Browsing by Author "Lin, CR"

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Application of heat treatment and dispersive strengthening concept in interlayer deposition to enhance diamond film adherence
(1997-10-31)
Lin, CR
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Kuo, CT
;
Chang, RM
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材料科學與工程學系
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Department of Materials Science and Engineering
Two different deposition processes were carried out to enhance adherence of diamond films on WC + 3 similar to 5%Co substrate with Ti-Si as the interlayer. One process can be called two-step diamond deposition process. Another process can be called interlayer heat treatment process. Diamond films were deposited by a microwave plasma chemical vapor deposition system. Ti and Si interlayer are deposited by DC sputter and an E-gun, respectively. Film morphologies, interface structure and film qualify were examined by SEM, XRD, Auger electron spectroscopy and Raman spectroscopy. The residual stresses and adhesion strengths of the films were determined by Raman spectroscopy and indentation adhesion testing, respectively. Comparing the regular one-step diamond deposition process with the present two different new processes, the average dP/dX values, which are a measure of the adherence of the film, are 354 kgf/mm, 494 kgf/mm and 787 kgf/mm, respectively. In other words, the interlayer heat treatment process gives the best film adherence on average. For the two-step diamond deposition process, the interlayer thickness and the percent diamond surface coverage of the first diamond deposition step are the main parameters, and there exists an optimum Ti thickness and percent diamond coverage for the best film adherence. The main contribution to better film adherence is not a large difference in residual stress, but is due to the following reasons. The interlayer heat treatment can transform amorphous Si to polycrystalline Si, and may form strong TiC and SiC bonding. The polycrystalline Si and the diamond particles from the first diamond deposition step can be an effective seeds to enhance diamond nucleation. Published by Elsevier Science S.A.
Brazing characteristics of diamond on various substrates with different brazing alloys
(1995)
Kuo, CT
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Lin, CR
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Lien, HM
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材料科學與工程學系
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Department of Materials Science and Engineering
Finite element analysis of hot embossing of polymer optical sheet
(2003)
Lin, CR
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Chen, RH
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Hung, C
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機械工程學系
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Department of Mechanical Engineering
Finite element simulation of the hot embossing process used in manufacturing polymer optical components was performed using MARC code. This research focuses mainly on predicting contractive deformation during the cooling procedure in making a polymer optical sheet. A nonlinear viscoelastic model of temperature and pressure-dependent material properties, exhibiting creep, was used to capture the properties of amorphous polymer material. The simulation of contractive deformation confirms with the results of corresponding experiments, indicating that this finite element model can be used to simulate the hot embossing of a polymer with acceptable results.
High adhesion and quality diamond films on steel substrate
(1998-06-01)
Lin, CR
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Kuo, CT
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材料科學與工程學系
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Department of Materials Science and Engineering
A process to deposit a diamond coating on steel substrates has been successfully developed. It includes the electroplating of nickel by using an electrolyte dispersed with micro-diamonds, and then a diamond deposition through a microwave plasma chemical vapor deposition system. The diamond films were characterized by Raman and CL spectroscopy, XRD, SEM and SEM line scanning. The results show a high diamond crystal quality, low residual stress (about 0.67 GPa) and high nucleation density. The adhesion of the films was evaluated by a cutting test and an interface examination. The results show that the retentivity of the diamond grits in the films after the cutting test is much better than that in the commercial electroformed diamond tools. The advantages of the process are: (1) the formation of nickel-carbon-hydrogen alloys to enhance diamond nucleation and growth, (2) the micro-diamonds acting as the seeds for diamond nucleation and growth, and forming effective mechanical interlocking with the nickel interlayer, and (3) the formation of good diffusion bonding of the nickel interlayer with the steel substrate. (C) 1998 Elsevier Science S.A.
Improvement in adhesion of diamond films on cemented WC substrate with Ti-Si interlayers
(1998-12-01)
Lin, CR
;
Kuo, CT
;
Chang, RM
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Diamond films were deposited on the cemented WC+(3-5)% Co substrates by a microwave plasma chemical vapor deposition system. The substrates were pretreated with various processing steps before diamond deposition, including: polishing, etching for Co removal, Ti coating by DC sputter, and amorphous Si coating by E-gun. The residual stress of the films was determined by both Raman shift and low incident beam angle X-ray diffraction (LIBAD) methods. The adhesion of the films was evaluated by indentation adhesion testing. The him morphology and film-substrate interface structure were examined by SEM and Auger electron spectroscopy, respectively. The results show that Ti-Si can be a good interlayer to improve film adhesion and inhibit diffusion of Co to the substrate surface on diamond nucleation. This is due to the formation of strong TiC and SiC bonding to enhance film adhesion; Si acts as a promoter for diamond nucleation, and the residual stress with application of interlayer is much lower than that interlayer-free. The results also show the existence of an optimum Ti thickness for the best film adhesion. (C) 1998 Elsevier Science S.A. All rights reserved.
Improvement of diamond film adhesion on cemented carbides (WC/Co) by using Ti and micro-diamonds as seeding germination
(1998-01-06)
Lin, CR
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Kuo, CT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Improvement of mechanical properties of electroplated diamond tools by microwave plasma CVD diamond process
(1998-11-10)
Lin, CR
;
Kuo, CT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The growth and surface modification of irregular diamond grains of electroplated diamond tools have been developed successfully. Results show that the adherence, cutting ability, and wear resistance of diamond grains are improved by this process. In this study, the crystallization and quality of diamond grains were determined by SEM (SE and BSE), Raman spectroscopy, and XRD determination. Tests using a block-on-ring tribotester were also carried out to examine the adherence, cutting ability, and wearing resistance of the electroplated diamond tools, The adherence of diamond grains was also observed on a SEM microphotograph of the cross-section view of specimens. SEM line scanning was performed to determine whether the alloy elements are effectual in promoting the diffusion bonding strength among diamonds, the interlayer and substrate. (C) 1998 Elsevier Science S.A. All rights reserved.
Origins of the residual stress in CVD diamond films
(1996-12-15)
Kuo, CT
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Lin, CR
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Lien, HM
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交大名義發表
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材料科學與工程學系
Diamond films were deposited on (100) Si wafer, WC (5%Co) and quartz substrate materials by a microwave plasma chemical vapor deposition (CVD) system. The effects of deposition and substrate conditions on residual stress of the films were systematically investigated The films were characterized by scanning electron microscopy, X-ray diffraction, Raman and indentation adhesion testing. The him structure including its non-diamond carbon content, crystal size, texture coefficient, film thickness and surface roughness were examined. The results show that the residual stress of the films is a function of the surface pretreatment, in addition to the substrate material and deposition conditions. The origins of the residual stress are mainly the thermal stress and the intrinsic stress. The intrinsic stress is mainly from the effect of the non-diamond carbon content in the diamond crystals, not at the crystal boundaries. A greater non-diamond carbon content in diamond crystals results in a greater residual stress. The texture of the films has no significant effect on the residual stress. A low compressive residual stress on Si wafer is beneficial to the adhesion of the film.
The characterisation and finite-element analysis of a polymer under hot pressing
(2002)
Lin, CR
;
Chen, RH
;
Hung, C
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機械工程學系
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Department of Mechanical Engineering
Finite-element simulation of the hot pressing process has been performed using ABAQUS. The viscoelastic polymer (polymethyl methacrylate) used in this study has mechanical properties that depend on the temperature and working pressure. Based on the nonlinear viscoelastic model, the polymer material behaviour is simulated successfully with the data obtained from material tests. Simulation results conform to related experiments, indicating that the approach can accurately predict pressure distribution within a polymer hot pressing.