bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Thermoelectric Properties of CoSb3-yTey
Authors: Ur Soon Chul , Kim Il Ho
Published: March 2009

Te-doped CoSb3 was prepared by the encapsulated induction melting, and its doping effects on the thermoelectric properties were investigated. Single phase d-CoSb3 was successfully obtained by the subsequent annealing at 773K for 24 hours. Tellurium atoms acted as electron donors by substituting antimony atoms. Thermoelectric properties were remarkably improved by the appropriate doping. Dimensionless figure of merit was obtained to be 0.83 at 700K for the CoSb2.8Te0.2 specimen.
Sinterbility of (Bi4-xLax)Ti3O12 Ceramics
Authors: Siriprapa Pasinee , Watcharapasorn Anucha , Jiansirisomboon Sukanda
Published: March 2009

This research studied the effects of sintering temperature and La3+ doping content on phase, microstructure and densification of bismuth lanthanum titanate (Bi4-xLaxTi3O12; BLT) ceramics when x = 0, 0.25, 0.5, 0.75 and 1.0, respectively. The BLT powders were prepared using a mixed-oxide method. The mixtures were calcined at 750°C for 4 h before being pressed and sintered at 1000-1150°C for 4 h. The result of phase analysis by X–ray diffraction (XRD) indicated the existence of orthorhombic phase for all sintering temperatures. The XRD peak intensities of the ceramics showed preferred orientation of a particular set of {00l}-type planes. The ceramics mainly composed of plate-like grains. Increasing the sintering temperature increased grain size and increased preferred grain orientation. The present of La3+ in BLT ceramics reduced preferred orientation especially at higher sintering temperature. Results of microstructural investigation agreed well with X-ray diffraction patterns.
ESR and Optical Absorption Spectra of Copper (II) Ions in Glasses
Authors: Kaewkhao Jakrapong , Rhianphumikarakit S. , Udomkan N.
Published: March 2009

Glasses in the system 20Na2O-Al2O3-13B2O3-6.3CaO-0.2Sb2O3-1.5PbO2-(58-x)SiO2-xCuO were prepared with x = 0.0, 0.2, 0.4, 0.6 and 0.8 mol% respectively. ESR absorption spectra due to Cu2+ (3d9) ions show that the ESR signal at 0.2 and 0.4 mol%CuO were similarity, the perpendicular g-value,g^ can be observed at 2.06 whereas the parallel g-value,g// cannot be observed. The line width of board line centers were depends on the increasing of concentration of CuO-doped. CuO-doped glasses give rise light blue green color. Confirm from optical absorption techniques as UV-VIS measurment reported were recorded at room temperature. The absorption band near 800 nm (2B1g®2B2g) is due to Jahn-Teller effect of Cu2+. Also absorption band at around 400 nm (2B1g®2Eg) could be found due to d-d transition of Cu2+ ion in the CuO doped glasses. The results obtained suggest that Cu ions substitutes as an accepted center for [SiO2]4+ in oxygen octahedral rhombohedral distortion.
Controlled-Release Material for Urea Fertilizer from Polylactic Acid
Authors: Papangkorn J. , Isaraphan C. , Phinhongthong S. , Opaprakasit Mantana , Opaprakasit Pakorn
Published: March 2009

Urea fertilizer is a major source of nitrogen, which is one of the essential nutrients for plant growth. Due to its uncontrollable release, this chemical can be wasted easily by leaching and volatilization that can adversely cause the contamination to the environment. In this work, a controlled-release material for urea fertilizer has been prepared by using degradable polylactic acid. Unlike other conventional controlled-release system, the resulting material is able to provide an efficient supply of urea fertilizer, without causing further contamination to the environment from residue material, as polylactic acid can be degraded in the environment. Micron-size particles of polylactic acid coated urea were prepared by employing atomizing technique. Effect of the preparation conditions; urea/PLA composition, PLA concentration, and pressure of atomizing gun on the particle size of material are investigated. The urea release rate of these samples is then studied by employing UV-Visible spectrophotometer. In addition, the effect of preparation conditions on shape and morphology of sample is determined by using Scanning Electron Microscope (SEM).
Controlled-Release Materials for Fertilizer Based on Lactic Acid Polymers
Authors: Jintakanon N. , Opaprakasit Pakorn , Petchsuk Atitsa , Opaprakasit Mantana
Published: March 2009

ontrolled-release materials for urea are prepared by spray coating urea granulates with lactic acid based homo- and co-polymers solutions. Percent coating as a function of polymer types, molecular weight, polymer concentration, and dose applications are examined by gravimetric analysis. Percentage of urea dissolution in water of the coated fertilizer is measured by monitoring refractive index of the solutions. Morphology of the polymer coating surfaces is revealed by Scanning Electron Microscopy (SEM). It was found that an amount of cracks and pin-holes, which is dependent on polymer types and molecular weight, plays a significant role in controlling the rate of urea release. Results from urea dissolution test also suggests that the synthesized poly(lactic acid-co-ethylene terephthalate) show urea-holding efficiency comparable to that of commercial PLA, despite its much lower molecular weight, indicating that the copolymer is potentially suitable for this specific application.
Ferroelectric Properties of Sn-Doped PZT–PNN Ceramics
Authors: Sutjarittangtham Krit , Intatha Uraiwan , Eitssayeam Sukum , Rujijanagul Gobwute
Published: March 2009

