检索结果-南通市图书馆

燃料电池式反应器中Pt和Pd中加入Bi用于催化乙醇发电并选择性联产醋酸盐

在线全文

学校读者我要写书评

暂无评论

燃料化学学报 2021年第10期49卷 1540-1548页

作者： Lima f.S. fontes E.H. Nandenha J. de Souza R.f.B. neto A.O. Instituto de Pesquisas Energéticas e Nucleares IPEN/CNEN-SPCEP 05508-900 São PauloSPBrazil

直接乙醇燃料电池作为便携式移动电源受到越来越多的关注,如乙醇能量密度高、可再生、无毒、清洁、便于储存和运输等优点。然而,乙醇燃料电池的研究也面临一些严重问题,其中c−c键断裂是最为挑战的问题之一。近年来有报道表明,乙醇的完... 详细信息

直接乙醇燃料电池作为便携式移动电源受到越来越多的关注,如乙醇能量密度高、可再生、无毒、清洁、便于储存和运输等优点。然而,乙醇燃料电池的研究也面临一些严重问题,其中c−c键断裂是最为挑战的问题之一。近年来有报道表明,乙醇的完全氧化(包含c−c键断裂过程)并没有显示出燃料电池效率的增加,相反乙醇不完全氧化的催化剂会导致更明显的催化电流增加。同时金属Bi掺杂会对催化剂产生电子效应和几何效应并有效增加碱性体系中催化剂的活性位中心和抗cO中毒能力。因此,本工作将铋掺杂在铂和钯中制备出PtBi/c和PdBi/c作为乙醇燃料电池催化剂,同时研究Bi掺杂催化剂对乙醇燃料电池性能以及乙醇的不完全氧化产物醋酸盐的影响,为乙醇燃料电池电-化学品联产提供一定的依据。以硼氢化钠为还原剂,Vulcan Xc-72(cabot)导电炭为载体制备了Pt/c、Pd/c、PtBi/c和PdBi/c(20%质量比)炭载催化剂,其中PtBi和PdBi原子比均为95∶5。首先将金属前驱体溶于H_(2)O/异丙醇溶液(50/50,体积比)中,加入Vulcan Xc-72导电炭黑充分混合,然后加入硼氢化钠在常温常压下充分反应,过滤洗涤干燥备用。其次,对所制备的催化剂进行TEM、XRD、XPS、电化学以及光谱电化学进行表征和测试。电化学、光谱电化学在三电极电解池中进行,将所制备的催化剂分散在超薄多孔电极上制备成工作电极,对电极为Pt片电极,参比电极为Ag/Agcl电极。电解液为碱性1 mol/L KOH的乙醇溶液,在电化学工作站上进行cV、LSV扫描以及在不同电位下测试溶液的ATR-fTIR谱。最后,燃料电池测试在一个面积为5 cm2的单电池上进行,阳极为2 mol/L乙醇+3 mol/L KOH溶液,流量为2 mL/min,阴极通入氧气,并研究催化剂的构成及性能对电池性能的影响。采用硼氢化钠还原法合成Pt/c、PtBi(95∶5)/c、Pd/c和PdBi(95∶5)/c。Pd/c和PdBi/c的晶体结构呈现fcc特征,Pt/c和PtBi/c的晶体结构也呈现fcc特征。XRD也揭示了铋原子对Pt晶体结构的影响。在1 mol/L KOH溶液中,异位XPS和循环伏安法显示这些金属具有较高的氧化态。透射电镜显示Pd/c有一定的纳米粒子聚集,PdBi/c有一定的有序结构。红外光谱(ATR-fTIR)结果表明,Bi效应由于吸附能力较弱,抑制了碳酸盐的生成,增加了醋酸盐的生成。由于醋酸盐优先生成,且不被碳酸盐离子毒害,PtBi/c具有最佳的电化学和DEfc性能。通过在Pt和Pd掺杂金属Bi制备具有电子调控的双金属炭载PtBi(95∶5)/c和PdBi(95∶5)/c催化剂,以增强乙醇氧化反应催化氧化过程。透射电镜(TEM)和X射线光电子能谱(XPS)结果表明,Bi含量不影响PdBi纳米颗粒的尺寸,但会影响PtBi纳米颗粒的尺寸。X射线衍射分析表明,Bi掺杂改变了Pt晶体结构中的晶格参数。此外,ATR-fTIR结果表明,碳酸盐的形成受到抑制,乙酸盐产量增加。极化曲线和功率密度曲线结果表明,PtBi/c催化剂具有更高的功率密度,几乎是Pt/c的6倍。在线性扫描伏安实验中,PtBi/c具有最高的电流密度(44 mW/cm2)和最低的起始电位(−0.6 V)。在电流-时间实验中,它也具有最高的最终电流密度。因此,在Pt和Pd中掺杂铋催化剂被证明是一种很有前途的燃料电池发电和醋酸盐的联产方法。

