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A high entropy carbide (TaNbTiV)C was fabricated via spark plasma sintering of high entropy powders that were prepared using a molten salt method. The as-fabricated high entropy carbide was then investigated for its high-temperature oxidation behavior at 850 °C, under atmospheres with three different oxygen contents (20 vol%, 40 vol%, and 60 vol%). After the high-temperature oxidation process, the main phases observed in all the specimens were incompletely oxidized phase (Nb x Ti 1-x)C y O 2-y and oxides (Nb 0.5 Ta 0.5) 2 O 5 , TiO 2 , and Nb 2 O 5. Importantly, the thickness of the oxide layer initially increased and then decreased as the oxygen content increased. When the oxygen content reached 40 vol%, the ceramic displayed severe oxidation behavior with observed thicker of the oxide layer, as well as numerous pores and cracks in the oxide layer. This work provides new insights into the oxidation behavior of high entropy carbides. [ABSTRACT FROM AUTHOR]

As a critical material for high-temperature components of aero-engines, the mechanical properties of Ti65 alloy, subjected to high-temperature and long-term thermal exposure, directly affect its service safety. The room-temperature tensile properties of the Ti65 alloy after thermal exposure to temperatures ranging from 450 °C to 650 °C for 100 h were investigated. The results indicate that as the thermal exposure temperature increases, the strength of Ti65 alloy initially increases and then decreases, while ductility exhibits a decreasing trend. The strength of the thermally exposed alloy positively correlates with the size and content of the α2 phase. The ductility of the thermally exposed alloy is comprehensively influenced by the surface oxidation behavior, α2 phase, and silicides. After the prolonged thermal exposure, stress concentration at the crack tips within the oxide layer was enhanced with the increased thickness of the surface TiO2 oxide layer, leading to premature fracture due to reduced alloy ductility. Furthermore, the α2 phase in the matrix promotes the planar slip of dislocations, while silicides at the α/β phase boundaries hinder dislocation motion, causing dislocation pile-ups. Both behaviors facilitate crack nucleation and deteriorate alloy ductility. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The electrical stimulation of pedicle screws is a technique used to ensure its correct placement within the vertebrae pedicle. Several authors have studied these screws' electrical properties with the objective of understanding if they are a potential source of false negatives. As titanium screws are anodized with different thicknesses of a high electrical resistance oxide (TiO2), this study investigated, using analytical, numerical, and experimental methods, how its thickness may affect pedicle screw's resistance and conductivity. Analytical results have demonstrated that the thickness of the TiO2 layer does result in a significant radial resistance increase (44.21 mΩ/nm, for Ø 4.5 mm), and a decrease of conductivity with layers thicker than 150 nm. The numerical approach denotes that the geometry of the screw further results in a decrease in the pedicle screw conductivity, especially after 125 nm. Additionally, the experimental results demonstrate that there is indeed an effective decrease in conductivity with an increase in the TiO2 layer thickness, which is also reflected in the screw's total resistance. While the magnitude of the resistance associated with each TiO2 layer thickness may not be enough to compromise the ability to use anodized pedicle screws with a high-voltage electrical stimulator, pedicle screws should be the subject of more frequent electrical characterisation studies. [ABSTRACT FROM AUTHOR]

Biomaterials are the basis for the development of medicine because they allow safe contact with a living organism. The aim of this work was to produce innovative oxide layers with a microporous structure on the surface of commercially pure titanium Grade 4 (CpTi G4) and to characterize their properties as drug carriers. The anodization of the CpTi G4 subjected to mechanical grinding and electrochemical polishing was carried out in a solution of 1M ethylene glycol with the addition of 40 g of ammonium fluoride at a voltage of 20 V for 2, 18, 24, and 48 h at room temperature. It was found that the longer the anodization time, the greater the number of pores formed on the CpTi G4 surface as revealed using the FE-SEM method, and the greater the surface roughness determined in profilometric tests. As the anodizing time increases, the amount of the drug in the form of gentamicin sulfate incorporated into the resulting pores decreases. The most favorable drug release kinetics profile determined via UV–VIS absorption spectroscopy was found for the CpTi G4 anodized for 2 h. [ABSTRACT FROM AUTHOR]

Silicon (Si) particle with small size used as anode material has been recognized for its ability to reduce the damage caused by volume expansion in liquid lithium-ion batteries. However, whether the same mechanism still exists for different particle sizes of Si in all-solid-state batteries (ASSBs), these have not been systematically investigated. In this work, Si particles with various sizes ranging from 30 to 1000 nm are investigated as regards the effect of Si particle size. It is revealed that the performance of Si particles in ASSBs is influenced by a combination of factors, including uniformity of the Si oxide layer, tap density, and expansion degree, which are all related to size of the Si particles. In order to investigate the effect of different particle sizes of Si, micron, sub-micron, and nano-silicon are set up in this work for electrochemical performance testing of all-solid-state batteries. Among all, sub-micron Si exhibits smaller impedance increase due to its tight contact and fewer voids and cracks after cycle. Such a structure demonstrates excellent conductive network and achieve the high initial Coulombic efficiency (ICE) of Si (78.37%) by exploiting the passivation effect of sulfides (Li6SP5Cl) solid electrolyte (SE) on the Si anode and the high voltage stability of halide SE (Li3InCl6). This work has certain reference significance for improving the conductivity of Si anode in ASSBs. [ABSTRACT FROM AUTHOR]

