Porous titania, alumina and zirconia ceramic woods with wood-like microstructures, analogous to that of silicified wood, were prepared from natural woods as templates. The production of these ceramic woods was performed by the following process: (1) infiltration of metal alkoxide into wood specimens, (2) hydrolysis of the alkoxide in the cell structure to form titania, alumina or zirconia gels, (3) firing in air to form titania, alumina or zirconia ceramic woods. The resulting titania, alumina and zirconia ceramic woods were studied by means of an X-ray diffractometer, a mercury porosimeter and a scanning electron microscope. The microstructure of these ceramic woods retained the same structure as that of the raw wood: with the pore sizes corresponding to those of the original wood, and the major pores being unidirectionally connected. (c) 2004 Elsevier Ltd. All rights reserved.

Monazite-type monoclinic form lanthanum orthovanadate (M-type LaVO4) was synthesized by precipitating it from the mixed solution of lanthanum chloride and ammonium vanadate (V) with the mixing atomic ratio (La/V) = 1 at 20 degreesC in the pH 5 to 9. However, M-type LaVO4 tended to coexist with zircon-type tetragonal form lanthanum orthovanadate (Z-type LaVO4) at pHs 5-8. The single phase M-type LaVO4 was obtained only pH 9. The La/V atomic ratio obtained from the chemical analysis (ICP method) was in the range 0.99-1.01. The specific surface area and crystallite size were 250 m(2)/g and 22 nm, respectively. Relative density larger than 95% was achieved when the green compacts of M-LaVO4 were sintered at 1500 degreesC for 3 h in air.

(2002). LaPO 4 -Containing Machinable Al 2 O 3 Ceramics. Phosphorus, Sulfur, and Silicon and the Related Elements: Vol. 177, No. 8-9, pp. 1915-1915.

Partial reduction of highly reactive NiAl2O4 Spinel was investigated concerning with the raw spinel powder prepared by thermal decomposition of Al-2(SO4)(3)-NiSO4 solid solutions. Solid solution of Al-2(SO4)(3) with NiSO4 was prepared from mixed aqueous solutions by a rapid dry using micro wave heating. The Ni2+ ion is soluble in the anhydrous aluminum sulfate crystal lattice over a wide range up to 65 mol % of (NiSO4) / (NiSO4 + Al-2(SO4)(3)). The anhydrous sulfate thermally decomposed to form the crystalline phases of spinel, eta-Al2O3 and NiO at 900 degreesC. The lattice parameter of the spinel changed linearly with the Ni content ranging from about 20 mol% to 50 mol% of (NiO) / (NiO + Al2O3) without any other crystalline phases coexisted. The compacted NiAl2O4 spinel powder buried in a carbon powder was heated to partially reduce. On heating up to 700 degreesC the NiO segregated from the spinel leading to its enrichment in Al2O3. Metal Ni appeared above 800 degreesC, coexisting with the NiO and the spinel. The lattice parameter of the spinel decreased with decreasing the content of Ni in the spinel. The alpha-Al2O3/Ni composite was formed after heating at 1300 degreesC, while three phases of the NiO, the metal Ni and the spinel were coexisted until heating at 1200 degreesC.

(2002). Effect of Spark Plasma Sintering on Densification and Mechanical Properties of LaPO 4 -ZrO 2 Composites. Phosphorus, Sulfur, and Silicon and the Related Elements: Vol. 177, No. 8-9, pp. 1919-1919.

A new type of composite PTC thermistor was fabricated from ZnO-varistor particles and silicone rubber. The non-ohmic varistor characteristics were held in the composites. The ZnO-varistor particles were found to behave as a conducting filler at voltage higher than the varistor voltage. The PTC effect appeared in the composites containing varistor particles with volume fraction over the percolation threshold (greater than or equal to 250 vol%). The electrical resistivity at room temperature and the temperature region showing PTC effect varied according to the applied voltage.

