Pure Nitrogen Gas Research Articles

Numerical and experimental investigation of cryogenic fluid flow characteristics on corrugated packing surfaces

Cryogenic distillation is a significant method for producing pure oxygen and nitrogen gas. In the past, due to the high cost and difficulty of conducting cryogenic experiments, the structured packings used in cryogenic distillation are mainly developed and designed by referring to the testing results of room-temperature fluids. The real flow characteristics of cryogenic fluids on structured packings, such as flow pattern and wettability which significantly determines the distillation performance, have seldom been revealed. In this study, with the help of a three-dimensional CFD model and a visual experimental setup, the liquid nitrogen (LN2) flow characteristics within the geometric unit of a 45° inclined packing element were revealed detailedly under different liquid loads and crimping angles. Comparison studies were also conducted to show the different film flow characteristics between water and LN2. Additionally, optimization of the crimping angles based on 250Y structured packing was explored. Both simulation and experiment show that the flow pattern and wetting mechanism of the hydraulic test on water are different from those of LN2 in the actual cryogenic distillation. The LN2 has much better film flow performance than water due to its different physical properties. In addition, it is found that the crimping angle has a significant effect on the wetting area ratio. For LN2, the crimping angle of 90° can basically result in a high enough wetting area ratio, while for water, the crimping angle as large as 120° is needed to achieve a high wetting area ratio. It shows that testing and designing the structured packing with water as the main working medium will bring apparent errors in real cryogenic distillation process.

Temperature stability of a Joule–Thomson microcooler operating with pure and mixed gases

Benefiting from the developments in micromachining technologies, Joule–Thomson (JT) cryogenic coolers have been miniaturized for cooling cold electronics based either on semiconductor, superconductor, or a combination of the two. The performance of these electronics is affected not only by temperature but also by temperature stability; however, many problems related to the temperature stability of JT microcoolers have not been solved. In this study, we investigate experimentally the performance of a JT microcooler operating with pure nitrogen gas, nitrogen/methane mixture, and nitrogen/ethylene mixture. The cool-down curves and the cooling powers of the microcooler operating with the three types of working fluids between 0.1 MPa and 6.0 MPa are presented. Based on the cooling power measurements, the effect of heat load on the temperature stability of the microcooler is discussed. The microcooler operating with nitrogen/ethylene mixture demonstrates the best temperature stability due to its characteristics of vapor–liquid–liquid equilibrium. Besides the properties of the working fluids, the degree of change in mass-flow rate of the microcooler also affects the temperature stability. This study is conducted to promote the widespread use of cryogenic electronics that are sensitive to the temperature fluctuation.

Build atmosphere aided texture control in additively manufactured FeCrAl steel by laser powder bed fusion

Through properly selecting the process atmosphere, involving pure argon gas (Ar) and nitrogen gas (N2), we have achieved the in-situ texture control of laser powder bed fusion (LPBF)-manufactured FeCrAl parts with fixed process parameters. The results, from crystallographic orientation analysis, indicate that a single crystalline-like microstructure is developed under the N2 process atmosphere while printing under the common Ar case results in a chessboard-like microstructure composed of strong fiber texture with 〈111〉 along the Z-axis (building direction) and cube texture with 〈001〉 parallel to X-, Y-, and Z-axes. The texture control mechanism under different process atmospheres has been elucidated by extracting the corresponding molten pool morphology information, that is flat molten pool for the N2 process atmosphere but keyhole one for the Ar case. The current findings demonstrate the feasibility of utilizing the process atmosphere of additive manufacturing to manipulate the crystallographic texture of metals.

