Controlled Carbon Content Research Articles

Effect of SiCN thin film interlayer for ZnO-based RRAM.

This study investigates the effect of silicon carbon nitride (SiCN) as an interlayer for ZnO-based resistive random access memory (RRAM). SiCN was deposited using plasma-enhanced chemical vapor deposition (PECVD) with controlled carbon content, achieved by varying the partial pressure of tetramethylsilane (4MS). Our results indicate that increasing the carbon concentration enhances the endurance of RRAM devices but reduces the on/off ratio. Devices with SiCN exhibited lower operating voltages and more uniform resistive switching behavior. Oxygen migration from ZnO to SiCN is examined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses, promoting the formation of conductive filaments (CFs) and lowering set voltages. Additionally, we examined the impact of top electrode oxidation on RRAM performance. The oxidation of the Ti top electrode was found to reduce endurance and increase low resistive state (LRS) resistance, potentially leading to device failure through the formation of an insulating layer between the electrode and resistive switching material. The oxygen storage capability of SiCN was further confirmed through high-temperature stress tests, demonstrating its potential as an oxygen reservoir. Devices with a 20 nm SiCN interlayer showed significantly improved endurance, with over 500 switching cycles, compared to 62 cycles in those with a 5 nm SiCN layer. However, the thicker SiCN layer resulted in a notably lower on/off ratio due to reduced capacitance. These findings suggest that SiCN interlayers can effectively enhance the performance and endurance of ZnO-based RRAM devices by acting as an oxygen reservoir and mitigating the top electrode oxidation effect.

Facile Synthesis of SiOx/C Composite with Homogeneous Distribution of SiOx and Carbon as Anodes for Superior Lithium‐Ion Batteries

AbstractSiOx/C composites with uniform distribution of silicon oxide (SiOx) and carbon are promising anodes for lithium‐ion batteries. However, designing the SiOx/C composites with uniformly dispersed of carbon at nanoscale and controllable carbon content is still a challenge. Herein, a series of SiOx/C composites with uniform carbon distribution were prepared by sol‐gel method and subsequent pyrolysis process, the carbon content can be easily adjusted just by selecting different organosilanes. Due to the uniformly dispersed of carbon at nanoscale, the obtained products showed the excellent energy storage performance. Particularly, when Bis(triethoxysilyl)benzene (BTEB) was used as the raw materials, due to the appropriate carbon content, the SiOx/C−B exhibited a high reversible capacity of 535 mAh g−1 at 0.1 A g−1 over 100 cycles. The cycle stability is preserved even after 300 cycles at a high current density of 1.0 A g−1, where the electrodes still supply a specific capacity of 389.7 mAh g−1.

Zavarivost između čelika tipa 304H i čelika tipa P91 za primene na visokim temperaturama

This paper presents research about weldability between two dissimilar steels, martensitic steel P91 and 304H austenitic steel. Both materials are being preferred as a structural material for higher temperature applications due to their good mechanical properties at high temperatures. The mechanical properties at high temperature, such as tensile strength and creep resistance, are very important factors that ensure the application of materials. The P91 is modified martensitic Cr steel with higher amount of chromium which improves the higher temperature strength and molybdenum that increases creep resistance. On the other hand, the 304H represents advance austenitic stainless steel with controlled carbon content, which makes it ideal for applications requiring good mechanical properties at elevated temperatures. With increasing the demand of high efficiency in the power generation industry the high temperature applications usually require joints between advanced austenitic stainless steels and new class martensitic stainless steels in order to achieve the goal with the increased steam parameters. Therefore, this paper focuses on the weldability assessment between these two different steels and the characteristics of the weld metal.

Tailoring the tribo-corrosion response of (CrNbTiAlV)CxNy coatings by controlling carbon content

High-entropy carbonitrides exhibit excellent properties in friction and corrosion. Here, the tribo-corrosion response of (CrNbTiAlV)CxNy coating were studied in 3.5 wt.% NaCl solution at room temperature. The doping of carbon makes the coating structure dense. When the carbon content of the coating is 40%, the coating exhibits maximum hardness (20.21 GPa). As the carbon content increases, the synergistic effect of tribo-corrosion on the coating gradually weakens, and friction coefficient decreases. The coating with 40% carbon content has the smallest change in static and dynamic current density (0.14 ×10−8 A/cm2), the smallest friction coefficient (0.28), and the smallest wear volume loss. These results show that the coating can effectively protect the substrate in case of tribo-corrosion.

