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1.
When heated by high-energy electron beam (EB), SiC can decompose into C and Si vapor. Subsequently, Si vapor reacts with metal oxide thin film on substrate surface and formats dense SiO2 thin film at high substrate temperature. By means of the two reactions, SiC/SiO2 composite thin film was prepared on the pre-oxidized 316 stainless steel (SS) substrate by electron beam-physical vapor deposition (EB-PVD) only using β-SiC target at 1000 °C. The thin film was examined by energy dispersive spectroscopy (EDS), grazing incidence X-ray asymmetry diffraction (GIAXD), scanning electron microscopy (SEM), atomic force microscopy (AFM), backscattered electron image (BSE), electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS) and Fourier transformed infra-red (FT-IR) spectroscopy. The analysis results show that the thin film is mainly composed of imperfect nano-crystalline phases of 3C-SiC and SiO2, especially, SiO2 phase is nearly amorphous. Moreover, the smooth and dense thin film surface consists of nano-sized particles, and the interface between SiC/SiO2 composite thin film and SS substrate is perfect. At last, the emissivity of SS substrate is improved by the SiC/SiO2 composite thin film. 相似文献
2.
Two-layer ZrO2/SiO2 and SiO2/ZrO2 films were deposited on K9 glass substrates by sol–gel dip coating method. X-ray photoelectron spectroscopy (XPS) technique was used to investigate the diffusion of ZrO2/SiO2 and SiO2/ZrO2 films. To explain the difference of diffusion between ZrO2/SiO2 and SiO2/ZrO2 films, porous ratio and surface morphology of monolayer SiO2 and ZrO2 films were analyzed by using ellipsometry and atomic force microscopy (AFM). We found that for the ZrO2/SiO2 films there was a diffusion layer with a certain thickness and the atomic concentrations of Si and Zr changed rapidly; for the SiO2/ZrO2 films, the atomic concentrations of Si and Zr changed relatively slowly, and the ZrO2 layer had diffused through the entire SiO2 layer. The difference of diffusion between ZrO2/SiO2 and SiO2/ZrO2 films was influenced by the microstructure of SiO2 and ZrO2. 相似文献
3.
A new type of multicoated silica/zirconia/silver (SiO2/ZrO2/Ag) core-shell composite microspheres is synthesized in this paper. In the process, ZrO2-decorated silica (SiO2/ZrO2) core-shell composites were firstly fabricated by the modification of zirconia on silica microspheres through the hydrolysis of zirconium precursor. Subsequently, on SiO2/ZrO2 composite cores, silver nanoparticles were introduced via ultrasonic irradiation and acted as “Ag seeds” for the formation of integrate silver shell by further reduction of silver ions using formaldehyde as reducer. The resulting samples were characterized by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared, energy-dispersive X-ray, and UV-vis spectroscopy, indicating that zirconia and silver layers were successfully coated on the surfaces of silica microspheres. 相似文献
4.
Novel egg-shell structured monometallic Pd/SiO2 and bimetallic Ca-Pd/SiO2 catalysts were prepared by an impregnation method using porous hollow silica (PHS) as the support and PdCl2 and Ca(NO3)2·4H2O as the precursors. It was found from transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) that Pd was loaded on PHS with a particle size of 5-12 nm in Pd/SiO2 samples and the Pd particle size in Ca-Pd/SiO2 was smaller than that in Pd/SiO2 since Ca could prevent Pd particles from aggregating. X-ray photoelectron spectroscopy (XPS) analyses exhibited that Pd 3d5/2 binding energies of Pd/SiO2 and Ca-Pd/SiO2 were 0.2 and 0.9 eV lower than that of bulk Pd, respectively, as a result of the shift of the electron cloud from Pd to oxygen in Pd/SiO2 and to both oxygen and Ca in Ca-Pd/SiO2. The activity of Ca-Pd/SiO2 egg-shell catalyst for CO hydrogenation and the selectivity to methanol, with a value of 36.50 mmolCO mol−1Pd s−1 and 100%, respectively, were much higher than those of the catalysts prepared with traditional silica gel as the support, owing to the porous core-shell structure of the PHS support. 相似文献
5.
