1000 results about "Silica particle" patented technology

The invention relates to the technical field of super-hydrophobic anti-icing coatings, in particular to a low-temperature thermochromic super-hydrophobic anti-icing coating and a preparation method thereof. According to the specific technical scheme, low-temperature thermochromic phase change microcapsules and nanoscale hydrophobic silicon dioxide particles are dispersed in an organic solvent, an adhesive and a curing agent are added, and the super-hydrophobic surface with the micro-nano hierarchical structure, the latent heat regulation function and the temperature visual feedback function is constructed through a spraying method. The obtained coating has excellent super-hydrophobicity, and water drop adhesion can be effectively reduced; the phase change microcapsules contained in the coating release latent heat during low-temperature solidification, and surface temperature reduction and icing are remarkably delayed; and meanwhile, the color of the coating is obviously and reversibly changed along with the reduction of the temperature, so that the visual early warning of the low-temperature icing risk is realized. The problems that a traditional super-hydrophobic coating is insufficient in low-temperature anti-icing long-term effect and lacks an early warning function are solved, the super-hydrophobic coating is suitable for low-temperature anti-icing occasions, and the sensing-regulation-protection integrated function is achieved.

The invention discloses a preparation method of a metal organic framework modified fluorine-free super-amphiphobic coating, and belongs to the technical field of super-amphiphobic coatings. According to the technical scheme, the method comprises the steps of preparation and modification of a metal organic framework and formation of a fluoride-free super-amphiphobic coating. Adding a metal oxide and nano silicon dioxide particles into a polyacrylic acid solution to form spherical particles; enabling the spherical particles to react with imidazole ligands to obtain metal organic framework particles with porous spherical structures, and wrapping nano silicon dioxide particles in the metal organic framework particles; modifying the metal organic framework particles by using a silane coupling agent; the preparation method comprises the following steps: firstly, attaching modified metal organic framework particles to the surface of a metal matrix, then attaching fluorine-free alkyl silane to the surface of the metal matrix, and heating and curing to obtain the fluorine-free super-amphiphobic coating. The fluorine-free super-amphiphobic coating is applied to the aspect of a metal surface super-amphiphobic coating, and the problems that an existing fluorine-free super-amphiphobic coating is poor in oleophobic and hydrophobic performance and poor in durability are solved.

Even when used for polishing a semiconductor wafer provided with a silicon nitride film, there is provided sulfonic acid-modified colloidal silica capable of forming a highly flat polished surface at high speed. Sulfonic acid-modified colloidal silica, wherein the sulfur content of the silica particles is 700 mass ppm or more and less than 3000 mass ppm per 1 g of the silica particles, the sulfur content in the solvent is 250 mass ppm or less per 1 g of the solvent, and the content of coarse particles having a particle size of 0.2 μm or more contained in the silica particles is 10,000,000 particles / mL or less when the silica particle concentration is 1 mass%.

Cerium oxide (CeO2) coated silica (SiO2) particles, optionally comprising the inorganic group-SO2X, and methods of making such particles. The addition of the cerium oxide (CeO2) coated silica (SiO2) particles to fluorinated polymers containing sulfonic acid functional groups increases their stability to free radical degradation when used in fuel cell applications or electrolytic applications.

The invention provides a preparation method of a nano super-hydrophobic material. The preparation method comprises the following steps: firstly, selecting nano silicon dioxide particles with the particle size of 20-50 nanometers, and matching the nano silicon dioxide particles with heptadecafluorodecyl trimethoxysilane and other raw materials; the nano silicon dioxide particles are subjected to surface modification for 3-5 hours at 40-60 DEG C by controlling the volume ratio of absolute ethyl alcohol to deionized water to be (3-5): 1 and the mass ratio of the long-chain alkyl silane coupling agent to the nano silicon dioxide particles to be (0.5-1.5): 1. Adding 0.1-0.5% hydrochloric acid or sulfuric acid for catalysis, and stirring at room temperature for 2-4 hours to form a sol-gel system; ultrasonically cleaning the substrate, activating with a sodium hydroxide solution, coating by a spraying, dip-coating or spin-coating method, and drying and curing at 60-80 DEG C for 2-3 hours to obtain a finished product. The water contact angle of the prepared material is not lower than 150 degrees, the rolling angle is not higher than 5 degrees, the performance is stable in the environment with the temperature ranging from-20 DEG C to 80 DEG C and the humidity ranging from 20% to 90%, and the water contact angle is still not lower than 140 degrees after more than 500 times of abrasive paper friction tests.