Investigation of ultrafine WC–Co–Fe–Ni–Cr3C2 cemented carbide microstructure and properties based on phase diagram thermodynamics

Abstract In this work, different Fe/Ni ratios with constant Co content were prepared to explore microstructure and properties of ultrafine WC-10 wt.%(Co–Fe–Ni)-Cr3C2 cemented carbides. The increase in Fe content in binder has difficulty in controlling carbon content. Therefore, the carbon window was determined by phase diagram to prepare carbon-balanced cemented carbides. The increase in Fe/Ni ratio in the binder deteriorates the uniformity of the binder phase distribution and refines the WC and binder phase grains by affecting the solubility of WC in binder and the wettability of the binder. Grain size, microstructural irregularities and solid solution strengthening of binder phase affect the mechanical properties of cemented carbides. The relative density of cemented carbide with Fe/Ni = 30:70 in the binder is 99.8 % and the transverse fracture strength is 2449 MPa maximum, but the fracture toughness is slightly low. Because of the passivation characteristics of Ni, the alloy with Fe/Ni = 0:100 in the binder has better resistance to corrosion resistance.

Analysis of a High-Strength Steel SMAW Database

Recently, Dr. Glyn M. Evans posted a large shielded metal arc (SMA) weld metal (WM) database on the ResearchGate website (researchgate.net). This database contains more than 950 WM compositions, along with their respective WM tensile and Charpy V-notch (CVN) impact properties. In particular, the CVN impact properties list the test temperatures that achieved 28 and 100 J impact energy for each WM composition. While the availability of this SMA WM database is a valuable and rare gift to the welding community, how could the welding community analyze this database to gain valuable insights? This paper utilizes a constraints-based model (CBM) as a simple and effective framework to organize and analyze this very large Fe-C-Mn SMA WM database. A CBM is built on the metallurgical principle that one needs to lower relevant solid-state phase transformation (i.e., austenite decomposition) temperatures to improve WM strength and fracture toughness while simultaneously reducing carbon content and Yurioka’s carbon equivalent number (CEN) to improve the weldability of high-strength steels. To this end, a CBM identifies and simultaneously solves several statistical (regression) equations that relate the chemical composition of high-strength steel WM with Yurioka’s CEN and selected solid-state phase transformation temperatures related to austenite decomposition. The results of the current effort demonstrate that the analysis of Evans’s shielded metal arc welding database using a CBM as a framework reaffirms that controlling carbon content, the value of the CEN, and calculated solid-state phase transformation temperatures, particularly the difference between the calculated Bs (bainite-start) and Ms (martensite-start) temperatures, is critical to developing and identifying high-performance, high-strength steel welding electrodes. A dual approach that manipulates the contents of principal alloy elements such as C, Mn, Ni, Cr, Mo, and Cu, and adds controlled amounts of Ti, B, Al, O, and N, appears to offer the best means to lower relevant solid-state phase transformation temperatures to produce high-strength and high-toughness WMs.

Facile synthesis of tungsten carbide-cobalt mixtures with clean surface and controllable carbon content

Tungsten carbide-cobalt (WC-Co) mixtures is the most critical material for cemented carbide. However, traditional preparation methods by using various carbon sources (e. g. carbon black, glucose, methane, carbon monoxide) cause severe carbon deposition. Consequently, traditional WC-Co mixtures exhibits uncontrollable carbon content. To address the challenge, we investigate the in-situ synthesis of WC-Co mixtures by supplying successive liquid methanol as a carbon source and nitrogen gas as a diluent. The as-prepared WC-Co mixture possesses clean surface and controllable carbon content, which are no need for removing excess carbon deposition by washing with water. The carbon nanolayers derived from methanol cracking gas appear on the surface of the intermediates, which can effectively prevent particle aggregation, efficiently increase the intimate contact probability of WC particles and Co particles, and greatly reduce the appearance of excess carbon deposition during subsequent carbonization processes. The present study offers insights on employing quantitative methanol cracking gas as reductive and carbonaceous atmosphere to mediate carbon content in the WC-Co composite powder, which presents a more economical and efficient pathway for large-scale synthesis of high-quality WC-Co mixtures with clean surface and controllable carbon content.

