Fabrication Of Plates Research Articles

Flexible micro manufacturing platform for the fabrication of PMMA microfluidic devices

In this work we present a micro manufacturing platform for the production of polymeric microfluidic devices on a mass scale, based on the integration of microinjection moulding and femtosecond laser (fs-laser) micromachining technologies. A mould prototype was designed for the fabrication of polymeric thin plates characterized by simplified microfeatures representative of typical Lab-on-a-Chip (LoC) devices. The injection moulding master tool includes replaceable metallic inserts, which were fabricated by exploiting the extreme flexibility and accuracy of fs-laser milling. Here, the laser process parameters have been studied and properly adjusted to meet the target geometry and surface quality of the mould inserts, which were subsequently characterized by confocal and SEM microscopy. The micro injection moulding (μIM) process parameters for the device production have been defined by complete three-dimensional filling and packing process simulations. Finally, the micro-injection mould with reconfigurable inserts was employed for the production of thin plates with simplified microfeatures using PMMA. The ability to reproduce these microfeatures via μIM is an essential step to approach to the mass-production of a polymeric LoC and the use of replaceable micro-inserts fabricated by direct fs-laser ablation promises high flexibility in the design and manufacturing of such devices.

Injection Molding of Carbon Nanotube-Filled, Polymer Composite Bipolar Plates

Bipolar plates are one of the primary components of polymer electrolyte membrane fuel cells. These plates deliver reactants to electrodes, remove reaction byproducts, transfer heat, provide mechanical stability, and conduct electrical current. While graphite is the most commonly used material for fabrication of bipolar plates, the machining costs associated with graphite are a major drawback to mass production. In addition, graphite-based plates make the greatest contribution to the weight of the fuel cell stack. For this reason, electrically-conductive polymer composites have been explored as an alternative to the traditional metal alloys commonly used for fuel cell bipolar plates [1]. Polymer composites can reduce both the weight and cost of the bipolar plate, while still providing sufficient electrical properties. In prior efforts, compression-molded, carbon fiber epoxy composites have shown promise to achieve the electrical conductivities needed for fuel cell bipolar plates [2]. While compression molding can be used for production of high volumes, injection molding is most ideal for the levels of mass production required for full scale commercialization of fuel cells. The main objective of this study is to investigate the suitability of injection molding polymer composites with sufficient electrical conductivities. Polymer composites based on nylon were developed for injection molding of bipolar plates. Carbon fiber was added to nylon at weight percentages ranging from 10 to 50%. The highest conductivity was obtained by direct injection molding. Results show that the percolation threshold for carbon fiber in nylon occurs around 25 wt%. Multi-walled carbon nanotubes were added to the direct injection-molded samples at weight percentages ranging from 2 to 4% to investigate the synergistic effects of adding multiple conductive fillers [3]. The addition of MWCNTs increases conductivities to United States Department of Energy technical targets for bipolar plate electrical conductivity (> 100 S/cm). Samples fabricated with MWCNTs and carbon fiber are shown to achieve up to 400% improvement in conductivity over samples with carbon fiber alone. The addition of carbon black as a third conductive filler, as well as the use of a polymer blend, may further increase electrical conductivity. [1] Mighri F, Huneault MA and Champagne MF. (2004) Electrically conductive thermoplastic blends for injection and compression molding of bipolar plates in the fuel cell application. Polymer Engineering & Science 44: 1755-1765.[2] Hwang IU, Yu HN, Kim SS, et al. (2008) Bipolar plate made of carbon fiber epoxy composite for polymer electrolyte membrane fuel cells. Journal of Power Sources 184: 90-94.[3] Shen L, Wang FQ, Yang H, et al. (2011) The combined effects of carbon black and carbon fiber on the electrical properties of composites based on polyethylene or polyethylene/polypropylene blend. Polymer Testing 30: 442-448. Figure 1

Effect of coating thickness and annealing temperature on ZrN coating failure of U-Mo particles under heat treatment

Zirconium nitride (ZrN) coating is used as a diffusion barrier layer on U-Mo powder surfaces to suppress interdiffusion layer formation. However, it has been reported that the structural integrity of the coating did not remain intact after fuel plate fabrication process. To assess the coating integrity during the fabrication process at high temperature, parametric studies were performed with different coating layer thicknesses and annealing temperatures for ZrN-coated U-7w.t.%Mo particles. The microstructure of the annealed samples was analyzed by using scanning emission microscopy (SEM) and X-ray diffraction. Finite element simulations were performed whether mechanical failure of the coating layer occurs under given annealing temperatures. The simulation results showed the effect of coating layer thickness and annealing temperature on the coating fracture. It was found that tensile hoop stress became larger to cause fracturing over the coating layers as the annealing temperature increased, which was consistent with the results of SEM analysis. By comparing experimental results with simulation results, the thresholds of coating layer thickness and annealing temperature for crack initiation was primarily determined by the U-7Mo particle size.

