Surface Treatment Of Materials Research Articles

Cure Behavior of the Liquid-Crystalline Epoxy/Carbon Nanotube System and the Effect of Surface Treatment of Carbon Fillers on Cure Reaction

The FT-IR spectra of carbon nanotubes (CN) and oxidated carbon nanotubes were obtained using diffuse reflection Fourier-transform infrared (DRIFT) spectroscopy. The cure behavior of the liquid-crystalline epoxy (LCE)/CN and the LCE/carbon black (CB) systems were investigated. The effect of surface treatment of the carbon nanotube on the cure behavior in the LCE/CN system was investigated with differential scanning calorimetry (DSC), and was compared with those of the CB. The heat of cure in the LCE/CN system was higher than that in the LCE/CB system. The activation energy was dependent on the concentration of the curing agent. The activation energies for the cure reaction were decreased as a result of surface treatment of carbon materials. It was possible to promote the curing reaction by the surface treatment of the carbon nanotube without decreasing the heat of cure. The isothermal kinetic parameters were obtained from the Kamal equation. TEM images of carbon nanotube: carbon nanotube bundle.

Metal-arc plasma ion implantation in a straight magnetic filter

Ion implantation is a well-known technique used in surface treatment of materials. During the 1980s, ion implantation using a sample immersed in an ionized gaseous medium (known as plasma immersion ion implantation) revealed to be an alternative to the conventional ion beam implantation. Development of this nonconventional surface processing using metallic ion species increased significantly when metal vacuum arcs began to be used as ion sources. In this paper, we present the experimental results obtained on Si wafers used as test targets, using metallic arc ion implantation. High-density plasmas (up to 10/sup 19/ m/sup -3/) made of aluminum vacuum arcs were used for the metallic implantation process. Arc currents of 200-700 A and 16 ms duration were pulsed every 30 s, and samples were biased from 2 kV to 10 kV with 50 /spl mu/s pulses at 700 Hz, using a hard tube pulser. A straight magnetic filter was used to clean the plasma from macroparticle contaminants, with complete filtering being achieved in samples oriented so that their surfaces were parallel to the plasma stream. This is an interesting alternative to 90/spl deg/ curved magnetic duct filters usually used for this purpose. High-resolution X-ray diffraction analysis shows that aluminum was successfully implanted.

Plasma needle: a non-destructive atmospheric plasma source for fine surface treatment of (bio)materials

A non-thermal plasma source (`plasma needle') generated under atmospheric pressure by means of radio-frequency excitation has been characterized. Plasma appears as a small (sub-mm) glow at the tip of a metal pin. It operates in helium, argon, nitrogen and mixtures of He with air. Electrical measurements show that plasma needle operates at relatively low voltages (200–500 V peak-to-peak) and the power consumption ranges from tens of milliwatts to at most a few watts. Electron-excitation, vibrational and rotational temperatures have been determined using optical emission spectroscopy. Excitation and vibration temperatures are close to each other, in the range 0.2–0.3 eV, rotational gas temperature is at most a few hundred K. At lowest power input the source has the highest excitation temperature while the gas remains at room temperature. We have demonstrated the non-aggressive nature of the plasma: it can be applied on organic materials, also in watery environment, without causing thermal/electric damage to the surface. Plasma needle will be used in the study of plasma interactions with living cells and tissues. At later stages, this research aims at performing fine, high-precision plasma surgery, like removal of (cancer) cells or cleaning of dental cavities.

Statistical studies on the light output and energy resolution of small LSO single crystals with different surface treatments combined with various reflector materials

The optimization of light output and energy resolution of scintillators is of special interest for the development of high resolution and high sensitivity PET. The aim of this work is to obtain statistically reliable results concerning optimal surface treatment of scintillation crystals and the selection of reflector material. For this purpose, raw, mechanically polished and etched LSO crystals (size 2×2×10 mm 3) were combined with various reflector materials (Teflon tape, Teflon matrix, BaSO 4) and exposed to a 22Na source. In order to ensure the statistical reliability of the results, groups of 10 LSO crystals each were measured for all combinations of surface treatment and reflector material. Using no reflector material the light output increased up to 551±35% by mechanical polishing the surface compared to 100±5% for raw crystals. Etching the surface increased the light output to 441±29%. The untreated crystals had an energy resolution of 24.6±4.0%. By mechanical polishing the surface it was possible to achieve an energy resolution of 13.2±0.8%, by etching of 14.8±0.7%. In combination with BaSO 4 as reflector material the maximum increase of light output has been established to 932±57% for mechanically polished and 895±61% for etched crystals. The combination with BaSO 4 also caused the best improvement of the energy resolution up to 11.6±0.2% for mechanically polished and 12.2±0.3% for etched crystals. Relating to the light output there was no significant statistical difference between the two surface treatments in combination with BaSO 4. In contrast to this, the statistical results of the energy resolution have shown the combination of mechanical polishing and BaSO 4 as the optimum.

