Effect Of Carbon Doping Research Articles

High-efficiency photocatalyst C@TiO2 with the synergy effect of carbon doping and phase transformation

High-efficiency photocatalyst C@TiO2 with the synergy effect of carbon doping and phase transformation

Carbon effect on tensile and wear behaviors for a dual-phase Fe61.5Cr17.5Ni13Al8 alloy

High entropy alloys (HEAs) series were produced by doping carbon into Fe61.5 Cr17.5Ni13-xAl8Cx (x = 0, 0.25, 0.5, and 1.5 at.%) by a vacuum arc melting. The carbon doping effect on the phase composition, mechanical properties, and wear behavior was studied. Fe61.5 Cr17.5Ni13Al8 alloy microstructure was a heterogeneous structure comprising FCC, BCC, and B2 phases. By introducing carbon into Fe61.5 Cr17.5Ni13-xAl8Cx (x = 0, 0.25, 0.5, and 1.5 at.%), the BCC phase fraction increased with decreasing FCC phase during annealing, accompanied by the formation of M23C6-like carbides at temperatures of 800 °C and 900 °C. The carbon-doped HEAs exhibited enhanced mechanical properties compared to the carbon-free HEAs, including higher tensile strength (1580 MPa), notable ductility (∼20 %), reduced friction coefficient (0.50), and improved wear resistance. Among the carbon-doped HEAs, the HEA with x = 0.5 at.% and annealed at 800 °C demonstrated exceptional wear resistance due to the compensations of attaining a balance between strength and elasticity.

Understanding the microstructure evolution of carbon-doped Sb2Te3 phase change material for high thermal stability memory application

The Sb2Te3 phase change material shows a growth-dominated crystallization mechanism with fast phase transition but poor thermal stability of the amorphous state. This work investigated the effects of carbon doping on the thermal stability, microstructure, and electrical properties of the Sb2Te3 material. The 10-year data retention temperature of the material increased to ∼147.3 °C and the size of the grains was limited to ∼10 nm by carbon doping. The formation of the C cluster upon crystallization was found at the grain boundaries, which was accelerated as the temperature increased due to the break of the Sb–C bonds. The memory device based on the carbon-doped Sb2Te3 material exhibited a switching speed of 15 ns and an endurance of ∼105 cycles with a resistance ratio of more than two orders of magnitude. This work suggests that the carbon-doped Sb2Te3 material is a promising candidate for memory applications that require high thermal stability, fast speed, and high endurance.

Effects of carbon doping on microstructure, electrochemical and tribo-corrosion performances of biocompatible TiZrNbTaMoCxNy coatings

To improve the longevity of medical devices in physiological environments, a series of TiZrNbTaMoCxNy coatings were fabricated on 316L stainless steel using RF magnetron sputtering. The work demonstrated that appropriate carbon doping can effectively enhance the density, electrochemical properties, and resistance to tribo-corrosion of the coatings. Among the tested samples, coating S4 with a carbon content of 24 at. % exhibited the lowest wear rate (6.496 × 10−7 mm3 N−1 m−1) during the tribo-corrosion tests, due to its favorable lubrication characteristic (COF = 0.127) and enhanced resistance to plastic deformation (H3/E2 = 0.78 Gpa). Additionally, coating S5 with a carbon content of 28 at. % showed superior electrochemical performance (icorr = 5.21 × 10−8 A), attributed to its higher coating density and ability to form passive films. Both S4 and S5 exhibited superior biocompatibility compared to 316L.

Tailoring thermoelectric properties through carbon doping and magnetic field variation: A comparative study in 2D h-BN and h-SiC

The purpose of this work is to study the effects of carbon doping on the thermoelectric properties of monolayer hexagonal boron nitride (h-BN) and hexagonal silicon carbide (h-SiC) in the presence of a magnetic field. We use a tight-binding model and Kubo formalism to calculate the effects of doping concentration, dopant type and applied magnetic field on the heat capacity, electrical conductivity, magnetic susceptibility, and thermoelectric figure of merit. Heat capacity displays a Schottky anomaly that is more prominent at lower dopant concentrations. In the presence of the magnetic field, the Schottky anomaly shifts to lower temperature and its intensity is reduced. The magnetic susceptibility of the doped structures is enhanced by both doping and a magnetic field. The p-type doped structures exhibit higher magnetic susceptibility intensity compared to the n-type doped structures, especially for h-SiC structure. The electrical and thermal conductivities rise from zero at low temperatures, with higher intensity for p-doped structures. Doped h-SiC has higher conductivity at low temperatures, but doped h-BN exceeds it at higher temperatures. A comparison of p- and n-doped h-SiC and h-BN reveals enhanced thermoelectric performance for p-doped structures, further improved by lower dopant concentrations and applied magnetic fields. Overall, the work provides new insights into optimizing the thermoelectric properties of doped h-BN and h-SiC nanostructures through doping and external fields.

