Cross-sectional Scanning Electron Microscopy Observation Research Articles

Exploring microstructural evolution, nitrogen depth profile, and dry wear performance in 31CrMoV9 steel through combined severe shot peening and plasma nitriding

The present study investigates the influence of severe shot peening (SSP) on the plasma nitriding behavior and sliding wear performance of 31CrMoV9 steel. Initially, the steel was austenitized at 880 °C, followed by oil quenching, and tempering at 520 °C for one hour. These samples were shot peened using high-carbon steel shots, resulting in an enhancement in surface hardness up to 447 HV, gradually converging to the initial martensitic hardness after 140 µm depth. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) scrutinized the initial and surface treated martensitic samples. Afterward, the plasma nitriding treatments were carried out at temperatures of 400 °C, 450 °C, and 500 °C for 8 hours in a 30% N2 + 70% H2 atmosphere and 300 Pa pressure. Microhardness testing, SEM, XRD, and glow-discharge optical emission spectroscopy (GDOES) evaluated both plasma nitrided (PN) and severe shot peened/plasma nitrided (SSP-PN) samples. Cross-sectional SEM observations revealed compound layer thicknesses of approximately 2.8 µm, 5.0 µm, and 6.3 µm for PN samples at 400 °C, 450 °C, and 500 °C, respectively. SSP-PN samples exhibited a substantial increase — roughly 71%, 44%, and 33% increase, respectively, compared to PN samples. GDOES analysis supported this trend and indicated enhanced nitrogen diffusion depth, particularly evident in SSP-PN samples at consistent temperatures. The XRD results showed the stability of Fe4N, Fe2–3N, and CrN phases at all three nitriding temperatures. Furthermore, the intensity of these phases increases with temperature and is augmented by the application of the SSP. Microhardness measurements indicated hardness escalation: from 775 HV to 980 HV at 400 °C, 932 HV to 1096 HV at 450 °C, and 1011 HV to 1205 HV at 500 °C due to SSP. Finally, the wear performance was investigated between the non-nitrided, SSP, PN, SSP-PN, samples. Initially, SSP led to decreased wear performance up to 500 m, followed by improved behavior up to 1500 m. At 400 °C, the SSP-PN sample exhibited a 12% lower wear rate than PN. At 450 °C and 1500 m, the SSP-PN sample displayed a 24% reduction, while at 500 °C, it showed a 27% reduction compared to PN. SEM observations indicated abrasion as the primary wear mechanism across all samples. The overall results indicated a significant similarity in the nitrogen depth profile, hardness depth, and wear performance between the SSP-PN sample at 450 °C and the PN sample at 500 °C. The fact suggested a potential reduction of approximately 50 °C in the typical plasma nitriding temperature for 31CrMoV9 steel as a result of the SSP process.

Microstructure and mechanical properties of Cf/SiC composite/GH99 joints brazed with BNi2-Ti composite filler

Abstract BNi2-Ti composite filler developed with which the brazing of Cf/SiC composite to GH99 superalloy was achieved in this study. The effects of Ti content (0-8 wt.%) and brazing temperature (1130-1190 °C) on the microstructure and mechanical properties of brazed joints were investigated. Cross-sectional scanning electron microscopy observations showed a defect-free bonding interface with the content of Ti ranging from 1 wt.% to 5 wt.%. Formation mechanism of the brazed joint shows that Cr in the brazing filler metal reacted with carbon fiber in the composite to produce Cr3C2 reaction layer while Ni infiltrated into composite reacted with SiC matrix to produce Ni3Si and C. The addition of Ti effectively suppressed the infiltration of Ni towards Cf/SiC composite, while reduced the quantity of large-sized Cr3C2 compounds, replaced by some uniformly dispersed TiC particles. As the brazing temperature increased, the volume fractions of Ni(s,s) in the brazing seam increased and Cr3C2 reaction layer gradually dissolved into the filler metal. When the Ti content was 3 wt.%, brazing temperature 1170 °C, the maximum shear strength of the brazed joint, 43.5 MPa, was achieved.

