Insulating ZnO film on silicon for MIS application

High resistive zinc oxide thin film (∼ 0·5 μm) was deposited on single crystalp-silicon (100) wafers by an inexpensive spray-CVD method and was characterized both optically and electrically. Al/ZnO/Si (MIS) device structure was subsequently fabricated and bothI − V andC − V characteristics were studied. The semiconductor-insulator interface charge density (D _it) was calculated by Terman method and was found to be 3·85 × 10¹¹ cm⁻²eV⁻¹.     

Leaching of manganese ore with aqueous sulphur dioxide solutions

Manganese can be easily leached from chemically inert manganese ore by aqueous solutions of SO₂. Total manganese dissolution occurs at 650 rpm, 0·2% solid, 426μm, pH=1 and 310 K in only 6–8 min. The rate data for managanese fits the equation: 1 − 2/3α − (1 −α)^2/3=kt. Diffusion through the siliceous layer appears to be rate-controlling.     

Synthesis of high-energy-density Pr2Fe14−x Co x B,x⩽3, magnets for practical applications

Stable magnetic powders, of 1–2μm particle size, of partially Co-substituted, Pr₂Fe_14−x Co _x B,x⩽3, alloys together with 2–4 at% excess Pr were prepared by rapidly quenching the associated melts into thin ribbons and then mechanical attriting the ribbons in the refined particle sizes. The saturation magnetizationM _s, remanent magnetizationJ _r, intrinsic coercivityH _ci and Curie temperatureT _c were studied in characterizing the powders for fabricating into sintered or polymer bonded magnets. It is found that the smallx=0·4–0·8 substitution of the Co on Fe sites in this series sensitively leads to an increase in the value ofH _ci, by as much as 40%, with the optimum value of 21 kOe atx ∼ 0·55, together with an improvement in theT _c from 292°C to 325°C, without significantly diluting theM _s∼150 emu/g andJ _r∼8·0 kG values. The Co-substituted Pr₂Fe₁₄B alloy particles are better stable and corrosion resistant in ambient atmosphere. The results are discussed with the microstructure and comparison with the data for Nd₂Fe₁₄B powders processed under the same conditions. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995     

Nanocrystalline materials for high temperature soft magnetic applications: A current prospectus

Conventional physical metallurgy approaches to improve soft ferromagnetic properties involve tailoring chemistry and optimizing microstructure. Alloy design involves consideration of induction and Curie temperatures. Significant in the tailoring of microstructure is the recognition that the coercivity, (H _c) is roughly inversely proportional to the grain size (D _g) for grain sizes exceeding ∼0·1−1 μm (where the grain size exceeds the Bloch wall thickness,δ). In such cases grain boundaries act as impediments to domain wall motion, and thus fine-grained materials are usually harder than large-grained materials. Significant recent development in the understanding of magnetic coercivity mechanisms have led to the realization that for very small grain sizesD _g<∼100 nm,H _c decreases sharply with decreasing grain size. This can be rationalized by the extension of random anisotropy models that were first suggested to explain the magnetic softness of transition-metal-based amorphous alloys. This important concept suggests that nanocrystalline and amorphous alloys have significant potential as soft magnetic materials. In this paper we have discussed routes to produce interesting nanocrystalline magnets. These include plasma (arc) production followed by compaction and primary crystallization of metallic glasses. A new class of nanocrystalline magnetic materials, HITPERM, having high permeabilities at high temperatures have also been discussed.     

Photoelectrochemical investigation on spray depositedn-CdIn2S4 thin films

Polycrystalline thin films ofn-CdIn₂S₄ have been spray deposited onto amorphous and fluorinedoped tin oxide (FTO) coated glass substrates at the optimized substrate temperature of 380°C. The films were characterized by X-ray diffraction (XRD) and optical absorption studies. XRD studies revealed that the films were polycrystalline with spinel cubic structure. The optical absorption studies showed the band gap energy to be 2·14 eV. Photoelectrochemical (PEC) investigations were carried out using cell configurationn-CdIn₂S₄/1 M NaOH+1 M Na₂S+1 M S/C. Using Butler model, the optical band gap and minority carrier diffusion length (L _P) were found to be 2·22 eV and 0·07 μm, respectively. Gartner’s model was used to calculate the minority carrier diffusion length and the donor concentration (N _D) for CdIn₂S₄ films at three different wavelengths.N _D was found to be of the order of 10¹⁶ cm⁻³.     

