Typical Surface Morphology Research Articles

Effect of co-substitution on structural, optical, dielectric and magnetic behavior of LaFeO3

Effect of co-substitution by Na at La site and Mn at Fe site of perovskite type LaFeO3 on its structural, optical, dielectric and magnetic properties at room temperature have been studied. Single phase nanocrystalline La1−xNaxFe1−yMnyO3 (x = y = 0–0.2) have been prepared by modified Pechini route. Substantial effect of substitution on structural property has been observed, which is clearly visible in view of changes in Fe/MnOFe/Mn bond angle and lattice strain. The substitution concentration dependent structural changes have also been confirmed by Fourier transform infrared (FTIR) spectrum in terms of upward shift of stretching mode (Fe/MnO) and downward shift of bending mode of vibrations (Fe/MnOFe/Mn). Typical nanocrystalline surface morphology has been observed with visible change in grain size on changes in concentration, which is also confirmed by X-ray diffraction (XRD). These changes have profound effect on magnetic property tailoring and appear to be correlated with Fe/MnOFe/Mn bond angle deviation and indirect exchange interactions between Fe and Mn ions via intervening Oxygen ion. Dielectric response (εr ∼ 103) at room temperature was observed on Na and Mn co-substituted LaFeO3. The dielectric spectrum shows typical non Debye type behavior. Modulus spectrum reveals shift of peak position toward higher frequency side with increasing concentration i.e. concentration dependent relaxation time. Electrical conductivity shows thermally activated Arrhenius type response with a maximum of ∼2.5 × 10−4 S cm−1 at 450 K for La0.85Na0.15Fe0.85Mn0.15O3. Both grain and grain boundary contribution to conduction mechanism has been observed.

Fatigue performance of superelastic NiTi near stress-induced martensitic transformation

The structural fatigue of superelastic NiTi was studied with special attention paid to the drop in fatigue performance commonly observed at the onset of the stress-induced martensitic transformation. We processed the superelastic NiTi wires into an hourglass shape as a result of which the stress induced martensitic transformation in tension is not localized as confirmed by digital image correlation measurements. The hourglass shaped samples were subjected to force controlled pull-pull fatigue tests at two distinct temperatures selected to investigate the fatigue of NiTi with and without the R-phase transformation involved, and to capture the effect of varying critical stress for the onset of B19′ martensitic transformation. Resulting fatigue curves expressed in terms of both the stress and the strain show a first degradation of fatigue performance at stresses more than 200MPa below the onset of the martensitic transformation. Furthermore, fatigue curves showed a temperature dependence which was successfully implemented into a modified Basquin’s power law model. Notably, the fatigue life drops down to 104 cycles before the nominal loadings reach the B19′ transformation regime. We further found that fatigue life is shorter for the B2-R-phase transformation regime than for the elasticity of the parent B2 austenite phase at low stresses when strains remain below 1%, however at higher strains the B2-R-phase transforming wire is better than the elastic one. Fatigue crack observations revealed crack initiation at the surface and its propagation towards the bulk resulting in a reduction of the cross-section and substantial increase in normal stresses. Martensitic transformation was triggered during the crack growth in samples nominally loaded in elastic or R-phase transformation regimes as confirmed by in-situ infrared thermography. As the crack grows with increasing speed, the activity of transformation processes at the tip gradually increases till unstable crack growth and final rupture occurs, as confirmed by in-situ thermography and stress hysteresis observations. The analysis of fracture surfaces revealed five different crack growth regimes - from quasi-cleavage at early crack growth, through propagation stage evidenced by striations, till the final ductile fracture evidenced by the typical fracture surface morphology.

