粘结剂含量对石墨材料电、热传导性能的影响

以煅后石油焦和煤沥青为基本原料，采用热压工艺制备了一系列石墨材料。考察了粘结剂含量对石墨材料电、热传导性能的影响。在实验基础上，阐明了粘结剂与骨料颗粒在热混捏与热压过程中相互作用原理。结果表明，石墨材料的传导性能不仅依赖于原料种类、粒度，而且与其质量百分配比也有关系。经过分析认为，粘结剂含量小于25W／％时，随着粘结剂含量的增加，石墨材料传导性能增强的原因可归结为石墨材料的骨料颗粒气孔率得到降低和颗粒间微裂纹减少所致；而粘结剂含量超过25W／％时，材料的传导性能随着粘结剂含量的增加而降低的原因可归结为骨料颗粒间粘结剂的γ组分以气态形式挥发使得材料气孔率增加所致。     

单组元钛掺杂石墨的导电性能及微观结构的研究

用煅烧石油焦作填料、煤焦油沥青作粘结剂、钛粉作催化剂,采用热压工艺在2600℃左右、8～10MPa条件下热压成型,制备出一系列不同质量配比的单组元钛掺杂石墨.考察了钛组元的质量配比对单组元钛掺杂石墨的导电、力学性能的影响以及微观结构的变化.实验结果表明,与相同工艺条件下制备的纯石墨材料相比较,催化剂钛不仅可以降低掺杂石墨材料的电阻率,而且可以提高材料的力学性能.室温下材料的层面方向上,单组元钛掺杂石墨DT-15的电阻率为1.96μΩ·m,抗弯强度可达50.2MPa.经XRD及Raman分析表明,原料中掺杂适量的钛粉,在材料制备过程中可以起到催化石墨化作用,使材料的石墨化度及微晶尺寸增大,晶面层间距降低.其中,DT-15的石墨化度为96.4%,微晶尺寸La为306nm.XRD物相分析表明,催化剂钛粉最终在材料中以TiC的形式存在,钛粉在材料制备过程中的催化石墨化作用可以用液相转化机理得到较为合理的解释.     

石墨材料导热性能与微晶参数关系的研究

用煅烧石油焦和煤沥青为基本原料，采用热压和石墨化工艺制备了几种纯石墨材料。考察了煤沥青的种类以及石墨化温度对石墨材料导热性能的影响。结果表明，粘结剂的种类和石墨化温度与石墨材料的导热性能有着密切的联系。石墨材料的导热性能对其石墨化度的敏感程度较大，尤其是当石墨化度较高时表现最为突出。研究结果还表明，室温时石墨材料的导热系数与其平均微晶尺寸La呈现出良好的线性关系，其直线方程为：λ=-86.66 7.26La；石墨的微晶层间距doo2与其平均微晶尺寸的倒数（1／La)也存在良好的线性关系，其直线方程为d002=0.3341 0.1664(1/La)。     

掺杂钛催化机理及其再结晶石墨导热性能的研究

用煅烧石油焦作填料、煤沥青作粘结剂、钛粉作添加剂,采用热压工艺制备了一系列不同质量配比的掺杂钛再结晶石墨.考察了不同质量配比的添加钛对再结晶石墨的热导率、抗弯强度的影响以及微观结构的变化.实验结果表明,与相同工艺条件下制备的纯石墨材料相比较,掺杂钛再结晶石墨的热导率、抗弯强度均有较大的提高.室温下,RG-15再结晶石墨的层面方向热导率可达424W/(m·k),抗弯强度可达50.2MPa.微观结构分析表明,少量的掺杂钛,即可使材料达到很高的石墨化度;过多的钛掺杂量不利于材料的热导率以及抗弯强度;原料中掺钛量为15wt％时,再结晶石墨的微晶发育以及排列程度最好,此材料的石墨化度为96.4％,微晶参数La为306nm.XRD物相分析表明,钛元素在再结晶石墨中以碳化钛的形式存在.钛对再结晶石墨制备过程的催化作用可以用液相转化机理来解释.     

短切炭纤维-炭复合材料的制备及传导性能和微观结构的研究

以中间相沥青基短切炭纤维和中间相沥青为原料,采用模压成型、炭化、致密化、高温石墨化等一系列常规工艺,制备了传导性能良好的炭/炭复合材料.主要考察了中间相沥青与中间相沥青基炭纤维质量配比对材料密度及传导性能的影响,并进一步研究了材料微晶参数的变化与材料性能的相关性.结果表明中间相沥青与纤维质量配比对材料的导热、导电性能以及微晶参数有很大影响.随着中间相沥青用量的增大,材料导热、导电性能均提高,石墨层间距d002减小,石墨微晶尺寸La、Lc增大;当中间相沥青与炭纤维质量比为 0.8时,制备出的炭/炭复合材料石墨微晶尺寸最大,常温传导性能最佳(垂直于压制方向的面向热导率为385W/(m·K),电阻率为2.85μΩ·m);进一步提高中间相沥青用量,石墨微晶尺寸La、Lc减小,材料的传导性能降低.     

