Influence Of Oxygen Content Research Articles

Influence of oxygen content on fatigue crack growth behavior of FGH96 superalloys

The fatigue crack growth (FCG) mechanism of FGH96 superalloys influenced by oxygen (O) was investigated in terms of grain structure and phase composition. The results reveal that the thinner powder oxide film process facilitates easier dissolution, and thus the fewer undissolved oxides as well as the movement of high-angle grain boundaries promote the generation of a uniform distributed small grains (SGs) within both the prior particle boundaries (PPB) interface and powder interior in the alloy with O content of 140 ppm. In contrast, the large number of undissolved oxide particles provides more recrystallization sites and thus the SGs clusters aggregate at the PPB interface in the alloy with O content of 340 ppm during sintering. A homogeneous distribution of SGs induces the uniform deformation of the alloy and thus stimulates the transgranular fracture of the coarse grains in alloy with O content of 140 ppm, in favor of a higher fatigue life. On the contrary, in the alloy with O content of 340 ppm, the SGs clusters forming on PPB interface results to the strain concentration at PPB, leading to the PPB fractured morphology and a serious reduction of the fatigue life. This study reveals that the generation of SGs is responsible for the FCG behavior and failure mechanism of the alloys, and suggests that regulating the uniform distribution of SGs or reducing the number of SGs during sintering plays an important role in improving the fatigue properties of powder metallurgy superalloys.

Influence of oxygen content on the properties of In2(OxS1−x)3 used as buffer material in Cu(In,Ga)Se2 solar cells

We investigate magnetron-sputtered In2(OxS1−x)3 compounds acting as an alternative buffer system to the solution-grown CdS or Zn(O,S) buffer layers in Cu(In,Ga)Se2 (CIGS) thin-film solar cells. The influence of the oxygen content on the solar cell performance, microstructure of the mixed systems, bandgap, and band offsets to CIGS is investigated experimentally and also characterized by calculations based on density functional theory. Samples in a series with different chemical compositions ranging from In2S3 to In2O3 are either directly deposited from ceramic targets or from a pure In2S3 target by reactive sputtering by adding O2 in the Ar sputtering gas. The binary compounds In2S3 and In2O3 sputtered at 220 °C substrate temperature from ceramic targets exhibit a crystalline structure, whereas the ternary In2(O,S)3 compounds are either nanocrystalline in the case of In2(O0.25S0.75)3 or amorphous for In2(O0.5S0.5)3 and In2(O0.75S0.25)3. For [O]/([O] + [S]) ratios above 0.25, the cell efficiencies decrease drastically, mainly due to lower open-circuit voltages (VOC). This behavior can be explained by an increase of the negative conduction band offset between the CIGS absorber and the oxygen-rich In2(OxS1−x)3 or In2O3 buffer, resulting in pronounced VOC losses. Adding oxygen to In2S3 with optical bandgap energies of around 2 eV results in a bowing of the values to below 2 eV and finally reaching values of around 2.7 eV for In2O3 if an indirect band transition is assumed. In summary, our results reveal that pronounced oxygen incorporation in In2S3 is not beneficial in terms of CIGS device efficiency because oxygen is electronically inactive and poorly miscible.

Influence of oxygen content on selective laser melting leading to the formation of spheroidization in additive manufacturing technology.

Selective laser melting (SLM) additive manufacturing technology with different oxygen contents leads to the appearance of spherical solids of different sizes on the surface of the part, which affects the mechanical properties of the part, surface roughness, etc. In this study, the SLM molding technique was applied using three different 316L metal powders with different oxygen contents. The spheroidization properties and morphology of the samples were observed using a Quanta 200 environmental scanning electron microscope (ESEM), and the samples were observed microscopically and subjected to EDX spectroscopy using metallographic microscopy, and the mechanical properties were investigated. The results of the study showed that when using gas atomized powders, no spheroidization occurred when the oxygen content of the powders was 5.44 ± 0.01% in all cases, whereas using water atomized powders produced spherical structures with larger dimensions. This observation was closely related to the shape and particle size of the powder. When 316L metal powder with an oxygen content of 4.52 ± 0.01% was used for molding, small spherical structures appeared on the surface of the samples. When metal powder with an oxygen content of 5.44 ± 0.01% was used for the molding, larger spherical structures appeared on the surface of the samples. When the powder with an oxygen content of 5.90 ± 0.01% was used for the molding, more small spherical structures and some large spherical structures appeared on the surface of the samples. This suggests that higher oxygen levels may inhibit the occurrence of spheroidization. EDX spectroscopic analysis revealed that the white matter on the surface of the samples without spheroidization was mainly composed of Fe and Cr, whereas the white matter on the surface of the large-sized spherical structures was mainly composed of Si and Mn, which may be related to the oxygenophilicity of the various substances.

