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Sample records for metallic porous structures

  1. Joining porous components to solid metal structures

    Science.gov (United States)

    Fortini, A.; Tulisiak, G.

    1972-01-01

    Process for joining porous metal material to solid metal structure without cracking or blockage of porous component is described. Procedures of electron beam welding and electroforming are discussed. Illustration of microstructure resulting from process is included.

  2. The structure of steady shock waves in porous metals

    Science.gov (United States)

    Czarnota, Christophe; Molinari, Alain; Mercier, Sébastien

    2017-10-01

    The paper aims at developing an understanding of steady shock wave propagation in a ductile metallic material containing voids. Porosity is assumed to be less than 0.3 and voids are not connected (foams are not considered). As the shock wave is traveling in the porous medium, the voids are facing a rapid collapse. During this dynamic compaction process, material particles are subjected to very high acceleration in the vicinity of voids, thus generating acceleration forces at the microscale that influence the overall response of the porous material. Analyzing how stationary shocks are influenced by these micro-inertia effects is the main goal of this work. The focus is essentially on the shock structure, ignoring oscillatory motion of pores prevailing at the tail of the shock wave. Following the constitutive framework developed by Molinari and Ravichandran (2004) for the analysis of steady shock waves in dense metals, an analytical approach of steady state propagation of plastic shocks in porous metals is proposed. The initial void size appears as a characteristic internal length that scales the overall dynamic response, thereby contributing to the structuring of the shock front. This key feature is not captured by standard damage models where the porosity stands for the single damage parameter with no contribution of the void size. The results obtained in this work provide a new insight in the fundamental understanding of shock waves in porous media. In particular, a new scaling law relating the shock width to the initial void radius is obtained when micro-inertia effects are significant.

  3. Mechanical and Structural Investigation of Porous Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Baran Sarac

    2015-06-01

    Full Text Available The intrinsic properties of advanced alloy systems can be altered by changing their microstructural features. Here, we present a highly efficient method to produce and characterize structures with systematically-designed pores embedded inside. The fabrication stage involves a combination of photolithography and deep reactive ion etching of a Si template replicated using the concept of thermoplastic forming. Pt- and Zr-based bulk metallic glasses (BMGs were evaluated through uniaxial tensile test, followed by scanning electron microscope (SEM fractographic and shear band analysis. Compositional investigation of the fracture surface performed via energy dispersive X-ray spectroscopy (EDX, as well as Auger spectroscopy (AES shows a moderate amount of interdiffusion (5 at.% maximum of the constituent elements between the deformed and undeformed regions. Furthermore, length-scale effects on the mechanical behavior of porous BMGs were explored through molecular dynamics (MD simulations, where shear band formation is observed for a material width of 18 nm.

  4. Metal filled porous carbon

    Science.gov (United States)

    Gross, Adam F [Los Angeles, CA; Vajo, John J [West Hills, CA; Cumberland, Robert W [Malibu, CA; Liu, Ping [Irvine, CA; Salguero, Tina T [Encino, CA

    2011-03-22

    A porous carbon scaffold with a surface and pores, the porous carbon scaffold containing a primary metal and a secondary metal, where the primary metal is a metal that does not wet the surface of the pores of the carbon scaffold but wets the surface of the secondary metal, and the secondary metal is interspersed between the surface of the pores of the carbon scaffold and the primary metal.

  5. Porous electrode apparatus for electrodeposition of detailed metal structures or microelectronic interconnections

    Science.gov (United States)

    Griffiths, Stewart K.; Nilson, Robert H.; Hruby, Jill M.

    2002-01-01

    An apparatus and procedure for performing microfabrication of detailed metal structures by electroforming metal deposits within small cavities. Two primary areas of application are: the LIGA process which manufactures complex three-dimensional metal parts and the damascene process used for electroplating line and via interconnections of microelectronic devices. A porous electrode held in contact or in close proximity with a plating substrate or mold top to ensure one-dimensional and uniform current flow into all mold cavities is used. Electrolyte is pumped over the exposed surface of the porous electrode to ensure uniform ion concentrations at this external surface. The porous electrode prevents electrolyte circulation within individual mold cavities, avoiding preferential enhancement of ion transport in cavities having favorable geometries. Both current flow and ion transport are one-dimensional and identical in all mold cavities, so all metal deposits grow at the same rate eliminating nonuniformities of the prior art.

  6. A statistical method for predicting sound absorbing property of porous metal materials by using quartet structure generation set

    International Nuclear Information System (INIS)

    Guan, Dong; Wu, Jiu Hui; Jing, Li

    2015-01-01

    Highlights: • A random internal morphology and structure generation-growth method, termed as the quartet structure generation set (QSGS), has been utilized based on the stochastic cluster growth theory for numerical generating the various microstructures of porous metal materials. • Effects of different parameters such as thickness and porosity on sound absorption performance of the generated structures are studied by the present method, and the obtained results are validated by an empirical model as well. • This method could be utilized to guide the design and fabrication of the sound-absorption porous metal materials. - Abstract: In this paper, a statistical method for predicting sound absorption properties of porous metal materials is presented. To reflect the stochastic distribution characteristics of the porous metal materials, a random internal morphology and structure generation-growth method, termed as the quartet structure generation set (QSGS), has been utilized based on the stochastic cluster growth theory for numerical generating the various microstructures of porous metal materials. Then by using the transfer-function approach along with the QSGS tool, we investigate the sound absorbing performance of porous metal materials with complex stochastic geometries. The statistical method has been validated by the good agreement among the numerical results for metal rubber from this method and a previous empirical model and the corresponding experimental data. Furthermore, the effects of different parameters such as thickness and porosity on sound absorption performance of the generated structures are studied by the present method, and the obtained results are validated by an empirical model as well. Therefore, the present method is a reliable and robust method for predicting the sound absorption performance of porous metal materials, and could be utilized to guide the design and fabrication of the sound-absorption porous metal materials

  7. Additive manufacturing technologies of porous metal implants

    Directory of Open Access Journals (Sweden)

    Yang Quanzhan

    2014-06-01

    Full Text Available Biomedical metal materials with good corrosion resistance and mechanical properties are widely used in orthopedic surgery and dental implant materials, but they can easily cause stress shielding due to the significant difference in elastic modulus between the implant and human bones. The elastic modulus of porous metals is lower than that of dense metals. Therefore, it is possible to adjust the pore parameters to make the elastic modulus of porous metals match or be comparable with that of the bone tissue. At the same time, the open porous metals with pores connected to each other could provide the structural condition for bone ingrowth, which is helpful in strengthening the biological combination of bone tissue with the implants. Therefore, the preparation technologies of porous metal implants and related research have been drawing more and more attention due to the excellent features of porous metals. Selective laser melting (SLM and electron beam melting technology (EBM are important research fields of additive manufacturing. They have the advantages of directly forming arbitrarily complex shaped metal parts which are suitable for the preparation of porous metal implants with complex shape and fine structure. As new manufacturing technologies, the applications of SLM and EBM for porous metal implants have just begun. This paper aims to understand the technology status of SLM and EBM, the research progress of porous metal implants preparation by using SLM and EBM, and the biological compatibility of the materials, individual design and manufacturing requirements. The existing problems and future research directions for porous metal implants prepared by SLM and EBM methods are discussed in the last paragraph.

  8. Experimental study of mixed convection heat transfer in a vertical duct filled with metallic porous structures

    International Nuclear Information System (INIS)

    Venugopal, G.; Balaji, C.; Venkateshan, S.P.

    2010-01-01

    This paper reports the results of an experimental investigation to examine the potential of a simple and inexpensive porous insert developed specifically for augmenting heat transfer from the heated wall of a vertical duct under forced flow conditions. The porous insert used in the study consists of a stack of metallic perforated plates filled inside the duct. The characteristic features of the porous medium model on the hydrodynamic and heat transfer behavior have been investigated. The porous medium model developed in the present study shows thermo- hydrodynamic performance similar to those seen in metal foams. A correlation has been developed for predicting the Nusselt number from the geometry under consideration. The key novelty in the present work is the development of a new correlation for the Nusselt number that does not require any information from hydrodynamic studies. Over the range of parameters considered, the largest increase in the average Nusselt number of 4.52 times that for clear flow is observed with a porous material of porosity of 0.85. (authors)

  9. Treatment of Severe Bone Defects During Revision Total Knee Arthroplasty with Structural Allografts and Porous Metal Cones

    DEFF Research Database (Denmark)

    Beckmann, Nicholas A; Mueller, Sebastian; Gondan, Matthias

    2015-01-01

    Aseptic loosening and focal osteolysis are the most common reasons for knee arthroplasty failure. The best treatment remains unclear. We reviewed the literature on the treatment of revision knee arthroplasty using bony structural allografts (476 cases) and porous metal cones (223 cases......) to determine if a difference in the revision failure rates was discernable. The failure rates were compared using a logistic regression model with adjustment for discrepancies in FU time and number of grafts used (femoral, tibial, or both). In this analysis, the porous implant shows a significantly decreased...

  10. Structural Contraction of Zeolitic Imidazolate Frameworks: Membrane Application on Porous Metallic Hollow Fibers for Gas Separation.

    Science.gov (United States)

    Cacho-Bailo, Fernando; Etxeberría-Benavides, Miren; David, Oana; Téllez, Carlos; Coronas, Joaquín

    2017-06-21

    Positive thermal expansion coefficients (TECs) of 52 × 10 -6 and 35 × 10 -6 K -1 were experimentally calculated in the -116 to 250 °C range for the III-phases of zeolitic imidazolate frameworks (ZIF) ZIF-9(Co) and ZIF-7(Zn), respectively, by means of the unit cell dimensions and volume of the materials in the monoclinic crystal system calculated from the XRD patterns. The unit cell dimensions and volume showed a significant expansion phenomenon as the temperature increased, by as much as 5.5% for ZIF-9-III in the studied range. To exploit the advantages of such thermal behavior, a new approach to the fabrication of ZIF-9-III membranes on thin, flexible, and highly porous nickel hollow fiber (Ni HF) supports by a versatile and easy-controllable microfluidic setup is herein reported. These Ni HF supports result from the sintering of 25-μm Ni particles and display very positive mechanical properties and bending resistance. As compared to the traditional polymer-based HF membranes, the ZIF metal-supported membrane exhibited good durability and robustness throughout its operation in a wide temperature range and after heating and cooling cycles. These benefits derive from (1) the pore-plugging membrane configuration resulting from the high porosity of the support and (2) the similarity between the TECs of the ZIF and the metallic support, both positive, which enhances their mutual compatibility. An increase in the H 2 /CO 2 separation selectivity at low temperatures (as high as 22.2 at -10 °C, along with 102 GPU permeance of H 2 ) was achieved, in agreement with the structural variations observed in the ZIF material.

  11. Hierarchical Porous Structures

    Energy Technology Data Exchange (ETDEWEB)

    Grote, Christopher John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-06-07

    Materials Design is often at the forefront of technological innovation. While there has always been a push to generate increasingly low density materials, such as aero or hydrogels, more recently the idea of bicontinuous structures has gone more into play. This review will cover some of the methods and applications for generating both porous, and hierarchically porous structures.

  12. Progress of Application Researches of Porous Fiber Metals

    Directory of Open Access Journals (Sweden)

    Jianyong Wang

    2011-04-01

    Full Text Available Metal fiber porous materials with intrinsic properties of metal and functional properties of porous materials have received a great deal of attention in the fundamental research and industry applications. With developments of the preparation technologies and industrial requirements, porous fiber metals with excellent properties are developed and applied in many industry areas, e.g., sound absorption, heat transfer, energy absorption and lightweight structures. The applied research progress of the metal fiber porous materials in such application areas based on the recent work in our group was reviewed in this paper.

  13. Progress of Application Researches of Porous Fiber Metals

    Science.gov (United States)

    Xi, Zhengping; Zhu, Jilei; Tang, Huiping; Ao, Qingbo; Zhi, Hao; Wang, Jianyong; Li, Cheng

    2011-01-01

    Metal fiber porous materials with intrinsic properties of metal and functional properties of porous materials have received a great deal of attention in the fundamental research and industry applications. With developments of the preparation technologies and industrial requirements, porous fiber metals with excellent properties are developed and applied in many industry areas, e.g., sound absorption, heat transfer, energy absorption and lightweight structures. The applied research progress of the metal fiber porous materials in such application areas based on the recent work in our group was reviewed in this paper. PMID:28879952

  14. Method for preparing porous metal hydride compacts

    Science.gov (United States)

    Ron, M.; Gruen, D.M.; Mendelsohn, M.H.; Sheft, I.

    1980-01-21

    A method for preparing porous metallic-matrix hydride compacts which can be repeatedly hydrided and dehydrided without disintegration. A mixture of a finely divided metal hydride and a finely divided matrix metal is contacted with a poison which prevents the metal hydride from dehydriding at room temperature and atmospheric pressure. The mixture of matrix metal and poisoned metal hydride is then compacted under pressure at room temperature to form porous metallic-matrix hydride compacts.

  15. Aerogels of 1D Coordination Polymers: From a Non-Porous Metal-Organic Crystal Structure to a Highly Porous Material

    Directory of Open Access Journals (Sweden)

    Adrián Angulo-Ibáñez

    2016-01-01

    Full Text Available The processing of an originally non-porous 1D coordination polymer as monolithic gel, xerogel and aerogel is reported as an alternative method to obtain novel metal-organic porous materials, conceptually different to conventional crystalline porous coordination polymer (PCPs or metal-organic frameworks (MOFs. Although the work herein reported is focused upon a particular kind of coordination polymer ([M(μ-ox(4-apy2]n, M: Co(II, Ni(II, the results are of interest in the field of porous materials and of MOFs, as the employed synthetic approach implies that any coordination polymer could be processable as a mesoporous material. The polymerization conditions were fixed to obtain stiff gels at the synthesis stage. Gels were dried at ambient pressure and at supercritical conditions to render well shaped monolithic xerogels and aerogels, respectively. The monolithic shape of the synthesis product is another remarkable result, as it does not require a post-processing or the use of additives or binders. The aerogels of the 1D coordination polymers are featured by exhibiting high pore volumes and diameters ranging in the mesoporous/macroporous regions which endow to these materials the ability to deal with large-sized molecules. The aerogel monoliths present markedly low densities (0.082–0.311 g·cm−3, an aspect of interest for applications that persecute light materials.

  16. Synthesis of Mesoporous Metal Oxides by Structure Replication: Thermal Analysis of Metal Nitrates in Porous Carbon Matrices

    Directory of Open Access Journals (Sweden)

    Christian Weinberger

    2015-08-01

    Full Text Available A variety of metal nitrates were filled into the pores of an ordered mesoporous CMK-3 carbon matrix by solution-based impregnation. Thermal conversion of the metal nitrates into the respective metal oxides, and subsequent removal of the carbon matrix by thermal combustion, provides a versatile means to prepare mesoporous metal oxides (so-called nanocasting. This study aims to monitor the thermally induced processes by thermogravimetric analysis (TGA, coupled with mass ion detection (MS. The highly dispersed metal nitrates in the pores of the carbon matrix tend to react to the respective metal oxides at lower temperature than reported in the literature for pure, i.e., carbon-free, metal nitrates. The subsequent thermal combustion of the CMK-3 carbon matrix also occurs at lower temperature, which is explained by a catalytic effect of the metal oxides present in the pores. This catalytic effect is particularly strong for oxides of redox active metals, such as transition group VII and VIII metals (Mn, Fe, Co, Ni, Cu, and Ce.

  17. Additive Manufacturing of Hierarchical Porous Structures

    Energy Technology Data Exchange (ETDEWEB)

    Grote, Christopher John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division. Polymers and Coatings

    2016-08-30

    Additive manufacturing has become a tool of choice for the development of customizable components. Developments in this technology have led to a powerful array of printers that t serve a variety of needs. However, resin development plays a crucial role in leading the technology forward. This paper addresses the development and application of printing hierarchical porous structures. Beginning with the development of a porous scaffold, which can be functionalized with a variety of materials, and concluding with customized resins for metal, ceramic, and carbon structures.

  18. A series of porous metal-organic frameworks with hendecahedron cage: Structural variation and drug slow release properties

    Science.gov (United States)

    Wei, Lian-Qiang; Li, Yue; Mao, Li-Yuan; Chen, Qing; Lin, Ning

    2018-01-01

    A series of porous MOFs with hendecahedron cage-liked cavity has been constructed from the [Cu2(COO)4] secondary building unit, H3L (H3L = [1,1';3',1'']Terphenyl-4,5',4''-tricarboxylic acid) and pyrazine derivatives varied with different sizes; the structural evolving of the hendecahedron cage and the application in drug delivery and controlled release were presented.

  19. Porous Materials - Structure and Properties

    DEFF Research Database (Denmark)

    Nielsen, Anders

    1997-01-01

    The paper presents some viewpoints on the description of the pore structure and the modelling of the properties of the porous building materials. Two examples are given , where it has been possible to connect the pore structure to the properties: Shrinkage of autoclaved aerated concrete and the p...... and the properties of lime mortar....

  20. Heavy metal ion adsorption onto polypyrrole-impregnated porous carbon.

    Science.gov (United States)

    Choi, Moonjung; Jang, Jyongsik

    2008-09-01

    Polypyrrole-impregnated porous carbon was readily synthesized using vapor infiltration polymerization of pyrrole monomers. The results show that the functionalized polymer layer was successfully coated onto the pore surface of carbon without collapse of mesoporous structure. The modified porous carbon exhibited an improved complexation affinity for heavy metal ions such as mercury, lead, and silver ions due to the amine group of polypyrrole. The introduced polypyrrole layer could provide the surface modification to be applied for heavy metal ion adsorbents. Especially, polymer-impregnated porous carbon has an enhanced heavy metal ion uptake, which is 20 times higher than that of adsorbents with amine functional groups. Furthermore, the relationship between the coated polymer amount and surface area was also investigated in regard to adsorption capacity.

  1. Size-effects in porous metals

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    The intrinsic size-effect for porous metals is investigated. The analyses are carried out numerically using a finite strain generalization of a higher order strain gradient plasticity model. Results for plane strain growth of cylindrical voids are presented in terms of response curves and curves...

  2. Size-effects in porous metals

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2007-01-01

    The intrinsic size-effect for porous metals is investigated. The analyses are carried out numerically using a finite strain generalization of a higher order strain gradient plasticity model. Results for plane strain growth of cylindrical voids are presented in terms of response curves and curves...

  3. POROUS STRUCTURE OF ROAD CONCRETE

    Directory of Open Access Journals (Sweden)

    M. K. Pshembaev

    2016-01-01

    Full Text Available Having a great number of concrete structure classifications it is recommended to specify the following three principal types: microstructure – cement stone structure; mesostructure – structure of cement-sand mortar in concrete; macrostucture – two-component system that consists of mortar and coarse aggregate. Every mentioned-above structure has its own specific features which are related to the conditions of their formation. Thus, microstructure of cement stone can be characterized by such structural components as crystal intergrowth, tobermorite gel, incompletely hydrated cement grains and porous space. The most important technological factors that influence on formation of cement stone microstructure are chemical and mineralogical cement composition, its grinding fineness, water-cement ratio and curing condition. Specific cement stone microstructure is formed due to interrelation of these factors. Cement stone is a capillary-porous body that consists of various solid phases represented predominantly by sub-microcrystals of colloidal dispersion. The sub-microcrystals are able adsorptively, osmotically and structurally to withhold (to bind some amount of moisture. Protection of road concrete as a capillary-porous body is considered as one of the topical issues. The problem is solved with the help of primary and secondary protection methods. Methods of primary protection are used at the stage of designing, preparation and placing of concrete. Methods of secondary protection are applied at the operational stage of road concrete pavement. The paper considers structures of concrete solid phase and characteristics of its porous space. Causes of pore initiation, their shapes, dimensions and arrangement in the concrete are presented in the paper. The highest hazard for road concrete lies in penetration of aggressive liquid in it and moisture transfer in the cured concrete. Water permeability of concrete characterizes its filtration factor which

  4. Fabrication, properties, and applications of porous metals with directional pores

    Science.gov (United States)

    NAKAJIMA, Hideo

    2010-01-01

    Lotus-type porous metals with aligned long cylindrical pores are fabricated by unidirectional solidification from the melt with a dissolved gas such as hydrogen, nitrogen, or oxygen. The gas atoms can be dissolved into the melt via a pressurized gas atmosphere or thermal decomposition of gaseous compounds. Three types of solidification techniques have been developed: mold casting, continuous zone melting, and continuous casting techniques. The last method is superior from the viewpoint of mass production of lotus metals. The observed anisotropic behaviors of the mechanical properties, sound absorption, and thermal conductivity are inherent to the anisotropic porous structure. In particular, the remarkable anisotropy in the mechanical strength is attributed to the stress concentration around the pores aligned perpendicular to the loading direction. Heat sinks are a promising application of lotus metals due to the high cooling performance with a large heat transfer. PMID:21084772

  5. Hierarchical structured graphene/metal oxide/porous carbon composites as anode materials for lithium-ion batteries

    International Nuclear Information System (INIS)

    Guo, Rong; Yue, Wenbo; Ren, Yu; Zhou, Wuzong

    2016-01-01

    Highlights: • CeO 2 and Co 3 O 4 nanoparticles display different behavior within CMK-3. • CMK-3-CeO 2 and Co 3 O 4 show various electrochemical properties • CMK-3-CeO 2 and Co 3 O 4 are further wrapped by graphene nanosheets. • Graphene-encapsulated composites show better electrochemical performances. - Abstract: As a novel anode material for lithium-ion batteries, CeO 2 displays imperceptible volumetric and morphological changes during the lithium insertion and extraction processes, and thereby exhibits good cycling stability. However, the low theoretical capacity and poor electronic conductivity of CeO 2 hinder its practical application. In contrast, Co 3 O 4 possesses high theoretical capacity, but undergoes huge volume change during cycling. To overcome these issues, CeO 2 and Co 3 O 4 nanoparticles are formed inside the pores of CMK-3 and display various electrochemical behaviors due to the different morphological structures of CeO 2 and Co 3 O 4 within CMK-3. Moreover, the graphene/metal oxide/CMK-3 composites with a hierarchical structure are then prepared and exhibit better electrochemical performances than metal oxides with or without CMK-3. This novel synthesis strategy is hopefully employed in the electrode materials design for Li-ion batteries or other energy conversion and storage devices.

  6. Sound absorption of porous metals at high sound pressure levels.

    Science.gov (United States)

    Wang, Xiaolin; Peng, Feng; Chang, Baojun

    2009-08-01

    This paper is a study about sound absorption properties of porous metals at high sound pressure levels. A method of deriving the nonlinear static flow resistance for highly porous fibrous metals is proposed by solving Oseen's equation to take account of the inertia effect, validated by experiments of airflow measurement. In order to predict nonlinear sound absorbing performance of a finite thickness porous metal layer, a numerical method is employed, verified by sound absorption measurement in an impedance tube. Accordingly, the effects of the nonlinear coefficient on the porous metal sound absorption are investigated.

  7. Development of porous structure simulator for multi-scale simulation of irregular porous catalysts

    International Nuclear Information System (INIS)

    Koyama, Michihisa; Suzuki, Ai; Sahnoun, Riadh; Tsuboi, Hideyuki; Hatakeyama, Nozomu; Endou, Akira; Takaba, Hiromitsu; Kubo, Momoji; Del Carpio, Carlos A.; Miyamoto, Akira

    2008-01-01

    Efficient development of highly functional porous materials, used as catalysts in the automobile industry, demands a meticulous knowledge of the nano-scale interface at the electronic and atomistic scale. However, it is often difficult to correlate the microscopic interfacial interactions with macroscopic characteristics of the materials; for instance, the interaction between a precious metal and its support oxide with long-term sintering properties of the catalyst. Multi-scale computational chemistry approaches can contribute to bridge the gap between micro- and macroscopic characteristics of these materials; however this type of multi-scale simulations has been difficult to apply especially to porous materials. To overcome this problem, we have developed a novel mesoscopic approach based on a porous structure simulator. This simulator can construct automatically irregular porous structures on a computer, enabling simulations with complex meso-scale structures. Moreover, in this work we have developed a new method to simulate long-term sintering properties of metal particles on porous catalysts. Finally, we have applied the method to the simulation of sintering properties of Pt on alumina support. This newly developed method has enabled us to propose a multi-scale simulation approach for porous catalysts

  8. Porous ceramic - metal composites obtained by infiltration methods

    Directory of Open Access Journals (Sweden)

    A. Boczkowska

    2013-07-01

    Full Text Available A pressure-vacuum infiltration (T = 720 ºC, p = 15 MPa, t = 15 min and gas-pressure infiltration (GPI in an autoclave (T = 700ºC, p=4 MPa, t=5 min were applied for infiltration of porous Al2O3 ceramics by cast aluminum alloy. Effect of the method of the infiltration on the microstructure and mechanical properties of ceramic-metal composites, was studied. Ceramic preforms were formed by method of copying the cellular structure of the polymer matrix. The results of the X-ray tomography proved very good infiltration of the pores by the metal for each method.

  9. Porous polymer networks and ion-exchange media and metal-polymer composites made therefrom

    Science.gov (United States)

    Kanatzidis, Mercouri G.; Katsoulidis, Alexandros

    2016-10-18

    Porous polymeric networks and composite materials comprising metal nanoparticles distributed in the polymeric networks are provided. Also provided are methods for using the polymeric networks and the composite materials in liquid- and vapor-phase waste remediation applications. The porous polymeric networks, are highly porous, three-dimensional structures characterized by high surface areas. The polymeric networks comprise polymers polymerized from aldehydes and phenolic molecules.

  10. Numerical evaluation of micro-structural parameters of porous supports in metal-supported solid oxide fuel cells

    DEFF Research Database (Denmark)

    Reiss, Georg; Frandsen, Henrik Lund; Brandstätter, Wilhelm

    2014-01-01

    Metallic supported Solid Oxide Fuel Cells (SOFCs) are considered as a durable and cost effective alternative to the state-of-the-art ceramic supported cell designs. In order to understand the mass and charge transport in the metal-support of this new type of cell a novel technique involving X...

  11. Porous carbonaceous electrode structure and method for secondary electrochemical cell

    Science.gov (United States)

    Kaun, Thomas D.

    1977-03-08

    Positive and negative electrodes are provided as rigid, porous carbonaceous matrices with particulate active material fixedly embedded. Active material such as metal chalcogenides, solid alloys of alkali metal or alkaline earth metals along with other metals and their oxides in particulate form are blended with a thermosetting resin and a solid volatile to form a paste mixture. Various electrically conductive powders or current collector structures can be blended or embedded into the paste mixture which can be molded to the desired electrode shape. The molded paste is heated to a temperature at which the volatile transforms into vapor to impart porosity as the resin begins to cure into a rigid solid structure.

  12. 3D Microstructure Modeling of Porous Metal Filters

    Czech Academy of Sciences Publication Activity Database

    Hejtmánek, Vladimír; Čapek, M.

    2012-01-01

    Roč. 2, č. 3 (2012), s. 344-352 ISSN 2075-4701. [International Conference on Porous Metals and Metallic Foams /7./. Busan, 18.09.2011-21.09.2011] R&D Projects: GA ČR(CZ) GAP204/11/1206; GA ČR GA203/09/1353 Institutional support: RVO:67985858 Keywords : porous metal filter * stochastic reconstruction * microstructural descriptors Subject RIV: CF - Physical ; Theoretical Chemistry

  13. Unconventional metal organic frameworks: porous cross-linked phosphonates.

    Science.gov (United States)

    Clearfield, Abraham

    2008-11-28

    The past decade has witnessed an exponential growth of metal organic framework compounds (MOFs). The defining character of these compounds is their porosity. However, in many cases no effort was made to show evidence that a stable porous structure has been achieved and that the pores may be accessed. In the present paper we describe recent work on porous pillared zirconium diphosphonates, and the newer and in many respects different characteristics of tin(iv) phosphonates. The Sn(IV) monophosphonates form spherical globules that exhibit very high surface areas. The surface area arises from their nano-sized particles that pack in a "house of cards" arrangement. Also, it is shown that the 1,4-monophenyldiphosphonic acid forms highly porous (250-400 m2 g(-1)) materials with Sn(IV) when prepared in alcohol-water media. This is not the case with analogous Zr(IV) compounds. The many variations in the syntheses of both the zirconium and tin aryl- and alkyldiphosphonate pillars and their combinations with spacers such as methyl- and monophenylphosphonic acid have created a variety of highly porous materials that are stable to 400 degrees C in air, highly stable in acid media, do not collapse when de-solvated, and can be post and presynthesis altered to include functional groups. Several new directions taken by other researchers are also described. However, it is emphasized in this presentation that the cross-linked compounds form particles that precipitate rapidly into nanoparticles that exhibit only short range order. Therefore, they differ from the more conventional MOFs in that they are not amenable to structure solution by X-ray or neutron diffraction techniques. Rather, they must be understood on the basis of modeling and indirect data from EM, NMR, and additional spectroscopic and textural studies.

  14. Development and Applications of Porous Tantalum Trabecular Metal Enhanced Titanium Dental Implants

    Science.gov (United States)

    Bencharit, Sompop; Byrd, Warren C.; Altarawneh, Sandra; Hosseini, Bashir; Leong, Austin; Reside, Glenn; Morelli, Thiago; Offenbacher, Steven

    2013-01-01

    Statement of Problem Porous tantalum trabecular metal has recently been incorporated in titanium dental implants as a new form of implant surface enhancement. However, there is little information on the applications of this material in implant dentistry. Methods We, therefore review the current literature on the basic science and clinical uses of this material. Results Porous tantalum metal is used to improve the contact between osseous structure and dental implants; and therefore presumably facilitate osseointegration. Success of porous tantalum metal in orthopedic implants led to the incorporation of porous tantalum metal in the design of root-from endosseous titanium implants. The porous tantalum three-dimensional enhancement of titanium dental implant surface allows for combining bone ongrowth together with bone ingrowth, or osseoincorporation. While little is known about the biological aspect of the porous tantalum in the oral cavity, there seems to be several possible advantages of this implant design. This article reviews the biological aspects of porous tantalum enhanced titanium dental implants, in particular the effects of anatomical consideration and oral environment to implant designs. Conclusions We propose here possible clinical situations and applications for this type of dental implant. Advantages and disadvantages of the implants as well as needed future clinical studies are discussed. PMID:23527899

  15. Ultralight porous metals. From fundamentals to applications

    International Nuclear Information System (INIS)

    Lu, T.

    2002-01-01

    Over the past few years a number of low cost metallic foams for application as the core of sandwich panels and net shaped parts have been produced. The main aim is to develop lightweight structures which are stiff, strong, absorb large amount of energy and are cheap, for application in the transport and construction industries. For example, the firewall between the engine and passenger compartment of an automobile must have adequate mechanical strength, good energy and sound absorbing properties, and adequate fire retardance. Metal foams provide all of these features, and are under serious scrutiny for this applications by a number of automobile manufacturers (e.g., BMW and Audi). Additional specialized applications for foam-cored sandwich panels range from heat sinks for electronic devices to crash barriers for automobiles, from the construction panels in lifts on aircraft carriers to the luggage containers of aircraft, from sound proofing walls along railway tracks and highways to acoustic absorbers in lean premixed combustion chambers. But there is a problem. Before metallic foams can find widespread application, their basic properties must be measured, and ideally modeled as a function of microstructural details, in order to give a design capability. This work aims at reviewing recent progress and present some new results on fundamental research regarding the micromechanical origins of the mechanical, thermal, and acoustic properties of metallic foams. (author)

  16. Facile preparation of hierarchically porous carbons from metal-organic gels and their application in energy storage.

    Science.gov (United States)

    Xia, Wei; Qiu, Bin; Xia, Dingguo; Zou, Ruqiang

    2013-01-01

    Porous carbon materials have numerous applications due to their thermal and chemical stability, high surface area and low densities. However, conventional preparing porous carbon through zeolite or silica templates casting has been criticized by the costly and/or toxic procedure. Creating three-dimensional (3D) carbon products is another challenge. Here, we report a facile way to prepare porous carbons from metal-organic gel (MOG) template, an extended metal-organic framework (MOF) structure. We surprisingly found that the carbon products inherit the highly porous nature of MOF and combine with gel's integrated character, which results in hierarchical porous architectures with ultrahigh surface areas and quite large pore volumes. They exhibit considerable hydrogen uptake and excellent electrochemical performance as cathode material for lithium-sulfur battery. This work provides a general method to fast and clean synthesis of porous carbon materials and opens new avenues for the application of metal-organic gel in energy storage.

  17. Facile preparation of hierarchically porous carbons from metal-organic gels and their application in energy storage

    Science.gov (United States)

    Xia, Wei; Qiu, Bin; Xia, Dingguo; Zou, Ruqiang

    2013-06-01

    Porous carbon materials have numerous applications due to their thermal and chemical stability, high surface area and low densities. However, conventional preparing porous carbon through zeolite or silica templates casting has been criticized by the costly and/or toxic procedure. Creating three-dimensional (3D) carbon products is another challenge. Here, we report a facile way to prepare porous carbons from metal-organic gel (MOG) template, an extended metal-organic framework (MOF) structure. We surprisingly found that the carbon products inherit the highly porous nature of MOF and combine with gel's integrated character, which results in hierarchical porous architectures with ultrahigh surface areas and quite large pore volumes. They exhibit considerable hydrogen uptake and excellent electrochemical performance as cathode material for lithium-sulfur battery. This work provides a general method to fast and clean synthesis of porous carbon materials and opens new avenues for the application of metal-organic gel in energy storage.

  18. Topological design and additive manufacturing of porous metals for bone scaffolds and orthopaedic implants: A review.

    Science.gov (United States)

    Wang, Xiaojian; Xu, Shanqing; Zhou, Shiwei; Xu, Wei; Leary, Martin; Choong, Peter; Qian, M; Brandt, Milan; Xie, Yi Min

    2016-03-01

    One of the critical issues in orthopaedic regenerative medicine is the design of bone scaffolds and implants that replicate the biomechanical properties of the host bones. Porous metals have found themselves to be suitable candidates for repairing or replacing the damaged bones since their stiffness and porosity can be adjusted on demands. Another advantage of porous metals lies in their open space for the in-growth of bone tissue, hence accelerating the osseointegration process. The fabrication of porous metals has been extensively explored over decades, however only limited controls over the internal architecture can be achieved by the conventional processes. Recent advances in additive manufacturing have provided unprecedented opportunities for producing complex structures to meet the increasing demands for implants with customized mechanical performance. At the same time, topology optimization techniques have been developed to enable the internal architecture of porous metals to be designed to achieve specified mechanical properties at will. Thus implants designed via the topology optimization approach and produced by additive manufacturing are of great interest. This paper reviews the state-of-the-art of topological design and manufacturing processes of various types of porous metals, in particular for titanium alloys, biodegradable metals and shape memory alloys. This review also identifies the limitations of current techniques and addresses the directions for future investigations. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. 21 CFR 888.3358 - Hip joint metal/polymer/metal semi-constrained porous-coated uncemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... porous-coated uncemented prosthesis. 888.3358 Section 888.3358 Food and Drugs FOOD AND DRUG... Devices § 888.3358 Hip joint metal/polymer/metal semi-constrained porous-coated uncemented prosthesis. (a) Identification. A hip joint metal/polymer/metal semi-constrained porous-coated uncemented prosthesis is a device...

  20. An In-Depth Structural Study of the Carbon Dioxide Adsorption Process in the Porous Metal-Organic Frameworks CPO-27-M.

    Science.gov (United States)

    Pato-Doldán, Breogán; Rosnes, Mali H; Dietzel, Pascal D C

    2017-04-22

    The CO 2 adsorption process in the family of porous metal-organic framework materials CPO-27-M (M=Mg, Mn, Co, Ni, Cu, and Zn) was studied by variable-temperature powder synchrotron X-ray diffraction under isobaric conditions. The Rietveld analysis of the data provided a time-lapse view of the adsorption process on CPO-27-M. The results confirm the temperature-dependent order of occupation of the three adsorption sites in the pores of the CPO-27-M materials. In CPO-27-M (M=Mg, Mn, Co, Ni, and Zn), the adsorption sites are occupied in sequential order, primarily because of the high affinity of CO 2 for the open metal sites. CPO-27-Cu deviates from this stepwise mechanism, and the adsorption sites at the metal cation and the second site are occupied in parallel. The temperature dependence of the site occupancy of the individual CO 2 adsorption sites derived from the diffraction data is reflected in the shape of the volumetric sorption isotherms. The fast kinetics and high reversibility observed in these experiments support the suitability of these materials for use in temperature- or pressure-swing processes for carbon capture. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Porous media fluid transport and pore structure

    CERN Document Server

    Dullien, F A L

    1992-01-01

    This book examines the relationship between transport properties and pore structure of porous material. Models of pore structure are presented with a discussion of how such models can be used to predict the transport properties of porous media. Portions of the book are devoted to interpretations of experimental results in this area and directions for future research. Practical applications are given where applicable, and are expected to be useful for a large number of different fields, including reservoir engineering, geology, hydrogeology, soil science, chemical process engineering, biomedica

  2. Porous metal oxide particles and their methods of synthesis

    Science.gov (United States)

    Chen, Fanglin; Liu, Qiang

    2013-03-12

    Methods are generally disclosed for synthesis of porous particles from a solution formed from a leaving agent, a surfactant, and a soluble metal salt in a solvent. The surfactant congregates to form a nanoparticle core such that the metal salt forms about the nanoparticle core to form a plurality of nanoparticles. The solution is heated such that the leaving agent forms gas bubbles in the solution, and the plurality of nanoparticles congregate about the gas bubbles to form a porous particle. The porous particles are also generally disclosed and can include a particle shell formed about a core to define an average diameter from about 0.5 .mu.m to about 50 .mu.m. The particle shell can be formed from a plurality of nanoparticles having an average diameter of from about 1 nm to about 50 nm and defined by a metal salt formed about a surfactant core.

  3. METHOD FOR PREPARING A POROUS POLYMER STRUCTURE

    NARCIS (Netherlands)

    Grijpma, D.W.; Hou, Q.; Feijen, Jan

    2003-01-01

    The present invention relates to a method for preparing a porous polymer structure. A polymer is dissolved in a first liquid or the polymer is brought into the liquid phase. To the solution are added particles which are insoluble in the first liquid, so that a suspension or dispersion results. The

  4. Deposited Micro Porous Layer as Lubricant Carrier in Metal Forming

    DEFF Research Database (Denmark)

    Arentoft, Mogens; Bay, Niels; Tang, Peter Torben

    2008-01-01

    A new porous coating for carrying lubricant in metal forming processes is developed. The coating is established by simultaneous electrochemical deposition of two pure metals. One of them is subsequently etched away leaving a porous surface layer. Lubricant can be trapped in the pores acting...... as lubricant reservoirs. Conventional friction tests for cold forming; ring compression and double cup extrusion tests are carried out with Molykote DX paste and mineral oil as lubricant. Both lubricants act as intended for the ring compressions test whereas only the low viscosity oil perform successfully...

  5. Positron annihilation lifetime spectroscopy (PALS) application in metal barrier layer integrity for porous low- k materials

    CERN Document Server

    Simon, Lin; Gidley, D W; Wetzel, J T; Monnig, K A; Ryan, E T; Simon, Jang; Douglas, Yu; Liang, M S; En, W G; Jones, E C; Sturm, J C; Chan, M J; Tiwari, S C; Hirose, M

    2002-01-01

    Positron Annihilation Lifetime Spectroscopy (PALS) is a useful tool to pre-screen metal barrier integrity for Si-based porous low-k dielectrics. Pore size of low-k, thickness of metal barrier Ta, positronium (Ps) leakage from PALS, trench sidewall morphology, electrical test from one level metal (1LM) pattern wafer and Cu diffusion analysis were all correlated. Macro-porous low-k (pore size >=200 AA) and large scale meso-porous low-k (>50~200 AA) encounter both Ps leakage and Cu diffusion into low-k dielectric in the 0.25 mu mL/0.3 mu mS structures when using SEMATECH in-house PVD Ta 250 AA as barrier layer. For small scale meso-porous (>20~50 AA) and micro- porous (<=20 AA) low-k, no Ps leakage and no Cu diffusion into low-k were observed even with PVD Ta 50 AA, which is proved also owing to sidewall densification to seal all sidewall pores due to plasma etch and ash. For future technology, smaller pore size of porous Si-based low-k (=<50 AA) will be preferential for dense low-k like trench sidewall to...

  6. From metal-organic squares to porous zeolite-like supramolecular assemblies

    KAUST Repository

    Wang, Shuang

    2010-12-29

    We report the synthesis, structure, and characterization of two novel porous zeolite-like supramolecular assemblies, ZSA-1 and ZSA-2, having zeolite gis and rho topologies, respectively. The two compounds were assembled from functional metal-organic squares (MOSs) via directional hydrogen-bonding interactions and exhibited permanent microporosity and thermal stability up to 300 °C. © 2010 American Chemical Society.

  7. Designing porous metallic glass compact enclosed with surface iron oxides

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Jae Young; Park, Hae Jin; Hong, Sung Hwan; Kim, Jeong Tae; Kim, Young Seok; Park, Jun-Young; Lee, Naesung [Hybrid Materials Center (HMC), Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Seo, Yongho [Graphene Research Institute (GRI) & HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Park, Jin Man, E-mail: jinman_park@hotmail.com [Global Technology Center, Samsung Electronics Co., Ltd, 129 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-742 (Korea, Republic of); Kim, Ki Buem, E-mail: kbkim@sejong.ac.kr [Hybrid Materials Center (HMC), Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)

    2015-06-25

    Highlights: • Porous metallic glass compact was developed using electro-discharge sintering process. • Uniform PMGC can only be achieved when low electrical input energy was applied. • Functional iron-oxides were formed on the surface of PMGCs by hydrothermal technique. - Abstract: Porous metallic glass compact (PMGC) using electro-discharge sintering (EDS) process of gas atomized Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} metallic glass powder was developed. The formation of uniform PMGC can only be achieved when low electrical input energy was applied. Functional iron-oxides were formed on the surface of PMGCs by hydrothermal technique. This finding suggests that PMGC can be applied in the new area such as catalyst via hydrothermal technique and offer a promising guideline for using the metallic glasses as a potential functional application.

  8. Wave Interaction with Porous Coastal Structures

    DEFF Research Database (Denmark)

    Jensen, Bjarne

    Porous breakwater structures are widely used as protection against waves for ports and harbours as well as for general coastal protection. The structures differers depending on the exact purpose e.g. harbour protection, detached breakwaters, groins, submerged breakwaters etc. Typical types...... to waves. The general design methods are based on a long tradition of experimental investigations in scale models. This has resulted in empirical design formulas which in combination with physical model tests during the design phase constitutes the typical approach to breakwater design. Numerical models...... are also applied as part of investigating and designing breakwaters. The models can provide more detailed information on some topics, such as pressure attenuation through the porous core material, while it is more difficult to simulate the direct destabilisation and movements of individual stones...

  9. Enhanced Structural Support of Metal Sites as Nodes in Metal-Organic Frameworks Compared to Metal Complexes

    OpenAIRE

    Das, Sanjit

    2013-01-01

    Metal-organic frameworks are a new class of crystalline, porous solid-state materials with metal ions periodically linked by organic linkers. This gives rise to one-, two- or three-dimensional structures. Here, we compare the stability of similar metal sites toward external ligand (solvent) induced disruption of the coordination environment in metal complexes and in metal-organic frameworks. Our experimental results show that a metal site as node of a metal-organic framework retains much high...

  10. Stochastic metallic-glass cellular structures exhibiting benchmark strength.

    Science.gov (United States)

    Demetriou, Marios D; Veazey, Chris; Harmon, John S; Schramm, Joseph P; Johnson, William L

    2008-10-03

    By identifying the key characteristic "structural scales" that dictate the resistance of a porous metallic glass against buckling and fracture, stochastic highly porous metallic-glass structures are designed capable of yielding plastically and inheriting the high plastic yield strength of the amorphous metal. The strengths attainable by the present foams appear to equal or exceed those by highly engineered metal foams such as Ti-6Al-4V or ferrous-metal foams at comparable levels of porosity, placing the present metallic-glass foams among the strongest foams known to date.

  11. Synthesis and characterization of hierarchically porous metal, metal oxide, and carbon monoliths with highly ordered nanostructure

    Science.gov (United States)

    Grano, Amy Janine

    Hierarchically porous materials are of great interest in such applications as catalysis, separations, fuel cells, and advanced batteries. One such way of producing these materials is through the process of nanocasting, in which a sacrificial template is replicated and then removed to form a monolithic replica. This replica consists of mesopores, which can be ordered or disordered, and bicontinuous macropores, which allow flow throughout the length of the monolith. Hierarchically porous metal oxide and carbon monoliths with an ordered mesopores system are synthesized for the first time via nanocasting. These replicas were used as supports for the deposition of silver particles and the catalytic efficiency was evaluated. The ordered silica template used in producing these monoliths was also used for an in-situ TEM study involving metal nanocasting, and an observation of the destruction of the silica template during nanocasting made. Two new methods of removing the silica template were developed and applied to the synthesis of copper, nickel oxide, and zinc oxide monoliths. Finally, hollow fiber membrane monoliths were examined via x-ray tomography in an attempt to establish the presence of this structure throughout the monolith.

  12. 21 CFR 888.3565 - Knee joint patellofemorotibial metal/polymer porous-coated uncemented prosthesis.

    Science.gov (United States)

    2010-04-01

    ... porous-coated uncemented prosthesis. 888.3565 Section 888.3565 Food and Drugs FOOD AND DRUG... Devices § 888.3565 Knee joint patellofemorotibial metal/polymer porous-coated uncemented prosthesis. (a) Identification. A knee joint patellofemorotibial metal/polymer porous-coated uncemented prosthesis is a device...

  13. Development of membrane filters with nanostructured porous layer by coating of metal nanoparticles sintered onto a micro-filter

    International Nuclear Information System (INIS)

    Park, Seok Joo; Park, Young Ok; Lee, Dong Geun; Ryu, Jeong In

    2008-01-01

    The membrane filter adhered with nanostructured porous layer was made by heat treatment after deposition of nanoparticle-agglomerates sintered in aerosol phase onto a conventional micron-fibrous metal filter as a substrate filter. The Sintered-Nanoparticle-Agglomerates-coated NanoStructured porous layer Membrane Filter (SNA-NSMF), whose the filtration performance was improved compared with the conventional metal membrane filters, was developed by adhesion of nanoparticle-agglomerates of dendrite structure sintered onto the micron-fibrous metal filter. The size of nanoparticle-agglomerates of dendrite structure decreased with increasing the sintering temperature because nanoparticle-agglomerates shrank. When shrinking nanoparticle-agglomerates were deposited and treated with heat onto the conventional micron-fibrous metal filter, pore size of nanostructured porous layer decreased. Therefore, pressure drops of SNA-NSMFs increased from 0.3 to 0.516 KPa and filtration efficiencies remarkably increased from 95.612 to 99.9993%

  14. Metal Chloride Induced Formation of Porous Polyhydroxybutyrate (PHB) Films: Morphology, Thermal Properties and Crystallinity

    Science.gov (United States)

    Tan, W. L.; Yaakob, N. N.; Zainal Abidin, A.; Abu Bakar, M.; Abu Bakar, N. H. H.

    2016-06-01

    Polyhydroxybutyrate (PHB) films with highly porous structures were synthesized using a one phase system comprising of metal chloride/methanol/PHB/chloroform (MCl2/CH3OH/PHB/CHCl3). SEM analyses confirmed that the MCl2 (where M = Cu2+ or Ni2+) induced porous structures with pore sizes ranging from 0.3 - 2.0 μm. The average pore size increased with the increasing MCl2 content. There existed weak physical interactions between the PHB chains and MCl2 as revealed by FTIR and NMR spectroscopies. The residue of MCl2 in the porous PHB film does not exert significant influence on the thermal stability of PHB. Nevertheless, the crystallinity of the prepared film is enhanced, as MCl2 acts as the nucleation sites to promote the growth of spherullites.

  15. Multiscale global identification of porous structures

    Science.gov (United States)

    Hatłas, Marcin; Beluch, Witold

    2018-01-01

    The paper is devoted to the evolutionary identification of the material constants of porous structures based on measurements conducted on a macro scale. Numerical homogenization with the RVE concept is used to determine the equivalent properties of a macroscopically homogeneous material. Finite element method software is applied to solve the boundary-value problem in both scales. Global optimization methods in form of evolutionary algorithm are employed to solve the identification task. Modal analysis is performed to collect the data necessary for the identification. A numerical example presenting the effectiveness of proposed attitude is attached.

  16. Band structures in fractal grading porous phononic crystals

    Science.gov (United States)

    Wang, Kai; Liu, Ying; Liang, Tianshu; Wang, Bin

    2018-05-01

    In this paper, a new grading porous structure is introduced based on a Sierpinski triangle routine, and wave propagation in this fractal grading porous phononic crystal is investigated. The influences of fractal hierarchy and porosity on the band structures in fractal graidng porous phononic crystals are clarified. Vibration modes of unit cell at absolute band gap edges are given to manifest formation mechanism of absolute band gaps. The results show that absolute band gaps are easy to form in fractal structures comparatively to the normal ones with the same porosity. Structures with higher fractal hierarchies benefit multiple wider absolute band gaps. This work provides useful guidance in design of fractal porous phononic crystals.

  17. Porous silicon based anode material formed using metal reduction

    Science.gov (United States)

    Anguchamy, Yogesh Kumar; Masarapu, Charan; Deng, Haixia; Han, Yongbong; Venkatachalam, Subramanian; Kumar, Sujeet; Lopez, Herman A.

    2015-09-22

    A porous silicon based material comprising porous crystalline elemental silicon formed by reducing silicon dioxide with a reducing metal in a heating process followed by acid etching is used to construct negative electrode used in lithium ion batteries. Gradual temperature heating ramp(s) with optional temperature steps can be used to perform the heating process. The porous silicon formed has a high surface area from about 10 m.sup.2/g to about 200 m.sup.2/g and is substantially free of carbon. The negative electrode formed can have a discharge specific capacity of at least 1800 mAh/g at rate of C/3 discharged from 1.5V to 0.005V against lithium with in some embodiments loading levels ranging from about 1.4 mg/cm.sup.2 to about 3.5 mg/cm.sup.2. In some embodiments, the porous silicon can be coated with a carbon coating or blended with carbon nanofibers or other conductive carbon material.

  18. Porous Al Current Collector for Dendrite-Free Na Metal Anodes.

    Science.gov (United States)

    Liu, Shan; Tang, Shan; Zhang, Xinyue; Wang, Aoxuan; Yang, Quan-Hong; Luo, Jiayan

    2017-09-13

    Na-based batteries are proposed as promising energy storage candidates for beyond Li-ion technology due to the higher natural earth of Na metal. For its high capacity and low potential, Na metal may carve itself a niche when directly used as anodes. Similar to or even more problematic than Li, however, uneven plating/stripping of Na leads to dendrite formation. As the plating substrates, current collectors have a paramount influence on the Na plating/stripping behaviors. Here we propose porous Al current collectors as the plating substrate to suppress Na dendrites. Al does not alloy with Na. It is advantageous over Cu current collectors in terms of cost and weight. The interconnected porous structure can increase available surface for Na to nucleate and decrease the Na + flux distribution, leading to homogeneous plating. The Na metal anodes can run for over 1000 cycles on porous Al with a low and stable voltage hysteresis and their average plating/stripping Coulombic efficiency was above 99.9%, which is greatly improved compared to planar Al. We used the porous Al for Na-O 2 , Na-Na 3 V 2 (PO 4 ) 3 cells with low Na amount and anode free Na-TiS 2 batteries and anticipate that using this strategy can be combined with further electrolyte and cathodes to develop high performance Na-based batteries.

  19. Gas storage in porous metal-organic frameworks for clean energy applications.

    Science.gov (United States)

    Ma, Shengqian; Zhou, Hong-Cai

    2010-01-07

    Depletion of fossil oil deposits and the escalating threat of global warming have put clean energy research, which includes the search for clean energy carriers such as hydrogen and methane as well as the reduction of carbon dioxide emissions, on the urgent agenda. A significant technical challenge has been recognized as the development of a viable method to efficiently trap hydrogen, methane and carbon dioxide gas molecules in a confined space for various applications. This issue can be addressed by employing highly porous materials as storage media, and porous metal-organic frameworks (MOFs) which have exceptionally high surface areas as well as chemically-tunable structures are playing an unusual role in this respect. In this feature article we provide an overview of the current status of clean energy applications of porous MOFs, including hydrogen storage, methane storage and carbon dioxide capture.

  20. Preparation of porous structures with shape memory properties from biodegradable polymeric networks

    NARCIS (Netherlands)

    Sharifi, Shahriar; Blanquer, Sebastien; Grijpma, Dirk W.

    2012-01-01

    Preparing porous biodegradable structures from shape memory polymers can combine the structure-defining properties of porous structures with the minimally invasive implanting possibilities of shape memory polymers. In this study, porous biodegradable shape memory structures were prepared using

  1. Metal-organic framework templated synthesis of porous inorganic materials as novel sorbents

    Energy Technology Data Exchange (ETDEWEB)

    Taylor-Pashow, Kathryn M. L.; Lin, Wenbin; Abney, Carter W.

    2017-03-21

    A novel metal-organic framework (MOF) templated process for the synthesis of highly porous inorganic sorbents for removing radionuclides, actinides, and heavy metals is disclosed. The highly porous nature of the MOFs leads to highly porous inorganic sorbents (such as oxides, phosphates, sulfides, etc) with accessible surface binding sites that are suitable for removing radionuclides from high level nuclear wastes, extracting uranium from acid mine drainage and seawater, and sequestering heavy metals from waste streams. In some cases, MOFs can be directly used for removing these metal ions as MOFs are converted to highly porous inorganic sorbents in situ.

  2. An approach to preparing porous and hollow metal phosphides with higher hydrodesulfurization activity

    International Nuclear Information System (INIS)

    Song Limin; Zhang Shujuan; Wei Qingwu

    2011-01-01

    This paper describes an effective method for the synthesis of metal phosphides. Bulk and supported Ni 2 P, Cu 3 P, and CoP were prepared by thermal treatment of metal and the amorphous red phosphorus mixtures. Porous and hollow Ni 2 P particles were also synthesized successfully using this method. The structural properties of these products are investigated using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), inductively coupled plasma (ICP-AES) and X-ray photoemission spectroscopy (XPS). A rational mechanism was proposed for the selective formation of Ni 2 P particles. In experimental conditions, the Ni 2 P/SiO 2 catalyst exhibits excellent hydrodesulfurization (HDS) activity for dibenzothiophene (DBT). - Graphical abstract: Bulk and supported Ni 2 P, Cu 3 P, and CoP were prepared by thermal treatment of their metal and amorphous red phosphorus mixtures. Porous and hollow Ni 2 P particles were successfully synthesized by this method also. In the experimental condition, a Ni 2 P/SiO 2 catalyst exhibits excellent hydrodesulfurization activity for dibenzothiophene. Highlights: → A new synthetic route by heat treating mixtures of metal and red phosphorus in flowing N 2 to prepare corresponding metal phosphides. → Porous and hollow Ni 2 P particles may successfully be obtained using the route. → It is very easy to synthesize other bulk and supported metal phosphides using the mixing of bulk and supported metal and red phosphorus by the method. → The Ni 2 P/SiO 2 catalyst synthesized by the route shows a good HDS of dibenzothiophene. → Its operation is simple (only heat treating pure metal and red phosphorus), and the reaction time is short (only 0.5 h).

  3. Porous Silicon Structures as Optical Gas Sensors

    Directory of Open Access Journals (Sweden)

    Igor A. Levitsky

    2015-08-01

    Full Text Available We present a short review of recent progress in the field of optical gas sensors based on porous silicon (PSi and PSi composites, which are separate from PSi optochemical and biological sensors for a liquid medium. Different periodical and nonperiodical PSi photonic structures (bares, modified by functional groups or infiltrated with sensory polymers are described for gas sensing with an emphasis on the device specificity, sensitivity and stability to the environment. Special attention is paid to multiparametric sensing and sensor array platforms as effective trends for the improvement of analyte classification and quantification. Mechanisms of gas physical and chemical sorption inside PSi mesopores and pores of PSi functional composites are discussed.

  4. Fabrication of porous zeolite/chitosan monoliths and their applications for drug release and metal ions adsorption.

    Science.gov (United States)

    Zhang, Yongli; Yan, Weiwei; Sun, Zhiming; Pan, Cheng; Mi, Xue; Zhao, Gang; Gao, Jianping

    2015-03-06

    Ordered porous zeolite/chitosan (Zel/Chi) monoliths were prepared by a unidirectional freeze-drying method, and their properties and structures were characterized by various instrumental methods. The metal ion adsorption and the drug release performance of the porous Zel/Chi monoliths were also studied. The release rate of cefalexin from drug-loaded Zel/Chi monoliths depended on the composition and porous structure of the monoliths. The metal ion adsorption capacity of the Zel/Chi monoliths was related to the concentration of the metal ions, the adsorption time and the Zel/Chi ratio. An experimentally maximum adsorption of 89 mg/g was achieved for Cu(2+) ions. The Zel/Chi monoliths with adsorbed Cu(2+) ions effectively catalyzed the reduction of 4-nitrophenol to 4-aminophenol and had good recyclability. They were easily recovered by simply removing them from the reaction system and rinsing them with water. Copyright © 2014. Published by Elsevier Ltd.

  5. NMR studies of metallic tin confined within porous matrices

    International Nuclear Information System (INIS)

    Charnaya, E. V.; Tien, Cheng; Lee, M. K.; Kumzerov, Yu. A.

    2007-01-01

    119 Sn NMR studies were carried out for metallic tin confined within synthetic opal and porous glass. Tin was embedded into nanoporous matrices in the melted state under pressure. The Knight shift for liquid confined tin was found to decrease with decreasing pore size. Correlations between NMR line shapes, Knight shift, and pore filling were observed. The melting and freezing phase transitions of tin under confinement were studied through temperature dependences of NMR signals upon warming and cooling. Melting of tin within the opal matrix agreed well with the liquid skin model suggested for small isolated particles. The influence of the pore filling on the melting process was shown

  6. Improving the fatigue performance of porous metallic biomaterials produced by Selective Laser Melting.

    Science.gov (United States)

    Van Hooreweder, Brecht; Apers, Yanni; Lietaert, Karel; Kruth, Jean-Pierre

    2017-01-01

    This paper provides new insights into the fatigue properties of porous metallic biomaterials produced by additive manufacturing. Cylindrical porous samples with diamond unit cells were produced from Ti6Al4V powder using Selective Laser Melting (SLM). After measuring all morphological and quasi-static properties, compression-compression fatigue tests were performed to determine fatigue strength and to identify important fatigue influencing factors. In a next step, post-SLM treatments were used to improve the fatigue life of these biomaterials by changing the microstructure and by reducing stress concentrators and surface roughness. In particular, the influence of stress relieving, hot isostatic pressing and chemical etching was studied. Analytical and numerical techniques were developed to calculate the maximum local tensile stress in the struts as function of the strut diameter and load. With this method, the variability in the relative density between all samples was taken into account. The local stress in the struts was then used to quantify the exact influence of the applied post-SLM treatments on the fatigue life. A significant improvement of the fatigue life was achieved. Also, the post-SLM treatments, procedures and calculation methods can be applied to different types of porous metallic structures and hence this paper provides useful tools for improving fatigue performance of metallic biomaterials. Additive Manufacturing (AM) techniques such as Selective Laser Melting (SLM) are increasingly being used for producing customized porous metallic biomaterials. These biomaterials are regularly used for biomedical implants and hence a long lifetime is required. In this paper, a set of post-built surface and heat treatments is presented that can be used to significantly improve the fatigue life of porous SLM-Ti6Al4V samples. In addition, a novel and efficient analytical local stress method was developed to accurately quantify the influence of the post

  7. Porous, rigid metal(III)-carboxylate metal-organic frameworks for the delivery of nitric oxide

    Science.gov (United States)

    Eubank, Jarrod F.; Wheatley, Paul S.; Lebars, Gaëlle; McKinlay, Alistair C.; Leclerc, Hervé; Horcajada, Patricia; Daturi, Marco; Vimont, Alexandre; Morris, Russell E.; Serre, Christian

    2014-12-01

    The room temperature sorption properties of the biological gas nitric oxide (NO) have been investigated on the highly porous and rigid iron or chromium carboxylate based metal-organic frameworks Material Institut Lavoisier (MIL)-100(Fe or Cr) and MIL-127(Fe). In all cases, a significant amount of NO is chemisorbed at 298 K with a loading capacity that depends both on the nature of the metal cation, the structure and the presence of additional iron(II) Lewis acid sites. In a second step, the release of NO triggered by wet nitrogen gas has been studied by chemiluminescence and indicates that only a partial release of NO occurs as well as a prolonged delivery at the biological level. Finally, an in situ infrared spectroscopy study confirms not only the coordination of NO over the Lewis acid sites and the stronger binding of NO on the additional iron(II) sites, providing further insights over the partial release of NO only in the presence of water at room temperature.

  8. Porous, rigid metal(III-carboxylate metal-organic frameworks for the delivery of nitric oxide

    Directory of Open Access Journals (Sweden)

    Jarrod F. Eubank

    2014-12-01

    Full Text Available The room temperature sorption properties of the biological gas nitric oxide (NO have been investigated on the highly porous and rigid iron or chromium carboxylate based metal-organic frameworks Material Institut Lavoisier (MIL-100(Fe or Cr and MIL-127(Fe. In all cases, a significant amount of NO is chemisorbed at 298 K with a loading capacity that depends both on the nature of the metal cation, the structure and the presence of additional iron(II Lewis acid sites. In a second step, the release of NO triggered by wet nitrogen gas has been studied by chemiluminescence and indicates that only a partial release of NO occurs as well as a prolonged delivery at the biological level. Finally, an in situ infrared spectroscopy study confirms not only the coordination of NO over the Lewis acid sites and the stronger binding of NO on the additional iron(II sites, providing further insights over the partial release of NO only in the presence of water at room temperature.

  9. Metal-adeninate vertices for the construction of an exceptionally porous metal-organic framework.

    Science.gov (United States)

    An, Jihyun; Farha, Omar K; Hupp, Joseph T; Pohl, Ehmke; Yeh, Joanne I; Rosi, Nathaniel L

    2012-01-03

    Metal-organic frameworks comprising metal-carboxylate cluster vertices and long, branched organic linkers are the most porous materials known, and therefore have attracted tremendous attention for many applications, including gas storage, separations, catalysis and drug delivery. To increase metal-organic framework porosity, the size and complexity of linkers has increased. Here we present a promising alternative strategy for constructing mesoporous metal-organic frameworks that addresses the size of the vertex rather than the length of the organic linker. This approach uses large metal-biomolecule clusters, in particular zinc-adeninate building units, as vertices to construct bio-MOF-100, an exclusively mesoporous metal-organic framework. Bio-MOF-100 exhibits a high surface area (4,300 m(2) g(-1)), one of the lowest crystal densities (0.302 g cm(-3)) and the largest metal-organic framework pore volume reported to date (4.3 cm(3) g(-1)).

  10. Porous silicon multitexture for photoelectric converter structures of solar energy

    OpenAIRE

    Yerokhov V. Yu.; Druzinin A. O.

    2009-01-01

    The possibility of creation of porous silicon’s multitexture, as material of structure of photoelectric converter (FEC) is shown. The morphological elements of porous silicon are considered relative to different pore parameters. The integral coefficient of frontal surface reflection of FEC with using of columnar multitexture in the range from 400 nm up to 1150 nm decreased.

  11. Porous silicon multitexture for photoelectric converter structures of solar energy

    Directory of Open Access Journals (Sweden)

    Yerokhov V. Yu.

    2009-06-01

    Full Text Available The possibility of creation of porous silicon’s multitexture, as material of structure of photoelectric converter (FEC is shown. The morphological elements of porous silicon are considered relative to different pore parameters. The integral coefficient of frontal surface reflection of FEC with using of columnar multitexture in the range from 400 nm up to 1150 nm decreased.

  12. Osteoinduction on acid and heat treated porous Ti metal samples in canine muscle.

    Science.gov (United States)

    Kawai, Toshiyuki; Takemoto, Mitsuru; Fujibayashi, Shunsuke; Akiyama, Haruhiko; Tanaka, Masashi; Yamaguchi, Seiji; Pattanayak, Deepak K; Doi, Kenji; Matsushita, Tomiharu; Nakamura, Takashi; Kokubo, Tadashi; Matsuda, Shuichi

    2014-01-01

    Samples of porous Ti metal were subjected to different acid and heat treatments. Ectopic bone formation on specimens embedded in dog muscle was compared with the surface characteristics of the specimen. Treatment of the specimens by H2SO4/HCl and heating at 600 °C produced micrometer-scale roughness with surface layers composed of rutile phase of titanium dioxide. The acid- and heat-treated specimens induced ectopic bone formation within 6 months of implantation. A specimen treated using NaOH followed by HCl acid and then heat treatment produced nanometer-scale surface roughness with a surface layer composed of both rutile and anatase phases of titanium dioxide. These specimens also induced bone formation after 6 months of implantation. Both these specimens featured positive surface charge and good apatite-forming abilities in a simulated body fluid. The amount of the bone induced in the porous structure increased with apatite-forming ability and higher positive surface charge. Untreated porous Ti metal samples showed no bone formation even after 12 months. Specimens that were only heat treated featured a smooth surface composed of rutile. A mixed acid treatment produced specimens with micrometer-scale rough surfaces composed of titanium hydride. Both of them also showed no bone formation after 12 months. The specimens that showed no bone formation also featured almost zero surface charge and no apatite-forming ability. These results indicate that osteoinduction of these porous Ti metal samples is directly related to positive surface charge that facilitates formation of apatite on the metal surfaces in vitro.

  13. Osteoinduction on acid and heat treated porous Ti metal samples in canine muscle.

    Directory of Open Access Journals (Sweden)

    Toshiyuki Kawai

    Full Text Available Samples of porous Ti metal were subjected to different acid and heat treatments. Ectopic bone formation on specimens embedded in dog muscle was compared with the surface characteristics of the specimen. Treatment of the specimens by H2SO4/HCl and heating at 600 °C produced micrometer-scale roughness with surface layers composed of rutile phase of titanium dioxide. The acid- and heat-treated specimens induced ectopic bone formation within 6 months of implantation. A specimen treated using NaOH followed by HCl acid and then heat treatment produced nanometer-scale surface roughness with a surface layer composed of both rutile and anatase phases of titanium dioxide. These specimens also induced bone formation after 6 months of implantation. Both these specimens featured positive surface charge and good apatite-forming abilities in a simulated body fluid. The amount of the bone induced in the porous structure increased with apatite-forming ability and higher positive surface charge. Untreated porous Ti metal samples showed no bone formation even after 12 months. Specimens that were only heat treated featured a smooth surface composed of rutile. A mixed acid treatment produced specimens with micrometer-scale rough surfaces composed of titanium hydride. Both of them also showed no bone formation after 12 months. The specimens that showed no bone formation also featured almost zero surface charge and no apatite-forming ability. These results indicate that osteoinduction of these porous Ti metal samples is directly related to positive surface charge that facilitates formation of apatite on the metal surfaces in vitro.

