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1.
以氧化钇、硝酸和硝酸铁为原料,氢氧化钾为矿化剂,采用水热合成法制备了钙钛矿结构铁酸钇正铁氧体(YFeO3)微晶.研究了水热反应时间、温度和溶液pH值对产物的物相组成、粒径大小和磁性能的影响,研究结果表明,在实验条件所在区间内,随着反应时间的增加和反应温度的升高,产物纯度逐渐变高.合成纯相YFeO3需要在一定的溶液pH值范围内.随溶液pH值的降低,产物颗粒的粒径变小,粒径分布变窄,并且晶粒的磁化强度增大.最佳的合成条件是pH值为9.5,温度为260℃,反应时间为60h. 相似文献
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湿式氧化催化剂RuO2/γ—A12O3的制备及降解苯酚的研究 总被引:3,自引:0,他引:3
采用浸渍法制备了4%质量分数的RuO2/γ-Al2O3催化剂,并利用XRD和SEM对催化剂进行了晶体结构表征。研究了催化剂制备的焙烧温度和时间、进水pH值和处理温度对RuO2/γ-Al2O3催化剂活性影响,并对其影响机制进行了初步探讨。结果表明,焙烧温度升高、焙烧时间延长会导致催化剂的活性组分RuO2的晶粒增长过大;在300℃经3h焙烧,形成的RuO2晶粒细小,苯酚溶液的COD(化学需氧量)去除率较高。在本研究的pH范围内,进水pH值为酸性时,COD去除率高于碱性时的COD去除率;当反应温度升高时,RuO2/γ-Al2O3催化剂降解苯酚的能力显著提高,且反应的诱导期明显缩短,当反应温度从150℃升高至180℃时,在进水pH值为5.6,反应2h后,此催化剂的COD去除率为96%以上。研究表明,RuO2/γ-Al2O3催化剂具有较好的活性和和稳定性。 相似文献
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在碱性条件下([NaOH] =0.008 mol/mL),以氯化钡(BaCl2·2H2O)和氧氯化锆(ZrOCl2·8H2O)为原料,采用传统水热法在低温下制备了锆酸钡(BaZrO3)微晶.利用XRD和SEM分别对产物进行了物相组成及微晶形貌的测试与表征.研究了反应温度为135℃时不同反应时间对产物微观结构及形貌变化的影响.结果表明:在135℃下反应2h即可合成纯相的BaZrO3粉体,且随着水热温度的升高,产物由无定形态变为类球状结构最终变为棱角分明的菱形十二面体结构,结晶程度提高,晶粒尺寸增大.通过对其结晶动力学研究,计算得到BagrO3微晶的表观成核活化能为24.36 kJ/mol. 相似文献
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湿式氧化催化剂RuO2/γ-Al2O3的制备及降解苯酚的研究 总被引:2,自引:0,他引:2
采用浸渍法制备了4;质量分数的RuO2/γ-Al2O3催化剂,并利用XRD和SEM对催化剂进行了晶体结构表征.研究了催化剂制备的焙烧温度和时间、进水pH值和处理温度对RuO2/γ-Al2O3催化剂活性影响,并对其影响机制进行了初步探讨.结果表明,焙烧温度升高、焙烧时间延长会导致催化剂的活性组分RuO2的晶粒增长过大;在300℃经3h焙烧,形成的RuO2晶粒细小,苯酚溶液的COD(化学需氧量)去除率较高.在本研究的pH范围内,进水pH值为酸性时,COD去除率高于碱性时的COD去除率;当反应温度升高时,RuO2/γ-Al2O3催化剂降解苯酚的能力显著提高,且反应的诱导期明显缩短,当反应温度从150℃升高至180℃时,在进水pH值为5.6,反应2h后,此催化剂的COD去除率为96;以上.研究表明,RuO2/γ-Al2O3催化剂具有较好的活性和和稳定性. 相似文献
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ZnO晶体的极性生长习性与双晶的形成机理 总被引:9,自引:8,他引:9
本文根据晶体负离子配位多面体的生长基元的观点,结合氧人锌晶体生长基元稳定能的计算,研究和分析了水热条件下氧化锌晶体的极性生长习性和双日 的形成机理。氧化锌晶本的生长习性明显地受生长时的物理化学条件(溶液的碱度,反应和矿化剂)的影响,晶粒形态表现为长柱状、单锥状和颗粒状;而且在不同的生长条件下可以形成不贩双晶晶粒。在以KBr为矿化剂的溶液中形成哑铃形双晶,双晶面为(0001);在中性或弱碱性溶液2中 相似文献
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采用L9(33)正交试验方案研究了溶液浓度、反应温度和pH值等三因素对共沉淀法制备锆酸钐粉体的影响.采用XRF、SEM等测试手段对纳米级锆酸钐粉的组分和形貌等进行表征,结果发现三因素对纳米级锆酸钐的组分有不同程度的影响:在共沉淀反应中,三因素相互作用,其中溶液浓度是影响其组分的主要因素;随着溶液浓度的升高,其组分差距增大,随着反应温度和pH值的升高,其组分差距表现出先增大后减小的趋势.当溶液浓度为0.6 mol/L、反应温度为50℃、pH值为10时为最佳制粉工艺,并在最佳工艺条件下制得了组分、形貌优良的纳米级锆酸钐粉. 相似文献
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采用基于在水热合成的过程中发生于液相、固相和溶液相界面处的相扩散和分离机制的液相(Liquid)-固相(Solid)-溶液相(Solution)(LSS)法成功地制备出具有规则形状的La(OH)3纳米晶,主要研究了水热反应釜填充比、水热反应温度等工艺因素对La(OH)3纳米晶的晶粒尺寸及相组成的影响.采用X射线衍射仪、纳米粒度分析仪和透射电子显微镜对所制备的La(OH)3纳米晶进行表征.结果表明:所制备的La(OH)3由直径约为10~40nm的纳米晶组成,晶粒尺寸分布均匀;随着水热反应温度从120℃增加到220℃,La(OH)3纳米晶结晶程度提高,晶粒的平均尺寸从14nm增加到40nm;在60~80;范围内,水热反应釜填充比对La(OH)3纳米晶的粒度影响不大. 相似文献
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本文以Na2S,S,FeSO4为反应物,通过调节溶液的pH值和反应温度,采用水热法合成了具有立方体形貌的黄铁矿型FeS2材料.采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)等手段对合成的FeS2材料进行了表征.在温度为500℃,相对湿度RH ≤1;的条件下,测试了其单体热电池的放电性能.XRD测试结果表明当1≤pH≤4时,产物为白铁矿和黄铁矿的混合物;当5≤pH≤11时,产物为单相黄铁矿.当反应温度T=95℃时,产物为白铁矿和黄铁矿的混合物;当反应温度110℃≤T≤200℃,产物为单相黄铁矿.SEM测试结果表明随着温度的增加,产物的粒径也随之增加,在140℃温度条件下合成了具有立方体形貌的颗粒.当1≤pH≤5,产物颗粒的形貌不规则,并且粒径的均一性差;当9≤pH≤12,产物颗粒具有立方形貌,粒径的均一性好;放电测试结果表明合成的单相黄铁矿FeS2材料可以降低浓差极化,提高材料的比容量、比能量. 相似文献
