CN108384518A - Compact aluminum oxide shell high-temperature phase change heat accumulation microcapsules and preparation method thereof - Google Patents

Abstract

The invention relates to a high-temperature phase change thermal storage microcapsule with a dense alumina shell and a preparation method thereof. The technical scheme is: mix according to the mass ratio of iodine: absolute ethanol: catalyst of 1: (3000-8000): (0.1-1) to obtain the solution. Under water bath and stirring condition, press iodine: the mass ratio of aluminum-silicon alloy powder is 1: (100～500), add aluminum-silicon alloy powder in the solution, then press iodine: the mass ratio of acetic acid is 1: (400～800) ), adding acetic acid. Stand still, filter, wash, and dry; then place in a muffle furnace, keep warm for 2-8 hours in an oxidizing atmosphere at 900-1300°C, and cool to room temperature to prepare dense alumina shell high-temperature phase-change thermal storage microcapsules . The invention has the characteristics of low cost, simple process and easy industrial production, and the high-temperature phase-change thermal storage microcapsules with dense alumina shell prepared by the method have good dispersibility, many heat cycles, high shell strength and high heat utilization rate.

Description

Dense alumina shell high temperature phase change heat storage microcapsules and preparation method thereof

technical field

The invention belongs to the technical field of high temperature phase change thermal storage microcapsules. Specifically, it relates to providing a high-temperature phase-change thermal storage microcapsule with a dense alumina shell and a preparation method thereof.

Background technique

Heat storage technology is a kind of energy storage technology that uses heat storage materials to store temporarily unnecessary heat, and then releases heat when heat is needed. Heat storage technology solves the time difference contradiction between heat supply and demand, and improves the utilization of heat. Therefore, it can be used for peak-shaving and valley-filling of power loads, solar energy storage, and recovery of industrial waste heat, so as to achieve the goal of developing new energy and saving old energy. Purpose.

The core issue of heat storage technology is the preparation and application of heat storage materials, among which phase change heat storage materials have become heat storage materials with good potential because of their high energy storage and adjustable phase change temperature. However, phase change heat storage materials are prone to problems such as phase change medium leakage and volume change during phase change, which limits the practical application of phase change heat storage materials. The preparation of phase change materials into phase change heat storage microcapsules is one of the main methods to solve the above problems. The phase change heat storage microcapsule is composed of a phase change material as a core and a coating material as a shell. Due to the advantages of non-corrosion, anti-medium leakage, high heat storage density and constant temperature during phase change, phase change thermal storage microcapsules have become a research hotspot in recent years.

Phase change materials are classified by phase change temperature, and phase change materials with a phase change temperature above 500°C are called high temperature phase change materials. Aluminum and aluminum-silicon alloys are one of the high-temperature phase change heat storage materials, which have the advantages of good thermal conductivity, good thermal stability, large latent heat of phase change, high thermal conductivity and high heat storage density. If aluminum or aluminum-silicon alloy is used as the core of phase change thermal storage microcapsules, the cladding material has the following requirements: good corrosion resistance, good cycle stability, high temperature stress intensity, and good oxidation resistance.

In recent years, some scholars have conducted some research on aluminum and aluminum-silicon alloys as phase-change heat storage materials, and disclosed some composite phase-change heat storage materials containing aluminum or aluminum-silicon alloys. For example, "a high-temperature composite phase-change thermal storage material and its preparation method" (201310175016.1) patented technology, this technology uses white clay, high-alumina bauxite and aluminum powder as raw materials, directly mixes them, presses them into shape, and roasts them at high temperature to obtain a A high-temperature composite phase-change heat storage material; "a cermet with phase-change heat storage function and its preparation method" (201310293700.X) patented technology, using aluminum-silicon alloy powder and corundum powder as raw materials, and sintering with magnesium oxide Auxiliary, through dry ball milling, molding and roasting, a cermet with phase change heat storage function is prepared. The above-mentioned technical methods all use phase change materials as raw materials directly in the preparation of composite phase change heat storage materials, and use the heat absorption and heat release of phase change materials when phase change occurs to achieve the purpose of heat storage. However, this direct mixed molding method is very easy to leak and overflow after the aluminum or aluminum-silicon alloy powder is melted during the firing process, and the liquid-phase aluminum or aluminum-silicon alloy will also reduce the high-temperature physical properties of the material.

