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1.
Hongrui Peng 《Materials Letters》2009,63(16):1404-1406
MnV2O6 nanostructures including nanorods, nanobelts, and nanosheets, have been synthesized by a facile hydrothermal reaction between Mn(CH3COO)2·4H2O and commercial V2O5. The synthesized products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The influences of synthetic parameters, such as, reaction time, temperature and medium, on the morphologies of the resulting products have been investigated. As the reaction temperatures increase from 120 °C to 180 °C, MnV2O6 nanorods and nanobelts are obtained, respectively. The time-dependent experimental results at 180 °C reveal that the sizes of MnV2O6 nanobelts increase gradually with the reaction proceeding. Interestingly, as the reaction is carried out with the aid of H2O2 solution, flower-like MnV2O6 nanosheets are formed. 相似文献
2.
Changyuan Hu Shuwang Duo Tingzhi Liu Wenkui Li Rongfa Zhang 《Materials Letters》2010,64(22):2472-2474
Anatase TiO2 coated multiwalled carbon nanotube (MWNT) nanocomposites were prepared by combining the sol-gel method with a self assembly technique at a low temperature. XRD, TEM, FTIR and XPS spectra were applied to characterize the crystal phase, microstructure, and other physicochemical properties of the sample. The results showed that MWNTs were covered with a 12-20 nm thickness layer of anatase TiO2 or surrounded by a 30 -290 nm thickness coating of anatase TiO2. The layer or coating is constructed of TiO2 nanoparticles about 5.8 nm. Furthermore, as-prepared composite was rich in surface hydroxyl groups. 相似文献
3.
In the present study the intestine-like binary SnO2/TiO2 hollow nanostructures are one-pot synthesized in aqueous phase at room temperature via a colloid seeded deposition process in which the intestine-like hollow SnO2 spheres and Ti(SO4)2 are used as colloid seeds and Ti-source, respectively. The novel core (SnO2 hollow sphere)-shell (TiO2) nanostructures possess a large surface area of 122 m2/g (calcined at 350 °C) and a high exposure of TiO2 surface. The structural change of TiO2 shell at different temperatures was investigated by means of X-ray diffraction and Raman spectroscopy. It was observed that the rutile TiO2 could form even at room temperature due to the presence of SnO2 core and the unique core-shell interaction. 相似文献
4.
A novel soft chemistry route (rheological phase reaction method) was developed to synthesize nanocrystalline NiFe2O4. The as-prepared samples were characterized by powder X-ray diffractometer (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The effects of the calcination temperature on the particle sizes and magnetic properties of the samples were investigated. The results indicated that the samples obtained by this method had the single-phase spinel. Particle sizes estimated from Scherrer's formula increased with the calcination temperature, which were consistent with the results of TEM. The magnetic properties of the samples were strongly affected by the calcination temperature. The coercivity initially increased and then decreased with increasing calcination temperature whereas the saturation magnetization continuously increased. 相似文献
5.
The complex fluorides Li2BeF4 and LiSrAlF6 were synthesized solvothermally at 180–240 °C and characterized by means of X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS). The different influence factors such as solvents, molar ratios of initial mixtures, reaction temperature and reaction time were investigated. The experimental results indicated that Li2BeF4 and LiSrAlF6 powders could be controllably synthesized in the solvothermal process. 相似文献
6.
Rice-like anatase TiO2 nanocrystals have been synthesized by hydrothermal treating Ti(OH)3 precursor in deionized water, which is easy to form in-situ a stable TiO2 aqueous dispersion and no post-synthetic purification process is required. The influences of synthetic parameters, such as reaction time and pH value, on the morphologies of the resulting nanocrystals have been investigated. It is found that the crystallinity and sizes of TiO2 nanocrystals increase with the reaction time increased. The pH value is important for controlling the sizes and shapes of TiO2 nanocrystals. As pH value increases from 2 to 11, spherical, rice-like, and rod-like TiO2 nanocrystals are obtained, respectively. The formation mechanism of rice-like anatase TiO2 nanocrystals is supposed to be a hydrothermal crystallization and Ostwald ripening process. 相似文献
7.
We report on the synthesis, structure and magnetic properties of a novel exchange bias system with Cr2O3/CrO2/Cr2O5 interfaces. Chromium oxide particles with mixed chromium valences were prepared by sintering CrO3 in air. X-ray diffraction patterns show that CrO3 lost its oxygen gradually with increasing temperature and time through Cr3O8, Cr2O5, CrO2, and finally Cr2O3 at temperatures above 760 K. X-ray photoelectron spectra indicate a low CrO2 content and a binding energy of 579.3 eV for Cr 2p3/2 photoelectrons in Cr2O5. Chromium dioxide was found to stably coexist with Cr2O3 and Cr2O5 in the particles. Magnetic measurements show hysteresis loop shifts in the sample, indicating an exchange bias induced by antiferromagnetic Cr2O3/Cr2O5 in ferromagnetic CrO2. An exchange bias of 9 mT at 5 K and a coercivity of 26.3 mT were observed in the chromium oxide particles containing CrO2. 相似文献
8.
