Microstructure and performance of Al-Si alloy with high Si content by high temperature diffusion treatment

The Al-Si alloy with high Si content was prepared by pressure infiltration. Microstructure observation shows that three-dimensional structure （3D-structure） is obtained from irregular sharp Si particles via high temperature diffusion treatment （HTDT）. Flat Si-Al interfaces transform to smooth curves, and Si phases precipitate in Al and Si-Al interface. The bonding of Si-Al interface is improved by HTDT, which improves the mechanical performance of Al-Si alloy. The bending strength of 3D-Al-Si alloy increases by 6% compared with that of Al-Si alloy, but the elastic modulus changes a little. The coefficient of thermal expansion （CTE） of the 3D-Al-Si alloy is 7.7×10^-6/℃ from 20℃ to 100 ℃, which decreases by 7% compared with that of Al-Si alloy. However, HTDT has little effect on the thermal conductivity of Al-Si alloy.

Eco-friendly synthesis of high silica zeolite Y with choline as green and innocent structure-directing agent

Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure‐directing agents(OSDAs),which are chronically hazardous to humans and the environment.It is a growing trend to develop an eco‐friendly and nuisanceless OSDA for zeolite synthesis.Herein,choline is employed as a non‐toxic and green OSDA to synthesize high silica Y zeolite with SiO2/Al2O3 ratios of 6.5–6.8.The prepared Y zeolite samples exhibited outstanding(hydro)thermal stability at ultrahigh temperature owing to the higher SiO2/Al2O3 ratio.The XRF,SEM,29Si‐NMR and 13Na+results suggested that choline plays a structure‐directing role in the synthesis of Y zeolite,while the feed molar fraction of Na+is a crucial determinant for the framework SiO2/Al2O3 ratio and the crystal morphology.

Physical and chemical performances of high Al steels

The effects of acid-soluble Al content on the physical and chemical performances of high Al steels were investigated. The results show that the distribution of acid-soluble Al in steel substrate is uniform. With increasing Al content, the strength and toughness of steels decrease a little but the hardness increases. The average yield strength and tensile strength are 425MPa and 570MPa, respectively, and the Rockwell hardness is 89.7. For non-Al steels the average oxidation rate is up to 0.421mg/(cm2·h) at 1373K. For high Al steels, when the mass fraction of Al is less than 5%, there is a thinner gray oxidized layer on surface and the oxidation rate is high; when the mass fraction of Al is more than 8.0%, the thin, close and yellow glossing film still exists, and the average oxidation rate is only 0.016mg/(cm2·h).

Growth of Hierarchically Structured High-Surface Area Alumina on FeCralloy~ Rods

The formation of metastable alumina phases due to the oxidation of commercial FeCralloy（R） rods （0.5 mm thickness） at various temperatures and time periods has been examined. This structured layer acts as an anchor to bind additional coatings of alumina via wash-coat techniques, thereby improving the layer thickness and increasing adhesion of the catalytic surface. Optimisation of the layer thickness and catalytic properties were conducted, using a range of analytical systems [scanning electron microscope （SEM）, energy dispersive X-ray （EDX） and X-ray diffraction （XRD）]. The modified FeCralloy（R） rods were tested in a fixed bed reactor rig to assess the impact on yield for the dehydrogenation of methylcyclohexane.

不同Al组分的扩散阻挡层对无杂质空位诱导量子阱混杂的影响

为了获得更好的量子阱混杂效果,深入探讨了不同Al组分的扩散阻挡层对无杂质空位诱导量子阱混杂的影响。首先在两种不同Al组分外延片表面上分别生长了一层200nm厚的SiO_(2)介质薄膜,然后在865~905℃温度范围内,进行了90s的高温快速热退火处理。实验结果表明,低铝结构的波长蓝移量更大,且光致发光(Photoluminescence,PL)谱的强度下降更小,这说明在无杂质空位诱导量子阱混杂中,外延结构中的Al和Ga对点缺陷扩散的影响是不同的,Ga更有利于点缺陷的扩散。研究结果为无杂质空位诱导量子阱混杂的理论研究及器件的外延结构设计提供了参考。