Application of high magnetic fields in advanced materials processing

Recently,steady magnetic fields avail-able from cryogen-free superconducting magnets open up new ways to process materials. In this paper,the main results obtained by using a high magnetic field to process several advanced materials are re-viewed. These processed objects primarily include superconducting,magnetic,metallic and nanome-ter-scaled materials. It has been found that a high magnetic field can effectively align grains when fab-ricating the magnetic and non-magnetic materials and make inclusions migrate in a molten metal. The mechanism is discussed from the theoretical view-point of magnetization energy.     

The Impact of Nanocomposite Materials on Lithium Ion Batteries

1 Results Lithiumion batteries have become the power source of choice for consumer electronic devices such as cell phones and laptop computers due to their high energy density and long cycle life. In addition,lithium-ion batteries are expected to be a major breakthrough in the hybrid vehicle field.Despite their successful commercial application,further performance improvement of the lithium ion battery is still required.Nanomaterials and nanotechnologies can lead to a new generation of lithium secondary batteries.Here we present recent progress on nanocomposite materials and nanotechniques in our studies for anode materials of lithium rechargeable batteries.     

Theory of Numerical Modeling of Constitutive Relation for Geotechnical Materials

Under the direction of the principle of interaction between plastic volumetric and shear strains, the general expression of constitutive relation for geotechnical materials has been derived within the framework of irreversible thermo- dynamics. The constitutive modeling, in fact, is an inverse problem that belongs to the medium inverse problems of model identification, which is expressed as a reversion of coefficient of differential equation. Thus the constitutive modeling of geotechnical materials will become the reversion of coefficient functions of the general expression of constitutive relation, which is carried out in the stress field （p,q） by means Of numerical techniques, so that is called numerical modeling. Applying the numerical modeling, a number of plasticity-based models for clay and sand have been obtained, which are able to characterize the fundamental features of deformation for geotechnieal materials. In addition, the approach of numerical modeling also can be applied to the situation of unsaturated soils by means of the Bishop＇s effective stress formula and Khalili＇s expression of effective stress parameter.     

Effects of hyaluronic acid－chitosan－gelatin complex on the apoptosis and cell cycle of L929 cells

With the development in the field of tissue engineering, the interaction between biomaterials and cells has been deeply studied. Viewing the cells seeded on the surface of materials as an organic whole, cell cycle and apoptosis are analyzed to deepen the study of cell compatibility on biomaterials, while cell proliferation and differentiation are studied at the same time. In this paper, hyaluronic acid is incorporated into the chitosan-gelatin system. Propidium iodide (PI) was used in cell cycle analysis and the double-staining of cells with annexin-V and PI was applied in cell apoptosis analysis. The results show that incorporated hyaluronic acid shortens the adaptation period of cells on the material surface, and then cells enter the normal cell cycle quickly. In addition, added hyaluronic acid inhibits cell apoptosis triggered by the membranes. Therefore, hyaluronic acid improves the cell compatibility of chitosan-gelatin system and benefits the design of biomimetic materials.     

Field Emission of SiCN Thin Films Bombarded by Ar^＋ Ions

SiCN thin films were synthesized by a radio frequency chemical vapor deposition (RFCVD) system on P-type Si (1 0 0) wafers using C2H4, SiH4 and N2 as raw materials.In order to get rid of the oxygen absorbed on the surface and improve the characteristics of electron field emission, Ax^ ions of low energy were used to bombard the samples. The field emission characteristics of SiCN thin films before and after Ar^ bombardment were studied in the super vacuum environment of 10^-6 Pa. It was showed that the turn-on field (defined as the point where the current-voltage curve shows a sharp increase in the current density) decreased from 38 V/μm before bombardment to 25 V/μm after bombardment. And the maximum emission current density increased from 159. 2 to 267. 4 μA/cm^2. The composition before and after Ar^ bombardment was compared using X-ray photoelec-tron spectroscopy (XPS). Our results illustrated that the field emission characteristics were improved after the bombardment of Ar^ .     

