Size-controlled preparation of α-calcium sulphate hemihydrate starting from calcium sulphate dihydrate in the presence of modifiers and the dissolution rate in simulated body fluid

Different-sized α-calcium sulphate hemihydrate (α-CSH) rods were hydrothermally prepared by converting calcium sulphate dihydrate at 110–140 °C in the presence of MgCl₂, sodium citrate (CANa), and sodium dodecyl benzene sulfonate (SDBS) as the modifiers. The α-CSH rods with the average diameters and the average lengths in the ranges of 2.6–5.2 and 17.5–33.1 μm, respectively, were tunably prepared. The presence of the modifiers favoured the formation of small-sized α-CSH rods. The effect of the modifiers on decreasing the diameters of α-CSH rods was in an order of SDBS > CANa > MgCl₂. The dissolution rates of the different-sized α-CSH rods prepared at 140 °C in simulated body fluid were in an order of α-CSH (CANa) > α-CSH (MgCl₂) > α-CSH (reference) > α-CSH (SDBS). The naked and small-sized α-CSH rods had high dissolution rates. The adsorption of SDBS on the surfaces of α-CSH rods decreased their dissolution rates.     

Co–Pt–W thin films electrodeposited from sulphate–gluconate baths

Co–Pt–W magnetic thin films were electrodeposited from gluconate baths. Electrochemical characterization (polarization behaviors and transient curves), microstructure and magnetic properties were investigated. It turned out that increase in gluconate concentration and bath pH shifted the deposition potential to more negative potentials. Microstructure of electrodeposited Co–Pt–W thin films was affected by the bath pH and gluconate concentration enormously. Samples obtained from Co–sulphate–gluconate at pH 8.0 and gluconate concentration 0.3 mol L^?1 exhibited single hcp phase with strong (0 0 1) PO. VSM and MFM measurement showed that perpendicular magnetic anisotropy occurred in the Co–Pt–W thin films prepared under these conditions.     

Controlled synthesis of gold nanosnakes assisted by poly(vinyl pyrrolidone)–sodium dodecyl sulphate aggregations

Anisotropic single-crystalline gold nanosnakes were synthesised in poly(vinyl pyrrolidone) (PVP)–sodium dodecyl sulphate (SDS) aggregation aqueous solution by reducing HAuCl₄ with PVP without any additional reducing agent. The crystal structures, growth process and the influence of SDS concentrations on the growth of gold nanosnakes have been investigated by X-ray diffraction and transmittance electron microscopy. In this approach, the peculiar structure of PVP–SDS aggregations is indispensable for the asymmetrical formation of gold nanosnakes. Without PVP–SDS aggregations, only long tortuous gold nanobelts were synthesised. When SDS concentration was increased from 3 to 10?mM, gold nanosnakes, nanokites and nanoplates were fabricated. To the best of our knowledge, this is the first report on the SDS-induced shape transformation from snake-like to plate-like at fixed low HAuCl₄ concentration in PVP–SDS aggregation aqueous solutions. Moreover, the gold nanosnakes exhibit excellent electrocatalytic property towards the oxidation of methanol indicating their potential applications in fuel cells, catalysis, biosensing and nanodevices.     

Synthesis of α-Fe2O3 via oxidative hydrolysis of iron(II) sulphate

The influence of the main reaction parameters (temperature, pH and concentration) in the oxidative hydrolysis of iron (II) sulphate in an acid medium on the properties of the obtained -Fe₂O₃ and its applicability in ferrite production has been studied. The addition of manganese(II) ions catalyses the process in the homogeneous phase, probably by activation of oxygen. The obtained results are discussed within the framework of the assumed reaction mechanism, which includes an homogeneous reaction and a heterogeneous one with the participation of the oxidative hydrolysis product -FeOOH.     

