RU2457182C1 - Method of producing nanodispersed nickel titanate - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in chemical and semiconductor industry. The method of producing nanodispersed nickel titanate involves preparation of an equimolar mixture of nanodispersed titanium dioxide and an anhydrous nickel salt, subsequent heating of that mixture to nickel titanate synthesis temperature and holding at that temperature. The titanium dioxide used is of an anatase modification obtained using a chloride technique, with initial anatase-rutile polymorphic transition temperature higher than nickel titanate synthesis temperature. The nickel salt used is nickel nitrate and the equimolar mixture is held at temperature in the range of 820-880°C for not less than 1 hour.

EFFECT: invention enables to obtain particle size-homogeneous nanodispersed nickel titanate and reduce power consumption of the process.

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Description

The claimed technical solution relates to the field of production of nanomaterials, and in particular to methods for producing nanodispersed nickel titanate.

In recent years, Russia, as well as around the world, has been actively working to obtain the most simple and efficient from the point of view of industrial use synthesis methods for various nanomaterials.

Nanodispersed transition metal titanates are widely known as magnetic and semiconductor materials with wide possibilities of use in the semiconductor industry, optical systems, and catalysts.

The synthesis of nickel titanate (Ni TiO ₃ ) is carried out by a variety of known methods using organic derivatives of titanium, for example, its oxalate complexes or tetrabutoxy titanium. The synthesis of NiTiO _{3 by} solid-phase interaction is complicated by the fact that at low temperatures (T <1000 ° C), along with the nickel titanate formed, nickel oxide (NiO) and titanium dioxide (TiO ₂ ) of rutile and anatase modifications remain in the system. High temperatures lead to an uncontrolled increase in particle size with different morphologies, as a result of which the particle sizes of the resulting product are heterogeneous and exceed the particle sizes of the starting titanium dioxide.

(1. Nickel titanate microtubes constructed by nearly spherical nanoparticles: Preparation, characterization and properties / Materials Research Bulletin - 2009 - 44 - p.1797-1801 / Yonghong Ni, Xinghong Wang, Jianming Hong.

2. Effects of Agedoped NiTiO ₃ on photoreduction ofmethylene blue under UV and visible light irradiation / Journal of Alloys and Compounds - 2009 - 479 - p.785-790 / Yi-Jing Lina, Yen-Hwei Chang, Guo-Ju Chen , Yee-Shin Chang, Yee-Cheng Chang.

3. Structural characterization of NiTiO ₃ nanopowders prepared by stearic acid gel method / Materials Letters - 2008 - 62 - p.3679-3681 / MSSadjadi, K.Zare, S. Khanahmadzadeh, M. Enhessari.)

Closest to the proposed method (prototype) is a method for the synthesis of nickel titanate, which includes preparing an equimolar mixture of finely dispersed titanium dioxide with a nickel salt, for example nickel carbonate, or nickel oxide, taking into account the weight loss of nickel salt during its calcination, further heating the equimolar mixture to a temperature above 1100 hail. C for 72 hours or more with periodic cooling and mixing (grinding) of the mixture (Bulletin of the Krasnoyarsk State University, series "Physics and Mathematics", No. 1, 2002, p. 89-93).

The disadvantages of this method are:

- low quality of the obtained product — nickel titanate — due to the non-uniform particle size of nickel titanate due to sintering of particles at high temperature, which makes it impossible to obtain nickel titanate with particle sizes not exceeding the particle size of the initial nanosized titanium dioxide;

- high energy intensity of the process due to the use of high heating temperatures and the duration of the synthesis process;

- high cost of the process due to the high energy intensity and duration of the process.

The technical task of the present invention is to improve the quality of the product, namely: obtaining a uniform particle size of nanodispersed nickel titanate, the particle size of which does not exceed the particle size of the initial titanium dioxide, while reducing energy consumption and the cost of the process for its production.

The problem is achieved in that in the known method, including the preparation of an equimolar mixture of nanosized titanium dioxide with anhydrous nickel salt, taking into account the loss of its mass during calcination, the subsequent heating of this mixture to the temperature of synthesis of nickel titanate and exposure at this temperature, in accordance with the invention in the titanium dioxide is anatase-modified titanium dioxide obtained by the chloride technology with an anatase-rutile polymorphic transformation onset temperature higher than synthesis of nickel titanate, nickel nitrate is used as a nickel salt, and the synthesis is carried out by holding the indicated equimolar mixture in the temperature range of 820-880 ° C for at least 1 hour.

The components of the initial equimolar mixture and the modes of the nickel titanate synthesis process were selected experimentally: a series of equimolar mechanical mixtures of nanodispersed titanium dioxide prepared by sulfate or chloride methods were prepared, and as the second reagent: basic nickel carbonate (NiOH) ₂ CO ₃ or nickel nitrate Ni (NO ₃ ) ₂ × 6H ₂ O:

mixture I - TiO ₂ (anatase obtained by the sulfate method) + Ni (NO ₃ ) ₂ × 6H ₂ O;

mixture II - TiO ₂ (anatase obtained by the chloride method) + Ni (NO ₃ ) ₂ × 6H ₂ O;

a mixture of III - TiO ₂ (anatase obtained by the sulfate method) + (NiOH) ₂ CO ₃ ;

mixture IV - TiO ₂ (anatase obtained by the chloride method) + (NiOH) ₂ CO ₃ .

