Microstructure and mechanical properties of TiAlN/SiO2 nanomultilayers synthesized by reactive magnetron sputtering

TiAlN/SiO₂ nanomultilayers with different SiO₂ layer thickness were synthesized by reactive magnetron sputtering. The microstructure and mechanical properties were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and nano-indentation. The results indicated that, under the template effect of B1-NaCl structural TiAlN layers, amorphous SiO₂ was forced to crystallize and grew epitaxially with TiAlN layers when SiO₂ layer thickness was below 0.6 nm, resulting in the enhancement of hardness and elastic modulus. The maximum hardness and elastic modulus could respectively reach 37 GPa and 393 GPa when SiO₂ layer thickness was 0.6 nm. As SiO₂ layer thickness further increased, SiO₂ transformed back into amorphous state and broken the coherent growth of nanomultilayers, leading to the decrease of hardness and elastic modulus.     

Simple synthesis of ZrO2/SiOx core/shell nanofibers using ZrSi2 with gallium

ZrO₂/SiO_x core/shell nanofibers with diameter ~ 50 nm were synthesized by the thermal oxidation of ZrSi₂ substrates with gallium. The crystalline ZrO₂ cores were grown with amorphous SiO_x shells. It is proposed that the growth of crystalline ZrO₂ core was guided by the prior supersaturation of Zr species in the molten gallium film, whereas the amorphous SiO_x shell could be attributed to the deposition of SiO vapor on the surface of ZrO₂ core. In addition, the ZrO₂/SiO_x core/shell nanofibers show a wide visible photoluminescence (PL) emission at 480 nm, which should originate from the SiO_x shells.     

Co-electrospinning fabrication and photocatalytic performance of TiO2/SiO2 core/sheath nanofibers with tunable sheath thickness

In this paper, core/sheath TiO₂/SiO₂ nanofibers with tunable sheath thickness were directly fabricated via a facile co-electrospinning technique with subsequent calcination at 500 °C. The morphologies and structures of core/sheath TiO₂/SiO₂ nanofibers were characterized by TGA, FESEM, TEM, FTIR, XPS and BET. It was found that the 1D core/sheath nanofibers are made up of anatase–rutile TiO₂ core and amorphous SiO₂ sheath. The influences of SiO₂ sheath and its thickness on the photoreactivity were evaluated by observing photo-degradation of methylene blue aqueous solution under the irradiation of UV light. Compared with pure TiO₂ nanofibers, the core/sheath TiO₂/SiO₂ nanofibers performed a better catalytic performance. That was attributed to not only efficient separation of hole–electron pairs resulting from the formation of heterojunction but also larger surface area and surface silanol group which will be useful to provide higher capacity for oxygen adsorption to generate more hydroxyl radicals. And the optimized core/sheath TiO₂/SiO₂ nanofibers with a sheath thickness of 37 nm exhibited the best photocatalytic performance.     

Hierarchical electrospun SiO2 nanofibers containing SiO2 nanoparticles with controllable surface-roughness and/or porosity

Herein we report that hierarchical electrospun SiO₂ nanofibers incorporated with SiO₂ nanoparticles with fiber diameters being ∼ 500 nm and particle sizes being tens of nanometers were developed through the combination of sol-gel process and electrospinning technique followed by high-temperature pyrolysis; and their morphologies and BET surface areas were examined. The study revealed that the pre-gelation of tetraethyl orthosilicate (TEOS) in spin dopes was important to achieve the morphological consistence of the electrospun precursor nanofibers and the resulting final SiO₂ nanofibers; additionally, SiO₂ nanoparticles appeared to be enriched on the fiber surface, while the surface-roughness and/or porosity of the nanofibers could be controlled through adjusting the incorporation amount of SiO₂ nanoparticles. The developed hierarchical electrospun SiO₂ nanofibers are expected to have important applications in composites (particularly dental composites) as well as catalyst support and adsorption.     

Use of Nanoindentation,Finite Element Simulations,and a Combined Experimental/Numerical Approach to Characterize Elastic Moduli of Individual Porous Silica Particles

This article describes the use of a combination of experimental nanoindentation and finite element numerical simulations to indirectly determine the elastic modulus of individual porous, micron-sized silica (SiO₂) particles. Two independent nanoindentation experiments on individual silica particles were employed, one with a Berkovich pyramidal nanoindenter tip, the other with a flat punch nanoindenter tip. In both cases, 3D finite element simulations were used to generate nanoindenter load–displacement curves for comparison with the corresponding experimental data, using the elastic modulus of the particle as a curve-fitting parameter. The resulting indirectly determined modulus values from the two independent experiments were found to be in good agreement, and were considerably lower than the published values for bulk or particulate solid silica. The results are also consistent with previously reported modulus values for nanoindentation of porous thin film SiO₂. Based on a review of the literature, the authors believe that this is the first article to report on the use of nanoindentation and numerical simulations in a combined experimental/numerical approach to determine the elastic modulus of individual porous silica particles.     

