Ar O2 Atmosphere Research Articles

Influence of sputtering atmosphere on the structural, biological, and electrochemical properties of tantalum-containing coatings on the NiTi alloy

The magnetron sputtering method was used to deposit tantalum-containing coatings on NiTi shape memory alloys under Ar, ArO2, and ArN2 atmospheres. The main focus of this research is on how the deposition atmosphere can significantly impact not only the morphological and microstructural properties of coatings but also their corrosion behavior and in vitro biocompatibility. In this research, FESEM observations, GI-XRD crystallinity measurements, AFM topographical investigations, electrochemical measurements, and MTT assay were employed to determine to what extent the deposition atmosphere affects the morphology, microstructure, roughness, corrosion behavior, and in vitro biocompatibility properties, respectively. FESEM studies reveal that tantalum sputtered under the Ar atmosphere has a more uniform, and compact structure, while round-like particles appear on the surface under ArO2 and ArN2 atmospheres. The GI-XRD patterns indicate that the substrate temperature of 300°C is not sufficient for the formation of crystallized structure. It has been shown that the sample deposited under the ArN2 atmosphere has more negative charges; this is associated with higher protein adsorption on its surface and increases endothelial proliferation rates. Moreover, the presence of Ta2O5 on the surface of the ArO2 atmosphere leads to the highest corrosion resistance.

Dependence of diode behaviour and photoresponse of Ga-doped ZnO (GZO)/p-Si junction on the carrier concentration of GZO layer

Ga-doped ZnO (GZO)/p-Si junctions were fabricated by reactive co-sputtering of Zn-GaAs target in Ar–O2 atmosphere. Highly degenerate GZO (carrier concentration ∼1021 cm−3) deposited at 4 % O2 forms non-rectifying contact with p-Si. GZO/p-Si diodes fabricated with moderately doped GZO layers deposited at 5 % O2, having carrier concentration ∼1019 cm−3 display low turn-on voltage (≲ 0.5 V) and ideality factor ≈ 2. Measurement of barrier height by temperature dependent I–V and built-in potential by C–V reveal respective values of (0.74 ± 0.07 eV) and (0.44 ± 0.04 eV), suggesting formation of Schottky type diodes. These diodes display nearly linear I–V characteristics under UV illumination, yielding photoresponsivity ∼1 A/W at ± 1 V. In contrast, GZO/p-Si diodes fabricated with lightly doped (non-degenerate) GZO layers deposited at 6–8 % O2, having carrier concentration ∼1018 cm−3, show higher turn-on voltages (4.5–6.5 V) and ideality factors of 2.5–2.7. I–V and C–V measurements reveal nearly equal values of barrier height and built-in potential, indicating formation of n-p heterojunctions, with near-elimination of conduction band discontinuity. Under UV illumination, I–V characteristics of these GZO/p-Si diodes display non-linear behaviour in forward bias and yield photoresponsivity of ∼0.1 A/W at ±1 V.

The microstructural evolution of sputtered ZnO epitaxial films to stress-relaxed nanorods

Epitaxial ZnO thin films and nanorods were grown on c-sapphire substrate by reactive sputtering of Zn in Ar-O2 atmosphere at substrate temperatures ranging from near room temperature to 700 °C. Scanning electron microscopy showed that with increase in substrate temperature, the morphology transformed from columnar films to vertically aligned ZnO nanorods. High resolution x-ray diffraction revealed improvement in crystalline and epitaxial quality with increase in substrate temperature, along with the decrease of edge dislocation density from 5 × 1012 cm−2 to 8 × 1010 cm−2. The films grown near room temperature showed large hydrostatic strain (∼6 × 10−3) and compressive intrinsic biaxial stress (-0.8 GPa), which decreased substantially with increase in substrate temperature, due to the desorption of excess oxygen and reduction in edge dislocation density. Above the substrate temperature of 500 °C, the intrinsic biaxial stress reversed from compressive to mildly tensile in the case of nanorods, due to the intrinsic tensile stress, originating from crystallite coalescence. Raman measurements correlate well with the changes in biaxial stress and confirm the improvements in crystallinity and epitaxial quality of nanorods grown at higher temperatures. Room temperature photoluminescence of the ZnO films showed weak near-band-edge emission, which enhanced drastically in the case of nanorods due to their superior microstructure and epitaxial quality.

