Search Results (96)

SiC nanowires (SiC_nw), due to their excellent dielectric properties, are promising high-temperature absorbing materials. However, the mechanism of their high-temperature absorption still requires further research. Therefore, porous SiC_nw/Si₃N₄ and SiC/Si₃N₄ ceramics with different SiC phase morphologies were fabricated using a simple precursor impregnation and pyrolysis method. The Fe impurity content of the Si₃N₄ powder raw material significantly affects the generation of SiC nanowires. When SiC exists in the form of nanowires, the excellent conductivity brought by the conductive network of the nanowires causes a significant response of the material’s permittivity to temperature. When the test temperature is room temperature, SiC_nw/Si₃N₄ has excellent absorption performance with a minimum reflection loss of −29.75 dB at 2.16 mm and an effective absorption bandwidth of 3.72 GHz at 2.54 mm. As the test temperature increases to 300 °C, the effective absorption bandwidth of SiC_nw/Si₃N₄ covers the entire X-band. The porous SiC_nw/Si₃N₄ ceramics exhibit excellent electromagnetic wave absorption performance, demonstrating significant application potential for high-temperature environments. Full article

To investigate the synthesis route and electromagnetic wave absorption performance of SiC nanowires (SiC-NWs), boron was simultaneously employed as both a catalyst and a dopant, and the doped nanowires were embedded into a silicone matrix to fabricate SiC-NW/silicone composites with enhanced mechanical properties and microwave attenuation. Boric acid significantly increased the yield of SiC-NWs, while boron doping enhanced both conductive and relaxation losses. The subsequent nanowire pull-out mechanism improved the tensile strength of the composites by 185%, reaching 5.7 MPa at a filler loading of 5 wt%. The three-dimensional SiC-NW network provided synergistic dielectric and conductive losses, along with good impedance matching, achieving a minimum reflection loss of −35 dB at a thickness of 3.5 mm and an effective absorption bandwidth of 4.2 GHz within the 8.2–12.4 GHz range, with a nanowire content of only 5 wt%. Full article

In this study we report on the structural, mechanical, and electrical characterization of different structures of vertically aligned zinc oxide (ZnO) nanowires (NWs) synthesized using hydrothermal methods. By optimizing the growth conditions, scanning electron microscopy (SEM) micrographs show that the ZnO NWs could reach an astounding 51.9 ± 0.82 µm in length, 0.7 ± 0.08 µm in diameter, and 3.3 ± 2.1 µm⁻² density of the number of NWs per area within 24 h of growth time, compared with a reported value of ~26.8 µm in length for the same period. The indentation modulus of the as-grown ZnO NWs was determined using contact resonance (CR) measurements using atomic force microscopy (AFM). An indentation modulus of 122.2 ± 2.3 GPa for the NW array sample with an average diameter of ~690 nm was found to be close to the reference bulk ZnO value of 125 GPa. Furthermore, the measurement of the piezoelectric coefficient (d₃₃) using the traceable ESPY33 tool under cyclic compressive stress gave a value of 1.6 ± 0.4 pC/N at 0.02 N with ZnO NWs of 100 ± 10 nm and 2.69 ± 0.05 µm in diameter and length, respectively, which were embedded in an S1818 polymer. Current–voltage (I-V) measurements of the ZnO NWs fabricated on an n-type silicon (Si) substrate utilizing a micromanipulator integrated with a tungsten (W) probe exhibits Ohmic behavior, revealing an important phenomenon which can be attributed to the generated electric field by the tungsten probe, dielectric residue, or conductive material. Full article

In situ-grown SiC nanowires (SiCnws) on SiC porous material (SiCnws@SiC) were prepared using sol–gel and carbothermal reduction methods, which substantially improves the electromagnetic wave absorption property of composite material. The crystallinity and purity of SiCnws are the best when the sintering temperature is 1600 °C. When the ratio of the carbon source (C) to the silicon source (Si) is 1:1, SiCnws@SiC composite exhibits excellent electromagnetic wave absorption performance, the minimum reflection loss is −56.95 dB at a thickness of 2.30 mm, and the effective absorption bandwidth covers 1.85 GHz. The optimal effective absorption bandwidth is 4.01 GHz when the thickness is 2.59 mm. The enhancement of the electromagnetic wave absorption performance of SiCnws is mainly attributed to the increase in the heterogeneous interface and multiple reflection and scattering caused by the network structure, increasing dielectric loss and conduction loss. In addition, defects could occur during the growth of SiCnws, which could become the center of dipole polarization and increase the polarization loss of composite materials. Therefore, in situ growth of SiCnws on SiC porous ceramics is a promising method to improve electromagnetic wave absorption. Full article

Typical wet-chemical methods for the preparation of silica nanowires use polyvinylpyrrolidone and n-pentanol. This study presents a polyethylene glycol-based emulsion template method for the synthesis of SiO₂ nanowires (SiO₂NWs) in isopropanol. By systematically optimizing key parameters (type of solvent, polyethylene glycol molecular weight and dosage, dosage of sodium citrate, ammonium and tetraethyl orthosilicate, incubation temperature and time), SiO₂NWs with diameters about 530 nm were obtained. Replacing polyvinylpyrrolidone with polyethylene glycol enabled anisotropic growth in isopropanol, overcoming the dependency on traditional solvents like n-pentanol. Scale-up experiments (10× volume) demonstrated robust reproducibility, yielding nanowires with consistent morphology (~580 nm diameter). After calcination at 500 °C for 1 h, the morphology of the nanowires did not change significantly. Full article

