CN108772569B - Hydrothermal preparation method of superfine nano tungsten powder - Google Patents

Hydrothermal preparation method of superfine nano tungsten powder Download PDF

Info

Publication number
CN108772569B
CN108772569B CN201810657397.XA CN201810657397A CN108772569B CN 108772569 B CN108772569 B CN 108772569B CN 201810657397 A CN201810657397 A CN 201810657397A CN 108772569 B CN108772569 B CN 108772569B
Authority
CN
China
Prior art keywords
hydrothermal
reaction
tungsten powder
powder
nano tungsten
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201810657397.XA
Other languages
Chinese (zh)
Other versions
CN108772569A (en
Inventor
马宗青
扈伟强
董智
柳楠
刘永长
王祖敏
余黎明
李冲
刘晨曦
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tianjin University
Original Assignee
Tianjin University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tianjin University filed Critical Tianjin University
Priority to CN201810657397.XA priority Critical patent/CN108772569B/en
Publication of CN108772569A publication Critical patent/CN108772569A/en
Application granted granted Critical
Publication of CN108772569B publication Critical patent/CN108772569B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER
    • B22F9/00Making metallic powder or suspensions thereof
    • B22F9/16Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/20Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds
    • B22F9/22Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from solid metal compounds using gaseous reductors
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B82NANOTECHNOLOGY
    • B82YSPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00Manufacture or treatment of nanostructures

Abstract

The invention provides a hydrothermal preparation method of superfine nano tungsten powder. Respectively dissolving one or more of dispersing agents cetyl trimethyl ammonium bromide CTAB, sodium dodecyl benzene sulfonate SDBS or sodium dodecyl sulfate SDS and ammonium metatungstate in water, clarifying, mixing, adjusting pH with nitric acid or hydrochloric acid, and performing ultrasonic treatment to fully disperse and dissolve to obtain a solution; placing the mixture into a reaction kettle for hydrothermal reaction; filtering, washing and drying suspension obtained by reaction after reaction; finally, hydrogen is used for two-step reduction to obtain the superfine nano tungsten powder. The hydrothermal preparation method by adding the dispersing agent has the advantages of no pollution and low cost, and the prepared powder has pure phase, small agglomeration and small crystal grains, the average crystal grain size reaches 10-30 nm, and the grain size distribution is extremely narrow. The method for preparing the superfine nano tungsten powder has obvious advantages.