High-Rate Homoepitaxial Growth of Heavily Boron-Doped Diamond (100) Films By Microwave Plasma-Enhanced Chemical Vapor Deposition Using High Microwave Power Density

Diamond is expected as a next-generation semiconductor material for high-power devices because of its high breakdown electric field, mobility, and thermal conductivity. For the power devices with high current operation, vertical structures are effective because the large contact area is easily obtained by trench structures in the same way as silicon and silicon carbide power devices. The low resistivity diamond single-crystal substrates are required to fabricate the diamond vertical power devices and are realized by heavy boron doping. The highest growth rate of heavily boron-doped ([B]film > 1020 atoms/cm3) diamond films obtained by microwave plasma-enhanced chemical vapor deposition (MPECVD) is 6 μm/h [1]. The higher growth rate is required for manufacturing cost reduction of the low resistivity diamond substrates. However, the higher the boron concentration is, the lower the growth rate of the diamond films becomes [1]. It is known that there are mainly two methods for increasing the growth rate of the diamond films. One is a nitrogen addition to the plasma. However, incorporated nitrogen into diamond acts as a donor, which is compensator for boron-doped diamond [2]. The other is high density of the microwave power input into the plasma. Therefore, we tried to change the shape of a diamond substrate holder for MPECVD to improve the growth rate by increasing the power density near the surface of substrate. Figure 1 shows the plasma states of (a) the conventional substrate holder and (b) the improved substrate holder. The improved substrate holder has a shallower bottom than the conventional one. In the case of the improved substrate holder, the top of the diamond substrate is higher than that of the holder, as shown in Fig.1(b). As a result, the diamond growth rate and incorporation of boron atoms into the diamond film are enhanced at the same time because the electric field is concentrated at the top surface of the diamond substrate and the radical density on the diamond surface increases. High-pressure, high-temperature (HPHT) synthetic Ib(100) single-crystal diamonds were used as substrates for the homoepitaxial diamond growth by MPECVD with a spherical resonator structure (Arios Inc. in Japan). Before the CVD growth, the diamond substrates were treated with HF diluted with H2O for 15 min. Next, the substrates were heated in 2:1 mixture of H2O2 and H2SO4 at 400°C for 15 min. The growth was carried out using CH4 and B(CH3)3 diluted with H2. The microwave power, the total pressure and the methane concentration were maintained at 900 W, 50 kPa and 2.4 %, respectively. The boron/carbon (B/C) ratios in the gas phase were fixed at 14,000 ppm for the conventional holder and 20,000 ppm for the improved substrate holder, respectively. The growth of the heavily boron-doped diamond films was conducted for two hours in the above conditions. After the growth, the surface morphologies of the heavily boron-doped diamond films were observed by optical microscopy (OM). The resistivities of the films were measured by a van der Pauw contact configuration and the growth rates were estimated by the micrometer. Figure 2 shows the OM images of typical surface morphologies of the heavily boron-doped diamond films grown on diamond (100) substrates by (a) the conventional substrate holder and (b) the improved substrate holder. Although the diamond film grown by the conventional substrate holder had some non-epitaxial crystallites with density of 1.6 × 104 cm-2, which degrade the diamond device performances, the diamond film grown by the improved substrate holder had no non-epitaxial crystallites. The resistivities of the films were 3.3 × 10-2 Ωcm for the improved substrate holder and 2.3 × 10-2 Ωcm for the conventional substrate holder, respectively. The boron concentrations in these films were 1~3 × 1020 cm-3, which is estimated from the growth condition. The growth rates were 29.5 μm/h for the improved substrate holder and 13.0 μm/h for the conventional substrate holder, respectively. The growth rate of 29.5 μm/h is the highest growth rate for heavily boron-doped ([B]film> 1020 cm-3) diamond films. Acknowledgements This work was partially supported by Adaptable and Seamless Technology Transfer Program through Target-driven R&D, JST, and Kanazawa University SAKIGAKE Project.

