Ar Gas Mixture Research Articles

Numerical investigation of non-equilibrium condensation of carbon dioxide from a gas mixture of carbon dioxide and argon in a supersonic nozzle under cryogenic conditions

This study involved a numerical investigation of the homogeneous nucleation of CO2 from a CO2–Ar gas mixture in a supersonic nozzle with a throat size of 2.11 mm, a total pressure of 61.15 kPa, and a total temperature of 293.15 K. The flow conditions covered the cryogenic temperature range (∼75 K). Therefore, the surface tension of the clusters was calculated using the Tolman–Tanaka correction, and nucleation growth was evaluated considering both free molecular and continuum regimes. Numerical simulations were conducted for a wide range of CO2 mole fractions (3%–39%). In particular, the effect of the CO2 mole fraction on the condensation-shock position—approximately the Wilson point—was investigated. For 3%, 12%, 24%, and 39%, the condensation shock occurred at 0.048, 0.043, 0.046, and 0.054 m from the throat, respectively. When the mole fraction was low (≤10%), the condensation-shock position moved downstream as the mole fraction decreased. This trend was attributed to a lower nucleation rate. In contrast, when the mole fraction was high (≥10%), the condensation-shock position moved downstream as the mole fraction increased. This was because the CO2 equilibrium pressure rose more rapidly than the CO2 vapor pressure as the mole fraction increases.

Double tube configuration of atmospheric pressure plasma jet for deposition of organic coatings in open air

A double coaxial tube configuration of atmospheric pressure plasma jet (APPJ) was compared with a single tube one for open air plasma polymerization. The effectiveness on minimizing the influence of ambient air during the deposition process was shown for a double tube APPJ i.e. Ar gas fed into the outer glass tube acted as a shielding gas. The inner tube, acted as the powered electrode was fed with a mixture of Ar gas with the precursor, i.e., toluene vapor, a non-oxygen containing precursor. The dynamics of gas flow and its dependence on composition was investigated with a Schlieren imaging system. Coatings obtained with both configurations were analyzed by fourier transform infra-red (FTIR) and x-ray photoelectron spectroscopy (XPS). The results show clearly that the argon shielding gas largely protects the diffusion of oxygen in the deposition zone, giving rise to polymers with much less oxygen incorporated in their structure, and a good retention of the aromatic rings of toluene. Furthermore, the area of the treated zone and the chemical composition of the coating deposited is highly localized (1 mm) in the double tube giving dense stable carbon films while the deposition in the single tube much bigger (6 mm), and the deposited coatings are unstable and easily washed away. Hence, the results obtained with this innovative system provide a new path in plasma polymerization and continuous treatments of large surfaces, with improved coating stability and chemical retention.

Effects of titanium and boron alloying with non-equimolar AlCrNbSiTi high entropy alloy nitride coatings

Among various fabrication technologies for high entropy alloy coatings, high power impulse magnetron sputtering (HiPIMS) technologies have been utilized to synthesize dense microstructure and high hardness coatings with enhanced mechanical and chemical properties. Mid-frequency (MF) pulses have been introduced in the off-time of HiPIMS pulses of the superimposed HiPIMS-MF system to improve the deposition rate. In this study, AlCrNbSiTiBN coatings were deposited using a superimposed HiPIMS-MF system connected to an Al4Cr2NbSiTi2 high entropy alloy target and a direct current (DC) power source for TiB2 target in a reactive Ar and N2 gas mixture. The DC power of the TiB2 target was varied to increase the titanium and boron contents. With increasing Ti and B contents, the microstructure transforms from loose granular and crystalline structure to denser and refined nanocrystalline phases. A residual stress-free coating with a B content of 4.2 at.%. and a hardness of 16.2 GPa was achieved without intentional heating and substrate bias. The poor corrosion resistance of the coatings with lower B contents can be enhanced with a further increase of B content up to 6.4 at.% and reaching a maximum of 10.3 times improvement than that of AISI 304 stainless steel.

