Crystalline Mesoporous Complex Oxides: Porosity‐Controlled Electromagnetic Response

A colloidal‐amphiphile‐templated growth is developed to synthesize mesoporous complex oxides with highly crystalline frameworks. Organosilane‐containing colloidal templates can convert into thermally stable silica that prevents the overgrowth of crystalline grains and the collapse of the mesoporosity. Using ilmenite CoTiO₃ as an example, the high crystallinity and the extraordinary thermal stability of its mesoporosity are demonstrated at 800 °C for 48 h under air. This synthetic approach is general and applicable to a series of complex oxides that are not reported with mesoporosity and high crystallinity, such as NiTiO₃, FeTiO₃, ZnTiO₃, Co₂TiO₄, Zn₂TiO₄, MgTi₂O₅, and FeTi₂O₅. Those novel materials make it possible to build up correlations between mesoscale porosity and surface‐sensitive physicochemical properties, e.g., electromagnetic response. For mesoporous CoTiO₃, there is a 3 K increase of its antiferromagnetic ordering temperature, compared with that of nonporous one. This finding provides a general guideline to design mesoporous complex oxides that allow exploring their unique properties different from bulk materials.     

Millisecond Anneal and Short-Channel Effect Control in Si CMOS Transistor Performance

In this letter, the effects of the millisecond anneal in conjunction with conventional spike anneal on the p-n junction formation in CMOS devices are studied. The results reveal that the millisecond and spike annealing sequence plays an important role in the implanted boron p+/n junction formation. On blanket Si wafers, the millisecond anneal followed by the spike anneal increases implanted boron solid solubility in crystalline silicon by ~18% compared to that obtained using reversed annealing sequence under the same annealing conditions. This result substantially alters the short-channel effect behaviors in the fabricated CMOS devices, resulting in opposite threshold-voltage behaviors in PMOS and NMOS devices when using boron as NMOS halo implant. The results also provide useful insights into ultrashallow-junction formation and short-channel effect control when scaling CMOS technology     

Ensemble climate simulations using a fully coupled ocean-troposphere-stratosphere general circulation model

Long-term transient simulations are carried out in an initial condition ensemble mode using a global coupled climate model which includes comprehensive ocean and stratosphere components. This model, which is run for the years 1860-2100, allows the investigation of the troposphere-stratosphere interactions and the importance of representing the middle atmosphere in climate-change simulations.The model simulates the present-day climate (1961-2000) realistically in the troposphere, stratosphere and ocean. The enhanced stratospheric resolution leads to the simulation of sudden stratospheric warmings; however, their frequency is underestimated by a factor of 2 with respect to observations.In projections of the future climate using the Intergovernmental Panel on Climate Change special report on emissions scenarios A2, an increased tropospheric wave forcing counteracts the radiative cooling in the middle atmosphere caused by the enhanced greenhouse gas concentration. This leads to a more dynamically active, warmer stratosphere compared with present-day simulations, and to the doubling of the number of stratospheric warmings. The associated changes in the mean zonal wind patterns lead to a southward displacement of the Northern Hemisphere storm track in the climate-change signal.     

强旋湍流气-固两相流动和煤粉燃烧数学模型及其在涡旋燃烧炉的应用(Ⅰ)——模型

结合新型燃煤涡旋燃烧炉的研制和冷、热态实验,建立并发展了二维强旋湍流气固两相流动和煤粉燃烧的数学模型,以此作为对涡旋燃烧炉内多相流动。传热和燃烧过程进行数值模拟和分析的基础。     

Solvent extraction of oil from soybean flour I— extraction rate,a countercurrent extraction system,and oil quality

Measurements of rates of oil extraction from either fine flour or soybean flakes in a column showed that oil extraction from flour was dependent on the volume of solvent, but oil extraction from flakes depended on time of contact rather than volume of solvent. We interpreted the data to mean that oil was being washed out of the fine flour with little diffusion involved, whereas in flakes, the limit on rate was diffusion of the solvent into and out of the tissue. Fine full fat flour worked well in a batchwise countercurrent extraction system with mixing and centrifugal separation. Because the oil dissolved immediately and reached equilibrium rapidly, the actual material balance was close to calculated values. However, due to the large hold-up volume, the separation of miscella from the meal required several mixing and separation stages. The oil resulting from this countercurrent extraction system had a superior quality with 37 ppm phosphorus, 0.08% free fatty acids, and a light color.     

