Properties Of Silicon Carbide Nanotubes Research Articles

Effect of anionic surfactant on dispersibility and luminescence of silicon carbide nanotubes

We investigated the relationship between the dispersibility and optical properties of silicon carbide nanotubes (SiCNTs). By dissolving the aggregation of SiCNTs using sodium cholate as an anionic surfactant, the cluster size decreased and the dispersibility improved with the increasing surfactant concentration. The macroscopic and microscopic photoluminescence properties were evaluated using excitation lights with variable spot size. The emission intensity of SiCNTs increased with the decreasing cluster size, owing to the improvement of the dispersibility, and the emission intensity of the well-dispersed SiCNTs increased superlinearly with the excitation density. These results indicate the presence of SiCNTs that recombine non-radiatively in the cluster, and the effect of their NTs is suppressed as the cluster size is reduced.

Molecular Dynamics Investigation on the Effect of MWCNTs on Thermo-Mechanical Properties of Amorphous Cellulose Reinforced with Silicon Carbide Nanotubes

Cellulose is a biopolymer frequently implemented as fibers and membranes to fabricate high-performance and multi-functional composites. In this study, the molecular dynamics simulation is used to investigate the effect of CNTs on elastic modulus, ultimate strength, and toughness properties of silicon carbide nanotubes (SiCNTs) reinforced cellulose nanocomposite. Based on the simulation results, the temperature of the surrounding environment controls the stress transfer at the nanotube-cellulose interface. As the cellulose expands with increasing temperature creating more void regions at the filler-matrix interface, the load transfer from cellulose to nanotubes is reduced, leading to a noticeable reduction in tensile properties of cellulose composite. This behavior critically affects the tensile strength of cellulose composite reinforced with multi-walled CNTs (MWCNTs). The single-walled CNT with a high aspect ratio increases the cellulose composite’s tensile strength and toughness, while the MWCNT introduces the most significant increase in cellulose stiffness. The difference in polarity between MWCNT and cellulose, along with the low aspect ratio of the external nanotube, would limit the capability of MWCNT in improving the tensile strength and toughness of cellulose. The single-walled SiCNTs are structurally unstable, and their stiffness degrades rapidly at high temperatures. Therefore, they are hybridized with CNTs to improve their stiffness and structural stability. SiCNT, which is hybridized with two CNTs, exhibits the best structural performance at 100, 300, and 500 K temperatures.

Effects of substitution of group-V atoms for carbon or silicon atoms on optical properties of silicon carbide nanotubes* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11574261 and 51132002) and the Natural Science Foundation of Hebei Province, China (Grant No. A2015203261).

Silicon carbide nanotubes (SiCNTs) have broad application prospects in the field of micro-nanodevices due to their excellent physical properties. Based on first-principles, the difference between optical properties of SiCNTs where C atom or Si atom is replaced by group-V element is studied. The results show that the optical absorptions of SiCNTs doped by different elements are significantly different in the band of 600 nm–1500 nm. The differences in photoconductivity, caused by different doping elements, are reflected mainly in the band above 620 nm, the difference in dielectric function and refractive index of SiCNTs are reflected mainly in the band above 500 nm. Further analysis shows that SiCNTs doped with different elements change their band structures, resulting in the differences among their optical properties. The calculation of formation energy shows that SiCNTs are more stable when group-V element replaces Si atom, except N atom. These research results will be beneficial to the applications of SiC nanomaterials in optoelectronic devices and provide a theoretical basis for selecting the SiCNTs’ dopants.

Investigating potential properties of (8,0) Silicon Carbide Nanotube for applications in band gap tuning

The changes in electronic and Magnetic properties of spin polarized silicon carbide nanotube (SiCNT), investigated using density functional theory and Quantum-Espresso computational package. In the present work, the electronic and magnetic properties of pristine, vacancy and transition metal(TM) doped (8,0) SWSiCNT are systematically investigated to give a detailed understanding of these materials. Magnetic moment were calculated, the electronic properties of zigzag (8,0) semiconductor silicon carbide nanotubes (SiCNTs) doped once at the time with Iron, Cobalt, Mnganse, Gadolinium and Hafinime. We have looked at the two possible scenarios where the guest atom X (Fe, Co, Mn, Gd, Hf), substituting in the Site of the Silicon atom X Si and carbon atom X C with different concentration, in the unit cell. We found that in the case of one atom Fe doped SiCNT, Co doped SiCNT, Mn doped SiCNT, Gd doped SiCNT and Hf doped SiCNT replacing a Silicon atom position annotated by Fe Si exhibits a magnetic moment of 1.99 μ B /cell and Mn Si exhibits a magnetic moment of 0.98 μ B /cell, Co Si exhibits a magnetic moment of 0.02 μ B /cell, whereas, in the case of two atom 2Fe doped SiCNT, 2Co doped SiCNT, 2Mn doped SiCNT, Gd doped SiCNT and Hf doped SiCNT replacing at two carbon atom position annotated by Fe Si exhibits a magnetic moment of 3.98 μ B /cell and Mn Si exhibits a magnetic moment of 1.99 μ B /cell, Also, two atom Cobalt replacing carbon, (CoC), induce a magnetic moment of 5.13 μ B and for three atom cobalt replacing Carbon 5.36. Substitution of three Cobalt in site of Silicon gives the maximum magnetic moment 9.00 μ B /cell but in contrast the calculated results show that the Co doping in Silicon carbide nanotube induces the ferromagnetism and metallic property for all concentrations.The calculated results show that the Mn doping in Silicon carbide nanotube induces the ferromagnetism and originates a half metallic (HM) gap at Fermi level (EF)in minority spin channel (MIC) for for 3.125 %, 6.25%, 9.37% and 12.75% concentrations. Moreover, the calculated results show that the Fe doping in Silicon carbide nanotube induces the ferromagnetism and Half Metalic property for 3.125%, 6.25% and 9.37% concentrations. Doping concentrations and dopant positions regulate the electronic structure and Magnetic property of the Silicon carbide nanotube, exhibiting both semiconducting and half-metallic behaviours as a response to the concentration of Transition Metals.

