bluuebunny/crossref_metadata_2025 huggingface dataset:
β → β + α Isothermal Phase Transformation in Ti17 Titanium Alloy: Chemical Composition and Crystallographic Aspect
Authors: Dehmas Moukrane , Kovac Julien , Appolaire Benoît , Aeby-Gautier Elisabeth , Denand Benoit , Da Costa Teixeira Julien
Published: July 2011

The partitioning of alloying elements between a and b phases was measured at different steps of the isothermal transformation at 710 and 610°C in Ti 17 alloy using EDX analyzer in the TEM. In addition, the transformation crystallography was determined. No differences in substitution elements were observed for a same transformation temperature in the a phase, however the composition varied with the transformation temperature. For the partial transformed specimens, gradient in composition were obtained. Results are compared to calculated compositions using ThermoCalc software and Saunders database.
Influence of Alloying Elements on Precipitation Behavior of VCN in Middle Carbon Steels
Authors: Senuma Takehide , Takemoto Yoshito
Published: July 2011

For lightening the hot forged automotive components such as connecting rods, crank shafts etc. the increase in their yield strength is an important technical issue. Recent developments indicate that it is a promising way to increase the yield strength of the components using the ferrite-pearlite microstructure strengthened by precipitation hardening of VC. In this study, the influence of alloying elements, cooling rate and aging temperature on the precipitation hardening behavior of V containing middle carbon steels was investigated. The precipitation hardening is very sensitive to cooling rate and aging temperature. The addition of Si reduced the sensitivity of the cooling rate. The deformation in the austenite region slightly decreases the precipitation hardening. From a detailed analysis, it was found out that the precipitation hardening is strongly influenced by the γ→α transformation behavior, which indicates that the interphase precipitation plays a significant role for the precipitation hardening.
M3C and M7C3 Carbide Precipitation in Modified H11 Tool Steel
Authors: Mesquita Rafael Agnelli , Kestenbach Hans Jürgen
Published: July 2011

Recent modifications in chemical composition have been applied commercially to high alloy tool steels, using different combinations of Cr, Si and Mo contents. Several reports have been published in the literature about the effects of such modifications on mechanical properties and tool performance, but only a few of these studies were concerned with the effects on secondary carbide formation. In previous papers, improvements in toughness and tempering resistance that were found in a 5% Cr tool steel (type H11 with lower Si contents) have been attributed to particular distributions of Cr-rich M7C3 particles. Although M7C3 carbides have been studied extensively in low alloy steels, some important differences have now been observed by the present authors for high alloy tool steels, especially regarding the effects of Si and Cr. The present work is concerned with the formation of Cr-rich M7C3 as well as Fe-rich M3C particles in modified H11 tool steels, discussing the precipitation sequence and particle distributions developed during tempering within the martensite microstructure. By means of transmission electron microscopy, the effect of Si on M3C cementite formation has been found to be responsible for a substantial change in the distribution of the M7C3 carbide phase, leading to a concentration of these particles at high energy interfaces in interlath and interpackage regions.
Interphase Boundary Precipitation of VC Accompanying Ferrite and Pearlite Transformation in Medium Carbon Steels
Authors: Miyamoto Goro , Behrang Poorganji , Furuhara Tadashi
Published: July 2011

Demands for medium carbon steels with high strength used for forging parts in automobile have been increasing. V addition to such steels leads to interphase boundary precipitation (IBP) of VC and thus an increase of strength. However, mechanism and strengthening effect of IBP have not been clarified in detail. In this study, precipitation of VC accompanying ferrite and pearlite transformations and its effect on hardness have been examined in medium carbon steels microalloyed with 0.3%V. Specimens transformed in a temperature range between 873 and 973K consist of pearlite and small amount of proeutectoid ferrite. Hardness increase by the V addition becomes larger by lowering transformation temperature at these temperatures. Meanwhile the alloying effect of V on the hardness remarkably decreases at 823K where bainite transformation takes place partly. TEM characterization has revealed that VC are precipitated in both of proeutectoid and pearlitic ferrites in the manner of fine rows parallel to the austenite / ferrite interphase boundary. The size of VC decreases and its number density increases by lowering transformation temperature, corresponding to the larger hardness increase. Orientation relationship analyses between ferrite and austenite in the V-added specimen based of EBSD measurements reveals that proeutectoid ferrite grows preferentially towards an austenite grain with which ferrite does not hold a specific orientation relationship, indicating that classical ledge mechanism does not play a role for interphase boundary precipitation of VC in this alloy.
Cluster Dynamics Study of Neutron Irradiation Induced Defects in Fe-12.5at%Cr Alloy
Authors: Gokhman Aleksandr R. , Ulbricht Andreas , Birkenheuer Uwe , Bergner Frank
Published: July 2011

Cluster dynamics (CD) is used to study the evolution of the size distributions of vacancy clusters (VC), self-interstitial atom (SIA) clusters(SIAC) and Cr precipitates in neutron irradiated Fe-12.5at%Cr alloys at T = 573 K with irradiation doses up to 12 dpa and a flux of 140 ndpa/s. Transmission electron microscopy (TEM) and small angle neutron scattering (SANS) data on the defect structure of this material irradiated at doses of 0.6 and 1.5 dpa are used to calibrate the model. A saturation behavior was found by CD for the free vacancy and free SIA concentrations as well as for the number density of the SIAC and the volume fraction of the Cr precipitates for neutron exposures above 0.006 dpa. The CD simulations also indicate the presence of VC with radii less than 0.5 nm and a strong SIAC peak with a mean diameter of about 0.5 nm, both invisible in SANS and TEM experiments. A specific surface tension of about 0.028 J/m2 between the a matrix and the Cr-rich a' precipitate was found as best fit value for reproducing the long-term Cr evolution in the irradiated Fe-12.5%Cr alloys observed by SANS.
On the Effect of Bulk Diffusion on the Initiation of the Discontinuous Precipitation Reaction: Phase-Field Simulations
Authors: Amirouche Lynda , Plapp Mathis
Published: July 2011