Structural and Physicochemical Properties of Carbon Doped Boron Nitride Fullerenes: Effect of Doping Level and Atomic Arrangement

AbstractThe effect of carbon doping on the structural and physicochemical properties of B12N12‐xCx [4, 6]‐fullerenes (0 ≤ x ≤ 6) (BNFs) is studied in the frame of the density functional theory. All non‐symmetry related isomers are modeled. Although carbon doping reduces the cohesive energy of the BNFs, most of them remain stable. It is found that the location of carbon atoms in the lowest‐energy isomers follows a definite sequence as the doping level increases. The results indicate that substitutional carbon lowers the gap energy and chemical hardness of BNFs, but it increases their electronegativity and electrophilicity index. Particularly, carbon doping makes BNFs more susceptible to nucleophilic attacks. Additionally, the charge redistribution and structural asymmetry generated by carbon doping endows BNFs with polar character. A dipole alignment parameter is introduced to elucidate some correlation between the atomic arrangement and the polarity of the systems. While carbon doping enhances the capability of BNFs to interact with other chemical species, possible toxicity concerns are highlighted. Finally, possible fingerprints to identify successful carbon doping through infrared and UV–vis spectroscopy are proposed.

A numerical study of carbon doping effect on paraffin-reinforced silica aerogel mechanical properties: A molecular dynamics approach

Aerogels are different types of porous and solid materials that exhibit a strange set of extraordinary material properties. Aerogels have great potential for use in the fields of heat, sound, electronics, and especially thermal insulation. This paper investigates the influence of carbon doping concentration on the mechanical properties of paraffin-reinforced silica aerogel (PRSA). To do this investigation, Young’s module (YM), stress–strain curve, and ultimate strength (US) values at various carbon-doped particles of 1 to 10 % were reported by molecular dynamics (MD) simulation. The results show that the PRSA, under the influence of carbon doping, has dual performance. To be more precise, by adding the amount of carbon doped from 1 to 3 %, the US and YM of the PRSA rose from 329.96 and 1137.20 MPa to 353.73 and 1268.44 MPa. In other words, the mechanical strength of the PRSA increases in a limited ratio. However, by increasing carbon doping from 3 to 10 %, the US and YM of the PRSA reduced to 306.233 and 1041.88 MPa, respectively. So, it is expected that the mechanical behavior of the PRSA matrix to be manipulated with carbon doping for actual applications.

Structural evolution of Ru/Te interaction for hydrogen generation engineered by proof of concept via carbon doping

Catalyst support with low conductivity and weak metal-support interaction is a tricky issue in advanced catalyst development. Herein, taking the semi-conductive Te nanorods supported Ru nanoparticles as an example, we proposed a proof of concept for carbon doping to engineer the Ru/Te interaction for efficient hydrogen evolution reaction (HER). It was found that the conventional approach for carbon layer formation over Te nanorods via glucose by hydrothermal approach (Te–C-1) was insufficient to boost the catalytic performance, but the deep carbonization via further thermal annealing of Te–C-1 can enhance the conductivity and metal-support interaction when supporting Ru nanoparticles (Ru/Te–C-2). The important conductivity and charge transfer ability improvement and strong electronic interaction were found by the electrochemical measurements and the spectroscopic analysis, probably resulting from the deep carbonization induced Te nanorods structure destruction and in-depth carbon doping. As a result, Ru/Te–C-2 showed a catalytic performance as good as the commercial Pt/C catalyst for HER, which required ultralow overpotentials of 39 and 34 mV to achieve 10 mA cm−2 in 0.5 M H2SO4 and 1.0 M KOH, respectively, when loaded on the glass carbon electrode; Besides, the catalytic kinetics, charge transfer ability, and catalytic efficiency were also improved due to the carbon doping effect; high catalytic stability was also indicated by the dynamic stability running for 2000 cycles and steady-state operation for 20 h in both acidic and alkaline media. Density-functional theory calculations show that carbon doping effectively promotes the electron transfer from Te to Ru, thus changing the electronic structure and the adsorption energy for H* adsorption, which facilitates the HER process. The current study showed the validation of carbon doping for enhanced metal-supporting interaction that will be instructive for conductivity improvement of the relevant catalyst in electrocatalysis reaction.

