Surface Carbon Content Research Articles

Nb添加肌焼き鋼の強切削加工後のガス浸炭における表面炭素濃度の異常低下現象

Nb添加肌焼き鋼の強切削加工後のガス浸炭における表面炭素濃度の異常低下現象

Nb添加肌焼鋼の高速切削加工後のガス浸炭における表面炭素濃度の異常低下メカニズム

Nb添加肌焼鋼の高速切削加工後のガス浸炭における表面炭素濃度の異常低下メカニズム

Effect of various parameters on properties of composite steel foams under variety of loading rates

Steel–steel composite metal foams (CMF) are manufactured using steel hollow spheres (with variety of different sphere sizes, surface roughness and carbon content) embedded in a stainless steel matrix through powder metallurgy technique and are investigated experimentally under compression loading with variety of loading rates. The microstructural and mechanical properties of the material were studied using optical and scanning electron microscopy, energy dispersive spectroscopy, quasi-static, and dynamic compressive loading up to 26m/s. It is observed that the yield and plateau strength as well as the energy absorption capabilities of the composite foams are increased with increasing loading rate and by decreasing sphere sizes. Such mechanical properties improved by additional carbon content in the sphere wall at strains below 17% while the effect of density, resulted from porosity content, showed an improvement on the densification strain and plateau strengths at higher than 17% strain. The effect of spheres surface roughness and carbon content on mechanical properties of CMF seemed to be minimal compared to other parameters. As a result, the features controlling the life time and performance of composite metal foams under static and dynamic loading have been categorized into two main groups. The first group that controls the yield and plateau strength of the foam at lower strain levels includes bonding strength between the spheres and matrix which is a function of the sphere surface roughness and the gradient chemical composition between the spheres and matrix. The second group that controls the relative density, densification strain and plateau strength at higher strain levels belongs to the sphere diameter and the porosity content in both spheres and matrix. Moreover, increasing the loading rate improves the yield strength of all CMF samples.

Systematische Untersuchung verschiedener Einflussgrößen auf die Maß- und Formänderungen von einsatzgehärteten Stirnrädern

Abstract Typically, highly stressed gears are heat treated to satisfy operational demands. Case hardening is a common heat treatment associated with power train components. In the heat treatment process complex distortion takes place, which has been studied in these examinations. Object of the actual investigations were spur wheels with small module. The case hardening was realized utilizing low pressure carburization with subsequent high pressure gas quenching in a heat treatment furnace of industrial proportion. The systematic analysis was guided using design of experiment methods. In strategic focus were the three contributing heat treatment steps heating, carburization and quenching. Heating related factors were the batch design and the preheating temperature. During carburization the temperature, carburization depth and surface carbon content were altered. Finally no quenching related variations were performed. The influences of the different parameters on the size and shape changes of the gear wheels were evaluated statistically. The identified main factors on size as well as on shape changes of the base body and the toothing will be presented and discussed.

Plasma Resistance and Etch Mechanism of High Purity SiC under Fluorocarbon Plasma

Etch rates of Si and high purity SiC have been compared for various fluorocarbon plasmas. The relative plasma resistance of SiC, which is defined as the etch rate ratio of Si to SiC, varied between 1.4 and 4.1, showing generally higher plasma resistance of SiC. High resolution X-ray photoelectron analysis revealed that etched SiC has a surface carbon content higher than that of etched Si, resulting in a thicker fluorocarbon polymer layer on the SiC surface. The plasma resistance of SiC was correlated with this thick fluorocarbon polymer layer, which reduced the reaction probability of fluorine-containing species in the plasma with silicon from the SiC substrate. The remnant carbon after the removal of Si as volatile etch products augments the surface carbon, and seems to be the origin of the higher plasma resistance of SiC.

