Oxygen Gas Flow Rate Research Articles

Optimization of plasma treatment variables for the improvement of carbon fibres/epoxy composite performance by response surface methodology

The purpose of the current work was to investigate the effect of oxygen plasma treatment of carbon fibre on the interfacial adhesion in carbon fibre/epoxy composites. The adhesion between the carbon fibre and matrix was examined by interlaminar shear strength (ILSS). It was observed that the composites prepared from plasma treated carbon fibre had higher ILSS compared with untreated fibres. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to study the changes in the surface morphology of carbon fibres and the fracture of carbon fibre/epoxy composite before and after plasma treatment. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) analysis indicated that the plasma process created hydroxyl and carboxyl groups at the surface of carbon fibres. An experimental design with the identified process parameters namely, treatment time, power and flow rate of oxygen gas was followed. Experiments were performed according to the design in order to optimize the plasma variables by response surface methodology (RSM) using Box Behnken design. A second-order polynomial model was developed to predict the ILSS of carbon fibre composites in relation with the changes in plasma parameters. The process conditions were optimized with the quadratic model and the most efficient conditions were confirmed by the empirical results.

Examination of Zinc Oxide Films Prepared by Magnetron Sputtering

Nano-structured zinc oxide thin films were deposited on corning glass substrate by magnetron sputtering process. Zinc oxide films were deposited at different gas ratio values of argon:oxygen kept at 2sccm:18sccm, 6sccm:14sccm, 10sccm:10sccm and 14sccm:6sccm. X-ray Diffraction (XRD) technique was used to characterize ZnO thin films. The XRD graphs indicate presence of (100) and (002) peaks for ZnO thin films. Contact angle and surface energy of nano-structured ZnO thin films were determined by contact angle goniometer. Zinc oxide films are hydrophobic by nature and their contact angle value varies from 98.3° to 102.1° with decrease in flow rate of oxygen gas and increase in argon gas flow rate. UV-Vis-NIR spectrophotometer was used to characterize optical properties of ZnO thin films.

Anomalous Hall effect in monodisperse CoO-coated Co nanocluster-assembled films

We have fabricated the uniform CoO-coated Co nanocluster-assembled films at various oxygen gas flow rates (fO) by using a plasma-gas-condensation method and studied their anomalous Hall effect (AHE). The longitudinal resistivity (ρxx) of all the films exhibits a minimum at a temperature of Tmin. With the increase of fO, Tmin shifts from 150 to 300K and has no longer change when fO is up to 0.10sccm. The saturated AHE resistivity (ρxyA) presents a near linear increase as fO rises. The anomalous Hall coefficient (Rs) at fO=0.20sccm is 4.9×10−9ΩcmG−1 at 300K, which is almost three orders of magnitude larger than bulk Co. Moreover, at fO=0 and 0.05sccm, the scaling exponents γ=1.2 and 1.24 in ρxyA∝ρxxγ are obtained in the region of 325–375K; At fO=0.10, 0.15 and 0.20sccm, ρxyA decreases with the increase of ρxx on a double-logarithmic scale, following a new scaling relation of log(ρxyA/ρxx)=a0+b0logρxx in two temperature ranges of 5–300K and 325–375K.

Limiting factors of carrier concentration and transport of polycrystalline Ga-doped ZnO films deposited by ion plating with dc arc discharge

We develop a deposition technology to enhance carrier concentration (N) together with the improvement of carrier transport of transparent conductive Ga-doped ZnO (GZO) polycrystalline films. 200-nm-thick GZO films were deposited on glass substrates at a temperature of 200°C by ion plating with dc arc discharge. We investigated the effects of oxygen (O2) gas flow rates (OFRs) and discharge current (ID) added between the plasma gun and resource pellet on structural and electrical properties of GZO films. The Ga2O3 contents in the resource pellets was 4.0wt.%. During film growth, O2 gas was introduced into the deposition chamber to control point defects. We found that OFR is the main limiting factor of N and the contribution of grain boundaries (GBs) scattering to carrier transport, whereas ID limits the carrier transport in grain bulk. By optimizing OFRs and ID to obtain high N and Hall mobility (μH) limited by intragrain scattering, we achieved GZO films with an electrical resistivity value of 1.96×10−4Ωcm, an N value of 1.25×1021cm−3 and a μH value of 25.4cm2/Vs.