DFT Calculation of Carbon-Doped TiO2 Nanocomposites.

Titanium dioxide (TiO2) has been proven to be an excellent material for mitigating the continuous impact of elevated carbon dioxide concentrations. Carbon doping has emerged as a promising strategy to enhance the CO2 reduction performance of TiO2. In this study, we investigated the effects of carbon doping on TiO2 using density functional theory (DFT) calculations. Two carbon doping concentrations were considered (4% and 6%), denoted as TiO2-2C and TiO2-3C, respectively. The results showed that after carbon doping, the band gaps of TiO2-2C and TiO2-3C were reduced to 1.58 eV and 1.47 eV, respectively, which is lower than the band gap of pure TiO2 (2.13 eV). This indicates an effective improvement in the electronic structure of TiO2. Barrier energy calculations revealed that compared to pure TiO2 (0.65 eV), TiO2-2C (0.54 eV) and TiO2-3C (0.59 eV) exhibited lower energy barriers, facilitating the transition to *COOH intermediates. These findings provide valuable insights into the electronic structure changes induced by carbon doping in TiO2, which can contribute to the development of sustainable energy and environmental conservation measures to address global climate challenges.

Effects of carbon doping on annealing behavior of a CoCrFeNiMn high-entropy alloy

A 1 at% carbon non-equiatomic doped Co19Cr5Fe38Ni19Mn19 high-entropy alloy was synthesized by vacuum arc-melting in a high-purity argon atmosphere, followed by homogenization, cold rolling, and annealing under various conditions. The evolutions of microstructure and mechanical properties during annealing were systematically studied and compared with the carbon free alloy. Results showed that nano-sized fibrous deformation grains were formed in the 90% cold rolled alloys, resulting in high strength but low plasticity. Recovery sub-structures and recrystallized grains gradually formed with increasing annealing temperature, leading to a significant decrease in defect density, thereby softening the materials and increasing their plasticity. The early stage of recovery was mainly related to the migration of vacancy and interstitial carbon atoms, while dislocation climb became the main recovery mechanism in the late recovery stage. The carbon-doped alloy exhibited a higher recovery activation energy compared with the carbon free alloy. Therefore, 1 at% interstitial carbon effectively increased the recovery and recrystallization resistance of the Co19Cr5Fe38Ni19Mn19 alloy.

Effect of carbon doping on corrosion resistance and conductivity of CrMoN-coated 316L stainless steel bipolar plates

Effect of carbon doping on corrosion resistance and conductivity of CrMoN-coated 316L stainless steel bipolar plates

Effect of carbon doping on the structure and superconductivity in AlB2‐type (Mo0.96Ti0.04)0.8${(\text{Mo}_{0.96}\text{Ti}_{0.04})}_{0.8}$B2

AbstractWe report the effect of carbon doping in Ti‐stabilized nonstoichiometric molybdenum diboride B2, which exhibits bulk superconductivity below Tc = 7.0 K. It is found that maintains the AlB2‐type phase with a uniform elemental distribution for x = 0.12 and 0.16. The substitution of carbon for boron leads to a slight increase in a‐axis, a remarkable reduction in c‐axis, the formation of planar defects along the (100) crystallographic planes, and a shift of the B 1s peaks toward higher binding energies. Contrary to B2, however, no superconductivity is observed down to 1.8 K for the C‐doped samples, which is ascribed to the electron filling of boron π bands resulting from the carbon doping.

The Effect of Carbon Doping on the Crystal Structure and Electrical Properties of Sb2Te3.

As a new generation of non-volatile memory, phase change random access memory (PCRAM) has the potential to fill the hierarchical gap between DRAM and NAND FLASH in computer storage. Sb2Te3, one of the candidate materials for high-speed PCRAM, has high crystallization speed and poor thermal stability. In this work, we investigated the effect of carbon doping on Sb2Te3. It was found that the FCC phase of C-doped Sb2Te3 appeared at 200 °C and began to transform into the HEX phase at 25 °C, which is different from the previous reports where no FCC phase was observed in C-Sb2Te3. Based on the experimental observation and first-principles density functional theory calculation, it is found that the formation energy of FCC-Sb2Te3 structure decreases gradually with the increase in C doping concentration. Moreover, doped C atoms tend to form C molecular clusters in sp2 hybridization at the grain boundary of Sb2Te3, which is similar to the layered structure of graphite. And after doping C atoms, the thermal stability of Sb2Te3 is improved. We have fabricated the PCRAM device cell array of a C-Sb2Te3 alloy, which has an operating speed of 5 ns, a high thermal stability (10-year data retention temperature 138.1 °C), a low device power consumption (0.57 pJ), a continuously adjustable resistance value, and a very low resistance drift coefficient.

