Synthesis of the Precursor of Aluminum–Calcium Oxide Systems by Anodic Oxidation of Aluminum in Aqueous Solutions

An aluminum oxide system is obtained by electrolysis with a soluble anode and by the subsequent thermal treatment of the precipitate. It is shown that this system can be modified with calcium oxide in the process of synthesis. The influence of the synthesis conditions (the anodic current density and the electrolyte composition) on the formation of finely dispersed particles of the aluminum–calcium systems is studied. The structure and properties of the powder particles obtained by the electrochemical method are studied using the methods of laser diffraction, X-ray diffraction analysis, and electron microscopy.     

GeS2-In2S3-CdS体系玻璃的形成与性能

通过实验确定了ＧｅＳ２－Ｉｎ２Ｓ３－ＣｄＳ体系的玻璃形成区,其玻璃形成区较小,主要是在富含ＧｅＳ２区域。研究了它的热性能和透红外性能,结果表明：ＧｅＳ２－Ｉｎ２Ｓ３－ＣｄＳ体系玻璃转变温度在５７３－６９３Ｋ之间,红外截止波长为１１μｍ,具有较大的红外载波和较低的声子能量。ＧｅＳ２－Ｉｎ２Ｓ３－ＣｄＳ体系玻璃的密度约为３．０ｇ／ｃｍ＾３,玻璃在空气中能稳定存在而无风化现象产生。     

坡缕石-In2O3/In2S3复合材料光催化降解甲基橙

以In2O3、硫代乙酰胺、坡缕石（PGS）为原料,采用水热法制备了不同PGS质量分数（20%~60%）负载In2O3/In2S3的复合材料（PGS-In2O3/In2S3）,通过XRD、SEM、TEM、BET、紫外-可见漫反射光谱等表征PGS-In2O3/In2S3的成分组成和内部结构,电化学工作站对其进行电化学交流阻抗测试（EIS）,考察不同PGS质量分数的PGS-In2O3/In2S3光催化降解甲基橙（MO）的性能、抗离子干扰和循环性能。结果表明,PGS-In2O3/In2S3的In2O3颗粒表面附着木耳状In2S3纳米片及针状PGS ,其在200~580 nm区域有较强的光吸收 。PGS质量分数为50%的50%PGS-In2O3/In2S3具有最佳的光催化降解MO活性,在可见光照下射30 min,20 mg的50%PGS-In2O3/In2S3对30 mL质量浓度为20 mg/L的MO水溶液的光催化降解率为9 8.8%。超氧基自由基（?O2?）、空穴（h+）是50%PGS-In2O3/In2S3光催化降解性能发挥的主要活性物种,除H2PO4-外,溶液中Cl-、Na+等常见阴、阳离子对其光催化降解MO没有影响;50%PGS-In2O3/In2S3对孔雀石绿（MG）、罗丹明B（RhB）、结晶紫（CV）、亚甲基蓝（MB）等染料均表现出较好的物理吸附和光催化降解效果。PGS与In2O3/In2S3间的内置电场,降低了In2O3/In2S3光生载流子的复合率,这是50%PGS-In2O3/In2S3具有良好光催化降解染料活性的关键。     

Armor Options: A Comparison of the Dynamic Response of Materials in the Aluminum Oxide–Aluminum Nitride Family

For armor applications, ceramic materials are often useful due to their high dynamic strength. In some instances, in addition to high strength, the armor must also be transparent, which significantly limits the choices of materials. Materials in the aluminum oxide–aluminum nitride family (including Al₂O₃ and AlON) are both strong and transparent. Only the end compound AlN is opaque. In this paper, the dynamic response to shock loading is examined for these materials to better understand the material response. Despite the chemical similarities, significant differences exist in the shock response and will be discussed.     