Application of mesoscale modeling optimization to development of advanced materials

The rapid development of computer modeling in recent years offers opportunities for materials preparation in a more economic and efficient way. In the present paper, a practicable route for research and development of advanced materials by applying the visual and quantitative modeling technique on the mesoscale is introduced. A 3D simulation model is developed to describe the microstructure evolution during the whole process of deformation, recrystallization and grain growth in a material containing particles. In the light of simulation optimization, the long-term stabilized fine grain structures ideal for high-temperature applications are designed and produced. In addition, the feasibility, reliability and prospects of material development based on mesoscale modeling are discussed.     

Microstructure-based multiphysics modeling for semiconductor integration and packaging

Semiconductor technology and packaging is advancing rapidly toward system integration where the packaging is co-designed and co-manufactured along with the wafer fabrication. However, materials issues, in par- ticular the mesoscale microstructure, have to date been excluded from the integrated product design cycle of electronic packaging due to the myriad of materials used and the complex nature of the material phenomena that require a multiphysics approach to describe. In the context of the materials genome initiative, we present an overview of a series of studies that aim to establish the linkages between the material microstructure and its responses by considering the multiple perspectives of the various mul- tiphysics fields. The microstructure was predicted using thermodynamic calculations, sharp interface kinetic models, phase field, and phase field crystal modeling techniques. Based on the predicted mesoscale microstruc- ture, linear elastic mechanical analyses and electromigra- tion simulations on the ultrafine interconnects were performed. The microstructural index extracted by a method based on singular value decomposition exhibits a monotonous decrease with an increase in the interconnect size. An artificial neural network-based fitting revealed a nonlinear relationship between the microstructure index and the average yon Mises stress in the ultrafine interconnects. Future work to address the randomness of microstructure and the resulting scatter in the reliability is discussed in this study.     

Nano Structure Plays an Important Role in the Present and Future Anode Materials of Li-ion Batteries

1 ResultsLi-ion batteries are the most promising secondary batteries for IT and EV applications, where it is required to increase the capacity and power capability to a great extent. In responding to the demand we have been studied on the anode materials especially paying attention on the improved graphite active materials and modified silicon. In both cases we realized that the nano-structured design plays an important role. In this paper the examples of nano-size structure working in the actual materials will be shown.     

Mechanism of Microwave Effects on Conductivity of Solution

The relation between microwave conductivity and normal conductivity of solution is compared in this thesis. By building mathematical model and theoretical analyses, it indicates that the relationship of in situ conductivity of solution in microwave field and temperature is similar to that in non-microwave field. It can be expressed by quadratic equation but the values of both conductivities are different. Microwave field has effect on the mean path δ or hot vibrational frequency v of ions in solution. In microwave field, the mean energy barrier, which ions must surmount as they transit, is the function relation to temperature.     

Safety characteristics of Li-ion batteries evaluated by in situ measurement techniques

Li-ion batteries hold an important place in the field of high power batteries because of their high open circuit voltage and associated high energy density. However, the safety is less satisfactory; therefore, the study of the factors that affect the safety of Li-ion batteries has much meaning to the safety design. In this paper, a set of apparatus was developed for in situ measurements, and several commercial materials including electrolyte, separator and electrode materials for Li-ion batteries were investigated by the in situ method. The results showed： 1） The electrolyte vapor pressure is influenced significantly by the component with low boiling point and increases rapidly with the increasing of temperature; 2） the shutdown of separator occurs at around 135℃ and the impedance increases approximately by two orders of magnitude; 3） carbon anode materials affect the most the volume changes of the cell, and the change for a graphite anode is much greater than that of a glassy carbon anode.     

Enhanced mechanical properties and formability of 316L stainless steel materials 3D-printed using selective laser melting

This study is conducted to develop an innovative and attractive selective laser melting (SLM) method to produce 316L stainless steel materials with excellent mechanical performance and complex part shape. In this work, the subregional manufacturing strategy, which separates the special parts from the components using an optimized process, was proposed. The results showed that produced 316L materials exhibited superior strength of~755 MPa and good ductility. In the as-built parts, austenite with preferred orientation of the (220) plane, δ-ferrite, and a small amount of CrO phases were present. In addition, the crystal size was fine, which contributed to the enhancement of the parts' mechanical properties. The structural anisotropy mechanism of the materials was also investigated for a group of half-sized samples with variable inclination directions. This technique was used to fabricate a set of impellers with helical bevels and high-precision planetary gears, demonstrating its strong potential for use in practical applications.     