Determination of Bovine Serum Albumin Adsorption Capacity of Newly Obtained Cellulose extracted from Glycyrrhiza glabra (Licorice)

AbstractExploration of biodegradable and renewable composites ingredients is of great importance. Up to now, roots extract of Glycyrrhiza glabra has been used for different medicinal purposes but remaining cellulose‐rich residues have not been evaluated for isolation of any green materials like cellulose. Here in this study, cellulose was successfully isolated from the roots of G. glabra by using conventional cellulose extraction method. The obtained product was characterized using FT‐IR, XRD, and SEM. FT‐IR and XRD analyses confirmed the identity of the product. The crystallinity index of cellulose isolates was calculated from XRD data as 70%. The cellulose content of the roots on dry basis was recorded as 48.5%. Three types of surface morphologies were observed: smooth non‐porous surface, surface with fibril bundles, and porous surface having thin cellulose fibrils. In addition, bovine serum albumin (BSA) adsorption capacity of G. glabra cellulose was determined and compared with that of commercial cellulose. Newly obtained cellulose from the roots of G. glabra exhibited a higher affinity for BSA protein at neutral pH.

FTIR, XRF, XRD and SEM characteristics of Permian shales, India

The emergence of shale gas as potential hydrocarbon resource has changed the global energy landscape. Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), X-ray florescence (XRF) and Scanning Electron Microscope (SEM) characteristics of thirty nine borehole shale samples belonging to the Barakar (Lower Permian), Barren Measures (Upper Permian) and Raniganj (Upper Permian) Formations from different parts of Raniganj basin, India were studied. FTIR analysis indicates the presence of aromatic hydrogen, aromatic carbon, aliphatic C–H stretching, aliphatic C–H bending, OH functional group within the organic matter and presence of kaolinite, quartz and carbonates within the studied samples. XRF studies indicate that the shales have undergone intermediate to strong weathering condition, and are marked by presence of clay minerals mainly illite and kaolinite. In addition to illite, kaolinite and quartz, alkali feldspar, siderite and calcite were identified within the shales through XRD. Marked development of amorphous character was noted in the XRD plot of one heat affected shale sample. FTIR analysis of this sample also indicates removal of aliphatics and disordering of kaolinite within the sample due to the impact of heat. Through SEM studies different types of surface morphologies, different types of pores and pore shapes in organic matter were identified. SEM studies also indicate intimate mixing of organic matter and mineral matter in shales even at submicroscopic levels. This intimate association appears to have impact on the retention of hydrocarbons by the mineral matrix during Rock Eval pyrolysis. The various micropores, microcracks, fracture traces, macropores and vacuoles may play significant role in diffusion and flow of hydrocarbons.

Thermoresponsive Wrinkles on Hydrogels for Soft Actuators

Thermoresponsive Wrinkles on Hydrogels for Soft Actuators

Effect of different parameters on machining of SiC/SiC composites via pico-second laser

Pico-second laser plays an important role in modern machining technology, especially in machining high hardness materials. In this article, pico-second laser was utilized for irradiation on SiC/SiC composites, and effects of different processing parameters including the machining modes and laser power were discussed in detail. The results indicated that the machining modes and laser power had great effect on machining of SiC/SiC composites. Different types of surface morphology and structure were observed under helical line scanning and single ring line scanning, and the analysis of their formulation was discussed in detail. It was believed that the machining modes would be responsible to the different shapes of machining results at the same parameters. The processing power shall also influence the surface morphology and quality of machining results. In micro-hole drilling process, large amount of debris and fragments were observed within the micro-holes, and XPS analysis showed that there existed Si–O bonds and Si–C bonds, indicating that the oxidation during processing was incomplete. Other surface morphology, such as pores and pits were discussed as well.