SiBNCx ceramics derived from single source polymeric precursor with controllable carbon structures for highly efficient electromagnetic wave absorption at high temperature

Precursor derived ceramic with controllable carbon content has the advantages of high temperature and adjustable dielectric properties, which has significant potential for the research the high temperature microwave absorbing materials. In this contribution, a series of single-source SiBNCx precursors are obtained using NH3, n-butylamine, and dichlorodiphenylsilane with n-butylamine as the carbon source ammonolysis trichlorosilylamino-dichloroborane (TADB) monomer and polymerization. Adjusting the carbon content of precursors directly leads to phase composition and performance differences of SiBNCx ceramics. For SiBNCx ceramics with no carbon or low-carbon content, it had almost no effect on electromagnetic waves. The transmission rate ranged from 98% to 78% in 2–18 GHz. When SiBNCx ceramics with carbon-rich structure, the tanδ of pyrolytic ceramics increased significantly, which has an obvious loss on electromagnetic wave. The minimum reflection coefficient (RCmin) values reached −64.75 dB, and the effective absorption bandwidth (EAB) was 3.8 GHz in the X band at room temperature. Importantly, EAB of the SiBNCx ceramics still cover more than 50% of the X band, RCmin can be as low as −24.9 dB at 600 °C. The strategy offers a new method to accurately control high temperature electromagnetic performance from molecular structure.

One-step combustion synthesis of carbon-coated NiO/Ni composites for lithium and sodium storage

Using carbon dioxide and nickel nitrate as the carbon and nickel sources respectively, a carbon-coated NiO/Ni (NiO/Ni@C) composite was synthesized via a one-step solution combustion method. Ethanolamine was used as the CO2 adsorption solution, with nickel nitrate dissolved in it to form the combustion precursor at a molecular level. The as-obtained NiO/Ni nanoparticles exhibited spherical morphology with an average size of 30 nm, and controlled carbon content ranging from 50 to 90 wt%. The NiO/Ni@C composites were investigated as anode material for lithium and sodium ion batteries, exhibiting high reversible specific capacity and excellent rate performance. The NiO/Ni@C-0.25 sample showed a reversible capacity of 125 mAh g−1 with a specific current of 0.1 A g−1 as sodium ion anode, and a capacity of 791 mAh g−1 with a specific current of 0.1 A g−1 after 150 cycles as lithium ion anode. Owing to the novel one-step combustion process and resulting superior electrochemical performance, the NiO/Ni@C composite is demonstrated as a prospective anode material for rechargeable lithium and sodium ion batteries.

VDM 601

Abstract VDM 601 (Nicrofer 6023 H) is a nickel-chromium-iron alloy with additions of aluminum and titanium. This alloy is specifically recommended for service above 550 °C (1020 °F) because of its superior creep-rupture properties resulting from its controlled carbon content and coarse grain size. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as heat treating, machining, and joining. Filing Code: Ni-769. Producer or source: VDM Metals GmbH.

Control of oxide non-metallic inclusions in production of IF steel

Modern trends in the automotive industry are aimed at reducing vehicle weight and increasing its safety. The high ductility of IF-BH steel in combination with increased strength allows the use of thinner rolled products in the car body structure. Achievement of high plastic properties in IF-BH steel is ensured by the low content of nitrogen and carbon (C <40 ppm, N <40 ppm) and controlled carbon content in the solid solution. The majority of sheet surface defects are associated with non-metallic inclusions. The presence of non-metallic inclusions in the finished product violates its homogeneity, deteriorates the surface properties of steel, fatigue strength and plastic characteristics of the metal. As a result of the work performed by the methods of fractional gas and micro-X-ray spectral analysis on a scanning electron microscope, metal samples of three IF-BH steel melts were analyzed, taken along the entire process chain of production. The main types of oxide non-metallic inclusions in the steel were quantitatively determined, as well as the total oxygen and nitrogen content in the metal. It is shown that the main types of oxide non-metallic inclusions in the investigated metal samples are aluminates, silicates and spinel. An increase in nitrogen content in the metal after breakdown of the vacuum on the VD was established, which indicates secondary oxidation of the metal. In metal of the samples in the section between the tundish and the crystallizer, nitrogen content in the metal increases which indicates the secondary metal oxidation. At the same time, the content of inclusions of aluminates in the metal increased and the number of inclusions of aluminum-magnesium spinel decreased. A mathematical model and software have been developed that describe the formation and removal of oxide nonmetallic inclusions. Adequacy of the program was confirmed by good convergence between the calculated and laboratory data on the total content [O] in various types of oxides for the first sample at the ladle-furnace unit and in the slab.