Influence of the argon admixture on the reactive oxide species formation inside an atmospheric pressure oxygen plasma jet

In this work, a new atmospheric pressure plasma generated in a wire-to-multiwire dielectric barrier discharge on pure oxygen is introduced. This special geometry of 13 wires (one central wire and 12 ones on the external tube) is feeding by a radio frequency (RF) power (13.56 MHz, 1 kW) and produces a stable discharge. The capacity of this device to produce oxygen reactive species and the influence of Ar gas mixture (1–3%) on this production are investigated. The main characteristics of this DBD plasma are measured using optical emission spectroscopy techniques. The rotational, vibrational, and excitation temperatures along with the electron density are determined from OH (A2Σ → X2Π) band and the Stark broadening of the hydrogen atomic line at 486.1 nm, respectively. The temporal evolution and spatial distribution of charged and reactive species in this plasma are also numerically studied by a Global scheme and a two-dimension fluid model based on drift–diffusion approximation. A kinetic dominated by electron collisions is obtained for this plasma. The generation and movement of electrons, positive and negative ions in the wire-to-multiwire configuration are analyzed and discussed according to changes the electric field and plasma frequency. It is shown that the density of both charged and reactive species increases by adding a small amount of argon to the oxygen plasma while the electron temperature reduces in this configuration. A high level of agreement is observed between the experimental and simulation results for the electron density and temperature in this DBD plasma.

Synthesis ranges for YBaFe4O7 and its topotactic oxidation in ambient air to YBaFeIII4O8.5

Conditions for YBaFe4O7 synthesis from oxide/carbonate amorphous precursors are investigated versus temperature and partial pressure of oxygen at high-temperature equilibrium with the sample in flowing atmosphere of humidified Ar and H2 gas mixtures. Upon topotactic oxidation in ambient air of the cooled-down product, YBaFeIII4O8.5 forms in a couple of minutes. Neutron powder diffraction suggests that added oxygens enter octahedral holes in the cubic closest packing of O and Ba atoms of YBaFe4O7. Up to two oxygen atoms add to some Fe coordination tetrahedra in the kagome-like layer of YBaFe4O7 in a disordered distribution described as partially occupied crystal-structure sites. The oxidized YBaFeIII4O8.5 is metastable and decomposes at high temperatures into FeIII oxides of barium or yttrium. The synthesized YBaFe4O7 is a powerful room-temperature O2 getter that can be reverted by annealing in the above gas mixture.

Study of apparent effective ionization coefficient in CO2 and Ar gas mixtures

Ar:CO2 gas mixtures have recently received research interest due to the possibly beneficial effects of Ar addition to CO2 for CO2 conversion using electrical discharges. For any gas discharge, knowledge of fundamental parameters, such as the effective ionization coefficient, is necessary to optimize the efficiency of the discharge for a particular application. The reduced apparent effective ionization coefficient αea/N is a measure of total ionization. αea/N is influenced by electron impact ionization, electron attachment and also by charge transfer reaction, Penning ionization, and photoionization. This study determined the αea/N of Ar:CO2 gas mixtures in the pressure range of 10–800 Torr and reduced electric field strength E/N range of 40–1200 Td utilizing a steady-state non-self-sustaining Townsend discharge. Experimental results were compared with calculations of Boltzmann equation solver BOLSIG+. Differences between measurements and calculations increased with decreasing CO2 content in the mixture down to 20%, and the differences were highest at low E/N values (below 150 Td). As the simple modification of the model, contribution of ionization of CO2 by Penning transfer from Ar* 3p53d excited states (13.86 eV) was added to the BOLSIG+ calculations, which resulted in good fit of the experimental measurements. Comparison of CO2 addition to Ar with the addition of O2 or N2 revealed that ionization of CO2 or O2 from Ar* 3p53d excited states influences ionization in Ar:CO2 and Ar:O2 mixtures but not in Ar:N2 mixtures, due to the different ionization energies of CO2, O2, and N2.

