微波辐射时间对木质陶瓷导电性能影响的研究

以烟杆和酚醛树脂为原料,采用微波辐射制备了高导电性能的烟杆基木质陶瓷。同时,研究了微波辐射时间对木质陶瓷体积电阻率的影响,并采用X射线衍射技术、激光喇曼光谱和扫描电镜对其微观结构进行了研究。实验结果表明:与常规加热制备木质陶瓷相比,采用微波辐射的方法可将制备时间缩短99.4%。当微波辐射时间为80s时,木质陶瓷的体积电阻率仅为0.97Ω·cm。通过样品XRD谱图和激光喇曼谱图的分析,随着微波辐射时间的延长,样品有序化程度的提高,根据Tuinstra-Koening经验公式计算所得的石墨微晶面网直径La与通过XRD图谱计算得到的值相近。通过SEM观察可知,当微波辐射时间达到80s时,样品中由酚醛树脂形成的玻璃炭与由烟杆炭形成的无定形炭已融合为一个整体,呈多孔状。     

CaO-Al_2O_3-MgO-SiO_2矿渣微晶玻璃陶瓷的制备及抗NaOH侵蚀性能

以包钢尾矿为主要原料,采用熔融法制备了Ca O-A1_2O_3-MgO-SiO_2系矿渣微晶玻璃陶瓷,采用X射线衍射(XRD)和扫描电子显微镜(SEM)对微晶玻璃陶瓷的物相组成及显微结构进行了表征,并研究了该微晶玻璃陶瓷的常温力学性能和抗Na OH化学侵蚀的动力学过程。结果表明:所制备微晶玻璃陶瓷的主晶相为透辉石,次晶相为石英,平均粒径约为142 nm;其显气孔率为0.05%,体积密度为3.0 g/cm3,常温抗折强度为71 MPa。Na OH侵蚀动力学研究表明:该微晶玻璃陶瓷的失重率随着侵蚀温度的升高而增大。采用阿伦尼乌斯方程和艾琳方程计算了Na OH侵蚀反应的活化能、反应焓及反应熵,其数值分别为40.8、37.9及–134.7 J/mol。     

石墨化竹炭的微观结构及其复合材料的制备与性能

采用SEM及XRD技术表征经2 800℃石墨化处理的竹炭的微观结构;以石墨化竹炭为导电骨料、酚醛树脂为粘结剂、炭黑为添加剂,采用模压成型法制备石墨化竹炭/酚醛树脂复合材料;考察石墨化竹炭的粒度、酚醛树脂用量、炭黑添加方式和用量、成型压力及固化温度等工艺因素对复合材料性能的影响。结果表明:增大竹炭粉粒的粒径、增加炭黑用量和提高固化温度有利于提高复合材料的导电性,但会不同程度地影响复合材料的力学性能、显气孔率和吸水率;随着酚醛树脂用量的增加,复合材料的抗弯强度提高,导电性、吸水率和显气孔率下降;提高成型压力可同时提高复合材料的性能;制备竹炭/酚醛树脂复合材料的最佳工艺条件为竹炭粒度≤75μm、树脂用量30%(质量分数)、炭黑用量5%(质量分数)、成型压力280 MPa、固化温度180℃。     

烧结温度对环氧树脂/竹基木陶瓷性能的影响

为了了解烧结温度对木陶瓷基本性能的影响,将浸渍了环氧树脂的竹粉和竹纤维压制成复合板材,在不同的温度下烧结而得到环氧树脂/竹基木陶瓷。采用X射线衍射仪（XRD）、扫描电镜（SEM）等测试设备研究了烧结温对其物相变化、微观结构和力学性能等方面的影响。结果表明：竹基木陶瓷是由石墨微晶所构成的多孔碳素材料,较高的烧结温度能够改善其石墨化程度,但不能完全石墨化;在微观形态上表现为三维网络结构,同时部分保存了竹材的天然结构特征;其显气孔率随着烧结温度的增加而增加,表观密度则显示出相反的特征;抗弯和抗压强度在低温处随烧结温度的提高而增加,但在1200℃之后有降低的趋势。同时,摩擦系数则随着烧结温度的提高而明显下降。当烧结温度为1200℃左右时,环氧树脂-竹基木陶瓷具有较好的性能。     

