A new homogeneous precipitation was carried out utilizing the mixed solutions of polyaminocarboxylate complexes of transition metal (Co²⁺, Fe²⁺, Ni²⁺ and Zn²⁺) and phosphate (NH₄H₂PO₄ or NaH₂PO₄) in order to prepare monodispersed crystalline particles. Monodispersed spherical particle of CoHPO₄·3H₂O was formed in the mixed solutions of 0.05M Co(edta)^2- and 0.15M NaH₂PO₄ at pH6.5 and 200°C for 4h and rod-like CoHPO₄·1.5H₂O was formed at pH4 and 200°C for 2h. Furthermore similar spherical Ni₃(PO₄)₂·8H₂O was formed in the mixed solutions of Ni(edta)^2- and NH₄H₂PO₄ at pH7 and 250°C for 2h. Fibrous Zn₂(OH)PO₄ was formed in the mixed solutions of Zn(nta)₂^2- and NH₄H₂PO₄ at pH4 and 250°C for 2h. The particle morphology could be controlled by adjusting a kind of metal polyaminocarboxylate, temperature and pH.

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Twenty of metal phosphates were investigated as humidity-sensing materials. Eight kinds of metal phosphates including Ti(HPO₄)·H₂O showed good humidity-sensing characteristics. Treating of Ti(HPO₄)·H₂O and Ce(HPO₄)₂·2H₂O with NaOH solution considerably lowered the electric resistance, which changed by about three orders of magnitude in the relative humidity range 11 to 94%.

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Titanium phosphates Ti(HPO₄)₂·nH₂O and their derived substances were investigated as humidity-sensitive materials. Among the sensor elements studied, TiP-1-NaOH-800 element which was prepared by immersing Ti(HPO₄)₂·H₂O in aqueous NaOH solution, followed by calcining at 800°C, exhibited the best performance from the viewpoint of humidity sensitivity and measurability. Suitable starting materials Ti(HPO₄)₂·nH₂O and optimum sintering conditions were also investigated.

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Different aluminum phosphates (AP) were prepared and examined from viewpoint of not only the selectivity but the specific activity for cis-2-butene isomerization. Amorphous AP catalysts were more active than crystalline AP catalysts. The selectivity (initial trans-2-butene/1-butene ratio) of an AP catalyst was sensitive to residual phosphate ions on the surface, but the selectivity was independ of whether the AP is X-ray amorphous or crystalline.

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Various aluminum phosphate-alumina mixed catalysts (APA) having different P/Al ratios were prepared, and their activity and selectivity for n-butene isomerization as well as their physical properties were examined. The APA catalysts consisted of crystalline aluminum phosphate and alumina. Some APA catalysts showed infinite selectivity (initial trans-2-butene/1-butene ratio) in cis-2-butene isomerization; this extraordinary selectivity indicates that the surfaces of the catalysts are occupied by aluminum phosphate featuring such selectivity. Others, however, showed no infinite selectivity, which suggests that alumina involved in them catalyzes the cis-2-butene isomerization too. It was also concluded that the active sites featuring the infinite selectivity were located in amorphous aluminum phosphate moiety in the neighborhood of catalytically inactive crystalline aluminum phosphate.

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Ion-exchanges of Cu²⁺, Zn²⁺, and Ag⁺ on layered phosphates of tetravalent metal, Zr(HPO₄)₂·H₂O (α-ZrP), Ti(HPO₄)₂·H₂O (α-TiP), Ti(HPO₄)₂·2H₂O (γ-TiP), Ce(HPO₄)₂·1.33H₂O(CeP), Zr(NaPO₄) (HPO₄) (NaH-ZrP), and Zr(NaPO₄)₂·H₂O (NaNa-ZrP), were studied. Although the uptakes of Cu²⁺ and Zn²⁺ into layered phosphates (α-ZrP, TiP, and CeP) were very low, those into NaH-ZrP and NaNaZrP were high. Ag⁺ was well ion-exchanged by layered phosphates except α-ZrP. Layered phosphates ion-exchanged with metal ions (Cu²⁺, Zn²⁺, and Ag⁺) easily adsorbed ill-smelling gases such as H₂S and CH₃SH.