Influence of Terbium Doping and Annealing on the Structural and Optical Characteristics of Sputtered Zinc Oxide Thin Films

This paper studied the structural and luminescent characteristics of undoped and doped-with-Tb3+-ions ZnO films of 200 nm and 600 nm thicknesses, grown via RF magnetron sputtering on (100) silicon substrate in Ar and Ar-O2 plasma. X-ray diffraction (XRD) patterns revealed a strong preferred orientation of ZnO and ZnO:Tb crystals of the wurtzite structure along the c-axis, perpendicular to the substrate. In the as-deposited ZnO:Tb films, the additional crystal phases, namely, Tb2O3, TbO2, and an amorphous phase, were revealed. The as-deposited undoped films were under tensile strain, that increased in the doped films. This proved the incorporation of the Tb3+ ions into the ZnO grains, and agreed with the Raman spectra investigation. The XRD data and atomic force microscopy study showed that Tb doping impeded the growth of grains and columns, respectively. The photoluminescence (PL) spectra of the doped films contained the UV band ascribed to exciton PL, a broad intrinsic defect-related band, and the narrow bands caused by the intra-shell transitions of the Tb3+ ions. Terbium doping suppressed ZnO emissions. The post-deposition rapid thermal annealing at up to 800 °C of both the undoped and doped films promoted tensile strain relaxation, grain growth, improvement in the ZnO crystal structure, and an increase in the exciton PL. The intensity of the Tb3+ PL changed non-monotonically, and was the highest for the film annealed at 600 °C. The conventional thermal annealing promoted the non-monotonic changes in the strains and grain sizes in such a way that, after annealing at 900 °C, their values became the same as in the as-deposited ZnO:Tb film. This structural change was accompanied by a decrease in the exciton and Tb3+ PL intensity. The formation of the Zn2SiO4 phase was observed via XRD, and confirmed via scanning electron microscopy. It was attributed to the interdiffusion through the film/substrate interface. The deposition in the Ar-O2 atmosphere is found to be more preferable for the formation of Tb3+ emission centers in the ZnO matrix.

Synthesis of crystalline silver niobate thin films opening pathways for future process development

Due to its high energy storage density at room temperature, silver niobate (AgNbO3) is one of the most promising lead-free dielectric perovskites for energy storage applications. In this work, reactive d.c. magnetron co-sputtering from Nb and Ag targets in Ar–O2 atmosphere at different substrate temperatures is employed to identify a process window for the synthesis of AgNbO3 thin films. Structural analysis by X-ray diffraction and Raman spectroscopy confirmed the formation of AgNbO3 at deposition temperatures of at least 550 °C or at post-annealing in ambient air at temperatures of at least 525 °C. Even though all deposited films contained a non-negligible amount of metallic Ag, an undesired inhomogeneity for the intended use of the films as antiferroelectric material in energy storage applications, the current work clearly shows the potential of reactive d.c. magnetron sputtering for the synthesis of lead-free crystalline perovskite thin films based on AgNbO3 and, hereby, opens pathways for future deposition process scalability.

Mechanical Properties and Oxidation Behavior of TaWSiN Films.