Aerobic oxidation of β-isophorone by tetraphenylporphyrin catalysts in pyridine solution

A kinetic study was conducted using five metallo-tetraphenylporphyrins (MTPPs) as catalysts for the aerobic oxidation reaction of β-isophorone (β-IP) to ketoisophorone (KIP). The oxidation reaction catalyzed by MTPPs (M=Cr, Mn, Fe, Co and Cu) was observed over a seven hour period under a range of experimental conditions. Changes in the specificity of conversion of reactant to the product, KIP, and the main side-product, α-isophorone (α-IP), were observed at temperatures ranging from 60°C to 75°C, in solvents with varying compositions of pyridine and β-IP, with different MTPP catalysts, oxygen gas flow rates, and solution agitation frequencies. Control experiments show that MTPP catalysts modestly increase the rate of KIP formation, but significantly improve specificity through the apparent suppression of α-IP formation. Analysis revealed that MnTPP (CH3COO−) produced the highest product specificity ratio [KIP]/[α-IP]. Given that all of the metals were in the 3+ oxidation state in this study and there was no observed binding by O2 to any of the MTPP catalysts, the catalytic mechanism is suggested to involve the binding of β-IP to the MTPP metal center. Binding of β-IP is most favorable when pyridine is the trans ligand, but β-IP is also observed to weakly bind when trans to acetate in the MnTPP adduct. This conclusion is supported by electronic absorption spectroscopy, resonance Raman spectroscopy and density functional theory (DFT) calculations. The role played by the catalyst appears to be the activation of hydrogen abstraction following the substrate's ligation to the metal, rather than the more traditional role of MTPPs as O2 activation catalysts by ligation of diatomic O2. β-IP oxidation is an example of a case where the catalyst appears to have a more important role for improving the specificity of the reaction (through decreasing side-product formation) rather than increasing the rate of product formation.

Effects of oxygen gas flow rates and Ga contents on structural properties of Ga-doped ZnO films prepared by ion-plating with a DC arc discharge

Structural properties of highly c-axis oriented polycrystalline Ga-doped ZnO (GZO) films prepared by ion-plating with a DC arc discharge were studied in terms of the oxygen gas flow rate (FO2) introduced into the chamber during the deposition process and the Ga2O3 content in the GZO sintered pellet. The X-ray diffraction (XRD) measurements revealed that the GZO films have the residual compressive stress along the a-axis direction (in-plane) and the tensile stress along the c-axis direction (out-of-plane). The increase in FO2 or the increase in Ga2O3 content was effective for relaxing the in-plane compressive stress induced by the so-called atomic peening effect. The positive correlation between the carrier concentration (n) and the primitive cell volume (V) would be due to the incorporation of Ga atoms substituting Zn sites (GaZns) together with the generation of n-type intrinsic defects or complex defects.

Microstructure, hardness and wear resistance of reactive sputtered Mo–O–N films on stainless steel substrate

The microstructure, hardness and wear property of Mo–O–N films deposited at different oxygen gas flow rates, fO2, on SUS304 stainless steel were investigated. The hardness, H, of the film increased with increasing fO2 in a low fO2 region (fO2≤0.05sccm) and reached a maximum value of about 32GPa because of grain refinement. With further increasing fO2, the H started to decrease due to the formation of the amorphous phase. Similarly, the effective Young's modulus, E*, of the film increased and then decreased with increasing fO2. It was found that the H/E* of the film could be enhanced by the addition of oxygen. The Mo–O–N film deposited at fO2=0.2sccm showed lower H and E*, but much higher H/E* than Mo–N film because of its considerably lower E*, which was due to the formation of a crystalline/amorphous mixed structure. The film deposited at fO2=0.2sccm with a crystalline/amorphous mixed structure showed the lowest μ in the present study and exhibited less frequent transverse cracking introduced by wear, as compared with that deposited at fO2=0.02sccm with a fine grain crystalline microstructure. These results indicate that the formation of the crystalline/amorphous mixed structure in the Mo–O–N film is effective to enhance the elasticity of the film without the associated large loss of the H, which leads to low μ and good wear resistance on the stainless steel substrate.