Intermetallic compound superconductor MgB2 was synthesized from spherical magnesium powder and lower purity amorphous boron powder by microwave direct heating. Powder X-ray diffraction (XRD) analysis indicates that the phases of the synthesis sample are MgB2 (major phase) and a small amount of MgO. Scanning electron microscope (SEM) observation shows that the MgB2 grain size is homogeneous and the particle size is about several hundreds of nanometers. The onset superconducting transition temperature of the MgB2 sample measured by the temperature dependence of magnetization measurement is about 37.6 K. The critical current density Jc calculated according to the Bean model are about 2.0 × 105 A/cm2 at 20 K in self-field and 1.0 × 105 A/cm2 at 20 K in 1 T applied field. 相似文献
9.
WO3 nanowires were fabricated by a hydrothermal method in the presence of K2SO4. The nanowires exhibit a well crystallized one-dimensional structure with 10 nm in diameter and several microns in length. Effects of other alkali salts (KNO3, NaNO3 and Na2SO4) on the morphologies of WO3 nanocrystals were also investigated. The important role of K2SO4 salt in the WO3 nanowires synthesis has been demonstrated. 相似文献
10.
Stefan Wiechmann 《Thin solid films》2009,517(24):6847-1504
The direct measurement of the thermo-optic coefficients of aluminium oxide, tantalum pentoxide and titanium dioxide thin films is presented. Using ellipsometry on monolithically integrated permutations of the layers of silicon, silicon dioxide and the material under test, allows the direct measurement of the overall thermo-optic coefficient accounting for thermally induced changes in the dielectric permittivity and density of the materials as well as the elasto-optic effect due to the non-matching thermal expansion coefficients of the different materials. 相似文献
11.
CeO2 nano-octahedrons were synthesized with a facile hydrothermal synthesis process where Ce(NO3)3·6H2O and urea were used as a cerium resource and mineralizer respectively and no surfactant or template was applied. The effects of synthesis parameters such as reaction temperature, reaction time, as well as the dosages of Ce (NO3)3·6H2O and urea were studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis were conducted to characterize the crystalline and morphology of the obtained CeO2 powders. The optimal reaction condition to prepare the CeO2 of the desired fluorite structure was established. The possible mechanism of synthesis of CeO2 with a nano-octahedron morphology was illustrated. 相似文献
12.
A novel preparation method to synthesize TiO2/SnO2 nanocrystalline sol under mild conditions was presented. Ti(OC4H9)4 used as a precursor was hydrolyzed in the rutile SnO2 nanocrystalline sol, and in-situ formed TiO2/SnO2 nanocrystalline sol. The crystal structure, morphology and photocatalysis performance of samples were investigated. The results show that the additional rutile SnO2 nano grains serve as heterogeneous crystal nucleus and exhibite the inducing effect on TiO2 grains growth, thus leading to the changes in crystalline phase and particle morphology. In addition, the photoluminescence (PL) spectra analysis indicates that TiO2/SnO2 composite structure induces a better charge separation, and thus the photocatalytic activity of TiO2/SnO2 sol is increased significantly compared with TiO2 sol. 相似文献
13.
采用超声辅助溶胶凝胶法制备了LaFeO3颗粒,进一步以碳纳米管(CNTs)为基底和钛酸丁酯为前体,通过一步水热法煅烧合成CNTs/TiO2/LaFeO3(CTF)三元异质结光催化复合材料。通过扫描电子显微镜(SEM)、X射线衍射分析(XRD)、氮气吸附-解吸等温线(BET)、紫外-可见分光光度计(UV-Vis)、光致发光光谱(PL)等表征手段对材料的形貌与特征结构、比表面积和孔径结构以及光学特征进行了分析,并在紫外光下通过降解活性黑五(RB5)测试样品的光催化性能。结果表明,以CNTs作为载体,能够有效提升LaFeO3/TiO2复合材料的光催化性能。当CNTs在复合材料中的质量占比为5%时,150 W汞灯照射下RB5的50 min去除率可达99.5%。CNTs一方面通过增加复合材料的比较面积为催化反应的进行提供了更多的活性位点,更为重要的是,CNTs作为光生载流子传输的通道加快了电荷分离效率,提升了复合材料的降解能力和催化反应动力学进程。 相似文献
14.
Qing Yang Miyoko TanakaShuhua Liang Kazuki OginoHiromichi Fujii Akihiro IshidaHirokazu Tatsuoka 《Thin solid films》2011,519(24):8538-8541
ZrO2/SiOx core/shell nanofibers with diameter ~ 50 nm were synthesized by the thermal oxidation of ZrSi2 substrates with gallium. The crystalline ZrO2 cores were grown with amorphous SiOx shells. It is proposed that the growth of crystalline ZrO2 core was guided by the prior supersaturation of Zr species in the molten gallium film, whereas the amorphous SiOx shell could be attributed to the deposition of SiO vapor on the surface of ZrO2 core. In addition, the ZrO2/SiOx core/shell nanofibers show a wide visible photoluminescence (PL) emission at 480 nm, which should originate from the SiOx shells. 相似文献
15.