Effect of Al Content on the Gas-Phase Dehydration of Glycerol over Silica-Alumina-Supported Silicotungstic Acid Catalysts

The gas-phase dehydration of glycerol to acrolein was carried out over silicotungstic acid (, HSiW) catalysts supported on , , and silica-aluminas with different Al contents. The HSiW catalysts supported on silica-aluminas showed higher glycerol conversions and acrolein yields during the initial 2 h at than did - and -supported HSiW catalysts. Among the tested catalysts, HSiW/ exhibited the highest space-time yield during the initial 2 h. The loaded HSiW species can change the acid types and suppress the formation of carbonaceous species on Al-rich silica-aluminas. The deactivated HSiW supported on silica-aluminas can be fully regenerated after calcination in air at . As long as the molar ratio between water and glycerol was in the range of 2-11, the acrolein selectivity increased significantly with increasing water content in the feed, while the surface carbon content decreased owing to the suppression of heavy compounds.

Super-Hydrophilicity of Stainless Steel Surface Induced by Heat Treatment with Gaseous Ozone

The hydrophilic states of stainless steel surface treated by the separate or combined use of gaseous ozone and heat were investigated by measuring the contact angle of a water droplet, the content of the surface carbon contaminants, and the adsorption isotherm of water vapor. Super-hydrophilic states of stainless steel plates were achieved only by the combined gaseous ozone/heat treatment. The contact angle of a water droplet on the plate decreased from 81° to less than 5° after treating at 120 to 180 °C under 2 vol% ambient gaseous ozone. It was found that the super-hydrophilization proceeded according to two different mechanisms. One is the decomposition of surface contaminants. There was a good correlation between the surface carbon content and the water contact angle over the range of 15 to 81°. The other is the once removal of surface hydroxyl groups followed by chemisorption of water on these dehydroxylated sites. As a result of the removal of contaminants and the rehydration, the total number of surface hydroxyl groups on stainless steel became larger than that on the original surface.

Metal organic chemical vapor deposition of ZnO from β‐ketoiminates

ZnO is a high‐mobility electron conductor being considered for high‐throughput electronics in flexible and transparent formats. We demonstrated the Zn β‐ketoiminate system, based on acetylacetimine with N‐propyl, isopropyl, and butyl groups, as a vehicle for preparing ZnO thin films for electronic applications. Surface carbon was a primary impurity, and the precursors studied afforded films with the lowest surface carbon contamination at deposition temperatures near 400°C. Thermal annealing of the films reduced the surface carbon content and afforded semiconducting materials. Annealing also gave larger‐grained, better connected films. Thinner films were associated with semiconducting as opposed to ohmic behavior; such films will be adaptable for transparent logic circuits. Copyright © 2012 John Wiley & Sons, Ltd.

EPR studies of radicals generated by γ-radiation in nanocrystalline hydroxyapatites prepared by dry milling

A set of 10 nanocrystalline carbonate-containing calcium hydroxyapatites (HAs) with various mean crystal sizes below 100nm was prepared by dry milling in air of commercial HA (platelets ca. 100nm in size). The obtained crystallites had prolate plate-like shapes as in the bone mineral. The apatites were then irradiated at room temperature by γ-rays (a 60Co γ-source, a 7kGy dose, an irradiation rate of 0.7kGy/h) and studied using electron paramagnetic resonance (EPR). Four different radiogenic radicals were observed: CO33- in the crystal lattice (in B sites formerly occupied by PO43-), CO3- and O− radicals on the crystal surface, while dosimetric CO2- radicals were distributed between both those compartments. Concerning the milling time, the radicals were accumulated and disappeared in the specific sequence, related to the crystal surface area, crystal size (crystallinity) and carbonate content. The strongest EPR signal was observed for the crystal dimensions comparable to those in the bone mineral.

