CN103556184B - A kind of full moist type nano-Ni/Fe 2o 4the preparation method of-NiO-Cu-Ni cermet inert anode - Google Patents

Abstract

The invention discloses a preparation method of an all-wetting nanometer NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anode. The present invention uses iron oxide, nickelous oxide or nickel oxide, copper powder, nickel powder, etc. As a dopant, water, absolute ethanol, polyvinylpyrrolidone (PVP) is used as a mixture of one or more substances as a surfactant, using planetary ball milling technology, cold isostatic pressing (CIP) technology and atmosphere sintering Technology, to obtain a NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anode with a grain size of 53nm and a density greater than 99%. The cermet inert anode can replace the current traditional carbon anode and is applied in the aluminum electrolytic cell. The inert anode produced by the inventive process does not produce harmful and poisonous gas, is environmentally friendly and has low production cost.

Description

A preparation method of fully wetted nanometer NiFe2O4-NiO-Cu-Ni cermet inert anode

technical field

The invention belongs to the technical field of powder metallurgy and molten salt electrolytic aluminum anode materials, and in particular relates to a preparation method of an all-wetting nanometer NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anode.

Background technique

At present, the aluminum electrolysis industry adopts the molten salt electrolysis method. The anode used is a carbon anode. The production process consumes a large amount of carbon materials and energy. The electrolysis process produces a large amount of greenhouse gases CO ₂ , CF ₄ , C ₂ F ₆ , asphalt flue gas and Substances such as carbonyl sulfide (COS) seriously pollute the environment. At the same time, due to the continuous consumption of the anode in the electrolysis production process, the anode needs to be adjusted and replaced continuously, which increases the labor intensity of the workers, and even makes it difficult to carry out stable production, which in turn leads to high energy consumption and low current efficiency in aluminum electrolysis. Due to the above problems, the use of inert anode materials in the aluminum electrolysis process is a hot research topic at present, and it is also an important development direction for the aluminum production industry to achieve energy saving, environmental protection, emission reduction and efficiency improvement. At present, there are many patents and research reports on inert anodes for molten salt electrolysis at home and abroad, but they still cannot meet the high electrical conductivity, corrosion resistance, high mechanical strength and other properties required by the current aluminum electrolysis industry. At present, the main patents related to the preparation of inert anode nanomaterials are not directly preparing nano-scale NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anodes, but by first preparing nano-scale NiFe ₂ O ₄ or NiO ceramic powder , and then add a certain amount of nano-NiFe ₂ O ₄ or NiO ceramic powder to the inert anode to prepare the inert anode to improve the conductivity, corrosion resistance and toughness of the anode material, but these methods have not been able to solve the problem of NiFe ₂ O ₄ - The problem of wetting ceramics by the metal phase in NiO-Cu-Ni cermet inert anodes. The wetting of the ceramic by the metal phase in the NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anode is the key to improve the performance of the anode material such as electrical conductivity, corrosion resistance, thermal shock resistance and mechanical connectivity. Therefore, it is of great significance to develop a simple, easy-to-operate, energy-saving, environmentally friendly, and low-cost method for directly preparing NiFe ₂ O ₄ -NiO-Cu-Ni nano-powders with good dispersion and fine particle size.

Contents of the invention

The purpose of the present invention is to provide a preparation method and process of a fully wetted nano-cermet inert anode for molten salt electrolytic aluminum, to solve the problem of non-wetting or poor wettability between metal and ceramics, and to overcome the existing cermets The inert anode has poor electrical conductivity, isolated and uneven distribution of metal in the ceramic matrix, poor corrosion resistance, poor thermal shock resistance, difficult processing and large-scale problems.

Another object of the present invention is to provide a method for directly preparing NiFe ₂ O ₄ -NiO-Cu-Ni nanopowder with good dispersion and fine particle size, which is simple, easy to operate, energy-saving and environmentally friendly, and low in cost, so that it is easy to realize Industrial production.

