Preparation, structure and solubility of Ca2KNa(PO4)2

Materials based on calcium alkali orthophosphate using for filling bone defects have been fabricated by means of solid state reaction method. The starting materials were selected from chemical reagents: CaHPO₄· 2H₂O, CaCO₃, Na₂CO₃, K₂CO₃and H₃PO₄(85%). After these materials were mixed stoichiometrically and dried at 200°C for 2 hours, the mixture was sintered in air at high temperature for 2 hours. The samples were characterized by X-ray diffraction. The results showed that the new materials contained only one crystal phase: Ca₂KNa(PO₄)₂, whether the sintering temperature was 1350 degrees C or higher if the material was designed as Ca₂KNa(PO₄)₂. Furthermore, the solubility was tested and it revealed that these materials containing Ca₂KNa(PO₄)₂had higher solubility than -TCP.     

Soft chemistry synthesis,structure and electrochemical characterization of iron phosphates Fe(H2PO4)3 and Fe(PO3)3

The iron phosphate, Fe(H₂PO₄)₃, was synthesized through a precipitation route by means of acidic media. As the compound is highly hygroscopic, the structure was solved ab initio by powder X-ray diffraction under nitrogen flow at room temperature and 200 °C. This phase is antiferromagnetic below 30 K. It converts into Fe(PO₃)₃ at 550 °C, after dehydration. Electrochemical characterizations, performed on the last compound, show irreversible decomposition into metallic iron.     

Crystallization and characterization of Na2(La,Me)Zr(PO4)3

Na₂(La, Me)Zr[PO₄]₃ (where Me=Co, Al, Cr) crystals have been grown by three methods: by chemical reaction; from highly concentrated phosphoric acid solutions; and by a hydrothermal technique. The advantages and disadvantages of each method to obtain these crystals have been discussed. Morphological, X-ray, chemical analysis and IR-spectral studies were performed on these crystals.     

Preparation and characterization of LiFe1/2Ni1/2VO4

A layered ceramic oxide, LiFe_1/2Ni_1/2VO₄ has been prepared using solid-state reaction technique. The preparation conditions have been optimized using thermogravimmetric analysis (TGA) studies. The formation of the material sample under the reported condition has been confirmed by X-ray diffraction (XRD) analysis. XRD analysis indicates the crystal structure to be orthorhombic with lattice parameter: a = 3.5637 Å, b = 17.7486 Å, c = 12.2884 Å. The phase morphology and surface properties studied using scanning electron microscopy (SEM), suggest a polycrystalline texture with reasonable number of the voids. Complex impedance analysis of the sample has indicated: (i) conduction due to bulk contribution at T ≤ 200 °C, (ii) the presence of grain boundary effects at T ≥ 200 °C, (iii) negative temperature coefficient of resistance (NTCR) behaviour and (iv) evidence of temperature dependent electrical relaxation phenomena in the sample. The DC conductivity (σ_DC) shows typical Arrhenius behaviour when observed as a function of the temperature. The activation energy value has been estimated to be 0.42 eV. σ_DC, as evaluated from complex impedance spectrum, shows a jump of nearly ∼4 orders of magnitude in the value at higher temperature when compared to that of the room temperature value. AC conductivity spectrum obeys Jonscher's universal power law. The results of σ_AC as a function of frequency are also discussed.     

无机溶胶-凝胶法制备B型和M型VO2粉体

以V2P5为原料,采用无机溶胶-凝胶法制备出V2O5粉体,在H2气氛下热处理得到了VO2(B)粉体,再在Ar气氛下热处理VO2(B)粉体,制备出了VO2(M)粉体.采用X射线衍射(XRD)、红外吸收光谱(IR)、差热分析(DTA)等方法对样品进行了成分和结构分析,结果表明,当热处理温度为500℃、H2浓度50%时,得到VO2(B)粉体;然后,在Ar气氛下分别经过550、600、650、700℃处理1h后,VO2由B型向M型转变,700℃处理成功制备出了VO2(M)粉体.     