Fabrication and investigation of the electrical performance of nitrogenated bilayer ZnO:N/ZnO thin-film transistors

In this study, a bilayer ZnO:N/ZnO thin-film transistors (TFTs) was designed to improve both the performance and stability of single-layer ZnO TFTs, using the effects of N-treatment on oxygen vacancy (VO) and the interface trap density. Bilayer ZnO:N/ZnO films and related TFTs were fabricated via radiofrequency magnetron sputtering in a mixture of Ar and N2 gas at 150 °C. The electrical performance and bias-stress stability were systematically investigated. The bilayer ZnO:N/ZnO TFT exhibited a linear field-effect mobility of 13.6 cm2/Vs, high current on-to-off ratio (Ion/Ioff) of 1 × 107, small threshold voltage (Vth) of 2.6 V, and low subthreshold swing of 0.32 V/decade compared with single-layer undoped ZnO and ZnO:N TFTs. Moreover, ZnO:N/ZnO TFT exhibited small threshold voltage shifts (∆Vth) of 0.8 and –0.9 V according to positive bias illumination stress and negative bias illumination stress measurements, respectively. X-ray photoelectron spectroscopy analysis showed that the N-treatment passivated the VO defects, reduced the density of interface traps, and controlled the carrier concentration. Thus, the performance and stability of the ZnO:N/ZnO TFTs were improved. Therefore, ZnO:N/ZnO TFTs have good application prospects in transparent thin-film electronics and flat-panel displays.

ON THE COMPARISON OF REACTIVE-ION ETCHING MECHANISMS FOR SiO2 AND Si3N4 IN HBr + Ar PLASMA

This work investigated the influence of component ratio in the HBr + Ar gas mixture on electro-physical plasma parameters, steady-state densities of active species and reactive-ion etching (RIE) kinetics for SiO2 and Si3N4 under conditions of inductive RF (13.56 MHz) discharge. The combination of plasma diagnostics by Langmuir probes and plasma modeling indicated that an increase in Ar content at constant gas pressure and input power a) caused an increase in electron temperature and densities of charged species; b) results in increasing ion bombardment intensity; and c) leads to the nearly proportional decrease in Br atoms density and flux. It was found that variations of SiO2 and Si3N4 etching rates vs. mixture composition are qualitatively similar while the maximum difference in corresponding absolute values takes place in pure HBr plasma. The analysis of RIE mechanisms was carried out using model-predicted data on fluxes of ions and bromine atoms. It was found that the dominant SiO2 etching mechanism is the ion-assisted chemical reaction which is characterized by the nearly-constant rate in the range of 0–80% Ar due to an increase in the effective reaction probability. That is why the noticeable intensification of physical sputtering with increasing Ar fraction in a feed gas causes the only weak growth of obtained SiO2 RIE rate. Oppositely, the Si3N4 etching process is mainly contributed by the physical sputtering while the efficiency of ion-stimulated chemical reaction is limited by the low reaction probability. This provides both slower etching process (especially in Ar-poor plasmas) and stronger sensitivity of etching rate to the change in mixture composition. For citation: Efremov A.M., Betelin V.B., Kwon K.-H. On the comparison of reactive-ion etching mechanisms for SiO2 and Si3N4 in HBr + Ar plasma. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 37-45. DOI: 10.6060/ivkkt.20236606.6786.

In-situ fabricated amorphous silicon quantum dots embedded in silicon nitride matrix: Photoluminescence control and electroluminescence device fabrication

Herein, we report that high-quality SiN:H films embedded with Si QDs were in-situ fabricated and prepared by the reactive facing target sputtering, which relies on tuning N2 and Ar mixture gas flow ratio. The size of Si QDs in SiN:H films can be tuned from 3.87 nm to 1.40 nm, which exhibit color-tunable photoluminescence from red to blue in the visible region. The microstructure evolution and optical properties of SiN:H films embedded with Si QDs were analyzed by FTIR, Raman, PL, and TRPL measurements, respectively. Considering their unique emission properties, SiN:H films embedded with Si QDs were especially utilized as the emitting layer for fabricating high-performance EL SiN-based LEDs. The broad EL emission properties of the devices were explored by both experimental observations and a theoretical model. This work offers a novel idea to prepare high-quality SiN:H films embedded with Si QDs and a deep understanding of their optoelectronic properties.

