Acid-base and sorption properties of amorphous titanium phosphate

Acid-base and sorption properties of amorphous titanium phosphate were studied. Three types of functional groups, H₂PO ₄ ^? , HPO ₄ ^2? , and OH^?, with pK 2.79, 5.13, and 11.2, respectively, were revealed by potentiometric titration. The sorption recovery of double-charged metal cations was studied, and the selectivity series was found: Mg²⁺ < Ca²⁺ < Mn²⁺ < Ni²⁺ < Zn²⁺ < Cu²⁺ < Co²⁺.     

The preparation,formation mechanism and magnetic properties of a Fe-Cr-Mn-N amorphous alloy

In this paper, the amorphous phase formation process, formation mechanism and magnetic properties, during the mechanical alloying (MA), have been investigated in Fe₆₀Cr₁₅Mn₁₀N₁₅ alloy, respectively. The results obviously indicate that amorphous Fe₆₀Cr₁₅Mn₁₀N₁₅ with a wide supercooled liquid region (SCLR, 82?K) can be obtained via 40?h MA process. With the milling time increasing gradually, the microstructures evolve from the initial crystalline powder, to completely amorphous phase, and eventually to amorphous phase with embedded Cr₂N. By calculation, the mixing chemical enthalpy ΔH^chem and amorphous formation enthalpy ΔH^form have been obtained as ?0.24?kJ/mol and ?6.610?kJ/mol, respectively, implying the existence of thermodynamic advantage for the amorphous phase formation. In addition, the effect of 7 at% B and 7 at% Mo addition on the amorphous phase formation have also been studied, however, the diffraction peaks corresponding to Mo (Cr₂N) still appear after 120?h milling. Meanwhile, isothermal annealing experiments were conducted at different temperatures, obtaining the microstructure evolution as: amorphous?→?amorphous alloy?+?Cr₂N?→?α-Fe?+?Cr₂N?→?α-Fe?+?CrN?+?Cr₂N. And the hysteresis loops in amorphous Fe₆₀Cr₁₅Mn₁₀N₁₅ undergoing both the MA process and isothermal annealing procedure provide us with the evidence that this alloy system can exhibit excellent soft magnetic properties.     

Deformation properties of amorphous alloys based on titanium

Translated from Fiziko-khimicehskay Mekhanika Materialov, Vol. 27, No. 3, pp. 77–79, May–June, 1991.     

A preliminary investigation into preparation and characterisation of a Raney titanium catalyst

A preliminary investigation is carried out into the preparation and characterisation of a Raney-type titanium catalyst. Titanium-40 wt % aluminium powder is used as the precursor alloy and caustic leaching as the preparation method. Leaching in 25 wt % NaOH solutions at both 50°C and 80°C results in preferential removal of aluminium and formation of a highly porous layer containing almost complete titanium. The thickness and the surface roughness of the leached layer increases with leaching time and to a less degree with higher solution temperature. The combined morphological and kinetic measurements suggest that a diffusion barrier built up in the solution/metal interphas plays a key role in the leaching process. Electrochemical tests performed with the leached powder show a significantly reduced overpotential towards cathodic hydrogen evolution reaction, thus a potentially promising catalyst. Further work is needed to establish optimal leaching parameters to increase its electrochemical activity.     

Biphasic calcium phosphate bioceramics: preparation, properties and applications

Biphasic calcium phosphate (BCP) bioceramics belong to a group of bone substitute biomaterials that consist of an intimate mixture of hydroxyapatite (HA), Ca₁₀(PO₄)₆(OH)₂, and beta-tricalcium phosphate (-TCP), Ca₃(PO₄)₂, of varying HA/-TCP ratios. BCP is obtained when a synthetic or biologic calcium-deficient apatite is sintered at temperatures at and above 700 °C. Calcium deficiency depends on the method of preparation (precipitation, hydrolysis or mechanical mixture) including reaction pH and temperature. The HA/-TCP ratio is determined by the calcium deficiency of the unsintered apatite (the higher the deficiency, the lower the ratio) and the sintering temperature. Properties of BCP bioceramics relating to their medical applications include: macroporosity, microporosity, compressive strength, bioreactivity (associated with formation of carbonate hydroxyapatite on ceramic surfaces in vitro and in vivo), dissolution, and osteoconductivity. Due to the preferential dissolution of the -TCP component, the bioreactivity is inversely proportional to the HA/-TCP ratio. Hence, the bioreactivity of BCP bioceramics can be controled by manipulating the composition (HA/-TCP ratio) and/or the crystallinity of the BCP. Currently, BCP bioceramics is recommended for use as an alternative or additive to autogeneous bone for orthopedic and dental applications. It is available in the form of particulates, blocks, customized designs for specific applications and as an injectible biomaterial in a polymer carrier. BCP ceramic can be used also as grit-blasting abrasive for grit-blasting to modify implant substrate surfaces. Exploratory studies demonstrate the potential uses of BCP ceramic as scaffold for tissue engineering, drug delivery system and carrier of growth factors.     

