The recent progress of two-dimensional NMR is described for improved structural studies of glasses, particularly of the connectivities of the various phosphate Qⁿ groups in terms of the nomenclature Q^njkl where the number of additional superscripts depends on the number of bridging oxygens n and where j, k and 1 denote the Q character of the bonded adjacent unit. Furthermore, applications of NMR for structural studies of plasma-sprayed hydroxyapatite are presented as well as studies of mesostructured aluminophosphates. 2D heteronuclear correlation NMR allows to locate the headgroup of the template molecule with respect to the inner surfaces of the layers.

抄録全体を表示

The performance of polymers of varying composition and molecular weight as calcium phosphate inhibitors has been investigated using the pH-stat method. Included in this study are the effects of soluble impurities and process variables on the performance of polymeric inhibitors. The results from this study help in the selection of an appropriate inhibitor for the treatment of industrial water systems.

抄録全体を表示

Phosphate glasses are of technological interest for electrochemical devices, as bioactive materials, and also for the electronic industry. Solid-state NMR, chiefly coupled with magic angle sample spinning (MAS), is a valuable technique to obtain information on short-range order and connectivity in phosphate glasses. In this paper the most recent advances in the field will be reviewed, and more emphasis will be given to solid-state glassy electrolytes.

抄録全体を表示

In this presentation emphasis has been placed on heterogeneous catalysts where phosphorous is a determining element. These correspond to phosphate based materials as vanadyl pyrophosphate used industrially for the oxidation of butane to maleic anhydride in the 630-670 K, iron phosphates and hydrogeno/hydroxy-phosphates for the oxidative dehydrogenation (ODH) of isobutyric acid to methacrylic acid in the 650-680K temperature range, zirconium hydrogeno-phosphates as layered compounds used to stabilise/entrappe catalytically active compounds as Al, Zr, or Cr, V hydroxy or hydroy-oxy macrocations species used in acid-type reactions as alkane cracking or partial oxidation reactions as ODH of light alkanes, respectively, microporous aluminophosphate molecular sieves (AIPO, MeAPO,EIAPO,..).
It is shown that the catalyst surface behave as a rather dynamic and labile surface, reconstructing under activation and/or catalytic reaction conditions and adapting itself to the stereochemistry of the reactants. In partial oxidation reactions the active sites are shown to have a molecular size and have several catalytic functions. The hydrocarbon molecule is first adsorbed, then activated, some of its hydrogen atoms are extracted while lattice oxygens are incorporated into it and electron transfer did occur through the solid material to allow oxidation reaction mechanism to proceed. The metal M cations are the active species and the role of the phosphate tetrahedra is not only to bind the MO₆, octahedra together to constitute a dense or layered compound but also to bring some specific redox and acid-base properties. In the case of microporous phosphates, the active sites are more localised and static, while their chemical (redox and/or acid-base) properties, molecular and spatial structures (porosity inducing shape selectivity) turned out to be the determining factors for their catalytic properties.

抄録全体を表示

In this paper the history, the spectacular scientific growth and the potential practical applications of phosphazene materials are presented, together with the reasons of their limited technologic development. The strategies that have been recently designed to overcome this situation are also illustrated.

抄録全体を表示

Crystalline ultraphosphates are a relatively new group of phosphate-rich compounds. We tried to find out a system of systematic order in crystal-chemical sense. Some selection rules as well as necessary conditions are given. In this way, we like to bring in some light into the building principles of these very interesting inorganic polymer compounds by our proposal.

抄録全体を表示

Two new porous gallophosphates were synthesized in aqueous medium using N,N,N',N'-tetramethylethylenediamine as organic template. The material obtained in the presence of fluoride anions corresponds to the fluorogallophosphate ULM-18 whereas, the other gallophosphate synthesized in the absence of F^- displays a new three-dimensional framework containing four-, five- and six-coordinated gallium atoms. The two materials were characterized by several techniques such as SEM, elemental analysis, powder X-ray diffraction and solid state NMR spectroscopy.