  14. Same-Side Platinum Electrodes for Metal Assisted Etching of Porous Silicon

    Science.gov (United States)

    2015-11-01

    Platinum Electrodes for Metal Assisted Etching of Porous Silicon by Matthew H Ervin and Brian Isaacson Sensors and Electron Devices Directorate...SUBTITLE Same-Side Platinum Electrodes for Metal Assisted Etching of Porous Silicon 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT

  15. The Hydrolytic Stability and Degradation Mechanism of a Hierarchically Porous Metal Alkylphosphonate Framework

    Directory of Open Access Journals (Sweden)

    Kai Lv

    2018-03-01

    Full Text Available To aid the design of a hierarchically porous unconventional metal-phosphonate framework (HP-UMPF for practical radioanalytical separation, a systematic investigation of the hydrolytic stability of bulk phase against acidic corrosion has been carried out for an archetypical HP-UMPF. Bulk dissolution results suggest that aqueous acidity has a more paramount effect on incongruent leaching than the temperature, and the kinetic stability reaches equilibrium by way of an accumulation of a partial leached species on the corrosion conduits. A variation of particle morphology, hierarchical porosity and backbone composition upon corrosion reveals that they are hydrolytically resilient without suffering any great degradation of porous texture, although large aggregates crack into sporadic fractures while the nucleophilic attack of inorganic layers cause the leaching of tin and phosphorus. The remaining selectivity of these HP-UMPFs is dictated by a balance between the elimination of free phosphonate and the exposure of confined phosphonates, thus allowing a real-time tailor of radionuclide sequestration. Moreover, a plausible degradation mechanism has been proposed for the triple progressive dissolution of three-level hierarchical porous structures to elucidate resultant reactivity. These HP-UMPFs are compared with benchmark metal-organic frameworks (MOFs to obtain a rough grading of hydrolytic stability and two feasible approaches are suggested for enhancing their hydrolytic stability that are intended for real-life separation protocols.

  16. Surface structure and adsorption properties of ultrafine porous carbon fibers

    International Nuclear Information System (INIS)

    Song Xiaofeng; Wang Ce; Zhang Dejiang

    2009-01-01

    Ultrafine porous carbon fibers (UPCFs) were successfully synthesized by chemical activation of electrospun polyacrylonitrile fibers. In the current approach, potassium hydroxide was adopted as activation reagent. UPCFs were systematically evaluated by scanning electron microscope and nitrogen adsorption. The mass ratio of potassium hydroxide to preoxidized fibers, activation temperature and activation time are crucial for producing high quality UPCFs. The relationships between porous structure and process parameters are explored. UPCFs were applied as adsorbent for nitrogen monoxide to be compared with commercial porous carbon fibers.

  17. Mechanical Performance of Amorphous Metallic Cellular Structures

    Science.gov (United States)

    Schramm, Joseph P.

    Metallic glass and metallic glass matrix composites are excellent candidates for application in cellular structures because of their outstanding plastic yield strengths and their ability to deform plastically prior to fracture. The mechanical performance of metallic-glass and metallic-glass-matrix-composite honeycomb structures are discussed, and their strength and energy absorption capabilities examined in quasi-static compression tests for both in-plane and out-of-plane loading. These structures exhibit strengths and energy absorption that well exceed the performance of similar structures made from crystalline metals. The strength and energy absorption capabilities of amorphous metal foams produced by a powder metallurgy process are also examined, showing that foams produced by this method can be highly porous and are able to inherit the strength of the parent metallic glass and absorb large amounts of energy. The mechanical properties of a highly stochastic set of foams are examined at low and high strain rates. It is observed that upon a drastic increase in strain rate, the dominant mechanism of yielding for these foams undergoes a change from elastic buckling to plastic yielding. This mechanism change is thought to be the result of the rate of the mechanical test approaching or even eclipsing the speed of elastic waves in the material.

  18. Freeze-Casting of Porous Biomaterials: Structure, Properties and Opportunities

    Directory of Open Access Journals (Sweden)

    Sylvain Deville

    2010-03-01

    Full Text Available The freeze-casting of porous materials has received a great deal of attention during the past few years. This simple process, where a material suspension is simply frozen and then sublimated, provides materials with unique porous architectures, where the porosity is almost a direct replica of the frozen solvent crystals. This review focuses on the recent results on the process and the derived porous structures with regards to the biomaterials applications. Of particular interest is the architecture of the materials and the versatility of the process, which can be readily controlled and applied to biomaterials applications. A careful control of the starting formulation and processing conditions is required to control the integrity of the structure and resulting properties. Further in vitro and in vivo investigations are required to validate the potential of this new class of porous materials.

  19. Electrospun porous structure fibrous film with high oil adsorption capacity.

    Science.gov (United States)

    Wu, Jing; Wang, Nü; Wang, Li; Dong, Hua; Zhao, Yong; Jiang, Lei

    2012-06-27

    A low-cost, high-oil-adsorption film consisting of polystyrene (PS) fibers is fabricated by a facile electrospinning method. Different fiber diameter and porous fiber's surface morphology play roles in oil adsorption capacity and oil/water selectivity. The results showed that oil adsorption capacity of PS oil sorbent film with small diameter and porous surface structure for diesel oil, silicon oil, peanut oil and motor oil were approximate to 7.13, 81.40, 112.30, and 131.63 g/g, respectively. It was higher than normal fibrous sorbent without any porous structure. The thinner porous PS oil sorbent also had excellent oil/water selectivity in the cleanup of oil from water.

  20. Topology optimization of 3D shell structures with porous infill

    DEFF Research Database (Denmark)

    Clausen, Anders; Andreassen, Erik; Sigmund, Ole

    2017-01-01

    This paper presents a 3D topology optimization approach for designing shell structures with a porous or void interior. It is shown that the resulting structures are significantly more robust towards load perturbations than completely solid structures optimized under the same conditions. The study...... indicates that the potential benefit of using porous structures is higher for lower total volume fractions. Compared to earlier work dealing with 2D topology optimization, we found several new effects in 3D problems. Most notably, the opportunity for designing closed shells significantly improves...

  1. Structure of zirconium dioxide based porous glasses

    Czech Academy of Sciences Publication Activity Database

    Gubanova, N. N.; Kopitsa, G. P.; Ezdakova, K. V.; Baranchikov, A. Y.; Angelov, Borislav; Feoktystov, A.; Pipich, V.; Ryukhtin, Vasyl; Ivanov, V. K.

    2014-01-01

    Roč. 8, č. 5 (2014), s. 967-975 ISSN 1027-4510 R&D Projects: GA ČR GAP208/10/1600; GA MŠk(XE) LM2011019; GA ČR GB14-36566G Institutional support: RVO:61389013 ; RVO:61389005 Keywords : zirconium dioxide * porous glasse * nanoparticles Subject RIV: CF - Physical ; Theoretical Chemistry; BG - Nuclear, Atomic and Molecular Physics, Colliders (UJF-V) Impact factor: 0.359, year: 2012

  2. Performance characteristics of porous alumina ceramic structures

    International Nuclear Information System (INIS)

    Latella, B.A.; Liu, T.

    2000-01-01

    Porous ceramics have found a wide range of applications as filters for liquids and gases. The suitability of materials for use in these types of applications depends on the microstructure (grain size, pore size and pore volume fraction) and hence the mechanical and thermal properties. In this study alumina ceramics with different levels of porosity and controlled pore sizes were fabricated and the surface damage and fracture properties were examined. Copyright (2000) The Australian Ceramic Society

  3. Porous Structure Characterization in Titanium Coating for Surgical Implants

    Directory of Open Access Journals (Sweden)

    M.V. Oliveira

    2002-09-01

    Full Text Available Powder metallurgy techniques have been used to produce controlled porous structures, such as the porous coatings applied for dental and orthopedic surgical implants, which allow bony tissue ingrowth within the implant surface improving fixation. This work presents the processing and characterization of titanium porous coatings of different porosity levels, processed through powder metallurgy techniques. Pure titanium sponge powders were used for coating and Ti-6Al7Nb powder metallurgy rods were used as substrates. Characterization was made through quantitative metallographic image analysis using optical light microscope for coating porosity data and SEM analysis for evaluation of the coating/substrate interface integrity. The results allowed optimization of the processing parameters in order to obtain porous coatings that meet the requirements for use as implants.

  4. Fractal Model for Acoustic Absorbing of Porous Fibrous Metal Materials

    Directory of Open Access Journals (Sweden)

    Weihua Chen

    2016-01-01

    Full Text Available To investigate the changing rules between sound absorbing performance and geometrical parameters of porous fibrous metal materials (PFMMs, this paper presents a fractal acoustic model by incorporating the static flow resistivity based on Biot-Allard model. Static flow resistivity is essential for an accurate assessment of the acoustic performance of the PFMM. However, it is quite difficult to evaluate the static flow resistivity from the microstructure of the PFMM because of a large number of disordered pores. In order to overcome this difficulty, we firstly established a static flow resistivity formula for the PFMM based on fractal theory. Secondly, a fractal acoustic model was derived on the basis of the static flow resistivity formula. The sound absorption coefficients calculated by the presented acoustic model were validated by the values of Biot-Allard model and experimental data. Finally, the variation of the surface acoustic impedance, the complex wave number, and the sound absorption coefficient with the fractal dimensions were discussed. The research results can reveal the relationship between sound absorption and geometrical parameters and provide a basis for improving the sound absorption capability of the PFMMs.

  5. Construction of hierarchically porous metal-organic frameworks through linker labilization

    Science.gov (United States)

    Yuan, Shuai; Zou, Lanfang; Qin, Jun-Sheng; Li, Jialuo; Huang, Lan; Feng, Liang; Wang, Xuan; Bosch, Mathieu; Alsalme, Ali; Cagin, Tahir; Zhou, Hong-Cai

    2017-05-01

    A major goal of metal-organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. Herein, we present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragments by acid treatment. We demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis.

  6. Investigations on the porous resistance coefficients for fishing net structures

    DEFF Research Database (Denmark)

    Chen, Hao; Christensen, Erik Damgaard

    2016-01-01

    The porous media model has been successfully applied to numerical simulation of current and wave interaction with traditional permeable coastal structures such as breakwaters. Recently this model was employed to simulate flow through and around fishing net structures, where the unknown porous...... validation cases were carried out to examine the performance of the numerical model. This includes steady current flow through plane net panels and circular fish cages, and wave interaction with plane net panels. A variety of fishing nets with different solidity ratios were used in the validation cases, from...

  7. Characterization of Ge Nano structures Embedded Inside Porous Silicon for Photonics Application

    International Nuclear Information System (INIS)

    Rahim, A.F.A.; Hashim, M.R.; Rahim, A.F.A.; Ali, N.K.

    2011-01-01

    In this work we prepared germanium nano structures by means of filling the material inside porous silicon (PS) using conventional and cost effective technique, thermal evaporator. The PS acts as patterned substrate. It was prepared by anodization of silicon wafer in ethanoic hydrofluoric acid (HF). A Ge layer was then deposited onto the PS by thermal evaporation. This was followed by deposition of Si layer by thermal evaporation and anneal at 650 degree Celsius for 30 min. The process was completed by Ni metal deposition using thermal evaporator followed by metal annealing of 400 degree Celsius for 10 min to form metal semiconductor metal (MSM) photodetector. Structural analysis of the samples was performed using energy dispersive x-ray analysis (EDX), scanning electron microscope (SEM), X-ray diffraction (XRD) and Raman spectroscopy (RS). EDX spectrum suggests the presence of Ge inside the pores structure. Raman spectrum showed that good crystalline structure of Ge can be produced inside silicon pores with a phase with the diamond structure by (111), (220) and (400) reflections. Finally current-voltage (I-V) measurement of the MSM photodetector was carried out and showed lower dark currents compared to that of Si control device. Interestingly the device showed enhanced current gain compared to Si device which can be associated with the presence of Ge nano structures in the porous silicon. (author)

  8. Metallated porphyrin based porous organic polymers as efficient electrocatalysts

    Science.gov (United States)

    Lu, Guolong; Zhu, Youlong; Xu, Kongliang; Jin, Yinghua; Ren, Zhiyong Jason; Liu, Zhenning; Zhang, Wei

    2015-10-01

    Developing efficient, stable and low-cost catalysts for Oxygen Reduction Reaction (ORR) is of great significance to many emerging technologies including fuel cells and metal-air batteries. Herein, we report the development of a cobalt(ii) porphyrin based porous organic polymer (CoPOP) and its pyrolyzed derivatives as highly active ORR catalysts. The as-synthesized CoPOP exhibits high porosity and excellent catalytic performance stability, retaining ~100% constant ORR current over 50 000 s in both alkaline and acidic media. Pyrolysis of CoPOP at various temperatures (600 °C, 800 °C, and 1000 °C) yields the materials consisting of graphitic carbon layers and cobalt nanoparticles, which show greatly enhanced catalytic activity compared to the as-synthesized CoPOP. Among them, CoPOP-800/C pyrolyzed at 800 °C shows the highest specific surface area and ORR activity, displaying the most positive half-wave potential (0.825 V vs. RHE) and the largest limited diffusion current density (5.35 mA cm-2) in an alkaline medium, which are comparable to those of commercial Pt/C (20 wt%) (half-wave potential 0.829 V vs. RHE, limited diffusion current density 5.10 mA cm-2). RDE and RRDE experiments indicate that CoPOP-800/C directly reduces molecular oxygen to water through a 4-e- pathway in both alkaline and acidic media. More importantly, CoPOP-800/C exhibits excellent durability and methanol-tolerance under acidic and alkaline conditions, which surpass the Pt/C (20 wt%) system.Developing efficient, stable and low-cost catalysts for Oxygen Reduction Reaction (ORR) is of great significance to many emerging technologies including fuel cells and metal-air batteries. Herein, we report the development of a cobalt(ii) porphyrin based porous organic polymer (CoPOP) and its pyrolyzed derivatives as highly active ORR catalysts. The as-synthesized CoPOP exhibits high porosity and excellent catalytic performance stability, retaining ~100% constant ORR current over 50 000 s in both

  9. Research on the sound absorption characteristics of porous metal materials at high sound pressure levels

    Directory of Open Access Journals (Sweden)

    Xiaopeng Wang

    2015-05-01

    Full Text Available Porous metal materials are widely used in noise control with high sound pressure applications such as aircraft engine liners and combustion chambers for rocket engines due to their excellent performance of sound absorption characteristics and distinguished advantages in heat resistance, lightness, and stiffness. Understanding the effect of sound pressure on the acoustic properties of these materials is crucial when attempting to predict silencer performance. In this article, we experimentally investigate the sound absorption characteristics of porous metal materials at high sound pressure level. The effects of material parameters on the sound absorption characteristics of porous metal materials under high sound pressure level are further explored experimentally. Measurements are carried out by using a standard impedance tube that has been modified to accommodate sound pressure level of up to 150 dB. The experimental results show that with the increase in sound pressure level, the effect of sound pressure level on the sound absorption characteristics yields different variation regularities in different frequencies. The sound absorption performance of porous metal materials increases with the increase in sound pressure level in low frequency, which is reasonably consistent with the theoretical results. Under high sound pressure level, the sound absorption characteristics are significantly dependent upon the material parameters such as the metal fiber diameter, the material porosity, and the material thickness. It could provide a reliable experimental validation for the applications of porous metal materials in the area of vibration and noise control at high sound pressure levels.

  10. Fabrication of Porous Silicon Nano structures Chemical Sensor

    International Nuclear Information System (INIS)

    Husairi, M.; Yusop, S.F.M.; Rusop, M.; Abdullah, S.; Husairi, M.; Yusop, S.F.M.; Abdullah, S.

    2011-01-01

    The result shows that when the potassium phosphate diffuses into a pore, the resistance of porous silicon nano structures (PSiN) was decreased drastically at about 81.82 %. It was also found that the resistance became stable at certain point after solution dropped. Resistance (average) of PSiN decrease with increase of chemical solution concentration dropped. (author)

  11. Modeling Kinetics of Distortion in Porous Bi-layered Structures

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Frandsen, Henrik Lund; Bjørk, Rasmus

    2013-01-01

    Shape distortions during constrained sintering experiment of bi-layer porous and dense cerium gadolinium oxide (CGO) structures have been modeled. Technologies like solid oxide fuel cells require co-firing thin layers with different green densities, which often exhibit differential shrinkage...

  12. Sintering of Multilayered Porous Structures: Part I-Constitutive Models

    DEFF Research Database (Denmark)

    Olevsky, Eugene; Tadesse Molla, Tesfaye; Frandsen, Henrik Lund

    2013-01-01

    Theoretical analyses of shrinkage and distortion kinetics during sintering of bilayered porous structures are carried out. The developed modeling framework is based on the continuum theory of sintering; it enables the direct assessment of the cofiring process outcomes and of the impact of process...

  13. Development of Pd Alloy Hydrogen Separation Membranes with Dense/Porous Hybrid Structure for High Hydrogen Perm-Selectivity

    Directory of Open Access Journals (Sweden)

    Jae-Yun Han

    2014-01-01

    Full Text Available For the commercial applications of hydrogen separation membranes, both high hydrogen selectivity and permeability (i.e., perm-selectivity are required. However, it has been difficult to fabricate thin, dense Pd alloy composite membranes on porous metal support that have a pore-free surface and an open structure at the interface between the Pd alloy films and the metal support in order to obtain the required properties simultaneously. In this study, we fabricated Pd alloy hydrogen separation membranes with dense/porous hybrid structure for high hydrogen perm-selectivity. The hydrogen selectivity of this membrane increased owing to the dense and pore-free microstructure of the membrane surface. The hydrogen permeation flux also was remarkably improved by the formation of an open microstructure with numerous open voids at the interface and by an effective reduction in the membrane thickness as a result of the porous structure formed within the Pd alloy films.

  14. Layer like porous materials with hierarchical structure

    Czech Academy of Sciences Publication Activity Database

    Roth, W. J.; Gil, B.; Makowski, W.; Marszalek, B.; Eliášová, Pavla

    2016-01-01

    Roč. 45, č. 12 (2016), s. 3400-3438 ISSN 0306-0012 R&D Projects: GA ČR GBP106/12/G015 Institutional support: RVO:61388955 Keywords : METAL-ORGANIC FRAMEWORK * SOLID ACID CATALYSTS * QUASI-EQUILIBRATED THERMODESORPTION Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 38.618, year: 2016

  15. Secondary creep of porous metal supports for solid oxide fuel cells by a CDM approach

    DEFF Research Database (Denmark)

    Esposito, L.; Boccaccini, D. N.; Pucillo, G. P.

    2017-01-01

    The creep behaviour of porous iron-chromium alloy used in solid oxide fuel cells (SOFCs) becomes relevant under SOFC operating temperatures. In this paper, the secondary creep stage of infiltrated and non-infiltrated porous metal supports (MS) was investigated and theoretically modelled by a cont......The creep behaviour of porous iron-chromium alloy used in solid oxide fuel cells (SOFCs) becomes relevant under SOFC operating temperatures. In this paper, the secondary creep stage of infiltrated and non-infiltrated porous metal supports (MS) was investigated and theoretically modelled...... as function of temperature, determined by the high temperature impulse excitation technique, was directly used to account for the porosity and the related effective stress acting during the creep tests. The proposed creep rate formulation was used to extend the Crofer® 22 APU Monkman-Grant diagram...

  16. Band structures in Sierpinski triangle fractal porous phononic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Kai; Liu, Ying, E-mail: yliu5@bjtu.edu.cn; Liang, Tianshu

    2016-10-01

    In this paper, the band structures in Sierpinski triangle fractal porous phononic crystals (FPPCs) are studied with the aim to clarify the effect of fractal hierarchy on the band structures. Firstly, one kind of FPPCs based on Sierpinski triangle routine is proposed. Then the influence of the porosity on the elastic wave dispersion in Sierpinski triangle FPPCs is investigated. The sensitivity of the band structures to the fractal hierarchy is discussed in detail. The results show that the increase of the hierarchy increases the sensitivity of ABG (Absolute band gap) central frequency to the porosity. But further increase of the fractal hierarchy weakens this sensitivity. On the same hierarchy, wider ABGs could be opened in Sierpinski equilateral triangle FPPC; whilst, a lower ABG could be opened at lower porosity in Sierpinski right-angled isosceles FPPCs. These results will provide a meaningful guidance in tuning band structures in porous phononic crystals by fractal design.

  17. Determination of the Darcy permeability of porous media including sintered metal plugs

    Science.gov (United States)

    Frederking, T. H. K.; Hepler, W. A.; Yuan, S. W. K.; Feng, W. F.

    1986-01-01

    Sintered-metal porous plugs with a normal size of the order of 1-10 microns are used to evaluate the Darcy permeability of laminar flow at very small velocities in laminar fluids. Porous media experiment results and data adduced from the literature are noted to support the Darcy law analog for normal fluid convection in the laminar regime. Low temperature results suggest the importance of collecting room temperature data prior to runs at liquid He(4) temperatures. The characteristic length diagram gives a useful picture of the tolerance range encountered with a particular class of porous media.

  18. Dimensions of luminescent oxidized and porous silicon structures

    Science.gov (United States)

    Schuppler, S.; Friedman, S. L.; Marcus, M. A.; Adler, D. L.; Xie, Y.-H.; Ross, F. M.; Harris, T. D.; Brown, W. L.; Chabal, Y. J.; Brus, L. E.; Citrin, P. H.

    1994-04-01

    X-ray absorption measurements from H-passivated porous Si and from oxidized Si nanocrystals, combined with electron microscopy, ir absorption, α recoil, and luminescence emission data, provide a consistent structural picture of the species responsible for the visible luminescence observed in these samples. The mass-weighted average structures in por-Si are particles, not wires, with dimensions significantly smaller than previously reported or proposed.

  19. A General Synthesis Strategy for Hierarchical Porous Metal Oxide Hollow Spheres

    Directory of Open Access Journals (Sweden)

    Huadong Fu

    2015-01-01

    Full Text Available The hierarchical porous TiO2 hollow spheres were successfully prepared by using the hydrothermally synthesized colloidal carbon spheres as templates and tetrabutyl titanate as inorganic precursors. The diameter and wall thickness of hollow TiO2 spheres were determined by the hard templates and concentration of tetrabutyl titanate. The particle size, dispersity, homogeneity, and surface state of the carbon spheres can be easily controlled by adjusting the hydrothermal conditions and adding certain amount of the surfactants. The prepared hollow spheres possessed the perfect spherical shape, monodispersity, and hierarchically pore structures, and the further experiment verified that the present approach can be used to prepare other metal oxide hollow spheres, which could be used as catalysis, fuel cells, lithium-air battery, gas sensor, and so on.

  20. Description of a Furnace for the Creation of Anisotropic Porous Metals

    Energy Technology Data Exchange (ETDEWEB)

    Gutsch, Thomas; Miszkiel, Mark; Schmale, David T.

    1999-05-01

    A furnace has been built for the purpose of producing anisotropic porous metals through solid-gas eutectic solidification. This process allows control of continuously formed anisotropic pores in metals and was discovered at the State Metallurgical Academic' University in Dnepropetrovsk Ukraine. The process incorporates hydrogen gas within the metal as it solidifies from the molten state. Metals which do not form hydrides, including iron, nickel, aluminum, copper and others can be formed in this manner. The furnace is housed within a ~.64 meter³ (30 ft³) ASME code stamped cylindrical stainless steel vacuum/pressure vessel. The vessel is a water chilled vertical cylinder with removable covers at the top and bottom. It can be evacuated to 20 mTorr or pressurized to 5.5 MPa (800 psi). A charge of 2700 cc (167 in³) of molten metal can be melted in a crucible in the upper portion within a watercooled 30 cm (12 in.) ID induction coil. A 175 kW Inductotherm power source energizes the coil. Vertical actuation of a ceramic stopper rod allows the molten metal to be tapped into a solidification mold beneath the melting crucible. The cylindrical mold rests on a water cooled copper base inducing directional solidification from the bottom. Mixtures of hydrogen and argon gases are introduced during the process. The system is remotely controlled and located in a structure with frangible walls specially designed for possible ambient pressure excursions as a result of equipment failure. This paper includes a general description of the furnace and operating procedure and a detailed description of the control, monitoring and interlock systems.

  1. Preparation of porous carbon particle with shell/core structure

    Directory of Open Access Journals (Sweden)

    2007-05-01

    Full Text Available Porous carbon particles with a shell/core structure have been prepared successfully by controlled precipitation of the polymer from droplets of oil-in-water emulsion, followed by curing and carbonization. The droplets of the oil phase are composed of phenolic resin (PFR, a good solvent (ethyl acetate and porogen (Poly(methyl methacrylate, PMMA. The microstructure was characterized in detail by scanning electron microscopy (SEM, transmission electron microscopy (TEM, nitrogen adsorption, and thermo gravimetric analysis (TGA. The obtained carbon particles have a capsular structure with a microporous carbon shell and a mesoporous carbon core. The BET surface area and porous volume are calculated to be 499 m2g-1 and 0.56 cm3g-1, respectively. The effects of the amount of porogen (PMMA, co-solvent (acetone and surfactant on the resultant structure were studied in detail.

  2. Hypercrosslinked porous polyporphyrin by metal-free protocol: characterization, uptake performance, and heterogeneous catalysis.

    Science.gov (United States)

    Feng, Li-Juan; Wang, Min; Sun, Zhi-Yong; Hu, Yun; Deng, Zhen-Tao

    2017-01-01

    Through metal-free protocol, hypercrosslinked porous polyporphyrin with permanent porosity was obatined via the Friedel-Crafts alkylation of tetracarbazolylporphyrin using formaldehyde dimethyl acetal as an external cross-linker. Its chemical structure and porosity was well characterized and confirmed. The BET specific surface area value of HCP-TCPP is 1050 m 2  g -1 and related dominant pore size is centered at 0.63 nm. The adsorption amount of methanol by HCP-TCPP is high up to 800 mg g -1 (about 25.0 mmol g -1 ) at its saturated vapor pressure, which is higher than that of toluene (600 mg g -1 , 6.5 mmol g -1 ). Further study indicates that polymer HCP-TCPP , possessing the high BET specific surface area and total pore volume, exhibits good hydrogen uptake of 3.44 wt % (77 K) and high carbon dioxide uptake of 41.1 wt % (298 K) at 18.0 bar. Besides, the obtained porous polymer can also be used as an effective heterogeneous catalyst for the Knoevenagel condensation between various aldehydes and malononitrile.

  3. Zeolitic materials with hierarchical porous structures.

    Science.gov (United States)

    Lopez-Orozco, Sofia; Inayat, Amer; Schwab, Andreas; Selvam, Thangaraj; Schwieger, Wilhelm

    2011-06-17

    During the past several years, different kinds of hierarchical structured zeolitic materials have been synthesized due to their highly attractive properties, such as superior mass/heat transfer characteristics, lower restriction of the diffusion of reactants in the mesopores, and low pressure drop. Our contribution provides general information regarding types and preparation methods of hierarchical zeolitic materials and their relative advantages and disadvantages. Thereafter, recent advances in the preparation and characterization of hierarchical zeolitic structures within the crystallites by post-synthetic treatment methods, such as dealumination or desilication; and structured devices by in situ and ex situ zeolite coatings on open-cellular ceramic foams as (non-reactive as well as reactive) supports are highlighted. Specific advantages of using hierarchical zeolitic catalysts/structures in selected catalytic reactions, such as benzene to phenol (BTOP) and methanol to olefins (MTO) are presented. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. The structure of expanding metals

    International Nuclear Information System (INIS)

    Winter, R.; Hensel, F.; Bodensteiner, T.; Glaeser, W.

    1985-01-01

    The liquid metal structure is investigated by neutron diffraction up to 2000 K and 200 bar by determining the structure factor SCQJ for liquid cesium and rubidium. The rather complicated experimental equipment is described. (BHO)

  5. Additively manufactured metallic porous biomaterials based on minimal surfaces

    DEFF Research Database (Denmark)

    Bobbert, F. S. L.; Lietaert, K.; Eftekhari, Ali Akbar

    2017-01-01

    types of triply periodic minimal surfaces (TPMS) that mimic the properties of bone to an unprecedented level of multi-physics detail. Sixteen different types of porous biomaterials were rationally designed and fabricated using selective laser melting (SLM) from a titanium alloy (Ti-6Al-4V). The topology...

  6. Quantifying the topology of porous structures

    Energy Technology Data Exchange (ETDEWEB)

    Kinney, J. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    Computerized x-ray tomography, with microscopic resolution, has been used to volumetrically visualize the evolution of porosity in a ceramic matrix composite during processing. The topological variables describing the porosity have been measured. The evolution of the porosity exhibits critical scaling behavior near final consolidation, and appears to be independent of the structure (universality).

  7. Pore structure and mechanical properties of directionally solidified porous aluminum alloys

    Directory of Open Access Journals (Sweden)

    Komissarchuk Olga

    2014-01-01

    Full Text Available Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional solidification. Hydrogen is driven out of the melt, and then the quasi-cylindrical pores normal to the solidification front are usually formed. In the research, the effects of processing parameters (saturation pressure, solidification pressure, temperature, and holding time on the pore structure and porosity of porous aluminum alloys were analyzed. The mechanical properties of Al-Mg alloys were studied by the compressive tests, and the advantages of the porous structure were indicated. By using the GASAR method, pure aluminum, Al-3wt.%Mg, Al-6wt.%Mg and Al-35wt.%Mg alloys with oriented pores have been successfully produced under processing conditions of varying gas pressure, and the relationship between the final pore structure and the solidification pressure, as well as the influences of Mg quantity on the pore size, porosity and mechanical properties of Al-Mg alloy were investigated. The results show that a higher pressure of solidification tends to yield smaller pores in aluminum and its alloys. In the case of Al-Mg alloys, it was proved that with the increasing of Mg amount, the mechanical properties of the alloys sharply deteriorate. However, since Al-3%Mg and Al-6wt.%Mg alloys are ductile metals, their porous samples have greater compressive strength than that of the dense samples due to the existence of pores. It gives the opportunity to use them in industry at the same conditions as dense alloys with savings in weight and material consumption.

  8. Synthesis of dual porous structured germanium anodes with exceptional lithium-ion storage performance

    Science.gov (United States)

    Kwon, Dohyoung; Ryu, Jaegeon; Shin, Myungsoo; Song, Gyujin; Hong, Dongki; Kim, Kwang S.; Park, Soojin

    2018-01-01

    Dual-porous Ge nanostructures are synthesized via two straightforward steps. Compared with conventional approaches related to porous Ge materials, different types of pores can be readily generated by adjusting the relative ratio of the precursor amounts for GeO2 and SiO2. Unlike using hard templates with different sizes for introducing secondary pores, this system makes a uniformly blended structure of porogen and active sites in the nanoscale range. When GeO2 is subjected to zincothermic reduction, it is selectively converted to pure Ge still connected to unreacted SiO2. During the reduction process, primary pores (larger than 50 nm) are formed by eliminating zinc oxide by-products, while inactive SiO2 with respect to zinc metal could contribute to retaining the overall structure. Finally, the HF treatment completely leaches remaining SiO2 and formed secondary pores (micro/mesopores) to complete the dual-porous Ge structure. The resulting Ge structure is tested as an anode material for lithium-ion batteries. The Ge electrode exhibits an outstanding reversibility and an exceptional cycling stability corresponding to a capacity retention of 100% after 100 cycles at C/5 and of 94.4% after 300 cycles at C/2. Furthermore, multi-scale pores facilitate a facile Li-ion accessibility, resulting in an excellent rate capability delivering ∼740 mAh g-1 at 5C.

  9. Uniform Microparticles with Controllable Highly Interconnected Hierarchical Porous Structures.

    Science.gov (United States)

    Zhang, Mao-Jie; Wang, Wei; Yang, Xiu-Lan; Ma, Bing; Liu, Ying-Mei; Xie, Rui; Ju, Xiao-Jie; Liu, Zhuang; Chu, Liang-Yin

    2015-07-01

    A simple and versatile strategy is developed for one-step fabrication of uniform polymeric microparticles with controllable highly interconnected hierarchical porous structures. Monodisperse water-in-oil-in-water (W/O/W) emulsions, with methyl methacrylate, ethylene glycol dimethacrylate, and glycidyl methacrylate as the monomer-containing oil phase, are generated from microfluidics and used for constructing the microparticles. Due to the partially miscible property of oil/aqueous phases, the monodisperse W/O/W emulsions can deform into desired shapes depending on the packing structure of inner aqueous microdrops, and form aqueous nanodrops in the oil phase. The deformed W/O/W emulsions allow template syntheses of highly interconnected hierarchical porous microparticles with precisely and individually controlled pore size, porosity, functionality, and particle shape. The microparticles elaborately combine the advantages of enhanced mass transfer, large functional surface area, and flexibly tunable functionalities, providing an efficient strategy to physically and chemically achieve enhanced synergetic performances for extensive applications. This is demonstrated by using the microparticles for oil removal for water purification and protein adsorption for bioseparation. The method proposed in this study provides full versatility for fabrication of functional polymeric microparticles with controllable hierarchical porous structures for enhancing and even broadening their applications.

  10. Unexpected variability of millennium green: structural color of Japanese jewel beetle resulted from thermosensitive porous organic multilayer.

    Science.gov (United States)

    Adachi, Eiki

    2007-09-01

    The Japanese jewel beetle (Chrysochroa fulgidissima) is one of the beautiful beetles showing metallic green color that is kept over a millennium. This is a typical structural color resulting from a multilayer, frequently seen in insects. It was found that the elytra unexpectedly change the color from original green to blue or red by heating at 200 degrees C or by immersing in bromoform for over 1 month. This variability implies that the multilayer consists of a thermosensitive porous material. The color change induced by heating was accompanied with elytron shrinkage; the sensitivity of the reflection peak was -0.6 nm/ degrees C in 30-65 degrees C. The porous structure was determined by positron annihilation lifetime spectroscopy; the averaged pore radius was around 0.25-0.30 nm, which is close to the size of the bromoform molecule. These features prove the thermosensitivity and porous structure of the multilayer although in unusual environments. (c) 2007 Wiley-Liss, Inc.

  11. Electroarchitected porous platinum on metallic multijunction nanolayers to optimize their optical properties for infrared sensor application.

    Science.gov (United States)

    Stanca, Sarmiza Elena; Haenschke, Frank; Zieger, Gabriel; Dellith, Jan; Dellith, Andrea; Ihring, Andreas; Belkner, Johannes; Meyer, Hans-Georg

    2018-01-09

    Tailoring the physicochemical properties of the metallic multijunction nanolayers is a prerequisite for the development of microelectronics. From this perspective, a desired lower reflectance of infrared radiation was achieved by an electrochemical deposition of porous platinum in nonaqueous media on silver mirror supported nickel-chrom and nickel-titanium metallic films with incremental decreasing thicknesses from 80 nm to 10 nm. The electroassembled architectures were examined by means of SEM and FTIR and it was observed that the layer and sublayer thicknesses and resistivities have a substantial effect upon the porous platinum morphology and its optical properties. It is here reported that the augmentation of the metallic layer electrical conductivity determines the electroformation of more compact platinum nanolayers. Moreover, the platinum black coating of metallic nanolayers causes a considerable decrease of the reflectance in the region from 1000 cm-1 to 8000 cm-1. © 2018 IOP Publishing Ltd.

  12. Porous materials with gradient and biporous structure, methods of their production

    International Nuclear Information System (INIS)

    Ilyuschenko, A.; Savich, V.; Pilinevich, L.; Rak, A.

    2001-01-01

    We have worked out the technology of production porous powder materials (PPMs) of bronze, nickel, corrosion resistant steel and titanium powders with gradient and (or) biporous structure: vibrating forming of metal powders (including in electromagnetic field); layer-by-layer forming of metal powders with pore-maker while different proportion of the latter in the layer; forming of powder polymer layer on the preliminary sintered metal PPM surface. We have worked out the technology of production biporous structure by the following methods: metal granules forming and sintering; forming and sintering of metal powder with granules (2-3 mm) and pores-forming powder (size of particles is 0,4-0,63 mm). The novelty is in creation of technological bases of pores sizes regulation from 5 mkm on one PPM surface to 120 mkm on the opposite PPM surface which thickness can be 2-6 mm. PPM porosity can be constant within 0,3-0,6 relative units. More effective are those PPM which pores sizes are changeable and also porosity (from 0,35 to 0,60) from one surface o the opposite one. Two-layer metal-polymer PPM have pores sizes of 20-40 mkm in polymer layer and porosity 0,4-0,5 and, correspondingly, in metal layer 80-100 mkm and 0,45-0,55. In biporous structures made of 2-3 mm metal granules the distance between granules is 300-600 mkm and in granules - 14-30 mkm. The integral porosity of such PPM is 0,55-0,70. The technology of forming and sintering metal powder with granules and pores-making powder (carbamide) enables to regulate the integral porosity within 0,7-0,8 and average pores sizes within 100-1000 mkm with average size of metal powder particles of 0,63-1,0 mm. (author)

  13. Metal working and dislocation structures

    DEFF Research Database (Denmark)

    Hansen, Niels

    2007-01-01

    Microstructural observations are presented for different metals deformed from low to high strain by both traditional and new metal working processes. It is shown that deformation induced dislocation structures can be interpreted and analyzed within a common framework of grain subdivision on a finer...... and finer scale down to the nanometer dimension, which can be reached at ultrahigh strains. It is demonstrated that classical materials science and engineering principles apply from the largest to the smallest structural scale but also that new and unexpected structures and properties characterize metals...

  14. Depolymerization of organosolv lignin using doped porous metal oxides in supercritical methanol

    NARCIS (Netherlands)

    Warner, Genoa; Hansen, Thomas S; Riisager, Anders; Beach, Evan S; Barta, Katalin; Anastas, Paul T

    An isolated, solvent-extracted lignin from candlenut (Aleurites moluccana) biomass was subjected to catalytic depolymerization in the presence of supercritical methanol, using a range of porous metal oxides derived from hydrotalcite-like precursors. The most effective catalysts in terms of lignin

  15. Expanded Organic Building Units for the Construction of Highly Porous Metal-Organic Frameworks

    NARCIS (Netherlands)

    Kong, G.Q.; Han, Z.D.; He, Y.; Qu, S.; Zhou, W.; Yildirim, T.; Krishna, R.; Zou, C.; Chen, B.; Wu, C.D.

    2013-01-01

    wo new organic building units that contain dicarboxylate sites for their self-assembly with paddlewheel [Cu2(CO2)4] units have been successfully developed to construct two isoreticular porous metal-organic frameworks (MOFs), ZJU-35 and ZJU-36, which have the same tbo topologies (Reticular Chemistry

  16. Highly porous Co(II)-salicylate metal-organic framework: synthesis, characterization and magnetic properties.

    Science.gov (United States)

    Das, Swapan K; Bhunia, Manas K; Motin Seikh, Md; Dutta, Saurav; Bhaumik, Asim

    2011-03-28

    A new porous Co(II)-salicylate metal-organic framework material has been synthesized hydrothermally through the reaction of Co(II) chloride with sodium salicylate under mild alkaline pH conditions. To get an idea about the structural aspect of the material from the powder X-ray diffraction (PXRD) pattern, MAUD program has been successfully utilized and the assigned peaks match very well with a new tetragonal phase (space group, P4mm) having the unit cell parameters: a = b = 12.957 (0.042) Å; c = 12.738 (0.019) Å; α = β = γ = 90°, V = 2138.73 Å(3). N(2) adsorption/desorption analyses suggested the material is highly porous in nature having high BET surface area and pore dimensions of 2.0-3.0 nm, which is within the range of small mesopores. Thermogravimetric analysis (TGA) revealed that the H(2)O molecules may be removed from the framework without collapsing the structure and the material is stable up to ca. 573 K. The material is characterized thoroughly by using different characterization tools such as TEM, SEM, UV-visible reflectance spectroscopy, FT IR spectroscopy and photoluminescence spectroscopy. X-Ray photoelectron spectroscopic (XPS) analysis was employed to understand the oxidation state of the cobalt atom and presence of other elements within the framework. The material shows interesting magnetic properties, where the magnetic moments monotonically increase with the decrease in temperature down to 9 K. Below 9 K there is a steep increase in magnetization on further lowering the temperature, thereby suggesting the onset of a long range ferromagnetic transition with ferromagnetic Curie temperature, T(C) = 8.5 K. Furthermore, the M-H curve at 2 K shows a clear hysteresis loop with a coercive field 150 Oe and remnant magnetization 0.8 μ(B)/f.u.

  17. Control of Partial Coalescence of Self-Assembled Metal Nano-Particles across Lyotropic Liquid Crystals Templates towards Long Range Meso-Porous Metal Frameworks Design

    Directory of Open Access Journals (Sweden)

    Ludovic F. Dumée

    2015-10-01

    Full Text Available The formation of purely metallic meso-porous metal thin films by partial interface coalescence of self-assembled metal nano-particles across aqueous solutions of Pluronics triblock lyotropic liquid crystals is demonstrated for the first time. Small angle X-ray scattering was used to study the influence of the thin film composition and processing conditions on the ordered structures. The structural characteristics of the meso-structures formed demonstrated to primarily rely on the lyotropic liquid crystal properties while the nature of the metal nano-particles used as well as the their diameters were found to affect the ordered structure formation. The impact of the annealing temperature on the nano-particle coalescence and efficiency at removing the templating lyotropic liquid crystals was also analysed. It is demonstrated that the lyotropic liquid crystal is rendered slightly less thermally stable, upon mixing with metal nano-particles and that low annealing temperatures are sufficient to form purely metallic frameworks with average pore size distributions smaller than 500 nm and porosity around 45% with potential application in sensing, catalysis, nanoscale heat exchange, and molecular separation.

  18. Control of Partial Coalescence of Self-Assembled Metal Nano-Particles across Lyotropic Liquid Crystals Templates towards Long Range Meso-Porous Metal Frameworks Design.

    Science.gov (United States)

    Dumée, Ludovic F; Lemoine, Jean-Baptiste; Ancel, Alice; Hameed, Nishar; He, Li; Kong, Lingxue

    2015-10-26

    The formation of purely metallic meso-porous metal thin films by partial interface coalescence of self-assembled metal nano-particles across aqueous solutions of Pluronics triblock lyotropic liquid crystals is demonstrated for the first time. Small angle X-ray scattering was used to study the influence of the thin film composition and processing conditions on the ordered structures. The structural characteristics of the meso-structures formed demonstrated to primarily rely on the lyotropic liquid crystal properties while the nature of the metal nano-particles used as well as the their diameters were found to affect the ordered structure formation. The impact of the annealing temperature on the nano-particle coalescence and efficiency at removing the templating lyotropic liquid crystals was also analysed. It is demonstrated that the lyotropic liquid crystal is rendered slightly less thermally stable, upon mixing with metal nano-particles and that low annealing temperatures are sufficient to form purely metallic frameworks with average pore size distributions smaller than 500 nm and porosity around 45% with potential application in sensing, catalysis, nanoscale heat exchange, and molecular separation.

  19. Sound transmission through an acoustic porous metasurface with periodic structures

    Science.gov (United States)

    Fang, Yi; Zhang, Xin; Zhou, Jie

    2017-04-01

    We report an analytical, numerical, and experimental study of sound transmission through a metasurface fabricated by porous materials, detailing systematically the factors that influence acoustic properties. The design of the metasurface is composed of four elements with varying properties, which are aligned in a periodic manner. The structures are carefully designed to form a uniform phase shift profile in one period. It is able to refract an incidence wave in an anomalous yet controllable way. A good agreement of refraction behavior between simulated and experimental results is achieved by the study. Furthermore, we systemically summarize the relationships between the refraction and the incidence angles for structures with various ratios of wavelengths and period lengths. Remarkably, the study proves that the propagation directions and the number of refracted waves are only affected by period lengths at a specified frequency. The phase shift profile only has an influence on energy distribution in the refraction region. The study suggests that a careful design of phase shift profile plays an important role in controlling sound energy distribution of the periodic structure, which is vital for applying this kind of porous metasurface in sound absorption and isolation in the future.

  20. Diatoms - nature's own nano-porous silica structures

    International Nuclear Information System (INIS)

    Butcher, K.S.A.; Phillips, M.R.

    2003-01-01

    Full text: We have investigated the luminescent output from the porous silica shells of the small aquatic plants called diatoms. Two closely spaced emission peaks, one orange peak at 620-640 nm (2.0 - 1.95 eV) and the other a yellow peak at 580 nm (2.15 eV), were observed by cathodoluminescence. Although the 2.0 - 1.95 eV peak has been commonly observed for silica based structures and may be associated with non-bridging oxygen hole centres, or a closely related variant, the 2.15 eV emission is not readily explained by this phenomenology and may be related to the diatom's porous nanostructure. Photoluminescence measurements, using the 325 nm line of a He-Cd laser as the excitation source, resulted in a strong blue emission with neither the orange nor yellow emissions, seen with cathodoluminescence, being present. The silica structures made available by the particular diatoms studied here were therefore shown to have very rich luminescent output characteristics. Coupled with the diversity of diatomic structure and porosity available for further study, this suggests that diatoms may have some potential for photonic applications

  1. Additively manufactured metallic porous biomaterials based on minimal surfaces : A unique combination of topological, mechanical, and mass transport properties

    NARCIS (Netherlands)

    Bobbert, F S L; Lietaert, K; Eftekhari, A A; Pouran, B; Ahmadi, S M; Weinans, H; Zadpoor, A A

    2017-01-01

    Porous biomaterials that simultaneously mimic the topological, mechanical, and mass transport properties of bone are in great demand but are rarely found in the literature. In this study, we rationally designed and additively manufactured (AM) porous metallic biomaterials based on four different

  2. 21 CFR 888.3535 - Knee joint femorotibial (uni-compartmental) metal/polymer porous-coated uncemented prosthesis.

    Science.gov (United States)

    2010-04-01

    .../polymer porous-coated uncemented prosthesis. 888.3535 Section 888.3535 Food and Drugs FOOD AND DRUG... prosthesis. (a) Identification. A knee joint femorotibial (uni-compartmental) metal/polymer porous-coated uncemented prosthesis is a device intended to be implanted to replace part of a knee joint. The device limits...

  3. Porous Poly(Ionic Liquid) Membranes as Efficient and Recyclable Absorbents for Heavy Metal Ions.

    Science.gov (United States)

    Ren, Yongyuan; Zhang, Jiandong; Guo, Jiangna; Chen, Fei; Yan, Feng

    2017-07-01

    Heavy metal ion pollution has become a serious environmental problem. Herein, this study reports the synthesis of poly(ionic liquid) (PIL) membranes via in situ photo-crosslinking of vinyl imidazole with both hydrophilic and hydrophobic ionic liquid monomers. The resultant amphiphilic polymer membranes are porous and exhibit high absorption capacity of metal ions (including Hg 2+ , Pb 2+ , Cu 2+ , Cd 2+ , and Zn 2+ ) in both high (1000 mg L -1 ) and low (10 mg L -1 ) concentration metal ion solutions. These metal ionic absorption membranes are easily regenerated in acid solution and can be reused without significant decreases of absorption capacity after many cycles. These PIL membranes may have potential applications as eco-friendly and safe heavy metal ion removal materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. An Efficient, Versatile, and Safe Access to Supported Metallic Nanoparticles on Porous Silicon with Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Walid Darwich

    2016-06-01

    Full Text Available The metallization of porous silicon (PSi is generally realized through physical vapor deposition (PVD or electrochemical processes using aqueous solutions. The former uses a strong vacuum and does not allow for a conformal deposition into the pores. In the latter, the water used as solvent causes oxidation of the silicon during the reduction of the salt precursors. Moreover, as PSi is hydrophobic, the metal penetration into the pores is restricted to the near-surface region. Using a solution of organometallic (OM precursors in ionic liquid (IL, we have developed an easy and efficient way to fully metallize the pores throughout the several-µm-thick porous Si. This process affords supported metallic nanoparticles characterized by a narrow size distribution. This process is demonstrated for different metals (Pt, Pd, Cu, and Ru and can probably be extended to other metals. Moreover, as no reducing agent is necessary (the decomposition in an argon atmosphere at 50 °C is fostered by surface silicon hydride groups borne by PSi, the safety and the cost of the process are improved.

  5. An Efficient, Versatile, and Safe Access to Supported Metallic Nanoparticles on Porous Silicon with Ionic Liquids.

    Science.gov (United States)

    Darwich, Walid; Haumesser, Paul-Henri; Santini, Catherine C; Gaillard, Frédéric

    2016-06-03

    The metallization of porous silicon (PSi) is generally realized through physical vapor deposition (PVD) or electrochemical processes using aqueous solutions. The former uses a strong vacuum and does not allow for a conformal deposition into the pores. In the latter, the water used as solvent causes oxidation of the silicon during the reduction of the salt precursors. Moreover, as PSi is hydrophobic, the metal penetration into the pores is restricted to the near-surface region. Using a solution of organometallic (OM) precursors in ionic liquid (IL), we have developed an easy and efficient way to fully metallize the pores throughout the several-µm-thick porous Si. This process affords supported metallic nanoparticles characterized by a narrow size distribution. This process is demonstrated for different metals (Pt, Pd, Cu, and Ru) and can probably be extended to other metals. Moreover, as no reducing agent is necessary (the decomposition in an argon atmosphere at 50 °C is fostered by surface silicon hydride groups borne by PSi), the safety and the cost of the process are improved.

  6. Research on the sound absorption characteristics of porous metal materials at high sound pressure levels

    OpenAIRE

    Xiaopeng Wang; Yinggang Li; Tianning Chen; Zhiping Ying

    2015-01-01

    Porous metal materials are widely used in noise control with high sound pressure applications such as aircraft engine liners and combustion chambers for rocket engines due to their excellent performance of sound absorption characteristics and distinguished advantages in heat resistance, lightness, and stiffness. Understanding the effect of sound pressure on the acoustic properties of these materials is crucial when attempting to predict silencer performance. In this article, we experimentally...

  7. On the capillary restriction in start-up regimes of liquid metal evaporation from capillary-porous surfaces

    International Nuclear Information System (INIS)

    Prosvetov, V.V.

    1979-01-01

    Evaporation of liquid metals from capillary-porous structures is one of the most effective methods of surface cooling, to which essential heat quantity is delivered at high temperatures. The paper deals with heat flux limitation, caused by incapability of core capillary forces to overcome pressure differential in heat carrier circulation shape in such evaporation regimes, when average length of free path of vapour molecule exceeds core cell size. Suggested are theoretical correlations for determination of critical heat flux density and temperature of liquid surface in starting regimes of liquid metal evaporation from rectangular slots and compound cores with screens made of foil with round perforations. The catculative and experimental values of critical heat flux density in starting regimes of sodium evaporation from rectangular slots satisfactorily agree with each other

  8. The plasma device for the high-heat plasma testing of refractory metals and inventing of new highly porous materials

    Science.gov (United States)

    Budaev, V. P.; Fedorovich, S. D.; Martynenko, Yu V.; Lukashevsky, M. V.; Gubkin, M. K.; Lazukin, A. V.; Karpov, A. V.; Shestakov, E. A.

    2017-11-01

    A unique plasma device has been constructed at the NRU “MPEI” for the study of plasma-surface interaction and the high-heat plasma testing of refractory metals, such as tungsten, molybdenum, steel and other plasma facing materials used in fusion reactor including the ITER. This plasma device is a multi-cusp linear stationary plasma confinement system. It has power-saving characteristics as well as compactness due to the employment of the 8-pole multicusp magnetic field configuration instead of a strong axial magnetic field. Experiments are planned to develop a novel technology for highly porous surface structure of the refractory metal with a pore size and nanofibers of 50 nanometers including tungsten “fuzz”.

  9. Does Increased Coefficient of Friction of Highly Porous Metal Increase Initial Stability at the Acetabular Interface?

    Science.gov (United States)

    Goldman, Ashton H; Armstrong, Lucas C; Owen, John R; Wayne, Jennifer S; Jiranek, William A

    2016-03-01

    Highly porous metal acetabular components illustrate a decreased rate of aseptic loosening in short-term follow-up compared with previous registry data. This study compared the effect of component surface roughness at the bone-implant interface and the quality of the bone on initial pressfit stability. The null hypothesis is that a standard porous coated acetabular cup would show no difference in initial stability as compared with a highly porous acetabular cup when subjected to a bending moment. Second, would bone mineral density (BMD) be a significant variable under these test conditions. In a cadaveric model, acetabular cup micromotion was measured during a 1-time cantilever bending moment applied to 2 generations of pressfit acetabular components. BMD data were also obtained from the femoral necks available for associated specimen. The mean bending moment at 150 μm was not found to be significantly different for Gription (24.6 ± 14.0 N m) cups vs Porocoat (25 ± 10.2 N m; P > .84). The peak bending moment tolerated by Gription cups (33.9 ± 20.3 N m) was not found to be significantly different from Porocoat (33.5 ± 12.2 N m; P > .92). No correlation between BMD and bending moment at 150 μm of displacement could be identified. The coefficient of friction provided by highly porous metal acetabular shells used in this study did not provide better resistance to migration under bending load when compared with a standard porous coated component. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Applications of porous electrodes to metal-ion removal and the design of battery systems

    International Nuclear Information System (INIS)

    Trost, G.G.

    1983-09-01

    This dissertation treats the use of porous electrodes as electrochemical reactors for the removal of dilute metal ions. A methodology for the scale-up of porous electrodes used in battery applications is given. Removal of 4 μg Pb/cc in 1 M sulfuric acid was investigated in atmospheric and high-pressure, flow-through porous reactors. The atmospheric reactor used a reticulated vitreous carbon porous bed coated in situ with a mercury film. Best results show 98% removal of lead from the feed stream. Results are summarized in a dimensionless plot of Sherwood number vs Peclet number. High-pressure, porous-electrode experiments were performed to investigate the effect of pressure on the current efficiency. Pressures were varied up to 120 bar on electrode beds of copper or lead-coated spheres. The copper spheres showed high hydrogen evolution rates which inhibited lead deposition, even at high cathodic overpotentials. Use of lead spheres inhibited hydrogen evolution but often resulted in the formation of lead sulfate layers; these layers were difficult to reduce back to lead. Experimental data of one-dimensional porous battery electrodes are combined with a model for the current collector and cell connectors to predict ultimate specific energy and maximum specific power for complete battery systems. Discharge behavior of the plate as a whole is first presented as a function of depth of discharge. These results are combined with the voltage and weight penalties of the interconnecting bus and post, positive and negative active material, cell container, etc. to give specific results for the lithium-aluminum/iron sulfide high-temperature battery. Subject to variation is the number of positive electrodes, grid conductivity, minimum current-collector weight, and total delivered capacity. The battery can be optimized for maximum energy or power, or a compromise design may be selected

  11. Depolymerization of organosolv lignin using doped porous metal oxides in supercritical methanol

    DEFF Research Database (Denmark)

    Warner, Genoa; Hansen, Thomas Søndergaard; Riisager, Anders

    2014-01-01

    An isolated, solvent-extracted lignin from candlenut (Aleurites moluccana) biomass was subjected to catalytic depolymerization in the presence of supercritical methanol, using a range of porous metal oxides derived from hydrotalcite-like precursors. The most effective catalysts in terms of lignin...... conversion to methanol-soluble products, without char formation, were based on copper in combination with other dopants based on relatively earth-abundant metals. Nearly complete conversion of lignin to bio-oil composed of monomers and low-mass oligomers with high aromatic content was obtained in 6. h at 310...

  12. Properties of open-cell porous metals and alloys for orthopaedic applications.

    Science.gov (United States)

    Lewis, Gladius

    2013-10-01

    One shortcoming of metals and alloys used to fabricate various components of orthopaedic systems, such as the femoral stem of a total hip joint replacement and the tibial plate of a total knee joint replacement, is well-recognized. This is that the material modulus of elasticity (E') is substantially larger than that of the contiguous cancellous bone, a consequence of which is stress shielding which, in turn, has been postulated to be implicated in a cascade of events that culminates in the principal life-limiting phenomenon of these systems, namely, aseptic loosening. Thus, over the years, a host of research programs have focused on the synthesis of metallic biomaterials whose E' can be tailored to match that of cancellous bone. The present work is a review of the extant large volume of literature on these materials, which are called open-cell porous metals/alloys (or, sometimes, metal foams or cellular materials). As such, its range is wide, covering myriad aspects such as production methods, characterization studies, in vitro evaluations, and in vivo performance. The review also includes discussion of seven areas for future research, such as parametric studies of the influence of an assortment of process variables (such as the space holder material and the laser power in the space holder method and the laser-engineered net-shaping process, respectively) on various properties (notably, permeability, fatigue strength, and corrosion resistance) of a given porous metal/alloy, innovative methods of determining fatigue strength, and modeling of corrosion behavior.

  13. Computational modelling of the Li effects on the electronic structure of porous silicon

    Science.gov (United States)

    Gomez-Herrera, María Lucero; Miranda Durán, Álvaro; Trejo Baños, Alejandro; Cruz Irisson, Miguel

    This work analyses the effects of Li impurities on the electronic structure of pSi by means of the density functional theory with the generalized gradient approximation and the supercell scheme. The porous structures were modeled by removing atoms in the [001] direction of an otherwise perfect Si crystal. All surface dangling bonds were saturated with H atoms. To model the Li impurities some H atoms are replaced with Li atoms at the surface. Results show additional bands around the Fermi level with the insertion of a single Li atom on the pore surface, which suggests a trap-like state of localized charge. With increasing concentration of surface Li the band gap gradually decreases approaching to a metallic behavior. This results could be important to the application of pSi in Li-ion batteries This work was partially supported by CONACYT infrastructure project 252749.

  14. Investigation of Alternative Approaches for Cleaning Mott Porous Metal Filters

    International Nuclear Information System (INIS)

    Poirier, M.R.

    2003-01-01

    The Department of Energy selected Caustic Side Solvent Extraction (CSSX) as the preferred cesium removal technology for Savannah River Site (SRS) waste. As a pretreatment step for the CSSX flowsheet, the incoming salt solution that contains entrained sludge is contacted with monosodium titanate (MST) to adsorb strontium and select actinides. The resulting slurry is filtered to remove the sludge and MST. Filter fouling occurs during this process. At times, personnel can increase the filtrate rate by backpulsing or scouring. At other times, the filtrate rate drops significantly and only chemical cleaning will restore filter performance. The current baseline technology for filter cleaning uses 0.5 M oxalic acid. The Salt Processing Project (SPP) at SRS, through the Tanks Focus Area, requested an evaluation of other cleaning agents to determine their effectiveness at removing trapped sludge and MST solids compared with the baseline oxalic acid method. A review of the technical literature identified compounds that appear effective at dissolving solid compounds. Consultation with the SPP management team, engineering personnel, and researchers led to a selection of oxalic acid, nitric acid, citric acid, and ascorbic acid for testing. Tests used simulated waste and actual waste as follows. Personnel placed simulated or actual SRS High Level Waste sludge and MST in a beaker. They added the selected cleaning agents, stirred the beakers, and collected supernate samples periodically analyzing for dissolved metals

  15. Biological strategies for improved osseointegration and osteoinduction of porous metal orthopedic implants.

    Science.gov (United States)

    Lewallen, Eric Alexander; Riester, Scott M; Bonin, Carolina A; Kremers, Hilal Maradit; Dudakovic, Amel; Kakar, Sanjeev; Cohen, Robert C; Westendorf, Jennifer J; Lewallen, David G; van Wijnen, Andre J

    2015-04-01

    The biological interface between an orthopedic implant and the surrounding host tissue may have a dramatic effect upon clinical outcome. Desired effects include bony ingrowth (osseointegration), stimulation of osteogenesis (osteoinduction), increased vascularization, and improved mechanical stability. Implant loosening, fibrous encapsulation, corrosion, infection, and inflammation, as well as physical mismatch may have deleterious clinical effects. This is particularly true of implants used in the reconstruction of load-bearing synovial joints such as the knee, hip, and the shoulder. The surfaces of orthopedic implants have evolved from solid-smooth to roughened-coarse and most recently, to porous in an effort to create a three-dimensional architecture for bone apposition and osseointegration. Total joint surgeries are increasingly performed in younger individuals with a longer life expectancy, and therefore, the postimplantation lifespan of devices must increase commensurately. This review discusses advancements in biomaterials science and cell-based therapies that may further improve orthopedic success rates. We focus on material and biological properties of orthopedic implants fabricated from porous metal and highlight some relevant developments in stem-cell research. We posit that the ideal primary and revision orthopedic load-bearing metal implants are highly porous and may be chemically modified to induce stem cell growth and osteogenic differentiation, while minimizing inflammation and infection. We conclude that integration of new biological, chemical, and mechanical methods is likely to yield more effective strategies to control and modify the implant-bone interface and thereby improve long-term clinical outcomes.

  16. Optical and structural properties of porous zinc oxide fabricated via electrochemical etching method

    International Nuclear Information System (INIS)

    Ching, C.G.; Lee, S.C.; Ooi, P.K.; Ng, S.S.; Hassan, Z.; Hassan, H. Abu; Abdullah, M.J.

    2013-01-01

    Highlights: • Hillock like porous structure zinc oxide was obtained via electrochemical etching. • Anisotropic dominance etching process by KOH etchant. • Reststrahlen features are sensitive to multilayer porous structure. • Determination of porosity from IR reflectance spectrum. -- Abstract: We investigated the optical and structural properties of porous zinc oxide (ZnO) thin film fabricated by ultraviolet light-assisted electrochemical etching. This fabrication process used 10 wt% potassium hydroxide solution as an electrolyte. Hillock-like porous ZnO films were successfully fabricated according to the field emission scanning electron microscopy results. The cross-sectional study of the sample indicated that anisotropic-dominated etching process occurred. However, the atomic force microscopic results showed an increase in surface roughness of the sample after electrochemical etching. A resonance hump induced by the porous structure was observed in the infrared reflectance spectrum. Using theoretical modeling technique, ZnO porosification was verified, and the porosity of the sample was determined

  17. Analysis of fluid flow and heat transfer in a double pipe heat exchanger with porous structures

    International Nuclear Information System (INIS)

    Targui, N.; Kahalerras, H.

    2008-01-01

    A numerical study of flow and heat transfer characteristics is made in a double pipe heat exchanger with porous structures inserted in the annular gap in two configurations: on the inner cylinder (A) and on both the cylinders in a staggered fashion (B). The flow field in the porous regions is modelled by the Darcy-Brinkman-Forchheimer model and the finite volume method is used to solve the governing equations. The effects of several parameters such as Darcy number, porous structures thickness and spacing and thermal conductivity ratio are considered in order to look for the most appropriate properties of the porous structures that allow optimal heat transfer enhancement. It is found that the highest heat transfer rates are obtained when the porous structures are attached in configuration B especially at small spacing and high thicknesses

  18. Cumulative effects of using pin fin heat sink and porous metal foam on thermal management of lithium-ion batteries

    International Nuclear Information System (INIS)

    Mohammadian, Shahabeddin K.; Zhang, Yuwen

    2017-01-01

    Highlights: • 3D transient thermal analysis of a pouch Li-ion cell has been carried out. • Using pin fin heat sink improves the temperature reduction at low pumping powers. • Using pin fin heat sink enhances the temperature uniformity at low air flow rates. • Porous aluminum foam insertion with pin fins improves temperature reduction. • Porous aluminum foam insertion with pin fins enhances temperature uniformity. - Abstract: Three-dimensional transient thermal analysis of an air-cooled module was carried out to investigate cumulative effects of using pin fin heat sink and porous metal foam on thermal management of a Li-ion (lithium-ion) battery pack. Five different cases were designed as Case 1: flow channel without any pin fin or porous metal foam insertion, Case 2: flow channel with aluminum pin fins, Case 3: flow channel with porous aluminum foam pin fins, Case 4: fully inserted flow channel with porous aluminum foam, and Case 5: fully inserted flow channel with porous aluminum foam and aluminum pin fins. The effects of porous aluminum insertions, pin fin types, air flow inlet temperature, and air flow inlet velocity on the temperature uniformity and maximum temperature inside the battery pack were systematically investigated. The results showed that using pin fin heat sink (Case 2) is appropriate only for low air flow velocities. In addition, the use of porous aluminum pin fins or embedding porous aluminum foam inside the air flow channel (Cases 3 and 4) are not beneficial for thermal management improvement. The combination of aluminum pin fins and porous aluminum foam insertion inside the air flow channel (Case 5) is a proper option that improves both temperature reduction and temperature uniformity inside the battery cell.

  19. Synthesis, characterization and quantitative analysis of porous metal microstructures: Application to microporous copper produced by solid state foaming

    Directory of Open Access Journals (Sweden)

    Mark A. Atwater

    2016-05-01

    Full Text Available Porous metals can be created through a wide variety of processing techniques, and the pore morphology resulting from these processes is equally diverse. The structural and functional properties of metal foams are directly dependent on the size, shape, interconnectedness and volume fraction of pores, so accurately quantifying the pore characteristics is of great importance. Methods for analyzing porous materials are presented here and applied to a copper-based metallic foam generated through solid state foaming via oxide reduction and expansion. This process results in large voids (10s of microns between sintered particles and small pores (10 microns to less than 50 nm within particles. Optical and electron microscopy were used to image the porosity over this wide range, and the pore characteristics were quantified using image segmentation and statistical analysis. Two-dimensional pore analysis was performed using the Chan-Vese method, and two-point correlation and lineal path functions were used to assess three-dimensional reconstructions from FIB tomography. Two-dimensional analysis reveals distinct size and morphological differences in porosity between particles and within them. Three-dimensional analysis adds further information on the high level interconnectedness of the porosity and irregular shape it takes, forming tortuous pathways rather than spherical cells. Mechanical polishing and optical microscopy allow large areas to be created and analyzed quickly, but methods such as focused ion beam (FIB sectioning can provide additional insight about microstructural features. In particular, after FIB milling is used to create a flat surface, that surface can be analyzed for structural and compositional information.

  20. Flow in Porous Media with Special Reference to Breakwater Structures

    DEFF Research Database (Denmark)

    Andersen, O. Holst

    A literature study concerning porous flow is carried out. For the stationary case, the hydraulic radius theory, for which some justification can be given based on Navier-Stokes equations, appears to be adequate. Three different porous flow regimes are identified and the associated flow resistance...

  1. A Polymer Encapsulation Strategy to Synthesize Porous Nitrogen-Doped Carbon-Nanosphere-Supported Metal Isolated-Single-Atomic-Site Catalysts.