Fabrication of tungsten and carbon clad plates by sinter bonding methods for divertor system characterization

Full tungsten divertor is employed for ITER, and the tungsten will be the most potential candidate for the surface material of plasma facing components in fusion reactor after DEMO. Under a Broader Approach (BA) activity, a satellite tokamak device JT-60SA is expected to contribute the investigation of many factors and issues related to the fusion plasma and components. JT-60SA has a future plan to transfer the surface of plasma facing components from carbon fiber reinforced carbon composite (CFC) to tungsten, and investigate the interaction of plasma and tungsten. For this plan, joining and coating technologies of tungsten on CFC is an important issue. Present research developed a fabrication method of the W/CFC clad plates and investigated the mechanical, microstructural and thermal properties of them.

Ultra‐thin carbon/silicon carbide composite bipolar plate for advanced fuel cells

AbstractThe first cut results on the development of ultra‐thin, low gas permeable, easily machineable, high electrical conductivity and high mechanical strength bipolar plate made up of carbon reinforced ceramic matrix are reported for the strategic application. Short carbon fiber reinforced silicon carbide matrix composite is fabricated by chopping continuous carbon fibers into discrete length, exfoliating and dispersing the exfoliated carbon fibers in silicon carbide powder and finally hot‐pressing to make the composite. Three compacts containing exfoliated carbon fiber contents of 20, 30, 50 vol. % in silicon carbide matrix are prepared and characterized for electrical, thermal, gas permeability, density, and mechanical properties. The composite plates with exfoliated carbon fiber vol. % of 50, offer excellent electrical conductivity, flexural and compressive strengths and gas permeability of 2.2 × 10‐7 cm‐3 cm‐2 s‐1. Carbon/silicon carbide plate shows 37.5 % and 4.7 % lower volume and weight, respectively on comparing with the best reported data of carbon/polymer composite plate. Competency of the material for bipolar plate fabrication is tested and found that the ceramic carbon composite may open up the new horizon for the fabrication of ultra‐thin bipolar plates for strategic applications.

Atomic layer deposition frequency-multiplied Fresnel zone plates for hard x-rays focusing

The design and fabrication of Fresnel zone plates for hard x-ray focusing up to 25 keV photon energies with better than 50 nm imaging half-pitch resolution is reported as performed by forming an ultrananocrystalline diamond (UNCD) scaffold, subsequently coating it with atomic layer deposition (ALD) with an absorber/phase shifting material, followed by back side etching of Si to form a diamond membrane device. The scaffold is formed by chemical vapor-deposited UNCD, electron beam lithography, and deep-reactive ion etching of diamond to desired specifications. The benefits of using diamond are as follows: improved mechanical robustness to prevent collapse of high-aspect-ratio ring structures, a known high-aspect-ratio etch method, excellent radiation hardness, extremely low x-ray absorption, and significantly improved thermal/dimensional stability as compared to alternative materials. Central to the technology is the high-resolution patterning of diamond membranes at wafer scale, which was pushed to 60 nm lines and spaces etched 2.2-μm-deep, to an aspect ratio of 36:1. The absorber growth was achieved by ALD of Ir, Pt, or W, while wafer-level processing allowed to obtain up to 121 device chips per 4 in. wafer with yields better than 60%. X-ray tests with such zone plates allowed resolving 50 nm lines and spaces, at the limit of the available resolution test structures.

Fabrication of TiO2 Thin Film-Based Fresnel Zone Plates by Nanosecond Laser Direct Writing

Fresnel zone plates (FZPs) have been gaining a significant attention by industry due to their compact design and light weight. Different fabrication methods have been reported and used for their manufacture but they are relatively expensive. This research proposes a new low-cost one-step fabrication method that utilizes nanosecond laser selective oxidation of titanium coatings on glass substrates and thus to form titanium dioxide (TiO2) nanoscale films with different thicknesses by controlling the laser fluence and the scanning speed. In this way, phase-shifting FZPs were manufactured, where the TiO2 thin-films acted as a phase shifter for the reflected light, while the gain in phase depended on the film thickness. A model was created to analyze the performance of such FZPs based on the scalar theory. Finally, phase-shifting FZPs were fabricated for different operating wavelengths by varying the film thickness and a measurement setup was built to compare experimental and theoretical results. A good agreement between these results was achieved, and an FZP efficiency of 5.5% to 20.9% was obtained when varying the wavelength and the oxide thicknesses of the zones.

