CN105502313B - A method for preparing gallium nitride nanocrystals using a twin-screw extruder - Google Patents

Abstract

The invention belongs to the field of inorganic compound semiconductor materials, and particularly relates to a method for preparing gallium nitride nanocrystals by using a double-screw extruder. Dissolving metal gallium salt in a water-soluble polymer aqueous solution to form slurry, pumping the slurry into a double-screw extruder, allowing the slurry to pass through a dispersing threaded element to coat the gallium salt in a hydrogel network structure formed by water-soluble polymers, and carbonizing the water-soluble polymers under shearing and high temperature conditions to form the gallium salt coated by a carbon network structure; adding thermoplastic rubber through an auxiliary material port, mixing and reacting, and forming a sheet through extrusion; and (3) drying the sheet in a tubular furnace, raising the temperature of the tubular furnace to 900-1200 ℃, introducing ammonia gas for reaction for 120-150 min, and stopping introducing the ammonia gas and cooling to room temperature in an argon atmosphere to obtain the light yellow gallium nitride nanocrystal with a regular crystal form. The gallium nitride crystal prepared by the method has the advantages of good surface appearance, regular crystal form, high yield, high purity and wide application value.

Description

A method for preparing gallium nitride nanocrystals using a twin-screw extruder

technical field

The invention belongs to the field of inorganic compound semiconductor materials, in particular to a method for preparing gallium nitride nanocrystals by using a twin-screw extruder.

Background technique

Gallium nitride, together with semiconductor materials such as silicon carbide (SiC) and diamond, is known as the third-generation semiconductor material. Compared with traditional silicon-based and gallium arsenide-based semiconductor materials, third-generation semiconductor materials such as gallium nitride are due to their The unique band gap range, excellent optical and electrical properties and excellent material properties can meet the working requirements of high-power, high-temperature, high-frequency and high-speed semiconductor devices, and have a wide range of applications in the automotive and aviation industries, medical, military and general lighting application prospects.

GaN material is a direct transition wide bandgap semiconductor material with a wide direct bandgap of 3.4eV. It is also an extremely stable and hard material with a high melting point. It has high electron saturation rate, small dielectric coefficient, good thermal conductivity and resistance Excellent properties such as high radiation intensity are ideal materials for making light-emitting diodes (LEDs), laser diodes (LDs) and high-temperature high-power integrated circuits. GaN also has strong atomic bonds, high thermal conductivity, good chemical stability (hardly corroded by any acid), high breakdown voltage and strong radiation resistance, etc. It is used in the synthesis of high-temperature gas sensor materials, high-density Information storage, high-speed laser printing, ultraviolet detectors, high-frequency microwave devices, and high-density integrated circuits also have broad application potential. Therefore, GaN materials have become a research hotspot in the field of optoelectronic materials.

Due to its unique structure and optoelectronic properties, gallium nitride nanocrystals have great application prospects. At present, the preparation of GaN materials can be obtained by chemical vapor deposition, pulsed laser deposition, sol-gel method, molecular beam epitaxy, etc. For example, Chinese Patent Publication No. CN101774552A discloses a preparation method of GaN nanocrystals. First, Ga ₂ O ₃

Add it into concentrated nitric acid, use microwave hydrothermal heating to form GaO ₂ H nanorods, then put GaO ₂ H nanorods powder into a tube furnace, react with ammonia gas at high temperature to obtain light yellow GaN nanocrystals, the advantages are The raw materials are relatively cheap, and the process is simple to operate. However, due to the need to use concentrated nitric acid in the preparation process, the safety factor is low, and the precursor nanorods are not conducive to the growth of gallium nitride crystals, so it is difficult to obtain high-quality gallium nitride crystals.