Numerical simulation of silica particle trajectory in flow field and silica particle spheroidizing in oxygen–acetylene flame spheroidization process

A numerical simulation was developed for particle trajectory in flow field and spheroidizing of silica particle in oxygen–acetylene flame spheroidization process. Gas flow field and silica particle behavior in oxygen–acetylene flame spheroidization process was simulated using a Computational Fluid Dynamics (CFD) package FLUENT. A model was proposed for optimizing spheroidization process of silica particle. Oxygen gas and acetylene gas were used as the continuous phase. Silica particle was used as the dispersed phase. The three-dimensional, steady and isothermal flow field was showed for illustrating the continuous phase and the dispersed phase. Conservation equations of mass and momentum for each phase were solved using the finite volume numerical technique. Various gas conditions were discussed systematically. The injected silica particle trajectories were simulated by using dispersed particle surface trajectory. The trajectories and spheroidizations of different size particles were analyzed. The results of numerical simulation reveal that the flame length was reasonable and overall temperature was highest when acetylene gas flow rate was 10L·min−1, oxygen gas flow rate was 20L·min−1 and powder carrying gas flow rate was 5L·min−1 and 40μm silica particles were difficult to finish spheroidizing within 5×10−4s. The comparison shows that temperature distribution, velocity distribution, particle trajectories, and deformation which were predicted by simulation, were in good agreement with the corresponding experimental results.

The Relation of Temperature Distribution on Silicon Wafer with Furnace Temperature and Gas Flow during Thermal Dry Oxidation Process

Silicon dioxide film has been used as the gate dielectric material in MOS device technology for decades. The film is normally grown in a diffusion furnace using a dry thermal oxidation process. As the device is scaled down to nanometer dimensions, the SiO2 film uniformity requirement is more stringent than ever. In this paper, the effect of furnace temperature and the flow rate of oxygen gas on wafer temperature distribution was investigated. The result was recorded by using the Infrared Thermometer with Dual Laser Targeting device (IRT5000). We have found that the uniformity of temperature distribution on the wafer is almost directly proportional to the O2 flow rate for the entire furnace temperature range (900 - 1050°C). On the other hand, the effect of O2 flow rate on wafer temperature distributions clearly shows two distinct regions; for furnace temperatures of less than 1000 °C, the higher the O2 flow rate, the better the uniformity. For the furnace temperatures of more than 1000 °C, we did not observe any clear dependency of wafer temperature distribution on O2 flow rate.

Effects of N2/O2 flow rate on the surface properties and biocompatibility of nano-structured TiOxNy thin films prepared by high vacuum magnetron sputtering**Project supported by the Higher Education Commission, Hong Kong Research Grants Council (RGC) General Research Funds (GRF), China (Grant No. 112212) and the City University of Hong Kong Applied Research Grant (ARG), China (Grant No. 9667066).

NiTi shape memory alloys (SMA) have many biomedical applications due to their excellent mechanical and biocompatible properties. However, nickel in the alloy may cause allergic and toxic reactions, which limit some applications. In this work, titanium oxynitride films were deposited on NiTi samples by high vacuum magnetron sputtering for various nitrogen and oxygen gas flow rates. The x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) results reveal the presence of different phases in the titanium oxynitride thin films. Energy dispersive spectroscopy (EDS) elemental mapping of samples after immersion in simulated body fluids (SBF) shows that Ni is depleted from the surface and cell cultures corroborate the enhanced biocompatibility in vitro.

An Analysis of Low-Pressure High-Frequency Plasma Chemical Vapor Deposition System for Flexible Solar Cell Characteristics

The flexible dye-sensitized solar cells have a need to improve adhesive property in each layer in order to increase efficiency of this solar cell. Flexible surface with Polyethylene naphthalate (PEN) were modified by using surface treatment from developed the low-pressure high-frequency Plasma Chemical Vapor Deposition system in order to improve adhesive characteristic. The oxygen plasma treatment can improve adhesive property of Polyethylene naphthalate (PEN) films and also cleaning surface. We were using the mixture of Ar and O2 gas for plasma treatment with oxygen gas flow rate from 0.1 L/min. to 0.5 L/min. while Ar gas flow rate was set at 10 L/min. and 5 minute for treatment time. The results indicate that using low-pressure high-frequency Plasma Chemical Vapor Deposition system can be possible improvement adhesive characteristic of PEN films with radical increased on films.

