Electrochemical performance of compounds Ho_6Fe_(23–x)Co_x (x=0,1,3)

Alloys with composition of Ho6Fe23–xCox (x=0,1,3) were prepared and examined by X-ray diffraction technique and automatic battery testing instrument.The compounds Ho6Fe23–xCox (x=0,1,3) crystallized in cubic Th6Mn23-type structure with space group Fm 3m (No.225).The electrochemical properties of these alloys such as discharge capacity,cycling performance and high rate dischargeability were investigated by battery testing instruments in alkaline electrolyte.Substitution of small amounts of Co for Fe in Ho6Fe...     

Electrical and structural properties of coevaporated NiSi2 ± x thin films

Electrical and microstructural changes of coevaporated amorphous NiSi_{2 ± x}(x ~ 0.2) thin films were studied by means of in situ resistivity measurements and hot-stage transmission electron microscopy. The crystallization process is controlled by nucleation and growth both during continuous heating and isothermal annealing. Initially, the growth is isotropic. The process of crystallization is associated with a rapid decrease in resistivity. The temperature at which crystallization starts is affected by the heating rate. The temperature coefficient of resistivity (TCR) changes from a negative value in the amorphous state to a positive value in the crystallized state. Enriching the alloy film by silicon lowers the crystallization temperature. Kinetic studies showed that the isothermal crysallization follows a sigmoidal curve. The activation energy for the crystallization process was found to be ~ 1.45 eV. The transformation mode parameter was experimentally determined to be ~2.     

Thermoelectric properties of Yb x Co_4 Sb_（12） system

Yb x Co 4 Sb 12 polycrystals were fabricated by vacuum melting combined with hot-press sintering.The effect of Yb-filling on thermoelectric property of unfilled skutterudite CoSb 3 was investigated,which indicated the enhancement of the power factor of the material.Transport properties of materials changed from semi-conductor to semi-metal during the measurement of electrical conductivity,which indicated the change of electronic band structure.The maximum value of electrical conductivity was about 190000 S/m at 300 K for all samples.On the basis of Yb-filling,power factor of Yb 0.2 Co 4 Sb 12 reached 5-6 mW/(m·K) during the measurement temperature.Thermal conductivity decreased with increase of Yb content,and the thermal conductivity of Yb 0.2 Co 4 Sb 12 reached 3.2 W/(m·K) at 600 K.The ZT value of Yb 0.2 Co 4 Sb 12 reached 1.16 at 700 K due to positive contribution from high power factor and low thermal conductivity.     

Thermoluminescence of BaFCl_xBr_（1－x）：Sm System and Assignment of Their Glow Peaks

ＴｈｅｒｍｏｌｕｍｉｎｅｓｃｅｎｃｅｏｆＢａＦＣｌ_ｘＢｒ_（１－ｘ）：ＳｍＳｙｓｔｅｍａｎｄＡｓｓｉｇｎｍｅｎｔｏｆＴｈｅｉｒＧｌｏｗＰｅａｋｓＣｈｅｎＷｅｉ；（陈伟）；ＳｕＭｉａｎ－Ｚｅｎｇ；（苏勉曾）（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，...     

Characterization of an Al-Y-Zn Intermetallic Particle Phase in Extruded Mg96−x Al x Zn2Y1.9La0.1 Alloys

