CN109338423B

CN109338423B - Method for preparing rare earth metal terbium film by low-cost electrochemical deposition

Info

Publication number: CN109338423B
Application number: CN201811192282.4A
Authority: CN
Inventors: 石忠宁; 张保国; 姚宇; 胡宪伟; 高炳亮; 王兆文
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2018-10-12
Filing date: 2018-10-12
Publication date: 2020-04-28
Anticipated expiration: 2038-10-12
Also published as: CN109338423A

Abstract

The invention relates to a method for preparing a rare earth metal terbium film by low-cost electrochemical deposition, belonging to the field of rare earth metal low-temperature electrodeposition. A method for preparing a rare earth metal terbium film by low-cost electrochemical deposition is characterized by comprising the following process steps: dissolving lithium nitrate in DMI to obtain DMI electrolyte of the lithium nitrate, placing the DMI electrolyte of the lithium nitrate in an electrolytic cell, adding anhydrous terbium chloride into the electrolytic cell, stirring and mixing the solution in the electrolytic cell to form a uniform system, controlling the temperature of the whole system to be 25-80 ℃, and controlling the electrolytic voltage range to be-2.0-2.4V vs Ag; in the electrodeposition process, anhydrous terbium chloride is supplemented into the electrolytic cell at intervals, and the molar concentration of the terbium chloride is controlled to be +/-2% of the initial concentration. The method provided by the invention can be used for preparing the rare earth metal terbium film with high efficiency and simultaneously remarkably reducing the energy consumption and the production cost.

Description

Method for preparing rare earth metal terbium film by low-cost electrochemical deposition

Technical Field

The invention relates to a method for preparing a rare earth metal terbium film by low-cost electrochemical deposition, belonging to the field of rare earth metal low-temperature electrodeposition.

Background

The rare earth elements are known as 'industrial vitamins', 'industrial monosodium glutamate' and 'mother of new materials', have irreplaceable excellent magnetic, optical and electrical properties, and play a great role in improving product performance, increasing product varieties and improving production efficiency. Because of large action and small dosage of rare earth, the rare earth has become an important element for improving the product structure, improving the technological content and promoting the technical progress of the industry, and is widely applied to the fields of metallurgy, military, petrochemical industry, glass ceramics, agriculture, new materials and the like. In particular, terbium is mainly applied to an activator of green powder in the three-primary-color phosphor, such as a terbium-activated phosphate matrix, a terbium-activated silicate matrix, and a terbium-activated cerium-magnesium aluminate matrix, which emit green light in an excited state. In addition, in the aspect of magneto-optical storage materials, terbium magneto-optical materials have reached the mass production scale in recent years, and magneto-optical disks developed by Tb-Fe amorphous films are used as computer storage elements, so that the storage capacity is improved by 10-15 times. Magneto-optical glass, terbium-containing faraday rotator glass, is a key material for the fabrication of rotators, isolators and circulators for widespread use in laser technology. The Tb-Dy-Fe magnetostrictive alloy is a novel material discovered only in the 70 s, half of the components in the alloy are Tb and Dy, sometimes holmium is added, and the rest is Fe, the alloy is firstly developed by Ames laboratory in the state of America, when the Tb-Dy-Fe magnetostrictive alloy is placed in a magnetic field, the change of the size of the Tb-Dy-Fe magnetostrictive alloy is larger than that of a common magnetic material, and the change can realize some precise mechanical movements. Terbium dysprosium iron is mainly used for sonar, and is widely applied to various fields at present, from fuel injection systems, liquid valve control, micro positioning to mechanical actuators, adjusting mechanisms of space telescopes, airplane wing adjusters and the like, so that the strategic metal element terbium has great significance.

