检索结果-南通市图书馆

Sputtering Deposition of Ultra-thin α-fe_2O_3 films for Solar Water Splitting

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2015年第6期31卷 655-659页

作者： Lichao Jia Karsten Harbauer Peter Bogdanoff Kluas Ellmer Sebastian fiechter helmholtz-zentrum berlin fr Materialien und energie Institute for Solar FuelsHahn-Meitner-Platz 114109 BerlinGermany

Ultra-thin α-fe2O3（hematite） films have been deposited by radio frequency（Rf） sputtering technique and photoelectrochemically investigated towards their ability to oxidize *** varying the deposition power and time as well as the sputter gas flow（argon）,the microstructure and morphology of the film were *** was found that the increment in the film thickness resulted in the loss of efficiency for solar water *** film with a thickness of 27 nm exhibited the best result with a maximum photocurrent of 0.25 mA cm-2at 1.23 *** of small amounts of O2to the sputter gas improved the photoactivity significantly.

关键词： Thin film Aematite Sputtering deposition Photoelec

Analytical model for describing ion guiding through capillaries in insulating polymers

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2015年第8期24卷 457-462页

作者：刘世东赵永涛王瑜玉 Stolterfoht N 程锐周贤明徐瑚珊肖国青 Institute of Modern Physics Chinese Academy of Sciences University of Chinese Academy of Sciences helmholtz–zentrum berlin fr Materialien und energie

An analytical description for guiding of ions through nanocapillaries is given on the basis of previous work. The current entering into the capillary is assumed to be divided into a current fraction transmitted through the capillary, a current fraction flowing away via the capillary conductivity and a current fraction remaining within the capillary, which is responsible for its charge-up. The discharging current is assumed to be governed by the frenkel–Poole process. At higher conductivities the analytical model shows a blocking of the ion transmission, which is in agreement with recent ***, it is shown that ion blocking observed in experiments is well reproduced by the analytical formula. furthermore, the asymptotic fraction of transmitted ions is determined. Apart from the key controlling parameter(charge-to-energy ratio), the ratio of the capillary conductivity to the incident current is included in the model. Differences resulting from the nonlinear and linear limits of the frenkel–Poole discharge are pointed out.

关键词： ion guiding charging and discharging time blocked transmission asymptotic transmission

Characterization and modeling of the temperature-dependent thermal conductivity in sintered porous silicon-aluminum nanomaterials

在线全文

学校读者我要写书评

暂无评论

Nano Research 2022年第6期15卷 5663-5670页

作者： Danny Kojda Tommy Hofmann Natalia Gostkowska-Lekner Klaus Habicht Department Dynamics and Transport in Quantum Materials Helmholtz-Zentrum Berlin für Materialien und Energie GmbHBerlin D-14109Germany Institute of Physics and Astronomy University of PotsdamPotsdam D-14476Germany

Nanostructured silicon and silicon-aluminum compounds are synthesized by a novel synthesis strategy based on spark plasma sintering(SPS)of silicon nanopowder,mesoporous silicon(pSi),and aluminum *** interplay of metal-assisted crystallization and inherent porosity is exploited to largely suppress thermal *** and temperaturedependent thermal conductivity studies allow us to elucidate the impact of porosity and nanostructure on the macroscopic heat *** electron microscopy along with quantitative image analysis is applied to characterize the sample morphology in terms of domain size and interpore distance *** demonstrate that nanostructured domains and high porosity can be maintained in densified mesoporous silicon *** contrast,strong grain growth is observed for sintered nanopowders under similar sintering *** observe that aluminum agglomerations induce local grain growth,while aluminum diffusion is observed in porous silicon and dispersed nanoparticles.A detailed analysis of the measured thermal conductivity between 300 and 773 K allows us to distinguish the effect of reduced thermal conductivity caused by porosity from the reduction induced by phonon scattering at nanosized *** a modified Landauer/Lundstrom approach the relative thermal conductivity and the scattering length are *** relative thermal conductivity confirms the applicability of Kirkpatrick’s effective medium *** extracted scattering lengths are in excellent agreement with the harmonic mean of log-normal distributed domain sizes and the interpore distances combined by Matthiessen’s rule.

关键词： thermal conductivity mesoporous silicon porosity spark plasma sintering nanoscale modeling

Insights into the kinetics–morphology relationship of 1-, 2-, and 3D TiNb_(2)O_(7) anodes for Li-ion storage

