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31.
Ga2O3-NiO复合氧化物的溶胶-凝胶法制备和气敏性能 总被引：2，自引：0，他引：2
用溶胶-凝胶法制备了Ga2O3-NiO复合金属氧化物气敏材料,对其相组成、电导和气敏性能作了研究.结果表明:镍镓物质的量比n(Ni2＋) : n(Ga3＋)=0.7～0.9:2、800 ℃下热处理4 h,得到纯相尖晶石型复合金属氧化物NiGa2O4.缺陷GaNi×的反应(GaNi×→GaNi’＋h●),使NiGa2O4呈p型半导体. n(Ni2＋) : n(Ga3＋)=1:2凝胶粉在800 ℃下热处理4 h,所得纳米微粉制作的元件在313 ℃工作温度下对C2H5OH有较高灵敏度和良好的选择性. 相似文献
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Two new Fe3O4 microspheres‐supported semi‐homogeneous catalysts, namely Fe3O4‐G4‐polyaminoamido (PAMAM) dendrimers‐Pd(0) and Fe3O4‐polyethylene glycols (PEGs)‐Pd(0) were synthesized and characterized by X‐ray powder diffraction, infrared spectrum, scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy and thermal gravimetric analysis, which can catalyze Suzuki coupling reactions. The performance of catalysts was tested for the reactions of aryl halides with phenyl boronic acid and compared with a heterogeneous catalyst Fe3O4‐(3‐aminopropyl)triethoxysilane (APTS)‐Pd(0), in which Fe3O4‐G4‐PAMAM dendrimers‐Pd(0) shows the best activity among the three catalysts. The order of the catalytic activities is Fe3O4‐G4‐PAMAM dendrimers‐Pd(0)>Fe3O4‐PEGs‐Pd(0)>Fe3O4‐APTS‐Pd(0). The catalysts can be quickly and completely recovered by simply applying a magnet of 105 mT and the efficiencies remain unaltered even after four recycles. 相似文献
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Let be the second largest eigenvalue of a graph. Powers (1988) [4] gave some upper bounds of for general graphs and bipartite graphs, respectively. Considering that these bounds are not always attainable for connected graphs, we present sharp upper bounds of for connected graphs and connected bipartite graphs in this paper. Moreover, the extremal graphs are completely characterized. 相似文献
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The self-assembly of 1,10-phenanthroline(phen) and 1,3-benzenedicarboxylic acid(H2bdc) with Pb(NO3)2 under solvothermal conditions in N,N-dimethylacetamide(DMA) gives rise to a one-dimensional chain coordination polymer, [Pb(phen)(bdc)](1), which was characterized by elemental analysis, FT-IR and single-crystal X-ray diffraction. This complex crystallizes in triclinic, space group P1 with a = 7.5595(6), b = 9.8199(8), c = 13.1663(11) , α = 69.7590(10), β = 80.6000(10), γ = 71.3180(10)o, Z = 2, C20H12N2O4Pb, Mr = 551.51, Dc = 2.112 g/cm3, F(000) = 520 and μ = 9.757 mm-1. The final R = 0.0304 and wR = 0.0763 for 3427 observed reflections with I 2σ(I) and R = 0.0365 and wR = 0.0894 for all data. The structure contains one crystallographic unique Pb(Ⅱ) atom, one phen molecule chelating with a Pb(Ⅱ) atom, and one bdc2- anion, acting as a bidentate bridging ligand linking the Pb(Ⅱ) atoms to form a one-dimensional structure. The two-dimensional layer and three-dimensional stacking structures are formed by C–H···O hydrogen bonding interactions. The thermal stable and fluorescent properties of 1 were investigated. PbO micro-crystal particles are produced by calcination of powder sample of complex 1. The obtained PbO is characterized and observed by XRD and SEM analyses. 相似文献
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Xue-Li Liu Yi-Fan Chen Jing-Jing Yang Si-Jin Li Hua-Le Xie Tian-Lin Ma 《Molecules (Basel, Switzerland)》2022,27(7)
A new type of hydroxyalkyl starch, γ-hydroxypropyl starch (γ-HPS), was prepared by etherification of alkali-activated starch with 3-chloropropanol. The reaction efficiency, morphological change, thermodynamic and apparent viscosity properties, and other physicochemical characteristics were described. The molar substitution (MS) of modified whole starch was determined to be 0.008, 0.017, 0.053, 0.106, and 0.178, with a ratio of 5%, 15%, 25%, 35%, and 45% 3-chloropropanol to starch (v/w), respectively. Compared to native starch, the granular size and shape and the X-ray diffraction pattern of γ-HPS are not very different. For low-substituted γ-HPS, the implications may be less evident. Thermal stability measurements by means of thermogravimetric analyses and differential scanning calorimetry (TGA-DSC) proved that thermal stability was reduced and water retaining capacity was increased after hydroxypropylation. Furthermore, the findings also showed that the solubility, light transmittance, and retrogradation of γ-HPS pastes could be improved by etherification. The greater the MS of the γ-HPS, the more its freeze–thaw stability and acid resistivity increased. In this study, we provide relevant information for the application of γ-HPS in food and non-food industries. 相似文献
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We consider the least square estimator for the parameters of Ornstein-Uhlenbeck processes dYs=(∑j=1kμjφj(s)-βYs)ds+dZsq,H,driven by the Hermite process Zsq,Hwith order q≥1 and a Hurst index H∈(1/2,1),where the periodic functionsφj(s),,j=1,...,κare bounded,and the real numbersμj,,j=1,...,κtogether withβ>0 are unknown parameters.We establish the consistency of a least squares estimation and obtain the asymptotic behavior for the estimator.We also introduce alternative estimators,which can be looked upon as an application of the least squares estimator.In terms of the fractional Ornstein-Uhlenbeck processes with periodic mean,our work can be regarded as its non-Gaussian extension. 相似文献
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以1,4,5,8-萘四羧酸为原料,在溶剂热条件下原位反应合成得到一个具有3D拓扑结构的发光钡基金属有机骨架(MOF):[Ba(dna)(H2O)2]n(1,H2dna=1,8-萘二甲酸酐-4,5-二羧酸),并通过单晶X射线衍射、元素分析、热重分析和粉末X射线衍射技术对其进行表征。结构分析表明,1包含一个π共轭基团和酸酐基团的有机配体dna2-,荧光和紫外研究表明其能灵敏地检测溶液中的芳香胺,可能是MOF结构中配体的酸酐基团和氨基之间的反应驱动的,这大大提高了荧光发射强度,并达到裸眼可见的颜色变化。此外,以配合物1为前驱体在中等温度下直接煅烧制得了单一晶型的纳米BaCO3颗粒。 相似文献
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