CN1974873A - Fast stable growth process of alumina film with nanometer pore array in relatively great pore distance - Google Patents

Abstract

The invention relates to a rapid and stable growth method of an aluminum oxide nano-hole array membrane with relatively large hole spacing in the technical field of nanometer materials. The steps are: first, prepare the phosphoric acid-water-ethanol electrolyte: the volume ratio of H ₂ O and C ₂ H ₅ OH is 4:1, the concentration of H ₃ PO ₄ is 0.25-0.5 mol/L, and the total volume of the electrolyte is 2L; second, aluminum sheet pretreatment: soak the round aluminum sheet in acetone, wipe it clean, rinse it with deionized water, and use a mixed solution of perchloric acid and ethanol to electrochemically polish it under constant pressure; third, Use a low-temperature constant temperature bath to reduce the temperature of the electrolyte to -5 to -10°C, and stir the electrolyte, and perform primary corrosion on the aluminum sheet under the conditions of an anodic oxidation voltage of 195V and a current density of 1500-4000Am ^-2 ; Fourth, soak the sample after the primary corrosion in the mixed aqueous solution of chromic acid, and keep the temperature at 60 ° C to remove the alumina produced by the primary corrosion; fifth, perform secondary corrosion on the sample under the same conditions as the third step .

Description

Rapid and Stable Growth Method of Aluminum Oxide Nanopore Array Membrane with Large Pore Spacing

technical field

The invention relates to a preparation method in the technical field of nanomaterials, in particular to a method for rapidly and stably growing an aluminum oxide nanohole array membrane with relatively large pore spacing.

Background technique

The aluminum oxide film synthesized by anodic corrosion technology has important applications in metal anti-corrosion protection, metal coloring, metal strength design, etc. The research on the structure design of the film and its synthesis process has attracted more and more attention and interest. . From 1953 to the work of the Aluminum Research Laboratory of the American Aluminum Preparation Company until the mid-1990s, the research systems of the researchers engaged in this work were mainly dense alumina membranes and disordered porous alumina membranes. In 1995, H. Masuda, Department of Chemistry, Kyoto University, Japan reported for the first time the synthesis of an Al ₂ O ₃ ordered nanopore array membrane in the journal Science. Due to its unique ordered structure and simple and cheap fabrication method, alumina ordered nanopore array film has unique and wide application prospects in many fields (for example, magnetic memory, solar cells, photonic crystals, etc.), thus causing Great interest and high attention of scientists.

The use of oxalic acid and sulfuric acid electrolytes can only obtain alumina ordered nanopore array membranes with a pore spacing of less than 100 nm, which limits the application of alumina ordered nanopore array membranes in some fields. Therefore, the development of aluminum oxide nanoporous array membranes with larger pore spacing (above hundreds of nm) has attracted people's attention. Some experimental results show that the aluminum oxide ordered pore array membrane with large pore spacing (hundreds of nm) can be prepared by using phosphoric acid electrolyte, but due to the anodic oxidation in phosphoric acid electrolyte, the required reaction voltage is very high (195V). , the oxidation reaction of the aluminum sheet in the electrolyte is very violent, and the heat is very large and very fast, which leads to the inability to carry out the experiment stably and continuously, and the high-quality aluminum oxide nanoporous array membrane cannot be obtained. Therefore, in order to ensure the constant temperature of the solution and the rapid heat dissipation on the surface of the aluminum sheet, the rapid heat dissipation technology must be used in the experiment, and the temperature of the reaction solution is required to be low (0°C). However, in the traditional method, in order to realize the stable growth of the aluminum oxide nanopore array film, it is kept at a very low growth rate (less than 200nm min ^-1 ), and in order to obtain high-quality larger pore spacing (hundreds of nm) The growth time required for the aluminum oxide nanopore array film is very long (more than 10 hours).

Found through literature search to prior art, "Self-Ordering of Anodic Porous Alumina" published by Sachiko Ono etc. on Electrochemical and Solid-State Letters (Electrochemical and Solid State Letters, 2004, No. 7, page B21-B24) Induced by Local Current Concentration: Burning" (self-ordering of anodic porous alumina induced by local current concentration: ablation), the paper proposes that high current density, that is, high electric field is the most important factor affecting the order of the pores. Using an anodic oxidation voltage of 195V, the electrolysis was carried out in 0.2mol/L phosphoric acid solution, and a more orderly arrangement of pores was observed around the ablated area. The disadvantage is that due to the ablation phenomenon, the film cannot grow stably, which affects the overall quality of the porous alumina film.

