水热合成法制备纳米磷灰石晶体比较研究

用水热合成方法在不同条件下制备了纳米级磷灰石晶体。结果表明：磷灰石晶体含有0H^-、CO3^2-、Na^ 、HPO4^2-离子；水热合成时温度越高，反应时间越长，磷灰石结晶度越高，晶体生长得更大更长；磷灰石沉积物老化时间越短，表面活性越高，水热处理时更容易生长成较大的晶体；压力条件下水热处理后的磷灰石晶体呈棒状，常压下水热处理的呈针状，且长径比较大。     

水热/溶剂热法形貌控制合成铜基微纳米晶体颗粒材料的研究进展

简述了利用水热/溶剂热法合成铜基微纳米晶体颗粒材料的最新研究进展。介绍了氧化亚铜、碱式碳酸铜、碱式钼酸铜、碱式氯化铜、碱式磷酸铜等铜基微纳米材料的合成方法。对铜基微纳米晶体颗粒材料生长机理和形貌控制合成进行了分析,获得了对铜基微纳米晶体颗粒材料生长规律的一般性认识,实现了在水热/溶剂热条件下对铜基微纳米晶体颗粒材料生长的形貌控制合成。     

氧化亚铜微纳米晶体形貌控制合成的研究进展

结合近些年国内外最新研究进展,按照球形、多面体、等级结构的顺序论述了不同形貌氧化亚铜晶体的合成方法。逐一介绍了不同形貌氧化亚铜的性质及其在不同领域的应用。其中,等级结构的氧化亚铜性能特殊,具有广阔的应用前景,将成为今后研究的热点。     

纳米Fe_3O_4/聚吡咯复合材料的形貌可控制备及电磁特性

为实现纳米Fe3O4/聚吡咯(PPy)复合材料的形貌可控合成,以十二烷基苯磺酸钠(NaDBS)为表面活性剂,运用乳液聚合方法制备了纳米Fe3O4/PPy复合材料。研究了体系中油相吡咯及表面活性剂用量对纳米Fe3O4/PPy复合材料表面形貌的影响规律,分析了纳米Fe3O4/PPy复合材料形貌与其电磁特性之间的关系。结果表明:吡咯用量的增加改变了体系中胶团的存在状态,使得纳米Fe3O4/PPy复合材料的形貌由草莓状向核-壳结构转变;体系中胶团的数量随着表面活性剂用量的改变发生变化,根据此规律调控了核-壳复合粒子内核的数量,从而得到了单核或多核的纳米Fe3O4/PPy复合材料。     

不同形貌TaCx晶须的制备及生长机理

通过不同的原料体系在合适的工艺条件下成功制备出碳化钽晶须（TaCx）。由Ta2O5-NaCl-C-Ni和Ta2O5-NaF-C-C12H22O11（蔗糖）体委制备的晶须呈平直的纤维形态，其生长机理为气-液-固（VLS）机制。由Ta2O5-KCl-C-Ni体系制备的晶须一部分通过VLS机理生长，而另一部分则通过LS机理生长，前者呈四方柱状，后者呈具有锥状柱体和之字形端部的特殊形貌。所有的原料体系均是在相近的工艺条件下进行，即反应温度1150-1350℃，氮气气氛保护。本工作对晶须的化学成分、形貌、晶体结构和生长机理进行了较详细的研究。     

ZrO_2纳米晶体形貌模拟及其最佳纳米尺度计算

采用量子化学计算软件Material Studio的Morphology模块BFDH法则模拟了四方氧化锆晶体生长稳定外形,并采用Castep模块的平面波基赝势法计算了ZrO2稳定外显的(101)、(110)、(002)面电子密度分布,以晶体模拟形貌像为基础,运用纳米计算方法通过对氧化锆不同纳米微粒总晶胞数、总原子数、表层活性原子及表层活性原子比例的计算,从晶体学理论角度确定了氧化锆纳米微粒的最佳纳米尺度为120nm。     

不同形貌CuO纳米粒子的制备与性能

采用CuSO4.5H2O、Cu(NO3)2、(CH2)6N4和NaOH为原料,采用沉淀法分别制备纤维状CuO纳米粒子和纺锤状CuO纳米粒子,用透射电镜和X射线衍射仪对产物的大小﹑形貌和组成进行表征;按质量比为9∶1的比例将黑索金分别与纤维状CuO纳米粒子和纺锤状CuO纳米粒子混合,对样品进行热失重测试分析,根据黑索金热分解温度的变化来衡量催化剂的活性。结果表明,采用沉淀法制备CuO纳米粒子时,反应温度、终点pH值对产物形貌有显著影响;不同形貌的CuO纳米粒子对黑索金的分解催化作用效果不同。     

反相微乳液法制备形貌可控的铁基纳米粒子

在反相微乳液体系中,用NaBH4还原FeCl2,合成Fe基纳米颗粒.采用TEM、FTIR、XRD和VSM分别对产物的粒径、形貌、物相和磁性能进行了表征.结果表明,改变表面活性剂AOT的浓度(n0)可以得到不同形貌的纳米粒子.同时,合成颗粒的表面被均匀地包覆了表面活性剂AOT,粒子的比饱和磁化强度为3.41×103 emu/kg,几乎无剩磁,具有顺磁性,可作为磁性能稳定的顺磁性材料.     

