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Abaca, also known as Manila hemp, is native to the Philippines, where it is grown as a commercial crop. It belongs to the Musasea family and is cultivated for ropes and fibers. The abaca fiber is a natural fiber with highest cellulose content. In this study, the effects of alkali treatments on mechanical properties and microstructure of abaca fibers are discussed. Abaca fibers were soaked in the aqueous solution of sodium hydroxide at the concentration from 3 to 15wt% for 5 minutes, and subsequently subjected to tensile tests and observations by scanning electron microscopy (SEM) to assess morphological changes caused by the alkali treatment. Fourier transform-infrared spectroscopy analysis demonstrated that the treatment led to the gradual removal of lignin and hemicelluloses from the abaca fibers. The cellulose crystallinity of abaca fibers was analyzed by an X-ray diffraction method. SEM images revealed that the lumen size decreased and shrunk with increasing alkali concentration. The tensile strength of the alkali-treated abaca fibers was higher than that of the untreated ones. The Young’s modulus increased with increasing alkali concentration up to 7wt% and then decreased. However, the strain at break decreased below 7wt% and then increased. The lumen size started to decrease from 7wt% alkali concentration.

In this work, the authors propose and verify a method of measuring the residual stress of {112}-oriented chromium nitride (CrN) layers in CrN/Cr multilayer thin films. The CrN layers of a CrN/Cr multilayer film deposited on a Ti6Al4V substrate by arc ion plating form both a randomly oriented mixed crystal structure and a {112}-oriented structure. Therefore, accurate stress measurement of the CrN layers cannot be performed by applying the sin2 ψ x-ray method assuming an isotropic homogeneous material. To overcome this obstacle, the proposed method to measure the residual stress uses four CrN-422 diffractions: at ψ = 0°, 33.56°, 48.19°, and 60.00°. Next, the authors vary the density of Cr droplets on the film surface to evaluate how it affects the residual stress in the CrN/Cr multilayer film. The results indicate that the Cr layer has a residual compressive stress of −350 to −530 MPa and that the two CrN layers have a very large residual compressive stress of −3.5 to −8.2 GPa. In addition, both residual compressive stresses decrease with increasing droplet density.In this work, the authors propose and verify a method of measuring the residual stress of {112}-oriented chromium nitride (CrN) layers in CrN/Cr multilayer thin films. The CrN layers of a CrN/Cr multilayer film deposited on a Ti6Al4V substrate by arc ion plating form both a randomly oriented mixed crystal structure and a {112}-oriented structure. Therefore, accurate stress measurement of the CrN layers cannot be performed by applying the sin2 ψ x-ray method assuming an isotropic homogeneous material. To overcome this obstacle, the proposed method to measure the residual stress uses four CrN-422 diffractions: at ψ = 0°, 33.56°, 48.19°, and 60.00°. Next, the authors vary the density of Cr droplets on the film surface to evaluate how it affects the residual stress in the CrN/Cr multilayer film. The results indicate that the Cr layer has a residual compressive stress of −350 to −530 MPa and that the two CrN layers have a very large residual compressive stress of −3.5 to −8.2 GPa. In addition, both residual co...

Chromium nitride (CrN) coatings were deposited on Al alloy substrates using the arc ion plating method with different bias voltages and different thicknesses. The residual stresses of these samples were measured via x-ray diffraction using the sin2 ψ method because the CrN crystals in the coatings were nonoriented. The stress gradient across the CrN coating was calculated from the curved 2θ-sin2 ψ diagram. In the case of CrN coatings deposited at low bias voltage, the compressive residual stress that formed at the substrate interface was larger than the stress at the surface of the CrN coating. Conversely, in the case of CrN coatings deposited at high bias voltage, the compressive residual stress on the surface of the CrN coating was larger than the stress on the interface with the substrate. In CrN coatings deposited at high bias voltage, very large compressive residual stress on the CrN coating surface decreased with increasing coating thickness.Chromium nitride (CrN) coatings were deposited on Al alloy substrates using the arc ion plating method with different bias voltages and different thicknesses. The residual stresses of these samples were measured via x-ray diffraction using the sin2 ψ method because the CrN crystals in the coatings were nonoriented. The stress gradient across the CrN coating was calculated from the curved 2θ-sin2 ψ diagram. In the case of CrN coatings deposited at low bias voltage, the compressive residual stress that formed at the substrate interface was larger than the stress at the surface of the CrN coating. Conversely, in the case of CrN coatings deposited at high bias voltage, the compressive residual stress on the surface of the CrN coating was larger than the stress on the interface with the substrate. In CrN coatings deposited at high bias voltage, very large compressive residual stress on the CrN coating surface decreased with increasing coating thickness.

