Modification Of Silica Research Articles

Modification of silica supported nickel catalysts with lanthanum for stability improvement in methane reforming with CO2

Dry reforming of methane (DRM) with excessive methane composition at CH4/CO2 = 1.2:1 was studied over lanthanum modified silica supported nickel catalysts (Ni-xLa-SiO2, x: 1, 2, 4, and 6% in the target weight percent of La). The catalysts were prepared by ammonia evaporation method. Nickel phyllosilicate and La2O3 were the main phases in calcined catalysts. The modification of La enhanced the formation of 1:1 and Tran-2:1 nickel-phyllosilicate. There existed an optimum content of La loading at 1.50 wt% in Ni–2La–SiO2 which resulted in its highest reduction degree (95.3%). The catalysts with appropriate amounts of La exhibited higher amount of CO2 adsorption and created more medium and strong base centers. The sufficient number of exposed metallic nickel sites to catalyze the reforming reaction, as well as enough medium and strong basic sites in Ni–La–SiO2 interface to accomplish the carbon removal were two important factors to attenuate catalyst deactivation. The catalyst stability evaluated at 750 °C for 10 h followed the order: Ni–2La–SiO2 > Ni–4La–SiO2 > Ni–1La–SiO2 ≈ Ni–6La–SiO2 > Ni–SiO2. Ni–2La–SiO2 catalyst possessed the lowest deactivation behavior, whose CH4 conversion dropped from 60.2 to 55.9% after 30 h operation at 750 °C, indicating its high resistance against carbon deposition and sintering.

Superfine coal powder modified by amorphous silica and its high reinforcing performance in styrene butadiene rubber

ABSTRACT Coal has good compatibility with polymer matrix due to the macromolecular feature similar to many polymers, and is considered an attractive alternative filler for carbon black (CB) obtained through expensive energy conversion processes. Therefore, a modified coal- silica reinforcing powder (MCS) was prepared by ultrafine grinding, in-situ coating of silica and surface modification, and compared with CB, fumed silica (FS) and precipitated silica (PS) in terms of enhanced capabilities in vulcanizates. The bulk structure coal particles are dissociated into lamellas about 50 nm in thickness after wet grinding, and evenly coated by nano-level silica particles modified by hexamethyldisilazane. The two particles are closely bound together through the Si−O−C bonds formed by condensation of Si−OH group of the silica and C− OH group of aromatic microcrystalline. The resulted MCS shows good dispersion and compatibility in rubber matrix. The mechanical properties and abrasion resistance of MCS filled vulcanizate are between that of CB filled and FS filled vulcanizates, and the rolling resistance and heat generation are significantly lower than that of CB or FS filled vulcanizates. MCS exhibits excellent comprehensive dynamic performance in rubber, which is a very attractive reinforcement material used as the substitute of CB to reduce vast carbon footprint.

Effect of the Surface Modification of Silica Nanoparticles on the Viscosity and Mechanical Properties of Silica/Epoxy Nanocomposites

ABSTRACT Silica/epoxy hybrid resin has high viscosity owing to its particle size and aggregation in the epoxy matrix, which leads to poor usability and processability. To control the size of the silica nanoparticles, surface modification of the colloidal silica (12 nm) was conducted in two steps using a silane coupling agent. The silica nanoparticles were then dispersed in the epoxy resin using an amphiphilic solvent with a high boiling point instead of mechanical dispersion. A nanosilica/epoxy hybrid resin with a low viscosity was obtained. The hybrid resin containing 3 wt% silica nanoparticles obtained a viscosity value that is 1.2% that of the neat epoxy resin. The tensile and flexural strengths of the silica/epoxy nanocomposite, as well as the impact strength of the silica/epoxy nanocomposite, were improved by plastic deformation cause by the introduction of silica nanoparticles. With silica nanoparticles loading of 10 wt%, the tensile strength of the silica/epoxy nanocomposite increased by 24%, and the impact strength increased by 112%. For higher amounts of loaded silica nanoparticles, the tensile strength of the silica/epoxy nanocomposite continuously increased, while the impact strength decreased.