Heterogeneous interfacial engineering of Pd/TiO2 with controllable carbon content for improved direct synthesis efficiency of H2O2

Series of heterogeneous interfacial engineered TiO2 (C-TiO2) with controllable carbon content were facilely synthesized by incipient-wet impregnation using glucose and subsequent thermal carbonization. The obtained C-TiO2 were used as catalytic supports to load Pd nanoparticles for H2O2 direct synthesis from H2 and O2. The as-prepared samples were systematically studied by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), air isothermal microcalorimeter, temperature-programmed reduction of H2 (H2-TPR), and so on. The catalytic results showed that H2O2 productivity and H2O2 selectivity of Pd/C-TiO2 firstly rose with increasing carbon content and then declined. Pd/C-TiO2 catalyst with 1.89 wt% of carbon content showed the best catalytic performance that had 61.2% of selectivity and 2192 mmol H2O2/gPd/h of productivity, which were significantly better than those of pristine Pd/TiO2 (45.2% and 1827 mmol H2O2/gPd/h). Various characterization results displayed that the carbon species were heterogeneously dispersed on TiO2 surface. Moreover, no obvious geometric transformation in supports and Pd nanoparticles were observed among different catalysts. The superficial hydrophobicity of Pd/C-TiO2 was gradually promoted with increasing carbon content, which led to the corresponding decrease in adsorption energy of H2O2 with catalysts. According to structure-performance relationship analyses, the heterogeneous interfacial engineering of carbon could maintain the interaction of Pd nanoparticles with TiO2 and simultaneously accelerate the H2O2 desorption. Both factors further determined the excellent H2O2 direct synthesis performance of Pd/C-TiO2.

Understanding hydrophobicity variations in dense medium ferrosilicon from different production routes

Dense medium ferrosilicon (FeSi) powders produced via submerged arc furnace smelting, granulation, and milling route show varying hydrophobicity, sometimes totally nonwetting, amounting to production losses. This does not occur in powders produced via induction furnace smelting and atomization. Although wetting is fundamentally a surface phenomenon, bulk property can dictate surface behavior. Hence, for detailed insight into the cause of the variation, particles of powders from different production routes were studied from surface to the core. Particle shapes differ clearly for the two production routes, but this was found inconsequential to the wetting behavior. Rather, size distribution, proportion of ultra‐fine particles in the powder, was seen to have effect, being more in the nonwetting sample. From the optical microscopy: in the granular particles (that is, before milling), it is visible that different phases formed from the Fe‐Si‐C system, and this will impact milling differently; particles from nonwetting milled powders show a notable surface layer, and in contrast, the atomized particles show more homogeneous equiaxed grains. From X‐ray photoelectron spectroscopy, argon ions sputtering, and depth composition profiling, graphitic carbon (C1s at 284.5 eV binding energy) was found on the surface for all samples at levels above bulk alloy composition but highest (65%) for the totally nonwetting sample. From these pointers, graphite coating on particles is responsible for varying hydrophobicity. Carbon affects solid FeSi microstructure, milling, and powder properties. Controlling carbon content from the smelting stands out for avoiding milled FeSi hydrophobicity. This is however not a straight forward minimization problem.

