CN1274886C - Method and apparatus for artificial synthetic rutile single crystal by TiO2 micropowder flame melt method - Google Patents
Method and apparatus for artificial synthetic rutile single crystal by TiO2 micropowder flame melt method Download PDFInfo
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- CN1274886C CN1274886C CN 03117997 CN03117997A CN1274886C CN 1274886 C CN1274886 C CN 1274886C CN 03117997 CN03117997 CN 03117997 CN 03117997 A CN03117997 A CN 03117997A CN 1274886 C CN1274886 C CN 1274886C
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Abstract
The present invention relates to a method and a device for artificial synthetic rutile single crystal by a TiO2 ultrafine powder flame fusion method, which belongs to the fields of single crystal growth and powder preparation techniques. The present invention adopts a coprecipitation method to prepare octahedrite phase TiO2 ultrafine powder and discloses a technical scheme for increasing powder purity, dispersivity and flowability in the process of precursor synthesis, calcination, etc. The adopted flame fusion method growth technique provides a complete set of technical skill for the existing gemstone flame smelting furnace artificial synthetic methods and comprises the procedures of combustion device and furnace reconstruction and single crystal growth and the processes of technical parameters, crystal oxidation annealing decolorization, etc. The TiO2 ultrafine powder preparation technique, the flame smelting furnace and the single crystal growth relevant technical method provided by the present invention can synthesize large rutile single crystal with the diameter phi of 25 to 27mm, the length of 40 to 50mm and 60 to 70% of visible wave band optical transmissivity.
Description
One, the technical field
The invention belongs to the technical field of single crystal growth and powder preparation.
Second, background Art
In foreign countries, in 1949, rutile single crystal is artificially synthesized by Moore (trans. Am. Inst. Mel. Engrs., 1949, 184: 194) of the United states for the first time by using a flame fusion method, the diameter of the crystal prepared at that time is less than 15mm, and the rutile single crystal can be prepared only by using high-purity powder under an oxidizing atmosphere, which is the theoretical basis of preparing rutile by using all the flame fusion methods at present, but the characters, crystal growth parameters and equipment structures of the powder are not mentioned in the literature; in 1953, Zhongzhu Xiudoctor (ャラミツクス, 1968, 3 (9): 731) of Tochigi chemical industry (Limited) (now Fuji titanium industry Limited) in Japan cooperated with the university of sorb to produce rutile single crystals with larger diameter by using a Zhongzhu flame melting single crystal furnace, but specific process conditions and parameters are not given, and the specific detailed structure of the Zhongzhu flame melting single crystal furnace proposed by the Yongji chemical industry (Limited) is not clear; in 1963, doped rutile crystals were prepared by a common three-tube burner flame melting single crystal furnace in caucasian (m.kestigian) (Nature, 1963, 197: 1006), and the related detailed structure is not clear; in 1965, adameski (j.a. adamski) (j.appl.phys, 1965, 36 (5): 1784) produced larger diameter rutile single crystals using a burner modified flame furnace under the growth conditions: the oxygen content of the inner tube is 5l/min, the hydrogen content of the middle tube is 12-21l/min, and the oxygen content of the outer tube is 14 l/min.
Since rutile crystals are very reduced near the melting point, they must be grown under a strong oxidizing atmosphere. However, the domestic existing equipment and method are all limited to the conditions of strong reducing atmosphere, so that the domestic equipment for preparing crystals, such as adomestic SJZ type sintering furnace, can not be used for preparing synthetic rutile single crystals.
In addition, TiO is necessary for synthesizing rutile monocrystal2Preparing TiO by using superfine powder as a growth material and adopting a sulfate system2The method of ultrafine powder was first proposed by japanese ligustrum guichen in 1956 (journal of industrial chemistry, 1956, 59: 498), and the principle of the reaction was:
the specific process adopted by the method comprises the following steps: adding equimolar concentrated sulfuric acid and ammonium sulfate aqueous solution into titanium tetrachloride for synthesis; maintaining the temperature at 50 deg.C for 48 hr, washing with ethanol, and filtering to obtain (NH)4)2TiO(SO4)2·H2O (abbreviation)ATS); then roasting ATS at 700 ℃ to obtain anatase-phase TiO2And (3) powder. However, the powder prepared by the process has the defects of large and uneven particle size, incomplete decomposition, easy bubble release during crystal growth and the like, and high-quality single crystals are difficult to obtain.
For domestic useTiO2The technology of artificial synthesis of rutile monocrystal by flame fusion method of superfine powder still belongs to the scientific research problem.
The existing single crystal has extremely high price which can reach 10000 dollars/kg due to the factors of complex equipment structure, high price, complex process, high preparation cost and the like of the preparation of the foreignrutile single crystal. However, the existing domestic equipment and method are limited to the conditions of strong reducing atmosphere, so that the invention of low-cost equipment and technology capable of forming strong oxidizing atmosphere and preparing rutile single crystals is needed.