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Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi3 existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species. 相似文献
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原位氮化法制备TiN纳米粉体 总被引:3,自引:0,他引:3
用溶胶凝胶法合成的纳米TiO2粉体作为原料,将该粉体在氨气中进行原位氮化制备了TiN纳米粉体.用XRD,TEM,化学分析等手段对合成的TiN纳米粉体的物相组成、形貌、成分进行了分析.实验分析表明:在1000℃和1100℃下分别氮化5h,可以制备粒径大约为40nm和80nm的TiN粉体,其TiN的含量分别为95.40;和98.37;;而在1000℃条件下氮化时间减少到2h时,TiN的含量仅为58.36;.氮化温度和氮化时间是合成纳米TiN的重要因素,提高合成温度和延长氮化时间均可形成纯度较高的TiN纳米粉体,但延长氮化时间更有利于获得粒径小的氮化钛粉体. 相似文献
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A novel homologous series of ethylene derivatives of thermotropic liquid crystals has been synthesized. The methoxy to octyloxy derivatives are nematogenic, the decyloxy to tetradecyloxy derivatives are smectogenic, in addition to nematogenic, and the hexadecyloxy homologue is smectogenic only. All the members of the series are enantiotropically mesogenic. Thermotropic behavior was determined by an optical polarizing microscope equipped with a heating stage and Differential Scanning Calorimetry (DSC) study. Analytical and spectral data confirm the molecular structures of homologues (infrared, nuclear magnetic resonance, mass spectra, X-ray, and DSC data). Textures of the nematic phase are threaded or Schlieren and that of smectic phase are focal conic fan-shaped of smectic A or C. Transition curves of the phase diagram behave in a normal manner except one or two deviations from the normal trend. The mesophase range (Sm+N) varies from 3°C to 44°C. The average thermal stability for smectic is 93°C and that for nematic 117.4°C. The LC behavior of the novel series is compared with a structurally similar known series. 相似文献
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P.J. Lezzi 《Journal of Non》2011,357(10):2086-2092
The enthalpy of mixing of mixed alkali (Na2O and K2O) silicate glasses containing various concentrations of alumina was determined using an ion-exchange equilibrium method. For glasses with a constant alkali concentration, the enthalpy of mixing was found to become less negative with alumina addition. Consistent with our previous results on the enthalpy of mixing of alumina-free mixed alkali silicate glasses, the magnitude of enthalpy of mixing exhibited a good correlation with the molar volume mismatch of the corresponding two single alkali glasses as well as with the extent of conductivity mixed alkali effect, e.g. excess activation energy of conductivity, ΔE. The reduction of the magnitude of the enthalpy of mixing with alumina addition can be attributed to the reduction of non-bridging oxygen and ionic field strength. Combining the present results with results obtained earlier, the magnitude of the enthalpy of mixing for all mixed alkali (Na2O and K2O) silicate glasses with and without alumina was expressed by a simple function of a modified Tobolsky parameter, which takes into account the alkali concentration and the difference in cation-to-effective anion distances. The enthalpy of mixing data of the mixed alkali glasses was then compared with reported experimental data on the conductivity of mixed alkali aluminosilicate glasses. What appears to be conflicting experimental data can be understood in terms of the magnitude of the enthalpy of mixing and we can conclude that the mixed alkali effect is closely correlated with the negative enthalpy of mixing. 相似文献
