Hongwei PAN
,
Shusen CHENG
金属学报(英文版)
doi:10.1016/S1006-7191(08)60102-7
In this paper, the subject of mathematical model is a series of math expressions, which is used to calculate different regions' volume fraction and analyze flow characterization in multi-strand tundish. But research about mathematical model for multi-strand tundish is few, and so far, there has been no acknowledged math model for multi-strand tundish to describe its flow characteristic. If Sahai's model, which is originally proposed for the case of single-strand tundish (proposed in reference[10], and this model is widely used in the world), is applied to describe flow feature in multi-strand tundish, the calculation results would be unreasonable. Based on the data of water-model experiment results, the sum of each strand's dead region's volume fraction is bigger than 100 %, and this obviously doesn't agree with reality; and the value of dead region's volume fraction is calculated to be minus according to mathematical simulation results data in another case. What's more, Sahai's model does not propose the standard of plotting the RTD-curve, and this makes scholars around the world can't achieve consensus of views about plotting RTD-curve. And the model doesn't consider the bypass flow and can't calculate its volume fraction, but bypass flow is critical to tundish metallurgy. And through Sahai's model, the calculation result of plug flow region's volume fraction is also not reasonable, because the model doesn't well describe the essence of plug flow. So these suggest that it is not reliable to apply Sahai's single-strand tundish model to multi-strand tundish case. Then a new model is attempted to propose in this paper for your discussion. In the new model, the standard of plotting RTD curve is definitely proposed, and relative calculation method is also proposed; and the feature of dead region is carefully studied and the model proposes a new method to calculate its volume fraction, and the calculation formula about its volume fraction can be adjustable according the actual demand; what's more, the new model considers the bypass flow and proposes a method to calculate its volume fraction for the first time, and then volume fraction of plug flow region, backmix flow region, dead region and bypass flow can be calculated and obtained at the same time; and this new model can better capture the deviation of reality flow pattern from ideal plug flow pattern, and reflects the feature of plug flow.
关键词:
Tundish
,
null
,
null
,
null
,
null
,
null
夏春霞
,
闫亚明
,
邓蜀平
,
白光君
,
蒋云峰
,
宋惠森
,
王钰
新型炭材料
doi:10.3969/j.issn.1007-8827.2001.04.013
聚丙烯腈(Polyacrylonitrile缩写为PAN)基炭纤维市场需求旺盛,但由于我国PAN基炭纤维生产企业规模小、产品性能低,产品占领不了市场,企业效益欠佳.通过经济规模方法的分析,就国内现有技术状况和两个样本生产线,用工程技术法对PAN基炭纤维的经济规模进行分析,为我国炭纤维产业化发展提供参考.分析表明,国内PAN基炭纤维经济规模的起点为200t/a～275t/a.
关键词:
PAN基炭纤维
,
经济规模
,
工程技术法
李常清
,
袁姗
,
罗荣
,
郭雅明
,
徐樑华
高分子材料科学与工程
将聚酰亚胺(PI)加入丙烯腈-衣康酸-二甲基亚砜体系进行聚丙烯腈(PAN)溶液聚合,湿法纺丝制备了PAN/PI复合纤维.利用流变仪、红外光谱、X射线衍射仪、扫描电镜、差示扫描量热仪等研究了PAN/PI溶液的性质和复合纤维的结构特点.研究发现,加入PI后,聚合物溶液的稳态黏度降低,弹性和粘性模量在低剪切速率区降低;PI作为成核剂,引起初生纤维结晶度增大、晶粒尺寸减小;PI与PAN的溶解性差异导致凝固加快,初生纤维形成皮芯结构;引起原丝体密度减小.PAN/PI纤维在N2下放热量较少,在空气中由于结构疏松放热量较大.
