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一种制备膨胀石墨的新方法及其压制品的性能研究 总被引:2,自引:0,他引:2
以粒径约0.5mm的天然鳞片石墨为宿主材料,以高氯酸液为氧化、插层剂,通过简单的酸液浸泡法直接热氧化转化天然鳞片石墨为膨胀石墨.用浓度为72%(质量分数)的高氯酸液在室温下浸泡天然鳞片石墨1~3min.后,在900下膨化,膨胀体积为549mL/g.以该条件制备的膨胀石墨为前驱体通过冷压成型的方法制备柔性石墨,利用材料万能试验机、微欧计、激光热导仪分别测试了该材料的抗拉强度、电阻率、导热率.实验结果表明:抗拉强度(T)、电阻率(ρ)同密度(d)呈线性正相关,其中T=12.1d-7.6,R=0.977;ρ=-3.97d 11.9,R=0.968.热导率同电阻率呈负相关性. 相似文献
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用柔性石墨制备低密度膨胀石墨块 总被引:1,自引:1,他引:0
通过在浓硫酸或浓硝酸中浸泡柔性石墨纸(板),然后在200℃~750℃膨化制备了低密度膨胀石墨块。研究了插层剂、插层时间和膨化温度对膨胀石墨块体积密度和外形完整程度的影响。结果表明:膨化温度越高,制得的膨胀石墨块密度越低,越难获得完整的外形。以浓硫酸或浓硝酸插层时,适宜的膨化温度分别约为550℃和650℃,插层时间应为3h以上。发现膨胀石墨块主要存在两种外观,一种为均匀膨胀,另一种为非均匀膨胀。 相似文献
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无硫高倍膨胀石墨的制备及影响因素探讨 总被引:19,自引:6,他引:19
以鳞片石墨、硝酸、乙酸酐、高锰酸钾为原料,采用化学法经氧化酸化插层、水洗、干燥、高温膨胀过程制备膨胀石墨,利用正交试验方法确定最佳工艺条件,并对相关影响因素及插层机理作了初步探讨。结果表明:按鳞片石墨:硝酸:乙酸酐:高锰酸钾(质量比)=1:0.7:1.5:0.4,反应时间90min,反应温度30℃~40℃的条件可以制备出膨胀体积达478mL/g的高倍无硫膨胀石墨。相关影响因素的大小依次为:高锰酸钾、硝酸、乙酸酐、反应时间,其中高锰酸钾的影响程度远大于其他三个因素。 相似文献
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混酸法制备低硫可膨胀石墨 总被引:9,自引:0,他引:9
用硫酸(98%)、硝酸(65%)和草酸的混合液与天然鳞片石墨反 制备低硫可膨石墨,最佳反应条件是:石墨、硫酸(8%)、硝酸(65%)、草的重量比为1:2.3:1.7:0.05,反庆时间为45min,反应温度为25℃,可膨胀石墨的含硫量为1.63%时,膨胀容积为250mL/g。其终端产品柔性石墨的含硫量为780ppm。 相似文献
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影响膨胀石墨膨胀容积因素的研究 总被引:3,自引:0,他引:3
以硫酸(98%)为插层剂、过氧化氢(30%)为氧化剂,用化学法制备膨胀石墨。通过正交实验确定最佳制备备件。结果表明:当石墨与硫酸重量比为1:3,硫酸与过氧化氢体积比为1:0.1,反应时间90min,反应温度50℃,膨化温度1000%,膨化时间20s时,膨胀石墨的膨胀容积可达250ml/g。 相似文献
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HClO_4-CrO_3-石墨层间化合物的制备及其性能 总被引:3,自引:0,他引:3
以天然鳞片石墨、CrO3、HClO4为原料,采用化学氧化法制备石墨层间化合物(GIC);研究了反应物用量、反应时间、反应温度对石墨层间化合物膨胀容积的影响。结果表明:按石墨∶三氧化铬∶高氯酸(质量比)=1∶0.3∶5,反应温度30℃,反应时间60min的条件,可制得膨胀容积为555mL.g-1的石墨层间化合物。采用FTIR、XRD、TG等技术对石墨层间化合物的组成、结构进行表征和分析得知:石墨层间的插入物为ClO4-、Cr2O72-。GIC性能特点测试结果说明:所制GIC具有低能耗性能、良好的真空安定性、较好的8毫米波动态衰减效果。 相似文献
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制备低硫可膨胀石墨的研究 总被引:18,自引:3,他引:15
研究了以过二硫酸铵作氧化剂低硫可膨胀石墨的制备,找到了在较低温度下,制备低硫可膨胀石墨的最佳条件。即过二硫酸铵和石墨的重量比为15%;反应温度为55℃;反应时间为40min;硫酸浓度为98%;硫酸与石墨的重量比为4∶1,草酸和硝酸(浓度为65%)的重量比为7.5%时,所制得的可膨胀石墨含硫量为0.65%,膨胀容积为200mL/g可膨胀石墨。并且,其终端产品柔性石墨具有优良的力学性能和抗氧化性能。 相似文献
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A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling. 相似文献
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O'Brien RS 《Radiation protection dosimetry》2003,105(1-4):95-100
Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides. 相似文献
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本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue. 相似文献
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V. Ya. Fateev 《Measurement Techniques》2011,54(7):774-780
Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically
investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity
of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN
may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or)
the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15%
for control media with dielectric permittivity in the range 2.2–30. 相似文献