Si-C Bonds Research Articles

Annulated 1,4-Disilabenzene-1,4-diide and Dihydrogen Splitting.

The isolation of silicon analogues of phenyl anions such as (C6H5)- and (C6H4)2- is challenging owing to their extremely high reactivity associated with their silylene character and weak C-Si π-interaction. Herein, we report the first annulated 1,4-disilabenzene-1,4-diide compound [(ADC)Si]2 (5) based on anionic dicarbene (ADC) scaffolds (ADC = PhC{N(Dipp)C}2; Dipp = 2,6-iPr2C6H3) as a green-yellow crystalline solid. Compound 5 is prepared by KC8 reduction of the Si(IV) chloride [(ADC)SiCl3]2 (3) or the cyclic bis-chlorosilylene [(ADC)SiCl]2 (4), which are also prepared for the first time. 5 is a neutral molecule, and each of the two-coordinated Si(I) atoms has a lone pair and an unpaired electron. Experimental and theoretical data indicate delocalization of the silicon unpaired electrons, resulting in a 6π-electron C4Si2 ring in 5. The diradical character (y) for 5 amounts to 15%. At room temperature, 5 readily reacts with dihydrogen (H2) to form the elusive bis-hydridosilylenes [(ADC)SiH]2 (Z)-6 and (E)-6. The [4 + 2]-cycloaddition of 5 and PhC≡CPh in yielding the barrelene-type bis-silylene [(ADC)SiCPh]2 (7) emphasizes the diradical reactivity of 5. With elemental sulfur, 5 results in the S2- and S3-bridged silathione derivatives [(ADC)Si(S)]2(μ-S2) (8a) and [(ADC)Si(S)]2(μ-S3) (8b). Moreover, the treatment of 5 with Fe2(CO)9 affords the Fe(0) complex [(ADC)Si(Fe(CO)4)]2(μ-CO) (9), in which each silicon atom serves as a two-electron σ-donor ligand and shares one electron with the bridging CO unit to form two Si-C bonds. The molecular structures of all compounds have been established by X-ray diffraction, and representative compounds have been analyzed by quantum chemical calculations.

Palladium-catalyzed double activation of Si-C(sp3) bond of benzosilacyclobutenes synergized with unexpected olefin migration and ring-opening hydrolysis

A regioselective silicon-carbon bond activation of silacycles has emerged as a powerful strategy to access organosilicon compounds with functional groups. In contrast, progress in the development of new reaction systems for the tandem and double Si-C bond activation of silacycles has lagged. In this regard, there have been no reports of Si-C(sp3) bond activation of benzosilacyclobutenes and its tandem transformations. Herein, we address this challenging, disclosing the first example of palladium-catalyzed double Si-C bond activation of benzosilacyclobutenes and its tandem ring expansion and ring-opening transformations, in which various functionalized silanols that have ester groups are synthesized in this reaction. The main feature of this novel transformation is the highly selective activation of the Si-C(sp3) bond of benzosilacyles to achieve [4 + 2] cycloaddition with ester-activated alkynes and subsequent ring-opening and σ-bond metathesis with H2O. Moreover, the DFT studies realized the origin of Si-C(sp3) bond activation, olefin migration, and ring-opening hydrolysis in the unprecedent reaction process.

Adjusting the Number of Functional Groups in Vicinal Bis(trichlorosilylated) Benzenes.

Organo(chloro)silanes are essential chemicals, but the synthesis of compounds of the formula RnSiCl4‒n with defined values of n is usually laborious. Herein, we first disclose that a [4+2]-cycloaddition between readily available Cl3SiC≡CSiCl3 and selected dienes provides facile access to vicinal bis(trichlorosilylated) benzenes and bicyclo[2.2.2]octa-2,5-dienes. Second, we show how the number of six Si‒Cl bonds in 1,2-(Cl3Si)2C6H2Me2 (1) can be selectively reduced to four or two by reaction with pinacol (H2pin) or catechol (H2cat), which act as Si···Si'-bridging and/or Si-chelating ligands. Third, we demonstrate that the thermolysis of compound 6, which contains a benzannulated eight-membered C2(SiCl2)2(μ-pin) ring with Si···Si'-bridging pin moiety, furnishes 13 with a benzannulated five-membered C2(SiCl2)2O ring via the release of pinacolone. Such cyclic disiloxanes are valuable building blocks for specialty silicones; an alternative assembly of the Si‒O‒Si unit by controlled hydrolysis of 1 is not feasible if the four valuable Si‒Cl functionalities are to be retained for further derivatization. Substitution of one Cl atom per Si site of 13 gives the rac-1,3-disila-2-oxaindane rac-15 with high selectivity.

