Thermal Oxidation Treatment Research Articles

Fermi level unpinning of metal/p-type 4H-SiC interface by combination of sacrificial oxidation and hydrogen plasma treatment

An ideal metal/p-type 4H-SiC interface with a “free-pinned” Fermi level has been achieved by the combination of sacrificial thermal oxidation (SO) and hydrogen plasma treatment (HPT) on the SiC surface. It is found that the Fermi level pinning could be attributed to the contaminants and defects of the p-type 4H-SiC surface. According to the X ray photoelectron spectroscopy and deep-level transient spectroscopy results, the oxygen and carbon contaminants decreased after SO. However, high-density carbon interstitial-related defects were generated close to the valance band during oxidation. With the subsequent HPT, the chemical residues and detrimental carbon-induced defects were eliminated by the reaction with hydrogen atoms. The p-type 4H-SiC surface was chemically and electrically well saturated with the surface Fermi level position close to the bulk position. An analytical model for the elimination of surface contaminants and defects was proposed to reveal the underlying mechanism of Fermi level depinning.

Ultrathin flexible graphene films with high thermal conductivity and excellent EMI shielding performance using large-sized graphene oxide flakes.

As the demand for wearable and foldable electronic devices increases rapidly, ultrathin and flexible thermal conducting films with exceptional electromagnetic interference (EMI) shielding effectiveness (SE) are greatly needed. Large-sized graphene oxide flakes and thermal treatment were employed to fabricate lightweight, flexible and highly conductive graphene films. Compared to graphene films made of smaller-sized flakes, the graphene film made of large-sized flakes possesses less defects and more conjugated domains, leading to higher electrical and higher thermal conductivities, as well as higher EMI SE. By compressing four-layer porous graphene films together, a 14 μm-thick graphene film (LG-4) was obtained, possessing EMI SE of 73.7 dB and the specific SE divided by thickness (SSE/t) of 25 680 dB cm2 g−1. The ultrahigh EMI shielding property of the LG-4 film originates from the excellent electrical conductivity (6740 S cm−1), as well as multi-layer structure composed of graphene laminates and insulated air pores. Moreover, the LG-4 film shows excellent flexibility and high thermal conductivity (803.1 W m−1 K−1), indicating that the film is a promising candidate for lightweight, flexible thermal conducting film with exceptional EMI shielding performance.

Thermal oxidation and hydrofluoric acid treatment on the sand‐blasted implant surface – a histologic histomorphometric and biomechanical study

Thermal oxidation and hydrofluoric acid treatment on the sand‐blasted implant surface – a histologic histomorphometric and biomechanical study

Size-tunable Ag nanoparticles sensitized porous ZnO nanobelts: controllably partial cation-exchange synthesis and selective sensing toward acetic acid

Porous ZnO nanobelts sensitized with Ag nanoparticles have been prepared via a partial cation-exchange reaction assisted by a thermal oxidation treatment, employing ZnSe·0.5N2H4 nanobelts as precursors. After partially exchanged with Ag+ cations, the belt-like morphology of the precursors is still preserved. Continuously calcined in air, they are in situ transformed into Ag nanoparticles sensitized porous ZnO nanobelts. The size of the Ag nanoparticles can be tuned through manipulating the amount of exchanging Ag+ cations. Considering the porous and belt-like nanostructure, sensing characteristics of ZnO and the catalytic activity of Ag nanoparticles, the gas sensing performances of the as-prepared Ag nanoparticles sensitized porous ZnO nanobelts have been carefully investigated. The results indicate that Ag nanoparticles significantly enhance the sensing performances of porous ZnO nanobelts toward typical volatile organic compounds. Especially, a good selectivity has been demonstrated toward acetic acid gas with a low detection limit less than 1 ppm. Furthermore, they also display a good reproducibility with a short response/recovery time due to the thin, uniform and porous sensing film, which is fabricated with the assembled technique and in situ calcined approach. Finally, their sensing mechanism has been further discussed.

