小角x射线散射确定TiNi薄膜中晶化粒子的长大激活能

用小角x射线散射技术研究以直流磁控溅射方法制备TiNi合金薄膜其退火生成的晶化粒子的长大行为 .发现在室温下溅射的TiNi合金薄膜存在小于 1nm尺寸的微空洞 ,将退火后薄膜的小角x射线散射强度扣除退火前微空洞产生的小角x射线散射强度 ,用这种方法得到的散射强度遵从Porod定律 ;而用通常方法扣除背底得到的散射强度结果不满足Porod定律 .TiNi合金薄膜在 733— 793K之间退火晶化粒子的长大激活能Eg=30 1kJ mol.

衬底温度对沉积的NiTi薄膜晶化行为的影响

将采用直流磁控溅射方法制备的NiTi薄膜沉积在热的衬底上,应用X射线散射和小角X射线散射技术研究了NiTi合金薄膜中生成的晶化粒子的界面特征和晶粒大小.结果表明:衬底加热可降低薄膜的晶化温度,衬底温度在350℃以上,溅射的NiTi薄膜已部分晶化;衬底温度在350、370℃和420℃溅射的NiTi薄膜,对应的晶化粒子的半径分别是2 40、2 59、2 81nm;薄膜中的晶化粒子以形核长大的方式进行,结晶粒子与基底之间有清晰的界面.

Synthesis,characterization and photocatalytic performance of rod-shaped Pt/PbWO_4 composite microcrystals

Rod-shaped PbW O4 microcrystals of length 1 μm were fabricated by a hydrothermal route and subsequent calcination. Pt nanoparticles（NPs） of different contents（0.5 wt%,1 wt% and 2 wt%） were subsequently deposited on the PbW O4 microcrystals,producing robust Pt/PbW O4 composite microcrystals. The PbW O4 microcrystals and Pt/PbW O4 photocatalysts were characterized by X-ray diffraction,N2 sorption measurements,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron,photoluminescence,Fourier-transform infrared,and ultraviolet-visible diffuse reflectance spectroscopies. The photocatalytic performances of the catalysts were evaluated by the consecutive photocatalytic degradation of acid orange II dye. The Pt/PbW O4 composite microcrystals exhibited high photocatalytic activity and stability. The deposition of Pt NPs produced surface plasmon resonance（SPR）,which induced a large visible light absorption. A Pt NP content of 1-2 wt% resulted in an ~2 times increase in photocatalytic activity,compared with the activity of Pt/PbW O4. The crystal structure and high crystallinity of PbW O4 resulted in its favorable photocatalytic property,and the SPR effect of the Pt NPs promoted visible light harvesting. The Pt NPs also enhanced the separation of photo-generated electrons and holes,which further promoted the photocatalytic reaction.

Grain refinement of magnesium alloys processed by severe plastic deformation

Grain refinement of AZ31 Mg alloy during cyclic extrusion compression （CEC） at 225-400 ℃ was investigated quantitatively by electron backscattering diffraction （EBSD）. Results show that an ultrafine grained microstructure of AZ31 alloy is obtained only after 3 passes of CEC at 225 ℃. The mean misorientation and the fraction of high angle grain boundaries （HAGBs） increase gradually by lowering extrusion temperature. Only a small fraction of {101^-2} twinning is observed by EBSD in AZ31 Mg alloys after 3 passes of CEC. Schmid factors calculation shows that the most active slip system is pyramidal slip {101^-1}〈1120〉and basal slip {0001}〈1120〉 at 225-350 ℃ and 400 ℃, respectively. Direct evidences at subgrain boundaries support the occurrence of continuous dynamic recrystallization （CDRX） mechanism in grain refinement of AZ31 Mg alloy processed by CEC.

