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The study investigates the effect of RF plasma on the commercial SS201 and Steel alloys physical, structural and nuclear properties, using an atmosphere of nitrogen (85%) plus acetylene (15%) at 500 W working for 0.5 h. The results were compared with untreated alloys and AISI304L. The study indicated the ability of RF plasma to improve both the mechanical and tribological properties of treated alloys compared to the original commercial alloys and the AISI304L, and achieve good shielding properties for industrial/nuclear applications. [Display omitted] • Commercial SS201 and steel alloys are common/essential materials for the construction of many industrial/nuclear applications. • The impact of RF plasma carbonitriding on the commercial alloys compared with the standard AISI304L has been investigated. • The carbonitriding surface engineering process upgrades both mechanical/tribological properties ofCommercial alloys. • The RF plasma process achieves equivalent radiation shielding properties for the carbonitrided commercial alloys. [ABSTRACT FROM AUTHOR]

Titanium nitrides have good tribo-mechanical and biomedical properties. They are employed to harden and protect cutting and sliding surfaces for industrial purpose and as a non-toxic outer-surface for bio-medical applications. In this study, pure titanium was nitrided using RF plasma technique. The microstructural, mechanical, tribological, electrochemical and biomedical properties of nitrided titanium were investigated. The X-ray diffraction demonstrates the formation of ε-Ti 2 N and the cubic δ-TiN phases after plasma nitriding. The microhardness of the nitride samples increases as the plasma-processing power increases up to 1300 HV 0.1 . That represents approximately 7-fold increment in the microhardness in comparison with the untreated titanium. High nitriding rate of 0.17 μm 2 /s was recorded for the sample that was treated at 650 W. The wear and corrosion resistance are improved after plasma nitriding. Moreover, the friction coefficient is reduced from nearly 0.75 for the untreated titanium to 0.25 for the nitride one. An enhancement in the biocompatibility of the nitrided titanium has been achieved. The number of grown mesenchymal stem cells was higher for nitrided substrates compared to that of the untreated titanium. The improved tribo-mechanical and electrochemical performance of the nitrided titanium can be attributed to the formation of super-hard titanium nitrided phases. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous carbon nitride thin films were deposited on polymer substrates using radio frequency (rf) plasma in a mixture of nitrogen (N2) and acetylene (C2H2) gasses. The samples were prepared at different rf plasma power (350, 400, 450, 500, and 550W), at constant plasma exposure time of 10min, and constant N2/C2H2 ratio of 50%. The crystal structure and surface morphology of the prepared samples were examined using X-ray diffraction and atomic force microscopy analysis, respectively. The absence of the carbon nitride diffraction peaks confirms the amorphous nature of these films. The root mean square roughness of the films increased from 3.77 to 25.22nm as the power increased from 350 to 550W. The thickness and the deposition rate were found to increase with increasing plasma power. Over the whole studied wavelength range, from 200 to 2500nm, the transmittance decreased with increasing plasma power. A shift in the onset of absorption towards higher wavelengths with increasing plasma power, indicating a decrease in the optical band gap, has been observed. The refractive index values were found to decrease while the extinction coefficient increased with increasing plasma power. [Copyright &y& Elsevier]

Abstract: Surface of 304 AISI austenitic stainless steel has been modified using duplex treatment technique of nitriding and carbonitriding. A thick modified nitrided layer, of approximately 20 µm, has been achieved when rf inductively coupled plasma was adjusted at 450 W for processing time of only 10 min. After performing the nitrided layer, the nitrided samples were carbonitrided using the same technique at different acetylene partial pressure ratios ranges from 10% to 70%, the balance was pure nitrogen. Different amount of nitrogen and carbon species are diffused underneath the surface through the nitrided layer during carbonitriding process and are found to be gas composition dependent. The treated samples were characterized by glow discharge optical spectroscopy, X-ray diffractometry, scanning electron microscopy and Vickers microhardness tester. The microstructure of the duplex treated layer indicates the formation of γ́-Fe4N, Fe3C, CrN and nitrogen-expanded austenite (γN). The thickness of the duplex treated layer increases with increasing the acetylene partial pressure ratio. The surface microhardness of duplex treated samples has been found to be gas composition dependent and increased by 1.29 fold in comparison to the nitrided sample. [Copyright &y& Elsevier]