Si-C atomic line achieving efficient electrocatalytic nitrogen reduction reactions

In this study, the concept of a Si-C atomic line (SCAL) featuring fully exposed atomic sites is introduced for the first time, and the SCAL serves as a highly efficient electrocatalyst for nitrogen reduction reactions (NRR). Thanks to the strong binding strength of the Si-C bonds (polar covalent bonds), the SCAL exhibits exceptional structural stability at 298.15 K. With a band gap of 1.86 eV characterized by a semiconductor, SCAL exhibits relatively high conductivity which is advantageous for electrocatalytic processes. N2 is adsorbed on the C sites in an end-on mode due to the most negative adsorption energy (–0.39 eV), and the nature of adsorption is s-p orbital hybridization. Based on the end-on N2 adsorption, the entire NRR pathway is simulated and shows a relatively low energy barrier of 0.50 eV, which is relatively low compared to reported metal-free NRR electrocatalysts. The charge transfer mechanism reveals that the active sites (C atoms) are responsible for charge transfer, while other parts of SCAL act as storage warehouses for charge. Moreover, SCAL demonstrates a preference for NRR over hydrogen evolution reaction (HER), underscoring its excellent electrocatalytic selectivity. This study opens new avenues for designing high-performance catalysts.

Phosphorus doped hydrogenated silicon oxycarbide: Film formation, properties and its application on silicon heterojunction solar cell

An ultrathin phosphorus doped hydrogenated microcrystalline silicon oxycarbide (n-μc-SiCO:H) layer deposited by plasma enhanced chemical vapor deposition (PECVD) method can be used as a window layer for silicon heterojunction solar cells. The optical and electrical properties of n-μc-SiCO:H films were controlled by PECVD deposition conditions. The interplay effects of H2, CO2 and PH3 to SiH4 gas ratio on the chemical composition, material structure and properties of n-μc-SiCO:H film were systematically determined. O, H, C and P atoms were observed to incorporate into the silicon network of n-μc-SiCO:H layer, while most of the atoms bond directly to Si atoms. Incorporation of oxygen and carbon atoms into n-μc-SiCO:H film, confirmed by XPS as formation of Si-O and Si-C bonds, enlarged the optical absorption band gap (Eg) value. Both film crystallinity and phosphorus concentration in n-μc-SiCO:H layer were observed to be controlled by the H2, CO2 and PH3 to SiH4 gas ratio. The electric performance of HJT solar cell was depended on the optical and electrical properties of n-μc-SiCO:H layer. An average efficiency (across ∼ 120 cells) of 26.32 % was achieved in cells with optimized deposition parameters for the n-μc-SiCO:H layer. The reaction gas ratio was also the dominant factor in determining the number and size of nanoscale Si crystallites embedded in the n-μc-SiCO:H layer. The conductivity of n-μc-SiCO:H layer was determined by the activated phosphorus concentration but independent of the total phosphorus concentration. It was also found that large concentrations of small Si crystallites of size less than 3 nm improved film conductivity.

Simulation of chemical reactions with methanol and oxalic acid on 4H-SiC surfaces before and after nanoabrasion

Previous work by our team has shown that not only can oxalic acid added to a reactive methanol polishing solution significantly further improve SiC polishing removal rate but also surface quality. However, due to the lack of fundamental information on the nature of the interfacial reaction, the reaction mechanism involved in continuously improving SiC polishing performance remains unresolved. This study explores the chemical interactions of pristine and nano-scratched surfaces with the reaction medium using a molecular dynamics (MD) model combined with the ReaxFF reaction force field. The results show that –OH and –CHn, methanol can effectively break the Si-C bond on the surface of silicon carbide and the high amount of OH and C=O in oxalic acid favors the formation of surface silicon oxides and the softening of the silicon carbide surface. The synergistic effect of oxalic acid and methanol in the pre-scratch system indirectly supports the notion that nanoabrasion caused by nano-abrasives enhances the chemical reactivity of polishing fluid components. In conjunction with the experimental data, a proposed reaction mechanism for organic acid-containing alcohol fluids with SiC based on non-aqueous solvent systems is presented. This may stimulate ideas for better developing and applying novel non-aqueous-based polishing fluids.

