Surface Of SiO2 Nanoparticles Research Articles

Enhancing the Mechanical Properties of Injectable Nanocomposite Hydrogels by Adding Boronic Acid/Boronate Ester Dynamic Bonds at the Nanoparticle-Polymer Interface.

Incorporating nanoparticles into injectable hydrogels is a well-known technique for improving the mechanical properties of these materials. However, significant differences in the mechanical properties of the polymer matrix and the nanoparticles can result in localized stress concentrations at the polymer-nanoparticle interface. This situation can lead to problems such as particle-matrix debonding, void formation, and material failure. This work introduces boronic acid/boronate ester dynamic covalent bonds (DCBs) as energy dissipation sites to mitigate stress concentrations at the polymer-nanoparticle interface. Once boronic acid groups were immobilized on the surface of SiO2 nanoparticles (SiO2-BA) and incorporated into an alginate matrix, the nanocomposite hydrogels exhibited enhanced viscoelastic properties. Compared to unmodified SiO2 nanoparticles, introducing SiO2 nanoparticles with boronic acid on their surface improved the structural integrity and stability of the hydrogel. In addition, nanoparticle-reinforced hydrogels showed increased stiffness and deformation resistance compared to controls. These properties were dependent on nanoparticle concentration. Injectability tests showed shear-thinning behavior for the modified hydrogels with injection force within clinically acceptable ranges and superior recovery.

Catalysis in Extreme Field Environments: A Case Study of Strongly Ionized SiO2 Nanoparticle Surfaces.

High electric fields can significantly alter catalytic environments and the resultant chemical processes. Such fields arise naturally in biological systems but can also be artificially induced through localized nanoscale excitations. Recently, strong field excitation of dielectric nanoparticles has emerged as an avenue for studying catalysis in highly ionized environments, producing extreme electric fields. While the dynamics of laser-driven surface ion emission has been extensively explored, understanding the molecular dynamics leading to fragmentation has remained elusive. Here, we employ a multiscale approach performing nonadiabatic quantum molecular dynamics (NAQMD) simulations on hydrogenated silica surfaces in both bare and wetted environments under field conditions mimicking those of an ionized nanoparticle. Our findings indicate that hole localization drives fragmentation dynamics, leading to surface silanol dissociation within 50 fs and charge transfer-induced water splitting in wetted environments within 150 fs. Further insight into such ultrafast mechanisms is critical for the advancement of catalysis on the surface of charged nanosystems.

Nanofluids with superhydrophobic nanoparticles for improved depressurization mechanism in low permeability reservoirs

Decreasing injection pressure and increasing water injection are crucial methods to enhance oil recovery in low permeability reservoirs. However, the high injection pressure, constrained by the reservoir's low porosity and permeability, limits the amount of injected water, consequently resulting in low recovery. In this study, inspired by the ''lotus effect'' of superhydrophobic wettability, we synthesized superhydrophobic nanoparticles by grafting fluorine-containing long chains onto the surfaces of SiO2 nanoparticles. Nanofluids with small particle size (7 nm), high stability, and strong hydrophobicity (162°) were prepared by compounding modified SiO2 nanoparticles with surfactants. The functional properties of the nanofluids revealed a depressurization rate of 23.13 % and the 23.90 % increase in flow rate at the channel center. Modified nanoparticles altered the surface wettability from hydrophilic to superhydrophobic. Surface free energy, determined using a three-probe-liquid method, demonstrated a significant reduction after hydrophobic modification. The surface hydrophobic interaction was tested and quantified by AFM measurements. The results show that the adhesion force is much larger than that of the unmodified hydrophilic surface. Through these analyses, we propose an efficient depressurization mechanism facilitated by the superhydrophobic layer formed by modified SiO2 nanoparticles. This work offers technical and theoretical support for the efficient development of low permeability reservoirs.