Abstract: The present work reports on the effect of input plasma processing power in the range of 350–650W on the microstructure and mechanical properties of plasma nitrided Ti. The plasma processing time was 20min and a gas mixture of 15% C2H2 and 85% N2 was used. The characteristics of the carbonitrided layer have been investigated by microhardness measurements, surface roughness measurements, optical microscopy, and X-ray diffraction. The measured surface hardness values of the compound layer shows a maximum of 2050HV0.1 for the sample treated at a plasma power of 550W. The thickness of the carbonitrided layer continuously increases as the plasma power increases. Moreover, the highest carbonitriding rate of 3.52μm2/s was observed when the input plasma power was adjusted at 600W. This high carbonitriding rate of treated titanium samples is ascribed to the high concentration of active carbon and nitrogen species in the plasma atmosphere and the formed microcracks in the near surface of the sample during the plasma processing. [Copyright &y& Elsevier]

Abstract: In this work, duplex treatment has been carried out using radio frequency (rf) plasma nitriding process and direct current (dc) magnetron sputtering of titanium. Nitriding of AISI 304 stainless steel, using rf plasma technique, created a thick modified layer of approximately 20 μm for short plasma processing time of 10 min. After nitriding process, a thin titanium nitride film has been deposited using dc magnetron sputtering of titanium for different nitrogen/argon gas pressure ratios. The treated samples were characterized via glow discharge optical spectroscopy, X-ray diffractometry, scanning electron microscopy, profile meter and Vickers microhardness tester. The elemental composition, thickness and microhardness values of the duplex treated layers are found to be gas composition dependent. The data shows that the microhardness of the duplex treated layer increases to 1.42 fold relative to the associate value of the nitrided one. Moreover, high deposition rate of 110 nm/min is obtained. [Copyright &y& Elsevier]

Inductively coupled radio frequency plasma surface treatment was applied to commercially pure titanium sheets. The goal was to increase the efficiency of the carbonitriding process, i.e., to decrease the plasma treatment time to a few tens of minutes instead of several hours. The effects of different plasma-processing times on the microstructure and mechanical properties of plasma-carbonitrided Ti were examined. The characteristics of the carbonitrided layer were investigated by microhardness testing, surface roughness measurements, optical microscopy and X-ray diffraction. The surface microhardness and the thickness of the compound layer of carbonitrided Ti increase with the plasma-processing time. Surface energy, yield strength and Young’s modulus for carbonitrided titanium were calculated from the Vickers microhardness data. An attempt was made to interpret the high carbonitriding rate and the high microhardness values of carbonitrided titanium with respect to previously published results. [ABSTRACT FROM AUTHOR]

Abstract: Radio frequency (RF) plasma nitriding using different input plasma processing powers (250–600 W) improves the surface of titanium by forming hard phases of TiN, Ti2N, and Ti (N) into the surface. The characteristics of the compound layer have been investigated by optical microscopy, microhardness measurements, and X-ray diffraction. The effect of plasma power on the sample temperature, electron temperature, and plasma density was studied using Langmuir double probe. The measured surface hardness value of the compound layer is 2190 HV 0.1 for treated sample at plasma power 500 W. The compound thickness continuously increases as the plasma power increases. The highest nitriding rate of 5.88 μm2/s was recorded when the input plasma power was adjusted at 550 W. This high nitriding rate of treated titanium samples is ascribed to the high concentration of active nitrogen species in the plasma atmosphere and the formed microcracks near to the surface of the sample during the plasma processing. We have proposed that at low input plasma power (low temperature) the interstitial diffusion is the main mechanism. However, vacancy-controlled diffusion for high input plasma power (high temperature) is probably the one needed to surmount the energy barrier. [Copyright &y& Elsevier]

Abstract: Plasma immersion ion implantation (PIII) has been employed for nitrocarburizing 304 stainless steel. The sample was treated at relatively low gas pressure of nitrogen and acetylene in the range of 10−3 mbar. The microstructure variation, the austenite lattices spacing and the phase transformations were studied in-situ during heating up to 800 °C and after cooling, using synchrotron X-ray diffraction. Glow discharge optical spectroscopy (GDOS), optical microscopy and hardness profile measurements have been used before and after thermal treatment to analyse the nitrocarburized layer. [Copyright &y& Elsevier]

