Synthesis of calcium phosphate powder from calcium lactate and ammonium hydrogen phosphate for the fabrication of bioceramics

A calcium phosphate powder has been synthesized from aqueous 0.25, 0.5, and 1.0 M calcium lactate and ammonium hydrogen phosphate solutions atat a Ca/P = 1, without pH adjusting. According to X-ray diffraction data, the as-synthesized powder consisted of brushite (CaHPO₄ · 2H₂O) and octacalcium phosphate (Ca₈(HPO₄)₂(PO₄)₄ · 5H₂O). After heat treatment in the range 500–700°C, the powders were gray in color because of the destruction of the reaction by-product. The powders heat-treated in the range 500–700°C consisted largely of γ-Ca₂P₂O₇. The ceramics prepared from the synthesized powders by firing at 1100°C consisted of β-Ca₂P₂O₇ and β-Ca₃(PO₄)₂.     

Synthesis of M(NpO<Subscript>4</Subscript>)<Subscript>2</Subscript>·<Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O (M = Mg,Ca, Sr,Ba) Using Н<Subscript>3</Subscript>ВО<Subscript>3</Subscript> Solutions and Properties of These Salts

Two procedures for preparing the compounds M(NpO₄)₂·nH₂O (M = Mg, Ca, Sr, Ba) using boric acid were suggested. In the first procedure, samples of freshly prepared salts M₃(NpO₅)₂·nH₂O (M = Ca, Sr, Ba) are treated with excess 0.5 M H₃BO₃ with vigorous stirring. In the process, the initially light green salts rapidly transform into black products of the general composition M(NpO₄)₂·nH₂O. In the second procedure, a measured volume of a Np(VII) solution with a known LiOH concentration was added to excess 0.5 M H3BO3 solution containing a calculated amount of Mg, Ca, Sr, or Ba nitrate. The reaction yields black precipitates of the same compounds as in the previous case. After washing with water and drying in an oxygen stream, the final products contain a small impurity of Np(VI). The IR spectra suggest that the compounds obtained are structurally related to the previously studied salts MNpO₄ (M = K–Cs), i.e., in their lattices there are neptunium–oxygen layers built of NpO₂³⁺ cations and bridging O atoms. New data on the properties of the compounds M₃(NpO₅)₂·nH₂O with M = Ca, Sr, and Ba were also obtained.     

Morphologies and properties of NiO particles prepared from NiSO<Subscript>4</Subscript>·6H<Subscript>2</Subscript>O and Ni(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>·6H<Subscript>2</Subscript>O by spray pyrolysis

Nickel oxide particles were prepared by spray pyrolysis of aqueous solutions of NiSO₄·6H₂O and Ni(NO₃)₂·6H₂O. In spray pyrolysis reactor hollow salt particles initially formed were collapsed by decomposition to reduce their size. For NiSO₄·6H₂O less hollowness of the primitive particles and its higher decomposition temperature made the oxide particles highly spherical with very smooth surface. On the other hand the particles prepared from Ni(NO₃)₂·6H₂O were so hollow and fragile with rough surface since they were formed on the liquid pool of the salt melt. The particle size decreased with the furnace set temperature while increased with the initial salt concentration. Single oxide particle was composed of many small nuclei without sintering whose size varied with the rate of decomposition. The crystallinity of the particles increased with both temperature and the initial salt concentration. Preliminary drying in diffusion dryer fixed the size of the oxide particles from NiSO₄·6H₂O at that of the primitive particles, independent of the temperature. However, by the preliminary drying the particles from Ni(NO₃)₂·6H₂O became more hollow and fragile, whose sizes decreased with the temperature.     

Formation of nanoscale tungsten oxide structures and colouration characteristics

In this work, pH dependent evolution of tungsten oxide (WO₃) nanostructures is being reported along with physical characteristics. The synthesis was carried out via an inexpensive solvothermal cum chemical reduction route, with sodium tungstate (Na₂WO₄) and cetyl trimethyl ammonium bromide (C₁₉H₄₂NBr) as main reactants. The X-ray diffraction, together with transmission electron microscopic studies have revealed formation of regular polyhedral nanocrystalline structures and fractals as one goes from higher pH (= 5·5) to lower pH (= 2) values. The average crystallite size, as calculated through Williamson–Hall plots, was varied within 2·8–6·8 nm for different pH samples. Fourier transform infrared spectroscopy reveals in-plane bending vibration δ (W–OH), observable at ∼1630 cm^− 1 and strong stretching ν (W–O–W) located at ∼814 cm^− 1. Raman spectroscopy has divulged WO₃ Raman active optical phonon modes positioned at ∼717 and 805 cm^− 1. The thermochromic and photochromic properties of the nanoscale WO₃ sample prepared at pH = 5·5, are also highlighted.     

