N2 Flow Rate Research Articles

Photocatalysis, wettability and optical properties of N-doped Cu2O/CuO thin films for smart coating applications

Abstract Undoped and nitrogen (N)_doped Cu2O/CuO thin films were deposited via reactive DC magnetron sputtering. The deposition was carried out by sputtering the Cu targets under various Ar/N2/O2 gas flow ratios. The structural, optical, wettability, and photocatalytic performance of the deposited films were investigated. A simple cubic Cu2O crystallographic phase is observed for the undoped film, whereas mixed cubic Cu2O and monoclinic CuO phases (Cu2O/CuO) are observed for the N_doped films. EDAX revealed that as the N2 flow rate increased the amount of nitrogen incorporated into the film increased. The transmittance and reflectance are affected by the incorporation of nitrogen into the films. The transmittance values decreased with increasing N2 flow rate, whereas the reflectance values increased. Both the refractive index and extinction coefficient almost increased with increasing N2 flow rate. A noticeable optical band gap narrowing from 2.55 eV to 2.39 eV was detected upon increasing the N2 flow from 0.0 to 190 sccm. The photoluminescence spectrum of the undoped sample contains five distinct bands at 518, 612, 654, 714 and 825 nm. These five maxima are attributed to the radiative decay of bound and free excitons, and oxygen vacancies (VO) After nitrogen incorporation, the photoluminescence intensity decreases and then increases again with increasing N2 flow rate. A reduction in the water contact angle was observed with increasing N2 flow rate. Upon Vis-light illumination, the N_doped Cu2O/CuO films reached superhydrophilicity faster than the undoped film did. The photocatalytic performance of the deposited Cu2O/CuO films was strongly enhanced with a small amount of N doping. The deposited films are promising for self-cleaning and photocatalytic degradation of organic wastes.

A HYBRID MEREC-TOPSIS APPROACH FOR THE IMPROVEMENT OF PHYSICAL VAPOUR DEPOSITED TITANIUM CARBO-NITRIDE COATING

Titanium carbo-nitride (TiCN) comes under the metal nitride group which can provide a combined property of titanium carbide (TiC) and titanium nitride (TiN) coating. TiCN Coating possess an excellent mechanical and tribological, properties which leads its application in many industries particularly in the Automotive and aerospace industries. TiCN films can be very hard and strong based on the composition and synthesis process. Physical Vapor Deposition (PVD) technique is widely used for the preparation of thin film coating because of its ability to precisely control the composition and thickness of the coatings. The properties of the developed coating significantly affect by the PVD process parameters and their levels. Multi-Criteria Decision Making (MCDM) methods are widely used in many sectors for the selection of process parameters based upon some specific criteria. In the present work TiCN coatings were synthesized by using one of the most widely used PVD method called magnetron sputtering. L16 orthogonal array was used as a design of experiment for the experimental work by varying the sputtering process parameters like bias voltage, N2 flow rate and substrate to target distance. After the synthesis, the developed films were tested using atomic force microscopy (AFM), Scanning electron microscopy (SEM), and Nanoindentation. From the characterization three response parameters such as hardness (H), Modulus of elasticity (E) and surface roughness (Ra) of the coating has been considered. A hybrid method based on improved removal effects of criteria- technique for order performance by similarity to ideal solution (MEREC-TOPSIS) approach has been considered for the for the process parameters selection. The results have also been compared with other weight calculation techniques. In all the cases it is observed that experiment no 16 and 15 have got the 1st and second rank respectively. However, experiment no 1 is the last rank in all the cases. From the correlation analysis it is found a strong positive correlation between MEREC-TOPSIS and other methods. The method provides a significant advancement in the selection of optimal parameters, ensuring enhanced coating properties crucial for industrial applications.

