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1.
ZSM-5 zeolite prepared by a hydrothermal method with the addition of seeds was treated with different concentrations of NaOH. The obtained samples were characterized by XRD, N2 adsorption, NH3-TPD, FT-IR, SEM, and studied in the catalytic performance of the hydration of cyclohexene to cyclohexanol. The characterization results showed that with the increase of NaOH concentration, the crystallinity of the treated samples decreased monotonously, and the acid sites of ZSM-5 zeolites first increased and then decreased, while more mesopores formed inside the ZSM-5 zeolites. The experimental results of catalytic performance showed that cyclohexene conversion can be improved through introducing the mesopores and enhancing the acidity of ZSM-5 with the NaOH treatment at a low concentration. The highest cyclohexene conversion of 12.8% was obtained when the concentrations of NaOH solution were in the range of 0.2–0.6 mol/L. The selectivity of cyclohexanol on all samples was higher than 99.6%.  相似文献   

2.
以木屑为原料,高温热解制备生物炭。以聚乙烯醇为粘结剂,采用混合法将生物炭与果胶复合,并负载磁性,经烘干定型制备果胶包覆的磁性生物炭材料（果胶@生物炭-Fe3O4）。采用扫描电镜（SEM）、X射线衍射（XRD）及N2吸附-脱附（BET）等方法对果胶@生物炭-Fe3O4进行表征,结合吸附实验分析其对Cu2+的吸附特性。结果表明,当生物炭、果胶、Fe3O4质量比为5：1：1,溶液pH值为6,吸附24 h,果胶@生物炭-Fe3O4对Cu2+吸附效果最好;二级动力学方程能较好地描述果胶@生物炭-Fe3O4对Cu2+的吸附过程,Freundlich模型能较好地拟合其吸附行为;SEM结果显示该材料具有不规则的孔隙结构;XRD分析显示纳米Fe3O4是其主要的晶体结构;BET测得其比表面积为25.654 m2·g-1,平均孔径为20.18 nm。  相似文献   

3.
The magnetic anisotropy of Fe25Ni75 nanocrystallites in the range of 10∼20 nm was measured by the law of approach to saturation. The samples were prepared by mechanical alloying process, and the average crystal size was determined by X-ray diffraction. The effective magnetic anisotropy of these fine particles is found In an order of 106 erg/cm3 that is much greater than that of normal crystal size of particles. The dependence of magnetic anisotropy on the particle size was studied. It has been demonstrated that the strain anisotropy occupies the most of the total magnetic anisotropy, and the internal strain is a critical factor for their magnetic properties. Supported by the Science Foundation of Shanghai Municipal Commission of Education (807965)  相似文献   

4.
以廉价的工业废弃物粉煤灰作为初始原料,四丙基氢氧化铵（TPAOH）为模板剂,分别采用两种合成方案制备出微孔分子筛ZSM-5样品。该法相较传统水热法,原料价廉易得,制备工艺简单。通过XRD、SEM、TR等手段对样品进行表征,发现两种方案均合成出了较高质量的ZSM-5,但形貌分别为薄片型和长六方体型。最后考察了其对水中Cr（Ⅵ）离子的吸附性能,结果表明合成的ZSM-5型样品对Cr（Ⅵ）离子有较好的吸附性能。  相似文献   

5.
Magnetic properties of nanocrystalline Fe60 Cr40 powders prepared by mechanical alloying in vacuum and air were investigated by utilizing the measurements of magnetization, X-ray diffraction, and ^67Fe M（oe）ssbauer spectrum. The results show that the Fe60 Cr40 powders keep the bcc structure during milling in air and vacuum. The saturation magnetization of the Fe60 Cr40 powders milled in vacuum and air decreases with the increase of the milling time up to 45 h. The decrease of saturation magnetization of the Fe60Cr40 powders milled in vacuum is due to the formation of Fe-Cr solid solution, while in air it is due to the formation of paramagnetic disorder structure and solid solution.  相似文献   

