Nano titanium dioxide is a white loose powder with strong UV shielding effect, good dispersion and weather resistance.Available forCosmetics、Functional fibre, plastics, coatings, paints and other fields, as a UV shielding agent to prevent UV damage.It can also be used as top coat of high-grade automobiles, with the effect of different colors depending on the angle.
Nano titanium dioxide, also known asTitanium dioxide。The diameter is below 100 nm, and the appearance of the product is white loose powder.It has anti thread, anti-bacterial, self-cleaning and anti-aging properties, and can be used in cosmetics, functional fibers, plastics, inks, coatings, paints, fine ceramics and other fields[1]。
Nano titanium dioxide mainly has two crystal forms: anatase and rutile.Rutile titanium dioxide is more stable and dense than anatase titanium dioxide, with higher hardness, density, dielectric constant and refractive index, and higher covering power and coloring power.However, anatase titanium dioxide has a higher reflectivity in the visible short wave part than rutile titanium dioxide, with a blue hue, and a lower ultraviolet absorption capacity than rutile titanium dioxide, and a higher photocatalytic activity than rutile titanium dioxide.Under certain conditions, anatase titanium dioxide can be transformed into rutile titanium dioxide.
classification
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1、 It can be divided into:Rutile type nano titanium dioxide and anatase type nano titanium dioxide.
2、 According to its surface characteristics, it can be divided into:Hydrophilic nano titanium dioxide and oleophilic nano titanium dioxide.
IIIAccording to appearance: There are powder and liquid. The powder is generally white, and the liquid is white and translucent.
Technical indicators
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The following indicators do not refer to the product indicators of a company, but are common in the market, so some data cannot be applied to a product.
technical data
Rutile type nanometer titanium dioxide
Anatase nanometer titanium dioxide
character
White powder
White powder
Crystal form
Rutile type
anatase
Rutile content%
ninety-nine
--
Particle size (nm)
20-50
15-50
Drying loss%
one
one
Loss on ignition%
10-25
ten
Surface characteristics
Hydrophilic or lipophilic
Hydrophilic or lipophilic
PH
6.5-8.5
6.5-8.5
Specific surface area (m2/g)
80-200
80-200
Heavy metals (as Pb)%
zero point zero zero one five
zero point zero zero one five
Arsenic (As) W%
zero point zero zero zero eight
zero point zero zero zero eight
Lead (Pb) W%
zero point zero zero zero five
zero point zero zero zero five
Mercury (Hg) W%
zero point zero zero zero one
zero point zero zero zero one
function
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Nano-TiO2 has very valuable optical properties and shows a bright prospect in the automotive industry and many fields.Nano-TiO2 also has high chemical stability, thermal stability, super hydrophilicity and non mobility, so it is widely used in anti ultraviolet materials, textiles, photocatalysts, self-cleaning glass, sunscreen, coatings, inksFood packaging materials, paper industry, aerospace industry, lithium battery.
Bactericidal function
Long term sterilization under the action of ultraviolet light.Experiments show that anatase nano-TiO2 with a concentration of 0.1mg/cm3 can completely kill malignant tumorsHella cellAnd withSuperoxide dismutaseWith the increase of (SOD) addition, the efficiency of TiO2 photocatalysis to kill cancer cells is also improved.The killing rate of Bacillus subtilis var. niger, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Salmonella, dental mycobacterium and Aspergillus reached more than 98%;Advanced treatment of tap water by TiO2 photocatalytic oxidation can greatly reduce the number of bacteria in the water;Adding nano-TiO2 into the coating can produce antibacterial and antifouling coatings that are bactericidal, antifouling, deodorizing and self-cleaning, and can be used in hospital wards, operating rooms, family toilets and other places where bacteria are concentrated and easy to reproduce to prevent infection, deodorize and deodorize.It can effectively kill harmful bacteria.