Third, the invention
To obtain TiO suitable for preparing rutile single crystals2The invention discloses an ultrafine powder, which is based on a sulfate technical system and adopts a coprecipitation method to prepare anatase phase TiO2And (3) ultrafine powder.
In order to overcome the problems that the existing foreign rutile single crystal preparation equipment has complex structure, high price and high preparation cost, and the existing domestic equipment and method are limited to the condition of strong reducing atmosphere, the invention provides low-cost equipment and technology capable of forming strong oxidizing atmosphere to prepare rutile single crystal. Can prepare rutile single crystal in batches, thus reducing the cost of the rutile crystal.
In order to achieve the purpose of the invention, the invention provides TiO2The preparation technology of the superfine powder material adopts a sulfate coprecipitation method, and the preparation process comprises the following steps: with equimolar amounts of TiCl4Solution, H2SO4And (NH)4)2SO4Mixing the three solutions, and stirring the mixed solution while keeping the constant temperature of 55-60 ℃; formed by mixing solutions of (NH)4)2TiO(SO4)2Filtering the complex crystal to obtain (NH)4)2TiO(SO4)2·H2O (ATS for short); repeatedly washing ATS with pure ethanol for many times, and fully drying at the temperature of 100-150 ℃; keeping the temperature of the screened superfine powder ATS at 750-800 ℃ for 2 hours for roasting, and stirring while roasting; cooling to obtain anatase type TiO2And (3) powder.
The technical scheme adopted by the equipment for preparing the rutile single crystal by transformation is as follows: in order to obtain the condition of crystal growth, the structures of a burner and a furnace pot of the SJZ type sintering furnace are modified. Particularly, aiming at the defect that the original burner cannot form strong oxidizing atmosphere due to insufficient oxygen supply, an annular multi-path oxygen inlet device is additionally arranged on the burner, and the oxygen inlet amount is increased to form the strong oxidizing atmosphere; aiming at the situation that a melting layer at the top is thick in the growth of rutile crystals and easily escapes when airflow is unstable or a temperature field is changed, the upper part of the inner wall of a hearth of a furnace pot is made into a multi-step type so as to keep the stability of a liquid material and ensure the growth of the crystals.
The improved equipment has simple and economic structure, can obtain the strong oxidizing atmosphere condition for crystal growth, and meets the process requirement for preparing the large-diameter rutile single crystal.
With the TiO of the invention2The method for artificially synthesizing the rutile crystal by using the ultrafine powder material and equipment comprises the following steps:
adding TiO into the mixture2Spraying the superfine powder, oxygen and hydrogen into a furnace pot, mixing and burning in the furnace pot, and forming crystal growth strong oxidizing atmosphere conditions by the working of a burner: outer tube oxygen of 100-Liter/hour. Then increasing the hydrogen flow rate to raise the furnace temperature so as to enable the crystal to shoulder. Keeping the hydrogen flow rate to make the crystal grow in an equal diameter.
The method has the characteristics of simple process, low equipment and preparation cost, easy realization of industrialization and product quality close to the level of similar foreign products. The crystal size reaches phi 25-27mm multiplied by 40-50 mm; the crystal light transmittance reaches 70 percent (in a visible wave band).
Description of the drawings
FIG. 1 is a schematic view of the burner and boiler structure of the apparatus;
fig. 2 is a top sectional view of a burner of the apparatus.
Fifth, detailed description of the invention
TiO of the invention2The specific preparation process of the superfine powder material comprises ① firstly preparing TiCl4Dropwise adding ice water into equimolar H at constant temperature of 55-60 DEG C2SO4And equimolar of (NH)4)2 SO 4②, mixing the three raw materials, standing and ageing for 12 hr to obtain (NH)4)2TiO(SO4)2The (NH) complex crystal is obtained by suction filtration4)2TiO(SO4)2·H2O (ATS for short), ③ washing ATS in pure ethanol, suction filtering for at least 2-3 times to dry and remove impurities, especially chlorine bridge, ④ grinding dried ATS, sieving with 200 mesh sieve to obtain superfine powder, ⑤ heating sieved superfine powder to 750 deg.C and 800 deg.C, maintaining for 2 hr, roasting while stirring to decompose ATS and avoid sintering, ⑥ cooling to obtain anatase TiO2And sieving the powder by a 250-mesh sieve to obtain the powder which is suitable for growing rutile crystals by a flame fusion method and has high purity, superfine property, high dispersibility and high fluidity. Anatase TiO obtained by the method of the invention2The powder is observed under a transmission electron microscope, and the particles are spherical, have uniform particle size of about 30nm and good dispersibility. The purity of the product reaches 99.99 percent through spectrum test. Through a screen vibration powder falling experiment, the powder has good fluidity which is about 2.5g/100 times.