Pyrolysis of hyphaene thebaica shell over ceramic tile dust-derived catalysts and assessment of the produced bio-oil

The purpose of this study is to demonstrate the potential of ceramic tile dust (CTD)-derived ZSM-5 zeolite (CZ) and its monodispersed composite with metal oxides (MgO and Fe2O3) in the catalytic pyrolysis of hyphaene thebaica shell (HTS). The HTS was pyrolysed in a Fixed-bed reactor at 400–600 °C, and 100–300 mL/min N2 flowrate. The maximum bio-oil production of 32 % was obtained at 500 °C and 150 mL/min N2 flowrate, with bio-oils containing 50 % acid and octadecenoic acids, as well as esters, phenols, aldehydes, ketones, ethers, aromatics, and hydrocarbons. A carboxymethyl cellulose templating agent was employed for the mesoporous zeolite synthesis from CTD. This resulted in the mesoporous zeolite with a predominant ZSM-5 crystal phase, exhibiting pore diameters ranging from 1.8-6 nm, 229 m2/g surface area and 1145 μmol/g total acidity. The catalytic pyrolysis of HTS was conducted using the ZSM-5 zeolite (CZ) and metal-oxide (MgO, Fe2O3, and Fe2O3/FeO) modified CZ, as monodispersed composite catalysts. Under best thermal pyrolysis conditions, CZ-Fe2O3, CZ-MgO, and CZ-Fe2O3/MgO demonstrated 22–23 % bio-oil yields. Notably, the CZ-Fe2O3/MgO catalyst exhibited the highest hydrocarbon yield at 16 %, while the CZ-MgO favoured the production of phenolics, esters, and alcohols. CZ-MgO also displayed the highest coking level at 7.5 %, indicating faster deactivation than the other catalysts. The synthesised catalysts exhibited remarkable catalytic activity, resulting in a notable improvement in the quality of bio-oils obtained from the intermediate pyrolysis of hyphaene thebaica shells in a fixed-bed reactor.

Structural, morphological, and chemical composition of ternary ZrHfN thin films deposited by reactive co-magnetron sputtering

This study focuses on a deposited ternary zirconium hafnium nitride (ZrHfN) thin film prepared using the reactive co-magnetron sputtering technique. The effect of the nitrogen (N2) flow rate on the films' structural, morphological, and chemical composition was investigated. The gracing-incidence X-ray diffraction (GIXRD) showed that all ZrHfN thin films exhibited a crystalline face-centered cubic structure with a strong (111) orientation. With increasing the N2 flow rate, the film's crystallography changed based on thermodynamic theory. The films demonstrated uniformity and homogeneity in their ternary nitride composition, as confirmed by transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) mapping and electron probe microanalyzer (EPMA). Chemical state analysis using X-ray photoelectron spectroscopy (XPS) indicated the presence of both nitride and oxynitride species in all samples. Notably, the atomic concentration of the main elements (Zr, Hf, and N) remained relatively stable over the controlled N2 flow rate range. However, the N2 flow rate played a crucial role in forming hafnium nitride and oxynitride chemical states, whereas it did not significantly influence the Zr phases, dominated by Zr oxides. Additionally, the hardness of the ternary ZrHfN thin films exhibited enhancement comparable to typical ternary nitrides.

Optimization of ethylene and propylene yields from n-hexane catalytic cracking over H-ZSM-5 catalyst using model based design of experiments (DOE)

Catalytic cracking of n-paraffins of varied carbon chain length (C6-C11) to represent light naphtha and gasoline was studied using extrudates of H-ZSM-5 (zeolite: binder = 70: 30) as a catalyst in a fixed bed reactor. Optimization of ethylene and propylene yields using model-based design of experiments (DOE) was carried out for n-hexane cracking by varying the temperature (550–650℃), weight hourly space velocity (3.3–9.9 h−1) and carrier gas (N2) flowrates (3–10 L/h). These variables showed significant effect on the conversion of n-hexane and yield of ethylene and propylene under studied reaction conditions. The Box-Behnken design coupled with response surface methodology was used to determine the effect of reaction temperature, WHSV and N2 flow rate on the yield of ethylene and propylene. Empirical models were constructed for the response variables namely n-hexane conversion, ethylene (E) yield, propylene (P) yield and total ethylene and propylene (E+P) yield. Main effect plot showed that the average yield of ethylene and propylene increased with increase in reaction temperature and decreased with increase in WHSV. The optimization study of multiple responses showed maximum 94.7% conversion of n-hexane and 46.1 wt% yield of ethylene and propylene at 650℃ catalyst bed temperature, 3.3 h−1 WHSV and 8.3 L/h N2 flow rate. The model predicted ethylene and propylene yields matched closely with experimental data for catalytic cracking of naphtha feed at 550 and 650℃ cracking temperature.

