bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of DC Power on Structural and Hydrophilic Activity of TiO2 Films
Authors: Salawan C. , Muakngam A. , Sukbot B. , Aiempanakit K. , Dumrongrattana Supattanapong
Published: March 2009

In this work, we present the effect of DC power from 100 W to 500 W on the structural and hydrophilic activity of TiO2 films. The TiO2 films were prepared by DC magnetron sputtering on the glass substrate without any external heating. The structure of TiO2 films were analyzed by atomic force microscope and X-ray diffraction. XRD patterns indicated the films were amorphous. The surface roughness and grain size were enlarged by the increasing of the DC power while the substrate temperature was climbed up with the increasing of the DC power. From the point of energetic ion bombardment, it was related with DC power between sputtering processes. The hydrophilic activity of TiO2 films were analyzed by the contact angle meter. The water contact angle decrease with increasing of the DC power.
Preparation and Properties of Thermal Insulation Putty for Exterior Wall Containing Sepiolite Composite Materials
Authors: Wang Fei , Liang Jin Sheng , Tang Qing Guo , Ding Yan , Wang Na
Published: March 2009

The composite materials for self-operating temperature were prepared by sepiolite and dodecanol as materials. Then thermal insulation putty for exterior wall was prepared by the sepiolite composite materials as main functional additives and acrylic emulsion as adhesive. The main properties of the putty films were studied by thermal insulation effect testing device. The results show that the putty films could arrest heat transmission effectively.
Preparation of Nano Titanium Dioxide Using Industrial Raw Material
Authors: Zhang Pei Xin , Zhang Dong Yun , Qiu Qi , Jing Li , Ren Xiang Zhong
Published: March 2009

In this paper, nano-sized titanium dioxide particles were prepared by homogeneous precipitation method using industrial TiOSO4 as raw material. The morphology, crystal structures and the crystal transformation were characterized using transmission electron microscopy (TEM), X-ray Diffraction (XRD), and thermogravimetry-differential thermogravimetric analyzer (TG-DTA) respectively. The impact factors on the production rate and the diameters of nano-TiO2 were investigated. The factors include the reaction temperature, the concentrations of reactants, the molar ratios of reactants, the reaction time, the calcination temperature, and the calcination time. The results indicated that nano anatase titanium dioxide in uniform phase could be obtained under a reaction temperature of 90°C, the concentration of TiO2+ at 0.8mol/L, the reaction time of 4h, the ratio of CO(NH2)2 to TiOSO4 as 1:3, followed by a calcination period of 2h under 600°C,
Research on the Mechanism of the Dissociation of Potassium Shale during Roasting
Authors: Han Yue Xin , Liu Jie , Yin Wan Zhong
Published: March 2009

It was studied that the process and mechanism of potassium extraction from the potassium-rich shale sample during roasting via SEM, XRD and thermal analysis (TG and DSC). The result of roasting test shows that roasting size has a little affect on ratio of potassium extraction, however, the effect of roasting temperature, roasting time and mNaOH:mshale on potassium extraction is significant. Under the optimum conditions, the ratio of potassium extraction is more than 88 %. SEM, XRD and thermal analysis shows that, during roasting, NaOH contributes to decomposition and melt of the minerals like potassium feldspar and muscovite in the sample and intact structure of minerals in the shale are broken down gradually and there are new crystal phases like kalsilite in the roasting products. Under alkali conditions, increasing roasting temperature promotes decomposition of silicate and aluminosilicate minerals.
Graphite-Nimonic Alloy Brazing
Authors: Moutis N.V. , Jimenez Cristina , Speliotis T. , Azpiroz X. , Mergia K.
Published: March 2009

A graphite sheet has been successfully brazed to a Nimonic 105 superalloy using a commercial TiCuSil paste. A chromium layer was deposited on the graphite surface by sputtering and controlled heat treatments were employed in order to develop a suitable microstructure. Scanning electron microscopy measurements showed rough, crack-free interfaces between the filler metal and both the graphite and nimonic parts. From metallographic examination a well defined layered structure of the metallic elements close to the filler/graphite interface has been found. The metallic elements transport from the interface to the carbon bulk where they fill all the graphite pores up to a depth up of 50 μm and form a layered structure within the pores.
Atomistic Simulation of ½<111> Screw Dislocations in BCC Tungsten
Authors: Fikar Jan , Schäublin Robin , Björkas Carolina
Published: March 2009

Atomistic simulations are used to describe the ½<111> screw dislocation in tungsten. Two different embedded atom model (EAM) potentials and one bond-order potential (BOP) are compared. A new analytical approach for constructing asymmetrical screw dislocations is presented.
Compression Tests of High Strength Steels
Authors: Mentl Vaclav , Bystricky Josef
Published: March 2009

