Nanotechnology is a new technology that was born and is emerging in the late 1980s. It mainly refers to the study of the laws and interactions of electrons, atoms and molecules in the composition system of matter in the range of 0.1~100nm. The will directly manipulates electrons, atoms or molecules to develop materials and products that are desired to have specific functional properties [1]. Nanotechnology is a highly interdisciplinary subject, which includes: nanosystem physics, nanochemistry, nanomaterials, nanobiology, nanoelectronics, nanofabrication, nanomechanics, nanomechanics. Nanotechnology has been applied
Building materials
, optics, medicine, semiconductor, information and communication, military and other fields [2, 3]. At present, nanomaterial technology is the only nanotechnology that can be realized [1].
Nanomaterials bring an unprecedented revolution in the development of building materials with its unique properties of light, electricity, heat and magnetism. A new coating developed by the flop phenomenon of nanomaterials, an antibacterial mildew coating developed by the self-cleaning function of nanomaterials, a PPR water supply pipe, a conductive coating developed by utilizing the conductive function of nano materials, and a nano material to shield ultraviolet rays Function can greatly improve PVC plastic steel
Door and window
Anti-aging yellowing performance, the use of nano-materials can greatly improve the strength of plastic pipes. It can be seen that nanomaterials have a very broad market application prospect and huge economic and social benefits in building materials.
In recent years, domestic and foreign countries have begun to explore the development and application of nanomaterials and nanotechnology in building materials, and have achieved some gratifying results. The classification is as follows:
1 nanotechnology in
Architectural Coatings
Application
The paint is the underwear (interior wall paint) and the outer coat (outer wall paint) of the building. Domestic traditional paints generally have defects such as poor suspension stability, aging resistance, poor scrub resistance and low finish. Nanocomposite coatings are a kind of coatings with anti-aging, anti-radiation, high peel strength or some special functions obtained by using nano-powders in coatings. The application of building materials (especially architectural coatings) has shown its unique charm [4].
The same kind of nanoparticles will have different effects at different particle sizes, and different kinds of nanoparticles can also play the same role in the coating. The use of nanocomposite coatings can be summarized as follows:
1.1 Optical application nano composite coating
The particle size of the nanoparticles is much smaller than the wavelength of visible light of 400 to 750 nm, which has a permeation effect, thereby ensuring high transparency of the nanocomposite coating. Nanoparticles have a strong absorption of ultraviolet light. Nano-particles such as TiO2 and SiO2 are added to the exterior wall architectural coating to improve weather resistance, and TiO2 is added to the automotive topcoat to improve the aging resistance of the automobile paint. Nano-SiO2 is an amorphous white powder (referred to as agglomerates), and has unsaturated residual bonds on the surface and hydroxyl groups in different bonding states, and its molecular state is a three-dimensional chain structure [5]. In general, the hydrogen bonds on the surface of the nanoparticles are quickly restored after the external shear force is removed, and the structure is rapidly reorganized. This shearing weakening reaction, which relies on time and external force to return to its original state, is called "thixotropy" [6]. Thixotropy is the main factor for nano-silica to improve the performance of traditional coatings [7]. Xu Guocai et al. [8] doped nano-silica into UV-curable coatings by nanoparticle filling method. Experiments show that nano-silica reduces the intensity of UV-irradiation coatings to absorb UV radiation, thereby reducing the curing speed of photo-curing coatings, but can significantly improve the hardness and adhesion of UV-curable coatings. In particular, rutile ultrafine TiO2 can also act as an effect pigment in automotive topcoats. When used in combination with other flake effect pigments such as aluminum powder pigments or pearlescent pigments, it can produce flops with opalescence. In the luxury car topcoat, this is the current use of nano-TiO2, and is one of the most successful examples of foreign nanomaterials used in coatings [9]. Nano zinc oxide is small in size and large in specific surface area
(3H-2000 series specific surface area tester professional team test the specific surface area of ​​nano materials)
The surface bond state is different from the inside of the particle, and the surface atom coordination is incomplete, which leads to an increase in the active position of the surface and an increase in the reaction contact surface. Therefore, the nano zinc oxide is also a good photocatalyst. Under ultraviolet light, it can decompose organic substances and act as an antibacterial and deodorizing agent. Photocatalysts with this property can be used in environmentally friendly coatings, and the addition of nano-ZnO to coatings can significantly improve the resistance of the coating to artificial aging.