以AgNO3,HAuCl4和正硅酸乙酯为主要原料,利用溶胶-凝胶法和旋涂技术,通过热处理和紫外光辐射还原得到了不同nAg/nAu(1∶0,2∶1,1∶2,0∶1)的Ag-Au合金/SiO2复合薄膜.从扫描电子显微镜和X射线衍射谱的结果可以看出得到的薄膜均匀性好,复合薄膜中合金颗粒的尺寸为10 nm左右.利用紫外-可见分光光谱仪研究了复合薄膜的光吸收性能,结果表明,随着nAg/nAu的降低,吸收峰的位置也由最初的Ag纳米粒子的等离子共振吸收峰430 nm附近,逐渐红移到Au纳米粒子的等离子共振吸收峰605和880 nm附近.从光吸收谱可以看出,nAg∶nAu=2∶1和1∶2的两个样品分别在515,730 nm附近和550,730 nm附近出现表面等离子共振吸收峰.这表明Au-Ag合金固溶体的形成.
关键词:
2')" href="#">Ag-Au合金/SiO2
紫外辐射
光吸收性能 相似文献
6.
This paper investigated the gaseous formaldehyde degradation by the amine-functionalized SiO2/TiO2 photocatalytic films for improving indoor air quality. The films were synthesized via the co-condensation reaction of methyltrimethoxysilane (MTMOS) and 3-aminopropyltrimethoxysilane (APTMS). The physicochemical properties of prepared photocatalysts were characterized with N2 adsorption/desorption isotherms measurement, X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FT/IR). The effect of amine-functional groups and the ratio of MTMOS/APTMS precursors on the formaldehyde adsorption and photocatalytic degradation were investigated. The results showed that the formaldehyde adsorption and photocatalytic degradation of the APTMS-functionalized SiO2/TiO2 film was higher than that of SiO2/TiO2 film due to the surface adsorption on amine sites and the relatively high of the specific surface area of the APTMS-functionalized SiO2/TiO2 film (15 times higher than SiO2/TiO2). The enhancement of the formaldehyde degradation of the film can be attributed to the synergetic effect of adsorption and subsequent photocatalytic decomposition. The repeatability of photocatalytic film was also tested and the degradation efficiency was 91.0% of initial efficiency after seven cycles. 相似文献
7.
Room temperature photoluminescence (PL) at around 600 nm from magnetron-sputtered SiO2 films co-doped with Ge is reported. The PL signal is observed in pure SiO2, however, its intensity increases significantly in the presence of Ge-nanocrystals (Ge-nc). The PL intensity has been optimized by varying the temperature of heat treatment, type of gas during heat treatment, concentration of Ge in the SiO2 films, and gas pressure during deposition. Maximum intensity occurs when Ge-nc of around 3.5 nm are present in large concentration in SiO2 layers deposited at fairly high gas pressure. Based on time resolved PL, and PL measurements after α-particle irradiation or H passivation, we attribute the origin of the PL to a defect in SiO2 (probably an O deficiency) that is excited through an energy transfer from Ge-nc. There is no direct PL from the Ge-nc; however, there is a strong coupling between excitons created in the Ge-nc and the SiO2 defect. 相似文献
8.
The influence of SiO2 on the dielectric properties of barium titanate ceramics was investigated. SiO2 had been doped solely and together with BaO into barium titanate before calcination. X-ray diffraction showed that all the ceramics were of a pure perovskite phase after sintering at 1275 °C for 2 h. For SiO2-doping, there was about 2.5 °C increase in Curie temperature per molar percentage of doping and the leakage current was obviously increased, especially at low voltages for relatively high doping levels. While for the co-doping of SiO2 and BaO, there was little change in Curie temperature. The point defects formed through the dopings were proposed responsible for the effects. It was suggested that SiO2 is important to barium titanate ceramics not only for sintering but also for modifying their properties. 相似文献
9.
采用溶胶-凝胶(sol-gel)工艺制备0.1 mol% Er3+掺杂Al2O3体系和SiO2-Al2O3复合体系粉末. 实验结果表明:5 mol%的SiO2复合加入Al2O3抑制γ→θ和θ→α相转变. 掺0.1 mol%Er3+:Al2O3体系粉末,900℃烧结,在1.47—1.63μm波段内光致发光(PL)谱为中心波长1.53 μm、半高宽56 nm的单一宽峰,1000—1200℃烧结,劈裂为多峰PL谱. 掺0.1 mol%Er3+:SiO2-Al2O3复合体系粉末,在高达1200℃烧结,仍保持中心波长1.53 μm的单一宽峰PL谱,由于—OH更完全的脱除,PL强度较900℃烧结Al2O3体系,SiO2-Al2O3复合体系均提高1个数量级.
关键词:
2-Al2O3复合体系')" href="#">SiO2-Al2O3复合体系
掺铒
溶胶-凝胶工艺
光致发光 相似文献
10.