Fabrication of DIRC radiator bars and plates at InSync, Inc.

Fabrication of quality radiator bars and plates is paramount to a successful DIRC project. This write up discusses the trials and tribulations of the manufacture of ∼600 bars for the BaBar DIRC project and discusses the history and current capabilities of InSync, Inc.

Effects of irradiation on the interface between U-Mo and zirconium diffusion barrier

Irradiated fuel plates were characterized by microscopy that focused on the interface between U–Mo and Zr. Before irradiation, there were three major sub-layers identified in the U–Mo/Zr interface, namely, UZr2, Mo2Zr, and U with low Mo. The typical total thickness of this U–Mo/Zr interaction is 2–3 μm. The UZr2 sub-layer formed during fuel plate fabrication remains stable after irradiation, without large bubbles/porosity accumulation. However, this sub-layer becomes increasingly discontinuous as burnup increases. The low-Mo sub-layer exhibits numerous sub-micron bubbles/porosity at low burnup. Larger, interconnected porosity in this sub-layer was observed in a medium-burnup fuel specimen. However, at higher burnup, regions with the extra-large bubbles/porosity (i.e., larger than 5 μm) were observed in the U-Mo fuel foil at least 5 μm away from the original location of this sub-layer. The mechanism for the formation of the extra-large bubbles/porosity is still unclear at this time. In general, the U–Mo/Zr interface in monolithic U–Mo fuels is relatively stable after irradiation. No large detrimental defects, such as large interfacial bubbles or cracks/delamination, were observed in the fuel plates characterized.

Manipulation of the response of human endothelial colony-forming cells by focal adhesion assembly using gradient nanopattern plates

Nano feature surfaces are of growing interest as materials for a controlled response of various cells. In this study, we successfully fabricated gradient nanopattern plates to manipulate the response of blood-derived hECFCs without any chemical stimulation. Interestingly, we find that the sensitive nanopillar size for manipulation of hECFCs is range between 120 nm and 200 nm, which decreased the area and increased the filopodial outgrowth of hECFCs. Furthermore, we only modulate the nanopillar size to increase ROCK expression can be an attractive method for modulating the cytoskeletal integrity and focal adhesion of hECFCs.

Transmission electron microscopy investigation of neutron irradiated Si and ZrN coated UMo particles prepared using FIB

Two fuel plates, containing Si and ZrN coated U-Mo fuel particles dispersed in an Al matrix, were irradiated in the BR2 reactor of SCK•CEN to a burn-up of ∼70% 235U. Five samples were prepared by INL using focused ion beam milling and transported to SCK•CEN for transmission electron microscopy (TEM) investigation. Two samples were taken from the Si coated U-Mo fuel particles at a burn-up of ∼42% and ∼66% 235U and three samples from the ZrN coated U-Mo at a burn-up of ∼42%, ∼52% and ∼66% 235U. The evolution of the coating, fuel structure, fission products and the formation of interaction layers are discussed. Both coatings appear to be an effective barrier against fuel matrix interaction and only on the samples having received the highest burn-up and power, the formation of an interaction between Al and U(Mo) can be observed on those locations where breaches in the coatings were formed during plate fabrication.

Fabrication of hard x-ray zone plates with high aspect ratio using metal-assisted chemical etching

Fresnel zone plates are widely used as nanofocusing optics for x-ray microscopy, where the spatial resolution is set by the width of the finest rings while the efficiency is set by their thickness. This leads to the requirement for high aspect ratio nanofabrication. Metal-assisted chemical etching and atomic layer deposition has already been used to produce high aspect ratio zone plate structures on unthinned silicon wafers. The authors demonstrate here a substantial improvement on the achieved aspect ratio up to a value of 500:1, by producing 16 nm wide platinum zones with thicknesses up to 8 μm. At the same time, the silicon substrate was thinned to 15 μm as required for a practically useful optic. First tests have shown 4.8% diffraction efficiency using 20 keV x rays. This x-ray focusing efficiency is higher than most Fresnel zone plates for this photon energy and near what has been achieved with multilayer-coated Kirkpatrick–Baez mirrors, and multilayer Laue lenses. Hard x-ray zone plates offer the advantages of easy alignment, energy tunability, and one can make many zone plates in a batch on a single silicon chip.