Influence of Oxygen Content in the Protective Gas on Pitting Corrosion Resistance of a 316L Stainless Steel Weld Joint.

Gas tungsten arc welding (GTAW) is commonly used for joining pipelines; however, it often leads to discoloration in the heat-affected zone (HAZ). In this study, 316L pipes were welded with different concentrations of oxygen present in the argon purge gas during welding. The objective of this study was to investigate the effect of oxygen concentration in the protective gas on the pitting corrosion resistance of welded pipes. The experimental results showed that the thickness of the oxide layer formed in the HAZ depends on the concentration of oxygen in the protective gas. Increasing the oxygen concentration in the protective gas resulted in an increase in pitting corrosion resistance until a critical value, beyond which the resistance decreased. The results showed that the thickness of the oxide layer formed in the HAZ depends on the concentration of oxygen in the protective gas. Increasing the oxygen concentration in the protective gas increased the pitting corrosion resistance until a critical value, beyond which the resistance decreased due to the formation of iron oxide. This study provides valuable insights for improving the corrosion resistance of welded pipes in the oil and gas industry.

Influence of oxygen content on melt pool dynamics in metal additive manufacturing: High-fidelity modeling with experimental validation

In the metal additive manufacturing process, the exposure to oxygen and its incorporation into the melt pool are usually deemed unfavorable, but cannot be completely eliminated. Yet, the understanding of this inevitable process remains limited. This work aims to shed light on the effect of oxygen content on melt pool dynamics through multiphysics thermal-fluid flow simulations of the laser powder bed fusion process. Our simulations reveal that oxygen sources from the powder, base plate and oxygen absorption from the atmosphere influences the melt pool dynamics. Although changes in oxygen content barely affect melt pool dimensions, they induce huge differences in the melt pool dynamics and the corresponding material composition distribution within the melt pool. Moreover, our model further clarifies and explains observed experimental phenomena. We demonstrate that the melt pool flow characteristics are responsible for the formation of oxygen-rich streaks observed in experiments regardless of inward or outward Marangoni circulation, while previous experimental studies attributed that to the outward circulation. Additionally, we show that sulfur content minimizes the effect of oxygen on Marangoni flow in iron alloys, and thus leads to the apparent consistency of surface roughness for additively manufactured iron alloys. This work is a fundamental development towards modeling for additive manufacturing under reactive atmospheres and provides unprecedented details on the effects of oxygen on melt pool dynamics. Consequently, this work can further offer practical guidance on powder reuse and adjusting manufacturing parameters for reused powders, thereby improving the sustainability of additive manufacturing.

Quality characteristics and analysis of input parameters on laser beam welding of hairpin windings in electric drives

The relevance of electric drives in individual mobility is continuously increasing. This requires the use of new manufacturing processes in automotive production. In modern stators, the so-called hairpin winding is used. The production process entails rectangular copper conductors (hairpin) to be contacted by laser beam welding. To avoid temperature peaks due to resistance heating in the current-carrying wire, a high cross-sectional area in the welding seam is required. Therefore, the pore volume must be considered. This is proven by thermographic investigations of electrically stressed hairpin connections. To optimize the welding process, effects of the previous manufacturing steps and the welding parameters themselves must be taken into account. This paper analyses systematically the impact of all translational and rotational deviations on the corresponding welding quality. The tests are performed by using a disk laser. A laser spot with a focus diameter of 170 μm is compared to a statically shaped beam, capable of distributing power in core and ring beam. As an additional parameter, the influence of oxygen content in the copper wire is investigated by using electrolytic tough pitch copper (Cu-ETP) and oxygen-free copper (Cu-OF). Furthermore, the interaction between an additional cutting step before contacting and the welding path is considered. X-ray computed tomography (CT) is used to analyse the welding quality. The main finding of the studies is the significant influence of the gap and height offset between the wire ends on the resulting cross-sectional area. In addition, a low oxygen content of the copper and the use of static beam shaping reduce weld spatters, porosity and increase process stability. Three geometries in the welding path perform better in gap bridging and cause less spatters.