Shape selective photoinduced electrochemical behavior of thin ZnO layers prepared by surfatron

Thin layers of ZnO were prepared by using a special modification of the plasma-enhanced chemical vapor deposition known as surfatron. This technique utilizes the principle of surface-wave discharge powered by microwave magnetron generator. Two types of substrate holder regimes (static and movable) were intentionally employed for the preparation of two types of surface morphologies. A series of ZnO films were yielded with thicknesses ranging from 60nm to 1500nm. The layers were analyzed by profilometry, scanning electron microscopy, X-ray diffraction, Raman spectroscopy, UV-light adsorption and by a number of electrochemical tests. All prepared samples were crystalline and possessing different surface morphologies. It was shown that the electrochemical response of the films was directly reflecting their surface morphology.

Fluctuation in physicochemical properties of chitins extracted from different body parts of honeybee

It is well known that physicochemical properties of chitin are related with the extraction method. Recently, it was revealed that some physicochemical properties of chitin are also related with taxonomical relationship. For the first time in this study, it was tested how these properties of chitin are affected by different body parts of one organism. The chitins were extracted from five different body parts (head, thorax, abdomen, legs and wings) of honeybee. These chitins were physicochemically characterized and differences among these body parts were identified. Highest chitin content was observed in legs (13.25%) while the lowest from thorax (6.79%). The surface morphologies of the isolated chitin structures from five different body parts were analyzed with SEM, as a result, five different types of surface morphologies were recorded. However, three different types of surface morphologies were observed only in abdomen. Maximum degradation temperatures (DTGmax) of thorax, abdomen, legs and wings were recorded between 359 and 367°C while DTGmax value of head chitin was found as 308°C.

Anomalous crack arrays in anisotropic-strained manganite on scandate substrates

We report that when (La,Sr)MnO3 films grown on orthorhombic (110)o DyScO3 (DSO) substrates once reach a critical thickness, anisotropic patterned cracks are introduced which propagate parallel to [1–10]o direction. The typical surface morphology and cross-sectional TEM are examined in order to clarify the formation of these cracks. The cause of crack propagation through the film and into the substrate is identified as the underlying large anisotropic strain and relatively low stiffness of DSO substrates. The electrical conduction in the crack region is found to be several orders of magnitude higher than that in the uncracked areas of the film. The energy dispersive x-ray-verified La0.7Sr0.3MnO3 deposited into cracks may be responsible for the anomalous conducting behaviors. Finally, a simple model is constructed for estimating substrate fracture toughness and calculating an upper bound of film fracture toughness.

Variation of fracture mode in micro-scale laser shock punching

Micro-scale laser shock punching is a high strain rate micro-forming method which uses the high-amplitude shock wave pressure induced by pulsed laser irradiation. The response of brass and pure titanium foils under the different ratio of laser beam diameter (d) to die hole diameter (D) in micro-scale laser shock punching was investigated experimentally and numerically. The typical fracture surface morphologies were observed using scanning electron microscope. Numerical simulations were conducted to predict the stress state of the workpiece before and after fracture. The influence of the ratio d/D on dynamic deformation and fracture of metal foils was characterized. The results demonstrate that both the crack locations and fracture surface morphologies of metal foils are strongly related to the ratio d/D. The fracture mode varies from a shear fracture mode to a mixed fracture mode, then to a tensile fracture mode as the ratio decreases. The stress state under the different ratio is discussed in detail and believed to be responsible for the variation.

An Investigation on Subsurface Microstructural Evolution and Mild to Severe Wear Transition in AZ51 Magnesium Alloy