Ultra-thin 304 stainless steel can be used to flexibly display substrates after they have been subjected to chemical mechanical polishing (CMP). The thickness of the chemical oxide layer directly affects the polishing efficiency and surface quality of 304 stainless steel. In the study presented in the following paper, the thickness variation of the chemical oxide layer of 304 stainless steel was analyzed following electrochemical corrosion under different oxidant concentration conditions. Furthermore, the impact of the oxidant concentration on the grooves, chips, and scratch depth–displacement–load curves was investigated during a nano-scratching experiment. Through this process, we were able to reveal the chemical reaction mechanism between 304 stainless steel materials and oxidizers. The corrosion rate was found to be faster at 8% oxidant content. The maximum values of the scratch depth and elastic–plastic critical load were determined to be 2153 nm and 58.47 mN, respectively. [ABSTRACT FROM AUTHOR]

In order to study the microscopic reaction mechanism and kinetic model of Al/PTFE, a reactive force field (ReaxFF) was used to simulate the interface model of the Al/PTFE system with different oxide layer thicknesses (0 Å, 5 Å, 10 Å), and the thermochemical behavior of Al/PTFE at different heating rates was analyzed by simultaneous thermal analysis (TG-DSC). The results show that the thickness of the oxide layer has a significant effect on the reaction process of Al/PTFE. In the system with an oxide layer thickness of 5 Å, the compactness of the oxide layer changes due to thermal rearrangement, resulting in the diffusion of reactants (fluorine-containing substances) through the oxide layer into the Al core. The reaction mainly occurs between the oxide layer and the Al core. For the 10 Å oxide layer, the reaction only exists outside the interface of the oxide layer. With the movement of the oxygen ions in the oxide layer and the Al atoms in the Al core, the oxide layer moves to the Al core, which makes the reaction continue. By analyzing the reaction process of Al/PTFE, the mechanism function of Al/PTFE was obtained by combining the shrinkage volume model (R3 model) and the three-dimensional diffusion (D3 model). In addition, the activation energy of Al/PTFE was 258.8 kJ/mol and the pre-exponential factor was 2.495 × 1015 min−1. The research results have important theoretical significance and reference value for the in-depth understanding of the microscopic chemical reaction mechanism and the quantitative study of macroscopic energy release of Al/PTFE reactive materials. [ABSTRACT FROM AUTHOR]

Abstract—The effect of ion implantation on the surface morphology, structure of oxide layers, and electrochemical properties of nickel titanium TiNi in a 0.9 wt % sodium chloride (NaCl) solution has been studied. It has been established that the modification of the TiNi surface with titanium and niobium ions at an irradiation dose of 1017 ion/cm2 increases the surface roughness and improves the corrosion properties, which manifests itself in the growth of the charge transfer resistance and the drop of the anodic current. The comparative transmission electron microscopy analysis of the structure of the oxide layers and study of their electrochemical properties have shown that the corrosion properties of TiNi are caused by the complex phase composition of the surface. In particular, the niobium ion-beam treatment has resulted in the formation of a thin (~2 nm) continuous amorphous oxide film with a low permittivity (ε = 44) on the TiNi surface. [ABSTRACT FROM AUTHOR]

30Cr3 is a novel ultra-high strength steel (UHSS) with excellent strength and plastic toughness, which has been mainly used in aerospace shells and stressed parts. Currently, there is still a lack of systematic research and comprehensive evaluation on the laser cleaning of this particular material. In this study, a nanosecond pulsed laser was employed for the cleaning process. First, the energy distribution model was derived, the influence of the spatial and temporal distribution of laser energy on the cleaning quality was discussed, and the cleaning experiment was conducted. The results showed that a laser energy density of 15 J/cm2, combined with the beam overlap rate 52% in the x-direction and 61% in the y-direction, can effectively remove the oxide layer and thoroughly expose the natural metal matrix. Then, under the optimum parameters, the oxygen content decreased from 22.3% to 3.4%, the Fe content increased from 54.5 to 83.4%, the Fe3+ peak disappeared in the X-ray photoelectron spectroscopy (XPS), a remelted layer of only 1 μm was observed. Last, the roughness was slightly reduced from 3.573 μm to 2.985 μm, the hardness was restored to the original hardness level of the substrate (∼260 HV), and the electron back scatter diffraction (EBSD) showed that the structure hardly changed after cleaning, the grain size was comparable to that of the matrix. These findings indicated that laser cleaning can effectively remove the oxide layer of 30Cr3 UHSS without damaging the properties of the base material, which has promising application in the cleaning of UHSS.

Due to the excellent activity and stability of MnCo 2 O 4 toward the oxygen evolution reaction (OER) in acidic solution, a Pb–MnCo 2 O 4 composite anode for zinc electrowinning was prepared by embedding dispersed MnCo 2 O 4 particles into a Pb matrix in a powder metallurgy process. In this work, the phase structure, chemical composition, and morphology of the oxide layers formed on Pure-Pb and Pb–MnCo 2 O 4 were analyzed by XRD, SEM, and EDS. Galvanostatic polorization, Tafel tests, and EIS measurements were performed to investigate the anodic potential variation and OER kinetics of the Pure-Pb and Pb–MnCo 2 O 4 composite anodes. Compared with that on the Pure-Pb anode, the oxide layer on Pb–MnCo 2 O 4 is thinner, more compact, and more stable in a 160 g L−1 H 2 SO 4 solution containing 4 g L−1 Mn2+. Consequently, the Pb–MnCo 2 O 4 composite anode exhibited a much lower anode slime production (8.7 mg) during 72 h of the simulated zinc electrowinning process. Despite the smaller surface area and lower PbO 2 content of the oxide layer, the Pb–MnCo 2 O 4 composite anode presented preferable OER kinetics with a lower OER charge transfer resistance (0.729 Ω cm2) and a smaller Tafel slope (90.74 mV dec−1), which contributed to a 70 mV reduction in the anodic potential compared with that of the Pure-Pb anode. • The anodic potential of Pb–MnCo 2 O 4 composite anode is 70 mV than the Pure-Pb anode. • The oxide layer on Pb–MnCo 2 O 4 is thinner, more compact, and more stable. • Pb–MnCo 2 O 4 exhibits a smaller tafel slope and lower charge transfer resistance of OER. • The incorporation of MnCo 2 O 4 significantly reduces the production of anode slime. [ABSTRACT FROM AUTHOR]

