Abstract: Wollastonite powder was selected as a starting material with carbonate as pore-forming agent
and binder added. The porous ceramics were prepared at different temperature by sintering method. The
process includes batching, granulating, pressing molding, drying and sintering. It is discussed the
influence of sintering temperature, dosage of binder, dosage of pore-forming agent, pressure of molding
and holding time on the performance of porous ceramics. According to the principle of particles stack, the
porous wollastonite ceramics for filtration with various diameters, shapes and porosity were fabricated by
serial experiments. These products have 1 to 10 microns in pore size, 30.04 to 66.15% in porosity, 2.82
m2/g in specific surface area.
Abstract: In this study, porous Si3N4 ceramics were fabricated by carbothermal reduction reaction
between silicon dioxide and carbon. The influences of different starting powders and sintering additives
on microstructure and mechanical properties were investigated. XRD analysis demonstrated the formation
of single-phase β-Si3N4 except for glass phase and minor of α-Si3N4 phase. SEM analysis showed
that the resultant porous Si3N4 ceramics occupied fine microstructure and uniform pore structure. The
samples with fine starting powder showed fine, high aspect ratio of β-Si3N4 grains and good mechanical
properties. The addition of Al2O3 accelerated the densification of porous Si3N4 ceramics. With an
increasing in the sintering additive content, the porosity decreased, the flexural strength increased.
Abstract: This paper describes the fabrication of porous reaction-bonded SiC ceramics with radial
directed pores and the application of these materials to transpiration cooling system of rocket engines. A
special mold is designed for freeze-casting process to prepare SiC cylinders with radial directed pores.
Green bodies with well-oriented pore structure are obtained from slurry with solid loading up to 47vol%.
The pore size is in the level of several tens micron. Green bodies with various porosities are infiltrated
with different amount of liquid Si. The intrinsic permeability of each sample is measured with air as
flowing media. It is concluded that permeability has relationship with not only the porosity but also the
pore structure of samples.
Abstract: Wood has strongly anisotropic cellular structure with 50-80 vol% porosity. It can be converted
into porous ceramics (e.g., SiC, SiC/Si, TiC, C/C, and TiO2) replicating the wood structure by various
processes. Previously porous cellular SiC ceramic was prepared by reaction of wood charcoal with
gaseous SiO generated remotely from an equimolar mixture of Si and SiO2. In the present work, poplar
charcoal was simply embedded in the powder mixture of Si and SiO2 and heated at 1600°C for 1 h in Ar to
produce porous SiC. Samples were also prepared by infiltration of Si melt (1500-1600°C, 2 h) and vapor
(1700°C, 2 h) into the charcoal for comparison. Samples prepared by Si melt infiltration showed 15-52%
conversion to SiC. Samples prepared by Si vapor infiltration showed severe damage such that the
conversion degree could not be measured. In contrast, samples prepared by the embedding process
showed full conversion to SiC (mostly β form) with good retention of the cellular structure of the original
wood. The embedding process is a simple and efficient way to produce porous cellular SiC from wood.
Abstract: Foaming and gelation of slurry is a recently invented processing route for fabricating porous
ceramic. According to the method, a mechanical stir process was introduced to the ceramic slurry added
with surfactant, then initiator was added to induce fast gelation between organic monomers and ceramic
powder, the green body was obtained after a subsequently drying process. At last, porous ceramic was
fabricated after sintering the green body at high temperature. Effects of surfactant volume content and
several stirring factors on porosity are studied in this paper. It results that there is a proportional
relationship between porosity and Reynolds number which only changes when stir time varies, different
slurry or surfactant volume content results in similar relationship between porosity and Reynolds number.
Abstract: A new process of internal gelation for preparing stabilized zirconia ceramic microspheres was
developed. The influences of process parameters such as process temperatures, raw material
concentrations, and the conditions of drying and calcining on the process and characteristics of the
microspheres were investigated in this paper. With Y2O3 and/or MgO as stabilized agents, the
microspheres had the characteristics of TZP or PSZ materials confirmed by XRD and SEM observations.
Abstract: In this paper, microspheres were prepared by using Chinese bauxite as raw materials through
centrifugal spray drying method. The microstructure and composition of ceramic microsphere were
investigated by X-ray diffraction, scanning electron microscope and X-ray energy spectrum. The particle
size was 10~100#m. The XRD analysis reveals that the main crystalline phase of the ceramic microsphere
were α-Al2O3 and mullite (3Al2O3•2SiO2). The Al2O3 content (chemical composition) of the microspheres
was little more than 70%, and the molar ratio of Al2O3/SiO2 was near to the molar ratio of alumina
and silica of mullite.
Abstract: The effects of different kneading sequences, chemical additives, and solid loadings to the
homogeneity and rheological behavior of the Al2O3/3Y-TZP (ZTA) feedstock were investigated. The
properties of the feedstock were analyzed by the torque rheometry, transmission optical microscopy (OM)
and scanning and transmission electron microscopy (SEM & TEM). The optimal kneading process was
determined when good homogeneity was reached. The concepts of critical solid loading and the
homogeneity of two-oxide systems, and the power consumption to reach best microstructure will be
introduced and quantitatively analyzed.
Abstract: High-purity alumina ceramics was prepared using high-purity α-Al2O3 powder as raw material,
nitrates or oxides of magnesium, chromium and copper as additives by a wet ball milling with a later dry
pressing forming and normal pressure sintering process. The influence of additives on the sintering
temperature, microstructure and bending strength of the prepared alumina ceramics was studies. The
results showed that the additive doped with nitrate can be dispersed uniformly in the body with molecule
scale, and the oxides obtained by decomposing of nitrates have the higher reactivity. Thus, the nitrate
additives have better capacity than oxide additives in reducing the sintering temperature and inhibiting
the abnormal grain growth, and the alumina ceramics prepared by adding of nitrate additives have higher
density and bending strength.
Abstract: We have demonstrated that textured Al2O3-mullite-SiC nanocomposites can be fabricated
by slip casting followed by partial oxidation – reaction sintering of mixed suspensions of Al2O3 and
SiC powders in a high magnetic field. The sintered density was changed by the degree of oxidation at
1200 and 1300. The degree of orientation of alumina in the nanocomposite was examined on the
basis of the X-ray diffraction patterns and scanning electron micrographs. It is confirmed that
alumina-oriented nanocomposites were fabricated. The three-point bending strength at room
temperature was observed for the nanocomposites.