Microstructural analyses of all-solid-state Li–S batteries using LiBH4-based solid electrolyte for prolonged cycle performance

Abstract Complex hydride materials have been widely investigated as potential solid electrolytes because they have good compatibility with the lithium metal anodes used in all-solid-state batteries. However, the development of all-solid-state batteries utilizing complex hydrides has been difficult as these cells tend to have short cycle lives. This study investigated the capacity fading mechanism of all-solid-state lithium–sulfur (Li–S) batteries using Li4(BH4)3I solid electrolytes by analyzing the cathode microstructure. Cross-sectional scanning electron microscopy observations after 100 discharge–charge cycles revealed crack formation in the Li4(BH4)3I electrolyte and an increased cathode thickness. Raman spectroscopy indicated that decomposition of the Li4(BH4)3I solid electrolyte occurred at a constant rate during the cycling tests. To combat these effects, the cycle life of Li–S batteries was improved by increasing the amount of solid electrolyte in the cathode.

Optimization of Electrolysis Conditions for Ti Film Electrodeposition from Water-Soluble KF–KCl Molten Salts

Optimized conditions for Ti film electrodeposition were investigated in water-soluble KF–KCl (45:55 mol%) molten salt at 923 K. K3TiF6 was prepared in the melt via a comproportionation reaction between K2TiF6 and Ti sponges. The K3TiF6 solubility was determined to be 1.48 mol%. Galvanostatic electrolysis was conducted on Ni plate substrates at various K3TiF6 concentrations (0.28, 0.70, and 1.43 mol%) and current densities (25–150 mA cm−2). Surface and cross-sectional scanning electron microscopy observations showed that adherent, compact, and smooth Ti films were obtained at higher K3TiF6 concentrations and lower current densities. A corrosion test was conducted for the Ti-coated Ni plate using linear sweep voltammetry, which showed that the Ti films have no cracks or voids.

Effect of MoS2 on transfer film formation and friction coefficients in NAO friction material

PurposeThe purpose of this paper is to investigate surroundings for transfer film formation and removal, the effect of the transfer film formation on friction coefficients, the effect of four different abrasive components, ZrO2, ZrSiO4, Al2O3 and Fe3O4, on transfer film formation and the effect of lubricating component MoS2 on transfer film formation and friction coefficients.Design/methodology/approachTwo different MoS2 contents of 5.5 and 8.5 per cent were added to friction materials with no MoS2 content, which have four different abrasive components, ZrO2, ZrSiO4, Al2O3, Fe3O4. Friction tests composed of three different stages were conducted for those materials, and the friction surfaces of the counterpart disks were examined by scanning electron microscopy (SEM) to access the formation of transfer film at each stage.FindingsFor the transfer film formation, high temperature was a prerequisite, but the magnitude of deceleration rate was not important. The effect of the transfer film formation was to reduce the friction coefficients for most friction materials. Friction coefficients of materials which contain lubricating component MoS2 were higher than those which contain no MoS2 for most friction materials. The effect of the lubricating component MoS2 was to suppress the formation of transfer film, thus resulting in increase in friction coefficients.Research limitations/implicationsThe transfer film was rather thin, with thickness of 1-2 µm for most friction materials. That hindered the examination of mechanical properties of the transfer film, such as hardness.Practical implicationsThis research explained the surroundings for transfer film formation, and its effect on friction coefficients. The research suggests to suppress the formation of transfer film to make friction materials with high friction coefficient, and the lubricating component MoS2 can be used for the purpose.Social implicationsDevelopment of high-friction-brake materials conventionally depends on the use of strong abrasive components, which may induce attacking of counterpart disks. The enhancement of friction coefficients with addition of MoS2 content is expected to open a new prospect in development of high-performance friction materials, which can be applicable to brake pads for racing cars.Originality/valueThe study is in pursuit of the transfer film formation in successive friction stages, which revealed the conditions for transfer film generation and removal. Specimen preparation for SEM observation of cross section of friction surface was painstaking to not damage the developed friction surface. The study revealed the effect of different abrasive components on transfer film formation and the effect of lubrication contents of MoS2 on transfer film formation and friction coefficients.