This study explored the structural characteristics, mechanical properties, and oxidation behavior of W-enriched TaWSiN films prepared through co-sputtering. The atomic ratios [W/(W + Ta)] of the as-deposited films maintained a range of 0.77-0.81. The TaWSiN films with a Si content of 0-13 at.% were crystalline, whereas the film with 20 at.% Si was amorphous. The hardness and Young's modulus of crystalline TaWSiN films maintained high levels of 26.5-29.9 GPa and 286-381 GPa, respectively, whereas the hardness and Young's modulus of the amorphous Ta7W33Si20N40 films exhibited low levels of 18.2 and 229 GPa, respectively. The oxidation behavior of TaWSiN films was investigated after annealing at 600 °C in a 1%O2-Ar atmosphere, and cone-like Ta0.3W0.7O2.85 oxides formed and extruded from the TaWSiN films.

Initiation characteristics of spark-ignited premixed hydrogen-oxygen flames with diluents of argon/nitrogen/carbon dioxide

The spark-ignition features of premixed H2 under Ar–O2 atmospheres are essential for the development of high-efficiency and zero-emission Argon Power Cycle engines. Therefore, constant-volume combustion vessel experiments are conducted at an initial temperature of 287 K, initial pressures of 0.1, 0.3, and 0.5 MPa, with diluents of Ar/N2/CO2. Excess oxygen ratio, defined as the ratio of O2 supplied to the O2 needed for stoichiometric combustion, ranges from 1.0 to 4.7. Dilution ratios, defined as the molar fractions of diluents in the diluent-O2 mixture, were separately 70%, 79%, and 88%. Results show that both high dilution ratios and high excess oxygen ratios lengthen the flame-initiation periods. With excess oxygen ratio of 3.3, when Ar dilution ratio increases from 79% to 88%, the flame-initiation period rises by a factor of five to ten. With Ar diluent ratio of 79%, when excess oxygen ratio increases from 2.5 to 4.7, the flame-initiation period rises from under 10 ms to over 60 ms. Both the application of Ar as the diluent and high initial pressures extend the flammability limits. With Ar dilution ratio of 79% and pressure no less than 0.3 MPa, the flammability limit on excess oxygen ratio is over 4.7. Furthermore, Ar can additionally shorten the flame-initiation periods. At 0.1 MPa, excess oxygen ratio of 2.5, when diluents are respectively Ar, N2, and CO2, the flame-initiation periods are 10, 19, and 41 ms. The research reveals that a spark-ignition Argon Power Cycle engine running with ultra-lean and highly diluted mixtures may be feasible.

Effect of the Working Gas Pressure on the Structure of ZnO Layers

Zinc oxide layers have been synthesized by magnetron sputtering of ZnO:Ga ceramic and ZnO:Ga + 10 wt % Zn cermet targets in an Ar atmosphere and by reactive sputtering of a zinc target in an Ar–O2 atmosphere. The effect of working gas pressure in the chamber on the growth and structure of ZnO layers has been studied. It has been established that, for all the target types used, the crystal structure of ZnO nanocrystallites forming the layer improves with an increase in working gas pressure. The effect of excess zinc in the reagent flow on the microstructure and properties of the ZnO layers has been analyzed by comparing the electron microscopy and X-ray diffraction data on the layers formed by sputtering targets of different types.

Effects of minerals and Fe3+ on sulfur removal and its release behavior during coal pyrolysis under different atmospheres

Yunnan anthracite coal (YN) with high FeS2, Pingshuo coal (PS) with high organic sulfur and Duerping coal (DEP) with 33.52% organic and 64.20% inorganic sulfur were selected to investigate the effects of minerals and Fe3+ on sulfur release behavior during coal pyrolysis under Ar and 3% O2–Ar atmospheres by pyrolysis connected with gas chromatogram (Py-GC) combined with pyrolysis coupled with mass spectrometer (Py-MS). It is found that the sulfur removal ratios and the total amount of sulfur-containing gases release of coal samples under 3% O2–Ar atmosphere are higher than those under Ar atmosphere, indicating that O2 participates in coal pyrolysis process. The effects of minerals on sulfur removal are affected by these coals types. However, effects of Fe3+ on sulfur removal are related to atmospheres. During pyrolysis, Fe3+ is beneficial for all sulfur compounds to decompose at lower temperature under 3% O2–Ar atmosphere, while inhibits sulfur removal under Ar atmosphere. The minerals in coals can absorb sulfur gases. However, Fe3+ can significantly promote COS and SO2 release at lower temperatures under both atmospheres. But Fe3+ inhibits H2S release under Ar atmosphere.

