阅读说明：本技术 一种氧化钆粉体的制备工艺 (Preparation process of gadolinium oxide powder ) 是由 胡彩云 李汉文 黄榕华 于 2021-03-01 设计创作，主要内容包括：本发明公开了一种氧化钆粉体的制备工艺,包括晶种制备、沉淀剂制备、沉淀过程、除杂过程、烘干过程、煅烧和表征测试。本发明采用饱和溶液作晶种,通过加热尿素溶液分解氨气来进行分步沉淀,能够得到可控的微细粉末,最终的氧化钆粉体比表面积范围达10-10.9m～2/g。大比表面积的氧化钆粉体因其颗粒小、比表面积大,表面吸附力强,表面能大,化学纯度高、分散性能好、热阻、电阻等方面都具有特异的性能,能比较完美地提高陶瓷电容粉体电子元件的节能、环保、高效、轻巧的性能,为建设节能型、科技型社会提供了一条路径。(The invention discloses a preparation process of gadolinium oxide powder, which comprises the steps of seed crystal preparation, precipitant preparation, precipitation process, impurity removal process, drying process, calcination and characterization test. The invention adopts saturated solution as seed crystal, and carries out fractional precipitation by heating urea solution to decompose ammonia gas, controllable fine powder can be obtained, and the final gadolinium oxide powder has specific surface area ranging from 10m to 10.9m 2 (ii) in terms of/g. The gadolinium oxide powder with large specific surface area has specific properties in the aspects of small particles, large specific surface area, strong surface adsorption force, large surface energy, high chemical purity, good dispersion performance, thermal resistance, resistance and the like, can perfectly improve the energy-saving, environment-friendly, efficient and light properties of the ceramic capacitor powder electronic component, and provides a path for building an energy-saving and scientific society.)

1. The preparation process of the gadolinium oxide powder is characterized by comprising the following steps of:

1) preparing seed crystals: dissolving gadolinium oxide into a gadolinium chloride solution with the concentration of 1.1860M/L by using hydrochloric acid, then heating to boil, evaporating water until crystals are separated out, stopping heating to obtain gadolinium chloride feed liquid, and cooling for later use;

2) preparing a precipitator: weighing urea, pouring the urea into a reaction vessel with stirring, adding deionized water, stirring while heating to 70-90 ℃, controlling the stirring speed to be 250-350r/min, and then allowing a large amount of bubbles to emerge to obtain urea solution;

3) and (3) precipitation process: dropwise adding the gadolinium chloride feed liquid obtained in the step 1) into the urea liquid obtained in the step 2), adjusting the dropwise adding speed of the solution to be 13-17ml/min, keeping the temperature at 70-90 ℃ in the precipitation process, simultaneously controlling the stirring speed to be 100-120r/min, stopping stirring and heating after the precipitation is finished after stirring for 25-35min, and aging for one hour;

4) impurity removal process: after aging is finished, pumping out supernatant, discharging the precipitate into a washing barrel, adding deionized water to wash impurities, detecting the content of chloride ions in a water outlet after continuous washing for multiple times, controlling the conductivity to be less than 10us/cm, pumping out surface water after washing, adding absolute ethyl alcohol to wash, and then performing solid-liquid separation by using a centrifuge;

5) and (3) drying: putting the separated solid gadolinium salt wet material into a vacuum drying oven for drying, setting the initial temperature to be 60 ℃, then heating to 10 ℃ every hour, keeping the temperature for one hour after heating to 110 ℃, stopping heating, and sieving the obtained dried gadolinium salt by using a sieve with 80-100 meshes;

6) and (3) calcining: calcining the dried gadolinium salt in a muffle furnace, rapidly heating to 800-;

7) characterization test: heating and degassing the product, performing a low-temperature physical adsorption method in nitrogen, measuring the equilibrium adsorption pressure and the volume of nitrogen adsorbed on the surface of a sample, occupying the surface of gadolinium oxide powder particles with gas molecules to measure the gas adsorption amount, and calculating to determine the specific surface area of gadolinium oxide according to a BET equation: =×+the conversion shows that the specific surface area of the product is in the range of 10-10.9m²Between/g, according to the expected value.

2. The process for preparing gadolinium oxide powder according to claim 1, wherein the concentration of hydrochloric acid in step 1) is 30-31%.

3. The gadolinium oxide powder preparation process of claim 1, wherein in step 2), the weight ratio of urea to deionized water is 1: (4-5).