Design of fast crystallization of nanosized zeolite omega crystals at higher temperatures

Fast crystallization of nanosized zeolite crystals is a very popular process used for practical zeolite catalyst applications. Herein, we report a designer crystallization process for nanosized zeolite omega crystals based on the relationship between the crystallization time and temperature in the Arrhenius equation. Compared to the conventional hydrothermal synthesis of zeolite omega(72 h at room temperature and 240 h at 100℃, MAZ-100), the crystallization of zeolite omega presented in this work only requires a very short time interval(5 h at 180℃, MAZ-180). Physicochemical characterizations, including XRD, SEM, N2 sorption isotherms, and 27 Al MAS NMR show that the product of zeolite omega(MAZ-180) has good crystallinity and uniform nanocrystals. More importantly, after the loading of Pt nanoparticles(0.5 wt%), the Pt/H-MAZ-180 catalyst exhibits higher isomer selectivity and lower cracking selectivity than those of the Pt/H-MAZ-100 catalyst in the hydroisomerization of n-dodecane. These results suggest the potential applications of these omega nanocrystals as supporting catalyst compounds in industrial processes.

Effect of soft Bi particles on grain refinement during severe plastic deformation

Two aluminum alloys,Al-8Zn and Al-6Bi-8Zn were subjected to equal channel angular pressing(ECAP)up to5passes at room temperature.The microstructural evolution and the grain refinement behavior of these alloys were systematically studied by electron backscatter diffraction(EBSD).After5passes of ECAP,ultrafine grained microstructures formed in both alloys.However,the grain structure in the Al-6Bi-8Zn alloy is much finer than that of Al-8Zn alloy,showing that the soft Bi particles have a strong influence on enhancing the grain refinement during ECAP.The strengths of the ECAP-processed materials were measured by hardness test and it showed that after5passes of ECAP,the hardness of the Al-6Bi-8Zn alloy was higher than that of the Al-8Zn alloy.The effects of soft Bi particles on the deformation behavior during ECAP and the final strength of the Al-6Bi-8Zn alloy were discussed.

Influence of Gravity on Structure of Colloidal Crystal Using Simulated Microgravity

Liquid mixtures of water and deuterium oxide as the liquid phase, were used to match the density of charged colloidal particles. Kossel diffraction method was used to detect the crystal structures. The experiments under the density-matched （g=0） and unmatched （g=1） conditions are compared to examine the influence of gravity on the crystal structures formed by self-assembly of 110 nm （in diameter） polystyrene microspheres. The result shows that the gravity tends to make the lattice constants of colloidal crystals smaller at lower positions, which indicates that the effect of gravity should be taken into account in the study of the colloidal crystals.

Influence of Crystal Size of USY Zeolite on Performance of Hydro-upgrading Catalysts

The effect of crystal size of USY zeolite on the performance of hydro-upgrading catalysts for treating catalytically cracked(FCC) LCO(light cycle oil) was studied.Three W-Ni catalysts supported on USY zeolites with different crystal sizes and Al2O3 were prepared by impregnation method.The catalysts were characterized by XRD and BET methods,and evaluated in a micro-reactor using tetralin as the model compound and in an 100-mL hydrogenation test unit using FCC LCO as the feedstock.By contrast,catalyst made from smaller crystal-size USY zeolite had higher external surface area and shorter pore length,having more hydrogenation activity sites and short contact time of reactant molecules with acidity sites.The evaluation results showed that the catalyst prepared on the basis of small crystal-size USY zeolite had higher tetralin conversion and better hydro-upgrading performance for treating FCC LCO.

