水热体系中表面活性剂对合成羟基磷灰石晶体的影响

以CaCO3和CaHPO4·2H2O为前驱物,利用XRD、SEM及FT-IR系统研究了水热体系中不同表面活性剂对合成羟基磷灰石(HAP)晶体微结构及晶体生长的影响,同时利用配位体理论对其生长机理进行了探讨.结果表明:不同类型表面活性剂对合成HAP晶体的分散性、微结构及结晶度有一定的影响,添加菲离子型表面活性剂制备的HAP晶体规整性、完整性、分散性、均一性、结晶度较好,长径比较大,呈一维纳米结构.非离子型表面活性剂种类的不同对HAP晶体的微结构及分散性也有一定的影响.阳离子型表面活性剂的加入对HAP晶体a、b轴方向的OH-Ca6,生长基元起到一定的促进作用,合成的HAP晶体长径比较小,长约1.1～1.5 μm,径向直径约为100～140 nm,阴离子型的促进作用明显大于阳离子型表面活性剂.EDS及FT-IR分析证实,水热环境下表面活性剂仅起到形貌调控和分散作用,对HAP产物的纯度没有任何影响.     

纳米镁铝水滑石的合成、微结构及吸附性能研究

本文以硝酸镁、硝酸铝为原料,以碳酸钠和氢氧化钠为沉淀剂和pH值调节剂,采用液相沉淀法制备了纳米镁铝水滑石层状化合物(Mg-Al-LDHs),利用X射线衍射(XRD)、扫描电镜(SEM)及X射线能谱分析仪(EDS)系统比较研究了pH值、反应温度、镁铝比等条件对合成LDHs晶体微结构及晶体生长的影响,同时利用生长基元的配位体理论对其生长机理进行了初步探讨,在此基础上,以甲基橙(MO)模拟染料废水为吸附对象,考察了最佳条件下制备的LDHs培烧产物的吸附性能和吸附机理.研究结果表明:pH值、温度的增加有利于生成结构单一、结晶性、规整性较好的镁铝水滑石晶体,产物晶粒尺寸及径厚比呈增大趋向.当反应温度等于或大于80℃时,温度的升高对镁铝水滑石晶体的形态影响较小.镁铝比的改变对产物的物相影响较小,但影响产物的结晶及生长,当镁铝比为3∶1时,所得产物晶粒的规整度、均一性最好,尺寸约为70-100 nm,厚度为20 nm左右,镁铝比为1∶1时,晶粒粒径明显减小,约为30 nm左右.最佳条件下合成的纳米镁铝水滑石焙烧产物具有较好的吸附性能,随着时间的增加,吸附脱色率逐渐增加,当吸附时间达到70 min,LDO对染料的吸附逐渐达到饱和平衡,脱色率达到90;以上,吸附动力学研究表明LDHs对甲基橙的吸附过程更符合准一级动力学方程,其R2值更接近1,吸附等温线符合Iangmuir模型.     

规整Cu-Zn-Mg-Al类水滑石的合成及其结构分析

以CuCl2·2H2O、ZnCl2·6H2O、MgCl2·6H2O、AlCl3·6H2O、Na2CO3为原料,采用丙三醇-水热法组装了优质铜-锌-镁-铝类水滑石.样品采用XRD、SEM、TEM、TG-DAT、N2吸附-解吸的分析方法进行了物相、粒度、晶体形貌结构、热分析和比表面分析.分析了不同介质条件对Cu-Zn-Mg-Al-HTlc类水滑石样品特征的影响.结果发现,在水热反应体系中加入体积分数为15;的丙三醇,反应温度为180 ℃,反应时间为18 h时可获得晶形好、板层结构显著、规整性好、分散性好的优质铜锌铁镁铝水滑石,估算薄层厚度约在36 nm左右.     

用天然水镁石球磨法制备Mg-Al水滑石的实验研究

以水镁石、硝酸铝和碳酸氢钠为原料,利用球磨方法通过机械力化学作用合成了Mg-Al水滑石,考查了球磨速度、球磨时间对合成水滑石的影响.研究表明,提高球磨转速有利于水滑石的形成与晶化,同时也有利于Al2O3的析出.适当延长球磨时间有利于水滑石的形成和结晶,但球磨时间过长,水滑石结构破坏.在500 r/min转速下球磨3h制备的水滑石纯度最高、结晶最好.用该方法制备的水滑石粒径较大,结晶度较低,热学行为特殊,可能与结构中富镁、贫铝有关.     