4. The process for preparing gadolinium oxide powder according to claim 1, wherein in step 2), the heating temperature is 90 ℃ and the stirring speed is 300 r/min.

5. The process for preparing gadolinium oxide powder according to claim 1, wherein in step 3), the dropping speed of the adjusting solution is 15ml/min, and the temperature is maintained at 90 ℃ during the precipitation process.

Technical Field

The invention relates to the technical field of chemical industry, in particular to a preparation process of gadolinium oxide powder.

Background

Gadolinium oxide is an important raw material of a novel rare earth functional material, is widely applied to the fields of fluorescent materials, single crystal materials, optical glass, magnetic materials and the like, and has higher requirements on the purity and the size of the gadolinium oxide in some high-end application fields, particularly in the MLCC (multilayer ceramic capacitor) industry. The gadolinium oxide powder with large specific surface area can greatly change the performance of the ceramic capacitor material, and the reliability of the MLCC ceramic powder can be effectively improved by adding a certain proportion of gadolinium oxide. The rare earth powder in the current market, particularly the rare earth oxide powder in the domestic market, can produce the rare earth oxide powder with large specific surface area only in the countries of Japan, Italy, Germany and the like, and the production quantity is limited. Therefore, the improvement of the large specific surface area of the gadolinium oxide powder has practical production and application significance for improving the performance of the MLCC ceramic powder.

Disclosure of Invention

The invention aims to provide a preparation process of gadolinium oxide powder, aiming at improving the large specific surface area of the gadolinium oxide powder.

In order to achieve the above purpose, the invention provides the following technical scheme:

a preparation process of gadolinium oxide powder comprises the following steps:

1) preparing seed crystals: dissolving gadolinium oxide into a gadolinium chloride solution with the concentration of 1.1860M/L by using hydrochloric acid, then heating to boil, evaporating water until crystals are separated out, stopping heating to obtain gadolinium chloride feed liquid, and cooling for later use;

2) preparing a precipitator: weighing urea, pouring the urea into a reaction vessel with stirring, adding deionized water, stirring while heating to 70-90 ℃, controlling the stirring speed to be 250-350r/min, and then allowing a large amount of bubbles to emerge to obtain a urea solution;

3) and (3) precipitation process: dropwise adding the gadolinium chloride feed liquid obtained in the step 1) into the urea solution obtained in the step 2), adjusting the dropwise adding speed of the solution to be 13-17ml/min, keeping the temperature at 70-90 ℃ in the precipitation process, simultaneously controlling the stirring speed to be 100-120r/min, stopping stirring and heating after the precipitation is finished after stirring for 25-35min, and aging for one hour; the stirring speed is controlled to be 100-120r/min, so that the pH value in the reaction process can be guaranteed to fluctuate within a certain range, and subsequent impurity removal is facilitated.

4) Impurity removal process: after aging is finished, pumping out supernatant, discharging the precipitate into a washing barrel, adding deionized water to wash impurities, detecting the content of chloride ions in a water outlet after continuous washing for multiple times, controlling the conductivity to be less than 10us/cm, pumping out surface water after washing, adding absolute ethyl alcohol to wash, and then performing solid-liquid separation by using a centrifuge;

5) and (3) drying: putting the separated solid gadolinium salt wet material into a vacuum drying oven for drying, setting the initial temperature to be 60 ℃, then heating to 10 ℃ every hour, keeping the temperature for one hour after heating to 110 ℃, stopping heating, and sieving the obtained dried gadolinium salt by using a sieve with 80-100 meshes; the condition of agglomeration of the solid gadolinium salt can be reduced by gradually drying, and the dispersion performance is good.

6) And (3) calcining: calcining the dried gadolinium salt in a muffle furnace, rapidly heating to 800-;

7) characterization test: heating and degassing the product, performing a low-temperature physical adsorption method in nitrogen, measuring the equilibrium adsorption pressure and the volume of nitrogen adsorbed on the surface of a sample, occupying the surface of gadolinium oxide powder particles with gas molecules to measure the gas adsorption amount, and calculating to determine the specific surface area of gadolinium oxide according to a BET equation: =×+the conversion shows that the specific surface area of the product is in the range of 10-10.9m²Between/g, according to the expected value.