The Impact of Thermal Enhance Layers on the Relaxation Effect in Analog RRAM

Computing-in-memory (CIM) with analog resistive random access memory (RRAM) has recently shown great potential in building energy-efficient hardware for artificial intelligence (AI). However, the relaxation effect of analog RRAM featuring post-programming conductance drift has become a key performance-limiting factor. In this work, a comprehensive study of the relaxation effect is presented from the analysis of its causes to the strategy for device optimization as well as the impact on CIM applications. An application-oriented quantitative indicator (relative deviation [RD]) is proposed to fairly evaluate the relaxation effect of different devices. In particular, the influence of oxygen content in different thermal enhanced layers (TELs) on the relaxation and maximum conductance value <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${G}_{max}$ </tex-math></inline-formula> of analog RRAM is studied. A theory of ternary oxide TEL is proposed to mitigate relaxation while maintaining low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${G}_{max}$ </tex-math></inline-formula> , which is experimentally validated by TaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> as TEL. Furthermore, neural network simulation is carried out to analyze the requirement for RRAM relaxation for CIM applications. This work provides a useful strategy for device optimization to suppress the relaxation effect by engineering the TEL.

Surface tension of liquid Fe-Ni, Fe-Cr, and Ni-Cr with physics-informed statistical modeling on the influence of oxygen content

• Accurate measurements of the surface tension of liquid Fe-Ni, Fe-Cr, and Ni-Cr using electromagnetic levitation. • A generalized parametric model was developed to predict the surface tension of binary alloys under the influence of oxygen. • The developed statistical model was successfully applied to predict the surface tension of liquid Fe-Ni-O. Surface tensions of liquid Fe-Ni, Fe-Cr, and Ni-Cr were measured by oscillating droplet method using the electromagnetic levitation technique. The measurements were performed in gas atmosphere of Ar-5% H 2 or Ar, where the resulting oxygen contents of the samples are less than 0.003 at.% and 0.03–0.10 at.%, respectively. The influence of oxygen on the surface tension is demonstrated to be significant, and the decrease in surface tension strongly depends on the oxygen contents and temperature. A Langmuir-based oxygen adsorption model for binary alloys was developed from a physics-informed statistical approach considering the distribution of oxygen allocation in different elements, which statistically predicts and physically interprets the oxygen-induced surface tension shift in binary alloy melts. This generalized parametric model was successfully applied to liquid Fe-Ni-O and showed a good agreement with the experimental data and the Butler model.

Influence of Oxygen Content on the Microstructure and Mechanical Properties of Hot Isostatically Pressed 30CrMnSiNi2A Ultra-High Strength Steel

Influence of Oxygen Content on the Microstructure and Mechanical Properties of Hot Isostatically Pressed 30CrMnSiNi2A Ultra-High Strength Steel

Influence of oxygen content on the manifestation of hazardous properties of coal seams

Purpose. To improve the regulatory framework for the safe conduct of mining operations, to establish the effect of mineral impurities and moisture on the accuracy of determining the oxygen content, under conditions close to those of coal seams. Methodology is based on the fact that practically for all coal seams of Donbass and the Lvov-Volyn basin indicators of consumer qualities of solid fuels have been established, but they characterize only one organic (combustible) part per dry ash-free state. In this case, the effect of mineral impurities (their content for many reservoirs exceeds 30-40%) and moisture on the change in oxygen content is not taken into account. The manifestation of many hazardous properties of coal seams depends on the ratio of oxygen content with other components of the organic mass and mineral impurities. To bring the quality indicators of coals to a state close to the conditions of mining operations, they were recalculated for each coal seams, taking into account the actual yield of ash and total moisture. Findings. The indicator of the release of volatile substances used in the normative documents for the safe conduct of mining operations for assessing the metamorphic transformations of coal seams does not determine the type of coal by their reduction. Restorability determines the properties of the organic mass based on the ratio of oxygen to its other main components. In addition to the organic mass in the dry ash-free state, the composition of solid fuels includes mineral impurities and moisture. They significantly affect the change in the ratio between the main components. The carbon content in the organic (combustible) mass is more informative in comparison with the yield of volatile substances, an indicator. It functionally controls the sum of the remaining components - hydrogen, nitrogen, sulfur and oxygen. To a lesser extent, but rather high, the closeness of the correlation interdependence was established between the content of oxygen and carbon in the dry ash-free state of the fuel. Such interdependence is completely eliminated when considering the fuel for its working condition, which indicates the random nature of the relationship between the main components of the organic mass and mineral impurities, including moisture, for each considered coal seams. Originality. For the first time, on the basis of statistical processing of experimental data on the quality of coals for almost all coal seams of the Donbass and the Lviv-Volyn basins, the possible limits of the oxygen content for the working state of the fuel were established, which makes it possible to individually consider for each coal seam the ratio between the main components of the organic mass and mineral impurities, including the presence of moisture. Practical implications. The research results make it possible to develop proposals for improving the regulatory framework in terms of predicting the hazardous properties of coal seams during mining operations.

