Electrochemical Processes at the Bi<Superscript>0</Superscript>–Bi<Superscript>3+</Superscript> Interface in Chloride Melts

For rational design of technological schemes for production of high-grade bismuth and to improve electrochemical bismuth refining, knowledge of physicochemical properties of low-valent bismuth compounds and the mechanisms underlying processes occurring at the Bi⁰–Bi³⁺ interface in molten salts is necessary. For this purpose, the kinetics and mechanism of formation of low-valent bismuth compounds in the Bi⁰–BiCl₃–ZnCl₂–NH₄Cl system by UV–Vis spectroscopy was studied. Chemical interactions between metallic bismuth and Bi³⁺ species in the melt give rise to Bi+ intermediates and [Bi₅]³⁺ clusters, which are registered by their characteristic absorption bands at approximately 18000 and 14000 cm^–1. The kinetic parameters for the Bi⁺ and [Bi₅]³⁺ formations are estimated from the dependence of intensities of these absorption bands on the time of contact between metallic bismuth and Bi³⁺ species in the melt. The rate constants characterizing the Bi⁺ and [Bi₅]³⁺ formations are estimated to be 3.33 × 10^–3 and 2.31 × 10^–3 s^–1, respectively. The mechanism of anodic bismuth dissolution is proposed, and the cathodic and anodic current efficiencies for bismuth are determined.     

Effect of SO<Subscript>4</Subscript> <Superscript>2-</Superscript>, Cl<Superscript>–</Superscript> and NO<Subscript>3</Subscript> <Superscript>-</Superscript> anions on the formation of iron oxide nanoparticles via microwave synthesis

In the present work iron oxide nanoparticles have been prepared by microwave assisted synthesis with the influence of different precursor salts and synthesis of magnetite, hematite, Iron oxide hydroxide and maghemite nanoparticles. Synthesized iron oxide nanoparticles were characterized with Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and Energy-dispersive X-ray Spectroscopy (EDX). XRD measurements show that the peaks of diffractogram are in agreement with the theoretical data of magnetite, hematite, FeO(OH) (Iron oxide hydroxide) and maghemite. Crystallite size of the particles was found to be 33, 45, 36 and 43.5 nm for Fe₃O₄, α-Fe₂O₃, FeO(OH) and γ-Fe₂O₃. FESEM studies indicated that size of the particles is observed in the range of about 19.4 to 46.7 nm (Fig. 2a, average 32 nm), 29.1 to 67.6 nm (Fig. 2b average 45 nm), 29.1 to 40.8 (Fig. 2c average 36.6 nm), 29.1 to 80 nm (Fig. 2d average 43.5) for Fe₃O₄, α-Fe₂O₃, FeO(OH) and γ-Fe₂O₃ respectively. EDX spectral analysis reveals the presence of carbon, oxygen, iron in the synthesized nanoparticles. The FTIR graphs indicated absorption bands due to O–H stretching, C–O bending, C–H stretching and Fe–O stretching vibrations.     

Characterization of γ and γ′ phases in 2<Superscript>nd</Superscript> and 4<Superscript>th</Superscript> generation single crystal nickel-base superalloys

A Ni based single crystal superalloy from the 2^nd generation, PWA 1484, and one from the 4^th generation, PWA 1497, were comparatively studied by scanning electron microscopy, energy dispersive X-ray spectroscopy and nanoindentation technique in an atomic force microscope (NI-AFM) after high temperature creep deformation. During primary creep of both generations of superalloys, γ′ precipitates start to coalesce and grow directionally. Further creep deformation leads to the topological inversion and coarsening of the rafted microstructure. The NI-AFM technique was used for measurements of the hardness of the γ and γ′ phases in as-received and creep deformed samples in various conditions. The g matrix of the PWA 1497 superalloy is on average 0.8 GPa harder than that of PWA 1484 that can be explained by higher content of Re and Ru, since they partition predominantly to the matrix phase.     

Microstructural Effects on the Mechanical Properties of ATI 718Plus<Superscript>®</Superscript> Alloy

Four microstructural variants of ATI 718Plus^® alloy (718Plus) have been investigated to elucidate the effects of grain size, precipitate size, morphology, and phase fraction (δ and γ′) on mechanical properties such as low cycle fatigue (LCF) life, fatigue crack growth rate (FCGR) properties, and dwell FCGR behavior at both 649°C and 704°C under 100 s dwell and nondwell conditions. Similar tests have also been performed on Waspaloy in two comparative microstructural conditions. LCF test results demonstrate that all four microstructural conditions of 718Plus have superior life compared with Waspaloy under all investigated test conditions. FCGR results show that, at both test temperatures, all microstructural conditions of 718Plus and Waspaloy exhibit identical behavior in the steady-state regime, except that 718Plus exhibits a much higher threshold stress intensity (ΔK _TH). However, the dwell FCGR results show that Waspaloy displays better steady-state crack growth resistance under dwell conditions. However, with a thermal exposed precipitate microstructure, 718Plus shows considerable improvement in this response.     