Mathematical modelling and virtual testing of components and structures represent a useful and economic tool for design and safety assessment. The basic mechanical properties which can be found in material standards are not relevant in cases where the real service conditions differ from those applied during standardised testing. Thus e.g. mechanical behaviour at higher strain rates can be interesting for the car components when the simulation of crash situations is used during structure development. The dynamic compression tests are usually performed by means of drop towers, by means of high speed hydraulic testing machines or Hopkinson bar method. At the Mechanical Testing Laboratory of the SKODA Research Inst. in Pilsen, Czech Republic, an instrumentation of Charpy pendulum testing machine was realised in order that it was possible to perfom dynamic compression tests, [1], and the compatibility of obtained results in comparison with traditional impact compression tests was verified within the round–robin carried out by TC5 ESIS Sub-Committee on “Mechanical Testing at Intermediate Strain Rates“, [2]. A new striking tup and load measurement system were designed and callibrated. At the same time, a new software was developed which makes it possible to evaluate the test force-deformation record. The goal of this study was 1. to check the possibility of compression testing of high strength materilas by mens of Charpy pendulum, and 2. to study the strain rate influence on basic mechanical properties.
Role of Cr and Ti Contents on the Microstructure and Mechanical Properties of ODS Ferritic Steels
Authors: Oksiuta Zbigniew , Baluc Nadine L.
Published: March 2009

Six oxide dispersion strengthened (ODS) ferritic steels, with the composition of Fe-(12-14)Cr-2W-(0.1-0.3-0.5)Ti-0.3Y2O3 (wt.%), have been prepared by mechanically alloying elemental powders of Fe, Cr, W, and Ti with Y2O3 nano-particles followed by hot isostatic pressing. The influence of the chemical composition on the microstructure and mechanical properties of various materials was studied. It was found that the chromium content has a significant influence on the microstructure and mechanical properties of the compacted ingots. The 14Cr ODS steel exhibits slightly higher ultimate tensile strength and yield strength values than the 12Cr ODS steel. The total elongation and uniform elongation of both materials, in general, decrease with raising the test temperature, although in the case of the 12Cr ODS steel the elongation is about 30% higher than that of the 14Cr ODS material. In what concerns the effect of titanium content it can be concluded that variations between 0.1 and 0.3% have no visible effects on the microstructure and Charpy impact properties of compacted specimens. However, the microstructure of specimens with 0.5%Ti contains large TiO2 particles with a size in the range of 50-500nm, which have detrimental influence on the mechanical properties of that material.
Strain Rate and Test Temperature Dependence on the Flow Properties of La2O3-Doped Tungsten
Authors: Uytdenhouwen I. , Chaouadi R. , Linke Jochen , Massaut V. , Van Oost G.
Published: March 2009

Tungsten and tungsten alloys are promising metals as protective materials for the armour in future fusion reactors. These metals exhibit the highest melting point, superior thermo-mechanical properties, low erosion and moderate neutron activation properties. The main drawback is their intrinsic brittleness at room temperature and their low recrystallization temperature. During thermal shock events in ITER, tungsten materials will exhibit various crack formations and failure mechanisms. The extensive heat loads on the surface of the material will create high thermal stresses, huge temperature rises and therefore large strain rates in the subsurface layers. This paper deals with the flow properties combining both temperature and strain rate effects of a lanthanum oxide dispersion strengthened tungsten material and the influence of grain orientation on its ductility. Promising results were obtained using a yield strength model based on a thermally-activated slip process that rationalizes the data.
Methods of Increasing Thermal Conductivity of Plasma Sprayed Tungsten-Based Coatings
Authors: Matějíček Jiří , Iždinský Karol , Vondrouš Petr
Published: March 2009

Tungsten is the main candidate material for the armor of plasma facing components for ITER and future fusion devices [1]. Plasma spraying is an alternative method for manufacturing tungsten-based coatings, including composites and graded layers, having a number of advantageous features [2]. On the other hand, the main limitation to application of these coatings on high heat flux components, is their low thermal conductivity, originating in the layered structure [3]. This paper is focused on four methods of improving the coatings’ thermal conductivity. First method consists in modification of the basic spraying parameters, which have a direct influence on the coating structure and therefore properties. The other three methods involve post-processing of the coatings: molten copper infiltration, laser remelting and densification by HIPping. The latter encompasses also tungsten-copper composites of various compositions. Experimental results, including structural and thermal characterization, are presented for each method. Finally, the applicability of these methods, from the point of view of manufacturing the plasma facing components, is discussed.
Non-Vacuum Electron Beam Welding
Authors: Dilthey U. , Gumenyuk A. , Masny H.
Published: March 2009

The electron beam has, for decades now, proven to be a most efficient and reliable tool for joining tasks in different application fields. Vacuum electron beam welding (EBW) has, for many years now, been a standard method for a great variety of industrial application fields. However, even out-of-vacuum (NV-EBW), the electron beam has become a high-productivity joining tool. The substantial weld depths which characterise vacuum electron beam welding are not achievable with the NV-EBW method – those weld depths characterise the vacuum electron beam
and are a result of its power density. The strong points of NV-EBW lie, mainly, in high-speed production. The achievable welding speeds reach up to 60 m/min when welding aluminium sheets and up to 25 m/min when welding steel plates.
The Effect of Pre-Straining on the Mechanical Behaviour of Self-Piercing Riveted Aluminium Alloy Sheets
Authors: Han Li , Young Ken W. , Hewitt R. , Chrysanthou A. , O'Sullivan J.M.
Published: March 2009