Binary system of 0.45Pb(Zr1/2Ti1/2)O3–0.55Pb(Ni1/3Nb2/3)O3with a composition close to the morphotropic phase boundary were investigated as a function of Sn doping (0.0-8.0 mole%). X-ray analysis showed that pure perovskite phase was observed for all samples. The density of the ceramic samples was increased with an increase of Sn concentration. However, microstructural analysis showed that Sn-doping has not a significant impact on grain size. Moreover, the increasing Sn-contant can reduce the remanent polarization but increase the dielectic contant.
A New Electrostatic Dispersion Method for Fine Powder in Air
Authors: Xu Zheng , Lu Shou Ci
Published: March 2009

A new electrostatic dispersion device was designed to reduce the agglomeration of fine powder in the air. This device is using the repulse force between particles which charged the same charge to prevent the particles from reuniting. The effects of charge voltage, particle size, the distant between electrode, and moisture content on the dispersion degree of the powder are discussed. The invalidation time of the electrostatic dispersion is also highlighted in the paper. The results show that the electrostatic dispersion is an effective method for the fine powders in the air. The charge voltage is the most important parameter for the dispersion. Middle size particle got best dispersion. When the distance between the electrodes is 24cm, the dispersion degree reaches the maximum. The humidity of the powder not only affects the charge of the powder, but also affects the dispersion degree of the powder.
Preparation of SiO2 Coated Cenosphere and Characterization of the Composite Powder
Authors: Su Ying , Lv Xing Dong , Gai Guo Sheng , Yang Yu Fen
Published: March 2009

An attempt was made to prepare the SiO2/cenosphere composite, for which a dense layer of SiO2 particles were successfully coated on the surface of cenospheres by chemical precipitation technique. Surface morphology was observed under SEM, and the exterior constitution was examined through EDX. The result indicated that the amount of SiO2 particles coating on cenospheres decreased with the increasing pH value and the declining reaction temperature, and the particle size reduced as reaction temperature fell down.
Surface Modification of Basic Magnesium Sulfate Whiskers
Authors: Han Yue Xin , Li Li Xia , Chen Xu , Zhang Song Bo , Wang Yu Bin , Wei Xin Chao
Published: March 2009

Surface modification was conducted on the basic magnesium sulfate whiskers (MSW) using sodium stearate. The modification performance was evaluated by comparing the activation index, oil absorption value, rest angle, and dispersibility in polypropylene (PP) resin prior to and after treatment. It was found that the surface properties of the whiskers were improved by sodium stearate modification. In particular, the improvement in the dispersibility in PP was significant. Surface characterization was conducted using scanning electron microscopy (SEM), thermogravimetric-differential scanning calorimetry (TG-DSC) and fourier transform infrared spectroscopy (FTIR) for the raw and modified whiskers. The results indicated the co-existence of both chemical and physical adsorptions of sodium stearate on the surfaces of MSW.
Surface Modification of SrAl2O4:Eu2+, Dy3+ Phosphors Using Silica Encapsulation
Authors: Li Rui Fang , Ye Jun Wei , Wang Jing Hui , Lu Xiao Bin , Lin Yuan , Ning Gui Ling
Published: March 2009

Silica encapsulated phosphors SrAl2O4:Eu2+, Dy3+ have been synthesized by non-homogeneous phase coring method, in which glycerol was firstly used as dispersion medium and hyper-dispersant was introduced as additive. IR, BET and scanning electron microscopy (SEM) demonstrated that a dense layer of silica was formed on the surface of phosphor SrAl2O4:Eu2+, Dy3+. The results showed that the encapsulated phosphors possess good properties in water-resistance, heat-resistance and dispersibility when encapsulation amount reached 8 wt. %. Moreover, the photoluminescence intensity of phosphors SrAl2O4:Eu2+, Dy3+ was improved apparently after surface modification. All results revealed that silica encapsulation would effectively improve alkaline earth aluminates phosphors’ properties and using glycerol as the dispersion medium is helpful to silica encapsulation.
Toughening of Polypropylene with Calcium Sulfate Whiskers Treated by Coupling Agents
Authors: Wang Xiao Li , Zhu Yi Min , Han Yue Xin , Yuan Zhi Tao , Yin Wan Zhong
Published: March 2009

Calcium sulfate whiskers are modified by three kinds of coupling agents. The modified calcium sulfate whiskers are then introduced into polypropylene to prepare calcium sulfate whiskers/PP composites. Mechanical strength tests show that notched izod impact of polypropylene increases dramatically by adding calcium sulfate whiskers. When a silicane coupling agent KH-570 is adopted to modify calcium sulfate whiskers at 30 % (w/w) of whiskers, the notched izod impact of composites can increase by nearly 60 %. SEM is utilized to observe the impact fracture surface morphology of the composites and the distribution of calcium sulfate whiskers in the PP matrix. The results indicate that the surface treatment can promote uniform distribution of calcium sulfate whiskers in the PP matrix, and improve the notched izod impact and toughness of composites. Coupling agents play a role in toughening for the calcium sulfate whiskers/PP composites.
Development of Mineral Processing Flowsheet for Hematite Benefication in Yezhugou, Liaoning, China
Authors: Lu Zhen Fu , Yin Wan Zhong , Chang Xiao Liang , Han Yue Xin
Published: March 2009