Discontinuous precipitation is a solid-state transformation involving the decomposition of a supersaturated matrix into two phases arranged periodically as alternate lamellae or rods, which is accompanied by a grain boundary migration. The rate-limiting step of this process is supposed to be boundary diffusion of solute along grain boundaries. However, volume diffusion is generally present as well, and its influence on the occurrence of the discontinuous precipitation reaction is at present not well understood. We investigate this problem using a phase-field model in which the bulk diffusivity, surface diffusivity and grain boundary mobility can all be varied independently. The main results are that (i) when volume diffusion is the dominant mechanism, a close analogy is observed between the precipitate growth and the growth of a crystalline finger in a channel, and (ii) both the geometry of the precipitate’s tip and the growth velocity are strongly influenced by the relative magnitudes of the bulk and surface diffusivities as well as by the grain boundary mobility. Steady-state growth is possible only for a finite range of precipitate spacings, which is limited for low spacings by a fold singularity and for large spacings by an oscillatory or a tip-splitting instability. The values of these limits are found to depend on the supersaturation as well as on the ratio of bulk and surface diffusivities.
Kinetics of Lamellar Decomposition Reactions in U-Nb Alloys
Authors: Hackenberg Robert E. , Volz Heather M. , Papin Pallas A. , Kelly Ann M. , Forsyth Robert T. , Tucker Tim J. , Clarke Kester D.
Published: July 2011

Discontinuous precipitation (DP) and discontinuous coarsening (DC) reactions have been observed in numerous alloy systems [1]. DP has been observed in the U-Nb system [2, 3, 4, 5]. The U-Nb phase diagram (Fig. 1) exhibits a continuous γ-BCC solid solution at high temperatures and a two-phase mixture of a-orthorhombic and γ-BCC below the 647°C monotectoid isotherm. The DP reaction occurs during continuous cooling and isothermal aging over 300-647°C. No metallographic evidence of a DC reaction in U-Nb has been published, although this is suggested from x-ray observations of distinct changes in the Nb content of the γ phase upon prolonged holding after the DP reaction [2, 3, 6]. This study will provide direct evidence for a DC reaction. Discontinuous and other aging reactions [7] are undesirable in U-Nb alloys, since they degrade corrosion resistance [5], ductility [8], and the shape-memory effect [9]. Hence, an improved understanding of the kinetics of these discontinuous phase transformations in U-Nb alloys is of practical interest.
Transmission Electron Microscopy Study of Microstructural Evolution in Nanograined Ni-Ti Microwires Heat Treated by Electric Pulse
Authors: Delville Remi , Malard Benoît , Pilch Jan , Sittner Petr , Schryvers Dominique
Published: July 2011

Transmission electron microscopy and mechanical testing were employed to investigate the evolution of microstructure and functional superelastic properties of 0.1mm diameter as-drawn Ni-Ti wires subjected to a non-conventional heat treatment by controlled electric pulse current. This method enables a finer control of the recovery and recrystallisation processes taking place during the heat treatment and accordingly a better control on the final microstructure. The best functional properties were obtained for heat-treated Ni-Ti wires having a nanograined microstructure (20-50 nm) partially recovered through polygonization and partially recrystallized. Such microstructure is highly resistant against dislocation slip upon cycling, while microstructures annealed for longer time and showing mostly recrystallized grains were prone to dislocation slip, particularly as the grain size exceeds 100 nm. The density of dislocation defects increased significantly with increasing grain size of the microstructure. The activity of three <100>/{011} slip systems was identified in the largest grains of 500-1200 nm. An additional mode of plastic deformation, {114} compound austenite twinning, was observed in the largest grains of fully recrystallized microstructures. It is proposed that dislocation slip (and possibly deformation twinning) occurring in superelastic cycling is coupled with the stress-induced martensitic transformation.
Evolution of Ar Implanted Amorphous Silicon Dioxide under High Voltage Electron Beam
Authors: Oliviero Erwan , Collin Sophie , Bachelet Cyril , Moeyaert Jeremy , Borodin Vladimir A. , Ruault Marie Odile
Published: July 2011

Amorphous silicon dioxide layers were implanted with 100 keV Ar ions to a relatively high fluence in a tentative to generate cavities in the oxide. Different oxide layers were used, obtained either by thermally growth or by chemical vapor deposition (CVD) on Si substrate. In all SiO2 layers, cavities are not formed in the as-implanted state. However, in the transmission electron microscope, under electron beam, the combined effect of irradiation induced defects and implanted rare gas leads to the formation of cavity bands giving the unique opportunity to observed in-situ cavity growth. The cavity morphology and their distribution are found to be dependent on the silicon dioxide growth process. For thermally grown SiO2 layer, a homogeneous cavity band is formed, centered at the mean ion path, with an average cavity size of 20 nm. For CVD SiO2 layer, slightly smaller cavities are formed in two distinct bands. The formation of cavities is discussed in light of gas and defects interaction and field-induced migration whereas the cavity distribution is discussed in terms of self-organization.
Stress Induced Phase Transformations in TRIP-Steel / Mg-PSZ Composites
Authors: Berek Harry , Aneziris Christos G. , Hasterok Manuel , Biermann Horst , Wolf Steffen , Krüger Lutz
Published: July 2011