Techno-Economic Feasibility Study for Organic and Plastic Waste Pyrolysis Pilot Plant in Malaysia

Organic and plastic waste (OPW) is diverted from landfills in order to lower carbon emissions. Nevertheless, modern pyrolysis techniques are frequently utilized in laboratories (using feedstocks that weigh less than 1 kg), which employ costly pure nitrogen gas (N2). This study developed a fast pyrolysis system to produce pyrolysis oil or liquid (PyOL) from OPW using flue gas as the pyrolysis agent. The added benefits included the efficient value-added chemical extractions and the non-thermal plasma reactor upgraded PyOL. OPW was also pyrolyzed at a pilot scale using flue gas fast pyrolysis in this study. In addition to lowering operational expenses associated with pure N2, flue gas reduced the lifecycle carbon emissions to create PyOL. The results indicated that considerable material agglomeration occurred during the OPW pyrolysis with an organic-to-plastic-waste (O/P) ratio of 30/70. Furthermore, the liquid yields were 5.2% and 5.5% when O/P was 100/0 (305 °C) and 99.5/0.5 (354 °C), respectively. The liquid yields also increased when polymers (polypropylene) were added, enhancing the aromatics. Two cases were employed to study their techno-economic feasibility: PyOL-based production and chemical-extraction plants. The mitigated CO2 from the redirected OPW and flue gas produced the highest revenue in terms of carbon credits. Moreover, the carbon price (from RM 100 to 150 per ton of CO2) was the most important factor impacting the economic viability in both cases. Plant capacities higher than 10,000 kg/h were economically viable for the PyOL-based plants, whereas capacities greater than 1000 kg/h were financially feasible for chemical-extraction plants. Overall, the study found that the pyrolysis of OPW in flue gas is a viable waste-to-energy technology. The low liquid yield is offset by the carbon credits that can be earned, making the process economically feasible.

Characterization and Optimization of Plasma Electrolytic Process for Conversion of Molecular Nitrogen to Ammonia in Aqueous Water at Atmospheric Pressure

Ammonia (NH3) is widely used in the chemical and agricultural industries and is of growing interest as a potential energy carrier. Most of the current global NH3 production utilizes the Haber-Bosch process which has a large environmental and physical footprint. For this reason, there have been substantial efforts to develop an alternative process that can be sustainable and distributed. Recently, plasma-based electrolysis reactors have shown promise to convert molecular nitrogen to various forms of fixed nitrogen such as ammonia, nitrate, and nitrite in water at atmospheric pressure. However, selectivity and control over the products has not been adequately demonstrated. In this work, we studied a plasma formed in pure nitrogen gas or mixtures containing nitrogen gas at the surface of liquid water. Various products were characterized in the liquid phase including ammonium ions, nitrate ions, nitrite ions, and hydrogen peroxide as a function of pH, discharge current, and time. In addition, continuous direct current (DC) was compared to pulsed DC voltage plasma operation. We find that the selectivity to different nitrogen products depends on the solution conditions. These results could be used to inform optimization and scale up of similar plasma-liquid systems for sustainable nitrogen fixation.

Novel Gas Phase Route Toward Patterned Deposition of Sputter‐Free Pt/Al Nanofoils

AbstractThis article reports a new approach toward fabrication and directed assembly of nanoparticulate reactive system (Nanofoils) on patterned substrates. Different from current state‐of‐the‐art, gas phase electrodeposition uses nanoparticles instead of atoms to form densely packed multilayered thin films at room temperature‐pressure. On ignition, the multilayer system undergoes an exothermic self‐propagating reaction. The numerous contact points between two metallic nanoparticulate layers aid in high heat release. Sub‐10‐nm Platinum (Pt) and Aluminum (Al) particles are synthesized through cathode erosion of metal electrodes in a flow of pure nitrogen gas (spark ablation). Pt/Al bilayer stacks with total thickness of 3–8 µm undergo self‐propagating reaction with a 10.3 mm s−1 wavefront velocity on local ignition. The reaction wavefront is captured using high speed videography. Calorimetry studies reveal two exothermic peaks suggesting Pt/Al alloy formation. The peak at 135 °C has a higher calorific value of 150 mW g−1 while the peak at 400 °C has a 12 mW g−1 exothermic peak. X‐ray diffraction study shows reaction‐products are cubic Al2Pt with small quantities of orthorhombic Al6Pt and orthorhombic AlPt2. Electron microscopy studies help draw a correlation between film morphology, bimetallic interface, nanoparticle oxidation, and self‐propagating reaction kinetics that is significant in broadening our understanding towards nanoparticulate reactive systems.

