Silicon Carbide Nanotubes Research Articles

Production of aluminium foams reinforced with silicon carbide and carbon nanotubes prepared by powder metallurgy method

In this study, aluminium foams reinforced with silicon carbide and carbon nanotubes were produced by powder metallurgy method. The master alloy aluminium powder (AlSi12) was used as the matrix material, titanium hydride (TiH2) powder was used as a foaming agent and silicon carbide (SiC) particles and carbon nanotubes (CNTs) were used as reinforcing elements. Therefore, 1% of TiH2 by weight and different proportions of SiCx/CNTy (x: 0%, 2%, 4%, 6%, y: 0%, 0.2%, 0.5%, 0.8%, 1%) were added into the master alloy AlSi12 powder and mixed. The mixed powders were further pressed at a pressing pressure of 600 MPa and a temperature of 430 °C. The pressed samples were subjected to the extrusion process at 430 °C, and samples having diameters of 11.76 mm were produced. The foamable precursor materials that were obtained in this manner were subjected to the foaming process at a temperature of 750 °C. The experimental results exhibited that the relative density values of more than 94% were obtained from the foamable precursor materials. It was determined that the CNT and SiC particles significantly affected the elastic–plastic deformation behaviour of the precursor materials. Further, increasing tendencies have been observed in the case of Young's modulus and averege stress in composite foams depending on an increase in the number of CNT and SiC particle.

Synthesis of novel hybrid carbon nanomaterials inside silicon carbide nanotubes by ion irradiation

A novel hybrid carbon nanomaterial was synthesized by ion irradiation of a C–SiC coaxial nanotube. The hybrid consisted of one-dimensionally stacked graphene nanodisks with diameters less than 50 nm and cylindrical multiwalled carbon nanotubes inside an amorphous SiC tubular layer. A sudden emergence of new continuous graphitic layers in the microstructure were observed by in situ transmission electron microscopy following ion irradiation, where these layers were perpendicular to the nanotube's length direction. The SiC crystals in the C–SiC coaxial nanotube became amorphous, also due to the ion irradiation, although the critical amorphization dose was higher than that for bulk SiC. Most remarkably, the carbon layer remained crystalline, even after an irradiation dose higher than 20 dpa (displacement per atom). Such results show that these carbon layers possess better resistance against amorphization when subjected to ion irradiation than the SiC layers in the C–SiC coaxial nanotube. The lattice plane spacing of the carbon layer increases up to the point when irradiation damage lead to the complete amorphization of SiC crystals, after which it starts to decrease. This demonstrates that the carbon layer experiences high compression stress during ion irradiation. Thus, the ion irradiation of C–SiC coaxial nanotubes gives rise to a novel development of the microstructure and can be considered as one of the new synthetic processes for making novel carbon nanomaterials.

Mechanics and dynamics of lysozyme immobilisation inside nanotubes

Lysozyme is an enzyme often used as an antibacterial agent in food industries and biochemical and pharmaceutical laboratories. Immobilisation of lysozyme by encapsulating in a nanotube has received much interest as it can enhance stability of the enzyme in ambient condition. Experimentally, various types of nanotubes have been proposed as a host for lysozyme. Here, we mathematically model the immobilisation process and the interaction between lysozyme and various types of nanotubes in order to compare the effectiveness of different nanotube materials. In this paper, we consider boron nitride, carbon, silicon, silicon carbide and titania nanotubes. For each type of nanotubes, we determine the critical radius that will maximise the interaction between the lysozyme molecule and the nanotube. Our results suggest that titania nanotube stands out as the most promising candidate for lysozyme storage and delivery. The model presented here can be extended to further investigate the interaction between different types of nanotube materials and protein structures for the development of effective molecular storage.

