Ag3PO4/g-C3N4异质结催化剂可见光降解黄连素

采用原位生长法制备Ag₃PO₄/g-C₃N₄异质结催化剂,在可见光照射下,催化氧化降解废水中的药物大分子黄连素。通过X射线衍射（XRD）、扫描电镜（SEM）、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-vis DRS）分析催化剂的组成和结构,并测试了Ag₃PO₄/g-C₃N₄降解黄连素的光催化活性。结果表明：利用可见光照射,g-C₃N₄掺杂量为0.7 g时,Ag₃PO₄/g-C₃N₄对黄连素的光催化降解活性最好,可见光反应15 min降解率达到100%,重复4次实验后降解率降至73.2%,其具有较好的光稳定性。自由基捕获实验证明h⁺和·O₂^-在降解黄连素废水中起主要作用,结合UV-vis DRS分析可知,Ag₃PO₄/g-C₃N₄遵循Z型异质结机理。     

Photocatalytic degradation of Basic Blue 41 dye under visible light over SrTiO3/Ag3PO4 hetero-nanostructures

In an attempt to develop nanostructured photocatalysts with high performance, SrTiO₃/Ag₃PO₄ hetero-nanostructures were successfully fabricated. The formed binary heterojunctions were composed of SrTiO₃ nanotubes prepared using liquid-phase deposition, and Ag₃PO₄ nanoparticles prepared using a sol–gel method. Synthesis details, including morphology, structure, and optical properties of the prepared photocatalysts, were characterized and comparatively discussed. The results showed that at an optimal ratio of SrTiO₃ to Ag₃PO₄ (20–80), the photocatalytic degradation of Basic Blue 41 under 80-min visible light irradiation is the maximum amount of 99%, which is about 4.4 and 1.5 times higher than that of pristine SrTiO₃ nanorods and Ag₃PO₄ nanoparticles, respectively. It can be due to the synergistic effect of two materials that provide high light absorption and charge carriers’ separation. Finally, a detailed possible mechanism for enhancing the photocatalytic activity of the SrTiO₃/Ag₃PO₄ hetero-nanostructures was proposed.     

基于正交实验优化不锈钢表面纳米孔结构制备工艺

目的通过正交实验优化不锈钢表面纳米孔制备工艺。方法通过田口实验方法设计正交试验优化工艺。采用含有氯化钠和硫脲的硝酸溶液阳极氧化制备纳米孔,在含有氯化钠、盐酸和硫酸的水溶液中进行扩孔处理。通过扫描电子显微镜、能谱仪对表面处理后的试样表面形貌和元素进行分析,应用软件统计SEM图片孔隙率,并将孔隙率作为响应指标,利用极差分析和方差分析研究阳极氧化工艺和扩孔时间对表面形貌及孔隙率的影响,并优化工艺参数。结果 SEM照片和5个水平的均值表明,硝酸浓度的提高有利于提高孔隙率,较高的硫脲浓度有利于形成均匀有序的纳米孔结构,氯化钠浓度、氧化时间、氧化电压和扩孔时间对表面形貌和孔隙率影响不明显。元素分析表明,纳米孔的材料仍然是不锈钢,而不是金属氧化物。正交实验优化的工艺参数是:硝酸的体积浓度为90 mL/L,硫脲的质量浓度为3.5 g/L,氯化钠的质量浓度为20 g/L,氧化时间为120 s,氧化电压为5.0 V,扩孔时间为50 s。结论通过实验验证,优化后的工艺能够制备出表面较平整、孔隙率较高的纳米孔结构。     

Production of Ag−ZnO powders by hot mechanochemical processing

Ag–CdO composites are still one of the most commonly used electrical contact materials in low-voltage applications owing to their excellent electrical and mechanical properties. Nevertheless, considering the restriction on using Cd due to its toxicity, it is necessary to find alternative materials that can replace these composites. In this study, the synthesis of Ag?ZnO alloys from Ag?Zn solid solutions was investigated by hot mechanochemical processing. The hot mechanochemical processing was conducted in a modified attritor mill at 138 °C under flowing O₂ at 1200 cm³/min for 3.0 h. The microstructure and phase evolution were investigated using X-ray diffractometry, field emission gun scanning electron microscopy and transmission electron microscopy. The results suggest that it is possible to complete the oxidation of Ag?Zn solid solution by hot mechanochemical processing at a low temperature and short time. This novel synthesis route can produce Ag?ZnO composites with a homogeneous distribution of nanoscale ZnO precipitates, which is impossible to achieve using the conventional material processing methods. Considering the fact that the fundamental approach to improving electric contact material performance resides in obtaining uniform dispersion of the second-phase in the Ag matrix, this new processing route could open the possibility for Ag?ZnO composites to replace non-environmentally friendly Ag?CdO.     

