首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
In this article, we illustrated the preparation method of γ-Al2O3 ultrafine particles. The particle size and morphology were decided by a transmission electron microscopy (TEM) and crystal patterns were determined by an X-ray diffractometer (XRD). γ-Al2O3 ultrafine particles have ultra characters in physics and chemistry, and the hydrogen peroxide biosensors based on it display not only fast response and high sensitivity, but also good stability.  相似文献   

2.
Ultrafine γ-Al2O3 particles are synthesized in Triton X-100/n-hexanol/cyclohexane/water water in oil(w/o) microemulsion by mixing two separately prepared microemulsions containing Al(NO)3 and (NH4)2CO3 respectively. The ultrafine Al2O3 particles are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) and their size and distribution are measured. The effects of water, surfactant and reactant concentrations on the particle size and distribution are studied. The results show that the particle size and distribution can be changed by varying the preparation conditions, and the size of the microemulsion droplets has a controlling effect on the size of the particles. A possible mechanism of ultrafine particles (UFPs) prepared by microemulsions is proposed.  相似文献   

3.
Using SnxTi1-xO2 as carriers, CuO/Sn0.9Ti0.1O2 and CuO/Sn0.7Ti0.3O2 catalysts with different loading amounts of copper oxide (CuO) were prepared by an impregnation method. The catalytic properties of CuO/Sn0.9Ti0.1O2 and CuO/Sn0.7Ti0.3O2 were examined using a microreactor-gas chromatography (GC) NO CO reaction system and the methods of BET (Brun- auer-Emmett-Teller), TG-DTA (themogravimetric and differential thermal analysis), X-ray diffraction (XRD) and H2-temperature programmed reduction (TPR). The results showed that NO conversions of Sn0.9Ti0.1O2 and Sn0.7Ti0.3O2 were 47.2% and 43.6% respectively, which increased to 95.3% and 90.9% at 6 wt% CuO loading. However, further increase in CuO loading caused a decrease in the catalytic activity. The nitrogen adsorption-desorption isotherm and pore-size distribution curve of Sn0.9Ti0.1O2 and Sn0.7Ti0.3O2 represented type IV of the BDDT (Brunauer, Deming, Deming and Teller) system and a typical mesoporous sample. There were two CuO diffraction peaks (2θ 35.5° and 38.7°), and the diffraction peak areas increased with increasing CuO loading. TPR analysis also detected three peaks (α, β and γ) from the CuO-loaded catalysts, suggesting that the α peak was the reduction of the highly dispersed copper oxide, the β peak was the reduction of the isolated copper oxide, and the γ peak was the reduction of crystal phase copper oxide. In addition, a fourth peak (δ) of the catalysts meant that the SnxTi1-xO2 mixed oxides could be reductive.  相似文献   

4.
Wang  Yunhao  Gao  Kaige  Ye  Chenliang  Li  Ang  Guo  Cuili  Zhang  Jinli 《天津大学学报(英文版)》2019,25(6):576-585
In this study,Pd-Mg(Al)-LDH/γ-Al_2O_3 and Pd-Mg(Al)Zr-LDH/γ-Al_2O_3 precursors were synthesized by impregnating Na_2PdCl_4 on Mg(Al)-LDH/γ-Al_2O_3 and Mg(Al)Zr-LDH/γ-Al_2O_3,and then the precursors were calcinated and reduced to obtain Pd-Mg(Al)-MMO/γ-Al_2O_3 and Pd-Mg(Al)Zr-MMO/γ-Al_2O_3 catalysts.Compared with Pd/γ-Al_2O_3 catalyst,the hydrogenation efficiency of Pd-Mg(Al)-MMO/γ-Al_2O_3 and Pd-Mg(Al)Zr-MMO/γ-Al_2O_3 increased by 15.7%and 24.0%,respectively.Moreover,the stability of Pd-Mg(Al)Zr-MMO/γ-Al_2O_3 catalyst was also higher than that of Pd/γ-Al_2O_3.After four runs,the hydrogenation efficiency of Pd/γ-Al_2O_3 decreased from 12.1 to 10.0 g/L,while that of Pd-Mg(Al)Zr-MMO/γ-Al_2O_3 decreased from 15.0 to 14.3 g/L.The active aquinones selectivities of all catalysts were almost 99%.The structures of the catalysts were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),N_2 adsorption-desorption,inductively coupled plasma-atomic emission spectrometry (ICP-AES),CO chemisorption analysis,transmission electron microscopy (TEM),temperature-programmed reduction with hydrogen (H_2-TPR),and X-ray photoelectron spectroscopy(XPS).The results indicate that the improved catalytic performance is attributed to the stronger interaction between Pd and Mg(Al)Zr-MMO/γ-Al_2O_3,smaller Pd particle size and higher Pd dispersion.This work develops an effective method to synthesize highly dispersed Pd nanoparticles based on the layered double hydroxides (LDHs) precursor.  相似文献   

