CO{sub 2} corrosion resistance of carbon steel in relation with microstructure changes

Energy Technology Data Exchange (ETDEWEB)

Ochoa, Nathalie, E-mail: nochoa@usb.ve [Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo., 89000, Caracas (Venezuela, Bolivarian Republic of); Vega, Carlos [Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Aptdo., 89000, Caracas (Venezuela, Bolivarian Republic of); Pébère, Nadine; Lacaze, Jacques [Université de Toulouse, CIRIMAT, UPS/INPT/CNRS, ENSIACET, 4 Allée Emile Monso, CS 44362, 31030 Toulouse Cedex 4 (France); Brito, Joaquín L. [Laboratorio de Físico-química de Superficies, Centro de Química, Instituto Venezolano de Investigaciones Cientificas (IVIC), Carretera Panamericana, Km 11, Altos de Pipe, Estado Miranda (Venezuela, Bolivarian Republic of)

2015-04-15

The microstructural effects on the corrosion resistance of an API 5L X42 carbon steel in 0.5 M NaCl solution saturated with CO{sub 2} was investigated. Four microstructures were considered: banded (B), normalized (N), quenched and tempered (Q&T), and annealed (A). Electrochemical measurements (polarization curves and electrochemical impedance spectroscopy) were coupled with surface analyses (scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS)) to characterize the formation of the corrosion product layers. Electrochemical results revealed that corrosion resistance increased in the following order: B < N < Q&T < A. From the polarization curves it was shown that specifically, cathodic current densities were affected by microstructural changes. SEM images indicated that ferrite dissolved earlier than cementite and a thin layer of corrosion products was deposited on the steel surface. XPS analyses revealed that this layer was composed of a mixture of iron carbonate and non-dissolved cementite. It was also found that the quantity of FeCO{sub 3} content on the steel surface was greater for Q&T and A microstructures. These results, in agreement with the electrochemical data, indicate that the deposition mechanism of iron carbonate is closely related to the morphology of the non-dissolved cementite, determining the protective properties of the corrosion product layers. - Highlights: • The effect of change in microstructure on CO{sub 2} corrosion resistance was evaluated. • An API 5LX 42 carbon steel was immersed in a 0.5 M NaCl solution saturated with CO{sub 2}. • Banded, normalized, quenched-tempered and annealed microstructures were considered. • Electrochemical measurements were coupled with surface analysis. • Morphology and distribution of undissolved Fe{sub 3}C control corrosion kinetics.

Carbonation-Related Microstructural Changesin Long-Term Durability Concrete

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Cláudio A. Rigo da Silva

2002-09-01

Full Text Available This paper discusses the effects of carbonation on the microstructure of Portland cement concrete for long-term durability applications. A class C40 concrete (characteristic compression strength between 40 MPa and 44 MPa on the 28th day, according to Brazilian standard NBR 8953 was chosen for the experimental study of the carbonation effects, from which test samples were molded for accelerated test under a 100%-CO2 atmosphere after physical and mechanical characterization. It was observed that carbonation provoked a reduction of 5% to 12% of the concrete open porosity accessible to water. Flexural strength values obtained after the carbonation tests revealed a decrease of 12% and 25% in relation to the values obtained before tests on the 28th and 91st days, respectively.

Carbons and carbon supported catalysts in hydroprocessing

Energy Technology Data Exchange (ETDEWEB)

Furimsky, Edward

2009-07-01

This book is a comprehensive summary of recent research in the field and covers all areas of carbons and carbon materials. The potential application of carbon supports, particularly those of carbon black (CB) and activated carbon (AC) in hydroprocessing catalysis are covered. Novel carbon materials such as carbon fibers and carbon nano tubes (CNT) are also covered, including the more recent developments in the use of fullerenes in hydroprocessing applications. Although the primary focus of this book is on carbons and carbon supported catalysts, it also identifies the difference in the effect of carbon supports compared with the oxidic supports, particularly that of the Al{sub 2}O{sub 3}. The difference in catalyst activity and stability was estimated using both model compounds and real feeds under variable conditions. The conditions applied during the preparation of carbon supported catalysts are also comprehensively covered and include various methods of pretreatment of carbon supports to enhance catalyst performance. The model compounds results consistently show higher hydrodesulfurization and hydrodeoxygenation activities of carbon supported catalysts than that of the Al{sub 2}O{sub 3} supported catalysts. Also, the deactivation of the former catalysts by coke deposition was much less evident. Chapter 6.3.1.3 is on carbon-supported catalysts: coal-derived liquids.

Effect of boron and carbon addition on microstructure and mechanical properties of Ti-15-3 alloy

International Nuclear Information System (INIS)

Sarkar, R.; Ghosal, P.; Muraleedharan, K.; Nandy, T.K.; Ray, K.K.

2011-01-01

Highlights: → Development of β Ti alloys with B and C addition for improved mechanical properties. → Detailed characterization of microstructural constituents using electron microscopy. → Microstructure-mechanical property correlation in this new class of alloys. → Strengthening mechanism in β Ti alloy in the presence of hard and non-deformable phases. - Abstract: A detailed microstructure-mechanical property correlation was carried out in beta titanium alloys (Ti-15V-3Al-3Sn-3Cr) with boron and carbon additions. The alloys were prepared by non-consumable vacuum arc melting followed by hot rolling. Microstructural characterization was carried out using an optical microscope, a scanning electron microscope (SEM), a transmission electron microscope (TEM) and a high resolution TEM (HRTEM). Addition of boron and carbon resulted in the precipitation of TiB and TiC, respectively, and these phases acted as reinforcements. Evaluation of mechanical properties in solution treated and solution treated plus aged condition showed strengthening in the boron and carbon containing alloy with respect to the base. Strengthening in solution treated condition was attributed to a synergistic effect of grain refinement and load transfer in the presence of non-deformable phases. On the other hand, higher strength in boron and carbon containing alloys on aging was ascribed to the presence of finer aged microstructures.

Microstructure and mechanical properties of internal crack healing in a low carbon steel

Energy Technology Data Exchange (ETDEWEB)

Xin, Ruishan [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University, Beijing 100084 (China); Ma, Qingxian, E-mail: maqxdme@mail.tsinghua.edu.cn [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University, Beijing 100084 (China); Li, Weiqi [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Key Laboratory for Advanced Materials Processing Technology of Ministry of Education, Tsinghua University, Beijing 100084 (China)

2016-04-26

The behavior of internal crack healing in a low carbon steel at elevated temperatures was investigated. The internal cracks were introduced into low carbon steel samples via the drilling and compression method. The microstructure of crack healing zone was observed using optical microscopy and scanning electron microscopy. The mechanical properties of crack healing zone at room temperature were tested. The results show that there are two mechanisms of crack healing in the low carbon steel. Crack healing is caused by atomic diffusion at lower temperatures, and mainly depends on recrystallization and grain growth at higher temperatures. The microstructural evolution of crack healing zone can be divided into four stages, and the fracture morphology of crack healing zone can be classified into five stages. At the initial healing stage, the fracture exhibits brittle or low ductile dimple fracture. The ultimate fracture mode is dimple and quasi-cleavage mixed fracture. Fine grain microstructures improve the ultimate tensile strength of crack healing zone, which is even higher than that of the matrix. The strength recovery rate is higher than that of the plasticity.

Analysis of microstructures for Co/Pd multilayer perpendicular magnetic recording media with carbon underlayer

International Nuclear Information System (INIS)

Asahi, T.; Kuramochi, K.; Kawaji, J.; Onoue, T.; Osaka, T.; Saigo, M.

2001-01-01

The effect of amorphous carbon underlayer thickness on the microstructure of the Co/Pd multilayer perpendicular magnetic recording media was investigated. From the magnetic force microscopy observation in the AC-demagnetized state of the Co/Pd multilayer media, the magnetic cluster size was observed to effectively decrease with an increase in carbon underlayer thickness, where the higher coercivity and the higher S/N ratio of the Co/Pd multilayer media were obtained with the thicker underlayer. Furthermore, the distribution of [1 1 1] orientation of FCC-Pd became broader, and the grain size decreased with an increase in the carbon underlayer thickness. These effects caused the magnetic exchange decoupling of Co/Pd multilayer media. We suggested that the change of microstructure was directly related to the surface roughness of the amorphous carbon underlayer

Heating effect of substrate of pulsed laser ablation deposition technique towards the orientation of carbon microstructure

International Nuclear Information System (INIS)

Choy, L.S.; Irmawati Ramli; Noorhana Yahya; Abdul Halim Shaari

2009-01-01

Full text: Carbon thin film has been successfully deposited by second harmonic Nd:YAG pulsed laser ablation deposition, PLAD. The topology and morphology of the deposited layers was studied by scanning electron microscopy (SEM) whereas emission dispersion X-ray (EDX) was used to determine the existence of elements that constitutes the microstructure. Substrate heated at 500 degree Celsius during the laser ablation showed the most homogenous lollipop microstructure as compared to mainly pillars of microstructure ablated at lower substrate temperature. It is found that this also avoid further diffusion of carbon into catalyst in forming iron carbide. (author)

Short and long carbon fibre reinforced Cu-matrix composites: microstructural results and structural origin of properties

International Nuclear Information System (INIS)

Buchgraber, W.

1997-01-01

Carbon fibre reinforced copper matrix composites possess properties of copper, i.e. excellent thermal and electrical conductivities, and properties of carbon fibre, i.e. a small thermal expansion coefficient. Since the desirable properties of the composite can be obtained by selecting the amount, type and orientation of the carbon fibres, it is considered to be suitable for use as electric and electronic materials. This lecture focuses on two-dimensional isotropic carbon fibre reinforced copper matrix composites with long or short carbon fibres. Short carbon fibre reinforced copper matrix composites have been produced by hot-pressing of copper coated short carbon fibres. During hot-pressing, the carbon fibres take on a preferred orientation in a plane perpendicular to the hot pressing direction. Within this plane the fibre orientation is random. Long carbon fibre reinforced copper matrix composites have been made by hot pressing of monolayers consisting of copper coated long carbon fibres. Different orientations of the monolayers will be compared. Both the physical and mechanical properties of the discussed composites are strongly influenced not only by the properties of its individual constituents, but also by the microstructure and properties of the fibre matrix interface. The problem of poor wettability of the carbon fibre by the copper matrix will be discussed. The microstructure of several types of carbon fibre reinforced copper matrix composites will be discussed. Their thermophysical properties will be compared with microstructural results. (author)

Bulk microstructure and local elastic properties of carbon nanocomposites studied by impulse acoustic microscopy technique

Science.gov (United States)

Levin, V.; Petronyuk, Yu.; Morokov, E.; Chernozatonskii, L.; Kuzhir, P.; Fierro, V.; Celzard, A.; Bellucci, S.; Bistarelli, S.; Mastrucci, M.; Tabacchioni, I.

2016-05-01

Bulk microstructure and elastic properties of epoxy-nanocarbon nanocomposites for diverse types and different content of carbon nanofiller has been studied by using impulse acoustic microscopy technique. It has been shown occurrence of various types of mesoscopic structure formed by nanoparticles inside the bulk of nanocomposite materials, including nanoparticle conglomerates and nanoparticle aerogel systems. In spite of the bulk microstructure, nanocarbon composites demonstrate elastic uniformity and negligible influence of nanofiller on elastic properties of carbon nanocomposite materials.

Microstructure and Mechanical Properties of Inconel 625 Alloy on Low Carbon Steel by Heat Treatment after Overlay Welding

International Nuclear Information System (INIS)

Kim, Seungpil; Jang, Jaeho; Kim, Jungsoo; Kim, Byung Jun; Sohn, Keun Yong; Nam, Dae-Geun

2016-01-01

Overlay welding technique is one of methods used to improve metal mechanical properties such as strength, toughness and corrosion resistance. Generally, Inconel 625 alloy is used for overlay welding layer on low carbon steels for economic consideration. However, the method produces some problems in the microstructure of the cast structure and some defects, caused by the elevated temperatures of the overlay process. To resolve these problems, heat treatments are required. In this study, Inconel 625 alloy was welded on a low carbon steel by the overlay welding process to investigate the resulting microstructure and mechanical properties. A double heat treatment was performed to improve the mechanical properties of the welding and substrate layers. It was found that Inconel 625 alloy had an austenite microstructure after the first heat treatment, but the low carbon steel had a ferrite-pearlite microstructure after the second heat treatment. After the double heat treatment, the sample showed the optimum hardness because of grain refinement and homogenization of the microstructure.

Microstructure and Mechanical Properties of Inconel 625 Alloy on Low Carbon Steel by Heat Treatment after Overlay Welding

Energy Technology Data Exchange (ETDEWEB)

Kim, Seungpil; Jang, Jaeho; Kim, Jungsoo; Kim, Byung Jun; Sohn, Keun Yong; Nam, Dae-Geun [Korea Institute of Industrial Technology, Busan (Korea, Republic of)

2016-08-15

Overlay welding technique is one of methods used to improve metal mechanical properties such as strength, toughness and corrosion resistance. Generally, Inconel 625 alloy is used for overlay welding layer on low carbon steels for economic consideration. However, the method produces some problems in the microstructure of the cast structure and some defects, caused by the elevated temperatures of the overlay process. To resolve these problems, heat treatments are required. In this study, Inconel 625 alloy was welded on a low carbon steel by the overlay welding process to investigate the resulting microstructure and mechanical properties. A double heat treatment was performed to improve the mechanical properties of the welding and substrate layers. It was found that Inconel 625 alloy had an austenite microstructure after the first heat treatment, but the low carbon steel had a ferrite-pearlite microstructure after the second heat treatment. After the double heat treatment, the sample showed the optimum hardness because of grain refinement and homogenization of the microstructure.

Microstructure, elastic and inelastic properties of partially graphitized biomorphic carbons

Science.gov (United States)

Orlova, T. S.; Kardashev, B. K.; Smirnov, B. I.; Gutierrez-Pardo, A.; Ramirez-Rico, J.; Martinez-Fernandez, J.

2015-03-01

The microstructural characteristics and amplitude dependences of the Young's modulus E and internal friction (logarithmic decrement δ) of biocarbon matrices prepared by beech wood carbonization at temperatures T carb = 850-1600°C in the presence of a nickel-containing catalyst have been studied. Using X-ray diffraction and electron microscopy, it has been shown that the use of a nickel catalyst during carbonization results in a partial graphitization of biocarbons at T carb ≥ 1000°C: the graphite phase is formed as 50- to 100-nm globules at T carb = 1000°C and as 0.5- to 3.0-μm globules at T carb = 1600°C. It has been found that the measured dependences E( T carb) and δ( T carb) contain three characteristic ranges of variations in the Young's modulus and logarithmic decrement with a change in the carbonization temperature: E increases and δ decreases in the ranges T carb 1300°C; in the range 1000 biocarbons carbonized in the presence of nickel correlates with the evolution of their microstructure. The largest values of E are obtained for samples with T carb = 1000 and 1600°C. However, the samples with T carb = 1600°C exhibit a higher susceptibility to microplasticity due to the presence of a globular graphite phase that is significantly larger in size and total volume.

Multiphase Microstructure in a Metastability-Assisted Medium Carbon Alloy Steel

Science.gov (United States)

Liu, Cheng; Cui, Xixi; Yang, Chen

2018-05-01

A medium carbon alloy steel is processed by austenizing at 900 °C for 30 min, then rapid quenching into a patented quenching liquid and holding at 170 °C for 5 min, finally isothermally holding at 250 °C for different times. The morphology and mechanical properties are performed by using optical microscopy and scanning electron microscopy. A multiphase microstructure characterized by a mixture of lenticular prior martensite (PM), fine needle bainitic ferrite and filmy retained austenite (RA) is obtained. It is found that the PM formed firstly upon quenching can accelerate the subsequent bainitic transformation and promote refinement of multiphase colonies. The results show that an optimum mechanical property of a 4000.9 MPa bending strength and a 2030 MPa tensile strength is achieved at 250 °C for 120 min, which is attributed to the multiphase microstructural characteristics and a high product of the volume fraction of RA and the carbon content of austenite.

Laser-Based Surface Modification of Microstructure for Carbon Fiber-Reinforced Plastics

Science.gov (United States)

Yang, Wenfeng; Sun, Ting; Cao, Yu; Li, Shaolong; Liu, Chang; Tang, Qingru

2018-05-01

Bonding repair is a powerful feature of carbon fiber-reinforced plastics (CFRP). Based on the theory of interface bonding, the interface adhesion strength and reliability of the CFRP structure will be directly affected by the microscopic features of the CFRP surface, including the microstructure, physical, and chemical characteristics. In this paper, laser-based surface modification was compared to Peel-ply, grinding, and polishing to comparatively evaluate the surface microstructure of CFRP. The surface microstructure, morphology, fiber damage, height and space parameters were investigated by scanning electron microscopy (SEM) and laser confocal microscopy (LCM). Relative to the conventional grinding process, laser modification of the CFRP surface can result in more uniform resin removal and better processing control and repeatability. This decreases the adverse impact of surface fiber fractures and secondary damage. The surface properties were significantly optimized, which has been reflected such things as the obvious improvement of surface roughness, microstructure uniformity, and actual area. The improved surface microstructure based on laser modification is more conducive to interface bonding of CFRP structure repair. This can enhance the interfacial adhesion strength and reliability of repair.

Analysis of composition and microstructural uniformity of hybrid glass/carbon fibre composites

Energy Technology Data Exchange (ETDEWEB)

Beauson, J.; Markussen, C.M.; Madsen, Bo

2013-09-01

In hybrid fibre composites, the intermixing of the two types of fibres imposes challenges to obtain materials with a well-defined and uniform microstructure. In the present paper, the composition and the microstructural uniformity of hybrid glass/carbon fibre composites mixed at the fibre bundle level are investigated. The different levels of compositions in the composites are defined and experimentally determined. The composite volume fractions are determined using an image analysis based procedure. The global fibre volume fractions are determined using a gravimetrical based method. The local fibre volume fractions are determined using volumetric calculations. A model is presented to predict the interrelation of volume fractions in hybrid fibre composites. The microstructural uniformity of the composites is analysed by the determined variation in composite volume fractions. Two analytical methods, a standard deviation based method and a fast Fourier transform method, are used to quantify the difference in microstructural uniformity between composites, and to detect and quantify any repeating pattern in the composite microstructure. (Author)

Effect of carbon content on formation of bimodal microstructure and mechanical properties of low-carbon steels subjected to heavy-reduction single-pass hot/warm deformation

Energy Technology Data Exchange (ETDEWEB)

Park, Hyung-Won, E-mail: wonipark@iis.u-tokyo.ac.jp [Graduate School of Engineering, The University of Tokyo, Komaba 4-6-1, Meguro-ku 153-8505, Tokyo (Japan); Yanagimoto, Jun [Institute of Industrial Science, The University of Tokyo, Komaba 4-6-1, Meguro-ku 153-8505, Tokyo (Japan)

2014-06-01

A compression test simulating heavy-reduction single-pass rolling was conducted to investigate the microstructural evolution based on the formation of a bimodal structure and the mechanical properties of 0.01% and 0.1% carbon steels and niobium steel. When thermomechanical processing was conducted near and above the critical transformation temperature (A{sub c3}), microstructures of all steels were significantly refined and consisted of equiaxed grains without elongated grains. Nevertheless, these microstructures showed weak or no formation of the bimodal structure or coarse grains with decreasing carbon content, while they showed bimodal structure formation when 0.2% carbon steel was used in our previous research. The average grain size of Nb steel was about 2 μm and its microstructure was uniformly refined. These may be attributed to a decrease in the number of nucleation sites with decreasing carbon content in low-carbon steels and the occurrence of nucleation at grain boundaries as well as in grain interiors in Nb steel during processing. Mechanical properties of all steels deformed above the critical transformation temperature exhibited high performance characteristics with superior strength and marked elongation. Their fractographs indicated ductile fracture, which was revealed by SEM observation after a tensile test.

Formation of carbon nano- and micro-structures on C+1 irradiated copper surfaces

International Nuclear Information System (INIS)

Ahmad, Shoaib

2013-01-01

A series of experiments has identified mechanisms of carbon nano- and micro-structure formation at room temperature, without catalyst and in the environment of immiscible metallic surroundings. The structures include threaded nano fibres, graphitic sheets and carbon onions. Copper as substrate was used due to its immiscibility with carbon. Energetic carbon ions (C + 1 ) of 0.2–2.0 MeV irradiated Cu targets. Cu substrates, apertures and 3 mm dia TEM Cu grids were implanted with the carbon. We observed wide range of μm-size structures formed on Cu grids and along the edges of the irradiated apertures. These are shown to be threaded nano fibers (TNF) of few μm thicknesses with lengths varying from 10 to 3000 μm. Secondary electron microscopy (SEM) identifies the μm-size structures while Confocal microscopy was used to learn about the mechanisms by which C + 1 irradiated Cu provides the growth environment. Huge carbon onions of diameters ranging from hundreds of nm to μm were observed in the as-grown and annealed samples. Transformations of the nanostructures were observed under prolonged electron irradiations of SEM and TEM. A mechanism for the formation of carbon nano- and micro-structures is proposed.

Liquid spreading on ceramic-coated carbon nanotube films and patterned microstructures

Science.gov (United States)

Zhao, Hangbo; Hart, A. John

2015-11-01

We study the capillary-driven liquid spreading behavior on films and microstructures of ceramic-coated vertically aligned carbon nanotubes (CNTs) fabricated on quartz substrates. The nanoscale porosity and micro-scale dimensions of the CNT structures, which can be precisely varied by the fabrication process, enable quantitative measurements that can be related to analytical models of the spreading behavior. Moreover, the conformal alumina coating by atomic layer deposition (ALD) prevents capillary-induced deformation of the CNTs upon meniscus recession, which has complicated previous studies of this topic. Washburn-like liquid spreading behavior is observed on non-patterned CNT surfaces, and is explained using a scaling model based on the balance of capillary driving force and the viscous drag force. Using these insights, we design patterned surfaces with controllable spreading rates and study the contact line pinning-depinning behavior. The nanoscale porosity, controllable surface chemistry, and mechanical stability of coated CNTs provide significantly enhanced liquid-solid interfacial area compared to solid microstructures. As a result, these surface designs may be useful for applications such as phase-change heat transfer and electrochemical energy storage. Funding for this project is provided by the National Institutes of Health and the MIT Center for Clean Water and Clean Energy supported by the King Fahd University of Petroleum and Minerals.

Effects of Processing Parameters on the Density and Microstructure of Pyrolytic Carbon

International Nuclear Information System (INIS)

Kim, Weon Ju; Park, Jeong Nam; Park, Jong Hoon; Cho, Moon Sung; Lee, Young Woo; Park, Ji Yeon

2007-01-01

Chemical vapor deposition (CVD) of pyrolytic carbon (PyC) and silicon carbide (SiC) has been applied to TRISO-coated fuel particles for high-temperature gas-cooled reactors (HTGR). The porous PyC coating layer, called the buffer layer, attenuates fission recoils and provides void volume for gaseous fission products and carbon monoxide. The inner PyC layer acts as a containment to gaseous products. The outer PyC layer protects the SiC coating layer by inducing a compressive stress and provides chemical compatibility with a graphite matrix in the fuel compact. The PyC layers undergo shrinkage due to neutron irradiation, affecting the design and modeling of fuel particles. Because the dimensional change of PyC depends on the detailed microstructure of PyC, it differs from one fabrication route to another one. This requires a new design of irradiation experiment applicable to spherical objects and leads to an international collaborative work called PYCASSO (PYrocarbon irradiation for Creep And Swelling/Shrinkage of Objects). KAERI proposed four different types of PyC layers coated on ZrO 2 particles, buffer with a density of 1.0 and dense PyCs with densities of 1.7, 1.9 and 2.1 g/cm 3 , for the irradiation experiment. In this study, we fabricated PyC-coated particles with various coating densities for supporting the PYCASSO experiment. We also investigated effects of processing parameters such as temperature, hydrocarbon concentration and gas flow rate on the density and microstructure of the PyC layer

Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7

Directory of Open Access Journals (Sweden)

Quanshun Luo

2017-07-01

Full Text Available Ultrahigh strength steel 56NiCrMoV7 was austempered at 270 °C for different durations in order to investigate the microstructure evolution, carbon partitioning behaviour and hardness property. Detailed microstructure has been characterised using optical microscopy and field emission gun scanning electron microscopy. A newly developed X-ray diffraction method has been employed to dissolve the bainitic/martensitic ferrite phase as two sub-phases of different tetragonal ratios, which provides quantitative analyses of the carbon partitioning between the resultant ferrites and the retained austenite. The results show that, a short-term austempering treatment was in the incubation period of the bainite transformation, which resulted in maximum hardness being equivalent to the oil-quenching treatment. The associated microstructure comprises fine carbide-free martensitic and bainitic ferrites of supersaturated carbon contents as well as carbon-rich retained austenite. In particular, the short-term austempering treatment helped prevent the formation of lengthy martensitic laths as those being found in the microstructure of oil-quenched sample. When the austempering time was increased from 20 to 80 min, progressive decrease of the hardness was associated with the evolution of the microstructure, including progressive coarsening of bainitic ferrite, carbide precipitating inside high-carbon bainitic ferrite and its subsequent decarbonisation.

Microstructures and mechanical properties of duplex low carbon steel

Science.gov (United States)

Alfirano; Eben, U. S.; Hidayat, M.

2018-04-01

The microstructures behavior of duplex cold-rolled low carbon steel for automotive applications has been investigated. Intercritical annealing treatment is commonly used to develop a duplex low carbon steel containing ferrite and martensite. To get a duplex phase ferrite and martensite, the specimens were heated at inter-critical annealing temperature of 775°C - 825°C, for heating time up to 20 minutes, followed by water-quenched. The hardness of specimens was studied. The optical microscopy was used to analyze the microstructures. The optimal annealing conditions (martensite volume fraction approaching 20%) at 775°C with a heating time of 10 minutes was achieved. The highest hardness value was obtained in cold-rolled specimens of 41% in size reduction for intercritical annealing temperature of 825°C. In this condition, the hardness value was 373 HVN. The correlation between intercritical annealing temperature and time can be expressed in the transformation kinetics as fγ/fe = 1-exp(-Ktn) wherein K and n are grain growth rate constant and Avrami’s exponent, respectively. From experiment, the value of K = 0.15 and n = 0.461. Using the relationship between temperatures and heating time, activation energy (Q) can be calculated that is 267 kJ/mol.

Dechlorination of Environmental Contaminants Using a Hybrid Nanocatalyst: Palladium Nanoparticles Supported on Hierarchical Carbon Nanostructures

Directory of Open Access Journals (Sweden)

Hema Vijwani

2012-01-01

Full Text Available This paper demonstrates the effectiveness of a new type of hybrid nanocatalyst material that combines the high surface area of nanoparticles and nanotubes with the structural robustness and ease of handling larger supports. The hybrid material is made by fabricating palladium nanoparticles on two types of carbon supports: as-received microcellular foam (Foam and foam with carbon nanotubes anchored on the pore walls (CNT/Foam. Catalytic reductive dechlorination of carbon tetrachloride with these materials has been investigated using gas chromatography. It is seen that while both palladium-functionalized carbon supports are highly effective in the degradation of carbon tetrachloride, the rate of degradation is significantly increased with palladium on CNT/Foam. However, there is scope to increase this rate further if the wettability of these structures can be enhanced in the future. Microstructural and spectroscopic analyses of the fresh and used catalysts have been compared which indicates that there is no change in density or surface chemical states of the catalyst after prolonged use in dechlorination test. This implies that these materials can be used repeatedly and hence provide a simple, powerful, and cost-effective approach for dechlorination of water.

Microstructural investigations of 0.2% carbon content steel

Science.gov (United States)

Tollabimazraehno, Sajjad; Hingerl, Kurt

2011-10-01

The effect of thermal annealing to get different phases on low carbon steel was investigated. Steel sheets (0.2 wt. % C) of 900 μm thickness were heat treated to produce different structures. All the samples have the same starting point, transformation to coarse austenite at 900 degree Celsius. The nano indentation results revealed that samples have different hadness. By making conventional SEM micrographs, focus ion beam maps, and Electron backscatter diffraction (EBSD) the microstructural development and grain boundary variation of transformed phases martensite, biainte, tempered martensite and different combination of these phases were studied.

Effects of Nb Modification and Cooling Rate on the Microstructure in an Ultrahigh Carbon Steel

Science.gov (United States)

Hecht, Matthew D.; Webler, Bryan A.; Picard, Yoosuf N.

2018-06-01

In this study, two different melting methods were used to investigate effects of Nb modification on microstructure in ultrahigh carbon steel (UHCS). Nb-free and Nb-modified UHCS samples were produced by melting and resolidifying an industrially produced base UHCS with and without addition of Nb powder. Microstructure was characterized using scanning electron microscopy, X-ray diffraction, and electron dispersive spectroscopy. Equilibrium computations of phase fractions and compositions were utilized to help describe microstructural changes caused by the Nb additions. Nb combined with C to form NbC structures before and during austenite solidification, reducing the effective amount of carbon available for the other phases. Cementite network spacing in the Nb-free samples was controlled by the cooling rate during solidification (faster cooling led to a more refined network). Network spacing in the Nb-modified UHCS could be enlarged by NbC structures that formed cooperatively with austenite.

Annealing effect on the microstructure modification and tribological properties of amorphous carbon nitride films

Science.gov (United States)

Wang, Zhou; Wang, Chengbing; Wang, Qi; Zhang, Junyan

2008-10-01

The influences of thermal annealing on the microstructural and tribological properties of amorphous carbon nitride films were investigated. X-ray photoelectron spectroscopy, Raman spectroscopy, and Fourier transform infrared spectrometer were utilized to characterize bond configuration and chemical state of the films. The results indicated that at low annealing temperatures (200 and 300 °C), the volatile species and surface contamination are easily dissociated without obvious bulk modification; while at high annealing temperatures (400 and 500 °C), the microstructure of carbon nitride films changed and favored a graphitization process, which indicated the growth of more graphitic film structures. The faint Raman signal of C≡N decreased with annealing temperature (TA) and completely disappeared at TA of 500 °C, indicating that nitrile bonds were thermal unstable under high temperature. Surprisingly, the tribological properties of the films showed a remarkably decreasing in friction coefficient as the TA increased; it is attributed to the graphitization of carbon nitride films during thermal annealing, which favored transfer film formation between the carbon nitride films and counterface materials. The transfer films benefit the decrease in coefficient of friction.

Microstructure, elastic, and inelastic properties of biomorphic carbons carbonized using a Fe-containing catalyst

Science.gov (United States)

Orlova, T. S.; Kardashev, B. K.; Smirnov, B. I.; Gutierrez-Pardo, A.; Ramirez-Rico, J.

2016-12-01

The microstructure and amplitude dependences of the Young's modulus E and internal friction (logarithmic decrement δ), and microplastic properties of biocarbon matrices BE-C(Fe) obtained by beech tree carbonization at temperatures T carb = 850-1600°C in the presence of an iron-containing catalyst are studied. By X-ray diffraction analysis and transmission electron microscopy, it is shown that the use of Fe-catalyst during carbonization with T carb ≥ 1000°C leads to the appearance of a bulk graphite phase in the form of nanoscale bulk graphite inclusions in a quasi-amorphous matrix, whose volume fraction and size increase with T carb. The correlation of the obtained dependences E( T carb) and δ( T carb) with microstructure evolution with increasing T carb is revealed. It is found that E is mainly defined by a crystalline phase fraction in the amorphous matrix, i.e., a nanocrystalline phase at T carb 1300°C. Maximum values E = 10-12 GPa are achieved for samples with T carb ≈ 1150 and 1600°C. It is shown that the microplasticity manifest itself only in biocarbons with T carb ≥ 1300°C (upon reaching a significant volume of the graphite phase); in this case, the conditional microyield stress decreases with increasing total volume of introduced mesoporosity (free surface area).

Effect of particulate matrix inhibitors on microstructure and properties of 2-D carbon-carbon composites

International Nuclear Information System (INIS)

Tlomak, P.; Takano, Shigeru; Wright, M.A.; Ju, Chien-Ping.

1991-01-01

Extended-life applications of structural carbon-carbon (C-C) composites involve multiple periods of operation in high-temperature oxidizing environments and as such require a reliable oxidation protection system (OPS). Advanced OPS's generally consist of an external ceramic coating combined with an in-depth matrix inhibitor. This work investigated the effects produced by particulate inhibitors doped on the matrix on the microstructure of 2D, PAN fiber-pitch matrix C-C's. Boron and zirconium-based particulate inhibitors were added to the matrix material prior to heat treatment. A process was developed to assure a uniform distribution of the inhibitors. Oxidation behavior of such matrix-inhibited composites was evaluated using isothermal oxidation tests. 5 refs

Selective laser melting of carbon/AlSi10Mg composites: Microstructure, mechanical and electronical properties

Energy Technology Data Exchange (ETDEWEB)

Zhao, Xiao; Song, Bo, E-mail: bosong@hust.edu.cn; Fan, Wenrui; Zhang, Yuanjie; Shi, Yusheng

2016-04-25

Carbon nanotubes/AlSi10Mg composites has drawn lots of attention in structural engineering and functional device applications due to its extraordinary high elastic modulus and mechanical strength as well as excellent electrical and thermal conductivities. In this study, the CNTs/AlSi10Mg composites was firstly prepared and then processed by selective laser melting. The powder preparation, SLM process, and microstructure evolution, properties were clarified. The results showed that CNTs were decomposed due to the direct interaction with the laser beam. The SLMed composites displayed a similar microstructure to that of SLMed AlSi10Mg. The common brittleness phase Al{sub 4}C{sub 3} didn't form, and the carbon dispersion strengthening was observed. The electrical resistivity of the composites was reduced significantly and the hardness was improved. - Highlights: • Carbon nanotubes/AlSi10Mg powder were prepared by slurry ball milling process. • Carbon nanotubes/AlSi10Mg composites were firstly prepared by SLM. • The electrical resistivity of the composites was significantly reduced and hardness was improved.

Thermal desorption of deuterium from modified carbon nanotubes and its correlation to the microstructure

NARCIS (Netherlands)

Lisowski, W.F.; Keim, Enrico G.; van den Berg, A.H.J.; Smithers, Mark A.; Smithers, M.A.

2006-01-01

The process of deuterium desorption from single-wall carbon nanotubes (SWNTs) modified by atomic (D) and molecular (D2) deuterium treatment was investigated in an ultrahigh vacuum environment using thermal desorption mass spectroscopy (TDMS). Microstructural and chemical analyses of SWNT material,

Silicon and aluminum doping effects on the microstructure and properties of polymeric amorphous carbon films

Energy Technology Data Exchange (ETDEWEB)

Liu, Xiaoqiang, E-mail: lxq_suse@sina.com [Material Corrosion and Protection Key Laboratory of Sichuan province, Sichuan University of Science and Engineering, Zigong 643000 (China); Hao, Junying, E-mail: jyhao@licp.cas.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Xie, Yuntao [Material Corrosion and Protection Key Laboratory of Sichuan province, Sichuan University of Science and Engineering, Zigong 643000 (China)

2016-08-30

Highlights: • Evolution of nanostructure and properties of the polymeric amorphous carbon films were firstly studied. • Si doping enhanced polymerization of the hydrocarbon chains and Al doping resulted in increase in the ordered carbon clusters of polymeric amorphous carbon films. • Soft polymeric amorphous carbon films exhibited an unconventional frictional behaviors with a superior wear resistance. • The mechanical and vacuum tribological properties of the polymeric amorphous carbon films were significantly improved by Si and Al co-doping. - Abstract: Polymeric amorphous carbon films were prepared by radio frequency (R.F. 13.56 MHz) magnetron sputtering deposition. The microstructure evolution of the deposited polymeric films induced by silicon (Si) and aluminum(Al) doping were scrutinized through infrared spectroscopy, multi-wavelength Raman spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The comparative results show that Si doping can enhance polymerization and Al doping results in an increase in the ordered carbon clusters. Si and Al co-doping into polymeric films leads to the formation of an unusual dual nanostructure consisting of cross-linked polymer-like hydrocarbon chains and fullerene-like carbon clusters. The super-high elasticity and super-low friction coefficients (<0.002) under a high vacuum were obtained through Si and Al co-doping into the films. Unconventionally, the co-doped polymeric films exhibited a superior wear resistance even though they were very soft. The relationship between the microstructure and properties of the polymeric amorphous carbon films with different elements doping are also discussed in detail.

Processing and refinement of steel microstructure images for assisting in computerized heat treatment of plain carbon steel

Science.gov (United States)

Gupta, Shubhank; Panda, Aditi; Naskar, Ruchira; Mishra, Dinesh Kumar; Pal, Snehanshu

2017-11-01

Steels are alloys of iron and carbon, widely used in construction and other applications. The evolution of steel microstructure through various heat treatment processes is an important factor in controlling properties and performance of steel. Extensive experimentations have been performed to enhance the properties of steel by customizing heat treatment processes. However, experimental analyses are always associated with high resource requirements in terms of cost and time. As an alternative solution, we propose an image processing-based technique for refinement of raw plain carbon steel microstructure images, into a digital form, usable in experiments related to heat treatment processes of steel in diverse applications. The proposed work follows the conventional steps practiced by materials engineers in manual refinement of steel images; and it appropriately utilizes basic image processing techniques (including filtering, segmentation, opening, and clustering) to automate the whole process. The proposed refinement of steel microstructure images is aimed to enable computer-aided simulations of heat treatment of plain carbon steel, in a timely and cost-efficient manner; hence it is beneficial for the materials and metallurgy industry. Our experimental results prove the efficiency and effectiveness of the proposed technique.

Effect of zirconium addition on the microstructure and performance of carbon foam

Energy Technology Data Exchange (ETDEWEB)

Li Wanqian [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Zhang Hongbo, E-mail: wanqian20089@126.com [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); Xiong Xiang; Xiao Feng [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China)

2010-05-15

A novel carbon foam was prepared from mixtures of mesophase pitch and dopant (zirconium), followed by foaming, carbonization and graphitization. The influence of Zr on the microstructure and properties of these foams was analyzed. Results have shown that Zr can promote the graphitization degree of carbon foams, which lead to an increase of thermal conductivity. The high bulk thermal conductivity of 63 W/m K was achieved with an addition of 3 wt% at heat treatment temperature of 2573 K. The d{sub 002} spacings of graphitic foams are found to decrease with the increase of dopant concentration in the pitch. SEM analysis also showed micro-cracks at the ligament of the doped graphitic foam, which might be responsible for the decrease of the compressive strength.

Effect of Mo Content on Microstructure and Property of Low-Carbon Bainitic Steels

Directory of Open Access Journals (Sweden)

Haijiang Hu

2016-07-01

Full Text Available In this work, three low-carbon bainitic steels, with different Mo contents, were designed to investigate the effects of Mo addition on microstructure and mechanical properties. Two-step cooling, i.e., initial accelerated cooling and subsequent slow cooling, was used to obtain the desired bainite microstructure. The results show that the product of strength and elongation first increases and then shows no significant change with increasing Mo. Compared with Mo-free steel, bainite in the Mo-containing steel tends to have a lath-like morphology due to a decrease in the bainitic transformation temperature. More martensite transformation occurs with the increasing Mo, resulting in greater hardness of the steel. Both the strength and elongation of the steel can be enhanced by Mo addition; however, the elongation may decrease with a further increase in Mo. From a practical viewpoint, the content of Mo could be ~0.14 wt. % for the composition design of low-carbon bainitic steels in the present work. To be noted, an optimal scheme may need to consider other situations such as the role of sheet thickness, toughness behavior and so on, which could require changes in the chemistry. Nevertheless, these results provide a reference for the composition design and processing method of low-carbon bainitic steels.

Microstructural Evolution During Cold Rolling and Subsequent Annealing in Low-Carbon Steel with Different Initial Microstructures

Science.gov (United States)

Ogawa, Toshio; Dannoshita, Hiroyuki; Maruoka, Kuniaki; Ushioda, Kohsaku

2017-08-01

Microstructural evolution during cold rolling and subsequent annealing of low-carbon steel with different initial microstructures was investigated from the perspective of the competitive phenomenon between recrystallization of ferrite and reverse phase transformation from ferrite to austenite. Three kinds of hot-rolled sheet specimens were prepared. Specimen P consisted of ferrite and pearlite, specimen B consisted of bainite, and specimen M consisted of martensite. The progress of recovery and recrystallization of ferrite during annealing was more rapid in specimen M than that in specimens P and B. In particular, the recrystallized ferrite grains in specimen M were fine and equiaxed. The progress of ferrite-to-austenite phase transformation during intercritical annealing was more rapid in specimen M than in specimens P and B. In all specimens, the austenite nucleation sites were mainly at high-angle grain boundaries, such as those between recrystallized ferrite grains. The austenite distribution was the most uniform in specimen M. Thus, we concluded that fine equiaxed recrystallized ferrite grains were formed in specimen M, leading to a uniform distribution of austenite.

Measurement of carbon nanotube microstructure relative density by optical attenuation and observation of size-dependent variations.

Science.gov (United States)

Park, Sei Jin; Schmidt, Aaron J; Bedewy, Mostafa; Hart, A John

2013-07-21

Engineering the density of carbon nanotube (CNT) forest microstructures is vital to applications such as electrical interconnects, micro-contact probes, and thermal interface materials. For CNT forests on centimeter-scale substrates, weight and volume can be used to calculate density. However, this is not suitable for smaller samples, including individual microstructures, and moreover does not enable mapping of spatial density variations within the forest. We demonstrate that the relative mass density of individual CNT microstructures can be measured by optical attenuation, with spatial resolution equaling the size of the focused spot. For this, a custom optical setup was built to measure the transmission of a focused laser beam through CNT microstructures. The transmittance was correlated with the thickness of the CNT microstructures by Beer-Lambert-Bouguer law to calculate the attenuation coefficient. We reveal that the density of CNT microstructures grown by CVD can depend on their size, and that the overall density of arrays of microstructures is affected significantly by run-to-run process variations. Further, we use the technique to quantify the change in CNT microstructure density due to capillary densification. This is a useful and accessible metrology technique for CNTs in future microfabrication processes, and will enable direct correlation of density to important properties such as stiffness and electrical conductivity.

Effect of starting microstructure upon the nucleation sites and distribution of graphite particles during a graphitising anneal of an experimental medium-carbon machining steel

Energy Technology Data Exchange (ETDEWEB)

Inam, A., E-mail: aqil.ceet@pu.edu.pk; Brydson, R., E-mail: mtlrmdb@leeds.ac.uk; Edmonds, D.V., E-mail: d.v.edmonds@leeds.ac.uk

2015-08-15

The potential for using graphite particles as an internal lubricant during machining is considered. Graphite particles were found to form during graphitisation of experimental medium-carbon steel alloyed with Si and Al. The graphite nucleation sites were strongly influenced by the starting microstructure, whether ferrite–pearlite, bainite or martensite, as revealed by light and electron microscopy. Favourable nucleation sites in the ferrite–pearlite starting microstructure were, not unexpectedly, found to be located within pearlite colonies, no doubt due to the presence of abundant cementite as a source of carbon. In consequence, the final distribution of graphite nodules in ferrite–pearlite microstructures was less uniform than for the bainite microstructure studied. In the case of martensite, this study found a predominance of nucleation at grain boundaries, again leading to less uniform graphite dispersions. - Highlights: • Metallography of formation of graphite particles in experimental carbon steel. • Potential for using graphite in steel as an internal lubricant during machining. • Microstructure features expected to influence improved machinability studied. • Influence of pre-anneal starting microstructure on graphite nucleation sites. • Influence of pre-anneal starting microstructure on graphite distribution. • Potential benefit is new free-cutting steel compositions without e.g. Pb alloying.

Composite Materials for Thermal Energy Storage: Enhancing Performance through Microstructures

Science.gov (United States)

Ge, Zhiwei; Ye, Feng; Ding, Yulong

2014-01-01

Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. PMID:24591286

Influence of microstructure on the low and high cycle fatigue behaviour of a medium carbon microalloyed steel

International Nuclear Information System (INIS)

Srivastava, V.; Padmanabhan, K.A.

2001-01-01

This paper reports the room temperature monotonic and cyclic stress-strain (CSS) response, the low and high cycle fatigue behaviour of a medium carbon microalloyed (MA) steel in different microstructural conditions obtained by isothermal transformation at 973, 773 and 573 K following austenitizing at 1123 K. The isothermal transformations resulted in coarse pearlite (CP), fine pearlite (FP), and acicular ferrite/bainite (AF/B) microstructures, respectively. In low cycle fatigue, the CP and FP microstructures exhibited cyclic softening at low total strain amplitudes ( cys ) of the material and was approximately equal to 0.7σ cys . (orig.)

Effect of Carbon Content on the Microstructure and Mechanical Properties of NbC-Ni Based Cermets

Directory of Open Access Journals (Sweden)

Shuigen Huang

2018-03-01

Full Text Available The aim of this work was to correlate the overall carbon content in NbC-Ni, NbC-Ni-VC and NbC-Ni-Mo starting powders with the resulting microstructure, hardness, and fracture toughness of Ni-bonded NbC cermets. A series of NbC-Ni, NbC-Ni-VC and NbC-Ni-Mo cermets with different carbon content were prepared by conventional liquid phase sintering for 1 h at 1420 °C in vacuum. Microstructural analysis of the fully densified cermets was performed by electron probe microanalysis (EPMA to assess the effect of carbon and VC or Mo additions on the NbC grain growth and morphology. A decreased carbon content in the starting powder mixtures resulted in increased dissolution of Nb, V, and Mo in the Ni binder and a decreased C/Nb ratio in the NbC based carbide phase. The Vickers hardness (HV30 and Palmqvist indentation toughness were found to decrease significantly with an increasing carbon content in the Mo-free cermets, whereas an antagonistic correlation between hardness and toughness was obtained as a function of the Mo-content in Mo-modified NbC cermets. To obtain optimized mechanical properties, methods to control the total carbon content of NbC-Ni mixtures were proposed and the prepared cermets were investigated in detail.

Effect of carbon additions on the as-cast microstructure and defect formation of a single crystal Ni-based superalloy

International Nuclear Information System (INIS)

Al-Jarba, K.A.; Fuchs, G.E.

2004-01-01

In an effort to reduce grain defects in large single crystal Ni-base superalloy components, carbon is intentionally added. In this study, the effect of carbon additions on the microstructure and solidification defect formation of a model Ni-based superalloy, LMSX-1, was examined. The results show that the tendency of the alloy to form all types of solidification defects decreased as the carbon content increased. The as-cast microstructures also exhibited a decrease in the amount of γ-γ' eutectic structure and an increase in the volume fraction of carbides and porosity, as the carbon content was increased. The carbides formed in these alloys were mostly of script-type MC carbides which formed continuous, dendritic networks in the interdendritic region. Microprobe analysis of the as-cast structures showed that the partitioning coefficients did not change with carbon additions. Therefore, the reduction in defect formation with increasing carbon content could not be attributed to changes in segregation behavior of alloying elements. Instead, the presence of these carbides in the interdendritic regions of the alloy appeared to have prevented the thermosolutal fluid flow

Microstructure and Properties of Polypropylene/Carbon Nanotube Nanocomposites

Directory of Open Access Journals (Sweden)

Dimitrios Bikiaris

2010-04-01

Full Text Available In the last few years, great attention has been paid to the preparation of polypropylene (PP nanocomposites using carbon nanotubes (CNTs due to the tremendous enhancement of the mechanical, thermal, electrical, optical and structural properties of the pristine material. This is due to the unique combination of structural, mechanical, electrical, and thermal transport properties of CNTs. However, it is well-known that the properties of polymer-based nanocomposites strongly depend on the dispersion of nanofillers and almost all the discussed properties of PP/CNTs nanocomposites are strongly related to their microstructure. PP/CNTs nanocomposites were, mainly, prepared by melt mixing and in situ polymerization. Young’s modulus, tensile strength and storage modulus of the PP/CNTs nanocomposites can be increased with increasing CNTs content due to the reinforcement effect of CNTs inside the polymer matrix. However, above a certain CNTs content the mechanical properties are reduced due to the CNTs agglomeration. The microstructure of nanocomposites has been studied mainly by SEM and TEM techniques. Furthermore, it was found that CNTs can act as nucleating agents promoting the crystallization rates of PP and the addition of CNTs enhances all other physical properties of PP. The aim of this paper is to provide a comprehensive review of the existing literature related to PP/CNTs nanocomposite preparation methods and properties studies.

Preparation, microstructure and hydrogen sorption properties of nanoporous carbon aerogels under ambient drying

International Nuclear Information System (INIS)

Tian, H Y; Buckley, C E; Mule, S; Paskevicius, M; Dhal, B B

2008-01-01

Organic aerogels are prepared by the sol-gel method from polymerization of resorcinol with furfural. These aerogels are further carbonized in nitrogen in order to obtain their corresponding carbon aerogels (CA); a sample which was carbonized at 900 deg. C was also activated in a carbon dioxide atmosphere at 900 deg. C. The chemical reaction mechanism and optimum synthesis conditions are investigated by means of Fourier transform infrared spectroscopy and thermoanalyses (thermogravimetric/differential thermal analyses) with a focus on the sol-gel process. The carbon aerogels were investigated with respect to their microstructures, using small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and nitrogen adsorption measurements at 77 K. SAXS studies showed that micropores with a radius of gyration of 2 g -1 displayed a reasonably high hydrogen uptake at 77 K with a maximum hydrogen sorption of 3.6 wt% at 2.5 MPa. These results suggest that CA are promising candidate hydrogen storage materials.

Electrochemical, morphological and microstructural characterization of carbon film resistor electrodes for application in electrochemical sensors

International Nuclear Information System (INIS)

Gouveia-Caridade, Carla; Soares, David M.; Liess, Hans-Dieter; Brett, Christopher M.A.

2008-01-01

The electrochemical and microstructural properties of carbon film electrodes made from carbon film electrical resistors of 1.5, 15, 140 Ω and 2.0 kΩ nominal resistance have been investigated before and after electrochemical pre-treatment at +0.9 V vs SCE, in order to assess the potential use of these carbon film electrodes as electrochemical sensors and as substrates for sensors and biosensors. The results obtained are compared with those at electrodes made from previously investigated 2 Ω carbon film resistors. Cyclic voltammetry was performed in acetate buffer and phosphate buffer saline electrolytes and the kinetic parameters of the model redox system Fe(CN) 6 3-/4- obtained. The 1.5 Ω resistor electrodes show the best properties for sensor development with wide potential windows, similar electrochemical behaviour to those of 2 Ω and close-to-reversible kinetic parameters after electrochemical pre-treatment. The 15 and 140 Ω resistor electrodes show wide potential windows although with slower kinetics, whereas the 2.0 kΩ resistor electrodes show poor cyclic voltammetric profiles even after pre-treatment. Electrochemical impedance spectroscopy related these findings to the interfacial properties of the electrodes. Microstructural and morphological studies were carried out using contact mode Atomic Force Microscopy (AFM), Confocal Raman spectroscopy and X-ray diffraction. AFM showed more homogeneity of the films with lower nominal resistances, related to better electrochemical characteristics. X-ray diffraction and Confocal Raman spectroscopy indicate the existence of a graphitic structure in the carbon films

Composite materials for thermal energy storage: enhancing performance through microstructures.

Science.gov (United States)

Ge, Zhiwei; Ye, Feng; Ding, Yulong

2014-05-01

Chemical incompatibility and low thermal conductivity issues of molten-salt-based thermal energy storage materials can be addressed by using microstructured composites. Using a eutectic mixture of lithium and sodium carbonates as molten salt, magnesium oxide as supporting material, and graphite as thermal conductivity enhancer, the microstructural development, chemical compatibility, thermal stability, thermal conductivity, and thermal energy storage performance of composite materials are investigated. The ceramic supporting material is essential for preventing salt leakage and hence provides a solution to the chemical incompatibility issue. The use of graphite gives a significant enhancement on the thermal conductivity of the composite. Analyses suggest that the experimentally observed microstructural development of the composite is associated with the wettability of the salt on the ceramic substrate and that on the thermal conduction enhancer. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microstructural development during the quenching and partitioning process in a newly designed low-carbon steel

Energy Technology Data Exchange (ETDEWEB)

Santofimia, M.J., E-mail: m.j.santofimianavarro@tudelft.nl [Materials Innovation Institute (M2i), Mekelweg 2, 2628 CD Delft (Netherlands); Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Zhao, L. [Materials Innovation Institute (M2i), Mekelweg 2, 2628 CD Delft (Netherlands); Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Petrov, R. [Department of Metallurgy and Materials Science, Ghent University, Technologiepark 903, 9052 Ghent (Belgium); Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Kwakernaak, C.; Sloof, W.G.; Sietsma, J. [Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands)

2011-09-15

This paper presents a detailed characterization of the microstructural development of a new quenching and partitioning (Q and P) steel. Q and P treatments, starting from full austenitization, were applied to the developed steel, leading to microstructures containing volume fractions of retained austenite of up to 0.15. The austenite was distributed as films in between the martensite laths. Analysis demonstrates that, in this material, stabilization of austenite can be achieved at significantly shorter time scales via the Q and P route than is possible via a bainitic isothermal holding. The results showed that the thermal stabilization of austenite during the partitioning step is not necessarily accompanied by a significant expansion of the material. This implies that the process of carbon partitioning from martensite to austenite occurs across low-mobility martensite-austenite interfaces. The amount of martensite formed during the first quench has been quantified. Unlike martensite formed in the final quench, this martensite was found to be tempered during partitioning. Measured volume fractions of retained austenite after different treatments were compared with simulations using model descriptions for carbon partitioning from martensite to austenite. Simulation results confirmed that the carbon partitioning takes place at low-mobility martensite-austenite interfaces.

Mechanical properties and hot-rolled microstructures of a low carbon bainitic steel with Cu-P alloying

International Nuclear Information System (INIS)

Cui, W.F.; Zhang, S.X.; Jiang, Y.; Dong, J.; Liu, C.M.

2011-01-01

Highlights: → Mechanical properties and microstructures of low carbon bainite steel are examined. → Cu-P alloying promotes strengthening and uniform plastic deformation. → Cu-P alloying delays recovery process during rolling interval. → Lowering rolling temperature is favorable to increasing toughness. - Abstract: A low carbon bainitic steel with Cu-P alloying was developed. The new steel aims to meet the demand of high strength, high toughness and resistance to chloride ion corrosion for the components used in the environment of sea water and oceanic atmosphere. Mechanical properties of the steel were tested and strengthening and toughening mechanisms were analyzed by comparing hot-rolled microstructures of the low carbon bainitic steels with and without Cu-P alloying. The results show that Cu-P alloying provided strong solution strengthening with weak effect on ductility. The toughness loss caused by Cu-P alloying could be balanced by increasing the amount of martensite/remained austenite (M/A island) at lower finishing temperature. The static recovery process during rolling interval was delayed by the interaction of phosphorous, copper atoms with dislocations, which was favorable to the formation of bainitic plates. Super-fine Nb(C, N) particles precipitated on dislocations had coherency with bainite ferrite at 830 deg. C finishing temperature. Raising finishing temperature to 880 deg. C, Nb(C, N) particles were prone to coarsening and losing coherency. It was also found that no accurate lattice match relationship among retained austenite, martensite and bainite in granular bainitic microstructure.

Mechanical properties and hot-rolled microstructures of a low carbon bainitic steel with Cu-P alloying

Energy Technology Data Exchange (ETDEWEB)

Cui, W.F., E-mail: wenfangcui@yahoo.com.cn [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China); Zhang, S.X. [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China); Technology Center of Laiwu Iron and Steel (Group) Co. Ltd., Laiwu 271104 (China); Jiang, Y. [School of Chemical Engineering, University of Queensland, Brisbane 4072 (Australia); Dong, J. [Technology Center of Laiwu Iron and Steel (Group) Co. Ltd., Laiwu 271104 (China); Liu, C.M. [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004 (China)

2011-08-15

Highlights: {yields} Mechanical properties and microstructures of low carbon bainite steel are examined. {yields} Cu-P alloying promotes strengthening and uniform plastic deformation. {yields} Cu-P alloying delays recovery process during rolling interval. {yields} Lowering rolling temperature is favorable to increasing toughness. - Abstract: A low carbon bainitic steel with Cu-P alloying was developed. The new steel aims to meet the demand of high strength, high toughness and resistance to chloride ion corrosion for the components used in the environment of sea water and oceanic atmosphere. Mechanical properties of the steel were tested and strengthening and toughening mechanisms were analyzed by comparing hot-rolled microstructures of the low carbon bainitic steels with and without Cu-P alloying. The results show that Cu-P alloying provided strong solution strengthening with weak effect on ductility. The toughness loss caused by Cu-P alloying could be balanced by increasing the amount of martensite/remained austenite (M/A island) at lower finishing temperature. The static recovery process during rolling interval was delayed by the interaction of phosphorous, copper atoms with dislocations, which was favorable to the formation of bainitic plates. Super-fine Nb(C, N) particles precipitated on dislocations had coherency with bainite ferrite at 830 deg. C finishing temperature. Raising finishing temperature to 880 deg. C, Nb(C, N) particles were prone to coarsening and losing coherency. It was also found that no accurate lattice match relationship among retained austenite, martensite and bainite in granular bainitic microstructure.

Variations of microstructure and properties of 690 MPa grade low carbon bainitic steel after tempering

Energy Technology Data Exchange (ETDEWEB)

Feng, Rui [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan Shandong 250061 (China); School of Materials Science and Engineering, Shandong University, Jinan Shandong 250061 (China); Li, Shengli, E-mail: lishengli@sdu.edu.cn [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan Shandong 250061 (China); School of Materials Science and Engineering, Shandong University, Jinan Shandong 250061 (China); Li, Zhenshun; Tian, Lei [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan Shandong 250061 (China); School of Materials Science and Engineering, Shandong University, Jinan Shandong 250061 (China)

2012-12-15

The variations of microstructure, mechanical properties and electrical resistivity of 690 MPa grade low carbon bainitic steel tempered at different temperatures were investigated with Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and double-arm Bridge. The results show that the appearance of granular bainite, decomposition of retained austenite, variations of dislocation density and solid solution of microalloying elements are the main reasons for variations of mechanical properties and electrical resistivity. Electrical resistivity reflects the solution content of microalloying elements and variations of dislocation density, which can be used as a fast and effective way to analyze the microstructure of materials.

Microstructure and mechanical properties of CVI carbon fiber/SiC composites

International Nuclear Information System (INIS)

Noda, T.; Araki, H.; Abe, F.; Okada, M.

1992-01-01

Microstructures and mechanical properties of carbon fiber/SiC composites prepared with chemical vapor infiltration (CVI) were examined to optimize the process conditions such as reactant and infiltration temperature. Ethyl-trichloro-silane (ETS) and methyl-trichloro-silane (MTS) were used as a source of SiC. CVI was conducted for 108 ks at maximum under a pressure of 13.3 kPa at 1273-1573 K. The composite with a density higher than 80% was obtained at 1373-1423 K and 1423-1374 K from ETS and MTS, respectively. The main matrix formed was β SiC for both reactants. However, silicon also deposited in SiC matrix for MTS. Preferential wettability of SiC to the carbon fiber was observed, and graphite was detected in the interface between the matrix and the carbon fiber by TEM. Mechanical properties were evaluated by bend tests at room temperature. High strength of around 800 MPa was obtained for the composites if the thickness of the surface coated layer was less than 50 μm. Apparent fracture thoughness of the present carbon fiber/SiC composite was 6-10 MPa m 1/2 at room temperature. (orig.)

Carbon a support for sulfide catalysts

NARCIS (Netherlands)

Vissers, J.P.R.; Lensing, T.J.; Mercx, F.P.M.; Beer, de V.H.J.; Prins, R.

1983-01-01

Two types of carbon materials, carbon black composite and carbon covered alumina, were studied for-their use as support for sulfide catalysts. The following parameters were varied: type of carbon black, carbon coverage of the alumina and carbon pretreatment. Pore size distributions were determined

Cathode deposits in fullerene formation — microstructural evidence for independent pathways of pyrolytic carbon and nanobody formation

Science.gov (United States)

Taylor, G. H.; Gerald, J. D. Fitz; Pang, L.; Wilson, M. A.

1994-01-01

Microstructures in cathode deposits formed during fullerene production by electrical arcing in helium have been examined in detail. This has provided new information about the mechanisms by which nanobodies (nanotubes and nanoparticles) and pyrolytic carbon are deposited. Nanobodies and pyrolytic carbon form independently; the former probably grow in the plasma then deposit on the electrode but much of the latter deposits directly on the electrode surface.

