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1.
Y^3＋-doped （Bi 1/2 Na 1/2） TiO 3-CaTiO 3-BaTiO 3 （BNCBT） positive temperature coefficient of resistivity （PTCR） ceramics sintered in air atmosphere were investigated in this study. （Bi 1/2 Na 1/2） TiO 3 （BNT） component can remarkably increase the onset temperature T c of PTCR ceramics with the expense of the resistivity R 25 increase. CaTiO 3 （9–27 mol%） component can decrease the resistivity, and adjust the effects of BNT phase on the T c point. For the sample containing 3 mol% CaTiO 3 , T c raises from 122 ℃ to 153 ℃ when only 0.6 mol% BNT added, while for the ones with higher CaTiO 3 content （9–27 mol%）, T c is only increased by a rate of 8–9℃/1.0 mol% BNT. The effects of BNT and CaTiO 3 components on R25/Rmin （negative temperature coefficient effect） are also discussed.  相似文献   

2.
Aluminum nitride （AlN）/borosilicate glass composites were prepared by the tape casting process and hot-press sintered at 950 ℃ with AIN and SiO2-B203-ZnO-Al2O3-Li2O glass as starting materials. We characterized and analyzed the variation of the microstructure, bulk density, porosity, dielectric constant, thermal conductivity and thermal expansion coefficient （TEC） of the ceramic samples as a function of AIN content. Results show that AIN and SiO2-B2O3-ZnO-Al2O3-Li2O glass can be sintered at 950 ℃, and ZnAI204 and Zn2SiO4 phase precipitated to form glass-ceramic. The performance of the ceramic samples was determined by the composition and bulk density of the composites. Lower AlN content was found redounding to liquid phase sintering, and higher bulk density of composites can be accordingly obtained. With the increase of porosity, corresponding decreases were located in the dielectric constant, thermal conductivity and TEC of the ceramic samples. When the mass fraction of AlN was 40%, the ceramic samples possessed a low dielectric constant （4.5-5.0）, high thermal conductivity （11.6 W/（m.K）） and a proper TEC （3.0× 10^-6 K^-1 which matched that of silicon）. The excellent performance makes this kind of low temperature co-fired ceramic a promising candidate for application in the micro-electronics packaging industry.  相似文献   

3.
Reaction mechanisms of SO2 with O3 and H2O2 were investigated using quantum chemistry ab initio methods. Structures of all reactants, products, and transition states were optimized at the B3LYP/6-311G＋（3df,2p） level, and energy calculations were made at the G2M level. SO2 reactions with O3 and H2O2 occurred by O-abstraction and OH-abstraction by SO2, respectively, at length forming SO3＋O2 （3Eg） and H2SO4. For SO2＋O3 reactions the barrier height was predicted to be 9.68 kcal/mol with a rate constant of 3.61 × 10^-23 cm^3/（molecule.s） at 300 K, which is below the experimental upper limit. The rate constant predicted for this reaction accords well with the one provided by National Institute for Standards and Technology （NIST） in 250-500 K. For SO2＋H2O2 reactions the barrier height was predicted to be 62.39 kcal/mol with a rate constant of 2.48× 10^-61 cm^3/（molecule.s） at 300 K.  相似文献   

4.
The influences of the PbO-B2O3-CuV2O6 （PBC） additives on the microwave dielectric properties of （Pb0.5Ca0.5） （Fe0.5Nb0.5）O3 （PCFN） ceramics were investigated as a function of sintering temperature from 950 ℃ to 1 100 ℃. The sintering temperature of the specimens with the glass could be lowered from 1125 ℃ to 1 025℃ without the degradation of microwave dielectric properties. The microwave results showed that the dielectric constant cr was not significantly different while Qf values decreased with the increase of CuV206 content of PBC glass. For the specimens doped with PB-CV0.1 glass （81% PbO-9% B203-10% CuV2O6） and sintered at 1 025 ℃ for 3 h, the microwave dielectric properties of Qf=4 823 GHz, Cr=107.1 with TCF=＋15.03 ×10^-6/℃ were obtained.  相似文献   

