Precipitation behavior and grain refinement of burnishing Al-Zn-Mg alloy

Burnishing is a unique strengthening approach to improve the strength of surface layer and remains the ductility of the interior of metallic materials. In this work, burnishing treatment was employed to improve the surface microstructure of naturally aged Al-Zn-Mg alloys after solid solution. Transmission electron microscopy, highresolution transmission electron microscopy, X-ray diffraction and nano-indentation were used to characterize the effects of the burnishing on the microstructures of surface layer and Guinier-Preston(GP) zones. It was indicated that GP zones uniformly distributed and dispersed in the matrix before burnishing, and the amount of GP zones decreased dramatically after burnishing processing. Additionally, the grains in the surficial layer were refined into nano-crystals with an average grain size of 78 nm. Burnishing treatment not only led to formation of large number of dislocation substructures in the sub-surface and near-matrix surface, but also promoted the precipitation of metastable η' phase at grain boundaries. The synergistic effects of the grain refinement, dislocation multiplication and the precipitation of η' phase strengthen the burnished layer of Al-Zn-Mg alloy.     

Insight of the dendrite deformation in Ni-based superalloys for increased misorientation along convergent boundaries

The dendrite growth and the associated misorientation evolution on the platform base of a single crystal investment casting were investigated. It was found that the long secondary dendrite arm(LSDA) grew through the whole platform, and a convergent boundary of dendrite arms(CBDA) formed simultaneously between the corresponding branched arms and the extended secondary arms from the blade zone. The corresponding orientation measurement confirmed that the misorientation of dendrite arms between the two sides of the CBDA monotonically increased from 5.9° at one platform edge to 33.5° at the other platform edge. Additionally, the LSDA dendrite deformation was also identified by the accumulated misorientation within the LSDA dendrite core. Furthermore, it was deduced that the increased misorientation along the CBDA was caused by the LSDA dendrite deformation, and the reason of LSDA dendrite deformation was further discussed based on the associated strain distribution around the LSDA. Because of a 33.5° misorientation along the CBDA, it was indicated that the dendrite deformation might be the formation mechanism of high angle boundary.     

Optimizing the fabrication of carbon nanotube electrode for effective capacitive deionization via electrophoretic deposition strategy

In order to obtain superior electrode performances in capacitive deionization(CDI), the electrophoretic deposition(EPD) was introduced as a novel strategy for the fabrication of carbon nanotube(CNT) electrode.Preparation parameters, including the concentration of slurry components, deposition time and electric field intensity, were mainly investigated and optimized in terms of electrochemical characteristic and desalination performance of the deposited CNT electrode. The SEM image shows that the CNT material was deposited homogeneously on the current collector and a non-crack surface of the electrode was obtained. An optimal preparation condition of the deposited CNT electrode was obtained and specified as the Al(NO3)3 M concentration of 1.3 × 10~(-2) mol/L, the deposition time of 30 min and the electric field intensity of 15 V/cm. The obtained electrode performs an increasing specific mass capacitance of 33.36 F/g and specific adsorption capacity of 23.93 mg/g, which are 1.62 and 1.85 times those of the coated electrode respectively. The good performance of the deposited CNT electrode indicates the promising application of the EPD methodology in subsequent research and fabrication of the CDI electrodes for CDI process.     

Effects of hot compression deformation temperature on the microstructure and properties of Al-Zr-La alloys

The main goal of this study is to investigate the microstructure and electrical properties of Al-Zr-La alloys under different hot compression deformation temperatures. In particular, a Gleeble 3500 thermal simulator was used to carry out multi-pass hot compression tests. For five-pass hot compression deformation, the last-pass deformation temperatures were 240, 260, 300, 340, 380, and 420℃, respectively, where the first-pass deformation temperature was 460℃. The experimental results indicated that increasing the hot compression deformation temperature with each pass resulted in improved electrical conductivity of the alloy. Consequently, the flow stress was reduced after deformation of the samples subjected to the same number of passes. In addition, the dislocation density gradually decreased and the grain size increased after hot compression deformation. Furthermore, the dynamic recrystallization behavior was effectively suppressed during the hot compression process because spherical Al₃Zr precipitates pinned the dislocation movement effectively and prevented grain boundary sliding.     

Chemical Composition and Antimicrobial Activity of Essential Oil of Asarum caulescene

Both essential oils of fresh and air-dried Asarum caulescene （Maxim.） were analyzed by GC-MS in three different polarities. The resuits show that thirty-four components were identified in the oils, and main compounds of both oils were β-pinene （7. 63% vs. 20. 77%）, 2 carene （8.94% vs. 7.99%）, β-phellandrene （7.80% vs. 14.39%）, 1,8-cineole （8. 91% vs. 13. 29%） and germacrone （46. 64% vs. 6.64%）, however, the content of monoterpene hydrocarhons（30.29% vs. 52. 30%） and oxygenated sesquiterpenes（47.69% vs. 10.65%） of both oils was different. The antimicrobial activity of the oil was evaluated against 3 fungi and 11 hacteria including 7 clinical isolated strains. Our results showed that both oils presented a broad antimicrobial spectrum, and compared with the essential oil from fresh herb, the extracted oil from dried herb had hetter antimicrohial activity, its minimum inhibitory concentration（cmi） values of dried herh were 0. 16-2. 5 g/L and lowest minimum bactericidal concentration（cmb ） value was 0.31 g/L.     