Characterization of iron oxide coatings prepared by MOCVD method from Fe(CO)5

This work dedicated the study of iron oxide deposition by metalorganic chemical vapour deposition (MOCVD) in hot-walls reactor with Fe(CO)5 in Ar-O2 atmosphere under pressure about 70 Pa. Phase and structure studied by x-ray photoelectron spectroscopy (XPS) and reflection high-energy electron diffraction(RHEED). This analysis also gives information for some common factors of MOCVD decomposition of Fe(CO)5. Topology of the coatings studied with atomic force microscopy (AFM) and scanning electron microscopy (SEM). Optical properties of the coatings studied with spectrophotometer. There was identificated that coatings which was made by MOCVD on Si 〈1 0 0〉 substrate has a cluster structure which size increase with deposition time and supposed Volmer-Weber growth mode.

Analysis on thermal behavior of fluorides and cyanides for heat-treating spent cathode carbon blocks from aluminum smelters by TG/DSC-MS & ECSA®

This paper adopts a novel data-processing method of ECSA® based on TG/DSC-MS system to basically study the characteristics of release and conversion of fluorides and cyanides during heat treatment of the spent cathode carbon block (SCCB). All the experiments were conducted at 10K⋅min-1 heating rate and under Ar or Ar-O2 atmospheres. The results indicate that the release of fluorides was just a steady but slow phase transition process under both Ar and Ar-O2 atmospheres, which can be comparatively accelerated when the carbon material was burnt. The cyanides were effectively decomposed at high temperature and at Ar-O2 atmosphere, with around three quarters of the cyanides being converted to the N2 and nearly a quarter being to the NO. Finally, analysis on the flue gas composition indicates that it had a more complicated composition of CO2, N2, NO, NO2, HCN under Ar-O2 atmosphere but only had a composition of CO2 and NO under Ar atmosphere.

Process stabilization during reactive high power impulse magnetron sputtering of Ce/Gd target

In this study, a simple approach to stabilize reactive high power impulse magnetron sputtering process in the transition zone between the metallic and oxide modes was investigated. The method is based on the use of peak current value as feedback and control signal. It was shown that the change in the state of the target surface causes almost instantaneous change in the amplitude and shape of the current pulses. To stabilize the deposition process, the pulse frequency was regulated to maintain a constant maximum discharge current. The hysteresis behavior and the variations of the pulse current waveforms over a wide range of O2 flow rates and pulse frequencies during a reactive HiPIMS deposition of gadolinia-doped ceria (GDC) thin films in an Ar-O2 atmosphere were examined. Stable process conditions were maintained at the O2 flow from 0.9 to 3.9 sccm by adjustment of the pulse frequency from 1.45 to 2.9 kHz. GDC films deposited using peak current regulation exhibited a stable stoichiometry and high deposition rate in comparison with films obtained without process stabilization.

Long-term stability of oxygen surface exchange kinetics of Pr0.8Ca0.2FeO3-δ against SO2-poisoning

The long-term stability of the oxygen exchange kinetics of the Sr- and Co-free solid oxide fuel cell (SOFC) and solid oxide electrolyser cell (SOEC) air electrode material Pr0.8Ca0.2FeO3-δ (PCF82) is investigated by in-situ dc-conductivity relaxation measurements. The chemical oxygen surface exchange coefficient kchem is determined as a function of time at 700 °C under ideal (O2-Ar atmosphere) and accelerated ageing conditions (O2-Ar with 2 ppm SO2). In pure O2-Ar PCF82 shows fast oxygen surface exchange kinetics with kchem = 6 × 10−4 cm s−1 and excellent stability for 1000 h. Due to the addition of 2 ppm SO2 to the test gas only a moderate degradation occurs with kchem decreasing to 8 × 10−5 cm s−1 during further 1000 h. Post-test analyses by scanning (transmission) electron microscopy and X-ray photoelectron spectroscopy show S-rich secondary phases in the near-surface region of the SO2-poisoned sample. These inactive phases occur in an island-like arrangement of relatively large crystals, whereas significant amounts of the surface remain unaffected. This effect explains the high stability of the oxygen exchange kinetics of PCF82 against SO2-poisoning in comparison to state-of-the art materials like La0.6Sr0.4CoO3-δ (LSC64).