    Science.gov (United States)

    Han, Aijuan; Chen, Wenxing; Zhang, Shaolong; Zhang, Maolin; Han, Yunhu; Zhang, Jian; Ji, Shufang; Zheng, Lirong; Wang, Yu; Gu, Lin; Chen, Chen; Peng, Qing; Wang, Dingsheng; Li, Yadong

    2018-03-06

    A novel polymer encapsulation strategy to synthesize metal isolated-single-atomic-site (ISAS) catalysts supported by porous nitrogen-doped carbon nanospheres is reported. First, metal precursors are encapsulated in situ by polymers through polymerization; then, metal ISASs are created within the polymer-derived p-CN nanospheres by controlled pyrolysis at high temperature (200-900 °C). Transmission electron microscopy and N 2 sorption results reveal this material to exhibit a nanospheric morphology, a high surface area (≈380 m 2 g -1 ), and a porous structure (with micropores and mesopores). Characterization by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure confirms the metal to be present as metal ISASs. This methodology is applicable to both noble and nonprecious metals (M-ISAS/p-CN, M = Co, Ni, Cu, Mn, Pd, etc.). In particular, the Co-ISAS/p-CN nanospheres obtained using this method show comparable (E 1/2 = 0.838 V) electrochemical oxygen reduction activity to commercial Pt/C with 20 wt% Pt loading (E 1/2 = 0.834 V) in alkaline media, superior methanol tolerance, and outstanding stability, even after 5000 cycles. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. NUMERICAL SIMULATION OF METAL MELT FLOWS IN MOLD CAVITY WITH CERAMIC POROUS MEDIA

    Directory of Open Access Journals (Sweden)

    Changchun Dong

    2016-05-01

    Full Text Available Process modeling of metal melt flow in porous media plays an important role in casting of metal matrix composites. In this work, a mathematical model of the metal melt flow in preform ceramic particles was used to simulate the flow behavior in a mold cavity. The effects of fluid viscosity and permeability (mainly affected by porosity of ceramic preforms on the flow behavior were analyzed. The results indicate that ceramic porous media have a significant effect on the flow behavior by contributing to a low filling velocity and sharp pressure drop in the cavity. The pressure drop has a linear relationship with the fluid velocity, and a nonlinear relationship with porosity. When the porosity is relatively small, the pressure drop is extremely large. When porosity exceeds a certain value, the pressure drop is independent of porosity. The relationship between viscosity and porosity is described, and it is shown that the critical porosity changes when the viscosity of the melt changes. However, due to the limited viscosity change, the critical porosity changes by less than 0.043.

  3. Structural sound absorption in liquid metals

    International Nuclear Information System (INIS)

    Niyazov, S.

    1993-01-01

    Present article is devoted to structural sound absorption in liquid metals. The study of sound absorption in liquid metals shown that in all studied objects the structural absorption of sound was observed. The mechanism of structural relaxation in molten metal was revealed.

  4. Metal foam - a material for heat engineering. Porous structures increase the efficiency of heat exchangers and cooling elements; Metallschaum - ein Werkstoff fuer die Waermetechnik. Offenporige Strukturen steigern die Effizienz von Waermeuebertragern und Kuehlelementen

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Franz

    2016-11-01

    Metal foams are increasingly developing into materials with diverse uses. While metal foams with closed pores have already become established as rigid and strong lightweight materials, the open-cell variant is suitable for thermal engineering applications. Until now, the material has been rarely used in heat exchangers or coolers because the production is expensive and its application little tested. Researchers at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Dresden now want to change this. Together with industry partners, they are further developing the production method, are characterising different metal foams and are testing them in practice.

  5. Hierarchically porous Ni monolith@branch-structured NiCo2O4 for high energy density supercapacitors

    Directory of Open Access Journals (Sweden)

    Mengjie Xu

    2016-06-01

    Full Text Available A variety of NiCo2O4 nanostrucutures ranging from nanowire to nanoplate and branched structures were successfully prepared via a simple hydrothermal process. The experimental results show that NiCo2O4 with branched structures possesses the best overall electrochemical performance. The improvement of energy density was explored in terms of hierarchically three-dimensional (3D metal substrates and a high specific area capacitance, and area energy density is obtained with hierarchically porous Ni monolith synthesized through a controlled combustion procedure.

  6. Ion conductivity and transport by porous coordination polymers and metal-organic frameworks.

    Science.gov (United States)

    Horike, Satoshi; Umeyama, Daiki; Kitagawa, Susumu

    2013-11-19

    Ion conduction and transport in solids are both interesting and useful and are found in widely distinct materials, from those in battery-related technologies to those in biological systems. Scientists have approached the synthesis of ion-conductive compounds in a variety of ways, in the areas of organic and inorganic chemistry. Recently, based on their ion-conducting behavior, porous coordination polymers (PCPs) and metal-organic frameworks (MOFs) have been recognized for their easy design and the dynamic behavior of the ionic components in the structures. These PCP/MOFs consist of metal ions (or clusters) and organic ligands structured via coordination bonds. They could have highly concentrated mobile ions with dynamic behavior, and their characteristics have inspired the design of a new class of ion conductors and transporters. In this Account, we describe the state-of-the-art of studies of ion conductivity by PCP/MOFs and nonporous coordination polymers (CPs) and offer future perspectives. PCP/MOF structures tend to have high hydrophilicity and guest-accessible voids, and scientists have reported many water-mediated proton (H(+)) conductivities. Chemical modification of organic ligands can change the hydrated H(+) conductivity over a wide range. On the other hand, the designable structures also permit water-free (anhydrous) H(+) conductivity. The incorporation of protic guests such as imidazole and 1,2,4-triazole into the microchannels of PCP/MOFs promotes the dynamic motion of guest molecules, resulting in high H(+) conduction without water. Not only the host-guest systems, but the embedding of protic organic groups on CPs also results in inherent H(+) conductivity. We have observed high H(+) conductivities under anhydrous conditions and in the intermediate temperature region of organic and inorganic conductors. The keys to successful construction are highly mobile ionic species and appropriate intervals of ion-hopping sites in the structures. Lithium (Li

  7. Interpretation of electrokinetic measurements with porous films: role of electric conductance and streaming current within porous structure.

    Science.gov (United States)

    Yaroshchuk, Andriy; Luxbacher, Thomas

    2010-07-06

    It is shown that in tangential electrokinetic measurements with porous films the porous structure makes contribution not only to the cell electric conductance (as demonstrated previously) but also to the observed streaming current. Both of these contributions give rise to dependences of streaming-potential and streaming-current coefficients on the channel height. However, due to the combined contribution of two phenomena, the dependence of streaming-potential coefficient on the channel height may be rather complicated and not allow for simple extrapolation. At the same time, the dependences of streaming-current coefficient and cell electric conductance on the channel height turn out linear and can be easily extrapolated to zero channel heights. This enables one to determine separately the contributions of external surface of porous film and of its porous structure to the streaming current and of the channel and porous structure to the cell electric conductance. This procedure is illustrated by the measurements of tangential electrokinetic phenomena and electric conductance with Millipore mixed-cellulose membrane filters of various average pore sizes (from 0.025 to 5 mum) in the so-called adjustable-gap cell of SurPASS electrokinetic instrument (Anton Paar GmbH). The design of this cell allows for easy and quasi-continuous variation of channel height as well as accurate determination of cell electric conductance, streaming-current coefficient, and channel height (from the cell hydraulic permeability). The quality of linear fits of experimental data has been found to be very good, and thus, the extrapolation procedures were quite reliable and accurate. Zeta-potentials could be determined of both external film and internal pore surfaces. It is demonstrated that the porous structures make considerable contributions to both streaming-current coefficient and cell electric conductance especially in the case of filters with larger pores. It is also found that, rather

  8. Evaluation of Heat Losses Behind the Front of the Detonation Moving Along the Metallic Porous Surface

    Directory of Open Access Journals (Sweden)

    S. V. Golovastov

    2016-01-01

    Full Text Available The paper considers a computational technique of the heat flow from the hot products of detonation combustion into the porous coating and estimates the efficiency of the coating layer that results in slowing the flame front down with disregard the transverse displacement of the combustion products weight of a hydrogen-air mixture.Initial thermodynamic parameters of combustion products on the porous coating surface have been estimated. A drag (stagnation temperature of flow was determined.The statement of task was to calculate the heat flow into the long cylindrical metal fiber with radius of 15 μm. The reference values of heat capacity and heat diffusivity were used to estimate a thermal diffusivity in a wide range of temperatures. An approximation of the parameters is given for a wide range of temperatures.The calculation algorithm using an explicit four-point scheme is presented. The convergence and accuracy of the results were confirmed. The theoretical estimation using cylindrical Bessel functions was made to prove the accuracy of the results.Total heat loss was estimated using the photos of moving detonation front and hot combustion gases.Comparison of the total heat loss and the amount of energy absorbed by a single fiber allowed us to find that the porous coating thickness, resulting in attenuation of detonation wave, is efficient.

  9. Structure and Stability of Deflagrations in Porous Energetic Materials

    Energy Technology Data Exchange (ETDEWEB)

    stephen B. Margolis; Forman A. Williams

    1999-03-01

    Theoretical two-phase-flow analyses have recently been developed to describe the structure and stability of multi-phase deflagrations in porous energetic materials, in both confined and unconfined geometries. The results of these studies are reviewed, with an emphasis on the fundamental differences that emerge with respect to the two types of geometries. In particular, pressure gradients are usually negligible in unconfined systems, whereas the confined problem is generally characterized by a significant gas-phase pressure difference, or overpressure, between the burned and unburned regions. The latter leads to a strong convective influence on the burning rate arising from the pressure-driven permeation of hot gases into the solid/gas region and the consequent preheating of the unburned material. It is also shown how asymptotic models that are suitable for analyzing stability may be derived based on the largeness of an overall activation-energy parameter. From an analysis of such models, it is shown that the effects of porosity and two-phase flow are generally destabilizing, suggesting that degraded propellants, which exhibit greater porosity than their pristine counterparts, may be more readily subject to combustion instability and nonsteady deflagration.

  10. Structural controls on anomalous transport in fractured porous rock

    Science.gov (United States)

    Edery, Yaniv; Geiger, Sebastian; Berkowitz, Brian

    2016-07-01

    Anomalous transport is ubiquitous in a wide range of disordered systems, notably in fractured porous formations. We quantitatively identify the structural controls on anomalous tracer transport in a model of a real fractured geological formation that was mapped in an outcrop. The transport, determined by a continuum scale mathematical model, is characterized by breakthrough curves (BTCs) that document anomalous (or "non-Fickian") transport, which is accounted for by a power law distribution of local transition times ψ>(t>) within the framework of a continuous time random walk (CTRW). We show that the determination of ψ>(t>) is related to fractures aligned approximately with the macroscopic direction of flow. We establish the dominant role of fracture alignment and assess the statistics of these fractures by determining a concentration-visitation weighted residence time histogram. We then convert the histogram to a probability density function (pdf) that coincides with the CTRW ψ>(t>) and hence anomalous transport. We show that the permeability of the geological formation hosting the fracture network has a limited effect on the anomalous nature of the transport; rather, it is the fractures transverse to the flow direction that play the major role in forming the long BTC tail associated with anomalous transport. This is a remarkable result, given the complexity of the flow field statistics as captured by concentration transitions.

  11. Screen-printed electrodes made of a bismuth nanoparticle porous carbon nanocomposite applied to the determination of heavy metal ions

    International Nuclear Information System (INIS)

    Niu, Pengfei; Gich, Martí; Roig, Anna; Fernández-Sánchez, César; Navarro- Hernández, Carla; Fanjul-Bolado, Pablo

    2016-01-01

    This work reports on the simplified fabrication and on the characterization of bismuth-based screen-printed electrodes (SPEs) for use in heavy metal detection. A nanocomposite consisting of bismuth nanoparticles and amorphous carbon was synthesized by a combined one-step sol-gel and pyrolysis process and milled down to a specific particle size distribution as required for the preparation of an ink formulation to be used in screen printing. The resulting electrochemical devices were applied to the detection of Pb(II) and Cd(II) ions in water samples. The porous structure of carbon and the high surface area of the bismuth nanoparticles allow for the detection of Pb(II) and Cd(II) at concentration levels below 4 ppb. The application of the SPEs was demonstrated by quantifying these ions in tap drinking water and wastewater collected from an influent of an urban wastewater treatment plant. (author)

  12. Fabrication, Structural Characterization and Uniaxial Tensile Properties of Novel Sintered Multi-Layer Wire Mesh Porous Plates.

    Science.gov (United States)

    Duan, Liuyang; Zhou, Zhaoyao; Yao, Bibo

    2018-01-17

    There is an increasing interest in developing porous metals or metallic foams for functional and structural applications. The study of the physical and mechanical properties of porous metals is very important and helpful for their application. In this paper, a novel sintered multilayer wire mesh porous plate material (WMPPs) with a thickness of 0.5 mm-3 mm and a porosity of 10-35% was prepared by winding, pressing, rolling, and subsequently vacuum sintering them. The pore size and total size distribution in the as-prepared samples were investigated using the bubble point method. The uniaxial tensile behavior of the WMPPs was investigated in terms of the sintering temperature, porosity, wire diameter, and manufacturing technology. The deformation process and the failure mechanism under the tensile press was also discussed based on the appearance of the fractures (SEM figures). The results indicated that the pore size and total size distribution were closely related to the raw material used and the sintering temperature. For the WMPPs prepared by the wire mesh, the pore structures were inerratic and the vast majority of pore size was less than 10 μm. On the other hand, for the WMPPs that were prepared by wire mesh and powder, the pore structures were irregular and the pore size ranged from 0 μm-50 μm. The experimental data showed that the tensile strength of WMPPs is much higher than any other porous metals or metallic foams. Higher sintering temperatures led to coarser joints between wires and resulted in higher tensile strength. The sintering temperature decreased from 1330 °C to 1130 °C and the tensile strength decreased from 296 MPa to 164 MPa. Lower porosity means that there are more metallurgical joints and metallic frameworks resisting deformation per unit volume. Therefore, lower porosities exhibit higher tensile strength. An increase of porosity from 17.14% to 32.5% led to the decrease of the tensile strength by 90 MPa. The coarser wires led to a bigger

  13. Fabrication, Structural Characterization and Uniaxial Tensile Properties of Novel Sintered Multi-Layer Wire Mesh Porous Plates

    Directory of Open Access Journals (Sweden)

    Liuyang Duan

    2018-01-01

    Full Text Available There is an increasing interest in developing porous metals or metallic foams for functional and structural applications. The study of the physical and mechanical properties of porous metals is very important and helpful for their application. In this paper, a novel sintered multilayer wire mesh porous plate material (WMPPs with a thickness of 0.5 mm–3 mm and a porosity of 10–35% was prepared by winding, pressing, rolling, and subsequently vacuum sintering them. The pore size and total size distribution in the as-prepared samples were investigated using the bubble point method. The uniaxial tensile behavior of the WMPPs was investigated in terms of the sintering temperature, porosity, wire diameter, and manufacturing technology. The deformation process and the failure mechanism under the tensile press was also discussed based on the appearance of the fractures (SEM figures. The results indicated that the pore size and total size distribution were closely related to the raw material used and the sintering temperature. For the WMPPs prepared by the wire mesh, the pore structures were inerratic and the vast majority of pore size was less than 10 μm. On the other hand, for the WMPPs that were prepared by wire mesh and powder, the pore structures were irregular and the pore size ranged from 0 μm–50 μm. The experimental data showed that the tensile strength of WMPPs is much higher than any other porous metals or metallic foams. Higher sintering temperatures led to coarser joints between wires and resulted in higher tensile strength. The sintering temperature decreased from 1330 °C to 1130 °C and the tensile strength decreased from 296 MPa to 164 MPa. Lower porosity means that there are more metallurgical joints and metallic frameworks resisting deformation per unit volume. Therefore, lower porosities exhibit higher tensile strength. An increase of porosity from 17.14% to 32.5% led to the decrease of the tensile strength by 90 MPa. The

  14. Metallated metal-organic frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.

    2017-02-07

    Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.

  15. Metallated metal-organic frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.

    2017-08-22

    Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.

  16. Synthesis and structural evaluation of freeze-cast porous alumina

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Douglas F., E-mail: souzadf@outlook.com [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Nunes, Eduardo H.M., E-mail: eduardohmn@gmail.com [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Pimenta, Daiana S.; Vasconcelos, Daniela C.L. [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Nascimento, Jailton F.; Grava, Wilson [Petrobras/CENPES, Avenida Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ CEP:21941-915 (Brazil); Houmard, Manuel [Department of Materials Engineering and Civil Construction, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 1, sala 3304 (Brazil); Vasconcelos, Wander L., E-mail: wlv@demet.ufmg.br [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil)

    2014-10-15

    In this work we fabricated alumina samples by the freeze-casting technique using tert-butanol as the solvent. The prepared materials were examined by scanning electron microscopy and X-ray microtomography. Next, they were coated with sol–gel silica films by dip-coating. Permeability tests were carried out in order to assess the permeation behavior of the materials processed in this study. We observed that the sintering time and alumina loading showed a remarkable effect on both the structural properties and flexural strength of the freeze-cast samples. Nitrogen adsorption tests revealed that the silica prepared in this study exhibited a microporous structure. It was observed that the presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance by about one order of magnitude. Because of the similar kinetic diameters of nitrogen and carbon dioxide, the CO{sub 2}/N{sub 2} system showed a separation efficiency that was lower than that observed for the He/CO{sub 2} and He/N{sub 2} systems. We noticed that increasing the feed pressure improved the separation capacity of the obtained materials. - Highlights: • Porous alumina samples obtained by the freeze-casting technique • Microporous silica coating prepared by a simple sol–gel dip-coating methodology • Samples examined by SEM, μ-CT, and nitrogen sorption tests • Mechanical tests were carried out in the freeze-cast samples. • The presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance.

  17. Investigation of the porous structure of glassy carbon by SAXS - an application of synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Braun, A.; Baertsch, M.; Schnyder, B.; Koetz, R.; Haas, O. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    The porous structure of Electrochemical Double Layer Capacitor (EDC) Electrodes was investigated using Small Angle X-ray Scattering (SAXS), assuming logarithmically normal distributed micropores. (author) 2 figs., 1 ref.

  18. A Zn-tib porous framework sandwiched with Keggin Synthesis, structure, photocatalytic and luminescent properties

    Science.gov (United States)

    Zhang, Zhuanfang; Ma, Huiyuan; Pang, Haijun; Zhang, Chunjing; Chai, Dongfeng; Hou, Yan

    2018-02-01

    A novel helical compound, Zn(Htib)(tib)PMo12O40 (1) (tib = 1, 3, 5-tris-(1-imidazolyl)-benzene) was hydrothermally synthesized. The structure has been determined by single-crystal X-ray diffraction analyses and characterized by IR, XPS, UV-Vis and XRD and elemental analyses. Single crystal X-ray analysis reveals that compound 1 possesses entangled double helixes, which is formed by a pair of right- and left- handed double helixes sharing Zn atoms and a part of tib ligands. The adjacent entangled double helixes are further fused together, and thus a wavy Zn-tib metal-organic layer is constructed. Finally, through hydrogen bonds, the neighboring Zn-tib metal-organic layers are interconnected in a staggering peak-load manner to give birth to a porous 3D supramolecular framework with large rhombus-like apertures, in which the [PMo12O40]3- (PMo12) anions were encapsulated into the open channel structure and sandwiched by the Zn-tib layers. Additionally, compound 1 exhibits high efficiency and stability, and well reproducibility towards photocatalytic degradation of RhB dye under UV irradiation. The fluorescence property of 1 was also investigated.

  19. Tailoring the supercapacitive performances of noble metal oxides, porous carbons and their composites

    Directory of Open Access Journals (Sweden)

    Panić Vladimir V.

    2013-01-01

    Full Text Available Porous electrochemical supercapacitive materials, as an important type of new-generation energy storage devices, require a detailed analysis and knowledge of their capacitive performances upon different charging/discharging regimes. The investigation of the responses to dynamic perturbations of typical representatives, noble metal oxides, carbonaceous materials and RuO2-impregnated carbon blacks, by electrochemical impedance spectroscopy (EIS is presented. This presentation follows a brief description of supercapacitive behavior and origin of pseudocapacitive response of noble metal oxides. For all investigated materials, the electrical charging/discharging equivalent of the EIS response was found to obey the transmission line model envisaged as so-called „resistor/capacitor (RC ladder“. The ladder features are correlated to material physicochemical properties, its composition and the composition of the electrolyte. Fitting of the EIS data of different supercapacitive materials to appropriate RC ladders enables the in-depth profiling of the capacitance and pore resistance of their porous thin-layers and finally the complete revelation of capacitive energy storage issues. [Projekat Ministarstva nauke Republike Srbije, br. 172060

  20. Test results from a helium gas-cooled porous metal heat exchanger

    International Nuclear Information System (INIS)

    North, M.T.; Rosenfeld, J.H.; Youchison, D.L.

    1996-01-01

    A helium-cooled porous metal heat exchanger was built and tested, which successfully absorbed heat fluxes exceeding all previously tested gas-cooled designs. Helium-cooled plasma-facing components are being evaluated for fusion applications. Helium is a favorable coolant for fusion devices because it is not a plasma contaminant, it is not easily activated, and it is easily removed from the device in the event of a leak. The main drawback of gas coolants is their relatively poor thermal transport properties. This limitation can be removed through use of a highly efficient heat exchanger design. A low flow resistance porous metal heat exchanger design was developed, based on the requirements for the Faraday shield for the International Thermonuclear Experimental Reactor (ITER) device. High heat flux tests were conducted on two representative test articles at the Plasma Materials Test Facility (PMTF) at Sandia National Laboratories. Absorbed heat fluxes as high as 40 MW/m 2 were successfully removed during these tests without failure of the devices. Commercial applications for electronics cooling and other high heat flux applications are being identified

  1. The role of oxygen in porous molybdenum electrodes for the alkali metal thermoelectric converter

    International Nuclear Information System (INIS)

    Williams, R.M.; Nagasubramanian, G.; Khanna, S.K.; Bankston, C.P.; Thakoor, A.P.; Cole, T.

    1986-01-01

    The alkali metal thermoelectric converter is a direct energy conversion device, utilizing a high alkali metal activity gradient to generate electrical power. Its operation is based on the unique ion conductive properties of beta''-alumina solid electrolyte. The major barrier to application of this device is identification of an electrode which can maintain optimum power densities for operation times of >10,000h. Thin, porous molybdenum electrodes have shown the best performance characteristics, but show a variety of time dependent phenomena, including eventual degradation to power densities 3-5 times lower than initial values. Several Na-Mo-O compounds, including Na/sub 2/MoO/sub 4/ and Na/sub 2/Mo/sub 3/O/sub 6/, are formed during AMTEC operation. These compounds may be responsible for enhanced Na transport through Mo electrodes via sodium ion conduction, and eventual performance degradation due to their volatilization and decomposition. No decomposition of beta''-alumina has been observed under simulated AMTEC operating conditions up to 1373 K. In this paper, we present a model for chemical reactions occurring in porous molybdenum electrodes. The model is based on thermochemical and kinetic data, known sodium-molybdenum-oxygen chemistry, x-ray diffraction analysis of molybdenum and molybdenum oxide electrodes, and the electrochemical behavior of the cell

  2. A Metal Chelating Porous Polymeric Support: The Missing Link for a Defect-free Metal-Organic Framework Composite Membrane

    KAUST Repository

    Barankova, Eva

    2017-02-06

    Since the discovery of size-selective metal-organic frameworks (MOFs), researchers have tried to incorporate these materials into gas separation membranes. Impressive gas selectivities were found, but these MOF membranes were mostly made on inorganic supports, which are generally too bulky and expensive for industrial gas separation. Forming MOF layers on porous polymer supports is industrially attractive but technically challenging. Two features to overcome these problems are described: 1) a metal chelating support polymer to bind the MOF layer, and 2) control of MOF crystal growth by contra-diffusion, aiming at a very thin nanocrystalline MOF layer. Using a metal chelating polythiosemicarbazide (PTSC) support and adjusting the metal and organic ligand concentrations carefully, a very compact ZIF-8 (ZIF=zeolitic imidazolate framework) layer was produced that displayed interference colors because of its smooth surface and extreme thinness-within the range of visible light. High performances were measured in terms of hydrogen/propane (8350) and propylene/propane (150) selectivity.

  3. A Metal Chelating Porous Polymeric Support: The Missing Link for a Defect-Free Metal-Organic Framework Composite Membrane.

    Science.gov (United States)

    Barankova, Eva; Tan, Xiaoyu; Villalobos, Luis Francisco; Litwiller, Eric; Peinemann, Klaus-Viktor

    2017-03-06

    Since the discovery of size-selective metal-organic frameworks (MOFs), researchers have tried to incorporate these materials into gas separation membranes. Impressive gas selectivities were found, but these MOF membranes were mostly made on inorganic supports, which are generally too bulky and expensive for industrial gas separation. Forming MOF layers on porous polymer supports is industrially attractive but technically challenging. Two features to overcome these problems are described: 1) a metal chelating support polymer to bind the MOF layer, and 2) control of MOF crystal growth by contra-diffusion, aiming at a very thin nanocrystalline MOF layer. Using a metal chelating poly-thiosemicarbazide (PTSC) support and adjusting the metal and organic ligand concentrations carefully, a very compact ZIF-8 (ZIF=zeolitic imidazolate framework) layer was produced that displayed interference colors because of its smooth surface and extreme thinness-within the range of visible light. High performances were measured in terms of hydrogen/propane (8350) and propylene/propane (150) selectivity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Structure and properties of porous films based on aliphatic copolyamide developed for cellular technologies

    Czech Academy of Sciences Publication Activity Database

    Dobrovol`skaya, I.P.; Popryadukhin, P.V.; Yudin, V. E.; Ivankova, E.M.; Elokhovskiy, V.Y.; Weishauptová, Zuzana; Balík, Karel

    2015-01-01

    Roč. 26, č. 1 (2015), article number 46 ISSN 0957-4530 Institutional support: RVO:67985891 Keywords : porous film * aliphatic copolyamide * structure * properties Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.272, year: 2015 http://www.stem-art.com/Library/Science/Structure%20and%20properties%20of%20porous%20films%20based%20on%20aliphatic%20copolyamide%20developed%20for%20cellular%20technologies.pdf

  5. Magnetic porous Fe3O4/carbon octahedra derived from iron-based metal-organic framework as heterogeneous Fenton-like catalyst

    Science.gov (United States)

    Li, Wenhui; Wu, Xiaofeng; Li, Shuangde; Tang, Wenxiang; Chen, Yunfa

    2018-04-01

    The synthesis of effective and recyclable Fenton-like catalyst is still a key factor for advanced oxidation processes. Herein, magnetic porous Fe3O4/carbon octahedra were constructed by a two-step controlled calcination of iron-based metal organic framework. The porous octahedra were assembled by interpenetrated Fe3O4 nanoparticles coated with graphitic carbon layer, offering abundant mesoporous channels for the solid-liquid contact. Moreover, the oxygen-containing functional groups on the surface of graphitic carbon endow the catalysts with hydrophilic nature and well-dispersion into water. The porous Fe3O4/carbon octahedra show efficiently heterogeneous Fenton-like reactions for decomposing the organic dye methylene blue (MB) with the help of H2O2, and nearly 100% removal efficiency within 60 min. Furthermore, the magnetic catalyst retains the activity after ten cycles and can be easily separated by external magnetic field, indicating the long-term catalytic durability and recyclability. The good Fenton-like catalytic performance of the as-synthesized Fe3O4/carbon octahedra is ascribed to the unique mesoporous structure derived from MOF-framework, as well as the sacrificial role and stabilizing effect of graphitic carbon layer. This work provides a facile strategy for the controllable synthesis of integrated porous octahedral structure with graphitic carbon layer, and thereby the catalyst holds significant potential for wastewater treatment.

  6. pH-dependent transport of metals through a reactive porous medium

    Science.gov (United States)

    Prigiobbe, V.; Bryant, S. L.

    2013-12-01

    Here we present a study on the effect of pH-dependent adsorption and hydrodynamic dispersion on metal transport through a reactive porous medium with hydrophilic surface. We investigate how the migration of a certain fraction of a metal can be facilitated by its competitive adsorption with protons. We performed laboratory experiments using a chromatographic column filled with silica beads coated with hydrous ferric oxide (HFO) and flooded initially with an acidic solution (pH 3) and then with an alkaline solution (pH > 7) containing either sodium, potassium, lithium, calcium, magnesium, strontium, or barium cations. Concentrations were chosen for which nonclassical transport is predicted. Highly resolved breakthrough curves measured with inline ion chromatography allowed us to observe in all cases the formation of a fast wave/pulse traveling at the interstitial fluid velocity and a retarded front. Classical theory of reactive transport through porous media predicts the formation of only the retarded front and assumes that hydrodynamic dispersion only smooths it without introducing an additional wave. Therefore, the fast wave is a notable exception to this theory. The mechanism responsible for this phenomenon is due to the interplay between hydrodynamic dispersion and pH-dependent adsorption. Hydrodynamic dispersion broadens the metal concentration front at the inlet of the column and creates a mixing zone where the high-pH solution containing the metal mixes with the low-pH solution initially present in the system. The resulting pH of the mixing zone spans a range where both the adsorption and the retardation of the metal are negligible. This leads to the formation of a metal plume, which then separates from the retarded front traveling at the interstitial fluid velocity as an isolated pulse. This fast transport phenomenon operates independently of other modes of rapid transport, such as colloid-facilitated transport and flow in fractures. A one

  7. Effect of polymer and additive on the structure and property of porous stainless steel hollow fiber

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Xiao-Hua; Bai, Yu; Cao, Yue; Xu, Zhen-Liang [East China University of Science and Technology, Shanghai (China)

    2014-08-15

    Porous stainless steel hollow fiber has been widely used due to its high mechanical strength, excellent thermal conductivity and good sealing properties compared with other porous supports. We successfully prepared porous stainless steel hollow fibers using polyacrylonitrile (PAN) as polymer via dry-wet spinning followed by sintering through temperature programming method. The PAN concentration had an obvious impact on the structure and property of porous stainless steel hollow fiber even if it would be burned off during sintering. The results showed that the morphology could be tuned by adjusting the concentration of PAN. With increasing PAN concentration in casting solution for spinning, the viscosity was increased dramatically, resulting in much compact structures with high pure water flux (higher than 3x10{sup 5} L·m{sup -2}·h{sup -1}·Pa{sup -1}). A more dense structure could be obtained by adding additive polyvinylpyrrolidone (PVP) as viscosity enhancer.

  8. Effects of pore structure and distribution on strength of porous Cu-Sn-Ti alumina composites

    Directory of Open Access Journals (Sweden)

    Biao ZHAO

    2017-12-01

    Full Text Available Porous Cu-Sn-Ti alumina composites were fabricated by sintering Cu-Sn-Ti alloy powders, graphite particles, and alumina hollow particles agent. The effects of the pore structure and distribution on the composites strength were evaluated. Different pore distributions were modeled by using finite element analysis to investigate the tensile strength of the composites. Furthermore, a fractal analysis-based box-covering algorithm was used on the Cu-Sn-Ti alumina composites topology graphs to better investigate the pore structure and distribution. Results obtained show that different sizes and concentrations of alumina hollow particles could result in different porosities from 20% to 50%. A larger pore size and a higher pore concentration reduce the strength, but provide more space for chip formation as a bonding material of a grinding wheel. The body-centered pore structure of the composites shows the highest stress under a tension load. The original composites topology graphs have been transformed to ordered distributed pore graphs based on the total pore area conservation. The information dimension magnitude difference between the original topology graphs and the ordered distributed circulars graphs is found to be linear with the Cu-Sn-Ti alumina composites strength. A larger difference renders a lower flexural strength, which indicates that uniform ordered distributed pores could benefit the composites strength. Keywords: Finite element analysis (FEA, Metal-matrix composites (MMCs, Microstructural analysis, Pore structure, Strength

  9. Infill Optimization for Additive Manufacturing-Approaching Bone-Like Porous Structures.

    Science.gov (United States)

    Wu, Jun; Aage, Niels; Westermann, Rudiger; Sigmund, Ole

    2018-02-01

    Porous structures such as trabecular bone are widely seen in nature. These structures are lightweight and exhibit strong mechanical properties. In this paper, we present a method to generate bone-like porous structures as lightweight infill for additive manufacturing. Our method builds upon and extends voxel-wise topology optimization. In particular, for the purpose of generating sparse yet stable structures distributed in the interior of a given shape, we propose upper bounds on the localized material volume in the proximity of each voxel in the design domain. We then aggregate the local per-voxel constraints by their p-norm into an equivalent global constraint, in order to facilitate an efficient optimization process. Implemented on a high-resolution topology optimization framework, our results demonstrate mechanically optimized, detailed porous structures which mimic those found in nature. We further show variants of the optimized structures subject to different design specifications, and we analyze the optimality and robustness of the obtained structures.

  10. Highly efficient nonprecious metal catalysts towards oxygen reduction reaction based on three-dimensional porous carbon nanostructures.

    Science.gov (United States)

    Zhu, Chengzhou; Li, He; Fu, Shaofang; Du, Dan; Lin, Yuehe

    2016-02-07

    Developing a low cost, highly active, durable cathode towards an oxygen reduction reaction (ORR) is one of the high-priority research directions for commercialization of low-temperature polymer electrolyte membrane fuel cells (PEMFCs). However, the electrochemical performance of PEMFCs is still hindered by the high cost and insufficient durability of the traditional Pt-based cathode catalysts. Under these circumstances, the search for efficient alternatives to replace Pt for constructing highly efficient nonprecious metal catalysts (NPMCs) has been growing intensively and has received great interest. Combining with the compositional effects, the accurate design of NPMCs with 3D porous nanostructures plays a significant role in further enhancing ORR performance. These 3D porous architectures are able to provide higher specific surface areas and larger pore volumes, not only maximizing the availability of electron transfer within the nanosized electrocatalyst surface area but also providing better mass transport of reactants to the electrocatalyst. In this Tutorial Review, we focus on the rational design and synthesis of different 3D porous carbon-based nanomaterials, such as heteroatom-doped carbon, metal-nitrogen-carbon nanostructures and a series of carbon/nonprecious metal-based hybrids. More importantly, their enhanced ORR performances are also demonstrated by virtue of their favorably porous morphologies and compositional effects. Finally, the future trends and perspectives for the highly efficient porous NPMCs regarding the material design are discussed, with an emphasis on substantial development of advanced carbon-based NPMCs for ORR in the near future.

  11. Fabrication of porous titanium scaffold with controlled porous structure and net-shape using magnesium as spacer.

    Science.gov (United States)

    Kim, Sung Won; Jung, Hyun-Do; Kang, Min-Ho; Kim, Hyoun-Ee; Koh, Young-Hag; Estrin, Yuri

    2013-07-01

    This paper reports a new approach to fabricating biocompatible porous titanium with controlled pore structure and net-shape. The method is based on using sacrificial Mg particles as space holders to produce compacts that are mechanically stable and machinable. Using magnesium granules and Ti powder, Ti/Mg compacts with transverse rupture strength (~85 MPa) sufficient for machining were fabricated by warm compaction, and a complex-shape Ti scaffold was eventually produced by removal of Mg granules from the net-shape compact. The pores with the average size of 132-262 μm were well distributed and interconnected. Due to anisotropy and alignment of the pores the compressive strength varied with the direction of compression. In the case of pores aligned with the direction of compression, the compressive strength values (59-280 MPa) high enough for applications in load bearing implants were achieved. To verify the possibility of controlled net-shape, conventional machining process was performed on Ti/Mg compact. Compact with screw shape and porous Ti scaffold with hemispherical cup shape were fabricated by the results. Finally, it was demonstrated by cell tests using MC3T3-E1 cell line that the porous Ti scaffolds fabricated by this technique are biocompatible. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Cost-Effective Fabrication of Inner-Porous Micro/Nano Carbon Structures.

    Science.gov (United States)

    Jiang, Shulan; Shi, Tielin; Tang, Zirong; Xi, Shuang

    2018-03-01

    This paper reports the fabrication of a new micro/nano carbon architecture array which owns the characteristics of inner-porous, desired conductivity and large effective surface area. The micro/nano inner-porous carbon structures were fabricated for the first time, with ordinary and cost-effective processes, including photolithography, oxygen plasma etching and pyrolysis. Firstly, micro/nano hierarchical photoresist structures array was generated through photolithography and oxygen plasma etching processes. By introducing a critical thin-film spin-coating step, and followed with carefully pyrolyzing process, the micro/nano photoresist structures were converted into innerporous carbon architectures with good electric connection which connected the carbon structures array together. Probably the inner-porous property can be attributed to the shrinkage difference between positive thin film and negative photoresist structures during pyrolyzing process. It is demonstrated that the simple method is effective to fabricate inner-porous carbon structures with good electric connection and the carbon structures can be used as electrochemical electrodes directly and without the addition of other pyrolysis or film coating processes. The electrochemical property of the carbon structures has been explored by cyclic voltammetric measurement. Compared with solid carbon microstructures array, the cyclic voltammetry curve of inner-porous carbon structures shows greatly enhanced current and improved charge-storage capability, indicating great potential in micro energy storage devices and bio-devices.

  13. Functionally Graded Metal-Metal Composite Structures

    Science.gov (United States)

    Brice, Craig A. (Inventor)

    2017-01-01

    Methods and devices are disclosed for creating a multiple alloy composite structure by forming a three-dimensional arrangement of a first alloy composition in which the three-dimensional arrangement has a substantially open and continuous porosity. The three-dimensional arrangement of the first alloy composition is infused with at least a second alloy composition, where the second alloy composition comprises a shape memory alloy. The three-dimensional arrangement is consolidated into a fully dense solid structure, and the original shape of the second alloy composition is set for reversible transformation. Strain is applied to the fully dense solid structure, which is treated with heat so that the shape memory alloy composition becomes memory activated to recover the original shape. An interwoven composite of the first alloy composition and the memory-activated second alloy composition is thereby formed in the multiple alloy composite structure.

  14. Strategy for Predicting Effective Transport Properties of Complex Porous Structures

    Czech Academy of Sciences Publication Activity Database

    Salejová, G.; Grof, Z.; Šolcová, Olga; Schneider, Petr; Kosek, J.

    2011-01-01

    Roč. 35, č. 2 (2011), s. 200-211 ISSN 0098-1354 Institutional research plan: CEZ:AV0Z40720504 Keywords : porous media * pore space reconstruction * effective diffusivity Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.320, year: 2011

  15. Electro-architected porous platinum on metallic multijunction nanolayers to optimize their optical properties for infrared sensor application

    Science.gov (United States)

    Stanca, Sarmiza Elena; Hänschke, Frank; Zieger, Gabriel; Dellith, Jan; Dellith, Andrea; Ihring, Andreas; Belkner, Johannes; Meyer, Hans-Georg

    2018-03-01

    Tailoring the physicochemical properties of the metallic multijunction nanolayers is a prerequisite for the development of microelectronics. From this perspective, a desired lower reflectance of infrared radiation was achieved by an electrochemical deposition of porous platinum in nonaqueous media on silver mirror supported nickel-chrome and nickel-titanium metallic films with incremental decreasing thicknesses from 80-10 nm. The electro-assembled architectures were examined by means of scanning electron microscopy and Fourier transform infrared spectroscopy and it was observed that the layer and sublayer thicknesses and resistivities have a substantial effect upon the porous platinum morphology and its optical properties. It is here reported that the augmentation of the metallic layer electrical conductivity determines the electroformation of more compact platinum nanolayers. Moreover, the platinum black coating of metallic nanolayers causes a considerable decrease of the reflectance in the region from 1000-8000 cm-1.

  16. Fabrication of a Ti porous microneedle array by metal injection molding for transdermal drug delivery.

    Science.gov (United States)

    Li, Jiyu; Liu, Bin; Zhou, Yingying; Chen, Zhipeng; Jiang, Lelun; Yuan, Wei; Liang, Liang

    2017-01-01

    Microneedle arrays (MA) have been extensively investigated in recent decades for transdermal drug delivery due to their pain-free delivery, minimal skin trauma, and reduced risk of infection. However, porous MA received relatively less attention due to their complex fabrication process and ease of fracturing. Here, we present a titanium porous microneedle array (TPMA) fabricated by modified metal injection molding (MIM) technology. The sintering process is simple and suitable for mass production. TPMA was sintered at a sintering temperature of 1250°C for 2 h. The porosity of TPMA was approximately 30.1% and its average pore diameter was about 1.3 μm. The elements distributed on the surface of TPMA were only Ti and O, which may guarantee the biocompatibility of TPMA. TPMA could easily penetrate the skin of a human forearm without fracture. TPMA could diffuse dry Rhodamine B stored in micropores into rabbit skin. The cumulative permeated flux of calcein across TPMA with punctured skin was 27 times greater than that across intact skin. Thus, TPMA can continually and efficiently deliver a liquid drug through open micropores in skin.

  17. Fabrication of a Ti porous microneedle array by metal injection molding for transdermal drug delivery.

    Directory of Open Access Journals (Sweden)

    Jiyu Li

    Full Text Available Microneedle arrays (MA have been extensively investigated in recent decades for transdermal drug delivery due to their pain-free delivery, minimal skin trauma, and reduced risk of infection. However, porous MA received relatively less attention due to their complex fabrication process and ease of fracturing. Here, we present a titanium porous microneedle array (TPMA fabricated by modified metal injection molding (MIM technology. The sintering process is simple and suitable for mass production. TPMA was sintered at a sintering temperature of 1250°C for 2 h. The porosity of TPMA was approximately 30.1% and its average pore diameter was about 1.3 μm. The elements distributed on the surface of TPMA were only Ti and O, which may guarantee the biocompatibility of TPMA. TPMA could easily penetrate the skin of a human forearm without fracture. TPMA could diffuse dry Rhodamine B stored in micropores into rabbit skin. The cumulative permeated flux of calcein across TPMA with punctured skin was 27 times greater than that across intact skin. Thus, TPMA can continually and efficiently deliver a liquid drug through open micropores in skin.

  18. Fabrication of metallic glass structures

    Science.gov (United States)

    Cline, C.F.

    1983-10-20

    Amorphous metal powders or ribbons are fabricated into solid shapes of appreciable thickness by the application of compaction energy. The temperature regime wherein the amorphous metal deforms by viscous flow is measured. The metal powders or ribbons are compacted within the temperature regime.

  19. Catalytic upgrading of sugar fractions from pyrolysis oils in supercritical mono-alcohols over Cu doped porous metal oxide

    NARCIS (Netherlands)

    Yin, Wang; Venderbosch, Hendrikus; Bottari, Giovanni; Krawzcyk, Krzysztof K.; Barta, Katalin; Heeres, Hero Jan

    In this work, we report on the catalytic valorization of sugar fractions, obtained by aqueous phase extraction of fast pyrolysis oils, in supercritical methanol (scMeOH) and ethanol (scEtOH) over a copper doped porous metal oxide (Cu-PMO). The product mixtures obtained are, in principle, suitable

  20. Characteristics of Wave Reflection for Vertical and Slit Caissons with Porous Structures

    Directory of Open Access Journals (Sweden)

    Tae-Hwa Jung

    2012-01-01

    Full Text Available Offshore structures are occasionally located at a relatively deep water region, the outside of breakwater. In this case, these structures may be damaged by the supposition of incident and reflected waves from a vertical breakwater. To prevent the damage, the reflected waves are controlled by installing porous structures at the face of the vertical breakwater. In this study, numerical experiments are carried out to identify the characteristics of wave reflection from the porous structures installing in front of a vertical or slit caisson.

  1. Infill Optimization for Additive Manufacturing - Approaching Bone-like Porous Structures

    DEFF Research Database (Denmark)

    Wu, Jun; Aage, Niels; Westermann, Ruediger

    2018-01-01

    Porous structures such as trabecular bone are widely seen in nature. These structures exhibit superior mechanical properties whilst being lightweight. In this paper, we present a method to generate bone-like porous structures asl ightweight infill for additive manufacturing. Our method builds upon...... and extends voxel-wise topology optimization. In particular, for the purpose of generating sparse yet stable structures distributed in the interior of a given shape, we propose upper bounds on the localized material volume in the proximity of each voxel in the design domain. We then aggregate the local per......-voxel constraints by their p-norm into an equivalent global constraint, in order to facilitate an efficient optimization process. Implemented on a high-resolution topology optimization framework, our results demonstrate mechanically optimized, detailed porous structures which mimic those found innature. We further...

  2. Processing and structural characterization of porous reforming catalytic films

    International Nuclear Information System (INIS)

    Hou Xianghui; Williams, Jey; Choy, Kwang-Leong

    2006-01-01

    Nickel-based catalysts are often used to reform methanol into hydrogen. The preparation and installation of these catalysts are costly and laborious. As an alternative, directly applying catalytic films onto the separator components can improve the manufacturing efficiency. This paper reports the successful deposition of adherent porous NiO-Al 2 O 3 -based catalytic films with well-controlled stoichiometry, using a single-step Aerosol Assisted Chemical Vapour Deposition (AACVD) method. The microstructure, composition and crystalline phase of the as-deposited catalytic films are characterized using a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared (FTIR) Spectrometer. The results have demonstrated the capability of AACVD to produce porous NiO-Al 2 O 3 -based catalytic films

  3. Structure of polyvalent metal halide melts

    International Nuclear Information System (INIS)

    Tosi, M.P.

    1990-12-01

    A short review is given of recent progress in determining and understanding the structure of molten halide salts involving polyvalent metal ions. It covers the following three main topics: (i) melting mechanisms and types of liquid structure for pure polyvalent-metal chlorides; (ii) geometry and stability of local coordination for polyvalent metal ions in molten mixtures of their halides with alkali halides; and (iii) structure breaking and electron localization on addition of metal to the melt. (author). 28 refs, 3 figs, 1 tab

  4. Structure Optimization of Porous Dental Implant Based on 3D Printing

    Science.gov (United States)

    Ji, Fangqiu; Zhang, Chunyu; Chen, Xianshuai

    2018-03-01

    In this paper, selective laser melting (SLM) technology is used to process complex structures. In combination with the theory of biomedicine, a porous implant with a porous structure is designed to induce bone cell growth. The mechanical strength advantage of SLM was discussed by observing the metallographic structure of SLM specimen with mechanical microscope and mechanical tensile test. The osseointegration of porous implants was observed and analyzed by biological experiments. By establishing a mechanical model, the mechanical properties of the bone implant combined with the jaw bone were studied by the simple mechanical analysis under static multi loading and the finite element mechanical analysis. According to the experimental observation and mechanical research, the optimization suggestions for the structure design of the implant made by SLM technology were put forward.

  5. Structural versatility of Metal-organic frameworks: Synthesis and Characterization

    KAUST Repository

    Alsadun, Norah S.

    2017-05-01

    Metal-Organic Frameworks (MOFs), an emerging class of porous crystalline materials, have shown promising properties for diverse applications such as catalysis, gas storage and separation. The high degree of tunability of MOFs vs other solid materials enable the assembly of advanced materials with fascinating properties for specific applications. Nevertheless, the precise control in the construction of MOFs at the molecular level remains challenging. Particularly, the formation of pre-targeted multi-nuclear Molecular Building Block (MBB) precursors to unveil materials with targeted structural characteristics is captivating. The aim of my master project in the continuous quest of the group of Prof. Eddaoudi in exploring different synthetic pathways to control the assembly of Rare Earth (RE) based MOF. After giving a general overview about MOFs, I will discuss in this thesis the results of my work on the use of tri-topic oriented organic carboxylate building units with the aim to explore the assembly/construction of new porous RE based MOFs. In chapter 2 will discuss the assembly of 3-c linkers with RE metals was then evaluated based on symmetry and angularity of the three connected linkers. The focus of chapter 3 is cerium based MOFs and heterometallic system, based on 3-c ligands with different length and symmetry. Overall, the incompatibility of 3-c ligands with the 12-c cuo MBB did not allow to any formation of higher neuclearity (˃6), but it has resulted in affecting the connectivity of the cluster.

  6. Effect of porous orthopaedic implant material and structure on load sharing with simulated bone ingrowth: A finite element analysis comparing titanium and PEEK.

    Science.gov (United States)

    Carpenter, R Dana; Klosterhoff, Brett S; Torstrick, F Brennan; Foley, Kevin T; Burkus, J Kenneth; Lee, Christopher S D; Gall, Ken; Guldberg, Robert E; Safranski, David L

    2018-04-01

    Osseointegration of load-bearing orthopaedic implants, including interbody fusion devices, is critical to long-term biomechanical functionality. Mechanical loads are a key regulator of bone tissue remodeling and maintenance, and stress-shielding due to metal orthopaedic implants being much stiffer than bone has been implicated in clinical observations of long-term bone loss in tissue adjacent to implants. Porous features that accommodate bone ingrowth have improved implant fixation in the short term, but long-term retrieval studies have sometimes demonstrated limited, superficial ingrowth into the pore layer of metal implants and aseptic loosening remains a problem for a subset of patients. Polyether-ether-ketone (PEEK) is a widely used orthopaedic material with an elastic modulus more similar to bone than metals, and a manufacturing process to form porous PEEK was recently developed to allow bone ingrowth while preserving strength for load-bearing applications. To investigate the biomechanical implications of porous PEEK compared to porous metals, we analyzed finite element (FE) models of the pore structure-bone interface using two clinically available implants with high (> 60%) porosity, one being constructed from PEEK and the other from electron beam 3D-printed titanium (Ti). The objective of this study was to investigate how porous PEEK and porous Ti mechanical properties affect load sharing with bone within the porous architectures over time. Porous PEEK substantially increased the load share transferred to ingrown bone compared to porous Ti under compression (i.e. at 4 weeks: PEEK = 66%; Ti = 13%), tension (PEEK = 71%; Ti = 12%), and shear (PEEK = 68%; Ti = 9%) at all time points of simulated bone ingrowth. Applying PEEK mechanical properties to the Ti implant geometry and vice versa demonstrated that the observed increases in load sharing with PEEK were primarily due to differences in intrinsic elastic modulus and not pore architecture (i.e. 4 weeks

  7. Porous ZnO nanosheet arrays constructed on weaved metal wire for flexible dye-sensitized solar cells

    Science.gov (United States)

    Dai, Hui; Zhou, Yong; Chen, Liang; Guo, Binglei; Li, Aidong; Liu, Jianguo; Yu, Tao; Zou, Zhigang

    2013-05-01

    Porous zinc oxide (ZnO) nanosheet (NS) arrays constructed by connected nanocrystallites were built on weaved metal wire (WMW) via hydrothermal treatment followed by calcination, and used as photoanodes for flexible dye-sensitized solar cells (DSSCs). An overall light-to-electricity conversion efficiency (η) of 2.70% was achieved for the DSSC under 100 mW cm-2 illumination, and this η was found to be much higher than that of the DSSC with ZnO nanowire (NW) as the photoanode (0.71%). The far superior performance of the DSSC with ZnO-NS is essentially attributed to: (i) the film consisting of nanosheets with interconnected nanocrystallites can allow relatively direct pathways for the transportation of electrons as the nanosheets have a regular structure with the sheets being oriented to the electrode; (ii) the nanocrystallites assembly and porous character of the nanosheets can provide a large surface area for dye adsorption, which is in favor of enhancing the light absorption and the light propagation; (iii) the nanopores embedded in the nanosheet can act as ``branch lines'' for more efficient electrolyte diffusion into the interstice of the densely packed nanosheets in the array. A further improvement in the efficiency of the DSSC with ZnO-NS was achieved through the atomic layer deposition (ALD) of an ultrathin titanium oxide (TiO2) layer onto the ZnO-NS layer. The larger charge transfer resistance along with the introduction of a TiO2 shell is thought to reduce the surface recombination and thus contribute to the increase in the open circuit voltage (Voc) of the DSCs and higher conversion efficiency (3.09%).Porous zinc oxide (ZnO) nanosheet (NS) arrays constructed by connected nanocrystallites were built on weaved metal wire (WMW) via hydrothermal treatment followed by calcination, and used as photoanodes for flexible dye-sensitized solar cells (DSSCs). An overall light-to-electricity conversion efficiency (η) of 2.70% was achieved for the DSSC under 100 mW cm

  8. Porous metal cones: gold standard for massive bone loss in complex revision knee arthroplasty? A systematic review of current literature.

    Science.gov (United States)

    Divano, Stefano; Cavagnaro, Luca; Zanirato, Andrea; Basso, Marco; Felli, Lamberto; Formica, Matteo

    2018-04-18

    Revision knee arthroplasty is increasing, and in that case, bone loss management is still a challenging problem. In the last years, the body of literature and interest surrounding porous metal cones has grown, but few systematic evaluations of the existing evidence have been performed. The aim of our systematic review is to collect and critically analyze the available evidence about metal cones in revision knee arthroplasty especially focusing our attention on indications, results, complications, and infection rate of these promising orthopaedic devices. We performed a systematic review of the available English literature, considering the outcomes and the complications of tantalum cones. The combinations of keyword were "porous metal cones", "knee revision", "bone loss", "knee arthroplasty", "periprosthetic joint infection", and "outcome". From the starting 312 papers available, 20 manuscripts were finally included. Only one included study has a control group. The main indication for metal cones is type IIb and III defects according AORI classification. Most of the papers show good clinical and radiological outcomes with low rate of complications. The examined studies provide encouraging clinical and radiological short-to-mid-term outcomes. Clinical studies have shown a low rate of aseptic loosening, intraoperative fractures, infection rate and a lower failure rate than the previous treatment methods. Higher quality papers are needed to draw definitive conclusions about porous metal cones.

  9. Ligand flexibility and framework rearrangement in a new family of porous metal-organic frameworks

    DEFF Research Database (Denmark)

    Hawxwell, Samuel M; Espallargas, Guillermo Mínguez; Bradshaw, Darren

    2007-01-01

    Ligand flexibility permits framework rearrangement upon evacuation and gas uptake in a new family of porous MOFs.......Ligand flexibility permits framework rearrangement upon evacuation and gas uptake in a new family of porous MOFs....

  10. Structure and properties of porous ceramic preforms made of α-alumina particles

    Directory of Open Access Journals (Sweden)

    J. W. Kaczmar

    2010-01-01

    Full Text Available Properties of ceramic preforms made of α-alumina particles for strengthening of metal based composite materials manufactured by squeeze casting are discussed in the paper. Composite materials strengthened with ceramic particles can be then plastically worked in order to remove the residual porosity and give the final net shape. There was investigated the permeability of porous preforms as the measure of the open porosity making possible the infiltration process with the molten metal, compression strength, bending strength and shear strength determining the stability of porous ceramic preforms during infiltration. Performed investigations allow to ascertain the occurrence of the open porosity in the porous preforms and strong effect of porosity on permeability. The largest permeability of 19 m2/Pa·s showed porous preforms characterized by porosity the of 90%. The strength properties increased with the decrease of preforms porosity and the prerforms characterized by 60% of porosity were characterized by the largest strength properties (bending strength Rg =7 MPa, compression strength Rc = 11.5 MPa, shear strength Rt = 4.0 MPa. The microscopic observations of fractures surfaces allow to evaluate quality and forming phenomena of the binder bridges connecting the ceramic particles.

  11. Synthesis and structures of metal chalcogenide precursors

    Science.gov (United States)

    Hepp, Aloysius F.; Duraj, Stan A.; Eckles, William E.; Andras, Maria T.

    1990-01-01

    The reactivity of early transition metal sandwich complexes with sulfur-rich molecules such as dithiocarboxylic acids was studied. Researchers recently initiated work on precursors to CuInSe2 and related chalcopyrite semiconductors. Th every high radiation tolerance and the high absorption coefficient of CuInSe2 makes this material extremely attractive for lightweight space solar cells. Their general approach in early transition metal chemistry, the reaction of low-valent metal complexes or metal powders with sulfur and selenium rich compounds, was extended to the synthesis of chalcopyrite precursors. Here, the researchers describe synthesis, structures, and and routes to single molecule precursors to metal chalcogenides.

  12. Manufacturing a Porous Structure According to the Process Parameters of Functional 3D Porous Polymer Printing Technology Based on a Chemical Blowing Agent

    Science.gov (United States)

    Yoo, C. J.; Shin, B. S.; Kang, B. S.; Yun, D. H.; You, D. B.; Hong, S. M.

    2017-09-01

    In this paper, we propose a new porous polymer printing technology based on CBA(chemical blowing agent), and describe the optimization process according to the process parameters. By mixing polypropylene (PP) and CBA, a hybrid CBA filament was manufactured; the diameter of the filament ranged between 1.60 mm and 1.75 mm. A porous polymer structure was manufactured based on the traditional fused deposition modelling (FDM) method. The process parameters of the three-dimensional (3D) porous polymer printing (PPP) process included nozzle temperature, printing speed, and CBA density. Porosity increase with an increase in nozzle temperature and CBA density. On the contrary, porosity increase with a decrease in the printing speed. For porous structures, it has excellent mechanical properties. We manufactured a simple shape in 3D using 3D PPP technology. In the future, we will study the excellent mechanical properties of 3D PPP technology and apply them to various safety fields.

  13. Synthesis of hierarchical porous carbon monoliths with incorporated metal-organic frameworks for enhancing volumetric based CO₂ capture capability.

    Science.gov (United States)

    Qian, Dan; Lei, Cheng; Hao, Guang-Ping; Li, Wen-Cui; Lu, An-Hui

    2012-11-01

    This work aims to optimize the structural features of hierarchical porous carbon monolith (HCM) by incorporating the advantages of metal-organic frameworks (MOFs) (Cu₃(BTC)₂) to maximize the volumetric based CO₂ capture capability (CO₂ capacity in cm³ per cm³ adsorbent), which is seriously required for the practical application of CO₂ capture. The monolithic HCM was used as a matrix, in which Cu₃(BTC)₂ was in situ synthesized, to form HCM-Cu₃(BTC)₂ composites by a step-by-step impregnation and crystallization method. The resulted HCM-Cu₃(BTC)₂ composites, which retain the monolithic shape and exhibit unique hybrid structure features of both HCM and Cu₃(BTC)₂, show high CO₂ uptake of 22.7 cm³ cm⁻³ on a volumetric basis. This value is nearly as twice as the uptake of original HCM. The dynamic gas separation measurement of HCM-Cu₃(BTC)₂, using 16% (v/v) CO₂ in N₂ as feedstock, illustrates that CO₂ can be easily separated from N₂ under the ambient conditions and achieves a high separation factor for CO₂ over N₂, ranging from 67 to 100, reflecting a strongly competitive CO₂ adsorption by the composite. A facile CO₂ release can be realized by purging an argon flow through the fixed-bed adsorber at 25 °C, indicating the good regeneration ability.

  14. Electromagnetic Behaviour of Metallic Wire Structures

    CERN Document Server

    Chui, S T

    2013-01-01

    Despite the recent development and interest in the photonics of metallic wire structures, the relatively simple concepts and physics often remain obscured or poorly explained to those who do not specialize in the field. Electromagnetic Behaviour of Metallic Wire Structures provides a clear and coherent guide to understanding these phenomena without excessive numerical calculations.   Including both background material and detailed derivations of the various different formulae applied, Electromagnetic Behaviour of Metallic Wire Structures describes how to extend basic circuit theory relating to voltages, currents, and resistances of metallic wire networks to include situations where the currents are no longer spatially uniform along the wire. This lays a foundation for a deeper understanding of the many new phenomena observed in meta-electromagnetic materials.   Examples of applications are included to support this new approach making Electromagnetic Behaviour of Metallic Wire Structures a comprehensive and ...

  15. Simulation of hot forming processes of refractory metals using porous metal plasticity models

    International Nuclear Information System (INIS)

    Parteder, E.; Riedel, H.; Sun, D.-Z.

    2001-01-01

    In this work two models for predicting the densification behavior of sintered refractory metals during hot working operations are presented. It is known from experiments and cell model calculations that the pore shape change has a significant influence on the densification behavior. Therefore this effect should be included in a continuum constitutive description. The first model presented is a phenomenological extension of the Gurson model, the second one is the model of Gologanu, Leblond and Devaux, which was implemented as a user material model into the finite-element-code ABAQUS. The numerical results are compared with the density distribution of a tapered disk made of pure molybdenum after the hot forming operation. (author)

  16. Experimental study on pore structure and performance of sintered porous wick

    Science.gov (United States)

    He, Da; Wang, Shufan; Liu, Rutie; Wang, Zhubo; Xiong, Xiang; Zou, Jianpeng

    2018-02-01

    Porous wicks were prepared via powder metallurgy using NH4HCO3 powders as pore-forming agent. The pore-forming agent particle size was varied to control the pore structure and equivalent pore size distribution feature of porous wick. The effect of pore-forming agent particle size on the porosity, pore structures, equivalent pore size distribution and capillary pumping performance were investigated. Results show that with the particle size of pore-forming agent decrease, the green density and the volume shrinkage of the porous wicks gradually increase and the porosity reduces slightly. There are two types of pores inside the porous wick, large-sized prefabricated pores and small-sized gap pores. With the particle size of pore-forming agent decrease, the size of the prefabricated pores becomes smaller and the distribution tends to be uniform. Gap pores and prefabricated pores inside the wick can make up different types of pore channels. The equivalent pore size of wick is closely related to the structure of pore channels. Furthermore, the equivalent pore size distribution of wick shows an obvious double-peak feature when the pore-forming agent particle size is large. With the particle size of pore-forming agent decrease, the two peaks of equivalent pore size distribution approach gradually to each other, resulting in a single-peak feature. Porous wick with single-peak feature equivalent pore size distribution possesses the better capillary pumping performances.

  17. Deformed metals - structure, recrystallisation and strength

    DEFF Research Database (Denmark)

    Hansen, Niels; Juul Jensen, Dorte

    2011-01-01

    It is shown how new discoveries and advanced experimental techniques in the last 25 years have led to paradigm shifts in the analysis of deformation and annealing structures of metals and in the way the strength of deformed samples is related to structural parameters. This is described in three...... sections: structural evolution by grain subdivision, recovery and recrystallisation and strength-structure relationships....

  18. Structural and optical properties in porous nanostructured semiconductors

    CERN Document Server

    Parkinson, M

    1998-01-01

    1st shell Si-Si co-ordination numbers and peak PL output to size changes in PS nanocrystallites. Ge K-edge EXAFS has been used to characterise porous Si sub x Ge sub 1 sub - sub x and, in conjunction with time-resolved luminescence, to assess this materials suitability for devices relative to PS. Time-resolved luminescence has been used to assess the spectral output of PS. The results indicate that quantum confinement is a strong factor in causing the blue-shifted PL emission of PS. In addition, detailed results of the temperature dependence of the PL have been obtained and mechanisms proposed to explain the blue shift of the PL peak as the temperature of the PS is reduced. The study of non-radiative processes in PS has allowed us to move a step closer to potential device applications using this material. Non-radiative processes in porous silicon (PS) have been examined using a variety of techniques to examine the effects on photoluminescence (PL) in order to determine the nature of the PL process and the abi...

  19. Structural analysis of highly porous γ-Al{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Samain, Louise [Department of Materials and Environmental Chemistry, Stockholm University, S-10691 Stockholm (Sweden); Jaworski, Aleksander; Edén, Mattias [Department of Materials and Environmental Chemistry, Physical Chemistry Division, Stockholm University, S-10691 Stockholm (Sweden); Ladd, Danielle M.; Seo, Dong-Kyun [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604 (United States); Javier Garcia-Garcia, F. [ICTS Centro Nacional de Microscopía Electrónica, Facultad CC. Químicas, Universidad Complutense de Madrid, Madrid E-28040 (Spain); Häussermann, Ulrich, E-mail: Ulrich.Haussermann@mmk.se.se [Department of Materials and Environmental Chemistry, Stockholm University, S-10691 Stockholm (Sweden)

    2014-09-15

    Two highly porous γ-aluminas, a commercial catalyst obtained from the calcination of boehmite and a highly mesoporous product obtained from amorphous aluminum (oxy)hydroxide via a sol–gel-based process were investigated by {sup 27}Al nuclear magnetic resonance (NMR), transmission electron microscopy (TEM), and atomic pair distribution function (PDF) analysis of synchrotron powder diffraction data. NMR data showed for both materials a distribution of tetrahedrally and octahedrally coordinated Al at a 0.30:0.70 ratio, which is typical for γ-aluminas. TEM studies revealed that rod-shaped particles with about 5 nm in thickness are the building blocks of the porous structure in both materials. These particles often extend to a length of 50 nm in the commercial catalyst and are considerably shorter in the sol–gel-based material, which has a higher surface area. Refinement of PDFs revealed the presence of a ∼1 nm scale local structure and the validity of a tetragonal average structure for both materials. This tetragonal average structure contains a substantial fraction of non-spinel octahedral Al atoms. It is argued that the presence of local structure is a general feature of γ-alumina, independent of precursor and synthesis conditions. The concentration of “non-spinel” Al atoms seems to correlate with surface properties, and increases with increasing pore size/surface area. This should have implications to the catalytic properties of porous γ-alumina. - Graphical abstract: Boehmite-derived and sol–gel synthesized porous γ-Al{sub 2}O{sub 3} possess identical structural properties, featuring a nm scale local structure and a tetragonal average structure. - Highlights: • Porous γ-Al{sub 2}O{sub 3} generally possesses a nm-scale local structure. • The tetragonal average structure contains a substantial fraction of “non-spinel” Al atoms. • The concentration of “non-spinel” Al atoms correlates with surface properties.

  20. Metal structures with parallel pores

    Science.gov (United States)

    Sherfey, J. M.

    1976-01-01

    Four methods of fabricating metal plates having uniformly sized parallel pores are studied: elongate bundle, wind and sinter, extrude and sinter, and corrugate stack. Such plates are suitable for electrodes for electrochemical and fuel cells.

  1. Structural modification of silicon during the formation process of porous silicon

    International Nuclear Information System (INIS)

    Martin-Palma, R.J.; Pascual, L.; Landa-Canovas, A.R.; Herrero, P.; Martinez-Duart, J.M.

    2005-01-01

    Direct examination of porous silicon (PS) by the use of high resolution transmission electron microscopy (HRTEM) allowed us to perform a deep insight into the formation mechanisms of this material. In particular, the structure of the PS/Si interface and that of the silicon nanocrystals that compose porous silicon were analyzed in detail. Furthermore, image processing was used to study in detail the structure of PS. The mechanism of PS formation and lattice matching between the PS layer and the Si substrate is analyzed and discussed. Finally, a formation mechanism for PS based on the experimental observations is proposed

  2. Pore structure and mechanical properties of directionally solidified porous aluminum alloys

    OpenAIRE

    Komissarchuk Olga; Xu Zhengbin; Hao Hai

    2014-01-01

    Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional solidification. Hydrogen is driven out of the melt, and then the quasi-cylindrical pores normal to the solidification front are usually formed. In the research, the effects of processing parameters (saturation pressure, solidification pressure, temperature, and holding time) on th...