Nitrogen profiles in materials implanted via plasma-based ion implantation

The lifetime of metallic components can be drastically increased by surface treatments ensuring a low friction coefficient, surface hardening and an anticorrosion coating. A promising method for such surface modifications is plasma-based ion implantation (PBII) of nitrogen. In order to improve and to obtain a better understanding of such a treatment, we have performed nitrogen implantation in different materials at various ion energy values using pure nitrogen and N 2/H 2 gas mixture plasmas. Fe and Ti samples were simultaneously treated in a large-volume PBII reactor in which the plasma is excited at the distributed electron cyclotron resonance. Si substrates were also implanted in order to characterize the nitrogen implantation efficiency by Fourier-transform infrared (FTIR) analysis. Profiles of the relative concentration of elements in the samples were deduced from X-ray photoelectron spectroscopy (XPS) analysis as a function of depth. The absolute concentration of implanted nitrogen was also obtained by nuclear reaction with 15N atoms implanted in metals via PBII from a 15N 2/ 14N 2 gas mixture. These results can be very useful for calibrating and improving PBII surface treatments of materials.

１２％Ｃｒ耐熱鋼のホウ化処理と固体粒子衝突に対する耐エロージョン性

In order to cope with the severe solid particle erosion damage of 12%Cr steel for steam turbine nozzles, erosion tests were conducted at high temperature, by using high velocity iron oxide for solid particles. With respect to the behavior of erosion damage, the effects of impact angles and velocity of iron oxide, hardness and surface treatments of target materials were made clear. And a boronized 12%Cr steel was superior resistant to the erosion. This paper describes the characteristics of boronized layer of 12%Cr steel with excellent erosion resistance, the relationship between damage and some erosion factors and the application of boronized 12%Cr steel nozzles in actual steam turbines.

Modified distributed electron cyclotron resonance ion source for the production of large diameter ion beams

The work presented in this article concerns the conception and the study of a multiantenna electron cyclotron resonance (ECR) ion source at 2.45 GHz dedicated to the surface treatment of large area materials. In this original device, a microwave plasma is created in a 20 cm in diameter ionization chamber. The 15 cm in diameter extracted ion beam has a current density of about 1 mA/cm2. The applicator is an N-way coaxial power divider in which the N=20 antennas are individually magnetized by internal SmCo bars in order to produce ECR zones in their vicinity. Moreover, the microwave plasma is confined by a multicusp magnetic structure surrounding the ionization chamber. The choice of the source geometry has been guided by the study of some theoretical considerations such as the characteristic diffusion length, the minimum breakdown field, and the penetration depth of the wave into the plasma. Simulations both of the electromagnetic field and the static magnetic field distribution have been carried out in order to validate the final choice of the source geometry. A full characterization of the ECR plasma and of the extracted ion beam was made with different experimental techniques. These results allow us to localize the plasma creation zones inside the ionization chamber. A 120 mA singly charged argon ion beam with a profile homogeneity better than ±5% over 10 cm was obtained 5 cm downstream the extraction system with a 300 W microwave power and a neutral argon pressure of 10−3 mbar in the ionizing chamber.

Hollow cathode plasma sources for large area surface treatment

Plasma generation over large areas using a hollow cathode discharge is described in this study. Radio frequency linear hollow cathodes in several arrangements, for operation at reduced gas pressure and suitable for scale-up, are presented. Examples of surface processing and coating by PVD, both by hollow cathode discharge (HCD) and hollow cathode arc (HCA), are given. A non-equilibrium atmospheric plasma source utilizing a fused hollow cathode (FHC) with its modular concept can be used for surface treatment, activation or cleaning of temperature sensitive materials at ambient atmosphere. Results on polyethylene and polyethyleneterephtalate activation are presented.