Thermally-driven scintillator flow in the SNO+ neutrino detector

The SNO+ neutrino detector is an acrylic sphere (radius 6 m) with a thin vertical neck containing almost 800 tonnes of liquid scintillator. The apparatus is immersed in a water-filled underground cavern, the neck protruding upward into a manifold above water level, with scintillator filling the sphere and rising up the neck some 6 m to an interface with purified nitrogen gas. Time-dependent flow simulations have been performed to investigate convective motion of the scintillator fluid, motivated by observations of a transient radon (222Rn) contamination layer which, over a period of two weeks, sank from near the base of the neck to the detector’s equator. According to simulations, this motion may have been induced by heat transfer through the detector wall, that resulted in buoyant ascending flow within a thin wall boundary layer and compensating sink elsewhere. This mechanism can result in transport down the neck to the sphere on a time scale of several hours. If the scintillator happens to be thermally stratified, the same forcing by a weak wall heat flux produces internal gravity waves in the spherical flow domain, at the Brunt–Väisälä frequency. Nevertheless as oscillatory motion is by its nature non-diffusive, simulations confirm that imposing strong thermal stratification over the depth of the neck can mitigate mixing due to transient heat fluxes.

Photocatalytic-proxone process application in the degradation of toluene-diisocyante, and methylene diphenyl diisocyanate from polluted air

Isocyanates are one of the most widely used semi-volatile compounds in various industries, including the polyurethane industry. Applying a hybrid advanced oxidation process to the degradation of toluene diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI) from polluted air were the main aims of the study. The BiOI@MOF/Zeolite nanocomposite was prepared by the solvothermal method. XRD, FT-IR, FESEM, EDAX, EDS element mapping, TEM, BET, XPS, and UV–vis spectra analysis were applied to indicate the nanocomposite characters. The effect of flow, ozone concentration, hydrogen peroxide concentration, initial isocyanates concentration, and relative humidity were investigated. The concentration of isocyanates measurement via NIOSH 5522 standard method. In the optimum conditions of the process, the supplementary studies were done. The results of the analysis of composite structure indicated that well synthesized had been done. Experimental results showed optimal operating conditions could degrade more than 90 % of isocyanates. The synergistic effect coefficient of the mechanisms was 2.03 and 2.34 for TDI and MDI, respectively. The stability of the process was observed in 6 consecutive steps. The residual ozone concentration in the system's outlet was negligible (0.047 mg/l). The CO2 and CO emissions proved that the mineralization of isocyanates occurred. The theoretical mineralization rate was 0.64 and 0.55 reported for TDI and MDI, respectively. The simultaneous presence of MDI and TDI in the reactor decreases the efficiency of the process. The pure oxygen gas, pure nitrogen gas, and atmospheric as a carrier gas showed different performances in the process of isocyanate removal (80.8, 35.4, and 61.7 % degradation in the simultaneous presence of MDI and TDI).

Effects of argon/nitrogen sputtering gas on the microstructural, crystallographic and piezoelectric properties of AlN thin films

The growth of highly crystalline c-plane AlN ‹002› is extremely difficult, entailing high temperature and ultra-high vacuum condition. In sputtering technique, the addition of nitrogen into argon sputtering gas can significantly assist the formation of AlN ‹002› at low temperature. We incorporated purified nitrogen gas and observed the consistent formation of single crystal ‹002› AlN thin film layer sputter-deposited on Mo/Si substrate from the AlN ceramic target. Small presence of oxygen content within AlN crystal relates to the preferential growth of AlN ‹002›. High oxygen content in AlN thin film due to the use of unpurified nitrogen and argon only sputtering gas prefers the formation of AlN ‹100›. Different AlN crystal structure has shown distinct thin film properties and piezoelectric response. This work provides a method to control the crystal structure of the sputter-deposited AlN thin film layer, either c-plane AlN ‹002›, a-plane AlN ‹100› or polycrystalline AlN.

