共查询到19条相似文献,搜索用时 79 毫秒
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Ce-MCM-48介孔分子筛的合成、表征和催化性能 总被引:7,自引:0,他引:7
尝试以混合模板剂pH调节水热合成掺入铈的介孔分子筛CeMCM48,并采用X射线衍射、高分辨透射电镜、紫外可见漫反射、X射线荧光光谱、氮气吸附脱附测试手段对样品进行表征.结果表明,新合成的掺铈介孔材料仍保持立方介孔的有序结构,有序性及吸附性能得到改善.所合成的掺铈的立方介孔分子筛对环己烷的液相氧化反应的催化活性和选择性较高.CeMCM48催化环己烷氧化反应的转化率较MCM48催化的转化率提高了8.3%~14.2%,对主要产物的选择性提高了63.4%~68.8%. 相似文献
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在研制AlGaN/GaN HEMT器件的基础上,采用ALD法制备了Al2O3 AlGaN/GaN MOSHEMT器件.通过X射线光电子能谱测试表明在AlGaN/GaN异质结材料上成功淀积了Al2O3薄膜.根据对HEMT和MOSHEMT器件肖特基电容、器件输出以及转移特性的测试进行分析发现:所制备的Al2O3薄膜与AlGaN外延层间界面态密度较小,因而MOSHEMT器件呈现出较
关键词:
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ALD
GaN
MOSHEMT 相似文献
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以钛酸四正丁酯和硝酸镧为原料, 以P123为模板剂,采用模板法合成了La掺杂型介孔TiO2光催化剂, 借助TGA-DSC、BET、XRD及UV-Vis等测试手段对样品进行了表征,并以苯酚为模型污染物考察了镧掺杂量对样品光催化活性的影响.结果表明: La掺杂介孔TiO2光催化剂孔径分布较均匀(~10 nm),比表面积可达165 m2/g.与纯介孔TiO2相比,经掺杂改性后的样品在紫外光区及可见光区的吸收显著增强,对光具有更高的利用率,La掺杂可显著提高介孔TiO2的光催化活性. 相似文献
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探讨生长α-Fe2O3和Fe3O4纳米线的一个可控制的合成过程. 在研究中发现,高磁性的α-Fe2O3纳米线已经成功地利用氧化辅助气固法结晶生成于Fe0.5Ni0.5合金基板上;若基板事先浸泡于草酸溶液中,随草酸浓度的增加,所生长的纳米线晶相会逐转变为Fe3O4,当草酸浓度达到0.75 mol/L时,所生长的纳米线几乎全部转变成Fe3O4晶相. 此外,实验结果也显示所生长的纳米线长度及直径会随着气固过程中的温度上升而增加,生长密度则会随着气固过程中的流量加大而上升. 此过程所提出的合成程序可在2 h內完成. 相似文献
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光催化降解有机污染物由于其具有低能耗和绿色环保的特点,已经成为研究的热点. 氧化铋纳米晶体的带隙在2.0∽2.8 eV之间,利用它催化可见光降解有机污染物具有较高的活性,从而引起了越来越多的关注. 尽管近年来已经开发了几种制备Bi2O3基半导体材料的方法,但是仍然难以用简单的方法大规模地制备高活性的Bi2O3催化剂. 因此,开发简单可行的大规模制备Bi2O3纳米晶体的方法对于工业废水处理的潜在应用具有重要意义. 本文通过蚀刻商用BiSn粉末,然后进行热处理,成功地大规模制备了多孔Bi2O3. 获得的多孔Bi2O3在亚甲基蓝(MB)的光催化降解中表现出优异的活性和稳定性. 对该机理的进一步研究表明,多孔Bi2O3合适的能带结构允许生成活性氧物种,例如O2-·和·OH,可有效降解MB. 相似文献
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本文应用基于二极管激光器的双路光腔衰荡光谱技术,分别对大气中NO3和N2O5浓度进行监测. 通过使用实验室标准样校正有效吸收腔长比RL和系统的总损耗系数?,并获得了NO3有效吸收截面. 该装置在时间分辨率为1 s时,对NO3的测量灵敏度达到1.1 pptv,N2O5被在线转换成NO3,从而被另一路光腔衰荡光谱装置探测. 利用该装置,对合肥市区冬季夜间大气中的NO3,N2O5浓度进行了实时监测. 通过对比一次大气快速清洁过程中氮氧化物、臭氧、PM2.5等组分的浓度变化,讨论了大气环境下可能影响NO3及N2O5浓度的因素. 相似文献
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以棉花纤维为模板,以钛酸四正丁酯、硝酸铈铵和磷钨酸为原料采用模板法制备了一系列铈和磷钨酸共掺杂的、具有中空纤维结构的TiO2光催化材料, 利用扫描电子显微镜、X射线衍射、BET和紫外-可见光谱等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征. 以苯酚溶液的光催化降解为模型反应,考察了不同掺杂量的样品在紫外和可见光下的光催化性能. 结果表明,用模板法制备的TiO2纤维材料具有中空结构,共掺杂的TiO2纤维在紫外和可见光条件下较纯TiO2纤维和单掺杂TiO2纤维对苯酚溶液具有更好的光催化降解效果, 且铈和磷钨酸的掺杂量显著影响该纤维材料的催化性能;当铈掺杂量为0.3mol%和磷钨酸掺杂量为2mol%,在500 oC焙烧2 h所得中空纤维材料的催化性能最佳,4 h即可使苯酚溶液的降解率达98.5%;重复使用4次仍可使苯酚溶液的降解率保持在87%以上,且该催化剂材料易于离心分离去除. 相似文献
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Mechanism of amorphous Ge2Sb2Te5 removal during chemical mechanical planarization in acidic H2O2 slurry
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In this paper, chemical mechanical planarization (CMP) of amorphous Ge2Sb2Te5 (a-GST) in acidic H2O2 slurry is investigated. It was found that the removal rate of a-GST is strongly dependent on H2O2 concentration and gradually increases with the increase in H2O2 concentration, but the static etch rate first increases and then slowly decreases with the increase in H2O2 concentration. To understand the chemical reaction behavior of H2O2 on the a-GST surface, the potentiodynamic polarization curve, surface morphology and cross-section of a-GST immersed in acidic slurry are measured and the results reveal that a-GST exhibits a from active to passive behavior for from low to high concentration of H2O2 . Finally, a possible removal mechanism of a-GST in different concentrations of H2O2 in the acidic slurry is described. 相似文献
