Accelerated transformation of brushite to octacalcium phosphate in new biomineralization media between 36.5 °C and 80 °C

This study investigated the hydrothermal transformation of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO₄·2H₂O) into octacalcium phosphate (OCP, Ca₈(HPO₄)₂(PO₄)₄·5H₂O) in seven different newly developed biomineralization media, all inspired from the commercial DMEM solutions, over the temperature range of 36.5 °C to 90 °C with aging times varying between 1 h and 6 days. DCPD powders used in this study were synthesized in our laboratory by using a wet-chemical technique. DCPD was found to transform into OCP in the Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^?, Cl^? and H₂PO₄^? containing aqueous biomineralization media in less than 72 h at 36.5 °C, without stirring. The same medium was able to convert DCPD into OCP in about 2 h at 75–80 °C, again without a need for stirring. Samples were characterized by using powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM).     

Ribbon-like and rod-like hydroxyapatite crystals deposited on titanium surface with electrochemical method

Homogeneous coatings were attained by electrochemical method in electrolytes containing Ca²⁺ and PO₄³⁻ ions with Ca/P ratio being 1.67. SEM observation showed that the hydroxyapatite (HAp,Ca₁₀(PO₄)₆(OH)₂) crystals prepared with higher concentration electrolyte (4 × 10^− 2 M Ca²⁺) are ribbon-like with thickness of nanometer size, a morphology seldom reported previously. In an electrolyte of lower concentration (6 × 10^− 4 M Ca²⁺), the HAp crystals formed are rod-like with a hexagonal cross section and diameter of about 70–80 nm. XRD patterns and IR spectra confirmed that the coatings consist of HAp crystals. TEM micrographs and SAD indicated that the longitude direction for both ribbon-like and rod-like crystal is [002], and the flat surface of the ribbon is (110). HRTEM showed that the ribbon-like crystal is a mixture of HAp and octacalcium phosphate (OCP, Ca₈H₂(PO₄)₆.5H₂O).     

Brushite (CaHPO4·2H2O) to octacalcium phosphate (Ca8(HPO4)2(PO4)4·5H2O) transformation in DMEM solutions at 36.5 °C

The purpose of this study was to investigate the transformation of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO₄·2H₂O) powders at 36.5 °C in DMEM (Dulbecco's Modified Eagle Medium) solutions. Two sets of brushite powders with different particle shapes were synthesized to use in the above DMEM study. The first of these brushite powders was prepared by using a method which consisted of stirring calcite (CaCO₃) powders in a solution of ammonium dihydrogen phosphate (NH₄H₂PO₄) from 6 to 60 min at room temperature. These powders were found to consist of dumbbells of water lily-shaped crystals. The second one of the brushite powders had the common flat-plate morphology. Both powders were separately tested in DMEM-immersion experiments. Monetite (DCPA, CaHPO₄) powders were synthesized with a unique water lily morphology by heating the water lily-shaped brushite crystals at 200 °C for 2 h. Brushite powders were found to transform into octacalcium phosphate (OCP, Ca₈(HPO₄)₂(PO₄)₄·5H₂O) upon soaking in DMEM (Dulbecco's Modified Eagle Medium) solutions at 36.5 °C over a period of 24 h to 1 week. Brushite powders were known to transform into apatite when immersed in synthetic (simulated) body fluid (SBF) solutions. This study found that DMEM solutions are able to convert brushite into OCP, instead of apatite.     

Study on the behaviour of ZnCoCu alloy electroplating

Ternary zinc–cobalt–copper alloys of wide range composition were deposited on to steel substrates from dilute metal sulphate bath. The bath consisted of 1–20 g dm⁻³ CuSO₄·5H₂O, 1–30 g dm⁻³ CoSO₄·7H₂O, 1–50 g dm⁻³ ZnSO₄·7H₂O, 20 g dm⁻³ Na₂SO₄ and 150–200 g dm⁻³ NH₂CH₂COOH. The effect of bath composition, current density and temperature on the cathodic potential, cathodic current efficiency and composition of the deposits were investigated. The codeposition of ZnCoCu alloys from these solutions can be classified as regular. Increasing current density enhances the rate of Zn deposition but suppresses that of Cu deposition. However, increasing the bath temperature favours Cu deposition. Co content in the deposits is hardly affected by changing these variables. Increasing Cu content in the bath or increasing the applied current density greatly improves the cathodic efficiency for the alloy deposition. X-ray diffraction studies showed that the deposits obtained at high current density (Zn-rich alloy) consisted of a cubic CuZn₂ phase, while that obtained at high temperature (Cu-rich alloy) consisted of a face, centred cubic CuCo phase. The structure and morphology of the deposited alloys were characterised by anodic stripping and SEM.     