Developing advanced underwater welding technology for titanium, which is the key structural material for underwater applications, is of great significance for the design, fabrication, and maintenance of submarine equipment. In this study, in order to investigate the underwater welding microstructure and mechanical properties of Ti-4Al-2V alloy, underwater wet laser welding was conducted on Ti-4Al-2V alloy using varying laser power. The microstructure and properties of the welding joints were characterized and analyzed. The microstructure of the heat-affected zone and fusion zone in the welding joints are not significantly different from those of welding in air, but a mixed oxide layer composed of Al2O3 and TiO2 is formed on the surface of the fusion zone. Due to internal stress, a large number of cracks initiate on the oxide layer and propagate to the joints. In the 4 kW and 5 kW joints, a penetrating crack formed due to the excessive accumulation of internal stress breaking up the α phase. The mechanical properties of the joints are significantly affected by the laser power. The tensile strength of the 3 kW and 4 kW joints is comparable to that of the base metal, which is about 600 MPa, while the 5 kW joint shows brittle fracture with no plastic deformation and 228 MPa strength. This research lays a solid foundation for understanding the underwater wet laser welding behavior of titanium alloys. [ABSTRACT FROM AUTHOR]

High-entropy alloys (HEAs) consisting of five or more components in an equimolar ratio are attracting increasing attention due to a unique combination of various properties. Doping HEAs with small amounts of certain elements (most often rare earth, trace or noble metals) is a promising way to improve the characteristics of such alloys and to control their properties. This paper reports the results on the microstructure, phase composition, and microhardness of as-cast AgxAl0.5CoCrCuyFeNi HEAs (x = 0, 0.1; y = 0.5, 1.0). The effect of silver addition on the oxidation behavior of the studied HEAs at 700°C was determined. The morphology, phase and chemical composition of the resulting oxide film were studied. It was shown that the introduction of silver improves the mechanical characteristics of the alloys, but deteriorates the oxidation resistance due to the formation of copper-silver eutectic in the alloy microstructure, leading to a change in the morphology and phase composition of the formed oxide layer. Along with the solid solution of (Al, Cr)2O3 oxides and CuCr2O4, NiCr2O4 spinels, the addition of silver leads to the formation of copper oxide CuO and a small amount of silver oxide Ag2O in the surface film. [ABSTRACT FROM AUTHOR]

The chemical and phase composition of oxide layers on U8, U10, and 45 tool steel samples formed by laser treatment is studied by X-ray photoelectron spectroscopy. In the surface layers of the samples, the depth of the oxide layers (Fe2O3, Fe3O4, FeO) is the same, but their thickness is different. That affects the tribological properties. [ABSTRACT FROM AUTHOR]

The effect of increasing the bonding pressure from 10 to 20 MPa (5 MPa interval) at 1050°C for 60 minutes on the diffusion bonded joint of reduced activation ferritic/martensitic (RAFM) steel was investigated. The results indicate that the quality of the bond improves accordingly with increasing bonding pressure. The oxide layer at the bonding interface underwent an evolution process from continuous to discontinuous and ultimately disappeared with the increase of bonding pressure. The optimal joint was achieved in this work at the pressure of 20 MPa. Considering the research of reliability of joints in engineering applications, the optimum joint was subjected to post-bonding heat treatment (PBHT) of 750°C for 90 minutes. The diffusion bonded sample subjected to PBHT exibits microstructural features and tensile properties similar to those of the base metal. It is noteworthy that the tensile fracture does not occur at the bonding interface, but in the base metal far away from the interface. This work can provide a feasible method for the removal of oxides at the diffusion bonding interface of RAFM steel and also contribute to the establishment and optimization of diffusion bonding processes, thereby improving the quality of the diffusion bonding joint.

Metal-ceramics dental prosthetic restorations are clinically recommended for their advantages related to good esthetic features along with strength and long-term clinical use. Given the importance of the quality of the metalceramic (M-C) bond, the metal substructure analysis has a major importance to the quality of the manufactured dental prosthesis. In the present study was analyzed the behavior of experimentally developed novel titanium alloys (TiZr, TiZrNbTa) comparatively with other frequently used titanium alloys (e.g., Ti Cp, Ti6Al4V) designated for the technology of mixed prosthetic restorations. All samples were been plated, simultaneously in the same conditions, with the same titanium specific compatible ceramic plating material (Ti22 Noritake). The examination of the surface of both components was performed by scanning electron microscopy SEM) analysis and EDS analysis, which showed differences in the characteristics of the oxide layer formed, depending on the composition of the metal substructure. The evaluation of the alloy-ceramic adhesion was performed by mechanical tests, which attest to the fact that the adhesion and the quality of the bond between metal and ceramic depend on the thickness of the oxide films formed. The results showed the superiority of titanium novel titanium alloys (TiZr, TiZrNbTa), having highest hardness values, highest values of shear strength, a continuous thin oxide films, and consequently, a better metal-ceramic adhesion. Comparatively, less ductile titanium alloys (TiZrNbTa/Ti3) are generating lower adhesion forces with values above 30MPa in some samples justifying less predictable clinical results.