Exploration of the structural,spectroscopic and thermal properties of double sulfate monohydrate NaSm(SO4)2·H2O and its thermal decomposition product NaSm(SO4)2

Samarium-sodium double sulfate crystalline hydrate NaSm(SO₄)₂·H₂O was obtained by the crystallization from an aqueous solution containing equimolar amounts of ions. The anhydrous salt of NaSm(SO₄)₂ was formed by a thermally induced release of the equivalent of water from NaSm(SO₄)₂·H₂O. The kinetic parameters of thermal decomposition were determined (E_a = 102 kJ/mol, A = 9·10⁶). The crystal structures of both compounds were refined from the X-ray powder diffraction data. Sulfate hydrate NaSm(SO₄)₂·H₂O crystallizes in the trigonal symmetry, space group P3₁21 (a = 6.91820(3) and c = 12.8100(1) Å, V = 530.963(7) ų). The anhydrous salt crystallizes in the triclinic symmetry, space group P-1 (a = 6.8816(2), b = 6.2968(2) and c = 7.0607(2) Å, α = 96.035(1), β = 99.191(1) and γ = 90.986(1)°, V = 300.17(1) ų). The vibrational properties of compounds are mainly determined by the sulfate group deformations. The luminescence spectra of both sulfates are similar and are governed by the transitions of samarium ions ⁴G_5/2 → ⁶H_J (J = 5/2, 7/2, 9/2 and 11/2). The anhydrous sulfate is stable up to 1100 K and undergoes an almost isotropic expansion when heated. After 1100 K, the compound decomposes into Sm₂(SO₄)₃ and Na₂SO₄.     

The preparation and growth of pure single crystals of K2Pt(CN)4Br0.3·3H2O and K2Pt(CN)4Cl0.3·3H2O

The preparation of pure single crystals of K₂Pt(CN)₄Br_0.3·3H₂O and K₂Pt(CN)₄Cl_0.3·3H₂O has been investigated. Crystals with reproducible d.c. conductivity and dielectric constants were obtained only when the mixed valence platinum salt contained one halide. The bromide complex was particularly susceptible to contamination by chloride, and a preparation scheme is presented which excludes the unwanted halide. The best quality crystals were grown by slow evaporation of solutions which were 1 molar in urea and 0.1 molar in the appropriate potassium halide.     

Phases of variable composition in crystallization of cesium phosphomolybdate

Cesium phosphomolybdate crystallizes from nitric acid solutions in the form of compounds with variable composition Cs _x H_3?x PO₄ · 12MoO₃ · nH₂O (x = 0.8?3.0). Irrespective of the x value, the crystals have invariable cubic body-centered lattice differing in the structure from the known ammonium salt. This cesium compound at x = 0.8?2.8 is very poorly soluble in acidic solutions: less than 0.2 mg Cs per liter. When cesium and ammonium ions are simultaneously present in the solution, crystallization results in the formation of a solid solution of cesium in ammonium phosphomolybdate, of ammonium in cesium phosphomolybdate, or of a mixture of these phases, depending on the conditions.     

Lithium borosulphate glasses: an analysis of glass transition temperature results

Lithium borosulphate glasses have been prepared in three different series: (a) (42·5 −x)Li₂O:57·5 B₂O₃:xLi₂SO₄; (b) 42·5Li₂O: (57·5 −x)B₂O₃:xLi₂SO₄ and (c) 42·5Li₂O:57·5B₂O₃:xLi₂SO₄. The glass transition temperature (T _g) of these glasses has been analysed on the basis of the fraction of four coordinated boron which governs the glass structure. The analysis reveals that the addition of Li₂SO₄ in series (a) and (b) gives rise to increased value of N₄ whereas, in series (c) it increases the number of non-bridging oxygens.     

