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1.
A series of Fe2-xCrxO3(x = 0, 0.4, 0.8, 1.2, 1.6, 2.0) mixed oxides have been prepared with the chemical coprecipitation method and characterized by specific surface area, transmission electron microscopy (TEM), powder X-ray diffraction (XRD), IR and Mössbauer spectroscopy. Single-phase Fe-Cr mixed oxide nano-crystalline powders with corundum structure are obtained, and the results of the five characterization methods are well accordant with each other. Furthermore, gas-sensitive properties of the sensors made of the oxide powders have been studied. 相似文献
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Das Pritam Kumar Mallik Arnab Kumar Molla Altaf Hossain Santra Apurba Kumar Ganguly Ranjan Saha Abhijit Kumar Sugam Aswal V. K. 《Journal of Thermal Analysis and Calorimetry》2022,147(10):5617-5635
Journal of Thermal Analysis and Calorimetry - Nanofluids have gained recent attention because of their potential applications in diverse engineering fields like enhancing thermal transport,... 相似文献
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Intrinsic viscosity of SiO2, Al2O3 and TiO2 aqueous suspensions 总被引:1,自引:0,他引:1
Rubio-Hernández FJ Ayúcar-Rubio MF Velázquez-Navarro JF Galindo-Rosales FJ 《Journal of colloid and interface science》2006,298(2):967-972
The viscosity of dilute suspensions of several metal oxides (SiO2, Al2O3 and TiO2) was measured at different pH values. The intrinsic viscosity, [eta], was derived from the concentration dependence of the viscosity. This magnitude was pH-dependent. A correlation with the shape of the kinetic unity has been proposed. 相似文献
4.
Enis S. Džunuzović Jasna V. Džunuzović Aleksandar D. Marinković Milena T. Marinović-Cincović Katarina B. Jeremić Jovan M. Nedeljković 《European Polymer Journal》2012,48(8):1385-1393
Nanocomposites based on poly(methyl methacrylate) (PMMA) and TiO2 nanoparticles were synthesized by in situ radical polymerization of MMA in solution. The surface of TiO2 nanoparticles was modified with four gallic acid esters (octyl, decyl, lauryl and cetyl gallate). The content of gallates present on the surface of TiO2 was calculated from the TGA results. The influence of length of hydrophobic tail of amphiphilic alkyl gallates on dispersability of surface modified TiO2 nanoparticles in PMMA matrix, the molecular weight and glass transition temperature of PMMA, as well as the thermal stability of the prepared PMMA/TiO2 nanocomposites in nitrogen and air was investigated. The influence of content of TiO2 nanoparticles on the properties of these nanocomposites was also examined. The formation of a charge transfer complex between the surface Ti atoms and the gallates was confirmed by FTIR and UV spectroscopy. TEM micrographs of the PMMA/TiO2 nanocomposites revealed that degree of TiO2 aggregation can be significantly lowered by increasing the length of aliphatic part of the used gallates. The molecular weight of PMMA slightly decreases with the increase of TiO2 content, indicating that used TiO2 nanoparticles act as radical scavengers during the polymerization of MMA. The presence of surface modified TiO2 nanoparticles do not have an influence on the mobility of PMMA chain segments leading to the same values of glass transition temperature for all investigated samples. Thermal and thermo-oxidative stability of the PMMA matrix are improved by introducing TiO2 nanoparticles modified with gallates. 相似文献
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《Journal of Molecular Catalysis #》1987,39(1):43-53
In situ reduction of previously adsorbed Pt4+ species on TiO2 (anatase) was employed to obtain highly active catalysts for hydrogen photoevolution from a methanol-water solution. A quantum yield as high as 22% was observed. Optimum platinum coverage and the most favourable reaction conditions were established. The influence of surface Cr2O3 admixtures on photoactivity of TiO2 was investigated. It was found that although the dopant shifts the anatase spectrum into the visible, it was not possible to obtain hydrogen with light of energy smaller than the bandgap of TiO2. However, a small amount of Cr2O3 on the TiO2 surface acts as a poor catalyst for hydrogen evolution. 相似文献
7.
