Improving oxidation resistance of porous FeAl-based intermetallics with high boron/yttrium alloying

The coalloying with high contents of chromium (Cr), boron (B) and yttrium (Y) for porous B2-structured FeAl intermetallics fabricated through reactive synthesis was conducted. The oxidation behaviors of porous FeAl-based materials were investigated by evaluating the pore-structure evolution, oxidation kinetics and oxide-scale configuration. The results show that with the coalloying of high contents of Cr, B and Y, the oxidation mass gains of porous FeAl materials at 600?800 °C are significantly reduced. The combination of B enriched on the surface of oxide scales and Y located at the scale?metal interface promotes the formation of thin protective nodular α-Al₂O₃ oxide scales. It is indicated that introducing relatively high contents of reactive elements such as B and Y can benefit the selective growth of α-Al₂O₃ scales at relatively low temperatures without pre-treatment.     

Influence of operation number on arc erosion behavior of Ag/Ni electrical contact materials

Arc erosion behavior of Ag/Ni materials with different operation numbers was investigated by OM, 3DOP and SEM. The results indicated that the arc erosion of Ag/10Ni electrical contact material fabricated by sintering? extrusion technology was more and more serious with the operation numbers increasing from 1000 to 40000. With the same operation numbers, the arc erosion on anode was more serious than that on cathode. Besides, the pores preferred to emerge around the arc effect spot during the first 10000 operations. And the morphology of the molten silver on cathode and anode was different due to the action of gravity and arc erosion. Furthermore, the relationships among arc energy, arc time, welding force, electric resistivity, temperature and mass change on contacts were discussed, which indicated that the mass loss on cathode was mainly caused by the fracture of molten bridge.     

High nitrogen carbon material with rich defects as a highly efficient metal-free catalyst for excellent catalytic performance of acetylene hydrochlorination

In this work,we developed a simple strategy to synthesize a carbon material with high nitrogen and rich carbon defects.Our approach polymerized diaminopyridine(DAP) and ammonium persulfate(APS).Following a range of different temperature pyrolysis approaches,the resulting rough surface was shown to exhibit edge defects due to N-doping on graphite carbon.A series of catalysts were evaluated using a variety of characterization techniques and tested for catalytic performance.The catalytic performance of the N-doped carbon material enhanced alongside an increment in carbon defects.The NC-800 catalyst exhibited outstanding catalytic activity and stability in acetylene hydrochlorination(C_2 H_2 GHSV=30 h~(-1),at 220℃,the acetylene conversion rate was 98%),with its stability reaching up to 450 h.Due to NC-800 having a nitrogen content of up to 13.46%,it had the largest specific surface area and a high defect amount,as well as strong C_2 H_2 and HCl adsorption.NC-800 has excellent catalytic activity and stability to reflect its unlimited potential as a carbon material.     

A study on the thermoelectric properties of ALD-grown aluminum-doped tin oxide with respect to nanostructure modulations

The thermoelectric properties of aluminum-doped tin oxide (ATO) thin films synthesized by thermal atomic layer deposition (ALD) were studied with respect to the aluminum concentration. The overall aluminum content in each layer was modulated by adjusting the relative number of tin oxide (SnO₂) and aluminum oxide (Al₂O₃) growth cycles, where a sequential process involving n cycles of SnO₂ growth followed by 1 cycle of Al₂O₃ deposition was performed (building up a super-cycle). The electrical conductivity (620 S/cm), free carrier concentration (1.23x10²¹ cm^-3), and power factor (0.49 mW/K²m) increase until their maximum values are reached when the Al content is approximately 1.50 at% of the cations, and decrease as more Al is added in. On the other hand, the Seebeck coefficient decreases monotonically as the Al content increases up to about 2.88 at%, and begins to increase with further Al doping. Here the thermoelectric efficiency is therefore determined primarily by the free carrier concentration, while the Seebeck coefficient appears to be influenced by the overall crystal structure.     

Method to characterize the fire behavior of materials assemblies

The fire behavior of various large samples polymers assemblies is an under‐researched topic. In fire risk assessment, the resultant heat release rate of burning different combustibles has to be known. To highlight interactions between components, 2 types of configurations were tested: juxtaposed and layered materials, using a specific radiant panel setup. For juxtaposed assemblies, results indicated that the more flammable component acted as an accelerator for the global combustion kinetics. For layered assemblies, 2 main phenomena were evidenced: the front material acted as a shield delaying the combustion of the backside material and the presence of a backside material induced a thermal thickening that slowed down the combustion of the front material. The experimental burning behaviors of the assembly were compared with a simulated one calculated from the superposition principle. This method was described by introducing a time offset and/or a slowdown factor in the model, confirmed with the use of different assemblies.     