1.2 absorbing nano composite coating
Due to the very small size of nano-fine powders and the ability to absorb electromagnetic waves, they have a strong absorption of radar waves and infrared rays of different wavelengths. Therefore, the coating modified by nanoparticles can be used as a stealth coating for military use. The United States has reported a "super" black body nano-absorbent material, that is, ultra-fine graphite powder nano-absorbing paint, the absorption rate of radar waves can reach 99% [10]. Foreign use of nano-scale carbonyl iron powder, nickel powder, ferrite powder has successfully formulated military stealth paint, applied to aircraft, warships, missiles, submarines and other weapons and equipment, so that it has stealth performance. Due to the advantages of absorption frequency bandwidth, light weight and thin thickness, nano-coating materials are expected to show their potential in future military stealth [11].
1.3 nanometer self-cleaning antibacterial coating
Irradiation of light can cause the surface of TiO2 to form a hydrophilic and lipophilic two-phase coexistence super-amphiphilic in the nano-region. For example, nano-antibacterial powders that have been industrially produced in China can be used in coatings to produce nano-bacterial coatings, which are applied to building materials, such as sanitary wares, indoor spaces, appliances, hospital operating rooms, and wards, walls, floors, etc. To sterilization, cleaning effect [12]. Nano-TiO2 particles can absorb short-wavelength light radiation above the forbidden band width under illumination with a wavelength of less than 400 nm, generate electron transitions, cause valence band electrons to be excited to the conduction band, and form electron-hole pairs to transfer energy to The surrounding medium induces a photochemical reaction and thus has photocatalytic properties.
Nano-ZnO is also a highly effective fungicide. Nano-zinc oxide can decompose negatively charged electrons (e-) in water and air (oxygen) under ultraviolet irradiation, while leaving positively charged holes (h+). This kind of hole can activate the oxygen in the air to become active oxygen, has strong chemical activity, and can react with various organic substances (including organic matter in bacteria), thereby killing most bacteria and viruses. Northwest University has conducted quantitative bactericidal tests of nano zinc oxide. When the concentration of nano zinc oxide is 1% within 5 minutes, the killing rate of Staphylococcus aureus is 98.86%, and the killing rate of Escherichia coli is 99.93%. Therefore, the addition of nano zinc oxide in cosmetics can not only shield ultraviolet sunscreen, but also antibacterial deodorization [13].
1.4 nanometer conductive coating
Japan's Matsushita Co., Ltd. has successfully developed nano-composite coatings with good electrostatic shielding. The nanoparticles used are Fe2O3, TiO2, ZnO and so on. These nano-oxide particles having semiconducting properties have higher electrical conductivity than conventional oxides at room temperature, and at the same time, the color of the nano-oxide particles is different, and the coating not only has electrostatic shielding properties, but also overcomes the monotonicity of the color of the coating. .
1.4.1 nanometer high mechanical properties coating
When the pigment particles of the important component of the coating reach the nanometer size and are dispersed in the coating film, the organic coating has a certain reinforcing effect due to the large interface and large bonding force, thereby improving the hardness of the coating. Impact resistance and wear resistance. In addition, the nanoparticles can also reduce the residual stress of the coating during the drying process, thereby enhancing the adhesion of the coating. Studies have shown that [8], nano-SiO2 particles can significantly improve the hardness and adhesion of coatings in UV-curable coatings, and the abrasion resistance and scratch resistance of furniture surface paints and automotive topcoats modified by nanomaterials. There is also a big improvement.
Application of 2 nanometer technology in concrete materials
With the in-depth development of social industrialization and the extensive development of China's infrastructure,
cement
As a traditional building material, concrete production and dosage are constantly increasing, and high-performance concrete has become a cement-based
Composite material
Research hotspots in the field. At the same time, many special fields require cement concrete to have certain functions, such as sound absorption, antifreeze, high strength and high toughness. Due to its excellent properties such as small size effect, quantum effect, surface and interface effect, nanomaterials can impart many different properties to traditional materials in terms of structure or function. The use of nanotechnology to develop new concrete can greatly improve the strength, construction performance and durability of concrete.
Application of 2.1 nanometer ore powder in cement concrete
Nano-mineral powders such as nano-SiO2, nano-CaCO3 and nano-silica powder can not only fill the voids of cement, improve the fluidity of concrete, but more importantly, improve the interface structure between cement stone and aggregate in concrete, so that the strength and resistance of concrete Both permeability and durability are improved.