Chamber for in situ WAXS, SAXS and GISAXS studies: application to plasma induced transformations in steels

A chamber for in situ WAXS, SAXS and GISAXS studies of polycrystalline and amorphous materials was designed and constructed. It is used under vacuum or filled with a gas mixture to operate as a reactor where a plasma for materials surface treatment is produced. The WAXS intensity is recorded by an external imaging plate moving parallel to the chamber axis, making it possible to obtain successive patterns during in situ studies of structural transformations. The chamber is also used for classical SAXS and GISAXS studies of thin films.

Pulsed electron beam facility (GESA) for surface treatment of materials

The paper describes the new pulsed electron beam facilities GESA designed for material surface treatment. These facilities ensure the possibility to realize melting depths of materials in the range of 10–100 μm. Parameters of the electron beam produced are as follows: electron energy 50–400 keV; beam current 200–500 A, beam cross-section 50–100 cm 2; pulse duration 5–250 μs, maximum power density at the target −6 MW/cm 2, maximum energy density 500 J/cm 2. All beam parameters are controlled independently.

Prediction of melt depth in selected architectural materials during high-power diode laser treatment

The development of an accurate analysis procedure for many laser applications, including the surface treatment of architectural materials, is extremely complicated due to the multitude of process parameters and materials characteristics involved. A one-dimensional analytical model based on Fourier's law, with quasi-stationary situations in an isotropic and inhomogeneous workpiece with a parabolic meltpool geometry being assumed, was successfully developed. This model, with the inclusion of an empirically determined correction factor, predicted high-power diode laser-induced melt depths in clay quarry tiles, ceramic tiles and ordinary Portland cement that were in close agreement with those obtained experimentally. It was observed, however, that as the incident laser line energy increased (>15 W mm −1 s −1/2), the calculated and the experimental melt depths began to diverge at an increasing rate. It is believed that this observed increasing discrepancy can be attributed to the fact the model developed neglects sideways conduction which, although it can be reasonably neglected at low-energy densities, becomes significant at higher energy densities since one-dimensional heat transfer no longer holds true.

Surface Heat Treatment of Facing and Other Materials with Concentrated Solar Energy

Surface treatment of building materials, ornamental ceramics, cover‐coat enamels, blast‐furnace and open‐hearth slags, and natural stones of the basalt type has been carried out with the use of solar furnaces and their simulators for the purpose of obtaining protective‐decorative vitreous and glazed coatings. The specific energy consumption and the optimum heat fluxes necessary to obtain high‐quality coatings have been determined. The results of searching investigations testify to the fact that renewable environmentally safe concentrated solar energy can be utilized in industry and the national economy for surface heat treatment of different materials by melting them in the air.

High power diode laser surface treatment of mullite crucible material

Alumina, as well as alumina/silica mixtures are well characterised materials used in a multitude of applications from insulators, crucibles to vacuum system windows. In this paper we present the application of a high power diode laser (HPDL) to surface treat the material from its sintered form into an amorphous, glass type glaze. The process has been monitored using a high speed motion analysis system. The laser treated glaze material is robust and exhibits good adherence to the bulk ceramic. The samples are analysed via XRD, EDX and optical microscopy. This technique could have potential applications in vacuum sealing or surface treatment of ceramic workpieces.

Innovative surface microcracking treatment of polymeric substrate to be coated with plasma sprayed stainless steel

Coating of organic substrates to improve properties has attracted interest because of the potential industrial applications for these materials. Thermal spraying is an attractive coating technology for this purpose owing to its high deposition rate relative to competing processes; however, actual industrial applications remain limited because of poor bonding between the polymeric substrate and the thermal sprayed deposit. Consequently, specific surface preparation of the polymer is required in most cases. In the present study, an innovative surface treatment of a polymeric material allowing subsequent buildup of a plasma sprayed coating is reported. This patented process, known as Pinpro, was successfully applied to coat an organic stereolithography substrate with an AISI 316 stainless steel thick (1 mm) deposit. The process consists in creating a population of surface microcracks in the polymer to provide mechanical anchoring for the steel deposit. Methods of surface preparation were investigated and optimised. The main surface modification mechanisms were elucidated and a phenomenological model of coating buildup on the treated substrate is proposed.

