Chemical etching of (100) GaAs in the (NH4)2Cr2O7-H2SO4-N H4Cl-H2O system

The etching solution containing ammonium dichromate, sulphuric acid and ammonium chloride in water solution allows for the investigation of the influence of individual active components and their concentration on the etching reaction with GaAs. The influence of these agents on etching as well as the temperature and stirring were examined. The etching rate increases with increasing Cl^– ion concentration, increases and subsequently decreases with the increasing of H⁺ ion concentration and remains constant in the wide range of oxidant anion concentration. The effect of stirring on etching rate allows us to estimate regions dominated by diffusion kinetics. The activation energy in the wide range of parameters is constant and equal to 60 kJ mol^–1. Microscopic observations reveal surfaces of various morphologies: smooth; covered with round hills; or with a network of veins. Various profiles of grooves arranged in various directions are revealed due to the preferential characteristic of etching; these profiles are also influenced by the mask material.     

Refinement of the structure of K2Cr2O7

The parameters for the structure of K₂Cr₂O₇ have been refined from 7511 observed reflections; $\text{a}{}_{\mathrm{o}}\text{= 7.4200(6)}\text{A}\text{?}$, $\text{b}{}_{\mathrm{o}}\text{= 13.399(3)}\text{A}\text{?}$, $\text{c}{}_{\mathrm{o}}\text{= 7.3845(9)}\text{A}\text{?}$, cosα = ?0.1396(2) (α = 98°2'), cosβ = ?0.0154(2) (β = 90°53'), cosγ = ?0.1078(2) (γ = 96°11'). The discrepancy factor R(F_o²) = 0.0702 with a type 2 extinction correction. The average CrO distances are 1.609Å (unshared) and 1.783Å (shared).     

Nucleation studies in supersaturated aqueous solutions of KH2PO4 doped with KBr and K2Cr2O7

Induction periods were measured for various supersaturated aqueous solutions of potassium dihydrogen orthophosphate doped separately with potassium bromide and potassium dichromate by the direct vision method. Various critical nucleation parameters were calculated based on the classical theory for homogeneous crystal nucleation and the results are reported and discussed. The critical nucleation parameters increased with increase in doping concentration for both the dopants considered.     

The bulk properties of the Na2SO4-H2O system in a wide range of the parameters of state

The constant-volume piezometer method is used to determine the density of aqueous solutions of sodium sulfate in the temperature range from 291 to 573 K and in the ranges of pressures from 2 to 40 MPa and concentrations from 0.088 to 1.116 mol/kg H₂O. In view of the available literature data, an equation is constructed describing the specific volumes of solution. Limiting partial molar volumes of electrolyte are calculated.     

ReP2O7: A new isomorph of ZrP2O7

Synthesis of ReP₂O₇, a new compound isomorphic with ZrP₂O₇, is reported along with unsuccessful attempts to synthesize MnP₂O₇. The lattice parameter of ReP₂O₇ was found to be $\text{a}{}_0\text{= 7.94 ± 0.02}\text{A}\text{?}$, and an indication of a “triple cell” superlattice sismilar to that of ZrP₂O₇ was found.     

InP/GaAs低温键合的新方法

通过对 InP/GaAs 异质键合实验方法的研究,提出了包括表面活化处理、真空预键合和退火热处理的三步法,在350℃低温下实现了InP/GaAs异质材料的键合。界面电流 电压(I V)特性的研究表明,350℃样品的界面过渡层极薄,电子主要以隧穿方式通过界面,而450℃的扩散使得过渡层增厚,界面电流 电压特性可视为双肖特基二极管的反向串联。同时,对键合样品也进行了拉力测试,实验结果表明 450℃样品的键合强度优于350℃样品。最后,对InP/GaAs异质材料的键合机理进行了探讨。     