At present, metal vacuum thermal reduction and high-temperature molten salt electrolysis are traditional preparation methods of rare earth metal terbium from the technical point of view, and the prepared metal terbium is deposited on a substrate material by adopting a vacuum evaporation deposition or sputtering deposition method. The above process has the disadvantages of high energy consumption, serious pollution, long flow path, strong corrosivity, complex operation, high requirement on equipment and the like. With the increasing tension of energy and the increasing prominence of environmental protection problems, how to obtain a high-quality rare earth metal terbium film and simultaneously reduce the pollution to the environment to the maximum extent and save energy and have convenient operation becomes the focus of attention of people. The electrodeposition method has the characteristics of convenient operation, simplicity, flexibility, low requirement on the shape of a substrate material and the like, and is widely researched. If the rare earth metal terbium thin film material can be prepared by electrodeposition at room temperature or near room temperature, the method is simple to operate, low in cost, reliable and safe. Because of the unusual activity and negative redox potential of terbium, terbium ions cannot be directly reduced to terbium metal on electrodes in an aqueous solution system due to the hydrogen evolution shielding effect, and thus the system for electrodepositing the metal terbium is generally a non-aqueous solvent. As a kind of non-aqueous solvent, which is also called as low-temperature molten salt, ionic liquid has properties of low melting point, low saturated vapor pressure, stable electrochemical properties, and the like, and is also widely used in research of electrochemical metallurgical processes. However, the synthesis process of the ionic liquid is complex, the exchange reaction is incomplete, competitive reaction and byproducts exist, and the obtained product needs to be purified and separated in multiple steps, so that the production cost of the ionic liquid and the possibility of environmental pollution are remarkably increased, and the green characteristic of the ionic liquid is reduced. The water content in the finally prepared ionic liquid product cannot be ensured, and the process of preparing the active metal terbium film by ionic liquid electrodeposition is seriously influenced. On the other hand, the electrochemical window of the conventional ionic liquid is narrow, the dissolving capacity of the conventional ionic liquid to common chlorides (such as magnesium chloride, calcium chloride, rare earth chloride and the like) is limited, and some common ionic liquids have high viscosity and are easy to absorb water in air, so that the practical application of the ionic liquid is limited to a great extent. Therefore, at present, the ionic liquid has been developed for hundreds of years, but the ionic liquid is only limited to scientific research in the field of metal electrodeposition, and has no large-scale practical application background.

Disclosure of Invention

Aiming at the existing problems, the invention provides a method for preparing a metal terbium film by electrolyzing terbium chloride at low temperature by using lithium nitrate (the purity is more than 99.9%) as a supporting electrolyte and using a novel aprotic strong polar solvent 1, 3-dimethyl-2-imidazolidinone (DMI) (the purity is more than 99.0%). The short-flow method for preparing the high-purity metal terbium film through electrodeposition by dissolving terbium chloride (the purity is not less than 99.9%) serving as a raw material in a DMI solvent containing 0.02-0.1 mol/L lithium nitrate has the advantages that the energy consumption and the production cost are obviously reduced while the rare earth metal terbium film is efficiently prepared.

A method for preparing a rare earth metal terbium film by low-cost electrochemical deposition is an electrodeposition method and comprises the following process steps:

s1, dissolving lithium nitrate in DMI at room temperature, wherein the molar concentration of the lithium nitrate in the DMI is 0.01-0.1 mol/L, and obtaining DMI electrolyte of the lithium nitrate, wherein the DMI is represented by the following structural formula:

s2, placing the DMI electrolyte of lithium nitrate into an electrolytic cell, adding anhydrous terbium chloride into the electrolytic cell, and stirring and mixing the solution in the electrolytic cell to form a uniform system, wherein the molar concentration of the terbium chloride is 0.01-0.05 mol/L, the temperature of the whole system is controlled to be 25-80 ℃, and the electrolytic voltage range is-2.0-2.4V vs Ag;

s3, in the electrolysis process, adding anhydrous terbium chloride into the electrolytic cell at intervals, and controlling the molar concentration of the terbium chloride to be +/-2% of the initial concentration.

In the technical scheme, the purity of the lithium nitrate and the purity of the terbium chloride are both not less than 99.9%; the DMI purity is not less than 99.0%.

The invention discloses a method for controlling the molar concentration of terbium chloride to be +/-2% of the initial concentration, which means that the molar concentration of terbium chloride is controlled to be 98-102% of the initial concentration.

In the invention, the 'vs Ag' in the 'electrolysis voltage range of-2.0 to-2.4V vs Ag' refers to a silver electrode as a reference electrode.

Preferably, in the step S1, the molar concentration of the lithium nitrate in the DMI is 0.02-0.1 mol/L.

Preferably, in the step S2, the molar concentration of terbium chloride is 0.02-0.05 mol/L.

Preferably, in the step S3, anhydrous terbium chloride is added into the electrolytic cell every 30min, and the molar concentration of terbium chloride is controlled to be around the initial concentration.

Preferably, the method includes a step S4 of sealing the terbium metal film formed on the cathode substrate together with the substrate material in a vessel containing dimethyl carbonate or kerosene every 60 min.