Anti ultraviolet function
Nano-TiO2 can not only absorb ultraviolet light, but also reflect and scatter ultraviolet light, and can also pass through visible light. It is a physical shielding ultraviolet protective agent with excellent performance and great development prospects.
Anti ultraviolet mechanism of nano titanium dioxide:
According to the different wavelengths, the ultraviolet ray can be divided into short wave region 190 ～ 280 nm, medium wave region 280 ～ 320 nm, and long wave region 320 ～ 400 nm.The ultraviolet ray energy in the short wave area is the highest, but it is blocked when passing through the ozone layer. Therefore, the ultraviolet rays in the medium wave area and the long wave area are generally harmful to the human body.
The strong UV resistance of nano titanium dioxide is due to its high refractive index and high photo activity.Its anti ultraviolet ability and mechanism are related to its particle size: when the particle size is large, the barrier to ultraviolet light is mainly reflection and scattering, and it is effective for ultraviolet light in both medium wave and long wave areas.The sun protection mechanism is simple covering, which belongs to general physical sun protection, and the sun protection ability is weak;With the decrease of particle size, light can pass through the particle surface of nano titanium dioxide, and the reflection and scattering of ultraviolet light in the long wave area are not obvious, while the absorption of ultraviolet light in the medium wave area is significantly enhanced.Its sunscreen mechanism is to absorb ultraviolet rays, mainly ultraviolet rays in the middle wave area.
It can be seen that the sunscreen mechanism of nano titanium dioxide to different wavelengths of ultraviolet light is different. The barrier to ultraviolet light in the long wave area is mainly scattering, and the barrier to ultraviolet light in the medium wave area is mainly absorption.
Nano titanium oxide with particle size less than 100nm has good ability of scattering and absorbing ultraviolet light.[2]
Anti ultraviolet function
The ultraviolet absorption ability of titanium oxide particles is related to their particle size.In the wavelength range of ultraviolet light (290 nm~400 nm), the ultraviolet absorption ability of titanium dioxide with particle size of 20 nm is much stronger than that of titanium dioxide with particle size of 200 nm[3]。
The sunscreen agent of nanometer titanium dioxide has strong absorption of ultraviolet light in UVB and UVA regions, and its absorption effect is much stronger than that of organic ultraviolet absorbers.
The optimal particle size of titanium dioxide absorbed by ultraviolet ray with a wavelength of 300 nm is 50 nm. With the increase of wavelength, the optimal particle size increases, and the absolute value of absorption decreases.However, in the high particle concentration with small particle spacing, the light scattering volume of particles is compressed, and the original scattering volume of particles is reduced. With the increase of particle concentration, the light scattering efficiency of particles is reduced[2]。
Table 1 Comparison of refractive index of several substances
Table 1 shows the refractive index of different substances.Compared with other materials, titanium dioxide has the highest refractive index.For cosmetics, the smaller the particle size, the greater the visible light transmittance, which can make the skin whiteness appear more natural and beautiful[4]。
Photocatalytic function
The research results show that under the action of sunlight or ultraviolet light, TiO2 is activated and generates free radicals with high catalytic activity, which can produce strong photooxidation and reduction capabilities, and can catalyze and photolysis various organic substances such as formaldehyde and some inorganic substances attached to the surface of objects.
Self cleaning function
TiO2 film has super hydrophilicity and super permanence under light, so it has anti fog function.If a layer of titanium oxide film is coated on the rear view mirror of an automobile, even if the moisture or water vapor in the air condenses, the condensed water will not form a single water drop, but will form a water film that spreads evenly on the surface, so there will be no light scattering fog on the surface.When rain water rushes through, the rain water attached to the surface will also quickly diffuse into a uniform water film, so that water drops will not form to disperse the line of sight, leaving the mirror surface bright and improving driving safety.