Porous yolk-shell structured Na3(VO)2(PO4)2F microspheres with enhanced Na-ion storage properties

Na3(VO)2(PO4)2F(NVPOF)has been considered as one potential candidate for sodium-ion batteries because of its high operating voltage and theoretical capacity.However,the poor intrinsic electronic conductivity significantly restricts its widespread application.In response to this drawback,we adopt the optimization strategy of tuning the morphology and structure to boost the electrical conductiv-ity and mitigate the capacity fading.In this paper,NVPOF microspheres with unique porous yolk-shell structure were fabricated via a facile one-step solvothermal method for the first time.By monitoring the morphological evolution with time-dependent experiments,the self-sacrifice and Ostwald ripening mechanism from rough spheres to yolk-shell structure was revealed.Benefited from the favorable inter-woven nanosheets shell,inner cavity and porous core structure,the resulting NVPOF electrode exhibits superior rate capability of 63 mA h g-1 at 20 C as well as outstanding long-cycling performance with the capacity retention up to 92.1％over 1000 cycles at 5 C.     

Nucleation studies in supersaturated aqueous solutions of (NH4)H2PO4 doped with (NH4)2C2O4·H2O

Induction periods were measured for various supersaturated aqueous solutions of ammonium dihydrogen orthophosphate doped with ammounium oxalate monohydrate by the direct vision method. Various critical nucleation parameters were calculated based on classical theory for homogeneous crystal nucleation and the results reported and discussed. The critical nucleation parameters increased with increase in doping concentration.     

Hydrolysis of tetracalcium phosphate in H3PO4 and KH2PO4

The activity product of tetracalcium phosphate (TTCP, Ca₄(PO₄)₂O), was determined at 37°C, and the hydrolysis of TTCP was investigated in 0.01–0.1 mol l^–1 H₃PO₄ and KH₂PO₄ solutions by means of calcium and phosphorus analyses, X-ray diffraction and infrared analysis. The activity product, defined as K _sp=(Ca²⁺)⁴ (PO ₄ ^3– )² (OH^–)², was 37.36 as pK _sp, which was smaller than that previously reported (42.4). TTCP easily hydrolysed to form calcium-deficient apatite (Ca-def OHAp, Ca_5–x (HPO₄) _x (PO₄)_3–x (OH)_1–x ), or dicalcium phosphate dihydrate (DCPD, CaHPO₄2H₂O), depending on the initial phosphate concentration. With 0.1 mol l^–1 H₃PO₄, TTCP hydrolysed to form DCPD within several minutes. In 0.025 mol l^–1 H₃PO₄ and 0.1 mol l^–1 KH₂PO₄, TTCP hydrolysed to form Ca-def OHAp through DCPD. In the latter solution, a small amount of octacalcium phosphate (OCP, Ca₈(H₂PO₄)₂(PO₄)₄5H₂O), was detected as an intermediate product. In 0.025 mol l^–1 KH₂PO₄, TTCP hydrolysed directly to form Ca-def OHAp. In 0.01 mol l^–1 H₃PO₄, hydrolysis of TTCP was not completed, although Ca-def OHAp was only a product. Thus the final product and the degree of hydrolysis depended on the pH and the overall Ca/P ratio in the reaction system. The rate of Ca-def OHAp formation seemed to be controlled by the dissolution rate of TTCP rather than the crystallization rate of the OHAp.     

