Showing papers by "University of Science and Technology Beijing published in 2010"
TL;DR: This work presents a new approach to selective separation of Na6(CO3)(SO4) from Na2(SO3) using a high-performance liquid chromatography method, which has shown good results in both the high-resolution and the low-resolution versions.
Abstract: [ ∗] L. Zhao , Prof. M. Antonietti , Dr. M.-M. Titirici Colloid Chemistry Department Max-Planck Institute for Colloids and Interfaces Am Muehlenberg 1, 14424 Potsdam (Germany) E-mail: Magdalena.Titirici@mpikg.mpg.de Prof. L.-Z. an , F M.-Q. Zhou , H. Guan , Qiao S. . YSchool of Materials Science and Engineering University of Science and Technology Beijing 100083 Beijing (China) E-mail: fanlizhen@ustb.edu.cn L. Zhao Institute of Coal Chemistry Chinese Academy of Sciences 27th Taoyuan South Road, 030001 Taiyuan (China)
848 citations
13 Dec 2010
TL;DR: A detailed study of 11 widely used internal clustering validation measures for crisp clustering and shows that S\_Dbw is the only internal validation measure which performs well in all five aspects, while other measures have certain limitations in different application scenarios.
Abstract: Clustering validation has long been recognized as one of the vital issues essential to the success of clustering applications. In general, clustering validation can be categorized into two classes, external clustering validation and internal clustering validation. In this paper, we focus on internal clustering validation and present a detailed study of 11 widely used internal clustering validation measures for crisp clustering. From five conventional aspects of clustering, we investigate their validation properties. Experiment results show that S\_Dbw is the only internal validation measure which performs well in all five aspects, while other measures have certain limitations in different application scenarios.
830 citations
TL;DR: In this article, a review summarizes the progress that has been made in recent years in developing thermoelectric materials with a high dimensionless figure of merits (ZT) and the related fabrication processes for producing nanostuctured materials.
Abstract: Thermoelectric effects enable direct conversion between thermal and electrical energy and provide an alternative route for power generation and refrigeration. Over the past ten years, the exploration of high-performance thermoelectric materials has attracted great attention from both an academic research perspective and with a view to industrial applications. This review summarizes the progress that has been made in recent years in developing thermoelectric materials with a high dimensionless figure of merits (ZT) and the related fabrication processes for producing nanostuctured materials. The challenge to develop thermoelectric materials with superior performance is to tailor the interconnected thermoelectric physical parameters — electrical conductivity, Seebeck coefficient and thermal conductivity — for a crystalline system. Nanostructures provide a chance to disconnect the linkage between thermal and electrical transport by introducing some new scattering mechanisms. Recent improvements in thermoelectric efficiency appear to be dominated by efforts to reduce the lattice thermal conductivity through nanostructural design. The materials focused in this review include Bi–Te alloys, skutterudite compounds, Ag–Pb–Sb–Te quaternary systems, half-Heusler compounds and some high-ZT oxides. Possible future strategies for developing thermoelectric materials are also discussed.
813 citations
TL;DR: A BMG composite that exhibits large tensile ductility with signifi cant work-hardening capability is reported, which offers a new paradigm for developing BMGs with improved ductility as practical engineering materials.
Abstract: Bulk metallic glasses (BMGs) have shown a unique combination of mechanical, chemical, and physical properties, [ 1–5 ] but their room-temperature brittleness has been the stumbling block for real structural applications. [ 6 , 7 ] To answer this challenge, the concept of developing composite microstructures by combining the glassy matrix with crystalline phases at different length scales has been developed, through which an improvement in tensile ductility has been obtained in several zirconium and titanium-based BMG composites. [ 8–13 ] However, these BMG composites showed a macroscopic strain softening phenomenon with an early onset of necking (i.e., the maximum strength occurs at the yield point) because of a lack of workhardening mechanisms (endows the materials with minute damage tolerance), which would give rise to serious engineering problems therefrom. In this Communication, we report a BMG composite that exhibits large tensile ductility with signifi cant work-hardening capability. Our current fi nding offers a new paradigm for developing BMGs with improved ductility as practical engineering materials. A work-hardening phenomenon in compression has been reported in both BMGs and BMG composites and a few scenarios were proposed for understanding the strain-hardening capability, such as severe lattice distortion in the crystalline phases, pile ups of dislocations close to the interfaces between the reinforced phases and matrix, [ 14 ] atomic-scale inhomogeneity in the amorphous phase, and stress-induced martensitic transformation. [ 15–17 ] To date, however, a working-hardening capability has not been discovered in tension for BMGs or their composites. Referring to the concept of the TRIP (transformationinduced plasticity) steels, [ 18 ] in this study, we attempted to fabricate a BMG composite with isolated spherical crystalline phases that undergo martensitic transformation during tensile deformation. With such a special composite structure, large tensile ductility and signifi cant work-hardening capability could be induced. Figure 1a shows a representative cross section of the current BMG composite, which demonstrates a typical BMG composite microstructure that contains spherical crystalline phases homogeneously embedded in the amorphous matrix.