抄録全体を表示

The method of chemical vapour transport (CVT) in a temperature gradient provides a versatile tool for synthesis, crystallization and purification of anhydrous transition metal phosphates. The whole span of now more than 60 phosphates grown on laboratory scale via the gas phase might be visualized by the thermally labile Pd₂P₂O₇ and RhPO₄, some low melting ultraphosphates (e. g.: CuP₄O₁₁, ZnP₄O₁₁) and a series of phosphates containing transition metals in otherwise not easy accessible oxidation states (e. g.: TiPO₄, V₂O(PO₄), Cr₃(PO₄)₂, Cr₂P₂O₇). The experiments are carried out in sealed silica ampoules at temperatures between 500 and 1100°C, depending on volatility and thermal stability of the phosphate. Plein chlorine or iodine in combination with a few mg of metal, metal phosphide or phosphorus as reducing agents have led to the best results with respect to crystal size, quality and growth rate. Heterogenous solid/gas as well as solid/solid equilibrium reactions determining the transport process will be discussed.

抄録全体を表示

One of the principal classes of flame retardants used in organic polymers is the phosphorus-compounds. In particular, inorganic phosphates have flame retardant properties of interest in thermoplastics. Ammonium phosphoric acids salts were first recommended two centuries ago and are still used today. However, new legislation is emphasizing the development of new flame retardant additives which are environmentally friendly. This paper reviews the different kind of inorganic phosphates used as flame retardants. It includes the use of red phosphorus, ammonium phosphates. We will also describe intumescent systems and low melting phosphate glasses.

抄録全体を表示

Simple dry process of the preparation of ammonium polyphosphate form V was studied using the system of ammonium orthophosphate-urea. Ammonium polyphosphate form V was prepared by heating a mixture with molar ratios (ammonium orthophosphate/urea) of 1/2.0 to 1/0.8 it 330 to 340 °C under wet ammonia which was made by passing air through 15 and 29% of ammonia water.

抄録全体を表示

The order-disorder, ferrielectric-paraelectric transition in lamellar CuInP₂S₆ is studied using ³¹P solid-state MAS-NMR spectroscopy in the temperature range 255<T<355K. Two center bands are observed at the lowest measured temperature while only one is detected at the highest temperature. The former two represent the inequivalent positions for the P atoms in the ferrielectric phase. The latter corresponds to the appearance of a twofold axis through the P-P bond as the Cu^I ions undergo double-well hopping motions in the paraelectric phase. At intermediate temperatures both ferrielectric and paraelectric type resonances contribute to the spectrum at ratios which are T-dependent, indicating a transition temperature T_c= 312±1K (310±1K) for a warming (cooling) cycle. The temperature range for the coexistence is unusually wide (>70K). The presence of the ferrielectric type resonance in the paraelectric regime may be ascribed to the nucleation of polar order, while the persistence of the paraelectric signal below T_c implies residual hopping motions.

抄録全体を表示

The aim of this work is reducing the iron content in crude phosphoric acid produced from dissolution of Abu-Tartur phosphate in sulphuric acid to an acceptable limit without a large reduction of P₂O₅ percentage. Several methods were used to reduce the iron content, but this work was focused on the precipitation method because the technique of this method is more suitable for Abu-Tartur project. Na₂CO₃(NaCO₂)₂, NaOH, KOH and K₄[Fe(CN)₆].3H₂O were used as a precipitating agent. The percentage of P₂O₅ and Fe in the filtrate were determined spectrophote-metrically and the precipitate was exposed to X-ray diffraction analysis. It is found that the most suitable materials are Na₂CO₃, NaOH and KOH, while sodium oxalate is a poor precipatating agent. Potassium ferrocyanide is a good one but it is not prefer because it is poisonous.

抄録全体を表示

The phosphorus pentoxide crystal with Pnam symmetry containing four P₂O₅ molecules in the unit cell was calculated by ab initio density functional theory in the local density approximation with a plane wave basis. The calculated optimized geometry is in a good agreement with experiment. The population analysis showed that the crystal has an ionic-covalent chemical bonding. An Ag atom impurity in the phosphorus pentoxide crystal was investigated within the periodic model. The distortion of the lattice around the impurity was analyzed in terms of PO₄ tetrahedra. The calculations showed that in spite of considerable deformation of the lattice the Ag impurity does not break the P-O bonding network.