Electroconductive composites were prepared from graphite as a filler material, piezoelectric ceramics as a matrix, and epoxy resin as a binder. When the filler volume fraction was near Vc on a percolation curve, the composite exhibited a nonlinear I-V characteristics, in analogy with varistors. It was assumed that this phenomenon was due to the distortion of the piezoelectric matrix upon applying a potential through the sample.

The machinable ceramics are the ceramics that can be drilled by machine. It has reported before. But they are low strength.1,2 In our study, Dy2O3-containing HAp ceramics were found to be machinable. The mixed powder of Dy2O3 and hydroxyapatite (Ca10(PO4)6(OH)2, HAp) with molar ratios ((Ca+Dy)/P) from 1.67 (HAp only) to 1.89 were uniaxially dry-pressed at 50 MPa to disks. The test specimens were sintered at 1200–1500◦C for 3 h in air. The phases observed mainly by XRD in the sintered body were HAp and Dy2O3. The relative density of the test specimens were almost above 95%. Three-point bending strength were 50∼90 Mpa, and fracture toughness were 0.8∼1.7 MPa·m0.5 of the test specimens sintered at 1250◦C. The test specimens presented machinability in the range of molar ratios 1.78–1.89.

Monazite-type LaPO4 was synthesized using the wet precipitation and mechanochemical reaction methods. Mixtures of xLaPO4–(1−x)ZrO2 (x=0–1) were dry-pressed to disks or plates and cold isostatically pressed (CIP) at 100MPa for 10min and then sintered at temperature between 1500 and 1600°C for 1, 3, and 5h in air, respectively. Relative densities larger than 96.8% (x≤0.4) and 92% (x=0.5–1) were achieved. It was found that these composites with x≥0.25 and single-phase LaPO4 were machinable, that is, they could be cut and drilled using conventional tungsten carbide metal-working tools. The drilling rates were measured by applying a fixed load of 49N to the drill at 6400rpm. X-ray diffraction results showed that the LaPO4 did not react with ZrO2, at least at 1600°C in air. The linear thermal expansion coefficient, thermal conductivity, bending strength, and Young’s modulus of the sintered composites were measured.

A new class of critical temperature resistor (CTR) was fabricated from metal/silica glass composites. The electrical resistivity of the composite with 20 vol% of Ag filler suddenly decreased from 10(5) to 10(1) Omega . m at about 300 degreesC, in analogy with the CTR characteristic observed in VO2 ceramics. It was assumed that this phenomenon was due to the high thermal expansion of the conducting filler in a low-thermal-expansion matrix: as the temperature increased, the conducting filler particles expanded to come into contact with one to another, resulting in a drop of resistivity at a critical temperature. The critical temperature varied with both the kind and the amount of metal filler.

Mixtures of (1 − x)LaPO4 and xAl2O3 (x = 0 to 1 mass) were dry-pressed to disks or bars. Relative densities larger than 94% and apparent porosities less the 6% were achieved when the specimens were sintered at 1600°C for 5 hours in air. The sintered ceramics (x = 0 to 0.7) were found to be machinable — they could be drilled easily using conventional metallic WC drills. The thermal and mechanical properties of the sintered (1 − x)LaPO4 - xAl2O3 composites had the following ranges: 10 × 10−6/°C (x = 0) to 9.0 × 10−6/°C(x = 1) (linear thermal expansion coefficient at 200°–1000°C); 5.0 (x = 0) to 43 W/(m·K)(x = 1) (thermal conductivity at 25°C); 140±19 (x=0) to 352±23 MPa (x = 1)(bending strength at room temperature); 5.7 (x = 0) to 16.5 GPa (x = 1) (Vickers hardness); and 155 (x = 0) to 400 GPa (x = 1) (Young's modulus).