436 citations
TL;DR: The combination of the superior adsorption and the magnetic properties of Fe(3)O(4) nanospheres can be useful as a powerful separation tool to deal with environmental pollution.
430 citations
TL;DR: In this article, Bismuth ferrite (BiFeO3) uniform microcrystals with various morphologies (microspheres and micro/submirocubes) were successfully synthesized by a controlled hydrothermal method.
Abstract: Bismuth ferrite (BiFeO3) uniform microcrystals with various morphologies (microspheres and micro/submirocubes) were successfully synthesized by a controlled hydrothermal method. The resulting microstructures were characterized using X-ray diffraction, scanning/transmission electron microscopies and Raman spectroscopy. Possible formation mechanism for BiFeO3 microcrystals was proposed. UV−vis spectra showed that the optical properties of the microsized BiFeO3 crystals were strongly related to their shape and size. We further demonstrated the useful photocatalytic activity of these regular-shaped structures as determined by degradation of Congo red under visible-light irradiation (λ > 400 nm). Additionally, magnetic responses were observed to be influenced by the morphology of as-synthesized BiFeO3 products, and the ferroelectric performance of BiFeO3 submicrocube was also studied by piezoelectric force microscopy (PFM). Being a multiferroic semiconductor with suitable narrow band gap (∼2.2 eV) and uniform ...
377 citations
TL;DR: The passivity of 316L stainless steel in borate buffer solution has been investigated by Mott-Schottky, atomic absorption spectrometry (AAS) and X-ray photoelectron spectroscopy (XPS) as mentioned in this paper.
293 citations
TL;DR: In this paper, an effective way to apply a vapor deposited chromium coating onto diamond particles was used to overcome the interface problem, and the results showed that the densification, interfacial bonding and thermal conductivity of coated composites were evidently enhanced compared to that of uncoated composites.
261 citations
TL;DR: In this article, a particle-compositing method was used for the first time to disperse different contents of multi-walled carbon nanotubes (CNTs) in micron sized copper powders, which were subsequently consolidated into CNT/Cu composites by spark plasma sintering (SPS).
228 citations
TL;DR: In this paper, an overview of new CO2 breakthrough technologies for iron and steel making was made, and the long-term approaches to achieving a significant reduction in CO2 emissions from the steel industry would be through developing and applying CO2-based breakthrough technologies, and through increasing use of renewable energy for the steel making.
Abstract: The global steel production has been growing for the last 50 years, from 200 Mt in 1950s to 1 240 Mt in 2006. Iron and steel making industry is one of the most energy-intensive industries, with an annual energy consumption of about 24 EJ, 5% of the world's total energy consumption. The steel industry accounts for 3%–4% of total world greenhouse gas emissions. Enhancing energy efficiency and employing energy saving/recovering technologies such as coke dry quechning (CDQ) and top pressure recovery turbine (TRT) can be short-term approaches to the steel industry to reduce greenhouse gas emission. The long-term approaches to achieving a significant reduction in CO2 emissions from the steel industry would be through developing and applying CO2 breakthrough technologies for iron and steel making, and through increasing use of renewable energy for iron and steel making. Thus, an overview of new CO2 breakthrough technologies for iron and steel making was made.
199 citations
TL;DR: In this paper, the effects of heat treatment temperature on crystalline phases formation, microstructure and magnetic properties of Mn-Zn ferrite powders were investigated by X-ray diffraction, thermogravimetric and differential thermal analysis, scanning electron microscopy and vibrating sample magnetometer.
TL;DR: In this paper, a PANI nanofibers were fabricated by interfacial polymerization in the presence of para-phenylenediamine (PPD), which not only has a profound impact on the polymers morphology, but can also improve their specific energy and specific capacitances.