Chinese Patent Publication No. CN1944268 discloses a method for preparing gallium nitride nanocrystals by a sol-gel method. First, a gallium oxide/amorphous carbon mixture is prepared by a sol-gel method, that is, gallium nitrate is dissolved in concentrated nitric acid, and citric acid is added. After heating and stirring for 2 hours, it becomes a transparent gel after cooling, put it into a ceramic tube after drying, and react with ammonia gas at a temperature of 850-950°C to obtain light yellow GaN nanocrystals. This method can produce a large number of particle diameters smaller than or equal to Bohr excitons However, due to the need to use concentrated nitric acid in the preparation process, the safety factor is low, and the area of the prepared nanocrystal is small, which affects the performance of the gallium nitride crystal and is not conducive to large-scale production.

However, in the above-mentioned method, due to the low crystal growth rate, long period, and the irregular shape of the generated crystals, the quality of gallium nitride nanocrystals is affected, and it is not easy to popularize the large-scale industrial production of gallium nitride nanocrystals. Therefore, it is necessary to find a simple The preparation of high-quality GaN nanocrystals quickly, quickly and cheaply has become the unremitting goal of researchers in the field of optoelectronic materials.

Contents of the invention

Aiming at the above problems, the present invention proposes a method for preparing gallium nitride nanocrystals using a twin-screw extruder. The method firstly dissolves metal gallium salt in water-soluble polymer aqueous solution to form a slurry, pumps the slurry into a twin-screw extruder, and the slurry passes through the dispersing screw element, so that the gallium salt is coated on the water-soluble polymer to form a condensate. In the glue network structure, the water-soluble polymer is carbonized under shear and high temperature conditions to form gallium salt covered by the carbon network structure; thermoplastic glue is added through the auxiliary material port, and the mixing reaction is extruded to form a thin sheet to obtain a thin sheet Preparation of gallium nitride crystals as gallium source and template for crystal growth. The preparation method of the present invention has good repeatability, low cost, no catalysis, no template, and is also environmentally friendly, and the grown gallium nitride crystal has good morphology, regular crystal form, high yield and high purity, and has good application prospect.

To achieve the above object, the present invention adopts the following technical solutions:

A method for preparing gallium nitride nanocrystals using a twin-screw extruder, characterized in that: using a twin-screw extruder as a reactor to prepare gallium nitride nanocrystals, comprising the following steps:

(1) Prepare water-soluble polymer and water to form a water-soluble polymer aqueous solution with a concentration of 60-120 g/L, mix metal gallium salt powder into the water-soluble polymer aqueous solution, and mix in a high-speed mixer at 3000-5000 Stir and mix at a speed of rpm for 10-20 minutes to obtain a mixed slurry;

(2) Pump the slurry obtained in step (1) into the feeding port of the twin-screw extruder, set the reaction temperature of the dispersing screw element section to 100~150°C, and pass the slurry through the dispersing screw element to coat the gallium salt in the water-soluble In the hydrogel network structure formed by the permanent polymer; then by shearing and carbonizing the screw element, the reaction temperature of this section is set at 180~240°C, and the water-soluble polymer is carbonized under the conditions of shearing and high temperature to form a carbon network structure. Coated gallium salt; add thermoplastic glue through the auxiliary material port, set the reaction temperature at 250~300°C, mix and react for 10~15min, and then form thin sheets by extrusion;

(3) Put the flakes obtained in step (2) into an aluminum oxide crucible, put them into the central constant temperature zone of the tube furnace, and dry them in an air atmosphere of 180~250°C for 15~30min;

(4) Introduce argon gas with a flow rate of 50 sccm into the tube furnace, raise the temperature of the tube furnace to 900~1200°C, control the heating rate at 8~20°C/min, stop argon gas flow, and feed in a flow rate of React with ammonia gas of 50-100 sccm for 120-150 min, stop the ammonia gas and replace it with argon gas for protection, cool to room temperature in an argon atmosphere, and obtain pale yellow gallium nitride nanocrystals.