Study on modification of nano silica by [3- (2-Aminoethyl) aminopropyl] trimethoxy silane (KH-792) to reinforce polymer film based on epoxy resin Epon 1001X75

The surface of nano silica (NS) was modified by [3- (2-Aminoethyl) aminopropyl] trimethoxy silane (KH-792) to increase surface activity. Evaluate the efficiency of grafting [3- (2-Aminoethyl) aminopropyl] trimethoxy silane (KH-792) into NS was characterized by Fourier Transform Infrared Spectrometry (FTIR) and Thermo Gravimetric Analysis (TGA). NS and modified nano silica (m-NS) were dispersed into epoxy resin Epon 1001X75 by mechanical stirring and ultrasonic vibration. Epoxy resin Epon 1001X75 was cured with Epikure 3125 (Epi3125). The structural morphology and dynamic mechanical properties of materials were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Dynamic Mechanical Analysis (DMA). The results showed that NS was modified with the content of 20 wt% KH-792 for the highest denaturation efficiency. With adding the content of 1 wt% NS (NS-1), the mechanical properties of epoxy polymer film Epon 1001X75/Epi3125/NS-1 increased the impact strength from 20kG.cm to 52.5 kG.cm (increased by 162.5%). Adding the content of 2 wt% m-NS (m-NS-2) improved the impact strength of epoxy polymer film Epon 1001X75/Epi3125/m-NS-2 from 20 kG.cm to 55 kG.cm (increased by 175%). The glass transition temperature (Tg) of epoxy polymer composites Epon 1001X75/Epi3125, Epon 1001X75/Epi3125/NS-1, and Epon 1001X75/Epi3125/m-NS-2 gradually increased by 48 °C, 75 °C, and 79 °C. The obtained results showed that m-NS with KH-792 increased the mechanical properties of epoxy polymer film Epon 1001X75/Epi3125.

Modification of the MCM-41 mesoporous silica and its influence on the hydration and properties of a cement matrix

Recently, there has been a growing interest in materials that make it possible to reduce cement consumption in the concrete technology while improving the parameters of a final product. In this paper the validity of using, as an admixture to cement, the mesoporous silica of the MCM-41 structure type (MCM-41), modified with funcosil (hydrophobizing agent), triethanolamine, iron nitrate, and gluconic acid, has been analyzed. The effectiveness of the modification was evaluated on the basis of chemical and phase composition analysis, while the effect of admixtures on the cement matrix (CM) properties was additionally evaluated on the basis of selected physico-mechanical parameters and a hydration heat analysis. The results showed the quantitative effect of the modifications on the MCM-41 and CM composition. All the admixtures affected the rate and total amount of heat released during the hydration process. The presence of the triethanolamine and gluconid acid significantly delayed the main peak of the hydration process while the presence of the iron nitrate and gluconid acid decreased the total amount of heat released. Regardless of the maturation time, an increase in the CM compressive strength with the modified MCM-41 and a decrease in the percentage water loss during drying were observed. Only the gluconic acid modification caused a deterioration in the strength parameters. In conclusion, the use of the MCM-41 and its modifications in the production process of cement composites can positively affect the properties of the final product.

Modification of SBA-15 mesoporous silica as an active heterogeneous catalyst for the hydroisomerization and hydrocracking of n-heptane.

In this study, a mesoporous SBA-15 silica catalyst was prepared and modified with encased 1% platinum (Pt) metal nanoparticles for the hydrocracking and hydroisomerization of n-heptane in a heterogeneous reaction. The textural and structural characteristics of the nanostructured silica, including both encased and non-encased nanoparticles, were measured using small-angle X-ray diffraction (XRD), nitrogen adsorption-desorption porosimetry, Brunauer–Emmett–Teller (BET) surface area analysis, Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Catalytic testing was carried out in a plug-flow reactor under highly controlled operating conditions involving the reactant flow rate, pressure, and temperature. Gas chromatography was used to analyze the species as they left the reactor. The results demonstrated that 1% Pt/SBA-15 has a high n-heptane conversion activity (approximately 85%). Based on the results of this experimental work, there is no selectivity in the SBA-15 catalysts for isomerization products because they are inactive at the relatively low temperature that is essential for hydroisomerization. On the other hand, the SBA-15 catalysts have a considerable selectivity for products that have cracks, owing to their ability to withstand extremely high temperatures (300–400 ​°C) as well as the availability of Lewis acid sites within the catalyst structure.