Self-piercing riveting as an alternative joining method to spot-welding has attracted
considerable interest from the automotive industry and has been widely used in aluminium intensive vehicles. Pressing and stamping are important processes in automotive production and result in additional straining on the vehicle body sheet material. It is therefore important to have knowledge of the effect of sheet pre-straining on the quality of the self-piercing riveted joints and on the mechanical behaviour of the riveted aluminium alloy sheets. This paper reports the influence of
sheet pre-straining on the static and fatigue behaviour of self-piercing riveted aluminium alloy sheet. Wrought aluminium alloy sheet, NG5754 with a nominal thickness value of 2mm was used to obtain pre-strained NG5754 sheets with pre-straining levels of 3%, 5% and 10%. The pre-strained NG5754 sheets were then joined in pair to create single riveted lap joints. Lap-shear and fatigue tests were performed on the self-piercing riveted joints. Microscopic inspection showed that the
joint quality was satisfactory despite the increasing sheet straining levels. The results showed that by increasing the pre-straining level up to 10%, the shear and fatigue strength also increased. The rate of increase of the static and fatigue strength differed as the pre-straining levels varied.
Mechanised Plasma-Powder-Arc-Welding (PPAW) of Aluminium Sheets
Authors: Wilden J. , Bergmann Jean-Pierre
Published: March 2009

The use of aluminium alloys rose in the last decade, as its specific mechanical properties allow a reduction of mass as for example in automotive. Moreover aluminium, due to its high corrosion resistance, is a very important material class in plant construction, where it is used for pipes or container till 250 °C. Aluminium can be welded with different technologies. Nowadays TIG and MIG are mainly used for example in plant construction or in mechanical engineering. Laser beam welding is a widely established technology in automotive. The advantage is the high energy
concentration, which leads to a high welding speed and a narrow heat affected zone. Plasma welding is applied when joining aluminium with alternating current, as an easy removal of the oxide layer in the surface of the weld pool is possible. Plasma-Powder-Arc-Welding (PPAW) method has been developed from Plasma Transferred Arc (PTA) weld surfacing and Plasma Arc Welding (PAW) methods by combining a small PAW torch (PAW is traditionally performed with wire as filler material) with powder filler material feeding as used in PTA-equipment. The coupling leads to a better mechanisation of the welding process as the consumable is fed directly through the welding torch. In this paper investigations on aluminium sheets (£ 2 mm) AA5xxx and AA6xxx using different powder materials are reported. The influence of the processing parameters and conditions on the process reliability, when welding with industrial robots butt and corner welds is investigated.
Conventional PPAW of aluminium is performed with AlSi12 filler material. A post processing of the joint, as for example anodising in order to improve corrosion resistance, leads to a very different optical aspect, as the colouration of the weld seam after anodising differs from the base material. Thanks to a correct choice of filler material it is possible to reduce the colour differences between base materials/heat affected zone and bead, so that the weldment can be set for high quality optical applications, too.
Problem Specific Design of Actuators for Micro Adjustment
Authors: Hagenah Hinnerk , Wurm T.
Published: March 2009

Ongoing miniaturisation of functional parts in electronic, optical and mechanical devices results in an increasing demand for precision. By means of laser beam forming of especially designed sheet metal parts within an assembly the needed high accuracy can be reached. The use of the so called actuators, their mounting within the assembly and their activation through laser irradiation are well known steps. The design however is a sophisticated process so far depending on the experience
of the designer. It is often determined in a time consuming iterative process. In this paper concepts and methods for an assistance system for the designer of actuator geometries using kinematic chains will be presented.
Asymmetric Incremental Sheet Forming
Authors: Jeswiet J.
Published: March 2009

The use of computers in manufacturing has enabled the development of several new
sheet metal forming processes. This paper describes modifications that have been made to traditional forming methods such as conventional spinning and shear forming, where deformation is localized. Recent advances have enabled this localized deformation to be accurately controlled and studied. Current developments have been focused on forming asymmetric parts using CNC technology, without the need for costly dies. Asymmetric Incremental Forming has the potential to revolutionize sheet metal forming, making it accessible to all levels of manufacturing.
Deformation Behaviour of Sheet Metals in Laser Assisted Hydroforming Processes
Authors: Tönshoff Hans Kurt , Bunte J. , Meier O. , Engelbrecht L.
Published: March 2009

Cupping small form elements in hydroforming processes requires high work pressures and clamping forces and thus high capital investments for presses. Localised laser heating used during sheet metal hydroforming processes should reduce the necessary work pressure. By reducing the yield strength and the strain hardening using local heating, small form elements can be formed at very low pressures of 2 MPa, whereas cold forming requires pressures which are 20-50 times
higher. Besides the proportion of forming temperature and work pressure, temperature distribution is very important and can be adjusted using a special laser beam forming optic or a scanning processing head. Line network analysises were carried out showing great improvements in the resulting plastic deformation distribution. In order to characterise the general improvement of the material’s formability, forming limit curves (FLC) were generated using the bulge-test. The results approve the extended forming limit of the laser assisted warm cupping process. Moreover, the mechanical properties and the grain structure of the form elements generated were determined. All investigations were carried out for a deep drawing steel, a 5182 aluminium alloy and an AZ31 magnesium alloy.
Improvement of Formability in Tube Hydroforming by Reduction of Friction with a High Viscous Fluid Flow
Authors: Geiger Manfred , Dal Bó P. , Hecht J.
Published: March 2009