Influence of oxygen addition on the discharge characteristics of an argon plasma jet at atmospheric pressure

Plasma jet is an important low-temperature plasma source in extensive application fields. To promote the production of active oxygen species, oxygen is often introduced into the inert working gas. However, the influence of oxygen content on the discharge characteristics of an argon plasma jet is not clear. Aim to this status, an argon plasma jet in a single-electrode geometry is employed to investigate the influence of oxygen concentration (C O) on discharge aspects. Results indicate that with increasing C O (≤ 0.6%), the plume transits from a diffuse morphology to a hollow structure. Electrical and optical measurements reveal that both discharge number per voltage cycle and pulse intensity alter with varying C O. Moreover, discharge morphologies of negative and positive discharges obtained by fast photograph also shift with varying C O. Besides, optical emission spectra are collected to investigate atomic C O, electron density, and electron temperature. The results mentioned above are explained qualitatively, which are believed to be of great significance for the applications of atmospheric pressure plasma jet.

Influence of oxygen content on structure, thermal stability, oxidation resistance, and corrosion resistance of arc evaporated (Cr, Al)N coatings

(CrxAl1-x)(OyN1-y)ε coatings with different oxygen fractions were prepared by cathodic arc evaporation through variation of injected oxygen flux, and elaborated concerning structure, mechanical properties, thermal stability, oxidation resistance, and electrochemical properties. A moderate addition of O into (Cr, Al)N coatings generates a (Cr, Al)(O, N) solid solution with a face-centered cubic structure, whereas an additional corundum-structured (Cr, Al)2O3 solid solution is formed with superfluous oxygen introduced. The addition of O effectively improves the thermal stability by retarding the formation of w-AlN as well as the dissociation of the CrN bond, allowing the oxynitride coatings to maintain higher hardness after annealing. Notably, a small fraction of O-addition (e.g. 8 or 21 at.% in non-metal sublattice) enhances significantly the resistance against oxidation to above 1100 °C by facilitating the formation of a protective Al-rich oxide scale. Further incorporation of O gives rise to a development of oxide scale with unity elemental distribution and hence results in inferior oxidation resistance. Nevertheless, the O-rich oxynitride coatings provide better protection against electrochemical corrosion while the N-rich coatings exhibit higher corrosion current as well as lower polarization resistance compared to the CrAlN coating.

Respiration of Invasive Bivalve Anadara kagoshimensis (Tokunaga, 1906) at 14-Days Starvation and Different Oxygen Content in Sea Water

The influence of oxygen content in sea water and 14-days starvation on respiration rate (RR) of the bivalve species, blood clam Anadara kagoshimensis (Tokunaga, 1906) has been studied. Clams with shell height 25–30 mm were used for experiments. The RR varied over a wide range, from maximal value 89.9 mgO2·l–1 (at 100% saturation) to 5.0 µgO2·h–1·gww–1 (at 76% saturation) at salinity 17–18 and temperature 18°C. The oxygen consumption of the blood clam was substantially lower compared to other benthic bivalves. Results suggest the ability of A. kagoshimensis to transition rapidly from aerobic to anaerobic metabolism under conditions that are not critical for them. Two-week starvation led to an increase in RRs of the blood clam A. kagoshimensis, which indicates an intensification of oxidative processes of organism by 35%–55%. Metabolic processes that require increased oxygen consumption are discussed.