Surface Modification by Friction Stir Processing of Low-Carbon Steel: Microstructure Investigation and Wear Performance

Science.gov (United States)

Sattari, Behnoosh; Shamanian, Morteza; Salimijazi, Farshid; Salehi, Mehdi

2018-02-01

A low-carbon steel sheet with a thickness of 5 mm was subjected to friction stir processing (FSP) by one to four different passes. The microstructures of different regions were characterized using the optical microscopy and electron backscatter diffraction. The Vickers micro-harness was measured at the distance of 200 μm below the processed surfaces. The influence of pass numbers (PNs) on wear resistance was studied in terms of coefficients of friction (CoFs), weight losses and wear rates. SEM topographies of the worn surfaces were also studied to evaluate the wear mechanisms. Microstructure observations showed that Widmänstatten ferrite plates were formed in stir zones (SZs) and heat affected zones. As PN increased, these grains were widened due to the increment of the carbon diffusivity and lengthened because of the high heat input and microstructure anisotropy. Besides, increasing the PN causes increasing of the hardness and wear resistance, simultaneously. Specifically, the wear rate in the SZ was reduced from 2.8 × 10-2 mm3 m-1 in base metal to 0.3 × 10-2 mm3 m-1 in sample which was subjected to 4 FSP passes. However, variation in PN had no considerable effect on CoFs. Oxidative wear mechanism was observed on the worn surface of the steel and the FSPed samples while more debris was formed by increasing the PNs.

Ameliorated Austenite Carbon Content Control in Austempered Ductile Irons by Support Vector Regression

Directory of Open Access Journals (Sweden)

Chan-Yun Yang

2013-01-01

Full Text Available Austempered ductile iron has emerged as a notable material in several engineering fields, including marine applications. The initial austenite carbon content after austenization transform but before austempering process for generating bainite matrix proved critical in controlling the resulted microstructure and thus mechanical properties. In this paper, support vector regression is employed in order to establish a relationship between the initial carbon concentration in the austenite with austenization temperature and alloy contents, thereby exercising improved control in the mechanical properties of the austempered ductile irons. Particularly, the paper emphasizes a methodology tailored to deal with a limited amount of available data with intrinsically contracted and skewed distribution. The collected information from a variety of data sources presents another challenge of highly uncertain variance. The authors present a hybrid model consisting of a procedure of a histogram equalizer and a procedure of a support-vector-machine (SVM- based regression to gain a more robust relationship to respond to the challenges. The results show greatly improved accuracy of the proposed model in comparison to two former established methodologies. The sum squared error of the present model is less than one fifth of that of the two previous models.

Microstructure of carbon derived from mangrove charcoal and its application in Li-ion batteries

International Nuclear Information System (INIS)

Liu Tao; Luo Ruiying; Qiao Wenming; Yoon, Seong-Ho; Mochida, Isao

2010-01-01

In this study, the microstructure of mangrove-charcoal-derived carbon (MC) was studied using XRD, STM and TEM. MC was found to consist of aligned quasi-spherical structural units with diameters of around 5-20 nm. It shows typical hard carbon characteristics, including a strongly disoriented single graphene layer and BSU, formed by two or three graphene layers stacked nearly parallel. Some curved and faceted graphene layers, especially closed carbon nanoparticles with fullerene-like, were observed in the as-prepared samples. MC was also evaluated as an anodic material for Li-ion batteries. MC carbonized at 1000 deg. C possessed the highest available discharge capacity (below 0.5 V) of 335 mAh g -1 , the high first-cycle coulombic efficiency of 73.7%, good rate and cyclic capability and PC-based electrolyte compatibility. 7 Li nuclear magnetic resonance (NMR) spectra of fully lithiated mangrove charcoal-derived carbons indicated the co-existence of three Li species.

Microstructure of carbon derived from mangrove charcoal and its application in Li-ion batteries

Energy Technology Data Exchange (ETDEWEB)

Liu Tao [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100083 (China); Luo Ruiying, E-mail: ryluo@buaa.edu.c [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100083 (China); Qiao Wenming [College of Chemical Engineering, East China University of Science and Technology, Shanghai 200237 (China); Yoon, Seong-Ho; Mochida, Isao [Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga, Fukuoka 816-8580 (Japan)

2010-02-01

In this study, the microstructure of mangrove-charcoal-derived carbon (MC) was studied using XRD, STM and TEM. MC was found to consist of aligned quasi-spherical structural units with diameters of around 5-20 nm. It shows typical hard carbon characteristics, including a strongly disoriented single graphene layer and BSU, formed by two or three graphene layers stacked nearly parallel. Some curved and faceted graphene layers, especially closed carbon nanoparticles with fullerene-like, were observed in the as-prepared samples. MC was also evaluated as an anodic material for Li-ion batteries. MC carbonized at 1000 deg. C possessed the highest available discharge capacity (below 0.5 V) of 335 mAh g{sup -1}, the high first-cycle coulombic efficiency of 73.7%, good rate and cyclic capability and PC-based electrolyte compatibility. {sup 7}Li nuclear magnetic resonance (NMR) spectra of fully lithiated mangrove charcoal-derived carbons indicated the co-existence of three Li species.

Microstructure and mechanical properties of carbon nanotubes reinforced aluminum matrix composites synthesized via equal-channel angular pressing

Energy Technology Data Exchange (ETDEWEB)

Zare, Hassan [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Jahedi, Mohammad, E-mail: mohammad.jahedi@unh.edu [Department of Mechanical Engineering, University of New Hampshire, Durham, NH 03824 (United States); Toroghinejad, Mohammad Reza; Meratian, Mahmoud [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Knezevic, Marko [Department of Mechanical Engineering, University of New Hampshire, Durham, NH 03824 (United States)

2016-07-18

In this work, 2 vol% carbon nanotubes (CNTs) reinforced aluminum (Al) matrix composites of superior microstructural homogeneity are successfully synthesized using Bc equal-channel angular extrusion (ECAP) route. The key step in arriving at high level of homogeneous distribution of CNTs within Al was preparation of the powder using simultaneous attrition milling and ultra-sonication processes. Microstructure as revealed by electron microscopy and absence of Vickers hardness gradients across the material demonstrate that the material reached the homogeneous state in terms of CNT distribution, porosity distribution, and grain structure after eight ECAP passes. To facilitate comparison of microstructure and hardness, samples of Al were processed under the same ECAP conditions. Significantly, the composite containing only 2 vol% exhibits 20% increase in hardness relative to the Al samples.

Characterisation of Microstructure of We43 Magnesium Matrix Composites Reinforced with Carbon Fibres

Directory of Open Access Journals (Sweden)

Gryc A.

2016-06-01

Full Text Available In the paper the microstructures of WE43 matrix composites reinforced with carbon fibres have been characterised. The influence of reinforcement type and T6 heat treatment (a solution treatment at 525°C for 8 h, a hot water quench and a subsequent ageing treatment at 250°C for 16 h on microstructure have been evaluated. The light microscope and scanning electron microscope investigations have been carried out. No significant differences in samples reinforced with non-coated textiles have been reported. The substantial changes in sample reinforced with nickel-coated textile have been observed. The segregation of alloying elements to the matrix-reinforcement layer has been identified. The T6 heat treatment caused the appearance of disperse precipitates of β phase, but the process cannot be considered as satisfactory (irregular distribution, low volume fraction, relatively large size.

Magnesium substitution in carbonated hydroxyapatite: Structural and microstructural characterization by Rietveld's refinement

Energy Technology Data Exchange (ETDEWEB)

Lala, S. [Materials Science Division, Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal (India); Ghosh, M.; Das, P.K. [Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India); Das, D. [UGC-DAE Consortium for Scientific Research, Kolkata 700098 (India); Kar, T. [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Pradhan, S.K., E-mail: skpradhan@phys.buruniv.ac.in [Materials Science Division, Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104, West Bengal (India)

2016-02-15

Four stoichiometric compositions of nanocrystalline Mg doped carbonated hydroxyapatite (cHAp) powders are synthesized by mechanical alloying (ball milling) the powder mixtures of CaCO{sub 3}, CaHPO{sub 4}.2H{sub 2}O and MgO in open air at room temperature. FTIR analysis confirms the A-type carbonation in all milled HAp powder samples (A-cHAp). Microstructure characterization in terms of lattice imperfections and phase quantification of ball milled samples are made by analyzing XRD patterns employing Rietveld's structure refinement method. Transmission electron microscopy (TEM) study of 15 mol % Mg doped A-cHAp sample reveals microstructure similar to that obtained from XRD pattern analysis. Cumulative effect of Mg substitution and mechanical alloying results in amorphization of a major part of crystalline A-cHAp, analogous to native bone mineral. Rietveld analysis reveals that the Ca2 vacancy site is energetically more favorable for occupation of Mg substitution. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay test reveals sufficiently high percentage cell viability confirming the cytocompatibility of the sample. - Graphical abstract: Mg substitution for Ca2 site. - Highlights: • Single phase Mg doped A-cHAp synthesized by mechanical alloying (MA). • FTIR analysis confirms A-type carbonation in HAp. • Amorphization of a part of crystalline A-cHAp due to MA and Mg insertion. • Mg{sup 2+} ions substitute the Ca2 vacancy site. • High cell viability under MTT assay.

Microstructure of Matrix in UHTC Composites

Science.gov (United States)

Johnson, Sylvia; Stackpoole, Margaret; Gusman, Michael I.; Chavez-Garia Jose; Doxtad, Evan

2011-01-01

Approaches to controlling the microstructure of Ultra High Temperature Ceramics (UHTCs) are described.. One matrix material has been infiltrated into carbon weaves to make composite materials. The microstructure of these composites is described.

Molecular dynamics study of radiation damage and microstructure evolution of zigzag single-walled carbon nanotubes under carbon ion incidence

Science.gov (United States)

Li, Huan; Tang, Xiaobin; Chen, Feida; Huang, Hai; Liu, Jian; Chen, Da

2016-07-01

The radiation damage and microstructure evolution of different zigzag single-walled carbon nanotubes (SWCNTs) were investigated under incident carbon ion by molecular dynamics (MD) simulations. The radiation damage of SWCNTs under incident carbon ion with energy ranging from 25 eV to 1 keV at 300 K showed many differences at different incident sites, and the defect production increased to the maximum value with the increase in incident ion energy, and slightly decreased but stayed fairly stable within the majority of the energy range. The maximum damage of SWCNTs appeared when the incident ion energy reached 200 eV and the level of damage was directly proportional to incident ion fluence. The radiation damage was also studied at 100 K and 700 K and the defect production decreased distinctly with rising temperature because radiation-induced defects would anneal and recombine by saturating dangling bonds and reconstructing carbon network at the higher temperature. Furthermore, the stability of a large-diameter tube surpassed that of a thin one under the same radiation environments.

Preparation, microstructure and hydrogen sorption properties of nanoporous carbon aerogels under ambient drying

Science.gov (United States)

Tian, H. Y.; Buckley, C. E.; Mulè, S.; Paskevicius, M.; Dhal, B. B.

2008-11-01

Organic aerogels are prepared by the sol-gel method from polymerization of resorcinol with furfural. These aerogels are further carbonized in nitrogen in order to obtain their corresponding carbon aerogels (CA); a sample which was carbonized at 900 °C was also activated in a carbon dioxide atmosphere at 900 °C. The chemical reaction mechanism and optimum synthesis conditions are investigated by means of Fourier transform infrared spectroscopy and thermoanalyses (thermogravimetric/differential thermal analyses) with a focus on the sol-gel process. The carbon aerogels were investigated with respect to their microstructures, using small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and nitrogen adsorption measurements at 77 K. SAXS studies showed that micropores with a radius of gyration of adsorption showed that larger mesopores were also present. Hydrogen storage properties of the CA were also investigated. An activated sample with a Brunauer-Emmett-Teller surface area of 1539 ± 20 m2 g-1 displayed a reasonably high hydrogen uptake at 77 K with a maximum hydrogen sorption of 3.6 wt% at 2.5 MPa. These results suggest that CA are promising candidate hydrogen storage materials.

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......-ray tomography and micro-structural modelling is presented in this work. The simulation technique comprises a novel treatment of the boundary conditions, which leads to more accurate effective transport parameters compared to those, which can be achieved with the conventional homogenisation procedures....... Furthermore, the porosity distribution in the metal-support was determined, which provided information about the inhomogeneous nature of the material. In addition to that, transport parameters for two identified, different dense layers of the metal-support are evaluated separately. The results...

Model for the interaction between interface migration and carbon diffusion during annealing of martensite-austenite microstructures in steels

International Nuclear Information System (INIS)

Santofimia, M.J.; Zhao, L.; Sietsma, J.

2008-01-01

The interaction between carbon partitioning from martensite to austenite and interface migration during annealing of martensite-austenite microstructures is modeled, assuming the same chemical potential of carbon in martensite and austenite at the interface and allowing the motion of the phase interface when a free-energy difference occurs. The simulations show that the motion of the martensite-austenite interface can be significant and can takes place in either direction

Growth of carbon nanotubes in arc plasma treated graphite disc: microstructural characterization and electrical conductivity study

Science.gov (United States)

Nayak, B. B.; Sahu, R. K.; Dash, T.; Pradhan, S.

2018-03-01

Circular graphite discs were treated in arc plasma by varying arcing time. Analysis of the plasma treated discs by field emission scanning electron microscope revealed globular grain morphologies on the surfaces, but when the same were observed at higher magnification and higher resolution under transmission electron microscope, growth of multiwall carbon nanotubes of around 2 nm diameter was clearly seen. In situ growth of carbon nanotube bundles/bunches consisting of around 0.7 nm tube diameter was marked in the case of 6 min treated disc surface. Both the untreated and the plasma treated graphite discs were characterized by X-ray diffraction, energy dispersive spectra of X-ray, X-ray photoelectron spectroscopy, transmission electron microscopy, micro Raman spectroscopy and BET surface area measurement. From Raman spectra, BET surface area and microstructure observed in transmission electron microscope, growth of several layers of graphene was identified. Four-point probe measurements for electrical resistivity/conductivity of the graphite discs treated under different plasma conditions showed significant increase in conductivity values over that of untreated graphite conductivity value and the best result, i.e., around eightfold increase in conductivity, was observed in the case of 6 min plasma treated sample exhibiting carbon nanotube bundles/bunches grown on disc surface. By comparing the microstructures of the untreated and plasma treated graphite discs, the electrical conductivity increase in graphite disc is attributed to carbon nanotubes (including bundles/bunches) growth on disc surface by plasma treatment.

Microstructure and mechanical properties of nickel coated multi walled carbon nanotube reinforced stainless steel 316L matrix composites by laser sintering process

Science.gov (United States)

Mahanthesha, P.; Mohankumar, G. C.

2018-04-01

Electroless Ni coated Multi-walled Carbon nanotubes reinforced with Stainless Steel 316L matrix composite was developed by Direct Metal Laser Sintering process (DMLS). Homogeneous mixture of Stainless Steel 316L powder and carbon nanotubes in different vol. % was obtained by using double cone blender machine. Characterization of electroless Ni coated carbon nanotubes was done by using X-ray diffraction, FESEM and EDS. Test samples were fabricated at different laser scan speeds. Effect of process parameters and CNT vol. % content on solidification microstructure and mechanical properties of test samples was investigated by using Optical microscopy, FESEM, and Hounsfield tensometer. Experimental results reveal DMLS process parameters affect the density and microstructure of sintered parts. Dense parts with minimum porosity when processed at low laser scan speeds and low CNT vol. %. Tensile fractured surface of test specimens evidences the survival of carbon nanotubes under high temperature processing condition.

Microstructure and tribology of carbon, nitrogen, and oxygen implanted ferrous materials

International Nuclear Information System (INIS)

Williamson, D.L.

1993-01-01

Nitrogen, carbon, and oxygen ions have been implanted into ferrous materials under unusual conditions of elevated temperatures and very high dose rates. The tribological durabilities of the resulting surfaces are examined with a special type of pin-on-disc wear test apparatus and found in most cases to be dramatically improved compared to surfaces prepared with conventional implantation conditions. Near-surface microstructures and compositions are characterized after implantation and after wear testing by backscatter Moessbauer spectroscopy, X-ray diffraction, scanning electron microscopy, and Auger electron spectroscopy. These data provide evidence for the predominant mechanisms responsible for the observed sliding wear behavior induced by each of the three species. (orig.)

Effect of Q&P heat treatment on fine microstructure and mechanical properties of a low-alloy medium-carbon steel

Science.gov (United States)

Jafari, Rahim; Kheirandish, Shahram; Mirdamadi, Shamsoddin

2018-01-01

The current research investigates the effect of ultrafine microstructure resulted from Quench and Partitioning (Q&P) process on obtaining ultra-high strengths in a low-alloy steel with 4wt.% carbon. The purpose of Q&P heat treatment is to enrich the austenite with carbon by partitioning of carbon from supersaturated martensite to austenite, in order to stabilize it to the room temperature. The microstructure, consequently, is consists of martensite, retained austenite and in some conditions bainite. Two-step Q&P heat treatment with quench and partitioning temperatures equal to 120°C and 300°C respectively were applied to the samples at different times. Mechanical behavior was studied by tensile test. The microstructure of the samples was observed using SEM, and TEM and to quantify the amount of retained austenite X-ray diffraction was used. The retained austenite grain size was estimated to be about 0.5 µm and the highest amount of retained austenite obtained was 10 vol%. All samples showed a yield strength and a tensile strength of above 900MPa and 1500MP respectively. The yield strength increased with increase in partitioning time, whereas tensile strength showed an inverse behavior. The elongation in samples varied from 5% to 9% which seemed to not have a direct connection with the amount of retained austenite, but instead it was related to the ferritic structures formed during partitioning such as coalesced martensite, bainite and tempered martensite.

Controllable synthesis of spongy carbon nanotube blocks with tunable macro- and microstructures

International Nuclear Information System (INIS)

Gui Xuchun; Lin Zhiqiang; Zeng Zhiping; Tang Zikang; Wang Kunlin; Wu Dehai

2013-01-01

Macroscopic carbon nanotubes (CNTs) with uniform structures are in great demand for use in composites and environmental materials. Here we demonstrate the controlled synthesis of spongy CNT blocks with isotropic properties and flexible, freestanding structures. The formation mechanism of the isotropic CNT sponges is discussed, based on its open-ended structure and initial formation in the vapor phase. The microstructure of the CNT sponges can be tuned by changing the flow rate of the carrier gas, resulting in CNT sponges with diameters ranging from 30.2 to 47.8 nm and wall thicknesses from 7 to 16 nm. The bulk density (5–25 mg cm −3 ), mechanical strength of the CNT sponges, and filling rate of ferromagnetic catalyst in the CNT sponges can also be modulated by controlling the supply rate of the carbon source, suggesting potential applications in mechanical energy absorption and environmental materials. (paper)

Adhered Supported Carbon Nanotubes

International Nuclear Information System (INIS)

Johnson, Dale F.; Craft, Benjamin J.; Jaffe, Stephen M.

2001-01-01

Carbon nanotubes (NTs) in excess of 200 μm long are grown by catalytic pyrolysis of hydrocarbon vapors. The nanotubes grow continuously without the typical extinction due to catalyst encapsulation. A woven metal mesh supports the nanotubes creating a metal supported nanotube (MSNT) structure. The 140 μm wide mesh openings are completely filled by 70 nm diameter multiwalled nanotubes (MWNTs). The MWNTs are straight, uniform and highly crystalline. Their wall thickness is about 10 nm (30 graphite layers). The adherent NTs are not removed from the support in a Scotch tape pull test. A 12.5 cm 2 capacitor made from two MSNT structures immersed in 1 M KCl has a capacitance of 0.35 F and an equivalent series resistance of 0.18 Ω. Water flows through the MSNT at a flow velocity of 1 cm/min with a pressure drop of 15 inches of water. With the support removed, the MWNTs naturally form a carbon nanocomposite (CNC) paper with a specific area of 80 m 2 /gm, a bulk density of 0.21 g/cm 3 , an open pore fraction of 0.81, and a resistivity of 0.16 Ω-cm

Effects of ion beam irradiation on the microstructures and strengths of different carbon fibers

International Nuclear Information System (INIS)

Oku, Tatsuo; Kurumada, Akira; Kawamata, Kiyohiro; Inagaki, Michio

1998-01-01

The high energy argon ion was irradiated to different carbon fibers with various microstructures. The cross-sectional structures and strengths properties have been evaluated before and after ion irradiation. As a result, the diameter of fibers decreased due to ion irradiation, except for the fiber with dual structure. The tensile strength also decreased due to ion irradiation, except for fibers which were not heat-treated. This suggests that it is necessary to consider not only the defects in the vertical cross-section but also changes in defect structures in the axial direction. The results of computer simulation indicated that argon ion with 175MeV/1μA produced homogeneous defects in the carbon fibers with the diameter of about 20 μm. (author)

Microstructure and failure behavior of dissimilar resistance spot welds between low carbon galvanized and austenitic stainless steels

International Nuclear Information System (INIS)

Marashi, P.; Pouranvari, M.; Amirabdollahian, S.; Abedi, A.; Goodarzi, M.

2008-01-01

Resistance spot welding was used to join austenitic stainless steel and galvanized low carbon steel. The relationship between failure mode and weld fusion zone characteristics (size and microstructure) was studied. It was found that spot weld strength in the pullout failure mode is controlled by the strength and fusion zone size of the galvanized steel side. The hardness of the fusion zone which is governed by the dilution between two base metals, and fusion zone size of galvanized carbon steel side are dominant factors in determining the failure mode

Effect of carbon content on microstructure and mechanical properties of hot-rolled low carbon 12Cr-Ni stainless steel

International Nuclear Information System (INIS)

Zheng, H.; Ye, X.N.; Li, J.D.; Jiang, L.Z.; Liu, Z.Y.; Wang, G.D.; Wang, B.S.

2010-01-01

Research highlights: → Hot-rolled ultra low carbon martensite is characterized by dislocation cells substructure. → The formation of dislocation cells is attributed to high Ms and low interstitial atoms content. → Hot-rolled ultra low carbon 12Cr-Ni stainless steel has excellent impact toughness. → Delta ferrite deteriorates the impact toughness of hot-rolled 12Cr-Ni stainless steel. - Abstract: 12Cr-Ni stainless steels containing different carbon contents from 0.004 wt.% to 0.034 wt.% were hot-rolled and air-cooled. Their corresponding microstructures were observed with optical microscope and transmission electron microscope, and the Vickers hardness, tensile and impact tests were also carried out. It was found that the martensitic morphology was significantly influenced by carbon content. The as-received ultra low carbon martensite in the steel containing 0.004 wt.% C is characterized by dislocation cells substructure. The formation of dislocation cells is attributed to high martensite finishing point (above 400 deg. C) and low interstitial atoms content. On the other hand, the martensite in the steel containing 0.034 wt.% C consists mainly of typical martensite laths because of low martensite finishing point and high interstitial atoms content which hinder dislocation motion. Furthermore, carbon content has an evident effect on the mechanical properties of 12Cr-Ni steels. The hardness and strength of the as-received steels increase with an increase in carbon content, but their elongation and impact toughness decrease with the carbon content. The steel containing 0.004 wt.% C has excellent impact toughness due to the ultra low carbon content in the martensite composed of dislocation cells.

Cyclic voltammetric investigations of microstructured and platinum-covered glassy carbon electrodes in contact with a polymer electrolyte membrane

Energy Technology Data Exchange (ETDEWEB)

Scherer, G G; Veziridis, Z; Staub, M [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Freimuth, H [Inst. fuer Mikrotechnik Mainz IMM, Mainz (Germany)

1997-06-01

Model gas diffusion electrodes were prepared by microstructuring glassy carbon surfaces with high aspect ratios and subsequent deposition of platinum. These electrodes were characterized by hydrogen under-potential deposition (H-upd) in contact with a polymer electrolyte membrane employing cyclic voltametry. H-upd was found on platinum areas not in direct contact to the solid electrolyte, as long as a continuous platinum-path existed. A carbon surface between platinum acts as barrier for H-upd. (author) 4 figs., 5 refs.

Effect of tempering on the microstructure and mechanical properties of a medium carbon bainitic steel

Energy Technology Data Exchange (ETDEWEB)

Kang, J. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Zhang, F.C., E-mail: zfc@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao 066004 (China); Yang, X.W. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Lv, B. [College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004 (China); Wu, K.M. [International Research Institute for Steel Technology, Wuhan University of Science and Technology, Wuhan 430081 (China); Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom)

2017-02-16

The effect of tempering on the microstructure and mechanical properties of a medium carbon bainitic steel has been investigated through optical microscopy, electron back-scattered diffraction, transmission electron microscopy and X-ray diffraction analyses. A nano-level microstructure containing plate-like bainitic ferrite and film-like retained austenite is obtained by isothermal transformation at Ms+10 °C followed by tempering within 240–450 °C. Results show that the sample tempered at 340 °C occupies the optimal balance of strength and toughness by maintaining a certain level of plasticity; samples tempered at 320 °C and 360 °C with low and high yield ratio come second. The microstructure of the steel is not sensitive to tempering temperatures before 360 °C. When the temperature is increased to 450 °C, the significantly coarsened bainitic ferrite plate and the occurrence of a small quantity of carbide precipitation account for its low toughness. The amount of retained austenite increases with the tempering temperature before 400 °C, followed by decreasing with further increase in the temperature. This behavior is related to the competition between retained austenite further transforming into bainite and decomposing into carbide during tempering.

Characterization of carbon ion implantation induced graded microstructure and phase transformation in stainless steel

Energy Technology Data Exchange (ETDEWEB)

Feng, Kai; Wang, Yibo [Shanghai Key laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Li, Zhuguo, E-mail: lizg@sjtu.edu.cn [Shanghai Key laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

2015-08-15

Austenitic stainless steel 316L is ion implanted by carbon with implantation fluences of 1.2 × 10{sup 17} ions-cm{sup −} {sup 2}, 2.4 × 10{sup 17} ions-cm{sup −} {sup 2}, and 4.8 × 10{sup 17} ions-cm{sup −} {sup 2}. The ion implantation induced graded microstructure and phase transformation in stainless steel is investigated by X-ray diffraction, X-ray photoelectron spectroscopy and high resolution transmission electron microscopy. The corrosion resistance is evaluated by potentiodynamic test. It is found that the initial phase is austenite with a small amount of ferrite. After low fluence carbon ion implantation, an amorphous layer and ferrite phase enriched region underneath are formed. Nanophase particles precipitate from the amorphous layer due to energy minimization and irradiation at larger ion implantation fluence. The morphology of the precipitated nanophase particles changes from circular to dumbbell-like with increasing implantation fluence. The corrosion resistance of stainless steel is enhanced by the formation of amorphous layer and graphitic solid state carbon after carbon ion implantation. - Highlights: • Carbon implantation leads to phase transformation from austenite to ferrite. • The passive film on SS316L becomes thinner after carbon ion implantation. • An amorphous layer is formed by carbon ion implantation. • Nanophase precipitate from amorphous layer at higher ion implantation fluence. • Corrosion resistance of SS316L is improved by carbon implantation.

Effect of volume ratio of liquid to solid on the interfacial microstructure and mechanical properties of high chromium cast iron and medium carbon steel bimetal

International Nuclear Information System (INIS)

Xiong Bowen; Cai Changchun; Lu Baiping

2011-01-01

Highlights: → Volume ratio of liquid to solid affects significantly the interfacial microstructure. → Elemental diffusion activity is increased by increasing volume ratio. → Mechanical property is improved by increasing volume ratio. - Abstract: The high chromium cast iron and medium carbon steel bimetal was fabricated by liquid-solid casting technology. The effect of volume ratios of liquid to solid (6:1, 10:1 and 12:1) on the interfacial microstructure and mechanical properties of bimetal was investigated. The interfacial microstructure was analyzed using scanning electron microscope (SEM) and transmission electron microscope (TEM). The shear strength and microhardness in as-cast condition were studied at room temperature. The results show that the volume ratios of liquid to solid affect significantly the interfacial microstructure. When liquid-solid volume ratio was 6:1, the unbonded region was detected in interface region because the imported heat energy cannot support effectively the diffusion of element, whereas, when liquid-solid volume ratios reach 10:1 and 12:1, a sound interfacial microstructure was achieved by the diffusion of C, Cr, Mo, Cu and Mn, and metallurgical bonding without unbonded region, void and hole, etc. was detected. With the increase of liquid-solid volume ratio, the elemental diffusion activity improves, resulting in the increase of width of interface transition region. At the same distance from interface, with the increase of liquid-solid volume ratio, the microhardness is degraded in HCCI, but increased in MCS. The shear strength is also improved with the increase of liquid-solid volume ratio.

Activated Carbon, Carbon Nanofiber and Carbon Nanotube Supported Molybdenum Carbide Catalysts for the Hydrodeoxygenation of Guaiacol

Directory of Open Access Journals (Sweden)

Eduardo Santillan-Jimenez

2015-03-01

Full Text Available Molybdenum carbide was supported on three types of carbon support—activated carbon; multi-walled carbon nanotubes; and carbon nanofibers—using ammonium molybdate and molybdic acid as Mo precursors. The use of activated carbon as support afforded an X-ray amorphous Mo phase, whereas crystalline molybdenum carbide phases were obtained on carbon nanofibers and, in some cases, on carbon nanotubes. When the resulting catalysts were tested in the hydrodeoxygenation (HDO of guaiacol in dodecane, catechol and phenol were obtained as the main products, although in some instances significant amounts of cyclohexane were produced. The observation of catechol in all reaction mixtures suggests that guaiacol was converted into phenol via sequential demethylation and HDO, although the simultaneous occurrence of a direct demethoxylation pathway cannot be discounted. Catalysts based on carbon nanofibers generally afforded the highest yields of phenol; notably, the only crystalline phase detected in these samples was Mo2C or Mo2C-ζ, suggesting that crystalline Mo2C is particularly selective to phenol. At 350 °C, carbon nanofiber supported Mo2C afforded near quantitative guaiacol conversion, the selectivity to phenol approaching 50%. When guaiacol HDO was performed in the presence of acetic acid and furfural, guaiacol conversion decreased, although the selectivity to both catechol and phenol was increased.

Computational modeling of elastic properties of carbon nanotube/polymer composites with interphase regions. Part I: Micro-structural characterization and geometric modeling

KAUST Repository

Han, Fei; Azdoud, Yan; Lubineau, Gilles

2014-01-01

A computational strategy to predict the elastic properties of carbon nanotube-reinforced polymer composites is proposed in this two-part paper. In Part I, the micro-structural characteristics of these nano-composites are discerned

Study of different nanostructured carbon supports for fuel cell catalysts

Science.gov (United States)

Mirabile Gattia, Daniele; Antisari, Marco Vittori; Giorgi, Leonardo; Marazzi, Renzo; Piscopiello, Emanuela; Montone, Amelia; Bellitto, Serafina; Licoccia, Silvia; Traversa, Enrico

Pt clusters were deposited by an impregnation process on three carbon supports: multi-wall carbon nanotubes (MWNT), single-wall carbon nanohorns (SWNH), and Vulcan XC-72 carbon black to investigate the effect of the carbon support structure on the possibility of reducing Pt loading on electrodes for direct methanol (DMFC) fuel cells without impairing performance. MWNT and SWNH were in-house synthesised by a DC and an AC arc discharge process between pure graphite electrodes, respectively. UV-vis spectrophotometry, scanning and transmission electron microscopy, X-ray diffraction, and cyclic voltammetry measurements were used to characterize the Pt particles deposited on the three carbon supports. A differential yield for Pt deposition, not strictly related to the surface area of the carbon support, was observed. SWNH showed the highest surface chemical activity toward Pt deposition. Pt deposited in different forms depending on the carbon support. Electrochemical characterizations showed that the Pt nanostructures deposited on MWNT are particularly efficient in the methanol oxidation reaction.

Effects of deformation and boron on microstructure and continuous cooling transformation in low carbon HSLA steels

Energy Technology Data Exchange (ETDEWEB)

Jun, H.J. [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Kang, J.S. [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Seo, D.H. [Technical Research Laboratories, POSCO, Pohang 545-090 (Korea, Republic of); Kang, K.B. [Technical Research Laboratories, POSCO, Pohang 545-090 (Korea, Republic of); Park, C.G. [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)]. E-mail: cgpark@postech.ac.kr

2006-04-25

The continuous-cooling-transformation (CCT) diagram and continuous cooled microstructure were investigated for low carbon (0.05 wt.% C) high strength low alloy steels with/without boron. Microstructures observed in continuous cooled specimens were composed of pearlite, quasi-polygonal ferrite, granular bainite, acicular ferrite, bainitic ferrite, lower bainite, and martensite depending on cooling rate and transformation temperature. A rapid cooling rate depressed the formation of pearlite and quasi-polygonal ferrite, which resulted in higher hardness. However, hot deformation slightly increased transformation start temperature, and promoted the formation of pearlite and quasi-polygonal ferrite. Hot deformation also strongly promoted the acicular ferrite formation which did not form under non-deformation conditions. Small boron addition effectively reduced the formation of pearlite and quasi-polygonal ferrite and broadened the cooling rate region for bainitic ferrite and martensite.

Mechano-Physical Properties and Microstructure of Carbon Nanotube Reinforced Cement Paste after Thermal Load.

Science.gov (United States)

Szeląg, Maciej

2017-09-11

The article presents the results obtained in the course of a study on the use of carbon nanotubes (CNTs) for the modification of a cement matrix. Carbon nanotubes were introduced into a cement paste in the form of an aqueous dispersion in the presence of a surfactant (SDS-sodium dodecyl sulfate), which was sonicated. The selected physical and mechanical parameters were examined, and the correlations between these parameters were determined. An analysis of the local microstructure of the modified cement pastes has been carried out using scanning electron microscope (SEM) and X-ray microanalysis (EDS). In addition, the effect of carbon nanotubes on the change in characteristics of the cementitious material exposed to the sudden, short-term thermal load, was determined. The obtained material was characterized by a much lower density than a traditional cement matrix because the phenomenon of foaming occurred. The material was also characterized by reduced durability, higher shrinkage, and higher resistance to the effect of elevated temperature. Further research on the carbon nanotube reinforced cement paste, with SDS, may contribute to the development of a modified cement binder for the production of a lightweight or an aerated concrete.

Mechano-Physical Properties and Microstructure of Carbon Nanotube Reinforced Cement Paste after Thermal Load

Science.gov (United States)

2017-01-01

The article presents the results obtained in the course of a study on the use of carbon nanotubes (CNTs) for the modification of a cement matrix. Carbon nanotubes were introduced into a cement paste in the form of an aqueous dispersion in the presence of a surfactant (SDS—sodium dodecyl sulfate), which was sonicated. The selected physical and mechanical parameters were examined, and the correlations between these parameters were determined. An analysis of the local microstructure of the modified cement pastes has been carried out using scanning electron microscope (SEM) and X-ray microanalysis (EDS). In addition, the effect of carbon nanotubes on the change in characteristics of the cementitious material exposed to the sudden, short-term thermal load, was determined. The obtained material was characterized by a much lower density than a traditional cement matrix because the phenomenon of foaming occurred. The material was also characterized by reduced durability, higher shrinkage, and higher resistance to the effect of elevated temperature. Further research on the carbon nanotube reinforced cement paste, with SDS, may contribute to the development of a modified cement binder for the production of a lightweight or an aerated concrete. PMID:28891976

Influence of the microstructure on the supercapacitive behavior of polyaniline/single-wall carbon nanotube composites

Energy Technology Data Exchange (ETDEWEB)

Gupta, Vinay; Miura, Norio [Art, Science and Technology Center for Cooperative Research, Environment and Energy, KASTEC, Kyushu University, Kasuga-shi, Fukuoka 816-8580 (Japan)

2006-06-19

Polyaniline/single-wall carbon nanotube (PANI/SWCNT) composites were prepared by in situ potentiostatic deposition of PANI onto SWCNTs at the potential of 0.75V versus SCE, with the aim to investigate the influence of microstructure on the specific capacitance of PANI/SWCNT composites. It was found that the specific capacitance of the PANI/SWCNT composites is strongly influenced by their microstructure, which is correlated to the wt.% of the PANI deposited onto the SWCNTs. The optimum condition, corresponding to the highest specific capacitance, 463Fg{sup -1} (at 10mAcm{sup -2}), was obtained for 73wt.% PANI deposited onto SWCNTs. The specific capacitance of the PANI/SWCNT composite electrode was highly stable, with a capacitive decrease of 5% during the first 500 cycles and just 1% during the next 1000 cycles, indicative of the excellent cyclic stability of the composite for supercapacitor applications. (author)

Hydrogenation of carbon monoxide over supported palladium catalysts

Energy Technology Data Exchange (ETDEWEB)

Fujimoto, K.; Hashimoto, H.; Kunugi, T.

1978-03-01

An alumina-supported 2% palladium catalyst had higher activity for carbon monoxide hydrogenation than a silica-supported 2% palladium catalyst, at 250/sup 0/-400/sup 0/C and 1 atm. The addition of lanthanum oxide or thorium oxide, but not of potassium oxide, to the silica-supported catalyst increased the conversion at 350/sup 0/C from 1.1% to 81.0% with a selectivity of 56.1% for methane, 1.4% for C/sub 2/ compounds, 0.1% for C/sub 3/ compounds, and 42.5% for carbon dioxide. Temperature-programed desorption of carbon monoxide in a hydrogen stream showed that of two desorption peaks observed for carbon monoxide, the one at higher temperature corresponded to the carbon monoxide species which hydrogenates to methane and that the area of this peak increased with increasing thorium content of the catalyst. Graphs, tables, and 12 references.

Preparation and electrochemistry of graphene nanosheets–multiwalled carbon nanotubes hybrid nanomaterials as Pd electrocatalyst support for formic acid oxidation

International Nuclear Information System (INIS)

Yang Sudong; Shen Chengmin; Lu Xiangjun; Tong Hao; Zhu Jiajia; Zhang Xiaogang; Gao Hongjun

2012-01-01

Highlights: ► Graphene nanosheets–MWCNTs (GNS–CNTs) composites as Pd electrocatalysts support were synthesized by in situ reduction method. ► The direct electrooxidation of HCOOH is improved on the GNS–CNTs based catalyst. ► Both activity and durability of GNS–CNTs based catalyst are improved greatly. ► Pd/GNS–CNTs catalysts exhibit excellent performance when the mass ratio of GO to CNTs is 5:1. - Abstract: Graphene nanosheets–MWCNTs (GNS–CNTs) composites were synthesized by in situ reduction method, and then palladium nanoparticles (NPs) were supported on the GNS–CNTs by a microwave-assisted polyol process. Microstructure measurements showed that the graphene nanosheets and the CNTs formed a uniform nanocomposite with CNTs absorbed on the graphene nanosheets surface and/or filled between the graphene nanosheets. Compared to Pd/Vulcan XC-72R carbon, Pd/GNS, or Pd/CNTs catalysts, the Pd/GNS–CNTs catalysts exhibit excellent electrocatalytic activity and stability for formic acid electro-oxidation when the mass ratio of GO to CNTs is 5:1. The superior performance of Pd/GNS–CNTs catalysts may arise from large surface area utilization for NPs and enhanced electronic conductivity of the supports. Therefore, the GNS–CNTs composite should be a promising carbon material for application as electrocatalyst support in fuel cells.

Carbon nanofibers: a versatile catalytic support

Directory of Open Access Journals (Sweden)

Nelize Maria de Almeida Coelho

2008-09-01

Full Text Available The aim of this article is present an overview of the promising results obtained while using carbon nanofibers based composites as catalyst support for different practical applications: hydrazine decomposition, styrene synthesis, direct oxidation of H2S into elementary sulfur and as fuel-cell electrodes. We have also discussed some prospects of the use of these new materials in total combustion of methane and in ammonia decomposition. The macroscopic carbon nanofibers based composites were prepared by the CVD method (Carbon Vapor Deposition employing a gaseous mixture of hydrogen and ethane. The results showed a high catalytic activity and selectivity in comparison to the traditional catalysts employed in these reactions. The fact was attributed, mainly, to the morphology and the high external surface of the catalyst support.

Highest recorded electrical conductivity and microstructure in polypropylene-carbon nanotubes composites and the effect of carbon nanofibers addition

Science.gov (United States)

Ramírez-Herrera, C. A.; Pérez-González, J.; Solorza-Feria, O.; Romero-Partida, N.; Flores-Vela, A.; Cabañas-Moreno, J. G.

2018-04-01

In the last decade, numerous investigations have been devoted to the preparation of polypropylene-multiwalled carbon nanotubes (PP/MWCNT) nanocomposites having enhanced properties, and in particular, high electrical conductivities (> 1 S cm-1). The present work establishes that the highest electrical conductivity in PP/MWCNT nanocomposites is limited by the amount of nanofiller content which can be incorporated in the polymer matrix, namely, about 20 wt%. This concentration of MWCNT in PP leads to a maximum electrical conductivity slightly lower than 8 S cm-1, but only by assuring an adequate combination of dispersion and spatial distribution of the carbon nanotubes. The realization of such an optimal microstructure depends on the characteristics of the production process of the PP/MWCNT nanocomposites; in our experiments, involving composite fabrication by melt mixing and hot pressing, a second re-processing cycle is shown to increase the electrical conductivity values by up to two orders of magnitude, depending on the MWCNT content of the nanocomposite. A modest increase of the highest electrical conductivity obtained in nanocomposites with 21.5 wt% MWCNT content has been produced by the combined use of carbon nanofibers (CNF) and MWCNT, so that the total nanofiller content was increased to 30 wt% in the nanocomposite with PP—15 wt% MWCNT—15 wt%CNF.

Effect of carbon content on the microstructure and mechanical properties of superfine Ti(C, N)-based cermets

International Nuclear Information System (INIS)

Liu Ning; Liu Xuesong; Zhang Xiaobo; Zhu Longwei

2008-01-01

As a new kind of tool materials which appeared in the seventies last century, the Ti (C, N)-based cermets have been widely used in recent years due to many of its good properties. The microstructure of Ti(C, N)-based cermets with various carbon content were studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and X-ray diffractometry (XRD). Vickers hardness and transverse rupture strength (TRS) were also measured. An increased carbon content resulted in the finer grain size, decreased solution strength of tungsten and molybdenum in the binder phase, and a higher volume fraction of heavy (Ti, Mo, W)(C,N) cores. If the addition of carbon content is too little or too much, the phase composition of material will deviate from the normal dual phase section and lead to the formation of the third phase: η-phase if the carbon content is too low or dissociative carbon if the carbon content is too high. And the formation of the third phase will remarkably deteriorate the mechanical properties of cermets

Interfacial charge distributions in carbon-supported palladium catalysts

DEFF Research Database (Denmark)

Rao, Radhika G.; Blume, Raoul; Hansen, Thomas Willum

2017-01-01

Controlling the charge transfer between a semiconducting catalyst carrier and the supported transition metal active phase represents an elite strategy for fine turning the electronic structure of the catalytic centers, hence their activity and selectivity. These phenomena have been theoretically...... and experimentally elucidated for oxide supports but remain poorly understood for carbons due to their complex nanoscale structure. Here, we combine advanced spectroscopy and microscopy on model Pd/C samples to decouple the electronic and surface chemistry effects on catalytic performance. Our investigations reveal...... treatments can be used to tune the interfacial charge distribution, hereby providing a strategy to rationally design carbon-supported catalysts.Control over charge transfer in carbon-supported metal nanoparticles is essential for designing new catalysts. Here, the authors show that thermal treatments...

Processing of composites based on NiO, samarium-doped ceria and carbonates (NiO-SDCC as anode support for solid oxide fuel cells

Directory of Open Access Journals (Sweden)

Lily Siong Mahmud

2017-09-01

Full Text Available NiO-SDCC composites consisting of NiO mixed with Sm-doped ceria (SDC and carbonates (Li2CO3 and Na2CO3 were sintered at different temperatures and reduced at 550 °C. The influence of reduction on structure of the NiO-SDCC anode support for solid oxide fuel cells (SOFCs was investigated. Raman spectra of the NiO-SDCC samples sintered at 500, 600 and 700 °C showed that after reducing at 550 °C NiO was reduced to Ni. In addition, SDC and carbonates (Li2CO3 and Na2CO3 did not undergo chemical transformation after reduction and were still detected in the samples. However, no Raman modes of carbonates were identified in the NiO-SDCC pellet sintered at 1000 °C and reduced at 550 °C. It is suspected that carbonates were decomposed at high sintering temperature and eliminated due to the reaction between the CO32– and hydrogen ions during reduction in humidified gases at 550 °C. The carbonate decomposition increased porosity in the Ni-SDCC pellets and consequently caused formation of brittle and fragile structure unappropriated for SOFC application. Because of that composite NiO-SDC samples without carbonates were also analysed to determine the factors affecting the crack formation. In addition, it was shown that the different reduction temperatures also influenced the microstructure and porosity of the pellets. Thus, it was observed that Ni-SDC pellet reduced at 800 °C has higher electrical conductivity of well-connected microstructures and sufficient porosity than the pellet reduced at 550 °C.

Nitrogen-doped carbon-supported cobalt-iron oxygen reduction catalyst

Science.gov (United States)

Zelenay, Piotr; Wu, Gang

2014-04-29

A Fe--Co hybrid catalyst for oxygen reaction reduction was prepared by a two part process. The first part involves reacting an ethyleneamine with a cobalt-containing precursor to form a cobalt-containing complex, combining the cobalt-containing complex with an electroconductive carbon supporting material, heating the cobalt-containing complex and carbon supporting material under conditions suitable to convert the cobalt-containing complex and carbon supporting material into a cobalt-containing catalyst support. The second part of the process involves polymerizing an aniline in the presence of said cobalt-containing catalyst support and an iron-containing compound under conditions suitable to form a supported, cobalt-containing, iron-bound polyaniline species, and subjecting said supported, cobalt-containing, iron bound polyaniline species to conditions suitable for producing a Fe--Co hybrid catalyst.

Microstructure and chemical bond evolution of diamond-like carbon films machined by femtosecond laser

Energy Technology Data Exchange (ETDEWEB)

Wang, Jing; Wang, Chunhui [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Liu, Yongsheng, E-mail: yongshengliu@nwpu.edu.cn [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Cheng, Laifei [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Weinan [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 10068 (China); Zhang, Qing [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Yang, Xiaojun [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 10068 (China)

2015-06-15

Highlights: • The machining depth was essentially proportional to the laser power. • The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. And the number of nanoparticles increased with the processing power as well. • It revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. • It showed that a great decrease of sp{sup 3}/sp{sup 2} after laser treatment. - Abstract: Femtosecond laser is of great interest for machining high melting point and hardness materials such as diamond-like carbon, SiC ceramic, et al. In present work, the microstructural and chemical bond evolution of diamond-like carbon films were investigated using electron microscopy and spectroscopy techniques after machined by diverse femtosecond laser power in air. The results showed the machining depth was essentially proportional to the laser power. The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. Considering the D and G Raman band parameters on the laser irradiation, it revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. X-ray photoelectron spectroscopy analysis showed a great decrease of sp{sup 3}/sp{sup 2} after laser treatment.

Effects of carbon concentration on microstructure and mechanical properties of as-cast nickel-free Co–28Cr–9W-based dental alloys

International Nuclear Information System (INIS)

Yamanaka, Kenta; Mori, Manami; Chiba, Akihiko

2014-01-01

We determined the effects of carbon concentration on the microstructures and tensile properties of the Ni-free Co–29Cr–9W–1Si–C (mass%) cast alloys used in dental applications. Alloy specimens prepared with carbon concentrations in the range 0.01–0.27 mass% were conventionally cast. Scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) revealed that precipitates had formed in all the alloy specimens. The σ phase, a chromium-rich intermetallic compound, had formed in the region between the dendrite arms of the low-carbon-content (e.g., 0.01C) alloys. Adding carbon to the alloys increased the amount of interdendritic precipitates that formed and changed the precipitation behavior; the precipitated phase changed from the σ phase to the M 23 C 6 carbide with increasing carbon concentration. Adding a small amount of carbon (i.e., 0.04 mass%) to the alloys dramatically enhanced the 0.2% proof stress, which subsequently gradually increased with increasing content of carbon in the alloys. Elongation-to-failure, on the other hand, increased with increasing carbon content and showed a maximum at carbon concentrations of ∼ 0.1 mass%. The M 23 C 6 carbide formed at the interdendritic region may govern the tensile properties of the as-cast Co–Cr–W alloys similar to how it governed those of the hot-rolled alloys prepared in our previous study. - Highlights: • Microstructure and tensile properties of C-doped Co–Cr–W cast alloys was studied. • Adding carbon stabilized the γ matrix and changed the precipitation behavior. • Formation of carbide precipitates strengthened C-doped Co–Cr–Mo alloys. • A maximum tensile elongation was obtained at carbon concentrations of ∼0.1 mass%

Carbon Contamination During Ion Irradiation - Accurate Detection and Characterization of its Effect on Microstructure of Ferritic/Martensitic Steels

Energy Technology Data Exchange (ETDEWEB)

Wang, Jing; Toloczko, Mychailo B.; Kruska, Karen; Schreiber, Daniel K.; Edwards, Danny J.; Zhu, Zihua; Zhang, Jiandong

2017-11-17

Accelerator-based ion beam techniques have been used to study radiation effects in materials for decades. Although carbon contamination induced by ion beam in target materials is a well-known issue, it has not been fully characterized nor quantified for studies in ferritic/martensitic (F/M) steels that are candidate materials for applications such as core structural components in advanced nuclear reactors. It is an especially important issue for this class of material because of the effect of carbon level on precipitate formation. In this paper, the ability to quantify carbon contamination using three common techniques, namely time-of-flight secondary ion mass spectroscopy (ToF-SIMS), atom probe tomography (APT) and transmission electron microscopy (TEM) is compared. Their effectiveness and short-comings in determining carbon contamination will be presented and discussed. The corresponding microstructural changes related to carbon contamination in ion irradiated F/M steels are also presented and briefly discussed.

Micrograph evidence of meniscus solidification and sub-surface microstructure evolution in continuous-cast ultralow-carbon steels

International Nuclear Information System (INIS)

Sengupta, J.; Shin, H.-J.; Thomas, B.G.; Kim, S.-H.

2006-01-01

Hooks and other sub-surface features in continuous-cast ultralow-carbon steel samples were examined using optical microscopy, electron backscattering diffraction, energy dispersive X-ray spectroscopy, and electron probe microanalysis techniques. Special etching reagents revealed dendrites growing from both sides of the line of hook origin. This line was found to represent the frozen meniscus and persisted into the final microstructure, as revealed by grain orientation measurements. A broken hook tip was observed in one micrograph, which explains the characteristic truncated shape of most hooks. Mold powder was found entrapped along the frozen meniscus. These results provide evidence of both solidification and subsequent overflow of the liquid steel meniscus. Thus, the instantaneous meniscus shape governs the shape and microstructure of the final hook, and the extent of the liquid steel overflow determines the shape of oscillation marks. This mechanism has important implications for the entrapment of inclusions and other surface defects

Morphological and microstructural studies on aluminizing coating of carbon steel

Energy Technology Data Exchange (ETDEWEB)

Samsu, Zaifol; Othman, Norinsan Kamil; Daud, Abd Razak; Hussein, Hishammuddin [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia)

2013-11-27

Hot dip aluminizing is one of the most effective methods of surface protection for steels and is gradually gaining popularity. The morphology and microstructure of an inter-metallic layer form on the surface of low carbon steel by hot dip aluminization treatment had been studied in detail. This effect has been investigated using optical and scanning electron microscopy, and X-ray diffraction. The result shows that the reaction between the steel and the molten aluminium leads to the formation of Fe–Al inter-metallic compounds on the steel surface. X-ray diffraction and electron microscopic studies showed that a two layer coating was formed consisting of an external Al layer and a (Fe{sub 2}Al{sub 5}) inter metallic on top of the substrate after hot dip aluminizing process. The inter-metallic layer is ‘thick’ and exhibits a finger-like growth into the steel. Microhardness testing shown that the intermetallic layer has high hardness followed by steel substrate and the lowest hardness was Al layer.

Effect of microstructure on the cleavage fracture strength of low carbon Mn-Ni-Mo bainitic steels

International Nuclear Information System (INIS)

Im, Young-Roc; Lee, Byeong-Joo; Oh, Yong Jun; Hong, Jun Hwa; Lee, Hu-Chul

2004-01-01

The effects of the microstructure on the cleavage fracture strength of low carbon Mn-Ni-Mo bainitic steels were examined. A four-point bend test and double-notched bend specimens were used to measure the cleavage fracture strength of the alloys and identify the cleavage initiating micro-cracks, respectively. The cleavage fracture strength and DBTT of Mn-Ni-Mo bainitic steels were strongly affected by the alloy carbon content. The decrease in the alloy carbon content resulted in a decrease in the inter-lath cementite-crowded layers and higher cleavage fracture strength. Micro-cracks that formed across the inter-lath cementite-crowded layers were observed to initiate cleavage fracture. The width of these inter-lath cementite-crowded layers was accepted as a cleavage initiating micro-crack size in the micro-mechanical modeling of the cleavage fracture, and the measured cleavage strength values of the bainitic Mn-Ni-Mo steels were well represented by the modified Griffith relationship

Single wall carbon nanotube supports for portable direct methanol fuel cells.

Science.gov (United States)

Girishkumar, G; Hall, Timothy D; Vinodgopal, K; Kamat, Prashant V

2006-01-12

Single-wall and multiwall carbon nanotubes are employed as carbon supports in direct methanol fuel cells (DMFC). The morphology and electrochemical activity of single-wall and multiwall carbon nanotubes obtained from different sources have been examined to probe the influence of carbon support on the overall performance of DMFC. The improved activity of the Pt-Ru catalyst dispersed on carbon nanotubes toward methanol oxidation is reflected as a shift in the onset potential and a lower charge transfer resistance at the electrode/electrolyte interface. The evaluation of carbon supports in a passive air breathing DMFC indicates that the observed power density depends on the nature and source of carbon nanostructures. The intrinsic property of the nanotubes, dispersion of the electrocatalyst and the electrochemically active surface area collectively influence the performance of the membrane electrode assembly (MEA). As compared to the commercial carbon black support, single wall carbon nanotubes when employed as the support for anchoring the electrocatalyst particles in the anode and cathode sides of MEA exhibited a approximately 30% enhancement in the power density of a single stack DMFC operating at 70 degrees C.

Understanding the role of carbon atoms on microstructure and phase transformation of high Nb containing TiAl alloys

Energy Technology Data Exchange (ETDEWEB)

Wu, Zeen; Hu, Rui; Zhang, Tiebang, E-mail: tiebangzhang@nwpu.edu.cn; Zhang, Fan; Kou, Hongchao; Li, Jinshan

2017-02-15

The microstructure and solidification behavior of high Nb containing TiAl alloys with the composition of Ti-46Al-8Nb-xC (x = 0.1, 0.7, 1.4, 2.5 at.%) prepared by arc-melting method have been investigated in this work. The results give evidence that the addition of carbon changes the solidification behavior from solidification via the β phase to the peritectic solidification. And carbon in solid solution enriches in the α{sub 2} phase and increases the microhardness. As the carbon content increases to 1.4 at.%, plate-shape morphology carbides Ti{sub 2}AlC (H phase) precipitate from the TiAl matrix which leads to the refinement microstructure. By aging at 1173 K for 24 h after quenching treatment, fine needle-like and granular shape Ti{sub 3}AlC (P phase) carbides are observed in the matrix of Ti-46Al-8Nb-2.5C alloy, which distribute along the lamellar structure or around the plate-shape Ti{sub 2}AlC. Transmission electron microscope observation shows that the Ti{sub 3}AlC carbides precipitate at dislocations. The phase transformation in-situ observations indicate that the Ti{sub 2}AlC carbides partly precipitate during the solid state phase transformation process. - Highlights: •Carbon changes the solidification behavior from β phase to peritectic solidification. •Dislocations in solution treated γ phase act as nucleation sites of Ti{sub 3}AlC precipitations. •Ti{sub 3}AlC precipitates as fine needle-like or granular shape in the solution treated matrix. •Ti{sub 2}AlC carbides precipitate during the solid state phase transformation process.

Effect of oxygen and hydrogen on microstructure of pyrolytic carbon deposited from thermal decomposition of methane and ethanol

Science.gov (United States)

Ren, Biyun; Zhang, Shouyang; He, LiQun; Gu, Shengyue

2018-05-01

Chemical vapor infiltration (CVI) is the most extensive industrial preparation of carbon/carbon (C/C) composites. Precursor affects the CVI process considerably. In the present study, using carbon fiber bundles as preforms, methane and ethanol as precursors, the C/C composites were densified by decomposition of various gases in CVI. The thickness and texture of deposited pyrolytic carbon (PyC) were characterized by polarized light microscopy (PLM). The microstructure of PyC was analyzed by Raman spectroscopy. The morphologies of PyC were characterized by scanning electron microscopy (SEM). The composition of PyC was detected by X-ray photoelectron spectroscopy (XPS). Adding hydrogen in methane precursor resulted in a sharp decrease in the deposition rate and texture of PyC. Mixture of methane and ethanol as the precursor improved the deposition rate and texture remarkably. Besides, O element in ethanol was not remained as a constitution of PyC, and it was removed before the formation of PyC.

Nitrogen: Unraveling the Secret to Stable Carbon-Supported Pt-Alloy Electrocatalysts

Science.gov (United States)

2013-10-01

release; distribution is unlimited. Nitrogen: unraveling the secret to stable carbon-supported Pt- alloy electrocatalysts The views, opinions and/or...Nitrogen: unraveling the secret to stable carbon-supported Pt-alloy electrocatalysts Report Title Nitrogen functionalities significantly improve...design and optimization of next generation high performance catalyst materials. Nitrogen: unraveling the secret to stable carbon-supported Pt-alloy

Activated carbon-supported CuO nanoparticles: a hybrid material for carbon dioxide adsorption

Science.gov (United States)

Boruban, Cansu; Esenturk, Emren Nalbant

2018-03-01

Activated carbon-supported copper(II) oxide (CuO) nanoparticles were synthesized by simple impregnation method to improve carbon dioxide (CO2) adsorption capacity of the support. The structural and chemical properties of the hybrid material were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (https://www.google.com.tr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0CCsQFjAC&url=http%3A%2F%2Fwww.intertek.com%2Fanalytical-laboratories%2Fxrd%2F&ei=-5WZVYSCHISz7Aatqq-IAw&usg=AFQjCNFBlk-9wqy49foh8tskmbD-GGbG9g&sig2=eKrhYjO75rl_Id2sLGpq4w&bvm=bv.96952980,d.bGg) (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), and Brunauer-Emmett-Teller (BET) analyses. The analyses showed that CuO nanoparticles are well-distributed on the activated carbon surface. The CO2 adsorption behavior of the activated carbon-supported CuO nanoparticles was observed by thermogravimetric analysis (TGA), temperature programmed desorption (TPD), Fourier transform infrared (FTIR), and BET analyses. The results showed that CuO nanoparticle loading on activated carbon led to about 70% increase in CO2 adsorption capacity of activated carbon under standard conditions (1 atm and 298 K). The main contributor to the observed increase is an improvement in chemical adsorption of CO2 due to the presence of CuO nanoparticles on activated carbon.

Functionalized Natural Carbon-Supported Nanoparticles as Excellent Catalysts for Hydrocarbon Production.

Science.gov (United States)

Sun, Jian; Guo, Lisheng; Ma, Qingxiang; Gao, Xinhua; Yamane, Noriyuki; Xu, Hengyong; Tsubaki, Noritatsu

2017-02-01

We report a one-pot and eco-friendly synthesis of carbon-supported cobalt nanoparticles, achieved by carbonization of waste biomass (rice bran) with a cobalt source. The functionalized biomass provides carbon microspheres as excellent catalyst support, forming a unique interface between hydrophobic and hydrophilic groups. The latter, involving hydroxyl and amino groups, can catch much more active cobalt nanoparticles on surface for Fischer-Tropsch synthesis than chemical carbon. The loading amount of cobalt on the final catalyst is much higher than that prepared with a chemical carbon source, such as glucose. The proposed concept of using a functionalized natural carbon source shows great potential compared with conventional carbon sources, and will be meaningful for other fields concerning carbon support, such as heterogeneous catalysis or electrochemical fields. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Micro-CT in situ study of carbonate rock microstructural evolution for geologic CO2 storage

DEFF Research Database (Denmark)

Zheng, Yi; Yang, Yan; Rogowska, M.

2017-01-01

to achieve this is to find a suitable condition to create a stable 3D space in carbonate rock by injecting liquid to prepare space for the later CO2 injection. Micro-CT imaging is a non-destructive 3D method that can be used to study the property changes of carbonate rocks during and after CO2 injection....... The advance in lab source based micro-CT has made it capable of in situ experiments. We used a commercial bench top micro-CT (Zeiss Versa XRM410) to study the microstructure changes of chalk during liquid injection. Flexible temporal CT resolution is essential in this study because that the time scales...... of coupled physical and chemical processes can be very different. The results validated the feasibility of using a bench top CT system with a pressure cell to monitor the mesoscale multiphase interactions in chalk....

Cathode-supported hybrid direct carbon fuel cells

DEFF Research Database (Denmark)

Gil, Vanesa; Gurauskis, Jonas; Deleebeeck, Lisa

2017-01-01

The direct conversion of coal to heat and electricity by a hybrid direct carbon fuel cell (HDCFC) is a highly efficient and cleaner technology than the conventional combustion power plants. HDCFC is defined as a combination of solid oxide fuel cell and molten carbonate fuel cell. This work...... investigates cathode-supported cells as an alternative configuration for HDCFC, with better catalytic activity and performance. This study aims to define the best processing route to manufacture highly efficient cathode-supported cells based on La0.75Sr0.25MnO3/yttria-stabilized zirconia infiltrated backbones...