An ultrasonic nanocrystal surface modification (UNSM) treatment was applied to improve the fatigue strength of typical SUS304 austenite stainless steel. A gradient nanocrystalline plastic deformation layer with increased hardness was created at the specimen surface after UNSM treatment. The average grain size at the top surface was refined to a few nanometers, and the whole thickness of the plastic deformation layer was ~ 30 to 200 μm, depending on the various treatment conditions. The hardened surface layer was assumed to be the main reason for the improvement in the fatigue strength. The increase in the fatigue strength was related to the UNSM applied static loads. In this work, it was found that a static load of 90 N was optimum to obtain a large cycle fatigue strength limit. Plastic deformation (strain)-induced martensitic transformations were also observed in the surface layer. The mechanism for further grain refinement based on martensitic transformations is discussed.

The structures of Cr-N films deposited by arc ion plating on steel substrates were investigated using a synchrotron radiation system that emits ultraintense X-rays. The Cr-N films were found to be mainly composed of {110} oriented CrN crystals, but they also had a small component of randomly oriented Cr2N crystals. The CrN220 diffraction shifts to a high diffraction angle as the annealing temperature increases. In contrast, the peak position of the Cr2N211 diffraction hardly changes with an increase in the annealing temperature up to 873 K. The ratio of nitrogen and oxygen to chromium at the film surface and inside in the film was estimated by Auger electron spectroscopy. After annealing at 973 K, the surface layer was oxidized, but the composition inside the Cr-N films (N/Cr = 0.83) remained unchanged. The residual stress in a 1600-nm-thick as-deposited CrN layer was found to be -11.0 GPa. The residual stresses of Cr-N films relaxed to thermal stress levels on annealing. However, the residual stress in the Cr2N layer could not be evaluated.

Residual stresses near the grain boundary of a bicrystal were measured by synchrotron radiation of SPring-8 at Japan Synchrotron Radiation Research Institute. A copper bicrystal specimen with a 90-degree tilt boundary was deformed 30% in tension. After the plastic extension, kink bands developed in a deformed matrix along the grain boundary. In this study, we focused on the residual stresses in the deformed matrix and the kink band. Residual stresses were evaluated by the X-ray single crystal measurement method. Stereographic projections were used to determine crystal orientations of deformed regions. Our observation showed that crystal orientations were different between the deformed matrix and the kink band. Residual stresses in the direction along the grain boundary in the deformed matrix and kink band were compressive. Residual stresses in the direction vertical to the grain boundary were seen opposite between the deformed matrix and the kink band.

TiO2 films are deposited on glass substrate in O2/Ar gas mixtures by facing target planar magnetron (FT-PM) sputtering, and the effects of the sputtering system on the crystal phases and axis orientation of TiO2 films are investigated for as-deposited films. Deposition is carried out by two systems: In the first system the opposing magnets have opposite polarites of internal permanent magnets in each target holder; this leads to confinement of the electrons therefore weak electron bombardment on the substrate. The result is poor grain growth with low quality anatase films with poor photocatalytic activity. In the second system the opposing magnets have the same polarities each other; the electron bombardment becomes strong and grain growth is enhanced. The results indicate a high quality anatase film with very good photocatalytic activity. [DOI: 10.1380/ejssnt.2009.290]

The behavior of electromigration-induced stress in Al–1.0% Si–0.5% Cu alloy interconnections was investigated in situ by synchrotron radiation at the SPring-8. The electromigration tests were performed as a function of applied current density. When the current was applied to the lines, 111 diffraction peak shifted to lower angle for all measurement points. This indicated that compressive stresses were present at all measurement positions in the lines. When the applied current was stopped, 111 diffraction peak reverted to its initial position for all measurement points. At constant current density, the position of 111 diffraction peak didn't change for any of the measurement positions.