This study focuses on extruded Mg_96?x Al _x Zn₂Y_1.9La_0.1 alloys, which contain the long period stacking ordered Mg₁₂ZnY phase. The presence of Al results in the precipitation of Al-Y-Zn precipitates, the crystal structure of which is not adequately described by ternary Al-Y-Zn phases reported in the literature. Therefore, the purpose of this investigation is to characterize the precipitates morphologically, chemically, and crystallographically. After casting, the precipitates exist as complexly shaped micron-scale clusters within the microstructure. After extrusion, the phase appears as slightly faceted particles with a plate-like morphology. The crystal structure is hexagonal and its space group is $ P6_{3} /mmc $ . For the specific composition of Mg_95.50Al_0.50Zn₂Y_1.9La_0.1, the lattice parameters of this ternary phase are a ≈ 8.98 Å and c ≈ 7.1 Å and the stoichiometry is near equiatomic. However, with decreasing Al content of the alloy, the c parameter, degree of atomic ordering, and Zn content of the phase are all observed to increase. Specifically, for Mg_95.75Al_0.25Zn₂Y_1.9La_0.1, c ≈ 7.3 Å, and the stoichiometry is approximately AlYZn₂.     

Magnetic Properties of Melt-Spun Nanocomposite PrloFe74-x Co10＋x C4B4（x=0,2,4,6,8） Ribbons

Phase evolution and magnetic properties of melt-spun Pr10Fe74-xCo10 xC4B4(x=0,2,4,6,8 ) alloy ribbons were investigated. Increasing the Co content is found to promote the generation of the 2: 14:1 phase, which results in a significant increase of coercivity and remanence.     

Catalysis of Ce_xZr_(1–x)O_2 for di-iso-propyl-ether hydration

The catalytic potential of CexZr1–xO2 in isopropyl ether(DIPE) hydration was explored. While the acidic H-zeolite catalyst was favorable for propylene formation through carbenium ion mechanism, Ce-ZSM-5 and CexZr1–xO2 catalysts improved product selectivity of isopropyl alcohol(IPA) through redox mechanism. The catalytic property of CexZr1–xO2 depended on the preparation method and variable, type of cerium precursor and Ce/Zr ratio. By means of characterizations with X-ray diffraction, N2 adsorption isotherms and NH3 temperature programmed desorption, tetragonal phase of CexZr1–xO2 was proposed as the active phase in which CeO2 and ZrO2 catalyzed synergistically the DIPE hydration with IPA product selectivity. The CexZr1–xO2 prepared from cerium sulfate precursor with co-precipitation hydrothermal method exhibited maximum catalytic activity and IPA product selectivity. The precursor effect was attributed to the stabilization of SO42– species on the tetragonal phase of CexZr1–xO2 and super solid acidity.     

Structural and Electrical Properties of Layered Pervoskite Manganites Nd2-2x Sr1＋2x Mn2O7 （x=0.25, 0.3, 0.4）

Tetragonally layered perovskite manganites of Nd2-2xSr1＋2xMn2O7（x =0.25, 0.3, 0.4） were fabricated by using solid-state reaction technique. Structural characterization of the compounds was investigated by X-ray diffraction （XRD） and FT-IR absorption spectra. The XRD patterns revealed that all the samples were single phase. X-ray photoemission spectroscopy （XPS） was used to investigate their electronic structures. It was found that manganese was in mixed states of Mn^3＋ and Mn^4＋ whereas lattice oxygen and chemical absorbed oxygen were existed in all the samples. The high temperature electrical properties of Nd2-2xSr1＋2xMn2O7 （x = 0.3, 0.4） were measured by standard four-probe technique. The results showed that both compounds had semi-conductivity behavior in the temperature range of 300 - 1073 K, and the electrical conduction was dominated by thermally activated behavior above 500 K.     

Chemical stability of simulated waste forms Zr_(1–x)Nd_xSiO_(4–x/2): Influence of temperature,pH and their combined effects

The chemical stability of simulated waste forms Zr_(1–x)Nd_xSiO_(4–x/2) was investigated using the static leach test(MCC-1) with lixiviants of three pH values(pH=4, 6.7 and 10) at three temperature points(40, 90 and 150 oC) for periods ranging from 1 to 42 d, and the influence of temperature, pH, as well as their combined effects were explored in detail. The results showed that all the normalized release rate of Nd firstly decreased with leaching time and closed to equilibrium after 14 d. As the temperature increased, the normalized release rate of Nd also increased, but it was no more than 3×10~(–5) g/(m~2·d). And, the normalized release rate of Nd reached the highest values(~5×10~(–5) g/(m~2·d)) when pH=4, whilst the normalized release rate of Nd remained the lowest value(~1×10~(–5) g/(m~2·d)) near neutral environment(pH=6.7).     

