Abstract: The effect of cooling rate and iron content on the solidification structures of copper-iron alloys had been investigated in this paper. The results show that the morphology of as-cast structure is mainly determined by iron content and the grain size is affected by both the iron content and cooling rate. The as-cast structure is obviously refined and its morphology changes gradually from columnar grains to equiaxed ones with the increase in iron content. When iron content is greater than 3% (in mass%) the as-cast structure is composed wholly of equiaxed grains. With the increase in cooling rate the as-cast structure is gradually refined and primary γ-Fe phase is gradually scattered uniformly throughout the matrix.
Abstract: Generalized gradient approximation (GGA) of the density function theory (DFT) was applied to calculate many properties including density of states, population analysis and electron density in NiAl and NiAl(Fe) to investigate the mechanism of improving room temperature ductility of B2-NiAl by Fe. It was shown that the strong bond to Al p and Ni d hybridization, which leads to the embrittlement of B2-NiAl at room temperature. Addition of Fe, which is beneficial to improve ambient ductility of B2-NiAl, weakens the impact of the bond to Al p and Ni d hybridization and enhances the interaction among next-nearest-neighbor Ni atoms to make the charge distribution uniform along <100>.
Abstract: In this study, the effects of microwave radiation intensity, initial moisture content and thickness on the properties of temperature development in Siberian Elm wood samples during the microwave drying have been investigated using a tailor made microwave drying equipment. The results show that with the increase of microwave radiation intensity and a decrease in initial moisture content and thickness, both the temperature and its rate of increase in wood rise rapidly. In the microwave drying, the temperature development curve presented three stages of variation: a sharp increase in temperature − a constant temperature − a slow warm-up.
Abstract: In this paper, Siberian elm (Ulmus pumila L) which was regarded as our research object was measured with the technology of Nuclear Magnetic Resonance (NMR) before and after being treated with microwave at different periods of time. By comparing the spin - spin relaxation time of hydrogen nuclear (T2) which can reflect the mobility of water molecules, the states and changes of the moisture distribution within the wood in the process of microwave treatment have been analyzed. The results indicate that in the initial stage of drying, the degree of the decline in bound water is greater than that in free water, for there may be a process of the transformation from bound water to free water; With the drying going on, the movement and expulsion mainly happen to free water above the fiber saturation point (FSP); In the later stage of drying, when the moisture content decreases near the FSP, bound water has also begun moving significantly on the expulsion of plenty of free water. In the final stage of drying, the decrease of hydrogen bonds in water molecules resulting from a plentiful reduction in free water, as well as the increased permeability within the wood caused by the microwave drying makes the relaxation time of free water to rise up.
Abstract: Incompatible numerical manifold method (INMM) uses interpolation functions based on the concept of partition of unity, and considers the asymptotic solution and the discontinuity of displacement. This paper describes the application of INMM to bi-material interfacial crack. The two dimensional near-tip asymptotic displacement functions are added to the trial function approximation. This enables the domain to be modeled by manifold elements without explicitly meshing the crack surfaces. The crack-tip enrichment functions are chosen as those that span the asymptotic displacement fields for an interfacial crack. The INMM facilitates the incorporation of the oscillatory nature of the singularity within a conforming manifold element approximation. The complex stress intensity factors for bi-material interfacial cracks are numerically evaluated. Good agreement between the numerical results and the analytical solutions for benchmark interfacial crack problems is realized.
Abstract: Graphene oxide (GO) was made by a modified Hummers method. Graphene oxide modified phenolic resin nanocomposites (GO/PF) were prepared by Steglich esterification, catalyzed by dicyclohexyl carbodiimide and 4-dimethylaminopyridine. The composites were characterized by Fourier transform infrared spectrometry, differential scanning calorimetry, X-ray powder diffraction, and scanning electron microscopy. The result revealed that the graphene oxide was absolutely exfoliated and covalent linked GO/PF composite was obtained. The thermal stability of PF is remarkably improved by modification with GO.
