工艺因素影响焦炭颗粒耐压强度的试验研究

焦炭颗粒的耐压强度一直是焦炭颗粒最重要的性质之一。利用最近提出的表征焦炭颗粒耐压强度的新方法，就模压压力、加压方式、粒度组成范围、粒度大小、粒度配比等因素对单粒度或多粒度组成焦炭颗粒耐压 强度的影响进行了较为详细的试验研究。结果表明：（1）焦炭颗粒的粒度大小和粒度范围均可用其原始平均细度来表征。焦炭颗粒的原始平均细度越大，其耐压强度系数也就越高；（2）多粒度组成焦炭颗粒混合料的耐压能力比单粒度组成混合料的耐压能力要高得多。对多粒度组成焦炭颗粒而言，模压压力及粒度组成配比对其耐压强度系数的影响不甚明显；（3）分阶段缓慢加压到位比一次快速加压到位有利于提高焦炭颗粒的耐压强度系数。     

提高粉体堆积密度的理论与实验研究

以Andreason理论和可压缩堆积模型为基础,对水煤浆颗粒进行了调质计算和堆积效率计算,通过实验验证了计算结果的准确性,探讨了粒度范围和添加量等因素对堆积效率的影响.结果表明,通过调质可以实现煤粉粒度分布的优化,使其尽可能靠近紧密堆积理论所规定的粒度分布特征;用可压缩堆积模型可以很好地预测粉体颗粒的堆积密度,经过调质后原料的堆积效率提高了6.0％;紧密堆积条件下,增大水煤浆颗粒粒度范围有利于提高其堆积效率;随着调质料的增加,系统堆积效率增大,且逼近紧密堆积条件下的堆积效率;只添加细粉时,堆积效率与原料的粒度组成相关.     

沥青种类和焦炭粒度组成对焦炭颗粒增强沥青基炭复合材料性能的影响

采用新型的模压半炭化成型工艺在大气环境下制备出了高密度、低成本的焦炭颗粒增强沥青基炭复合材料（简称CRPCC材料）。研究了煤沥青的种类、沥青焦中添加冶金焦以及焦炭颗粒的粒度组成配比对CRPCC材料的密度和抗压强度的影响。结果表明：煤沥青的软化点高，用其制备的CRPCC材料的密度和抗压强度未必就高；沥青焦中添加一定含量的冶金焦，则可制备出密度和抗压强度更好的CRPCC材料。     

加工参数对微孔PC泡孔性能的影响

采用模压法成功制备了薄型微孔聚碳酸酯（PC）片材,研究了加工参数（发泡时间、发泡压力和发泡温度）对泡孔性能的影响,结果表明：泡孔尺寸随发泡时间的延长先减小后增大,随发泡压力的增加而减小,随发泡温度的增加而增大;泡孔密度的变化趋势随与泡孔尺寸的变化趋势相反;相对密度则随加工参数的增加而降低。通过比较各加工参数对泡孔性能的影响,可以发现发泡时间对微孔PC片材泡孔性能影响最大,且最佳的发泡时间约为8min。     

乙醇/水混合溶剂沉淀法制备聚酰胺6粉体及表征

在不同的乙醇/水混合溶剂条件下通过溶剂沉淀法成功制备了聚酰胺6(PA6)粉体,采用扫描电子显微镜、X射线衍射仪、差示扫描量热仪、激光粒度分析仪等仪器对粉体的形貌、热性能、粒径及分布、堆积角和密度进行了分析。结果表明,随着混合稀释剂中乙醇体积分数的增加,溶剂与聚合物间的相互作用力增大,粉体形貌由蓬松不规则结构变为较为规整的近球体结构,粉体粒径大幅降低至78.8 μm且分布变窄;粉体的晶型没有发生变化,但是晶体完善度发生了改变,熔融温度降低;粉体的堆积角逐渐降低,而密度逐渐增加;混合溶剂的溶解度参数对所生产PA6粉体的性能有着重要的影响。     

