石墨－MDF水泥基复合材料屏蔽电磁波性能

研究了石墨、聚合物（ＰＶＡ）及材料厚度对石墨－ＭＤＦ（Ｍａｃｒｏ－Ｄｅｆｅｃｔ－Ｆｒｅｅ）水泥基复合材料屏蔽电磁波性能的影响及其机理．结果表明；当石墨添加量超过１８ｖ．％时，材料对２００—１６００ＭＨｚ的电磁波有１０—４０ｄＢ的衰减效果，屏蔽效率Ｓ随材料中聚合物增加而降低，随材料厚度增加而升高，随电磁波的频率ｆ的增加有升高的趋势．当石墨在水泥基体里形成导电网络时，材料的电阻车ρｖ发生显著变化，即出现渗滤阈值（ＰｅｃｏｌａｔｉｏｎＴｈｒｅｓｈｏｌｄ）现象后，具有较好的屏蔽性能，屏蔽电磁波主要以吸收电磁波为主．     

偶联剂KH和聚合物PVA在硫铝酸盐─MDF水泥中的作用机理

以硫铝酸盐水泥为基材，采用有机聚合物ＰＶＡ，并且在ＭＤＦ（Ｍａｃｒｏ—Ｄｅｆｅｃｔ—Ｆｒｅｅ）水泥中添加偶联剂ＫＨ，制备出抗折强度大于１７０ＭＰａ，抗压强度达２４０ＭＰａ的新型ＭＤＦ水泥、同时，借助于Ｘ射线光电子能谱分析（ＸＰＳ），红外光谱分析（ＩＲ）等测试手段研究了偶联剂ＫＨ和聚合物ＰＶＡ在硫铝酸盐－ＭＤＦ水泥中的作用机理     

偶联剂KH和聚合物PVA在硫铝酸盐—MDF水泥中的作用机理

以硫铝酸盐水泥为基材，采用有机聚合物ＰＶＡ，并且在ＭＤＦ水泥中添加偶联剂ＫＨ，制备出抗折强度大于１７０ＭＰａ，抗压强度达２４０ＭＰａ的新型ＭＤＦ水泥。同时，借助于Ｘ射线光电子能谱分析（ＸＰＳ），红外光谱分析（ＩＲ）等测试手段研究了偶联剂ＫＨ和聚合物ＰＶＡ的硫铝酸盐－ＭＤＦ水泥中的作用机理。     

一种工业氧化铝的疲劳特性

利用光滑和缺口试件研究了一种工业氧化铝陶瓷的动疲劳特性，给出了一种预测疲劳强度的简便方法，当加载速率σ〈σｃ时（σ≈２０ＭＰａ）试件的动疲劳强度σＤＦ随σ增大而升高，当σ〉σｃ，趋势出现逆转，对于应力集中系数Ｋ１不同试件，σＤＦ－σ关系曲线相互平行，并可用参量Ｋ１σＤＦ归一化。统计分析显示，疲劳强度有可能遵从正态分布或对正态分布，采用本文定义的等效应力，可获得光滑及接口试件的统一ＳＰＴ（Ｓｔｒｅｎ     

各向异性的粘结钕铁硼／铁氧体永磁复合材料的磁性能

采用高性能的各向异性ＨＤＤＲ－Ｎｄ－Ｆｅ－Ｂ磁粉和铁氧分与塑料复合,制成了各向异性粘结ＮｄＦｅＢ／铁氧体复合永磁材料研究了它们的磁性能。结果表明,随ＨＤＤＲ－Ｎｄ－Ｆｅ－Ｂ含量增加,各向异性的塑料粘结ＨＤＤＲ－Ｎｄ－Ｆｅ－Ｂ／铁氧体复合永磁材料磁性能ｂＨｃ和密度几乎是线性增大,而ｊＨｃ,（ＢＨ）ｍａｘ和Ｂｃ开始都增大,当达到一定值后基本保持不变,出现一平台,随后又继续增大,但ｊＨｃ与Ｂｒ和（ＢＨ）     

