Multilayer WNbN/WNbC, WN/WC and NbN/NbC Coatings: Vacuum-Arc Deposition Strategy and Microstructure Assessment

Emerging detection of carbon-based gases with multiple bonds by activating Mo[dbnd]O bonding in Na, Sb-codoped NiMoO4

Preparation and high-temperature oxidation behavior of a nanoscale remelting layer on TiBw/TC4 composites by electron beam remelting

Purpose. To evaluate the feasibility of electric resistance welding for corrosion-resistant steels with different phase compositions and thicknesses. Research methods. To investigate the characteristics of electric resistance welding for corrosion-resistant sheet steels with different structural classes, a comparative analysis of spot and roller welding methods was conducted. The analysis considered factors such as steel thickness, the combination of steel grades in the welded joint, and the available welding equipment. Experimental methods were employed to determine optimal welding parameters, including welding current (Tw), electrode compression force (Fw), and welding current pulse duration (τw). The strength of the welds was assessed using standard testing methods. Results. The study substantiates the selection of welding parameters for corrosion-resistant steels with different phase compositions, considering steel thickness and grade combinations. The steels studied – martensitic-ferritic class (06X18ч, 08X18ч) and ferritic class (03X18TБчГР, 05X18TФч, 08X18T1) – are suitable for electric resistance welding without significant restrictions. Scientific novelty. This study identifies the effects of welding parameters and the thicknesses of corrosion-resistant steel sheets with different phase compositions on the structure and mechanical properties of welds, both for homogeneous and dissimilar steel grades. Practical value. The findings demonstrate that the structure and mechanical properties of welds made from both homogeneous and heterogeneous steel compositions meet the functional requirements for various applications.

The dynamics of expansion, thermodynamics, and chemical reactions in laser-produced plasmas is of general interest for all laser ablation applications. This study investigates the complex morphology and behavior of reactive species in nanosecond laser-produced uranium plasmas. Comparing plasma morphology in various inert and reactive ambient gases provides information about the role of gas-phase chemistry in plume hydrodynamics. Background gases including nitrogen and argon foster collisional interactions leading to more significant plume confinement and the increase in persistence of uranium species. On the other hand, environments containing reactive gases such as oxygen promote chemical reactions between the plasma and ambient species. By comparing the expansion dynamics of uranium plumes in nitrogen, air, and argon, we discover that chemical reactions modify the hydrodynamics of the plume at later times of its evolution in the air background. Furthermore, we observe that varying the concentration of oxygen in the fill gas promotes different reaction pathways that lead to the formation of uranium oxides. The reaction pathways from atoms to diatomic to polyatomic molecules strongly vary with ambient oxygen concentration. Lower oxygen concentrations enhance the formation of uranium monoxide from atomic uranium, whereas higher oxygen concentrations tend to depopulate both atomic uranium and uranium monoxide concentrations through the formation of more complex uranium oxides.

In Taiwan, the force flower treatment of pineapple usually used calcium carbide (CaC2) solution, but it was unstable. For this reason, the object of this study was to clear the ingredients in CaC2 solution which affected flower induction and found chemicals that may be replaced CaC2 solution. Mature pineapple plants were treated with CaC2 solution, CaC2 gas (acetylene gas), ethylene gas, CaC2 solution without acetylene gas, or first treated with 1-MCP then CaC2 gas. Results showed that CaC2 solution, acetylene gas, and ethylene gas could induce plants to flower. Plants treated with 1-MCP or CaC2 solution without acetylene gas did not flower, suggesting that acetylene gas was the main ingredient in CaC2 solution which stimulated flowering. Most of the plants bloomed at 50 days after forced flowering. The nitrogen and calcium content in the green part of the leaves of flowering plants was higher than in non-flowering plants. And the ratios of total soluble sugar to total nitrogen in flowering plants were lower than in non-flowering plants. There were no significant differences in starch content and nitrogen/ calcium ratios between flowering and non-flowering plants. Ethylene production in leaf discs was induced by treatments with CaC2 supernatant liquid, CaC2 solution without acetylene gas, or CaC2 solution on leaf discs. Results showed that CaC2 supernatant liquid could induce more ethylene production than CaC2 solution did, but ethylene production was decrease after treatment with CaC2 solution without acetylene gas, suggested that the precipitates in the CaC2 solution could affect acetylene-induced ethylene production. The white-green and light green sections of D leaf in pineapple plants were found to produce the most ethylene. Leaf discs from these sections were examined for the ability to further produce ethylene by using chemicals and hormones. KH2PO4, 0.1mM kinetin, 0.5ppm IBA, K2HPO4, CaCl2, and Ca(NO3)2 could not induce leaf discs to produce more ethylene. However, there was obvious ethylene production by leaf discs after treatment with CuSO4, the highest ethylene production rate being from the concentration of 0.5mM CuSO4 at 25℃. But there was even more ethylene production when leaf discs were dipped in 5mM CuSO4 aqueous solution for 10 minutes. For example, the ethylene production rate for 5mM CuSO4 at 6-12 hr was 3.5 times higher than discs incubated in 0.5mM CuSO4. CuSO4 ability to produce ethylene may be stimulated by ACC synthase activity. Results also showed the leaf discs produced a large amount of ethylene after treatment with ethephon. Leaf discs could produce ethylene after CuSO4 treatment, so CuSO4 applying to the plants then evaluated the capability of flower induction. Pineapple plants were treated with CaC2 solution, oil-coated CaC2, different concentrations of CaCl2 or CuSO4 (0.5, 1, and 2mM), and ethephon for forcing flowers. Among them, ethephon treatment was more efficienct: 85% in flowering rate. The flowering rate of CaC2 solution and oil-coated CaC2 was 21%. Other treatments did not force flowering. The nitrogen content in the white part of D leaf was decreased with the forced flowering time, from 1.45 to 0.51%; and the green part of the leaf was maintained between 1 to 1.2%; but the nitrogen content in the green part of the leaf was significantly increased after ethephon forced flowering treatment. The total soluble sugar in the green part of the leaf before flowering by ethephon treatment was lower than other treatments, but starch had no significant difference between treatments. CuSO4 could induce considerable ethylene production from leaf discs but very little from whole plants. The reason for failure of flower induction may be due to the fact that the quantity of ethylene production was too low to induce flowering, or there was wax on the leaf surfaces which obstructed cupric ions from entering the leaf tissues and resulted in flowering failure.

