铝硅合金熔体在多孔石墨中的浸渗动力学

石墨/铝复合材料因其独特的高温稳定性在轨道交通等领域具有重要应用价值。由于石墨、铝熔体的物理属性差异,需要利用压力浸渍法驱动铝熔体进入石墨基体孔隙、以提高复合材料的机械强度与导电性。铝熔体的浸渗动力学过程对复合材料的最终性能具有关键影响作用,其高度依赖于石墨相和铝相之间的界面润湿性。文中基于实验测试和数值模拟,系统研究了硅的体积分数对铝硅熔体在多孔石墨结构中浸渗动力学的影响。结果表明,添加硅元素能有效促进铝熔体的渗透,在较短的填充时间内获得高的填充率。由于局部孔隙残余气体作用,硅元素对合金熔体浸渗的促进作用存在极限。同时,论文对铝硅合金熔体在多孔石墨结构中渗流过程中的压力场、速度场进行了分析,并重点对复合材料的电导率进行了讨论。

Fabrication of porous g-C_3N_4 and supported porous g-C_3N_4 by a simple precursor pretreatment strategy and their efficient visible-light photocatalytic activity

Porous g-C_3N_4 and supported porous g-C_3N_4 were fabricated for the first time by a simple strategy using pretreated melamine as a raw material and pretreated quartz rod as a substrate.The formation of a richly porous microstructure can be attributed to the co-existence of different pore-fabricating units in the preparation system for porous g-C_3N_4.The richly porous microstructure endowed the as-prepared porous g-C_3N_4 with an excellent photocatalytic activity.The as-prepared supported porous g-C_3N_4 exhibited considerable stability because of the existence of chemical interaction between porous g-C_3N_4 and the quartz rod substrate.The photocatalytic activity of the supported porous g-C_3N_4 was competitive with that of porous g-C_3N_4 in powder form because neither the surface migration of photogenerated electrons nor the diffusion of the target organic pollutant were affected by the construction of the quartz rod reactor.The photocatalytic activity of the as-prepared porous g-C_3N_4 and supported porous g-C_3N_4 was preliminarily evaluated by the treatment of single-component organic wastewater under visible-light irradiation.Subsequently,the as-prepared porous g-C_3N_4 was further applied in conventional hydrogen evolution and a new system for simultaneous hydrogen evolution with organic-pollutant degradation.The hydrogen yield and degradation efficiency both increased with increasing photocatalytic activity of the as-prepared materials in the system for simultaneous hydrogen evolution with organic-pollutant degradation.

Direct fabrication of highly porous graphene/TiO_2 composite nanofibers by electrospinning for photocatalytic application

We reported the fabrication of highly porous graphene/TiO2 composite nanofibers in the form of a nonwoven mat by electrospinning followed by calcination in air at 450°C.The graphene can uniformly disperse in highly porous TiO2 nanofibers.The highly porous graphene/TiO2 composite nanofibers exhibited excellent catalytic activities.The new method for producing graphene/TiO2 composite nanofibers is versatile and can be extended to fabricate various types of metal oxide and graphene nanocomposites.

High conductive graphene assembled films with porous micro-structure for freestanding and ultra-low power strain sensors

Graphene emerges as an ideal material for constructing high-performance strain sensors,due to its superior mechanical property and high conductivity.However,in the process of assembling graphene into macroscopic materials,its conductivity decreases significantly.Also,tedious fabrication process hinders the application of graphene-based strain sensors.In this work,we report a freestanding graphene assembled film(GAF)with high conductivity((2.32±0.08)×105 S m-1).For the sensitive materials of strain sensors,it is higher than most of reported carbon nanotube and graphene materials.These advantages enable the GAF to be an ultra-low power consumption strain sensor for detecting airflow and vocal vibrations.The resistance of the GAF remains unchanged with increasing temperature(20-100℃),exhibiting a good thermal stability.Also,the GAF can be used as a strain sensor directly without any flexible substrates,which greatly simplifies the fabrication process in comparison with most reported strain sensors.Additionally,the GAF used as a pressure sensor with only^4.7μW power is investigated.This work provides a new direction for the preparation of advanced sensors with ultra-low power consumption,and the development of flexible and energy-saving electronic devices.