Characterization of M(H2PO4)2·2H2O (M = Mn,Co, Ni) and their in situ thermal decomposition by magnetic measurements

It has been established that M(H₂PO₄)₂·2H₂O (M = Mn, Co, Ni) are paramagnetics between 173 and 353 K with weak antiferromagnetic exchange interaction between the metal ions. In situ magnetic measurements during the thermal decomposition of the salts show that the oxidation state and the octahedral coordination of M²⁺ are preserved. From the data obtained it could be supposed that in M(H₂PO₄)₂·2H₂O (M = Co, Ni) this process is topotactic with no long-range diffusion transport. In Mn(H₂PO₄)₂·2H₂O, the formation of the large variety of intermediate products probably requires more drastic rearrangement and diffusion of the manganese ions during the complex transformations, which reflect on both the value and the sign of the θ constants. M₂P₄O₁₂ (M = Mn, Co, Ni), which are the final decomposition products of the corresponding dihydrogen phosphates are paramagnetics in the temperature range of 295–573 K with antiferomagnetic interactions between the metal ions. The lattice parameters of Ni(H₂PO₄)₂·2H₂O have been calculated. It crystallizes in the monoclinic system with a = 7.228(1) Å; b = 9.778(1) Å; c = 5.306(1) Å; β = 94.50(1)°, SG P2₁/n with Z = 2.     

Effect of solvent ratio on the properties of highly oriented sprayed fluorine-doped tin oxide thin films

Transparent conducting thin films of F:SnO₂ have been deposited onto preheated glass substrates by a spray pyrolysis technique using pentahydrate stannic chloride (SnCl₄·5H₂O) and ammonium fluoride (NH₄F) as precursors and mixture of water and propane-2-ol as solvent. The concentration of SnCl₄·5H₂O and NH₄F is kept fixed and the ratio of water and propane-2-ol solvent in the spraying solution is varied. A fine spray of the source solution using air as a carrier gas has grown films of thickness up to 995 nm. Optical absorption, X-ray diffraction, Van der Pauw technique for measurement of a sheet resistance and Hall effect measurements at room temperature for determination of carrier density and conductivity have been used. The as-deposited films are of polycrystalline SnO₂ with a tetragonal crystal structure and are preferentially having orientation along the (200) direction with texture coefficient as high as 6.16. The average grain size for the as-deposited sample is found to be of the order of 44 nm. The films have moderate optical transmission (up to 70–85% at 550 nm). The figure of merit (ϕ) values vary from 1.95 · 10^− 3 to 35.68 · 10^− 3 Ω^− 1. The films are heavily doped, degenerate and exhibit n-type electrical conductivity. The lowest sheet resistance (R_s) for the optimized sample is 5.1 Ω. The films have a resistivity of 5.43 · 10^− 4 Ω cm and mobility around 7.38 cm² V^− 1 s^− 1.     

Solid-phase crystallization of spray-dried glucose powders: A perspective and comparison with lactose and sucrose

The solid-phase crystallization growth kinetics of spray-dried sugar powders, including glucose, lactose and sucrose, have been studied from water-induced crystallization experiments at a relative humidity of 75% and temperatures from 15 to 40 °C on amorphous powders of these sugars produced in a laboratory-scale spray dryer (Buchi B290). All results have shown that the enthalpies and Gibbs Free Energies of activation of the sugars studied here increase during the crystallization process, suggesting that the binding energy needed for the formation of an activated complex increases as the moisture content decreases. The enthalpies of activation for glucose, lactose and sucrose crystallization have been compared by the Activated Rate equation and found to be 58 ± 8 kJ mol⁻¹, 39 ± 2 kJ mol⁻¹ and 68 ± 4 kJ mol⁻¹, for glucose, lactose and sucrose, respectively, Similarly, the entropies of activation have been calculated as −92 ± 27 J mol⁻¹ K⁻¹, −156 ± 6 J mol⁻¹ K⁻¹ and −60 ± 5 J mol⁻¹ K⁻¹ for glucose, lactose and sucrose, respectively. These different numerical values may be expected from the different structures of the sugars.     