Assembly of β-SiC Nanowires film and humidity sensing performance

β-SiC materials have been seen as the third-generation semiconductor widely used in kinds of photoelectric device, high temperature electronics, and other fields. Compared with ordinary semiconductors, β-SiC materials have huge potential application in replacing monocrystalline silicon in extreme environments because of their numerals extraordinary chemical and physical properties. Based on this, β-SiC nanowires obviously are more desirable in any way. Here, we present a modified chemical vapor deposition (CVD) method to synthesis β-SiC nanowires, which needs no protect gas, and transfer it to Si/SiO₂ substrates equipped with Au electrodes. The microstructure of the as-prepared samples is tested by field emission scanning electron microscopy (FESEM). The humidity sensing performance of electronic device is measured by electrochemical workstation test equipment. It shows that the resistance of β-SiC nanowires increases with increasing environment humidity within very short response/recovery time-0.5 seconds/0.5 seconds and also performs excellent cycling stability. Such advantage superiorities make it highly possible to apply β-SiC nanowires into various environments.     

Explosive Synthesis of Ultradisperse Aluminum Oxide in an Oxygen‐Containing Medium

Explosive synthesis of ultradisperse aluminum oxide in an oxygencontaining medium is studied. Synthesis conditions that are most optimal for production of the material in the ultradisperse state are determined. A physical model of the process is proposed. It is shown that attenuation of the shock wave causes separation of the shockcompressed material into liquid and solid layers. Possible mechanisms of aluminum combustion with subsequent dispersion of aluminum into the oxygencontaining medium of the explosive chamber are considered. It is shown that ultradisperse aluminum oxide powder is produced mainly from the second layer of the shockcompressed material. Experimental dependences of the yield of the disperse fraction on synthesis conditions are explained using the model proposed.     

Hot Photoluminescence in γ-In2Se3 Nanorods

The energy relaxation of electrons in γ-In₂Se₃ nanorods was investigated by the excitation-dependent photoluminescence (PL). From the high-energy tail of PL, we determine the electron temperature (T _e) of the hot electrons. The T _e variation can be explained by a model in which the longitudinal optical (LO)-phonon emission is the dominant energy relaxation process. The high-quality γ-In₂Se₃ nanorods may be a promising material for the photovoltaic devices.     

Anodic Oxidation of Nitric Oxide on Au/Nafion®: Kinetics and Mass Transfer

The rate determining step for the anodic oxidation of nitric oxide on Au/Nafion^® was experimentally and theoretically found to beNO + Au Au–NO_ads The anodic oxidation of nitric oxide was first order with respect to nitric oxide. The reaction rate constant increased from 3.3×10^–5 to 9.6×10^–5cm s^–1 as the applied potential increased from 0.74 to 0.77V. The anodic oxidation of nitric oxide was controlled by the electrochemical kinetics when the anodic potential was less than 0.8 V. When the potential was greater than 1.0 V, it was located in the mass transfer region. The limiting current increased from 1184 to 1589A with increase in gas flow rate from 250 to 750ml min^–1 when the potential was set at 1.05 V and the concentration of nitric oxide was 100 ppm. The diffusion resistance in the gas diffusion layer can be neglected for gas flow rates greater than 750 ml min^–1. The diffusivity of nitric oxide and the equivalent diffusion layer thickness within the porous electrode were evaluated to be 3.43×10^–4cm²s^–1 and 0.051 cm, respectively.     

红外梯度折射率GeS2-In2S3-CsCl硫系微晶玻璃制备与性能研究

梯度折射率红外成像系统可在保持成像性能的基础上,极大降低系统的尺寸、质量和成本,有望推进红外成像系统向轻小型发展.然而,目前没有可用的红外梯度折射率光学材料.本文基于65GeS2-25In2S3-10CsCl硫系玻璃,利用梯度温度场热诱导析出轴向梯度分布的β-In2S3纳米晶体,制得梯度折射率透明硫系微晶玻璃.结果表明:析出的β-In2S3晶体为不同晶面取向纳米晶组成的多晶结构,尺寸约为25 nm,且晶体尺寸、数量与梯度温度场密切相关;制得的梯度折射率硫系微晶玻璃仍保持良好的长波红外透过率,且其10μm处最大折射率差Δn达0.047.     