Preferably, the electrolysis process takes a high-purity tungsten sheet (the purity is more than or equal to 99.99%) as an anode and takes a pure copper sheet (the purity is more than or equal to 99.99%) or a pure aluminum sheet (the purity is more than or equal to 99.9%) as a cathode.

Preferably, the inter-polar distance between the anode and the cathode is 15 mm.

Compared with the existing method for preparing the metal terbium film, the method has the following advantages:

(1) the process flow is shortened, the production energy consumption is obviously reduced, the production cost is reduced, the operation environment is improved, and the method is simple and flexible;

(2) the novel low-temperature aprotic strong-polarity solvent is adopted for electrodeposition, the defects of high energy consumption, high temperature and serious equipment corrosion when a high-temperature molten salt electrolyte is adopted can be reduced and eliminated, the operation is easy, and in addition, the DMI solvent has the characteristics of excellent solubility and high dielectric constant for terbium chloride, no toxicity, good chemical and thermal stability, no corrosion to copper and iron, high boiling point, high flash point, low melting point, easiness in recovery and good safety performance. Importantly, the DMI solvent has a large-scale chemical production background, the cost is greatly reduced compared with a molten salt system and ionic liquid, and in addition, the DMI can be synthesized by waste plastics and greenhouse gas carbon dioxide, so that the DMI solvent is obvious in green property and has large-scale application capability and prospect. The method and the process can prepare the rare earth metal terbium film by electrodeposition at low temperature, the obtained product has high purity and lower requirement on equipment, and the method and the process can be used for large-scale production to improve the efficiency and the yield and provide technical reserve and theoretical support for low-cost green preparation of the rare earth metal.

Drawings

FIG. 1 is an SEM image of the product obtained in example 8 on a copper cathode plate.

Detailed Description

The following non-limiting examples are presented to enable those of ordinary skill in the art to more fully understand the present invention and are not intended to limit the invention in any way.

The test methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.

The purity of the anhydrous terbium chloride adopted in the embodiment of the invention is 99.9%, the purity of the lithium nitrate is 99.9%, and the purity of the DMI is 99.0%.

In the embodiment of the invention, the Shanghai Chenghua electrochemical workstation is used as an electrolysis power supply.

The anode of the embodiment of the invention is a high-purity tungsten sheet (the purity is more than or equal to 99.9 percent), and the area of the anode is 1cm²The cathode is a high-purity copper sheet (the purity is more than or equal to 99.99 percent) or an aluminum sheet (the purity is more than or equal to 99.99 percent), and the area of the cathode is 1cm²The reference electrode is silver wire (purity is more than or equal to 99.99%, diameter is 0.05 cm).

In the embodiment of the invention, the content of terbium element is detected by adopting ICP (inductively coupled plasma atomic emission spectrometry); the film thickness measurement means is SEM (scanning Electron microscope).

The method for preparing the rare earth metal terbium film by low-cost electrochemical deposition in the following embodiment is an electrodeposition method and comprises the following process steps:

s1, dissolving lithium nitrate in DMI at room temperature, wherein the molar concentration of the lithium nitrate in the DMI is 0.01-0.1 mol/L, and obtaining DMI electrolyte of the lithium nitrate;

s2, placing the DMI electrolyte of lithium nitrate into an electrolytic cell, adding anhydrous terbium chloride into the electrolytic cell, and stirring and mixing the solution in the electrolytic cell to form a uniform and transparent system, wherein the molar concentration of the terbium chloride is 0.01-0.05 mol/L, the temperature of the whole system is controlled to be 25-80 ℃, and the electrolytic voltage range is-2.0-2.4V vs Ag;

Example 1

Preparing electrolyte raw materials comprising terbium chloride and lithium nitrate and a solvent DMI, and stirring and mixing the electrolyte raw materials and the solvent DMI in an electrolytic cell to form an electrolyte system, wherein the molar concentrations of the terbium chloride and the lithium nitrate are respectively 0.01mol/L and 0.01 mol/L. Controlling the constant temperature of an electrolyte system to be 25 ℃, the electrolytic voltage to be-2.0V (vs Ag), and the cathode material to be a high-purity aluminum sheet; after 30min of electrolysis, terbium chloride is added for one time to ensure that the concentration of the terbium chloride in the system is 0.01 mol/L; and collecting and storing the substrate together with the deposit after electrolyzing for 60 min. The characterization detection shows that metal terbium can be effectively deposited, the total content of terbium element detected by ICP is 76.62%, the deposited film obtained by SEM observation is a uniform and compact deposited film, and the thickness of the terbium film is 0.27 microns.