Two-dimensional silicon-carbon hybrids with a honeycomb lattice: New family for two-dimensional photovoltaic materials

We predict a series of new two-dimensional(2D) inorganic materials made of silicon and carbon elements(2D SixC1?x) based on density functional theory. Our calculations on optimized structure, phonon dispersion, and finite temperature molecular dynamics confirm the stability of 2D SixC1?x sheets in a two-dimensional, graphene-like, honeycomb lattice. The electronic band gaps vary from zero to 2.5 e V as the ratio x changes in 2D SixC1?x changes, suggesting a versatile electronic structure in these sheets. Interestingly, among these structures Si0.25C0.75 and Si0.75C0.25 with graphene-like superlattices are semimetals with zero band gap as their ? and ?* bands cross linearly at the Fermi level. Atomic structural searches based on particle-swarm optimization show that the ordered 2D SixC1?x structures are energetically favorable. Optical absorption calculations demonstrate that the 2D silicon-carbon hybrid materials have strong photoabsorption in visible light region, which hold promising potential in photovoltaic applications. Such unique electronic and optical properties in 2D SixC1?x have profound implications in nanoelectronic and photovoltaic device applications.

Highly Sensitive Protein Sensor Based on Thermally-Reduced Graphene Oxide Field-Effect Transistor

We report the fabrication of a highly sensitive field-effect transistor （FET） biosensor using thermally-reduced graphene oxide （TRGO） sheets functionalized with gold nanoparticle （NP）-antibody conjugates. Probe antibody was labeled on the surface of TRGO sheets through Au NPs and electrical detection of protein binding （Immunoglobulin G/IgG and anti-lmmunoglobulin G/anti-lgG） was accomplished by FET and direct current （dc） measurements. The protein binding events induced significant changes in the resistance of the TRGO sheet, which is referred to as the sensor response. The dependence of the sensor response on the TRGO base resistance in the sensor and the antibody areal density on the TRGO sheet was systematically studied, from which a correlation of the sensor response with sensor parameters was found： the sensor response was more significant with larger TRGO base resistance and higher antibody areal density. The detection limit of the novel biosensor was around the 0.2 ng/rnL level, which is among the best of,＇eported carbon nanomaterial-based protein sensors and can be further optimized by tuning the sensor structure.

Rutile TiO2 Microspheres with Exposed Nano-Acicular Single Crystals for Dye-Sensitized Solar Cells

Uniquely structured rutile TiO2 microspheres with exposed nano-acicular single crystals have been successfully synthesized via a facile hydrothermal method. After calcination at 450 ℃ for 2 h, the futile TiO2 microspheres with a high surface area of 132 m2/g have been utilized as a light harvesting enhancement material for dye-sensitized solar cells （DSSCs）. The resultant DSSCs exhibit an overall light conversion efficiency of 8.41% for TiO2 photoanodes made of futile TiO2 microspheres and anatase TiO, nanoparticles （mass ratio of 1：1）, significantly higher than that of pure anatase TiO2 nanoparticle photoanodes of similar thickness （6.74%）. Such a significant improvement in performance can be attributed to the enhanced light harvesting capability and synergetic electron transfer effect. This is because the photoanodes made of futile TiO2 microsphere possess high refractive index which improves the light utilisation efficiency, suitable microsphere core sizes （450-800 nm） to effectively scatter visible light, high surface area for dye loading, and synergetic electron transfer effects between nanoparticulate anatase and nano-acicular futile single crystals phases giving high electron collection efficiency.

Phase Transition and Physical Properties of InS

Using the crystal structure prediction method based on particle swarm optimization algorithm, three phases （Pnnm, C2/m and Pm-3m） for InS are predicted. The new phase Pm-3m of InS under high pressure is firstly reported in the work. The structural features and electronic structure under high pressure of InS are fully investigated. We predicted the stable ground-state structure of InS was the Pnnm phase and phase transformation of InS from Pnnm phase to Pm-3m phase is firstly found at the pressure of about 29.5 GPa. According to the calculated enthalpies of InS with four structures in the pressure range from 20 GPa to 45 GPa, we find the C2/m phase is a metastable phase. The calculated band gap value of about 2.08 eV for fnS with Pnnm structure at 0 GPa agrees well with the experimental value. Moreover, the electronic structure suggests that the C2/m and Pm-3m phase are metallic phases.