There are also some scholars who have studied the production of aluminum or aluminum-silicon alloy phase change heat storage microcapsules: "A kind of Al/Al ₂ O ₃ heat storage material and its preparation method" (201010127955.5) patented technology, using aluminum powder as raw material, The core-shell composite phase change heat storage material with Al ₂ O ₃ wrapped Al powder was prepared by cooling in oxygen atmosphere after atomization. This kind of composite phase change heat storage material with core-shell structure has high requirements on equipment, complex preparation process and difficult control, and the prepared shell is thin, which is difficult to meet the strength requirement. "A high-temperature phase-change thermal storage microcapsule and its preparation method" (201710502031.0) patented technology, using aluminum-silicon alloy powder as raw material, directly treating it with aluminum dihydrogen phosphate solution to form a phase-change thermal storage microcapsule green body, or The green body is fired to form a high-temperature phase-change thermal storage microcapsule with a dense shell. The preparation method of such microcapsules is simple, but the prepared microcapsules are bonded to each other, which makes it difficult to meet the industrial application with high requirements for dispersibility.

Contents of the invention

The invention aims to overcome the defects of the prior art, and aims to provide a method for preparing dense alumina shell high-temperature phase-change thermal storage microcapsules with low cost, simple process and easy industrial production. The dense alumina shell high-temperature phase-change thermal storage microcapsules prepared by the method have good dispersibility, many heat cycles, high shell strength and high heat utilization rate.

For realizing above-mentioned task, the step of the technical solution adopted in the present invention is:

Step 1, according to the mass ratio of iodine: dehydrated ethanol: catalyst is 1: (3000～8000): (0.1～1), adding the iodine and the catalyst into the dehydrated ethanol, stirring for 10～30min , to obtain a solution.

Step 2, according to the mass ratio of iodine: aluminum-silicon alloy powder is 1: (100-500), add the aluminum-silicon alloy powder to the solution, and stir for 6-12 hours in a water bath at 60-90°C , to obtain a suspension.

Step 3, according to the mass ratio of iodine: acetic acid being 1: (400-800), adding the acetic acid to the suspension under 60-90°C water bath and stirring conditions; standing for 1-12h, filtering, washing the filtered material alternately with absolute ethanol and deionized water until the pH value is neutral, and drying to a constant weight to obtain a high-temperature phase change thermal storage microcapsule body.

Step 4: Put the high-temperature phase change thermal storage microcapsule body in a muffle furnace, raise the temperature to 900-1300°C at a rate of 3-10°C/min in an oxidizing atmosphere, keep it warm for 2-8 hours, and cool to At room temperature, high temperature phase change heat storage microcapsules with dense alumina shell were prepared.

The I content of the iodine is ≥99.0wt%.

The particle diameter of the aluminum-silicon alloy powder is 20-74 μm, and the Si content in the aluminum-silicon alloy powder is 0.1-44 wt%.

The catalyst is more than one of mercuric chloride and aluminum trichloride.

The concentration of said acetic acid is greater than 98%.

The oxygen partial pressure in the oxidizing atmosphere is ≥0.03GPa.

Owing to adopting above-mentioned technical scheme, the present invention has following positive effect compared with prior art:

The invention uses iodine, absolute ethanol, catalyst, aluminum-silicon alloy powder and acetic acid as raw materials to prepare a high-temperature phase change thermal storage microcapsule green body, and then heats it under the condition of oxidizing atmosphere and 900-1300°C for 2-8 hours to obtain the High temperature phase change heat storage microcapsules with dense alumina shell. The preparation method has low raw material cost, simple process, easy control and easy industrial production.