The structure of the apparatus of the present invention is described in detail below with reference to the accompanying drawings:
as shown in figure 1 and figure 2, the equipment for preparing rutile single crystals mainly comprises a burner [1]and a furnace pot [8]. The top of the burner [1]is provided with an inner pipe [2]which is filled with oxygen and is provided with a central pipe [3]which is filled with hydrogen, and the hydrogen input from the central pipe enters the burner through a porous plate [4]. The annular multi-path oxygen inlet device added on the burner [1]is an annular outer pipe [5], the outer pipe is provided with an air inlet [6]for inputting oxygen, the wall of the burner [1]is provided with a plurality of inclined holes [7], 6 to 8 inclined holes can be arranged according to requirements, one end of each inclined hole [7]is communicated with the outer pipe [5], and the other end is communicated with the inner cavity of the burner. When the burner works, oxygen introduced from the air inlet enters the burner from each inclined hole along the annular outer pipe, and is mixed and combusted with oxygen and hydrogen sprayed out from the inner pipe and the central pipe, so that strong oxidizing atmosphere required by crystal growth can be obtained in the combustion chamber.
As shown in figure 1, the upper stepped inner wall of the furnace pot (8) is provided with at least more than 2 steps (9), the structure can effectively reduce the impact of gas turbulence on crystals, the temperature field in the furnace is more stable, and the isothermal zone is enlarged accordingly, thereby providing conditions for the growth of large-diameter crystals.
The process of synthesizing rutile crystal artificially by using the equipment of the invention is as follows:
firstly, igniting hydrogen, and adjusting the oxygen amount of the inner pipe and the outer pipe: the outer tube oxygen is 100-200 l/h, the inner tube oxygen is 300-450 l/h, and the central tube hydrogen is 200-300 l/h, so as to reach the atmosphere required by the crystal growth in the combustion chamber. Seed crystal inserted on the pull rod is lifted into a sight hole [10]in the furnace pot]At the center, the hydrogen flow of the central tube is slowly increased to melt the top of the seed crystal, and the hydrogen-oxygen ratio is 1.5: 1. Then opening the blanking device, TiO2The superfine powder enters a combustion chamber under the carrying of oxygen in an inner pipe, and the oxygen and hydrogen in the outer pipe and a central pipe are sprayed into a furnace pot to be mixed and combusted to generate high temperature so as to enable TiO to be subjected to2The superfine powder is melted into liquid and falls on the top of the melted seed crystal. Then increasing the hydrogen flow to slowly raise the furnace temperature, at the moment, the hydrogen-oxygen ratio is 1.8: 1, simultaneously increasing the powder feeding amount and the dropping rate to expand the shoulder of the crystal, keeping the hydrogen flow after the required diameter is reached, enabling the crystal to grow in an equal diameter, and simultaneously turning off all gas sources after the required length is reached, thus finishing the growth.
The crystal which is just generated is dark blue black, oxidation annealing decolorization is needed to be carried out in a muffle furnace with oxygen, and the oxidation annealing process comprises the following steps: putting the crystal into a muffle furnace, introducing oxygen from a furnace mouth, and then starting to heat up at the heating rate of 1 ℃/min until the temperature is 1400 ℃ and 1500 ℃, wherein the time is about 24 hours; keeping the temperature at the temperature for 24 hours; finally, the temperature is reduced to room temperature, the temperature reduction rate is 1 ℃/minute, and about 24 hours are needed.
The crystal production process is specifically described below by taking the preparation of a single rutile single crystal 20mm in diameter in the (001) direction as an example:
using 250 mesh anatase phase TiO in the improved apparatus of the present invention2The superfine powder is used as a growth material. TiO 22The superfine powder is prepared by the method. The preparation process comprises the following steps: first, a seed crystal is cut in the (001) direction. In the equipment, firstly, hydrogen is ignited, then the oxygen content in the inner tube is adjusted to 350 liters/hour, the oxygen content in the outer tube reaches 120 liters/hour, and the hydrogen content in the central tube is 200 liters/hour, so that a strong oxidizing atmosphere required by crystal growth is formed in the combustion chamber. The seed crystal inserted on the pull rod is lifted to the center of the sight hole in the furnace pot, and the hydrogen flow is adjusted to 230 hours/liter to melt the top of the seed crystal. Opening the blanking device, and oxygen in the inner tube clamps the TiO2Mixing and burning the powder, oxygen in the outer pipe and hydrogen in the central pipe, spraying the mixture into a furnace pot, keeping the gas proportion after the crystals automatically expand to 4-5 mm, and opening the settling device to enable the pull rod to slowly descend. Then, the hydrogen is slowly increased to expand the shoulders of the crystal, the powder feeding amount and the descending speed are increased, the diameter of the crystal reaches about 20mm after 1 hour, and the hydrogen flow reaches about 260 hours/liter. Keeping the hydrogen content unchanged, and enabling the crystal to grow in an equal diameter manner and reach the length of 40mm after 4 hours. All gas sources are turned off at the same time when the growth is finished. And cooling the crystal in the furnace for half an hour, taking out, annealing according to an annealing process, and keeping the temperature at 1450 ℃ for 24 hours, wherein the annealing time is 3 days.