As a critical material for high-temperature components of aero-engines, the mechanical properties of Ti65 alloy, subjected to high-temperature and long-term thermal exposure, directly affect its service safety. The room-temperature tensile properties of the Ti65 alloy after thermal exposure to temperatures ranging from 450 °C to 650 °C for 100 h were investigated. The results indicate that as the thermal exposure temperature increases, the strength of Ti65 alloy initially increases and then decreases, while ductility exhibits a decreasing trend. The strength of the thermally exposed alloy positively correlates with the size and content of the α2 phase. The ductility of the thermally exposed alloy is comprehensively influenced by the surface oxidation behavior, α2 phase, and silicides. After the prolonged thermal exposure, stress concentration at the crack tips within the oxide layer was enhanced with the increased thickness of the surface TiO2 oxide layer, leading to premature fracture due to reduced alloy ductility. Furthermore, the α2 phase in the matrix promotes the planar slip of dislocations, while silicides at the α/β phase boundaries hinder dislocation motion, causing dislocation pile-ups. Both behaviors facilitate crack nucleation and deteriorate alloy ductility.

In this paper, the durability, the wear resistance, the tribological behavior, and the wear particles flow of the Anodic Aluminum Oxide Film 5083 were studied under cyclic loading. Different anodizing durations (reaction times (RT)) and applied currents (J) were tested. Besides, a tribological model with a correlation between the friction coefficient and the wear mechanisms of the oxide layer was established. Postmortem analyses were investigated using scanning electron microscopy (SEM), energy-dispersive x-rays (EDX), and profilometry analyses. Experimental results were shown that the increase in the RT improves the durability of the 5083-aluminum alloy oxide layer. Moreover, when RT increased, the stability of friction coefficient was improved, and the surfaced pores were more filled with micro-sized wear particles, inducing the establishment of a compacted layer. Consequently, the 5083-aluminum alloy oxide layer was shown important tribological characteristics such as the durability and wear resistance after hundreds of rubbing cycles. It was concluded that three stages characterized the friction behavior and the wear particle flow under cycling: firstly, a friction coefficient stable stage with the establishment of an internal flow that feeds the contact (internal source flow); the second stage is the progressive increase in the friction coefficient, while the wear particles were crushed and compacted to form a smooth layer, constituting the continuous internal flow; and the third stage is the return of the stable state of the friction coefficient, where the smooth layers spread, and the pores filled with the powder. [ABSTRACT FROM AUTHOR]

Copyright of Iraqi Journal of Laser is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For the dry storage of Canada Deuterium Uranium (CANDU) spent nuclear fuels, the integrity of Zircaloy-4 fuel cladding has to be verified. However, the formation of ~10 µm-thick oxide layers in typical CANDU reactor operating conditions takes several years, which makes sample preparation a slow process. To overcome such limitations, in this study, an accelerated formation of an oxide layer on Zircaloy-4 cladding tube was developed with a combination of high-temperature water corrosion (HT-WC) and air oxidation (AO). First, Zircaloy-4 tubes were corroded in oxygenated (2 ppm dissolved oxygen) high-temperature water (360 °C/19.5 MPa) for 500 h. Then, the tubes were air-oxidized at 500 °C for 30 h. Finally, the tubes were corroded again in HT-WC for 500 h to produce ~10 µm-thick oxide layers. The morphology and characteristics of the oxide layer in each step were analyzed using X-ray diffraction, scanning and transmission electron microscopy. The results showed that the oxide layer formed in the accelerated method was comparable to that formed in HT-WC in terms of morphology and oxide phases. Thus, the accelerated oxide formation method can be used to prepare an oxidized Zircaloy-4 cladding tube for CANDU fuel integrity analysis. [ABSTRACT FROM AUTHOR]

The electrical stimulation of pedicle screws is a technique used to ensure its correct placement within the vertebrae pedicle. Several authors have studied these screws’ electrical properties with the objective of understanding if they are a potential source of false negatives. As titanium screws are anodized with different thicknesses of a high electrical resistance oxide (TiO2), this study investigated, using analytical, numerical, and experimental methods, how its thickness may affect pedicle screw’s resistance and conductivity. Analytical results have demonstrated that the thickness of the TiO2 layer does result in a significant radial resistance increase (44.21 mΩ/nm, for Ø 4.5 mm), and a decrease of conductivity with layers thicker than 150 nm. The numerical approach denotes that the geometry of the screw further results in a decrease in the pedicle screw conductivity, especially after 125 nm. Additionally, the experimental results demonstrate that there is indeed an effective decrease in conductivity with an increase in the TiO2 layer thickness, which is also reflected in the screw’s total resistance. While the magnitude of the resistance associated with each TiO2 layer thickness may not be enough to compromise the ability to use anodized pedicle screws with a high-voltage electrical stimulator, pedicle screws should be the subject of more frequent electrical characterisation studies.