The optical sheet has a first surface and a second surface facing the first surface. The substrate and the functional layer are provided in this order from the second surface toward the first surface. The functional layer contains a binder resin, hollow silica particles, and metal oxide particles other than silica particles. The arithmetic average roughness Sa of the first surface is 5.2 nm or less.

To provide an organosilica sol in which hollow silica particles containing aluminum atoms are dispersed in a polymer, especially an organosilica sol formed by dispersing the hollow silica particles in a polymer having a rotaxane structure.SOLUTION: There are provided a hollow silica organosol containing components (A), (B), and (C), wherein the organosol contains component (C) in an amount of 0.001 mass% or more and 90 mass% or less based on the total amount of the organosol (100 mass%), and a method for producing the same. (A) Component: a hollow silica particle containing aluminum atoms, wherein the amount of aluminum atoms present throughout the hollow silica particle is 120 to 50,000 ppm / SiO2 per gram of the hollow silica particle, calculated as Al2O3. (B) Component: a polymer with a molecular weight of 1000 or more, containing ester, ether, or hydroxy group, and additionally possessing an acrylic structure. (C) Component: Organic solvent.SELECTED DRAWING: None

To provide a coated fertilizer having a hydrophilic surface.SOLUTION: A coated fertilizer comprises: a granular fertilizer core; a first coated layer that is formed on a surface of the granular fertilizer core and is composed of a first coating composition including an acrylic polymer; and a second coated layer that is formed on the first coated layer and is composed of a second coating composition including an acrylic polymer, fine silicon powder, polymer sponge powder, and a hydrophilic substance. A silica particle layer is provided on a surface of the fine silicon powder.SELECTED DRAWING: Figure 1

The invention discloses a flue gas water-based three-phase foam system and a profile control method, the flue gas water-based three-phase foam system comprises dispersed-phase gas, suspended-phase solid particles and continuous-phase liquid, the liquid comprises the following components in percentage by weight: 0.5-2.0 wt% of a foaming agent, 0.05-0.5 wt% of a stabilizer, 0.05-0.2 wt% of a thickening agent, 0.1-0.8 wt% of a suspending agent, 0.3-1.0 wt% of inorganic salt and the balance of liquid preparation water; the gas comprises flue gas or mixed gas of one or at least two of nitrogen, natural gas, carbon dioxide, air and flue gas and the flue gas; the solid particles comprise one or a mixture of at least two of silicon dioxide particles, montmorillonite particles, bentonite particles, kaolin particles and fly ash particles, and the particle sizes of the solid particles are from nanometer to micrometer. According to the method, the flue gas discharged by the steam-injection boiler is captured and treated and then is injected into the stratum together with the water-based three-phase foam system and the steam segmented plug according to a certain proportion to assist in steam recovery of the thickened oil, so that the recovery rate of the thickened oil can be increased, the emission of greenhouse gases can be reduced, the capture, storage and utilization of CO2 can be realized, and the environmental protection situation requirements of carbon peak reaching and green development are met.

The present invention discloses a transparent super-hydrophobic cultural relic protection material and a preparation method thereof. The method first grafts a hydrolyzed silane coupling agent onto the surface of silica, and then utilizes the amino group of the hydrolyzed silane coupling agent to react with the carboxyl group of a chain fatty acid to graft a chain alkyl group onto the surface of silica particles. The prepared material has excellent super-hydrophobicity, a large contact angle of water droplets on the coating surface, and a small rolling angle, making it difficult for water droplets to stay on the coating surface, thereby effectively preventing moisture penetration. At the same time, due to the transparency of the silica particles and the chain fatty acid, the coating can maintain a high transparency and will not block or change the original color and pattern of the cultural relic. The silane coupling agent acts as a bridge connecting the silica particles and the chain fatty acid, which can enhance the chemical bonding inside the coating, making the coating less prone to aging and cracking, and giving the material good high-temperature resistance and the advantage of resisting ultraviolet light, thereby extending the preservation life of the cultural relic.

The present application provides a heat exchanger and a manufacturing method of a heat exchanger. The heat exchanger includes a metal substrate, the metal substrate has a fluid channel for circulating a heat exchange medium; and the heat exchanger further includes a coating, the coating includes resin, silica and titanium dioxide, and the coating is arranged to cover at least part of a surface of the metal substrate. Silica particles and titanium dioxide particles are conducive to the formation of a complex micro-nano structure, and leveling and stability of hydrophilic resin contribute to long-term maintenance of the micro-nano structure. The coating of the heat exchanger according to the present application has excellent hydrophilic durability.