Solid solutions of La2(SO4)3 and Al2(SO4)3 were prepared by rapidly drying mixed aqueous solutions using micro-wave heating. The La3+ion is soluble into the anhydrous aluminum sulfate crystal lattice up to about 6mol%. On heating the thermal decomposition starts at 830°C for the pure Al2(SO4)3, while at 760°C for 6mol% La2(SO4)3 contained Al2(SO4)3. The anhydrous aluminum sulfate solid solution thermally decomposes into the η-Al2O3 without any other crystalline phases. The LaAl11O18 is formed after heating the desulfurized product at 1300°C without forming LaAlO3 when the content of La2O3 is less than 6mol%.The La3+ doping increases the stability of η-Al2O3 at high temperatures. The phase transformation of alumina takes place above 1350°C when the amount of La2O3 is 5mol%.

The Dy-containing β-Ca3(PO4)2 (abbreviated as β-TCP) ceramics obtained by heating the mixtures of DyPO4 and β-TCP with DyPO4/β-TCP (abbreviated as D/T)=0.10–0.25 in molar ratio sintered at 1300°C for 3 h in air were found to be machinable; they can be drilled and cut easily using conventional inexpensive metallic Fe–Mo–W drills or gravers. The maximum relative density was 97% at 1300°C, over 98% at 1350–1400°C. The bending strength, Vickers’ hardness and linear thermal expansion coefficient of the specimens (D/T=0.10–0.25) sintered at 1300°C for 3 h were in the range of 30–50 MPa, 2–3 GPa and 11×10−6 °C−1–12×10−6 °C−1 (20–900°C), respectively.

Solid solution of MgSO4 and Al2(SO4)3 was prepared from mixed aqueous solutions by rapid dry using micro-wave heating. The Mg2+ ion is soluble into the anhydrous aluminum sulfate crystal lattice over a wide range up to near the equimolar composition of MgSO4 and Al2(SO4)3. The anhydrous aluminum sulfate solid solution, at first, thermally decompose into the mixture of η-Al2O3 and MgSO4. The crystalline spinel phase appears at the second step of the thermal decomposition. The lattice parameters of the spinel changes linearly with the Mg content ranging from 0.5 to 0.8 at the fraction of MgAl2O4/(MgAl2O4+Al2O3). The produced nonstoichiometric spinel solid solutions must be metastable because the stable region of the composition of the spinel solid solutions is very narrow at the heating temperature employed to the thermal decomposition.

Solid solutions of La-2(SO4)(3) and Al-2(SO4)(3) were prepared by rapidly drying mixed aqueous solutions using micro-wave heating. The La3+ ion is soluble into the anhydrous aluminum sulfate crystal lattice up to about 6 mol%. On heating the thermal decomposition starts at 830 degrees C for the pure Al-2(SO4)(3), while at 760 degrees C for 6 mol% La-2(SO4)(3) contained Al-2(SO4)(3). The anhydrous aluminum sulfate solid solution thermally decomposes into the eta-Al2O3 without any other crystalline phases. The LaAl11O18 is formed after heating the desulfurized product at 1300 degrees C without forming LaAlO3 when the content of La2O3 is less than 6 mol%. The La3+ doping increases the stability of eta-Al2O3 at high temperatures. The phase transformation of alumina takes place above 1350 degrees C when the amount of La2O3 is 5 mol%.

Poorly crystalline rhabdophane-(Yb or Lu) was synthesized by precipitation from mixed aqueous solutions of Ln(NO3)3 (Ln = Yb or Lu), (NH4)2HPO4, and citric acid with the mixing mole ratios of (NH4)2HPO4/Ln(NO3)3 = 4 and citric acid/Ln(NO3)3 = 5 to 30, at pH 7 and 90°C for 7 to 30 days. However, unknown XRD peaks and C–O bond FTIR absorption peaks were observed for the precipitates. These peaks disappeared with increasing heating temperature up to 400°C in air, and single phase rhabdophane-(Yb or Lu) was obtained when heated at 400 to 800°C in air. Chemical formulas of the single phase rhabdophane were YbPO4·0.4H2O and LuPO4·0.5H2O, respectively. The water corresponding to 0.4H2O (or 0.5H2O) was zeolitic water. The lattice constants are a = 0.676 and c = 0.626 nm for Yb, and a = 0.674 and c = 0.630 nm for Lu. Rhabdophane-(Yb or Lu) changed into the xenotime structure above 860°C, which was stable even at 1800°C in air.

