Influence of surfactant type on the dispersion state and properties of graphene nanoplatelets reinforced aluminium matrix nanocomposites

Graphene dispersion in aluminium matrix is a critical concern for the attainment of composite improved mechanical and tribological properties which hinders broad applications of Al nanocomposites. Herein, graphene nanoplatelets (GNPs) dispersion in Al matrix achieved by colloidal processing, i.e., combining sonication and surfactant dispersing aid. In this work, the performance of the two types of surfactant (anionic, sodium dodecyl benzene sulfonate (SDBS), and nonionic polymeric, ethyl cellulose (EC)) were evaluated for effective GNPs dispersion in a solvent and Al matrix. Surfactant assisted GNPs solvent dispersion characterized through sedimentation test and UV-vis spectroscopy to optimize surfactant concentration. Density, hardness, wear properties and microstructural characterizations of GNPs/Al powder and sintered discs were performed to gauge the effect of surfactant type. It was found that surfactant addition enhances dispersion ability of GNPs than neat GNPs but at low GNPs fractions. The results show that EC assisted GNPs/Al nanocomposites of 0.5 wt% GNPs concentration has shown an increase in hardness (31%) and reduce wear rate (98%). Whereas, 0.3 wt% SDBS assisted GNPs/Al nanocomposites shown maximal increases in hardness (18%) and reduce wear rate (98%) as compared to pure aluminium, respectively. Conclusively, it has been revealed that polymeric EC based surfactant GNPs owing to steric repulsion shows better dispersion effect resulting in high density and improved wear resistance and performed better than SDBS based surfactant GNPs in Al matrix.     

Reduced graphene oxide-multiwalled carbon nanotubes hybrid film with low Pt loading as counter electrode for improved photovoltaic performance of dye-sensitised solar cells

In this work, the role of reduced graphene oxide (rGO) with hyperbranched surfactant and its hybridisation with multiwalled carbon nanotubes (MWCNTs) and platinum (Pt) nanoparticles (NPs) as counter electrode (CE) were investigated to determine the photovoltaic performance of dye-sensitised solar cells (DSSCs). Sodium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulphonate (TC14) surfactant was utilised as dispersing and stabilising agent in electrochemical exfoliation to synthesise graphene oxide (GO) as initial solution for rGO production prior to its further hybridisation and fabrication as thin film. A chemical reduction process utilising hydrazine hydrate was conducted to produce rGO due to the low temperature process and water-based GO solution. Subsequently, hybrid solution was prepared by mixing 1 wt% MWCNTs into the produced rGO solution. TC14-rGO and TC14-rGO_MWCNTs hybrid solution were transferred into fluorine-doped tin oxide substrate to fabricate thin film by spraying deposition method. Finally, the CE films were prepared by coating with thin Pt NPs. Photoanode film was prepared by a two-step process: hydrothermal growth method to synthesise titanium dioxide nanowires (TiO₂ NWs) and subsequent squeegee method to apply TiO₂ NPs. According to solar simulator measurement, the highest energy conversion efficiency (η) was achieved by using CE-based TC14-rGO_MWCNTs/Pt (1.553%), with the highest short current density of 4.424 mA/cm². The highest η was due to the high conductivity of CE hybrid film and the morphology of fabricated TiO₂ NWs/TiO₂ NPs. Consequently, the dye adsorption was high, and the photovoltaic performance of DSSCs was increased. This result also showed that rGO and rGO_MWCNTs hybrid can be used as considerable potential candidate materials to replace Pt gradually.     

基于I-DEAS的加工中心换刀机械手运动仿真

以I DEAS MS8三维工程软件为平台 ,对TH63 5 0卧式加工中心换刀机械手进行三维实体装配。以装配模型为基础 ,对换刀机械手进行机构建模和换刀运动仿真。通过机械手换刀运动干涉检验和分析 ,得到机械手换刀运动并发时序图 ,提出了缩短机械手换刀运动时间的措施     

乳化体系中无溶剂合成环氧棉籽油

在乳化剂存在条件下,以磷酸为催化剂,过氧化氢与棉籽油反应合成了环氧棉籽油。通过核磁共振氢谱、红外光谱及黏度测定方法对产物的结构进行了表征,并采用国标法对产物的环氧值、碘值、酸值和色泽进行了测定。同时考察了乳化剂及有机酸种类、反应时间、反应温度及反应物配比对产物各项指标的影响。实验结果表明：无溶剂条件下,以脂肪醇聚氧乙烯醚（MOA-3）为乳化剂,用过氧化氢环氧化用甲酸酸化的棉籽油,可获得优质环氧棉籽油增塑剂。产物的环氧值为6.12%,碘值（100g）为3.67g,酸值为0.32 mg/g。此方法避免了使用有机溶剂,而且副产物生成量减少,提高了产品质量。     