The absolute ethanol used in the present invention reacts with the aluminum in the aluminum-silicon alloy under the synergistic action of the iodine and the catalyst to generate aluminum ethylate. The generated aluminum ethoxide is in the form of a gel, and under the action of nucleation, the aluminum ethoxide can easily coat the surface of the aluminum-silicon alloy without affecting the excellent dispersibility of the aluminum-silicon alloy powder. The aluminum ethoxide on the surface of the aluminum-silicon alloy undergoes an esterification reaction with acetic acid to produce aluminum hydroxide with two acetate groups. The acetate group of this aluminum hydroxide will decompose between 316 and 477°C during the roasting process to form amorphous alumina. Amorphous alumina finally begins to transform into alumina coating on the surface of aluminum-silicon alloy powder at 900-1300°C. Therefore, the high-temperature phase-change thermal storage microcapsules prepared with dense alumina shells have high thermal cycle times and high compressive strength, and can be used as raw materials for preparing high-temperature phase-change thermal storage composite material blocks.

The dense alumina shell high-temperature phase-change heat storage microcapsules prepared by the invention solve the problem that aluminum-silicon alloys are easily leaked after being melted as phase-change heat storage materials in the application process; they can effectively provide protection for aluminum-silicon alloys in molten state , to avoid the loss of aluminum-silicon alloy and the resulting corrosion, and increase the cycle times of aluminum-silicon alloy.

The dense alumina shell high-temperature phase change heat storage microcapsules prepared by the present invention effectively utilize the latent heat of phase change of the aluminum-silicon alloy, and improve the utilization rate and utilization efficiency of heat; the dense alumina shell high temperature phase change heat storage microcapsules The use temperature is high, which can meet the high temperature heat exchange of solar power plants, industrial furnaces and heat recovery of high temperature industrial waste gas.

Therefore, the present invention has the characteristics of low cost, simple process and easy industrial production. The high-temperature phase change heat storage microcapsules with dense alumina shell prepared by the method have good dispersibility, many thermal cycles, high shell strength and high heat utilization rate. high.

Detailed ways

The present invention will be further described below in combination with specific embodiments, which are not intended to limit the scope of protection thereof.

In order to avoid duplication, the materials involved in this specific embodiment are first described in a unified manner as follows, and will not be repeated in the embodiments:

The I content of the iodine is ≥99.0wt%.

The particle diameter of the aluminum-silicon alloy powder is 20-74 μm, and the Si content in the aluminum-silicon alloy powder is 0.1-44 wt%.

The catalyst is more than one of mercuric chloride and aluminum trichloride.

The concentration of said acetic acid is greater than 98%.

The oxygen partial pressure in the oxidizing atmosphere is ≥0.03GPa.

Example 1

A high-temperature phase-change thermal storage microcapsule with a dense alumina shell and a preparation method thereof. The steps of the preparation method described in this embodiment are:

Step 1, according to the mass ratio of iodine: dehydrated ethanol: catalyst is 1: (3000～6000): (0.1～0.5), adding the iodine and the catalyst into the dehydrated ethanol, stirring for 10～17min , to obtain a solution.

Step 2, according to the mass ratio of iodine: aluminum-silicon alloy powder is 1: (100-300), add the aluminum-silicon alloy powder to the solution, and stir for 6-8 hours in a water bath at 60-70°C , to obtain a suspension.

Step 3, according to the mass ratio of iodine: acetic acid being 1: (400-600), adding the acetic acid to the suspension under 60-70°C water bath and stirring conditions; standing for 1-5h, filtering, washing the filtered material alternately with absolute ethanol and deionized water until the pH value is neutral, and drying to a constant weight to obtain a high-temperature phase change thermal storage microcapsule body.

Step 4: Put the high-temperature phase change thermal storage microcapsule body in a muffle furnace, raise the temperature to 900-1100°C at a rate of 3-6°C/min in an oxidizing atmosphere, keep it warm for 2-4 hours, and cool to At room temperature, high temperature phase change heat storage microcapsules with dense alumina shell were prepared.

Example 2

A high-temperature phase-change thermal storage microcapsule with a dense alumina shell and a preparation method thereof. The steps of the preparation method described in this embodiment are:

Step 1, by iodine: dehydrated alcohol: the mass ratio of catalyst is 1: (4000～7000): (0.3～0.7), described iodine and described catalyst are added in described dehydrated alcohol, stir 16.5～23.5 min, the solution is obtained.

Step 2, according to the mass ratio of iodine: aluminum-silicon alloy powder is 1: (200-400), add the aluminum-silicon alloy powder to the solution, and stir for 8-10 hours in a water bath at 70-80°C , to obtain a suspension.

Step 3, according to the mass ratio of iodine: acetic acid is 1: (500 ~ 700), under the condition of 70 ~ 80 ℃ water bath and stirring, add the acetic acid to the suspension; let stand for 4.5 ~ 8.5h , filtered, and the filtered material was alternately washed with absolute ethanol and deionized water until the pH value was neutral, and dried to a constant weight to obtain a high-temperature phase change thermal storage microcapsule green body.

Step 4: Put the high-temperature phase-change thermal storage microcapsule body in a muffle furnace, raise the temperature to 1000-1200°C at a rate of 5-8°C/min in an oxidizing atmosphere, keep it warm for 4-6 hours, and cool to At room temperature, high temperature phase change heat storage microcapsules with dense alumina shell were prepared.

Example 3

A high-temperature phase-change thermal storage microcapsule with a dense alumina shell and a preparation method thereof. The steps of the preparation method described in this embodiment are:

Step 1, according to the mass ratio of iodine: dehydrated ethanol: catalyst is 1: (5000～8000): (0.6～1), adding the iodine and the catalyst into the dehydrated ethanol, stirring for 23～30min , to obtain a solution.

Step 2. According to the mass ratio of iodine: aluminum-silicon alloy powder as 1: (300-500), add the aluminum-silicon alloy powder to the solution, and stir for 10-12 hours in a water bath at 80-90°C , to obtain a suspension.

Step 3, according to the mass ratio of iodine: acetic acid is 1: (600 ~ 800), under the condition of 80 ~ 90 ℃ water bath and stirring, add the acetic acid to the suspension; let it stand for 8 ~ 12h, filtering, washing the filtered material alternately with absolute ethanol and deionized water until the pH value is neutral, and drying to a constant weight to obtain a high-temperature phase change thermal storage microcapsule body.

Step 4: Put the high-temperature phase change thermal storage microcapsule body in a muffle furnace, raise the temperature to 1100-1300°C at a rate of 7-10°C/min in an oxidizing atmosphere, keep it warm for 6-8 hours, and cool to At room temperature, high temperature phase change heat storage microcapsules with dense alumina shell were prepared.

Compared with the prior art, this specific embodiment has the following positive effects:

In this specific embodiment, iodine, absolute ethanol, catalyst, aluminum-silicon alloy powder, and acetic acid are used as raw materials to prepare a high-temperature phase-change thermal storage microcapsule green body, which is then kept in an oxidizing atmosphere at 900-1300°C for 2-8 hours. The high-temperature phase change heat storage microcapsules with dense alumina shell were prepared. The preparation method has low raw material cost, simple process, easy control and easy industrial production.

The anhydrous ethanol used in this specific embodiment reacts with the aluminum in the aluminum-silicon alloy under the synergistic action of iodine and a catalyst to form aluminum ethoxide. The generated aluminum ethoxide is in the form of a gel, and under the action of nucleation, the aluminum ethoxide can easily coat the surface of the aluminum-silicon alloy without affecting the excellent dispersibility of the aluminum-silicon alloy powder. The aluminum ethoxide on the surface of the aluminum-silicon alloy undergoes an esterification reaction with acetic acid to produce aluminum hydroxide with two acetate groups. The acetate group of this aluminum hydroxide will decompose between 316 and 477°C during the roasting process to form amorphous alumina. Amorphous alumina finally begins to transform into alumina coating on the surface of aluminum-silicon alloy powder at 900-1300°C. Therefore, the high-temperature phase-change thermal storage microcapsules prepared with dense alumina shells have high thermal cycle times and high compressive strength, and can be used as raw materials for preparing high-temperature phase-change thermal storage composite material blocks.

