高剂量中子辐照6H-SiC晶体的退火特性

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.     

文摘

<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),     

延长炭化时间对聚酰亚胺前驱体炭化材料的结构和性能的影响

研究聚酰亚胺(PI)薄膜在1 000℃炭化不同时间获得的炭膜的结构与性能,并利用XRD、Raman、TEM等测试手段对其进行表征。结果表明,随着炭化时间的延长,XRD中2θ衍射角先增大后减小,在炭化9 h时达到最大,即最接近单晶石墨的衍射峰26°。ID/IG的变化规律与之一致,随着时间延长先增大后减小。这可能是由于随着时间的延长,炭化程度增加,炭膜中石墨碎晶成分增加,ID/IG增加。继续延长炭化时间,炭膜中石墨碎晶趋向于完整排列,ID/IG减小。炭膜的电导率也相应先增加后减小,在炭化9 h时达到最大。这与XRD和Laman的表征结果一致。     

单轴取向聚乳酸制品的结晶行为研究

借助差示扫描量热仪(DSC)、广角 X 射线衍射仪(WAXD)研究了单轴取向后聚乳酸(PLA)膜片的结晶行为,实验发现,取向后样品的 DSC 曲线在熔融过程出现了2个熔融峰,对应于 WAXD 图谱中29.9°和31.0°这2个晶面衍射峰。结果表明,拉伸取向能够提高制品的结晶度,同时发生晶型转变;当拉伸温度不低于110℃、拉伸倍率不小于400%时,出现了(003)β晶面衍射峰,部分α晶向β晶转变,滑石粉能促进此过程发生,添加1份滑石粉可使 PLA的结晶度从18.5%提高至37.48%。     

玻璃炭的催化石墨化试验

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。     

聚丙烯腈基炭纳米球的制备

采用低浓度水相分散聚合的方法合成了粒径在230 nm～250 nm的聚丙烯腈球,对其依次经过冷冻干燥、氧化及炭化工艺,用扫描电镜对炭化后的样品形貌进行了观察.结果表明,聚丙烯腈球炭化后转化为粒径在170 nm～190 nm之间的炭纳米球.炭纳米球经1 500 ℃,2 300 ℃及2 800 ℃的高温处理后,X射线衍射仪分析表明,在2 300 ℃处理温度以上可以得到石墨化度明显增加的炭纳米球.     

硫逸出对高温炭性能的影响——噻蒽及噻蒽-蒽母体

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)。     

炭化温度对掺杂改性树脂炭结构及其抗氧化性能的影响

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℃。     

文摘

98014 玻璃炭的小角度 X 射线衍射及其石墨化/[刊,日]福山胜也,西泽节,四川惠子//炭素—1998,№182:85～90用小角度 X 射线衍射法研究了由酚醛树脂在950℃及在各种不同热处理温度下(HTT)制得的玻璃炭试样的结构。对于热处理温度高达1800℃的试样,随热处理温度增加,衍射强度逐渐增加,近似接近一个渐近值。在高于1800℃的热处理温度时,试样的衍射强度迅速增加。     

纳米AlN增强C/C复合泡沫材料制备及机理研究

融合韧带网络型泡沫炭与微球型泡沫炭的结构特点,并结合同质复合材料与异质复合材料的互补优点,用填充了纳米AlN的酚醛树脂胶作韧带网络将酚醛树脂微球六角密排,再经过炭化、石墨化处理,成功地制备了纳米AlN/C复合泡沫样品。对该样品进行扫描电镜和X射线衍射测试,结果表明生成的直径在400～500 nm范围的炭纤维和尺寸在150～200 nm之间的纳米AlN颗粒共同增强韧带网络。同时,对纳米AlN增强C/C复合泡沫材料的机理进行了分析解释。     

氢气纯度分析方法准确性的探讨

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…     

COMPARISON OF METHODS OF ANALYSIS OF GYPSUM1

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.     

SEDIMENTATION OF BINARY MIXTURES OF PARTICLES OF UNEQUAL DENSITIES AND OF DIFFERENT SIZES

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.     

HEASUREHENT OF INSTANTANEOUS RATES OF LOSS OF VOIATILE COMPOUNDS DURING DRYING OF DROPS

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.     

茶多酚提取方法进展

本文综述了国内外现有茶多酚提取方法的现状以及近期的研究进展，并对其优缺点进行了评价。这将有助于中低档茶的综合利用和茶多酚的进一步开发应用。     

ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES

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 T_a. 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.     

环氧树脂羟基值测定方法的研究

利用乙酸酐、吡啶和浓硫酸混合的乙酰化试剂测定环氧树脂中羟基值含量的方法具有操作简便、滴定终点明显和分析结果误差小等优点。     

骑式摩托车油箱喷涂工艺的改进

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。     

几种针状焦性能对比

针状焦分石油系和煤系两大类,这主要取决于针状焦的原料来源。在同一系列中由于原料不同和工艺条件不同 ,针状焦的各自性能也不相同。针状焦是生产超高功率石墨电极和高功率石墨电极的主要原料 ,针状焦的性能对石墨电极的质量有至关重要的影响。所以对针状焦性能以及其对石墨电极质量影响的研究十分必要的。以下是常用的几种进口针状焦和国产针状焦的性能对比。１原料性能分析对比原料试样包括４种针状焦 ,其中两种为进口针状焦：三菱针状焦和新日化针状焦;另两种为国产针状焦：鞍山针状焦和锦州针状焦。其中除锦州针状焦是石油系针状焦外…     

聚酰亚胺的合成法

本文评述了缩聚型聚酰亚胺的主要合成方法和近年来国际上在合成中所做的探索。