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Papers - Yan, Jiwang

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Molecular Dynamics Investigation of Nanometric Cutting of Single-Crystal Silicon Using a Blunt Tool

Ameli Kalkhoran S., Vahdati M., Yan J.

JOM (JOM) 71 ( 12 ) 4296 - 4304 2019

ISSN 10474838

© 2019, The Minerals, Metals & Materials Society. A cutting process is strongly affected by depth of cut (h0) and tool edge radius (re), the relationship of which is described by relative tool sharpness (RTS = h0/re). In nanometric cutting, the depth of cut is far smaller than the tool edge radius, thus the tool is actually a very blunt one with a highly negative effective tool rake angle (~ − 90°). However, most previous studies have assumed the tool is extremely sharp with a nanometric edge radius, and to date there is very little literature on the cutting mechanism for a blunt tool (RTS < 1). In this study, the material deformation/removal behavior and forces under a small RTS from 1 to 0 were investigated via molecular dynamics. The results show that the surface integrity and chip formation are strongly affected by RTS. As RTS is reduced to 0.25 or smaller, rubbing and ploughing occur with no material removal. In such a circumstance, the force angle drops sharply with remarkable subsurface damage formation in the workpiece. These findings are distinctly different from the common belief, and provide new information for the optimization of the silicon wafer manufacturing process.

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Study on infrared transmittance of si-polymer hybrid structure press molded using a coupling agent

Ishide H., Yan J.

International Journal of Automation Technology (International Journal of Automation Technology) 13 ( 6 ) 817 - 824 2019

ISSN 18817629

© 2019, Fuji Technology Press. All rights reserved. Hybrid structures of single-crystal silicon and high-density polyethylene (HDPE) with high transmittance in the mid-to-far infrared region are used as infrared lens substrates. The hybrids are usually fabricated by high-precision press molding. The Si-HDPE hybrid lens previously fabricated had a low transmittance in the 9–10 μm wavelength region, thereby limiting its application for human body detection. In this study, a Si-polymer hybrid structure was fabricated using a new polymer without any silane coupling agent. Interfacial adhesion between the polymer and the Si substrate was realized with an extremely thin (a few micron thick) layer of an interfacial silane coupling agent. The press molding conditions that led to improved bonding strength and infrared transmittance of the hybrid substrate were investigated. A transmittance similar to that of a single-crystal Si substrate was achieved in the 9–10 μm wavelength range.

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Generation of microcones on reaction-bonded silicon carbide by nanosecond pulsed laser irradiation

Meshram T., Yan J.

International Journal of Advanced Manufacturing Technology (International Journal of Advanced Manufacturing Technology) 108 ( 4 ) 1039 - 1048 2019

ISSN 02683768

© 2019, Springer-Verlag London Ltd., part of Springer Nature. Silicon carbide (SiC) is heavily used in the industry due to its resistance to chemical wear and excellent mechanical properties such as high hardness and high stiffness. However, these properties make it difficult to produce micro and nanostructures on the surface of SiC by conventional methods. In this study, high-density microcones that protrude ~ 10 μm above the initial surface have been fabricated by nanosecond pulsed Nd:YAG laser irradiation (λ = 532 nm) on reaction-bonded SiC. Geometrically aligned cones were also fabricated by modifying the laser scanning path, and effect of different parameters such as pulse frequency, laser fluence was studied. It was observed that the surface morphology of microcones was affected by the pulse width and beam overlap. X-ray spectroscopy and Raman spectroscopy showed that the microcones were mainly composed of silicon. Formation of these cone structures made the surface highly superhydrophilic with a contact angle of ~ 0°.

