采用高频磁场去除太阳能级硅熔体中的SiC粒子(英文)

高质量硅材料在光伏太阳能和电子设备中具有重要应用,然而原料中的非金属颗粒和金属杂质严重影响其电学性能和力学性能。由于SiC粒子会降低光伏电池的力学性能并导致分流问题,因此在制备太阳能电池之前必须将这些杂质从硅材料中去除。利用磁场去除液态金属中的非金属杂质是制备高纯金属的一项尖端技术。利用该方法去除冶金级硅材料中的SiC粒子,并结合杂质去除经典模型和计算流体力学对熔体中粒子浓度和分离效率进行计算。为检验该方法的有效性,采用感应炉进行多次实验。结果表明:该方法能有效去除非金属杂质,提纯硅熔体,且实验结果与模型的预测结果相符。     

2026铝合金热变形及热处理过程中的微观组织演变(英文)

研究2026铝合金在温度为300-450°C和应变速率为0.01-10s-1的变形条件与固溶时效热处理后微观组织之间的关系。结果表明:热处理后的再结晶和析出特性与热变形时的温度补偿应变速率Z有关。在低Z条件下,热处理后会形成少量细小的再结晶晶粒,热变形过程产生的高角度亚晶粒和粗大析出物被保留下来;高Z条件下,热处理后会产生大量细小等轴晶再结晶晶粒,热变形过程产生的高密度晶胞和相对细小的动态析出物被热处理后完整的亚晶粒和相对粗化的析出物所替代。热处理后的平均再结晶晶粒尺寸随着Z值的增加而减小。建立两者的定量关系式。     

Fe_(70)Cr_(18)Mo_2Si_1B_9单辊激冷带中的特殊结晶现象

本文研究了真空下不同转速的Fe_(70)Cr_(18)Mo_2Si_1B_9单辊激冷带的显微组织,并与大气带作了比较。除了常见的均质形核与非均质形核的结晶过程之外,还出现具有强择优取向的自由面表层α-Fe柱状晶以及尺寸达μm级的α-Fe球状晶。可用动量传递模式的单辊带形成理论解释这些现象。早期过冷液态中的预存核是该材料能否形成非晶的控制因素。     

ZK60镁合金热变形过程中的应变强化与动态再结晶行为(英文)

研究ZK60合金的高温流变应力行为。分别采用Kocks-Mecking模型和Avrami方程对合金的应变强化和动态再结晶过程进行模拟,在此基础上,构建一个考虑合金动态再结晶软化的流变应力方程并对流变应力进行预测。结果表明:预测曲线与实验结果具有很高的相关系数,所构建的流变应力方程能准确地描述热变形过程中合金的流变应力行为。微观组织观察表明在变形初期合金组织主要为动态回复组织,随着应变增加,逐渐转变为再结晶组织。     

Determination of trap levels in CZT:In by thermally stimulated current spectroscopy

Many defects in semi-insulating (SI) cadmium zinc telluride (Cd_1-xZn_xTe or CZT) ingots grown by the melt methods act as trapping centers to introduce deep levels in the band gap, which has strong effects on CZT detection properties. The thermally stimulated current (TSC) spectroscopy was used to measure these traps, and the initial rise method and the simultaneous multiple peaks analysis (SIMPA) method were introduced to characterize trap levels in SI-CZT:In. The results show that there is a larger error in the determination for the trap peaks with the initial rise method due to the interference of overlapping peaks, while the SIMPA method demonstrates a better performance in resolving these overlapping peaks simultaneously for a full characterization of trap levels. On this basis, a theoretical SIMPA fitting, which is composed of ten trap levels and a deep donor level E_DD dominating the dark current in SI-CZT:In, is achieved. Furthermore, the reason of high resistivity in CZT:In was explained by the relationship between E_DD level and Fermi level.     

Study of relaxations in epoxy polymer by thermally stimulated depolarization current (TSDC) and dielectric relaxation spectroscopy (DRS)

Thermally stimulated depolarization current (TSDC) and dielectric relaxation spectroscopy (DRS) techniques were employed to study the relaxations and the conductivity phenomena in epoxy-based polymer. In addition to the primary α relaxation process associated with the glass–rubber transition, significant interfacial relaxation and ionic conduction process have been revealed. The ac conductivity is temperature and frequency dependent and shows a dc plateau at low frequencies. Above the glass transition temperature, dc conductivity is described by a Vogel–Tamman–Fulcher–Hesse (VFTH) equation while it shows Arrhenius behaviour at higher temperatures.     

Detection of thermally grown oxides in thermal barrier coatings by nondestructive evaluation

The thermal-barrier coatings (TBC) sprayed on hot-section components of aircraft turbine engines commonly consist of a partially stabilized zirconia top-coat and an intermediate bond-coat applied on the metallic substrate. The bond-coat is made of an aluminide alloy that at high engine temperatures forms thermally grown oxides (TGO). Although formation of a thin layer of aluminum oxide at the interface between the ceramic top-coat and the bond-coat has the beneficial effect of protecting the metallic substrate from hot gases, oxide formation at splat boundaries or pores within the bond-coat is a source of weakness. In this study, plasma-sprayed TBC specimens are manufactured from two types of bond-coat powders and exposed to elevated temperatures to form oxides at the ceramic-bond-coat boundary and within the bond-coat. The specimens are then tested using nondestructive evaluation (NDE) and destructive metallography and compared with the as-manufactured samples. The objective is to determine if NDE can identify the oxidation within the bond-coat and give indication of its severity. While ultrasonic testing can provide some indication of the degree of bond-coat oxidation, the eddy current (EC) technique clearly identifies severe oxide formation within the bond-coat. Imaging of the EC signals as the function of probe location provides information on the spatial variations in the degree of oxidation, and thereby identifies which components or areas are prone to premature damage.     