抄録全体を表示

Nearly the middle region of the composition-triangle representing the system Li₂O-Al₂O₃-P₂O₅ was explored with respect to the dependence of the properties of the final product on both its nominal composition and preparation route. The conventional melt-quenching, precipitation, and the sol-gel methods were used. Thermal analysis and x-ray diffraction patterns were used for comparisons.
Some trend of change regarding the glass forming region and crystalline forms among each series of compositions could be noticed. These changes seem to depend on the preparation method. An increase of Al₂O₃ lead to a decrease of the crystallinity of the product sample from solutions but not from melts. Devitrified samples show Li₃PO₄ and AlPO₄ crystallization.

抄録全体を表示

The present work reports the thermal rearrangement of hydrogen phosphates of iron and alkaline metals into condensed phosphates.

抄録全体を表示

Three new phases were identified in the ternary system Bi₂O₃-PbO-P₂O₅: PbBiPO₅, Pb₄BiPO₈ and Pb₅Bi₁₈P₄O₄₂. PbBiPO₅ displays a phase transformation from triclinic to monoclinic symmetry at 725°C. The crystal structures of Pb₄BiPO₈ and Pb₅Bi₁₈P₄O₄₂ were solved from single crystal diffraction data. The formula described previously as PbBi₃PO₈ was revised and is more likely Pb₃Bi₁₀P₃O_25.5, equivalent to PbBi_3.33PO_8.5. Its crystal structure displays a distorded 3 x 3 x 3 superstructure of a tetragonal variety of 3δ-Bi₂O₃ type

抄録全体を表示

Anhydrous phosphates of transition metals exhibit a surprising variety of colours. Even phosphates of the same cation show significantly different electronic absorption spectra. Using calculations within the framework of the angular overlap model a detailed correlation can be obtained between the observed electronic transitions and the particular coordination geometry of M³⁺ in a series of anhydrous phosphates (M(PO₃)₃, MPO₄, M₄(P₂O₇)₃, and M₄P₆Si₂O₂₅) of trivalent vanadium and chromium. Our investigation gives evidence for the strong influence of the coordination number of oxygen on its coordination behaviour towards M³⁺. While isotropic π-bonding is observed for such O^2- coordinated by P⁵⁺ and one M³⁺, oxygen with C. N.=3 (P⁵⁺ and 2 M³⁺) exhibits anisotropic π-bonding towards M³⁺. Thus the π-interaction M³⁺-O^2- within the plane through the two M³⁺ and the bridging O^2- is significantly reduced compared to the interaction perpendicular to this plane.

抄録全体を表示

The trustworthy preparation method of the uncommon phase of NaH₂PO₄·H₂O is establised. It is realized in the way where hydration water is introduced into anhydrous NaH₂PO₄ by being soaked in the liquid media. Its thermal behaviour and solid-state ³¹P NMR spectrum are compaired with those of the common phase.

抄録全体を表示

The new compound BiCoPO₅, monoclinic, P2₁/n, a = 7.2470(1)Å, b =11.2851 (2) Å, c = 5.2260(1) Å and β= 107.843(1)°, Z = 4, was synthesized and structurally characterized by powder X- ray diffraction. It is isostructural with bismuth nickel oxyphosphate BiNiOPO₄. The crystal structure is built up from a complex tridimensional assembly of (Co/Ni)₂O₁₀ dimers linked by PO₄ groups. This forms large tunnels running along c which host Bi³⁺ cations. Smaller tunnels running along a and crossing the latter were also evidenced. It is noteworthy that the original BiNiPO₅ lattice is appreciably increased with Co²⁺ cations as the transition metal. The Bi³⁺ cation is surrounded by a strongly distorted oxygen octahedron. Reducing the Bi-O bonds to the three shortest, Bi environment can be considered as tetrahedral considering the BiO₃Lp polyhedron, Lp = 6s² lone pair. The lone pair localisation was performed from electrostatic interactions and revealed Lp - Bi distance of 0.68 Å and 0.58 Å, for Co²⁺ and Ni²⁺ compounds respectively.

