共查询到20条相似文献,搜索用时 38 毫秒
1.
G. Fu N.H. Loh S.B. Tor B.Y. Tay Y. Murakoshi R. Maeda 《Applied Physics A: Materials Science & Processing》2005,81(3):495-500
The micro powder injection molding (μPIM) process was used to fabricate metallic microstructures in this paper. The production of 316L stainless steel microstructures arrays with the dimensions of ∅ 100 μm×height200 μmand∅ 60 μm × height 191 μm is presented. Injection molding was conducted on a conventional injection molding machine and silicon mold inserts with vertical sidewall made by deep reactive ion etching (DRIE) were used. Molded parts with microstructures were well obtained after selecting suitable processing parameters based on the feedstock characteristics. Then the molded parts were debound catalytically and sintered. Sintering at different temperature was conducted under vacuum. The effects of sintering temperatures were evaluated based on the polished and etched micrographs of the sintered microstructures. Finally Young’s Modulus of sintered microstructure was evaluated using nano-indenter.PACS 81.20.Ev 相似文献
2.
L. Liu N.H. Loh B.Y. Tay S.B. Tor Y. Murakoshi R. Maeda 《Applied Physics A: Materials Science & Processing》2006,83(1):31-36
Micro metal injection molding (μMIM) is being developed by some researchers for possible mass production of metallic microcomponents. Knowledge of densification and grain growth of structures in the micrometer regime is important for the design of microcomponents due to their impacts on dimensional tolerance and mechanical properties. In this paper, the effects of sintering temperature and time on densification and grain growth of stainless steel microsize structures fabricated by μMIM were investigated. In particular, the density of the microsize structures was compared with that of the components, dimensions in the millimeter range, on which the microsize structures reside. Models proposed by Kang, Brook, and Zhao and Harmer were used to study the densification and grain growth kinetics of microsize structures of ∅100μmat the final stage of sintering. Dense layers were formed on the microsize structures. Thus, the density of the microsize structures is higher than that of the microstructured components. The thickness of the dense layers increased with either increasing temperature or time. Zhao and Harmer’s model for lattice diffusion controlled densification and Brook’s grain growth model for lattice diffusion controlled pore drag exhibited good fits for the experimental results of microsize structures. PACS 81.20.Ev 相似文献
3.
The novel nanosecond laser micro-manufacturing of three-dimensional metallic structures 总被引:1,自引:0,他引:1
A micro-manufacturing technology is presented which allows the direct forming of three-dimensional metallic microstructures.
We replicate micro grid array structures on metallic foil surface. This investigation reveals that three-dimensional metallic
microstructures have a high spatial resolution at the micron-level. Numerical simulation results show that the material deformation
process is characterized by an ultrahigh strain rate. In addition, this method can fabricate large-area metallic microstructures
directly by single pulse. The replication cost is independent of the microstructures complexity. Therefore, laser micro-manufacturing
technology will be a potential laser microforming method which is characterized by low-cost, high efficiency.
PACS 83.50.Uv; 41.75.Jv; 62.50.+P; 81.20.Hy; 42.62.Cf 相似文献
4.
Liu L. Loh N. H. Tay B. Y. Tor S. B. Yin H. Q. Qu X. H. 《Applied Physics A: Materials Science & Processing》2011,103(4):1145-1151
Micro powder injection molding (μPIM) has been developed as a potential technique for mass production of microcomponents in microsystems due to its shaping
complexity at low cost, in which sintering is a crucial step to dictate the final properties of the microcomponents. In this
paper, final-stage sintering behavior of 316L stainless steel microsize structures prepared by μPIM, φ100 μm and φ60 μm, respectively, was studied. The effect of size reduction in the regime of micrometers on the density of various microsize
structures was investigated. Sintering kinetics of the microsize structures of φ100 μm and φ60 μm were studied based on particle level sintering models. It is found that the microsize structures of φ60 μm had higher density than the microsize structures of φ100 μm given the same sintering condition. The results indicate that size reduction in the regime of micrometers facilitated
densification of microsize structures. The grain growth mechanism of microsize structures varied with size. Whereas the grain
growth of the microsize structures of φ100 μm is governed by surface-diffusion-controlled pore drag, the grain growth of the microsize structures of φ60 μm is controlled by boundary diffusion. During densification, the microsize structures, φ100 μm and φ60 μm, are both controlled by lattice diffusion. The corresponding activation energies are reported in the paper. 相似文献
5.