Microstructural evolution and mechanical properties of low-carbon steel treated by a two-step quenching and partitioning process

Energy Technology Data Exchange (ETDEWEB)

Yan, Shu [The State Key Laboratory of Rolling & Automation, Northeastern University, Shenyang 110819 (China); Liu, Xianghua, E-mail: liuxh@mail.neu.edu.cn [The State Key Laboratory of Rolling & Automation, Northeastern University, Shenyang 110819 (China); Research Academy, Northeastern University, Shenyang 110819 (China); Liu, Wayne J [Research Academy, Northeastern University, Shenyang 110819 (China); Lan, Huifang; Wu, Hongyan [The State Key Laboratory of Rolling & Automation, Northeastern University, Shenyang 110819 (China)

2015-07-29

The quenching and partitioning (Q&P) process is studied in Ti-bearing low-carbon steel. Detailed characterization of the microstructural evolution is performed by means of optical microscopy, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results indicate that the investigated steel subjected to the Q&P process forms a multiphase microstructure of primarily lath martensite, with small amounts of plate-type martensite and retained austenite. The distribution and morphology of the retained austenite are observed; moreover the relationship between the phase fraction of the retained austenite, its carbon concentration, and the partitioning conditions is established. Carbides preferentially precipitate within the plate-type martensite at first, and gradually form in the martensitic laths over time during the partitioning step. Additionally, titanium precipitations contribute to both the refinement of prior austenite grains and the improvement of strength by precipitation strengthening. The results of mechanical properties testing indicate that the samples partitioned at 400 °C exhibit a superior combination of strength and elongation, with products of the two properties ranging between 19.6 and 20.9 GPa%. Based on analysis of work hardening behavior it is determined that the higher ductility is closely related to the higher phase fraction and/or stability of retained austenite.

Microstructure and partitioning behavior characteristics in low carbon steels treated by hot-rolling direct quenching and dynamical partitioning processes

International Nuclear Information System (INIS)

Li, Yun-jie; Li, Xiao-lei; Yuan, Guo; Kang, Jian; Chen, Dong; Wang, Guo-dong

2016-01-01

In this work, a new process and composition design are proposed for “quenching and partitioning” or Q&P treatment. Three low carbon steels were treated by hot-rolling direct quenching and dynamical partitioning processes (DQ&P). The effects of proeutectoid ferrite and carbon concentration on microstructure evolution and mechanical properties were investigated. The present work obtained DQ&P prototype steels with good mechanical properties and established a new notion on compositions for Q&P processing. Microstructures were characterized by means of electro probe microanalyzer (EPMA), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD), especially the morphology and size of retained austenite. Mechanical properties were measured by uniaxial tensile tests. The results indicated that introducing proeutectoid ferrite can increase the volume fraction of retained austenite and thus improve mechanical properties. TEM observation showed that retained austenite included the film-like inter-lath austenite and blocky austenite located in martensite/ferrite interfaces or surrounded by ferrites. It was interesting that when the carbon concentration is as low as ~ 0.078%, the film-like inter-lath untransformed austenite cannot be stabilized to room temperature and almost all of them transformed into twin martensite. The blocky retained austenite strengthened the interfaces and transformed into twin martensite during the tensile deformation process. The PSEs of specimens all exceeded 20 GPa.%. - Highlights: •This study focused on a new process: Q&P process applying dynamical partitioning. •Ferrite can increase the volume fraction of retained austenite. •The film-like austenite and the blocky austenite were observed. •The low carbon steels treated by new process reached PSEs higher than 20 GPa.%.

Subgenual Cingulum Microstructure Supports Control of Emotional Conflict

Science.gov (United States)

Keedwell, Paul A.; Doidge, Amie N.; Meyer, Marcel; Lawrence, Natalia; Lawrence, Andrew D.; Jones, Derek K.

2016-01-01

Major depressive disorder (MDD) is associated with specific difficulties in attentional disengagement from negatively valenced material. Diffusion MRI studies have demonstrated altered white matter microstructure in the subgenual cingulum bundle (CB) in individuals with MDD, though the functional significance of these alterations has not been examined formally. This study explored whether individual differences in selective attention to negatively valenced stimuli are related to interindividual differences in subgenual CB microstructure. Forty-six individuals (21 with remitted MDD, 25 never depressed) completed an emotional Stroop task, using happy and angry distractor faces overlaid by pleasant or unpleasant target words and a control gender-based Stroop task. CBs were reconstructed in 38 individuals using diffusion-weighted imaging and tractography, and mean fractional anisotropy (FA) computed for the subgenual, retrosplenial, and parahippocampal subdivisions. No significant correlations were found between FA and performance in the control gender-based Stroop task in any CB region. However, the degree of interference produced by angry face distractors on time to identify pleasant words (emotional conflict) correlated selectively with FA in the subgenual CB (r = −0.53; P = 0.01). Higher FA was associated with reduced interference, irrespective of a diagnosis of MDD, suggesting that subgenual CB microstructure is functionally relevant for regulating attentional bias toward negative interpersonal stimuli. PMID:27048427

Nitrogen-doped carbon nanotubes as a metal catalyst support

CSIR Research Space (South Africa)

Mabena, LF

2011-05-01

Full Text Available ., which are among the most commonly used heterogeneous catalyst supports (Mart??nez-Me?ndez et al. 2006). Catalyst activity depends on the particle size and appropriate dis- tance between each particle. These catalysts deposited on a support... supported Pt electrodes. Appl Catal B Environ 80:286?295 Maldonado S, Morin S, Stevenson KJ (2006) Structure, composition, and chemical reactivity of carbon nanotubes by selective nitrogen doping. Carbon 44:1429?1437 Mart??nez-Me?ndez S, Henr??quez Y...

The carbon footprint of behavioural support services for smoking cessation.

Science.gov (United States)

Smith, Anna Jo Bodurtha; Tennison, Imogen; Roberts, Ian; Cairns, John; Free, Caroline

2013-09-01

To estimate the carbon footprint of behavioural support services for smoking cessation: text message support, telephone counselling, group counselling and individual counselling. Carbon footprint analysis. Publicly available data on National Health Service Stop Smoking Services and per unit carbon emissions; published effectiveness data from the txt2stop trial and systematic reviews of smoking cessation services. Carbon dioxide equivalents (CO2e) per 1000 smokers, per lifetime quitter, and per quality-adjusted life year gained, and cost-effectiveness, including social cost of carbon, of smoking cessation services. Emissions per 1000 participants were 8143 kg CO2e for text message support, 8619 kg CO2e for telephone counselling, 16 114 kg CO2e for group counselling and 16 372 kg CO2e for individual counselling. Emissions per intervention lifetime quitter were 636 (95% CI 455 to 958) kg CO2e for text message support, 1051 (95% CI 560 to 2873) kg CO2e for telephone counselling, 1143 (95% CI 695 to 2270) kg CO2e for group counselling and 2823 (95% CI 1688 to 6549) kg CO2e for individual counselling. Text message, telephone and group counselling remained cost-effective when cost-effectiveness analysis was revised to include the environmental and economic cost of damage from carbon emissions. All smoking cessation services had low emissions compared to the health gains produced. Text message support had the lowest emissions of the services evaluated. Smoking cessation services have small carbon footprints and were cost-effective after accounting for the societal costs of greenhouse gas emissions.

Microstructural Evolution of Inconel 625 and Inconel 686CPT Weld Metal for Clad Carbon Steel Linepipe Joints: A Comparator Study

Science.gov (United States)

Maltin, Charles A.; Galloway, Alexander M.; Mweemba, Martin

2014-07-01

Microstructural evolution of Inconel 625 and Inconel 686CPT filler metals, used for the fusion welding of clad carbon steel linepipe, has been investigated and compared. The effects of iron dilution from the linepipe parent material on the elemental segregation potential of the filler metal chemistry have been considered. The results obtained provide significant evidence to support the view that, in Inconel 686CPT weld metal, the segregation of tungsten is a function of the level of iron dilution from the parent material. The data presented indicate that the incoherent phase precipitated in the Inconel 686CPT weld metal has a morphology that is dependent on tungsten enrichment and, therefore, iron dilution. Furthermore, in the same weld metal, a continuous network of finer precipitates was observed. The Charpy impact toughness of each filler metal was evaluated, and the results highlighted the superior impact toughness of the Inconel 625 weld metal over that of Inconel 686CPT.

The Effect of Simulated Thermomechanical Processing on the Transformation Behavior and Microstructure of a Low-Carbon Mo-Nb Linepipe Steel

Science.gov (United States)

Cizek, P.; Wynne, B. P.; Davies, C. H. J.; Hodgson, P. D.

2015-01-01

The present work investigates the transformation behavior of a low-carbon Mo-Nb linepipe steel and the corresponding transformation product microstructures using deformation dilatometry. The continuous cooling transformation (CCT) diagrams have been constructed for both the fully recrystallized austenite and that deformed in uniaxial compression at 1148 K (875 °C) to a strain of 0.5 for cooling rates ranging from 0.1 to about 100 K/s. The obtained microstructures have been studied in detail using electron backscattered diffraction complemented by transmission electron microscopy. Heavy deformation of the parent austenite has caused a significant expansion of the polygonal ferrite transformation field in the CCT diagram, as well as a shift in the non-equilibrium ferrite transformation fields toward higher cooling rates. Furthermore, the austenite deformation has resulted in a pronounced refinement in both the effective grain (sheaf/packet) size and substructure unit size of the non-equilibrium ferrite microstructures. The optimum microstructure expected to display an excellent balance between strength and toughness is a mix of quasi-polygonal ferrite and granular bainite (often termed "acicular ferrite") produced from the heavily deformed austenite within a processing window covering the cooling rates from about 10 to about 100 K/s.

Stability of retained austenite in multi-phase microstructure during austempering and its effect on the ductility of a low carbon steel

Energy Technology Data Exchange (ETDEWEB)

Xie, Z.J.; Ren, Y.Q.; Zhou, W.H. [School of Materials Science and Engineering, University of Science and Technology, Beijing (China); Yang, J.R. [Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan (China); Shang, C.J., E-mail: cjshang@ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology, Beijing (China); Misra, R.D.K. [Laboratory for Excellence in Advanced Steel Research, Center for Structural and Functional Materials, Institute for Material Research and Innovation, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70503 (United States)

2014-05-01

The contribution of multi-phase microstructure and retained austenite on mechanical properties of austempered and intercritical annealed Fe–0.23C–1.8Mn–1.35Si (wt%) steel was studied. The multi-phase microstructure comprised of intercritical ferrite (IF), bainite/martensite, and retained austenite. During austempering, the retained austenite was stabilized, which was studied using a combination of experimental (XRD, TEM) and thermodynamic analysis. The termination of bainitic transformation combined with carbon rejection into residual austenite during the second step austempering treatment is believed to be the underlying basis for stabilization of retained austenite. This led to significant increase in uniform and total elongation (25% and 36%, respectively) and the product of tensile strength and % elongation was 33 GPa%. The work hardening behavior of retained austenite exhibited a three-stage process such that necking was delayed. The increased work hardening rate is attributed to the multi-phase microstructure and TRIP effect.

Effect of the reaction time on the microstructure and porous texture of carbon materials obtained by chlorination of Ti(C{sub 5}H{sub 5})Cl{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Araujo-Pérez, D.J. [Centro de Investigación en Micro y Nanotecnología, Universidad Veracruzana, 94294, Boca del Río, Veracruz (Mexico); González-García, P., E-mail: pedro.gonzalez@cidesi.edu.mx [CONACYT Research Fellow – Centro de Ingeniería y Desarrollo Industrial, 76130, Querétaro, Querétaro (Mexico); Poisot, M. [Instituto de Química Aplicada, Universidad del Papaloapan, 68301, San Juan Bautista Tuxtepec, Oaxaca (Mexico); García-González, L. [Centro de Investigación en Micro y Nanotecnología, Universidad Veracruzana, 94294, Boca del Río, Veracruz (Mexico)

2015-09-15

Carbon materials have been obtained by the chlorination reaction of Ti(C{sub 5}H{sub 5})Cl{sub 2} at 900 °C, varying the reaction time at 30, 60, 90 and 120 min. The average microstructure, studied by X ray powder diffraction, suggest that these materials consist mainly of disordered carbon with low graphitization degree (from 13.5 to 16.5%). These results are in agreement with the Raman data since the D band (at ≈ 1350 cm{sup −1}) indicates that disordered carbon networks have appeared. The calculated in-plane correlation length increases from 4.04 to 4.70 nm as the chlorination time increases from 30 to 120 min. The textural analyses reveal adsorption isotherms type 1 with hysteresis H4, microporous areas as high as 855 m{sup 2}/g and pore volume of 0.55 cm{sup 3}/g. Additionally, an important contribution of mesoporosity, around 3.6 nm, was also detected. - Highlights: • Micro-mesoporous carbon materials were obtained by chlorination of Ti(C{sub 5}H{sub 5}){sub 2}Cl{sub 2} at 900 °C. • The effect of chlorination exposure time on the microstructure and textural properties was studied. • Microstructural analysis by XRD and Raman showed that carbon samples are mainly disordered. • N{sub 2} adsorption/desorption isotherms showed isotherms type 1 with hysteresis H4. • Micropore size increases at longer chlorination time; in contrast, pore volume decreases.

Effect of supercritical carbon dioxide pasteurization on natural microbiota, texture, and microstructure of fresh-cut coconut.

Science.gov (United States)

Ferrentino, Giovanna; Balzan, Sara; Dorigato, Andrea; Pegoretti, Alessandro; Spilimbergo, Sara

2012-05-01

The objective of the present study was the evaluation of the effectiveness of supercritical carbon dioxide (SC-CO(2)) as a nonthermal technology for the pasteurization of fresh-cut coconut, as an example of ready-to-eat and minimally processed food. First, the inactivation kinetics of microbiota on coconut were determined using SC-CO(2) treatments (pressures at 8 and 12 MPa, temperatures from 24 to 45 °C, treatment times from 5 to 60 min). Second, the effects of SC-CO(2) on the hardness and microstructure of fresh-cut coconut processed at the optimal conditions for microbial reduction were investigated. SC-CO(2) treatment of 15 min at 45 °C and 12 MPa induced 4 log CFU/g reductions of mesophilic microorganisms, lactic acid bacteria, total coliforms, and yeasts and molds. The hardness of coconut was not affected by the treatment but the samples developed an irregular and disorderly microstructure. Results suggested the potential of SC-CO(2) in preserving fresh-cut fruits and ready-to-eat products. © 2012 Institute of Food Technologists®

Carbon Nanofibers as Catalyst Support for Noble Metals

NARCIS (Netherlands)

Toebes, M.L.

2004-01-01

In the quest for new and well-defined support materials for heterogeneous catalysts we explored the potential of carbon nanofibers (CNF). CNF belongs to the by now extensive family of synthetic graphite-like carbon materials with advantageous and tunable physico-chemical properties. Aim of the work

Impact of Cutting Forces and Chip Microstructure in High Speed Machining of Carbon Fiber – Epoxy Composite Tube

Directory of Open Access Journals (Sweden)

Roy Y. Allwin

2017-09-01

Full Text Available Carbon fiber reinforced polymeric (CFRP composite materials are widely used in aerospace, automobile and biomedical industries due to their high strength to weight ratio, corrosion resistance and durability. High speed machining (HSM of CFRP material is needed to study the impact of cutting parameters on cutting forces and chip microstructure which offer vital inputs to the machinability and deformation characteristics of the material. In this work, the orthogonal machining of CFRP was conducted by varying the cutting parameters such as cutting speed and feed rate at high cutting speed/feed rate ranges up to 346 m/min/ 0.446 mm/rev. The impact of the cutting parameters on cutting forces (principal cutting, feed and thrust forces and chip microstructure were analyzed. A significant impact on thrust forces and chip segmentation pattern was seen at higher feed rates and low cutting speeds.

Effects of carbon nanotubes on the microstructure and mechanical properties of the wrought Mg–2.0Zn alloy

International Nuclear Information System (INIS)

Zeng, Xiao-shu; Liu, Yong; Huang, Qiu-yu; Zeng, Gang; Zhou, Guo-hua

2013-01-01

The effects of carbon nanotubes (CNTs) on the microstructure and mechanical properties of wrought Mg alloys with of 2.0 wt% of Zn content (Mg–2.0Zn) are investigated by the optical microscope (OM), transmission electron microscope (TEM), scanning electron microscope (SEM) and uniaxial tensile test. Different contents of CNTs are added separately in the as-cast ingots and as-extruded samples. The results showed that CNTs could greatly refine the microstructure of both as-cast alloy and as-extruded alloy. The tensile strength, yield strength, elongation and elasticity modulus of the alloy with CNTs were improved to different extents. Remarkably, the increase of elongation reached approximately 80%. The fracture surface of the alloy with CNTs mainly consisted of dimples with toughness rupture modes. Therefore, it suggests that CNTs could enhance the plasticity of wrought Mg–2.0Zn alloy without the reduction of strength

Morphology and microstructure of composite materials

Science.gov (United States)

Tiwari, S. N.; Srinivansan, K.

1991-01-01

Lightweight continuous carbon fiber based polymeric composites are currently enjoying increasing acceptance as structural materials capable of replacing metals and alloys in load bearing applications. As with most new materials, these composites are undergoing trials with several competing processing techniques aimed at cost effectively producing void free consolidations with good mechanical properties. As metallic materials have been in use for several centuries, a considerable database exists on their morphology - microstructure; and the interrelationships between structure and properties have been well documented. Numerous studies on composites have established the crucial relationship between microstructure - morphology and properties. The various microstructural and morphological features of composite materials, particularly those accompanying different processing routes, are documented.

Subgenual Cingulum Microstructure Supports Control of Emotional Conflict.

Science.gov (United States)

Keedwell, Paul A; Doidge, Amie N; Meyer, Marcel; Lawrence, Natalia; Lawrence, Andrew D; Jones, Derek K

2016-06-01

Major depressive disorder (MDD) is associated with specific difficulties in attentional disengagement from negatively valenced material. Diffusion MRI studies have demonstrated altered white matter microstructure in the subgenual cingulum bundle (CB) in individuals with MDD, though the functional significance of these alterations has not been examined formally. This study explored whether individual differences in selective attention to negatively valenced stimuli are related to interindividual differences in subgenual CB microstructure. Forty-six individuals (21 with remitted MDD, 25 never depressed) completed an emotional Stroop task, using happy and angry distractor faces overlaid by pleasant or unpleasant target words and a control gender-based Stroop task. CBs were reconstructed in 38 individuals using diffusion-weighted imaging and tractography, and mean fractional anisotropy (FA) computed for the subgenual, retrosplenial, and parahippocampal subdivisions. No significant correlations were found between FA and performance in the control gender-based Stroop task in any CB region. However, the degree of interference produced by angry face distractors on time to identify pleasant words (emotional conflict) correlated selectively with FA in the subgenual CB (r = -0.53; P = 0.01). Higher FA was associated with reduced interference, irrespective of a diagnosis of MDD, suggesting that subgenual CB microstructure is functionally relevant for regulating attentional bias toward negative interpersonal stimuli. © The Author 2016. Published by Oxford University Press.

Carbon Dioxide Separation with Supported Ionic Liquid Membranes

Energy Technology Data Exchange (ETDEWEB)

Luebke, D.R.; Ilconich, J.B.; Myers, C.R.; Pennline, H.W.

2007-04-01

Supported liquid membranes are a class of materials that allow the researcher to utilize the wealth of knowledge available on liquid properties as a direct guide in the development of a capture technology. These membranes also have the advantage of liquid phase diffusivities higher than those observed in polymeric membranes which grant proportionally greater permeabilities. The primary shortcoming of the supported liquid membranes demonstrated in past research has been the lack of stability caused by volatilization of the transport liquid. Ionic liquids, which possess high carbon dioxide solubility relative to light gases such as hydrogen, are an excellent candidate for this type of membrane since they have negligible vapor pressure and are not susceptible to evaporation. A study has been conducted evaluating the use of several ionic liquids, including 1-hexyl-3-methyl-imidazolium bis(trifuoromethylsulfonyl)imide, 1-butyl-3-methyl-imidazolium nitrate, and 1-ethyl-3-methyl-imidazolium sulfate in supported ionic liquid membranes for the capture of carbon dioxide from streams containing hydrogen. In a joint project, researchers at the University of Notre Dame lent expertise in ionic liquid synthesis and characterization, and researchers at the National Energy Technology Laboratory incorporated candidate ionic liquids into supports and evaluated the resulting materials for membrane performance. Initial results have been very promising with carbon dioxide permeabilities as high as 950 barrers and significant improvements in carbon dioxide/hydrogen selectivity over conventional polymers at 37C and at elevated temperatures. Results include a comparison of the performance of several ionic liquids and a number of supports as well as a discussion of innovative fabrication techniques currently under development.

The effects of neutron irradiation on the structure of carbon-carbon composites

International Nuclear Information System (INIS)

Burchell, T.D.; Eatherly, W.P.; Hollenberg, G. W.; Slagle, O.D.; Watson, R.D.

1991-01-01

In this paper irradiation behavior of carbon fibers and carbon-carbon composites are discussed in terms on simple microstructural models. Previous data are discussed in terms of these models. New data are presented for the irradiation-induced dimensional changes of selected carbon-carbon composites. The influence of fiber precursor on carbon- carbon irradiation performance is discussed

Electrochemical characteristics and microstructure of activated carbon powder supercapacitors for energy storage

International Nuclear Information System (INIS)

Gonsalves, T.C.; Faria, R.N.; Silva, F. M.; Vieira, L.S.; Casini, J.C.S.

2016-01-01

In recent years, extensive investigations have concentrated on the study and improvement of supercapacitors electrode materials. The electric devices produced with these materials are used for stored energy over time periods ranging from seconds to several days. The main factor determining the energy storage time of a supercapacitor is its self-discharge rate. This property concerns to the gradual decrease in the electric potential that occurs when the supercapacitor terminals are left unconnected to either a charging circuit or an electric load. Self-discharge is attenuated with a decrease in room temperature and lifetime is enhanced. This paper addresses this aspect and reports the results of a work carried out on a systematic study with supercapacitors with nominal capacitance of 1.0 rated at a DC potential of 5.5 V and 10.0 F at 2,7 V. The specific capacitance, internal resistance and self-discharge of commercial activated carbon electrode supercapacitors have been investigated. Specific capacitances were measured in this study using cyclic voltammetry (CV). Specific capacitances of 44.4 and 66.7 Fg-1 were determined for distinct carbon electrodes supercapacitors. Self-discharge were carried out at room temperature and close to the freezing point. Internal resistances of the supercapacitors were calculated using the discharge curve at room temperature. The microstructures of the electrode material have been investigated using scanning electron microscopy (SEM). (author)

Electrochemical characteristics and microstructure of activated carbon powder supercapacitors for energy storage

Energy Technology Data Exchange (ETDEWEB)

Gonsalves, T.C.; Faria, R.N. [Universidade de Sao Paulo (USP), SP (Brazil); Silva, F. M.; Vieira, L.S.; Casini, J.C.S., E-mail: julio.casini@ifro.edu.br [Instituto Federal de Educacao, Ciencia e Tecnologia de Rondonia (IFRO), Calama, RO (Brazil)

2016-07-01

In recent years, extensive investigations have concentrated on the study and improvement of supercapacitors electrode materials. The electric devices produced with these materials are used for stored energy over time periods ranging from seconds to several days. The main factor determining the energy storage time of a supercapacitor is its self-discharge rate. This property concerns to the gradual decrease in the electric potential that occurs when the supercapacitor terminals are left unconnected to either a charging circuit or an electric load. Self-discharge is attenuated with a decrease in room temperature and lifetime is enhanced. This paper addresses this aspect and reports the results of a work carried out on a systematic study with supercapacitors with nominal capacitance of 1.0 rated at a DC potential of 5.5 V and 10.0 F at 2,7 V. The specific capacitance, internal resistance and self-discharge of commercial activated carbon electrode supercapacitors have been investigated. Specific capacitances were measured in this study using cyclic voltammetry (CV). Specific capacitances of 44.4 and 66.7 Fg-1 were determined for distinct carbon electrodes supercapacitors. Self-discharge were carried out at room temperature and close to the freezing point. Internal resistances of the supercapacitors were calculated using the discharge curve at room temperature. The microstructures of the electrode material have been investigated using scanning electron microscopy (SEM). (author)

Investigation of altenative carbon materials for fuel-cell catalyst support

DEFF Research Database (Denmark)

Larsen, Mikkel Juul

In order to ensure high utilization of the catalyst material in a polymer electrolyte membrane fuel cell (PEMFC) it is usually fixed in the form of nanoparticles on a supporting material. The catalyst is platinum or a platinum alloy, and the commonly used support is carbon black (CB). Although...... structured carbon forms such as graphitized CBs, carbon nanotubes (CNTs), and carbon nanofibres (CNFs). This thesis concerns the investigation of an array of different materials which may prospec-tively replace the conventional materials used in the catalyst. The study comprised 13 carbon samples which...... nanotubes (GMWCNTs), and graphitized carbon nanofibre (CNF), while the Pt/C samples were platinized samples of some of the CNTs and CNFs (Pt/FWCNT, Pt/GMWCNT, and Pt/CNF, respectively) as well as two commercial Pt/CB reference catalysts. Comparative analyses have been performed in order to be able to assess...

High-performance carbon-coated ZnMn2O4 nanocrystallite supercapacitors with tailored microstructures enabled by a novel solution combustion method

Science.gov (United States)

Abdollahifar, Mozaffar; Huang, Sheng-Siang; Lin, Yu-Hsiang; Lin, Yan-Cheng; Shih, Bing-Yi; Sheu, Hwo-Shuenn; Liao, Yen-Fa; Wu, Nae-Lih

2018-02-01

Although ZnMn2O4 is widely studied as Li-ion battery anodes, it remains a challenge to tailor suitable microstructures of the oxide for supercapacitor applications. Carbon-coated ZnMn2O4 (C@ZMO) nanocrystallites showing high-performance pseudocapacitor behaviours in neutral aqueous electrolyte are for the first time successfully synthesised via a novel solution combustion process using polyethylene glycol as a multifunctional microstructure-directing agent. Controlling the molecular weight and amount of the polymer in the combustion solution enables the formation of highly-crystalline C@ZMO having substantially higher, by more than 5 folds, specific surface areas with mesoporous structures and conformal carbon coating via the one-pot synthesis process. The resulting C@ZMO supercapacitor electrodes in Na2SO4(aq) electrolyte exhibit ideal capacitive behaviours with specific capacitances up to 150 F g-1 and cycle stability showing no capacitance fade after 10,000 cycles at 60% of full capacity and >99% Coulombic efficiency. This study not only illustrates a new powerful synthesis route capable of producing conductive mesoporous crystalline oxide-based nanomaterials for energy storage applications but also reveals a new class of high-performance pseudocapacitive materials for neutral aqueous electrolytes.

Microstructure of wood charcoal prepared by flash heating

NARCIS (Netherlands)

Kurosaki, F; Ishimaru, K; Hata, T; Bronsveld, P; Kobayashi, E; Imamura, Y

2003-01-01

Carbonized wood prepared by flash heating at 800 degreesC for I h shows a different microstructure and surface chemical structure than char formed after slow heating at 4 degreesC/min to 800 degreesC for I h. Flash heating produces pores that are surrounded by aggregates of carbon structures 25 to

Transport of Carbonate Ions by Novel Cellulose Fiber Supported Solid Membrane

Directory of Open Access Journals (Sweden)

A. G. Gaikwad

2012-06-01

Full Text Available Transport of carbonate ions was explored through fiber supported solid membrane. A novel fiber supported solid membrane was prepared by chemical modification of cellulose fiber with citric acid, 2′2-bipyridine and magnesium carbonate. The factors affecting the permeability of carbonate ions such as immobilization of citric acid-magnesium metal ion -2′2-bipyridine complex (0 to 2.5 mmol/g range over cellulose fiber, carbon-ate ion concentration in source phase and NaOH concentration in receiving phase were investigated. Ki-netic of carbonate, sulfate, and nitrate ions was investigated through fiber supported solid membrane. Transport of carbonate ions with/without bubbling of CO2 (0 to 10 ml/min in source phase was explored from source to receiving phase. The novel idea is to explore the adsorptive transport of CO2 from source to receiving phase through cellulose fiber containing magnesium metal ion organic framework. Copyright © 2012 BCREC UNDIP. All rights reserved.Received: 25th November 2011; Revised: 17th December 2011; Accepted: 19th December 2011[How to Cite: A.G. Gaikwad. (2012. Transport of Carbonate Ions by Novel Cellulose Fiber Supported Solid Membrane. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (1: 49– 57.  doi:10.9767/bcrec.7.1.1225.49-57][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.1.1225.49-57 ] | View in 

Basic metal carbonate supported gold nanoparticles: enhanced performance in aerobic alcohol oxidation

NARCIS (Netherlands)

Yang, J.; Guan, Y.; Verhoeven, M.W.G.M.; Santen, van R.A.; Li, Can; Hensen, E.J.M.

2009-01-01

Gold nanoparticles supported by basic hydrozincite or bismuth carbonate are excellent catalysts for liquid-phase aerobic alcohol oxidation: the performance of a series of metal (Zn, Bi, Ce, La, Zr) carbonate supported gold catalysts depends strongly on the basicity of the support material.

In Situ Study of Phase Transformations during Non-Isothermal Tempering of Bainitic and Martensitic Microstructures

Directory of Open Access Journals (Sweden)

S. Hesamodin Talebi

2017-09-01

Full Text Available Phase transformations during non-isothermal tempering of bainitic or martensitic microstructures obtained after quenching of a medium-carbon low-alloy steel was studied. The microstructures correspond to different locations of an as-quenched large-sized forged ingot used as a die material in the automotive industry. High-resolution dilatometry experiments were conducted to simulate the heat treatment process, as well as to investigate different phenomena occurring during non-isothermal tempering. The microstructures were characterized using optical and scanning electron microscopy. Dilatometry analyses demonstrated that tempering behavior varied significantly from bainitic to martensitic microstructures. Retained austenite, which exists between bainitic ferrite sheaves, decomposes to lower bainite causing a remarkable volume increase. It was found that this decomposition finishes below 386 °C. By contrast, martensite tempering was accompanied with a volume decrease due to the decomposition of medium-carbon martensite to low carbon martensite and carbides.

The effect of heat treatment on microstructure evolution in artificially aged carbon nanotube/Al2024 composites synthesized by mechanical alloying

International Nuclear Information System (INIS)

Pérez-Bustamante, R.; Pérez-Bustamante, F.; Maldonado-Orozco, M.C.; Martínez-Sánchez, R.

2017-01-01

Although carbon nanotubes/aluminum (CNT/Al) composites are promising materials in the production of structural components, their mechanical behavior under overaging conditions has not been considered. In this paper the effect of CNTs on the microstructural and mechanical behavior of a 2024 aluminum alloy (Al2024) synthesized by mechanical alloying (MA) and powder metallurgy routes is discussed, as well as the effect of aging heat treatments at different temperatures and aging times. The mechanical behavior of composites was screened by hardness measurements as function of aging time. After 96 h of aging time, composites showed mechanical stability in their hardness performance. Images from transmission electron microscopy showed that the mechanical stability of composites was due to a homogeneous dispersion of CNTs in the aluminum matrix and a subsequent alteration in the kinetics of precipitation is due to their presence in the aluminum matrix. Even though strengthening precipitation took place during aging, this was not the main strengthening mechanism observed in composites. - Highlights: • Dispersion of carbon nanotubes during mechanical alloying • Microstructural evolution observed by HRTEM. • Mechanical performance evaluated through micro-hardness test. • Increased mechanical performance at high working temperatures • Acceleration of kinetics of precipitation due to CNTs, and milling conditions

The effect of heat treatment on microstructure evolution in artificially aged carbon nanotube/Al2024 composites synthesized by mechanical alloying

Energy Technology Data Exchange (ETDEWEB)

Pérez-Bustamante, R. [Centro de Investigación en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnología, Miguel de Cervantes No.120, C.P. 31109 Chihuahua, Chih. (Mexico); Pérez-Bustamante, F. [Universidad Autónoma de Chihuahua (UACH), Facultad de Ciencias Químicas, Circuito No. 1 Nuevo Campus Universitario, C.P. 31125 Chihuahua, Chih. (Mexico); Maldonado-Orozco, M.C. [Universidad Autónoma de Chihuahua (UACH), Facultad de Ingeniería, Circuito No. 1 Nuevo Campus Universitario, C.P. 31125 Chihuahua, Chih. (Mexico); Martínez-Sánchez, R., E-mail: roberto.martinez@cimav.edu.mx [Centro de Investigación en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnología, Miguel de Cervantes No.120, C.P. 31109 Chihuahua, Chih. (Mexico)

2017-04-15

Although carbon nanotubes/aluminum (CNT/Al) composites are promising materials in the production of structural components, their mechanical behavior under overaging conditions has not been considered. In this paper the effect of CNTs on the microstructural and mechanical behavior of a 2024 aluminum alloy (Al2024) synthesized by mechanical alloying (MA) and powder metallurgy routes is discussed, as well as the effect of aging heat treatments at different temperatures and aging times. The mechanical behavior of composites was screened by hardness measurements as function of aging time. After 96 h of aging time, composites showed mechanical stability in their hardness performance. Images from transmission electron microscopy showed that the mechanical stability of composites was due to a homogeneous dispersion of CNTs in the aluminum matrix and a subsequent alteration in the kinetics of precipitation is due to their presence in the aluminum matrix. Even though strengthening precipitation took place during aging, this was not the main strengthening mechanism observed in composites. - Highlights: • Dispersion of carbon nanotubes during mechanical alloying • Microstructural evolution observed by HRTEM. • Mechanical performance evaluated through micro-hardness test. • Increased mechanical performance at high working temperatures • Acceleration of kinetics of precipitation due to CNTs, and milling conditions.

Numerical evaluation of oxide growth in metallic support microstructures of Solid Oxide Fuel Cells and its influence on mass transport

DEFF Research Database (Denmark)

Reiss, Georg; Frandsen, Henrik Lund; Persson, Åsa Helen

2015-01-01

is evaluated by determining an effective diffusion coefficient and the equivalent electrical area specific resistance (ASR) due to diffusion over time. It is thus possible to assess the applicability (in terms of corrosion behaviour) of potential metallic supports without costly long-term experiments......-temperature corrosion theory, and the required model parameters can be retrieved by standard corrosion weight gain measurements. The microstructure is reconstructed from X-ray computed tomography, and converted into a computational grid. The influence of the changing microstructure on the fuel cell performance...

Phase-field modelling of microstructure formation during the solidification of continuously cast low carbon and HSLA steels

Science.gov (United States)

Böttger, B.; Apel, M.; Santillana, B.; Eskin, D. G.

2012-07-01

Cracking in continuous casting of steels has been one of the main problems for decades. Many of the cracks that occur during solidification are hot tears. To better understand the factors leading to this defect, microstructure formation is simulated for a low carbon (LCAK) and two high strength low alloyed (HSLA) steel grades during the initial stage of the process where the first solidified shell is formed inside the mould and where breakouts typically occur. 2D simulation is performed using the multiphase-field software MICRESS [1], which is coupled to the thermodynamic database TCFE6 [2] and the mobility database MOB2 [2], taking into account all elements which may have a relevant effect on the mechanical properties and structure formation during or subsequent to solidification. The use of a moving-frame boundary condition allows travelling through the entire solidification history starting from the slab surface, and tracking the morphology changes during growth of the shell. A heterogeneous nucleation model is included to permit the description of morphological transitions between the initial solidification and the subsequent columnar growth region. Furthermore, a macroscopic one-dimensional temperature solver is integrated to account for the transient and nonlinear temperature field during the initial stage of continuous casting. The external heat flux boundary conditions for this process were derived from thermal process data of the industrial slab caster. The simulation results for the three steel grades have been validated by thickness measurements of breakout shells and microstructure observation of the corresponding grades. Furthermore, the primary dendrite spacing has been measured across the whole thickness of the shell and compared with the simulated microstructures. Significant microstructure differences between the steel grades are discussed and correlated with their hot-cracking behavior.

Phase-field modelling of microstructure formation during the solidification of continuously cast low carbon and HSLA steels

International Nuclear Information System (INIS)

Böttger, B; Apel, M; Santillana, B; Eskin, D G

2012-01-01

Cracking in continuous casting of steels has been one of the main problems for decades. Many of the cracks that occur during solidification are hot tears. To better understand the factors leading to this defect, microstructure formation is simulated for a low carbon (LCAK) and two high strength low alloyed (HSLA) steel grades during the initial stage of the process where the first solidified shell is formed inside the mould and where breakouts typically occur. 2D simulation is performed using the multiphase-field software MICRESS, which is coupled to the thermodynamic database TCFE6 and the mobility database MOB2, taking into account all elements which may have a relevant effect on the mechanical properties and structure formation during or subsequent to solidification. The use of a moving-frame boundary condition allows travelling through the entire solidification history starting from the slab surface, and tracking the morphology changes during growth of the shell. A heterogeneous nucleation model is included to permit the description of morphological transitions between the initial solidification and the subsequent columnar growth region. Furthermore, a macroscopic one-dimensional temperature solver is integrated to account for the transient and nonlinear temperature field during the initial stage of continuous casting. The external heat flux boundary conditions for this process were derived from thermal process data of the industrial slab caster. The simulation results for the three steel grades have been validated by thickness measurements of breakout shells and microstructure observation of the corresponding grades. Furthermore, the primary dendrite spacing has been measured across the whole thickness of the shell and compared with the simulated microstructures. Significant microstructure differences between the steel grades are discussed and correlated with their hot-cracking behavior.

A comparison of alumina, carbon and carbon-covered alumina as support for Ni-Mo-F additives: gas oil hydroprocessing studies

Energy Technology Data Exchange (ETDEWEB)

Boorman, P.M.; Kydd, R.A.; Sorensen, T.S.; Chong, K.; Lewis, J.M.; Bell, W.S. (University of Calgary, Calgary, AB (Canada). Dept. of Chemistry)

1991-01-01

Catalysts with 3 wt% NiO, 15 wt% MoO{sub 3} and 0-6.9 nominal wt% fluoride supported on alumina, carbon and carbon-covered alumina were studied to examine the role of fluoride and the influence of the support on hydroprocessing on Alberta gas oil. Experiments were carried out in a batch reactor at 410{degree}C and 6.9 MPa initial H{sub 2} pressure. It was found that fluoride promotion enhances cracking and hydrogenation reactions resulting in decreased aromatic and sulphur contents in the gas oil. The promotion is dependent on the type of support and is related to the strength of the fluoride-support interaction and the accessibility of the fluoride to the surface hydroxyl groups on the support. A maximum in activity at 3.6 wt% fluoride was observed for the alumina-supported catalysts whereas higher loadings of fluoride were required for carbon-covered alumina-supported catalysts to see an improvement over their carbon-supported counterparts. However, the carbon-covered alumina-supported catalysts seem to have a lower propensity for coke deposition than their alumina counterparts. 27 refs., 1 fig., 4 tabs.

A comparison of alumina, carbon and carbon-covered alumina as supports for Ni-Mo-F additives: gas oil hydroprocessing studies

Energy Technology Data Exchange (ETDEWEB)

Boorman, P.M.; Kydd, R.A.; Sorensen, T.S.; Chong, K.; Lewis, J.M.; Bell, W.S. (Calgary Univ., AB (Canada). Dept. of Chemistry)

1992-01-01

Catalysts with 3 wt% NiO, 15 wt% MoO{sub 3} and 0-6.9 nominal wt% fluoride supported on alumina, carbon and carbon-covered alumina were studied to examine the role of fluoride and the influence of the support on hydroprocessing on Alberta gas oil. Experiments were carried out in a batch reactor at 410{sup o}C and 6.9 MPa initial H{sub 2} pressure. It was found that fluoride promotion enhances cracking and hydrogenation reactions resulting in decreased aromatic and sulphur contents in the gas oil. The promotion is dependent on the type of support and is related to the strength of the fluoride-support interaction and the accessibility of the fluoride to the surface hydroxyl groups on the support. A maximum in activity at 3.6 wt% fluoride was observed for the alumina-supported catalysts whereas higher loadings of fluoride were required for carbon-covered alumina-supported catalysts to see an improvement over their carbon supported counterparts. However, the carbon-covered alumina supported catalysts seem to have a lower propensity for coke deposition than their alumina counterparts. (author).

Study on microstructure and mechanical characteristics of low-carbon steel and ferritic stainless steel joints

Energy Technology Data Exchange (ETDEWEB)

Sarkari Khorrami, Mahmoud; Mostafaei, Mohammad Ali; Pouraliakbar, Hesam, E-mail: hpouraliakbar@alum.sharif.edu; Kokabi, Amir Hossein

2014-07-01

In this work, examinations on the microstructure and mechanical properties of plain carbon steel and AISI 430 ferritic stainless steel dissimilar welds are carried out. Welding is conducted in both autogenous and using ER309L austenitic filler rod conditions through gas tungsten arc welding process. The results indicate that fully-ferritic and duplex ferritic–martensitic microstructures are formed for autogenous and filler-added welds, respectively. Carbide precipitation and formation of martensite at ferrite grain boundaries (intergranular martensite) as well as grain growth occur in the heat affected zone (HAZ) of AISI 430 steel. It is found that weld heat input can strongly affect grain growth phenomenon along with the amount and the composition of carbides and intergranular martensite. Acquired mechanical characteristics of weld in the case of using filler metal are significantly higher than those of autogenous one. Accordingly, ultimate tensile strength (UTS), hardness, and absorbed energy during tensile test of weld metal are increased from 662 MPa to 910 MPa, 140 Hv to 385 Hv, and 53.6 J m{sup −3} to 79 J m{sup −3}, respectively by filler metal addition. From fracture surfaces, predominantly ductile fracture is observed in the specimen welded with filler metal while mainly cleavage fracture occurs in the autogenous weld metal.

Computational modeling of elastic properties of carbon nanotube/polymer composites with interphase regions. Part I: Micro-structural characterization and geometric modeling

KAUST Repository

Han, Fei

2014-01-01

A computational strategy to predict the elastic properties of carbon nanotube-reinforced polymer composites is proposed in this two-part paper. In Part I, the micro-structural characteristics of these nano-composites are discerned. These characteristics include networks/agglomerations of carbon nanotubes and thick polymer interphase regions between the nanotubes and the surrounding matrix. An algorithm is presented to construct three-dimensional geometric models with large amounts of randomly dispersed and aggregated nanotubes. The effects of the distribution of the nanotubes and the thickness of the interphase regions on the concentration of the interphase regions are demonstrated with numerical results. © 2013 Elsevier B.V. All rights reserved.

Fatigue crack growth behaviors in hot-rolled low carbon steels: A comparison between ferrite–pearlite and ferrite–bainite microstructures

International Nuclear Information System (INIS)

Guan, Mingfei; Yu, Hao

2013-01-01

The roles of microstructure types in fatigue crack growth behaviors in ferrite–pearlite steel and ferrite–bainite steel were investigated. The ferrite–bainite dual-phase microstructure was obtained by intermediate heat treatment, conducted on ferrite–pearlite hot-rolled low carbon steel. This paper presents the results from investigation using constant stress-controlled fatigue tests with in-situ scanning electron microscopy (SEM), fatigue crack growth (FCG) rate tests, and fatigue fractography analysis. Microscopy images arrested by in-situ SEM showed that the fatigue crack propagation in F–P steel could become unstable more ealier compared with that in F–B steel. The fatigue cracks in ferrite–pearlite were more tortuous and could propagate more freely than that in ferrite–bainite microstructures. However, frequent crack branching were observed in ferrite–bainite steel and it indicated that the second hard bainite phase effectively retarded the crack propagation. The variation of FCG rate (da/dN) with stress intensity factor range (ΔK) for F–P and F–B steels was discussed within the Paris region. It was shown that FCG rate of F–P steel was higher than that of F–B steel. Moreover, the fatigue fracture surface analysis proved that grain boundaries could also play a role in the resistance of crack propagation.

Microstructural characteristics of DU-xMo alloys with x = 7-12 wt%

International Nuclear Information System (INIS)

Burkes, Douglas E.; Hartmann, Thomas; Prabhakaran, Ramprashad; Jue, J.-F.

2009-01-01

Microstructural, phase, and impurity analyses of six depleted uranium-molybdenum alloys were obtained using optical metallography, X-ray diffraction, and carbon/nitrogen/oxygen determination. Uranium-molybdenum alloy foils are currently under investigation for the conversion of high-power research reactors using high-enriched uranium fuel to accommodate the use of low-enriched uranium fuel. Understanding basic microstructural behavior of these foils is an important consideration in determining the impact of fabrication processes and in anticipating performance of the foils in a reactor. Average grain diameter decreased with increasing molybdenum content. Lattice parameter decreased with increasing molybdenum content, and no significant degree of phase decomposition or crystallographic ordering was caused by processing and post-processing conditions employed in this study. Impurity concentration, specifically carbon, inhibited the degree of microstructural recrystallization but did not appear to impact other microstructural traits, such as γ-phase retention or lattice parameter.

Nano carbon supported platinum catalyst interaction behavior with perfluorosulfonic acid ionomer and their interface structures

DEFF Research Database (Denmark)

Andersen, Shuang Ma

2016-01-01

behavior of Nafion ionomer on platinized carbon nano fibers (CNFs), carbon nano tubes (CNTs) and amorphous carbon (Vulcan). The interaction is affected by the catalyst surface oxygen groups as well as porosity. Comparisons between the carbon supports and platinized equivalents are carried out. It reveals......The interaction between perfluorosulfonic acid ionomer and supported platinum catalyst is essential. It directly influences platinum accessibility, stability of carbon support and platinum, proton conductivity and electron conductivity in an electrode. In this study, we compare the adsorption...... that the platinization step modifies the surface nature of the carbon supports in terms of specific surface area, crystallinity and especially porosity; therefore, ionomer adsorption over carbon is not always representative for the ionomer adsorption over carbon supported catalyst, though indicative. Moreover...

Radiofrequency cold plasma nitrided carbon steel: Microstructural and micromechanical characterizations

International Nuclear Information System (INIS)

Bouanis, F.Z.; Bentiss, F.; Bellayer, S.; Vogt, J.B.; Jama, C.

2011-01-01

Highlights: → C38 carbon steel samples were plasma nitrided using a radiofrequency (rf) nitrogen plasma discharge. → RF plasma treatment enables nitriding for non-heated substrates. → The morphological and chemical analyses show the formation of a uniform thickness on the surface of the nitrided C38 steel. → Nitrogen plasma active species diffuse into the samples and lead to the formation of Fe x N. → The increase in microhardness values for nitrided samples with plasma processing time is interpreted by the formation of a thicker nitrided layer on the steel surface. - Abstract: In this work, C38 carbon steel was plasma nitrided using a radiofrequency (rf) nitrogen plasma discharge on non-heated substrates. General characterizations were performed to compare the chemical compositions, the microstructures and hardness of the untreated and plasma treated surfaces. The plasma nitriding was carried out on non-heated substrates at a pressure of 16.8 Pa, using N 2 gas. Surface characterizations before and after N 2 plasma treatment were performed by means of the electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS) and Vickers microhardness measurements. The morphological and chemical analysis showed the formation of a uniform structure on the surface of the nitrided sample with enrichment in nitrogen when compared to untreated sample. The thickness of the nitride layer formed depends on the treatment time duration and is approximately 14 μm for 10 h of plasma treatment. XPS was employed to obtain chemical-state information of the plasma nitrided steel surfaces. The micromechanical results show that the surface microhardness increases as the plasma-processing time increases to reach, 1487 HV 0.005 at a plasma processing time of 8 h.

Radiofrequency cold plasma nitrided carbon steel: Microstructural and micromechanical characterizations

Energy Technology Data Exchange (ETDEWEB)

Bouanis, F.Z. [Universite Lille Nord de France, F-59000 Lille (France); Unite Materiaux et Transformations (UMET), Ingenierie des Systemes Polymeres, CNRS UMR 8207, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Bentiss, F. [Laboratoire de Chimie de Coordination et d' Analytique, Faculte des Sciences, Universite Chouaib Doukkali, B.P. 20, M-24000 El Jadida (Morocco); Bellayer, S.; Vogt, J.B. [Universite Lille Nord de France, F-59000 Lille (France); Unite Materiaux et Transformations (UMET), Ingenierie des Systemes Polymeres, CNRS UMR 8207, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France); Jama, C., E-mail: charafeddine.jama@ensc-lille.fr [Universite Lille Nord de France, F-59000 Lille (France); Unite Materiaux et Transformations (UMET), Ingenierie des Systemes Polymeres, CNRS UMR 8207, ENSCL, BP 90108, F-59652 Villeneuve d' Ascq Cedex (France)

2011-05-16

Highlights: {yields} C38 carbon steel samples were plasma nitrided using a radiofrequency (rf) nitrogen plasma discharge. {yields} RF plasma treatment enables nitriding for non-heated substrates. {yields} The morphological and chemical analyses show the formation of a uniform thickness on the surface of the nitrided C38 steel. {yields} Nitrogen plasma active species diffuse into the samples and lead to the formation of Fe{sub x}N. {yields} The increase in microhardness values for nitrided samples with plasma processing time is interpreted by the formation of a thicker nitrided layer on the steel surface. - Abstract: In this work, C38 carbon steel was plasma nitrided using a radiofrequency (rf) nitrogen plasma discharge on non-heated substrates. General characterizations were performed to compare the chemical compositions, the microstructures and hardness of the untreated and plasma treated surfaces. The plasma nitriding was carried out on non-heated substrates at a pressure of 16.8 Pa, using N{sub 2} gas. Surface characterizations before and after N{sub 2} plasma treatment were performed by means of the electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS) and Vickers microhardness measurements. The morphological and chemical analysis showed the formation of a uniform structure on the surface of the nitrided sample with enrichment in nitrogen when compared to untreated sample. The thickness of the nitride layer formed depends on the treatment time duration and is approximately 14 {mu}m for 10 h of plasma treatment. XPS was employed to obtain chemical-state information of the plasma nitrided steel surfaces. The micromechanical results show that the surface microhardness increases as the plasma-processing time increases to reach, 1487 HV{sub 0.005} at a plasma processing time of 8 h.

Characterization of a surface modified carbon cryogel and a carbon supported Pt catalyst

Directory of Open Access Journals (Sweden)

BILJANA M. BABIĆ

2007-08-01

Full Text Available A carbon cryogel, synthesized by carbonization of a resorcinol/formaldehyde cryogel and oxidized in nitric acid, was used as catalyst support for Pt nano-particles. The Pt/C catalyst was prepared by a modified polyol synthesis method in an ethylene glycol (EG solution. Characterization by nitrogen adsorption showed that the carbon cryogel support and the Pt/C catalyst were mesoporous materials with high specific surface areas (SBET > 400 m2 g-1 and large mesoporous volumes. X-Ray diffraction of the catalyst demonstrated the successful reduction of the Pt precursor to metallic form. TEM Images of the Pt/C catalyst and Pt particle size distribution showed that the mean Pt particle size was about 3.3 nm. Cyclic voltammetry (CV experiments at various scan rates (from 2 to 200 mV s-1 were performed in 0.5 mol dm-3 HClO4 solution. The large capacitance of the oxidized carbon cryogel electrode, which arises from a combination of the double-layer capacitance and pseudocapacitance, associated with the participation of surface redox-type reactions was demonstrated. For the oxidized carbon cryogel, the total specific capacitance determined by 1/C vs. ν0.5 extrapolation method was found to be 386 F g-1. The hydrogen oxidation reaction at the investigated Pt/C catalyst proceeded as an electrochemically reversible, two-electron direct discharge reaction.

Carbon price and wind power support in Denmark

International Nuclear Information System (INIS)

Gavard, Claire

2016-01-01

This paper aims at characterizing the conditions of wind power deployment in order to infer a carbon price level that would provide wind power with comparable advantage over fossil fuel technologies as effective wind support policies. The analysis is conducted on Denmark after the electricity market liberalization. Probit and tobit techniques are employed to take account of a potential threshold effect. I find that the level and type of the support policy are the dominant drivers of deployment. A feed-in tariff significantly brings more wind power in than a premium policy. The additional capacity installed monthly increases by more than 1 MW for each additional €/MWh of support. This is compared to the effect of the electricity price, investment cost, interest rate and general economic activity. If the policy is a premium, I find that 23€/MWh of support in addition to electricity price is needed to observe the connection of new turbines to the grid with a 0.5 probability. I convert this support level into a carbon price of 27€/ton if wind power competes with coal, and 48€/t if it competes with gas. - Highlights: •I analyze wind power development in Denmark between 2000 and 2010. •I use probit and tobit techniques to assess the determinants of this deployment. •The level and policy type of wind power support are the main drivers. •I deduct the critical level of premium needed to trigger wind power. •I convert this into an equivalent carbon price and I find that it is below 50€/ton.

Preparation of supported electrocatalyst comprising multiwalled carbon nanotubes

Science.gov (United States)

Wu, Gang; Zelenay, Piotr

2013-08-27

A process for preparing a durable non-precious metal oxygen reduction electrocatalyst involves heat treatment of a ball-milled mixture of polyaniline and multiwalled carbon nanotubes in the presence of a Fe species. The catalyst is more durable than catalysts that use carbon black supports. Performance degradation was minimal or absent after 500 hours of operation at constant cell voltage of 0.40 V.

Microstructure and mechanical properties of in situ casting TiC/Ti6Al4V composites through adding multi-walled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Ya, Bin; Zhou, Bingwen; Yang, Hongshuo; Huang, Bingkun; Jia, Fei; Zhang, Xingguo, E-mail: zxgwj@dlut.edu.cn

2015-07-15

Highlights: • Adding MWCNTs in situ casting fabricating TiC/Ti6Al4V composites is first reported. • The solidification process of in situ casting TiC/Ti6Al4V composites is discussed. • Microstructure shows remarkable correlations with adding MWCNTS. • Strength and plasticity show remarkable correlations with adding MWCNTs. - Abstract: In this study, multi-walled carbon nanotubes (MWCNTs) were added as carbon sources to fabricate in situ casting TiC/Ti6Al4V (TC4) composites. The effects of MWCNTs on the microstructure and mechanical properties are studied. The composites are analyzed by X-ray diffraction, field-emission scanning electron microscope and electron probe microanalysis. The fracture behavior of TiC/TC4 composites are also studied. Smaller size of TiC particles and grain compared with TC4-graphite composites can be observed. The tensile strength of TC4-MWCNTs composites is about 1110.1 MPa, which is higher than that of TC4-graphite composites, about 1003.6 MPa. Fracture behavior also was changed by adding MWCNTs in situ casting TiC/TC4 composites.

Electrophoretic deposition of carbon nanotubes on a carbon fiber surface with different index graphitization

International Nuclear Information System (INIS)

Almeida, E.C.; Baldan, M.R.; Ferreira, N.G.; Edwards, E.R.

2009-01-01

Full text: The purpose of this work is to examine the electrophoretic deposition of carbon nanotubes powder on carbon fibers, produced at different heat treatments temperatures. Besides, a systematic study of the effects of graphitization index from substrate on the structure and morphology of CNTs has been available. Carbon fibers were produced from polyacrylonitrile at three different heat treatments temperatures, 1000, 1500 and 2000 deg C. The carbon fibers microstructure or its graphitization index may be controlled by the heat treatments temperatures. The electrophoretic deposition of carbon nanotubes was obtained with the powder of carbon nanotubes dispersed in water by ultrasonication to obtain dispersions of 0.05 mg/mL. The carbon fibers were immersed in the nanotube dispersion, and a positive potential of 10 V/cm was applied. Morphology and microstructure of carbon nanotubes on carbon fibers were obtained by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. (author)

Graphitic Carbon Nitride as a Catalyst Support in Fuel Cells and Electrolyzers

International Nuclear Information System (INIS)

Mansor, Noramalina; Miller, Thomas S.; Dedigama, Ishanka; Jorge, Ana Belen; Jia, Jingjing; Brázdová, Veronika; Mattevi, Cecilia; Gibbs, Chris; Hodgson, David; Shearing, Paul R.; Howard, Christopher A.; Corà, Furio; Shaffer, Milo; Brett, Daniel J.L.

2016-01-01

Highlights: • Graphitic carbon nitride (gCN) describes many materials with different structures. • gCNs can exhibit excellent mechanical, chemical and thermal resistance. • A major obstacle for pure gCN catalyst supports is limited electronic conductivity. • Composite/Hybrid gCN structures show excellent performance as catalyst supports. • gCNs have great potential for use in fuel calls and water electrolyzers. - Abstract: Electrochemical power sources, such as polymer electrolyte membrane fuel cells (PEMFCs), require the use of precious metal catalysts which are deposited as nanoparticles onto supports in order to minimize their mass loading and therefore cost. State-of-the-art/commercial supports are based on forms of carbon black. However, carbon supports present disadvantages including corrosion in the operating fuel cell environment and loss of catalyst activity. Here we review recent work examining the potential of different varieties of graphitic carbon nitride (gCN) as catalyst supports, highlighting their likely benefits, as well as the challenges associated with their implementation. The performance of gCN and hybrid gCN-carbon materials as PEMFC electrodes is discussed, as well as their potential for use in alkaline systems and water electrolyzers. We illustrate the discussion with examples taken from our own recent studies.

Allotropic Carbon Nanoforms as Advanced Metal-Free Catalysts or as Supports

Directory of Open Access Journals (Sweden)

Hermenegildo Garcia

2014-01-01

Full Text Available This perspective paper summarizes the use of three nanostructured carbon allotropes as metal-free catalysts (“carbocatalysts” or as supports of metal nanoparticles. After an introductory section commenting the interest of developing metal-free catalysts and main features of carbon nanoforms, the main body of this paper is focused on exemplifying the opportunities that carbon nanotubes, graphene, and diamond nanoparticles offer to develop advanced catalysts having active sites based on carbon in the absence of transition metals or as large area supports with special morphology and unique properties. The final section provides my personal view on future developments in this field.

Microstructural characteristics of Al-alloyed austempered ductile irons

International Nuclear Information System (INIS)

Kiani-Rashid, A.R.; Edmonds, D.V.

2009-01-01

Microstructural development after austempering ductile irons containing 0.48% and 4.88%Al has been studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental irons were made by green sand casting and gravity die casting. After austenitising at 920 deg. C for 90 min, an austempering treatment at 400 deg. C for times up to 100 min resulted in microstructures consisting of carbide-free bainitic ferrite with considerable amounts of high carbon retained austenite.

Microstructural properties of non-supported microporous ceramic membrane top-layers obtained by the sol-gel process

NARCIS (Netherlands)

de Lange, Rob; de Lange, R.S.A.; Hekkink, J.H.A.; Hekkink, J.H.A.; Keizer, Klaas; Burggraaf, Anthonie; Burggraaf, A.J.

1996-01-01

Dried and calcined non-supported membrane top-layers of SiO2, SiO2/TiO2, SiO2/ZrO2 (10, 20 and 30 mol% TiO2 and ZrO2, respectively) and SiO2/Al2O3 (10 mol% AlO1.5) were prepared using acid catalyzed hydrolysis and condensation of alkoxides in ethanol. The microstructure was determined using nitrogen

Microstructural Properties and HDS Activity of CoMo Catalysts Supported on Activated Carbon, Al2O3, ZrO2 and TiO2

Czech Academy of Sciences Publication Activity Database

Soukup, Karel; Procházka, Martin; Kaluža, Luděk

2015-01-01

Roč. 43, č. 2015 (2015), s. 841-846 ISSN 1974-9791. [International Conference on Chemical and Process Engineering - ICheaP12 /12./. Milano, 19.05.2015-22.05.2015] R&D Projects: GA ČR GAP106/11/0902 Institutional support: RVO:67985858 Keywords : CoMo catalysts * surface area * activated carbon Subject RIV: CF - Physical ; Theoretical Chemistry

Effect of Deformation Temperature on Microstructure Evolution and Mechanical Properties of Low-Carbon High-Mn Steel

Directory of Open Access Journals (Sweden)

Adam Grajcar

2018-01-01

Full Text Available This work addresses the influence of deformation temperature in a range from −40°C to 200°C on the microstructure evolution and mechanical properties of a low-carbon high-manganese austenitic steel. The temperature range was chosen to cope at the time during sheet processing or car crash events. Experimental results show that yield stress and ultimate tensile strength gradually deteriorate with an increase in the tensile testing temperature. The dominant mechanism responsible for the strain hardening of steel changes as a function of deformation temperature, which is related to stacking fault energy (SFE changes. When the deformation temperature rises, twinning decreases while a role of dislocation slip increases.

A Silicon detector system on carbon fiber support at small radius

International Nuclear Information System (INIS)

Johnson, Marvin E.

2004-01-01

The design of a silicon detector for a p(bar p) collider experiment will be described. The detector uses a carbon fiber support structure with sensors positioned at small radius with respect to the beam. A brief overview of the mechanical design is given. The emphasis is on the electrical characteristics of the detector. General principles involved in grounding systems with carbon fiber structures will be covered. The electrical characteristics of the carbon fiber support structure will be presented. Test results imply that carbon fiber must be regarded as a conductor for the frequency region of interest of 10 to 100 MHz. No distinction is found between carbon fiber and copper. Performance results on noise due to pick-up through the low mass fine pitch cables carrying the analogue signals and floating metal is discussed

Micro-structural evolution and biomineralization behavior of carbon nanofiber/bioactive glass composites induced by precursor aging time.