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Fabrication of porous composite by high-pressure sintering of silicon cutting chips and metal particles

Y. Sunaba, N. Tachikawa, Y. Katayama, J. Yan

Journal of the Japan Society for Abrasive Technology 62 ( 11 ) 584 - 588 2018.11

Research paper (scientific journal), Joint Work, Accepted

Experimental investigation of RB-SiC using Cu–CNF composite electrodes in electrical discharge machining

P. J. Liew, Z. Nurlishafiqa, Q. Ahsan, T. Zhou, J. Yan

The International Journal of Advanced Manufacturing Technology (International Journal of Advanced Manufacturing Technology) 98 ( 9-12 ) 3019 - 3028 2018.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 02683768

© 2018, Springer-Verlag London Ltd., part of Springer Nature. The performances of carbon nanofiber (CNF) reinforced copper (Cu) composite electrodes on the reaction-bonded silicon carbide (RB-SiC) ceramic were experimentally investigated by using electrical discharge machining (EDM). The effects of CNF content on material removal rate (MRR), electrode wear ratio (EWR), surface roughness (SR) and surface topography were examined. Results indicated that the addition of CNF to the Cu electrode increased the MRR of the workpiece. In addition, increasing the added CNF content increased the EWR of the Cu–CNF composite electrode and the SR of the machined surface. The results of one-way ANOVA indicated that the Cu–1.0 wt% CNF composite electrode exhibited the optimal MRR and EWR values, although this electrode resulted the maximum SR on the RB-SiC machined surface.

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Surface flattening and nanostructuring of steel by picosecond pulsed laser irradiation

T. Kobayashi, H. Sera, T. Wakabayashi, H. Endo, Y. Takushima, J. Yan

Nanomanufacturing and Metrology (Nanomanufacturing and Metrology) 1 ( 4 ) 217 - 224 2018.09

Research paper (scientific journal), Joint Work, Accepted, ISSN 2520811X

© 2018, International Society for Nanomanufacturing and Tianjin University and Springer Nature. Steel is used as a mold material for press/injection molding of plastic products. High accuracy and releasing ability are required for a steel mold surface. This paper proposes a surface finishing method for steel molds by using picosecond pulsed laser irradiation. The process involves two steps: one is surface flattening by removing the surface asperity through laser ablation, and the other is forming nanoscale laser-induced periodic surface structures (LIPSS) on the flattened surface. The two steps are realized by using the same laser at controlled laser fluence and focus position. Experimental results showed that LIPSS was successfully formed after surface flattening under specific ranges of laser fluence and defocus length. Furthermore, plastic forming experiments demonstrated that a steel surface with LIPSS significantly decreased the effective contact area and, in turn, reduced the mold releasing force. These findings provide the possibility of fabricating high-performance steel molds by picosecond pulsed laser irradiation.

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Surface Roughness in Ultrasonic-Assisted and Conventional Milling of Soda-Lime Glass

Y. El-Taybany, M. Hossam, J. Yan, H. El-Hofy

International Journal of Machining and Machinability of Materials (International Journal of Machining and Machinability of Materials) 20 ( 1-2 ) 82 - 99 2018.09

Research paper (scientific journal), Joint Work, Accepted, ISSN 17485711

© 2019 Inderscience. All Rights Reserved. Glass has an increasing demand in many industrial fields such as micro-channels and micro reactors in fluidic applications, lab-on-a-chip in medical applications, and micro lens arrays and optical devices. Machining of glass as one of hard-to-machine materials is challengeable due to its distinctive properties of high strength, hardness, and brittleness. Facing these challenges, ultrasonic-assisted milling (UAM); an advanced machining process; was provided for its effectiveness in machining such hard-to-machine materials. In this paper, the effects of feed rate, depth of cut, ultrasonic-vibration assistance, and cutting fluid on surface roughness in UAM of soda-lime glass compared with conventional milling (CM) were investigated. Results showed that, by introducing ultrasonic-vibration, higher surface roughness was obtained. The optimal cutting conditions were attained using response surface methodology. At the optimised parametric setting, the minimum surface roughness was found to be at wet conventional milling.