Fe73.5Cu1Mo3Si13.5B9非晶合金的晶化动力学

用ＤＴＡ，结合ＸＲＤ，ＴＥＭ研究了Ｆｅ７３．５Ｃｕ１Ｍｏ３Ｓｉ１３．５Ｂ９软磁非晶合金的晶化动力学，结果表明，该合金在４７８℃时析出ａ－Ｆｅ相，晶化初期激活能量最小（１４８ｋＪ．ｍｏｌ＾－１），它随晶化学量的增加而增大，在ＸＣ为５０－７８％时，呈极大值（５１０ｋＪ．ｍｏｌ＾－１）随退火温度的升高，α－Ｆｅ相的数目增多，但尺寸基本不变。为１４－１６ｍｍ。     

PVDF中空纤维滤膜的形态结构

用Ｌ－Ｓ相转换法制备了聚偏氟乙烯（ＰＶＤＦ）中空纤维不对称滤膜。铸膜液由聚合物、溶剂和添加剂组成。用电子显微镜（ＳＥＭ）考察了聚合物浓度、添加剂用量及种类对膜形态结构的影响。实验结果表明，聚合物浓度对膜形态结构有显著影响，当铸膜液中聚合物浓度较低时，无论用什么种类添加剂，都能形成大、且多的孔，但孔的形状随添加剂不同而异。当恒定聚合物浓度时，添加剂的用量对膜形态结构有很大的影响，但孔的大小及多少与添加剂含量的多少不成正比。     

塑料粘结钕铁硼─铁氧体材料的复合效应研究

本文研究了ＮｄＦｅＢ－铁氧体－塑料３者复合成的永磁材料的复合效应。结果表明塑料粘结ＮｄＦｅＢ－铁氧体复合材料的＿ｂＨｃ、＿ｊＨｃ、（ＢＨ）＿ｍ随ＮｄＦｅＢ含量增加而升高，呈中间偏凹的趋势，压缩强度和硬度下降；同时随着塑料含量增加，磁性能Ｂ＿ｒ，＿ｂＨｃ，（ＢＨ）＿ｍ降低，而内禀矫顽力＿ｊＨｃ却上升。     

等温退火Fe_（73．5）Cu_1Mo_3Si_（13．5）B_9合金的纳米晶结

本文用ＸＲＤ和ＴＥＭ研究了Ｆｅ_（７３．５）Ｃｕ_１Ｍｏ_３Ｓｉ_（１３．５）Ｂ_９非晶合金在５２０℃，２０－１２０ｍｉｎ退火后形成的纳米晶结构。结果表明，晶化相为局部具有ＤＯ_３超结构的α－Ｆｅ（Ｓｉ），尺寸约为１４ｎｍ，α－Ｆｅ（Ｓｉ）晶粒由ＤＯ_３有序区和无序区组成。随退火时间的延长，α－Ｆｅ（Ｓｉ）的体积分数，Ｓｉ含量及ＤＯ３有序区尺寸增加。在退火时间为６０ｍｉｎ时，残余非晶相处于一特殊结构状态。α－Ｆｅ（Ｓｉ）相和残余非晶相结构对合金的起始磁导率均有影响。     

以聚六亚甲基碳酸酯二醇和聚四亚甲基醚二醇为基的聚氨酯的合成…

以聚六亚甲基碳酸酯二醇（ＰＨＭＣＤ）和聚四亚甲基醚二醇（ＰＴＭＥＧ），４．４’－对二苯基甲烷二导氰酸酯（ＭＤＩ）及１．４－丁二醇（ＢＤＯ）合成线型聚碳酸酯聚氨酯，研究了其软段相的Ｔｇ，力学性能和流变特性。结果表明随ＰＨＭＣＤ含量增大，聚合物的拉伸强度增加，而熔体的表观粘度则降低。     

钒电池集流体用聚四氟乙烯导电塑料的制备与性能

报道了制备钒电池集流体用聚四氟乙烯导电塑料的制备方法,研究了不同种类和不同用量的炭系导电填料对聚四氟乙烯导电塑料性能的影响,探讨了导电填料层积复合法对样品的性能影响。研究结果表明,石墨填料是聚四氟乙烯导电塑料中较理想的导电填料;用量77%的石墨能够在样品中形成完整的导电网络,相应的体积电阻率为0.070Ω.cm,拉伸强度12MPa;层积复合法能够大幅度地提高样品的导电性;高温烧结工序能够提高样品的导电性能;样品具有良好的防渗漏、耐强酸腐蚀和电化学腐蚀性能;该材料可用作钒电池的集流体,有望在钒电池中得到应用。     