TiO_2对堇青石多孔陶瓷微观结构和性能的影响

以叔丁醇为成形介质和造孔剂,二氧化钛为烧结助剂,采用凝胶注模成形和无压烧结工艺制备堇青石多孔陶瓷.研究了添加5%(体积分数,下同)二氧化钛对堇青石多孔陶瓷的气孔率、微观结构、力学性能和气孔结构的影响,并对样品的断口形貌进行观察.结果表明,在1175 ℃烧结温度条件下,与不添加二氧化钛相比,当二氧化钛含量为5%时,所得堇青石多孔陶瓷的气孔率和开口气孔率分别由76.9%和96.4%下降为72.4%和95.1%,线性收缩率从20.7%提高到22.1%,而抗压强度则由3.23 MPa提高到5.83 MPa,气孔尺寸均呈单峰分布,中位孔径由2.29 μm下降到1.62 μm.二氧化钛的加入提高了堇青石粉末的低温烧结性能,在未明显降低堇青石多孔陶瓷气孔率以及未改变其气孔结构、孔径尺寸分布的前提下,材料的力学性能得到了显著改善.     

石墨坩埚性能的影响因素分析

以鳞片状石墨、碳化硅、硅粉、高岭土为主要原料制备石墨坩埚,研究了石墨坩埚性能的影响因素.结果表明:随着碳化硅含量的增加,试样体积密度增大,气孔率减小,失重率降低,抗氧化性提高;升高氧化温度和延长氧化时间,会使石墨坩埚的失重率增大,降低其抗氧化性;显微组织分析表明,碳化硅含量的增加和烧成温度的上升,都会增强试样的致密性.     

发泡压力对中间相沥青基泡沫炭结构及性能的影响

以AR中间相沥青为原料,在4、5、7、10MPa下用恒压自发泡工艺制备泡沫炭生料,经炭化、石墨化处理后分别获得炭化泡沫炭和石墨化泡沫炭。采用SEM和OM观察泡沫炭的微观形貌,采用XRD分析泡沫炭的晶体结构,并测定泡沫炭的压缩强度和热导率。结果表明:随着发泡压力的升高,孔泡变得均匀,韧带片层结构变得规则有序,但发泡压力增大到一定程度后,闭孔增多,韧带有序结构变差;当发泡压力为10MPa时,炭化和石墨化试样的压缩强度达到最大值,分别为8.16MPa和3.42MPa;当发泡压力为7MPa时,石墨化试样的热导率达到最大值,61.0W/(m·K)。     

有机硅树脂粘结Al_2O_3粉制备陶瓷型芯

以球形Al_2O_3颗粒为基体、液态有机硅树脂为粘结剂,通过干压法制备Al_2O_3陶瓷型芯,考察有机硅树脂加入量对焙烧后陶瓷型芯微观组织形貌、物相组成、显气孔率、线性收缩率、体积密度以及抗弯强度的影响。结果表明,1 500℃烧结温度下,有机硅树脂浓度为0.5wt%时,其均匀分布在球形Al_2O_3颗粒周围,此时陶瓷型芯显气孔率为39%、体积密度2.4 g/cm~3、线性收缩率0.7%及抗弯强度35.9 MPa,在硅树脂考察范围内抗弯强度达最高。     

石英含量对刚玉基陶瓷型芯材料性能的影响

研究了石英含量对刚玉墓陶瓷型芯强度、收缩率、气孔率和体积密度的影响.试验结果表明:在相同的烧结温度下,随着石英含量的增加,型芯的抗弯强度、收缩率不断增大;相同SiO2含量,型芯的抗弯强度、收缩率随烧结温度的升高而增大;在相同的烧结温度下,随着SiO2含量的增多,样品的显气孔率先增加后减小,存在极值;同一成分含量,当SiO2含量≦15%,随烧结温度的升高,样品的显性气孔率增加,而当SiO2为20%,1450℃烧结时型芯的显性气孔率最大.SEM、XRD、EDS分析结果表明,玻璃相的生成和消耗关系是影响型芯显气孔率的重要因素.     