Functionalized Mesoporous Silica as Doxorubicin Carriers and Cytotoxicity Boosters.

Mesoporous silica nanoparticles (MSNs) bearing methyl, thiol or glucose groups were synthesized, and their encapsulation and release behaviors for the anticancer drug Doxorubicin (Dox) were investigated in comparison with nonporous homologous materials. The chemical modification of thiol-functional silica with a double bond glucoside was completed for the first time, by green thiol-ene photoaddition. The MSNs were characterized in terms of structure (FT-IR, Raman), morphology (TEM), porosity (nitrogen sorption–desorption) and Zeta potential measurements. The physical interactions responsible for the Dox encapsulation were investigated by analytic methods and MD simulations, and were correlated with the high loading efficiency of MSNs with thiol and glucose groups. High release at pH 5 was observed in most cases, with thiol-MSN exhibiting 98.25% cumulative release in sustained profile. At pH 7.4, the glucose-MSN showed 75.4% cumulative release, while the methyl-MSN exhibited a sustained release trend. The in vitro cytotoxicity was evaluated on NDHF, MeWo and HeLa cell lines by CellTiter-Glo assay, revealing strong cytotoxic effects in all of the loaded silica at low equivalent Dox concentration and selectivity for cancer cells. Atypical applications of each MSN as intravaginal, topical or oral Dox administration route could be proposed.

Porous silica modification with sulfuric acids and potassium fluorides as catalysts for biodiesel conversion from waste cooking oils

Porous silica modification with sulfuric acids and potassium fluorides as catalysts for biodiesel conversion from waste cooking oils

Rubber Rail Pad Reinforced by Modified Silica Using GPTMS and Sulfenamide Accelerator

The interaction between silica and rubber is very important for the production of high performance rubber. Silica surface modification with silane is a general method that aims to enhance the reinforcement efficiency of silica. In this study, a new surface modification of silica with silane and the chemical reaction with sulfenamide accelerator were investigated. The (gamma-glycidoxypropyl) trimethoxysilane (GPTMS) was used as a silane. The N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and N-tert-butyl-2-benzothiazole sulfenamide (TBBS) were used as sulfenamide accelerators. The FTIR spectra results indicate that the GPTMS and sulfenamide accelerators (CBS and TBBS) could successfully form on the silica surface. The new modification is capable of significantly enhancing the reinforcement efficiency; more than the conventional silica surface modification by GPTMS (m-silica). In particular, modifying silica with GPTMS and TBBS (m-silica-TBBS) is capable of increasing the crosslink density and mechanical properties more efficiently than modified silica with GPTMS and CBS (m-silica-CBS), m-silica, silica (unmodified), and unfilled natural rubber. This is due to the presence of GPTMS, which plays an important role in increasing the chemical cross-linking in the rubber chain, while TBBS, as a sulfenamide accelerator, provides a high accelerator to sulfur ratio, which is able to give a more efficient vulcanization. With the reinforcement of a rubber rail pad with silica surface modification, the results indicate that the increment of m-silica-TBBS loading could reduce the deformation percentage of the rubber rail pad more than m-silica and m-silica loading. This is mainly due to the static spring improvement, which results in a stiffer material.

Deposition of poly(furfuryl alcohol) in mesoporous silica template controlled by solvent polarity: A cornerstone of facile and versatile synthesis of high-quality CMK-type carbon replicas. Nanocasting of SBA-15, SBA-16, and KIT-6

Six CMK-n replicas (n = 3, 5, 6, 7, 8, and 9) were synthesized using a new, facile and versatile method based on a surface-selective deposition of poly(furfuryl alcohol) onto the silica matrix. The concept of the synthesis relies on the in situ polycondensation of the carbon precursor in a toluene suspension of the hard template. Preferential pre-adsorption of the monomer onto silica provides even coverage of its surface with polymer, which is a prerequisite to the formation of highly ordered carbon negative structures (either hollow- or rod-type). The procedure is operated under ambient pressure and at moderate temperature, and a preliminary modification of silica and vacuo carbonization are no longer needed. A systematic study on materials (SEM, TEM, XRD, N2, and Ar adsorption) evidenced that the proposed pathway offers the preparation of carbon mesostructures featuring excellent structural and textural parameters while maintaining the morphology of the mother silica. CO2 adsorption revealed inhomogeneous porosity of the carbonaceous material itself. The rod-type replicas showed a core-shell structure, in which each carbon rod was built of the outer nonporous shell enveloping the microporous core. In contrast, the hollow-type carbons were constituted of non-microporous turbostratic carbon.

Preparation and pervaporation performance of PVA membrane with biomimetic modified silica nanoparticles as coating

Polyvinyl alcohol (PVA) has been widely used in pervaporation dehydration due to its low price and good stability. However, the inherent “trade-off” effect of polymer membrane makes the pervaporation performance relatively limited. In this work, the rough and super-hydrophilic surface were constructed by biomimetic modification of silica (SiO2) coating on the PVA membrane, which achieved simultaneous growth of total flux and separation factor compared with the control, and overcame the “trade-off” effect. The morphology, structure and hydrophilicity of membranes were characterized. Results demonstrated that PVA/polydopamine (PDA)/SiO2 composite membranes had strong hydrophilicity and high surface roughness. In addition, the effects of SiO2 loading amount, operating temperature, feed ethanol concentration and long-term stability on the ethanol dehydration performance were investigated. For the PVA/PDA/SiO2-6 composite membrane, total flux was 1388 g m−2 h−1, and the separation factor was 150(69 °C,90 wt% ethanol concentration), which was 1.8 times and 1.4 times that of the pristine PVA membrane, respectively.

Modification and performance analysis of pigment red 122 by fumed silica

In order to improve the properties of pigment red 122 (P.R.122), fumed silica was used as the adsorption carrier of pigment modification, and pigment red 122 was modified by precipitation-adsorption modification method, and a number of performance tests and characterization analysis of the pigments before and after modification were carried out. The effects of fumed silica modification on the color light, coloring power, dispersibility and hiding power of pigment red 122 were studied, and the structure and properties of pigment before and after modification were analyzed by means of particle size distribution analysis, scanning electron microscope (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TG-DTG). The results show that: when the addition of fumed silica is 10%, the properties of the modified pigments are enhanced to a certain extent; when the addition of fumed silica reached 20%, the crystal form of the modified pigment did not change significantly, and the color light, coloring power, water dispersibility, hiding power and heat resistance of the modified pigment were significantly enhanced. It is obvious that the performance of pigment red 122 modified by fumed silica is more excellent, which has a certain guiding significance for the research and development of new varieties and high-quality pigment red.

Synergistic modification of ZIF and silica on carbon spheres to enhance the flame retardancy of composites coatings