Some research reports [14], when the nanomaterials are added in an amount of 1% to 3% of the cement, and mixed with other mixtures in a high-speed mixer, the prepared nano-composite cement structural materials are in the 7d and 28d ages. The cement hardening strength is about 50% higher than that of the non-added nano material, and the properties such as toughness and durability are also greatly improved. Li Ying et al. [15] studied the effects of silica fume and nano-sized SiO2 on the water demand of cement paste. Studies have shown that when the nano-scale SiO2 content reaches 8% of the cement content, the water demand of the cement slurry doubles. At the same time, the study found that when the cement dosage is 8% and 10%, the small spheres of nano-scale SiO2 are filled between the silica ash particles, forming a good particle gradation structure with silica fume. When the two are added at the same time and the nano-scale SiO2 is 1% and the silica ash is 9%, the water demand does not increase twice, and the interaction between the two is very obvious.
2.2 Application of nano metal powder in concrete
Due to the surface effect of the nanomaterial, the activity of the nanomaterial is increased, so that the nano metal powder has two special properties. One is that the strength and hardness of the nano metal powder are high, and the strength and hardness of the nano metal powder decrease with the decrease of the grain size. Continuously improved, but also showed very good plastic toughness; second, nano metal powder is a good absorbing material [16]. By utilizing the special properties of the above-mentioned nano metal powder, if it is incorporated into cement concrete, it can be made into a functional electromagnetic shielding concrete.
Application of 2.3 nanometer metal oxides in concrete
Anatase nano-TiO2 is an excellent photocatalyst with special functions such as air purification, sterilization, deodorization and surface self-cleaning [17]. The use of nano-TiO2 has the characteristics of purifying air to prepare photocatalytic concrete. It purifies the exhaust gas emitted by the motor vehicle, and decomposes and removes harmful pollutants such as sulfur dioxide and nitrogen oxides emitted by motor vehicles. It plays a role in purifying the air [18, 19, 20].
Electromagnetic shielding can be carried out using nano metal oxide materials, and can also be used to prepare smart cement concrete [21, 22], such as self-inspection cement concrete. This cement concrete has strong electrical conductivity and also has a sensing effect. This kind of intelligent cement concrete can be used for civil engineering
engineering
The real-time and long-term monitoring of the structure makes it easy to monitor the cracking and damage of the concrete structure and its damage assessment, detecting the weight of the vehicle and the speed of the vehicle. This is a revolution in the detection of concrete performance.
2.4 Application of polymer/inorganic nanocomposites in concrete
Due to the excellent properties of polymer/inorganic nanocomposites, its theoretical and applied research has become a hot spot in composite materials [23-26], and it is also possible to be applied in cement concrete. The use of polymer/inorganic nanocomposites in cement concrete not only improves the compressive, tensile and flexural strength of concrete, but also improves its durability. Incorporate a certain amount of polymer/inorganic nanocomposites into the concrete mixture to uniformly disperse them in the concrete, and use the conductivity of the polymer/inorganic nanocomposites to test the change of resistance and establish the relationship between the resistance and the load. The model can thus destroy the concrete structure.
3 nanotechnology in
Ceramic material
Application
Application of 3.1 nanometer materials in high temperature resistant ceramics
In the early 1990s, Japan Nihara first reported that nanocomposite ceramics with nano-sized SiC particles as the second phase have high mechanical properties and many unique properties. The cermet containing 20% ​​nano-cobalt powder is a high temperature resistant material for rocket jets. Oxide nanomaterials are superior to homogenous traditional ceramic materials in this respect, and the effect of adding other nanoparticles to the ceramic matrix is ​​also being studied. The potential of nanotechnology in ceramics is immeasurable [27, 28].
In recent years, researches on nanocomposite ceramics at home and abroad have shown that the introduction of nano-dispersed phase in micron-scale matrix for composite can greatly improve the fracture strength and fracture toughness of materials (2 to 4 times), and increase the use temperature by 400-600. °C, at the same time, can also improve the hardness, elastic modulus, creep resistance and fatigue resistance of the material.
3.2 Application of Nanomaterials in Health Antibacterial Ceramics
The antibacterial series of nano materials mainly include TiO2 series, Ag series, Cu series, ZnO series, etc., which are mainly incorporated into ceramic glaze or incorporated into ceramic surface layer to produce antibacterial ceramic glaze.
brick
And sanitary ceramics and other products, mainly used for wall decoration, kitchen, bathroom and bathroom. In the process of producing antibacterial ceramics, if you add far-infrared ceramic powder, you can make antibacterial health ceramics with composite function. This product continuously radiates infrared rays, which can promote human microcirculation, increase blood flow, and improve human body. Cold resistance, disease resistance and anti-aging ability.