A systematic study was undertaken with surface of titanium nitrided by Rf inductively coupled plasma. The continuous plasma processing time was changed from only 3 to 40 min in steps of 5 min or less. The other plasma parameters were fixed. The effect of cyclic plasma processing time on titanium sample was investigated too. The single period of plasma processing was adjusted to be 25 min and the nitriding process was repeated twice, triplet, and quadruple. X-ray diffraction (XRD), optical micrograph (OM), and Vickers microhardness (HV) were employed as analytical techniques. The results clearly show that the surface hardness and nitriding rate increase incessantly as the continuous plasma processing time increases to reach the maximum values of 2150 HV0.1 at 40 min and 3.38 μm2/s at 30 min, respectively. This behavior may be attributed to formation of new hard phases α-Ti(N), δ-TiN, and #x03B5;-Ti2N in the treated layer. In this interval, the active nitrogen species penetrate faster through surface grain boundaries and through the formed surface microcraks of titanium sample. For relatively long nitriding time more than 30 min of continuous plasma processing, the rate of nitriding decreases. The formed nitrided phases might block the previously formed microcracks in the treated layer. Therefore, the penetration of nitrogen species rate through these microcracks decreases and the rate of nitriding process decreases consequently. Using cyclic nitriding method yielded an increase in the microhardness of titanium sample to be 2650 HV0.1 with relatively high rate of nitriding. These investigations show that the short Rf plasma processing time treatment and cyclic nitriding method play an important role for producing hard surface titanium with high rate of nitriding. [Copyright &y& Elsevier]

Abstract: Plasma immersion ion implantation (PIII) has been used to modify the surface properties of 304 austenitic stainless steel (AISI). The influence of working gas pressure, 0.2–1.0 Pa, and substrate temperature, 300–500 °C, on the microstructure, treating rate, nitrogen/carbon concentration depth profile, and surface microhardness was investigated. A gas composition of 25% C2H2, 75% N2, r.f. plasma power input of 350 W, and a negatively biased potential of 30 kV were fixed during the experiment. The experimental results show that the substrate temperature and the diffusion process of nitrogen and carbon depend on the gas pressure inside the plasma chamber. The thickness of the modified layer has been found to be more than 30 μm for samples were treated in the plasma for 60 min. The results show also that the values of diffusion coefficient and surface microhardness of the treated samples are high to be 3.4×10−1 μm2/s and 1880 kg/mm2, respectively. [Copyright &y& Elsevier]

Adding C2H2 gas to nitrogen gas during r.f. plasma processing has significant influence on the properties of 304 austenitic stainless steel. The elemental depth profiles of the compound layer were investigated by glow discharge optical spectroscopy. Different treatment gas compositions of N2/C2H2 mixtures (0–100% in steps of 10 or 5% in some cases) have been investigated. The total gas pressure during the plasma processing was 8.4×10-2 mbar. The sample temperature was approximately 550 °C with an insignificant variation for different gas compositions. A high rate of diffusion of carbonitriding has been obtained without initial sputter removal of the surface oxide layer, which demonstrates that the surface oxide layer does not play a crucial role during r.f. plasma carburizing and carbonitriding of stainless steel. The nitrogen concentration and the compound layer thickness increase, when 10% of C2H2 is added. With further increase in the C2H2 ratio, they decrease again gradually. The carbon depth profiles for the same samples show lower concentration and opposite tendency with respect to the nitrogen content. X-ray diffraction was used to characterize the microstructure of the compound layers. Fe2N, Fe3N, CrN, nitrogen-expanded austenite (γn) and carbon-expanded austenite (γc) phases are detected. The relative proportions of the phases are critically dependent on the N2/C2H2 ratio. Depending on the N2/C2H2 ratio, the microhardness value increases by a factor between 2 and 6. The carbonitrid layer exhibits a corrosion resistance better than pure nitrided and carburized layers. [Copyright &y& Elsevier]

Radio frequency (rf) inductively coupled plasma was used for carbonitriding the surface of AISI-304 austenitic stainless steel (ASS) samples at different input plasma powers (300–650 W). The morphology and the microstructure of the treated surfaces of carbonitrided austenitic stainless steel samples (CNASS) were examined by optical microscopy (OM) and scanning electron microscopy (SEM). The surface hardness of the treated surfaces as well as the microhardness profile of the samples was measured. X-Ray diffraction was employed to investigate the structure of product phases as a result of carbonitriding process. The results indicate that by using the rf plasma technique, we can greatly improve the tribomechanical properties of these materials. The high rate of carbonitriding (1 μm2/s) and the high hardness of CNASS (1375 Hv, 0.1) at plasma input power 550 W have been interpreted in terms of nitrogen and carbon concentration gradients, and microcracks formed in the surface during the plasma process in the compound layer. [Copyright &y& Elsevier]