Description

Hydrothermal preparation method of superfine nano tungsten powder
Technical Field
The invention provides a technology of a hydrothermal preparation method of ultrafine nano tungsten powder added with a dispersing agent, belonging to the technical field of powder preparation engineering.
Background
Compared with the common polycrystalline material, the nano material has more excellent mechanical property and is considered as a novel material with very wide application prospect in the 21 st century. The nano tungsten powder is used for preparing superfine (nano) tungsten hard alloy and other materials. It is the raw material of high quality X-ray tube tungsten target and tungsten foil with thickness up to micron level, on the other hand, the production of ultra-fine grain hard alloy must use ultra-fine tungsten powder as raw material. The ultra-fine grain hard alloy has high hardness, wear resistance, red hardness and higher obdurability, can solve the processing problem of certain special materials, and is widely used for manufacturing metal cutting tools, micro drills of printed circuit boards, needles of dot matrix printers and other precision tools, precision dies, wear-resistant parts and the like. In addition, the nano tungsten powder has great demand in the fields of electronic industry, fine chemical industry, surface technology, aerospace industry and the like.
The ultra-fine nano powder generally refers to powder with the diameter of less than 100nm and has extremely high sintering activity. For the nano tungsten powder, the crystal grain is smaller, the crystal boundary is more, the impurity elements are distributed more uniformly, and the ductile-brittle transition temperature is also reduced; the smaller the crystal grain, the more the recovery and recrystallization at high temperature are hindered, the higher the recrystallization temperature is, the lower the low-temperature brittleness is; the smaller the crystal grain, the higher the strength hardness and the plastic toughness. However, the finer the nano tungsten powder is, the more difficult the preparation is.
The existing preparation methods of the superfine nano tungsten powder comprise the traditional methods such as a high-energy ball milling method, a gas evaporation method, a self-propagating high-temperature reduction method, a tungstate method, a spray drying method and the like, and each method has certain limitations. The hydrothermal preparation method is rarely related, and the related literature of preparing about 10nm of ultrafine nano tungsten powder by the hydrothermal method is not shown. Under the hydrothermal environment, the metal salt solution can precipitate metal oxide to obtain metal oxide with smaller crystal grains, and tungsten crystal grains obtained during the subsequent hydrogen reduction are smaller. Impurities are not introduced in the hydrothermal method, crystal grains are smaller, but metal oxides precipitated later in the hydrothermal process are deposited on the metal oxide crystal grains precipitated earlier, and the crystal grains grow and are agglomerated. The invention provides a technology of a hydrothermal preparation method for preparing ultrafine nano tungsten powder by adding a dispersing agent.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a hydrothermal preparation technology for preparing ultrafine nano tungsten powder by adding a dispersing agent, and the high-purity and uniform mixing is realized. The average grain size of the obtained composite powder can be as fine as about 10nm by the technology, and the grain size distribution is extremely narrow. The basic principle of the hydrothermal preparation is that ammonium metatungstate is fully dissolved and hydrolyzed at high temperature and high pressure to generate oxide.
When the dispersing agents cetyl trimethyl ammonium bromide CTAB, sodium dodecyl benzene sulfonate SDBS and sodium dodecyl sulfate SDS are added, an adsorption layer is formed on the surface when tungsten oxide is separated out, a layer of film consisting of the dispersing agents is formed, so that the charges on the surface of solid particles are increased, the solid particles mutually repel due to the same charges, the reaction force between the particles forming the three-dimensional obstruction is improved, the particle aggregation is inhibited in the solidification process, and the growth of crystal grains is reduced. The hydrothermal preparation method by adding the dispersing agent has the advantages of no pollution and low cost, and the prepared powder has pure phase, small agglomeration and small crystal grains, the average crystal grain size reaches 10-30 nm, and the grain size distribution is extremely narrow.
The specific technical scheme is as follows:
a hydrothermal preparation method of ultrafine nano tungsten powder is characterized by comprising the following steps:
(1) respectively dissolving a dispersing agent and ammonium metatungstate in deionized water, mixing the materials together after clarification, adjusting the pH to 1-3, and carrying out ultrasonic treatment for 0.33-1.5 h with the ultrasonic power of 100-200W to obtain a mixed solution;
(2) then carrying out hydrothermal reaction in a reaction kettle, and filtering, washing and drying the suspension after the reaction;
(3) finally, pure hydrogen is used for two-step reduction to obtain the superfine nano tungsten powder.
The dispersing agent in the step (1) is one or more of cetyl trimethyl ammonium bromide CTAB, sodium dodecyl benzene sulfonate SDBS or sodium dodecyl sulfate SDS; the mass of the dispersing agent is 2-10% of that of the ammonium metatungstate.