The water-soluble polymer described in the above step (1) is at least one of polyacrylamide, polyacrylic acid, polyethylene glycol, and hydroxymethyl cellulose; the metal gallium salt is gallium nitrate, gallium chloride , gallium acetate, and gallium oxalate; the amount of the water-soluble polymer is 12-20% of the mass of the metal gallium salt.

The thermoplastic adhesive in the above step (2) is at least one of thermoplastic polyurethane, thermoplastic acrylic, and thermoplastic styrene-butadiene rubber; the amount of the thermoplastic adhesive is 4-8% of the mass of the water-soluble polymer.

For the twin-screw extruder described in the above step (2), the length-to-diameter ratio of the screw is 40~45:1; the screw is set at one time from the feed end to the end as a dispersed thread element, a shear carbonized thread element, a compressed thread element, A reverse threaded element, wherein a sheet die is disposed between the compression threaded element and the reversed threaded element.

The invention discloses a method for preparing gallium nitride nanocrystals using a twin-screw extruder. First, metal gallium salt is dissolved in a water-soluble polymer aqueous solution, and a slurry is formed under high-speed stirring, and the slurry is pumped into a twin-screw extruder. machine, the slurry passes through the dispersing screw element, so that the gallium salt is coated in the hydrogel network structure formed by the water-soluble polymer, and the water-soluble polymer is carbonized under the conditions of shear and high temperature to form a carbon network structure-coated Gallium salt: thermoplastic glue is added through the auxiliary material port, the mixing reaction is extruded to form a thin sheet, and the thin sheet is used as a gallium source and a template for crystal growth and placed in a tube furnace. Under high temperature conditions, ammonia diffuses evenly into the sheet through the carbon network structure , and the nitridation reaction occurs with the gallium salt wrapped in the network structure, so that the gallium nitride nanocrystals grow uniformly on the thin sheet template. The mixture flake formed by twin-screw extrusion has a carbon network structure, which is conducive to the uniform distribution of the gallium source, increases the surface area of the reactant, and enables the ammonia gas to completely and rapidly react with the gallium source for nitriding, and the flake is nitriding The growth of gallium crystals provides a template, so that the crystals grow uniformly on the thin slices, forming nanocrystals with good morphology and regular crystal structure. At the same time, the thermoplastic glue in the sheet decomposes and carbonizes under high temperature conditions, which will not affect the purity of gallium nitride nanocrystals. The gallium nitride crystal prepared by the invention not only has high purity and fast reaction, but also the generated nano crystal has better shape and complete crystal structure.

A method for preparing gallium nitride nanocrystals using a twin-screw extruder in the present invention has outstanding features and beneficial effects compared with the prior art:

1. The present invention uses a twin-screw extruder to prepare gallium nitride nanocrystals. The gallium salt is coated in a hydrogel network structure formed by a water-soluble polymer, and the twin-screw extrusion reaction is used to form a carbon nanocrystal. Gallium salt flakes coated with a network structure, using the flakes as gallium sources and templates to prepare gallium nitride crystals, increase the surface area of the reactants, so that ammonia can completely and rapidly react with the gallium source for nitriding, and the flakes are nitrided The growth of gallium crystals provides a template, so that the crystals grow uniformly on the thin slices, forming nanocrystals with good morphology and regular crystal structure.

2. The gallium nitride crystal prepared by the present invention has good morphology, regular crystal form, high yield, high purity, high crystal growth rate, short synthesis time, and good application prospects.

3. The method for preparing gallium nitride nanocrystals provided by the present invention has the advantages of good repeatability of the preparation method, low cost of raw materials, low production technical requirements, no catalysis, no template, and is environmentally friendly, easy to promote and scale production, etc. advantage.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments, and the present invention is not limited thereto. Without departing from the idea of the above-mentioned method of the present invention, various replacements or improvements made according to common technical knowledge and conventional means in this field shall be included in the protection scope of the present invention.