Co-MgAl三元类水滑石的合成、微结构及吸附性能研究

采用水热法制备了Co-MgAl三元类水滑石层状化合物(HTLcs),利用X射线衍射(XRD)、扫描电镜(SEM)比较研究了不同Co2+比例条件下对合成产物物相、晶体微结构及晶体生长的影响,同时利用生长基元的配位体理论对其合成机理进行了初步探讨.以甲基橙(MO)模拟染料废水为吸附对象,比较研究了三元类水滑石与二元水滑石焙烧产物的吸附性能和吸附机理.研究结果表明:钴离子同层板二价镁离子存在着交换作用,钴离子掺杂量的不同,没有影响水滑石固有的层板结构,但影响了构建钴镁铝三元类水滑石过程中各晶面的生长.Co∶Mg∶Al为1∶2∶1的HTLcs经过500 ℃焙烧后,焙烧产物(LDO)仍呈现片状结构.但径向尺寸和厚度同焙烧前相比略有减小,产物的均一性、规整性相比焙烧前变差,其对甲基橙模拟染料废水的吸附脱色性能随着时间的增加,呈缓慢增加的趋势,达到吸附平衡需要时间更长为70 min,脱色率仅为60;左右,明显低于二元镁铝水滑石焙烧产物(MgAl-LDO)(90;).吸附动力学研究表明Co-MgAl-LDO焙烧产物对甲基橙的吸附过程更符合准二级动力学方程,吸附等温线符合Freundlich模型,而二元MgAl-LDO对甲基橙的吸附过程较符合准一级动力学方程,吸附等温线符合Langmuir模型.     

规整锌铝类水滑石的合成及其结构分析

采用改进的水热法合成了六方状规整的锌铝类水滑石,样品采用XRD、SEM、N2吸附-解吸进行了物相、形貌及比表面分析.结果发现,当在水热反应体系中加入体积分数为25;的乙二醇,反应温度T=180℃,反应时间t=20 h时可获得显著的板层结构、晶形好、分散性好、规整性好、优质的Zn-Al类水滑石,谢乐公式估算粒子粒径约在39.24 nm左右.     

微波水热法制备Mg-Al水滑石纳米晶

以MgO和Al(OH)3为起始反应物,用微波水热法在180℃反应30 min,可以制备出平均晶粒度约35 nm的高结晶度单相纳米晶Mg-Al水滑石.用XRD、SEM对合成产物进行了表征.随反应温度升高和时间的延长,合成产物中杂相减少,Mg-Al水滑石晶粒度逐渐增大.在180℃反应仅1 min,即可获得平均晶粒度为约27 nm Mg-AlLDHs,杂相只有微量MgO.微波水热法能够促进起始反应物快速水解,形成Mg-Al LDHs晶核和晶粒长大.     

水热法制备微米级钇铝石榴石(YAG)晶体

本文采用水热法,以Al(OH)3和Y2O3为前驱物,3 mol/L KOH作矿化剂,高温430 ℃,反应24 h,合成了微米级Y3Al5O12晶体.对合成材料的结构和形貌进行了测量分析,用差示扫描量热仪(DSC)和热重分析仪(TGA)测量分析了热性能.实验结果表明,所合成产物的成分、结构与前驱物中Y2O3与Al(OH)3的摩尔比有关.当Y∶ Al的摩尔比为1∶ 3时合成的纯相钇铝石榴石Y3Al5O12(YAG)晶体,呈立方体形,最大尺度超过100 μm.     

金属有机骨架ZIF-67材料的合成及微结构调控研究

以甲醇为溶剂,室温下合成金属有机骨架结构的ZIF-67,利用XRD、SEM等系统的研究了有机溶剂添加量、金属离子与有机配体配比、搅拌速度、时间、钴源以及不同醇溶剂对ZIF-67 晶体的结晶度、形貌、晶体尺寸变化规律的影响,并初步探究了其影响机理.基于不同影响因素的系统分析及机理探究,对可控合成结晶度高,分散性好,形貌规整,尺寸均一的ZIFs材料意义重大.     

高炉渣基A型沸石的合成及对Pb2+离子的吸附

以内蒙古包钢高炉渣为前驱体,采用水热法成功合成了高炉渣基A型沸石,通过XRD、SEM表征其微观结构,并研究其对Pb2离子的吸附性能.研究结果表明,提取高炉渣中的SiO2和Al2O3分别为硅源和铝源,再外加一定比例铝源能够合成高炉渣基A型沸石,最佳合成条件为:n(SiO2)/n(Al2O3)=0.24、nH2O/n(SiO2)=98、水热时间为12 h和水热温度为100℃.所合成的高炉渣基A型沸石对Pb2离子具有较强的吸附性能,吸附率高达94.82;,符合拟二级动力学模型,属于多分子层的吸附,吸附容易进行,平衡吸附量为39.37 mg/g.     