Nano-TiO2 has a strong "super hydrophilicity", it is not easy to form water droplets on its surface, and nano-TiO2 can act on hydrocarbons under visible light irradiation.With this effect, a thin layer of nano-TiO2 can be coated on the surface of glass, ceramics and ceramic tiles. The organic pollutants adsorbed on the surface of titanium oxide can be decomposed into CO2 and O2 by using the photocatalytic reaction of titanium oxide. Together with the remaining inorganic substances, they can be washed clean by rain, thus realizing the self-cleaning function.Self cleaning ceramic tiles have been successfully developed in the laboratory in Tokyo, Japan. There is a thin layer of nano TiO2 on the surface of this new product. Any substance that sticks to the surface, including oil stains and bacteria, can further oxidize these hydrocarbon substances into gases or easily wiped off substances due to the catalytic effect of nano TiO2 under the irradiation of light.Nano-TiO2 photocatalysis makes it easy to clean the glass of high-rise buildings, ceramic tiles that are easy to stick in kitchens, car rear-view mirrors and front window glass.
Battery raw material
Nano titanium dioxide (TA18) is added to the lithium battery:
1. Nano titanium dioxide has excellent high rate performance and cycle stability, rapid charge and discharge performance, high capacity, good reversibility of de intercalation lithium, and has good application prospects in the field of lithium batteries.
1) Nano titanium dioxide can effectively reduce the capacity degradation of lithium batteries, increase the stability of lithium batteries, and improve the electrochemical performance.
2) Improve the specific capacity of battery materials for first discharge.
3) The polarization of LiCoO2 during charging and discharging is reduced, so that the material has higher discharge voltage and more stable discharge effect.
4) Appropriate amount of nano titanium dioxide can exist in a loose state, which reduces the inter particle stress and the micro strain of structure and volume caused by the cycling process, and increases the stability of the battery.
2. In chemical energy solar cells, nano titanium dioxide crystals have the characteristics of high photoelectric conversion rate, can greatly improve the energy conversion rate of solar cells, low cost, simple process and stable performance.Its photoelectric efficiency is stable at more than 10%, and its production cost is only 1/5~1/10 of that of silicon solar cells. Its service life can reach more than 20 years.
3. In nickel cadmium battery, nanometer titanium dioxide has good conductivity and wide temperature working range.
Alternate PVA
In the process of fiber spinning into yarn, sizing is necessary to reduce warp breakage.The size PVA used in China since 1950s and 1960s isPolymer compoundIt is difficult to degrade in natural environment.Therefore, it is listed as "unclean slurry" in some European countries and has been explicitly prohibited to use.EU's restriction on PVA will also be China's cotton textile exportsGreen trade barriersFocus.developmentGreen and environment-friendly slurryIt is the "broken wall" goal that the domestic textile industry has been seeking to replace the refractory PVA.
Nano titanium dioxide T25F is used in textile size. Through the perfect combination with starch, it can improve the comprehensive weaving performance of yarn, reduce the amount of PVA, shorten the boiling time, reduce the size cost, improve the sizing efficiency, and also solve many problems such as PVA size is not easy to desize, environmental pollution, etc.Nano titanium dioxide is mainly used to replace PVA in yarn to achieve smooth adhesionhairiness, fill the gap and lubricate.
High grade automobile paint
When nano titanium dioxide (T20Q) and aluminum powder mixed pigment or nano titanium dioxide coated mica pearlescent pigment are added to the coating, the coating can produce mysterious and variable angular heterochromatic effect, mainly because when the incident light shines on nano titanium dioxide particles, the blue light will be strongly scattered due to the small particle size,Results The green light and red light (in yellow phase) excluding blue light are reflected by the aluminum sheet into positive and negative light, that is, the scattered light is the light with strong blue phase, and the reflected light is the light with strong yellow phase (gold). Different colors can be seen with different viewing angles.The titanium dioxide T20Q microcrystal with a particle size of dozens of nanometers also gives the coating metal luster effect, pearlescent effect, flash effect and hyperchromic effect, making the car surface we can see as if it is pearl flakes shining, giving people a sense of depth and hierarchy.
This is the secret of the color changing car. As a high-tech, nanotechnology is changing our life!
Other functions
Nano titanium dioxide also has good degradation effect on some plastics, Freon and surfactant SDBS.
Others found that TiO2 also has the absorption function for harmful gases. For example, the alkene polymer fiber containing TiO2 is coated on the ceramics containing calcium phosphate to absorb different acid-base gases for a long time.
In view of the above functions, nanometer titanium dioxide has a very broad prospect.The research and utilization of it will bring great changes to people's lives.
purpose
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Cosmetics
Any titanium dioxide has certain ultraviolet absorption function, and excellent chemical stability, thermal stability, non-toxic and other properties.Ultrafine titanium dioxide has a stronger ability to absorb ultraviolet rays due to its smaller particle size (transparent) and greater activity. In addition, it is determined that titanium dioxide is the most widely used inorganic raw material in cosmetics because of its achromatic power, hiding power, clear color tone, low abrasion resistance and good dispersibility.The world annual consumption of titanium dioxide in the cosmetics industry was estimated to be 3500-4000t in the 1980s and 5000-10000t in 2010.Titanium dioxide of different quality can be selected according to its different functions in cosmetics.
The whiteness and opacity of titanium white can make cosmetics have a wide range of colors. When titanium white is used as a white additive, anatase titanium white is mainly used, but rutile titanium white should be used when considering the hiding power and sun resistance.
Titanium dioxide used in cosmetics has high purity requirements and strict requirements for the content of harmful impurities.For example, the EC Food Additives Regulation (which is applicable to cosmetics) stipulates that the acid soluble substances of titanium dioxide for cosmetics are<0.35%, As<5 × 10-6, Pb<20 × 10-6, Sb<100 × 10-6, Cu<100 × 10-6, Cr<100 × 10-6, Zn<50 × 10-6, BaSO4<5 × 10-6, (Sb+Cu+Cr+Zn+BaSO4)<200 × 10-6, and Hg cannot be detected.
According to the regulations on food, drugs and cosmetics issued by the US Food and Drug Administration (FDA), the total amount of SiO4 and/or Ai2O3 used as dispersant additives for titanium dioxide in cosmetics should not exceed 2%, Pb<10 × 10-6, As<1 × 10-6, Sb<2 × 10-6, Hg<1 × 10-6.In addition, the burning loss at 800 ℃ after drying at 105 ℃ for 3h shall not be more than 0.5%.The content of water-soluble matter shall not be more than 0.3%. The content of titanium dioxide after drying at 105 ℃ for 3h shall not be less than 99.0%, and the average particle size shall be less than 1μm。
Nanometer titanium dioxide is transparent, so it has many excellent characteristics and functions in blocking ultraviolet rays, transmitting visible light and safety that are not available in general cosmetics raw materials.
Nano titanium dioxide can not only scatter ultraviolet light (wavelength 200nm - 400nm), but also absorb ultraviolet light, so its ability to shield ultraviolet light is extremely strong, and it can be used as an excellent sunscreen agent to manufacture sunscreen cosmetics.
As nano titanium dioxide is transparent, it can be used to make transparent skin cream. This skin cream cream is delicate and has a natural skin feel. It is very popular in Japan and other countries. Every year, Japan needs 1000 tons of nano titanium dioxide as the raw material for sunscreen used in cosmetics.
Whitening with natural skin color
Titanium dioxide has very low coloring power, so it is made into skin color powder. No additional pigment is needed in production, which avoids the harm to human body caused by the addition of a large number of pigments, and also avoids the pigment precipitation after the cosmetics are put in place for a long time.