抄録全体を表示

Ultraphosphates are polymeric phosphates and not yet fully investigated. The connection of their anionic network is very varied caused by different influences of the cations and their position in the network.

抄録全体を表示

Ultraphosphates are condensed phosphates characterized by anionic networks of two- and three connected PO₄ tetrahedra. Cations essentially influence the structure pattern od such anionic networks, which are demostrated on examples of SrHP₅O₁₄ and NiHP₅O₁₄ ultraphosphates.

抄録全体を表示

Phase equilibrium in the systems Ln₂O₃ - P₂O₅ - H₂O, (Ln = La-Lu and Y, molar ratio P₂O₅/Ln₂O₃ = (3÷10)/1) has been studied within the temperature range of 25-350 °C by thin layer method. The following phosphates have been synthesized: LnPO₄·nH₂O (Ln = La-Eu), LnH₃(PO₄)₂· 2H₂O (Ln = Sm-Dy, Lu, Y), LnH₃(PO₄)₂·0.5H₂O (Ln = Ho-Lu, Y), LnH₃(PO₄)₂ (Ln = Tb-Lu, Y), Ln(H₂PO₄)₃ (Ln = Nd-Dy), LnHP₂O₇ (Ln = Eu-Lu, Y), Ln₂P₄O₁₃-II (Ln = Ho-Lu, Y), Ln₄(P₄O₁₂)₃ (Ln = Tm-Lu), Ln(PO₃)₃-I (Ln = Ln-Gd), Ln(PO₃)₃-II (Ln= Tb-Lu, Y), Ln(PO₃)_3-C (Ln = Sm-Lu, Y), LnH(PO₃)_4-I (Ln = Sm, Eu), LnH(PO₃)_4-II (Ln = Eu-Er, Y), LnP₅O_14-I (Ln = La-Gd), LnP₅O_14-II (Ln = Tb- Lu, Y), Ln₂P₄O₁₃-I (Ln = Gd-Lu, Y); Ln₄(P₂O₇)₃ (Ln = Gd-Lu, Y). Thermal transformations of these compounds have been studied within the temperature range of 25-1000 °C. Lattice parameters of some synthesized phosphates have been calculated. Comparative diagram of crystallization fields for stable phases of rare earth phosphates has been constructed.

抄録全体を表示

Mu-4 is a new layered aluminophosphate [(C₂H₅)₂NH₂]₄ [Al₈P₁₀O₄₀H₂][H₂O]_2.5 obtained from a quasi non-aqueous system involving diethylformamide (DEF) as the main solvent. During the synthesis, DEF is decomposed into protonated diethylamine which is occluded in the structure. The latter consists of double layers of double 4-ring units connected through 4-, 6- and 8-membered rings. ²⁷Al and ³¹ P MAS, ²⁷ Al 3Q MAS, ¹H-³¹ P CP-MAS and ²⁷Al→³¹P heteronuclear correlation NMR experiments were performed in order to confirm the structure of this layered aluminophosphate.

抄録全体を表示

Partial study of the Na₂O-CaO-P₂O₅-SiO₂ system evidenced two compounds corresponding to Na₂Ca₅(PO₄)₄ and NaCa₆(PO₄)₃SiO₄, instead of Na₃Ca₆(PO₄)₅ and Na₂Ca₄(PO₄)₂SiO₄ previously reported in the literature. Na₂Ca₅(PO₄)₄ and NaCa₆(PO₄)₃SiO₄ are ordered phases both belonging to a large solid solution domain with general formula Na_2-xCa_5+x(PO₄)_4-x(SiO₄)_x. The Na_2-xCa_5+x(PO₄)_4-x(SiO₄)_x solid solution structure was shown to be a superstructure of the glaserite-type structure.

