Synthesis of nanosized group IV borides in ionic melts of anhydrous sodium tetraborate

The preparation of nanosized Group IV metal diborides by reacting powdery titanium, zirconium, and hafnium with fine-grained boron in Na₂B₄O₇ ionic melts in the temperature range 600–850°C has been studied. Nanosized titanium, zirconium, and hafnium diborides are formed at temperatures of at least 750°C.     

Thermal decomposition of potassium tetraborate tetrahydrate to anhydrous potassium tetraborate in a fluidized bed

Production of anhydrous potassium tetraborate from potassium tetraborate tetrahydrate (PTT) was investigated in a controlled fluidized bed calcinatory (FBC). Single step calcination gives a puffed product with very low bulk density and the calcination of potassium tetraborate tetrahydrate is incomplete since agglomeration starts at temperature higher than 250 °C. Effect of the temperature on the bulk density of the product obtained at the end of single step is given and compared with theoretical calculation. In order to obtain anhydrous potassium tetraborate, dehydration should be carried out at least two stages. The most important step dominating the final bulk density is the first step. Dehydration of potassium tetraborate tetrahydrate up to 85% K₂B₄O₇ content and temperature lower than 150 °C in the first step gives commercial available product at final stage. As a result, both puffed and denser anhydrous potassium tetraborate of 99.5% purity with bulk density around 0.4 and 0.7 g cm⁻³ has been produced by two and three stage calcinations.     

Synthesis and vibrational analysis of new anhydrous oxochloroperchlorato complexes of titanium IV

Chlorine trioxide Cl₂O₆ added on an excess of TiCl₄ gives a series of anhydrous oxo-chloro-perchlorato complexes of titanium IV corresponding to the formula: Ti₆O₄Cl_x(ClO₄)_16−x. x increases with the molar ratio TiCl₄: Cl₂O₆ and reaction time. Infrared and Raman spectra of these compounds are consistent with polymeric structure containing bridging bidentate perchlorato groups stongly bonded to the metal.     

The analysis of anhydrous titanium trichloride

Titrimetric determinations of titanium and chloride were examined for their suitability in establishing the stoichiometry of titanium trichloride. Aluminium metal reduction of titanium(IV) to titanium(III) in aqueous sulphuric acid solution gave higher precision than the Jones Reductor procedure ; in both cases exceptional care was necessary before titration in order to prevent some reoxidation of reduced titanium by dissolved oxygen in the titrant. Deaerating the ferric alum titrant and delivering it under nitrogen made it possible to obtain a virtually complete titanium recovery. A convenient apparatus is described. A procedure is also described for the elimination of interference in the Volhard chloride determination due to the presence of high concentrations of titanium sulphate and of gelatin used for sample encapsulation.     

Synthesis of sodium titanium phosphate at ultra-low temperature

Powders of the Nasicon material NaTi₂(PO₄)₃ were directly synthesized at ultra-low temperature. NaTi₂(PO₄)₃ was obtained by mixing the initial reagents titanium hydroxide, 85 % H₃PO₄, and NaH₂PO₄·2H₂O at 85 °C for 3.5 h or at 125 °C for 1.5 h. The raw materials and synthesized products were characterized for purity, crystal structure, particle size, and powder morphology by thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), and UV–visible diffuse reflectance spectroscopy. XRD results revealed that NaTi₂(PO₄)₃ powders with rhombohedral crystal structure were synthesized at 85 and 125 °C. SEM patterns showed that the as-prepared products were agglomerated and that each of the agglomerations consisted of many small grains 50–80 nm in diameter.     

