共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Alagiri Sharifah Bee Abdul Hamid 《Journal of Materials Science: Materials in Electronics》2014,25(8):3572-3577
In this study, the preparation of α-Fe2O3 nanoparticles using curcuma and tea leaves extract are reported. The curcuma and tea leaves are acted as a reductant and stabilizer. The crystal structure and particle size of the as-synthesized materials were measured through X-ray diffraction. X-ray diffraction patterns revealed that the as-prepared samples were α-Fe2O3 nanoparticles with well-crystallized rhombohedral structure and the crystallite sizes of the α-Fe2O3 nanoparticles are 4 and 5 nm. Scanning electron microscopy images showed that the prepared samples have spherical shape. The purity and properties of the as-synthesized α-Fe2O3 nanoparticles were measured by Raman spectroscopy. The chemical compositions of the as-prepared α-Fe2O3 nanoparticles have been analyzed by Fourier transform infrared spectroscopy. The absorption edge of the α-Fe2O3 nanoparticles are 561 and 551 nm. The photocatalytic activity of the α-Fe2O3 nanoparticles was measured by degradation of methylene orange and the α-Fe2O3 nanoparticles showed the excellent photocatalytic performance. 相似文献
2.
In this study, various α-Fe2O3 (hematite) nanostructures were prepared on Fe foils by sonoelectrochemical anodization method. The principal component of the electrolyte was ethylene glycol contained 0.3 wt.% NH4F. The α-Fe2O3 surface shapes have been controlled by varying the water volume ratios (WVR) in electrolyte solution. The α-Fe2O3 samples were characterized by field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy, grazing incidence x-ray diffraction, and UV-vis absorbance spectra. As the variation of WVR, the α-Fe2O3 samples showed different surface morphologies of nanoparticles, nanorods, nanoporous, and nanoleaflets. The visible light photocatalytic activity of the α-Fe2O3 nanostructures was investigated by degradation of methylene blue, and the α-Fe2O3 nanoporous sample showed the best photocatalytic performance. 相似文献
3.
O. S. I. Fayomi A. P. I. Popoola A. A. Daniyan 《Particulate Science and Technology》2017,35(4):418-425
Multifunctional composite coatings of Zn?ZnO?Cr2O3 were deposited electrolytically on prepared carbon mild steel (CS) from Zn electrolyte, having Zn2+ ions and uniformly dispersed nano ZnO?Cr2O3 particulates. The corrosion resistance characteristics of the deposited coatings were evaluated using the linear polarization measurement method in 3.65% NaCl. The microstructural properties of the produced multilayered coatings were evaluated by scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), x-ray diffraction (XRD), and atomic force microscope (AFM). Thermal deformations were observed after 4 h at 250°C and the mechanical response of the coated samples was investigated using a diamond-based Dura Scan microhardness tester and a MTR-300dry abrasive wear tester. From the results, a significant improvement in the corrosion performance of coatings was observed with bath containing less than 2 g/L. The microhardness, thermal stability, and anti-wear properties of Zn?ZnO?Cr2O3 shows improved performance against Zn?ZnO coating matrixes, which was attributed to dispersive strengthening effect and grain induced effect of the ZnO/Cr2O3 particulate. 相似文献
4.
ZrO2 (3 mol% Y2O3) tetragonal and t-ceramics (displacively formed ceramics) were compared with ZrO2 ceramics (3 mol% Ln2O3, where Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Er, or Yb) processed in an identical manner. Sintering at 1500 °C for 2 h produced mainly tetragonal polytypes for the dopants with smaller ionic radii than Dy(i.e., Er, Y and Yb) but when ZrO2 was reaction sintered with dopants with larger ionic radii excessive monoclinic phase transformation and associated microcracking resulted. High-temperature annealing in the cubic stability regime and rapid cooling through the tetragonal stability regime was used to fabricate t-composites of ZrO2 doped with Y, Yb, Er or Dy. Room-temperature fracture toughness and strength values are explained on the basis of a ferroelastic-cubic-to-tetragonal transformation. The domain structure was viewed by transmission optical microscopy (TOM) or transmission electron microscopy (TEM). 相似文献
5.