Effect of Coordinate Bond in Molecular Recognition of Enrofloxacin with Imprinted Polymers

1 Results Molecular imprinting is a technique for the preparation of functional materials with molecular recognition properties.Molecular imprinted polymers (MIPs) have become an increasingly active field of study for the construction of new material capable of molecular recognition.In general,MIPs are synthesized by polymerization of cross-linking complexes of template molecules and functional monomers.After removing the template molecules from de polymers,binding sites are formed by functional monomer derived residues complementary for the template molecules[1]. According to the principle,the stability of monomer-template complexes present in the solution prior to polymerization as well as the polymerization reaction itself undoubtedly play a dominant role in determining the recognition performance of the polymer.     

Nano-bio interfaces probed by advanced optical spectroscopy: From model system studies to optical biosensors

Research in biology and medicine is a rapidly expanding field incorporating some of the most fundamental questions concerning structure, function, and purpose. The forefront of new research demands access to advanced techniques and instrumentation capable of probing these unanswered questions. Over the past several decades, nano-scale materials and devices ranging from quasione dimensional quantum dots to two dimensional graphene sheets have been engineered and have found applications in nano-bio imaging and spectroscopy. In this review, the incorporation of nanomaterials into three influential spectroscopic and microscopic techniques including fluorescence microscopy, surface plasmon resonance, and sum frequency generation will be introduced. Fluorescence imaging has visualized nanomaterials as compliments or replacements to comparable organic fluorphores, act as a quencher for FRET-based sensing, and serve as a nanoscaffold for molecular beacons. Their versatility in coating materials makes nanomaterials an excellent targeting molecule for any cellular macromolecule or structure. In addition to the targeting capabilities of nanomaterials in fluorescence imaging, surface plasmon resonance has incorporated nanomaterials for applications in signal enhancement, selectivity of target molecules, and the development of more refined and accurate detection. Functionalized nano-particles enhance the capabilities of sum frequency generation vibrational spectroscopy by providing unique surface chemistry which alters target molecule interactions and orientations. In summary, the incorporation of nanomaterials has greatly enhanced the field of biology and medicine and has allowed for the continual advancement of not only research but instrument development.     

Experimental Research on Methane Control of Mining Upper Protective Layers

In order to solve coal and gas outbursts during mining coal seam,studying on related problems were carried out. According to the theories of mining upper protective layer,proper mining plan were designed and performed through field experiment. By means of examining several parameters obtained from the field experiment,the protective effects were evaluated and the protective scope and related parameters were determined. The results of field experiment show that the danger of outbursts was evidently eliminated and the method of mining protective layers is effective and the safety and economic benefits are remarkable. The research has really applied worth and will give beneficial references to mining area with analogous conditions.     

Influence of Thermal Flow Field of Cooling Tower on Recirculation Ratio of a Direct Air-Cooled System for a Power Plant

In order to get thermal flow field of direct air-cooled system, the hot water was supplied to the model of direct air-cooled condenser（ACC）. The particle image velocimetery （PIV） experiments were carried out to get thermal flow field of a ACC under different conditions in low velocity wind tunnel, at the same time, the recirculation ratio at cooling tower was measured, so the relationship between flow field characteristics and recirculation ratio of cooling tower can be discussed. From the results we can see that the flow field configuration around cooling tower has great effects on average recirculation ratio under cooling tower. The eddy formed around cooling tower is a key reason that recirculation produces. The eddy intensity relates to velocity magnitude and direction angle, and the configuration of eddy lies on the geometry size of cooling tower. So changing the flow field configuration around cooling tower reasonably can decrease recirculation ratio under cooling tower, and heat dispel effect of ACC can also be improved.     

