CN101948318A - Nanometer powder of titanium oxide coated by zinc oxide and preparation method thereof - Google Patents

Abstract

The invention discloses a zinc oxide-coated titanium oxide nano-powder and a preparation method thereof, belonging to the technical field of functional materials. The nanopowder includes a zinc oxide coating layer and titanium oxide nanoparticles; it also includes a transition layer of a titanium oxide zinc composite phase; the titanium oxide nanoparticles contain nitrogen with a molar percentage of 0.1 to 50%; the coating The molar ratio of zinc oxide in the layer to titanium oxide in the nanoparticles is 0.05-0.3:1. The preparation method is to use sol-gel method to use tetrabutyl titanate as titanium source and urea as nitrogen source to prepare nitrogen-containing titanium oxide nanoparticles, and then use co-precipitation method to use soluble zinc salt as raw material, ammonia-ammonium mixed solution Zinc oxide was prepared as a precipitant, and nitrogen-containing titanium oxide nanoparticles were coated. The invention simultaneously overcomes the disadvantages of low photocatalytic performance and poor temperature resistance of general titanium oxide nanopowders, and is a composite nanopowder with excellent performance, advanced and practical, and reasonable performance-price ratio.

Description

Zinc oxide-coated titanium oxide nanopowder and preparation method thereof

technical field

The invention relates to a functional ceramic material, in particular to a zinc oxide-coated titanium oxide nano-powder with high photocatalytic efficiency and high temperature resistance and a preparation method thereof.

Background technique

Nano-titanium oxide semiconductor photocatalysis technology has attracted widespread attention as a new type of environmental pollutant reduction technology. Due to the high antibacterial efficiency, long-lasting antibacterial effect, non-toxic health and environmental friendliness of nano-titanium photocatalytic antibacterial ceramics, it has become a research hotspot in various countries in recent years.

Studies have shown that titanium oxide has three isomers: anatase type, rutile type and brookite type, of which only anatase type titanium oxide has obvious photocatalytic and bactericidal properties. However, the general anatase type titanium oxide has a wide band gap (3.2eV), can only absorb the energy in the ultraviolet region that only accounts for 7% of solar radiation, and has low photon quantum efficiency, that is, the utilization rate of solar energy is low, and it is not conducive to indoor use; another On the one hand, at higher temperatures (550-700°C, depending on the specific morphology and preparation method), the anatase-type titanium oxide will be rapidly converted into rutile-type titanium oxide, and its photocatalytic efficiency will decrease sharply. Therefore, the temperature resistance of general nano-titanium oxide antibacterial ceramics is low, which leads to low sintering temperature in the preparation process, resulting in low density and hardness. Under the use, which seriously limits its application and promotion.

In order to overcome the defects in the above two aspects, people use various methods to modify the titanium ore-type titanium oxide, such as selecting a variety of ions for doping treatment to reduce the band gap, so that the effective absorption range extends to the visible light region, thereby improving Solar energy efficiency; and ion doping will also affect its anatase-rutile crystal transformation temperature, but in general, ion doping alone has a very limited effect on improving the temperature resistance of nano-titanium oxide.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of low photocatalytic efficiency and low temperature resistance of titanium oxide in the prior art, and provide a zinc oxide-coated titanium oxide by combining nitrogen doping and coating zinc oxide Nanopowder and its preparation method.

In order to solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a nano-powder of zinc oxide coated titanium oxide, which includes a coating layer of zinc oxide and nanoparticles of titanium oxide; a transition layer, the transition layer is located between the coating layer and the nanoparticles; the titanium oxide nanoparticles contain nitrogen with a molar content of 0.1 to 50%; the zinc oxide in the coating layer and the nanoparticles The molar ratio of titanium oxide is 0.05-0.3:1.

In the above technical scheme, there is a transition layer of the titanium oxide zinc composite phase between the nanoparticles of titanium oxide and the cladding layer of zinc oxide, and the Ti-O-Zn bond of the titanium oxide zinc composite phase will prevent the TiO crystal _grains from growing. large, promotes lattice distortion, and improves the activity of the composite powder; at the same time, the existence of the transition layer enables the formation of chemical bonds between the titanium oxide nanoparticles and the zinc oxide coating layer, and the strong binding force is beneficial to the composite powder at high temperature. Calcination still maintains a high photocatalytic activity. However, there is no report of such a transition layer in the prior art.