Control of surface composition and microstructure of nano super-hydrophilic TiO2-CuOy coatings through reactive sputtering to improve antibacterial ability, corrosion resistance, and biocompatibility

In this work, the TiO2-CuOy antibacterial superhydrophilic nano-coating succeeded to be prepared on titanium sheet via the reactive magnetron sputtering, influence of oxygen content on the surface morphology, phase composition and structure of TiO2-CuOy coatings were investigated, the bonding of TiO2-CuO system to O2 molecule in TiO2-CuO-O2 systems was simulated through molecular dynamics, and the corresponding antibacterial, biological and physical properties were also studied. Results showed that CuOy transformed from Cu to Cu2O to CuO as the oxygen increased from 0% to50%, TiO2-CuOy coatings consisted of nano-grains, the surface roughness showed a decline trend with decreased grain size, it was consistent with the simulation result in TiO2-CuO-O2 system. After being irradiated under UV, TiO2-CuOy coatings became super-hydrophilic, which obtained enhanced properties in anti-bacteria, cytocompatibility and corrosion resistance. Owing to smaller grain size and surface roughness, higher copper ions releasing amount, CuOy either in Cu2O or CuO type performed better compared to normal nano-copper, in which TiO2-Cu2O coating was nontoxic and significantly promoted MC3T3-E1 cells proliferation, especially its antibacterial rate reached 99.985% to S.aureus under 2 h direct contact, which was able to prevent the infections occurring at the operation site in the early implantation.

Effect of O2 on AC Partial Discharge and Decomposition Behavior of C4F7N/CO2/O2 Gas Mixture

This paper focus on the influence of oxygen on the partial discharge (PD) and decomposition characteristics of C4F7N/CO2/O2 gas mixture as eco-friendly gas insulating medium. The PD characteristic parameters and phase resolved partial discharge (PRPD) patterns of C4F7N/CO2/O2 gas mixture are, respectively, extracted and constructed. The influences of oxygen content and applied voltage on the PD and decomposition characteristics of C4F7N/CO2/O2 gas mixture are investigated based on gas chromatography-mass spectrometry (GC-MS). We find that the addition of 2-4% O2 to C4F7N/CO2 gas mixture can significantly inhibit the negative half-cycle PDs and the generation of most by-products (CF4, C2F6, C3F6, CO, C2F6O3, CF3CN, C2F5CN, C2N2). With the oxygen content higher than 6%, the accumulation discharge magnitude and discharge repetition rates of C4F7N/CO2/O2 gas mixture increase sharply, accompanying the intensification of decomposition and deterioration of insulation strength. There is a positive correlation between the mean discharge magnitude and gas mixture decomposition intensity. To avoid the serious impact of PD fault on gas insulated equipment (GIE), the optimal oxygen addition in C4F7N/CO2/O2 gas mixture should not exceed 6%.

Oxygen addition in biomedical Ti–Nb alloys with low Nb contents: Effect on the microstructure and mechanical properties

Ti–Nb alloys have been widely researched for biomedical applications because of their excellent mechanical properties, corrosion resistance, and superior biocompatibility. In this investigation, the influence of oxygen content on the microstructure and mechanical properties of Ti–Nb alloys with relatively low Nb contents was evaluated. Arc-melted Ti–Nb–O ingots (Nb contents were 15, 17.5, 20, and 22.5 wt% and O contents were 0.15, 0.25, and 0.40 wt%) were hot-rolled and solution-treated at 1200 °C for 1 h, followed by furnace cooling. These samples were characterized by scanning electron microscopy, differential scanning calorimetry, compression tests, and measuring hardness and Young's modulus. The furnace-cooled alloys exhibited typical α + β microstructures, in which the thickness of the α plates decreased with increasing Nb content and increased slightly with increasing oxygen content. A similar behavior was observed for the apparent β-transus, which decreased with increasing Nb content, and increased with increasing oxygen content. The obtained hardness and 0.2% compressive yield stress improved with increasing concentrations of alloying elements. This was due to the solid-solution strengthening promoted by Nb and oxygen, and microstructural refinement induced by Nb addition. The Young's modulus was found to increase very slowly with increasing oxygen content. Owing to the enhancement in yield stress and the small change in elastic modulus with increasing oxygen content, alloys can be designed and produced with high mechanical strength/Young's modulus ratios, favoring their application as biomaterials.

