Search Results (12)

Ultrafine nano-grinding of silicon–carbon ores combined with sodium hexametaphosphate (SHMP) treatment enhanced silica dispersion and effectively separated silica and carbon particles. The hydrophobic nature of carbon promoted its re-agglomeration and sedimentation, achieving selective carbon enrichment. Characterization via FTIR, Raman spectroscopy, and TEM revealed two types of amorphous carbon with distinct structural features. BET analysis indicated a specific surface area of 92 m²/g for the carbon-rich fraction, suggesting potential applications in catalysis and energy storage after further activation. Full article

Multifunctional polymer composites containing micro/nano hybrid reinforcements have attracted intensive attention in the field of materials science and engineering. This paper develops a multi-phase analytical model for investigating the effective electrical conductivity of micro-silicon carbide (SiC) whisker/nano-carbon black (CB) polymer composites. First, CB nanoparticles are dispersed within the non-conducting epoxy to achieve a conductive CB-filled nanocomposite and its electrical conductivity is predicted. Some critical microstructures such as volume percentage and size of nanoparticles, and interphase characteristics surrounding the CB are micromechanically captured. Next, the electrical conductivity of randomly oriented SiC-containing composites in which the nanocomposite and whisker are considered as the matrix and reinforcement phases, respectively, is estimated. Influences of whisker aspect ratio and volume fraction on the effective electrical conductivity of the SiC/CB-containing polymer composites are explored. Some comparison studies are performed to validate the accuracy of the model. It is observed before the percolation threshold that the addition of nanoparticles with a uniform dispersion can improve the electrical conductivity of the polymer composites containing SiC/CB hybrids. Moreover, the results show that the electrical conductivity is more enhanced by the decrease in nanoparticle size. Interestingly, the composite percolation threshold is significantly reduced when SiC whiskers with a higher aspect ratio are added. This work will be favorable for the design of electro-conductive polymer composites with high performances. Full article

The innovative design of the microstructure of silicon-based composite anodes in Li-ion batteries holds great potential for overcoming inherent limitations, such as the significant volume change experienced by silicon particles. In this study, TiFeSi₂/C composites prepared using micro, nano, and porous silicon showed reversible capacities of 990.45 mAh.g⁻¹, 1137.69 mAh.g⁻¹, and 1045.43 mAh.g⁻¹ at C/10. The results obtained from the electrochemical characterization show that the porous structure of the composite anode material created via acid etching reduced silicon expansion during the lithiation/delithiation processes. The void spaces formed in the inner structure of the porous silicon and the presence of carbon increased the electronic conductivity between the silicon particles and, on the other hand, lowered the overall diffusion distance of Li⁺. This study confirms that TiFeSi₂/C prepared with porous silicon dispersed in a transition metal matrix delivers better electrochemical performance compared to micro and nano silicon with a retention of 80.16%. Full article

In this review, the operating principles of the nano-impact test technique are described, compared and contrasted to micro- and macro-scale impact tests. Impact fatigue mechanisms are discussed, and the impact behaviour of three different industrially relevant coating systems has been investigated in detail. The coating systems are (i) ultra-thin hard carbon films on silicon, (ii) DLC on hardened tool steel and (iii) nitrides on WC-Co. The influence of the mechanical properties of the substrate and the load-carrying capacity (H³/E²) of the coating, the use of the test to simulate erosion, studies modelling the nano- and micro-impact test and performing nano- and micro-impact tests at elevated temperature are also discussed. Full article

This study details the investigation of a black powder potential ore that was first obtained from Jiangxi, China. Its species, composition, and morphology are unknown. Preliminary tests revealed that the silica (SiO₂) content of this ore is >70%. To test this ore more comprehensively, its mineralogical parameters (such as mineral composition, ore particle size, and mineral morphology) are investigated using X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), differential scanning calorimetry–thermogravimetry (DSC-TG), Fourier-transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), laser particle size analysis, and elemental analysis (EA). Based on these analyses, it is determined that it is micro/nano silicon-carbon ore, and its genesis and species are discussed herein. The gangue minerals, such as α-quartz, kaolinite, pyrite, and muscovite, are finely disseminated and encapsulated by fixed carbon. The ore has an uneven morphology, with many holes and depressions. Moreover, nano-sized needle-like quartz and quartz wrapped by carbon are found on the surface of the ore. According to our results, this ore may have been formed by the long-term accumulation and consolidation of phytoliths. These results provide a technical reference for the development and utilization of the identified micro/nano silicon-carbon ore. Full article