The size of nanometer titanium dioxide particles is closely related to their anti ultraviolet ability.When the particle size is equal to or less than half of the wavelength of light wave, the reflection and scattering amount of light is the largest, and the shielding effect is the best.The wavelength of ultraviolet ray is between 190~400nm, so the particle size of nanometer titanium dioxide cannot be greater than 200nm, preferably not greater than 100nm.However, the smaller the particles, the better. If the particles are too small, they are easy to be reunited, which is not conducive to dispersion. They are also easy to block the pores of the skin, which is not conducive to ventilation and sweat elimination.Generally speaking, when the particle size is between 30~100nm, the UV shielding effect is the best.Because of its fine particles, high transparency of the finished product, and its ability to pass through visible light, the skin whiteness is natural when adding cosmetics, which overcomes the shortcomings of some organic substances or pigment grade titanium dioxide that are opaque and make the skin appear unnatural pale.[5]
Antibacterial agent
At present, nano-TiO2 has become one of the hot spots of development and research due to its excellent antibacterial properties.Nano-TiO2 is widely used in antibacterial water treatment devices, food packaging, sanitary commodities (antibacterial floor tiles, antibacterial ceramic sanitary facilities, etc.), cosmetics, textiles, antibacterial tableware and chopping boards, antibacterial carpets, new house decoration and new furniture to remove harmful gases, refrigerators made of antibacterial mortar, antibacterial coating, antibacterial stainless steel plate, aluminum plate, etc. for constructionDurable consumer goods such as medical dressings and medical equipment.
Most antibacterial substances are organic substances, which are widely used in food, detergents, textiles and cosmetics.However, they have some shortcomings such as poor heat resistance, volatile, easy to decompose and produce harmful substances, and poor safety.For this reason, people have actively developed and researched some inorganic antibacterial agents, and ultrafine TiO2 is one of them.Since the amount of antibacterial agent in the product needs to reach a certain level, the following principles must be followed when selecting the antibacterial agent:
⑴ It is safe and non-toxic to human body, and has no irritation to skin;
⑵ Strong antibacterial ability and wide antibacterial range;
(3) There shall be no odor and strange smell, and the appearance color shall be light and the smell shall be small;
(4) Good thermal stability, no discoloration, decomposition, volatilization, deterioration, etc. under high temperature;
(5) Low price, easy source, etc.
Ultrafine TiO2 is an inorganic component, non-toxic, tasteless, and non irritating, with good thermal stability and heat resistance, non combustion, and white color, which fully conforms to the above principles.
prospect
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Nano-TiO2 is a transparent material with UV shielding function and color effect.Since its transparency and anti ultraviolet function are highly unified, it has been widely used in many aspects, such as sun protection, plastic film products, wood protection, transparent durable finish, fine ceramics, etc.Especially in the late 1980s, after the successful application of this kind of effect pigment, which can produce an attractive "color with corner" effect, in the top coat of luxury cars, it attracted worldwide attention. Developed countries such as the United States, Japan, Europe and other countries are very active in this research work, have invested a lot of manpower and material resources, and formulated long-term plans,So far, they have made many amazing achievements in the fierce competition in the international market, and have formed a high-tech nano material industry. The production of this high value-added high functional fine inorganic material has received good economic and social benefits. Nano oxide materials are also becoming a hot topic in China's industry.
With the deepening of the research on nanomaterials, people pay more and more attention to the nano assembly system and the material system of nanostructures synthesized by artificial assembly, which means that the research on nanomaterials can design, assemble, and create new systems according to people's wishes, and more purposefully make the system have the characteristics that people want, and make technological leaps,It has further opened the market for the application of nano materials, and has formed a large number of high-tech products in a wide range of fields.For example, magnetic memory, optical memory, liquid crystal display and optical functional film in information and communication;Original parts development in electronics, solar power supply in energy, thermal insulator, sensors in measurement and control technology;Structural ceramics, functional ceramics and other anti-aging rubber, functional paintPhotocatalysisDegradation agents, cleaning and antibacterial materials, ultra-high magnetic energy balance earth water magnets, etc.Among the market growth of nanomaterials, the products manufactured by o-3-dimensional structure technology, ultra precision processing technology, ultra-thin film production technology and transverse structure technology have the greatest market growth potential.