Hai Wang Jun HuangChao Wang Dapeng LiLiyun Ding Yun Han 《Applied Surface Science》2011,257(13):5739-5745
Aminated-CoFe2O4/SiO2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. Glucose oxidase (GOD) was immobilized on CoFe2O4/SiO2 NPs via cross-linking with glutaraldehyde (GA). The optimal immobilization condition was achieved with 1% (v/v) GA, cross-linking time of 3 h, solution pH of 7.0 and 0.4 mg GOD (in 3.0 mg carrier). The immobilized GOD showed maximal catalytic activity at pH 6.5 and 40 °C. After immobilization, the GOD exhibited improved thermal, storage and operation stability. The immobilized GOD still maintained 80% of its initial activity after the incubation at 50 °C for 25 min, whereas free enzyme had only 20% of initial activity after the same incubation. After kept at 4 °C for 28 days, the immobilized and free enzyme retained 87% and 40% of initial activity, respectively. The immobilized GOD maintained approximately 57% of initial activity after reused 7 times. The KM (Michaelis-Menten constant) values for immobilized GOD and free GOD were 14.6 mM and 27.1 mM, respectively. 相似文献
11.
SiO2@Gd2MoO6:Eu3+ core-shell phosphors were prepared by the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays were used to characterize the resulting SiO2@Gd2MoO6:Eu3+ core-shell phosphors. The XRD results demonstrate that the Gd2MoO6:Eu3+ layers on the SiO2 spheres begin to crystallize after annealing at 600 °C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have a near perfect spherical shape with narrow size distribution (average size ca. 600 nm), are not agglomerated, and have a smooth surface. The thickness of the Gd2MoO6:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (50 nm for four deposition cycles). The Eu3+ shows a strong PL luminescence (dominated by 5D0-7F2 red emission at 613 nm) under the excitation of 307 nm UV light. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles. 相似文献
12.
Aminated-CoFe2O4/SiO2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. By optimizing the preparation conditions, monodisperse CoFe2O4/SiO2 NPs with high amino groups’ density were obtained, which is necessary for enzyme immobilization. TEM confirm that the sample is a core/shell structure. These aminated-CoFe2O4/SiO2 NPs have narrow size distributions with a mean size of about 60 nm. Moreover, the aminated-CoFe2O4/SiO2 NPs can be easily dispersed in aqueous medium. The experimental results also show that the NPs have superparamagnetism, indicating that the aminated-CoFe2O4/SiO2 NPs can be used as an effective carrier for the enzyme immobilization. 相似文献
13.
Byeol HanSeung-Won Lee Kwangchol ParkChong-Ook Park Sa-Kyun RhaWon-Jun Lee 《Current Applied Physics》2012,12(2):434-436
We produced dielectric stacks composed of ALD SiO2 and ALD Al2O3, such as SiO2/Al2O3, Al2O3/SiO2, and SiO2/Al2O3/SiO2, and measured the leakage currents through the stacks in comparison with those of the single oxide layers. SiO2/Al2O3 shows lowest leakage current for negative bias region below 6.4 V, and Al2O3/SiO2 showed highest current under negative biases below 4.5 V. Two distinct electron conduction regimes are observed for Al2O3 and SiO2/Al2O3. Poole-Frenkel emission is dominant at the high-voltage regime for both dielectrics, whereas the direct tunneling through the dielectric is dominant at the low-voltage regime. The calculated transition voltage between two regimes for SiO2 (6.5 nm)/Al2O3 (12.6 nm) is −6.4 V, which agrees well with the experimental observation (−6.1 V). For the same EOT of entire dielectric stack, the transition voltage between two regimes decreases with thinner SiO2 layer. 相似文献
14.
Yumin Liu Aili Wang Dongzhi Zhang Chunyan Liu Jun Chen Hui Feng Hengping Yao Tingshun Jiang 《Applied Surface Science》2008,254(9):2809-2819
SiO2-coated TiO2 powders were prepared by the chemical deposition method starting from rutile TiO2 and Na2SiO3. The SiO2-coated TiO2 powders were characterized by X-ray photoelectron spectroscopy, Zeta-potential analysis, Fourier transform infrared spectroscopy, and transmission electron microscopy. The evolution of island-like and uniform coating layers was found to depend upon the ratio of Na2SiO3 to TiO2, reaction temperature, and pH. The whiteness and brightness of the SiO2-coated TiO2 powders increased in response to an increase in the SiO2 loading, but there was a maximum value among the light scattering indexes. The SiO2-coated TiO2 powders possessed more negative Zeta potentials than the naked TiO2. The dispersibility of the SiO2-coated TiO2 powders with the continuous and uniform SiO2 coating layers was higher than that of the naked TiO2 and the SiO2-coated TiO2 powders with the island-like SiO2 coating layers. 相似文献
15.
