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以煤焦油基沥青为原料,在420~450℃的范围内热解制备中间相沥青,用所制得的沥青在6~8MPa的压力下升温发泡,保温一段时间,然后再经过碳化和石墨化制得一种性能优良的导热材料--碳泡沫,其导热系数最高可以达到110W/(m·K).讨论了沥青中间相含量、发泡时的压力、保温时间、升温速率对泡沫导热性能的影响:随着中间相沥青含量的增加,所制备的碳泡沫的导热系数明显提高,中间相由0%提高到100%时,导热系数由77.5W/(m·K)上升到110W/(m·K);发泡时保温时间的影响相对于成型压力更为明显,保温时间从1h提高到4h,导热系数会由85 W/(m·K)上升到100W/(m·K);发泡的压力对导热系数的影响不是很明显. 相似文献
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加热条件对炭泡沫材料孔结构和性能的影响 总被引:2,自引:0,他引:2
以AR沥青为原料,利用高压釜在不同恒温条件下制备了炭泡沫,并测定了其孔结构、体积密度、显气孔率、压缩强度、常温热导率以及微晶参数.结果表明:相对于短恒温时间,长恒温时间制得的炭泡沫孔径大(412nm)、显气孔率高(83.82%)、体积密度小(0.34g/cm~3)、压缩强度高(4.92MPa),多孔连通结构更丰富.经过石墨化处理后,石墨泡沫呈现出较高的常温热导率(71.34W/(m·K))和较小的层片间距d_(002)(0.33556nm).石墨泡沫的常温比导热率能达到210(W·(m·K)~(-1)) /(g·cm~(-3)),是铜的5倍,铝的4倍. 相似文献
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中间相沥青基泡沫炭的制备、结构及性能 总被引:3,自引:0,他引:3
以萘系中间相沥青为原料,考察了发泡条件、炭化和石墨化工艺对所制泡沫炭结构和性能的影响.结合粘温曲线、TG-DTG热重曲线以及不同发泡条件下泡沫炭的表面形貌分析,其最佳发泡条件为:发泡温度600℃,升温速率5℃/min,发泡压力5MPa.石墨化升温速率越低越有利于泡沫炭石墨微晶的生长及压缩强度的提高,其中以5℃/min升温至2800℃并恒温30min所制泡沫炭的压缩强度达1.38MPa. 相似文献
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利用超声分散的方法,使改性后的碳纳米管(m-CNTs)在中间相沥青中均匀分散,通过自挥发发泡法制备出不同m-CNTs含量的中间相沥青基泡沫炭。用TEM、SEM等分析方法研究了不同m-CNTs的添加量对泡沫炭结构和性能的影响。实验结果表明,与CNTs相比,m-CNTs的分散性有所提高;添加一定量的m-CNTs后,泡沫炭的平均泡孔尺寸有所减小,并且微裂纹数减少;当m-CNTs的添加量达到5%(质量分数)时,泡沫炭的热导率和压缩强度均达到最大,分别为137W/(m.K)和12.1MPa。 相似文献
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以天然鳞片石墨粉为骨料炭、中间相沥青作粘结剂、以及Si,Ti为添加剂,利用热压工艺制备了系列炭/陶复合材料.考察了热压温度对材料物理性能和微观结构的影响.研究表明:随着热压温度的升高,最终材料的导热率和热扩散系数都单调增大;而抗弯和抗压强度则有所下降.当热压温度为2700℃时,在平行于石墨层方向材料的温热导热率、热扩散系数、抗弯和抗压强度分别为654W/m·K,413mm2/s,34.5,31.5MPa.当热压温度为2300℃时,材料微晶的定向排列程度就较高,晶格排列也较为规则.利用XRD,SEM,TEM等考察了材料的微观结构,探讨了材料导热性能与微观结构之间的相互关系. 相似文献
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本文制备了四种低密度炭/炭保温材料,分析了材料成型结构、基体炭类型、处理温度以及材料密度对导热系数的影响。结果表明:针刺整体毡结构导热系数最大,薄毡粘接结构导热系数最小,而厚毡粘接和薄毡与厚毡交替铺层结构的导热系数介于两者之间。树脂炭基体的炭/炭保温材料导热系数小于热解炭基体的导热系数。对于薄毡粘接结构低密度炭/炭保温材料随着处理温度的升高,导热系数呈上升的趋势。同样,薄毡粘接结构低密度炭/炭保温材料随着密度的增大,导热系数增大。 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
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A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
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On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill. 相似文献
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Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß. 相似文献
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The end of over unit products of more than Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits beer wine yellow wine fruit syrup wine others cover over % of the national top-branded liquor products.…… 《中国标准化(英文版)》2008,25(1):30
The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.…… 相似文献
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Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster. 相似文献