  3. Palladium Nanoparticle Incorporated Porous Activated Carbon: Electrochemical Detection of Toxic Metal Ions.

    Science.gov (United States)

    Veerakumar, Pitchaimani; Veeramani, Vediyappan; Chen, Shen-Ming; Madhu, Rajesh; Liu, Shang-Bin

    2016-01-20

    A facile method has been developed for fabricating selective and sensitive electrochemical sensors for the detection of toxic metal ions, which invokes incorporation of palladium nanoparticles (Pd NPs) on porous activated carbons (PACs). The PACs, which were derived from waste biomass feedstock (fruit peels), possess desirable textural properties and porosities favorable for dispersion of Pd NPs (ca. 3-4 nm) on the graphitic PAC substrate. The Pd/PAC composite materials so fabricated were characterized by a variety of different techniques, such as X-ray diffraction, field-emission transmission electron microscopy, gas physisorption/chemisorption, thermogravimetric analysis, and Raman, Fourier-transform infrared, and X-ray photon spectroscopies. The Pd/PAC-modified glassy carbon electrodes (GCEs) were exploited as electrochemical sensors for the detection of toxic heavy metal ions, viz., Cd(2+), Pb(2+), Cu(2+), and Hg(2+), which showed superior performances for both individual as well as simultaneous detections. For simultaneous detection of Cd(2+), Pb(2+), Cu(2+), and Hg(2+), a linear response in the ion concentration range of 0.5-5.5, 0.5-8.9, 0.5-5.0, and 0.24-7.5 μM, with sensitivity of 66.7, 53.8, 41.1, and 50.3 μA μM(-1) cm(-2), and detection limit of 41, 50, 66, and 54 nM, respectively, was observed. Moreover, the Pd/PAC-modified GCEs also show perspective applications in detection of metal ions in real samples, as illustrated in this study for a milk sample.

  4. Porous Structured Ni-Fe-P Nanocubes Derived from a Prussian Blue Analogue as an Electrocatalyst for Efficient Overall Water Splitting.

    Science.gov (United States)

    Xuan, Cuijuan; Wang, Jie; Xia, Weiwei; Peng, Zongkai; Wu, Zexing; Lei, Wen; Xia, Kedong; Xin, Huolin L; Wang, Deli

    2017-08-09

    Exploring nonprecious metal electrocatalysts to replace the noble metal-based catalysts for full water electrocatalysis is still an ongoing challenge. In this work, porous structured ternary nickel-iron-phosphide (Ni-Fe-P) nanocubes were synthesized through one-step phosphidation of a Ni-Fe-based Prussian blue analogue. The Ni-Fe-P nanocubes exhibit a rough and loose porous structure on their surface under suitable phosphating temperature, which is favorable for the mass transfer and oxygen diffusion during the electrocatalysis process. As a result, Ni-Fe-P obtained at 350 °C with poorer crystallinity offers more unsaturated atoms as active sites to expedite the absorption of reactants. Additionally, the introduction of nickel improved the electronic structure and then reduced the charge-transfer resistance, which would result in a faster electron transport and an enhancement of the intrinsic electrocatalytic activities. Benefiting from the unique porous nanocubes and the chemical composition, the Ni-Fe-P nanocubes exhibit excellent hydrogen evolution reaction and oxygen evolution reaction activities in alkaline medium, with low overpotentials of 182 and 271 mV for delivering a current density of 10 mA cm -2 , respectively. Moreover, the Ni-Fe-P nanocubes show outstanding stability for sustained water splitting in the two-electrode alkaline electrolyzer. This work not only provides a facile approach for designing bifunctional electrocatalysts but also further extends the application of metal-organic frameworks in overall water splitting.

  5. Production of large-scale, freestanding vanadium pentoxide nanobelt porous structures

    Science.gov (United States)

    Yun, Yong Ju; Kim, Byung Hoon; Hong, Won G.; Kim, Chang Hee; Kim, Yark Yeon; Jeong, Eun-Ju; Jang, Won Ick; Yu, Han Young

    2012-02-01

    Large-scale, freestanding, porous structures of vanadium pentoxide nanobelts (VPNs) were successfully prepared using the template-free freeze-drying method. The porous and multi-layered VPN macrostructures are composed of randomly oriented long nanobelts (over 100 μm) and their side length can be controlled up to a few tens of centimetres. Also, the bulk density and surface area of these macrostructures are 3-5 mg cm-3 and 40-80 m2 g-1, respectively, which are similar to those of the excellent adsorbents. In addition, the removal efficiency measurements of ammonia molecules revealed that the VPN porous structures can adsorb the ammonia molecules with the combinations of van der Waals forces and strong chemical bonding by functional groups on the VPN surface.

  6. Structure, composition and morphology of bioactive titanate layer on porous titanium surfaces

    Science.gov (United States)

    Li, Jinshan; Wang, Xiaohua; Hu, Rui; Kou, Hongchao

    2014-07-01

    A bioactive coating was produced on pore surfaces of porous titanium samples by an amendatory alkali-heat treatment method. Porous titanium was prepared by powder metallurgy and its porosity and average size were 45% and 135 μm, respectively. Coating morphology, coating structure and phase constituents were examined by SEM, XPS and XRD. It was found that a micro-network structure with sizes of bone-like carbonate-hydroxylapatite showing a good biocompatibility was detected on the coating surface. And the redundant Ca advanced the bioactivity of the coating. Thus, the present modification is expected to allow the use of the bioactive porous titanium as artificial bones even under load-bearing conditions.

  7. Cotransport of Herbaspirillum chlorophenolicum FA1 and heavy metals in saturated porous media: column studies and modeling approaches

    Science.gov (United States)

    Li, X.; Xu, H.; Wu, J.

    2017-12-01

    For in situ biodegradation of organic contaminants in soil and groundwater, precise prediction and monitoring of the movement of the bio-agent is vital for the effectiveness of the subsurface bioremediation technologies. Therefore, the fate and transport of functional microorganisms in porous media has been extensively investigated in the literature, and the effects of a number of physical and chemical factors have been explored. During the bioremediation of contaminated sites, it is highly likely that functional bacteria and heavy metals would be simultaneously present for heavy metals often co-exist with organic contaminants like polycyclic aromatic hydrocarbons (PAHs) in polluted environment. To date, relevant studies on the interactions between heavy metals and functional agents such as PAHs-degrading bacteria are lacking and thus require investigation. In this study, the cotransport of bioremediation agents and heavy metals were evaluated through batch and column experiments. Herbaspirillum chlorophenolicum FA1, a pure bacterial strain capable of absorbing heavy metals and degrading polycyclic aromatic hydrocarbons (PAHs), was used as the model remediation agent, and metal ions of Pb(Ⅱ) and Cd(Ⅱ) were used as the representative heavy metals. Effects of metal species, the concentration of heavy metals, the sequence of entering the media, and the activity of biomass were investigated in detail. In addition, numerical simulations of breakthrough curves (BTC) data were also performed for information gathering. Results of this study could advance our understanding of interactions between functional bacteria and heavy metals during bioremediation process and help to develop successful bioremediation strategies.This work was financially supported by the National Natural Science Foundation of China -Xinjiang Project (U1503282), the National Natural Science Foundation of China (41030746, 41102148), and the Natural Science Foundation of Jiangsu Province (BK20151385

  8. Recent advances in porous nanoparticles for drug delivery in antitumoral applications: inorganic nanoparticles and nanoscale metal-organic frameworks.

    Science.gov (United States)

    Baeza, Alejandro; Ruiz-Molina, Daniel; Vallet-Regí, María

    2017-06-01

    Nanotechnology has provided new tools for addressing unmet clinical situations, especially in the oncology field. The development of smart nanocarriers able to deliver chemotherapeutic agents specifically to the diseased cells and to release them in a controlled way has offered a paramount advantage over conventional therapy. Areas covered: Among the different types of nanoparticle that can be employed for this purpose, inorganic porous materials have received significant attention in the last decade due to their unique properties such as high loading capacity, chemical and physical robustness, low toxicity and easy and cheap production in the laboratory. This review discuss the recent advances performed in the application of porous inorganic and metal-organic materials for antitumoral therapy, paying special attention to the application of mesoporous silica, porous silicon and metal-organic nanoparticles. Expert opinion: The use of porous inorganic nanoparticles as drug carriers for cancer therapy has the potential to improve the life expectancy of the patients affected by this disease. However, much work is needed to overcome their drawbacks, which are aggravated by their hard nature, exploiting the advantages offered by highly the ordered pore network of these materials.

  9. Probing mesoscopic structures in hierarchically structured materials and porous media by small-angle scattering

    International Nuclear Information System (INIS)

    Sen, D.

    2010-01-01

    Small-angle neutron (SANS) and X-ray scattering (SAXS) are powerful techniques to investigate structural features of inhomogeneities i.e., the density fluctuations in condensed matter, on a length scale ranging from one nanometer up to one micron. 'Structural features' include size or size distribution, shape, dimensionality, inter-particle spatial correlation etc. Mesoscopic structure in hierarchically structured materials, where density fluctuations exist over a wide length scale, may be probed by combined usage of small-angle and ultra small-angle neutron or X-ray scattering. Such hierarchically structured micrometric grains may be synthesized by evaporation induced self assembly of nanoparticles. Rate of drying and physico-chemical properties of the virgin colloidal suspension are important aspects in determining the morphology of the grains as well as the inter-particle interactions within grains. Meso/macro pores can be templated in such grains by adding soft template materials and followed by calcinations. In this lecture, applications of SANS/SAXS on such hierarchically structured grains, synthesized by spray drying technique, will be discussed. In addition, a few applications of SANS/SAXS to probe porous materials and non-Euclidean systems will also be elaborated. In some cases, Monte Carlo based simulations have been performed in order to understand the observations from the scattering experiments and these will also be talked about. (author)

  10. Dynamic compressibility of air in porous structures at audible frequencies

    DEFF Research Database (Denmark)

    Lafarge, Denis; Lemarinier, Pavel; Allard, Jean F.

    1997-01-01

    Measurements of dynamic compressibility of air-filled porous sound-absorbing materials are compared with predictions involving two parametere, the static thermal permeability k'_0 and the thermal characteristic dimension GAMMA'. Emphasis on the notion of dynamic and static thermal permeability...... of the viscous forces. Using both parameters, a simple model is constructed for the dynamic thermal permeability k', which is completely analogous to the Johnson et al. [J. Fluid Mech. vol. 176, 379 (1987)] model of dynamic viscous permeability k. The resultant modeling of dynamic compressibility provides...... predictions which are closer to the experimental results than the previously used simpler model where the compressibility is the same as in identical circular cross-sectional shaped pores, or distributions of slits, related to a given GAMMA'....

  11. High temperature ceramic/metal joint structure

    Science.gov (United States)

    Boyd, Gary L. (Inventor)

    1991-01-01

    A high temperature turbine engine includes a hybrid ceramic/metallic rotor member having ceramic/metal joint structure. The disclosed joint is able to endure higher temperatures than previously possible, and aids in controlling heat transfer in the rotor member.

  12. Some interesting structural features and metallated hypervalent ...

    Indian Academy of Sciences (India)

    Administrator

    The metallation of hypervalent species/electron deficient molecules 1 of main group elements with transition metals through nucleophilic substitution reactions has resulted in the isolation of some novel products 2. These synthetic species have some interesting structural features. An overview of our experience in this field is ...

  13. Structure and properties of metals

    CERN Document Server

    Kurzydlowski, K J

    1999-01-01

    Metals are one of the most widely used types of engineering materials. Some of their properties, e.g. elastic constants, can be directly related to the nature of the metallic bonds between the atoms. On the other hand, macro- and $9 microstructural features of metals, such as point defects, dislocations, grain boundaries, and second phase particles, control their yield, flow, and fracture stress. Images of microstructural elements can be obtained by modern $9 imaging techniques. Modern computer aided methods can be further used to obtain a quantitative description of these microstructures. These methods take advantage of the progress made in recent years in the field of image processing, $9 mathematical morphology and quantitative stereology. Quantitative description of the microstructures are used for modeling processes taking place under the action of applied load at a given temperature and test (service) environment. $9 These model considerations can be illustrated on the example of an austenitic stainless...

  14. Heat removal from bipolar transistor by loop heat pipe with nickel and copper porous structures.

    Science.gov (United States)

    Nemec, Patrik; Smitka, Martin; Malcho, Milan

    2014-01-01

    Loop heat pipes (LHPs) are used in many branches of industry, mainly for cooling of electrical elements and systems. The loop heat pipe is a vapour-liquid phase-change device that transfers heat from evaporator to condenser. One of the most important parts of the LHP is the porous wick structure. The wick structure provides capillary force to circulate the working fluid. To achieve good thermal performance of LHP, capillary wicks with high permeability and porosity and fine pore radius are expected. The aim of this work was to develop porous structures from copper and nickel powder with different grain sizes. For experiment copper powder with grain size of 50 and 100 μm and nickel powder with grain size of 10 and 25 μm were used. Analysis of these porous structures and LHP design are described in the paper. And the measurements' influences of porous structures in LHP on heat removal from the insulated gate bipolar transistor (IGBT) have been made.

  15. Heat Removal from Bipolar Transistor by Loop Heat Pipe with Nickel and Copper Porous Structures

    Directory of Open Access Journals (Sweden)

    Patrik Nemec

    2014-01-01

    Full Text Available Loop heat pipes (LHPs are used in many branches of industry, mainly for cooling of electrical elements and systems. The loop heat pipe is a vapour-liquid phase-change device that transfers heat from evaporator to condenser. One of the most important parts of the LHP is the porous wick structure. The wick structure provides capillary force to circulate the working fluid. To achieve good thermal performance of LHP, capillary wicks with high permeability and porosity and fine pore radius are expected. The aim of this work was to develop porous structures from copper and nickel powder with different grain sizes. For experiment copper powder with grain size of 50 and 100 μm and nickel powder with grain size of 10 and 25 μm were used. Analysis of these porous structures and LHP design are described in the paper. And the measurements’ influences of porous structures in LHP on heat removal from the insulated gate bipolar transistor (IGBT have been made.

  16. Single-Crystal to Single-Crystal Transformation of a Nonporous Fe(II) Metal-Organic Framework into a Porous Metal-Organic Framework via a Solid-State Reaction.

    Science.gov (United States)

    Spirkl, Sebastian; Grzywa, Maciej; Reschke, Stephan; Fischer, Jonas K H; Sippel, Pit; Demeshko, Serhiy; Krug von Nidda, Hans-Albrecht; Volkmer, Dirk

    2017-10-16

    We report the synthesis of an air-stable nonporous coordination compound based on iron(II) centers, formate anions, and a 4,4'-bipyrazole (H 2 BPZ) ligand. Upon thermal treatment, a porous metal-organic framework (MOF) formed due to decomposition of the incorporated formate anions. This decomposition step and the following structural changes constituted a single-crystal to single-crystal transformation. The resulting [Fe(BPZ)] framework contained tetrahedrally coordinated iron(II) metal centers. The framework was sensitive toward oxidation by molecular oxygen even at temperatures of 183 K, as followed by oxygen sorption measurements and a color change from colorless to metallic black. The semiconductor properties of the oxidized material were studied by diffuse reflectance UV/vis/NIR spectroscopy and dielectric spectroscopy.

  17. Non-Fickian transport in porous media with bimodal structural heterogeneity.

    Science.gov (United States)

    Bijeljic, Branko; Rubin, Shira; Scher, Harvey; Berkowitz, Brian

    2011-03-01

    Tracer tailing in breakthrough curves in porous media with two distinct porosities is analyzed in terms of the dynamic responses of experimental fixed bed columns filled either with solid or porous beads. The flow is fast in the column interstitial space between beads (for both solid and porous beads) but slow within the porous beads that act as controlled 'traps' constituting an immobile zone. The transport is quantified using a Continuous Time Random Walk (CTRW) framework, which accounts for domains with controlled structural and flow heterogeneity associated with two distinct spatial and time spectra. We first demonstrate that breakthrough curves for a column containing solid glass beads exhibit non-Fickian transport, quantifiable both in fitting and validation mode by a CTRW based on a power law transition time distribution. We then examine breakthrough curves in the porous bead case, obtaining fits with a two-scale CTRW model that accounts explicitly for the two time spectra. Because the porous beads are uniform, tracer trapping within them is described by a simple first-order approximation trap model, with relatively weak capture and relatively faster release rates. The extent of tailing apparent in the porous bead breakthrough curves, due to the traps, can be quantitatively distinguished from the contribution to tailing due to mobile zone non-Fickian transport. A parameter study of the two-scale CTRW adds further insight into the dynamics of the process, showing the interaction between the advective non-Fickian transport and the mass exchange to immobile regions. Copyright © 2010 Elsevier B.V. All rights reserved.

  18. Electronic band structure in porous silicon studied by photoluminescence and photoluminescence excitation spectroscopy

    International Nuclear Information System (INIS)

    Lee, Ki-Won; Kim, Young-You

    2004-01-01

    In this research, we used photoluminescence (PL) and photoluminescence excitation (PLE) to visualize the electronic band structure in porous silicon (PS). From the combined results of the PLE measurements at various PL emission energies and the PL measurements under excitation at various PLE absorption energies, we infer that three different electronic band structures, originating from different luminescent origins, give rise to the PL spectrum. Through either thermal activation or diffusive transfer, excited carriers are moved to each of the electronic band structures.

  19. Surface Roughness and Morphology Customization of Additive Manufactured Open Porous Ti6Al4V Structures

    Science.gov (United States)

    Pyka, Grzegorz; Kerckhofs, Greet; Papantoniou, Ioannis; Speirs, Mathew; Schrooten, Jan; Wevers, Martine

    2013-01-01

    Additive manufacturing (AM) is a production method that enables the building of porous structures with a controlled geometry. However, there is a limited control over the final surface of the product. Hence, complementary surface engineering strategies are needed. In this work, design of experiments (DoE) was used to customize post AM surface treatment for 3D selective laser melted Ti6Al4V open porous structures for bone tissue engineering. A two-level three-factor full factorial design was employed to assess the individual and interactive effects of the surface treatment duration and the concentration of the chemical etching solution on the final surface roughness and beam thickness of the treated porous structures. It was observed that the concentration of the surface treatment solution was the most important factor influencing roughness reduction. The designed beam thickness decreased the effectiveness of the surface treatment. In this case study, the optimized processing conditions for AM production and the post-AM surface treatment were defined based on the DoE output and were validated experimentally. This allowed the production of customized 3D porous structures with controlled surface roughness and overall morphological properties, which can assist in more controlled evaluation of the effect of surface roughness on various functional properties. PMID:28788357

  20. Temperature induced development of porous structure of bituminous coal chars at high pressure

    Directory of Open Access Journals (Sweden)

    Natalia Howaniec

    2016-01-01

    Full Text Available The porous structure of chars affects their reactivity in gasification, having an impact on the course and product distribution of the process. The shape, size and connections between pores determine the mechanical properties of chars, as well as heat and mass transport in thermochemical processing. In the study the combined effects of temperature in the range of 973–1273 °K and elevated pressure of 3 MPa on the development of porous structure of bituminous coal chars were investigated. Relatively low heating rate and long residence time characteristic for the in-situ coal conversion were applied. The increase in the temperature to 1173 °K under pressurized conditions resulted in the enhancement of porous structure development reflected in the values of the specific surface area, total pore volume, micropore area and volume, as well as ratio of the micropore volume to the total pore volume. These effects were attributed to the enhanced vaporization and devolatilization, as well as swelling behavior along the increase of temperature and under high pressure, followed by a collapse of pores over certain temperature value. This proves the strong dependence of the porous structure of chars not only on the pyrolysis process conditions but also on the physical and chemical properties of the parent fuel.

  1. Mimicking Bone Healing Process to Self Repair Concrete Structure Novel Approach Using Porous Network Concrete

    NARCIS (Netherlands)

    Sangadji, S.; Schlangen, H.E.J.G.

    2013-01-01

    To repair concrete cracks in difficult or dangerous conditions such as underground structures or hazardous liquid containers, self healing mechanism is a promising alternative method. This research aims to imitate the bone self healing process by putting porous concrete internally in the concrete

  2. Surface Roughness and Morphology Customization of Additive Manufactured Open Porous Ti6Al4V Structures

    Directory of Open Access Journals (Sweden)

    Martine Wevers

    2013-10-01

    Full Text Available Additive manufacturing (AM is a production method that enables the building of porous structures with a controlled geometry. However, there is a limited control over the final surface of the product. Hence, complementary surface engineering strategies are needed. In this work, design of experiments (DoE was used to customize post AM surface treatment for 3D selective laser melted Ti6Al4V open porous structures for bone tissue engineering. A two-level three-factor full factorial design was employed to assess the individual and interactive effects of the surface treatment duration and the concentration of the chemical etching solution on the final surface roughness and beam thickness of the treated porous structures. It was observed that the concentration of the surface treatment solution was the most important factor influencing roughness reduction. The designed beam thickness decreased the effectiveness of the surface treatment. In this case study, the optimized processing conditions for AM production and the post-AM surface treatment were defined based on the DoE output and were validated experimentally. This allowed the production of customized 3D porous structures with controlled surface roughness and overall morphological properties, which can assist in more controlled evaluation of the effect of surface roughness on various functional properties.

  3. Preparation of interconnected highly porous polymeric structures by a replication and freeze-drying process

    NARCIS (Netherlands)

    Hou, Q.; Grijpma, Dirk W.; Feijen, Jan

    2003-01-01

    Three-dimensional degradable porous polymeric structures with high porosities (93-98%) and well-interconnected pore networks have been prepared by freeze-drying polymer solutions in the presence of a leachable template followed by leaching of the template. Templates of the pore network were prepared

  4. Improved Modeling Approaches for Constrained Sintering of Bi-Layered Porous Structures

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Frandsen, Henrik Lund; Esposito, Vincenzo

    2012-01-01

    Shape instabilities during constrained sintering experiment of bi-layer porous and dense cerium gadolinium oxide (CGO) structures have been analyzed. An analytical and a numerical model based on the continuum theory of sintering has been implemented to describe the evolution of bow and densificat...

  5. Fabrication of Meso-Porous Sintered Metal Thin Films by Selective Etching of Silica Based Sacrificial Template

    Directory of Open Access Journals (Sweden)

    Ludovic F. Dumee

    2014-08-01

    Full Text Available Meso-porous metal materials have enhanced surface energies offering unique surface properties with potential applications in chemical catalysis, molecular sensing and selective separation. In this paper, commercial 20 nm diameter metal nano-particles, including silver and copper were blended with 7 nm silica nano-particles by shear mixing. The resulted powders were cold-sintered to form dense, hybrid thin films. The sacrificial silica template was then removed by selective etching in 12 wt% hydrofluoric acid solutions for 15 min to reveal a purely metallic meso-porous thin film material. The impact of the initial silica nano-particle diameter (7–20 nm as well as the sintering pressure (5–20 ton·m−2 and etching conditions on the morphology and properties of the final nano-porous thin films were investigated by porometry, pyknometery, gas and liquid permeation and electron microscopy. Furthermore, the morphology of the pores and particle aggregation during shear mixing were assessed through cross-sectioning by focus ion beam milling. It is demonstrated that meso-pores ranging between 50 and 320 nm in average diameter and porosities up to 47% can be successfully formed for the range of materials tested.

  6. Porous graphene-based membranes for water purification from metal ions at low differential pressures.

    Science.gov (United States)

    Park, Jaewoo; Bazylewski, Paul; Fanchini, Giovanni

    2016-05-14

    A new generation of membranes for water purification based on weakly oxidized and nanoporous few-layer graphene is here introduced. These membranes dramatically decrease the high energy requirements of water purification by reverse osmosis. They combine the advantages of porous and non-oxidized single-layer graphene, offering energy-efficient water filtration at relatively low differential pressures, and highly oxidized graphene oxide, exhibiting high performance in terms of impurity adsorption. In the reported fabrication process, leaks between juxtaposed few-layer graphene flakes are sealed by thermally annealed colloidal silica, in a treatment that precedes the opening of (sub)nanometre-size pores in graphene. This process, explored for the first time in this work, results in nanoporous graphene flakes that are water-tight at the edges without occluding the (sub)nanopores. With this method, removal of impurities from water occurs through a combination of size-based pore rejection and pore-edge adsorption. Thinness of graphene flakes allows these membranes to achieve water purification from metal ions in concentrations of few parts-per-million at differential pressures as low as 30 kPa, outperforming existing graphene or graphene oxide purification systems with comparable flow rates.

  7. Asymmetric supercapacitors with metal-like ternary selenides and porous graphene electrodes

    KAUST Repository

    Xia, Chuan

    2016-04-14

    Asymmetric supercapacitors provide a promising approach to fabricate capacitive energy storage devices with high energy and power densities. In this work, asymmetric supercapacitors with excellent performance have been fabricated using ternary (Ni, Co)0.85Se on carbon fabric as bind-free positive electrode and porous free-standing graphene films as negative electrode. Owing to their metal-like conductivity (~1.67×106 S m−1), significant electrochemical activity, and superhydrophilic nature, our nanostructured ternary nickel cobalt selenides result in a much higher areal capacitance (2.33 F cm−2 at 4 mA cm−2), better rate performance and cycling stability than their binary selenide equivalents, and other ternary oxides and chalcogenides. Those hybrid supercapacitors can afford impressive areal capacitance and stack capacitance of 529.3 mF cm−2 and 6330 mF cm−3 at 1 mA cm−2, respectively. More impressively, our optimized asymmetric device operating at 1.8 V delivers a very high stack energy density of 2.85 mWh cm−3 at a stack power density of 10.76 mW cm−3, as well as 85% capacitance retention after 10,000 continuous charge-discharge cycles. Even at a high stack power density of 1173 mW cm−3, this device still deliveries a stack energy density of 1.19 mWh cm−3, superior to most of the reported supercapacitors.

  8. Design and Synthesis of Novel Porous Metal-Organic Frameworks (MOFs) Toward High Hydrogen Storage Capacity

    Energy Technology Data Exchange (ETDEWEB)

    Mohamed, Eddaoudi [USF; Zaworotko, Michael [USF; Space, Brian [USF; Eckert, Juergen [USF

    2013-05-08

    Statement of Objectives: 1. Synthesize viable porous MOFs for high H2 storage at ambient conditions to be assessed by measuring H2 uptake. 2. Develop a better understanding of the operative interactions of the sorbed H2 with the organic and inorganic constituents of the sorbent MOF by means of inelastic neutron scattering (INS, to characterize the H2-MOF interactions) and computational studies (to interpret the data and predict novel materials suitable for high H2 uptake at moderate temperatures and relatively low pressures). 3. Synergistically combine the outcomes of objectives 1 and 2 to construct a made-to-order inexpensive MOF that is suitable for super H2 storage and meets the DOE targets - 6% H2 per weight (2kWh/kg) by 2010 and 9% H2 per weight (3kWh/kg) by 2015. The ongoing research is a collaborative experimental and computational effort focused on assessing H2 storage and interactions with pre-selected metal-organic frameworks (MOFs) and zeolite-like MOFs (ZMOFs), with the eventual goal of synthesizing made-to-order high H2 storage materials to achieve the DOE targets for mobile applications. We proposed in this funded research to increase the amount of H2 uptake, as well as tune the interactions (i.e. isosteric heats of adsorption), by targeting readily tunable MOFs:

  9. Cleavable porous silicon based hybrid material for pre-enrichment of trace heavy metal ions

    Energy Technology Data Exchange (ETDEWEB)

    Li Shaoyuan [National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology, Kunming 650093 (China); Faculty of Metallurgical and energy engineering, Kunming University of Science and Technology, Kunming 650093 (China); Ma Wenhui, E-mail: mwhsilicon@163.com [National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology, Kunming 650093 (China) and Faculty of Metallurgical and energy engineering, Kunming University of Science and Technology, Kunming 650093 (China); Zhou Yang, E-mail: zhouyangnano@163.com [National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology, Kunming 650093 (China) and Faculty of Metallurgical and energy engineering, Kunming University of Science and Technology, Kunming 650093 (China); Wang Yanfeng [Faculty of Metallurgical and energy engineering, Kunming University of Science and Technology, Kunming 650093 (China); Li Wei [National Engineering Laboratory for Vacuum Metallurgy, Kunming University of Science and Technology, Kunming 650093 (China); Faculty of Metallurgical and energy engineering, Kunming University of Science and Technology, Kunming 650093 (China); Chen Xiuhua [Faculty of Physical Science and Technology, Yunnan University, Kunming 650091 (China)

    2012-05-15

    The paper reports on the preparation of the cleavable porous silicon (PSi) based hybrid material and application in pre-enrichment of trace heavy metal ions. The cleavable groups (benzimidazoledithio) were grafted on the PSi surface by a stepwise covalent process. PSi was first obtained by anodization of bulk silicon wafers and was subsequently silanized by 3-mercaptopropyltriethoxysilane (MPTS) to synthesize MPTS-PSi, the MPTS-PSi was further converted into pyridyldithio-terminated PSi (PDT-PSi), and finally, the PDT-PSi reacted with 2-mercaptobenzimidazole to form the benzimidazoledithio modified PSi (BDT-PSi). Scanning electron microscopy (SEM) was used to characterize the morphology of freshly prepared and modified PSi. Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy were performed to confirm the effectiveness of each step graft. According to the UV-vis spectra analysis, the disulfide linkage of BDT-PSi can be dissociated in presence of reduced glutathione (GSH). The pre-enrichment efficiency of BDT-PSi was investigated at the different pH for the different metal species (Cd, Hg, Pb, Cu and Co). The results show that the BDT-PSi possesses a similar preferential adsorption trend (Cd > Cu Much-Greater-Than Hg {approx} Pb {approx} Co) at different pH (from 2.0 to 6.0). At pH 5.0, the best pre-enrichment efficiency for Cd ions is observed, the concentration of Cd is increased more than ten times and the recovery is found to be 95.4%.

  10. Cleavable porous silicon based hybrid material for pre-enrichment of trace heavy metal ions

    Science.gov (United States)

    Li, Shaoyuan; Ma, Wenhui; Zhou, Yang; Wang, Yanfeng; Li, Wei; Chen, Xiuhua

    2012-05-01

    The paper reports on the preparation of the cleavable porous silicon (PSi) based hybrid material and application in pre-enrichment of trace heavy metal ions. The cleavable groups (benzimidazoledithio) were grafted on the PSi surface by a stepwise covalent process. PSi was first obtained by anodization of bulk silicon wafers and was subsequently silanized by 3-mercaptopropyltriethoxysilane (MPTS) to synthesize MPTS-PSi, the MPTS-PSi was further converted into pyridyldithio-terminated PSi (PDT-PSi), and finally, the PDT-PSi reacted with 2-mercaptobenzimidazole to form the benzimidazoledithio modified PSi (BDT-PSi). Scanning electron microscopy (SEM) was used to characterize the morphology of freshly prepared and modified PSi. Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy were performed to confirm the effectiveness of each step graft. According to the UV-vis spectra analysis, the disulfide linkage of BDT-PSi can be dissociated in presence of reduced glutathione (GSH). The pre-enrichment efficiency of BDT-PSi was investigated at the different pH for the different metal species (Cd, Hg, Pb, Cu and Co). The results show that the BDT-PSi possesses a similar preferential adsorption trend (Cd > Cu ≫ Hg ˜ Pb ˜ Co) at different pH (from 2.0 to 6.0). At pH 5.0, the best pre-enrichment efficiency for Cd ions is observed, the concentration of Cd is increased more than ten times and the recovery is found to be 95.4%.

  11. Preparation and applications of monolithic structures containing metal-organic frameworks.

    Science.gov (United States)

    Lv, Yongqin; Tan, Xinyi; Svec, Frantisek

    2017-01-01

    Metal-organic frameworks are a new category of advanced porous materials with large surface areas and porosities, uniform pore sizes, tunable surface chemistry, and structural diversity. In combination with monoliths, they allow the fine tuning of desired interactions required in a variety of applications. This review article summarizes results of recent studies focused on synthetic strategies enabling incorporation of metal-organic frameworks in monolithic structures. A diverse array of applications including chromatographic separation, solid-phase microextraction, sample enrichment, heterogeneous catalysis, and enzymatic catalysis are also described. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Minerals with metal-organic framework structures.

    Science.gov (United States)

    Huskić, Igor; Pekov, Igor V; Krivovichev, Sergey V; Friščić, Tomislav

    2016-08-01

    Metal-organic frameworks (MOFs) are an increasingly important family of advanced materials based on open, nanometer-scale metal-organic architectures, whose design and synthesis are based on the directed assembly of carefully designed subunits. We now demonstrate an unexpected link between mineralogy and MOF chemistry by discovering that the rare organic minerals stepanovite and zhemchuzhnikovite exhibit structures found in well-established magnetic and proton-conducting metal oxalate MOFs. Structures of stepanovite and zhemchuzhnikovite, exhibiting almost nanometer-wide and guest-filled apertures and channels, respectively, change the perspective of MOFs as exclusively artificial materials and represent, so far, unique examples of open framework architectures in organic minerals.

  13. Metal-Matrix Composites and Porous Materials: Constitute Models, Microstructure Evolution and Applications

    National Research Council Canada - National Science Library

    Castafieda, P

    2000-01-01

    Constitutive models were developed and implemented numerically to account for the evolution of microstructure and anisotropy in finite-deformation processes involving porous and composite materials...

  14. Smart release of doxorubicin loaded on polyetheretherketone (PEEK) surface with 3D porous structure.

    Science.gov (United States)

    Ouyang, Liping; Sun, Zhenjie; Wang, Donghui; Qiao, Yuqin; Zhu, Hongqin; Ma, Xiaohan; Liu, Xuanyong

    2018-03-01

    It is important to fabricate an implant possessing environment sensitive drug delivery. In this work, the construction of 3D porous structure on polyetheretherketone (PEEK) surface and pH sensitive polymer, chitosan, was introduced. The smart release of doxorubicin can be realized on the 3D porous surface of PEEK loading chitosan. We give a feasible explanation for the effect of chitosan on smart drug release according to Henderson-Hasselbalch equation. Furthermore, the intracellular drug content of the cell cultured on the samples with highest chitosan is significantly higher at pH 4.0, whereas lower at pH 7.4 than other samples. The smart release of doxorubicin via modification with chitosan onto 3D porous PEEK surface paves the way for the application of PEEK in drug loading platform for recovering bone defect caused by malignant bone tumor. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Hierarchically Porous Carbon Materials for CO 2 Capture: The Role of Pore Structure

    Energy Technology Data Exchange (ETDEWEB)

    Estevez, Luis [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Barpaga, Dushyant [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Zheng, Jian [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Sabale, Sandip [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Patel, Rajankumar L. [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Zhang, Ji-Guang [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; McGrail, B. Peter [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Motkuri, Radha Kishan [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States

    2018-01-17

    With advances in porous carbon synthesis techniques, hierarchically porous carbon (HPC) materials are being utilized as relatively new porous carbon sorbents for CO2 capture applications. These HPC materials were used as a platform to prepare samples with differing textural properties and morphologies to elucidate structure-property relationships. It was found that high microporous content, rather than overall surface area was of primary importance for predicting good CO2 capture performance. Two HPC materials were analyzed, each with near identical high surface area (~2700 m2/g) and colossally high pore volume (~10 cm3/g), but with different microporous content and pore size distributions, which led to dramatically different CO2 capture performance. Overall, large pore volumes obtained from distinct mesopores were found to significantly impact adsorption performance. From these results, an optimized HPC material was synthesized that achieved a high CO2 capacity of ~3.7 mmol/g at 25°C and 1 bar.

  16. Pore structure, mechanical properties and polymer characteristics of porous materials impregnated with methylmethacrylate

    International Nuclear Information System (INIS)

    Hastrup, K.

    1976-05-01

    The pore structure of porous materials plays a decisive role with regard to many properties of the materials. One therefore expects property improvement due to impregnation to be mostly brought about as a result of pore structure modification. This supposition formed the basis for the project here presented, which had the main aim of investigating polymer impregnation in relation to pore structure. Objectives were: 1) to examine the pore structure of hardened cement paste, beech wood and porous glass before and after gas-phase impregnation with methyl-methacrylate monomer and in situ polymerization, 2) to investigate the influence of the pore structure on the molecular weight of the polymer, 3) to investigate the influence of the degree of pore filling on the elastic modulus, damping coefficient and bending strength. (author)

  17. Light Modulation and Water Splitting Enhancement Using a Composite Porous GaN Structure.

    Science.gov (United States)

    Yang, Chao; Xi, Xin; Yu, Zhiguo; Cao, Haicheng; Li, Jing; Lin, Shan; Ma, Zhanhong; Zhao, Lixia

    2018-02-14

    On the basis of the laterally porous GaN, we designed and fabricated a composite porous GaN structure with both well-ordered lateral and vertical holes. Compared to the plane GaN, the composite porous GaN structure with the combination of the vertical holes can help to reduce UV reflectance and increase the saturation photocurrent during water splitting by a factor of ∼4.5. Furthermore, we investigated the underlying mechanism for the enhancement of the water splitting performance using a finite-difference time-domain method. The results show that the well-ordered vertical holes can not only help to open the embedded pore channels to the electrolyte at both sides and reduce the migration distance of the gas bubbles during the water splitting reactions but also help to modulate the light field. Using this composite porous GaN structure, most of the incident light can be modulated and trapped into the nanoholes, and thus the electric fields localized in the lateral pores can increase dramatically as a result of the strong optical coupling. Our findings pave a new way to develop GaN photoelectrodes for highly efficient solar water splitting.

  18. Adsorption by and artificial release of zinc and lead from porous concrete for recycling of adsorbed zinc and lead and of porous concrete to reduce urban non-point heavy metal runoff.

    Science.gov (United States)

    Harada, Shigeki; Yanbe, Miyu

    2018-04-01

    This report describes the use of porous concrete at the bottom of a sewage trap to prevent runoff of non-point heavy metals into receiving waters, and, secondarily, to reduce total runoff volume during heavy rains in urbanized areas while simultaneously increasing the recharge volume of heavy-metal-free water into underground aquifers. This idea has the advantage of preventing clogging, which is fundamentally very important when using pervious materials. During actual field experiments, two important parameters were identified: maximum adsorption weight of lead and zinc by the volume of porous concrete, and heavy metal recovery rate by artificial acidification after adsorption. To understand the effect of ambient heavy metal concentration, a simple mixing system was used to adjust the concentrations of lead and zinc solutions. The concrete blocks used had been prepared for a previous study by Harada & Komuro (2010). The results showed that maximum adsorption depended on the ambient concentration, expressed as the linear isothermal theory, and that recovery depended on the final pH value (0.5 or 0.0). The dependence on pH is very important for recycling the porous concrete. A pH of 0.5 is important for recycling both heavy metals, especially zinc, (8.0-22.1% of lead and 42-74% of zinc) and porous concrete because porous concrete has not been heavily damaged by acid. However, at a pH of 0.0, the heavy metals could be recovered: 30-60% of the lead and 75-125% of the zinc. At a higher pH, such as 2.0, no release of heavy metals occurred, indicating the safety to the environment of using porous concrete, because the lowest recorded pH of rainfall in Japan is. 4.0. Copyright © 2018 Elsevier Ltd. All rights reserved.

  19. Topological representation of the porous structure and its evolution of reservoir sandstone under excavation-induced loads

    Directory of Open Access Journals (Sweden)

    Ju Yang

    2017-01-01

    Full Text Available The porous structure of a reservoir rock greatly influences its evolutive deformation and fracture behavior during excavation of natural resources reservoirs. Most numerical models for porous structures have been used to predict the quasi-static mechanical properties, but few are available to accurately characterize the evolution process of the porous structure and its influence on the macroscopic properties of reservoir rocks. This study reports a novel method to characterize the porous structure of sandstone using its topological parameters and to determine the laws that govern the evolutive deformation and failure of the topological structure under various uniaxial compressive loads. A numerical model of the porous sandstone was established based on the pore characteristics that were acquired using computed tomography imaging techniques. The analytical method that integrates the grassfire algorithm and the maximum inscribed sphere algorithm was proposed to create the 3-D topological model of the deformed porous structure, through which the topological parameters of the structure were measured and identified. The evolution processes of the porous structure under various loads were characterized using its equivalent topological model and parameters. This study opens a new way to characterize the dynamic evolution of the pore structure of reservoir sandstone under excavation disturbance.

  20. Metal-organic frameworks: structure, properties, methods of synthesis and characterization

    International Nuclear Information System (INIS)

    Butova, V V; Soldatov, M A; Guda, A A; Lomachenko, K A; Lamberti, C

    2016-01-01

    This review deals with key methods of synthesis and characterization of metal-organic frameworks (MOFs). The modular structure affords a wide variety of MOFs with different active metal sites and organic linkers. These compounds represent a new stage of development of porous materials in which the pore size and the active site structure can be modified within wide limits. The set of experimental methods considered in this review is sufficient for studying the short-range and long-range order of the MOF crystal structure, determining the morphology of samples and elucidating the processes that occur at the active metal site in the course of chemical reactions. The interest in metal-organic frameworks results, first of all, from their numerous possible applications, ranging from gas separation and storage to chemical reactions within the pores. The bibliography includes 362 references

  1. Applications of hierarchically structured porous materials from energy storage and conversion, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine.

    Science.gov (United States)

    Sun, Ming-Hui; Huang, Shao-Zhuan; Chen, Li-Hua; Li, Yu; Yang, Xiao-Yu; Yuan, Zhong-Yong; Su, Bao-Lian

    2016-06-13

    Over the last decade, significant effort has been devoted to the applications of hierarchically structured porous materials owing to their outstanding properties such as high surface area, excellent accessibility to active sites, and enhanced mass transport and diffusion. The hierarchy of porosity, structural, morphological and component levels in these materials is key for their high performance in all kinds of applications. The introduction of hierarchical porosity into materials has led to a significant improvement in the performance of materials. Herein, recent progress in the applications of hierarchically structured porous materials from energy conversion and storage, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine is reviewed. Their potential future applications are also highlighted. We particularly dwell on the relationship between hierarchically porous structures and properties, with examples of each type of hierarchically structured porous material according to its chemical composition and physical characteristics. The present review aims to open up a new avenue to guide the readers to quickly obtain in-depth knowledge of applications of hierarchically porous materials and to have a good idea about selecting and designing suitable hierarchically porous materials for a specific application. In addition to focusing on the applications of hierarchically porous materials, this comprehensive review could stimulate researchers to synthesize new advanced hierarchically porous solids.

  2. Preparation and Characterization of a Hydrophobic Metal-Organic Framework Membrane Supported on Thin Porous Metal Sheet

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jian; Canfield, Nathan L.; Liu, Wei

    2016-02-29

    A hydrophobic metal-organic framework (MOF) UiO-66-CH3 is prepared and its solvothermal stability is investigated in comparison to UiO-66. It is confirmed that the MOF stability is enhanced by introduction of the two methyl groups, while the water adsorption is reduced. Given its hydrophobicity and stability, UiO-66-CH3 is proposed as an attractive membrane material for gas separation under moisture conditions. The UiO-66-CH3 membrane is prepared on a 50µm-thin porous Ni support sheet for the first time by use of a secondary growth method. It is found that uniform seed coating on the support is necessary to form a continuous membrane. In addition to growth time and temperature, presence of a modulator in the growth solution is found to be useful for controlling hydrothermal membrane growth on the seeded support. A dense, inter-grown membrane layer is formed by 24-h growth over a temperature range from 120 oC to 160 oC. The membrane surface comprises 500 nm octahedral crystals, which are supposed to grow out of the original 100 nm spherical seeding crystals. The separation characteristics of resulting membranes are tested with pure CO2, air, CO2/air mixture, and humid CO2/air mixture. CO2 permeance as high as 1.9E-06 mol/m2/s/Pa at 31oC is obtained. Unlike the hydrophilic zeolite membranes, CO2 permeation through this membrane is not blocked by the presence of water vapor in the feed gas. The results suggest that this MOF framework is a promising membrane material worth to be further investigated for separation of CO2 and other small molecules from humid gas mixtures.

  3. Power handling of a liquid-metal based CPS structure under high steady-state heat and particle fluxes

    NARCIS (Netherlands)

    Morgan, T. W.; Vertkov, A.; Bystrov, K.; Lyublinski, I.; Genuit, J. W.; Mazzitelli, G.

    2017-01-01

    Liquid metal infused capillary porous structures (CPSs) are considered as a potential divertor solution for DEMO due to their potential power handling capability and resilience to long term damage. In this work the power handling and performance of such Sn-based CPS systems is assessed both

  4. Three-dimensional pore structure and ion conductivity of porous ceramic diaphragms

    OpenAIRE

    Wiedenmann, Daniel; Keller, Lukas; Holzer, Lorenz; Stojadinović, Jelena; Münch, Beat; Suarez, Laura; Fumey, Benjamin; Hagendorfer, Harald; Brönnimann, Rolf; Modregger, Peter; Gorbar, Michal; Vogt, Ulrich F.; Züttel, Andreas; Mantia, Fabio La; Wepf, Roger

    2013-01-01

    The ion conductivity of two series of porous ceramic diaphragms impregnated with caustic potash was investigated by electrochemical impedance spectroscopy. To understand the impact of the pore structure on ion conductivity, the three-dimensional (3-D) pore geometry of the diaphragms was characterized with synchrotron x-ray absorption tomography. Ion migration was calculated based on an extended pore structure model, which includes the electrolyte conductivity and geometric pore parameters, fo...

  5. Manipulation of fluids in three-dimensional porous photonic structures with patterned surface properties

    Energy Technology Data Exchange (ETDEWEB)

    Aizenberg, Joanna; Burgess, Ian; Mishchenko, Lidiya; Hatton, Benjamin; Loncar, Marko

    2017-12-26

    A three-dimensional porous photonic structure, whose internal pore surfaces can be provided with desired surface properties in a spatially selective manner with arbitrary patterns, and methods for making the same are described. When exposed to a fluid (e.g., via immersion or wicking), the fluid can selectively penetrate the regions of the structure with compatible surface properties. Broad applications, for example in security, encryption and document authentication, as well as in areas such as simple microfluidics and diagnostics, are anticipated.

  6. Super high conductivity effect in metal-polymer-metal structures

    Science.gov (United States)

    Ionov, Alexander N.; Zakrevskii, V. A.; Svetlichny, V. M.; Rentzsch, R.

    2003-06-01

    We have observed that films of a polyimide precursor of poly[4,4'-bis(4"-N-phenoxy)diphenyl-sulfone] amid acid of 1,3-bis(3',4-dicarboxyphenoxy) benzene which is called type (1) polymer- or co-poly[4,4'-bis(4"-N-phenoxy)diphenyl-sulfone-α,ω-bis(η-amino propyl)oligodimethylsiloxane]imide of 1,3-bis(3',4-dicarboxyphenoxy)benzene type (2) polymer, placed between two metallic electrodes become highly conducting in a relatively small electric field (E<1 V/cm). If the metallic electrodes (Sn, Nb) in sandwich structures were in the superconducting state an effective resistance of zero was recorded. A typical current-voltage characteristic of an S-P-S structure looks like a Josephson type. We hve experimentally shown that for a S-P-S structure, a point contact between the superconductor and the polymer film plays the role of a weak link.

  7. Studies on metal-dielectric plasmonic structures.

    Energy Technology Data Exchange (ETDEWEB)

    Chettiar, Uday K. (Purdue University, West Lafayette, IN); Liu, Zhengtong (Purdue University, West Lafayette, IN); Thoreson, Mark D. (Purdue University, West Lafayette, IN); Shalaev, Vladimir M. (Purdue University, West Lafayette, IN); Drachev, Vladimir P. (Purdue University, West Lafayette, IN); Pack, Michael Vern; Kildishev, Alexander V. (Purdue University, West Lafayette, IN); Nyga, Piotr (Purdue University, West Lafayette, IN)

    2010-01-01

    The interaction of light with nanostructured metal leads to a number of fascinating phenomena, including plasmon oscillations that can be harnessed for a variety of cutting-edge applications. Plasmon oscillation modes are the collective oscillation of free electrons in metals under incident light. Previously, surface plasmon modes have been used for communication, sensing, nonlinear optics and novel physics studies. In this report, we describe the scientific research completed on metal-dielectric plasmonic films accomplished during a multi-year Purdue Excellence in Science and Engineering Graduate Fellowship sponsored by Sandia National Laboratories. A variety of plasmonic structures, from random 2D metal-dielectric films to 3D composite metal-dielectric films, have been studied in this research for applications such as surface-enhanced Raman sensing, tunable superlenses with resolutions beyond the diffraction limit, enhanced molecular absorption, infrared obscurants, and other real-world applications.

  8. Structural analysis of porous rock reservoirs subjected to conditions of compressed air energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Friley, J.R.

    1980-01-01

    Investigations are described which were performed to assess the structural behavior of porous rock compressed air energy storage (CAES) reservoirs subjected to loading conditions of temperature and pressure felt to be typical of such an operation. Analyses performed addressed not only the nominal or mean reservoir response but also the cyclic response due to charge/discharge operation. The analyses were carried out by assuming various geometrical and material related parameters of a generic site. The objective of this study was to determine the gross response of a generic porous reservoir. The site geometry for this study assumed a cylindrical model 122 m in dia and 57 m high including thicknesses for the cap, porous, and base rock formations. The central portion of the porous zone was assumed to be at a depth of 518 m and at an initial temperature of 20/sup 0/C. Cyclic loading conditions of compressed air consisted of pressure values in the range of 4.5 to 5.2 MPa and temperature values between 143 and 204/sup 0/C.Various modes of structural behavior were studied. These response modes were analyzed using loading conditions of temperature and pressure (in the porous zone) corresponding to various operational states during the first year of simulated site operation. The results of the structural analyses performed indicate that the most severely stressed region will likely be in the wellbore vicinity and hence highly dependent on the length of and placement technique utilized in the well production length. Analyses to address this specific areas are currently being pursued.

  9. Highly porous micro-roughened structures developed on aluminum surface using the jet of rotating arc discharges at atmospheric pressure

    Science.gov (United States)

    Asadollahi, Siavash; Farzaneh, Masoud; Stafford, Luc

    2018-02-01

    Aluminum 6061 samples were exposed to the jet of an atmospheric pressure rotating arc discharge operated in either nitrogen or air. After multiple passes of treatment with an air-based plasma jet at very short source-to-substrate distances, scanning electron microscopy combined with x-ray photoelectron spectroscopy revealed a highly porous micro-roughened alumina-based structure on the surface of aluminum. Based on optical emission spectroscopy and high-speed optical imaging of the jet interacting with aluminum samples, it was found that the process is mainly driven by the energy transfer from the plasma source to the surface through transient plasma-transferred arcs. The occurrence of multiple arc discharges over very short time scales can induce rapid phase transformations of aluminum with characteristics similar to the ones usually observed during laser ablation of materials with femto- to nanosecond laser pulses or during the formation of cathode spots on the surface of metals.

  10. Design of water debinding and dissolution stages of metal injection moulded porous Ti foam production

    OpenAIRE

    Shbeh, M.M.; Goodall, R.

    2015-01-01

    Foams are advanced materials with controlled meso- and micro-structure, with huge potential in a variety of applications such as in the biomedical and automotive sectors. One promising technique for the production of Ti foams is Metal Injection Moulding in combination with Space Holders (MIMSH). Most existing work in the literature on MIM-SH foams reports very long debinding and dissolution periods that can extend for more than two days. In this paper, the effect on process speed of different...

  11. Magneto-mechanical impedance of metallic structures.

    Science.gov (United States)

    Zagrai, Andrei N

    2009-01-01

    Impedance measurements with a magneto-elastic active sensor are explored for inferring the magneto-mechanical impedance (MMI) of a metallic structure. It is shown that the MMI contains electrical response of the sensor and both electrical and mechanical structural responses. An analytical model is suggested that accounts for electrical characteristics of the sensor, sensor/structure electromagnetic interaction, and multimodal structural dynamic behavior. The model is validated with a set of MMI experiments demonstrating feasibility of deducing structural natural frequencies and structural vibration modes.

  12. A novel approach for the fabrication of carbon nanofibre/ceramic porous structures

    KAUST Repository

    Walter, Claudia

    2013-11-01

    This paper describes the fabrication of hybrid ceramic/carbon scaffolds in which carbon nanofibres and multi-walled carbon nanotubes fully cover the internal walls of a microporous ceramic structure that provides mechanical stability. Freeze casting is used to fabricate a porous, lamellar ceramic (Al2O3) structure with aligned pores whose width can be controlled between 10 and 90μm. Subsequently, a two step chemical vapour deposition process that uses iron as a catalyst is used to grow the carbon nanostructures inside the scaffold. This catalyst remains in the scaffold after the growth process. The formation of the alumina scaffold and the influence of its structure on the growth of nanofibres and tubes are investigated. A set of growth conditions is determined to produce a dense covering of the internal walls of the porous ceramic with the carbon nanostructures. The limiting pore size for this process is located around 25μm. © 2013 Elsevier Ltd.

  13. Synthesis of LiMnPO4 porous structures under mixed solvents system.

    Science.gov (United States)

    Pei, Zhenzhao; Zhang, Xia; Gao, Xiang

    2013-04-01

    Porous structure LiMnPO4 with pore size from 4 to 9 nm was successfully synthesized in mixed solvents. By changing ratios of glycerol to distilled water and stirring time, LiMnPO4 morphologies were adjusted. Shuttles with different sizes and porous structure of LiMnPO4 were formed in sequence. Ratio of glycerol to distilled water influences the solubility of LiMnPO4 and solutions viscosity. This factor and stirring time are both causes influencing the nucleation rate and diffusion rate of the initial formed particles of final products. Through adjusting these factors, chemicals with specific morphology can be obtained. The phase composition was investigated by X-ray diffraction (XRD), and the microstructure was verified by transmission electron microscopy (TEM). This synthetic method provides us a new idea to obtain new structure materials.

  14. Monodisperse Carbon Nanospheres with Hierarchical Porous Structure as Electrode Material for Supercapacitor

    Science.gov (United States)

    Yang, Xiutao; Xia, Hui; Liang, Zhongguan; Li, Haiyan; Yu, Hongwen

    2017-09-01

    Carbon nanospheres with distinguishable microstructure were prepared by carbonization and subsequent KOH activation of F108/resorcinol-formaldehyde composites. The dosage of triblock copolymer Pluronic F108 is crucial to the microstructure differences. With the adding of F108, the polydisperse carbon nanospheres (PCNS) with microporous structure, monodisperse carbon nanospheres (MCNS) with hierarchical porous structure, and agglomerated carbon nanospheres (ACNS) were obtained. Their microstructure and capacitance properties were carefully compared. As a result of the synergetic effect of mono-dispersion spheres and hierarchical porous structures, the MCNS sample shows improved electrochemical performance, i.e., the highest specific capacitance of 224 F g-1 (0.2 A g-1), the best rate capability (73% retention at 20 A g-1), and the most excellent capacitance retention of 93% over 10,000 cycles, making it to be the promising electrode material for high-performance supercapacitors.

  15. Development of a Computer Application to Simulate Porous Structures

    Directory of Open Access Journals (Sweden)

    S.C. Reis

    2002-09-01

    Full Text Available Geometric modeling is an important tool to evaluate structural parameters as well as to follow the application of stereological relationships. The obtention, visualization and analysis of volumetric images of the structure of materials, using computational geometric modeling, facilitates the determination of structural parameters of difficult experimental access, such as topological and morphological parameters. In this work, we developed a geometrical model implemented by computer software that simulates random pore structures. The number of nodes, number of branches (connections between nodes and the number of isolated parts, are obtained. Also, the connectivity (C is obtained from this application. Using a list of elements, nodes and branches, generated by the software, in AutoCAD® command line format, the obtained structure can be viewed and analyzed.

  16. Supercritical Carbon Dioxide-Soluble Ligands for Extracting Actinide Metal Ions from Porous Solids

    International Nuclear Information System (INIS)

    Dietz, Mark L.

    2001-01-01

    Numerous types of actinide-bearing waste materials are found throughout the DOE complex. Most of these wastes consist of large volumes of non-hazardous materials contaminated with relatively small quantities of actinide elements. Separation of these wastes into their inert and radioactive components would dramatically reduce the costs of stabilization and disposal. For example, the DOE is responsible for decontaminating concrete within 7000 surplus contaminated buildings. The best technology now available for removing surface contamination from concrete involves removing the surface layer by grit blasting, which produces a large volume of blasting residue containing a small amount of radioactive material. Disposal of this residue is expensive because of its large volume and fine particulate nature. Considerable cost savings would result from separation of the radioactive constituents and stabilization of the concrete dust. Similarly, gas diffusion plants for uranium enrichment contain valuable high-purity nickel in the form of diffusion barriers. Decontamination is complicated by the extremely fine pores in these barriers, which are not readily accessible by most cleaning techniques. A cost-effective method for the removal of radioactive contaminants would release this valuable material for salvage. The objective of this project is to develop novel, substituted diphosphonic acid ligands that can be used for supercritical carbon dioxide extraction of actinide ions from solid wastes. Specifically, selected diphosphonic acids, which are known to form extremely stable complexes with actinides in aqueous and organic solution, are to be rendered carbon dioxide-soluble by the introduction of appropriate alkyl- or silicon-containing substituents. The metal complexation chemistry of these new ligands in SC-CO2 will then be investigated and techniques for their use in actinide extraction from porous solids developed

  17. 3D modelling of microscopic structure of ring‑porous wood

    Directory of Open Access Journals (Sweden)

    R. Neugebauer

    2009-01-01

    Full Text Available Nowadays many scientific 3D models of wood are available. These models are suitable only for simulation of physical fields movements in wood but not for educational purposes especially demonstration of microscopic structure of wood.3D structure of ring-porous hardwood species was created. European ash (Faraxinus excelsior L. was selected due to its relatively simple wood structure than other wood species within ring-porous group. The model was created by manual modelling process in Rhinoceros 4.0 that is a software for visualization and modelling. Microslides were prepared from sample of ash to take micro photos that were used as a visual source for modelling. Beside these pictures made by authors of this paper other microphotos from wood anatomy publications were used. Created 3D model of ash is a VRML object (Virtual Reality Modelling Language. This format is available to viewing and presentation with severe freeware VRML browsers. These VRML browsers are available as a plug-in for standard internet browsers or as standalone VRML browsers. The model is useful for studying and teaching microscopic structure of ring‑porous hardwood species. It was created such a way to be as exact copy of original anatomical structure of ash wood as possible. The paper may be used as a cue for other authors to create their own 3D models of different wood kinds.

  18. [Application of UV spectroscopy in structural studies of metal centre of metal-protein].

    Science.gov (United States)

    Liang, H; Zhou, Y; Shen, P

    1997-02-01

    The principle of UV spectroscopy applied in structural studies of metal centre of complexes is introduced in this paper. Several examples prove that such spectroscopy is an effective technical method in structural studies of metal centre of metal-protein.

  19. CTAB-Assisted Hydrothermal Synthesis of WO3 Hierarchical Porous Structures and Investigation of Their Sensing Properties

    Directory of Open Access Journals (Sweden)

    Dan Meng

    2015-01-01

    Full Text Available WO3 hierarchical porous structures were successfully synthesized via cetyltrimethylammonium bromide- (CTAB- assisted hydrothermal method. The structure and morphology were investigated using scanning electron microscope, X-ray diffractometer, transmission electron microscopy, X-ray photoelectron spectra, Brunauer-Emmett-Teller nitrogen adsorption-desorption, and thermogravimetry and differential thermal analysis. The result demonstrated that WO3 hierarchical porous structures with an orthorhombic structure were constructed by a number of nanoparticles about 50–100 nm in diameters. The H2 gas sensing measurements showed that well-defined WO3 hierarchical porous structures with a large specific surface area exhibited the higher sensitivity compared with products without CTAB at all operating temperatures. Moreover, the reversible and fast response to H2 gas and good selectivity were obtained. The results indicated that the WO3 hierarchical porous structures are promising materials for gas sensors.

  20. Small angle neutron and X-ray studies of carbon structures with metal atoms

    Science.gov (United States)

    Lebedev, V. T.; Szhogina, A. A.; Bairamukov, V. Yu

    2017-05-01

    Encapsulation of metal atoms inside carbon single-wall cages or within multi-layer cells has been realized using molecular precursors and high temperature processes transforming them into desirable structures. Endohedral fullerenols Fe@C60(OH)X with 3d-metal (iron) have been studied by SANS in aqueous solutions where they form stable globular clusters with radii R C ∼ 10-12 nm and aggregation numbers N C ∼ 104. This self-assembly is a crucial feature of paramagnetic fullerenols as perspective contrast agents for Magneto-Resonance Imaging in medicine. Cellular carbon-metal structures have been created by the pyrolysis of diphthalocyanines of lanthanides and actinides. It was established that these ultra porous matrices consist of globular cells of molecular precursor size (∼ 1 nm) which are aggregated into superstructures. This provides retain of metal atoms inside matrices which may serve for safety storage of spent fuel of nuclear power plants.

  1. Small angle neutron and X-ray studies of carbon structures with metal atoms

    International Nuclear Information System (INIS)

    Lebedev, V T; Szhogina, A A; Yu Bairamukov, V

    2017-01-01

    Encapsulation of metal atoms inside carbon single-wall cages or within multi-layer cells has been realized using molecular precursors and high temperature processes transforming them into desirable structures. Endohedral fullerenols Fe@C 60 (OH) X with 3d-metal (iron) have been studied by SANS in aqueous solutions where they form stable globular clusters with radii R C ∼ 10-12 nm and aggregation numbers N C ∼ 10 4 . This self-assembly is a crucial feature of paramagnetic fullerenols as perspective contrast agents for Magneto-Resonance Imaging in medicine. Cellular carbon-metal structures have been created by the pyrolysis of diphthalocyanines of lanthanides and actinides. It was established that these ultra porous matrices consist of globular cells of molecular precursor size (∼ 1 nm) which are aggregated into superstructures. This provides retain of metal atoms inside matrices which may serve for safety storage of spent fuel of nuclear power plants. (paper)

  2. Designing of Metallic Photonic Structures and Applications

    International Nuclear Information System (INIS)

    Yong-Sung Kim

    2006-01-01

    In this thesis our main interest has been to investigate metallic photonic crystal and its applications. We explained how to solve a periodic photonic structure with transfer matrix method and when and how to use modal expansion method. Two different coating methods were introduced, modifying a photonic structure's intrinsic optical properties and rigorous calculation results are presented. Two applications of metallic photonic structures are introduced. For thermal emitter, we showed how to design and find optimal structure. For conversion efficiency increasing filter, we calculated its efficiency and the way to design it. We presented the relation between emitting light spectrum and absorption and showed the material and structural dependency of the absorption spectrum. By choosing a proper base material and structural parameters, we can design a selective emitter at a certain region we are interested in. We have developed a theoretical model to analyze a blackbody filament enclosed by a metallic mesh which can increase the efficiency of converting a blackbody radiation to visible light. With this model we found that a square lattice metallic mesh enclosing a filament might increase the efficiency of incandescent lighting sources. Filling fraction and thickness dependency were examined and presented. Combining these two parameters is essential to achieve the maximum output result

  3. Robust hydrophobic polyurethane fibrous membranes with tunable porous structure for waterproof and breathable application

    Science.gov (United States)

    Gu, Jiatai; Gu, Haihong; Cao, Jin; Chen, Shaojie; Li, Ni; Xiong, Jie

    2018-05-01

    In this work, novel nanofibrous membranes with waterproof and breathable (W&B) performance were successfully fabricated by the combination of electrospinning and surface modification technology. This fibrous membranes consisted of polyurethane (PU), NaCl, and fluoroalkylsilane (FAS). Firstly, The fibrous construction and porous structure of fibrous membranes were regulated by tuning the NaCl concentrations in PU solutions. Then, the obtained PU/NaCl fibrous membranes were further modified with fluoroalkylsilane (FAS) to improve hydrophobic property. The synergistic effect of porous structure and hydrophobicity on waterproof and breathable performance was investigated. Furthermore, the mechanical property of fibrous membranes was deeply analysed on the basis of macromolecule orientation and adhesive structure. Benefiting from the optimized porous structure and hydrophobic modification, the resultant fibrous membranes exhibited excellent waterproof (hydrostatic pressure of 1261 Mbar), breathable (water vapor transmission (WVT) rate of 9.06 kg m-2 d-1 and air permeability of 4.8 mm s-1) performance, as well as high tensile strength (breakage stress of 10.4 MPa), suggesting a promising candidate for various applications, especially in protective clothing.

  4. Pore structures and mechanical properties of porous titanium scaffolds by bidirectional freeze casting.

    Science.gov (United States)

    Yan, Leiming; Wu, Jisi; Zhang, Lei; Liu, Xinli; Zhou, Kechao; Su, Bo

    2017-06-01

    Porous titanium scaffolds with long-range lamellar structure were fabricated using a novel bidirectional freeze casting method. Compared with the ordinarily porous titanium materials made by traditional freeze casting, the titanium walls can offer the structure of ordered arrays with parallel to each other in the transverse cross-sections. And titanium scaffolds with different pore width, wall size and porosity can be synthesized in terms of adjusting the fabrication parameters. As the titanium content was increased from 15vol.% to 25vol.%, the porosity and pore width decreased from 67±3% to 50±2% and 80±10μm to 67±7μm, respectively. On the contrary, as the wall size was increased from 18±2μm to 30±3μm, the compressive strength and stiffness were increased from 58±8MPa to 162±10MPa and from 2.5±0.7GPa to 6.5±0.9GPa, respectively. The porous titanium scaffolds with long-range lamellar structure and controllable pore structure produced in present work will be capable of having potential application as bone tissue scaffold materials. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. High adsorptive γ-AlOOH(boehmite)@SiO2/Fe3O4 porous magnetic microspheres for detection of toxic metal ions in drinking water.

    Science.gov (United States)

    Wei, Yan; Yang, Ran; Zhang, Yong-Xing; Wang, Lun; Liu, Jin-Huai; Huang, Xing-Jiu

    2011-10-21

    γ-AlOOH(boehmite)@SiO(2)/Fe(3)O(4) porous magnetic microspheres with high adsorption capacity toward heavy metal ions were found to be useful for the simultaneous and selective electrochemical detection of five metal ions, such as ultratrace zinc(II), cadmium(II), lead(II), copper(II), and mercury(II), in drinking water.

  6. Synthesis-Structure-Performance Relationships for Supported Metal Catalysts

    NARCIS (Netherlands)

    Munnik, Peter|info:eu-repo/dai/nl/328228524

    2014-01-01

    Heterogeneous catalysts, which consist of many metal nanoparticles supported on highly porous, mechanically strong and chemically inert supports, are at the center of many existing as well as new and more sustainable processes, such as energy conversion and storage, nanoelectronics and the catalytic

  7. Structure and assembly of scalable porous protein cages

    NARCIS (Netherlands)

    Sasaki, Eita; Böhringer, Daniel; van de Waterbeemd, Michiel; Leibundgut, Marc; Zschoche, Reinhard; Heck, Albert J R; Ban, Nenad; Hilvert, Donald

    2017-01-01

    Proteins that self-assemble into regular shell-like polyhedra are useful, both in nature and in the laboratory, as molecular containers. Here we describe cryo-electron microscopy (EM) structures of two versatile encapsulation systems that exploit engineered electrostatic interactions for cargo

  8. Chemical synthesis of porous web-structured CdS thin films for photosensor applications

    International Nuclear Information System (INIS)

    Gosavi, S.R.; Nikam, C.P.; Shelke, A.R.; Patil, A.M.; Ryu, S.-W.; Bhat, J.S.; Deshpande, N.G.