Surface and catalytic properties of CuO/MgO system doped with K2O and Cr2O3

The effects of doping of CuO/MgO system with K₂O or Cr₂O₃ (1–6 wt.%) on its surface and catalytic properties were investigated. The analytical techniques employed were XRD, nitrogen adsorption at −196 °C and decomposition of H₂O₂ at 30–50 °C. The results revealed that K₂O-treatment of the system investigated, followed by calcinations at 400 °C resulted in the conversion of some of the surface copper oxide into potassium coprate K₃Cu₅O₄ phase whose diffraction lines disappeared upon heating at 500 °C. Chromium oxide-doping did not lead to the formation of any copper oxide-Cr₂O₃ compound(s) in the treated sarples calcined at 400 and 500 °C. Also, K₂O-doping conducted at 400 °C increased the degree of crystallinity and particle size of MgO phase and exerted opposite effects in the crystallinity and particle size of CuO phase. The doping process either with K₂O or Cr₂O₃ effected a measurable progressive decrease (42–53%) in the specific surface area of the investigated system subjected to heat treatment at 400 and 500 °C. However, the opposite effect was observed upon doping with 1 and 2 wt.% Cr₂O₃ followed by heating at 500 °C. The catalytic activity of the investigated system decreased by doping with K₂O. The addition of 6 wt.% effected a decrease of 78% and 68% in the value of the reaction rate constant per unit surface area for the catalytic reaction carried out at 30 °C (k_{30 °C}⁻) over the doped catalysts calcined at 400 and 500 °C, respectively. Cr₂O₃-doping on the other hand, much increased the catalytic activity of the treated samples and an increase of 106% and 80% in the value of k_{30 °C} was observed upon doping with 6 wt.% Cr₂O₃ for the solids calcined at 400 and 500 °C, respectively. The results were discussed in terms of creation of new in pairs and conversion of some active sites (surface CuO) into less active site (K₃Cu₅O₄).     

炭纳米管的提纯重铬酸钾氧化法

介绍了一种新的、不同于常用的气相氧化法的炭纳米管纯化方法。采用 Ｋ２ Ｃｒ２ Ｏ７ 作为氧化剂将炭纳米颗粒氧化,并从热力学和动力学的角度对反应的可行性进行了分析,考察了硫酸用量、硫酸浓度、反应时间等因素反应的影响,确定了最佳工艺条件：硫酸浓度１∶１ （ Ｖ） Ｈ２ Ｓ Ｏ４∶ Ｋ２ Ｃｒ２ Ｏ７＝ ６∶１（ｍ ｏｌ）、反应时间２ ｈ、反应温度１４０℃,同时对纯化机理进行了解释。     

炭纳米管的提纯-重铬酸钾氧化法

介绍了一种新的、不同于常用的气相氧化法的炭纳米管纯化方法。采用Ｋ２Ｃｒ２Ｏ７作为氧化剂将炭纳米颗粒氧化,并从热力学和动力学的角度对反应的可行性进行了分析,考察了硫酸用量、硫酸浓度、反应时间等因素反应的影响,确定了最佳工艺条件：硫酸浓度１：１（Ｖ）Ｈ２ＳＯ４：Ｋ２Ｃｒ２Ｏ＝６：１（ｍｏｌ）、反应时间２ｈ、反应温度１４０℃,同时对纯化机理进行了解释。     

Excited state characteristics of the Li2B4O7 and KLiB4O7 glasses activated by Cr3+ ions

The excited state characteristics by means of the excited state absorption (ESA), optical gain and bleaching spectra have been measured for prototype glasses with Li₂B₄O₇ (LBO) and KLiB₄O₇ (KLBO) compositions activated by Cr³⁺ ions. The work addressed to search for novel attractive media for broadband lasers and amplifiers, is a completion of detailed spectroscopic evaluation described in earlier papers. One of the examined materials (KLBO), in accordance with optimistic comments given in previous work, reveals a very broad gain spectrum in the near IR, which itself is interesting in view of very few reports on glasses showing optical gain for Cr³⁺ ions in the low-field local environment. The ESA/gain/bleaching spectra, registered with equipment of improved sensitivity, have been reproduced by calculations, and detailed single configuration coordinate diagram, based on experimental data, has been created for interpretation.     

