铝表面超疏水复合涂层的制备及其表面性能

目的 通过在纯铝表面构筑超疏水涂层,优化金属铝表面,并强化其应用性能。方法 采用阳极氧化法在铝表面构筑具有纳米孔洞的Al2O3薄膜,再利用全氟癸基三乙氧基硅烷修饰表面,得到超疏水复合涂层,并研究氧化电位和表面修饰时间对纳米结构的构筑及疏水性能的影响,研究超疏水复合涂层表面润湿性、防污、自清洁和抗结冰性能。结果 控制阳极氧化条件,在氧化电位为16～18V、氧化时间为1h时,得到1～2μm的“花瓣”聚集叠加成的多级粗糙结构。通过6 h的表面修饰,得到了接触角为163.6°的超疏水性复合膜层。进一步对该超疏水膜层的性能进行分析发现,经超疏水膜层修饰后铝具有优异的防污性能;相较于纯铝,经超疏水膜层修饰后铝片的电化学阻抗模值高达105?·cm2,而电流密度仅为1.81×10-9 A/cm2;在高温和低温环境下,超疏水膜层均能保持超疏水性能;经砂纸来回打磨200 cm后,膜层的接触角仍大于150°。结论 经阳极氧化纯铝得到具有多级粗糙结构的阳极氧化膜,并通过表面修饰可制备接触角高达163.6°的超疏水性复合膜层。该超疏水复合涂层具有优异的耐腐蚀性、自清洁性、耐污染性,以及良好的耐蚀性、机械稳定性和...     

Development of carbon-filled gas diffusion layer for polymer electrolyte fuel cells

The fabrication and electrochemical performance of polymer electrolyte fuel cells based on a carbon-filled gas diffusion layer (CFGDL) were studied in detail. The CFGDL consists of a PE-704 carbon electrode backing filled with a mixture of carbon powder and PTFE. The results obtained from the performance evaluation and cyclic voltammetry (CV) analyses indicate that the loading of the carbon powder in the CFGDL plays a critical role in the performance of the fuel cell and utilization of Pt, but the presence of PTFE in the CFGDL has less influence. The carbon content in the CFGDL not only affects the area specific resistance of the CFGDL but also affects the Pt utilization of the catalyst layer, the total cell resistance and thus the cell performance. The optimal performance of the PEFC was obtained when the CFGDL was filled with carbon to 6 mg cm⁻² and PTFE of 40%. The relationship between the surface morphology and microstructure of the CFGDL and the electrocatalytic activity of the cell is also discussed.     

Reaction mechanisms of graphene oxide chemical reduction by sulfur-containing compounds

We used density functional theory to study the reaction mechanisms of chemical reduction of graphene oxide (GO) by the sulfur-containing compounds HSO₃⁻ and H₂SO₃. We studied the reaction energy profiles for the following reactions: dehydroxylation of GO with one and two hydroxyl groups, de-epoxidation of GO with one or two epoxy groups and decarboxylation and decarbonylation of GO with carboxyl and carbonyl groups. We found that hydroxyl and epoxide groups could be easily reduced because of the lower energy barriers, whereas decarboxylation and decarbonylation reactions are not kinetically and thermodynamically easy because of the higher energy barriers. These reaction mechanisms at the atomistic level are not only supported by Chen’s experimental results [J. Phys. Chem. C 2010, 114, 19885], but are also beneficial for the development of new agents that could efficiently reduce GO.     

Evaluation of P2O5 distribution inside the main clinker minerals by the application of EPMA method

The formation of Portland clinker phases has taken place in thermodynamically non-equilibrium state between macro-oxides CaO, SiO₂, Al₂O₃, Fe₂O₃ and MgO from raw meal and P₂O₅ from bone meal. The paper deals with the study of clinker minerals as solid solutions with P₂O₅ during the clinkerization of raw mixture containing bone meal (BM). The ash of BM has contributed as a raw material to the formation of different clinker phases. Electron probe microanalysis (EPMA) method was used to determine the preferential distribution of P₂O₅ inside calcium silicate phases and its influence upon C₂S/C₃S ratio. Basing on these results, composition of solid solution of C₂S and C₃S was established.     

