Narrow Results

High-porosity materials, such as chamotte and mullite, possess a heat of fusion. Owing to their properties, these materials can be used with success as damping materials in containers for airplane, automobile, etc. transportation of radioactive or highly toxic materials. Experimental studies of the dynamic properties have been executed with using some original modifications of the Kolsky method. These modified experiments have allowed studying the dynamic compressibility of high-porosity chamotte at deformations up to 80% and amplitudes up to 50 MPa. The equations of the mathematical model describing shock compacting of chamotte as a highly porous, fragile, collapsing material are presented. Deformation of high-porous materials at non-stationary loadings is usually accompanied by fragile destruction of interpore partitions as observed in other porous ceramic materials. Comparison of numerical and experimental results has shown their good conformity.

Nano-sized mullite was synthesized by mechano-chemical, sol-gel/milling, process. Aluminum nitrate and tetraethyl ortho silicate were used as precursors to prepare the single phase gel. The prepared gel was subjected to intense mechanical activation using a planetary ball mill prior to annealing. DTA/TGA results showed that mullitization temperature significantly decreases due to mechanical activation as mullite starts to form at 1094°C in unmilled sample whereas intermediate milling for 20 hours decreases this temperature to 988°C. Also, mullite formation occurs at 1021 and 1003°C for samples milled for 5 and 10 hours, respectively. SEM results showed that the morphology of the products was altered by the intermediate mechanical activation. Calculation of the mullite crystallite sizes indicated that they were indeed in nano scale and this result was confirmed by TEM investigations which shows the mean crystallite size of 70 nm.