It is commonly known that precipitation of secondary phase in non-ferrous alloys will affect the mechanical properties of them. But due to the nature of dual-phase low-alloy high-carbon steel and its high potential of precipitation of cementite, there is limited study on tailoring the mechanical and corrosion properties of this grade of steel by controlling the precipitation of different phases. Predicting and controlling precipitation behaviour on this grade of steel is of great importance towards producing more advanced applications using this low-cost alloy. In this study the new concept of selective-precipitation process for controlling the mechanical and corrosion behaviour of dual-phase low-alloy high-carbon steel has been introduced. We have investigated the precipitation of different phases using in-situ observation ultra-high temperature confocal scanning laser microscopy, image analyser – ImageJ, scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and electron probe microanalysis (EPMA). Volume fraction of each phase including retained austenite, martensite and precipitated phases was determined by X-ray diffraction (XRD), electrochemical corrosion test by Tafel extrapolation method and hardness performance by nanoindentation hardness measurement. The experimental results demonstrated that, by controlling the precipitations inside the matrix and at grain boundaries through heat treatment, we can increase the hardness of steel from 7.81 GPa to 11.4 GPa. Also, corrosion resistance of steel at different condition has been investigated. This new approach will open new possibility of using this low-cost steel for high performance applications.

Nitriding process using ammonia gas as a nitrogen source has been carried out with the aim of improving the surface quality of nodular cast iron until the highest surface hardness reaches 426.2 HV. In this study, the nitriding process was carried out with a variety of advanced processes using nitrogen gas in the fluidized bed reactor and without using nitrogen gas in the muffle furnace with a constant variable nitriding time of 4 hours. The continued process is 2 hours each, while the gas composition used is 80% ammonia and 20% nitrogen with a total gas flow of 0.7 m2 hour−1. From the result of SEM test analysis obtained in the advanced process variations with nitrogen gas in the fluidized bed reactor and without nitrogen gas in the muffle furnace, on the surface of nodular cast iron a nitride layer was formed in the form of Fe3N and Fe4N. The largest average thickness formed in advanced process specimens using nitrogen gas in the fluidized bed reactor was 24.64 µm and without using nitrogen gas was 6.06 µm. The EDX test analysis showed that the specimens that received treatment with nitrogen gas had a nitrogen gas content of 43.7% higher than the specimens that did not receive the treatment. The hardness test results showed the distribution of hardness values in specimens that received treatment with nitrogen and without nitrogen. The highest surface hardness is 560.6 HV on the surface of the specimen with nitrogen gas while the specimen without nitrogen gas has a hardness of 426.2 HV.