Example 2

Preparing electrolyte raw materials comprising terbium chloride and lithium nitrate and a solvent DMI, and stirring and mixing the electrolyte raw materials and the solvent DMI in an electrolytic cell to form an electrolyte system, wherein the molar concentrations of the terbium chloride and the lithium nitrate are respectively 0.02mol/L and 0.02 mol/L. Controlling the constant temperature of an electrolyte system to be 35 ℃, the electrolytic voltage to be-2.1V (vs Ag), and the cathode material to be a high-purity copper sheet; after 30min of electrolysis, terbium chloride is added for one time to ensure that the concentration of the terbium chloride in the system is 0.02 mol/L; and collecting and storing the substrate together with the deposit after electrolyzing for 60 min. The characterization detection shows that metal terbium can be effectively deposited, the total content of terbium element detected by ICP is 97.47%, the deposited film obtained by SEM observation is a uniform and compact deposited film, and the thickness of the terbium film is 0.23 micrometer.

Example 3

Preparing electrolyte raw materials comprising terbium chloride and lithium nitrate and a solvent DMI, and stirring and mixing the electrolyte raw materials and the solvent DMI in an electrolytic cell to form an electrolyte system, wherein the molar concentrations of the terbium chloride and the lithium nitrate are 0.03mol/L and 0.03mol/L respectively. Controlling the constant temperature of an electrolyte system to be 45 ℃, the electrolytic voltage to be-2.2V (vs Ag), and the cathode material to be a high-purity aluminum sheet; after 30min of electrolysis, terbium chloride is added for one time to ensure that the concentration of the terbium chloride in the system is 0.03 mol/L; and collecting and storing the substrate together with the deposit after electrolyzing for 60 min. The characterization and detection result shows that metal terbium can be effectively deposited, the total content of terbium element detected by ICP is 97.74%, and the deposited film obtained by SEM observation is a uniform and compact deposited film, and the thickness of the terbium film is 0.26 micron.

Example 4

Preparing electrolyte raw materials comprising terbium chloride and lithium nitrate and a solvent DMI, and stirring and mixing the electrolyte raw materials and the solvent DMI in an electrolytic cell to form an electrolyte system, wherein the molar concentrations of the terbium chloride and the lithium nitrate are 0.04mol/L and 0.04mol/L respectively. Controlling the constant temperature of an electrolyte system to be 55 ℃, the electrolytic voltage to be-2.3V (vs Ag), and the cathode material to be a high-purity copper sheet; after 30min of electrolysis, terbium chloride is added for one time to ensure that the concentration of the terbium chloride in the system is 0.04 mol/L; and collecting and storing the substrate together with the deposit after electrolyzing for 60 min. The characterization and detection result shows that metal terbium can be effectively deposited, the total content of terbium element detected by ICP is 99.75%, the deposited film obtained by SEM observation is a uniform and compact deposited film, and the thickness of the terbium film is 0.33 microns.

Example 5

Preparing electrolyte raw materials comprising terbium chloride and lithium nitrate and a solvent DMI, and stirring and mixing the electrolyte raw materials in an electrolytic cell to form an electrolyte system, wherein the molar concentrations of the terbium chloride and the lithium nitrate are respectively 0.05mol/L and 0.06 mol/L. Controlling the constant temperature of an electrolyte system to be 65 ℃, the electrolytic voltage to be-2.4V (vs Ag), and the cathode material to be a high-purity aluminum sheet; after 30min of electrolysis, terbium chloride is added for one time to ensure that the concentration of the terbium chloride in the system is 0.05 mol/L; and collecting and storing the substrate together with the deposit after electrolyzing for 60 min. The characterization and detection result shows that metal terbium can be effectively deposited, the total content of terbium element detected by ICP is 99.52%, the deposited film obtained by SEM observation is a uniform and compact deposited film, and the thickness of the terbium film is 0.36 micrometer.

