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1.
通过脉冲电沉积,外延生长出小单元长度的Bi2Te3/Sb超晶格纳米线.借助哈曼方法,测量了超晶格纳米线阵列的热电性能,330 K时的ZT值可达0.15.研究了Bi2Te3/Sb超晶格纳米线阵列器件的制冷或者加热能力,发现器件的上下表面的最大温差可以达到6.6 K.  相似文献   

2.
Bi2O2CO3 nanosheet with a thickness of less than 20 nm was synthesized via hydrothermal and solvothermal process. The properties of the as-prepared nanosheet were characterized by X-ray diffraction, scanning electron microscopy, and diffuse reflectance spectra. The electronic structure was investigated using first-principle calculations. Application of the as-prepared Bi2O2CO3 nanosheet in photocatalysis was also studied.  相似文献   

3.
Al2O3 /TiN double and Al2O3/Cr/TiN triple coatings were produced on stainless steel substrates using plasma-detonation techniques. Investigation of the microstructure and characteristics of the coatings after the preparation was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). The corrosion resistance of the coatings was studied in several electrolytic solutions (0.5 M H2SO4, 1 M HCl, 0.75 M NaCl) using electrochemical techniques (open circuit potential, cyclovoltammetry and potentiodynamic polarization). The obtained results showed, in most of the cases, an improvement of the corrosion resistance, except in NaCl solutions. The effect of the controlled thickness of TiN and Cr layers as well as the additional treatment with a high-current electron beam was also investigated. Nuclear reaction analysis (NRA), Rutherford backscattering spectroscopy (RBS) and scanning electron microscopy (SEM) were applied for the characterization of the samples before and after the corrosion experiments.  相似文献   

4.
Hui Li 《哲学杂志》2016,96(6):551-559
The microstructure features of carbides precipitated at twin boundary and Σ9 grain boundary (GB) in nickel-based Alloy 600 after aging at 715?°C for different time were investigated by high-resolution transmission electron microscopy. The carbides precipitated at incoherent twin boundary and Σ9 GB were identified as M23C6. The bar-like carbides grow parallel to each other and into each side of grain nearby incoherent twin boundary, while only growth into one side nearby Σ9 GB is observed. The carbides precipitated at incoherent twin and Σ9 GBs contain twins. The carbides have (1?1?1) matrix // (1?1?1) M23C6 orientation relationship with the nearby matrix. Based on the experimental results, the formation of twinning microstructure features in the M23C6 is discussed.  相似文献   

5.
采用固相合成工艺,制备了Bi05Ba05Fe05Ti049Nb001O3(BBFTN)热敏陶瓷,借助X射线衍射仪、扫描电子显微镜、阻温测试仪和交流阻抗谱考察其微结构、直流电阻、介电特性、阻抗和电学模量方面的电学性能. 结果表明:BBFTN材料依然为立方钙钛矿结构,平均晶粒尺寸约为10 μm,晶格常数相对于BaTiO3的晶格常数有所变大;室温电 关键词: 05Ba05Fe05Ti049Nb001O3')" href="#">Bi05Ba05Fe05Ti049Nb001O3 微结构 电学性能  相似文献   

6.
周传仓  刘发民  丁芃  蔡鲁刚  钟文武  张嬛 《中国物理 B》2010,19(6):67503-067503
Brannerite MnV 2 O 6 with plate-like shape is successfully synthesized by hydrothermal method.Its crystal structure and morphology are investigated by x-ray diffraction (XRD),scanning electron microscopy (SEM),transmission electron microscope (TEM),high resolution transmission electron microscopy (HRTEM) and select area electronic diffraction (SAED).The results show that the brannerite MnV 2 O 6 with monoclinic structure has a uniform plate-like shape with a diameter of about 5-8 μm and a thickness of about 500 nm.SAED patterns further confirm the structure of the brannerite MnV 2 O 6 and the single crystalline character of the plate crystal.Magnetic properties are measured by superconducting quantum interference device (SQUID) in a temperature range of 2-300 K under a magnetic field of 1 T.The magnetic measurement results indicate that the material undergoes an antiferromagnetic transition with a N’eel temperature of 17 K.Above 50 K,the inverse susceptibility is fitted well to the Curie-Weiss law with a calculated moment of 5.98 μ B.Finally,the origin of antiferromagnetic behaviour in the brannerite MnV 2 O 6 is explained by means of Anderson model.  相似文献   

7.
Thin films of pure TiO2 have been prepared using both spin-coating and sputter-deposition techniques on sapphire and quartz substrates. The structural characteristics of the films have been investigated in detail using Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM). When annealed in vacuum, all films demonstrate room temperature ferromagnetism, while the air-annealed samples show much smaller, often negligible, magnetic moments. The magnetization of the vacuum-annealed sputtered samples depends on film thickness, with the volume magnetization decreasing monotonically with increasing thickness. Furthermore, the magnetization per unit area also decreases slightly with increasing film thickness. These results suggest that ferromagnetism in the vacuum-annealed TiO2 films is mediated by surface defects or interfacial effects, but does not arise from stoichiometric crystalline TiO2.  相似文献   