Effect of Aluminium Addition on Glass Forming Ability of Nd55-x Al10＋x Fe15 Co20 （x = 0, 5, 10） Alloys

Nd55-x Al10＋x Fe15 （x =0, 5, 10） bulk glass-forming alloys with distinct glass transition in differential scanning calorimetry （DSC） traces were obtained by suction casting, The glass forming ability （GFA） of the alloys was investigated. It was found that the reduced glass transition temperature （Trg） and the parameter γ of the alloys increased with the increasing concentration of Al. The glass formation enthalpy of the alloys was calculated based on Miedema＇s model, and it was suggested that the GFA of the alloys could be enhanced by the decrease of the glass formation enthalpy with Al additions.     

新型USB音频集成电路CX2077x、CX3102x

商科胜讯系统公司推出CX2077x和CX3102x产品系列。CX2077又是业界第一个USB音频集成电路，在单一芯片封装上集成了片上数字信号处理器、三色LED脉冲宽度调制和LED驱动器。这两种产品是嵌入式音频解决方案的一部分，专门针对耳机、麦克风、坞站和扬声器等USB音频外设而设计。     

Chemical State, Site, Solid Solubility, and Magnetism of Fe in the Ferropericlase (Mg1–x Fe x )O Produced by Ball Milling of MgO and Fe

Ferropericlase (Mg_1–x Fe _x )O solid solution was prepared by ball milling of the mixture of MgO with a rock-salt structure and metal Fe powders in atmosphere and at room temperature. Differing from (Mg_1–x Fe _x )O prepared at high temperature by using MgO and FeO as starting materials, the solution of Fe in MgO is not continuous but limited in the ball milling process, and the solubility limit is less than 30 at. pct. About 92 pct of the Fe ions occupy the site of tetrahedral oxygen coordination in trivalent Fe (Fe³⁺) with high spin, whereas about 8 pct of the Fe ions occupy the site of octahedral oxygen coordination in bivalent Fe (Fe²⁺) with high spin. The Fe³⁺ and Fe²⁺ ions do not show a ferromagnetic but show a paramagnetic state. The as-milled (Mg_1–x Fe _x )O is metastable and decomposes to ferropericlase (Mg_1–y Fe _y )O (where y < x) and MgFe₂O₄ with spinel structure as annealed above 773 K (500  °C), and the content of Fe in the (Mg_1–y Fe _y )O increases with increasing annealing temperature. A bulk (Mg_1–x Fe _x )O was fabricated by annealing the as-milled (Mg_1–x Fe _x )O powders at 973 K (700  °C). It shows n-type conductivity, which is attributed to an electronic small polaron with an activation energy of 0.135 eV.     

重要极限lim(x→0)(1+x)1/x=e的一个推广

我们把重要极限lim(x→0)(1+x)1/x=e推广为lim(x→0)(1+a(x))β(x)=elim(x)β(x)x→0,其中lim(x→0)a(x)=0,lim(x→0)β(x)=∞.从而可以简化这一类型的极限计算.     

The Effect of Bath Parameters on the Electrocrystallisation of Cox–Cu100−x Alloys on Stainless Steel Cathode