Tube hydroforming is an advanced technology for the manufacturing of lightweight
components with complex shape. The forming results can be usually improved if axial feeding at the tube ends is enabled. For very long parts, however, due to the high friction forces acting at high pressure in the feeding zone between tube and die, no material movement towards the expansion area occurs. The tube is only upset in the feeding zone, no compressive stresses take place in the expansion area and the forming results are not satisfactory. This can be avoided by eliminating friction and by inducing additional tangential stresses in axial direction on the tube surface of the feeding area. This paper presents the investigations performed in this direction by using a high viscous fluid flowing along the internal and external surface of the tube. The flow helps to reduce the friction force and allows the sliding between the tube and the tool surface. Experimental tests of tube upsetting under pressure will show the effects of the medium flow on the thickening of the tube wall. Not only increased sliding and homogeneous thickening will be obtained, but even an increase
of the wall thickness in the area close to the expansion zone will be shown. This effect is even stronger when the yield stress in the expansion zone is reduced by means of a previous local heat treatment.
Influence of an Incremental Deformation on Material Behaviour and Forming Limit of Aluminium Al99,5 and QT-Steel 42CrMo4
Authors: Meyer Lothar W. , Gahlert C. , Hahn F.
Published: March 2009

By cyclic torsion tests on thin walled tubular specimens the influence of a resulting strain increment per cycle on the plastic flow behaviour of Al99,5 and normalised QT-steel 42CrMo4 has been investigated. Thereby large shear amplitudes were chosen and the amount of forward and backward shear was varied. In both materials with increasing portion of backward shear a transition from cyclic hardening to cyclic softening was observed. It has been demonstrated that a certain ratio of forward and backward shear can cause a rise of the forming limit, which can exceed by far the value for monotonic deformation. The mechanical behaviour under cyclic incremental deformation is associated with certain substructure evolution. In dependency on deformation parameters especially the formation of dislocation cells and subgrains has been observed.
3D-Characterisation of Sheet Metal and Roller Surfaces by Means of Confocal Microscopy
Authors: Valentin J. , Weber M.A. , Brodmann R. , Sharp A.
Published: March 2009

The measurement and evaluation of sheet metal surface characteristics is of increasing importance, due to the significant functional impact on finishing processes like forming and varnishing. For a comprehensive and useful description of textured topographies including nonstatistical characteristics, a simple profile evaluation based on 2D roughness parameters is no longer sufficient. The introduction of area-imaging white light confocal microscopy offers, in contrast to tactile profiling methods of comparable accuracy, the clear advantage of contact-free and extremely fast 3D data capture. The capabilities and benefits of this technology in interaction with
sophisticated 3D area analysis methods are demonstrated by measurement examples of sheet metal and roller surfaces. A newly-developed mobile confocal measurement system for direct roller measurements is introduced.
Microstructural Changes Determining Joint Strength in Friction Stir Welding of Aluminium Alloys
Authors: Barcellona A. , Buffa Gianluca , Contorno D. , Fratini Livan , Palmeri D.
Published: March 2009

In the paper the results of a wide experimental activity on friction stir welding (FSW) of aluminum alloys are reported. In particular the butt joints of two different materials, namely AA1050-O and AA6082-T6 were considered. Grains dimensions and precipitates density were investigated both in the parent materials and after the welding processes. Furthermore post-welding heat treatments effects on the joint strength were studied.
Transient Simulation of Electromagnetic Forming of Aluminium Tubes
Authors: Karch C. , Roll Karl
Published: March 2009

The recent push to use more aluminium in automobiles has stimulated interest in
understanding electromagnetic forming (EMF), which uses induced electromagnetic fields to generate high strain rates during the forming process. The high strain rates increase the formability of aluminum materials and might reduce elastic spring-back and wrinkling of the workpiece. Primary emphasis is placed on including of all relevant physical phenomena, which govern the process, as well as their numerical representation by means of simplified electrical equivalent circuits for the EMF machine and fully coupled field approach of the transient electromagnetic and mechanical phenomena. Moreover, the thermal effects due to Joule heating by eddy currents and plastic work are considered. The numerical model predicts the electromagnetic field, temperature, stress, and deformation properties that occur during the forming process. The numerical results of the tube deformation are compared with available experimental data.
A Study of the Effect of Process Variables on the Stamp Forming of Rectangular Cups Using Fibre-Metal Laminate Systems
Authors: Mosse L. , Cantwell Wesley J. , Cardew-Hall M.J. , Compston Paul , Kalyanasundaram Shankar
Published: March 2009

The quality of the part and the robustness of the process in stamp-forming of sheet
materials are determined by a number of variables. This study looks at the application of the stamping process to a Fibre-Metal Laminate (FML) material system and the effect of the process variables on the formability characteristics of these material systems. The effect of pre-heating temperature on the splitting and wrinkling behaviour has been investigated for two different FML systems. It has been found that different FML systems exhibit different failure modes.
High Quality Magnesium Sheets for Automotive Applications
Authors: Bach Friedrich Wilhelm , Rodman M. , Rossberg A.
Published: March 2009