Corrosion of titanium diboride in molten FLiNaK(eut)

Pure and enriched titanium dibromide (TiB₂) samples (prepared by hot isostatic pressing) with different mole ratios of Ni and Ta were investigated in contact with molten eutectic salt (FLiNaK_(eut); LiF/NaF/KF 42.5 mole %: 11.5 mole %: 42.0 mole %) at 600°C. Corrosion resistance of the materials was studied, the mass losses and depths of corrosion were calculated, and sample surfaces were investigated by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). Nickel addition decreased the corrosion resistance of TiB₂. Simultaneous additions of both elements, Ni and Ta, as well as the addition of Ta only showed reducing effect on grain formation and they increased the corrosion resistance which is highest in the last case.     

Solubilities and vapour pressures of saturated aqueous solutions of sodium tetraborate,sodium carbonate,and magnesium sulfate and freezing-temperature lowerings of sodium tetraborate and sodium carbonate solutions

Solubilities and vapour pressures of water over saturated solutions of sodium tetraborate, sodium carbonate, and magnesium sulfate and freezing-temperature lowerings of sodium tetraborate and sodium carbonate solutions were determined and compared with the literature data. These results permitted the evaluation of osmotic and activity coefficients and molar enthalpies of vaporization.     

Surface tension and density of a sodium hydroxide melt

The surface tension and density of a sodium hydroxide melt were determined experimentally in a wide temperature range.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 12, 2004, pp. 2054–2055.Original Russian Text Copyright © 2004 by Patrov, Yurkinskii.     

Synthesis of benzotriazolylsuccinimides in melt

N-Phenyl-3-(benzotriazol-1-yl)pyrrolidine-2,5-dione was synthesized by condensation of N-phenylmaleimide with benzotriazole in melt. The adducts of 2 moles of benzotriazole to different bismaleimides, namely, bis[3-(benzotriazol-1-yl)pyrrolidine-2,5-diones] were obtained under analogous conditions. These adducts, according to the data from ¹H and ¹³C NMR spectroscopy, contain also (benzotriazol-2-yl)succinimide and residual maleimide fragments.     

Water vapor adsorption behavior of sodium deoxycholate anhydrous forms

Pseudopolymorphism of sodium deoxycholate (NaDC) was investigated. Intact NaDC (dihydrate) was dried at 60 degrees C under reduced pressure resulting an anhydrous amorphous phase. On the other hand, intact NaDC was altered to an anhydrous crystalline form by heating at 200 degrees C. The water vapor adsorption and desorption isotherms of dehydrated NaDCs were determined using an automatic gravimetric water vapor adsorption analyzer. In the case of NaDC dehydrated at 60 degrees C, the weight was increased in rising relative humidity and it was transformed into the NaDC tetrahydrate above 60% RH, which was identified by TG/DTA and powder X-ray diffraction. During the water vapor adsorption process of the sample dehydrated at 200 degrees C, the NaDC dihydrate was obtained in the range of 50 to 70% RH and then transformed into the NaDC octahydrate above 85% RH. The NaDC octahydrate was characterized by TG/DTA and powder X-ray diffraction for the first time. During the desorption process, the octahydrate was changed to the tetrahydrate between 80 and 40% RH.     

Electron deformation density in titanium diboride chemical bonding in TiB2

Titanium diboride, TiB₂, crystallizes in the AlB₂-type structure, hexagonal P6/mmm. The conventional, free atom crystal structure refinement led to R=2.23%, and including extinction corrections to R=1.58%. Multipole refinements with multipoles up to order four (hexadecapole) reduced the R value to 1.21%. Difference density maps revealed charge deficiencies on the boron sites and broadbands of charge accumulations between the boron atoms indicating a graphitic B-delocalization of the boron sp² hybrid orbitals.     

Vibrational studies of anhydrous lithium,sodium and potassium oxalates

The IR and Raman spectra of sodium oxalate and the IR spectrum of lithium oxalate are re-examined. The Raman spectrum of lithium oxalate is presented for the first time. A recent structural study is used as the basis for the first detailed vibrational study of anhydrous potassium oxalate, phase II.     