Qian Sun 《Applied Surface Science》2008,254(13):3774-3779
The lithium electrochemistry of SiO2 thin film prepared by reactive radio frequency sputtering has been investigated for the first time. The reversible discharge capacities of SiO2/Li cells cycled between 0.01 and 3.0 V are found in the range from 416 to 510 mAh/g during the first 100 cycles. By using ex situ transmission electron microscopy, selected-area electron diffraction and X-ray photo-electron spectroscopy measurements, both Li-Si alloying process and the reversible conversion reaction of SiO2 into Li2Si2O5 are proposed in the lithium electrochemical reaction of SiO2. SiO2 film electrode with high-reversible capacity and good cycle performance exhibits it potential anode material for future lithium-ion batteries. 相似文献
16.
Au/SiO2 nanocomposite films were fabricated on Si (111) substrates by radio frequency (RF) magnetron sputtering technique and annealing at different temperature for 20 min (mode A) and at 1000 °C for different annealing time (mode B). The nanocomposite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL). SEM results demonstrate that the size of Au crystallites in mode A first increases and then decreases, on increasing annealing temperature, according to the results of XRD spectra. Analysis of PL spectra in mode B shows that the intensity of the emission peak at 440 nm and 523 nm early increases and late decreases, with increasing annealing time at 1000 °C. The origin of the emission peak at around 440 nm was related to the size and quantity of Au particles and one of the emission peak at around 523 nm was related to the nanostructure of films in agreement with SEM imagines. Experimental results indicated that morphology, microstructure and luminescence of Au/SiO2 nanocomposite films showed close affinity with annealing temperature and annealing time. 相似文献
17.
Yunsheng Zhang Aili Wang Min Ren Zhuomin Gu Yumin Liu Yutang Shen Longbao Yu Tingshun Jiang 《Applied Surface Science》2010,257(4):1351-1360
Binary Al2O3/SiO2-coated rutile TiO2 composites were prepared by a liquid-phase deposition method starting from Na2SiO3·9H2O and NaAlO2. The chemical structure and morphology of binary Al2O3/SiO2 coating layers were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, TG-DSC, Zeta potential, powder X-ray diffraction, and transmission electron microscopy techniques. Binary Al2O3/SiO2 coating layers both in amorphous phase were formed at TiO2 surfaces. The silica coating layers were anchored at TiO2 surfaces via Si-O-Ti bonds and the alumina coating layers were probably anchored at the SiO2-coated TiO2 surfaces via Al-O-Si bonds. The formation of continuous and dense binary Al2O3/SiO2 coating layers depended on the pH value of reaction solution and the alumina loading. The binary Al2O3/SiO2-coated TiO2 composites had a high dispersibility in water. The whiteness and brightness of the binary Al2O3/SiO2-coated TiO2 composites were higher than those of the naked rutile TiO2 and the SiO2-coated TiO2 samples. The relative light scattering index was found to depend on the composition of coating layers. 相似文献
18.
Han-Yu Hsieh 《Journal of luminescence》2009,129(6):595-4194
Manganese-doped zinc silicate (Zn2SiO4:Mn) is a kind of phosphor material that has a photo-luminescent (PL) and cathode-luminescent (CL) properties with intensive green light emission at 520 nm. The particles consisting of SiO2@Zn2SiO4:Mn (SiO2 core-Zn2SiO4:Mn shell) were synthesized via colloidal process and forced precipitation. After drying, the Zn/Mn precipitates were coated on the surface of SiO2 particles. The Zn/Mn precipitates reacted with SiO2 and transformed to Zn2SiO4:Mn by suitable calcination. The microstructure, crystalline phase, and luminescent characteristics of the products were studied. Besides, a CL device consisting of the core-shell powder was characterized. 相似文献
19.
20.
采用反应磁控溅射法制备了一系列不同SiO2层厚度的AlN/SiO2纳米多层膜,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,研究了SiO2层在多层膜中的晶化现象及其对多层膜生长方式及力学性能的影响. 结果表明,由于受AlN六方晶体结构的模板作用,溅射条件下以非晶态存在的SiO2层在其厚度小于0.6 nm时被强制晶化为与AlN相同的六方结构赝晶体并与AlN形成共格外延生长. 由于不同模量的两调制层存在晶格错配度,多层膜中产生了拉、压交变的应力场,使得多层膜产生硬度升高的超硬效应. SiO2随层厚的进一步增加又转变为以非晶态生长,多层膜的外延生长结构受到破坏,其硬度也随之降低.
关键词:
2纳米多层膜')" href="#">AlN/SiO2纳米多层膜
赝晶化
应力场
超硬效应 相似文献