The development of reliable, highly sensitive hydrogen sensors is crucial for the safe implementation of hydrogen-based energy systems. This paper proposes a novel way to enhance the performance of hydrogen sensors through integrating Pd-SnO₂ nanofilms on the substrate with silicon nanowires (SiNWs). The samples were fabricated via a simple and cost-effective process, mainly consisting of metal-assisted chemical etching (MaCE) and electron beam evaporation. Structural and morphological characterizations were conducted using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The experimental results showed that, compared to those without SiNW structure or decorative Pd nanoparticles, the Pd-decorated SnO₂ nanofilm integrated on the SiNW substrates exhibited significantly improved hydrogen sensing performance, achieving a response time of 9 s at 300 °C to 1.5% H₂ and a detection limit of 1 ppm. The enhanced performance can be primarily attributed to the large surface area provided by SiNWs, the efficient hydrogen spillover effect facilitated by Pd nanoparticles, and the abundant oxygen vacancies present on the surface of the SnO₂ nanofilm, as well as the Schottky barrier formed at the heterojunction interface between Pd and SnO₂. This study demonstrates a promising approach for developing high-performance H₂ sensors characterized by ultrafast response times and ultralow detection limits. Full article

The wettability and high-temperature mechanical properties of porous BN/Si₃N₄ ceramics brazed with SiTi22 (wt. %) filler were studied. It is manifested that SiTi22 filler presents remarkable wetting and spreading capabilities on the porous BN/Si₃N₄ ceramic surface. An interfacial reaction layer is generated at the interface, and the thickness of the reaction layer initially grows and subsequently remains constant with the escalation of temperature. Carbon coating modification is beneficial to the wettability and high-temperature mechanical properties of porous BN/Si₃N₄ ceramics. The wetting driving force is mainly controlled by the interfacial reaction at the three-phase line of the wetting front. The mechanical properties of the carbon-coated joints are significantly enhanced in comparison with uncoated joints. The joint strength attains a maximum value of roughly 73 MPa in the shear test implemented at 800 °C. The strength of the joint is significantly enhanced mainly due to the TiN_0.7C_0.3 particles that consume energy by changing the crack propagation direction, and the SiC nanowires strengthen the connection by bridging. Full article

The search for a synthesis method to create longer ZnO NWAs with high-quality vertical alignment, and the investigation of their electrical properties, have become increasingly important. In this study, a hydrothermal method for growing vertically aligned arrays of ZnO nanowires (NWs) using localized heating was utilized. To produce longer NWs, the temperature environment of the growth system was optimized with a novel reaction container that provided improved thermal insulation. At a process temperature above ~90 °C, ZnO NWs reached a length of ~26.8 µm within 24 h, corresponding to a growth rate of 1.1 µm/h, nearly double the rate of 0.6 µm/h observed in traditional chemical bath growth using a glass reactor. The densely grown NWs (~1.9/µm²), with a diameter of ~0.65 µm, exhibited a preferred hexagonal c-axis orientation and were vertically aligned to the (100) silicon (Si) substrate. These NW structures have multiple applications, e.g., in piezotronic strain sensors, gas sensing, and piezoelectric energy harvesting. As proof of concept, a piezoelectric nanogenerator (PENG) was fabricated by embedding the NWs in an S1818 polymer matrix over a 15 mm × 15 mm area. Under repeated impulse-type compressive forces of 0.9 N, a maximum peak output voltage of ~95.9 mV was recorded, which is higher by a factor of four to five than the peak output voltage of 21.6 mV previously obtained with NWs measuring ~1.8 µm in length. Full article

Silicon carbide (SiC) single crystals have great prospects for high-temperature energy storage due to their robust structural stability, ultrahigh power output, and superior temperature stability. However, energy density is an essential challenge for SiC-based devices. Herein, a facile two-step strategy is proposed for the large-scale synthesis of a unique architecture of SiC nanowires incorporating MnO₂ for enhanced supercapacitors (SCs), arising from the synergy effect between the SiC nanowires as a highly conductive skeleton and the MnO₂ with numerous active sites. The SiC@MnO₂ integrated electrode-based SCs with ionic liquid (IL) electrolytes were assembled and delivered outstanding energy and power density, as well as a great lifespan at 150 °C. This impressive work offers a novel avenue for the practical application of SiC-based electrochemical energy storage devices with high energy density under high temperatures. Full article

