Silica Aerogel Research and Application

Byadmin

Jul 25, 2023

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Aerogel is the name of a Nano-scale solid material made by the Sol-gel method. This method uses a drying method that replaces the liquid phase with gas. Such as gelatin, gum Arabic, silica aerogel , hair, nails, etc. Aerogels are also gels with swelling, thixotropy or de-sizing properties.Aerogel, the world’s smallest dense material, is made of solid material. The density is three kilograms per cubic foot. The most common aerogel type is silicon aerogel. There are several types of aerogels including silicon, sulfur, metal oxides, metals and carbon. Aerogel, a compound term, is made up of aero as an adjective which means flying. Gel is a gel. Literally means flying gel. Any gel can be called aerogel, as long as the gel can be dried out and separated from the solvent inside, but still retain its shape.
Preparation of silica Aerogel
S. Kistler named Aerogel. S. Kistler was the first to name Aerogel. silica aerogel He defined aerogel by supercritical method as the material that is obtained by supercritically dry wet gel. Aerogel is defined by most people in the mid-late 1990s with the advent and development of atmospheric dry technology. The aerogel structure is a multi-branched Nano-porous three-position network with high permeability. The bulk density of aerogel is adjustable between 0.003-0.500g/cm-3. The density of the air is 0.00129g/cm3.

In most cases, the preparation of aerogel involves a sol gel process and a process of supercritical drying. Sol-gel is a process that involves controlling the hydrolysis conditions and polycondensation reactions of a solution. This results in nanoclusters forming and adhering to one another to form gel. To prevent damage to material structures caused by surface tension within the micropores, the gel is treated with the supercritical process. It is then placed in a vessel under pressure and heated to change the liquid into the supercritical fluid. Surface tension is no longer present. When the supercritical liquid is removed from the pressure vessel at this point, a low-density porous gas with a continuous nano-scale network structure is produced. Material gel.

As a thermal insulation material
The nano-network structure in silicon aerogel is so thin that it effectively limits local thermal excitation. In addition, its thermal conductivity at solid state is 2 to 3 orders of magnitude less than glassy materials. Nano-pores prevent gas molecules from contributing to heat conduction. The silicone aerogel’s refractive indices is very close to one, and its annihilation factor for both infrared and visual light is greater than 100. It transmits sunlight well and blocks infrared radiation, making it a great transparent thermal insulation. It is used in the solar energy usage and energy-saving of buildings. The radiant heat conduction in silicon aerogel is further reduced by doping. At room temperature and under pressure, the thermal conductivity for carbon-doped aerospace gel can be as low a 0.013 w/m K. This is the solid with the lowest conductivity. As a replacement for polyurethane, it is expected that this material will be used to insulate refrigerators. Silicon aerogel, when combined with titanium dioxide, can become a new high-temperature thermal insulating material. Thermal conductivity of silicon aerogel at 800K only is 0.03w/mK. This material will be further developed for use in military products.
The low sound speed of the sonic wave is one of its main characteristics. silicon aerogel The material is ideal for acoustic delay and high temperature sound insulation. It has a wide acoustic-impedance range (103 – 107 kg/m2 s) and is a good acoustic resistance material for ultrasonic detection. As an example, the most commonly used acoustic turns Zp = 1 is a good example. It is possible to use ultrasonic generators or detectors that are 5 x L07 kg/m2*s Piezoelectric ceramics. However, the acoustic resistant of air only is 400 kg/m2*s. A silicon aerogel coupling between air and piezoelectric is made of a thin layer of 1/4 wavelength. It can improve sound wave transmission efficiency and reduce signal-to noise ratio in device application. Experimental results indicate that using silica with a 300 kg/m3 density as a coupling medium can increase the sound by 30 dB. Silica aerogels with a gradient of density will increase sound intensity.
In the chemical and environmental industries. Aerogels with nanostructures can be used to filter gas in a different way. The material is unique in that it has a uniform distribution of pore sizes and a large porosity. It is an efficient gas filtration material. It is a material that is much larger than the standard table. Aerogels have a wide range of applications as new catalysts and catalyst carriers.

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