The wear behavior of as-cast AZ51 alloy was investigated using a pin-on-disc configuration within a load range of 20–380 N and a sliding speed range of 0.1–4.0 m/s under dry sliding conditions. The coefficient of friction and wear rate were measured as a function of applied load at various sliding speeds. Morphologies and chemical compositions of worn surfaces were analyzed for determination of wear mechanisms using scanning electron microscope (SEM) and energy-dispersive X-ray spectrometry (EDS). Microstructural evolution, plastic deformation, and hardness of the subsurfaces as well as worn surface hardness were characterized by confocal scanning laser microscopy and hardness testing for the establishment of a corresponding relationship between microstructural evolution and mild to severe wear transition in AZ51 alloy. The results show that there exists a strong relationship between wear behavior and subsurface microstructural evolution; that is, surface oxidation and strain hardening originating from plastic deformation of the microstructure prevail in mild wear regime, whereas thermal softening with dynamic recrystallization (DRX) in subsurface and surface melting dominate in severe wear regime. With increasing load and sliding speed to certain critical states, the friction-induced heat accumulation activates DRX in subsurface and surface melting successively, leading to a rapid rise in wear rate and typical worn surface morphology with extruded edges or multilayered structure edges. The mild to severe wear transition is determined to be controlled by initiation of DRX in the subsurface of AZ51 alloy.

Evolution of the surface morphology of AlN epitaxial film by HVPE

The evolution of the surface morphologies of AlN films grown by hydride vapor phase epitaxy (HVPE) was studied using atomic force microscopy (AFM). Our results indicate that, after an initial growth time of 10min, the surface is dominated by hexagonal-prism-shaped islands. Dislocation mediated surface structures of spiral hillocks are observed to cover the surface when the growth time extends to 1h. Upon further extending the growth time to 3h, the typical surface morphologies change and the density of dislocation decreases by one order. We also discuss the relationship between the diffusion behaviors of adatoms on the crystal surface with the shape of the terrace edges around dislocations. Explorations into the evolution of the surface morphology of AlN epitaxial films are crucial for understanding the origin and subsequent annihilation of dislocations, as well as to promote improved dislocation reduction techniques for III-nitride materials.

Role of Surface Industrial Finishing Process of Joint Implant UHMWPE on their Tribological Behaviour

Joint implants have as bearing couples metal on metal, ceramic on metal and metal on polyethylene. The most widely used bearing couple for artificial joint systems is the combination of a polyethylene (PE) acetabular liner and a cobalt–chromium (Co–Cr) alloy femoral head. Although highly used, it is known that wearing of the polyethylene part of total joint implants is the primary cause of premature failure of total joint replacements [1]. Polyethylene particles tend to migrate into the joint creating inflammation, ostelysis and, in the end the loss of the implant. Industrials use different method for the surface finishing process of the polyethylene part of joint implants that lead to different types of surface morphologies. In this study, using atomic force microscopy technique and tribological methods, we have investigated the influence of polyethylene surface morphology on mechanical properties, degradation and friction. Results have shown that polyethylene surfaces obtained by high speed turning machine lead to low friction coefficient and less degradation of the surface during friction test.

Hyperpolarizability calculation and kinetic effect of impurities on LVP

In order to investigate microscopic second order nonlinear optical properties of L-valinium picrate (LVP) crystals, the molecular dipole moment, polarizability, and first hyperpolarizability are estimated by density functional theory (DFT). Apart from that, a quantitative study using Atomic force microscopy (AFM) combined with crystal growth experiments on the effects of impurities (magnesium and copper) on LVP is presented. Two-dimensional (2D) nucleation growth mechanism and typical surface morphologies are described and discussed. In the presence of impurities, the decreasing of the size of 2D islands is probably incurred by the reducing of the step kinetic coefficient. From the supersaturation dependence of the normal growth rate, the effective step edge free energies are evaluated as γ0=2.90kT, γMg=2.76kT, γCu=2.95kT.

Coexistence of bunching and meandering instability in simulated growth of 4H-SiC(0001) surface

Bunching and meandering instability of steps at the 4H-SiC(0001) surface is studied by the kinetic Monte Carlo simulation method. Change in the character of step instability is analyzed for different rates of particle jumps towards step. In the experiment effective value of jump rates can be controlled by impurities or other growth conditions. An anisotropy of jump barriers at the step influences the character of surface structure formed in the process of crystal growth. Depending on the growth parameters different surface patterns are found. We show phase diagrams of surface patterns as a function of temperature and crystal growth rate for two different choices of step kinetics anisotropy. Jump rates which effectively model high inverse Schwoebel barrier (ISB) at steps lead either to regular, four-multistep or bunched structure. For weak anisotropy at higher temperatures or for lower crystal growth rates meanders and mounds are formed, but on coming towards lower temperatures and higher rates, we observe bunch and meander coexistence. These results show that interplay between simple dynamical mechanisms induced by the asymmetry of the step kinetics and step movement assisted by the step edge diffusion are responsible for different types of surface morphology.