A lager amount of iron ore is to be exploited in Yezhugou region, Liaoning Province. Analysis indicated that the main valuable mineral was fine-grained hematite and the total iron content was 28.22%. A process flowsheet of gravity concentrtion - high intensity magnetic separartion – reverse flotation was established, and operating conditions of each operation were also determined through batch tests. In closed-circut tests under the same operation conditions, the following results were obtained: iron content of the concentrate 64.95%, concentrate recovery 81.04%, and iron content of the tailings 8.26%.
Flow Field Characteristic Analyses of a Turbo Air Classifier’s Rotor Cage and its Structurally Improved Counterpart
Authors: Yang Qing Liang , Liu Jia Xiang , Zhou Yun Bo
Published: March 2009

The turbo air classifier is one of the most widely used equipment in powder classification. The complex flow behaviour inside it, however, prevents material experiments from providing information about its internal separation mechanisms. A study of the interaction of structural variables is therefore undertaken examining air flow behaviour, specifically the air flow between the blades of the rotor cage. The investigation of these flow field characteristics made use of the computational fluid dynamics (CFD) to simulate the air flow in the classifier. It was found that the inlet velocity of the turbo air classifier and the rotary speed of the rotor cage are two of the dominating, non-structural factors that affect velocity distributions in the region between the rotor cage blades. Once the inlet velocity settles, a critical rotary speed must be present to smoothen the flow field between the blades, resulting in an excellent classification performance.
Three-dimensional velocity measurements of the region between the blades by laser Doppler velocimeter (LDV) were performed to test the results of the flow field simulation. This revealed that when inlet velocity is invariable, the velocity distributions in the region between the blades are at its most symmetric with the critical rotary speed of the rotor cage making it more favourable for classification. The velocity measurement results are likewise in good agreement with the results of the flow field simulation.
Newly structured rotor cages are also simulated and compared with a conventional turbo air classifier, air flow in the newly structured model is smoother. The distributions of radial and tangential velocities are more symmetric and the trend of the rotating vortex between the blades attenuates, particularly when the rotary speed is high. The newly structured rotor cages can therefore achieve higher classification performances.
Preparation and Properties of Nanocomposites Containing Polypropylene and Palygorskite
Authors: Wang Fei , Tang Qing Guo , Liang Jin Sheng
Published: March 2009

Polypropylene-palygorskite composites were prepared by melt mixing, using polypropylene as polymer matrix and palygorskite as inorganic components. The couple-agent modification of palygorskite was introduced in detail and the relation between structure and properties of polypropylene composites was mainly studied. The characterization on structure of polypropylene composites indicated that after modified by couple-agent，the dispersity of palygorskite in the polymer matrix was improved. The results showed that mechanical properties of composites were improved generally due to the addition of modified palygorskite. In addition, the optimum conditions of palygorskite modification for surface free energy of palygorskite and impact ductility of composites were deduced respectively by orthogonal range analysis.
Improved Mechanical Properties of Ti2AlNb-Based Intermetallic Alloys and Composites
Authors: Shagiev M.R. , Galeyev R.M. , Valiakhmetov Oleg R. , Safiullin Rinat V.
Published: March 2009

Mechanical properties of a Ti2AlNb-based intermetallic alloy both at room and elevated temperatures were considerably improved due to formation of a homogeneous microstructure with the average grain size of about 300 nm. At room temperature, elongations up to 25% were obtained and the ultimate strength reached 1400 MPa. The alloy exhibited superplastic behavior in the temperature range of 850-1000°C. The maximum elongation of 930% and steady state flow stress 50 of about 125 MPa were obtained at 900°C and strain rate of 4.210-3 s-1. The nanostructured material was used for production of intermetallic sheets and multilayer composite plates consisting of alternating layers of orthorhombic intermetallic and commercial high temperature titanium alloy. Ti2AlNb-based sheets and composites exhibited improved mechanical properties.
Thermomechanical Modelling of Copper Matrix Composites Reinforced with Tungsten Fibres
Authors: Ríos A. , Martín-Meizoso A.
Published: March 2009

The purpose of this work is to investigate and understand the thermomechanical behaviour of copper matrix composites with long fibres. The effects of the volume fraction of fibres are considered in this analysis. A micromechanical finite element model has been used to study the behaviour of the copper matrix composites reinforced with tungsten fibres, which undergo thermal cycling conditions. Furthermore, regular and random arrangements of fibres are considered
Brazing Technology for Plasma Facing Components in Nuclear Fusion Applications Using Low and Graded CTE Interlayers
Authors: Gualco Carlo , Grattarola Marco , Federici Alberto , Mataloni Francesco , Iždinský Karol , Simančik F. , Schwarz Bernhard , García-Rosales C. , López-Galilea I.
Published: March 2009