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Multi-scale dimple creation on metallic glass by a two-step method involving nanoindentation and polishing

H. Huang, J. Yan

Applied Surface Science (Applied Surface Science) 462 565 - 574 2018.06

Research paper (scientific journal), Joint Work, Accepted, ISSN 01694332

© 2018 Elsevier B.V. Creation of micro dimples on material surface is significant for their functional applications. Because of unique properties, metallic glasses are regarded as emerging structural and functional materials but they are also a kind of difficult-to-cut materials due to high hardness and easy to crystallization and oxidation. In this study, a new method was proposed to fabricate micro dimples on metallic glass surface, which consisted of two steps, nanoindentation experiments to form the pre-indent array followed by polishing. Via this two-step method, square and rectangle dimples were successfully formed which exhibited multi-scale features with one relatively large dimple with width in micron-scale and depth in nanometer-scale, together with relatively small residual indents in nanometer-scale distributed on its bottom surface. The experimental results indicated that the depth of multi-scale dimples was affected by the spatial interval between two indents and the polishing time. Under the used experimental conditions, for the same polishing time, the depth of the large dimple was decreased when increasing the interval; for the same interval, with increase in the polishing time, the depth of the large dimple was also decreased. The possible formation mechanism of the large dimple was discussed, which was mainly ascribed to the enhanced material removal at the position of pre-indent array because of the concentration of polishing particles by the pre-indents.

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The coupling effects of laser thermal shock and surface nitridation on mechanical properties of Zr-based metallic glass

H. Huang, M. Jiang, J. Yan

Journal of Alloys and Compounds (Journal of Alloys and Compounds) 770 864 - 874 2018.06

Research paper (scientific journal), Joint Work, Accepted, ISSN 09258388

© 2018 Elsevier B.V. Laser processing is a versatile tool for applications in the field of metallic glasses (MGs). Previous studies reported that surface nitridation, i.e. the formation of ZrN phase, occurred when laser irradiation of Zr-based MG was performed in nitrogen gas. Additionally, it was reported that laser thermal shock usually softened the irradiated surface. Therefore, the coupling effects of laser thermal shock and surface nitridation on mechanical characteristics of Zr-based MG should be further clarified. For this purpose, in this study, laser irradiation of Zr-based MG was conducted under various experimental conditions, followed by evaluating the surface characteristics by X-ray diffraction (XRD), nanoindentation, and energy-dispersive X-ray (EDX) spectroscopy. Experimental results indicated that the nanoindentation hardness, serrated flow, and surface shear bands were significantly affected by laser irradiation in nitrogen gas. Both surface softening and hardening were observed which depended on the experimental conditions. A competition mechanism between laser thermal shock and the introduction of ZrN phase was employed to rationalize these results. Furthermore, the affecting layer of ZrN phase along the depth direction was measured by EDX. The obtained results suggest a new method to introduce secondary phase into Zr-based MG surface and further to tune the mechanical characteristics of MGs.

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Softening of Zr-based metallic glass induced by nanosecond pulsed laser irradiation

H. Huang, M. Jiang, J. Yan

Journal of Alloys and Compounds (Journal of Alloys and Compounds) 754 215 - 221 2018.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 09258388

© 2018 Elsevier B.V. Laser irradiation has been recently used to tune the mechanical properties of metallic glasses (MGs). However, the mechanism for plasticity improvement by laser irradiation is still not completely clear and requires further investigation. In this study, nanosecond pulsed laser irradiation is applied on a Zr-based MG surface under various laser powers, scanning speeds, and numbers of irradiation cycles. Then, the mechanical properties of the as-cast and laser-irradiated MG surfaces are characterized by nanoindentation tests. In particular, the indentation hardness, load-depth curve, serrated flow, and residual indent morphology of the surfaces are compared. The results show that the nanosecond pulsed laser irradiation softens the irradiated regions; the effect of the irradiation is slightly dependent on the laser irradiation parameters, and especially the laser scanning speed. Furthermore, laser irradiation considerably affects serrated flows in the load-depth curve and shear bands on the top surface, denoting different plastic deformation characteristics compared with the non-irradiated sample. These differences could be rationalized in terms of laser irradiation-induced formation of pre-existing shear bands in the subsurface layer, as well as thermal effects. The present results are expected to enhance the general understanding of the effects of laser irradiation on the mechanical properties of MGs.