The structure and residual stresses of TiN films deposited by arc ion plating (AIP) on a steel substrate were investigated using a synchrotron radiation system that emits ultra-intense X-rays. In a previous study, the crystal structures of TiN films deposited by AIP were found to be strongly influenced by the bias voltage. When high bias voltages were used, TiN films that were approximately 200 nm thickness had a preferred orientation of {110}, whereas TiN films that were approximately 600 nm thickness has a multilayer film orientation of {111}/{110}. In this present study, the two-tilt method was used to evaluate the residual stresses in TiN films by measuring lattice strains in two directions determined by the crystal orientation. Residual stresses in 600-nm-thick as-deposited TiN films were found to be −10.0 GPa and −8.0 GPa for {111}- and {110}-textured layers, respectively, while they were −8.0 GPa for {110}-textured layers in 200-nm-thick as-deposited TiN films. Residual stresses of both films relaxed to thermal stress levels upon annealing.

Stress-assisted atomic migration occurs in thin films due to thermal stress development, followed by hillock and void formation on a film surface. Relation between thermal stresses and hillock formation was investigated on copper films with and without passivation layer. Copper films with a thickness of 10, 50 and 100 nm on oxidized silicon wafer were prepared for investigating thermal stress and hillock formation. In-situ thermal stress observation by X-ray measurement revealed that compressive stresses develop in an early stage of heating followed by a sudden decrease in the temperature region between 100 and 200 deg. In a cooling stage, stresses in a film linearly changed with decreasing temperature to form a tensile residual stress state. Surface morphology is observed by optical microscope and SEM after the heat cycle as well as at elevated temperatures in a vacuum chamber. Dome-like swells were formed on an AlN passivation layer. Almost of all of the swells on 100 nm thick film collapsed after the heat treatment up to 350 deg whereas the swells on 10 nm thick film had no collapse excepting a few case. Comparing with the film without passivation, the swell is considered to be the result of atomic migration of copper film to form hillocks in the interface between copper film and AlN passivation film during heating. Atoms are considered to migrate reversibly into the copper film in the cooling stage, resulting to make vacant hall in the swell of AlN film and then collapse due to tensile stress development.

A break of wiring by stress-migration becomes a problem with an integrated circuit such as LSI. The present study investigates residual stress in SiO2/Cu/TiN film deposited on glass substrates. A TiN layer, as an undercoat, was first deposited on the substrate by arc ion plating and then Cu and SiO2 layers were deposited by plasma coating. The crystal structure and the residual stress in the deposited multi-layer film were investigated using in-lab. X-ray equipment and a synchrotron radiation device that emits ultra-high-intensity X-rays. It was found that the SiO2 film was amorphous and both the Cu and TiN films had a strong {1 1 1} orientation. The Cu and TiN layers in the multi thick (Cu and TiN:1.0 μm)-layer film and multi thin (0.1 μm)-layer film exhibited tensile residual stresses. Both tensile residual stresses in the multi thin-layer film are larger than the multi thick-layer film. After annealing at 400 °C, these tensile residual stresses in both the films increased with increasing the annealing temperature. Surface swelling formations, such as bubbles were observed in the multi thick-layer film. However, in the case of the multi thin-layer films, there was no change in the surface morphology following heat-treatment.

In-situ observation of thermal stress in thin films deposited on a silicon substrate was made by synchrotron radiations. The specimens prepared in this experiment were nano-size thin aluminum films with SiO2 passivation. The thickness of the films was 10 nm, 20 nm and 50 nm. Residual stress in the as-deposited state was tensile. Compressive stress was developed in the heating cycle up to 300 oC and tensile stresses developed in the cooling cycle. The thermal stresses in the 50 nm film showed non-linear behavior in the first heating cycle from the room temperature to 300 oC. However, they linearly behaved in the first cooling cycle and the second thermal cycle. On the other hand, the thermal stresses in the 10 nm film behaved almost linearly without any hysteresis in the first and the second thermal cycles. The mechanism of thermal stress behavior of thin films is discussed.

In this study, evaluation of residual stress in nano-TiO2 film on ITO glass is carried out. The films with thickness less than 30 nm are prepared by the dual-arcs magnetron sputtering with gas pressure 10 and 20 Pa. The surface microstructure and grain morphology of the nano-TiO2 films are observed by the atomic force microscopy (AFM). In order to accurately evaluate the residual stress in the film, the Young’s modulus of the film is determined by the nanoindentation with three point bending method at first, then the internal residual stress in the film is measured by high energy X-ray diffraction with the synchrotron radiation facility Spring-8. The measured residual stresses of nano-TiO2 films prepared with gas pressure 10 and 20 Pa are -11.6 and -9.1 GPa, respectively. It is shown that the residual stress of TiO2 films decrease with the increasing of gas pressure.