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Solid acid property derived from loading phosphate and sulfate ions on silica, and their catalytic property will be described. Silica is neutral, neither acidic nor basic, and non-active to olefin isomerizations. The surface of silica was found to turn into very strongly acidic by being exchanged with these ions. Silica modified with phosphate ions was considerably active for 1-butene isomerization comparable to that modified by sulfate ions. The mechanism for the appearance of acid sites was thought to be the same to both cases.

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Spherical Hydroxyapatite was synthesized using a wet chemical method directly. When titrating a calcium hydroxide suspension into a phosphoric acid aqueous solution to which pyrophosphate has been added as a coagulant, aggregates of CaHPO₄·2H₂O were produced if the synthesis temperature is 40-60°C, and aggregates of CaHPO₄ were formed if 70-90°C; and when maintaining these aggregates in a pH7.0 suspension, they changed to spherical HAp after 24 hours of constant stirring. The structure of the sphaerite appeared as aggregate of fine HAp particles. To make sphaerites of HAp, it is thought that aggregates of CaHPO₄·2H₂O or CaHPO₄ must be produced, and when these change into HAp, sphaerites are made by locally increasing the solubility in the surface vicinity of the aggregates.

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Amorphous calcium phosphate (ACP) was synthesized by dropping rapidly aqueous ammonia into calcium dihydrogenphosphate monohydrate (Ca(H₂PO₄)₂·H₂O, MCP) solution. The composition of ACP was given within the wide range of Ca/P atomic ratio 1.25~1.55 and was distinguished to three kinds (H-ACP, M-ACP and L-ACP) by different Ca/P atomic ratios. Thermal behavior of water molecule in three types of ACP was investigated by X-ray diffraction, thermal analysis (TG-DTA) and Fourier transformation infrared spectroscopy (FT-IR). Two kinds, the water molecule in ACP existed adsorbed water and bound water. Distinction of these water molecules was possible from Arrehenius plot by relating between heating rates (β) and upper temperature of endothermic peaks (Tm) with thermal analysis (TG-DTA). The activation energy for dehydration of adsorbed water and bound water until about 125°C was able to determine from the gradient of Arrehenius plot. For example, the activation energy for dehydration of bound water in H-ACP of high calcium type (Ca/P atomic ratio 1.55) was 26.4 kcal/mol. It was considered that bound water was stabilized by increasing Ca/P atomic ratio in ACP.

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Ceramic composite coating of biocompatible hydroxy-apatite and yttria-stabilized zirconia was performed using an electrophoretic deposition technique. Use of the mixed solvent of acetylacetone and alcohol was effective for the control of the composition of coating layers; the powders of hydroxyapatite and yttria-stabilized zirconia showed different deposition behavior depending on the mixed ratio of the two solvents.

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Hydroxyapatite (HA) coated with β-tricalcium phosphate (β-TCP), HA and β-TCP with 60% porosity were implanted into the quadriceps femoris muscles of adult rabbits. These rabbits were sacrificed 4, 12 and 24 weeks after the implantation. The weight of HA was increased obviously after 4, 12 and 24 weeks. The biological hydroxyapatite containing carbonate was formed on the HA surface. The weight of β-TCP was slightly decreased after 24 weeks. The weight of β-TCP coated HA was scarcely changed, but the weight tended to increase at 24 weeks. Thus β-TCP coated HA behaved like β-TCP initially after implantation, and then behaved like HA in vivo.

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The powder of amorphous calcium phosphate (ACP) containing 20mass% water, prepared from aqueous solution of Ca(NO₃)₂ and (NH₄)₂HPO₄, was hot-pressed hydrothermally at the temperatures from 100 to 300°C under 50 MPa for 2 h. Translucent hydroxyapatite ceramics were prepared by hydrothermal hot-pressing at 300°C. This hydroxyapatite was calcium deficient apatite with the Ca/P ratio of 1.59. In simulated body fluid, carbonate hydroxyapatite layer was formed on the surface of the translucent apatite ceramics.