<Superscript>57</Superscript>Fe Mössbauer spectroscopy of synthesized ɛ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles

Magnetic nanoparticles have promising applications in many areas, for example optics, electronics, biology, medicine, etc. The primary goal of this study was to synthesize nanoparticles of magnetic ?-Fe₂O₃ embedded in amorphous SiO₂. The structure and properties of the final product have been found to depend strongly on the initial conditions of preparation. The Mössbauer spectroscopy analysis of the samples was complemented by the study of X-ray powder diffraction, magnetic measurements, and high-resolution transmission electron microscopy.     

VUV photoluminescence of La<Subscript>1−x</Subscript>Gd<Subscript>x</Subscript>PO<Subscript>4</Subscript>:Tb<Superscript>3+</Superscript> green phosphors synthesized by ultrasonic spray pyrolysis

(La_1−xGd_x)_0.94PO₄:Tb_0.06 (0 ≤ x ≤ 1.0) green phosphors were synthesized by an ultrasonic spray pyrolysis process. The annealed (La_1−xGd_x)_0.94PO₄:Tb_0.06 phosphors exhibited the formation of a single-phase oxide with the monoclinic monazite structure. Higher Gd³⁺ content yielded a smaller lattice parameter. The phosphors emitted green light due to the ⁵D₄→⁷F_J (J = 3, 4, 5, and 6) transition of Tb³⁺ at 489 nm, 543 nm, 585 nm, and 621 nm, respectively. The predominant peak at 543 nm was nearly a single peak, which was responsible for the green color emission. Among the (La_1−xGd_x)_0.94PO₄:Tb_0.06 phosphors, the strongest emission intensity was obtained for (La_0.25Gd_0.75)_0.94PO₄:Tb_0.06.     

Nanostructured Si,Mg, CO<Subscript>3</Subscript><Superscript>2−</Superscript> Substituted Hydroxyapatite Coatings Deposited by Liquid Precursor Plasma Spraying: Synthesis and Characterization

In this study, a novel liquid precursor plasma spraying (LPPS) process was used to deposit Si, Mg, CO₃ ²⁻ substituted hydroxyapatite (HA) coatings (alone and cosubstituted) onto Ti-6Al-4V substrates. Salts of silicon, magnesium, and carbonate elements were directly added into the HA liquid precursor for subsequent plasma spraying. The phase composition, structure, and morphology of all HA coatings were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The results indicated that the trace elements were successfully incorporated into the HA structure and nanostructured coatings were obtained for all doped HA formulations. The incorporation of trace elements into the HA structure reduced its crystallinity, especially when silicon, magnesium and carbonate ions entered simultaneously into the HA structure. FTIR spectra showed that the Si-HA and Mg-HA coatings had decreased intensities in both the O-H and P-O bands and that the CO₃ ²⁻-HA coating was mainly a B-type carbonate-substituted HA. The results showed that the LPPS process is an effective and simple method to synthesize trace element substituted biomimetic HA coatings with nanostructure.     

Influence of Fe and Ti addition on properties of Na<Superscript>+</Superscript>-β/β″-alumina solid electrolytes

Transition metal (Fe, Ti)-doped Na⁺–β/β″-alumina samples were synthesized via a solid-state reaction, and the sintered specimens were characterized using X-ray diffraction, scanning electron microscopy, densitometry, and impedance analysis. The results indicated that both the sintered density and β"-alumina fraction were effectively improved by doping with Fe and Ti because of the increased concentration of Al³⁺ ion vacancies in the Na⁺–β/β″-alumina. These vacancies promoted stabilization of the β″-alumina phase and densification by providing a diffusion path for Al³⁺ ions. The presence of Fe and Ti in the alumina increased the grain boundary diffusivity, thereby improving the mass transport. Thus, anisotropic grain growth occurred with increasing dopant content. However, excessive liquid-phase formation during sintering occurred when the amount of Ti was greater than 2.0 mol%, and the lowered sintered density decreased the ionic conductivity of the Na⁺-β/β″-alumina because the ionic conductivity behavior has a closer relationship to the trend of sintered density. The highest ionic conductivities of the Fe- and Ti-doped sintered specimens were 1.4 × 10^-1 S/cm (10.0 mol% Fe-doped) and 1.6 × 10^-1 S/cm (1.5 mol% Ti-doped) at 350 °C.     