Example 6

Preparing electrolyte raw materials comprising terbium chloride and lithium nitrate and a solvent DMI, and stirring and mixing the electrolyte raw materials in an electrolytic cell to form an electrolyte system, wherein the molar concentrations of the terbium chloride and the lithium nitrate are 0.025mol/L and 0.08mol/L respectively. Controlling the constant temperature of an electrolyte system to be 75 ℃, the electrolytic voltage to be-2.4V (vs Ag), and the cathode material to be a high-purity copper sheet; after 30min of electrolysis, terbium chloride is added for one time to ensure that the concentration of the terbium chloride in the system is 0.025 mol/L; and collecting and storing the substrate together with the deposit after electrolyzing for 60 min. The characterization and detection result shows that metal terbium can be effectively deposited, the total content of terbium element detected by ICP is 99.61%, the deposited film obtained by scanning SEM observation is a uniform and compact deposited film, and the thickness of the terbium film is 0.37 microns.

Example 7

Preparing electrolyte raw materials comprising terbium chloride and lithium nitrate and a solvent DMI, and stirring and mixing the electrolyte raw materials and the solvent DMI in an electrolytic cell to form an electrolyte system, wherein the molar concentrations of the terbium chloride and the lithium nitrate are respectively 0.035mol/L and 0.1 mol/L. Controlling the constant temperature of an electrolyte system to be 80 ℃, the electrolytic voltage to be-2.3V (vs Ag), and the cathode material to be a high-purity aluminum sheet; after 30min of electrolysis, terbium chloride is added for one time to ensure that the concentration of the terbium chloride in the system is 0.035 mol/L; and collecting and storing the substrate together with the deposit after electrolyzing for 60 min. The characterization and detection result shows that metal terbium can be effectively deposited, the total content of terbium element detected by ICP is 99.74%, the deposited film obtained by SEM observation is a uniform and compact deposited film, and the thickness of the terbium film is 0.43 microns.

Example 8

Preparing electrolyte raw materials comprising terbium chloride and lithium nitrate and a solvent DMI, and stirring and mixing the electrolyte raw materials in an electrolytic bath to form an electrolyte system, wherein the molar concentrations of the terbium chloride and the lithium nitrate are 0.015mol/L and 0.1mol/L respectively. Controlling the constant temperature of an electrolyte system to be 55 ℃, the electrolytic voltage to be-2.3V (vs Ag), and the cathode material to be a high-purity copper sheet; after 30min of electrolysis, terbium chloride is added for one time to ensure that the concentration of the terbium chloride in the system is 0.015 mol/L; and collecting and storing the substrate together with the deposit after electrolyzing for 60 min. The characterization and detection result shows that metal terbium can be effectively deposited, the total content of terbium element detected by ICP is 99.98%, and the deposited film obtained by SEM observation is a uniform and compact deposited film, and the thickness of the terbium film is 0.46 micrometer.

Claims

1. A method for preparing a rare earth metal terbium film by low-cost electrochemical deposition is characterized by comprising the following steps: the method is an electrodeposition method and comprises the following process steps:

s2, placing the DMI electrolyte of lithium nitrate into an electrolytic cell, adding anhydrous terbium chloride into the electrolytic cell, and stirring and mixing the solution in the electrolytic cell to form a uniform system, wherein the molar concentration of the terbium chloride is 0.01-0.05 mol/L, the temperature of the whole system is controlled to be 25-80 ℃, and the electrolytic voltage is-2.0-2.4V vs Ag;

s3, in the electrodeposition process, adding anhydrous terbium chloride into the electrolytic cell at intervals, and controlling the molar concentration of the terbium chloride to be +/-2% of the initial concentration.

2. The method of claim 1, wherein: in the step S1, the molar concentration of lithium nitrate in DMI is 0.02-0.1 mol/L.

3. The method of claim 1, wherein: in the step S2, the molar concentration of terbium chloride is 0.02-0.05 mol/L.

4. The method of claim 1, wherein: in the step S3, anhydrous terbium chloride is added into the electrolytic cell every 30min, and the molar concentration of the terbium chloride is controlled to be +/-2% of the initial concentration.

5. The method of claim 1, wherein: the method includes a step S4 of loading the metal terbium thin film formed on the cathode substrate with the substrate material into a closed vessel containing dimethyl carbonate or kerosene every 60 min.

6. The method of claim 1, wherein: in the electrodeposition process, a high-purity tungsten sheet is used as an anode, and a pure copper sheet or a pure aluminum sheet is used as a cathode.

7. The method of claim 6, wherein: the inter-polar distance between the anode and the cathode was 15 mm.