Microstructure and corrosion properties of Al1-xWxN coatings for potential use in gas turbine blades

Herein, a numerical approach of Al1-xWxN thin film coatings on Inconel 738LC superalloys for thermal barrier applications has been studied and the experimental analysis includes deposition of Al1-xWxN films on Si (100), glass and transparent quartz substrates at 40 % N2 flow rate using a dual target DC reactive magnetron sputtering technique to investigate the morphology, microstructure, chemical bonding and corrosion behaviour. AFM analysis revealed the rms roughness, Sq and average roughness, Sa increased with the increasing W content from 22 to 70 at.%. It was found that Al1-xWxN films tend to form tiny valleys on the film surface because the values of surface skewness, Ssk lie below zero. The TEM image showed a branched snowflake structure for the specimen of Al0.58W0.42N films with discrete spots in the SAED pattern, confirming the microcrystalline nature. The blue-shifting of Ecorr towards positive potential confirmed the lower corrosion resistance of WN films than those of AlN. XRD spectra of Al0.58W0.42N films showed an amorphous nature devoid of peaks, which is also confirmed by the SAED pattern. The quasi-passive oxide layer formation was spontaneous for WN films compared to the AlN films. The bending vibrations of AlN and WN showed the coordination environment of the metal centre in the Al1-xWxN films. The computational results indicated that the thermal barrier properties of Al1-xWxN films decreased with the increasing W content, i.e., AIN > Al0.58 W0.42N > WN.

A comparative study on the structure and properties of TiAlSiN coatings deposited by FCVA and HiPIMS

The TiAlSiN coating has garnered significant interest due to its exceptional hardness, high oxidation resistance temperature, robust film-substrate bond strength, excellent wear resistance, and superior thermal stability. The energetic ion beam technology has emerged as a potent method for fabricating thin films. In this study, TiAlSiN films were deposited utilizing magnetic filtered cathode vacuum arc (FCVA) and high power pulsed magnetron sputtering (HiPIMS), and their respective structures and properties were meticulously investigated and contrasted. Upon comparative analysis, it was observed that the elemental composition of the FCVA films underwent a pronounced change with the same. Depending on the desired film thickness, the deposition rate of the FCVA system was found to be superior over the same duration. The crystallographic structure of the films fabricated by both systems predominantly featured an fcc-(Ti,Al)N phase. Notably, at an N2 flow rate of 40 sccm, the film deposited via HiPIMS demonstrated remarkable hardness (27.04 GPa), an elevated H/E* ratio (0.103), and superior wear resistance (7.24×10−6 mm3/N∙m). The films produced by these two deposition methods exhibited discernible differences and clear trends in hardness, adhesion strength, and tribological properties. This research provides a valuable reference for selecting the most appropriate deposition process and parameters based on the desired attributes of the coatings.

Highly efficient and eco-friendly process for selective recovery of copper from waste printed circuit boards via pyrolysis and ammoniacal solvoleaching