Herein, carbon spheres (CS) were obtained by a simple hydrothermal reaction using glucose as the raw material, which can be used as a green, cost-effective inorganic flame retardant. Then, the zeolitic imidazolate framework-8 (ZIF) nanoparticles were uniformly anchored on the surface of the CS, which could promote the formation of carbon residues, while the release of inert gas could reduce the substrate surface temperature, thereby delaying the combustion reaction. In addition, the SiO2 film was coated on the surface of ZIF-loaded CS (CS/ZIF) to fill the micropores left by thermal decomposition of ZIF nanoparticles. More importantly, the residual SiO2 shell after combustion can effectively improve the barrier effect of char layer on flame and heat. The effect of the obtained CS/ZIF@SiO2 hybrids on the fire performance of epoxy resins was characterized by fire performance tests. The experimental results showed that the backside temperature of the CS/ZIF@SiO2 based composite coating was stabilized at the lowest value (173.6 ℃) due to the combined effect of ZIF nanoparticles and silica film. In addition, the CS/ZIF@SiO2/EP showed the maximum expansion height and expansion rate after burning in a muffle furnace for 60 min. Meanwhile, the composite coating exhibited the maximum residual carbon (29.1%) and thermal decomposition temperature (Tmax, 378.1 ℃). The results of smoke density test proved that the composite coating had higher smoke suppression effect compared with other samples.

Superhydrophobic coating based on silica derived from bagasse modified with vinyltriethoxysilane and copper (Cu) as antibacterial agent

Prevention of material degradation can be achieved through the coating. Surface coating is an economically advantageous method in producing desired characteristics and auxiliary aesthetics of surface material. Modern coating processes usually use nanomaterial technology made from silica. Silica can be taken from various sources, such as bagasse waste. Bagasse has high silica content up to 88%. Coating material from silica has good adhesion, good protective properties that allow it to withstand the diffusion of water vapor, ions, and oxygen to metal surfaces. Modified silica can be used to produce superhydrophobic surfaces. The addition of vinyl groups to silica can improve the elastic and mechanical properties without much variation in density or thermal conductivity. The addition of vinyltriethoxysilane can create uniform distribution of nanoparticles. Modification of silica can be done to procure anti-bacterial properties. Copper (Cu) is often used as a high activity anti-bacterial with a fairly affordable cost. With the supplementary anti-bacterial properties, material damages attributed to bacteria may be prevented or reduced. This review aims to provide an overview of the production of superhydrophobic coatings using different methods, analyze the characteristics of synthesized materials, and choose suitable methods for producing superhydrophobic coatings. This review proposes the fabrication of silica superhydrophobic coating with the sol-gel method modified through the addition of vinyl and Cu as an anti-bacterial. This recommendation is based on the literature study that has been carried out.

One for All and All in One: Modified Silica Kit-based Protocol for simultaneous sample-specific Extraction of DNA from a Variety of Source Materials

Protocols utilized for the extraction of DNA vary significantly with regards to steps involved and duration of the overall procedure due to materialspecific requirements for ensuring the highest possible yield in recovery of DNA. This variation mostly affects aspects of sample preparation and digestion steps required to release the DNA from the sample material.

Preparation and characterization of modified amphiphilic nano-silica for enhanced oil recovery

In this study, 3-aminopropyltriethoxysilane (APTES) and octyltriethoxysilane (OTES) reacted with nano-silica (NS), and the hydrophobicity, wettability and oil displacement performance of the modified nanoparticles (OAS) were changed by adjusting the amount of OTES. The synthesized amphiphilic silica was characterized by elemental analysis, flourier transform infrared spectrometer (FT-IR), thermogravimetric analysis (TG) and transmission electron microscopy (TEM). The results showed that the modification of silica was successful and showed different changes with the increase of the amount of modifier OTES. Besides, zeta potential, particle size measurement and transmission electron microscopy results show that OAS particles can maintain good stability. OAS-3 particles can change the core wettability from oil wet to neutral wet, and can significantly reduce the interfacial tension, which reduce the interfacial tension from 14.9 mN/m to 10.4 mN/m. In addition, the OAS particles also have a good emulsification effect, which can keep the emulsion stable for a long time. In the core flooding experiment, the modified amphiphilic silica particles can improve oil recovery. Compared with NS, OAS-3 particles have the best oil displacement effect, and the oil recovery can be increased by 10.3%. which has a certain potential in the application of enhanced oil recovery.

