Thermionic Vacuum Arc Research Articles

Corrosion behavior of graphene coated Ti-6Al-4 V alloy by anodic plasma coating method

In this study, graphene layers were deposited onto Ti-6Al-4 V plates by Thermionic Vacuum Arc (TVA) deposition technology to improve the corrosion resistance of biomedical material. For this purpose, the distance from the sample (4 and 7 cm) and duration of coating (5 and 15 mins) parameters were tested. The corrosion performance of the sample was carried out using electrochemical tests in 0.9 wt% NaCl medium. Furthermore, the applied coatings were characterized by using FESEM, AFM, EDS, and FTIR devices. The microstructural findings revealed that the graphene coating was found dispersed in the grain and grain boundaries and was applied successfully to the surface of Ti-6Al-4 V for all applied TVA parameters. In general, the corrosion potential of the coated sample was more anodic when compared to the uncoated sample. The passivation area of the sample TP21 was more prominent, and the corrosion current was lower than in other samples. Furthermore, the polarization resistance was higher, and the corrosion rate was 8 times lower compared to the uncoated sample. Graphene coatings are promising anticorrosion coating materials for Ti-6Al-4 V.

Investigation of substrate effect on Co-doped ZnO thin films prepared by thermionic vacuum arc technique

• The substrate effect was investigted fort h Co-ZnOthin film. • The average crystallite size is 20 and 25 nm. • The band gap value of the Co-doped ZnO thin film was calculated as 3.22 eV. In this paper, the substrate effect on cobalt-doped ZnO thin films and crystal defects on optical properties of the sample have been investigated. The structural, elemental, surface and optical properties of the films were characterized using X-ray diffraction (XRD), atomic force microscopy, field emission scanning electron microscopy and UV-Vis spectrophotometry. The XRD results confirm the polycrystalline nature and formation of ZnO (100) plane for both substrates was detected. Metal oxide and bimetal oxide structures were determined using by XRD analyses. Average crystallite size of the films has been computed as 20 and 25 nm on the glass and Si substrates, respectively. The thicknesses of the films were recorded as 85 and 90 nm on the glass and Si substrates, respectively. The mean transmittance value was measured as 71%. The band gap value of Co-doped ZnO thin film was calculated as 3.22 eV. The Urbach energy was achieved as 227 meV depending on the lattice distortions and structural defects. According to obtain results, TVA is a promising method for Co doped ZnO thin film production.

Synthesis of Cobalt-Nickel Aluminate Spinels Using the Laser-Induced Thermionic Vacuum Arc Method and Thermal Annealing Processes.

To obtain highly homogeneous cobalt-nickel aluminate spinels with small crystallite sizes, CoNiAl alloy thin films were primarily deposited using Laser-induced Thermionic Vacuum Arc (LTVA) as a versatile method for performing processing of multiple materials, such as alloy/composite thin films, at a nanometric scale. Following thermal annealing in air, the CoNiAl metallic thin films were transformed into ceramic oxidic (Co,Ni)Al2O4 with controlled composition and crystallinity suitable for thermal stability and chemical resistance devices. Structural analysis revealed the formation of (Co,Ni)Al2O4 from the amorphous CoNiAl alloys. The mean crystallite size of the spinels was around 15 nm. Thermal annealing induces a densification process, increasing the film thickness together with the migration process of the aluminum toward the surface of the samples. The sheet resistance changed drastically from 200-240 Ω/sq to more than 106 Ω/sq, revealing a step-by-step conversion of the metallic character of the thin film to a dielectric oxidic structure. These cermet materials can be used as inert anodes for the solid oxide fuel cells (SOFCs), which require not only high stability with respect to oxidizing gases such as oxygen, but also good electrical conductivity. These combination metal-ceramics are known as bi-layer anodes. By controlling the crystallite size and the interplay between the oxide/metal composite, a balance between stability and electrical conductivity can be achieved.