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.

Tight-binding description of the silicon carbide nanotubes

The electronic and optical properties of silicon carbide nanotubes (SiCNTs) have been investigated using tight binding calculations based on previous density functional theory (DFT) studies. The optical spectra of SiCNTs are dependent on the diameter and chirality and their energy gap (Eg) reduction shows dependence on radius and electric field. The Eg of SiCNTs decreases linearly with electric field until reaches zero and semiconductor metallic transition occurs. Based on the dependence of band gap reduction on radius and electric field strength, the Eg explained in terms of radius and electric field with an explicit relation.

Theoretical studies of the lithium atom on the silicon carbide nanotubes

Based on density functional theory method, we have investigated structural, electronic, and magnetic properties of lithium (Li) atom adsorbed on silicon carbide (SiC) zigzag (9,0) and armchair (5,5) nanotubes. Effective adsorptions are found on both inner- and outer-side of the SiC nanotubes, with adsorption energies ranging from 1.03 to 1.71 eV. Interestingly, we have found that SiC nanotubes exhibit different behaviors with several Li adsorption sites. Li adsorptions on the s-Si and s-H sites of the outer surface and all the five sites of the inner surface in zigzag (9,0) nanotube emerge metallic features, whereas adsorptions on other sides of (9,0) and all sites of armchair (5,5) SiC nanotubes show semiconducting characters. The calculating results also indicate that lithium adsorptions on most sites of SiC nanotubes yield spontaneous magnetization, where net magnetic moment is 1 μ B . Additionally, spin density of states, spin density distribution, and charge density difference are also calculated to investigate the electronic and magnetic properties of SiC nanotubes induced by Li adsorption.

Modal analysis of silicon carbide nanotubes using structural mechanics

This article discusses the vibrational properties of silicon carbide nanotubes with various dimensions, chiralities and boundary conditions. The molecular mechanics-based finite element method is applied to study the mode shapes and natural frequencies of the silicon carbide nanotubes. The results reveal that the natural frequencies of the nanotubes increase with decreasing length, but they do not show monotone behaviors vs. diameter changes. The reasons are discussed in detail.

Electronic and Optical Properties of Silicon Carbide Nanotubes and Nanoparticles Studied by Density Functional Theory Calculations: Effect of Doping and Environment

Electronic and Optical Properties of Silicon Carbide Nanotubes and Nanoparticles Studied by Density Functional Theory Calculations: Effect of Doping and Environment

A study of the size-dependent elastic properties of silicon carbide nanotubes: First-principles calculations

The size dependence of elastic properties in single-walled silicon carbide nanotubes are investigated by first-principles calculations. We found the Youngʼs modulus of the nanotubes increases with increasing diameter and is inversely proportional to Si–C bond length, whereas the Poisson ratio shows an opposite trend. For small tubes the elastic properties change dramatically with the tube size. While for the tubes with the diameter larger than 8 Å, the difference of these properties is small and almost independent of the size and symmetry. The strength of bonding between Si and C atoms is elucidated by the amount of the charge transfer calculated by the Bader analysis.

Investigation on influence of antisite defects on electronic structure and optical properties of silicon carbide nanotube

Electronic structure and optical properties of a (5, 5) single-walled silicon carbide nanotube are studied with first principles calculation based on density functional theory. Depression and salient are formed near CSi defect and SiC defect in the surface of the nanotube. Defect energy levels are formed near the bottom of conduction band, which results in an n-type conductivity for nanotubes with antisite defects. In dielectric functions parallel and perpendicular to the axis of the nanotube, novel resonance peak is formed from transitions between top of the conduction band and the defect energy level.

Theoretical study on transport properties of a BN co-doped SiC nanotube

We investigate the electronic transport properties of silicon carbide nanotubes (SiCNT) in presence of both boron (B) and nitrogen (N) impurities. The results show that co-doping BN impurities suppresses the important negative differential resistance (NDR) property. NDR suppression is attributed to the introduction of new electronic states near the Fermi level followed by weak orbital localization. BN co-doping results in exponential current–voltage (I–V) characteristics which is in contrast to linear I–V characteristics for individual boron and nitrogen doped SiCNTs. HOMO has no contribution from B impurity, whereas, LUMO has contribution from N impurity at low and high bias.

Electronic properties of finite‐length silicon carbide nanotubes

AbstractThe electronic properties of silicon carbide nanotubes (SiCNT) as a function of length, were investigated by means of density functional theory (DFT). We found that the increasing nanotube length yields a higher localization of the lowest unoccupied and highest occupied molecular orbitals (LUMO and HOMO), thus affecting the behavior of the band gap and chemical reactivity of the SiCNTs. It is also found that structural stability increases for longer and larger nanotubes. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)