不同形貌ZnS纳米晶合成的研究进展

形貌及尺寸规整可控的ZnS纳米晶的合成是目前非常有发展前途的研究领域。按纳米维数、对不同形貌的ZnS纳米晶的合成方法进行了介绍和综述,并提出了它的发展方向。     

不同形貌ZnO微纳米材料的熔盐控制合成

ZnO是一种具有重要应用价值的半导体材料,近年来对它的合成研究成为关注的热点。基于此,在化学分解反应与化学合成反应两种不同路线下,通过简单的熔盐反应成功获得了不同形貌的ZnO微纳米材料。用X射线衍射仪(XRD)和扫描电子显微镜(SEM)分别对产物的结构和形貌进行了表征。同时,对其形成机理进行了简单的探讨。     

Single crystal growth,structure and properties of TlHgBr3

High-quality inclusion-free single crystals of ternary thallium mercury bromide, TlHgBr₃, were successfully grown by Bridgman–Stockbarger method. For the pristine surface of the TlHgBr₃ single crystal, X-ray photoelectron core-level and valence-band spectra were measured. The comparison on a common energy scale of the X-ray photoelectron valence-band spectrum of TlHgBr₃ and the X-ray emission Br Kβ₂ band, representing peculiarities of the energy distribution of the Br 4p states revealed that the main contribution of the valence Br p states, occurred in the upper portion of the valence band, with also their significant contributions in other valence band regions. It has been determined that TlHgBr₃ is a semiconductor with the bandgap energy value of E_g = 2.51 eV at 100 K. The E_g value decreased up to 2.44 eV when temperature increased to 300 K.     

Comparison for the crystal structure,synthesis and microwave dielectric properties of alkaline earth orthophosphates

A₃(PO₄)₂ compounds have different crystal structures when A sites are occupied by Ca or heavy alkaline earth metal atoms (Sr or Ba). The compounds with isomorphous crystal structure were synthesized by solid-state reaction method when the A-site atoms were Sr or Ba, and their crystal structure and microstructure of the sintered ceramics were investigated by X-ray powder diffraction (XRD) and scanning electron microscope (SEM), respectively. The microwave dielectric properties were measured using a network analyzer. It was found that Ba₃(PO₄)₂ could be sintered at 1060 °C, while the α-Sr₃(PO₄)₂ ceramics that has a smaller Sr²⁺ ionic radius, could be sintered at 1200 °C, and higher relative densities were obtained. The dielectric constant (?) of the α-Sr₃(PO₄)₂ is higher than that of Ba₃(PO₄)₂, but Ba₃(PO₄)₂ has a higher Q × f value than that of β-Ca₃(PO₄)₂ and α-Sr₃(PO₄)₂, which could be interpreted by the differences in ionic polarizability and bond strength. The temperature coefficients of resonant frequency (τ_f) for all samples with isomorphous crystal structure have positive values, ranging between +11 and +66 ppm °C⁻¹.     

Effects of precursors on the crystal structure and photoluminescence of CdS nanocrystalline

A series of cadmium sulfide (CdS) nanocrystalline were synthesized by precipitation from a mixture of aqueous solutions of cadmium salts and sulfur salts without adding any surface-termination agent. Their crystal structures and particle sizes were determined by X-ray diffraction (XRD). The CdS nanocrystalline precipitated from different precursors exhibited three cases: cubic phase, hexagonal phase and a hybrid of cubic and hexagonal phases. The photoluminescence (PL) of cadmium salt precursors and CdS nanocrystalline is also analyzed. Similar spectral band structure of cadmium salt precursors and CdS nanocrystalline is found. The PL of 3.4, 2.4 and 2.0 nm sized CdS nanocrystalline with the same crystal structure indicated quantum confinement effect.     

Relationship between mechanical properties and crystal structure in cocrystals and salt of paracetamol

Abstract

Objectives were to study mechanical properties of various solid forms of paracetamol and relate to their crystal structures. Paracetamol form I (PRA), its cocrystals with oxalic acid (PRA-OXA) and 4,4-bipyridine (PRA-BPY) and hydrochloride salt (PRA-HCL) were selected. Cocrystals and salt were scaled-up using rational crystallization methods. The resulting materials were subjected to different solid-state characterizations. The powders were sieved and 90–360?µm sieve fraction was considered. These powders were examined by scanning electron microscopy (SEM) and densities were determined. Tablets were made at applied pressures of 35–180?MPa under controlled conditions and the tablet height, diameter and hardness were measured. Tensile strength and porosity of the tablets were estimated using well known models. Crystal structures of these systems were visualized and slip planes were identified. Cocrystal and salt of PRA were physically pure. Sieved powders had comparable morphologies and particle size. The apparent and theoretical densities of powders were similar, but no clear trends were observed. The tensile strengths of these compacts were increased with increasing pressure whereas tabletability decreased in the order oxalic acid?>?PRA-HCL?≈?PRA-OXA?>?BPY?>?PRA-BPY. Tablet tensile strength decreases exponentially with increasing porosity with the exception of PRY-BPY and BPY. Slip plane prediction based on attachment energies may not be independently considered. However, it was possible to explain the improved mechanical properties of powders based on the crystal structure. Cocrystallization and salt formation have introduced structural features that are responsible for improved tableting properties of PRA.     

