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Aluminium metal matrix composites (AMMCs) are the fastest developing materials for structural applications due to their high specific weight, modulus, resistance to corrosion and wear, and high temperature strength. Carbon nanotubes (CNTs) is known as the material of the twenty-first century for its various applications in structural components for their high specific strength as well as functional materials for their exciting thermal and electrical characteristics. The present study comprise a systematic literature review of Al/CNT nanocomposites fabricated through a solid state friction stir processing. The present review is primarily focussed on the dispersion and survivability of CNTs in the Al matrix because these are the key factors in deciding the mechanical properties of the fabricated composite. Additionally, the formability, weldability and machinability of the FSPed fabricated composites reinforced with CNTs are also summarised here. Based on the detailed literature review, following research gaps are identified which require a critical and more focussed attention of the scientific community working in this research area: (i) the presence of agglomeration or clustering of CNTs in the composite, (ii) survivability and shortening of CNTs during FSP, (iii) interfacial reactions or the formation of reaction products (such as Al4C3) between Al matrix and CNTs, and (iv) the unidirectional alignment of CNTs in the fabricated composite. Important suggestions for further research in effective dispersion of CNTs with its preserved structure by FSP are also provided.

The synthesis of graphene and graphene quantum dots (GQDs) employing various approaches with a range of precursors, chemicals, and parameters has been reported. Most of the top-down and bottom-up techniques employ strong and hazardous chemical environments, complicated and tedious procedures, are time-consuming, and often require special equipment. Another drawback of the techniques reported is the production of agglomerated, inhomogeneous, and non-dispersible graphene in aqueous solvents or organic solvents, thus limiting its application. This work specifically and comprehensively describes the electrochemical exfoliation of graphene and GQDs, which is often considered as a simple one-step, facile, non-hazardous, and highly efficient technique yet favourable for mass production. A brief discussion on the advantageous and challenges of the electrochemical technique and applications of the electrochemically exfoliated graphene and GQDs is also presented.

We report the rapid single-step flame synthesis of hydrophobic carbon layers (C-layers) on the surface of stainless-steel (SS) substrates using vaporized biodiesel as the fuel. A co-flow canola methyl ester/air diffusion flame is used to generate a hydrophobic monolayer on the surface of the metal substrate upon its insertion into the reaction zone. Carbon deposition on the surface of the SS substrates varies by changing the SS disk’s position in the post-flame, and by varying its exposure time. The thickness and mass of the flame-formed monolayer varied depending on the substrate’s insertion point into the flame. However, the variation of mass did not significantly impact the C-layer’s uniformity or hydrophobicity. We hypothesize that a small “inner-cone” of the biodiesel flame along with a high soot propensity can result in an ideal medium to form uniform hydrophobic C-layers of unique hierarchical surface structure. This is supported by introducing SS substrates in methane/air flames formed using the same co-flow burner. The hydrophobic property of the carbon deposits was quantified by measuring the contact angle of water droplets placed on the film’s surface. A water droplet drop test was conducted on the flame-formed hydrophobic layers to study their wettability property.

The effect of multi-walled carbon nanotubes (MWCNT) coating in the presence of polyethyleneimine (PEI) of different molecular weights (MW) on the interfacial shear strength (IFSS) of carbon fiber/acrylonitrile–butadiene–styrene (ABS) and carbon fiber/epoxy composites was investigated. The IFSS between the carbon fiber and the polymer was evaluated by means of single fiber microbonding test. The results indicated that uses of the carbon fibers uncoated and coated with pristine, low MW PEI-treated, and high MW PEI-treated MWCNT significantly influenced the IFSS of both thermoplastic and thermosetting carbon fiber composites as well as the carbon fiber surface topography. The incorporation of low MW (about 1300) PEI into the carboxylated MWCNT was more effective not only to uniformly coat the carbon fiber with the MWCNT but also to improve the interfacial bonding strength between the carbon fiber and the polymer than that of high MW (about 25,000) PEI. In addition, carbon fiber/epoxy composite exhibited the IFSS much higher than carbon fiber/ABS composite due to the chemical interactions between the epoxy resin and amine groups existing in the PEI-treated MWCNT.

The present work reports the effect of different functionalization methodologies on surface modification of porous carbon and its efficacy for benzene adsorption. The virgin and surface-modified adsorbents were characterized by FTIR, N2 sorption analysis, SEM, and Boehm titration. The adsorption isotherms were measured at different temperatures using a highly sensitive magnetic suspension microbalance. At lower benzene concentration, the virgin carbon was found to possess reasonable adsorption capacity, while at higher benzene concentration, the surface-modified carbon tends to perform better. The maximum benzene adsorption capacity at 25 °C and vapor pressure of 90 mbar is as follows: 467 mg/g (NORIT-AC), 227 mg/g (AC-APS (1 M)), 388 mg/g (Norit-AC-HT), 492 mg/g (AC-HNO3), and 531 mg/g (AC-H2SO4).

