal and Electrical Properties of
the Lead Compounds PbS and PbTe Precipitated in
Chemical Solution Method Tariq Zarouri, Hadeel Fakas Albeed *
Dept. of Physics, Faculty of Science, University of Aleppo
*Postgraduate Student (MSc.)
Abstract PbS and PbTe were prepared using the chemical bath
deposition technique at room temperatures.
Seebeck coefficient was measured for lead compounds (PbS-
PbTe), the values of which ranged between (0.07-0.12) mVk-1
for
PbTe and (0.02-0.09) mVk-1
for PbS. It has good values which are
useful in electro thermic devices used in power generation.
The effect of the presence of impurity on Seebeck coefficient
and the effect of samples thickness were studied.
From dc measurement, I-V characteristic of the resistivity,
activation energy, and power factor was calculated. From Seebeck
coefficient, the type of semiconductor was found to be P-type.
Received 3/7/2014
Accepted 13/10/2014
Res. J. of .Aleppo Univ. Basic Science Series No. 98 2014
89
Studying the Effect of the Pomegranates (Juice, Arils) on
HbA1c Level, Serum Fasting Glucose and Liver Enzymes
in Type II Diabetes Patients Ahmed Kumary*, Hachem Alhussein**, Omama Alloush***
*Dept. of Zoology, Faculty of Science, University of Aleppo
**Dept. of Internal Medicine, Faculty of Medicine, University of Aleppo
***Postgraduate Student (MSc.) Dept. of Zoology, Faculty of Science, University of
Aleppo
Abstract The aim of this study is to investigate the effect of each of
pomegranate juice and pomegranate arils on glycated hemoglobin,
serum fasting glucose and liver enzymes (AST, ALT) levels in type II
diabetic patients treated by oral hypoglycaemic drugs.
This experimental study was performed on 60 diabetic
patients, from national diabetes program, ministry of health, Syria.
We concluded that patients treated by oral hypoglycaemic drug
and pomegranate (juice and arils) diet revealed lower serum levels of
glycated hemoglobin, fasting glucose and liver enzymes (AST, ALT)
than the control. On the other hand, when comparing between
pomegranate forms, patients treated by oral hypoglycaemic drug and
only pomegranate arils diet revealed lower serum levels of glycated
hemoglobin, fasting glucose and liver enzymes (AST, ALT) than those
treated by oral hypoglycaemic drug and only pomegranate juice diet.
Statistical analyses in this study illustrated significant positive
correlation between glycated hemoglobin and serum fasting glucose
which means that glycated hemoglobin is an important indicator which
reflects the average of 3 months of serum fasting glucose
concentration.
Keywords: pomegranate, Type 2 Diabetes, oral hypoglycaemic drug, glycated
hemoglobin, serum fasting glucose, liver enzymes.
Received 20/8/2014
Accepted 13/10/2014