共查询到20条相似文献,搜索用时 15 毫秒
1.
In situ DRIFTS研究NO在Cu-ZSM-5上的表面吸附及选择性催化还原 总被引:1,自引:1,他引:0
Cu-ZSM-5分子筛催化剂选择性催化还原NO具有较好的低温活性,在613 K时NO还原成N2的转化率达70.6%。原位漫反射红外光谱(In situ DRIFTS)是研究催化剂表面吸附物种及催化机理的重要方法,应用该方法在298~773 K范围原位考察了以C3H6为还原剂及富O2 条件下,NO在Cu-ZSM-5催化剂上的表面吸附及选择性催化还原。认为NO在Cu-ZSM-5催化剂上还原为N2的过程中,NO以一系列NOx吸附态形式与丙稀的活化物种(CxHy或CxHiyOz)反应,生成有机中间体,再进一步反应,最终生成N2。有机中间体存在一个明显的从有机胺物种到腈(或—CN)再到有机氮氧物种(R—NO2或R—ONO)的过程,催化剂表面形成有机中间物种是关键步骤,Cu的作用是促进NOx形成,O2 的作用是促进C3H6活化,并且是有效产生有机-氮氧化物不可缺少的条件。 相似文献
2.
Deposition and characterization of TiAlSiN nanocomposite coatings prepared by reactive pulsed direct current unbalanced magnetron sputtering 总被引:3,自引:0,他引:3
Harish C. Barshilia Moumita Ghosh Shashidhara Raja Ramakrishna K.S. Rajam 《Applied Surface Science》2010,256(21):6420-6426
This work reports the performance of high speed steel drill bits coated with TiAlSiN nanocomposite coating at different Si contents (5.5-8.1 at.%) prepared using a four-cathode reactive pulsed direct current unbalanced magnetron sputtering system. The surface morphology of the as-deposited coatings was characterized using field emission scanning electron microscopy. The crystallographic structure, chemical composition and bonding structure were evaluated using X-ray diffraction, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, respectively. The corrosion behavior, mechanical properties and thermal stability of TiAlSiN nanocomposite coatings were also studied using potentiodynamic polarization, nanoindentation and Raman spectroscopy, respectively. The TiAlSiN coating thickness was approximately 2.5-2.9 μm. These coatings exhibited a maximum hardness of 38 GPa at a silicon content of approximately 6.9 at.% and were stable in air up to 850 °C. For the performance evaluation, the TiAlSiN coated drills were tested under accelerated machining conditions by drilling a 12 mm thick 304 stainless steel plate. Under dry conditions the uncoated drill bits failed after drilling 50 holes, whereas, TiAlSiN coated drill bits (Si = 5.5 at.%) drilled 714 holes before failure. Results indicated that for TiAlSiN coated drill bits the tool life increased by a factor of more than 14. 相似文献
3.
β-FeSi2 thin films were prepared on Si (1 1 1) substrates by pulsed laser deposition (PLD) with a sintering FeSi2 target and an electrolytic Fe target. The thin films without micron-size droplets were prepared using the electrolytic Fe target; however, the surface without droplets was remarkably rougher using the Fe target than using the FeSi2 target. After deposition at 600 °C and then annealing at 900 °C for 20 h, XRD indicated that the thin film prepared using the Fe target had a poly-axis-orientation, but that prepared using the FeSi2 target had a one-axis-orientation. The PL spectra of the thin films prepared using the FeSi2 and Fe targets at a growth temperature of 600 °C and subsequently annealed at 900 °C for 20 h had A-, B- and C-bands. Moreover, it was found that the main peak at 0.808 eV (A-band) in the PL spectrum of the thin films prepared using the FeSi2 target was the intrinsic luminescence of β-FeSi2 from the dependence of PL peak energy on temperature and excitation power density. 相似文献
4.
J.R. CasanovaE.A. Heredia C.D. BojorgeH.R. Cánepa G. KellermannA.F. Craievich 《Applied Surface Science》2011,257(23):10045-10051
Nanocrystalline ZnO thin films prepared by the sol-gel dip-coating technique were characterized by grazing incidence X-ray diffraction (GIXD), atomic force microscopy (AFM), X-ray reflectivity (XR) and grazing incidence small-angle X-ray scattering (GISAXS). The structures of several thin films subjected to (i) isochronous annealing at 350, 450 and 550 °C, and (ii) isothermal annealing at 450 °C during different time periods, were characterized. The studied thin films are composed of ZnO nanocrystals as revealed by analysing several GIXD patterns, from which their average sizes were determined. Thin film thickness and roughness were determined from quantitative analyses of AFM images and XR patterns. The analysis of XR patterns also yielded the average density of the studied films. Our GISAXS study indicates that the studied ZnO thin films contain nanopores with an ellipsoidal shape, and flattened along the direction normal to the substrate surface. The thin film annealed at the highest temperature, T = 550 °C, exhibits higher density and lower thickness and nanoporosity volume fraction, than those annealed at 350 and 450 °C. These results indicate that thermal annealing at the highest temperature (550 °C) induces a noticeable compaction effect on the structure of the studied thin films. 相似文献
5.
