共查询到20条相似文献,搜索用时 31 毫秒
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以TiCl4和BaCl2为主要原料,用微波法一步成功合成纳米BaTiO3,采用X射线衍射谱(XRD)、扫描电镜(SEM)、漫反射吸收谱(DRS)、介电常数谱和热重一差热分析(TG-DTA)表征,XRD和SEM分析表明,合成的BaTiO3为纯的立方相纳米BaTiO3,颗粒大小均匀,分散性好,晶粒粒径在90nm左右;DRS和介电常数测试表明,纳米BaTiO3禁带宽度为3.4eV,具有良好的介电性能;TG-DTA和XRD测试表明,在400℃以前,纳米BaTiO3表面吸附的残余有机物质燃烧放热,有l-4%左右的热失重,对应在290℃左右有较强的放热峰;1000℃煅烧后才有部分立方相的BaTiO3转化成了四方相的BaTiO3,纳米BaTi03表现出了良好的热稳定性。 相似文献
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ZrO2 powder was prepared by the gel combustion technique using citric acid as a fuel and nitrate as an oxidant. Calcination at 600 °C of the dried powder, obtained after sluggish combustion of the citrate–nitrate gel, produced nanocrystalline ZrO2 powder. The Rietveld refinement of the powder XRD data clearly suggested the presence of predominantly tetragonal phase of zirconia. TEM studies showed the agglomerated powder composed of nearly spherical nanocrystals of about 10 nm. The absence of cubic phase of zirconia was conclusively inferred by Raman spectroscopy. 相似文献
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S. Jayakumar P.V. AnanthapadmanabhanK. Perumal T.K. ThiyagarajanS.C. Mishra L.T. SuA.I.Y. Tok J. Guo 《Materials Science and Engineering: B》2011,176(12):894-899
Nano-crystalline ZrO2 powder has been synthesized via reactive plasma processing. The synthesized ZrO2 powders were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and FTIR spectroscopy. The synthesized powder consists of a mixture of tetragonal and monoclinic phases of zirconia. Average crystallite size calculated from the XRD pattern shows that particles with crystallite size 20 nm or less than 20 nm are in tetragonal phase, whereas particles greater than 20 nm are in the monoclinic phase. TEM results show that particles have spherical morphology with maximum percentage of particles distributed in a narrow size from about 15 nm to 30 nm. 相似文献
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Buscaglia MT Buscaglia V Viviani M Dondero G Röhrig S Rüdiger A Nanni P 《Nanotechnology》2008,19(22):225602
Hollow particles of barium titanate were obtained by a two-step process combining colloidal chemistry and solid-state reaction. BaCO(3) crystals (size ≈1?μm) suspended in a peroxy-Ti(IV) aqueous solution were coated with an amorphous TiO(2) shell using a precipitation process. Calcination of the BaCO(3)@TiO(2) core-shell particles at 700?°C resulted in the formation of BaTiO(3) hollow particles (shell thickness of ≈70?nm) which retain the morphology of the BaCO(3) crystals. Formation of the cavity occurs because out-diffusion of the core phase is much faster than in-diffusion of the shell material. X-ray diffraction (XRD) and Raman spectroscopy indicate that the hollow particles possess a tetragonal ferroelectric structure with axial ratio c/a = 1.005. Piezoresponse force microscopy has shown strong piezoactivity and 180° ferroelectric domains. The process described provides a general route to fabricate hollow ferroelectric structures of several compounds. 相似文献
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A novel route was developed to prepare PbS and HgS nanocrystals in ethanol solvent in the presence of sodium hydroxide by microwave heating method. PbS and HgS nanocrystals were obtained with an average size of approximately 10 and 6 nm, respectively. In the reaction, mercury acetate and lead acetate were used as mercury and lead source; sulfur powder was employed as chalcogenide source. The products were characterized by X-ray powder analysis (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–Vis absorption spectroscopy. The probable mechanism was presented. 相似文献
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Anwar MS Kumar S Ahmed F Arshi N Lee CG Koo BH 《Journal of nanoscience and nanotechnology》2012,12(2):1555-1558
Sphere-like rutile TiO2 nanocrystals have been synthesized by sol-gel method followed by hydrolysis of titanium tetrachloride in deionized water in the presence of ammonium hydroxide as hydrolysis catalyst. The as-prepared TiO2 nanoparticles have single rutile phase with average diameter approximately 26.4 nm. The results show that the temperature has a great influence on the particle size distribution and also crystalline phase (rutile) of TiO2 nanoparticles is consistent with the temperature. Characterization of the as-prepared nanocrystalline powder was carried out by different techniques such as powder X-ray diffraction (XRD), field emission transmission electron microscopy (FE-TEM) and Raman spectroscopy. 相似文献