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Sodium chondroitin-6-sulfate (Na₂Chs) was adsorbed by hydroxyapatite (HAP), while polyvinylpyrrolidone (PVP) was not. When these polymers were mixed in an aqueous phase, polymer coil of PVP excluded that of Na₂Chs, resulting in increases in chemical potential and adsorption amount of Na₂Chs. It seemed as if Na₂Chs was concentrated by PVP. The concentration effect of non-adsorbable polymer, PVP, on the adsorption amount of Na₂Chs was discussed.

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Whisker-like hydroxyapatite (HAp) was synthesized by an aqueous ammonia neutralization method using nitrogen carrier. Acidic-aqueous solutions containing 0.167 mol·dm^-3 Ca(NO₃)₂ and 0.1 mol·dm^-3 (NH₄)₂HPO₄ were heated at three different temperatures (70°C, 75°C and 80°C) for 24h and then at 95°C for 24h; during this process the solutions were neutralized with nitrogen-carrier gases saturated with various concentrations of aqueous ammonia. The flow rate of nitrogen carrier was 0.1 dm³·min^-1. The obtained whisker-like HAp had Ca/P ratios of 1.59 to 1.62, which were non-stoichiometric compositions. The products were whisker-like and/or tape-like and/or acicular crystals. In the above three conditions, the mean values of long-axis size distribution and aspect ratio of whisker-like HAp were 14.5μm and 14.2 at 70°C, 18.1μm and 19.3 at 75°C, and 12.9μm and 13.2 at 80°C, respectively.

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Silicate-containing hydroxyapatite( SiAp) and hydroxyapatite (HAp) have been hydrothermally synthesized at 150°C under saturated steam pressure, Previously, the cation-exchange characteristics of these apatites in aqueous solution were investigated and the superior cation-exchange characteristics of SiAp seemed to be due to loosening effect on skeletal structure of the apatite by substitution of SiO₄^4- for PO₄^3- ions, In the present study, SiAp has been characterized mainly by X-ray photoelectron spectroscopy (XPS), and it has been confirmed that SiO₄^4- ions instead of SiO₂ were introduced into hydroxyapatite structure.

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Polyvinylpyrrolidone (PVP) alone was scarcely adsorbed to the surface of hydroxyapatite (HAP). However, its amount of adsorption increased with the concentration of sodium dodecylsulfate (SDS) added in an aqueous phase. SDS was adsorbed by HAP through electrostatic attraction between negative charge of its polar head group and positive sites on HAP, while hydrocarbon tail of the adsorbed SDS captured segments of polymer coil of PVP through hydrophobic interaction, resulting in the formation of the surface complex. Surface modification of biological HAP by amphiphilic compounds seemed significant in the formation of animal hard tissues.

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Three kinds of glasses in the system CaO-Al₂O₃-SiO₂ with different compositions were mixed with calcium phosphate powders. The mixture was formed into cylindrical shape, and then treated hydrothermally at the temperatures from 100 to 250°C under the saturated vapor pressure of water. The mixture of glasses and β-tricalcium phosphate (β-TCP) could be hardened under hydrothermal conditions. The hardened material prepared at 250°C from the CaO-rich glass and β-TCP had a compressive strength of about 40 MPa. According to XRD and SEM observation for the hardened material, hydroxyapatite fine crystals were precipitated in its matrix.