Composite materials and micro- and macrostructure designs have been the focus of numerous scientific studies over the past few years according to their crashworthiness [1-3]. Crashworthiness is concerned with the absorption of energy through controlled failure mechanisms and modes that enable a defined load profile during energy absorption [4]. Cellular materials, such as metal foams, are materials which display a unique combination of physical and mechanical properties, e.g. for crash box applications. The defining characteristic of metal foams is a very high porosity, typically in the range of 70 to 90 vol. %. In principle, cellular metals can be manufactured from gas, liquid or solid phases and currently the most advanced methods involve melt-metallurgical processes [5]. Several groups have produced foam structures by using hollow spheres to form the cells of the material [5, 6]. These materials exhibited plateau stresses of 5 MPa and 23 MPa respectively, with volume specific energy absorptions SEA of 2 MJ/m3 and 10 MJ/m3 respectively, up to 50 % strain [6, 7]. By combining ceramics with ductile metals, failure-tolerant metal matrix composites (MMCs) can be created. With regard to application of the MMCs as wear resistant materials in metal forming tools a prolongation of the life time and the resultant reduced equipment downtimes have been achieved by active steel infiltrating of porous zirconia structures with the aid of Ti as activator [8]. A very promising approach concerning zirconia/steel - composite materials with superior mechanical properties has been demonstrated by Guo et al. using a low-alloyed TRIP steel in combination with an Y-PSZ – ceramic [9, 10]. In a previous study honeycomb structures were formed from composites of high-alloyed austenitic stainless TRIP-steel AISI 304 with Mg-PSZ with different mixing proportions due to ceramic extrusion at room temperature and sintering at 1350 °C for 2 h in an 99.9 % Argon atmosphere [11]. One of the most promising manufacturing route to produce open cell composite foams is based on the patent of Schwartzwalder [12] by the replication method using polyurethane sponge as a template. The polymer foam is impregnated in a powder slurry (this first coating contributes as an adhesive porous layer for further coating processes), the ceramic slurry is squeezed out of the functional pores and cold spray coatings are applied in order to eliminate defects out of the squeezing process and reach the critical wall thickness for acceptable mechanical properties. In [13] the authors reported about foams with 90 Vol% high alloyed TRIP-steel and 10 Vol% Mg-PSZ. Up to 50 % compressive strain a remarkable enhancement of the SEA was observed in comparison to comparable structures with TRIP-steel only.
Fullerene-Metal Composites: Phase Transformations During Milling and Sintering
Authors: Santana Ileana Irais , Robles Hernandez Francisco Carlos , Garibay-Febles Vicente , Calderon Hector A.
Published: July 2011

Composites of Fe-C60 and Al C60 produced by mechanical milling and sinterized by Spark Plasma Sintering are investigated with special attention to the mechanical properties of the products. The processing involves phase transformations of the fullerenes that are interesting to follow and characterize. This involves formation of tetragonal/rhombohedral diamond and carbides during sintering and milling. Transmission Electron Microscopy (TEM) and Raman Spectroscopy techniques are also used to confirm preliminary results of X Ray Diffraction (XRD) related to the formation of nanostructures i.e., grain size of the crystals during mechanical milling and after sintering, spatial distribution of phases and the different phases that are developed during processing.
Martensitic Transformations Using a Two-Body Isotropic Potential: Strain-Stress Simulations and Superelasticity in Monocrystals
Authors: Laguna Fabiana , Jagla Eduardo
Published: July 2011

We use an isotropic interaction potential for a set of classical identical particles to model martensitic transformations and the processes that are usually associated with them. We performed 2D numerical simulations of a strain-stress experiment and show that superelastic effect is present in our model.
Effect of Thermomechanical Processing on the Microstructure and Retained Austenite Stability during In Situ Tensile Testing Using Synchrotron X-Ray Diffraction of NbMoAl TRIP Steel
Authors: Pereloma Elena V. , Zhang Lai Chang , Liss Klaus Dieter , Garbe Ulf , Almer Jonathan , Schambron Thomas , Beladi Hossein , Timokhina Ilana B.
Published: July 2011

In this work we compare and contrast the stability of retained austenite during tensile testing of Nb-Mo-Al transformation-induced plasticity steel subjected to different thermomechanical processing schedules. The obtained microstructures were characterised using optical metallography, transmission electron microscopy and X-ray diffraction. The transformation of retained austenite to martensite under tensile loading was observed by in-situ high energy X-ray diffraction at 1ID / APS. It has been shown that the variations in the microstructure of the steel, such as volume fractions of present phases, their morphology and dimensions, play a critical role in the strain-induced transition of retained austenite to martensite.
From Nanocomposite Aerogels to Glass Ceramics for Nuclear Wastes Containment
Authors: Woignier Thierry , Reynes Jerome , Calas Sylvie
Published: July 2011

Nanocomposite aerogel is proposed as a host matrix for the synthesis of glass ceramics. The large porosity is used as a sponge to incorporate chemical species getting a two phases material. We describe the steps of the synthesis of glass ceramics for nuclear waste containment, from nanocomposite aerogels loaded with actinides surrogates (Ce and Nd). The glass synthesis is obtained without melting, by a control of several solid phase transformations: sintering, viscous flow, crystallization and foaming. Thanks to their high resistance to thermal shock and water corrosion, these glass ceramics are certainly good candidates as actinides containment materials.
Influence of the Austempering Temperature on the Microstructure and Crystallography of a Carbide-Free Bainitic Steel
Authors: Hell Jean Christophe , Dehmas Moukrane , Geandier Guillaume , Gey Nathalie , Allain Sebastien , Hazotte Alain , Chateau Jean Philippe
Published: July 2011