Investigation on corrosion resistance of electroless Ni-W-P coatings co-deposited with SiO2 nanoparticles

The corrosion of materials in sea environment are generally caused by salt spray, tidal action and adhesion of marine organisms. It is necessary to ensure the materials possess the required strength and good corrosion resistance during operation. Although the existing Ni-W-P electroless plating can provide a certain degree of corrosion protection, its corrosion resistance is still limited under harsh marine condition. SiO2 nanoparticles have received extensive concern due to their excellent corrosion resistance, which has been considered as potential candidates for enhancing corrosion resistance in multicomponent electroless coatings. In this study, the electroless Ni-W-P coatings with SiO2 nanoparticles co-deposition on the Q235 substrate was prepared. The coating was characterized through scanning electron microscopy (SEM), x-ray diffraction (XRD), polarization techniques, and electrochemical impedance spectroscopy (EIS). As a result, the Ni-W-P coating co-deposited with SiO2 nanoparticles demonstrates superior corrosion resistance compared to the pure Ni-W-P coating. The surface of SiO2 nanoparticles contain three distinct bonded hydroxyl functional groups, which can influence the ionic reaction in the plating solution and the deposition of elements in the coating. After modified by PVA, it can be uniformly dispersed in the coating, and the composite coating with SiO2 nanoparticles co-deposited is transformed into a nanocrystalline structure. The even distribution of SiO2 nanoparticles fill the defects within the coating, leading to a reduction in porosity, permeability, and susceptibility to penetration of corrosive media. Concurrently, the nanoparticles facilitate surface passivation, forming a stable interface with substrate and coating that inhibits electrochemical reactions and diminishes the rate of self-corrosion reactions. The good and stable corrosion resistance is achieved at the SiO2 concentration of 9 g l−1 and PVA concentration of 1.08 g l−1. These findings offer valuable insights for addressing corrosion challenges in the field of marine engineering.

Eco-friendly synthesis of amino and carboxyl-functionalized silica nanoparticles for enhanced adsorption of water pollutants

Green synthesised nanoparticles (NPs) have garnered significant attention as a rapidly expanding category of materials with diverse applications. In this context, plants are widely acknowledged as a highly favourable option for green synthesis due to their adherence to the eco-friendly pathway of NPs biosynthesis. The objective of green synthesis is to reduce the utilisation of hazardous chemicals. The utilisation of silica (SiO2) NPs, synthesised from biomass as adsorbents, has shown great potential particularly in removing toxic materials from environment. When it comes to adsorbing water pollutants, functionalized SiO2 NPs are seen as potential option. However, certain functional group onto the surface of SiO2 NPs have higher affinity towards a particular pollutant. In this work, a simple and eco-friendly synthesis method (using waste bamboo leaves) have been utilised for production of SiO2 NPs. Further, a silylating procedure was used to functionalize SiO2 NPs with amine (A-SiO2) and carboxyl groups (C–SiO2) for determining adsorption capabilities towards anionic and cationic dyes i.e., Naphthol green-B (NGB) and brilliant green (BG). The adsorption mechanism has been discussed in view of different adsorption isotherm models. According to batch investigations, the functionalized SiO2 NPs showed different behaviour for dyes depending upon nature of dyes and the functional groups. The results of the study revealed that A-SiO2 NPs were having adsorption capacity of 122.10 mg/g for anionic dye (NGB) while C–SiO2 NPs showed adsorption capacity of 114.41 mg/g for cationic dye (BG). Additionally, these NPs exhibit good recyclability up to 5 cycles of reuse. Novelty of this study is the reduced energy needs for the green synthesis of the SiO2 NPs using bamboo leaves and the effect of different functional groups on the adsorption capacity of the NPs. Overall, this study provides a sustainable, and reusable approach for effective dye removal from wastewater, addressing both environmental and economic problems.

Synthesis of cobalt nanoparticles in aqueous solutions assisted by polymer/inorganic hybrid

Hydrophilic polymer/inorganic hybrids (PIH) containing silica nanoparticles and polyacrylamide chains proved to be effective matrices for the in situ synthesis of cobalt nanoparticles. PIH sample was synthesized by free-radical polymerization of acrylamide from the unmodified surface of SiO2 nanoparticles and characterized by elemental analysis, dynamic thermogravimetric analysis, static light scattering, potentiometric titration, viscometry and transmission electron microscopy (TEM). The processes of borohydride reduction of cobalt ions from the Co(NO3)2·6H2O solution to nanoparticles in water medium and aqueous solutions of PIH were studied as a function of the concentrations of metal salt and hybrid concentrations using UV-Vis spectroscopy and TEM. A special approach to characterize the kinetics and efficiency of CoNPs formation in water medium and hybrid solutions using UV-Vis spectroscopy was implemented. The kinetic parameters of the CoNPs formation process as well as the yield, size, and morphology of nanoparticles in hybrid solutions and water medium at various concentrations of metal salt and hybrid were determined. The growth of both concentrations of reagents had a positive effect on the rate of formation of metal nanoparticles and their yield, but in all cases, the reduction process developed much slower in hybrid solutions compared to pure water. The morphology of the CoNPs/PIH nanocomposites was mainly represented by separate swollen hybrid particles containing metal nanoparticles with dav~3 nm.