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Material removal mechanism and surface integrity in ultraprecision cutting of porous titanium

M. Heidari, J. Yan

Precision Engineering (Precision Engineering) 52 356 - 369 2018.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 01416359

© 2018 Elsevier Inc. Porous titanium presents unique material properties with a wide variety of mechanical and biomedical applications. Porous titanium components fabricated by near net-shape technologies require further machining processes to improve the surface quality and form accuracy, and in turn, the added value of the products. In this work, major factors dominating the surface integrity in ultraprecision cutting of porous titanium using single-crystal diamond tools were investigated. The results demonstrated that the presence of pores significantly changed mechanism of cutting. The chip morphology and surface topography depended on pore size and undeformed chip thickness. At an extremely small undeformed chip thickness, a majority pores were closed due to the welding phenomenon, leading to a sharp drop of surface porosity. In contrast, large pores cause craters on the machined surface and segmentation of chips and protruding lamella, especially at a large undeformed chip thickness. A coolant could lubricate the tool-workpiece interface and the shear deformation, which decreased cutting forces. On the other hand, the rapid cooling effect enhanced the work hardening effect and increase the hardness of the machined surface. Tool wear in cutting porous titanium is suppressed compared with that of pure titanium, especially in wet cutting.

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Nanosecond pulsed laser irradiation of sapphire for developing microstructures with deep V-shaped grooves

N. Takayama, S. Asaka, J. Yan

Precision Engineering (Precision Engineering) 52 440 - 450 2018.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 01416359

© 2018 Elsevier Inc. A nanosecond pulsed Nd:YAG laser was used to irradiate a sapphire substrate to produce 3-dimensional microstructures with sharp V-shaped grooves. In initial experiments, where single grooves were machined, a maximum taper angle of ∼79° was obtained. At constant laser parameters, the taper angle remained constant. As the taper angle increases from a flat surface, the irradiated area increases while incident fluence decreases; once the incident fluence approaches the ablation threshold, the taper angle becomes constant. The taper angle could be controlled by the laser fluence, scanning speed and incident angle of the laser beam. Using these results, a kind of surface microstructure, comprised of micropyramids with steep walls, was successfully machined for optical measurement applications. The surface roughness, transmittance and crystallinity of the microstructure surface could be controlled by the laser scanning speed. By applying the taper formation mechanism proposed in this study, the micromachining of sharp microstructures with steep walls on various hard brittle materials becomes possible.

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Microgrooving of a single-crystal diamond tool using a picosecond pulsed laser and some cutting tests

N. Takayama, J. Ishizuka, J. Yan

Precision Engineering (Precision Engineering) 53 252 - 262 2018.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 01416359

© 2018 Elsevier Inc. Irradiation of a single-crystal diamond tool was performed with a picosecond pulsed laser to produce a tool with a microgrooved edge. This tool was then used in a metal cutting process to transfer the edge grooves onto a workpiece. Suitable conditions for laser irradiation on the diamond tool were experimentally investigated in terms of groove shape and laser-induced damage to diamond. Two different kinds of cutting experiments were performed; a uniformly grooved surface and a hierarchically structured surface were obtained. The chip formation mechanisms in the metal grooving process were examined. A copper workpiece was rapidly machined the surface of which had microgrooves with a pitch of a few micrometers. An increase of the contact angle was observed on the grooved surface, indicating the improvement of water repellency. This study presents an efficient method to machine microgrooves on metal materials for functional surfaces.

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Nanoscale surface patterning of diamond utilizing carbon diffusion reaction with a microstructured titanium mold

J. Yan, Y. Imoto

CIRP Annals – Manufacturing Technology (CIRP Annals) 67 ( 1 ) 181 - 184 2018.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 00078506

© 2018 A novel method was proposed for generating nanoscale surface patterns on single-crystal diamond by carbon diffusion with a microstructured titanium mold under controlled temperature and pressure. The depth, geometry, and surface integrity of the fabricated patterns were investigated by laser micro-Raman spectroscopy and white-light interferometry, and the titanium molds were analyzed by energy dispersive X-ray spectroscopy. The results showed that at specific temperatures and pressures, three-dimensional patterns with a depth of tens of nanometers and sloped/curved walls could be generated on a diamond surface after a few minutes, without causing any surface graphitization. The intensity profile and penetration depth of carbon atoms into the titanium were experimentally measured.