The crystal orientation and residual stress in gallium nitride (GaN) films deposited on a single-crystal (0001) sapphire substrate using a new sputtering system are examined through x-ray diffraction measurements as part of a study of low-temperature sputtering techniques for GaN. The new rf sputtering system has an isolated deposition chamber to prevent contamination with impurities, and is expected to produce high-purity nitride films. GaN films are deposited at various substrate temperatures and constant gas pressure and input power. This new system is found to produce GaN films with good crystal orientation, with the c-axes of GaN crystals oriented normal to the substrate surface. The crystal size of films deposited at high temperature is larger than that deposited at low Ts. All films except that deposited at 700oC exhibit compressive residual stress, and this residual stress is found to decrease with increasing temperature. Finally, the film deposited at 700 oC was tinged with white, and the surface contained numerous micro-cracks.

Laser peening has recently been developed as a surface modification technique. When a high-energy laser pulse irradiates a material surface submerged in water, high-pressure plasma is generated immediately on the surface. The plasma induces an impulse wave that penetrates into the surface layer. In the present study, a laser beam of diameter about 10mm is converged by the converging lens with focal length of 250mm, and irradiates the aluminum surface. The second harmonic generation of Yttrium-Aluminum-Garnet (YAG) laser was used at a pulse frequency of 10 Hz. The effect of laser power density and scanning speed on residual stress in the laser peened aluminum alloy surface was investigated by X-ray diffraction. The following results were obtained : (1) compressive residual stress was induced in the surface of all samples ; (2) many fused traces and many micro-cracks were formed in laser peened aluminum surface ; (3) for the series of experiments with the fixed scanning speed of 2.0mm/s, the maximum compressive residual stress was induced at the laser power density of 31MW/mm2 ; and (4) for the fixed laser power density of 61 MW/mm2, that was induced at scanning speed of 1.0mm/s.

The crystal orientation and residual stress in gallium nitride (GaN) films deposited on a single-crystal (0001) sapphire substrate using a sputtering system are examined through x-ray diffraction measurements as part of a study of low-temperature sputtering techniques for GaN. The rf sputtering system has an isolated deposition chamber to prevent contamination with impurities, and is expected to produce high-purity nitride films. GaN films are deposited at various substrate temperatures and constant gas pressure and input power. This system is found to produce GaN films with good crystal orientation, with the c axes of GaN crystals oriented normal to the substrate surface. The crystal size of films deposited at high temperature is larger than that deposited at low Ts. All films except that deposited at 973 K exhibit compressive residual stress, and this residual stress is found to decrease with increasing temperature. Finally, the film deposited at 973 K was tinged with white, and the surface contained nu...

Internal stresses in thin copper films with or without passivation were investigated by the diffraction method using an in-lab X-ray apparatus and a synchrotron radiation system. The in-lab X-ray stress equipment primarily measures the stresses m films thicker than 100 nm, whereas the synchrotron radiation system can measure stresses in films as thin as 8 nm. The residual stresses in the copper films were tensile in all cases. Thermal stress development was investigated in the heating and cooling processes. In the case of thick films, the internal stress decreased to the compressive side in an early stage of the heating process followed by non-linear behavior. In the cooling stage, the stresses in the film changed to tensile and increased to the final state at room temperature. The stress difference between the heating and cooling cycle was shown as a hysteresis loop in thick films. A thin film exhibits neither hysteresis loop nor a non-linear relation in a thermal stress change during a thermal cycle.

Crystal orientation and residual stress in GaN films deposited by radio frequency sputtering with gallium nitride powder target are investigated by X-ray diffraction as functions of nitrogen concentration ( C N 2 ) in the atmosphere gas consisting of argon and nitrogen. In addition, the film surfaces are observed by atomic force microscopy. The following results are obtained: (1) GaN films deposited by sputtering with the powder target attained good crystal orientation, with the c -axis oriented normal to the substrate surface; (2) film thickness decreased with increasing nitrogen concentration ( C N 2 ); (3) the film deposited at C N 2 =20% had the largest crystal grain size, and the film deposited at C N 2 =0% had the smallest; (4) the film deposited at C N 2 =20% had the best c -axis orientation, and that deposited at C N 2 =0% had the poorest; (5) tensile residual stress occurred in films deposited at C N 2 ⩽20%, and compressive residual stress over −1 GPa occurred in films deposited at C N 2 ⩾50%.

