Design of Unidirectional Freeze-Casting Device

Members: John Simmonds

Joe HastingsMichael Harty

Michael BeachyMichael Cook (MET Department)

Department of Mechanical and Aerospace EngineeringOld Dominion University, Norfolk, VA 23529

Gantt Chart

Actual Freeze-casting device Freeze-casting device Schematic

Equipment Design

Equipment Design

Proposed Changes to Freezing DeviceBoth arms on one supporting rod enables direct measurement transference between them.

Current Freezing DeviceTwo separate arms. One for liquid height measurement and one for sample height

Proposed Liquid Level indicator arm

Sample Arm

Dewar

Liquid Nitrogen

Height Adjustment Nut

Thermal Measuring System• K type thermocouples do not have a high enough degree of accuracy for our

experimental system. (Standard: +/- 2.2C or +/- .75%)• Due to this issue, a different thermal measuring system was installed to more

accurately and precisely detect the temperature gradients during ceramic slurry trials. • T type thermocouples replaced the K Types and new data logging software and

interface have been installed.

-150 -100 -50 0 50 100 150

-4

-3

-2

-1

0

1

2

3

4

5

K Type vs T TypeThermocouple

K TypeT Type

Temperature

Mill

ivol

ts

Thermocouple

The T type thermocouple is the current sensor used to understand freeze front velocities within our experiment. We replaced the K type thermocouple along with

the data acquisition interface for the T type thermocouple and the Omega QuadTemp interface. The improvements are seen by a greater degree of accuracy within the temperature range of our experiment. Another improvement with the new interface can be seem with the ability to use four thermocouples vice the two

that were supported by the Vernier Data Logger.

Convective Boundary Layer Omission

The insulating sleeve, as previously discussed reduced the convective effects of the surrounding nitrogen gas on the sides of the sample. This allowed the sample to be frozen from the bottom upwards only. The original sleeve was made from a high density polyethylene foam and although fit snuggly it allowed a small convective current around the plate.The new sleeve is made from a low density Styrofoam. The sleeve is made from (4) individual sections that were glued together, wherein the lowest section center chamber was made to a smaller diameter that allows the plate to rest on and blocks the convective layers.

Present Freeze-casting device Configuration

Convective Boundary Layer Omission

The new sleeve is made from a low density Styrofoam. The sleeve is made from (4) individual sections that were glued together, wherein the lowest section center chamber was made to a smaller diameter that allows the plate to rest on and blocks the convective layers.

Dewar insulating Sleeve

Sample Analysis

Currently, samples have been produced at the following heights above liquid level: 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm and 65mm.

The samples were freeze-dried and begun to be sintered. The initial inspection under a 10x and 100x microscope show promising signs of unidirectional platelet formation and alignment.