Relevant research also shows that the market application and development of nanomaterials will accelerate in the next 10 years, because patents in the field of nanomaterials in industrial countries have been increasing at an annual rate of more than 20% since 1993.The data shows that the scientific research investment of western industrial countries in nanomaterials and related fields reaches about 7.5 billion US dollars every year.The international competition in this field is becoming increasingly fierce.
Preparation method
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There are many methods to prepare nano-TiO2, which can be basically summarized as physical method and chemical method.Physical method, also known as mechanical crushing method, has high requirements for crushing equipment;Chemical method can be divided into gas phase method (CVD), liquid phase method and solid phase method.
Physical deposition
Physical vapor depositionMethod (PVD) is to use high stable heat sources such as arc, high frequency or plasma to heat raw materials, gasify them or form plasma, and then suddenly cool them to condense them into nanoparticles.Among them, vacuum evaporation is the most commonly used method.The particle size and distribution can be controlled by changing the gas pressure and heating temperature.This method can also be used to prepare single oxide, composite oxide, carbide and metal powder.
Chemical deposition
Chemical vapor depositionMethod (CVD) uses the vapor of volatile metal compounds to generate the required compounds through chemical reaction. The nano-TiO2 prepared by this method has fine particle size, high chemical activity, spherical particles, good monodispersity, good visible light transmittance, and strong ability to absorb and shield ultraviolet rays.The process is easy to scale up and realize continuous production, but the one-time investment is large. At the same time, the problem of powder collection and storage needs to be solved.
CVD method can be divided into gas phase oxidation method, gas phase synthesis method, gas phase pyrolysis method and gas phase hydrogen flame method.
Gas phase hydrogen flame method: it is obtained by burning titanium tetrachloride hydrogen flame, and the reaction mode is as follows:
Compaction density * (approximate) according to DIN EN ISO 787/11, Aug.1983
g/l
About 130
Water content * 2 hours at 105 ℃
Wt.%
≤1.5
Loss on ignition Materials dried at 105 ℃ for 2 hours and burned at 1000 ℃ for 2 hours
Wt.%
≤2.0
PH value in 4% dispersion
3.4-4.5
TiOtwoContent based on burned material
Wt.%
≥99.5
AltwoOthreeContent based on burned material
Wt.%
≤0.300
SiOtwoContent based on burned material
Wt.%
≤0.200
FetwoOthreeContent based on burned material
Wt.%
≤0.010
HCL content is based on the material after ignition
≤0.300
Mocker,45μM sieve residue according to DIN ISO 787/X Ⅷ, Apr.1984
Wt.%
≤0.05
Action mechanism
Vapor phase nano-TiO2 has a large specific surface area. The surface atomic number, surface energy and surface tension increase sharply with the decrease of particle size. The small size effect, surface effect, quantum size effect and macro quantum tunneling effect lead to the thermal, magnetic, optical, sensitive properties and surface stability of nanoparticles different from those of conventional particles.Due to the characteristics of the electronic structure of TiO2, when exposed to light, it generates highly chemically active superoxide anion free radicals and hydrogen oxygen free radicals to attack organic substances and degrade organic pollutants.When encountering bacteria, it will directly attack bacterial cells, causing the degradation of organic matter in bacterial cells, so as to kill bacteria and decompose them.Vapor phase nano titanium dioxide can not only affect the bacterial fecundity, but also destroy the cell membrane structure of bacteria, so as to completely degrade bacteria and prevent secondary pollution caused by endotoxin. Nano titanium dioxide is a non soluble material. When degrading organic pollutants and killing and sterilizing, it does not decompose and dissolve itself, has a lasting photocatalytic effect, and has a lasting sterilizationEffect of pollutant degradation
Application Properties
1. It has no scattering effect on the incident visible light, and has strong UV shielding ability and excellent transparency. As a new material, it has been widely used in cosmetics, coatings, paints and other products.