Wenshuang Zhang Xinyong Li Qidong Zhao Yang Hou Yu Shen Guohua Chen 《Materials Chemistry and Physics》2011
Uniform α-Fe2O3 nanotubes with small aspect ratio were successfully fabricated by a hydrothermal method. In situ Fourier-transform infrared spectroscopy was used to study the mechanistic details of adsorption and photocatalytic oxidation of naphthalene over theα-Fe2O3 nanotubes. A possible degradation mechanism of naphthalene was proposed. 相似文献
6.
The charge storage characteristics of the high-κ HfAlO nanocrystal memory capacitors prepared by atomic layer deposition in an n-Si/SiO(2)/HfAlO/Al(2)O(3)/Pt structure have been investigated after high-temperature annealing treatment. The high-resolution transmission electron microscopy image shows that the diameter of high-κ HfAlO nanocrystal is<2?nm. The high-κ HfAlO nanocrystals have been also confirmed by x-ray photoelectron spectroscopy measurement. Due to the formation of high-κ HfAlO nanocrystals with the high-temperature (~900?°C) annealing treatment, a large hysteresis memory window of 3.7?V at a sweeping gate voltage <10?V is observed as compared to that of the as-deposited memory capacitors. A hysteresis memory window of ~1.7?V with a small sweeping gate voltage of ± 5?V is also observed. A small equivalent oxide thickness (EOT) of 5.6?nm is obtained due to the high-κ memory structure design. A significant memory window of ΔV≈0.7?V at 20?°C and ΔV≈0.6?V at 85?°C is observed after 10(4)?s of retention time, due to the charge confinement in the high-κ HfAlO nanocrystals. 相似文献
7.
Ning Zhao Lixi Wan Liqiang Cao Daquan Yu Shuhui Yu Rong Sun 《Materials Letters》2011,65(23-24):3574-3576
Polycrystalline BaTiO3/Ba0.6Sr0.4TiO3/SrTiO3 (BT/BST/ST) multilayer thin films with different periodicities have been deposited on Pt/Ti/SiO2/Si substrates by using a sol–gel method. The multilayer thin films were crack free, compact and crystallized in a perovskite structure. The dielectric constant of the multilayer thin films was significantly increased and the dielectric loss was almost the same as those of uniform BT, ST and BST thin films. The dielectric constant increased with increasing stacking periodicity as the thickness of each individual layer decreased. The multilayer thin films showed excellent dielectric properties and can be promisingly used for the dielectric layer of silicon-based embedded capacitors in package substrate. 相似文献
8.
Amanda dos Santos Joyce R. Araujo Sandra M. Landi Alexei Kuznetsov José M. Granjeiro Lidia Ágata de Sena Carlos Alberto Achete 《Journal of materials science. Materials in medicine》2014,25(7):1769-1780
In this work, a porous and homogeneous titanium dioxide layer was grown on commercially pure titanium substrate using a micro-arc oxidation (MAO) process and Ca–P-based electrolyte. The structure and morphology of the TiO2 coatings were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, and profilometry. The chemical properties were studied using electron dispersive X-ray spectroscopy (SEM–EDS) and X-ray photoelectron spectroscopy. The wettability of the coating was evaluated using contact angle measurements. During the MAO process, Ca and P ions were incorporated into the oxide layer. The TiO2 coating was composed of a mixture of crystalline and amorphous structures. The crystalline part of the sample consisted of a major anatase phase and a minor rutile phase. A cross-sectional image of the coating–substrate interface reveals the presence of voids elongated along the interface. An osteoblast culture was performed to verify the cytocompatibility of the anodized surface. The results of the cytotoxicity tests show satisfactory cell viability of the titanium dioxide films produced in this study. 相似文献
9.