8.
High-k polycrystalline Pr2O3 and amorphous LaAlO3 oxide thin films deposited on Si(0 0 1) are studied. The microstructure is investigated using X-ray diffraction and scanning electron microscopy. Optical properties are determined in the 0.75-6.5 eV photon energy range using spectroscopic ellipsometry. The polycrystalline Pr2O3 films have an optical gap of 3.86 eV and a dielectric constant of 16-26, which increases with film thickness. Similarly, very thin amorphous LaAlO3 films have the optical gap of 5.8 eV, and a dielectric constant below 14 which also increases with film thickness. The lower dielectric constant compared to crystalline material is an intrinsic characteristic of amorphous films.  相似文献   

9.
A novel one‐dimensional electromagnetic nanocomposite of polypyrrole (PPY) containing carbon nanotubes (CNTs)/Ni0.75Zn0.25Fe2O4 was synthesized by an in‐situ polymerization method. The composite was characterized by x‐ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and Fourier transform infrared. The XRD results confirmed that PPY, CNTs, and Ni0.75Zn0.25Fe2O4 coexisted in the composite. The TEM and HRTEM results indicated that PPY coated the surface of the CNTs/Ni0.75Zn0.25Fe2O4 with a thickness of 15–30 nm. The lattice spacings, according to the first main peak of the CNTs, Ni0.75Zn0.25Fe2O4, and PPY, was about 0.34 nm, 0.25 nm, and 0.42 nm, respectively. The FTIR result also indicated that the PPY formed in the composite. A test of magnetic properties indicated that the composite was ferromagnetic with the saturated magnetization of 12.86 electromagnetic units (emu)/g, and the coercive of 127.18 Oersted (Oe).  相似文献   

10.
Beta-gallium oxide (β-Ga2O3) nanobelts were synthesized through microwave plasma chemical vapor deposition (MPCVD) of liquid-phase gallium containing H2O in Ar atmosphere using silicon as the substrate. Unlike the common microwave plasma method, the H2O, not mixture of the gas, was employed to synthesize the nanostructures. β-Ga2O3 nanobelts prepared by MPCVD have not been reported. The thickness of β-Ga2O3 nonobelts was 20–30 nm and length of them was tens to hundreds of microns. The morphology and structure of the products were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Possible growth mechanisms of the β-Ga2O3 nanobelts are briefly discussed.  相似文献   

11.
Well-defined flower-like Cd(OH)2 microstructures have been successfully synthesized via a simple aqueous solution route, using CdCl2 and NaOH as the reactants, and triethanolamine (TEA) as the modifying agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis spectrometer were used to characterize the products. SEM and TEM images illustrated that the flower-like Cd(OH)2 bundles consisted of hexagonal nanoplates with thickness of about 50 nm. The adsorption of TEA on (0 0 1) plane of the growing Cd(OH)2 crystal leads to the flower petals in appearance. Further experiments evidenced that the positively charged Cd(OH)2 could effectively adsorb or separate the negatively charged dye molecules.  相似文献   

12.
ZnGa2O4:Cr3+ thin films with bright red emission were synthesized using a sol-gel process, characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Auger electron spectroscopy (AES) and UV-vis and fluorescence spectrophotometry measurements. Effects of calcining temperature, film thickness, calcining duration and substrates on the crystal structure and photoluminescent property have been investigated. It is found that the crystallinity, Ga/Zn ratio and band gap energy (Eg) are significant factors influencing optical characteristics, while the nature of substrates affect the surface morphologies of ZnGa2O4:Cr3+ thin films.  相似文献   

13.
InAs0.6P0.4 epilayers grown on InP (100) substrates using two-step growth method by LP-MOCVD were investigated. A low temperature (450 °C) In0.18Ga0.82As buffer layer was introduced to relax the lattice mismatch between the InAs0.6P0.4 epilayer and the InP substrate. The influence of In0.18Ga0.82As buffer layer thickness and epilayer’s growth temperature on crystalline quality of InAs0.6P0.4 epilayer was characterized by Scanning electron microscopy, X-ray diffraction, Hall measurements, Transmission electron microscopy and Photoluminescence. The experimental results showed that the crystalline quality of InAs0.6P0.4 epilayers could be greatly improved by optimizing the In0.82Ga0.18As buffer layer thicknesses and the InAs0.6P0.4 epilayer’s growth temperatures. It was found that, when In0.82Ga0.18As buffer layer thickness was 100 nm and InAs0.6P0.4 epilayer’s growth temperature was 580 °C, the InAs0.6P0.4 epilayer exhibited the best crystalline quality and properties.  相似文献   

