Silane Deposition Research Articles

Grafting of pyrrole onto cellulosic lyocell fibres via (3-chloropropyl)triethoxysilane anchor

The high number of reactive groups present in the cellulose structure form the chemical basis for chemical derivatisation through many different chemical pathways. Silane anchors are available with a variety of moieties that offer many functionalisation options of cellulose fibres. It is therefore important to investigate the deposition and grafting of silanes on such substrates. In this paper, the grafting of (1-(3-(triethoxysilyl)propyl))-1H-pyrrole (PySi) onto a cellulosic lyocell fibre based textile was investigated. Depending on the amount of silane applied, a maximum amount of 0.09 mmol PySi/g cellulose was observed to form covalent bonds with the cellulose lyocell fibres. A maximum of 0.36 mmol PySi/g cellulose was deposited on the fibre substrate, of which 0.27 mmol could be removed by solvent extraction. The results can be explained by a limited number of binding sites available on the cellulose surface suited for covalent bond formation with PySi. In addition, a simple method for quantifying the amount of silane on cellulose fibres using thermogravimetric analysis (TGA) is presented. The results found for the behaviour of PySi on cellulose material contribute to a better understanding of the heterogeneous modification of cellulose.

Wettability patterning of titanium surfaces through pulsed laser melting for enhanced condensation heat transfer

Wettability engineering of different surfaces has been in the spotlight for the last few decades for enhanced condensation heat transfer in various applications. In this study, we experimentally investigated the water vapor condensation on a wettability-tailored Titanium-based (Ti-6Al-4V) grade 5 alloy. We utilize the microsecond laser to texture the surface by melting at various scanning speeds to realize a wide range of scalable surface structures. We further render these surfaces hydrophobic through chemical vapor deposition of silane at atmospheric pressure. Further water vapor condensation experiments are performed on these surfaces. The results show that the increased surface roughness due to laser-based melting altered the surface wettability of the Ti-surface and made it hydrophilic, exhibiting water drop contact angles ranging between 18° and 56° for the scan speeds between 25mm/s and 50 mm/s, respectively. The vapor deposition of silane on laser-melted Ti-surfaces lowered its surface energy and made them hydrophobic, showing contact angles of water drop up to ~106° specifically at lower scan speeds (~ 25 mm/s). Finally, the vapor condensation experiments showed an enhanced amount of condensed water collection with dropwise mode compared to the bare Ti surface due to a change in the wetting nature altered by laser melting.

Modeling Silane Deposition in Nanoporous Carbon for High-Capacity Si/C Composite Anodes

Si/nanoporous carbon composites are promising anode materials for high-energy-density lithium-ion batteries. Chemical vapor deposition of Si into nanoporous carbon is an efficient approach to synthesize high-performance Si/nanoporous carbon composites. While attractive performance has been demonstrated experimentally, there is a lack of modeling work to understand how experimental conditions and carbon properties affect deposition geometry and uniformity. This study aims to develop a general model of chemical vapor deposition of silicon into nanoporous carbon in a tube furnace, which describes key processes such as advection, diffusion, and reaction kinetics. Various parameters such as temperature, pressure, tube length, flow rate, surface area, and pore size were investigated to determine their effects on deposition uniformity and filling portion along the tube. The simulation results align with experimental results reasonably. The model predicts that lower temperature, lower pressure, higher flow rate, less carbon loading, and lower specific surface area favor better uniformity across the whole tube furnace. This work provides valuable insights for optimizing the operating conditions in tube reactors and can contribute to the advancement of deposition processes.