RSiC-WC复相陶瓷的性能及烧结机理

以不同配比的粗、细SiC粉体和WC粉体为原料,在2200℃以上烧结得到RSiC-WC复相陶瓷.采用XRD、SEM和EDS对复相陶瓷的物相组成和微观形貌进行分析,并测定其开口气孔率、抗弯强度和电阻率.结果表明RSiC-WC复相陶瓷中以6H-SiC和WC为主晶相,存在少量W2C晶相.烧结产物中SiC颗粒再结晶程度良好,WC在烧结温度下与SiC晶粒润湿性好.RSiC-WC复相陶瓷的最低开口气孔率、最高抗弯强度和最低电阻率分别为19.2%、109MPa和15mΩ·cm.体系中SiC晶粒生长遵循蒸发-凝聚的烧结机理,WC则以W-C液相在SiC晶粒界面处聚集,抑制了SiC晶粒的长大.高温下形成的W-C液相能明显降低复相陶瓷的开口气孔率,使烧结体致密化.因而,添加一定量的WC改善复相陶瓷的力学性能,并对其电学性能起到调节作用.     

酚醛树脂用量对木陶瓷性能的影响

砂光木粉浸渍酚醛树脂经干燥、热压后在真空条件下烧结处理后制得了碳/碳复合材料(木陶瓷)。分析了酚醛树脂用量对木陶瓷尺寸收缩率、碳得率、力学性能、耐磨性的影响,并利用全自动元素分析仪检测了酚醛树脂用量对木陶瓷元素组成的影响,利用扫描电子显微镜(SEM)和X射线衍射(XRD)分析了酚醛树脂用量对木陶瓷微观形貌和结构的影响。结果表明,随着酚醛树脂用量的增加,木陶瓷的碳得率增大,尺寸收缩呈下降趋势,力学性能增强,耐磨性明显提高,木陶瓷中C、H含量降低,O、N的总含量升高;SEM观察结果说明,随着酚醛树脂用量的增加,木陶瓷内酚醛树脂碳化形成的玻璃碳更加明显,但对XRD谱图没有明显影响。当木粉与酚醛树脂的质量比为40∶60时,木陶瓷的结构与性能最稳定,并具有较好的力学性能和耐磨性。     

利用废弃棉短绒制备多孔SiC陶瓷及其性能的研究

以废弃的棉短绒和酚醛树脂为原料,通过模压成型,固化,碳化和渗硅制备出微观结构均匀的多孔碳和多孔碳化硅.通过SEM照片可以看出,由棉短绒纤维的杂乱排列和碳化时不同的收缩率产生了相互连通不规则的孔,在多孔碳化硅结构中也得以保留.经过三点弯曲测试,多孔碳化硅的气孔率随着排硅时间的增加而增加,强度和韧性随着捧硅时间的增加而减小.     

Improvement of water/resin wettability of graphite using carbon black nano particles coating via ink media

Carbon coated graphite with high resin and water wettability characteristics could expand the refractory and carbon–carbon composites application in different fields. Improvement of water and resin wettability of graphite using carbon black coating via ink media is reported. Present method is based on preparing colloidal disperion of carbon black in ink followed by adding proper amount of graphite to the mixture which was dried and heat treated at 250 °C afterwards. The results showed that by controlling the amount of carbon black in ink and optimizing the process, a uniform coating with a thickness of 50 nm could be developed on the graphite surface.The wettability was evaluated by measuring contact angle and the microstructure of samples was characterized by optic microscope (OM) and scanning electron microscope (SEM). Also Raman spectroscopy was employed to support the results. The microstructure of coating was found to be uniform composed of carbon black nanoparticles. It was also demonstrated that the coating that could enhance the phenolic resin wettability was well. We also showed the coating could be applied on other ceramic particles such as MgO.     

