Study of the solid-liquid equilibria in the LiPO3-Y(PO3)3 binary system

The LiPO₃-Y(PO₃)₃ system has been studied for the first time. Microdifferential thermal analysis (μ-DTA), infrared spectroscopy (IR) and X-ray diffraction were used to investigate the liquidus and solidus relations. The only new compound observed within this system is LiY(PO₃)₄, melting incongruently at 1104 K. An eutectic appears at 4±1 mol% Y(PO₃)₃ at 933 K. LiY(PO₃)₄ crystallizes in the monoclinic system C_2/c with a unit cell: a=16.201(4) Å, b=7.013(2) Å, c=9.573(2) Å, β=125.589(9)°, Z=4 and V=884.5 Å³, which is isostructural to LiNd(PO₃)₄. The infrared absorption spectrum indicates that this salt is a chain polyphosphate.     

Microwave driven hydrothermal synthesis of Ba1−xSrxTiO3 nanoparticles

Ba_1−xSr_xTiO₃ (BST) nanopowders with composition x = 0.1-0.4 have been prepared using microwave driven hydrothermal synthesis (MDHS). A low temperature process has been chosen in order to avoid high temperature heat treatment leading to particle growth and agglomeration. MDHS method allows obtaining the nanocrystalline powder samples during relatively short period of time (10 min) and therefore MDHS was optimized. In case of the phase evolution studies the XRD measurements were performed. The average size of crystallites was estimated using Scherrer equation. TEM and SEM images were taken for the detailed analysis of the grain size, surface and morphology.     

Ammonium hydrogen difluoride induced fluorination of hydroxyapatite

Ammonium hydrogen difluoride (NH₄HF₂) was used as a fluorinating agent for the fluorination of hydroxyapatite. The process was carried out at room temperature by pH cycle method, at 80 °C by reflux method and at 900 °C by solid state reaction. The products obtained in all the three methods were analyzed by powder XRD and FT-IR techniques to confirm fluorination. FT-IR spectra showed the decrease in the intensity of ‘OH’ stretching band at 3571 cm⁻¹ and complete disappearance of ‘OH’ bending band at 632 cm⁻¹. Appearance of a new peak at around 740 cm⁻¹ (due to the formation of .H-F. bond) was observed in all the spectra. Similarly, powder XRD patterns exhibited higher angle shift in 2θ values of high intense peaks associated with (300), (112) and (211) planes when compared to parent hydroxyapatite. Both the structural and spectroscopic analyses confirmed partial fluorination of hydroxyapatite.     

Preparation of irregular mesoporous hydroxyapatite

An irregular mesoporous hydroxyapatite (meso-HA), Ca₁₀(PO₄)₆(OH)₂, is successfully prepared from Ca(NO₃)₂·4H₂O and NH₄H₂PO₄ using surfactant cetyltrimethyl ammonium bromide (CTAB) as template. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) results reveal that the positive head of CTAB is assembled on the surface precipitated HA and much NH₄⁺ is enclosed in precipitated HA before calcination. Field scanning electron microscope (FSEM) reveals that there exist many interconnected pores throughout the HA reticular skeleton. Nitrogen adsorption–desorption experiment exhibits a mesoporous material type IV curve, and pore size distribution calculated from the desorption branch of the isotherms based on Barrett–Joyner–Halenda (BJH) model shows that most pores throughout the HA reticular skeleton are sized at about 40 nm, but the pores are not uniform on the whole, owning to decomposition of the “organic” CTAB templating structures and ammonium salt enclosed in the precipitated HA. The specific surface area of irregular meso-HA is calculated to be 37.6 m²/g according to the Brunauer–Emmett–Teller (BET) equation. Moreover, after polylactic acid/meso-HA (PLA/meso-HA) composites degraded 12 weeks in normal saline at 37 °C, the interconnected pores throughout the HA skeleton were enlarged and sized in micron degree, which resemble trabecular bone structure very much.     