Needle extraction device for rapid and quantitative gas chromatographic determination of volatile chlorinated hydrocarbons and benzene in soil

A rapid and quantitative analytical method for volatile chlorinated hydrocarbons and benzene, such as chloroethylene, dichloromethane, and carbon tetrachloride, in soil samples was developed using a needle-type extraction device packed with activated carbon-based adsorbents. The soil sample of 10 g was placed in a glass cartridge and fixed with quartz wool to make sure not to move during the extraction process. After the internal standard solution was spiked into the soil sample, the cartridge was sealed with a polytetrafluoroethylene adapter, and the needle extraction device was used to collect the headspace gas. Analytes were purged from the soil sample and collected on the adsorbent, while pure nitrogen gas was introduced to the soil sample during the sample collection. The sampling time was approximately 10 min for 100 mL of gas sampling. After the sampling process, the extraction needle was directly inserted into a heated injection port of gas chromatography equipped with flame ionization detector (GC-FID) or that hyphenated to mass spectrometry (GC–MS). The extracted VOCs were thermally desorbed and simultaneously introduced to a GC capillary column for subsequent separation and determination. The limit of detection and limit of quantification of all the examined analytes was less than 20 and 60 ng/10 g soil in GC-FID and less than 2.5 and 7.5 ng/10 g soil in the case of GC–MS. Linear calibration curves were obtained up to 10 μg/10 g soil for all the analytes. The relative standard deviations of the ratio of analyte peak area and internal standard peak area were less than 10%. The recovery and sensitivity of analytes confirmed in the proposed method were compared with that obtained with a standard method conventionally employed.

Demonstration of MOCVD-grown BGaN with over 10% boron composition

BGaN is an emerging ultrawide bandgap semiconductor with important applications ranging from power electronics to ultraviolet light emitters. To date, BGaN boron composition has been limited to <10% in the wurtzite phase. Herein, a 200 nm thick high quality mixed-phase BGaN film was grown via horizontal–reactor metalorganic chemical vapor deposition with boron composition exceeding 10%. The growth was performed under low temperature and pressure conditions of 600 °C and 75 Torr, respectively, with a growth rate of 0.29 µm/h. Triethylborane and triethylgallium were used as the source gases for boron and gallium, respectively. Pure nitrogen gas was used as the carrier for all reactants. A root mean square roughness value of 2.56 nm was determined using an atomic force microscopy scan on an area of 5 × 5 µm2. X-ray diffraction (XRD) 2θ–ω scans show a nearly lattice-matched BGaN/AlN film corresponding to a boron composition of ∼10%. A mixed wurtzite and zincblende phase was confirmed via an XRD pole figure and transmission electron microscopy. Additionally, the high crystalline quality of the mixed (002)wz/(111)ZB planes was shown using an XRD rocking curve with 810 arcsec full width at half maximum. The boron composition was precisely measured as 15% using Rutherford backscattering spectrometry combined with nuclear reaction analysis.