In the step (1), the concentration of the ammonium metatungstate in the mixed solution is as follows: 0.03-0.1 g/mL; adjusting the pH value to 1-3 by using nitric acid or hydrochloric acid.
The filling amount of the reaction kettle in the step (2) is 70-90%; the hydrothermal reaction temperature is 170-190 ℃, and the heat preservation time is 24-36 h; filtering with deionized water or distilled water for 2-4 times.
The temperature and time of the two-step reduction in the step (3) are respectively as follows: 550-650 ℃ for 1-2 h; 700-800 ℃ for 1.5-2.5 h. The invention has the advantages that:
1. compared with the traditional mechanical alloying method, the hydrothermal preparation method can realize accurate regulation and control on the size and the shape of the crystal grain on the basis of ensuring the purity, and the whole process has no pollution.
2. By a hydrothermal preparation method of adding different dispersing agents, crystal grains are obviously refined, and ultrafine nano tungsten powder with the particle size of about 10nm can be obtained by the finest.
3. Compared with other processes, the powder prepared by a hydrothermal method with the addition of the dispersing agent has dozens of times smaller grains and extremely narrow particle size distribution, so that the temperature is reduced by 100-200 ℃ in the subsequent calcining and reducing processes, the required calcining and reducing time is relatively shortened by 0.5-2 h, and the waste of resources is reduced.
4. The method not only can realize the preparation of the superfine nano tungsten powder, but also is very suitable for preparing a large amount of powder in a single batch.
Drawings
FIG. 1: SEM picture of ultra-fine nano tungsten powder prepared in example 1;
FIG. 2: XRD pictures of the ultra-fine nano tungsten powder prepared in example 1;
FIG. 3: SEM picture of ultra-fine nano tungsten powder prepared in example 2;
FIG. 4: SEM picture of ultra-fine nano-tungsten powder prepared in example 4;
FIG. 5: SEM picture of ultra-fine nano-tungsten powder prepared in example 5.
Detailed Description
The features of the present invention are further described below by way of examples, but the present invention is not limited to the following examples.
Example 1
(1) 0.3g of dispersant cetyl trimethyl ammonium bromide CTAB and 3g of ammonium metatungstate AMT are respectively dissolved in 30mL of deionized water, the two are mixed together after clarification, the mixture is added to 100mL of deionized water (the concentration of AMT is 0.03g/mL, the mass of CTAB is 10% of the mass of ammonium metatungstate), the pH value is adjusted to 1 by nitric acid, and the mixture is fully dissolved and dispersed by ultrasonic treatment (the ultrasonic treatment power is 100W, and the ultrasonic time is 1h) to prepare a solution.
(2) And (3) placing the solution into a reaction kettle with the filling amount of 80%, carrying out hydrothermal reaction at 180 ℃, and keeping the temperature for 24 hours.
(3) After the reaction, the resulting suspension was filtered and washed with deionized water 2 times, then dried under vacuum at 60 ℃ for 8 h.
(4) And calcining the powder in air flow at 500 ℃ for 0.5h to remove residual dispersant to obtain tungsten oxide powder.
(5) And (3) carrying out two-step reduction on the tungsten oxide powder in hydrogen gas flow (keeping the temperature at 600 ℃ for 1.5h and keeping the temperature at 800 ℃ for 1.5h) to obtain the superfine nano tungsten powder. And finally, cooling the precursor powder to room temperature in a hydrogen atmosphere to obtain the ultrafine nano tungsten powder with uniform grain size and the average grain size of 22.5nm, wherein the surface appearance is shown in figure 1, and the phase is shown in figure 2. The powder prepared by the hydrothermal method with the dispersant is pure in phase, does not have the phenomenon of particle size bimodal distribution, and has the advantages of extremely small crystal grains and extremely narrow particle size division.
Example 2
(1) 0.5g of dispersant cetyl trimethyl ammonium bromide CTAB and 10g of ammonium metatungstate AMT are respectively dissolved in 30mL of deionized water, the two are mixed together after clarification, the mixture is added to 100mL of deionized water (the concentration of AMT is 0.1g/mL, the mass of CTAB is 5% of the mass of ammonium metatungstate), the pH value is adjusted to 2 by nitric acid, and the mixture is fully dissolved and dispersed by ultrasonic treatment (the ultrasonic treatment power is 200W, and the ultrasonic time is 0.33h) to prepare a solution.
(2) Putting the solution into a reaction kettle with the filling amount of 70 percent, carrying out hydrothermal reaction at 170 ℃, and keeping the temperature for 36 hours.
(3) After the reaction, the resulting suspension was filtered and washed 3 times with deionized water, and then vacuum dried at 60 ℃ for 8 h.
(4) And calcining the powder in air flow at 500 ℃ for 0.5h to remove residual dispersant to obtain tungsten oxide powder.
(5) And (3) carrying out two-step reduction on the tungsten oxide powder in hydrogen gas flow (keeping the temperature at 550 ℃ for 2h and keeping the temperature at 700 ℃ for 2h) to obtain the superfine nano tungsten powder. And finally, cooling the precursor powder to room temperature in a hydrogen atmosphere to obtain the ultrafine nano tungsten powder with uniform grain size and the average grain size of 12.5nm, wherein the surface appearance is shown in figure 3. The powder prepared by the hydrothermal method with the dispersant is pure in phase, does not have the phenomenon of particle size bimodal distribution, and has the advantages of extremely small crystal grains and extremely narrow particle size division.