In the step 1) of the invention, gadolinium oxide is dissolved into gadolinium chloride solution with 1.1860M/L concentration by using hydrochloric acid, when the concentration of reactants is in a lower level, the supersaturation degree of the solution is small, the nucleation driving power is small, the growth rate of crystal nucleus is greater than the formation rate and has enough time to grow up, the formed salt crystal is flat hexahedron, the surface is flat and smooth, and the monodispersity is good. When the concentration of reactants is in a higher level, the supersaturation degree of the solution is increased, the nucleation driving force is increased, a large number of small crystal nuclei are generated and then grow up, and a slender strip hexahedron or quadrangular prism structure with more regular appearance, more uniform granularity and good dispersibility is formed. Therefore, the reactant concentration should not be too low to form uniform salt precursor crystals. Therefore, the invention dissolves the gadolinium oxide into gadolinium chloride solution with 1.1860M/L concentration by using hydrochloric acid, and can generate uniform and regular salt precursor crystals.

The invention adopts urea solution as precipitant, in the prior art, oxalic acid solution is mainly used as precipitant, but rare earth oxide prepared by oxalate precipitation method has larger granularity and wide distribution, can not meet the special requirements of high and new materials, has low precipitation rate and high required cost, and adopts urea solution as precipitant and heats urea to gradually release NH₄The precipitation method has the advantages of low cost, high product yield, fine granularity, large specific surface area and mature industrialization.

The invention continuously heats and keeps the temperature at 70-90 ℃ in the precipitation process, can continuously decompose ammonia gas by continuously heating urea, and performs fractional precipitation by ammonia gas and gadolinium chloride feed liquid. Wherein the urea decomposition reaction formula is as follows:

（NH₂）₂CO+3H₂O=2NH₄OH+CO₂↑

the precipitation reaction is as follows:

GdCL₃+3NH₄OH=Gd（OH）3+3NH₄CL

the precipitant is slowly decomposed by chemical reaction in the solution, the precipitate uniformly appears in the whole solution, and the precipitate is in a quasi-equilibrium state in the precipitation process, so that the defect that the precipitate cannot uniformly appear in the whole solution due to local nonuniformity of the precipitant when the precipitant is added into the solution from the outside is overcome. The urea aqueous solution can be decomposed at 70-90 ℃ to produce NH₄OH, NH produced during slower reaction₄The OH can be distributed uniformly in the salt solution so that the precipitate is produced uniformly.

Further, the concentration of the hydrochloric acid in the step 1) is 30-31%. The concentration of the hydrochloric acid is set to be 30-31%, so that the high-concentration rare earth chloride gadolinium oxide powder can be obtained more easily.

Further, in the step 2), the weight ratio of the urea to the deionized water is 1: (4-5).

Further, in the step 2), the heating temperature is 90 ℃, and the stirring speed is 300 r/min.

Further, in the step 3), the dropping speed of the adjusting solution is 15ml/min, and the temperature is kept at 90 ℃ during the precipitation process.

Compared with the prior art, the preparation process of the gadolinium oxide powder provided by the invention has the following beneficial effects:

the invention adopts saturated gadolinium chloride solution as seed crystal, and the step-by-step precipitation is carried out by heating urea solution to decompose ammonia gas, controllable fine powder can be obtained, and the specific surface area range of the final gadolinium oxide powder reaches 10-10.9m²(ii) in terms of/g. The gadolinium oxide powder with large specific surface area has specific properties in the aspects of small particles, large specific surface area, strong surface adsorption force, large surface energy, high chemical purity, good dispersion performance, thermal resistance, resistance and the like, can perfectly improve the energy-saving, environment-friendly, efficient and light properties of the ceramic capacitor powder electronic component, and provides a path for building an energy-saving and scientific society.

Detailed Description

The present invention will be described in detail with reference to specific examples.

Example 1

A preparation process of gadolinium oxide powder comprises the following steps:

1) preparing seed crystals: dissolving 125g of gadolinium oxide with 30% hydrochloric acid to obtain a gadolinium chloride solution with the concentration of 1.1860M/L, heating to boil, evaporating water until crystals are separated out, stopping heating to obtain gadolinium chloride feed liquid, and cooling for later use;

2) preparing a precipitator: weighing 100g of urea, pouring the urea into a reaction vessel with a stirrer, adding 400ml of deionized water, stirring while heating to 70 ℃, controlling the stirring speed to be 250r/min, and then discharging a large amount of bubbles to obtain a urea solution;

3) and (3) precipitation process: dropwise adding the gadolinium chloride feed liquid obtained in the step 1) into the urea solution obtained in the step 2), adjusting the dropwise adding speed of the solution to be 17ml/min, keeping the temperature at 80 ℃ in the precipitation process, simultaneously controlling the stirring speed to be 100r/min, stopping stirring after 25min, stopping stirring, stopping heating, and aging for one hour; the stirring speed is controlled to be 100r/min, so that the pH value in the reaction process can be guaranteed to fluctuate within a certain range, and subsequent impurity removal is facilitated.