Science.gov (United States)

Jia, Xiaolong; Tang, Tianhong; Cheng, Dan; Zhang, Cuihua; Zhang, Ran; Cai, Qing; Yang, Xiaoping

2015-12-01

Bioactive glass (BG)-containing carbon nanofibers (CNFs) are promising orthopaedic biomaterials. Herein, CNF composites were produced from electrospinning of polyacrylonitrile (PAN)/BG sol-gel precursor solution, followed by carbonization. Choosing 58S-type BG (mol%: 58.0% SiO2-26.3% CaO-15.7% P2O5) as the model, micro-structural evolution of CNF/BG composites was systematically evaluated in relating to aging times of BG precursor solution. With aging time prolonging, BG precursors underwent morphological changes from small sol clusters with loosely and randomly branched structure to highly crosslinked Si-network structure, showing continuous increase in solution viscosity. BG precursor solution with low viscosity could mix well with PAN solution, resulting in CNF composite with homogeneously distributed BG component. Whereas, BG precursor gel with densely crosslinked Si-network structure led to uneven distribution of BG component along final CNFs due to its significant phase separation from PAN component. Meanwhile, BG nanoparticles in CNFs demonstrated micro-structural evolution that they transited from weak to strong crystal state along with longer aging time. Biomineralization in simulated body fluid and in vitro osteoblasts proliferation were then applied to determine the bioactivity of CNF/BG composites. CNF/BG composites prepared from shorter aging time could induce both faster apatite deposition and cell proliferation rate. It was suggested weakly crystallized BG nanoparticles along CNFs dissolved fast and was able to provide numerous nucleation sites for apatite deposition, which also favored the proliferation of osteoblasts cells. Aging time could thus be a useful tool to regulate the biological features of CNF/BG composites. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis of SiC microstructures in Si technology by high dose carbon implantation: Etch-stop properties

International Nuclear Information System (INIS)

Serre, C.; Perez-Rodriguez, A.; Romano-Rodriguez, A.; Calvo-Barrio, L.; Morante, J.R.; Esteve, J.; Acero, M.C.; Skorupa, W.; Koegler, R.

1997-01-01

The use of high dose carbon ion implantation in Si for the production of membranes and microstructures is investigated. Si wafers were implanted with carbon doses of 10 17 and 5 x 10 17 cm -2 , at an energy of 300 keV and a temperature of 500 C. The structural analysis of these samples revealed the formation of a highly stable buried layer of crystalline β-SiC precipitates aligned with the Si matrix. The etch-stop properties of this layer have been investigated using tetramethyl-ammonium hydroxide as etchant solution. Secondary ion mass spectrometry measurements performed on the etched samples have allowed an estimate of the minimum dose needed for obtaining an etch-stop layer to a value in the range 2 to 3 x 10 17 ions/cm 2 . This behavior has been explained assuming the existence of a percolation process in a SiC/Si binary system. Finally, very thin crystalline membranes and self-standing structures with average surface roughness in the range 6 to 7 nm have been obtained

Piezoelectric Microstructured Fibers via Drawing of Multimaterial Preforms.

Science.gov (United States)

Lu, Xin; Qu, Hang; Skorobogatiy, Maksim

2017-06-06

We demonstrate planar laminated piezoelectric generators and piezoelectric microstructured fibers based on BaTiO 3 -polyvinylidene and carbon-loaded-polyethylene materials combinations. The laminated piezoelectric generators were assembled by sandwiching the electrospun BaTiO 3 -polyvinylidene mat between two carbon-loaded-polyethylene films. The piezoelectric microstructured fiber was fabricated via drawing of the multilayer fiber preform, and features a swissroll geometry that have ~10 alternating piezoelectric and conductive layers. Both piezoelectric generators have excellent mechanical durability, and could retain their piezoelectric performance after 3 day's cyclic bend-release tests. Compared to the laminated generators, the piezoelectric fibers are advantageous as they could be directly woven into large-area commercial fabrics. Potential applications of the proposed piezoelectric fibers include micro-power-generation and remote sensing in wearable, automotive and aerospace industries.

Failure Modes of a Unidirectional Ultra-High-Modulus Carbon-Fiber/Carbon-Matrix Composite

National Research Council Canada - National Science Library

Zaldivar, R

1998-01-01

The objective of this study was to observe the effects of various microstructural features on the in situ, room-temperature tensile fracture behavior of an ultra-high-modulus, unidirectional carbon/carbon (C/C...

Microstructure and wear behavior of austempered high carbon high silicon steel

Directory of Open Access Journals (Sweden)

Acharya Palaksha

2018-01-01

Full Text Available In the present investigation, the influence of austempering temperature and time on the microstructure and dry sliding wear behavior of high silicon steel was studied. The test specimens were initially austenitised at 900°C for 30 minutes, thereafter austempered at various temperatures 280°C, 360°C and 400°C, for varying duration from 30 to 120 minutes. These samples after austempering heat treatment were subsequently air cooled to room temperature, to generate typical ausferritic microstructures and then correlated with the wear property. The test outcomes demonstrate the slight increase in specific wear rate with increase in both austempering temperature and time. Specific wear rate was found to be minimum at an austempering temperature of 280°C, that exhibits lower bainite microstructure with high hardness, on the other hand specific wear rate was found to be slightly high at increased austempering temperatures at 360°C and 400°C, due to the upper bainite structure that offered lower hardness to the matrix. The sample austempered at 280°C for 30 minutes offered superior wear resistance when compared to other austempering conditions, mainly due to the presence of fine acicular bainitic ferrite along with stabilized retained austenite and also some martensite in the microstructure.

Processing parameters investigation for the fabrication of self-supported and freeform polymeric microstructures using ultraviolet-assisted three-dimensional printing

International Nuclear Information System (INIS)

Farahani, R D; Lebel, L L; Therriault, D

2014-01-01

Ultraviolet-assisted three-dimensional (3D) printing (UV-3DP) was used to manufacture photopolymer-based microdevices with 3D self-supported and freeform features. The UV-3DP technique consists of the robotized deposition of extruded filaments, which are rapidly photopolymerized under UV illumination during the deposition process. This paper systematically studies the processing parameters of the UV-3DP technique using two photo-curable polymers and their associated nanocomposite materials. The main processing parameters including materials' rheological behavior, deposition speed and extrusion pressure, and UV illumination conditions were thoroughly investigated. A processing map was then defined in order to help choosing the proper parameters for the UV-3DP of microstructures with various geometries. Compared to self-supported features, the accurate fabrication of 3D freeform structures was found to take place in a narrower processing region since a higher rigidity of the extruded filament was required for structural stability. Finally, various 3D self-supported and freeform microstructures with high potential in micro electromechanical systems, micro-systems and organic electronics were fabricated to show the capability of the technique. (paper)

Advanced Steel Microstructural Classification by Deep Learning Methods.

Science.gov (United States)

Azimi, Seyed Majid; Britz, Dominik; Engstler, Michael; Fritz, Mario; Mücklich, Frank

2018-02-01

The inner structure of a material is called microstructure. It stores the genesis of a material and determines all its physical and chemical properties. While microstructural characterization is widely spread and well known, the microstructural classification is mostly done manually by human experts, which gives rise to uncertainties due to subjectivity. Since the microstructure could be a combination of different phases or constituents with complex substructures its automatic classification is very challenging and only a few prior studies exist. Prior works focused on designed and engineered features by experts and classified microstructures separately from the feature extraction step. Recently, Deep Learning methods have shown strong performance in vision applications by learning the features from data together with the classification step. In this work, we propose a Deep Learning method for microstructural classification in the examples of certain microstructural constituents of low carbon steel. This novel method employs pixel-wise segmentation via Fully Convolutional Neural Network (FCNN) accompanied by a max-voting scheme. Our system achieves 93.94% classification accuracy, drastically outperforming the state-of-the-art method of 48.89% accuracy. Beyond the strong performance of our method, this line of research offers a more robust and first of all objective way for the difficult task of steel quality appreciation.

Self-supported carbon electrodes obtained by tape casting

Directory of Open Access Journals (Sweden)

Rubio-Marcos, F.

2006-06-01

Full Text Available This paper describes the preparation and electrochemical response of self-supported carbon electrodes prepared by tape casting. The dc electrical conductivity, σ, of the electrodes was determined by four-wire resistance measurements and a relation between the graphite/organic additives ratio and the electrical conductivity was established. The application of these self-supported carbon electrodes as working electrodes in analytical techniques was also evaluated using norepinephrine as electroactive substance in cyclic voltammetry and chronoamperometry. The results were compared with the traditional electrodes, carbon paste electrodes (CPEs, showing that the new self-supported carbon electrodes had both lower background noise and higher analytical response.

Este artículo describe la preparación y respuesta electroquímica de electrodos de carbono autosoportados preparados mediante colado en cinta. La conductividad eléctrica en corriente continua de este nuevo tipo de electrodos de carbono se ha determinado usando el método de cuatro puntas y se ha establecido una relación ente la relación grafito/aditivos orgánicos y la conductividad eléctrica. La aplicación de estos electrodos autosoportados como electrodos de trabajo en diversas técnicas electroanalíticas también se ha evaluado, empleando norepinefrina como analito en voltametría cíclica y en cronoamperometría. Los resultados se compararon con los obtenidos empleando los electrodos de pasta de carbono tradicionales como electrodos de trabajo, viéndose que la señal de los nuevos electrodos autosoportados poseía menor ruido de fondo y mayor respuesta analítica.

Phosphorus poisoning of molybdenum sulfide hydrodesulfurization catalysts supported on carbon and alumina

NARCIS (Netherlands)

Bouwens, S.M.A.M.; Vissers, J.P.R.; Beer, de V.H.J.; Prins, R.

1988-01-01

Phosphorus-containing Mo sulfide catalysts supported on ¿-Al2O3 and activated carbon were evaluated for their thiophene HDS activities. Phosphorus was added as phosphoric acid to the carrier material prior to the molybdenum component. The thiophene HDS activity of the carbon-supported catalysts was

N-Doped Carbon Xerogels as Pt Support for the Electro-Reduction of Oxygen

Directory of Open Access Journals (Sweden)

Cinthia Alegre

2017-09-01

Full Text Available Durability and limited catalytic activity are key impediments to the commercialization of polymer electrolyte fuel cells. Carbon materials employed as catalyst support can be doped with different heteroatoms, like nitrogen, to improve both catalytic activity and durability. Carbon xerogels are nanoporous carbons that can be easily synthesized in order to obtain N-doped materials. In the present work, we introduced melamine as a carbon xerogel precursor together with resorcinol for an effective in-situ N doping (3–4 wt % N. Pt nanoparticles were supported on nitrogen-doped carbon xerogels and their activity for the oxygen reduction reaction (ORR was evaluated in acid media along with their stability. Results provide new evidences of the type of N groups aiding the activity of Pt for the ORR and of a remarkable stability for N-doped carbon-supported Pt catalysts, providing appropriate physico-chemical features.

Microstructural characteristics and mechanical properties of carbon nanotube reinforced aluminum alloy composites produced by ball milling

International Nuclear Information System (INIS)

Raviathul Basariya, M.; Srivastava, V.C.; Mukhopadhyay, N.K.

2014-01-01

Highlights: • 6082 Al alloy composite with 2 wt% multiwalled carbon nanotubes prepared by milling. • Effect of milling time on structure and property evolution has been studied. • The reinforced composite powders showed a drastic crystallite size refinement. • The presence of carbon nanotube led to a two fold increase in the hardness and modulus. • The composite powder showed good thermal stability studied by DTA. - Abstract: The influence of milling time on the structure, morphology and thermal stability of multi-walled carbon nanotubes (MWCNTs) reinforced EN AW6082 aluminum alloy powders has been studied. After structural and microstructural characterization of the mechanically milled powders micro- and nano-hardness of the composite powder particles were evaluated. The morphological and X-ray diffraction studies on the milled powders revealed that the carbon nanotubes (CNTs) were uniformly distributed and embedded within the aluminum matrix. No reaction products were detected even after long milling up to 50 h. Nanotubes became shorter in length as they fractured under the impact and shearing action during the milling process. A high hardness of about 436 ± 52 HV is achieved for the milled powders, due to the addition of MWCNTs, after milling for 50 h. The increased elastic modulus and nanohardness can be attributed to the finer grain size evolved during high energy ball milling and to the uniform distribution of hard CNTs in the Al-alloy matrix. The hardness values of the composite as well as the matrix alloy compares well with that predicted by the Hall–Petch relationship

Analysis of microstructural variation and mechanical behaviors in submerged arc welded joint of high strength low carbon bainitic steel

Energy Technology Data Exchange (ETDEWEB)

Lan, Liangyun, E-mail: lly.liangyun@gmail.com [State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819 (China); Qiu, Chunlin; Zhao, Dewen; Gao, Xiuhua; Du, Linxiu [State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819 (China)

2012-12-15

Microstructural variation in high strength low carbon bainitic steel weldment was investigated in detail by means of optical microscope, transmission electron microscope and scanning electron microscope equipped with electron backscattered diffraction. The results showed that the welded joint has various microstructures such as acicular ferrite, coarse granular ferrite and fine polygonal ferrite. The martensite-austenite (MA) constituent has a variable structure in each sub-zone, which includes fully martensite and fully retained austenite. Meanwhile, the fine grained heat affected zone has higher content of retained austenite than the welded metal (WM) and coarse grained heat affected zone (CGHAZ). The orientation relationship between retained austenite and product phases in the WM and CGHAZ is close to Kurdjumov-Sachs relationship. However, the polygonal ferrite in the fine grained HAZ has no specific orientation relationship with the neighboring retained austenite. The toughness of the coarse grained region is much lower than that of the WM because the coarse bainite contains many large MA constituents to assist the nucleation of microcracks and coarse cleavage facet lowers the ability to inhibit the crack propagation.

Reduced graphene oxide supported gold nanoparticles for electrocatalytic reduction of carbon dioxide

Science.gov (United States)

Saquib, Mohammad; Halder, Aditi

2018-02-01

Electrochemical reduction of carbon dioxide is one of the methods which have the capability to recycle CO2 into valuable products for energy and industrial applications. This research article describes about a new electrocatalyst "reduced graphene oxide supported gold nanoparticles" for selective electrochemical conversion of carbon dioxide to carbon monoxide. The main aim for conversion of CO2 to CO lies in the fact that the latter is an important component of syn gas (a mixture of hydrogen and carbon monoxide), which is then converted into liquid fuel via well-known industrial process called Fischer-Tropsch process. In this work, we have synthesized different composites of the gold nanoparticles supported on defective reduced graphene oxide to evaluate the catalytic activity of reduced graphene oxide (RGO)-supported gold nanoparticles and the role of defective RGO support towards the electrochemical reduction of CO2. Electrochemical and impedance measurements demonstrate that higher concentration of gold nanoparticles on the graphene support led to remarkable decrease in the onset potential of 240 mV and increase in the current density for CO2 reduction. Lower impedance and Tafel slope values also clearly support our findings for the better performance of RGOAu than bare Au for CO2 reduction.

Effect of carbon additive on microstructure evolution and magnetic properties of epitaxial FePt (001) thin films

International Nuclear Information System (INIS)

Ding, Y.F.; Chen, J.S.; Liu, E.; Lim, B.C.; Hu, J.F.; Liu, B.

2009-01-01

FePt:C thin films were deposited on CrRu underlayers by DC magnetron co-sputtering. The effects of C content, FePt:C film thickness and substrate temperature on the microstructural and magnetic properties of the epitaxial FePt (001) films were studied. Experimental results showed that even with 30 vol.% C doping, the FePt films could keep a (001) preferred orientation at 350 deg. C . When a FePt:C film was very thin (< 5 nm), the film had a continuous microstructure instead of a granual structure with C diffused onto the film surface. With further increased film thickness, the film started to nucleate and formed a column microstructure over continuous FePt films. A strong exchange coupling in the FePt:C films was believed to be due to the presence of a thin continuous FePt layer attributed to the carbon diffusion during the initial stage of the FePt:C film growth. Despite the presence of a strong exchange coupling in the FePt:C (20 vol.% C) film, the SNR ratio of the FePt:C media was about 10 dB better than that of the pure FePt media. The epitaxial growth of the FePt:C films on the Pt layers was observed from high resolution TEM cross sectional images even for the films grown at about 200 deg. C . The TEM images did not show an obvious change in the morphology of the FePt:C films deposited at different temperatures (from 200 deg. C to 350 deg. C ), though the ordering degree and coercivity of the films increased with increased substrate temperature

Nanoscale microstructural characterization of a nanobainitic steel

Energy Technology Data Exchange (ETDEWEB)

Timokhina, I.B., E-mail: ilana.timokhina@eng.monash.edu.au [Centre for Material and Fibre Innovation, Deakin University, Victoria 3216 (Australia); Beladi, H. [Centre for Material and Fibre Innovation, Deakin University, Victoria 3216 (Australia); Xiong, X.Y. [Monash Centre for Electron Microscopy, Monash University, Victoria 3800 (Australia); Adachi, Y. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Hodgson, P.D. [Centre for Material and Fibre Innovation, Deakin University, Victoria 3216 (Australia)

2011-08-15

A 0.79 C-1.5 Si-1.98 Mn-0.98 Cr-0.24 Mo-1.06 Al-1.58 Co (wt.%) steel was isothermally heat treated at 200 deg. C for 10 days and 350 deg. C for 1 day to form a nanoscale bainitic microstructure consisting of nanobainitic ferrite laths with high dislocation density and retained austenite films. The microstructures of the samples were characterized by transmission electron microscopy and atom probe tomography. Despite the formation of nanoscale bainite with a high volume fraction of retained austenite in both steels, the ductility of both steels was surprisingly low. It is believed that this was associated with the formation of carbon-depleted retained austenite after isothermal transformation at 200 deg. C due to the formation of high number of Fe-C clusters and particles in the bainitic ferrite laths and carbon-enriched austenite after isothermal transformation at 350 deg. C.

Microstructure Evolution and Chemical Analysis on Carbon Steels and Fe-Cr-Mo Alloys after FAC Simulation Tests

International Nuclear Information System (INIS)

Kim, Seunghyun; Kim, Taeho; Lee, Yun Ju; Kim, Ji Hyun

2017-01-01

Flow-accelerated corrosion (FAC) is an environment assisted degradation of structural materials, which usually occurs in pipelines of power plants. There have been many studies to investigate the fundamental mechanism and corresponding countermeasures against FAC, and recently the carbon steels have been replaced by ASTM A 335 P22, which contains approximately 2.2 wt.% of Cr and 1 wt.% of Mo. By enhancing passivity of P22 by Cr, it is reported that FAC rate has been greatly reduced. However, while corrosion behavior of Fe-based alloys is relatively well known, their behavior under high-temperature flowing water is not well investigated. In other words, effects of Cr and its corrosion and oxidation behavior is not clearly revealed. Furthermore, it is known that Mo enhances the pitting corrosion resistance of alloys however its mechanism is not clearly investigated. Recently, replacement of Mo in alloy contents has been widely studied because of the cost of Mo. Carbon steels undergo severe environmental-assisted degradation behavior so called FAC, and as its countermeasure the carbon steel has been replaced by P22 which contains Cr and Mo. It is generally known that Cr and Mo enhances passivity of Fe-based alloys however their corrosion and oxidation behavior has not been fully investigated especially in high-temperature flowing water environments. In this study, we employed HRTEM and synchrotron XAS techniques in order to investigate detailed microstructure evolution and chemical bonding of the commercialized carbon steel and the Fe-Cr-Mo alloys. From the analysis, it is found that while carbon steels exhibit porous oxide P22 exhibit oxide structures with thin Cr-rich oxide and spinel. Therefore, carbon steel undergoes severe FAC compared to P22 however effects of Cr and Mo and their behavior in high-temperature flowing water will be investigated.

Imaging brain tumour microstructure.

Science.gov (United States)

Nilsson, Markus; Englund, Elisabet; Szczepankiewicz, Filip; van Westen, Danielle; Sundgren, Pia C

2018-05-08

Imaging is an indispensable tool for brain tumour diagnosis, surgical planning, and follow-up. Definite diagnosis, however, often demands histopathological analysis of microscopic features of tissue samples, which have to be obtained by invasive means. A non-invasive alternative may be to probe corresponding microscopic tissue characteristics by MRI, or so called 'microstructure imaging'. The promise of microstructure imaging is one of 'virtual biopsy' with the goal to offset the need for invasive procedures in favour of imaging that can guide pre-surgical planning and can be repeated longitudinally to monitor and predict treatment response. The exploration of such methods is motivated by the striking link between parameters from MRI and tumour histology, for example the correlation between the apparent diffusion coefficient and cellularity. Recent microstructure imaging techniques probe even more subtle and specific features, providing parameters associated to cell shape, size, permeability, and volume distributions. However, the range of scenarios in which these techniques provide reliable imaging biomarkers that can be used to test medical hypotheses or support clinical decisions is yet unknown. Accurate microstructure imaging may moreover require acquisitions that go beyond conventional data acquisition strategies. This review covers a wide range of candidate microstructure imaging methods based on diffusion MRI and relaxometry, and explores advantages, challenges, and potential pitfalls in brain tumour microstructure imaging. Copyright © 2018. Published by Elsevier Inc.

Methanol and ethanol electrooxidation on Pt and Pd supported on carbon microspheres in alkaline media

Energy Technology Data Exchange (ETDEWEB)

Xu, Changwei; Cheng, Liqiang; Liu, Yingliang [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Shen, Peikang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

2007-05-15

Noble metal (Pt, Pd) electrocatalysts supported on carbon microspheres (CMS) are used for methanol and ethanol oxidation in alkaline media. The results show that noble metal electrocatalysts supported on carbon microspheres give better performance than that supported on carbon black. It is well known that palladium is not a good electrocatalyst for methanol oxidation, but it shows excellently higher activity and better steady-state electrolysis than Pt for ethanol electrooxidation in alkaline media. The results show a synergistic effect by the interaction between Pd and carbon microspheres. The Pd supported on carbon microspheres in this paper possesses excellent electrocatalytic properties and may be of great potential in direct ethanol fuel cells. (author)

Carbon materials derived from chitosan/cellulose cryogel-supported zeolite imidazole frameworks for potential supercapacitor application.

Science.gov (United States)

Li, Zehui; Yang, Lan; Cao, Hongbin; Chang, Yu; Tang, Kexin; Cao, Zhiqin; Chang, Junjun; Cao, Youpeng; Wang, Wenbo; Gao, Meng; Liu, Chenming; Liu, Dagang; Zhao, He; Zhang, Yi; Li, Mingjie

2017-11-01

In order to promote sustainable development, green and renewable clean energy technologies continue to be developed to meet the growing demand for energy, such as supercapacitor, fuel cells and lithium-ion battery. It is urgent to develop appropriate nanomaterials for these energy technologies to reduce the volume of the device, improve the efficiency of energy conversion and enlarge the energy storage capacity. Here, chitosan/cellulose carbon cryogel (CCS/CCL) were designed and synthesized. Through the introduction of zeolite imidazole frameworks (ZIFs) into the chitosan/cellulose cryogels, the obtained materials showed a microstructure of ZIF-7 (a kind of ZIFs) coated chitosan/cellulose fibers (CS/CL). After carbonizing, the as-prepared carbonized ZIF-7@cellulose cryogel (NC@CCL, NC is carbonized ZIF-7) and carbonized ZIF-7@chitosan cryogel (NC@CCS) exhibited suitable microspore contents of 34.37% and 30%, respectively, and they both showed an internal resistance lower than 2Ω. Thereby, NC@CCL and NC@CCS exhibited a high specific capacitance of 150.4Fg -1 and 173.1Fg -1 , respectively, which were much higher than those of the original materials. This approach offers a facile method for improving the strength and electronic conductivity of carbon cryogel derived from nature polymers, and also efficiently inhibits the agglomeration of cryogel during carbonization in high temperature, which opens a novel avenue for the development of carbon cryogel materials for application in energy conversion systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Modeling Percolation in Polymer Nanocomposites by Stochastic Microstructuring

Directory of Open Access Journals (Sweden)

Matias Soto

2015-09-01

Full Text Available A methodology was developed for the prediction of the electrical properties of carbon nanotube-polymer nanocomposites via Monte Carlo computational simulations. A two-dimensional microstructure that takes into account waviness, fiber length and diameter distributions is used as a representative volume element. Fiber interactions in the microstructure are identified and then modeled as an equivalent electrical circuit, assuming one-third metallic and two-thirds semiconductor nanotubes. Tunneling paths in the microstructure are also modeled as electrical resistors, and crossing fibers are accounted for by assuming a contact resistance associated with them. The equivalent resistor network is then converted into a set of linear equations using nodal voltage analysis, which is then solved by means of the Gauss–Jordan elimination method. Nodal voltages are obtained for the microstructure, from which the percolation probability, equivalent resistance and conductivity are calculated. Percolation probability curves and electrical conductivity values are compared to those found in the literature.

Sulfidation of carbon-supported iron oxide catalysts

NARCIS (Netherlands)

Ramselaar, W.L.T.M.; Hadders, R.H.; Gerkema, E.; Beer, de V.H.J.; Oers, van E.M.; Kraan, van der A.M.

1989-01-01

The sulfidation of carbon-supported iron oxide catalysts was studied by means of in-situ Mössbauer spectroscopy at temperatures down to 4.2 K. The catalysts were dried in two different ways and then sulfided in a flow of 10% H2S in H2 at temperatures between 293 and 773 K. Thiophene

Gauging citizen support for a low carbon fuel standard

International Nuclear Information System (INIS)

Rhodes, Ekaterina; Axsen, Jonn; Jaccard, Mark

2015-01-01

Since 2007, several variations of a low carbon fuel standard (LCFS) have been implemented around the world. While emerging research tends to focus on greenhouse gas emission reductions from an LCFS, no studies have assessed the policy's political acceptability—a critical component of implementation. We elicit public support for an existing LCFS in British Columbia and a hypothetical (proposed) LCFS for the rest of Canada using survey data collected from a representative sample of Canadian citizens (n=1306). Specifically, we assess: (1) citizen awareness of British Columbia's LCFS, (2) stated citizen support for the LCFS, and (3) how individual characteristics relate to levels of citizen support. We find that British Columbia's LCFS is almost unknown among British Columbia respondents, but once explained, 90% of respondents support it. We refer to this combination of low knowledge and high support as “passive support.” We find similarly broad support in all other Canadian provinces, implying that citizen opposition is unlikely in jurisdictions considering an LCFS. Statistical analysis identifies some individual characteristics associated with LCFS support, including attitudes, demographics, and contextual factors. Results indicate where policymakers might anticipate opposition if it arises due to increased policy stringency or media coverage. - Highlights: • Most citizens are unaware of British Columbia's low carbon fuel standard (LCFS). • We observe passive support: low awareness and high support of the policy. • An LCFS achieves broad support among British Columbia's and Canadian citizens. • Households relying on single occupancy vehicles are less likely to support an LCFS

Unique microstructure and excellent mechanical properties of ADI

Directory of Open Access Journals (Sweden)

Jincheng Liu

2006-11-01

Full Text Available Amongst the cast iron family, ADI has a unique microstructure and an excellent, optimised combination of mechanical properties. The main microstructure of ADI is ausferrite, which is a mixture ofextremely fine acicular ferrite and stable, high carbon austenite. There are two types of austenite in ADI:(1 the coarser and more equiaxed blocks of austenite between non-parallel acicular structures, which exist mainly in the last solidified area, and (2 the thin films of ustenite between the individual ferriteplatelets in the acicular structure. It is this unique microstructure, which gives ADI its excellent static and dynamic properties, and good low temperature impact toughness. The effect of microstructure on the mechanical properties is explained in more detail by examining the microstructure at the atomic scale. Considering the nanometer grain sizes, the unique microstructure, the excellent mechanical properties,good castability, (which enables near net shape components to be produced economically and in large volumes, and the fact that it can be 100% recycled, it is not overemphasized to call ADI a high-tech,nanometer and “green” material. ADI still has the potential to be further improved and its production and the number of applications for ADI will continue to grow, driven by the resultant cost savings over alternative materials.

CTAB assisted microwave synthesis of ordered mesoporous carbon supported Pt nanoparticles for hydrogen electro-oxidation

International Nuclear Information System (INIS)

Zhou, Jian-Hua; He, Jian-Ping; Ji, Ya-Jun; Dang, Wang-Juan; Liu, Xiao-Lei; Zhao, Gui-Wang; Zhang, Chuan-Xiang; Zhao, Ji-Shuang; Fu, Qing-Bin; Hu, Huo-Ping

2007-01-01

Mesoporous carbon with ordered hexagonal structure derived from the co-assembly of triblock copolymer F127 and resol was employed as the carbon support of Pt catalysts for hydrogen electro-oxidation. Structural characterizations revealed that the mesoporous carbon exhibited large surface area and uniform mesopores. The Pt nanoparticles supported on the novel mesoporous carbon were fabricated by a facile CTAB assisted microwave synthesis process, wherein CTAB was expected to improve the wettability of carbon support as well as the dispersion of Pt nanoparticles. X-ray diffraction and transmission electron microscopy were applied to characterize the Pt catalysts. It was found that the Pt nanoparticles were uniform in size and highly dispersed on the mesoporous carbon supports. The cyclic voltammograms in sulfuric acid demonstrated that the electrochemical active surface area of Pt catalysts prepared with CTAB was two times than that without CTAB

Effect of sodium monofluorophosphate treatment on microstructure and frost salt scaling durability of slag cement paste

International Nuclear Information System (INIS)

Copuroglu, O.; Fraaij, A.L.A.; Bijen, J.M.J.M.

2006-01-01

Sodium-monofluorophosphate (Na-MFP) is currently in use as a surface applied corrosion inhibitor in the concrete industry. Its basic mechanism is to protect the passive layer of the reinforcement steel against disruption due to carbonation. Carbonation is known as the most detrimental environmental effect on blast furnace slag cement (BFSC) concrete with respect to frost salt scaling. In this paper the effect of Na-MFP on the microstructure and frost salt scaling resistance of carbonated BFSC paste is presented. The results of electron microscopy, mercury intrusion porosimetry (MIP) and X-ray diffraction (XRD) are discussed. It is found that the treatment modifies the microstructure and improves the resistance of carbonated BFSC paste against frost salt attack

Microstructure and abrasive wear properties of M(Cr,Fe7C3 carbides reinforced high-chromium carbon coating produced by gas tungsten arc welding (GTAW process

Directory of Open Access Journals (Sweden)

Soner BUYTOZ

2010-01-01

Full Text Available In the present study, high-chromium ferrochromium carbon hypereutectic alloy powder was coated on AISI 4340 steel by the gas tungsten arc welding (GTAW process. The coating layers were analyzed by optical microscopy, X-ray diffraction (XRD, field-emission scanning electron microscopy (FE-SEM, X-ray energy-dispersive spectroscopy (EDS. Depending on the gas tungsten arc welding pa-rameters, either hypoeutectic or hypereutectic microstructures were produced. Wear tests of the coatings were carried out on a pin-on-disc apparatus as function of contact load. Wear rates of the all coating layers were decreased as a function of the loading. The improvement of abrasive wear resistance of the coating layer could be attributed to the high hardness of the hypereutectic M7C3 carbides in the microstruc-ture. As a result, the microstructure of surface layers, hardness and abrasive wear behaviours showed different characteristics due to the gas tungsten arc welding parameters.

Microstructural characterization of PAN based carbon fiber reinforced nylon 6 polymer composites

Science.gov (United States)

Munirathnamma, L. M.; Ningaraju, S.; Kumar, K. V. Aneesh; Ravikumar, H. B.

2018-04-01

Microstructural characterization of nylon 6/polyacrolonitrile based carbon fibers (PAN-CFs) of 10 to 40 wt% has been performed by positron lifetime technique (PLT). The positron lifetime parameters viz., o-Ps lifetime (τ3), o-Ps intensity (I3) and fractional free volume (Fv) of nylon 6/PAN-CF composites are correlated with the mechanical properties viz., Tensile strength and Young's modulus. The Fv show negative deviation with the reinforcement of 10 to 40 wt% of PAN-CF from the linear additivity relation. The negative deviation in nylon 6/PAN-CF composite suggests the induced molecular packing due to the chemical interaction between the polymeric chains of nylon 6 and PAN-CF. This is evident from Fourier Transform Infrared Spectrometry (FTIR) studies. The FTIR results suggests that observed negative deviation in PALS results of nylon 6/PAN-CF reinforced polymer composites is due to the induced chemical interaction at N-H-O sites. The improved tensile strength (TS) and Young's modulus (YM) in nylon 6/PAN-CF reinforced polymer composites is due to AS4C (surface treated and epoxy coated) PAN-CF has shown highest adhesion level due to better stress transfer between nylon 6 and PAN-CF.

On the Growth and Microstructure of Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition

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Handuja Sangeeta

2010-01-01

Full Text Available Abstract Carbon nanotubes (CNTs were deposited on various substrates namely untreated silicon and quartz, Fe-deposited silicon and quartz, HF-treated silicon, silicon nitride-deposited silicon, copper foil, and stainless steel mesh using thermal chemical vapor deposition technique. The optimum parameters for the growth and the microstructure of the synthesized CNTs on these substrates are described. The results show that the growth of CNTs is strongly influenced by the substrate used. Vertically aligned multi-walled CNTs were found on quartz, Fe-deposited silicon and quartz, untreated silicon, and on silicon nitride-deposited silicon substrates. On the other hand, spaghetti-type growth was observed on stainless steel mesh, and no CNT growth was observed on HF-treated silicon and copper. Silicon nitride-deposited silicon substrate proved to be a promising substrate for long vertically aligned CNTs of length 110–130 μm. We present a possible growth mechanism for vertically aligned and spaghetti-type growth of CNTs based on these results.

A review of carbon-based and non-carbon-based catalyst supports for the selective catalytic reduction of nitric oxide.

Science.gov (United States)

Anthonysamy, Shahreen Binti Izwan; Afandi, Syahidah Binti; Khavarian, Mehrnoush; Mohamed, Abdul Rahman Bin

2018-01-01

Various types of carbon-based and non-carbon-based catalyst supports for nitric oxide (NO) removal through selective catalytic reduction (SCR) with ammonia are examined in this review. A number of carbon-based materials, such as carbon nanotubes (CNTs), activated carbon (AC), and graphene (GR) and non-carbon-based materials, such as Zeolite Socony Mobil-5 (ZSM-5), TiO 2 , and Al 2 O 3 supported materials, were identified as the most up-to-date and recently used catalysts for the removal of NO gas. The main focus of this review is the study of catalyst preparation methods, as this is highly correlated to the behaviour of NO removal. The general mechanisms involved in the system, the Langmuir-Hinshelwood or Eley-Riedeal mechanism, are also discussed. Characterisation analysis affecting the surface and chemical structure of the catalyst is also detailed in this work. Finally, a few major conclusions are drawn and future directions for work on the advancement of the SCR-NH 3 catalyst are suggested.

Carbon Nitride Materials as Efficient Catalyst Supports for Proton Exchange Membrane Water Electrolyzers

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Ana Belen Jorge

2018-06-01

Full Text Available Carbon nitride materials with graphitic to polymeric structures (gCNH were investigated as catalyst supports for the proton exchange membrane (PEM water electrolyzers using IrO2 nanoparticles as oxygen evolution electrocatalyst. Here, the performance of IrO2 nanoparticles formed and deposited in situ onto carbon nitride support for PEM water electrolysis was explored based on previous preliminary studies conducted in related systems. The results revealed that this preparation route catalyzed the decomposition of the carbon nitride to form a material with much lower N content. This resulted in a significant enhancement of the performance of the gCNH-IrO2 (or N-doped C-IrO2 electrocatalyst that was likely attributed to higher electrical conductivity of the N-doped carbon support.

Ruthenium oxide/carbon composites with microporous or mesoporous carbon as support and prepared by two procedures. A comparative study as supercapacitor electrodes

International Nuclear Information System (INIS)

Pico, F.; Morales, E.; Fernandez, J.A.; Centeno, T.A.; Ibanez, J.; Rojas, R.M.; Amarilla, J.M.; Rojo, J.M.

2009-01-01

Composites are prepared by deposition of nanoparticles of RuO 2 .xH 2 O (1-4 nm) on two carbons: microporous carbon (1.3 nm of average micropore size) and mesoporous carbon (11 nm of average mesopore size). Two-preparation procedures are used: (i) procedure A consisting of repetitive impregnations of the carbons with RuCl 3 .0.5H 2 O solutions, and (ii) procedure B based on impregnation of the carbons with Ru(acac) 3 vapour. The procedure B leads to supported RuO 2 .xH 2 O particles that appear more crystalline than those obtained by the procedure A. Specific capacitance and specific surface area of the composites are discussed as functions of the RuO 2 content, and different dependences for the composites derived from the two carbons are found. Mesoporous carbon is better support than microporous carbon. Procedure A leads to supported RuO 2 .xH 2 O particles with higher specific capacitance than the particles deposited by procedure B

Ruthenium oxide/carbon composites with microporous or mesoporous carbon as support and prepared by two procedures. A comparative study as supercapacitor electrodes

Energy Technology Data Exchange (ETDEWEB)

Pico, F. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), Sor Juana Ines de la Cruz 3, Cantoblanco, E-28049-Madrid (Spain); Morales, E. [Instituto de Ciencia y Tecnologia de Polimeros (ICTP), CSIC, Juan de la Cierva 3, E-28006-Madrid (Spain); Fernandez, J.A.; Centeno, T.A. [Instituto Nacional del Carbon (INCAR), CSIC, Francisco Pintado Fe 26, E-33011-Oviedo (Spain); Ibanez, J. [Centro Nacional de Investigaciones Metalurgicas (CENIM), CSIC, Avda. Gregorio del Amo 8, E-28040-Madrid (Spain); Rojas, R.M.; Amarilla, J.M. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), Sor Juana Ines de la Cruz 3, Cantoblanco, E-28049-Madrid (Spain); Rojo, J.M. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), Sor Juana Ines de la Cruz 3, Cantoblanco, E-28049-Madrid (Spain)], E-mail: jmrojo@icmm.csic.es

2009-03-01

Composites are prepared by deposition of nanoparticles of RuO{sub 2}.xH{sub 2}O (1-4 nm) on two carbons: microporous carbon (1.3 nm of average micropore size) and mesoporous carbon (11 nm of average mesopore size). Two-preparation procedures are used: (i) procedure A consisting of repetitive impregnations of the carbons with RuCl{sub 3}.0.5H{sub 2}O solutions, and (ii) procedure B based on impregnation of the carbons with Ru(acac){sub 3} vapour. The procedure B leads to supported RuO{sub 2}.xH{sub 2}O particles that appear more crystalline than those obtained by the procedure A. Specific capacitance and specific surface area of the composites are discussed as functions of the RuO{sub 2} content, and different dependences for the composites derived from the two carbons are found. Mesoporous carbon is better support than microporous carbon. Procedure A leads to supported RuO{sub 2}.xH{sub 2}O particles with higher specific capacitance than the particles deposited by procedure B.

Effect of carbon content on the microstructure and creep properties of a 3rd generation single crystal nickel-base superalloy

Energy Technology Data Exchange (ETDEWEB)

Li, X.W.; Liu, T. [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Wang, L., E-mail: wangli@imr.ac.cn [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Liu, X.G.; Lou, L.H. [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhang, J. [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

2015-07-15

Effect of carbon content on the microstructure and creep properties of a 3rd generation single crystal nickel-base superalloy has been investigated by the scanning electron microscope, X-ray computed tomography and electron probe microanalyzer. With the increase of the carbon content, MC carbides evolve from octahedral to well-developed dendrite, which promotes the formation of microporosity. Moreover, the volume fraction of porosity increases in the experimental alloys after solution heat treatment. As a result, the increase in the size of MC carbides and the porosity has a detrimental effect on the low temperature and high stress creep behavior of the alloys. The specimen crept at 850 °C and 586 MPa with the carbon content of 430 ppm shows the shortest rupture life due to the largest primary creep strain. However, the creep behavior of the alloy at 1120 °C and 140 MPa gets better as the carbon content increases from 88 to 430 ppm. TCP phase is observed near the fracture surfaces of the alloys, which explores as a potential cause for the creep rupture. However, the formation of TCP phase is effectively suppressed for decreasing segregation of the alloying elements, which results in the improvement of the creep life in the alloy with 430 ppm carbon at 1120 °C and 140 MPa.

The microstructure and morphology of carbon black: A study using small angle neutron scattering and contrast variation

International Nuclear Information System (INIS)

Hjelm, R.P. Jr.; Seeger, P.A.; Wampler, W.A.; Gerspacher, M.

1994-01-01

This is a study of the microstructure of particles of an experimental high surface area carbon black (HSA) and of the morphology of the particle aggregates using small-angle neutron scattering and the method of contrast variation. Contrast variation was effected by studying suspensions of the carbon black in cyclohexane containing different fractions of deuterocyclohexane. We find that the approximately 29 nm diameter HSA particles are arranged as small, linear aggregates with average aggregation number between 4 and 6. The structure averaged over the particle population is best represented by a prolate ellipsoid of revolution with semi axes 14.5 and 76.4 nm. The surface of the aggregates appears smooth over length scales longer than 1 nm, which places an upper limit on the surface roughness observed by other methods. The intemal structure of the aggregates is described by a shell-core model, with the shell density being consistent with a graphitic structure and the core being of lower density, more like amorphous carbon. Some fraction of the core volume (0.1 to 0.2) is taken up by voids that are not accessible to the solvent. An estimate of the shell thickness gives 1 to 2 nm along the ellipsoid minor axis and 6 to 10 nm along the major axis. The particles of the aggregate appear to be fused so that the less dense amorphous core is continuous through the inner parts of the aggregate. The information that can be obtained on the internal structure using contrast variation is limited by nonheterogeneity in the chemical composition of carbon black aggregates

Carbon-Supported PtRuMo Electrocatalysts for Direct Alcohol Fuel Cells

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José L.G. Fierro

2013-10-01

Full Text Available The review article discusses the current status and recent findings of our investigations on the synthesis and characterization of carbon-supported PtRuMo electrocatalysts for direct alcohol fuel cells. In particular, the effect of the carbon support and the composition on the structure, stability and the activity of the PtRuMo nanoparticles for the electrooxidation of CO, methanol and ethanol have been studied. Different physicochemical techniques have been employed for the analysis of the catalysts structures: X-ray analytical methods (XRD, XPS, TXRF, thermogravimetry (TGA and transmission electron microscopy (TEM, as well as a number of electrochemical techniques like CO adsorption studies, current-time curves and cyclic voltammetry measurements. Furthermore, spectroscopic methods adapted to the electrochemical systems for in situ studies, such as Fourier transform infrared spectroscopy (FTIRS and differential electrochemical mass spectrometry (DEMS, have been used to evaluate the oxidation process of CO, methanol and ethanol over the carbon-supported PtRuMo electrocatalysts.

High-resolution optical microscopy of carbon and graphite

International Nuclear Information System (INIS)

Cook, W.H.; Allen, M.D.; Leslie, B.C.; Gray, R.J.

1975-01-01

The ceramographic preparation of carbonaceous materials varying in crystalline quality, amorphous carbon to well crystallized graphite, is described. In a two-step process, using alumina and diamond polishing compounds, one can prepare more samples, obtain a substantial saving in man hours, avoid rounding material around pores, and obtain flatter surfaces than were obtainable with earlier, conventional methods. Improved resolution of microstructural details is achieved without impregnation with epoxy resins or other materials to support the porous structures. Use of rotatable, half-wave retardation (sensitive tint) enhances the microstructural definition in both color and black and white. These innovations were extensively used as part of the examination of nuclear grades of graphite before and after exposure to fast neutrons at temperatures from 650 to 1100 0 C; typical examples are discussed. (auth)

Microstructure of depleted uranium under uniaxial strain conditions

International Nuclear Information System (INIS)

Zurek, A.K.; Embury, J.D.; Kelly, A.; Thissell, W.R.; Gustavsen, R.L.; Vorthman, J.E.; Hixson, R.H.

1997-01-01

Uranium samples of two different purities were used for spall strength measurements. Samples of depleted uranium were taken from very high purity material (38 ppM carbon) and from material containing 280 ppM C. Experimental conditions were chosen to effectively arrest the microstructural damage at two places in the development to full spall separation. Samples were soft recovered and characterized with respect to the microstructure and the form of damage. This allowed determination of the dependence of spall mechanisms on stress level, stress state, and sample purity. This information is used in developing a model to predict the mode of fracture

Protolytic carbon film technology

Energy Technology Data Exchange (ETDEWEB)

Renschler, C.L.; White, C.A.

1996-04-01

This paper presents a technique for the deposition of polyacrylonitrile (PAN) on virtually any surface allowing carbon film formation with only the caveat that the substrate must withstand carbonization temperatures of at least 600 degrees centigrade. The influence of processing conditions upon the structure and properties of the carbonized film is discussed. Electrical conductivity, microstructure, and morphology control are also described.

Analysis of composition and microstructural uniformity of hybrid glass/carbon fibre composites

DEFF Research Database (Denmark)

Beauson, Justine; Markussen, Christen Malte; Madsen, Bo

2013-01-01

level are investigated. The different levels of compositions in the composites are defined and experimentally determined. The composite volume fractions are determined using an image analysis based procedure. The global fibre volume fractions are determined using a gravimetrical based method. The local...... methods, a standard deviation based method and a fast Fourier transform method, are used to quantify the difference in microstructural uniformity between composites, and to detect and quantify any repeating pattern in the composite microstructure....

Anti-aging Friction of Carbonate Fault Mirror and its Microstructural Interpretation

Science.gov (United States)

Park, Y.; Ree, J. H.; Hirose, T.

2017-12-01

In our slide-hold-slide (SHS) friction tests on carbonate fault rocks, fault mirror (FM), light reflective mirror-like fault surface, shows almost zero or slightly negative aging rate of friction (`anti-aging' friction), whereas carbonate faults without FM exhibit a positive aging rate. We analyzed microstructures from three types of carbonate faults to explore the cause of the anti-aging friction of FM. The three types of fault rocks before SHS tests were made from Carrara marble; (i) FM, (ii) crushed gouge of former FM (CF), and (iii) gouge produced by pre-shearing of Carrara marble (PR). The fault zone of FM before SHS tests consists of sintered nanograin patches smeared into negative asperities of wall rocks (thickness up to 150 μm) and a sintered gouge layer between wall rocks (thickness up to 200 μm) that is composed of tightly-packed nanograins (50-500 nm in size) with triple junctions and angular-subangular fragments (a few-100 μm) of sintered nanograin aggregates. A straight and discrete Y-shear surface defines a boundary between the gouge layer and the nanograin patches or between the layer and wall rock. CF specimens before SHS tests are composed of patches of sintered nanograins as in FM specimens and a porous gouge layer with finer nanograins (a few-20 nm in size) and angular fragments of former FM. PR specimens before SHS tests are composed of damaged wall rocks and porous gouge with finer nanograins (a few-tens of μm). After SHS tests, sintered appearance of grains within the fault zones of CF and PR indicates the increase in interparticle bonding and also in contact area by grain aggregation. In contrast, the gouge layer of FM specimens after SHS tests consists mostly of angular fragments of sintered nanograin aggregates. The angular shape of the fragments indicates little increase in bonding and contact area between the fragments. Tightly sintered nanograins in FM specimens would have a lower chemical reactivity with their size coarser and

Properties and microstructure of graphitised ZrC/C or SiC/C composites

Energy Technology Data Exchange (ETDEWEB)

Qiu, H.P.; Han, L.J.; Liu, L.

2005-07-01

Doped graphites were prepared from calcined coke, coal-tar pitch and dopants (Zr, Si and Si-Zr) by hot-pressing in order to investigate the effects of the composition and amount of dopants on their thermal conductivity, electrical resistivity, bending strength and microstructure. Experimental results showed that the single element (Zr or Si) and bi-element (Si-Zr) graphitised doped-carbons exhibited highly improved conductivity, but the bending strength is lower in the case of Si-doped graphite. Microstructure analyses showed that the d(002) spacing decreased with the increasing dopant concentration for the single element (Zr or Si) doped graphite. From this result, it is inferred that the degree of graphitization increased. The thermal conductivity of a (9% Zr, 2% Si) graphitised doped-carbons is 380 W m{sup -1} K{sup -1}. Correlations between the composition and content of dopants and the microstructure of doped graphite are tentatively discussed.

Influence of Austempering Heat Treatment on Microstructure and Mechanical Properties of Medium Carbon High Silicon Steel

Science.gov (United States)

Palaksha, P. A.; Ravishankar, K. S.

2017-08-01

In the present investigation, the influence of austempering heat treatment on the microstructure and mechanical properties of medium carbon high silicon steel was evaluated. The test specimens were machined from the as-received steel and were first austenitised at 900 °C for 45 minutes, followed by austempering heat treatment in salt bath at various temperatures 300 °C, 350 °C and 400 °C for a fixed duration of two hours, after that those specimens were air-cooled to room temperature. The characterization studies were carried out using optical microscope, scanning electron microscope (SEM) and x-ray diffractometer (XRD) and then correlated to the hardness and tensile properties. Results indicate that, the specimens austempered at lower temperature i.e. at 300 °C, which offered high hardness, tensile strength and lower ductility (1857 MPa and 13.3 %) due to the presence of acicular bainite i.e. lower bainite and also some martensite in the microstructure. At 350 °C, reduction in the tensile strength and hardness was observed, but comparatively higher ductility, which was favored by the presence of bainite laths i.e. upper bainitic structure along with higher retained austenite content. Finally at 400 °C, reduction in both ductility and tensile strength was observed, which is due to the precipitation of carbides between the banite laths, however good strain hardening response was observed at austempering temperatures of 350 °C and 400 °C.

Microstructure Reconstruction of Sheet Molding Composite Using a Random Chips Packing Algorithm

Energy Technology Data Exchange (ETDEWEB)

Huang, Tianyu; Xu, Hongyi; Chen, Wei

2017-04-06

Fiber-reinforced polymer composites are strong candidates for structural materials to replace steel and light alloys in lightweight vehicle design because of their low density and relatively high strength. In the integrated computational materials engineering (ICME) development of carbon fiber composites, microstructure reconstruction algorithms are needed to generate material microstructure representative volume element (RVE) based on the material processing information. The microstructure RVE reconstruction enables the material property prediction by finite element analysis (FEA)This paper presents an algorithm to reconstruct the microstructure of a chopped carbon fiber/epoxy laminate material system produced by compression molding, normally known as sheet molding compounds (SMC). The algorithm takes the result from material’s manufacturing process as inputs, such as the orientation tensor of fibers, the chopped fiber sheet geometry, and the fiber volume fraction. The chopped fiber sheets are treated as deformable rectangle chips and a random packing algorithm is developed to pack these chips into a square plate. The RVE is built in a layer-by-layer fashion until the desired number of lamina is reached, then a fine tuning process is applied to finalize the reconstruction. Compared to the previous methods, this new approach has the ability to model bended fibers by allowing limited amount of overlaps of rectangle chips. Furthermore, the method does not need SMC microstructure images, for which the image-based characterization techniques have not been mature enough, as inputs. Case studies are performed and the results show that the statistics of the reconstructed microstructures generated by the algorithm matches well with the target input parameters from processing.

Influence of the Synthesis Method for Pt Catalysts Supported on Highly Mesoporous Carbon Xerogel and Vulcan Carbon Black on the Electro-Oxidation of Methanol

Directory of Open Access Journals (Sweden)

Cinthia Alegre

2015-03-01

Full Text Available Platinum catalysts supported on carbon xerogel and carbon black (Vulcan were synthesized with the aim of investigating the influence of the characteristics of the support on the electrochemical performance of the catalysts. Three synthesis methods were compared: an impregnation method with two different reducing agents, sodium borohydride and formic acid, and a microemulsion method, in order to study the effect of the synthesis method on the physico-chemical properties of the catalysts. X-ray diffraction and transmission electron microscopy were applied. Cyclic voltammetry and chronoamperometry were used for studying carbon monoxide and methanol oxidation. Catalysts supported on carbon xerogel presented higher catalytic activities towards CO and CH3OH oxidation than catalysts supported on Vulcan. The higher mesoporosity of carbon xerogel was responsible for the favored diffusion of reagents towards catalytic centers.

Suspended 3D pyrolytic carbon microelectrodes for electrochemistry

DEFF Research Database (Denmark)

Hemanth, Suhith; Caviglia, Claudia; Keller, Stephan Sylvest

2017-01-01

with cyclic voltammetry (CV) and impedance spectroscopy (EIS) using potassium ferri-ferrocyanide redox probe in a custom made batch system with magnetic clamping. Different 3D pyrolytic carbon microelectrodes were compared and the optimal design displayed twice the peak current and half the charge transfer......Carbon microelectrodes have a wide range of applications because of their unique material properties and biocompatibility. This work presents the fabrication and characterization of suspended pyrolytic carbon microstructures serving as three-dimensional (3D) carbon microelectrodes...... for electrochemical applications. A 3D polymer template in epoxy based photoresist (SU-8) was fabricated with multiple steps of UV photolithography and pyrolysed at 900 °C to obtain 3D carbon microelectrodes. The pyrolytic carbon microstructures were characterized by SEM, Raman spectroscopy and XPS to determine...

Preparation and thermal properties characterization of carbonate salt/carbon nanomaterial composite phase change material

International Nuclear Information System (INIS)

Tao, Y.B.; Lin, C.H.; He, Y.L.

2015-01-01

Highlights: • Nanocomposite phase change materials were prepared and characterized. • Larger specific surface area is more efficient to enhance specific heat. • Columnar structure is more efficient to enhance thermal conductivity. • Thermal conductivity enhancement is the key. • Single walled carbon nanotube is the optimal nanomaterial additive. - Abstract: To enhance the performance of high temperature salt phase change material, four kinds of carbon nanomaterials with different microstructures were mixed into binary carbonate eutectic salts to prepare carbonate salt/nanomaterial composite phase change material. The microstructures of the nanomaterial and composite phase change material were characterized by scanning electron microscope. The thermal properties such as melting point, melting enthalpy, specific heat, thermal conductivity and total thermal energy storage capacity were characterized. The results show that the nanomaterial microstructure has great effects on composite phase change material thermal properties. The sheet structure Graphene is the best additive to enhance specific heat, which could be enhanced up to 18.57%. The single walled carbon nanotube with columnar structure is the best additive to enhance thermal conductivity, which could be enhanced up to 56.98%. Melting point increases but melting enthalpy decreases with nanomaterial specific surface area increase. Although the additives decrease the melting enthalpy of composite phase change material, they also enhance the specific heat. As a combined result, the additives have little effects on thermal energy storage capacity. So, for phase change material performance enhancement, more emphasis should be placed on thermal conductivity enhancement and single walled carbon nanotube is the optimal nanomaterial additive

Microstructure and Property of Mn-Nb-B Low Carbon Bainite High Strength Steel Under Ultra-fast Cooling

Directory of Open Access Journals (Sweden)

WANG Bing-xing

2016-07-01

Full Text Available Using the Mn-Nb-B low carbon bainite high strength steel with the reducing production technology as the research target, the deformation behavior and phase transformation behavior were studied by the thermal simulation testing machine. Combining with the characteristics of the medium and heavy plate production line, the controlled rolling and controlled cooling technology based on ultra-fast cooling were designed to produce low cost high strength construction machinery steel with superior comprehensive mechanical properties. The strengthening mechanisms such as grain refinement strengthening, precipitation strengthening are effective to produce the Mn-Nb-B low carbon bainite high strength steel. The yield strength and tensile strength of the product reach to 678MPa and 756 MPa respectively, the elongation A50 is 33% and the impact energy at -20℃ is 261J. The microstructure of the steel is composed of granular bainite, acicular ferrite and lath bainite. A large number of fine, point, granular M/A constituents and dislocation structures dispersively distributed inside the matrix, and also tiny and dispersed (Nb,Ti (C,N precipitates are observed by transmission electron microscopy.

Study creep in 4340 steels with different microstructure and plasma carbon nitridation processing

International Nuclear Information System (INIS)

Abdalla, A.J.; Carrer, I.R.; Barboza, M.J.R.; Baggio-Scheid, V.H.; Moura Neto, C.; Reis, D.A.P.

2010-01-01

From the AISI 4340 bars specimens were made-for-test of creep, they were subjected to different heat treatments for the formation of multiphase microstructures. After this initial treatment, a lot of the specimens were tested in creep. One second batch of specimens was treated with a plasma carbonitriding, and later, were also tested. The carbonitriding layer and microstructure were characterized with X-ray analysis, laser confocal microscopy and hardness testing. Tests showed that the hardness in the steel was reduced due to thermochemical treatment at 500 deg C. We observed variation in creep behavior due to different microstructures formed. After the plasma treatment, there was a considerable reduction in the rate of creep and an increase in the time required for fracture. (author)

High Performance Nanocatalysts Supported on Micro/Nano Carbon Structures Using Ethanol Immersion Pretreatment for Micro DMFCs

International Nuclear Information System (INIS)

Lin, Liang-You; Wu, Yi-Shiuan; Chang, Chaun; Tseng, Fan-Gang

2013-01-01

In this paper, highly dense platinum (Pt) nanocatalysts were successfully deposited on the hydrophilically-treated nano/micro carbon supports with an ethanol (EtOH) immersion pretreatment and an acidic treatment for the performance improvement of methanol oxidation reaction (MOR). In order to thoroughly immerse the three-dimensional, interwoven structures of the carbon cloth fibers with a 6 M sulfuric acid surface modification, which increasing more oxygen-containing functional groups on the surfaces of the carbon supports, the EtOH immersion pretreatment of the carbon supports was utilized prior to the sulfuric acid treatment. Subsequently, Pt catalysts were reduced on the modified carbon supports by a homemade open-loop reduction system (OLRS) [1] For comparisons, carbon cloth (CC) and carbon nanotube on CC (CNT/CC) supports were employed with and without EtOH immersion pretreatments before Pt catalyst reduction. In the cyclic voltammetry (CV) curves, the electrosorption charges of hydrogen ion (Q H ) and the peak current density (I P ) of the fabricated Pt/CC and Pt/CNT/CC electrodes with the EtOH immersion pretreatments can efficiently be enhanced due to more active Pt sites for electrocatalytic reactions

Flexible Carbon Aerogels

Directory of Open Access Journals (Sweden)

Marina Schwan

2016-09-01

Full Text Available Carbon aerogels are highly porous materials with a large inner surface area. Due to their high electrical conductivity they are excellent electrode materials in supercapacitors. Their brittleness, however, imposes certain limitations in terms of applicability. In that context, novel carbon aerogels with varying degree of flexibility have been developed. These highly porous, light aerogels are characterized by a high surface area and possess pore structures in the micrometer range, allowing for a reversible deformation of the aerogel network. A high ratio of pore size to particle size was found to be crucial for high flexibility. For dynamic microstructural analysis, compression tests were performed in-situ within a scanning electron microscope allowing us to directly visualize the microstructural flexibility of an aerogel. The flexible carbon aerogels were found to withstand between 15% and 30% of uniaxial compression in a reversible fashion. These findings might stimulate further research and new application fields directed towards flexible supercapacitors and batteries.

Microstructure evolution of Fe-based nanostructured bainite coating by laser cladding

International Nuclear Information System (INIS)

Guo, Yanbing; Li, Zhuguo; Yao, Chengwu; Zhang, Ke; Lu, Fenggui; Feng, Kai; Huang, Jian; Wang, Min; Wu, Yixiong

2014-01-01

Highlights: • The laser cladding and isothermal holding are used to fabricate nanobainite coating. • Fine prior austenite is obtained to accelerate the bainite transformation. • Low transformation temperature results in fine bainite ferrite and film austenite. • Retained austenite volume fraction in bainite coating is determined by XRD. • Evolution of carbon content in austenite and ferrite is analyzed. - Abstract: A Fe-based coating with nano-scale bainitic microstructure was fabricated using laser cladding and subsequent isothermal heat treatment. The microstructure of the coating was observed and analyzed using optical microscope (OM), field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The results showed that nanostructured bainitic ferrite and carbon-enriched retained austenite distributed uniformly in the coating. Blocky retained austenite was confined to the prior austenite grain boundaries resulting from the elements segregation. The bainitic microstructure obtained at 250 °C had a finer scale compared with that obtained at 300 °C. The volume fraction of austenite increased with increasing transformation temperature for the fully transformed bainitic coating. The bainitic transformation was accelerated as a result of the fine prior austenite generated during the laser cladding. The evolution of the carbon contents in bainitic ferrite and retained austenite revealed the diffusionless mechanism of the bainitic transformation

Microstructure evolution in carbon-ion implanted sapphire

International Nuclear Information System (INIS)

Orwa, J. O.; McCallum, J. C.; Jamieson, D. N.; Prawer, S.; Peng, J. L.; Rubanov, S.