The effects of the guide field on the structures of electron density depletions in collisionless magnetic reconnection

Two-dimensional particle-in-cell simulations are performed to investigate the formation of electron density depletions in collisionless magnetic reconnection.In anti-parallel reconnection,the quadrupole structures of the out-of-plane magnetic field are formed,and four symmetric electron density depletion layers can be found along the separatrices due to the effects of magetic mirror.With the increase of the initial guide field,the symmetry of both the out-of-plane magnetic field and electron density depletion layers is distorted.When the initial guide field is sufficiently large,the electron density depletion layers along the lower left and upper right separatrices disappear.The parallel electric field in guide field reconnection is found to play an important role in forming such structures of the electron density depletion layers.The structures of the out-of-plane magnetic field By and electron depletion layers in anti-parallel and guide field reconnection are found to be related to electron flow or in-plane currents in the separatrix regions.In anti-parallel reconnection,electrons flow towards the X line along the separatrices,and are directed away from the X line along the magnetic field lines just inside the separatrices.In guide field reconnection,electrons can only flow towards the X line along the upper left and lower right separatrices due to the existence of the parallel electric field in these regions.     

Identification of weed species with hyperaccumulative characteristics of heavy metals

In order to promote the effective and economic remediation of soils contaminated with single Cd and Cd combined with Ph, Cu and Zn, a field-screening study on weed hyperaccumulators was carried out on the basis of field pot-culture experiments used to determine characteristics of weed plants enduring and accumulating heavy metals. In this study, 54 weed species belonging to 20 families from agricultural fields of the Shengyang suburbs were tested. The results showed that Taraxracum mongolicum, Solanum nigrum and Conyza canadensis could strongly tolerate single Cd and Cd-Pb-Cu-Zn combined pollution, had high Cd-accumulative ability, and generally possessed basic characteristics of hyperaccumulators. Because there are synergic and antagonistic effects among Cd, Pb, Cu and Zn, singlefactor pollution tests should be done as well as combined pollution tests during the identification of hyperaccumulators to ensure the efficiency of phytoremediation and the practical significance of hyperaccumulators identified. The field pot-culture experiment should be a new tentative method to screen out accumulative and tolerant species in view of its obvious advantages such as simple operation, low cost, and easy identification of investigated plants.     

Adjustable character of microwave attenuation in BaTiO3 electrorheological fluids

The behavior of microwave attenuation in BaTiO3 electrorheological fluids is studied when considering microwave propagation in the directions perpendicular and parallel to the particle chains, respectively. In the former case, the microwave attenuation increases with field strength when the particle concentration is low, and the increase of the particle concentration can also increase the microwave attenuation. However, when the particle concentration exceeds a critical value, the attenuation will first increase then decrease with field strength. At the same time, the higher the field strength, the greater the change of microwave attenuation. Moreover, there is a saturation field strength. When the field strength is lower than the saturated one, the change of microwave attenuation is fast. On the other hand, in the case of microwave propagation parallel to the particle chains, the microwave attenuation increases with the field strength monotonously. In addition, the variation of microwave attenuation with the field strength shows relaxation effect. The adjustable character of microwave attenuation in BaTiO3 ER fluids can be attributed to the dielectric changes resulting from the field-induced-structural transformation and the polarization of BaTiO3.     

Ferroelectricity of weak-polar organic molecules in alternate Langmuir-Blodgett multilayer films

Pyroelectric material is a polar solid and has been interested since the 1960s. Today it is one of important materials used in infrared detectors[1]. With the development of the devices, the focus point on the materials applied has been transferred from bulk materials to film ones. Ferroelectric material is a kind of pyroelectric materials which spontaneous polarization can be reversed with the direction change of external electric field. Observation of ferroelectric hysteresis loop or not cou…     

First-principles study of the effects of Si doping on geometric and electronic structure of closed carbon nanotube

The effects of Si doping on geometric and electronic structure of closed carbon nanotube （CNT） are studied by, a first-principles method, DMol. It is found that the local density of states at the Fermi level （Er） increases due to the Si-doping and the non-occupied states above the Er go down toward the lower energy range under an external electronic field. In addition, due to the doping of Si, a sub-tip on the CNT cap is formed, which consisted of the Si atom and its neighbor C atoms. From these results it is concluded that Si-doping is beneficial to the CNT field emission properties.