Monovacancy-hydrogen interaction in pure aluminum: Experimental and ab-initio theoretical positron annihilation study

We report here on hydrogen-vacancy interactions in high purity aluminum by employing positron annihilation spectroscopy (PAS) analysis of hydrogen-loaded samples, aiming to study the mobility of vacancies. The samples were heat treated at 893 K in an atmosphere consisting of a mixture of H2 and Ar gas and, thus, loaded with hydrogen. The samples were then quenched to ice water and subsequently measured in-situ at different temperatures. In parallel we performed ab-initio density functional theory (DFT) calculations of lifetimes of positrons trapped in vacancies associated with 1–8 H atoms. Our experimental results suggest in comparison with the ab-initio calculations that complexes of vacancies with one hydrogen atom (V-H pairs) were formed in Al samples annealed in a mixture of H2 and Ar gas. Furthermore, hydrogen absorbed in aluminum immobilizes vacancies, i.e. the recovery of vacancies is delayed from 220 K up to around 280 K. At that temperature, V-H complexes start to dissociate, and hydrogen atoms previously bound to vacancies are released. In contrast, for Al samples not loaded with hydrogen isolated monovacancies become mobile around 220 K. In both cases mobile vacancies start to form vacancy clusters. From our experimental data we determined that the formation energy of monovacancies in Al is 0.62 ± 0.01 eV. This value is in very good agreement with 0.63 eV obtained by our ab-initio DFT calculations.

Selective Sulfation Roasting for Cobalt and Lithium Extraction from Industrial LCO-Rich Spent Black Mass

The extraction of cobalt from secondary resources has become crucial, as cobalt has been identified as a strategically important and critical raw material due to the high risks of supply chain disruptions. In this work, selective sulfation roasting was investigated as a potential recycling strategy to extract cobalt and lithium from an industrial lithium cobalt oxide (LCO)-rich black mass. Additionally, the effect of graphite on metal extraction was studied. In the first set of experiments, the sieved black mass fraction containing both cathode and anode materials was directly roasted in a predetermined composition of gas mixtures of SO2, O2, and Ar for 1 h at 850 °C. The gas composition was determined from Kellogg’s diagram to allow for the selective sulfation of Co and Li. In another set of experiments, the carbon present in the black mass was first removed by roasting the material in Ar for 2 h and then in an Ar and O2 gas mixture for five hours at 600 °C. Afterward, selective sulfation roasting was performed in mixtures of SO2, O2, and Ar gas similar to the previous set of experiments. For comparison, similar experiments were performed at 800 °C. The sulfation roasted black mass was leached in water to study the efficiency of Co extraction into the solution. Interestingly, the presence of carbon was found to be beneficial for Co extraction. The extraction efficiency for the first case (with carbon present in the raw material) was observed to be more than three times higher than in the second case (with carbon removed) for sulfation at 850 °C. The extraction efficiency and purity of the extracted Co were found to be better for higher temperature sulfation roasting conditions due to faster reaction kinetics. It was also found that almost all of the Li could be recovered while extracting Co. The maximum efficiency of the extraction was 99.51% Li and 61.21% Co for roasting under a gas flow of 10% SO2-10% O2-Ar at 850 °C for 60 min. These results suggest that Co and Li can be selectively extracted from the black mass by sulfation roasting pre-treatment followed by leaching in water. In holistic processing, the leach residue can then be further subjected to battery metal processing by state-of-the-art methods.

