CN112795873A - Preparation method of alkali metal rubidium for multi-alkali photocathode - Google Patents

Preparation method of alkali metal rubidium for multi-alkali photocathode Download PDF

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CN112795873A
CN112795873A CN202011543428.2A CN202011543428A CN112795873A CN 112795873 A CN112795873 A CN 112795873A CN 202011543428 A CN202011543428 A CN 202011543428A CN 112795873 A CN112795873 A CN 112795873A
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rubidium
alkali
preparation
metal
chromate
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田文怀
牛春明
张超
赵焕磊
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University of Science and Technology Beijing USTB
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University of Science and Technology Beijing USTB
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/24—Vacuum evaporation
    • C23C14/26—Vacuum evaporation by resistance or inductive heating of the source
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
    • C22B26/10—Obtaining alkali metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B5/00—General methods of reducing to metals
    • C22B5/02—Dry methods smelting of sulfides or formation of mattes
    • C22B5/04—Dry methods smelting of sulfides or formation of mattes by aluminium, other metals or silicon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/14—Metallic material, boron or silicon

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Abstract

A preparation method of alkali metal rubidium for a multi-alkali photoelectric cathode belongs to the technical field of low-light-level night vision photoelectric cathodes. The method comprises two parts of selection of a reducing agent and preparation of a salt evaporator. Metal yttrium (Y) is selected as a reducing agent to replace metal rubidium (Rb) in rubidium chromate, and the chemical reaction formula is as follows: 2Y +3Rb2CrO4 → 6Rb +3CrO3+ + Y2O3 and CrO3 are unstable and are easily decomposed into oxides between +3 and +6 valences; the reaction was carried out under vacuum with heating at 800 ℃. The preparation of the alkali salt evaporator is divided into the preparation of the original powder of the evaporator, the mixing of the internal mixed powder, the preparation of the shell strip and the assembly of the mixed powder and the shell strip. Metal yttrium (Y) is selected as a reducing agent, and is heated at 800 ℃ under the vacuum condition to perform oxidation-reduction reaction with rubidium chromate; during the evaporation process of the prepared alkali salt evaporator, the evaporation current and the evaporation characteristic are more stable, manual intervention is not needed, the uniform and equivalent rubidium (Rb) alkali metal steam with no pollution and high purity is prepared, and a high-performance uniform alkali metal rubidium film is deposited on a substrate after condensation.