Influence of oxygen content on the corrosion behaviour of 316 L stainless steel in the simulated cathodic environment of proton exchange membrane fuel cell

316 L stainless steel (316 L SS) was melted in three different vacuum degree environments, and the oxygen content of the melted 316 L SS was measured using a routine method (ISO 15351:1999). The results revealed that oxygen content decreased with increasing vacuum degree during the melting process. Then, the influence of oxygen content on the corrosion behaviour of 316 L SS in the simulated cathodic environment of proton exchange membrane fuel cells (PEMFCs) was investigated using potentiodynamic curves, electrochemical impedance spectroscopy (EIS), Mott-Schottky plots, auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The results show that decreasing the oxygen content can significantly increase the passivity of 316 L SS in the simulated cathodic environment. EIS and Mott-Schottky plot results show that a passive film can be formed on 316 L SS in a simulated cathodic environment, and the compactness and resistance of the passive film increase with decreasing oxygen content, indicating improved corrosion protection of the passive film. Meanwhile, the passive film exhibits semiconductive characteristics, and the defect density decreases with decreasing oxygen content, implying increased homogeneity and stability of the passive film on 316 L SS. The AES and XPS results show that the passive film on 316 L SS consists of an inner Cr2O3 film and an outer iron oxide film, in which the thickness of the passive film and the content of the inner Cr2O3 film increase with decreasing oxygen content. Thus, it can be concluded that the corrosion protection of the passive film on 316 L SS increases with decreasing oxygen content considering the main corrosion protection contribution of the Cr2O3 film.

Transparent SiOxCyHz Barrier Film Prepared by PECVD with Upper and Lower Pair Electrode Rolls Structure

Flexible and transparent barrier film is demanded in the fields of organic solar thin-film cells, flexible organic light-emitting diodes, electronic paper and vacuum insulation boards. To prepare films with high water resistance, flexible SiOxCyHz films were prepared on PET using HMDSO as monomer and Oxygen (O2) as reaction gas. SiOxCyHz films were prepared by plasma enhanced chemical vapor deposition (PECVD) with upper and lower pair electrode rolls structure, with the width of electrode rolls up to 600 mm. The influences of oxygen content, film thickness, oxygen/monomer ratio, reaction vacuum degree on water vapor transmission rate (WVTR) were studied. This coating method of oxide high barrier film has great application potential in the development of barrier film industry.

Influence of the active TaN/ZrO x /Ni memristor layer oxygen content on forming and resistive switching behavior

The influence of oxygen content in active zirconium oxide layers on the electrophysical properties of TaN/ZrO x /Ni memristors is investigated. The [O]/[Zr] atomic ratio (x) in the oxide layers was varied in the range from 1.56 to 2.0 by changing the partial oxygen pressure during their deposition by ion-beam sputtering deposition. The ZrO x film compositions were analyzed using x-ray photoelectron spectroscopy and density functional theory simulations. The multiple resistive switching phenomenon in TaN/ZrO x /Ni memristors was found to occur in a certain range of x ≥ 1.78. With the x value decreasing in the oxide layers, the forming voltage of memristors decreased. Furthermore, at the lower edge of x values the switchable range, they no longer required forming. At the same time, as the x value decreased, the memory window (I ON/I OFF ratio) also decreased from 5 to 1 order of magnitude due to an increase in the memristor conductivity in the high resistance state. In order to identify the underlying conduction mechanism of TaN/ZrO x /Ni memristors, their current–voltage curves in low and high resistance states were analyzed in the temperature range from 250 to 400 K for the samples with x = 1.78 (forming-free) and 1.97 (which required forming). It was found that, for both samples, the conductivity in the low-resistance state is characterized by the trap-free space-charge-limited current (SCLC) model, whereas the conductivity in the high-resistance state is characterized by the trap-mediated SCLC model. The possible origins of structural defects involved in the memristor conductivity and resistive switching are discussed based on the obtained results.

The influence of oxygen content on the borrowing SERS activity of tin oxides/noble metal composites

Surface enhanced Raman spectroscopy (SERS), as a powerful tool that its sensitive to detect organics hazardous pollutants and analyze the plasmon-driven catalysis reaction with its fingerprint characteristics. And the SERS property of substrate can be effectively enhanced with charge-transferring between the substrate and analyte by utilizing the borrowing SERS activity strategy. Considering the transition metal elements represent multiple valence states, the synergistic interaction of noble metal/transition metal oxides heterostructures can be further modulated with oxygen contents variation of transition metal oxides. In this work, we report the fabrication of high specific area Sn3O4 hollow hierarchical nanostructures with a simple hydrothermal method, which have mixed-valence of Sn2+ and Sn4+. And the composites were prepared with Au coating and the SERS properties of the nanostructures were investigated by detection of rhodamine 6G. The effect of the oxygen content of the transition metal oxides on their SERS performance was analyzed with annealing process. It was found that a high oxygen atomic ratio induced by heat treatment increased the SERS effect of the Au-coated nanostructures for R6G molecules. This property may prove to be very useful in the future research on the borrowing SERS activity of composites of noble metals and metal oxides.