Wettability and optical properties of SnO–SnO2–Sb2O3 thin films deposited by simultaneous RF and DC magnetron sputtering

The SnO–SnO2–Sb2O3 films were deposited by simultaneous RF and DC magnetron sputtering. Increasing the ratio of O2/Ar pressure raised the intensity of the (311) peak of cubic Sb2O3 and the (200) peak of tetragonal SnO2, but clearly reduced the intensity of the (101) peak of tetragonal SnO2. According to visible-photoluminescence analyses, the blue shift of the PL peak can be attributed to the combination of smaller grains and higher compressive strain in the SnO–SnO2–Sb2O3 films. The nonlinear refractive indices of SnO–SnO2–Sb2O3 films deposited in a pure Ar or a mixed Ar–O2 atmosphere were measured by Moiré deflectometry, and were of the order of 10−8 cm2 W−1. At a higher ratio of O2/Ar pressure, a transparent SnO–SnO2–Sb2O3 film exhibited a lower surface roughness, better hydrophilicity, a higher linear refractive index and a lower extinction coefficient.

Change in Thermal Conductivity By Hydrogen Intercalation in Amorphous WO3 Film

We are developing “thermal switching materials”, whose thermal conductivity varies over a wide range. It has a wide range of applications such as temperature controls, thermal energy storages and so on. WO3 is expected as a thermal switching material because the electrical conductivity of WO3 can widely change owing to the metal-insulator transition (MIT) caused by hydrogen interactions. Moreover, hydrogens can be intercalated into and deintercalated from WO3 film reversibly and quickly by an electrochemical reaction. Therefore, the thermal conductivity is expected to change reversibly. Here, we report the thermal conductivity changes in WO3 film associated with hydrogen intercalations. WO3 film was prepared on ITO coated glass at room temperature by RF magnetron sputtering method in an Ar-O2 atmosphere. The total pressure and the oxygen content of the atmosphere were 4.0 Pa and 13%, respectively. The thickness of WO3 film was 0.7-1.4 μm. Hydrogen intercalations into WO3 film on ITO coated glass were performed in an 0.5 M H2SO4 electrolyte with a Pt counter electrode and a calomel reference electrode. The structure of the films was determined by x-ray diffraction analysis. The thermal diffusivity of the films was measured by an ac calorimetric method and the thermal conductivity was calculated by the differential method using measured thermal diffusivity. The electrical conductivity was measured by a four-point probe method. X-ray diffraction measurements showed that the WO3 films were amorphous. The value of thermal conductivity decreased with increasing hydrogen content x in H x WO3, from x = 0 to x = 0.33, and the value of thermal conductivity increased markedly with increasing x above x = 0.33. The hydrogen content of x = 0.33 is close to that of MIT. On the other hand, the electrical conductivity after MIT was 1×105 times higher than that before MIT. However, a variation of the electron thermal conductivity given from the electrical conductivity by the Wiedemann-Franz law is much smaller than a variation of the thermal conductivity. Therefore, the lattice thermal conductivity is expected to contribute to a change in the thermal conductivity. Present results indicate that the thermal conductivity of WO3 film can be controlled by hydrogen intercalations and potentialize the hydrogen-induced active control of thermal switches.