抄録全体を表示

Silylation of α-zirconium phosphate was carried out using various silanes in toluene at >70 °C in a nitrogen atmosphere. The silylating reagents were dimethyldichlorosilane, dimethyloctadecylchlorosilane, dimethoxymethylchlorosilane and 1,2-bis(dimethylchlorosilyl)ethane. It was necessary to intercalate organic bases such as n-alkylamines prior to the silylation. The Si-C vibration was observed in the IR spectra of products. Unlike alkylamine derivatives of the phosphate, silylated derivatives kept their basal spacings up to about 500 °C. Furthermore, contrary to the fact that α-zirconium phosphate changes to pyrophosphate above 700 °C, pyrophosphate was not observed on heating even at 1000 °C. Silylated derivatives were thought to be changed to layered compounds containing silica as a pillar in the interlayer space by heat treatment.

抄録全体を表示

Influence of Eu³⁺ introduction on structure and properties of K₃Ln(PO₄)(VO₄)_2-x (Ln = Y, La, Gd) is investigated. Samples of K₃Ln_1-yEu_y(PO₄)_x(VO₄)_2-x(Ln = Y, La, Gd; 0≤x≤2) were received by solid state method by multistep annealing from 70 to 750 °C with use of Ln₂O₃ (Ln= Y, La, Eu, Gd), KH₂PO₄, NH₄VO₃ and K₂CO₃. There are restrict or wide solid solution range is observed in systems under investigation.

抄録全体を表示

The vaporization of gallium phosphate GaPO₄ was studied by high-temperature mass spectrometry. ·Standard enthalpies of formation and atomization (kJ/mol) were derived for GaPO₃(g) (-661±35 and 1997±36), and for GaPO₂ (g) (-373±36 and 1460±37) respectively. A number of regularities are revealed from the analysis of qualitative and quantitative vapor compositions.

抄録全体を表示

Calcium phosphates are used extensively as biomaterials for promoting bone growth and improving the fixation of bone to dental and orthopaedic devices. Calcium phosphates were introduced in the early 1980's, and are used as implants today, however more work is being conducted to produce a higher quality coating. Due to the low mechanical strength, it has been used as a filler material or a coating. Initially, hydroxyapatite was the desired material for application in coatings due to its compositional similarity to the inorganic phase of bone, but thermal decomposition during processing has produced various unexpected chemical phases. It has become necessary to expand the collection of characterization techniques to fully describe the nature of the coating and ensure a good quality coating.
A transfer of analysis techniques from thermal spray science, minerology and chemistry have been necessary to achieve a more detailed description of the coating. Characterisation is necessary for powder synthesis and preparation, coating production, and analysis of histological sections and retrieved prostheses. The latter mentioned stages require more analysis techniques for a full characterization. Techniques incorporate structural, compositional, chemical phase, microstructural, strength and dissolution assessment methods. This paper will outline the characteristics that are addressed at each characterisation stage and list the different techniques that are presently used in industry. The additional analysis requirements that still need to be developed to completely describe the coating will be described.

抄録全体を表示

Microporous ceramic-like materials can be obtained at low temperature (4 to 50 °C) from aqueous suspensions of nanocrytsalline apatite. They were associated with organic macromolecules (albumin, casein, gelatin) and their Young's modulus was determined by ultrasonic transmission technique. Young's modulus of the composites with gelatin and albumin were higher than that of mineral blocks with the same maturation time whereas casein-apatite associations gave weaker Young's modulus. This different behavior was attributed to variations in the porosity of the materials. Such associations may have potential applications as biomaterials.

抄録全体を表示

Calcium deficient hydroxyapatite with Ca/P atomic ratio comprised between 1.5 and 1.667 were densified by hot pressing. Hot pressed powders were transformed into hydroxyapatite-tricalcium phosphate biphasic ceramics. After hot pressing at 1200°C, fracture strength remained below 100MPa, this was explained by the allotropic transformation β→α of TCP above 1150°C. Ceramics hot pressed at 1100°C had a fracture strength of 150 MPa when the composition contained between 8 wt% and 12 wt% of β-TCP. For lower or higher β-TCP content the strength dropped. This proved the necessity of a precise determination of Ca/P ratio. Quantitative X-ray diffraction analysis allowed a better precision than wet chemical analysis with deviations below 0.005 on Ca/P values.