关键词：甲醇氧化反应 Bi掺杂电-化学品联产

characterization of yttria-stabilized zirconia films deposited by dip-coating on La_(0.7)Sr_(0.3)MnO_(3) substrate:Influence of synthesis parameters

在线全文

学校读者我要写书评

暂无评论

Journal of Advanced ceramics 2013年第1期2卷 55-62页

作者： Jacqueline c.MARRERO Nielson f.P.RIBEIRO célia f.MALfATTI Mariana M.V.M.SOUZA Escola de Química-Universidade federal do Rio de Janeiro(UfRJ) Centro de TecnologiaBloco Esala 206Ilha do FundãoCEP 21941-909Rio de JaneiroRJBrazil Departamento de Metalurgia Universidade Federal do Rio Grande do Sul(UFRGS)Campus do ValeSetor 4Prédio 75Sala 234CEP 91501-970Porto AlegreRSBrazil

Yttria-stabilized zirconia(YSZ,ZrO_(2)-8%Y2O_(3))films were deposited onto lanthanum strontium manganite(LSM,La_(0.7)Sr_(0.3)MnO_(3))substrates using dip-coating process aiming for the application in solid oxide fuel cells(SOfcs).YSZ precursor was prepared by sol-gel method;three values of the organic/inorganic concentration ratio(1,3 and 5)were utilized and the sol viscosity was adjusted(60 mPa·s and 100 mPa·s)before deposition on the *** influence of these synthesis parameters on the structure and morphology of the deposited films was examined by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The films showed characteristic peaks of LSM,YSZ(with cubic structure)and secondary phases of SrZrO_(3) and La_(2)O_(3).Depending on the synthesis conditions,crack-free,homogeneous and well adhered films were obtained,with thickness of 11-24μm.

关键词： YSZ films LSM sol-gel dip-coating

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

重介子

科学通报 1956年第5期 29-36页

作者： c.f.鲍威尔世界科学工作者协会副主席英国布利斯托尔大学教授

一核型原子:中子、质子和电子我们现在所知道的物质的原子的结构是由盧瑟福和他的同事所发现的,这是我们人类创造性的想像力的伟大成就之一。根据这种原子结构的说法,一切原子都是由一个中央原子核及其周围的负电子所构成的;我们可以用... 详细信息

一核型原子:中子、质子和电子我们现在所知道的物质的原子的结构是由盧瑟福和他的同事所发现的,这是我们人类创造性的想像力的伟大成就之一。根据这种原子结构的说法,一切原子都是由一个中央原子核及其周围的负电子所构成的;我们可以用一百种左右的化学元素来解释我们所知道的各种不同形式的物质,这些化学元素根据原子核的正电荷和其周围的相适应的电子数而各不相同。

关键词：介子超子平均寿命强子重子平均预期寿命寿命(生物) 原子核衰变方式

Male contraception:prospects for the new millennium

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Asian Journal of Andrology 2000年第1期2卷 3-12页

作者： W.M.Hair f.c.W.Wu Department of Medicine University of Manchester Manchester MI3 9WL UKDepartment of Medicine University of Manchester Manchester MI3 9WL UK

Effective regulation of human fertility has global consequences in terms of resource depletion, pollution and pover-ty. current family planning services predominantly target a female clientele with few significant developments in malefertility regulation for over a century. The last two decades have witnessed a gathering interest, initially from the scien-tific community, and laterally from industry, in the development of safe, reliable, reversible methods of contraceptionfor men. This review summarises the methods of male fertility regulation which are currently available and critically ex-amines the published data on novel developments in male hormonal contraception which offer the potential of improvedcontraceptive choice for all in new millennium. (Asian J Androl 2000; 2: 3 - 12)