Controlling the phenolic resin-based amorphous carbon content for enhancing cycling stability of Si nanosheets@C anodes for lithium-ion batteries

Carbon-coated Si nanosheets (Si NSs@C) nanocomposites with different carbon contents are successfully controlled and synthesized by the method of DC arc-discharge plasma, followed by phenolic resin pyrolysis at high temperature. The electrochemical performances of these nanocomposites as the anodes of lithium-ion batteries (LIBs) are investigated. The Si NSs with an average size of 31 nm and a thickness of 2.4 nm are surrounded by phenolic resin-derived amorphous carbon, forming a cladding structure. In the nanocomposites, Si NSs play a leading role in the reaction with Li+ ions, while the amorphous carbon mainly provides a highly conductive matrix for good contact among Si NSs active phases, which further facilitates the diffusion and transport of Li+ ions and electrons. The carbon matrix can also protect Si NSs from direct contact with the electrolyte, to ensure the formation of stable SEI films in cycles. Electrochemical performances indicate that the Si NSs@C nanocomposite electrode with the carbon content of 66.4 wt% delivers a stable discharge specific capacity of 822 mAh g−1 at a current density of 100 mA g−1 after 200 cycles and a better rate capability, confirming the predominant role of the controlled carbon content in the enhancement of the cycling stability of such Si-based anodes for LIBs.

Synthesis and densification of zirconium diboride prepared by carbothermal reduction

Using boron powder as additive, the preparation of zirconium diboride (ZrB2) by carbothermal reduction was investigated. The results show that the carbothermal reduction cannot be completely done until the temperature is more than 1900 °C. The ZrB2 particles prepared without boron (B) additive at 1900 °C for 3 h are rodlike and show a preferential grain growth along [001] direction. B additive changes the heat effect of the raw materials. With B additive, the morphology of ZrB2 particles turns to be regular shape. The average particle size is about 3.6 μm with 2.5 wt% B additives. With more B additive, the shape of particles turns to be round like and the average particle size is decreased to 2.3 μm when 5 wt% B is added. The existence of oxides in grain boundary is a key factor to keep ZrB2 ceramic from deep densification. Using ZrB2 powder prepared with 5 wt% B additives, by controlling carbon content in ZrB2 powder, ZrB2 ceramic with 93% relative density is hot-pressed.

γ-Iron Phase Stabilized at Room Temperature by Thermally Processed Graphene Oxide.

Stabilizing nanoparticles on surfaces, such as graphene, is a growing field of research. Thereby, iron particle stabilization on carbon materials is attractive and finds applications in charge-storage devices, catalysis, and others. In this work, we describe the discovery of iron nanoparticles with the face-centered cubic structure that was postulated not to exist at ambient conditions. In bulk, the γ-iron phase is formed only above 917 °C, and transforms back to the thermodynamically favored α-phase upon cooling. Here, with X-ray diffraction and Mössbauer spectroscopy we unambiguously demonstrate the unexpected room-temperature stability of the γ-phase of iron in the form of the austenitic nanoparticles with low carbon content from 0.60% through 0.93%. The nanoparticles have controllable diameter range from 30 nm through 200 nm. They are stabilized by a layer of Fe/C solid solution on the surface, serving as the buffer controlling carbon content in the core, and by a few-layer graphene as an outermost shell.

Single composite target magnetron sputter deposition of crystalline and amorphous SiC thin films

The formation of crystalline and amorphous SiC films by single-composite target magnetron sputter deposition process is demonstrated. In this process, graphite pieces were placed on a Si target to form a composite single target. The graphite coverage area (GCA) was varied between 4 to 18% to achieve controllable carbon content in the films with stoichiometry being achieved at ∼13% GCA. The films on Si substrates crystallized into the 21 H polytype of SiC, without any additional heating during deposition. However, SiC films deposited on quartz substrates under the same processing conditions are amorphous. These films show high transparency (greater than 80%) in the visible and near infrared regions with an optically measured band gap of 3.4 eV and refractive index of 1.96 at a wavelength of 1300 nm.

N-rich carbon coated CoSnO3derived fromin situconstruction of a Co–MOF with enhanced sodium storage performance

A series of CoSnO3–NC nanobox materials with controllable carbon content were acquired by thein situcarbonization of CoSnO3–MOFs, showing a controllable N-rich carbon content range from 7.5% to 24.6%.