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Hao Wen Zhifu Liu Jiao Wang Qunbao YangYongxiang Li Jerry Yu 《Applied Surface Science》2011,257(23):10084-10088
Nb2O5 nanorod array films were synthesized by a facile hydrothermal process using niobium metal foil and NH4F as precursors. The Nb2O5 nanorods stand on the niobium metal foil substrate and are less than 100 nm in diameter and about 1 μm in length. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) characterizations indicate that these nanorods have orthorhombic structure and grew longitudinally along 〈0 0 1〉 direction. The nanorod growth mechanism was discussed. Thermal annealing at a temperature below 500 °C did not change the microstructure of nanorods but improve the crystallinity. The Nb2O5 nanorod array films have been tested as cathode material for lithium battery, which showed a good specific capacity up to 380 mAh g−1 even after 50 charge/discharge cycles. 相似文献
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以介孔分子筛MCM-48为载体,采用水热法制备了负载磷钨酸H3PW12O40(HPW)的多金属氧酸盐催化剂HPW/MCM-48。利用傅里叶变换红外光谱(FT-IR)、小角度X射线粉末衍射(XRD)、氮气吸附检测和高分辨透射电子显微镜(HRTEM)对其结构进行了表征,并以农药吡虫啉和百草枯为对象,考察了所制备的HPW/MCM-48的光催化降解活性。结果表明,采用水热法制备的催化剂保持了MCM-48的介孔分子筛结构和HPW的Keggin结构,比表面积783.35m2·g-1,孔体积1.46cm3·g-1,平均孔径2.76nm,相比于母体HPW,HPW/MCM-48的比表面积大大增加;在365nm紫外光下反应14h后,20mg剂量HPW/MCM-48催化剂能使50mL,10mg·L-1吡虫啉和百草枯的降解率分别达57.38%和63.79%,而HPW对两种农药的降解率在25%左右,空白组降解率均低于5%,说明负载后HPW对两农药的降解活性显著增强。动力学考察表明,HPW/MCM-48对农药降解过程符合一级动力学方程,对吡虫啉和百草枯这两种农药的降解速率常数Ka分别为0.089和0.117h,半衰期t1/2为7.8和5.9h。 相似文献
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C. Li 《Applied Surface Science》2010,256(22):6801-6804
Fe2O3/Al2O3 catalysts were prepared by solid state reaction method using α-Fe2O3 and γ-Al2O3 nano powders. The microstructure and surface properties of the catalyst were studied using positron lifetime and coincidence Doppler broadening annihilation radiation measurements. The positron lifetime spectrum shows four components. The two long lifetimes τ3 and τ4 are attributed to positronium annihilation in two types of pores distributed inside Al2O3 grain and between the grains, respectively. With increasing Fe2O3 content from 3 wt% to 40 wt%, the lifetime τ3 keeps nearly unchanged, while the longest lifetime τ4 shows decrease from 96 ns to 64 ns. Its intensity decreases drastically from 24% to less than 8%. The Doppler broadening S parameter shows also a continuous decrease. Further analysis of the Doppler broadening spectra reveals a decrease in the p-Ps intensity with increasing Fe2O3 content, which rules out the possibility of spin-conversion of positronium. Therefore the decrease of τ4 is most probably due to the chemical quenching reaction of positronium with Fe ions on the surface of the large pores. 相似文献