High-rate performance of xLiFePO4·yLi3V2(PO4)3/C composite cathode materials synthesized via polyol process

xLiFePO₄·yLi₃V₂(PO₄)₃/C composite cathode materials were synthesized via a polyol process, using LiOH·H₂O, Fe₃(PO₄)₂·8H₂O, V₂O₅ and H₃PO₄ as raw materials, citric acid and PEG as carbon sources, and TEG as both a solvent and a reductant. Structural and morphological characterizations of as-prepared materials were carried out by X-ray diffraction (XRD) as well as scanning electron microscopy (SEM), respectively. Furthermore, electrochemical properties of as-prepared materials were analyzed by charge–discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). XRD results indicated that the composites consisting of an olivine phase of LiFePO₄ and a monoclinic phase of Li₃V₂(PO₄)₃ are well-crystallized. It is found that the LF_0.6P·LV_0.4P/C composite exhibited better electrochemical performance than pristine LFP/C and LVP/C at 5 C and 10 C rate and delivered 126 mAh g^?1 and 110 mAh g^?1, respectively. The favorable particles morphology with less than 100 nm size and low extent agglomeration is believed as a factor. In addition, the co-existence of V³⁺-doped LiFePO₄/C and Fe²⁺-doped Li₃V₂(PO₄)₃/C was supposed as another reason.     

Synthesis of LiFePO4/C doped with Mg2+ by reactive extrusion method

Reactive extrusion method is used to synthesizing LiMg_xFe_1−xPO₄/C, using LiOH⋅H₂O, FeC₂O₄⋅2H₂O, P₂O₅ and nano-MgO as raw materials and glucose as carbon source. Samples are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), TG–DTA analysis and electrochemical performance test. Results show that amorphous product can be achieved after the reactive extrusion process. The particle size increases with the increase of magnesium content. Appropriately Mg²⁺ doping can reduce the electrode polarization effectively without seriously effect on material structure and morphology. LiMg_0.04Fe_0.96PO₄/C, showing the best electrochemical performances, has an initial discharge capacity of 155, 148, 140 and 137 mA h g⁻¹ at 0.2 C, 0.5 C, 1 C and 2 C rate, respectively. The discharge capacities remain above 99% after 20 cycles.     

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.     

Spectroscopic evaluation of Zn(PO3)2:Dy3+ glass as an active medium for solid state yellow laser

A spectroscopic investigation of zinc phosphate glass activated with 1.0, 5.0 and 10.0 mol% of Dy(PO₃)₃ is performed through absorption and luminescence spectra and decay times to study its potentialities for yellow laser operation upon excitation at 399 nm, which fits to the requirements of GaN LEDs. In the 1.0 mol% Dy(PO₃)₃-doped glass a quantum efficiency of 80 ± 5% was estimated for the dysprosium ⁴F_9/2 level luminescence, the ⁴F_9/2 → ⁶H_13/2 yellow emission shows greater intensity than the ⁴F_9/2 → ⁶H_15/2 blue emission, as well as a very high optical gain, which might make this glass phosphor a promising gain medium for solid state yellow laser pumped by GaN LEDs.     

Hydrothermal synthesis and indication of room temperature ferromagnetism in CeO2 nanowires

Bundle of CeO₂ nanowires have been successfully synthesized by a simple hydrothermal process using Ce(NO₃)₃·6H₂O as cerium source and NaH₂PO₄·2H₂O as mineralizer, into which no surfactant or template was introduced. The synthesized nanowires were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy and magnetization measurements. The XRD results indicated that CeO₂ nanowires have fluorite structure. Magnetization measurements indicate that CeO₂ nanowires exhibit room temperature ferromagnetism with remanent magnetization (M_r) and coercivity (H_C) of about 7.44 × 10^? 4 (emu/g) and 27.19 Oe, respectively, which may results due to the presence of defects in the CeO₂ nanowires.     