The purpose of the present invention is achieved in this way, the preparation method of the fully wetted nanometer NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anode is characterized in that it comprises the following steps:

A. Precursor ceramic powder preparation: Add water to the mixture of Fe ₂ O ₃ and NiO or Ni ₂ O ₃ , after wet ball milling and drying, place it in a sintering furnace for calcination, and control the calcination temperature to prepare NiFe ₂ O ₄ -NiO precursor ceramic powder;

B. Preparation of mixed nano-powder: use the ceramic powder prepared in step A as one of the raw materials, add Cu powder and Ni powder for mixing, and add a small amount of Ti powder, MnO ₂ , V ₂ O ₅ , MgO and CaO, etc. Mixtures of one or more substances and other dopants, adding one or more mixtures of water, absolute ethanol or polyvinylpyrrolidone (PVP) for secondary planetary ball milling, drying, and ball milling to obtain NiFe ₂ Mixed nanopowder of O ₄ -NiO-Cu-Ni;

C. Put the mixed nano-powder prepared in step B in a rubber sheath, vibrate, vacuumize and shape, and then use cold isostatic pressing to obtain a cylindrical green body;

D. Put the green body prepared in step C into a vacuum furnace or an atmosphere furnace for sintering, the sintering temperature is 650°C-950°C, and sintering in a vacuum or an inert gas atmosphere, and finally obtain molten salt electrolysis, metal phase and ceramics The phase is completely wetted, the grain size is 53nm, and the high density NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anode.

The present invention has the following advantages:

(1) Polyvinylpyrrolidone (PVP) was introduced and dissolved in absolute ethanol to form composite grinding aids, dispersants, film-forming agents and binders; in addition, PVP can well disperse finely ground powders and form The more stable coating film covers the powder, reduces the activity of the nano-powder, and improves the stability of the nano-powder;

(2) Cold isostatic pressing is used to improve the efficiency and yield of powder forming, reduce the consumption of powder, and reduce production costs;

(3) The sintering temperature of the compact is greatly reduced, that is, the sintering temperature of the common method is 1200°C to 1400°C, while the sintering temperature of the inert anode prepared by the process method of the present invention is only 650°C to 900°C, which has a large energy-saving and consumption-reducing capabilities;

(4) The inert anode obtained by sintering nano powder solves the problem of non-wetting or poor wettability between metal and ceramics;

(5) By replacing the TiO ₂ doping in the common method by Ti doping, the metal Cu in the sintered inert anode no longer overflows, and the complete wetting between the metal and the ceramic is achieved to achieve spreading;

(6) Increase the density of the material to over 99%, increase the thermal shock resistance to 185.71%, and reduce the static corrosion rate to below 2.046mm/y.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

detailed description

The present invention will be further described below in conjunction with the examples, but the present invention is not limited in any way, and any transformation made based on the teaching of the present invention falls within the protection scope of the present invention.

The preparation method of the all-wetting nanometer NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anode of the present invention comprises the following steps:

A. Preparation of precursor ceramic powder: mix Fe ₂ O ₃ and NiO or Ni ₂ O ₃ (that is, "mixture of Fe ₂ O ₃ and NiO" or "mixture of Fe ₂ O ₃ and Ni ₂ O ₃ ") , adding water, wet ball milling, drying, placing in a sintering furnace for calcination, and controlling the calcination temperature to prepare NiFe ₂ O ₄ -NiO precursor ceramic powder;

B. Preparation of mixed nano-powder: use the ceramic powder prepared in step A as one of the raw materials, add Cu powder and Ni powder for mixing, and add a small amount of Ti powder, MnO ₂ , V ₂ O ₅ , MgO and CaO, etc. Add one or more mixtures of water, absolute ethanol or polyvinylpyrrolidone for secondary planetary ball milling, dry, and pulverize the ball mill to obtain NiFe ₂ O ₄ - Mixed nanopowder of NiO-Cu-Ni;

C. Put the mixed nano-powder prepared in step B in a rubber sheath, vibrate, vacuumize and shape, and then use cold isostatic pressing to obtain a cylindrical green body;

D. Put the green body prepared in step C into a vacuum furnace or an atmosphere furnace for sintering at a temperature of 650°C to 950°C in a vacuum or an inert gas atmosphere to finally obtain molten salt electrolysis, metal phase and ceramics The phase is completely wetted, the grain size is 53nm, and the high density NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anode.

The weight ratio of Fe ₂ O ₃ and NiO or Ni ₂ O ₃ in the step A is 1:0.1~5.

The calcination temperature in the step A is 900-1200°C.