Contents of the invention

Aiming at the deficiencies and defects in the prior art, the invention provides a method for rapid and stable growth of aluminum oxide nano-hole array membranes with relatively large hole spacing. In the invention, ethanol is added to the electrolytic solution to lower its freezing point, so that the temperature of the electrolytic solution is reduced to ten degrees below zero without freezing. The added ethanol can not only reduce the freezing point of the electrolyte, but also act as a cooling agent to take away a large amount of heat generated during the growth of the aluminum oxide film. In this low temperature environment, the rapid and stable growth of the anodic aluminum oxide film under high field (1500-4000A m ^-2 ) is realized by means of a conventional stirring device.

The present invention is realized through the following technical solutions, and the concrete steps are:

First, prepare the phosphoric acid-water-ethanol electrolyte: the volume ratio of H ₂ O and C ₂ H ₅ OH is 4:1, the concentration of H ₃ PO ₄ is 0.25-0.5mol/L, and the total volume of the electrolyte is 2L;

Second, aluminum sheet pretreatment: soak a circular aluminum sheet with a diameter of 2 cm (purity greater than or equal to 99.999%) in acetone for 20 minutes, wipe the surface with a cotton ball, and rinse it with deionized water. Electrochemical polishing of a 1:4 mixed solution of perchloric acid and ethanol under constant pressure;

Third, use a low-temperature constant temperature tank to lower the temperature of the electrolyte to -5 to -10°C, and stir the electrolyte. Under the conditions of an anodic oxidation voltage of 195V and a current density of 1500-4000Am ^-2 , the aluminum sheet is corrode for several minutes at a time;

Fourth, soak the sample after the primary corrosion in a mixed aqueous solution of phosphoric acid (6wt.%) and chromic acid (1.8wt.%) at a temperature of 60°C for several hours to remove the alumina produced by the primary corrosion;

Fifth, the sample is subjected to secondary corrosion under the same conditions as in the third step, and the corrosion time is within ten minutes.

The porous anodized aluminum prepared by the invention has the advantages of stable and rapid growth (4-10 μm min ^-1 ), uniform pore size and high orderly arrangement of pores. Compared with the traditional method, the present invention increases the efficiency of preparing porous anodic aluminum oxide membrane by nearly 100 times, and no ablation phenomenon occurs during the preparation process, the membrane growth is very stable, and the pore size uniformity and pore arrangement order are also improved. Greatly improve. More importantly, at an anodic oxidation voltage of 195V, different anodic oxidation current densities (1500-4000A m ^-2 ) can be obtained by adjusting phosphoric acid concentration, electrolyte temperature, area ratio of anode and cathode, etc., and then obtained Porous anodized aluminum oxide membranes with different pore spacing (320-380nm). This provides an effective method for obtaining porous anodized aluminum oxide membranes with freely adjustable pore spacing.

Detailed ways

The embodiments of the present invention are described in detail below: this embodiment is implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are provided, but the protection scope of the present invention is not limited to the following embodiments.

Example 1

The electrolyte is prepared from H ₂ O, C ₂ H ₅ OH and H ₃ PO ₄ , wherein the volume ratio of H ₂ O and C ₂ H ₅ OH is 4:1, and the content of H ₃ PO ₄ is 0.25mol/L. The total volume of the solution is 2L. Soak a circular aluminum sheet with a diameter of 2 cm (purity greater than or equal to 99.999%) in acetone for 20 minutes, wipe the surface with a cotton ball, rinse with deionized water, and use perchloric acid with a volume ratio of 1:4 The mixed solution with ethanol was electrochemically polished under constant pressure. Use a low-temperature thermostat to lower the temperature of the electrolyte to -5°C, and corrode the aluminum sheet for 5 minutes at a time under the conditions of an anode voltage of 195V and a current density of 1500mA/ ^m2 by means of conventional stirring means. The sample after the primary corrosion was immersed in a mixed aqueous solution of phosphoric acid (6wt.%) and chromic acid (1.8wt.%) at a temperature of 60°C for 4 hours to remove the alumina produced by the primary corrosion. Under the same conditions as the primary corrosion, the sample was subjected to secondary corrosion for 10 minutes. The prepared porous alumina membrane has a hexagonal close-packed distribution of surface structural units, highly ordered pore distribution, a pore diameter of 80nm, a pore spacing of 380nm, a barrier layer thickness of 150nm, and a film thickness of about 40μm.

