In order to compare the spark plasma sintedng （SPS） process plus hot isostatic press （HIP） with vacuum sintedng plus HIP, an investigation was carried out on the topography, microstructure and gain size distributi...
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In order to compare the spark plasma sintedng （SPS） process plus hot isostatic press （HIP） with vacuum sintedng plus HIP, an investigation was carried out on the topography, microstructure and gain size distribution of nanocrystalline WC-10Co composite powder and the sintered specimens prepared by SPS plus HIP and by vacuum sintering plus HIP by means of atomic force microscopy （AFM）. The mechanical properties of the sintered specimens were also investigated. It is very easy to find cobalt lakes in the specimen prepared by vacuum sintering plus HIP process. But the microstructure of the specimen prepared by SPS plus HIP is more homogeneous, and the grain size is smaller than that prepared by vacuum sintering plus HIP. The WC-10Co ultrafine cemented carbide consolidated by SPS plus HIP can reach a relative density of 99.4%, and the transverse rupture strength （TRS） is higher than 3540 MPa, the Rockwell A hardness （HRA） is higher than 92.8, the average grain size is smaller than 300 nm, and the WC-10Co ultrafine cemented carbide with excellent properties is achieved. The specimen prepared by SPS with HIP has better properties and microstructure than that prepared by vacuum sintering with HIP.
Mass production of ZnO nanobelts and hexagonal nanorods has been successfully synthesized on CuO catalyzed porous silicon （PS） using a simple vapour-solid （VS） growth method. A comparison of their morphologies is ...
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Mass production of ZnO nanobelts and hexagonal nanorods has been successfully synthesized on CuO catalyzed porous silicon （PS） using a simple vapour-solid （VS） growth method. A comparison of their morphologies is investigated by scanning electron microscopy （SEM）. The transmission electron microscopy （TEM） confirms that ZnO nanobelts and nanorods are single crystalline with the growth direction of （0110） and （0001）, respectively. Field emission tests indicate that the ZnO nanostructures on porous silicon have low turn-on field of about 3.6 V/μm （at 1.0μA/cm^2） and the threshold field of about 8.3 V/μm （at 1.0mA/cm^2）, high emission site density （ESD） of approximately 104 cm^-2.
In this paper, a new micromechanical method, the Weighted Residual Self-consistent Scheme (WRSCS), is developed for the prediction of the effective thermal conductivity of particulate composites with arbitrary configu...
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In this paper, a new micromechanical method, the Weighted Residual Self-consistent Scheme (WRSCS), is developed for the prediction of the effective thermal conductivity of particulate composites with arbitrary configurations. The method is based on the concept of the traditional Self-consistent Scheme (SCS). For some special configurations of inclusions, such as spherical or ellipsoidal, the effective conductivity of the composite can be solved without much difficulty using SCS. But for the composite with inclusion of arbitrary geometry, such as polygon or other irregular configurations, it is difficult to get an analytic solution. In the WRSCS, the arbitrary inclusion configuration is modeled by applying collocation points at interface. Based on SCS micromechanical model, the local fields inside the inclusion can be evaluated by using the solution of a single inclusion in an infinite matrix and inclusion interaction is taken into account through the yet unknown average equivalent medium. The solution for calculating the potential field inside the inclusion is obtained by means of Weighted Residual Method (WRM). Using the WRSCS, the effective thermal conductivities for composites with different inclusion's geometry are calculated. For the case of spherical inclusion, the results from the WRSCS show good agreements with the one from traditional SCS [7, 8]. Examining results corresponding to different inclusion's geometry, it shows that the effective thermal conductivity depends not only on the volume fractions and the properties of components, but also on the inclusion's configuration.
Monodispersed mesoporous silicon dioxide microspheres were prepared by polymerization-induced colloid aggregation (PICA) method and calcined at 850°C. The prepared samples were characterized with scanning electro...
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Monodispersed mesoporous silicon dioxide microspheres were prepared by polymerization-induced colloid aggregation (PICA) method and calcined at 850°C. The prepared samples were characterized with scanning electron microscopy (SEM), thermogravimetry (TG) and BET surface areas. The results showed that the obtained SiO2 microspheres had an average diameter of about 2.0 μm, a surface area of 253.3 m2g-1, an average pore volume of 0.62 mLg-1, and an average pore diameter of 7.9 nm. The formation mechanism of SiO2 spherical particles was discussed.
The functionally graded thermal barrier coating (TBC) serves in high temperature and/or high temperature gradient environment for a long time. According to the experimental and theoretical research, in the metal subst...
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ISBN:
(纸本)0878499709
The functionally graded thermal barrier coating (TBC) serves in high temperature and/or high temperature gradient environment for a long time. According to the experimental and theoretical research, in the metal substrate and the metal-rich interlayer creep deformation will appear under high temperature environment. In order to design and optimize the compositional distribution of FGM, it is necessary to analyze the stress and strain responses taking into account the creep phenomenon of the materials. In this article, the thermo-mechanical responses of ceramic/metal functionally graded TBC in work environment are analyzed by a finite element method. The creep phenomenon of the metal and the interlayers are taken into account. The numerical results indicate that the creep behavior of all interlayers, even for the ceramic-rich interlayer, cannot be neglected in analysis. It is suggested that the creep phenomenon of the material is important in the functionally graded TBC systems.