In Plasma Facing Components (PFCs) for nuclear fusion reactors, the protective material, carbon based or tungsten, has to be joined to the copper alloy heat sink for optimum heat transfer. High temperature vacuum brazing is a possible joining process as long as a proper interlayer is introduced to mitigate the residual stresses due to the mismatch of thermal expansion coefficient (CTE). Pure copper can act as plastic compliant layer, however for carbon based materials a proper structuring of the joining surface is necessary to meet the thermal fatigue lifetime requirements. In this work pure molybdenum and tungsten/copper Metal Matrix Composites (W-wires in Cu-matrix) interlayers have been studied as alternative to pure copper for carbon based protective materials in flat tile configuration. Finite element simulations of the brazing process have been performed to evaluate the expected residual stress reduction near the metal-carbon interface. In fact it has been demonstrated that stiff low CTE interlayers can shift the peak stresses from the weak carbon-metal interface to the strongest metal-metal one. Relevant samples have been manufactured and subjected to preliminary metallographic and thermal shock tests. Results obtained so far are encouraging and active cooled mock-ups are being prepared for high heat flux testing. Research work is in progress as regards monoblock configuration with both Wf/Cu MMC and graded Cu/W plasma sprayed and HIPped layers.
Microcharacterization of Damage in Materials for Advanced Nuclear Fission Plants
Authors: Pouchon Manuel A. , Chen Jia Chao , Hoffelner W.
Published: March 2009

Miniature and sub-miniature samples were used for determination of mechanical properties of materials for advanced fission plants. Results from indentation and focused ion beam prepared micro-samples, punch tests and thin strip (irradiation) creep tests are shown. The results allow conclusions concerning materials damage. Irradiation damage profiles were determined with indentation. Results from micro-pillar tests showed a good agreement with results from conventional samples in case of oxide dispersion strengthened steels. Thin strip irradiation creep experiments revealed a negligible influence of dispersoid size/distribution on creep rates. Punch tests of fibre reinforced materials showed consistent results which still need quantitative analysis.
Preparation of Polymer-Nanodiamond Composites with Improved Properties
Authors: Karbushev Valeriy V. , Konstantinov Ivan I. , Parsamyan Irina L. , Kulichikhin Valery G. , Popov Vladimir A. , George Thomas F.
Published: March 2009

An efficient method is developed to achieve improved dispersion of detonation nanodiamond particles in amorphous thermoplastic matrices. For an estimation of the nanodiamond distribution in slices, a method of optical and transmission electron microscopy is used. The complex set of mechanical properties of polymer-nanodiamond composites is considered: tensile properties, Izod impact strength and Brinell hardness. It is found that the reinforcing and toughening effects of uniformly-dispersed nanoparticles on polymer matrices is pronounced at lower loading compared with traditional mixing procedure.
Tube and Sheet Hydroforming-Advances in Material Modeling, Tooling and Process Simulation
Authors: Altan Taylan , Palaniswamy H. , Ambrogio G. , Aue-u-Ian Yingyot
Published: March 2009

Tube Hydroforming is a well accepted production technology in automotive industry
while sheet hydroforming is used in selected cases for prototyping and low volume production. Research in advanced methods (warm sheet and tube hydroforming, double blank sheet hydroforming, combination of hydroforming and mechanical sizing, use of multi-point and elastic blank holders) is expanding the capabilities of hydroforming technologies to produce parts from Al and Mg alloys, as well as Ultra High Strength Steels. In the development of advanced hydroforming methods, experience based knowledge is not readily available. Thus, robust process simulation is required, along with adequate material modeling and identification of friction coefficients as input to process simulation. This paper gives an overview of advanced hydroforming methods, including examples of novel machine and tooling designs. The use of reliable process simulation is illustrated with examples that demonstrate the significance of material and friction date for making accurate
predictions. Advanced simulation methods for warm forming and for programming multiple-point blank holder are also discussed. This review illustrates that hydroforming continues to make advances and has the potential to make many contributions to production technology in the near future.
FE Simulation of Sheet Metal Forming – State of the Art in Automotive Industry
Authors: Haepp H.J. , Rohleder M.
Published: March 2009

Nowadays feasibility studies using finite element analysis are performed in very early
design phases of sheet metal parts forming. Further, simulation technology is used to optimize the first forming stage. Because of the ever intensifying international competition and the increased use of high-strength steels and aluminum alloys, the absorption of springback deviations is a great challenge, especially in the automotive industry. The application of numerical computation to predict springback deviations and to create compensated die designs in early design phases of sheet metal
parts forming becomes essential. At DaimlerChrysler the numerically based compensation of springback deviations during the die development process of complex car parts is achieved. However, developments to optimize and compensate dies automatically or to predict form deviations on assemblies are still necessary.
Computing Welding Distortion: Comparison of Different Industrially Applicable Methods
Authors: Tikhomirov D. , Rietman Bert , Kose K. , Makkink M.
Published: March 2009

Welding distortion is one of the major concerns of the industrial joining practice. In order to obtain optimal welding parameters many experiments have to be carried out. Numerical simulation enables a virtual examination of the welding distortion without performing expensive experiments. In this contribution some industrially applicable methods of weld modeling are discussed. They enable the fast distortion assessment in the pre-development stage. The application of these methods on a complex automotive part is conducted followed by a comparison of computed distortion with measured values. Furthermore, aspects of integration of weld modeling into the virtual product chain are addressed.
Chances and Challenges in Joining by Forming with a Flat Counter Tool
Authors: Neugebauer Reimund , Mauermann R. , Dietrich Stephan
Published: March 2009