Nickel-Catalyzed Reductive Protocol To Access Silacyclobutanes with Unprecedented Functional Group Tolerance.

While significant progress has been made in the area of transition metal-catalyzed ring-opening and formal cycloaddition reactions of 1,1-disubstituted silacyclobutanes (SCBs), synthesizing these SCBs-particularly those bearing additional functional groups-continues to present synthetic challenges. In this context, we present a novel Ni-catalyzed reductive coupling reaction that combines 1-chloro-substituted silacyclobutanes with aryl or vinyl halides and pseudohalides, thereby obviating the need for organometallic reagents. This method facilitates the generation of 1,1-disubstituted silacyclobutanes with a remarkable tolerance for various functional groups. This approach serves as a complementary and more step-economical alternative to the commonly used yet moisture- and air-sensitive nucleophilic substitution reactions involving Grignard or lithium reagents. Our initial mechanistic studies indicate that this reaction is initiated by oxidative cleavage of the Si-Cl bond in 1-chlorosilacyclobutanes, which represents a distinct mechanism from the previously documented reductive coupling processes involving carbon electrophiles and chlorosilanes.

Transformative potential: Utilizing Teos-modified mugwort for sustainable construction

Exploring innovative materials derived from natural sources holds significant promise in pursuing sustainable construction practices. This study investigates the modification of mugwort (Artemisia dubia Wall.) with TEOS (tetraethyl orthosilicate) and its application as a sustainable reinforcement material in construction applications. It aims to integrate the plant's inherent strength with TEOS-enhanced mechanical properties and assess the feasibility of incorporating TEOS-modified mugwort into a lime-based matrix. The modified mugwort and its lime-based composite characterisation were conducted using FTIR, SEM-EDS, thermogravimetric analysis, compressive strength tests, and nitrogen adsorption analysis. FTIR analysis showcases significant structural enhancements post-modification, corroborated by SEM-EDS findings indicating increased silicon content. Peaks at 2915, 2845, and 1256 cm⁻¹ confirm successful modification with octadecyl amine and Si-C bond integration. Silica-related peaks at 1052, 801, and 456 cm⁻¹ indicate the presence of Si-O-Si structures. SEM analysis observes the presentation of Si as a layer confirming line scan position results, and EDS analysis findings indicate an increased silicon content of 15.16 %. Thermogravimetric analysis of modified samples displayed improved stability at low temperatures and more significant mass loss at high temperatures (72.01 % for modified and 28.91 % for unmodified samples) due to the decomposition of new chemical components. Nitrogen adsorption measurements reveal enhanced porosity in modified mugwort, suggesting diverse applications. The surface area of modified mugwort increased by 85 % compared to unmodified samples. Compressive strength analyses underscore the material's suitability for construction, with modified samples exhibiting denser structures at 8.5 % and higher strength at 13.3 % compared to unmodified samples. Macrostructure analysis further supports this, highlighting enhanced compatibility with binding materials. Overall, modified mugwort emerges as a versatile, eco-friendly reinforcement material with improved mechanical and thermal properties, poised for various applications in sustainable construction.

Thermal stability and pyrolysis mechanism of decamethyltetrasiloxane (MD2M) as a working fluid for organic Rankine cycle

The thermal stability of working fluids is a crucial property studied in the selection of organic Rankine cycle fluids, as they may undergo decomposition at elevated temperatures. In previous studies, siloxanes have been identified as promising choices for ORCs. However, research on the thermal stability of siloxanes in ORCs has been relatively limited. This study investigates the thermal stability and pyrolysis mechanism of MD2M through a combination of experiment, DFT simulation, and ReaxFF-MD calculation. The experiment revealed that MD2M exhibits poor thermal stability, with a decomposition rate of approximately 1.82 % at 200 °C in 72h. Consequently, it is unsuitable for operating in ORCs at temperatures of 200 °C and above. The primary gas products in the pyrolysis of MD2M include CH4, C2H6, C2H4, CO, and CO2, among others. ReaxFF-MD and DFT elucidated the thermal decomposition mechanism of MD2M. The Gibbs free energy barriers for Si–C bond cleavage reactions are relatively lowest, measured at 352.98 and 341.33 kJ mol−1, respectively. Simultaneously, methylation of the terminal Si atom is likely to represent the primary reaction pathway for the initial decomposition.