We elaborated two carbide-free bainitic steels with different microstructures through specific heat treatments and alloy design. EBSD analysis was used to point out major differences in these microstructures. In-situ characterizations of the bainitic transformation were performed by high energy synchrotron diffraction to go further into the study of each phase characteristics. The elaborated microstructures exhibited various phase fractions of bainitic ferrite, retained austenite and blocks of martensite and retained austenite. Moreover, the volume fraction of retained austenite increased with higher austempering temperatures. On the other hand, the austempering temperatures showed a strong influence on the kinetics of the bainitic transformation. Isothermal transformation under Ms showed a two stage transformation which led first to the formation of self-tempered martensite and then to bainitic ferrite. Furthermore, the evolution of the austenitic cell parameter showed enrichment in carbon ruled by diffusional mechanisms.
Grain Scale Analysis of Variant Selection during the Gamma-Epsilon-Alpha' Phase Transformation in Austenitic Steels
Authors: Malet Loic , Sinclair Chad W. , Jacques Pascal , Godet Stéphane
Published: July 2011

Austenitic steels can exhibit a complex transformation sequence during deformation. Indeed, the austenitic phase transforms first into bands of ε (HCP) martensite. This transformation is then followed by the formation of α’ (BCC) martensite. In this study, the crystallography of the transformation together with the occurrence of variant selection is studied at the scale of individual austenite grains. About ten prior austenite grains deformed at different strain levels in uniaxial tension were analysed by means of EBSD techniques. One of the classical approaches to predict the variant selection phenomenon is based on the calculation of the interaction energy between the macroscopic stress and the shape deformation associated with the formation of the product phase. The formation of the α’ variants was observed to lead to a very strong variant selection that cannot be fully explained by energetic criterion. It is suggested that the crystallography of the transformation sequence can account for the unexpected variants.
Finite Element Simulation and Optimisation of Ageing Precipitation in Nickel Base Superalloys with a Low Gamma-Prime (g’) Volume Fraction
Authors: Tancret Franck , Guillemet Philippe , Fournier Dit Chabert Florent , Le Gall René , Castagné Jean François
Published: July 2011

A finite element approach is used to simulate the precipitation of Ni3(Al,Ti) intermetallics in nickel-based superalloys containing a low volume fraction of spherical g’ precipitates, in which precipitation occurs following nucleation and growth mechanisms. Classical differential equations of nucleation and growth are implemented in the software Comsol (formerly Femlab), to compute the number of precipitates per unit volume and their mean size. Another originality of the model is the use of thermodynamic quantities coming from phase diagram computations (Thermo-Calc), like the temperature variation of the equilibrium g’ volume fraction, and the evolution of the concentration of g’ forming elements (Al, Ti) in the matrix with the volume fraction of precipitates. Once adjusted to experiment in the case of isothermal ageings, the model can be used to simulate precipitation during complex thermal histories. Finally, automatic heat treatment optimisation procedures are proposed and tested, which can reduce heat treatment times by a factor of more than five.
Quasicrystalline Phase Transformation in the Quaternary and Ternary Systems AlCuMnFe and AlPdMn
Authors: Beauchesne Jean Tristan , Caillard Daniel , Quiquandon Marianne , Gratias Denis
Published: July 2011

An uniﬁed structural model has been devised [1] that describes both icosahedral phasesi-AlPdMn and i-AlCuFe. The model suggests that possible icosahedral structures could be found inalloys with general composition Al61:8(PdjCu)21:35(MnjFe)8:29(AljFejMn)4:28(AljCu)4:28. Applied to the systems AlCuMnFe [2] and AlPdFe [3], thisformula leads to the compositions Al66:08Cu21:35Mn8:29Fe4:28 and Al70:36Pd21:35Fe8:29 that have bothbeen synthetized by rapid quenching and annealing.The as-quenched quaternary alloy Al66:08Cu21:35Mn8:29Fe4:28 exhibits a F-icosahedral phase that trans-forms into a decagonal phase after annealing. Its 10-fold axis aligns along one of the 5-fold axes ofthe icosahedral phase. This implies a group-subgroup transformation, with the kernel group ̅5m, anal-ogous to the one observed during CFC to HCP transformations, with kernel ̅3m.The as-quenched and annealed ternary alloy Al70:36Pd21:35Fe8:29 is similar to i-AlPdMn with an iso-morphic substitution of Mn with Fe. A study of the phase diagram of the system AlPdFe [3] showsthat the results are compatible with the structural model proposed here in strong relations with thosepresented in [1] for i-AlPdMn.
Phase Transformations in Amorphous Bilayer Ribbons
Authors: Svec Peter , Svec Sr. Peter , Matko Igor , Skorvánek Ivan , Kováč Jozef , Janickovic Dusan , Vlasák Gabriel
Published: July 2011

Bilayer ribbons were prepared by rapid quenching from the melt using a double-nozzle technique. The composition of the layers was selected from the Fe/Co-Si-B and Fe-Cu-Nb-Si-B systems, respectively. Ribbons with typical thickness of 45-50 microns and width of 6 mm and 10 mm exhibited amorphous structure of both layers in as-quenched state. Temperature dependencies of electrical resistivity, dilatation and magnetization have been investigated in the amorphous state and during crystallization of both layers, which take place at different temperatures. The results combined with investigation of the structures formed in each layer and at the layer interface were compared to those of single-layer ribbons having the compositions of each layer, respectively.
Ordering in Highly Supersaturated Alpha-Fe-C
Authors: Sinclair Chad W. , Perez Michel
Published: July 2011