Antiviral compounds and one new iridoid glycoside from Cornus officinalis

From Cornus officinalis Sieb. et Zucc., bioassay-guided fractionation led to the isolation of four active tannin compounds with high effectiveness of inhibiting Hepatitis C virus NS3 serine protease in vitro. The compounds are: 1,2,3,6-tetragalloyl-β-D-glucopyranose (1), 1,2,3,4,6- pentagalloyl-β-D-glucopyranose (2), Tellimagrandin Ⅰ (3) and Tellimagrandin Ⅱ (4). The four compounds could inhibit HCV NS3 protease in vitro with IC50 values of 6.98, 5.11, 7.0 and 4.8 μmol/L respectively. In addition, a new iridoid glycoside (5) was also isolated from Cornus officinalis Sieb. et Zucc., which was assigned to be 7-O-butyl morroniside by spectroscopic analysis.     

CaT1 manifests the pore properties of the calcium-release-activated calcium channel

The calcium-release-activated Ca2+channel, ICRAC, is a highly Ca2+-selective ion channel that is activated on depletion of either intracellular Ca2+ levels or intracellular Ca2+ stores. The unique gating of ICRAC has made it a favourite target of investigation for new signal transduction mechanisms; however, without molecular identification of the channel protein, such studies have been inconclusive. Here we show that the protein CaT1 (ref. 4), which has six membrane-spanning domains, exhibits the unique biophysical properties of ICRAC when expressed in mammalian cells. Like ICRAC, expressed CaT1 protein is Ca2+ selective, activated by a reduction in intracellular Ca2+ concentration, and inactivated by higher intracellular concentrations of Ca2+. The channel is indistinguishable from ICRAC in the following features: sequence of selectivity to divalent cations; an anomalous mole fraction effect; whole-cell current kinetics; block by lanthanum; loss of selectivity in the absence of divalent cations; and single-channel conductance to Na+ in divalent-ion-free conditions. CaT1 is activated by both passive and active depletion of calcium stores. We propose that CaT1 comprises all or part of the ICRAC pore.     

Molecular Dynamics Simulation of Dealloyed Layer-induced Tensile Stress in Cu3Au

During stress corrosion cracking of Cu₃Au alloy, there is a dealloyed layer on its surface because of preferential dissolution of Cu, and there is a linear distribution of Cu vacancy concentration in the dealloyed layer. Molecular dynamics simulation has been done on the three-dimensional crystal (about 148 000 atoms) by employing the embedded-atom method (EAM) potential. Simulation shows that Cu₃Au crystal in which there is a dealloyed layer on one surface and one end is fixed will be deflected after relaxing for a long time because of a tensile stress generated at or near the dealloyed layer interface. The deflection and then the tensile stress increase with increasing the depth of dealloyed layer and the vacancy concentration in the dealloyed layer.     

Effect of annealing on composition,structure and electrical properties of Au layers grown on different thickness Cr layers

110 nm-thick Au layers were sputter-deposited on unheated glasses coated about a 10 nm-thick and a 50 nm-thick Cr layer respectively. The Au/Cr bilayer films were annealed in a vacuum of 1 mPa at 300℃ for 2, 5 and 30 min, respectively. Auger electron spectroscopy, X-ray diffraction and Field emission scanning electron microscopy were used to analyze the composition and structure of the Au layers. The resistivity of the bilayer films was measured by using four-point probe technique. The adhesion of the bilayer films to the substrate was tested using tape tests. The amount of Cr atoms diffusing into the Au layer increases with increasing the annealing time, resulting in a decrease in lattice constant and an increase in resistivity of the Au layer. The content of Cr inside the Au layer grown on the thinner Cr layer is less than that grown on the thicker Cr layer. For the Au/Cr bilayer films, the lower resistivity and the good adhesion to the glass substrate can be obtained at a shorter annealing time for a thinner Cr layer.     

Predicting the martensite transformation start-temperature of low alloy steel based on fuzzy identification

A method of fuzzy identification based on T-S fuzzy model was proposed for predicting temperature M_s from chemical composition, austenitizing temperature and time for low alloy steel. The degree of membership of each sample was calculated with fuzzy clustering algorithm. Kalman filtering was used to identify the consequent parameters. Compared with the results obtained by empirical models based on the same data, the results by the fuzzy method showed good precision. The accuracy of the fuzzy model is almost 6 times higher than that of the best empirical model. The influence of alloying elements, austenitizing temperature and time on M_s was analyzed quantitatively by using the fuzzy model. It is shown that there exists a nonlinear relationship between the contents of alloying elements in steels and their M_s, and the effects of austenltizing temperature and time on M_s temperature cannot be neglected.