티타늄 수소화물(TiH2) 분말을 원료로 사용하여 Ti 소결체를 제조하였다. 원료분말은 수소화-탈수소화법(HDH법)에 의해 제조한 상용분말이었으며 비교를 위해 동일한 입도를 갖는 Ti 분말도 함께 소결하였다. TiH2는 소결체의 밀도를 현저하게 촉진하였으며 TiH2→Ti+H2의 탈수소반응에 의해 생성되 청정한 Ti분말이 소결을 촉진하기 때문인 것으로 판단된다. 같은 이유로 TiH2소결체의 산소농도는 Ti 소결체보다 낮게 나타났다. 소결체의 잔류수소는 소결온도가 증가함에 따라 감소하였으며 1200˚C 이상에서는 5 ppm 이하의 낮은 값을 나타냈다. 소결체의 경도는 소결밀도 및 산소량에 비례하는 것으로 나타났다. TiH2분말의 cubic→tetragonal 변태온도는 X-선 회절분석 결과 16~20˚C 구간으로 밝혀졌다.

Based on the pore filling theory, the microstructure evolution during liquid-phase sintering has been analyzed in terms of interrelationship between average grain size and relative density. For constant liquid volume fraction, the microsturucture trajectories reduced to a single curve in a grain size(x)-density(y) map, regardless of grain growth constant. The slope of curves in the map was inversely proportional to average pore size, while it increased fapidly with liquid volume fraction. Increase in pore volume fraction retarded the densification considerably, but showed marginal effect on the slope. The activation energy of densification was predicted to be the same as that of grain growth as long as the liquid volume fraction is constant for any temperature range studied. The present analyses on microstricture evolution may demonstrate the usefulness of pore filling theory and provide a guideline for process optimization of liquid-phase sintering.

This paper is aimed to study the computer simulation of sintering process for ceramics by Monte Carlo and molecular dynamics methods. Plural mechanisms of mass transfer were designed in the MC simulation of sintering process for micron size particles; the transfer of pore lattices for shrinkage and the transfer of solid lattices for grain growth ran in the calculation arrays. The MD simulation was performed in the case of nano size particles of ionic ceramics and showed the characteristic features in sintering process at atomic levels. The MC and MD simulations for sintering process are useful for microstructural design for ceramics.

In all larger hardmetal workshops furnaces for dewaxing, vacuum sintering or vacuum and overpressure sintering are today's standard. The furnace technology is well established. Equipment specifications such as operating overpressure, determine sintering cost, product quality, safety and reliability of the furnace and ultimately influence the competitiveness of the hard metal procucer in the global market. Essential furnace requirements are an efficient utilization of the furnace, an environmental friendly dewaxing system, high temperature uniformity, metallurgical treatment with process gases, as well as reduced cooling time by means of rapid cooling. Examples of reduced sintering costs are described achieved using a new design of vacuum sintering furnace with an improved rapid cooling device, cooling times are reduced by up to 45%. Additionally, a cost comparison of two different designs of vacuum overpressure sintering furnaces are included.

For the purpose of investigating the effect of sintering atmosphere and carbon addition on sintered density and microstructural characteristics, the M3/2 grade high speed steel powders with the addition of carbon are sintered in vacuum and gas atmosphere. With the addition of 0 wt%C, 0.45wt%C and 1.15 wt%C the optimum sintering temperatures decrease down to , and respectively for the vacuum sintered specimen, and also decrease down to , and for the gas sintered specimen. The threshold temperatures for full densification decrease steeply with increasing carbon content of the sintered specimen, while this temperatures are slowly decreased at high carbon content. The vacuum sintered specimen shows the primary carbides of MC and type at the optimum sintering temperature, and eutectic carbides of and Fe-Cr type are produced in the oversintered specimen. The gas sintered specimen exhibits M6C and Fe-Cr type primary carbides at the optimum sintering temperature. The eutectic carbides of and Fe-Cr type and MX type carbonitride are shown for the oversintered specimen in the gas atmosphere. The hardness of gas sintered specimen shows high value of 830-860 Hv due to the increment of carbide precipitation.

The initial sintering behaviour of the powder injection molded (PIMed) W-l5wt%Cu nanocomposite powder was investigated. The W-Cu nanocomposite powder was produced by the mechanochemical process consisting of high energy ball-milling and hydrogen reduction of W blue powder-CuO mixture. Solid state sintering of the powder compacts was conducted at for 2~10 hours in hydrogen at mosphere. The sintering behaviour was examined and discussed in terms of microstructural developments such as W-Cu aggregate formation, pore size distribution and W grain growth. The volume shrinkage of PIM specimen was slightly larger than that of PM(conventional PM specimen), being due to fast local densification in the PIM. Remarkable decrease of carbon and oxygen in the PIM enhanced local densification in the early stage of solid state sintering process with eliminating very fine pores less than 10 nm. In addition, such local densiflcation in the PIM is presumably responsible for mitigating of W-grain growth in the initial stage.

Sintering kinetics of ball-milled was studied with the addition of Ni. powder with the average particle size of 1 was obtained from ball-milling of 10 powder. Small amount of Ni was added to the ball-milled powder by salt solution and reduction method. The powder was compacted into cylindrical shape at 200 MPa and isothermally sintered in a atmosphere at the temperature range of 1100~ for 3~600 minutes. The changes of linear shrinkage and sintered density were monitored as a function of sintering time. The microstructure was observed by using optical microscopy and scanning electron microscopy. Phases were identified by X-ray diffratometer and electro-probe micro analysis. Sintering kinetics of Ni-added powder was compared to as-milled powder and the apparent activation energy was calculated from Arrhenius plot.

실험계획법을 이용하여 유리분말의 소결시 그 기공량에 영향을 미치는 각종 소결조건의 영향을 정량적으로 조사하였다. 본 실험범위내에서 결합제 유리의 총기공량, 개기공량 그미고 폐기공량은 모두 소결온도에 의해 가장 큰 영향을 받고 그 다음으로 소결온도에서의 유지시간에 의해 영향을 받으며 승온속도의 경우 그 영향이 상대적으로 미미함을 확인할 수 있었다. 이러한 결과들로부터 실제공정에 있어 승온속도보다는 다른 소결인자, 특히 소결온도를 조절하는 것이 결합제 유리의 기공량 조절에 가장 중요하리라 판단되며 실험계획법을 이용함으로써 보다 정확한 공전조건을 모색할 수 있었다.

A new low melting inorganic binder, monoclinic , has been developed for Selective Laser Sintering (SLS) of alumina powder by dehydration process of boron oxide powder in a vacuum oven at . It led to better green SLS parts and higher bend strength far green and fired parts compared to other inorganic binders such as aluminum and ammmonium phosphate. This appeared to be due to its low viscosity and better wettability of the alumina particle surface. A low density single phase ceramic, aluminum borate (), and multiphase ceramic composites, , were successfully developed by laser processing of alumina-monoclinic powder blends followed by post-thermal processing; both and have whisker-like grains. The physical and mechanical properties of these SLS-processed ceramic parts were correlated to the materials and processing parameters. Further densification of the ceramic composites was carried out by infiltration of colloidal silica, and chromic acid into these porous SLS parts followed by heat-treatment at high temperature (). The densities obtained after infiltration and subsequent firing were between 75 and 80% of the theoretical densities. The bend strengths are between 15 and 33 MPa.