Description

Preparation method of alkali metal rubidium for multi-alkali photocathode
Technical Field
The invention belongs to the technical field of low-light-level night vision photocathodes, and provides a method for generating pollution-free, high-purity, uniform and equal-quantity rubidium (Rb) alkali metal steam under specific conditions in a photocathode production process by utilizing a chemical reaction principle.
Background
When light irradiates on a specific material, the electrochemical properties inside the material are changed, and the light energy is converted into electric energy, which is called photoelectric effect. The photoelectric effect is classified into an external photoelectric effect and an internal photoelectric effect. Photocathodes are materials that can emit photoelectrons using the external photoelectric effect. The conventional photocathodes mainly comprise a multi-alkali photocathode ([ Cs ] Na2KSb) and a double-alkali photocathode (K2CsSb), the properties of the multi-alkali cathode and the double-alkali cathode are similar, the multi-alkali photocathode has higher sensitivity in visible light and near infrared regions, and the double-alkali photocathode has higher sensitivity in the visible light range.
Alkali metals (Li, Na, K, Rb, Cs) are important elements constituting the photocathode. In preparing photocathodes, alkali metal sources are required: (1) the produced alkali metal has high purity and emits little harmful gas; (2) the production of alkali metal is easy to control; (3) higher alkali metal yield.
Disclosure of Invention
The invention aims to select metal yttrium (Y) as a reducing agent to replace metal rubidium (Rb) in rubidium chromate according to the strength of the metal property of an element, the strength of first ionization energy of the element and Gibbs free energy in chemical thermodynamics, mix the metal yttrium (Y) and rubidium chromate powder according to a specific proportion, prepare an alkali salt evaporator with an electrothermal alloy (Ni80Cr20), and then carry out vacuum evaporation to generate uniform and equal-quantity rubidium (Rb) alkali metal steam without pollution.
A method for preparing alkali metal rubidium for a multi-alkali photoelectric cathode comprises the following steps:
(1) selection of reducing agent
According to the strength of the metal property of the element, the strength of the first ionization energy of the element and the Gibbs free energy in chemical thermodynamics, metal yttrium (Y) is selected as a reducing agent to replace metal rubidium (Rb) in rubidium chromate through experimental tests, and the chemical reaction formula is as follows: 2Y +3Rb2CrO4 → 6Rb +3CrO3+ + Y2O3 and CrO3 are unstable and are easily decomposed into oxides between +3 and +6 valences; the reaction is carried out under the vacuum condition by heating at 800 ℃, and the reaction temperature is strictly controlled in the reaction process;
(2) preparation of alkali salt evaporator
The preparation of the alkali salt evaporator comprises the preparation of original powder of the evaporator, the mixing of internal mixed powder, the preparation of a shell strip and the assembly of the mixed powder and the shell strip;
the alkali salt evaporator mixed powder is mainly prepared from two components of alkali metal salt rubidium chromate (Rb2CrO4) and a reducing agent yttrium (Y), wherein the component preparation proportion range is rubidium chromate: and yttrium is 3-6: 7-4, taking rubidium chromate as an alkali metal salt, wherein chromate is fragile, and the developed and purified rubidium chromate is directly ground manually by using a mortar; after grinding, carrying out particle size screening, and reserving rubidium chromate powder with the required particle size; reducing the diameter of an electrothermal alloy (Ni80Cr20) strip on a rolling mill, wherein the thickness of the strip is 200-300 mu m, preparing a shell meeting the requirement, adding mixed powder, preparing a complete alkali salt evaporator, and performing vacuum evaporation on the alkali salt evaporator to generate pollution-free, high-purity, uniform and equivalent rubidium (Rb) alkali metal steam;
(3) the rubidium (Rb) alkali metal vapor is condensed and then deposited on a substrate to form a high-performance and uniform alkali metal rubidium film.
Further, the original powder is a metal yttrium reducing agent, which can be obtained by direct purchase, and the two powders are mixed by a barrel-changing three-dimensional motion mixer, and simultaneously, a roller ball mill is used for auxiliary mixing.
Further, the diameter reduction pass is 8 passes.
Further, the vacuum evaporation conditions are as follows: in the high vacuum thermal resistance evaporation system, a resistance heating evaporation source is adopted, a power supply is connected, and the vacuum degree reaches 10-6～10-7Pa, the evaporation current is about 8200mA, and the photocurrent is increased by 9.8-16.5 mV/s.
According to the invention, metal yttrium (Y) is selected as a reducing agent, and can perform redox reaction with rubidium chromate under specific conditions (heating at 800 ℃ under vacuum conditions); in the evaporation process of the prepared alkali salt evaporator, the evaporation current and the evaporation characteristic are more stable, manual intervention is not needed, and the uniform and equivalent rubidium (Rb) alkali metal steam with no pollution and high purity is successfully prepared.
Drawings
FIG. 1 is a differential thermal curve of a reductant yttrium (Y) mixed powder;
FIG. 2 is a flow chart of the initial preparation of rubidium chromate;
FIG. 3 SEM topography of the mixed powder.
Detailed Description
1. Selection of reducing agent