Water based processing of LiFePO4/C cathode material for Li-ion batteries utilizing freeze granulation

A water based solid state synthesis of LiFePO4 has been conducted by utilizing freeze granulation. Various processing conditions were tested and achieved powder properties were characterized by density, XRD, specific surface area, carbon content, conductivity and SEM. Freeze granulation, a novel method for precursor preparation was shown to be an effective method to provide high degree of homogeneity prior to calcination and high ultimate yield of pure LiFePO4. Cathodes were manufactured by water based as well as NMP system based tape casting. A commercial LiFePO4/C powder was also characterized and used to manufacture cathodes as comparison in this study. Charge cycling tests showed promising results with high capacity and long term stability, well in the range of what the commercial powder provided. Post-milling of calcined powder prior to paste preparation for tape casting tended, however, to retard the capacity owing to disturbed carbon distribution and loss of conductivity of the LiFePO4/C. In comparison with the solvent system for cathode manufacturing, the water based system gave similar cell performance, illustrating the possibility to apply a more environmentally sustainable processing of Li-battery cells.

Atmospheric pressure diffuse plasma in ambient air for ITO surface cleaning

Effects of atmospheric filament-free diffuse plasma in ambient air and oxygen by Diffuse Coplanar Surface Barrier Discharge (DCSBD) on surface of indium tin oxide (ITO) were studied. The DCSBD plasma treatment resulted in significant reduction of water contact angles (even for 1s long treatment). The decrease can be explained by the chemical changes on surface. These were studied by XPS which shows considerable decrease in the carbon surface concentration. The detailed analysis of C1s peak indicates the increase of the highest binding energy component of the C1s peak that corresponds to polar bonds with oxygen, which may be also related to decrease of water contact angle. AFM measurement showed no significant effect of plasma on ITO surface morphology.

Unburned carbon from bagasse fly ash as a support for a VOC oxidation catalyst

Unburned carbon in bagasse fly ash has been separated and activated under different conditions for use as a support for loading iron catalysts. These were tested for the total oxidation of n-butanol. The sequence of Fe loading affected the textural properties and the composition of the activated carbon. The sample loaded with Fe after activation had higher surface area and carbon content compared to sample activated after Fe loading. The sample with Fe loaded on separated carbon without activation had low surface area, low carbon content and poor activity in n-butanol oxidation. The Fe loaded activated carbon samples derived from bagasse fly ash had high surface area and their catalytic activities were comparable to that of commercial carbon. In comparison with the steam activated samples, the Fe loaded phosphoric acid activated carbon showed a higher thermal stability during the catalytic test due to the presence of COP linkage.

Methodical investigation of distortion biasing parameters during case hardening of spur wheels

AbstractHighly stressed gears are typically heat treated to satisfy operational demands. Case hardening is a common heat treatment associated with power train components. In the heat treatment process complex distortion processes take place, which were studied in these examinations. Object of the actual investigations were spur wheels with module 2.557 and 42 teeth on the wheel with a helix angel of 23°. The case hardening was realized utilizing low pressure carburisation with subsequent high pressure gas quenching in a heat treatment furnace of industrial proportion. The systematic analysis was guided using design of experiment methods. In strategic focus were the three contributing heat treatment steps of heating, carburisation and quenching. Heating related factors were the batch design, the heat transfer and the preheating temperature. During carburisation the temperature, carburisation depth and surface carbon content as well as the atmosphere during diffusion were altered. Finally the quenching related variation was the hardening temperature. The identified main factors on size as well as shape changes of the base body and the toothing will be presented and discussed.

Characterization of Fly Ash Generated from Matla Power Station in Mpumalanga, South Africa

In this study, fly ash was obtained from Matla power station and the physicochemical properties investigated. The fly ash was characterized by x‐ray fluorescence, x‐ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectrometry. Surface area, particle size, ash and carbon contents, pH, and point of zero charge were also measured. The results showed that the fly ash is alkaline and consists mainly of mullite (Al6Si2O13) and quartz (SiO2). Highly toxic metals As, Sb, Cd, Cr, and Pb as well as metals that are essential to health in trace amounts were also present. The storage and disposal of coal fly ash can thus lead to the release of leached metals into soils, surface and ground waters, find way into the ecological systems and then cause harmful effect to man and its environments.