膨胀石墨蠕虫的红外衰减性能研究

本文报道了不同膨胀容积的膨胀石墨蠕虫的红外衰减实验结果,并将其与常用的红外干扰材料--天然鳞片状石墨的红外衰减性能作了对比研究.结果表明:膨胀石墨蠕虫比天然鳞片状石墨具有更好的红外衰减性能.膨胀石墨蠕虫的红外衰减性能与该材料的膨胀容积有关,膨胀容积大,红外衰减性能好.     

Preparation and characterization of Nylon-6/exfoliated graphite composite via a combination method of in situ polymerization and thermal expansion

Nylon-6/exfoliated graphite (Nylon-6/EG) composite was prepared via a combination method of in situ polymerization and thermal expansion and characterized via scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Otherwise, the resistivity value of Nylon-6/EG composite was measured, and the volume resistivity value was calculated as well as. The characterization showed that Nylon-6/EG composite had the morphology of the graphite worm and was structured by EG and Nylon-6, which covered on the surface of EG. The result exhibited that the volume resistivity of Nylon-6/EG composite would decrease when the dosage of EG increased. When the mass percent of EG was 1%, the the volume resistivity value of Nylon-6/EG composite could reach 2.3 × 10⁶ Ω cm. This shows that the combination method not only is very effective and reliable but also can play an important role in preparing antistatic Nylon-6 composite.     

The elastic and compressive properties of hybrid metal matrix composites/hexagonal prismatic cellular solids

An analysis is presented of the elastic and compressive properties of hybrid metal matrix composite (MMC) materials containing a uniform distribution of hexagonal prismatic cells which form closely spaced arrays separated by thin walls. The cell walls are considered to be reinforced by chopped fibers, whiskers, or particulates, thus forming a MMC. Exact derivations of the moment of inertia, elastic moduli, and compressive strength are presented, and approximations to these expressions are discussed. Results of these analyses are applied to the calculations of elastic moduli, flexural rigidity, and compressive strength of a square beam. Comparisons are made between the cases of unreinforced aluminum and steel cell walls and the cases of graphite chopped fiber reinforced aluminum and tungsten chopped fiber or whisker reinforced steel. The axial modulus and flexural rigidity of this type of structure made from Gr/Al composite are superior to unreinforced steel cellular structures only when the volume fraction of reinforcement exceeds about 30%. The material with reinforced cell walls is distinctly superior to its unreinforced counterpart by a factor of 4·3 at 50 volume percent graphite chopped fiber in aluminum.     

Effects of graphite particle addition upon the abrasive wear of polymer surfaces

The abrasive wear performance of vinyl ester resins modified with various volume fractions (5, 10, 15, 20 and 30%) of graphite powder has been measured. Using a conveyor belt driven testing machine developed locally, it has been possible to realistically simulate the effect of three-body abrasive wear upon these graphite modified polymer samples. A comparison of the calculated dimensionless wear rates obtained for these surfaces reveals that the effect of the graphite powder depends strongly upon the volume fraction of particles in the resin matrix. It appears that, for intermediate volume fractions, the presence of graphite powder in the resin matrix reduces the abrasive wear of the polymer surface. Scanning electron microscopy has been used to probe the mechanisms of abrasive wear of the pure resin and graphite modified surfaces. It appears that the embedded graphite particles can act as a lubricant during the abrasion process thus reducing the wear rate. The effect of increasing graphite powder volume fraction upon the abrasive wear mechanism is discussed.     