The electrocrystallisation of the alloys of Co_x–Cu_100?x onto stainless steel cathode was investigated by performing cyclic voltammetry (CV) to understand the mechanism of deposition. The deposit morphology and crystal structure of deposit were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The kinetic parameters were obtained from the cathodic polarisation of the CV to predict the electron transfer mechanism in the process. The transfer coefficient value (α) of the kinetic parameter revealed that both cathodic and anodic processes were unsymmetrical. It was demonstrated that the current efficiency of the deposit increased from 96.8% at pH 4.0 to 99.2% at pH 7, and then it dropped to 89.7% at pH 8. Before the deposition of the Co–Cu alloy, the initial copper deposition occurred at ??0.24 V and peaked at ??0.66 V. This was followed by the deposition of the Co–Cu alloy at ??1.04 V, which occurred after the deposition potential of Cu²⁺ (??0.24 V) and Co²⁺ (??0.89 V). The current then increasesd with a small increment in applied potential due to subsequent diffusion-controlled copper reduction along with the co-deposition of Co. The variation in the kinetic parameters was also reflected in the current efficiencies, the deposit morphologies, the crystallographic orientations and the nucleation overpotential values. The percentage of cobalt content in the alloy was observed to decrease in at.% from 54.35% at pH 4 to 49.86% at pH 6 and further to 20.62% at pH 8. The structure of the deposited alloy confirmed the formation of a single solid solution phase having different planes such as (222), (311), (220), (200) and a sharp peak due to face-centred cubic structure with (111) plane. This strong peak along with other similar peaks were observed in all the XRD of the deposit obtained at pH 4, 6 and 8. The morphology of the deposit characterised by the SEM showed that the deposit changed from a bitter gourd to a regular cauliflower-like structure as the pH value changed from 4 to 8.

     

Nanocrystalline Gd_(1–x)Ca_xFeO_3 sensors for detection of methanol gas

The sol-gel method was used to prepare the nanocrystalline Gd_(1–x)Ca_xFeO_3 (x=0–0.4) powders. The XRD results showed that all the Gd_(1–x)Ca_xFeO_3 (x=0–0.4) compounds crystallized as perovskite phase with orthorhombic structure. The doping of Ca in GdFeO_3 not only reduced the resistance, but also enhanced the response to methanol. The Gd_(0.9)Ca_(0.1)FeO_3 showed the best response to methanol among Gd_(1–x)Ca_xFeO_3 sensors. Besides, it showed good selectivity to methanol among methanol, ethanol, CO and formaldehyde gases. The responses at 260 oC for Gd_(0.9)Ca_(0.1)FeO_3-based sensor to 600 ppm methanol, ethanol and CO gases were 117.7, 72.7 and 31.9, respectively. Even at quite low gas concentrations, Gd_(0.9)Ca_(0.1)FeO_3-based sensor had an obvious response. At 260 °C, the response of 1.54 was obtained to be 45 ppm methanol. The experimental results showed that nanocrystalline Gd_(0.9)Ca_(0.1)FeO_3 based sensor can be used to detect methanol gas.     

Thermal and transport properties of La_(2–x)Nd_xMo_2O_9

Single-phase La_(2–x)Nd_xMo_2O_9(0≤x≤1.8) compounds were prepared using solid-state reaction technique. Their structural and thermal p roperties were characterized by room and high temperatures X-ray diffraction(XRD), thermo gravimetric analysis-differential scanningcalorimetry(TG-DSC), and high temperature Raman spectra. The transport properties were investigated using D.C. four-probe technique and Hebb-Wagner polarization method. The substitution limit of Nb~(3+) in La_(2–x)Nd_xMo_2O_9 was determined to be in the range of 1.8x1.9, and the cubic lattice parameter of La_(2–x)Nd_xMo_2O_9 decreased linearly with the increasing of x. When the Nb~(3+) substitution content x was larger than 0.6, the α/β phase transition could be depressed to such a great degree that the phase transition thermal enthalpy was not detected by DSC. The temperature dependence of electrical conductivities for La_(1.4)Nd_xMo_2O_9 below 873 K and that for LaNdMo_2O_9 below 923 K obeyed the Arrhenius law, while above 873 and 923 K Vogel-Tammann-Fulcher(VTF) model could describe the conduction behaviors satisfactorily. The transition of transport mechanism from Arrhenius to VTF was caused by the change of structure, which was supported by the high temperature XRD and Raman results. The ionic transport number of La_(1.4)Nd_xMo_2O_9 in air was larger than 0.99 at 1073 K, and with the increasing of temperature it was close to 0.98 at 1173 K. In view of the phase transition, thermal expansion and conductivity properties, La_(1.4)Nd_xMo_2O_9 should be a promising electrolyte material in La_(2–x)Nd_xMo_2O_9 series.     