4) Impurity removal process: after aging is finished, pumping out supernatant, discharging the precipitate into a washing barrel, adding deionized water to wash impurities, detecting the content of chloride ions in a water outlet after continuous washing for multiple times, controlling the conductivity to be less than 10us/cm, pumping out surface water after washing, adding absolute ethyl alcohol to wash, and then performing solid-liquid separation by using a centrifuge;

5) and (3) drying: putting the separated solid gadolinium salt wet material into a vacuum drying oven for drying, setting the initial temperature to be 60 ℃, then heating to 10 ℃ every hour, keeping the temperature for one hour after heating to 110 ℃, stopping heating, and sieving the obtained dried gadolinium salt by using a sieve with 80-100 meshes;

6) and (3) calcining: calcining the dried gadolinium salt in a muffle furnace, quickly heating to 950 ℃ for 1 hour, keeping the temperature for 2 hours, naturally cooling to normal temperature, and sieving by a 150-mesh sieve to obtain gadolinium oxide powder;

7) characterization test: heating and degassing the product, performing a low-temperature physical adsorption method in nitrogen, measuring the equilibrium adsorption pressure and the volume of nitrogen adsorbed on the surface of a sample, occupying the surface of gadolinium oxide powder particles with gas molecules to measure the gas adsorption amount, and calculating to determine the specific surface area of gadolinium oxide according to a BET equation: =×+the specific surface area of the product was 10.4m in terms of conversion²In terms of/g, meets the expectations.

Example 2

A preparation process of gadolinium oxide powder comprises the following steps:

1) preparing seed crystals: dissolving 130g of gadolinium oxide with 31% hydrochloric acid to obtain a gadolinium chloride solution with the concentration of 1.1860M/L, heating to boil, evaporating water until crystals are separated out, stopping heating to obtain gadolinium chloride feed liquid, and cooling for later use;

2) preparing a precipitator: weighing 100g of urea, pouring the urea into a reaction vessel with a stirrer, adding 500ml of deionized water, stirring while heating to 80 ℃, controlling the stirring speed to be 350r/min, and then discharging a large amount of bubbles to obtain a urea solution;

3) and (3) precipitation process: dropwise adding the gadolinium chloride feed liquid obtained in the step 1) into the urea solution obtained in the step 2), adjusting the dropwise adding speed of the solution to be 13ml/min, keeping the temperature at 70 ℃ in the precipitation process, simultaneously controlling the stirring speed to be 120r/min, stopping stirring after 35min, stopping stirring, stopping heating, and aging for one hour; the stirring speed is controlled to be 120r/min, so that the pH value in the reaction process can be guaranteed to fluctuate within a certain range, and subsequent impurity removal is facilitated.

4) Impurity removal process: after aging is finished, pumping out supernatant, discharging the precipitate into a washing barrel, adding deionized water to wash impurities, detecting the content of chloride ions in a water outlet after continuous washing for multiple times, controlling the conductivity to be less than 10us/cm, pumping out surface water after washing, adding absolute ethyl alcohol to wash, and then performing solid-liquid separation by using a centrifuge;

5) and (3) drying: putting the separated solid gadolinium salt wet material into a vacuum drying oven for drying, setting the initial temperature to be 60 ℃, then heating to 10 ℃ every hour, keeping the temperature for one hour after heating to 110 ℃, stopping heating, and sieving the obtained dried gadolinium salt by using a sieve with 80-100 meshes;

6) and (3) calcining: calcining the dried gadolinium salt in a muffle furnace, quickly heating to 800 ℃ for 1 hour, keeping the temperature for 1.5 hours, naturally cooling to normal temperature, and sieving by a 200-mesh sieve to obtain gadolinium oxide powder;

7) characterization test: heating and degassing the product, performing a low-temperature physical adsorption method in nitrogen, measuring the equilibrium adsorption pressure and the volume of nitrogen adsorbed on the surface of a sample, occupying the surface of gadolinium oxide powder particles with gas molecules to measure the gas adsorption amount, and calculating to determine the specific surface area of gadolinium oxide according to a BET equation: =×+the specific surface area of the product is 10m in conversion²In terms of/g, meets the expectations.