Comparison of different surface treatments of carbon fibers used as reinforcements in epoxy composites: Interfacial strength measurements by in-situ scanning electron microscope tensile tests

In-situ characterization of the fiber/matrix interfacial failure behavior at microscopic scale is important to optimize the fiber surface treatment and to design high performance composites. In this study, in-situ tensile tests in scanning electron microscope (SEM) were used to investigate the interfacial adhesion strength of epoxy composites reinforced by four kinds of carbon fibers (CF)—raw CF, desized CF, carbon nanotube-grafted CF (CNT-CF) and oxidized CNT-CF. The crack initiation position and fracture failure mode were well recorded. The strains and the interfacial adhesion strength were obtained for these four kinds of composites. It was found that the interfacial strength decreased from 53 MPa to 48 MPa after removing the sizing on carbon fiber surface. However, by grafting CNTs on the CF surface, the interfacial strength reached 55 MPa and was further increased to 58 MPa after a simple thermal oxidation treatment. Moreover, energy dispersion X-ray analysis (EDX) was carried out using scanning transmission electron microscopy (STEM). The EDX mapping demonstrated that oxygen aggregated at the interfaces of raw CF/epoxy and oxidized CNT-CF/epoxy. Thus, a combination of CNT grafting with chemical functionalization should be necessary to achieve high performance carbon fiber reinforced polymer composites.

3D porous cellular NiCoO2/graphene network as a durable bifunctional electrocatalyst for oxygen evolution and reduction reactions

In this work, a 3D porous cellular NiCoO2/graphene (NC-GN) network is readily synthesized using a sodium dodecyl sulfate (SDS)-templated strategy via filtration assembly of NiCoO2 precursor and partially reduced graphene oxide (rGO) nanosheets, freeze-casting, and thermal treatment processes. The 3D porous cellular NiCoO2/graphene (NC-GN) network demonstrates advantageous bifunctional electrocatalytic durability and activity toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), owing to its fascinating 3D morphology, the high conductivity of graphene oxide (rGO) nanosheets, and catalytic active sites of NiCoO2 binary transition oxides. In comparison with the commercial OER electrocatalyst (IrO2) and ORR electrocatalyst (Pt/C), the 3D porous cellular NiCoO2/graphene (NC-GN) network exhibits superior OER catalytic performance with a satisfactory overpotential of 436 mV vs. RHE at 10 mA cm−2. Furthermore, the 3D porous NC-GN network displays a good ORR catalytic activity with an adequate half-wave potential of 665 mV vs. RHE. The cycling stability and limiting current density of the 3D porous NC-GN network towards OER and ORR are both better than the commercial IrO2 and Pt/C catalysts. The 3D porous cellular NiCoO2/graphene (NC-GN) network shows excellent potentials toward various energy conversion applications such as metal-air batteries, fuel cells, and water splitting.

Thermal oxidation and hydrofluoric acid treatment on the sandblasted implant surface: A histologic histomorphometric and biomechanical study.

This study aimed to analyze and compare the topographical, chemical, and osseointegration characteristics of a sandblasted acid-etched surface (SLA group), a sandblasted thermally oxidized surface (SO group), and a surface chemically modified by hydrofluoric (HF) acid (SOF group). Following the preparation and characterization of the relevant surfaces, 90 implants (30 for each group) were placed on the pelvic bone of six sheep. Resonance frequency analysis (RFA), insertion (ITV), removal torque value (RTV), and histomorphometric analyses (BIC%) were performed after three and 8weeks of healing. The results were analyzed by nonparametric tests (p<0.05). The roughness value (Ra) in the SOF group was significantly lower than the SLA and the SO group (p=0.136, p<0.001, respectively). This resulted in a substantially inferior ITV 14.83N/cm (SD: 4.04) than those achieved in the SLA and SO groups (19.50 (SD: 6.07) and 20.17N/cm (SD: 8.95), respectively; p=0.001). A statistically significant change in the RFA from the baseline (47.36 ISQ, SD: 6.93) to the 3rd week (62.56 ISQ, SD: 5.29) was observed in the SOF group only (p=0.008). The highest postplacement RFA and RTV values were measured from the SLA group (61.11 ISQ, SD: 7.51 and 78.22N/cm, SD: 28.73). The early-term (3rd week) BIC% was highest in the SO group (39.93%, SD: 16.14). After 8weeks, the differences in BIC% values were statistically not significant. Adjunct HF acid application on the thermally oxidized surface did not provide an additional benefit compared to the sandblasted and acid-etched surface (SLA group).