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研究了在复合电铸过程中,当其它工艺参数一定时,复合电铸层的沉积速率及其厚度随时间的变化趋势, 以及复合电铸层表面微观形貌随电沉积时间的变化趋势.测定了复合电铸层的组织成分,并就纳米颗粒在复合电铸层表面和横截面上分布的均匀性进行了评价.结果表明,复合电铸层表面平整,组织均匀致密,其组成主要是镍和所复合的纳米颗粒,纳米颗粒较为均匀地分散在复合电铸层中. 相似文献
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N. G. Kakazey L. A. Klockov I. I. Timofeeva T. V. Sreckovic B. A. Marinkovic M. M. Ristic 《Crystal Research and Technology》1999,34(7):859-866
Zinc-oxide powder was tribophysically activated in a high-energy vibro mill in a continual regime in air for 3, 30 and 300 minutes with the purpose of modifying the powders physico-chemical properties. By analyzing of data obtained by X-ray powder diffraction, electron diffraction and transmission electron microscopy, the values of distances between corresponding crystallographic planes, average domain sizes of coherent scattering, i.e. crystallites, width of diffraction lines due to the existence of microstrains, and microstrain values, minimal dislocation densities, dislocation density due to microstrain and real dislocation density, and also average distances between dislocations were determined. The dependence of these values on the activation time was established, which enabled analysis of the evolution of the defect structure of zinc-oxide powders during tribophysical activation by grinding in the described regime. 相似文献
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Yu. G. Terent'yeva V. M. Yashchuk O. M. Snitserova M. Yu. Losytsky 《Molecular Crystals and Liquid Crystals》2017,642(1):81-88
This article presents the results of spectral investigations of white blood human cells including absorption, fluorescence and phosphorescence (using low-temperature measurements). For this research, the main optical centres were identified and local distribution of emitting and absorbing centres into white blood human cells was determined. In addition, the spectra of normal and pathological (B-cell chronic lymphocytic leukemia, B-CLL) cells were compared. 相似文献
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O. Dryuchko D. Storozhenko A. Vigdorchik N. Bunyakina I. Ivanytska K. Kytaihora 《Molecular Crystals and Liquid Crystals》2018,672(1):199-214
AbstractThe complex study provides a reliable idea of ??the trends in the joint behavior of structural components in the water-salt systems of nitrate precursors of REE, alkaline, alkaline earth metals in the preparatory stages of the processes of forming multicomponent oxide polyfunctional materials on their basis with thermal activation. Stages of such transformations are revealed; The regularities of complex and phase formation in systems and factors influencing them are determined; A number of physicochemical properties of the intermediate phases formed - coordination lanthanides nitrates: their composition, types of compounds, atomic-crystalline structure, regularities of transformations during heat treatment were studied. 相似文献