Glasses and Amorphous Materials by J. Zarzycki - Article Example

The difference that is seen between the glass and the corresponding liquid state is well demonstrated by the temperature/volume relation during cooling. The temperature rate at which the transition of the glass state and rubbery state occurs is known as the glass transition temperature. There are different types of amorphous materials such as plate glass, vector, pyrex, and fused silica. All these materials have unique properties and processing procedures. Tempering mainly occurs during the thermal process where the strength of the glass is determined by the different behavior of thermal expansion with regards to heating and cooling(Zarzycki).

SinteringBased on the high melting temperature as well as their brittle nature some ceramics excluding glasses cannot be rolled like polymers and metals. Thus they depend more on atomic diffusion in order to process them. Sintering is referred to as the process of changing the microstructures of the materials through heating it until it reaches a temperature in which diffusion occurs easily. Sintering occurs in various states. The liquid state sintering consists of densification and coarsening.

Densification is the process of removing free energy through the elimination of porosity while coarsening is the removal process of free energy through increasing the average size of the grain. During these states some fraction of the material being prepared is molten.Amorphous materials also use some sintering mechanisms such as viscous flow, surface diffusion and Evaporation-condensation(Zarzycki). There are various sintering techniques that are used: conventional sintering, microwave sintering and spark plasma sintering(SPS).

Conventional sintering mainly occurs as a result of Joule heating that occurs in surrounding furnace elements. On the other hand, microwave sintering occurs when heating is internally based on the interaction of the microwaves and the material. Spark Plasma Sintering is the process in which electricity is transmitted through electrically conducive samples that are under uniaxial compression. The process is also known as field-assisted sintering technique or pulsed electric current sintering technique.

Ceramic powder processingCeramic is regarded as inorganic materials that are simply non-metallic. They are quite resistant to high temperatures and also act as good resistance to low electrical conductivity as well as corrosion. The formation process of ceramic involves the manufacturing of compacted powder to a body that is then sintered at very high temperatures. The characteristic requirements of the component are based on the manufacturing process that is used. There are various processes involved in ceramic powder processing: slip casting, tape casting, direct consolidation, pressing and injection molding (Zarzycki).

Slip casting is a shaping process that works well with complex geometries and thus produces materials with good homogeneity. Tape casting is mainly used for manufacturing thin sheets. Direct consolidation is a shaping process that builds on the transformation of powder into a fixed body. Pressing is used for manufacturing simple geometric shapes and finally, injection molding is used for manufacturing series of small relative objects.