Formation and structure of zinc-substituted calcium hydroxyapatite

Zn-substituted Ca hydroxyapatites were synthesized by precipitation method under the specific conditions (pH 8, 90 °C) and their structural properties were investigated. The substituting limit of Zn was estimated at about 15 mol%. The lattice parameter a decreased up to 5 mol% Zn, and started to increase over 5 mol% Zn. The lattice parameter c monotonously decreased with increase in Zn fraction. The increase in lattice parameter a for higher Zn fraction was ascribed to increasing amount of lattice H₂O which substituted for OH sites in the apatite structure. The lattice H₂O in the Zn-substituted apatites was lost by the heat treatment at 400 °C. As a result, both the lattice parameters a and c of the heat-treated apatites decreased with increasing Zn fraction. Only the difference in ionic radius between Zn²⁺ (0.074 nm) and Ca²⁺ (0.099 nm) was decisive to the change in both lattice parameters after the heat treatment at 400 °C.     

Stabilization of γ-La2S3 by alkali metal ion doping

La₃S₄ is known to crystallize in a defect cubic Th₃P₄ structure. The effect of alkali metal ion doping in the lacunar La_3−xS₄ structure has been studied. Compounds with molecular formula La_3−xA_xS₄ (A = Li, Na and K) with varying A/La ratios (0.1, 0.15, 0.2, 0.25 and 0.3) have been synthesized by gas-solid reaction method. The band gap increases with increase in dopant concentration. The optical properties show an increase in yellowness of the doped compositions when compared to the parent phase.     

Phase transformation of calcium phenyl phosphate in calcium hydroxyapatite using alkaline phosphatase at body temperature

Layered calcium phenyl phosphate ((C₆H₅PO₄)_0.92(HPO₄)_0.08Ca·1.3H₂O: CaPP), which is composed of a multilayer alternating bimolecular layer of phenyl groups and amorphous calcium phosphate phase, was treated in aqueous media including different amounts of enzyme such as alkaline phosphatase (ALP) at pH = 9.6 and 37 °C for 48 h. Treating the CaPP in the absence of ALP took place only the dissolution of this material. When the CaPP particles were treated in the presence ALP, calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂: Hap) was formed. The yielded Hap contained no phenyl group and the molar ratio Ca/P of this material was 1.66, almost corresponding to 1.67 of the stoichiometric Ca/P ratio of Hap. TEM observation revealed that the irregular-shaped CaPP particles disappeared and rod-shaped Hap nano-particles were generated. The particle length and crystallite size of Hap were slightly increased on increasing the additive amount of ALP. These facts allow us to infer that the CaPP particles are dissolved, hydrolyzed and recrystallized to Hap by treating with ALP in aqueous media at body temperature of 37 °C and that the ALP plays as a catalyst for hydrolysis of phenyl phosphate ions. This phase transformation of CaPP in Hap in the presence of ALP resembles to the formation mechanism of Hap in animal organism.     

Magnetic properties of nano-clusters lanthanum chromite powders doped with samarium and strontium ions synthesized via a novel combustion method

A novel approach to synthesize a single-phase orthorhombic perovskite lanthanum chromite LaCrO₃ clusters doped with Sm³⁺ and Sr²⁺ ions via gel combustion route was reported. The producing materials were synthesized using metal nitrates as oxidizers and triethanol amine (TEA), N-butyl amine (NBA) or ethylene diamine (EDA) as a fuel. The effect of the annealing temperature, type of organic fuel and the variation of the samarium and/or strontium substitution and its impact on crystal structure, crystallite size, microstructure and magnetic properties of the LaCrO₃ powders formed was systematically studied. The results revealed that a well crystalline single phase of pure LaCrO₃ can be achieved at annealing temperature from 800 to 1000 °C for 2 h. Moreover, each organic carrier materials exhibited a different degree of effectiveness in the synthesis of the mixed oxide powders. The crystal structure was influenced by doped Sm³⁺ and/or Sr²⁺ ions. The crystallite size of the produced powders was increased with the increase the annealing temperature, increasing the Sm³⁺ ion and the decrease of Sr²⁺ ion substitution. The microstructures of the produced powders were found to be nanoclusters octahedra-like shaped. The saturation magnetization of the LaCrO₃ powders increased continuously with an increase in the Sm³⁺ ion concentration and it decreased with an increase in the Sr²⁺ ion up to 0.3 at annealing temperature of 1000 °C for 2 h. The maximum saturation magnetization (0.279 emu/g) was achieved at the Sm³⁺ ion molar ratio 0.3 and annealing temperature 1000 °C. Moreover, wide coercivities can be obtained at different synthesis conditions (49.25 to 522  Oe).     