Surface modification of Al6061-SiC surface composite through impregnation of graphene, graphite & carbon nanotubes via FSP: A tribological study

Fabricating high wear resistance Al matrix composite without sacrificing its ductility and thermal properties is a critical issue in the designing of Al-based composites. In present study, a detailed wear mechanism of Al-SiC surface composite modified by the impregnation of Graphene, Graphite & carbon nanotubes through friction stir processing (FSP) is documented. The results revealed that with SiC and graphene nanoplatelets (GNP) reinforcements the friction coefficient and specific wear rate decreased by ~34% and ~50% as compared to as-received Al6061 alloy respectively. On the other hand, combination of SiC and carbon nanotubes (CNT) reinforcements severely deteriorates the wear resistance of the composite. The layered structure, large specific surface area and the wrinkled morphology of the graphene flakes are the primary reasons for the increased wear resistance. The exfoliation of GNP to few layered graphene (FLG) under the effect of plastic flow stresses during FSP also contributes significantly to the improvement of surface properties. The abrasion is identified as the dominant wear mechanism in Al-SiC-Graphite & Al-SiC-GNP hybrid composite. Whereas, delamination due to adhesion with the counter surface is the leading mechanism in Al-SiC-CNT hybrid composite. Various characterization strategies such as microstructural characterization through SEM, interfacial study through TEM and phase analysis through XRD corroborate the results. Finally, GNP is identified as the best reinforcement among the carbon family for improvement in wear resistance of Al6061-SiC surface composite.

Band gap tuning of defective silicon carbide nanotubes under external electric field: Density functional theory

We have theoretically investigated the effect of applying longitudinal and transverse electric field on silicon carbide nanotubes with different orientations of Stone Wales defects. We found that each type of Stone Wales defects maintained different formation energy. We have also successfully proved that the orientation of Stone Wales defects in silicon carbide nanotubes response quite differently upon applying external electric field, whereas, two important and interesting phenomena were observed. First, the semiconductor-metal phase transition occurred in silicon carbide nanotubes as well as the three types of Stone Wales defects. However, clear band gap variations were observed in all silicon carbide nanotubes under study. Second, the band gap variations in pristine silicon carbide nanotubes and nanotubes with different orientations of Stone Wales defects have the same trend, even though all silicon carbide nanotubes have clear band gap values under different strengths of the applied external electric field. However, band gap tuning under longitudinal electric field is less significant compared to band gap tuning under the transverse electric field.

Dielectric properties of porous SiC/Si3N4 ceramics by polysilazane immersion-pyrolysis

The SiC nanotubes were synthesized on porous Si3N4 matrix by polysilazane immersion-pyrolysis. The β-SiC and free C contents increased with the increasing dipping times, which cause some clear vibration and loss peaks of the dielectric constant patterns emerged at around 12.9 GHz and 14.7 GHz in the samples of 20 wt% and 30 wt% benzoic acid, respectively. The reflectivity of the obtained ceramics were −7dB ∼ −10dB from the frequency of 8 GHz–18 GHz, which means that the amount of 80%–90% electromagnetic wave could be attenuated. The ceramics containing 40 wt% benzoic acid showed the high loss, low reflectivity and a wide absorbing band, indicating the high absorbing efficiency and good dielectric properties.

Nanomaterial ink for on-site painted sensor on studies of the electrochemical detection of organophosphorus pesticide residuals of supermarket vegetables

This work reports a paintable electrode ink for on-site direct detection of parathion residuals from vegetable products. The electrode ink was mainly fabricated by silicon carbide and multi-walled carbon nanotubes and the resulted painted electrode was further stabilized by a layer of chitosan acting as a fixing glue. The painted electrode shows significant sensitivity for parathion with a detection limit of 20ngmL−1. In on-site practice of real samples the painted electrode was successfully used to monitor the parathion residuals on some common local supermarket vegetables such as Chinese cabbage, sweet potato leaf and cucumber, with satisfied results of recoveries between 76.0% and 96.2%.

