ZnO异质复合对纳米TiO2晶型转变和晶粒生长的影响

以TiCl4,ZnSO4溶液为原料,采用液相沉淀法制备了不同ZnO/TiO2摩尔比的纳米复合粉体.对合成的纳米复合晶的相变、晶粒生长过程以及紫外-可见光吸收性能进行了研究.结果表明:纳米TiO2经ZnO复合后,其晶型转变和晶粒生长均受到抑制.当ZnO为30%(摩尔分数)时,且采用氨水滴入TiCl4和ZnSO4溶液中的沉淀方式制备的ZnO/TiO2纳米复合晶的晶型转变和晶粒生长最缓慢.紫外-可见光吸收测试表明:800℃煅烧的ZnO/TiO2复合粉体的吸收强度比纯TiO2的高;900～1 050℃煅烧的复合粉体,虽然紫外区的吸收强度有所下降,但其光吸收带边比纯TiO2纳米晶的有显著红移.     

用聚合物前驱体法低温合成铌酸锂纳米粉体

用聚合物前驱体法,以柠檬酸为配位剂．乙二醇为酯化剂．水为溶剂合成纳米铌酸锂（LiNbO3）粉体。研究发现：当柠檬酸和金属离子的摩尔比（下同）为3：1,柠檬酸和乙二醇的为1：2时,可形成稳定的Li-Nb前驱体溶液和凝胶。用差热-热重分析研究凝胶前驱体的热分解历程。用X射线衍射分析和红外光谱分析研究凝胶前驱体及其不同温度下煅烧所得粉体的相组成和结构。结果表明：Li-Nb凝胶前驱体在加热过程中分解形成LizCO3相．Li2CO3与Nb2O3发生固相反应生成LiNbO3。凝胶前驱体经800℃煅烧2h可以制备纯钙钛矿型的纳米LiNbO3粉体。     

低温熔盐法制备纳米钨酸钴

以钨酸钠和氯化钴为原料,采用硝酸锂-硝酸钠熔盐法制备出纳米钨酸钴粉体,考察了合成温度对粉体相结构、形貌和光吸收性能的影响,初步探讨了合成机理。结果表明:熔盐与钨酸钴前驱体质量比为6∶1,在210,270,340℃分别反应8 h,可以制备出具有钨锰铁矿结构的单斜相纳米钨酸钴;随着温度的升高,粉体结晶程度提高,平均粒径依次增加,在紫外区和可见光区对光呈现出不同程度的吸收;熔盐条件下,粉体的生长过程由扩散机制控制。低温熔盐法具有合成温度低、操作简单、易于规模化生产等优点。     

纳米氧化锌表面包覆氧化铝复合粉体制备及其光催化活性

在制备ZnO的前驱物 ? 碱式碳酸锌的过程中原位包覆Al2O3，与在ZnO粉体表面包覆的传统工艺相比减少了多次引起粒子团聚的工艺过程，改善了包覆效果. TEM观察表明，包覆的ZnO复合粉体粒径为50 nm左右、包覆层厚为3~5 nm. XPS分析表明，包覆层为Al2O3和ZnO. 光催化活性的测试表明，包覆后的纳米ZnO光催化活性得到了明显降低. 包覆后的纳米ZnO紫外线吸收性能与未包覆的纳米ZnO基本相同，保证了其优异的紫外吸收性能.     

肤色纳米氧化锌的制备及其紫外屏蔽性能测试

以ZnSO.47 H2O、（NH4）2CO3为原料,通过液相法制备出前驱物Zn5（OH）6（CO3）2。将其在350℃处理2 h,得到ZnO粉末。采用XRD对产品的物相组成、粒度进行分析。并考察原料配比、煅烧工艺对纳米氧化锌的颜色、紫外吸收强度的影响。实验结果表明,当原料配比为1∶3时,经350℃煅烧2 h所得的纳米氧化锌色彩均匀、紫外吸收强度较高。     

煅烧温度对ZnO光催化活性的影响

本文以ZnC2O4·2H2O和（NH4）2CO3为原料,采用沉淀法合成前驱体Zn5（OH）6（CO3）2,将前驱体在不同的温度下进行煅烧,制备ZnO纳米粉体。通过XRD和TEM对产品进行了表征,研究氧化锌生长动力学表明,其动力学指数为1．0。以甲基橙为有机污染物考查了煅烧温度对ZnO光催化活性的影响。结果表明,ZnO光...     