Biomaterials are the basis for the development of medicine because they allow safe contact with a living organism. The aim of this work was to produce innovative oxide layers with a microporous structure on the surface of commercially pure titanium Grade 4 (CpTi G4) and to characterize their properties as drug carriers. The anodization of the CpTi G4 subjected to mechanical grinding and electrochemical polishing was carried out in a solution of 1M ethylene glycol with the addition of 40 g of ammonium fluoride at a voltage of 20 V for 2, 18, 24, and 48 h at room temperature. It was found that the longer the anodization time, the greater the number of pores formed on the CpTi G4 surface as revealed using the FE-SEM method, and the greater the surface roughness determined in profilometric tests. As the anodizing time increases, the amount of the drug in the form of gentamicin sulfate incorporated into the resulting pores decreases. The most favorable drug release kinetics profile determined via UV–VIS absorption spectroscopy was found for the CpTi G4 anodized for 2 h.

In this study, the SiBCN-Ti series ceramics with different Ti contents were fabricated, and the oxidation resistance and microstructural evolution of the ceramics at 1500 °C for different times were explored. The results show that with the increase in oxidation time, pores and bubbles are gradually formed in the oxide layer. When the oxidation time is less than or more than 4 h, the Ti(C, N) in the ceramics will maintain its initial structure or mostly transform to TiN. The introduction of Ti content can promote the formation of rutile silicate glass, thus healing the cracks and improving the oxidation resistance of the ceramics effectively.

Ultra-thin 304 stainless steel can be used to flexibly display substrates after they have been subjected to chemical mechanical polishing (CMP). The thickness of the chemical oxide layer directly affects the polishing efficiency and surface quality of 304 stainless steel. In the study presented in the following paper, the thickness variation of the chemical oxide layer of 304 stainless steel was analyzed following electrochemical corrosion under different oxidant concentration conditions. Furthermore, the impact of the oxidant concentration on the grooves, chips, and scratch depth–displacement–load curves was investigated during a nano-scratching experiment. Through this process, we were able to reveal the chemical reaction mechanism between 304 stainless steel materials and oxidizers. The corrosion rate was found to be faster at 8% oxidant content. The maximum values of the scratch depth and elastic–plastic critical load were determined to be 2153 nm and 58.47 mN, respectively.

Anodizing is an electrolytic coating process that converts aluminum into aluminum oxide. The anodizing process is widely used in the manufacturing industry, especially in automotive components. Its utilization has benefits such as resistance to scratches, ease of maintenance, and added decorative value. The purpose of this study was to determine the effect of time variations on the hardness and thickness of the oxide layer in the 6xxx series of aluminum anodizing processes. The variation of time used in the immersion process is 20, 30, and 40 minutes, with an electric current of 2 amps and a voltage of 24 volts. After that, the dyeing and sealing process is carried out. The tests carried out included testing of hardness (Vickers) and the thickness of the oxide layer (coating thickness gauge). The results of the highest hardness test of 112.9 VHN were obtained at a time variation of 40 minutes, with an average layer thickness of 5.07 m. It can be said that the amount of time spent in the anodizing process has an effect on how hard the oxide layer gets and how thick it is on the 6xxx series of aluminum metal.

The oxide film on the surface of the grinding wheel plays a very important role in ultrasonic-assisted electrolytic in-process dressing (UA-ELID) grinding. In order to investigate the influence of ultrasonic vibration on the characteristics of oxide film on the surface of grinding wheel in compound grinding, the formation mechanism of oxide film on the surface of grinding wheel under ultrasonic action was analyzed theoretically from two aspects: the change of single grain trajectory caused by ultrasonic vibration and the effect of ultrasonic cavitation. The pre-dressing tests were conducted with different pre-dressing times to observe the oxide layer properties at different pre-dressing stages. The grinding tests were conducted after pre-dressing to verify the grinding performance of oxide layer under different pre-dressing methods. The results show that after the ultrasonic vibration of the grinding wheel is added during electrolytic in-process dressing (ELID) process, the holes and cracks of the oxide film on the surface of the grinding wheel are greatly reduced during the whole pre-dressing process. In addition, the pre-dressing current decreases more stably and the current is smaller when it reaches stability. After the pre-dressing, the thickness of the oxide film is reduced by about 35 % and the hardness is increased by about 70 % compared with the ordinary pre-dressing process. The grinding test results show that the oxide film obtained by ultrasonic vibration of the additional grinding wheel is more conducive to improving the surface quality of the grinding process. Therefore, compared with the ordinary pre-dressing process, the density and uniformity of oxide film on the surface of grinding wheel is better and the hardness is higher after the additional ultrasonic vibration of grinding wheel. It is beneficial to improve the surface quality of workpiece.

Metal-ceramics dental prosthetic restorations are clinically recommended for their advantages related to good aesthetic features along with strength and long-term clinical use. Given the importance of the quality of the metalceramic (M-C) bond, the metal substructure analysis has a major importance to the quality of the manufactured dental prosthesis. In the present study was analyzed the behavior of experimentally developed novel titanium alloys (TiZr, TiZrNbTa) comparatively with other frequently used titanium alloys (e.g., Ti Cp, Ti6Al4V) designated for the technology of mixed prosthetic restorations. All samples were been plated, simultaneously in the same conditions, with the same titanium specific compatible ceramic plating material (Ti22 Noritake). The examination of the surface of both components was performed by scanning electron microscopy SEM) analysis and EDS analysis, which showed differences in the characteristics of the oxide layer formed, depending on the composition of the metal substructure. The evaluation of the alloy-ceramic adhesion was performed by mechanical tests, which attest to the fact that the adhesion and the quality of the bond between metal and ceramic depend on the thickness of the oxide films formed. The results showed the superiority of titanium novel titanium alloys (TiZr, TiZrNbTa), having highest hardness values, highest values of shear strength, a continuous thin oxide films, and consequently, a better metal-ceramic adhesion. Comparatively, less ductile titanium alloys (TiZrNbTa/Ti3) are generating lower adhesion forces with values above 30MPa in some samples justifying less predictable clinical results. [ABSTRACT FROM AUTHOR]