The Hydrogen Effect on the Electronic and Optical Behavior of SiC:Mn(5,0) NT: by DFT

The electronic, magnetic and optical properties of the SiC(5,0) nanotube (NT) with Mn impurity and by adding the H atom have been calculated by DFT framework. The SiC:Mn(5,0) NT leads the metallic property by electronic anisotropy. Furthermore, adsorption of the H atom to SiC:Mn(5,0) enhances the metallic and ferromagnetic behavior. Results are indicating the stability of the SiC:Mn(5,0) and under H adsorption in the energy viewpoint. These compounds illustrate the anisotropy in optical coefficients such as dielectric function, energy loss function (ELF) and absorption based on the light angle which originated from depolarization effect.

Electronic properties of silicon carbide nanotube with Stone Wales defects under uniaxial pressure: A computational study

We investigated the effect of uniaxial pressure on pristine silicon carbide nanotubes and silicon carbide nanotubes with different orientations of Stone Wales defects. Based on Si-C bond orientation, three types of Stone Wales defects might be created. We performed our calculations using density functional theory with Dmol3 code. We studied the changes in electrical properties after introducing different orientations of Stone Wales defects to silicon carbide nanotubes. In addition, we systematically applied uniaxial pressure on the four different samples. The influences of uniaxial pressure on the geometry of silicon carbide nanotube with different orientations of Stone Wales defects were obtained by the analysis of band structure as well as monitoring the variations in Fermi energy, valence band and conduction band.

Study of the stability and interwall distance of (6,0)@(n,0) double-walled silicon carbide nanotubes by the vdW-DFT method

In this work, the stability and electronic structure of zigzag double-walled silicon carbide nanotubes (DWSiCNTs) (6,0)@(n,0) (with n=11-17) were investigated by using ab initio Van der Waals density functional. By calculating the formation energy and the binding energy of each double walled nanotube, the best interwall distance for the outer nanotube was indicated. The results revealed that (13,0) nanotube could be the best external nanotube for the (6,0) internal nanotube with 3.53 Ainterwall distance to make (6,0)@(13,0) DWSiCNT. The structural calculations also revealed that all studied silicon carbide nanotubes were semiconductors and their energy gap decreased from the single one to the double-walled one. Moreover, with raising the nanotube diameter, the energy gap increased, such that at the most stable double-walled nanotube, its value was about 0.216 eV.

Feasibility of Pristine and Decorated AlN and SiC Nanotubes in Sensing of Noble Gases: A DFT study

AbstractThe periodic boundary condition density functional theory framework was recruited in order to study the reactivity and electronic sensitivity of aluminium nitride (AlN) and silicon carbide (SiC) nanotubes as well as the gallium‐doped aluminium nitride (AlN(Ga)) and germanium‐doped silicon carbide (SiC(Ge)) nanotubes toward noble gases (NGs). In this respect, the adsorption possibility of the He, Ne, Ar, and Kr NGs onto the exterior surface of AlN, SiC, AlN(Ga) and SiC(Ge) nanotubes in the form of single‐walled armchair (5,5) was comprehensively and comparatively investigated. All possible configurations were considered and optimized at B3LYP/6‐311G (d) level of theory for each unit cells. Moreover, the single point energy calculations were applied on the completed nanotube/gas systems using different functionals including B3LYP, WB97X‐3D, M062X, and CAM−B3LYP in combination with 6–311G (d) and DEF2‐TZVP basis sets. It was found that, there are tiny differences between any possible configurations of gas and nanotube systems, and therefore, the most stable configuration of each system was chosen for further analyses such as density of state, natural bond orbital, and quantum theory of atoms in molecules in order to better understand the intermolecular interaction between NGs and nanotubes. The obtained results indicate that, the Ga‐doped and Ge‐doped nanotubes are more profound in the sensing of NGs compared to the pristine nanotubes.

Impact of polarized nanotube surface on ultrathin mesogen film properties: Computer simulation study.