Magnetocaloric properties,microhardness and corrosion resistance of Gd_(100–x)Zr_x alloys

With the intention to improve its mechanical properties and corrosion resistance,the magnetocaloric metal Gd was alloyed with Zr by arc melting and heat treatment.All Gd_(100-x)Zr_x(x=0,0.5,1,1.5,2) alloys with various Zr dopings showed hexagonal crystal structure.The Curie temperatures(TCs) of Zr doped alloys were lower than that of Gd by ~2 K.The maximum magnetic entropy changes of Gd_(99.5)Zr_(0.5) alloy under magnetic field changes of 0-2 T and 0-5 T were 5.27 and 9.41 J/(kg·K),respectively,which were larger than that of pure Gd metal.The addition of a small amount of Zr increased the microhardness of Gd by at least 29.3%.The corrosion resistance of Gd was also improved by Zr doping,demonstrated by increased corrosion potential and reduced corrosion current density in electrochemical polarization curves measurements.These enhanced properties were beneficial to the potential applications of Gd_(100-x)Zr_x alloys as magnetic refrigerants at room temperature.     

半导体化合物Hg_（1－x）Cd_xTe中x值的测定

半导体化合物Ｈｇ_（１－ｘ）Ｃｄ_ｘＴｅ具有大的光学吸收系数，适于制波长为８～１４μｍ的红外探测器。由于禁带宽度随化合物的组分而变化，在Ｈｇ_（１－ｘ）Ｃｄ_ｘＴｅ中ｘ值的变化对红外探测器的性能有根大影响。本文用配有ＴＮ－５５００能谱仪的ＪＳＭ－８４０扫描电镜测定此化合物中不同试样的ｘ分布值。用从实验中得到的镉的重量百分比计算出每种试样２５个点的ｘ值、ｘ的平均值及均方差，测量误差为４．５％，ｘ平均值的计算结果与用Ｘ荧光方法测量的ｘ值一致。     

Effect of Mn Substitution on Microstructure Evolution and Magnetic Phase Transition in La(Fe1−x Mn x )10.8Co0.7Si1.5 Compounds

The influences of Mn substitution for Fe on microstructures of La(Fe_1?x Mn _x )_10.8Co_0.7Si_1.5 (x = 0, 0.01, 0.02, 0.03) alloys in both the as-cast state and the annealed state have been studied. The results show that Mn substitution promotes the fining of the as-cast microstructure and increases the formation of 1:13 phase significantly when annealed. An almost single 1:13 phase is obtained for x = 0.01 when annealed at 1373 K (1100 °C) for 3 days, while a large amount of impurity phases is still present for x = 0. By increasing the amount of Mn to x = 0.02, a more purified annealed microstructure can be obtained. However, further substitution of Mn up to x = 0.03 is harmful for the formation of 1:13 phase. The Curie temperature T _C of the annealed La(Fe_1?x Mn _x )_10.8Co_0.7Si_1.5 (x = 0, 0.01, 0.02, 0.03) varies monotonously with Mn content x, decreasing from ~279 K (6 °C) for x = 0 to ~236 K (?37 °C) for x = 0.03. When x = 0.01, a higher maximum entropy change (?ΔS)_max of 5.3 J/(kgK) and relative cooling power (RCP) of 166 J/kg can be obtained under a magnetic field of 2T. Further substitution of Mn (x = 0.02) results in a slight decrease of (?ΔS)_max, whereas a larger RCP can still be kept.