Magnetic silica surface functionalized palladium catalyst: A modular approach for C-C cross-coupling reactions in water

A novel Pd immobilized catalyst has been prepared via surface modification of magnetic silica and characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), UV–Vis spectroscopy, X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) and inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis. The prepared composite material found to be highly efficient and recyclable heterogeneous catalyst for the Suzuki coupling reaction in aqueous medium with high turnover number (TON) of 1138 and turnover frequency (TOF) of 2276 h−1. The Pd content of the catalyst was 0.09 mol% and afforded excellent to good yield of biaryls from a wide variety of aryl halides, including electron- withdrawing and releasing groups. The catalyst was reused up to six cycles with 97% efficiency for the Suzuki coupling reaction.

Chemical etching of fused silica after modification with two-pulse bursts of femtosecond laser.

Bursts of femtosecond laser pulses were used to record internal modifications inside fused silica for selective chemical etching. Two-pulse bursts with a variable energy ratio between those pulses at a fixed inter-pulse duration of 14.5 ns were applied for the first time. The selective chemical etching rate of the laser-modified material with the burst of two pulses was compared to the single-pulse regime when etching in HF and KOH etchants. The advantage of the burst-mode processing was demonstrated when etching was performed in the KOH solution. More regular nanogratings were formed, and the etching initiation was more stable when burst pulses were applied for fused silica modification. The vertical planar structures were obtained using the two-pulse bursts with an energy ratio of 1:2, increasing the etching rate by more than 35% compared to the single-pulse processing. The highest ever reported selectivity of 1:2000 was demonstrated by introducing the two-pulse burst mode.

Stepwise surface modification of mesoporous silica and its use in poly(urethane‐urea) composite films

AbstractThe compatibility between polymer matrix and filler is a vital issue in the fabrication of composites with desirable properties. To enhance the interfacial adhesion between matrix and filler, various surface modification treatments are applied. The objective of this study was to increase the affinity of silica and poly(urethane‐urea)s (PUUs), thereby improving the mechanical properties of the resulting composites. Stepwise surface modification of mesoporous silica with amine‐containing dendrimers was done. Various techniques were used to confirm the surface‐modified structure during the stepwise reaction. Additionally, the N2 adsorption–desorption method indicated a gradual reduction in surface area, pore diameter and pore volume of the particles, which warrants the gradual propagation of the dendrimers on the surface and also inside the pores. A type IV isotherm was obtained in this analysis. Two types of pre‐synthesized PUUs were chosen for composite preparation containing the surface‐modified silica with 0.5, 1, 2.5 and 5 wt% concentrations. Due to the high affinity of the dendrimers containing amine moieties on the particles with polyurethane, a proper dispersion of particles in the matrix was achieved based on scanning electron micrographs. Tensile measurements showed an increased Young's modulus and strength of polyurethane films as a result of addition of the particles. However, no significant improvement in the tensile performance of the composites was seen above 2.5 wt% particle loading due to some particle aggregations. © 2021 Society of Industrial Chemistry.

Functionalized Nanosilica for Vulcanization Efficiency and Mechanical Properties of Natural Rubber Composites

Accelerator functional character was introduced on nanosilica by chemical reaction of sodium isopropyl xanthate (SIPX) with nanosilica (NS). Functional characteristics of nanosilica were confirmed by elemental analysis, thermogravimetric analysis, and infrared spectroscopy. This SIPX functionalized nanosilica (SIPX-NS) incorporated natural rubber (NR) composites were used to evaluate the dispersion of silica in rubber and also the interaction between rubber and filler. The finely dispersed SIPX-NS particles in the NR matrix are revealed from the morphological analysis. Subtle changes in the surface chemistry of silica had a profound influence on dispersibility in the NR matrix. NR 4SIPX-NS composite showed an increase in tensile strength by 10%, flex crack initiation resistance by 13%, tensile strength retention by 16% and cure time reduced by 2 min relative to those of NR 3NS composite. This simple, efficient and cost-effective surface modification of silica improved the vulcanization efficiency and mechanical performance of NR composites and has great potential in the fabrication of high-performance polymer composites.Graphical abstract