Inactivation of spoilage organisms on baby spinach leaves using high voltage atmospheric cold plasma (HVACP) and assessment of quality

Cold plasma technology has previously shown potential as a novel, non-thermal technology for decontaminating foods and improving food safety. The study explores the potential of a nitrogen gas-based high voltage atmospheric cold plasma (HVACP) system to eliminate native microbiota from baby spinach leaves using a high purity (99.99%) nitrogen gas. The effect of HVACP was also evaluated over a storage period of 7 days at 4 °C. Up to 2.6 and 3.5 log10 CFU/sample of microbiota were eliminated until 7 days of refrigerated storage after 2.0 and 5.0 min (mins) of cold plasma exposure, respectively. 16 s rRNA sequencing revealed the presence of persistent Pseudomonas strains such as P. fluorescens, P. libanensis and Pseudomonas gessardii and elimination of other competitive microbial strains such as Bacillus spp., Exiguobacterium spp., and Pantoea spp. A five-minute, indirect, 80 kV HVACP treatment reduced 3.51 log10 CFU/sample after 7 days of refrigerated storage at 4 °C, compared to an untreated control with 7.50 log10 CFU/sample, without significantly affect the texture profile, color or moisture content of the leaves, serving as a promising non-destructive decontamination technology.

Nonequilibrium Factor in the Structure of a Curved Shock Wave Refracted Into an Intensively Heated Medium

The role of thermal nonequilibrium state in the structure of a curved shock wave during its refraction into an intensively heated medium has been studied analytically and numerically. At elevated gas temperatures common for optical discharges and for moderate-to-strong shock intensities, the width of the zone of variable specific heat is on sub- to mm scale, and thus is comparable to the geometrical scale of the problem. The asymptotic temperature gap, the specific temperature distribution in the zone, and the relaxation zone width are discussed in connection with the changes in the contrast level of the shock images obtained with shadow techniques. Numerical examples are presented in spherical and elliptical geometries for the conditions of a laser-induced breakdown in pure nondissociating nitrogen gas.

Effect of Electrode Profile and Polarity on Performance of Pressurized Sparkgap Switch

Sparkgap are most widely used closing switches in various high-voltage pulsed power systems and its reliable operation at desired voltage level is very essential. Conventionally by adjusting the filling gas pressure inside sparkgap switch, breakdown voltage level is altered but switching characteristics such as stability in hold-off voltage at various pressures, breakdown delay, plasma channel formation, and erosion rate are mainly dictated by adopted electrode profile and its dimensions, inter-electrode gap length and polarity. In this paper, experimental results obtained on breakdown characteristics of four different electrode geometries—Plane Parallel, Hemi-spherical, Bruce, and Rogowski and also a generalized criterion for fixing major dimensions of electrode and inter-gap length to ensure uniform electric field in the inter-electrode region are reported. All electrodes are of brass material and have common radius and thickness of 25 mm and 18 mm, respectively (surface finish <1 µm). Experiments performed on various electrode profiles in gap lengths of 2 mm to 5 mm range with pure nitrogen (N2) gas pressurization up to 50 psi reveal that among all profiles, Rogowski performs most reliably having stable hold-off voltage in wide operating range. Hold-off voltage magnitude and breakdown delay was commonly obtained higher for negative polarity in all trials. A comprehensive overview of experimental investigation reported herein compares suitability of various electrode profiles and polarity for reliable switching.

Calibration methods for VSCs measured on AS-TD-GC-SCD.

Volatile sulfur compounds (VSCs) are key odorous compounds from emissions of various odour sources because they are odorous and generally have very low odour threshold values. Identification and quantification of them through air server-thermal desorber-gas chromatography-sulfur chemiluminescence detector (AS-TD-GC-SCD) become more and more popular, although VSCs can be determined by other detectors. To find a valid, practical and quick calibration method is also an important step in their analytical processes. This study compared three different sample preparation and unity sampling methods using both gas standards (with 10 VSCs balanced in pure nitrogen gas) and liquid standards of 7 VSCs. For liquid standard sample preparation, two solvents (methanol and n-pentane) were tested and their calibration results were compared. The study revealed that the three calibration methods with both manual and dynamic dilution of VSC standard gases can achieve satisfactory calibration results with nice linear regression and correlation coefficient (r2). The dynamic dilution and loop sampling method is recommended because of its better reliability and time-saving processing. For calibration of VSCs with liquid standards, preparing the samples using dissolved VSCs in n-pentane and analysing them using the loop sampling method achieved best calibration results. For dimethyl trisulfide (DMTS), its calibration cannot obtain as good results as other sulfur compounds even using the best performance calibration method.