Polishing performance and material removal mechanism in the solid-phase Fenton reaction based polishing process of SiC wafer using diamond gel disc

The use of SiC wafer is widespread in many fields, especially in aerospace, energy, 5 G communications, and microelectronics. Chemical-mechanical polishing (CMP) is the primary method used for achieving an ultra-smooth surface on SiC wafers. However, CMP suffers from low efficiency, leading to increased processing time and costs. To address this issue, we developed a novel diamond gel polishing disc that incorporates SiO2/Fe3O4 (S/F) powder. The disc enhances polishing efficiency through a solid-phase Fenton reaction between the disc and SiC. The research investigates the reaction mechanism and the material removal model of the polishing process using SEM, TEM, and XPS analysis. Experimental studies are conducted to assess the polishing performance and validate the effectiveness of the theoretical model. The findings indicate that SiC undergo a solid-phase Fenton reaction with polishing disc mixed S/F powder (SG-S/F disc) during polishing. The Fenton reaction generates hydroxyl radicals (·OH), which break the Si-C and Si-Si bonds in the crystal structure, leading to the formation of a softer nanoscale amorphous oxide layer on the SiC surface. The cyclic generation and removal of this oxide layer enable highly efficient polishing of SiC wafers. Compared to a gel disc without S/F (SG disc), SiC polished with the SG-S/F disc exhibits superior surface quality. Additionally, the material removal rate (MRR) of the SG-S/F disc reaches 1.42 μm/h, representing a 51.1 % improvement over that of the SG disc. These results clearly demonstrate that the solid-phase Fenton reaction significantly enhances the polishing performance of the gel polishing disc.

Atomistic Removal Mechanisms of SiC in Hydrogen Peroxide Solution.

To elucidate the atomic mechanisms of the chemical mechanical polishing (CMP) of silicon carbide (SiC), molecular dynamics simulations based on a reactive force field were used to study the sliding process of silica (SiO2) abrasive particles on SiC substrates in an aqueous H2O2 solution. During the CMP process, the formation of Si-O-Si interfacial bridge bonds and the insertion of O atoms at the surface can lead to the breakage of Si-C bonds and even the complete removal of SiC atoms. Furthermore, the removal of C atoms is more difficult than the removal of Si atoms. It is found that the removal of Si atoms largely influences the removal of C atoms. The removal of Si atoms can destroy the lattice structure of the substrate surface, leading the neighboring C atoms to be bumped or even completely removed. Our research shows that the material removal during SiC CMP is a comprehensive result of different atomic-level removal mechanisms, where the formation of Si-O-Si interfacial bridge bonds is widespread throughout the SiC polishing process. The Si-O-Si interfacial bridge bonds are the main removal mechanisms for SiC atoms. This study provides a new idea for improving the SiC removal process and studying the mechanism during CMP.

Flame retardant, toughened, reinforced, transparent and long shelf-life one-component epoxy resins via a P/N/Si-containing hyperbranched polymer

One-component epoxy resins (OCEPs) cured from latent imidazole-based curing agents that exhibit high toughness, high strength, high fire safety, long shelf life, low dielectric properties and transparency are eagerly awaited in advanced manufacturing. However, existing research on latent imidazole-based curing agents/OCEPs mainly focuses on simultaneously improving their flame retardancy and shelf life, but neglects their poor toughness, strength and dielectric properties, and often compromises their transparency. Herein, a hyperbranched polymer (Si-DP) containing P/N/Si was fabricated to further improve the flame retardancy, toughness, strength and dielectric properties of EP10 (the transparent OCEPs comprising the latent imidazole-based curing agent PHI-HPP). EP10 containing Si-DP (EP10/Si-DP) boasted a shelf life longer than 81 days. The synergistic flame-retardant effect of P, N and Si elements enabled EP10/Si-DP3 to achieve a UL-94 V-0 rating with a limiting oxygen index of 33.9 %, the peak heat release rate and total smoke production of EP10/Si-DP5 were reduced by 44.4 % and 25.5 %, respectively, compared with EP10. The increased free volume and Si-O flexible bonds resulted in a 261.1 % higher impact strength of EP10/Si-DP5 than EP10. The excellent interfacial bonding of Si-DP with epoxy resins and the increased rigidity groups led to 74.0 % and 60.7 % higher tensile and flexural strengths of EP10/Si-DP5 than EP10, respectively. The intramolecular cavities and the low-polar Si-C bonds of Si-DP reduced the dielectric constant and dielectric loss of EP10/Si-DP. Meanwhile, EP10/Si-DP maintained inherent excellent transparency and high glass transition temperature (Tg). Carbon fiber epoxy composites prepared from EP10/Si-DP5 exhibited remarkable improvement in flame retardancy, smoke suppression as well as mechanical and interfacial performances. Overall, this research proposes an effective approach for preparing long shelf-life OCEPs with excellent overall performance.