Crystalline structure and magnetic and magneto-optical properties of MnSbBi thin films

Mn–Sb–Bi thin films were prepared by successive r.f. or d.c. sputter deposition of elements in a trilayer configuration with either Bi or Sb as the first layer. In-situ transmission electron microscopy (TEM) observations were conducted to investigate the morphology and structure of the films, both as-deposited and after annealing at 623 K for 5 h in a high vacuum furnace. The morphology and structure of all the films are highly dependent on the first-deposited layer. For the annealed film in the configuration of Mn/Bi/Sb// a well-defined hexagonal Mn–Sb–Bi NiAs type structure with the c-axis perpendicular to the film surface was observed. The grain size (100 nm) was two times larger than that of the film having Bi as the first layer. In both kinds of film the easy direction of magnetisation was very close to the film plane. The polar Kerr rotation from the two film structures was approximately 1.0°.     

Crystal structure and magnetic properties of the compound FeDy6Sb2

The crystal structure of a compound FeDy₆Sb₂ was determined by X-ray powder diffraction using the Rietveld method. The compound crystallizes in the hexagonal, space group P6¯2m (No. 189) with the Fe₂P structure type and lattice parameters a = 0.81449(5) nm, c = 0.41641(3) nm, z = 1 and D_calc = 8.842 g/cm³. The maximum magnetic entropy change ΔS_M for the compound is 3.41 J kg^− 1 K^− 1 near its Curie temperature (143.4 K) on the magnetic field changes of 0-2.0 T.     

Preparation and electromagnetic wave absorption properties of hollow Co,Fe@air@Co and Fe@Co nanoparticles

In this study, hollow Co, Fe@air@Co and Fe@Co nanoparticles (NPs) have been synthesized respectively by electroless plating Co shell on Fe core and controlling reaction time based on galvanic cell reaction between Co shell and Fe core in hydrochloric acid at room temperature. The electromagnetic (EM) wave absorption properties of these three NPs are also been investigated. The results indicate that the relationship between Fe core and Co shell is critical to the EM wave absorption properties of hollow Co, Fe@air@Co and Fe@Co nanoparticles when blended with 70?wt% in paraffin-based samples. Fe@air@Co nanoparticles shows the best EM wave absorption properties with minimum reflection loss of ?42.75?dB and effective bandwidth of 4.1?GHz under ?10?dB. The present work has a significant potential for the development of EM wave absorbing materials with core-shell structure.     

The structure and optical properties of ZnO films on various LiNbO3 substrates

ZnO films thin films have been deposited on glass and three different LiNbO₃ (LNO) substrates at room temperature using radio frequency magnetron sputtering. The structure and optical properties of the films were investigated by X-ray diffraction (XRD), optical transmission spectroscopy and spectro-photometry. XRD analysis shows that all the films are hexagonal wurtzite structure, and there is compressive strain in the films. Typical optical transmittance values in the order of 80% were obtained for all the films, and the band gaps are in the range of 3.273-3.282 eV. The Photo-Luminescence (PL) spectra results indicate that the type of substrate affects the photoluminecence of ZnO films significantly, and the films on rotated Y-cut 128° LNO substrates have strong UV emission at room temperature.     

A study of the electromagnetic properties of Cobalt-multiwalled carbon nanotubes (Co-MWCNTs) composites

Electroless plating was utilized to deposit Cobalt (Co) on the surface of multi-walled carbon nanotubes (MWCNTs), and the technological parameters of electroless plating were optimized. To obtain optimized processing parameters, field-emission scanning electron microscope (FESEM) as well as energy dispersive spectroscopy (EDS) results were presented to show the morphology, components of as-prepared Co-MWCNTs. Based on the optimized processing parameters, Co-MWCNTs were prepared and filled into the epoxy resin to fabricate Co-MWCNTs composites. The electromagnetic properties of pure MWCNTs composites and Co-MWCNTs composites were studied. To sum up, the pure MWCNTs composites with a filler concentration of 2 wt% had an intense absorbing peak at 15.20 GHz, where the highest reflection loss (R) reached −21.41 dB. Compared to the pure MWCNTs composite at the same concentration, the Co-MWCNTs composites showed a higher impedance which implies a better potential absorbing property and makes Co-MWCNTs probable to be utilized in electromagnetic absorbing field.     

静压法合成含硼金刚石结构及电阻特性研究

采用在铁基触媒中加入硼铁粉的方法制成Fe-Ni-C-B系触媒,用静压法合成含硼金刚石。研究了含硼金刚石的形貌、晶体结构和电阻-温度曲线。实验结果表明,在不同温度区间内,金刚石具有不同的电离能,分析了其原因。同时测得此含硼金刚石的最高工作温度为773K左右。为高温半导体金刚石的研究提供了实验基础。