Functionalization of Mesoporous Silicas as Strategy for Obtaining Nanocomposites with Controlled Graphitic Domains Quantity and Carbon Content.

We report in this work the use of a synthetic procedure to prepare silica-carbon composites with controlled carbon content and number of graphitic nanocarbon domains. This synthetic protocol was applied to prepare carbon nanostructures supported at two different amorphous silicas that have similar disordered pore system structure but different specific surface areas and pore volumes. The carbon nanostructures were obtained by the silica surface grafting with different amounts of 2,3-dihydroxynaphthalene (DN) using a dehydration reaction followed by pyrolysis at temperatures between 973 and 1173 K. We observed that the number of the graphitic nanodomains and the carbon loading at the pyrolysed samples could be tuned by the synthetic parameters during the functionalization and thermal treatment steps, as by the textural properties of the support.

Systematic Investigation of Carbon Supported Ru Based Chalcogenides As ORR Catalysts and Their Application in Safc

The primary consideration in enabling solid acid fuel cells operating at 250oC such as those using CsH2PO4 (CDP) from reaching commercial reality is based on the cost of the MEA, where noble metal loading is a critical factor. In addition there is the perennial issue of carbon corrosion. The former has been extensively considered in the seminal article by Gasteiger et. al.1 Typical operating conditions for CDP, 250oC, Reformate/Air are 200 mA/cm2, 0.7 V vs RHE. This translates to 120-140 mW/cm2. Considering the typical Pt loading of >3 mg/cm2 for CDP we have a requirement of 11-25 g(Pt)/KW. Contrast this with the current loading of 0.5-1.1 g(Pt)/KW at ≥ 0.65 V vs. RHE for a lower temperature (typically 800C) polymer electrolyte fuel cell, which represents a ten to twenty fold loading difference between the two types of fuel cell technologies. The goal therefore is to significantly lower Pt loading. This presentation critically examines the potential use of chalcogenides as oxygen reduction reaction (ORR) catalyst to either replace or embellish noble metal catalysts. Hence, the overall objectives of this effort and the associated portfolio of catalysts are specifically aimed at lowering the Pt loading requirement per KW as well as ensure durable performance over the lifetime of the fuel cell. While Pt based system is the focal point of ORR catalysis in acidic conditions, a wide range of non-noble group metals (non PGM) are viable options in alkaline condition. This disparity arises due to dissimilar double layer structures in acid and alkaline conditions, which provides a kinetic facility to the underlying electrode surface in alkaline media2. This presentation will demonstrate a detailed investigation of ruthenium based chalcogenide catalyst, which is a promising non PGM catalyst alternative. Mechanistic details showcasing ORR pathways in acid and alkaline electrolyte will be discussed. In addition to electrochemical data, in situ X- ray absorption spectroscopy (XAS) results will be discussed. Taking advantage of the XAS analysis, correlation with the electrochemical data will be drawn. The effect of chalcogen modification on Ru surface and a detailed description of the active site will be provided. Advantages such as controlled carbon content, limited carbon corrosion and resistance to anion poisoning suggest Ru based chalcogenide catalysts as potential cathode catalyst in fuel cells, such as solid acid fuel cell (SAFC). SAFC such as that using cesium dihydrogen phosphate as electrolyte exhibit anhydrous proton transfer (2) thereby enabling simpler humidification and balance of plant required for reformation of most fuels. Actual fuel cell polarization curves will be used to compare with comparable Pt/C cathodes. In conclusion, a comprehensive discussion on ruthenium based chalcogenide catalyst will be made, emphasizing on structural details, ORR mechanistic pathways and SAFC performance. Acknowledgement: The authors gratefully acknowledge the financial support from Arpa- E, US DOE under a grant led by SAF Cell Inc., Pasadena, CA. Use of Stanford Synchrotron Radiation Light Source (SSRL), Stanford Linear Accelerator Center is supported by U.S Dept. of Energy under contract number DE- AC02-76SF00515. Use of beamline 2-2 at SSRL was partially supported by National Synchrotron Light Source II, Brookhaven National Laboratory, under U.S Dept. of Energy under contract number DE-SC0012704.