Thionation of β-lactams to β-thiolactams by silica-supported P2S5

In this paper, an improved method for the thionation of β-lactams is described. Using a solid-supported P₂S₅ reagent and heating under reflux conditions, β-thiolactams were obtained in good to excellent yields. Also the reaction time reduced significantly compared with that achieved under the more conventional method using P₂S₅ alone. Furthermore, inexpensive and easily available starting materials simple reaction conditions and a simple purification process are some other advantages of this method.     

Research of positron annihilation and hydration of doped β-C2S

The lifetime spectrum of positron in β-C₂S of added Na₂O or P₂O₅ is studied with positron annihilation technique. According to the theory of the capture of positron, we discuss the relationship between lifetime spectrum parameters obtained through experiment and the microstructure of β-C₂S. The results show that the long living component τ₂ (about 470 ps) represents the capture of positron in the defects of Ca²⁺ vacancies and that the intensity of I₂ of τ₂ decreases with the increasing of Na⁺ and increases with the increasing of P⁵⁺. The results also verify that Na⁺ replaces Ca²⁺ and creates anion vacancies; while P⁵⁺ replaces Si⁴⁺ and creates cation vacancies. Vacancy concetration increases Na⁺ and P⁵⁺. Our work shows that the positron annihilation technique is a useful tool for studying the change of microstructure defects in doped β-C₂S. The relationship between heat treatment and hydration activity of doped β-C₂S and its impurities are also studied and discussed.     

Fabrication of pressureless sintered dense β-SiAlON via a reaction-bonding route with ZrO2 addition

A reaction-bonding and post-sintering process was applied to fabricate pressureless sintered β-Si_6?ZAl_ZO_ZN_8?Z (Z = 1–3) ceramics with monoclinic ZrO₂ added to the starting powder. Samples with ZrO₂ showed enhanced nitridation and achieved near theoretical density following post-sintering, although this could not be achieved in the samples produced without ZrO₂. Thus the ZrO₂ is effective in both enhancing the nitridation of Si and as a sintering additive for densification of β-SiAlON. Part of the added monoclinic ZrO₂ was transformed to tetragonal ZrO₂, and the ZrN phase was also formed due to reaction with nitrogen during the reaction-bonding process. After the post-sintering process, the ZrN phase remained only in the Z = 3 composition. In the other compositions the ZrN reacted with SiO₂ to form both tetragonal and monoclinic ZrO₂ phases. These differences are explained in terms of the increasing densification and grain growth for Al₂O₃ rich compositions and the ZrN being trapped inside such grains in the case of the Z = 3 sample.     

Fabrication and thermoelectric properties of SrTiO3–TiO2 composite ceramics

The paper presents the results of preparing biphase SrTiO₃–TiO₂ ceramics as a promising system for n-type thermoelectrics using the features of a two-dimensional electron gas. Ceramics was obtained by reactive spark plasma sintering of SrCO₃ and TiO₂. The dynamics of phase transformations are shown; it is clarified that phase transformations are not the driving force of sintering. The mutual stabilization of the SrTiO₃ and TiO₂ phases is shown. Unique data on the assessment of the temperature gradient in the system have been obtained. A comparison of the thermoelectric characteristics of biphasic ceramics and its constituent phases allows concluding that the role of the two-dimensional electron gas is reduced to modulating the properties of bulk phases. Clear signs of size quantization were detected by the X-ray luminescence method, which is expressed in the blueshift of the luminescence spectrum by 22.3 ± 0.8 meV.     

Methods and Approaches of the Sol–Gel Technology for the Surface Modification of Aluminum Oxide Powders

The results of studies, sol–gel synthesis, and the sedimentation stability of complex multicomponent sol–gel systems of the “silica sol modified with Co(NO₃)₂ · 6H₂O, Al(NO₃)₃ · 9H₂O with α-Al₂O₃ or γ-Al₂O₃ as highly dispersed filler” type are generalized. The physical–chemical processes accompanying the formation of modifying layers on the powder oxide particles are examined. The promising prospects of applying α-Al₂O₃ powders modified with a silicate layer of the composition (wt %) 1.2K₂O · 3Al₂O₃ · 3.2CaO · 12.5Na₂O · 28.1B₂O₃ · 52SiO₂ in the fabrication of ceramic materials with improved strength characteristics are demonstrated.     