Microstructural evolution of the oxidized ZnO:Cu films tuned by high magnetic field

Microstructures and native defects are very important for the optical, electrical and magnetic properties of ZnO-based materials. In this study, microstructures of the Cu-doped ZnO (ZnO:Cu) films were changed by applying high magnetic field (HMF) during different growth processes of the as-deposited Zn-Cu films and the subsequent thermal oxidation treatment. The effects of the microstructure evolutions on the defects formation and photoluminescence performance are examined. The results show that the interaction between magnetization and thermal motion promotes (002) preferred orientation of the as-deposited Zn-Cu films. Meanwhile, the variation of the atomic deposition sites due to the HMF leads to the significant differences of surface morphology of the as-deposited films. The application of the HMF during the oxidation affects the adsorption sites of O2− and leads the surface spherical particles change to rod-like particles. Moreover, the HMF shows more significant effects during the deposition of the Zn-Cu films in enhancing on the amount of the oxygen vacancy, which improves green emission of the ZnO:Cu films.

INFLUENCE OF ISOTHERMAL OXIDATION ON CORROSION RESISTANCE OF TITANIUM IN BOVINE SERUM

The thermal oxidation treatment is an innovative and simple method for modifiying the surface properties of titanium such as enhance corrosion and wear resistance. The effects of isothermal oxidation immersion time on the surface properties and corrosion behavior under bovine serum of cp-Ti were studied in this paper. The treatment was done at 700&lt;sup&gt;o&lt;/sup&gt;C for 0 to 36 hours in furnace chamber. The surface microhardness, surface roughness, wettability and polarization potentiodynamic corrosion of cp-Ti were determined. The result shows the surface microhardness, surface roughness, wettability and corrosion resistance of the cp-Ti enhanced by isothermal oxidation treatment. The presence of the oxide layer on the surface in the form of TiO&lt;sub&gt;2&lt;/sub&gt; rutile and Ti&lt;sub&gt;3&lt;/sub&gt;O are responsible to enhance the surface properties and corrosion behavior

Study the formation of porous surface layer for a new biomedical titanium alloy

In the present work, chemical treatment using hydrogen peroxide (H2O2) oxidation and subsequent thermal treatment was applied to create a uniform porous layer over the surface of a new metastable β-Ti alloy. The results revealed that this oxidation treatment can create a stable ultrafine porous film over the oxidized surface. This promoted the electrochemical characteristics of H2O2-treated Ti-Zr-Nb (TZN) alloy system, presenting nobler corrosion behavior in simulated body fluid (SBF) comparing with untreated sample.

Effects of Laser Processing Parameters on Texturized Layer Development and Surface Features of Ti6Al4V Alloy Samples

Surface engineering is widely used in different areas, such as the aerospace industry or the biomechanical and medical fields. Specifically, laser surface modification techniques may obtain specific surface finishes for special applications. In texturing laser procedures, the control of processing parameters has a great influence on the geometry and characteristics of the treated area. When these processes are carried out on titanium alloys, thin oxide layers are usually developed on the irradiated surface, formed through the thermochemical combination of vaporized material with atmospheric oxygen in the air. In thermal oxidation treatments of Ti6Al4V, the highest concentration of oxides is mainly composed by rutile (TiO2), producing surface property modifications such as hardness, among others. In this research, a thermochemical oxidation of Ti6Al4V alloy has been performed through laser texturing, using laser scanning speed (Vs) and pulse rate (f) as process control variables, and its influence on the beam absorption capacity of the modified layer have been analyzed. Combined evaluations of microgeometrical features and mechanical properties, such as hardness, verified that, by means of laser texturing treatments, the ability to generate specific topographies and increase the initial hardness of the alloy is obtained. The most advantageous results for the increase of hardness by thermochemical oxidation have been detected in low scan speeds of laser beam treatments, resulting in an increase of approximately 270% using a scanning speed of 10 mm/s. On the other hand, a dependence between roughness values, in terms of Ra and Rz, and the energy density of pulse (Ed) has been observed, showing higher values of roughness for a 17.68 J/cm2 energy density of pulse.