Step coverage of the barrier films deposited onto patterned photoresist

In this study, silicon oxynitride (SiOxNy) films and three-paired organosilicon/SiOxNy multilayered structures prepared by the plasma-enhanced chemical vapor deposition were respectively deposited onto the polyethylene terephthalate and silicon substrate with overcut and undercut patterned photoresist to mimic the packaging of the patterned organic light emitting diodes (OLEDs) and surface contaminants. The step coverage at the bottom and sidewall surface was conducted from the cross-sectional scanning electron microscopy observations. A methodology for investigating the position-dependent coverage at the concave region of the sidewall surface on the undercut patterns was developed. The increase in the water vapor transmission when these barrier structures were deposited onto polyethylene terephthalate substrate was linked to the decrease in their coverage at the sidewall surface, which was ascribed to the reduction in the diffusion path for water vapor permeation. It also was demonstrated that the degradation in the barrier property was significant as those structures coated onto the undercut patterns originating from the precursors hardly arrived at the concave region. However, although the film growth at the concave region of the sidewall surface was limited, paired organosilicon/SiOxNy structures still showed a superior barrier property to that of single SiOxNy film as the appearance of the organosilicon film in the paired structure was favorable to prolonging the diffusion length for water vapor permeation. The investigation into the barrier structures coated onto the patterned surface was beneficial for better understanding the package reliability on the patterned OLED devices.

In Vivo Study on Degradation Behavior and Histologic Response of Pure Magnesium in Muscles

When an orthopedics device is implanted into bone injury site, it will contact the soft tissue (skeletal muscle, fascia, ligament etc.) except for bone. Magnesium based biodegradable metals are becoming an important research object in orthopedics due to their bioactivity to promote bone healing. In this study, pure Mg rods with and without chemical conversion coating were implanted into the muscle tissue of rabbits. Implants and their surrounding tissues were taken out for weight loss measurement, cross-sectional scanning electron microscopy observation, elemental distribution analysis and histological examination. The results showed that the chemical conversion coating would increase the in vivo corrosion resistance of pure Mg and decrease the accumulation of calcium (Ca) and phosphorus (P) elements around the implants. For the bare magnesium implant, both Ca and P contents in the surrounding tissues increased at the initial stage of implantation and then decreased at 12 weeks implantation, while for the magnesium with chemical conversion coating, Ca and P contents in the surrounding tissues decreased with the implantation time, but were not significant. The histological results demonstrated that there was no calcification in the muscle tissue with implantation of magnesium for up to 12 weeks. The chemical conversion coating not only increased the in vivo corrosion resistance of pure Mg, but also avoided the depositions of Ca and P in the surrounding tissues, meaning that pure magnesium should be bio-safe when contacting with muscle tissues.

Electrochemical Characteristics of Densely-Packed Li(Ni1/3Co1/3Mn1/3)O2 Single Crystals As an Additive-Free Electrodes for Advanced Lithium-Ion Secondary Battery