The weight percentage of the precursor of the B step is 70-85%, the weight percentage of the mixture of Cu powder and Ni powder is 10-25%; the weight percentage of the mixture of Ti powder, MnO ₂ , V ₂ O ₅ , MgO, CaO The percentage is 1~5%.

The water, absolute ethanol, and polyvinylpyrrolidone (PVP) in the step B can be used as surfactants in the process of preparing the powder.

The mass fraction of each component of the fully wetted nanometer NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anode in the step D is: NiFe ₂ O ₄ powder 66.3%-75.6%, NiO powder 10%-15% , Cu powder 14% ~ 17%, Ni powder 2% ~ 5%; trace dopant content are: Ti powder 0 ~ 2%, MnO ₂ powder 0 ~ 1%, V ₂ O ₅ powder 0 ~ 1.5%, MgO powder 0~1%, CaO powder 0~1%.

Example 1

Weigh industrial-grade iron oxide powder and nickelous oxide in a weight ratio of 1:1, add 65% water, and use a ball mill to grind for 6 hours. The obtained slurry is dried at 100°C for 24 hours, and then calcined at 1100°C to obtain NiO Excessive 10% NiFe ₂ O ₄ powder. Take NiFe ₂ O ₄ -10%NiO powder as one of the raw materials, add chemically pure 14% Cu powder, 3% Ni powder in proportion; trace dopant 0.5% Ti powder, 1% MnO ₂ powder, 1.5% V ₂ O ₅ powder, 1% MgO powder and 1% CaO powder, then add 60% absolute ethanol and 1% PVP in mass fraction, ball mill for 12 hours, and evaporate the obtained mixed slurry to recover absolute ethanol. The mixture was dried for 12 hours, and the obtained material was pulverized to prepare a mixed nano-powder with an average particle size of 43.7 nm. Put the prepared nano-powder into a bag with good plasticity and high strength, vibrate or compact it to form the desired shape, preliminarily determine the size, vacuumize the blank to remove the gas in the material, and then cool it under 240MPa, etc. Static pressure forming to obtain the desired compact. The green compact is protected by argon (Ar) and sintered at 700°C for 12 hours to obtain an inert anode of NiFe ₂ O ₄ -NiO-Cu-Ni cermet.

Implementation effect: The inert anode material completely replaces the traditional carbon anode material. After the inert anode material is applied to the production of electrolytic aluminum, the current efficiency reaches 95%, the cell voltage drops to 390mv, and the life of the electrolytic cell increases to more than 2000 days.

Example 2

Weigh industrial-grade iron oxide powder and nickel oxide powder at a weight ratio of 1:1.5, add 65% water, and use a ball mill to mix and grind for 6 hours. The resulting slurry is dried at 100°C for 24 hours, crushed and calcined at 1200°C to obtain NiO Excessive 15% NiFe ₂ O ₄ powder. Using NiFe ₂ O ₄ -15%NiO powder as one of the raw materials, add chemically pure 10% Cu powder, 2% Ni powder in proportion; trace dopant 0.5% Ti powder, 0.5% MnO ₂ powder, 2% V ₂ O ₅ powder, 1.2% MgO powder and 0.8% CaO powder, then add 60% absolute ethanol and 1% PVP in mass fraction, ball mill for 12 hours, and evaporate the obtained mixed slurry to recover absolute ethanol. The mixture was dried for 12 hours, and the obtained material was pulverized to prepare a mixed nano-powder with an average particle size of 43.7 nm. Put the prepared nano-powder into a bag with good plasticity and high strength, vibrate or compact it to form the desired shape, preliminarily determine the size, vacuumize the blank to remove the gas in the material, and then cool it under 240MPa, etc. Static pressure forming to obtain the desired compact. The green compact is protected by argon (Ar) and sintered at 700°C for 12 hours to obtain a high-quality NiFe ₂ O ₄ -NiO-Cu-Ni cermet inert anode.

Implementation effect: The inert anode material completely replaces the traditional carbon anode material. After the inert anode material is applied to the production of electrolytic aluminum, the current efficiency reaches 94%, the cell voltage drops to 385mv, and the life of the electrolytic cell increases to more than 2000 days.