Although the silicon oxide (SiO₂) as an anode material shows potential and promise for lithium-ion batteries (LIBs), owing to its high capacity, low cost, abundance, and safety, severe capacity decay and sluggish charge transfer during the discharge–charge process has caused a serious challenge for available applications. Herein, a novel 3D porous silicon oxide@Pourous Carbon@Tin (SiO₂@Pc@Sn) composite anode material was firstly designed and synthesized by freeze-drying and thermal-melting self-assembly, in which SiO₂ microparticles were encapsulated in the porous carbon as well as Sn nanoballs being uniformly dispersed in the SiO₂@Pc-like sesame seeds, effectively constructing a robust and conductive 3D porous Jujube cake-like architecture that is beneficial for fast ion transfer and high structural stability. Such a SiO₂@Pc@Sn micro-nano hierarchical structure as a LIBs anode exhibits a large reversible specific capacity ~520 mAh·g⁻¹, initial coulombic efficiency (ICE) ~52%, outstanding rate capability, and excellent cycling stability over 100 cycles. Furthermore, the phase evolution and underlying electrochemical mechanism during the charge–discharge process were further uncovered by cyclic voltammetry (CV) investigation. Full article

Carbonized elastomer-based composites (CECs) possess a number of attractive features in terms of thermomechanical and electromechanical performance, durability in aggressive media and facile net-shape formability, but their relatively low ductility and strength limit their suitability for structural engineering applications. Prospective applications such as structural elements of micro-electro-mechanical systems MEMS can be envisaged since smaller principal dimensions reduce the susceptibility of components to residual stress accumulation during carbonization and to brittle fracture in general. We report the results of in situ in-SEM study of microdeformation and fracture behavior of CECs based on nitrile butadiene rubber (NBR) elastomeric matrices filled with carbon and silicon carbide. Nanostructured carbon composite materials were manufactured via compounding of elastomeric substance with carbon and SiC fillers using mixing rolling mill, vulcanization, and low-temperature carbonization. Double-edge notched tensile (DENT) specimens of vulcanized and carbonized elastomeric composites were subjected to in situ tensile testing in the chamber of the scanning electron microscope (SEM) Tescan Vega 3 using a Deben microtest 1 kN tensile stage. The series of acquired SEM images were analyzed by means of digital image correlation (DIC) using Ncorr open-source software to map the spatial distribution of strain. These maps were correlated with finite element modeling (FEM) simulations to refine the values of elastic moduli. Moreover, the elastic moduli were derived from unloading curve nanoindentation hardness measurements carried out using a NanoScan-4D tester and interpreted using the Oliver–Pharr method. Carbonization causes a significant increase of elastic moduli from 0.86 ± 0.07 GPa to 14.12 ± 1.20 GPa for the composite with graphite and carbon black fillers. Nanoindentation measurements yield somewhat lower values, namely, 0.25 ± 0.02 GPa and 9.83 ± 1.10 GPa before and after carbonization, respectively. The analysis of fractography images suggests that crack initiation, growth and propagation may occur both at the notch stress concentrator or relatively far from the notch. Possible causes of such response are discussed, namely, (1) residual stresses introduced by processing; (2) shape and size of fillers; and (3) the emanation and accumulation of gases in composites during carbonization. Full article

Cross-scale self-similar hierarchical micro–nano structures in living systems often provide unique features on surfaces and serve as inspiration sources for artificial materials or devices. For instance, a highly self-similar structure often has a higher fractal dimension and, consequently, a larger active surface area; hence, it would have a super surface performance compared to its peer. However, artificial self-similar surfaces with hierarchical micro–nano structures and their application development have not yet received enough attention. Here, by introducing solvent-assisted UV-lasering, we establish an elegant approach to fabricate self-similar hierarchical micro–nano structures on silicon. The self-similar structure exhibits a super hydrophilicity, a high light absorbance (>90%) in an ultra-broad spectrum (200–2500 nm), and an extraordinarily high efficiency in heat transfer. Through further combinations with other techniques, such surfaces can be used for capillary assembling soft electronics, surface self-cleaning, and so on. Furthermore, such an approach can be transferred to other materials with minor modifications. For instance, by doping carbon in polymer matrix, a silicone surface with hierarchical micro–nano structures can be obtained. By selectively patterning such hierarchical structures, we obtained an ultra-high sensitivity bending sensor. We believe that such a fabrication technique of self-similar hierarchical micro–nano structures may encourage researchers to deeply explore the unique features of functional surfaces with such structures and to further discover their potentials in various applications in diverse directions. Full article