We studied properties of monolayer films of n-cyanobiphenyl (with n=5,...,8) series of mesogens anchored on the surface of single walled boron nitride nanotube. In order to assess the impact of substrate polarization on the ordering effects we compare translational and reorientational dynamics of the films with the characteristics of analogous carbon and silicon carbide nanotube based systems. We observed significant increase of the ordering degree accompanied by increased thermal stability. This ordering is less selective than those induced by the silicon carbide nanotube, which were previously reported. The antiparallel orientation of the nearest neighboring mesogens is predominant, while the system does not exhibit any long-range spatial correlations which indicates that the size of the domains is constrained to this region. These features might be of potential importance in the design of novel optoelectronic devices.

Recent Advances in the Processing and Properties of Alumina⁻CNT/SiC Nanocomposites.

An alumina-based nanocomposite is fabricated through the addition of secondary nanophase material to an alumina matrix to alter and tailor the properties of alumina. The addition to alumina of semi-conductive materials, such as silicon carbide (SiC), and high conductive materials, such as carbon nanotubes with a characteristic size in the nanometer range, can alter the mechanical strength, hardness, toughness, and electrical and thermal properties of alumina. This paper discusses recent advances in the synthesis of alumina–SiC and alumina-carbon nanotube (CNT) nanopowders and their consolidation using conventional and non-conventional techniques. Mechanical (hardness, fracture toughness and flexural strength) and functional (thermal and electrical) properties are discussed. The influence of the microstructure on the properties of alumina–SiC and alumina–CNT nanocomposites is discussed. Furthermore, potential applications and current related research trends are described.

On the nanoscale behaviour of single-wall C, BN and SiC nanotubes

The paper presents a numerical study of defect-free single-wall carbon, boron nitride and silicon carbide armchair and zigzag nanotubes, through a simple stick-and-spring model, based on Morse and cosine potential functions. The study investigates the relaxed configuration of the tubes and gives a comprehensive evaluation of their elastic constants, which is performed by framing tensile, torsional and radial tests within the membrane behaviour of a Donnell thin shell model. Extensive comparisons with reference ab-initio results are given and used to refine some parameters of the potential functions for hexagonal silicon carbide nanomaterials.

Structural and electronic transport properties of a SiC chain encapsulated inside a SiC nanotube: first-principles study.

Silicon carbide (SiC) chains and silicon carbide nanotubes (SiCNTs), as promising one-dimensional nanostructures, have potential applications in more controllable nanoelectronic devices. In this paper, we design a completely new hybrid structure with encapsulation of a linear SiC chain inside a SiCNT, using first-principles calculation and the non-equilibrium Green's function formalism to systematically investigate the structural stability and electronic properties, particularly the quantum transport properties. It is found that, due to the nanotube-chain interaction, the stability of this structure is mainly provided by the charge transfer from the hosting tube to the guest chain. Furthermore, the transport properties of the hybrid structure confirm that encapsulation of a SiC chain within a SiCNT can significantly enhance the electronic transport of the component system in a wide range of high voltage. The distance and the unique coupling configuration between the encapsulated system and the electrodes are demonstrated to be other important factors that affect the transport behaviours. We hope that our study of encapsulation may offer a significant starting point for the design of new materials related to low-dimensional SiC nanostructures and possibly open a novel path towards stability and conductivity enhancement.

First Principle Study on Optical Properties of Tri-Group Doped (6,6) SiC Nanotubes**Supported by the National Natural Science Foundation of China under Grant Nos 11574261 and 51132002, and the Natural Science Foundation of Hebei Province under Grant No A2015203261.

The optical properties of tri-group (B, Al, Ga, In) doped (6,6) SiC nanotubes (SiCNTs) are studied from first principles. The results show that the main absorption and dispersion of SiCNTs caused by the intrinsic transition appear in the ultraviolet-visible region (below 500 nm), and the tri-group doping increases the minimum dielectric constant value resulting in enhanced transmittance. In addition, the tri-group doping can introduce a weak absorption and dispersion region in the near-mid-infrared region, and the response peak blue shifts as the diameter of the doping atom increases. Comparative studies of reflectance, absorptivity, and transmittance show that the key factors affecting the transmittance of SiCNTs are reflectance (or refractive index) rather than absorption coefficient.