Design and fabrication of multi-functional equipment to produce gaseous nitrogen/oxygen and water from ambient air

Mother earth provides all the necessary resources for the existence of life. Despite the rich resources of water on our planet, majority of world’s total population experiences water shortage annually. Studies have shown that with the increase of global warming, the average humidity of ambient air is rising annually. Due to the decrease of water table on land, alternative sources of acquiring potable water can be of great utility. Out of the several methods available to tap potable water, this paper aims to achieve an alternate source of receiving fresh water directly from ambient air. This process is completely different from distillation. The ambient air also comprises a majority of Nitrogen, and this N2 is used for the purpose of creating an inert environment in packaging industries and for the purpose of extinguishing fire, a multi-functional equipment has been fabricated in order to extract water, along with pure Nitrogen gas from the residual dry air. A Pressure Swing Adsorption (PSA) system is used to separate the Nitrogen from remaining air molecules based on their relative molecular size. In the current industrial sectors, the valves required to actuate the flow of air in PSA system are controlled by PLC circuits and Cam followers. These electro-mechanical components are overpriced. In this work electronic timers are used to actuate the valve timing, which resulted in economical. The system fabricated is simple in construction and it is easy to replace the Carbon Molecular Sieves (CMS) with Zeolite Molecular Sieves in order to obtain Oxygen gas as the pure product that can be used to help Covid-19 patients using medical grade filters. The system can be scaled up with larger mass of CMS, bigger PSA towers and greater compressor power in order to increase productivity.

Experimental Study of the Effect of Precursor Composition on the Microstructure of Gallium Nitride Thin Films Grown by the MOCVD Process

Abstract Chemical vapor deposition (CVD) is a widely used manufacturing process for obtaining thin films of materials like silicon, silicon carbide, graphene, and gallium nitride that are employed in the fabrication of electronic and optical devices. Gallium nitride (GaN) thin films are attractive materials for manufacturing optoelectronic device applications due to their wide band gap and superb optoelectronic performance. The reliability and durability of the devices depend on the quality of the thin films. The metal-organic chemical vapor deposition (MOCVD) process, which uses compounds that contain metals and organic ligands as precursors in a CVD reactor, is a common technique used to fabricate high-quality GaN thin films. The deposition rate and uniformity of thin films are critical to a successful and useful process. These are determined by the thermal transport processes and chemical reactions occurring in the reactor, and are manipulated by controlling the operating conditions and the reactor geometrical configuration. In this study, the epitaxial growth of GaN thin films on sapphire (Al2O3) substrates is carried out in two commercial MOCVD systems: a vertical rotating disk MOCVD reactor and a close-coupled showerhead MOCVD reactor. The surface morphology and crystal quality of GaN thin films have been examined using atomic force microscopy (AFM) and scanning electron microscope (SEM). This paper focuses on the composition of the precursor and the carrier gases since earlier studies have shown the importance of precursor composition. The results show that the flow rate of trimethylgallium (TMG), which is the main ingredient in the process, has a significant effect on the deposition rate and uniformity of the films. Also, the carrier gas plays an important role in deposition rate and uniformity. Using hydrogen as a carrier gas enhances the quality of the thin film but a lower deposition rate occurs on the wafer surface. On the other hand, a high flow rate of pure nitrogen gas improves the growth rate of the film. However, it decreases the uniformity of the film and promotes carbon contamination on the wafer surface. Thus, the use of an appropriate mixture of hydrogen and nitrogen as the carrier gas can improve the deposition rate and quality of GaN thin films.