On the inhomogeneity of the transition surface layer of the solid core of the earth

Different geophysical data and conclusions of theoretical models, which can give information about the behavior of the solid and liquid cores of the Earth as well as about the existence of a transition layer as a temperature-hysteresis region at a relatively weak first-order phase transition, are compared. It is concluded that liquid inclusions inevitably exist in this region; these inclusions are involved (due to the complex convective processes occurring in the liquid core) in the transport of light materials from some areas of the solid-core surface. The porosity and permeability of the transition layer determine the seismic acoustic inhomogeneities in these areas, which contact the convective flows in the liquid core. In particular, this explains the well-known ??east-west?? effect. Obviously, the model of the crystalline core is not the only possible alternative for a model of a core with a metallic glasslike structure.     

Study of the influence of the rare-earth elements on the properties of lead iodide

Lead iodide (PbI₂) shows excellent electronic properties for detection of ionizing radiation. We report the introduction of rare-earth elements and other elements as admixtures during synthesis to study their influence on the quality of single crystals. Synthesized material as well as single crystals have been characterized by measurements of electrical resistivity and low-temperature photo luminescence and index of refraction. The structural quality with respect to polytypes was analysed by electron back scatter diffraction. Makyoh topography was applied for surface studies.     

On the role of the porous shell of the solid core of the earth in the anomalous heat and mass flow to the mantle

The model of the pressure-induced first-order phase transition of a metal melt to the metallicglass state considers a thermodynamically nonequilibrium porous near-surface shell of the solid core of the Earth, which contacts cyclonic vortices in the liquid core. Anomalous flows of heat and light-material mass to the mantle from the solid core at these contact points are calculated. These anomalous flows are shown to be comparable with the observed ones under the assumption of a rapid increase in the melt viscosity at pressures of 1–10 Mbar, which is characteristic of a solid core. In this case, the porous layer permeability may be very low.     

Effect of the temperature on the TMOS sono-hydrolysis and a study of the structure of the resulting aged sonogels

The effect of temperature on the oxalic acid catalyzed sono-hydrolysis of tetramethoxysilane (TMOS) was studied by means of a heat flux calorimetric method. The activation energy of the process was measured as (24.5 ± 0.8) kJ/mol in the temperature range between 10 and 50 °C. The structural characteristics of the resulting sonogels, after long period of aging in saturated conditions, were studied by means of small angle X-ray scattering. The structure can be described as formed by ∼2.7 nm mean size mass fractal-like aggregates (clusters) of primary silica particles of ∼0.3 nm mean size, all imbibed in a liquid phase. The average mass fractal dimension of the clusters was found to be 2.58. The primary particle density was estimated as 2.23 g/cm³, in good agreement with the value frequently quoted for fused silica. The volume fraction of the clusters in the saturated sonogels was estimated as about 28%. The moment in which the meniscus of the liquid phase penetrates into the clusters under rapid evaporation process has been detected by an inflection in the first derivative of the curve of weight loss in a simple thermogravimetric test.     

Computer Modelling of the Light Propagation through the Complex Anisotropy Systems - the way of a Determination of the Optical Parameters of the Liquid Crystal Displays

A mathematical and numerical method for an analysis of a liquid crystal displays (LCD) has been presented. The assumptions of the calculations of a light propagation through the display are shown. The real conditions of a work of these displays have been taken into account. Basing of this mathematical model a computer program for a numerical modelling of the optical parameters of LC displays working in real conditions has been worked out. This program makes possible to obtain the most important parameters of a display such as: contrast ratio, luminance in on- and off-state, spectral characteristics of light and its colour coordinates in these both states. The results obtained from this program have been verified experimentally. Very high conformity of these results has been obtained.     

Experimental Investigations of the Conditions for the Formation of the Liquid Crystalline State of Polymers

The diagrams of state for concentrated PBG solution in coordinates relating volume fraction-geometric asymmetry and volume fraction-temperature are investigated. The order parameter for macromolecules in the anisortropic phase is dettermined. The experimental data compare with the existing theoretical models for th formation of the liquid crystalline state in solutions of stiff polymer molecule. It is shown that experimental data are in good quantitative agreement with the Flory's lattice model.     

Influence of the Crystal Structure of the Nucleus on the Morphology of t-ZnO Tetrapods

Crystallography Reports - A new approach to simulating the morphology of hierarchical nanocrystals has been proposed on the example of ZnO nanotetrapods. Within this approach, twinning is...     

Features of the magnetic state of the layered Fe-V nanostructure of the superconductor-ferromagnet type

The magnetic state of the V(39 nm)/20 [V(3 nm)/Fe(3 nm)] nanostructure has been investigated by polarized neutron reflectometry in the temperature range from 1.6 to 30 K in magnetic fields from 0.2 to 15 kOe. The data obtained indicate that the superconductivity of vanadium layers may affect magnetic ordering both over the depth of the structure and in its plane.