Molecular dynamics and molecular statics have been used to explore the transition between the partially Zener ordered state of carbon in octahedral sites. In this communication we have specifically used isothermal molecular dynamics with a recent Fe-C EAM potential to examine the observed high temperature transition from the Zener ordered state where carbon resides on only 1/3 of all octahedral sites to a state where all octahedral sites are available for occupation. It is shown that the Zener ordered state begins to disorder at temperatures well below the transition temperature and that this disordering occurs without any spatial correlation.
Experiment Study on ELID Grinding of TN85 Cermets
Authors: Tong Fu Qiang , Zhang Fei Hu , Luan Dian Rong
Published: July 2011

TN85 cermets is one kind of particle reinforced metal matrix composites, which is high hardness, good wear resistance, and bring great difficulties in processing, so it is necessary to study the processing performance. During the test on ELID grinding TN85 cermets, it is found that plastic removal is the main ways during grinding TN85 cermets materials. The powder particle size of W2.5 diamond wheel is successfully used in full removal of TN85 cermets plastic, the surface roughness value of rms: 16.81nm and Ra: 12.52nm. The results showed that: ELID grinding wheel with diamond powder technology can be used in ultra-precision machining TN85 cermets.
Experiment on Non-Uniformity of Material Removal on Wafer Surface in Wafer CMP
Authors: Su Jian Xiu , Du Jia Xi , Chen Xi Qu , Ning Xin , Kang Ren Ke
Published: July 2011

In the manufacturing process of ultra large scale integrated circuits (ULSI), chemical mechanical polishing (CMP) has already become a practical and main planarization technology because of its global and local planarization ability. The non-uniformity of material removal on wafer surface is one of important indicators of surface precision in wafer CMP process. In this paper, According to the σ calculation method, the calculation equation of the non-uniformity of material removal was put forward. Then, the CMP experiments on the non-uniformity of material removal were conducted under different rotational speed on a CMP machine CP-4. The WaferCheck-7200 equipment, with the theory of non-contact capacitive thickness measurement, was used to detect the thickness of each point on silicon wafer surface. After calculation, the non-uniformity of material removal on the silicon surface was obtained under different polishing speed. The test results can provide some theoretical guide for further understanding the form mechanism of the non-uniformity of material removal and the material removal mechanism in wafer CMP.
3D Finite Element Analysis of Pile-up Formation in Abrasive Machining at Low Speed
Authors: Yu Wei , Feng Qiang , Ren Cheng Zu
Published: July 2011

Abrasive machining is widely used as final machining process. It is still challenged to investigate the fundamental knowledge on the formation mechanism of groove and pile-up in single abrasive particle cutting. A 3D finite element analysis model to simulate single abrasive particle scratching on bearing steel (52100) workpiece with low cutting speed is proposed. An adaptive meshing technique is applied to handle large mesh deformation problem of the scratching process. The formation process of groove and pile-up for workpiece material is indentified qualitatively. The simulated results show that cutting speed has little effect on lateral profile. The height and area of pile-up increase with increase of depth of cut.
Diamond Films Synthesis with a DC Arc Plasma Jet: Effect of Substrate Temperature on Quality of Diamond Films
Authors: Chen Rong Fa , Dai Liang Gang , Zhu Rui , Zhang Xian Liang , Liu Tao , Pan Yi , Zuo Dun Weng
Published: July 2011

. High quality diamond film wafers with different thickness are prepared by high power DC arc plasma jet CVD (DCPJ CVD) method using a CH4/Ar/H2 gas mixture. The effect of substrate temperature on the quality of diamond film was studied with theoretical analysis and experimental investigation. The results indicate that different structures in diamond film may grow with different substrate temperatures. The temperatures of 800°C, 900°C and 1000°C were tested in the experiments. The quality of diamond film showed the best at the temperature of 900°C. Characterization by X-ray diffraction, Raman spectroscopy and SEM analysis are also carried out.
Study on Characterization of Cationic Polyelectrolyte Modified Benzoguanamine Formaldehyde/Silica Composite Abrasives Slurry
Authors: Xu Xue Feng , Zhao Bin Shan , Yang Yu Zhi , Guo Quan , Peng Wei
Published: July 2011

In this paper, the adsorption characteristics of cationic polyelectrolyte PDADMAC on BGF particles and the Zeta potential of BGF particles have been investigated. A new type of composite abrasives slurry was obtained with cationic polyelectrolyte modified BGF particles and its polishing performance was studied. Experimental results showed that the Zeta potential of the modified BGF particles was changed from negative to positive and the maximum value (+35mv) was obtained when the adsorption saturation was achieved, and the adsorption capacity of SiO2 abrasives on BGF particles was improved significantly. The material removal rate was 469nm/min with the modified BGF/SiO2 composite abrasives slurry containing 5% SiO2 and 3% modified BGF particles, increasing by 47% and 89% than those of the unmodified BGF/SiO2 composite abrasives slurry (319nm/min) and the single silica abrasives slurry (248nm/min), respectively.
Study on Prediction Models of Milling Force for T10 Hardened Steel
Authors: Wu Jing Quan , Li Guang Hui , Liu Can , Tan Guang Yu
Published: July 2011