Example 1

(1) Prepare polyacrylamide and water to make a polyacrylamide aqueous solution with a concentration of 60 g/L, mix gallium nitrate powder into the polyacrylamide aqueous solution, and the amount of polyacrylamide is 12% of the amount of gallium nitrate; Stir and mix at a speed of 3000 rpm in a high-speed mixer for 20 min to obtain a mixed slurry;

(2) Pump the slurry obtained in step (1) into the feeding port of the twin-screw extruder, set the reaction temperature of the dispersing screw element section to 100°C, and pass the slurry through the dispersing screw element, so that the gallium salt is coated on the polyacrylamide In the formed hydrogel network structure; then by shearing and carbonizing the threaded element, set the reaction temperature of this section to 240°C, and carbonize the polyacrylamide molecules under shear and high temperature conditions to form a gallium salt covered by the carbon network structure ; Add 4% thermoplastic polyurethane with an amount of water-soluble polymer through the auxiliary material port, set the reaction temperature to 250°C, knead and react for 15 minutes, and then form flakes by extrusion;

(3) Place the flakes obtained in step (2) in an aluminum oxide crucible, put them in the central constant temperature zone of the tube furnace, and dry them in an air atmosphere of 180°C for 30 minutes;

(4) Introduce argon gas with a flow rate of 50 sccm into the tube furnace, raise the temperature of the tube furnace to 900°C, control the heating rate at 8°C/min, stop argon flow, and feed ammonia with a flow rate of 100 sccm Gas reaction was carried out for 120 min, the ammonia gas was stopped and replaced with argon gas for protection, and cooled to room temperature in an argon atmosphere to obtain pale yellow gallium nitride nanocrystals.

Example 2

(1) Prepare polyacrylic acid and water to make a polyacrylic acid aqueous solution with a concentration of 90 g/L, mix gallium chloride powder into the polyacrylic acid aqueous solution, and the amount of polyacrylic acid is 15% of the amount of gallium chloride; Stir and mix at a speed of 3500rpm for 15 min to obtain a mixed slurry;

(2) Pump the slurry obtained in step (1) into the feeding port of the twin-screw extruder, set the reaction temperature of the dispersing screw element section to 120 °C, and pass the slurry through the dispersing screw element, so that the gallium salt is coated on the polyacrylic acid to form In the hydrogel network structure; then by shearing the carbonized screw element, set the reaction temperature of this section to 200 ° C, and carbonize the polyacrylic acid molecules under shear and high temperature conditions to form a gallium salt covered by the carbon network structure; Add thermoplastic acrylic acid with an amount of 5% of the amount of water-soluble polymer in the auxiliary material port, set the reaction temperature to 250°C, knead and react for 15 minutes, and then form flakes by extrusion;

(3) Place the flakes obtained in step (2) in an aluminum oxide crucible, put them in the central constant temperature zone of the tube furnace, and dry them in an air atmosphere at 200 °C for 25 min;

(4) Introduce argon gas with a flow rate of 50 sccm into the tube furnace, raise the temperature of the tube furnace to 1000°C, control the heating rate at 10°C/min, stop argon flow, and feed ammonia with a flow rate of 80 sccm Gas reaction was carried out for 120 min, the ammonia gas was stopped and replaced with argon gas for protection, and cooled to room temperature in an argon atmosphere to obtain pale yellow gallium nitride nanocrystals.