Structural and Magnetic Specificities of Fe-B Thin Films Obtained by Thermionic Vacuum Arc and Magnetron Sputtering

Fe-B based compounds are of high interest due to their special properties and the wide range of involved applications. While B is the element that facilitates the increase in the hardness and the degree of wear resistance, it is also an effective glass former, controlling the formation of a much-desired amorphous structure with specific magnetic properties. Major difficulties related to the proper engineering of Fe-B thin films lay especially in their preparation under well-defined compositions, which in turn, should be accurately determined. The present study closely analyzes the morpho-structural and magnetic properties of thin coatings of Fe-B of approximately 100 nm thickness and with the nominal B content ranging from 5 at. % to 50 at. %. The comparison between films obtained by two preparation methods, namely, the thermionic vacuum arc and the magnetron sputtering is envisaged. Morpho-structural properties were highlighted using X-ray diffraction supplemented with X-ray reflectometry and scanning electron microscopy, whereas the elemental investigations were performed by X-ray dispersive spectroscopy and Rutherford back-scattering spectroscopy. The magnetic properties of the Fe-B layers were carefully investigated by the vectorial magneto-optic Kerr effect and conversion electron Mössbauer spectroscopy. The high capability of Mössbauer Spectroscopy to provide the phase composition and the B content in the formed Fe-B intermetallic films was proven, in correlation to Rutherford back-scattering techniques, and to explain their magnetic properties, including the magnetic texture of interest in many applications, in correlation with longitudinal magneto-optic-Kerr-effect-based techniques.

Development of corrosion resistance of reinforcement steel bars with nano-silver coatings

The aims of this study are to examine the effect of metallic coatings on reinforcement from the perspective of the durability properties of concrete structures. Also, consider the importance of laboratory production of cover while investigating how it can be applied to steel. In this research, to increase the corrosion resistance of the structural steel, the reinforcements were coated with thin films with a system called thermionic vacuum arc (TVA). As a result of recent studies, it has been observed that such thin films protect the reinforcement from corrosion. In this study, the effect of coated reinforcement on corrosion, which is one of the most important structural defects, was investigated. The applied coatings are nano-sized and protect the structural steel against corrosion reactions occurring on the surface. Moreover, these coatings increase the adherence between concrete and reinforcement. Specifically, for this study, silver (Ag) was used as a coating component. After the coating process was completed, the reinforcements were placed in cylindrical concrete samples and their resistance to corrosion was measured with the help of the accelerated corrosion technique. The results show that the rebars coated with the TVA system was prolonged the damage occurrence time (first crack) and diminished the corrosion reactions that occurred on the reinforcement surface.

Optical and surface properties of Gd-doped ZnO thin films deposited by thermionic vacuum arc deposition technology

In this paper, Zinc oxide (ZnO) was doped with Gadolinium (Gd) and it was deposited onto the glass and silicon substrates by thermionic vacuum arc (TVA) method to examine its morphological, compositional, and optical properties. The results show that the substrates strongly affect the morphological structures of the thin films. According to the obtained information, the surface roughness was found to be 38 nm and 6 nm for silicon and glass respectively. The images showed that the surface onto the glass had more symmetry and more regular grains. The optical properties of the nano composite on the glass substrate were analyzed with an optical interferometer and UV–Vis spectrophotometer. Absorbance, transparency, and refractive index of the thin film were obtained. It also had a relatively high refractive index. Furthermore, it was found that the band gap of ZnO decreased. The band gap of the deposited thin film was found 3.3 eV.

Corrosion Testing of CrNx-Coated 310 H Stainless Steel under Simulated Supercritical Water Conditions.

The paper’s aim is the assessment of corrosion behaviour of a CrNx-coated 310 H stainless steel under simulated supercritical water conditions (550 °C and 25 MPa) for up to 2160 h. The CrNx coating was obtained by the thermionic vacuum arc (TVA) method. The oxides grown on this coating were characterized using metallographic and gravimetric analysis, SEM with EDS, and grazing incidence X-ray diffraction (GIXRD). A diffusion mechanism drives oxidation kinetics because it follows a parabolic law. By XRD analysis, the presence of Cr2O3 and Fe3O4 on the surface of the autoclaved CrNx-coated 310 H samples were highlighted. Corrosion susceptibility assessment was performed by electrochemical impedance spectroscopy (EIS) and linear potentiodynamic polarization. EIS impedance spectra show the presence of two capacitive semicircles in the Nyquist diagram, highlighting both the presence of the CrNx coating and the oxide film formed during autoclaving on the 310 H stainless steel. Very low corrosion rates, with values up to 11 nm × year−1, obtained in the case of autoclaved for 2160 h, CrNx-coated samples indicated that the oxides formed on these samples are protective and provide better corrosion resistance. The determination of micro hardness Vickers completed the above investigation.