To represent the relation between force and cutting parameters in milling T10 hardened steel, single factor milling experiments with different cutting parameters were done. The experimental result showed that there exited maximum inflection point in force curve under different speeds, and the relation between force and cutting parameters could not be represented with an uniform mathmatical equation. Respective prediction modal of milling force in low speed and high speed were set up using least-square method, which was significant at level of α=0.0005, and its result of R- test was higher than 0.98. This study indicates that the applicable prediction modals in milling T10 steel with low and high speed are different, predict modals being set up can be used to estimate milling force.
Study on Speed and Acceleration Characteristics of 100 nm Scale Motion Platform Driven by Linear Servo Motors
Authors: Li Guang Hui , Wu Peng , Ni Xiao Long , Peng Wen Fang , Tan Guang Yu
Published: July 2011

A control method for 100 nm scale motion platform driven by linear servo motors is investigated using a PMAC controller. The control of speed and acceleration is improved by adjusting the PMAC parameters. High-quality speed and acceleration characteristics is obtained, which provides a basis and reference for the application of the platform to high-speed and high-precision feed system.
Slot Grinding of Advanced Ceramics with Brazed Diamond Cut-Off Wheels
Authors: Chen Mei , Zhang Feng , Shen Jian Yun , Guo Hua , Xu Xi Peng
Published: July 2011

Based on the analysis of problems of diamond cut-off wheels used in slot grinding of ceramics at present, a brazed diamond cut-off wheel was produced and analyzed. Two typical advanced ceramics, alumina and silicon nitride, were used as the workpiece materials. In the experiments of slot grinding of ceramics, grinding ratio, wear process of the wheel and grinding quality of the work were studied. Experimental results showed that the brazed diamond cut-off wheel obtained good grinding ratio and abrasive resistance. The surface roughness of ground silicon nitride was better than that of alumina.
Influence of Zinc Particles on Oxidation Resistance of Diamond/Borosilicate Glass Composites
Authors: Wang Yan Hui , Zhang Xiang Hong , Zang Jian Bing , Cheng Xiao Zhe , Zhang Jin Hui
Published: July 2011

Oxidization of diamond in the sintering process of diamond/borosilicate glass composites would result in low compressive fracture strength (CFS) of the grit and uncontrolled expansion with many irregular pores in the composites, causing low bending strength of the tools. In this paper diamond/borosilicate glass composites were prepared by cold pressing and sintering at 850 C for 120 min in air. An active element Zn was incorporated into the composites in order to resolve the above issues. The effects of Zn contents on the properties of the composites was investigated by the bending strength tests, the volume expansion rate tests, differential scanning calorimeter test (DSC), thermogravimetry (TG), X-ray diffraction analysis (XRD), and scanning electron microscope (SEM). The results showed Zn was oxidized and then converted to ZnAl2O4 and Zn2SiO4 phases during sintering. The bending strength improved and the expansion phenomenon was inhibited for the composites with various Zn additions. The maximum bending strength and minimum volume expansion rate were obtained for the composite GZ8. This Zn content resulted in a decrease of volume expansion rate from 8.57% to -20.53%, and an increase in bending strength from 28.49 MPa to 74.02 MPa compared with the composite GZ0. The CFS results of the diamond grits separated from GZ0 and GZ8 was 21N and 26N, respectively.
Raman Analysis of the Silicon Wafer Scratched by Single Point Diamond
Authors: Chen Zhuo , Wei Xin , Xie Xiao Zhu , Ren Qing Lei
Published: July 2011

This paper presents a Raman analysis of the monocrystalline silicon wafer scratched by single point diamond. Si-III and Si-XII phases are found to be existence in the scratched silicon surface, which is the result of the phase transformation. A mathematical model was developed to calculating the molar concentration of phase of the silicon. Based on the mathemathical model, the relationship between the molar concentrations of the Si-I phase and the applied load was analysied.
The Study of Vibration Effects on Precision Grinding Surface Quality
Authors: Bi Guo , Guo Yin Biao
Published: July 2011

The paper was dedicated to surface grinding, in which axisymmetric surface and non-axisymmetric surface are presented. Machined traces deviate from the vibration waveform because of the geometrical interference between the wheel and the workpiece. Simulation and experimental results indicate that the spectrum of the machined trace is competent for the detection of the vibration source. The deviation of the machined trace from the vibration waveform is greatly influenced by operating parameters, and reasonable choice of them is beneficial to surface smoothness.
Numerical and Physical Modelling of Aluminium Barbotage Process
Authors: Saternus Mariola , Merder Tomasz , Warzecha Piotr
Published: July 2011

Today the aluminium refining process, especially barbotage is one of the most essential necessary technological stages in obtaining aluminium. It gives possibility to remove undesirable hydrogen and non-metallic and metallic inclusions from aluminium. Phenomena that take place during the barbotage process are rather complicated, but the knowledge about their character enables to optimize and control this process. Modelling research is used to outline these phenomena. Physical and mathematical modelling can be applied in carrying out aluminium barbotage process. Mathematical modelling uses numerical methods to solve the system of differential equations. The paper presents results of physical and numerical modelling of the refining process taking place in the continuous reactor URC-7000. Physical modelling was carried out for the different flow rate of refining gas (argon). It was in the range between 2 to 25 dm3/min. Numerical calculation was done using commercial program in Computational Fluid Dynamics (CFD). Model Volume of Fluid (VOF) was applied in modelling the multiphase flow. Obtained results were compared in order to verify the numerical settings and correctness of the choice.
Phospho-SXXE/D Motif Mediated TNF Receptor 1–TRADD Death Domain Complex Formation for T Cell Activation and Migration
Authors: Guan Ying-jie , Zhang Zhe , Yu Chen , Ma Li , Hu Weiling , Xu Li , Gao Jin-Song , Chung Chun-Shiang , Wang Lijuan , Yang Zhong-Fa , Fast Loren D. , Chung Alicia S. , Kim Minsoo , Ayala Alfred , Zhuang Shougang , Zheng Shusen , Chin Y. Eugene
Published: July 2011