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Synthetic calcium deficient hydroxyapatite (CDHA) nanorods (<100?nm) were rapidly prepared with the help of a new continuous microwave assisted flow synthesis (CMFS) reactor in 5?min only from aqueous solution of calcium hydroxide and orthophosphoric acid at pH 8.5. The effect of various reaction parameters like, pH, concentration, temperature, residence time, degree of crystallinity and particle surface area were studied in detail. The phase purity, particle size and morphology of the powder samples were characterised by techniques such as X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy and FTIR and Raman spectroscopy. With the help of X-ray photoelectron spectroscopy, the chemical analysis was completed. Measurements were taken into account to estimate the particle size following the dynamic light scattering. The results showed that the employed synthesis procedure offered an efficient and economical route to achieve high quality nano-sized products with suitable size and low level of impurities. 相似文献
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《Materials Letters》2006,60(9-10):1170-1173
Nano sized zirconia (ZrO2) powders doped with different amount of yttria (Y2O3) (3, 5 and 8 mol%) were prepared through coprecipitation method. The crystallite size estimated from the X-ray peak broadening is around 10 nm. Phase identification was carried out using XRD and Raman spectroscopy. Raman spectroscopic study of the synthesized materials show clear evidence of the presence of single phase cubic structure in the case of 8 mol% Y2O3 doped fully stabilized zirconia (8Y-FSZ); tetragonal phase in the case of zirconia doped with 3 mol% Y2O3 (3Y-TZP-tetragonal zirconia polycrystal) and a mixture of cubic and tetragonal phases for 5 mol% Y2O3 doped partially stabilized zirconia (5Y-PSZ). Raman technique is therefore an effective tool to distinguish the phases present in the calcined nano sized powders of zirconia. 相似文献
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Patra CR Patra S Gabashvili A Mastai Y Koltypin Y Gedanken A Palchik V Slifkin MA 《Journal of nanoscience and nanotechnology》2006,6(3):845-851
In this article, a simple microwave route was applied for the synthesis of nanoflakes and dendrite-type beta-indium sulfide (In2S3) in high yield (> 97%), using a homogeneous mixture of indium(lll)chloride and thiourea in an ethylene glycol (EG)/polyethylene glycol (PEG400) solvent. The reaction was conducted in a simple domestic microwave oven (DMO). Powder X-ray diffraction (XRD), low resolution and high resolution transmission electron microscopy (LRTEM and HRTEM), selected area electron diffraction (SAED), and energy dispersive X-ray spectroscopy (EDS), were applied to investigate the crystallinity, structure, morphology, and composition of the In2S3 nano-materials. Both the as-synthesized and calcined In2S3 products were a body-centered tetragonal (bct) phase, observed by XRD and HRTEM. The length and width of the resulting nanoflakes were in the range of 70-600 nm and 4-10 nm, respectively. The optical band gap of the powder was determined by diffuse reflectance spectroscopy (DRS) and was found to be 2.44 eV. The electronic properties of the products were studied by measuring the optical absorption spectra using photoacoustic spectroscopy. The band gap calculated by this method was found to be 2.52 eV. A possible mechanism for the formation of nanoflakes/dendrites-type In2S3 was also discussed. 相似文献
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Ahmed F Kumar S Arshi N Anwar MS Kim GW Heo SN Byon ES Lee SH Lyu NJ Koo BH 《Journal of nanoscience and nanotechnology》2012,12(7):5464-5468
We report the synthesis of pure and Mn doped ZnO in the form of nanosheets using a simple and single step procedure involving a microwave assisted chemical method. As prepared Mn-doped ZnO nanosheets were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultra violet-visible (UV-Vis), Raman spectroscopy and magnetization measurements. The structural studies using XRD and TEM revealed the absence of Mn-related secondary phases and showed that Mn-doped ZnO comprise a single phase nature with wurtzite structure. FESEM and TEM micrographs show that the average diameter of Mn-ZnO assembled nanosheets is about approximately 50 nm, and the length of a Mn-doped ZnO nanosheet building block which is made up of thin mutilayered sheets is around approximately 300 nm. Concerning the Raman scattering spectra, the shift in peak position of E2 (high) mode toward low frequencies due to the Mn doping could be explained well by means of the spatial correlation model. Magnetic measurements showed that Mn-doped ZnO nanosheets exhibit ferromagnetic ordering at or above room temperature. 相似文献
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E. Thamarai Selvi S. Meenakshi Sundar 《Journal of Materials Science: Materials in Electronics》2018,29(1):38-48