凹凸棒石基碳复合陶粒的制备和特性研究

考察了物料配比和煅烧工艺对以凹凸棒石粘土、锯末(造孔剂)和水玻璃(粘结剂)为原料,在氮气保护气氛下煅烧制备凹凸棒石基碳复合陶粒性能的影响,利用复合陶粒的抗压强度、显气孔率优化材料配比和煅烧工艺,并通过XRD、SEM表征复合陶粒特性。结果表明凹凸棒石粘土、锯末、水玻璃的最佳质量配比为68∶20∶12,在最佳煅烧条件下(700℃),可以制备出满足国家标准的水处理用陶粒,浸泡实验表明凹凸棒石基碳复合陶粒具有优异的耐水性能;该材料有利于微生物的附着。     

粘结NdFeB磁体的制备工艺

利用NdFeB 磁粉、聚酰亚胺制备了粘结NdFeB 磁体。研究了磁粉粒度、偶联剂用量、粘结剂用量、成型压力和粘结剂性能对粘结磁体磁性能及力学性能的影响。实验结果表明,合理的粒度配比(粗∶细为33∶67) 、偶联剂用量(磁粉0. 9 %) 、粘结剂用量(磁粉3. 2 %) 、合适的压力(600 MPa) 以及以聚酰亚胺作为粘结剂,可以获得具有较好磁性能和力学性能的粘结NdFeB 磁体。      

药用植物剩余物发泡缓冲包装材料的制备及性能研究

以药用植物剩余物纤维为主要原料,淀粉 / PVA 胶黏剂为基体,添加一定量发泡剂及相关助剂,在密闭模具内热压成形了发泡缓冲包装材料。 通过实验与分析,确定了制备材料的工艺与实验条件,研究了药用植物纤维粒度、发泡剂用量、发泡温度及淀粉 / PVA 配比对材料性能的影响。     

双组元掺杂钛硅再结晶石墨传导性能的研究

用煅烧石油焦作填料,煤沥青作粘结剂,钛粉和硅粉作添加剂,采用热压工艺制备了一系列双组元掺杂再结晶石墨.考察了不同质量配比的添加剂对再结晶石墨的热导率、电阻率和抗弯强度的影响以及微观结构的变化.实验结果表明,与相同工艺条件下制备的纯石墨材料相比较,掺杂15wt％钛粉再结晶石墨的传导以及力学性能有较大幅度的提高.在掺杂钛粉15wt％、硅粉<2wt％时,双组元再结晶石墨的常温热导率随着硅粉的掺杂量的增加有所提高.当掺杂钛粉及硅粉分别为15wt％和2wt％时,再结晶石墨RG-TiSi-152的常温热导率可达494W/m·K.但是当掺杂钛粉15wt％、硅粉>2wt％时,随着硅粉的继续增加,再结晶石墨的常温热导率反而降低.而双组元掺杂钛硅再结晶石墨的导电以及力学性能却随着硅粉的掺杂量的增加而降低.XRD分析表明,对于双组元掺杂钛硅再结晶石墨而言,钛元素最终在材料中以碳化钛形式存在,而硅元素则大都以气态形式被逸出,XRD物相图谱中未发现硅及其碳化物的存在.材料RG-TiSi-152的微晶尺寸La以及晶面层间距d₀₀₂分别为864和0.3355nm.     

聚苯胺石墨原位聚合导电涂料的研制及其性能

以苯胺为主要原料,过硫酸铵为氧化剂,盐酸为掺杂剂,再掺入石墨粉原位聚合制备聚苯胺石墨微乳液,以环氧树脂作粘结剂制备复合导电涂料,140℃,固化24 h,表征了涂层电导率、硬度、附着力和固化程度等。结果表明:聚苯胺石墨复合材料的电导率与聚苯胺相比有大幅提高,且石墨含量为5%时导电性能最好;环氧树脂的加入能强化聚苯胺石墨导电涂料的硬度和附着力。其组分的最佳配比为:石墨5%,三氟化硼乙胺固化剂14%,环氧树脂与聚苯胺质量比1.0∶2.5。     

高定向石墨块的控制制备及其导热性能影响因素研究

以廉价易得的高结晶度天然鳞片石墨(NG)和中间相沥青为原料, 采用中温热模压一次成型再高温炭化、石墨化处理可以制备高密度、高定向、高导热石墨块体材料。XRD、SEM和PLM分析表明该石墨块具有高度择优取向结构, 其内部石墨片垂直热压方向有序堆积排列。原料中鳞片石墨和沥青粘结剂的组成和配比以及制备工艺参数等对所制石墨材料的面向导热性能有显著影响。采用86wt%+32目鳞片石墨和14wt%AR中间相沥青在500℃、10 MPa下热模压成型的炭块经1000℃炭化、2800℃石墨化后样品的热物理综合性能较好, 其体积密度达到1.91 g/m³以上, 室温面向热导率为550 W/(m·K), 3000℃石墨化室温面向热导率高达620 W/(m·K)。     

A simple method for the estimation of optimum binder content in baked carbon mixes

