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In recent years, with the continuous improvement of people's living standards and the enhancement of health awareness, in addition to requiring modern ceramic products to have the various functions of traditional ceramics, it must also have functions such as antibacterial deodorization and good health. Nowadays, the housing is well sealed, the ventilation is poor, and the temperature of the room is relatively high. This environment provides conditions for the growth of mold and bacteria; especially the modern residential buildings are dense, the floors are high, and people spend more time indoors. Both provide more opportunities for environmental pollution. All of this calls for the application of antimicrobial materials.

The application of nanotechnology in antibacterial and antibacterial activities represents a people-oriented effort. Nanotechnology refers to the assembly and creation of new substances with specific functions by directly manipulating individual atoms and molecules in the nanometer size range. When the constituent material particles are as small as nanometers, this material is called a nanomaterial. Because nanoparticles have a series of special properties, such as small particle size, large specific surface area, large amount of dangling bonds and unsaturated bonds on the surface, the nanoparticles have high surface activity and many nanometer mesopores on the surface. Structure, the large specific surface area of ​​the nanocarrier creates favorable conditions for the full contact of the antibacterial agent and the bacteria, and improves the sterilization efficiency.

Antibacterial mechanism of nano antibacterial ceramics

In the early 1990s, due to the successful development of inorganic antibacterial materials, antibacterial building materials were able to rise. Currently, inorganic antibacterial materials on the market are mainly divided into three categories:

Photocatalytic inorganic antibacterial material,

Photocatalytic semiconductor materials include TiO2, ZrO2, V2O3, ZnO, CdS, SeO2, GaP, SiC, etc. In the glaze of the product, nano materials with ZnO or TiO2 components are added, which generate conduction band electrons under illumination conditions. And valence band holes, holes attract electrons, have oxidizing ability, have strong reactivity, can react with H2O or OH ions adsorbed on the surface to form a strong oxidizing hydroxyl group, and strong oxidizing property by hydroxyl group It kills cells and penetrates cell membranes, destroys membrane structure, degrades toxins produced by cells, and also absorbs harmful substances in the air to purify the air.

Metal ion metal oxide type inorganic antibacterial material

Metal ions are mainly silver ions, and the antibacterial action of silver ions and their compounds has long been known and widely used. Using ultra-clean technology, silver ions are used as antibacterial agents. After contact with water, glazed surface can precipitate silver ions and directly enter the bacteria to destroy the growth of bacteria. The antibacterial mechanism of silver-based inorganic antibacterial agents has two explanations. One is silver ion. The slow release bactericidal antibacterial mechanism, and the second is the active oxygen sterilization mechanism. The antibacterial mechanism of silver ion sustained-release sterilization means that the antibacterial agent slowly releases Ag+ during its use, because Ag+ can destroy the bacterial cell membrane at a very low concentration or strongly attract the base of the enzyme protein in the bacterial body, and rapidly bind to it. Together, it reduces the activity of the cell protoplast-active enzyme and has an antibacterial effect. Therefore, by the sustained release of Ag+, the inorganic antibacterial agent can exert a long-lasting antibacterial effect. The active oxygen antibacterial mechanism of silver ions shows that the high oxidation state of silver has extremely high reducibility. Under the action of light, the antibacterial agent reacts with water or air to form active oxygen O-2 and ×OH, which has strong redox. effect.

Rare earth activated photocatalytic composite inorganic antibacterial material:

Photocatalytic and metal ion-based inorganic antibacterial materials, although developing rapidly and widely used, have different drawbacks. For example, metal ion and metal oxide antibacterial materials mostly have photochromism problems. TiO2 photocatalytic antibacterial materials have problems such as low solar energy utilization rate and low quantum efficiency. In addition, materials with strong photocatalytic effects such as ZnO and CeO2 have poor stability and are difficult to apply. In response to these problems, domestic researchers have developed rare earth-activated photocatalytic composite inorganic antibacterial materials.

The nano-composite rare earth antibacterial material is added to the glaze formulation, and the rare earth element can oxidize water into active radicals and negative oxygen ions having strong oxidizing ability, and when it acts with the bacterial cell membrane, the purpose of killing bacteria can be achieved. The 4f orbital electrons of the rare earth elements are similar to the 6s electron energy level, so that the coordination of the rare earth elements is variability, and the electrons of the 4f sublayer can function as "backup chemical bonds" or "remaining atomic valences". The electrons transferred during the valence state change of rare earth elements can activate and participate in the photocatalytic reaction, reduce the association degree of water molecules and promote the generation of hydroxyl radicals. Rare earth-activated inorganic antibacterial health-care materials utilize photocatalytic action of semiconductor materials, activation of rare earth elements, and nano-composite technology and coating technology at the atomic level to exchange rare earth ions into multi-layer nano-clay, and simultaneously package TiO2 and ZnO. Covering it, increasing the yield of hydroxyl radicals, improving the antibacterial efficiency of the material, and making the material have excellent antibacterial properties under indoor light conditions. Rare earth activated photocatalytic composite antibacterial material can be used to prepare a variety of antibacterial functional building materials. It has cooperated with enterprises in Hebei, Guangdong, Shandong and other places to develop successful antibacterial ceramic tiles, antibacterial sanitary ware, antibacterial coatings, antibacterial ceilings and other new building materials. .