The synthesis of high sinterability (Zr, Hf)C and SiC hybrid nanocrystalline particles by sol-gel method

Multi-phase UHTCs are favoured for their superior ablation resistance and mechanical properties. In this work, to improve the efficiency and decrease the sintering temperature and pressure, the (Zr, Hf)C and SiC hybrid nanocrystalline particles were prepared via the sol-gel method combining carbothermal reduction at 1600 °C. Utilizing their high sinterability, a relative density of 96.1% (Zr, Hf) C–SiC composite was obtained at the conditions of 1900 °C and 30 MPa using SPS technology. XPS and FT-IR results demonstrate that Zr, Hf, and Si were successfully trapped in the cross-linking structure of the precursors. Precursors of Zr, Hf, and Si reached a molecular-level mixture in the gel phase. SEM, XPS, and XRD characterization showed that the Si–C bond was formed preferentially, leading to the emergence of SiC whiskers and SiC wrapped (Zr, Hf)C with increasing temperature. And, the (Zr, Hf)C can be easily generated during solid solution reaction. Eventually, a nanoscale mixture of (Zr, Hf)C and SiC particles was successfully obtained at 1600 °C. The hardness and compressive strength of the (Zr, Hf)C–SiC composite were 12.94 GPa and 622 MPa, respectively. Comparing usual sintering processes (over 2000 °C and 35 MPa), the reason for the improved sinterability can be attributed to the high sintering activity of the (Zr, Hf)C and SiC hybrid particles, and the existence of the solid solution and nano-SiC.

Analysis of the variation in mechanical properties of α- and β-SiC under high-temperature Si-ion irradiation

The mechanical properties of silicon carbide (SiC) under high-temperature irradiation have been one of the focal issues for its application in nuclear systems, but the relevant mechanisms remain elusive. In this work, two SiC polytypes inducing α- and β-phase were irradiated by 1.35 MeV Si5+ with a fluence of 1.81 × 1016 ions/cm2 at 550 °C and 750 °C, respectively, to investigate the characteristics of irradiation-induced defects and structure and the variation of mechanical properties. Irradiation significantly affected the mechanical properties of both α- and β-SiC. The nanohardness and modulus of α-SiC increased with the increase of irradiation temperature, while for β-SiC they first increased and then decreased significantly. The results of GIXRD and Raman spectra indicated the irradiation-induced defects, lattice deformation, and the changes in the intensity of the Si-C bond region. It was found that the TEM characterization of irradiated SiC samples with numerous point defect clusters, extended defects and a legible defect band. Moreover, the nanohardness and modulus of both SiC types exhibited a critical temperature dependence and were affected by different dominant factors at high temperatures. The potential mechanisms governing the variation in mechanical properties at elevated temperatures of two irradiated SiC polytypes were explored.

Fluorinated benzothiadiazole fluorescent probe based on ICT mechanism for highly selectivity and sensitive detection of fluoride ion

Excessive fluoride ion (F-) in the environment can affect health and even endanger life when ingested by the human body. However, most fluoride probes have the disadvantages of low sensitivity and long detection time. Herein, fluorescent probe 3a is successfully synthesized by linking two acetylenyltrimethylsilyl groups at both ends of the fluorinated benzothiadiazole core. After the addition of F- to 3a, the emission at 436 nm is significantly quenched and slightly blue-shifted. It is confirmed by electrospray ionization high-resolution mass spectrometry (ESI-HRMS) and density functional theory calculations (DFT) that these changes are due to the F- triggered Si-C bond cleavage and the subsequent inactivation of intramolecular charge transfer (ICT). The detection limit and response time of probe 3a for F- are 10-8 mol/L and 25 s, respectively. Importantly, fluorescent material 3a can be processed into portable test tools for the visual detection of fluoride ion.