Photocatalytic decolorization of methylene blue dye by Ag3PO4–AgX (X = Cl−, Br− and I−) under visible light

Three kinds of Ag₃PO₄–AgX (X = Cl⁻, Br⁻ and I⁻) were prepared by the co-precipitation method between AgNO₃ and Na₂HPO₄ + KX (X = Cl⁻, Br⁻ and I⁻) solutions. Their photocatalytic activities were also investigated by decolorization of a methylene blue solution. Under visible light irradiation, photocatalytic decolorization of the dye using Ag₃PO₄–AgX as photocatalyst could occur by interaction between a hole in the valence band of the photocatalyst and the methylene blue dye molecules as it cannot detect the emission of 7-hydroxylcoumarin. AgCl and AgBr induce the Ag₃PO₄ to increase its photocatalytic decolorization efficiency. On the other hand, the compound Ag₃PO₄–AgI also showed a high adsorption for methylene blue in the dark.     

Oxygen-deficient ammonium vanadate for flexible aqueous zinc batteries with high energy density and rate capability at −30 °C

Aqueous zinc batteries (AZBs) have received significant attention owing to environmental friendliness, high energy density and inherent safety. However, lack of high-performance cathodes has become the main bottleneck of AZBs development. Here, oxygen-deficient NH₄V₄O_10−x·nH₂O (NVOH) microspheres are synthesized and used as cathodes for AZBs. The experimental test and theoretical calculations demonstrate that the oxygen vacancies in the lattice lower the Zn²⁺ diffusion energy barrier, which enables fast Zn²⁺ diffusion and good electrochemical performance in a wide temperature range. The suppressed side reactions also can help to improve the low temperature performance. NVOH shows a high energy density of 372.4 Wh kg⁻¹ and 296 Wh kg⁻¹ at room temperature and −30 °C, respectively. Moreover, NVOH maintains a 100% capacity retention after 100 cycles at 0.1 A g⁻¹ and ∼94% capacity retention after 2600 cycles at 2 A g⁻¹ and −30 °C. Investigation into the mechanism of the process reveals that the capacity contribution of surface capacitive behaviors is dominant and capacity attenuation is mainly caused by the decay of diffusion-controlled capacity. Furthermore, flexible AZBs can steadily power portable electronics under different bending states, demonstrating its great potential in wide-temperature wearable device.     

Preparation and characterization of hydroxyapatite synthesized from oyster shell powders

The ready availability and the low cost of oyster shells, which is composed predominantly of calcium carbonate with rare impurities, along with natural wastes are attractive features for converting the biological material into hydroxyapatite (HA) powders for biomedical applications. The HA powder was synthesized using oyster shell powders and dicalcium phosphate dihydrate (CaHPO₄·2H₂O, DCPD) through ball milling and subsequently heat treatment. The HA was initiated through sintering the 1-h milled sample at 1000 °C for 1 h, while pure HA phase is formed after sintering the 10-h milled sample. The as-prepared samples, obtained after 5 or 10 h of milling and then heat-treating at 1000 °C for 1 h, contain the phase of β-tricalcium phosphate (β-TCP). Moreover, the result of FTIR analysis showed that the as-prepared HA sample is A- and B-type carbonate-containing calcium phosphates. The as-synthesize HA powder containing trace elements Mg and Sr exhibited good crystallinity (96.3%) and high phase-purity.     

Microwave-assisted hydrothermal synthesis of zinc oxide particles starting from chloride precursor

Zinc oxide (ZnO) was synthesized using a microwave assisted hydrothermal (MAH) process based on chloride/urea/water solution and under 800 W irradiation for 5 min. In the bath, Zn²⁺ ions reacted with the complex carbonate and hydroxide ions to form zinc carbonate hydroxide hydrate (Zn₄CO₃(OH)₆·H₂O), and the conversion from Zn₄CO₃(OH)₆·H₂O to ZnO was synchronously achieved by a MAH process. The as-prepared ZnO has a sponge-like morphology. However, the initial sponge-like morphology of ZnO could change to a net-like structure after thermal treatment, and compact nano-scale ZnO particles were finally obtained when the period of thermal treatment increased to 30 min. Pure ZnO nanoparticles was obtained from calcination of loose sponge-like ZnO particles at 500 °C. The analysis of optical properties of these ZnO nanoparticles showed that the intensity of 393 nm emission increased with the calcination temperature because the defects were reduced and the crystallinity was improved.     