In order to make magnesium sheets a competitive material alternative for highly
sophisticated light-weight constructions the complete process chain for their production has to be investigated. In laboratory scale new alloys, casting techniques and optimized rolling and heat treatment schedules have been developed. At the Institute for Metal Forming and Metal Forming Machine Tools (IFUM) the forming capacity of magnesium sheets has been investigated. Derived from the strict quality requirements of e.g. the automotive industry, testing methods concerning mechanical properties, corrosion resistance and surface quality have been developed. It has been shown that the controlled development of a suited microstructure is the key factor for ensuring the requested product properties. Together with research and manufacturing partners the results were transferred to industrial practice and a closed loop process chain for the production of high quality magnesium sheets has been established.
Do Advanced Material Models Contribute to Accuracy in Industrial Sheet Forming Simulations?
Authors: van den Boogaard Ton , Wisselink H. H. , Huétink J.
Published: March 2009

The accuracy of material models can have a large impact on the overall accuracy of material forming simulations in general and sheet forming simulations in particular. For large strain plastic deformations, the material model usually consists of a yield function and a hardening relation, optionally including the influence of temperature and strain rate. In large-scale simulations it is favourable to keep the model as simple as possible. The ‘allowable’ error in a material model should be in balance with other errors, like the discretisation error and errors in contact and friction modelling.
The required accuracy depends on the application and the goal of the analysis. In many occasions, strain rate and temperature dependency can be ignored, but for warm forming this is clearly not the case. Furthermore, numerical simulation of the onset of necking requires a much better material model than needed for the calculation of the global deformation field before necking.
Enhanced Semi-Analytical Process Simulation of Air Bending
Authors: Ridane N. , Jaksic D. , Kleiner Matthias , Heller B.
Published: March 2009

The air bending process is one of the most widely used process for the manufacturing of sheet metal bending parts made of thin as well as of thick sheet metal. Although the air bending process offers a very high production potential due to its great flexibility, it is associated with certain problems which can negatively influence the shape and dimensional accuracy of the bending parts. Examples for such negative influences are the springback of the material, the batch variations,
or the deflections of the bending machine and tools. These differences have to be considered either in the determination of the process parameters or they have to be compensated later on in the manufacturing process itself. A well established approach to calculate process data for forming processes is the use of a process simulation. At the Institute of Forming Technology and Lightweight Construction (IUL) a simulation software called Sheet Metal Bending Simulation (SMBS) has been developed and successfully been tested for the field of sheet metal bending, based on semi-analytical approaches. Although it already provides very satisfactory results in general, disturbances such as material and batch variations as well as the deflections of C-frame, machine table, and press brake ram can still negatively affect the prediction of the punch displacement necessary to achieve a certain bend angle. While material and batch variations cannot properly be considered in a process simulation at present, the afore mentioned influences offer a promising potential for improvements. Therefore, in order to further improve the accuracy of predicted
quantities such as punch displacement and bending angle, a new module describing the elastic machine behaviour of press brakes has been developed and successfully been integrated in the process simulation SMBS. Experimental investigations have been carried out on a conventional CNC press brake to verify the efficiency of the newly implemented approach.
Experimental and Numerical Study of Intense Shear Banding for Al-Alloy under Uniaxial Tension
Authors: Duan Xin Jian , Jain Mukesh K. , Bruhis M. , Wilkinson David S.
Published: March 2009

The occurrence of intense shear band is a prelude to failure in many Al-sheet materials. In the present study, a full field optical system measurement technique (digital image correlation) and the finite element method are used to characterize the sequence of deformation in uniaxial tension before and after the intense shear band formation in AA6111-T4. The results indicate good agreement between the measurement and the predictions in terms of shear band width, strain distribution along the gauge length and the failure mode.
Flexibly Rolled Sheet Metal and Its Use in Sheet Metal Forming
Authors: Kopp R. , Wiedner C. , Meyer A.
Published: March 2009

Light weight construction is a construction philosophy which aims at maximum weight
reduction. Reasons for light weight construction can be very diverse. One main cause can be to improve fuel efficiency. This can be achieved by use of load optimised sheet thicknesses. Another reason can be the increasing demands on crash performances by optimisation of local properties. This paper presents two production processes of flexibly rolled blanks, one with longitudinal and the other one with latitudinal thickness transitions. Both of them have been developed at the
Institute of Metal Forming (IBF) and yet found their way into series production. The potential of these processes is already proved by a large range of products, especially in automotive industries. Some special deep drawing tests with flexibly rolled blanks have been conducted and their results are presented. Also process simulation has been carried out at the IBF and will be explained. One possibility with regard to optimise these products is shortly introduced. Completing this paper an outlook is given.
Characteristics of ZnMgO Thin Films Prepared by the Sol-Gel Method
Authors: Wei Min , Deng H. , Chen H. , Chen J.J.
Published: March 2009