Example 3

Weigh industrial-grade iron oxide powder in a weight ratio of 1:2.0, add 70% water, and use a ball mill to mix and grind for 8 hours. The obtained slurry is dried at 100°C for 24 hours, and then calcined at 1050°C to obtain NiO excess of 12%. NiFe ₂ O ₄ powder. Using NiFe ₂ O ₄ -12%NiO powder as one of the raw materials, add chemical grade 15% Cu powder, 3% Ni powder in proportion; trace dopant 1%Ti powder, 1%MnO ₂ powder, 1.0%V ₂ O ₅ powder, 1.5% MgO powder and 1% CaO powder, then add 70% absolute ethanol and 3% PVP in the mass fraction, ball mill for 30 hours, and evaporate the obtained mixed slurry to recover absolute ethanol, at 80°C The mixture was dried for 12 hours, and the obtained material was pulverized to prepare a mixed nano-powder with an average particle size of 43.7 nm. Put the prepared nano-powder into a bag with good plasticity and high strength, vibrate or compact it to form the desired shape, set the size in rough steps, vacuumize the preform to remove the gas in the material, and then cool it under 280MPa The desired compact is obtained by isostatic pressing. The green compact was protected by argon (Ar) and sintered at 800°C for 12 hours to obtain an inert anode of NiFe2O4-NiO-Cu-Ni cermet.

Implementation effect: The inert anode material completely replaces the traditional carbon anode material. After the inert anode material is applied to the production of electrolytic aluminum, the current efficiency reaches 94.5%, the cell voltage drops to 385mv, and the life of the electrolytic cell increases to more than 2000 days.

Claims (3)

1. a full moist type nano-Ni/Fe ₂o ₄the preparation method of-NiO-Cu-Ni cermet inert anode, is characterized in that comprising the steps:

Prepared by A, precursor ceramic powder: by Fe ₂o ₃with NiO or Ni ₂o ₃by weight being that 1:0.1 ~ 5 mix, adding water in mixture after wet ball grinding, drying, being placed in sintering oven and calcining, controlling calcining temperature, be prepared into NiFe ₂o ₄-NiO precursor ceramic powder;

B, the preparation of mixing nano-powder: with the precursor ceramic powder prepared in step A for raw material, add Cu powder, Ni powder mixes, and add Ti powder, MnO ₂, V ₂o ₅, MgO, CaO mixture as trace doped thing, add dehydrated alcohol and polyvinylpyrrolidone mixture carries out secondary planetary type ball-milling, dry, ball milling material is pulverized and is obtained containing NiFe ₂o ₄the mixing nano-powder of-NiO-Cu-Ni; The weight percent of precursor ceramic powder is 70 ~ 85%, Cu powder, the weight percent of Ni powder mixture is 10 ~ 25%, Ti powder, MnO ₂, V ₂o ₅, MgO, CaO the weight percent of mixture be 1 ~ 5%;

C, the mixing nano-powder prepared in step B is placed in rubber package set, jolt ramming, vacuumize sizing after, adopt cold isostatic compaction, obtain cylindrical shape green compact;

D, the green compact prepared are placed in vacuum oven or atmosphere furnace sinter in step C, sintering temperature is 650 DEG C ~ 950 DEG C, sinters in vacuum or inert gas atmosphere, finally obtains fused salt electrolysis use, metallographic phase and ceramic phase complete wetting, grain-size is 53nm, the NiFe that density is high ₂o ₄-NiO-Cu-Ni cermet inert anode.

2. full moist type nano-Ni/Fe according to claim 1 ₂o ₄the preparation method of-NiO-Cu-Ni cermet inert anode, is characterized in that calcining temperature described in step A is 900 ~ 1200 DEG C.

3. full moist type nano-Ni/Fe according to claim 1 ₂o ₄the preparation method of-NiO-Cu-Ni cermet inert anode, is characterized in that full moist type nano-Ni/Fe described in D step ₂o ₄the massfraction of each component of-NiO-Cu-Ni cermet inert anode is: NiFe ₂o ₄powder 66.3% ~ 75.6%, NiO powder 10% ~ 15%, Cu powder 14% ~ 17%, Ni powder 2% ~ 5%; Trace doped thing content is respectively: Ti powder 0 ~ 2%, MnO ₂powder 0 ~ 1%, V ₂o ₅powder 0 ~ 1.5%, MgO powder 0 ~ 1%, CaO powder 0 ~ 1%.