This study proposes a process combining pyrolysis and ammoniacal solvoleaching to selectively recover Cu from waste printed circuit boards (WPCBs). Optimal pyrolysis conditions were determined by investigating parameters such as temperature, heating rate, N2 flow rate, holding time and particle size. Under the conditions: 500 °C temperature, 20 °C/min heating rate, 0.3 L/min N2 flow rate, 10 min time and +9.50 mm particle size, ∼25% of weight loss was obtained. The pyrolyzed mass underwent further physical separation process involving impact crushing, magnetic- and gravity separations to enrich metals into a concentrate. Copper in the resulting concentrate was selectively extracted using a one-stage ammoniacal leaching and solvent extraction process (ammoniacal solvoleaching), employing an oxime-based organic extractant, LIX 84-I with a small volume of NH4OH. Ammoniacal solvoleaching was optimized by considering parameters such as stirring speed, time, LIX 84-I concentration, volume of aqueous ammonia, temperature and pulp density. Under the following conditions: 500 rpm, 0.3/0.3/10 (g/mL/mL) of sample/NH4OH/LIX 84-I (0.8 M), 3 h time and 25 °C temperature, quantitative Cu dissolution was achieved after two-stage solvoleaching. Cu solvoleaching followed the Avrami model, with an activation energy of 28.95 kJ/mol in the temperature range 15–45 °C (298–318 K) for the mixed control mechanism. LIX 84-I could be recycled without loss of extraction performance. Cu concentration was further enriched during stripping stage using H2SO4. A flowsheet for the sustainable metal recovery from WPCBs was developed.

Operation enhancement of the H2 shaft furnace: a numerical study on the impact of N2 mixing in feed gas

Abstract Focusing on improving the performance of the hydrogen (H2)-based direct reduction shaft furnace (HSF), the current work was undertaken to evaluate the potential benefits of an operation featuring nitrogen (N2) mixing in feed gas using a computational fluid dynamics (CFD) model that describes the in-furnace gas-solid countercurrent reactive flows. A set of simulation cases was carried out under different N2 flow rates and top pressures. Variation in the latter operating parameter was conducted with the intent to mitigate the issue of H2 dilution caused by N2 mixing. The results showed that the in-furnace thermochemical state deteriorates if the N2 flow rate is inadequate. The state is gradually improved by increasing the N2 flow rate as more sensible heat is delivered into the process, thereby resulting in better degrees of solid reduction and H2 utilization. An increase in the top pressure gives rise to higher gas density that enhances the driving force and thus facilitates the reduction reaction. A higher solid reduction degree is consequently achieved by elevating the top pressure. When the top pressure exceeds 5.0 atm, however, the increase in solid reduction degree becomes marginal, while the energy required for compressing the feed gas continues to rise linearly.

High performance symmetric supercapacitors based on Au incorporated CrN thin films fabricated by reactive magnetron sputtering

Recently, transition metal nitrides are being investigated extensively as potential supercapacitor material. In the present study, Au incorporated CrN (Au_CrN) thin films have been synthesized using reactive magnetron co-sputtering technique for application as supercapacitor electrode material. Films have been prepared at different Ar to N2 flow rates keeping total deposition pressure constant to achieve the required structural phase in the sample. Electrochemical properties of the deposited materials have been investigated with a three-electrode system in 0.5 M H2SO4 aqueous electrolyte. The CrN thin film deposited under 3:1 Ar: N2 partial pressure or flow rate ratio shows the highest specific capacitance. Upon Au incorporation, the film shows an areal capacitance of 56.8 mFcm−2 at 1.0 mAcm−2discharge current density which is an almost nine-fold enhancement in specific capacitance value compared to pristine CrN sample. Symmetric supercapacitors have also been developed by sandwiching two identical Au_CrN thin film electrodes, which have found to deliver excellent specific capacitance of 86.03 mFcm−2at 1.0 mAcm−2 discharge current density with no decline in capacitance value till 20,000 cycles. Furthermore, it can deliver a high energy density of 52.02mWhcm−2and a power density of 0.12mWcm−2. The electrochemical properties of the supercapacitors fabricated with the Au_CrN thin film electrodes are found to be better than most of the results reported so far in the literature with CrN electrodes. Results of the present study clearly demonstrate that these Au enhanced CrN films prepared by easily scalable and highly reproducible magnetron sputtering technique have great potential as a high capacitance supercapacitor electrode material.