Residual stresses in TiN films on a steel substrate were investigated with ordinary in-lab X-ray equipment and a synchrotron radiation device that emits ultra-high-intensity X-rays. Specimens prepared in this study were TiN films with different thicknesses deposited on a stainless-steel substrate by arc-ion plating. The minimum thickness that allows the residual stress measurement was 0.8 μm by in-lab equipment, but it was below 0.1 μm by synchrotron radiation. We found extremely large compressive residual stresses even in a 0.1-μm-thick film; the level of residual stress was almost constant for the films with thickness of 0.1 to 0.8 μm.

The formation of ultra-high-density ferromagnetic column arrays beyond 1 Tera/inch2 was investigatedusing porous alumina films formed on Si substrate. It was empirically known that a pitch of nanohole array shrunk with a reduction of anodic voltage. We carried out anodic oxidation of sputtered Al film at the anodic voltage below 10V, and found that the density of the nanohole arraysincreased significantly with a reduction of the anodic voltage.and reached 1.5 Tera/inch2 when the anodic voltage was 5.0 V. We also succeeded in the electro-plating of Co column array in these fine holes.The Co column arrays formed by electroplating in the nanoholes were polycrystalline. and showed perpendicular magnetic anisotropy when their aspect ratio was larger than 3. The coercive field of Co columns tended to increase with a reduction of the hole diameter, which was confirmed by micromagnetic simulation based on the LLG equations. These results strongly suggest that ferromagnetic nano column arrays buried in porous alumina film on substrate have a high potential for application to a future ultra-high density magnetic recording media.

Graduation research is a comprehensive activity among several design subjects composed in a four-year undergraduate course. The design subjects in a curriculum demand several abilities such as (1) collection and application of information, (2) creativity, (3) problem finding, (4) group activities and (5) presentation. These abilities can be assessed and promoted by practicing presentations. This paper deals with the way of presentation assessment in the activities of graduation research and its development through 2000, 2001 and 2002 academic years. A coalition consisting of five seminar groups began to develop the presentation assessment. This assessment was then extended to the whole engineering departments in Tokushima University. It was clarified that the presentation assessment in activities of graduation work is an effective method to promote presentation ability and self-studying skill of the students.

The generation of intense flux of energetic oxygen ions in the sputtering of Zr target in Ar+O 2 atmosphere is investigated. The energetic negative oxygen ions were detected using a constructed probe. The photoemission intensity of sputtered Zr atoms was observed in order to monitor the surface oxidization of the Zr target. The results indicate that the surface of the Zr target undergoes rapid oxidization during sputtering. The generation of the intense flux of energetic negative oxygen ions is considered to occur as a result of sputtering the heavily oxidized Zr target.

The crystal orientation of GaN films deposited on fused quartz substrates by rf planar magnetron sputtering using a mesh to guard against plasma exposure was investigated by X-ray diffraction. Sample films were deposited at constant N 2 gas pressure and input power at a range of substrate temperatures between 84°C and 600°C. It was found that GaN films with good crystal orientation can be produced by rf sputtering with the c -axis of GaN crystals oriented normal to the substrate surface in almost all films produced. The crystal 0 0·2 orientation was good at substrate temperatures exceeding 300°C, however, films deposited at 600°C peeled from the substrate. The fine mesh installed to protect the film from exposure to plasma was found to be very useful for depositing films with a good crystal orientation of 0 0·2, and the best crystal orientation was realized for a film deposited by sputtering with a target to mesh separation of 30 mm.

本論文では新しく開発したプレゼンテーションによるアウトカムズ評価の方法を紹介する.この評価では,教師のみならず学生も評価に加わる.評価項目として,プレゼンテーションの内容およびプレゼンテーションの技法のそれぞれについて数項目を設定した.プレゼンテーション評価によって,表現力は向上し,また,評価能力も経験を重ねることによって高揚することが明らかになった.創成科目である「創造演習」,「創造実習」および「卒業研究」について実施した結果を紹介する.