Experimental Investigation and Analysis of Ecofriendly Compression Molded Woven Plant Fibre Polyester Composite

Polymer matrix composites are widely applied for the manufacturing of components employed in hostile environments to increase the service life and sometimes at a later stage for the reclamation of worn out parts. Every decade, numerous materials and techniques are being introduced and developed for the effective protection of low cost bulk materials out of which the fabrication of components could be done. Among such techniques hand layup, matched die mould methods, contact mould methods, filament winding and pultrusion methods has being employed increasingly in the process industries which has several significant advantages over other processes. It has become a process of its reliability, better process control, ease of use, good surface finish and closeness of dimensions. One among the method matched die mould method was selected as the process of preparation of the composite plate in the presented work. However, there are some inherent problems with control of resin flow, application of high temperature for curing during fabrication process. To address those main problems, a systematic investigation was carried out. The selected material is natural plant fibre available in abundant called “Crotalaria juncea” and is being employed as a green manuring plant in agriculture. In the investigation, the fibre is taken in two different forms of random and woven orientations and plate fabrication is done with unsaturated polyester resin as the matrix. The investigation is on woven orientation of biaxial, biaxially stitched and unidirectional woven types were done using the fibre to the size of the plate to be fabricated. Woven fibres of these three types were done at fibre design centre, Kerala. It was found that the fabrication could be done by placing two layer and three layer of the woven mat alone. So for the three woven types, two layer and three layer plates were fabricated to give about six plates in total. Here again to arrive at a closeness value for each combination, three plates were fabricated and the average value is got by testing. Tensile, flexural, impact and shear testing was done on all the plates as per ASTM standards and the responses were noted and plots were drawn and studied for the orientation for which the material possessed best property. The second part of the study was, with the experimental results got from the woven orientation, analysis was done by ANSYS and LS-DYNA software for the mechanical property and the responses got, was matching with the experimental testing methods and found that both the results were nearly the same thereby optimizing the results achieved. This is presented in detail in the forth coming chapters. The studies revealed that the fibre parameters taken had a significant influence on the mechanical properties. It was found that at a particular weight fraction the mechanical properties achieved the highest values in case of random orientation and particular woven orientations in case woven types. The increase in layers also had an influence over the property of the material. This composite prepared also initiates us in preparing newer composites with existing natural fibers, which haven’t been yet explored and which can reduce the cost. This gives way also in preparation of the same and releasing a newer variety of material to the Engineering industry which can be suited for some required application.

Fabrication of Fresnel plates on optical fibres by FIB milling for optical trapping, manipulation and detection of single cells

The development of economical optical devices with a reduced footprint foreseeing manipulation, sorting and detection of single cells and other micro particles have been encouraged by cellular biology requirements. Nonetheless, researchers are still ambitious for advances in this field. This paper presents Fresnel zone and phase plates fabricated on mode expanded optical fibres for optical trapping. The diffractive structures were fabricated using focused ion beam milling. The zone plates presented in this work have focal distance of ~5 µm, while the focal distance of the phase plates is ~10 µm. The phase plates are implemented in an optical trapping configuration, and 2D manipulation and detection of 8 µm PMMA beads and yeast cells is reported. This enables new applications for optical trapping setups based on diffractive optical elements on optical fibre tips, where feedback systems can be integrated to automatically detect, manipulate and sort cells.

Continuous cubic phase microplates for generating high-quality Airy beams with strong deflection.

Owing to the distinguishing properties of nondiffraction, self-healing, and transverse acceleration, Airy beams have attracted much attention in the past decade. To date, a simple approach for exquisitely fabricating cubic phase plates with both continuous variation of phase and micro size still remains challenging, which limits the generation of high-quality Airy beams for integrated micro-optics. Here, we report the elaborate design and fabrication of a continuous cubic phase microplate (CCPP) for generating high-quality Airy beams in micrometer scale. A CCPP with a precise size (60 μm×60 μm×1.1 μm) is fabricated by femtosecond laser direct writing, exhibiting a high optical efficiency (∼79%). The high-quality Airy beam generated via the CCPP demonstrates an unprecedentedly strong deflection (∼4.2 μm within a 90μm propagation distance) as well as being diffraction-free. Our research on the design and fabrication of miniature Airy phase plates paves the way toward high-performance integrated optics, optical micromanipulation, and optical imaging.