Spark plasma sintering of TiN ceramics codoped with SiC and CNT

In this research, we investigated the effects of SiC and multi-walled carbon nanotube (MWCNTs) addition on the densification and microstructure of titanium nitride (TiN) ceramics. Four samples including monolithic TiN, TiN-5 wt% MWCNTs, TiN-20 vol% SiC and TiN-20 vol% SiC-5 wt% MWCNTs were prepared by spark plasma sintering at 1900 °C for 7 min under 40 MPa pressure. X-ray powder diffraction patterns and scanning electron microscope (SEM) micrographs of the prepared ceramics showed that no new phase was formed during the sintering process. The highest calculated relative density was related to the TiN ceramic doped with 20 vol% SiC, while the sample doped with 5 wt% MWCNTs presented the lowest density. In addition, the SEM investigations revealed that the addition of sintering aids e.g. SiC and MWCNTs leads to a finer microstructure ceramic. These additives generally remain within the spaces among the TiN particles and prohibit extensive grain growth in the fabricated ceramics.

CH3NH3PbX3 (X\u2009=\u2009I, Br) encapsulated in silicon carbide/carbon nanotube as advanced diodes

We employ first-principles density functional theory (DFT) calculations to study CH3NH3PbX3 (X = I, Br) and its encapsulation into the silicon carbide nanotube and carbon nanotube (CNT). Our results indicate that these devices show diode behaviors which act on negative bias voltage but do not work under positive voltage. When they are encapsulated into SiC nanotube and CNT, their electronic properties would be changed, especially, electric currents mainly exist at positive bias region. Corresponding transmission spectra and density of states are provided to interpret the transport mechanism of the CH3NH3PbX3 (X = I, Br) as a diode. These findings open a new door to microelectronics and integrated circuit components, providing theoretical foundation for innovation of the new generation of electronic materials.

The adsorption of bromomethane onto the exterior surface of aluminum nitride, boron nitride, carbon, and silicon carbide nanotubes: A PBC-DFT, NBO, and QTAIM study

The adsorption of bromomethane (CH3Br) onto the outer surface of the pristine armchair (5,5) single-walled aluminum nitride nanotube (AlNNT), boron nitride nanotube (BNNT), carbon nanotube (CNT), and silicon carbide nanotube (SiCNT) were investigated using density functional theory (DFT). The geometry optimization was performed by using the PBEPBE/6-31G(d) level of theory through 1D periodic boundary conditions (in which, each unit cell containing 40 atoms). Moreover, NBO and QTAIM analyses were also performed by using the same level of theory but using the complete nanotubes (each nanotube consists of 200 atoms). For further investigation, single point energy calculations were applied to each system using the CAM-B3LYP/DEF2-TZVP level of theory. The obtained adsorption energies indicate that among all of the aforementioned nanotubes, AlNNT exhibits the strongest affinity for the adsorption of the CH3Br molecule with the most negative adsorption energy. Based on the NBO and QTAIM results, it can be inferred that CH3Br tends to be chemisorbed onto the AlN and SiC nanotubes, whereas, in the case of CNT and BNNT, the adsorption is through weak van der Waals interactions and a physisorption process. Therefore, the results of this work may be useful in designing new types of nanosensor devices.

The Effects of Radial Compression on the Electronic Properties and Hydrogen Adsorption of SiC Nanotubes

The electronic properties of radially deformed SiC nanotubes (SiCNT) are studied by density functional theory. It is found that the band gap of zig‐zag SiCNT can be engineered by radial compression. The reason for this is found by examining bond length/angle modification and by group theoretical analysis. In addition, the variation of the binding energy of H, in deformed SiCNT, is also studied. The analysis of the structural changes of the CSiH or SiCH bond length/angle, as well as the inspection of the molecular orbitals, shows that tunable hydrogen adsorption is feasible as for its carbon or boron nitride counterparts.