Preparation of Zn-doped β-tricalcium phosphate (β-Ca3(PO4)2) bioceramics

Pure β-tricalcium phosphate (β-TCP) and Zn-doped (600, 2900, 4100, 7000, 9300 and 10,100 ppm) β-TCP samples were prepared by using a wet chemical/coprecipitation synthesis technique, followed by calcination at 1000 °C in air. Precursor powders of the coprecipitation process were Ca-deficient nanoapatites (i.e., Ca/P molar ratio varying from 1.49 to 1.51) with needlelike but agglomerated particles of 30 nm thickness. In vitro culture tests performed by mouse osteoblast-like cells showed that the samples doped with 2900 to 4100 ppm Zn showed the highest cell viability (via Live/Dead counts), and with a further increase in the Zn-content towards 1 wt.% the number of dead cells in the well plates started to increase. Alkaline phosphatase (ALP) activity peaked for the β-TCP sample doped with 4100 pm Zn. The sample surface roughness, measured by non-contact profilometry, was also found to have an effect on the Live/Dead cell counts, and the highest cell viability encountered in this study corresponded to the surface with the least roughness.     

Crystal structure of a new organic dihydrogenomonophosphate (C6H8N3O)2(H2PO4)2

Chemical preparation, X-ray single-crystal, thermal behavior, and IR spectroscopy investigations are given for a new organic cation dihydrogenomonophosphate (C₆H₈N₃O)₂(H₂PO₄)₂ (denoted IAHP) in the solid state. This compound crystallizes in the orthorhombic space group P2₁2₁2₁. The unit cell dimensions are: a = 7.422(3) Å, b = 12.568(5) Å, c = 20.059(8) Å with V = 1871.1(13) Å³ and Z = 4. The structure has been solved using direct method and refined to a reliability R factor of 0.029. The atomic arrangement can be described as inorganic layers of H₂PO₄⁻ anions between which are located the organic groups (C₆H₈N₃O)⁺ through multiple hydrogen bonds.     

Low thermal expansion materials: a comparison of the structural behaviour of La0.33Ti2(PO4)3, Sr0.5Ti2(PO4)3 and NaTi2(PO4)3

Variable temperature neutron powder diffraction data have been used to examine the structural mechanism of unusual thermal expansion behaviour in La_0.33Ti₂(PO₄)₃ (LaTP). These data are compared to those we have recently reported for the related systems NaTi₂(PO₄)₃ (NaTP) and Sr_0.5Ti₂(PO₄)₃ (SrTP), which differ in the extent of occupation of the extra-framework MI (La, Sr, Na) cation sites. The root cause of the unusual behaviour is ascribed to the differing expansivities of the occupied and vacant MI sites. This leads to cooperative rotations of TiO₆ and PO₄ polyhedra, which can be used to quantify and rationalise the overall anisotropic thermal expansion behaviour.     

有机/无机杂化钙钛矿(C4H9NH3)2ZnCl4的制备与表征

合成了新型的有机/无机杂化钙钛矿（C4H9NH3）2ZnCl4,采用元素分析、红外光谱和X射线衍射对其结构进行了表征,结果表明这种材料具有规则的层状结构,有序性高,热分析结果表明（C4H9NH3）2ZnCl4在170℃的高温处存在一个固-固相转变。     

Visible light induced H2PO(4)(-) removal over CuAlO2 catalyst

The delafossite CuAlO₂ is successfully used for the visible light driven H₂PO₄⁻ reduction. It is prepared from the nitrates decomposition in order to increase the ratio of reaction surface per given mass. CuAlO₂ is a narrow band gap semiconductor which exhibits a good chemical stability with a corrosion rate of 1.70 μmol year⁻¹ at neutral pH. The flat band potential (+0.25 V_SCE) is determined from the Mott-Schottky characteristic. Hence, the conduction band, positioned at (−1.19 V_SCE), lies below the H₂PO₄⁻ level yielding a spontaneous reduction under visible illumination. The photocatalytic process is investigated under mild conditions and 30% conversion occurs in less than ∼6 h with a quantum efficiency of ∼0.04% under full light. The concentration decreases by a factor of 39% after a second cycle. The photoactivity follows a first order kinetic with a rate constant of 6.6 × 10⁻² h⁻¹. The possibility of identifying the reaction products via the intensity-potential characteristics is explored. The decrease of the conversion rate over illumination time is due to the competitive water reduction.