New insights into the formation of silicon-oxygen layer on lithium metal anode via in situ reaction with tetraethoxysilane

Lithium metal-based secondary batteries are very promising for next generation power battery due to their high energy density.However,lithium anodes suffer from poor electrochemical reversibility in organic electrolytes due to Li dendrites and instability of the solid electrolyte interphase.Recent research demonstrated that the problem can be alleviated via tetraethoxysilane(TEOS)treated lithium metal to form a silicon oxide layer on the lithium surface,however,its reaction mechanism is controversial.Herein,we deeply explore the reaction mechanism between TEOS and Li and propose:Fresh Li can directly react with TEOS even though no lithium hydroxide exists on the lithium surface,and the participation of water will accelerate the reaction process.Moreover,it was found that the silicon oxide layer can promote the uniform deposition of lithium ions by providing lithiophilic nucleation sites,thereby achieving a long cycle life of Li metal batteries.

THE EFFECT OF THE ACID CATALYST ON THE PREPARATION OF MQ SILICONE RESINS

MQ silicone resins were prepared through hydrolytic condensation of ethyl polysilicate or tetraethoxysilane and hexamethyl disiloxane. The unit ratio of the MQ resins was determined by Si-29-NMR. The relationship of the unit ratio of the product resins with that in the feed was studied. When the reaction was catalyzed by aqueous hydrochloric acid, and the unit ratio of M to Q in the feed was more than 1, the unit ratio of the product was usually lower than that of the feed. The MQ silicon with an unit ratio of M/Q > 2 could not be obtained. However, if the reaction was catalyzed by concentrated sulfuric acid and the reverse hydrolysis process was employed, MQ silicone resin with very high M/Q ratio was successfully prepared.

Synthesis of Silica Decorated MWCNTs for Field Emission Property

A novel route to nanocomposites containing surface modified multiwalled carbon nanotubes(MWCNTs) by silica thin film is reported.The effect of chemical oxidation on the surface of MWCNTs by using different acid-treatments is studied.The acidic processes are characterized by Raman spectroscopy,thermogravimetry analysis,scanning electron microscopy,and transmission electron microscopy.MWCNTs can be coated homogeneously with silica film by using tetraethoxysilane(TEOS) as a precursor in a sol-gel process.Varying the shell thickness of amorphous silica coating layers on MWCNTs exhibits excellent thermal stability,reliability,and lifetime of field emission properties,especially down to less than 10 nm.

Effect of Y-Methacryloxypropyltrimethoxysilane (MPS) and Tetraethoxysilane (TEOS) Towards Preparation of Oil Absorbent Foams from Polyvinyl Alcohol (PVA) Reinforced with Microfibrillated Cellulose (MFC)

Increasing usage of foams in various industry sectors had causing serious disposal problems once it reaches the end of its life-cycle.Herein,PVA-MFC foam was prepared by freeze-drying using polyvinyl alcohol(PVA)and microfibrillated cellulose(MFC)as a reinforced material from sugarcane bagasse(SCB).In this study,the PVA-MFC foam was chemically silylated with Y-methacryloxypropyltrimethoxysilane(MPS)and tetraethoxysilane(TEOS).The wetting ability and mechanical strength of the silylated_(2,20)PVA-MFC foam was greatly enhanced compared with unmodified_(2,20)PVA-MFC foam.The silane chemicals(MPS and TEOS)had been confirmed grafted on_(2,20)PVA-MFC foam due to the presence of Si-C and Si-O-C stretching vibration as showed in Fourier Transform Infrared(FTIR)spectra and cloud-like coating of porous pore was observed in scanning electron microscopy(SEM)images.The silylated_(2,20)PVA-MFC foam(MPS and TEOS)exhibited a series of desirable properties such as lower swelling ratio and high absorption capacity of solvents and oils but had low thermal stability in thermogravimetric(TGA)analysis.The characterization of_(2,20)PVA-MFC foam using TEOS was further investigated.A significant difference in morphology was clearly observed between the unmodified and silylated_(2,20)PVA-MFC-TEOS foam through field emission scanning electron microscopy(FESEM)images.The X-ray photoelectron(XPS)analysis of silylated_(2,20)PVA-MFC-TEOS foam confirmed the presence of C,O and trace amount of Si elements.These synthesized_(2,20)PVA-MFC foam could be a promising material for broad range of polymer foam applications.

Enhanced consolidation efficacy and durability of highly porous calcareous building stones enabled by nanosilica-based treatments

Outdoor building stones are suffering from serious degradation.To restore internal cohesion and to alleviate the disintegration of decayed stones,consolidation treatment is necessary and significant.Up to date,no fully satisfactory consolidation agent and its application methodology are available,mainly due to the limited penetration depth of consolidants,low compatibility,or poor durability in environmental conditions.Herein,in this study,aiming to design an effective and enduring method for the consolidation of highly porous calcareous stones,nanosilica-based consolidation treatments were tested and compared with traditional compounds(tetraethoxysilane,alkylalkoxysilane,barium hydroxide).In order to evaluate their performance and compatibility,a series of standard tests,including the Drilling Resistance Measurement System(DRMS)test,surface color measurement,vapor diffusivity measurement,and peeling test,were carried out.Besides,the penetration depth and distribution profiles of consolidants were estimated by exploiting elemental raster scanning of SEM-EDS analysis performed throughout the thickness of samples.More importantly,by employing a climatic chamber,the artificial ageing test was also conducted by simulating harsh atmospheric conditions.After accelerated ageing,the performance of all consolidants was assessed again.Results demonstrated that the application of nanosilica(<10 nm in dimension)by cellulose poultice,followed by adding tetraethoxysilane with the classical method“wet on wet”,is the best consolidation approach,in terms of in-depth consolidation efficacy,compatibility with the stone substrate,surface cohesion strength and performance durability in environmental conditions.Moreover,the treated surface is not hydrophobic,which allows further grouting and adhesion operations usually required for the restoration of historic buildings.