The behaviour of semiconducting graphene quantum dots (GQDs), as good candidates for various biological carrier applications and optical sensing, are necessary to be studied under various conditions. In this study, GQD models were generated according to the geometrical and chemical specifications of synthesized GQDs to achieve the most realistic models. The GQDs’ bandgap and distribution of their electric surface charges were obtained using computational chemistry method. Finite element analysis was conducted on pristine and defective GQDs to study Young and shear modulus. Buckling load and resonant frequency modes of GQDs were calculated analytically and demonstrated under various boundary conditions. The dimension of GQDs has an average of 3.5 ± 0.4 nm, with an interlayer spacing of 0.36–0.40 nm. Computational chemistry studies revealed the characteristic zero-band-gap nature of graphene. Finite element studies showed that the by introducing the inevitable dislocation, mono atom vacancy and Stone–Wales defects to GQD models, their mechanical properties reduces to approach data from experimental investigations, whereas an increase in the number of layers does not influence the obtained results significantly.

We report the comparative study of electronic and optical properties of (6,1) SWCNT from GGA and DFT-1/2 methods. (6,1) SWCNT is a low-bandgap semiconductor, which falls within (n1−n2)/3≠ integer. The calculated bandgaps are 0.371 eV and 0.462 eV from GGA and DFT-1/2, respectively. Thus, DFT-1/2 enhanced the electronic bandgap by 24.52%. From both GGA and DFT-1/2 approaches (6,1) SWCNT exhibits an indirect bandgap along Γ−Δ symmetry. However, the percentage change in direct–indirect bandgap is negligibly small, i.e., 4.1% and 3.7% from GGA and DFT-1/2, respectively. The refractive index measured along x-axis (nx) approaches unity, indicating transparent behaviour, while that along z-axis (nz) goes as high as ∼3.82 for photon energy 0.0−0.15 eV, exhibiting opaque behaviour. Again, the value of nz drops below unity at photon energy ∼0.18 eV and again approaches ∼1 for higher energy ranges. The optical absorption is highly anisotropic and active within the infrared region.

In this study, nitric acid oxidation with varied treatment temperature and time was conducted on the surfaces of polyacrylonitrile-based ultrahigh modulus carbon fibers. Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and surface tension/dynamic contact angle instruments were used to investigate changes in surface topography and chemical functionality before and after surface treatment. Results showed that the nitric acid oxidation of ultrahigh modulus carbon fibers resulted in decreases in the values of the crystallite thickness Lc and graphitization degree. Meanwhile, increased treating temperature and time made the decreases more obviously. The surfaces of ultrahigh modulus carbon fibers became much more activity and functionality after surface oxidation, e.g., the total surface energy of oxidized samples at 80 °C for 1 h increased by 27.7% compared with untreated fibers. Effects of surface nitric acid oxidation on the mechanical properties of ultrahigh modulus carbon fibers and its reinforced epoxy composites were also researched. Significant decreases happened to the tensile modulus of fibers due to decreased Lc value after the nitric acid oxidation. However, surface treatment had little effect on the tensile strength even as the treating temperature and processing time increased. The highest interfacial shear strength of ultrahigh modulus carbon fibers/epoxy composites increased by 25.7% after the nitric acid oxidation. In the final, surface oxidative mechanism of ultrahigh modulus carbon fibers in the nitric acid oxidation was studied. Different trends of the tensile strength and tensile modulus of fibers in the nitric acid oxidation resulted from the typical skin–core structure.

The XYZ 3-dimensional thermal conductivities of the C/C up to 2000 °C were measured by a laser fash method. Carbon fberreinforced carbon composites (C/C) were generally developed for aerospace missions due to their excellent thermal resistivity at ultrahigh temperature. C/C must endure harsh environments such as thousands of degrees Celsius without degradation of its mechanical properties. To solve this problem, among the passive thermal protection system, we suggest a method of conducting more heat through the mono-axial direction, which resulted in ease of the thermal rise in the heat receiving part. For example, the X-43A fight applied unbalanced C/C (UCC) with diferent carbon fber orientation ratios according to the XY direction in the leading edge part. To investigate the diference in thermal conductivity between unbalanced C/C (UCC) and balanced C/C (BCC), unbalanced and balanced preforms were prepared by a needle punching process, and then they were densifed by pitch infltration and a carbonization process. We compared and analyzed the efects of unbalanced C/C(UCC) and balanced C/C (BCC) structures on the thermal conductivity. We also designed the “rule of mixtures” equation for calculating thermal conductivities of each C/C using reported data of carbon fber and graphite matrix. Our calculations of thermal conductivity ratio match the ratio of real data.