Recent progress in wood preservative research has led to the use of insoluble copper carbonate in the form of nano- to micron-sized particles in combination with known triazole fungicides to combat fungal decay and thus decrease physical material properties. Evidently, particle-based agents could lead to issues regarding impregnation of a micro-structured material like wood. In this study, we analyzed these limitations via silicon dioxide particles in impregnation experiments of pine and beech wood. In our experiments, we showed that limitations already existed prior to assumed particle size thresholds of 400–600 nm. In pine wood, 70 nm sized particles were efficiently impregnated, in contrast to 170 nm particles. Further we showed that surface functionalized silica nanoparticles have a major impact on the impregnation efficiency. Silica surfaces bearing amino groups were shown to have strong interactions with the wood cell surface, whereas pentyl chains on the SiO₂ surfaces tended to lower the particle–wood interaction. The acquired results illustrate an important extension of the currently limited knowledge of nanoparticles and wood impregnation and contribute to future improvements in the field of particle-based wood preservatives. Full article

The nano-silica sol was prepared by sol-gel method, and the boric acid, urea, cyanoguanidine, melamine cyanurate (MCA), 1-hydroxyethane 1,1-diphosphonic acid (HEDP), and 6H-dibenz (C,E) (1,2) oxaphosphorin-6-oxide (DOPO) were added to the silica sol to modify the flame retardant through physical doping and chemical bonding. According to the formula proposed by Lewin, the calculation of flammability parameters were obtained by the limiting oxygen index meter, the micro calorimeter, the vertical burner, and the thermogravimetric analyzer proved that there was a synergistic or additive effect between the B/N/P flame retardant and the silica sol. Fourier transform infrared (FT-IR) spectrum, scanning electron microscopy, and pyrolysis gas chromatography-mass spectrometry were used to characterize the morphology, structure, and pyrolysis products of treated silk fabric and residues after combustion. The results show that the flame retardancy of silica-boron sol is mainly caused by endothermic reaction and melt covering reaction. Silicon-nitrogen sol acts as a flame retardant through endothermic reaction, release of gases, and melting coverage. Silicon-phosphorus sol achieves flame retardancy by forming an acid to promote formation of a carbon layer and melting coverage. Silica sol and other flame retardants show excellent flame retardanty after compounding, and have certain complementarity, which can balance the dosage, performance, and cost of flame retardants, and is more suitable for industrial development. Full article

Glassy carbon is a graphenic form of elemental carbon obtained from pyrolysis of carbon-rich precursor polymers that can be patterned using various lithographic techniques. It is electrically and thermally conductive, mechanically strong, light, corrosion resistant and easy to functionalize. These properties render it very suitable for Carbon-microelectromechanical systems (Carbon-MEMS) and nanoelectromechanical systems (Carbon-NEMS) applications. Here we report on the fabrication and characterization of fully operational, microfabricated glassy carbon nano-tips for Atomic Force Microscopy (AFM). These tips are 3D-printed on to micro-machined silicon cantilevers by Two-Photon Polymerization (2PP) of acrylate-based photopolymers (commercially known as IP-series resists), followed by their carbonization employing controlled pyrolysis, which shrinks the patterned structure by ≥98% in volume. Tip performance and robustness during contact and dynamic AFM modes are validated by morphology and wear tests. The design and pyrolysis process optimization performed for this work indicate which parameters require special attention when IP-series polymers are used for the fabrication of Carbon-MEMS and NEMS. Microstructural characterization of the resulting material confirms that it features a frozen percolated network of graphene sheets accompanied by disordered carbon and voids, similar to typical glassy carbons. The presented facile fabrication method can be employed for obtaining a variety of 3D glassy carbon nanostructures starting from the stereolithographic designs provided by the user. Full article

Micro- and nano-structured electrodes have the potential to improve the performance of Li-ion batteries by increasing the surface area of the electrode and reducing the diffusion distance required by the charged carriers. We report the numerical simulation of Lithium-ion batteries with the anode made of core-shell heterostructures of silicon-coated carbon nanofibers. We show that the energy capacity can be significantly improved by reducing the thickness of the silicon anode to the dimension comparable or less than the Li-ion diffusion length inside silicon. The results of simulation indicate that the contraction of the silicon electrode thickness during the battery discharge process commonly found in experiments also plays a major role in the increase of the energy capacity. Full article