Remote plasma chemical vapor deposition of silicon oxycarbide film with a styrene-containing precursor and in situ O2 plasma treatment

In this paper, a study was conducted on silicon oxycarbide thin-film deposition using remote plasma chemical vapor deposition. A di-methyldimethoxysilane)2styrene (MDMS)2styrene precursor and CH4 plasma were used in the deposition process, and in situ oxygen plasma treatment was performed to control the carbon content and properties of the thin film. During the deposition process, the thin-film growth rate was found to be almost constant regardless of in situ plasma treatment. This means that in situ oxygen plasma treatment had no significant effect on thin-film growth itself. Auger electron spectroscopy analysis revealed that the carbon content of the deposited thin film was 43 % when only deposition was performed, but could be lowered to 3 % by in situ oxygen plasma treatment, which demonstrated that the carbon content can be controlled in a relatively wide range. X-ray photoelectron spectroscopy showed that it was possible to preserve SiC bonds even as the oxygen content increased with the number of in situ plasma treatments. The refractive index increased from 1.33 to 1.49, indicating a decrease in the number of pores and an increase in density. Meanwhile, the dielectric constant increased with the oxygen content, but did not exceed 3.9 due to the SiC bond structure. As the pore size decreased, the leakage current tended to decrease to 9.51 × 10−9 A/cm2 in an electric field of 1 MV/cm, and the breakdown voltage increased. Finally, it was possible to improve the etching characteristic through plasma treatment by lowering the wet etch rate from 78 to 19 Å/min.

Cu-O-Si-C interface-induced high-adhesion and anticorrosion of the DLC coatings on inner wall of copper tube prepared by PECVD

Deposition of well-adherent diamond-like‑carbon (DLC) films on copper is relatively difficult due to weak bonds between copper and carbon. The Cu-O-Si-C nanostructure was proposed to improve the adhesion and the corrosion-resistance of multilayer Si-DLC/DLC film on an inner surface of copper tube prepared by PECVD. First, the copper alloy was pretreated by oxygen. Then mixture gas of tetramethylhexylsilane (TMS) and oxygen was used to deposit interlayer, and finally multilayer Si-DLC/DLC film was deposited using the gas C2H2 and argon. Transmission Electron Microscope (TEM) demonstrated that there existed CuSiO3, CuO, SiC, SiO2 nanostructures in the interlayer. And X-ray Photoelectron Spectroscopy (XPS) proved that there were actually CuO, SiC and SiO bonds at the interface. These bonds and compounds enhanced the adhesion between multilayer Si-DLC/DLC film and copper substrate. The polarization potential was significantly improved to −0.07 V, achieved through the process of oxygen pre-implantation and the combined deposition of oxygen and TMS. Furthermore, the adhesion of the film was estimated by the Rockwell test and reached HF1-HF2. The Cu-O-Si-C microstructure plays a crucial role in enhancing the adhesion and corrosion resistance of multilayer Si-DLC/DLC film.

Experimental and theoretical study on the thermal stability and pyrolysis mechanism of octamethyltrisiloxane (MDM) with lubricating oil

In actual organic Rankine cycle systems (ORCs), the inclusion of lubricating oil in the working fluid is nearly unavoidable. Under the condition of high-temperature operation, the presence of lubricating oil can potentially exacerbate the thermal stability of the working fluid. The impact of polyol ester (POE) and mineral lubricant on the thermal stability of octadethyltrisiloxane (MDM) is studied. Results indicate that both POE and mineral lubricant contribute to the decomposition of MDM to a certain extent. Specifically, at a 5.0% mass fraction of POE and mineral lubricant, MDM remains its stable at 230 °C and 210 ℃, respectively. However, as the mass fraction of lubricant increases, the decomposition of MDM intensifies, with mineral lubricant exhibiting a more pronounced effect compared to POE lubricant. Regarding pyrolysis products, the presence of lubricants leads to an increase in CH4, C2H6 and C2H4 gases. Furthermore, the addition of lubricant promotes the formation of siloxane oligomers, particularly MD5M to MD9M, and enhances the production of unidentified products. Compared to MDM, both POE and mineral lubricant molecules exhibit lower bond dissociation Gibbs free energies. The free radicals generated from lubricant decomposition are prone to hydrogen abstraction reactions with MDM to promote MDM decomposition. Moreover, ReaxFF simulation results demonstrate that lubricant molecules also enhanced the activation of MDM and increased its susceptibility to Si-C bond cleavage. Following the removal of the methyl group, the Si-O bonds in the radicals are more likely to break, leading to the formation of additional siloxane oligomers through Si-O bond recombination. Kinetic analysis reveals that the apparent activation energy of MDM decomposition drops from 134.4 kJ∙mol−1 to 110.8 kJ∙mol−1 as the mass fraction of n-hexadecane (model compounds for mineral lubricant) rises from 0% to 10.30%.