14.
Superconducting MgB2 thick film has been prepared via hybrid physical-chemical vapor deposition method on Al2O3 (0001) substrate by using B2H6 and magnesium ingot as raw materials reacted from 730 to 830°C for 40 min under 20 to 30 kPa. Its thickness is about 40 μm. The MgB2 thick film shows T c (onset) = 39.0 K and T c (0) = 37.2 K. X-ray diffraction pattern shows that the film grown along (101) direction has small amount of impurities of Mg and MgO. Scanning electron microscopy and energy dispersive X-ray spectroscopy indicated that these impurities existed indeed and were Mg rich. The MgO film was formed on the surface of the MgB2 thick film to further protect the sample from oxidation. We presented a new mechanism for the formation of the thick film. Translated from Chinese Journal of Low Temperature Physics, 2005, 27(1) (in Chinese)  相似文献   

15.
Single-phase β-FeSi2 films on silicon (1 0 0) were fabricated by pulse laser deposition. The structure and crystal quality of the samples were characterized by X-ray diffraction and Fourier transform infrared spectroscopy. The field scanning electron microscopy showed that the film thickness increases with the increasing of the laser fluence. Moreover, atomic force microscopy observations revealed the changes of surface properties with different laser fluence. Based upon all experimental results, it is found that 7 J/cm2 is the most favorable for the formation of β-FeSi2 thin films.  相似文献   

16.
Fully-surrounded Zn3P2/ZnS core/shell nanowires (NWs) were synthesized for the first time via a two-step method: a catalyst free chemical vapor deposition followed by a low-pressure vulcanization process. Field emission scanning electron microscopy, high-resolution transmission electron microscopy, and high-angle angular dark field scanning transmission electron microscopy were used to characterize the morphologies, crystal structure, and element composition of the core/shell NWs. The band structure analysis demonstrates that the Zn3P2/ZnS core-shell NW type-II heterostructures have bright potential in photovoltaic nanodevice applications. The core/shell NW growth method used here can be extended to other material system.  相似文献   

17.
周传仓  刘发民  丁芃 《中国物理 B》2009,18(11):5055-5060
β-Mn2V2O7 crystals with strip shape are successfully prepared by the molten salt method in a closed crucible,and are characterized by x-ray diffraction (XRD),scanning electron microscopy (SEM),transmission electron microscopy (TEM),selected area of electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM).The results indicate that the sample is of the β-Mn2V2O7 crystal with monoclinic symmetry,level natural cleavage facets and directional growth.Magnetic properties are measured by vibration sample magnetometry (VSM) at room temperature,and the magnetic hysteresis loop indicates that the β-Mn2V2O7 has anti-ferromagnetic properties with low coercive force and remnant magnetization.The magnetic measurement results in different directions exhibit that the β-Mn2V2O7 has magnetic anisotropy,which is due to the fact that the magnetic interaction energy of the β-Mn2V2O7 is lowest only when the electron configuration is in a certain direction.  相似文献   

18.
研究了Si3N4层在ZrN/Si3N4纳米多层膜中的晶化现象及其对多层膜微结构与力学性能的影响. 一系列不同Si3N4层厚度的ZrN/Si3N4纳米多层膜通过反应磁控溅射法制备. 利用X射线衍射仪、高分辨透射电子显微镜和微力学探针表征了多层膜的微结构和力学性能. 结果表明,由于受到ZrN调制层晶体结构的模板作用,溅射条件下以非晶态存在的Si3N4层在其厚度小于0.9 nm时被强制晶化为NaCl结构的赝晶体,ZrN/Si3N4纳米多层膜形成共格外延生长的柱状晶,并相应地产生硬度升高的超硬效应. Si3N4随层厚的进一步增加又转变为非晶态,多层膜的共格生长结构因而受到破坏,其硬度也随之降低.  相似文献   

19.
It is difficult to obtain the crystallographic alignment for stoichiometric Nd2Fe14B alloys by applying the melt-spun and subsequent hot-pressing and hot-deformation techniques. However, the enhanced alignment and magnetic properties of die-upset nano-crystal Nd2Fe14B magnets have been obtained by Nb addition in the present paper. The magnetic properties studies show that Nb addition leads to the remarkable increase of remanence Br and intrinsic coercivity Hci, which is due to the improvement of c-axis texture and refinement of microstructure. Microstructure studies using transmission electron microscopy (TEM) and X-ray diffraction (XRD) reveal that Nb atoms are enriched at grain boundary and the NbFeB phase is observed with increasing Nb content. Since some Fe atoms in the Nd2Fe14B phase participate in the formation of NbFeB phase, the excessive Nd atoms may be enriched at grain boundary, which may improve the physical property of grain boundary and provide a mass transport pass for preferential growth of oriented Nd2Fe14B grains, thus leading to the enhanced alignment and magnetic properties.  相似文献   

20.
By using top seeding melt-textured growth process, single domain GdBa2Cu3O7−δ bulk superconductor has been fabricated successfully in growth with the additions of two Nd2BaCuO5 (Nd123) seeds. Both microstructure and superconducting properties were investigated from the seed position to the boundary of the sample. The experiments showed the enhanced superconducting properties such as the critical current density (Jc) and the irreversibility (Birr) in the edge of the domain and the part between two seeds. The additions of two Nd123 seeds accumulate the richer Gd2BaCuO5 inclusion particles and improve the Jc at the edge of single domain, which is confirmed by scanning electron microscopy.  相似文献   

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