Mechanism of tribofilm formation on Ti6Al4V oxygen diffusion layer in a simulated body fluid

An Oxygen Diffusion Layer (ODL) was generated on the surface of Ti6Al4V alloy by thermal oxidation treatment. In vitro tests for cytotoxicity were performed in the presence of Ti6Al4V and the ODL samples with the culture of G292 Cells using MTT assay. The results showed a similar cell viability in the presence of the both samples. Wear behaviour of Ti6Al4V and the ODL samples was investigated in a phosphate buffered saline solution under a normal load of 30N at a sliding velocity of 0.1m/s. The worn surface and subsurface of the samples were studied using SEM, STEM, TEM, XPS, AFM, nano-hardness and surface profilometry. A bio-tribofilm was observed on the worn surface of the ODL. TEM studies showed that the tribofilm had an amorphous structure and contained oxygen and phosphorous as confirmed by XPS and EDS analysis. AFM images also revealed that the tribofilm consisted of compacted fine debris. The formation of the tribofilm on the ODL with higher hardness and strength resulted in a decrease of about 95% in the wear rate compared with Ti6Al4V alloy.

Thermal oxidation induced high electrochemical activity of boron-doped nanocrystalline diamond electrodes

Thermal oxidation treatment was executed on boron-doped nano-crystalline diamond (B-NCD) films to change both the microstructure and the terminal groups of grains and grain boundaries. Their contributions to the electrochemical activity and electrical properties were investigated. The grain boundaries become narrowing, with ordered graphite phase firstly, and then they become disordered for long time oxidized treatment. This causes that the mobility of the B-NCD electrodes increases to 84.97cm2/Vs after 30min oxidation and then it decreases obviously with oxidation time further increasing. Nanocrystalline diamond grains with high carrier concentration are growing larger and naked on the B-NCD electrode’s surface after oxidization. Also, part of the terminal CH groups on the grain phases turn to CO groups with positive electron affinity, which is prone to attract electrons from nearby anions. These results lead to larger electrochemical activity area with quick charge transfer rate in the surface of B-NCD electrode. The silane is used to shield the OH sites from electrochemical activity. The covered area become less with the oxidized time, further confirming that the electrochemical reaction mainly occurs on the grain phases and the OH groups is mainly growing in grain boundaries.

Effect of Thermal Oxidation on Microstructure and Corrosion Behavior of the PVD Hf-Coated Mg Alloy

Hafnium coatings are fabricated on magnesium alloys by magnetron sputtering and are further submitted to the thermal oxidation treatment at temperature of 200, 300, and 400 °C. The thin hafnium oxide film and new grain boundaries are observed on the hafnium coatings during the appropriate treatment temperature (300 °C). These changes in microstructure result in surface densification, oxidation, and low porosity of the treated coating that significantly decrease its susceptibility to corrosion. Consequently, the thermal oxidation treatment hafnium coating exhibits a more positive corrosion potential, lower corrosion current density, and higher polarization resistance than that of the as-deposited coating using an electrochemical system. Moreover, the enhanced adhesion of the treated coating produced by applying an appropriate treatment temperature facilitates an efficient long-term protection of magnesium alloy.