The parallel pathways of hydrogen oxidation reaction on high active decorated Ni–YSZ electrode in electrochemical cell with GDC protective layer

In this study, we considered the electrochemical behavior of a symmetrical electrochemical cell with a highly conductive supporting La0.88Sr0.12Ga0.82Mg0.18O2.85 electrolyte, a protective Ce0.82Gd0.18O2–δ layer and highly active Ni + Zr0.84Y0.16O1.92 electrodes in H2 + H2O + Ar gas mixtures at constant partial pressure of H2, H2O and constant ratio pH2/pH2O. It is shown that the presence of a protective Ce0.82Gd0.18O2–δ layer makes it possible to significantly increase the electrode activity by about 7 times at 800 °C and about 24 times at 700 °C. After the introduction of highly dispersed particles of cerium oxide into the electrode by the method of solution impregnation, the polarization resistance of electrode was about 0.03 Ω cm2 at 800 °C. It is shown that in the case of decorated electrodes, the mechanism of hydrogen oxidation includes two parallel pathways. One is similar to the hydrogen oxidation route for conventional nickel–ceramic electrodes, and the second includes slow stages of oxygen ions transport both in ceria particles and in the protective Ce0.82Gd0.18O2–δ layer. It is shown for the first time that with an increase in oxygen partial pressure the ratio of the rates of these pathways changes.

Database Development of SiO2 Etching with Fluorocarbon Plasmas Diluted with Various Noble Gases of Ar, Kr, and Xe.

In the semiconductor industry, fluorocarbon (FC) plasma is widely used in SiO2 etching, with Ar typically employed in the dilution of the FC plasma due to its cost effectiveness and accessibility. While it has been reported that plasmas with other noble gases, namely Kr and Xe, have distinct physical properties such as electron density and temperature, their implementation into plasma etching has not been sufficiently studied. In this work, we conducted SiO2 etching with FC plasmas diluted with different noble gases, i.e., FC precursors of C4F8 and CH2F2 with Ar, Kr, or Xe, under various gas flow rates of each as well as plasma diagnostics for the process interpretation. We show that Ar, Kr, and Xe gas mixtures depend on the FC precursor flow rate and the pattern width in a significantly different manner and we elucidate these findings based on plasma diagnostic results. The results of this work are expected to offer a practical etching database for diverse applications including plasma process engineering and the development of plasma simulation in the semiconductor industry.

Effects of gas saturation and sparging on sonochemical oxidation activity in open and closed systems, Part I: H2O2 generation

Cavitational/sonochemical activity can be significantly enhanced or reduced depending on the gases dissolved in the liquid. Although many researchers have suggested the order of importance of dissolved gas conditions that affect the degree of sonoluminescence (SL), sonochemiluminescence (SCL), and compound degradation, the most suitable gas condition for sonochemical oxidation reactions is currently unknown. In this study (Part I), the effects of gas saturation and sparging on the generation of H2O2 were investigated in a 28-kHz sonoreactor system. Four gas modes, saturation/closed, saturation/open, sparging/closed, and sparging/open, were applied to Ar, O2, N2, and binary gas mixtures. The change in dissolved oxygen (DO) concentration during ultrasonic irradiation was measured and was used as an indicator of whether the gaseous exchange between liquid and air altered the gas content of the liquid. Considerable difference in the DO concentration was observed for the gas saturation/open mode, ranging from –11.5 mg/L (O2 100 %) to +4.3 mg/L (N2 100 %), while no significant difference was observed in the other gas modes. The change in the gas content significantly reduced the linearity for H2O2 generation, which followed pseudo-zero-order kinetics, and either positively or negatively affected H2O2 generation. Ar:O2 (75:25) and Ar:O2 (50:50) resulted in the highest and second-highest H2O2 generation for both gas saturation and sparging, respectively. In addition, gas sparging resulted in much higher H2O2 generation for all gas conditions compared to gas saturation; this was because of the significant change in the cavitational active zone and concentrated ultrasonic energy, which formed a bulb-shaped active zone, especially for the Ar/O2 mixtures adjacent to the transducer at the bottom. The sparging flow rate and position also significantly affected H2O2 generation; the highest H2O2 generation was obtained when the sparger was placed at the bottom adjacent to the transducer, with a flow rate of 3 L/min.In Part II, the generation of nitrogen oxides, including nitrite (NO2–) and nitrate (NO3–), was investigated using the same ultrasonic system with three gas modes: saturation/open, saturation/closed, and sparging/closed.