1年生を対象とした導入教育である創造演習において,平成12年度および平成13年度に実施した課題「ルーツを探れ!」の成果について報告する.この課題は,機械工学分野のある事項に対してそのルーッを調査し,その事項がどのような背景で起こり,どのような発展経緯をとって現在に至っているかを3人のグループでまとめあげる作業を行う.この作業を通して発見や創造の過程を学ぶことができる.最終的にこの実習では,学生の創造基礎能力,グループ活動能力,報告書作成能力およびプレゼンテーション能力の向上が期待できる.とくに,プレゼンテーション能力は,学生参加型評価の導入により大きな向上が確認された.

The crystal orientation and residual stress development in AlN films deposited by dc planar magnetron sputtering on a glass substrate were investigated by atomic force microscopy (AFM) and X-ray diffraction. The microscopic surface morphology, the film thickness and the crystal orientation were investigated for films that were deposited at a constant N 2 gas pressure and a constant heating temperature of the substrate at various input powers. The following results were obtained: (1) the crystal grain size and the film thickness increased with increasing input power; (2) c -axis orientation was slightly good at high input power; (3) tensile residual stresses were obtained at low input power and large compressive stresses were obtained at high input powers of P =154 and 180 W.

TiN coatings on cutting tools have greatly succeeded in prolongation of tool lives. In the present study, TiN film deposition was tried on a surface of aluminum and aluminum alloy substrates by means of an arc ion plating (AIP) method and an ion beam mixing (IBM) method. The aim is to develop aluminum-based materials having strong wear resistance. In order to examine the hardness and residual stress of TiN films, the bias the voltage and N2 gas pressure were varied in the AIP treatment and the titanium deposition rate was changed in the IBM treatment. Vickers hardness test revealed high values (HV=1800-2400). The TiN films coated by the AIP and the IBM methods exhibited very high {111} and {110} preferred orientations, respectively. The two-exposure X-ray stress measuring method was used to measure residual stresses in the TiN film. Large compressive residual stresses of -6.3--2.3GPa were developed at lower N2 gas pressures for the AIP method and at higher Ti deposition rates for the IBM method. A wear experiment was also made with a ball-on-disk type wear testing machine. The depth and the width of wear traces on the surface of specimens were greatly reduced when TiN coatings were applied.

TiN films were deposited on aluminum and stainless steel substrates by arc ion plating (AIP). Bias voltages, nitrogen gas pressures and arc currents were changed to examine their role on the hardness and residual stress of a TiN film. Vickers microhardness tests revealed high hardness value (HV = 2250–2500) which depends on both nitrogen gas pressures and arc currents. From the X-ray diffraction pattern, it was found that the crystal orientation of the TiN film markedly varied with the bias voltage. Residual stresses in the TiN film were measured by the two-exposure X-ray stress analysis as a function of the nitrogen gas pressure, arc current. Very high compressive residual stresses, −5 GPa in the films on aluminum substrates and −7 GPa in the film on a stainless steel substrate, were observed.

The structure and residual stresses of ZnO films synthesized by a planar magnetron sputtering system with two facing targets were investigated by X-ray diffraction. ZnO films were deposited onto a sheet of Corning 7059 glass. The X-ray diffraction pattern shows that the film has high 00·1 orientation. Residual strains were measured on various diffraction lines that appear at special angles ψ from the surface normal. The strains taken from positive and negative ψ differed from each other. This behavior is deduced from the existence of a shear stress component in a cross-section of the film. The magnitude of the shear stress increased with increasing current density of the Zn target as well as with decreasing argon gas pressure.

TiN film, 3 μm in thickness, was deposited on aluminum (JIS A 1050) and aluminum alloy (JIS A 2017 and JIS A 5052) substrates by an Arc Ion Plating (AIP) method. Bias voltage and N2 gas pressure were changed to examine their role on hardness and residual stress of TiN film. Wear experiment was also conducted using a ball-on-disk type wear apparatus. Vickers hardness tests revealed high value (HV=2 100∼2 400) which depends on both bias voltage and N2 gas pressure. The TiN films exhibited very high {111} preferred orientation. Residual stresses in the TiN film were measured by the two-exposure X-ray stress measuring method as a function of N2 gas pressure. Very high compressive residual stresses, -6.3∼-4.6GPa, were observed. The depth of wear scars on the surface of the processed specimens were greatly shallow.