Vertically Aligned Carbon Nanotubes (VACNTs)-coated fexible aluminium (Al) foil is studied as an electrode for supercapacitor applications. VACNTs are grown on Al foil inside thermal Chemical Vapor Deposition (CVD) reactor. 20 nm thick layer of Fe is used as a catalyst while Ar, H2 and C2H2 are used as precursor gases. The efect of growth temperature on the structure of CNTs is studied by varying the temperature of CVD reactor from 550 °C to 625 °C. Better alignment of VACNTs arrays on Al foil is recorded at 600 °C growth temperature in comparison to other processing temperatures. Cyclic voltammetry results shows that VACNTs-coated Al foil has a specifc capacitance of~3.01 F/g at a scan rate of 50 mV/s. The direct growth of VACNT array results in better contact with Al foil and thus low ESR values observed in impedance spectroscopy analysis. This leads to a fast charge–discharge cycle as well as a very high value of power density (187.79 kW/ kg) suitable for high power applications. Moreover, wettability study shows that the fabricated VACNT electrode has a contact angle of more than 152° which signifes that it is a superhydrophobic surface and hence shows lower specifc capacitance in comparison to reported values for VACNT array. Therefore, it is necessary to develop suitable post-processing strategies to make VACNTs hydrophilic to realize their full potential in supercapacitor applications.

A simulation based (DFT) study is performed on activated 2D-carbon sheet without and with vacancies of central carbon atoms, and explored the electronic properties. The inter-atomic distance at the center of activated carbon sheet is gradually increased with increasing number of vacancies. We get lower binding energy with three vacancies, and higher without a vacancy. A covalent bond is found between C–C atoms, density of states exhibit a semiconductor nature of a system without vacancy, and metallic nature in the presence of vacancies. There are higher peaks of resultant anti-bonding states with three vacancy system and it exhibits higher amorphous nature which causes higher electron concentration, mobility and higher electrical conductivity.

Using frst-principles theory, this work investigated the Cu-doping behavior on the N-vacancy of the C3N monolayer and simulated the adsorption performance of Cu-doped C3N (Cu–C3N) monolayer upon two dissolved gases (H2 and C2H2). The calculations meant to explore novel candidate for sensing application in the feld of electrical engineering evaluating the operation status of the transformers. Our results indicated that the Cu dopant could be stably anchored on the N- vacancy with the Eb of − 3.65 eV and caused a magnetic moment of 1 μB. The Cu–C3N monolayer has stronger performance upon C2H2 adsorption than H2 give the larger Ead, QT and change in electronic behavior. The frontier molecular orbital (FMO) theory indicates that Cu–C3N monolayer has the potential to be applied as a resistance-type sensor for detection of such two gases, while the work function analysis evidences its potential as a feld-efect transistor sensor as well. Our work can bring benefcial information for exploration of novel sensing material to be applied in the feld of electrical engineering, and provide guidance to explore novel nano-sensors in many felds.

This study aims to investigate the efect of an aluminum chromium nitride (AlCrN) coating on tool wear and hole quality in the conventional drilling process of carbon fber-reinforced plastic (CFRP) composites, titanium alloy (Ti), and CFRP–Ti stack workpieces popular in the aerospace industry. The advanced arc plasma acceleration (APA) method of physical vapor deposition (PVD) was used for all AlCrN coatings. The drilling experiments were conducted with uncoated drills as well as AlCrN-coated drills. When drilling CFRP only, the AlCrN coating was removed at the drill cutting edges and the margin area, which suggests the carbon fbers abraded the coatings. When drilling Ti only, the AlCrN-coated drill mitigated the Ti adhesion formation, which resulted in less tool wear. In addition, hole quality for both CFRP and Ti was improved when the coating was used versus the uncoated tool. The machinability of CFRP–Ti stacks in the drilling process was improved by utilizing the advanced AlCrN coating on the WC tool in terms of drilling forces and

The purpose of this study was to remove lead and arsenic ions from aqueous solutions using the activated carbon prepared from Citrus limon tree leaves. Characteristics of the prepared adsorbent were studied thoroughly using BET, SEM, EDS and mapping, XRD, and RAMAN analyses. The results of experiments showed that the highest adsorption efciencies were 97.67% and 95.89% for Pb (II) and As (III), respectively. Additionally, the adsorbent was successfully regenerated four times and therefore it was able to perform the adsorption and desorption processes well. Moreover, the results of adsorption kinetics showed that the pseudo second-order kinetic model was more efective for the description of adsorption mechanism of both metals. Furthermore, the equilibrium studies indicated that Langmuir and Freundlich isotherm models were desirable for lead and arsenic ions, respectively

Nitrogen-doped carbon dots (CDts) with tunable fuorescence properties in aqueous media were synthesized hydrothermally. The excitation wavelength variation to obtain the maximum emission produced a blue shift in the emission peaks upon dilution in an aqueous solution. The shift can be explained by a re-absorption phenomenon in a concentrated solution. The interparticle interaction within was responsible to show dilution-dependent optical behavior. The as-synthesized solution of CDts did not show any prominent absorption peak over a wide range. However, upon dilution, two peaks became predominant. The concentration-dependent behavior was observed during the interaction with metal cations. Cationic salts of Co(II) and Hg(II) caused quenching at diferent dilutions of CDts. This might be explained by the exposure of diferent surface functional groups during dilution and metal-ion–CDts charge transfer. The quenched fuorescence of CDts was rescued using ascorbic acid. Therefore, the one-pot detection of Co(II)/Hg(II) and ascorbic acid was designed through a ‘Turn Of/On’ phenomenon.