A method for producing spherical silica particles according to the present disclosure includes: a raw material silica particle preparation step of preparing a liquid dispersion of raw material silica particles from a raw material solution obtained by dissolving silicic acid in a mixed solvent of water and an organic solvent in the presence of a basic substance; and a heating step of heating the liquid dispersion or the raw material silica particles so as to remove an organic substance contained in the liquid dispersion, thereby preparing spherical silica particles. The mixed solvent has a relative permittivity of 21 or higher and 40 or lower, and a quaternary ammonium derived from the basic substance is blended in a blending ratio of 0.3 or higher and 0.8 or lower in terms of molar ratio with respect to a silicon element derived from the silicic acid.

The invention discloses a high-strength, light-weight and multifunctional composite shell for a warhead, and relates to the field of ship protection, the composite shell comprises a front protection layer, a rear protection layer and a composite sandwich panel arranged between the front protection layer and the rear protection layer, the composite sandwich panel is of a honeycomb structure, and the composite sandwich panel is of a honeycomb structure. The honeycomb structure is filled with energy-absorbing substances. The energy absorption substance is shear thickening glue doped with silicon dioxide particles. By manufacturing the light multifunctional composite shell and integrating the energy absorption layer, the impact resistance and fragment penetration resistance of the shell are improved. Material distribution is optimized, light weight and structural strength are balanced, a shear thickening material (STG) is added, and multi-dimensional energy dissipation is achieved.

The invention belongs to the technical field of temporary plugging agents, and relates to a medium-temperature drilling fluid nano temporary plugging agent and a preparation method thereof. The temporary plugging agent is prepared from the following raw materials in parts by mass: 10 to 15 parts of small-particle-size coated silicon dioxide, 15 to 20 parts of medium-particle-size coated silicon dioxide, 30 to 50 parts of large-particle-size coated silicon dioxide, 15 to 20 parts of fiber, 5 to 8 parts of polyether diglycidyl ether, 5 to 8 parts of hyperbranched polyethyleneimine, 1 to 1.5 parts of water-soluble cellulose and 0.5 to 1 part of cationic quaternary ammonium salt. The coated silicon dioxide takes chitosan and glutaraldehyde as wall raw materials and silicon dioxide as a core material, and the particle size of the small-particle-size core material is 0.3-1 mu m; the particle size of the medium-particle-size particle core material is 150-250 microns; the particle size of the large-particle-size particle core material is 250-350 microns, the coated silicon dioxide particles are bonded together through a microscopic interpenetrating network formed by the reaction of hyperbranched polyethyleneimine and polyether diglycidyl ether, and the particles are matched with fibers to improve the bearing strength.

The invention relates to the technical field of composite fibers, in particular to a light-absorbing and heat-generating composite fiber and a preparation method thereof.The preparation process comprises the following steps that 1, core-shell structure light-absorbing and heat-generating particles are prepared; (2) carrying out surface modification on ferroferric oxide coated silicon dioxide particles; (3) in-situ polymerization; and (4) melt spinning. According to the scheme, nano ferroferric oxide is selected as a core light absorption material, and due to a unique Fe < 2 + > / Fe < 3 + > mixed valence electronic structure, while wide-spectrum light absorption is realized, oxidative photo-generated holes are hardly generated, so that the photocatalytic degradation risk similar to titanium dioxide is avoided from the source, and the long-term stability of a polymer matrix is guaranteed; in combination with in-situ polymerization, axial gradient magnetic field spinning processes and the like, the washing resistance, aging resistance and strength of the light-absorbing and heating composite fiber are synchronously improved.

The invention relates to the technical field of fire extinguishing agents, and particularly discloses a lithium battery fire extinguishing agent and a preparation method thereof. The degradable surfactant is selected from at least one of alkyl glycoside and fatty acid methyl ester sulfonate; the particle size of the nanoscale silicon dioxide particles is 10 to 100 nm; the composite flame retardant is formed by compounding an organic phosphorus compound and graphene oxide according to a mass ratio of 1: (0.5-2); the antifreeze agent is selected from at least one of ethylene glycol and propylene glycol; the thickening agent is selected from at least one of xanthan gum and sodium carboxymethyl cellulose; the preservative is selected from at least one of sodium benzoate and potassium sorbate; through the synergistic effect of the composite flame retardant, the fire extinguishing efficiency is remarkably improved, reburning is inhibited, in addition, nano silicon dioxide is uniformly dispersed after being subjected to surface modification to form a compact heat insulation layer, the degradable surfactant and the environment-friendly preservative are combined, and the agent is free of toxic residues.