Example 3
(1) 0.1g of sodium dodecyl benzene sulfonate SDBS and 5g of ammonium metatungstate AMT are respectively dissolved in 30mL of deionized water, the two are mixed together after clarification, the mixture is added to 100mL of deionized water (the concentration of AMT is 0.05g/mL, the mass of CTAB is 2% of the mass of ammonium metatungstate), the pH value is adjusted to 3 by nitric acid, and the mixture is fully dissolved and dispersed by ultrasonic treatment (the ultrasonic treatment power is 150W, and the ultrasonic time is 1.5h) to prepare a solution.
(2) And (3) placing the solution into a reaction kettle with the filling amount of 90%, carrying out hydrothermal reaction at 190 ℃, and keeping the temperature for 24 hours.
(3) After the reaction, the resulting suspension was filtered and washed 4 times with deionized water, and then dried under vacuum at 60 ℃ for 12 hours.
(4) And calcining the powder in air flow at 500 ℃ for 0.5h to remove residual dispersant to obtain tungsten oxide powder.
(5) And (3) carrying out two-step reduction on the tungsten oxide powder in hydrogen gas flow (keeping the temperature at 650 ℃ for 1h and keeping the temperature at 750 ℃ for 1.5h) to obtain the superfine nano tungsten powder. And finally, cooling the precursor powder to room temperature in a hydrogen atmosphere to obtain the ultrafine nano tungsten powder with uniform grain size and the average grain size of 29.5 nm. The powder prepared by the hydrothermal method with the dispersant is pure in phase, does not have the phenomenon of particle size bimodal distribution, and has the advantages of extremely small crystal grains and extremely narrow particle size division.
Example 4
(1) 0.3g of dispersing agent Sodium Dodecyl Sulfate (SDS) and 3g of Ammonium Metatungstate (AMT) are respectively dissolved in 30mL of deionized water, the mixture is mixed after clarification, the mixture is added to 100mL of deionized water (the concentration of AMT is 0.03g/mL, the mass of CTAB is 10% of the mass of ammonium metatungstate), the pH value is adjusted to 1 by hydrochloric acid, and the mixture is fully dissolved and dispersed by ultrasonic treatment (the ultrasonic treatment power is 100W, and the ultrasonic time is 1h) to prepare a solution.
(2) And (3) placing the solution into a reaction kettle with the filling amount of 80%, carrying out hydrothermal reaction at 180 ℃, and keeping the temperature for 30 hours.
(3) After the reaction, the resulting suspension was filtered and washed 3 times with distilled water, and then dried under vacuum at 60 ℃ for 8 hours.
(4) And calcining the powder in air flow at 500 ℃ for 0.5h to remove residual dispersant to obtain tungsten oxide powder.
(5) And (3) carrying out two-step reduction on the tungsten oxide powder in hydrogen gas flow (keeping the temperature at 600 ℃ for 1.5h and keeping the temperature at 700 ℃ for 2.5h) to obtain the superfine nano tungsten powder. And finally, cooling the precursor powder to room temperature in a hydrogen atmosphere to obtain the superfine nano tungsten powder with uniform grain size and the average grain size of 19.5nm, wherein the surface appearance is shown in figure 4. The powder prepared by the hydrothermal method with the dispersant is pure in phase, does not have the phenomenon of particle size bimodal distribution, and has the advantages of extremely small crystal grains and extremely narrow particle size division.
Example 5
(1) 0.15g of dispersant cetyl trimethyl ammonium bromide CTAB and 0.15g of dispersant sodium dodecyl sulfate SDS are dissolved in 30mL of deionized water together, 3g of ammonium metatungstate AMT is dissolved in another 30mL of deionized water, the two solutions are mixed together after clarification, the mixture is added to 100mL (the concentration of AMT is 0.03g/mL, the mass of the dispersant is 10% of the mass of ammonium metatungstate) by using deionized water, the pH value is adjusted to 1 by using nitric acid, and the mixture is fully dissolved and dispersed by using ultrasonic treatment (the ultrasonic treatment power is 100W, and the ultrasonic time is 1h) to prepare a solution.
(2) And (3) placing the solution into a reaction kettle with the filling amount of 80%, carrying out hydrothermal reaction at 170 ℃, and keeping the temperature for 24 hours.
(3) After the reaction, the resulting suspension was filtered and washed 3 times with deionized water, and then vacuum dried at 60 ℃ for 8 h.
(4) And calcining the powder in air flow at 500 ℃ for 0.5h to remove residual dispersant to obtain tungsten oxide powder.
(5) And (3) carrying out two-step reduction on the tungsten oxide powder in hydrogen gas flow (keeping the temperature at 600 ℃ for 1.5h and keeping the temperature at 800 ℃ for 1.5h) to obtain the superfine nano tungsten powder. And finally, cooling the precursor powder to room temperature in a hydrogen atmosphere to obtain the ultrafine nano tungsten powder with uniform grain size and the average grain size of 18.9nm, wherein the surface appearance is shown in figure 5. The powder prepared by the hydrothermal method with the dispersant is pure in phase, does not have the phenomenon of particle size bimodal distribution, and has the advantages of extremely small crystal grains and extremely narrow particle size division.