抄録全体を表示

Needle-like apatite crystals were formed on pure titanium plate by a hydrothermal-electrochemical method at 100-200°C in an electrolyte containing calcium and phosphate ions. The width and length of the apatite needles increased with the electrolyte temperature. The aspect ratio of the apatite decreased with it. Pure titanium plates with the hydrothermal-electrochemically coated apatite at 100-200°C were soaked in a simulated body fluid from 3 to 27 weeks at 37°C. After soaking, the changes in weight of the specimens were measured, and the surfaces of the specimens were characterized. The specimens having fine apatite needles formed at 100°C showed the largest weight gain due to the deposition of the carbonate containing apatite having low crystallinity.

抄録全体を表示

Constant composition methods have been used to investigate the mechanisms of crystal growth and dissolution of calcium phosphate minerals. Interfacial tensions between water and each of these surfaces were calculated from measured contact angles using surface tension component theory. The interfacial tension values, -4.2, 4.3, 10.4 and 18.5 mJm^-2 for dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP), hydroxyapatite (HAP) and fluorapatite (FAP), respectively, compare well with those calculated from dissolution kinetics experiments and provide information concerning the growth and dissolution mechanisms. The much smaller interfacial tensions of OCP and DCPD in contact with water compared with those of HAP and FAP support the observation that the crystallization of the latter phases was often preceded by the formation OCP and DCPD and that both OCP and DCPD could serve as precursors to apatite growth. In addition, the ability of a surface to nucleate mineral phases is closely related to the magnitude of the interfacial energies which are also important in understanding stability of calcium phosphate colloidal dispersions.

抄録全体を表示

A number of materials have shown to be capable of inducing apatite formation in metasatble calcium- and phosphate-containing solutions known as simulated body fluids (SBFs). All these apatite inducers have a great number of acidic hydroxyl groups on their surfaces that include SiOH, TiOH and COOH. A hypothesis is thus proposed that a material could induce apatite formation when there are a large number of acidic OH groups present on its surface. These acidic OH groups could be introduced in the material via sol-gel processing routes and/or generated on the surface of a material as a result of its interaction with the solutions. The knowledge has been applied to develop a new process of growing an apatite film on titanium implants for enhancement of their fixation in bone.

抄録全体を表示

Organised Molecular Systems have been used to control the synthesis of calcium phosphate, through to the role of surfactant molecules at the mineral-organic interface. The influence of various parameters on the nature of the solid obtained has been examined: nature of the oil, type of surfactant, (Ca/P)r atomic ratio in the reactants, and also ageing. This method of synthesis allows the size and the morphology to be controlled and nanometric crystals to be obtained.

抄録全体を表示

Spherical particles of cattle bone-originated apatites (r-HAp) were prepared by a consecutive procedure as dissolution-precipitation, spray-drying, and heat-treatment processes. The r-HAp particles obtained had effective pore structures for liquid chromatographic separation of the five proteins such as bovine serum albumin, myoglobin from horse skeletal muscle, ribonuclease A from bovine pancreas, lysozyme from chicken egg white, and cytochrome c from horse heart. The adsorption surface functions of the particles for the liquid chromatography were designed by optimizing the spray-drying conditions using a two fluid-nozzle and heat-treatment temperatures. The column packed with the r-HAp particles gave high resolution and excellent durability for the five proteins-separation because of no change in the pore size distribution curves even after more than sample injection of 300 times.

抄録全体を表示

The effect of ultrasonic vibration on the particle size distribution of hydroxyapatite chemically precipitated from eggshells and H₃PO₄, or alternatively from calcium acetate and Na₃PO₄?12H₂O, was evaluated. For the case of hydroxyapatite aqueous suspensions with pH>10, with no particle-dispersing agent added, the average particle size decreased from 40 to 3μm in five minutes by employing an ultrasonic power of 61.75 watts and a frequency of 20 KHz.