Structure and performance of N-doped amorphous carbon films (a-C: N) on stainless steel surfaces for bipolar plates in proton exchange membrane fuel cells

Stainless steel bipolar plates (BPPs) are anticipated to supersede traditional graphite BPPs in proton exchange membrane fuel cells (PEMFCs) owing to their superior machinability, enhanced mechanical strength, and cost-effectiveness. Nevertheless, stainless steel BPPs are susceptible to corrosion and dissolution in acidic environments over extended periods, leading to the formation of a passivation film that diminishes conductivity. In this study, amorphous carbon (a-C) films with varying N doping contents were deposited onto 304L stainless steel foil using the cathodic arc ion plating technique. This was achieved by manipulating the N2 flow rate. The research investigated the impact of N doping on the microstructure, corrosion resistance, interfacial contact resistance (ICR), and hydrophobicity of the a-C films on stainless steel surfaces. The findings reveal that the various a-C films significantly enhance the performance of 304L stainless steel under simulated PEMFCs operating conditions. While N-doped a-C (a-C: N) films are advantageous for reducing ICR, incorporating N results in a decrease in C-sp3 content and density, ultimately leading to a decrease in the corrosion resistance of films. Additionally, the hydrophobicity of the a-C films diminishes with increasing N content. Consequently, N doping is not conducive to improving the overall performance of a-C films on the surface of 304L stainless steel bipolar plates under simulated PEMFCs operating conditions.

Improving corrosion and conductivity of Ti-doped amorphous carbon film coated on 316L stainless steel bipolar plates by nitrogen atoms doping

Amorphous carbon films have recently attracted extensive attention as surface functional films for bipolar plates with excellent conductivity and anti-corrosion properties. In this research, to determine the influence of the amorphous carbon film doped with titanium and nitrogen on the efficiency of proton exchange membrane fuel cells (PEMFCs) and clarify the effect of N atoms on Ti doped amorphous carbon, a series of Ti, N co-doped amorphous carbon films are built on 316L stainless steel at different N2 flow rates. This study provides detailed research about the influence of N atoms content on the microstructure, morphology evolution, corrosion resistance and interfacial contact resistance (ICR) of Ti, N co-doped amorphous carbon films. The results reveal that the N doping of the Ti-doped amorphous carbon film has the potential to enhance the C-sp2 content and refine the grain. The characterization results indicate that introducing N atoms into Ti doped amorphous carbon can reduce the ICR of the film to 2.38 mΩ cm2. The introduction of N atoms can also enhance the anti-corrosive characteristics of the titanium singly doped amorphous carbon film. The Ti, N co-doped film can be used as candidate materials applied to metal bipolar plates.

Establishing aqueous two-phase flotation coupled with preparative high performance liquid chromatography and its application for the purification of astragalin from Flaveria bidentis

The strategy of aqueous two-phase flotation (ATPF) followed by preparative high performance liquid chromatography (prep-HPLC) was established and used for the separation of astragalin from Flaveria bidentis. In the ATPF, the effects of sublation solvent, solution pH, (NH4)2SO4 concentration in aqueous solution, cosolvent, N2 flow rate, flotation time and volumes of the PEG phase on the recovery of astragalin were investigated in detail, and the optimal conditions of ATPF were selected: 50 wt% PEG1000 ethanol solvent as the flotation solvent, pH 4, 350 g/L of (NH4)2SO4 concentration in 5 % ethanol aqueous phase, 40 mL/min of N2 flow rate, 30 min of flotation time, 10.0 mL of flotation solvent volume and twice. After ATPF enrichment, the flotation product was further purified by prep-HPLC. As determined by HPLC, the purity of astragalin was 98.8 %.

Enhanced production of naphtha-range compounds from arundo donax via catalytic fast pyrolysis using SAPO-11