A New-Generation Pilot Ozone-Generating Plant

A new-generation pilot ozone-generating plant with a 0.25 kg O3/h capacity is developed. It allows studies in the 1–5 nm3/h oxygen gas flow rate range at cooling water temperature up to +5°C, electric power up to 5 kW, and discharge gap variation from 0.1 mm. It is shown that ozone generators having brazed aluminum plate-fin electrodes with nanostructured barrier anodic oxide coating have indubitable advantages over the existing ones. In this case, alongside the optimization of ozone generator output parameters, it is possible to get ozone in high and superhigh concentrations.

Tandem mass spectrometry (ICP-MS/MS) for overcoming molybdenum oxide interferences on Cd determination in milk

It is well known that molybdenum oxides affect Cd determination by inductively coupled plasma mass spectrometry (ICP-MS). It is proposed here a procedure for simultaneous determination of Cd and Mo. The effectiveness of the ICP-MS with tandem configuration (ICP-MS/MS) using octopole reaction system (ORS3) pressurized with oxygen gas and MS/MS mode to overcome Mo oxide-based interferences on Cd determination was evaluated. Cadmium was determined as free atom ion and Mo was determined as MoO2+ employing a 0.5mLmin−1 oxygen gas flow rate into the ORS3. Non-fat and whole milk powder certified reference materials (NIST SRM 8435 and SRM 1549) were used for checking the accuracy of the proposed procedure. The microwave-assisted digestion was carried out using diluted nitric acid solution (2.6molL−1 HNO3) and hydrogen peroxide (30%mm−1). According to Student's t-test, reference and determined values were in agreement at a 95% confidence level, except for 111Cd and 113Cd in SRM 1549.

高密度プラズマアシスト蒸着により作製したSiO<sub>2</sub>およびNb<sub>2</sub>O<sub>5</sub>薄膜の光学的・機械的特性

As a main optical thin-film material, SiO2 has a low refractive index in the UV-visible wavelength region. It is used widely for optical coatings with superior environmental resistance. In contrast, Nb2O5 is a high refractive index material. To improve their mechanical properties, SiO2 and Nb2O5 single-layer thin films were prepared using high-density plasma assisted vapor deposition. Plasma conditions were varied by changing the coil current related to energy intensity, and the oxygen gas flow rate related to ionization. Analyses of SiO2 and Nb2O5 thin films using XRD revealed amorphous composition irrespective of the assist. However, cross-sectional SEM images showed that thin film densification differed according to the assist. Furthermore, XPS showed differences in SiO2 thin films from the bonding state according to the assist. The Nb2O5 thin films exhibited slight differences according to the assist. Surface roughness measurements and abrasion resistance tests were done for thin films deposited under various plasma conditions. The plasma-assisted deposited SiO2 films were much more durable than non-assist films. The refractive indexes of the films were measured using optical transmission spectra and ellipsometry. Results show correlation between the durability and the refractive indexes. The film packing density was related to the durability. No difference was found in the durability for Nb2O5 between plasma-assisted deposited films and non-assisted deposited ones. However, a difference was found in the refractive index between the films of two types. The film hardness was measured using nanoindentation. The Nb2O5 films were harder than the SiO2 films. The Nb2O5 film stiffness was also three times greater than that of SiO2 films. However, the damage to plasma-assisted SiO2 films was less than that to plasma-assisted Nb2O5 films. This high stiffness is expected to cause plastic deformation. Future investigations must examine the relations among film packing density, durability, hardness, and stiffness.

Influence of the oxygen plasma parameters on the atomic layer deposition of titanium dioxide

The influence of the oxygen plasma parameters on the morphology and optical properties of TiO2 thin films has been extensively analyzed in plasma enhanced atomic layer deposition (PEALD) processes. Crystalline aggregates with the anatase phase have been identified on the film surface at a low deposition temperature (down to 70 °C) under specific plasma conditions. Up to 70% surface coverage by anatase crystallites is obtained at low oxygen gas flow rates and high plasma power. The hillocks abundance is correlated with high ion flux and electron density and with the resulting enhanced ion bombardment of the surface. Altering the plasma conditions is an important parameter besides temperature to control the morphology of the titania film for specific applications such as photocatalysis or functional optical coatings. Specifically, photocatalytic titania coatings on polymer substrates could benefit of such low temperature PEALD processes with abundant anatase crystallites; whereas optical coatings require smooth, high refractive index titania as obtained with low plasma power and high oxygen flow rate.

Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet.

The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment.

Hybrid ozonation–microfiltration system for the treatment of surface water using ceramic membrane

The aim of this work was the investigation of performance efficiency of a hybrid system, integrating two processes, i.e. membrane filtration and ozone oxidation, as a potential method for the contaminated surface water quality improvement and the mitigation of membrane fouling. Ozone–oxygen gas mixture at various flow rates (and corresponding ozone concentrations) was introduced into the experimental vessel by gas spargers, located at the bottom of vessel and producing fine gas bubbles. Ozone–oxygen gas flow rates ranged from 0.3L/min to less than 0.05L/min, while ozone amounts in the gas mixture added to the system varied from 6.6mg to less than 1.1mg O3/min of experiment, respectively. Ozonation and ceramic membrane microfiltration were performed simultaneously. Treated water samples were collected and analyzed for major quality parameters, i.e. turbidity, pH, UV254 absorbance and Total Organic Carbon (TOC) content. The permeates were also analyzed with the HPLC technique for the estimation of molecular weights of resulting humic acids oxidation products. The hybrid process of membrane microfiltration–ozonation resulted in substantial reduction of membrane fouling rate for all the examined concentrations and flow rates of ozone, while the quality of permeate varied, depending on the ozone concentration used. With the optimum ozone dosage the quality of permeate for single microfiltration and hybrid processes were similar, while the addition of ozone to the system resulted in a substantial fouling reduction.

Influences of oxygen gas flow rate on electrical properties of Ga-doped ZnO thin films deposited on glass and sapphire substrates

The Ga-doped ZnO (GZO) films deposited on glass and c-plane sapphire substrates have been comparatively studied in order to explore the role of grain boundaries in electrical properties. The influences of oxygen gas flow rates (OFRs) during the deposition by ion-plating were examined. The dependences of carrier concentration, lattice parameters, and characteristic of thermal desorption of Zn on the OFR showed common features between glass and sapphire substrates, however, the Hall mobility showed different behavior. The Hall mobility of GZO films on glass increased with increasing OFR of up to 15sccm, and decreased with further increasing OFR. On the other hand, the Hall mobility of GZO films on c-sapphire increased for up to 25sccm. The role of grain boundary in polycrystalline GZO films has been discussed.

Band gap modulation of ZnTe1-xOx alloy film by control of oxygen gas flow rate during reactive magnetron sputtering

The band gap energy of ZnTe1-xOx alloy films grown on c-plane sapphire substrates was modulated by controlling the argon-oxygen ratio during radio frequency magnetron sputtering. The ZnTe1-xOx samples were deposited at a substrate temperature of 200 °C and with gas mixtures of 2%–8% oxygen in argon. The optical transparency of the ZnTe1-xOx samples was measured in the 1.5–6.0 eV energy range by optical transmission spectra. The optical band gap, obtained from plots of (αhν)2 as a function of hν, increased from 2.2 to 4.9 eV with increasing oxygen ratio, believed to be a result of a change in bonding structure through composition exchange during film deposition by reactive magnetron sputtering. These results show that the band gap energy of ZnTe1-xOx, ZnOTeO, and (ZnO)1-x(TeO2)x alloy films can be modulated, making them more suited for applications as windows and as active layers for ZnTe-based intermediate band solar cells.

Properties of O-Doped CuI Thin Films by Chemical Vapor Deposition (CVD) at Different Deposition Flow Rate

The effect of oxygen doping to the properties of CuI thin films was studied. The doping of oxygen to the CuI thin films was done by using single furnace chemical vapor deposition (CVD) method at different oxygen gas flow rate (e.g 10, 20, 30, 40 and 50 sccm). The CuI thin film was first deposited by using mister atomizer at constant CuI solution concentration of 0.05M. The surface morphology and electrical properties of O-doped CuI was studied. The field emission scanning electron microscopy (FESEM) was used to observe the morphology of O-doped CuI thin films. The FESEM images revealed that all the CuI thin films deposited were uniform with the existence of nanostructured CuI particle. The EDX measurement confirm the existence of Cu:I in the films and also the variation of oxygen ratio in the CuI thin films as the oxygen was introduced. The resistivity of 101 Ωcm to 103 Ωcm at constant voltage of-5V to 5V was obtained for the O-doped CuI thin films.