Synthesis of bipyramidal gold nanoparticle-[C60]fullerene nanowhisker composites and catalytic reduction of 4-nitrophenol

The seed solution was prepared by dissolving hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), trisodium citrate dihydrate (C₆H₅Na₃O₇·2H₂O), and sodium borohydride (NaBH₄) in distilled water. The resulting reddish-purple seed solution was stirred for 3 h at room temperature. The growth solution was prepared by mixing hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), cetyltrimethylammonium bromide (CTAB, (C₁₆H₃₃)N(CH₃)₃Br), silver nitrate (AgNO₃), hydrochloric acid (HCl), and ascorbic acid (C₆H₈O₆) in distilled water. Subsequently, 100 μL of this seed solution was transferred into 10 mL of the growth solution. The mixed solution was maintained at 30 °C for 3 h to obtain a solution of bipyramidal gold nanoparticles. The bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were synthesized by applying the liquid-liquid interfacial precipitation (LLIP) method to a saturated solution of C₆₀ in toluene, the solution of bipyramidal gold nanoparticles, and isopropyl alcohol. The prepared bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of these composites was confirmed in the reduction of 4-nitrophenol by UV-Vis spectroscopy.     

Magneto-dielectric effect in Pb(Zr0·52Ti0·48)O3 filled nanoporous Ni 0 ·5Zn 0 ·5Fe 2 O 4 composite

Nanoporous Ni_0·5Zn_0·5Fe₂O₄ particles of diameter, ~ 9·5 nm, were synthesized by citric acid assisted thermal decomposition in an autoclave. The BET surface area measured was 80 m² g^???1 and the average pore diameter was 2·5 nm. By soaking the particles in a suitable precursor solution and then subjecting them to a heat treatment at 923 K for 3 h, Pb(Zr_0·52Ti_0·48)O₃ was grown within the nanopores. X-ray and electron diffraction studies confirmed the presence of both these phases. The nanocomposites showed ferromagnetic behaviour over the temperature range 2–300 K. No ferroelectric hysteresis loop could be found which was consistent with the earlier theoretical prediction of loss of ferroelectricity below a critical thickness of 2·4 nm. Good magneto-dielectric response of the order of 7% at a magnetic field of 9 kOe was recorded for the present system. This is believed to arise due to a negative magnetostriction coefficient of Ni_0·5Zn_0·5Fe₂O₄ which exerted a compressive strain on Pb(Zr_0·52Ti_0·48)O₃ thereby lowering the tetragonality in its crystal structure.     

Synthesis of Zn/Co/Fe-layered double hydroxide nanowires with controllable morphology in a water-in-oil microemulsion

The Zn/Co/Fe-layered double hydroxide nanowires were synthesized via a reverse microemulsion method by using cetyltrimethyl ammonium bromide (CTAB) /n-hexane/n-hexanol/water as Soft-Template. ZnSO₄, CoSO₄, Fe₂(SO₄)₃ and urea were used as raw materials. The influence of reaction temperature, time, urea concentration and Cn (molar ratio of cetyltrimethyl ammonium bromide to water) on the structure and morphology of Zn/Co/Fe-layered double hydroxides was investigated. The samples were characterized using Transmission Electron Microscopy (TEM), Inductively Coupled Plasma (ICP), X-ray Diffraction (XRD) and Infrared Absorption Spectrum (IR). The results indicate that higher temperature is beneficial to the formation of layered double hydroxides, but particles apart from nanowires could be produced if temperature is up to 120 °C. By varying the temperature, reaction time, urea concentration and Cn, we got the optimum conditions of synthesizing uniform Zn/Co/Fe-layered double hydroxide nanowires: 100 °C, more than 12 h, Cn: 30–33, urea concentration: 0.3 M.     

Influence of halide ions on inhibitive performance of cetyl trimethyl ammonium bromide in various concentrations of phosphoric acid for cold rolled steel

The influence of chloride ions on inhibitive performance of cetyl trimethyl ammonium bromide (CTAB) in 1.0-4.0 M of phosphoric acid (H₃PO₄) for cold rolled steel has been studied using weight loss and Tafel polarization techniques. The effect of acid concentration on corrosion inhibition and the effectiveness of inhibitors at 1.0-4.0 M of H₃PO₄ have been examined. The results reveal that a synergistic effect has been observed for CTAB with NaCl at each acid concentration. In 1.0 M H₃PO₄, the polarization curves show that the complex is a mixed-type inhibitor.     