Synthesis and sensor propeties of crown-containing derivatives of 4-(1,5-diphenyl-Δ<Superscript>2</Superscript>-pyrazolin-3-yl)-1,8-naphthalimide

Previously undescribed derivatives of 4-(1,5-diphenyl-Δ²-pyrazoline-3-yl)-1.8-naphthalimide that contain a moiety of benzo-15-crown-5- and N-phenylaza-15-crown-5-ether in the composition of the N-aryl substituent at the imide nitrogen atom of the naphthalimide nucleus have been synthesized. The derived compounds have a long-wavelength band in the absorption spectra in the region of 480 nm owing to charge transfer from the electron-donor pyrazoline moiety onto the carbonyl groups of the carboxyimide group. The fluorescence peaks are located in the region of 670 nm. In the series of the synthesized pyrazolinylnaphthalimides, the effect of the nature of the N-aryl moiety on the spectral-luminescent properties has been analyzed. It has been shown that the annelation of the 15-crown-5-ether moiety with the benzene ring of the N-phenyl substituent of 4-pyrazolinyl-N-phenyl naphthalimide does not change the position of bands in the absorption and fluorescence spectra and has little effect on the fluorescence quantum yield. At the same time, the presence of the N-phenylaza-15-crown-5-ether group in the composition of the N-aryl moiety leads to a small hypsochromic shift of the peaks in the absorption and emission spectra and to a decrease in fluorescence intensity attributed to the occurrence of a nonradiative process of electron transfer from the N-aryl substituent onto the photoexcited naphthalimide chromophore. The proposed explanation for the observed spectral effects has been confirmed by the data of semi-empirical quantum-chemical calculations using the PM6 method. The complexation of crown-containing 4-pyrazolinylnaphthalimides was studied employing alkaline earth metal cations (Mg²⁺ and Ca²⁺) in acetonitrile solutions. ¹H NMR spectroscopy has revealed that the coordination of the cation occurs through the crown-ether receptor. Upon complexation, in the absorption and fluorescence spectra, a bathochromic shift of the peaks of the long-wavelength bands by 6–15 nm was observed. The binding of the Mg²⁺ cations by the benzo-15-crown-5-ether derivative of naphthalimide was accompanied by fluorescence quenching, while in the case of 4-pyrazolinylnaphthalimide containing an N-phenylaza-crown-ether moiety in the N-aryl substituent, during the complexation with the Ca²⁺ cations, fluorescence buildup was observed. The spectrofluorometric titration data were used to determine the stability constants of complexes of crown-containing naphthalimides with alkaline earth metal cations with a composition of 1: 1 in acetonitrile. These studies have shown that the synthesized compounds are promising from the standpoint of developing fluorescent sensors for cation analysis.     

Influence of the surface morphology of aluminum foil on the probability of heterogeneous recombination of О(<Superscript>3</Superscript>Р) atoms in oxygen plasma

The process of recombining oxygen atoms on the surface of an aluminum foil and thin film is investigated in the positive column of the DC glow discharge in oxygen at a gas pressure of 200 Pa, a discharge current of 50 mA, and surface temperatures of 350–530 K. It is shown that an increase in the average surface roughness leads to a decrease of the probability of the heterogeneous recombination of O(³P) atoms. The values of the apparent activation energy for the process of heterogenic recombination of oxygen atoms are calculated.     

Influence of Al Addition on Oxidation Behavior of Cu–Ni–Cr Alloys at 973–1073 K in 1.01 × 10<Superscript>2</Superscript> kPa Pure Oxygen

The oxidation behavior of Cu–20Ni–15Cr–2.5Al and Cu–20Ni–20Cr–2.5Al alloys was studied at 973–1073 K in 1.01 × 10² kPa pure oxygen. The oxidation kinetics exhibited large deviations from the parabolic rate law and were comprised of three or four quasi-parabolic stages. Oxidation rates of the present alloys were much lower than those previously reported for a Cu–20Ni–20Cr alloy. Cu–20Ni–15Cr–2.5Al alloy formed a continuous scale of chromia in contact with the alloy, while at other locations, the scale formed deep protrusions into alloy along β phases. Cu–20Ni–20Cr–2.5Al alloy formed a continuous scale of chromia with a small quantity of light and unoxidized precipitates of α phase, especially at 1073 K. There was a thin layer depleted in Cr beneath the continuous scales of chromia. The addition of 2.5 at.% Al to Cu–Ni–Cr alloy made the diffusion of reactive component Cr become much faster and facilitated the formation of a continuous external scale of chromia for a lower Cr content.     

