Sintering Of Ceramic Materials Research Articles

Diffusion in Microwave-Heated Ceramics

Microwave heating is an increasingly important method of chemical activation in both the laboratory and industrial processing. The increased breadth of microwave applications has not, however, been accompanied by a corresponding depth of understanding of microwave heating. The question of what constitutes a “microwave effect” remains unresolved, and that of whether “nonthermal” microwave activation takes place remains controversial. The effects of microwaves in solid materials and in biomolecules, in particular, are incompletely understood. In this paper, a method is described in which the effects of microwave heating may be investigated during the sintering of ceramic materials. By comparison of the diffusion rates parallel with, and perpendicular to, a polarized microwave field, the effects of thermal energy may be separated from those that are directly due to the microwaves. The results suggest that there is an enhanced sintering rate that is due to the presence of the microwave field, which becomes le...

Precursors for the Synthesis of Ceramic Oxide Materials

Classical techniques for solid-phase synthesis of oxide materials used in the production of ceramics and refractories are revised from the standpoint of thermodynamics and kinetics. The theoretical aspects of alternative methods for the synthesis of powdered materials involving chemical and thermochemical techniques for homogenization of precursor mixtures are discussed and routes to the efficient sintering of ceramic materials with required properties are outlined.

Some Features of Coalescence Processes and Mechanisms in Systems of Nonmetallic Crystalline Particles

The influence of particle size, presence of soluble impurities, and the development of solid-state polytype transitions in systems of nonmetallic crystalline particles on coalescence mechanisms during sintering is considered. The following cases that have not been studied previously are discussed. Coalescence is activated by oxygen during sintering fine plasma chemical powders of AlN, TiC, and TiN. Its mechanism may be considered as alloy formation realized by movement of a boundary between areas differing in oxygen concentration. Development of this coalescence governs the formation of collective grain growth centers. Polytype transitions in self-bonded SiC give rise to the occurrence of Ostwald coalescence accomplished as recrystallization by the “grain in grain” type. Polytype transitions in SiC and AlN may cause the growth of fine monopolytype grains at the expense of coarse grains consisting of a collection of multilayer polytypes. On the example of silicon-bonded SiC it is shown that during liquid-phase sintering of ceramic materials with solubility of solid phase in the liquid phase three types of Ostwald coalescence may be realized differing in the mass-transfer mechanisms: reprecipitation through the liquid phase (solution of carbon in silicon); joining of two or more single original SiC particles by a single-crystal shell forming as a result of crystallization of the condensed phase from the melt-solution; combined reprecipitation through a liquid phase and recrystallization by migration of boundaries between particles.

Fractal characterization of the compaction and sintering of ferrites

A novel parameter, the fractal exponent D E, is derived using the concept of fractal scaling. The fractal exponent D E relates the development of a feature within a material to the development of the size of the material. As an application, structural changes during the compaction and sintering of ceramic materials have been characterized with the fractal exponent D E. Samples taken during the processing of (Mn,Zn)-ferrite, a soft magnetic ceramic material, were analysed with porosimetry. Results show that the fractal exponent D E provides additional insight into the processing.

Intensification of sintering of mullite-cordierite ceramics using mineralizers

The effect of various mineralizers on the process of sintering of ceramic materials in the MgO – Al2O3 – SiO2 system is investigated. The possibility of decreasing the firing temperature and expanding the firing interval of cordierite-mullite ceramics by using these mineralizers is demonstrated.

Investigations on radiation processing in kazakhstan

The gamma and beta irradiations result in increasing of adsorbents capacity, improving weak links between neighbouring grains in HTSC ceramic, facilitating technological processes on raw material utilization, oil refining, sintering of ceramic materials, decreasing of electric resistance temperature coefficient of nichromium, synthesizing a new types of water-soluble and water-swelling polymers.

Reaction Sintering of Ceramic Materials by Microwave Heating

ABSTRACTMicrowave heating was used to reaction sinter Al2O3 + SiO2 and Al2O3 + TiO2 powder mixtures to prepare mullite and aluminum titanate ceramics, respectively. In comparison with conventional heating, microwave heating leads to a decrease in the temperatures of treatment of 50 to 100°C.

Influence of original greenware porosity and solid-phase hydration on the sintering of ceramic materials

We revealed and analyzed two cases of intensification of sintering ceramic materials. The first of these develops during the sintering of greenware of reduced porosity; and the second — with a certain hydration of the particles of solid phase in the original greenware.

Calculation of the sintering parameters of viscous solids

The actual rate of deformation of a viscous material during sintering is one and a half to two times greater than has been supposed up to now on the basis of calculations allowing only for the radial component of stress. Various problems in the field of sintering of ceramic materials can be solved with comparative ease using force-type, rather than energy-type, relationships and Volterra's viscoelastic analogy.