Very recently, we fabricated (WO3)x–(TiO2)1−x layers via micro-arc oxidation process under different applied voltages. Morphological and topographical studies, accomplished by SEM and AFM techniques, revealed that the pores size as well as the surface roughness increased with the voltage. Phase structure and chemical composition of the layers were also investigated by XRD and XPS and the results showed the grown layers consisted of titanium and tungsten oxides. It was found that WO3 dispersed in the TiO2 matrix and also doped into the TiO2 lattice. In addition, optical properties of the synthesized layers were studied employing a UV–vis spectrophotometer. Band gap energy of the layers was approximately determined as 2.87 eV. Finally, methylene blue was selected as a model material and its degradation rate on the surface of the layers was measured to determine the photocatalytic efficiency. The degradation rate constants were measured as 2.2 × 10−2 and 0.9 × 10−2 min−1 under ultraviolet and visible irradiations. 相似文献
10.
Ma Lijun Xu Jing Liu Zhenlu Liu Ye Liu Xinyu Xu Shengming 《Journal of Materials Science》2022,57(12):6734-6748
Journal of Materials Science - In the field of photocatalysis, the recombination of photogenerated holes and electrons is still an urgent problem to be solved. Among many measures, constructing... 相似文献
11.
Jiaojiao Ye Yunfei Liu Yinong Lu Jianxiang Ding Chengjian Ma Hao Qian Zhenglei Yu 《Journal of Materials Science: Materials in Electronics》2014,25(10):4632-4637
The energy-storage properties of SrTiO3-doped (15, 20, 25, and 30 mol%) 0.80Bi1/2Na1/2TiO3–0.20Bi1/2K1/2TiO3 lead-free antiferroelectric ceramics were investigated by two-step sintering method. The ceramics with higher SrTiO3 content had smaller grain sizes and a more homogeneous distribution. About 25 mol% SrTiO3 doping induced antiferroelectric properties, showing a typical double hysteresis loops, accompanied by a large energy density. The first sintering temperature of the ceramics had main impact on the relative density, and the high relative density possessed large external breakdown strength. The optimum electrical performances with a low remanent polarization (Pr = 1.9 μC/cm2), a low coercive field (Ec = 1.7 kV/cm) and a large energy density (W = 0.97 J/cm3) at 10 Hz were obtained at 1,190 °C for a SrTiO3 content of 25 mol%. 相似文献
12.
M. Le Gall A. M. Huntz B. Lesage C. Monty J. Bernardini 《Journal of Materials Science》1995,30(1):201-211
In many cases, alumina scales are assumed to grow predominantly by oxygen diffusion, but some authors have found that the growth can be controlled by aluminium diffusion. These mechanisms can be modified by active elements. The problem with alumina is that there is a lack of data about self-diffusion coefficients, and, due to the stoichiometry of alumina, diffusion data correspond to an extrinsic diffusion mechanism so that it is not possible to compare oxygen and aluminium diffusion coefficients. In order to obtain information about the alumina scale growth mechanism, oxygen (18O) and aluminium (26Al) self-diffusion coefficients in Al2O3 were determined in the same materials and in the same experimental conditions, thus allowing a direct comparison. For both isotopes, bulk and sub-boundary diffusion coefficients were determined in single crystals of undoped alumina. Grain-boundary diffusion coefficients have been computed only for oxygen diffusion in polycrystals. Oxygen diffusion has been also studied for yttria-doped -alumina in the lattice, sub-boundaries and grain boundaries. Oxygen and aluminium bulk diffusion coefficients are of the same order of magnitude. In the sub-boundaries, aluminium diffusion is slightly faster than oxygen diffusion. Yttria doping induces a slight increase of the oxygen bulk diffusion, but decreases the grain-boundary diffusion coefficients on account of segregation phenomena. These results are compared with the oxidation constants of alumina former alloys (alloys which develop an alumina scale by oxidation). It appears that neither lattice self-diffusion nor grain boundary self-diffusion can explain the growth rate of alumina scales. Such a situation is compared to the case of Cr2O3. 相似文献
13.