The preparation method of the zinc oxide-coated titanium oxide nanopowder is carried out according to the following steps:

① Prepare tetrabutyl titanate and urea with a molar ratio of 2.5:1 to 7.5:1, the volume of the tetrabutyl titanate is V1mL; prepare glacial acetic acid and urea with a molar ratio of 1:10 to 1:20 The mixed solution of water and ethanol, the volume of described glacial acetic acid is V2mL; The volume is the distilled water of V3mL; Wherein, V1: V2: V3 is 2.5～7.5:1:1～2; Prepare saturated soluble zinc salt solution, wherein Zn The molar ratio of ²⁺ to tetrabutyl titanate is 0.05 to 0.3:1;

2. with dehydrated alcohol, the urea described in step 1. is dissolved, under stirring, add step 1. the mixed solution of glacial acetic acid and dehydrated alcohol, be 98% nitric acid with mass concentration and adjust pH value to be 2, stir 0.5 ~1h; then slowly drop into V1mL of tetrabutyl titanate under rapid stirring, and stir for 1~5h; then slowly drop into V3mL of distilled water under rapid stirring to obtain solution A;

③ Stir the solution A obtained in step ② at room temperature for 3 to 5 hours to form a transparent gel, and age it in airtight storage for 1 to 7 days; then dry at 80°C and 120°C for 1 to 5 hours respectively; cool and grind; then Incubate at 400-600°C for 1-5 hours to obtain powder B;

④ Adjust the pH of the soluble zinc salt solution to 4.5-6.5, add the powder B obtained in step ③, drop in 2-3 drops of dispersant, then sonicate for 10-30 minutes, stir for 10-30 minutes; slowly drop in ammonia- Adjust the pH of the ammonium mixed solution to 6.5-8.5, stir for 30-60 minutes, and precipitate the precursor of zinc oxide-coated titanium oxide;

⑤ Filtrate the precursor, soak it with absolute ethanol, wash and filter, then heat the obtained precursor at 800-1050°C for 1-3 hours at a heating rate of 5-10°C/min, cool naturally, and grind to obtain The zinc oxide in the transition layer is coated with titanium oxide nanopowder.

In the above technical solution, the main innovation is to combine the introduction of nitrogen source and the coating of zinc oxide by a two-step method, so that the photocatalytic performance and temperature resistance of the obtained nano-powder are greatly improved at the same time.

The beneficial effect produced by adopting the above technical scheme is that the ceramic material prepared by the present invention has high photocatalytic efficiency and high temperature resistance at the same time, and can be used as a new type of safe high-performance antibacterial ceramic material for indoor and outdoor industrial and civil occasions .

Description of drawings

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the XRD figure of the nanopowder prepared by embodiment 1-3 of the present invention;

Fig. 2 is a comparison chart of the degradation rate of methyl orange between Example 1 of the present invention and pure titanium dioxide powder.

Detailed ways

Embodiment one

① Prepare tetrabutyl titanate and urea with a molar ratio of 5:1, the volume of the tetrabutyl titanate is V1; prepare a mixed solution of glacial acetic acid and absolute ethanol with a molar ratio of 1:19, the The volume of glacial acetic acid is V2; the volume is distilled water of V3; wherein, V1: V2: V3 is 5: 1: 1.67; prepare saturated zinc nitrate solution, wherein the mol ratio of Zn2+ and tetrabutyl titanate is 0.1: 1;

2. urea is dissolved in step 1. with dehydrated alcohol, under electromagnetic stirring, add step 1. the mixed solution of glacial acetic acid and dehydrated alcohol, be 98% concentrated nitric acid solution with mass concentration and adjust pH value to be 2, Stir for 0.5 to 1 hour; then slowly drop in V1mL of tetrabutyl titanate described in step ① under rapid stirring, and stir for 5 hours; then slowly drop in V3mL of distilled water under rapid stirring to obtain solution A;

③ Stir the solution A obtained in step ② at room temperature for 3 hours to form a transparent gel, airtightly age for 3 days; then dry at 80°C and 120°C for 3 hours respectively; cool and grind; then keep warm at 500°C for 2h , to get powder B;

4. be that the pH of described zinc nitrate solution is adjusted to 5.5 with the concentrated nitric acid of 98% with mass concentration, add the powder B obtained in the step 3., drop into 2～3 volume ratios and be 1: 1 sodium dodecylbenzenesulfonate and vinyl ether, then sonicate for 10 min, and stir for 30 min; slowly drop ammonia-ammonium mixed solution to adjust the pH to 7.5, stir for 30 min, and precipitate the precursor of zinc oxide-coated titanium oxide; the ammonia-ammonium mixed solution has a mass concentration of 60 mL. 500mL of mixed solution prepared by 25-28% ammonia water and 120g ammonium carbonate;

⑤Filter the precursor described in step ④, and soak and filter the precursor three times with absolute ethanol to fully deacidify and dehydrate the precursor, and then place the processed precursor in a muffle furnace to Raise the temperature at a rate of 5-10°C/min to 800°C, keep it warm for 3 hours, cool naturally, and grind to obtain nano-powders of zinc oxide-coated titanium oxide.

The zinc oxide-coated titanium oxide nanopowder prepared above includes a coating layer of zinc oxide and nanoparticles of titanium oxide; it also includes a transition layer of the titanium oxide zinc composite phase, and the transition layer is located between the nanoparticles and the coating. Between layers; the titanium oxide nanoparticles contain 28.6% nitrogen by mole; the molar ratio of the zinc oxide in the coating layer to the titanium oxide in the nanoparticles is 0.1:1.

Compared with pure titanium oxide powder, the photocatalytic activity of the zinc oxide-coated titanium oxide nanopowder prepared in this example is greatly improved no matter under visible light irradiation or ultraviolet light irradiation, see FIG. 2 .

Embodiment two and embodiment three

The difference from Example 1 is that the holding temperatures in step ⑤ are 900°C and 950°C respectively.

The nanopowders prepared in Examples 1 to 3 were analyzed by XRD respectively, and their XRD patterns are shown in FIG. 1 . It can be seen from the figure that the nanopowder prepared by the present invention still has a mixed crystal structure of anatase phase and rutile phase after being calcined at 950° C., and the crystal particle size is about 75 nm. However, the titanium oxide powder prepared by the general method will rapidly transform from anatase-type titanium oxide to rutile-type titanium oxide at 550-700°C. It can be seen that the zinc oxide-coated titanium oxide nano-powder prepared by the present invention increases the crystal transformation temperature by 200° C., and significantly improves the high temperature resistance.

In addition, an obvious zinc titanate (ZnTiO ₃ ) peak appears in the diffraction pattern, indicating the existence of a transition layer. Because the two-step method was used in the sample preparation process, firstly, titanium oxide crystals were prepared, and then zinc oxide was coated on its surface, and there was no melting phenomenon during the subsequent sintering process. It exists between titanium oxide and zinc oxide as a transition layer, and does not exist as independent grains.

Embodiment four

① Prepare tetrabutyl titanate and urea with a molar ratio of 2.5:1, the volume of the tetrabutyl titanate is V1; prepare a mixed solution of glacial acetic acid and absolute ethanol with a molar ratio of 1:10, the The volume of glacial acetic acid is V2; the volume is distilled water of V3; wherein, V1: V2: V3 is 2.5: 1: 2; prepare saturated zinc sulfate solution, wherein the mol ratio of Zn2+ and tetrabutyl titanate is 0.15: 1;

②Dissolve the urea with absolute ethanol, add a mixed solution of glacial acetic acid and absolute ethanol under stirring, adjust the pH value to 2 with a concentrated nitric acid solution with a mass concentration of 98%, and stir for 0.5 to 1 h; then stir rapidly slowly drop into the tetrabutyl titanate, and stir for 1 h; then slowly drop into the distilled water under rapid stirring to obtain solution A;

③ Stir the solution A obtained in step ② at room temperature for 5 hours to form a transparent gel, and seal it for 7 days; then dry it at 80°C and 120°C for 5 hours respectively; cool and grind it; then keep it warm at 600°C for 5 hours , to get powder B;

④ Adjust the pH of the zinc nitrate solution to 4.5, add the powder B obtained in step ③, drop in 2 to 3 drops of sodium dodecylbenzenesulfonate, then sonicate for 30 minutes, stir for 10 minutes; slowly drop in ammonia-ammonium mixture Adjust the pH of the solution to 6.5, stir for 60 minutes, and precipitate the precursor of zinc oxide-coated titanium oxide;

⑤ Filter the precursor, soak it with absolute ethanol, wash and filter, then heat up to 850°C at a rate of 5-10°C/min, keep it warm for 1h, cool naturally, and grind to obtain zinc oxide-coated titanium oxide nanopowder .

The zinc oxide-coated titanium oxide nanopowder prepared above includes a coating layer of zinc oxide and titanium oxide nanoparticles; it also includes a transition layer of the titanium oxide zinc composite phase; the titanium oxide nanoparticles contain a molar percentage of 44.4% nitrogen; the molar ratio of zinc oxide in the coating layer to titanium oxide in the nanoparticles is 0.15:1.

The nano-powder was analyzed by XRD, and the XRD result showed that the composite powder still had a mixed crystal structure of anatase phase and rutile phase after being calcined at 850° C., and the crystal particle size was 67 nm. The zinc oxide-coated titanium oxide nanopowder prepared in this example has significantly improved temperature resistance and photocatalytic performance.