Two new joining methods for sheet metal parts, dieless clinching and dieless
rivet-clinching are introduced in this paper. With these methods all formable materials can be joined. Contrary to conventional technology in joining by forming these new methods are working with a flat anvil as a counter tool instead of a contoured die, which has a number of advantages. The process has become simpler, the process reliability is increased, misalignments of the joining tools don’t effect the quality of the connection anymore and even new applications, such as the joining of materials with a limited malleability become possible. Examples of realized connections and FE-calculations of the joining processes are presented.
Active Material Flow Control during High-Pressure Sheet Metal Forming
Authors: Groche Peter , Metz C.
Published: March 2009

During forming of non-rotationally symmetric sheet metal parts at high pressures nonuniform deformation conditions arise in the flange area. These deformations vary in height and consequently lead to heterogeneous sheet thickness distributions. When using semi-rigid tools, high clamping forces are necessary in order to compensate for the developing sheet thickness variations in the flange area and to avoid leakages of the system or wrinkling. Moreover, the heterogeneous distribution of the clamping force is strengthened by press inaccuracies. This results in a higher
surface pressure distribution on one side of the flange and finally in a non-uniform material flow out of the flange area. The development of a segmented active-elastic blank holder enables an active material flow control of the flange movement during sheet metal forming at high pressures. The local elasticity of the active-elastic blank holder is based on an optimized layout of the local tool rigidity. For this purpose, different grooves were integrated below the blank holder surface. This paper provides an overview of the developed technology, advantages with regard to the part’s quality, and recent results comparing the production of non-rotationally symmetric parts with segmented active-elastic tools vs. semi-rigid tools.
Custom Manufacture of a Solar Cooker – A Case Study
Authors: Jeswiet J. , Duflou Joost R. , Szekeres Alexander , Lefebvre P.
Published: March 2009

Single Point Incremental Forming is a new process, which has been developed to make both Rapid Prototyped products and low volume product batches from Sheet Metal. This paper presents a case study of the manufacture of a solar cooker cavity for developing country applications. In the first instance the request was for a rapid prototype, which quickly evolved into a request for low volume production of solar cookers for the developing country market. The paper describes the manufacture of the solar cooker cavity, and shows how the possibility of manufacturing part of the solar cooker, by Single Point Incremental Forming, gives rise to the possibility of manufacturing other parts for the solar cooker less expensively.
Quantitative Validation of FEM Simulations for Incremental Sheet Forming Using Optical Deformation Measurement
Authors: Bambach M. , Hirt Gerhard , Ames J.
Published: March 2009

The present paper focuses on a new methodology to quantitatively evaluate finite element calculations on incremental sheet forming (ISF). ISF is a new manufacturing process for prototypes and small lot sizes. In ISF, a part is manufactured by the CNC-driven movement of a simple tool, giving rise to very challenging problems concerning the efficient modeling of the alternating contact
conditions and the material's response to the cyclic deformation. The quantitative validation of the finite element analysis is achieved by an optical deformation measurement system which has been enhanced by a new calibration procedure, yielding a precisely defined local coordinate system for deformation measurements during forming. In combination with mapping algorithms for large point sets, this allows for a quantitative validation of process simulations and material input data.
Thermal Characterization of Friction Stir Welded Butt Joints
Authors: Beccari S. , D'Acquisto L. , Fratini Livan , Salamone C.
Published: March 2009

In the paper the thermal characterization of friction stir welding processes (FSW) of aluminium alloys is presented. In particular both embedded thermocouples and a thermography analysis were utilized in order to acquire the temperature vs. time curves in point of interests of the joints and the temperature distributions, respectively. Such kind of results are very important in order to investigate the material conditions during the FSW process.
Developments and Trends in Laser Welding of Sheet Metal
Authors: Vollertsen Frank
Published: March 2009

There is some remarkable progress in laser beam welding of sheet metal which is driven by the advent of improved laser systems and process technologies. Here, potentials for reducing distortion and avoiding hot cracking are highlighted, and examples of current developments are given in the field of thin and thick sheet metal welding including spot welding of difficult-to-weld materials and material combinations.
Statistical Investigations on Friction Stir Welded Aluminum Tailored Blanks for a Robust Process Window
Authors: Giera Arthur , Merklein Marion , Geiger Manfred
Published: March 2009

The multifarious applications of aluminum alloys in different industrial domains are
based on the mechanical properties as well as the light weight characteristics, which allow energy saving for the products in use. Nevertheless aluminum alloys are considered to be difficult to weld by conventional welding processes. This paper deals with cost-effective friction stir welding of thin sheet aluminum alloys in
thicknesses of about 1 mm to widen the possible range of applications. Based on former studies results will be shown how an optimized tool geometry increases the mechanical properties of friction stir welded parts. The characteristics of these friction stir welded thin sheets will be analysed in a statistical evaluation in order to detect the interactions and dependencies of the process parameters. By highlighting the main process parameters and their significances a process window for friction stir welded blanks of AA5182 and AA6016 is presented.
Size-Effects in Micro-Metal Sheet Forming of Unalloyed Copper and Brass
Authors: Tsai M.C. , Chen Y.A. , Wu C.F. , Chen Fuh Kuo
Published: March 2009