Diamond-like carbon (DLC) films have been deposited using three different
techniques: (a) electron cyclotron resonance---plasma source ion
implantation, (b) low-pressure dielectric barrier discharge, (c)
filtered---pulsed cathodic arc discharge. The surface and mechanical properties of
these films are compared using atomic force microscope-based tests. The experimental results
show that hydrogenated DLC films are covered with soft surface layers
enriched with hydrogen and sp$^{3}$ hybridized carbon while the soft surface
layers of tetrahedral amorphous carbon (ta-C) films have graphite-like
structure. The formation of soft surface layers can be associated with the
surface diffusion and growth induced by the low-energy deposition process.
For typical CVD methods, the atomic hydrogen in the plasmas can contribute
to the formation of hydrogen and sp$^{3}$ hybridized carbon enriched
surface layers. The high-energy ion implantation causes the
rearrangement of atoms beneath the surface layer and leads to an increase in film
density. The ta-C films can be deposited using the medium energy carbon ions
in the highly-ionized plasma. 相似文献
6.
J. Aguado-Serrano R.M. Martín-Aranda V. Gómez-Serrano 《Applied Surface Science》2006,252(17):6075-6079
The sol-gel method has been applied for the synthesis of a series of acid metal-carbon xerogels (with M = V, Cr, Mo and Ni) by polymerisation of resorcinol with formaldehyde in the presence of metallic precursors. A blank sample was also prepared without any metal addition. The xerogels were heated in nitrogen at 1000 °C to obtain the pyrolysed products. The samples were characterised by different techniques such as thermal-mass spectrometry analysis, gas physisorption, and mercury porosimetry. In addition, the acid character of the pyrolysed products was tested by the Claisen-Schmidt condensation between benzaldehyde and acetophenone for the formation of chalcones. 相似文献
7.
Surface oxidation of vanadium dioxide films prepared by radio frequency magnetron sputtering
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper reports that the thermochromic vanadium dioxide films were deposited on various transparent substrates by radio frequency magnetron sputtering, and then aged under circumstance for years. Samples were characterized with several different techniques such as x-ray diffraction, x-ray photoelectron spectroscopy, and Raman, when they were fresh from sputter chamber and aged after years, respectively, in order to determine their structure and composition. It finds that a small amount of sodium occurred on the surface of vanadium dioxide films, which was probably due to sodium ion diffusion from soda-lime glass when sputtering was performed at high substrate temperature. It also finds that aging for years significantly affected the nonstoichiometry of vanadium dioxide films, thus inducing much change in Raman modes. 相似文献
8.
We report the use of the time-of-flight secondary ion mass spectrometry (ToF-SIMS) technique to determine whether the patterned bank is suitable for inkjet printing, by evaluating the phobicity contrast between two regions, the glass substrate inside pixels and the surface of the resist bank. We first examined the effect of plasma treatment on the ink spreading behavior inside pixels. The phobicity contrast was optimized by removing residues inside the pixels and by providing high phobicity on the bank surface. We show that ToF-SIMS spectra and mass-resolved images are effective tools in examining the existence of organic contaminants inside pixels and predicting the actual inkjet printing behavior. The ToF-SIMS technique will find promising applications that are related to surface characteristics where conventional contact angle measurement is hard to apply due to geometrical and technical restrictions. 相似文献
9.
10.
A simple method of thermal evaporation to fabricate micro and nanostructures of zinc oxide was presented. ZnO micro and nanostructures, prepared under different quantity of O2, were characterized by techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and analytical transmission electron Microscope. The SEM images indicated that the products prepared under the condition of sufficient O2 were needle-like microrods and the samples synthesized under the condition of deficient O2 were nanorods and nanowires with very high aspect ratio. The results of XRD and Raman shifts revealed that the ZnO micro and nanostructures synthesized under different quantity of O2 were both single crystalline with the hexagonal wurtzite structure. The HRTEM images indicated that the ZnO nanowire prepared under the condition of deficient O2 was single crystalline and grown along the direction of [0 0 1]. Photoluminescence measurement was carried out and it showed that the spectra of ZnO micro and nanostructures prepared under different quantity of O2 exhibited similar emission features. In addition, the growth mechanism of ZnO micro and nanostructures was preliminarily discussed. 相似文献
11.