Introduction Lithium ion rechargeable batteries (LIBs) have been used in many applications, including portable devices and electric vehicles (EVs). The improvement of volumetric capacity and cycle life are strongly required for extending their operating time and traveling distance. Electrodes in commercially available LIBs include an active material with a conductive agent and a binder. Since the volumetric ratio of the active material and others is approximately 50:50, an increase in the packing density of the active material is directly linked to the improvement of the energy density. Ultimately, it can be said that electrode consisting of only the active materials is desirable for the achievement of higher energy density LIBs. In this study, we demonstrate the preparation and the electrochemical characterization of densely-packed Li(Ni1/3Co1/3Mn1/3)O2 (NCM) single crystal electrodes, directly deposited on current collector substrate by using flux growth approaches. Experimental The flux-method, which is one of the liquid-phase method, was used for the growth of NCM crystals on Pt substrate via a heterogeneous nucleation reaction. Regent-grade LiNO3, Ni(NO3)·6H2O, Co(NO3)·6H2O, and Mn(NO3)·6H2O were used as raw materials and Li2MoO4 was used as a flux. A designated amount of Li2MoO4 was added to the stoichiometric amount of raw materials of NCM. After dry mixing, the mixture was put on the Pt substrate (φ = 14 mm) placed on the bottom of alumina crucible. Then, the crucibles were heated to 900 or 1000 °C for 10 h. The NCM/Pt electrode substrate was washed with warm water for the separation with the remaining flux. The shape and structure of the crystal layers were characterized by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The electrochemical properties of the NCM crystal layers were determined by galvanostatic charge-discharge tests of half-cells using both 2032 coin-type cells and pouch cells. Results and Discussions Primary single crystals with well-developed facets, whose size are 5–10 μm, were directly and densely grown from a Pt substrate. The typical optical and SEM images of the crystal layer grown from Li2MoO4 flux with 60 mol% of solute concentration is shown in Figure. The crystal layer was primary attributed to layered NCM phase crystallized into R-3m lattice, as determined by XRD profiles. Cross-sectional SEM observation revealed that small voids with submicron meter scale were formed insides of the NCM crystal layers. The electrode density was roughly estimated to be 3.7 g·cc-1. The reaction conditions such as a solute concentration strongly influenced the morphology and density of the electrodes. Their electrochemical properties of the NCM crystal layers were studied as an additive-free electrode by using coin cell system having Li metal electrode as a counter electrode. The cut-off voltage range is 2.8 to 4.3 V and the current density was controlled to be 20 μA·cm-2. The current capacity of the cell was found to be increased from 200 to 2000 μAh range in proportional to the weight of the NCM crystals, implies that the electrolyte penetrates homogeneously into the whole electrode, leading not to make critical internal resistances. The specific discharge capacity of first cycle was 96 mAh·g-1 with low coulomb efficiency of 67%. These poor capacity and large irreversible capacity were primary associated to the formation of Li2 MeO2 (Me = transition metal) phase in the balk and of any resistant layer at the electrolyte interface. In facts, the flat plateau was appeared at 1.2 V (vs. Li+/Li) under the lower limiting voltage extending to 1.0 V. Furthermore, introducing ultra-thin layer of Li4Ti5O12 homogeneously coated on the NCM electrodes significantly improved the specific discharge capacity to be 130 mAh·g-1. We also demonstrated a pouch cell test consisted of the NCM crystal layer cathode and a Si/CNT composite anode for achieving high energy density. The detail of the data on this matter will present at PRiME2016. Conclusions We proposed herein a new possibilities on electrode structure for achieving high energy LIBs. Directly grown NCM crystal layer from the current corrector by using flux growth approaches realized high energy density additive-free electrode of LIBs. Acknowledgments This research is partially supported by JST-CREST and KAKENHI (25249089). Figure 1

Thermal conductivity of titanium aluminum silicon nitride coatings deposited by lateral rotating cathode arc

A series of physical vapour deposition titanium aluminum silicon nitride nanocomposite coating with a different (Al+Si)/Ti atomic ratio, with a thickness of around 2.5μm were deposited on stainless steel substrate by a lateral rotating cathode arc process in a flowing nitrogen atmosphere. The composition and microstructure of the as-deposited coatings were analyzed by energy dispersive X-ray spectroscopy, and X-ray diffraction, and cross-sectional scanning electron microscopy observation. The titanium nitride (TiN) coating shows a clear columnar structure with a predominant (111) preferential orientation. With the incorporation of Al and Si, the crystallite size in the coatings decreased gradually, and the columnar structure and (111) preferred orientation disappeared. Thermal conductivity of the as-deposited coating samples at room temperature was measured by using pulsed photothermal reflectance technique. Thermal conductivity of the pure TiN coating is about 11.9W/mK. With increasing the (Al+Si)/Ti atomic ratio, the coatings' thermal conductivity decreased monotonously. This reduction of thermal conductivity could be ascribed to the variation of coatings' microstructure, including the decrease of grain size and the resultant increase of grain boundaries, the disruption of columnar structure, and the reduced preferential orientation.

