The flow field is very important for the proton exchange membrane fuel cell (PEMFC). In this paper the PEMFC with different kind of section channels is modeled and optimized design by the PEM module of the Fluent soft...
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The flow field is very important for the proton exchange membrane fuel cell (PEMFC). In this paper the PEMFC with different kind of section channels is modeled and optimized design by the PEM module of the Fluent software. And the result shows that the performance of the PEMFC with rectangle, semicircle, triangle or trapezoid section is not too much difference, but the performance of the PEMFC with changing section channel is much better than that of the above mentioned ones.
Titanium diboride based composites, good candidates for contact materials, have high hardness, Young＇s modulus, high temperature stability, and excellent electrical, thermal conductivity. However a good interface of ...
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Titanium diboride based composites, good candidates for contact materials, have high hardness, Young＇s modulus, high temperature stability, and excellent electrical, thermal conductivity. However a good interface of TiB2/Cu is very difficult to achieve for oxidation of TiB2. To avoid this oxidation behavior, the in situ combusting synthesistechnology, SHS, was used to prepare TiB2/Cu composite. The characters of Ti-B-xCu SHS were studied in detail, such as combustion temperature, products phases and grain size. Based on the experimental results a proper technology way of self-high temperature synthesis plus quick press （SHS/QP） was determined and compact TiB2/Cu composites with relative density over than 97 pct of the theoretical were fabricated by this method. The properties and microstructures of these TiB2 based composites were also investigated.
TiB2 powders coated with BN were prepared by Hybridization System making use of dry impact blending method to achieve powder surface modification. Parameters of coating were analyzed and the most appropriate condition...
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TiB2 powders coated with BN were prepared by Hybridization System making use of dry impact blending method to achieve powder surface modification. Parameters of coating were analyzed and the most appropriate condition was summarized. Scan electron microscope of JSM-5610LV and transmission electron microscope of H-600STEM/EDS were used to observe the microstructure of coated powders. Results show that treatment time, rotation speed, granularity ratio of TiB2 to BN, pretreatment of materials etc influence the coating results evidently. Mixing raw materials and coating with BN under the appropriate condition can get round TiB2/BN composite powder with smooth surface and compact coating layer.
When boiler runs under certain pressure and temperature, the disfigurement and crack will propagate, resulting in failure of the boiler drum. According to the Assess criterion of Pressure Container's Disfigurement...
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When boiler runs under certain pressure and temperature, the disfigurement and crack will propagate, resulting in failure of the boiler drum. According to the Assess criterion of Pressure Container's Disfigurement, the maximal stress value in the dangerous area for 125MW boiler drum and its change within certain time frame under different working conditions are found out by means of finite element method. The allowable length of crack is calculated with COD mode and the yearly crack-propagating value is predicted and analyzed.
Based on the boundary conditions of the running parameters and test data of 125 MW boiler drum, the transient thermal stress, mechanical stress and whole stresses of the boiler drum under four different working condit...
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Based on the boundary conditions of the running parameters and test data of 125 MW boiler drum, the transient thermal stress, mechanical stress and whole stresses of the boiler drum under four different working conditions were computed by finite element methods under 3-dimension model. The relationship among the three kinds of stresses was discussed as well as the spot of maximum stress and its varying tendency with the time was obtained.
The residual stresses on the surface of the d ifferently ground and polished silicon nitride ceramics were measured using X-r ay diffraction and identified by *** effect of the residual stress on the be nding strengt...
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The residual stresses on the surface of the d ifferently ground and polished silicon nitride ceramics were measured using X-r ay diffraction and identified by *** effect of the residual stress on the be nding strength was *** investigations show that the grinding proces s can introduce subatantial tensile residual stresses up to 290MPa on the surfac e of silicon nitride ceramics,which has a significant effect on reducing the ben ding strength of the ceramics after ***,in comparison with the ceramic s with a rough surface,the ceramics with a mirror image surface may have a lower *** can smooth the residual *** we evaluate the qualit y of the ceramic components after grinding,we must take residual stress into con sideration. The grinding methods and grinding conditions must be carefully selec ted in order to get the favorite residual stress as well as the surface smoothne ss.