Anodic oxidation of Pb2+ → PbO2 in chloride solutions

The anodic oxidation of Pb²⁺ → PbO₂ on Pt has been studied in chloride solutions using a potentiostatic technique to fix the potential below, at and above E_Cl2/Cl⁻. With saturated PbCl₂ and 0·5 M NaCl saturated with PbCl₂, the coulometric efficiency is 100 per cent at potentials < E_{Cl2/Cl ⁻}, but with 1·2 M NaCl saturated with PbCl₂ the efficiency is <100 per cent.This decrease in efficiency in high concentrations of Cl⁻ is attributed to (a) specific adsorption of Cl⁻ on the Pt thus preventing easy adsorption of OH⁻ (b) formation of chloro-complexes due to the reaction of Cl⁻ with Pb²⁺ and PbO₂.The results provide an explanation for the inability of the Pb—Pt bi-electrode to form PbO₂ in high concentrations of Cl⁻.     

Fabrication of tunable bandgap epitaxial β-(AlxGa1−x)2O3 films using a spin-coating method

β-(Al_xGa_1−x)₂O₃ films have several critical properties of interest to the research community, including a wide bandgap that may be used in the development of new electronic, optoelectronic, and photonic devices. Here we demonstrate the first time fabricated metal-alkoxide-based spin-coated single-phase epitaxial β-(Al_xGa_1−x)₂O₃ films on c-sapphire substrates with orientation and good crystallinity that is comparable to the films fabricated using other film deposition techniques, such as molecular beam epitaxy and chemical vapor deposition. Using this technique, we generated films with broad Al compositions (x) of 0.3, 0.5, and 0.7 with bandgap energies of 5.15, 5.56, and 6.16 eV, respectively, estimated from the X-ray photoelectron spectroscopy inelastic energy-loss spectra. Photoluminescence emission spectra in the ultraviolet and visible (blue) wavelength range highlighted several intrinsic defects in the film structure that functioned as luminescence centers, including self-trapped exciton and recombining donor-to-acceptor band. Detailed analysis of the structural and optical properties of β-(Al_xGa_1−x)₂O₃ epitaxial films revealed that this low-cost and scalable solution-deposition approach coupled with a spin-coating technique could be used to fabricate β-(Al_xGa_1−x)₂O₃ films with tunable properties.     

Fabrication of Al2O3–ZrO2 ceramics with high porosity and strength

This study describes the synthesis of ceramics, in which a micrometre-sized Al₂O₃–ZrO₂ nanopowder was used as an oxide base for the hardening of the materials. To a suspension of this mixed metal oxide, the pore-forming crystallisation additives camphor and carbamide were added to produce ceramics with thin permeable pores. Camphor crystallised in the oxide suspension in the form of single pentagonal stars and сarbamide crystallised in the form of thin elongated needles. The use of the different crystallisation additives allowed the formation of ceramics after sintering that have both permeable and complex pore morphologies, where anisotropic properties were observed using carbamide as an additive but not when camphor was used. The total porosity of the resulting ceramics was 51.3%, with a compressive strength in the range of 17.3–92.3 MPa.     

Fabrication and microstructure of Al2O3–ZrO2(3Y)–SiC nanocomposites

Al₂O₃–ZrO₂(3Y)–SiC composite powder was prepared by the heterogeneous precipitation method. Calcinating temperature of the powder was important to obtain dense sintered body. The nanocomposites were got by hot-pressing, and addition of ZrO₂ did not raise the sintering temperature. Some Al₂O₃ grain shape was elongated, and Al₂O₃ grain size was about μm. Nano SiC particles were observed uniformly distributing throughout the composites, and most of them were located within the matrix grains. Because SiC particles located within ZrO₂ grains influenced the phase transformation of ZrO₂, the sintering of nanocomposites, which controlled grain size and transformable ZrO₂ amount, become important to get high performance. The strength of 80 wt% Al₂O₃–15 wt% ZrO₂–5 wt% SiC nanocomposites was 555 MPa, and toughness was 3·8 MPa m^1/2, which were higher than those of monolithic Al₂O₃ ceramics. ©