Hydrothermal Synthesis of K2ZrSi6O15 , K2ZrSi3O9 , K2ZrSi2O7, and ZrSiO4 in the System KOH–ZrO2–SiO2–H2O

The phase relations in the KOH–ZrSiO₄–H₂O, KOH–ZrO₂(cr)–SiO₂–H₂O, and KOH–ZrO₂(nanocr)–SiO₂–H₂O systems were studied at 400°C, 0.1 GPa, and KOH concentrations from 2 to 46 wt %. The crystallization fields of K₂ZrSi₆O₁₅, K₂ZrSi₃O₉, K₂ZrSi₂O₇, and ZrSiO₄ were located. The potassium zirconosilicates have open-framework structures made up of corner-shared ZrO₆ octahedra and SiO₄ tetrahedra. The composition of the crystallizing silicates is shown to depend on the nature of the starting Zr- and Si-containing materials.     

Specific heat in the NH4NO3-HNO3-H2O system

The specific heat has been measured in this ternary system. A theoretical study has been made of the effects of temperature and of the electrolyte concentrations (NH₄NO₃ and HNO₃) on the specific heat.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 1, pp. 90–91, January, 1985.     

Specific Features of Anodic Dissolution of Copper in H2SO4 + H2O and H2SO4 + CuSO4 + H2O Systems

We investigate anodic dissolution of copper in H₂SO₄ + H₂O and H₂SO₄ + H₂O + CuSO₄ systems, which model solutions for the electrochemical production of copper (+2) sulfate. Ultimate densities of anodic current in the temperature range 20–80°C for a voltage up to 8 V were found. We show that a concentration of copper ions ( Cu²⁺) of 1.5–2.0 moles/liter in the anolyte is the limiting one in the electrochemical production of solutions of copper (+2) sulfate.     

Dielectric properties of K2Zn2(SO4)3 and (NH4)2 Mg2(SO4)3

Dielectric constant (ɛ), dielectric loss (tan δ) and conductivity (σ) for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ have been measured over the frequency range 100 Hz — 100 kHz and in temperature range 30°C — 400°C. The values of static dielectric constant at room temperature are 7.67 and 4.80 for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively. The plots of log σ against reciprocal temperature at different frequencies of these samples merge into a straight line beyond 250°C and the activation energies calculated in this region are found to be 0.67 eV and 1.98 eV for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively.     

Optical and DSC studies of the Na2B4O7-Pb3O4 glass system

A series of glass samples were prepared from admixtures of Na₂B₄O₇ and Pb₃O₄ and results are reported for optical absorption, infrared absorption spectra and differential scanning calorimetry (DSC) as a function of lead content up to 40mol%. It is found that the addition of lead oxide decreases the optical energy gap and shifts the optical absorption edges towards lower energies in the range from 4.96 to 3.29 eV. The addition of lead oxide does not seem to introduce any new absorption band as compared with the infrared spectrum of pure sodium tetraborate glass.     

Gd2O2SO4粉体的合成及其晶体结构确定

通过750℃,2h煅烧Gd2O3和H2SO4(摩尔比1:1)的前驱体方法合成了Gd2O2SO4粉体.利用Gd2O2SO4的X射线粉末衍射数据和Material Studio 4.0 Reflex模块中Powder solve技术和Rietveld精修方法对Gd2O2SO4的晶体结构进行了研究.研究表明:Gd2O2SO4具有空间群为PMNB(62)的正交晶系,晶胞参数为a=1.2996nm,b=0.8117nm,c=0.4184nm,V=0.440698nm3,Z=4,计算密度为6.6949g/cm3,并确定了晶胞中原子的位置,Rietveld精修得到的Rwp=9.15%.