Mg-doped (≤15at%) ZnO thin films were prepared on quartz glass substrates by sol-gel method using a spinning-techniques. The films were charactered by X-ray diffraction , UV Vis-NIR double beam spectrophotometer and a SHIMADZU fluorespectrometer. It was found that optimally crystallized when the Mg concentration is 9at% were obtained. A photoluminescence study at room temperature revealed a blue shift in the near band edge emission peak with increasing of Mg content , which is agreement with the observation from the optical transmittance measurement. The photoconductive UV detectors based on these films were investigated, and the result showed that highest response was obtained from the photodecters fabricated by films with 15at% Mg concentration.
Test on Sound Transmission Characteristic of PTFE Micro-Aperture Membrane
Authors: Lin Wan Feng , Lou Wen Zhong , Xu Jing , Song Ren Long , Hu Liang
Published: March 2009

: It is a test of sound transmission characteristic of PTFE Micro-aperture Membrane,through it we found that the PTFE Micro-aperture Membrane is an excellent material of sound transmission for its special structure, though the basic rule is of no difference from normal material. Something more important, from test data, it was discovered that PTFE will not affect sound transmission when aperture diameter reaches 0.22m, which is valuable for the research of sound transmission on Micro-aperture.
The Research on Sacrificial Layer in the Fabrication of Micro Electromagnetic Relay
Authors: Liu Ben Dong , Li De Sheng , Yang Jia Hui
Published: March 2009

The armature fabricated with the sacrificial layer techniques is an important part of micro electromagnetic relay. So the sacrificial layer is one of the key fabrication processes in the realization of prototype of micro electromagnetic relay. In this paper several sacrificial layers including Copper, Polyimide and Positive photoresist are studied based on the investigation of the research on sacrificial layer and binding the characteristic of micro electromagnetic relay’s fabrication process.
Single Neuron Adaptive PID Control of the Silicon-Based Integrated Micro Nano-Positioning XY-Stage
Authors: Wang Jia Chou , Rong Wei Bin , Sun Li Ning , Li Xin Xin
Published: March 2009

An integrated micro xy-stage is designed and fabricated for application in nanometer-scale operation and nanometric positioning precision. This device integrates the functions of both actuating and sensing in the same silicon ship and is mainly composed of a silicon-based xy-stage, electrostatics comb actuator and a displacement sensor. In this paper a robust control strategy based on single neuron adaptive PID control theory is developed for silicon-based xy-stage, considering electrical, mechanical, and stiffness models. Single neuron adaptive PID control enables compact realization of a robust controller tolerant of device characteristics variation, types of inherent instabilities, and improving dynamical characteristics. The experimental results verified that the controller is more suitable for the silicon integrated micro xy-stage, under which the settling time is less than 2.5ms and the repeatability error is better than ±24.9nm. In addition, the presented control scheme is simple to implement in practical application.
Metrology Method of Line Edge Roughness with Nanometer Scale Precision Using Atomic Force Microscopes
Authors: Li Ning , Zhao Xue Zeng , Wang Wei Jie
Published: March 2009

This paper proposes a methodology method for line edge roughness (LER) measurement and characterization using atomic force microscope. The definition and origins of LER are discussed firstly. A LER quantificational method using image processing and threshold method is presented, which is used to analyze AFM images of Silicon lines and extract LER characteristics. Then the energy distribution of LER is determined by the multi-scale analysis based on wavelet transform and the parameters of multi-scale characterization were given. The experiment data shows that this method can offer an effective quantitative analysis of LER.
The Effect of Different Flow Patterns on Anode Fluid Behaviors of Micro Direct Methanol Fuel Cells
Authors: Zhang Bo , Zhang Yu Feng , Liu Xiao Wei , Zhang Peng
Published: March 2009

Based on the visualization technology, we investigated experimentally the effect of different flow patterns on anode fluid behaviors of the μDMFC (Micro Direct Methanol Fuel Cell) with a transparent material under the same condition. Stainless steel mesh was utilized as the current collector which was distinct from the carbon cloth or carbon paper. Four dissimilar flow patterns were developed and tested. The observation of the effect of different flow patterns revealed that movements of dilute methanol solutions and CO2 gas bubbles in the dot and parallel flow fields represented more difficult, which could result in a decline of the μDMFC performance. The study also showed that a channel blocking in the single-serpentine flow field would be extremely terrible which could lead to a fuels leaking of the μDMFC, meanwhile the liquid-gas flow was more fluent and stable in a double-serpentine flow field. Therefore, due to its advantages, a double-serpentine flow pattern is more suitable for the μDMFC application compared with the other flow patterns.
The Design of a MEMS Surface Resonant Magnetometer
Authors: Hu Mu Zhi , You Zheng , Yang Jian Zhong , Wu Ling Qi
Published: March 2009