Example 2

The electrolyte is prepared from H ₂ O, C ₂ H ₅ OH and H ₃ PO ₄ , wherein the volume ratio of H ₂ O and C ₂ H ₅ OH is 4:1, and the content of H ₃ PO ₄ is 0.3mol/L. The total volume of the solution is 2L. Soak a circular aluminum sheet with a diameter of 2 cm (purity greater than or equal to 99.999%) in acetone for 20 minutes, wipe the surface with a cotton ball, rinse with deionized water, and use perchloric acid with a volume ratio of 1:4 The mixed solution with ethanol was electrochemically polished under constant pressure. Use a low-temperature thermostat to lower the temperature of the electrolyte to -6°C, and corrode the aluminum sheet for 3 minutes at a time under the conditions of an anode voltage of 195V and a current density of 2000mA/ ^m2 by means of conventional stirring means. The sample after the primary corrosion was soaked in a mixed aqueous solution of phosphoric acid (6wt.%) and chromic acid (1.8wt.%) at a temperature of 60°C for 2 hours to remove the alumina produced by the primary corrosion. Under the same conditions as the primary corrosion, the sample was subjected to secondary corrosion for 10 minutes. The prepared porous alumina membrane has a hexagonal close-packed distribution of surface structural units, highly ordered pore distribution, a pore diameter of 90nm, a pore spacing of 360nm, a barrier layer thickness of 140nm, and a film thickness of about 50μm.

Example 3

The electrolyte is prepared from H ₂ O, C ₂ H ₅ OH and H ₃ PO ₄ , wherein the volume ratio of H ₂ O and C ₂ H ₅ OH is 4:1, and the content of H ₃ PO ₄ is 0.5mol/L. The total volume of the solution is 2L. Soak a circular aluminum sheet with a diameter of 2 cm (purity greater than or equal to 99.999%) in acetone for 20 minutes, wipe the surface with a cotton ball, rinse with deionized water, and use perchloric acid with a volume ratio of 1:4 The mixed solution with ethanol was electrochemically polished under constant pressure. Use a low-temperature thermostat to lower the temperature of the electrolyte to -10°C, and corrode the aluminum sheet for 2 minutes at a time under the conditions of an anode voltage of 195V and a current density of 4000mA/ ^m2 by means of conventional stirring means. The sample after the primary corrosion was soaked in a mixed aqueous solution of phosphoric acid (6wt.%) and chromic acid (1.8wt.%) at a temperature of 60°C for 3 hours to remove the alumina produced by the primary corrosion. Under the same conditions as the primary corrosion, the sample was subjected to secondary corrosion for 10 minutes. The prepared porous alumina membrane has a hexagonal close-packed distribution of surface structural units, highly ordered pore distribution, a pore diameter of 120nm, a pore spacing of 320nm, a barrier layer thickness of 120nm, and a film thickness of about 100μm.

Claims (8)

1, a kind of fast stable growth process of alumina film with nanometer pore array of relatively great pore distance is characterized in that, concrete steps are:

The first, preparation phosphoric acid-water-ethanol electrolytic solution: H wherein ₂O and C ₂H ₅The OH volume ratio is 4: 1, H ₃PO ₄Concentration is 0.25-0.5mol/L, and the electrolytic solution cumulative volume is 2L;

The second, aluminium flake pre-treatment: circular aluminium flake is put into acetone soak,, and use deionized water rinsing, use perchloric acid and alcohol mixed solution electrochemical etching under constant-pressure conditions with its surperficial wiped clean;

The 3rd, use low temperature thermostat bath electrolyte temperature to be reduced to-5～-10 ℃ of temperature, and electrolytic solution is stirred, be that 195V, current density are 1500-4000Am at anodic oxidation voltage ^-2Condition under aluminium flake is once corroded;

The 4th, the sample after once corroding to be soaked in the chromic acid mixed aqueous solution, temperature remains on 60 ℃, to remove the aluminum oxide that once corrosion produces;

The 5th, under the condition identical, sample is carried out anticaustic with the 3rd step.

2, the fast stable growth process of the alumina film with nanometer pore array of relatively great pore distance according to claim 1 is characterized in that, described circular aluminium flake, its diameter are 2cm, adopts purity more than or equal to 99.999% aluminium flake.

3, the fast stable growth process of the alumina film with nanometer pore array of relatively great pore distance according to claim 1 is characterized in that, in second step, and described immersion, the time is 20 minutes.

4, the fast stable growth process of the alumina film with nanometer pore array of relatively great pore distance according to claim 1 is characterized in that, described perchloric acid and alcohol mixed solution, and perchloric acid and ethanol volume ratio are 1: 4.

5, the fast stable growth process of the alumina film with nanometer pore array of relatively great pore distance according to claim 1 is characterized in that, described once corrosion, and the time is 2～5 minutes.

6, the fast stable growth process of the alumina film with nanometer pore array of relatively great pore distance according to claim 1 is characterized in that, in the 4th step, and described immersion, the time is 2～4 hours.

7, the fast stable growth process of the alumina film with nanometer pore array of relatively great pore distance according to claim 1 is characterized in that, described phosphoric acid and chromic acid mixed aqueous solution, and wherein the weight percent of phosphoric acid and chromic acid is respectively 6% and 1.8%.

8, the fast stable growth process of the alumina film with nanometer pore array of relatively great pore distance according to claim 1 is characterized in that, described anticaustic, and the time is within ten minutes.