Claims (1)

1. A hydrothermal preparation method of ultrafine nano tungsten powder is characterized by comprising the following steps:
(1) respectively dissolving a dispersing agent and ammonium metatungstate in deionized water, mixing the materials together after clarification, adjusting the pH to 2-3, and carrying out ultrasonic treatment for 0.33-1.5 h at the ultrasonic power of 150-200W to obtain a mixed solution;
(2) then carrying out hydrothermal reaction in a reaction kettle, and filtering, washing and drying the suspension after the reaction;
(3) finally, pure hydrogen is used for two-step reduction to obtain superfine nano tungsten powder;
the dispersing agent in the step (1) is one or more of cetyl trimethyl ammonium bromide, sodium dodecyl benzene sulfonate and sodium dodecyl sulfate; the mass of the dispersing agent is 2-10% of that of the ammonium metatungstate;
in the step (1), the concentration of the ammonium metatungstate in the mixed solution is as follows: 0.03-0.1 g/mL; adjusting pH with nitric acid or hydrochloric acid;
the filling amount of the reaction kettle in the step (2) is 70-90%; the hydrothermal reaction temperature is 180-190 ℃, and the heat preservation time is 24-36 h; filtering for 2-4 times by using deionized water or distilled water;
the temperature and time of the two-step reduction in the step (3) are respectively as follows: 550-650 ℃ for 1-2 h; 700-800 ℃ for 1.5-2.5 h.
CN201810657397.XA 2018-06-25 2018-06-25 Hydrothermal preparation method of superfine nano tungsten powder Active CN108772569B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201810657397.XA CN108772569B (en) 2018-06-25 2018-06-25 Hydrothermal preparation method of superfine nano tungsten powder

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201810657397.XA CN108772569B (en) 2018-06-25 2018-06-25 Hydrothermal preparation method of superfine nano tungsten powder

Publications (2)

Publication Number Publication Date
CN108772569A CN108772569A (en) 2018-11-09
CN108772569B true CN108772569B (en) 2021-03-16