    2015-01-01

    The photo-activity of chemically deposited cadmium sulphide (CdS) thin film has been studied. The simple chemical route nucleates the CdS films with size up to the mean free path of the electron. Growth Kinematics of crystalline hexagonal CdS phase in the thin film form was monitored using X-ray diffraction. The time limitation set for the formation of the amorphous/nano-crystalline material is 40 and 60 min. Thereafter enhancement of the crystalline orientation along the desired plane was identified. Web-like porous structured surface morphology of CdS thin film over the entire area is observed. With decrease in synthesis time, increase of band gap energy i.e., a blue spectral shift was seen. The activation energy of CdS thin film at low and high temperature region was examined. It is considered that this activation energy corresponds to the donor levels associated with shallow traps or surface states of CdS thin film. The photo-electrochemical performance of CdS thin films in polysulphide electrolyte showed diode-like characteristics. Exposure of light on the CdS electrode increases the photocurrent. This suggests the possibility of production of free carriers via excited ions and also the light harvesting mechanism due to porous web-structured morphology. These studies hint that the obtained CdS films can work as a photosensor. - Highlights: • Photoactivity of chemically synthesized cadmium sulphide (CdS) thin films was studied. • Web-like porous structured surface morphology of CdS thin film over the entire area was observed. • Blue spectral shift with lowering of the synthesis time suggests films can act as a window layer over the absorber layer. • Porous web-structured CdS thin films can be useful in light harvesting

  9. Method for Impeding Degradation of Porous Silicon Structures

    Science.gov (United States)

    Vilentchouk, Biana Godin; Ferrari, Mauro

    2011-01-01

    This invention relates to surface modification of porosified silicon (pSi) structures with poly(alkylene) glycols for the purpose of controlled degradation of the silicon matrix and tailored release of encapsulated substances for biomedical applications. The pSi structures are currently used in diverse biomedical applications including bio-molecular screening, optical bio-sensoring, and drug delivery by means of injectable/orally administered carriers and implantable devices. The size of the pores and the surface chemistry of the pSi structure can be controlled during the microfabrication process and thereafter. A fine regulation of the degradation kinetics of mesoporous silicon structures is of fundamental importance. Polyethylene glycols (PEGs) represent the major category of surface modifying agents used in classical drug delivery systems and in pharmaceutical dosage forms. PEGylation enables avoidance of RES uptake, thus prolonging circulation time of intravenously injectable nanovectors. PEG molecules demonstrate little toxicity and immunogenicity, and are cleared from the body through the urine (molecular weight, MW less than 30 kDa) or in the feces (MW greater than 30kDa). The invention focuses on the possibility of finely tuning the degradation kinetics of the pSi nanovectors and other structures through surface conjugation of PEGs with various backbone lengths/MWs. To prove the concept, pSi nanovectors were covalently conjugated to seven PEGs with MW from 245 to 5,000 Da and their degradation kinetics in physiologically relevant media (phosphate buffer saline, PBS pH7.4, and fetal bovine serum) was assessed by the elemental analysis of the Si using inductive coupled plasma atomic emission spectroscopy (ICP-AES). The conjugation of the PEG with lowest MW to the nanovectors surface did not induce any change in the degradation kinetics in serum, but inhibited degradation and consequently the release of orthosilicic acid into buffer. When PEGs with the longer

  10. Effect of process control agent on the porous structure and mechanical properties of a biomedical Ti-Sn-Nb alloy produced by powder metallurgy.

    Science.gov (United States)

    Nouri, A; Hodgson, P D; Wen, C E

    2010-04-01

    The influence of different amounts and types of process control agent (PCA), i.e., stearic acid and ethylene bis-stearamide, on the porous structure and mechanical properties of a biomedical Ti-16Sn-4Nb (wt.%) alloy was investigated. Alloy synthesis was performed on elemental metal powders using high-energy ball milling for 5h. Results indicated that varying the PCA content during ball milling led to a drastic change in morphology and particle-size distribution of the ball-milled powders. Porous titanium alloy samples sintered from the powders ball milled with the addition of various amounts of PCA also revealed different pore morphology and porosity. The Vickers hardness of the sintered titanium alloy samples exhibited a considerable increase with increasing PCA content. Moreover, the addition of larger amounts of PCA in the powder mixture resulted in a significant increase in the elastic modulus and peak stress for the sintered porous titanium alloy samples under compression. It should also be mentioned that the addition of PCA introduced contamination (mainly carbon and oxygen) into the sintered porous product. Crown Copyright 2009. Published by Elsevier Ltd. All rights reserved.

  11. Structure and assembly of scalable porous protein cages

    Science.gov (United States)

    Sasaki, Eita; Böhringer, Daniel; van de Waterbeemd, Michiel; Leibundgut, Marc; Zschoche, Reinhard; Heck, Albert J. R.; Ban, Nenad; Hilvert, Donald

    2017-03-01

    Proteins that self-assemble into regular shell-like polyhedra are useful, both in nature and in the laboratory, as molecular containers. Here we describe cryo-electron microscopy (EM) structures of two versatile encapsulation systems that exploit engineered electrostatic interactions for cargo loading. We show that increasing the number of negative charges on the lumenal surface of lumazine synthase, a protein that naturally assembles into a ~1-MDa dodecahedron composed of 12 pentamers, induces stepwise expansion of the native protein shell, giving rise to thermostable ~3-MDa and ~6-MDa assemblies containing 180 and 360 subunits, respectively. Remarkably, these expanded particles assume unprecedented tetrahedrally and icosahedrally symmetric structures constructed entirely from pentameric units. Large keyhole-shaped pores in the shell, not present in the wild-type capsid, enable diffusion-limited encapsulation of complementarily charged guests. The structures of these supercharged assemblies demonstrate how programmed electrostatic effects can be effectively harnessed to tailor the architecture and properties of protein cages.

  12. On the structure of heavy metals

    International Nuclear Information System (INIS)

    Friedel, J.

    1958-01-01

    The properties of the last series of Mendeleef's table are compared with those of the elements of the preceding series. This comparison suggests an electronic structure of the 'transition metal' type, with narrow bands, at the beginning of this series (up to certain phases at least of plutonium); then of the rare earth metal type, with independent non-saturated internal layers, further on in the series. The 5 f orbits seem to play an important part in these two types of structure, from uranium on. A more detailed study of the very heavy elements (americium and beyond) and alloys would allow these conclusions to be confirmed. Certain general points, concerning the nature of homopolar connections and paramagnetism in the transition metals, are developed in an additional section. (author) [fr

  13. Electronic structure of hcp transition metals

    DEFF Research Database (Denmark)

    Jepsen, O.; Andersen, O. Krogh; Mackintosh, A. R.

    1975-01-01

    Using the linear muffin-tin-orbital method described in the previous paper, we have calculated the electronic structures of the hcp transition metals, Zr, Hf, Ru, and Os. We show how the band structures of these metals may be synthesized from the sp and d bands, and illustrate the effects...... of hybridization, relativistic band shifts, and spin-orbit coupling by the example of Os. By making use of parameters derived from the muffin-tin potential, we discuss trends in the positions and widths of the energy bands, especially the d bands, as a function of the location in the periodic table. The densities...... of states of the four metals are presented, and the calculated heat capacities compared with experiment. The Fermi surfaces of both Ru and Os are found to be in excellent quantitative agreement with de Haas-van Alphen measurements, indicating that the calculated d-band position is misplaced by less than 10...

  14. Atomic layer deposition TiO2 coated porous silicon surface: Structural characterization and morphological features

    International Nuclear Information System (INIS)

    Iatsunskyi, Igor; Jancelewicz, Mariusz; Nowaczyk, Grzegorz; Kempiński, Mateusz; Peplińska, Barbara; Jarek, Marcin; Załęski, Karol; Jurga, Stefan; Smyntyna, Valentyn

    2015-01-01

    TiO 2 thin films were grown on highly-doped p-Si (100) macro- and mesoporous structures by atomic layer deposition (ALD) using TiCl 4 and deionized water as precursors at 300 °C. The crystalline structure, chemical composition, and morphology of the deposited films and initial silicon nanostructures were investigated by scanning electron microscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy and X-ray diffraction (XRD). The mean size of TiO 2 crystallites was determined by TEM, XRD and Raman spectroscopy. It was shown that the mean crystallite size and the crystallinity of the TiO 2 are influenced dramatically by the morphology of the porous silicon, with the mesoporous silicon resulting in a much finer grain size and amorphous structure than the macroporous silicon having a partially crystal anatase phase. A simple model of the ALD layer growth inside the pores was presented. - Highlights: • The morphology and chemical composition of TiO 2 and porous Si were established. • The approximate size of TiO 2 nanocrystals was estimated. • The model of the atomic layer deposition coating in the porous Si was presented

  15. Enhanced Transdermal Permeability via Constructing the Porous Structure of Poloxamer-Based Hydrogel

    Directory of Open Access Journals (Sweden)

    Wen-Yi Wang

    2016-11-01

    Full Text Available A major concern for transdermal drug delivery systems is the low bioavailability of targeted drugs primarily caused by the skin’s barrier function. The resistance to the carrier matrix for the diffusion and transport of drugs, however, is routinely ignored. This study reports a promising and attractive approach to reducing the resistance to drug transport in the carrier matrix, to enhance drug permeability and bioavailability via enhanced concentration-gradient of the driving force for transdermal purposes. This approach simply optimizes and reconstructs the porous channel structure of the carrier matrix, namely, poloxamer 407 (P407-based hydrogel matrix blended with carboxymethyl cellulose sodium (CMCs. Addition of CMCs was found to distinctly improve the porous structure of the P407 matrix. The pore size approximated to normal distribution as CMCs were added and the fraction of pore number was increased by over tenfold. Transdermal studies showed that P407/CMCs saw a significant increase in drug permeability across the skin. This suggests that P407/CMC with improved porous structure exhibits a feasible and promising way for the development of transdermal therapy with high permeability and bioavailability, thereby avoiding or reducing use of any chemical enhancers.

  16. Effects of Artificial Ligaments with Different Porous Structures on the Migration of BMSCs

    Directory of Open Access Journals (Sweden)

    Chun-Hui Wang

    2015-01-01

    Full Text Available Polyethylene terephthalate- (PET- based artificial ligaments (PET-ALs are commonly used in anterior cruciate ligament (ACL reconstruction surgery. The effects of different porous structures on the migration of bone marrow mesenchymal stem cells (BMSCs on artificial ligaments and the underlying mechanisms are unclear. In this study, a cell migration model was utilized to observe the migration of BMSCs on PET-ALs with different porous structures. A rabbit extra-articular graft-to-bone healing model was applied to investigate the in vivo effects of four types of PET-ALs, and a mechanical test and histological observation were performed at 4 weeks and 12 weeks. The BMSC migration area of the 5A group was significantly larger than that of the other three groups. The migration of BMSCs in the 5A group was abolished by blocking the RhoA/ROCK signaling pathway with Y27632. The in vivo study demonstrated that implantation of 5A significantly improved osseointegration. Our study explicitly demonstrates that the migration ability of BMSCs can be regulated by varying the porous structures of the artificial ligaments and suggests that this regulation is related to the RhoA/ROCK signaling pathway. Artificial ligaments prepared using a proper knitting method and line density may exhibit improved biocompatibility and clinical performance.

  17. Antibacterial Characteristics of Lotus-Type Porous Copper

    OpenAIRE

    Lee, Jin-Soo; Lee, Yun-Soo; Kim, Mok-Soon; Hyun, Soong-Keun; Kang, Chang-Ho; So, Jae-Seong; Yoon, Eui-Han

    2013-01-01

    Lotus-type porous copper with long cylindrical pores aligned parallel to the solidification direction was studied for use as an antibacterial material. The antibacterial performance of lotus-type porous copper samples with different specific surface areas against Escherichia coli was investigated. The results confirmed that the antibacterial effect gradually increased with specific surface area. The correlation between the pore structure of lotus-type porous metals and their antibacterial eff...

  18. EXAFS study on dynamic structural property of porous morph-genetic SiC

    International Nuclear Information System (INIS)

    Ding, J.; Sun, B.H.; Fan, T.X.; Zhang, D.; Kamada, M.; Ogawa, H.; Guo, Q.X.

    2005-01-01

    Novel porous morph-genetic silicon carbide has been fabricated through sintering treatment, after infiltrating the methyl organic silicone resin to the bio-template. Its dynamic transition of structure during sintering process is investigated by extended X-ray absorption fine structure (EXAFS) for the first time. By analyzing Si K-edge EXAFS, it is found that the coordination number of the nearest C shell remains almost unchanged while that of the nearest Si shell dramatically changes when the structure is transformed from amorphous into crystalline state

  19. Porous structure of oxide bismuth-molybdenum catalysts applied to silica gel

    International Nuclear Information System (INIS)

    Mikhajlenko, E.L.; Tarasova, D.V.; Razumova, N.V.

    1982-01-01

    A study was made on the formation of porous structure of oxide bismuth-molybdenum catalysts applied to silica gel. It has been shown that the structure and phase composition of the catalysts are determined by an initial state of a carrier. When a stabilized zol is used as a carrier its purification during the synthesis takes place as a result of the sodium ion interaction with molybdenum and bismuth ions with the formation of NaBi(MoO 4 ) 2 phase. The change in the catalyst structure during heat treatment is specified by the carrier caking in the presence of the Bi 2 (MoO 4 ) 3 fusible phase

  20. Layered Structures in Deformed Metals and Alloys

    DEFF Research Database (Denmark)

    Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu

    2014-01-01

    Layered structures characterize metals and alloys deformed to high strain. The morphology is typical lamellar or fibrous and the interlamellar spacing can span several length scales down to the nanometer dimension. The layered structures can be observed in bulk or in surface regions, which is shown...... by the way of examples of different processing routes: friction, wire drawing, shot peening, high pressure torsion and rolling. The interlamellar spacing reaches from 5-10 nanometers to about one micrometer and the analysis will cover structural evolution, strengthening parameters and strength-structure...... relationships. Finally, the results will be discussed based on universal principles for the evolution of microstructure and properties during plastic deformation of metals and alloys from low to high strain....

  1. MetalS(3), a database-mining tool for the identification of structurally similar metal sites.

    Science.gov (United States)

    Valasatava, Yana; Rosato, Antonio; Cavallaro, Gabriele; Andreini, Claudia

    2014-08-01

    We have developed a database search tool to identify metal sites having structural similarity to a query metal site structure within the MetalPDB database of minimal functional sites (MFSs) contained in metal-binding biological macromolecules. MFSs describe the local environment around the metal(s) independently of the larger context of the macromolecular structure. Such a local environment has a determinant role in tuning the chemical reactivity of the metal, ultimately contributing to the functional properties of the whole system. The database search tool, which we called MetalS(3) (Metal Sites Similarity Search), can be accessed through a Web interface at http://metalweb.cerm.unifi.it/tools/metals3/ . MetalS(3) uses a suitably adapted version of an algorithm that we previously developed to systematically compare the structure of the query metal site with each MFS in MetalPDB. For each MFS, the best superposition is kept. All these superpositions are then ranked according to the MetalS(3) scoring function and are presented to the user in tabular form. The user can interact with the output Web page to visualize the structural alignment or the sequence alignment derived from it. Options to filter the results are available. Test calculations show that the MetalS(3) output correlates well with expectations from protein homology considerations. Furthermore, we describe some usage scenarios that highlight the usefulness of MetalS(3) to obtain mechanistic and functional hints regardless of homology.

  2. Design of multi-layered porous fibrous metals for optimal sound absorption in the low frequency range

    Directory of Open Access Journals (Sweden)

    Wenjiong Chen

    2016-01-01

    Full Text Available We present a design method for calculating and optimizing sound absorption coefficient of multi-layered porous fibrous metals (PFM in the low frequency range. PFM is simplified as an equivalent idealized sheet with all metallic fibers aligned in one direction and distributed in periodic hexagonal patterns. We use a phenomenological model in the literature to investigate the effects of pore geometrical parameters (fiber diameter and gap on sound absorption performance. The sound absorption coefficient of multi-layered PFMs is calculated using impedance translation theorem. To demonstrate the validity of the present model, we compare the predicted results with the experimental data. With the average sound absorption (low frequency range as the objective function and the fiber gaps as the design variables, an optimization method for multi-layered fibrous metals is proposed. A new fibrous layout with given porosity of multi-layered fibrous metals is suggested to achieve optimal low frequency sound absorption. The sound absorption coefficient of the optimal multi-layered fibrous metal is higher than the single-layered fibrous metal, and a significant effect of the fibrous material on sound absorption is found due to the surface porosity of the multi-layered fibrous.

  3. Porous Foam Based Wick Structures for Loop Heat Pipes

    Science.gov (United States)

    Silk, Eric A.

    2012-01-01

    As part of an effort to identify cost efficient fabrication techniques for Loop Heat Pipe (LHP) construction, NASA Goddard Space Flight Center's Cryogenics and Fluids Branch collaborated with the U.S. Naval Academy s Aerospace Engineering Department in Spring 2012 to investigate the viability of carbon foam as a wick material within LHPs. The carbon foam was manufactured by ERG Aerospace and machined to geometric specifications at the U.S. Naval Academy s Materials, Mechanics and Structures Machine Shop. NASA GSFC s Fractal Loop Heat Pipe (developed under SBIR contract #NAS5-02112) was used as the validation LHP platform. In a horizontal orientation, the FLHP system demonstrated a heat flux of 75 Watts per square centimeter with deionized water as the working fluid. Also, no failed start-ups occurred during the 6 week performance testing period. The success of this study validated that foam can be used as a wick structure. Furthermore, given the COTS status of foam materials this study is one more step towards development of a low cost LHP.

  4. Tunable, omnidirectional structural color on reflection based on metal-SiOx-metal structure

    Science.gov (United States)

    Yang, Chenying; Mao, Kening; Shen, Weidong; Fang, Bo; Fang, Xu; Zhang, Xing; Zhang, Yueguang; Liu, Xu

    2016-12-01

    An omnidirectional structural color based on the metal-SiOx-metal stack structure is proposed, which can present the same perceived color for a broad range of incidence angles. The tunable structural color can be obtained with adjustable intermediate dielectric layer by simply adjusting the deposition condition, especially the oxygen flow rate during the deposition processes. The resonance condition can be satisfied across the whole visible light region with this special dielectric. The strong absorption caused by the resonance within the metal-SiOx-metal structure accounts for the efficient spectral filtering feature, and the constant phase shift within the dielectric layer leads to angle insensitivity of this color filter. This simple color tuning method for omnidirectional structural colors can have a great potential in various applications such as displaying, imaging, colorful decoration, anti-counterfeiting and so forth.

  5. Dirac cones in isogonal hexagonal metallic structures

    Science.gov (United States)

    Wang, Kang

    2018-03-01

    A honeycomb hexagonal metallic lattice is equivalent to a triangular atomic one and cannot create Dirac cones in its electromagnetic wave spectrum. We study in this work the low-frequency electromagnetic band structures in isogonal hexagonal metallic lattices that are directly related to the honeycomb one and show that such structures can create Dirac cones. The band formation can be described by a tight-binding model that allows investigating, in terms of correlations between local resonance modes, the condition for the Dirac cones and the consequence of the third structure tile sustaining an extra resonance mode in the unit cell that induces band shifts and thus nonlinear deformation of the Dirac cones following the wave vectors departing from the Dirac points. We show further that, under structure deformation, the deformations of the Dirac cones result from two different correlation mechanisms, both reinforced by the lattice's metallic nature, which directly affects the resonance mode correlations. The isogonal structures provide new degrees of freedom for tuning the Dirac cones, allowing adjustment of the cone shape by modulating the structure tiles at the local scale without modifying the lattice periodicity and symmetry.

  6. Surface binding of polypyrrole on porous silicon hollow nanospheres for Li-ion battery anodes with high structure stability.

    Science.gov (United States)

    Du, Fei-Hu; Li, Bo; Fu, Wei; Xiong, Yi-Jun; Wang, Kai-Xue; Chen, Jie-Sheng

    2014-09-17

    Uniform porous silicon hollow nano-spheres are prepared without any sacrificial templates through a magnesio-thermic reduction of mesoporous silica hollow nanospheres and surface modified by the following in situ chemical polymerization of polypyrrole. The porous hollow structure and polypyrrole coating contribute significantly to the excellent structure stability and high electrochemical performance of the nanocomposite. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Catalysis in a porous molecular capsule: activation by regulated access to sixty metal centers spanning a truncated icosahedron.

    Science.gov (United States)

    Kopilevich, Sivil; Gil, Adrià; Garcia-Ratés, Miquel; Bonet-Ávalos, Josep; Bo, Carles; Müller, Achim; Weinstock, Ira A

    2012-08-08

    The 30 cationic {Mo(V)2O4(acetate)}(+) units linking 12 negatively charged pentagonal "ligands," {(Mo(VI))Mo(VI)5O21(H2O)6}(6-) of the porous metal-oxide capsule, [{Mo(VI)6O21(H2O)6}12{Mo(V)2O4(acetate)}30](42-) provide active sites for catalytic transformations of organic "guests". This is demonstrated using a well-behaved model reaction, the fully reversible cleavage and formation of methyl tert-butyl ether (MTBE) under mild conditions in water. Five independent lines of evidence demonstrate that reactions of the MTBE guests occur in the ca. 6 × 10(3) Å(3) interior of the spherical capsule. The Mo atoms of the {Mo(V)2O4(acetate)}(+) linkers--spanning an ca. 3-nm truncated icosahedron--are sterically accessible to substrate, and controlled removal of their internally bound acetate ligands generates catalytically active {Mo(V)2O4(H2O)2}(2+) units with labile water ligands, and Lewis- and Brønsted-acid properties. The activity of these units is demonstrating by kinetic data that reveal a first-order dependence of MTBE cleavage rates on the number of acetate-free {Mo(V)2O4(H2O)2}(2+) linkers. DFT calculations point to a pathway involving both Mo(V) centers, and the intermediacy of isobutene in both forward and reverse reactions. A plausible catalytic cycle--satisfying microscopic reversibility--is supported by activation parameters for MTBE cleavage, deuterium and oxygen-18 labeling studies, and by reactions of deliberately added isobutene and of a water-soluble isobutene analog. More generally, pore-restricted encapsulation, ligand-regulated access to multiple structurally integral metal-centers, and options for modifying the microenvironment within this new type of nanoreactor, suggest numerous additional transformations of organic substrates by this and related molybdenum-oxide based capsules.

  8. Phase separation of borosilicate glass with molybdenum oxide addition and pore structure of porous glass

    International Nuclear Information System (INIS)

    Tanaka, Hiroshi; Yazawa, Tetsuo; Eguchi, Kiyohisa

    1985-01-01

    Porous glass prepared by acid leaching of phase-separated soda borosilicate glass usually contains colloidal silica which originates from the silica component in the borate phase. Molybdenum trioxide was added to the starting borosilicate glass to prevent the formation of colloidal silica. It promoted the opacification of the starting glass. Opaque glasses in as-cast state showed a spherical phase-separated structure and were amorphous by X-ray doffraction. The phase separation was related to the solubility of molybdenum oxide in the glass. The phase separation occurs at a high temperature and proceeds rapidly in the cooling process of the cast glass. Another type of phase separation, which was assigned to the phase separation in the ternary soda borosilicate glass, took place during the heat treatment of the opaque glasses. When the phase-separated structure of the heat-treated glasses is interconnected, the porous glasses composed of silica skeleton are obtained by the acid leaching of the phase-separated glasses. The colloidal silica in the porous glass increased with increasing silica content of the starting glass and at the same time the volume of the pores of skeleton decreased markedly. (author)

  9. Permeability estimations and frictional flow features passing through porous media comprised of structured microbeads

    Science.gov (United States)

    Shin, C.

    2017-12-01

    Permeability estimation has been extensively researched in diverse fields; however, methods that suitably consider varying geometries and changes within the flow region, for example, hydraulic fracture closing for several years, are yet to be developed. Therefore, in the present study a new permeability estimation method is presented based on the generalized Darcy's friction flow relation, in particular, by examining frictional flow parameters and characteristics of their variations. For this examination, computational fluid dynamics (CFD) simulations of simple hydraulic fractures filled with five layers of structured microbeads and accompanied by geometry changes and flow transitions are performed. Consequently, it was checked whether the main structures and shapes of each flow path are preserved, even for geometry variations within porous media. However, the scarcity and discontinuity of streamlines increase dramatically in the transient- and turbulent-flow regions. The quantitative and analytic examinations of the frictional flow features were also performed. Accordingly, the modified frictional flow parameters were successfully presented as similarity parameters of porous flows. In conclusion, the generalized Darcy's friction flow relation and friction equivalent permeability (FEP) equation were both modified using the similarity parameters. For verification, the FEP values of the other aperture models were estimated and then it was checked whether they agreed well with the original permeability values. Ultimately, the proposed and verified method is expected to efficiently estimate permeability variations in porous media with changing geometric factors and flow regions, including such instances as hydraulic fracture closings.

  10. The processes of vaporization in the porous structures working with the excess of liquid

    Directory of Open Access Journals (Sweden)

    Genbach Alexander A.

    2017-01-01

    Full Text Available The processes of vaporization in porous structures, working with the excess of liquid are investigated. With regard to the thermal power plants new porous cooling system is proposed and investigated, in which the supply of coolant is conducted by the combined action of gravity and capillary forces. The cooling surface is made of stainless steel, brass, copper, bronze, nickel, alundum and glass, with wall thickness of (0.05-2•10-3 m. Visualizations of the processes of vaporization were carried out using holographic interferometry with the laser system and high speed camera. The operating conditions of the experiments were: water pressures (0.01-10 MPa, the temperature difference of sub-cooling (0-20°C, an excess of liquid (1-14 of the steam flow, the heat load (1-60•104 W/m2, the temperature difference (1-60°C and orientation of the system (± 0 - ± 90 degrees. Studies have revealed three areas of liquid vaporization process (transitional, developed and crisis. The impact of operating and design parameters on the integrated and thermal hydraulic characteristics was defined. The optimum (minimum flow rate of cooling fluid and the most effective type of mesh porous structure were also defined.

  11. Investigation on the structural characterization of pulsed p-type porous silicon

    Science.gov (United States)

    Wahab, N. H. Abd; Rahim, A. F. Abd; Mahmood, A.; Yusof, Y.

    2017-08-01

    P-type Porous silicon (PS) was sucessfully formed by using an electrochemical pulse etching (PC) and conventional direct current (DC) etching techniques. The PS was etched in the Hydrofluoric (HF) based solution at a current density of J = 10 mA/cm2 for 30 minutes from a crystalline silicon wafer with (100) orientation. For the PC process, the current was supplied through a pulse generator with 14 ms cycle time (T) with 10 ms on time (Ton) and pause time (Toff) of 4 ms respectively. FESEM, EDX, AFM, and XRD have been used to characterize the morphological properties of the PS. FESEM images showed that pulse PS (PPC) sample produces more uniform circular structures with estimated average pore sizes of 42.14 nm compared to DC porous (PDC) sample with estimated average size of 16.37nm respectively. The EDX spectrum for both samples showed higher Si content with minimal presence of oxide.

  12. Repair of periprosthetic pelvis defects with porous metal implants: a finite element study.

    Science.gov (United States)

    Levine, Danny L; Dharia, Mehul A; Siggelkow, Eik; Crowninshield, Roy D; Degroff, Dale A; Wentz, Douglas H

    2010-02-01

    Periacetabular osteolysis is a potentially difficult surgical challenge, which can often drive the choice of reconstruction methods used in revision hip replacement. For smaller defects, impaction of bone grafts may be sufficient, but larger defects can require filler materials that provide structural support in addition to filling a void. This study utilized finite element analysis (FEA) to examine the state of stress in periprosthetic pelvic bone when subjected to a stair-climbing load and in the presence of two simulated defects, to show the effect of implanting a defect repair implant fabricated from Trabecular Metal. Even a small medial bone defect showed a local stress elevation of 4x compared with that seen with an acetabular implant supported by intact periacetabular bone. Local bone stress was much greater (8x the baseline level) for a defect case in which the loss of bone superior to the acetabular implant permitted significant migration. FEA results showed that a repair of the small defect with a Trabecular Metal restrictor lowered periprosthetic bone stress to a level comparable to that in the case of a primary implant. For the larger defect case, the use of a Trabecular Metal augment provides structural stabilization and helps to restore the THR head center. However, stress in the adjacent periprosthetic bone is lower than that observed in the defect-free acetabulum. In the augment case, the load path between the femoral head and the pelvis now passes through the augment as the superior rim of the acetabulum has been replaced. Contact-induced stress in the augment is similar in magnitude to that seen in the superior rim of the baseline case, although the stress pattern in the augment is noticeably different from that in intact bone.

  13. Structure of extremely nanosized and confined In-O species in ordered porous materials

    International Nuclear Information System (INIS)

    Ramallo-Lopez, J.M.; Renteria, M.; Miro, E.E.; Requejo, F.G.; Traverse, A.

    2003-01-01

    Perturbed-angular correlation, x-ray absorption, and small-angle x-ray scattering spectroscopies were suitably combined to elucidate the local structure of highly diluted and dispersed InO x species confined in the porous of the ZSM5 zeolite. This novel approach allow us to determined the structure of extremely nanosized In-O species exchanged inside the 10-atom-ring channel of the zeolite, and to quantify the amount of In 2 O 3 crystallites deposited onto the external zeolite surface

  14. Effects of particle size and forming pressure on pore properties of Fe-Cr-Al porous metal by pressureless sintering

    Science.gov (United States)

    Koo, Bon-Uk; Yi, Yujeong; Lee, Minjeong; Kim, Byoung-Kee

    2017-03-01

    With increased hydrogen consumption in ammonia production, refining and synthesis, fuel cells and vehicle industries, development of the material components related to hydrogen production is becoming an important factor in industry growth. Porous metals for fabrication of hydrogen are commonly known for their relative excellence in terms of large area, lightness, lower heat capacity, high toughness, and permeability. Fe-Cr-Al alloys not only have high corrosion resistance, heat resistance, and chemical stability but also ductility, excellent mechanical properties. In order to control powder size and sintering temperature effects of Fe-Cr-Al porous metal fabrication, Fe-Cr-Al powder was classified into 25-35 μm, 35-45 μm, 45-75 μm using an auto shaking sieve machine and then classified Fe-Cr-Al powders were pressed into disk shapes using a uniaxial press machine and CIP. The pelletized Fe-Cr-Al specimens were sintered at various temperatures in high vacuum. Properties such as pore size, porosity, and air permeability were evaluated using perm-porosimetry. Microstructure and phase changes were observed with SEM and XRD. Porosity and relative density were proportionated to increasing sintering temperature. With sufficient sintering at increasing temperatures, the pore size is expected to be gradually reduced. Porosity decreased with increasing sintering temperature and gradually increased necking of the powder.

  15. Experimental Study of Structure/Behavior Relationship for a Metallized Explosive

    Science.gov (United States)

    Bukovsky, Eric; Reeves, Robert; Gash, Alexander; Glumac, Nick

    2017-06-01

    Metal powders are commonly added to explosive formulations to modify the blast behavior. Although detonation velocity is typically reduced compared to the neat explosive, the metal provides other benefits. Aluminum is a common additive to increase the overall energy output and high-density metals can be useful for enhancing momentum transfer to a target. Typically, metal powder is homogeneously distributed throughout the material; in this study, controlled distributions of metal powder in explosive formulations were investigated. The powder structures were printed using powder bed printing and the porous structures were filled with explosives to create bulk explosive composites. In all cases, the overall ratio between metal and explosive was maintained, but the powder distribution was varied. Samples utilizing uniform distributions to represent typical materials, discrete pockets of metal powder, and controlled, graded powder distributions were created. Detonation experiments were performed to evaluate the influence of metal powder design on the output pressure/time and the overall impulse. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  16. The lamellar structure of reactive mixtures in porous media: Pore scale experimental imaging and upscaling

    Science.gov (United States)

    Le Borgne, T.; De Anna, P.; Turuban, R.; Jimenez-Martinez, J.; Tabuteau, H.; Meheust, Y.; Ginn, T. R.; Dentz, M.

    2014-12-01

    Effective reaction rates in porous media are controlled by the spatial organization of chemical species concentrations at the pore scale. From high resolution millifluidic pore scale imaging of reactive tracers we report experimental evidence of the formation of well-developed lamellar structures in reactive mixtures transported through porous media (de Anna et al., Environ. Sci. Technol., 2014). The latter are highlighted by a chemioluminescent reaction producing photons that localize along spatially coherent lines, representing hotspots of mixing and reaction at pore scale. These elongated spatial structures are naturally created by the stretching action of the pore scale velocity field, which induces a dynamic deformation of the material elements carrying solutes (Le Borgne et al., Phys. Rev. Lett., 2013). This particular spatial organization is shown to have a major impact on global reactivity by increasing the surface available for reactive mixing and by enhancing local chemical gradients (de Anna et al., Geophys. Res. Lett. 2014). We quantify this phenomenon for different flow topologies using a reactive lamella representation, which links fluid deformation, diffusion and reaction at the elementary scale. The upscaled reaction rates, estimated by integrating the distribution of local deformation rates, are shown to follow different temporal behavior depending on the distribution of local velocity gradients. This approach allows for the systematic evaluation of the temporal evolution of upscaled reaction rates, and establishes a direct link between the global reaction efficiency and the spatial characteristics of the underlying pore scale flow field.References:[1] P. de Anna, J. Jimenez-Martinez, H. Tabuteau, R. Turuban, T. Le Borgne, M. Derrien,and Yves Méheust, Mixing and reaction kinetics in porous media : an experimental pore scale quantification, Environ. Sci. Technol.48, 508-516, 2014. [2] de Anna, P., Dentz, M., Tartakovsky A. and Le Borgne, T., The

  17. Eddy current technologies for thick metal structures

    International Nuclear Information System (INIS)

    Takagi, Toshiyuki; Endo, Hisashi

    2004-01-01

    One of approach of an eddy current testing (ECT) for thick metal structures is introduced. The detection limit of ECT is capable of enlarging thick more than 10 mm, which is ordinarily about 5 mm, by the design of probe. On the basis of results of numerical analysis, the defect detection in thick and shape is evaluated by the distribution of experimental ECT signals. The problems of ECT for thick metal structures and measures, approach to probe design, the specifications of probe, evaluation of experimental results and defect detection are described. By ECT fast simulator, good slit sharp is simulated in the case of 10 and 20 mm of EDM slit length and 5, 10 and 15 mm of slit height. (S.Y.)

  18. Hierarchical porous structured zeolite composite for removal of ionic contaminants from waste streams and effective encapsulation of hazardous waste

    Energy Technology Data Exchange (ETDEWEB)

    Al-Jubouri, Sama M. [Chemical Engineering & Analytical Science, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Curry, Nicholas A. [Materials Science, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Holmes, Stuart M., E-mail: stuart.holmes@manchester.ac.uk [Chemical Engineering & Analytical Science, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)

    2016-12-15

    A hierarchical structured composite made from clinoptilolite supported on date stones carbon is synthesized using two techniques. The composites are manufactured by fixing a natural zeolite (clinoptilolite) to the porous surface of date stones carbon or by direct hydrothermal synthesis on to the surface to provide a supported high surface area ion-exchange material for metal ion removal from aqueous streams. The fixing of the clinoptilolite is achieved using sucrose and citric acid as a binder. The composites and pure clinoptilolite were compared to test the efficacy for the removal of Sr{sup 2+} ions from an aqueous phase. The encapsulation of the Sr{sup 2+} using either vitrification or a geo-polymer addition was tested to ensure that the hazardous waste can be made safe for disposal. The hierarchical structured composites were shown to achieve a higher ion exchange capacity per gram of zeolite than the pure clinoptilolite (65 mg/g for the pure natural clinoptilolite and 72 mg/g for the pure synthesized clinoptilolite) with the synthesized composite (160 mg/g) having higher capacity than the natural clinoptilolite composite (95 mg/g). The rate at which the equilibria were established followed the same trend showing the composite structure facilitates diffusion to the ion-exchange sites in the zeolite.

  19. Nano structured porous anodized aluminium oxide by using C2H2O4 for electronic applications: Study of the cell potential effects on formation of porous alumina

    International Nuclear Information System (INIS)

    Nur Hafiza Mohd Najib; Derman, M.N.M.; Nuzaihan, M.N.; Nazwa, T.; Azniza, A.

    2011-01-01

    In this research, a nano porous anodized aluminium oxide AAO thin film was successfully grown onto oxide layer on silicon substrate. The anodization of Si/ SiO 2 / Al substrate was conducted in a vigorous stirring oxalic acid bath solution. The rate of growth, morphology and also the kinetic study of the AAO thin film were investigated. The resulting array, pores structure and pores density of AAO strongly depends on an applied voltage of the anodizing process. (author)

  20. Characterization of nano structured metallic materials

    International Nuclear Information System (INIS)

    Marin A, M.; Gutierrez W, C.; Cruz C, R.; Angeles C, C.

    1997-01-01

    Nowadays the search of new materials with specific optical properties has carried out to realize a series of experiments through the polymer synthesis [(C 3 N 3 ) 2 (NH) 3 ] n doped with gold metallic nanoparticles. The thermal stability of a polymer is due to the presence of tyazine rings contained in the structure. The samples were characterized by High Resolution Transmission Electron Microscopy, X-ray diffraction by the Powder method, Ft-infrared and its thermal properties by Differential Scanning Calorimetry (DSC) and Thermogravimetry (TGA). One of the purposes of this work is to obtain nano structured materials over a polymeric matrix. (Author)

  1. THE STRUCTURE ANALYTICAL RESEARCH OF POROUS PERMEABLE WIRE MATERIAL (in Russian

    Directory of Open Access Journals (Sweden)

    Andrzej JAKUBOWSKI

    2016-04-01

    Full Text Available The details of making technology of porous permeable material with use of wire are allowed to carry out the analytical research of structure and structural characteristics of wire winding body. Its permit for prognostication the final proper-ties of material, that is produced by the following deformation treatment (diameter reduction. Due to the regular orga-nized arrangement of wire, the coil of winding body is considered as a multispan continuous beam, but a contact of coils – as interaction of two cylinders. Possibility of exactly calculation of the contacts between coils is allowed to go over the single fragment displacements into deformation of whole winding body. During research of deformation processes in regards of winding body geometry and used wire mechanical properties, the structural characteristics of porous permea-ble wire material are expected. The optimal number of winding layers, eliminating the distortion of organized final struc-ture, is established. The material pressure–compactness relation is obtained in order to control the technological condi-tions of winding and drafting for guarantee the product required properties.

  2. Non-Noble Metal Nanoparticles Supported by Postmodified Porous Organic Semiconductors: Highly Efficient Catalysts for Visible-Light-Driven On-Demand H2Evolution from Ammonia Borane.

    Science.gov (United States)

    Zhang, Hao; Gu, Xiaojun; Song, Jin; Fan, Na; Su, Haiquan

    2017-09-27

    From the viewpoint of controlling the visible-light-driven activities of catalysts containing metal nanoparticles (NPs) by tuning the microstructures of semiconducting supports, we employed a postsynthetic thermal modification approach to prepare carbon nitride (C 3 N 4 ) species featuring different microstructures and then we synthesized Co and Ni NPs supported by these C 3 N 4 species, which were used to catalyze the room-temperature H 2 evolution from ammonia borane (NH 3 BH 3 ). The systematic investigation showed that the catalysts had different activities under light irradiation. Compared with the pristine C 3 N 4 -based catalyst, all the modified C 3 N 4 -based catalysts had enhanced activities. The highest active Co catalyst with a total turnover frequency of 93.8 min -1 was successfully obtained, which exceeded the values of all the reported heterogeneous noble metal-free catalysts. The structure characterizations indicated that the postmodified porous C 3 N 4 species had the different band structures, photoluminescence lifetime, and photocurrent density under visible light irradiation, leading to the different separation efficiency of photogenerated charge carriers. These characteristics helped us regulate the electronic characteristics of Co and Ni NPs in the supported catalysts and then led to the significantly different and enhanced activity in the visible-light-driven H 2 evolution.

  3. Stabilization of Metal-Loaded Ion-Exchange Resin with a Porous Silica Supporter Through Thermal Treatment

    Energy Technology Data Exchange (ETDEWEB)

    Kim, I-T. Park, H-S.; Yoo, J-H.; Kim, J-H.

    2003-02-25

    A new ion exchanger with porous silica as a supporting material and diphosphonic acid as a functional chelating group has been developed at ANL for the effective removal of transition metals and actinide ions from very acidic radioactive liquid wastes. The applicability of this resin for the treatment of low- and/or intermediate-level aqueous waste from nuclear power plants (NPP) has not been reported in scientific literature, but is under study now in Korea. The major radioisotopes in NPP radioactive liquid waste are Cs and Co in neutral pH ranges. This study on the thermal stabilization of metal-loaded waste resin has been carried out in parallel with the sorption experiment. Thermal treatment of metal (Co, Cs or U) loaded resin was accomplished to see the possibility of enhancing the safety and stability of the final product during transportation and disposal. In this paper, characteristics of the metal-loaded resins before and after heat treatment at three different thermal conditions were investigated and compared with each other to see the effectiveness of the thermal treatment method.

  4. Hydrophilicity/porous structure-tuned, SiO2/polyetherimide-coated polyimide nonwoven porous substrates for reinforced composite proton exchange membranes.

    Science.gov (United States)

    Lee, Jung-Ran; Won, Ji-Hye; Kim, Na-Young; Lee, Moo-Seok; Lee, Sang-Young

    2011-10-15

    Porous substrate-reinforced composite proton exchange membranes have drawn considerable attention due to their promising application to polymer electrolyte membrane fuel cells (PEMFCs). In the present study, we develop silica (SiO(2)) nanoparticles/polyetherimide (PEI) binders-coated polyimide (PI) nonwoven porous substrates (referred to as "S-PI substrates") for reinforced composite membranes. The properties of S-PI substrates, which crucially affect the performance of resulting reinforced composite membranes, are significantly improved by controlling the hygroscopic SiO(2) particle size. The 40 nm S-PI substrate (herein, 40 nm SiO(2) particles are employed) shows the stronger hydrophilicity and highly porous structure than the 530 nm S-PI substrate due to the larger specific surface area of 40 nm SiO(2) particles. Based on the comprehensive understanding of the S-PI substrates, the structures and performances of the S-PI substrates-reinforced composite membranes are elucidated. In comparison with the 530 nm S-PI substrate, the hydrophilicity/porous structure-tuned 40 nm S-PI substrate enables the impregnation of a large amount of a perfluorosulfonic acid ionomer (Nafion), which thus contributes to the improved proton conductivity of the reinforced Nafion composite membrane. Meanwhile, the reinforced Nafion composite membranes effectively mitigate the steep decline of proton conductivity with time at low humidity conditions, as compared to the pristine Nafion membrane. This intriguing finding is further discussed by considering the unusual features of the S-PI substrates and the state of water in the reinforced Nafion composite membranes. Copyright © 2011 Elsevier Inc. All rights reserved.

  5. Selective Adsorption of CO2 from Light Gas Mixtures Using a Structurally Dynamic Porous Coordination Polymer**

    Energy Technology Data Exchange (ETDEWEB)

    Kristi L. Kauffman, Jeffrey T. Culp, Andrew J. Allen, Laura Espinal, Winnie Wong-Ng, Thomas D.

    2010-01-01

    The selective adsorption of CO{sub 2} from mixtures with N{sub 2}, CH{sub 4}, and N{sub 2}O in a dynamic porous coordination polymer (see monomer structure) was evaluated by ATR-FTIR spectroscopy, GC, and SANS. All three techniques indicate highly selective adsorption of CO{sub 2} from CO{sub 2}/CH{sub 4} and CO{sub 2}/N{sub 2} mixtures at 30 C, with no selectivity observed for the CO{sub 2}/N{sub 2}O system.

  6. Sintering of Multilayered Porous Structures: Part II – Experiments and Model Applications

    DEFF Research Database (Denmark)

    Ni, De Wei; Olevsky, Eugene; Esposito, Vincenzo

    2013-01-01

    for the determination of the shear viscosities ratio of the layer fully dense materials. This original technique enables the derivation of all the input parameters for the bilayer sintering modeling from one set of optical dilatometry measurements, including the conversion between real and specific times of sintering......, the layers’ relative sintering intensity, and the shear viscosities ratio of the layer fully dense materials. These optical dilatometry measurements are conducted simultaneously for each individual layer and for a symmetric trilayered porous structure based on the two layers utilized in the bilayered system...

  7. Strategy for chemotherapeutic delivery using a nanosized porous metal-organic framework with a central composite design

    Directory of Open Access Journals (Sweden)

    Li YP

    2017-02-01

    Full Text Available Yingpeng Li,1 Xiuyan Li,2 Qingxia Guan,2 Chunjing Zhang,2 Ting Xu,2 Yujing Dong,2 Xinyu Bai,2 Weiping Zhang3 1College of Pharmacy, Tianjin University of Traditional Chinese Medicine, Tianjin, 2College of Pharmacy, Heilongjiang University of Traditional Chinese Medicine, Harbin, People’s Republic of China; 3Pope John XXIII High School, Everett, MA, USA Background: Enhancing drug delivery is an ongoing endeavor in pharmaceutics, especially when the efficacy of chemotherapy for cancer is concerned. In this study, we prepared and evaluated nanosized HKUST-1 (nanoHKUST-1, nanosized metal-organic drug delivery framework, loaded with 5-fluorouracil (5-FU for potential use in cancer treatment.Materials and methods: NanoHKUST-1 was prepared by reacting copper (II acetate [Cu(OAc2] and benzene-1,3,5-tricarboxylic acid (H3BTC with benzoic acid (C6H5COOH at room temperature (23.7°C±2.4°C. A central composite design was used to optimize 5-FU-loaded nanoHKUST-1. Contact time, ethanol concentration, and 5-FU:material ratios were the independent variables, and the entrapment efficiency of 5-FU was the response parameter measured. Powder X-ray diffraction, scanning electron microscopy (SEM, transmission electron microscopy (TEM, and nitrogen adsorption were used to determine the morphology of nanoHKUST-1. In addition, 5-FU release studies were conducted, and the in vitro cytotoxicity was evaluated.Results: Entrapment efficiency and drug loading were 9.96% and 40.22%, respectively, while the small-angle X-ray diffraction patterns confirmed a regular porous structure. The SEM and TEM images of the nanoHKUST-1 confirmed the presence of round particles (diameter: approximately 100 nm and regular polygon arrays of mesoporous channels of approximately 2–5 nm. The half-maximal lethal concentration (LC50 of the 5-FU-loaded nanoHKUST-1 was approximately 10 µg/mL.Conclusion: The results indicated that nanoHKUST-1 is a potential vector worth developing as a

  8. Metallizing porous scaffolds as an alternative fabrication method for solid oxide fuel cell anodes

    Science.gov (United States)

    Ruiz-Trejo, Enrique; Atkinson, Alan; Brandon, Nigel P.

    2015-04-01

    A combination of electroless and electrolytic techniques is used to incorporate nickel into a porous Ce0.9Gd0.1O1.90 scaffold. First a porous backbone was screen printed into a YSZ electrolyte using an ink that contains sacrificial pore formers. Once sintered, the scaffold was coated with silver using Tollens' reaction followed by electrodeposition of nickel in a Watts bath. At high temperatures the silver forms droplets enabling direct contact between the gadolinia-doped ceria and nickel. Using impedance spectroscopy analysis in a symmetrical cell a total area specific resistance of 1 Ωcm2 at 700 °C in 97% H2 with 3% H2O was found, indicating the potential of this fabrication method for scaling up.

  9. Creep behaviour of porous metal supports for solid oxide fuel cells

    DEFF Research Database (Denmark)

    Boccaccini, Dino; Frandsen, Henrik Lund; Sudireddy, Bhaskar Reddy

    2014-01-01

    The creep behaviour of porous ironechromium alloy used as solid oxide fuel cell support was investigated, and the creep parameters are compared with those of dense strips of similar composition under different testing conditions. The creep parameters were determined using a thermo-mechanical anal......The creep behaviour of porous ironechromium alloy used as solid oxide fuel cell support was investigated, and the creep parameters are compared with those of dense strips of similar composition under different testing conditions. The creep parameters were determined using a thermo......-mechanical analyser with applied stresses in the range from 1 to 15 MPa and temperatures between 650 and 800 _C. The GibsoneAshby and Mueller models developed for uniaxial creep of open-cell foams were used to analyse the results. The influence of scale formation on creep behaviour was assessed by comparing the creep...

  10. Comparative analysis of the possibility of applying low-melting metals with the capillary-porous system in tokamak conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lyublinski, I. E., E-mail: lyublinski@yandex.ru; Vertkov, A. V., E-mail: avertkov@yandex.ru; Semenov, V. V., E-mail: darkfenix2006@mail.ru [OAO Krasnaya Zvezda (Russian Federation)

    2016-12-15

    The use of capillary-porous systems (CPSs) with liquid Li, Ga, and Sn is considered as an alternative for solving the problem of creating plasma-facing elements (PFEs) of the fusion neutron source (FNS) and the DEMO-type reactor. The main advantages of CPSs with liquid metal compared with hard materials are their stability with respect to the degradation of properties in tokamak conditions and capability of surface self-restoration. The evaluation of applicability of liquid metals is performed on the basis of the analysis of their physical and chemical properties, the interaction with the tokamak plasma, and constructive and process features of in-vessel elements with CPSs implementing the application of these metals in a tokamak. It is shown that the upper limit of the PFE working temperature for all low-melting metals under consideration lies in the range of 550–600°Ð¡. The decisive factor for PFEs with Li is the limitation on the admissible atomic flux into plasma, while for those with Ga and Sn it is the corrosion resistance of construction materials. The upper limit of thermal loads in the steady-state operating mode for the considered promising PFE design with the use of Li, Ga, and Sn is close to 18–20 MW/m{sup 2}. It is seen from the analysis that the use of metals with a low equilibrium vapor pressure of (Ga, Sn) gives no gain in extension of the region of admissible working temperatures of PFEs. However, with respect to the totality of properties, the possibility of implementing the self-restoration and stabilization effect of the liquid surface, the influence on the plasma discharge parameters, and the ability to protect the PFE surface in conditions of plasma perturbations and disruption, lithium is the most attractive liquid metal to create CPS-based PFEs for the tokamak.

  11. Osteoinduction of porous Ti implants with a channel structure fabricated by selective laser melting.

    Science.gov (United States)

    Fukuda, A; Takemoto, M; Saito, T; Fujibayashi, S; Neo, M; Pattanayak, Deepak K; Matsushita, T; Sasaki, K; Nishida, N; Kokubo, T; Nakamura, T

    2011-05-01

    Many studies have shown that certain biomaterials with specific porous structures can induce bone formation in non-osseous sites without the need for osteoinductive biomolecules, however, the mechanisms responsible for this phenomenon (intrinsic osteoinduction of biomaterials) remain unclear. In particular, to our knowledge the type of pore structure suitable for osteoinduction has not been reported in detail. In the present study we investigated the effects of interconnective pore size on osteoinductivity and the bone formation processes during osteoinduction. Selective laser melting was employed to fabricate porous Ti implants (diameter 3.3mm, length 15 mm) with a channel structure comprising four longitudinal square channels, representing pores, of different diagonal widths, 500, 600, 900, and 1200 μm (termed p500, p600, p900, and p1200, respectively). These were then subjected to chemical and heat treatments to induce bioactivity. Significant osteoinduction was observed in p500 and p600, with the highest observed osteoinduction occurring at 5mm from the end of the implants. A distance of 5mm probably provides a favorable balance between blood circulation and fluid movement. Thus, the simple architecture of the implants allowed effective investigation of the influence of the interconnective pore size on osteoinduction, as well as the relationship between bone quantity and its location for different pore sizes. Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  12. Tough and strong porous bioactive glass-PLA composites for structural bone repair.

    Science.gov (United States)

    Xiao, Wei; Zaeem, Mohsen Asle; Li, Guangda; Bal, B Sonny; Rahaman, Mohamed N

    2017-08-01

    Bioactive glass scaffolds have been used to heal small contained bone defects but their application to repairing structural bone is limited by concerns about their mechanical reliability. In the present study, the addition of an adherent polymer layer to the external surface of strong porous bioactive glass (13-93) scaffolds was investigated to improve their toughness. Finite element modeling (FEM) of the flexural mechanical response of beams composed of a porous glass and an adherent polymer layer predicted a reduction in the tensile stress in the glass with increasing thickness and elastic modulus of the polymer layer. Mechanical testing of composites with structures similar to the models, formed from 13-93 glass and polylactic acid (PLA), showed trends predicted by the FEM simulations but the observed effects were considerably more dramatic. A PLA layer of thickness -400 µm, equal to -12.5% of the scaffold thickness, increased the load-bearing capacity of the scaffold in four-point bending by ~50%. The work of fracture increased by more than 10,000%, resulting in a non-brittle mechanical response. These bioactive glass-PLA composites, combining bioactivity, high strength, high work of fracture and an internal architecture shown to be conducive to bone infiltration, could provide optimal implants for healing structural bone defects.

  13. The structure of small metal clusters

    Science.gov (United States)

    Bauschlicher, C. W., Jr.; Pettersson, L. G. M.

    1986-01-01

    One metal atom surrounded by its 12 nearest neighbors is considered for both D(3d) (face-centered cubic-like) and D(3h) (hexagonal close-packed-like) geometries. For Al and Be, the neutral cluster and the positive and negative ions are considered for idealized (all bonds equal) and distorted geometries. The D(3d) geometry is found to be the lowest for Be13, while the D(3h) geometry is lower for Al13. This is the reverse of what is expected based upon the bulk metal structures, Be(hcp) and Al(fcc). Al13 is found to have only small distortions, while Be13 shows large distortions for both the D(3d) and D(3h) geometries. The ions have geometries which are similar to those found for the neutral systems. Both all-electron and effective core potential calculations were carried out on the X13 clusters; the agreement is very good.

  14. Magic structures of binary metallic clusters

    Science.gov (United States)

    Ferrando, Riccardo

    2005-03-01

    The structure of binary metallic clusters is investigated by a variety of computational tools, ranging from genetic and basin-hopping global optimization algorithms, to molecular dynamics, and to density-functional calculations. Three different binary systems are investigated: Ag-Cu, Ag-Ni, and Ag-Pd. A new family of magic cluster structures is found. These clusters have the common feature of presenting a perfect core-shell chemical arrangement (with an outer Ag shell of monoatomic thickness) and of being polyicosahedra, that is being made of interpenetrating icosahedra of 13 atoms. Core-shell polyicosahedra are of special stability, which originates from the interplay of different factors. First of all, polyicosahedra are very compact structures, so that they maximize the number of nearest-neighbor bonds for a given size. However, in single-element clusters, these bonds are not optimal, since inner bonds are strongly compressed and surface bonds are expanded. This is the contrary of what is required from the bond order -bond length correlation in metals, which favors contracted surface bonds. In binary clusters, the situation is different. Substituting the inner atoms of a single-element polyicosahedron with different atoms of smaller size, the bonds can relax close to their optimal distance. This leads naturally to the appearance of core-shell polyicosahedra. In Ag-Cu, Ag-Ni and Ag-Pd the formation of these structures is reinforced by the tendency of Ag atoms to surface segregation. A similar mechanism of structural relaxation, originating from the interplay of cluster geometry and bond order - bond length correlation, is also the cause of the destabilization of icosahedral structures in pure Pt and Au clusters . In these clusters, the compressed inner atoms of the icosahedra can relax because of the formation of rosette structures at vertices in the outer layer.

  15. Simulation of CO2 Injection in Porous Media with Structural Deformation Effect

    KAUST Repository

    Negara, Ardiansyah

    2011-06-18

    Carbon dioxide (CO2) sequestration is one of the most attractive methods to reduce the amount of CO2 in the atmosphere by injecting it into the geological formations. Furthermore, it is also an effective mechanism for enhanced oil recovery. Simulation of CO2 injection based on a suitable modeling is very important for explaining the fluid flow behavior of CO2 in a reservoir. Increasing of CO2 injection may cause a structural deformation of the medium. The structural deformation modeling in carbon sequestration is useful to evaluate the medium stability to avoid CO2 leakage to the atmosphere. Therefore, it is important to include such effect into the model. The purpose of this study is to simulate the CO2 injection in a reservoir. The numerical simulations of two-phase flow in homogeneous and heterogeneous porous media are presented. Also, the effects of gravity and capillary pressure are considered. IMplicit Pressure Explicit Saturation (IMPES) and IMplicit Pressure-Displacements and an Explicit Saturation (IMPDES) schemes are used to solve the problems under consideration. Various numerical examples were simulated and divided into two parts of the study. The numerical results demonstrate the effects of buoyancy and capillary pressure as well as the permeability value and its distribution in the domain. Some conclusions that could be derived from the numerical results are the buoyancy of CO2 is driven by the density difference, the CO2 saturation profile (rate and distribution) are affected by the permeability distribution and its value, and the displacements of the porous medium go to constant values at least six to eight months (on average) after injection. Furthermore, the simulation of CO2 injection provides intuitive knowledge and a better understanding of the fluid flow behavior of CO2 in the subsurface with the deformation effect of the porous medium.

  16. Porous carbon-coated ZnO nanoparticles derived from low carbon content formic acid-based Zn(II) metal-organic frameworks towards long cycle lithium-ion anode material

    International Nuclear Information System (INIS)

    Gao, Song; Fan, Ruiqing; Li, Bingjiang; Qiang, Liangsheng; Yang, Yulin

    2016-01-01

    Graphical abstract: The nanocomposites constructed from Zn-based MOFs exhibit low carbon content with super-high rate capability and long cycling life. - Highlights: • Novel ZnO@porous carbon matrix nanocomposites are constructed by pyrolysis of Zn-based MOFs. • The nanocomposites constructed with Zn-based MOFs show low carbon content. • The constructed nanocomposites exhibit high energy density, super-high rate capability and long cycling life. - Abstract: Single-C formic acid-based metal-organic frameworks (MOFs) are used to construct novel ZnO@porous carbon matrix nanocomposites by controlled pyrolysis. In the constructed nanocomposites, the porous carbon matrices act as a confined support to prevent agglomeration of the ZnO nanoparticles and create a rapid electron conductive network. Meanwhile, the well-defined, continuous porous structured MOFs provide a large specific surface area, which increases the contact of electrolyte-electrode and improves the penetration of electrolyte. Especially, the reasonable choice of formic acid-based MOFs construct the low carbon content composite, which contribute to the high energy density and long cycle life. The constructed nanocomposites show stable, ultrahigh rate lithium ion storage properties of 650 mAh g −1 at charge/discharge rate of 1 C even after 200 cycles.

  17. Effect of rigidity of porous structure on electrochemical behavior of pristine Li4Ti5O12 microspheres

    International Nuclear Information System (INIS)

    Jia, Zhenyong; Zhou, Qun; Li, Xiaowei; Fu, Yu; Ming, Hai; Zheng, Junwei

    2015-01-01

    Highlights: • Rigid porous framework of Li 4 Ti 5 O 12 microspheres can be fabricated by mutual molten growth of primary particles. • Well-confined nanosized tortuous channels are formed inside Li 4 Ti 5 O 12 microspheres. • Li 4 Ti 5 O 12 microspheres with rigid porous structures exhibit greatly enhanced electrochemical performance. - Abstract: Highly controllable porous architecture is desirable to tailor the physical and chemical properties of functional materials in advanced lithium ion batteries. Here, porous microspheres of spinel lithium titanate (Li 4 Ti 5 O 12 ), a promising alternative anode material for lithium ion batteries, are fabricated by mutual molten growth method in a controllable manner. The key role of the rigidity of the porous structure on the performance of the electrode materials in lithium ion batteries is demonstrated. Rigid framework of the materials is formed by second growth of the primary particles that fused together to generate an interconnected nanopore system inside the spheres, leading to better electrolyte diffusion and lower interparticle contact resistance, relative to the non-porous counterpart. The pristine Li 4 Ti 5 O 12 microspheres with uniform pore distribution and continuous framework exhibit high tap density, remarkable reversible capacity and rate capability, as well as excellent cycling stability. The present method is scalable and may provide a new approach to fabricate other candidate electrode materials for applications that require both high power and high volumetric energy density

  18. Validating metal binding sites in macromolecule structures using the CheckMyMetal web server

    Science.gov (United States)

    Zheng, Heping; Chordia, Mahendra D.; Cooper, David R.; Chruszcz, Maksymilian; Müller, Peter; Sheldrick, George M.

    2015-01-01

    Metals play vital roles in both the mechanism and architecture of biological macromolecules. Yet structures of metal-containing macromolecules where metals are misidentified and/or suboptimally modeled are abundant in the Protein Data Bank (PDB). This shows the need for a diagnostic tool to identify and correct such modeling problems with metal binding environments. The "CheckMyMetal" (CMM) web server (http://csgid.org/csgid/metal_sites/) is a sophisticated, user-friendly web-based method to evaluate metal binding sites in macromolecular structures in respect to 7350 metal binding sites observed in a benchmark dataset of 2304 high resolution crystal structures. The protocol outlines how the CMM server can be used to detect geometric and other irregularities in the structures of metal binding sites and alert researchers to potential errors in metal assignment. The protocol also gives practical guidelines for correcting problematic sites by modifying the metal binding environment and/or redefining metal identity in the PDB file. Several examples where this has led to meaningful results are described in the anticipated results section. CMM was designed for a broad audience—biomedical researchers studying metal-containing proteins and nucleic acids—but is equally well suited for structural biologists to validate new structures during modeling or refinement. The CMM server takes the coordinates of a metal-containing macromolecule structure in the PDB format as input and responds within a few seconds for a typical protein structure modeled with a few hundred amino acids. PMID:24356774

  19. Silver nanoparticles embedded over porous metal organic frameworks for carbon dioxide fixation via carboxylation of terminal alkynes at ambient pressure.

    Science.gov (United States)

    Molla, Rostam Ali; Ghosh, Kajari; Banerjee, Biplab; Iqubal, Md Asif; Kundu, Sudipta K; Islam, Sk Manirul; Bhaumik, Asim

    2016-09-01

    Ag nanoparticles (NPs) has been supported over a porous Co(II)-salicylate metal-organic framework to yield a new nanocatalyst AgNPs/Co-MOF and it has been thoroughly characterized by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), energy dispersive X-ray spectrometry (EDX), high-resolution transmission electron microscopy (HR-TEM), UV-vis diffuse reflection spectroscopy (DRS) and N2 adsorption/desorption analysis. The AgNPs/Co-MOF material showed high catalytic activity in the carboxylation of terminal alkynes via CO2 fixation reaction to yield alkynyl carboxylic acids under very mild conditions. Due to the presence of highly reactive AgNPs bound at the porous MOF framework the reaction proceeded smoothly at 1atm CO2 pressure. Moreover, the catalyst is very convenient to handle and it can be reused for several reaction cycles without appreciable loss of catalytic activity in this CO2 fixation reaction, which suggested a promising future of AgNPs/Co-MOF nanocatalyst. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Performance and impedance studies of thin, porous molybdenum and tungsten electrodes for the alkali metal thermoelectric converter

    Science.gov (United States)

    Wheeler, B. L.; Williams, R. M.; Jeffries-Nakamura, B.; Lamb, J. L.; Loveland, M. E.; Bankston, C. P.; Cole, T.

    1988-01-01

    Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optimum performance as alkali metal thermoelectric converter electrodes at thicknesses less than 1.0 micron when used with molybdenum or nickel current collector grids. Power densities of 0.40 W/sq cm for 0.5-micron molybdenum films at 1200 K and 0.35 W/sq cm for 0.5-micron tungsten films at 1180 K were obtained at electrode maturity after 40-90 h. Sheet resistances of magnetron sputter deposited films on sodium beta-double-prime-alumina solid electrolyte (BASE) substrates were found to increase very steeply as thickness is decreased below about 0.3-double-prime 0.4-micron. The ac impedance data for these electrodes have been interpreted in terms of contributions from the bulk BASE and the porous electrode/BASE interface. Voltage profiles of operating electrodes show that the total electrode area, of electrodes with thickness less than 2.0 microns, is not utilized efficiently unless a fairly fine (about 1 x 1 mm) current collector grid is employed.

  1. Tunable and selective conversion of 5-HMF to 2,5-furandimethanol and 2,5-dimethylfuran over copper-doped porous metal oxides

    NARCIS (Netherlands)

    Kumalaputri, Angela J; Bottari, Giovanni; Erne, Petra M; Heeres, Hero J; Barta, Katalin

    Tunable and selective hydrogenation of the platform chemical 5-hydroxymethylfurfural into valuable C-6 building blocks and liquid fuel additives is achieved with copper-doped porous metal oxides in ethanol. A new catalyst composition with improved hydrogenation/hydrogenolysis activity is obtained by

  2. A metal-organic framework-templated synthesis of γ-Fe2O3 nanoparticles encapsulated in porous carbon for efficient and chemoselective hydrogenation of nitro compounds.

    Science.gov (United States)

    Li, Yang; Zhou, Yu-Xiao; Ma, Xiao; Jiang, Hai-Long

    2016-03-18

    The γ-Fe2O3 nanoparticles well dispersed in porous carbon were fabricated via a Fe-based metal-organic framework-templated pyrolysis. The resultant product exhibits excellent catalytic activity, chemoselectivity and magnetic recyclability for the hydrogenation of diverse nitro compounds under mild conditions.

  3. Microstructure and in vitro cellular response to novel soy protein-based porous structures for tissue regeneration applications.

    Science.gov (United States)

    Olami, Hilla; Zilberman, Meital

    2016-02-01

    Interest in the development of new bioresorbable structures for various tissue engineering applications is on the rise. In the current study, we developed and studied novel soy protein-based porous blends as potential new scaffolds for such applications. Soy protein has several advantages over the various types of natural proteins employed for biomedical applications due to its low price, non-animal origin and relatively long storage time and stability. In the present study, blends of soy protein with other polymers (gelatin, pectin and alginate) were added and chemically cross-linked using the cross-linking agents carbodiimide or glyoxal, and the porous structure was obtained through lyophilization. The resulting blend porous structures were characterized using environmental scanning microscopy, and the cytotoxicity of these scaffolds was examined in vitro. The biocompatibility of the scaffolds was also evaluated in vitro by seeding and culturing human fibroblasts on these scaffolds. Cell growth morphology and adhesion were examined histologically. The results show that these blends can be assembled into porous three-dimensional structures by combining chemical cross-linking with freeze-drying. The achieved blend structures combine suitable porosity with a large pore size (100-300 µm). The pore structure in the soy-alginate scaffolds possesses adequate interconnectivity compared to that of the soy-gelatin scaffolds. However, porous structure was not observed for the soy-pectin blend, which presented a different structure with significantly lower porosities than all other groups. The in vitro evaluation of these porous soy blends demonstrated that soy-alginate blends are advantageous over soy-gelatin blends and exhibited adequate cytocompatibility along with better cell infiltration and stability. These soy protein scaffolds may be potentially useful as a cellular/acellular platform for skin regeneration applications. © The Author(s) 2015.

  4. (abstract) Experimental and Modeling Studies of the Exchange Current at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary

    Science.gov (United States)

    Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kikkert, S.

    1993-01-01

    The microscopic mechanism of the alkali ion-electron recombination reaction at the three phase boundary zone formed by a porous metal electrode in the alkali vapor on the surface of an alkali beta'-alumina solid electrolyte (BASE) ceramic has been studied by comparison of the expected rates for the three simplest reaction mechanisms with known temperature dependent rate data; and the physical parameters of typical porous metal electrode/BASE/alkali metal vapor reaction zones. The three simplest reactions are tunneling of electrons from the alkali coated electrode to a surface bound alkali metal ion; emission of an electron from the electrode with subsequent capture by a surface bound alkali metal ion; and thermal emission of an alkali cation from the BASE and its capture on the porous metal electrode surface where it may recombine with an electron. Only the first reaction adequately accounts for both the high observed rate and its temperature dependence. New results include crude modeling of simple, one step, three phase, solid/solid/gas electrochemical reaction.