UV Irradiated SiO2 Nanoparticles as Insulin and Immunoglobulin Molecule Carriers

Abstract Insulin and immunoglobulin therapy is commonly administered through injections that are invasive and painful. They cannot be taken orally because digestive enzymes break them down. To protect against enzymes, drug molecules may be “packed”, which decreases interaction of the active surface of the molecule with the environment. Silica nanoparticles (SiO2) may be used to attach proteins like insulin or immunoglobulin for use in drug delivery. They are stable and biocompatible. Exposing SiO2 nanoparticles to UV radiation may control molecule–nanoparticle attachment because of their electrostatic interactions. This study demonstrates the influence of UV radiation of SiO2 nanoparticles on insulin and immunoglobulin molecule attachment. Alteration of the surface electric potential of SiO2 nanoparticles by UV radiation was determined using electron work function measurements. Influence of radiation on formation of molecule-nanoparticle complexes was assessed by spectrophotometry of their sedimentation rate in solution. Increasing UV exposure time negatively charges the surfaces of SiO2 nanoparticles. Insulin exhibits better adsorption with SiO2 nanoparticles compared to immunoglobulin, likely due to favourable conditions promoting attractive electrostatic interactions. Longer UV exposure weakens insulin adsorption but does not significantly affect immunoglobulin adsorption.

A study on functionalization process of silicon dioxide nanoparticles for hydrophobic coating applications

Functionalized nano‐SiO2 is an inorganic compound that exhibits hydrophobic properties upon the addition of a silane group through a chemical reaction. This property is highly effective in surface modification for various substrates, including glass, metal, and ceramics. These surface modifications find applications in self‐cleaning, anti‐fogging coatings, and water‐repellent materials. In this work, the role of nano‐SiO2 and Hexadecyltrimethoxysilane (HDTMS) functionalized nano‐SiO2 has been synthesized successfully by the sol–gel method for coating applications. The outcomes of water contact angle (WCA), analysis, Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), scanning electron microscope (SEM), and transmission electron microscope (TEM) observations revealed the successful grafting of hydrophobic long‐chain alkyl groups from HDTMS onto the surface of SiO2 nanoparticles. Notably, when the ratio of SiO2 nanoparticles to HDTMS is 0.25:1, the WCA of the functionalized SiO2 nanoparticles is enhanced significantly. This value is 5.35 times greater than the initial angle of contact before the modification, leading to the achievement of a super hydrophobic property.

β-Cyclodextrin modified SiO2 nanofluid for enhanced oil recovery

Recently, with the deterioration of oil storage conditions, the extraction of oil has been limited. In this experiment, β-cyclodextrin (β-CD) was grafted onto the surface of SiO2 nanoparticles. The structure and morphology of nanoparticles were analyzed by various characterization tools to effectively validate the synthesis of nanomaterials. In addition, it was experimentally demonstrated that the developed β-CD-SiO2 nanofluid has excellent stability and salt resistance. Finally, the comparative studies of the nanofluids were carried out by wettability, interfacial tension (IFT), Pickering emulsion, viscosity, and core flooding experiments. The results showed that β-CD-SiO2 nanofluid exhibited better performance: β-CD-SiO2 nanofluid changed the contact angle (CTA) of carbonate plate from 131.5º to 90.1º; the IFT was significantly reduced from about 35 mN/m to 22.5 mN/m; the emulsion droplets formed were fine and dense; the viscosity increased and viscosity not changed with shear rate; and total crude oil recovery up to 59.2%, 23.9% higher than using water drives. Overall, these results showed the great potential of β-CD-SiO2 nanofluid in ultra-low permeability reservoirs.