Family

ID=64025463

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201810657397.XA Active CN108772569B (en) 2018-06-25 2018-06-25 Hydrothermal preparation method of superfine nano tungsten powder

Country Status (1)

Country Link
CN (1) CN108772569B (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109794267A (en) * 2019-02-28 2019-05-24 陕西科技大学 A kind of WO3/NaSO4The preparation method of composite material
CN112760677A (en) * 2020-12-28 2021-05-07 中国科学技术大学 Iridium-tungsten alloy nano material, preparation method thereof and application of iridium-tungsten alloy nano material as acidic oxygen evolution reaction electrocatalyst

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5284614A (en) * 1992-06-01 1994-02-08 General Electric Company Method of forming fine dispersion of ceria in tungsten
CN106799500B (en) * 2017-01-05 2019-03-29 天津大学 The preparation method of ultrafine tungsten powder
CN107052356B (en) * 2017-01-18 2019-01-15 天津大学 A kind of preparation method of the tungsten of core-shell structure-yttrium oxide superfine composite precursor powder
CN107322002B (en) * 2017-06-28 2020-01-17 合肥工业大学 Rare earth oxide doped tungsten-based composite powder and preparation method thereof
CN107282938B (en) * 2017-07-12 2019-04-02 河南科技大学 A kind of rear-earth-doped tungsten powder and preparation method thereof
CN107900373B (en) * 2017-12-07 2020-11-13 崇义章源钨业股份有限公司 Superfine W-Cu composite powder and preparation method thereof

Also Published As

Publication number Publication date
CN108772569A (en) 2018-11-09

Similar Documents

Publication Publication Date Title
CN108788173B (en) Hydrothermal preparation method of superfine yttrium oxide doped tungsten composite powder
CN108772569B (en) Hydrothermal preparation method of superfine nano tungsten powder
CN104630532B (en) A kind of preparation method of carbide and rare earth oxide complex intensifying carefully brilliant tungsten material
CN105518169A (en) Method for preparing rare-earth oxide dispersion strengthened fine-grained tungsten material
CN109128141B (en) Preparation method of nano WC-Co composite powder
CN106994517B (en) A kind of preparation method of high-thermal-conductivity low-expansibility W-Cu encapsulating material
CN106077695B (en) A kind of preparation method of high-copper tungsten copper nano composite powder
CN111545767B (en) Preparation method of nanoscale multicomponent alloy
CN103056376A (en) Method for preparing spherical nanostructure tungsten/cobalt carbide compound powder
CN108580920A (en) A kind of preparation method of flake silver powder
CN102251130B (en) Preparation method of superfine grain cemented carbide
CN111206164A (en) Preparation method of high-performance ultra-fine grain molybdenum-lanthanum alloy
CN106636834B (en) Inhibit the method and ultra-fine cemented carbide preparation process that hard alloy crystal grain is grown up
CN107900373B (en) Superfine W-Cu composite powder and preparation method thereof
CN106799500B (en) The preparation method of ultrafine tungsten powder
CN108500288A (en) A kind of preparation method of flake copper powder
Liu et al. Preparation of Co powders for cemented carbides in China
CN110434346B (en) Method for refining large-particle-size pure copper or copper alloy particles by high-energy ball milling method
CN109351985B (en) Method for preparing metal rhenium powder by hydrothermal hydrogen reduction
CN103801706A (en) Molybdenum powder for ceramic metallizing and preparing method of molybdenum powder
CN102581289B (en) Method for preparing monodisperse high-crystallinity silver powder
CN105965026B (en) It is a kind of that the method for preparing nanometer MeC W powder is spray-dried with colloidal sol non-homogeneous phase deposition
CN105798317B (en) A kind of preparation method of polyhedron Sub-micron Tungsten Powder
CN111154995B (en) Superfine tungsten carbide based on doped bonding phase and preparation method thereof
CN110014161B (en) Method for preparing spherical tungsten-based powder

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant