SiOx Encapsulated in Graphene Bubble Film: An Ultrastable Li‐Ion Battery Anode

SiO_x is proposed as one of the most promising anodes for Li‐ion batteries (LIBs) for its advantageous capacity and stable Li uptake/release electrochemistry, yet its practical application is still a big challenge. Here encapsulation of SiO_x nanoparticles into conductive graphene bubble film via a facile and scalable self‐assembly in solution is shown. The SiO_x nanoparticles are closely wrapped in multilayered graphene to reconstruct a flake‐graphite‐like macrostructure, which promises uniform and agglomeration‐free distribution of SiO_x in the carbon while ensures a high mechanical strength and a high tap density of the composite. The composites present unprecedented cycling stability and excellent rate capabilities upon Li storage, rendering an opportunity for its anode use in the next‐generation high‐energy LIBs.     

In Situ Mesopore Formation in SiOx Nanoparticles by Chemically Reinforced Heterointerface and Use of Chemical Prelithiation for Highly Reversible Lithium-Ion Battery Anode (Small 16/2023)

SiO_x is a promising next-generation anode material for lithium-ion batteries. However, its commercial adoption faces challenges such as low electrical conductivity, large volume expansion during cycling, and low initial Coulombic efficiency. Herein, to overcome these limitations, an eco-friendly in situ methodology for synthesizing carbon-containing mesoporous SiO_x nanoparticles wrapped in another carbon layers is developed. The chemical reactions of vinyl-terminated silanes are designed to be confined inside the cationic surfactant-derived emulsion droplets. The polyvinylpyrrolidone-based chemical functionalization of organically modified SiO₂ nanoparticles leads to excellent dispersion stability and allows for intact hybridization with graphene oxide sheets. The formation of a chemically reinforced heterointerface enables the spontaneous generation of mesopores inside the thermally reduced SiO_x nanoparticles. The resulting mesoporous SiO_x-based nanocomposite anodes exhibit superior cycling stability (≈100% after 500 cycles at 0.5 A g⁻¹) and rate capability (554 mAh g⁻¹ at 2 A g⁻¹), elucidating characteristic synergetic effects in mesoporous SiO_x-based nanocomposite anodes. The practical commercialization potential with a significant enhancement in initial Coulombic efficiency through a chemical prelithiation reaction is also presented. The full cell employing the prelithiated anode demonstrated more than 2 times higher Coulombic efficiency and discharge capacity compared to the full cell with a pristine anode.     

The influences of poly(lactic-co-glycolic acid) (PLGA) coating on the biodegradability, bioactivity, and biocompatibility of calcium silicate bioceramics

Calcium silicate (CaSiO₃) bioceramics and polyesters have complementary qualities as potential bone substituted materials. In this study, sintered CaSiO₃ bioceramics were prepared and coated with poly(lactic-co-glycolic acid) (PLGA), and the influences of the PLGA coating on the degradation, hydrophilicity, bioactivity, and biocompatibility of CaSiO₃ ceramics were investigated. The results showed that the degradation rate was reduced, while hydrophilicity was decreased with the increase of the polymer coating. In addition, the polymer coating resulted in a decrease of the alkaline pH value during the degradation of the ceramics, which indicated an increase of the cell biocompatibility, confirmed by the attachment and proliferation of rMSCs on the surface of the polymer-coated ceramics. Furthermore, the apatite-forming ability of the PLGA-coated CaSiO₃ bioceramics was maintained. This study suggested that the coating with PLGA might be a useful method to improve the integrative properties of CaSiO₃ bioceramics for applications in bone regeneration and bone tissue engineering.     

Influence of N atomic percentages on cell attachment for CN<Subscript>x</Subscript> coatings

Carbon film is an excellent candidate for use as a biocompatible coating due to its excellent properties. However, considerable attention has just been focused on the biocompatibility of diamond-like carbon (DLC) in recent years. It is difficult to find reports on the investigations of the biocompatibility of CN_x so far. It is well known that CN_x has similar structural characteristics as that of DLC. Its excellent mechanical and tribological properties are comparable to that of DLC. In addition, it is probable that the presence of nitrogen leads to a positive effect on biocompatibility. So, this work focusses on cell attachment of CN_x coating and the relation between nitrogen atomic percentage and cell attachment. CN_x coatings were prepared using magnetron sputtering under two N₂ partial pressures for the evaluation of relation between nitrogen atomic percentage and cell attachment. Cell culture tests using human endothelial cells and mouse fibroblasts were performed. Both coatings resulted in no adverse effects on the cells in culture. Compared with CN_x (x = 0.088), CN_x (x = 0.149) film provided a better surface for normal cellular attachment, spreading and proliferation without apparent impairment of cell physiology. At the same time, the coatings exhibited excellent tribological and corrosion performance. XPS and AES analyses showed that higher nitrogen atomic percentage might lead to a positive effect on the cell attachment.     