Micro-metal forming technologies are mass production methods, net shape forming,
low-cost procedures and quality controlled processes. Its scale region is in the range of the margin area between conventional precision manufacturing and silicon-based technology. The first paper to study the field of micro metal forming was written in 1989. Up to now, there have been many papers in this field but the results of the experiments do not reach the same conclusions. It should be noted that it is not possible to apply the know-how of conventional forming processes to the field of
micro-metal forming due to the so-called size effects. In this study, two kinds of sheet materials such as C12000 and C26000 copper alloys are used to do a micro-upsetting experiment and micro-tensile experiment. It can be found that the size effects of micro-metal forming in C12000 agree with the description in previously published papers. However, the C26000 alloy has high matrix strength and significant fine grain strengthening that produce different size-effects of micro-metal forming. In this paper, we compare these two materials and suggest explanations for this problem. Therefore, the result can provide a general solution and discussion of micro-metal forming processes in unalloyed copper and brass.
Springback Analysis of Sheet Metals Regarding Material Hardening
Authors: Schikorra Marco , Govindarajan R. , Brosius Alexander , Kleiner Matthias
Published: March 2009

The phenomenon of springback of thin-walled sheet metal parts after forming is a well
known problem of forming technology in general, but particularly since the finite element simulation offers the opportunity to predict geometrical and material properties after forming. Irrespective of the intensive efforts in the previous years, a reliable and accurate prediction of springback deviations by use of the finite element simulation is still not possible. This paper deals with the numerical and experimental analysis of the springback effect itself, which dependents on the final stress states
of a part after the forming process. Experimental investigations have been carried out to analyze geometrical accuracy in loaded and unloaded conditions to isolate the springback effect. Additional finite element simulations have been conducted in order to compare the experimental and numerical results and to determine the geometrical differences and their reasons. Two experimental set-ups are being discussed: Air bending on the one hand, which offers good access to the specimen in the testing equipment, and draw bending on the other hand, which is characterized by a simple strain state, but also by strain reversal within the tests. Both experiments were
carried out using DP600 and X5CrNi18.10 with three different sheet thicknesses and bend radii and were compared with according FE-models. An additional shear test experiment has been developed to characterize the material behavior of the tested sheet metals for strain reversal. Furthermore, the importance of the Bauschinger effect and usable hardening models were analyzed. This study intended
to investigate reasons for insufficient form and dimensional accuracy between simulations and experiments after springback and to propose modeling methods to improve the accuracy.
A Global Approach of the Finite Element Simulation of Hot Stamping
Authors: Hein P.
Published: March 2009

The use of quenched boron steel components is an economic way to achieve significant improvements in terms of weight saving and crash performance. The material and process knowledge on the hot stamping of boron steels (e.g. Arcelor’s USIBOR 1500 P®) by the stampers needs to be extended and accurate simulation tools must be developed to support the growth of this forming technology. This paper simultaneously addresses the specific requirements of the hot stamping simulation and the current state of the art in this field. A specific approach is presented for the detection of the process limits within the simulation tool. A software chain has been set up with the target to decrease the computation times.
Determination of Mechanical Properties for the Hydroforming of Magnesium Sheets at Elevated Temperature
Authors: Hecht J. , Pinto S. , Geiger Manfred
Published: March 2009

Thanks to the low weight, magnesium alloys feature high specific strength and stiffness properties. Thus they prove to be promising materials for todays ambitious automotive light weight construction efforts. Due to their comparative low formability at room temperature the process of magnesium sheet hydroforming can be improved at temperatures higher than 200 °C by the activation of additional sliding planes. This paper illustrates the determination of mechanical properties for the hydroforming of magnesium sheets at elevated temperature. In particular the mechanical behavior at elevated temperature was investigated by means of the tensile test and of the hydraulic bulge test. For the determination of the strains an optical measurement system was introduced into the experimental set-up. The exact knowledge of the strain condition in the area of diffuse necking enabled the determination of the flow curve in the tensile test also beyond the uniform elongation. The influence of temperature and strain rate was analyzed as well as the influence of uni- and biaxial stress state on the flow curve. Using circular and elliptic dies with different aspect ratio the hydraulic bulge test served to determinate the forming limit curves at three
different elevated temperatures.
Effective Stripper-Holding on High Speed Precision Blanking of Electronic Machine Parts
Authors: Sekine F.
Published: March 2009

The blanking of thin sheet metals using progressive dies is an important process on
production of precision electronic machine parts. As a model of IC leadframe, an I-shaped and an Lshaped models were blanked and influences of blanking conditions on dimensional accuracy of blanked lead were examined. Furthermore, a mechanical model is proposed to explain the affect of the blanking conditions on product accuracy. In these days, more fine leads are required as electronic machines become more precise and accurate. It must be treated that leads are firmly held
for blanking leadframes accurately. In this paper, an effective method of stripper holding leads strongly are discussed and a new method using newly designed stripper is proposed. Consequently the effect of it on lead accuracy is proved.
Hydrodynamic Lubrication in a Nanoscale Bearing
Authors: Xiang Chang Zheng , Wang Yu Juan , Chen Yun Fei
Published: March 2009