Arundo donax, acknowledged for its elevated energy content, substantial biomass yield and rapid growth, stands as an alluring candidate for biofuel production. In this investigation, a molecular sieve-based catalyst was utilized to scrutinize the catalytic fast pyrolysis (CFP) of Arundo donax, aiming for the production of naphtha-range compounds. The study also encompassed the evaluation of pyrolysis product yields within a fixed-bed reactor. The systematic exploration included an assessment of the impacts arising from catalyst type, temperature, weight hourly space velocity (WHSV), and N2 flow rate. The results demonstrated that at 500 °C, WHSV of 1 h−1 and N2 flow rate of 300 ml/min, SAPO-11 exhibited a selectivity of 64.55% to naphtha-range compounds and 64.55% to isomerous naphtha-range compounds. This was in stark contrast to the control group, which contained no catalyst (with a selectivity of 41.40% and 3.19%, respectively), SAPO-41 (with a selectivity of 11.02% and 9.55%, respectively) and HZSM-5 (with a selectivity of 59.89% and 53.51%, respectively). Additionally, SAPO-11 yielded the highest bio-oil compared to other catalysts (SAPO-11 of 28.52 wt% > none of 19.48 wt% > HZSM-5 of 18.90 wt% > SAPO-41 of 13.11 wt%). The conclusions drawn from these findings imply that the synthesized SAPO-11 catalyst exhibited superior catalytic activity and isomerization proficiency in contrast to other catalysts (SAPO-41 and HZSM-5). Remarkably, under the specified conditions of SAPO-11 catalyst, temperature = 500 °C, WHSV = 1 h−1 and N2 flow rate = 200 ml/min, the CFP process yielded a remarkable maximum absolute yield of the naphtha-range compound at 25.82 wt%, with an isomerized naphtha-range compound absolute yield of 25.35 wt%.

Plasma Bombardment-Induced Amorphization of (TiNbZrCr)Nx High-Entropy Alloy Nitride Films

The (TiNbZrCr)Nx high-entropy nitride films (HENFs) were prepared by high-power pulsed magnetron sputtering (HPPMS). The effect of the N2 flow rate (FN) on the HPPMS plasma discharge, film composition, microstructure, residual stress, tribological properties, and corrosion resistance was investigated. Results show that, with the increase in FN, plasma discharge is enhanced. Firstly, the introduced N atoms react with Ti, Nb, Cr, and Zr to form an FCC nitride phase structure. Then, with the increase in plasma bombardment on the deposited film, the HENFs undergo amorphization to form an FCC+ amorphous structure, accompanied by a decrease in grain size and a change in the preferred orientation from (1 1 1) to (2 0 0). The HENFs deposited at FN = 8 sccm show the highest hardness of 27.8 GPa. The HENFs deposited at FN = 12 sccm present the best tribological properties, with a low wear rate of 4.0 × 10−6 mm3N−1m−1. The corrosion resistance of the (TiNbZrCr)Nx HENFs shows a strong correlation with the amorphous phase. The corrosion resistance of the FCC nitride film is the worst, and the corrosion resistance gradually increases with the amorphous transformation of the film. Based on the above results, nanocomposite high-entropy films can be prepared using HPPMS technology and exhibit excellent, comprehensive performance.

Characterization of Cr/CrN nano multilayers obtained through reactive sputtering with different degrees of unbalance in the magnetron

Nanoscale hard coatings of bilayers of Cr/CrN were obtained and characterized through unbalanced magnetron sputtering (UBMS) in an atmosphere of Ar and Ar + N2 on silicon and hardened and tempered H13 steel, with a degree of unbalanced K0 between 0.87 and 1.37. The deposition parameters were as follows: a power of 160 watts, Ar and N2 flow rates of 9 and 3 sccm, and a substrate target distance of 5 cm. A Gen coa VT 100 magnetron with varying degrees of unbalance, obtained by displacing its central magnet, was used. The electrochemical behavior of these coatings was characterized using the technique of potentiodynamic anodic polarization. The coatings' microstructure and hardness were analyzed via X-ray diffraction (XRD) and nanoindentation tests; Cr, CrN, and Cr2N phases were obtained, with a hardness that increases with the degree of unbalance between 18.90 and 24.97 GPa.