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2024年第4期17卷 2770-2780页

作者： Wenlei Xu Yaolin Xu Veronika Grzimek Andrea Martin Thorsten Schultz Patrícia ARusso Yan Lu Norbert Koch Nicola Pinna Department of Chemistry IRIS Adlershof and the Center for the Science of Materials BerlinHumboldt-Universität zu BerlinBrook-Taylor-Str.212489 BerlinGermany Department of Electrochemical Energy Storage Helmholtz-Zentrum Berlin für Materialien und EnergieHahn-Meitner-Platz 114109 BerlinGermany Institut für Physik and IRIS Adlershof Humboldt-Universität zu BerlinBrook-Taylor-Str.212489 BerlinGermany Joint Research Group of Molecular Systems Helmholtz-Zentrum Berlin für Materialien und Energie12489 BerlinGermany

understanding the influence of electrode material’s morphology on electrochemical behavior is of great significance for the development of rechargeable batteries,however,such studies are often limited by the inability to precisely control the morphology of electrode ***,nanostructured titanium niobium oxides(TiNb_(2)O_(7))with three different morphologies(one-dimensional(1D),two-dimensional(2D),and three-dimensional(3D))were synthesized via a facile microwave-assisted solvothermal *** influence of the morphological dimension of TiNb_(2)O_(7) as electrode material on the electrochemical performance in Li-ion batteries(LIBs)and the underlying correlation with the electrochemical kinetics were studied in detail.2D TiNb_(2)O_(7)(TNO-2D)shows a superior rate capability and cycling stability,associated with improved kinetics for charge transfer and Li-ion diffusion,compared to the 1D and 3D *** X-ray diffraction measurements reveal the structural stability and crystallographic evolution of TNO-2D upon lithiation and delithiation and correlate the Li-ion diffusion kinetics with the lattice evolution during battery charge and ***,carbon-coated TNO-2D achieves enhanced rate capability(205 mAh·g^(-1) at 50 C)and long-term cycling stability(87%after 1000 cycles at 5 C).This work provides insights into the rational morphology design of electrode materials for accelerated charge transfer and enhanced fast-charging capability,pushing forward the development of electrode materials for high-power rechargeable batteries in future energy storage.

关键词： morphological dimension electrochemical kinetics lithium-ion batteries TiNb_(2)O_(7) structural evolution

Al-driven peculiarities of local coordination and magnetic properties in single-phase Al_(x)-CrfeCoNi high-entropy alloys

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2022年第6期15卷 4845-4858页

作者： Alevtina Smekhova Alexei Kuzmin Konrad Siemensmeyer Chen Luo Kai Chen florin Radu Eugen Weschke Uwe Reinholz Ana Guilherme Buzanich Kirill V.Yusenko helmholtz-zentrum berlin für Materialien und energie(HZB) D-12489Germany Institute of Solid State Physics University of LatviaLV-1063Latvia Bundesanstalt für Materialforschung und-prüfung(BAM) D-12489Germany

Modern design of superior multi-functional alloys composed of several principal components requires in-depth studies of their local structure for developing desired macroscopic ***,peculiarities of atomic arrangements on the local scale and electronic states of constituent elements in the single-phase face-centered cubic(fcc)-and body-centered cubic(bcc)-structured high-entropy Alx-CrfeCoNi alloys(x=0.3 and 3,respectively)are explored by element-specific X-ray absorption spectroscopy in hard and soft X-ray energy *** based on the reverse Monte Carlo approach allow to perform a simultaneous fit of extended X-ray absorption fine structure spectra recorded at K absorption edges of each 3d constituent and to reconstruct the local environment within the first coordination shells of absorbers with high *** revealed unimodal and bimodal distributions of all five elements are in agreement with structure-dependent magnetic properties of studied alloys probed by magnetometry.A degree of surface atoms oxidation uncovered by soft X-rays suggests different kinetics of oxide formation for each type of constituents and has to be taken into account.X-ray magnetic circular dichroism technique employed at L2,3 absorption edges of transition metals demonstrates reduced magnetic moments of 3d metal constituents in the sub-surface region of in situ cleaned fcc-structured Al0.3-CrfeCoNi compared to their bulk *** to nanostructured versions of multicomponent alloys,such studies would bring new insights related to effects of high entropy mixing on low dimensions.

关键词： high-entropy alloys reverse Monte Carlo magnetism element-specific spectroscopy extended X-ray absorption fine structure(EXAfS) X-ray magnetic circular dichroism(XMCD)

Bionic Photovoltaic Panels Bio-Inspired by Green Leaves

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2010年第3期7卷 284-293页

作者： MatthiasZhr Dennis friedrich Tania Y.Kloth Gerhard Goldmann Helmut Tributsch Technische fachhochschule berlin helmholtz-zentrum

In strong solar light, silicon solar panels can heat up by 70℃ and, thereby, loose approximately one third of their efficiencyfor electricity generation. Leaf structures of plants on the other hand, have developed a series of technological adaptations,which allow them to limit their temperature to 40-45℃ in full sunlight, even if water evaporation is suppressed. This is accomplishedby several strategies such as limitation of leaf size, optimization of aerodynamics in wind, limitation of absorbedsolar energy only to the useful fraction of radiation and by efficient thermal emission. Optical and infrared thermographicmeasurements under a solar simulator and in a streaming channel were used to investigate the corresponding properties of leavesand to identify suitable bionic model systems. Experiments started with the serrated structure of ordinary green leaves distributedover typical twig structures and finally identified the Australian palm tree Licuala ramsayi as a more useful bionic model. Itcombines a large area for solar energy harvesting with optimized aerodynamic properties for cooling and is able to restructureitself as a protection against strong winds. The bionic models, which were constructed and built, are analyzed and discussed.