抄録全体を表示

On dynamic calcination of synthetic apatites in air-SO₂ flow up to 750-900 °C formation of CaSO₄ and Ca₂P₂O₇, and at 800-950 °C, a reaction between them with the formation ofβ-Ca₃(PO₄)₂ and partial evolvement of SO₂ takes place. The amount of SO₂ bound and evolved depends on the composition of the apatite.

抄録全体を表示

The use of calcium phosphate hydraulic cements for conditioning radioactive elements, such as Sr⁹⁰, seems very interesting. The strontium was incorporated in various amounts in the liquid phase (0-10% weight). After hardening, the cement is formed by a poorly crystallized strontium calcium apatite. The incorporation of Sr in the apatitic lattice was evidenced by the correlation between the amount of Sr and the crystalline state, the (002) diffraction line shift and the thermal decomposition. This thermal decomposition (> 600°C) leads to stoichiometric and stable apatites. Mechanical properties increases with Sr % weight.

抄録全体を表示

The bond nature of a (NaPO₃)_n-containing basic refractory material was investigated versus the heating temperature. At room temperature, the raw binder (NaPO₃)n was shown to contain an average of 15 units per chain leading to a binding gel formation when the refractory material is added with water. As the raw mix temperature increases, the gel converts into a mixed sodium calcium phosphate phase stable in the temperature range [500-1000°C]. Beyond 1100°C, the mixed sodium calcium phosphate reacts with intergranular silicate phases. It transforms, then, into a mixed sodium calcium silicophosphate solid solution. This high temperature silicophosphate bond exhibits a lower decomposition kinetic than that of the mixed sodium calcium phosphate which decomposes, at low temperature, into β-NaCaPO₄ and Ca₅(PO₄)₃OH.

抄録全体を表示

The release and the retention of radon-222, from sedimentary phosphate in which it is formed, is studied in this paper.
Radon emanation parameters were determined in the temperature range 20-900°C. The heat treatment may be regarded as having two effects: an immediate effect (radon release) and a long term effect (retention of radon).
Radon degassing rate and radon emanating power, corresponding bulk to those effects, were measured.
Structural stability of apatite was maintained during heat treatment and an expansion of apatite lattice with increasing temperature was observed.
A linear relation between radon emanation and density multiplying specific surface area.

抄録全体を表示

Porous hydroxyapatite (HAp) films were formed on α-Al₂O₃ substrate by spray-pyrolysis technique, using starting solutions with the Ca/P ratios of 0.50 and 3.00. The crystalline phase of the resulting films was mainly HAp; the films were porous and the thickness was ~30 μm. Even after Scotch tape (#810) was adhered to the films and then taken off from the substrates, the films were still present on the substrate. The biocompatibility of the α-Al₂O₃ coated with HAp was examined using osteoblastic cells (MC3T3-E1). The cells on the α-Al₂O₃ coated with HAp were proliferated in a similar manner to the case of control (dish for cell culture) and the α-Al₂O₃ substrate without HAp coating; the alkaline phosphatase (ALP) activity of the cells cultured on the α-Al₂O₃ coated with HAp for 21 days showed the highest value among the examined specimens.

抄録全体を表示

The present work has been undertaken to compare the effect of maturation and chemical treatments by CO₃^2- and F^-- ions on the crystallinity and the electrical properties of a synthetic poorly crystallised carbonate-apatites. The tendency of these materials to crystallise during maturation or following F^- treatment was accompanied by improvement of their ionic conductivity, while a decrease of the crystallinity caused by CO₃^2- ions occurred with reducing of the conductivity. Frequency dependant ionic conductivity was either attenuated gradually during maturation and rapidly succeeding F^- treatment or accentuated following CO₃^2- treatment. These results were explained by the short-range organisation of sites with time, and by occurrence of structural order or disorder in back of chemical treatments.