Example 3

(1) Prepare polyethylene glycol and water to make a polyethylene glycol aqueous solution with a concentration of 100 g/L, mix gallium acetate powder into the polyethylene glycol aqueous solution, and the amount of polyethylene glycol is equal to the amount of gallium acetate 18%; In a high-speed mixer, stir and mix at a speed of 4000rpm for 15 min to obtain a mixed slurry;

(2) Pump the slurry obtained in step (1) into the feed port of the twin-screw extruder, set the reaction temperature of the dispersing screw element section to 150°C, and pass the slurry through the dispersing screw element to coat the gallium salt on the polyethylene In the hydrogel network structure formed by alcohol; then by shearing and carbonizing the screw element, set the reaction temperature of this section to 200°C, and carbonize the polyethylene glycol molecules under the conditions of shearing and high temperature to form a carbon network structure-coated Gallium salt; add thermoplastic styrene-butadiene rubber in an amount of 6% of the amount of water-soluble polymer through the auxiliary material port, set the reaction temperature at 280 °C, mix and react for 12 minutes, and then form thin sheets by extrusion;

(3) Place the flakes obtained in step (2) in an aluminum oxide crucible, put them in the central constant temperature zone of the tube furnace, and dry them in an air atmosphere at 230 °C for 20 min;

(4) Introduce argon gas with a flow rate of 50 sccm into the tube furnace, raise the temperature of the tube furnace to 1100°C, control the heating rate at 15°C/min, stop argon flow, and feed ammonia with a flow rate of 60 sccm Gas reaction was carried out for 150 min, the ammonia gas was stopped and replaced with argon gas for protection, and cooled to room temperature in an argon atmosphere to obtain pale yellow gallium nitride nanocrystals.

Example 4

(1) Mix hydroxymethyl cellulose and water to make a hydroxymethyl cellulose aqueous solution with a concentration of 120 g/L, mix gallium oxalate powder into the hydroxymethyl cellulose aqueous solution, and the dosage of hydroxymethyl cellulose is 20% of the amount of gallium oxalate; stir and mix for 10 min at a speed of 4500 rpm in a high-speed mixer to obtain a mixed slurry;

(2) Pump the slurry obtained in step (1) into the feeding port of the twin-screw extruder, set the reaction temperature of the dispersing screw element section to 150°C, and pass the slurry through the dispersing screw element, so that the gallium salt is coated on the methylol In the hydrogel network structure formed by cellulose; then by shearing and carbonizing the screw element, set the reaction temperature of this section to 180 ℃, and carbonize the hydroxymethyl cellulose molecules under the conditions of shearing and high temperature to form a carbon network structure wrapped Gallium salt coated; add thermoplastic glue with an amount of 7% of the amount of water-soluble polymer through the auxiliary material port, set the reaction temperature at 300 °C, knead and react for 10 minutes, and then form a thin sheet by extrusion;

(3) Place the flakes obtained in step (2) in an aluminum oxide crucible, put them in the central constant temperature zone of the tube furnace, and dry them in an air atmosphere of 250 °C for 15 min;

(4) Introduce argon gas with a flow rate of 50 sccm into the tube furnace, raise the temperature of the tube furnace to 1150°C, control the heating rate at 20°C/min, stop argon flow, and feed ammonia with a flow rate of 50 sccm Gas reaction was carried out for 150 min, the ammonia gas was stopped and replaced with argon gas for protection, and cooled to room temperature in an argon atmosphere to obtain pale yellow gallium nitride nanocrystals.

Example 5

(1) Prepare polyethylene glycol and water to make a polyethylene glycol aqueous solution with a concentration of 120 g/L, mix gallium nitrate powder into the polyethylene glycol aqueous solution, and the dosage of polyethylene glycol is 1/2 of that of gallium nitrate 20%; Stir and mix at a speed of 5000rpm in a high-speed mixer for 10min to obtain a mixed slurry;

(2) Pump the slurry obtained in step (1) into the feed port of the twin-screw extruder, set the reaction temperature of the dispersing screw element section to 150°C, and pass the slurry through the dispersing screw element to coat the gallium salt on the polyethylene In the hydrogel network structure formed by alcohol; then by shearing and carbonizing the screw element, set the reaction temperature of this section to 200 °C, and carbonize the polyethylene glycol molecules under the conditions of shearing and high temperature to form a carbon network structure-coated Gallium salt; add thermoplastic polyurethane in an amount of 8% of the amount of polyethylene glycol through the auxiliary material port, set the reaction temperature to 300°C, knead and react for 10 minutes, and then form a thin sheet by extrusion;