The alkali metal rubidium is very strong in metallicity, several elements such as Nb, Zr, Al, Ti, ZrAl16 and Y are selected primarily as reducing agents according to the strength of the metallicity, the strength of first ionization energy of the elements and Gibbs free energy in chemical thermodynamics, the reducing agents are subjected to particle size screening by using a standard inspection sieve in a vacuum glove box, reducing agent powder with the particle size of 150-350 meshes is reserved, rubidium chromate powder with the particle size of 200-300 meshes is obtained in the same way, and then the rubidium chromate powder is mixed with the reducing agent powder such as Nb, Zr, Al, Ti, ZrAl16 and Y according to the ratio of 3: 7, mixing them together, mixing them in a tumbling ball mill for 10 hours, taking out the mixed powders, subjecting the mixed powders to thermodynamic analysis, performing differential scanning analysis in a synchronous thermal analyzer, plotting the analysis results into a differential thermal curve (DTA curve), and performing in-depth analysis, wherein only yttrium (Y) reacts with rubidium chromate, and as can be seen from fig. 1, the reaction occurs at around 770 ℃, and metal yttrium (Y) is selected as a reducing agent.
2. Preparation of alkali salt evaporator
2.1 preparation of evaporator raw powder
The alkali salt evaporator mixed powder is mainly prepared from two components, namely alkali metal salt rubidium chromate (Rb2CrO4) and reducing agent metal yttrium (Y). Considering the problems of environmental pollution, three wastes and the like, the preparation of the rubidium chromate can select a molten salt chromite salt cleaning technology, namely a liquid-phase oxidation method: according to the figure 2, the chromite is subjected to oxidative decomposition in a liquid phase flowing medium of RbOH, and rubidium chromate coarse crystals are separated from the leaching slurry and then purified to obtain a rubidium chromate product. The prepared rubidium chromate is placed in a vacuum drying oven for drying, the drying temperature is 60 ℃, the drying time is 4 hours, the chromate is fragile and can be directly ground by using a mortar, and the prepared rubidium chromate is ground in the vacuum glove box in a manual grinding mode after the drying is finished. The particle size range of the rubidium chromate powder is controlled to be 150-500 meshes, after grinding is completed, a standard inspection sieve is used for carrying out particle size screening, and the rubidium chromate powder with the required particle size is reserved. The reducing agent yttrium can be obtained by direct purchase, but the purchased yttrium metal powder needs to be subjected to component test, the hydrogen content, the nitrogen content and the oxygen content of the yttrium metal powder are strictly lower than 0.6%, meanwhile, the particle size range of the yttrium powder is controlled to be 120-400 meshes, in order to ensure the accuracy of the particle size, a standard inspection sieve is still used for sieving the yttrium powder, and the yttrium metal powder with the required particle size is reserved. And taking the obtained rubidium chromate powder and metal yttrium powder out of the vacuum glove box, and putting the rubidium chromate powder and the metal yttrium powder into a vacuum drying box, wherein the drying temperature is 50 ℃, and the drying time is 6-8 h.
2.2 blending of internal Mixed powders
After drying, taking out the rubidium chromate powder and the metal yttrium powder in the vacuum drying oven, and mixing the two powders according to a certain proportion, wherein the proportion range is rubidium chromate: and yttrium is 3-6: and 7-4, mixing the two kinds of powder by adopting a mechanical mixing method, and performing auxiliary mixing by using a roller ball mill in order to ensure the uniformity of mechanical mixing and simultaneously damage the granularity of the prepared original powder as little as possible. The rotating speed is 100-200 r/min, the mixing time is 10-16 h, the mixed powder is stored in a vacuum drying oven, heated, dried and stored for more than 24 h, and moisture and other impurity gases absorbed by the rubidium chromate in the whole powder mixing process are removed. About 1g of the mixed powder was taken out to prepare an SEM sample, and the morphology and uniformity of the mixed powder were observed, and it was found from FIG. 3 that the powder was uniformly mixed.
2.3 preparation of the strip of casing
The shell strip (Ni80Cr20) can be obtained by purchasing, the thickness of the strip is 200-300 mu m, the strip with proper length is taken for surface pretreatment, firstly, the surface of the strip is wiped by using dust-free paper, then, 1000-mesh abrasive paper is used for polishing, finally, the strip is curled into a larger circle, the strip is placed into a 1L beaker, acetone is added until the strip is completely submerged, the opening of the beaker is sealed by using a preservative film and is placed into an ultrasonic cleaning machine, the cleaning temperature is set to be 45 ℃, the cleaning time is set to be 20min, the acetone remained on the surface of the strip is removed by using the dust-free paper again after the cleaning is finished, and the strip is placed properly.
2.4 Assembly of the Mixed powder with the strip of casing
Processing the strip material on a rolling mill, processing the strip material into a tubular shape after the first rolling, putting the mixed powder into the processed tube for continuous rolling and drawing, and sequentially carrying out 8-pass rolling and drawing to prepare the complete alkali salt evaporator.
The alkali salt evaporator is put into a vacuum evaporator for vacuum evaporation, a resistance heating evaporation source is adopted, a power supply is switched on, the evaporation current is about 8200mA, the evaporation rate is easier to control, the evaporation characteristic is more stable, pollution-free, high-purity, uniform and equivalent rubidium (Rb) alkali metal steam is generated, and a high-performance and uniform alkali metal rubidium film is deposited on a substrate.