2010-01-01

Carbon ions of MeV energy were implanted into sapphire to fluences of 1x10 17 or 2x10 17 cm -2 and thermally annealed in forming gas (4% H in Ar) for 1 h. Secondary ion mass spectroscopy results obtained from the lower dose implant showed retention of implanted carbon and accumulation of H near the end of range in the C implanted and annealed sample. Three distinct regions were identified by transmission electron microscopy of the implanted region in the higher dose implant. First, in the near surface region, was a low damage region (L 1 ) composed of crystalline sapphire and a high density of plateletlike defects. Underneath this was a thin, highly damaged and amorphized region (L 2 ) near the end of range in which a mixture of i-carbon and nanodiamond phases are present. Finally, there was a pristine, undamaged sapphire region (L 3 ) beyond the end of range. In the annealed sample some evidence of the presence of diamond nanoclusters was found deep within the implanted layer near the projected range of the C ions. These results are compared with our previous work on carbon implanted quartz in which nanodiamond phases were formed only a few tens of nanometers from the surface, a considerable distance from the projected range of the ions, suggesting that significant out diffusion of the implanted carbon had occurred.

Palladium and palladium-tin supported on multi wall carbon nanotubes or carbon for alkaline direct ethanol fuel cell

Science.gov (United States)

Geraldes, Adriana Napoleão; Furtunato da Silva, Dionisio; Martins da Silva, Júlio César; Antonio de Sá, Osvaldo; Spinacé, Estevam Vitório; Neto, Almir Oliveira; Coelho dos Santos, Mauro

2015-02-01

Pd and PdSn (Pd:Sn atomic ratios of 90:10), supported on Multi Wall Carbon Nanotubes (MWCNT) or Carbon (C), are prepared by an electron beam irradiation reduction method. The obtained materials are characterized by X-Ray diffraction (XRD), Energy dispersive X-ray analysis (EDX), Transmission electron Microscopy (TEM) and Cyclic Voltammetry (CV). The activity for ethanol electro-oxidation is tested in alkaline medium, at room temperature, using Cyclic Voltammetry and Chronoamperometry (CA) and in a single alkaline direct ethanol fuel cell (ADEFC), in the temperature range of 60-90 °C. CV analysis finds that Pd/MWCNT and PdSn/MWCNT presents onset potentials changing to negative values and high current values, compared to Pd/C and PdSn/C electrocatalysts. ATR-FTIR analysis, performed during the CV, identifies acetate and acetaldehyde as principal products formed during the ethanol electro-oxidation, with low conversion to CO2. In single fuel cell tests, at 85 °C, using 2.0 mol L-1 ethanol in 2.0 mol L-1 KOH solutions, the electrocatalysts supported on MWCNT, also, show higher power densities, compared to the materials supported on carbon: PdSn/MWCNT, presents the best result (36 mW cm-2). The results show that the use of MWCNT, instead of carbon, as support, plus the addition of small amounts of Sn to Pd, improves the electrocatalytic activity for Ethanol Oxidation Reaction (EOR).

Improved critical current densities of bulk MgB.sub.2./sub. using carbon-coated amorphous boron

Czech Academy of Sciences Publication Activity Database

Muralidhar, M.; Higuchi, M.; Jirsa, Miloš; Diko, P.; Kokal, I.; Murakami, M.

2017-01-01

Roč. 27, č. 4 (2017), s. 1-4, č. článku 6201104. ISSN 1051-8223 Institutional support: RVO:68378271 Keywords : carbon-encapsulated boron * critical current density * flux pinning * micro-structure Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.092, year: 2015

X-ray CT for quantitative food microstructure engineering: The apple case

International Nuclear Information System (INIS)

Herremans, Els; Verboven, Pieter; Defraeye, Thijs; Rogge, Seppe; Ho, Quang Tri; Hertog, Maarten L.A.T.M.; Verlinden, Bert E.; Bongaers, Evi; Wevers, Martine; Nicolai, Bart M.

2014-01-01

Highlights: • Diffusivity of O 2 and CO 2 in Braeburn tissue were computed from X-ray micro-CT data. • Diffusivities were different for the distinct stages of ‘Braeburn’ browning disorder. • Microstructural gas transport constants were implemented in models of intact fruit. • We simulated internal O 2 concentrations for longterm storage treatments of Braeburn. • This engineering approach can optimize internal quality of apple during CA storage. - Abstract: Apple fruit is a major crop that can be supplied year-round due to low temperature storage in a controlled atmosphere with a reduced oxygen concentration and an increased carbon dioxide concentration. The low temperature and dedicated gas concentration levels are designed to provide optimal conditions that prevent ripening while maintaining the fundamental respiratory metabolism necessary for energy supply in the cells that ensures cell and tissue integrity during storage of the fruit. If the concentration of oxygen is too low or that of carbon dioxide too high, a fermentation metabolism is induced that causes the production of off-flavours, results in insufficient energy supply, leading to cell collapse and consequent tissue browning and cavity formation. The microstructural arrangement of cells and intercellular spaces in the apple create specific pathways for transport of the respiratory gasses oxygen and carbon dioxide. We used X-ray CT to characterise the changes in the microstructure of ‘Braeburn’ apple during the development of internal storage disorders. Multiscale modeling was applied to understand the changes in oxygen and carbon dioxide concentrations and respiration and fermentation rates in the apple during the disorder development in controlled atmosphere storage of ‘Braeburn’ apple fruit. The 3D microstructure geometries of healthy, brown tissue and tissue with cavities were created to solve the micro-scale gas-exchange model for O 2 and CO 2 using the finite volume method

X-ray CT for quantitative food microstructure engineering: The apple case

Energy Technology Data Exchange (ETDEWEB)

Herremans, Els, E-mail: els.herremans@biw.kuleuven.be [BIOSYST-MeBioS, KU Leuven, Willem de Croylaan 42, 3001 Leuven (Belgium); Verboven, Pieter; Defraeye, Thijs; Rogge, Seppe; Ho, Quang Tri; Hertog, Maarten L.A.T.M. [BIOSYST-MeBioS, KU Leuven, Willem de Croylaan 42, 3001 Leuven (Belgium); Verlinden, Bert E. [VCBT, Flanders Centre of Postharvest Technology, Willem de Croylaan 42, 3001 Leuven (Belgium); Bongaers, Evi [Bruker microCT, Kartuizersweg 3B, 2550 Kontich (Belgium); Wevers, Martine [MTM, KU Leuven, Kasteelpark Arenberg 44, 3001 Leuven (Belgium); Nicolai, Bart M. [BIOSYST-MeBioS, KU Leuven, Willem de Croylaan 42, 3001 Leuven (Belgium); VCBT, Flanders Centre of Postharvest Technology, Willem de Croylaan 42, 3001 Leuven (Belgium)

2014-04-01

Highlights: • Diffusivity of O{sub 2} and CO{sub 2} in Braeburn tissue were computed from X-ray micro-CT data. • Diffusivities were different for the distinct stages of ‘Braeburn’ browning disorder. • Microstructural gas transport constants were implemented in models of intact fruit. • We simulated internal O{sub 2} concentrations for longterm storage treatments of Braeburn. • This engineering approach can optimize internal quality of apple during CA storage. - Abstract: Apple fruit is a major crop that can be supplied year-round due to low temperature storage in a controlled atmosphere with a reduced oxygen concentration and an increased carbon dioxide concentration. The low temperature and dedicated gas concentration levels are designed to provide optimal conditions that prevent ripening while maintaining the fundamental respiratory metabolism necessary for energy supply in the cells that ensures cell and tissue integrity during storage of the fruit. If the concentration of oxygen is too low or that of carbon dioxide too high, a fermentation metabolism is induced that causes the production of off-flavours, results in insufficient energy supply, leading to cell collapse and consequent tissue browning and cavity formation. The microstructural arrangement of cells and intercellular spaces in the apple create specific pathways for transport of the respiratory gasses oxygen and carbon dioxide. We used X-ray CT to characterise the changes in the microstructure of ‘Braeburn’ apple during the development of internal storage disorders. Multiscale modeling was applied to understand the changes in oxygen and carbon dioxide concentrations and respiration and fermentation rates in the apple during the disorder development in controlled atmosphere storage of ‘Braeburn’ apple fruit. The 3D microstructure geometries of healthy, brown tissue and tissue with cavities were created to solve the micro-scale gas-exchange model for O{sub 2} and CO{sub 2} using the

Microstructure and mechanical properties of carbon fiber reinforced ...

Indian Academy of Sciences (India)

68

Alumina; composites; carbon fiber reinforcement; sol; mechanical properties. 1. Introduction ... The reinforcement was 3D carbon fiber (T300 3k, ex-PAN carbon fiber ... where f(a/H) = 2.9(a/H)1/2 – 4.6(a/H)3/2 + 21.8(a/H)5/2. – 37.6(a/H)7/2 + ...

Sea urchin-like mesoporous carbon material grown with carbon nanotubes as a cathode catalyst support for fuel cells

Energy Technology Data Exchange (ETDEWEB)

Kuo, Ping-Lin; Hsu, Chun-Han; Li, Wan-Ting; Jhan, Jing-Yi; Chen, Wei-Fu [Department of Chemical Engineering, National Cheng Kung University, Tainan 70101 (China)

2010-12-15

A sea urchin-like carbon (UC) material with high surface area (416 m{sup 2} g{sup -1}), adequate electrical conductivity (59.6 S cm{sup -1}) and good chemical stability was prepared by growing carbon nanotubes onto mesoporous carbon hollow spheres. A uniform dispersion of Pt nanoparticles was then anchored on the UC, where the Pt nanoparticles were prepared using benzylamine as the stabilizer. For this Pt loaded carbon, cyclic voltammogram measurements showed an exceptionally high electrochemically active surface area (EAS) (114.8 m{sup 2} g{sup -1}) compared to the commonly used commercial E-TEK catalyst (65.2 m{sup 2} g{sup -1}). The durability test demonstrates that the carbon used as a support exhibited minor loss in EAS of Pt. Compared to the E-TEK (20 wt%) cathode catalyst, this Pt loaded UC catalyst has greatly enhanced catalytic activity toward the oxygen reduction reaction, less cathode flooding and considerably improved performance, resulting in an enhancement of ca. 37% in power density compared with that of E-TEK. Based on the results obtained, the UC is an excellent support for Pt nanoparticles used as cathode catalysts in proton exchange membrane fuel cells. (author)

Microstructure Evolution and Mechanical Behavior of a CMnSiAl TRIP Steel Subjected to Partial Austenitization Along with Quenching and Partitioning Treatment

Science.gov (United States)

Kong, H.; Chao, Q.; Cai, M. H.; Pavlina, E. J.; Rolfe, B.; Hodgson, P. D.; Beladi, H.

2018-02-01

The present study investigated the microstructure evolution and mechanical behavior in a low carbon CMnSiAl transformation-induced plasticity (TRIP) steel, which was subjected to a partial austenitization at 1183 K (910 °C) followed by one-step quenching and partitioning (Q&P) treatment at different isothermal holding temperatures of [533 K to 593 K (260 °C to 320 °C)]. This thermal treatment led to the formation of a multi-phase microstructure consisting of ferrite, tempered martensite, bainitic ferrite, fresh martensite, and retained austenite, offering a superior work-hardening behavior compared with the dual-phase microstructure (i.e., ferrite and martensite) formed after partial austenitization followed by water quenching. The carbon enrichment in retained austenite was related to not only the carbon partitioning during the isothermal holding process, but also the carbon enrichment during the partial austenitization and rapid cooling processes, which has broadened our knowledge of carbon partitioning mechanism in conventional Q&P process.

Active carbon supported molybdenum carbides for higher alcohols synthesis from syngas

DEFF Research Database (Denmark)

Wu, Qiongxiao; Chiarello, Gian Luca; Christensen, Jakob Munkholt

This work provides an investigation of the high pressure CO hydrogenation to higher alcohols on K2CO3 promoted active carbon supported molybdenum carbide. Both activity and selectivity to alcohols over supported molybdenum carbides increased significantly compared to bulk carbides in literatures...

Advanced microstructures based on poly(trimethylene carbonate) microfabrication and stereolithography

NARCIS (Netherlands)

Schüller-Ravoo, S.

2011-01-01

There is an evident need in the biomedical field to develop (new) materials with tailored properties for specific applications. In addition it is essential to be able to process these materials into desired two- and three-dimensional shapes and (micro)structures. Microfabrication, and especially

Process intensification by combination of activated carbon supported catalysts and alternative energy sources

OpenAIRE

Calvino Casilda, Vanesa; Pérez-Mayoral, E.

2014-01-01

[EN] Activated carbons are well known for their catalytic properties and for being used as a catalyst support in heterogeneous catalysis. Activated carbons possess most of the desired properties of a catalyst support; inertness towards unwanted reactions, stability under regeneration and reaction conditions, suitable mechanical properties, tunable surface area, porosity, and the possibility of being manufactured in different size and shape. On the other hand, the in...

Microstructural characterization of pipe bomb fragments

International Nuclear Information System (INIS)

Gregory, Otto; Oxley, Jimmie; Smith, James; Platek, Michael; Ghonem, Hamouda; Bernier, Evan; Downey, Markus; Cumminskey, Christopher

2010-01-01

Recovered pipe bomb fragments, exploded under controlled conditions, have been characterized using scanning electron microscopy, optical microscopy and microhardness. Specifically, this paper examines the microstructural changes in plain carbon-steel fragments collected after the controlled explosion of galvanized, schedule 40, continuously welded, steel pipes filled with various smokeless powders. A number of microstructural changes were observed in the recovered pipe fragments: deformation of the soft alpha-ferrite grains, deformation of pearlite colonies, twin formation, bands of distorted pearlite colonies, slip bands, and cross-slip bands. These microstructural changes were correlated with the relative energy of the smokeless powder fillers. The energy of the smokeless powder was reflected in a reduction in thickness of the pipe fragments (due to plastic strain prior to fracture) and an increase in microhardness. Moreover, within fragments from a single pipe, there was a radial variation in microhardness, with the microhardness at the outer wall being greater than that at the inner wall. These findings were consistent with the premise that, with the high energy fillers, extensive plastic deformation and wall thinning occurred prior to pipe fracture. Ultimately, the information collected from this investigation will be used to develop a database, where the fragment microstructure and microhardness will be correlated with type of explosive filler and bomb design. Some analyses, specifically wall thinning and microhardness, may aid in field characterization of explosive devices.

Engineering catalytic activity via ion beam bombardment of catalyst supports for vertically aligned carbon nanotube growth

Science.gov (United States)

Islam, A. E.; Nikolaev, P.; Amama, P. B.; Zakharov, D.; Sargent, G.; Saber, S.; Huffman, D.; Erford, M.; Semiatin, S. L.; Stach, E. A.; Maruyama, B.

2015-09-01

Carbon nanotube growth depends on the catalytic activity of metal nanoparticles on alumina or silica supports. The control on catalytic activity is generally achieved by variations in water concentration, carbon feed, and sample placement on a few types of alumina or silica catalyst supports obtained via thin film deposition. We have recently expanded the choice of catalyst supports by engineering inactive substrates like c-cut sapphire via ion beam bombardment. The deterministic control on the structure and chemistry of catalyst supports obtained by tuning the degree of beam-induced damage have enabled better regulation of the activity of Fe catalysts only in the ion beam bombarded areas and hence enabled controllable super growth of carbon nanotubes. A wide range of surface characterization techniques were used to monitor the catalytically active surface engineered via ion beam bombardment. The proposed method offers a versatile way to control carbon nanotube growth in patterned areas and also enhances the current understanding of the growth process. With the right choice of water concentration, carbon feed and sample placement, engineered catalyst supports may extend the carbon nanotube growth yield to a level that is even higher than the ones reported here, and thus offers promising applications of carbon nanotubes in electronics, heat exchanger, and energy storage.

Relation microstructure-propriétés mécaniques d'un acier martensitique inoxydable

Directory of Open Access Journals (Sweden)

Badinier Guillaume

2013-11-01

Full Text Available The relationship between microstructure and mechanical properties of MaX (1.4006 martensitic stainless steel has been studied. Optical microscopy was used to characterize the microstructure and the volume fraction of retained ferrite was measured by image analysis. Mechanical properties were measured in uni-axial tensile testing and a composite model has been developed to capture the effect of both the retained ferrite and the carbon content of the martensitic phase. First results show a reasonable correlation between the experimental stress-strain curves and the model. Results are discussed in view of a previous study on plain martensitic carbon steels.

Microstructures and phase transformations in interstitial alloys of tantalum

International Nuclear Information System (INIS)

Dahmen, U.

1979-01-01

The analysis of microstructures, phases, and possible ordering of interstitial solute atoms is fundamental to an understanding of the properties of metal-interstitial alloys in general. As evidenced by the controversies on phase transformations in the particular system tantalum--carbon, our understanding of this class of alloys is inferior to our knowledge of substitutional metal alloys. An experimental clarification of these controversies in tantalum was made. Using advanced techniques of electron microscopy and ultrahigh vacuum techology, an understanding of the microstructures and phase transformations in dilute interstitial tantalum--carbon alloys is developed. Through a number of control experiments, the role and sources of interstitial contamination in the alloy preparation (and under operating conditions) are revealed. It is demonstrated that all previously published work on the dilute interstitially ordered phase Ta 64 C can be explained consistently in terms of ordering of the interstitial contaminants oxygen and hydrogen, leading to the formation of the phases Ta 12 O and Ta 2 H

Constitution, microstructure, mechanical properties, and performance of magnetron-sputtered carbon films with additions of silicon

Energy Technology Data Exchange (ETDEWEB)

Bauer, C. [Forschungszentrum Karlsruhe GmbH, Institut fuer Materialforschung I, Postfach 3640, 76021 Karlsruhe (Germany); Leiste, H.; Stueber, M.; Ulrich, S.; Holleck, H.

2003-11-01

Amorphous carbon films with additions of silicon were deposited by non-reactive magnetron sputtering on WC-Co hard metal and on silicon substrates. The targets were hot-pressed, homogenous mixtures of graphite and silicon carbide powder. Additional argon ion bombardment of the growing film was applied by a substrate bias varied between 0V and -800 V. The deposited amorphous carbon films with two different silicon contents (5 at.% and 23 at.% respectively) were characterised with respect to their microstructure, density, thickness, residual stress, Vickers hardness, Young's modulus, critical load of failure, friction coefficient, and wear behaviour. The residual stress of the carbon films could be remarkably lowered by silicon additions (23 at.%). The hardness reached high values (2200 HV0.05) and the friction coefficient for unlubricated sliding friction against a steel (1.3505) counterpart was as low as 0.06. (Abstract Copyright [2003], Wiley Periodicals, Inc.) [German] Amorphe Kohlenstoffschichten mit Zusaetzen von Silizium wurden nichtreaktiv durch Magnetronzerstaeubung auf Substraten aus WC-Co Hartmetall und Silizium abgeschieden. Die neuartigen Targets wurden durch Heisspressen einer homogenen Mischung aus Graphit- und Siliziumcarbidpulver hergestellt. Durch Anlegen einer elektrischen Substratvorspannung von 0 V bis -800 V wurden die aufwachsenden Schichten zusaetzlich mit Argonionen unterschiedlicher Energie beschossen. Die abgeschiedenen amorphen Kohlenstoffschichten mit Zusaetzen von Silizium (5 at% bzw. 23 at%) wurden hinsichtlich Struktur, Dichte, Dicke, Eigenspannungen, Vickershaerte, reduziertem Elastizitaetsmodul, kritischer Last des Versagens im Ritztest, Reibwert und Verschleissverhalten untersucht. Fuer Schichten mit hohem Siliziumgehalt (23 at%) erfolgte eine erhebliche Reduzierung der Eigenspannung, die Haerte wurde bei sehr hohen Werten stabilisiert (2200 HV0,05) und der Reibungskoeffizient fuer ungeschmierte Gleitreibung gegen Stahl (1

The Effect of Prestrain Temperature on Kinetics of Static Recrystallization, Microstructure Evolution, and Mechanical Properties of Low Carbon Steel

Science.gov (United States)

Akbari, Edris; Karimi Taheri, Kourosh; Karimi Taheri, Ali

2018-05-01

In this research, the samples of a low carbon steel sheet were rolled up to a thickness prestrain of 67% at three different temperatures consisted of room, blue brittleness, and subzero temperature. Microhardness, SEM, and tensile tests were carried out to evaluate the static recrystallization kinetics defined by the Avrami equation, microstructural evolution, and mechanical properties. It was found that the Avrami exponent is altered with change in prestrain temperature and it achieves the value of 1 to 1. 5. Moreover, it was indicated that prestraining at subzero temperature followed by annealing at 600 °C leads to considerable enhancement in tensile properties and kinetics of static recrystallization compared to room and blue brittleness temperatures. The prestraining at blue brittleness temperature followed by annealing treatment caused, however, a higher strength and faster kinetics compared with that at room temperature. It was concluded that although from the steel ductility point of view, the blue brittleness temperature is called an unsuitable temperature, but it can be used as prestraining temperature to develop noticeable combination of strength and ductility in low carbon steel.

Fuel cell testing of Pt–Ru catalysts supported on differently prepared and pretreated carbon nanotubes

International Nuclear Information System (INIS)

Tokarz, Wojciech; Lota, Grzegorz; Frackowiak, Elzbieta; Czerwiński, Andrzej; Piela, Piotr

2013-01-01

Proton-exchange membrane fuel cell (PEMFC) testing of Pt–Ru catalysts supported on differently prepared multiwall carbon nanotube (MCNT) supports was performed to elucidate the influence of the different supports on the operating characteristics of the catalysts under real direct methanol fuel cell (DMFC) anode and H 2 -PEMFC anode conditions. The MCNTs were either thin, entangled or thick, disentangled. Pretreatment of the MCNTs was also done and it was either high-temperature KOH etching or annealing (graphitization). The performance of the catalysts was compared against the performance of a commercial Pt–Ru catalyst supported on a high-surface-area carbon black. Among the different MCNT supports, the graphitized, entangled support offered the best performance in all tests, which was equal to the performance of the commercial catalyst, despite the MCNT catalyst layer was ca. 2.2 times thicker than the carbon black catalyst layer. Even for an MCNT catalyst layer, which was almost 7 times thicker than the carbon black catalyst layer, the transport limitations were not prohibitive. This confirmed the expected potential of nanotube supports for providing superior reactant transport properties of the PEMFC catalyst layers

Quantitative characterization of microstructure of pure copper processed by ECAP

Czech Academy of Sciences Publication Activity Database

Šedivý, O.; Beneš, V.; Ponížil, P.; Král, Petr; Sklenička, Václav

2013-01-01

Roč. 32, č. 2 (2013), s. 65-75 ISSN 1580-3139 Institutional support: RVO:68081723 Keywords : electron backscatter diffraction * ultrafine-grained metals * microstructure * microstructure characterization * grain boundaries Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.697, year: 2013

The Effect of Welding Process on the Microstructure of HY-130 Steel Weldments

Science.gov (United States)

1988-12-01

rates. Cooling is continuous, therefore continuous cooling transformation ( CCT ) diagrams may be used to predict the microstructure of the particular...weld metal composition. A schematic CCT diagram for low-carbon steel [Ref. 12] is included at Figure 3. This summarizes the weld metal microstructure...the driving force for the reaction. From the CCT diagram it is seen that increasing the cooling rate would increase the formation of acic- ular

Thermal degradation kinetics of polyketone based on styrene and carbon monoxide

International Nuclear Information System (INIS)

Mu, Jiali; Fan, Wenjun; Shan, Shaoyun; Su, Hongying; Wu, Shuisheng; Jia, Qingming

2014-01-01

Highlights: • The PK were synthesized from carbon monoxide and styrene in the presence of PANI-PdCl 2 catalyst and PdCl 2 catalyst. • The structures and thermal behaviors of PK prepared by homogenous and the supported catalyst were investigated. • The microstructures of PK were changed in the supported catalyst system. • The alternating PK copolymer (PANI-PdCl 2 catalyst) was more thermally stable than PK (PdCl 2 catalyst). • The degradation activation energy values were estimated by Flynn–Wall–Ozawa method and Kissinger method. - Abstract: Copolymerization of styrene with carbon monoxide to give polyketones (PK) was carried out under homogeneous palladium catalyst and polyaniline (PANI) supported palladium(II) catalyst, respectively. The copolymers were characterized by 1 H NMR, 13 C NMR and GPC. The results indicated that the PK catalyzed by the supported catalyst has narrow molecular weight distribution (PDI = 1.18). For comparison purpose of thermal behaviors of PK prepared by the homogeneous and the supported catalyst, thermogravimetric (TG) analysis and derivative thermogravimetric (DTG) were conducted at different heating rates. The peak temperatures (396–402 °C) for PK prepared by the supported catalyst are higher than those (387–395 °C) of PK prepared by the homogeneous catalyst. The degradation activation energy (E k ) values were estimated by Flynn–Wall–Ozawa method and Kissinger method, respectively. The E k values, as determined by two methods, were found to be in the range 270.72 ± 0.03–297.55 ± 0.10 kJ mol −1 . Structures analysis and thermal degradation analysis revealed that the supported catalyst changed the microstructures of PK, resulting in improving thermal stability of PK

Thermal degradation kinetics of polyketone based on styrene and carbon monoxide

Energy Technology Data Exchange (ETDEWEB)

Mu, Jiali, E-mail: jiaqm411@163.com; Fan, Wenjun; Shan, Shaoyun; Su, Hongying; Wu, Shuisheng; Jia, Qingming

2014-03-01

Highlights: • The PK were synthesized from carbon monoxide and styrene in the presence of PANI-PdCl{sub 2} catalyst and PdCl{sub 2} catalyst. • The structures and thermal behaviors of PK prepared by homogenous and the supported catalyst were investigated. • The microstructures of PK were changed in the supported catalyst system. • The alternating PK copolymer (PANI-PdCl{sub 2} catalyst) was more thermally stable than PK (PdCl{sub 2} catalyst). • The degradation activation energy values were estimated by Flynn–Wall–Ozawa method and Kissinger method. - Abstract: Copolymerization of styrene with carbon monoxide to give polyketones (PK) was carried out under homogeneous palladium catalyst and polyaniline (PANI) supported palladium(II) catalyst, respectively. The copolymers were characterized by {sup 1}H NMR, {sup 13}C NMR and GPC. The results indicated that the PK catalyzed by the supported catalyst has narrow molecular weight distribution (PDI = 1.18). For comparison purpose of thermal behaviors of PK prepared by the homogeneous and the supported catalyst, thermogravimetric (TG) analysis and derivative thermogravimetric (DTG) were conducted at different heating rates. The peak temperatures (396–402 °C) for PK prepared by the supported catalyst are higher than those (387–395 °C) of PK prepared by the homogeneous catalyst. The degradation activation energy (E{sub k}) values were estimated by Flynn–Wall–Ozawa method and Kissinger method, respectively. The E{sub k} values, as determined by two methods, were found to be in the range 270.72 ± 0.03–297.55 ± 0.10 kJ mol{sup −1}. Structures analysis and thermal degradation analysis revealed that the supported catalyst changed the microstructures of PK, resulting in improving thermal stability of PK.

Pyrolytic carbon coatings for nuclear fuels from commercial butane

International Nuclear Information System (INIS)

Abdelrazek, I.D.; Abdelhalim, A.S.

1976-01-01

Uranium dioxide and graphite semi-spherical particles (average diameter = 300 um) were coated with pyrolytic carbon at relatively low temperatures (800 to 1200 0 C). The spouting gas was a mixture of commercial butane and nitrogen. The hydrocarbon served as a source for carbon whereas nitrogenated as a diluent and a support for the bed. The total gas flow rate was 3.5 lit/min and the hydrocarbon content varied from 3 to 10%. Coating efficiencies ranging from 4 to 25 percent were obtained. The densities of the coatings varied from 1.25 g/cm 3 (which corresponds to coatings of laminar microstructures) and 1.82 g/cm 3 (which suggests the formation of isotropic coatings. Metallographic examination (using polarized light) of the pyrolytic carbon formed at the experimental conditions indicated the possibility of using the coatings for nuclear fuel applications

The microstructure, mechanical and friction properties of protective diamond like carbon films on magnesium alloy

Science.gov (United States)

Zou, Y. S.; Wu, Y. F.; Yang, H.; Cang, K.; Song, G. H.; Li, Z. X.; Zhou, K.

2011-12-01

Protective hard coatings deposited on magnesium alloys are believed to be effective for overcoming their poor wear properties. In this work, diamond-like carbon (DLC) films as hard protective films were deposited on AZ91 magnesium alloy by arc ion plating under negative pulse bias voltages ranging from 0 to -200 V. The microstructure, composition and mechanical properties of the DLC films were analyzed by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and nanoindentation. The tribological behavior of uncoated and coated AZ91 magnesium alloy was investigated using a ball-on-disk tribotester. The results show that the negative pulse bias voltage used for film deposition has a significant effect on the sp3 carbon content and mechanical properties of the deposited DLC films. A maximum sp3 content of 33.3% was obtained at -100 V, resulting in a high hardness of 28.6 GPa and elastic modulus of 300.0 GPa. The DLC films showed very good adhesion to the AZ91 magnesium alloy with no observable cracks and delamination even during friction testing. Compared with the uncoated AZ91 magnesium alloy, the magnesium alloy coated with DLC films exhibits a low friction coefficient and a narrow, shallow wear track. The wear resistance and surface hardness of AZ91 magnesium alloy can be significantly improved by coating a layer of DLC protective film due to its high hardness and low friction coefficient.

The microstructure, mechanical and friction properties of protective diamond like carbon films on magnesium alloy

International Nuclear Information System (INIS)

Zou, Y.S.; Wu, Y.F.; Yang, H.; Cang, K.; Song, G.H.; Li, Z.X.; Zhou, K.

2011-01-01

Protective hard coatings deposited on magnesium alloys are believed to be effective for overcoming their poor wear properties. In this work, diamond-like carbon (DLC) films as hard protective films were deposited on AZ91 magnesium alloy by arc ion plating under negative pulse bias voltages ranging from 0 to -200 V. The microstructure, composition and mechanical properties of the DLC films were analyzed by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and nanoindentation. The tribological behavior of uncoated and coated AZ91 magnesium alloy was investigated using a ball-on-disk tribotester. The results show that the negative pulse bias voltage used for film deposition has a significant effect on the sp 3 carbon content and mechanical properties of the deposited DLC films. A maximum sp 3 content of 33.3% was obtained at -100 V, resulting in a high hardness of 28.6 GPa and elastic modulus of 300.0 GPa. The DLC films showed very good adhesion to the AZ91 magnesium alloy with no observable cracks and delamination even during friction testing. Compared with the uncoated AZ91 magnesium alloy, the magnesium alloy coated with DLC films exhibits a low friction coefficient and a narrow, shallow wear track. The wear resistance and surface hardness of AZ91 magnesium alloy can be significantly improved by coating a layer of DLC protective film due to its high hardness and low friction coefficient.

The microstructure, mechanical and friction properties of protective diamond like carbon films on magnesium alloy

Energy Technology Data Exchange (ETDEWEB)

Zou, Y.S., E-mail: yshzou75@gmail.com [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu, 210094 (China); Wu, Y.F.; Yang, H.; Cang, K. [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu, 210094 (China); Song, G.H. [School of Materials Science and Engineering, Shenyang University of Technology, Shenyang, Liaoning, 110178 (China); Li, Z.X.; Zhou, K. [School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu, 210094 (China)

2011-12-01

Protective hard coatings deposited on magnesium alloys are believed to be effective for overcoming their poor wear properties. In this work, diamond-like carbon (DLC) films as hard protective films were deposited on AZ91 magnesium alloy by arc ion plating under negative pulse bias voltages ranging from 0 to -200 V. The microstructure, composition and mechanical properties of the DLC films were analyzed by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and nanoindentation. The tribological behavior of uncoated and coated AZ91 magnesium alloy was investigated using a ball-on-disk tribotester. The results show that the negative pulse bias voltage used for film deposition has a significant effect on the sp{sup 3} carbon content and mechanical properties of the deposited DLC films. A maximum sp{sup 3} content of 33.3% was obtained at -100 V, resulting in a high hardness of 28.6 GPa and elastic modulus of 300.0 GPa. The DLC films showed very good adhesion to the AZ91 magnesium alloy with no observable cracks and delamination even during friction testing. Compared with the uncoated AZ91 magnesium alloy, the magnesium alloy coated with DLC films exhibits a low friction coefficient and a narrow, shallow wear track. The wear resistance and surface hardness of AZ91 magnesium alloy can be significantly improved by coating a layer of DLC protective film due to its high hardness and low friction coefficient.

Nanostructured Carbon Materials as Supports in the Preparation of Direct Methanol Fuel Cell Electrocatalysts

Directory of Open Access Journals (Sweden)

María Jesús Lázaro

2013-08-01

Full Text Available Different advanced nanostructured carbon materials, such as carbon nanocoils, carbon nanofibers, graphitized ordered mesoporous carbons and carbon xerogels, presenting interesting features such as high electrical conductivity and extensively developed porous structure were synthesized and used as supports in the preparation of electrocatalysts for direct methanol fuel cells (DMFCs. The main advantage of these supports is that their physical properties and surface chemistry can be tailored to adapt the carbonaceous material to the catalytic requirements. Moreover, all of them present a highly mesoporous structure, diminishing diffusion problems, and both graphitic character and surface area can be conveniently modified. In the present work, the influence of the particular features of each material on the catalytic activity and stability was analyzed. Results have been compared with those obtained for commercial catalysts supported on Vulcan XC-72R, Pt/C and PtRu/C (ETEK. Both a highly ordered graphitic and mesopore-enriched structure of these advanced nanostructured materials resulted in an improved electrochemical performance in comparison to the commercial catalysts assayed, both towards CO and alcohol oxidation.

Mixed structures in continuously cooled low-carbon automotive steels

International Nuclear Information System (INIS)

Khalid, F.A.; Edmonds, D.V.

1993-01-01

Mixed microstructures have been studied in low- carbon microalloyed steels suitable for automotive applications, after continuous cooling from the hot-rolled condition. Microstructural features such as polygonal ferrite, bainitic and acicular ferrite and microphase constituent are identified using transmission electron microscopy. The influence of these mixed structures on the tensile strength, impact toughness and fracture behaviour is examined. It is found that improvements in impact toughness as compared with microalloyed medium- carbon ferrite/pearlite steels can be achieved from these predominantly acicular structures developed by controlling alloy composition and continuous cooling of these lower carbon steels. (orig.)

Formation of Medium Carbon TRIP Steel Microstructure During Annealing in the Intercritical Temperature Range

Directory of Open Access Journals (Sweden)

Kokosza A.

2014-10-01

Full Text Available The paper presents the results of research conducted on austenite formation in the microstructure of 41MnSi6-5 TRIP steel during annealing in the intercritical temperature range. The influence of the annealing temperature on the volume fraction of retained austenite in the microstructure of the investigated steel after water quenching was also determined.

Effect of substrate bias voltage on tensile properties of single crystal silicon microstructure fully coated with plasma CVD diamond-like carbon film

Science.gov (United States)

Zhang, Wenlei; Hirai, Yoshikazu; Tsuchiya, Toshiyuki; Tabata, Osamu

2018-06-01

Tensile strength and strength distribution in a microstructure of single crystal silicon (SCS) were improved significantly by coating the surface with a diamond-like carbon (DLC) film. To explore the influence of coating parameters and the mechanism of film fracture, SCS microstructure surfaces (120 × 4 × 5 μm3) were fully coated by plasma enhanced chemical vapor deposition (PECVD) of a DLC at five different bias voltages. After the depositions, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermal desorption spectrometry (TDS), surface profilometry, atomic force microscope (AFM) measurement, and nanoindentation methods were used to study the chemical and mechanical properties of the deposited DLC films. Tensile test indicated that the average strength of coated samples was 13.2-29.6% higher than that of the SCS sample, and samples fabricated with a -400 V bias voltage were strongest. The fracture toughness of the DLC film was the dominant factor in the observed tensile strength. Deviations in strength were reduced with increasingly negative bias voltage. The effect of residual stress on the tensile properties is discussed in detail.

Carbon fiber microelectrodes modified with carbon nanotubes as a new support for immobilization of glucose oxidase

International Nuclear Information System (INIS)

Wen, H.; Nallathambi, V.; Chakraborty, D.; Barton, S.C.

2011-01-01

Carboxylated carbon nanotubes were coated onto carbon microfiber electrodes to create a micron-scale bioelectrode. This material has a high surface area and can serve as a support for immobilization of enzymes such as glucose oxidase. A typical carbon nanotube loading of 13 μg cm -1 yields a coating thickness of 17 μm and a 2000-fold increase in surface capacitance. The modified electrode was further coated with a biocatalytic hydrogel composed of a conductive redox polymer, glucose oxidase, and a crosslinker to create a glucose bioelectrode. The current density on oxidation of glucose is 16.6 mA cm-2 at 0.5 V (vs. Ag/AgCl) in oxygen-free glucose solution. We consider this approach to be useful for designing and characterizing surface treatments for carbon mats and papers by mimicking their local microenvironment. (author)

Studies on the core-support carbon material for VHTR, (1)

International Nuclear Information System (INIS)

Matsuo, Hideto; Saito, Tamotsu; Fukuda, Yasumasa; Sasaki, Yasuichi; Hasegawa, Takashi.

1979-11-01

To obtain information of core-support carbon material for VHTR, thermal conductivity and electrical resistivity of three domestic carbon blocks were measured. Results indicated the need for development of carbon material with lower thermal conductivity for VHTR. These two were also measured of the samples heat-treated between 1000 0 C and 3040 0 C for one hour. Thermal conductivity increased with heat-treatment above 1200 0 C and resistivity stayed constant between 1500 0 C and 2000 0 C. The results should be useful in choosing the final heat-treatment temperature in carbon material production. The changes of Lorentz number with heat treatment were classified into three heat-treatment temperature regions of below 1500 0 C, 1500 0 C - 2500 0 C, and above 2500 0 C; the results are interpreted with a graphitization model. (author)

Energy and climate hand-in-hand: Financing RES-E support with carbon revenues

International Nuclear Information System (INIS)

Verde, Stefano F.; Pazienza, Maria Grazia

2016-01-01

In Italy, the cost of support for renewable electricity (RES-E) is largely recovered through the “A3 surcharge”, which weighs heavily on electricity bills. Using household survey data, we show the A3 surcharge is markedly regressive. Carbon taxation in the non-ETS sector is envisaged as a means to reduce CO_2 emissions cost-effectively and generate revenue to lower the A3 surcharge. A non-ETS carbon tax would be less regressive than the A3 surcharge and its cost would be more evenly distributed across households. We calculate the revenue of a €20/tCO_2 non-ETS carbon tax would have allowed a cut in the A3 surcharge of about 68% in 2011, and 39% in 2012. The impact of the carbon tax plus the reduced A3 surcharge would have been less regressive, but the cost higher for most households. The restrictions imposed in the simulations mean the results are only appropriate to render first-round effects of the reform. Policy relevance: In the vast majority of the EU Member States, the cost of RES-E support is largely paid by electricity consumers, most often through specific surcharges. Rising electricity prices are a common concern given the implications for competitiveness and equity. The Member States facing this issue could conveniently address it through environmental tax reforms consistent with the Climate and Energy Package. Replacing RES-E surcharges with carbon taxes in the non-ETS sector would permit cost-effective reduction of CO_2 emissions while allocating the cost of RES-E support more equitably. The difference in regressivity would stem from the different consumption patterns of home fuels (including electricity) and motor fuels across income distribution. A cross-country comparison of energy household budget shares proves the structural nature of this difference between home fuels and motor fuels. Moreover, the notion that electricity consumers should pay for RES-E support is questioned on the grounds that electricity is a basic necessity good and RES

A phenyl-sulfonic acid anchored carbon-supported platinum catalyst for polymer electrolyte fuel cell electrodes

International Nuclear Information System (INIS)

Selvarani, G.; Sahu, A.K.; Choudhury, N.A.; Sridhar, P.; Pitchumani, S.; Shukla, A.K.

2007-01-01

A method, to anchor phenyl-sulfonic acid functional groups with the platinum catalyst supported onto a high surface-area carbon substrate, is reported. The use of the catalyst in the electrodes of a polymer electrolyte fuel cell (PEFC) helps enhancing its performance. Characterization of the catalyst by Fourier transform infra red (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and point-of-zero-charge (PZC) studies suggests that the improvement in performance of the PEFC is facilitated not only by enlarging the three-phase boundary in the catalyst layer but also by providing ionic-conduction paths as well as by imparting negative charge to platinum sites with concomitant oxidation of sulfur present in the carbon support. It is argued that the negatively charged platinum sites help repel water facilitating oxygen to access the catalyst sites. The PEFC with modified carbon-supported platinum catalyst electrodes exhibits 40% enhancement in its power density as compared to the one with unmodified carbon-supported platinum catalyst electrodes

Highly Active, Carbon-supported, PdSn Nano-core, Partially ...

African Journals Online (AJOL)

Carbon-supported, Pt partially covered, PdSn alloy nanoparticles (Pt-PdSn/C) were synthesized via a metathetical reaction of PdSn alloy nanoparticles, and a platinum precursor. The electrochemical activity was evaluated by methanol oxidation. The Pt-PdSn/C catalysts were characterized by transmission electron ...

Microstructural characteristics and toughness of the simulated coarse grained heat affected zone of high strength low carbon bainitic steel

International Nuclear Information System (INIS)

Lan Liangyun; Qiu Chunlin; Zhao Dewen; Gao Xiuhua; Du Linxiu

2011-01-01

Highlights: → Total toughness can be separated into crack initiation energy and crack propagation energy. → Small effective grain size of lath martensite can improve the crack propagation energy. → MA constituent is mainly responsible for the low toughness of coarse bainite specimens. → High angle packet boundary in coarser bainite has few contributions to improving crack propagation energy. - Abstract: The correlation of microstructural characteristics and toughness of the simulated coarse grained heat affected zone (CGHAZ) of low carbon bainitic steel was investigated in this study. The toughness of simulated specimens was examined by using an instrumented Charpy impact tester after the simulation welding test was conducted with different cooling times. Microstructure observation and crystallographic feature analysis were conducted by means of optical microscope and scanning electron microscope equipped with electron back scattered diffraction (EBSD) system, respectively. The main microstructure of simulated specimen changes from lath martensite to coarse bainite with the increase in cooling time. The deterioration of its toughness occurs when the cooling time ranges from 10 to 50 s compared with base metal toughness, and the toughness becomes even worse when the cooling time increases to 90 s or more. The MA (martensite-austenite) constituent is primary responsible for the low toughness of simulated CGHAZ with high values of cooling time because the large MA constituent reduces the crack initiation energy significantly. For crack propagation energy, the small effective grain size of lath martensite plays an important role in improving the crack propagation energy. By contrast, high misorientation packet boundary in coarse bainite seems to have few contributions to the improvement of the toughness because cleavage fracture micromechanism of coarse bainite is mainly controlled by crack initiation.

Microstructural characteristics and toughness of the simulated coarse grained heat affected zone of high strength low carbon bainitic steel

Energy Technology Data Exchange (ETDEWEB)

Lan Liangyun, E-mail: lly.liangyun@gmail.com [State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819 (China); Qiu Chunlin; Zhao Dewen; Gao Xiuhua; Du Linxiu [State Key Laboratory of Rolling Technology and Automation, Northeastern University, Shenyang 110819 (China)

2011-11-25

Highlights: {yields} Total toughness can be separated into crack initiation energy and crack propagation energy. {yields} Small effective grain size of lath martensite can improve the crack propagation energy. {yields} MA constituent is mainly responsible for the low toughness of coarse bainite specimens. {yields} High angle packet boundary in coarser bainite has few contributions to improving crack propagation energy. - Abstract: The correlation of microstructural characteristics and toughness of the simulated coarse grained heat affected zone (CGHAZ) of low carbon bainitic steel was investigated in this study. The toughness of simulated specimens was examined by using an instrumented Charpy impact tester after the simulation welding test was conducted with different cooling times. Microstructure observation and crystallographic feature analysis were conducted by means of optical microscope and scanning electron microscope equipped with electron back scattered diffraction (EBSD) system, respectively. The main microstructure of simulated specimen changes from lath martensite to coarse bainite with the increase in cooling time. The deterioration of its toughness occurs when the cooling time ranges from 10 to 50 s compared with base metal toughness, and the toughness becomes even worse when the cooling time increases to 90 s or more. The MA (martensite-austenite) constituent is primary responsible for the low toughness of simulated CGHAZ with high values of cooling time because the large MA constituent reduces the crack initiation energy significantly. For crack propagation energy, the small effective grain size of lath martensite plays an important role in improving the crack propagation energy. By contrast, high misorientation packet boundary in coarse bainite seems to have few contributions to the improvement of the toughness because cleavage fracture micromechanism of coarse bainite is mainly controlled by crack initiation.

The effect of the multi-pass non-circular drawing sequence on mechanical properties and microstructure evolution of low-carbon steel

International Nuclear Information System (INIS)

Lee, Jung Wan; Baek, Hyun Moo; Hwang, Sun Kwang; Son, Il-Heon; Bae, Chul Min; Im, Yong-Taek

2014-01-01

Highlights: • A multi-pass non-circular drawing sequence is proposed to make high-strength wires. • The sequence was designed and applied for a low-carbon steel wire up to the 10th pass. • Many LAGBs and small grain size of the wire produced by the sequence were obtained. • High plastic deformation was imposed on the wire, resulting in grain refinement. • The sequence made fine-grained wires with improved UTS, ductility and fatigue life. - Abstract: In this study, the multi-pass non-circular drawing sequence was investigated for manufacturing high-strength wires with better ductility in a simple continuous way without adding additional alloys and heat treatment considering the effect of microstructure evolution and die geometry of the sequence on the mechanical properties of low-carbon steel during the process. For this purpose, the non-circular drawing sequence was designed and applied up to the 10th pass at room temperature. Mechanical properties and microstructure evolution of the specimen processed by the sequence were investigated by tension, Vickers micro-hardness, electron backscattering diffraction (EBSD), and fatigue tests compared with those for the conventional wire-drawing process. From the EBSD results, the higher low angle grain boundaries length per unit area and smaller average grain size of the specimen processed by the non-circular drawing sequence were obtained than those of the specimen processed by the wire-drawing process for the 8th pass. These results indicated that more plastic deformation was imposed in the material by the non-circular drawing sequence, resulting in grain refinement of the deformed specimen compared to the wire-drawing process. It is demonstrated that the multi-pass non-circular drawing sequence could be beneficial in producing fine-grained wires with improved ultimate tensile strength, ductility, and fatigue property by simply changing drawing dies geometry of the conventional wire-drawing process

Magnetic Carbon Supported Palladium Nanoparticles: An Efficient and Sustainable Catalyst for Hydrogenation Reactions

Science.gov (United States)

Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for the hydrogenation of alkenes and reduction of aryl nitro compounds.

Enhancing Microstructure and Mechanical Properties of AZ31-MWCNT Nanocomposites through Mechanical Alloying

Directory of Open Access Journals (Sweden)

J. Jayakumar

2013-01-01

Full Text Available Multiwall carbon nanotubes (MWCNTs reinforced Mg alloy AZ31 nanocomposites were fabricated by mechanical alloying and powder metallurgy technique. The reinforcement material MWCNTs were blended in three weight fractions (0.33%, 0.66%, and 1% with the matrix material AZ31 (Al-3%, zinc-1% rest Mg and blended through mechanical alloying using a high energy planetary ball mill. Specimens of monolithic AZ31 and AZ31-MWCNT composites were fabricated through powder metallurgy technique. The microstructure, density, hardness, porosity, ductility, and tensile properties of monolithic AZ31 and AZ31-MWCNT nano composites were characterized and compared. The characterization reveals significant reduction in CNT (carbon nanoTube agglomeration and enhancement in microstructure and mechanical properties due to mechanical alloying through ball milling.

Evaluation of microstructural difference in low alloy steel (SA508 CI.3) by magnetic measurements

International Nuclear Information System (INIS)

Chi, Se Hwan; Park, Duck Gun; Hong, Jun Hwa; Kuk, Il Hium; Song, Sook Hyang; Shur, Dong Soo

1997-01-01

Magnetic measurements on SA 508 Cl. 3 low alloy reactor pressure vessel (RPV) steels of three different refining processes were conducted to prepare baseline magnetic properties for future comparison with that of irradiated one and to examine the correlation between microstructures and magnetic parameters. TEM(transmission electron microscopy) on thin films and carbon replications were performed for microstructural investigation, and microhardness, tensile and fracture toughness tests were conducted for mechanical properties measurement. Barkhausen noise analysis was conducted and hysteresis parameters were measured. Microstructure, mechanist and magnetic properties were interpreted together to explore their inter-relationship. Also the applicability of a magnetic nondestructive evaluation method for monitoring fine microstructural changes in low alloy steels of complicated microstructure was examined. The results showed that, of all magnetic parameters, Barkhausen noise amplitudes show consistent change with microstructure (grain size, carbide microstructure, lath width) and hardness of the materials. For monitoring microstructural and mechanical property changes of low alloy steel under service environment of reactor pressure vessel steels, Barkhausen noise amplitude and coercivity appear to be as key magnetic parameters useful for nondestructive evaluation.

Effect of cerium addition on microstructures of carbon-alloyed iron ...

Indian Academy of Sciences (India)

All the alloys exhibited a typical two-phase microstructure consisting of Fe3AlC carbides in an iron aluminide matrix. In the alloy without Ce addition, large bulky carbides were equally distributed throughout the matrix with many smaller precipitates interspersed in between. In the alloy with Ce addition, the carbide grain sizes ...

YBa_2Cu_3O_{7-δ} : in pursuit of the ideal microstructure

Science.gov (United States)

Smith, D. S.; Suasmoro, S.; Lejeune, M.; Rabier, J.; Denanot, M. F.; Heintz, J. M.; Magro, C.; Bonnet, J. P.

1992-02-01

This paper examines the role of different factors in the microstructure of ceramic YBa2Cu3O{7-δ} with emphasis on its electrical response. In particular we discuss : 1. the effect of microstructural variations on j_c and ρ_{300}, 2. measurement of j_c, 3. the presence of minor phases and carbonates, 4. oxygen uptake and microcracks, 5. plastic deformation and related structural defects. Dans cet article, nous examinons d'une part la réponse électrique de céramiques supraconductrices massives de type YBa2Cu3O{7-δ} et d'autre part sa relation avec la microstructure. Nous présenterons successivement : 1. L'incidence de modifications microstructurales sur les valeurs de j_c et ρ_{300}, 2. les mesures expérimentales de j_c, 3. la présence de phases minoritaires et de carbonates, 4. la reprise d'oxygène et la microfissuration, 5. la déformation plastique et les défauts structuraux associés.

Carbon Deposition in Solid Oxide Cells during Co-Electrolysis of H2O and CO2

DEFF Research Database (Denmark)

Tao, Youkun; Ebbesen, Sune Dalgaard; Mogensen, Mogens Bjerg

2014-01-01

current densities from 1.5 to 2.25 A/cm2 and reactant (H2O + CO2) conversion of up to 67%. Delamination and carbon nano-fibers were observed at the Ni-YSZ|YSZ interface for two cells with a dense microstructure operated at electrolysis current densities of 2.0 and 2.25 A/cm2 and a conversion of 59% and 67...... and the active Ni-YSZ electrode. Carbon nano-fibers were only observed close to the YSZ electrolyte, indicating a very reducing atmosphere and a large over-potential gradient in the active electrode, being highest at the interface to the bulk electrolyte and decreasing toward the Ni-YSZ support.......Carbon formation during co-electrolysis of H2O and CO2 in Ni-YSZ supported Solid Oxide Electrolysis Cells (SOECs) may occur, especially at high current density and high conversion. In order to evaluate the carbon formation limits, five galvanostatic tests were performed in this work at electrolysis...

Graphitization kinetics of fluidized-bed pyrolytic carbons

International Nuclear Information System (INIS)

Beatty, R.L.

1975-08-01

Graphitization of 12 fluidized-bed pyrocarbons was studied as a function of heat-treatment time and temperature (1350 to 3000 0 C) to investigate the effect of initial microstructure on the graphitization process. The term ''graphitization'' is defined to include any thermally induced structural change, whether or not any layer stacking order is attained. A broad range of CVD microstructures was prepared at temperatures from 1150 to 1900 0 C and various propylene and methane concentrations. The twelve carbons spanned a wide range of graphitizabilities, primarily as a function of deposition temperature. Hydrocarbon concentration was of much less importance except for deposition at 1900 0 C. Hydrogen content of the as-deposited carbons decreased with increasing temperature of deposition, and initial graphitization behavior of the low-temperature carbons appeared to be related to hydrogen content and evolution. Rates of change in the parameters varied widely throughout the range of heat-treatment times (HTt) and temperatures (HTT) for the different carbons showing differences between the more graphitizable or ''soft'' carbons from the nongraphitizing or ''hard'' carbons. ΔH for nongraphitizing carbons was 175 +- 15 kcal below 1950 0 C, 240 +- 35 kcal at 1950 to 2700 0 C, and 330 +- 20 kcal above 2700 0 C. For graphitizing carbons deposited at 1150 0 C, values near 245 kcal were obtained from anti chi data for the HTT range 1350 to 1650 0 C, while densification data yielded values of about 160 kcal in the same range. The behaviors observed for graphitizable carbons above 2000 0 C are consistent with literature. Different kinetic behaviors below 2000 0 C were shown to be due to different initial microstructures as well as to different parameters measured. (U.S.)

Leveraging a temperature-tunable, scale-like microstructure to produce multimodal, supersensitive sensors

KAUST Repository

Tai, Yanlong; Bera, Tushar Kanti; Yang, Zhenguo; Lubineau, Gilles

2017-01-01

The microstructure of a flexible film plays an important role in its sensing capability. Here, we fabricate a temperature-dependent wrinkled single-walled carbon nanotube (SWCNT)/polydimethyl-siloxane (PDMS) film (WSPF) and a wrinkle-dependent scale

Effect of Heat Treatment on Microstructure and Hardness of Grade 91 Steel

Directory of Open Access Journals (Sweden)

Triratna Shrestha

2015-01-01

Full Text Available Grade 91 steel (modified 9Cr-1Mo steel is considered a prospective material for the Next Generation Nuclear Power Plant for application in reactor pressure vessels at temperatures of up to 650 °C. In this study, heat treatment of Grade 91 steel was performed by normalizing and tempering the steel at various temperatures for different periods of time. Optical microscopy, scanning and transmission electron microscopy in conjunction with microhardness profiles and calorimetric plots were used to understand the microstructural evolution including precipitate structures and were correlated with mechanical behavior of the steel. Thermo-Calc™ calculations were used to support the experimental work. Furthermore, carbon isopleth and temperature dependencies of the volume fraction of different precipitates were constructed.

A high-performance mesoporous carbon supported nitrogen-doped carbon electrocatalyst for oxygen reduction reaction

Science.gov (United States)

Xu, Jingjing; Lu, Shiyao; Chen, Xu; Wang, Jianan; Zhang, Bo; Zhang, Xinyu; Xiao, Chunhui; Ding, Shujiang

2017-12-01

Investigating low-cost and highly active electrocatalysts for oxygen reduction reactions (ORR) is of crucial importance for energy conversion and storage devices. Herein, we design and prepare mesoporous carbon supported nitrogen-doped carbon by pyrolysis of polyaniline coated on CMK-3. This electrocatalyst exhibits excellent performance towards ORR in alkaline media. The optimized nitrogen-doped mesoporous electrocatalyst show an onset potential (E onset) of 0.95 V (versus reversible hydrogen electrode (RHE)) and half-wave potential (E 1/2) of 0.83 V (versus RHE) in 0.1 M KOH. Furthermore, the as-prepared catalyst presents superior durability and methanol tolerance compared to commercial Pt/C indicating its potential applications in fuel cells and metal-air batteries.

Effect of carbon on the microstructure, mechanical properties and metal ion release of Ni-free Co-Cr-Mo alloys containing nitrogen.

Science.gov (United States)

Mori, Manami; Yamanaka, Kenta; Kuramoto, Koji; Ohmura, Kazuyo; Ashino, Tetsuya; Chiba, Akihiko

2015-10-01

This paper investigated the effect of carbon addition on the microstructure and tensile properties of Ni-free biomedical Co-29Cr-6Mo (mass%) alloys containing 0.2 mass% nitrogen. The release of metal ions by the alloys was preliminarily evaluated in an aqueous solution of 0.6% sodium chloride (NaCl) and 1% lactic acid, after which samples with different carbon contents were subjected to hot rolling. All specimens were found to primarily consist of a γ-phase matrix due to nitrogen doping, with only the volume fraction of M23C6 increasing with carbon concentration. Owing to the very fine size of these carbide particles (less than 1 μm), which results from fragmentation during hot rolling, the increased formation of M23C6 increased the 0.2% proof stress, but reduced the elongation-to-failure. Carbon addition also increased the amount of Co and Cr released during static immersion; Co and Cr concentrations at the surfaces, which increased with increasing the bulk carbon concentrations, possibly enhanced the metal ion release. However, only a very small change in the Mo concentration was noticed in the solution. Therefore, it is not necessarily considered a suitable means of improving the strength of biomedical Co-Cr-Mo alloys, even though it has only to date been used in this alloy system. The results of this study revealed the limitations of the carbon strengthening and can aid in the design of biomedical Co-Cr-Mo-based alloys that exhibit the high durability needed for their practical application. Copyright © 2015 Elsevier B.V. All rights reserved.

Hydrogenation of carbon monoxide on WO/sub 3/-Supported ruthenium catalysts

Energy Technology Data Exchange (ETDEWEB)

Yoshinari, Tomohiro; Suganuma, Fujio; Sera, Chikara

1988-01-01

In this study, a WO/sub 3/-supported catalyst was prepared to conduct hydrogenation of CO for examining the product distribution and composition of hydrocarbons, using a gamma-alumina-supported catalyst for comparison. These catalysts were used under pressure to conduct a distributive reaction and the desorbing behavior of CO or H/sub 2/ at elevated temperature was measured to examine the influence of the type of carrier or the method of preparation on the activity and the distribution of products formed. The WO/sub 3/-supported catalyst gave a carbon chain length distribution that did not comply with the rule of Schulz-Flory, giving a composition richer in the isomers. Carbon number distribution is affected by Ru-dispersion, and the selectivity of isomers depends on the acidity of the carrier. Formed products distribution of the WO/sub 3/-supported reaction is attributable to the secondary reaction, which relates to the acidic point of the carrier, of the primary product formed on the metal. (7 figs, 4 tabs, 18 refs)

Hydrogen storage behaviors of platinum-supported multi-walled carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Park, Soo-Jin; Lee, Seul-Yi [Department of Chemistry, Inha University, 253 Nam-gu, Incheon 402-751 (Korea, Republic of)

2010-12-15

In this work, the hydrogen storage behaviors of multi-walled carbon nanotubes (MWNTs) loaded by crystalline platinum (Pt) particles were studied. The microstructure of the Pt/MWNTs was characterized by X-ray diffraction and transmission electron microscopy. The pore structure and total pore volumes of the Pt/MWNTs were analyzed by N{sub 2}/77 K adsorption isotherms. The hydrogen storage capacity of the Pt/MWNTs was evaluated at 298 K and 100 bar. From the experimental results, it was found that Pt particles were homogeneously distributed on the MWNT surfaces. The amount of hydrogen storage capacity increased in proportion to the Pt content, with Pt-5/MWNTs exhibiting the largest hydrogen storage capacity. The superior amount of hydrogen storage was linked to an increase in the number of active sites and the optimum-controlled micropore volume for hydrogen adsorption due to the well-dispersed Pt particles. Therefore, it can be concluded that Pt particles play an important role in hydrogen storage characteristics due to the hydrogen spillover effect. (author)

The structure of nano-palladium deposited on carbon-based supports

International Nuclear Information System (INIS)

Pikna, Ľubomír; Milkovič, Ondrej; Saksl, Karel; Heželová, Mária; Smrčová, Miroslava; Puliš, Pavel; Michalik, Štefan; Gamcová, Jana

2014-01-01

Nano-palladium catalysts, prepared using the same procedure with the same metal content (3 wt%) and two different supports, activated carbon (Pd/C) and activated carbon—multiwalled carbon nanotubes (Pd/C/CNT), are discussed. The simple technique of deposition reduction was applied in the preparation of these two types of Pd catalysts. TEM, XRD analysis, EXAFS signal analysis, and XANES were used for sample characterization. In both samples, transmission electron microscopy identified nanosized Pd particles with nearly spherical morphology but different sizes. The mean diameters of the particles on Pd/C and Pd/C/CNT were estimated to be 5.4 nm and 7.8 nm, respectively. The EXAFS signal analysis showed that Pd atoms on the particle surfaces were coordinated by 4 oxygens to form a PdO monolayer covering a metallic core. The XANES signal analysis indicated a smaller particle size for Pd/C (∅ 5 nm) than for Pd/C/CNT (∅ 10 nm), in good agreement with the TEM observations. - Graphical abstract: Visualization of metallic core (left), oxide monolayer (middle) and nanoparticle of diameter 5 nm (right). - Highlights: • Pd catalysts were prepared on two types of supports: carbon and carbon nanotubes. • BET, TEM, XRD characterization of prepared catalysts. • XAFS: Concentration of Pd in samples Pd/C and Pd/C/CNT. • EXAFS and XANES signal analysis of catalysts. • Visualisation of atoms arrangement at the Pd nanoparticle surface

Microstructural characterization samples of Cariri stones

International Nuclear Information System (INIS)

Costa, D.L.; Fernandes, I.M.M.; Farias, R.M.C.; Braga, A.N.S.; Menezes, R.R.; Neves, G.A.