A detailed study is presented of the optimum amount of binder in various carbon mixes consisting of calcined petroleum coke of different particle size distributions as filler and coal tar pitch as binder. These fillers were subjected to bulk density measurements prior to wet mixing with various amounts of binder and were then shaped into cylinderical blocks by compression moulding. The blocks obtained were measured for green apparent density before being baked to a temperature of 950° C. The baked blocks were then subjected to apparent density, electrical resistivity and crushing strength measurements. The optimum binder contents for these baked carbon mixes obtained on the basis of maximum apparent density, maximum crushing strength and minimum resistivity, were plotted against the bulk density of the corresponding fillers. The optimum binder content on the basis of apparent baked density and crushing strength is found to be an inverse function of the bulk density of the filler. Thus, knowing the bulk density of the particular filler, it is possible to predict the optimum binder content in the corresponding carbon mix with the product diameters up to 19 mm.     

Carbon/ceramics composites — Preparation and properties

Fabrication methods for carbon/ceramics composites were established by using two different processes of hot-pressing and pressureless sintering without any binder phase. In the hot pressing method, some boron compounds were found to be an effective aid for sintering and graphitization of coke powder above 2000°C under some pressure. When the content of boron compound such as B₄C was high, graphite/B₄C composites could be fabricated. If some other ceramic powder such as NbC, TiC or TaC was mixed in addition to the B₄C, three component composites with graphite matrix could be obtained. In pressureless sintering method, raw coke carbon powder was ground for a long time to be transformed in to a sinterable and non-graphitizing-type carbon powder. From a mix of ceramic powders such as SiC or B₄C with the ground coke powder, the composites of carbon/SiC or carbon/SiC/B₄C systems could be fabricated by heat-treatment under normal pressure.Some properties of the graphite samples and carbon/ceramic composites were investigated. It was found that their mechanical properties were much better than those of conventional graphite samples and the resistance to oxidation and corrosion was also excellent. It is suggested that the composites could be applied as bearing or mechanical seals both for use in high temperature environments and as machine parts in contact with some molten metals.     

Graphite and boron carbide composites made by hot-pressing

Composites consisting of graphite and boron carbide were made by hot-pressing mixed powders of coke carbon and boron carbide. The change of relative density, mechanical strength and electrical resistivity of the composites and the X-ray parameters of coke carbon were investigated with increase of boron carbide content and hot-pressing temperature. From these experiments, it was found that boron carbide powder has a remarkable effect on sintering and graphitization of coke carbon powder above the hot-pressing temperature of 2000° C. At 2200° C, electrical resistivity of the composite and d(002) spacing of coke carbon once showed minimum values at about 5 to 10 wt% boron carbide and then increased. The strength of the composite increased with increase of boron carbide content. It was considered that some boron from boron carbide began to diffuse substitutionally into the graphite structure above 2000° C and densification and graphitization were promoted with the diffusion of boron. Improvements could be made to the mechanical strength, density, oxidation resistance and manufacturing methods by comparing with the properties and processes of conventional graphites.     

无限微热源法合成β-SiC粉体

采用无限微热源法从原料、原料级配、供电功率和供电时间对合成β-SiC微粉产品的产率和品率的影响进行了探讨,并对合成β-SiC微粉产品进行了粒度测试和XRD分析。研究表明,无烟煤和石墨作碳源合成所得β-SiC微粉品率和产率比石油焦和石墨作碳源高,且晶相生成比较完整;原料粒度越细,产物粒度越细;合理控制给电功率和足够的保温时间是合成的关键;产物产率达25.63%,一级品率达77.63%,一级和二级总品率达98%。     

流延法制备高热导率定向石墨/高分子复合片层材料(英文)

以天然鳞片石墨为原料,PVB为黏结剂,PEG和DBP混合物为增塑剂,通过流延工艺在室温下制备了定向排列的石墨/聚合物片层复合材料。系统分析了不同黏结剂用量和流延刀口高度下复合片层材料的定向排列状况,并探讨了定向排列程度对其热导率的影响。XRD和SEM的结果表明,石墨/聚合物复合片层材料显示了不同程度的定向排列。热导率测试结果表明,片层复合材料的热导率随着定向排列程度的提高而增大。通过优化黏结剂的用量和流延刀口高度制备了具有较高热导率的片层复合材料,其热导率最高可达490 W/(m.K)。     

基于BP神经网络的汽车摩擦材料性能预测与配方优化

采用钢纤维、玻璃纤维、铜纤维、矿物纤维等增强纤维,石油焦碳、人造石墨、天然石墨等摩擦调节组元,以及树脂、丁腈橡胶、丁苯橡胶等粘接剂制备汽车摩擦材料.选用BP神经网络建模,以原材料配方为输入变量、摩擦磨损试验数据为输出变量,采用L-M算法对网络进行训练,并进行摩擦磨损性能预测和配方优化.结果表明,隐层神经元为4的单隐层神经网络结构模拟效果较好,性能曲面预测图能表现出原材料的组合性能,采用该网络优化试样的性能测试结果与预测值的相对误差小于20%.