(3) Place the flakes obtained in step (2) in an aluminum oxide crucible, put them in the central constant temperature zone of the tube furnace, and dry them in an air atmosphere at 250 °C for 20 min;

(4) Introduce argon gas with a flow rate of 50 sccm into the tube furnace, raise the temperature of the tube furnace to 1200°C, control the heating rate at 20°C/min, stop argon flow, and feed ammonia with a flow rate of 80 sccm Gas reaction was carried out for 120 min, the ammonia gas was stopped and replaced with argon gas for protection, and cooled to room temperature in an argon atmosphere to obtain pale yellow gallium nitride nanocrystals.

Claims (3)

1. A kind of 1. method that gallium nitride nano crystal is prepared using double screw extruder, it is characterised in that:Utilize twin-screw extrusion Machine prepares gallium nitride nano crystal for reactor, and specific preparation method comprises the following steps：

   （1）Water soluble polymer and water are configured to the water soluble polymer aqueous solution that concentration is 60 ~ 120 g/L, by gallium Salt powder is mixed to join in water soluble polymer aqueous solution, is stirred in homogenizer with the speed of 3000 ~ 5000 rpm 10 ~ 20 min of mixing obtain mixed slurry；

   （2）By step（1）In obtained slurry be pumped into double screw extruder charge door, scattered screwing element section reaction temperature is set It spends for 100 ~ 150 DEG C, slurry makes gallium salt be coated on the hydrogel network knot of water soluble polymer formation by disperseing screwing element In structure；Then by shearing the screwing element that is carbonized, this section of reaction temperature is set for 180 ~ 240 DEG C, under shearing and hot conditions Water soluble polymer is made to be carbonized, forms the gallium salt coated by carbon network structure；Thermoplastic cement is added in by auxiliary material mouth, reaction is set Temperature is 250 ~ 300 DEG C, is kneaded 10 ~ 15min of reaction, then forms thin slice by squeezing；The wherein described double screw extruder, Screw slenderness ratio is 40 ~ 45:1；Screw rod is once arranged to scattered screwing element, shearing carbonization screw thread member by feed end terminad Part, compression screwing element, reverse-flight elements, wherein setting sheet die between compression screwing element and reverse-flight elements；

   （3）By step（2）In obtained thin slice be placed in alundum (Al2O3) crucible, be put into the middle part flat-temperature zone of tube furnace, 180 ~ Dry 15 ~ 30min under 250 DEG C of air atmosphere；

   （4）The argon gas that flow is 50sccm is passed through into tube furnace, the temperature of tube furnace is warming up to 900 ~ 1200 DEG C, control rises Warm rate is 8 ~ 20 DEG C/min, stops logical argon gas, is passed through the ammonia that flow is 50 ~ 100 sccm and reacts 120 ~ 150 min, stops Logical ammonia changes argon gas into and is protected, and is cooled to room temperature in argon atmosphere, obtains faint yellow gallium nitride nano crystal.
2. 2. a kind of method that gallium nitride nano crystal is prepared using double screw extruder according to claim 1, feature It is step（1）Described in water soluble polymer be polyacrylamide, polyacrylic acid, polyethylene glycol, in hydroxymethyl cellulose At least one；The gallium salt is at least one of gallium nitrate, gallium chloride, acetic acid gallium, oxalic acid gallium；Described is water-soluble Property high molecular dosage be gallium salt quality 12 ~ 20%.
3. 3. a kind of method that gallium nitride nano crystal is prepared using double screw extruder according to claim 1, feature It is step（2）Described in thermoplastic cement be thermoplastic polyurethane, thermoplastic acrylic, in thermoplastic styrene butadiene rubber at least It is a kind of；The dosage of thermoplastic cement is the 4 ~ 8% of water soluble polymer quality.