In this paper, a MEMS surface resonant magnetometer based on Lorentz force is presented. This magnetometer has three current carriers to sense the magnetic field and changes into deflection of beams which will be detected by the comb-capacitance. The alternating current carried by oscillate beams has the same frequency as resonant frequency of the magnetometer structure to make the deflection magnified Q (Quality-factor) times, therefore, it becomes more easily to measure. In this paper, the mechanical model of the sensitive element is established. The equations of stiffness of the system, deflection, first-order resonance frequency and sensitivity are setup and simulated in ANSYS, as well as second-order to fourth-order modal, and harmonic excitation response simulation. It can be seen that the simulation results are in good accordance with the theoretical calculations, which proves the feasibility and the rationality of the theoretical model. The dimensions of the structure are designed, as well as the processing sequence Anodic Silicon-Glass Bonding and Silicon DRIE Multi-user Bulk Micromachining Process which will be used to manufacture the magnetometer. The MEMS surface resonant magnetometer has a high sensitivity, simple structure and easy to manufacture. The prototype sensors are being manufactured in NEDI now.
Error Autocompensation of Micromachined Gyroscopes
Authors: Qin Zi Ming , Yuan Wei Zheng , Chang Hong Long , Xie Jian Bing
Published: March 2009

. Error autocompensation using a non-MEMS micromotor is used to reduce the drift of micromachned gyroscopes. Theoretic deviation, numerical simulation and experiments are carried out. Test results show that the bias instability of micromachined gyroscopes is reduced from 542°/h to 39°/h, which makes their high end applications possible
Substrate Dependent Morphologies and Luminescence Properties of ZnO Nanostructures Prepared by Thermal Evaporation
Authors: Zhuang Bin Ping , Lai Fa Chun , Lin Li Mei , Lin Ming Bao , Qu Yan , Huang Zhi Gao
Published: March 2009

High density ZnO nanostructures were fabricated on Au coated Si and quartz substrates through once and the same oxidative evaporation of pure zinc powder. The coated side of the substrate was intentionally positioned in two directions of face and back to the zinc sources. Structure, morphology and optical properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, Raman spectra and room temperature photoluminescence measurements. The results showed that the samples on the different substrates with different directions have three different morphologies, including film-, rod- and comb-like nanostructures. Photoluminescence spectra of the samples showed the various bands centered in UV (380-390 nm), blue (470-490 nm), green (500-550 nm) and orange (610-620 nm) region. It demonstrates that the substrate material and the direction of substrate significantly affect the growth of ZnO nanostructures.
Preparation and Optical Absorption Properties of CuO/SiO2 Nanocomposite Films Fabricated by Sol-Gel Technique
Authors: Liu Jia Qin , Wu Yu Cheng , Li Guang Hai , Zhan Li De
Published: March 2009

CuO/SiO2 nanocomposite films were prepared by sol-gel process combined with the dip-coating technique. The mean diameter of CuO nanoparticles formed during the heat treatment process and mainly lay in the pores of mesoporous SiO2 matrix increased by increasing the heat treatment temperature. Consequently, compared with mesoporous SiO2 matrix, the pore volume and specific surface area of prepared samples descend. The diffraction peaks of Cu and CuO and the crystalline diffraction ring of CuO with body centered cubic structure can be clearly observed after heat-treated in air and H2 at 800 oC for 1h. By increasing the heat treatment temperature and concentration of CuO, a slightly red-shift could be observed.
Analysis of Temperature Effects on a Fully-Symmetrical Micromachined Gyroscope
Authors: Chen Wei Ping , Guo Yu Gang , Chen Xiao Liang , Chen Hong , Zhao Zhen Gang
Published: March 2009

This paper researches on the temperature effects of a fully-symmetrical micromachined gyroscope. The Young’s modulus and thermal expansion coefficient of silicon vary with the environment temperature, which affects the modes’ resonant frequencies of micromachined gyroscopes. The effects of temperature fluctuation on the modes’ resonant frequencies is simulated by the FEM software ANSYS. The simulation results show that the fully-symmetrical gyroscope’s resonance frequencies decrease with the increase of temperature and the decrease degree nearly 0.256Hz/°C, but the two modes’ resonance frequencies matches well. The micromachined gyroscope’s dynamic characteristics are tested. The resonant frequencies and the quality factor are reduced with the increase of temperature and the decrease degree of the fit linear about the resonant frequencies is 0.276 Hz/°C. The test results are in good accordance with the simulation results.
A Novel Structure of Membrane Electrode Assembly for DMFC
Authors: Suo Chun Guang , Liu Xiao Wei , Wang Xi Lian
Published: March 2009

Membrane electrode assembly (MEA) is the key component of direct methanol fuel cell (DMFC), the structure and its preparation methods may bring great effects on the cell performances. Due to the requirement of the high performance of the MEA for the micro direct methanol fuel cell (DMFC), we provide a novel double-catalyst layer MEA using CCM-GDE (Catalyst Coated Membrane，CCM；Gas Diffusion Electrode，GDE) fabrication method. The double-catalyst layer is formed with an inner catalyst layer (in anode side: PtRu black as catalyst, in cathode side: Pt black as catalyst) and an outer catalyst layer (in anode side: PtRu/C as catalyst, in cathode side: Pt/C as catalyst). The fabrication procedures are important to the new structured MEA, thus three kinds of fabrication methods are studied, including CCM-GDE, GDE-Membrane and CCM-GDL methods. It was found that the CCM-GDE technology may enhance the contact properties between the catalyst and PEM, and increase the electrode reaction areas, resulted in increasing the performance of the DMFC.
PDMS Microlens Arrays Fabrication Method Based-on Parylene C Lift-Off
Authors: Tong Jian Hua , Sun Yu
Published: March 2009