Kinetics of Technetium Reactions: XV. Tc(IV) Oxidation with Persulfate Ions in HClO<Subscript>4</Subscript> Solution

Tc(IV) is oxidized with persulfate ions in HClO₄ solution by reactions with both S₂O ₈ ²⁻ ion and product of its thermal decomposition, Caro acid, H₂SO⁵. The reaction rate at 35°C and solution ionic strength μ = 1 is described by the equation d[Tc(IV)]/dt = k ₁[Tc(IV)][S₂O ₈ ²⁻ ] + k ₃[Tc(IV)][HSO ₅ ⁻ ]/[H⁺], where k ₁ = 0.88±0.04 l mol⁻¹ min⁻¹ and k ₃ = 110±5 min⁻¹. With increasing ionic strength to μ = 2, both rate constants decrease (k ₁ = 0.58±0.08 l mol⁻¹ min⁻¹ and k ₃ = 52±2 min⁻¹ at 35°C). The activation energy of the overall reaction is 77.7±8.1 kJ mol⁻¹. The mechanisms of both reactions are discussed. __________ Translated from Radiokhimiya, Vol. 47, No. 2, 2005, pp. 145–149. Original Russian Text Copyright ? 2005 by V. Koltunov, Gomonova, G. Koltunov.     

Kinetics of Reactions of Np and Pu Ions with Hydrazine Derivatives: XVIII. Reaction between Np(V) and Hydroxyethylhydrazine

The Np(V) reduction with hydroxyethylhydrazine is described by the equation −d[Np(V)]/dt = k ₁[Np(V)][HOC₂H₄N₂H ₄ ⁺ ] + k ₂[Np(V)][Np(IV][H⁺]^1.8, reflecting its main and autocatalytic pathways. The rate constants are k ₁ = 0.31±0.04 l mol⁻¹ min⁻¹ and k ₂ = 4.04±0.11 l^2.8 mol^−2.8 min⁻¹ at 80°C and ionic strength μ = 4. The activation energies are E ₁ = 90±6 and E ₂ = 116±4 kJ mol⁻¹, respectively. The autocatalytic pathway is limited by the reaction between hydroxyethyldiazenium ions, HOC₂H₄N₂H ₂ ⁺ and protonated Np(V) ions. __________ Translated from Radiokhimiya, Vol. 47, No. 2, 2005, pp. 150–153. Original Russian Text Copyright ? 2005 by V. Koltunov, Baranov, G. Koltunov.     

Dielectric characterization of poly(methyl methacrylate) geometrically confined into mesoporous SiO2 glasses

Characteristics of the dielectric relaxation mechanisms (γ,β,β′,α andρ) in poly(methyl methacrylate) (PMMA) and hybrids of PMMApolymerized into 5 nm SiO₂ pore matrices were studied by means of the thermally stimulated depolarization currents (TSD) technique, applied in the range 10–460 K. Low frequency relaxations (10 μHz–10 mHz) were investigated by measuring the isothermal discharging current, with the loss factorɛ”(f) determined using a new development of the Hamon method. Compared to pure PMMA, the hybrids presented a 14 to 18 degrees reduction of the TSDβ-relaxation maximum (T_β) and a drastic high temperature shift of the prominent syndiotacticα-peak. The average energy barrier for dipole (re)orientation (W) slightly decreases for both theα andβ relaxations. The latter observations, as well as the time evolution of the TSD spectra, are discussed in terms of the variation of the initiator (azobisisobutyronitrile) content and the effects of polymerization in spatial confinements (e.g. reduced monomer-to-polymer conversion at high initiator loadings and interaction effects). The shifts reflect the presence of several antagonistic mechanisms controlling the molecular dynamics of the polymeric phase. The extent of the polymer-SiO₂ hydrogen bonding interaction induces an increase of the energy barrier for the activation of the motions of the carboxymethyl lateral groups (β-process) and parts of the main chain (α-process). On the other hand, the reduction of the chain entanglements (due to the pore-directed propagation of polymerization) loosens several steric hindrances on the rotational motion of the side group, explaining the accompanying decrease of W. Received: 9 October 2000 / Reviewed and accepted: 10 October 2000     

Modified sol-gel process for the preparation of BaTiO3 and PbTiO3 ferroelectric films