In the present study, Fe and Si powders (3:1 in atomic proportion) were mechanical alloyed and subsequently treated under different anneal conditions. The changes of phase composition and structure during the mechanic...
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In the present study, Fe and Si powders (3:1 in atomic proportion) were mechanical alloyed and subsequently treated under different anneal conditions. The changes of phase composition and structure during the mechanical alloying and following heat treatment processes were mainly studied. The results showed that the XRD peaks of Fe were gradually broadened and weakened with the increase of the milling time associated with the shifting from low angles to high angles, and the main phase changed into α-Fe (Si) solid solution after milling for 20h. When the product was heat treated below 400°C, the main phase remained α-Fe (Si). While it was treated above 400°C, ordered Fe3Si phase was found and the XRD peaks of Fe3Si became sharper with the further increase of the temperature.
The fracture of the functionally graded thermal barrier coating (TBC) under the thermal loads is a key for the engineering application of this kind of materials. In the previous studies, the functionally graded TBC is...
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ISBN:
(纸本)0878499709
The fracture of the functionally graded thermal barrier coating (TBC) under the thermal loads is a key for the engineering application of this kind of materials. In the previous studies, the functionally graded TBC is usually simplified into a laminate by homogenizing the material of each interlayer as an isotropic layer. Nevertheless, this method is a macro equivalent method, which neglected the microstructure characteristics of materials. In this paper, the computational micromechanics method (CMM) is employed to study the fracture problem of the functionally graded TBC with the interface crack. Essentially, CMM is a finite element analytical method based on the real microstructure of materials, which combines the digital image processing technique, the auto mesh generation technique with the finite element method. Firstly, the microstructure photos of the functionally graded TBC are required. Secondly, the digital image processing technique and the auto mesh generation technique are used to construct the finite element model. Finally, the finite element method is utilized for the fracture analysis of the functionally graded TBC under the thermal shock loads. Moreover, the problem is also analyzed using the macro equivalent method and the results from the two methods are compared. The temperature field obtained using CMM is basically consistent with the one obtained from the macro equivalent method and the influences of the interface crack on the temperature fields are limited in a local region. But results of the driving forces for the crack propagation, J-integrals, from the two methods are quite different. Comparing with the CMM results, J-integrals from the macro equivalent method are smaller. It means that the macro equivalent method tends to underestimate the driving force of the interface crack. On the other hand, the prediction of the critical location of the interface crack from the two methods is also different. Since the influence of the microstructure
作者：
王友法Biomedical Materials and Engineering Research Center
Wuhan University of TechnologyWuhan 430070ChinaState Key Lab of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China
Inorganic nanoparticles were used to treat cancer cells us well as normal cells. Ca9Sr（ PO4）6（OH）2 nanopartides were prepared through homogeneous precipitation method. Strontium hydroxide, calcium hydroxide solat...
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Inorganic nanoparticles were used to treat cancer cells us well as normal cells. Ca9Sr（ PO4）6（OH）2 nanopartides were prepared through homogeneous precipitation method. Strontium hydroxide, calcium hydroxide solation and monocalcium phosphate were used as initial materials. The strontium-doped hydroxyapatite nanoparticles were characterized by XRD, PCS and AFM. The nanoparticles were applied to interact with human bepatocellular carcinoma cells Bel-7402 and nornud liver cells L-02. Experimental results revealed that nano strontium-strontium apatiw has different bioeffects on proliferation of these two kinds of cells.
The HAP nanoparticles were synthesized with a chemical co-precipitation method. It was monodispersed in needle shape, Its average diameter was 30 nm and length was 70 nm. Human liver cancer cells and normal hepatic ce...
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The HAP nanoparticles were synthesized with a chemical co-precipitation method. It was monodispersed in needle shape, Its average diameter was 30 nm and length was 70 nm. Human liver cancer cells and normal hepatic cells were treated by hydroxyapatite nanopartides. SR-XRF analysis was used to detect the content variation of calcium and phosphor elements in cancer cells when the cells were treated by hydroxyapatite nanoparticles. It was introduced to reveal the anti-cancer mechanism of HAP nanoparticles. Experiments verified that the contents of calcium and phosphor elements in hepatocelltdar carcinoma had been obviously increased after the cells were treated by hydroxyapatite nanoparticles. And the contents increased with hydroxyapatite concentration and treatment time increasing. The Ca/P molar ratio in treated cell was different from both that in hydroxyapatite and that in untreated cancer cell. Apatite nanoparticles evidently altered the calcium and phosphor environmeats in treated hepatocellalar carcinoma cells. That finally halted the proliferation of carcinoma cells.
Two types of electromagnetic edge dams were analyzed by using finite element method in present paper. The magnetic vector potential method and edge element method were used. The distributions of the magnetic field, th...
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Two types of electromagnetic edge dams were analyzed by using finite element method in present paper. The magnetic vector potential method and edge element method were used. The distributions of the magnetic field, the eddy current intensity and the magnetic force were obtained from the computing. The differences in these fields were explained according to the two types of electromagnetic dam, and characters of their application in twin roll casting were also discussed.
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