In vitro response of primary rat osteoblasts to titania/hydroxyapatite coatings compared with transformed human osteoblast-like cells

The biocompatibility of titania/hydroxyapatite (TiO₂HA) composite coatings, at different ratio obtained by sol–gel process, was investigated studying the behavior of primary cultures of rat osteoblastic cells, isolated by femoral trabecular bone tissue. Moreover, the results have been compared with the response of human osteoblast-like MG63 cell line. Cytotoxicity of coatings was assessed by lactate dehydrogenase activity (LDH). The cellular behavior was analyzed by the cell proliferation (MTT test), cell morphology (SEM) and the biochemical markers evaluation of osteoblastic phenotype, such as alkaline phosphatase activity (ALP) and osteocalcin production. The results showed that TiO₂/HA coatings have no toxic effects and seemed to be a good support for cell adhesion and proliferation. Moreover, these materials allowed the differentiation of osteoblasts, stimulating the expression of alkaline phosphatase activity. The responses of the primary rat osteoblasts and human osteoblast-like MG63 cell line grown onto these coatings were similar in terms of proliferation and ALP activity. Differences were found considering the osteocalcin production. The results show that these coatings, thanks to their chemical composition and the deposition technique, are very promising for the potential orthopedic and dental applications.     

Successive nucleation and a rodlike growth of SiOx nanoparticles into the pore bottoms of an anodic alumina template

Although the SiO_x nanoparticles were previously reported to electrochemically nucleate from the bottoms of the pore array formed in the AAO/Ti/Si system, new applications of anodic aluminum oxide templates, i.e., successive nucleation and a rodlike growth of SiO_x nanoparticles, were observed utilizing the subsequent annealing technique after the nanoparticle precipitation. Tailoring the pore bottom profile by doping type and level of wafers also critically affected to nucleate the SiO_x nanoparticles from the pore bottoms. By anodization, as previously reported, only one nanoparticle per each pore was generally precipitated from the pyramid-shaped Si-containing TiO_x nanopillars; however, subsequent annealing under a low pressure of hydrogen enabled the successive precipitation of nanoparticles. Annealing under atmospheric pressure with H₂ and N₂ resulted in the rodlike growth of a single nanoparticle without successive nanoparticle precipitation.     

Corrosion behavior of Cu–SiO<Subscript>2</Subscript> nanocomposite coatings obtained by electrodeposition in the presence of cetyl trimethyl ammonium bromide

Copper silica composite coatings are an attractive alternative to chromium and nickel coatings in order to avoid environmental problems and for application in electrical devices. However, co-deposition of SiO₂ particles with metals occurs to a rather limited extent, generally under 1%, due to the hydrophilicity of SiO₂, which makes the incorporation of particles in a metallic matrix difficult. To overcome this drawback, the influence of cetyl trimethyl ammonium bromide (CTAB) on the deposition and corrosion behavior of Cu–SiO₂ coatings on steel has been studied. It was established that CTAB plays a beneficial role in SiO₂ suspension stabilization, promotes the co-deposition of nanoparticles in the copper matrix and improves the deposit morphology and structure. Consequently, a higher corrosion resistance of Cu–SiO₂ deposits obtained in the presence of CTAB was noticed. The most important effect was observed in the case when CTAB was used in concentration of 10⁻³ M in the electroplating bath.     

Real-time evaluation of thickness, optical properties and stoichiometry of SiOx gas barrier coatings on polymers

Silicon oxide (SiO_x) coatings have been exploited for packaging applications due to their exceptional properties. They can be fabricated by a number of techniques, including Electron Beam Evaporation (EBE); an easily applicable method in industrial scale. The SiO_x films' thickness and stoichiometry are the key parameters for the achievement of the final functional properties of the systems. The need to reduce material waste as well as the time required for the evaluation of the systems, make real-time monitoring and control requisite. This work highlights a methodology based on real-time Multi-Wavelength Ellipsometry for the monitoring of the EBE processes of SiO_x coatings on poly(ethylene terephthalate) membranes. It is presented a thorough correlation between the basic optical parameters, such as refractive index and Penn gap, and the SiO_x films' thickness, stoichiometry, composition and functional properties, such as oxygen permeation.     

Osteoblast interaction with laser cladded HA and SiO2-HA coatings on Ti–6Al–4V

In order to improve the bioactivity and biocompatibility of titanium endosseous implants, the morphology and composition of the surfaces were modified. Polished Ti–6Al–4V substrates were coated by a laser cladding process with different precursors: 100 wt.% HA and 25 wt.% SiO₂-HA. X-ray diffraction of the laser processed samples showed the presence of CaTiO₃, Ca₃(PO₄)₂, and Ca₂SiO₄ phases within the coatings. From in vitro studies, it was observed that compared to the unmodified substrate all laser cladded samples presented improved cellular interactions and bioactivity. The samples processed with 25 wt.% SiO₂-HA precursor showed a significantly higher HA precipitation after immersion in simulated body fluid than 100 wt.% HA precursor and titanium substrates. The in vitro biocompatibility of the laser cladded coatings and titanium substrate was investigated by culturing of mouse MC3T3-E1 pre-osteoblast cell line and analyzing the cell viability, cell proliferation, and cell morphology. A significantly higher cell attachment and proliferation rate were observed for both laser cladded 100 wt.% HA and 25 wt.% SiO₂-HA samples. Compared to 100 wt.% HA sample, 25 wt.% SiO₂-HA samples presented a slightly improved cellular interaction due to the addition of SiO₂. The staining of the actin filaments showed that the laser cladded samples induced a normal cytoskeleton and well-developed focal adhesion contacts. Scanning electron microscopic image of the cell cultured samples revealed better cell attachment and spreading for 25 wt.% SiO₂-HA and 100 wt.% HA coatings than titanium substrate. These results suggest that the laser cladding process improves the bioactivity and biocompatibility of titanium. The observed biological improvements are mainly due to the coating induced changes in surface chemistry and surface morphology.     

Instantaneous formation of SiOx nanocomposite for high capacity lithium ion batteries by enhanced disproportionation reaction during plasma spray physical vapor deposition

Nanocomposite SiO_x particles have been produced by a single step plasma spray physical vapor deposition (PS-PVD) through rapid condensation of SiO vapors and the subsequent disproportionation reaction. Core-shell nanoparticles, in which 15 nm crystalline Si is embedded within the amorphous SiO_x matrix, form under typical PS-PVD conditions, while 10 nm amorphous particles are formed when processed with an increased degree of non-equilibrium effect. Addition of CH₄ promotes reduction in the oxygen content x of SiO_x, and thereby increases the Si volume in a nanocomposite particle. As a result, core-shell nanoparticles with x = 0.46 as anode exhibit increased initial efficiency and the capacity of lithium ion batteries while maintaining cyclability. Furthermore, it is revealed that the disproportionation reaction of SiO is promoted in nanosized particles attaining increased Si diffusivity by two orders of magnitude compared to that in bulk, which facilitates instantaneous composite nanoparticle formation during PS-PVD.     

Silicon oxide coatings as protection against corrosion

Silicon oxide films (SiO_x(0≲x≲2)) were deposited onto Inconel 617 alloy for the purpose of corrosion protection in an impure helium environment. The protective behaviour of the deposited films was examined as a function of their chemical composition. The hypostoichiometric SiO_x (x < 2) coatings showed poor protective effects. Rather, they enhanced carburization of the Inconel 617 substrate. This is because the interdiffusion of silicon and nickel is faster than the oxidation of SiO_x to form protective SiO₂. In the helium environment used, the rate of supply of oxygen was quite low. Stoichiometric SiO₂ coatings, however, showed good protective qualities. They protected the Inconel 617 substrate from carburization and from selective oxidation at 1170 and 1270 K for 200 h. However, some deterioration in the protective effect is expected for longer exposure to this environment at 1270 K.     

Characteristics of SiOx-cored composite nanowires with Ag shell layers

This paper reports the preparation of Ag-coated SiO_x nanowires and analyzes changes in the structural properties and photoluminescence (PL) spectra induced by a thermal annealing process. The thermal induced changes in the sample morphology, generating Ag nanoparticles on the core of SiO_x nanowires and crystalline structures were affected, facilitating the generation of the Ag₂SiO₃ phase. The overall shape of the PL spectrum was changed significantly by both the Ag-coating and the subsequent thermal annealing. Possible emission mechanisms were discussed. This study gives insight into the annealing process regarding various coaxial one-dimensional materials, particularly with metal shell layers.     

Characterization and antibacterial performance of ZrCN/amorphous carbon coatings deposited on titanium implants

Titanium (Ti)-based materials have been used for dental/orthopedic implants due to their excellent biological compatibility, superior mechanical strength and high corrosion resistance. The osseointegration of Ti implants is related to their composition and surface treatment. Better biocompatibility and anti-bacterial performances of Ti implant are beneficial for the osseointegration and for avoiding the infection after implantation surgery. In this study, nanocomposite ZrCN/amorphous carbon (a-C) coatings with different carbon contents were deposited on a bio-grade pure Ti implant material. A cathodic-arc evaporation system with plasma enhanced duct equipment was used for the deposition of ZrCN/a-C coatings. Reactive gas (N₂) and C₂H₂ activated by the zirconium plasma in the evaporation process were used to deposit the ZrCN/a-C coatings. To verify the susceptibility of implant surface to bacterial adhesion, Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans), one of the major pathogen frequently found in the dental implant-associated infections, was chosen for in vitro anti-bacterial analyses. In addition, the biocompatibility of human gingival fibroblast (HGF) cells on coatings was also evaluated by a cell proliferation assay. The results suggested that the ZrCN/a-C coatings with carbon content higher than 12.7 at.% can improve antibacterial performance with excellent HGF cell compatibility as well.     

Synthesis of Pt-immobilized on silica and polystyrene-encapsulated silica and their applications as electrocatalysts in the proton exchange membrane fuel cell

Nano sized Pt particles were successfully immobilized onto SiO₂ and polystyrene-encapsulated silica core shell (SiO₂@PS). To make the immobilization of Pt onto both silica and polystyrene-encapsulated silica core shell, SiO₂ was first functionalized with -NH₂ using 3-amino propyl trimethoxysilane (APTMS) while for core shell, the negatively charged surface of polystyrene (PS) was changed with positive charge by cationic surfactant such as cetyltrimethylammonium chloride (CTACl) to make the formation of SiO₂ shell on preformed PS sphere. Transmission electron micrograph (TEM) images shows that Pt nanoparticles immobilized onto SiO₂ and SiO₂@PS were to be 3-4 nm without agglomeraiton. The energy dispersive spectroscope (EDS) shows that Pt contents on both SiO₂ and SiO₂@PS were to be 21.45% and 20.28%, respectively. In case of Pt-SiO₂@PS, it is believed that Pt should have been immobilized onto PS surface and pore within SiO₂ shell as well as SiO₂ surface. The MEA fabricated with Pt-SiO₂@PS shows better cell performance than of Pt-SiO₂.     

Fabrication of Lamellar Nanosphere Structure for Effective Stress‐Management in Large‐Volume‐Variation Anodes of High‐Energy Lithium‐Ion Batteries

The use of high‐capacity anode materials to overcome the energy density limits imposed by the utilization of low‐theoretical‐capacity conventional graphite has recently drawn increased attention. Until now, stress management (including strategies relying on size, surface coating, and free volume control) has been achieved by addressing the critical problems originating from significant anode volume expansion upon lithiation. However, commercially viable alternatives to graphite have not yet been found. A new stress‐management strategy relying on the use of a lamellar nanosphere Si anode is proposed. Specifically, nanospheres comprising ≈50 nm Si nanoparticles encapsulated by SiO_x /Si/SiO_x /C layers with thicknesses of <20 nm per layer are synthesized via one‐pot chemical vapor deposition in various atmospheres. SiO_x is found to act as a stress management interlayer when it is located between Si and mitigates stress intensification on the surface layer, allowing nanospheres to maintain their morphological integrity and promoting the formation of a stable solid electrolyte interphase layer during cycling. When tested using an industrial protocol, a full cell comprising a nanosphere/graphite blended anode and a lithium cobalt oxide cathode achieve an average energy density of 2440.2 Wh L^?1 (1.72 times higher than that of conventional graphite) with a capacity retention ratio of 80% after 101 cycles.     