Catalytic photodegradation of organic contaminants by means of UV light has been demonstrated for gas sensors based on composites of TiO2-SnO2. Thin film resistive-type gas sensors of TiO2-SnO2 have been deposited at 350 °C by RF sputtering from a Ti-SnO2 target with varying surface ratio of SnO2/Ti. Photodegradation experiments of bromothymol blue by UV light have been performed by means of the optical spectrophotometry over the wavelength range extending from 300 nm to 600 nm. The influence of the UV illumination on the sensor response to 100-20,000 ppm of H2 has been investigated in situ on motor oil contaminated sensors. It has been found that sequential exposures to UV light lead to a partial recovery of the sensor signal to hydrogen. 相似文献
16.
较差的光催化产氢效率极大地阻碍了TiO2光催化剂的工业化应用。为此,本文在含有NH4VO3的磷酸盐溶液中,采用等离子体电解氧化(PEO)法制备了多孔TiO2/V2O5复合膜光催化剂,通过扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射(XRD)、X射线光电子谱(XPS)和紫外可见漫反射光谱(UV-Vis DRS)对其组成、结构及光吸收性质进行了表征,并采用气相色谱评价了薄膜催化剂的光催化产氢性能,研究了电解液中NH4VO3含量对膜的结构、组成和光催化产氢性能的影响。结果表明:复合膜催化剂主要由锐钛矿和金红石型TiO2组成,具有微孔结构,V2O5主要以无定形形式存在于膜中,与TiO2有很强的相互作用,影响TiO2的晶面间距。研究发现,元素V抑制了TiO2的结晶和金红石型TiO2的形成,扩大了薄膜的光学吸收范围。针对Na2S+ Na2SO3溶液中的光催化产氢性能的研究显示,在质量浓度为1 g/L NH4VO3的电解液中制备的TiO2/V2O5薄膜的光催化活性最高,优于近年来报道的其他光催化剂。光催化重复实验表明,该复合膜催化剂具有较高的稳定性和较为恒定的光催化活性。 相似文献
17.
The electronic energy levels of the six-coordinated Mn4+ ion in the pyrochlores Y2B2O7 (B = Sn4+, Ti4+) have been computed using the exchange charge model of crystal field theory. The calculated Mn4+ energy levels and their trigonal splitting are in good agreement with the experimental spectra. The calculated crystal field parameters show that the higher crystal field strength in Y2Sn2O7 arises from an increased orbital overlap effect between the Mn4+ ion and the nearest oxygen ions, which are located at the 48f crystallographic position of the pyrochlore lattice. This increased overlap in Y2Sn2O7 occurs despite the fact that the Mn4+-O2− bond distance in Y2Sn2O7 is longer than in Y2Ti2O7 and is attributed to a lack of hybridization (covalent bonding) between the filled 2p orbital of oxygen ion occupying the 48f site of the pyrochlore lattice and the filled Sn4+ 4d10 orbital. The low temperature emission spectrum of Mn4+ activated Y2Sn2O7 is analyzed in terms of a weak zero phonon line (R-line) with accompanying vibrational side bands. 相似文献
18.
Cu2SnSe3 thin films were prepared by single-step D.C. sputtering at 100-400 °C for 3 h using targets composed of Cu2Se and SnSe2 in three different ratios of 2/1 (target A), 1.8/1 (target B), and 1.6/1 (target C). The advantages of self-synthesized SnSe2 instead of commercially available SnSe for depositing Cu2SnSe3 thin films were demonstrated. Effects of target composition and substrate temperature on the properties of Cu2SnSe3 thin films were investigated. Structure, surface morphology, composition, electrical and optical properties at different process conditions were measured. The 400 °C-sputtered films obtained from target B display with direct band gap of 0.76 eV, electrical resistivity of 0.12 Ω cm, absorption coefficient of 104-105 cm− 1, carrier concentration of ∼ 1.8 × 1019 cm− 3, and electrical mobility of 2.9 cm2/V s. 相似文献
19.
The microstructure of thin HfO2-Al2O3 nanolaminate high κ dielectric stacks grown by atomic vapor deposition has been studied by attenuated total reflection spectroscopy (ATR) and 8 eV spectroscopic ellipsometry (SE). The presence of Al2O3 below HfO2 prevents the crystallisation of HfO2 if an appropriate thickness is used, which depends on the HfO2 thickness. A thicker Al2O3 is required for thicker HfO2 layers. If crystallisation does occur, we show that the HfO2 signature in both ATR and 8 eV SE spectra allows the detection of monoclinic crystallites embedded in an amorphous phase. 相似文献
20.
CuInS2 and CuGaS2 thin films have been prepared sequentially from elemental evaporation sources onto conventional soda lime glass substrates heated at 350 °C during the deposition process. The gradient in the structure and composition of the stacked layers has been investigated for the two possible growth sequences. Structural depth profiling and crystallographic phase analysis were performed by grazing incidence X-ray diffraction. The atomic distribution in the films depth was analyzed by X-ray photoelectron spectroscopy combined with sputter etching. Formation of the quaternary compound CuIn1 − xGaxS2, with a high Ga content x > 0.80, has been detected with different distribution depending on the growth sequence. 相似文献