Synthesis of β-silicon carbide nanofiber from an exfoliated graphite and amorphous silica

Silicon carbide (SiC) nanofibers were synthesized from exfoliated graphite containing silica particles at 1425 °C in a 25% H₂/Ar atmosphere. Two types of SiC nanofibers with different morphologies were formed depending on the silica content. A higher silica content led to straight nanofibers with a regular diameter size. The SiC nanofibers derived from the exfoliated graphite/40 wt% SiO₂ powder mixture contained a large number of stacking faults and grew along the [1 1 1] direction. A gas–gas reaction mechanism was proposed to explain the formation of SiC nanofibers.     

静电纺丝法制备尼龙-6/SiO2-TiO2杂化纳米纤维

采用静电纺丝法结合溶胶凝胶技术,制备了尼龙-6/SiO2-TiO2杂化纳米纤维。采用红外光谱（FT-IR）、X射线衍射（XRD）、UV-vis、热重分析（TG）和扫描电镜（SEM）等对杂化纳米纤维进行分析表征。结果表明,随着SiO2-TiO2溶胶的引入,电纺纤维的结晶度下降,耐热性能提升。尼龙-6电纺纤维的平均直径约为...     

The preparation and mechanical properties of novel PVA/SiO2 film

The aim of this work is the evaluation of the mechanical properties of composite PVA/SiO₂. A powder impregnation process with integrated inline continuous plasma of SiO₂ was used to produce PVA/SiO₂ composite. PVA/SiO₂ composite was processed into test laminates by compression mounding and the interface-dominated composite properties were studied. When compared to PVA, the mechanical properties of PVA/SiO₂ were significantly increased, such as tensile strength, tensile modulus and elongation at break, and the damping capacity of PVA/SiO₂ film increased with increasing ratio of SiO₂.     

Preparation, structure and photoluminescence properties of SiO2/ZnO nanocables via electrospinning and vapor transport deposition

SiO₂/ZnO nanocables were prepared by the combination of electrospinning technology and vapor transport deposition procedure. X-ray diffraction patterns indicated that ZnO with wurtzite structure was deposited on SiO₂ nanofibers templates successfully. Field emission scanning electron microscopy and transmission electron microscopy showed that the products were core/shell nanocables with a narrow distribution of the core/shell diameters. The nanocables showed a strong near band edge emission in ultraviolet region and a weak deep level emission at room temperature in their photoluminescence (PL) spectra. The anomalous temperature characteristic of integrated PL intensity in temperature-dependent PL spectra was discussed by considering carrier injection across the interface of SiO₂/ZnO nanocables.     

A simple route to disperse silver nanoparticles on the surfaces of silica nanofibers with excellent photocatalytic properties

In this work, monodispersed silver nanoparticles decorated SiO₂ nanofibers were synthesized by electrospinning method, followed by thermal treatment at 600 °C. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) were used to characterize the composite nanofibers. Accordingly, the detailed formation mechanism of SiO₂/Ag composite nanofibers was discussed. Furthermore, an excellent catalytic activity of SiO₂/Ag composite fibers was observed by a degradation reaction of methyl orange (MO) dye.     

Growth of SiOx nanofibers using FeSi and β-FeSi2 substrates with Ga droplets

The growth of SiO_x nanofibers on iron silicide substrates with Ga droplets was examined. It is found that well-aligned, highly oriented nanofibers were grown in an orderly fashion with a high density from FeSi substrates. Though the length of the nanofibers depends on the growth time and the growth temperature, their diameters were about 20 nm throughout the nanofibers grown under the examined growth conditions. On the other hand, although the evidence of the growth of highly oriented, dense and well-aligned nanofibers was not obtained, the growth of small piece of nanofibers was evident, for the use of β-FeSi₂ substrates.     

Li+‐Containing,Continuous Silica Nanofibers for High Li+ Conductivity in Composite Polymer Electrolyte