Piezoelectric properties,hysteresis behaviour and dielectric properties of PMN-PZT ceramics

Ferroelectric and piezoelectric properties ofxPb(Mg_1/3Nb_2/3)O₃−(1−x)Pb (Zr_0·55Ti_0·45)O₃ system have been investigated. X-ray diffraction patterns indicate rhombohedral and cubic structures. Maximum dielectric constant and piezoelectric properties are exhibited by 0·5–0·5 PMN-PZT composition.P _r is high in 0·6–0·4 PMN-PZT composition.     

Characterization,dielectric and electrical behaviour of BaTiO3 nanoparticles prepared via titanium(IV) triethanolaminato isopropoxide and hydrated barium hydroxide

A new sol-precipitation technique for the preparation of nano BaTiO₃ crystallite has been developed by reacting 0·2 M each of Ti(IV) triethanolaminato isopropoxide and hydrated barium hydroxide in methanol such that the molar ratio of Ba : Ti is 1·02 at 80 °C under stirring (1200 rpm) for one hour in alkaline media using tetra methyl ammonium hydroxide (TMAH). It was calcined at 100 °C for 12 h. Structural and compositional properties were investigated by XRD, SEM, EDX, TEM, SAED and DLS techniques. FT–IR and TG–DTA were used to characterize its purity and the thermal stability. The BaTiO₃ particles prepared were found to be spherical, homogeneous and cubic in structure. The particle size was found to be 23–31 nm. The dielectric constant and dissipation factor after sintering at 400 °C were 5379 and 0·63, respectively at 100 Hz frequency. The a.c. conductivity (σ _a.c.) was found to be 2 × 10^–5 S-cm^–1 at room temperature (30 °C). It increased with increasing temperature up to 50 °C and decreased with further increase in temperature. The impedance was 3·37 × 10⁵ ohms at room temperature. It decreased with increasing frequency.     

Evolution and temperature dependence of ZnO formation by high power sonication

The sonochemical reaction between varying concentrations of zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and hexamethylenetetramine (C₆H₁₂N₄) in a 150 W dual transducer sonicator resulted in different phases of zinc compounds. Single phase zinc oxide (ZnO) was exclusively obtained in the case of 0.05 M. By tracking the products synthesized at 50 °C, zinc hydroxide (Zn(OH)₂) was formed in the first 40 min and replaced by ZnO after prolonged sonication. Zn(OH)₂ was also present in a mixed phase with ZnO when the reagent concentration was reduced to 0.01 M. The increase in the synthesis temperature up to 80 °C reduced defects and free radicals but introduced zinc hydroxide nitrate hydrate (Zn₅(OH)₈(NO₃)₂(H₂O)₂) which is a dominant phase from the reaction between highly concentrated reagents (0.1 M). High temperature and sonication power in this system tend to cause agglomerations into irregular microparticles.     

Quaternary co-electrodeposition of the Cu2ZnSnS4 films as potential solar cell absorbers

Cu₂ZnSnS₄ (CZTS) films are successfully prepared on Mo substrate by electrochemical epitaxial method. An electrolyte contains 0.124 M CuSO₄·5H₂O, 0.14 M ZnSO₄, 0.13 M SnCl₂·2H₂O, 0.16 M Na₂S₂O₃·5H₂O, 2.25 M NaOH, 1.36 M C₆H₅Na₃O₇, 1.00 M C₄H₆O₆. The equilibrium potential for quaternary co-electrodeposited solution is set at ?1.1 ～ ?1.20 V. The results show that elements are deposited in the following sequence: Cu/S/Zn/S/Cu/S/Sn/S…. The ternary and quaternary compounds are formed with the increasing temperature during annealing. Finally the CZTS film can be well formed at 550 °C. The resistivity of CZTS is about 5.6 × 10⁴ Ω cm.     