Microwave dielectric properties of MgCo2(VO4)2 ceramics synthesized by a sol–gel method

MgCo₂(VO₄)₂ (MCV) ceramics have been prepared by a sol–gel method as potential candidates for use in microwave applications as a low-temperature co-fired ceramic (LTCC). The sintering and microwave dielectric properties of sol–gel processed MCV were compared with those of solid-state reaction processed MCV. The results showed that sol–gel processed MCV had a higher sinterability due to its much finer particle size. The sol–gel processed MCV was also found to have superior microwave dielectric properties compared with solid-state reaction processed MCV especially at low sintering temperatures.     

Boroaluminosilicate glass-ceramics containing mullite-type Cr3+:Al4B2O9 nanocrystals with broadband near-infrared luminescence

Multi-component silicate glass is an ideal matrix for fabricating glass-ceramics because of its excellent physical-chemical stability and high optical transmittance. In this paper, a series of Cr³⁺ doped multi-component silicate glasses were designed for the preparation of glass-ceramics that crystalizes mullite-type Cr³⁺:Al₄B₂O₉ nanocrystals. When excited at 450 nm, the obtained GCs exhibit a broadband NIR luminescence band covering a spectral region from 650 to 1200 nm. Two different crystallographic sites of Cr³⁺ in Al₄B₂O₉ nanocrystal are considered to account for the observed broadband luminescence. Due to the controllable size and uniformly dispersion of precipitated nanoparticles, this boroaluminosilicate glass-ceramic could find potential applications as monolithic near-infrared light sources in solid-state light emitting devices.     

Research and application prospect of short carbon fiber reinforced ceramic composites

With the advantage of high temperature resistance, low expansion, low density and excellent thermal stability, carbon fiber reinforced ceramic composites have a very wide range of applications in aerospace, military, energy, chemical industries and transportation. Short carbon fiber reinforced ceramic composites are characterized by simple processes, low manufacturing costs, short preparation times and automated production, can be used in fields such as friction materials and thermal protection system. This paper reviews the current status and recent advances in research on homogenization techniques, mechanical properties, thermal properties and frictional properties of short carbon fiber reinforce ceramic composites. Different processing routes for short carbon fiber reinforced ceramic composites, including reactive melt infiltration (RMI), hot pressing (HP), spark plasma sintering (SPS) and pressureless sintering, the advantages and drawbacks of each method are briefly discussed. The future development direction of low-cost manufacturing short carbon fiber reinforced ceramic composites is prospected.     

Influence of silica promotion on NiCe/MgAlSi catalysts for the oxy-steam reforming of biogas to syngas

This work has exploited the effects of silica on magnesium aluminum silicate supported NiCe based catalysts (NiCe/MgAlSi) prepared using sol-gel method followed by incipient wetness impregnation for syngas production through oxy-steam reforming (OSR) of biogas. Measurements investigating the effects of increasing Si/Al molar ratio (0–5) on activity and carbon deposition were performed in a once-through flow reactor at atmospheric pressure and temperatures of 600, 700, and 800 °C with a fixed GHSV of 45,000 ml g_cat⁻¹ h⁻¹ and molar feed ratio of CH₄/CO₂/O₂/H₂O = 1/0.67/0.1/0.3. The catalysts were characterized by N₂-physisorption, XRD, SEM, HRTEM, TGA, Raman, and ICP-OES. In the results, the addition of silica has been found to increase Ni crystallite sizes and decrease carbon deposition. Thus, NiCe/MgAlSi with Si/Al = 5 is promising, exhibiting high conversions of CH₄ (91.7%), CO₂ (80.4%), and H₂/CO ratio of 1.6 without carbon deposition and good stability for 120 h at 800 °C.