The stable oxide layers formed by chemical or electron-beam treatments of TiNi shape memory alloys are able to provide a good corrosion resistance and prevent release of toxic Ni. The mechanisms responsible for corrosion behavior of Ti-bearing alloys are currently not completely clear. In this work, the structure and electrochemical properties of surface oxides on TiNi alloy and Ti-Ni-Ta-Si surface alloy were examined. The glassy structure of the surface alloy was produced by a liquid phase mixing of Ti60Ta30Si10 (at.%) film with a TiNi substrate using a low-energy high-current electron beam. The reference electropolished TiNi alloy and the Ti-Ni-Ta-Si surface alloy exhibit thin (2-4 nm) glassy-crystalline oxide layers varying by chemistry and phase composition as confirmed using high-resolution transmission electron microscopy and x-ray photoelectron spectroscopy. It is shown that during anodic polarization in 0.9% NaCl and Lock-Ringer solutions, the oxide layer on the Ti-Ni-Ta-Si surface alloy possesses an enhanced passivation ability compared to the reference sample. We have revealed that the absence of oxidation species Ni2+ and the lower nickel concentration in the subsurface layer are closely related with corrosion resistance. A scheme describing the formation of corrosion products via transport of nickel ions through the free volumes (interstitial spaces, interfaces between clusters/particles) inside the oxide layer was proposed. [ABSTRACT FROM AUTHOR]

The effect of the electrolyte composition for hard anodizing of aluminum on the corrosion resistance of the synthesized anodic coatings was studied. The hard anodizing was carried out at temperatures of –4–0°C for 60 min at a current density of 5 A/ dm2. The basic electrolyte was a 20% aqueous solution of H2SO4. Hydrogen peroxide (H2O2) was added to the electrolyte in concentrations of 30; 50; 70 and 100 g/L to determine strong oxidants influence on the characteristics of the anode layers. The concentration of 70 g/L H2O2 in the electrolyte, which ensures the synthesis of the thickest and least porous coating, was optimal. At the initial moment of immersion of anodic coatings synthesized in hydrogen peroxide electrolyte, their corrosion resistance decreases. When peroxide electrolyte concentration increases from 30 to 100 g/L, corrosion currents increase by 30 and 90%, respectively. However, with increasing exposure of coatings in the environment, their corrosion current density decreases more intensively with a decrease in their porosity. After 14 days, no dependence of the coatings corrosion durability on the composition of the electrolyte observed, what indicated a complete closure of the pores. [ABSTRACT FROM AUTHOR]

The present study is an endeavor to understand the wear and friction behavior of EN8 steel and Inconel X-750 alloy tribo-pair under dry and lubricated conditions. Initial experiments were performed under dry conditions at different loads (50–200 N) and sliding speeds (0.14–0.47 m/s). To investigate the effect of lubricants, the experiments were performed under two lubricants (SEA20W40 and SAE20W40 + MoS2) at the same range of loads and speeds. Ex-situ analysis of worn-out surfaces of both disc and pin was performed through scanning electron microscope (SEM). Chemical composition of worn-out surfaces of disc and pin was evaluated through energy disperse x-ray spectroscopy (EDS). Under dry conditions, formation of oxide layer was noticed. The significant improvement in wear and friction was observed under lubricated conditions as compared to dry conditions. Also, by mixing micron-size MoS2 particles to the normal lubricant SAE20W40, significant improvement in wear and friction was perceived due to the formation of boundary layer film. [ABSTRACT FROM AUTHOR]

Electrical contacts can be found in all industries today. In these applications lubricants are essential because they protect the metal connectors from friction and fretting corrosion, which generate wear and may lead to an isolating oxide layer and finally the destruction of the electrical connection. Measurements on customary lubricants for electrical connectors were conducted with high regard to oxidation stability, wear and friction characteristics. The selected samples also differ in the thickener systems. Besides typically non-conductive lubricants for electrical contacts, there are lubricants with high electrical conductivity required mainly for EDM bearings (electrical discharge machining) to not promote a system failure. Currently, action is taken in the industry to define standards to measure the electrical conductivity of lubricants. [ABSTRACT FROM AUTHOR]

A technique, which can explain the behavior of fires by using microstructural and oxide examinations of melted marks on copper wire, has been required for fire investigators. However, a study on the microstructural and oxide evolution after a fire is insufficient due to various and complicated fire conditions. In this research, changes in surface morphology, oxide layer thickness, oxidation kinetics, and microstructure were investigated at various annealing temperatures and times on the melted mark on the copper wire. The results show that the copper dendrites surrounded by (Cu+Cu2O) eutectic structure under Cu2O and CuO surface is the fingerprint of melted mark on copper wire annealed between 220°C and 600°C. At an annealing temperature of 800°C to 1000°C, the characteristic microstructure of the melted mark is Cu2O precipitates without dendrites in grains under a single layer of Cu2O. Moreover, the diffusion processes contributed to Cu2O growth could be as follows: lattice diffusion at 220°C to 400°C and grain boundary diffusion at 400°C to 1000°C. [ABSTRACT FROM AUTHOR]

