共查询到19条相似文献,搜索用时 93 毫秒
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以油系针状焦为原料,在1 500~3 000℃范围内,探索不同石墨化温度对二次颗粒石墨微晶层间距d002、微晶堆砌厚度Lc和微晶基面宽度La等微观结构的演变,揭示了碳原子从二维无序到三维有序排列的规律。研究结果表明:随着石墨化温度的升高,石墨微晶层间距逐渐减小,晶粒尺寸变大,同时石墨微晶的d002与La的倒数具有一定的线性关系;同时研究了不同石墨化温度对二次颗粒电化学性能的影响,二次颗粒的首次比容量、首次效率及真密度随石墨化温度的升高而增加;温度在2500℃及以上时,充放电曲线呈U型且存在稳定的电压平台;石墨化温度在3 000℃时,油系针状焦的首次比容量和首次库伦效率分别可达343 mAh/g、94.7%。 相似文献
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主要从压型石墨管热膨胀的特性着手,分析了浮头列管式石墨换热器在使用过程中易损坏的根本原因,并提出了使用浸渍石墨管解决这一问题的方法及优势。 相似文献
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提出一种简单的估算石墨化过程任意时刻温度的方法,以便于时时了解石墨化过程的温度,这对于处理好生产效率与成品率之间的矛盾具有很大的经济意义。 相似文献
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研究生产工艺对针状焦晶体结构的影响,包括延迟焦化、高温煅烧、热捏合-成型、高温石墨化等工艺过程,并采用了X射线衍射分析、扫描电镜、热膨胀仪、偏光显微镜等方法对结果进行了分析表征。结果表明:煤沥青经490℃炭化过程得到生焦,偏光显微镜和扫描电镜证实晶体结构得到改善,呈明显的纤维状结构,流线型较好;生焦在1 500℃下进行煅烧,经X射线衍射分析得知,晶体层面距d002减小,由0.3518 nm降到0.3468 nm,说明生焦的有序结构得到了进一步发展;通过测定石墨电极的CTE值,当针状焦和黏结剂的比例由10誜4改变为10誜5时,电极的CTE值由3.224×10-6/℃降至2.724×10-6/℃。 相似文献
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Summary: Polymeric thermosetting composites can be used as metal substitutes for certain applications if they possess high temperature stability in air, low coefficient of thermal expansion (CTE), and sufficient flexural strength, in combination with competitive costs. Commercial bismaleimide, bisnadimide, and cyanate ester thermosetting materials were selected due to their excellent thermal stability. Low CTEs were achieved by adding high loading levels of fused silica or silicon nitride fillers. Several optimized composites were fabricated by varying the materials, composition, and cure conditions. Characteristic composite properties, such as CTE, thermal stability, glass transition temperature (Tg), flexural strength, and filler distribution were investigated. The best system developed consists of Matrimide 5292, a commercial two‐component bismaleimide resin, filled with 75% Silbond FW100EST, and additionally reinforced with 0.5% Twaron short fibers. This composite is distinguished by a CTE around 15 ppm · K−1, a Tg around 340 °C, flexural strength above 100 MPa, and attractive material costs.
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以NZP族低热膨胀陶瓷Ca1-xBaxZr4(PO4)6(0≤x≤1)系列中的零膨胀组成Ca0.85Ba0.15Zr4P6O24为例,着重研究了不同添加剂对该零膨胀陶瓷的热膨胀异向性、平均热膨胀系数和导热性能的影响规律。实验结果表明,在烧结过程中添加质量分数1%SiO2或3%SiC均能够降低Ca0.85Ba0.15Zr4P6O24的热膨胀异向性,但与此同时,第二相的加入使Ca0.85Ba0.15Zr4P6O24的热膨胀系数有所上升。质量分数为1%~7%SiC晶须的加入反而导致NZP族陶瓷导热性能进一步降低,原因是SiC抑制了晶粒生长。 相似文献
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Cordierite ceramics were prepared by using talc, bauxite and kaolin clay as starting materials. According to the detected resuh of XRD step-scanning from 25° to 35° by a high temperature X-ray diffractometer, 20 and d values of five peaks of cordierite crystal were ascer- rained. Then the least squares technique was used to cal- culate the crystal parameters : at 25 ℃ , a = b = O. 981 8 nm, c =0. 927 4 nm, V=O. 774 3 nm3 ; at 600 ℃ , a =b =O. 982 0 nm, c=0.9252 nm, V=O. 773 5 nm3. The crystal volumetric coefficient of thermal expansion (CTE) and linear CTE along a and c axes were calcu- lated, αv = 2. 33 × 10-6℃-1, αa = αb, = 3. 27 × 10-6℃ -1 , αc = -4.19 ×10-6℃ -1. The average CTE of cordierite crystal is as low as O. 78 × 10-6℃ -1 相似文献
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微晶玻璃的组成及热处理制度与热膨胀系数关系的研究 总被引:4,自引:0,他引:4
采用传统的熔体冷却法制得Li2O-A l2O3-SiO2系统的基础玻璃。利用DTA制定了相应的热处理制度,测定了玻璃热处理前后的热膨胀系数,并利用XRD研究了经热处理后的微晶玻璃的晶体相组成。结果表明:具有复合晶核剂TiO2 ZrO2和采用二步热处理制度所得的微晶玻璃热膨胀系数更小,且随着二步热处理制度温度的升高,微晶玻璃热膨胀系数更小,相应的玻璃结构也越致密。 相似文献
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TATB基PBX的热膨胀系数研究 总被引:3,自引:1,他引:3
用线膨胀仪测试了TATB基PBX的线膨胀系数(CTE),分析了配方、工艺等因素对PBX的CTE的影响情况。结果表明,氟聚合物粘结的TATB基PBX在室温—70℃间的CTE值很大,粘结剂氟聚合物在物理特性上的差别对TATB基PBX的CTE影响很小,而替用玻璃化转变温度高于75℃的高聚物可使PBX在室温—70℃间的CTE值显著下降。与钢模压制方法相比,采用等静液压方法可以便TATB基PBX药柱在室温—70℃的CTE值降低30%以上。冷热循环处理也可在一定程度上降低PBX的CTE值。 相似文献
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Aaron D. Krawitz Daniel G. Reichel Richard Hitterman 《Journal of the American Ceramic Society》1989,72(3):515-517
The thermal expansion of WC from 20 to 900 K was measured in the a and c axial directions using high-resolution neutron powder diffraction. Third-order polynomials have been calculated from the expansion curves. The results complement and are compared with prior data in the 293 to 900 K region. 相似文献