A novel self-powered filterless narrow-band near-infrared photodiode of Cu2S/Si p+-p isotype heterojunction device with very low visible light noise

This study aims to achieve a filterless, narrow-band, near-infrared photodiode based on a p+-Cu2S/p-Si isotype heterojunction device. The device is developed by depositing 60 nm thick Cu2S thin film on Si substrates from Copper Sulfide pieces via the Thermionic Vacuum Arc technique (TVA). The molecular structure of the thin film is analyzed by utilizing Raman and X-Ray photoelectron spectroscopy (XPS) and confirmed to be in the Cu2S phase. Moreover, the high hole concentration in Cu2S is correlated with XPS results. The photodiode exhibits a response climax centered at 1049 nm and a full-width at half-maximum (FWHM) value of 104 nm. An outstanding responsivity value of 375 mA/W (at 0 V bias) is obtained at a peak wavelength of 1049 nm, which surpasses most filterless, narrow-band photodiodes. Furthermore, while operating at 0 V bias, the photodiode showed an excellent specific detectivity value of 4.17 × 1011 Jones with a 1.7 × 103 on/off ratio (at 1049 nm, 11.47 mW/cm2), in addition to its high photocurrent stability and response speed (under 0.8 s). In light of these findings, this proof-of-concept device is a great candidate as a filterless, narrow-band, NIR self-powered photodiode.

Efficient Removal of Methylene Blue and Ciprofloxacin from Aqueous Solution Using Flower-like, Nanostructured ZnO Coating under UV Irradiation.

Flower-like ZnO architectures assembled with many nanorods were successfully synthesized through Thermionic Vacuum Arc, operated both in direct current (DC-TVA) and a pulsed mode (PTVA), and coupled with annealing in an oxygen atmosphere. The prepared coatings were analysed by scanning-electron microscopy with energy-dispersive X-ray-spectroscopy (SEM-EDX), X-ray-diffraction (XRD), and photoluminescence (PL) measurements. By simply modifying the TVA operation mode, the morphology and uniformity of ZnO nanorods can be tuned. The photocatalytic performance of synthesized nanostructured ZnO coatings was measured by the degradation of methylene-blue (MB) dye and ciprofloxacin (Cipro) antibiotic. The ZnO (PTVA) showed enhancing results regarding the photodegradation of target contaminants. About 96% of MB molecules were removed within 60 min of UV irradiation, with a rate constant of 0.058 min−1, which is almost nine times higher than the value of ZnO (DC-TVA). As well, ZnO (PTVA) presented superior photocatalytic activity towards the decomposition of Cipro, after 240 min of irradiation, yielding 96% degradation efficiency. Moreover, the agar-well diffusion assay performance against both Gram-positive and Gram-negative bacteria confirms the degradation of antibiotic molecules by the UV/ZnO (PTVA) approach, without the formation of secondary hazardous products during the photocatalysis process. Repeated cyclic usage of coatings revealed excellent reusability and operational stability.

Deep understanding in physical and electrochemical performance of WO3–TiO2 nanocomposite thin films deposited onto ITO and FTO coated glass substrates using a thermionic vacuum arc deposition system

In this work, WO3–TiO2 nanocomposite thin films were deposited via thermonic vacuum arc technique and the physical and electrochemical features of these nanocomposites were investigated. The average transmittance values were obtained 66.9% and 58.7%, particularly the mean absorbance values were 0.49 and 0.59 onto ITO and FTOcoated glass substrate. The optical band gap of the layers were calculated 2.59 and 2.62 eV upon ITO and FTO coated glass substrates, respectively. Measurement outputs show that both coated thin films are conductive and good storage capabilities for Li+ ions. The reversibility of the films is calculated at 7% and 15% on ITO coated glass and FTO coated glass substrates, respectively. Considering that WO3 and TiO2 materials separately show high quality electrochromic properties, it is aimed to produce these two materials as composites and to examine their electrochromic properties using different producing techniques.

