共查询到20条相似文献,搜索用时 46 毫秒
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采用浓度为1∶1的盐酸浸取硼泥中的镁得到氯化镁溶液,以氢氧化钾为沉淀剂与氯化镁反应生成氢氧化镁,氢氧化镁经煅烧后制得氧化镁。研究了浸出温度、浸出时间、盐酸与硼泥比例对硼泥中镁浸出率的影响,通过DSC曲线确定了氢氧化镁的最佳煅烧温度,利用XRD和SEM对产物氧化镁进行了表征。结果表明,在浸出盐酸足量的条件下,反应温度对镁浸出率影响最大。硼泥中镁浸出的最佳工艺条件为:浸出温度85℃,浸出时间30min;盐酸体积与硼泥质量比4∶1。氢氧化镁在600℃下煅烧2.5h得到平均粒径小于100nm的氧化镁粉体。 相似文献
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将石墨态氮化碳(g-C_3N_4)和聚电解质络合物(PEC)相结合,以聚丙烯腈(PAN)超滤膜为基底制备PEC/g-C_3N_4杂化膜,考察了杂化膜的渗透汽化有机溶剂脱水性能.用傅里叶红外光谱、扫描电镜和低场核磁等表征了杂化膜的组成、形貌和水在膜中的状态.研究了g-C_3N_4含量、PEC浓度和抽滤溶液体积等成膜因素和进料液温度、进料液水含量、分离体系等操作条件对杂化膜渗透汽化性能的影响.结果表明,在最优制膜条件和操作温度下,PEC/g-C_3N_4杂化膜对进料液中乙醇质量分数为90%的乙醇/水体系通量和透过液水质量分数分别为2 560 g/(m~2·h)和98.0%,且PEC/g-C_3N_4杂化膜具有良好的运行稳定性. 相似文献
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以石棉尾矿硫酸酸浸液为原料,经过氧化、除铁后得到硫酸镁滤液,采用氨水沉淀法制备氢氧化镁,研究氨水用量、反应温度、反应时间对制备氢氧化镁的影响,并对制备的氢氧化镁样品进行表征。结果表明,利用石棉尾矿酸浸液制备氢氧化镁的适宜工艺条件如下:200 mL酸浸液需要氨水的体积为150 mL,反应温度为70℃,反应时间为40 min;在适宜条件下制备的产物中氢氧化镁的质量分数为93.31%,中位粒径d50为8.42μm,比表面积为35.14 m2/g,白度为98.6%;X射线衍射分析显示氢氧化镁结晶良好。 相似文献
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采用气压式毛细管流变仪对聚丙烯腈/二甲基乙酰胺/聚乙烯吡咯烷酮(PAN/DMAc/PVP)中空纤维铸膜液的流变性能进行了研究.实验结果表明,该铸膜液属假塑型流体.物料性质,如PAN分子量、PAN质量分数、添加剂质量分数会影响体系的流动性能.PAN分子量为Mη=13.1×104、PAN质量分数为14%、添加剂PVP质量分数为10%时,该铸膜液的流动性最好.另外,温度对体系的流动性也有影响.对特定的PAN铸膜体系来说,升高温度使体系的黏度降低,流动性变好;而当体系中PAN分子量增大、PAN质量分数增加时,体系的黏度增大,活化能变大,因而对温度的敏感性也增强. 相似文献
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《中国粉体技术》2015,(6):33-39
以轻烧镁粉为原料,氨水为沉淀剂,利用直接沉淀法合成"卡房"状高纯氢氧化镁粉体;通过单因素实验研究硫酸镁的浓度、反应温度、反应时间、氨水与镁离子的物质的量比和搅拌转速对氢氧化镁合成的影响,确定最佳反应条件;分别利用添加不同分散剂和水热法对制得样品进行改性;采用扫描电子显微镜、X射线衍射和X射线荧光对样品进行表征。结果表明:不同类型的分散剂均对氢氧化镁的改性效果不明显;水热法改性后氢氧化镁的结晶度等性质均有不同程度的改善,改性时添加浓度为6 mol/L的氢氧化钠效果最佳,可得极性弱、形貌规则、热稳定性良好、结晶度高的氢氧化镁粉体,其中氢氧化镁的质量分数大于99.94%,收率为87.92%。 相似文献
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目的 研究溶液质量分数和非溶剂体积分数对PVC薄膜表面形貌和疏水性能的影响,以获得具有超疏水表面的PVC薄膜。方法 以四氢呋喃为良溶剂、乙醇为非溶剂,利用非溶剂诱导相分离的原理,采用旋涂法在玻璃基底上制备超疏水的聚氯乙烯(PVC)涂膜;通过对PVC样品的疏水性、表面形貌、结晶性能和热性能进行分析,探究溶液质量分数以及非溶剂的体积分数对PVC样品性能的影响。结果扫描电镜和接触角测试表明,添加一定体积分数的乙醇使得所制备的PVC样品形成了多孔膜层以及纳米级聚合物球粒,从而提高了PVC样品的疏水性。XRD测试结果表明,添加乙醇并不会改变PVC样品的无定形结构。结论 PVC溶液质量分数对所制备PVC样品的疏水性能和表面结构没有明显影响,乙醇体积分数为30%~40%时,可形成表面水接触角大于150°的超疏水表面。 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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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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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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Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995. 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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An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a
rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate
agreement is demonstrated between the derived relations and experimental data. 相似文献