Application status of nanotechnology in ceramics

Domestic research and application

China has been researching antibacterial materials since 1993. The first breakthroughs in antibacterial agents are China Building Materials Research Institute (Titanium), Jingdezhen Ceramic Institute, Wuhan University of Technology (Silver), etc. The center has successfully developed nanomaterial antibacterial agents for the leading companies and Tsinghua University and Zhejiang University. Shanghai Taigu Technology Co., Ltd. and Zhejiang Jindiiya have all produced finished products, and they are in Chongqing Siwei, Fuling Jiantao, Jiangsu Yixing Liantao, Fujian Haosheng and other companies produce samples of wall tiles and sanitary ceramics, and some have been put into mass production. Foshan Diamond Ceramics Co., Ltd. uses nanotechnology to improve the glaze performance of building sanitary ceramics. By introducing nanotechnology into the glaze formulation and process, the glaze of the product has self-cleaning and anti-fouling properties, and the glaze texture is obviously superior to the existing products. The production cost has not increased much, and it can be mass-produced. The products meet the national quality standards.

Jiangsu Changshu Elephant Building Ceramic Co., Ltd. has successfully developed a high-tech new product of “Nano Antibacterial Ceramic (Jade) Craft Brick” on the basis of the successful development and production of high-grade glazed ceramic tile new products. The product adopts imported nano antibacterial and far-infrared powder materials, and the antibacterial metal ions and the purple sand enamel tires are matched into the carrier and the ceramic glaze. After high-pressure molding and high-temperature calcination, the product meets the national standard in addition to the conventional performance ( In addition to GB/T4100.2-1999), it also has permanent functions such as antibacterial, bactericidal, anti-mildew and far-infrared health care, which further expands the use of ceramic wall tiles and is a brand-new green health care product. At present, the elephant company has formed a large-scale production. The first batch of products have been exported to foreign countries not long ago, and are favored by domestic and foreign merchants.

According to reports, in addition to the basic use of general ceramic wall tiles, nano-antibacterial ceramic tiles also have special functions such as antibacterial, bactericidal, anti-mildew, far-infrared health care, and can be widely used in public places such as operating rooms, wards, kitchens, toilets, etc. And the wall decoration and protection of the family can effectively prevent the growth and reproduction of bacteria, reduce the infection of bacteria and improve the public health.

Shandong Weifang Meilin Sanitary Ware Co., Ltd. adopts nano-rare earth composite inorganic antibacterial agent to generate holes by using the atomic surface of rare earth elements to generate catalytic reaction with water and air system to generate active oxygen free radicals, and then reactive oxygen free radicals pass through the damage. The bacterial cell nucleus inhibits the synthesis of bacterial proteins, interferes with the synthesis of cell walls and bacterial nucleic acids, and achieves the purpose of inhibiting bacterial growth and killing bacteria, and has a long-lasting antibacterial effect. The 24-hour antibacterial rate against Staphylococcus aureus is as high as 99.7%, and it can also significantly increase the concentration of negative ions in the air near the surface. The fresh air has many functions such as antibacterial, self-cleaning, health care and environmental protection.

Foreign research and application

From an industrial point of view, antibacterial ceramics have developed rapidly since the 1990s. The United States attaches great importance to nanomaterials and their research in antibacterial research. It is reported that the US government has doubled the investment in nanomaterial research in three years, from $250 million to $500 million. To accelerate the development of this technology, the White House has taken temporary emergency measures to expand funding from $1.7 billion to $2.5 billion.

Japan's Olongsi and other antibacterial toilets and wash basins are made by fully homogenizing 50% silver phosphate, 49.5% clay and 0.5% calcium fluoride, adding deionized water to make 50% solids. The slurry is ground in a ball mill, and after being slurried, a 10 μm thick coating layer is sprayed onto the unfired sanitary ceramic glaze layer and mixed with the glaze on the sanitary ceramic product, and fired at 1200 ° C to obtain a slurry. Antibacterial sanitary ceramic products were tested and 105/ml of E. coli was killed after 24 hours of contact with the glaze.

The products of INAX and TOTO, two of Japan's largest building sanitary ceramics companies, have been made into antibacterial products and put on the market. In addition to building sanitary ceramics, plastics, enamels, metals and coatings are also developed for antibacterial development. Germany and South Korea have used antibacterial materials in building sanitary ceramics, household ceramics, and coatings.