一种含银电热浆料的研制

研究了以微量银粉、石墨粉、碳黑、填充料(滑石粉、利德粉和氧化铝粉)及聚合物树脂粘合剂,配制电热浆料。用平均粒径小于1.5μm的超细银粉(2%),与石墨粉、碳黑、填充料(合计67%)及聚合树脂粘合剂(31%)混合配制成电热浆料,粘覆在酚醛树脂板上室温固化后,所得电热膜具有较低的电阻率及较好的附着力,可用作薄型电暖器加热片。     

浸渍-碳化工艺对碳/碳复合材料力学性能的影响

采用碳纤维针刺整体毡作为增强体,硼酚醛树脂作为基体先驱体,用浸渍碳化的方法制备C/C复合材料.考察了在不同的浸渍压力和碳化温度下材料力学性能的差异.分析结果表明:不仅密度是影响碳/碳复合材料力学性能的重要因素,纤维和基体的结合状况以及基体碳的结构也是决定材料强度和断裂方式的重要因素.随着工艺参数的改变,碳/碳复合材料的断裂模式可以由“假塑性断裂”向“脆性断裂”转变.     

Preparation of composite electroheat carbon film

1INTRODUCTIONThe electroheat carbon fil mis a newfunction-al electroheat fil m developed based on the electro-heat coating.Due to its good electroheat propertyand equivalent volume resistivity as nickel at roomtemperature,it can be widely used in electroheator relevant advanced technological fields such asportable low-voltage electric food warmer,ricecooker and heater,as a kind of lowvoltage electro-heat material[15].The existing electroheat coatingdeveloped by Acme chemicals&Insulating o…     

INFLUENCE OF HEAT TREATMENT ON OXIDATION PROPERTIES OF C／C COMPOSITES FABRICATED BY HIGH PRESSURE IMPREGNATION CARBONIZATION

Felt base carbon/carbon composites fabricated by super-high pressure impregnation carbonization process (SPIC) were heat treated at high temperature 2773K. The oxidation properties of felt base carbon/carbon composites were investigated at different temperatures (773-1173K), and the microstructures of carbon/carbon composites were studied by SEM and X-ray diffraction. The experimental results showed that the interlaminar distance of (002) plane (d002 ) deceased while the microcrystaUine stack height (Lc) increased. The oxidation rate of felt base carbon/carbon composites was invariable at certain temperatures. The oxidation mechanism of carbon/carbon composites changed remarkably at the oxidation temperature 973K. At the initial oxidation stage of carbon/carbon composites, carbon matrix was oxidized much more rapidly than carbon felt.     

Study of shrinkage porosity in spheroidal graphite cast iron

This study aims at identifying the relationship between the shrinkage cavities and the solidification structure in spheroidal graphite cast iron. Cast samples specially designed to contain shrinkage cavities were used. The solidification macrostructure was revealed using the Direct Austempering After Solidification method, while the solidification microstructure was revealed by using colour etching. At the midsection of the pieces, the shrinkage cavities and the solidification structure were observed jointly. The study showed that the classification of shrinkage porosity found in literature does not correspond to the ductile iron solidification model recognized by most of the scientific community. Early solidification models, and therefore shrinkage formation mechanisms, were proposed in instances when there was not a thorough knowledge of the morphology of the solid phases during solidification. Nowadays, defects formation mechanisms can be described with higher accuracy. Therefore, an updated classification of shrinkage porosity for spheroidal graphite iron is proposed.