Surface Energy Characteristics and Impact of Natural Minerals on Aggregate–Bitumen Bond Strengths and Asphalt Mixture Durability

The surface free energy of a solid is a material property that influences its interaction with other solids, liquids, and gases. Mineral aggregates are mixed with bitumen in the production of asphalt mixtures, and the interaction of aggregates with bitumen, water, or chemical modifiers affects the overall performance of the mixtures and, in turn, the pavement structure. A comprehensive characterization of the minerals that make up these aggregates can be used to explain the interactions between the aggregates and components used to bind the aggregates including bitumen, water, and chemical additives. This paper combines several techniques to quantify and describe or catalog mineral properties. These properties primarily include surface free energy, specific surface area, and surface carbon content of some of the most common minerals found in aggregates. The paper presents data that exemplify how this information can be used to characterize the moisture-induced stripping potential for bitumen–mineral combinations. Results indicate that a simple energy ratio calculated on the basis of adhesive bond energies from surface free energy measurements of the minerals and the bitumen can predict performance in asphalt mixtures and that a few minerals can form thermodynamically stable bonds with some bitumens that are inherently resistant to stripping.

The effect on chalk recrystallization after treatment with oxidizing agents

Chalk consists of the fossilized remains of the hard parts from some species of unicellular algae. These algae use polysaccharides to control the morphology of their shields, called coccoliths, which are made of from 20 to 60 individual, sub-micrometer size calcite crystals. This biogenic calcite has resisted recrystallization during the more than 65 million years of diagenesis. In this study, we examined the effect of oxidizing agents on the ability of the chalk to recrystallize. Samples from a North Sea drill core that had never been exposed to oil and Rørdal chalk from the Ålborg Portland quarry, north Jutland, Denmark, were treated with oxidizing agents to remove organic material and the recrystallization rates were determined. We treated the chalk with solutions of NaOCl and H 2O 2 with and without 0.1 M NaCl and monitored recrystallization in CaCO 3 saturated 0.1 M NaCl solutions using H 14CO 3 − as a tracer. X-ray photoelectron spectroscopy (XPS) showed that initially, the North Sea chalk had a higher surface concentration of organic carbon than the Ålborg sample, but it decreased significantly after the oxidizing treatment. Loss of C O correlated with higher recrystallization rates; rate increase was highest (~ 50%) after H 2O 2 treatment. Our results demonstrate that through geological time, miniscule amounts of organic material remain associated with the chalk surface and act as an inhibitor for chalk recrystallization. This implies that the polysaccharides originally made by the algae to control coccolith morphology have contributed to hindering chalk diagenesis to limestone, keeping the biogenic particles much smaller, even after 65 million years, than inorganic calcite grown in the lab for a few days.

Predictions of soil surface and topsoil organic carbon content through the use of laboratory and field spectroscopy in the Albany Thicket Biome of Eastern Cape Province of South Africa

In recent years it has been shown that laboratory and field visible near infrared spectroscopy (VNIRS) allows for the accurate prediction of soil organic carbon (SOC) — more rapidly, less expensively, and at larger scales than conventional soil laboratory methods. VNIRS might find application in the restoration assessment of the degraded, semi-arid subtropical thickets of the Albany Thicket Biome (ATB) of the Eastern Cape Province of South Africa. During the twentieth century, the semi-arid forms of the ATB suffered heavy browsing by goats, transforming the dense closed-canopy shrubland into an open savannah-like system. This paper presents a study dealing with SOC estimation of soil surface (0–5 mm) and topsoil (0–200 mm) in the degraded ATB, through the combination of soil spectroscopy and partial least square regression (PLSR). Spectroscopic measurements and soil samples were collected along a transect in the ATB. The PLSR models developed with laboratory and field spectra gave good predictions of SOC, with root mean square error of validation (RMSEV) < 5.0 and 5.5 g C kg − 1 , respectively. The use of the full visible near-infrared spectral range gave better SOC predictions than using either visible or near-infrared separately. The resampling simulation of the field surface spectra to the 232 channels of the satellite-born EnMAP sensor gave good SOC predictions for laboratory conditions (RPD > 2), but low accuracy (RMSE: 9.88 g C kg − 1 ) for field model. The results of this research study indicated that, for the ATB, (i) combining soil spectroscopy and PLSR does favor accurate prediction of SOC, (ii) the predictions of surface SOC can be used as a proxy of topsoil SOC, and (iii) there is potential for future application of satellite-born hyperspectral data for SOC content predictions.

