Preparation of high-purity SiC ceramics with good plasma corrosion resistance by hot-pressing sintering

High-purity SiC ceramic devices are applied in semiconductor industry owing to their outstanding properties. Nevertheless, it is difficult to densify SiC ceramics without any sintering additive even by HP sintering. In this work, high-purity and dense SiC ceramics were fabricated by HP sintering with very low amounts of sintering aids. Residual B content was only 556 ppm and relative density was more than 99.5%. Furthermore, thermal conductivity of as-prepared SiC ceramics was improved from 155 W m^?1 K^?1 to 167 W m^?1 K^?1 by increasing holding time and their plasma corrosion resistance was promoted in the meantime. The as-prepared high-purity SiC ceramics have broad application prospects in the field of semiconductor industry.     

电子工业用高纯氮的生产

生产电子工业用高纯氮的制氮装置 ,其要点和难点是一氧化碳和氢的清除。采用一氧化碳转换炉和特殊的冷箱内流程组织 ,可以生产纯度为 99 9999%以上的高纯氮。对制取电子工业用高纯氮制氮装置与常规制氮装置加氮终端净化器两种流程进行了比较。     

降低高纯铅中的Cu、Bi、Sn等杂质含量

本文叙述了用电解精炼法在制备高纯铅过程中，降低铜、铋、锡杂质含量的各种措施和试验结果，比较详细地介绍了用硫化法降低电解液中的铜、铋、锡杂质的新工艺。     

二氧化锰和硫化锰两矿法制备高纯硫酸锰

利用天然二氧化锰粉与硫化锰精矿为原料制备高纯一水硫酸锰,并取得了初步成功。其最优工艺为：以二氧化锰与硫的摩尔比为2．25：1,在温度90~C条件下浸出3h后,除渣,再用A试剂1．5倍理论用量除去硫酸锰溶液中的钾钠,按工业硫化钡1．5倍理论用量除去各重金属,用氟化锰5倍理论用量除去钙镁后蒸发结晶烘干,得到高纯一水硫酸锰产品。     

铟生产中锌含量的控制

研究了在铟生产中的置换过程和电解精炼过程中的酸度对锌含量的影响,以及锌含量的控制。在置换过程中,当酸含量控制在15～25g/L时,能控制反应的速度,从而降低粗铟中锌的含量;在电解精炼中,溶液的pH值为2～3,可使铟中锌的含量降低至0 5μg/g,并提出了采用硫酸或氢氧化钠来控制溶液酸度的方法;用海绵铟熔铸阳极时,采用NaOH熔炼的同时,加入NaCl能降低碱性熔渣的黏度,提高NaOH对Zn(OH)2、Na2ZnO2等的吸收能力,降低铟中锌的含量。     

The influence of small hydrogen addition on the structural and magnetocaloric properties of high-purity nanocrystalline terbium

Hydrogen absorption often induces changes of various properties of rare-earth metals. In this paper, we study the influence of hydrogenation on the structural, magnetic and magnetocaloric properties of high-purity nanocrystalline terbium. Strong (00l) texture present in the parent Tb sample is practically destroyed after the hydrogenation procedure. We observe formation of agglomerates of different sizes and shapes depending on the hydrogen content in the samples. We find traces of β-hydride (TbH₂) in the main α-hydride TbH_x phase. For TbH_x with x = 0.25 and 0.5 at.H/f.u. The effect of hydrogenation on the magnetocaloric properties is studied in magnetic fields up to 9 T. The magnetocaloric effect decreases after hydrogenation. The -ΔS_M(T) curves feature a table-like effect in the vicinity of the magnetic phase transitions in magnetic fields exceeding 1 T.     

Synthesis of CaO·2MgO·8Al2O3 (CM2A8) and its slag resistance mechanism

CM₂A₈ is a solid solution of MA and CA₆. As a component in the ternary phase diagram of CaO-Al₂O₃-MgO, it was not reported in detail. So in this work, analytically pure CaO, MgO and Al₂O₃ were adopted as starting materials and batched stoimotrically according to CM₂A₈. The raw materials were ground, mixed, shaped and reaction-sintered at different temperatures (1550 °C, 1650 °C, 1700 °C, and 1750 °C) to synthesize CM₂A₈. The synthesized specimens were analyzed by XRD, SEM, and TEM and the corrosion mechanism against LF slag was also researched. The results show that high-purity CM₂A₈ can be synthesized by reaction sintering at 1750 °C. During synthesis, granular MA and flake CA₆ form and grow together; at 1650 °C, they solid-solve together to form C₂M₂A₁₄. As the temperature rises, solid solution reaction goes on, which results in the disappearance of CA₆, C₂M₂A₁₄, and MA in succession and forms high-purity CM₂A₈ growing towards hexagonal column crystals. In the high temperature reaction between CM₂A₈ and steel slag, Ca²⁺ in the slag reacts with CM₂A₈ to form CA₂, damaging the structure of CM₂A₈ and releasing excessive Mg²⁺ and Al³⁺ which move towards the molten slag. As the reaction between Ca²⁺ and CM₂A₈ proceeds, a dense CA₂ coating forms on the surface of CM₂A₈. The slag viscosity increases as well because of the entrance of Mg²⁺ and Al³⁺. Thus, the formation of the CA₂ coating and the enhancement of the slag viscosity restrain the penetration and corrosion of slag towards CM₂A₈.     

Comprehensive analysis of minimum grain size in pure aluminum using friction stir processing

A friction stir processing (FSP) technique has been developed for use with aluminum and magnesium alloys, with the goal of high-strain-rate processing. In this study, we treat the microstructures of aluminum samples, of three levels of purity, manipulating their grain sizes, making them finer, using FSP. Grain sizes decreased with an increase in the Zener-Hollomon parameter, at all purity levels. However, the recrystallized grain of FSP-ed ultra-high-purity (99.999%) aluminum was particularly large, compared to the grain sizes of lower-purity (99% and 99.99%) aluminum, when subjected to the same processing conditions. The grain size reached a certain minimum value at high-strain-rates of processing, which we report for each purity level herein.     

Thermally stimulated current spectroscopy of high-purity semi-insulating 4H-SiC substrates

High-purity semi-insulating (HPSI) 4H-SiC has been widely used as a substrate material for AlGaN/GaN high electron-mobility transistors because of its fairly good lattice match with GaN and its high thermal conductivity. To control material quality, it is important to understand the nature of the deep traps. For this purpose, we have successfully applied thermally stimulated current (TSC) spectroscopy to investigate deep traps in two HPSI 4H-SiC samples grown by physical vapor transport (PVT) and high-temperature chemical vapor deposition (HTCVD), respectively. Fundamentals of TSC spectroscopy, typical TSC spectra obtained on the two samples, and theoretical fittings of a boron-related trap (peaked at ∼ 150 K) will be presented. Based on literature data for deep traps in conductive 4H-SiC, the impurity and point-defect nature of several commonly observed TSC traps, peaked at ∼105 K (0.22 eV), ∼150 K (0.29 eV), ∼175 K (∼0.33 eV), ∼260 K (∼0.53 eV), ∼305 K (∼0.63 eV), and ∼360 K (0.91 eV), in the HPSI 4H-SiC will be discussed.     

ICP-AES测定高纯二氧化钛中微量铬元素

运用HF-HClO4-H2SO4消解高纯二氧化钛,ICP-AES法测定其中的微量着色杂质铬。采用基体匹配法消除样品中钛基体的影响。该方法简便、可靠、准确,方法的精密度小于5%改为方法的精密度在0.34%～4.11%之间,结果满意。