Improved Corrosion Protection of Stainless Steel by Two Dimensional BN Nanomaterial Coating

Boron nitride (BN) nano coating was deposited on 304 type stainless steel sheets by standard thermionic vacuum arc (TVA) as a physical vapour deposition method. Deposited BN nano coating was characterized by attenuated total reflectance Fourier transform infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy and X-ray diffraction analyses tools. Corrosion performances of un-coated and BN nano material coated steel samples were investigated in 1 M H2SO4 solution using Eocp-time curves, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. BN nano coating was found to provide anodic protection to the steel and reduced significantly corrosion rate of 304 steel in acidic medium. Long term corrosion tests results demonstrated that the BN nano coating has ability to protect the 304 stainless steel in sulfuric acid corrosive media during 10 d and the protective behavior of the BN nano coating results from passivation effect of the coating against the attack of corrosive environment. Finally, BN nano coating is a promising two dimensional coating material for corrosion protection of stainless steel.

Substrate effect on electrochromic properties of Nb2O5:TiO2 nanocomposite thin films deposited by thermionic vacuum arc

In this paper, substrate effect on electrochromic properties of Nb2O5:TiO2 nanocomposite thin films have been investigated. Thin films have been deposited by thermionic vacuum arc deposition technology. Nb2O5 and TiO2 are known to be electrochromic materials. Nb/Ti rate was obtained 1.4. Average thicknesses of the films were found as 113 nm and 111 nm and band gap values for bleached states were calculated as 3.96 eV and 3.85 eV for the films deposited onto ITO and FTO coated glass substrates, respectively. The coloration efficiency values were calculated as 17 cm2/C and 26 cm2/C for the film onto ITO layered glass substrate and 31 cm2/C, 23 cm2/C and 24 cm2/C for the film onto FTO layered glass substrate at a different wavelength values in the visible region. The obtained results shows that films for each transparent conductive oxide material is promising material to obtain the high performance TiO2 active layer.

Synthesis and characterization of some C-Ti based multilayer and composite nanostructures

Carbon-Titanium multilayer and composite thin films were obtained by Thermionic Vacuum Arc (TVA) method. The nanostructured films consisted by a carbon base layer and seven alternatively Titanium and Carbon layers were deposed on Silicon substrate. As well, to give C-Ti multilayer films with different percentages in Ti and C of layers, a thick Carbon base layer was deposed on Si substrate, and then seven Ti-C layers. In order to achieve the successively layers with C, and Ti different percentages, were adjusted the discharge parameters of C and Ti plasma sources to obtain the desired composition of layers. By changing of substrate temperature, and on the other hand the bias potential up to –700V, different batches of samples were obtained. Characterization of structural properties of films was achieved by Grazing Incidence X-ray Diffraction (GIXRD) and Electron Microscopy technique (TEM). The measurements show that increase of the substrate temperature reveal the changes in TixCy lattice parameters. The tribological measurements were performed using a ball-on-disk system with normal forces of 0.5, 1, 2, 3N respectively and a Bruker Hystrion TI 980 TriboIndenter. Was found that the coefficient of friction depends on the synthesis temperature, bias voltage and also by the C content, Ti content and amount of TiC nanocrystallites. To characterize the electrical conductive properties, the electrical surface resistance versus temperature have been measured, and then the electrical conductivity is calculated. Using the Wiedeman-Frantz law was obtained the thermal conductivity.

The Synergistic Effect of the Laser Beam on the Thermionic Vacuum Arc Method for Titanium-Doped Chromium Thin Film Deposition

Laser-Induced Thermionic Vacuum Arc (LTVA) provides a better way to produce uniform metallic thin films than the classical Thermionic Vacuum Arc (TVA) method. In Ti-doped chromium thin films produced using LTVA, the amorphous chromium is superimposed with small bcc chromium nanoparticles. These amorphous/crystalline structures with small crystallites induce lower roughness and electrical resistivity, reducing electron–phonon scattering and increasing charge transport across LTVA thin films. A significant shift in resistivity for the LTVA samples is observed due to electron scattering on the phonon–crystalline structures in the TVA samples which exhibit larger crystallites. Meanwhile, the wettability measurements reveal a higher contact angle, resulting in a lower surface free energy and consecutively lower dissociation energy for the LTVA-produced thin films than the TVA samples.