Growth of zinc ferrite aligned nanorods for liquefied petroleum gas sensing

Present paper reports the fabrication of zinc ferrite thin film sensor having two different types of surface morphologies (mixed shaped nanorods and vertically aligned nanorods) and their growth mechanism. The LPG sensing properties of the vertically aligned assembled nanorods are found improved significantly in comparison to mixed shaped nanorods. When we compare our sensor performance with other thin film sensors, it is found that the sensor performance obtained in this work is definitely better than that of others. Thus our investigation demonstrates the potential application of aligned nanorods in the fabrication of LPG sensor operable at room temperature.

Hydrodynamics Analysis of Air Flow over Pitted Surface

The pits is a typical biomimetic surface morphology, typically it is beneficial to reduce the flow drag on the wall surface. In this paper, a method combining theoretical analysis and numerical simulation is adopted, it carries out a flow and stress analysis on the wall surface distributed by 3mm-diameter pits with typical bionic surface morphology, reveals the forms down stream flow field and the pit internal as well as the distribution of stress, it also analyzes the relationship between the viscous drag of the pit wall surface, the pressure drag and the flow drag, comparing the size of the downstream shear stress of the smooth wall and wall surface distributed with pits, investigates the mechanism of the downstream shear stress decreases on the biomimetic pit wall surface.

Dynamic fracture characteristics of Fe78Si9B13 metallic glass subjected to laser shock loading

The response of the Fe78Si9B13 metallic glass under different ratio of laser beam diameter (d) to die hole diameter (D) in micro scale laser punching was investigated. The typical fracture surface morphologies were observed using scanning electron microscope. The influence of the ratio d/D on dynamic deformation and fracture of metallic glasses foils was characterized. The results show that the dynamic fracture behavior of the Fe78Si9B13 metallic glass is sensitive to the ratio d/D. In the case of d/D=1.75, the fracture surface is occupied by numerous liquid droplets, indicating that the temperature rise in an adiabatic shear band is beyond the melting temperature of the material. On the other hand, the fracture surface is covered dominantly with a mixture of shear steps, cellular patterns, liquid droplets and melted belts at d/D=0.70. According to the general mechanical analysis, the specimen fails in a shear fracture mode at d/D=1.75 due to the existence of shear stresses, while the fracture occurs in a tensile fracture mode at d/D=0.70 under the effect of bidirectional tensile stresses.

Low-cycle fatigue behavior of extruded Mg–10Gd–2Y–0.5Zr alloys

The low-cycle fatigue properties of extruded Mg–10Gd–2Y–0.5Zr (GW102k) magnesium alloy have been studied and compared to those of conventional extruded AZ31 magnesium alloy. Typical post-fatigue microstructure and surface morphology features are presented for both the GW102k and AZ31 alloy. It is found that GW102k alloy contains a large amount of precipitated particles and possesses a relatively weak basal texture, which gives rise to near symmetric yield asymmetry. Different from AZ31 alloy, the GW102k alloy shows near-symmetric stress–strain hysteresis loops and marginal cyclic hardening. This symmetry significantly reduces tensile mean stress during low-cycle fatigue process. Due to the small reversible plastic zone size, the GW102k alloy shows rough faceted fracture surfaces in the fatigue crack propagation zone. Accordingly, the low-cycle fatigue life of GW102k alloy is found to be longer than that of AZ31 alloy.