Effect of copper pretreatment on the zincate process and subsequent electroplating of a protective copper/nickel deposit on the AZ91D magnesium alloy

To obtain a durable Ni coating with excellent adhesion strength on an AZ91D Mg alloy, a pretreatment was performed with a small amount of Cu 2+ ions added to the activation bath used in the pretreatment prior to the plating process. In the pretreatment activation process, a high density Cu layer was deposited on both the α-phase and β-phase areas of the substrate accompanied with Mg dissolution. The Cu deposit acted as nucleation seeds for the Zn deposition in the following zincate process which provided a uniform and dense Zn layer almost completely covering the substrate. Then a thin Cu layer was electroplated on this zincated substrate as an undercoating for the succeeding electroplating with Ni. Cross-sectional scanning electron microscopy observations showed that the Cu deposited by the pretreatment enabled the deposition of a protective Ni layer with few defects. This structure also contributed to the improvement of adhesion strength and corrosion resistance as compared with the non-Cu added sample.

Comparison of Bottom‐up Filling in Electroless Plating with an Addition of PEG, PPG and EPE

AbstractThe bottom‐up filling capabilities of electroless copper plating bath with an addition of additives, such as polyethylene glycol (PEG), polypropylene glycol (PPG) and triblock copolymers of PEG and PPG with ethylene oxide terminal blocks termed EPE, were investigated by the cross‐sectional scanning electron microscopy (SEM) observation of sub‐micrometer trenches. Though three additives had inhibition for electroless copper deposition, the suppression degrees of three additives were different. EPE‐2000 had the strongest suppression for electroless copper deposition, and the suppression of PEG‐2000 was the weakest. The bottom‐up filling capability of electroless copper was investigated in a plating bath containing different additives with the concentration of 2.0 mg/L. The cross‐sectional SEM observation indicated the trenches with the width of 280 nm and the depth of 475 nm were all completely filled by the plating bath with an addition of EPE‐2000, but the trenches were not completely filled by the plating bath with an addition of PEG‐2000 or PPG‐2000, and some voids appeared. Linear sweep voltammetry measurement indicated that three additives all inhibited the cathodic reduction reaction and the anodic oxidation reaction, and the inhibition of EPE‐2000 was the strongest among three additives, which agreed with that of the deposition rate of electroless copper. Significant differences in surface roughness of deposited copper film were observed by UV‐visible near‐infrared for different suppressors, and the bright and smooth of deposited copper film were in accordance with the inhibition of three additives.

Characteristics of a tungsten film electrodeposited in a KF–B2O3–WO3 melt and preparation of W–Cu–W three-layered films for heat sink application

A tungsten film of 13 μm in thickness was obtained on a copper substrate by galvanostatic electrolysis at 30 mA cm−2 for 40 min in a KF–B2O3–WO3 (67:26:7 mol%) melt at 850 °C. By cross-sectional scanning electron microscopy observation and energy dispersive X-ray analysis, the tungsten layer was found to be compact and free from cracks, voids and melt inclusion. The X-ray diffractometry analysis revealed that the phase was α-tungsten, and that (222) plane was significantly oriented parallel to the substrate. By nanoindentation, its hardness was found to be 8.4 GPa, which was larger than that of single crystal tungsten. Its Young’s modulus was measured to be 410 GPa, which was similar with the reported value of single crystal tungsten. Its coefficient of linear thermal expansion and thermal conductivity were 4.5 × 10−6 K−1 and 178 W m−1 K−1, respectively, which were similar values for the tungsten produced by a conventional powder metallurgy method. Finally, W–Cu–W three-layered films were prepared for a heat sink application. It was confirmed that a three-layered film having a desired coefficient of linear thermal expansion can be prepared easily by this new molten salt method.

Bottom-Up Filling in Electroless Plating with an Addition of PEG–PPG Triblock Copolymers

In this article, a bottom-up copper filling for different submicrometer trenches was investigated by an electroless deposition technique using a triblock copolymer of poly(ethylene glycol) (PEG)-Cpoly(propylene glycol) (PPG)-CPEG with ethylene oxide terminal blocks as an additive. The bottom-up filling behavior of the electroless copper bath for different trenches was investigated in a plating bath containing 1.0 mg/L EPE-8000. The cross-sectional scanning electron microscopy observation indicated that the trenches with different widths ranging from 110 to 640 nm were all filled completely by electroless copper. The inhibitions of EPE-8000 for both cathodic and anodic reactions were studied.

