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1.
Pervaporation (PV) is a membrane technology that holds great promise for industrial applications. To better understand the PV mechanism, PV dehydrations of various types of organic solvents (methanol, ethanol, iso-propanol, tert-butanol, and acetone) were performed on five types of organosilica and two types of silicon carbide-based membranes, all with different pore sizes. Water permeance was dependent on the types of organic aqueous solutions, which suggested that organic solvents penetrated the pores and hindered the permeation of water. In addition, water permeance of various types of membranes in PV was well correlated with hydrogen permeance in single-gas permeation. Furthermore, a clear correlation was obtained between the permeance ratio in PV and that in single-gas permeation, which was confirmed via the modified-gas translation model. These correlations make it possible to use single-gas permeation properties to predict PV performance.  相似文献   
2.
The damage induced in 3C-SiC epilayers on a silicon wafer by 2.3-MeV Si ion irradiation for fluences of 1014, 1015, and 1016 cm−2, was studied by conventional and high-resolution transmission electron microscopy (TEM/HRTEM). The evolution of extended defects and lattice disorder is followed in both the 3C-SiC film and Si substrate as a function of ion fluence, with reference to previous FTIR spectroscopy data. The likelihood of athermal unfaulting of native stacking faults by point defect migration to the native stacking faults is discussed in relation to damage recovery. Threshold energy densities and irradiation doses for dislocation loop formation and amorphous phase transformation are deduced from the damage depth profile by nuclear collisions. The role of electronic excitations on the damage recovery at high fluence is also addressed for both SiC and Si.  相似文献   
3.
采用复合溶胶–凝胶法结合后续热处理,制备了具有包埋结构的氧化亚硅/碳(SiOx/C)复合负极材料。扫描电子显微镜分析结果表明:氧化亚硅纳米颗粒嵌入在无定形碳中。电化学性能测试表明:SiOx/C复合材料具有较高的比容量、优异的循环稳定性和倍率性能。材料在0.1 A/g的电流密度下100次循环后的可逆比容量为710 m A·h/g,容量几乎无衰减;在1.6 A/g的电流密度下,可逆比容量为380 m A·h/g。优异的电化学性能是由于材料的包埋结构能有效地缓冲SiOx充放电过程中的体积膨胀,保证材料的结构完整性和电化学循环稳定性。  相似文献   
4.
For the purpose of developing biodegradable magnesium alloys with suitable properties for biomedical applications, Mg–Zn–Ca–Cu metallic glasses were prepared by copper mold injection methods. In the present work, the effect of Cu doping on mechanical properties, corrosion behavior, and glass-forming ability of Mg66Zn30Ca4 alloy was studied. The experimental findings demonstrated that the incorporation of Cu decreases the corrosion resistance of alloys, but increases the microhardness and degradation rate slightly. However, the addition of a trace amount of Cu can make the samples have antibacterial properties. Therefore, Mg–Zn–Ca–Cu has great advantages in clinical implantation and is the potential implant material.  相似文献   
5.
The glass-to-mold adhesion in precision glass molding could severely degrade the quality of molded optics and shorten the lifespan of the precious molds. Since the consequences of adhesion take effect during the separation between glass and molds, it is important to investigate the debonding behaviors of a typical glass molding interface. To this end, here we perform a probe tack test procedure for borosilicate glass BK7, where debonding is conducted at molding temperature and specific velocity. We fully characterize the debonding behaviors using the peak adhesion stress σmax and the work of debonding Wdeb. Experiments show that when temperature is decreased from 690°C to 655°C at 10 μm/s, σmax continuously increases, while Wdeb first increases but then sharply decreases. When the debonding velocity is increased from 10 to 50 μm/s at 680°C, σmax also increases while Wdeb overall decreases. Therefore, the debonding behaviors are highly temperature and rate dependent. More importantly, depending on the debonding conditions, three debonding types are identified, that is, the cohesive bulk deformation, the cohesive-interfacial transition and the interfacial fracture. The cohesive type can be converted into the interfacial fracture, by either decreasing temperature or increasing the debonding velocity. Based on the Wdeb criterion, the three debonding regimes can be clearly distinguished. Finally, analyses on the temperature and velocity experimental results are unified by incorporating the reduced crack velocity aTvc. The dependences of both viscoelasticity and Wdeb on aTvc qualitatively explain the transition condition for different debonding types. Concerning these findings, the work of debonding not only supplements the characterization of adhesion strength, but also throws insightful light on revealing the debonding mechanisms.  相似文献   
6.