DyF&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;掺杂热变形NdFeB磁体的微观结构和性能

基于热变形技术,研究制备了DyF3掺杂热变形NdFeB磁体的微观结构和磁性能。结果表明,通过热变形,磁体获得了具有明显C轴取向特征的扁平形状晶粒,其剩磁从前驱体烧结磁体的0.77 T提高至 1.34 T,提升了近74%。此外,热变形过程起到了晶界扩散的作用,使得DyF3进一步扩散至NdFeB主相之中,形成了(Nd, Dy)2Fe14B相,从而减小了因热变形带来的矫顽力损失。电化学测试表明,热变形过程可提高磁体腐蚀电位和减小电流密度。变形条件800 ℃/70%时,磁体具有最佳的综合磁性能和电化学性能,其磁性能可达：Br=1.34 T,Hcj=1225 kA/m和(BH)max=286 kJ/m3。     

"仿制"和"创新"

有资料表明,德国通过相关部门对当地三百多家企业进行问卷调查,结果显示有2/3的企业认为自己面临产品仿制和技术剽窃的威胁,并且堪称在中国发生几率最高.报告中还指出,近些年中国产品与技术剽窃水平有了一个新的发展,即从原先的个别元件组件到整台设备乃至整条生产线过渡.使德国很多企业不再考虑向中国转移自己的研发部门.而上述这种水...     

Synthesis and characterization of Ba<Subscript>0.5</Subscript>Sr<Subscript>0.5</Subscript>Co<Subscript>0.8</Subscript>Fe<Subscript>0.2</Subscript>O<Subscript>3−σ</Subscript>

Perovskite-type Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCFO) powders were synthesized using two methods, solid-state reaction (SSR) method and citrate-EDTA complexing method (CC-EDTA). Then the powders were pressed to green disks of 19 mm in diameter and sintered at 1140°C for 5 h. The shrinkage rate and relative density of the membranes prepared from the perovskite-type powders were determined and calculated, and the powders and derived membranes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the shrinkage rates of the two kinds of disks are nearly the same (about 10%). The disks prepared by the SSR method had a bigger grain size and lower relative density than those prepared by the CC-EDTA method. The conductivity of the membranes prepared by the SSR method was about 38 S/cm, higher than that of the membranes prepared by the CC-EDTA method, which was about 30 S/cm, at the same temperature of 600°C.     

TiAl合金表面阴极微弧沉积Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;陶瓷涂层的生长过程与相组成

目的：利用阴极微弧沉积技术在预处理后的TiAl合金表面制备了Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;陶瓷涂层,研究了涂层的生长过程和相组成。方法：采用电子扫描电镜(SEM、EDS)、电子透射电镜(TEM)、X射线衍射(XRD)等方法,对Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;涂层的生长过程中的微观形貌、组织成分以及晶体结构的演变进行了研究与分析。结果：TiAl合金表面阴极微弧沉积过程中,在阴极表面发生非晶态Al(OH)&lt;sub&gt;3&lt;/sub&gt;的吸附、脱水烧结形成Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;陶瓷涂层的沉积。结论：Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;涂层生长分前期Ⅰ、中期Ⅱ和后期Ⅲ三个阶段,前期起弧阻挡层被击穿,涂层生长较慢、组织致密且与基体结合良好;反应中期涂层生长较快,Al(OH)&lt;sub&gt;3&lt;/sub&gt;不断吸附和脱水烧结,涂层结晶度提高;反应后期涂层生长速度变缓,表层组织疏松、多孔,相组成为87.5 %的α–Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;和12.5 %的γ–Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;。     