Rf plasma nitriding processes have been used recently for surface treatment. 304 Austenitic stainless steel has been nitrided using an inductively coupled rf plasma. High rates of nitriding and relatively high microhardness have been achieved. The effect of plasma power and plasma processing time on the rate of nitriding and the microstructure was investigated. A high nitriding rate of 3 μm2/s and a microhardness value of 1800 HV0.1 were achieved under optimum plasma conditions. The interpretation is based on a new approach that the microcracks in the surface, at a certain ambient temperature and plasma, can create traps for the active nitrogen species. The nitrogen concentration and temperature gradient can also draw some of the nitrogen species towards the bulk side. The microhardness can be explained in terms of the high concentration of nitrided phases created under the surface of the treated samples. [Copyright &y& Elsevier]

Graphene Oxide (GO) has attracted strong research interest due to its unique mechanical, thermal, electrical, and magnetic properties. Herein, a simple oxygen plasma process is used as an eco-friendly, novel and effective surface treatment technique to enhance the microstructure, adhesion force, and electrical properties of the GO films. GO films were treated in a plasma oxygen environment at a constant RF power of 300 W and different processing times ranging from 0 to 7 min. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy are utilized to examine changes in the type of surface groups and the distribution of bonds energy before and after plasma treatment. Additionally, the effect of RF oxygen plasma treatment on other properties, such as thermal stability, surface roughness, contact angle, work of adhesion, wettability, electrical conductivity, and sheet resistance has been studied. XPS data revealed that RF oxygen plasma treatment reduced the amount of oxygen-containing groups (such as epoxides (O–C O), carbonyls (C–O–C), and carboxyl's (O–C O) from 48.8% for the as - prepared GO film to 33.56% after 5 min of treatment. In addition, the average surface roughness (Ra) increased from ~7.8 of as-prepared GO film to ~8.7 μm, while the work of adhesion improved to reach 134.84 mN/m. However, with increasing plasma processing time up to 7 min, the thermogravimetric analysis (TGA) of the treated GO film showed a weight loss difference of 51.66%. Furthermore, introducing a high amount of C O bonds (carbonyl and SP2 groups of carbon atoms) after plasma treatment improved the electrical conductivity to a value of 0.156 S/m. The current results indicate that the properties of GO can be tuned by varying the degree of oxidation, which may pave the way for new developments in GO-based applications. [Display omitted] • Graphene oxide (GO) films were chemically synthesized with high quality and uniformity. • RF oxygen plasma treatment has improved GO sheets physical and chemical properties. • Plasma surface treatment of GO enhanced the chemical functionalization, reduction levels and exhibited good electrical properties.. • RF oxygen plasma treatment reduced the amount of oxygen-containing groups such as (O–C=O), (C–O–C), and (O–C=O). • [ABSTRACT FROM AUTHOR]

The aim of this work was to examine the influence of radio frequency (rf) power on ZnO films synthesized by means of chemical vapor transport technique in inductively coupled plasma (ICP). As the rf power increased, with a fixed processing time of only 8 min, the temperature inside the reactor tube, the thickness and surface roughness of the formed polycrystalline ZnO films increased. The morphology of the ZnO films changed to oblate, webby like cloud-grains, nanoslices, and a mixture of nanorods and nanograins with changing the rf power from 300 to 500 W. Mixed phases of hexagonal ZnO and hexagonal Zn were found for samples synthesized at 300 and 500 W whereas single hexagonal ZnO was synthesized at 350, 400 and 450 W. The optical band gap decreased from 3.35 eV to 3.05 eV with increasing the rf power from 300 W to 500 W. The refractive index and extinction coefficient values were mainly increased with increasing the rf power. The electrical resistivity was generally decreased with increasing rf power and has values between 1.38 × 10−2 - 2.83 × 10−3 Ωcm. The obtained results might be important for useful applications of ZnO films grown by chemical vapor transport with the assistance of ICP. [ABSTRACT FROM AUTHOR]

The paper aims to investigate the mechanical and radiation shielding properties of two tungsten-based alloys manufactured by powder technology; their features when compared with two standard stainless steel grades for advanced nuclear applications. Multiple measurements were performed to characterize the alloys' structural and mechanical properties. XRD analysis and average surface roughness measurements showed the crystalline and morphological structure of the alloys. Surface microhardness added to the abrasive wear analysis showed the final wear resistance of the selected alloys. In addition, the shielding features against gamma and fast neutrons radiation were calculated. The superior characteristics of W-based alloys manufactured by powder technology make them suitable to be used in advanced nuclear power units. [Display omitted] • The powder technology has been used to manufacture two tungsten-based alloys. Their physical, mechanical and tribological features were compared with other two stainless steel alloys for application at the nuclear power reactors. • Powder technology is unique and controls the final properties of produced materials, including porosity, density, and uniform morphology of the material texture. • Tungsten based alloys exhibit excellent tribological properties. They are suitable for components subjected to high mechanical stresses and sliding contact in nuclear reactors. • Tungsten based alloys achieve higher density than stainless steel alloys,They are more effective in shielding against gamma radiation. • It is recommended to use Tungsten-based alloys prepared by the powder technology at the higher energy range 0.1 to 20 MeV for the nuclear applications. [ABSTRACT FROM AUTHOR]