  5. Electromigration and the structure of metallic nanocontacts

    Science.gov (United States)

    Hoffmann-Vogel, R.

    2017-09-01

    This article reviews efforts to structurally characterize metallic nanocontacts. While the electronic characterization of such junctions is relatively straight forward, usually it is technically challenging to study the nanocontact's structure at small length scales. However, knowing that the structure is the basis for understanding the electronic properties of the nanocontact, for example, it is necessary to explain the electronic properties by calculations based on structural models. Besides using a gate electrode, controlling the structure is an important way of understanding how the electronic transport properties can be influenced. A key to make structural information directly accessible is to choose a fabrication method that is adapted to the structural characterization method. Special emphasis is given to transmission electron microscopy fabrication and to thermally assisted electromigration methods due to their potential for obtaining information on both electrodes of the forming nanocontact. Controlled electromigration aims at studying the contact at constant temperature of the contact during electromigration compared to studies at constant temperature of the environment as done previously. We review efforts to calculate electromigration forces. We describe how hot spots are formed during electromigration. We summarize implications for the structure obtained from studies of the ballistic transport regime, tunneling, and Coulomb-blockade. We review the structure of the nanocontacts known from direct structural characterization. Single-crystalline wires allow suppressing grain boundary electromigration. In thin films, the substrate plays an important role in influencing the defect and temperature distribution. Hot-spot formation and recrystallization are observed. We add information on the local temperature and current density and on alloys important for microelectronic interconnects.

  6. Lightweight Cellular Metals with High Structural Efficiency

    Science.gov (United States)

    2003-09-01

    10-2 10-1 0.01 0.1 Open-Cell Closed-Cell ERG Fraunhofer Alulight Alporas Cymat Relative Density, ρ* /ρ s Closed-Cell Open-Cell 10-4 10-3 10-2 10-1...0.01 0.1 Open-Cell Closed-Cell ERG Fraunhofer Alulight Alporas Cymat Relative Density, ρ* /ρ s Closed-Cell Open-Cell Stochastic Foams: Modulus and...Structures NATO ARW 22 Stiffness limited design at minimum weight Applications of Cellular Metals Cymat , Inc. Messiah College Beams (free area), columns

  7. Electronic Structure of the Actinide Metals

    DEFF Research Database (Denmark)

    Johansson, B.; Skriver, Hans Lomholt

    1982-01-01

    Some recent experimental photoelectron spectroscopic results for the actinide metals are reviewed and compared with the theoretical picture of the basic electronic structure that has been developed for the actinides during the last decade. In particular the experimental data confirm the change from...... itinerant to localized 5f electron behaviour calculated to take place between plutonium and americium. From experimental data it is shown that the screening of deep core-holes is due to 5f electrons for the lighter actinide elements and 6d electrons for the heavier elements. A simplified model for the full...

  8. Underwater laser cutting of metallic structures

    International Nuclear Information System (INIS)

    Alfille, J.P.; Schildknecht, J.; Ramaswami, V.S.

    1993-01-01

    In the frame of an european contract, the feasibility of the underwater cutting with a CO 2 laser power is studied. The aim of this work is the dismantling metallic structures of reactors pools. The paper analyzes the general concept of the experimental device, the underwater cutting head, the experimenting vessel, examples of cuttings in dismantling situation with a 500 W CO 2 laser, and examples of cuttings with a 5 kW CO 2 laser. (author). 2 refs., 9 figs., 2 tabs

  9. Heterometallic metal-organic framework-templated synthesis of porous Co3O4/ZnO nanocage catalysts for the carbonylation of glycerol

    Science.gov (United States)

    Lü, Yinyun; Jiang, Yating; Zhou, Qi; Li, Yunmei; Chen, Luning; Kuang, Qin; Xie, Zhaoxiong; Zheng, Lansun

    2017-12-01

    The efficient synthesis of glycerol carbonate (GLC) has recently received great attention due to its significance in reducing excess glycerol in biodiesel production as well as its promising applications in several industrial fields. However, the achievement of high conversion and high selectivity of GLC from glycerol in heterogeneous catalytic processes remains a challenge due to the absence of high-performance solid catalysts. Herein, highly porous nanocage catalysts composed of well-mixed Co3O4 and ZnO nanocrystals were successfully fabricated via a facile heterometallic metal-organic framework (MOF)-templated synthetic route. Benefiting from a high porosity and the synergistic effect between Co3O4 and ZnO, the as-prepared composite catalysts exhibited a significantly enhanced production efficiency of GLC in the carbonylation reaction of glycerol with urea compared to the single-component counterparts. The yield of GLC over the Co50Zn50-350 catalyst reached 85.2%, with 93.3% conversion and near 91% GLC selectivity, and this catalytic performance was superior to that over most heterogeneous catalysts. More importantly, the proposed templated synthetic strategy of heterometallic MOFs facilitates the regulation of catalyst composition and surface structure and can therefore be potentially extended in the tailoring of other metal oxide composite catalysts.

  10. In Vitro Corrosion Assessment of Additively Manufactured Porous NiTi Structures for Bone Fixation Applications

    Directory of Open Access Journals (Sweden)

    Hamdy Ibrahim

    2018-03-01

    Full Text Available NiTi alloys possess distinct functional properties (i.e., shape memory effect and superelasticity and biocompatibility, making them appealing for bone fixation applications. Additive manufacturing offers an alternative method for fabricating NiTi parts, which are known to be very difficult to machine using conventional manufacturing methods. However, poor surface quality, and the presence of impurities and defects, are some of the major concerns associated with NiTi structures manufactured using additive manufacturing. The aim of this study is to assess the in vitro corrosion properties of additively manufactured NiTi structures. NiTi samples (bulk and porous were produced using selective laser melting (SLM, and their electrochemical corrosion characteristics and Ni ion release levels were measured and compared with conventionally fabricated NiTi parts. The additively manufactured NiTi structures were found to have electrochemical corrosion characteristics similar to those found for the conventionally fabricated NiTi alloy samples. The highest Ni ion release level was found in the case of 50% porous structures, which can be attributed to their significantly higher exposed surface area. However, the Ni ion release levels reported in this work for all the fabricated structures remain within the range of most of values for conventionally fabricated NiTi alloys reported in the literature. The results of this study suggest that the proposed SLM fabrication process does not result in a significant deterioration in the corrosion resistance of NiTi parts, making them suitable for bone fixation applications.

  11. Porous poly(vinyl alcohol)/sepiolite bone scaffolds: Preparation, structure and mechanical properties

    International Nuclear Information System (INIS)

    Killeen, Derek; Frydrych, Martin; Chen Biqiong

    2012-01-01

    Porous poly(vinyl alcohol) (PVA)/sepiolite nanocomposite scaffolds containing 0–10 wt.% sepiolite were prepared by freeze-drying and thermally crosslinked with poly(arylic acid). The microstructure of the obtained scaffolds was characterised by scanning electron microscopy and micro-computed tomography, which showed a ribbon and ladder like interconnected structure. The incorporation of sepiolite increased the mean pore size and porosity of the PVA scaffold as well as the degree of anisotropy due to its fibrous structure. The tensile strength, modulus and energy at break of the PVA solid material that constructed the scaffold were found to improve with additions of sepiolite by up to 104%, 331% and 22% for 6 wt.% clay. Such enhancements were attributed to the strong interactions between the PVA and sepiolite, the good dispersion of sepiolite nanofibres in the matrix and the intrinsic properties of the nanofibres. However, the tensile properties of the PVA scaffold deteriorated in the presence of sepiolite because of the higher porosity, pore size and degree of anisotropy. The PVA/sepiolite nanocomposite scaffold containing 6 wt.% sepiolite was characterised by an interconnected structure, a porosity of 89.5% and a mean pore size of 79 μm and exhibited a tensile strength of 0.44 MPa and modulus of 14.9 MPa, which demonstrates potential for this type of materials to be further developed as bone scaffolds. - Highlights: ► Novel PAA-crosslinked PVA/sepiolite nanocomposite scaffolds were prepared. ► They were highly porous with interconnected structures and exhibited good mechanical properties. ► The effects of sepiolite nanofibres on structure and properties of the scaffolds were investigated. ► Sepiolite nanofibres improved the mechanical properties of the solid material significantly.

  12. Stability of bulk metallic glass structure

    Energy Technology Data Exchange (ETDEWEB)

    Jain, H.; Williams, D.B.

    2003-06-18

    The fundamental origins of the stability of the (Pd-Ni){sub 80}P{sub 20} bulk metallic glasses (BMGs), a prototype for a whole class of BMG formers, were explored. While much of the properties of their BMGs have been characterized, their glass-stability have not been explained in terms of the atomic and electronic structure. The local structure around all three constituent atoms was obtained, in a complementary way, using extended X-ray absorption fine structure (EXAFS), to probe the nearest neighbor environment of the metals, and extended energy loss fine structure (EXELFS), to investigate the environment around P. The occupied electronic structure was investigated using X-ray photoelectron spectroscopy (XPS). The (Pd-Ni){sub 80}P{sub 20} BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni){sub 80}P{sub 20} BMGs can be explained in terms of the stability of Pd{sub 60}Ni{sub 20}P{sub 20} and Pd{sub 30}Ni{sub 50}P{sub 20}, glasses at the end of BMG formation. The atomic structure in these alloys is very similar to those of the binary phosphide crystals near x=0 and x=80, which are trigonal prisms of Pd or Ni atoms surrounding P atoms. Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd{sub 40}Ni{sub 40}P{sub 20} is further described by a weighted average of those of Pd{sub 30}Ni{sub 50}P{sub 20} and Pd{sub 60}Ni{sub 20}P{sub 20}. Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms. The Nagel and Tauc criterion, correlating a decrease in the density of states at the Fermi level with an increase in the glass stability, was consistent with greater stability of the Pd{sub x}Ni{sub (80-x)}P{sub 20} glasses with respect to the binary alloys of P. A valence electron concentration of 1.8 e/a, which

  13. Creep Behavior of Porous Supports in Metal-support Solid Oxide Fuel Cells

    DEFF Research Database (Denmark)

    Boccaccini, Dino; Frandsen, Henrik Lund; Blennow Tullmar, Peter

    2013-01-01

    metal supports, where high corrosion resistance is a major design requirement. The four variables affecting creep rate are strain, time, temperature, and stress level and make creep difficult to quantify. In this work, the creep parameters of a SOFC metal support have been determined for the first time...

  14. Computation of the Structure Factor of Some Transition Liquid Metals

    African Journals Online (AJOL)

    Applying the solution of the Percus-Yevic equation to a one component hard sphere system and using the recently developed potential for liquid transition liquid metals, the structure factor of transition liquid metals were computed. The peak height and peak position of the structure factor of the liquid metals were studied.

  15. Properties of structural materials in liquid metal environment

    International Nuclear Information System (INIS)

    Borgstedt, H.U.

    1991-12-01

    The proceedings contain 16 contributions to the following topics: 1. Creep-Rupture Behaviour of Structural Materials in Liquid Metal Environment; 2. Behaviour of Materials in Liquid Metal Environment under Off-Normal Conditions; 3. Fatigue and Creep-Fatigue of Structural Materials in Liquid Metal Environment; and 4. Crack Propagation in Liquid Sodium. (MM)

  16. Advanced Metal Foam Structures for Outer Space

    Science.gov (United States)

    Hanan, Jay; Johnson, William; Peker, Atakan

    2005-01-01

    A document discusses a proposal to use advanced materials especially bulk metallic glass (BMG) foams in structural components of spacecraft, lunar habitats, and the like. BMG foams, which are already used on Earth in some consumer products, are superior to conventional metal foams: BMG foams have exceptionally low mass densities and high strength-to-weight ratios and are more readily processable into strong, lightweight objects of various sizes and shapes. These and other attractive properties of BMG foams would be exploited, according to the proposal, to enable in situ processing of BMG foams for erecting and repairing panels, shells, containers, and other objects. The in situ processing could include (1) generation of BMG foams inside prefabricated deployable skins that would define the sizes and shapes of the objects thus formed and (2) thermoplastic deformation of BMG foams. Typically, the generation of BMG foams would involve mixtures of precursor chemicals that would be subjected to suitable pressure and temperature schedules. In addition to serving as structural components, objects containing or consisting of BMG foams could perform such functions as thermal management, shielding against radiation, and shielding against hypervelocity impacts of micrometeors and small debris particles.

  17. Structural evaluation and animal implantation of porous eggshell wastederived hydroxyapatite graft as bone substitution

    Directory of Open Access Journals (Sweden)

    Yudha Mathan Sakti Rahadyan Magetsari

    2014-08-01

    Full Text Available The development of hydroxyapatite graft with high economically value is needed for orthopedic practice in developing countries. Eggsell waste is well known as natural substance for calcium resource. It has been used as raw material in producing hydroxyapatite. This study was conducted to synthesize porous hydroxyapatite from eggshell waste and evaluate its activity as bone substitution. The porous hydroxyapatite graft was manufactured from eggshell and sugar as a raw material using hydrothermal process. The porous eggshell waste-derived hydroxyapatite (EW-HAP graft was characterized using X ray difractometer (XRD and analytical scanning electron microscope (SEM and compared with commercial hydroxyapatite (HAP JCPDS 09-432 graft (Bangros® as standard. The porous EW-HAP graft obtained was then implanted on critically sized femoral defects surgically created in the right thigh of male Wistar rats (Rattus norvegicus with Bangros® as control. Radiological examination using XRD and histological examination using hematoxyline-and-eosin staining of the bone femour were performed at 28 days after implantation. The results showed that the XRD pattern for EW-HAP was likely similar with the HAP standard. However, the SEM examination showed that the pasticle size of EW-HAP graft (2.5-3 μm was higher than those HAP standard graft (1.5-2 μm. Radiographs according to the International of Limb Salvage (ISOLS radiological evaluation system between EW-HAP graft (6.1 ± 1.45 and HAP control graft (6.9 ± 2.10 was not significantly different (p>0.05. Moreover, histological examination according to Lane and Shandu scoring system between the both graft (4.0 ± 0.94 versus 4.4 ± 0.92 was also not significantly different (p>0.05. It can be concluded that the structure EW-HAP graft is similar with HAP graft standard. The both grafts have also equal outcome as bone substitution.

  18. Finite element analysis and cellular studies on advanced, controlled porous structures with subsurface continuity in bio-implantable titanium alloys.

    Science.gov (United States)

    Lambert, P; Ankem, S; Wyatt, Z; Ferlin, K M; Fisher, J

    2014-01-01

    Highly-porous metallic implant onlay materials (specifically those containing surface pores that intersect beneath the onlay surface) have been investigated recently for their potential to reduce bone resorption and to improve the overall stability of the implant. In the current study, sub-surface interconnectivity of high-aspect-ratio pores was created directly in the substrate of an implant material using wire electrical discharge machining (EDM). This technique was used to produce intersecting pores with diameters of 180-250 μm on a clinically relevant implant material—commercially pure (CP) Grade 4 Ti—with a very high degree of control over pore morphology. These pores resulted in no significant microstructural modification to the surrounding Ti, and the inner pore surfaces could be thermally oxidized to produce a microrough, bioactive TiO2 layer. Finite element analysis of Ti models containing these EDM-attainable intersecting pore geometries suggested they produce higher bone/implant interface strengths and lower susceptibility to stress shielding of the surrounding bone as compared with models containing simpler surface geometries. In vitro experiments using mesenchymal stem cells (MSCs) demonstrated mineralized tissue ingrowth of ∼ 300 μm into EDM-produced pores. This amount of ingrowth is expected to allow for full interlocking of mineralized tissue and implant given the proper pore structure design. Copyright © 2013 Wiley Periodicals, Inc., a Wiley Company.

  19. Investigation of the adsorption properties and structures of porous materials for adsorptive removal of pollutants from water

    OpenAIRE

    ZAHRA ABBASI

    2017-01-01

    Adsorption is a low cost and effective method for the removal of non-biodegradable and harmful pollutants from water which has been widely used in industry. Porous and nanoporous materials such as metal organic frameworks (MOFs) and fly ash wastes were used as adsorbents for the removal of pollutants from water. The study showed MOF adsorbent could be fabricated as beads for easy handling and recycling due to the very low buoyancy. Temperature of heat treatment had significant effect on adsor...

  20. Enhanced oil displacement by nanofluid's structural disjoining pressure in model fractured porous media.

    Science.gov (United States)

    Zhang, Hua; Ramakrishnan, T S; Nikolov, Alex; Wasan, Darsh

    2018-02-01

    Nanofluids for improved oil recovery has been demonstrated through laboratory corefloods. Despite numerous experimental studies, little is known about the efficacy of nanofluids in fractured systems. Here, we present studies of nanofluid injection in fractured porous media (both water-wet and oil-wet) formed by sintering borosilicate glass-beads around a dissolvable substrate. The fracture inside the porous medium is characterized and visualized using a high resolution X-ray microtomography. Based on a simple displacement theory, the nanofluid injection is conducted at a rate where structural disjoining pressure driven oil recovery is operational. An additional 23.8% oil was displaced using nanofluid after brine injection with an overall recovery efficiency of 90.4% provided the matrix was in its native wettability state. But only 6% additional oil was displaced by nanofluid following brine injection when the bead-pack was rendered oil-wet. Nanofluids appear to be a good candidate for enhanced oil recovery (EOR) in fractured water-wet to weakly water-wet media but not necessarily for strongly oil-wet systems. Our laboratory studies enable us to understand limitations of nanofluids for improving oil recovery in fractured media. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Scattering of ultrasonic waves from porous piezoelectric multilayered structures immersed in a fluid

    International Nuclear Information System (INIS)

    Vashishth, Anil K; Gupta, Vishakha

    2012-01-01

    The interest in porous piezoelectric materials is due to the demand for low-frequency hydrophone/actuator devices for use in underwater acoustic systems and other oceanographic applications. Porosity decreases the acoustic impedance, thus improving the transfer of acoustic energy to water or biological tissues. The impedance mismatching problem between the dense piezoelectric materials and the surrounding medium can be solved by inclusion of porosity in dense piezoceramics. The complete description of acoustic propagation in a multilayered system is of great interest in a variety of applications, such as non-destructive evaluation and acoustic design, and there is need for a flexible model that can describe the reflection and transmission of ultrasonic waves in these media. The present paper elaborates a theoretical model, based on the transfer matrix method, for describing reflection and transmission of plane elastic waves through a porous piezoelectric laminated plate, immersed in a fluid. The analytical expressions for the reflection coefficient, transmission coefficient and acoustic impedance are derived. The effects of frequency, angle of incidence, number of layers, layer thickness and porosity are observed numerically for different configurations. The results obtained are deduced for the piezoelectric laminated structure, piezoelectric layer and poro-elastic layer immersed in a fluid, which are in agreement with earlier established results and experimental studies. (paper)

  2. Effect of Surfactant Concentration in the Emulsions on the Process of Oleophilic Porous Structures Imbibition

    Directory of Open Access Journals (Sweden)

    Shtyka Olga S.

    2016-01-01

    Full Text Available The spontaneous imbibition has been a subject of the scientific interest being a background process for numerous industrial technologies and occurring in the natural environment. In literature the experimental and theoretical results regarding this phenomenon describe a media imbibition with single-phase liquids and the relation between the process rate and media characteristics. The imbibition of oleophilic porous structures with two-phase liquids, only one phase of which was wetting, is an objective of the current publication. The main purpose is to estimate the influence of both surfactant fraction and the dispersed phase concentration on the mentioned process. The imbibition rate was investigated during model experiments with stabilized oil-in-water emulsions having the dispersed phase concentrations of 10 vol%, 30 vol% and 50 vol%. The prepared emulsions differed with fraction of the added surfactant, i.e. 1 vol%, 2 vol% and 5 vol%. The obtained results allowed to conclude that at the him≥0.02 m, the dispersed phase concentration and viscosity decreased versus height. However, the raise of the surfactant fraction caused the increase of mass and height of the imbibed emulsions in porous medium. Moreover, this provided increasing of viscosity and a change of emulsions behaviour as a liquid.

  3. The preparation of microfluidic architecture with monolithic materials using a dual porous silica structure.

    Science.gov (United States)

    Birch, Christopher; Esfahani, Mohammad Mehdi Nasr; Shaw, Kirsty J; Kemp, Cordula; Haswell, Stephen James; Dyer, Charlotte

    2017-11-01

    A microfluidic device (MD) has been developed which features a porous silica (PS) monolithic disk synthesized from tetramethyl orthosilicate, incorporated into the device post-fabrication and sealed in place with a second PS monolithic layer, synthesized from potassium silicate. This dual porous silica (DPS) structure provides a pathway for sample introduction to the MD and offers an ideal platform for solid phase extraction (SPE) methodologies which can be rapidly and efficiently integrated into a chip-based format. All silica disk manufacture and functionalization was carried out in batch to provide a readily scalable method of production. Application of this design for processing samples was demonstrated using two alternative nucleic acid purification chemistries, yielding polymerase chain reaction amplifiable DNA extracted from 150 μL of human urine in less than 35 min. It is proposed that this DPS system could be further developed for a diverse range of chip-based SPE applications, providing an interface facilitating sample delivery and enabling SPE on-chip. Furthermore, to the author's knowledge it is the first reporting of two different types of PS amalgamated in a single MD. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Geological structure impact on the exchange between fractures and matrix for the fractured porous media

    International Nuclear Information System (INIS)

    Roubinet, D.

    2010-01-01

    Fractured porous media are characterized by the presence of fractures at several scales with heterogeneous properties implying areas highly permeable by comparison with the rock. Hydraulically, these media are characterized by short reaction times, due to the fractures, and long reaction times, due to the rock. These media are important for several topics as contaminated sites, element storage and resources exploitation. The main challenge of fracture porous media modeling is the representation of the geometrical and physical heterogeneities. As an exact representation of the medium is not possible, it is necessary to determine the key properties of the medium. This study aims at determining the impact of the geometrical and physical properties of the fractures and the matrix from the local to the global scales. A first part consists in creating methods to evaluate structure effects on the exchange between the fractures and the matrix and a second part consists in using these methods on several media. Finally, we describe a new discrete dual-porosity model taking into account the properties of the media characterizing its behavior. (author)

  5. High-throughput aided synthesis of the porous metal-organic framework-type aluminum pyromellitate, MIL-121, with extra carboxylic acid functionalization.

    Science.gov (United States)

    Volkringer, Christophe; Loiseau, Thierry; Guillou, Nathalie; Férey, Gérard; Haouas, Mohamed; Taulelle, Francis; Elkaim, Erik; Stock, Norbert

    2010-11-01

    A new porous metal-organic framework (MOF)-type aluminum pyromellitate (MIL-121 or Al(OH)[H(2)btec]·(guest), (guest = H(2)O, H(4)btec = pyromellitic acid) has been isolated by using a high-throughput synthesis method under hydrothermal conditions. Its structure was determined from powder X-ray diffraction analysis using synchrotron radiation (Soleil, France) and exhibits a network closely related to that of the MIL-53 series. It is a three-dimensional (3D) framework containing one-dimensional (1D) channels delimited by infinite trans-connected aluminum-centered octahedra AlO(4)(OH)(2) linked through the pyromellitate ligand. Here the organic ligand acts as tetradendate linker via two of the carboxylate groups. The two others remain non-bonded in their protonated form, and this constitutes a rare case of the occurrence of both bonding and non-bonding organic functionalities of the MOF family. The non-coordinated -COOH groups points toward the channels to get them an open form configuration. Within the tunnels are located unreacted pyromellitic acid and water species, which are evacuated upon heating, and a porous MIL-121 phase is obtained with a Brunauer-Emmett-Teller (BET) surface area of 162 m(2) g(-1). MIL-121 has been characterized by IR, thermogravimetry (TG) analyses, and solid state NMR spectroscopy employing a couple of two-dimensional (2D) techniques such as (1)H-(1)H SQ-DQ BABA, (1)H-(1)H SQ-SQ RFDR, (27)Al{(1)H} CPHETCOR and (27)Al MQMAS.

  6. Thermal Transport in Porous Media with Application to Fuel Cell Diffusion Media and Metal Foams

    Science.gov (United States)

    Sadeghi, Ehsan

    Transport phenomena in high porosity open-cell fibrous structures have been the focus of many recent industrial and academic investigations. Unique features of these structures such as relatively low cost, ultra-low density, high surface area to volume ratio, and the ability to mix the passing fluid make them excellent candidates for a variety of thermofluid applications including fuel cells, compact heat exchangers and cooling of microelectronics. This thesis contributes to improved understanding of thermal transport phenomena in fuel cell gas diffusion layers (GDLs) and metal foams and describes new experimental techniques and analytic models to characterize and predict effective transport properties. Heat transfer through the GDL is a key process in the design and operation of a proton exchange membrane (PEM) fuel cell. The analysis of this process requires determination of the effective thermal conductivity as well as the thermal contact resistance (TCR) associated with the interface between the GDL and adjacent surfaces/ layers. The effective thermal conductivity significantly differs in through-plane and in-plane directions due to anisotropy of the GDL micro-structure. Also, the high porosity of GDLs makes the contribution of TCR against the heat flow through the medium more pronounced. A test bed was designed and built to measure the thermal contact resistance and effective thermal conductivity in both through-plane and in-plane directions under vacuum and ambient conditions. The developed experimental program allows the separation of effective thermal conductivity and thermal contact resistance. For GDLs, measurements are performed under a wide range of compressive loads using Toray carbon paper samples. To study the effect of cyclic compression, which may happen during the operation of a fuel cell stack, measurements are performed on the thermal and structural properties of GDL at different loading-unloading cycles. The static compression measurements are

  7. Factors governing the metal coordination number in metal complexes from Cambridge Structural Database analyses.

    Science.gov (United States)

    Dudev, Minko; Wang, Jonathan; Dudev, Todor; Lim, Carmay

    2006-02-02

    The metal coordination number (CN) is a key determinant of the structure and properties of metal complexes. It also plays an important role in metal selectivity in certain metalloproteins. Despite its central role, the preferred CN for several metal cations remains ambiguous, and the factors determining the metal CN are not fully understood. Here, we evaluate how the CN depends on (1) the metal's size, charge, and charge-accepting ability for a given set of ligands, and (2) the ligand's size, charge, charge-donating ability, and denticity for a given metal by analyzing the Cambridge Structural Database (CSD) structures of metal ions in the periodic table. The results show that for a given ligand type, the metal's size seems to affect its CN more than its charge, especially if the ligand is neutral, whereas, for a given metal type, the ligand's charge and charge-donating ability appear to affect the metal CN more than the ligand's size. Interestingly, all 98 metal cations surveyed could adopt more than than one CN, and most of them show an apparent preference toward even rather than odd CNs. Furthermore, as compared to the preferred metal CNs observed in the CSD, those in protein binding sites generally remain the same. This implies that the protein matrix (excluding amino acid residues in the metal's first and second coordination shell) does not impose severe geometrical restrictions on the bound metal cation.

  8. Bioresorbable Ca-phosphate-polymer/metal and Fe-Ag nanocomposites for macro-porous scaffolds with tunable degradation and drug release

    Science.gov (United States)

    Gotman, I.; Swain, S. K.; Sharipova, A.; Gutmanas, E. Y.

    2016-11-01

    Bioresorbable implants are increasingly gaining popularity as an attractive alternative to traditional permanent bone healing devices. The advantage of bioresorbable implantable devices is that they slowly degrade over time and disappear once their "mission" is accomplished. Thus, no foreign material is left behind that can cause adverse effects on the host, such as long term local or systemic immune response and stress-shielding related bone atrophy. Resorbable materials considered for surgical implant applications include degradable polymers, Ca phosphate ceramics (CaP) and corrodible metals. Degradable polymers, such as polycaprolactone and lactic acid are weak, lack osteoconductivity and degrade to acidic products that can cause late inflammation. Resorbable CaP ceramics (e.g., β-TCP) are attractive materials for bone regeneration bear close resemblance to the bone mineral, however they are intrinsically brittle and thus unsuitable for use in load-bearing sites. Moreover, introducing high porosity required to encourage better cellular ingrowth into bone regeneration scaffolds is detrimental to the mechanical strength of the material. In present work we review and discuss our results on development of strong bioresorbable Ca-phosphate-polymer/metal nanonocomposites and highly porous scaffolds from them. By introduction of nanoscale ductile polymer or metal phase into CaP ceramic an attempt was made to mimic structure of natural bone, where nanocrystallites of CaP ceramic are bonded by thin collagen layers. Recent results on development of high strength scaffolds from Fe-Ag nanocomposites are also reported. High energy milling of powders followed by cold sintering—high pressure consolidation at ambient temperature in combination with modified porogen leaching method was employed for processing. The developed nanocomposites and scaffolds exhibited high mechanical strength coupled with measurable ductility, gradual lost weight and strength during immersion in

  9. Porous metal-organic framework Cu3(BTC)2as catalyst used in air-cathode for high performance of microbial fuel cell.

    Science.gov (United States)

    Tian, Pei; Liu, Di; Li, Kexun; Yang, Tingting; Wang, Junjie; Liu, Yi; Zhang, Song

    2017-11-01

    Metal-organic framework Cu 3 (BTC) 2 , prepared by an easy hydrothermal method, was used as the oxygen-based catalyst in microbial fuel cell (MFC). The maximum power density of Cu 3 (BTC) 2 modified air-cathode MFC was 1772±15mWm -2 , almost 1.8 times higher than the control. BET results disclosed high specific surface area of 2159.7m 2 g -1 and abundant micropores structure. Regular octahedron and porous surface of Cu 3 (BTC) 2 were observed in SEM. XPS testified the existence of divalent copper in the extended 3D frameworks, which importantly acted as the Lewis-acid sites or redox centers in ORR. Additionally, the total resistance decreased by 42% from 17.60 to 10.24Ω compared with bare AC electrode. The rotating disk electrode test results showed a four-electron transfer pathway for Cu 3 (BTC) 2 , which was crucial for electrochemical catalytic activity. All the structural and electrochemical advantages make Cu 3 (BTC) 2 a promising catalyst for ORR in MFC. Copyright © 2017. Published by Elsevier Ltd.

  10. Structural characterization of water-metal interfaces

    Science.gov (United States)

    Ryczko, Kevin; Tamblyn, Isaac

    2017-08-01

    We analyze and compare the structural, dynamical, and electronic properties of liquid water next to prototypical metals including Pt, graphite, and graphene. Our results are built on Born-Oppenheimer molecular dynamics (BOMD) generated using density functional theory (DFT) which explicitly include van der Waals (vdW) interactions within a first principles approach. All calculations reported use large simulation cells, allowing for an accurate treatment of the water-electrode interfaces. We have included vdW interactions through the use of the optB86b-vdW exchange correlation functional. Comparisons with the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional are also shown. We find an initial peak, due to chemisorption, in the density profile of the liquid water-Pt interface not seen in the liquid water-graphite interface, liquid water-graphene interface, nor interfaces studied previously. To further investigate this chemisorption peak, we also report differences in the electronic structure of single water molecules on both Pt and graphite surfaces. We find that a covalent bond forms between the single water molecule and the Pt surface but not between the single water molecule and the graphite surface. We also discuss the effects that defects and dopants in the graphite and graphene surfaces have on the structure and dynamics of liquid water.

  11. Magnetic porous carbon nanocomposites derived from metal-organic frameworks as a sensing platform for DNA fluorescent detection

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Hongliang, E-mail: hltan@jxnu.edu.cn; Tang, Gonge; Wang, Zhixiong; Li, Qian; Gao, Jie; Wu, Shimeng

    2016-10-12

    Metal-organic frameworks (MOFs) have emerged as very fascinating functional materials due to their tunable nature and diverse applications. In this work, we prepared a magnetic porous carbon (MPC) nanocomposite by employing iron-containing MOFs (MIL-88A) as precursors through a one-pot thermolysis method. It was found that the MPC can absorb selectively single-stranded DNA (ssDNA) probe to form MPC/ssDNA complex and subsequently quench the labelled fluorescent dye of the ssDNA probe, which is resulted from the synergetic effect of magnetic nanoparticles and carbon matrix. Upon the addition of complementary target DNA, however, the absorbed ssDNA probe could be released from MPC surface by forming double-stranded DNA with target DNA, and accompanied by the recovery of the fluorescence of ssDNA probe. Based on these findings, a sensing platform with low background signal for DNA fluorescent detection was developed. The proposed sensing platform exhibits high sensitivity with detection limit of 1 nM and excellent selectivity to specific target DNA, even single-base mismatched nucleotide can be distinguished. We envision that the presented study would provide a new perspective on the potential applications of MOF-derived nanocomposites in biomedical fields. - Highlights: • A MOF-derived magnetic porous carbon-based DNA fluorescent sensor was developed. • The MPC can absorb selectively single-stranded DNA probe and subsequently quench its labelled fluorescent dye. • The DNA fluorescent sensor showed excellent selectivity and high sensitivity.

  12. Highly Conductive Porous Transition Metal Dichalcogenides via Water Steam Etching for High-Performance Lithium-Sulfur Batteries.

    Science.gov (United States)

    Xiao, Zhubing; Yang, Zhi; Zhou, Liujiang; Zhang, Linjie; Wang, Ruihu

    2017-06-07

    Lithium-sulfur (Li-S) batteries show significant advantages for next-generation energy storage systems owing to their high energy density and cost effectiveness. The main challenge in the development of long-life and high-performance Li-S batteries is to simultaneously facilitate the redox kinetics of sulfur species and suppress the shuttle effect of polysulfides. In this contribution, we present a general and green water-steam-etched approach for the fabrication of H- and O-incorporated porous TiS 2 (HOPT). The conductivity, porosity, chemisorptive capability, and electrocatalytic activity of HOPT are enhanced significantly when compared with those of raw TiS 2 . The synthetic method can be expanded to the fabrication of other highly conductive transition metal dichalcogenides such as porous NbS 2 and CoS 2 . The as-obtained HOPT can serve as both a substitute of conductive agents and an additive of interlayer materials. The optimal electrode delivers discharge capacities of 950 mA h g -1 after 300 cycles at 0.5 C and 374 mA h g -1 after 1000 cycles at 10 C. Impressively, an unprecedented reversible capacity of 172 mA h g -1 is achieved after 2500 cycles at 30 C, and the average capacity fading rate per cycle is as low as 0.015%. Importantly, four half-cells based on this electrode in series could drive 60 light-emitting diode indicator modules (the nominal power 3 W) after 20 s of charging. The instantaneous current and power of this device on reaching 275 A g -1 and 2611 W g -1 , respectively, indicate outstanding high-power discharge performance and potential applications in electric vehicles and other large-scale energy storage systems.

  13. On the formation of porous structure during the synthesis of macroporous copolymers based on glycidyl methacrylate

    Directory of Open Access Journals (Sweden)

    Jovanović Slobodan M.

    2004-01-01

    Full Text Available The results obtained during the investigation of the influence of the inert component composition and the type of copolymerization reaction on the porosity parameters of the macroporous copolymer of glycidyl methacrylate (GMA and ethylene glycol dimethacrylate (EGMA [abbreviated poly(GMA-co-EG-DMA] are presented. A mixture of cyclohexanol and aliphatic alcohol or non-ionic surfactants with hydrophilic-lipophilic balance values (HLB of 5 or 9 was used as the inert component. The copolymerization was performed in suspension and in a cast. It was shown that poly(GMA-co-EGDMA samples with enhanced porosity were obtained in the case of copolymerization in a cast, compared with samples obtained by suspension copolymerization. Also, it was concluded that the inert component solubility parameter cannot be used as the only criterium which determines the formation of the macro porous structure in poly(GMA-co-EGDMA.

  14. Two-dimensional modeling of electrochemical and transport phenomena in the porous structures of a PEMFC

    Energy Technology Data Exchange (ETDEWEB)

    Sahraoui, Melik [Institut Preparatoire aux Etudes d' Ingenieurs de Tunis (IPEIT) (Tunisia); Kharrat, Chafik; Halouani, Kamel [UR: Micro-Electro-Thermal Systems (METS-ENIS), Industrial Energy Systems Group, Institut Preparatoire aux Etudes d' Ingenieurs de Sfax (IPEIS), University of Sfax, B.P: 1172, 3018 Sfax (Tunisia)

    2009-04-15

    A two-dimensional CFD model of PEM fuel cell is developed by taking into account the electrochemical, mass and heat transfer phenomena occurring in all of its regions simultaneously. The catalyst layers and membrane are each considered as distinct regions with finite thickness and calculated properties such as permeability, local protonic conductivity, and local dissolved water diffusion. This finite thickness model enables to model accurately the protonic current in these regions with higher accuracy than using an infinitesimal interface. In addition, this model takes into account the effect of osmotic drag in the membrane and catalyst layers. General boundary conditions are implemented in a way taking into consideration any given species concentration at the fuel cell inlet, such as water vapor which is a very important parameter in determining the efficiency of fuel cells. Other operating parameters such as temperature, pressure and porosity of the porous structure are also investigated to characterize their effect on the fuel cell efficiency. (author)

  15. Porous carbons

    Indian Academy of Sciences (India)

    ... area in the range of 2500 m2 /gm can be developed by controlled pyrolysis and physical activation of amorphous carbon fibres. Active carbon fibres with unmatchable pore structure and surface characteristics are present and futuristic porous materials for a number of applications from pollution control to energy storage.

  16. Assembling metal oxide nanocrystals into dense, hollow, porous nanoparticles for lithium-ion and lithium-oxygen battery application

    Science.gov (United States)

    Ming, Jun; Wu, Yingqiang; Park, Jin-Bum; Lee, Joong Kee; Zhao, Fengyu; Sun, Yang-Kook

    2013-10-01

    New dense hollow porous (DHP) metal oxide nanoparticles that are smaller than 100 nm and composed of Co3O4, FeOx, NiO and MnOx were prepared by densely assembling metal oxide nanocrystals based on the hard-template method using a carbon colloid as a sacrificial core. These nanoparticles are quite different from the traditional particles as their hollow interior originates from the stacking of nanocrystals rather than a spherical shell. The DHP nanoparticles preserve the intriguing properties of nanocrystals and possess desirable surface area and pore volume that enhance the active surface, which ultimately benefits applications such as lithium-ion batteries. The DHP Co3O4 nanoparticles demonstrated an enhanced capacity of 1168 mA h g-1 at 100 mA g-1vs. 590 mA h g-1 of powders and stable cycling performance greater than 250 cycles when used as an anode material. Most importantly, the electrochemical performance of DHP Co3O4 nanoparticles in a lithium-O2 battery was also investigated for the first time. A low charge potential of ~4.0 V, a high discharge voltage near 2.74 V and a long cycle ability greater than 100 cycles at a delivered capacity of 2000 mA h g-1 (current density, 200 mA g-1) were observed. The performances were considerably improved compared to recent results of mesoporous Co3O4, Co3O4 nanoparticles and a composite of Co3O4/RGO and Co3O4/Pd. Therefore, it would be promising to investigate such properties of DHP nanoparticles or other hollow metal (oxide) particles for the popular lithium-air battery.New dense hollow porous (DHP) metal oxide nanoparticles that are smaller than 100 nm and composed of Co3O4, FeOx, NiO and MnOx were prepared by densely assembling metal oxide nanocrystals based on the hard-template method using a carbon colloid as a sacrificial core. These nanoparticles are quite different from the traditional particles as their hollow interior originates from the stacking of nanocrystals rather than a spherical shell. The DHP

  17. C-V Test Structures for Metal Gate CMOS

    NARCIS (Netherlands)

    Bankras, R.G.; Tiggelman, M.P.J.; Negara, M. Adi; Sasse, G.T.; Schmitz, Jurriaan

    2006-01-01

    Gate leakage has complicated the layout and measurement of C-V test structures. In this paper the impact of metal gate introduction to C-V test structure design is discussed. The metal gate allows for wider-gate structures and for the application of n+-p+ diffusion edges. We show, both theoretically

  18. Metallacyclopentadienes: structural features and coordination in transition metal complexes

    International Nuclear Information System (INIS)

    Dolgushin, Fedor M; Yanovsky, Aleksandr I; Antipin, Mikhail Yu

    2004-01-01

    Results of structural studies of polynuclear transition metal complexes containing the metallacyclopentadiene fragment are overviewed. The structural features of the complexes in relation to the nature of the substituents in the organic moiety of the metallacycles, the nature of the transition metals and their ligand environment are analysed. The main structural characteristics corresponding to different modes of coordination of metallacyclopentadienes to one or two additional metal centres are revealed.

  19. Preparation of porous poly(trimethylene carbonate structures for controlled release applications using high pressure CO2

    NARCIS (Netherlands)

    Nalawade, S.P.; Hennink, W.E.; Westerman, D.; Feijen, J.; Sam, A.P.; Leeke, G.; Santos, R.C.D.; Grijpma, Dirk W.; Feijen, Jan

    2008-01-01

    Porous poly(trimethylene carbonate) structures can readily be prepared using high pressure CO2. Differences in CO2 solubility in the polymer matrix at the different processing temperatures and pressures lead to different pore morphologies upon depressurization. Furthermore, crystallization of the

  20. Morphologies and wetting properties of copper film with 3D porous micro-nano hierarchical structure prepared by electrochemical deposition

    International Nuclear Information System (INIS)

    Wang, Hongbin; Wang, Ning; Hang, Tao; Li, Ming

    2016-01-01

    Highlights: • A 3D porous micro-nano hierarchical structure Cu films were prepared. • The evolution of morphology and wettability with deposition time was reported. • The effects of EDA on the microscopic morphology were revealed. • A high contact angle of 162.1° was measured when deposition time is 5 s. • The mechanism of super-hydrophobicity was illustrated by two classical models. - Abstract: Three-dimensional porous micro-nano hierarchical structure Cu films were prepared by electrochemical deposition with the Hydrogen bubble dynamic template. The morphologies of the deposited films characterized by Scanning Electronic Microscopy (SEM) exhibit a porous micro-nano hierarchical structure, which consists of three levels in different size scales, namely the honeycomb-like microstructure, the dendritic substructure and the nano particles. Besides, the factors which influenced the microscopic morphology were studied, including the deposition time and the additive Ethylene diamine. By measuring the water contact angle, the porous copper films were found to be super-hydrophobic. The maximum of the contact angles could reach as high as 162.1°. An empirical correlation between morphologies and wetting properties was revealed for the first time. The pore diameter increased simultaneously with the deposition time while the contact angle decreased. The mechanism was illustrated by two classical models. Such super-hydrophobic three-dimensional hierarchical micro-nano structure is expected to have practical application in industry.

  1. Poly(vinyl alcohol)/cellulose nanofibril hybrid aerogels with an aligned microtubular porous structure and their composites with polydimethylsiloxane

    Science.gov (United States)

    Tianliang Zhai; Qifeng Zheng; Zhiyong Cai; Lih-Sheng Turng; Hesheng Xia; Shaoqin Gong

    2015-01-01

    Superhydrophobic poly(vinyl alcohol) (PVA)/ cellulose nanofibril (CNF) aerogels with a unidirectionally aligned microtubular porous structure were prepared using a unidirectional freeze-drying process, followed by the thermal chemical vapor deposition of methyltrichlorosilane. The silanized aerogels were characterized using various techniques including scanning...

  2. Study the Synthesis, Characterization and Immersion of Dense and Porous Bovine Hydroxyapatite Structures in Hank's Balanced Salt Solution

    Science.gov (United States)

    Eslami, N.; Mahmoodian, R.; Hamdi, M.; Khatir, Nadia Mahmoudi; Herliansyah, M. K.; Rafieerad, Ali Reza

    2017-04-01

    The bone-bonding potential of biomaterials is evaluated in vitro through examining the surface apatite formation in Hank's media to enhance biocompatibility, which is also applicable to facilitate in vivo osseointegration of implantable devices. Hence, bovine hydroxyapatite (BHA) bioceramic structures have been used in various biomedical applications such as orthopedic implants. In this article, the microstructure, in vitro bioactivity, and nanomechanical properties of the synthesized dense and porous BHA are investigated via scanning electron microscopy, x-ray diffraction, energy-dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, and nanoindentation analysis. From the obtained results, porous BHA mostly possesses adequate requirements for substitution as implants in the human body.

  3. On hydrophilicity improvement of the porous anodic alumina film by hybrid nano/micro structuring

    Science.gov (United States)

    Wang, Weichao; Zhao, Wei; Wang, Kaige; Wang, Lei; Wang, Xuewen; Wang, Shuang; Zhang, Chen; Bai, Jintao

    2017-09-01

    In both, laboratory and industry, tremendous attention is paid to discover an effective technique to produce uniform, controllable and (super) hydrophilic surfaces over large areas that are useful in a wide range of applications. In this investigation, by combing porous anodic alumina (PAA) film with nano-structures and microarray of aluminum, the hydrophilicity of hybrid nano-micro structure has been significantly improved. It is found some factors can affect the hydrophilicity of film, such as the size and aspect ratio of microarray, the thickness of nano-PAA film etc. Comparing with pure nano-PAA films and microarray, the hybrid nano-micro structure can provide uniform surface with significantly better hydrophilicity. The improvement can be up to 84%. Also, this technique exhibits good stability and repeatability for industrial production. By optimizing the thickness of nano-PAA film and aspect ratio of micro-structures, super-hydrophilicity can be reached. This study has obvious prospect in the fields of chemical industry, biomedical engineering and lab-on-a-chip applications.

  4. Honeycomb-like porous 3D nickel electrodeposition for stable Li and Na metal anodes

    NARCIS (Netherlands)

    Xu, Y.; Menon, A.S.; Harks, P.P.R.M.L.; Hermes, D.C.; Haverkate, L.A.; Unnikrishnan, S.; Mulder, F.M.

    2018-01-01

    Li and Na metals have the highest theoretical anode capacity for Li/Na batteries, but the operational safety hazards stemming from uncontrolled growth of Li/Na dendrites and unstable electrode-electrolyte interfaces hinder their real-world applications. Recently, the emergence of 3D conductive

  5. Membrane distillation with porous metal hollow fibers for the concentration of thermo-sensitive solutions

    NARCIS (Netherlands)

    Shukla, Sushumna

    2014-01-01

    This thesis presents an original approach for the concentration of thermo-sensitive solutions: the Sweep Gas Membrane Distillation (SGMD) process. A new membrane contactor with metallic hollow fibers has been designed and allows the distillation process to be operational at low temperature. Heat is

  6. Structural disorder in metallic glass-forming liquids.

    Science.gov (United States)

    Pan, Shao-Peng; Feng, Shi-Dong; Wang, Li-Min; Qiao, Jun-Wei; Niu, Xiao-Feng; Dong, Bang-Shao; Wang, Wei-Min; Qin, Jing-Yu

    2016-06-09

    We investigated structural disorder by a new structural parameter, quasi-nearest atom (QNA), in atomistic configurations of eight metallic glass-forming systems generated through molecular dynamics simulations at various temperatures. Structural analysis reveals that the scaled distribution of the number of QNA appears to be an universal property of metallic liquids and the spatial distribution of the number of QNA displays to be clearly heterogeneous. Furthermore, the new parameter can be directly correlated with potential energy and structural relaxation at the atomic level. Some straightforward relationships between QNA and other properties (per-atom potential energy and α-relaxation time) are introduced to reflect structure-property relationship in metallic liquids. We believe that the new structural parameter can well reflect structure disorder in metallic liquids and play an important role in understanding various properties in metallic liquids.

  7. Constructed ILs coated porous magnetic nickel cobaltate hexagonal nanoplates sensing materials for the simultaneous detection of cumulative toxic metals

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Yuanyuan; Zhang, Lei, E-mail: zhanglei63@126.com

    2017-07-05

    Highlights: • A novel sensor material based on ionic liquids@nickel cobaltate was constructed. • Various morphologies of NiCo{sub 2}O{sub 4} were synthesized for electrocatalytic comparison. • ILs@NiCo{sub 2}O{sub 4}-P was used to detect cumulative toxic metals for the first time. • The sensor displayed well reproducibility, excellent selectivity and sensitivity. • The method was applied to detect practical samples with satisfactory results. - Abstract: The different morphologies of magnetic nickel cobaltate (NiCo{sub 2}O{sub 4}) electrocatalysts, consisting of nanoparticles (NiCo{sub 2}O{sub 4}-N), nanoplates (NiCo{sub 2}O{sub 4}-P) and microspheres (NiCo{sub 2}O{sub 4}-S) were fabricated. It was found that the electrocatalytic properties of the sensing materials were strongly dependent on morphology and specific surface area. The porous NiCo{sub 2}O{sub 4} hexagonal nanoplates coupled with ILs as modified materials (ILs@NiCo{sub 2}O{sub 4}-P) for the simultaneous determination of thallium (Tl{sup +}), lead (Pb{sup 2+}) and copper (Cu{sup 2+}), exhibited high sensitivity, long-time stability and good repeatability. The enhanced electrocatalytic activity was attributed to relatively large specific surface area, excellent electronic conductivity, and unique porous nanostructure. The analytical performance of the constructed electrode on detection of Tl{sup +}, Pb{sup 2+} and Cu{sup 2+} was examined using differential pulse anodic stripping voltammetry (DPASV). Under optimal conditions, the electrode showed a good linear response to Tl{sup +}, Pb{sup 2+}and Cu{sup 2+} in the concentration range of 0.1–100.0, 0.1–100.0 and 0.05–100.0 μg/L, respectively. The detection limits (S/N = 3) were 0.046, 0.034 and 0.029 μg/L for Tl{sup +}, Pb{sup 2+} and Cu{sup 2+}, respectively. The fabricated sensor was successfully applied to detect trace Tl{sup +}, Pb{sup 2+} and Cu{sup 2+} in various water and soil samples with satisfactory results. Hence, this work

  8. Porous copper template from partially spark plasma-sintered Cu–Zn ...

    Indian Academy of Sciences (India)

    Administrator

    Dezincification and pore formation are conducted on sintered 0∙5 mm thick 12 mm diameter disc samples. The size, distribution and nature of pores in porous templates of Cu are then investigated using optical microscopy and SEM–EDS analysis. Keywords. Metal; corrosion; porous structure; sintering; powder metallurgy. 1.

  9. MetalPDB in 2018: a database of metal sites in biological macromolecular structures.

    Science.gov (United States)

    Putignano, Valeria; Rosato, Antonio; Banci, Lucia; Andreini, Claudia

    2018-01-04

    MetalPDB (http://metalweb.cerm.unifi.it/) is a database providing information on metal-binding sites detected in the three-dimensional (3D) structures of biological macromolecules. MetalPDB represents such sites as 3D templates, called Minimal Functional Sites (MFSs), which describe the local environment around the metal(s) independently of the larger context of the macromolecular structure. The 2018 update of MetalPDB includes new contents and tools. A major extension is the inclusion of proteins whose structures do not contain metal ions although their sequences potentially contain a known MFS. In addition, MetalPDB now provides extensive statistical analyses addressing several aspects of general metal usage within the PDB, across protein families and in catalysis. Users can also query MetalPDB to extract statistical information on structural aspects associated with individual metals, such as preferred coordination geometries or aminoacidic environment. A further major improvement is the functional annotation of MFSs; the annotation is manually performed via a password-protected annotator interface. At present, ∼50% of all MFSs have such a functional annotation. Other noteworthy improvements are bulk query functionality, through the upload of a list of PDB identifiers, and ftp access to MetalPDB contents, allowing users to carry out in-depth analyses on their own computational infrastructure. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  10. Size, shape, and crystallinity of luminescent structures in oxidized Si nanoclusters and H-passivated porous Si

    Science.gov (United States)

    Schuppler, S.; Marcus, M. A.; Xie, Y. H.; Harris, T. D.; Brown, W. L.; Chabal, Y. J.; Szajowski, P. J.; Friedman, S. L.; Adler, D. L.; Ross, F. M.

    1994-11-01

    Near-edge and extended x-ray absorption fine structure measurements from a wide variety of H-passivated porous Si samples and oxidized Si nanocrystals, combined with electron microscopy, ir-absorption, alpha-recoil, and luminescence emission data, provide a consistent structural picture of the species responsible for the luminescence observed in these systems. For luminescent porous Si samples peaking in the visible region, i. e., less than or equal 700nm, their mass-weighted-average structures are determined here to be particles - not wires, whose short-range character is crystalline - not amorphous, and whose dimensions - typically less than 15 angstrom - are significantly smaller than previously reported or proposed. These results depend only on sample luminescence behavior, not on sample preparation details, and thus have general implications in describing the mechanism responsible for visible luminescence in porous silicon. New results are also presented which demonstrate that the observed luminescence is unrelated to either the photo-oxidized Si species in porous Si or the interfacial suboxide species in the Si nanocrystals.

  11. Supercooling and cold energy storage characteristics of nano-media in ball-packed porous structures

    Directory of Open Access Journals (Sweden)

    Zhao Qunzhi

    2015-04-01

    Full Text Available The presented experiments aimed to study the supercooling and cold-energy storage characteristics of nanofluids and water-based nano-media in ball-packed porous structures (BPS. Titanium dioxide nanoparticles (TiO2 NPs measuring 20nm and 80nm were used as additives and sodium dodecyl benzene sulphonate (SDBS was used as anionic surfactant. The experiments used different concentrations of nanofluid, distilled with BPS of different spherical diameter and different concentrations of nano-media, and were conducted 20 times. Experimental results of supercooling were analysed by statistical methods. Results show that the average and peak supercooling degrees of nanofluids and nano-media in BPS are lower than those of distilled water. For the distilled water in BPS, the supercooling degree decreases on the whole with the decrease of the ball diameter. With the same spherical diameter (8mm of BPS, the supercooling degree of TiO2 NPs measuring 20nm is lower than the supercooling degree of distilled water in BPS. Step-cooling experiments of different concentrations of nanofluids and nano-media in BPS were also conducted. Results showed that phase transition time is reduced because of the presence of TiO2 NPs. The BPS substrate and the NPs enhance the heat transfer. Distilled water with a porous solid base and nanoparticles means the amount of cold-energy storage increases and the supercooling degree and the total time are greatly reduced. The phase transition time of distilled water is about 3.5 times that of nano-media in BPS.

  12. Corrosion Behavior of Brazed Zinc-Coated Structured Sheet Metal

    Directory of Open Access Journals (Sweden)

    A. Nikitin

    2017-01-01

    Full Text Available Arc brazing has, in comparison to arc welding, the advantage of less heat input while joining galvanized sheet metals. The evaporation of zinc is reduced in the areas adjacent to the joint and improved corrosion protection is achieved. In the automotive industry, lightweight design is a key technology against the background of the weight and environment protection. Structured sheet metals have higher stiffness compared to typical automobile sheet metals and therefore they can play an important role in lightweight structures. In the present paper, three arc brazing variants of galvanized structured sheet metals were validated in terms of the corrosion behavior. The standard gas metal arc brazing, the pulsed arc brazing, and the cold metal transfer (CMT® in combination with a pulsed cycle were investigated. In experimental climate change tests, the influence of the brazing processes on the corrosion behavior of galvanized structured sheet metals was investigated. After that, the corrosion behavior of brazed structured and flat sheet metals was compared. Because of the selected lap joint, the valuation of damage between sheet metals was conducted. The pulsed CMT brazing has been derived from the results as the best brazing method for the joining process of galvanized structured sheet metals.

  13. Encapsulation of Metallic Na in an Electrically Conductive Host with Porous Channels as a Highly Stable Na Metal Anode.

    Science.gov (United States)

    Luo, Wei; Zhang, Ying; Xu, Shaomao; Dai, Jiaqi; Hitz, Emily; Li, Yiju; Yang, Chunpeng; Chen, Chaoji; Liu, Boyang; Hu, Liangbing

    2017-06-14

    Room-temperature Na ion batteries (NIBs) have attracted great attention because of the widely available, abundant sodium resources and potentially low cost. Currently, the challenge of the NIB development is due primarily to the lack of a high-performance anode, while the Na metal anode holds great promise considering its highest specific capacity of 1165 mA h/g and lowest anodic potential. However, an uneven deposit, relatively infinite volume change, and dendritic growth upon plating/stripping cycles cause a low Coulombic efficiency, poor cycling performance, and severe safety concerns. Here, a stable Na carbonized wood (Na-wood) composite anode was fabricated via a rapid melt infusion (about 5 s) into channels of carbonized wood by capillary action. The channels function as a high-surface-area, conductive, mechanically stable skeleton, which lowers the effective current density, ensures a uniform Na nucleation, and restricts the volume change over cycles. As a result, the Na-wood composite anode exhibited flat plating/stripping profiles with smaller overpotentials and stable cycling performance over 500 h at 1.0 mA/cm 2 in a common carbonate electrolyte system. In sharp comparison, the planar Na metal electrode showed a much shorter cycle life of 100 h under the same test conditions.

  14. Porous titanium bases for osteochondral tissue engineering

    Science.gov (United States)

    Nover, Adam B.; Lee, Stephanie L.; Georgescu, Maria S.; Howard, Daniel R.; Saunders, Reuben A.; Yu, William T.; Klein, Robert W.; Napolitano, Anthony P.; Ateshian, Gerard A.

    2015-01-01

    Tissue engineering of osteochondral grafts may offer a cell-based alternative to native allografts, which are in short supply. Previous studies promote the fabrication of grafts consisting of a viable cell-seeded hydrogel integrated atop a porous, bone-like metal. Advantages of the manufacturing process have led to the evaluation of porous titanium as the bone-like base material. Here, porous titanium was shown to support the growth of cartilage to produce native levels of Young’s modulus, using a clinically relevant cell source. Mechanical and biochemical properties were similar or higher for the osteochondral constructs compared to chondral-only controls. Further investigation into the mechanical influence of the base on the composite material suggests that underlying pores may decrease interstitial fluid pressurization and applied strains, which may be overcome by alterations to the base structure. Future studies aim to optimize titanium-based tissue engineered osteochondral constructs to best match the structural architecture and strength of native grafts. Statement of Significance The studies described in this manuscript follow up on previous studies from our lab pertaining to the fabrication of osteochondral grafts that consist of a bone-like porous metal and a chondrocyte-seeded hydrogel. Here, tissue engineered osteochondral grafts were cultured to native stiffness using adult chondrocytes, a clinically relevant cell source, and a porous titanium base, a material currently used in clinical implants. This porous titanium is manufactured via selective laser melting, offering the advantages of precise control over shape, pore size, and orientation. Additionally, this manuscript describes the mechanical influence of the porous base, which may have applicability to porous bases derived from other materials. PMID:26320541

  15. Structural Metals in the Group I Intron: A Ribozyme with a Multiple Metal Ion Core

    Energy Technology Data Exchange (ETDEWEB)

    Stahley,M.; Adams, P.; Wang, J.; Strobel, S.

    2007-01-01

    Metal ions play key roles in the folding and function for many structured RNAs, including group I introns. We determined the X-ray crystal structure of the Azoarcus bacterial group I intron in complex with its 5' and 3' exons. In addition to 222 nucleotides of RNA, the model includes 18 Mg2+ and K+ ions. Five of the metals bind within 12 Angstroms of the scissile phosphate and coordinate the majority of the oxygen atoms biochemically implicated in conserved metal-RNA interactions. The metals are buried deep within the structure and form a multiple metal ion core that is critical to group I intron structure and function. Eight metal ions bind in other conserved regions of the intron structure, and the remaining five interact with peripheral structural elements. Each of the 18 metals mediates tertiary interactions, facilitates local bends in the sugar-phosphate backbone or binds in the major groove of helices. The group I intron has a rich history of biochemical efforts aimed to identify RNA-metal ion interactions. The structural data are correlated to the biochemical results to further understand the role of metal ions in group I intron structure and function.

  16. Dual-Mode Patch Filter with Metal Wall Structures

    Directory of Open Access Journals (Sweden)

    D. Kang

    2013-01-01

    Full Text Available A dual-mode patch filter with metal wall structures is presented. The proposed structure consists of substrate 1 with metal wall structures and substrate 2 with a patch resonator. Because the symmetry of the structure can be perturbed by both long and short strips of the metal wall structures, the dual mode is achieved. The inductive element is introduced to the patch resonator through vias of the metal wall structures. The capacitive element is introduced through a gap between the patch resonator and the metal strips. The measured 3 dB fractional bandwidth for the passband is 10.4%, and the measured minimum insertion loss is 1.3 dB.

  17. A New Method for the Deposition of Metallic Silver on Porous Ceramic Water Filters

    Directory of Open Access Journals (Sweden)

    Kathryn N. Jackson

    2018-01-01

    Full Text Available A new method of silver application to a porous ceramic water filter used for point-of-use water treatment is developed. We evaluated filter performance for filters manufactured by the conventional method of painting an aqueous suspension of silver nanoparticles onto the filter and filters manufactured with a new method that applies silver nitrate to the clay-water-sawdust mixture prior to pressing and firing the filter. Filters were evaluated using miscible displacement flow-through experiments with pulse and continuous-feed injections of E. coli. Flow characteristics were quantified by tracer experiments using [3H]H2O. Experiments using pulse injections of E. coli showed similar performance in breakthrough curves between the two application methods. Long-term challenge tests performed with a continuous feed of E. coli and growth medium resulted in similar log removal rates, but the removal rate by nanosilver filters decreased over time. Silver nitrate filters provided consistent removal with lower silver levels in the effluent and effective bacterial disinfection. Results from continued use with synthetic groundwater over 4 weeks, with a pulse injection of E. coli at 2 and 4 weeks, support similar conclusions—nanosilver filters perform better initially, but after 4 weeks of use, nanosilver filters suffer larger decreases in performance. Results show that including silver nitrate in the mixing step may effectively reduce costs, improve silver retention in the filter, increase effective lifespan, and maintain effective pathogen removal while also eliminating the risk of exposure to inhalation of silver nanoparticles by workers in developing-world filter production facilities.

  18. Characterization of nano-porous oxides containing aqueous heavy metallic ions

    International Nuclear Information System (INIS)

    Louisfrema, Wilfried

    2016-01-01

    Porous crystalline aluminosilicates such as cationic zeolites, are widely studied because of their adsorption, ion exchange and catalytic properties, which explain their use in many industrial applications. Examples of the latter, which involve in particular multivalent cations, include detergents/softeners, catalytic cracking, or decontamination. Such industrial applications of zeolites all exploit their adsorption properties, which vary as a function of the pore size, comparable to the adsorbing molecules, or chemical composition, which results in charges within the framework, and in turn strong binding or repulsive sites. Importantly, in such applications zeolites are hydrated. Water is involved in the microscopic processes and thus influences all properties of the material. Molecular modeling is a weapon of choice to predict and understand the microscopic properties of the hydrated material, which are difficult to access experimentally. More precisely, the present modeling work deals with the behavior of multivalent cations in hydrated zeolites, in collaboration with experimentalists. Our study on zeolite Y faujasite first allowed us to clarify the migration of sodium cations upon dehydration and to predict the cation localization in the hydrated material in the presence of divalent cations. Furthermore, we rationalized the coupled migration of cations and deformation of the framework upon water adsorption. To this end, we have developed a new method for the analysis of cation localization. The good performance of a polarizable force field demonstrated here paves the way for the study of the dynamics of the whole system, following in particular the simultaneous migration of cations and deformation of the framework. Such an approach could be later extended to other multivalent ions of industrial interest (rare Earths, f-block elements,...). (author)

  19. Properties of structural materials in liquid metal environment. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Borgstedt, H.U. [ed.

    1991-12-15

    The International Working Group on Fast Reactors (IWGFR) Specialists Meeting on Properties of Structural Materials in Liquid Metal Environment was held during June 18 to June 20, 1991, at the Nuclear Research Centre (Kernforschungszentrum) in Karlsruhe, Germany. The Specialists Meeting was divided into five technical sessions which addressed topics as follows: Creep-Rupture Behaviour of Structural Materials in Liquid Metal Environment; Behaviour of Materials in Liquid Metal Environments under Off-Normal Conditions;Fatigue and Creep-Fatigue of Structural Materials in Liquid Metal Environment; Crack Propagation in Liquid Sodium; and Conclusions and recommendations. Individual papers have been cataloged separately.

  20. Preparation of carbon nano-riber washcoat on porous silica foam as structured catalyst support.

    NARCIS (Netherlands)

    Liu, P.; Liu, Pingle; Lefferts, Leonardus

    2006-01-01

    This paper reports how a hairy layer of carbon nano-fibers can be prepared on the macro-porous silica foam produced by the sphere templating method. Firstly, three-dimensional close-packed crystals of polystyrene spheres are assembled on porous disk substrate by vacuum filtration or evaporation. The

  1. Reconstruction of Colloidal Spheres by Targeted Etching: A Generalized Self-Template Route to Porous Amphoteric Metal Oxide Hollow Spheres.

    Science.gov (United States)

    Pan, Jia Hong; Bai, Yuqing; Wang, Qing

    2015-04-21

    Despite the significant progress in developing various synthetic strategies for metal oxide hollow spheres (h-MO), the so-far explored materials are mostly chemically inert metal oxides. Very few attempts have been made for amphoteric metal oxides such as Al2O3 and ZnO due to the difficulties in the control of the dissolution and recrystallization process. Herein, a facile self-template route to the synthesis of amphoteric h-MO with tunable size and shell thickness is developed by targeted etching via an acid-base reaction. With the protection of polyvinylpyrrolidone (PVP) on the surface, the interior of metal oxide solid colloidal spheres (c-MOs) that possess radially divergent structures could be selectively etched with acid/alkali as an etchant, forming h-MO of Al2O3 and ZnO. Our results also show that a wide variety of metal oxide colloidal spheres can be potential self-templates for targeted etching, which paves the way for developing a generalized strategy for the synthesis of various metal oxide hollow spheres.

  2. Metal oxide nanoparticle transport in porous media – an analysis about (un)certainties in environmental research

    International Nuclear Information System (INIS)

    Heidmann, I

    2013-01-01

    Research about the fate and behavior of engineered nanoparticles in the environment is despite its wide applications still in the early stages. The fast-growing area of nanoparticle research and the high level of uncertainty create a big challenge for describing clearly the recent state of the current scientific knowledge. Therefore, in this study the certain knowledge, the known uncertainties and the identified knowledge gaps concerning mobility of engineered metal oxide nanoparticles in porous media are analyzed. The mobility of nanoparticles is mainly investigated in model laboratory studies under well-defined conditions, which are often not realistic for natural systems. In these model systems, nanoparticles often retain in the pore system due to aggregation and sedimentation. However, under environmental conditions, the presence of natural organic matter may cause stabilization or disaggregation of nanoparticles and favors therefore higher mobility of nanoparticles. Additionally, potential higher mobility of particles using preferential flow paths is not considered. Knowledge of the long-term behavior of nanoparticles concerning disaggregation, dissolution or remobilization in soils under environmental conditions is scarce. Scientific uncertainty itself is rarely mentioned in the research papers. Seldom known methodically uncertainties in nanoparticle characterization are referred to. The uncertainty about the transferability of the results to environmental conditions is discussed more often. Due to the sparse studies concerning natural material or natural pore systems, certain conclusions concerning the mobility of nanoparticles in the soil environment are not possible to drawn.