The invention relates to high-elastic coated thermofuse adhesive lining cloth and a preparation process thereof, and belongs to the technical field of textiles. The adhesive lining cloth adopts a double-layer structure design of a hot melting core layer and an elastic shell layer, the core layer is composed of polyamide, polyester, nanoscale silicon dioxide particles and ethylene-vinyl acetate, and the shell layer is composed of a thermoplastic polyurethane elastomer and a modified additive. The preparation process comprises the steps of core layer and shell layer material preparation, coaxial double-layer spinning, base cloth pretreatment, thermofuse and base cloth compounding, post-treatment and the like. The adhesive lining cloth has excellent elastic recovery rate (91-95%), adhesive strength (16.5-21.5 N / 5cm) and air permeability (95-135 cm < 3 > / cm < 2 > / s), the adhesive strength retention rate reaches 87-90% after 50 times of standard washing, and the adhesive lining cloth is suitable for various types such as silk, knitted fabric, elastic fabric and outdoor functional fabric, and has the advantages of being simple in preparation process, low in cost and the like. The defects of traditional bonding lining cloth in the aspects of elasticity, bonding strength, air permeability, hand feeling, durability and the like are overcome, and an ideal lining cloth solution is provided for modern clothes.

The invention discloses a hollow silicon dioxide particle. The ratio of the hollow area of the hollow silicon dioxide particle to the total area of the particle in a transmission electron microscope photo is 10-96%; the average maximum diameter of the hollow silica particles is 100 nm to 10 [mu] m; a shell layer of the hollow silicon dioxide particle is formed by stacking nano particles, the average diameter of nano convex particles in the shell layer is 4-100 nm, and the ratio of the average diameter of the nano convex particles to the average maximum diameter of the hollow silicon dioxide particle is 1 / 2500-1 / 5. The ratio of the average diameter of the nanometer protruding particles on the surfaces of the hollow silicon dioxide particles to the average maximum diameter of the hollow silicon dioxide particles ranges from 1 / 2500 to 1 / 5, so that the bonding force between the hollow silicon dioxide particles serving as filler and resin is high, the fluidity is good when the hollow silicon dioxide particles are added into the resin, and the hollow silicon dioxide particles are suitable for serving as packaging filler of semiconductor devices.

The invention belongs to the technical field of radio frequency identification, and discloses an RFID etching antenna production process. The preparation method comprises the following steps: pretreating a base material such as polyimide (PI) or polyethylene glycol terephthalate (PET), uniformly coating a composite anti-corrosion layer, performing high-precision ultraviolet laser positioning exposure, performing precise chemical etching under dynamic closed-loop control, subsequently removing photoresist, neutralizing, drying, spraying an anti-oxidation coating and the like. And the manufactured RFID antenna has the advantages of smooth antenna conductive circuit edge, uniform etching depth and excellent signal transmission performance. Compared with a traditional process, nano silicon dioxide particles are introduced into a formula of an anti-corrosion layer material, a galvanometer scanning system is adopted to realize precise laser positioning, and a closed-loop dynamic regulation and control system is formed by utilizing electrochemistry, temperature control and image feedback, so that the etching depth is controlled within + / -2 microns, the production yield is improved to 98.5% or above, and the production cost is reduced. Meanwhile, the consumption of chemical reagents and the environmental pollution are obviously reduced.

The invention discloses toothpaste which is pasty and comprises an abrasive, a humectant, a foaming agent, water, a bacteriostatic agent povidone iodine, 0.5 wt%-5 wt% of magnesium carbonate particles and 5 wt%-15 wt% of chitosan.The toothpaste has the advantages that cross-linking points are formed through electrostatic attraction between a positively charged chitosan acid solution and negatively charged povidone iodine and silicon dioxide particles; the preparation method comprises the following steps: preparing chitosan by virtue of a sol-gel method so as to realize gelation of the chitosan, uniformly dispersing silicon dioxide particles, povidone iodine and magnesium carbonate nanoparticles in the chitosan gel to obtain pasty toothpaste with good performance, the pasty toothpaste has relatively good stability, and the gel structure can also be used as a carrier to load and slowly release povidone iodine, so that the antibacterial action time of the povidone iodine is prolonged, and long-acting antibacterial protection is provided. The toothpaste disclosed by the invention has a good cleaning effect and antibacterial performance, is suitable for more user groups, especially crowds with sensitive oral cavities, and has important market requirements and application prospects.