K. Maaz S. Karim S.K. Hasanain J.L. Duan 《Journal of magnetism and magnetic materials》2009,321(12):1838-1842
Magnetic nanoparticles of nickel ferrite (NiFe2O4) have been synthesized by co-precipitation route using stable ferric and nickel salts with sodium hydroxide as the precipitating agent and oleic acid as the surfactant. X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses confirmed the formation of single-phase nickel ferrite nanoparticles in the range 8-28 nm depending upon the annealing temperature of the samples during the synthesis. The size of the particles (d) was observed to be increasing linearly with annealing temperature of the sample while the coercivity with particle size goes through a maximum, peaking at ∼11 nm and then decreases for larger particles. Typical blocking effects were observed below ∼225 K for all the prepared samples. The superparamagnetic blocking temperature (TB) was found to be increasing with increasing particle size that has been attributed to the increased effective anisotropy energy of the nanoparticles. The saturation moment of all the samples was found much below the bulk value of nickel ferrite that has been attributed to the disordered surface spins or dead/inert layer in these nanoparticles. 相似文献
12.
Vineet Singh 《Journal of Physics and Chemistry of Solids》2009,70(7):1074-1079
In the present study we have synthesized CdS semiconducting quantum dots by the chemical precipitation method using Thioglycerol as the capping agent. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) are employed to characterize the size, morphology and crystalline structure of the as-prepared material. The synthesized QPs have a mixture of cubical and hexagonal crystal symmetry with 12 nm average diameter. Ultraviolet-visible (UV-vis) absorption spectroscopy is used to calculate the band gap of the material and blue shift in absorption edge. Confinement of the optical phonon modes in the QPs is studied by Raman spectroscopy, while FTIR for identification of chemical bonds in the nanomaterial. Multiple cadmium and sulphur defects were observed by employing the photoluminescence (PL) method. 相似文献
13.
非水体系中吡啶和乙腈在铂电极上竞争吸附的表面增强拉曼光谱研究 总被引:2,自引:0,他引:2
继非水体系中CO在过渡金属表面吸附的表面增强拉曼光谱(SERS)研究之后,本文是又一篇关于非水体系中过渡金属表面SERS研究的文章。从拉曼谱峰的变化结果发现,吡啶在Pt电极表面是强烈的化学吸附,并且由于其吸附的量和吸附取向随电位在不断地变化,与水体系中吡啶(Py)在Pt电极表面的吸附相比较,SERS谱峰除了强度较低之外,在可研究的电位区间、谱峰位置以及其随电位变化等方面都存在着不同,这缘于结构较为复杂的有机溶剂分子在电极表面组成了更为复杂的界面结构,造成固/液界面的电迁移等电极动力学过程发生了变化,为了说明这一现象,文中还采用强吸附离子I^-进行研究,得到相似的结果。 相似文献
14.
Sarawuth Labuayai Vinich Promarak Santi Maensiri 《Applied Physics A: Materials Science & Processing》2009,94(4):755-761
This paper reports the synthesis and optical properties of nanocrystalline ZnO powders with crystallite sizes of 32.5 (±1.4)–43.4
(±0.4) nm prepared by a direct thermal decomposition of zinc acetate at the temperatures of 400, 500, 600, and 700°C for 4
h. The structure of the prepared samples was studied by XRD and FTIR spectroscopy, confirming the formation of wurtzite structure.
The morphology of the samples revealed by SEM was affected by the thermal decomposition temperature, causing the formations
of both nanoparticles and nanorods with different size and shape in the samples. The synthesized powders exhibited the UV
absorption below 400 nm (3.10 eV) with a well defined absorption peak at around 285 nm (4.35 eV). The estimated direct bandgaps
were obtained to be 3.19, 3.16, 3.14, and 3.13 eV for the ZnO samples thermally decomposed at 400, 500, 600, and 700°C, respectively.
All the samples exhibited room-temperature photoluminescence (PL) showing a strong UV emission band at ∼395 nm (3.14 eV),
a weak blue band at ∼420 nm (2.95 eV), a blue–green band at ∼485 nm (2.56 eV), and a very weak green band at ∼529 nm (2.35 eV).
The mechanisms responsible for photoluminescence of the samples are discussed. 相似文献
15.
L.L. Yang 《Applied Surface Science》2009,255(19):8197-8201
Indium tin oxide embedded with silver particles (ITO-Ag-ITO) multilayer films are deposited on the surface of fibers as reflective coatings through layer-by-layer method. Surface of fibers was modified by sodium dodecylbenzene sulfonate which is used as an excellent surfactant to increase the charge negativity of fibers. Silver layer was in situ obtained due to the reduction of SnCl2. Based on the electrostatic adsorption mechanism, scanning electron microscope (SEM) and electron dispersive spectroscopy (EDS) results show that multilayer films are well deposited onto fibers smoothly and densely. Transmission tests show that multilayer coated fibers have better near infrared (NIR) and Fourier transform infrared (FT-IR) reflectivity due to the embedded silver layer and the reflectivity is increased during high-temperature densification process. 相似文献
16.