15 Oct 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the susceptibility to hydrogen induced cracking (HIC) was evaluated for X120 steels containing different amounts of Mn and Al in a H2S environment, and the hydrogen trapping efficiency was investigated by measuring the permeability (J∞L) and the apparent diffusivity (Dapp).
Abstract: The susceptibility to hydrogen induced cracking (HIC) was evaluated for X120 steels containing different amounts of Mn and Al in a H2S environment. The hydrogen trapping efficiency was investigated by measuring the permeability (J∞L) and the apparent diffusivity (Dapp). The results demonstrated that larger amount of the inclusions, and larger area and volume fraction of the inclusions make steels more susceptible to HIC. The steel with a microstructure consisting of granular bainite and M/A (martensite/austenite) microconstituents is more susceptible to HIC. The ability of the microstructure and the inclusions to trap hydrogen was explained in terms of the apparent diffusivity (Dapp), permeability (J∞L), and solubility of hydrogen in steels (capp). The lower the values of Dapp and J∞L and the higher the value of capp are, the more the hydrogen trapping occurs in the steel, and the more the steel is susceptible to HIC.
TL;DR: This paper incorporates time delays into the ordinary differential equation models based on SIR and SEIR epidemic models with a general nonlinear incidence rate and proves the global stability of the endemic equilibrium and the disease-free equilibrium for time delays of any length in each model.
TL;DR: A survey of the key issues associated with the development in the Chinese iron and steel industry and current situations of energy consumption is described in this paper, where some measures for the industry in terms of the economic policy of China's 11th five-year plan are also presented.
TL;DR: In this paper, a hierarchical lamellar porous carbon material was prepared with fish scale using a natural template, which demonstrated that fish scale is a promising candidate precursor to prepare low cost but high performance porous carbon materials.
Abstract: A hierarchical lamellar porous carbon material was prepared with fish scale using a natural template. Electric double layer capacitors electrodes prepared from this kind of porous carbon exhibited exceptional ration ability which demonstrated that fish scale is a promising candidate precursor to prepare low cost but high performance porous carbon material.
TL;DR: In this article, mesoporous anatase TiO2 spheres were prepared by hydrothermal treatment of the titanium diglycolate precursors, and a high light-to-electricity conversion of 8.20% was achieved, indicating a 40% increase in the conversion efficiency compared to the standard Degussa P25 photoanode.
Abstract: In this study, well-crystallized mesoporous anatase TiO2 spheres were prepared by hydrothermal treatment of the titanium diglycolate precursors. These spheres are submicrometer-sized and consist of packed nanocrystallites with diameters of ∼8 nm, and possess a specific surface area of 193 m2 g−1 and main pore sizes of ∼5 nm. We demonstrated that due to the large particle diameters and ultrahigh specific surface areas, mesoporous TiO2 microspheres can enhance the light harvesting within the photoanodes for dye-sensitized solar cells (DSSCs), and meanwhile, their good crystallinity and better interparticle connections caused by partially oriented attachment of primary particles result in the effective charge transport through the film of mesoporous TiO2 spheres. A high light-to-electricity conversion of 8.20% has been achieved, indicating a 40% increase in the conversion efficiency compared to the standard Degussa P25 photoanode.
TL;DR: In this article, a three-phase (NBT-MWNT)/polyvinylidene fluoride nanocomposite with a significantly enhanced dielectric constant (643 at 103 Hz) and a gradually decreased loss was reported.
Abstract: The carbon nanotube (CNT) has been chosen as an excellent candidate for acquiring high dielectric constant polymer matrix composites according to percolation theory. However, its nanometer-scale dimension makes it naturally form bundles, which makes it difficult to use. Compared with chemical modification of multiwalled carbon nanotube (MWNT), the incorporation of the third component (nanosized BaTiO3 (NBT)) particles into MWNT/polymer composites would realize the uniform dispersion of MWNT without sacrificing the inherent properties of MWNT. We reported a three-phase (NBT-MWNT)/polyvinylidene fluoride nanocomposite with a significantly enhanced dielectric constant (643 at 103 Hz) and a gradually decreased loss, which was extremely hard to be realized at the same time for composites only filled by conductive MWNT filler. Adjustable dielectric properties were discovered by employing the three-phase system due to the nanocomposites microstructure change. Furthermore, impedance analysis and simulated circuit...