Optical properties of Nb2O5 doped ZnO nanocomposite thin film deposited by thermionic vacuum arc

In this study, Nb2O5: ZnO nanocomposite thin film has been deposited by thermionic vacuum arc and then surface and optical properties of Nb2O5: ZnO nanocomposite thin film have been investigated. The surface and optical properties were investigated by a scanning electron microscopy and atomic force microscopy. Optical properties and band gap value were determined by UV-Vis spectrophotometer. Thickness of the film was determined as 25 nm. Weight percentages of Zn and Nb elements were found as 99.85% and 0.15%, respectively. Deposited thin films were transparent. Artificial intelligence (AI) technique is a promising and an alternative technique for research and development to determine the properties of a material. For this aim, optical band gap predictions were done. The band gap energy value was calculated 3.08 eV. The band gaps of 3.39 eV and 3.62 eV were estimated by Gaussian processes regression and Gaussian processes regression with synthetic minority over-sampling technology model, respectively. Estimated band gap value is close to the estimated value from the Tauc model. It is acceptable for the determination. But, crystal diameter and atom number values were nearly the same as experimental and predicted values. As a result, AI techniques are useful techniques for the determination of the film properties.

Influence of oxygen effect in coating layer on tensile bond strength of PMMA

Polymethylmethacrylate (PMMA) is a widely used denture base material in dental practice and the improvement of its properties is important for improving the quality of treatment. The aim of this study is to increase the tensile bond strength between PMMA and soft liner with Thermionic Vacuum Arc. Surface properties were evaluated by Scanning Electron Microscope, Energy-Dispersive X-ray Analysis, and Atomic Force Microscope after the tensile bond strength test. As a result, the ZnO coating with TVA positively affects the PMMA surface properties compared to Ag and SnO2 groups and promising for clinical use.

Influence of Annealing Temperature in Ito Thin Films Prepared by Thermionic Vacuum Arc (Tva) Technique

Influence of Annealing Temperature in Ito Thin Films Prepared by Thermionic Vacuum Arc (Tva) Technique

NANOSTRUCTURED Ti-C THIN FILMS DEPOSITED BY THERMIONIC VACUUM ARC (TVA) TECHNOLOGY

Nanostructured titanium-carbon nanostructured thin films were prepared using the Thermionic Vacuum Arc (TVA) technology in different configurations under a varied number of Ti/C combinations at high base pressure of 1 x 10-6Torr with and without graded compositions. The layers consisting of about lOOnm Carbon base layer and seven 40nm alternatively Ti and C layers were deposited on Silicon substrates. On the other hand, in order to obtain C-Ti multilayer structures with variable thickness and different percentages in C and Ti oflayers, a 20nm thick C layer was first deposed on Si substrate and then seven Ti-C layers, each ofthese having thickness of up to 40nm were deposed. To perform the successively layers with various thickness were changed the discharge parameters for C and Ti plasma sources to obtain the desirable thickness. By changing ofsubstrate temperature between room temperature and 300°C and on the other hand the bias voltage up to -700V, different batches of samples were obtained for this study. The films were characterized by surface morphology, and microstructure, through Rutherford Backscattering Spectrometry (RBS), Raman Spectroscopy, Transmission Electron Microscopy (TEM), Grazing Incidence X-ray diffraction (GIXRD). Tribological and electrical measurements are also presented.

Electron Irradiation of Titanium-Doped Chromium Nanostructured Thin Films for Higher Conductive Electrodes

The low-energy electron irradiation improves the electrical properties of the Ti-doped chromium thin films obtained by Laser-assisted Thermionic Vacuum Arc (LTVA). The irradiation doses, between 0.6 C/m2 and 326.4 C/m2, operate as a nanozonal melting effect, decreasing the metallic alloy's roughness, and increasing the electrical conductivity at a depth up to 8 nm. Therefore, the grain sizes of the surface nanostructures are increased after irradiation, but the surface roughness is substantially improved. By tailoring the surface parameters like crystallinity and roughness of the metallic thin films used as electrodes in the OLED technologies, a reduction of the Schottky contacts between the metal and semiconductor contact is expected. This fact minimizes the contact resistance between the metallic and semiconductor thin films and increases the charge injection across the OLED sandwich structures

The effect of Cu doping on optical and surface properties of ZnO thin films fabricated by thermionic vacuum arc (TVA) deposition

The effect of Cu doping on optical and surface properties of ZnO thin films fabricated by thermionic vacuum arc (TVA) deposition