Hi Nicalon, Hi Nicalon S, Sylramic, and Sylramic iBN SiC fibers were exposed to ~60 μg/cm2 of Na2SO4 in a 0.1% SO2/O2 gaseous environment for times between 0.75 and 24 h at 1000°C. After exposure, the corrosion products were characterized using SEM, EDS, ICP-OES, TEM, and EFTEM to determine their high-temperature resistance to Na2SO4 and key reaction mechanisms. All SiC fiber types tested in this work exhibited little resistance to Na2SO4 deposit-induced attack relative to their behavior in dry O2 environments. It was found that Hi-Nicalon displayed the least resistance to Na2SO4 deposit-induced attack due to excess carbon content resulting in the formation of a highly porous crystalline oxide and promotion of basic corrosion conditions. All fiber types formed a crystalline SiO2 reaction product, either cristobalite or tridymite. Sylramic and Sylramic iBN formed a crystalline SiO2 reaction layer containing TiO2 needles due oxidation of TiB2 particles. Additionally, Na2SO4 deposits resulted in pitting of all fiber surfaces.  相似文献   
7.
Ferrites are materials of interest due to their broad applications in high technological devices and a lot of research has been focused to synthesize new ferrites. In this regard, an effort has been devoted to synthesize spinel Pr–Ni co-substituted strontium ferrites with a nominal formula of Sr1-xPrxFe2-yNiyO4 (0.0 ≤ x ≤ 0.1, 0.0 ≤ y ≤ 1.0). The cubic structure of pure and Pr–Ni co-substituted strontium ferrite samples calcinated at 1073 K for 3 h has been confirmed through X-ray diffraction (XRD). Average sizes of crystallites (18–25 nm) have been estimated from XRD analysis and nanometer particle sizes of synthesized ferrites have been further verified by scanning electron microscopy (SEM). SEM results have also shown that particles are mostly agglomerated and all the samples possess porosity. It has been observed that at 298 K, the values of resistivity (ρ) increase, while that of AC conductivity, dielectric loss, and dielectric constants decrease with increasing amounts of Pr3+ and Ni2+ ions. The values of dielectric parameters initially decrease with frequency and later become constant and can be explained on the basis of dielectric polarization. Electrochemical impedance spectroscopy (EIS) studies show that the charge transport phenomenon in ferrite materials is mainly controlled via grain boundaries. Overall, synthesized ferrite materials own enhanced resistivity values in the range of 1.38 × 109–1.94 × 109 Ω cm and minimum dielectric losses, which makes them suitable candidates for high frequency devices applications.  相似文献   
8.
9.
在多晶硅太阳能电池的生产过程中, 金刚线切割技术(Diamond wire sawn, DWS)具有切割速度快、精度高、原材料损耗少等优点, 受到了广泛关注。金刚线切割多晶硅表面形成的损伤层较浅, 与传统的酸腐蚀制绒技术无法匹配, 金属催化化学腐蚀法应运而生。金属催化化学腐蚀法制绒具有操作简单、结构可控且易形成高深宽比的绒面等优点, 具有广阔的应用前景。本文总结了不同类型的金属催化剂在制绒过程中的腐蚀机理及其形成的绒面结构, 深入分析和讨论了具有代表性的银、铜的单一及复合催化腐蚀过程及绒面结构和电池片性能。最后对金刚线切割多晶硅片表面的金属催化化学腐蚀法存在的问题进行了分析, 并展望了未来的研究方向。  相似文献   
10.
针对青藏高原某选厂生产的含Cu 28.93%、含Mo 0.78%、含SiO2 8.05%、含MgO 1.02%的铜钼混合精矿铜钼分选效率不高、钼精矿品质差等问题开展选矿工艺研究。结果表明:铜钼混合精矿经1粗4精2扫开路铜钼分离浮选试验后可获得含铜1.05%、含钼30.56%的钼精矿,钼精矿品位偏低。通过对钼精矿进行X射线衍射及工艺矿物学分析可知,钼精矿品位不佳的主要原因是滑石类脉石矿物含量高。降镁小型试验结果表明,对铜钼混合精矿进行预处理,添加酸化水玻璃+CMC作为滑石抑制剂,可有效降低铜钼精矿中的硅、镁含量,且对铜、钼指标影响较小。降镁预处理后的铜钼精矿磨细后,采用1粗5精2扫的抑铜浮钼浮选工艺流程进行闭路试验,可获得含铜0.65%、铜回收率0.04%,含钼47.63%、钼回收率92.43%的钼精矿及含铜31.88%、铜回收率99.96%,含钼0.08%、钼回收率7.57%的铜精矿,试验指标良好,实现了铜钼高效分离,得到合格的铜钼精矿产品。为现场铜钼分离改造提供了技术支持。  相似文献   
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