Physical foundations for surface treatment of materials with low energy, high current electron beams

The paper presents a review of original investigations on the surface modification of metallic materials with low energy (up to 40keV), high current (up to 40J/cm2) electron beams of microsecond duration. Based on material research and on simulations of temperature and stress fields, the regularities and mechanisms for the changes in the defect structure and in the strain–stress state of pure metals (Fe) on pulsed heating are considered. The peculiarities of the formation of non-equilibrium structure-phase states and graded structures on pulsed melting of film–substrate (Fe–Ta, Al–Si, and Al–C) systems have been studied. For a broad spectrum of structural and tool materials (steels, aluminum and titanium alloys, hard alloys) it has been shown that the most pronounced changes in the structure-phase state occur in the near-surface layer quenched from the liquid state, where the velocity of the crystallization front reaches its maximum. In this layer, the second phases are partially or completely dissolved, and oversaturated solid solutions and nanosized second-phase segregates are formed. This substantially improves the electrochemical and strength properties of the surface layer. It has been established that the action of dynamic stresses has the result that the modified layer with enhanced strength properties is substantially thicker than the heat-affected zone.

Flame-assisted laser surface treatment of refractory materials for crack-free densification

A study to improve the integrity and reliability of alumina-based refractory bricks, installed as linings in furnaces and incinerators, is being conducted. Owing to the inherent porosity of such heat-insulating materials, problems associated with molten slag penetration and chemical degradation are often encountered. It is known that denser refractories degrade less rapidly since such penetration is hindered. One aim for the current research is to seal the surfaces of these refractory materials by laser surface processing. In this way the bulk properties of the brick are retained, while the surface properties are improved. This paper reports on the results of an investigation to determine the optimum laser processing parameters that produce a zone of densified material containing few defects at the refractory surface. The high thermal stresses usually associated with laser treatment are often relieved by fracture of the laser-treated zone. However, by using a novel flame-assisted laser surface treatment, a reduction in thermal stress has been achieved, resulting in a crack-free, dense laser-treated zone. This treated zone should reduce or even eliminate the ingress of molten slags and gases, thus providing a reduced area for attack by corrosive species.

Design of an UHV reactor system for plasma surface treatment of polymer materials

A research-orientated multi-reactor system for surface processing with low-pressure, non-equilibrium plasmas is described. Its special design enables detailed investigation of plasma-physical aspects of multi-step plasma surface processing. It includes specialized plasma reactors, and specimen sizes up to 200 mm×20 mm can be handled. The plasma and surface analytical equipment is capable of measuring distributions on an area with a diameter of 200 mm. Examples of applications for plasma-chemical surface modification of polymeric biomaterials demonstrate how the system can bridge the gap between processing-orientated plasma reactor systems and research reactors designed for plasma diagnostics.

Mechanical Surface Treatments of Lightweight Materials—Effects on Fatigue Strength and Near-Surface Microstructures

Mechanical surface treatments such as shot peening or deep rolling are well-known processes to improve the fatigue strength of metallic components. This is due to favorable microstructural alterations in relatively thin surface layers as a consequence of near-surface inhomogeneous plastic deformations. Typical examples demonstrate the fatigue-strength increase for mechanically surface-treated specimens. Existing possibilities to improve the fatigue strength of welded joints by mechanical surface treatments are also included. In the case of lightweight materials (e. g. magnesium- or aluminum-base alloys), process parameters must be well adapted in individual cases to achieve optimum near-surface material states, taking into account the wide range of mechanical properties attainable as a result of their specific material microstructure. The effects of process parameters and microstructures on near-surface materials properties resulting from mechanical surface treatments are demonstrated with examples. Depth distributions of macroresidual and microresidual stresses are analyzed together with microstructural observations. An important point for the effectiveness of mechanical surface treatments is the stability of the near-surface material states during loading history. This aspect is treated for the case of fatigue loading.

Field emission from tetrahedral amorphous carbon as a function of surface treatment and substrate material

To understand the mechanism of electron field emission from diamond-like carbon, tetrahedral amorphous carbon (ta-C) films were subjected to Ar, H2, and O2 plasma treatments to change their surface condition and were deposited on substrates of different work function. The threshold fields and current densities for undoped ta-C are found to be significantly improved by the plasma treatments, largely due to an increase in emission site density, while little dependence was found on work function of substrate. This suggests that the main barrier to emission from ta-C is at the front surface.

Effect of surface treatment and back contact material on field emission from tetrahedral amorphous carbon

The location of the barrier for electron field emission from diamond-like carbon is identified by subjecting tetrahedral amorphous carbon (ta-C) films to H 2 , O 2 and Ar plasma treatments to change their chemical termination and etch off any surface layers, and to deposit ta-C on substrates of different work function. Emission thresholds and current densities for undoped ta-C are found to be greatly increased by the plasma etching, due to an increase in emission site density, whereas little dependence was found on the work function of the back contact.