2. It is used for plastic, rubber and functional fiber products. It can improve the anti-aging ability, anti pulverization ability, weather resistance and product strength, while maintaining the color luster of the product and extending the service life of the product
3. Used for printing ink, coating and textile, which can improve its adhesion, anti-aging and scrub resistance
4. It can be used in paper industry to improve printability and impermeability
5. Due to its small particle size and high activity, it can not only reflect and scatter ultraviolet rays, but also absorb ultraviolet rays, so it has a stronger ability to block ultraviolet rays and is widely used in sunscreen cosmetics
6. With good light stability, non-toxic and harmless, and high photoelectric conversion rate, it is the most commonly used material for photoelectric solar energy conversion
Application Skills
(1) Adding organic dye sensitizers or transition metal elements to the gas phase nano-TiO2 can increase the range of light wavelength.
(2) The catalytic performance of gas phase nano titanium dioxide attached to activated carbon will be greatly improved.
(3) Adding hydrophilic fumed silica into fumed TiO2 can also improve its catalytic performance.
Liquid phase method
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The liquid phase method is to select metal salts that can be dissolved in water or organic solvents, make them dissolve, and mix them evenly in ionic or molecular state, then select a suitable precipitant or adopt processes such as evaporation, crystallization, sublimation, hydrolysis, etc., to uniformly deposit or crystallize metal ions, and then dehydrate or thermally decompose them to obtain powders.It can also be divided into colloidal method, sol-gel method and deposition method.The deposition method can be divided into direct deposition method and uniform deposition method.
sol-gel
Acid is added to make it form sol, and slurry colloidal particles are obtained after surfactant treatment, and nano TiO2 particles are obtained after heat treatment.
Sol gel method
Sol gel method (S-G method for short) is to use organic or inorganic salts as raw materials, carry out hydrolysis and polycondensation reactions in organic media, make the solution go through the sol-gel process to get the gel, and the gel is heated (or frozen), dried and calcined to get the product.The powder obtained by this method is uniform, well dispersed, high purity, low calcination temperature, easy to control reaction, few side reactions, simple process operation, but the cost of raw materials is high.
Precipitation method
A. Direct precipitation method
The reactor capacity is:
Ti0SO4+2NH3·H2O → Ti0(OH)2↓ + （NH4）2 SO4
Ti0(OH)2 → Ti02(s)+H2O
This method is simple and easy to operate, the product cost is low, the equipment and technical requirements are not too strict, but it is difficult to precipitate and wash, impurities are easily introduced into the product, and the particle distribution is wide.
B. Homogeneous precipitation method
The uniform precipitation method is to use a certain chemical reaction to slowly and evenly release the crystal forming ions in the solution from the solution. In this method, a precipitant (such as urea) is added, which does not react with the precipitated substance immediately, but slowly generates the precipitant in the whole solution through chemical reaction.The product particles obtained by this method are uniform, dense, and easy to filter and wash. It is a promising method for industrialization.
Solid phase synthesis
The solid phase synthesis of nano-TiO2 is carried out by thermal decomposition or solid solid reaction of solid materials.It includes redox method, pyrolysis method and reaction method.In this paper, the commonly used metatitanic acid pyrolysis method is introduced to prepare nano-TiO2.The nano-TiO2 prepared by this method has wide particle size distribution, simple process, easy operation and can be produced in batches.
toxicity
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Toxicological report of nano titanium dioxide (2013 report of Ministry of Health, Labor and Welfare of Japan)
Acute oral toxicity
5000mg/kg
Skin irritation
negative
Chronic toxicity
0.15mg/m3 (breathing)
Reproductive and developmental toxicity
Impossible to judge (the poisoning mode and high concentration in the test cannot be realized in real life)