Abstract: The present work describes the surface improvement and biocompatibility of TiAl24Nb10 intermetallic alloy using rf plasma nitriding. The nitriding process was carried out at different plasma power from 400W to 650W where the other plasma conditions were fixed. Grazing incidence X-ray diffractometry (GIXRD), Auger electron spectroscopy (AES), tribometer and a nanohardness tester were employed to characterize the nitrided layer. Further potentiodynamic polarization method was used to describe the corrosion behavior of the un-nitrided and nitrided alloy. It has been found that the Vickers hardness (HV) and corrosion resistance values of the nitrided layers increase with increasing plasma power while the wear rates of the nitrided layers reduce by two orders of magnitude as compared to those of the un-nitrided layer. This improvement in surface properties of the intermetallic alloy is due to formation of a thin modified layer which is composed of titanium nitride in the alloy surface. Moreover, all modified layers were tested for their sustainability as a biocompatible material. Concerning the application area of biocompatibility, the present treated alloy show good surface properties especially for the nitrided alloy at low plasma power of 400W. [Copyright &y& Elsevier]

Abstract: ZnO thin films were prepared by thermal oxidation of metallic Zn films and nitrided by an inductively coupled rf plasma. The effects of successive plasma processing cyclic times on structural and optical properties as well as electrical resistivity were examined by different characterization techniques. A small amount of nitrogen was detected at the film–substrate interface. The grain size decreased slightly as the treatment time increased. The surface roughness of examined films increased while the thickness decreased with increasing plasma treatment time. The electrical resistivity decreased about four orders of magnitude when the sample nitrided for 15min. However, the transmittance increased as the plasma treatment time increased. The optical band gap increased from 2.76 to 3.02eV with increasing plasma treatment time from 0 to 15min. [Copyright &y& Elsevier]

The depth dependence of elemental composition, phase distribution, and cross-sectional morphology of rf plasma nitrocarburized 304 austenitic stainless steel were investigated using glow discharge optical spectroscopy (GDOS), grazing incidence X-ray diffraction (GIXRD), and optical microscopy, respectively. A step-wise mechanical polishing method was used to remove successive sublayers of the treated surface. It was found that the properties of the nitrocarburized layer depend critically on the plasma gas composition, which controls the supersaturation of nitrogen and carbon through the compound layer depth. Iron nitride phases and/or nitrogen-expanded austenite (γN) were detected in the nitrocarburized layer prepared at high plasma nitrogen (N2) content. In the compound layer processed at high plasma carbon (C2H2) content, besides the carbon-expanded austenite phase (γC), carbide phases were found predominantly in the top-layer, in which the carbon concentration has a maximum value of ∼2 wt.%. The lattice expansion of the expanded austenite phases changes with sampling depth, depending on local variations in nitrogen and carbon content. The applied rf plasma processing power influences significantly nitrogen and carbon distribution in the treated sublayers. [Copyright &y& Elsevier]

TiN/TiO x N y bilayer films with various TiN thicknesses were prepared using direct current (d.c.) reactive magnetron sputtering. The ratio of N/O in the bilayer films increased with increasing TiN top layer thickness. The observed crystalline peaks for the bilayer films, for different TiN layer thicknesses, were indexed to anatase TiO 2 with tetragonal structure. Only 0.31° peak shift, to lower 2θ angles was detected. FESEM indicated that the morphology of TiO x N y single layer is consisted of elongated nanocrystals with diameters in the range of 27.9–46.8 nm and the diameters of the nanocrystallites changed slightly with increasing the thickness of TiN layer. The transmittance, absorbance, reflectance spectra and the optical constants of the bilayer films were presented. The photoelectrochemical performance for water splitting of TiN/TiO x N y bilayer films was studied by examination both the continuous and chopped photocurrent density under light illumination. The photocurrent density increases with increasing TiN top layer up to a thickness of 9 nm, after which a reduction in photocurrent is observed. The wettability of TiN/TiO x N y bilayer films could be transformed by UV illumination from hydrophobic to hydrophilic. [ABSTRACT FROM AUTHOR]