2014-01-01

Ornamental rocks are among the most promising areas of business in the mining sector, thus resulting in the need for addition of aesthetic beauty, there were investments in quality, safety and characterization in its various fields of application. Based on this, this paper aims to microstructural characterization of a class of these rocks: the Stones Cariri, also known as limestone, calcareous rocks that are composed primarily of calcium and magnesium carbonate, but may vary due its origin. For this, four samples were studied with two of the Apodi Plateau and two of the Araripe, which were characterized physically and structurally through micro testing, chemical analysis, X-ray diffraction, optical micrograph and porosimetry. The results show that calcitic and dolomitic lime is present porosity ranging from 5 to 15% of pores with a concentration between 100nm and 10mm and many microstructural heterogeneity. (author)

Processing of a new high strength high toughness steel with duplex microstructure (Ferrite + Austenite)

International Nuclear Information System (INIS)

Martis, Codrick J.; Putatunda, Susil K.; Boileau, James

2013-01-01

Highlights: ► This new steel has exceptional combination of high strength and fracture toughness. ► Austempering treatment resulted in a very fine scale bainitic ferrite microstructure. ► As the austempering temperature increases yield strength and toughness decreases. ► Maximum fracture toughness of 105 MPa √m is obtained after austempering at 371 °C. ► A relationship between fracture toughness and the parameter σ y (X γ C γ ) 1/2 was observed. - Abstract: In this investigation a new third generation advanced high strength steel (AHSS) has been developed. This steel was synthesized by austempering of a low carbon and low alloy steel with high silicon content. The influence of austempering temperature on the microstructure and the mechanical properties including the fracture toughness of this steel was also examined. Compact tension and cylindrical tensile specimens were prepared from a low carbon low alloy steel and were initially austenitized at 927 °C for 2 h and then austempered in the temperature range between 371 °C and 399 °C to produce different microstructures. The microstructures were characterized by X-ray diffraction, scanning electron microscopy and optical metallography. Test results show that the austempering heat treatment has resulted in a microstructure consisting of very fine scale bainitic ferrite and austenite. A combination of very high tensile strength of 1388 MPa and fracture toughness of 105 MPa √m was obtained after austempering at 371 °C

Tools to support GHG emissions reduction : a regional effort, part 1 - carbon footprint estimation and decision support.

Science.gov (United States)

2010-09-01

Tools are proposed for carbon footprint estimation of transportation construction projects and decision support : for construction firms that must make equipment choice and usage decisions that affect profits, project duration : and greenhouse gas em...

Progress in Studies on Carbon and Silicon Carbide Nanocomposite Materials

International Nuclear Information System (INIS)

Xiao, P.; Chen, J.; Xian-feng, X.

2010-01-01

Silicon carbide nanofiber and carbon nanotubes are introduced. The structure and application of nanotubers (nanofibers) in carbon/carbon composites are emphatically presented. Due to the unique structure of nanotubers (nanofibers), they can modify the microstructure of pyrocarbon and induce the deposition of pyrocarbon with high text in carbon/carbon composites. So the carbon/carbon composites modified by CNT/CNF have more excellent properties.

Synthesis of carbon-supported nickel catalysts for the dry reforming of CH{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Fidalgo, B.; Zubizarreta, L.; Bermudez, J.M.; Arenillas, A.; Menendez, J.A. [Instituto Nacional del Carbon, CSIC, Apartado 73, 33080 Oviedo (Spain)

2010-07-15

A series of carbon-based nickel (Ni) catalysts was prepared in order to investigate the effect of the preparation method on the dispersion of Ni and its final catalytic activity in the dry reforming of methane, i.e. CH{sub 4} + CO{sub 2} 2H{sub 2} + 2CO. Three parameters were studied: (i) the influence of the surface chemistry of the carbon used as support; (ii) the method of drying (conventional vs. microwave drying); and, (iii) the temperature of the reduction stage. In order to study the role of the surface chemistry of the commercial activated carbon used as support, the active carbon was tested as received and oxidized. Although a better Ni dispersion was achieved over the oxidized support, the conversions were much lower. It was also found that microwave drying offers various advantages over conventional drying, the main one being that less time is required to prepare the catalyst. Two reduction temperatures were used (300 and 500 C), being found that it is necessary to adjust this parameter to prevent the Ni particles from sintering. (author)

Microstructure and surface properties of lignocellulosic-based activated carbons

Science.gov (United States)

González-García, P.; Centeno, T. A.; Urones-Garrote, E.; Ávila-Brande, D.; Otero-Díaz, L. C.

2013-01-01

Low cost activated carbons have been produced via chemical activation, by using KOH at 700 °C, from the bamboo species Guadua Angustifolia and Bambusa Vulgaris Striata and the residues from shells of the fruits of Castanea Sativa and Juglans Regia as carbon precursors. The scanning electron microscopy micrographs show the conservation of the precursor shape in the case of the Guadua Angustifolia and Bambusa Vulgaris Striata activated carbons. Transmission electron microscopy analyses reveal that these materials consist of carbon platelet-like particles with variable length and thickness, formed by highly disordered graphene-like layers with sp2 content ≈ 95% and average mass density of 1.65 g/cm3 (25% below standard graphite). Textural parameters indicate a high porosity development with surface areas ranging from 850 to 1100 m2/g and average pore width centered in the supermicropores range (1.3-1.8 nm). The electrochemical performance of the activated carbons shows specific capacitance values at low current density (1 mA/cm2) as high as 161 F/g in the Juglans Regia activated carbon, as a result of its textural parameters and the presence of pseudocapacitance derived from surface oxygenated acidic groups (mainly quinones and ethers) identified in this activated carbon.

Physicochemical investigations of carbon nanofiber supported Cu/ZrO2 catalyst

International Nuclear Information System (INIS)

Din, Israf Ud; Shaharun, Maizatul S.; Subbarao, Duvvuri; Naeem, A.

2014-01-01

Zirconia-promoted copper/carbon nanofiber catalysts (Cu‐ZrO 2 /CNF) were prepared by the sequential deposition precipitation method. The Herringbone type of carbon nanofiber GNF-100 (Graphite nanofiber) was used as a catalyst support. Carbon nanofiber was oxidized to (CNF-O) with 5% and 65 % concentration of nitric acid (HNO 3 ). The CNF activated with 5% HNO 3 produced higher surface area which is 155 m 2 /g. The catalyst was characterized by X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) and N 2 adsorption-desorption. The results showed that increase of HNO 3 concentration reduced the surface area and porosity of the catalyst

Flexible and self-powered temperature-pressure dual-parameter sensors using microstructure-frame-supported organic thermoelectric materials

Science.gov (United States)

Zhang, Fengjiao; Zang, Yaping; Huang, Dazhen; di, Chong-An; Zhu, Daoben

2015-09-01

Skin-like temperature- and pressure-sensing capabilities are essential features for the next generation of artificial intelligent products. Previous studies of e-skin and smart elements have focused on flexible pressure sensors, whereas the simultaneous and sensitive detection of temperature and pressure with a single device remains a challenge. Here we report developing flexible dual-parameter temperature-pressure sensors based on microstructure-frame-supported organic thermoelectric (MFSOTE) materials. The effective transduction of temperature and pressure stimuli into two independent electrical signals permits the instantaneous sensing of temperature and pressure with an accurate temperature resolution of cost and large-area fabrication, make MFSOTE materials possess promising applications in e-skin and health-monitoring elements.

thesis of high-purity carbon nanotubes over alumina and silica supported bimetallic catalysts

Directory of Open Access Journals (Sweden)

Sanja Ratković

2009-10-01

Full Text Available Carbon nanotubes (CNTs were synthesized by a catalytic chemical vapor deposition method (CCVD of ethylene over alumina and silica supported bimetallic catalysts based on Fe, Co and Ni. The catalysts were prepared by a precipitation method, calcined at 600 °C and in situ reduced in hydrogen flow at 700 °C. The CNTs growth was carried out by a flow the mixture of C2H4 and nitrogen over the catalyst powder in a horizontal oven. The structure and morphology of as-synthesized CNTs were characterized using SEM. The as-synthesized nanotubes were purified by acid and basic treatments in order to remove impurities such as amorphous carbon, graphite nanoparticles and metal catalysts. XRD and DTA/TG analyses showed that the amounts of by-products in the purified CNTs samples were reduced significantly. According to the observed results, ethylene is an active carbon source for growing high-density CNTs with high yield but more on alumina-supported catalysts than on their silica- supported counterparts. The last might be explained by SMSI formed in the case of alumina-supported catalysts, resulting in higher active phase dispersion.

Microstructural and compositional Evolution of Compound Layers during Gaseous Nitrocarburizing

DEFF Research Database (Denmark)

Du, Hong; Somers, Marcel A.J.; Ågren, John

2000-01-01

Compound layers developed at 848 K during gaseous nitrocarburizing of iron and iron-carbon specimens were investigated for several combinations of N and C activities imposed at the specimen surface by gas mixtures of NH3, N2, CO2 and CO. The microstructural evolution of the compound layer was stu...

Effects of heat treatment influencing factors on microstructure and mechanical properties of a low-carbon martensitic stainless bearing steel

Energy Technology Data Exchange (ETDEWEB)

Li, Shaohong; Yuan, Xiaohong; Jiang, Wen; Sun, Hudai; Li, Jun [School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Zhao, Kunyu, E-mail: zhaokunyu.kmust@gmail.com [School of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Yang, Maosheng [Department of Structural Materials, Central Iron and Steel Research Institute, Beijing 100081 (China)

2014-05-01

The effects of different heat treatment parameters and cryogenic treatment (−75 °C) on microstructural changes and mechanical properties of a low-carbon martensitic stainless bearing steel were investigated. These analyses were performed via the optical microscope (OM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The obtained results showed that the execution of cryogenic treatment on quenched and tempered bearing steel increases hardness, tensile strength and decreases toughness with the increment of cryogenic treatment and tempering cycles. This paper also showed that the cryogenic cycle's treatment incorporating tempering can refine the martensite laths resulting in improvement of tensile strength. In addition, cryogenic treatment further reduces the retained austenite content but it cannot make retained austenite transform into martensite completely even tempering at high temperature.

Effects of heat treatment influencing factors on microstructure and mechanical properties of a low-carbon martensitic stainless bearing steel

International Nuclear Information System (INIS)

Li, Shaohong; Yuan, Xiaohong; Jiang, Wen; Sun, Hudai; Li, Jun; Zhao, Kunyu; Yang, Maosheng

2014-01-01

The effects of different heat treatment parameters and cryogenic treatment (−75 °C) on microstructural changes and mechanical properties of a low-carbon martensitic stainless bearing steel were investigated. These analyses were performed via the optical microscope (OM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The obtained results showed that the execution of cryogenic treatment on quenched and tempered bearing steel increases hardness, tensile strength and decreases toughness with the increment of cryogenic treatment and tempering cycles. This paper also showed that the cryogenic cycle's treatment incorporating tempering can refine the martensite laths resulting in improvement of tensile strength. In addition, cryogenic treatment further reduces the retained austenite content but it cannot make retained austenite transform into martensite completely even tempering at high temperature

Microstructure and surface properties of lignocellulosic-based activated carbons

International Nuclear Information System (INIS)

González-García, P.; Centeno, T.A.; Urones-Garrote, E.; Ávila-Brande, D.; Otero-Díaz, L.C.

2013-01-01

Highlights: ► Activated carbons were produced by KOH activation at 700 °C. ► The observed nanostructure consists of highly disordered graphene–like layers with sp 2 bond content ≈ 95%. ► Textural parameters show high surface area (≈ 1000 m 2 /g) and pore width of 1.3–1.8 nm. ► Specific capacitance reaches values as high as 161 F/g. - Abstract: Low cost activated carbons have been produced via chemical activation, by using KOH at 700 °C, from the bamboo species Guadua Angustifolia and Bambusa Vulgaris Striata and the residues from shells of the fruits of Castanea Sativa and Juglans Regia as carbon precursors. The scanning electron microscopy micrographs show the conservation of the precursor shape in the case of the Guadua Angustifolia and Bambusa Vulgaris Striata activated carbons. Transmission electron microscopy analyses reveal that these materials consist of carbon platelet–like particles with variable length and thickness, formed by highly disordered graphene–like layers with sp 2 content ≈ 95% and average mass density of 1.65 g/cm 3 (25% below standard graphite). Textural parameters indicate a high porosity development with surface areas ranging from 850 to 1100 m 2 /g and average pore width centered in the supermicropores range (1.3–1.8 nm). The electrochemical performance of the activated carbons shows specific capacitance values at low current density (1 mA/cm 2 ) as high as 161 F/g in the Juglans Regia activated carbon, as a result of its textural parameters and the presence of pseudocapacitance derived from surface oxygenated acidic groups (mainly quinones and ethers) identified in this activated carbon.

Underground coal gasification with integrated carbon dioxide mitigation supports Bulgaria's low carbon energy supply

Science.gov (United States)

Nakaten, Natalie; Kempka, Thomas; Azzam, Rafig

2013-04-01

Underground coal gasification allows for the utilisation of coal reserves that are economically not exploitable due to complex geological boundary conditions. The present study investigates underground coal gasification as a potential economic approach for conversion of deep-seated coals into a high-calorific synthesis gas to support the Bulgarian energy system. Coupling of underground coal gasification providing synthesis gas to fuel a combined cycle gas turbine with carbon capture and storage is considered to provide substantial benefits in supporting the Bulgarian energy system with a competitive source of energy. In addition, underground voids originating from coal consumption increase the potential for geological storage of carbon dioxide resulting from the coupled process of energy production. Cost-effectiveness, energy consumption and carbon dioxide emissions of this coupled process are investigated by application of a techno-economic model specifically developed for that purpose. Capital (CAPEX) and operational expenditure (OPEX) are derived from calculations using six dynamic sub-models describing the entire coupled process and aiming at determination of the levelised costs of electricity generation (COE). The techno-economic model is embedded into an energy system-modelling framework to determine the potential integration of the introduced low carbon energy production technology into the Bulgarian energy system and its competitiveness at the energy market. For that purpose, boundary conditions resulting from geological settings as well as those determined by the Bulgarian energy system and its foreseeable future development have to be considered in the energy system-modelling framework. These tasks comprise integration of the present infrastructure of the Bulgarian energy production and transport system. Hereby, the knowledge on the existing power plant stock and its scheduled future development are of uttermost importance, since only phasing-out power

NiMo-sulfide supported on activated carbon to produce renewable diesel

Directory of Open Access Journals (Sweden)

Nancy Y Acelas

2017-03-01

Full Text Available Due to their weak polarity and large surface area, activated carbon supports have the potential to enhance the dispersion of metal-sulfides. It is expected that the absence of a strong metal-support interaction can result in the formation of a very active and stable Ni-Mo-S phase. In this study, catalysts with different amounts of nickel and molybdenum supported on a commercial activated carbon were prepared by a co-impregnation method and characterized by BET, XRF, and SEM techniques. The catalytic activity for hydroprocessing of Jatropha oil was evaluated in a batch reactor, and the composition of the liquid and gaseous products were determined. Results showed that gaseous products are mainly composed of high amounts of propane and small amounts of other light hydrocarbons (C1 to C5. Liquid hydrocarbon products consisted of a mixture containing mainly n-paraffins of C15-C18 and some oxygenated compounds. The catalysts with a mass fraction of 3 % Ni, 15 % Mo (Ni3Mo15/AC presented the highest selectivity toward C17-C18 hydrocarbons, with a product distribution similar to a commercial alumina-supported Ni-Mo-S catalyst.

Structure-activity relationships of carbon-supported platinum-bismuth and platinum-antimony oxidation catalysts

CSIR Research Space (South Africa)

Maphoru, MV

2017-04-01

Full Text Available Compositional and morphological studies on supported platinum are important for the improvement and expanded use of catalysts for oxidative coupling reactions. Nanocomposites consisting of 5% Pt supported on activated carbon and promoted with 5% Bi...

Effect of Strength and Microstructure on Stress Corrosion Cracking Behavior and Mechanism of X80 Pipeline Steel in High pH Carbonate/Bicarbonate Solution

Science.gov (United States)

Zhu, Min; Du, Cuiwei; Li, Xiaogang; Liu, Zhiyong; Wang, Shengrong; Zhao, Tianliang; Jia, Jinghuan

2014-04-01

The stress corrosion cracking (SCC) behaviors and mechanisms of X80 pipeline steels with different strength and microstructure in high pH carbonate/bicarbonate solution were investigated by slow strain rate testing and electrochemical test. The results showed that the cracking mode of low strength X80 steel composed of bulky polygonal ferrite and granular bainite in high pH solution was intergranular (IGSCC), and the SCC mechanism was anodic dissolution (AD). While the mixed cracking mode of high strength X80 steel consisted of fine acicular ferrite and granular bainite was intergranular (IGSCC) in the early stage, and transgranular (TGSCC) in the later stage. The decrease of pH value of crack tip was probably the key reason for the occurrence of TGSCC. The SCC mechanism may be a mixed mode of AD and hydrogen embrittlement (HE), and the HE mechanism may play a significant role in the deep crack propagation at the later stage. The cracking modes and SCC mechanisms of the two X80 steels were associated with its microstructure and strength.

A monetary plan for upgrading climate finance and support the low-carbon transition

International Nuclear Information System (INIS)

Hourcade, Jean Charles; Cassen, Christophe

2015-01-01

This article examines how carbon finance can be part of a general reform of the financial system. Climate policies can indeed stimulate a sustainable and inclusive climate finance, in line with the call of the Cancun Agreement for a paradigm shift in climate negotiations. The mechanism described in this article is based on the adoption by Parties to the negotiations of a social value of carbon to trigger a wave of low-carbon investments in the world. Central banks offer credit lines for commercial banks backed by this social value of carbon, which are then used to cut the risk to invest in low- carbon investments. A future agreement in Paris next year should support this type of mechanisms.

Fabrication and characterization of nanocomposites reinforced by carbon nanotubes - (1) synthesis of carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Hseuh Hsiangming; Tai Nyanhwa; Perng Tongping [Dept. of Material Science, National Tsing-Hwa Univ., TW (China); Chyou Sander [Taiwan Power Research Inst., Taiwan Power Co., Taipei (China)

2003-07-01

Multi-walled carbon nanotubes (MWCNTs) produced by floating catalyst method were used for reinforcing material in polymeric nanocomposites. Five different kinds of carbon sources (benzene, toluene, xylene, cyclo-hexane, n-hexane) were used as precursors in the thermal chemical vapor deposition process. The products were collected and examined by Raman, HRTEM, and FESEM. The differences in microstructure and morphologies among these products are analyzed and discussed. (orig.)

Durability of Carbon Nanofiber (CNF) & Carbon Nanotube (CNT) as Catalyst Support for Proton Exchange Membrane Fuel Cells

DEFF Research Database (Denmark)

Andersen, Shuang Ma; Borghei, Maryam; Lund, Peter

2013-01-01

a standard polyol method were prepared and fabricated as cathodes of Membrane Electrode Assemblies (MEA) for PEMFC. Both the catalysts as such and the MEAs made out of them were evaluated regarding to thermal and electrochemical stability using traditional carbon black (Vulcan XC72) as a reference. Thermal...... gravimetric analysis (TGA), cyclic voltammetry (CV), polarization curve and impedance spectroscopy were applied on the samples under accelerated stress conditions. The carbon nano-materials demonstrated better stability as support for nano-sized platinum catalyst under PEMFC related operating conditions. Due...

Effect of carbon and manganese on the microstructure and mechanical properties of 9Cr2WVTa deposited metals

Science.gov (United States)

Wang, Jian; Rong, Lijian; Li, Dianzhong; Lu, Shanping

2017-03-01

Six 9Cr2WVTa deposited metals with different carbon and manganese contents have been studied to reveal the role of major elements, which guide for the design of welding consumables for reduced activation ferritic/martensitic steel and meet for the requirements of accelerator driven systems-lead fusion reactors. The typical microstructure for the 9Cr2WVTa deposited metals is the lath martensite along with the fine stripe δ-ferrite. The chemical compositions influence the solidification sequence and therefore, change the δ-ferrite content in the deposited metal. The impact toughness for the 9Cr2WVTa deposited metals decreases remarkably when the δ-ferrite content is more than 5.2 vol%, also the impact toughness decreases owing to the high quenching martensite formation. Increasing the level of manganese addition, α phase of each alloy shifts to the bottom right according to the CCT diagram.

Performance Analysis of a Recycled Concrete Interfacial Transition Zone in a Rapid Carbonization Environment

Directory of Open Access Journals (Sweden)

Gongbing Yue

2018-01-01

Full Text Available Based on the characteristics of recycled concrete interface structures, a multi-interface reconstruction model was established. To study the microstructure evolution of the interfacial transition zone (ITZ during the carbonization process of recycled concrete, the microstructure characteristics of the ITZ of C30, C40, and C50 grade recycled concrete and the mortar matrix before and after carbonization were studied through the microhardness tester and SEM. The results show that the microhardness values of the ITZ and the mortar matrix are obviously increased and that the width of the ITZ decreases, while the ITZ performance of the C50 grade recycled concrete is not significantly changed. The ITZ exhibits a large amount of granular CaCO3 after carbonization, the pores are refined, and microcracks are generated. Overall, there are significant differences in the microstructures between the ITZ and the mortar matrix before and after carbonization.

Microstructure and high-temperature tribological properties of Si-doped hydrogenated diamond-like carbon films

Science.gov (United States)

Zhang, Teng Fei; Wan, Zhi Xin; Ding, Ji Cheng; Zhang, Shihong; Wang, Qi Min; Kim, Kwang Ho

2018-03-01

Si-doped DLC films have attracted great attention for use in tribological applications. However, their high-temperature tribological properties remain less investigated, especially in harsh oxidative working conditions. In this study, Si-doped hydrogenated DLC films with various Si content were synthesized and the effects of the addition of Si on the microstructural, mechanical and high-temperature tribological properties of the films were investigated. The results indicate that Si doping leads to an obvious increase in the sp3/sp2 ratio of DLC films, likely due to the silicon atoms preferentially substitute the sp2-hybridized carbon atoms and augment the number of sp3 sites. With Si doping, the mechanical properties, including hardness and adhesion strength, were improved, while the residual stress of the DLC films was reduced. The addition of Si leads to higher thermal and mechanical stability of DLC films because the Si atoms inhibit the graphitization of the films at an elevated temperature. Better high-temperature tribological properties of the Si-DLC films under oxidative conditions were observed, which can be attributed to the enhanced thermal stability and formation of a Si-containing lubricant layer on the surfaces of the wear tracks. The nano-wear resistance of the DLC films was also improved by Si doping.

The microstructure of type 304 stainless steel implanted with titanium and carbon and its relation to friction and wear tests

International Nuclear Information System (INIS)

Follstaedt, D.M.; Pope, L.E.; Knapp, J.A.; Picraux, S.T.; Yost, F.G.

1983-01-01

The authors have used transmission electron microscopy to examine the microstructure of type 304 stainless steel which was ion implanted with high doses (2 X 10 17 atoms cm -2 ) of titanium and carbon. It is found that the resulting surface alloy is an amorphous phase similar to that observed when pure iron is identically implanted. This result is important for identifying the mechanisms by which the coefficient of friction and the wear depth are reduced in unlubricated pin-on-disc tests of type 304 stainless steel implanted with titanium and carbon. The effect of temperature on the amorphous alloy during annealing in the microscope has also been examined. It is found that devitrification begins after 15 min at 500 0 C and that the alloy fully crystallizes into f.c.c., b.c.c. and TiC phases after 15 min at 650 0 C. A comparison of mechanical test results from devitrified specimens with results from amorphous specimens demonstrates that the reduction in the coefficient of friction correlates with the presence of the amorphous layer, whereas the reduction in the wear depth is obtained for both amorphous and crystalline alloys. (Auth.)

Pt and PtRu nanoparticles supported on N-doped carbons as electrocatalysts for methanol electro oxidation

Energy Technology Data Exchange (ETDEWEB)

Pereira, Viviane Santos; Silva, Julio Cesar Martins; Oliveira Neto, Almir; Spinace, Estevam Vitorio, E-mail: viviane_sp_saopaulo@yahoo.com.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2016-07-01

Full text: Methanol is a liquid transportation fuel that can be produced from fossil or renewable resources. Fuel cells employing methanol directly as fuel (Direct Methanol Fuel Cell - DMFC) are very attractive as power source for portable, mobile and stationary applications [1]. PtRu/C electrocatalyst has been considered the best electrocatalyst for methanol electro-oxidation, however, its performance is strongly dependent on the method of preparation and on the characteristics of the carbon support. N-doped carbons with different N contents (1, 2 and 5 wt%) were prepared by thermal treatment of carbon with urea at 800 deg C. Pt and PtRu nanoparticles were supported on N-doped carbons by coreduction of Pt(IV) and Ru(III) ions using an alcohol-reduction process [2]. The obtained materials were characterized by Energy Dispersive X-ray spectroscopy, X-ray diffraction, Transmission electron microscopy and Cyclic Voltammetry. Pt and PtRu nanoparticles supported on N-doped carbons showed superior performance for methanol electro-oxidation when compared to the materials supported on non-modified carbon and to Pt/C and PtRu/C commercial electrocatalysts. Pt/C and PtRu/C prepared with the carbon modified with 2.5 wt% of N content showed the best activities. (author) [1] Y. Zhou, K. Neyerlin, T.S. Olson, S. Pylypenko, J. Bult, H.N. Dinh, T. Gennett, Z. Shao and R. O'Hayre, Energy Environ. Sci. 3, 1437 (2010); [2] E.V. Spinace, A.Oliveira Neto, T.R.R. Vasconcellos, M. Linardi, J. Power Sources 137, 17 (2004)

Microstructure-Sensitive Modeling of High Cycle Fatigue (Preprint)

Science.gov (United States)

2009-03-01

liquid nitrogen bath to obtain complete martensitic transformation at the surface. This is followed by tempering at 500°C for 1.5 hours to achieve...microstructure of martensite [38-42] and the scales over which process-induced strengthening effects are realized in components, it is quite challenging to...Deformation and fracture in martensitic carbon steels tempered at low temperatures. Metallurgical and Materials Transactions A: Physical Metallurgy and

Electrospun fibrous electrodes with tunable microstructure made of polyaniline/multi-walled carbon nanotube suspension for all-solid-state supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Liang, Junsheng; Su, Shijie; Fang, Xu [Key Laboratory for Micro/Nano Technology and System of Liaoning Province, Dalian University of Technology, Dalian 116023 (China); Wang, Dazhi, E-mail: d.wang@dlut.edu.cn [Key Laboratory for Micro/Nano Technology and System of Liaoning Province, Dalian University of Technology, Dalian 116023 (China); Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian 116023 (China); Xu, Shuangchao [Key Laboratory for Precision and Non-traditional Machining Technology of Ministry of Education, Dalian University of Technology, Dalian 116023 (China)

2016-09-15

Highlights: • Electrospun PANI/MWCNT fibrous electrodes for supercapacitor were prepared. • Microstructure of electrodes is tunable by changing the electrospin parameters. • Fiber-diameter dependence of the electrode performance was observed. • High performance and good stability of electrospun electrodes were obtained. - Abstract: Electrospinning technique was used to prepare high performance fibrous electrodes with tunable microstructure for all-solid-state electrochemical supercapacitor. Symmetrically sandwiched supercapacitors consisting of flexible electrospun polyaniline (PANI)/multi-walled carbon nanotube (MWCNT) electrodes and polyvinyl alcohol (PVA)/sulfuric acid (H{sub 2}SO{sub 4}) gel electrolyte were assembled. Tunable microstructure of the fibrous electrode was obtained by changing the electrospinning parameters including the collector–needle distance (CND) and the suspension flow rate (SFR). Results show that, higher CND combining with lower SFR can result in a smaller average diameter of the electrospun fibers and hence improve the electrode performance. When the CND changes from 80 to 140 mm, the average fiber diameter will decrease from 2.89 to 1.21 μm, and the specific surface area of the electrode can increase from 57 to 83 m{sup 2}·g{sup −1}. The corresponding specific capacitance of the electrospun electrode will therefore increase from 129.5 to 180 F·g{sup −1}, leading to a synchronous improvement of the energy density of the supercapacitor from 18 to 25 Wh·kg{sup −1}. On the other hand, the supercapacitors using fibrous electrodes in this work also show good rate capability and cycling stability. Using the electrode with an average fiber diameter of 1.21 μm, the specific capacitances can maintain 131 F·g{sup −1} at a current density of 4 A·g{sup −1}, which is 73% of the specific capacitance of the same sample at a current density of 0.5 A·g{sup −1}. And the specific capacitance of the electrode can retain 89

Electrospun fibrous electrodes with tunable microstructure made of polyaniline/multi-walled carbon nanotube suspension for all-solid-state supercapacitors

International Nuclear Information System (INIS)

Liang, Junsheng; Su, Shijie; Fang, Xu; Wang, Dazhi; Xu, Shuangchao

2016-01-01

Highlights: • Electrospun PANI/MWCNT fibrous electrodes for supercapacitor were prepared. • Microstructure of electrodes is tunable by changing the electrospin parameters. • Fiber-diameter dependence of the electrode performance was observed. • High performance and good stability of electrospun electrodes were obtained. - Abstract: Electrospinning technique was used to prepare high performance fibrous electrodes with tunable microstructure for all-solid-state electrochemical supercapacitor. Symmetrically sandwiched supercapacitors consisting of flexible electrospun polyaniline (PANI)/multi-walled carbon nanotube (MWCNT) electrodes and polyvinyl alcohol (PVA)/sulfuric acid (H_2SO_4) gel electrolyte were assembled. Tunable microstructure of the fibrous electrode was obtained by changing the electrospinning parameters including the collector–needle distance (CND) and the suspension flow rate (SFR). Results show that, higher CND combining with lower SFR can result in a smaller average diameter of the electrospun fibers and hence improve the electrode performance. When the CND changes from 80 to 140 mm, the average fiber diameter will decrease from 2.89 to 1.21 μm, and the specific surface area of the electrode can increase from 57 to 83 m"2·g"−"1. The corresponding specific capacitance of the electrospun electrode will therefore increase from 129.5 to 180 F·g"−"1, leading to a synchronous improvement of the energy density of the supercapacitor from 18 to 25 Wh·kg"−"1. On the other hand, the supercapacitors using fibrous electrodes in this work also show good rate capability and cycling stability. Using the electrode with an average fiber diameter of 1.21 μm, the specific capacitances can maintain 131 F·g"−"1 at a current density of 4 A·g"−"1, which is 73% of the specific capacitance of the same sample at a current density of 0.5 A·g"−"1. And the specific capacitance of the electrode can retain 89% after 1500 charge/discharge cycles.

9-12% Cr heat resistant steels. Alloy design, TEM characterisation of microstructure evolution and creep response at 650 C

International Nuclear Information System (INIS)

Rojas Jara, David

2011-01-01

response was established. All crept samples showed a significant increase of sub-grain size and a reduction of the dislocation density. Hot deformed samples showed better creep strength than non hot-deformed samples, due to homogenisation of the microstructure. The tempering temperature affected the dislocation density and the sub-grain sizes, influencing the creep behaviour. 9% Cr alloys were designed supported by ThermoCalc. Two sets of alloys were produced: 9% Cr alloys with 0.1 % C and 0.05% C and 9% Cr alloys containing ∝ 0.03% Ti again with 0.1% C and 0.05% C (always wt%). Microstructure investigations showed good agreement with the predicted phases of the thermodynamic modeling. The volume fraction of precipitated M 23 C 6 carbides is directly related to the carbon content of the alloys. Hardening of the Ti-containing alloys by precipitation of fine dispersed Ti-based MX particles was achieved. The precipitation of these carbides was limited to the austenisation and tempering treatment used. The microstructure evolution (sub-grain and particle size) during creep at 650 C / 100MPa was investigated by STEM-HAADF. The sub-grain size evolution and the coarsening of precipitates (MX carbonitrides, M 23 C 6 and Laves phase) were more pronounced for Ti-containing alloys. 9Cr alloys without Ti and with low carbon content presented the highest creep strength of all investigated alloys.

9-12% Cr heat resistant steels. Alloy design, TEM characterisation of microstructure evolution and creep response at 650 C

Energy Technology Data Exchange (ETDEWEB)

Rojas Jara, David

2011-03-21

evolution and creep response was established. All crept samples showed a significant increase of sub-grain size and a reduction of the dislocation density. Hot deformed samples showed better creep strength than non hot-deformed samples, due to homogenisation of the microstructure. The tempering temperature affected the dislocation density and the sub-grain sizes, influencing the creep behaviour. 9% Cr alloys were designed supported by ThermoCalc. Two sets of alloys were produced: 9% Cr alloys with 0.1 % C and 0.05% C and 9% Cr alloys containing ∝ 0.03% Ti again with 0.1% C and 0.05% C (always wt%). Microstructure investigations showed good agreement with the predicted phases of the thermodynamic modeling. The volume fraction of precipitated M{sub 23}C{sub 6} carbides is directly related to the carbon content of the alloys. Hardening of the Ti-containing alloys by precipitation of fine dispersed Ti-based MX particles was achieved. The precipitation of these carbides was limited to the austenisation and tempering treatment used. The microstructure evolution (sub-grain and particle size) during creep at 650 C / 100MPa was investigated by STEM-HAADF. The sub-grain size evolution and the coarsening of precipitates (MX carbonitrides, M{sub 23}C{sub 6} and Laves phase) were more pronounced for Ti-containing alloys. 9Cr alloys without Ti and with low carbon content presented the highest creep strength of all investigated alloys.

Microstructure of ultra high performance concrete containing lithium slag.

Science.gov (United States)

He, Zhi-Hai; Du, Shi-Gui; Chen, Deng

2018-04-03

Lithium slag (LS) is discharged as a byproduct in the process of the lithium carbonate, and it is very urgent to explore an efficient way to recycle LS in order to protect the environments and save resources. Many available supplementary cementitious materials for partial replacement of cement and/or silica fume (SF) can be used to prepare ultra high performance concrete (UHPC). The effect of LS to replace SF partially by weight used as a supplementary cementitious material (0%, 5%, 10% and 15% of binder) on the compressive strengths and microstructure evolution of UHPC has experimentally been studied by multi-techniques including mercury intrusion porosimetry, scanning electron microscope and nanoindentation technique. The results show that the use of LS degrades the microstructure of UHPC at early ages, and however, the use of LS with the appropriate content improves microstructure of UHPC at later ages. The hydration products of UHPC are mainly dominated by ultra-high density calcium-silicate-hydrate (UHD C-S-H) and interfacial transition zone (ITZ) in UHPC has similar compact microstructure with the matrix. The use of LS improves the hydration degree of UHPC and increases the elastic modulus of ITZ in UHPC. LS is a promising substitute for SF for preparation UHPC. Copyright © 2018 Elsevier B.V. All rights reserved.

The microstructure of petroleum vacuum residue films for bituminous concrete: a microscopy approach

NARCIS (Netherlands)

Sourty, E.; Tamminga, A.Y.; Michels, M.A.J.; Vellinga, W.P.; Meijer, H.E.H.

2011-01-01

Selected carbon-rich refinery residues (‘binders’) mixed with mineral particles can form composite materials (‘bituminous concrete’) with bulk mechanical properties comparable to those of cement concrete. The microstructural mechanism underlying the remarkable composite properties has been related

Synthesis of Mg2Cu nanoparticles on carbon supports with enhanced hydrogen sorption kinetics

NARCIS (Netherlands)

Au, Y.S.; Ponthieu, M.; van Zwienen, M.; Zlotea, C.; Cuevas, F.; de Jong, K.P.; de Jongh, P.E.

2013-01-01

The reaction kinetics and reversibility for hydrogen sorption were investigated for supported Mg2Cu nanoparticles on carbon. A new preparation method is proposed to synthesize the supported alloy nanoparticles. The motivation of using a support is to separate the nanoparticles to prevent sintering

Methanol Electro-Oxidation on Pt-Ru Alloy Nanoparticles Supported on Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Yangchuan Xing

2009-09-01

Full Text Available Carbon nanotubes (CNTs have been investigated in recent years as a catalyst support for proton exchange membrane fuel cells. Improved catalyst activities were observed and attributed to metal-support interactions. We report a study on the kinetics of methanol electro-oxidation on CNT supported Pt-Ru alloy nanoparticles. Alloy catalysts with different compositions, Pt53Ru47/CNT, Pt69Ru31/CNT and Pt77Ru23/CNT, were prepared and investigated in detail. Experiments were conducted at various temperatures, electrode potentials, and methanol concentrations. It was found that the reaction order of methanol electro-oxidation on the PtRu/CNT catalysts was consistent with what has been reported for PtRu alloys with a value of 0.5 in methanol concentrations. However, the electro-oxidation reaction on the PtRu/CNT catalysts displayed much lower activation energies than that on the Pt-Ru alloy catalysts unsupported or supported on carbon black (PtRu/CB. This study provides an overall kinetic evaluation of the PtRu/CNT catalysts and further demonstrates the beneficial role of CNTs.

Oxidation of CO and Methanol on Pd-Ni Catalysts Supported on Different Chemically-Treated Carbon Nanofibers

Directory of Open Access Journals (Sweden)

Juan Carlos Calderón

2016-10-01

Full Text Available In this work, palladium-nickel nanoparticles supported on carbon nanofibers were synthesized, with metal contents close to 25 wt % and Pd:Ni atomic ratios near to 1:2. These catalysts were previously studied in order to determine their activity toward the oxygen reduction reaction. Before the deposition of metals, the carbon nanofibers were chemically treated in order to generate oxygen and nitrogen groups on their surface. Transmission electron microscopy analysis (TEM images revealed particle diameters between 3 and 4 nm, overcoming the sizes observed for the nanoparticles supported on carbon black (catalyst Pd-Ni CB 1:2. From the CO oxidation at different temperatures, the activation energy Eact for this reaction was determined. These values indicated a high tolerance of the catalysts toward the CO poisoning, especially in the case of the catalysts supported on the non-chemically treated carbon nanofibers. On the other hand, apparent activation energy Eap for the methanol oxidation was also determined finding—as a rate determining step—the COads diffusion to the OHads for the catalysts supported on carbon nanofibers. The results here presented showed that the surface functional groups only play a role in the obtaining of lower particle sizes, which is an important factor in the obtaining of low CO oxidation activation energies.

Carbon/H-ZSM-5 composites as supports for bi-functional Fischer-Tropsch synthesis catalysts

NARCIS (Netherlands)

Valero-Romero, M.J.; Sartipi, S.; Sun, X.; Rodríguez-Mirasol, J.; Cordero, T.; Kapteijn, F.; Gascon, J.

2016-01-01

Mesoporous H-ZSM-5–carbon composites, prepared via tetrapropylammonium hydroxide (TPAOH) post treatment of H-ZSM-5 followed by deposition of pyrolytic carbon, have been used as the support for the preparation of Co-based Fischer–Tropsch catalysts. The resulting catalysts display an improved

Evaluation of coke microstructure and its effects on graphite fabrication

International Nuclear Information System (INIS)

Fotourehchian, S.; Ahmadi, S.

2001-01-01

A variety of applications for cokes (metallurgy, petroleum, etc.) have been defined in parallel to the new industrial technology growth. Coke is rich in carbon and has the main role in manufacturing carbonaceous materials such as graphite, steel, silicon carbide, titanium carbide, etc. Among the most important applications of different variety of cokes is their usage for different graphite fabrications. The crystalline structure of graphite (hexagonal with sp 2 hybrid) is based upon the microstructure of coke and it causes anisotropy in properties of produced graphite. Thus, the study of macrostructure and anisotropy degree of cokes is of importance. There are several theoretical and experimental methods to determine the Coke's microstructure and anisotropy. Numerous tests have been conducted on different variety of cokes based on the used method. Here, it is attempted to introduce an applied method to determine the microstructure and anisotropy degree of cokes based upon the kind of application

Carbon-Based Regenerable Sorbents for the Combined Carbon Dioxide and Ammonia Removal for the Primary Life Support System (PLSS)

Science.gov (United States)

Wojtowicz, Marek A.; Cosgrove, Joseph E.; Serio, Michael A.; Manthina, Venkata; Singh, Prabhakar; Chullen, Cinda

2014-01-01

Results are presented on the development of reversible sorbents for the combined carbon dioxide and trace-contaminant (TC) removal for use in Extravehicular Activities (EVAs). Since ammonia is the most important TC to be captured, data on TC sorption presented in this paper are limited to ammonia, with results relevant to other TCs to be reported at a later time. The currently available life support systems use separate units for carbon dioxide, trace contaminants, and moisture control, and the long-term objective is to replace the above three modules with a single one. Furthermore, the current TC-control technology involves the use of a packed bed of acid-impregnated granular charcoal, which is non-regenerable, and the carbon-based sorbent under development in this project can be regenerated by exposure to vacuum at room temperature. The objective of this study was to demonstrate the feasibility of using carbon sorbents for the reversible, concurrent sorption of carbon dioxide and ammonia. Several carbon sorbents were fabricated and tested, and multiple adsorption/vacuum-regeneration cycles were demonstrated at room temperature, and also a carbon surface conditioning technique that enhances the combined carbon dioxide and ammonia sorption without impairing sorbent regeneration.

Microstructure and grain size effects on irradiation hardening of low carbon steel for reactor tanks

International Nuclear Information System (INIS)

Milasin, N.

1964-05-01

Irradiation hardening of steel for reactor pressure vessels has been studied extensively during the past few years. A great number of experimental results concerning the behaviour of these steels in the radiation field and several review papers (1,2) have been published. Most of the papers deal with the effects of specific metallurgical factors or irradiation conditions (temperature, flux) on irradiation hardening and embrittlement. In addition, a number of experiments are performed to give evidence on the mechanism of irradiation hardening of these steels. However, this mechanism is still unknown due to the complexity of steel as a system. Among different methods used in radiation damage studies, the changes of mechanical properties have been mainly investigated. By using Hall-Petch's empirical relation, σ y =σ i +k y d -1/2 between lower yield stress, σ y , and grain size, 2d, the information about the effect of irradiation on the parameters σ i and k y is obtained. Taking as a base interpretation of σ i and k y given by Petch and his co-workers it has been concluded that radiation does not change the stress to start slip but that it increase the friction that opposes the passage of free dislocations across a slip plane. In attempting to apply Hall-Petch's relation to one unirradiated ferritic steel with a carbon content higher than 0.15% some difficulties were encountered. The results obtained indicate that the influence of grain size can not be isolated from other factors introduced by the treatments used to produce different grain sizes. This paper deals with a similar problem in the case of irradiated steel. The results obtained give the changes of the mechanical properties of steel in neutron irradiation field as a function of microstructure and grain size. In addition, the mechanical properties of irradiated steel are measured after annealing at 150 deg C and 450 deg C. On the basis of the experimental results obtained the relative microstructure and

EFFECT OF STRAIN RATE ON MICROSTRUCTURE OF A LOW CARBON STEEL WIRE

Directory of Open Access Journals (Sweden)

H BOUHALAIS

2011-12-01

microstructure of the material in as received and deformed conditions. It is found that tensile properties depend on the wiredrawing area reduction (τw. The annealing temperatures and the grain size are determined; they also vary with τw .

EBSD Analysis of Relationship Between Microstructural Features and Toughness of a Medium-Carbon Quenching and Partitioning Bainitic Steel

Science.gov (United States)

Li, Qiangguo; Huang, Xuefei; Huang, Weigang

2017-12-01

A multiphase microstructure of bainite, martensite and retained austenite in a 0.3C bainitic steel was obtained by a novel bainite isothermal transformation plus quenching and partitioning (B-QP) process. The correlations between microstructural features and toughness were investigated by electron backscatter diffraction (EBSD), and the results showed that the multiphase microstructure containing approximately 50% bainite exhibits higher strength (1617 MPa), greater elongation (18.6%) and greater impact toughness (103 J) than the full martensite. The EBSD analysis indicated that the multiphase microstructure with a smaller average local misorientation (1.22°) has a lower inner stress concentration possibility and that the first formed bainitic ferrite plates in the multiphase microstructure can refine subsequently generated packets and blocks. The corresponding packet and block average size decrease from 11.9 and 2.3 to 8.4 and 1.6 μm, respectively. A boundary misorientation analysis indicated that the multiphase microstructure has a higher percentage of high-angle boundaries (67.1%) than the full martensite (57.9%) because of the larger numbers and smaller sizes of packets and blocks. The packet boundary obstructs crack propagation more effectively than the block boundary.

Influence of Nitrogen Gas Flow Rate on The Microstructural and Mechanical Properties of Tin Deposited Carbon Steel Synthesized by Cae

Directory of Open Access Journals (Sweden)

A. Mubarak

2017-11-01

Full Text Available This paper reports on the preparation of titanium nitride (TiN thin films on carbon steel plates, using cathodic arc evaporation CAE PVD technique. We studied and discussed the effect of various nitrogen gas flow rates on microstructural and mechanical properties of TiN-coated carbon steel plates. The coating properties investigated in this work included the surface morphology, thickness of deposited coating, adhesion between the coating and substrate, coating composition, coating crystallography, hardness and surface characterization using a field emission scanning electron microscope (FE-SEM with energy dispersive X-ray (EDX, Xray diffraction (XRD with glazing incidence angle (GIA technique, scratch tester, hardness testing machine, surface roughness tester and atomic force microscope (AFM. SEM analyses showed that all the films had columnar and dense structures with clearly defined substrate-film interfacial layers. The hardness of TiN-coated carbon steel was noted six times more than the hardness of uncoated one. An increase in nitrogen gas flow rate showed; decrease in the formation of macro-droplets, average roughness (Ra and root-mean-square (RMS values in CAE PVD technique. During XRD-GIA studies, it was observed that by increasing the nitrogen gas flow rate, the main peak [1,1,1] shifted toward the lower angular position. Microhardness of TiN-coated carbon steel showed about six times increase in hardness than the uncoated one. Scratch tester results showed an average adhesion between the coating material and substrate. Thanks to the high resolution power could be observed that by increasing nitrogen gas flow rate there was percentage increase in the bearing ratio while percentage decrease in histogram.

Preparation and mechanical properties of carbon nanotube-silicon nitride nano-ceramic matrix composites

Science.gov (United States)

Tian, C. Y.; Jiang, H.

2018-01-01

Carbon nanotube-silicon nitride nano-ceramic matrix composites were fabricated by hot-pressing nano-sized Si3N4 powders and carbon nanotubes. The effect of CNTs on the mechanical properties of silicon nitride was researched. The phase compositions and the microstructure characteristics of the samples as well as the distribution of carbon nanotube in the silicon nitride ceramic were analyzed by X-ray diffraction and scanning electron microscope. The results show that the microstructure of composites consists mainly of α-Si3N4, β-Si3N4, Si2N2O and carbon natubes. The addition of proper amount of carbon nanotubes can improve the fracture toughness and the flexural strength, and the optimal amount of carbon nanotube are both 3wt.%. However the Vickers hardness values decrease with the increase of carbon nanotubes content.

Highly Loaded Carbon Black Supported Pt Catalysts for Fuel Cells

Czech Academy of Sciences Publication Activity Database

Kaluža, Luděk; Larsen, M.J.; Zdražil, Miroslav; Gulková, Daniela; Vít, Zdeněk; Šolcová, Olga; Soukup, Karel; Koštejn, Martin; Bonde, J.L.; Maixnerová, Lucie; Odgaard, M.

2015-01-01

Roč. 256, NOV 1 (2015), s. 375-383 ISSN 0920-5861 R&D Projects: GA MŠk(CZ) 7HX13003 EU Projects: European Commission(XE) 303466 - IMMEDIATE Institutional support: RVO:67985858 Keywords : carbon black * fuell cell * electrocatalyst Subject RIV: CI - Industrial Chemistry , Chemical Engineering Impact factor: 4.312, year: 2015

Electrochemically controlled winding and unwinding of substrate-supported carbon nanoscrolls

Czech Academy of Sciences Publication Activity Database

Tarábková, Hana; Zelinger, Zdeněk; Janda, Pavel

2018-01-01

Roč. 20, č. 8 (2018), s. 5900-5908 ISSN 1463-9076 R&D Projects: GA ČR(CZ) GA17-05167s Institutional support: RVO:61388955 Keywords : electrochemistry * carbon nanoscrolls * electrical energy Subject RIV: CG - Electrochemistry OBOR OECD: Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis) Impact factor: 4.123, year: 2016

Nano-Scale Au Supported on Carbon Materials for the Low Temperature Water Gas Shift (WGS Reaction

Directory of Open Access Journals (Sweden)

Paula Sánchez

2011-12-01

Full Text Available Au-based catalysts supported on carbon materials with different structures such as graphite (G and fishbone type carbon nanofibers (CNF-F were prepared using two different methods (impregnation and gold-sol to be tested in the water gas shift (WGS reaction. Atomic absorption spectrometry, transmission electron microscopy (TEM, temperature-programmed oxidation (TPO, X-ray diffraction (XRD, Raman spectroscopy, elemental analyses (CNH, N2 adsorption-desorption analysis, temperature-programmed reduction (TPR and temperature-programmed decomposition were employed to characterize both the supports and catalysts. Both the crystalline nature of the carbon supports and the method of gold incorporation had a strong influence on the way in which Au particles were deposited on the carbon surface. The higher crystallinity and the smaller and well dispersed Au particle size were, the higher activity of the catalysts in the WGS reaction was noted. Finally, catalytic activity showed an important dependence on the reaction temperature and steam-to-CO molar ratio.

Improved hydrogen generation from alkaline NaBH{sub 4} solution using cobalt catalysts supported on modified activated carbon

Energy Technology Data Exchange (ETDEWEB)

Xu, Dongyan; Guo, Qingjie; Yue, Xuehai [College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China); Dai, Ping [College of Electromechanical Engineering, Qingdao University of Science and Technology, Qingdao 266061 (China)

2008-12-15

Hydrogen production from alkaline sodium borohydride (NaBH{sub 4}) solution via hydrolysis process over activated carbon supported cobalt catalysts is studied. Activated carbons are used in their original form and after liquid phase oxidation with HNO{sub 3}. The changes in surface functional groups of the activated carbon are detected by FTIR spectroscopy. The effects of HNO{sub 3} oxidation on the properties of the activated carbon and the resulting catalyst performance are investigated. FTIR analysis reveals that the oxidative treatment leads to the formation of various functional groups on the surface of the activated carbon. Cobalt catalysts supported on the modified activated carbon are found to exhibit higher activity and stability. (author)

Fabrication variables affecting the structure and properties of supported carbon molecular sieve membranes for hydrogen separation

KAUST Repository

Briceño, Kelly

2012-10-01

A high molecular weight polyimide (Matrimid) was used as a precursor for fabricating supported carbon molecular sieve membranes without crack formation at 550-700°C pyrolysis temperature. A one-step polymer (polyimide) coating method as precursor of carbon layer was used without needing a prior modification of a TiO 2 macroporous support. The following fabrication variables were optimized and studied to determine their effect on the carbon structure: polymeric solution concentration, solvent extraction, heating rate and pyrolysis temperature. Two techniques (Thermogravimetric analysis and Raman spectroscopy) were used to determine these effects on final carbon structure. Likewise, the effect of the support was also reported as an additional and important variable in the design of supported carbon membranes. Atomic force microscopy and differential scanning calorimetry quantified the degree of influence. Pure gas permeation tests were performed using CH 4, CO, CO 2 and H 2. The presence of a molecular sieving mechanism was confirmed after defects were plugged with PDMS solution at 12wt%. Gas selectivities higher than Knudsen theoretical values were reached with membranes obtained over 650°C, showing as best values 4.46, 4.70 and 10.62 for H 2/N 2, H 2/CO and H 2/CH 4 ratio, respectively. Permeance values were over 9.82×10 -9mol/(m 2Pas)during pure hydrogen permeation tests. © 2012 Elsevier B.V.

Fabrication variables affecting the structure and properties of supported carbon molecular sieve membranes for hydrogen separation

KAUST Repository

Briceñ o, Kelly; Montané , Daniel; Garcia-Valls, Ricard; Iulianelli, Adolfo; Basile, Angelo

2012-01-01

A high molecular weight polyimide (Matrimid) was used as a precursor for fabricating supported carbon molecular sieve membranes without crack formation at 550-700°C pyrolysis temperature. A one-step polymer (polyimide) coating method as precursor of carbon layer was used without needing a prior modification of a TiO 2 macroporous support. The following fabrication variables were optimized and studied to determine their effect on the carbon structure: polymeric solution concentration, solvent extraction, heating rate and pyrolysis temperature. Two techniques (Thermogravimetric analysis and Raman spectroscopy) were used to determine these effects on final carbon structure. Likewise, the effect of the support was also reported as an additional and important variable in the design of supported carbon membranes. Atomic force microscopy and differential scanning calorimetry quantified the degree of influence. Pure gas permeation tests were performed using CH 4, CO, CO 2 and H 2. The presence of a molecular sieving mechanism was confirmed after defects were plugged with PDMS solution at 12wt%. Gas selectivities higher than Knudsen theoretical values were reached with membranes obtained over 650°C, showing as best values 4.46, 4.70 and 10.62 for H 2/N 2, H 2/CO and H 2/CH 4 ratio, respectively. Permeance values were over 9.82×10 -9mol/(m 2Pas)during pure hydrogen permeation tests. © 2012 Elsevier B.V.

Pd nanoparticles supported on ultrahigh surface area honeycomb-like carbon for alcohol electrooxidation

Energy Technology Data Exchange (ETDEWEB)

Yan, Zaoxue; He, Guoqiang; Zhang, Guanghui; Meng, Hui; Shen, Pei Kang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

2010-04-15

The honeycomb-like porous carbon was prepared using glucose as carbon source and solid core mesoporous shell (SCMS) silica as templates. The material was characterized by physical and electrochemical methods. The results showed that the honeycomb-like porous carbon was consisted of hollow porous carbon (HPC) which gave an ultrahigh BET surface area of 1012.97 m{sup 2} g{sup -1} and pore volume of 2.19 cm{sup 3} g{sup -1}. The porous walls of the HPC were formed in the mesoporous shells of the silica templates. The HPC was used as the support to load Pd nanoparticles (Pd/HPC) for alcohol electrooxidation. It was highly active for methanol, ethanol and isopropanol electrooxidation. The peak current density for ethanol electrooxidation on Pd/HPC electrode was five times higher than that on Pd/C electrode at the same Pd loadings. The mass activity for ethanol electrooxidation was 4000 A g{sup -1} which is much higher compared to the data reported in the literature. The highly porous structure of such HPC can be widely used as support for uniform dispersing metal nanoparticles to increase their utilization as electrocatalysts. (author)

Hydrodeoxygenation of phenols as lignin models under acid-free conditions with carbon-supported platinum catalysts.

Science.gov (United States)

Ohta, Hidetoshi; Kobayashi, Hirokazu; Hara, Kenji; Fukuoka, Atsushi

2011-11-28

Carbon-supported Pt catalysts are highly active and reusable for the aqueous-phase hydrodeoxygenation of phenols as lignin models without adding any acids. It is suggested that Pt/carbon facilitates the hydrogenation of phenols and the hydrogenolysis of the resulting cyclohexanols.

Vertically Aligned Carbon Nanotube Arrays as Efficient Supports for Faradaic Capacitive Electrodes

Science.gov (United States)

Oguntoye, Moses; Holleran, Mary-Kate; Roberts, Katherine; Pesika, Noshir

Supercapacitors are notable for their ability to deliver energy at higher power (compared to batteries) and store energy at higher density (compared to capacitors) as well as exhibit a long cycle life. In our efforts to further the development of supercapacitors, our focus is on using vertically aligned carbon nanotubes (VACNT) as supports for faradaic capacitive electrode materials. The objective is to develop electrodes functioning in an inexpensive aqueous environment with small potential windows, that store energy at a higher density than carbon materials alone. We describe the different approaches explored to overcome the challenges of non-uniform deposition, poor wetting and array collapse. Materials that are electrochemically anchored to VACNT supports include NiCo2O4, VOx, Fe2O3 and Co-Mn mixed oxides. In each case, the specific capacitance obtained using the VACNT arrays as supports is significantly more than that obtained by direct deposition onto current collectors or by using VACNT alone. The ease of VACNT growth and the degree of coating control achievable using electrodeposition means there is much potential in exploring them as supports for capacitive electrode materials.

Metal/Carbon Hybrid Nanostructures Produced from Plasma-Enhanced Chemical Vapor Deposition over Nafion-Supported Electrochemically Deposited Cobalt Nanoparticles

Directory of Open Access Journals (Sweden)

Mohammad Islam

2018-04-01

Full Text Available In this work, we report development of hybrid nanostructures of metal nanoparticles (NP and carbon nanostructures with strong potential for catalysis, sensing, and energy applications. First, the etched silicon wafer substrates were passivated for subsequent electrochemical (EC processing through grafting of nitro phenyl groups using para-nitrobenzene diazonium (PNBT. The X-ray photoelectron spectroscope (XPS and atomic force microscope (AFM studies confirmed presence of few layers. Cobalt-based nanoparticles were produced over dip or spin coated Nafion films under different EC reduction conditions, namely CoSO4 salt concentration (0.1 M, 1 mM, reduction time (5, 20 s, and indirect or direct EC reduction route. Extensive AFM examination revealed NP formation with different attributes (size, distribution depending on electrochemistry conditions. While relatively large NP with >100 nm size and bimodal distribution were obtained after 20 s EC reduction in H3BO3 following Co2+ ion uptake, ultrafine NP (<10 nm could be produced from EC reduction in CoSO4 and H3BO3 mixed solution with some tendency to form oxides. Different carbon nanostructures including few-walled or multiwalled carbon nanotubes (CNT and carbon nanosheets were grown in a C2H2/NH3 plasma using the plasma-enhanced chemical vapor deposition technique. The devised processing routes enable size controlled synthesis of cobalt nanoparticles and metal/carbon hybrid nanostructures with unique microstructural features.

Microstructure taxonomy based on spatial correlations: Application to microstructure coarsening

International Nuclear Information System (INIS)

Fast, Tony; Wodo, Olga; Ganapathysubramanian, Baskar; Kalidindi, Surya R.

2016-01-01

To build materials knowledge, rigorous description of the material structure and associated tools to explore and exploit information encoded in the structure are needed. These enable recognition, categorization and identification of different classes of microstructure and ultimately enable to link structure with properties of materials. Particular interest lies in the protocols capable of mining the essential information in large microstructure datasets and building robust knowledge systems that can be easily accessed, searched, and shared by the broader materials community. In this paper, we develop a protocol based on automated tools to classify microstructure taxonomies in the context of coarsening behavior which is important for long term stability of materials. Our new concepts for enhanced description of the local microstructure state provide flexibility of description. The mathematical description of microstructure that capture crucial attributes of the material, although central to building materials knowledge, is still elusive. The new description captures important higher order spatial information, but at the same time, allows down sampling if less information is needed. We showcase the classification protocol by studying coarsening of binary polymer blends and classifying steady state structures. We study several microstructure descriptions by changing the microstructure local state order and discretization and critically evaluate their efficacy. Our analysis revealed the superior properties of microstructure representation is based on the first order-gradient of the atomic fraction.

Deformation bands in porous carbonate grainstones: Field and laboratory observations

NARCIS (Netherlands)

Cilona, A.; Baud, P.; Tondi, E.; Agosta, F.; Vinciguerra, S.; Rustichelli, A.; Spiers, C.J.

2012-01-01

Recent field-based studies documented deformation bands in porous carbonates; these structures accommodate volumetric and/or shear strain by means of pore collapse, grain rotation and/or sliding. Microstructural observations of natural deformation bands in carbonates showed that, at advanced stages

Uniform, dense arrays of vertically aligned, large-diameter single-walled carbon nanotubes.

Science.gov (United States)

Han, Zhao Jun; Ostrikov, Kostya

2012-04-04

Precisely controlled reactive chemical vapor synthesis of highly uniform, dense arrays of vertically aligned single-walled carbon nanotubes (SWCNTs) using tailored trilayered Fe/Al(2)O(3)/SiO(2) catalyst is demonstrated. More than 90% population of thick nanotubes (>3 nm in diameter) can be produced by tailoring the thickness and microstructure of the secondary catalyst supporting SiO(2) layer, which is commonly overlooked. The proposed model based on the atomic force microanalysis suggests that this tailoring leads to uniform and dense arrays of relatively large Fe catalyst nanoparticles on which the thick SWCNTs nucleate, while small nanotubes and amorphous carbon are effectively etched away. Our results resolve a persistent issue of selective (while avoiding multiwalled nanotubes and other carbon nanostructures) synthesis of thick vertically aligned SWCNTs whose easily switchable thickness-dependent electronic properties enable advanced applications in nanoelectronic, energy, drug delivery, and membrane technologies.