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Microwave characteristics of MgB2/Al2O3 superconducting thin films were investigated by coplanar resonator technique. The thin films studied have different grain sizes resulting from different growth techniques. The experimental results can be described very well by a grain-size model which combines coplanar resonator theory and Josephson junction network model. It was found that the penetration depth and surface resistance of thin films with smaller grain sizes are larger than those of thin films with larger grain sizes. 相似文献
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Li ZhangYoshio Hashimoto Toshinori TaishiIsao Nakamura Qing-Qing Ni 《Applied Surface Science》2011,257(15):6577-6582
A novel flower-shaped Bi2O3 superstructure has been successfully synthesized by calcination of the precursor, which was prepared via a citric acid assisted hydrothermal process. The precursor and Bi2O3 were characterized with respect to morphology, crystal structure and elemental chemical state by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was shown that both the precursor and Bi2O3 flower-shaped superstructure were constructed of numerous nanosheets while the nanosheets consisted of a great deal of nanoparticles. Furthermore, key factors for the formation of the superstructures have been proposed; a mechanism for the growth of the superstructure has been presented based on the FESEM investigation of different growth stages. 相似文献
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Brannerite MnV 2 O 6 with plate-like shape is successfully synthesized by hydrothermal method.Its crystal structure and morphology are investigated by x-ray diffraction (XRD),scanning electron microscopy (SEM),transmission electron microscope (TEM),high resolution transmission electron microscopy (HRTEM) and select area electronic diffraction (SAED).The results show that the brannerite MnV 2 O 6 with monoclinic structure has a uniform plate-like shape with a diameter of about 5-8 μm and a thickness of about 500 nm.SAED patterns further confirm the structure of the brannerite MnV 2 O 6 and the single crystalline character of the plate crystal.Magnetic properties are measured by superconducting quantum interference device (SQUID) in a temperature range of 2-300 K under a magnetic field of 1 T.The magnetic measurement results indicate that the material undergoes an antiferromagnetic transition with a N’eel temperature of 17 K.Above 50 K,the inverse susceptibility is fitted well to the Curie-Weiss law with a calculated moment of 5.98 μ B.Finally,the origin of antiferromagnetic behaviour in the brannerite MnV 2 O 6 is explained by means of Anderson model. 相似文献
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Nanocrystalline Y2Si2O7:Eu phosphor with an average size about 60 nm is easily prepared using silica aerogel as raw material under ultrasonic irradiation and annealing temperature at 300-600 °C and this nanocrystalline decomposes into Y2O3:Eu and silica by heat treatment at 700-900 °C. The excitation broad band centered at 283 and 254 nm results from Eu3+ substituting for Y3+ in Y2Si2O7 and Y2O3/SiO2, respectively. Compared with Y2O3:Eu/SiO2 crystalline, the PL excitation and emission peaks of Y2Si2O7:Eu nanocrystalline red-shift and lead to the enhance of its luminescence intensity due to the different chemical surroundings of Eu3+ in above nanocrystallines. The decrease of PL intensity may be ascribed to quenching effect resulting from more defects in Y2O3:Eu/SiO2 crystalline. 相似文献