ZrO2和Al2O3在金红石型TiO2表面的包覆研究 总被引:3,自引:0,他引:3
以(NaPO3)6为分散剂,用化学沉积法对金红石型TiO2进行了锆、铝氧化物包膜。研究了包覆过程中,TiO2的分散、ZrO2和Al2O3用量、反应pH值以及时间对二氧化钛的亨特白度(Wh)和光泽度(L)的影响,并采用扫描电镜(SEM)、透射电镜(TEM)、X光电子能谱(XPS)和沉降性试验对包覆前后的二氧化钛进行了表征,得到包锆、包铝氧化物的优化工艺条件。研究了二氧化钛表面包锆、铝氧化物的包覆机理和表面结构。经过其表面包膜处理,二氧化钛的颜料性能得到明显改善。 相似文献
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Achelhi K Masse S Laurent G Roux C Laghzizil A Saoiabi A Coradin T 《Langmuir : the ACS journal of surfaces and colloids》2011,27(24):15176-15184
Zirconia-hydroxyapatite nanocomposites were prepared by sol-gel deposition of zirconium oxide from a zirconium alkoxide in the presence of apatite colloidal suspension under ultrasonication. The material porosity evolves from mainly microporous zirconia to mesoporous hydroxyapatite, with decreasing surface area and increasing pore volume. XRD studies indicate that the apatite phase is well-preserved within the composite materials. The homogeneous dispersion of apatite colloids within the zirconia network was supported by TEM observations and nitrogen sorption measurements. (31)P solid-state NMR studies suggest that partial dissolution of apatite may have occurred during the preparation, leading to the adsorption of phosphate species on zirconia particles. This is confirmed by XRD studies of nanocomposites after thermal treatment that demonstrate the preferred formation of tetragonal over monoclinic ZrO(2) in the presence of hydroxyapatite. In order to investigate the surface properties of these novel materials, the adsorption of Pb(2+), Cr(3+), and Cr(2)O(7)(2-) was evaluated. Metal cations were preferentially adsorbed on apatite-rich composites, whereas Cr(2)O(7)(2-) shows a good affinity for the zirconia-rich phases. Zirconia-apatite materials showed the most promising performance in terms of recyclability. These nanocomposites that combine microporosity, mesoporosity and dual sorption properties for these species appear as interesting materials for metal ion remediation and may also find applications as biomaterials. 相似文献
10.
Chromium oxides supported on TiO2 showed good activity for the selective catalytic reduction of NO by NH3.The catalytic activity of Cr2O3-SO42-/TiO2 catalyst was greatly enhanced by the addition of SO42-into TiO2 support.The catalyst surface properties were characterized with NH3-TPD(temperature programmed desorption) and H2-TPR(temperature programmed reduction).The sulphate on the catalyst surface could enhance the acidity and redox of the catalyst obviously.The reaction mechanism on this catalyst was researched in detail by in situ diffuse reflectance Fourier transform infrared(FTIR) spectroscope.Eley-Rideal and Langmuir-Hinshelwood mechanism existed simultaneously for selective catalytic reduction(SCR) reaction of NO over Cr2O3-SO42-/TiO2 catalyst. 相似文献
11.