Dual-effects of carbon doping on the recrystallization kinetics of the Cantor alloy during mid-temperature annealing

In this study, the comprehensive effects of carbon doping on the recrystallization process and the corresponding mechanical performance of the Cantor alloy during mid-temperature (700 °C) annealing were investigated. In the early stage of recrystallization, i.e., before 7 min annealing, abundant M23C6 carbides form preferentially along deformation bands and hence accelerate recrystallization process by providing dense heterogeneous nucleation sites. The fast consuming of the stored defects by recrystallization in this stage leads to the drastic decrease of strength but the regain of ductility. Detailed characterization on the precipitation behavior further shows that the initial fine carbide (≤10 nm in size) firstly enriches in carbon only, and then gradually grows to perfect M23C6 as controlled by the diffusion of Cr. In the later stage of recrystallization, e.g., after 7 min annealing, these carbides coarsen and Zener-pin grain boundaries from further migration, which in turn suppress the overall recrystallization process. In this stage the mechanical properties vary slightly as a result of the balance between the slowly deceased amount of hard non-recrystallized regions and the slowly increased carbide volume fraction.

Effect of carbon doping on magnetic flux pinning and superconducting performance in FeSe0.5Te0.5 single crystals

A series of carbon-doped single crystals with nominal composition FeSe0.5Te0.5 were synthesized by a self-flux method. X-ray diffraction indicated that the lattice parameter c increases with increasing carbon content, suggesting that carbon atoms enter the lattice. The critical current densities were measured and the flux pinning mechanism and its change with doping were analyzed. These samples showed a higher J c in high magnetic fields as well as a narrower superconducting transition. We studied the impact of the introduction of carbon into FeSe0.5Te0.5 on the temperature dependence of the irreversibility field H irr(T) and upper critical field (H c2). The pinning mechanism for the system was obtained via analysis of J c.

Ti3C2 MXene derived carbon-doped TiO2 multilayers anchored with Fe2O3 nanoparticles as anode for enhanced lithium-ion storage

Transition-metal carbides, carbonitrides, and nitrides (MXene) as an emerging two-dimensional semiconductor has open an ideal pathway for fabricating various TiO2-based functional materials. In this work, we demonstrate a simple and one-step heat treatment for the fabrication of Ti3C2 MXene-derived carbon-doped TiO2/Fe2O3 composite for superior lithium-ion batteries (LIBs). As an anode, the as-fabricated composite delivers an excellent lithium-ion storage of 538 mA h/g at a current density of 0.1 A/g and superior rate performance of 152.6 mA h/g at a higher current density of 5 A/g, which is 6 times higher than that of C-doped TiO2 electrode. In addition, a remarkable cyclic stability with 88.46 % capacity retention is also obtained for the composite anode at a current density of 1 A/g after 1000 cycles. Based on various characterizations, the greatly enhanced electrochemical performance can be attributed to the synergistic effects of carbon doping, layered structures of TiO2, and the anchoring of Fe2O3 nanoparticles, which effectively promote the charge transport kinetics. This study will broaden the Ti3C2 MXene application in LIBs and meanwhile provide an alternative method for synthesizing more efficient anode materials.

Effects of Carbon Doping and DC Bias Voltage on Microstructure and Mechanical Properties of AlCrCN Films Synthesized via HiPIMS.

This work compares the hardness and adhesion properties of AlCrN and AlCrCN hard coatings synthesized via HiPIMS using Al70Cr30 and Cr targets. The hardness and adhesion properties of AlCrCN films were optimized by performing deposition under various C2H2 flow rates (5, 8, 10, 13, 15, or 20 sccm) and DC bias voltages (−40, −60, −80, −100, or −120 V). EPMA results clearly indicated that the carbon content was increased from 1.9 to 12.2 at.% with increasing C2H2 flow rate from 5 to 20 sccm. XPS results confirmed a various content of chemical bonds (Cr-N, C-N, sp2, and sp3) with various C2H2 flow rate. Grain and columnar refinement in AlCrCN were derived from XRD, TEM, and SAED results. The higher hardness (28.6 GPa) and Young’s modulus (358 GPa) were obtained using an C2H2 flow rate of 5 sccm and a bias voltage of −60 V. Both of which subsequently decreased to 13.5 GPa and 212 GPa, respectively. This can be attributed to the C-N bond inhibiting the development of metal-N bonds. Increasing the bias voltage to −120 V increased the hardness to 32.9 GPa and the Young’s modulus to 372 GPa. Note that the application of bias voltage to enhance hardness should also be applicable to carbon-doped AlCrN films as well. All samples presented good adhesion characteristics (class 1; ISO26443:2008-06).