5.
SO4^2- / TiO2-La2O3, a novel solid superacid, was prepared and its catalytic activities at different synthetic conditions are discussed with esterification of n-butanoic acid and n-butyl alcohol as probing reaction. The optimum conditions have also been found, mole ratio of n（La^3＋）：n（Ti^4＋） is 1：34, the soaked consistency of H2SO4 is 0.8 tool/L, the soaked time of HESO4 is 24 h, the calcining temperature is 480 ℃, the calcining time is 3 h. Then it was applied in the catalytic synthesis often important ketals and acetals as catalyst and revealed high catalytic activity. Under these conditions on which the molar ratio of aldehyde/ketone to glycol is l： 1.5, the mass ratio of the catalyst used in the reactants is 0.5%, and the reaction time is 1.0 h, the yields of ketals and acetals can reach 41.4%-95.8%.  相似文献   

6.
Thirty-six daily time interval PM2.5 samples were collected in different seasonal dates in urban Shanghai, and the concentrations of four anions （Cl- , NO3-, SO4^2-, C2O4^2-） and five cations （NH＋, Na＋, K＋, Ca2＋, Mg2＋） were analyzed with ion chromatography. Sulfate, nitrate and ammonium were found to be the dominant species, accounting for about 80% of the total ions. The daily nitrate to sulfate mass ratio ranged from 0.31 to 0.82, indicating that coal combustion was still the main pollution source in Shanghai. The equivalent ratio of ammonium to stun of nitrate and sulfate showed fixed diurnal variation pattern in all the sampling days with higher values in the nighttime, suggesting that fine particles in the night were more neutralized. The oxalate to sulfate ratio was lower in the winter sampling days than that in hotter summer and autumn sampling days. Oxalate was significantly correlated with sulfate in winter sampling days, but not in the summer and autumn, suggesting that the formation mechanism of oxalate and sulfate was similar in winter, however different in hot days.  相似文献   

7.
In this paper, the characteristics of fluid mixing time in a novel extra-loop fluidized bed were studied. The results showed that the mixing time was shortened with the increase of fluid velocity. All the discrete numbers of the reactor were above 0.2. The serial number n was 2.5 -3.0. It was judged accordingly that the reactor fluid state was continous stirred tank reactor （CSTR） mainly. When the inspiratory capacity increased the mixing time of the reactor was shortened. Thus the air input was beneficial for the fluid mixing. During the three phases mixing process, the mixing time of the reactor could be decreased by the n increase of carrier and air loading together, but the change was not significant. The parameters affecting the reactor fluid state were fluid velocity, inspiratory capacity and carrier. KLa could be increased with the air loading increase, and at the same gas/liquid ratio when the pressure drop was high, KL~ value was increased. The amount of carrier complex influence on KLa. As the carrier loading continued to increase, its value had been dropped but the changes was not significant, and optimization condition was found at above 800 1 000 g carrier loading （pouzzolane） or 600 g PVC. Under gas/liquid ratio of 0.8% -5.2%, KLa was （0.62-1.37）×10^-2· s^-1.  相似文献   

8.
To investigate the seismic behavior of connections composed of steel reinforced ultra high strength concrete （SRUHSC） column and reinforced concrete （RC） beam, six interior strong-column-weak-beam connection specimens were tested subjected to reversal cyclic load. Effects of applied axial load ratio and volumetric stirrup ratio on ductility, energy dissipation capacity, strength degradation and rigidity degradation were discussed. It was found that all connection specimens failed in bending in a ductile manner with a beam plastic hinge. The ductility and energy dissipation capacity increased with the decrease of applied axial load ratio or increase of volumetric stirrup ratio. The displacement ductility coefficient and equivalent damping coefficient lay between those of steel reinforced ordinary concrete connection and those of reinforced concrete connection. The applied axial load ratio and volumetric stirrup ratio had less influence on the strength degradation and more influence on the stiffness degradation. The stiffness degraded sharply with the decrease of volumetric stirrup ratio or increase of applied axial load ratio. The experimental results indicate that SRUHSC column and RC beam connection exhibited better seismic performance and can provide reference for engineering application.  相似文献   