Effect of Surface Properties of Nanoparticles on the Crystallization Behavior of Polypropylene/Polypropylene‐g‐Silica Nanocomposites

AbstractIn order to investigate the effect of surface properties of nanoparticles (NPs) on the crystallization behavior of nanocomposite, three kinds of silica (SiO2) NPs are dispersed in isotactic polypropylene (iPP) matrix by solution blending method. Specifically, the poor compatibility between inorganic bare SiO2 NPs and organic PP matrix triggers the formation of aggregates and induces the fractionated crystallization with two crystallization peaks at higher particle loading (Φ), i.e., main crystallization peak (MCP) and low temperature crystallization peak (LCP, always located at 124.0 °C). Once short PP chains (0.9 × 104 g mol−1) are grafted onto the surface of SiO2 NPs, the nanocomposites with all Φ only exhibit a single MCP which is attributed to the strong interfacial interaction. With the increase of grafting chain length (9 × 104 g mol−1), the more stretched conformation of grafting chains can provide numerous heterogeneous nucleation sites and significantly accelerate the crystallization rate of PP chains near the surface of SiO2 NPs, which lead to the formation of an extra high temperature crystallization peak (HCP, almost kept constant at 133.0 °C). The occurrence of various crystallization peaks implies that the surface properties of nanoparticles play a vital role in the nucleation ability of nanoparticles.

Surface modification boosts dispersion stability of nanoparticles in dielectric fluids

Achieving stable dispersion of nanoparticles in dielectric fluids is a challenging task, as there are complex and diverse influencing factors, requiring molecular-level understanding of the nanoparticle aggregation. In this paper, we conducted long-time molecular simulations of dielectric nanofluids containing fifteen SiO2 nanoparticles, systematically varying the length of alky chains grafted onto their surface to explore their impact on the aggregation process. Our results reveal that appropriate surface modification can dramatically increase the dispersion stability of nanoparticles in dielectric fluids. SiO2 nanoparticles lacking alkyl chains exhibit a strong tendency to approach each other, and form aggregates in natural esters, because of the Coulombic energy from heteroatoms of SiO2 nanoparticles. Despite the differences in the length of grafted alkyl chains on the surface of SiO2 nanoparticles, all of them, regardless of their length, are capable of effectively shielding the Coulombic interactions and increasing the van der Waals interaction with natural esters, thereby reducing the aggregation tendency of nanoparticles. Furthermore, the smaller diffusion ability, caused by the steric hindrance effect, of surface-modified SiO2 nanoparticles also inhibits their collision and subsequent aggregation.

Fluorescence “light-up” sensor based on ligand/SiO2@NH2@cyanuric chloride nanoparticle interactions in alliance with salt dehydration for berberine detection

Berberine (BBR) is an important anti-inflammatory drug for the treatment of intestinal diseases. The quantification of BBR is required in clinical medicine because long-term or excessive intake can lead to drug resistance and adverse effects. In this study, SiO2@NH2@cyanuric chloride (CNCl) nanoparticles (NPs) were successfully prepared by covalently incorporating CNCl onto the surface of SiO2 NPs. Furthermore, a novel fluorescence “light-up” sensor for assaying BBR was established based on the interaction between BBR and SiO2@NH2@CNCl NPs. Although BBR was non-emissive in aqueous media, its fluorescence was considerably augmented because of the interaction with the as-prepared SiO2@NH2@CNCl NPs, and the enhancement factor was approximately three times larger than that of pure SiO2 NPs. Compared with SiO2 NPs, SiO2@NH2@CNCl NPs can interact with BBR through electrostatic interactions and π-π stacking. These interactions restricted the intramolecular motion and charge transfer of BBR, resulting in fluorescence enhancement. The sensor was sensitive, with a linear response over a concentration range of 25–2500 nM (R2 = 0.9905) and a detection limit (3σ/k) of 4.7 nM, and it had good selectivity for BBR in the presence of bovine serum albumin, amino acids, and metal ions. When the sensor was applied to real serum samples, rapid extraction and salt dehydration occurred to improve the efficiency of pretreatment, and satisfactory standard recovery rates (95%–96%) were achieved even when only small amounts of acetonitrile was used for protein precipitation. This strategy could serve as a reference for other studies requiring the analysis of drugs in biological samples.