5.
1IntroductionThe synthesis and characterization of nano-struc-tured materials are the subject of intense current re-search.Hyperfineγ-Fe2O3particle with good perfor-mance,such as magnetism,catalysis,gas-sensitivityand so on,are widely applied in various fields[1].It ishighly significant to research and develop the methodsfor synthesis of nanometerγ-Fe2O3.With the development of nano-science and nano-technology,the methods for preparation ofγ-Fe2O3have been greatly progressed,for example,…  相似文献   

6.
Cucumber and rice plants with varying ammonium (NH4 +) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO3 −)-grown plants, cucumber plants grown under NH4 +-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO2) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O2-independent alternative electron flux, and increased O2-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH4 +-grown plants had a higher O2-independent alternative electron flux than NO3 −-grown plants. NO3 − reduction activity was rarely detected in leaves of NH4 +-grown cucumber plants, but was high in NH4 +-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO3 − assimilation, an effect more significant in NO3 −-grown plants than in NH4 +-grown plants. Meanwhile, NH4 +-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO3 − reduction, regardless of the N form supplied, while NH4 +-sensitive plants had a high water-water cycle activity when NH4 + was supplied as the sole N source.  相似文献   

7.
Activities of FeO in CaO-SiO2-Al2O3-MgO-FeO slags were determined at 1673 K by electrochemical of the solid electrolyte cell： Mo [Mo＋MoOu[ZrO2（MgO）[Fe＋（CaO-SiO2-Al2O3-MgO-FeO）＋Ag[Fe. The influences of slag compositions and basicity on FeO activities were analyzed. The results reveal that, for slags of fixed （%CaO）/（%SiO2） ratio, MgO and Al2O3 content, there was an increase of FeO activities with increase of FeO content. For slags with constant {（%CaO）＋ （%MgO）}/（%SiO2） ratio, fixed FeO and A1203 content, FeO activities decreased when MgO content increased from 5% to 10%, and increased with the increase of MgO content when it was over 10%. The FeO activities increased when （%CaO）/（%SiO2） ratio changed from 1.03 to 1.30 in the slags of constant MgO, FeO and Al2O3 content.  相似文献   

8.
With InCl3·4H2O being used as raw materials, the precursor of nano-sized In2O3 powder was prepared by hydrolysis, peptization and gelation of InCl3·4H2O. After calcination, nano-sized In2O3 powder was obtained. The powder was characterized by thermo-gravimetric and differential thermal analysis (TG-DTA), X-ray diffractometry (XRD) and transmission electron microscopy (TEM), respectively. Calculation revealed that the mean crystalline size increased with increasing the calcination temperature, but crystal lattice distortion rate decreased with the increasing in the average crystalline size. This indicated that the smaller the particle size, the bigger the crystal lattice distortion, the worse the crystal growing. The activation energies for growth of nano-sized In2O3 were calculated to be 4.75 kJ·mol−1 at the calcination temperature up to 500°C; and 66.40 kJ·mol−1 at the calcination temperature over 600°C. TEM photos revealed that the addition of the chemical additive (OP-10) greatly influenced the morphology and size of In2O3 particles.  相似文献   

9.
In this study, we used a simple impregnation method to prepare Fe–Ce–O x catalysts and tested them regarding their low-temperature (200–300 °C) selective catalytic reduction (SCR) of NO using NH3. We investigated the effects of Fe/Ce molar ratio, the gas hourly space velocity (GHSV), the stability and SO2/H2O resistance of the catalysts. The results showed that the FeCe(1:6)O x (Ce/Fe molar ratio is 1:6) catalyst, which has some ordered parallel channels, exhibited good SCR performance. The FeCe(1:6)O x catalyst had the highest NO conversion with an activity of 94–99% at temperatures between 200 and 300 °C at a space velocity of 28,800 h?1. The NO conversion for the FeCe(1:6)O x catalyst also reached 80–98% between 200 and 300 °C at a space velocity of 204,000 h?1. In addition, the FeCe(1:6)O x catalyst demonstrated good stability in a 10-h SCR reaction at 200–300 °C. Even in the presence of SO2 and H2O, the FeCe(1:6)O x catalyst exhibited good SCR performance.  相似文献   