Effect of porosity on the manufacturing of U3O8-Al dispersion fuel plates

The pore volume present in the starting fuel meat of dispersion fuel plates influences the behavior of its deformation during the fuel plate fabrication by rolling to a great extent. This study was carried out to investigate the influence of pore content in the starting fuel meat on the manufacturing of aluminum-base dispersion fuel plates. Factors that affect the residual porosity present in the meat of the fuel plate were investigated. Results showed that the residual pore volume of aluminum-base dispersion-type U3O8-Al fuel plates depends on the characteristics of the starting fuel meat, which is fabricated by pressing. The residual pore volume depends on the U3O8 concentration. For a particular U3O8 concentration, the rolling process establishes a constant pore volume, which is called equilibrium porosity. The equilibrium porosity is insensitive to the initial pore volume present in the starting fuel meat. The research showed that fuel meat integrity was greatly influenced by the initial porosity of the fuel meat. U3O8-Al dispersion fuel plates were successfully fabricated with uranium loading above 3.0 gU/cm3. This uranium loading is equivalent to the one used in the U3Si2-Al dispersion fuel, currently operating at the IEA-R1 research reactor of the Nuclear and Energy Research Institute – IPEN/CNEN-SP. The U3O8-Al dispersion fuel can substitute the silicide fuel with advantages such as lower price and simpler manufacturing process.

Fabrication of continuous phase plates with small structures based on recursive frequency filtered ion beam figuring.

Large surface gradient and extensive mid-to-high spatial frequency in continuous phase plates (CPPs) with small structures make it difficult to achieve high-precision fabrication. An ion beam figuring (IBF) technology to fabricate CPPs with such characteristics is proposed in this paper. In order to imprint CPP microstructures with smaller spatial periods even down to 1mm in shorter time, we present a multi-pass IBF approach with different ion beam sizes based on the frequency filtering method. We discuss the selection principle and when to reduce ion beam sizes for different procedures to control dwell time and adequately exert the corrective capability in detail. This filtering method can obtains better surface quality in a faster way compared to the non filtering traditional IBF method. The experimental results verify this optimized method can effectively imprint complex microstructures with spatial period as small as 0.7 mm, surface peak-to-valleys (PV) smaller than 200nm and surface gradient as large as 1.8μm/cm to within 10 nm root-mean-square (RMS) of design specifications, which displays the advantages of our fabrication method.

Fabrication of metallic bipolar plates in PEM fuel cell using semi-stamp rubber forming process

Metal is considered to be a good material for a bipolar plate due to its good electrical conductivity, excellent mechanical properties, and low cost. In this study, fabrication of metallic bipolar plates with serpentine flow field microchannels was investigated by a novel rubber pad forming process. Stainless steel 316 with thickness of 0.1 mm was used. Polyurethane rubbers with the hardness of shore A40, A55, A65, and A90 and the thickness of 10, 20, and 30 mm were used in this study to manufacture bipolar plates. At first, convectional rubber pad forming process was used to produce bipolar plates by some experimental tests. In this step, the effect of applied force, rubber hardness, and rubber thickness on filling percentage, thickness distribution, and dimensional accuracy was investigated. The results showed that filling percentage would increase by rising applied force, but channel depth was not equal in different directions. Increases in rubber hardness led to improving uniformity in channel depth. In addition, decreases in rubber hardness and increases in rubber thickness caused higher filling volumes. However, maximum filling percentage, dimensional accuracy, and thickness distribution in convectional rubber forming process were not satisfying. Thus, a novel method was developed in this study in order to improve the quality of fabricated bipolar plates named semi-stamp rubber forming. The results indicated that using semi-stamp rubber forming instead of convectional rubber forming would lead to 11.7, 9, and 1.075% improvement in filling percentage, thinning percentage, and dimensional accuracy, respectively. According to the results, the developed model (semi-stamp rubber forming) could be a feasible technique in fabricating metallic bipolar plates.

Zone Plate Fabrication Using a Low Power Femtosecond Laser

With an advantage in photonic integration and device miniaturization, fabrication of micron sized diffractive optical elements has gained attention due to their low volume, light weight and flexible design. We discuss the fabrication of phase zone plates in soda-lime and borosilicate glass using a femtosecond laser, and its characterization. Our technique of fabrication involves a one-step laser direct writing process in comparison to the popular photolithography based micro-structuring. In this work, the femtosecond laser oscillator system is used to successfully fabricate phase zone plate structures at low energies and high repetition rate. In addition to this, a laser induced breakdown spectroscopy (LIBS) study was done to confirm the consistency of glass obtained from different manufacturers through its composition

大高宽比硬X射线波带片制作及聚焦测试

大高宽比硬X射线波带片制作及聚焦测试