Magnesium alloys are more widely used at higher temperatures. However, it is not well known whether oxide layer, produced at high temperature, could show corrosion protection. Thus, the corrosion behaviors of oxidized AZW800 alloy were investigated by hydrogen evolution and electrochemical measurements to evaluate effect of oxide layer on corrosion resistance. The results showed that corrosion of removed oxide layer AZW800 alloy showed characteristic of localized corrosion, leaving randomly bulky pits. While reserved oxide layer AZW800 alloy exhibited a relatively uniform corrosion. The results indicated that oxide layer could hinder corrosion of oxidized AZW800 alloy in the initial period of immersion. While subsequently, aggravated corrosion would occur owing to defects of oxide layer and less protective products film. Besides, present of oxide layer eliminated micro-galvanic couple on alloy surface. The synergistic effect of elimination of micro-galvanic couple on alloy surface and alkalization effect transforms localized corrosion into relatively uniform corrosion of alloys.

In order to study the oxidation corrosion protection of key components of carrier aero engine, the high temperature oxidation behavior of the Ni-based powder metallurgy(PM) superalloys FGH4095 and FGH4096 in air at the temperature range of 750-1100 ℃ was investigated. The oxidation kinetics curves were determined by static weighing method. The structure, composition, and morphology of the surface oxide scale as well as its cross section were analyzed by metallographic microscope, scanning electron microscope (SEM), electron probe microanalyzer (EPMA) and X-ray diffractometer (XRD). The results show that two kinds of alloys belong to the grade of full oxidation resistance at 750-900 ℃ and oxidation resistance at 1000-1100 ℃. The actual service temperature of both alloys is below 900 ℃, so they exhibit excellent oxidation resistance in their operating temperature range.At 750-900 ℃, the oxidation resistance of the two alloys is similar without obvious difference. The oxide film is intact without peeling.The oxide films of FGH4095 and FGH4096 are composed of two layers after high temperature oxidation. The internal layer is mainly Al2O3.The outer layer of FGH4095 is composed of Cr2O3, Nb2O5 and TiO2. The outer layer of FGH4096 is composed of only Cr2O3 and TiO2.At 1100 ℃, both alloys are obviously oxidized and a large number of oxide scales crack. Due to the different compositions of the alloys, the oxidation resistance of the two alloys varies greatly at this temperature.In contrast, FGH4095 alloy exhibits better oxidation resistance.

Steam superheaters are used to increase the temperature and transport the flowing superheated water vapor before it enters the steam turbine. Creep-resistant steels with required high resistance to high-temperature oxidation are used for production of superheaters. The elimination of the protective oxide layer formation on the steel surface limits their upper application temperature in a water vapor containing environment. In this paper, the oxidation behavior of MarBN (MARtensitic 9Cr steel strengthened by Boron and MX Nitrides) steel exposed for 1000 h at 600 and 650 °C in a mixed atmosphere of air + 10% water vapor was analyzed. The oxidation mechanism was discussed on the basis of oxidation kinetics, morphological observations, microscopic and XRD analysis of the oxide layer. The oxidation kinetics was governed by the parabolic law. SEM analysis and XRD analysis showed that the outer steel oxide layer after 1000 h exposure at 600 °C was mainly composed of hematite Fe2O3 and a small proportion of Cr2O3. The inner oxide layer was composed of (FeMnCr)2O4 and Cr2O3. The steel surface after 1000 h of oxidation at 650 °C, the outer oxide layer consisted of hematite Fe2O3, Cr-rich phase and magnetite Fe3O4, and the inner oxide layer was mainly iron-chromium-manganese spinel (FeMnCr)2O4.

In order to study the microscopic reaction mechanism and kinetic model of Al/PTFE, a reactive force field (ReaxFF) was used to simulate the interface model of the Al/PTFE system with different oxide layer thicknesses (0 Å, 5 Å, 10 Å), and the thermochemical behavior of Al/PTFE at different heating rates was analyzed by simultaneous thermal analysis (TG-DSC). The results show that the thickness of the oxide layer has a significant effect on the reaction process of Al/PTFE. In the system with an oxide layer thickness of 5 Å, the compactness of the oxide layer changes due to thermal rearrangement, resulting in the diffusion of reactants (fluorine-containing substances) through the oxide layer into the Al core. The reaction mainly occurs between the oxide layer and the Al core. For the 10 Å oxide layer, the reaction only exists outside the interface of the oxide layer. With the movement of the oxygen ions in the oxide layer and the Al atoms in the Al core, the oxide layer moves to the Al core, which makes the reaction continue. By analyzing the reaction process of Al/PTFE, the mechanism function of Al/PTFE was obtained by combining the shrinkage volume model (R3 model) and the three-dimensional diffusion (D3 model). In addition, the activation energy of Al/PTFE was 258.8 kJ/mol and the pre-exponential factor was 2.495 × 1015 min−1. The research results have important theoretical significance and reference value for the in-depth understanding of the microscopic chemical reaction mechanism and the quantitative study of macroscopic energy release of Al/PTFE reactive materials.