Microstructure of Brownish and Blackish Color on Bizen Stoneware Fired in a Firewood Kiln and Reproduction of Brownish Color

Bizen stoneware is produced by firing shaped green clay in a firewood kiln at around 1200°C. The brownish and blackish colors that appear on the stoneware surface in a firewood kiln do not appear on stoneware heated in an electric furnace. The brownish color was found to be caused by the formation of single crystalline, branched, dendritic, Al-substituted ε-Fe2O3 particles. Composite particles consisting of Al-substituted ε-Fe2O3 and Fe-substituted spinel solid solution also formed on the stoneware surface. In this study, we successfully prepared brownish samples that were similar in color to Bizen stoneware by annealing at 1200°C for 2 h in air after heating Bizen clay pellets with K2CO3 at 1230°C under a 10 vol% CO and 90 vol% Ar gas mixture in an electric furnace instead of firing in a firewood kiln. Dendritic hematite particles also formed on the reproduced samples. The blackish color on Bizen stoneware fired in a firewood kiln was caused by the formation of augite [(Ca,Mg,Fe)2Si2O6], which was produced by a reaction between the Bizen clay and firewood ash.

Thermal Annealing Effect on the Structure, Optical and Electrical Properties of Lanthanum Manganite Thin Films Prepared by Reactive Co-Sputtering

Lanthanum manganite (LMO) thin films were deposited by co-sputtering La and Mn targets in an Ar and O2 gas mixture. The films were synthesized on silicon and fused silica substrates. The influences of thermal annealing on the structure, optical and electrical properties of LMO films were investigated. The results exhibited a correlation between these properties. In the amorphous state, an increase in annealing temperature improved the optical transmission and decreased the electrical capacitance. The beginning of crystallization at 600 °C was manifested by a strong increase in the capacitance and a decrease in the optical transmission. At higher annealing temperature, polycrystalline films were obtained with different optical and electrical characteristics. On the other hand, the annealed LMO films showed a photocurrent effect during exposure to a weak LED light.

On mechanisms influencing etching/polymerization balance in multi-component fluorocarbon gas mixtures

In this work, we performed both experimental and model-based study of plasma parameters, steady-state gas phase compositions and heterogeneous process kinetics in CF4 + C4F8 + Ar and CF4 + CHF3 + Ar gas mixtures under the condition of 13.56 MHz inductively-coupled plasma. As constant input parameters we used gas pressure (6 mTorr) and input power (700 W) while variable ones were fluorocarbon component ratios and bias power. It was found that the substitution of CF4 for any second fluorocarbon gas a) results in rather weak effects on electrons- and ions-related plasma characteristics (especially in the case of C4F8); and b) causes sufficient changes in kinetics of neutral species that accelerate the formation of polymerizing radicals and suppress the F atoms density (especially in the case of CHF3). The latter is due to the effective decay of F atoms in the CHFx + F → CFx + HF reaction family. On the contrary, the variation of bias power does not influence kinetics of plasma active species, but changes only the ion bombardment intensity (and thus, the ion-induced reaction kinetics) through the negative dc bias voltage. The phenomenological (based on the gas-phase-related tracing parameters) analysis of heterogeneous process kinetics indicated that the fluorocarbon gas ratio represents the more effective tool to adjust etching characteristics, polymerization rate and the fluorocarbon film thickness. The last two values were found to be always higher in C4F8 - containing plasmas.