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Noncontact on-machine measurement system based on capacitive displacement sensors for single-point diamond turning

X. Li, Z. Zhang, H. Hu, Y. Li, L. Xiong, X. Zhang, J. Yan

Optical Engineering (Optical Engineering) 57 ( 4 ) 044105 2018.04

Research paper (scientific journal), Joint Work, Accepted, ISSN 00913286

© 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). On-machine measurements can improve the form accuracy of optical surfaces in single-point diamond turning applications; however, commercially available linear variable differential transformer sensors are inaccurate and can potentially scratch the surface. We present an on-machine measurement system based on capacitive displacement sensors for high-precision optical surfaces. In the proposed system, a position-Trigger method of measurement was developed to ensure strict correspondence between the measurement points and the measurement data with no intervening time-delay. In addition, a double-sensor measurement was proposed to reduce the electric signal noise during spindle rotation. Using the proposed system, the repeatability of 80-nm peak-To-valley (PV) and 8-nm root-mean-square (RMS) was achieved through analyzing four successive measurement results. The accuracy of 109-nm PV and 14-nm RMS was obtained by comparing with the interferometer measurement result. An aluminum spherical mirror with a diameter of 300 mm was fabricated, and the resulting measured form error after one compensation cut was decreased to 254 nm in PV and 52 nm in RMS. These results confirm that the measurements of the surface form errors were successfully used to modify the cutting tool path during the compensation cut, thereby ensuring that the diamond turning process was more deterministic. In addition, the results show that the noise level was significantly reduced with the reference sensor even under a high rotational speed.

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Characterization of recrystallized depth and dopant distribution in laser recovery of grinding damage in single-crystal silicon

K. Niitsu, Y. Tayama, T. Kato, H. Maehara, J. Yan

Materials Science in Semiconductor Processing (Materials Science in Semiconductor Processing) 82 54 - 61 2018.04

Research paper (scientific journal), Joint Work, Accepted, ISSN 13698001

© 2018 Elsevier Ltd A nanosecond pulsed Nd:YAG laser was irradiated on a boron-doped single-crystal silicon wafer with a diamond grinding finish to recover the grinding-induced subsurface damage. In order to visualize and measure the depth of the laser melted/recrystallized layer, small-angle beveled polishing was performed in pure water followed by KOH etching. It enabled the direct observation of the recrystallized region using a differential interference microscope and the measurement of its depth using a white light interferometer. Crystallinity analysis of the recrystallized region was carried out by using laser micro-Raman spectroscopy, and the dopant concentration profile was characterized by using radio frequency glow discharge optical emission spectrometry (rf-GD-OES). The results showed that the crystallinity and boron distribution in the recrystallized region changed after laser recovery. The dopant concentration becomes higher at the boundary of the recrystallized region and the bulk. This study demonstrates the possibility of boron concentration control by using suitable laser parameters.

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Fracture toughness and sliding properties of magnetron sputtered CrBC and CrBCN coatings

Q. Wang, F. Zhou, Q. Ma, M. Callisti, T. Polcar, J. Yan

Applied Surface Science (Applied Surface Science) 443 635 - 643 2018.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 01694332

© 2018 Elsevier B.V. CrBC and CrBCN coatings with low and high B contents were deposited on 316L steel and Si wafers using an unbalanced magnetron sputtering system. Mechanical properties including hardness (H), elastic modulus (E) and fracture toughness (K Ic ) as well as residual stresses (σ) were quantified. A clear correlation between structural, mechanical and tribological properties of coatings was found. In particular, structural analyses indicated that N incorporation in CrBC coatings with high B content caused a significant structural evolution of the nanocomposite structure (crystalline grains embedded into an amorphous matrix) from nc-CrB 2 /(a-CrB x , a-BC x ) to nc-CrN/(a-BC x , a-BN). As a result, the hardness of CrBC coating with high B content decreased from 23.4 to 16.3 GPa but the fracture toughness was enhanced. Consequently, less cracks initiated on CrBCN coatings during tribological tests, which combined with the shielding effect of a-BN on wear debris, led to a low friction coefficient and wear rate.