, nano-antibacterial technology key and development trend

The ceramics industry develops the type of antibacterial products. Since photocatalytic antibacterial agents require light or even ultraviolet light, this problem must be considered when the environment of sunlight is not often seen. Inorganic antibacterial agents, especially nano antibacterial agents, do not require photocatalysis or even water and moisture, so they can be used in large quantities indoors. Is it possible to choose: all interior wall tiles, floor tiles, sanitary ware, and more indoor opportunities. Such products should be made of inorganic antibacterial agents, especially for nanomaterial antibacterial type products. For exterior wall products such as exterior wall tiles, due to sufficient sunlight, photocatalytic antibacterial agents can be used, and it is best to develop "hydrophilic self-cleaning" products. Because the high-rise exterior wall absorbs moisture from the air, it maintains self-cleaning and has an antibacterial effect.

The main problems of nano antibacterial technology:

At present, there are at least three technical problems in the antibacterial ceramic technology, which makes it widely restricted in industrial applications. The first is how the glazed doped antibacterial ceramics can effectively dissolve the effective antibacterial substances and exert antibacterial effect. Secondly, how can the photocatalytic antibacterial ceramics improve the photocatalytic efficiency and solve the problem of film aging; third, how can it be fast? Visually detecting the difference between antibacterial ceramics and ordinary ceramics, this is the key to being recognized by consumers.

At the same time, the antibacterial ceramics must also solve the problems of distortion of the surface color of the ceramic surface caused by the addition of the antibacterial material, poor gloss, insufficient bonding force between the coating layer and the ceramic surface, poor durability, and high cost. The fundamental solution to the above problems depends on in-depth basic research, especially the application of basic research. Further research on these issues will not only lead to a major breakthrough in antibacterial ceramic technology, but also enable antibacterial ceramics to truly enter the market on a large scale.

Both inorganic antibacterial agents and nano antibacterial agents can be used for high temperature firing of building sanitary ceramics. However, the higher the firing temperature, the lower the antibacterial rate of the obtained ceramic. Therefore, it is easier to make interior wall tiles with high antibacterial rate, followed by floor tiles, and sanitary ceramics is the most difficult. In addition, the addition of 1 to 2% of the silver-loaded antibacterial agent will reduce the initial melting temperature of the glaze for some glazes. Some glazes will react with certain antibacterial agents at high temperatures, destroying the structure of the antibacterial agent and causing some of the antibacterial agents. Problems such as precipitation of substances, which are worth noting when selecting the type of antibacterial agent and glaze. In order to improve the temperature resistance of the antibacterial agent and ensure that the same antibacterial agent can be applied to high temperature firing, a research unit is working on a "wrapping" structure antibacterial agent similar to the coated coloring material to facilitate the antibacterial agent at a higher temperature. Boiled under.

Prospects for the application of nano antibacterial technology:

Antibacterial ceramic products have been put on the market in many developed countries abroad. Although there are reports of results and a small number of products on the market in China, compared with the production of ceramics in China, it is still in the primary development stage. Nevertheless, we are still convinced that the integration of traditional ceramics and environmental functions will be one of the main research directions in the 21st century ceramics field. If reducing pollution, reducing energy consumption, improving processes, and improving quality are the technical transformation goals of the ceramic industry, then developing ecological and environmentally friendly ceramics, improving human living environment, and improving the quality of life are the development directions of the ceramic industry.

Antimicrobial products have a wide range of development prospects, and in the case of building sanitary ceramics, they are used in buildings, homes and public places. Like daily ceramics, it is closely related to the health of everyone, especially in the bathroom, kitchen, hospital, swimming pool, bathroom and other places where human activities are frequent, and it is easy to grow and spread various germs. With the general improvement of human material living standards and civilization level, the awareness of human self-protection is increasing, and it is increasingly urgent to create a vision to minimize the pathogen environment. Human beings have strengthened their prevention on "imports" and "exports", and commonly used antibacterial daily-use ceramics and building sanitary ceramics to prevent "diseases from entering the mouth", reducing the pollution of excreta and the demand for cross-infection in public places. This is the fundamental reason for the broad development prospects of antibacterial building sanitary ceramics. It can be predicted that antibacterial building sanitary ceramic products will be favored by more people, and nano antibacterial agents will be widely used in the ceramic industry.

In short, nanomaterials is one of the most important areas of application in the field of nanotechnology. The integration of nanotechnology into traditional fields will play an important role in promoting product upgrading. Nano antibacterial ceramics have high safety, strong broad-spectrum antibacterial properties and long-lasting antibacterial time. These products have been favored by people after they are put on the market. The market potential of antibacterial ceramic products is huge and the prospects are very broad. With the improvement of people's living standards and the increasing emphasis on quality of life and the environment, the application fields and market prospects of nano-antibacterial ceramics will also expand.

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