关键词： contraception male contraceptive agents male contraceptive devices gonadotropins testosterone androgen

Effects of aluminum co-doping on photoluminescence properties of ce^(3+)-doped SiO_2 glasses

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2010年第S1期28卷 206-210页

作者： Lf KOAO H.c.SWART f.B.DEJENE Department of Physics University of the Free State(Qwaqwa Campus)Private Bag X13Phuthaditjhaba9866South Africa Department of Physics University of the Free StateP.O.Box 339Bloemfontein9300South Africa

SiO2 glasses co-doped with Al3+ ions were prepared by a sol-gel method by holding 0.5% of ce3+ ions constant and varying the Al3+ ions *** stability,the structural,chemical and the optical properties of the samples were studied by using differential scanning calorimetric(DSc),thermo gravimetric analysis(TGA),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),UV-vis spectroscopy and photoluminescence spectroscopy(PL).The DSc and TGA of samples depicted that the presence of dopant and co-dopant decreased the endothermic peak temperature and the yield *** images showed that the particles were in the nano-range and spherical in *** XRD showed that all the samples were *** UV absorption measurements indicated that the presence of Al3+ ions significantly reduced the SiO2 absorption band,increased the absorbance intensity of SiO2 and decreased the transmittance as compared to the presence of the ce3+ ions *** photoluminescence results displayed an optimum increase in luminescence intensity when the ratio of Al:ce was 10:1 and further increase in aluminum content quenched the luminous intensity.

关键词： SiO2:ce Al when sol-gel molar ration nano-size luminescence enhancement rare earths

Zinc-oxide/PDMS-clad tapered fiber saturable absorber for passively mode-locked erbium-doped fiber laser

在线全文

学校读者我要写书评

暂无评论

chinese Physics B 2021年第5期30卷 384-389页

作者： f D Muhammad S A S Husin E K Ng K Y Lau c A c Abdullah M A Mahdi Department of Physics Faculty of ScienceUniversiti Putra Malaysia43400 UPM SerdangSelangorMalaysia Wireless and Photonics Networks Research centre Faculty of EngineeringUniversiti Putra Malaysia43400 UPM SerdangSelangorMalaysia Department of Electronics and Nanoengineering Tietotie 3Aalto University02150 EspooFinland

We propose and demonstrate a passively mode-locked erbium-doped fiber laser(EDfL)based on zinc-oxide/polydimethylsiloxane(ZnO/PDMS)saturable absorber(SA)that evanescently interacts with the light on a tapered *** ZnO/PDMS composite is coated on the whole surface of the tapered fiber to guarantee the maximum efficiency of the SA device,with a measured insertion loss of 0.87 dB and a modulation depth of 6.4%.The proposed laser can generate soliton mode-locking operation at a threshold power of 33.07 *** generated output pulse yields a repetition rate and pulse width of 9.77 MHz and 1.03 ps,*** results indicate that the proposed ZnO/PDMS-clad tapered fiber could be useful as an efficient,compatible,and low-cost SA device for ultrafast laser applications.

关键词： zinc-oxide saturable absorber tapered fiber mode-locked fiber laser

A new strategy for corrosion protection of porous stainless steel using polypyrrole films

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2020年第2期37卷 85-95页

作者： c.Garcia-cabezon c.Garcia-Hernandez M.L.Rodriguez-Mendez f.Martin-Pedrosa Materials Engineering E.I.I.Universidad de Valladolid47011 ValladolidSpain UVASENS E.I.I.Universidad de Valladolid47011 ValladolidSpain

In this work,a method to improve the protection against corrosion of porous sintered stainless steel is *** is based on the electrodeposition of polypyrrole(PPy)layers doped with a large size counterion such as dodecylbenzenesulphonic acid(DBSA),a conducting polymer with high corrosion resistance and good *** efficacy of PPy coating depends on the adequate adhesion between the metal substrate and the coating *** protection against corrosion has been tested using 316 L stainless steel(SS)powder sintered at different conditions to evaluate the effect of the sintering atmosphere(nitrogen and vacuum)and cooling rates(furnace and water)on corrosion resistance,while wrought 316 L SS has been used as reference *** addition,two electrochemical deposition techniques have been tested to select the most *** circuit potential evolution,anodic polarization measurements and electrochemical impedance spectra have been used to evaluate corrosion protection in phosphate buffer saline *** has been evidenced that a more homogeneous and stable coating was obtained in the case of porous stainless *** corrosion potential shifted to nobler values and the anodic polarization branch became more *** porous samples have a good passivation performance with a lower stable passive current density and a higher breakdown *** transfer electronic resistance and the impedance module increase more than one order of ***,the porosity of sintered stainless steel is seen as an advantage for the improvement of the adherence of the PPy *** best corrosion protection is found for samples sintered in nitrogen and water-cooled.