The Adhesion‐Enhanced Contact Electrification and Efficiency of Triboelectric Nanogenerators

In the present work, the contact electrification of polymers that differ in adhesion strength is studied. Electrical current is measured along with adhesion in macroscale contacting‐separation experiments. Additionally, local adhesion and roughness are studied with atomic force microscopy to get deeper insight into relations between surface properties and electrification. Measurements reveal that higher surface charge is formed on more adhesive surfaces, thus confirming covalent bond cleavage as a mechanism for contact electrification of polymers. Investigated materials possess enhanced contact electrification making them attractive candidates for the conversion of mechanical energy to electrical in triboelectric nanogenerator devices.     

镍钴电池Co-S负极材料的电化学特性研究

通过水热法制备Co-S材料,结合XRD分析其相结构,SEM和EDS分析其表面形貌及元素种类,采用充放电测试、循环伏安和交流阻抗法对其进行电化学特性研究。结果表明,该合金仅含有Co3S4、Co9S8和Co(OH)2, 结晶性良好,呈交叉生长的纳米薄片状,放电电流密度为150 mA/g时的最大放电容量为393.1mAh/g,50次循环后的容量保持率高达80.6%。当放电电流密度为1200 mA/g时,该电极的高倍率放电性能为79.3%。通过循环伏安和交流阻抗分析可知Co-S电极主要发生Co/Co(OH)2的法拉第反应,不可逆产物CoOOH的生成降低了活性物质的利用率,导致放电容量衰减。     

基于功能参数的渐进成形件表面质量表征研究

目的 以圆锥台成形件为例，基于粗糙表面的区域支承率曲线，进行了用功能参数表征表面几何形貌的研究，以全面、准确、定量地表征渐进成形件的表面质量，预测表面性能。方法 用渐进成形工艺加工成形角分别为35°、45°和55°的圆锥台件，将各圆锥台的成形面分为顶部、中部和底部三个区域，并使用三维表面轮廓仪，在上述三个区域中随机测量各4个样本。根据ISO 25178-2:2012，将各样本表面的区域支承率曲线分为峰区、核心区和谷区，选用部分功能参数——核心区高度Sk、峰区材料体积Vmp、核心区材料体积Vmc和谷区空隙体积Vvv表征表面，并与常用的高度表征参数——Sa、Sq、Ssk和Sku进行比较。结果 成形件表面的Ssk和Sku的计算值极不稳定，变异系数（标准偏差与均值之比）最高值分别可达127.67%和39.11%，Sa、Sq的最大变异系数分别为4.41%和4.26%，虽然它们的参数计算值较为稳定，但常无法体现表面形貌的实际差异。功能参数独立表征不同功能区，Sk和Vmc的最大变异系数分别为9.32%和7.73%，说明同一表面各处，在长期工作阶段具有较为一致的表面性能，Vmp和Vvv的最大变异系数分别为60.53%和31.25%，说明表面各处峰、谷区的形貌有所不同，因而在磨合时间、磨粒存储等方面会有不同的表现。结论 粗糙表面的三维本质要求用三维表征参数才能全面表征其几何形貌。高度参数虽然计算简单，但常难以解读它们的物理意义，无法定量评价表面性能；功能参数具有明确的物理意义，可为表征表面质量、预测表面性能提供定量、实用的方法。     

Facile synthesis of tubular magnetic carbon nanofibers by hypercrosslinked polymer design for microwave adsorption

In this study, a simple and efficient method for fabrication of tubular magnetic carbon nanofibers (TMCF) has been developed. Firstly, tubular polymer nanofiber precursors are synthesized by confined self-condensation method. After carbonization of polymer and in situ transformation of FeCl₃ at high temperature, TMCF loaded with Fe nanoparticles is obtained. It has been found that carbonization temperature has significant effects on conductivity, specific surface area, pore volume, defects number in carbon component, and magnetic content of TMCF. The influence of composition, structure, and filler content on microwave absorption properties is revealed. Meanwhile, the microwave absorption mechanism has been analyzed in depth, which benefits from the designed unique structure. The TMCF obtained at 700°C exhibited best performance with the filler content of 15%. The minimum reflection loss is −47.33 dB@2.2 mm, the effective absorption bandwidth is 6.5 GHz (RL < 10 dB), and the matching frequency is 14.1 GHz. The obtained TMCF is lightweight and possess excellent microwave absorption ability, which can be widely used as highly efficient microwave absorber.     

东峡煤矿主煤流运输系统智能化集控设计

通过对东峡煤矿主煤流运输系统的改造,设计了一套智能化集控系统,采用变频驱动,并结合料流传感器,增设无线基站、本安网络摄像仪和语音扩播终端等设备,实现了带式输送机载荷分布的自动调节,提高了系统的可靠性和运行效率,实现了减员、节能、增效的目的。