Isothermal exposure during the synthesis was carried out in a laboratory furnace of the SNOL type with temperature fluctuations in the heating zone of ± 5 ° C.

Mixtures I-IV were isothermally kept in the temperature range of 700-850 ° C with an interval of 50 ° C.

The quantitative content of nickel titanate obtained from various mixtures at different heating temperatures and the synthesis time is presented in Table 1. It was found that the synthesis of nickel titanate in mixture II occurs at 95-97% within 1 hour. The increase in the content of nickel titanate in this mixture with an increase in the calcination time from 1 h to 3 h is insignificant and amounts to only 3-5%.

Quantitative data on the phase composition of the mixtures after isothermal exposure, obtained by x-ray phase analysis, are presented in table 1. Analysis of the data presented shows that in calcined mixtures I, III and IV, the equimolar mixture does not completely convert to nickel titanate. During heat treatment of mixture II, the complete conversion of the equimolar mixture to nickel titanate occurs within 3 hours at a temperature of 850 ° C. Whereas at temperatures of 800–850 ° С, mixtures of I and IV form a rutile modification of titanium dioxide, which does not interact with NiO.

For the synthesis of nickel titanate, titanium dioxide with a particle size of 20 ± 5 nm was used. Obtained in accordance with the proposed method, Nickel titanate also had a particle size of 20 ± 5 nm.

Thus, as a result of the experiments, it was found that the proposed method allows to obtain high-quality nickel nanosized titanate due to the production of a product with a uniform particle size, the particle sizes of which do not exceed the particle sizes of the initial titanium dioxide. In addition, the proposed method has a significantly lower energy intensity compared with the prototype due to the use of low heating temperatures and a short duration of the synthesis process, as well as lower cost due to the low energy intensity and duration of the process.

The invention is illustrated in the table.

Table 1 presents the phase compositions of the investigated initial mixtures containing titanium dioxide obtained by various technologies, and different salts of Nickel; as well as the yield of nickel titanate from the starting mixtures after isothermal exposure for 1 or 3 hours at the temperatures indicated in the table.

The proposed method is as follows.

As the starting components, titanium dioxide (TiO ₂ ) of the anatase modification of the Solikamsk Magnesium Plant, obtained by the chloride technology, and 6-hydrated nickel nitrate (Ni (NO ₃ ) ₂ × 6H ₂ O) are selected. In this case, the initial titanium dioxide has a start temperature of the anataz-rutile polymorphic transformation equal to 900 ° C and an average particle size of 20 nm. Then, in laboratory conditions, the mass loss of the initial nickel nitrate during calcination is established. To do this, an accurate sample of nickel nitrate weighing 1 g is placed in a pre-calcined quartz crucible and calcined at a temperature of 800 ° C for 3 hours.

Then follows the preparation of an equimolar mixture. The equimolar mixture is prepared from the above starting components in the following weight ratios:

- 51.7 g of titanium dioxide TiO ₂ anatase modification obtained by the chloride technology, Solikamsk magnesium plant;

- 161.0 g of 6 hydrated nickel nitrate Ni (NO ₃ ) ₂ × 6H ₂ O.

The mixture is prepared in an agate mortar by thoroughly mixing titanium dioxide and nickel nitrate, taken in equimolar ratios, in alcohol until a suspension of a uniform color is obtained. Then the suspension is dried at a temperature of 80-100 ° C, stirring periodically (1 time in 10 minutes). After evaporation of the alcohol, the mixture is stirred again.

The resulting equimolar mixture is placed in a furnace with a temperature in the working zone of 850 ± 5 ° C and calcined at this temperature for at least 1 hour. According to x-ray phase analysis, the output of Nickel titanate after an hour is 96%. When holding at the indicated temperature for 3 hours, the yield of nickel titanate is 100%.

Using X-ray diffraction analysis in combination with microscopy, it was found that the particle size of the obtained nickel titanate was 20 ± 5 nm.

The proposed method for producing nickel titanate has the following advantages compared to the prototype and other known methods:

- high quality of the obtained product — nickel titanate — due to its dispersion not exceeding the dispersion of the initial titanium dioxide, and also due to ensuring uniform particle size of the finished product;

- low energy intensity of the process due to the use of low heating temperatures and the short duration of the synthesis process;

- low cost of the synthesis process due to the low energy intensity and duration of the process.

Claims (1)

A method for producing nanodispersed nickel titanate, comprising preparing an equimolar mixture of nanodispersed titanium dioxide with an anhydrous nickel salt, then heating the mixture to a temperature for synthesizing nickel titanate and holding at this temperature, characterized in that anatase titanium dioxide obtained from chloride is used as titanium dioxide technology, with the temperature of the onset of the polymorphic transformation of anataz-rutile above the temperature of the synthesis of nickel titanate, nitrate of nickel, and exposure is carried equimolar mixture in the temperature range 820-880 ° C for at least 1 h.