Synthesis of narrow-band red-emitting SrLiAl3N4:Eu2+ phosphor and the study of its influencing factors on luminescence performance

In this paper, safer raw materials were used to synthesize SrLiA13N4:Eu[Formula: see text] phosphors under high purity nitrogen gas by high-temperature solid-state method, and the effects of activator doping concentration, calcination temperature, calcination time and matrix lattice cation substitution on their luminescence performance were studied. All the samples can emit red light effectively excited by ultraviolet or blue light, and the narrow-band red emission peak is at [Formula: see text]651 nm. Energy Dispersive Spectroscopy (EDS) results show that the Eu[Formula: see text] element has been successfully doped and uniformly distributed. The X-ray powder diffraction (XRD) pattern showed that impurities of AlN and SrO were present in the synthesized samples, and the impurity phase was significantly reduced or eliminated with the increase of calcination temperature. The relationship between luminescence intensity of phosphor and Eu[Formula: see text] doping concentration indicates that with the increase of Eu[Formula: see text] doping concentration, the luminescence intensity of powder first increases and then decreases, and the optimal doping concentration is 0.02. Concentration quenching will occur if the doping amount of Eu[Formula: see text] continues to increase. The addition of Ca makes it replace Sr in the crystal lattice, resulting in the reduction of field force in the lattice expansion crystal, resulting in the reduction of luminescence intensity, the red shift of emission peak, and the increase of half height and width. The results exhibit that SrLiAl3N4:Eu[Formula: see text] may be a more suitable phosphor than CaLiAl3N4:Eu[Formula: see text] as a narrow-band red component in white LEDs.

BLEND OF METAL OXIDES AND POLYANILINE ON PLATINUM ELECTRODES FOR DISSOLVED OXYGEN SENSORS

In this study, we report the detection of dissolve oxygen (DO) by using a blend of Ruthenium oxide and polyaniline (PANI) coated on platinum electrodes. Optical properties of the PANI were characterized by using Ultraviolet - Visible (UV-Vis) and Fourier-transform infrared (FTIR) spectroscopy. In order to study the sensitivity of the thin films of the PANI and PANI: Ruthenium oxide blend, cyclic voltammetry (CV) measurements was performed with the platinum electrodes coated with the thin films of PANI: Ruthenium oxide. The electrolyte solutions were prepared from the phosphate buffer and had the salinity of 20‰ and pH 7.3. The CV measurements were carried out when the electrodes were put in the electrolyte solutions which had various DO concentrations by purging pure nitrogen and oxygen gases. The DO concentrations in the experiments were measured by a commercial dissolved oxygen probe. The correlation between the current in the CV measurements and DO concentrations was determined. The effect of the blending ratio of the metal oxide and PANI on the electrochemical signal was also specified. The results showed that the platinum electrodes with PANI: Ruthenium oxide blend coating exhibited a high possibility as electrochemical sensor for detection of low levels of DO in aqueous phase.

Fabrication of In Situ TiN Ceramic Particle Reinforced High Entropy Alloy Composite Coatings by Laser Cladding Processing

Abstract In situ TiN ceramic particle reinforced FeCoNiCrMnTi high entropy alloy coating was fabricated by laser cladding processing at high purity nitrogen gas atmosphere on the AISI 304 stainless steel substrate. The effect of Ti addition on the microstructure, phase structure, and wear properties of the coatings was investigated. The results showed that the phase structure of the coatings was mainly face-centered cubic (FCC)-type γ phase. A few of cubic or flower-like TiN ceramic were formed after adding titanium into the FeCoNiCrMn powder. When atomic ratio of Ti exceeds 0.5, Laves phases appeared in the coatings. With increasing of Ti, the micro-hardness and wear resistance of the coatings increased, but friction coefficient and crack resistance of the coatings reduced. Suitable Ti content in the FeCoNiCrMnTix, laser composite coating, had higher resistance to adhesive wear, oxidation wear, and cracking resistance.