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The synthesis of various rare-earth cyclo-tetraphosphates, La₄(P₄O₁₂)₃·14H₂O (LaP_4m), Ce₄(P₄O₁₂)₃·13H₂O(CeP_4m), Pr₄(P₄O₁₂)₃·13H₂O(PrP_4m), and Nd₄(P₄O₁₂)₃·13H₂O(NdP_4m), were prepared and their thermal behaviors were investigated using TG-DTA, HPLC, and X-ray diffraction analysis.
1) LaP_4m, PrP_4m, and NdP_4m gradually decomposed to relatively short-chain phosphates, ortho-(P₁), pyro-(P₂), tri-(P₃), tetra-(P₄), and oligophosphates(P_oligo, n=5-14), with the elimination of water of crystallization. With an increase of temperature, their phosphates condensed to insoluble phosphates(P_insoluble). The decomposition of P_4m and the condensation of short-chain phosphates formed proceeded faster under humid air than dry air. In the range of temperature of 600~700°C, amorphous P_insoluble changed to cyclo-triphosphate(MP_3m, M=La, Pr, and Nd). The crystallinity of their cyclo-triphosphates was better one heated in humid air than in dry air. MP_3m changed to orthophosphate, LaPO₄, PrPO₄, and NdPO₄, with the evolution of P₂O₅ above 1000°C.
2) Ce₄P_4m also decomposed to short-chain phosphates such as ortho-(P₁), pyro-(P₂), tri-(P₃), and tetraphosphate (P₄) with the elimination of water of crystallization, followed by the dehydration-condensation reaction of short-chain phosphates and the oxidation reaction of Ce³⁺ to Ce⁴⁺, resulting in accelerating the hydrolysis reaction and in depressing the dehydration-condensation reaction because of formation of stable CeP₂O₇. CeP₂O₇ crystallized by 600°C. At the temperature above 1000°C, CePO₄ was formed through cerium cyclo-triphosphate (CeP_3m).
All of the rare-earth phosphates prepared didn't melt up to 1050°C.

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Degradation products of cyclo-octaphosphate and linear octaphosphate under several conditions were analyzed using the liquid chromatographic system recently devised by us. cyclo-Polyphosphates larger than tetramer, cyclo-penta- and -hexaphosphate were found in the degradation products in weakly acidic media and in the presence of Al³⁺ and Cu²⁺ ions. The mechanism of these cyclo-polyphosphate abstractions in the hydrolysis reactions of octaphosphate is discussed.

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The reaction of glycine (Gly) or L-α-alanine (Ala) with inorganic sodium cyclo-triphosphate hexahydrate (P_3m), Na₃P₃O₉·6H₂O, gave dipeptide [glycylglycine (GlyGly) or alanylalanine (AlaAla)] and the phosphorylated products of amino acids. Maximum yields of GlyGly and AlaAla were 17.9 and 5.6%, at pH9 and room temperature, respectively. Four kinds of dipeptide (GlyGly, AlaAla, GlyAla, and AlaGly) were produced in the reaction of P_3m with the mixture of Gly and Ala.

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Sodium triphosphate hexahydrate and lithium triphosphate pentahydrate were prepared by adding, respectively, sodium chloride and lithium chloride into triphosphate solution. Sodium triphosphate hexahydrate decomposed to produce ortho- and diphosphates below 200°C. The ortho- and diphosphates were polymerized to triphosphate at 300 to 600°C. Lithium triphosphate pentahydrate degraded to produce ortho- and diphosphates at around 100°C. On heating at a temperature higher than 180°C, the thermally produced ortho- and diphosphates reorganized to diphosphate and oligophosphates with chain lengths longer than that of triphosphate and did not reproduce triphosphate.

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Sodium superionic conductor in the Na₂O-Y₂O₃-P₂O₅-SiO₂ system was synthesized by sol-gel method. The obtained samples with a composition of Na_5.2Y_0.8P_0.4Si_3.6O_12.0 showed high conductivity at 310°C of σ₃₁₀=9.3×10^-2Scm^-1. Using this solid electrolyte, Na/S cell was prepared. Open-circuit voltage of the cell was 1.94V at 310°C and the transport number was calculated at 0.990. The results of measurement of durability and discharge behavior for the cell suggested that minuteness and homogeneity were very important to evaluate solid electrolyte of Na/S cell was well as conductivity.

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