Highly sensitive electrochemical detection of gallic acid in tea samples by using single-walled carbon nanotubes@silica dioxide nanoparticles decorated electrode

In this work, a simple and efficient gallic acid (GA) electrochemical sensor was successfully fabricated by using silica dioxide (SiO2) nanoparticles@single-walled carbon nanotubes (SWCNT) nanocomposite modified glassy carbon electrode (SWCNT@SiO2/GCE). The SWCNT@SiO2/GCE sensor was applied for the highly sensitive electrochemical detection of GA for the first time. For the SWCNT@SiO2 nanocomposite, SWCNT with interconnected carbon conductive network possessed high conductivity property, large specific area, and efficient charge transport channels. The abundant hydroxyl groups and silanol groups on the surface of SiO2 nanoparticles were good for the enrichment of GA molecules on the surface of SWCNT@SiO2/GCE. Moreover, SWCNT could greatly compensate for the non-conductivity of SiO2 nanoparticles. The synergistic effect of SWCNT and SiO2 nanoparticles enhanced the electrochemical determination performance of GA. The SWCNT@SiO2/GCE sensor exhibited good GA determination performance (pH=2.0, linear GA concentration: 0.03–20 μM, limit of detection: 8.05 nM). The fabricated sensor also showed good reproducibility, reproducibility, and anti-interference performance. In addition, the SWCNT@SiO2/GCE sensor presented good practical application performance for the detection of GA in tea samples (Recovery rate: 95.2–103.6%; relative standard deviation: 2.03–4.50%). This work exhibits a novel approach for the sensitive determination of GA in green tea and black tea samples.

Ionic liquid modified SiO2 nanoparticles as coreactant of Ru(bpy)32+ ECL and its application in the detection of glutathione

In this work, a novel electrochemiluminescence (ECL) signal amplification strategy was proposed based on SiO2nanoparticles modified with ionic liquids (ILs) as a coreactant for Ru(bpy)32+ ECL. The defects of silica nanospheres could combine with H2O and act as the oxidation center of ECL reaction to enhance the anodic ECL of Ru(bpy)32+. The modification of ILs on the surface of SiO2 nanoparticles could further enhance Ru(bpy)32+ ECL due to its excellent conductive activity and the adsorption ability for Ru(bpy)32+. ECL resonance energy transfer (RET) between MnO2 nanosheets and Ru(bpy)32+ could efficiently quench the ECL signal. In the presence of glutathione (GSH), the redox reaction between MnO2 nanosheets and GSH could cut the pathway for the RET and restore the ECL signal. As a consequence, the designed sensor exhibited outstanding performance for the detection of GSH in the concentration range of 50 nM to 50 μM with a low detection limit of 41.8 nM. Importantly, this work explored the possibility of using green and non-toxic coreactants for ECL, which will provide new avenue for the fabrication of biosensor.

New insights into the heat capacity enhancement of nano-SiO2 doped alkali metal chloride molten salt for thermal energy storage: A molecular dynamics study

Molten salts and their based nanofluids are important media for heat transfer and thermal energy storage in concentrated solar power (CSP) system. To improve the overall efficiency of the CSP plants, it is important to increase the specific heat capacity of molten salt to the extent possible. Nanomaterials have been doped in molten salt to enhance the specific heat capacity of molten salt; however, the mechanism of enhancement in specific heat capacity caused by doping of nanoparticles in molten salt is still unclear. In this work, the Buckingham force field parameters for alkali metal chloride molten salts (KCl, NaCl, LiCl) were first derived and carefully validated. The specific heat capacities, viscosities, and self-diffusion coefficients of pure molten salts and the specific heat capacities of molten-salt-based nanofluids with SiO2 nanoparticles were investigated by molecular dynamics (MD) simulations. The calculated thermophysical properties of the chloride molten salts using the derived Buckingham potential parameters are in good agreement with the experimental data, and the overall prediction performance is better than that of the BMH potential. Results show that the specific heat capacity of molten salt first increases and then decreases with increasing SiO2 doping ratio, reaching a maximum value at 1 wt%. The specific heat capacities of KCl, NaCl and LiCl nanofluids with 1 wt% SiO2 nanoparticle are increased by 6.2 %, 8.6 % and 19.8 % compared to the base salts, respectively. Number density, radial distribution function, coordination number curves, and energy of the nanofluid system were systematically analyzed. It is found that the increase of the specific heat capacities of the molten salt-based nanofluids can be explained by the energy and coordination number change caused by the number density mismatch of cations and anions. Interestingly, the local delamination of cations around SiO2 nanoparticle surfaces in LiCl-SiO2 nanofluids is clearly observed and visualized for the first time; it is a phenomenon well explained by the analysis of number density and contributes to the further enhancement of the heat capacity. The findings of this work could provide important fundamentals in understanding and designing more efficient molten salt nanocomposites for thermal energy storage in future studies.