关键词:
聚丙烯腈纤维
,
聚酰亚胺
,
原液改性
,
晶态结构
谢奔
,
朱波
,
王政
,
井敏
,
王进军
,
张春雷
,
吴益民
功能材料
为了提高聚丙烯腈（PAN）初生纤维的可拉伸性能,将溶液纺丝得到的初生纤维进行不同时间的恒温干燥处理,研究其拉伸性能随干燥时间的变化规律。结果表明,干燥处理可以大幅度提升PAN初生纤维的力学性能,其拉伸强力可达10.3cN,断裂伸长可达263.5%;随着干燥时间的延长,纤维的可拉伸性能增强,经过10h干燥后的初生纤维具有最佳可牵伸性能;而拉伸速率的提高可以有效促进未干燥初生纤维的拉伸变形,而对干燥处理后纤维的拉伸性能的影响不大。用SEM观察纤维断裂形貌发现,PAN纤维的致密性随牵伸比的增加而提高。
关键词:
聚丙烯腈
,
初生纤维
,
干燥
,
拉伸性能
,
断裂形貌
Wangxi ZHANG
,
Jie LIU
,
Jieying LIANG
,
null
,
null
,
null
材料科学技术（英文）
Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning electron microscope (SEM), density method and optical microscope were used to characterize the preoxidation extent. A conventional approach, e:g., density aim, to evaluate the extent of preoxidation is not very exact. A DSC curve of a PAN precursor only can provide general information, major in the temperature regime of preoxidation reaction. However, the evaluation of a preoxidation extent, especially from conventional preoxidation temperature with a great span regime of 200~400℃, is put forward in this paper, in which the evolution of core/shell morphological structure is a kind of straightforward evidence.
关键词:
Preoxidation
,
null
,
null
葛继均
,
周花
,
崔永芳
,
张志英
高分子材料科学与工程
对无机粒子填充的PAN渗透蒸发支撑膜进行了初步的研究.考察了不同填充量和填充体系及拉伸热定型的后处理工艺对膜通量和粘弹性的影响.结果表明,不同填充量和填充体系对膜通量及粘弹性的影响不明显;而拉伸和热定型的后处理工艺条件对膜通量和粘弹性有较大的影响.随拉伸比的提高,膜通量迅速增大,膜的稳定性变好,具有很好的耐热性,而膜的截流率却几乎不变.此外,还就膜的耐热机理进行了初步探讨.
关键词:
聚丙烯腈
,
无机粒子
,
支撑膜
,
耐热性机理
张欢
,
谭毅
,
施伟
,
李佳艳
材料导报
液流电池是实现可再生能源大规模应用的新型绿色二次电池,其中电极材料的性能对于液流电池的实际应用具有重要意义.聚丙烯腈基(PAN)碳毡是液流电池的首选电极材料,为了进一步提高PAN碳毡电极材料的亲水性和电化学活性,近些年有关PAN碳毡的改性研究成为了热点.介绍了液流电池的工作原理及其电极材料,着重介绍了液流电池用改性PAN碳毡电极材料的研究现状,并展望了制备PAN碳毡电极材料的发展趋势.
关键词:
PAN碳毡
,
电极材料
,
改性
,
液流电池
,
电池性能
Dongxin HE
,
Chengguo WANG
,
Yujun BAI
,
Bo ZHU
材料科学技术（英文）
To find out the high-quality polyacrylonitrile (PAN) fibers, some differences are sought by comparing domestic PAN fibers with the foreign ones. X-ray diffractometer (XRD), transmission electron microscope (TEM), Fourier transform infrared (FT-IR) spectrometer, elemental analyzer, tensile-testing machine and high-temperature differential scanning calorimeter (DSC) are used to characterize the individual microstructure, chemical structure, elemental content, mechanical properties and thermal properties. It is found that high-quality PAN fibers have high density, lower titre, higher or adequate tensile strength, and they also have better conglomeration structure, smaller crystal dimension with dispersive distribution, less microvoids and flaws.
关键词:
Polyacrylonitrile (PAN) fiber
,
聚丙烯腈纤维
,
碳纤维