9.
Photocatalytic reduction of 6-chloro-3-nitrotoluene-4-sulfonic acid （CNSA） was studied in UV-irradiated TiO2 suspensions in the presence of methanol and surfactants. A mixture of CNSA, TiO2, water, additives and surfac- tants was put into a quartz glass reactor with a jacket, which was irradiated with a high pressure Hg lamp in the purg- ing of nitrogen gas. With methanol, the conversion of CNSA increased from 7.7% to 34.6%. Three surfactants signifi- cantly promoted the photocatalytic reduction conversion in reduced order of sodium dodecylbenzenesulfonate （DBS）, cetyltrimethylammonium bromide （CTAB） and sodium dodecylsulfate （SDS）. In suspensions involving DBS and CTAB respectively, CNSA conversion increased in consistence with the adsorption ratio with methanol, but varied inversely with the adsorption ratio without methanol. But no obvious influence on the adsorption ratio was observed with or without methanol added when the SDS concentration was critical micelle concentration （cmc）. The photocata- lytic reduction of CNSA was enhanced in UV-irradiated TiO2 suspensions in the presence of methanol and surfactants. Methanol inhibited the recombination of photogenerated holes and electrons efficiently. Surfactants around 1 cmc led to the highest reduction conversion.  相似文献   

10.
Leaf senescence is often caused by water deficit and the chimeric gene PSA612-1PT is an auto-regulated gene delaying leaf senescence. Using in vitro leaf discs culture system, the changes of contents of chlorophylls, carotenoids, soluble protein and thiobarbituric acid reactive substance （TBARS） and antioxidant enzymes activities were investigated during leaf senescence of PSA612-1PT modified gerbera induced by osmotic stress compared with the control plant （wild type）. Leaf discs were incubated in 20%, 40% （w/v） polyethylene glycol （PEG） 6 000 nutrient solution for 20 h under continuous light [ 130 μmol/（m^2·s）]. The results showed that the contents of chlorophylls, carotenoids and soluble protein were decreased by osmotic stress with the decrease being more pronounced at 40% PEG, but that, at the same PEG concentration the decrease in the transgenic plants was significantly lower than that in the control plant. The activities of superoxide dismutase （SOD）, catalases （CAT）, ascorbate peroxidase （APX）, guaiacol peroxidase （GPX） and dehydroascorbate reductase （DHAR） were stimulated by PEG treatment. However, the increases were higher in PSA612-IPT transgenic plants than in the control plants, particularly at 40% PEG treatment. Lipid peroxidation （TBARS content） was increased by PEG treatment with the increase being much lower in transgenic plant than in the control plant. It could be concluded that the increases in the activities ofantioxidant enzymes including SOD, CAT, APX, GPX and DHAR were responsible for the delay of leaf senescence induced by osmotic stress.  相似文献   

11.
Activities of FeO in CaO-SiO2-Al2O3-MgO-FeO slags were determined at 1673 K by electrochemical measurements of the solid electrolyte cell: Mo |Mo MoO2[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 (?O)/(%SiO2) ratio, MgO and Al2O3 content, there was an increase of FeO activities with increase of FeO content. For slags with constant {(?O) (%MgO)}/(%SiO2) ratio, fixed FeO and Al,2O3 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 (?O)/(%SiO2) ratio changed from 1.03 to 1.30 in the slags of constant MgO, FeO and Al2O3 content.  相似文献   

12.
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   

13.
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   

14.
利用EF-H_2O_2-FeO_X法深度处理畜牧业养殖废水,结果表明,当pH值为3,电压为24 V,反应时间为45 min,电解质投加量为0.8 g/L,PAM投加量为2.5 mg/L时,对畜牧业养殖废水的深度处理效果最佳,COD的去除率可以达到99.1%。此方法具有成本低、设备简单、效果好等优点,在畜牧业养殖废水的深度处理领域具有广阔的应用前景。  相似文献   

15.
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   

16.
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   

17.
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18.
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   

19.
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   

20.
Nine limiting binaries of Al2O3-SiO2-Re2O3(Re=Nd, Sm, Gd and La) system are assessed. The binary diagrams or experimental information from Toropov, Mizuno, Aramaki, Bondar, Rolin and Coutures are optimized with the substitutional model of Kaufman and Nesor and the approximate formula of fusion free energy for rare earth element oxides of Wu and Pelton. The extracted Gibbs free energies of pure solid oxides and stoichiometric phases and the solution parameters are used to estimate the corresponding binaries, liquidus surfaces and a series of isothermal sections of four ternaries Al2O3-SiO2-Nd2O3, Al2O3-SiO2-Sm2O3, Al2O3-SiO2-Gd2O3, and Al2O3-SiO2-La2O3. In the Al2O3-SiO2-Gd2O3 system samples as fired at exact temperature with different compositions were analyzed by X-ray diffractometer and the detected results are fitted with the calculation of isothermal sections. Supported by State Key Lab of High Performance Ceramics and Superfine Micro-structure (9517 and 9708)  相似文献   

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