XPS Study of the Chemical Surface Engineering on Ultra-Thin Inaln Layers: Evaluation of Thermal Stability to Oxygen Exposure

III-V nitride materials combine unique properties such as a direct and tuneable band gap from n-IR (InN, 0.7 eV) to n-UV (AlN, 6.2 eV). Among the electronic devices, AlGaN/GaN and InAlN/GaN device structures are commonly developed for HEMT (high electron mobility transistors). The strong advantage of InxAl1-xN is a spontaneous high polarization leading to an extremely high carrier density in 2DEG (about 3.5 x 1013 cm-2). Moreover, the near lattice matched composition with GaN is achieved for x = 0.17 - 0.20, leading to a strain-free heterojunction which drastically reduce the structural defects [1]. As a high difference is encountered in growth temperature between InN (600°C) and AlN (1100°C), the main difficulty resides in making a high crystalline quality and a good homogeneity of InAlN layers [2]. Nevertheless, MOCVD gives excellent composition uniformity and good device performance for ultra thin-layers (from 7 to 9 nm thickness). III-V nitride materials are known to be chemically stable at working temperature and poorly reactive to air exposure. Nevertheless, higher annealing temperatures (more than 800°C) are needed during engineering when ohmic contact is performed. Such materials request high performances and little variations on the surface chemistry can harm the quality of 2DEG. Moreover, InAlN/GaN structure shows a lower thermal stability compared to AlGaN/GaN devices [3]. Only few studies describe the thermal stability of InAlN layers [4]. Some workers show a better thermal stability for a slower rate of growth in MOCVD [5], whereas others focus on an ohmic contact annealing at a lower temperature of 600°C to 650°C [6]. In this work, we choose to study by XPS the chemical surface engineering on InAlN ultra-thin layers at higher temperature, from 850°C to 950°C, under O2 rich and Ar atmosphere, in order to detect the possible degradation mechanisms usually running through the HEMT elaboration process. XPS characterizations lead us to an accurate analyze on the major effects of the thermal treatments. The table Figure 1 (a) shows that the O2 thermal treatment at 850°C drastically increase the oxygen content and decrease the nitrogen content, justifying the formation of an ultra-thin oxide layer on surface. After the O2 thermal treatment, carbon content is very low, around 6 at%, showing layers with a very few contamination. The additional Ar thermal treatment at 850°C has practically no impact on the layer. Concerning the InAlN matrix, an important chemical change is observed at high energy (404 eV) in the N1s band. Figure 1 (b) shows the evolution of the N1s peak for InAlN as-grown layer, and layers annealed 850°C and 950°C under O2 rich atmosphere for 1 min. Area ratios shows an evolution in the proportion of the additional N1s peak at 404 eV from 32% for the annealing at 850°C to 56% for the annealing at 950°C. The very strong gap of 6.7 eV, observed between the later and the N1s peak at 397.3 eV accredited to InAlN, is attributed to interstitial N2 molecules trapped in the structure [7]. Enlargement of the N1s band at 397.3 eV can also be seen. This effect could be attributed to N-N bonded defect in structures [8]. The aging of the samples shows that the N2 interstitial molecules are slowly decreased after 2 months and almost totally gone after 1 year. Unlike this evolution, N-N defects still present inside the matrix even after 1 year of aging justifying that those defects are deeply incorporated inside the InAlN layer. To our knowledge, this unusual behavior was not reported before on InAlN layers. Indeed, the surface modification using physical process such as N2 plasma or chemical solution process such as NH4OH treatment will be also getting into details.

Compositional Variation of X-ray Excited Optical Luminescence from Mn Doped MgAl2O4

X-ray excited luminescence has been evaluated using Mn doped spinel crystals grown under 50 vol% O2-Ar atmosphere with various Mg compositions, x = MgO/Al2O3, from 0.2 to 1.5. Peak wavelength of X-ray luminescence increases from 515 to 525 nm with composition, x. Peak intensity of X-ray luminescence, which varies with composition, is stronger in crystals with Mg-poor compositions. Mn doped MgAl2O4 is suggested to be potentially useful detector of CuKα X-ray, because of its linear correlation between luminescence peak intensity and X-ray power.