Example 3

A preparation process of gadolinium oxide powder comprises the following steps:

1) preparing seed crystals: dissolving 120g of gadolinium oxide with 30% hydrochloric acid to obtain a gadolinium chloride solution with the concentration of 1.1860M/L, heating to boil, evaporating water until crystals are separated out, stopping heating to obtain gadolinium chloride feed liquid, and cooling for later use;

2) preparing a precipitator: weighing 186g of urea, pouring the urea into a reaction vessel with a stirrer, adding 500ml of deionized water, stirring while heating to 90 ℃, controlling the stirring speed to be 300r/min, and then discharging a large amount of bubbles to obtain a urea solution;

3) and (3) precipitation process: dropwise adding the gadolinium chloride feed liquid obtained in the step 1) into the urea solution obtained in the step 2), adjusting the dropwise adding speed of the solution to be 15ml/min, keeping the temperature at 90 ℃ in the precipitation process, simultaneously controlling the stirring speed to be 110r/min, stopping stirring after 30min, stopping stirring, stopping heating, and aging for one hour; the stirring speed is controlled to be 110r/min, so that the pH value in the reaction process can be guaranteed to fluctuate within a certain range, and subsequent impurity removal is facilitated.

4) Impurity removal process: after aging is finished, pumping out supernatant, discharging the precipitate into a washing barrel, adding deionized water to wash impurities, detecting the content of chloride ions in a water outlet after continuous washing for multiple times, controlling the conductivity to be less than 10us/cm, pumping out surface water after washing, adding absolute ethyl alcohol to wash, and then performing solid-liquid separation by using a centrifuge;

5) and (3) drying: putting the separated solid gadolinium salt wet material into a vacuum drying oven for drying, setting the initial temperature to be 60 ℃, then heating to 10 ℃ every hour, keeping the temperature for one hour after heating to 110 ℃, stopping heating, and sieving the obtained dried gadolinium salt by using a sieve with 80-100 meshes;

6) and (3) calcining: calcining the dried gadolinium salt in a muffle furnace, quickly heating to 900 ℃ for 1 hour, keeping the temperature for 1.8 hours, naturally cooling to normal temperature, and sieving by a 180-mesh sieve to obtain gadolinium oxide powder;

7) characterization test: heating and degassing the product, performing a low-temperature physical adsorption method in nitrogen, measuring the equilibrium adsorption pressure and the volume of nitrogen adsorbed on the surface of a sample, occupying the surface of gadolinium oxide powder particles with gas molecules to measure the gas adsorption amount, and calculating to determine the specific surface area of gadolinium oxide according to a BET equation: =×+the specific surface area of the product was 10.9m in terms of conversion²In terms of/g, meets the expectations.

Comparative example 1

The difference from example 3 is that the precipitant in comparative example 1 is a solution of industrial oxalic acid, which is prepared by dissolving industrial oxalic acid with deionized water to a concentration of 15% at a temperature of 20-25 c, and filtering to obtain the precipitant.

Comparative example 2

The difference from example 3 is that the temperature was maintained at normal temperature during the precipitation in step 3) of comparative example 2.

Comparative example 3

The difference from example 3 is that comparative example 3 does not include a drying process.

The gadolinium oxide powders obtained in examples 1 to 3 and comparative examples 1 to 3 were prepared by the BET equation: =×+the specific surface area was measured, and the results are shown in table 1:

TABLE 1

	Specific surface area
		Example 1	10.4m2/g
Example 2	10m2/g
		Example 3	10.9m2/g
Comparative example 1	5.0m2/g
		Comparative example 2	4.6m2/g
Comparative example 3	7.3m2/g

As can be seen from Table 1, the specific surface areas of examples 1 to 3 are much better than those of comparative examples 1 to 3. Comparing comparative example 1 and example 3, it is clear that the specific surface area of the gadolinium oxide powder can be greatly increased by using urea instead of industrial oxalic acid in the precipitant. As is clear from comparison between comparative example 2 and example 3, when the temperature during the precipitation process is normal temperature, the specific surface area of the gadolinium oxide powder is greatly reduced. As can be seen from comparison between comparative example 3 and example 3, the specific surface area of the gadolinium oxide powder is reduced to some extent without performing the drying step.

The features of the embodiments and embodiments described above may be combined with each other without conflict.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.