微氧化烧结制备掺杂Y2O3的SiC陶瓷及含镉模拟废水处理

采用了微氧化烧结制备了不同Y₂O₃质量分数（0%、2%、4%、6%）的多孔SiC陶瓷，通过对陶瓷的晶体结构、微观形貌、物理性能和Cd²⁺的去除率测试发现：添加了Y₂O₃的SiC陶瓷出现了较多的第二相Y₂SiO₇、Y₅Si₃C_0.5，随着Y₂O₃的质量分数增加逐渐升高，主相的衍射峰的强度有降低。扫描电子显微镜测试发现，SiC陶瓷的尺寸在2.5 μm，Y₂O₃引入后，SiC陶瓷的晶粒尺寸降低，高温烧结时液相的含量增加，熔体粘度降低，晶粒结合更加紧密，Y₂O₃的引入提高了多孔陶瓷的体积密度，Y₂O₃质量分数为6%SiC的体积密度最大为2.21 g/cm³。热导率随着Y₂O₃质量分数的增加呈现出先升高后降低的趋势。金属Cd²⁺的过滤测试表明：随着Y₂O₃质量分数增加，Cd²⁺的残留质量浓度、膜通量和去除率先降低后升高，当掺杂质量分数为4%时，Cd²⁺残留质量浓度最低为0.042 mg/L，膜通量达到了最大值572 L/（m²·h），去除率最大为99.95%，相比未掺质量分数杂体系的去除率提高了0.14%。随着溶液pH值的逐渐增大，金属Cd²⁺的残留质量浓度逐渐降低、去除率逐渐升高，pH≥9时最终均趋于稳定。综合来看，多孔SiC陶瓷的助烧剂Y₂O₃最佳掺量为4%。     

Elimination of bis(trimethylsilyl)stannylene from tris(trimethylsilyl)stannylated zirconocene and hafnocene chlorides

Reactions of (Me₃Si)₃SnK with Cp₂MCl₂ (M = Zr, Hf) give the respective stannylated metallocene chlorides. These complexes display a tendency to eliminate bis(trimethylsilyl)-stannylene under Cp₂M(Cl)SiMe₃ formation.     

1200 V碳化硅功率MOSFET低温特性的实验表征及分析

碳化硅功率MOSFET是宽禁带功率半导体器件的典型代表,具有优异的电气性能。基于低温环境下的应用需求,研究了1200 V碳化硅功率MOSFET在77.7 K至300 K温区的静/动态特性,定性分析了温度对碳化硅功率MOSFET性能的影响。实验结果显示,温度从300 K降低至77.7 K时,阈值电压上升177.24%,漏-源极击穿电压降低32.99%,栅极泄漏电流降低82.51%,导通电阻升高1142.28%,零栅压漏电流降低89.84%(300 K至125 K)。双脉冲测试显示,开通时间增大8.59%,关断时间降低16.86%,开关损耗增加48%。分析发现,碳化硅功率MOSFET较高的界面态密度和较差的沟道迁移率,是导致其在低温下性能劣化的主要原因。     

Effects of hydroxyl groups and hydrogen passivation on the structure,electrical and optical properties of silicon carbide nanowires

The effects of hydrogen and hydroxyl passivation on the structure, electrical and optical properties of SiCNWs were investigated. The passivation performance of different atoms (groups) were discussed by analyzing the distribution of electronic states and the polarity of chemical bonds. The results show that passivation can improve the stability of SiCNWs structure, and the effect of hydroxyl is better than hydrogen passivation. And hydrogen and hydroxyl passivation both increase the band gap of SiCNWs, and the changing trend of band gap is relevant to the polarity of the covalent bond formed by the passivation of surface atoms. Moreover, passivation enhances the stability of the optical properties of SiCNWs, resulting in narrowing of light absorption, photoconductivity and other spectra, and the response peak shifts to the deep ultraviolet region, which means that hydrogen or hydroxyl passivation of SiCNWs is likely to be a candidate material for deep ultraviolet micro-nano optoelectronic devices.     

Predicting and researching adsorption configurations of pyridazine on Si(100) surface by means of X-ray spectroscopies in theory

The landscape of organic molecule on Si(100) surface has a great significance for organic functionalisation of Si semiconductor. Several possible adsorption configurations for pyridazine on Si(100) surface have been forecasted by systemic comparison and investigation. The C1s XPS and NEXAFS spectra of these adsorption systems based on density functional theory and full core-hole potential approximation have been calculated. Although the sensibility of XPS to these adsorption configurations is not very strong, these configurations can be absolutely distinguished by NEXAFS spectra, which will bring tremendous reference to the future experimental study. Mode II, III, V and VI have a significantly higher adsorption energy, which are most likely to be present in experiment. In addition, we have made the research on specific sources of the peaks in spectra by analysing their decomposed NEXAFS spectra, the results show that the Carbon atoms which do not bond to surface atoms, make the most contribute to the intensity of characteristic peaks in spectra.     