Determination of residual stress in spherical balls by resonant ultrasound spectroscopy

In this study, resonant ultrasound spectroscopy (RUS) for determining residual stress in small size spherical balls was examined. Natural frequencies of spherical balls with residual stress were analysed by finite element method. Resonant frequencies of spherical balls were experimentally measured by a RUS system. Both natural frequencies in the analysis and the resonant frequencies measured in the experiment decreased as the compressive circumferential stress at the ball surface increased. It was concluded, on the basis of both analytical and experimental results, that the measurement of the resonant frequency by the RUS system along with the analysis of natural frequency are effective for determining the values and distributions of unknown residual stress in spheres.     

硫酸亚铁电流滴定法测定铱化合物中铱量

采用硫酸亚铁电流滴定法测定铱化合物中铱元素含量,对化合物的溶解方法、试剂用量、吹气条件、共存元素干扰及测定过程影响因素等进行了研究并获得了最佳实验条件。结果表明,样品经过盐酸-过氧化氢高温高压处理转化后,可使铱价态统一为Ir(Ⅳ),再用硫酸亚铁电流滴定法测定。该方法可以避免某些铱化合物在常规溶解过程中由于铱价态不一致而导致的检测结果失真。方法的测定范围10%～60%,加标回收率99.75%～100.13%;四氯化铱、三氯化铱、氯铱酸、氯铱酸铵、醋酸铱、乙酰丙酮铱6种铱化合物的测定精密度均在0.10%～0.25%之间,均能很好满足铱化合物中高量铱测定的精密度和准确度要求。     

Determination of elastic moduli for a spherical specimen by resonant ultrasound spectroscopy

Resonant ultrasound spectroscopy (RUS) is based on the principle that mechanical resonant response of solids depends on its elastic moduli, shape and density. Elastic moduli or the other properties can be identified from resonant frequencies as inverse problem. In this study, the method to determine elastic moduli of a spherical specimen without information of resonant mode was described. We confirmed that resonant frequencies have to be measured under condition of free surface, and adequate number of resonant frequencies used in calculation needs enough number to include the sensitive mode to Poisson's ratio. By this method, we determined elastic moduli of BK-7 glass. The calculated frequencies from the elastic moduli determined by this technique had good agreement with the measured, the absolute accuracies for the Δf was less than 0.4%.     

核级Ag-In-Cd合金中Ag,In,Cd的测定

研究了一种测定核级Ag-In—Cd合金中Ag，In，Cd的新方法。以电位滴定法用氯化钠标准溶液测定Ag；氯化钠溶液沉淀Ag与In，Cd分离，移取部分滤液，调节pH至2．5，以EDTA标准溶液测定In；继续调节pH至5．5，以EDTA标准溶液测定Cd。其RSD为：Ag0．11％，In0．2％，Cd0．5％。试样分析回收率为：In101.9％～102．4％，Cd99．6％-101．1％.     

Determination of vanadium in food and traditional Chinese medicine by graphite furnace atomic absorption spectroscopy

Various experimental conditions were described for the vanadium determination by graphite furnace atomic absorption spectroscopy (GFAAS). The experiments showed that when atomization took place under the conditions where the combination of a pyrolytic coating graphite tube and fast raising temperature were used and the temperature was stable, the signal peak shapes could be improved, the sensitivity was enhanced, and the memory effect was removed. The vanadium in food and traditional Chinese medicinal herbs can be accurately determined using the standard curve method.     

低压电磁铆接放电电流分析

线圈放电电流对铆接力起决定作用,铆接力是顺利实现铆接的关键因素。放电电流可采用幅值和频率等参数描述。该文在放电回路分析的基础上,通过电阻分流器法测量成形线圈放电电流,分析低压电磁铆接系统参数对线圈放电电流的影响。研究结果表明,在低压电磁铆接下,线圈放电电流为一衰减震荡波形,幅值在kA级,周期为ms级,能顺利实现直径4mmTA1铆钉的成形。同时线圈匝数、导线截面尺寸、放电电容和驱动片厚度等参数,对低压电磁铆接放电电流的幅值和周期均产生较大的影响。在成形中需优化电阻、电感和电容三者的匹配关系,以满足不同工艺放电电流的要求。     

Characterisation of tungsten coatings by pulsed current plating from molten salt in air atmosphere

Pure and compact tungsten coatings with high (200)-orientation were successfully electrodeposited from Na₂WO₄–WO₃ binary oxide molten salt by direct and pulse current techniques on copper based alloy substrate in air atmosphere at 1173 K. The tungsten coatings and copper alloy substrates combined well with no obvious voids and cracks. In addition, the influence of pulse plating on the microstructure, crystal structure and Vickers microhardness of coatings, adhesive strength between coatings and substrates as well as the current efficiency was investigated. It was also observed that applied pulse current led to tungsten coatings with better mechanical properties than those obtained by direct current plating. In addition, a tungsten coating of 500 μm which had lower oxygen content and higher adhesive strength than the coating obtained by the plasma spray method was obtained.