10.
The relation of boron trifluoride concentration with conductivity in boron trifluoride methanol solution (BF3-CH3OH)was power exponent fitted in low concentration range. The kinetics of the reaction between boron trifluoride methanol complex and sodium methoxide to produce enriched 10B methylborate was proposed based on a detailed mechanism study, and was verified by acid-base titration method and conductivity method. It was found that this reaction is first order reaction and the rate constant is 0.022 min?1 at 338 K(65 °C), the activity energy is 65 kJ/mol. In addition, it was found that the conductivity method is more feasible to measure the kinetic curve than acid-base titration method.  相似文献   

11.
The use of a biotrickling filter was investigated for a pilot field-scale elimination of NH3 gas and other odorous gases from a composting plant in Tongzhou District, Beijing. The inlet gas flow rate was 3500 m3/h and NH3 concentration fluctuated between 2.76–27.84 mg/m3, while the average outlet concentration was 1.06 mg/m3 with an average of 94.9% removal. Critical volumetric loading (removal efficiency=100%) was 11.22 g-N/(m3·h). The odor concentration removal was 86.7%. NH3 removal efficiency decreased as the free ammonia (FA) in the trickling liquid increased. The pressure drop was maintained at about 50 Pa/m and was never more than 55 Pa/m. During the experiment, there was neither backflushing required nor any indication of clogging. Overall, the biotrickling filter was highly efficient and cost-effective for the simultaneous biodegradation of NH3 and other odorous gases from composting, suggesting the possibility of treating odorous gases at the industrial level.  相似文献   

12.
INTRODUCTION Metal hydrides are special alloys which absorb and desorb hydrogen reversibly. At room temperature, metal hydrides could absorb as much hydrogen as liquid hydrogen of the same volume under much lower pressure and much higher temperature (Güther and Otto, 1999). Massive reaction heat is generated accompanying this reaction, which could be used for waste heat recovery, solar energy utilization and re-frigeration with no side effect to environment (Izhvanov et al., 1996). Con…  相似文献   

13.
In2O3 Ultrafine Powder Synthesis by Sol—Gel Method   总被引：1，自引：0，他引：1  
The precursor of ultrafine In2O3 powder was prepared by the hydrolysis,peptization and gelation of InCl3.4H2O used as raw material.After calcination,ultrafine In2O3 powder was obtained.The particles were characterized by the methods of thermo-gravimetric and differential thermal analysis(TG-DTA),X-ray diffractometry(XRD) and transmission electron microscopy(TEM).respectively.  相似文献   

14.
Chemically processed Nb-doped SrTiO3 films and properties   总被引：1，自引：0，他引：1  
Homogeneous, crack-free SrNbxTi1−x O3 thin films on (110) silicon substrates were successfully fabricated by sol-gel processing. The optimum route and conditions were systematically investigated. Sr(OAc)2 glacial acctic acid solution, after being refluxed and reacted with tartrate, formed Sr(OAc)2(C4H6O6)2; Ti(OBu)4 formed Ti(OAc)4−x (AcAc)x after having the ligand partially exchanged with AcAc, while Nb(OC2H5)5 formed (OAc)2Nb(AcAc) (C4H6O6) by exchanging of ligand in glacial acetic acid with (CH3CO)2O. All the metal species after undergoing partial hydrolysis and polymerization with hydroxyl or oxygen, formed SrNbxTi1−x O13 cluster sol. Methyl cellulose (MCL) caused SrNbxTi1−x O3 sol to have polymeric structure and easily form films. SrNbxTi1−x O3 films with perovskite were subsequently formed after being annealed at 650∼750 °C for 60 min in 25% N2+75% H2 (volume ratio) atmosphere. Resistivity of the SrNb0.1Ti0.9O3 films at room temperature was 64 μω·cm, a particular T 2 temperature dependence of the resistivity, from 25 K up to room temperature, was observed. Project (No. 2002CB613305) supported by the National Basic Research Program (973) of China  相似文献   

15.
Ultra-high vacuum gaseous hydrogen permeation experiments on Fe3Al-based alloy were performed in the temperature range of 330∼450°C with an upstream hydrogen pressure between 3. 38×104 Pa and 7.28×104 Pa. The results show that the hydrogen diffusivity and permeability in Fe3Al-based alloy obey Arrhenius relationship in the experimental temperature range and the hydrogen permeation process is controlled by the lattice diffusion of hydrogen at relative high temperature. The activation energy of hydrogen diffusion in the Fe3Al-based alloy was found to be 75 kJ/mol. Supported by the National Natural Science Foundation of China (59895157)  相似文献   