Biomass-derived carbon doping to enhance the current carrying capacity and flux pinning of an isotopic Mg11B2 superconductor

Low activation isotopic boron (11B) based magnesium diboride (Mg11B2) superconductors doped with biomass-derived activated carbon were synthesized using 11B and magnesium powder via solid-state reaction. The effect of carbon doping on the lattice structure and superconducting properties of Mg11B2 bulks were evaluated using X-ray powder diffraction, high resolution transmission electron microscopy, scanning electron microscopy and magnetization measurements. Precise refinement of structural parameters indicates successful substitution of carbon in Mg11B2 bulks. The critical current density (Jc) of carbon doped Mg11B2 synthesized at 650 °C was enhanced more than two times compared with the pure Mg11B2 bulk. Similar improvement was observed for the Mg11B2 bulks heat-treated at 800 °C. This enhancement is due to successful substitution of biomass-derived carbon with high surface area into Mg11B2 lattice. The flux pinning mechanism of pure and doped Mg11B2 bulks were investigated using the Dew-Hughes model. This study provides information regarding enhancement of the Jc of low activation Mg11B2 superconductors suitable for next-generation fusion magnets.

Rapid flame synthesis of carbon doped defective ZnO for electrocatalytic CO2 reduction to syngas

A strategy was established to develop a promising catalyst for electrochemical CO2 reduction to syngas. The ZnO doped carbon with oxygen vacancies was successfully prepared by rapid flame synthesis. Through manipulation of fabrication parameters, carbon compositions and oxygen vacancies in the catalysts were controllable. How the different contents of carbon doped in the catalyst effected on the electrocatalytic activities were investigated. Density functional theory (DFT) calculations reveal that carbon doping reduce the carbon monoxide desorption energy in rate-limiting step, which contributes to CO2 conversion to CO. The synergistic effect of carbon doping and oxygen vacancy in the catalyst transform the rate-determining step of the overall reaction and decrease the change in free energy for the formation of CO and H2, which facilitates the control of CO/H2 ratio in the syngas. The ZnO rich in carbon doping and oxygen vacancies exhibits large current density for CO2 electrochemical reduction of 27.07 mA/cm2 at -1.2 V vs. RHE, where the maximum FE for CO production is 71%. The range of CO/H2 ratio is adjustable and the maximum range is from 0.67 to 2.7, which is applicable for the further conversion of target fuels and chemicals. The carbon doped defective ZnO prepared by flame synthesis provides a new option for catalyst design.

Nitrogen Fixation at the Edges of Boron Nitride Nanomaterials: Synergy of Doping.

Synthesis of ammonia at ambient conditions is very demanding yet challenging to achieve due to the production of ammonia fuel, which is considered to be a future fuel for sustainable energy. In this context, computational studies on the catalytic activity of the edge sites of boron nitride nanomaterials for possible nitrogen reduction into ammonia have been investigated. Geometrical and electronic properties of zigzag and armchair B-open edges of BN sheet (BOE) models have been unraveled to substantiate their catalytic nature. Results reveal that BOE sites exhibit very high potential determining steps (PDS) of 2.0 eV. Doping of carbon (C) at the nitrogen center, which is vicinal to the BOE site reduces the PDS of the N2 reduction reaction (NRR) (to 1.18–1.33 eV) due to the regulation of charge distribution around the active BOE site. Further, the NRR at the C doped at various edge sites of a boron nitride sheet (BNS) has also been studied in detail. Among the 12 new C-doped defective BNS models, 9 model catalysts are useful for nitrogen activation through either chemisorption or physisorption. Among these, ZC N , AC N , and ZC BV models are efficient in catalyzing NRR with lower PDS of 0.86, 0.88, and 0.86 eV, respectively. The effect of carbon doping in tuning the potential requirements of NRR has been analyzed by comparing the relative stability of intermediates on the catalyst with and without carbon doping. Results reveal that C-doping destabilizes the intermediates compared to non-doped systems, thereby reducing the possibility of catalyst poisoning. However, their interactions with catalysts are good enough so that the NRR activity of the catalyst does not decrease due to C-doping.