Hydrous oxides of titanium: cation exchange properties and kinetics of exchange

The ion exchange properties of hydrous titania gels of different particle sizes, precipitated from titanous chloride through the agency of ammonium carbonate and hydroxide have been studied. Such studies were carried out under acidic and alkaline conditions with respect to Cu²⁺, Ni²⁺, Co²⁺ and Cr³⁺ ions.In the case of gels precipitated by ammonium carbonate, oxygen gas was used as the oxidizing agent whereas with ammonium hydroxide as precipitant, oxidation was performed with hydrogen peroxide.Ion exchange capacities were determined by visible spectrophotometry. Increasing the pH of preparation lead to an increase in exchange capacities of the hydroxide precipitated gels that are characterized to be mesoporous. Such an increase is not observed in the case of carbonate precipitated microporous gels. It is shown that in the latter case the NH ₄ ⁺ ions generated by the initial interaction of (NH₄)₂CO₃ with the acidic titanous chloride lead to the formation of titania exchangers that are predominantly in the ammonium form. The textural characteristics of the exchanger resulting from different conditions of preparation is a significant contributing parameter to the resulting data.Ageing of the microporous titania samples markedly reduces the exchanger capacity of the smaller Ni²⁺ ions but increases that of the bulkier Cr³⁺ as a result of the presence of some wide pores that appear upon agglomeration. The presence of Cr³⁺ ions in the hydroxo form in solution seems to inhibit its exchange with the appropriate surface species.Studies on the kinetics of exchange with respect to the Ni²⁺ ions seem to indicate that a particle diffusion mechanism is partly or completely responsible for the rate of exchange.     

The preparation of cadmium phosphate and cadmium zinc phosphate glasses and their electrical and optical properties

The preparation of a range of glasses based on CdO-P₂O₅ and CdO-ZnO-P₂O₅ is described and data are reported on density, electrical conductivity and optical absorption. The electrical conduction is electronic rather than ionic and is due to hopping between localized states. The optical absorption is due to forbidden indirect electronic transitions.     

Blends of biodegradable polyesters by reactive blending: preparation, characterisation and properties

Blends of poly--caproIactone (PCL) and poly--hydroxybutyrate (PHB) were prepared by mixing the two polymers in the presence of dicumylperoxide (DCPO) in solution of chlorobenzene. Similarly blends were obtained by mixing the two polymers with no peroxide added. The blends were prepared in a break of composition, from 85% wt PHB/15% wt PCL to 15% wt PHB/85% wt PCL, respectively. Also pure polymers were reacted with DCPO in the same way of the blends. Thermal (DSC), spectroscopic, mechanical (tensile tests) and morphological SEM)analyses were performed on the blends and on the pure polymers. Significant differences were found in the chemical-physical characteristics of the blends with and without peroxide.     

Performance properties of titanium phosphate ion exchanger utilized for commercial production in liquid radioactive waste treatment systems

A comparative study of the physicochemical and performance properties of samples of Ti(OH)_1.36·(HPO₄)_1.32·2.3H₂O ion exchanger in the finely dispersed and granulated forms, utilized for commercial production, was made. The sorption of Cs and Sr cations from solutions of various compositions was studied in batch experiments, and the diffusion coefficients of the exchanging ions were determined. The hydrolytic stability of the ion exchangers was examined with the aim to determine the optimal operation conditions. Experiments showed that the cation exchangers based on titanium phosphate are the most efficient in removal from liquid radioactive waste of induced radioactive isotopes of corrosion products, which is due to formation of weakly dissociating compounds of nonferrous metal ions with functional groups of the ion exchangers in the sorbent phase.     

非晶合金变压器铁芯制备及性能研究

采用宽度低的国产非晶合金带材制成铁芯后沿着带材宽度方向叠加成为高度合适的铁芯,并对其进行线切割,研究了铁芯切缝处的结构、形貌及切割前后工频下的磁性能。结果表明,线切割后切缝处结构由非晶态向晶态发生转变;切割后不改变铁芯的饱和磁感应强度,但磁化困难,损耗增加,铁芯切割后在B=1.3T,f=50Hz下的励磁容量由切割前0.32VA/kg增加到7.70VA/kg,损耗值由0.16W/kg增加到0.30W/kg;铁芯叠加不影响其磁性能,此法适用于制备非晶合金变压器。     

纳米Ni-SiC非晶态复合镀层的制备工艺及性能研究

采用超声-电沉积法,在45钢表面制备纳米Ni-SiC非晶态复合镀层.研究镀液中纳米SiC粒子的悬浮量、超声功率和电沉积条件对复合镀层的影响.利用扫描电镜、电子探针、显微硬度计和摩擦磨损试验机等对复合镀层的形貌、组织结构及性能进行分析研究.结果表明,采用适当的超声-电沉积工艺(SiC粒子的悬浮量4 g/L,超声功率200 W),可以制备性能较好的纳米Ni-SiC复合镀层,其磨损量约为镍镀层的1/5,显微硬度是镍镀层的3倍左右.     