Resilient Si@C architecture fabricated by mechanochemical conjugation and thermal reduction for lithium storage: Simulation on interfacial state evolution

Synchronal comminution via high-energy bead milling not only efficiently pulverizes Si particles and exfoliates graphene oxide (GO) sheets but also facilitates Si surface functionalization and intensify Si-C conjugation. After a thermal reduction, a well-wrapped Si@C anode material can be fabricated for lithium storage. The discharge specific capacities of this Si@C composite sustain at 1110.3 mAh g−1 after 300 cycles at 1 A g−1 and 316.4 mAh g−1 for 800 cycles at 5 A g−1, which are respectively 1.35 and 2.07 times that of its random blended Si/C counterpart. By employing molecular dynamics (MD) simulations with ReaxFF reactive force field to investigate the mechanochemical reactions between Si and GO amidst high-energy milling, an atomic scale portrayal of Si crystal fragmentation and Si-C bonding can be depicted. Analyses focusing on the differential forces exerted on various Si crystal planes, coupled with potential energy (PE) trends, reveal a higher propensity for cleavage in (111) plane, with (311) plane followed. Radial distribution function (RDF) outcomes indicate that ball milling leads to substantial disruption of crystalline order in Si particles, generating a plethora of Si dangling bonds. This disruption stimulates the formation of SiOOC, SiOC and SiC bonds at the Si/C interface, thus enhancing the integration of GO with Si substrate. Subsequent thermal reduction processes not only restore the structural order of Si and GO but also consolidate Si/C bonding.

Control of Biological Surface States on Chlorine-Doped Amorphous Silica Particles and Their Effective Absorptive Ability for Antibody Protein.

Amorphous silica particles (ASPs) have low biotoxicity and are used in foodstuffs; however, the adsorption states of proteins on their surfaces have not yet been clarified. If the adsorption states can be clarified and controlled, then a wide range of biological and medical applications can be expected. The conventional amorphous silica particles have the problem of protein adsorption due to the strong interaction with their dense silanol groups and denaturation. In this study, the surfaces of amorphous silica particles with a lower silanol group density were modified with a small amount of chlorine during the synthesis process to form a specific surface layer by adsorbing water molecules and ions in the biological fluid, thereby controlling the protein adsorption state. Specifically, the hydration state on the surface of the amorphous silica particles containing trace amounts of chlorine was evaluated, and the surface layer (especially the hydration state) for the adsorption of antibody proteins while maintaining their steric structures was evaluated and discussed. The results showed that the inclusion of trace amounts of chlorine increased the silanol groups and Si-Cl bonds in the topmost surface layer of the particles, thereby inducing the adsorption of ions and water molecules in the biological fluid. Then, it was found that a novel surface layer was formed by the effective adsorption of Na and phosphate ions, which would change the proportion of the components in the hydration layer. In particular, the proportion of the free water component increased by 21% with the doping of chlorine. Antibody proteins were effectively adsorbed on the particles doped with trace amounts of chlorine, and their steric adsorption states were evaluated. It was found that the proteins were clearly adsorbed and maintained the steric state of their secondary structure. In the immunoreactivity tests using streptavidin and biotin, biotin bound to the chlorine-doped particles showed efficient reactivity. In conclusion, this study is the first to discover the surface layer of the amorphous silica particles to maintain the steric structures of adsorbed proteins, which is expected to be used as a carrier particle for antibody test kits and immunochromatography.