Reactions of isoflavone and 2-hydroxyisoflavanone with sodium ethoxide in anhydrous ethanol

Recent observation /1,4/ on the existence and unreactivity of IV under basic conditions, as well as its part in the inhibitory effect on the decomposition into deoxybenzoin is unequivocally proved by comparing the decompositions of I and VI. It is also shown that the decomposition of I is detemined neither by the character of the solvent nor by the nucleophilic character of the reactant, but by the possibility of the formation of IV.

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IV , I VI. , I . , , IV.

     

超声陈化法制备纳米NaY分子筛及形成机理研究

Nano-sized NaY zeolite was synthesized from metakaolin in the hydrothermal synthesis system by using ultrasonic during aging time.The process of crystallizing NaY zeolite was studied by XRD、SEM、ICP OES ,and the formation mechanism of nano-sized NaY zeolite was researched,finally the conditions of synthesizing nano-sized zeolite NaY had been brought forward.     

Synthesis and proton conductivity of anhydrous dendritic electrolytes

Water soluble PEG cored dendritic hexa-acid which comprises peripheral carboxylic acidic groups were prepared via nucleophilic substitution reactions. Novel anhydrous proton conducting electrolytes were prepared by incorporation of the heterocyclic protogenic solvent imidazole (Im) into PEG cored dendritic hexa acid, (PEG-HA), at several molar ratios of Im to-COOH units of PEG-HA. The complexation of PEG-HA and Im was illustrated by infrared spectroscopy (FT-IR). The materials are thermally stable up to 150 °C as evidenced by thermogravimetry analysis (TGA). Differential scanning calorimetry (DSC) results verified that the organic electrolytes are homogeneous and amorphous. The proton conductivities were characterized by means of AC impedance spectroscopy and a maximum conductivity of 1 × 10⁻³ S/cm was measured at 120 °C in the anhydrous state.      

Flame-retardancy and photocatalytic properties of cellulosic fabric coated by nano-sized titanium dioxide

We have investigated the effect of titanium dioxide as a durable finish on the flammability and photocatalytic self-cleaning of cellulosic fabric. Nano-sized titanium dioxide particles were successfully synthesized and deposited onto cellulosic fibers with good compatibility, significant photocatalytic self-cleaning activity, and flame-retardancy properties using the sol–gel process at low temperature. The photocatalytic activity was tested by measuring the photodegradation of methylene blue under ultraviolet–visible illumination, and also flame-retardancy effect was tested by flammability tester. The samples have been characterized by several techniques such as scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy, X-ray diffraction, and thermogravimetric analysis. The titanium dioxide nanoparticles with 10–20 nm in size have been found to form a homogeneous thin film on the fiber surface which shows efficient photocatalytic and flame-retardancy properties. This preparation technique can also be applied to new fabrics to create self-cleaning and flame-retardancy properties in them.     

浸渍-煅烧法合成纳米氧化铜的研究

纳米氧化铜是一种重要的功能材料,在高温超导、有机催化、传感器、锂离子电极材料等方面均具有广泛的应用前景.由于CuO在应用效果上与其形貌、粒径大小以及粒径分布有密切关系,因此,纳米CuO的可控研究仍具有重要意义.     

Limited stability of the pH reference material sodium tetraborate decahydrate (“borax”)

Thermogravimetric and X-ray powder diffraction analyses revealed that the pH reference material sodium tetraborate decahydrate (“borax”) is not a stable substance but, loosing some of its water of crystallization, transforms slowly into the pentahydrate. The connected pH changes of the solutions are opposite to and larger than, those expected according to the dilution value of the decahydrate as shown by differential potentiometric measurements. The transformation rate depends on the storing time in the closed original container, the time of and after the first exposure of the material to the atmosphere, the frequency of and the relative humidity during subsequent exposures, and the temperature. The transformation reaction is not understood in detail. However, the experiments showed that sodium tetraborate decahydrate is a reliable pH reference material, whose pH is constant within ΔpH=±0.005 within at least two years after preparation, even if occasionally exposed to the atmosphere. Further work will show whether this time limit can be somewhat extended.