Highly Selective Photoelectroreduction of Carbon Dioxide to Ethanol over Graphene/Silicon Carbide Composites

Using sunlight to produce valuable chemicals and fuels from carbon dioxide (CO₂), i.e., artificial photosynthesis (AP) is a promising strategy to achieve solar energy storage and a negative carbon cycle. However, selective synthesis of C₂ compounds with a high CO₂ conversion rate remains challenging for current AP technologies. We performed CO₂ photoelectroreduction over a graphene/silicon carbide (SiC) catalyst under simulated solar irradiation with ethanol (C₂H₅OH) selectivity of>99 % and a CO₂ conversion rate of up to 17.1 mmol g_cat⁻¹ h⁻¹ with sustained performance. Experimental and theoretical investigations indicated an optimal interfacial layer to facilitate the transfer of photogenerated electrons from the SiC substrate to the few-layer graphene overlayer, which also favored an efficient CO₂ to C₂H₅OH conversion pathway.     

CycloSiFA: The Next Generation of Silicon-Based Fluoride Acceptors for Positron Emission Tomography (PET)

The ring-opening Si-fluorination of a variety of azasilole derivatives cyclo-1-(iPr₂Si)−4-X−C₆H₃−2-CH₂NR ( 4 : R=2,6-iPr₂C₆H₃, X=H; 4 a : R=2,4,6-Me₃C₆H₂, X=H; 9 : R=2,6-iPr₂C₆H₃, X=tBuMe₂SiO; 10 : R=2,6-iPr₂C₆H₃, X=OH; 13 : R=2,6-iPr₂C₆H₃, X=HCCCH₂O; 22 : R=2,6-iPr₂C₆H₃, X=tBuMe₂SiCH₂O) with different ¹⁹F-fluoride sources was studied, optimized and the experience gained was used in a translational approach to create a straightforward ¹⁸F-labelling protocol for the azasilole derivatives [¹⁸F] 6 and [¹⁸F] 14 . The latter constitutes a potential clickable CycloSiFA prosthetic group which might be used in PET tracer development using Cu-catalysed triazole formation. Based on our findings, CycloSiFA has the potential to become a new entry into non-canonical labelling methodologies for radioactive PET tracer development.     

SiO_2微球固相萃取-火焰原子吸收光谱法测定水样中痕量Ag(Ⅰ)

本文通过水热合成法制备了SiO2微球,并研究SiO2微球在弱碱性条件下对Ag(Ⅰ)的吸附性能,建立了SiO2微球固相萃取-火焰原子吸收光谱法(AAS)测定痕量Ag(Ⅰ)的新方法。结果表明:在0.02mol·L-1 NaOH溶液介质中,Ag(Ⅰ)能被定量吸附,且能被2.0mL的12g·L-1硫脲-4%HCl混合液快速定量洗脱。方法的检出限(3σ)为0.59μg·L-1,富集倍数为50。该方法用于水样中痕量Ag(Ⅰ)的测定,加标回收率在95.0%~104.0%范围。     

催化反应制备碳化硅纳米粉体的密度泛函理论计算及实验研究

以Si_(55),Si_(43)M_(12)和Si_(37)M_(18)(M=Fe,Co或Ni)团簇为模型,采用密度泛函理论(DFT)研究了Fe,Co及Ni纳米团簇催化硅粉转化为SiC的机理.计算结果表明,Fe,Co及Ni纳米催化剂先与Si形成合金,拉长并弱化Si—Si键的强度,起到活化Si粉的作用;合金的形成有利于C原子的吸附及Si原子和C原子间的反应;Fe的催化能力强于Co和Ni.在此基础上,以Si粉和酚醛树脂为原料,以Fe,Co及Ni硝酸盐为催化剂前驱体,通过微波加热反应制备了3C-SiC纳米粉体.研究了催化剂种类、反应温度、催化剂用量和反应时间等对制备3C-SiC纳米粉体的影响.结果表明,催化剂Fe,Co和Ni的加入均可显著降低3C-SiC的合成温度.当以2.0%(质量分数)的Fe为催化剂时,Si粉在1100℃下反应30 min后即可全部转化为3C-SiC纳米粉体;而在相同条件下,无催化剂时Si粉的完全转化温度为1250℃;Fe的催化效果优于Co和Ni,与DFT计算结果吻合.     

锂离子电池硅氧化物负极首次库伦效率的影响因素与提升策略

硅氧化物(SiO_x, 0<x≤2)具有高的比容量和低的嵌锂电位, 且体积膨胀率显著低于纯硅负极, 因而被认为是替代传统石墨负极材料的理想选择之一. 然而SiO_x负极在首次嵌锂过程中表面形成的固体电解质界面膜(SEI)以及大量的不可逆产物, 造成其首次库伦效率偏低, 严重阻碍了SiO_x负极的实际应用. 本文从SiO_x的结构模型出发, 系统阐述了SiO_x负极的嵌锂机理以及首次库伦效率低的原因; 归纳了SiO_x负极首次库伦效率的提升策略及其研究进展; 并对提升SiO_x负极首次库伦效率的未来发展方向进行了展望.