Xiaoli Dong Yong Shao Xinxin Zhang Hongchao Ma Xiufang Zhang Fei Shi Chun Ma Mang Xue 《Research on Chemical Intermediates》2014,40(8):2953-2961
The Fe3O4/TiO2/Bi2O3 composites were synthesized by a sol–gel method and used as improved photocatalysts for the degradation of methyl orange (MO) under simulated sunlight at room temperature. The as-prepared Fe3O4/TiO2/Bi2O3 composites were characterized by X-ray diffraction, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (DRS). TEM analysis reveals that the composite has a core–shell structure and diameters of Fe3O4 core is about 200 nm. DRS results reveal that all composites showed red shift in optical absorption. TiO2, Fe3O4, and Bi2O3 exist mainly as separate phases in the Fe3O4/TiO2/Bi2O3 composites based on XPS analysis. The photocatalytic degradation of MO with the prepared photocatalysts was studied under simulated sunlight illumination. Photocatalytic reactivity test indicated that the removal efficiency of MO with the Fe3O4/TiO2/Bi2O3 photocatalyst was higher than that of pure TiO2 and Fe3O4/TiO2. Recovery rate of Fe3O4/TiO2/Bi2O3 photocatalysts achieved 80 % after five times reuse. 相似文献
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The electronic and magnetic properties of CaCu3Cr4O12 and CaCu3Cr2Sb2O12 are investigated by the use of the full-potential linearized augumented plane wave (FPLAPW) method. The calculated results indicate that CaCu3Cr4O12 is a ferrimagnetic and half-metallic compound, in good agreement with previous theoretical studies. CaCu3Cr2Sb2O12 is a ferrimagnetic semiconductor with a small gap of 0.136 eV. In both compounds, because Cr4+ 3d (d2) and Cr3+ 3d (d3) orbitals are less than half filled, the coupling between Cr-Cu is antiferromagnetic, whereas that between Cu-Cu and Cr-Cr is ferromagnetic. The total net spin moment is 5.0 and 3.0 microB for CaCu3Cr4O12 and CaCu3Cr2Sb2O12, respectively. In CaCu3Cr4O12, the 3d electrons of Cr4+ are delocalized, which strengthens the Cr-Cr ferromagnetic coupling. For CaCu3Cr2Sb2O12, the doping of nonmagnetic ion Sb5+ reduces the Cr-Cr ferromagnetic coupling, and the half-filled Cr3+ t2g (t2g3) makes the chromium 3d electrons localized. In addition, the ordering arrangement of the octahedral chromium and antimony ions also prevents the delocalization of electrons. Hence, CaCu3Cr2Sb2O12 shows insulating behavior, in agreement with the experimental observation. 相似文献
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本文以制革含铬革屑为原材料,基于矿物鞣剂复鞣的原理,将Ti(IV)均匀、稳定地负载到含铬革屑上,在氮气氛围下,经高温热解制备得到C/Cr2O3/TiO2光催化剂,并研究了其对四环素(TC)的光催化降解效果及机理。结果表明,C/Cr2O3/TiO2光催化剂具有明显的介孔结构,比表面积较大,为277.47 m2·g-1,Cr2O3和TiO2已实现复合并负载在生物炭(C)上。通过光催化降解发现,在模拟自然光照下,当催化剂用量为0.04 g,TC初始浓度为50 mg·L-1,溶液pH为2时,TC的去除率可高达99.99%。结合自由基捕获实验发现,C/Cr2O3/TiO2光催化剂对TC的降解作用主要依靠反应体系中产生的大量·O2-,·OH和h+。 相似文献
14.
α- Fe2O3-TiO2复合晶膜的制备及光催化特性的研究 总被引:7,自引:0,他引:7
α-Fe2O3和Ti02均为n型半导体,在紫外光照射下可使亚甲基蓝发生氧化还原反应,使之降解.α-Fe2O3禁带宽度(2.2eV)比Ti02的禁带宽度(3.1eV)小,而其吸收光于的效率大于Ti02,在催化降解亚甲基蓝时表现出比Ti02更高的活性.α-Fe2O3-Ti02复合晶体的光吸收强度要比单一α-Fe2O3晶体的光吸收强度明显增强.在α-Fe2O3中掺入少量Ti02后,在紫外光照射下对亚甲基蓝的降解显示出更高的活性. 相似文献
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采用高温固相反应法合成了Cr2O3/TiO2复合材料, 运用X射线衍射(XRD)、扫描电子显微镜(SEM)、充放电测试、循环伏安(CV)、电化学阻抗谱(EIS)等对其结构、形貌和电化学性能进行了表征. 研究结果表明: TiO2掺杂能够显著改善Cr2O3的充放电循环性能, Cr2O3/TiO2复合材料在充放电循环22周后仍有454 mAh·g-1的可逆循环容量, 容量保持率达到了73.6%, 主要归因于TiO2掺杂能够显著提高Cr2O3的电导率. Cr2O3/TiO2复合材料首次放电过程中由于电极体积膨胀导致的固体电解质相界面(SEI)膜迅速增厚和活性材料电导率的降低可能是其首次充放电过程中存在较大不可逆容量和循环容量衰减的重要原因. 相似文献
16.