Bromination of Pd Compounds during Thermal Decomposition of Tetrabromobisphenol A

We conducted thermal tests using the reagent tetrabromobisphenol A (TBBPA) and various Pd compounds to study the chemical forms of Pd obtained during the pyrolytic and oxidative decomposition of TBBPA. Thermal testing was conducted in an electric furnace at temperatures of 280°C - 800°C in an Ar or Ar-O2 (5%) atmosphere for a heating period of 40 min. Scanning electron microscopy-energy dispersive X-ray spectroscopy results revealed that Pd bromide was formed in the mixture of TBBPA and PdO after heating to 450°C in the Ar atmosphere. In addition, thermogravimetry-differential thermal analysis showed that as the heating temperature was increased from 350°C to 730°C, weight loss occurred at a nearly constant rate, indicating that Pd bromide decomposed in this temperature range.

Effects of atmospheres on sulfur release and its transformation behavior during coal thermolysis

In this study, Pinshuo (PS) coal with high organic sulfur content was selected to investigate the effects of atmospheres on sulfur release and its transformation during thermolysis. Pyrolysis connected with gas chromatography (Py-GC) was used to analyze the sulfur containing gases of H2S, COS and SO2. Sulfur K-edge XANES was carried out to study the sulfur transformation after thermolysis. For PS raw, deashed and depyrited coals, the order of effect of atmospheres on sulfur removal is 3% O2-Ar > CO2 > 85% CO2-Ar > 75% CO2-Ar > Ar. The trends about the effects of 3% O2-Ar atmosphere on sulfur removal and char yield are similar to CO2 atmosphere, but desulfurization rate is slightly higher under 3% O2-Ar atmosphere than that under CO2 atmosphere, while the char yield is much lower under 3% O2-Ar than that under CO2. This indicates that CO2 atmosphere is a moderate atmosphere for sulfur removal. SO2 release concentration, its maximum peak temperature and its release amount is the highest under 3% O2-Ar atmosphere. Meanwhile, most of sulfurs in the gas phase is SO2 under 3% O2-Ar atmosphere and H2S under 85% CO2-Ar, 75% CO2-Ar and Ar. However, H2S, COS and SO2 are all relatively high under pure CO2 atmosphere. Based on the analysis of sulfur K-edge XANES, more thiophenes are easily gathered in the chars after thermolysis under those atmospheres. Thiophenes peak in the char under 3% O2 - Ar atmosphere are lower than other atmospheres, which indicates some stable thiophenes are relatively easier to decompose under this atmosphere. This is also in agreement with the higher sulfur removal under 3% O2 - Ar atmosphere. According to the similar XANES spectra of thiophenes, the effects of those three CO2 atmospheres on sulfur transformation in the chars are almost the same, but desulfurization rate is the highest under pure CO2 atmosphere.

Oxidation Behavior of Molten Cu-Be Binary and Cu-Be-X (X = Ca or Zr) Ternary Alloys at 1423 K (1150 °C) Under Controlled Oxygen Partial Pressure

The oxidation behavior of molten Cu-Be binary and Cu-Be-X (Ca or Zr) ternary alloys was investigated by exposing these molten alloy systems to various Ar-O2 atmospheres to control the oxygen partial pressure from 10 to 105 Pa at 1423 K (1150 °C). The experimental results clarified that the oxygen partial pressure in gas phase affects the morphology of the oxide formed on the surface of the alloy and the oxidation rate of beryllium. At lower oxygen partial pressure, a molten Cu-Be alloy is covered with a homogeneous and compact internal layer of BeO, which leads to a minimization of the beryllium oxidation rate. By adding a small amount of calcium or zirconium into the molten Cu-0.5 mass pct Be alloy, a protective BeO layer is formed even at higher oxygen partial pressure, resulting in achievement of a significant reduction in the beryllium oxidation rate.