Powder injection molding (PIM) is a high-volume manufacturing technique for fabricating ceramic and metal components that have complex shapes. In PIM design, it is important to know the injection molding behavior at different powder-polymer compositions so as to understand the trade-offs between ease-of-fabrication, process throughput, and part quality at the design stage. A limited database of materials properties at different powder-polymer compositions is a significant challenge that needs to be addressed in order to conduct accurate computer simulations that aid part and mold design in PIM. However, accurate material property measurements are expensive and time-consuming. In order to resolve these conflicting challenges it is hypothesized that experimental measurements of material properties of a filled polymer at a specific filler content combined with similar measurements of unfilled polymer will be adequate to estimate the dependence of properties on filler content using rule-of-mixture models. To this end, this article focuses on a literature review of experimental data obtained from measurements of rheological, thermal, and mechanical properties for a wide range of powder-polymer mixtures at various filler volume fractions. The experimental data were compared to property estimates using various predictive models. It is expected that the current review will be valuable in selecting appropriate predictive models for estimating properties based on the input data requirements for commercially available mold-filling simulation platforms such as Moldflow® and PIMSolver®. The combined protocol will be useful to design new materials and component geometries as well as optimize process parameters while eliminating expensive and time-consuming trial-and-error practices prevalent in PIM. 相似文献
6.
Sk.F. Ahmed P.K. Ghosh S. Khan M.K. Mitra K.K. Chattopadhyay 《Applied Physics A: Materials Science & Processing》2007,86(1):139-143
We have observed low-macroscopic field electron emission from wide bandgap nanocrystalline Al doped SnO2 thin films deposited on glass substrates. The emission properties have been studied for different anode-sample spacings and for different Al concentrations in the films. The turn-on field and approximate work function were calculated and we have tried to explain the emission mechanism from this. The turn-on field was found to vary in the range 5.6–7.5 V/μm for a variation of anode sample spacing from 80–120 μm. The turn-on field was also found to vary from 4.6–5.68 V/μm for a fixed anode-sample separation of 80 μm with a variation of Al concentration in the films 8.16–2.31%. The Al concentrations in the films have been measured by energy dispersive X-ray analysis. Optical transmittance measurement of the films showed a high transparency with a direct bandgap ∼3.98 eV. Due to the wide bandgap, the electron affinity of the film decreased. This, along with the nanocrystalline nature of the films, enhanced the field emission properties. PACS 81.20.Fw; 61.10.-i; 79.70.+q 相似文献
7.
K.M. Nowak H.J. Baker D.R. Hall 《Applied Physics A: Materials Science & Processing》2006,84(3):267-270
We report a novel “cold” self-cleaning technique for processing low temperature co-fired ceramic (LTCC) in the “green” state at high resolution and high speed, using a low power carbon dioxide laser. A particle ejection process involving both the ceramic grains and the organic binder produces material removal rates of >100 μm per pulse with lateral processing resolution of 50 μm and depth resolution comparable to ceramic grain size with no heat-effected zone or other deleterious thermal effects. The process has been used to drill microvias and to machine arbitrary shapes with high resolution. PACS 79.20.Ds; 42.62.Cf; 42.55.Lt; 81.20.Wk 相似文献
8.
