Resistive RAM ( Resistive RAM (ReRAM) Technology ) Technology ...
Fire Resistive Materials: MICROSTRUCTURE
description
Transcript of Fire Resistive Materials: MICROSTRUCTURE
![Page 1: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/1.jpg)
Fire Resistive Materials: MICROSTRUCTURE
Performance Assessment and Optimization of Fire Resistive Materials
NISTJuly 14, 2005
![Page 2: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/2.jpg)
MicrostructureExperimental
3-D Tomography2-D optical, SEM
Confocal microscopy
Modeling3-D Reconstruction
ParametersPorosity
Pore SizesContact Areas
Properties(all as a function of T)
ThermalHeat CapacityConductivity
DensityHeats of Reaction
AdhesionPull-off strength
Peel strengthAdhesion energy
Fracture toughness
EquipmentTGA/DSC/STASlug calorimeter
DilatometerBlister apparatus
Materials Science-Based Studies of Fire Resistive Materials
EnvironmentalInterior
Temperature, RH, load
ExteriorTemperature, RH, UV, load
Performance PredictionLab scale testingASTM E119 Test
Real structures (WTC)
![Page 3: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/3.jpg)
Importance of Microstructure• As with most materials, microstructure of FRMs will significantly
influence many performance properties– Adhesion and mechanical properties (fracture toughness)– Heat transfer
• Conduction• Convection (of steam and hot gases)• Radiation
• What are some critical microstructural parameters for porous FRMs?– Porosity (density, effective thermal conductivity)– Pore size (radiation transfer)– Pore connectivity (convection, radiation)
• What are some applicable techniques for characterizing the microstructure of FRMs?– Optical microscopy– Scanning electron microscopy (SEM)– X-ray microtomography
![Page 4: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/4.jpg)
Optical Microscopy• Can apply to cast or
fracture surfaces• Minimal specimen
preparation required• Can estimate total coarse
porosity and “maximum” pore size
• Two-dimensional so limited information on porosity connectivity
![Page 5: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/5.jpg)
Scanning Electron Microscopy
• Higher resolution view than optical microscopy
• Tradeoffs between magnification and having a representative field of view
• More specimen preparation may be required
• Two-dimensional
![Page 6: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/6.jpg)
X-ray Microtomography• Inherently three-
dimensional• Intensity of signal
based on x-ray transmission (local density) of material
• Voxels dimensions of 10 μm readily available– 1 μm at specialized
facilities (e.g., ESRF in France)
![Page 7: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/7.jpg)
BFRL Experience with Microtomography• With CSTB and ESRF (France), in 2001, created
the visible cement dataset, a first-of-its-kind view of the 3-D microstructure of hydrating cement paste and plaster of Paris– http://visiblecement.nist.gov
• With FHWA, Penn State, and others, have imaged thousands of three-dimensional coarse and fine aggregates as part of the ongoing VCCTL consortium
• In 2004, with Penn State, imaged a variety of fire resistive materials including fiber-based, gypsum-based, and intumescent materials
![Page 8: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/8.jpg)
X-ray Microtomography of Unexposed Gypsum-Based FRM
From Center for Quantitative Imaging, Penn State Univ.
![Page 9: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/9.jpg)
X-ray Microtomography of Flame-Exposed Intumescent Coating FRM
From Center for Quantitative Imaging, Penn State Univ.
![Page 10: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/10.jpg)
Microstructure Thermal Conductivity
• Segment 3-D microstructures into pores and solids (binary image)
• Extract a 200x200x200 voxel subvolume from each microstructure data set
• Separate and quantify volume of each “pore” (erosion/dilation, watershed segmentation-Russ, 1988, Acta Stereologica)
• Input segmented subvolume into finite difference program to compute thermal conductivity (compare to measured values)
![Page 11: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/11.jpg)
Three-Dimensional X-ray Microtomography
• Three-dimensional images of isolated poresGypsum-based Fiber/cement-based
![Page 12: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/12.jpg)
Thermal Conductivity Computation
-Use finite difference technique with conjugate gradient solver (Garboczi, 1998, NISTIR)-Put a temperature gradient across the sample and solve for heat flow at each node-Compute equivalent k value for composite material
Q = -kA (dT/dx)
Porosity: kpore
“Solid”: ksolid
Q-Need to know values for kpore and ksolid (itself microporous)
![Page 13: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/13.jpg)
Thermal Conductivity of Porous Solids
ppppvpvpkk solidPS
3/23/2
3/23/2
1)(1
where • v = kpore/ksolid
• ksolid = thermal conductivity of solid material,
• p = porosity = (max –matl)/max
max = density of solid material in the porous system, matl = density of the porous material, and
• kpore = thermal conductivity of pore = kgas-cond + krad
Theory of Russell (1935, J Amer Ceram Soc)
![Page 14: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/14.jpg)
Radiation Term
3
316 ETrkrad
where• σ = Stefan-Boltzmann constant
(5.669x10-8 W/m2/K4),• E = emissivity of solid (1.0 for a black body), • T = absolute temperature (K), and
• r = radius of pore (m)
kpore= krad + kgas-cond
For spherical pores (Loeb, 1954, J Amer Ceram Soc):
![Page 15: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/15.jpg)
Applicability of Russell/Loeb Theory
FRM A and B are both fiber/portland cement-basedPore sizes estimated as “maximum radius” from optical microscopy
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 200 400 600 800 1000 1200
Temperature (oC)
k [W
(/m•K
)]
FRM-A 0.5 mm pores
FRM-A (measured)
FRM-B (measured)
FRM-B 0.75 mm pores
![Page 16: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/16.jpg)
Microstructure Modeling Results: Gypsum-Based Material FRM C
Complication- gypsum to anhydrite conversionkgypsum ≈ 1.2 W/m•K kanhydrite≈ 4.8 W/m•K (Horai, 1971)
0.05
0.10
0.15
0.20
0.25
0.30
0 200 400 600 800 1000 1200
Temperature ( oC)
k [W
/(m•K
)]
Measured data
Model (gypsum/anhydrite)
Model (constant k-gypsum)
![Page 17: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/17.jpg)
Microstructure Modeling Results: Fiber/Cement-Based Material FRM B
Complications– Anisotropy of microstructure– Radiation transfer through connected pores (Flynn and Gorthala, 1997)
0.000.050.100.150.200.250.300.350.400.450.50
0 200 400 600 800 1000 1200
Temperature ( oC)
k (W
/m•K
)
Measured data
No erosions (x,y)
No erosions (z)
![Page 18: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/18.jpg)
k vs. Porosity and Pore SizeFRM ρ
(kg/m3)
Porosity Poreradius (mm)
k (23 oC)
[W/(m•K)]
k (1000 oC)
[W/(m•K)]
A-fiber 313.7 87.5 % 0.5 0.0534 0.3708
B-fiber 236.8 91.2 % 0.75 0.0460 0.5010
C-gypsum 292.4 87.2 % 0.2 0.0954 0.2618
![Page 19: Fire Resistive Materials: MICROSTRUCTURE](https://reader033.fdocuments.us/reader033/viewer/2022051117/56815d96550346895dcbb5c8/html5/thumbnails/19.jpg)
Summary• Microstructure is paramount to thermal
performance of FRMs• Powerful microstructure characterization
techniques exist and are becoming more commonplace
• Computational techniques are readily available for predicting thermal conductivity from microstructure-based inputs
• Opens possibilities for microstructure-based design and optimization of new and existing FRMs