Claims (4)

1. A method for preparing alkali metal rubidium for a multi-alkali photoelectric cathode is characterized by comprising the following preparation steps:
(1) selection of reducing agent
According to the strength of the metal property of the element, the strength of the first ionization energy of the element and the Gibbs free energy in chemical thermodynamics, metal yttrium (Y) is selected as a reducing agent to replace metal rubidium (Rb) in rubidium chromate through experimental tests, and the chemical reaction formula is as follows: 2Y +3Rb2CrO4 → 6Rb +3CrO3+ + Y2O3 and CrO3 are unstable and are easily decomposed into oxides between +3 and +6 valences; the reaction is carried out under the vacuum condition by heating at 800 ℃, and the reaction temperature is strictly controlled in the reaction process;
(2) preparation of alkali salt evaporator
The preparation of the alkali salt evaporator comprises the preparation of original powder of the evaporator, the mixing of internal mixed powder, the preparation of a shell strip and the assembly of the mixed powder and the shell strip;
the alkali salt evaporator mixed powder is mainly prepared from two components of alkali metal salt rubidium chromate (Rb2CrO4) and a reducing agent yttrium (Y), wherein the component preparation proportion range is rubidium chromate: and yttrium is 3-6: 7-4, taking rubidium chromate as an alkali metal salt, wherein chromate is fragile, and the developed and purified rubidium chromate is directly ground manually by using a mortar; after grinding, carrying out particle size screening, and reserving rubidium chromate powder with the required particle size; reducing the diameter of an electrothermal alloy (Ni80Cr20) strip on a rolling mill, wherein the thickness of the strip is 200-300 mu m, preparing a shell meeting the requirement, adding mixed powder, preparing a complete alkali salt evaporator, and performing vacuum evaporation on the alkali salt evaporator to generate pollution-free, high-purity, uniform and equivalent rubidium (Rb) alkali metal steam;
(3) the rubidium (Rb) alkali metal vapor is condensed and then deposited on a substrate to form a high-performance and uniform alkali metal rubidium film.
2. A method for preparing an alkali metal rubidium for a multi-alkali photocathode as claimed in claim 1, wherein the original powder is a reducing agent metal yttrium, and is obtained by direct purchase, and the two powders are mixed by a barrel-changing three-dimensional motion mixer, and are mixed by a roller ball mill.
3. The method for preparing the alkali metal rubidium for the multi-alkali photocathode according to claim 1, wherein the diameter reduction processing pass is 8 passes.
4. A method for preparing alkali rubidium metal for a multi-alkali photocathode according to claim 1, wherein the vacuum evaporation conditions are as follows: in the high vacuum thermal resistance evaporation system, a resistance heating evaporation source is adopted, a power supply is connected, and the vacuum degree reaches 10-6～10- 7Pa, the evaporation current is about 8200mA, and the photocurrent is increased by 9.8-16.5 mV/s.
CN202011543428.2A 2020-12-22 2020-12-22 Preparation method of alkali metal rubidium for multi-alkali photocathode Pending CN112795873A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115125491A (en) * 2022-06-15 2022-09-30 北方夜视技术股份有限公司 Method for measuring evaporation characteristic of alkali source for preparing multi-alkali photocathode

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001072439A (en) * 1999-08-31 2001-03-21 Toshiba Corp Method and apparatus for producing radiation image tube and method and apparatus for generating alkali metal used therefor
US20090110807A1 (en) * 2007-10-25 2009-04-30 Applied Materials, Inc. Method for coating and apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001072439A (en) * 1999-08-31 2001-03-21 Toshiba Corp Method and apparatus for producing radiation image tube and method and apparatus for generating alkali metal used therefor
US20090110807A1 (en) * 2007-10-25 2009-04-30 Applied Materials, Inc. Method for coating and apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
吴文伟: "《无机化学》", 31 August 2009, 国防工业出版社 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115125491A (en) * 2022-06-15 2022-09-30 北方夜视技术股份有限公司 Method for measuring evaporation characteristic of alkali source for preparing multi-alkali photocathode

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Application publication date: 20210514