16.
The pure γ-Ca2SiO4 （]t-C2S） phase was prepared at 1623 K of calcining temperature, 10 h of holding time and furnace cooling. The 13-C2S phase was obtained through γ-C2S conversion with the following calcination system which was adopted at 1473 K of calcining temperature, 1 h of holding time and then water-cooling. The conversion rate of γ-C2S was studied by the Rietveld quantitative laboratory X-ray powder diffraction supported by synchrotron X-ray diffraction images. The refinement results show that the final conversion rate of γ-C2S is higher than 92%. The absolute error of the γ-C2S conversion rate between two Rietveld refinements （sample with or without α-Al2O3） is 3.6%, which shows that the Rietveld quantitative X-ray diffraction analysis is an appropriate and accurate method to quantify the γ-C2S conversion rate.  相似文献   

17.
In order to clarify the equilibrium components in the hydrolysis solution of boron trifluoride(BF_3-H_2O),the BF_3-H_2O was prepared by mixing BF_3-CH_3OH with large amount of water,in which the stoichiometric concentration of BF_3 is less than 0.1 mol/L.Two ionic equilibrium models were proposed to simulate the hydrolysis equilibrium of BF_3 and tested by special acid-base titration technique.The most accurate ion equilibrium constants were determined.The model,which was assumed to have no HF,was proved to be more representative for the real system and used to simulate the hydrolysis equilibrium of BF_3.The simulation suggested that H~+,BF_4~-,BF_3OH~- and H_3BO_3 were the main species in the dilute hydrolysis solution,while BF_2(OH)_2~- and F~- were insignificant species whose concentrations were both in the order of 10~(-4) mol/L magnitude,and BF(OH)_3~- could be omitted because its concentration almost equaled zero.Meanwhile,the equilibrium constant of the overall ionic reaction at 25℃ was obtained as 161.6.  相似文献   

18.
Molecular O2 and H2O are the vital requirements of contemporary life. The evolution of the atmosphere and oceans, therefore, necessarily predates metazoan evolution on the earth. The prebiotic primary atmosphere had CH4, NH3 and H2 as the chief components and was O2-deficient. Dissociation of CH4 and NH3 paved the way for the secondary atmosphere composed principally of CO2.  相似文献   

19.
ZnFe2O4 and ZnFe2O4-based materials were tested to obtain the electrical conductivity and corrosion resistance in melting bath for aluminum electrolysis. The results proved that adequate additives, such as Ni2O3 CuO, Cu, ZnO and CeO2 would increase the electrical conductivity, and the ZnFe2O4-based anodes with these additives were of good corrosion resistance. The current density on anode, the mole ratio of NaF/AlF3 (MR) and the content of alumina in the bath effect the anode corrosion rate in different way. Project supported by the Science Foundation of Liaoning Province, P. R. China (95 – 156)  相似文献   

20.

Objectives

To investigate the effects of different nitrate sources on the uptake, transport, and distribution of molybdenum (Mo) between two oilseed rape (Brassica napus L.) cultivars, L0917 and ZS11.

Methods

A hydroponic culture experiment was conducted with four nitrate/ammonium (NO3 ?:NH4 +) ratios (14:1, 9:6, 7.5:7.5, and 1:14) at a constant nitrogen concentration of 15 mmol/L. We examined Mo concentrations in roots, shoots, xylem and phloem sap, and subcellular fractions of leaves to contrast Mo uptake, transport, and subcellular distribution between ZS11 and L0917.

Results

Both the cultivars showed maximum biomass and Mo accumulation at the 7.5:7.5 ratio of NO3 ?:NH4 + while those were decreased by the 14:1 and 1:14 treatments. However, the percentages of root Mo (14.8% and 15.0% for L0917 and ZS11, respectively) were low under the 7.5:7.5 treatment, suggesting that the equal NO3 ?:NH4 + ratio promoted Mo transportation from root to shoot. The xylem sap Mo concentration and phloem sap Mo accumulation of L0917 were lower than those of ZS11 under the 1:14 treatment, which suggests that higher NO3 ?:NH4 + ratio was more beneficial for L0917. On the contrary, a lower NO3 ?:NH4 + ratio was more beneficial for ZS11 to transport and remobilize Mo. Furthermore, the Mo concentrations of both the cultivars’ leaf organelles were increased but the Mo accumulations of the cell wall and soluble fraction were reduced significantly under the 14:1 treatment, meaning that more Mo was accumulated in organelles under the highest NO3 ?:NH4 + ratio.

Conclusions

This investigation demonstrated that the capacities of Mo absorption, transportation and subcellular distribution play an important role in genotype-dependent differences in Mo accumulation under low or high NO3 ?:NH4 + ratio conditions.
  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号