A universal electrolyte for the plasma electrolytic oxidation of aluminum and magnesium alloys

The plasma electrolytic oxidation (PEO) of aluminum and magnesium alloys is carried out in electrolytes which contain the same reactants, but in fundamentally different concentrations. In this research the possibility of the PEO of aluminum and magnesium alloys in a universal electrolyte is studied. The two most commonly encountered alloys, namely, aluminum alloy 5052 and magnesium alloy AZ91D, are chosen. The oxide layers obtained are studied using SEM, EDX, XRD, and a microhardness tester. The corrosion properties are determined using a potentiostat. The effect of variation of the silicate concentration in the electrolyte on the growth kinetics of the coating and its qualitative characteristics is discussed. It is shown that at Na₂SiO₃·5H₂O concentrations in the electrolyte ranging from 3.2 to 32 g l^− 1, the rate of growth of the oxide layer increases from 15 to 55 μm h^− 1 with significant variation of the phase composition of the coating. The greatest hardness of an oxide ceramic layer was obtained in the outer sublayer on the magnesium alloys (874.7 HV₁₀) and in the inner sublayer on the aluminum alloys (1123 HV₁₀). The most favorable combination of physical and chemical properties for both alloys is obtained in an electrolyte containing 12.72 g l^− 1 Na₂SiO₃·5H₂O.     

Chemical synthesis and stabilization of magnesium substituted brushite

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) is the most ubiquitous calcium phosphate phase used in implant coatings and more recently in gene/drug delivery applications due to its chemical stability under normal physiological conditions (37 °C, pH ～ 7.5, 1 atm.). However, different calcium phosphate phases, such as brushite (CaH(PO₄)?2(H₂O)) and tricalcium phosphate (Ca₃(PO₄)₂) which are thermodynamically unstable under physiological conditions are also being explored for biomedical applications. One way of stabilizing these phases under physiological conditions is to introduce magnesium to substitute for calcium in the brushite lattice. The role of magnesium as a stabilizing agent for synthesizing brushite under physiological conditions at room temperature has been studied. Chemical analysis, Fourier transform infrared spectroscopy and X-ray diffraction have also been conducted to validate the formation of magnesium substituted brushite under physiological conditions.     

Crystal structure,thermal analysis and IR spectrometric investigation of l-tyrosine hydrazide diphosphate monohydrate

The monoclinic crystal structure of (C₉H₁₅N₃O₂)₂P₂O₇·H₂O denoted DLTHDP [a = 14.626(1), b = 6.1990(2), c = 14.562(1) Å, β = 97.289(3)°, Z = 2, monoclinic P2₁, D_cal = 1.508, D_mes = 1.49 g cm⁻³] has been solved using direct methods and refined to a reliability factor R = 4.37% for 2079 independent reflections. The DLTHDP structure can be described by infinite polyanions [P₂O₇·H₂O]_n⁴ⁿ⁻ organized in chains parallel to the b-direction and located at z = 1/2, alternating with organic cations associated in ribbons spreading along the a-direction. Multiple hydrogen bonds originating from amine, hydroxyl groups and water molecules donors [NH…O(N) and O(W)H…O] connect the different components of the lattice. The IR data of DLTHDP is reported and discussed according to the theoretical group analysis and by comparison with IR results of similar compounds. The coupled thermogravimetric analysis (TGA)–differential thermal analysis (DTA) thermal study shows the departure of one water molecule, confirming the hydrated character of this compound.     

Synthesis of green-emitting (Gd,La, Tb)2O(WO4)2 phosphors

Green-emitting (Gd_1−x−yLa_xTb_y)₂O(WO₄)₂ (0 ⩽ x ⩽ 0.05, 0.05 ⩽ y ⩽ 0.15) phosphors were synthesized in a single phase form by the conventional solid-state reaction method, and their photoluminescent properties were characterized. The (Gd_1−x−yLa_xTb_y)₂O(WO₄)₂ phosphors showed strong and broad excitation bands from 230 to 350 nm, corresponding to the energy transition from the 4f⁸ to 4f⁷5d configuration of Tb³⁺ and the charge-transfer (CT) transition of O²⁻−W⁶⁺. The oxytungstate phosphors exhibited typical emission peaks assigned to the transition from ⁵D₄ to ⁷F_J (J = 6, 5, 4, and 3) of Tb³⁺, and the luminescence emission intensity was effectively enhanced by the La³⁺ doping into the host Gd₂O(WO₄)₂ lattice. The highest green emission intensity was obtained for (Gd_0.87La_0.03Tb_0.10)₂O(WO₄)₂, where the relative emission intensity was 63% that of a commercial green-emitting (La_0.52Ce_0.31Tb_0.17)PO₄ phosphor.