Immobilization of lipase on silica nanoparticles by adsorption followed by glutaraldehyde cross-linking.

In this study, Candida antarctica lipase B was immobilized on silica (SiO2) nanoparticles by physical adsorption, and then cross-linked with glutaraldehyde (GA) to prepare cross-linked immobilized lipase (CLIL). During the condition of 1.28mg/mL lipase concentration, 25℃ temperature, 2h adsorption time, 0.01% GA (V/V) 7.5mL and 2h cross-linking time, the highest recovery activity of CLIL reached 87.82 ± 0.07% (22.55 ± 0.025U/mg). Scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM) confirmed that lipase was immobilized on the surface of SiO2 nanoparticles. The changes in secondary structures of CLIL indicated that cross-linking changed the secondary structure of lipase protein, which made the structure of CLIL more stable. Compared with the free lipase, the thermal stability and storage stability of CLIL was significantly improved, and the t1/2 at 60°C was extended. Studies had shown that it was a feasible method to obtain CLIL by cross-linking after adsorbing lipase on SiO2 nanoparticles.

Tailor-made mesoporous SiO2/Au thin film with a substitutable interface for highly sensitive and selective room-temperature gas detection of VOCs

Trace amounts of volatile organic compounds (VOCs) were detected in Au chip interfaces modified with mesoporous SiO2 nanomaterials by using a surface plasmon resonance (SPR) technique. With Kretchmann-configuration SPR, it was possible to detect interactive and specific signal changes between a SiO2/Au gas-sensor surface and acetone, formaldehyde, and methane gases at room temperature. A dielectric spacing layer on Au was expanded and SPR signals were amplified by the mesoporous SiO2 nanoparticles with a large surface area and surface properties that were easily modified with specific ligands and became highly sensitive to, and selective for, the target gas molecules. A phosphonitrilic chloride trimer (PNCT), a universal self-assembled monolayer (SAM), and post-treatment for simple substitutions of ligands equipped the surfaces of SiO2 nanoparticles with targeted receptors, which resulted in the sensitive and selective detection of acetone to CH3-, formaldehyde to NH2-, and methane to Cl-functional groups. The chips modified with each functional group had a response time of about 2 s for concentrations of each gas that ranged from 0.2 to 3.0 ppm. The sensors modified with the functional groups showed limit of detection (LOD) values of 0.3, 0.6, and 0.5 ppm, respectively, which exceeded the Occupational Safety and Health Administration (OSHA) regulations, and limit of quantification (LOQ) values of 0.9, 1.8, and 1.6 ppm. Relative humidity of 45 ∼ 84 % under ambient air had negligible influence on the baseline signals in this SPR gas-sensing system. These sensors have the potential to monitor VOCs in both environmental and indoor settings.

Enhanced thermal energy storage performance of molten salt for the next generation concentrated solar power plants by SiO2 nanoparticles: A molecular dynamics study