Developing advanced underwater welding technology for titanium, which is the key structural material for underwater applications, is of great significance for the design, fabrication, and maintenance of submarine equipment. In this study, in order to investigate the underwater welding microstructure and mechanical properties of Ti-4Al-2V alloy, underwater wet laser welding was conducted on Ti-4Al-2V alloy using varying laser power. The microstructure and properties of the welding joints were characterized and analyzed. The microstructure of the heat-affected zone and fusion zone in the welding joints are not significantly different from those of welding in air, but a mixed oxide layer composed of Al2O3 and TiO2 is formed on the surface of the fusion zone. Due to internal stress, a large number of cracks initiate on the oxide layer and propagate to the joints. In the 4 kW and 5 kW joints, a penetrating crack formed due to the excessive accumulation of internal stress breaking up the α phase. The mechanical properties of the joints are significantly affected by the laser power. The tensile strength of the 3 kW and 4 kW joints is comparable to that of the base metal, which is about 600 MPa, while the 5 kW joint shows brittle fracture with no plastic deformation and 228 MPa strength. This research lays a solid foundation for understanding the underwater wet laser welding behavior of titanium alloys.

Welding is an important manufacturing process for joining complex parts. Despite their widespread use, there exist some drawbacks in the existing liquid-state (e.g., formation of undesirable heat-affected zones around weld area) and solid-state (e.g., high equipment and tooling costs, low production rates, and difficulty in joining intricate geometries) methods. These limitations continually spur the search for new joining processes to improve existing welding methods or develop new ones that circumvent these limitations. To provide a “greener” and low-cost alternative to the traditional welding processes that often produce “soft” heat affected zones (HAZs), we develop and evaluate the expansion of cold spray process—a solid-state high-velocity particle deposition process—to solid-state welding, a process we term cold spray welding (CSW). Using well-defined processing parameters, we cold spray welded (CSWed) AA 6061-T651 plate and compared the results with Tungsten inert gas (TIG) welded counterpart. Although TIG-welded samples exhibit higher tensile properties than CSWed samples (at least based on the CS processing parameters used in this study), our findings show that CSW indeed circumvents major drawbacks in traditional welding processes, including negligible microstructural alterations and the inhibition of deleterious phase transformation and suppression of deleterious HAZ. The examination of CSWed parts reveals low yield strength is connected to ubiquitous microvoids that are formed due to lack of metallurgical bonding; these microvoids act as microcrack initiation sites. We proceed to establish a failure mechanism in the CSWed part to provide direction for future optimization.

This study shows that in an atmosphere containing water vapor, the oxide layer on the surface of the 9CrNB steel MarBN (Martensitic 9Cr steel strengthened by Boron and MX Nitrides) was formed by an outer layer of hematite Fe2O3 and Cr2O3 and an inner two-phase layer of Fe3O4 and Fe3O4 + (Fe, Cr)2O4, which was confirmed by XRD analysis. Part of the layer consisted of nodules and pores that were formed during the increase in oxides when the present H2O(g) acted on the steel surface. The diffusion mechanism at temperatures of 600 and 650 °C and at longer oxidation times supported the "healing process" with a growing layer of Fe oxides and the presence of Cr and minor alloying elements. The effects of alloying elements were quantified using a concentration profile of the oxide layer based on quantitative SEM analysis, as well as an explanation of the mechanism influencing the structure and chemical composition of the oxide layer and the steel-matrix–oxide interface. In addition to Cr, for which the content reached the requirement of exceeding 7.0 wt. % in the inner oxide layer, W, Co, Mn, and Si were also found in increased concentrations, whether in the form of the present Fe-Cr spinel oxide or as part of a continuously distributed layer of Mn2O3 and SiO2 oxides at the steel-matrix–oxide interface. After long-term high-temperature oxidation, coarser carbides of the M23C6 type (M = Fe,W) significantly depleted in Cr were formed at the oxide-layer/matrix interface. In the zone under the oxide layer, very fine particles of MC (M = V, Nb, and to a lesser extent also Cr in the particle lattice of the given phase) were observed, with a higher number of particles per unit area compared to the state before oxidation. This fact was a consequence of Cr diffusion to the steel surface through the subsurface zone. [ABSTRACT FROM AUTHOR]

India’s growing power demands and emission norms require more efficient coal-based power plants. The shifting of power plants from subcritical to ultra-supercritical (USC) steam conditions could improve efficiency by 12% and reduce CO2 emissions by 35%. There is a need to develop and qualify materials under ultra-supercritical steam conditions with high temperatures and high pressures in laboratory scale. The sample materials were exposed to high temperatures of 700 °C under air and high pressure steam at 700 °C/243 bars for 1000 h in as-received and grain-boundary-enhanced conditions. Grain boundary enhancement included optimization of a thermo-mechanical process involving cold rolling and annealing of samples. The effect of air and steam oxidation on IN 617, a nickel-based candidate superalloy, was analysed. Steam oxidation was performed on a custom-built PARR 4650 series autoclave, and the oxidized samples were characterised under scanning electron microscopy, to evaluate the oxide scales. The grain-boundary-engineered material performed better than the as-received samples. IN 617 overall fared better under both air and steam conditions, with far less weight gains.

Based on the widely used wet metal-assisted electroless etching, we develop in this work a novel vapor-phase silver-assisted chemical etching (VP-Ag-ACE) suitable for the elaboration of highly doped p-silicon (Si) nanostructures with strong, visible, and multi-peak photoluminescence (PL) emissions. The lateral and vertical etching rates (LER and VER) were discussed based on the etching mechanism of the VP-Ag-ACE. The antireflective suitability of the vapor-etched layer has been evaluated by a reflectivity measurement and exhibits reflectivity values lower than 3%. The PL emission at both room and low temperatures emissions were deeply discussed and correlated with the structural properties of the Si morphologies and their surface states based on the FTIR results. [ABSTRACT FROM AUTHOR]