Fong-Zhi Chen Cheng-Huan Chen Cheng-Hsien Wu Ching-Hsiang Kuo Jyh-Rou Sze Wei-Yao Hsu Yuan-Chieh Cheng 《Optical Review》2012,19(4):238-241
This paper introduces the development of a double-sided micro lens array (DSMLA) for application in micro laser projectors. For commercial mass production, it is necessary to investigate the concurrent engineering of optical design, mold fabrication, and plastic injection molding at once. This experiment based the design of the micro lens array on the scalar diffraction theory. The proposed DSMLA can simultaneously shape red, green, and blue laser beams into a uniform projection pattern. An ultra precision diamond turning machine using a slow tool servo method fabricated the mold. The study considered optical design constraints from the feedback of mold fabrication and plastic injection molding, measuring and comparing fabricated samples with calculated results. Experimental results show that the fabricated DSMLAs achieve the desired function and application feasibility for micro laser projectors. 相似文献
9.
F.E. Livingston H. Helvajian 《Applied Physics A: Materials Science & Processing》2005,81(8):1569-1581
A novel variable UV laser processing technique was developed that enables the concurrent fabrication of structures in photosensitive
glass-ceramic (PSGC) materials that range from the micro-scale to the meso-scale domains. This technique combines the advantages
of direct-write volumetric laser patterning and batch chemical processing. The merged non-thermal laser fabrication approach
relies on the ability to precisely and selectively alter the chemical etch rate of the PSGC by varying the laser exposure
during pattern formation. The present study determined that the chemical etch rate of a commercial photosensitive glass-ceramic
(FoturanTM, Schott Corp., Germany) in dilute hydrofluoric (HF) acid is strongly dependent on the incident laser irradiance during patterning
at λ=266 nm and λ=355 nm. For low laser irradiances, the etch rate ratio (Rexposed/Runexposed) increased nearly linearly with laser irradiance. The slopes of the linear ranges of the etch rate ratios were measured to
be 435.9±46.7 μm2/mW and 46.2±2.3 μm2/mW for λ=266 nm and λ=355 nm, respectively. For high laser irradiances, the measured etch rate ratio saturated at ∼30:1 with
a maximum absolute etch rate of 18.62±0.30 μm/min. The maximum absolute chemical etch rate was independent of the exposure
wavelength. Consequently, variation of the laser exposure during direct-write patterning permits the formation of variegated
and proximal high and low aspect ratio structures on a common substrate. The results show that adjacent microstructures with
aspect ratios ranging from <1:1 to ∼30:1 can be fabricated in a single, simultaneous batch chemical etch step without the
need for a complex masking sequence or post-process ablation step. This new technique facilitates rapid prototype processing
with pattern and component uniformity, and achieves material processing over large areas without incurring high cost.
PACS 42.62.-b; 42.79.-e; 81.05.Kf; 81.20.-n 相似文献
10.
J. Bekesi J. J. J. Kaakkunen W. Michaeli F. Klaiber M. Schoengart J. Ihlemann P. Simon 《Applied Physics A: Materials Science & Processing》2010,99(4):691-695
A new two-step method, facilitating the rapid generation of super-hydrophobic surface structures via parallel laser processing
followed by a replica generation by injection molding is reported. A self-made fused silica-based diffractive optical element
(DOE) is applied to distribute the laser energy into a 25×25 dot matrix. This DOE is used as a transmission mask for surface
ablation of metal molds, applying short-pulse UV laser pulses. In a subsequent process step, replicas of the processed stamp
are produced by variothermal injection molding, enabling the mass production of the surface pattern on plastics parts. The
resulting topography facilitates a super-hydrophobic behavior of the fabricated components. 相似文献
11.