Role of Concurrent Cavitation in the Fracture of a Superplastic Zirconia—Alumina Composite

Superplastic zirconia-alumina composites exhibit very large elongations to failure of ≳500% under optimum conditions. A quantitative microstructural study reveals that the composite is susceptible to considerable internal cavitation, with the level of cavitation increasing with increasing strain rate. The observed inverse relationship between the level of cavitation and the elongation to failure suggests strongly that the tensile ductility is limited by the evolution of cavitation damage during superplastic deformation.     

微生物发酵对猪肉脯品质的影响

以猪里脊肉为原料,分别接种0.02%商业发酵剂THM-17(木糖葡萄球菌、戊糖片球菌)、VHI-41(木糖葡萄球菌、戊糖片球菌、植物乳杆菌)、PROMIX-5(木糖葡萄球菌、类植物乳杆菌、清酒乳杆菌)和WBX-43(木糖葡萄球菌、肉葡萄球菌)制成4组猪肉脯,以未发酵型猪肉脯为对照组,采用排序检验法对样品进行感官评定并测定其pH值、红度值a*、水分活度和水分含量,筛选适宜生产发酵猪肉脯的发酵剂。结果表明,发酵能够显著影响猪肉脯的pH值进而影响其组织状态、色泽和口感,改善产品品质。发酵剂PROMIX-5制成的产品组织状态最好,WBX-43和PROMIX-5促进产品发色作用效果,红度值达到22和25,VHI-41制成的猪肉脯pH值最低(4.8),不适宜用于生产猪肉脯。添加0.02%发酵剂WBX-43或PROMIX-5制成的猪肉脯在外观、风味和色泽方面均优于传统工艺猪肉脯。     

Strain rate-dependent deformation in bulk metallic glasses

Metallic glasses have metastable structures. As a result, their plastic deformation is dependent upon structural dynamics. In the present paper, we present data obtained from Zr-base and La-base metallic glasses and discuss the kinetic aspects of plastic deformation, including both homogeneous and heterogeneous deformation. In the case of homogeneous deformation (typically occurring in the supercooled liquid region), Newtonian behavior is not universally observed and usually takes place only at low strain rates. At high strain rates, non-Newtonian behavior is usually observed. It is demonstrated that this non-Newtonian behavior is associated with in situ crystallization of the amorphous structure. In the case of heterogeneous deformation (occurring at room temperature), deformation is controlled by localized shear banding. The plastic deformation of a La-base metallic glass is also investigated using instrumented nanoindentation experiments over a broad range of indentation strain rates. At low rates, the load-displacement curves during indentation exhibit numerous serrations or pop-ins, but these serrations become less prominent as the indentation rate is increased. Using the tip velocity during pop-in as a gauge of serration activity, we find that serrated flow is only significant at indentation strain rates below a certain critical value.     

Fine‐structure superplasticity in materials

Abstract

Superplastic forming is a viable net‐shape forming technology. It is an attractive manufacturing technique because it bypasses machining, joining and riveting, and reduces material waste. This paper reviews the history and progress in the field of superplasticity. Fundamental understandings, such as microstructural prerequisites and deformation mechanisms, and technological applications for superplasticity are discussed. A wide range of structural materials, including metals, intermetallics, and ceramics are presented. Some of the most recent advances, for example, high strain rate superplasticity, low temperature superplasticity, and the development of ultrafine‐grained materials for superplasticity are also described.     

Pesting of the high-temperature intermetallic MoSi2

Degradation resulting from environmental effects on the properties of high-temperature intermetallics has recently stimulated much interest in the materials science community. Most notably, iron, nickel, and titanium aluminides were found to be more ductile at room temperature when tested in vacuum or dry oxygen as compared to laboratory air. Environmental oxidation can also degrade materials to a measurable, sometimes catastrophic, extent. For example, an important oxidation-induced degradation phenomenon observed in intermetallics is pest disintegration. It was first observed in molybdenum disilicide in 1955. Since then, pest disintegration has been reported in many intermetallics, including silicides, aluminides, and beryllides. This article examines the pesting of MoSi₂ and presents kinetic processes responsible for pesting.