Application of 3.3 nanometer materials in environmentally friendly ceramics
The porous ceramic (ceramic microporous material) material produced by nanotechnology can be used for filtration separation of industrial waste gas. Porous ceramics have good heat and chemical resistance, and have long life and maintenance-free features. The photocatalytic effect of nanomaterials can be used to catalyze the decomposition of automobile exhaust. The novel ceramics carrying TiO2 photocatalyst and Cu ion catalyst can directly decompose NOx into N2 and O2 at normal temperature, and can also be made into a ceramic material that directly absorbs and fixes SO2. These materials are made of veneer tiles to purify the atmosphere and improve the quality of the environment.
3.4 Application of Nanomaterials in Green Energy Ceramics
Solar ceramics, far-infrared ceramics, etc. are made by using the special optical electromagnetic properties of nanoparticles, which are used for building finishes, can develop solar energy, regulate the ambient temperature, and promote people's health.
3.
The specific surface area of ​​a 5 nanometer material is a very important parameter. The specific surface area is the surface area per gram of solid material in m2/g; the national standard for specific surface area testing is a low temperature nitrogen adsorption BET multipoint method based on BET theory (
GB/T19587-2004
). The main point of the specific surface area measured by the nitrogen adsorption BET multi-point method is: in the range of 5-30% nitrogen partial pressure, the adsorption amount of the adsorbent (the powder to be tested) to nitrogen is measured at different partial pressure points of nitrogen, and adsorption is made. The isotherm, the specific surface area of ​​the adsorbent can be calculated by the BET formula to determine the saturated adsorption amount of the monolayer when the surface of the adsorbent is covered with nitrogen molecules to cover the monolayer. The 3H-2000BET-M specific surface measuring instrument is a high-precision analytical instrument based on the national specific surface testing standard. It has 7 domestic leading technologies; such as the only integrated in-situ purge processing function in China, for chromatographic specific surface testing. The problem of purging treatment between different nitrogen partial pressure points is required, which makes the purging treatment between different nitrogen partial pressure points more convenient and efficient, and reduces the influence of continuous testing on accuracy; the only program-controlled wind-heat assisting device in China, After achieving full automation, it is guaranteed to obtain sharp and rapid desorption peaks and reduce background error; the only chromatographic concentration detection system in China makes the nitrogen partial pressure detection accuracy increase by 10 times relative to the flow method; the six-way valve injector program control, The only quantitative tube program-controlled switching function in China; the only granularity report function in China; the instrument parameter software is displayed at the same time, the large-screen LCD hardware display on the instrument makes the instrument working state parameters clear at a glance, the operation is more reliable; and the liquid nitrogen temperature monitoring, Detector gas shutoff protection, detector thermostat, important part sound prompts, make 3H-2000BET-M specific surface meter test Accuracy, stability and safety, and ease of operation have reached and partially surpassed the performance of similar instruments abroad. The 3H-2000 series has a large number of customers in the country, and is a well-known brand of surface instruments.
4 nanotechnology in other applications
Construction steel is also one of the widely used engineering materials in modern civil engineering. It is also developing in the direction of high strength and light weight, especially the use of nanotechnology to develop its own fireproof and anticorrosive steel, which will promote the faster development of steel structure.
After using super-parent interface material technology on the surface of building materials such as glass and ceramic tiles, the contact angle of water droplets or oil droplets with the surface is close to zero, thereby achieving self-cleaning and anti-fog effects, and making glass, ceramics and other building materials used as external walls. It can also be used as a lotus flower without dyeing. This is the magical effect of nano-interface material technology to traditional building materials.
The use of nanomaterials can increase the strength of plastics (polymer materials) while also providing toughening. The advent of nanomaterials provides new opportunities for the synthesis of new reinforced plastics and provides a new way for the modification of traditional reinforced plastics. By uniformly dispersing the dispersed nanoparticles into the resin material, the purpose of comprehensively improving the properties of the reinforced plastic can be achieved. By adding nano-materials, the strength and elongation of the plastic can be significantly improved, the wear resistance can be improved, the surface finish of the material can be improved, and the anti-aging property can be improved.
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