In TNF-treated cells, TNFR1, TNFR-associated death domain protein (TRADD), Fas-associated death domain protein, and receptor-interacting protein kinase proteins form the signaling complex via modular interaction within their C-terminal death domains. In this paper, we report that the death domain SXXE/D motifs (i.e., S381DHE motif of TNFR1-death domain as well as S215LKD and S296LAE motifs of TRADD-death domain) are phosphorylated, and this is required for stable TNFR1–TRADD complex formation and subsequent activation of NF-κB. Phospho-S215LKD and phospho-S296LAE motifs are also critical to TRADD for recruiting Fas-associated death domain protein and receptor-interacting protein kinase. IκB kinase β plays a critical role in TNFR1 phosphorylation of S381, which leads to subsequent T cell migration and accumulation. Consistently, we observed in inflammatory bowel disease specimens that TNFR1 was constitutively phosphorylated on S381 in those inflammatory T cells, which had accumulated in high numbers in the inflamed mucosa. Therefore, SXXE/D motifs found in the cytoplasmic domains of many TNFR family members and their adaptor proteins may serve to function as a specific interaction module for the α-helical death domain signal transduction.
The Purinergic G Protein-Coupled Receptor 6 Inhibits Effector T Cell Activation in Allergic Pulmonary Inflammation
Authors: Giannattasio Giorgio , Ohta Shin , Boyce Joshua R. , Xing Wei , Balestrieri Barbara , Boyce Joshua A.
Published: July 2011

We show that the P2Y6 receptor, a purinergic G protein-coupled receptor with a high affinity for the nucleotide uridine diphosphate, is an important endogenous inhibitor of T cell function in allergic pulmonary inflammation. Mice conditionally deficient in P2Y6 receptors [p2ry6 (flox/flox);cre/+ mice] exhibited severe airway and tissue pathology relative to P2Y6-sufficient [p2ry6 (flox/flox)] littermates (+/+ mice) when treated intranasally with an extract of the dust mite Dermatophagoides farinae (Df). P2Y6 receptors were inducibly expressed by lung, lymph node, and splenic CD4+ and CD8+ T cells of Df-treated +/+ mice. Df-restimulated P2Y6-deficient lymph node cells produced higher levels of Th1 and Th2 cytokines, and polyclonally stimulated P2Y6-deficient CD4+ T cells proliferated faster than comparably stimulated P2Y6-sufficient cells. The absence of P2Y6 receptors on CD4+ cells, but not APCs, was sufficient to amplify cytokine generation. Thus, P2Y6 receptors protect the lung against exuberant allergen-induced pulmonary inflammation by inhibiting the activation of effector T cells.
Cutting Edge: β-Catenin Is Dispensable for T Cell Effector Differentiation, Memory Formation, and Recall Responses
Authors: Prlic Martin , Bevan Michael J.
Published: July 2011

The molecular mechanisms that regulate mature T cell fate and enable cells to differentiate into memory T cells are largely unknown. Memory T cells share certain key features with stem cells: they both have the ability to self-renew and are long-lived. The Wnt–β-catenin signaling pathway is a key player in regulating stem cell self-renewal and differentiation. We generated a conditional knockout mouse that specifically lacks β-catenin in mature T cells and report in this article that β-catenin is not involved in regulating effector versus memory T cell differentiation. β-catenin–deficient memory T cells were phenotypically and functionally indistinguishable from control cells and made normal recall responses. β-catenin deficiency does not affect T cell migration, T cell function in a model of chronic infection, or lymphopenia-induced proliferation. Together, our data suggest that self-renewal and differentiation are regulated differently in memory T cells compared with epithelial and hematopoietic stem cells.
Bacteroides fragilis Enterotoxin Upregulates Intercellular Adhesion Molecule-1 in Endothelial Cells via an Aldose Reductase-, MAPK-, and NF-κB–Dependent Pathway, Leading to Monocyte Adhesion to Endothelial Cells
Authors: Roh Hyun Cheol , Yoo Do Young , Ko Su Hyuk , Kim Young-Jeon , Kim Jung Mogg
Published: July 2011

Enterotoxigenic Bacteroides fragilis (ETBF) produces a ∼20-kDa heat-labile enterotoxin (BFT) that plays an essential role in mucosal inflammation. Although a variety of inflammatory cells is found at ETBF-infected sites, little is known about leukocyte adhesion in response to BFT stimulation. We investigated whether BFT affected the expression of ICAM-1 and monocytic adhesion to endothelial cells (ECs). Stimulation of HUVECs and rat aortic ECs with BFT resulted in the induction of ICAM-1 expression. Upregulation of ICAM-1 was dependent on the activation of IκB kinase (IKK) and NF-κB signaling. In contrast, suppression of AP-1 did not affect ICAM-1 expression in BFT-stimulated cells. Suppression of NF-κB activity in HUVECs significantly reduced monocytic adhesion, indicating that ICAM-1 expression is indispensable for BFT-induced adhesion of monocytes to the endothelium. Inhibition of JNK resulted in a significant attenuation of BFT-induced ICAM-1 expression in ECs. Moreover, inhibition of aldose reductase significantly reduced JNK-dependent IKK/NF-κB activation, ICAM-1 expression, and adhesion of monocytes to HUVECs. These results suggest that a signaling pathway involving aldose reductase, JNK, IKK, and NF-κB is required for ICAM-1 induction in ECs exposed to BFT, and may be involved in the leukocyte–adhesion cascade following infection with ETBF.
Omega-3 Fatty Acid-Derived Mediators 17(R)-Hydroxy Docosahexaenoic Acid, Aspirin-Triggered Resolvin D1 and Resolvin D2 Prevent Experimental Colitis in Mice
Authors: Bento Allisson Freire , Claudino Rafaela Franco , Dutra Rafael Cypriano , Marcon Rodrigo , Calixto João B.
Published: July 2011