6.
The influence of calcination temperature on TiO2 nanotubes＇ catalysis for TiO2/UV/03 was investigated. TiO2 nanotubes （TNTs） were prepared via the sol-gel method and calcined at 300--700 ℃, which were labeled as TNTs-300, TNTs-400, TNTs-500, TNTs-600 and TNTs-700, respectively. TNTs were characterized by transmission electron microscopy （TEM） and X-ray diffraction （XRD）. It is found that TNTs calcined at 400 ℃ showed the best thermal stability. When the calcination temperature increased from 400 ℃ to 700 ℃, the special structure of tubes was destroyed and gradually converted into nanorods and/or particles. The transformation from anatase to rutile occurred at 600 ℃, and the rutile phase was enhanced when the calcination temperature was increased to over 600 ℃. The calcina- tion temperature＇s influence on TNTs＇ adsorption activity for for TiO2/UV/O3 was investigated in landfill leachate solution chemical oxygen demand （COD） and catalytic activity In landfill leachate solution, the adsorption activity of COD decreased in the reduced order of TNTs-300, TNTs-400, TNTs-500, TNTs-600 and TNTs-700. In photocatalytic ozonation, TNTs-400 showed the best catalytic activity while TNTs-700 exhibited the worst. In other three processes, the COD removal of TNTs-300/UV/O3 was higher than those of TNTs-500/UV/O3 and TNTs-600/UV/O3 in the first 20 rain, and then became close to those of the latter two in the following 40 rain. Compared with TNTs-300 and TNTs- 400, TNTs-600 had the best anti-fouling activity, while TNTs-500 and TNTs-700 had lower anti-fouling activity than the former three. In photocatalytic ozonation, the calcination temperature of 400 ℃ was appropriate when TNTs were obtained at the synthesis temperature of 105 ℃.  相似文献   

7.
Indium oxide nanocrystals with mesoporous structure were successfully synthesized by using triblock copolymer as a template, and characterized by thermogravimetry-differential scanning calorimeter (TG-DSC), X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and N2 adsorption. A high EO/PO ratio is thought to be the key point to prepare mesoporous In2O3. The results show that the average pore diameter of the products is 6 nm, the BET surface area is 54.78 m2/g, and the adsorbing pore volume is 0.345 cm3/g. After comparing with normal indium oxide nanoparticles by BET test, mesoporous indium oxide demonstrates a large difference in adsorbing pore volume and average pore diameters from normal ones. Project supported by the Leading Academic Discipline Project of Shanghai Municipal Education Commission (Grant No.J50102)  相似文献   

8.
Systematic studies of the transport properties of La0.67Ca0.33Mn1?xFe x O3 (x=0–0.3) systems showed that with increasing Fe-doping contentx the resistance increases and the insulator-metal transition temperature moves to lower temperature. For small doping content, the transport property satisfies metal transport behavior below the transition temperature, and above the transition temperature it satisfies the small polaron model. This behavior can be explained by Fe3+ doping, which easily forms Fe3+?O2??Mn4+ channel, suppressing the double exchange Mn3+?O2??Mn4+ channel and enhancing the spin scattering of Mn ions induced by antiferromagnetic clusters of Fe ions.  相似文献   

9.
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   

10.
以含有模板剂的介孔氧化硅原粉（HMS）作为原料,通过浸溃法引入微孔沸石合成导向剂,再利用有机模板剂作为介孔产生的模板,通过干凝胶转换方法将介孔材料孔壁晶化得到微孔一介孔复合孔分子筛．采用X射线衍射（XRD）、红外光谱（IR）法对样品的结晶度进行了表征,采用氮气吸附等温线测定了样品比表面积和孔分布．结果表明：全硅HMS介孔分子筛在180℃经过6h水蒸汽加热转化后,无定形介孔氧化硅转化为微孔沸石,结晶度达到80％,比表面和孔体积分别为595m^2·g^-1和0．65cm^3·g^-1．而含铝HMS介孔分子筛,因铝的引入阻碍了沸石的转化．当HMS分子筛Si／Al比达到25时,在180℃经过6h水蒸汽加热,所得样品（MZ25．6）孔壁仍为无定型结构．  相似文献   

11.
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   

12.
This new type nanocomposite powder was prepared with electroless plating enhanced by ultrasonic wave. High-resolution transmission electron microscopy (HRTEM) showed that As-plated particles have nanometer scale average size. X-ray diffraction (XRD) analysis showed the presence of a noncrystalline structure in the plating layer on the nano-Al2O3 matrix. The content of the plating layer was analyzed by energy dispersive X-ray spectroscopy (EDX) technology. The plating layer content was adjustable by changing the solution concentration.  相似文献   

13.
Single phase Fe5C2 intermetallic compound was prepared by mechanical alloying method. The phase and crystal structure of sample were analyzed with X-ray differaction spectrum. The decomposing temperature of the Fe5C2 compound is 596.4℃ determined by the DSC curve. It is further shown that the size of nanometer crystal grain is an important condition for carrying out the solid state reaction at room temperature and normal pressure.  相似文献   