The PAn-PEO-PAn triblock copolymer with the PEG chain length of 400 was synthesized by chemical oxidation copolymerization of aniline and α,ω-bis（p-aminophenyl）poly（ethylene glycol）and characterized by FT-IR and...
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The PAn-PEO-PAn triblock copolymer with the PEG chain length of 400 was synthesized by chemical oxidation copolymerization of aniline and α,ω-bis（p-aminophenyl）poly（ethylene glycol）and characterized by FT-IR and *** experimental results show that the copolymer particles are of μtypical core-shell structure after the self-assembly process in *** conductivity is much lower than that of the pure *** suspension containing 20 vol% PAn-PEO-PAn tiblock copolymer in silicone oil exhibits.a typical electrorheological （ER） effect in DC electric *** it shows a lower leakage current density than that of the pure PAn-based ER ***,the PEO shell hinders the electric hop among PANI chains and decreases the current density of ER fluids in an external electric *** the same time the interface polarity improves the ER effects.
This paper studied the thermal stresses of ceramicl metal gradient thermal barrier coating which combines the conceptions of ceramic thermal barrier coating （TBC） and functionally gradient material （FGM）. Thermal ...
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This paper studied the thermal stresses of ceramicl metal gradient thermal barrier coating which combines the conceptions of ceramic thermal barrier coating （TBC） and functionally gradient material （FGM）. Thermal stresses and residual thermal stresses were calculated by an ANSYS finite element analysis software. Negative thermal expansion coefficient method was proposed and element birth and death method was applied to analyze the residual thermal stresses which have non-uniform initial temperature field. The numerical results show a good agreement with the analytical results and the experimental results.
La substituted Ba(Mg_ 1/3Nb_ 2/3)O_3 ceramics was expected to enhance the 1∶2 ordering degree of B-site ions due to the existence of vacancies that promote cation movement and result in improvement of the Q_f value. ...
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La substituted Ba(Mg_ 1/3Nb_ 2/3)O_3 ceramics was expected to enhance the 1∶2 ordering degree of B-site ions due to the existence of vacancies that promote cation movement and result in improvement of the Q_f value. The relation between the microstructure and microwave dielectric properties of Ba_ 1-xLa_ 2x/3(Mg_ 1/3Nb_ 2/3)O_3 ceramics was investigated. La substituted Ba(Mg_ 1/3Nb_ 2/3)O_3 ceramics can improve the sinterability of specimens. Both 1:2 ordering degree and grain size increase as A-site vacancies increase. This can be explained by the existence of vacancies that promote cation movement. The Q_f value increase with small La content, then decrease rapidly. The highest Q_f value achieved in this investigation is about 55000 GHz for Ba_ 0.995La_ 0.01/3(Mg_ 1/3Nb_ 2/3)O_3. The improvement of Q_f value with A-site vacancies is related to the increase of the degree of B-site ordering and grain size of the specimen.
A series of bulk polycrystalline La1-xLixMnO3 samples with x ranging from 0.1 to 0.5 was prepared by sol-gel method,X-ray diffraction patterns show that the crystal structures are single rhombohedral perorskite for th...
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A series of bulk polycrystalline La1-xLixMnO3 samples with x ranging from 0.1 to 0.5 was prepared by sol-gel method,X-ray diffraction patterns show that the crystal structures are single rhombohedral perorskite for the x≤0.3 sample and the impurity appears when x〉*** the same synthesized conditions,the higher Li content samples display a higher content of liquid phase content and larger mean grain sizes,which leads to the increases of the effect of the grain *** experimental results show that the change of the ferromagnetic transition temperature and the resistivity can attribute to the effect of the grain boundary and the connectivity of the inter grains as well as the ratio of Mn^3＋ to Mn^4＋.
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