过乙酸氧化法制备环氧环己烷的工艺研究

用过乙酸作氧化剂在二氯甲烷体系中氧化环己烯制得了环氧环己烷。考察了各种影响因素,得到最优工艺条件为:环己烯与过乙酸质量比为1∶1.25,溶剂二氯甲烷用量为环己烯质量的2倍,保持反应体系pH为5.8,反应温度为25℃,滴加反应时间和保温反应时间都为1.5 h。经精馏处理后,产品收率达到79.0%,产品纯度达到99.2%。     

原位XPS分析Al2O3作为势垒层的Er2O3/Si结构

在超高真空条件下,通过脉冲激光沉积(PLD)技术制作了Er2O3/Al2O3/Si多层薄膜结构,原位条件下利用X射线光电子能谱(XPS)研究了Al2O3作为势垒层的Er2O3与Si界面的电子结构.XPS结果表明,Al2O3中Al的2p芯能级峰在低、高温退火前后没有变化;Er的4d芯能级峰来自于硅酸铒中的铒,并非全是本征氧化铒薄膜中的铒;衬底硅的芯能级峰在沉积Al2O 3时没有变化,说明Al2O3薄膜从沉积到退火不参与任何反应,与Si界面很稳定;在沉积Er2O3薄膜和退火过程中,有硅化物生成,表明Er2O3与Si的界面不太稳定,但随着Al2O3薄膜厚度的增加,其硅化物中硅的峰强减弱,含量减少,说明势垒层很好地起到了阻挡扩散的作用.     

利用分子印迹技术分离植物中的生物碱

分子印迹技术是制备具有分子识别能力聚合物的技术.它在印迹分子存在的情况下功能性单体与交联剂共聚制得高交联的聚合物网络,移去印迹分子后就得到了对印迹分子具有分子记忆效应的分子印迹聚合物.作为一种新型的分离介质,在分离、环境分析和催化科学等领域中极具发展潜力.本实验研究了模板分子、功能单体、交联剂、溶剂等对印迹聚合物制备的影响.并对聚合物方法的优势进行了较为详细的讨论.通过紫外光度法研究了模板分子(CF)与功能单体(AA)的相互作用,预测聚合物的选择性和结合机理.     

离子液体体系中过氧化氢氧化油酸合成壬二酸

以离子液体BMIMPF6为溶剂,采用钨酸为催化剂,50％的H2O2氧化油酸合成了高纯度壬二酸。通过考察催化剂用量、溶剂类型、环氧化产物碘值、离子液体循环使用次数、氧化裂解反应时间等因素对目标产物壬二酸收率及品质的影响,得出合成壬二酸的最佳条件为：60℃下,原料油酸、过氧化氢、钨酸、离子液体以1．0：3．0：0．04：1．24（摩尔比）混合反应1h后,用25％的过氧乙酸在90℃继续氧化裂解3h,可得产品壬二酸,收率为39％。产品通过FT-IR及GC-MS等手段进行了表征,纯度高达99％。环氧化产物与离子液体BMIMPF6易于分离,分离后的离子液体10次以内可以重复使用,其结构及性能基本保持不变。     

The performance and degradation of Pt electrocatalysts on novel carbon carriers for PEMFC applications

Electrocatalyst stability is an important factor influencing the performance of polymer electrolyte membrane (PEM) fuel cells and is essential in maintaining the cell output. The aim of this work was to elucidate factors which influence the stability of platinum supported onto graphitic nanofibres (Pt/GNFs) and to compare the performance of these materials with the commonly used Pt/Vulcan electrocatalyst. Platinum nanoparticles (average diameter of 6.9 nm) were supported on GNFs which were prepared by chemical vapour deposition over an unsupported nickel oxide (NiO) catalyst precursor. The performance of Pt/GNFs based electrodes were studied by cyclic voltammetry and a single-cell fuel cell test and were compared with a commercially available carbon nanostructure, Vulcan XC-72, which was also impregnated with Pt nanoparticles. Characterisation of the pre- and post-operation of the Pt/GNFs by XRD and TEM showed that structural changes of the Pt had occurred during testing. It was found that the average diameter of each grain and the degree of agglomeration among particles was increased, creating elongated clusters of Pt along the carbon fibre. Analysis of electrocatalyst post-operation also identified that the sulphate from the Nafion membrane was reacting with the Pt surface forming platinum sulphide (PtS). These phases were confirmed by the presence of low intensity, but sharp XRD peaks, attributed to a few large diameter particles (49 nm). These two factors resulted in current density dropping from 0.2 A/cm² to 0.1 A/cm² (at 0.70 V) over a 25 h test period.