Tunable plasmonic resonance of gallium nanoparticles by thermal oxidation at low temperatures

The effect of the oxidation of gallium nanoparticles (Ga NPs) on their plasmonic properties is investigated. Discrete dipole approximation has been used to study the wavelength of the out-of-plane localized surface plasmon resonance in hemispherical Ga NPs, deposited on silicon substrates, with oxide shell (Ga2O3) of different thickness. Thermal oxidation treatments, varying temperature and time, were carried out in order to increase experimentally the Ga2O3 shell thickness in the NPs. The optical, structural and chemical properties of the oxidized NPs have been studied by spectroscopic ellipsometry, scanning electron microscopy, grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy. A clear redshift of the peak wavelength is observed, barely affecting the intensity of the plasmon resonance. A controllable increase of the Ga2O3 thickness as a consequence of the thermal annealing is achieved. In addition, simulations together with ellipsometry results have been used to determine the oxidation rate, whose kinetics is governed by a logarithmic dependence. These results support the tunable properties of the plasmon resonance wavelength in Ga NPs by thermal oxidation at low temperatures without significant reduction of the plasmon resonance intensity.

Capacitive Deionization Performance of Thermally Surface Modified Activated Carbon Cloth Electrodes

Capacitive deionization (CDI) is a low energy desalination technology with long-cycle life, which utilizes high-porosity capacitive electrodes for capturing ions from flowing saline water [1, 2]. Though still suffering from relatively low desalination capacity, one major advantage of CDI technology is its low energy requirement and high rate operation for desalination. In recent years, much effort has been put on improving electrode materials for CDI applications. These studies have mostly focused either on the use of novel electrode materials or on surface modifications (e.g. metal oxide growth, chemical treatment, and thermal treatment) of the existing CDI electrode materials [1, 3, 4]. Although thermal treatment of carbon electrodes for improved charge storage is a well-established approach, the effects of various thermal treatment procedures on the performance of CDI electrodes still remain unexplored. Inherent similarities between the operating principles of supercapacitors and CDI technology might make one to think a similar correlation could be established between thermal treatment and the CDI performance. However, due to major differences in required charge storage mechanisms, a detailed study on various treatment conditions should be conducted to understand which conditions specifically promote better ion adsorption in CDI electrodes. Motivated by this, the effects of different thermal treatment conditions (i.e., temperature and gases) on salt adsorption performances of the activated carbon cloth (ACC) electrodes were investigated. Major discrepancy between stored charge versus salt adsorption capacity (SAC) was observed for different treatment conditions. To better assess these effects, additional BET and Raman tests on the ACC electrodes were also conducted. Results indicated interesting observations regarding charge storage capacity and SAC for different treatment conditions, which highlights the importance of selecting a suitable thermal treatment condition for enhancing the CDI performance of ACC electrodes.

Removal of Cationic Neutral Red Dye from Aqueous Solutions using Natural and Modified Rice Straw

Modified colloidal carbons were prepared by reacting colloidal carbon obtained from rice straw with thermal oxidation, nitric acid and urea treatment. The textural and chemistry characteristics of the surface of non-modified and modified carbons were obtained from nitrogen adsorption at -196oC, elemental analysis and fourier transform infrared (FTIR) techniques. The uptake of cationic neutral red (NR) dye from aqueous solutions by these carbons was determined by kinetic and equilibrium experiments. The surface area and the total pore volume decreased, whereas the pore radius increased after the treatment with nitric acid.The surface pH of un–modified carbon was basic while those of modified carbons were acidic. Urea treated carbons with the lowest acidic character and high nitrogen content presented the lowest NR dye uptake capacity. The maximum removal of NR dye was obtained at a pH of 4. The amount of adsorption by the investigated carbons was found to depend on the amount of surface acidity. The adsorption results were analyzed considering Langmuir, Freundlich and Dubinin-Radushkevich(D-R) models. The adsorption of NR dye onto the assessed adsorbents is of the physical sorption type following pseudo – first – order kinetic.Nitric acid modification brought about a significant rise in NR dye adsorption which was ascribed to the formation of oxygen containing acidic groups on the surface of adsorbent.The equilibrium adsorption data of NR dye were well fitted with Langmuir and D-R models.