Extraordinary thermal emission properties of the metallic surface microstructures induced by femtosecond lasers are investigated
in both experiment and theory. Within the spectral range of 4–17 μm, the measured maximum thermal emissivities at different
temperatures enhance significantly to about 100%. Especially for the coral-like surface structure, the improved thermal emission
behaviors can extend largely over the whole spectrum rather than happening at some distinctive wavelengths. Moreover, the
enhancement factor of the thermal emissivity is observed to depend on the wavelength and the idiographic morphology of the
microstructures. This phenomenon can be understood well by equivalent recognizing the SPP field coupling assisted transmission
of blackbody radiation through the microstructured interfaces, and the finite-difference time-domain simulations elucidate
the underlying physical pictures. 相似文献
12.
T.V. Kononenko S.V. Garnov S.M. Pimenov V.I. Konov V. Romano B. Borsos H.P. Weber 《Applied Physics A: Materials Science & Processing》2000,71(6):627-631
Laser ablation of thin TiN films deposited on steel substrates has been studied under wide-range variation of irradiation
conditions (pulsewidth, wavelength, energy density and spot size). It has been demonstrated that both picosecond (150–300 ps)
and nanosecond (5–9 ns) laser pulses were suitable for controllable ablation and microstructuring of a 1-μm-thick TiN film
unlike longer 150-ns pulses. The ablation rate was found to be practically independent of the wavelength (270–1078 nm) and
pulsewidth (150 ps–9 ns), but it increased substantially when the size of a laser spot was reduced from 15–60 μm to 3 μm.
The laser ablation technique was applied to produce microstructures in the thin TiN films consisting of microcraters with
a typical size of 3–5 μm in diameter and depth less than 1 μm. Tests of lubricated sliding of the laser-structured TiN films
against a steel ball showed that the durability of lubricated sliding increased by 25% as compared to that of the original
TiN film.
Received: 28 July 1999 / Accepted: 17 April 2000 / Published online: 20 September 2000 相似文献
13.
Periodic metallic nano/microstructures have received a great a deal of attention in the photonics research community over the last few decades due to their intriguing optical properties. Three‐dimensional metallic nano/microstructures such as metallic photonic crystals, metamaterials, and plasmonic devices possess unique characteristics of tailored thermal radiation, negative refraction and deep subwavelength confinement of light. In this article, the recent progress on the experimental methods for the realisation of three‐dimensional periodic metallic and thin metal film coated dielectric nano/microstructures operating from optical to mid‐infrared frequencies has been reviewed. Advancement of the state‐of‐the‐art nanofabrication methods over the last few decades have led to the development of metallic nano/microstructures of diverse geometries, high resolution features and large scale production. The recent progress in the novel fabrication methods have inspired the development of functional and exciting photonic devices based on periodic metallic nano/microstructures with various applications in photonics including communications, photovoltaics, and biophotonics. 相似文献
14.
Modeling and theoretical characterization of piezoelectric micro ultrasonic transducer (pMUT) using ZnO film sandwiched between nickel aluminum bronze (CuAl10Ni5Fe4) electrodes was reported in this paper. The transducer is targeted to be utilized in sonar applications. Analyses on the
model were carried out using finite element method. Model’s dimensional parameters were optimized for desired performance.
Simplified technique was proposed to determine transmit and receive sensitivities of the model. As the result, micro ultrasonic
transducer model with resonance frequency of 40 kHz was proposed with estimated receive and transmit sensitivities of −93
dB re 1 V/μPa and 137 dB re 1 μPa/V, respectively. Further model validations require actual device fabrication and this will
be included in our future works. 相似文献
15.
E. Neiss J.-L. Rehspringer L. Mager A. Fort J. Fontaine P. Montgomery M. Flury S. Robert 《Applied Physics A: Materials Science & Processing》2008,92(2):351-356
Ultraviolet laser machining of a hybrid organic/inorganic material prepared via a sol–gel process has been studied for the
fabrication of kinoforms or surface relief diffractive optical elements. The hybrid mixes silicon and titanium oxides and
an organic network in order to improve the mechanical properties. Different material compositions have been investigated.