膨胀石墨/石蜡相变复合材料有效导热系数的数值计算

通过膨胀石墨粉与石蜡混合制备相变复合材料可有效提高该储能材料的传热性能。为研究膨胀石墨/石蜡相变复合材料的导热机制,提出了膨胀石墨粉与石蜡混合后的3尺度层次固体有效导热系数计算方法。然后,通过数值模拟计算得到了具有不同体积分数和不同导热系数的膨胀石墨导热颗粒的膨胀石墨/石蜡相变复合材料的有效导热系数。结果表明:膨胀石墨能够有效地提高石蜡的导热性能,当膨胀石墨的体积分数为10%时,膨胀石墨/石蜡相变复合材料的有效导热系数是纯石蜡的9倍。此外,提高底层尺度的石墨片与石蜡的混合程度及降低底层尺度石墨的体积分数都能有效提高膨胀石墨/石蜡相变复合材料的有效导热系数。所得结论为探究膨胀石墨粉提高相变复合材料导热系数的机理奠定了基础。     

Radionuclides in Irradiated Graphite of Uranium–Graphite Reactors: Decontamination of Sleeves Using Liquid Reagents

To examine the possibility of disposal of irradiated graphite in ground near-surface repositories, the concentration and spatial distribution of radionuclides in the volume of irradiated graphite sleeves of industrial uranium–graphite reactors was studied, and the efficiency of decontamination using liquid reagent treatment methods was evaluated. The radionuclide distribution in the graphite volume is extremely heterogeneous on the 10–100 μm scale. The degree of decontamination using solutions with high acid concentrations and fluoride ions added does not exceed 16–25% for ¹⁴C and 15–19% for ³⁶Cl. Under these treatment conditions, no structural changes occur in graphite, and ¹⁴С bound with the graphite surface via sorption is removed. Significant differences in the efficiency of the reagent decontamination of irradiated graphite from various producers were revealed.     

ABS/石墨复合材料的交直流导电特性及流变性能

研究了石墨填充丙烯腈-丁二烯-苯乙烯共聚物(ABS)复合材料的直流(DC)和交流(AC)导电特性和线性粘弹行为。电性能测试结果表明,石墨体积分数为13.21%~16.36%时,ABS/石墨复合材料的DC电阻率突降6个数量级,说明发生电学逾渗;同时,AC电阻率在低频区不随频率而变化,且AC阻抗复平面图中阻抗实部与阻抗虚部呈现半圆弧,进一步证明导电网络的形成。流变性能测试结果表明石墨体积分数为10.24%~13.21%时复合体系的储能模量和复数黏度出现跳跃,损耗因子(tanδ)的峰值减小且逐渐向高频移动,说明复合体系从"类液态"转变为"类固态",发生流变逾渗现象。流变逾渗阈值小于导电逾渗阈值是因为传递电子时石墨之间的距离比阻碍聚合物分子链运动时石墨之间的距离小。     

Influence of alloy element distributions on austempered ductile irons

The influence of alloy element distributions on austempered ductile iron microstructure and austempering treatment was analysed by a cellular automaton model that considers the ausferritic and martensitic transformations. The initial microstructure is modelled as spherical graphite nodules inserted in an austenitic matrix, in which the alloy elements are distributed in a uniform or non-uniform way. The study is performed for different chemical compositions and graphite nodule sizes. Delays in the development of ausferritic transformation are produced by the increment of graphite nodule size and the presence of alloy element microsegregations. Moreover, microsegregation reduces the final volume fraction of ferrite platelets. The predicted retained austenite volume fraction is in good agreement with the experimental measurements reported in the literature.     

Initial stage of isothermal decomposition of austenite to ferrite and graphite in spheroidal graphite cast iron

Abstract

The isothermal decomposition of austenite to ferrite and graphite in a spheroidal graphite cast iron was investigated by dilatometry, metallography, and image analysis. The results gave quantitative, although indirect, information on the kinetics of carbon transfer from austenite to graphite, as well as on the kinetics of the austenite to ferrite and graphite transformation. The relationship between the kinetics and the graphite nodule count was highlighted. The incubation period before ferrite growth was found to be associated with a global contraction of the material, in spite of the related increase in the graphite volume fraction. Calculations showed good agreement with experimental results, except for the rate of carbon transfer, which was found to be much slower experimentally than predicted by calculations based on the volume diffusion of carbon. Possible reasons for this discrepancy are discussed.