TL;DR: In this paper, a new processing concept was developed to produce nano-structured metal-matrix composite coatings, which combines sol-gel and electroless plating techniques to prepare highly dispersive oxide nano-particle reinforced composite materials.
Abstract: A new processing concept has been developed to produce nano-structured metal-matrix composite coatings. This method combines sol-gel and electroless plating techniques to prepare highly dispersive oxide nano-particle reinforced composite coatings. Transparent TiO2 sol was added into the standard electroless plated Ni–P solution at a controlled rate to produce Ni–P–TiO2 nano-composite coatings on Mg alloys. The coating was found to have a crystalline structure. The nano-sized TiO2 particles (∼ 15 nm) were well dispersed into the Ni–P coating matrix during the co-deposition process. This technique can effectively avoid the agglomeration of nano-particles in the coating matrix. As a result, the microhardness of the composite coatings were significantly increased to ∼ 1025 HV200 compared to ∼ 710 HV200 of the conventional composite coatings produced with solid particle mixing methods. Correspondingly, the wear resistance of the new composite coatings was also greatly improved.
TL;DR: In this article, the electrocaloric effect of BaTiO3 multilayer thin film structure was investigated by direct measurement and theoretical calculation, which showed a much higher EC effect of 0.91 J/g at 80°C under the same electric field.
Abstract: The electrocaloric (EC) effect of BaTiO3 multilayer thick film structure was investigated by direct measurement and theoretical calculation. The samples were prepared by the tape-casting method, which had 180 dielectric layers with an average thickness of 1.4 μm. The thermodynamic calculation based on the polarization-temperature curves predicted a peak heat adsorption of 0.32 J/g at 80 °C under 176 kV/cm electric field. The direct measurement via differential scanning calorimeter showed a much higher EC effect of 0.91 J/g at 80 °C under same electric field. The difference could result from the different trends of changes of electric polarization and lattice elastic energy under ultrahigh electric field.
TL;DR: Using alloy design, an Fe77Mo5P9C7.5B1.5 bulk metallic glass matrix composite reinforced by in situ formed ductile α-Fe dendrites has been developed as discussed by the authors.
TL;DR: It is found that the complex atomic configuration in metallic glasses can be interpreted globally as a combination of the spherical-periodic order and local translational symmetry.
Abstract: In this Letter, we have revealed the common structural behavior of metallic glasses through scrutinizing the evolution of pair distribution functions from metallic liquids to glasses and statistically analyzing pair distribution functions of 64 metallic glasses It is found that the complex atomic configuration in metallic glasses can be interpreted globally as a combination of the spherical-periodic order and local translational symmetry The implications of our study suggest that the glass transition could be visualized mainly as a process involving in local translational symmetry increased from the liquid to glassy states
TL;DR: In this article, three-dimensional ZnO micro/nanorod networks were synthesized through the direct evaporation of metal zinc and graphite powders in Ar and O2 at 910 °C without any catalyst.
Abstract: Three-dimensional ZnO micro/nanorod networks were synthesized through the direct evaporation of metal zinc and graphite powders in Ar and O2 at 910 °C without any catalyst. The micro/nanorod networks of as-synthesized ZnO were characterized by using scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction. The branches within one network show very regular cross orientation. The nanorods follow a growth direction [0001]. Mircrowave absorption properties of the ZnO netlike structures have been investigated in detail. The reflection loss (RL) of the netlike structures and nanotetrapod-shaped ZnO were calculated by using the relative complex permeability and permittivity. And the value of minimum RL for the composite with 50 vol % ZnO netlike structures is −37 dB at 6.2 GHz with a thickness of 4.0 mm. These results provide a wide insight for the netlike structure ZnO as desirable materials for the fabrication of micro/nanoscale functional electromagnetic shield dev...
TL;DR: In this article, the elastic properties and structural parameters of cubic single crystals as well as tetragonal, orthorhombic, and rhombohedral BaTiO3 single domain states are obtained using first-principles calculations under the local density approximation.
Abstract: Predicting the domain structures and properties in both bulk single crystal and thin film ferroelectrics using the phase-field approach requires the knowledge of fundamental mechanical, electrical, and electromechanical coupling properties of a single-domain state. In this work, the elastic properties and structural parameters of cubic single crystals as well as tetragonal, orthorhombic, and rhombohedral BaTiO3 single domain states are obtained using first-principles calculations under the local density approximation. The calculated lattice constants, bulk modulus, and elastic constants are in good agreement with experiments for both the cubic paraelectric phase and the low-temperature ferroelectric phases. Spontaneous polarizations for all three ferroelectric phases and the electrostrictive coefficients of cubic BaTiO3 are also computed using the Berry’s phase approach, and the results agree well with existing experimentally measured values.