14.
Molecule matters     
The synthesis of a FeVI complex in an octahedral coordination geometry has been achieved recently by Wieghardt and coworkers. This is only the second hexavalent iron complex known after the tetrahedral ferrate ion, [FeO4]2?. The synthesis of the new FeVI complex involves a low temperature photolysis of an FeIV(N3) precursor which leads to the formation of the FeVI complex containing a Fe≡N triple bond. The structural characterization of the FeVI complex has been achieved by a variety of spectroscopic techniques including Mössbauer spectroscopy and X-ray absorption spectroscopy. Experimentally it is found that the FeVI complex is diamagnetic. Theoretical calculations reveal that the FeVI complex has an electronic configuration 3d2 (S = 0); the d electrons are paired in a dxy orbital.  相似文献   

15.
The acidities of different SiO2/Al2O3 ratio ZSM-5 zeolites, CBV3024E, CBV5524G and CBV8014 were investigated with temperature-programmed desorption of ammonia and diffuse reflectance infrared Fourier transform spectroscopy, and their catalytic performances were evaluated to screen the optimal CBV8014 catalyst for ethylene oligomerization. The mesoporosity development in CBV8014 zeolite was conducted by desilication in alkaline medium. The porous characteristics, structural properties and acidic properties of parent and alkali-treated CBV8014 zeolites were studied, and their catalytic performances were evaluated, indicating that CBV8014 treated by 0.2 mol/L NaOH solution has an appropriate mesoporosity development, well preservation of catalyst acidity and crystallinity, good catalytic activity and stability, and high liquid fuel yield for ethylene oligomerization. The effect of reaction pressure on ethylene oligomerization over 0.2HZ catalyst was also investigated, and JP-8 likely hydrocarbon jet fuel was obtained by using 0.2HZ catalyst at 0.344 75 MPa with a high catalyst stability and high liquid yield.  相似文献   

16.
BaFe12O19 powders with nanocrystaUine sizes were produced by sol-gel auto-combustion method. The precursors were prepared under the molar ratios of citric acid to the metal nitrate of 0.5, 1.0 and 1.5. Appropriate ethylene diamine （C2H8N2） was added in order to adjust pH of 7. The ions distribution of citric acid at different pH explains the effect of citric acid in the starting solution. The XRD patterns of the as-burnt powders and annealing powders show different phases for different citric acid content. In addition, the lattice constants （a, c） derived from X-ray diffraction pattern were changed from 0.58881 nm to 0.58997 nm and 2.32057 nm to 2.32296 nm respectively. The data from VSM indicated that the powder with high citric acid content took on good magnetic properties. Pure single BaFe12O19 of the specific maximum magnetization M（1 T）≈ 49.73 Am^2/kg, the specific remanent magnetization Mr ≈ 30.77 Am^2/kg and the coercive force He≈ 467 kA/m was produced when the molar ratios of citric acid to the metal nitrate was 1.5.  相似文献   

17.
A series of Lil-xNaxV3O8 materials was prepared by solution reaction followed by calcination method and their electrochemical performances in 2 M LieSOa-water-ethanol solution as negative electrodes for aqueous electrolyte lithium ion battery were studied and compared each other. X-ray diffraction analysis revealed that partially substituting sodium for lithium in LiV3Os could increase the interlayer distances of （100） plane. Cyclic voltammetric experiments have demonstrated that the Li^＋ insertion and extraction kinetics of Li0.7Na0.3V3O8 is superior to that of LiV3O8. Charge/discharge results showed that the discharge specific capacity of Li0.7Na0.3V3O8 electrode is higher than that of LiV3O8 electrode.  相似文献   

18.
The magnetic properties of as-quenched and annealed Fe73.5Ag1Nb3Si13.5B9 alloys were investigated. X-ray diffraction was used to monitor the structure changes of the samples under different annealing temperatures. It was found that by Cu addition, the crystallization temperature T x1 of Fe-Nb-Si-B alloy is decreased, whereas by Ag addition, the T x1 is increased. A small amount of α-Fe and Ag were obtained after the sample was annealed at 500°C for 1 h. With increasing the annealing temperature, Fe23B6, Fe2B, Fe3B were separated out and magnetic properties of the samples were impaired quickly. A mostly single nanocrystalline grain of a-Fe phase could not be obtained in the annealed samples.  相似文献   

19.
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   

20.
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   

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