Chloride molten salt is the most promising thermal energy storage materials for the next generation concentrated solar power (CSP) plants. In this work, to enhance the thermal performance of KNaCl2 molten salts, composited thermal energy storage (CTES) materials based on amorphous SiO2 nanoparticles and KNaCl2 were proposed and designed under the guidance of the material composition design strategy. The molecular dynamics simulation method has been conducted to investigate the thermal storage properties and analyze the mechanism of heat transfer improvement from the perspective of microstructure evolution, thermal diffusion properties and energy changes. Thermal conductivity, viscosity, and specific heat capacity of CTES materials at high temperatures with different volume fractions of nanoparticles were predicted to provide reference data for the design of heat transfer systems in CSP plants. The study discovered that increasing the volume fraction of nanoparticles increases the thermal conductivity and specific heat capacity of the systems significantly, with the maximum increase of 25.28% and 7.87%, respectively. Moreover, the enhancement of heat transfer characteristics is the result of the formation of a compressed interface layer with a thickness 5 Å on the outer surface of SiO2 nanoparticles. This work has important guiding significance for the material selection and composition design of molten salt-nanoparticle composite materials used for next-generation CSP plants.

Effect of surface modification of SiO2 particles on the interfacial and mechanical properties of PBS composites

AbstractIn this study, WPU@SiO2 nanoparticles were obtained by grafting waterborne polyurethane (WPU) on the surface of silicon dioxide (SiO2). Then, WPU@SiO2 nanoparticles were introduced into the matrix of polybutylene succinate (PBS) to prepare a series of PBS/WPU@SiO2 composites. The dispersibility and interfacial compatibility of filler and matrix can be improved obviously by grafting a layer of WPU onto the surface of SiO2 nanoparticles. The FTIR and TGA results showed that WPU was successfully grafted onto the surface of SiO2. According to polarizing microscope images, it is clear that the size of the pure PBS crystals is much larger than that of the PBS/WPU@SiO2, and a large number of crystals are evenly distributed in the PBS/WPU@SiO2 composite. In addition, DSC and TGA results indicated that PBS/WPU@SiO2 composite films show excellent thermal properties. Meanwhile, the initial thermal decomposition temperature of PBS/WPU@SiO2 composite films is about 366–374°C. For the 10 wt% WPU@SiO2 reinforced PBS‐based composite films, the tensile strength reached the ultimate value (38.49 MPa), which is 32.04% higher than that of pure PBS. Based on its excellent mechanical and thermal properties, the PBS/WPU@SiO2 composites have a broad application prospect in the field of biodegradable materials.

Study of the Adsorption Behavior of Surfactants on Carbonate Surface by Experiment and Molecular Dynamics Simulation.

Surfactants adsorption onto carbonate reservoirs would cause surfactants concentrations decrease in surfactant flooding, which would decrease surfactant efficiency in practical applications of enhanced oil recovery (EOR) processes. Different surfactants could be classified as cationic surfactants, anionic surfactants, non-ionic surfactants according to the main charge, or be classified as chemical surfactant and bio-surfactant according to the surfactant origin. However, the research on different type surfactants adsorption on carbonate reservoirs surface differences was few. Therefore, five representative surfactants (CTAB, SDS, TX-100, sophorolipid, rhamonilipid) adsorption effect onto carbonate reservoirs surface was studied. Owing to the fact that the salinity and temperature in underground carbonate reservoirs were high during the EOR process, it is vital to study the salinity effect and temperature effect on surfactant adsorption. In this study, different surfactants species, temperature and salinity adsorption onto carbonate reservoirs were studied. The adsorption isotherms were fitted by Langmuir, Freundlich, Temkin and Linear models, and the first three models fitting effect were good. The results showed that cationic surfactants adsorption quantity was higher than anionic surfactants, and the non-ionic surfactants adsorption quantity was the lowest. When the temperature increased, the surfactants adsorption would decrease, because the adsorption process was exothermic process, and increasing temperature would inhibit the adsorption. The higher salinity would increase surfactants adsorption because higher salinity could compress electric double layer. In order to decrease surfactants adsorption, SiO2 nanoparticles and TiO2 nanoparticles were added to surfactants solutions, and then surfactants could adsorb onto nanoparticles surface, then the steric hindrance between surfactant molecules would increase, which could decrease surfactants adsorption. Contact angle results indicated that surfactants adsorption made the carbonate reservoir wettability alteration. In the end, surfactants (with or without SiO2 nanoparticles) adsorption onto carbonate reservoirs mechanism were studied by molecular dynamics simulation. The simulation results indicated that the surfactants molecules could adsorb onto SiO2 nanoparticles surface, and then the surfactants adsorption quantity onto carbonate rocks would decrease, which was in accordance with the experiments results.