(Zn0.8Mg0.2)TiO3–xTiO2 composite ceramics has been prepared via the solid-phase synthesis method. TiO2 was employed to tone temperature coefficient of resonant frequency (τf) and stabilize hexagonal (Zn, Mg)TiO3 phase. 3ZnO–B2O3 was effective to promote sintering. The movement of grain boundary was obvious because of the liquid phase sintering. The scanning electron microscope (SEM) photographs and energy dispersive spectrometer (EDS) patterns showed that segregation and precipitation of dissociative (Zn, Mg)TiO3 grains occurred at grain boundary during sintering. SnO2 was used as inhibitor to prevent the grain boundary from moving. The dielectric behaviors of specimen strongly depended on structural transition and microstructure. We found that 1.0 wt.% 3ZnO–B2O3 doped (Zn, Mg)TiO3–0.25TiO2 ceramics with 0.1 wt.% SnO2 additive displayed excellent dielectric properties (at 1000 °C): ?r = 27.7, Q × f = 65,490 GHz (at 6.07 GHz) and τf = −8.88 ppm °C−1. The above-mentioned material was applied successfully to make multilayer ceramic capacitors (MLCCs), which exhibited an excellent electrical property. The self-resonance frequency (SRF) and equivalent series resistance (ESR) of capacitor decreased with capacitance increasing, and the quality factor (Q) of capacitor reduced as frequency or capacity increased. 相似文献
14.
通过系统地测量(La2/3Ca1/3)(Mn(3-x)/3Fex/3)O3(x=0、0.1、0.2、0.3的体系样品的电阻率-温度关系以及一定温度下磁电阻率与磁场的关系,发现随x的变化其磁电阻率峰和电阻率峰均发生位移,磁电阻率峰值增大,并伴生磁电阻率峰展宽效应.作者认为由于Fe的替代,引起体系中Mn3+/Mn4+比率及磁矩的变化,加之外场对磁有序结构的调制作用,从而影响了Mn3+-O-Mn4+的双交换作用,最终导致磁电阻行为发生变化. 相似文献
15.
《Materials Letters》2004,58(3-4):378-383
Nanostructured Cu–Al2O3 composite powders were synthesized by thermochemical process. The synthesis procedures are (1) preparation of precursor powder by spray-drying of solution made from water-soluble copper and aluminum nitrates, (2) air heat treatments to evaporate volatile components in the precursor powder and synthesis of nanostructured CuO+Al2O3, and (3) CuO reduction by hydrogen into pure Cu. The suggested procedures stimulated the formation of the γ-Al2O3, and different alumina formation behaviors appeared with various heat-treating temperatures. The mean particle size of the final Cu–Al2O3 composite powders produced was 20 nm, and the electrical conductivity and hardness in the hot-extruded bulk were competitive with Cu–Al2O3 composite by the conventional internal oxidation process. 相似文献
16.
This paper highlights the comparative co-catalytic efficiency of different shapes of prepared Ag nanoparticles of size much larger as well as smaller than titania for the Ag–TiO2 photocatalysis. Quantum sized Ag nanospheres (4_8 nm), nanorod (length 70–75 nm and width 30–38 nm), polygonal nanosphere (80–120 nm) and truncated triangles (side length 70–140 nm) are prepared by solvothermal process. The co-catalytic activities of these Ag nanostructures were investigated by mixing them with TiO2 for the photocatalytic degradation of aqueous salicylic (0.5 mM) and benzoic acid (0.5 mM) under UV light (125 W-Hg arc, 10.4 mW cm−2) irradiation. The Ag co-catalysis effect imparted to TiO2 follows as polygonal nanosphere > nanorod > truncated triangle > small nanosphere due to the formation of many Ag–TiO2 interfaces by a single large-sized Ag nanoparticle than smaller one. As the surface coverage of Ag particles by TiO2 decreases, the Ag–TiO2 photoactivity is decreased accordingly. The efficient adsorption of salicylic acid to TiO2 surface through –COOH and –OH groups render its higher photodegradation rate (1.8–2.7 × 10−2 μmol min−1) than benzoic acid (1.5–2.5 × 10−2 μmol min−1) having one chelating –COOH group. Zeta potential and conductance measurement of photoreaction mixture were carried out to investigate the ionic interaction-adsorption of reactant substrates over Ag–TiO2 surface. 相似文献
17.