干熄炉内平均换热系数的研究

根据干熄炉内焦炭换热的特点，用干熄炉模型对焦炭粒度和冷却气体流量等参数进行了试验。结果表明，平均体积换热系数随焦炭粒度变小而急剧增加。     

水泥粉体颗粒的新型PH堆积模型的研究

已有的水泥粉体颗粒堆积模型有一些不足,不能完全满足水泥粉体颗粒这一特定的体系,为了实现水泥的高效应用,本文借助等径球理论在Horsfied堆积模型基础之上提出一种新的PH堆积模型.满足该模型粒度分布要求的粉体颗粒具有较高的堆积密度和较少的细颗粒含量,同时增加了3～ 32 μm部分颗粒,应用于水泥粉体颗粒体系后,水泥水化样具有较高的抗压强度和较低的孔隙率.     

硫酸钡粉体在PVC-U复合材料中的应用

对硫酸钡粉体应用于PVC—U复合材料进行了初步研究，着重论述了各组分对复合材料的力学性能和相对密度的影响，利用激光粒度测试仪对硫酸钡粉体进行了测试，得到了粒径分布曲线和累计曲线。结果表明，PVC树脂质量对复合材料的力学性能影响很大，对相对密度影响不大：当硫酸钡用量相同时，硫酸钡的活化与否与粒径大小对复合材料的相对密度影响不大；当硫酸钡用量增加时，复合材料拉伸强度降低，相对密度增加；随着DOP用量的增加，复合材料的拉伸强度降低，断裂伸长率显著增大，相对密度下降。     

高性能机械用炭石墨材料制备工艺研究北大核心

通过实验研究了粉体颗粒粒径、成型方式、成型压力等制备工艺对机械用炭石墨材料性能的影响。结果表明,材料的抗折强度和抗压强度随着粉体颗粒粒径的减小而增大,模压成型方式是最适合于机械用炭石墨材料的成型方式,模压成型最佳的成型压力区间为220~250 MPa。     

助磨剂的助磨作用及对粉体流变性能的影响

选用五种助磨剂，对四种有代表性的物料进行了助磨实验，同时测试了磨后物料粉体的流变特性。分析了助磨效能、粉体流变性能和助磨机理三者的关系。研究结果显示：当助磨剂使粉体的流动性增强、堆积密度增大时，助磨效果趋于增强     

Dependence of Compaction Efficiency in Dry Pressing on the Particle Size Distribution

The compact densification with pressing pressure (compaction efficiency) was determined to be sensitive to the particle size distribution. For the three types of alumina powders used in this research, the compaction efficiency increased with increasing particle size. It has been demonstrated that if the compact density versus log (pressure) has a linear relationship for any two types of powders, so do the blends of the two powders. A model is proposed which can predict the compaction efficiency of a binary particle system based on the Furnas particle packing model and consider the packing efficiency as a function of forming pressure. The composition of the binary mixture at which the highest density is obtained under high pressures is also the composition having the largest compaction efficiency. When coarse particles were added to this composition, the compaction efficiency slowly decreased, and when fine particles were added, the compaction efficiency rapidly decreased. For a continuous particle size distribution, the highest compaction efficiency is related to the average value of -log (porefraction).     

焦炭超细粉末特性的研究

对焦炭超细粉末的粒度分布、粒度与粉末比表面积、粒度与粉末电阻率的关系，以及粒度对粘结剂用量和产品强度的影响进行了研究。     

基于可压缩堆积模型的透水混凝土配合比设计

基于可压缩堆积模型,以全孔隙率为设计指标,提出了一种考虑成型过程和集料级配影响的透水混凝土配合比设计方法.该方法首先根据可压缩堆积模型挑选出干堆积密实度较高的级配集料,引入反映成型过程影响的比例因子λ建立了集料在透水混凝土中的堆积密实度与其干堆积密实度之间的关系,进而确定出单位体积透水混凝土的集料用量;然后根据集料用量和水灰比,计算得到透水混凝土的水泥浆体体积和水泥用量.对依据该方法设计的透水混凝土性能验证试验表明,实测全孔隙率与设计全孔隙率非常吻合,达到预设目标;透水混凝土强度随小粒径集料体积分数的变化趋势与集料干堆积密实度的相近,但是并非干堆积密实越高则强度越高,强度还受到集料粒径的影响.     