Preparation and oxidation of composite TiN–AlN films from alkoxide solutions by plasma-enhanced CVD

Composite and compositionally graded (CGed) TiN–AlN films were deposited on Si wafers at 600 °C from Ti- and Al-alkoxide solutions by N 2 plasma-enhanced chemical vapor deposition (CVD). The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Vickers micro-hardness. In the composite TiN–AlN films, the Ti and Al contents varied linearly and complementarily with solution composition, the N content ranging from 35 to 40 at.%. In the CGed films, the Al component decreased complementarily with increasing Ti toward the substrate. Cross-sectional SEM observation showed both films to be about 1 μm thick with a columnar structure. Oxidation of the composite and CGed films was performed at 500, 700, and 900 °C in air for 1 h. The improvement of oxidation resistance in both composite and CGed films is discussed on the basis of the XRD and SEM observations, and the XPS analysis of the oxidized films.

Characterization of AlGaAs/GaAs vertical-cavity surface-emitting laser diode grown on Si substrate by MOCVD

An AlGaAs/GaAs multi-quantum well vertical-cavity surface-emitting laser diode (VCSELD) has been grown on a Si substrate using metalorganic chemical vapor deposition. The VCSELD structure grown on a Si substrate consists of ten quantum well active layers and a 23-pairs of AlAs/Al 0.1Ga 0.9As distributed Bragg reflector (DBR). The VCSELD on a Si substrate exhibited a threshold current of 82 mA and a threshold current density of 4.2 kA/cm 2 under continuous-wave (cw) condition at 150 K. Cross-sectional scanning electron microscopy observation showed quasi-periodic zigzag roughness and nonuniformity in the DBR structure. Auger-electron spectroscopy also showed compositional transitions at the heterointerfaces of DBR. A low reflectivity of the DBR on Si substrate is caused by the degraded heterointerfaces, which prevent 300 K cw operation for the VCSELD grown on Si.

Selective area etching of III–V semiconductors using TDMAAs and TDMASb in metalorganic molecular beam epitaxy chamber

Abstract Selective area etching of SiO 2 -masked GaAs using trisdimethylaminoarsenic (TDMAAs) is studied. GaAs substrates are partly masked with stripe shaped SiO 2 films along the [0 1 1] and [0 1 1] directions. Cross-sectional scanning electron microscopy observation shows that the etched shape depends on both the direction of the mask and substrate temperature, and is almost independent of the TDMAAs flow rate. At low substrate temperatures, the (1 1 1)B surface is preferentially formed and a V-shaped groove is formed for the [0 1 1] mask direction. With increasing substrate temperature, the V-groove changes to the channel with vertical side walls due to the drastic increase of the etching rate of (1 1 1)B. For the [0 1 1] mask direction, the vertical (0 1 1) plane is formed at all temperatures. It is found that etched shapes are determined by the difference of etching rates and that etching rates are influenced by the crystal structure on the surface. On the other hand, the etching rate of GaSb by TDMASb is independent of substrate surface orientation. This is because the bond strength of GaSb is weak and the etching proceeds along the direction of molecular beams. Enhanced etching rate is observed for InP by TDMAAs, which is explained by the formation of thin InAs layer on InP due to the irradiation of As released from TDMAAs.

Three-dimensional numerical simulation of local oxidation of silicon

The nitride mask bending stress is modeled in three dimensions by using the beam bending theory. The stress effect on the oxide growth is taken into account for the accurate evaluation of the oxide shape. The three-dimensional behavior of oxide growth is investigated by using three typical mask structures, which are called the hole (contact), island, and line structures. The mask structure effect and narrow mask effect on the bird's beak length are simulated and discussed in comparison with the experimental data obtained by the top-view scanning electron microscopy (SEM) observation. Three-dimensional effects of the oxide thickness of local oxidation of silicon (LOCOS) structures are predicted by comparing simulations with two-dimensional effects obtained by the cross-sectional SEM observation. It is found that the bird's beak length at the corner of the mask edge is much enhanced in the hole structure and retarded in the island structure. This result is explained by the three-dimensional effect on the oxidant diffusion and the nitride bending stress.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>