A Pyrene–Poly(acrylic acid)–Polyrotaxane Supramolecular Binder Network for High‐Performance Silicon Negative Electrodes

Although being incorporated in commercial lithium‐ion batteries for a while, the weight portion of silicon monoxide (SiO_x, x ≈ 1) is only less than 10 wt% due to the insufficient cycle life. Along this line, polymeric binders that can assist in maintaining the mechanical integrity and interfacial stability of SiO_x electrodes are desired to realize higher contents of SiO_x. Herein, a pyrene–poly(acrylic acid) (PAA)–polyrotaxane (PR) supramolecular network is reported as a polymeric binder for SiO_x with 100 wt%. The noncovalent functionalization of a carbon coating layer on the SiO_x is achieved by using a hydroxylated pyrene derivative via the π–π stacking interaction, which simultaneously enables hydrogen bonding interactions with the PR–PAA network through its hydroxyl moiety. Moreover, the PR's ring sliding while being crosslinked to PAA endows a high elasticity to the entire polymer network, effectively buffering the volume expansion of SiO_x and largely mitigating the electrode swelling. Based on these extraordinary physicochemical properties of the pyrene–PAA–PR supramolecular binder, the robust cycling of SiO_x electrodes is demonstrated at commercial levels of areal loading in both half‐cell and full‐cell configurations.     

Synthesis and magnetic properties of Ni–SiO2 nanocomposites

Nanocomposite Ni_(1 − x)/(SiO₂)_x soft magnetic materials were synthesized by a simple sol–gel combined hydrogen reduction method. The crystal structure of the particles was determined by X-ray diffraction (XRD). The shapes and sizes of the metal particles embedded in the SiO₂ matrix were determined by transmission electron microscopy (TEM), and magnetic properties were measured by the vibrating samples magnetometer (VSM). The obtained nanocomposite material is composed of nanoparticles coated with a thin SiO₂ layer, and with the content of the silicon increase, the thickness of the silica shells increase and the saturation magnetization decrease. The diameter of Ni particle in the sample is about 30–40 nm. The influence of the Ni content and preparation conditions on the microstructures and magnetic properties were discussed.     

Gold catalysts for the abatement of environmentally harmful materials: Modeling the structure dependency

FeO_x, TiO₂ and CeO_x layers were deposited by pulsed laser deposition (PLD) technique onto Au films or Au nanoparticles supported on SiO₂/Si(100). The samples were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS) and their reactivity was studied in catalytic CO oxidation. Comparison was made with reference samples of FeO_x/SiO₂/Si(100), TiO₂/SiO₂/Si(100), CeO_x/SiO₂/Si(100) and Au/SiO₂/Si(100) layers. The catalytic activity of the metal-oxide/Au/SiO₂/Si(100) samples must be attributed to active sites located on the metal-oxides overlayer modified by gold underneath, since no Au was exposed to the surface according to the XPS and SIMS. We found a promoting effect of gold on the catalytic activity of the FeO_x overlayer and an inhibiting effect of gold on the TiO₂ and CeO_x overlayers. These findings are discussed in terms of electronic interactions at the Au/metal oxide interface.     

Comparisons and analyses of the properties of laser-induced damage to SiO2 and ZnS

To compare the optical damage resistance ability of SiO₂ and ZnS, the processes of electrons reproduction of the two materials have been studied. The relationship of multiphoton ionization rate, avalanche ionization rate and the multiphoton parameter <?x?+?1?> with the intensity of the incident laser is calculated. The damage thresholds induced by the laser with different pulse widths are calculated too. In addition, the respectable role of the recombination and diffusion for an electron in the electronic proliferation processes is examined. Calculation results show that SiO₂ has a higher damage threshold while τ?<?1?ns, and ZnS has a higher damage threshold while τ?>?1?ns.     

Synthesis of Thin Films with Controlled Absorption Using a Jet High-Frequency Induction Plasmatron

The authors investigate SiO _x and TiO _x (0 < x < 2) thin-film coatings with controlled absorption which are produced using a jet high-frequency plasma under conditions of dynamic vacuum.