溶胶-凝胶燃烧法制备SmBO3粉体的工艺条件及其光吸收性能

研究了溶胶-凝胶燃烧法制备SmBO3前驱体过程中的各种影响因素,考察了煅烧温度及煅烧时间对所合成的SmBO3粉体光吸收性能的影响. 结果表明,当加热温度为80℃、H2O/(Sm+B)摩尔比为30、pH值为2、柠檬酸/(Sm+B) 摩尔比为1:1时获得的凝胶在180℃下发生稳定的自燃烧反应,得到白色蓬松的前驱体. 前驱体经750℃煅烧2 h后得到的SmBO3粉体平均颗粒尺寸为100 nm. 在1.05~1.15 mm波长范围,SmBO3粉体对光存在较强的吸收,在1.07 mm波长附近反射率达最低值,约为0.41%,而在1.06 mm波长处反射率约为0.6%.     

醇-水法制备Al2O3-ZrO2复合粉体及其表征

以Al(OH)3和ZrOCl2·8H2O为起始原料,以NH4HCO3为沉淀剂,在醇-水混合溶液中获得前驱体,将前驱体在空气中煅烧,制备了Al2O3-ZrO2复合粉体.探讨了不同煅烧温度对Al2O3-ZrO2复合粉体的物相组成和显微形貌的影响.采用综合热分析仪、X-射线衍射仪、扫描电镜等手段对粉体进行表征.结果表明:前驱体中含锆化合物主要以无定形的形式存在,当煅烧温度为600℃时,粉体中出现较强的t-ZrO2衍射峰,Al(OH)3的衍射峰肖失.当煅烧温度增加到1200℃时,粉体中主要存在α-Al2O3和t-ZrO2主晶相衍射峰.前驱体经600℃热处理后所制备的Al2O3-ZrO2复合粉体粒度分布均匀且大多数颗粒在50 ～ 100 nm之间;随着煅烧温度的升高,Al2O3-ZrO2复合粉体颗粒出现长大,且其显微形貌由球状颗粒为主逐渐向球状、片状以及短棒状等多样化结构过渡.     

纳米ZnO／聚乙烯薄膜和纳米TiO2／聚乙烯薄膜紫外屏蔽性能的比较

采用母粒法,分别将纳米ZnO、TiO2粉体添加到线型低密度聚乙烯中,再经挤出吹膜系统吹塑成膜,研究了两种粉体薄膜紫外屏蔽性能的差异.结果发现:纳米ZnO、纳米TiO2两种粉体均使得聚乙烯薄膜紫外屏蔽性能有一定程度的提高,但是在相同粉体质量分数下,在不同的波段,二者的光透过能力存在差异.虽然在紫外光波段纳米ZnO阻隔效果不如纳米TiO2;但是纳米ZnO颗粒与TiO2相比,具有较好的可见光透过性,从而对纳米复合粉体应用时的透明性影响小.     

共沉淀法制备纳米镁铬尖晶石粉体

镁铬尖晶石具有较高的熔点而被广泛应用于耐火材料中。而常规镁铬尖晶石粉体因烧结温度较高，铬蒸发而使得耐火材料的致密度难以提高。为改善镁铬耐火材料的烧结性能，进行了纳米镁铬尖晶石粉体的研究：以Cr(NO3)3，Mg(NO3)2，PEG-400和CO(NH2)2为原料，采用共沉淀法获得了铬酸镁纳米粉(nc2o3：nMgo=1：1)的前驱体，经过超临界流体干燥(SCFD)制备出镁铬二元纳米气凝胶，经600℃煅烧后获得了纳米级立方相镁铬尖晶石粉体。经XRD，DSC-TG，BET和透射电镜分析，结果表明：前驱体纳米粉的比表面积为350～780m^2／g，平均粒径为1～2nm，煅烧后的纳米粉的比表面积为36～65m^2／g，平均粒径为5～10nm。     

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。