More than 60 mol% Zr4+ ion (ZrO2/ (Al2O3 + ZrO2)) is soluble into anhydrous Al-2(SO4)(3) crystal lattice. The apparent crystallite size decreases with increasing Zr4+ content, and the thermal decomposition temperature reduces at contents of zirconia > 20 mol % , Alumina/zirconia composite powders, in which an amorphous zirconia phase is dispersed in a matrix of fine eta-alumina particles, are obtained by thermal decomposition of the sulfate solid solution. Tetragonal phase of zirconia crystallizes at 1100 degrees C and the crystallinity increases with increasing the temperature of the heat-treatment. When mono-dispersed ultra fine particles of zirconia are added to eta-alumina formed by thermal decomposition of pure anhydrous aluminum sulfate, the eta-->alpha phase transformation of alumina is suppressed, and the effect increases with increasing the amount of the additive. On the contrary, a small quantity of ZrO2 < 1 mol % drastically suppresses the phase transformation of alumina formed by decomposition of sulfate solid solution. But, when ZrO2 content is more than 1 mol %, the eta-->alpha phase transformation of alumina is accelerated, The acceleration effect becomes larger with increasing the content of ZrO2.

The anhydrous aluminum sulfate powder composed of rhombohedral single-crystal grains was prepared by precipitation from a concentrated sulfuric acid solution. The average grain size and the size distribution was 3.8±0.7μm. Thermal decomposition behavior of the anhydrous aluminum sulfate was investigated by thermogravimetric measurements. The kinetics of the thermal decomposition fitted to a contracting volume model with an apparent activation energy of 360 kJ/mol. The mobility of the reaction boundary of the thermal decomposition at 760°C was estimated to be about 7.0×10-5μm/s. The temperature dependence of the mobility was expressed by an Arrhenius type equation.

Xenotime‐type RPO4 (R = Y, Er, Yb, or Lu) powder was dry‐pressed into disks and bars. The disks and bars could be sintered to a relative density of greaterthan equal to98% in air without cracking at 1300° (R = Yb or Lu) or 1500°C (R = Y or Er), depending on the grain size. The linear thermal expansion coefficient (at 1000°C), thermal conductivity (at 20°C), and bending strength (at 20°C) of the xenotime‐type RPO4 ceramics were 6.2 10‐6/°C, 12.02 W(mK)‐1, and 95 ± 29 MPa for R = Y; 6.0 10‐6/°C, 12.01 W(mK)‐1, and 100 ± 21 MPa for R = Er; 6.0 10‐6/°C, 11.71 W(mK)‐1, and 135 ± 34 MPa for R = Yb; and 6.2 10‐6/°C, 11.97 W(mK)‐1, and 155 ± 25 MPa for R = Lu. The xenotime‐type RPO4 ceramics did not react with SiO2, TiO2, Al2O3, ZrO2, or ZrSiO4, even at 1600°C for 3 h in air, and were stable in aqueous solutions of HCl, H2SO4, HNO3, NaOH, and NH4OH at 20°C.

In recent polymorphism studies of gallium phthalocyanines, a new crystal form of hydroxygallium phthalocyanine (Type V HOGaPc) was obtained. It shows an extremely high photosensitivity (E(1/2)=1.3 mJ/m(2) at 780 nm) and excellent thermal stability. Furthermore, its photosensitivity is not affected by changing humidity. Hence, it is an useful charge generation material for an IR photoreceptor. From the TGA and Rietveld analysis of the Type V crystal, it is indicated that the highly photosensitive characteristic of this pigment does not depend on sensitization by water. The high sensitivity is attributed to the specific crystal structure and to the presence of the hydroxyl group, both of which are favorable for charge generation.