为探讨胞嘧啶(Cytosine,Cy)在基底银表面的吸附特性和规律,采用表面增强拉曼散射(SERS)光谱对其吸附行为进行分析,并结合量子化学密度泛函理论(DFT)/B3LYP计算方法对Cy分子的常规拉曼光谱(NRS)及Cy与Ag团簇吸附的SERS光谱进行计算,与测定结果进行比对且对其拉曼峰进行系统指认及归属,理论计算结合实测值探讨了Cy在基底Ag上的增强效应和吸附行为。考察了Cy分子在Ag纳米粒子上的不同吸附时间、浓度、pH等条件对SERS光谱的影响及优化,发现pH影响最大,在中性和强碱性条件下的增强效应明显优于酸性。Cy分子存在2种不同的异构体和3种不同的存在形态,并随酸度变化相互转化而达动态平衡。基于Cy在不同pH时的形态分布和相应的SERS变化规律,结合DFT算得的Cy分子中的电荷分布及在银基底表面的吸附机制,详细探讨了酸碱对Cy分子的SRES光谱影响的内因和吸附机理,指出在中性和弱碱性时,是Cy中的N3和O与Ag形成配位吸附;在pH大于11时,N与Ag形成配位吸附,而O与Ag形成共价吸附。 相似文献
17.
ZnO-SDS hybrid thin films were grown on ITO glass using the potentiostatic electrodeposition route from aqueous zinc nitrate solution containing surfactant sodium dodecyle sulfanate (SDS). The electrochemical process of the hybrid films was analyzed by comparing the cyclic voltammetric curve and current-time curve with those of pure ZnO film. Results showed that the addition of a small amount of SDS could decrease the deposition current density, and inhibit the growth of ZnO crystals significantly. The hybrid films electrodeposited at −0.9 V for 30 min exhibited smooth and platelet-like morphology, with the film thickness of about 110 nm. The well-defined ZnO-SDS lamellar structures could be clearly observed, with two interlayer spaces of 35.1 and 30.9 Å, respectively. Optical analysis showed that the hybrid films had good optical quality, and exhibited the fundamental absorption edge of ZnO at 380 nm. 相似文献
18.
Erwu Niu Li Li Guohua Lv Wenran Feng Huan Chen Songhua Fan Size Yang Xuanzong Yang 《Applied Surface Science》2007,253(12):5223-5227
Tantalum nitride films were deposited on silicon wafer and steel substrates by cathodic vacuum arc in N2/Ar gas mixtures. The chemical composition, crystalline microstructure and morphology of the films were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. According to the results, film composition and microstructure depends strongly on the N2 partial pressure and the applied negative bias (Vs). 相似文献
19.
Ba(Zr0.05Ti0.95)O3 (BZT) thin films grown on Pt/Ti/SiO2/Si(1 0 0) substrates were prepared by chemical solution deposition. The structural and surface morphology of BZT thin films has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed that the random oriented BZT thin film grown on Pt/Ti/SiO2/Si(1 0 0) substrate with a perovskite phase. The SEM surface image showed that the BZT thin film was crack-free. And the average grain size and thickness of the BZT film are 35 and 400 nm, respectively. Furthermore, the chemical states and chemical composition of the films were determined by X-ray photoelectron spectroscopy (XPS) near the surface. The XPS results show that Ba, Ti, and Zr exist mainly in the forms of BZT perovskite structure. 相似文献
20.
S. Erdo?an C. Akmil-Ba?ar Ç. Sar?c?-Özdemir G. ?çduygu 《Applied Surface Science》2005,252(5):1324-1331
Waste apricot supplied by Malatya apricot plant (Turkey) was activated by using chemical activation method and K2CO3 was chosen for this purpose. Activation temperature was varied over the temperature range of 400-900 °C and N2 atmosphere was used with 10 °C/min heat rate. The maximum surface area (1214 m2/g) and micropore volume (0.355 cm3/g) were obtained at 900 °C, but activated carbon was predominantly microporous at 700 °C. The resulting activated carbons were used for removal of Ni(II) ions from aqueous solution and adsorption properties have been investigated under various conditions such as pH, activation temperature, adsorbent dosage and nickel concentration. Adsorption parameters were determined by using Langmuir model. Optimal condition was determined as; pH 5, 0.7 g/10 ml adsorbent dosage, 10 mg/l Ni(II) concentration and 60 min contact time. The results indicate that the effective uptake of Ni(II) ions was obtained by activating the carbon at 900 °C. 相似文献