Selective growth of Ge nanowires by low-temperature thermal evaporation

High-quality single-crystalline Ge nanowires with electrical properties comparable to those of bulk Ge have been synthesized by vapor-liquid-solid growth using Au growth seeds on SiO(2)/Si(100) substrates and evaporation from solid Ge powder in a low-temperature process at crucible temperatures down to 700?°C. High nanowire growth rates at these low source temperatures have been identified as being due to sublimation of GeO from substantial amounts of GeO(2) on the powder. The Ge nanowire synthesis from GeO is highly selective at our substrate temperatures (420-500?°C), i.e., occurs only on Au vapor-liquid-solid growth seeds. For growth of nanowires of 10-20?μm length on Au particles, an upper bound of 0.5?nm Ge deposition was determined in areas of bare SiO(2)/Si substrate without Au nanoparticles.     

采用冷却倾斜板铸造方法生产悬架零部件用EN Aw 6082铝合金锻坯(英文)

对采用冷却倾斜板铸造方法生产EN AW 6082铝合金锻坯用于制备悬架零部件的可行性进行研究。采用冷却倾斜板铸造方法生产的EN AW 6082铝合金坯料具有细小的均匀组织,可直接用于锻造生产而不需要另外的均匀化处理。这可能是因为铸造开始时采用较小的过热和冷却倾斜板上发生较多的凝固所致。对采用冷却倾斜板铸造和均匀化处理的含或者不含Cr的EN AW 6082铝合金坯料,通过锻造生产的悬架零部件均具有均匀的组织,经过标准的人工时效处理后硬度可达到HV110。     

铝含量对AS系列铸造镁合金机械加工性能的影响(英文)

研究铝含量对AS系列铸造镁合金机械加工性能的影响。通过测量切削力和表面粗糙度对镁合金的机械加工性能进行评估。研究合金的微观结构和拉伸性能。结果表明,切削力随着铝含量的增加而增大;AS91镁合金的表面粗糙度和力学性能最高;对力学性能有影响的主要机制是存在金属间相Mg2Si和Mg17Al12。在机械加工镁合金中,切削力随着切割速度的增大而增大。所测得的数据与机械加工合金的力学性能一致。     

Effect of Cr and Zr on the grain structure of extruded EN AW 6082 alloy

The effects of Cr and Zr addition on the coarse grain surface layer in EN AW 6082 tube extrusions were investigated. The decoration of the tube surfaces and the weld seams with coarse recrystallized grains reflects the strain as well as the temperature gradients that predominate across the section of the tubes during extrusion. The recrystallization resistance provided by Mn does not suffice to avoid the coarse surface grains. With structural features that are almost identical to those of the base 6082 alloy, the 6082 alloy with 0.06 wt% Zr also fails to offer any improvement. The coarse grain surface layer is much thinner and recrystallization is entirely avoided across the weld seams upon the addition of 0.15 wt% Cr. The superior recrystallization resistance of the revised alloy is attributed to the increase in the population of the Cr-rich Al(Cr,Mn,Fe)Si as well as (Al, Si)₃Zr dispersoid particles. It is reasonable to conclude that the coaddition of Zr and Cr has a favourable impact on the resistance to recrystallization of EN AW 6082 alloy.     

Ultrasonic characterization of lactose dissolution

The ultrasonic properties (at 2.25 MHz) of lactose solutions and suspension of lactose crystals (d ∼ 50 μm) were measured as a function of concentration (0–40 wt.%). Ultrasonic velocity increased linearly with concentration regardless of the state of dissolution of the lactose crystals while ultrasonic attenuation was low and concentration-independent when the lactose was dissolved and increased approximately linearly with the concentration of suspended crystals. Therefore the amount of lactose present and the state of dissolution can be determined simultaneously with single ultrasonic sensor. A sensor based on this principle was applied to a stirred tank and used to measure the time taken to mix powdered lactose into a solution and the time for the added lactose to dissolve.     

Effect of Starch Induced Bacterial Growth and Amylase Production in Bacillus subtilis

The amylases produced by a Bacillus subtilis were purified from three different media which occurred nonstarch, starched and after eight hours shocked by starch media. Purified enzymes were compared each other Km, purification steps, thermal stability, pH and bacterial growth. In shocked medium, bacterial growth and amylase production are much more than in starched medium. The enzyme was stable at 65°C in three media. Km values were found different in three media where maltose inhibited the amylase activity. This inhibition is a competitive inhibition.     

A preliminary study on the manufacturing aluminum–potassium feldspar metal matrix composite materials

This study reports the results of a preliminary study of manufacturing aluminum–potassium feldspar metal matrix composites including its castability and mechanical properties. The material was composed considering 0.25 %, 0.5 %, and 0.75 % additive ratios to examine the impact of the amount of potassium feldspar on the material and mechanical properties of the manufactured aluminum metal matrix composite material. Aluminum alloy (A356) was utilized as the matrix of the composition. The composite material was manufactured by the stir casting technique. The modulus of elasticity, yield strength, tensile strength, elongation, density, and quality index of the material parameters was taken into account to determine the materials′ practicality. The preliminary results indicated that potassium feldspar is a promising mineral to be utilized as an additive for aluminum metal matrix composites since it has a positive impact on mechanical properties. By optimizing the casting parameters, the positive aspects of the potassium feldspar may make the material more practical to be utilized in vast engineering applications.