The preparation and properties of an antimony sulphide glass

A glass has been prepared in the Sb₂S₃PbS system at compositions very close to 80 mol % Sb₂S₃: 20 mol % PbS. It has been studied by powder x-ray diffraction, optical and high resolution transmission microscopy and infra-red spectroscopy, and its decomposition characterised by differential scanning calorimetry. Hardness values are also reported. This glass displays a wide range of transparency from 4.5 to 16.5 μm and may be of interest for a number of infrared applications. Structural studies indicate that it is formed of SbS and PbS polyhedra similar to those found in the crystalline PbSbS sulphides, and recrystallisation of the glass, observed by electron microscopy shows that the rearrangement of the polyhedra in transforming from the glass state to the crystalline state is feasible. The formation of the glass and its limited composition range are discussed in terms of the strain involved in linking the PbS and SbS polyhedra together and this leads to a number of suggestions as to how the existence region over which the glass forms could be expanded.     

环境功能负离子涂料的制备及抗菌性能研究

采用溶胶-凝胶法以Na2SiO3为包覆剂成功地制备了分散性优良负离子粉体，通过不同的添加量，研制能够产生最大负离子浓度的功能涂料。进行了负离子涂料的抗菌性研究，实验结果表明负离子材料具有抗菌性，抗菌效果与涂料的负离子产生量、负离子材料粒径、涂料的距离密切相关，并从微观上对负离子杀菌进行了分析，验证了负离子的生物学效应。     

Role of aluminum ion implantation on microstructure, microhardness and corrosion properties of titanium alloy

Ti-Al-Zr alloy was implanted with Al at cumulative doses between 1 × 10¹⁷ and 1 × 10¹⁸ ions/cm². The results indicate that the Al-implanted layers are ∼0.1 μm thick and are composed almost entirely of an amorphous layer. Implanted layer hardness is dose dependent and is increased by more than a factor of 4 for the high-dose implanted specimen when compared with that of the substrate material. The corrosion resistance of the sample was markedly improved after aluminum implantation.     

Effect of ion bombardment on the properties of sputtered amorphous silicon

In order to investigate the effect of argon ion bombardment on the properties of amorphous silicon, films were deposited by r.f. sputtering under various r.f. powers. The argon ion bombardment reduces the hydrogen content in the films and favours SiH₂ bond formation. These results were supported by IR spectroscopy, optical and electrical measurements.     

Structural, mechanical, and frictional properties of titanium nitride films exposed to continuous ion beam bombardment

The influence of low-dose (10¹⁴–10¹⁵ cm⁻²) ion bombardment on the structural, mechanical, and frictional properties of titanium nitride films has been studied and results are presented. It is shown that at these doses plastic deformation processes take place in the target material, which change the degree of crystallinity. By selecting the bombardment conditions, the properties of TiN films can be varied fairly widely. Pis’ma Zh. Tekh. Fiz. 24, 64–68 (February 12, 1998)     

新型通用离子交换膜的研究与实践

基于离子交换膜的电膜技术,由于其独特的离子传递特性,可以进行离子物系的分离分级,在清洁生产、节能减排、环境保护、能量转换等方面有着广泛的应用前景。然而,目前国内相关均相离子膜产品尚处于起步阶段,以日本为首的国家对我国进行相关技术封锁和价格垄断。正是基于这样的产业背景和现实意义,开发出新型的均相离子膜制备路线尤为重要。本课题组提出了一种简单而通用的侧链型离子化芳香族聚合物的合成方法,即“离子单体聚酰基化”均相离子交换膜制备路线,并通过ATRP法来设计离子交换膜的主链憎水、侧链亲水的接枝结构,通过对接枝密度和接枝长度进行调节,实现对膜性能的调控,以满足不同的应用过程对膜性能的要求。此种均相离子交换膜的制备工艺及产业化生产攻关,可以打破以日本为首的国家对我国离子膜产品的技术封锁,实现具有我国自主知识产权的离子膜技术的产业化。制备条件温和、制备工艺简单、快捷,而且整个过程没有传统方法中常用的季铵化或磺化步骤,有效地简化工艺和降低环境污染,可用于扩散渗析、普通电渗析以及双极膜电渗析过程对高性能离子交换膜材料的需求。该系列离子交换膜在特种废水处理、有机酸生产、氨基酸分离纯化、重金属废水处理等诸多领域得到了广泛的使用,均取得了较为满意的使用效果。     

Production and characterisation of amorphous alloys at varanasi

Amorphous alloys, more commonly referred to as metallic glasses, represent a striking advance in inorganic materials technology of recent times. While the probable atomic arrangements in noncrystalline alloys have aroused scientific curiosity, their unusual mechanical strength, attractive magnetic properties and remarkable corrosion resistance have excited technological interest. This report describes the progress of research at Varanasi on the following aspects: adaptation, innovation and development of techniques for rapid solidification, study and refinement of structural models, calculation of thermodynamic quantities, evaluation of strength and corrosion resistance and studies of glass to crystal transition. A brief report on the progress in research on metallic glasses of the Rapid Solidification group at the Banaras Hindu University, Varanasi.