The dense alumina shell high-temperature phase-change heat storage microcapsules prepared in this specific embodiment solve the problem that aluminum-silicon alloys are easily leaked after being melted as phase-change heat storage materials in the application process; Provide protection to avoid the loss of Al-Si alloy and the resulting corrosion, and increase the cycle times of Al-Si alloy.

The dense alumina shell high-temperature phase change heat storage microcapsules prepared in this specific embodiment effectively utilize the latent heat of phase change of the aluminum-silicon alloy, which improves the utilization rate and utilization efficiency of heat; the high-temperature phase change heat storage microcapsules of the dense alumina shell The use temperature of microcapsules is high, which can meet the high-temperature heat exchange of solar power plants, industrial furnaces and heat recovery of high-temperature industrial waste gas.

Therefore, this specific embodiment has the characteristics of low cost, simple process and easy industrial production. The high-temperature phase-change thermal storage microcapsules with dense alumina shells prepared by this method have good dispersibility, many thermal cycles, high shell strength and heat dissipation. High utilization rate.

Claims (7)

1. A preparation method of dense alumina shell high-temperature phase-change thermal storage microcapsules, characterized in that the steps of the preparation method are: Step 1, according to the mass ratio of iodine: dehydrated ethanol: catalyst is 1: (3000～8000): (0.1～1), adding the iodine and the catalyst into the dehydrated ethanol, stirring for 10～30min , to obtain the solution; Step 2, according to the mass ratio of iodine: aluminum-silicon alloy powder is 1: (100-500), add the aluminum-silicon alloy powder to the solution, and stir for 6-12 hours in a water bath at 60-90°C , to obtain the suspension; Step 3, according to the mass ratio of iodine: acetic acid being 1: (400-800), adding the acetic acid to the suspension under 60-90°C water bath and stirring conditions; standing for 1-12h, Filtration, washing the filtered material with absolute ethanol and deionized water alternately until the pH value is neutral, drying to constant weight, and obtaining a high-temperature phase change thermal storage microcapsule green body; Step 4: Put the high-temperature phase change thermal storage microcapsule body in a muffle furnace, raise the temperature to 900-1300°C at a rate of 3-10°C/min in an oxidizing atmosphere, keep it warm for 2-8 hours, and cool to At room temperature, high temperature phase change heat storage microcapsules with dense alumina shell were prepared. 2. The preparation method of the dense alumina shell high-temperature phase change thermal storage microcapsules according to claim 1, characterized in that the I content of the iodine is ≥ 99.0wt%. 3. The method for preparing dense alumina shell high-temperature phase-change heat storage microcapsules according to claim 1, characterized in that the particle size of the aluminum-silicon alloy powder is 20-74 μm, and the Si content in the aluminum-silicon alloy powder is 0.1-44wt%. 4. The method for preparing dense alumina-shelled high-temperature phase-change thermal storage microcapsules according to claim 1, characterized in that the catalyst is at least one of mercuric chloride and aluminum trichloride. 5. The method for preparing dense alumina shell high-temperature phase-change thermal storage microcapsules according to claim 1, characterized in that the concentration of the acetic acid is greater than 98%. 6. The method for preparing dense alumina-shelled high-temperature phase-change thermal storage microcapsules according to claim 1, characterized in that the oxygen partial pressure in the oxidizing atmosphere is ≥0.03MPa. 7. A dense alumina shell high temperature phase change heat storage microcapsule, characterized in that the dense alumina shell high temperature phase change heat storage microcapsule is according to any one of claims 1-6 The method for preparing dense alumina shell high-temperature phase-change heat storage microcapsules prepares dense alumina shell high-temperature phase-change heat storage microcapsules.