Provided are: a fluororesin sheet having both a low linear expansion coefficient (CTE) and improved adhesion to a copper foil having a smooth surface; and a copper-clad laminate using the fluororesin sheet. A fluororesin sheet containing a fluororesin and silica particles, the fluororesin sheet having an oxygen element ratio of 3.0 at% or more and a linear expansion coefficient (CTE) of 100 ppm / DEG C or less when measured by X-ray photoelectron spectroscopy (XPS) on one or both surfaces thereof.

The invention discloses an environment-friendly anti-icing and deicing coating as well as a preparation method and application thereof, and aims to solve the problems of low efficiency, high corrosivity, serious environmental pollution and the like in the traditional anti-icing and deicing technology. The coating material is prepared from the following components: deionized water, polyvinylpyrrolidone, propylene glycol, glycerol, fumed silica, granular silica, ethanol, potassium acetate and a waterborne polyurethane coating. The invention further provides a preparation method of the coating material, and the coating material is applied to anti-icing of metal and plastic substrates and has dual functions of preventing icing and rapidly removing ice. The coating has the advantages of being good in durability, environmentally friendly, free of corrosion to base materials and the like, is particularly suitable for anti-icing protection of equipment such as rails, wind power blades and cables, remarkably improves the operation and maintenance efficiency of key facilities and equipment, reduces the maintenance cost and has important economic and social benefits.

The invention relates to the technical field of reinforced concrete, in particular to a preparation technology of a reinforced concrete telegraph pole, the performance of the concrete telegraph pole is improved through a multi-scale fiber synergistic toughening method, when the telegraph pole bears a bending load, steel fibers firstly play a role to restrain large cracks, and when micro cracks appear, the steel fibers play a role to restrain the large cracks. The denser composite fiber network bears stress to realize multi-stage crack resistance, which is combined with the high early strength characteristic of the sulphoaluminate cement, so that the telegraph pole has excellent impact resistance and fatigue resistance while obtaining extremely high early strength; the surface of the aggregate modified by the silicon dioxide aerogel is covered with a high-activity and high-specific-surface-area nano silicon dioxide layer, and in an alkali-rich and calcium-rich environment provided by sulfo-aluminate water cement hydration, the nano silicon dioxide and a cement hydration product are subjected to a violent pozzolanic reaction, so that the surface of the aggregate is modified by the sulfo-aluminate water cement; therefore, the compressive strength and the flexural tensile strength of the concrete are remarkably improved.

The present invention relates to a polishing composition containing abrasive grains and a dispersing medium, in which a pH is less than 5.0, the abrasive grains are surface-modified silica particles in which an organic acid is immobilized on a surface thereof, a surface coverage of silanol groups present on the surface of the surface-modified silica particles is more than 0% and 6.0% or less, and an average primary particle diameter of the abrasive grains is 20 nm or more and 100 nm or less. According to the present invention, there is provided a means capable of improving a polishing removal rate of a silicon oxide film and polishing a silicon oxide film and a silicon nitride film at the substantially same rate.

The invention discloses a composite resin material for packaging a fuel cell and a preparation method of the composite resin material. The composite resin comprises bisphenol F type epoxy resin, alicyclic epoxy resin, acrylate resin, a toughening agent, nano silicon dioxide particles, a long-chain aliphatic amine curing agent, an imidazole accelerant and graphene coating carbon fibers. Bisphenol F and alicyclic epoxy resin are compounded, acrylate resin is combined to form a rigid-flexible three-dimensional network matrix, nano-silica treated by a silane coupling agent is introduced to improve moisture resistance, and graphene coating carbon fibers with oxygen-containing groups on the surface are utilized to enhance interface bonding force. And a cross-linked network is regulated and controlled through the coordination of the long-chain fatty amine curing agent and the imidazole accelerant. The obtained composite resin has excellent temperature resistance, moisture resistance, mechanical properties and interface bonding strength, effectively solves the problem of performance degradation of a traditional packaging material in high-temperature, high-humidity and corrosive environments, and meets the strict use requirements of fuel cells.