Embodiment five

The difference from Example 1 is that

Step 1. prepare tetrabutyl titanate and urea with a molar ratio of 7.5:1, the volume of said tetrabutyl titanate is V1; prepare a mixed solution of glacial acetic acid and absolute ethanol with a molar ratio of 1:15, the The volume of described glacial acetic acid is V2; The volume is the distilled water of V3; Wherein, V1: V2: V3 is 7.5: 1: 1; Prepare saturated zinc nitrate solution, wherein the mol ratio of Zn2+ and tetrabutyl titanate is 0.30: 1 ;

In step ④, adjust the pH of the zinc nitrate solution to 6.5, add the powder B obtained in step ③, drop in 2 to 3 drops of vinyl ether, then sonicate for 30 minutes and stir for 10 minutes; slowly drop in the ammonia-ammonium mixed solution to adjust the pH to 8.5;

In step ⑤, the heating rate is increased to 1050°C.

In the prepared zinc oxide-coated titanium oxide nanopowder, the titanium oxide nanoparticles contain nitrogen with a molar content of 21.1%; the zinc oxide in the coating layer and the titanium oxide in the nanoparticles are The molar ratio is 0.30:1.

Claims (5)

1. a zinc oxide coats the nano-powder of titanium oxide, and it comprises the coating layer of zinc oxide and the nanoparticle of titanium oxide; It is characterized in that also comprising the transition layer of the compound phase of titanyl zinc, described transition layer is between coating layer and nanoparticle; Comprise molar content in the nanoparticle of described titanium oxide and be 0.1～50% nitrogen; The mol ratio of the titanium oxide in zinc oxide in the described coating layer and the described nanoparticle is 0.05～0.3: 1.

2. zinc oxide according to claim 1 coats the preparation method of the nano-powder of titanium oxide, it is characterized in that carrying out according to following step:

1. prepare mol ratio and be 2.5～7.5: 1 tetrabutyl titanate and urea, the volume of described tetrabutyl titanate is V1mL; Prepare mol ratio and be 1: 10～20 the Glacial acetic acid and the mixing solutions of dehydrated alcohol, the volume of described Glacial acetic acid is V2mL; Preparing volume is the distilled water of V3mL; Wherein, V1: V2: V3 is 2.5～7.5: 1: 1～2; Prepare saturated soluble zinc salts solution, wherein Zn ²⁺With the mol ratio of tetrabutyl titanate be 0.05～0.3: 1;

2. with dehydrated alcohol with the urea dissolving of step described in 1., under agitation add the mixing solutions of the 1. described Glacial acetic acid of step and dehydrated alcohol, be that 98% nitre acid for adjusting pH value is 2 with mass concentration, stirring 0.5～1h; Under stirring fast, slowly splash into the tetrabutyl titanate of V1mL then, stir 1～5h; Under stirring fast, slowly splash into the distilled water of V3mL again, get solution A;

3. with step 2. the gained solution A at room temperature stirred 3～5 hours, form transparent gel, airtight ageing 1-7 days; Then successively 80 ℃ and 120 ℃ dry 1～5 hour respectively; Grind the cooling back; Be incubated 1～5h down at 400～600 ℃ then, get powder B;

4. regulate pH to 4.5～6.5 of described soluble zinc salts solution, add the 3. powder B of middle gained of step, splash into 2～3 dispersion agents, ultrasonic then 10～30min, stirring 10～30min; Slowly splash into ammonia-ammonium mixing solutions and regulate pH to 6.5～8.5, stir 30～60min, separate out the precursor that zinc oxide coats titanium oxide;

5. filter described presoma, and with soaked in absolute ethyl alcohol, filter wash, with heat-up rate to 800～1050 ℃ insulation 1～3h of 5～10 ℃/minute, naturally cooling grinds then, the zinc oxide that must contain transition layer coats the nano-powder of titanium oxide.

3. zinc oxide according to claim 2 coats the preparation method of the nano-powder of titanium oxide, it is characterized in that described soluble zinc salts solution is zinc nitrate solution or solution of zinc sulfate.

4. zinc oxide according to claim 2 coats the preparation method of the nano-powder of titanium oxide, it is characterized in that described dispersion agent is Sodium dodecylbenzene sulfonate and/or Vinyl Ether.

5. zinc oxide according to claim 2 coats the preparation method of the nano-powder of titanium oxide, it is characterized in that described ammonia-ammonium mixing solutions is the mixing solutions 500mL of 25-28% ammoniacal liquor and the preparation of 120g volatile salt for the 60mL mass concentration.

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