TL;DR: In this paper, the corrosion behavior of AZ91 magnesium alloy in dilute NaCl solutions was studied using electrochemical measurements, whereby a corrosion map in terms of electrode potential and chloride concentration [Cl − ] was obtained.
TL;DR: The normalized adsorption coefficient (K/K(HW)) of DPEs indicates that π-π electron-donor-acceptor (EDA) interaction was also important for adsorbed on the surface area of CNTs.
Abstract: Dialkyl phthalate esters (DPEs), with endocrine disrupting functions, are widely used and categorized as priority pollutants. Carbon nanotubes (CNTs) as strong adsorbents could influence the fate, transport, and bioavailability of DPEs in the environment. Understanding adsorptive interactions between CNTs and DPEs is critical to the environmental applications of CNTs. Adsorption of DPEs by one type of single-walled CNTs (SWCNT) and three multiwalled CNTs (MWCNT) was evaluated. For a given CNT, the adsorptive affinity correlated well with hydrophobicity of DPEs with an order of dimethyl phthalate (DMP) DEP-PYR > DBP-PYR. Calculated monolayer adsorption capacities (log Q) were bigger (for DMP and DEP) than or approximately equal to (for DBP) the estimated adsorption capacities (log Q(0)), implying that the DPEs were adsorbed on the surface area of CNTs. For a given DPE, the adsorptive capacities decreased with the increasing outer diameters of CNTs in the order of SWCNT > MWCNT10 > MWCNT20 > MWCNT40.
TL;DR: A chiral nematic liquid crystal/chiral ionic liquid composite with unique electro-optical characteristics is reported that can be switched electrically between three different light states: transparent, scattering, and mirror reflecting.
Abstract: A chiral nematic liquid crystal/chiral ionic liquid composite with unique electro-optical characteristics is reported. The composite can be switched electrically between three different light states: transparent, scattering, and mirror reflecting (see images). Moreover, the reflection bandwidth can be controlled accurately and reversibly by adjusting the intensity of the electric field applied.
TL;DR: Experimental results and theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacialthermal resistance can induce a significant degradation in thermal Conductivity for CNT/Cu composites.
Abstract: Carbon nanotube–copper (CNT/Cu) composites have been successfully synthesized by means of a novel particles-compositing process followed by spark plasma sintering (SPS) technique. The thermal conductivity of the composites was measured by a laser flash technique and theoretical analyzed using an effective medium approach. The experimental results showed that the thermal conductivity unusually decreased after the incorporation of CNTs. Theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacial thermal resistance can induce a significant degradation in thermal conductivity for CNT/Cu composites. The influence of sintering condition on the thermal conductivity depended on the combined effects of multiple factors, i.e. porosity, CNTs distribution and CNT kinks or twists. The composites sintered at 600°C for 5 min under 50 MPa showed the maximum thermal conductivity. CNT/Cu composites are considered to be a promising material for thermal management applications.
TL;DR: The proposed fuzzy-filtering method can get a better noise-attenuation performance when frequency ranges of noises are known beforehand, and can be used for discrete-time nonlinear systems in the Takagi-Sugeno (T-S) form.
Abstract: This paper is concerned with the problem of fuzzy-filter design for discrete-time nonlinear systems in the Takagi-Sugeno (T-S) form. Different from existing fuzzy filters, the proposed ones are designed in finite-frequency domain. First, a so-called finite-frequency l2 gain is defined that extends the standard l2 gain. Then, a sufficient condition for the filtering-error system with a finite-frequency l2 gain is derived. Based on the obtained condition, three fuzzy filters are designed to deal with noises in the low-, middle-, and high-frequency domain, respectively. The proposed fuzzy-filtering method can get a better noise-attenuation performance when frequency ranges of noises are known beforehand. An example about a tunnel-diode circuit is given to illustrate its effectiveness.
TL;DR: In order to enhance the pretreatment effect of dyeing wastewater, comparison experiments of coagulation micro-bubble floatation and conventional air bubble flotation were carried out as discussed by the authors.