Microlenses are important components in optical data interconnects and MEMS-based microscopy imaging. Several microfabrication processes have been developed for the production of microlens arrays. However, assembly of microlens arrays is usually required. In this paper, we demonstrate the application of PDMS membrane patterning based on parylene C lift-off to the construction of PDMS microlens arrays on a glass substrate without an assembly step.
The I-V Characteristics and Percolation Threshold of the Cement-Based Materials Filled with Multi-Walled Carbon Nanotubes
Authors: Luo Jian Lin , Duan Zhong Dong
Published: March 2009

Some multi-walled carbon nanotubes (NMWTs) were firstly dispersed in aqueous solution with surfactant ultrasonic dispersion process, then mixed into cement matrix, casting six groups cement-based materials filled with varying NMWTs additions (nwt) (NFCMs), and as comparison, the plain referential cement paste was fabricated. The ampere-volt (I-V) characteristics and percolation threshold of this type of nanocomposites were focused by four-electrode method. Results show that, the I-V features of the reference has obvious nonlinearity due to polarized reaction within cement hydrated electrolytes after being induced by passing 0~±30 V voltages, those of the NFCMs with six different nwt still have somewhat nonlinear traits, which mainly attribute to the double-layer coatings between NMWTs and out-encapsulated cement hydration isolation. The resistivity (ρ) of the NFCM nanocomposite steadily decreases with the increment of nwt, which contributes to superior capabilities of charge transporter and near-field emission of NMWTs, and the overlapped chance of physical contacts between conducting aggregates of NMWTs and bulk matrix increases by nwt enhancing; although there is still some fluctuation on ρ, but it becomes weaker and weaker by nwt increasing. The percolation threshold of the NFCMs is nwt being 2.0%, and the integrated network pathways at micro-scale form between NMWTs each other through the correspondent NFCM, also revealed in microstructure.
Preparation of Self-Assembly Monolayer by Scratching Si(100) Surface in the Presence of Aryl Diazonium Salts
Authors: Shi Li Qiu , Sun Tao , Yu Feng , Dong Shen , Yuan Fu Long
Published: March 2009

Mechanical scratching and chemical self-assembling can be combined to fabricate nano- or micro-scale functional structures on the oxide-coated silicon. The chemo-active species, such as NO2C6H4 groups, can be produce from aryldiazonium salt due to the breaking of chemical bond of silicon substrate when the diamond tool scratches the silicon sample in the presence of 4-benzoic nitryl diazonium tetrafluoroborate (NO2C6H4N2BF4). They may then induce grafting of an organic monolayer on the substrate via Si-C connection. The surface morphologies before and after chemomechanical reaction are characterized with Atomic Force Microscopy (AFM). We propose that chemomechanical reaction, which occurred during scratching the silicon surface, produce NO2C6H4 groups from aryldiazonium salt. The NO2C6H4 groups further bond with surface Si atoms via Si-C covalent bonds as confirmed from Infrared Spectroscopy (IR) results. To better understand the framework of the self-assembly monolayers (SAMs) on Si (100) surface, the first principles calculation at density functional theory levels has been employed to investigate the binding energy, bonds length and bonds angle. The reduced energy of system illuminates that the SAMs can be fabricated easily between aryldiazonium salt and Si (100) surface. The stability of system can be improved and SAMs can firmly stay on Si (100) surface.
Static Torsion of a Magnetostrictive Bimorph with In-Plane Anisotropy
Authors: Narsu Bai , Yun Guo Hong
Published: March 2009

A model for the bending and twisting deformation of the giant magnetostrictive cantilever is established in the framework of the principle of minimal free energy and four-parameter bending regime. The angular and magnitude dependence of the torsion and flexion response on the external field was discussed for cantilever beam. The torsion behavior of the cantilever is very sensitive to the external field and shows a hysteresis. Furthermore, the torsion hysteresis of the cantilever calculated by our model qualitatively agrees with recent experimental result, which suggests that our model is effective in describing the cantilever system with magnetic anisotropy.
Molecular Dynamics Simulation on the Out-of Plane Thermal Conductivity of Single-Crystal Carbon Thin Films
Authors: Zhang Xing Li , Sun Zhao Wei , Wu Guo Qiang
Published: March 2009

In this article, we select corresponding Tersoff potential energy to build potential energy model and investigate the thermal conductivities of single-crystal carbon thin-film. The equilibrium molecular dynamics (EMD) method is used to calculate the nanometer thin film thermal conductivity of diamond crystal at crystal direction (001), and the non-equilibrium molecular dynamics (NEMD) is used to calculate the nanometer thin film thermal conductivity of diamond crystal at crystal direction (111). The results of calculations demonstrate that the nanometer thin film thermal conductivity of diamond crystal is remarkably lower than the corresponding bulk experimental data and increase with increasing the film thickness, and the nanometer thin film thermal conductivity of diamond crystal relates to film thickness linearly in the simulative range. The nanometer thin film thermal conductivity also demonstrates certain regularity with the change of temperature. This work shows that molecular dynamics, applied under the correct conditions, is a viable tool for calculating the thermal conductivity of nanometer thin films.