Nonequilibrium molecular dynamics simulation is used to simulate the hydrodynamics lubrication in the nanoscale bearing. A physical model of the nanascale bearing that the thin liquid water film confined between two solid walls has been set up. The simulation results indicate that the hydrodynamic pressure profiles as the macroscopic state are formed in nanoscale bearings. The hydrodynamic pressure increases with increasing shear velocity, and corresponding load capacity also increases with increasing sliding velocity of the upper driven wall. These results are in accordance with classical Reynolds’ theory about hydrodynamic lubrication. On the other hand, the shear thinning behavior of the liquid water film appears, so that effective viscosity decreases under high shear velocity. Although effective viscosity of water film decreases under high shear velocity, this phenomenon doesn’t affect the hydrodynamic lubrication of the nanoscale bearing.
Effect of Ag Doping on Structural, Optical and Electrical Properties of SnS:Ag Thin Films Prepared by Pulse Electroposition
Authors: Yang Yong Li , Cheng Shu Ying , Lai Song Lin
Published: March 2009

Silver-doping in SnS films can improve the semiconducting properties of SnS films. Based on our previous research, SnS:Ag thin films were deposited on ITO coated glass by pulse electro-deposition in order to study their structural, optical and electrical properties. SnS:Ag thin films were characterized with X-ray diffraction (XRD) , Scanning Electron Microscope (SEM) and some other methods. The primary composition of the films is SnS, but maybe there is a little quantity of SnS2, Ag8SnS6 and other compounds. The doped films exhibit good crystallization with big grain size. They have an optical gap of 1.66~1.89eV and a high absorption coefficient (α＞5×104cm-1). Hall measurement has shown that all the samples are of p-type conduction with low resistivity of the order of 10-3Ω•cm, and the carrier concentration increases to 1019cm-3 after Ag-doping. In conclusion, the semiconducting properties of the SnS films have been improved by silver-doping. Thus, SnS:Ag thin films can be used as solar cells absorbers.
Analysis of Coupled Electro-Thermal-Mechanical of Micro Gas Pressure Sensor Based on Micro-Hotplate Technology
Authors: Jin Ren Cheng , Zhang Wu Jin , Tang Zhe Nan , Wang Jia Qi , Shao Ming Liang
Published: March 2009

The effect of micro-hotplate (MHP) thermal deformation on the signal output of the MHP-based micro gas pressure sensor is investigated. Combining electro-thermal theoretical analysis and thermal-mechanical finite element modeling, different electro-thermal-mechanical analysis models of the sensors are built and solved at constant current condition and constant temperature condition respectively. The calculated results show that the MHP thermal deformation has little effect on the sensor signal output over the entire pressure range at constant current condition, I=0.7mA. While at constant temperature condition, Ts=400K, thermal deformation has little effect on the sensor signal output at low gas pressure, but at high pressure the effect are great. Moreover, according to the thermal-mechanical analysis, we find that optimizing thickness distribution of thin films in the MHP suspended structure can reduce thermal deformation effectively at higher temperature when the lateral dimension is same, which presents a practicable method to improve the sensor stability.
Experimental Studies of the Surface Forces on Micro Gap Plates with Different Bumps
Authors: Shen Xue Jin , Qi Wei Jun
Published: March 2009

An experimental analysis of the influence of the bumps on the surface forces in micro gap plates is presented. Because of extremely small sizes of micromechanical structures in MEMS, surface forces between micromechanical components may become significant to influence behaviors of microelectromechanical devices. The bumps are important in micro structures as they change the adhesion condition of the plates, and will influence the surface forces in micro gap plates greatly. To identify relative importance of surface forces with bumps, the experimental instrument which consists of the V-shaped electrothermal microactuator, the suspended plate and the flexible beam is designed. The displacements of the suspended plate with different bumps are measured by experiments, and the surface forces are got by calculation. By analysis, it could be found that the surface force increases with the increasing drive voltage and the increasing normal voltage, and the surface force gets the minimum when the number of the bumps is 9.
Study of Nanosecond Pulse Laser Micro-Fabrication
Authors: Liu Chun Yang , Fu Xing , Wu Yong , Sun Feng Ming , Hu Xiao Tang
Published: March 2009

We study some microstructures fabricated by designed 355nm ultraviolet nanosecond pulse laser micromachining system, which consists of LASER, mechanical and optical structure, 3D work platform, and control system. Nanosecond pulse LASER, with 40ns pulse duration, is chosen as the light source. Mechanical and optical structure is designed for laser beam focusing. Computer software resolves the graphics. And control system based on DSP and FPGA is designed to drive the 3D work platform. Raster sensor is used to measure the real distance that the platform moves. Using this system, some experiments are analyzed and some parameters are optimized. Some microstructures are also fabricated on single crystal silicon wafer and organic glass. The lines of fabricated graphics are 20-40um wide and smooth, with less effect of heat.
Synthesis and Characterization of the Core-Shell CdTe/ZnS Quantum Dots
Authors: Xu Shi Chao , Yao Cui Cui , Zhang Ji Mei , Dai Zhao , Zheng Guo , Sun Bo , Sun Shu Qing , Han Qing , Hu Fei , Zhou Hong Ming
Published: March 2009