Synthesis and characterization of reduced transition metal oxides and nanophase metals with hydrazine in aqueous solution

Reduction of the first row (3d) transition metal complexes in aqueous solution using hydrazine as the reducing agent has been investigated systematically. Nanoscale reduced metal oxides such as VO₂(B), Cr₂O₃ were obtained through hydrazine reduction followed by proper thermal treatments. Nanocrystalline γ-Mn₂O₃ was synthesized directly through aqueous phase reduction at room temperature. Nanoclusters of cobalt, copper and the one-dimensional single crystal nickel nanowhiskers were synthesized by direct reduction without post-annealing process. All the products were characterized on their structure and micro-morphology. The reaction details and features were described and discussed.     

A solvothermal synthesis of ultra-fine iron phosphide

Powder iron phosphide (FeP) has been prepared via a benzene-thermal synthesis with the reaction of anhydrous iron chloride (FeCl₃) and sodium phosphide (Na₃P) at 180-190°C. The product was analyzed by X-ray photoelectron spectroscopy (XPS), and the results show the mole ratio of Fe:P is 1.12. X-ray diffraction (XRD) pattern can be indexed to the orthorhombic cell of FeP with the lattice constant a=5.191, b=3.101, and c=5.789 Å. Transmission electron microscope (TEM) images indicate that average particle size is about 200 nm in diameter.     

The growth of lanthanum phosphate (rhabdophane) nanofibers via the hydrothermal method

Hexagonal LaPO₄ (rhabdophane) nanofibers are synthesized and characterized. TEM images show that the synthesized LaPO₄ nanofibers are about 5-50 nm in diameter and up to several micrometers long. The morphologies of the product are strongly dependent on the pH value of the reaction solution.     

Synthesis and regulation of α-LiZnPO4·H2O via a solid-state reaction at low-heating temperatures

A simple and novel route for the synthesis of a lithium zinc phosphate hydrate, α-LiZnPO₄·H₂O, was studied, and the target product was obtained with LiH₂PO₄·H₂O and ZnCO₃ as raw materials and polyethylene glycol-400 (PEG-400) as a surfactant via a one step solid-state reaction at room temperature (25 °C). The product was characterized with X-ray powder diffraction (XRD), thermogravimetric analysis and the 1st derivativative of thermogravimetric analysis (TG/DTG) and Fourier transform infrared spectroscopy (FTIR). The comparison experimental results suggested that aging temperature controlled the products of the synthesis, that is, the α-LiZnPO₄·H₂O was formed when the reaction mixture was aged at room temperature, and the α-LiZnPO₄ was obtained when the reaction mixture was aged at 80 °C.     

Structure and Magnetic Properties of S-doped Mn_3O_4/S Composited Nanoparticles and Mn_3O_4 Nanoparticles

Composited nanoparticles,consisting of Mn3O4,S-doped Mn3O4 and S,were synthesized by co-precipitation reaction and Mn3O4 nanoparticles were then obtained after removing the pure S from the composited nanoparticles.The Mn3O4-type phase with larger lattice constant a was formed by doping sulfur.At fixed temperatures below Curie temperature(TC),the magnetization of the S-doped Mn3O4/S composited nanoparticles was smaller than that of the Mn3O4 nanoparticles.The blocking temperature was 36.3 and 34.8 K for Sdoped Mn3O4/S composite and Mn3O4 nanoparticles,respectively.The anisotropy field of S-doped Mn3O4/S composite was determined to be about 55.3 kOe.     