(Digital Presentation) Mo Added Zr Oxide-Based Thin Film for Oxygen Evolution Catalyst in Alkaline Solution

On Oct. 4, 2021, Hydrogen energy ministerial meeting (H2 EM 2021) was held by the ministry of economy, trade and industry (METI) of Japanese government as online special event with cabinet members and officials from 29 countries, regions, and organizations. In the meeting, “Global Hydrogen Review 2021” and was released to propose the policy toward hydrogen-based society. In the open session, the water electrolysis was one of the main session, and participants shared their commitment to improve the performance of water electrolysis units and optimize the relevant systems with a view toward reducing the costs of “Green Hydrogen”, and exchanged views on topics including the future prospects for the “Green Hydrogen” market [1]. Here, “Green Hydrogen” is the hydrogen which is produced by the electricity from renewable energies introducing in our previous study [2].Alkaline water electrolysis (AWE) has already commercialized all over the world and recently applied its system for the Power-to-Gas (PtG) in Europe and Japan such as Fukushima hydrogen energy research field (FH2R). In the FH2R, one of the largest module of AWE has operated from 2020. However, we found that the degradation of Ni anode occurs operating by variable renewable energy (VNE) from our previous report [3]. From this point of view, the alternative anode with high durability against VNE should be required for green hydrogen production. We focused on zirconium oxide-based electrocatalyst (ZrOx) and have studied its catalytic activity for oxygen evolution reaction (OER) [4]. In this study, we have investigated the activity and durability of ZrOx with and without Mo addition for the OER in alkaline solution.Zr compound films were formed on Ti rods as a base material, using the R.F. magnetron sputtering. Gas atmosphere in the chamber was a mixture of Ar and O2 gas. After polishing and washing, the Ti rods were heated at 300 oC for Zr oxide-based film without any addition (ZrOx), and 350 oC for Zr oxide-based film with Mn addition (Mn-ZrOx). Sputtering power and sputtering time were fixed at 150 W and 20 min, respectively. All electrochemical measurements were carried out using a three-electrode cell at 30 oC in 7 M KOH. A reversible hydrogen electrode (RHE) and a carbon plate were used as a reference and a counter electrode, respectively. ZrOx or Mo-ZrOx was used as working electrode. In order to evaluate the catalytic activity for the OER, slow scan voltammetry (SSV) was performed under N2 atmosphere. Current density (i geo) was based on the geometric surface area of the working electrode. The resistance of the film (R film) and charge transfer (R ct) was evaluated by AC impedance spectroscopic measurements in the frequency range from 105 to 10−1 Hz.Figure 1 shows polarization curves of ZrOx and Mo-ZrOx. The i geo for the OER on Mo-ZrOx has obviously larger than that of ZrOx. According to the cyclic voltammograms (CV) of both sample, the electric double layer (C dl) of Mo-ZrOx from CV was larger than that of ZrOx. This trend was similar to the result reported in previous study [5], and it is suggested that the C dl becomes larger by the effect of Mo addition. From the results of electrochemical impedance spectroscopy (EIS), both ZrOx and Mo-ZrOx are n-type semiconductor. Moreover, the slope of Mott-Schottky plot on Mo-ZrOx was more gentle than that on ZrOx and it is suggested that the electric conductivity of Mo-ZrOx was larger than that of ZrOx. Thus, the reason why the i geo for the OER on Mo-ZrOx has larger than that of ZrOx is that both improvement of the increase of C dl and the electric conductivity of sample.Acknowledgement: This work is partially supported by Iketani Science and Technology Foundation.Reference[1] https://www.meti.go.jp/english/press/2021/1008_001.html[2] K. Ota, A. Ishihara, K. Matsuzawa, and S. Mitsushima, Electrochemistry, 78, 970 (2010).[3] H. Ichikawa, K. Matsuzawa, Y. Kohno, I. Nagashima, Y. Sunada, Y. Nishiki, A. Manabe, and S. Mitsushima, ECS Trans., 58(33), 9 (2014).[4] K. Matsuzawa, A. Ishihara, A. Ohshi, S. Mitsushima, and K. Ota, Mater. Sci. Eng. B, 267, 115112 (2020).[5] Y. Takasu, T. Ohnuma, W. Sugimoto, and Y. Murakami, Electrochemistry, 67, 1187 (1999). Figure 1