Farha Masood P. Chen Tariq Yasin Fariha Hasan Bashir Ahmad Abdul Hameed 《Journal of materials science. Materials in medicine》2013,24(8):1927-1937
The synthesis of microbial polyhydroxyalkanoate is investigated in this work for it potential application as drug carrier for cancer therapy. The bacterial isolate Bacillus cereus FB11 has synthesized poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer under nutrient stress conditions using glucose as a sole carbon source. The FTIR spectrum of the purified copolymer showed the characteristic absorption bands at 1,719, 1,260 and 2,931 cm?1 attributing to C=O, C–O stretching and C–H vibrations, respectively. The result of 1H-NMR confirmed that it was composed of 88 mol % of 3-hydroxybutyrate and 12 mol % of 3-hydroxyvalerate monomeric subunits. The nanoparticles were fabricated from copolymer and used as a carrier for anticancer drug ellipticine. The in vitro drug release studies showed that % inhibition of A549 cancer cell line receiving ellipticine loaded poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) nanoparticles was two-fold higher in comparison to ellipticine alone. This drug delivery system offers exciting possibilities for cancer therapy by increasing the bioavailability of anti-neoplastic drug to the tumor site. 相似文献
18.
通过固相反应法合成了具有光致变色性质的La(2-x)/3(Ag(0)1-2x/3Ag(I)x)TiO3(简称Ag-LST)钙钛矿结构复合氧化物粉体,采用XRD、XPS、ICP和SEM等实验技术对Ag-LST进行了表征.结果表明,Ag-LST具有立方晶相钙钛矿结构,其表面层元素组成为Ag:La:Ti=0.45:0.60:1.00.研究了Ag-LST的光致变色性质,在紫外光(300W汞灯)下照射Ag-LST 1min,样品的颜色从棕黄色转变为蓝紫色;在可见光(500W氙灯)下照射Ag-LST 1h,样品恢复为原来的棕色.Ag-LST的光致变色性质可能与Ag(0)-Ag(I)相互转换有关. 相似文献
19.
《Materials at High Temperatures》2013,30(4):324-335
AbstractTiAlYN/CrN and CrAlYN/CrN nanoscale multilayer coatings were deposited on γ-TiAl specimens using magnetron sputtering techniques. The nitride layers were manufactured by unbalanced magnetron sputtering (UBM) and high power impulse magnetron sputtering (HIPIMS). The CrAlYN/CrN coatings had an oxy-nitride overcoat. On some of the coated samples an additional alumina topcoat was deposited. The oxidation behaviour of the different coatings was investigated at 750 and 850°C performing quasi-isothermal oxidation tests in laboratory air. Mass change data were measured during exposure up to failure or the maximum exposure length of 2500 h. When exposed to air at 750°C, the Ti-based nitride films exhibited higher oxidation resistance than the Ti – 45Al –8Nb substrate material. The alumina topcoat enhanced the oxidation protection of this coating system, acting as diffusion barrier to oxygen penetration. At 850°C, the TiAlYN/CrN films exhibited poor stability and rapidly oxidised, and therefore were not applicable for long-term protective coatings on γ-TiAl alloys. The beneficial effect of the additional Al2O3 layer was less pronounced at this exposure temperature. The Cr-based nitride films exhibited high oxidation resistance during exposure at 850°C. HIPIMS deposition improved the oxidation behaviour of the CrAlYN/CrN nanoscale multilayer coatings in comparison to UBM coatings. For these coatings, the decomposed and partially oxidised nitride films were an effective barrier to oxygen inward diffusion. The alumina topcoat did not significantly increase the oxidation resistance of the γ-TiAl alloy coated with Cr-based nitride films. 相似文献
20.
In this paper, electro-codeposition based on electrophoretic deposition and electrolytic deposition was developed to prepare Al2O3-Y2O3 composite thin film coatings on a γ-TiAl based alloy. Scanning electron microscope observations showed that the Al2O3-Y2O3 composite coatings were very compact and consisted of uniform nano-particles after microwave sintering. Cyclic oxidation at 900 °C indicated that the Al2O3-Y2O3 composite thin film coatings improved the oxidation and scale spallation resistance of the γ-TiAl alloy significantly. The superior oxidation and spallation resistance of the coatings were attributed to the suppression of outward diffusion of Ti and Al and inward diffusion of O, the promoted selective oxidation of Al in the γ-TiAl alloy, and the improved adhesion of oxide scale induced by the Al2O3-Y2O3 composite thin film coatings. 相似文献