This brief review covers the thermoelectric properties of one-dimensional materials, such as nanowires and nanotubes. The highly localised peaks of the electronic density of states near the Fermi levels of these nanostructured materials improve the Seebeck coefficient. Moreover, quantum confinement leads to discrete energy levels and a modified density of states, potentially enhancing electrical conductivity. These electronic effects, coupled with the dominance of Umklapp phonon scattering, which reduces thermal conductivity in one-dimensional materials, can achieve unprecedented thermoelectric efficiency not seen in two-dimensional or bulk materials. Notable advancements include carbon and silicon nanotubes and Bi₃Te₂, Bi, ZnO, SiC, and Si_1−xGe_x nanowires with significantly reduced thermal conductivity and increased ZT. In all these nanowires and nanotubes, efficiency is explored as a function of the diameter. Among these nanomaterials, carbon nanotubes offer mechanical flexibility and improved thermoelectric performance. Although carbon nanotubes theoretically have high thermal conductivity, the improvement of their Seebeck coefficient due to their low-dimensional structure can compensate for it. Regarding flexibility, economic criteria, ease of fabrication, and weight, carbon nanotubes could be a promising candidate for thermoelectric power generation. Full article

This computational research study will compare the specific charge capacity (SCC) between lithium ions inserted into crystallized silicon (c-Si) nanowires with that of sodium ions inserted into amorphous silicon (a-Si) nanowires. It will be demonstrated that the potential energy V(r) within a lithium–silicon nanowire supports a coherent energy state model with discrete electron particles, while the potential energy of a sodium–silicon nanowire will be discovered to be essentially zero, and, thus, the electron current that travels through a sodiated silicon nanowire will be modeled as a free electron with wave-like characteristics. This is due to the vast differences in the electric fields of lithiated and sodiated silicon nanowires, where the electric fields are of the order of ${10}^{10}$ V/m and ${10}^{-15}$ V/m, respectively. The main reason for the great disparity in electric fields is the presence of optical amplification within lithium ions and the absence of this process within sodium ions. It will be shown that optical amplification develops coherent optical interactions, which is the primary reason for the surge of specific charge capacity in the lithiated silicon nanowire. Conversely, the lack of optical amplification is the reason for the incoherent optical interactions within sodium ions, which is the reason for the low presence of SCC in sodiated silicon nanowires. Full article

For the first time, we have implemented new kinds of ISFETs based on silicon carbide (SiC). Thanks to its chemical inertness, SiC is an interesting semiconductor for the development of chemically robust and biocompatible ISFETs. The challenge is to replace Si NWFETs for biochemical sensing due to the lack of long-term stability of Si NWs in aqueous solutions. More particularly, we fabricated a micro/nanowire SiC-based ion-sensitive junction field-effect transistor (SiC-ISJFET) and studied its sensitivity to pH variations. The obtained sensitivity reaches 500 mV/pH, making it the first SiC pH sensor with performance equaling that of the latest NWFET Si-based pH sensors. Full article

In order to address the anti-ablation of carbon/carbon (C/C) composites, SiC nanowires (SiCnws) network-modified C/C-ZrB₂-ZrC-SiC composites were prepared through the one-step precursor conversion method. With an optimized B-Si-Zr sol-precursor, uniformly dispersed SiCnws and ceramic particles forming an interlocking structure were synchronous in situ grown in the C/C matrix. During ablation, the partially oxidized SiCnws networks with molten SiO₂ surface can stabilize the oxide protecting layer and heal the microcracks efficiently in combination with the refractory ZrO₂ particles, thus significantly improving the anti-ablation properties of the composites. This study lays the foundation for the high temperature and long-term anti-oxidation and anti-ablation application of C/C composites in the aerospace industry. Full article

The influence of nanomechanical tensile behavior on electron transport is especially interesting for ultra-thin SiC nanowires (NWs) with different diameters. Our studies theoretically show that these NWs can hold stable electron transmission in some strain ranges and that stretching can enhance the electron transmission around the Fermi level (E_F) at the strains over 0.5 without fracture for a single-atom SiC chain and at the strains not over 0.5 for thicker SiC NWs. For each size of SiC NW, the tensile strain has a tiny effect on the number of device density of states (DDOSs) peaks but can increase the values. Freshly broken SiC NWs also show certain values of DDOSs around E_F. The maximum DDOS increases significantly with the diameter, but interestingly, the DDOS at E_F shows little difference among the three sizes of devices in the late stage of the stretching. Essentially, high electron transmission is influenced by high DDOSs and delocalized electronic states. Analysis of electron localization functions (ELFs) indicates that appropriate tensile stress can promote continuous electronic distributions to contribute electron transport, while excessively large stretching deformation of SiC NWs would split electronic distributions and consequently hinder the movement of electrons. These results provide strong theoretical support for the use of ultra-thin SiC NWs in nano-sensors for functional and controllable electronic devices. Full article

In this paper, the laser pulse time compression technique, based on stimulated Brillouin scattering (SBS) and passive laser–induced breakdown (LIB) series technology, is investigated. By doping a SiC nanowire in a CCl₄ solution of an LIB breakdown medium, the LIB generation threshold is reduced, and the stability of the LIB compression output is improved. When OD is 0.2, the output pulse width is 254.4 ps, and the corresponding energy conversion efficiency and pulse compression rate are 34.2% and 50.2%, respectively. Our experiment proves the feasibility of this scheme. Full article