Microstructure evolution and mechanical properties of refractory high-entropy alloy nitride film

The (TiZrNbMo)Nx refractory high-entropy alloys (RHEAs) nitride films were fabricated using reactive magnetron sputtering by modifying the N2 flow rate ratio in the mixed N2 + Ar atmosphere. The incorporation of the N element induced a phase transition in the (TiZrNbMo)Nx films from body-centered cubic (BCC) to face-centered cubic (FCC) structure, accompanied by increasing in the amorphous phase. With the introduction of N2, the hardness of (TiZrNbMo)Nx films firstly increased significantly to 25.2 GPa when the N2 flow rate ratio was at 50 % and then decreased slightly to 18.5 GPa when the N2 flow rate ratio was at 75 %. Theoretical analysis shows that the doping of N element enhances the solid strengthening effect, with the formation of nitride phases and grain boundary (GB) strengthening effect significantly contributing to the enhanced hardness. Furthermore, the addition of N element can also inhibit grain rotation and GB sliding during deformation. This work provides a new insight into understanding the structure and properties of refractory high-entropy alloy films.

Nitrogen admixture effects on growth characteristics and properties of carbon nanowalls

The plasma functionalization of carbon nanowalls (CNWs) is of great interest due to their potential applications in electron field emission and energy storage devices. In this study, the effects of nitrogen on the growth and properties of CNWs are thoroughly investigated by varying a wide range of the N2 concentrations in the CH4/H2/N2 discharge plasma. Nitrogen-doped carbon nanowalls (NCNWs) were synthesized in a single-step growth using the hydrogen radical injection plasma-enhanced chemical vapor deposition technique. The formation of dense NCNWs was found to be enhanced by nitrogen and was three times higher in the sample with a 150 sccm N2 flow rate than in the sample without N2 addition (N-0). As the N2 concentration increased from 0 to 200 sccm, the morphology of CNWs changed from relatively straight to curly-like nanowall structures. A high-resolution optical emission spectroscopic observation shows that as N2 flow increased, CN radicals became the dominant species, suppressing the formation of C2 and CH. Photoelectron spectroscopy analysis revealed the nitrogen doping effect on graphene layers at high N2 concentrations. According to Raman and Transmission Electron Microscopy analyses, the NCNWs had more branched and thicker nanowalls with higher defect concentrations than the N-0 sample. The wettability of NCNWs was improved, particularly for the sample with a N2 flow rate of 150 sccm.

Influence of N2 Flow Rate on the Microstructure, Mechanical, and Tribological Properties of Ti-Al-Cr-N Coating: Dry Milling Investigation on 6061 Aluminum Alloy

Influence of N2 Flow Rate on the Microstructure, Mechanical, and Tribological Properties of Ti-Al-Cr-N Coating: Dry Milling Investigation on 6061 Aluminum Alloy

Development of Fe0 biochar composites synergistically activated with MgFe2O4 and Fe2+ through one-step pyrolyzing Fe sludge and MgCl2 for enhanced aqueous Cr(VI) removal

The surface passivation layer on Fe0 severely restricts its reactivity during environmental decontamination. In this study, a new composite—an Fe0 biochar composite (Fe0/BC) coupled with MgFe2O4 and Fe2+—was first developed for enhanced Cr(VI) removal by simple co-pyrolysis of Fe sludge (FS) with MgCl2. The characterization results demonstrated that MgFe2O4 and Fe0 could be formed simultaneously at 700 ℃. However, MgFe2O4 disappeared at temperatures of 800 and 900 ℃. By varying the flow rate of N2 and holding time, Fe0/BC was further optimized based on the determined MgCl2 to FS mass ratio (1.9:10.0) and temperature (700 °C). The optimal Fe0/BC (MBC700120-400–30) achieved a Cr(VI) removal efficiency of 97.67%, which was 2.43 times higher than that of the unmodified Fe0/BC obtained at 700 ℃. This enhanced reactivity was directly related to the electron transfer of Fe0 stimulated by MgFe2O4 as well as the conversion of passive corrosion products into Fe3O4 facilitated by soluble Fe2+ components. The predicted maximum adsorption capacity of MBC700120-400–30 was 85.43 mg/g (pH = 5) and the removal of Cr(VI) was dominated by chemisorption. The reduction of Cr(VI) to Cr(Ⅲ) was identified as the principal removal mechanism. Overall, this study demonstrates a novel strategy for developing functional Fe0-based materials for water contamination treatment.