Core-shell quantum dots are colloidal particles consisting of a semiconductor core and a shell material as an outer coating layer. It can be utilized to develop sensitive methods for the detection of specific biological entities, such as microbial species, their transcription products, and single genes etc. The goal of current research is to synthesize CdTe and core-shell CdTe/ZnS quantum dots (QDs) with an improved process, and to investigate their properties. Well-dispersed CdTe core was prepared in aqueous phase with using 3-mercaptopropionic acid (MPA) as stabilizer under conditions of pH 9.1, temperature of 100 °C, refluxing for 6h, and mol ratio of Cd2+/Te2-/MPA is 1:0.5:2.4. Average size of 8 nm CdTe core was conformed via transmission electron microscopy (TEM). Core-shell CdTe/ZnS QDs were then synthesized to improve the optical properties and biocompatibility of CdTe core. Various conditions were researched to obtain the core-shell QDs with the best optical properties, such as quantum yields, fluorescence intensity etc. The results indicated that the core-shell qualified CdTe/ZnS was prepared under conditions of pH 9.0, temperature of 45 °C, refluxing for 1h, and mol ratio of CdTe/S2-/Zn2+ is 4/1/1. CdTe/ZnS with average size of 10 nm were achieved and conformed via TEM. Moreover, red shift of a maximum emission wavelength from 547 nm of CdTe to 587 of CdTe/ZnS was observed via fluorescence spectrum (FS), which inferred the growth of QDs and formation of ZnS shells. The achieved ZnS shell make CdTe core less toxic and more biocompatible, it will be useful in biological labeling, diagnostic process and biosensing system based on fluorescence resonance energy transition (FRET).
DNA Biosensors Based on Self-Assembled Multi-Walled Carbon Nanotubes
Authors: Pang Jie Chun , Zhang Ji Mei , Xiao Yi Yun , Dai Zhao , Xu Shi Chao , Guo Ning , Zheng Guo
Published: March 2009

A novel electrochemical DNA biosensor system based on multi-walled carbon nanotubes(MWCNTs) was presented in this paper. In order to make multi-walled carbon nanotubes being perpendicularly standing on Au electrode via Au-S chemical bonding, we cut multi-walled carbon nanotubes (1.5 m) into short pipes (200-300 nm). Then, the shortened nanotubes were further modified by thiolization reaction with cysteamine (NH2CH2CH2SH). The –SH modified MWCNTs, gold nanoparticles and 5’ end –SH modified DNA (HS-DNA) as nucleotide probes were self-assembled onto the surface of Au electrode respectively. The DNA biosensors based on self-assembled MWCNTs had a higher current response compared to those based on random MWCNTs. When the target DNA concentration was 4.0×10–9 mol/L to 1.2×10-8 mol/L, the cathodic peak current of Au electrode system with the AQDS as indicator was linearly related, and the detection limit was about 6.5×10-9 mol/L. In addition, the developed DNA biosensors also had a high selectivity of hybridization detection.
Fabrication and Testing of Hard X-Ray Hourglass Lenses
Authors: Liang Jing Qiu , Zhu Yan Qing , Cui Nai Di , Liang Zhong Zhu , Le Zhi Chun , Yi Fu Ting , Hou Feng Jie , Zhu Pei Ping , Dong Wen , Wang Wei Biao
Published: March 2009

Based on the refraction theory of the lens, the SU-8 photoresist hard X-ray hourglass lenses with three different structure parameters are fabricated. The mask-back exposure technique is introduced to fabricate the lenses. The focusing performance of this device is tested at Beijing Synchrotron Radiation Facility (BSRF). At the distance of 1.65m from the lenses, an obviously focusing performance in one dimension is observed. The relative intensity of the lenses with the largest gain is about 217.7, the gain of the lens is about 1.15, and the dimension of the focus is about 33µm. The focusing performance of this device can be improved through the developing of the mask-back exposure technique.
High-Surface-Quality and Wider-Modulation-Range Continuous Face-Sheet Micro Deformable Mirror Based on SOI
Authors: Tian Li , Li Xiao Ying , Qiao Da Yong , Yan Bin
Published: March 2009

A new type of continuous face-sheet micro deformable mirror was designed and fabricated based on SOI (Silicon-on-Insulator) technology for high optical efficiency applications in adaptive optics system. SOI provided a Silicon-Insulator-Silicon structure, and the insulator-layer of the three-layer structure was taken as etch-stop layer in deep silicon etching, which made the suspended bulk silicon membrane obtained easily. And the reflective face did not suffer etch-step due to the protection of insulator-layer. The mirror was composed of 5-um-thick and 10-mm-diameter flexible bulk silicon membrane, and actuated by 69 electrostatic actuators which evaporated on glass substrate. SOI and glass wafer were bonded together by anodic bonding, forming a separation gap of 15um between the mirror face and electrostatic pad, which offered a maximum effectual displacement of 5um by considering the pull-in effect. Fabrication process was introduced in detail. Bulk silicon micromachining was employed, methods mainly include Inductivity Coupled Plasma (ICP) etching and Si/Glass anodic bonding technique.
Fabrication and Performance Analysis of PMMA Substrate Diffuser/Nozzle Micro-Pump by CNC Milling Machine
Authors: Tian Li , Wang Wei , Liu Xiao Wei , Zhang Ying , Ji Shu Yi
Published: March 2009

A new low cost high performance PMMA micropump, developed for microfluidic system, is presented. According to the orifice flow theory, a diffuser/nozzle structure is fabricated with precision milling process, and packaged with the film-sealing at the condition of thermal bonding process. The size parameter of the diffuser/nozzle structure is 2.5mm *150µm, 8° conical angle, the volume of PMMA micropump is 14×14×2.5 mm3. And experimental results show that the PMMA micropump can produce a maximum back pressure of 1906.1Pa and a maximum flow rate of 564µL/min under 220 V, 500Hz squired wave power supply.