Fe₇₃Si₁₅Nb₃B₈Cu₁铁芯薄带的热处理工艺研究

本文对用Finemet型Fe73Si15Nb3B8Cu1快淬薄带制备的铁芯增加预退火处理,再在540 oC晶化退火处理得到退火铁芯。结果表明,随着预退火温度提高,预退火的薄带及再经晶化退火的薄带的韧性均逐渐降低,预退火后非晶薄带的第一晶化温度变化不大,而第二晶化峰值温度向高温方向偏移,预退火扩大了非晶薄带晶化退火的温度范围,有利于获得性能更加稳定的非晶纳米晶薄带;增加预退火处理的薄带的晶粒尺寸比直接晶化退火薄带的晶粒分布更均匀,其中在450 oC预退火的薄带经晶化退火后,晶粒尺寸在8~15 nm之间。增加预退火的铁芯样品,其振幅磁导率和铁损较直接退火的均有明显改善,其中经450 oC预退火的铁芯具有最大的振幅磁导率（μa=8.6×104, f=10 kHz）和最小的交流铁损（P0.5/10k=8.7 W/kg）,分别较直接退火的铁芯升高了16.0%,下降了17.1%。     

Spark Plasma Sintering of α/β Si<Subscript>3</Subscript>N<Subscript>4</Subscript> Ceramics with MgO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and MgO-Y<Subscript>2</Subscript>O<Subscript>3</Subscript> as Sintering Additives

In the present work, the α/β Si₃N₄ ceramics were fabricated by spark plasma sintering (SPS) at 1400-1500 °C for 6 min with 3wt.%MgO + 5wt.%Al₂O₃ and 3wt.%MgO + 5wt.%Y₂O₃ as sintering additives. The results showed that the phase composition, microstructure and mechanical properties of α/β Si₃N₄ ceramics were highly dependent on the type of sintering additive. The incomplete phase transformation from α to β occurred in the presence of an oxynitride (Mg-Al(Y)-Si-O-N) liquid phase. Compared with MgO-Al₂O₃, MgO-Y₂O₃ can significantly improve the β conversion rate of as-sintered α/β Si₃N₄ ceramics. And the as-sintered ceramics using MgO + Al₂O₃ as sintering additives had higher mechanical properties.     

Zn_²⁺掺杂对共沉淀法制备Ce:Gd₃Ga₃Al₂O₁₂陶瓷粉体闪烁性能的影响

本文利用化学共沉淀法制备Zn_²⁺共掺的Ce:GAGG陶瓷粉体。研究了Zn_²⁺共掺的Ce:GAGG陶瓷前驱粉体的TG/DTA和FTIR曲线;分析了不同煅烧温度对Ce:GAGG陶瓷粉体相、形貌和颗粒度分布的影响;系统研究了Zn_²⁺含量对Ce:GAGG陶瓷粉体光致发光,辐射发光,激发光谱和荧光寿命的影响。研究表明：前驱粉体在883℃的相组成为GdAlO₃相和GAGG相;前驱粉体在煅烧温度为900℃时,完全转化为GAGG相;当煅烧温度为1200℃时,GAGG颗粒尺寸控制在20nm~60nm,分布均匀;随着 Zn_²⁺含量的变化,光致发光和辐射发光强度也相应变化,特别的,当Zn_²⁺含量为0.4mol%时,光致发光和辐射发光强度达到最大值;随着Zn_²⁺掺杂含量的上升,荧光寿命出现下降的趋势。因此,Zn_²⁺含量对Ce:GAGG陶瓷粉体的辐射发光具有明显的影响,对降低荧光寿命具有积极的作用,对于提高GAGG闪烁材料的快速响应具有重要意义。     

Air Oxidation of a Ni<Subscript>53</Subscript>Nb<Subscript>20</Subscript>Ti<Subscript>10</Subscript>Zr<Subscript>8</Subscript>Co<Subscript>6</Subscript>Cu<Subscript>3</Subscript> Glassy Alloy at 400–550 °C

Air-oxidation behavior of a Ni₅₃Nb₂₀Ti₁₀Zr₈Co₆Cu₃ amorphous ribbon was studied at 400–550 °C. The oxidation kinetics of the amorphous alloy followed a two-stage parabolic rate law with its oxidation rates steadily increasing with temperature. The steady-state oxidation rate constants of the alloy were faster than those of pure Ni. Triplex scales formed on the glassy alloy, containing an outer layer of NiO. The scales formed in the intermediate layer consisted of Nb₂O₅, NiO, and uncorroded α-Ni, while an additional Nb₂Zr₆O₁₇ phase was also detected in the inner layer. The formation of multilayered scales is responsible for the faster oxidation for the Ni6-AR.     

Ferromagnetic manganites La<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ca<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>MnO<Subscript>3</Subscript>

A brief review of properties of the ferromagnetic manganites La_{1 − x} Ca _x MnO₃ is given. Lattice properties, magnetic properties, transport phenomena, magnetic resonance, and the results of neutron diffraction and optical studies are considered. Special attention is paid to effects observed near the Curie temperature.