关键词： Stainless steel Powder metallurgy Protection corrosion Electrodeposited films Polymer coatings

combustion synthesis, characterization and luminescence properties of barium aluminate phosphor

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2014年第9期32卷 806-811页

作者： A.H. Wako f.B Dejene H.c Swart Department of Physics University of the Free State (Qwaqwa Campus) Department of Physics University of the Free State

The blue-green emitting Eu2＋ and Nd3＋ doped polycrystalline barium aluminate （BaAI204：Eu2＋,Nd3＋） phosphor, was prepared by a solution-combustion method at 500 ℃without a post-annealing process. The characteristic variation in the structural and luminescence properties of the as-prepared samples was evaluated with regards to a change in the Ba/A1 molar ratio from 0.1：1 to 1.4：1. The morphologies and the phase structures of the products were characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）, while the optical properties were investigated using ultra-violet （UV） and photoluminescence （PL） spectroscopy, respectively. The XRD and TEM results revealed that the average crystallite size of the BaAl2O4：Eu2＋,Nd3＋ phosphor was about 70 urn. The broad-band UV-excited luminescence of the phosphors was observed at 2max=500 um due to transitions from the 4f^65d1 to the 4f7 configuration of the Eu2＋ ion. The PL results indicated that the main peaks in the emission and excitation spectrum of phosphor particles slightly shifted to the short wavelength due to the changes in the crystal field due to the structure changes caused by the variation in the quantity of the Ba ions in the host lattice.

关键词： BaAl2O4:Eu2+,Nd3+ persistence luminescence Eu2+ and Nd3+ doping rare earths

Stream-dwelling fungal decomposer communities along a gradient of eutrophication unraveled by 454 pyrosequencing

在线全文

学校读者我要写书评

暂无评论

fungal Diversity 2015年第1期70卷 127-148页

作者： S.Duarte f.Bärlocher J.Trabulo f.cássio c.Pascoal centre of Molecular and Environmental Biology(cBMA) Department of BiologyUniversity of MinhoCampus de Gualtar4710-057 BragaPortugal Department of Biology Mount Allison UniversitySackvilleNB E4L 1G7Canada

Microbial decomposers,especially a fungal group called aquatic hyphomycetes,play a critical role in processing plant litter in freshwaters by increasing its palatability to invertebrate ***,communities of aquatic hyphomycetes have been assessed through the identification of spores,which misses non-sporulating *** new technologies,454 pyrosequencing stands out as most promising for large-scale species ***,very few attempts have been made to validate its effectiveness for assessing the diversity of stream-dwelling fungal *** attempted to gain greater insight into the diversity of aquatic.f.ngal communities in streams exposed to various degrees of eutrophication by using the 454 pyrosequencing technology.A total of 173,889 ITS2 pyrosequencing reads with hits for fungi were obtained from the 5 investigated *** majority of operational taxonomic units(OTUs)belonged to Ascomycota and the identification to the genus level was achieved for 169 *** the total,135,257 reads(ca.78%)showed close affinities to aquatic hyphomycete *** showed declining fungal diversity in the most eutrophic streams,which was congruent with a reduced diversity found through spore *** patterns revealed by connecting representative OTUs to ITS sequences from aquatic hyphomycetes were similar to those determined by traditional spore identification ***,454 pyrosequencing provided a more comprehensive view of fungal diversity;it captured almost twice as many taxa as spore *** study vali-dates the effectiveness of 454 pyrosequencing for surveying the diversity of stream-dwelling fungal decomposer *** application may accelerate the use of these communities for monitoring the integrity of freshwaters.

关键词： freshwater ecosystems Plant litter decomposition Aquatic.f.ngi ITS region