Abstract. Global climate change is one of the most important scientific, societal and economic contemporary challenges. Fundamental understanding of the major processes driving climate change is the key problem which is to be solved not only on a global but also on a regional scale. The accuracy of regional climate modelling depends on a number of factors. One of these factors is the adequate and comprehensive information on the anthropogenic impact which is highest in industrial regions and areas with dense population – modern megacities. Megacities are not only “heat islands”, but also significant sources of emissions of various substances into the atmosphere, including greenhouse and reactive gases. In 2019, the mobile experiment EMME (Emission Monitoring Mobile Experiment) was conducted within the St. Petersburg agglomeration (Russia) aiming to estimate the emission intensity of greenhouse (CO2, CH4) and reactive (CO, NOx) gases for St. Petersburg, which is the largest northern megacity. St. Petersburg State University (Russia), Karlsruhe Institute of Technology (Germany) and the University of Bremen (Germany) jointly ran this experiment. The core instruments of the campaign were two portable Bruker EM27/SUN Fourier transform infrared (FTIR) spectrometers which were used for ground-based remote sensing measurements of the total column amount of CO2, CH4 and CO at upwind and downwind locations on opposite sides of the city. The NO2 tropospheric column amount was observed along a circular highway around the city by continuous mobile measurements of scattered solar visible radiation with an OceanOptics HR4000 spectrometer using the differential optical absorption spectroscopy (DOAS) technique. Simultaneously, air samples were collected in air bags for subsequent laboratory analysis. The air samples were taken at the locations of FTIR observations at the ground level and also at altitudes of about 100 m when air bags were lifted by a kite (in case of suitable landscape and favourable wind conditions). The entire campaign consisted of 11 mostly cloudless days of measurements in March–April 2019. Planning of measurements for each day included the determination of optimal location for FTIR spectrometers based on weather forecasts, combined with the numerical modelling of the pollution transport in the megacity area. The real-time corrections of the FTIR operation sites were performed depending on the actual evolution of the megacity NOx plume as detected by the mobile DOAS observations. The estimates of the St. Petersburg emission intensities for the considered greenhouse and reactive gases were obtained by coupling a box model and the results of the EMME observational campaign using the mass balance approach. The CO2 emission flux for St. Petersburg as an area source was estimated to be 89 ± 28 ktkm-2yr-1, which is 2 times higher than the corresponding value in the EDGAR database. The experiment revealed the CH4 emission flux of 135 ± 68 tkm-2yr-1, which is about 1 order of magnitude greater than the value reported by the official inventories of St. Petersburg emissions (∼ 25 tkm-2yr-1 for 2017). At the same time, for the urban territory of St. Petersburg, both the EMME experiment and the official inventories for 2017 give similar results for the CO anthropogenic flux (251 ± 104 tkm-2yr-1 vs. 410 tkm-2yr-1) and for the NOx anthropogenic flux (66 ± 28 tkm-2yr-1 vs. 69 tkm-2yr-1).

Theoretische Modellierung aktiver Zentren von molybdänabhängigen Enzymen

Using DC- Plasma Enhanced Chemical Vapor Deposition (PECVD) system, the impact of pure Co on the growth of diamond-like carbon (DLC) nano-structures was investigated. In this study, Acetylene (C2H2) was diluted in H2 and used as the reaction gas and Co nano-particles were used as the catalyst. The effect of preparing Co catalyst on temperatures of 240ο C and 350ο C and growth conditions was studied. The results showed that the Co catalyst sputtering at 350ο-C temperature has a significant impact on purity, morphology, and synthesized diamond-like carbon nano- structures. This research was conducted to investigate the effect of catalyst preparation and growth conditions. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy were used to characterize the diamond-like carbon nano- structures produced under different conditions.Using DC- Plasma Enhanced Chemical Vapor Deposition (PECVD) system, the impact of pure Co on the growth of diamond-like carbon (DLC) nano-structures was investigated. In this study, Acetylene (C2H2) was diluted in H2 and used as the reaction gas and Co nano-particles were used as the catalyst. The effect of preparing Co catalyst on temperatures of 240ο C and 350ο C and growth conditions was studied. The results showed that the Co catalyst sputtering at 350ο-C temperature has a significant impact on purity, morphology, and synthesized diamond-like carbon nano- structures. This research was conducted to investigate the effect of catalyst preparation and growth conditions. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy were used to characterize the diamond-like carbon nano- structures produced under

