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在温度为60~80℃的条件下用剂量为1.72×1019n/crm2的中子对6H-SiC晶体进行了辐照,利用X射线衍射等方法观测了中子辐照引起的缺陷及其恢复.重点追踪6H-SiC的(006)、(0012)晶面的衍射峰并进行实验观测.中子辐照对晶体造成了严重的损伤,使其内部产生了大量的缺陷,在某些被测晶面甚至出现非晶化.通过等时退火,缺陷逐渐消失,晶格开始恢复,其恢复特性由退火温度决定.通过X射线衍射峰的峰高和峰型发现,在温度低于600℃时,辐照损伤几乎不变,超过600℃后,温度越高,晶格恢复现象越明显.原来经辐照呈非晶化的晶面逐渐恢复有序,(006)面衍射峰的半高宽随退火温度的升高呈线性恢复.利用此种线性规律可以制作无线传感器,从而实现对某些复杂环境的温场测试. 相似文献
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《炭素技术》2015,(3)
<正>KCl对酚醛树脂炭化生长碳纤维的影响[刊,中]/吴小贤,李红霞,刘国齐,等//耐火材料,2015,49(1):1-5为了促进酚醛树脂在炭化过程中的石墨化,以工业液态酚醛树脂为碳源,微米尺度的KCl为催化剂,经混合、六亚甲基四胺固化处理后,在埋炭1 000℃保温3 h热处理条件下,研究了KCl添加量(掺入酚醛树脂质量的1%、3%、5%和7%)对树脂炭的物相、微观结构的影响及炭纤维的生长机制。结果表明:KCl催化后提高了树脂炭的石墨化程度,树脂炭中原位生长较多炭纤维和片状炭,炭纤维直径为30~200nm,长度可达10~20μm;KCl最优添加量为5%(质量分数), 相似文献
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一、前言在钍增殖反应堆的设计中,采用糠醇作粘结剂,将小块石墨粘结成所需尺寸和形状的堆内构件。粘缝材料经固化、炭化后,形成玻璃炭。玻璃炭和石墨结构不同,导致其性能上存在较大的差异。特别是在辐照条件下,更是如此。据报导,将玻璃炭辐照至6.4×10~(20)nvt(E>0.18Mev)时尺寸收缩大于4%,这几乎为石墨的10倍。而当辐照至1.5×10~(22)nvt(E>50kev)时,密度提高33%,四块样品碎裂了三块。玻璃炭的辐照稳定性如此之差,这对石墨粘结件用于反应堆内是一个严重的威胁。事实上,未经石墨化处理的粘结样品,在经受7.9×10~(22)nvt(600℃,E>0.18Mev)后,粘缝即遭破坏。而据我们实验,用糠醇粘结未经石墨化处理的样品辐照至4.3×10~(20)nvt后,粘缝强度明显下降。因此,必须消除粘缝与基体在结构及性能上的不均匀性。 相似文献
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研究了噻葸、葸、及17%噻蒽和83%蒽混合物的炭化(525℃)和石墨化(2500℃),噻葸炭化后生成密度较低的非石墨化炭。1200~2500℃热处理时,由于硫的不断逸出,闭气孔率增加,引起密度进一步下降。混合物炭化后生成可石墨化炭,与葸在同样温度下的炭化物具有相同的晶体参数,但与蒽的炭化物相比,混合物的炭化物在热处理过程中密度下降比较明显,硫含量的减小主要发生在1400~1600℃。密度的变化似乎是由于微晶顺序的破坏使得直径小于2000A的开气孔的体积增加而产生的。混合物炭化产物和所报道的高硫石油焦类似,在石墨化过程中产生不可逆膨胀(晶胀)。 相似文献
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炭化温度对掺杂改性树脂炭结构及其抗氧化性能的影响 总被引:1,自引:0,他引:1
研究了炭化温度对掺杂改性树脂炭结构及其抗氧化性能的影响。借助于X射线衍射仪、红外光谱仪、扫描电子显微镜和差示扫描量热仪对掺杂改性树脂炭化后的炭结构及其抗氧化性能进行了表征。结果表明:在埋炭条件下,炭化温度对掺杂改性树脂炭化后的炭结构有显著影响:随炭化温度升高,掺杂改性树脂炭化后的炭结构逐渐向石墨化碳结构方向演化;当炭化温度为600℃时,掺杂物表面开始有大量碳晶须生成,晶须的直径约为50~100nm,长度约为几百纳米,随炭化温度升高,碳晶须长径比提高,但碳晶须的产量逐渐下降;当炭化温度为1 000℃时,掺杂物表面生成大量的碳微球,碳微球的直径约为100~500nm。与树脂炭相比,掺杂改性树脂炭化后碳产物的氧化峰值温度提高了约80℃。 相似文献
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ONACCURACYOFANALYSISOFOFHYDROGEN1前言我公司目前应用的氢气纯度分析方法有两种,一种是爆炸反应法,另一种是焦性没食子酸吸收法。几年来,人们对两种分析方法的准确性曾有过褒贬不一的评论。这里我们也谈谈自己粗浅的观点。2爆炸法测定氢气纯度一定量的氢气样品与适量的空气之均匀混合物因反应后生成液体水而引起气体体积减少,减少的体积等于参加反应气体体积之和。其中l/3为氧气,2/3为氢气。根据氢气取样量和反应前后混气体体积之差,以及氢气在反应中的体积比例关系,可计算出样品的氢气纯度。计算公式式中:A一混… 相似文献
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P. P. Budnikoff 《Journal of the American Ceramic Society》1924,7(11):817-820
The different analytical methods proposed for the evaluation of gypsum have been subjected to an experimental test. A combination method, consisting of a fusion with KHCO3 and determination of CaO by KMnO4 titration, the SO3 by Andrews method of titration of BaCrO4 has been found to give very reliable results with the least consumption of time. 相似文献