Claims (7)
1. By TiO2Method for artificially synthesizing rutile monocrystal by ultrafine flame fusion method and preparing TiO by sulfate coprecipitation method2Ultra-fine powder: equimolar of TiCl4Solution, H2SO4And (NH)4)2SO4Mixing the three solutions, and stirring the mixed solution while keeping the constant temperature of 55-60 ℃; formed by mixing solutions of (NH)4)2TiO(SO4)2Filtering the complex crystal to obtain (NH)4)2TiO(SO4)2·H2O (ATS for short); repeatedly cleaning ATS with pure ethanol at 100 deg.CDrying thoroughly at-150 ℃; the screened superfine powder ATS is roasted by keeping the temperature at 750-800 ℃ for 2 hours, stirred while being roasted, and cooled to obtain TiO2Powder, which is characterized in that: adding TiO into the mixture2Spraying the superfine powder, oxygen and hydrogen into a furnace, adjusting the gas flow to 200 liters/h of oxygen inthe outer tube and 450 liters/h of oxygen in the inner tube, and 300 liters/h of hydrogen in the central tube to achieve a strong oxidation atmosphere, and then increasing the hydrogen flow to raise the furnace temperature to expand the shoulders of the crystal; keeping the hydrogen flow rate to make the crystal grow in an equal diameter.
2. The process of claim 1, wherein ① the TiCl is first introduced4Dropwise adding ice water into equimolar H at constant temperature of 60 DEG C2SO4And equimolar of (NH)4)2SO4②, mixing, standing, aging for 12 hr to obtain (NH)4)2TiO(SO4)2The (NH) complex crystal is obtained by suction filtration4)2TiO(SO4)2·H2O (ATS), ③ washing ATS in pure ethanol, filtering repeatedly to remove impurities, ④ grinding dried ATS, sieving, ⑤ heating sieved ATS to 800 deg.C, maintaining for 2 hr, calcining while stirring to decompose ATS and avoid sintering, ⑥ cooling to obtain TiO2And sieving the powder with a 250-mesh sieve to obtain the finished product powder.
3. The method of claim 1, further comprising: the hydrogen-oxygen ratio for increasing the hydrogen flow is from 1.5: 1 to 1.8: 1.
4. The method of claim 1, further comprising: adjusting the oxygen amount of the inner tube to 350 liters/h, the oxygen amount of the outer tube to 120 liters/h, the hydrogen amount of the central tube to 200 liters/h to achieve a strong oxidizing atmosphere, and then increasing the hydrogen flow from 230 liters/h to 260 liters/h to increase the furnace temperature to ensure that the crystal grows in an equal diameter after shoulder expanding.
5. An apparatus for carrying out the process for artificially synthesizing rutile single crystals as set forth in claim 1, which comprises a burner and a furnace, characterized in that: the combustor is provided with an annular multi-path oxygen inlet device; the upper part of the inner wall of the hearth of the boiler is in a step shape.
6. The apparatus of claim 5, wherein: the annular multi-path oxygen inlet device is an annular outer pipe, the outer pipe is provided with an oxygen inlet for inputting oxygen, the wall of the burner is provided with a plurality of inclined holes, one end of each inclined hole is communicated with the outer pipe, and the other end of each inclined hole is communicated with the inner cavity of the burner.
7. The apparatus of claim 5, wherein: the number of the steps on the upper part of the inner wall of the hearth is more than 2.
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| CN105369342B (en) * | 2015-11-25 | 2017-10-31 | 沈阳工程学院 | A kind of sensing heating rutile monocrystal growth furnace and its prepare rutile method |
| CN111139530A (en) * | 2020-01-20 | 2020-05-12 | 北京科技大学 | Rutile TiO2Single crystal ultrahigh vacuum treatment process |
| CN111118602A (en) * | 2020-02-10 | 2020-05-08 | 沈阳工程学院 | Three-tube combustor based on crystal growth in oxygen-enriched atmosphere |
| CN114351240A (en) * | 2022-01-06 | 2022-04-15 | 沈阳工程学院 | Preparation method for preparing scandium acid dysprosium monocrystal precursor by flame melting method |
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