Nowadays a vast majority of the steel produced worldwide is via the continuous casting process route because this is the most low-cost, efficient and high quality method to mass produce metal products in a variety of sizes and shapes. Most of the continuous casters are the initial manufacturing step of a product which is very close to the final shape, reducing the need for further finishing. During continuous casting the liquid steel is solidified under controlled conditions of heat extraction to a semi-finished product that can subsequently be processed until final shape is reached. However, there is no perfect process and cracking during solidification of continuously cast steel slabs has been one of the main problems in casting for many years. In literature many terms are used for the phenomenon of crack formation at temperatures close to the solidus temperature, e.g. hot tearing, hot shortness, hot cracking or solidification cracking. Regardless of the name, hot tears represent a failure that occurs during casting in the regions of a solidifying slab that are at temperatures between solidus (TS) and liquidus (TL) and are subjected to simultaneously acting tensile and compressive stresses. The three steel grades considered in this study are a Low carbon aluminium killed (LCAK) steel grade, a high strength low alloyed (HSLA) steel grade, micro-alloyed with extra additions of vanadium, nitrogen and niobium, and a low-range HSLA (LR-HSLA), with the same concentration of niobium but a lower concentration of vanadium and nitrogen. The purpose of this study has been to investigate the differences between these three steel grades, with respect to hot tearing sensitivity upon solidifying in a thin slab caster. This research originates from the industrial demand for defect-free high-speed casting of steels and this thesis focuses on the thermo-mechanical behaviour of steel grades in relation to the solidification conditions in the continuous casting mould. Although these steel grades are not very different in chemical composition, thermodynamic calculations showed that the two HSLA steel grades have different propensity to the peritectic reaction upon solidification due to the combination of elements in the chemical composition that are either ferrite or austenite stabilisers. In order to better understand the special behaviour of the HSLA grade, compared with the LR-HSLA and the potential precipitation of TiN, phase field microstructure simulations have been performed, showing that TiN can form already during the latest stage of solidification, even when very low amounts of this element are present. If TiN particles trigger the coalescence of dendrite trunks, then it is possible to understand why, for a given Ti content an increased N content present in the HSLA grade can help to reduce the risk of hot tearing. Segregating elements in steel can influence the hot tearing susceptibility as they can widen the brittle temperature range (?TB), displacing its lower limit to lower temperatures. Unique hot tensile tests were carried out in the temperature range involving solidification, where the results suggest that among the studied steel grades, the LCAK steel grade has the lowest strength during solidification and a broader ?TB. Fractographic studies of the samples fractures above the non-equilibrium solidus revealed low melting phases even at temperatures as low as 1360 oC. These low-melting films do have an effect on the hot tearing behaviour of commercial steel grades. The LCAK is particularly prone to develop non-metallic particles at the last stages of solidification. Whilst the study with the Mould Cracking Simulator did not confirm the increased hot tearing susceptibility of the LCAK and LR-HSLA, it did partially substantiate that the modifications on its design are novel in the way that no other physical model of cracking during continuous casting is able to simulate the process in such a way that it resembles the industrial process. Despite the alloys tested during the first few experiments were not the same alloy compositions studied in this thesis, the results of the Mould Cracking Simulator are very promising. It is expected that this new physical model will help in the study of the thermomechanical properties of commercial steels motivated by the continuous trend towards improved casting productivity by increasing casting speed and higher quality, as well as for the development of new steel grades.

Fatigue crack growth behaviour of wire arc additively manufactured steels

Synthesis–structure correlations of manganese–cobalt mixed metal oxide nanoparticles

ABSTRACTTiN film is applied as a diffusion barrier and an adhesion promotion layer in the ultralarge scale integrated circuit (ULSI) devices. These TiN thin films are usually deposited by sputtering and chemical vapor deposition (CVD) methods. The CVD method is now studied intensively due to its satisfiable step coverage and compatibility with current device fabrication process. There are several different CVD methods already proposed such as LPCVD, MOCVD and PECVD. These proposed CVD methods have many disadvantages such as impurity incorporation and particle generation due to gas phase reactions between source and reactant gases. To solve these problems, we propose a new CVD method to reduce impurities and particles which is the pulsed source chemical vapor deposition (PS-CVD) method. In this method, the source, reactant and purge gases are introduced into reaction chamber, separately. TiN films are deposited using TiCl4, NH3 and Ar by alternately introducing into reaction chamber. In detail, TiCl4 source is introduced and adsorbed on Si substrate and then Ar gas purges this source gas. Continuously, NH3 gas in supplied into reaction chamber and adsorbed on the Ti-adsorbed Si substrate and then Ar gas is again introduced to purge NH3 gas. These four steps are one cycle. The main variables in this experiment are source pulse time, source purge time, reactant pulse time, reactant purge time, and so on. The deposition characteristics are also different depending on substrate temperatures. Above the thermal decomposition temperatures, the film thickness is a function of the source pulse time like conventional CVD. Below the thermal decomposition temperatures, the film thickness is saturated and exhibits a constant value in this temperature range. The TiN film thickness depends only on the number of deposition cycle. The process window were determined by experimentally in this temperature range. Process variables were established, and then TiN films were deposited. The characteristics of this TiN diffusion barrier were analyzed. The surface microroughness, the chemical composition and contaminant contents were measured by AFM, SEM and AES. A crystal structure and the phase identification were performed with using XRD and the sheet resistance was measured by a four point probe. These results will be discussed and compared with the results of TiN formed by sputtered and conventional CVD methods.

Feasibility of aluminium nitride formation in aluminum alloys