A modified method for preparing barium and lead titanate films is suggested, which combines precipitation from solution and elements of sol-gel processing. The ∼1-μm-thick BaTiO₃/Pt and PbTiO₃/Pt films deposited on Pt foil are transparent, show good adhesion, and have the 1 : 1 : 3 stoichiometry. The films are finegrained, with a mean grain size of 0.1–0.2 μm. The barium titanate films are characterized byt _C = 110-125°C, ε₂₀ = 167-500, tanδ₂₀ = 0.015-0.06, ε_max = 1050,P _s= 3.2 μC/cm²,E _c = 14 kV/cm, ρ = (5-7) × 10⁹ Ω cm, andV _br = 80-150 kV/cm. The lead titanate films are characterized byc/a = 1.056, ε₂₀ = 105-110, tanδ₂₀ = 0.11-0.16,P _s = 4.1 μC/cm²,E _c = 34 kV/cm, ρ = (0.8-3.0) × 10⁹ Ω cm, andV _br = 50-100 kV/cm.     

Preferred orientation of AlN plates prepared by chemical vapour deposition of AlCl3 + NH3 system

Aluminium nitride (AlN) plates about 1 mm thick (maximum) were prepared by chemical vapour deposition (CVD) at the maximum deposition rate of 430 nm s⁻¹ using AlCl₃, NH₃ and H₂ gases at deposition temperatures,T _dep, of 873–1473 K. The effects of deposition conditions on the preferred orientation, morphology and micro-structure were investigated. WhenT _dep was less than 1073 K, the resulting CVD AlN plates contained some impurity chlorine and the aluminium content exceed the nitrogen content. WhenT _dep exceeded 1173 K, no chlorine was detected, and the Al/N atomic ratio matched the stoichiometric value. The lattice parameters (a=0.311 nm,c=0.4979 nm) and density (3.26×10³ kgm⁻³) were in agreement with values reported previously. The crystal planes oriented parallel to the substrates changed from (1 1 ˉ2 0) to (1 0 ˉ1 0) to (0001) with increasing total gas pressure (P _tot) and decreasingT _dep. This tendency is discussed thermodynamically and is explained by the change of supersaturation in the gas phase.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。     

Assurance of the Uniformity of Measurements of the Power of Laser Radiation

On the basis of an analysis of the principle underlying the construction of standards and systems designed for reproduction of the unit of mean power and energy of laser radiation, it is shown that these standards consist of unified subsystems that carry the principal metrological load. By means of such a division, it is possible to realize a systems-engineering synthesis of standards with preassigned error. __________ Translated from Izmeritel'naya Tekhnika, No. 11, pp. 20–23, November, 2005.     

方波幅度的测量不确定度

介绍了用众数法评价方波幅度时的不确定度分析和评价过程;讨论了主要的不确定度来源,包括众数判别区间的影响、波形测量系统幅度测量误差的影响等等;给出了减小不确定度的主要措施,并结合一个实例,给出了方波幅度的不确定度评价结果。     

Assurance of the Uniformity of Measurements of Energy of Short-Pulse Coherent Radiation

Ways of creating unified automatized reference (calibration) and standard measurement equipment for the purpose of developing a subsystem for the assurance of the uniformity of measurements of the energy of short-pulse laser radiation are considered. __________ Translated from Izmeritel'naya Tekhnika, No. 11, pp. 24–28, November, 2005.     

水线震荡对斜拉桥拉索风雨激振稳定性的作用

从理论和试验两个方面研究了水线震荡对斜拉桥拉索风雨激振稳定性的作用。建立了拉索和水线的运动方程，应用李雅普诺夫函数给出了水线不平衡角的判别公式。设计了一种新型的带有可运动人工水线的拉索模型，并进行了风洞试验。理论和试验结果表明，水线震荡是导致拉索风雨激振具有较大不稳定范围的主要原因。试验结果证明了理论模型和分析的结果是正确的。     

二硝基重氮酚重氮化反应机理再探

文中依据杂化理论分析了亚硝酸的结构特点，主要以分子结构理论为基础，从理论上指出在ＤＤＮＰ重氮化反应中，可能是氯化亚硝酰作为重氮反应的亲电试剂，其进攻发生在氨基的氮上，从而推测了获得ＤＤＮＰ的反应历程。     

逻辑分析仪部分参数测量结果的不确定度评定

介绍了逻辑分析仪部分参数测量结果的不确定度分析评定方法,评定过程及结论,可应用在对于计量标准进行相应指标的不确定度评定分析上。     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Calculation of the Heat of Combustion of Hydrocarbon Components of Fuels

Development is continued of the empirical method for the calculation of the heat of combustion of organic compounds and, in particular, of hydrocarbons of different structures by the additive scheme based on their chemical structure.