Modified oxidative thermal treatment for the preparation of isotropic pitch towards cost-competitive carbon fiber

A modified oxidative thermal treatment was developed to increase the softening point of a pitch precursor while minimizing the pitch yield loss. An O2/N2 mixed gas was used as the reaction gas, and the softening point and pitch yield variations were measured at different O2 concentrations. As a result, when softening point increased from 130 to 249 °C, the pitch yield remained almost constant (only 0.6% drop). Structural analysis performed via MALDI-TOF, FTIR, and 1H and 13NMR showed that condensation reaction between pitch molecules in the presence of O2-containing gas followed a different mechanism depending on the O2 concentration. In addition, the precursors were spun into pitch fibers and carbonized at 1100 °C. During the spinning, they exhibited excellent spinnability without breakage for more than 10 min of spinning. The obtained carbon fibers showed high tensile strengths comparable to that of a commercial isotropic-pitch-derived carbon fiber (0.83 GPa). The current study showed that the modified thermal treatment is useful for the preparation of cost-competitive pitch precursors suitable for carbon fiber production.

Effect of thermal oxidation treatment on pH sensitivity of AlGaN/GaN heterostructure ion-sensitive field-effect transistors

In this article, AlGaN/GaN heterostructure ion-sensitive field-effect transistors (ISFETs) were prepared and evaluated by thermal oxidation treatment on the AlGaN surface. The ISFETs were fabricated on the AlGaN/GaN heterostructure and then thermally oxidized with dry oxygen in 600, 700, and 800°C, respectively. It indicates that the performance of the AlGaN/GaN heterostructure ISFETs, such as noise and sensitivity, has been improved owing to the thermal oxidation treatment process at different temperatures. The X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results indicate that after thermal oxidation treatment at different temperatures, hydroxide who possesses high surface state density will transfer to oxide owing to the higher chemical stability of the latter. Moreover, a crystalline α-Al2O3 phase generated at 700°C can not only provide a relatively smooth surface, but also improve the sensitivity to 57.7mV/pH for the AlGaN/GaN heterostructure ISFETs, which is very close to the Nernstian limit.

Enhancement of wear and corrosion resistance of low modulus β-type Zr-20Nb-xTi (x = 0, 3) dental alloys through thermal oxidation treatment

In order to obtain material with low elastic modulus, good abrasion resistance and high corrosion stability as screw for dental implant, the biomedical Zr-20Nb and Zr-20Nb-3Ti alloy with low elastic modulus were thermal oxidized respectively at 700°C for 1h and 600°C for 1.25h to obtain the compact oxidized layer to improve its wear resistance and corrosion resistance. The results show that smooth compact oxidized layer (composed of monoclinic ZrO2, tetragonal ZrO2 and 6ZrO2-Nb2O5) with 22.6μm–43.5μm thickness and 1252–1306HV hardness can be in-situ formed on the surface of the Zr-20Nb-xTi (x=0, 3). The adhesion of oxidized layers to the substrates is determined to be 58.35–66.25N. The oxidized Zr-20Nb-xTi alloys reveal great improvement of the pitting corrosion resistance in comparison with the un-oxidized alloys. In addition, the oxidized Zr-20Nb-3Ti exhibits sharply reduction of the corrosion rates and the oxidized Zr-20Nb shows higher corrosion rates than un-oxidized alloys, which is relevant with the content of the t-ZrO2. Wear test in artificial saliva demonstrates that the wear losses of the oxidized Zr-20Nb-xTi (x=0, 3) are superior to pure Ti. All of the un-oxidized Zr-20Nb-xTi (x=0, 3) alloys suffer from serious adhesive wear due to its high plasticity. Because of the protection from compact oxide layer with high adhesion and high hardness, the coefficients of friction and wear losses of the oxidized Zr-20Nb-xTi (x=0, 3) alloys decrease 50% and 95%, respectively. The defects on the oxidized Zr-20Nb have a negative effect on the friction and wear properties. In addition, after the thermal oxidation, compression test show that elastic modulus and strength of Zr-20Nb-xTi (x=0, 3) increase slightly with plastic deformation after 40% of transformation. Furthermore, stripping of the oxidized layer from the alloy matrix did not occur during the whole experiments. As the surface oxidized Zr-20Nb-3Ti alloy has a combination of excellent performance such as high chemical stability, good wear resistance performance and low elastic modulus, moderate strength, it is considered an alternative material as dental implant.