Highly active carbon supported Pd cathode catalysts for direct formic acid fuel cells

Energy Technology Data Exchange (ETDEWEB)

Mikolajczuk-Zychora, A., E-mail: amikolajczuk@ichf.edu.pl [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Borodzinski, A.; Kedzierzawski, P.; Mierzwa, B. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Mazurkiewicz-Pawlicka, M. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Faculty of Chemical and Process Engineering, Warsaw University of Technology, Warynskiego 1, Warsaw (Poland); Stobinski, L. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Faculty of Chemical and Process Engineering, Warsaw University of Technology, Warynskiego 1, Warsaw (Poland); Ciecierska, E. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw (Poland); Zimoch, A.; Opałło, M. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland)

2016-12-01

Highlights: • Palladium catalyst used on the cathode DFAFC is comparable to commercial platinum catalyst. • The treatment of carbon supports in nitric acid(V) increases the electrochemically available metal surface area and the catalytic activity in oxygen reduction reaction of catalysts. - Abstract: One of the drawbacks of low-temperature fuel cells is high price of platinum-based catalysts used for the electroreduction of oxygen at the cathode of the fuel cell. The aim of this work is to develop the palladium catalyst that will replace commonly used platinum cathode catalysts. A series of palladium catalysts for oxygen reduction reaction (ORR) were prepared and tested on the cathode of Direct Formic Acid Fuel Cell (DFAFC). Palladium nanoparticles were deposited on the carbon black (Vulcan) and on multiwall carbon nanotubes (MWCNTs) surface by reduction of palladium(II) acetate dissolved in ethanol. Hydrazine was used as a reducing agent. The effect of functionalization of the carbon supports on the catalysts physicochemical properties and the ORR catalytic activity on the cathode of DFAFC was studied. The supports were functionalized by treatment in nitric acid for 4 h at 80 °C. The structure of the prepared catalysts has been characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscope (TEM) and cyclic voltammetry (CV). Hydrophilicity of the catalytic layers was determined by measuring contact angles of water droplets. The performance of the prepared catalysts has been compared with that of the commercial 20 wt.% Pt/C (Premetek) catalyst. The maximum power density obtained for the best palladium catalyst, deposited on the surface of functionalized carbon black, is the same as that for the commercial Pt/C (Premetek). Palladium is cheaper than platinum, therefore the developed cathode catalyst is promising for future applications.

Physicochemical investigations of carbon nanofiber supported Cu/ZrO{sub 2} catalyst

Energy Technology Data Exchange (ETDEWEB)

Din, Israf Ud, E-mail: drisraf@yahoo.com, E-mail: maizats@petronas.com.my; Shaharun, Maizatul S., E-mail: drisraf@yahoo.com, E-mail: maizats@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS (Malaysia); Subbarao, Duvvuri, E-mail: duvvuri-subbarao@petronas.com.my [Department of Chemical Engineering, Universiti Teknologi PETRONAS (Malaysia); Naeem, A., E-mail: naeeem64@yahoo.com [National Centre of Excellence in Physical Chemistry, University of Peshawar (Pakistan)

2014-10-24

Zirconia-promoted copper/carbon nanofiber catalysts (Cu‐ZrO{sub 2}/CNF) were prepared by the sequential deposition precipitation method. The Herringbone type of carbon nanofiber GNF-100 (Graphite nanofiber) was used as a catalyst support. Carbon nanofiber was oxidized to (CNF-O) with 5% and 65 % concentration of nitric acid (HNO{sub 3}). The CNF activated with 5% HNO{sub 3} produced higher surface area which is 155 m{sup 2}/g. The catalyst was characterized by X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) and N{sub 2} adsorption-desorption. The results showed that increase of HNO{sub 3} concentration reduced the surface area and porosity of the catalyst.

Transfer of microstructure pattern of CNTs onto flexible substrate using hot press technique for sensing applications

International Nuclear Information System (INIS)

Mishra, Prabhash; Tai, Nyan-Hwa; Harsh; Islam, S.S.

2013-01-01

Graphical abstract: - Highlights: • Successfully transfer of microstructure patterned CNTs on PET substrate. • Demonstrate as resistor-based NH 3 gas sensor in the sub-ppm range. • Excellent photodetector having instantaneous response and recovery characteristics. • An effective technique to grow and produce flexible electronic device. - Abstract: In this work, we report the successful and efficient transfer process of two- dimensional (2-D) vertically aligned carbon nanotubes (CNTs) onto polyethylene terephthalate (PET) substrate by hot pressing method with an aim to develop flexible sensor devices. Carbon nanotubes are synthesized by cold wall thermal chemical vapor deposition using patterned SiO 2 substrate under low pressure. The height of the pattern of CNTs is controlled by reaction time. The entire growth and transfer process is carried out within 30 min. Strong adhesion between the nanotube and polyethylene terephthalate substrate was observed in the post-transferred case. Raman spectroscopy and scanning electron microscope (SEM) studies are used to analyze the microstructure of carbon nanotube film before and after hot pressing. This technique shows great potential for the fabrication of flexible sensing devices. We report for the first time, the application of patterned microstructure developed by this technique in the development of gas sensor and optoelectronic device. Surface resistive mode is used for detection of ammonia (NH 3 ) gas in the sub-ppm range. An impressive photoconducting response is also observed in the visible wavelength. The reproducibility of the sample was checked and the results indicate the possibility of use of carbon nanotube as gas sensor, photodetector, CCDs etc

Transfer of microstructure pattern of CNTs onto flexible substrate using hot press technique for sensing applications

Energy Technology Data Exchange (ETDEWEB)

Mishra, Prabhash [Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Nano-Sensor Research Laboratory, F/O Engineering and Technology, Jamia Millia Islamia, Jamia Nagar, New Delhi (India); Tai, Nyan-Hwa [Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Harsh [Nano-Sensor Research Laboratory, F/O Engineering and Technology, Jamia Millia Islamia, Jamia Nagar, New Delhi (India); Islam, S.S., E-mail: safiul5996@gmail.com [Nano-Sensor Research Laboratory, F/O Engineering and Technology, Jamia Millia Islamia, Jamia Nagar, New Delhi (India)

2013-08-01

Graphical abstract: - Highlights: • Successfully transfer of microstructure patterned CNTs on PET substrate. • Demonstrate as resistor-based NH{sub 3} gas sensor in the sub-ppm range. • Excellent photodetector having instantaneous response and recovery characteristics. • An effective technique to grow and produce flexible electronic device. - Abstract: In this work, we report the successful and efficient transfer process of two- dimensional (2-D) vertically aligned carbon nanotubes (CNTs) onto polyethylene terephthalate (PET) substrate by hot pressing method with an aim to develop flexible sensor devices. Carbon nanotubes are synthesized by cold wall thermal chemical vapor deposition using patterned SiO{sub 2} substrate under low pressure. The height of the pattern of CNTs is controlled by reaction time. The entire growth and transfer process is carried out within 30 min. Strong adhesion between the nanotube and polyethylene terephthalate substrate was observed in the post-transferred case. Raman spectroscopy and scanning electron microscope (SEM) studies are used to analyze the microstructure of carbon nanotube film before and after hot pressing. This technique shows great potential for the fabrication of flexible sensing devices. We report for the first time, the application of patterned microstructure developed by this technique in the development of gas sensor and optoelectronic device. Surface resistive mode is used for detection of ammonia (NH{sub 3}) gas in the sub-ppm range. An impressive photoconducting response is also observed in the visible wavelength. The reproducibility of the sample was checked and the results indicate the possibility of use of carbon nanotube as gas sensor, photodetector, CCDs etc.

Synthesis of Carbon Nano tubes Using Anadara Granosa Shells as Catalyst Support

International Nuclear Information System (INIS)

Mohd Zobir Hussein; Mohd Zobir Hussein; Salwani Asyikin Zakarya; Siti Halimah Sarijo

2011-01-01

The synthesis of carbon nano tubes (CNTs) by chemical vapor deposition (CVD) method using natural calcite prepared from Anadara granosa shells (CS), as metal catalyst support was studied. Hexane and iron were used as carbon precursor and catalyst, respectively. The as synthesised CNTs was characterized using XRD, TEM and FESEM. From the XRD patterns the CNTs peak can be seen more incisive after purification process and from the FESEM micrographs the CNTs can be seen as a bunch of rope-like structures. (author)

Immersion Calorimetry for the Characterization of PD Catalysts Supported on Activated Carbon

Directory of Open Access Journals (Sweden)

Liliana Giraldo

2009-01-01

Full Text Available Activated carbons obtained from coconut peel were oxidized using hydrogen peroxide. Superficial characteristics of these carbons were determined through N2 and CO2 isotherms and functional groups were characterized by TPD. Finally, the microcalorimetry technique was used in order to obtain the immersion enthalpies in diverse liquids and established the relation between them and the results obtained by the other characterization techniques. The results suggested that the immersion calorimetry allow establishing the difference between the supports and the catalysts.

Pt-Ru nanoparticles supported on functionalized carbon as electrocatalysts for the methanol oxidation

International Nuclear Information System (INIS)

Salgado, J.R.C.; Fernandes, J.C.S.; Botelho do Rego, A.M.; Ferraria, A.M.; Duarte, R.G.; Ferreira, M.G.S.

2011-01-01

Highlights: → The functionalized carbon using acid solutions contains surface oxygenated groups. → Uniform dispersion of PtRu nanoparticles on the carbon surface was achieved. → Physical analysis showed the formation of PtRu alloy catalysts on functionalized carbon. → PtRu alloy catalysts on functionalized carbon enhanced the methanol oxidation rate. - Abstract: Platinum-ruthenium alloy electrocatalysts, for methanol oxidation reaction, were prepared on carbons thermally treated in helium atmosphere or chemically functionalized in H 2 O 2 , or in HNO 3 + H 2 SO 4 or in HNO 3 solutions. The functionalized carbon that is produced using acid solutions contains more surface oxygenated functional groups than carbon treated with H 2 O 2 solution or HeTT. The XRD/HR-TEM analysis have showed the existence of a higher alloying degree for Pt-Ru electrocatalysts supported on functionalized carbon, which present superior electrocatalytic performance, assessed by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy, as compared to electrocatalysts on unfunctionalized carbon. It also was found that Pt-Ru alloy electrocatalysts on functionalized carbon improve the reaction rate compared to Pt-Ru on carbons treated with H 2 O 2 solution and thermally. A mechanism is discussed, where oxygenated groups generated from acid functionalization of carbon and adsorbed on Pt-Ru electrocatalysts are considered to enhance the electrocatalytic activity of the methanol oxidation reaction.

Relationship of bainitic microstructure to impact toughness in Cr-Mo and Cr-W steels

International Nuclear Information System (INIS)

Klueh, R.L.; Alexander, D.J.

1992-01-01

Non-classical bainite microstructures can develop during continuous cooling of low-carbon alloy steels. These differ from classical upper and lower bainite developed by isothermal transformation. Two non-classical bainite microstructures were produced in a 3Cr-1.5Mo0.25V-0.lC steel using different cooling rates after austenitizing--water quenching and air cooling. The carbide-free acicular bainite formed in the quenched steel had a lower ductile-brittle transition temperature (DBTT) than the granular bainite formed in the air-cooled steel. With increasing tempering parameter (defined bv tempering time and temperature), the DBTT of both decreased and approached a common value, although the final value occurred at a much lower tempering parameter for the quenched steel than for the air-cooled steel. The upper-shelf enery was similarly affected by microstructure. These observations along with similar observations in two Cr-W steels indicate that control of the bainite microstructure can be used to optimize strength and toughness

Composition and microstructure of beryllium carbide films prepared by thermal MOCVD

Energy Technology Data Exchange (ETDEWEB)

He, Yu-dan; Luo, Jiang-shan; Li, Jia; Meng, Ling-biao; Luo, Bing-chi; Zhang, Ji-qiang; Zeng, Yong; Wu, Wei-dong, E-mail: wuweidongding@163.com

2016-02-15

Highlights: • Non-columnar-crystal Be{sub 2}C films were firstly prepared by thermal MOCVD. • Beryllium carbide was always the dominant phase in the films. • α-Be and carbon existed in films deposited below and beyond 400 °C, respectively. • Morphology evolved with temperatures and no columnar grains were characterized. • The preferred substrate temperature for depositing high quality Be{sub 2}C films was 400 °C. - Abstract: Beryllium carbide films without columnar-crystal microstructures were prepared on the Si (1 0 0) substrate by thermal metal organic chemical vapor deposition using diethylberyllium as precursor. The influence of the substrate temperature on composition and microstructure of beryllium carbide films was systematically studied. Crystalline beryllium carbide is always the dominant phase according to XRD analysis. Meanwhile, a small amount of α-Be phase exists in films when the substrate temperature is below 400 °C, and hydrocarbon or amorphous carbon exists when the temperature is beyond 400 °C. Surfaces morphology shows transition from domes to cylinders, to humps, and to tetraquetrous crystalline needles with the increase of substrate temperature. No columnar grains are characterized throughout the thickness as revealed from the cross-section views. The average densities of these films are determined to be 2.04–2.17 g/cm{sup 3}. The findings indicate the substrate temperature has great influences on the composition and microstructure of the Be{sub 2}C films grown by thermal MOCVD.

In-Situ Roughening of Polymeric Microstructures

Science.gov (United States)

Shadpour, Hamed; Allbritton, Nancy L.

2010-01-01

A method to perform in-situ roughening of arrays of microstructures weakly adherent to an underlying substrate was presented. SU8, 1002F, and polydimethylsiloxane (PDMS) microstructures were roughened by polishing with a particle slurry. The roughness and the percentage of dislodged or damaged microstructures was evaluated as a function of the roughening time for both SU8 and 1002F structures. A maximal RMS roughness of 7-18 nm for the surfaces was obtained within 15 to 30 s of polishing with the slurry. This represented a 4-9 fold increase in surface roughness relative to that of the native surface. Less than 0.8% of the microstructures on the array were removed or damage after 5 min of polishing. Native and roughened arrays were assessed for their ability to support fibronectin adhesion and cell attachment and growth. The quantity of adherent fibronectin was increased on roughened arrays by two-fold over that on native arrays. Cell adhesion to the roughened surfaces was also increased compared to native surfaces. Surface roughening with the particle slurry also improved the ability to stamp molecules onto the substrate during microcontact printing. Roughening both the PDMS stamp and substrate resulted in up to a 20-fold improvement in the transfer of BSA-Alexa Fluor 647 from the stamp to the substrate. Thus roughening of micron-scale surfaces with a particle slurry increased the adhesion of biomolecules as well as cells to microstructures with little to no damage to large scale arrays of the structures. PMID:20423129

Effects of tempering on internal friction of carbon steels

International Nuclear Information System (INIS)

Hoyos, J.J.; Ghilarducci, A.A.; Salva, H.R.; Chaves, C.A.; Velez, J.M.

2011-01-01

Research highlights: → Time tempering dependent microstructure of two steels is studied by internal friction. → Internal friction indicates the interactions of dislocations with carbon and carbides. → Internal friction detects the first stage of tempering. → Precipitation hardening is detected by the decrease in the background. - Abstract: Two steels containing 0.626 and 0.71 wt.% carbon have been studied to determine the effects of tempering on the microstructure and the internal friction. The steels were annealed at 1093 K, quenched into water and tempered for 60 min at 423 K, 573 K and 723 K. The increase of the tempering time diminishes the martensite tetragonality due to the redistribution of carbon atoms from octahedrical interstitial sites to dislocations. Internal friction spectrum is decomposed into five peaks and an exponential background, which are attributed to the carbide precipitation and the dislocation relaxation process. Simultaneous presence of peaks P1 and P2 indicates the interaction of dislocations with the segregated carbon and carbide precipitate.

Microstructural development and mechanical properties of iron based cermets processed by pressureless and spark plasma sintering

International Nuclear Information System (INIS)

Alvaredo, P.; Gordo, E.; Van der Biest, O.; Vanmeensel, K.

2012-01-01

Highlights: ► Processing of Fe-based cermets by pressureless sintering and spark plasma sintering. ► Influence of carbon content on the sintering mechanism and hardness. ► The cermet phase diagram was calculated and permits to explain the microstructure. ► SPS provides ferritic matrix and different carbide distribution than CPS samples. ► Pressureless sintered samples contain retained austenite at room temperature. - Abstract: Iron-based cermets are an interesting class of metal-ceramic composites in which properties and the factors influencing them are to be explored. In this work the metal matrix contains Cr, W, Mo and V as alloying elements, and the hard phase is constituted by 50 vol% of titanium carbonitride (TiCN) particles. The work studies the influence of the C content and the processing method on the sinterability, microstructure and hardness of the developed cermet materials. For that purpose, cermet samples with different C content in the matrix (0 wt%, 0.25 wt%, 0.5 wt%, 1.0 wt%) were prepared by conventional pressureless sintering (CPS) and, in order to achieve finer microstructures and to reduce the sintering time, by spark plasma sintering (SPS). The density and hardness (HV30) of the processed materials was evaluated, while their phase composition and microstructure was characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The equilibrium phase diagram of the composite material was calculated by ThermoCalc software in order to elucidate the influence of the carbon content on the obtained phases and developed microstructures.

Self-supporting activated carbon/carbon nanotube/reduced graphene oxide flexible electrode for high performance supercapacitor

Energy Technology Data Exchange (ETDEWEB)

Li, Xing; Tang, Yao; Song, Junhua; Yang, Wei; Wang, Mingshan; Zhu, Chengzhou; Zhao, Wengao; Zheng, Jianming; Lin, Yuehe

2018-04-30

A self-supporting and flexible activated carbon/carbon nanotube/reduced graphene oxide (AC/CNT/RGO) film has been rationally designed for constructing high- performance supercapacitor. The AC/CNT/RGO film is prepared by anchoring the AC particles with a 3D and porous framework built by hierarchically weaving the 1 D CNT and 2D RGO using their intrinsic van der Waals force. The CNT network is beneficial for improving the electronic conductivity of the electrode, while the AC particles could effectively suppress the aggregation of RGO and CNT due to their blocking effect. The synergistic effects among the AC, CNT and RGO validate the AC/CNT/RGO as a promising electrode for supercapacitor, exhibiting greatly enhanced electrochemical performances in comparison with the pure RGO film, pure CNT film and AC electrode. The AC/CNT/RGO electrode delivers a high specific capacitance of 101 F g-1 at the current density of 0.2 A g-1, offering a maximum energy density of 30.0 W h kg-1 in organic electrolyte at the cut-off voltage range of 0.001~3.0 V. The findings of this work open a new avenue for the design of self-supporting electrodes for the development of flexible and light weight energy storage supercapacitor.

Characterization of D2 tool steel friction surfaced coatings over low carbon steel

International Nuclear Information System (INIS)

Sekharbabu, R.; Rafi, H. Khalid; Rao, K. Prasad

2013-01-01

Highlights: • Solid state coating by friction surfacing method. • D2 tool steel is coated over relatively softer low carbon steel. • Defect free interface between tool steel coating and low carbon steel substrate. • D2 coatings exhibited higher hardness and good wear resistance. • Highly refined martensitic microstructure in the coating. - Abstract: In this work D2 tool steel coating is produced over a low carbon steel substrate using friction surfacing process. The process parameters are optimized to get a defect free coating. Microstructural characterization is carried out using optical microscopy, scanning electron microscopy and X-ray diffraction. Infrared thermography is used to measure the thermal profile during friction surfacing of D2 steel. Wear performance of the coating is studied using Pin-on-Disk wear tests. A lower rotational speed of the consumable rod and higher translational speed of the substrate is found to result in thinner coatings. Friction surfaced D2 steel coating showed fine-grained martensitic microstructure compared to the as-received consumable rod which showed predominantly ferrite microstructure. Refinement of carbides in the coating is observed due to the stirring action of the process. The infrared thermography studies showed the peak temperature attained by the D2 coating to be about 1200 °C. The combined effect of martensitic microstructure and refined carbides resulted in higher hardness and wear resistance of the coating

Nanostructured carbon-supported Pd electrocatalysts for ethanol oxidation: synthesis and characterization

Science.gov (United States)

Gacutan, E. M.; Climaco, M. I.; Telan, G. J.; Malijan, F.; Hsu, H. Y.; Garcia, J.; Fulo, H.; Tongol, B. J.

2012-12-01

The need to lower the construction cost of fuel cells calls for the development of non-Pt based electrocatalysts. Among others, Pd has emerged as a promising alternative to Pt for fuel cell catalysis. This research aims to investigate the synthesis and characterization of nanostructured Pd-based catalysts dispersed on carbon support as anode materials in direct ethanol fuel cells. For the preparation of the first Pd-based electrocatalyst, palladium nanoparticles (NPs) were synthesized via oleylamine (OAm)-mediated synthesis and precursor method with a mean particle size of 3.63 ± 0.59 nm as revealed by transmission electron microscopy (TEM). Carbon black was used as a supporting matrix for the OAm-capped Pd NPs. Thermal annealing and acetic acid washing were used to remove the OAm capping agent. To evaluate the electrocatalytic activity of the prepared electrocatalyst towards ethanol oxidation, cyclic voltammetry (CV) studies were performed using 1.0 M ethanol in basic medium. The CV data revealed the highest peak current density of 11.05 mA cm-2 for the acetic acid-washed Pd/C electrocatalyst. Meanwhile, the fabrication of the second Pd-based electrocatalyst was done by functionalization of the carbon black support using 3:1 (v/v) H2SO4:HNO3. The metal oxide, NiO, was deposited using precipitation method while polyol method was used for the deposition of Pd NPs. X-ray diffraction (XRD) analysis revealed that the estimated particle size of the synthesized catalysts was at around 9.0-15.0 nm. CV results demonstrated a 36.7% increase in the catalytic activity of Pd-NiO/C (functionalized) catalyst towards ethanol oxidation compared to the non-functionalized catalyst.

Tensile test of a silicon microstructure fully coated with submicrometer-thick diamond like carbon film using plasma enhanced chemical vapor deposition method

Science.gov (United States)

Zhang, Wenlei; Uesugi, Akio; Hirai, Yoshikazu; Tsuchiya, Toshiyuki; Tabata, Osamu

2017-06-01

This paper reports the tensile properties of single-crystal silicon (SCS) microstructures fully coated with sub-micrometer thick diamond like carbon (DLC) film using plasma enhanced chemical vapor deposition (PECVD). To minimize the deformations or damages caused by non-uniform coating of DLC, which has high compression residual stress, released SCS specimens with the dimensions of 120 µm long, 4 µm wide, and 5 µm thick were coated from the top and bottom side simultaneously. The thickness of DLC coating is around 150 nm and three different bias voltages were used for deposition. The tensile strength improved from 13.4 to 53.5% with the increasing of negative bias voltage. In addition, the deviation in strength also reduced significantly compared to bare SCS sample.

Microstructure-Property Correlation in Low-Si Steel Processed Through Quenching and Nonisothermal Partitioning

Science.gov (United States)

Bansal, Gaurav K.; Rajinikanth, V.; Ghosh, Chiradeep; Srivastava, V. C.; Kundu, S.; Ghosh Chowdhury, S.

2018-05-01

In the present investigation, an attempt has been made to stabilize austenite by carbon partitioning through quenching and nonisothermal partitioning (Q&P) technique. This will eliminate the need for additional heat-treatment facility to perform isothermal partitioning or tempering process. The presence of retained austenite in the microstructure helps in increasing the toughness, which in turn is expected to improve the abrasion resistance of steels. The carbon partitioning from different quench temperatures has been performed on two different alloys, with low-Si content (0.5 wt pct), in a salt bath furnace atmosphere, the cooling profile of which closely resembles the industrially produced hot-rolled coil cooling. The results show that the stabilization of retained austenite is possible and gives rise to increased work hardening, better impact toughness and abrasive wear loss comparable to that of a fully martensitic microstructure. In contrast, tempered martensite exhibits better wear properties at the expense of impact toughness.

Microstructural evolution of cold-sprayed Inconel 625 superalloy coatings on low alloy steel substrate

International Nuclear Information System (INIS)

Chaudhuri, Atanu; Raghupathy, Y.; Srinivasan, Dheepa; Suwas, Satyam; Srivastava, Chandan

2017-01-01

This study illustrates microstructural evolution of INCONEL 625 superalloy coatings cold-sprayed on a 4130 chrome alloy steel with medium carbon content. INCONEL 625 powder (5–25 μm) were successfully cold sprayed without any oxidation. The comprehensive microstructure analysis of the as-sprayed coatings and of the substrate-coating interface was carried out using EBSD, TEM, and XRD. The coating microstructure at the substrate-coating interface was markedly different from the microstructure away from the interface. The coating microstructure at steel-coating interface consisted of a fine layer of small grains. The microstructure beyond this fine layer can be divided into splats, inter splat and intra splat boundaries. Both splat and splat boundaries exhibited deformation induced dislocations. Dynamic recovery of dislocations-ridden regions inside the splat was responsible for the development of sub grain structure inside a splat with both low and high angle grain boundaries. Splat-splat (inter splat) boundary consisted of a relatively high density of dislocations and shear bands as a result of adiabatic shear flow localisation. This flow instability is believed to enhance the microstructural integrity by eliminating porosity at splat-splat boundaries. Based on the microstructural analysis using electron microscopy, a plausible mechanism for the development of microstructure has been proposed in this work. Cold spray technique can thus be deployed to develop high quality coatings of commercial importance. - Graphical abstract: Schematics of the evolution of microstructure at the 4130 steel substrate close to interface. i) initial deformation close to interface. ii) Accumulation of dislocation in the substrate. iii) Formation of cell structure due to dislocation tangling and arrangement. iv) Dislocation rearrangement and subgrain formation. v.a) Formation HAGB from dislocation accumulation into LAGB. v.b) HAGB formation through DRX by progressive lattice rotation

Synthesis of carbon-supported copper catalyst and its catalytic performance in methanol dehydrogenation

Energy Technology Data Exchange (ETDEWEB)

Shelepova, Ekaterina V. [Boreskov Institute of Catalysis SB RAS, pr. Ac. Lavrentieva, 5, Novosibirsk, 630090 (Russian Federation); National Research Tomsk Polytechnic University, Lenin av., 30, Tomsk, 634050 (Russian Federation); Vedyagin, Aleksey A., E-mail: vedyagin@catalysis.ru [Boreskov Institute of Catalysis SB RAS, pr. Ac. Lavrentieva, 5, Novosibirsk, 630090 (Russian Federation); National Research Tomsk Polytechnic University, Lenin av., 30, Tomsk, 634050 (Russian Federation); Ilina, Ludmila Yu.; Nizovskii, Alexander I. [Boreskov Institute of Catalysis SB RAS, pr. Ac. Lavrentieva, 5, Novosibirsk, 630090 (Russian Federation); Tsyrulnikov, Pavel G. [Institute of Hydrocarbon Processing SB RAS, Neftezavodskaya st., 54, Omsk, 644040 (Russian Federation)

2017-07-01

Highlights: • Carbon-supported copper catalyst was studied in dehydrogenation of methanol. • Reduction temperature affected size of Cu particles and Cu{sup 0}/Cu{sup 2+} ratio. • Reduction at 400 °C was required to obtain high methyl formate yield. - Abstract: Carbon-supported copper catalyst was prepared by incipient wetness impregnation of Sibunit with an aqueous solution of copper nitrate. Copper loading was 5 wt.%. Temperature of reductive pretreatment was varied within a range of 200–400 °C. The samples were characterized by transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron and X-ray absorption spectroscopies. Catalytic activity of the samples was studied in a reaction of methanol dehydrogenation. Silica-based catalyst with similar copper loading was used as a reference. It was found that copper is distributed over the surface of support in the form of metallic and partially oxidized particles of about 12–17 nm in size. Diminished interaction of copper with support was supposed to be responsible for high catalytic activity.

The development and deployment of low-carbon energy technologies: The role of economic interests and cultural worldviews on public support

International Nuclear Information System (INIS)

Cherry, Todd L.; García, Jorge H.; Kallbekken, Steffen; Torvanger, Asbjørn

2014-01-01

Large-scale deployment of low-carbon energy technologies is crucial to mitigating climate change, and public support is an important barrier to policies and projects that facilitate deployment. This paper provides insights to the origins of public opposition that can impede the adoption of low-carbon technologies by investigating how perceptions are shaped by local economic interests and individual cultural worldviews. The research considers both carbon capture and storage and wind energy technologies because they differ in maturity, economic impact and resource base. Further, for each technology, the research examines support for two types of policies: deployment in local community and public funding for research and development. Results indicate the influence of economic interests and cultural worldviews is policy specific. Individual cultural worldviews do not affect support for the deployment of technology, but they do significantly influence a person's support for publicly funded research and development. Conversely, local economic interests have a significant role in determining support for deployment, while they do not affect support for research and development. - Highlights: • We investigate factors that shape public support for low-carbon energy technologies. • We consider two low-carbon energy technologies and two stages of implementation. • Economic interests and cultural worldviews influence support but in different stages

The analysis of bainitic ferrite microstructure in microalloyed plate steels through quantitative characterization of intervariant boundaries

Energy Technology Data Exchange (ETDEWEB)

Kang, Singon, E-mail: sikang@mines.edu [Advanced Steel Processing and Products Research Center, Colorado School of Mines, Golden, CO 80401 (United States); Speer, John G.; Regier, Ryan W. [Advanced Steel Processing and Products Research Center, Colorado School of Mines, Golden, CO 80401 (United States); Nako, Hidenori [Advanced Steel Processing and Products Research Center, Colorado School of Mines, Golden, CO 80401 (United States); Materials Research Laboratory, Kobe Steel Ltd., Kobe, Hyogo 651-2271 (Japan); Kennett, Shane C. [Advanced Steel Processing and Products Research Center, Colorado School of Mines, Golden, CO 80401 (United States); Exponent Failure Analysis Associates, Menlo Park, CA 94025 (United States); Findley, Kip O. [Advanced Steel Processing and Products Research Center, Colorado School of Mines, Golden, CO 80401 (United States)

2016-07-04

Electron backscatter diffraction (EBSD) measurements were performed to investigate the bainitic ferrite microstructure in low-carbon, microalloyed steels with varying C and Mn contents. Fully austenitized samples were isothermally heat treated at temperatures ranging from 450 to 550 °C to form bainitic ferrite. The bainitic ferrite microstructures and boundary characteristics obtained from the EBSD measurements were analyzed based on an inferred Kurdjumov-Sachs (K-S) orientation relationship. The heat treated samples exhibit a microstructure composed of laths and the lath aspect ratio tends to increase at lower isothermal heat treatment temperatures. High fractions of boundary misorientation angles below 5° are observed, which are due to lath boundaries in the microstructure. Additionally, misorientations of approximately 7°, 53° and 60° are observed, which are related to the sub-block, packet, and block boundaries, respectively. With decreasing isothermal heat treatment temperature, there is an increase of block boundaries; these boundaries are intervariant boundaries between different blocks within a packet, most of which have the misorientation angle of 60°. The specimens with a higher carbon level contained increased length of block boundaries, whereas the addition of Mn moderated the dependence of block boundary length on the heat treatment temperature within the experimental temperature range. Meanwhile, the length of intervariant boundaries of both packet and sub-block character did not vary much with heat treatment temperature and alloy composition.

Studies on the reactive melt infiltration of silicon and silicon-molybdenum alloys in porous carbon

Science.gov (United States)

Singh, M.; Behrendt, D. R.

1992-01-01

Investigations on the reactive melt infiltration of silicon and silicon-1.7 and 3.2 at percent molybdenum alloys into porous carbon preforms have been carried out by process modeling, differential thermal analysis (DTA) and melt infiltration experiments. These results indicate that the initial pore volume fraction of the porous carbon preform is a critical parameter in determining the final composition of the raction-formed silicon carbide and other residual phases. The pore size of the carbon preform is very detrimental to the exotherm temperatures due to liquid silicon-carbon reactions encountered during the reactive melt infiltration process. A possible mechanism for the liquid silicon-porous (glassy) carbon reaction has been proposed. The composition and microstructure of the reaction-formed silicon carbide has been discussed in terms of carbon preform microstructures, infiltration materials, and temperatures.

Theoretical design and advanced microstructure in super high strength steels

International Nuclear Information System (INIS)

Caballero, F.G.; Santofimia, M.J.; Garcia-Mateo, C.; Chao, J.; Garcia de Andres, C.

2009-01-01

A theoretical design procedure based on phase transformation theory alone has been successfully applied to design steels with a microstructure consisting of a mixture of bainitic ferrite and retained austenite. Using thermodynamics and kinetics models, a set of four carbide free bainitic steels with a 0.3 wt.% carbon content were designed and manufactured following a thermomechanical treatment consisting of hot rolling and two-step cooling. The designed steels present significant combinations of strength and ductility, with tensile strengths ranging from 1500 to 1800 MPa and total elongations over 15%. However, a carbon content of 0.3 wt.% is still high for in-use properties such as weldability. In this sense, a reduction in the average carbon content of advanced bainitic steels was proposed. Improved bainitic steels with a carbon content of 0.2 wt.% reached combinations of strength and ductility comparable to those in TRIP assisted steels.

Patterned functional carbon fibers from polyethylene

Energy Technology Data Exchange (ETDEWEB)

Hunt, Marcus A [ORNL; Saito, Tomonori [ORNL; Brown, Rebecca H [ORNL; Kumbhar, Amar S [University of North Carolina, Chapel Hill; Naskar, Amit K [ORNL

2012-01-01

Patterned, continuous carbon fibers with controlled surface geometry were produced from a novel melt-processible carbon precursor. This portends the use of a unique technique to produce such technologically innovative fibers in large volume for important applications. The novelties of this technique include ease of designing and fabricating fibers with customized surface contour, the ability to manipulate filament diameter from submicron scale to a couple of orders of magnitude larger scale, and the amenable porosity gradient across the carbon wall by diffusion controlled functionalization of precursor. The geometry of fiber cross-section was tailored by using bicomponent melt-spinning with shaped dies and controlling the melt-processing of the precursor polymer. Circular, trilobal, gear-shaped hollow fibers, and solid star-shaped carbon fibers of 0.5 - 20 um diameters, either in self-assembled bundle form, or non-bonded loose filament form, were produced by carbonizing functionalized-polyethylene fibers. Prior to carbonization, melt-spun fibers were converted to a char-forming mass by optimizing the sulfonation on polyethylene macromolecules. The fibers exhibited distinctly ordered carbon morphologies at the outside skin compared to the inner surface or fiber core. Such order in carbon microstructure can be further tuned by altering processing parameters. Partially sulfonated polyethylene-derived hollow carbon fibers exhibit 2-10 fold surface area (50-500 m2/g) compared to the solid fibers (10-25 m2/g) with pore sizes closer to the inside diameter of the filaments larger than the sizes on the outer layer. These specially functionalized carbon fibers hold promise for extraordinary performance improvements when used, for example, as composite reinforcements, catalyst support media, membranes for gas separation, CO2 sorbents, and active electrodes and current collectors for energy storage applications.

Activated carbon supported CaO for conversion of palm oil to ...

African Journals Online (AJOL)

In this study, activated carbon supported CaO catalyst was used for the transesterification reaction of palm oil. The catalyst was prepared according to the conventional incipient witness impregnation method. Kinetic experiment was performed in a batch reactor in the presence of heterogeneous catalyst for a wide range of ...

Understanding the Interaction between a Steel Microstructure and Hydrogen

Science.gov (United States)

Depover, Tom; Laureys, Aurélie; Wallaert, Elien

2018-01-01

The present work provides an overview of the work on the interaction between hydrogen (H) and the steel’s microstructure. Different techniques are used to evaluate the H-induced damage phenomena. The impact of H charging on multiphase high-strength steels, i.e., high-strength low-alloy (HSLA), transformation-induced plasticity (TRIP) and dual phase (DP) is first studied. The highest hydrogen embrittlement resistance is obtained for HSLA steel due to the presence of Ti- and Nb-based precipitates. Generic Fe-C lab-cast alloys consisting of a single phase, i.e., ferrite, bainite, pearlite or martensite, and with carbon contents of approximately 0, 0.2 and 0.4 wt %, are further considered to simplify the microstructure. Finally, the addition of carbides is investigated in lab-cast Fe-C-X alloys by adding a ternary carbide forming element to the Fe-C alloys. To understand the H/material interaction, a comparison of the available H trapping sites, the H pick-up level and the H diffusivity with the H-induced mechanical degradation or H-induced cracking is correlated with a thorough microstructural analysis. PMID:29710803

Graphene supported Sn-Sb rate at carbon core-shell particles as a superior anode for lithium ion batteries

Energy Technology Data Exchange (ETDEWEB)

Chen, Shuangqiang; Chen, Peng; Wang, Yong [Department of Chemical Engineering, School of Environmental and Chemical Engineering, Shanghai University (China); Wu, Minghong; Pan, Dengyu [Institute of Nanochemistry and Nanobiology, Shanghai Univ. (China)

2010-10-15

This paper reports the preparation and Li-storage properties of graphene nanosheets(GNS), GNS supported Sn-Sb rate at carbon (50-150 nm) and Sn-Sb nanoparticles (5-10 nm). The best cycling performance and excellent high rate capabilities were observed for GNS-supported Sn-Sb rate at carbon core-shell particles, which exhibited initial capacities of 978, 850 and 668 mAh/g respectively at 0.1C, 2C and 5C (1C = 800 mA/g) with good cyclability. Besides the GNS support, the carbon skin around Sn-Sb particles is believed to be a key factor to improve electrochemical properties of Sn-Sb. (author)

Microstructural investigations on carbonate fault core rocks in active extensional fault zones from the central Apennines (Italy)

Science.gov (United States)

Cortinovis, Silvia; Balsamo, Fabrizio; Storti, Fabrizio

2017-04-01

The study of the microstructural and petrophysical evolution of cataclasites and gouges has a fundamental impact on both hydraulic and frictional properties of fault zones. In the last decades, growing attention has been payed to the characterization of carbonate fault core rocks due to the nucleation and propagation of coseismic ruptures in carbonate successions (e.g., Umbria-Marche 1997, L'Aquila 2009, Amatrice 2016 earthquakes in Central Apennines, Italy). Among several physical parameters, grain size and shape in fault core rocks are expected to control the way of sliding along the slip surfaces in active fault zones, thus influencing the propagation of coseismic ruptures during earthquakes. Nevertheless, the role of grain size and shape distribution evolution in controlling the weakening or strengthening behavior in seismogenic fault zones is still not fully understood also because a comprehensive database from natural fault cores is still missing. In this contribution, we present a preliminary study of seismogenic extensional fault zones in Central Apennines by combining detailed filed mapping with grain size and microstructural analysis of fault core rocks. Field mapping was aimed to describe the structural architecture of fault systems and the along-strike fault rock distribution and fracturing variations. In the laboratory we used a Malvern Mastersizer 3000 granulometer to obtain a precise grain size characterization of loose fault rocks combined with sieving for coarser size classes. In addition, we employed image analysis on thin sections to quantify the grain shape and size in cemented fault core rocks. The studied fault zones consist of an up to 5-10 m-thick fault core where most of slip is accommodated, surrounded by a tens-of-meters wide fractured damage zone. Fault core rocks consist of (1) loose to partially cemented breccias characterized by different grain size (from several cm up to mm) and variable grain shape (from very angular to sub

Carbon Support Surface Effects in the Gold-Catalyzed Oxidation of 5-Hydroxymethylfurfural

NARCIS (Netherlands)

Donoeva, Baira; Masoud, Nazila; De Jongh, Petra E.

2017-01-01

Oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid is an important transformation for the production of bio-based polymers. Carbon-supported gold catalysts hold great promise for this transformation. Here we demonstrate that the activity, selectivity, and stability of the

The role of Ni in sulfided carbon-supported Ni-Mo hydrodesulfurization catalysts

NARCIS (Netherlands)

Bouwens, S.M.A.M.; Barthe-Zahir, N.; Beer, de V.H.J.; Prins, R.

1991-01-01

The thiophene hydrodesulfurization activities of Ni and Ni---Mo sulfide catalysts supported on activated carbon were measured at atmospheric pressure and the catalyst structures were studied by means of X-ray photoelectron spectroscopy, dynamic oxygen chemisorption, and chemical sulfur analysis. The

Generalization of the existing relations between microstructure and yield stress from ferrite-pearlite to high strength steels

Energy Technology Data Exchange (ETDEWEB)

Iza-Mendia, A., E-mail: aiza@ceit.es [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 Donostia-San Sebastian, Basque Country (Spain); Gutierrez, I. [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 Donostia-San Sebastian, Basque Country (Spain)

2013-01-20

A series of available equations allows the yield and the tensile strength of low carbon ferrite-pearlite microstructures to be expressed as a function of the optical grain size, steel composition and interstitials in solution. Over the years, as the complexity of steel microstructures has increased, some additional terms have been added to account for precipitation and forest dislocation contributions. In theory, this opens the door for an extension of these equations to bainitic microstructures. Nevertheless, there is a series of difficulties that needs to be overcome in order to improve prediction accuracy. In the present work, different microstructures (ferrite-pearlite, bainite, quenched, and quenched and tempered) were produced and tension tested in a C-Mn-Nb steel. Optical microscopy and EBSD (Electron Back Scattered Diffraction) were applied and the results were compared as a function of the tolerance angle. Based on this work, an adaptation to Pickering's equation is proposed, including its extension to other microstructures rather than ferrite-pearlite.

Ruthenium supported on nitrogen-doped carbon nanotubes for the oxygen reduction reaction in alkaline electrolyte; Poster

CSIR Research Space (South Africa)

Mabena, LF

2012-07-01

Full Text Available . Recently, several researchers have shown that nitrogen modified carbon nanotubes (CNTs) are good electrocatalyst supports and that they enhance the electrocatalytic activity for the ORR. Nitrogen-doped carbon nanotubes (N-CNTs) prepared via thermal chemical...

Microstructure characterization and magnetic properties of nano structured materials

International Nuclear Information System (INIS)

Sun, X.C.

2000-01-01

The present thesis deals with the unique microstructural properties and their novel magnetic properties of core-shell Ni-Ce nano composite particles, carbon encapsulated Fe, Co, and Ni nanoparticles and the nano crystallization behavior of typical ferromagnetic Fe 78 Si 9 B 13 ribbons. These properties have intensively been investigated by high resolution transmission electron microscopy (HREM), X-ray diffraction (XRD), scanning electron microscopy (Sem), X-ray energy dispersive spectroscopy (Eds.); selected area electron diffraction pattern (SAED), Ft-IR, differential scanning calorimeter (DSC). In addition, magnetic moments measurements at different temperatures and applied fields have been performed by transmission Moessbauer spectroscopy, superconducting quantum interference device magnetometer (SQUID), and vibrating sample magnetometer (VSM). The present studies may provide the insights for the better understanding of the correlation between the unique microstructure and novel magnetic properties for several magnetic nano structured materials. (Author)

Synthesis of gold nano-catalysts supported on carbon nanotubes by using electroless plating technique

International Nuclear Information System (INIS)

Ma Xicheng; Li Xia; Lun Ning; Wen Shulin

2006-01-01

Gold nanoparticles supported on carbon nanotubes were prepared by using electroless plating technique. High-resolution transmission electron microscopy (HRTEM) has shown that spherical gold nanoparticles were homogeneously dispersed on the surfaces of the carbon nanotubes with a distribution of particle sizes sharply at around 3-4 nm in diameter. The results presented in this work will probably provide new catalysts with better performances

Multi-Scale Microstructure and Mechanical Properties of High Carbon Eutectic Tantalum Carbide Reinforced with Carbon Nanotubes

Science.gov (United States)

2012-07-02

found to increase with SPS temperature in other materials such as hydroxyapatite [35]. At the SPS temperature of 1850 ◦C, the grain size was found to...sample. Hardness and elasticmodulus are found to increase by 22% and 18% respectively for 100MPa samples by addition of long CNTs. Raman spectroscopy...accelerating voltage of 300kV was used to study the microstructure. To study the effect of the processing conditions on the CNT structure, micro- Raman

Psychopathic traits modulate microstructural integrity of right uncinate fasciculus in a community population.

Science.gov (United States)

Sobhani, Mona; Baker, Laura; Martins, Bradford; Tuvblad, Catherine; Aziz-Zadeh, Lisa

2015-01-01

Individuals with psychopathy possess emotional and behavioral abnormalities. Two neural regions, involved in behavioral control and emotion regulation, are often implicated: amygdala and ventromedial prefrontal cortex (VMPFC). Recently, in studies using adult criminal populations, reductions in microstructural integrity of the white matter connections (i.e., uncinate fasciculus (UF)) between these two neural regions have been discovered in criminals with psychopathy, supporting the notion of neural dysfunction in the amygdala-VMPFC circuit. Here, a young adult, community sample is used to assess whether psychopathic traits modulate microstructural integrity of UF, and whether this relationship is dependent upon levels of trait anxiety, which is sometimes used to distinguish subtypes of psychopathy. Results reveal a negative association between psychopathic traits and microstructural integrity of UF, supporting previous findings. However, no moderation of the relationship by trait anxiety was discovered. Findings provide further support for the notion of altered amygdala-VMPFC connectivity in association with higher psychopathic traits.

Psychopathic traits modulate microstructural integrity of right uncinate fasciculus in a community population

Directory of Open Access Journals (Sweden)

Mona Sobhani

2015-01-01

Full Text Available Individuals with psychopathy possess emotional and behavioral abnormalities. Two neural regions, involved in behavioral control and emotion regulation, are often implicated: amygdala and ventromedial prefrontal cortex (VMPFC. Recently, in studies using adult criminal populations, reductions in microstructural integrity of the white matter connections (i.e., uncinate fasciculus (UF between these two neural regions have been discovered in criminals with psychopathy, supporting the notion of neural dysfunction in the amygdala–VMPFC circuit. Here, a young adult, community sample is used to assess whether psychopathic traits modulate microstructural integrity of UF, and whether this relationship is dependent upon levels of trait anxiety, which is sometimes used to distinguish subtypes of psychopathy. Results reveal a negative association between psychopathic traits and microstructural integrity of UF, supporting previous findings. However, no moderation of the relationship by trait anxiety was discovered. Findings provide further support for the notion of altered amygdala–VMPFC connectivity in association with higher psychopathic traits.

Carbon nanocages: a new support material for Pt catalyst with remarkably high durability.

Science.gov (United States)

Wang, Xiao Xia; Tan, Zhe Hua; Zeng, Min; Wang, Jian Nong

2014-03-24

Low durability is the major challenge hindering the large-scale implementation of proton exchange membrane fuel cell (PEMFC) technology, and corrosion of carbon support materials of current catalysts is the main cause. Here, we describe the finding of remarkably high durability with the use of a novel support material. This material is based on hollow carbon nanocages developed with a high degree of graphitization and concurrent nitrogen doping for oxidation resistance enhancement, uniform deposition of fine Pt particles, and strong Pt-support interaction. Accelerated degradation testing shows that such designed catalyst possesses a superior electrochemical activity and long-term stability for both hydrogen oxidation and oxygen reduction relative to industry benchmarks of current catalysts. Further testing under conditions of practical fuel cell operation reveals almost no degradation over long-term cycling. Such a catalyst of high activity, particularly, high durability, opens the door for the next-generation PEMFC for "real world" application.

Characterization of amorphous and nanocrystalline carbon films

International Nuclear Information System (INIS)

Chu, Paul K.; Li Liuhe

2006-01-01

Amorphous and nanocrystalline carbon films possess special chemical and physical properties such as high chemical inertness, diamond-like properties, and favorable tribological proprieties. The materials usually consist of graphite and diamond microstructures and thus possess properties that lie between the two. Amorphous and nanocrystalline carbon films can exist in different kinds of matrices and are usually doped with a large amount of hydrogen. Thus, carbon films can be classified as polymer-like, diamond-like, or graphite-like based on the main binding framework. In order to characterize the structure, either direct bonding characterization methods or the indirect bonding characterization methods are employed. Examples of techniques utilized to identify the chemical bonds and microstructure of amorphous and nanocrystalline carbon films include optical characterization methods such as Raman spectroscopy, Ultra-violet (UV) Raman spectroscopy, and infrared spectroscopy, electron spectroscopic and microscopic methods such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, transmission electron microscopy, and electron energy loss spectroscopy, surface morphology characterization techniques such as scanning probe microscopy (SPM) as well as other characterization methods such as X-ray reflectivity and nuclear magnetic resonance. In this review, the structures of various types of amorphous carbon films and common characterization techniques are described

Microstructure and grain size effects on irradiation hardening of low carbon steel for reactor tanks

Energy Technology Data Exchange (ETDEWEB)

Milasin, N [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

1964-05-15

Irradiation hardening of steel for reactor pressure vessels has been studied extensively during the past few years. A great number of experimental results concerning the behaviour of these steels in the radiation field and several review papers (1,2) have been published. Most of the papers deal with the effects of specific metallurgical factors or irradiation conditions (temperature, flux) on irradiation hardening and embrittlement. In addition, a number of experiments are performed to give evidence on the mechanism of irradiation hardening of these steels. However, this mechanism is still unknown due to the complexity of steel as a system. Among different methods used in radiation damage studies, the changes of mechanical properties have been mainly investigated. By using Hall-Petch's empirical relation, {sigma}{sub y}={sigma}{sub i}+k{sub y} d{sup -1/2} between lower yield stress, {sigma}{sub y}, and grain size, 2d, the information about the effect of irradiation on the parameters {sigma}{sub i} and k{sub y} is obtained. Taking as a base interpretation of {sigma}{sub i} and k{sub y} given by Petch and his co-workers it has been concluded that radiation does not change the stress to start slip but that it increase the friction that opposes the passage of free dislocations across a slip plane. In attempting to apply Hall-Petch's relation to one unirradiated ferritic steel with a carbon content higher than 0.15% some difficulties were encountered. The results obtained indicate that the influence of grain size can not be isolated from other factors introduced by the treatments used to produce different grain sizes. This paper deals with a similar problem in the case of irradiated steel. The results obtained give the changes of the mechanical properties of steel in neutron irradiation field as a function of microstructure and grain size. In addition, the mechanical properties of irradiated steel are measured after annealing at 150 deg C and 450 deg C. On the basis of

Visualization of Wave Propagation and Fine Structure in Frictional Motion of Unconstrained Soft Microstructured Tapes

DEFF Research Database (Denmark)

Heepe, Lars; Filippov, Alexander E.; Kovalev, Alexander E.

2017-01-01

from previous friction tests of microstructured elastomers fixed onto a rigid support, allowing only for shear deformations of surface microstructures and the backing layer, but not for stretching of the entire sample. Three different types of microstructured tapes were tested and their frictional...... behavior compared to results from numerical simulations. In both experimental and numerical cases, visualization of wave propagation and fine structure in friction is obtained....

Nanostructured carbon-supported Pd electrocatalysts for ethanol oxidation: synthesis and characterization

International Nuclear Information System (INIS)

Gacutan, E M; Tongol, B J; Climaco, M I; Telan, G J; Malijan, F; Hsu, H Y; Garcia, J; Fulo, H

2012-01-01

The need to lower the construction cost of fuel cells calls for the development of non-Pt based electrocatalysts. Among others, Pd has emerged as a promising alternative to Pt for fuel cell catalysis. This research aims to investigate the synthesis and characterization of nanostructured Pd-based catalysts dispersed on carbon support as anode materials in direct ethanol fuel cells. For the preparation of the first Pd-based electrocatalyst, palladium nanoparticles (NPs) were synthesized via oleylamine (OAm)-mediated synthesis and precursor method with a mean particle size of 3.63 ± 0.59 nm as revealed by transmission electron microscopy (TEM). Carbon black was used as a supporting matrix for the OAm-capped Pd NPs. Thermal annealing and acetic acid washing were used to remove the OAm capping agent. To evaluate the electrocatalytic activity of the prepared electrocatalyst towards ethanol oxidation, cyclic voltammetry (CV) studies were performed using 1.0 M ethanol in basic medium. The CV data revealed the highest peak current density of 11.05 mA cm −2 for the acetic acid-washed Pd/C electrocatalyst. Meanwhile, the fabrication of the second Pd-based electrocatalyst was done by functionalization of the carbon black support using 3:1 (v/v) H 2 SO 4 :HNO 3 . The metal oxide, NiO, was deposited using precipitation method while polyol method was used for the deposition of Pd NPs. X-ray diffraction (XRD) analysis revealed that the estimated particle size of the synthesized catalysts was at around 9.0–15.0 nm. CV results demonstrated a 36.7% increase in the catalytic activity of Pd–NiO/C (functionalized) catalyst towards ethanol oxidation compared to the non-functionalized catalyst. (paper)

Laser absorption of carbon fiber reinforced polymer with randomly distributed carbon fibers

Science.gov (United States)

Hu, Jun; Xu, Hebing; Li, Chao

2018-03-01

Laser processing of carbon fiber reinforced polymer (CFRP) is a non-traditional machining method which has many prospective applications. The laser absorption characteristics of CFRP are analyzed in this paper. A ray tracing model describing the interaction of the laser spot with CFRP is established. The material model contains randomly distributed carbon fibers which are generated using an improved carbon fiber placement method. It was found that CFRP has good laser absorption due to multiple reflections of the light rays in the material’s microstructure. The randomly distributed carbon fibers make the absorptivity of the light rays change randomly in the laser spot. Meanwhile, the average absorptivity fluctuation is obvious during movement of the laser. The experimental measurements agree well with the values predicted by the ray tracing model.

Microstructure of a safe-end dissimilar metal weld joint (SA508-52-316L) prepared by narrow-gap GTAW

Energy Technology Data Exchange (ETDEWEB)

Ming, Hongliang [Key Laboratory of Nuclear Materials and Safety Assessment, Liaoning Key Laboratory for Safety and Assessment Technique of Nuclear Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049 (China); Zhang, Zhiming [Key Laboratory of Nuclear Materials and Safety Assessment, Liaoning Key Laboratory for Safety and Assessment Technique of Nuclear Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Wang, Jianqiu, E-mail: wangjianqiu@imr.ac.cn [Key Laboratory of Nuclear Materials and Safety Assessment, Liaoning Key Laboratory for Safety and Assessment Technique of Nuclear Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Han, En-Hou [Key Laboratory of Nuclear Materials and Safety Assessment, Liaoning Key Laboratory for Safety and Assessment Technique of Nuclear Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Wang, Peipei; Sun, Zhiyuan [Shanghai Research Center for Weld and Detection Engineering Technique of Nuclear Equipment, Shanghai 201306 (China)

2017-01-15

The microstructure, residual strain and interfacial chemical composition distribution of a safe-end dissimilar metal weld joint (DMWJ, SA508-52-316L) prepared by narrow-gap gas-tungsten arc welding (NG-GTAW) were studied by optical microscope (OM) and scanning electron microscope equipped with an energy dispersive X-ray microanalysis (SEM/EDX) and an electron back scattering diffraction (EBSD) system. Complex microstructure and chemical composition distribution are found, especially at the SA508-52 interface and the 52-316L interface. In brief, a complicated microstructure transition exists within the SA508 heat affected zone (HAZ); the residual strain, the fraction of high angle random grain boundaries and low angle boundaries decrease with increasing the distance from the fusion boundary in 316L HAZ; neither typical type II boundary nor obvious carbon-depleted zone is found near the SA508-52 interface; dramatic and complicated changes of the contents of the main elements, Fe, Cr and Ni, are observed at the distinct interfaces, especially at the SA508-52 interface. No carbon concentration is found at the SA508-52 interface. - Highlights: •Residual strain and GBCD change as a function of the distance from FB in 316L HAZ. •Neither type II boundary nor obvious carbon-depleted zone is found in SA508 HAZ. •No carbon concentration is found at the SA508-52 interface. •The middle part of the DMWJ has the highest residual strain.

Effect of Spheroidizing Annealing on Microstructure and Mechanical Properties of High-Carbon Martensitic Stainless Steel 8Cr13MoV

Science.gov (United States)

Yu, Wen-Tao; Li, Jing; Shi, Cheng-Bin; Zhu, Qin-Tian

2017-02-01

The effects of holding time during both austenitizing and spheroidizing on microstructure and mechanical properties of high-carbon martensitic stainless steel 8Cr13MoV were experimentally studied. The results showed that the amount of carbides and the proportion of fine carbides decrease first and then increase with the increase in austenitizing time ( t 1) in the case of short spheroidizing time ( t 2), whereas the amount of the lamellar carbides increases. In the case of long t 2, both the amount of carbides and the proportion of fine carbides decrease, and the amount of the lamellar carbides did not increase. The hardness of the steel decreases first and then increases with the increase of t 1. Under the conditions of different t 1, the change in the size of carbides and hardness of the steel show a same trend with the variation of t 2. The size of spheroidized carbides increases, whereas the hardness of the steel decreases with increasing t 2. The longer the holding time of austenitizing, the higher is the spheroidizing rate at the earlier stage. However, the spheroidizing rate shows an opposite trend with t 1 at the later stage of spheroidizing. The effect of cooling rate on microstructure is similar with t 2. With increasing cooling rate, the dimension of carbides became smaller, and the amount of lamellar carbides increased. The elongation of the sample fracture exhibits no corresponding relationship with holding time, whereas it is closely related to the precipitation of secondary carbides caused by the alloying elements segregation.

Preparation and physical properties of vapour-deposited carbon-carbon composites

International Nuclear Information System (INIS)

Loll, Philippe

1976-01-01

In its first part, this research thesis reports a bibliographical study on methods of preparation of various types of vapour-deposited (CVD) carbons, and the author notices that only structure and texture properties of these macroscopically homogeneous pyro-carbons have been studied in detail. For a better understanding of the behaviour of carbon-carbon composites, this thesis thus reports the study of the relationships between physical properties, macroscopic texture and microscopic structure. A densification installation and methods of characterisation have been developed. The fabrication process and its installation are presented (oven with its temperature and gas rate controls, study of its thermal gradient, substrate, heat treatments), and the study and characterisation of carbon-carbon composites are reported: structure and texture properties (studied by optic and scanning electronic microscopy, density measurements, and X-ray diffraction), physical properties (electronic paramagnetic resonance, static magnetism, electric and thermal conductivity). In the last part, the author comments and discusses the obtained results: conditions of preparation, existence, physical properties of the different observed microstructures [fr

Microstructured reactor for electroorganic synthesis

Energy Technology Data Exchange (ETDEWEB)

Bouzek, Karel, E-mail: bouzekk@vscht.c [Department of Inorganic Technology, Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6 (Czech Republic); Jiricny, Vladimir [Institute of Chemical Process Fundamentals, v.v.i., Academy of Sciences of the Czech Republic, Rozvojova 2, 165 02 Prague 6 (Czech Republic); Kodym, Roman [Department of Inorganic Technology, Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6 (Czech Republic); Kristal, Jiri [Institute of Chemical Process Fundamentals, v.v.i., Academy of Sciences of the Czech Republic, Rozvojova 2, 165 02 Prague 6 (Czech Republic); Bystron, Tomas [Department of Inorganic Technology, Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6 (Czech Republic)

2010-11-30

In the present work a brief overview of microstructured devices, the advantages and disadvantages as well as the principles of a multiscale design approach are presented. The advantages mainly comprise uniform current density distribution, local control of the process parameters, high single-pass conversion of the reactant and reduced concentration of the supporting electrolyte needed to perform the reaction. The main challenge with this type of cell is gas evolution, a typical reaction taking place at the counter-electrode. The phenomena discussed are documented using the example of anodic methoxylation of 4-methylanisole. An analysis was made of the two-phase flow hydrodynamics inside the microstructured cell. The range of operational conditions suitable for the desired reaction was identified. The results were used together with the information on the electrode reaction kinetics in the form of the Butler-Volmer-type equation for the design of a suitable bipolar microstructured cell. A bipolar cell optimized to perform the desired reaction is reported. The results are compared with the published data. An analysis was performed that proved that the performance of the existing technology is more demanding in terms of energy consumption for the separation of the final product from the reaction mixture. The process intensification was evaluated on the basis of the available data.

Carbon Nanofiber Supported Transition-Metal Carbide Catalysts for the Hydrodeoxygenation of Guaiacol

NARCIS (Netherlands)

Jongerius, A.; Gosselink, R.W.; Dijkstra, J.; Bitter, J.H.; Bruijnincx, P.C.A.; Weckhuysen, B.M.