Ni-doped SnO2 nanoparticles were synthesized by the microwave oven assisted solvothermal method. The structural characterization was done by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy. The outcomes confirmed that Ni-doped SnO2 nanoparticles have a pure rutile-type tetragonal phase of SnO2 structures with a high degree of crystallization and a crystallite size of 10–14 nm. Popcorn like SEM morphology of the nickel doped sample is shown. Optical characterization was done by UV–Vis spectrometer, fluorescence spectroscopy and electron paramagnetic resonance spectroscopy. Magnetic characterization was done by vibrating sample magnetometer (VSM). The VSM measurements revealed that the Ni doped SnO2 powder samples were diamagnetic at room temperature. This diamagnetic result is in contradiction to earlier published results. 相似文献
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CdS microtrumpets with the length being of about 4 μm and the bell wall being of 100 nm have been prepared using a cadmium di-(2-ethylhexyl) phosphoric acid chelate as the precursor by a two-phase thermal approach. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-vis spectroscopy. The effects of temperature, reaction time, and co-surfactant on the morphology were also examined. It was found that the co-surfactant triethanolamine plays a crucial role in the formation of the cubic phase trumpet-like CdS microstructures. 相似文献
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Romano-Trujillo R Rosendo E Ortega M Morales-Sánchez A Gracia JM Díaz T Nieto G García G Luna-López JA Pacio M 《Nanotechnology》2012,23(18):185602
Lead selenide nanoparticles (PbSe NPs) have been obtained through an easy and low cost route using colloidal synthesis in aqueous solution. The synthesis was carried out at room temperature using Extran (Na?P?O??, NaOH and H?O) as surfactant. Hydrochloric acid (HCl) was used to eliminate the generated by-products. The size of PbSe NPs was varied by changing the Pb:Se molar concentration. The PbSe NPs were characterized by powder x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The XRD measurements showed that the PbSe NPs have the face-centered cubic phase structure. The crystal size was found to be between 14 and 20 nm as calculated from the XRD patterns and these values were corroborated with SEM and TEM. Additionally, HRTEM micrographs showed crystalline planes at (200), (220) and (111) of the PbSe NPs, in agreement with the XRD results. 相似文献
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Mahesh BhagwatA.V. Ramaswamy A.K. TyagiVeda Ramaswamy 《Materials Research Bulletin》2003,38(13):1713-1724
Structural studies of Cu-doped zirconia samples with varying Cu content have been carried out. Copper-zirconia samples containing 2-20 mol% Cu were prepared by the co-precipitation technique using tetramethylammonium hydroxide as the precipitating agent and calcined at 773 K in air. The powder XRD data following Rietveld refinement revealed stabilization of zirconia in both tetragonal and cubic phases for all the samples with some monoclinic impurity phase. A decrease in the unit cell parameters of the cubic and tetragonal phase indicates incorporation of copper in the zirconia lattice of both the phases. An increase in the copper concentration (up to 20 mol%) stabilizes zirconia into the cubic phase at the expense of the tetragonal phase, with a decrease in the crystallite size (6-8 nm). Rietveld refinement of the high temperature XRD data reveals that both cubic and tetragonal phases exist up to 723 K with the cubic phase dominating (80% at 723 K). At temperature higher than 723 K, cubic phase gets transformed into the tetragonal phase, which further transforms into the monoclinic phase at 1173 K. At 1173 K, copper comes out of the cubic zirconia lattice forming a separate copper oxide phase and only the tetragonal and monoclinic polymorphs of zirconia exist. 相似文献
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Barbosa JG Pereira MR Moura C Mendes JA Almeida BG 《Journal of nanoscience and nanotechnology》2011,11(10):8700-8704
Barium titanate (BaTiO3) thin films have been prepared by electrophoretic deposition on p-doped and platinum covered silicon (Si) substrates. Their structure, nanostructure and dielectric properties were characterized. The as-deposited films were polycrystalline and composed by barium titanate nanograins with an average grain size approximately 9 nm. Annealing at high temperatures promoted grain growth, so that the samples annealed at 600 degrees C presented average grain sizes approximately 24 nm. From Raman spectroscopy measurements it was found that the tetragonal (ferroelectric) BaTiO3 phase was stabilized on the films. Also, at higher annealing temperatures, cation disorder was reduced on the films. From measurements of the temperature dependence of the dielectric permittivity the corresponding paraelectric-ferroelectric phase transition was determined. The observed transition temperature (approximately 100 degrees C) was found to be below the BaTiO3 bulk or thick film values, due to the small nanosized grains composing the films. 相似文献