锦州石油焦性能及其生产普通石墨电极的质量

通过对锦州焦与大庆焦的对比实验，分析了锦州焦的特性。与大庆焦相比，锦州焦的灰分偏高，挥发分偏低、硫含量稍高，煅后焦颗粒强度大，堆积密度大；用锦州焦制造的各种规格石墨电极，其CTE、体积密度、强度、电阻率均比大庆焦的高。     

自烧结炭材料的制备和性能研究

考察了球磨时间对生焦粉的粒度、粒度分布、挥发分含量的影响．以及生焦粉的上述物性参数对自烧结炭材料性能的影响，并初步分析了其影响机制。     

Influence of carbon structure of the anode on the synthesis of single-walled carbon nanotubes in a carbon arc plasma

Arc plasma evaporation of carbon electrodes doped with various catalysts is one of the most effective methods of single-walled carbon nanotube fabrication. It was found that the reaction yield is strongly influenced not only by the appropriate choice of the catalyst(s), but also by the type of carbon material used for electrode fabrication. Several different carbon powders i.e. graphite powders, glassy carbon and coke, have been tested in order to establish which parameters (primary particle size, granulation, density or conductivity of the electrode) affected the outcome of the reaction the most. The highest yield of single-walled nanotubes was found for anodes fabricated from graphite powders, whilst the electrodes made from glassy carbon or coke yielded significantly smaller amounts of nanotubes. The reaction zone where carbon radicals nucleate (close to the arc gap) was probed by optical absorption spectroscopy. The estimated temperature distributions and contents of C₂ radicals did not depend on the anode characteristics.     

带金属嵌件的手机外壳注塑成型翘曲变形分析

在Moldflow模拟分析的基础上,通过正交试验研究了熔体温度、模具温度、注射时间、保压压力、保压时闻和冷却时间等工艺参数对带金属嵌件的手机外壳注塑成型翘曲变形的影响,并优化了成型工艺.结果表明,保压时间和保压压力对翘曲变形的影响最大,最佳工艺组合为:熔体温度310℃,模具温度120℃,注射时间0.3 s,保压压力14...     

Cavity pressure control during the cooling stage in thermoplastic injection molding

The evolution of cavity pressure during the injection molding cycle has a strong influence on the quality of the molded part. The injection molding cycle can be divided into three stages: filling, packing, and cooling. In a previous paper, the authors reported on the design and implementation of a strategy to control cavity pressure during filling and packing. This paper deals with cavity pressure control during the cooling phase. A coolant temperature control system has been designed for the control of cavity pressure during the cooling phase. Alternative variables have been defined to describe changes in cavity pressure during the cooling phase. The concept of controlled pressure cooling time (CPCT) has been defined and selected as the most appropriate controlled variable. The dynamics of CPCT have been studied in relation to coolant temperature. A control system for CPCT has been designed and implemented. Finally, the paper shows that the control of CPCT is an effective approach for the control of cavity pressure during cooling.     

Experimental investigation and molecular dynamics simulations of the effect of processing parameters on the filling quality of injection-molded micropillars

Microinjection molding has been attracting increasing attention and application in fabricating products with functional surface microstructures. The processing parameters, packing pressure, and melt temperature have important effects on the filling quality. In order to study the mechanisms of the packing pressure and melt temperature on the filling quality of micropillars, a simulation model of injection molding of nanopillars was constructed by molecular dynamics software and a series of injection molding experiments of micropillars were carried out in this paper. Subsequently, the mechanisms were analyzed qualitatively. The results showed that the frozen layers were formed at the interface between the polymer melt and mold under the action of heat transfer, which prevented effective filling of the polymer melt. The filling quality of the micropillars could be improved significantly via increasing the melt temperature and the packing pressure, but the mechanisms were different. To be specific, the increase of the packing pressure could make more polymer melts fill into the cavity fully. Thus, the density of the micropillars was increased and the filling quality could be improved. The forming rate of frozen layers could be slowed down by increasing the melt temperature. As a result, the purpose of improving the filling quality was achieved.