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A model is developed for the sedimentation from a suspension of two particle species of unequal densities and of different sizes. The composition and the thickness of various layers in the sediments are predicted using graphical and analytical methods. The model predictions were in excellent agreement with experimental results, when the particle size ratio was ≥ 108. When size ratio of the particles was 2.60 and 4.31 the agreement occurred in about 50 percent of the cases. 相似文献
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A novel technique serves to monitor instantaneous rates of loss of a volatile solute from a suspended drop during drying. A highly sensitive electron capture detector is used to monitor concentrations of SF6 released into a flowing gas stream from a suspended, drying drop. Simultaneously, the appearance and morphological development of the drop are monitored with a video camera. This provides the wherewithal of relating instantaneous rates of loss of the volatile solute to particular events during the development of particle morphology.
Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology. 相似文献
Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology. 相似文献
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ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES 总被引:5,自引:0,他引:5
Viscosity of Simple Soda-Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log10 viscosity amounting to 0.6, those of Washburn et al., being relatively too high. If correction for this is made, the isothermal curves of log10 viscosity as a function of soda content are smooth up to 50% Na2O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO2, 2Na2O) due to Molecular Substitution of CaO, MgO and Al2O3 for Na2O The effect is clearly brought out by plotting (from the results of English) the change of log10η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature Ta. If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log10η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A12O3) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al2O3) per 100°. At the aggregation temperature the change of log10η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al2O3. Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log10η due to substitution of an oxide for Na2O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na2O-CaO-SiO2. Change of Viscosity of Glass (4SiO2, 2Na2O) due to of Substitution of B2O3 for SiO2 The change of log10η (from the results of English) is plotted as a function of temperature, and also the change of log10η per per cent B2O3. The curves are more complex than for the substitution for Na2O. 相似文献
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面对日益激烈的市场竞争,摩托车油箱外观质量越来越成为影响销售的因素之一。文章介绍了改进工艺后的油箱涂装,该涂装体系提高了油箱外观的丰满度,降低了油箱涂装的生产成本。 相似文献