Corrosion resistance of Cr2O3-Al2O3 ceramics by molten sodium sulphate–vanadium pentoxide

This report describes an investigation of the hot corrosion resistance of Cr₂O₃-Al₂O₃ ceramics in V₂O₅-Na₂SO₄ molten salt. Adding Cr₂O₃ to Al₂O₃ improves the hot corrosion resistance of Al₂O₃ ceramics, and thickness of the damage zone depends on the sintering temperature and the Cr₂O₃ content. Corrosion of the Cr₂O₃-Al₂O₃ ceramics is caused by the formation of a liquid of the dissolved Na₂O-V₂O₅-(Al,Cr)₂O₃ system and by dissolution of the Cr₂O₃-Al₂O₃ ceramics into this liquid. The corrosion rate of the Cr₂O₃-Al₂O₃ ceramics becomes smaller than that of the Al₂O₃ ceramics because dissolution rate of grains into the liquid phase occurring in grain boundaries decreases, compared with the Al₂O₃ ceramics. If the sintering temperature is elevated, grain growth would occur to enhance the corrosion resistance of the ceramics.     

Effect of plating time on growth of nanocrystalline Ni–P from sulphate/glycine bath by electroless deposition method

Nanocrystalline nickel phosphorus (NC-Ni–P) deposits from sulphate/glycine bath using a simple electroless deposition process is demonstrated. In the present investigation, nanoporous alumina films are formed on the aluminium surface by anodization process followed by deposition of nickel onto the pores by electroless plating method. Anodic aluminium oxide surface was first sensitized and activated by using palladium chloride solution before immersing into the electroless nickel bath. Electroless nickel plating was carried out from the optimized bath by changing the deposition time from 20 to 1800 s at a constant temperature of 80 °C and a pH of 4·0. Surface morphology, elemental composition, structure and reflectance of the deposits have been analysed by using scanning electron microscopy, atomic force microscopy, energy dispersive X-ray analysis, X-ray diffractometry and UV-visible spectroscopic studies, respectively. Electroless nickel deposits formed at an early stage produces dense uniform nanocrystals containing higher percentage of atomic phosphorus with cubic Ni (111) structure. As the deposition time increased, nanocrystalline sharp peak became amorphous and dimension of the crystal size varied from 54 to 72 nm.     

Behaviour of α-Fe2O3 (hematite), prepared by oxidation precipitation of ferrous sulphate,on heating

The effects of heating-Fe₂O₃ (hematite) prepared by oxidation precipitation of ferrous sulphate, at temperatures up to 700° C were studied. It was found that, in the course of heating, losses of structurally-bound water occured, accompanied by the formation and removal of pores, the lattice constants changed and the optical properties were modified, an effect which is important from the standpoint of the use of hematite as ferric pigment. With increasing annealing temperature, the complementary wavelength was shifted to higher values and the spectral purity of the pigment colour was decreased.     

Electrochemical deposition of Ni–TiN nanocomposite coatings and the effect of sodium dodecyl sulphate surfactant on the coating properties

Ni–TiN nanocomposite coatings were prepared by using electrochemical deposition in a Watt’s bath containing TiN particles to increase the hardness of Ni. The effects of deposition current density, electrolyte agitation speed and the number of particles in the solution on the amount of incorporated particles in the coating process were investigated. The optimum deposition current density of 4 A dm^?2 and agitation speed of 450 rpm were obtained. The effect of sodium dodecyl sulphate (SDS) anionic surfactant on the amount of particles in the coatings was investigated. It was observed that the maximum amount of incorporated particles, with a value of 7.5% by volume, was created in the current density of 4 A dm^?2, stirring rate of 450 rpm, 30 g l^?1 TiN particles and in the presence of 0.6 g l^?1 SDS anionic surfactant.     

Synthesis and characterization of a new organic sulphate, [2,3-(CH3)2C6H3NH3]HSO4·H2O

Crystals of a new hybrid compound C₈H₁₂N⁺, HSO₄^?·H₂O were synthesized in aqueous solution and characterized by X-ray diffraction and IR absorption spectroscopy. This compound crystallizes in the orthorhombic non-centrosymmetrical space group P2₁2₁2₁ and an unit cell with a = 5.74(2) Å, b = 9.17(2) Å, c = 21.34(4) Å, V = 1124(6) Å³, and Z = 4. Its crystal structure is a packing of alternated inorganic and organic layers parallel to (a,b) planes. The different components are connected by a bi-dimensional network of strong OH…O and NH…O hydrogen bonds. Then, in order to detect phase transitions and watch changes in the conductivity behaviour, investigations by DTA–TG and differential scanning calorimetry (DSC) and electrical conductivity measurements were carried out.