  3. MetalPDB: a database of metal sites in biological macromolecular structures.

    Science.gov (United States)

    Andreini, Claudia; Cavallaro, Gabriele; Lorenzini, Serena; Rosato, Antonio

    2013-01-01

    We present here MetalPDB (freely accessible at http://metalweb.cerm.unifi.it), a novel resource aimed at conveying the information available on the three-dimensional (3D) structures of metal-binding biological macromolecules in a consistent and effective manner. This is achieved through the systematic and automated representation of metal-binding sites in proteins and nucleic acids by way of Minimal Functional Sites (MFSs). MFSs are 3D templates that describe the local environment around the metal(s) independently of the larger context of the macromolecular structure embedding the site(s), and are the central objects of MetalPDB design. MFSs are grouped into equistructural (broadly defined as sites found in corresponding positions in similar structures) and equivalent sites (equistructural sites that contain the same metals), allowing users to easily analyse similarities and variations in metal-macromolecule interactions, and to link them to functional information. The web interface of MetalPDB allows access to a comprehensive overview of metal-containing biological structures, providing a basis to investigate the basic principles governing the properties of these systems. MetalPDB is updated monthly in an automated manner.

  4. Photocatalytic evaluation of self-assembled porous network structure of ferric oxide film fabricated by dry deposition process

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yunchan; Kim, Hyungsub; Lee, Geon-Yong; Pawar, Rajendra C.; Lee, Jai-Sung; Lee, Caroline Sunyong, E-mail: sunyonglee@hanyang.ac.kr

    2016-09-15

    Ferric oxide powder in the alpha phase (α-Fe{sub 2}O{sub 3}) was deposited on an aluminum oxide (Al{sub 2}O{sub 3}) substrate by a nanoparticle deposition system using the dry deposition method. X-ray diffraction (XRD) images confirmed that the phase of the deposited α-Fe{sub 2}O{sub 3} did not change. The deposited α-Fe{sub 2}O{sub 3} was characterized in terms of its microstructure using scanning electron microscopy (SEM). A porous network microstructure formed when small agglomerates of Fe{sub 2}O{sub 3} (SAF) were deposited. The deposition and formation mechanism of the microstructure were investigated using SEM and three-dimensional (3D) profile analysis. First, a dense coating layer formed when the film was thinner than the particle size. After that, as the film thickness increased to over 5 μm, the porous network structure formed by excavating the surface of the coating layer as it was bombarded by particles. Rhodamine B (RhB) was degraded after 6 h of exposure to the Fe{sub 2}O{sub 3} coating layer with SAF, which has good photocatalytic activity and a high porous network structure. The kinetic rate constants of the SAF and large agglomerates of Fe{sub 2}O{sub 3} (LAF) were calculated to be 0.197(h{sup −1}) and 0.128(h{sup −1}), respectively, based on the absorbance results. Using linear sweep voltammetry, we confirmed that the photoelectric effect occurred in the coating layer by measuring the resulting current under illuminated and dark conditions. - Graphical abstract: Self-assembled porous photocatalytic film fabricated by dry deposition method for water purification. - Highlights: • Different sizes of Fe{sub 2}O{sub 3} agglomerates were used to form porous network structure. • Fe{sub 2}O{sub 3} agglomerate particles were deposited using solvent-free process. • Self-assembled porous network microstructure formed better with small agglomerates of Fe{sub 2}O{sub 3}. • Fabricated porous network structure showed its potential to be used

  5. Band structure engineered layered metals for low-loss plasmonics

    DEFF Research Database (Denmark)

    Gjerding, Morten Niklas; Pandey, Mohnish; Thygesen, Kristian Sommer

    2017-01-01

    dichalcogenide TaS2, due to an extraordinarily small density of states for scattering in the near-IR originating from their special electronic band structure. On the basis of this observation, we propose a new class of band structure engineered van der Waals layered metals composed of hexagonal transition metal...

  6. Porous Silicon—A Versatile Host Material

    Directory of Open Access Journals (Sweden)

    Klemens Rumpf

    2010-02-01

    Full Text Available This work reviews the use of porous silicon (PS as a nanomaterial which is extensively investigated and utilized for various applications, e.g., in the fields of optics, sensor technology and biomedicine. Furthermore the combination of PS with one or more materials which are also nanostructured due to their deposition within the porous matrix is discussed. Such nanocompounds offer a broad avenue of new and interesting properties depending on the kind of involved materials as well as on their morphology. The filling of the pores performed by electroless or electrochemical deposition is described, whereas different morphologies, reaching from micro- to macro pores are utilized as host material which can be self-organized or fabricated by prestructuring. For metal-deposition within the porous structures, both ferromagnetic and non-magnetic metals are used. Emphasis will be put on self-arranged mesoporous silicon, offering a quasi-regular pore arrangement, employed as template for filling with ferromagnetic metals. By varying the deposition parameters the precipitation of the metal structures within the pores can be tuned in geometry and spatial distribution leading to samples with desired magnetic properties. The correlation between morphology and magnetic behaviour of such semiconducting/magnetic systems will be determined. Porous silicon and its combination with a variety of filling materials leads to nanocomposites with specific physical properties caused by the nanometric size and give rise to a multiplicity of potential applications in spintronics, magnetic and magneto-optic devices, nutritional food additives as well as drug delivery.

  7. The Surface Structure of Ground Metal Crystals

    Science.gov (United States)

    Boas, W.; Schmid, E.

    1944-01-01

    The changes produced on metallic surfaces as a result of grinding and polishing are not as yet fully understood. Undoubtedly there is some more or less marked change in the crystal structure, at least, in the top layer. Hereby a diffusion of separated crystal particles may be involved, or, on plastic material, the formation of a layer in greatly deformed state, with possible recrystallization in certain conditions. Czochralski verified the existence of such a layer on tin micro-sections by successive observations of the texture after repeated etching; while Thomassen established, roentgenographically by means of the Debye-Scherrer method, the existence of diffused crystal fractions on the surface of ground and polished tin bars, which he had already observed after turning (on the lathe). (Thickness of this layer - 0.07 mm). Whether this layer borders direct on the undamaged base material or whether deformed intermediate layers form the transition, nothing is known. One observation ty Sachs and Shoji simply states that after the turning of an alpha-brass crystal the disturbance starting from the surface, penetrates fairly deep (approx. 1 mm) into the crystal (proof by recrystallization at 750 C).

  8. PLLA-collagen and PLLA-gelatin hybrid scaffolds with funnel-like porous structure for skin tissue engineering.

    Science.gov (United States)

    Lu, Hongxu; Oh, Hwan Hee; Kawazoe, Naoki; Yamagishi, Kozo; Chen, Guoping

    2012-12-01

    In skin tissue engineering, a three-dimensional porous scaffold is necessary to support cell adhesion and proliferation and to guide cells moving into the repair area in the wound healing process. Structurally, the porous scaffold should have an open and interconnected porous architecture to facilitate homogenous cell distribution. Moreover, the scaffolds should be mechanically strong to protect deformation during the formation of new skin. In this study, the hybrid scaffolds were prepared by forming funnel-like collagen or gelatin sponge on a woven poly(l-lactic acid) (PLLA) mesh. The hybrid scaffolds combined the advantages of both collagen or gelatin (good cell-interactions) and PLLA mesh (high mechanical strength). The hybrid scaffolds were used to culture dermal fibroblasts for dermal tissue engineering. The funnel-like porous structure promoted homogeneous cell distribution and extracellular matrix production. The PLLA mesh reinforced the scaffold to avoid deformation. Subcutaneous implantation showed that the PLLA-collagen and PLLA-gelatin scaffolds promoted the regeneration of dermal tissue and epidermis and reduced contraction during the formation of new tissue. These results indicate that funnel-like hybrid scaffolds can be used for skin tissue regeneration.

  9. PLLA–collagen and PLLA–gelatin hybrid scaffolds with funnel-like porous structure for skin tissue engineering

    Science.gov (United States)

    Lu, Hongxu; Oh, Hwan Hee; Kawazoe, Naoki; Yamagishi, Kozo; Chen, Guoping

    2012-01-01

    In skin tissue engineering, a three-dimensional porous scaffold is necessary to support cell adhesion and proliferation and to guide cells moving into the repair area in the wound healing process. Structurally, the porous scaffold should have an open and interconnected porous architecture to facilitate homogenous cell distribution. Moreover, the scaffolds should be mechanically strong to protect deformation during the formation of new skin. In this study, the hybrid scaffolds were prepared by forming funnel-like collagen or gelatin sponge on a woven poly(l-lactic acid) (PLLA) mesh. The hybrid scaffolds combined the advantages of both collagen or gelatin (good cell-interactions) and PLLA mesh (high mechanical strength). The hybrid scaffolds were used to culture dermal fibroblasts for dermal tissue engineering. The funnel-like porous structure promoted homogeneous cell distribution and extracellular matrix production. The PLLA mesh reinforced the scaffold to avoid deformation. Subcutaneous implantation showed that the PLLA–collagen and PLLA–gelatin scaffolds promoted the regeneration of dermal tissue and epidermis and reduced contraction during the formation of new tissue. These results indicate that funnel-like hybrid scaffolds can be used for skin tissue regeneration. PMID:27877537

  10. Preparation of degradable porous structures based on 1,3-trimethylene carbonate and D,L-lactide (co)polymers for heart tissue engineering

    NARCIS (Netherlands)

    Pego, AP; Siebum, B; Van Luyn, MJA; Van Seijen, XJGY; Poot, AA; Grijpma, DW; Feijen, J

    2003-01-01

    Biodegradable porous scaffolds for heart tissue engineering were prepared from amorphous elastomeric (co)polymers of 1,3-trimethylene carbonate (TMC) and D,L-lactide (DLLA). Leaching of salt from compression-molded polymer-salt composites allowed the preparation of highly porous structures in a

  11. SELECTED PHYSICAL PROPERTIES OF EXTRUDED COMPOSITES TYPE OF POROUS PVC-METAL

    Directory of Open Access Journals (Sweden)

    Aneta Tor-Świątek

    2014-09-01

    Full Text Available The article presents studies of selected physical and mechanical properties of hybrid materials type of polymer-metal. In the frame of this work modification of PVC with the iron and copper powder in amount of 0, 1.5 and 3% and blowing agent in amount of 0, 0.5, 1% was done. Extrudates in a form of pipe were tested to determine density, porosity, maximum tensile stress, stress at break, modulus of elasticity and elongation with break. The samples were also observed in a microscope. The studies have shown significant influence of the added components on the properties tested.

  12. Porous PDMS structures for the storage and release of aqueous solutions into fluidic environments.

    Science.gov (United States)

    Thurgood, Peter; Baratchi, Sara; Szydzik, Crispin; Mitchell, Arnan; Khoshmanesh, Khashayar

    2017-07-11

    Typical microfluidic systems take advantage of multiple storage reservoirs, pumps and valves for the storage, driving and release of buffers and other reagents. However, the fabrication, integration, and operation of such components can be difficult. In particular, the reliance of such components on external off-chip equipment limits their utility for creating self-sufficient, stand-alone microfluidic systems. Here, we demonstrate a porous sponge made of polydimethylsiloxane (PDMS), which is fabricated by templating microscale water droplets using a T-junction microfluidic structure. High-resolution microscopy reveals that this sponge contains a network of pores, interconnected by small holes. This unique structure enables the sponge to passively release stored solutions very slowly. Proof-of-concept experiments demonstrate that the sponge can be used for the passive release of stored solutions into narrow channels and circular well plates, with the latter used for inducing intracellular calcium signalling of immobilised endothelial cells. The release rate of stored solutions can be controlled by varying the size of interconnecting holes, which can be easily achieved by changing the flow rate of the water injected into the T-junction. We also demonstrate the active release of stored liquids into a fluidic channel upon the manual compression of the sponge. The developed PDMS sponge can be easily integrated into complex micro/macro fluidic systems and prepared with a wide array of reagents, representing a new building block for self-sufficient microfluidic systems.

  13. Utilization of Pebax 1657 as structure directing agent in fabrication of ultra-porous ZIF-8

    Energy Technology Data Exchange (ETDEWEB)

    Jomekian, A. [Gas Engineering Department, Ahvaz Faculty of Petroleum Engineering, Petroleum University of Technology (PUT), Post Office Box 63431, Ahvaz (Iran, Islamic Republic of); Faculty of Chemical Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran (Iran, Islamic Republic of); Behbahani, R.M., E-mail: behbahani@put.ac.ir [Gas Engineering Department, Ahvaz Faculty of Petroleum Engineering, Petroleum University of Technology (PUT), Post Office Box 63431, Ahvaz (Iran, Islamic Republic of); Mohammadi, T. [Faculty of Chemical Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran (Iran, Islamic Republic of); Kargari, A. [Department of Petrochemical Engineering, Amirkabir University of Technology (AUT), Mahshahr (Iran, Islamic Republic of)

    2016-03-15

    Ultra porous ZIF-8 particles synthesized using PEO/PA6 based poly(ether-block-amide) (Pebax 1657) as structure directing agent. Structural properties of ZIF-8 samples prepared under different synthesis parameters were investigated by laser particle size analysis, XRD, N{sub 2} adsorption analysis, BJH and BET tests. The overall results showed that: (1) The mean pore size of all ZIF-8 samples increased remarkably (from 0.34 nm to 1.1–2.5 nm) compared to conventionally synthesized ZIF-8 samples. (2) Exceptional BET surface area of 1869 m{sup 2}/g was obtained for a ZIF-8 sample with mean pore size of 2.5 nm. (3) Applying high concentrations of Pebax 1657 to the synthesis solution lead to higher surface area, larger pore size and smaller particle size for ZIF-8 samples. (4) Both, Increase in temperature and decrease in molar ratio of MeIM/Zn{sup 2+} had increasing effect on ZIF-8 particle size, pore size, pore volume, crystallinity and BET surface area of all investigated samples. - Highlights: • The pore size of ZIF-8 samples synthesized with Pebax 1657 increased remarkably. • The BET surface area of 1869 m{sup 2}/gr obtained for a ZIF-8 synthesized sample with Pebax. • Increase in temperature had increasing effect on textural properties of ZIF-8 samples. • Decrease in MeIM/Zn{sup 2+} had increasing effect on textural properties of ZIF-8 samples.

  14. Tunable porous structure of carbon nanosheets derived from puffed rice for high energy density supercapacitors

    Science.gov (United States)

    Hou, Jianhua; Jiang, Kun; Tahir, Muhammad; Wu, Xiaoge; Idrees, Faryal; Shen, Ming; Cao, Chuanbao

    2017-12-01

    The development of green and clean synthetic techniques to overcome energy requirements have motivated the researchers for the utilization of sustainable biomass. Driven by this desire we choose rice as starting materials source. After the explosion effect, the precursor is converted into puffed rice with a honeycomb-like structures composed of thin sheets. These honeycomb-like macrostructures, effectively prevent the cross-linking tendency towards the adjacent nanosheets during activation process. Furthermore, tuneable micro/mesoporous structures with ultrahigh specific surface areas (SBET) are successfully designed by KOH activation. The highest SBET of 3326 m2 g-1 with optimized proportion of small-mesopores is achieved at 850 °C. The rice-derived porous N-doped carbon nanosheets (NCS-850) are used as the active electrode materials for supercapacitors. It exhibites high specific capacitance specifically of 218 F g-1 at 80 A g-1 in 6 M KOH and a high-energy density of 104 Wh kg-1 (53 Wh L-1) in the ionic liquid electrolytes. These are the highest values among the reported biomass-derived carbon materials for the best of our knowledge. The present work demonstrates that the combination of "puffing effect" and common chemical activation can turn natural products such as rice into functional products with prospective applications in high-performance energy storage devices.

  15. Viscoelastic polymer flows and elastic turbulence in three-dimensional porous structures.

    Science.gov (United States)

    Mitchell, Jonathan; Lyons, Kyle; Howe, Andrew M; Clarke, Andrew

    2016-01-14

    Viscoelastic polymer solutions flowing through reservoir rocks have been found to improve oil displacement efficiency when the aqueous-phase shear-rate exceeds a critical value. A possible mechanism for this enhanced recovery is elastic turbulence that causes breakup and mobilization of trapped oil ganglia. Here, we apply nuclear magnetic resonance (NMR) pulsed field gradient (PFG) diffusion measurements in a novel way to detect increased motion of disconnected oil ganglia. The data are acquired directly from a three-dimensional (3D) opaque porous structure (sandstone) when viscoelastic fluctuations are expected to be present in the continuous phase. The measured increase in motion of trapped ganglia provides unequivocal evidence of fluctuations in the flowing phase in a fully complex 3D system. This work provides direct evidence of elastic turbulence in a realistic reservoir rock - a measurement that cannot be readily achieved by conventional laboratory methods. We support the NMR data with optical microscopy studies of fluctuating ganglia in simple two-dimensional (2D) microfluidic networks, with consistent apparent rheological behaviour of the aqueous phase, to provide conclusive evidence of elastic turbulence in the 3D structure and hence validate the proposed flow-fluctuation mechanism for enhanced oil recovery.

  16. Internal structure of magnetic porous glasses and the related ferroelectric nanocomposites

    Science.gov (United States)

    Naberezhnov, A. A.; Ryukhtin, V.; Sysoeva, A. A.

    2017-02-01

    The internal structure of empty porous micro- and macroporous magnetic glasses and the related nanocomposites containing NaNO2 and KNO3 embedded in pores of the glasses has been investigated using small-angle neutron scattering. The characteristic sizes of magnetite particles in matrices and the sizes of nanoparticles embedded in ferroelectric materials have been estimated. It has been shown that, for microporous glasses in the momentum transfer range 0.35 nm-1 small-angle neutron scattering intensity on the momentum transfer has two characteristic regions: the first region corresponds well to the Porod's law Q -4 (smooth surface), and the second region is consistent with the mass fractal reflecting the internal structure of channels in the microporous glass. For macroporous glasses over the entire momentum transfer range 0.35 nm-1 scattering intensity is described by the dependence I( Q) Q - n with α = 3.96 ± 0.02; i.e., in these glasses, there is a system of channels with sufficiently smooth surfaces.

  17. Unusual structural and electronic properties of porous silicene and germanene: insights from first-principles calculations.

    Science.gov (United States)

    Ding, Yi; Wang, Yanli

    2015-01-01

    Using first-principles calculations, we investigate the geometric structures and electronic properties of porous silicene and germanene nanosheets, which are the Si and Ge analogues of α-graphyne (referred to as silicyne and germanyne). It is found that the elemental silicyne and germanyne sheets are energetically unfavourable. However, after the C-substitution, the hybrid graphyne-like sheets (c-silicyne/c-germanyne) possess robust energetic and dynamical stabilities. Different from silicene and germanene, c-silicyne is a flat sheet, and c-germanyne is buckled with a distinct half-hilled conformation. Such asymmetric buckling structure causes the semiconducting behaviour into c-germanyne. While in c-silicyne, the semimetallic Dirac-like property is kept at the nonmagnetic state, but a spontaneous antiferromagnetism produces the massive Dirac fermions and opens a sizeable gap between Dirac cones. A tensile strain can further enhance the antiferromagnetism, which also linearly modulates the gap value without altering the direct-bandgap feature. Through strain engineering, c-silicyne can form a type-II band alignment with the MoS 2 sheet. The combined c-silicyne/MoS 2 nanostructure has a high power conversion efficiency beyond 20% for photovoltaic solar cells, enabling a fascinating utilization in the fields of solar energy and nano-devices.

  18. Morphological Characterization and Effective Thermal Conductivity of Dual-Scale Reticulated Porous Structures

    Directory of Open Access Journals (Sweden)

    Simon Ackermann

    2014-10-01

    Full Text Available Reticulated porous ceramic (RPC made of ceria are promising structures used in solar thermochemical redox cycles for splitting CO2 and H2O. They feature dual-scale porosity with mm-size pores for effective radiative heat transfer during reduction and µm-size pores within its struts for enhanced kinetics during oxidation. In this work, the detailed 3D digital representation of the complex dual-scale RPC is obtained using synchrotron submicrometer tomography and X-ray microtomography. Total and open porosity, pore size distribution, mean pore diameter, and specific surface area are extracted from the computer tomography (CT scans. The 3D digital geometry is then applied in direct pore level simulations (DPLS of Fourier’s law within the solid and the fluid phases for the accurate determination of the effective thermal conductivity at each porosity scale and combined, and for fluid-to-solid thermal conductivity from 10−5 to 1. Results are compared to predictions by analytical models for structures with a wide range of porosities 0.09–0.9 in both the strut’s µm-scale and bulk’s mm-scale. The morphological properties and effective thermal conductivity determined in this work serve as an input to volume-averaged models for the design and optimization of solar chemical reactors.

  19. Understanding metallic bonding: Structure, process and interaction by Rasch analysis

    Science.gov (United States)

    Cheng, Maurice M. W.; Oon, Pey-Tee

    2016-08-01

    This paper reports the results of a survey of 3006 Year 10-12 students on their understandings of metallic bonding. The instrument was developed based on Chi's ontological categories of scientific concepts and students' understanding of metallic bonding as reported in the literature. The instrument has two parts. Part one probed into students' understanding of metallic bonding as (a) a submicro structure of metals, (b) a process in which individual metal atoms lose their outermost shell electrons to form a 'sea of electrons' and octet metal cations or (c) an all-directional electrostatic force between delocalized electrons and metal cations, that is, an interaction. Part two assessed students' explanation of malleability of metals, for example (a) as a submicro structural rearrangement of metal atoms/cations or (b) based on all-directional electrostatic force. The instrument was validated by the Rasch Model. Psychometric assessment showed that the instrument possessed reasonably good properties of measurement. Results revealed that it was reliable and valid for measuring students' understanding of metallic bonding. Analysis revealed that the structure, process and interaction understandings were unidimensional and in an increasing order of difficulty. Implications for the teaching of metallic bonding, particular through the use of diagrams, critiques and model-based learning, are discussed.

  20. Metal Nanoparticles Deposited on Porous Silicon Templates as Novel Substrates for SERS

    Directory of Open Access Journals (Sweden)

    Lara Mikac

    2015-12-01

    Full Text Available In this paper, results on preparation of stable and uniform SERS solid substrates using macroporous silicon (pSi with deposited silver and gold are presented. Macroporous silicon is produced by anodisation of p-type silicon in hydrofluoric acid. The as prepared pSi is then used as a template for Ag and Au depositions. The noble metals were deposited in three different ways: by immersion in silver nitrate solution, by drop-casting silver colloidal solution and by pulsed laser ablation (PLA. Substrates obtained by different deposition processes were evaluated for SERS efficiency using methylene blue (MB and rhodamine 6G (R6G at 514.5, 633 and 785 nm. Using 514.5 nm excitation and R6G the limits of detection (LOD for macroporous Si samples with noble metal nanostructures obtained by immersion of pSi sample in silver nitrate solution and by applying silver colloidal solution to pSi template were 10–9 M and 10–8 M respectively. Using 633 nm laser and MB the most noticeable SERS activity gave pSi samples ablated with 30000 and 45000 laser pulses where the LODs of 10–10 M were obtained. The detection limit of 10–10 M was also reached for 4 mA cm–2-15 min pSi sample, silver ablated with 30000 pulses. Macroporous silicon proved to be a good base for the preparation of SERS substrates.

  1. A unified picture of the crystal structures of metals

    International Nuclear Information System (INIS)

    Soederlind, P.; Eriksson, O.; Johansson, B.; Wills, J.M.; Boring, A.M.

    1995-01-01

    The crystal structures of the light actinides have intrigued physicists and chemists for several decades. Simple metals and transition metals have close-packed, high-symmetry structures, such as body-centred cubic, face-centred cubic hexagonal close packing. In contrast, the structures of the light actinides are very loosely packed and of low symmetry -tetragonal, orthorhombic and monoclinic. To understand these differences, we have have performed total-energy calculations, as a function of volume, for both high- and low-symmetry structures of a simple metal (aluminium), a non-magnetic transition metal (niobium), a ferromagnetic transition metal (iron) and a light actinide (uranium). We find that the crystal structure of all these metals is determined by the balance between electrostatic (Madelung) interactions, which favour high symmetry, and a Peierls distortion of the crystal lattice, which favours low symmetry. We show that simple metals and transition metals can adopt low-symmetry structures on expansion of the lattice; and we predict that, conversely, the light actinides will undergo transitions to structures of higher symmetry on compression. (author)

  2. Data mining of metal ion environments present in protein structures.

    Science.gov (United States)

    Zheng, Heping; Chruszcz, Maksymilian; Lasota, Piotr; Lebioda, Lukasz; Minor, Wladek

    2008-09-01

    Analysis of metal-protein interaction distances, coordination numbers, B-factors (displacement parameters), and occupancies of metal-binding sites in protein structures determined by X-ray crystallography and deposited in the PDB shows many unusual values and unexpected correlations. By measuring the frequency of each amino acid in metal ion-binding sites, the positive or negative preferences of each residue for each type of cation were identified. Our approach may be used for fast identification of metal-binding structural motifs that cannot be identified on the basis of sequence similarity alone. The analysis compares data derived separately from high and medium-resolution structures from the PDB with those from very high-resolution small-molecule structures in the Cambridge Structural Database (CSD). For high-resolution protein structures, the distribution of metal-protein or metal-water interaction distances agrees quite well with data from CSD, but the distribution is unrealistically wide for medium (2.0-2.5A) resolution data. Our analysis of cation B-factors versus average B-factors of atoms in the cation environment reveals substantial numbers of structures contain either an incorrect metal ion assignment or an unusual coordination pattern. Correlation between data resolution and completeness of the metal coordination spheres is also found.

  3. A Scalable Synthesis Pathway to Nanoporous Metal Structures.

    Science.gov (United States)

    Coaty, Christopher; Zhou, Hongyao; Liu, Haodong; Liu, Ping

    2018-01-23

    A variety of nanoporous transition metals, Fe, Co, Au, Cu, and others, have been readily formed by a scalable, room-temperature synthesis process. Metal halide compounds are reacted with organolithium reductants in a nonpolar solvent to form metal/lithium halide nanocomposites. The lithium halide is then dissolved out of the nanocomposite with a common organic solvent, leaving behind a continuous, three-dimensional network of metal filaments that form a nanoporous structure. This approach is applicable to both noble metals (Cu, Au, Ag) and less-noble transition metals (Co, Fe, Ni). The microstructures of these nanoporous transition metals are tunable, as controlling the formation of the metal structure in the nanocomposite dictates the final metal structure. Microscopy studies and nitrogen adsorption analysis show these materials form pores ranging from 2 to 50 nm with specific surface areas from 1.0 m 2 /g to 160 m 2 /g. Our analysis also shows that pore size, pore volume, and filament size of the nanoporous metal networks depend on the mobility of target metal and the amount of lithium halide produced by the conversion reaction. Further, it has been demonstrated that hybrid nanoporous structures of two or more metals could be synthesized by performing the same process on mixtures of precursor compounds. Metals (e.g., Co and Cu) have been found to stabilize each other in nanoporous forms, resulting in smaller pore sizes and higher surface areas than each element in their pure forms. This scalable and versatile synthesis pathway greatly expands our access to additional compositions and microstructures of nanoporous metals.

  4. Microdroplet engineering for microbioassay and synthesis of functional structured porous particles

    Science.gov (United States)

    Rastogi, Vinayak

    We present methods where sessile or suspended microdroplets are used to develop applications in the areas of bio-detection, photonics, drug delivery and catalysis. The first technique we report is for droplet-on-a-chip microbioassays. The assays are performed in droplet micro-containers suspended on the surface of high density fluorinated oil and are based on the process of agglutination of antibody-coated particles. Droplet microbioassays for the detection of Ricin were designed and their performance was compared to the standard handheld field assays. These droplet microbioassays were found to be 10 times more sensitive in terms of analyte concentration while requiring 100 times smaller volumes. We developed a model for the agglutination kinetics and mass transfer processes inside the droplets, which correlates well with the experimental data. The second technique that we developed uses droplet templates dispensed on superhydrophobic substrates for the fabrication of a new class of three dimensional hierarchical microsphere assemblies. The technique is termed Dry Self Assembly (DSA) since the fabricated supraparticles are easily detached from the substrate and collected unlike methods where assembled structures are suspended in liquid environment. The sessile droplet templates cast the final supraparticles into light diffracting near-spherical assemblies. When illuminated with a collimated beam of light, the structures exhibit unique ring shaped color diffraction patterns on their surface. The experimental observations for the angular position and wavelength corresponding to a spot on the rings are interpreted using a surface diffraction grating model. We also tailored the DSA method to produce both shape-anisotropic and composition-anisotropic supraparticles. The shape anisotropy was demonstrated by fabricating "doughnut" assemblies using droplets of both pure silica suspensions and silica mixed with gold nanoparticles. The composition anisotropy was realized by

  5. Structural optimization of 3D porous electrodes for high-rate performance lithium ion batteries.

    Science.gov (United States)

    Ye, Jianchao; Baumgaertel, Andreas C; Wang, Y Morris; Biener, Juergen; Biener, Monika M

    2015-02-24

    Much progress has recently been made in the development of active materials, electrode morphologies and electrolytes for lithium ion batteries. Well-defined studies on size effects of the three-dimensional (3D) electrode architecture, however, remain to be rare due to the lack of suitable material platforms where the critical length scales (such as pore size and thickness of the active material) can be freely and deterministically adjusted over a wide range without affecting the overall 3D morphology of the electrode. Here, we report on a systematic study on length scale effects on the electrochemical performance of model 3D np-Au/TiO2 core/shell electrodes. Bulk nanoporous gold provides deterministic control over the pore size and is used as a monolithic metallic scaffold and current collector. Extremely uniform and conformal TiO2 films of controlled thickness were deposited on the current collector by employing atomic layer deposition (ALD). Our experiments demonstrate profound performance improvements by matching the Li(+) diffusivity in the electrolyte and the solid state through adjusting pore size and thickness of the active coating which, for 200 μm thick porous electrodes, requires the presence of 100 nm pores. Decreasing the thickness of the TiO2 coating generally improves the power performance of the electrode by reducing the Li(+) diffusion pathway, enhancing the Li(+) solid solubility, and minimizing the voltage drop across the electrode/electrolyte interface. With the use of the optimized electrode morphology, supercapacitor-like power performance with lithium-ion-battery energy densities was realized. Our results provide the much-needed fundamental insight for the rational design of the 3D architecture of lithium ion battery electrodes with improved power performance.

  6. VOPcPhO:P3HT composite micro-structures with nano-porous surface morphology

    Energy Technology Data Exchange (ETDEWEB)

    Azmer, Mohamad Izzat [Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ahmad, Zubair, E-mail: zubairtarar@qu.edu.qa [Center for Advanced Materials (CAM), Qatar University, P. O. Box 2713, Doha (Qatar); Sulaiman, Khaulah, E-mail: khaulah@um.edu.my [Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Touati, Farid [Department of Electrical Engineering, College of Engineering, Qatar University, P. O. Box 2713, Doha (Qatar); Bawazeer, Tahani M. [Department of Chemistry, Faculty of Applied Science, Umm Al-Qura University, Makkah (Saudi Arabia); Alsoufi, Mohammad S. [Mechanical Engineering Department, College of Engineering and Islamic Architecture, Umm Al-Qura University, Makkah (Saudi Arabia)

    2017-03-31

    Highlights: • VOPcPhO:P3HT micro-structures with nano-porous surface morphology have been formed. • Multidimensional structures have been formed by electro-spraying technique. • The electro-sprayed films are very promising for the humidity sensors. - Abstract: In this paper, composite micro-structures of Vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine) (VOPcPhO) and Poly (3-hexylthiophene-2,5-diyl) (P3HT) complex with nano-porous surface morphology have been developed by electro-spraying technique. The structural and morphological characteristics of the VOPcPhO:P3HT composite films have been studied by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The multidimensional VOPcPhO:P3HT micro-structures formed by electro-spraying with nano-porous surface morphology are very promising for the humidity sensors due to the pore sizes in the range of micro to nano-meters scale. The performance of the VOPcPhO:P3HT electro-sprayed sensor is superior in term of sensitivity, hysteresis and response/recovery times as compared to the spin-coated one. The electro-sprayed humidity sensor exhibits ∼3 times and 0.19 times lower hysteresis in capacitive and resistive mode, respectively, as compared to the spin-coated humidity sensor.

  7. Structural studies of ZnS:Cu (5 at %) nanocomposites in porous Al{sub 2}O{sub 3} of different thicknesses

    Energy Technology Data Exchange (ETDEWEB)

    Valeev, R. G., E-mail: rishatvaleev@mail.ru; Trigub, A. L.; Chukavin, A. I.; Beltiukov, A. N. [Physical-Technical Institute, Russian Academy of Sciences (Ural Branch) (Russian Federation)

    2017-02-15

    We present EXAFS, XANES, and X-ray diffraction data on nanoscale ZnS:Cu (5 at %) structures fabricated by the thermal deposition of a ZnS and Cu powder mixture in porous anodic alumina matrices with a pore diameter of 80 nm and thicknesses of 1, 3, and 5 μm. The results obtained are compared with data on ZnS:Cu films deposited onto a polycor surface. According to X-ray diffraction data, the samples contain copper and zinc compounds with sulfur (Cu{sub 2}S and ZnS, respectively); the ZnS compound is in the cubic (sphalerite) and hexagonal (wurtzite) modifications. EXAFS and XANES studies at the K absorption edges of zinc and copper showed that, in samples deposited onto polycor and alumina with thicknesses of 3 and 5 μm, most copper atoms form the Cu{sub 2}S compound, while, in the sample deposited onto a 1-μm-thick alumina layer, copper atoms form metallic particles on the sample surface. Copper crystals affect the Zn–S interatomic distance in the sample with a 1-μm-thick porous Al{sub 2}O{sub 3} layer; this distance is smaller than in the other samples.

  8. Engineering chiral porous metal-organic frameworks for enantioselective adsorption and separation

    Science.gov (United States)

    Peng, Yongwu; Gong, Tengfei; Zhang, Kang; Lin, Xiaochao; Liu, Yan; Jiang, Jianwen; Cui, Yong

    2014-07-01

    The separation of racemic molecules is of substantial significance not only for basic science but also for technical applications, such as fine chemicals and drug development. Here we report two isostructural chiral metal-organic frameworks decorated with chiral dihydroxy or -methoxy auxiliares from enantiopure tetracarboxylate-bridging ligands of 1,1‧-biphenol and a manganese carboxylate chain. The framework bearing dihydroxy groups functions as a solid-state host capable of adsorbing and separating mixtures of a range of chiral aromatic and aliphatic amines, with high enantioselectivity. The host material can be readily recycled and reused without any apparent loss of performance. The utility of the present adsorption separation is demonstrated in the large-scale resolution of racemic 1-phenylethylamine. Control experiments and molecular simulations suggest that the chiral recognition and separation are attributed to the different orientations and specific binding energies of the enantiomers in the microenvironment of the framework.

  9. Photocatalytic, Morphological and Structural Properties of the TiO2-SiO2-Ag Porous Structures Based System

    Directory of Open Access Journals (Sweden)

    Gábor Kovács

    2015-03-01

    Full Text Available TiO2-SiO2-based nanocomposites with highly porous structures are gaining ever increasing attention due to their specific properties and large variability of synthesis pathways together with wide information on the impact of the synthesis on the activity of the catalyst. This thereby offers an alternative approach to traditional/commercially available photocatalysts. In our work TiO2-SiO2 based aerogels were obtained and modified with various amount of Ag nanoparticles, using different synthesis pathways. In the first instance their photocatalytic activity was examined in detail, by observing major differences toward salicylic acid and correlating them with their morphological and structural properties (investigating their mesoporous character, band-gap values, crystallinity grade etc.. Applying different techniques such as diffuse reflectance spectroscopy (DRS, X-ray diffraction measurements (XRD, transmission electron microscopy (TEM, Raman- and X-ray photoelectron spectroscopy (XPS the nanoparticles and their composite morphological and structural details were successfully evaluated. Major differences were observed in the activity towards salicylic acid.

  10. Structural analysis of anodic porous alumina used for resistive random access memory

    International Nuclear Information System (INIS)

    Lee, Jeungwoo; Nigo, Seisuke; Kato, Seiichi; Kitazawa, Hideaki; Kido, Giyuu; Nakano, Yoshihiro

    2010-01-01

    Anodic porous alumina with duplex layers exhibits a voltage-induced switching effect and is a promising candidate for resistive random access memory. The nanostructural analysis of porous alumina is important for understanding the switching effect. We investigated the difference between the two layers of an anodic porous alumina film using transmission electron microscopy and electron energy-loss spectroscopy. Diffraction patterns showed that both layers are amorphous, and the electron energy-loss spectroscopy indicated that the inner layer contains less oxygen than the outer layer. We speculate that the conduction paths are mostly located in the oxygen-depleted area.

  11. Electronic structure of disordered transition metals within scattering theory

    International Nuclear Information System (INIS)

    Yakyibchuk, P.M.; Volkov, O.V.; Vakarchuk, S.O.

    2005-01-01

    Here we present a new approach to the calculation of density of states of disordered transition metals based on the T-matrix framework presented by Lloyd within generalized Ziman's theory of transport properties and energy structure of disordered metals. This approach makes it possible to avoid such difficulties of familiar calculations as renormalized perturbation theory. We have achieved double hill energy resonance for transition metals at Fe and Co groups caused by hybridization potential. So the results are in good correlation with model presentation of energy structure of these metals conduction band for explaining magnetic and transport properties

  12. Surface Structures of Model Metal Catalysts in Reactant Gases.

    Science.gov (United States)

    Tao, Franklin Feng; Ralston, Walter T; Liu, Huimin; Somorjai, Gabor A

    2018-01-18

    Atomic scale knowledge of the surface structure of a metal catalyst is essential for fundamentally understanding the catalytic reactions performed on it. A correlation between the true atomic surface structure of a metal catalyst under reaction conditions and the corresponding catalytic performance is the key in pursuing mechanistic insight at a molecular level. Here the surface structures of model, metal catalysts in both ultrahigh vacuum (UHV) and gaseous environments of CO at a wide range of pressures are discussed. The complexity of observed surface structures in CO is illustrated, driving the necessity for visualization of the catalytic metals under realistic reaction conditions. Technical barriers for visualization of metal surfaces in situ at high temperature and high pressure are discussed.

  13. Selective adsorption in two porous triazolate-oxalate-bridged antiferromagnetic metal-azolate frameworks obtained via in situ decarboxylation of 3-amino-1,2,4-triazole-5-carboxylic acid

    Science.gov (United States)

    Hou, Juan-Juan; Xu, Xia; Jiang, Ning; Wu, Ya-Qin; Zhang, Xian-Ming

    2015-03-01

    Solvothermal reactions of metal salts, 3-amino-1,2,4-triazole-5-carboxylic acid (H2atzc) and ammonium oxalate in different temperature produced two metal azolate frameworks, namely, [Cu3(atzc)2(atz)(ox)]·1.5H2O (1) and [Co5(atz)4(ox)3(HCOO)2]·DMF (2) (H2atzc=3-amino-1,2,4-triazole-5-carboxylic acid, Hatz=3-amino-1,2,4-triazole, and ox=oxalate), in which the atzc precusor was in situ decarboxylated. Structural determination reveals that 1 contains [Cu3(atzc)2(atz)]2- layers of mixed μ4-atzc and μ3-atz ligands, which are pillared by ox2- groups to form a 3D porous framework. Compound 2 contains 2D layers with basic spindle-shaped decanuclear units, which extended by ox2- and formates to form 3D porous framework. Gas adsorption investigation revealed that two kinds of frameworks exhibited selective CO2 over N2 sorption. Moreover, activated 2 shows H2 storage capacity. Additionally, magnetic properties of both the compounds have been investigated.

  14. Characterization of multi-scale porous structure of fly ash/phosphate geopolymer hollow sphere structures: from submillimeter to nano-scale.

    Science.gov (United States)

    Li, Ruifeng; Wu, Gaohui; Jiang, Longtao; Sun, Dongli

    2015-01-01

    In the present work, the porous structure of fly ash/phosphate geopolymer hollow sphere structures (FPGHSS), prepared by pre-bonding and curing technology, has been characterized by multi-resolution methods from sub-millimeter to nano-scale. Micro-CT and confocal microscopy could provide the macroscopic distribution of porous structure on sub-millimeter scale, and hollow fly ashes with sphere shape and several sub-millimeter open cells with irregular shape were identified. SEM is more suitable to illustrate the distribution of micro-sized open and closed cells, and it was found that the open cells of FPGHSS were mainly formed in the interstitial porosity between fly ashes. Mercury porosimeter measurement showed that the micro-sized open cell of FPGHSS demonstrated a normal/bimodal distribution, and the peaks of pore size distribution were mainly around 100 and 10 μm. TEM observation revealed that the phosphate geopolymer was mainly composed of the porous area with nano-pores and dense areas, which were amorphous Al-O-P phase and α-Al2O3 respectively. The pore size of nano-pores demonstrated a quasi-normal distribution from about 10 to 100 nm. Therefore, detailed information of the porous structure of FPGHSS could be revealed using multiple methods. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. 2D nickel oxide nanosheets with highly porous structure for high performance capacitive energy storage

    Science.gov (United States)

    Li, Zijiong; Zhang, Weiyang; Liu, Yanyue; Guo, Jinjin; Yang, Baocheng

    2018-01-01

    Developing advanced electrochemical electrode materials with excellent performance is critical to their future energy storage devices. Herein, we design and synthesize two-dimensional (2D) porous structure nickel oxide (NiO) nanosheets via a facile and scalable hydrothermal approach, and further heating. The effects of heating time on the electrochemical performances are investigated. The results indicate that the maximum specific capacitance is achieved for NiO nanosheets when heating temperature and time are 300 °C and 3 h, respectively (namely NiO-3). The as-prepared NiO-3 nanosheet are grown uniform on the skeleton of reduced graphene oxide (rGO). The optimum NiO/rGO displays a reversible discharge capacity of 781.7 F g-1 at 1 A g-1, and shows an ultra-long life-span with over 94% capacitance retention after 4000 cycles. The enhanced electrochemical properties for NiO/rGO can be ascribed to a collaborative effect between NiO and rGO, which possess high capacitance storage ability and excellent conductivity, respectively.

  16. Effects of confinement in meso-porous silica and carbon nano-structures

    International Nuclear Information System (INIS)

    Leon, V.

    2006-07-01

    Physico-chemical properties of materials can be strongly modified by confinement because of the quantum effects that appear at such small length scales and also because of the effects of the confinement itself. The aim of this thesis is to show that both the nature of the confining material and the size of the pores and cavities have a strong impact on the confined material. We first show the effect of the pore size of the host meso-porous silica on the temperature of the solid-solid phase transition of silver selenide, a semiconducting material with enhanced magnetoresistive properties under non-stoichiometric conditions. Narrowing the pores from 20 nm to 2 nm raises the phase transition temperature from 139 C to 146 C. This result can be explained by considering the interaction between the confining and confined materials as a driving force. The effects of confinement are also studied in the case of hydrogen and deuterium inside cavities of organized carbon nano-structures. The effects that appear in the adsorption/desorption cycles are much stronger with carbon nano-horns as the host material than with C60 pea-pods and single-walled carbon nano-tubes. (author)

  17. Porous Structures in Stacked, Crumpled and Pillared Graphene-Based 3D Materials.

    Science.gov (United States)

    Guo, Fei; Creighton, Megan; Chen, Yantao; Hurt, Robert; Külaots, Indrek

    2014-01-01

    Graphene, an atomically thin material with the theoretical surface area of 2600 m 2 g -1 , has great potential in the fields of catalysis, separation, and gas storage if properly assembled into functional 3D materials at large scale. In ideal non-interacting ensembles of non-porous multilayer graphene plates, the surface area can be adequately estimated using the simple geometric law ~ 2600 m 2 g -1 /N, where N is the number of graphene sheets per plate. Some processing operations, however, lead to secondary plate-plate stacking, folding, crumpling or pillaring, which give rise to more complex structures. Here we show that bulk samples of multilayer graphene plates stack in an irregular fashion that preserves the 2600/N surface area and creates regular slot-like pores with sizes that are multiples of the unit plate thickness. In contrast, graphene oxide deposits into films with massive area loss (2600 to 40 m 2 g -1 ) due to nearly perfect alignment and stacking during the drying process. Pillaring graphene oxide sheets by co-deposition of colloidal-phase particle-based spacers has the potential to partially restore the large monolayer surface. Surface areas as high as 1000 m 2 g -1 are demonstrated here through colloidal-phase deposition of graphene oxide with water-dispersible aryl-sulfonated ultrafine carbon black as a pillaring agent.

  18. Porous structure and surface chemistry of phosphoric acid activated carbon from corncob

    Science.gov (United States)

    Sych, N. V.; Trofymenko, S. I.; Poddubnaya, O. I.; Tsyba, M. M.; Sapsay, V. I.; Klymchuk, D. O.; Puziy, A. M.

    2012-11-01

    Active carbons have been prepared from corncob using chemical activation with phosphoric acid at 400 °C using varied ratio of impregnation (RI). Porous structure of carbons was characterized by nitrogen adsorption and scanning electron microscopy. Surface chemistry was studied by IR and potentiometric titration method. It has been shown that porosity development was peaked at RI = 1.0 (SBET = 2081 m2/g, Vtot = 1.1 cm3/g), while maximum amount of acid surface groups was observed at RI = 1.25. Acid surface groups of phosphoric acid activated carbons from corncob includes phosphate and strongly acidic carboxylic (pK = 2.0-2.6), weakly acidic carboxylic (pK = 4.7-5.0), enol/lactone (pK = 6.7-7.4; 8.8-9.4) and phenol (pK = 10.1-10.7). Corncob derived carbons showed high adsorption capacity to copper, especially at low pH. Maximum adsorption of methylene blue and iodine was observed for carbon with most developed porosity (RI = 1.0).

  19. The pore wall structure of porous semi-crystalline anatase TiO2

    International Nuclear Information System (INIS)

    Kim, Man-Ho; Doh, Jeong-Mann; Han, Seong Chul; Chae, Keun Hwa; Yu, Byung-Yong; Hong, Kyung Tae; Jackson, Andrew; Maryland Univ., College Park, MD; Anovitz, Lawrence M.

    2011-01-01

    The structure of porous TiO 2 prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2 and the pore was not sharp. A density gradient of around 40-60 A at the pore wall (i.e. the interface between the pore and the TiO 2 matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO 2 matrix and the pores filled with liquid H 2 O/D 2 O mixtures was 51/49%(v/v) H 2 O/D 2 O, yielding an estimated mass density of 3.32 g cm -3 . The specific surface area of the sample derived from the (U)SANS data was around 939-1003 m 2 cm -3 (283-302 m 2 g -1 ). (orig.)

  20. The pore wall structure of porous semi-crystalline anatase TiO2.

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dr Man-Ho [National Institute of Standards and Technol/University of Maryland, College Park; Doh, Dr. Jeong-Mann [Harbin Institute of Technology & Korea Institute of Science and Technology; Han, Seong Chul [Harbin Institute of Technology & Korea Institute of Science and Technology; Chae, Keun Hwa [Harbin Institute of Technology & Korea Institute of Science and Technology; Yu, Byung-Yong [Harbin Institute of Technology & Korea Institute of Science and Technology; Hong, Kyung Tea [Harbin Institute of Technology & Korea Institute of Science and Technology; Jackson, Andrew [NIST Center for Neutron Research (NCRN), Gaithersburg, MD; Anovitz, Lawrence {Larry} M [ORNL

    2011-01-01

    The structure of porous TiO2 prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2 and the pore was not sharp. A density gradient of around 40 60 A at the pore wall (i.e. the interface between the pore and the TiO2 matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO2 matrix and the pores filled with liquid H2O/D2O mixtures was 51/49%(v/v) H2O/D2O, yielding an estimated mass density of 3.32 g cm3. The specific surface area of the sample derived from the (U)SANS data was around 939 1003 m2 cm3 (283 302 m2 g1).

  1. Structural properties of porous materials and powders used in different fields of science and technology

    CERN Document Server

    Volfkovich, Yury Mironovich; Bagotsky, Vladimir Sergeevich

    2014-01-01

    This book provides a comprehensive and concise description of most important aspects of experimental and theoretical investigations of porous materials and powders, with the use and application of these materials in different fields of science, technology, national economy and environment. It allows the reader to understand the basic regularities of heat and mass transfer and adsorption occurring in qualitatively different porous materials and products, and allows the reader to optimize the functional properties of porous and powdered products and materials. Written in an straightforward and transparent manner, this book is accessible to both experts and those without specialist knowledge, and it is further elucidated by drawings, schemes and photographs. Porous materials and powders with different pore sizes are used in many areas of industry, geology, agriculture and science. These areas include (i) a variety of devices and supplies; (ii) thermal insulation and building materials; (iii) oil-bearing geologic...

  2. Kinetic and steric differences in adsorption in two porous metal-organic frameworks

    Science.gov (United States)

    Lask, Kathleen; Krungleviciute, Vaiva; Bulut, Murat; Migone, Aldo; Lee, J.-Y.; Li, Jing

    2008-03-01

    Kinetic and steric differences are two of the three fundamental mechanisms underlying the use of adsorption in applications to gas mixture separations. We present experimental results on kinetics and equilibrium adsorption measurements of tetrafluoromethane and argon on two metal-organic framework (MOF) materials: RPM1-Co or [Co3(bpdc)3bpy].4DMF.H2O] (bpdc = biphenyldicarboxylate, bpy = 4,4'-bipyridine, DMF = N,N- dimethylformamide) and Cu-BTC or Cu3(BTC)2(H2O)3 (BTC = benzene-1,3,5-tricarboxylate). The adsorbates display significant differences in their kinetics on RPM1-Co (i.e., there are sizable differences in the time required for each gas to reach equilibrium after it is allowed access to the substrate). Our equilibrium measurements show that CF4 is sterically precluded from adsorbing in the small tetrahedral-shaped side pockets present in Cu-BTC. We will compare our experimental results with predictions for how adsorption kinetics depends on the size of the adsorbate and on those of the pores present in the substrate.

  3. Poly(ε-caprolactone)/gelatin composite electrospun scaffolds with porous crater-like structures for tissue engineering

    Science.gov (United States)

    Hwang, Patrick T.J.; Murdock, Kyle; Alexander, Grant C.; Salaam, Amanee D.; Ng, Joshua I.; Lim, Dong-Jin; Dean, Derrick; Jun, Ho-Wook

    2016-01-01

    Electrospinning has been widely used to fabricate scaffolds imitating the structure of natural extracellular matrix (ECM). However, conventional electrospinning produces tightly compacted nanofiber layers with only small superficial pores and a lack of bioactivity, which limit the usefulness of electrospinning in biomedical applications. Thus, a porous poly(ε-caprolactone) (PCL)/gelatin composite electrospun scaffold with crater-like structures was developed. Porous crater-like structures were created on the scaffold by a gas foaming/salt leaching process; this unique fiber structure had more large pore areas and higher porosity than the conventional electrospun fiber network. Various ratios of PCL/gelatin (concentration ratios: 100/0, 75/25, and 50/50) composite electrospun scaffolds with and without crater-like structures were characterized by their microstructures, surface chemistry, degradation, mechanical properties, and ability to facilitate cell growth and infiltration. The combination of PCL and gelatin endowed the scaffold with both structural stability of PCL and bioactivity of gelatin. All ratios of scaffolds with crater-like structures showed fairly similar surface chemistry, degradation rates, and mechanical properties to equivalent scaffolds without crater-like structures; however, craterized scaffolds displayed higher human mesenchymal stem cell (hMSC) proliferation and infiltration throughout the scaffolds after 7-day culture. Therefore, these results demonstrated that PCL/gelatin composite electrospun scaffolds with crater-like structures can provide a structurally and biochemically improved three-dimensional ECM-mimicking microenvironment. PMID:26567028

  4. Poly(ɛ-caprolactone)/gelatin composite electrospun scaffolds with porous crater-like structures for tissue engineering.

    Science.gov (United States)

    Hwang, Patrick T J; Murdock, Kyle; Alexander, Grant C; Salaam, Amanee D; Ng, Joshua I; Lim, Dong-Jin; Dean, Derrick; Jun, Ho-Wook

    2016-04-01

    Electrospinning has been widely used to fabricate scaffolds imitating the structure of natural extracellular matrix (ECM). However, conventional electrospinning produces tightly compacted nanofiber layers with only small superficial pores and a lack of bioactivity, which limit the usefulness of electrospinning in biomedical applications. Thus, a porous poly(ε-caprolactone) (PCL)/gelatin composite electrospun scaffold with crater-like structures was developed. Porous crater-like structures were created on the scaffold by a gas foaming/salt leaching process; this unique fiber structure had more large pore areas and higher porosity than the conventional electrospun fiber network. Various ratios of PCL/gelatin (concentration ratios: 100/0, 75/25, and 50/50) composite electrospun scaffolds with and without crater-like structures were characterized by their microstructures, surface chemistry, degradation, mechanical properties, and ability to facilitate cell growth and infiltration. The combination of PCL and gelatin endowed the scaffold with both structural stability of PCL and bioactivity of gelatin. All ratios of scaffolds with crater-like structures showed fairly similar surface chemistry, degradation rates, and mechanical properties to equivalent scaffolds without crater-like structures; however, craterized scaffolds displayed higher human mesenchymal stem cell (hMSC) proliferation and infiltration throughout the scaffolds after 7-day culture. Therefore, these results demonstrated that PCL/gelatin composite electrospun scaffolds with crater-like structures can provide a structurally and biochemically improved three-dimensional ECM-mimicking microenvironment. © 2016 Wiley Periodicals, Inc.

  5. Porous media modeling and micro-structurally motivated material moduli determination via the micro-dilatation theory

    Science.gov (United States)

    Jeong, J.; Ramézani, H.; Sardini, P.; Kondo, D.; Ponson, L.; Siitari-Kauppi, M.

    2015-07-01

    In the present contribution, the porous material modeling and micro-structural material parameters determination are scrutinized via the micro-dilatation theory. The main goal is to take advantage of the micro-dilatation theory which belongs to the generalized continuum media. In the first stage, the thermodynamic laws are entirely revised to reach the energy balance relation using three variables, deformation, porosity change and its gradient underlying the porous media as described in the micro-dilatation theory or so-called void elasticity. Two experiments over cement mortar specimens are performed in order to highlight the material parameters related to the pore structure. The shrinkage due to CO2 carbonation, porosity and its gradient are calculated. The extracted values are verified via 14C-PMMA radiographic image method. The modeling of swelling phenomenon of Delayed Ettringite Formation (DEF) is studied later on. This issue is performed via the crystallization pressure application using the micro-dilatation theory.

  6. Thermal Annealing induced relaxation of compressive strain in porous GaN structures

    KAUST Repository

    Ben Slimane, Ahmed

    2012-01-01

    The effect of annealing on strain relaxation in porous GaN fabricated using electroless chemical etching is presented. The Raman shift of 1 cm-1 in phonon frequency of annealed porous GaN with respect to as-grown GaN corresponds to a relaxation of compressive strain by 0.41 ± 0.04 GPa. The strain relief promises a marked reduction in threading dislocation for subsequent epitaxial growth.

  7. Electronic and chemical structure of metal-silicon interfaces

    Science.gov (United States)

    Grunthaner, P. J.; Grunthaner, F. J.

    1984-01-01

    This paper reviews our current understanding of the near-noble metal silicides and the interfaces formed with Si(100). Using X-ray photoemission spectroscopy, we compare the chemical composition and electronic structure of the room temperature metal-silicon and reacted silicide-silicon interfaces. The relationship between the interfacial chemistry and the Schottky barrier heights for this class of metals on silicon is explored.

  8. Structure and properties of porous TiNi(Co, Mo)-based alloy produced by the reaction sintering

    Science.gov (United States)

    Artyukhova, Nadezda; Yasenchuk, Yuriy; Chekalkin, Timofey; Gunther, Victor; Kim, Ji-Soon; Kang, Ji-Hoon

    2016-10-01

    Modern medical technologies have developed many new devices that can be implanted into humans to repair, assist or take the place of diseased or defective bones, arteries and even organs. The materials, especially porous ones, used for these devices have evolved steadily over the past twenty years with TiNi-based alloys replacing stainless steels and titanium. The aim of the paper is to presents results for examination of porous TiNi(Co,Mo)-based alloys intended further to be used in clinical practice. The structure and properties of porous TiNi-based alloys obtained by reaction sintering of Ti and Ni powders with additions of Co and Mo have been studied. It has been shown that alloying additions both Co and Mo inhibit the compaction of nickel powders in the initial stage of sintering. The maximum irreversible strain of porous samples under loading in the austenitic state is fixed with the Co addition, and the minimum one is fixed with the Mo addition. The Co addition leads to the fact that the martensite transformation in the TiNi phase becomes close to a one-step, and the Mo addition leads to the fact that the martensite transformation becomes more uniform. Both Co and Mo lead to an increase in the maximum accumulated strain as a result of the formation of temperature martensite. The additional increase in the maximum accumulated strain of the Ti50Ni49Co1 alloy is caused by decreased resistance of the porous Ni γ -based mass during the load.

  9. Metal nanoparticle direct inkjet printing for low-temperature 3D micro metal structure fabrication

    International Nuclear Information System (INIS)

    Ko, Seung Hwan; Nam, Koo Hyun; Chung, Jaewon; Hotz, Nico; Grigoropoulos, Costas P

    2010-01-01

    Inkjet printing of functional materials is a key technology toward ultra-low-cost, large-area electronics. We demonstrate low-temperature 3D micro metal structure fabrication by direct inkjet printing of metal nanoparticles (NPs) as a versatile, direct 3D metal structuring approach representing an alternative to conventional vacuum deposition and photolithographic methods. Metal NP ink was inkjet-printed to exploit the large melting temperature drop of the nanomaterial and the ease of the NP ink formulation. Parametric studies on the basic conditions for stable 3D inkjet printing of NP ink were carried out. Furthermore, diverse 3D metal microstructures, including micro metal pillar arrays, helices, zigzag and micro bridges were demonstrated and electrical characterization was performed. Since the process requires low temperature, it carries substantial potential for fabrication of electronics on a plastic substrate

  10. Atomic layer deposition TiO{sub 2} coated porous silicon surface: Structural characterization and morphological features

    Energy Technology Data Exchange (ETDEWEB)

    Iatsunskyi, Igor, E-mail: igoyat@amu.edu.pl [NanoBioMedical Centre, Adam Mickiewicz University, 85 Umultowska str., 61-614, Poznan (Poland); Department of Experimental Physics, Odessa National I.I. Mechnikov University, 42, Pastera str., 65023 Odessa (Ukraine); Jancelewicz, Mariusz; Nowaczyk, Grzegorz [NanoBioMedical Centre, Adam Mickiewicz University, 85 Umultowska str., 61-614, Poznan (Poland); Kempiński, Mateusz [NanoBioMedical Centre, Adam Mickiewicz University, 85 Umultowska str., 61-614, Poznan (Poland); Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poland (Poland); Peplińska, Barbara [NanoBioMedical Centre, Adam Mickiewicz University, 85 Umultowska str., 61-614, Poznan (Poland); Department of Macromolecular Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan (Poland); Jarek, Marcin; Załęski, Karol [NanoBioMedical Centre, Adam Mickiewicz University, 85 Umultowska str., 61-614, Poznan (Poland); Jurga, Stefan [NanoBioMedical Centre, Adam Mickiewicz University, 85 Umultowska str., 61-614, Poznan (Poland); Department of Macromolecular Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan (Poland); Smyntyna, Valentyn [Department of Experimental Physics, Odessa National I.I. Mechnikov University, 42, Pastera str., 65023 Odessa (Ukraine)

    2015-08-31

    TiO{sub 2} thin films were grown on highly-doped p-Si (100) macro- and mesoporous structures by atomic layer deposition (ALD) using TiCl{sub 4} and deionized water as precursors at 300 °C. The crystalline structure, chemical composition, and morphology of the deposited films and initial silicon nanostructures were investigated by scanning electron microscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy and X-ray diffraction (XRD). The mean size of TiO{sub 2} crystallites was determined by TEM, XRD and Raman spectroscopy. It was shown that the mean crystallite size and the crystallinity of the TiO{sub 2} are influenced dramatically by the morphology of the porous silicon, with the mesoporous silicon resulting in a much finer grain size and amorphous structure than the macroporous silicon having a partially crystal anatase phase. A simple model of the ALD layer growth inside the pores was presented. - Highlights: • The morphology and chemical composition of TiO{sub 2} and porous Si were established. • The approximate size of TiO{sub 2} nanocrystals was estimated. • The model of the atomic layer deposition coating in the porous Si was presented.

  11. Effect of hydrothermal modification on the porous structure and thermal properties of carbon-silica adsorbents (carbosils)

    International Nuclear Information System (INIS)

    Skubiszewska-Zieba, J.; Charmas, B.; Leboda, R.; Staszczuk, P.; Kowalczyk, P.; Oleszczuk, P.

    2003-01-01

    Characterisation of porous structure and thermal properties of unmodified and hydrothermally modified (using H 2 O 2 , under high pressure conditions) carbon-silica adsorbents (carbosils) prepared by dichloromethane pyrolysis (under dynamic conditions) on the surface of narrow pore silica were discussed. The analysis was made based on the data of low-temperature nitrogen adsorption/desorption isotherms, transmission electron microscopy (TEM) and the results of differential thermal analysis. It was stated that both porous structure and thermal properties of tested samples are in correlation with the morphology and topography of the carbon deposit. This deposit forms globules and aggregates whose size and position on the inner and outer surface of silica depends on the time of its carbonisation. It was stated that hydrothermal treatment (HTT) of the carbosils changes both the porous structure and thermal properties of the tested samples. As a result of HTT of silica, decondensation and recondensation of orthosilic acid on large particles of silica takes place. Then a decrease in the specific surface area and increase in the radius of pores are observed. In the case of carbosils these changes are smaller and depend on the accessibility of the silica surface, which is connected with topography of carbon deposit

  12. Structured nanoporous surfaces from hybrid block copolymer micelle films with metal ions.

    Science.gov (United States)

    Kim, Minsoo P; Kim, Hyeong Jun; Kim, Bumjoon J; Yi, Gi-Ra

    2015-03-06

    We present a novel method for producing structured nanoporous thin films using block copolymer (BCP) micelles loaded with metallic ions. The BCP micellar thin films containing gold (Au) ions were prepared by spin-coating poly(styrene-block-4-vinylpyridine) (PS-b-P4VP) micelle solutions in which Au precursors (AuCl4(-)) were selectively loaded onto the P4VP core. When the micellar films were exposed to cetyltrimethylammonium bromide (CTAB) solutions, the Au precursors were selectively extracted from the P4VP domains due to their strong electrostatic interaction with CTAB, leading to the formation of pores in the micelles. Consequently, regularly patterned nanoporous surfaces were formed. By controlling the molecular weight (Mn) of PS-b-P4VP and the amount of Au precursors (λ) that were loaded in the P4VP domains, the pore size and depth could be tuned precisely. In particular, when a sufficient amount of Au precursors was loaded (λ  ≥ 0.3), the porous surface nanostructure was well developed. In addition, the pore size and depth of the nanostructure increased as the λ value increased. For instance, when the λ value increased from 0.3 to 1.0, the pore size increased from 22.8 nm to 28.8 nm, and the pore depth increased from 2.1 nm to 3.2 nm. Interestingly, the transition from the nonporous structures to the porous structures in the micellar film could be reversibly controlled by adding and removing the Au precursors in the film. Moreover, our method for the preparation of nanoporous films can be extended to micellar film by incorporating other metal ions such as silver (Ag) and iron (Fe).

  13. Synthesis and characterization of porous structured ZnO thin film for dye sensitized solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Marimuthu, T.; Anandhan, N., E-mail: anandhan-kn@rediffmail.com; Mummoorthi, M. [School of Physics, Alagappa University, Karaikudi – 630 003 (India); Dharuman, V. [Department of Bioelectronics and Biosensors, Alagappa University, Karaikudi – 630 003 (India)

    2016-05-23

    Zinc oxide (ZnO) and zinc oxide/eosin yellow (ZnO/EY) thin films were potentiostatically deposited onto fluorine doped tin oxide (FTO) glass substrate. Effect of eosin yellow dye on structural, morphological and optical properties was studied. X-ray diffraction patterns, micro Raman spectra and photoluminescence (PL) spectra reveal hexagonal wurtzite structure with less atomic defects in 101 plane orientation of the ZnO/EY film. Scanning electron microscopy (SEM) images show flower for ZnO and porous like structure for ZnO/EY thin film, respectively. DSSC was constructed and evaluated by measuring the current density verses voltage curve.

  14. MetalPDB: a database of metal sites in biological macromolecular structures

    OpenAIRE

    Andreini, Claudia; Cavallaro, Gabriele; Lorenzini, Serena; Rosato, Antonio

    2013-01-01

    We present here MetalPDB (freely accessible at http://metalweb.cerm.unifi.it), a novel resource aimed at conveying the information available on the three-dimensional (3D) structures of metal-binding biological macromolecules in a consistent and effective manner. This is achieved through the systematic and automated representation of metal-binding sites in proteins and nucleic acids by way of Minimal Functional Sites (MFSs). MFSs are 3D templates that describe the local environment around the ...

  15. Hollow needle used to cut metal honeycomb structures

    Science.gov (United States)

    Gregg, E. A.

    1966-01-01

    Hollow needle tool cuts metal honeycomb structures without damaging adjacent material. The hollow needle combines an electrostatic discharge and a stream of oxygen at a common point to effect rapid, accurate metal cutting. The tool design can be varied to use the hollow needle principle for cutting a variety of shapes.

  16. Thin films of metal oxides on metal single crystals: Structure and growth by scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Galloway, H.C.

    1995-12-01

    Detailed studies of the growth and structure of thin films of metal oxides grown on metal single crystal surfaces using Scanning Tunneling Microscopy (STM) are presented. The oxide overlayer systems studied are iron oxide and titanium oxide on the Pt(III) surface. The complexity of the metal oxides and large lattice mismatches often lead to surface structures with large unit cells. These are particularly suited to a local real space technique such as scanning tunneling microscopy. In particular, the symmetry that is directly observed with the STM elucidates the relationship of the oxide overlayers to the substrate as well as distinguishing, the structures of different oxides

  17. Symmetry-guided synthesis of highly porous metal-organic frameworks with fluorite topology.

    Science.gov (United States)

    Zhang, Muwei; Chen, Ying-Pin; Bosch, Mathieu; Gentle, Thomas; Wang, Kecheng; Feng, Dawei; Wang, Zhiyong U; Zhou, Hong-Cai

    2014-01-13

    Two stable, non-interpenetrated MOFs, PCN-521 and PCN-523, were synthesized by a symmetry-guided strategy. Augmentation of the 4-connected nodes in the fluorite structure with a rigid tetrahedral ligand and substitution of the 8-connected nodes by the Zr/Hf clusters yielded MOFs with large octahedral interstitial cavities. They are the first examples of Zr/Hf MOFs with tetrahedral linkers. PCN-521 has the largest BET surface area (3411 m(2) g(-1)), pore size (20.5×20.5×37.4 Å) and void volume (78.5%) of MOFs formed from tetrahedral ligands. This work not only demonstrates a successful implementation of rational design of MOFs with desired topology, but also provides a systematic way of constructing non-interpenetrated MOFs with high porosity. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Aircraft Metal Skin Repair and Honeycomb Structure Repair; Sheet Metal Work 3: 9857.02.