2013-01-01

Hydrodeoxygenation (HDO) studies over carbon nanofiber-supported (CNF) W2C and Mo2C catalysts were performed on guaiacol, a prototypical substrate to evaluate the potential of a catalyst for valorization of depolymerized lignin streams. Typical reactions were executed at 55 bar hydrogen pressure

N, P-codoped Mesoporous Carbon Supported PtCox Nanoparticles and Their Superior Electrochemical toward Methanol Oxidation

Science.gov (United States)

Cui, Hangjun; Li, Yueming; Liu, Shimin

2018-03-01

In this report, a novel strategy by using the N, P co-doped mesoporous carbon structure as catalyst support to enhance the electrochemical catalytic activity of Pt-based catalysts is proposed. The as-synthesized PtCox@N, P-doped mesoporous carbon nanocomposties have been studied as an anode catalyst toward methanol oxidation, exhibiting greatly improved electrochemical activity and stability compared with Pt@mesoporous carbon. The synergistic effects of N, P dual-doping and porous carbon structure help to achieve better electron transport at the electrode surface, which eventually leads to greatly enhanced catalytic activity compared to the pristine Pt/mesoporous carbon.…

Copolymerization of carbon monoxide and styrene catalyzed by resin-supported palladium polymer

Directory of Open Access Journals (Sweden)

2007-02-01

Full Text Available Polyketone was prepared by the copolymerization of carbon monoxide (CO and styrene (ST catalyzed by o-phenylenediamine resin-supported palladium acetate. Effects of each catalytic system component such as 2,2’-bipyridine, 1,4-quinone and p-toluene-sulphonate on the copolymerization were investigated. The resin-supported catalyst and the copolymerization product were characterized by infrared spectroscopy (IR, differential scanning calorimetry (DSC, thermogravimetry (TG, X-ray photoelectron spectroscopy (XPS, Scanning Electron Microscopy (SEM. Results indicated that the resin-supported catalyst has excellent catalytic property. Furthermore, partial catalytic activity was maintained after the catalyst was used for five times.

An investigation into carbon nanostructured materials as catalyst support in proton exchange membrane fuel cells

DEFF Research Database (Denmark)

Veltzé, Sune

acid treatment on the Vapour Grown Carbon Fibers™ manufactured by Showa Denko K. K. From these fibres, twelve platinised samples were investigated, of which one was platinised by a platinum phtalocyanine impregnation method, two were platinised by the polyol method and the remaining by the Bönnemann......Polymer electrolyte fuel cells (PEFCs) are among the key research areas concerning clean cost-effective energy. Carbon nano fibres (CNF), single walled carbon nano tubes (SWCNT), multi walled carbon nano tubes (MWCNT) and other related materials are among the possible successors to standard carbon...... black support materials for low platinum containing electrocatalyst. This is partly due to their high electronic conductivity. Partly due to their high surface area needed for the dispersion of nanoparticulate metal-clusters. In addition carbon nano-structures (CNF, SWCNT, MWCNT etc.) are more durable...

Understanding the microstructure of coal during carbonization using rheometry and {sup 1}H NMR

Energy Technology Data Exchange (ETDEWEB)

Karen M. Steel; Miguel C. Diaz; John W. Patrick; Colin E. Snape [University of Nottingham, Nottingham (United Kingdom). Nottingham Fuel and Energy Centre, School of Chemical, Environmental and Mining Engineering

2005-07-01

High-temperature rheometry and {sup 1}H NMR have been combined to assess the microstructural changes taking place during carbonization of four coals with varying volatile matter contents. A linear relationship exists between the logarithm of the material's complex viscosity and the fraction of hydrogen present in rigid structures for the resolidification region in which the material is liquid-like with small amounts of dispersed solid. The Krieger-Dougherty suspension equation fits the data, however, the fit parameters are not realistic. This is thought to be due to the fact that the solid which forms does not entirely behave like a suspension, as the solid regions join together rather than pack together. The relationship is best characterized by the Arrhenius viscosity equation and bears similarity with thermosetting polymer networks. Results suggest that resolidification occurs through progressive crosslinking and cyclization reactions within the liquid medium, giving rise to a network structure leading to a gel point. Horizontal positioning of the curves depends on the relative proportions of solid material arising from unsoftened coal and from resolidified structures. Correcting the curves to neglect the contribution from unsoftened coal indicates that while the unsoftened material has a fairly equant shape, the resolidified material has a much higher hydrodynamic volume. The gel point occurs when the ratio of hydrogen present in resolidified structures to that still present in liquid form is 2:3. 27 refs., 8 figs., 4 tabs.

Surface tailored single walled carbon nanotubes as catalyst support for direct methanol fuel cell

Science.gov (United States)

Kireeti, Kota V. M. K.; Jha, Neetu

2017-10-01

A strategy for tuning the surface property of Single Walled Carbon Nanotubes (SWNTs) for enhanced methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) along with methanol tolerance is presented. The surface functionality is tailored using controlled acid and base treatment. Acid treatment leads to the attachment of carboxylic carbon (CC) fragments to SWNT making it hydrophilic (P3-SWNT). Base treatment of P3-SWNT with 0.05 M NaOH reduces the CCs and makes it hydrophobic (P33-SWNT). Pt catalyst supported on the P3-SWNT possesses enhanced MOR whereas that supported on P33-SWNT not only enhances ORR kinetics but also possess good tolerance towards methanol oxidation as verified by the electrochemical technique.

Graphitized Carbon: A Promising Stable Cathode Catalyst Support Material for Long Term PEMFC Applications.

Science.gov (United States)

Mohanta, Paritosh Kumar; Regnet, Fabian; Jörissen, Ludwig

2018-05-28

Stability of cathode catalyst support material is one of the big challenges of polymer electrolyte membrane fuel cells (PEMFC) for long term applications. Traditional carbon black (CB) supports are not stable enough to prevent oxidation to CO₂ under fuel cell operating conditions. The feasibility of a graphitized carbon (GC) as a cathode catalyst support for low temperature PEMFC is investigated herein. GC and CB supported Pt electrocatalysts were prepared via an already developed polyol process. The physical characterization of the prepared catalysts was performed using transmission electron microscope (TEM), X-ray Powder Diffraction (XRD) and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis, and their electrochemical characterizations were conducted via cyclic voltammetry(CV), rotating disk electrode (RDE) and potential cycling, and eventually, the catalysts were processed using membrane electrode assemblies (MEA) for single cell performance tests. Electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SEM) have been used as MEA diagonostic tools. GC showed superior stability over CB in acid electrolyte under potential conditions. Single cell MEA performance of the GC-supported catalyst is comparable with the CB-supported catalyst. A correlation of MEA performance of the supported catalysts of different Brunauer⁻Emmett⁻Teller (BET) surface areas with the ionomer content was also established. GC was identified as a promising candidate for catalyst support in terms of both of the stability and the performance of fuel cell.

Film of lignocellulosic carbon material for self-supporting electrodes in electric double-layer capacitors

Directory of Open Access Journals (Sweden)

Tsubasa Funabashi

2013-09-01

Full Text Available A novel thin, wood-based carbon material with heterogeneous pores, film of lignocellulosic carbon material (FLCM, was successfully fabricated by carbonizing softwood samples of Picea jezoensis (Jezo spruce. Simultaneous increase in the specific surface area of FLCM and its affinity for electrolyte solvents in an electric double-layer capacitor (EDLC were achieved by the vacuum ultraviolet/ozone (VUV/O3 treatment. This treatment increased the specific surface area of FLCM by 50% over that of original FLCM. The results obtained in this study confirmed that FLCM is an appropriate self-supporting EDLC electrode material without any warps and cracks.

Electrochemical behavior of platinum nanoparticles on a carbon xerogel support modified with a [(trifluoromethyl)-benzenesulfonyl]imide electrolyte.

Science.gov (United States)

Liu, Bing; Mei, Hua; DesMarteau, Darryl; Creager, Stephen E

2014-12-11

A monoprotic [(trifluoromethyl)benzenesulfonyl]imide (SI) superacid electrolyte was used to covalently modify a mesoporous carbon xerogel (CX) support via reaction of the corresponding trifluoromethyl aryl sulfonimide diazonium zwitterion with the carbon surface. Electrolyte attachment was demonstrated by elemental analysis, acid-base titration, and thermogravimetric analysis. The ion-exchange capacity of the fluoroalkyl-aryl-sulfonimide-grafted carbon xerogel (SI-CX) was ∼0.18 mequiv g(-1), as indicated by acid-base titration. Platinum nanoparticles were deposited onto the SI-grafted carbon xerogel samples by the impregnation and reduction method, and these materials were employed to fabricate polyelectrolyte membrane fuel-cell (PEMFC) electrodes by the decal transfer method. The SI-grafted carbon-xerogel-supported platinum (Pt/SI-CX) was characterized by X-ray diffraction and transmission electron microscopy to determine platinum nanoparticle size and distribution, and the findings are compared with CX-supported platinum catalyst without the grafted SI electrolyte (Pt/CX). Platinum nanoparticle sizes are consistently larger on Pt/SI-CX than on Pt/CX. The electrochemically active surface area (ESA) of platinum catalyst on the Pt/SI-CX and Pt/CX samples was measured with ex situ cyclic voltammetry (CV) using both hydrogen adsorption/desorption and carbon monoxide stripping methods and by in situ CV within membrane electrode assemblies (MEAs). The ESA values for Pt/SI-CX are consistently lower than those for Pt/CX. Some possible reasons for the behavior of samples with and without grafted SI layers and implications for the possible use of SI-grafted carbon layers in PEMFC devices are discussed.

Microstructure characterization and magnetic properties of nano structured materials

Energy Technology Data Exchange (ETDEWEB)

Sun, X.C

2000-07-01

The present thesis deals with the unique microstructural properties and their novel magnetic properties of core-shell Ni-Ce nano composite particles, carbon encapsulated Fe, Co, and Ni nanoparticles and the nano crystallization behavior of typical ferromagnetic Fe{sub 78}Si{sub 9}B{sub 13} ribbons. These properties have intensively been investigated by high resolution transmission electron microscopy (HREM), X-ray diffraction (XRD), scanning electron microscopy (Sem), X-ray energy dispersive spectroscopy [eds.]; selected area electron diffraction pattern (SAED), Ft-IR, differential scanning calorimeter (DSC). In addition, magnetic moments measurements at different temperatures and applied fields have been performed by transmission Moessbauer spectroscopy, superconducting quantum interference device magnetometer (SQUID), and vibrating sample magnetometer (VSM). The present studies may provide the insights for the better understanding of the correlation between the unique microstructure and novel magnetic properties for several magnetic nano structured materials. (Author)

Conversion of biomass-derived sorbitol to glycols over carbon-materials supported Ru-based catalysts

Science.gov (United States)

Guo, Xingcui; Guan, Jing; Li, Bin; Wang, Xicheng; Mu, Xindong; Liu, Huizhou

2015-11-01

Ruthenium (Ru) supported on activated carbon (AC) and carbon nanotubes (CNTs) was carried out in the hydrogenolysis of sorbitol to ethylene glycol (EG) and 1,2-propanediol (1,2-PD) under the promotion of tungsten (WOx) species and different bases. Their catalytic activities and glycols selectivities strongly depended on the support properties and location of Ru on CNTs, owning to the altered metal-support interactions and electronic state of ruthenium. Ru located outside of the tubes showed excellent catalytic performance than those encapsulated inside the nanotubes. Additionally, the introduction of WOx into Ru/CNTs significantly improved the hydrogenolysis activities, and a complete conversion of sorbitol with up to 60.2% 1,2-PD and EG yields was obtained on RuWOx/CNTs catalyst upon addition of Ca(OH)2. Stability study showed that this catalyst was highly stable against leaching and poisoning and could be recycled several times.

Microstructure evolution and microstructure/mechanical properties relationships in alpha+beta titanium alloys

Science.gov (United States)

Lee, Eunha

In this study, the microstructural evolution of Timetal 550 was investigated. Timetal 550 showed two types of phase transformations (martensitic and nucleation and growth) depending on the cooling rate from the beta region. The alpha phase initially precipitated at the prior beta grain boundaries, and it had a Burgers OR with one of the adjacent grains. It was found that colonies could grow, even in the fast-cooled Timetal 550 sample, from the grain boundary alpha into the prior beta grain with which it exhibited the Burgers OR. Three orientation relationships were also found between alpha laths in the basketweave microstructure. Microhardness testing demonstrated that fast-cooled Timetal 550 samples with basketweave microstructure were harder than slowly-cooled samples with colony microstructure. Orientation-dependent deformation was found in the colony microstructure. Specifically, when the surface normal is perpendicular to the [0001] of alpha, the material deforms easily in the direction perpendicular to the [0001] of alpha. Fuzzy logic and Bayesian neural network models were developed to predict the room temperature tensile properties of Timetal 550. This involved the development of a database relating microstructural features to mechanical properties. A Gleeble 3800 thermal-mechanical simulator was used to develop various microstructures. Microstructural features of tensile-tested samples were quantified using stereological procedures. The quantified microstructural features and the tensile properties were used as inputs and outputs, respectively, for modeling the relationships between them. The individual influence of five microstructural features on tensile properties was determined using the established models. The microstructural features having the greatest impact on UTS and YS were the thickness of alpha laths and the width of grain boundary alpha layer, and the microstructural features having the greatest impact on elongation were the thickness of

Microstructure investigations of Ba-Sr mixed ferrites, using SEM technique

International Nuclear Information System (INIS)

Amighian, J.; Mozaffari, M.

1996-01-01

A series of isotropic Ba-Sr mixed ferrites were prepared, using a conventional dry technique. The starting materials were hematite by product of Isfahan steel factory, strontium carbonate from Merck company and barium carbonate obtained from local source. The principle phase of the samples was chosen to have a composition in the form of (BaO) sub 1-x (SrO) sub x nFe sub 2 O sub 3, in which x varied between 0 to l and n was varied between 5 to 6. The raw materials were thoroughly mixed and fired in an electrical furnace for 2 hours. They were then milled in an vibrating ball mill, in which the optimum milling time for each sample was obtained. After annealing at 750 degree C, the powders were compacted in a cylindrical die under 5 tons/cm sup 2. The compacts were then mixed with a binder and sintered in air for 10 minutes at their optimum temperatures. Using SEM technique, the microstructure of the samples were investigated. Using a permeameter, the coercive force Hc and remanent induction Br were measured. The microstructures obtained from SEM technique can be used to control the sintering stage in ferrite fabrication

A carbon in molten carbonate anode model for a direct carbon fuel cell

Energy Technology Data Exchange (ETDEWEB)

Li Hongjiao; Liu Qinghua [Tianjin Key Laboratory of Catalysis Science and Technology, School of Chemical Engineering, Tianjin University, Weijing Road 92, Tianjin 300072 (China); State Key Laboratory for Chemical Engineering (Tianjin University), School of Chemical Engineering, Tianjin University, Weijing Road 92, Tianjin 300072 (China); Li Yongdan, E-mail: ydli@tju.edu.c [Tianjin Key Laboratory of Catalysis Science and Technology, School of Chemical Engineering, Tianjin University, Weijing Road 92, Tianjin 300072 (China); State Key Laboratory for Chemical Engineering (Tianjin University), School of Chemical Engineering, Tianjin University, Weijing Road 92, Tianjin 300072 (China)

2010-02-15

The electrochemical oxidation of carbon at the anode of a direct carbon fuel cell (DCFC) includes charge transfer steps and chemical steps. A microstructural model of carbon particle is built, in which perfect graphene stacks are taken as the basic building blocks of carbon. A modified mechanism taking account of the irreversibility of the process and supposing that the electrochemical oxidation of carbon takes place only at the edges of the graphene sheets is proposed. A Tafel type overall rate equation is deduced along with expressions of exchange current density (j{sub 0}) and activation polarization (eta{sub act}). The performance of carbon black and graphite as the fuel of DCFC is examined. It has been found that j{sub 0} is in the range of 0.10-6.12 mA cm{sup -2} at 923-1123 K and eta{sub act} is in the range of 0.024-0.28 V at 923-1123 K with current density in 10-120 mA cm{sup -2}. Analysis of the j{sub 0}, eta{sub act} values and the product composition reveals that the charge transfer steps as well as the oxygen ion absorption steps are both important for the reaction rate. The activity of the carbon material with respect to atom location is introduced to the open circuit potential difference (OCP) calculation with Nernst equation.

Manganese Dioxide Supported on Porous Biomorphic Carbons as Hybrid Materials for Energy Storage Devices.

Science.gov (United States)

Gutierrez-Pardo, Antonio; Lacroix, Bertrand; Martinez-Fernandez, Julian; Ramirez-Rico, Joaquin

2016-11-16

A facile and low-cost method has been employed to fabricate MnO 2 /C hybrid materials for use as binder-free electrodes for supercapacitor applications. Biocarbon monoliths were obtained through pyrolysis of beech wood, replicating the microstructure of the cellulosic precursor, and serve as 3D porous and conductive scaffolds for the direct growth of MnO 2 nanosheets by a solution method. Evaluation of the experimental results indicates that a homogeneous and uniform composite material made of a carbon matrix exhibiting ordered hierarchical porosity and MnO 2 nanosheets with a layered nanocrystalline structure is obtained. The tuning of the MnO 2 content and crystallite size via the concentration of KMnO 4 used as impregnation solution allows to obtain composites that exhibit enhanced electrochemical behavior, achieving a capacitance of 592 F g -1 in electrodes containing 3 wt % MnO 2 with an excellent cyclic stability. The electrode materials were characterized before and after electrochemical testing.

Cooling rate and microstructure of surface layers of 5KhNM steel, machined by electroerosion method

International Nuclear Information System (INIS)

Foteev, N.K.; Ploshkin, V.V.; Lyakishev, V.A.; Shirokov, S.V.

1982-01-01

The cooling rate and microstructure of surface layers of steel 5KhNM machined by electroerosion method have been studied. It is shown that the difference in heating rate of the surface layers with electric discharge over the 5KhNM steel samples depth results in the intensive size reduction of the microstructure. In the surface layer alongside with martensite residual austenite is present, the lattice period of which increases with the increase of pulse duration, carbide phase of complex composition appears, and concentrational heterogeneity in alloying elements (except carbon) is absent

Cooling rate and microstructure of surface layers of 5KhNM steel, machined by electroerosion method

Energy Technology Data Exchange (ETDEWEB)

Foteev, N.K.; Ploshkin, V.V.; Lyakishev, V.A.; Shirokov, S.V.

1982-01-01

The cooling rate and microstructure of surface layers of steel 5KhNM machined by electroerosion method have been studied. It is shown that the difference in heating rate of the surface layers with electric discharge over the 5KhNM steel samples depth results in the intensive size reduction of the microstructure. In the surface layer alongside with martensite residual austenite is present, the lattice period of which increases with the increase of pulse duration, carbide phase of complex composition appears, and concentrational heterogeneity in alloying elements (except carbon) is absent.

Graphene-Like 2D Porous Carbon Nanosheets Derived from Cornstalk Pith for Energy Storage Materials

Science.gov (United States)

Gao, Kezheng; Niu, Qingyuan; Tang, Qiheng; Guo, Yaqing; Wang, Lizhen

2018-01-01

Biomass materials from different organisms or different parts (even different periods) of the same organism have different microscopic morphologies, hierarchical pore structures and even elemental compositions. Therefore, carbon materials inheriting the unique hierarchical microstructure of different biomass materials may exhibit significantly different electrochemical properties. Cornstalk pith and cornstalk skin (dried by freeze-drying) exhibit significantly different microstructures due to their different biological functions. The cornstalk skin-based carbon (S-carbon) exhibits a thick planar morphology, and the Barrett-Emmett-Teller (BET) surface area is only about 332.07 m2 g-1. However, cornstalk pith-based carbon (P-carbon) exhibits a graphene-like 2D porous nanosheet structure with a rough, wrinkled morphology, and the BET surface area is about 805.17 m2 g-1. In addition, a P-carbon supercapacitor exhibits much higher specific capacitance and much better rate capability than an S-carbon supercapacitor in 6 M potassium hydroxide (KOH) electrolyte.

Influence of the sintering temperature in the microstructure of foam glass obtained from waste glass

International Nuclear Information System (INIS)

Pokorny, A.; Vicenzi, J.; Bergmann, C.P.

2012-01-01

In this work, foam glasses were produced from grounded soda-lime glass and a synthetic carbonate, used as a foaming agent, with a similar composition to a dolomite lime, added with different oxides (SiO 2 , Al 2 O 3 , Fe 2 O 3 , MnO 2 , Na 2 O, K 2 O, TiO 2 and P 2 O 5 ). The objective was to evaluate the influence of sintering temperature on the properties and microstructure of the obtained material. In addition, the effect of addition of the oxides in the expansion of the ceramic bodies was evaluated. The ceramic bodies were formulated with 3 weight percent of synthetic carbonate, uniaxially pressed and fired within the temperature range from 700 deg C to 950 deg C, with a heating rate of 150K/h. The technological characterization of the ceramic bodies involved the determination of the volumetric expansion and their microstructures have been characterized by optical microscopy and scanning electron microscopy. The experimental results have shown foam glass can be obtained from grounded soda-lime glass, using synthetic carbonate, with the introduction of the different oxides, as foaming agent. (author)

Artificial Microstructures to Investigate Microstructure-Property Relationships in Metallic Glasses

Science.gov (United States)

Sarac, Baran

Technology has evolved rapidly within the last decade, and the demand for higher performance materials has risen exponentially. To meet this demand, novel materials with advanced microstructures have been developed and are currently in use. However, the already complex microstructure of technological relevant materials imposes a limit for currently used development strategies for materials with optimized properties. For this reason, a strategy to correlate microstructure features with properties is still lacking. Computer simulations are challenged due to the computing size required to analyze multi-scale characteristics of complex materials, which is orders of magnitude higher than today's state of the art. To address these challenges, we introduced a novel strategy to investigate microstructure-property relationships. We call this strategy "artificial microstructure approach", which allows us to individually and independently control microstructural features. By this approach, we defined a new way of analyzing complex microstructures, where microstructural second phase features were precisely varied over a wide range. The artificial microstructures were fabricated by the combination of lithography and thermoplastic forming (TPF), and subsequently characterized under different loading conditions. Because of the suitability and interesting properties of metallic glasses, we proposed to use this toolbox to investigate the different deformation modes in cellular structures and toughening mechanism in metallic glass (MG) composites. This study helped us understand how to combine the unique properties of metallic glasses such as high strength, elasticity, and thermoplastic processing ability with plasticity generated from heterostructures of metallic glasses. It has been widely accepted that metallic glass composites are very complex, and a broad range of contributions have been suggested to explain the toughening mechanism. This includes the shear modulus, morphology

Microstructural investigations of zirconium oxide—on core–shell structure of carbon nanotubes

International Nuclear Information System (INIS)

Pal, Kaushik; Kang, Dong Jin; Kim, Jin Kuk

2011-01-01

Single-walled carbon nanotubes and multi-walled carbon nanotubes/ZrO 2 nanocomposites were obtained by isothermal hydrolyzing and chemical precipitation method for both the carbon nanotubes. The coating was taken place by dispersion of both the carbon nanotubes in ZrOCl 2 ·8H 2 O aqueous solution. However, a highly conformal and uniform monoclinic zirconia coating was deposited on multi-walled carbon nanotubes rather than single-walled carbon nanotubes by this new and simple method. Also, it has been observed that the thickness of the individual carbon nanotube after zirconia coating was increased by isothermal hydrolyzing process rather than traditional chemical precipitation method and it has been confirmed by high-resolution transmission electron microscopy study.

Dehydrogenation of Ethylbenzene with Carbon Dioxide as Soft Oxidant over Supported Vanadium-Antimony Oxide Catalyst

Energy Technology Data Exchange (ETDEWEB)

Hong, Do Young; Vislovskiy, Vladislav P.; Yoo, Jin S.; Chang, Jong San [Korea Research Institute of Chemical Technology, Daejeon (Korea, Republic of); Park, Sang Eon [Inha University, Incheon (Korea, Republic of); Park, Min Seok [Mongolia International University, Ulaanbaatar (Mongolia)

2005-11-15

This work presents that carbon dioxide, which is a main contributor to the global warming effect, could be utilized as a selective oxidant in the oxidative dehydrogenation of ethylbenzene. The dehydrogenation of ethylbenzene over alumina-supported vanadium-antimony oxide catalyst has been studied under different atmospheres such as inert nitrogen, steam, oxygen or carbon dioxide as diluent or oxidant. Among them, the addition of carbon dioxide gave the highest styrene yield (up to 82%) and styrene selectivity (up to 97%) along with stable activity. Carbon dioxide could play a beneficial role of a selective oxidant in the improvement of the catalytic behavior through the oxidative pathway.

Elaboration of a microstructured inkjet-printed carbon electrochemical capacitor

Energy Technology Data Exchange (ETDEWEB)

Pech, David; Brunet, Magali; Fabre, Norbert; Mesnilgrente, Fabien; Conedera, Veronique; Durou, Hugo [LAAS-CNRS, Universite de Toulouse, 7 av. du Colonel Roche, F-31077 Toulouse (France); Taberna, Pierre-Louis; Simon, Patrice [CIRIMAT-CNRS, Universite de Toulouse, 118 route de Narbonne, F-31062 Toulouse (France)

2010-02-15

Carbon-based micro-supercapacitors dedicated to energy storage in self-powered modules were fabricated with inkjet printing technology on silicon substrate. An ink was first prepared by mixing an activated carbon powder with a PTFE polymer binder in ethylene glycol stabilized with a surfactant then deposited by inkjet on patterned gold current collectors with the substrate heated at 140 C in order to assure a good homogeneity. Electrochemical micro-capacitors with electrodes in an interdigital configuration were fabricated, and characterized using electrochemical techniques in 1 M Et{sub 4}NBF{sub 4} propylene carbonate electrolyte. These micro-devices show an excellent capacitive behavior over a wide potential range of 2.5 V for a cell capacitance of 2.1 mF cm{sup -2}. The newly developed technology will allow the integration of the storage device as close as possible to the MEMS-based energy harvesting device, minimizing power losses through connections. (author)

Noncovalently functionalized graphitic mesoporous carbon as a stable support of Pt nanoparticles for oxygen reduction

Energy Technology Data Exchange (ETDEWEB)

Shao, Yuyan; Zhang, Sheng; Kou, Rong; Wang, Chongmin; Viswanathan, Vilayanur; Liu, Jun; Wang, Yong; Lin, Yuehe [Pacific Northwest National Laboratory, Richland, WA 99352 (United States); Wang, Xiqing; Dai, Sheng [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2010-04-02

We report a durable electrocatalyst support, highly graphitized mesoporous carbon (GMPC), for oxygen reduction in polymer electrolyte membrane (PEM) fuel cells. GMPC is prepared through graphitizing the self-assembled soft-template mesoporous carbon (MPC) under high temperature. Heat-treatment at 2800 C greatly improves the degree of graphitization while most of the mesoporous structures and the specific surface area of MPC are retained. GMPC is then noncovalently functionalized with poly(diallyldimethylammonium chloride) (PDDA) and loaded with Pt nanoparticles by reducing Pt precursor (H{sub 2}PtCl{sub 6}) in ethylene glycol. Pt nanoparticles of {proportional_to}3.0 nm in diameter are uniformly dispersed on GMPC. Compared to Pt supported on Vulcan XC-72 carbon black (Pt/XC-72), Pt/GMPC exhibits a higher mass activity towards oxygen reduction reaction (ORR) and the mass activity retention (in percentage) is improved by a factor of {proportional_to}2 after 44 h accelerated degradation test under the potential step (1.4-0.85 V) electrochemical stressing condition which focuses on support corrosion. The enhanced activity and durability of Pt/GMPC are attributed to the graphitic structure of GMPC which is more resistant to corrosion. These findings demonstrate that GMPC is a promising oxygen reduction electrocatalyst support for PEM fuel cells. The approach reported in this work provides a facile, eco-friendly promising strategy for synthesizing stable metal nanoparticles on hydrophobic support materials. (author)

VLSI electronics microstructure science

CERN Document Server

1981-01-01

VLSI Electronics: Microstructure Science, Volume 3 evaluates trends for the future of very large scale integration (VLSI) electronics and the scientific base that supports its development.This book discusses the impact of VLSI on computer architectures; VLSI design and design aid requirements; and design, fabrication, and performance of CCD imagers. The approaches, potential, and progress of ultra-high-speed GaAs VLSI; computer modeling of MOSFETs; and numerical physics of micron-length and submicron-length semiconductor devices are also elaborated. This text likewise covers the optical linewi

Microstructural research on hot strips of low carbon steel produced by a compact strip production line under different thermal histories

International Nuclear Information System (INIS)

Yu Hao; Chen Qixiang; Kang Yonglin; Sun Yi

2005-01-01

Coupons with the same composition and thickness (4.0 mm nominal gauge) obtained from hot strips of low carbon steel underwent a series of investigations to analyze the microstructural characteristics and mechanisms responsible for their differences in mechanical properties. Two different industrial technologies were adopted, although the strips used in this research were produced on the same Compact Strip Production (CSP) line. One of the strips was produced with a routine γ→α CSP thermal history, but the other with a γ→α→γ* conventional thermal history. The only difference between them was that one technology had a α→γ* thermal history. Different specimens of both types of strips were prepared for metallographic observation, tensile tests, electron back-scattered diffraction tests and positron annihilation technique tests. Experimental results showed that the differences in mechanical properties could be ascribed to dissimilarities not only in the grain size and textural components but also in dislocation density

Nitrogen Doped Ordered Mesoporous Carbon as Support of PtRu Nanoparticles for Methanol Electro-Oxidation

Directory of Open Access Journals (Sweden)

David Sebastián

2018-04-01

Full Text Available The low oxidation kinetics of alcohols and the need for expensive platinum group metals are still some of the main drawbacks for the commercialization of energy efficient direct alcohol fuel cells. In this work, we investigate the influence of nitrogen doping of ordered mesoporous carbon (CMK as support on the electrochemical activity of PtRu nanoparticles. Nitrogen doping procedures involve the utilization of pyrrole as both nitrogen and carbon precursor by means of a templating method using mesoporous silica. This method allows obtaining carbon supports with up to 14 wt. % nitrogen, with an effective introduction of pyridinic, pyrrolic and quaternary nitrogen. PtRu nanoparticles were deposited by sodium formate reduction method. The presence of nitrogen mainly influences the Pt:Ru atomic ratio at the near surface, passing from 50:50 on the bare (un-doped CMK to 70:30 for the N-doped CMK catalyst. The electroactivity towards the methanol oxidation reaction (MOR was evaluated in acid and alkaline electrolytes. The presence of nitrogen in the support favors a faster oxidation of methanol due to the enrichment of Pt at the near surface together with an increase of the intrinsic activity of PtRu nanoparticles.

Surface sites on carbon-supported Ru, Co and Ni nanoparticles as determined by microcalorimetry of CO adsorption

International Nuclear Information System (INIS)

Cerro-Alarcon, M.; Maroto-Valiente, A.; Rodriguez-Ramos, I.; Guerrero-Ruiz, A.

2005-01-01

The adsorption of CO on carbon-supported metal (Ru, Co and Ni) catalysts was studied by microcalorimetry. A correlation of the results thus obtained with those reported for monocrystals or with other studies available in the scientific literature for supported metal catalysts, including infrared spectroscopy data, enables the determination of the type of exposed crystalline planes and/or of the different types of CO adsorbed species. The results obtained suggest that the energetic distribution of the surface sites depends on the carbon support material and on the applied reduction treatment. In this way, the use of a high surface area graphite (clean of surface oxygen groups) leads to an electron density enrichment on the small metal particles (Ru) and, in general, to a higher heterogeneity of the active surface sites. The elimination of surface oxygen functional groups (with the reduction treatment at the higher temperature) of the carbon molecular sieve support leads to changes in the surface structure of the metal particles and, consequently, to higher CO adsorption heats, particularly for Ru and Co

Approved parallel methods for characterisation of solid carbon

International Nuclear Information System (INIS)

Fitzer, E.

1976-01-01

The contribution gives instructions for the work routine for 1) qualitative radiographic characterization of the microstructural order of solid carbon specimens, 2) X-ray determination of the mean interlattice plane distance anti c/2 of carbons, 3) determination of the helium density of carbons by means of the reference pycnometer, 4) determination of the specific surface area of carbon samples from nitrogen absorption. These instructions for the characterization of solid carbons are the first step towards a collection and comparison of the methods used in the participating countries. The international carbon groups (carbon societies) plan to supplement this collection for every international carbon conference. This collection will serve as a basis for the establishment of international working instructions. (orig./IHOE) [de

Flexible and self-powered temperature-pressure dual-parameter sensors using microstructure-frame-supported organic thermoelectric materials.

Science.gov (United States)

Zhang, Fengjiao; Zang, Yaping; Huang, Dazhen; Di, Chong-an; Zhu, Daoben

2015-09-21

Skin-like temperature- and pressure-sensing capabilities are essential features for the next generation of artificial intelligent products. Previous studies of e-skin and smart elements have focused on flexible pressure sensors, whereas the simultaneous and sensitive detection of temperature and pressure with a single device remains a challenge. Here we report developing flexible dual-parameter temperature-pressure sensors based on microstructure-frame-supported organic thermoelectric (MFSOTE) materials. The effective transduction of temperature and pressure stimuli into two independent electrical signals permits the instantaneous sensing of temperature and pressure with an accurate temperature resolution of pressure-sensing sensitivity of up to 28.9 kPa(-1). More importantly, these dual-parameter sensors can be self-powered with outstanding sensing performance. The excellent sensing properties of MFSOTE-based devices, together with their unique advantages of low cost and large-area fabrication, make MFSOTE materials possess promising applications in e-skin and health-monitoring elements.

Effect of microalloying elements on microstructure and properties of quenched and tempered constructional steel

Science.gov (United States)

Ma, Qingshen; Huang, Leqing; Di, Guobiao; Wang, Yanfeng; Yang, Yongda; Ma, Changwen

2017-09-01

The effects of microalloying elements Nb, V and Ti on microstructure and properties of quenched and tempered steel were studied. Results showed that the addition of microalloying elements led to the formation of bainite and increased strength, while the austenization and ferrite transformation temperature was barely affected, i.e. 10°C. Microalloying elements shortened the incubation time for bainite transformation by refinement of austenite grain, and decreased the hardenability by forming carbides and therefore reducing the carbon content of super-cooled austenite. Either of them promoted the bainite transformation. The better tempering stability was ascribed to the as hot-rolled bainite microstructure and secondary carbide precipitation during tempering.

The Development and Microstructure Analysis of High Strength Steel Plate NVE36 for Large Heat Input Welding

Science.gov (United States)

Peng, Zhang; Liangfa, Xie; Ming, Wei; Jianli, Li

In the shipbuilding industry, the welding efficiency of the ship plate not only has a great effect on the construction cost of the ship, but also affects the construction speed and determines the delivery cycle. The steel plate used for large heat input welding was developed sufficiently. In this paper, the composition of the steel with a small amount of Nb, Ti and large amount of Mn had been designed in micro-alloyed route. The content of C and the carbon equivalent were also designed to a low level. The technology of oxide metallurgy was used during the smelting process of the steel. The rolling technology of TMCP was controlled at a low rolling temperature and ultra-fast cooling technology was used, for the purpose of controlling the transformation of the microstructure. The microstructure of the steel plate was controlled to be the mixed microstructure of low carbon bainite and ferrite. Large amount of oxide particles dispersed in the microstructure of steel, which had a positive effects on the mechanical property and welding performance of the steel. The mechanical property of the steel plate was excellent and the value of longitudinal Akv at -60 °C is more than 200 J. The toughness of WM and HAZ were excellent after the steel plate was welded with a large heat input of 100-250 kJ/cm. The steel plate processed by mentioned above can meet the requirement of large heat input welding.

Three-dimensional structure of Au nanoparticles supported on amorphous silica and carbon substrates

International Nuclear Information System (INIS)

Bruma, A; Li, Z Y

2012-01-01

Scanning Transmission Electron Microscope (STEM) has been employed to study the three-dimensional structure of gold (Au) nanoparticles deposited by means of thermal evaporation in high vacuum on amorphous silica (a-SiO 2 ) and amorphous carbon (a-C) supports. By performing quantitative analysis on the evolution of the high angle annular dark field (HAADF) images, we studied the influence of the nature and the temperature of support on the growth mode of gold nanoparticles.

Effect of double quenching and tempering heat treatment on the microstructure and mechanical properties of a novel 5Cr steel processed by electro-slag casting

International Nuclear Information System (INIS)

Liu, Jian; Yu, Hao; Zhou, Tao; Song, Chenghao; Zhang, Kai

2014-01-01

The effect of double quenching and tempering (DQT) treatment as well as conventional high temperature quenching and tempering (CQT) treatment on the microstructures and mechanical properties of low carbon 5Cr martensitic as cast steel produced by electroslag casting was investigated. The microstructure changes were characterized by optical microscope (OM), scanning electron microscope (SEM), electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). The characteristics of carbides precipitated during tempering were analyzed on both carbon extraction replica and thin foil samples by TEM. The mechanical performance was evaluated by Vickers hardness test, tensile test, and Charpy V-notch impact test at ambient temperature. The results of microstructure study indicated that DQT treatment led to a finer microstructure than that of CQT. The carbides of the tempered samples were identified as M 7 C 3 . The carbides along the prior austenite grain boundaries nucleated directly while those within the laths should be transformed from cementite which formed at the early tempering stage. Compared with CQT condition, yield strength slightly increased after DQT treatment, and impact toughness improved a lot. The strengthening mechanisms were analyzed and it was found that grain refining and precipitation strengthening were mainly responsible for the increase of strength. The superior toughness of DQT condition was attributed to the finer microstructure resulting in more frequent deflections of the cleavage crack and the smaller size of carbides along the prior austenite boundaries. EBSD analysis showed that both martensitic block and packet of low carbon 5Cr tempered martensitic steel could hinder crack propagation, while the latter was more effective

Effect of double quenching and tempering heat treatment on the microstructure and mechanical properties of a novel 5Cr steel processed by electro-slag casting

Energy Technology Data Exchange (ETDEWEB)

Liu, Jian, E-mail: healygo@163.com; Yu, Hao, E-mail: yuhao@ustb.edu.cn; Zhou, Tao, E-mail: zhoutao130984@163.com; Song, Chenghao, E-mail: songchenghao28@126.com; Zhang, Kai, E-mail: zhangkai8901@126.com

2014-12-01

The effect of double quenching and tempering (DQT) treatment as well as conventional high temperature quenching and tempering (CQT) treatment on the microstructures and mechanical properties of low carbon 5Cr martensitic as cast steel produced by electroslag casting was investigated. The microstructure changes were characterized by optical microscope (OM), scanning electron microscope (SEM), electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). The characteristics of carbides precipitated during tempering were analyzed on both carbon extraction replica and thin foil samples by TEM. The mechanical performance was evaluated by Vickers hardness test, tensile test, and Charpy V-notch impact test at ambient temperature. The results of microstructure study indicated that DQT treatment led to a finer microstructure than that of CQT. The carbides of the tempered samples were identified as M{sub 7}C{sub 3}. The carbides along the prior austenite grain boundaries nucleated directly while those within the laths should be transformed from cementite which formed at the early tempering stage. Compared with CQT condition, yield strength slightly increased after DQT treatment, and impact toughness improved a lot. The strengthening mechanisms were analyzed and it was found that grain refining and precipitation strengthening were mainly responsible for the increase of strength. The superior toughness of DQT condition was attributed to the finer microstructure resulting in more frequent deflections of the cleavage crack and the smaller size of carbides along the prior austenite boundaries. EBSD analysis showed that both martensitic block and packet of low carbon 5Cr tempered martensitic steel could hinder crack propagation, while the latter was more effective.

Hierarchically structured nanoporous carbon tubes for high pressure carbon dioxide adsorption

Directory of Open Access Journals (Sweden)

Julia Patzsch

2017-05-01

Full Text Available Mesoscopic, nanoporous carbon tubes were synthesized by a combination of the Stoeber process and the use of electrospun macrosized polystyrene fibres as structure directing templates. The obtained carbon tubes have a macroporous nature characterized by a thick wall structure and a high specific surface area of approximately 500 m²/g resulting from their micro- and mesopores. The micropore regime of the carbon tubes is composed of turbostratic graphitic areas observed in the microstructure. The employed templating process was also used for the synthesis of silicon carbide tubes. The characterization of all porous materials was performed by nitrogen adsorption at 77 K, Raman spectroscopy, infrared spectroscopy, thermal gravimetric analysis (TGA, scanning electron microscopy (SEM as well as transmission electron microscopy (TEM. The adsorption of carbon dioxide on the carbon tubes at 25 °C at pressures of up to 30 bar was studied using a volumetric method. At 26 bar, an adsorption capacity of 4.9 mmol/g was observed. This is comparable to the adsorption capacity of molecular sieves and vertically aligned carbon nanotubes. The high pressure adsorption process of CO2 was found to irreversibly change the microporous structure of the carbon tubes.

Carbon-Supported Iron Oxide Particles

DEFF Research Database (Denmark)

Meaz, T.; Mørup, Steen; Koch, C. Bender

1996-01-01

A carbon black ws impregnated with 6 wt% iron using an aqueous solution of iron nitrate. The impregnated carbon was initially dried at 125 C. The effect of heating of the iron oxide phase was investigated at temperatures between 200 and 600 C using Mossbauer spectroscopy. All heat treatments were...... done in an oxygen-containing atmosphere. Ferrihydrite is formed and is stable at and below a temperature of 300 C. At 600 C small particles of maghemite is the dominant iron oxide. A transformation reaction is suggested....

The hydrogen and oxygen content of self-supporting carbon foils prepared by dc glow discharge in ethylene

International Nuclear Information System (INIS)

Tait, N.R.S.; Tolfree, D.W.L.; John, P.; Odeh, I.M.; Thomas, M.J.K.; Tricker, M.J.; Wilson, J.J.B.; England, J.B.A.; Newton, D.

1980-01-01

The hydrogen and oxygen content of self-supporting carbon films produced by dc glow discharge have been determined using a precise method involving the elastic scattering of 25 MeV α-particles. The number of carbon-hydrogen bonds has been determined for similar samples using infrared spectroscopy. The results are compared with those for samples made by the carbon arc process. Assuming that the glow discharge carbon contains graphitic regions surrounded by amorphous tetrahedrally bonded material to which hydrogen can attach, a simple estimate is made of the relative numbers of carbon atoms in the two forms. (orig.)

Preparation and characterization of carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating for carbon/carbon composites

International Nuclear Information System (INIS)

Leilei, Zhang; Hejun, Li; Kezhi, Li; Shouyang, Zhang; Qiangang, Fu; Yulei, Zhang; Jinhua, Lu; Wei, Li

2014-01-01

Highlights: • CSH coatings were prepared by combination of magnetron sputter ion plating, CVD and UECD. • Na + and CO 3 2− were developed to co-substitute hydroxyapatite. • SiC nanowires were introduced into Na-doped carbonated hydroxyapatite. • CSH coatings showed excellent cell activity and cell proliferation behavior. - Abstract: A carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating (CSH coating) was prepared on carbon/carbon composites using a combination method of magnetron sputter ion plating, chemical vapor deposition and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the CSH coating was consisted of three components: carbon layer, SiC nanowires and Na-doped carbonated hydroxyapatite. The carbon layer provided a dense and uniform surface structure for the growth of SiC nanowires. The SiC nanowires exhibited a porous structure, favoring the infiltration of Na-doped carbonated hydroxyapatite crystals. The Na-doped carbonated hydroxyapatite could infiltrate into the pores of SiC nanowires and finally cover the SiC nanowires entirely with a needle shape. The osteoblast-like MG63 cells were employed to assess the in vitro biocompatibility of the CSH coating. The MG63 cells favorably spread and grew well across the CSH coating surface with plenty of filopods and microvilli, exhibiting excellent cell activity. Moreover, the CSH coating elicited higher cell proliferation as compared to bare carbon/carbon composites. In conclusion, the CSH offers great potential as a coating material for future medical application in hard tissue replacement

Preparation and characterization of carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating for carbon/carbon composites

Energy Technology Data Exchange (ETDEWEB)

Leilei, Zhang, E-mail: zhangleilei1121@aliyun.com; Hejun, Li; Kezhi, Li; Shouyang, Zhang; Qiangang, Fu; Yulei, Zhang; Jinhua, Lu; Wei, Li

2014-09-15

Highlights: • CSH coatings were prepared by combination of magnetron sputter ion plating, CVD and UECD. • Na{sup +} and CO{sub 3}{sup 2−} were developed to co-substitute hydroxyapatite. • SiC nanowires were introduced into Na-doped carbonated hydroxyapatite. • CSH coatings showed excellent cell activity and cell proliferation behavior. - Abstract: A carbon/SiC nanowire/Na-doped carbonated hydroxyapatite multilayer coating (CSH coating) was prepared on carbon/carbon composites using a combination method of magnetron sputter ion plating, chemical vapor deposition and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the CSH coating was consisted of three components: carbon layer, SiC nanowires and Na-doped carbonated hydroxyapatite. The carbon layer provided a dense and uniform surface structure for the growth of SiC nanowires. The SiC nanowires exhibited a porous structure, favoring the infiltration of Na-doped carbonated hydroxyapatite crystals. The Na-doped carbonated hydroxyapatite could infiltrate into the pores of SiC nanowires and finally cover the SiC nanowires entirely with a needle shape. The osteoblast-like MG63 cells were employed to assess the in vitro biocompatibility of the CSH coating. The MG63 cells favorably spread and grew well across the CSH coating surface with plenty of filopods and microvilli, exhibiting excellent cell activity. Moreover, the CSH coating elicited higher cell proliferation as compared to bare carbon/carbon composites. In conclusion, the CSH offers great potential as a coating material for future medical application in hard tissue replacement.

VLSI electronics microstructure science

CERN Document Server

1982-01-01

VLSI Electronics: Microstructure Science, Volume 4 reviews trends for the future of very large scale integration (VLSI) electronics and the scientific base that supports its development.This book discusses the silicon-on-insulator for VLSI and VHSIC, X-ray lithography, and transient response of electron transport in GaAs using the Monte Carlo method. The technology and manufacturing of high-density magnetic-bubble memories, metallic superlattices, challenge of education for VLSI, and impact of VLSI on medical signal processing are also elaborated. This text likewise covers the impact of VLSI t

Microstructure Optimization of Dual-Phase Steels Using a Representative Volume Element and a Response Surface Method: Parametric Study

Science.gov (United States)

Belgasam, Tarek M.; Zbib, Hussein M.

2017-12-01

Dual-phase (DP) steels have received widespread attention for their low density and high strength. This low density is of value to the automotive industry for the weight reduction it offers and the attendant fuel savings and emission reductions. Recent studies on developing DP steels showed that the combination of strength/ductility could be significantly improved when changing the volume fraction and grain size of phases in the microstructure depending on microstructure properties. Consequently, DP steel manufacturers are interested in predicting microstructure properties and in optimizing microstructure design. In this work, a microstructure-based approach using representative volume elements (RVEs) was developed. The approach examined the flow behavior of DP steels using virtual tension tests with an RVE to identify specific mechanical properties. Microstructures with varied martensite and ferrite grain sizes, martensite volume fractions, carbon content, and morphologies were studied in 3D RVE approaches. The effect of these microstructure parameters on a combination of strength/ductility of DP steels was examined numerically using the finite element method by implementing a dislocation density-based elastic-plastic constitutive model, and a Response surface methodology to determine the optimum conditions for a required combination of strength/ductility. The results from the numerical simulations are compared with experimental results found in the literature. The developed methodology proves to be a powerful tool for studying the effect and interaction of key microstructural parameters on strength and ductility and thus can be used to identify optimum microstructural conditions.

Money: A Market Microstructure Approach

OpenAIRE

Krueger, Malte

2008-01-01

The current discussion about the future of the financial system draws heavily on a set of theories known as the ‘New Monetary Economics’. The New Monetary Economics predicts that deregulation and financial innovation will lead to a moneyless world. This paper uses a market microstructure approach to show that a common medium of exchange that serves as unit of account will remain a necessary instrument to reduce transaction costs. This finding is supported by empirical evidence from foreign...

A Comparative Study of the Effect of MgO and CaCO3 as Support Materials in the Synthesis of Carbon Nanotubes with Fe/Co as Catalyst

Directory of Open Access Journals (Sweden)

Ezekiel D. Dikio

2014-01-01

Full Text Available A comparative study of the effect of magnesium oxide and calcium carbonate as support material in the synthesis of carbon nanotubes using the catalyst Fe/Co is presented. The synthesized carbon nanotubes were characterized with Raman spectroscopy, scanning electron spectroscopy (SEM, high-resolution transmission electron microscopy (HRTEM, X-ray diffraction spectroscopy (XRD, and energy dispersive spectroscopy (EDS. The morphology of the carbon nanotubes synthesized with magnesium oxide as support material gives rise to carbon nanotubes with consistent and well-defined structure unlike that synthesized with calcium carbonate. The ID/IG ratio of synthesized carbon nanotubes (CNTs was 0.8544 for magnesium oxide supported compared to 0.8501 for calcium carbonate supported carbon nanotube.

De-oxygenation of CO2 by using Hydrogen, Carbon and Methane over Alumina-Supported Catalysts

Directory of Open Access Journals (Sweden)

R.Y. Raskar

2012-06-01

Full Text Available The de-oxygenation of CO2 was explored by using hydrogen, methane, carbon etc., over alumina supported catalysts. The alumina-supported ruthenium, rhodium, platinum, molybdenum, vanadium and magnesium catalysts were first reduced in hydrogen atmosphere and then used for the de-oxygenation of CO2. Furthermore, experimental variables for the de-oxygenation of CO2 were temperature (range 50 to 650 oC, H2/CO2 mole ratios (1.0 to 5, and catalyst loading (0.5 to 10 wt %. During the de-oxygenation of CO2 with H2 or CH4 or carbon, conversion of CO2, selectivity to CO and CH4 were estimated. Moreover, 25.4 % conversion of CO2 by hydrogen was observed over 1 wt% Pt/Al2O3 catalyst at 650 oC with 33.8 % selectivity to CH4. However, 8.1 to 13.9 % conversion of CO2 was observed over 1 wt% Pt/Al2O3 catalyst at 550 oC in the presence of both H2 and CH4. Moreover, 42.8 to 79.4 % CH4 was converted with 9 to 23.1 % selectivity to CO. It was observed that the de-oxygenation of CO2 by hydrogen, carbon and methane produced carbon, CO and CH4. © 2012 BCREC UNDIP. All rights reservedReceived: 6th February 2012; Revised: 23rd April 2012; Accepted: 24th April 2012[How to Cite: R. Y. Raskar, K. B. Kale, A. G. Gaikwad. (2011. De-oxygenation of CO2 by using Hydrogen, Carbon and Methane over Alumina-Supported Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (1: 59-69.  doi:10.9767/bcrec.7.1.1631.59-69][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.1.1631.59-69 ] | View in 

Carbon supported ultrafine gold phosphorus nanoparticles as highly efficient electrocatalyst for alkaline ethanol oxidation reaction

International Nuclear Information System (INIS)

Li, Tongfei; Fu, Gengtao; Su, Jiahui; Wang, Yi; Lv, Yinjie; Zou, Xiuyong; Zhu, Xiaoshu; Xu, Lin; Sun, Dongmei; Tang, Yawen

2017-01-01

Graphical abstract: We develop a new kind of carbon supported gold-phosphorus (Au-P/C) electrocatalyst by a facile and novel phosphorus reduction method, and demonstrate the Au-P/C is a highly active and stable electrocatalyst for the ethanol oxidation reaction. - Highlights: • Au-P/C catalyst is synthesized by a facile and novel white-phosphorus reduce method. • AuP particles with ultrafine particle-size are uniformly dispersed on carbon support. • Au-P/C catalyst exhibits much higher content of P 0 than reported metal/P catalysts. • Au-P/C catalysts show excellent catalytic properties for ethanol oxidation reaction. - Abstract: Herein, we develop a new kind of carbon supported gold-phosphorus (Au-P/C) electrocatalyst for the alkaline ethanol oxidation reaction (EOR). The Au-P/C catalysts with different Au/P ratio (i.e., AuP/C, Au 3 P 2 /C and Au 4 P 3 /C) can be obtained by a facile and novel hot-reflux method with white phosphorus (P 4 ) as reductant and ethanol as solvent. The crystal structure, composition and particle-size of the Au-P/C catalysts are investigated by X-ray diffraction (XRD), Energy Dispersive Spectrometer (EDS), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), etc. The results demonstrate that Au-P/C catalysts present an alloy phase with the high content of P, ultrafine particle-size and high dispersity on carbon support, which results in excellent electrocatalytic activity and stability towards the EOR compared with that of the free-phosphorus Au/C catalyst. In addition, among the various Au-P/C catalysts with different Au/P ratio, the AuP/C sample exhibits the best electrocatalytic performance in comparison with other Au 3 P 2 /C and Au 4 P 3 /C samples.

Recent progress in solution plasma-synthesized-carbon-supported catalysts for energy conversion systems

Science.gov (United States)

Lun Li, Oi; Lee, Hoonseung; Ishizaki, Takahiro

2018-01-01

Carbon-based materials have been widely utilized as the electrode materials in energy conversion and storage technologies, such as fuel cells and metal-air batteries. In these systems, the oxygen reduction reaction is an important step that determines the overall performance. A novel synthesis route, named the solution plasma process, has been recently utilized to synthesize various types of metal-based and heteroatom-doped carbon catalysts. In this review, we summarize cutting-edge technologies involving the synthesis and modeling of carbon-supported catalysts synthesized via solution plasma process, followed by current progress on the electrocatalytic performance of these catalysts. This review provides the fundamental and state-of-the-art performance of solution-plasma-synthesized electrode materials, as well as the remaining scientific and technological challenges for this process.

Microstructure and mechanical properties of ion-beam-produced Fe-Ti-(N), Fe-Ti-(C), and Fe-Ti-(C,N) surface films

Science.gov (United States)

Hirvonen, J.-P.; Nastasi, M.; Zocco, T. G.; Jervis, T. R.

1990-06-01

Ion-mixed films of Fe53 Ti47 were produced by ion irradiating a Fe-Ti multilayer structure on AISI 304 stainless steel. The ion-mixed films were subsequently implanted with nitrogen, carbon, or both carbon and nitrogen. The microstructure following nitrogen implantation consisted of a bcc solid solution of iron and titanium and finely dispersed TiN precipitates. In the cases of carbon or carbon and nitrogen implantation, a two-phase structure consisting of an amorphous matrix with TiC or Ti(C,N) precipitates was found. All these films initially possessed improved tribological properties as revealed by lowered friction and increased wear resistance. However, after an extended test of 1000 wear cycles, a reduced friction was only observed for the carbon or carbon and nitrogen implanted samples. The wear track on the dual implanted surface was extremely smooth, while the surface of the nitrogen-implanted sample was partly worn through, causing the friction to increase to the level of the untreated sample. The improved tribological properties of the implanted films are attributed to an increase in surface hardness. However, the surface hardness is unable to explain differences between different implantations. In the case of the dual carbon and nitrogen implantation, improvements appear to be in part the result from an increased capability to accommodate plastic deformation. These conclusions are supported by transmission electron microscope studies of the wear tracks as well as by nanoindentation measurements.

METHANE DRY REFORMING OVER Ni SUPPORTED ON PINE SAWDUST ACTIVATED CARBON: EFFECTS OF SUPPORT SURFACE PROPERTIES AND METAL LOADING

Directory of Open Access Journals (Sweden)

Rafael García

2015-05-01

Full Text Available The influence of metal loading and support surface functional groups (SFG on methane dry reforming (MDR over Ni catalysts supported on pine-sawdust derived activated carbon were studied. Using pine sawdust as the catalyst support precursor, the smallest variety and lowest concentration of SFG led to best Ni dispersion and highest catalytic activity, which increased with Ni loading up to 3 Ni atoms nm-2. At higher Ni loading, the formation of large metal aggregates was observed, consistent with a lower "apparen" surface area and a decrease in catalytic activity. The H2/CO ratio rose with increasing reaction temperature, indicating that increasingly important side reactions were taking place in addition to MDR.

Effect of caffeine inhibitor in corrosion rate and microstructure of KS01 carbon steel and AISI 1045 at media sea water

International Nuclear Information System (INIS)

Sulistioso Giat S; Setyo Purwanto; Deswita; Ari Handayani; Berta Vidyananda

2013-01-01

Many synthetic materials are good inhibitors for the prevention of corrosion . Many inhibitors are toxic, because of the influence of these toxic properties, recently use organic materials as corrosion inhibitors, that are not hazardous and environmentally friendly. In this study caffeine compounds used as corrosion inhibitors. This compound could be used as corrosion inhibitor because of the existence of their chemical groups that containing free electron pair, that is nitrogen. Corrosion rate testing conducted in sea water medium taken from the Northern region of Indramayu with variations of the concentration of caffeine 0, 50, 100, 150, and 200 ppm to determine the optimum concentration of caffeine in corrosion rate of carbon steel AISI 1045 and KS01 that a widely used on the cooling system in the industry. Corrosion rate of KS-01 steel before used in inhibitor media is 25,07 mpy that less than corrosion rate of carbon steel AISI 1045, is 45,82 mpy . The results of this study indicate that caffeine is able to inhibit the corrosion rate of both of samples with optimum efficiency KS01 for 64.38%, and AISI 1045 of 66.63%. The optimum concentration of caffeine to inhibited AISI 1045 is 150 ppm and for KS01 is 100 ppm,. Beside that analysis of microstructure for both samples have done, for media before and after inhibitor addition. (author)

Hierarchical nanostructured hollow spherical carbon with mesoporous shell as a unique cathode catalyst support in proton exchange membrane fuel cell.

Science.gov (United States)

Fang, Baizeng; Kim, Jung Ho; Kim, Minsik; Kim, Minwoo; Yu, Jong-Sung

2009-03-07

Hierarchical nanostructured spherical carbon with hollow macroporous core in combination with mesoporous shell has been explored to support Pt cathode catalyst with high metal loading in proton exchange membrane fuel cell (PEMFC). The hollow core-mesoporous shell carbon (HCMSC) has unique structural characteristics such as large specific surface area and mesoporous volume, ensuring uniform dispersion of the supported high loading (60 wt%) Pt nanoparticles with small particle size, and well-developed three-dimensionally interconnected hierarchical porosity network, facilitating fast mass transport. The HCMSC-supported Pt(60 wt%) cathode catalyst has demonstrated markedly enhanced catalytic activity toward oxygen reduction and greatly improved PEMFC polarization performance compared with carbon black Vulcan XC-72 (VC)-supported ones. Furthermore, the HCMSC-supported Pt(40 wt%) or Pt(60 wt%) outperforms the HCMSC-supported Pt(20 wt%) even at a low catalyst loading of 0.2 mg Pt cm(-2) in the cathode, which is completely different from the VC-supported Pt catalysts. The capability of supporting high loading Pt is supposed to accelerate the commercialization of PEMFC due to the anticipated significant reduction in the amount of catalyst support required, diffusion layer thickness and fabricating cost of the supported Pt catalyst electrode.

High-temperature effects on the electrical properties and macrostructure of carbon composites

International Nuclear Information System (INIS)

Zhmurikov, E.I.; Gubin, K.V.; Romanenko, A.I.; Anikeeva, O.B.; Burgina, E.B.; Tsybulya, S.V.; Titov, A.T.; Tecchito, L.

2006-01-01

Conductivity of samples of carbon composites MPG-6 and MPG-7 as starting ones, so and after irradiation by powerful electron beam with the energy of 1.4 MeV and heating by alternative current to temperatures beyond 2500 Deg C is measured. Heating and irradiation as shown to rise of decreasing the conductivity of the samples and increasing the defectiveness at a level of microstructure. Sensible changing of the microstructure in the samples during heating up to temperature of decomposition does not indicate by X-ray analysis. It is excepted that the strength of carbon composites is limited by intercrystalline or intergranular boundaries [ru

Relationship Between Solidification Microstructure and Hot Cracking Susceptibility for Continuous Casting of Low-Carbon and High-Strength Low-Alloyed Steels: A Phase-Field Study

Science.gov (United States)

Böttger, B.; Apel, M.; Santillana, B.; Eskin, D. G.

2013-08-01

Hot cracking is one of the major defects in continuous casting of steels, frequently limiting the productivity. To understand the factors leading to this defect, microstructure formation is simulated for a low-carbon and two high-strength low-alloyed steels. 2D simulation of the initial stage of solidification is performed in a moving slice of the slab using proprietary multiphase-field software and taking into account all elements which are expected to have a relevant effect on the mechanical properties and structure formation during solidification. To account for the correct thermodynamic and kinetic properties of the multicomponent alloy grades, the simulation software is online coupled to commercial thermodynamic and mobility databases. A moving-frame boundary condition allows traveling through the entire solidification history starting from the slab surface, and tracking the morphology changes during growth of the shell. From the simulation results, significant microstructure differences between the steel grades are quantitatively evaluated and correlated with their hot cracking behavior according to the Rappaz-Drezet-Gremaud (RDG) hot cracking criterion. The possible role of the microalloying elements in hot cracking, in particular of traces of Ti, is analyzed. With the assumption that TiN precipitates trigger coalescence of the primary dendrites, quantitative evaluation of the critical strain rates leads to a full agreement with the observed hot cracking behavior.

The effects of laser welding parameters on the microstructure of ferritic and duplex stainless steels welds

Science.gov (United States)

Pekkarinen, J.; Kujanpää, V.

This study is focused to determine empirically, which microstructural changes occur in ferritic and duplex stainless steels when heat input is controlled by welding parameters. Test welds were done autogenously bead-on-plate without shielding gas using 5 kW fiber laser. For comparison, some gas tungsten arc welds were made. Used test material were 1.4016 (AISI 430) and 1.4003 (low-carbon ferritic) type steels in ferritic steels group and 1.4162 (low-alloyed duplex, LDX2101) and 1.4462 (AISI 2205) type steels in duplex steels group. Microstructural changes in welds were identified and examined using optical metallographic methods.