关键词： bionics photovoltaic panel green leaves heat control Licuala ramsayi

Three-dimensional structured on-chip stacked zone plates for nanoscale X-ray imaging with high efficiency

在线全文

学校读者我要写书评

暂无评论

Nano Research 2014年第4期7卷 528-535页

作者： Stephan Werner Stefan Rehbein Peter Guttmann Gerd Schneider helmholtz-zentrum berlin fur Materialien und energie GmbH Institute for Soft Matter and Functional Materials Albert-Einstein-Straβe15 12489 Berlin Germany

fresnel zone plates are the key optical elements for nanoscale focusing of X-ray beams with high spatial resolution. Conventional zone plates manufactured by planar nanotechnology processes are limited by the achievable aspect ratios of their zone structures. Additionally, ultra-high resolution X-ray optics with high efficiency requires three-dimensional （3-D） shaped tilted zones. The combination of high spatial resolution and high diffraction efficiency is a fundamental problem in X-ray optics. Based on electrodynamical simulations, we find that the optimized zone plate profile for volume diffraction is given by zone structures with radially increasing tilt angles and decreasing zone heights. On-chip stacking permits the realization of such advanced 3-D profiles without significant loss of the maximum theoretical efficiency. We developed triple layer on-chip stacked zone plates with an overlay accuracy of sub-2 nm which fulfills the nanofabrication requirements. Efficiency measurements of on-chip stacked zone plates show significantly increased values compared to conventional zone plates.

关键词： X-ray optics fresnel zone plates X-ray imaging X-ray microscopy volume diffraction

Analysis of Dimer Impurity in Polyamidoamine Dendrimer Solutions by Small-angle Neutron Scattering

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2019年第8期37卷 827-833页

作者： Tian-fu Li Yi-Yun Cheng Yu Wang Hui Wang Dong-feng Chen Yun-Tao Liu Li Zhang Wen-Ze Han Rong-Deng Liu Zi-Jun Wang Chun-Ming Yang Charl J. Jafta Daniel Clemens Uwe Keiderling China Institute of Atomic Energy Beijing 102413 China Key Laboratory of Regulatory Biology School of Life Sciences East China Normal University Shanghai 200062 China Shanghai Synchrotron Radiation facility Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201204 China helmholtz-zentrum berlin fürmaterialien und energie Lise-Meitner-Campus Berlin 14109 Germany

Dimer impurity in the solution of a generation five(G5) polyamidoamine(PAMAM) dendrimer has been investigated by small-angle neutron scattering(SANS). The existence of dimer impurity in dendrimer solution was evidenced by indirect fourier transform(IfT) analysis of the SANS data, in which the maximum dimension of particles in solution was found to be about twice the diameter of G5 dendrimer. We then developed an analytical model which accounts for the scattering contribution from both dendrimer monomer and dimer. The experimental data were well fitted by using the established model. The results showed that the amount of dimer impurities is significant for the measured three batches of G5 PAMAM dendrimers.

关键词： PAMAM dendrimer Dimer impurity Small-angle neutron scattering Scattering model

Anomalies in the short-range local environment and atomic diffusion in single crystalline equiatomic CrMnfeCoNi highentropy alloy

在线全文

学校读者我要写书评

暂无评论

Nano Research 2024年第6期17卷 5336-5348页

作者： Alevtina Smekhova Daniel Gaertner Alexei Kuzmin Ana Guilherme Buzanich Goetz Schuck Ivo Zizak Gerhard Wilde Kirill V.Yusenko Sergiy Divinski helmholtz-zentrum berlin für Materialien und energie(HZB) D-12489 BerlinGermany Institute of Materials Physics University of MünsterD-48149 MünsterGermany Institute of Solid State Physics University of LatviaLV-1063 RigaLatvia Bundesanstalt für Materialforschung und–prüfung(BAM) D-12489 BerlinGermany

Multi-edge extended X-ray absorption fine structure(EXAfS)spectroscopy combined with reverse Monte Carlo(RMC)simulations was used to probe the details of element-specific local coordinations and component-dependent structure relaxations in single crystalline equiatomic CrMnfeCoNi high-entropy alloy as a function of the annealing *** representative states,namely a high-temperature state,created by annealing at 1373 K,and a low-temperature state,produced by long-term annealing at 993 K,were compared in *** features identified in atomic configurations of particular principal components indicate variations in the local environment distortions connected to different degrees of compositional disorder at the chosen representative *** detected changes provide new atomistic insights and correlate with the existence of kinks previously observed in the Arrhenius dependencies of component diffusion rates in the CrMnfeCoNi high-entropy alloy.

关键词： high-entropy alloys diffusion short-range order extended X-ray absorption fine structure(EXAfS) reverse Monte Carlo