    Science.gov (United States)

    Dade County Public Schools, Miami, FL.

    The course helps students determine types of repairs, compute repair sizes, and complete the repair through surface protection. Course content includes goals, specific objectives, protection of metals, repairs to metal skin, and honeycomb structure repair. A bibliography and post-test are appended. A prerequisite for this course is mastery of the…

  19. Stimulated emission of surface plasmons by electron tunneling in metal-barrier-metal structures

    Science.gov (United States)

    Siu, D. P.; Gustafson, T. K.

    1978-01-01

    It is shown that correlation currents arising from the superposition of pairs of states on distinct sides of a potential barrier in metal-barrier-metal structures can result in inelastic tunneling through the emission of surface plasmons. Net gain of an externally excited plasmon field is possible.

  20. Mixed colloidal suspensions of reduced graphene oxide and layered metal oxide nanosheets: useful precursors for the porous nanocomposites and hybrid films of graphene/metal oxide.

    Science.gov (United States)

    Lee, Yu Ri; Kim, In Young; Kim, Tae Woo; Lee, Jang Mee; Hwang, Seong-Ju

    2012-02-20

    Homogeneously mixed colloidal suspensions of reduced graphene oxide, or RGO, and layered manganate nanosheets have been synthesized by a simple addition of the exfoliated colloid of RGO into that of layered MnO(2). The obtained mixed colloidal suspensions with the RGO/MnO(2) ratio of ≤0.3 show good colloidal stability without any phase separation and a negatively charged state with a zeta (ζ) potential of -30 to -40 mV. The flocculation of these mixed colloidal suspensions with lithium cations yields porous nanocomposites of Li/RGO-layered MnO(2) with high electrochemical activity and a markedly expanded surface area of around 70-100 m(2)  g(-1). Relative to the Li/RGO and Li/layered MnO(2) nanocomposites (≈116 and ≈167 F g(-1)), the obtained Li/RGO-layered MnO(2) nanocomposites deliver a larger capacitance of approximately 210 F g(-1) with good cyclability of around 95-97 % up to the 1000th cycle, thus indicating the positive effect of hybridization on the electrode performances of RGO and lithium manganate. Also, an electrophoretic deposition of the mixed colloidal suspensions makes it possible to easily fabricate uniform hybrid films composed of graphene and manganese oxide. The obtained films show a distinct electrochemical activity and a homogeneous distribution of RGO and MnO(2). The present experimental findings clearly demonstrate that the utilization of the mixed colloidal suspensions as precursors provides a facile and universal methodology to synthesize various types of graphene/metal oxide hybrid materials. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Comparative study of porous amorphous a-Si1-xCx films and a-Si1-xCx membranes on structural and luminescence properties

    International Nuclear Information System (INIS)

    Boukezzata, A.; Nezzal, G.; Guerbous, L.; Keffous, A.; Gabouze, N.; Belkacem, Y.; Manseri, A.; Brighet, A.; Kechouane, M.; Menari, H.

    2011-01-01

    Electrochemical etching of amorphous SiC in fluoride solution was studied. Anodic dissolution and passivation are observed for p-type electrodes under dark illumination. The dissolution of p-type a-Si 1-x C x is found to be under mixed transport/kinetic control; the diffusion current is of first order in fluoride concentration. Porous etching was not observed in this case. The surface finish of 6H-SiC depends on the experimental conditions; both uniform and porous etching is observed. In this paper, we report the formation of porous p-type amorphous SiC (a-Si 1-x C x ) films, elaborated previously by DC magnetron sputtering and analyze the porous layers (PSC) using scanning electron microscopy, spectrophotometer and photoluminescence. The crystal structures and the preparation conditions of porous SiC are shown to have an effect on the structural and electrical properties of the material obtained. SEM observation indicates that the porous a-Si 1-x C x layers have shown some specific feature; a semi-cylindrical structure of the porous network has been observed. - Research highlights: →Macroporous amorphous silicon carbide (PSC) by anodization. →Membrane of amorphous silicon carbide by KOH etching. → Membrane a-Si1-xCx and PSC for humidity sensors. The work is not still published.

  2. Large Lateral Photovoltaic Effect in Metal-(Oxide-Semiconductor Structures

    Directory of Open Access Journals (Sweden)

    Chongqi Yu

    2010-11-01

    Full Text Available The lateral photovoltaic effect (LPE can be used in position-sensitive detectors to detect very small displacements due to its output of lateral photovoltage changing linearly with light spot position. In this review, we will summarize some of our recent works regarding LPE in metal-semiconductor and metal-oxide-semiconductor structures, and give a theoretical model of LPE in these two structures.

  3. Large lateral photovoltaic effect in metal-(oxide-) semiconductor structures.

    Science.gov (United States)

    Yu, Chongqi; Wang, Hui

    2010-01-01

    The lateral photovoltaic effect (LPE) can be used in position-sensitive detectors to detect very small displacements due to its output of lateral photovoltage changing linearly with light spot position. In this review, we will summarize some of our recent works regarding LPE in metal-semiconductor and metal-oxide-semiconductor structures, and give a theoretical model of LPE in these two structures.

  4. Porous structure and surface chemistry of phosphoric acid activated carbon from corncob

    International Nuclear Information System (INIS)

    Sych, N.V.; Trofymenko, S.I.; Poddubnaya, O.I.; Tsyba, M.M.; Sapsay, V.I.; Klymchuk, D.O.; Puziy, A.M.

    2012-01-01

    Highlights: ► Phosphoric acid activation results in formation of carbons with acidic surface groups. ► Maximum amount of surface groups is introduced at impregnation ratio 1.25. ► Phosphoric acid activated carbons show high capacity to copper. ► Phosphoric acid activated carbons are predominantly microporous. ► Maximum surface area and pore volume achieved at impregnation ratio 1.0. - Abstract: Active carbons have been prepared from corncob using chemical activation with phosphoric acid at 400 °C using varied ratio of impregnation (RI). Porous structure of carbons was characterized by nitrogen adsorption and scanning electron microscopy. Surface chemistry was studied by IR and potentiometric titration method. It has been shown that porosity development was peaked at RI = 1.0 (S BET = 2081 m 2 /g, V tot = 1.1 cm 3 /g), while maximum amount of acid surface groups was observed at RI = 1.25. Acid surface groups of phosphoric acid activated carbons from corncob includes phosphate and strongly acidic carboxylic (pK = 2.0–2.6), weakly acidic carboxylic (pK = 4.7–5.0), enol/lactone (pK = 6.7–7.4; 8.8–9.4) and phenol (pK = 10.1–10.7). Corncob derived carbons showed high adsorption capacity to copper, especially at low pH. Maximum adsorption of methylene blue and iodine was observed for carbon with most developed porosity (RI = 1.0).

  5. Porous structure and surface chemistry of phosphoric acid activated carbon from corncob

    Energy Technology Data Exchange (ETDEWEB)

    Sych, N.V.; Trofymenko, S.I.; Poddubnaya, O.I.; Tsyba, M.M. [Institute for Sorption and Endoecology Problems, National Academy of Sciences of Ukraine, 13 General Naumov St., 03164 Kyiv (Ukraine); Sapsay, V.I.; Klymchuk, D.O. [M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine, 2 Tereshchenkivska St., 01601 Kyiv (Ukraine); Puziy, A.M., E-mail: alexander.puziy@ispe.kiev.ua [Institute for Sorption and Endoecology Problems, National Academy of Sciences of Ukraine, 13 General Naumov St., 03164 Kyiv (Ukraine)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Phosphoric acid activation results in formation of carbons with acidic surface groups. Black-Right-Pointing-Pointer Maximum amount of surface groups is introduced at impregnation ratio 1.25. Black-Right-Pointing-Pointer Phosphoric acid activated carbons show high capacity to copper. Black-Right-Pointing-Pointer Phosphoric acid activated carbons are predominantly microporous. Black-Right-Pointing-Pointer Maximum surface area and pore volume achieved at impregnation ratio 1.0. - Abstract: Active carbons have been prepared from corncob using chemical activation with phosphoric acid at 400 Degree-Sign C using varied ratio of impregnation (RI). Porous structure of carbons was characterized by nitrogen adsorption and scanning electron microscopy. Surface chemistry was studied by IR and potentiometric titration method. It has been shown that porosity development was peaked at RI = 1.0 (S{sub BET} = 2081 m{sup 2}/g, V{sub tot} = 1.1 cm{sup 3}/g), while maximum amount of acid surface groups was observed at RI = 1.25. Acid surface groups of phosphoric acid activated carbons from corncob includes phosphate and strongly acidic carboxylic (pK = 2.0-2.6), weakly acidic carboxylic (pK = 4.7-5.0), enol/lactone (pK = 6.7-7.4; 8.8-9.4) and phenol (pK = 10.1-10.7). Corncob derived carbons showed high adsorption capacity to copper, especially at low pH. Maximum adsorption of methylene blue and iodine was observed for carbon with most developed porosity (RI = 1.0).

  6. The pore wall structure of porous semi-crystalline anatase TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Man-Ho; Doh, Jeong-Mann; Han, Seong Chul; Chae, Keun Hwa; Yu, Byung-Yong; Hong, Kyung Tae [Korea Institute of Science and Technology, Seoul (Korea, Republic of); Jackson, Andrew [NIST National Institute of Standards and Technology, Gaithersburg, MD (United States). Center for Neutron Research; Maryland Univ., College Park, MD (United States). Dept. of Materials Science and Engineering; Anovitz, Lawrence M. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Chemical Sciences Div.

    2011-12-15

    The structure of porous TiO{sub 2} prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2 and the pore was not sharp. A density gradient of around 40-60 A at the pore wall (i.e. the interface between the pore and the TiO{sub 2} matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO{sub 2} matrix and the pores filled with liquid H{sub 2}O/D{sub 2}O mixtures was 51/49%(v/v) H{sub 2}O/D{sub 2}O, yielding an estimated mass density of 3.32 g cm{sup -3}. The specific surface area of the sample derived from the (U)SANS data was around 939-1003 m{sup 2} cm{sup -3} (283-302 m{sup 2} g{sup -1}). (orig.)

  7. Band structure engineered layered metals for low-loss plasmonics

    Science.gov (United States)

    Gjerding, Morten N.; Pandey, Mohnish; Thygesen, Kristian S.

    2017-04-01

    Plasmonics currently faces the problem of seemingly inevitable optical losses occurring in the metallic components that challenges the implementation of essentially any application. In this work, we show that Ohmic losses are reduced in certain layered metals, such as the transition metal dichalcogenide TaS2, due to an extraordinarily small density of states for scattering in the near-IR originating from their special electronic band structure. On the basis of this observation, we propose a new class of band structure engineered van der Waals layered metals composed of hexagonal transition metal chalcogenide-halide layers with greatly suppressed intrinsic losses. Using first-principles calculations, we show that the suppression of optical losses lead to improved performance for thin-film waveguiding and transformation optics.

  8. Alkali metal ion templated transition metal formate framework materials: synthesis, crystal structures, ion migration, and magnetism.

    Science.gov (United States)

    Eikeland, Espen; Lock, Nina; Filsø, Mette; Stingaciu, Marian; Shen, Yanbin; Overgaard, Jacob; Iversen, Bo Brummerstedt

    2014-10-06

    Four transition metal formate coordination polymers with anionic frameworks, namely, Na[Mn(HCOO)3], K[Mn(HCOO)3], Na2[Cu3(HCOO)8], and K2[Cu5(HCOO)12], were synthesized using a mild solution chemistry approach. Multitemperature single-crystal (100-300 K) and powder X-ray diffraction studies of the compounds reveal structures of large diversity ranging from cubic chiral Na-Mn formate to triclinic Na-Cu formate. The structural variety is caused by the nature of the transition metals, the alkali metal ion templation, and the versatility of the formate group, which offers metal-metal coordination through three different O-C-O bridging modes (syn-syn, syn-anti, anti-anti) in addition to metal-metal bridging via a single oxygen atom. The two manganese(II) compounds contain mononuclear, octahedrally coordinated moieties, but the three-dimensional connectivity between the manganese octahedra is very different in the two structures. The two copper frameworks, in contrast, consist of binuclear and mononuclear moieties (Na-Cu formate) and trinuclear and mononuclear moieties (K-Cu formate), respectively. Procrystal electron density analysis of the compounds indicates one-dimensional K(+)-ion conductivity in K-Mn and K-Cu, and the nature of the proposed potassium ion migration is compared with results from similar analysis on known Na(+) and K(+) ion conductors. K-Mn and Na-Mn were tested as cathode materials, but this resulted in poor reversibility due to low conductivity or structural collapse. The magnetic properties of the compounds were studied by vibrating sample magnetometric measurements, and their thermal stabilities were determined by thermogravimetric analysis and differential thermal analysis. Despite structural differences, the metal formates that contain the same transition metal have similar magnetic properties and thermal decomposition pathways, that is, the nature of the transition metal controls the compound properties.

  9. Investigation of structural properties, electrical and dielectrical characteristics of Al/Dy2O3/porous Si heterostructure

    Science.gov (United States)

    Cherif, A.; Jomni, S.; Belgacem, W.; Hannachi, R.; Mliki, N.; Beji, L.

    2014-04-01

    This paper describes the structural properties, electrical and dielectric characteristics for the first time of the high-k Dy2O3 oxide film deposited on the porous Si substrate by electron beam deposition under ultra vacuum. Structural and morphological characterizations are investigated by a scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and X-ray diffraction measurements (XRD). The electrical and dielectric characteristics of the Al/Dy2O3/porous Si heterostructure are studied through current- voltage I (V), capacitance-voltage C (V), conductance- and capacitance-frequency dependencies (G (f) and C (f)). Therefore, the dominant conduction mechanisms for the Al/Dy2O3/porous Si heterostructure are extracted from the determining of Schottky coefficient (βSC) and Poole-Frenkel coefficient (βPF). The experimental values of βSC and βPF coefficients are calculated from I (V) characteristics and compared with theoretical values, thus, the appropriate model has been proposed. The C (V) characteristics at different frequencies revealed a large frequency-dispersion, indicative of a significant density of interface states. Furthermore, the G (f) characteristics were well fitted by the modified law GAC(f)=A1f+A2f and the results showed frequency dependent and evidence of two different behaviors in ac conductance i.e. the low-frequency conductivity is due to long-range ordering (frequency-independent) and high frequency conduction due to the localized orientation hopping mechanism. The Nyquist diagrams are used to identify the equivalent circuit, so, the Al/Dy2O3/porous Si heterostructure is accurately modeled at frequency ranges from 10 Hz to 1000 kHz, as a two parallel elements (RC) network placed in series.

  10. Role of low flow and backward flow zones on colloid transport in pore structures derived from real porous media.

    Science.gov (United States)

    Li, Xiqing; Li, Zhelong; Zhang, Dongxiao

    2010-07-01

    To examine the relevance of low flow zones and flow vortices to colloid transport in real porous media, lattice-Boltzmann (LB) simulations were combined with X-ray microtomography (XMT) to simulate flow fields in glass beads and quartz sand. Backward flow zones were demonstrated to be widely present in both porous media, with a greater volume fraction in the former relative to the latter porous media. Glass beads in the XMT images were approximated as spheres and their coordinates and radii were extracted to allow reconstruction of pore structures. LB simulations were again performed and the simulated flow fields in the reconstructed pore structures were coupled to a three-dimensional particle tracking algorithm. Particle tracking simulations demonstrated that significant amounts of colloids stayed in the simulated domains for long periods (up to 50 pore volumes). The percentages of colloids with long residence time increased as the depth of the secondary energy minimum increased. The majority of the colloids with long residence time were translated to low flow zones while being associated with grain surfaces via secondary minima. A small fraction of colloids entered low flow zones without being associated with the grains surfaces. Backward flow zones were also found to trap a small fraction of colloids for significantly long time (up to 10 pore volumes). In overall, however, backward flow zones trapped fewer colloids for shorter durations than low flow zones. In summary, this work demonstrates the importance of temporary trapping of colloids by the low flow and backward flow zones in real porous media. This trapping process can explain a number of intriguing experimental observations.

  11. Chemical compatibility of structural materials in alkali metals

    International Nuclear Information System (INIS)

    Natesan, K.; Rink, D.L.; Haglund, R.

    1995-01-01

    The objectives of this task are to (a) evaluate the chemical compatibility of structural alloys such as V-5 wt.%Cr-5 wt.%Ti alloy and Type 316 stainless steel for application in liquid alkali metals such as lithium and sodium-78 wt.% potassium (NaK) at temperatures in the range that are of interest for International Thermonuclear Experimental Reactor (ITER); (b) evaluate the transfer of nonmetallic elements such as oxygen, nitrogen, carbon, and hydrogen between structural materials and liquid metals; and (c) evaluate the effects of such transfers on the mechanical and microstructural characteristics of the materials for long-term service in liquid-metal-environments

  12. Hypervelocity Impact Evaluation of Metal Foam Core Sandwich Structures

    Science.gov (United States)

    Yasensky, John; Christiansen, Eric L.

    2007-01-01

    A series of hypervelocity impact (HVI) tests were conducted by the NASA Johnson Space Center (JSC) Hypervelocity Impact Technology Facility (HITF) [1], building 267 (Houston, Texas) between January 2003 and December 2005 to test the HVI performance of metal foams, as compared to the metal honeycomb panels currently in service. The HITF testing was conducted at the NASA JSC White Sands Testing Facility (WSTF) at Las Cruces, New Mexico. Eric L. Christiansen, Ph.D., and NASA Lead for Micro-Meteoroid Orbital Debris (MMOD) Protection requested these hypervelocity impact tests as part of shielding research conducted for the JSC Center Director Discretionary Fund (CDDF) project. The structure tested is a metal foam sandwich structure; a metal foam core between two metal facesheets. Aluminum and Titanium metals were tested for foam sandwich and honeycomb sandwich structures. Aluminum honeycomb core material is currently used in Orbiter Vehicle (OV) radiator panels and in other places in space structures. It has many desirable characteristics and performs well by many measures, especially when normalized by density. Aluminum honeycomb does not perform well in Hypervelocity Impact (HVI) Testing. This is a concern, as honeycomb panels are often exposed to space environments, and take on the role of Micrometeoroid / Orbital Debris (MMOD) shielding. Therefore, information on possible replacement core materials which perform adequately in all necessary functions of the material would be useful. In this report, HVI data is gathered for these two core materials in certain configurations and compared to gain understanding of the metal foam HVI performance.

  13. A Novel 3D Printer to Support Additive Manufacturing of Gradient Metal Alloy Structures, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Gradient metal alloy structures possess multi-functional properties that conventional monolithic metal counterparts do not have. Such structures can potentially...

  14. A Novel 3D Printer to Support Additive Manufacturing of Gradient Metal Alloy Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Gradient metal alloy structures possess multi-functional properties that conventional monolithic metal counterparts do not have. Such structures can potentially...

  15. Crystal structures of Dronpa complexed with quenchable metal ions provide insight into metal biosensor development.

    Science.gov (United States)

    Kim, In Jung; Kim, Sangsoo; Park, Jeahyun; Eom, Intae; Kim, Sunam; Kim, Jin-Hong; Ha, Sung Chul; Kim, Yeon Gil; Hwang, Kwang Yeon; Nam, Ki Hyun

    2016-09-01

    Many fluorescent proteins (FPs) show fluorescence quenching by specific metal ions, which can be applied towards metal biosensor development. In this study, we investigated the significant fluorescence quenching of Dronpa by Co(2+) and Cu(2+) ions. Crystal structures of Co(2+) -, Ni(2+) - and Cu(2+) -bound Dronpa revealed previously unseen, unique, metal-binding sites for fluorescence quenching. These metal ions commonly interact with surface-exposed histidine residues (His194-His210 and His210-His212), and interact indirectly with chromophores. Structural analysis of the Co(2+) - and Cu(2+) - binding sites of Dronpa provides insight into FP-based metal biosensor engineering. © 2016 Federation of European Biochemical Societies.

  16. Influence of the Surface Layer on the Electrochemical Deposition of Metals and Semiconductors into Mesoporous Silicon

    Energy Technology Data Exchange (ETDEWEB)

    Chubenko, E. B., E-mail: eugene.chubenko@gmail.com; Redko, S. V.; Sherstnyov, A. I.; Petrovich, V. A.; Kotov, D. A.; Bondarenko, V. P. [Belarusian State University of Information and RadioElectronics (Belarus)

    2016-03-15

    The influence of the surface layer on the process of the electrochemical deposition of metals and semiconductors into porous silicon is studied. It is shown that the surface layer differs in structure and electrical characteristics from the host porous silicon bulk. It is established that a decrease in the conductivity of silicon crystallites that form the surface layer of porous silicon has a positive effect on the process of the filling of porous silicon with metals and semiconductors. This is demonstrated by the example of nickel and zinc oxide. The effect can be used for the formation of nanocomposite materials on the basis of porous silicon and nanostructures with a high aspect ratio.

  17. Structural refinement and coarsening in deformed metals

    DEFF Research Database (Denmark)

    Hansen, N.; Huang, X.; Xing, Q.

    2005-01-01

    The microstructural refinement by plastic deformation is analysed in terms of key parameters, the spacing between and the misorientation angle across the boundaries subdividing the structure. Coarsening of such structures by annealing is also characterised. For both deformed and annealed structures...

  18. Porous Fe21Cr7Al1Mo0.5Y metal supports for oxygen transport membranes: Thermo-mechanical properties, sintering and corrosion behaviour

    DEFF Research Database (Denmark)

    Glasscock, Julie; Mikkelsen, Lars; Persson, Åsa Helen

    2013-01-01

    An Fe21Cr7Al1Mo0.5Y alumina-forming stainless steel is designed and evaluated as a material for porous supports for oxygen transport membranes. The thermal expansion coefficient, elastic modulus and creep rates of the alloy are presented. The microstructure, porosity and pre-oxidation conditions...... resistance compared with an FeCr steel of similar composition and porosity. Modelling of the alloy lifetime as a function of surface area and Al-content was performed, and lifetimes over 30 000 h are predicted for a metal support with 30% porosity operating at a temperature of 750 C, where the oxidation...

  19. Structure and Permeability of Porous Silicon Investigated by Self-Diffusion NMR Measurements of Ethanol and Heptane

    Directory of Open Access Journals (Sweden)

    Puibasset J.

    2016-07-01

    Full Text Available The adsorption and phase transitions of confined fluids in nanoporous materials have been studied intensely because of both their fundamental interest and their crucial role in many technologies. Questions relating to the influence of the confinement of fluids, and the disorder or elastic deformation of porous solids on the liquid-gas phase transition are still under debate. Model systems are needed to understand the adsorption phenomenon. In this context, Porous Silicon (PoSi, which is a single crystal obtained by etching a (100 silicon wafer is an excellent candidate. Indeed, it consists of non-connected tubular pores running parallel to the [100] axis perpendicular to the wafer surface, with transverse sections with a polygonal shape of nanometric size whose areas are widely distributed. Once detached from the wafer, free PoSi membranes can be considered a nanoscale disordered honeycomb. Adsorption/desorption experiments have been performed to characterize the structure: they have shown that evaporation occurs collectively, an intriguing observation generally associated with a disordered pore structure with many interconnections through narrow necks. The characterization of fluid mobility inside the pores should give complementary information about the pore structure and topology. This paper focuses on the dynamics of a fluid confined inside the structure of porous silicon, and in particular the self-diffusion measurements (pulsed field gradient spin echo Nuclear Magnetic Resonance (NMR. The results show a strong anisotropy of the self-diffusion tensor, as expected in this highly anisotropic structure. However, a non-zero self-diffusion in the directions perpendicular to the pore axis is observed. In order to interpret these puzzling results, molecular and Brownian dynamics calculations are underway.

  20. Surface sealing using self-assembled monolayers and its effect on metal diffusion in porous low-k dielectrics studied using monoenergetic positron beams

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira, E-mail: uedono.akira.gb@u.tsukuba.ac.jp [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Armini, Silvia; Zhang, Yu [IMEC, Kapeldreef 75, B-3001 Heverlee, Leuven (Belgium); Kakizaki, Takeaki [Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Krause-Rehberg, Reinhard [Department of Physics, Martin Luther University Halle, 06099 Halle (Germany); Anwand, Wolfgang; Wagner, Andreas [Institute for Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden (Germany)

    2016-04-15

    Graphical abstract: - Highlights: • Pores with cubic pore side lengths of 1.1 and 3.1 nm coexisted in the low-k film. • For the sample without the SAM sealing process, metal atoms diffused from the top Cu/MnN layer into the OSG film and were trapped by the pores. Almost all pore interiors were covered by those metals. • For the sample damaged by a plasma etch treatment before the SAM sealing process, self-assembled molecules diffused into the OSG film, and they were preferentially trapped by larger pores. - Abstract: Surface sealing effects on the diffusion of metal atoms in porous organosilicate glass (OSG) films were studied by monoenergetic positron beams. For a Cu(5 nm)/MnN(3 nm)/OSG(130 nm) sample fabricated with pore stuffing, C{sub 4}F{sub 8} plasma etch, unstuffing, and a self-assembled monolayer (SAM) sealing process, it was found that pores with cubic pore side lengths of 1.1 and 3.1 nm coexisted in the OSG film. For the sample without the SAM sealing process, metal (Cu and Mn) atoms diffused from the top Cu/MnN layer into the OSG film and were trapped by the pores. As a result, almost all pore interiors were covered with those metals. For the sample damaged by an Ar/C{sub 4}F{sub 8} plasma etch treatment before the SAM sealing process, SAMs diffused into the OSG film, and they were preferentially trapped by larger pores. The cubic pore side length in these pores containing self-assembled molecules was estimated to be 0.7 nm. Through this work, we have demonstrated that monoenergetic positron beams are a powerful tool for characterizing capped porous films and the trapping of atoms and molecules by pores.

  1. Water in Metal-Organic Frameworks: A Computational Study of Adsorption in Porous Materials in the Presence of Ambient Humidity

    Science.gov (United States)

    Ghosh, Pritha

    Metal-organic frameworks, or MOFs, are a class of porous crystalline materials renowned for their chemically tunable nature. In this work, molecular-level modeling is used to assess MOFs as potential adsorbents for a variety of applications where ambient humidity is present, such as toxic gas capture, nerve agent decomposition, and sensing via changes in proton conductivity. The concept of hydrophobicity in MOFs is explored from a number of angles. Classical simulation methods and quantum chemistry calculations are used to predict adsorption behavior and to shed light on experimentally observed phenomena. Hydrophobic MOFs are attractive candidates for selective gas capture under ambient conditions, and in this work hydrophobic MOFs are examined for two particular applications: ammonia capture and CO2 capture. In the first study, GCMC simulations are used to evaluate a set of three hydrophobic MOFs for ammonia capture at three humidity conditions: 0% relative humdity (RH), 36% RH, and 80% RH. In the second study, GCMC simulations predict the CO2 loading in a hydrophobic fluorinated MOF at 80% RH, which is the humidity of flue gas. In both of these studies, results demonstrate that hydrophobic MOFs are equally capable of capturing the target adsorbate under humid or dry conditions. In related work, water adsorption behavior is investigated for a fairly hydrophilic Zr MOF, and it is revealed that missing linker defects engender hydrophilicity in this framework. An ideal, defect-free version of this Zr MOF demonstrates hydrophobic behavior. Additionally, perfluoroalkane adsorption is predicted in a related material, a faujasite-type zeolite, and the results suggest the presence of co-adsorbed water molecules. MOFs with coordinated solvent molecules can be used as catalysts and novel chemical sensors. In this work, quantum chemistry calculations are used to study the interaction of a nerve agent simulant with a Zr MOF node. Results indicate that it is favorable for a

  2. Surface/structure functionalization of copper-based catalysts by metal-support and/or metal-metal interactions

    Science.gov (United States)

    Konsolakis, Michalis; Ioakeimidis, Zisis

    2014-11-01

    Cu-based catalysts have recently attracted great attention both in catalysis and electro-catalysis fields due to their excellent catalytic performance and low cost. Given that their performance is determined, to a great extent, by Cu sites local environment, considerable efforts have been devoted on the strategic modifications of the electronic and structural properties of Cu sites. In this regard, the feasibility of tuning the local structure of Cu entities by means of metal-support or metal-metal interactions is investigated. More specifically, the physicochemical properties of Cu entities are modified by employing: (i) different oxides (CeO2, La2O3, Sm2O3), or (ii) ceria-based mixed oxides (Ce1-xSmxOδ) as supporting carriers, and (iii) a second metal (Cobalt) adjacent to Cu (bimetallic Cu-Co/CeO2). A characterization study, involving BET, XRD, TPR, and XPS, reveal that significant modifications on structural, redox and electronic properties of Cu sites can be induced by adopting either different oxide carriers or bimetallic complexes. Fundamental insights into the tuning of Cu local environment by metal-support or metal-metal interactions are provided, paving the way for real-life industrial applications.

  3. Structure and properties of transition metal-metalloid glasses based on refractory metals

    International Nuclear Information System (INIS)

    Johnson, W.L.; Williams, A.R.

    1979-01-01

    The structure and properties of several new transition metal-metalloid (TM/sub 1-x/M/sub x/) metallic glasses based on refractory transition metals (e.g. Mo, W, Ru etc.) have been systemically investigated as a function of composition. The structure of the alloys has been investigated by x-ray diffraction methods and measurements of superconducting properties, electrical resistivity, density, hardness, and mechanical behavior were made. These data are used in developing a novel description of the structure of TM/sub 1-x/M/sub x/ glasses. The experimental evidence suggests that an ideal amorphous phase forms at a specific composition x/sub c/ and that this phase has a well defined atomic short range order. For metallic glasses having x x/sub c/. This novel picture can explain the variation of many properties of these glasses with metalloid concentration

  4. Structural refinement and coarsening in deformed metals

    DEFF Research Database (Denmark)

    Hansen, N.; Huang, X.; Xing, Q.

    2005-01-01

    The microstructural refinement by plastic deformation is analysed in terms of key parameters, the spacing between and the misorientation angle across the boundaries subdividing the structure. Coarsening of such structures by annealing is also characterised. For both deformed and annealed structur......, good agreement has been found between experimental measurements of the flow stress and calculated values. Commercial purity aluminium is used as an example and deformed by cold rolling and by accumulative roll bonding....

  5. Reactionary - electrodiffusion equations of transport processes of electrolyte solutions of radioelements through porous clayey structures

    Directory of Open Access Journals (Sweden)

    T.V.Shymchuk

    2007-01-01

    Full Text Available The statistical model of the water solution of radioactive elements and the porous clayey matrix is proposed. The generalized transport equations for the description of diffusion, sorption,radiative processes and chemical reactions are obtained taking into account the electromagnetic processes.

  6. Thermal and structural stability of composite systems based on polyaniline deposited on porous polyethylene films

    Czech Academy of Sciences Publication Activity Database

    Elyashevich, G. K.; Sidorovich, A. V.; Smirnov, M. A.; Kuryndin, I. S.; Bobrova, N. V.; Trchová, Miroslava; Stejskal, Jaroslav

    2006-01-01

    Roč. 91, č. 11 (2006), s. 2786-2792 ISSN 0141-3910 Grant - others:Russian Foundation for Basic Research 04-03-32229 Institutional research plan: CEZ:AV0Z40500505 Keywords : polyaniline * polyethylene porous films * composites Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.174, year: 2006

  7. Novel approach to make concrete structures self-healing using porous network concrete

    NARCIS (Netherlands)

    Sangadji, S.; Schlangen, E.

    2012-01-01

    Many researchers proposed self healing mechanism using hollow fibres and or microcapsule containing a modifying agent dispersed in the concrete to prolong its service life and make it more durable. A novel self healing concrete concept is proposed in this paper by using porous network concrete

  8. Porous silicon in solar cell structures : a review of achievements and modern directions of further use

    NARCIS (Netherlands)

    Yerokhov, VY; Melnyk, [No Value

    1999-01-01

    Porous silicon, which is being obtained by electrochemical etching of silicon wafers in electrolytes on the base of hydrofluoric acid, recently attracted the attention of specialists in photovoltaics even more due to a number of its unique properties. However, at present, acceptable results are

  9. Metal-Free Counter Electrode for Efficient Dye-Sensitized Solar Cells through High Surface Area and Large Porous Carbon

    Directory of Open Access Journals (Sweden)

    Pavuluri Srinivasu

    2011-01-01

    Full Text Available Highly efficient, large mesoporous carbon is fabricated as a metal-free counter electrode for dye-sensitized solar cells. The mesoporous carbon shows very high energy conversion efficiency of 7.1% compared with activated carbon. The mesoporous carbon is prepared and characterized by nitrogen adsorption, scanning electron microscopy (SEM, and transmission electron microscopy (TEM. The nitrogen adsorption data reveals that the material possesses BET specific surface area ca.1300 m2/g and pore diameter 4.4 nm. Hexagonal rod-like morphology and ordered pore structure of mesoporous carbon are confirmed by electron microscopy data. The better performance of this carbon material is greatly benefited from its ordered interconnected mesoporous structure and high surface area.

  10. Ultrafine-grained porous titanium and porous titanium/magnesium composites fabricated by space holder-enabled severe plastic deformation

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Yuanshen, E-mail: yuanshen.qi@monash.edu [Centre for Advanced Hybrid Materials, Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia); Contreras, Karla G. [Monash Institute of Medical Engineering, Faculty of Engineering, Monash University, Clayton, Victoria 3800 (Australia); Jung, Hyun-Do [Liquid Processing & Casting Technology R& D Group, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Kim, Hyoun-Ee [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Advanced Institutes of Convergence Technology, Seoul National University, Gwanggyo, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-270 (Korea, Republic of); Lapovok, Rimma [Centre for Advanced Hybrid Materials, Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia); Estrin, Yuri, E-mail: yuri.estrin@monash.edu [Centre for Advanced Hybrid Materials, Department of Materials Engineering, Monash University, Clayton, Victoria 3800 (Australia); Laboratory of Hybrid Nanostructured Materials, NUST MISiS, Moscow 119490 (Russian Federation)

    2016-02-01

    Compaction of powders by equal channel angular pressing (ECAP) using a novel space holder method was employed to fabricate metallic scaffolds with tuneable porosity. Porous Ti and Ti/Mg composites with 60% and 50% percolating porosity were fabricated using powder blends with two kinds of sacrificial space holders. The high compressive strength and good ductility of porous Ti and porous Ti/Mg obtained in this way are believed to be associated with the ultrafine grain structure of the pore walls. To understand this, a detailed electron microscopy investigation was employed to analyse the interface between Ti/Ti and Ti/Mg particles, the grain structures in Ti particles and the topography of pore surfaces. It was found that using the proposed compaction method, high quality bonding between particles was obtained. Comparing with other powder metallurgy methods to fabricate Ti with an open porous structure, where thermal energy supplied by a laser beam or high temperature sintering is essential, the ECAP process conducted at a relatively low temperature of 400 °C was shown to produce unique properties. - Highlights: • Porous Ti and porous Ti/Mg composite scaffolds were fabricated successfully. • Space holder-enabled severe plastic deformation was first used in this application. • Silicon particles as sacrificial space holders were used for the first time. • Ultrafine-grained microstructure and good bonding between particles were obtained. • Good preosteoblast cell response to as-manufactured porous Ti was achieved.

  11. Ultrafine-grained porous titanium and porous titanium/magnesium composites fabricated by space holder-enabled severe plastic deformation

    International Nuclear Information System (INIS)

    Qi, Yuanshen; Contreras, Karla G.; Jung, Hyun-Do; Kim, Hyoun-Ee; Lapovok, Rimma; Estrin, Yuri

    2016-01-01

    Compaction of powders by equal channel angular pressing (ECAP) using a novel space holder method was employed to fabricate metallic scaffolds with tuneable porosity. Porous Ti and Ti/Mg composites with 60% and 50% percolating porosity were fabricated using powder blends with two kinds of sacrificial space holders. The high compressive strength and good ductility of porous Ti and porous Ti/Mg obtained in this way are believed to be associated with the ultrafine grain structure of the pore walls. To understand this, a detailed electron microscopy investigation was employed to analyse the interface between Ti/Ti and Ti/Mg particles, the grain structures in Ti particles and the topography of pore surfaces. It was found that using the proposed compaction method, high quality bonding between particles was obtained. Comparing with other powder metallurgy methods to fabricate Ti with an open porous structure, where thermal energy supplied by a laser beam or high temperature sintering is essential, the ECAP process conducted at a relatively low temperature of 400 °C was shown to produce unique properties. - Highlights: • Porous Ti and porous Ti/Mg composite scaffolds were fabricated successfully. • Space holder-enabled severe plastic deformation was first used in this application. • Silicon particles as sacrificial space holders were used for the first time. • Ultrafine-grained microstructure and good bonding between particles were obtained. • Good preosteoblast cell response to as-manufactured porous Ti was achieved.

  12. Synthesis and structural characterization of alkali metal arsinoamides.

    Science.gov (United States)

    Chen, Xiao; Gamer, Michael T; Roesky, Peter W

    2017-12-20

    The aminoarsane Mes 2 AsN(H)Ph was prepared from Mes 2 AsCl and aniline in good yields. Deprotonation of Mes 2 AsN(H)Ph with suitable alkali metal bases resulted in the corresponding alkali metal derivatives. Thus, reaction of Mes 2 AsN(H)Ph with nBuLi, NaN(SiMe 3 ) 2 , or KH gave the metal complexes [(Mes 2 AsNPh){Li(OEt 2 ) 2 }], [(Mes 2 AsNPh){Na(OEt 2 )}] 2 , and [(Mes 2 AsNPh){K(THF)}] 2 . These are the first metal complexes ligated by an arsinoamide. All solid-state structures were established by single crystal X-ray diffraction. The lithium compounds form a monomer in the solid-state, whereas the sodium and the potassium derivatives are dimers. In the dimeric compounds intra- and intermolecular π-interaction of the aromatic rings with the metal atoms is observed.

  13. One-Electron Theory of Metals. Cohesive and Structural Properties

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt

    The work described in the report r.nd the 16 accompanying publications is based upon a one-electron theory obtained within the local approximation to density-functional theory, and deals with the ground state of metals as obtained from selfconsistent electronic-structure calculations performed...... by means of the Linear Muffin-Tin Orbital (LMTO) method. It has been the goal of the work to establish how well this one-electron approach describes physical properties such as the crystal structures of the transition metals, the structural phase transitions in the alkali, alkaline earth, and rare earth...

  14. Defects with deep levels in a semiconductor structure of a photoelectric converter of solar energy with an antireflection film of porous silicon

    Science.gov (United States)

    Tregulov, V. V.; Litvinov, V. G.; Ermachikhin, A. V.

    2017-11-01

    Defects in a semiconductor structure of a photoelectric converter of solar energy based on a p-n junction with an antireflection film of porous silicon on the front surface have been studied by current deeplevel transient spectroscopy. An explanation of the influence of thickness of a porous-silicon film formed by electrochemical etching on the character of transformation of defects with deep levels and efficiency of solarenergy conversion is proposed.

  15. Method and apparatus for diamond wire cutting of metal structures

    Science.gov (United States)

    Parsells, Robert; Gettelfinger, Geoff; Perry, Erik; Rule, Keith

    2005-04-19

    A method and apparatus for diamond wire cutting of metal structures, such as nuclear reactor vessels, is provided. A diamond wire saw having a plurality of diamond beads with beveled or chamfered edges is provided for sawing into the walls of the metal structure. The diamond wire is guided by a plurality of support structures allowing for a multitude of different cuts. The diamond wire is cleaned and cooled by CO.sub.2 during the cutting process to prevent breakage of the wire and provide efficient cutting. Concrete can be provided within the metal structure to enhance cutting efficiency and reduce airborne contaminants. The invention can be remotely controlled to reduce exposure of workers to radioactivity and other hazards.

  16. The stellar content, metallicity and ionization structure of HII regions

    NARCIS (Netherlands)

    Martin-Hernandez, NL; Vermeij, R; Tielens, AGGM; van der Hulst, JM; Peeters, E

    Observations of infrared fine-structure lines provide direct information on the metallicity and ionization structure of H II regions and indirectly on the hardness of the radiation field ionizing these nebulae. We have analyzed a sample of Galactic and Magellanic Cloud H II regions observed by the

  17. Proximity effect in normal metal-multiband superconductor hybrid structures

    NARCIS (Netherlands)

    Brinkman, Alexander; Golubov, Alexandre Avraamovitch; Kupriyanov, M. Yu

    2004-01-01

    A theory of the proximity effect in normal metal¿multiband superconductor hybrid structures is formulated within the quasiclassical Green's function formalism. The quasiclassical boundary conditions for multiband hybrid structures are derived in the dirty limit. It is shown that the existence of

  18. Structural properties of low-density liquid alkali metals

    Indian Academy of Sciences (India)

    The static structure factors of liquid alkali metals have been modelled at temperatures close to their melting points and a few higher temperatures using the reverse Monte Carlo (RMC) method. The positions of 5000 atoms in a box, with full periodicity, were altered until the experimental diffraction data of the structure factor ...

  19. Wear Properties of Porous NiTi Orthopedic Shape Memory Alloy

    Science.gov (United States)

    Wu, Shuilin; Liu, Xiangmei; Yeung, K. W. K.; Xu, Z. S.; Chung, C. Y.; Chu, Paul K.

    2012-12-01

    Porous NiTi shape memory alloy (SMA) scaffolds have great potential to be used as orthopedic implants because of their porous structure and superior physical properties. Its metallic nature provides it with better mechanical properties and Young's modulus close to that of natural bones. Besides allowing tissue ingrowth and transfer of nutrients, porous SMA possesses unique pseudoelastic properties compatible to natural hard tissues like bones and tendons, thus expediting in vivo osseointegration. However, the nickel release from debris and the metal surface may cause osteocytic osteolysis at the interface between the artificial implants and bone tissues. Subsequent mobilization may finally lead to implant failure. In this study, the wear properties of porous NiTi with different porosities processed at different treatment temperatures are determined. The results of the study show that the porosity, phase transformation temperature, and annealing temperature are major factors influencing the wear characteristics of porous NiTi SMA.

  20. Structural and optical properties of thin films porous amorphous silicon carbide formed by Ag-assisted photochemical etching

    International Nuclear Information System (INIS)

    Boukezzata, A.; Keffous, A.; Cheriet, A.; Belkacem, Y.; Gabouze, N.; Manseri, A.; Nezzal, G.; Kechouane, M.; Bright, A.; Guerbous, L.; Menari, H.

    2010-01-01

    In this work, we present the formation of porous layers on hydrogenated amorphous SiC (a-SiC: H) by Ag-assisted photochemical etching using HF/K 2 S 2 O 8 solution under UV illumination at 254 nm wavelength. The amorphous films a-SiC: H were elaborated by d.c. magnetron sputtering using a hot pressed polycrystalline 6H-SiC target. Because of the high resistivity of the SiC layer, around 1.6 MΩ cm and in order to facilitate the chemical etching, a thin metallic film of high purity silver (Ag) has been deposited under vacuum onto the thin a-SiC: H layer. The etched surface was characterized by scanning electron microscopy, secondary ion mass spectroscopy, infrared spectroscopy and photoluminescence. The results show that the morphology of etched a-SiC: H surface evolves with etching time. For an etching time of 20 min the surface presents a hemispherical crater, indicating that the porous SiC layer is perforated. Photoluminescence characterization of etched a-SiC: H samples for 20 min shows a high and an intense blue PL, whereas it has been shown that the PL decreases for higher etching time. Finally, a dissolution mechanism of the silicon carbide in 1HF/1K 2 S 2 O 8 solution has been proposed.

  1. Organosilane with gemini-type structure as the mesoporogen for synthesis of hierarchical porous ZSM-5 zeolite

    KAUST Repository

    Zhu, Haibo

    2016-02-08

    A new kind of organosilane (1,6-bis (diethyl(3-trimethoxysilylpropyl)ammonium) hexane bromide) with a gemini-type structure was prepared and used as a mesoporogen for the synthesis of hierarchical porous ZSM-5 zeolite. There are two quaternary ammonium centers along with double hydrolysable -RSi(OMe)3 fragments in the organosilane, which results in a strong interaction between this mesoporogen and silica-alumina gel. The organosilane can be easily incorporated into ZSM-5 zeolite structure during the crystallization process, and it was finally removed by calcination leading to secondary pores in ZSM-5. The synthesized ZSM-5 has been systematically studied by XRD, nitrogen adsorption, SEM, TEM, TG and solid-state one-dimensional (1D) and two-dimensional (2D) NMR, which reveals information on its detailed structure. It has a hierarchical porosity system, which combines the intrinsic micropores coming from the crystalline structure and irregular mesopores created by the organosilane template. Moreover, the mesoposity including pore size and volume within ZSM-5 can be systematically tuned by changing the organosilane/TEOS ratios, which confirms this organosilane has high flexibility of using as template for the synthesis of hierarchical porous zeolite.

  2. Ternary metal-rich sulfide with a layered structure

    Science.gov (United States)

    Franzen, Hugo F.; Yao, Xiaoqiang

    1993-08-17

    A ternary Nb-Ta-S compound is provided having the atomic formula, Nb.sub.1.72 Ta.sub.3.28 S.sub.2, and exhibiting a layered structure in the sequence S-M3-M2-M1-M2-M3-S wherein S represents sulfur layers and M1, M2, and M3 represent Nb/Ta mixed metal layers. This sequence generates seven sheets stacked along the [001] direction of an approximate body centered cubic crystal structure with relatively weak sulfur-to-sulfur van der Waals type interactions between adjacent sulfur sheets and metal-to-metal bonding within and between adjacent mixed metal sheets.

  3. Sub-parts per million NO2 chemi-transistor sensors based on composite porous silicon/gold nanostructures prepared by metal-assisted etching.

    Science.gov (United States)

    Sainato, Michela; Strambini, Lucanos Marsilio; Rella, Simona; Mazzotta, Elisabetta; Barillaro, Giuseppe

    2015-04-08

    Surface doping of nano/mesostructured materials with metal nanoparticles to promote and optimize chemi-transistor sensing performance represents the most advanced research trend in the field of solid-state chemical sensing. In spite of the promising results emerging from metal-doping of a number of nanostructured semiconductors, its applicability to silicon-based chemi-transistor sensors has been hindered so far by the difficulties in integrating the composite metal-silicon nanostructures using the complementary metal-oxide-semiconductor (CMOS) technology. Here we propose a facile and effective top-down method for the high-yield fabrication of chemi-transistor sensors making use of composite porous silicon/gold nanostructures (cSiAuNs) acting as sensing gate. In particular, we investigate the integration of cSiAuNs synthesized by metal-assisted etching (MAE), using gold nanoparticles (NPs) as catalyst, in solid-state junction-field-effect transistors (JFETs), aimed at the detection of NO2 down to 100 parts per billion (ppb). The chemi-transistor sensors, namely cSiAuJFETs, are CMOS compatible, operate at room temperature, and are reliable, sensitive, and fully recoverable for the detection of NO2 at concentrations between 100 and 500 ppb, up to 48 h of continuous operation.

  4. T-Shaped Emitter Metal Structures for HBTs

    Science.gov (United States)

    Fung, King Man; Samoska, Lorene; Velebir, James; Muller, Richard; Echternach, Pierre; Siegel, Peter; Smith, Peter; Martin, Suzanne; Malik, Roger; Rodwell, Mark; hide

    2006-01-01

    Metal emitter structures in a class of developmental InP-based high-speed heterojunction bipolar transistors (HBTs) have been redesigned to have T-shaped cross sections. T-cross-section metal features have been widely used in Schottky diodes and high-electron-mobility transistors, but not in HBTs. As explained, the purpose served by the present T cross-sectional shapes is to increase fabrication yields beyond those achievable with the prior cross-sectional shapes.

  5. From Metal Cluster to Metal Nanowire: A Topological Analysis of Electron Density and Band Structure Calculation

    Directory of Open Access Journals (Sweden)

    Yu Wang

    2002-01-01

    Full Text Available Abstract:We investigate a theoretical model of molecular metalwire constructed from linear polynuclear metal complexes. In particular we study the linear Crn metal complex and Cr molecular metalwire. The electron density distributions of the model nanowire and the linear Crn metal complexes, with n = 3, 5, and 7, are calculated by employing CRYSTAL98 package with topological analysis. The preliminary results indicate that the bonding types between any two neighboring Cr are all the same, namely the polarized open-shell interaction. The pattern of electron density distribution in metal complexes resembles that of the model Cr nanowire as the number of metal ions increases. The conductivity of the model Cr nanowire is also tested by performing the band structure calculation.

  6. Flower-like hierarchical structures consisting of porous single-crystalline ZnO nanosheets and their gas sensing properties to volatile organic compounds (VOCs)

    International Nuclear Information System (INIS)

    Meng, Fanli; Hou, Nannan; Ge, Sheng; Sun, Bai; Jin, Zhen; Shen, Wei; Kong, Lingtao; Guo, Zheng; Sun, Yufeng; Wu, Hao; Wang, Chen; Li, Minqiang

    2015-01-01

    Highlights: • Flower-like hierarchical structures consisting of porous single-crystalline ZnO nanosheets were synthesized. • The flower-like hierarchical structured ZnO exhibited higher response and shorter response and recovery times. • The sensing mechanism of the flower-like hierarchical has been systematically analyzed. - Abstract: Flower-like hierarchical structures consisting of porous single-crystalline ZnO nanosheets (FHPSCZNs) were synthesized by a one-pot wet-chemical method followed by an annealing treatment, which combined the advantages between flower-like hierarchical structure and porous single-crystalline structure. XRD, SEM and HRTEM were used to characterize the synthesized FHPSCZN samples. The sensing properties of the FHPSCZN sensor were also investigated by comparing with ZnO powder sensor, which exhibited higher response and shorter response and recovery times. The sensing mechanism of the FHPSCZN sensor has been further analyzed from the aspects of electronic transport and gas diffusion

  7. Computer design of porous active materials at different dimensional scales

    Science.gov (United States)

    Nasedkin, Andrey

    2017-12-01

    The paper presents a mathematical and computer modeling of effective properties of porous piezoelectric materials of three types: with ordinary porosity, with metallized pore surfaces, and with nanoscale porosity structure. The described integrated approach includes the effective moduli method of composite mechanics, simulation of representative volumes, and finite element method.

  8. Co-adsorption and sequential adsorption of the co-existence four heavy metal ions and three fluoroquinolones on the functionalized ferromagnetic 3D NiFe2O4porous hollow microsphere.

    Science.gov (United States)

    Liu, Xueyan; Liu, Mingyang; Zhang, Lei

    2018-02-01

    Functionalized magnetic microsphere NiFe 2 O 4 (MS-NiFe 2 O 4 ) with a 3D hierarchical porous hollow structure was fabricated using urea as the modifier and soft templates by a simple one-pot solvothermal method. The constructed MS-NiFe 2 O 4 shows excellent dual functions which can not only undergo simultaneous rapid removal of the co-existence metal ions (Cu 2+ , Cd 2+ , Cr 3+ and Zn 2+ ions), but also availably adsorb fluoroquinolone (FQs) (ciprofloxacin (CIP), enrofloxacin (ENR) and norfloxacin (NOR)), and is easily recycled using an external magnetic field. The removal efficiency of eight targets could all reach up to 80% within 60min at pH 5. The independent adsorption of single contaminants, the competitive adsorption of multiple heavy metal ions/organic contaminants, the simultaneous and sequential adsorption of the co-existence of inorganic and organic contaminants onto MS-NiFe 2 O 4 were explored in detail. Competition adsorption occurred between the same type of contaminants. For different types of contaminants, four metal ions did not affect the adsorption of the other three FQs in the sequential and simultaneously adsorption system, and vice versa. The possible adsorption mechanism between targets and MS-NiFe 2 O 4 was revealed. Copyright © 2017. Published by Elsevier Inc.

  9. Femtosecond differential transmission measurements on low temperature GaAs metal-semiconductor-metal structures

    DEFF Research Database (Denmark)

    Keil, Ulrich Dieter Felix; Hvam, Jørn Märcher; Tautz, S.

    1997-01-01

    We report on differential transmission measurements on low temperature grown (LT)-GaAs with and without applied electrical fields at different wavelengths. Electrical fields up to 100 kV/cm can be applied via an interdigitated contact structure to our LT GaAs samples which have been removed from....... The response time of a biased metal-semiconductor-metal detector, therefore, exceeds the carrier life time of the substrate material. (C) 1997 American Institute of Physics....

  10. Ectopic osteogenesis and angiogenesis regulated by porous architecture of hydroxyapatite scaffolds with similar interconnecting structure in vivo.

    Science.gov (United States)

    Li, Jinyu; Zhi, Wei; Xu, Taotao; Shi, Feng; Duan, Ke; Wang, Jianxin; Mu, Yandong; Weng, Jie

    2016-10-01

    The macro-pore sizes of porous scaffold play a key role for regulating ectopic osteogenesis and angiogenesis but many researches ignored the influence of interconnection between macro-pores with different sizes. In order to accurately reveal the relationship between ectopic osteogenesis and macro-pore sizes in dorsal muscle and abdominal cavities of dogs, hydroxyapatite (HA) scaffolds with three different macro-pore sizes of 500-650, 750-900 and 1100-1250 µm were prepared via sugar spheres-leaching process, which also had similar interconnecting structure determined by keeping the d/s ratio of interconnecting window diameter to macro-pore size constant. The permeability test showed that the seepage flow of fluid through the porous scaffolds increased with the increase of macro-pore sizes. The cell growth in three scaffolds was not affected by the macro-pore sizes. The in vivo ectopic implantation results indicated that the macro-pore sizes of HA scaffolds with the similar interconnecting structure have impact not only the speed of osteogenesis and angiogenesis but also the space distribution of newly formed bone. The scaffold with macro-pore sizes of 750-900 µm exhibited much faster angiogenesis and osteogenesis, and much more uniformly distribution of new bone than those with other macro-pore sizes. This work illustrates the importance of a suitable macro-pore sizes in HA scaffolds with the similar interconnecting structure which provides the environment for ectopic osteogenesis and angiogenesis.

  11. Role of the effect of electric field redistribution in the variation of the characteristics of open metal—insulator—metal "sandwich" structures under the action of moisture

    Science.gov (United States)

    Mordvintsev, V. M.; Levin, V. L.; Kudryavtsev, S. E.; Tsvetkova, L. A.

    2015-09-01

    We report on the results of numerical simulation of the effect of electric field redistribution in the insulating gap of the open TiN-SiO2-W metal-insulator-metal "sandwich" structure upon the formation of an insulating film layer with an elevated permittivity at the free end as a result of absorption of moisture by the porous silicon dioxide obtained by plasmachemical deposition. It is shown that the effect of electric field redistribution can explain all experimentally observed changes in the electric parameters caused by the action of moisture.

  12. Micro-CT-based improvement of geometrical and mechanical controllability of selective laser melted Ti6Al4V porous structures

    Energy Technology Data Exchange (ETDEWEB)

    Van Bael, S., E-mail: Simon.Vanbael@mech.kuleuven.be [Department of Mechanical Engineering, Division of Production Engineering, Machine Design and Automation, Katholieke Universiteit Leuven, Celestijnenlaan 300B, B-3001 Leuven (Belgium); Department of Mechanical Engineering, Division of Biomechanics and Engineering Design, Katholieke Universiteit Leuven, Celestijnenlaan 300C, B-3001 Leuven (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Minderbroedersstraat 8A, B-3000 Leuven (Belgium); Kerckhofs, G., E-mail: Greet.Kerckhofs@mtm.kuleuven.be [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Minderbroedersstraat 8A, B-3000 Leuven (Belgium); Moesen, M., E-mail: Maarten.Moesen@mtm.kuleuven.be [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Minderbroedersstraat 8A, B-3000 Leuven (Belgium); Pyka, G., E-mail: Gregory.Pyka@mtm.kuleuven.be [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Minderbroedersstraat 8A, B-3000 Leuven (Belgium); Schrooten, J., E-mail: Jan.Schrooten@mtm.kuleuven.be [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Minderbroedersstraat 8A, B-3000 Leuven (Belgium); and others

    2011-09-15

    Highlights: {yields} Selective laser melting as a production tool for porous Ti6Al4V structures. {yields} Significant mismatch between designed and as-produced properties. {yields} Decreasing mismatch using a micro-CT-based protocol. {yields} Mismatch of pore size decreased from 45% to 5%. {yields} Increased morphological controllability increases mechanical controllability. - Abstract: Despite the fact that additive manufacturing (AM) techniques allow to manufacture complex porous parts with a controlled architecture, differences can occur between designed and as-produced morphological properties. Therefore this study aimed at optimizing the robustness and controllability of the production of porous Ti6Al4V structures using selective laser melting (SLM) by reducing the mismatch between designed and as-produced morphological and mechanical properties in two runs. In the first run, porous Ti6Al4V structures with different pore sizes were designed, manufactured by SLM, analyzed by microfocus X-ray computed tomography (micro-CT) image analysis and compared to the original design. The comparison was based on the following morphological parameters: pore size, strut thickness, porosity, surface area and structure volume. Integration of the mismatch between designed and measured properties into a second run enabled a decrease of the mismatch. For example, for the average pore size the mismatch decreased from 45% to 5%. The demonstrated protocol is furthermore applicable to other 3D structures, properties and production techniques, powder metallurgy, titanium alloys, porous materials, mechanical characterization, tomography.

  13. Metal Oxide Nano structures: Synthesis, Properties, and Applications

    International Nuclear Information System (INIS)

    Xu, L. H.; Patil, D. S.; Yang, J.; Xiao, J.

    2015-01-01

    In recent years, nano structured materials have attracted wide attention due to their fascinating optical and electrical properties, which make these materials potentially suitable for applications in electronics, optics, photonics, and sensors. Some metal oxides show a wide variety of morphologies such as nano wires, nano rods, nano tubes, nano rings, and nano belts. Synthesis and investigation of these metal-oxide nano structures are beneficial not only for understanding the fundamental phenomena in low dimensional systems, but also for developing new-generation nano devices with high performance.

  14. Structural study of conventional and bulk metallic glasses during annealing

    International Nuclear Information System (INIS)

    Pineda, E.; Hidalgo, I.; Bruna, P.; Pradell, T.; Labrador, A.; Crespo, D.

    2009-01-01

    Metallic glasses with conventional glass-forming ability (Al-Fe-Nd, Fe-Zr-B, Fe-B-Nb compositions) and bulk metallic glasses (Ca-Mg-Cu compositions) were studied by synchrotron X-ray diffraction during annealing throughout glass transition and crystallization temperatures. The analysis of the first diffraction peak position during the annealing process allowed us to follow the free volume change during relaxation and glass transition. The structure factor and the radial distribution function of the glasses were obtained from the X-ray measurements. The structural changes occurred during annealing are analyzed and discussed.

  15. Structural transformations in liquid metallic glassformers

    International Nuclear Information System (INIS)

    Son, L.; Ryltcev, R.; Sidorov, V.; Sordelet, D.

    2007-01-01

    The statistics and thermodynamics of quasi-chemical bonds in glass forming liquid alloys have been described by method used in polymer statistics. It is shown that this bonging results in structural anomalies of two types. The first corresponds to relaxation of metastable globular state, which takes place at lower temperature, while the second one represents the drastic change of mean length of quasi-polymers

  16. Study on Topology Optimization Design, Manufacturability, and Performance Evaluation of Ti-6Al-4V Porous Structures Fabricated by Selective Laser Melting (SLM).

    Science.gov (United States)

    Xu, Yangli; Zhang, Dongyun; Zhou, Yan; Wang, Weidong; Cao, Xuanyang

    2017-09-07

    The combination of topology optimization (TOP) and selective laser melting (SLM) provides the possibility of fabricating the complex, lightweight and high performance geometries overcoming the traditional manufacturing "bottleneck". This paper evaluates the biomechanical properties of porous structures with porosity from 40% to 80% and unit cell size from 2 to 8 mm, which are designed by TOP and manufactured by SLM. During manufacturability exploration, three typical structures including spiral structure, arched bridge structure and structures with thin walls and small holes are abstracted and investigated, analyzing their manufacturing limits and forming reason. The property tests show that dynamic elastic modulus and compressive strength of porous structures decreases with increases of porosity (constant unit cell size) or unit cell size (constant porosity). Based on the Gibson-Ashby model, three failure models are proposed to describe their compressive behavior, and the structural parameter λ is used to evaluate the stability of the porous structure. Finally, a numerical model for the correlation between porous structural parameters (unit cell size and porosity) and elastic modulus is established, which provides a theoretical reference for matching the elastic modulus of human bones from different age, gender and skeletal sites during innovative medical implant design and manufacturing.

  17. Improved Joining of Metal Components to Composite Structures

    Science.gov (United States)

    Semmes, Edmund

    2009-01-01

    Systems requirements for complex spacecraft drive design requirements that lead to structures, components, and/or enclosures of a multi-material and multifunctional design. The varying physical properties of aluminum, tungsten, Invar, or other high-grade aerospace metals when utilized in conjunction with lightweight composites multiply system level solutions. These multi-material designs are largely dependent upon effective joining techAn improved method of joining metal components to matrix/fiber composite material structures has been invented. The method is particularly applicable to equipping such thin-wall polymer-matrix composite (PMC) structures as tanks with flanges, ceramic matrix composite (CMC) liners for high heat engine nozzles, and other metallic-to-composite attachments. The method is oriented toward new architectures and distributing mechanical loads as widely as possible in the vicinities of attachment locations to prevent excessive concentrations of stresses that could give rise to delaminations, debonds, leaks, and other failures. The method in its most basic form can be summarized as follows: A metal component is to be joined to a designated attachment area on a composite-material structure. In preparation for joining, the metal component is fabricated to include multiple studs projecting from the aforementioned face. Also in preparation for joining, holes just wide enough to accept the studs are molded into, drilled, or otherwise formed in the corresponding locations in the designated attachment area of the uncured ("wet') composite structure. The metal component is brought together with the uncured composite structure so that the studs become firmly seated in the holes, thereby causing the composite material to become intertwined with the metal component in the joining area. Alternately, it is proposed to utilize other mechanical attachment schemes whereby the uncured composite and metallic parts are joined with "z-direction" fasteners. The

  18. Adsorption and separation of propane and propylene by porous hexacyanometallates

    Energy Technology Data Exchange (ETDEWEB)

    Autie-Castro, G. [Instituto de Ciencia y Tecnologia de Materiales, Universidad de La Habana (Cuba); Autie, M. [Instituto de Ciencia y Tecnologia de Materiales, Universidad de La Habana (Cuba); Centro de Ingenieria y Proyectos (CIPRO), ISPJAE, La Habana (Cuba); Reguera, E., E-mail: ereguera@yahoo.com [Instituto de Ciencia y Tecnologia de Materiales, Universidad de La Habana (Cuba); Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada del IPN, Unidad Legaria, Mexico DF (Mexico); Moreno-Tost, R.; Rodriguez-Castellon, E.; Jimenez-Lopez, A.; Santamaria-Gonzalez, J. [Departamento de Quimica Inorganica, Cristalografia y Mineralogia, Facultad de Ciencias, Universidad de Malaga (Spain)

    2011-01-15

    The separation capability for mixtures of propane and propylene by porous frameworks representatives of transition metal hexacyanometallates was studied from adsorption data under equilibrium conditions at 273.15 K and from inverse gas chromatography profiles at different column temperatures. Samples of two porous solids were considered; Cd{sub 3}[Co(CN){sub 6}]{sub 2}, which is representative of Prussian blue analogues (cubic structure) with a porous framework related to vacancies for building block, and Zn{sub 3}[Co(CN){sub 6}]{sub 2} (rhombohedral phase) where the porous framework results from the tetrahedral coordination for the Zn atoms. The two materials were found to be able for the mixtures separation, with the highest separation ability for the rhombohedral phase under equilibrium conditions but, in dynamic conditions the cubic one shown a better separation, which was ascribed to a kinetic contribution related to a smaller windows size.

  19. Joining of Metal-Plastics-Hybrid Structures Using Laser Radiation by Considering the Surface Structure of the Metal

    Directory of Open Access Journals (Sweden)

    Christian Hopmann

    2016-01-01

    Full Text Available Lightweight construction is a central technology in today’s industrial production. One way to achieve the climate goals is the production of hybrid compounds of metal and plastic. The manufacturing process for these hybrid parts can be divided into in-mold assembly and postmold assembly. The postmold assembly includes thermal joining by laser, which is applied in the context of this paper. For the investigations, four plastics (MABS, PA6.6-GF35, PP, and PC, which differ in their properties, and three metals (unalloyed steel, stainless steel, and aluminum are combined and analyzed. These materials have been used, since they have a huge significance in the automotive industry. Preliminary studies showed that an adhesive bond between the two materials is achieved using metal with a structured surface. According to these studies, three structuring processes for metals (selective laser melting (SLM, NRX, and a welded metallic tissue are tested. The quality of the material/structure combinations is tested in tensile-shear-tests, microscopy images, and alternating climate tests. Compounds with SLM-Structure achieve highest strength, while compounds with aluminum are much more complex to manufacture.

  20. Influence of the metakaolin on porous structure of matrixes based in mk/cement

    Directory of Open Access Journals (Sweden)

    Frías, M.

    2000-09-01

    Full Text Available The incorporation of pozzolanic materials in the manufacturing of blended cement has a positive effect on the improvement of blended mortar and concretes performances. These active additions modify porous structure, impeding or delaying the access of aggressive solutions and, therefore materials more durable are possible of obtaining. An increase or decrease on the durability of blended pastes, mortars and concretes will depend on chemical and mineralogical compositions, fineness and reaction kinetics of these pozzolans. The current work shows the results of a research carried out in blended pastes to know the effect of activated material (metakaolin on the microporosity of pastes elaborated with different amounts of mk (0-25%. A water/ binder ratio of 0,55 was used. Samples were cured at 20ºC for 360 days. The evolution of total, capilary and gel porosity as well as average pore size were carried out through mercury intrusion porosimeter (MIP. Also, the helium pycnometer as alternative method to obtain additional information about porosity above 1,4 Å was used. A good correlation between both methods has been obtained. In addition, it is proposed the best mk content for the elaboration of mk-blended pastes.

    La incorporación de materiales puzolánicos presenta un efecto positivo en la mejora de las prestaciones de los morteros y hormigones mixtos. Estos modifican la estructura porosa, impidiendo o retrasando el acceso de los medios agresivos y, por lo tanto, contribución a la obtención de materiales mixtos más durables. La mayor o menor durabilidad de las pastas, morteros y hormigones mixtos dependerá de la composición química, mineralógica, finura y de la cinética de reacción de estas adiciones activas. En el presente trabajo se recogen los resultados de una investigación llevada a cabo para conocer el efecto de un material activado (metacaolin en la microporosidad de pastas, elaboradas con diferentes contenidos de