27Al Solid-State Magic-Angle Spinning NMR Studies of Aluminum Powder Particle Surfaces Treated with a Methyltriethoxysilane Coupling Agent under Acidic Conditions

We report on the reaction between methyltriethoxysilane (MTES) and micrometer-sized aluminum particles, facilitated by HCl. This reaction ultimately produces silane-coated aluminum particles. Using 27Al magic-angle spinning solid-state nuclear magnetic resonance, we find that aluminum powder starts with a mixture of tetrahedrally, pentahedrally, and octahedrally coordinated aluminum, with the pentahedral species dominating. In the presence of HCl, however, the aluminum undergoes a restructuring, so that octahedrally coordinated aluminum is the dominant species. Using diffuse reflectance infrared spectroscopy to confirm the deposition of silane, we find that this restructuring of the aluminum in the presence of HCl is both a sufficient and necessary condition for the deposition of the silane.

Study of Dislocation Bending During Film Growth by a Multiscale Scheme

AbstractDepositing on the patterned substrate in chemical vapor deposition is one of the most effective approaches to produce low‐dislocation‐density films. Existing experiments indicate that dislocation bending is the main cause of decreasing dislocation. However, what drives dislocation segments (DSs) to bend remains unclear, and existing numerical methods do not explain the mechanism fully. In this study, a multiscale scheme based on molecular dynamics (MD) and kinetic Monte Carlo (KMC) is proposed to unravel the multiscale mechanism of DSs bending. In this scheme, MD is employed to identify the off‐lattice structure and to calculate the diffusion activation energies. KMC is used to perform the temporal evolution of the deposition process. In a proof‐of‐concept, the growth rate and the film morphology in silane deposition are predicted in the cross‐scale comparable to the experimental measurements. With the proposed multiscale scheme, the calculated activation energies show that the repeated lateral deposition and the obliquely upward deposition of the dislocated atoms contribute to DSs bending. Moreover, the sharp decrease of dislocation density is quantitatively elucidated by the scheme. The study provides fundamental insight into dislocation bending reduction during crystal thin film growth.

Corrosion Protection of Az91d Mg Alloy by Open-Air Plasma Assisted Deposition of Silane Based Coating

Corrosion Protection of Az91d Mg Alloy by Open-Air Plasma Assisted Deposition of Silane Based Coating

Corrosion Protection of Az91d Mg Alloy by Open-Air Plasma Assisted Deposition of Silane Based Coating

Corrosion Protection of Az91d Mg Alloy by Open-Air Plasma Assisted Deposition of Silane Based Coating

Enhanced Filtration Characteristics and Reduced Bacterial Attachment for Reverse Osmosis Membranes Modified by a Facile Method

In this study, we report the facile surface modification of reverse osmosis (RO) membranes for improved filtration as well as bacterial resistance properties. Thin films of two silanes, 3-aminopropyltriethoxysilane (3-APS) and 6-aminohexylaminotriethoxysilane (6-AHAS), were dip-coated on commercial RO membranes, and their nitrogen atoms subsequently quaternized. Analyses of the modified membranes via scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy confirmed the “peak and valley” morphology of the original membrane, silane deposition, and N quaternization, respectively. The original membrane showed a water contact angle of ∼90–100° that was significantly decreased after silane coating: 63° for 3-APS and ∼52° for 6-AHAS. Filtration experiments with a high-salinity feed revealed significant improvements in the permeate flux (∼25–40%) and salt rejection (∼10–15%) after the surface modification. Bacterial adhesion studies with two different species, Bacillus subtilis and Pseudomonas aeruginosa, showed significantly reduced cell attachment on the modified membranes. In addition, the coated and quaternized membranes significantly restricted the biological activity and colony formation of both strains with a bacteriostasis rate of ∼75%. The enhanced filtration and antifouling capabilities of the modified membranes were attributed to the presence of polar functionalities (R4N+).

Effect of diamond-like nanocomposite as antireflection layer on multi-crystalline silicon solar cells

Silicon nitride (SiNX) is conventionally used as antireflection coating (ARC) on p-type Silicon solar cells. But synthesis of SiNX involves two toxic and highly flammable gases ammonia (NH3) and silane (SiH4). To overcome this, an alternative material instead of SiNx was investigated. Diamond-like nanocomposite (DLN) is such a material whose deposition as ARC follows less hazardous pathway and produces better performance in many respect compare to SiNX. DLN film is deposited by a radio frequency plasma enhanced chemical vapour deposition (rfPECVD) process by using liquid precursor Hexamethyl disilazane (HMDSN) in argon (Ar) plasma. In this paper, the authors have compared electrical and optical parameters of multicrystalline silicon solar cells (mc-Si) for two different antireflection coatings SiNx and DLN. DLN film is characterized by FTIR and Raman spectroscopy. Optical properties are estimated by UV–Vis-NIR spectrophotometer. Electrical properties are measured by I-V simulator under 1.5 AM condition. The minimum reflection has been achieved 4.86% at 797 nm wavelength. The short circuit current density, JSC and open circuit voltage, VOC have been achieved from finished mc-Si solar cell are 32.54 mA/cm2 and 0.582 V respectively. Results prompt to conclude that DLN as ARC is comparable to SiNX. Thus silane and ammonia free DLN deposition as ARC, could be a good alternative of SiNX.

Perflurooctyltriethoxy silane and carbon nanotubes-modified PVDF superoleophilic nanofibre membrane for oil-in-water adsorption and recovery

Due to the increased rate of oil spills leading to environmental water pollution, the synthesis of nanofibre membranes with controlled superhydrophobic/superoleophilic properties has received remarkable attention for oil-water separation. In this research, superhydrophobic-superoleophilic nanofibre membranes were successfully prepared through a three-step deposition of perflurooctyltriethoxy silane (POTS) to carbon nanotubes (CNTs) followed by dispersing the mixture in polyvinylidene fluoride (PVDF) polymer solution prior to electrospinning. Upon the addition of POTS/CNTs on the nanofibre membranes, the hydrophobicity increased from 96.35° to 143.30°, thus, resulting in improved oil adsorption capacity from 60.20 to 111.4 g·g-1. The intraparticle diffusion model provided the information on external mass transfer and diffusion of the oil from the oleophilic sites of the adsorption active sites. The CNTs/POTS-modified PVDF nanofibre membranes demonstrated high adsorption efficiencies ∼ 99% towards avocado, sunflower, engine, and motor oils. Based on Chi-square test statistics, the adsorption of oils on CNTs/POTS-modified PVDF nanofibre membranes followed the first-order kinetics. The rate constants increased from 0.019 to 0.034 g·g-1 min-1 upon the incorporation of CNTs/POTS on PVDF nanofibre membranes; thus, indicating the improvement of adsorption of oils. Remarkably, PVDF-based nanofibre membranes were recycled and reused for more than 37 cycles, confirming their potential application for environmental oil-water separation.

Gas Separation Silica Membranes Prepared by Chemical Vapor Deposition of Methyl-Substituted Silanes.

The effect on the gas permeance properties and structural morphology of the presence of methyl functional groups in a silica membrane was studied. Membranes were synthesized via chemical vapor deposition (CVD) at 650 °C and atmospheric pressure using three silicon compounds with differing numbers of methyl- and methoxy-functional groups: tetramethyl orthosilicate (TMOS), methyltrimethoxysilane (MTMOS), and dimethyldimethoxysilane (DMDMOS). The residence time of the silica precursors in the CVD process was adjusted for each precursor and optimized in terms of gas permeance and ideal gas selectivity criteria. Final H2 permeances at 600 °C for the TMOS-, MTMOS-, and DMDMOS-derived membranes were respectively 1.7 × 10−7, 2.4 × 10−7, and 4.4 × 10−8 mol∙m−2∙s−1∙Pa−1 and H2/N2 selectivities were 990, 740, and 410. The presence of methyl groups in the membranes fabricated with the MTMOS and DMDMOS precursors was confirmed via Fourier-transform infrared (FTIR) spectroscopy. From FTIR analysis, an increasing methyl signal in the silica structure was correlated with both an improvement in the hydrothermal stability and an increase in the apparent activation energy for hydrogen permeation. In addition, the permeation mechanism for several gas species (He, H2, Ne, CO2, N2, and CH4) was determined by fitting the gas permeance temperature dependence to one of three models: solid state, gas-translational, or surface diffusion.

Facile preparation of antiadhesive and biocidal reverse osmosis membranes using a single coating for efficient water purification

Surface modification of reverse osmosis membranes by the deposition of antifouling coatings is a popular strategy for the control of membrane biofouling. This study reports the preparation of simultaneously anti-adhesive and biocidal membrane surfaces by dip-coating of a single silane, N1-(3-trimethoxysilylpropyl) diethylenetriamine. The operational parameters for surface modification such as acid concentration and immersion time were optimized to obtain the best results. To improve the bacterial killing capabilities, the silane films were quaternized using ethyl iodide. Subsequent characterization of the coated membranes with Fourier Transform Infra Red (FTIR) spectroscopy confirmed the presence of the silane on the membrane surface. Surface elemental analysis of the modified surfaces using X-ray Photoelectron Spectroscopy (XPS) confirmed the quaternization of the Nitrogen atoms. Advanced microscopy techniques (Scanning Electron & Atomic force) revealed a smoothening of the coated surface after quaternization. Contact angle measurements showed a significant increase in surface hydrophilicity after silane deposition (from ∼85° to58°)and a slightly further increase upon quaternization (∼58–53°). Bacterial adhesion and antimicrobial studies with a B. subtilis species showed much significantly lower no. of bacterial cells on the coated and quaternized surface with a killing rate of more than 80%. Cross-flow filtration tests using a custom-built laboratory setup showed that the presence of coating did not compromise on the permeation characteristics; infact, quaternization resulted in a significant improvement (∼50%) in the permeate water flux. The coated membranes were quite effective in retarding biofilm formation and subsequent permeate flux decline in long-term fouling experiments with bacteria-containing water.

Superhydrophobic–superoleophilic electrospun nanofibrous membrane modified by the chemical vapor deposition of dimethyl dichlorosilane for efficient oil–water separation

ABSTRACTSuperhydrophobic and superoleophilic functionalized electrospun poly(vinylidene fluoride) (PVDF) membranes with water repellence, breathability, and oil‐sorption and oil–water separation properties were achieved with a combination of an electrospinning technique and the chemical vapor deposition of dichlorodimethyl silane. The samples were laterally characterized by scanning electron microscopy, atomic force microscopy, water contact angle measurement, and Fourier transform infrared spectroscopy. The maximum water contact angle value was 152.0 ± 2.5° for the PVDF nanofibrous membranes with 500 μL of deposited silane (PMS2) obtained under certain conditions. The PMS2 membranes showed 100.0, 93.7, 23.3, 35.0, and 100.0% separation efficiencies for n‐hexane, kerosene, crude oil, frying oil, and toluene, respectively. The understudy membrane exhibited reasonable waterproofness and remarkable breathability (water vapor transition rate = 215.21 g/m2.h). Moreover, the superhydrophobic and superoleophilic nanofibrous membranes also showed good reusability, stability, moderate water‐repellent properties, breathability, antifouling properties, and oil–water separation ability after several cycles. These properties confirmed potential in feasible applications, including protective cloths and in the purification of oil‐polluted water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47621.

Facile Protection of Lithium Metal for All-Solid-State Batteries.

A nanolayer of reactive propyl acrylate silane groups was deposited on a lithium surface by using a simple dipping method. The polymerization of cross‐linkable silane groups with a layer of ally‐ether‐ramified polyethylene oxide was induced by UV light. SEM analysis revealed a good dispersion of silane groups grafted on the lithium surface and a layer of polymer of about 4 μm was obtained after casting and reticulation. The electrochemical performance for the unmodified and modified lithium electrodes were compared in symmetrical Li/LLZO/Li cells. Stable plating/stripping and low interfacial resistance were obtained when the modified lithium was utilized, indicating that the combination of silane and polymer deposition is promising to increase Li‐metal/garnet contact.