Laser ablation of the hybrid material is observed at low laser fluence (measured threshold fluence of 125 mJ/cm2 at 248 nm/6 ns) and shows that the process is well adapted to micro-patterning by laser machining means. The best observed
depth resolution is 60± 20 nm and appears to be limited by the ablation setup. Finally, the fabrication of an effective diffractive
optical element and its operation at 1.06 μm are described.
PACS 81.20.Fw; 79.20.Ds; 42.79.-e 相似文献
16.
Manuj Nahar Ignacio F. Gallardo Kristofer L. Gleason Michael F. Becker John W. Keto Desiderio Kovar 《Journal of nanoparticle research》2011,13(8):3455-3464
A continuous aerosol process has been studied for producing nanoparticles of oxides that were decorated with smaller metallic
nanoparticles and are free of organic stabilizers. To produce the oxide carrier nanoparticles, an aerosol of 3–6 μm oxide
particles was ablated using a pulsed excimer laser. The resulting oxide nanoparticle aerosol was then mixed with 1.5–2.0 μm
metallic particles and this mixed aerosol was exposed to the laser for a second time. The metallic micron-sized particles
were ablated during this second exposure, and the resulting nanoparticles deposited on the surface of the oxide nanoparticles
producing an aerosol of 10–60 nm oxide nanoparticles that were decorated with smaller 1–5 nm metallic nanoparticles. The metal
and oxide nanoparticle sizes were varied by changing the laser fluence and gas type in the aerosol. The flexibility of this
approach was demonstrated by producing metal-decorated oxide nanoparticles using two oxides, SiO2 and TiO2, and two metals, Au and Ag. 相似文献
17.
We introduce a class of regularisable infinite dimensional principal fibre bundles which includes fibre bundles arising in
gauge field theories like Yang-Mills and string theory and which generalise finite dimensional Riemannian principal fibre
bundles induced by an isometric action. We show that the orbits of regularisable bundles have well defined, both heat-kernel
and zeta function regularised volumes. We introduce a notion of μ-minimality ( ) for these orbits which extend the finite dimensional one. Our approach uses heat-kernel methods and yields both “heat-kernel”
(obtained via heat-kernel regularisation) and “zeta function” (obtained via zeta function regularisation) minimality for specific
values of the parameter μ. For each of these notions, we give an infinite dimensional version of Hsiang's theorem which extends
the finite dimensional case, interpreting μ-minimal
orbits as orbits with extremal (μ-regularised) volume.
Received: 27 November 1995 / Accepted: 30 May 1997 相似文献
18.
19.
F.L. Pratt S.J. Blundell P.A. Pattenden W. Hayes K.H. Chow A.P. Monkman T. Ishiguro K. Ishida K. Nagamine 《Hyperfine Interactions》1997,106(1-4):33-38
We report studies of spin dynamics in the conducting polymers polyaniline and polypyrrole using both μ+SR and μ-SR techniques. These measurements reveal characteristic field dependences and cutoff frequencies for the muon spin relaxation
which can be related to the spin diffusion process. Clear evidence is seen for increased spin localisation at low temperatures
where a crossover occurs from two or three dimensional spin diffusion to a one dimensional diffusion regime.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Uncooled microbolometer detector: recent developments at ULIS 总被引:1,自引:0,他引:1
Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Fire-fighting,
predictive maintenance, process control and thermography are a few of the industrial applications which could take benefit
from uncooled infrared detector. Therefore, to answer these markets, a 35-μm pixel-pitch uncooled IR detector technology has
been developed enabling high performance 160×120 and 384×288 arrays production. Besides a wide-band version from uncooled
320×240/45 μm array has been also developed in order to address process control and more precisely industrial furnaces control.
The ULIS amorphous silicon technology is well adapted to manufacture low cost detector in mass production. After some brief
microbolometer technological background, we present the characterization of 35 μm pixel-pitch detector as well as the wide-band
320×240 infrared focal plane arrays with a pixel pitch of 45 μm.
The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 59570M (2005). 相似文献