Solid‐state electrolytes have recently attracted significant attention toward safe and high‐energy lithium chemistries. In particular, polyethylene oxide (PEO)‐based composite polymer electrolytes (CPEs) have shown outstanding mechanical flexibility and manufacturing feasibility. However, their limited ionic conductivity, poor electrochemical stability, and insufficient mechanical strength are yet to be addressed. In this work, a novel CPE supported by Li⁺‐containing SiO₂ nanofibers is developed. The nanofibers are obtained via sol–gel electrospinning, during which lithium sulfate is in situ introduced into the nanofibers. The uniform doping of Li₂SO₄ in SiO₂ nanofibers increases the Li⁺ conductivity of SiO₂, generates mesopores on the surface of SiO₂ nanofibers, and improves the wettability between SiO₂ and PEO. As a result, the obtained SiO₂/Li₂SO₄/PEO CPE yields high Li⁺ conductivity (1.3 × 10^?4 S cm^?1 at 60 °C, ≈4.9 times the Li₂SO₄‐free CPE) and electrochemical stability. Furthermore, the all‐solid‐state LiFePO₄‐Li full cell demonstrates stable cycling with high capacities (over 80 mAh g^?1, 50 cycles at C/2 at 60 °C). The Li⁺‐containing mesoporous SiO₂ nanofibers show great potential as the filler for CPEs. Similar methods can be used to incorporate Li salts into other filler materials for CPEs.     

Electrospun SiO2/WO3/NiWO4 decorated carbon nanofibers for an efficient electrocatalytic hydrogen evolution

The SiO₂/WO₃/NiWO₄ composites modified carbon nanofibers (SiWNi-CNFs) were prepared by a facile electrospinning method with following carbonization process under nitrogen atmosphere. The as-obtained SiWNi-CNFs were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectra (XPS), X-ray powder diffraction (XRD), FT-IR spectroscopy and Raman spectroscopy. As revealed by the electrochemical measurement, the SiWNi-CNFs prepared with SiW₁₂/NiAc₂ molar ratio of 1:1 presented best hydrogen evolution activity with a small Tafel slope (48?mV dec^?1) among all the as-prepared samples. Notably, the as-prepared catalysts exhibit a small onset potential (0.29?V vs. reversible hydrogen electrode), high current density and excellent stability. The experimental results pointed that the SiWNi-CNFs processes more efficient hydrogen evolution properties than that other contrast samples. This is due to the SiO₂/WO₃/NiWO₄ composite modified on the surface of carbon nanofibers can generate numerous active sites from the synergistic effect of each component. At the same time, the intimate combination of ternary oxide and carbon nanofibers can accelerate the electron transfer, enhance the stability and hinder the aggregation of active components during the carbonization. Moreover, the net-like structure stacked by carbon nanofibers should render the exposure of active sites and facilitate the mass transport for the HER process.     

Formation of electrospun nylon-6/methoxy poly(ethylene glycol) oligomer spider-wave nanofibers

A methoxy poly(ethylene glycol) (MPEG) oligomer with a viscous nylon-6 supporting solution was fabricated and polymerized simultaneously to form a nanofiber network structure via electrospinning. This network consisted of thin MPEG nanofibers and thick nylon-6 nanofibers, which were arranged in a spider-web like structure. These two different nanofibers were separated from the electrospun mat by extraction of MPEG using water. This result showed that the hybrid nanocomposite mat consisted of two different interconnecting polymeric nanofibers. We propose that this interconnection is due to the formation of hydrogen bonds between MPEG and nylon-6 molecules. This spider-web structure formed by electrospinning was responsible for increasing the mechanical strength and the wetability of nylon-6 mat in the presence of small amounts of MPEG.     

Elastic properties of lanthanum aluminosilicate glasses

The elastic properties of two series of lanthanum aluminosilicate glasses (15La₂O₃-xAl₂O₃-(85−x)SiO₂ and 25La₂O₃-yAl₂O₃-(75−y)SiO₂, where x, y=15, 20, 25, 30, 35 mol%), were obtained by the ultrasonic pulse-echo technique, at room temperature. The correlation of elastic stiffness, the cross-link density, and the fractal bond connectivity of these glasses are discussed. The derived experimental values of Young’s modulus, bulk modulus, shear modulus and Poisson’s ratio for our glasses are compared with those theoretically calculated values in terms of the Makishima-Mackenzie model.     

Electrospun nylon-6 spider-net like nanofiber mat containing TiO2 nanoparticles: A multifunctional nanocomposite textile material

In this study, electrospun nylon-6 spider-net like nanofiber mats containing TiO₂ nanoparticles (TiO₂ NPs) were successfully prepared. The nanofiber mats containing TiO₂ NPs were characterized by SEM, FE-SEM, TEM, XRD, TGA and EDX analyses. The results revealed that fibers in two distinct sizes (nano and subnano scale) were obtained with the addition of a small amount of TiO₂ NPs. In low TiO₂ content nanocomposite mats, these nanofiber weaves were found uniformly loaded with TiO₂ NPs on their wall. The presence of a small amount of TiO₂ NPs in nylon-6 solution was found to improve the hydrophilicity (antifouling effect), mechanical strength, antimicrobial and UV protecting ability of electrospun mats. The resultant nylon-6/TiO₂ antimicrobial spider-net like composite mat with antifouling effect may be a potential candidate for future water filter applications, and its improved mechanical strength and UV blocking ability will also make it a potential candidate for protective clothing.     