Resolvins of the D series are generated from docosahexaenoic acid, which are enriched in fish oils and are believed to exert beneficial roles on diverse inflammatory disorders, including inflammatory bowel disease (IBD). In this study, we investigated the anti-inflammatory effects of the aspirin-triggered resolvin D1 (AT-RvD1), its precursor (17(R)-hydroxy docosahexaenoic acid [17R-HDHA]) and resolvin D2 (RvD2) in dextran sulfate sodium (DSS)- or 2,4,6-trinitrobenzene sulfonic acid-induced colitis. Our results showed that the systemic treatment with AT-RvD1, RvD2, or 17R-HDHA in a nanogram range greatly improved disease activity index, body weight loss, colonic damage, and polymorphonuclear infiltration in both colitis experimental models. Moreover, these treatments reduced colonic cytokine levels for TNF-α, IL-1β, MIP-2, and CXCL1/KC, as well as mRNA expression of NF-κB and the adhesion molecules VCAM-1, ICAM-1, and LFA-1. Furthermore, AT-RvD1, but not RvD2 or 17R-HDHA, depended on lipoxin A4 receptor (ALX) activation to inhibit IL-6, MCP-1, IFN-γ, and TNF-α levels in bone marrow-derived macrophages stimulated with LPS. Similarly, ALX blockade reversed the beneficial effects of AT-RvD1 in DSS-induced colitis. To our knowledge, our findings showed for the first time the anti-inflammatory effects of resolvins of the D series and precursor 17R-HDHA in preventing experimental colitis. We also demonstrated the relevant role exerted by ALX activation on proresolving action of AT-RvD1. Moreover, AT-RvD1 showed a higher potency than 17R-HDHA and RvD2 in preventing DSS-induced colitis. The results suggest that these lipid mediators possess a greater efficacy when compared with other currently used IBD therapies, such as monoclonal anti-TNF, and have the potential to be used for treating IBD.
Contribution of Alanine-76 and Serine Phosphorylation inα-Synuclein Membrane Association and Aggregation in Yeasts
Authors: Fiske Michael , Valtierra Stephanie , Solvang Keith , Zorniak Michael , White Michael , Herrera Sara , Konnikova Alina , Brezinsky Rebecca , DebBurman Shubhik
Published: July 2011

In Parkinson's disease (PD), misfolded and aggregatedα-synuclein protein accumulates in degenerating midbrain dopaminergic neurons. The amino acid alanine-76 inα-synuclein and phosphorylation at serine-87 and serine-129 are thought to regulate its aggregation and toxicity. However, their exact contributions toα-synuclein membrane association are less clear. We found thatα-synuclein is indeed phosphorylated in fission yeast and budding yeast, the two models that we employed for assessingα-synuclein aggregation and membrane association properties, respectively. Surprisingly, blocking serine phosphorylation (S87A, S129A, and S87A/S129A) or mimicking it (S87D, S129D) alteredα-synuclein aggregation in fission yeast. Either blocking or mimicking this phosphorylation increased endomembrane association in fission yeast, but only mimicking it decreased plasma membrane association in budding yeast. Polar substitution mutations of alanine-76 (A76E and A76R) decreasedα-synuclein membrane association in budding yeast and decreased aggregation in fission yeast. These yeast studies extend our understanding of serine phosphorylation and alanine-76 contributions toα-synuclein aggregation and are the first to detail their impact onα-synuclein's plasma membrane and endomembrane association.
Bridging Molecular Genetics and Biomarkers in Lewy Body and Related Disorders
Authors: Ho Gilbert J. , Liang Willie , Waragai Masaaki , Sekiyama Kazunari , Masliah Eliezer , Hashimoto Makoto
Published: July 2011

Recent advances have been made in defining the genetic and molecular basis of dementia with Lewy bodies (DLBs) and related neurodegenerative disorders such as Parkinson′s disease (PD) and Parkinson′s disease dementia (PDD) which comprise the spectrum of “Lewy body disorders” (LBDs). The genetic alterations and underlying disease mechanisms in the LBD overlap substantially, suggesting common disease mechanisms. As with the other neurodegenerative dementias, early diagnosis in LBD or even identification prior to symptom onset is key to developing effective therapeutic strategies, but this is dependent upon the development of robust, specific, and sensitive biomarkers as diagnostic tools and therapeutic endpoints. Recently identified mutations in the synucleins and other relevant genes in PD and DLB as well as related biomolecular pathways suggest candidate markers from biological fluids and imaging modalities that reflect the underlying disease mechanisms. In this context, several promising biomarkers for the LBD have already been identified and examined, while other intriguing possible candidates have recently emerged. Challenges remain in defining their correlation with pathological processes and their ability to detect DLB and related disorders, and perhaps a combined array of biomarkers may be needed to distinguish various LBDs.