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排序方式: 共有173条查询结果,搜索用时 140 毫秒
91.
92.
目的 对氟醚橡胶FM-2D在空气与飞马Ⅱ号润滑油中的热老化行为与机理进行研究。方法 开展氟醚橡胶高温贮存试验,在热氧、热油的介质环境下,研究氟醚橡胶的力学性能退化规律。试验后对样品的拉伸性能、压缩性能以及硬度进行检测,并且利用傅里叶红外光谱仪、扫描电子显微镜以及X射线电子能谱对试验后样品进行检测。结果 通过热老化试验,发现氟醚橡胶在200℃以下能够长期维持较好的力学性能。试验温度在200℃以上,氟醚橡胶的力学性能出现明显退化趋势,并且在热空气与热油中的老化趋势不同。在220℃的热空气老化31 d后,氟醚橡胶的拉伸强度下降27.0%,断裂伸长率增大89.8%,压缩应力松弛率为34.6%,硬度下降8.7%。在220℃的热油老化31 d后,氟醚橡胶的拉伸强度下降85.9%,断裂伸长率下降83.9%,压缩应力松弛率为-17.5%,硬度上升4.2%。结论 在热空气老化过程中,橡胶分子链受热氧影响发生断裂,使其强度下降;在热油老化过程中,油介质和高温的耦合作用使橡胶的交联网络失效,橡胶发硬变脆。 相似文献
93.
Iordanidis A Buckman J Triantafyllou AG Asvesta A 《Environmental geochemistry and health》2008,30(5):391-405
The aim of this study was to characterise individual airborne particles collected from the Ptolemais-Kozani region (Western Macedonia), northern Greece. Throughout a 1-year period (March 2003 to February 2004), we collected several filters that captured airborne particles at seven sampling sites distributed throughout the area. The airborne particles captured on the filters were then characterised by environmental scanning electron microscopy (ESEM) coupled with energy-dispersive X-ray analysis (EDX). The particles were categorised as geogenic, biogenic and anthropogenic. The main anthropogenic airborne particles were fly ash (released from lignite-fired power plants) and carbonaceous (soot and char) and metalliferous (mainly iron- and copper-enriched) particulates. We present here characteristic ESEM and EDX spectra for the airborne particles and underline the presence of characteristic primary and secondary sulphates. 相似文献
94.
Abboud IA 《Environmental geochemistry and health》2008,30(5):445-463
Urinary stone diseases are increasing in the Middle East. The majority of urinary stone cases are found in the northern part of the country. Stone samples taken from patients living in the Irbid area were collected from Princess Basma Hospital. The present study concentrates on the mineralogical and chemical composition of the urinary stones and on the effective environmental factors that assist in developing the different types of urinary stones. Using X-ray diffraction techniques, the mineralogical composition of the urinary stones was found to be as follows: oxalate, cholesten, and uric acid, with cystine stones occuring more frequently than the others. Cholesten and calcium oxalate stones are the most dominant types of stones. Calcium oxalate is the most common type of oxalate stone. Calcium oxalate is represented in: whewellite, wheddellite, and calcium carbonate oxalate hydrate minerals, in addition to other minerals such as brushite, ammonium phosphate, vaterite, valleriite, and bobierrite from other types of stones. Bobierrite (phosphate group) is a new mineral reported in urinary stones, and this has not been determined in any previous study worldwide. Apatite (calcium phosphate) is deduced using scanning electron microscope (SEM) images. The SEM technique determined crystal forms and systems, shapes, morphological features, and the names of the minerals forming urine stones, while optical properties are studied by polarizing microscope. X-ray fluorescence technique determined the concentrations of major and some trace elements. It revealed that Ca is the main constituent of the urinary stones, especially those composed of calcium oxalate and calcium phosphate. The concentration of trace elements was Ba = 1.57, P = 3.61, Fe = 1.78, S = 2.08, Zr = 4.63, Mo = 3.92, Cu = 1.89, Co = 1.56, and F = 4.2% and was higher in the urinary stones of Jordanian patients than in foreigners in the country. Questionnaires completed by patients suggest that the most significant factors directly effecting the formation of stones are water, climate conditions, food rich in protein and rich in different chemicals. Moreover, some drugs and diseases might also help in developing other stones. 相似文献
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96.
便携式XRF测定仪在土壤检测中的应用及其影响因素 总被引:3,自引:0,他引:3
研究了便携式X射线荧光光谱仪(PXRF)的仪器性能,评估了其检出限、准确度及精密度,并和常规实验室检测方法比对进一步评估其性能,分析两者间的相关性和差异性。进一步探究了影响PXRF测定的2个最主要因素(土壤含水量和粒径)。结果表明:PXRF具备良好的仪器性能,8种元素的检出限为0.62~8.01 mg/kg,除Cd和Hg外,精密度均低于7%,准确度范围为-7.5%~11.1%。Pb、Cr、Cu、Zn、Ni、As的PXRF测定值与常规实验室方法测定值有良好的相关性,特别是Cu、Zn,相关系数可达0.873、0.832,而Cd和Hg的相关性则较弱。土壤含水量和土壤粒径会影响PXRF的测定性能,鲜样测定检测值普遍小于干样,0.15、2 mm粒径下检测值具有较强的相关性。研究旨在为PXRF的现场应用提供 参考,该方法可应用于初步监测和应急监测,实现土壤重金属元素的快速测定。 相似文献
97.
Lazar M. Kaluđerović Zorica P. Tomić Darko P. Ašanin Rada D. Đurović-Pejčev Branka J. Kresović 《Journal of environmental science and health. Part. B》2018,53(8):503-509
The results presented in this paper show an impact of the concentration of the aromatic organic cation on the adsorption of acetochlor on the surface of the organic-modified montmorillonite. Natural montmorillonite from Bogovina (Boljevac municipality, Serbia) was used for organic modification in this experiment. Cation exchange capacity of this montmorillonite (86 mmol 100 g?1 of clay) was determined using the methylene blue method. In pretreatment, montmorillonite was modified with NaCl. For the purpose of organic modification, three different concentrations of phenyltrimethylammonium chloride (PTMA) have been selected, based on calculated CEC value: 43 mmol 100 g?1 of clay (0.5 CEC), 86 mmol 100 g?1 of clay (1 CEC) and 129 mmol 100 g?1 of clay (1.5 CEC). The changes in the properties of the inorganic and organic modified montmorillonite were examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and batch equilibrium method. Freundlich coefficients show higher uptake of the herbicide by montmorillonite modified with PTMA, compared to inorganic-modified montmorillonite. The results also indicate the influence of the organic cation concentration on the adsorption of the selected herbicide. 相似文献
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100.
应用能量色散X射线荧光光谱法建立了生物质燃料中磷含量的快速测定方法。对比分析压片压力条件、基体效应和干扰元素,明确了能量色散X射线荧光光谱法的测试条件,通过加标回收率实验、标准样品测试、ICP-OES方法对比等获得实验结果。实验结果表明:能量色散X射线荧光光谱法用于生物质燃料样品的分析,标准工作曲线线性相关系数为0.998 3,方法检出限为0.4 mg/kg,平均加标回收率为98.1%,测定值的相对标准偏差为1.36%~4.92%,标准样品磷含量在标准值不确定度内,能量色散X射线荧光光谱法与行业标准ICP-OES方法的准确度和精密度不存在显著性差异,可应用于生物质中磷含量的环境监测。 相似文献