Laser synthesis of iron nanoparticles as effective catalysts for the growth of vertically aligned MWCNTs with amorphous shell

Vertically aligned multi-walled carbon nanotubes (MWCNTs) are attractive for use in nanoelectronics, nanosensors, electrodes for energy storage and harvesting devices, composites, weaving yarns and many other devices. However, in order to reach practical relevance in these applications, the vertically aligned MWCNTs must be dense and sufficient height. Fulfilling those requirements is often challenging. Herein, we report production of high density vertically aligned MWCNTs with amorphous shell on iron nanoparticles by the modified CVD method in the tube flow reactor via catalytic pyrolysis of acetylene. The iron thin films of thickness from 0.5 to 68 nm were obtained by the pulsed laser deposition in droplet-free mode on single crystal silicon substrates (100). The obtained films of the thickness from 0.5 to 20 nm were arrays of nanoparticles with a size from 5 to 17 nm as a result of thermal annealing. These nanoparticles were used as catalysts for the growth of MWCNTs. SEM investigations have shown that height of the obtained vertically aligned MWCNTs depends on the thickness of the initial iron film. The height of the MWCNTs array of 42 µm was achieved on the iron nanoparticles obtained after annealing the metal film of 5 nm thickness. The growth temperature of the obtained MWCNTs array was 700 °C at the volume flow ratio of the C2H2 and H2(5 %)/Ar gas mixture was 1:4. TEM investigations have shown that the diameter of the obtained MWCNTs reached 15–20 nm with amorphous shell thickness of 5–10 nm. Four distinguished Raman peaks at 1360, 1603, 2711, and 2932 cm− 1 correspond to the D-band, G-band, 2D-band, and (D + G)-band, respectively and confirm the formation MWCNTs with good graphitization.

Laser synthesis of iron nanoparticles as effective catalysts for the growth of vertically aligned MWCNTs with amorphous shell

Vertically aligned multi-walled carbon nanotubes (MWCNTs) are attractive for use in nanoelectronics, nanosensors, electrodes for energy storage and harvesting devices, composites, weaving yarns and many other devices. However, in order to reach practical relevance in these applications, the vertically aligned MWCNTs must be dense and sufficient height. Fulfilling those requirements is often challenging. Herein, we report production of high density vertically aligned MWCNTs with amorphous shell on iron nanoparticles by the modified CVD method in the tube flow reactor via catalytic pyrolysis of acetylene. The iron thin films of thickness from 0.5 to 68 nm were obtained by the pulsed laser deposition in droplet-free mode on single crystal silicon substrates (100). The obtained films of the thickness from 0.5 to 20 nm were arrays of nanoparticles with a size from 5 to 17 nm as a result of thermal annealing. These nanoparticles were used as catalysts for the growth of MWCNTs. SEM investigations have shown that height of the obtained vertically aligned MWCNTs depends on the thickness of the initial iron film. The height of the MWCNTs array of 42 µm was achieved on the iron nanoparticles obtained after annealing the metal film of 5 nm thickness. The growth temperature of the obtained MWCNTs array was 700 °C at the volume flow ratio of the C2H2 and H2(5%)/Ar gas mixture was 1:4. TEM investigations have shown that the diameter of the obtained MWCNTs reached 15–20 nm with amorphous shell thickness of 5–10 nm. Four distinguished Raman peaks at 1360, 1603, 2711, and 2932 cm− 1 correspond to the D-band, G-band, 2D-band, and (D + G)-band, respectively and confirm the formation MWCNTs with good graphitization.