&lt;i&gt;In Vivo&lt;/i&gt; Behaviour of the Synthetic Porous Hydroxyapatite Prepared by Low Temperature Microwave Processing and Comparison with Deproteinized Bovine Bone

The aim of this study was to evaluate the osteoconductive properties of synthetic porous hydroxyapatite prepared by low-temperature microwave processing OssaBase® HA (SPHA) in comparison with biological apatite, non-sintered deproteinized bovine bone Bio-Oss® (DBB). The materials were implanted into the bone sockets of the tibia of Beagle dogs for 3 and 6 months. The bone response to granules of the materials of similar sizes was compared. Histological analysis of the specimens with histomorphometry was performed at different times after in vivo implantation. Based on the histological analysis, the level of bone formation in the spaces between the implanted granules and through the interconnected pores of both implanted materials within a cortical region was significantly higher (bone area ingrowth 72–85%) than within a cancellous bone site (bone area ingrowth 16–28%) at three and six months after implantation. According to our study, the bioactive and osteoconductive properties (bone implant contact and bone area ingrown) of the synthetic porous hydroxyapatite are very high and comparable with the biological apatite, non-sintered deproteinized bovine bone. The favourable influence of the high specific surface area and carbonate content of the synthetic, porous hydroxyapatite on bone formation was confirmed.

Evaluation of Microstructural, Mechanical Properties and Corrosion Behavior of AISI Type 316LN Stainless Steel and Modified 9Cr-1Mo Steel Exposed in a Dynamic Bimetallic Sodium Loop at 798 K (525 °C) for 16,000 Hours

Changes occurring in the chemical composition, microstructure, mechanical properties, and carburization behavior of type 316LN stainless steel and modified 9Cr-1Mo steel on exposure to flowing sodium at 798 K (525 °C) for 16,000 hours in a bimetallic loop are discussed in this article. Type 316LN stainless steel revealed a degraded layer of approximately 5 μm depth. No significant microstructural changes were observed in the case of modified 9Cr-1Mo steel exposed to sodium. The carburization depth in type 316LN stainless steel was approximately 100 μm and the surface carbon concentration was 0.374 wt pct. In the case of modified 9Cr-1Mo steel, the carbon concentration at the surface was approximately 3.50 wt pct and the depth of carburization was nearly 75 μm. The concentration of nickel and chromium decreased from the bulk to the surface of type 316LN stainless steel, leading to the formation of a ferrite layer. The concentration of these two elements reached the original matrix concentration at around 30 μm. Sodium-exposed material indicated an increase in yield strength by 10 pct and reduction in ductility by 34 pct vis-a-vis annealed material. No such changes in strength and ductility were observed in the case of modified 9Cr-1Mo steel. A decrease in impact energy was noticed for sodium-exposed type 316LN stainless steel and modified 9Cr-1Mo steel vis-a-vis as-received material.

XPS investigation of vacuum annealed vertically aligned ultralong ZnO nanowires

The surface properties of vertically aligned ZnO nanowires grown by chemical vapour deposition on GaN using a gold layer as a catalyst are investigated by X-ray Photoelectron Spectroscopy as a function of annealing temperature in ultra high vacuum (UHV). The nanowires are 8.5 μm long and 60 nm wide. 87% of the surface carbon content was removed after annealing at 500 °C in UHV. Analysis of the gold intensity suggests diffusion into the nanowires after annealing at 600 °C. Annealing at 300 °C removes surface water contamination and induces a 0.2 eV upward band bending, indicating that adsorbed water molecules act as surface electron donors. The contaminants re-adsorbed after 10 days in UHV and the surface band bending caused by the water removal was reversed. The UHV experiment also affected the nanowires arrangement causing them to bunch together. These results have clear implications for gas sensing applications with ZnO NWs.