抄録全体を表示

The purpose of this work was to study the conditions of synthesis of octacalcium phosphate. During the process of synthesis, reactant addition time of the calcium acetate solution to the ammonium dihydrogenophosphate solution as well as the reaction temperature were found to be determinant on the composition of the final solid. Synthesis performed with pH 5 and at a constant temperature of 60°C, DCPD (CaHPO₄·2H₂O) was obtained for addition times of the calcium solution between 30min and 1h30min and OCP (Ca₈H₂(PO₄)₆·5H₂O) was obtained for addition times superior to 2h without exceeding 5h. Synthesis performed with pH 5 and at a constant addition time of the calcium solution (2h45min), DCPD (CaHPO₄·2H₂O) was obtained at temperatures below 60°C, OCP (Ca₈H₂(PO₄)₆·5H₂O) was found at temperatures in the range of 60 to 80°C, and HAp (Ca₅(PO₄)₃(OH)) was obtained above 80°C.

抄録全体を表示

Calcium phosphate growth on phosphorus ion implanted titanium substrate was studied. Phosphorus ions were implanted into titanium substrates with an acceleration energy of 45 KeV and in amounts of 1x10¹⁶-3x10¹⁷ ion/cm². After immersion in SBF solution, calcium phosphate was formed on the phosphorus ion implanted titanium substrate. The implanted phosphorus ions reach a depth of 200-300 nm from the surface and phosphorus ions do not exist on the surface as a result of ion implantation as revealed using AES. So implanted phosphorus ions do not participate in the calcium formation. The surface oxide of titanium grew up to 100nm and was covered by hydroxyl group in SBF solution. Calcium or phosphate ions in SBF solution can be adsorbed by the oxide surface. The deposition of calcium phosphate involves adsorption of calcium or phosphate ions leading to an elevation of the calcium or phosphate ions which in turn must accelerate the formation of calcium phosphate.

抄録全体を表示

Lanthanum phosphate powders were synthesised from precipitation using three different routes. Depending on synthesis conditions, these powders have the monoclinic structure of monazite (LaPO₄) or the hexagonal structure of rhabdophane (LaPO₄,0.5H₂O). Chemical analysis gave a La/P ratio of about 0.9. Rhabdophane phase remained stable up to 650°C and transformed into monazite at higher temperature.

抄録全体を表示

CaO-SiO₂ amorphous powder were coated with calcium phosphate in order to apply the coated powder as an adsorbent, which has large surface area and various adsorption sites. The coating of the amorphous powder, which was 0.5μm in particle size, led to be the formation of low-crystalline HAp powder that has the particle size of 20μm. The morphology of the coated powder was independent of the compositions in core powders but would depend on only the Ca²⁺ and PO₄^3- concentrations in coating solutions.

抄録全体を表示

Fixation of orthopedic titanium implants to living bone is one of keys to achieve a successful result but still developing. Enhancement of bone formation around the implants can make a contribution to long-term stable fixation. In this study, spherical HAP ceramics (φ400-500μm) were implanted in the surface of cylinder shape pure titanium by the loading up to 1 kN at 1173 K to enhance bone formation around the implant. By this method, the spherical HAP ceramics were mechanically held on the surface of the pure titanium.

抄録全体を表示

Colloidal Ca₁₀(PO₄)₆(OH)₂ (CaHAP) particles doped with Ti(IV) ions in different atomic ratios, Ti/(Ca+Ti) = X_Ti, by a coprecipitation method were characterized by TEM, UV, FTIR, XPS and ICP. The photocatalytic activity of the modified CaHAP particles was confirmed by acetaldehyde decomposition. Ca(II) ions of CaHAP were substituted by Ti(IV) ions in one to one at X_Ti ≤ 0.1. When doped at X_Ti > 0.1 irregular particles of amorphous titanium phosphate were formed besides long rectangular particles of CaHAP. X_Ti of the surface phase of the particles was much less than that of the whole particle; Ti(IV) is less contained in the surface phase than the bulk one. UV absorption took place on Ti(IV)-doped CaHAP particles but not on unmodified particles. The decomposition of acetaldehyde by Ti(IV)-doped particles under UV irradiation was detected, while the unmodified CaHAP particles was inactive for the reaction.

抄録全体を表示