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Ultraprecision cutting of fluoride glass

ISHIZUKA Jun, NAGASAWA Keisuke, MIKAMI Masayuki, YAN Jiwang

Journal of the Japan Society for Abrasive Technology (The Japan Society for Abrasive Technology) 62 ( 2 ) 88 - 93 2018.02

Accepted, ISSN 0914-2703

Severe diamond tool wear may be caused by a chemical reaction between SiO2 in glass and diamond during ultraprecision cutting of silica glass, because silica glass is based on SiO2. This study demonstrated that adopting fluoride glass, which has no SiO2 constituent, as the workpiece reduced tool edge retreat to 1/22 of that of silica glass. This was because the fluoride glass contains no SiO2, which reacts chemically with diamond and leads to severe tool wear. Ductile mode cutting of fluoride glass was realized for long cutting distance. As an application, an aspherical glass lens was produced by ultraprecision cutting. In addition, the tool wear, surface generation, and chip formation mechanisms were investigated.

Ultraprecision cutting of single-crystal calcium fluoride for fabricating micro flow cells

R. Komiya, T. Kimura, T. Nomura, M. Kubo, J. Yan

Journal of Advanced Mechanical Design, Systems, and Manufacturing (Journal of Advanced Mechanical Design, Systems and Manufacturing) 12 ( 1 ) 17-00388, 1 - 13 2018.02

Research paper (scientific journal), Joint Work, Accepted

© 2018 The Japan Society of Mechanical Engineers. Single-crystal infrared (IR) spectroscopy is a promising method for protein structure analysis, where a protein crystal sample is fixed in a micro flow cell. Single-crystal calcium fluoride (CaF2) is expected as the flow cell substrate material for its excellent optical property. However, CaF2 is a highly brittle material having strong anisotropy, thus is extremely difficult to machine. Up to date, there is no available literature on fabrication of CaF2 flow cells. In this study, micro flow cells of single-crystal CaF2 were fabricated by ultraprecision cutting technology. Fly cutting was conducted using a single-crystal diamond tool having straight edges to generate a depth-varying rectangle cross section for the flow cell. The effects of cutting direction, workpiece orientation, undeformed chip thickness and tool rake angle on cutting behavior were investigated. Based on experiments and analysis, optimal conditions for ductile machining of micro grooves in CaF2 were identified. As a result, a 10 μm deep CaF2 micro flow cell with surface roughness of 2.4 nmRa was successfully fabricated. Using the fabricated flow cell, IR spectroscopic analysis of a protein single crystal at room temperature was succeeded. This study demonstrated the effectiveness of ultraprecision cutting technology in CaF2 micro flow cell fabrication, which contributes to the IR analysis of protein, and in turn, the advance of life science.

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Nanometer-scale chip formation and surface integrity of pure titanium in diamond turning

M. Heidari, J. Yan

International Journal of Advanced Manufacturing Technology (International Journal of Advanced Manufacturing Technology) 95 ( 1-4 ) 479 - 492 2018.02

Research paper (scientific journal), Joint Work, Accepted, ISSN 02683768

© 2017, Springer-Verlag London Ltd. Titanium is attracting great attentions in aerospace and medical applications where high surface quality plays an important role in improving the product performance. For developing nano-precision machining technology for titanium, clarification of the nanometer-scale chip formation mechanism is essential. In this study, the surface formation mechanism of pure titanium in ultraprecision cutting tests using single-crystal diamond tools was investigated. The results demonstrated that decreasing undeformed chip thickness from the micrometer scale down to the nanometer scale had profound impacts on the shear angle, specific cutting force, and chip morphology. Chip tearing phenomenon occurred when undeformed chip thickness is smaller than a critical value (~ 100 nm), which significantly affected the chip morphology and machined surface integrity. In nanometer-scale cutting, tool feed mark is no longer a major reason of surface roughness; instead, material plucking, debris, scratches, and chip adhesion influenced the surface integrity. The high pressure generated in the nanometer-scale cutting caused a hardness increase in workpiece material and promoted workpiece material adhesion to the tool surface, as well as tool wear.

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