Abstract: A paste with as low as 300°C sintering temperature was prepared by using nano silver particles and ethyl cellulose solution. The rheological and thixotropic behaviors of the typical paste were characterized and their effects on the screen printing ability were analyzed in details. The paste demonstrates a typical shear thinning rheological behavior and thixotropic of pseudoplastic fluid. The apparent viscosity decreased rapidly with the increase of the shear rate. The paste is proper for the manufacturing electrical components at a low temperature as low as 300°C.
Abstract: Surface treatment before glass bonding is an important and critical issue for glass-based lab-on-chip fabrication. In the present article we verified five different activation methods for obtaining sound thermal assisted direct bonding (TADB) on glasses. Glass surface has been investigated by means of water contact angle, X-ray photoelectron spectroscopy (XPS). The optimum surface activation method for TADB on glasses was found to be H2SO4:H2O2 (3:1 by volume) followed by HNO3. By using the TADB optimized activation method, the glass bonding strength higher than 32MPa was obtained with a glass the roughness of 50 nm.
Abstract: A hierarchical porous carbon derived from phenolic resin (PF) was processed using ethylene glycol (EG) and starch as double porogens. The influences of composition of starting mixture, including the two porogens and PF, on morphological properties and microstructure of the porous carbon were investigated. It was demonstrated that the content of starch and the relative content of EG to PF played key roles in determining the number, size and formation of the hierarchical pores, which in turn led to changes in the properties and the microstructure of the porous carbon. In particular, the number of the first-level pores (diameter ~10–40 μm) increased with the content of starch increasing, and the high relative content of EG to PF contributed to the formation of the second-level pores (diameter ~0.5–2 μm), which were closely related to the formation mechanisms of the two-level pores, respectively. Under the present experimental conditions, sufficiently high starch content can result in the microstructural abnormalities, such as the incomplete decomposition of starch and the formation of the third-level pores which originated from the stack of discrete carbon particles.
Abstract: Thermo-sensitive gel is a kind of macromolecular material with temperature sensibility character. It is liquid under room temperature, and it can be changed to semisolid gel under animal body temperature. Then the medicament in the gel can be released gradually, to gain the sustained-release. We can make use of this character. The makeup of thermo-sensitive gel has a lot of ways, and recently the most in common use is PNIPA. It can be used in tumor cavity’s coating sustained-release chemotherapy after surgical operation, all use methods including：1. Brain glioma re-growing always be happened in tumor local site after neurosurgery operation, and inosculate the chemotherapy medicament into chitosan nanospheres slow-releasing particulates. Then mix into the thermosensitive gel , to be made to spray. During neurosurgical operation, after the surgical treatment for tumor, we spray it in the brain parenchyma cave remain after cutting tumor. When the thermosensitive gel meets the animal temperature, it is changed to membrane-wise glue attached to the tumor cave face. Then after surgical it can absorb moisture nearby, and gel membrane and chitosan nanospheres will release medicament continually. After glioma surgical treatment, the chemotherapy is slowly released partially. 2. Stereotactic surgery injection release interstitial chemotherapy. Under stereotactic apparatus inject gel into the centre of tumor, then the gel changes to colloid from liquid, and then the gel no outflow from tumor. The stereotactic technology offers the effective biopsy, diagnose and accurate and safe administration route for malignant glioma in brain’s depth which cannot be surgical treatment. 3. Embolization chemotherapy in tumor vasculature. Inject the thermosensitive gel into tumor artery, and some parts of gel curdle gradually, then it can embolize tumor capillary network, to interdict the blood to tumor, to control tumor’s growth. In the meantime medicament in gel release gradually, to win the chemotherapy. 4. Cerebral aneurysms and cerebral arteriovenous malformation embolization. Thermosensitive gel makes use of the difference between room temperature and animal heat to make embolism.