Sodium alginate incorporated with magnesium nitrate as a novel solid biopolymer electrolyte for magnesium-ion batteries

Solid biopolymer electrolytes have gained much attention in recent years. Due to their various advantages, it can be used in advanced electrochemical devices. The present study focuses on synthesizing and characterizing natural solid biopolymer electrolytes that consist of sodium alginate as the host polymer and magnesium nitrate (Mg(NO₃)₂.6H₂O) as the ionic dopant via solution casting technique. X-ray diffraction analysis of prepared solid biopolymer electrolytes validates the increase in the amorphous nature as salt concentration increases. The interaction and the complexation between the host biopolymer and the magnesium salt are confirmed by Fourier transforms infrared spectroscopy. The solid biopolymer electrolyte composition of 40 M wt.% NaAlg:60 M wt.% Mg(NO₃)₂·6H₂O possesses optimum ionic conductivity value of the order of 4.58?×?10^?3 S cm^?1 as observed by the AC impedance spectroscopy analysis at room temperature. The glass transition temperature (T_g) of the prepared solid biopolymer electrolytes has been studied using differential scanning calorimetry. Linear sweep voltammetry study reveals that the highest magnesium ion-conducting membrane has electrochemical stability of 3.5 V. Further, an optimum ionic conducting solid biopolymer membrane (40 M wt.% NaAlg:60 M wt.% Mg(NO₃)₂·6H₂O) has been utilized to fabricate a primary magnesium ion conducting battery. The open circuit voltage of the proposed solid biopolymer membrane is 1.93 V, and the performance of the battery has been studied.

     

YBa2SnO5·5, a novel ceramic substrate for YBCO and BiSCCO superconductors

YBa₂SnO_5·5 has been synthesized and sintered as single phase material for its use as substrate for both YBCO and BiSCCO superconductors. YBa₂SnO_5·5 has a complex cubic perovskite (A₂BB’O₆) structure with the lattice constanta = 8·430 Å. The dielectric constant and loss factor of YBa₂SnO_5·5 are in a range suitable for its use as substrate for microwave applications. YBa₂SnO_5·5 is found to be chemically compatible with both YBCO and BiSCCO superconductors. The thick film of YBCO screen printed on polycrystalline YBa₂SnO_5·5 substrate gave aT _c(0) of 92 K and a critical current density (J _c) of 4 × 10⁴ A/cm² at 77 K. A screen printed BiSCCO thick film on YBa₂SnO_5·5 substrate gaveT _c(0) = 110 K and current density 3 × 10³ A/cm² at 77 K.     

Formation and stabilization of Pickering emulsions using salt-sensitive core–shell cationic nanoparticles

Pickering emulsions known for their solid emulsifiers and brilliant stability characters have attracted many researchers’ attention. The controlled stability and demulsification of emulsion are necessary in some cases such as crude oil extraction and drug release. Stimuli-responsive Pickering emulsion could provide suitable controllability and emerged in the last decade. Among various controllable factors, salt ion is known as a critical parameter, but it is rarely investigated. Here, core–shell cationic nanoparticles with a poly-(2-aminoethyl methacrylate hydrochloride) shell and a polystyrene core were used in the preparation of Pickering emulsion. The size and morphology of nanoparticles were monitored by transmission electron microscopy and dynamic light scattering. The microstructure and stability of the formed Pickering emulsion were studied via dynamic light scattering and a polarizing optical microscope under various salt ion types and concentrations. The effect of salt types (Cl^?, ClO₄^?, and PO₄^3?) and salt concentrations on the Pickering emulsion was investigated. Cl^?, ClO₄^?, and PO₄^3? are in situ generated from NaCl, NaClO₄, and (NaPO₃)₆, respectively. It showed that PO₄^3? (100–1000 mM) was unable to form stable Pickering emulsion, while Cl^? and ClO₄^? could induce stable Pickering emulsions under optimized conditions. Furthermore, after increasing the salt concentration over a critical salt concentration, the Pickering emulsion underwent rapid demulsification. This work revealed the effects of salt on size, conformation, charge, wettability, interaction, and adsorption state of nanoparticles and proposed the stability mechanisms of the Pickering emulsion. This opened up more potential applications in the field of controlled demulsification, petroleum recovery, catalyst recovery, and so on triggered by salt ions.

Graphical abstract

Salt could affect the size, conformation, and interaction of core–shell cationic nanoparticles, which then affect the formation mechanism and stability properties of Pickering emulsions from them.