Multi-walled carbon nanotubes fabricated by electrospinning of acrylonitrile/nylon solution and subsequent carbonization

The poly(acrylonitrile) (PAN) nanofiber web interpenetrated nylon-6 nanofiber supporters were prepared by electrospinning of an acrylonitrile (AN)/nylon-6 solution. It was realized that the average diameters of PAN and nylon-6 nanofiber were 20 and 100 nm, respectively, and that the PAN nanofibers constructed spider-mat networks which were supported by the robust nylon-6 nanofiber pillars. After stabilization and carbonization above 600 degrees C, both hollow-shaped and bamboo-shaped multi-walled carbon nanotubes (MWCNTs) were formed with the diameter range from 5 to 20 nm. The morphology and structure of MWCNTs had been further investigated by the combination techniques of transmission electron microscopy (TEM), electron diffraction (ED), X-ray diffraction (XRD) and elemental analyzer (EA).     

Crystallization behavior of PA6/SiO2 organic–inorganic hybrid material

Poly 2-hydroxy propylmethacrylate-methyl methacrylate/SiO₂ (PHPMA-MMA/SiO₂), an active composite was used to synthesize polyamide-6/SiO₂ (PA6/SiO₂) organic–inorganic hybrid materials via blending method. X-ray diffraction analysis (XRD) results showed that the addition of PHPMA-MMA/SiO₂ composite induced PA6 to transit from α to γ crystal form. The nonisothermal crystallization kinetics of PA6 and PA6/SiO₂ hybrid materials was investigated by differential scanning calorimetry (DSC). Jeziorny method derived from Avrami analysis and a method developed by Liu were employed to describe the nonisothermal crystallization process of PA6 and PA6/SiO₂ hybrid materials. Based on our experimental data, if the relative degree of crystallinity was approximately 60% or more, the Jeziorny method was not valid to describe the nonisothermal crystallization process, while Liu method was successful to describe the whole nonisothermal crystallization process. When X(t) was below about 60%, the crystallization rates of PA6 and PA6/SiO₂ hybrid materials were very approximate, but when X(t) was approximately 60% or more, the crystallization rate of PA6 was quicker than that of PA6/SiO₂ hybrid materials. Moreover, the addition of PHPMA-MMA/SiO₂ composite decreased the crystallization activation energy ΔE calculated by Kissinger equation because of the γ transition.     

SiO2/sulfonated poly ether ether ketone (SPEEK) composite nanofiber mat supported proton exchange membranes for fuel cells

A composite membrane of silica (SiO₂)/sulfonated poly (ether ether ketone) (SPEEK) nanofiber mat impregnated with Nafion was fabricated and evaluated for its potential use as a proton conductor for high temperature polymer electrolyte membrane fuel cells. The supporting SiO₂/SPEEK composite nanofibrous skeleton was prepared via electrospinning of a mixture of SPEEK solution and silica sol prepared from tetraethyl orthosilicate (TEOS). The control of hydrolysis and condensation of TEOS enabled to form entangled SiO₂ networks miscible to SPEEK solution. The prepared SiO₂/SPEEK nanofiber mat was impregnated with Nafion^® to completely fill the inter-fiber voids to prepare a dense membrane. The morphology of the nanofiber mat and the composite membrane were observed by scanning electron microscopy and the presence of SiO₂ and SPEEK in the prepared nanofibers was confirmed by FTIR spectroscopy. Proton conductivity and swelling of the membrane were measured. The H₂/O₂ single cell test using the composite membrane as a PEM was performed. At a high temperature and low humidity condition (120 °C and 40 % RH), the maximum power density was 170 mW/cm² for the Nafion-impregnated SiO₂/SPEEK (40/60 w/w) composite nanofiber membrane that was 2.4 times higher than recast Nafion (71 mW/cm²) while SPEEK film failed.     

LaOCl nanofibers derived from electrospun PVA/Lanthanum chloride composite fibers

Electrospun nanofibers of poly (vinyl alcohol) (PVA)/Lanthanum (Ш) chloride (LaCl₃) composite were employed to prepare the LaOCl nanofibers by calcination. TG-DSC was used to investigate the thermal property of precursor, while FT-IR, XRD, FESEM and TPD were employed to characterize the derived LaOCl nanofibers. Results indicate that the addition of LaCl₃ leads to the formation of fork segments in the structure of electrospun PVA/LaCl₃ composite nanofibers, therefore, changing the decomposition behavior of the fibers. Pure LaOCl fibers with a diameter range of 90-220 nm can be obtained by calcination of electrospun PVA/LaCl₃ composite nanofibers at 700 °C for 7 h. The resultant LaOCl nanofibers show a good sensing behavior for CO₂ gas.