银钇合金组织研究

采用真空感应炉熔炼制备Ag-9.89%Y二元合金棒,借助金相显微镜、扫描电镜、X射线衍射仪和电子探针研究分析合金的铸态组织特征。结果表明,Ag-Y合金中存在块状和方形环状的初生Ag51Y14化合物相,以初生Ag51Y14相为中心形成向四周发散呈鱼鳞状交替分布的共晶组织。初生Ag51Y14相中的钇含量高于共晶Ag51Y14相。初生Ag51Y14相边界局部直接生长出共晶组织,局部围绕银固溶体组织,环状初生Ag51Y14组织里侧和外侧组织结构相似。共晶组织片层细小,平行生长方向组织呈层片状,垂直生长方向组织呈点状,2种区域含有相同的银和钇含量。     

键合参数对AgAuPdRu键合线键合性能影响研究

利用扫描电镜研究φ0.025 mm的Ag-0.8Au-0.3Pd-0.03Ru银基键合线不同键合参数对无空气焊球(free air ball,FAB)形状及球焊点、楔焊点形貌的影响,结果表明,烧球电流或者烧球时间其中之一不变时,FAB直径随着烧球时间(烧球电流一定)和烧球电流(烧球时间一定)的增加而增大,烧球电流为30 mA、烧球时间为700 μs时,键合线FAB呈标准圆球形;键合压力一定时,键合线球焊点焊盘直径随着超声功率的增大而显著增加,键合功率为80 mW、键合压力0.30 N时,球焊点具有较好的微观形貌;键合压力为0.25 N,超声功率为80 mW时,楔焊点具有规则的鱼尾形貌,并具有较好的连接强度。     

Surface chemistry of SnO2 nanowires on Ag-catalyst-covered Si substrate studied using XPS and TDS methods

In this paper we investigate the surface chemistry, including surface contaminations, of SnO₂ nanowires deposited on Ag-covered Si substrate by vapor phase deposition (VPD), thanks to x-ray photoelectron spectroscopy (XPS) in combination with thermal desorption spectroscopy (TDS). Air-exposed SnO₂ nanowires are slightly non-stoichiometric, and a huge amount of C contaminations is observed at their surface. After the thermal physical desorption (TPD) process, SnO₂ nanowires become almost stoichiometric without any surface C contaminations. This is probably related to the fact that C contaminations, as well as residual gases from air, are weakly bounded to the crystalline SnO₂ nanowires and can be easily removed from their surface. The obtained results gave us insight on the interpretation of the aging effect of SnO₂ nanowires that is of great importance for their potential application in the development of novel chemical nanosensor devices.     

Microwave-assisted green synthesis of Ag/reduced graphene oxide nanocomposite as a surface-enhanced Raman scattering substrate with high uniformity

A nanocomposite of silver nanoparticles/reduced graphene oxide (Ag/rGO) has been fabricated as a surface-enhanced Raman scattering (SERS) substrate owing to the large surface area and two-dimensional nanosheet structure of rGO. A facile and rapid microwave-assisted green route has been used for the formation of Ag nanoparticles and the reduction of graphene oxide simultaneously with L-arginine as the reducing agent. By increasing the cycle number of microwave irradiation from 1 and 4 to 8, the mean diameters of Ag nanoparticles deposited on the surface of rGO increased from 10.3 ± 4.6 and 21.4 ± 10.5 to 41.1 ± 12.6 nm. The SERS performance of Ag/rGO nanocomposite was examined using the common Raman reporter molecule 4-aminothiophenol (4-ATP). It was found that the Raman intensity of 4-ATP could be significantly enhanced by increasing the size and content of silver nanoparticles deposited on rGO. Although the Raman intensities of D-band and G-band of rGO were also enhanced simultaneously by the deposited Ag nanoparticles which limited the further improvement of SERS detection sensitivity, the detectable concentration of 4-ATP with Ag/rGO nanocomposite as the SERS substrate still could be lowered to be 10⁻¹⁰ M and the enhancement factor could be increased to 1.27 × 10¹⁰. Furthermore, it was also achievable to lower the relative standard deviation (RSD) values of the Raman intensities to below 5%. This revealed that the Ag/rGO nanocomposite obtained in this work could be used as a SERS substrate with high sensitivity and homogeneity.     

PVP作为保护剂制备Ag纳米粒子

以聚乙烯吡咯烷酮(PVP)为分散剂和保护剂,分别用乙醇和高分子化合物聚乙烯醇(PVA)作还原剂制备银纳米粒子,通过控制反应时间、PVP和PVA的含量及硝酸银的浓度,在90℃回流条件下得到纳米银颗粒。采用红外光谱对聚合物结构进行表征,紫外-可见光谱表征反应物浓度对制备银纳米粒子尺寸分布的影响,扫描电镜观察纳米粒子和聚合物网络形貌,X射线衍射分析银纳米粒子的晶体结构。     

Optimal conditions of isobutane dehydrogenation in radial flow moving bed hydrogen-permselective membrane reactors to enhance isobutene and hydrogen production

In the isobutane dehydrogenation process, coupling reaction and separation and optimization of the intensified process can improve the isobutane conversion and selectivity, reduce operational costs and lets to produce pure hydrogen. In this research, the radial flow moving bed reactors in the Olefex technology have been supported by Pd–Ag membrane plate to remove hydrogen from the reaction zone. The reactions occur in the tube side and the hydrogen is permeated from the reaction zone to the sweep gas stream. The proposed configuration has been modeled heterogeneously based on the mass and energy conservation laws considering reaction networks. To prove the accuracy of the considered model, the simulation results of the conventional process have been compared against available plant data. The Genetic algorithm as an effective method in the global optimization has been considered to optimize the operating condition of membrane reactors to enhance isobutene productivity. In this optimal configuration, the isobutene production has been enhanced about 3.7%.