O. V. Mokhnachuk S. A. Solov’ev A. I. Senkevich 《Theoretical and Experimental Chemistry》2006,42(1):48-52
We have established that the thermal stability of supported Pd/Al2O3 catalysts is increased after they are modified by rare earth oxides (La2O3, Ce2O3). We have observed the effect of thermal activation of an aluminopalladium catalyst modified by lanthanum oxide. This effect
is apparent in the increase of the specific catalytic activity in the reaction of high-temperature reduction of nitrogen oxides
by methane after heat treatment of the catalyst at 850 °C. We have used X-ray photoelectron spectroscopy (XPS) to show that
the reason for the thermal activation effect is stabilization of palladium in the Pd1+ state.
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Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 1, pp. 44–48, January–February, 2006. 相似文献
17.
采用电沉积-热解法在3Cr25Ni7N合金表面制备了Y2O3薄膜,并研究了薄膜处理对合金在1000℃空气中的抗高温氧化性能的影响。氧化动力学曲线、SEM及XRD分析结果表明,Y2O3薄膜处理使合金表面氧化膜以尖晶石结构为主,氧化膜致密,有效地抑制了Cr2O3的挥发反应,且氧化膜与基体的附着性好,因此合金在高温下的抗氧化性能得到提高,这与氧化钇薄膜在较低温度下抗高温氧化性能提高的机制是不同的。在不同温度下,Y2O3薄膜处理均可以有效提高合金的抗高温氧化性能。 相似文献
18.
采用铝阳极氧化法制备了Al2O3-Al-体型多孔氧化铝载体,再采用电沉积技术将TiO2沉积到氧化铝多孔的纳米孔道内,制备了催化精馏专用SO42-/TiO2-Al2O3-Al型固体酸催化剂,并以乙酸乙酯合成为模型反应,考察了水封条件,电沉积电压、电沉积时间等制备工艺条件对催化剂活性的影响.实验结果表明,适宜的制备条件为水封温度为50℃,水封时间为1 h,电沉积电压为6V,电沉积时间为30 min,在此制备条件下,醋酸转化率为31.34%.采用扫描电镜(SEM),X射线衍射分析(XRD)手段对所制备催化剂进行了表征.结果表明:阳极氧化铝膜的结构为无定型结构,TiO2在载体上呈高度分散状态. 相似文献
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Phase relations in the pseudobinary system ZnO-Ga2O3 were investigated at 1723 K. The homologous phase Ga2O3(ZnO)m was formed in a region 9 ≦ n ≦ 38 for ZnO: Ga2O3 = n: 1, and Ga-doped ZnO (wurtzite structure) was in n ≧ 398. In between the two regions (i.e. 38 < n < 398) a composite of Ga-doped ZnO and the homologous phase Ga2O3(ZnO)mmax (mmax ≈ 38) was formed. Thermoelectric properties of the composite were examined along with Ga-doped ZnO and the homologous phase Ga2O3(ZnO)33. In the composite, the homologous phase appears to be very effective in lowering the thermal conductivity. As a result of a trade-off relationship between the power factor and the thermal resistivity, thermoelectric performance happened to be roughly the same for the composite and Ga-doped ZnO samples. 相似文献