Modeling of Chemical Vapor Deposition of Silane for Silicon Production in a Spouted Bed via Discrete Element Method Coupled with Eulerian Model

A CFD–DEM coupling model was applied to the silicon production by silane chemical vapor deposition in a spouted bed to investigate local phase movements, mass transfer, heat transfer, and the deposition rate of silicon. Silicon particle growth by heterogeneous deposition on the seed particle and fines formation in the gas phase were included. In addition, the scavenging effect was also considered in the particle growth mechanism. The spouted bed has advantages to promote heterogeneous deposition time due to a larger solid holdup and higher gas residence time in the annulus region. Furthermore, the effects of operating conditions, i.e., inlet gas temperature, silane composition, and gas velocity, on the reactor performance were investigated in detail, and some guidelines are provided for the choice of operating conditions. Verification of solid movement results with the experimental data and correlations show good agreement. In addition, the axial profile of bed voidage agrees well with correlation.

Silane Deposition via Gas-Phase Evaporation and High-Resolution Surface Characterization of the Ultrathin Siloxane Coatings

Siloxane coatings for surfaces are essential in many scientific and industrial applications. We describe a straightforward gas-phase evaporation technique in inert atmosphere and introduce a practical and reliable silanization protocol adaptable to different silane types. The primary aim of depositing ultrathin siloxane films on surfaces is to enable a reproducible and homogenous surface functionalization without agglomeration effects during the layer formation. To realize high-quality and large-area coatings, it is fundamental to understand the reaction conditions of the silanes, the process of the siloxane layer formation, and the possible influence of the substrate morphology. We used three typical silane types to exemplify the potential and versatility of our process: aminopropyltriethoxysilane, glycidoxypropyltrimethoxysilane, and 1 H,1 H,2 H,2 H-perfluorooctyl-trichlorosilane. The ultrathin siloxane layers, which are generally difficult to characterize, were precisely investigated with high-resolution surface-characterization methods to verify our concept in terms of reproducibility and coating quality. Our results show that this gas-phase evaporation protocol is easily adaptable to all three, widely used silane types also enabling a large-area upscale.

Sorption capacity of hydrophobic cellulose cryogels silanized by two different methods

The production of cellulose cryogels for petroleum sorption is a relevant study since cellulose is an economical, renewable, biodegradable and abundant source in the environment. However, as this material is of hydrophilic character it is necessary to modify the hydrophobicity of the cellulose fiber surfaces by using organosilanes, for example. The aim of this work is the development of hydrophobic cellulose cryogels for application in petroleum sorption. For this, was compared the sorption capacity of cryogels silanized by methyltrimethoxysilane (MTMS) through two methods: vapor deposition and addition of silane to cellulose suspension. For the samples with MTMS addition to the cellulose suspension, modifying the MTMS fiber surfaces increased the water contact angle on average by 112°. For the samples modifyed by vapor deposition the increase was of 119°. The most effective silanization method was by vapor deposition where the petroleum sorption capacity was 50% higher than by the cellulose addition method.

Amphiphilic Nanofiber‐Based Aerogels for Selective Liquid Absorption from Electrospun Biopolymers

Hierarchically structured and ultralight pullulan/poly(vinyl alcohol) (pullulan/PVA) aerogels or sponges are prepared from short electrospun nanofibers using solid templating. The architecture of the aerogel consists of cell‐like pores of 50–100 µm interconnected by a network of entangled nanofibers with 2–5 µm pores. Such structures allow rapid liquid uptake with high liquid holding capacities at the same time. The amphiphilic nature of the aerogel from the electrospun biopolymer is switched by chemical vapor deposition of silane. This allows the selective separation of liquids based on their different relative dielectric constants, which is of high interest for oil spilled waters and produced water. Furthermore, silylation improves the aerogel's overall mechanical stability by 18% while increasing its density by only 5%. Scanning electron microscopy in situ compression studies reveal the importance of the fibrous entanglement and the open‐porous architecture for the high bendability and mechanical resilience of the aerogels. Solid templating of short electrospun nanofibers facilitates the design of a fascinating class of ultralight aerogels while prevailing the fibrous character and the versatility of electrospinning.