The calcium based fullerenoïd Ca33Bi22.7Al48O139.05: An enantiomorphic structure of strontium aluminate

The aluminate Ca₃₃Bi_22.7Al₄₈O_139.05, having an enantiomorphic structure from the first fullerenoid oxide Sr₃₃Bi_24.25Al₄₈O_141.375, has been isolated. The structure, solved by X-ray single crystal diffraction is built up from an aluminate framework made of AlO₄ tetrahedra connected through corners and forming a huge “Al₈₄O₂₁₀” sphere where the Al atoms are disposed like the carbon atoms in the C₈₄ fullerene. Difference between the Ca and Sr-phases lies in the composition and the structure of the [Bi_xO_y] cluster stuffing the aluminate sphere. In the Ca-phase, the cluster formulated “Bi_22.7O_45.05” can be ideally described as built up from BiO₆ octahedra, BiO₄L trigonal bipyramids and BiO₃L tetrahedra. The EDS chemical analyses reveal a large domain of cationic stoichiometry, as observed for the Sr-phase. The high resolution electron microscopy (HREM) images of regular zones are in good agreement with the images calculated from the single crystal structure.     

Disorder in layered hydroxides: synthesis and DIFFaX simulation studies of Mg(OH)2

Powder X-ray diffraction (PXRD) patterns of magnesium hydroxides precipitated under different conditions exhibit characteristic non-uniform broadening of Bragg peaks which cannot be explained merely on the basis of Scherrer broadening. The broadening is shown to arise due to interstratification and turbostratic disorder.     

High-pressure synthesis of a new calcium thioborate, CaB2S4

A new calcium thioborate, CaB₂S₄, was synthesized at high-pressure/temperature condition of 6.2 GPa and 800-1100 °C. The crystal structure was refined by the Rietveld method using powder X-ray diffraction data. The compound crystallizes into a cubic unit cell (a=11.210 Å, space group: Pa3), isostructural with a high-pressure polymorph of calcium borate, CaB₂O₄-IV. The unit cell consists of three-dimensional linkage of BS₄-tetrahedra, and calcium atoms have coordination number of 12.     

Fabrication and dissolution behavior of hollow hydroxyapatite microspheres intended for controlled drug release

Hollow hydroxyapatite (HA) microspheres were fabricated by a simple spray drying method in this study. Moreover, the dissolution behavior of these hollow HA microspheres after immersion in simulated body fluid (SBF) was also studied. The results indicated that the dissolution of the HA microspheres in SBF is not homogeneous in a layer-by-layer fashion but was preferential at different locations of the particle surface. Generically, dissolution preferentially occurs on the location with looser structure and high porosity of the microspheres. The degradable HA microspheres are expected to have potential applications in bone local drug delivery systems.     

Planar defects in layered hydroxides: Simulation and structure refinement of β-nickel hydroxide

Although nickel hydroxide can be obtained by various methods in a highly ordered form, this work shows that most such preparations are not free of stacking faults. The stacking faults belong to more than one type, which differ from one another in their structure as described by the local stacking sequence. The incidence of such residual stacking faults varies in the range 1-3% depending on the method of preparation.     

Synthesis of layered double hydroxides from eggshells

Ca-Al and Ca-Fe layered double hydroxides (LDHs) were successfully synthesized from chicken eggshells by an ultrasonic wave assistant method. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) techniques. XRD and TEM analyses showed that the 4Ca-Al LDHs were of high purity but other samples were not. The present study provides a simple, efficient and environmental friendly method to obtain LDHs from biowaste eggshells, in which additional alkaline solution is not required for synthesis. Moreover, eggshells provide all the requisite bivalent metal ions, which are needed to form layered double hydroxides.     

Synthesis and distribution of cations in substituted lead phosphate lacunar apatites

Synthesis of apatites, Pb_7.4Bi_0.3Na_2.3(PO₄)₆ (I), Pb_7.36Bi_0.32Na_2.08Li_0.24(PO₄)₆ (II) and Pb_5.78Bi_0.81Ca_0.60Na_2.81(PO₄)₆ (III), with anion vacancy were carried out during solid state reactions. The three compounds of apatite-type structure crystallize in the hexagonal system, space group P6₃/m. In every compound, a preferential occupation of the (6h) site by Pb and Bi cations is shown revealing the influence of their lone electronic pair. The introduction of calcium increases the quantity of bismuth in these apatites. Alkaline metals occupy mainly the (4f) site. Infrared spectroscopy is correlated to the bonding scheme. A connection between the cations occupying (4f) sites and the c cell parameters is presented.