A heat control member comprises a mixture of a) silica aerogel particles having particle sizes in a range from 0.1 mm to 5 mm and b) hydrophobic silica-containing particles having a methanol number of at least 30 and a particle size D50 of 100 microns or less, the mixture having a particle size distribution of silica-containing particles having at least two peaks. The silica aerogel particles and hydrophobic silica containing particles are present in a ratio from 1:99 to 99:1; and the heat control member has a thermal conductivity at 25° C. of from 5 to 30 mW / m.K and a thickness of 0.1-10 mm.

The invention discloses a composite coating material for a lithium ion battery positive electrode, a composite coating and application of the composite coating material, the inner core of the composite coating material is nano silicon dioxide particles, the shell of the composite coating material is of an organic-inorganic hybrid structure, and the organic-inorganic hybrid structure is formed by reaction of a quaternary ammonium salt surfactant and a silane coupling agent. The composite coating adopts a core-shell structure, the core is nano silicon dioxide particles, and the shell is an organic-inorganic hybrid layer formed by reaction of a quaternary ammonium salt surfactant and a silane coupling agent. The nano silicon dioxide of the inner core effectively prevents electron transfer through high insulativity, and the hybrid structure of the shell combines the flexibility of organic matters and the rigidity of inorganic matters, so that the composite material can adapt to the volume change in the charging and discharging process of the electrode and can resist the physical penetration of lithium dendrites. Due to the dual characteristics, the safety is remarkably improved while the high-efficiency operation of the battery is maintained by the coating.

The present invention provides a sulfonic acid-modified colloidal silica which has excellent long-term stability of metal adsorption amount and is capable of suppressing the amount of residual abrasive grains on a polished metal surface after polishing and cleaning.　This sulfonic acid-modified colloidal silica contains silica particles, and is characterized in that: (1) the surfaces of the silica particles are modified with a sulfonic acid group; (2) the Cu ion adsorption amount of the silica particles is 5.00-110.00 µmol / g; (3) the ratio (Cu ion adsorption amount (µmol / g) / S content (µmol / g)) of the Cu ion adsorption amount to the S content of the silica particles is 0.50 or more; and (4) the rate of change over time of the Cu ion adsorption amount of the silica particles is 1.30 or less as measured by the measurement method described below. [Measurement method of the rate of change over time of the Cu ion adsorption amount of the silica particles] The sulfonic acid-modified colloidal silica is left to stand at 25°C for 3 months. The Cu ion adsorption amount (µmol / g) of the silica particles before standing and the Cu ion adsorption amount (µmol / g) of the silica particles after standing are measured and the rate of change over time of the Cu ion adsorption amount of the silica particles is calculated by the following formula. (Rate of change over time of Cu ion adsorption amount of silica particles) = (Cu ion adsorption amount (µmol / g) of silica particles after standing) / (Cu ion adsorption amount (µmol / g) of silica particles before standing)

The invention relates to an aperture-adjustable porous carbon material and a preparation method and application thereof. The preparation method comprises the following steps: adding an alkali solution into a phenol source, stirring, heating to 60-90 DEG C, adding an aldehyde source solution, stirring, cooling to room temperature, and adding an acid solution to adjust the mixed solution to be neutral, so as to obtain a phenolic resin oligomer solution; evaporating water, and adding low-carbon alcohol to prepare a phenolic aldehyde low-carbon alcohol solution; preparing silicon dioxide sol, wherein the particle size of silicon dioxide particles is controlled by adjusting the pH value; the preparation method comprises the following steps: mixing and stirring a phenolic low-carbon alcohol solution and silicon dioxide sol at 35-45 DEG C, washing, filtering and drying to obtain a silicon dioxide-phenolic resin composite carbon source; carrying out carbonization treatment on the silicon dioxide-phenolic resin composite carbon source to obtain a carbonized product with a carbon skeleton and an S O < 2 > template; and carrying out wet etching treatment on the carbonized product, selectively etching the S < O2 > template so as to form holes in positions occupied by S < O2 > particles, and then washing, filtering and drying to obtain the porous carbon material with the adjustable aperture.

Provided is a colloidal silica which, when used as an abrasive grain for polishing, hardly leaves silica particles on the polished surface and can form a polished surface with reduced surface roughness. A colloidal silica in which silica particles are dispersed in a solvent, wherein the true specific gravity of the silica particles by the liquid phase substitution method is 1.60 or more and 2.20 or less, and the value of composite parameter 1 calculated by a specific formula is 10 or more and 200 or less.