Reversible Na-Ion Uptake in Si Nanoparticles

Na ion batteries attract significant research interest since they provide potentially high energy density while using low cost and abundant sodium as the active ion. Si has been extensively investigated for its operation as anode in lithium based batteries since it has a high theoretical lithiation capacity up to Li4.4Si. However, the sodium analogue with successful reversible electrochemical sodiation of Si has not been reported yet. Si sodiation is anticipated to be different with respect to phase behaviour, insertion voltages and kinetic barriers when compared to Li ion, for instance because of the difference in ionic radius of Na+ (0.97 Å) and Li+(0.68 Å). From thermal synthesis of Na-Si materials it is known that NaSi is the most Na rich phase for Na-Si binary compounds, which would enable a sizeable capacity of 954 mAh/g. Anticipating that nanoscaling is of advantage for the kinetics of ion insertion and extraction, we studied Si particles with much reduced size (~ 20 nm) containing a large fraction of amorphous Si. The nano particles were obtained from Expanding Thermal Plasma Chemical Vapour Deposition (ETPCVD) of silane. The materials consist of aggregated individual nano particles with a very thin silicon oxide layer that forms after contact with air. The work presented here reports, to our knowledge for the first time, reversible electrochemical Na ion uptake in these Si based materials for a significant capacity. The desodiation capacity is stable around 260 mAh/g, while the initial sodiation shows a large irreversible Na loss attributed to SEI formation. The experiments show that during Na insertion a two phase equilibrium may be present between NaSi and Si: x Na + Si -> x NaSi + (1-x) Si, where the NaSi becomes amorphous. For desodiation a sloping voltage profile is observed indicative of a solid solution behaviour. Therefore we propose that desodiation occurs as NaSi -> Na1-xSi + x Na, where the Na1-xSi phase remains amorphous. After 100 cycles all Si has been transformed to amorphous phases, and no crystalline nano Si particles remain. In conclusion, nanoparticles containing both amorphous and crystalline Si, produced by ETPCVD, demonstrate an excellent reversible capacity of 279 mAh/g for Si at 10 mA/g and a capacity retention of 248 mA/g after 100 cycles at 20 mA/g. Significant reversible capacities can be achieved at high dis-/charge rates as well. Nanoscaling benefits the Na insertion and extraction kinetics in Si although reversible Na uptake and release for the full theoretical capacity has not been reached. Initial amorphous and crystalline Si are performing an equally active role in the electrochemical sodiation. Coexistence of Si and NaSi may occur during Na insertion into amorphous Si and on the surface of the Si crystallites; while a solid solution desodiation reaction is evidenced when Na is being extracted. Y. Xu, E. Swaans, S. Basak, H. W. Zandbergen, D. M. Borsa, F. M. Mulder, Adv. Energy Mater. 2015, doi 10.1002/aenm.201501436 early view Figure 1

The determination of the optimum hydrolysis time for silane films deposition

There is an increased controversy regarding when the actual silane deposition process takes place, whether or not the silane solution should be left for a longer time before the silanization, so that a maximum concentration of hydroxil groups is achieved. The proposed method uses a specifically designed electrochemical cell to monitor the behaviour of the silane solution during hydrolisation process versus time. The main characteristic parameters are reunited into a goal function (the temperature influence is also taken into account) used for supplying the maximum coordinates, graphical method or from the first derivative. The results may be used further for the silane deposition process, so that the best possible coating is obtained.