CN113072335B

CN113072335B - Nano hierarchical pore silicon-based heat insulation material for heat distribution pipeline and preparation method thereof

Info

Publication number: CN113072335B
Application number: CN202010011484.5A
Authority: CN
Inventors: 何其霖; 高相东; 王金波; 杨海亮; 顾景磊
Original assignee: Ningbo Wanli Pipeline Co ltd; Shanghai Institute of Ceramics of CAS
Current assignee: Ningbo Wanli Pipeline Co ltd; Shanghai Institute of Ceramics of CAS
Priority date: 2020-01-06
Filing date: 2020-01-06
Publication date: 2022-07-22
Anticipated expiration: 2040-01-06
Also published as: CN113072335A

Abstract

The invention relates to a nanometer hierarchical pore silicon-based heat insulation material for a heat distribution pipeline and a preparation method thereof, in particular to a millimeter-micron-nanometer hierarchical pore silicon-based material and a preparation method thereof, wherein the millimeter-micron-nanometer hierarchical pore silicon-based material comprises the following raw materials: 5-55 wt% of superfine cementing material; 10-42 wt% of micron-sized filler, 1-5 wt% of foaming agent, 0.1-5 wt% of foam fixing agent, 1-8 wt% of additive and 25-50 wt% of water, wherein the content of each component is 100 wt%; the superfine cementing material is selected from at least one of pure portland cement, ordinary portland cement, aluminate cement and sulphoaluminate cement, and the average grain size of the superfine cementing material is less than or equal to 5 microns; the micron-sized filler is an inert filler or/and an active filler, and the average particle size is 5-100 microns; the admixture is a solid-phase admixture or/and a liquid-phase admixture.

Description

Nano hierarchical pore silicon-based heat insulation material for heat distribution pipeline and preparation method thereof

Technical Field

The invention relates to a nanometer hierarchical pore silicon-based heat insulation material for a heat distribution pipeline and a preparation method thereof, in particular to a millimeter-micron-nanometer hierarchical pore silicon-based material, a preparation method thereof and application thereof in heat distribution pipeline heat insulation, belonging to the field of heat distribution pipeline heat insulation materials.

Background

A thermal conduit refers to a conduit for transporting hot water or steam. The heat distribution pipeline is usually several kilometers or even tens of kilometers long, which leads to inevitable loss and loss of heat energy in the transportation process, and brings direct influence to the economic benefit of enterprises. How to improve the heat energy transmission efficiency of a heat distribution pipeline and make heat preservation measures of the pipeline are important problems to be solved urgently by current heat distribution enterprises and are also important components of the current national energy conservation and emission reduction strategy.

The current common materials for thermal pipeline insulation include: glass wool, rock wool, polyurethane foam, aluminum silicate fiber felt, aerogel insulation felt, microporous calcium silicate, and the like, each of which has advantages and disadvantages. For example, polyurethane foam has good heat insulation effect but does not resist high temperature; glass wool, rock wool and the like are high-temperature resistant, have good heat conductivity coefficient, and are easy to absorb water and pulverize; the aerogel heat-insulating felt has the lowest heat conductivity coefficient, is high-temperature resistant and not pulverized, but has high price. Therefore, research and development of novel pipeline thermal insulation materials are the hot spots in the field at present. Chinese patent (application number 201910124831.2) discloses a polyurethane foam which takes sepiolite and expanded perlite as heat-preservation filler and basalt fiber honeycomb fabric as reinforcing material, and has the characteristics of good heat preservation and insulation, low density, flame retardance, tensile strength and the like, but the existence of polyurethane limits the maximum use temperature of the polyurethane foam. Chinese patent application No. 201810791718.5 discloses a pipe thermal insulation material containing alumina aerogel, closed-cell expanded perlite, volcanic ash, modified palygorskite and the like as main components, which has good strength but a high thermal conductivity. Chinese patent (application No. 201810372389.0) discloses a high-strength stable pipeline thermal insulation material based on granite fiber and aerogel, but because of adopting silane coupling agent raw materials, the price is high, and the mechanical property is not high. Chinese patent (application No. 201711357899.2) discloses a high-temperature-resistant pipeline heat-insulating material based on silicon-aluminum composite gel and blast furnace slag, but the price is expensive due to the adoption of organic metal raw materials and a high-temperature process. Chinese patent (application number 201510367815.8) discloses an ultralight pipeline heat-insulating material based on quartz powder, quicklime, red mud and bentonite, which has good heat insulation and mechanical properties, but the cost is high due to high-temperature and high-pressure steam curing. In addition, ordinary-grade portland cement can only endure the temperature of 300 ℃ at most, has poor stability at high temperature, is generally used below 200 ℃, has greatly reduced strength above 300 ℃, has various problems of cracking, corrosion and the like, and cannot be used in the application scene of the thermal pipeline heat-insulating shell. Generally, the pipeline heat-insulating material in the current market is difficult to achieve coordination in aspects of high-efficiency heat insulation, high temperature resistance, high strength, low density, low cost and the like, and development of a novel heat pipeline heat-insulating material and technology is very necessary.

Disclosure of Invention

In view of the above problems, the present invention aims to develop an inorganic thermal insulation material which is suitable for thermal insulation of high-temperature thermal pipelines, has high strength, low density, high-efficiency thermal insulation and high-temperature resistance, and is low in cost, and a preparation method thereof.

In one aspect, the invention provides a millimeter-micron-nanometer hierarchical pore silicon-based material, which comprises the following raw materials in percentage by weight: 5-55 wt% of superfine cementing material; 10-42 wt% of micron-sized filler, 1-5 wt% of foaming agent, 0.1-5 wt% of foam fixing agent, 1-8 wt% of additive and 25-50 wt% of water, wherein the content of each component is 100 wt%; the superfine cementing material is selected from at least one of pure portland cement, ordinary portland cement, aluminate cement and sulphoaluminate cement, and the average grain size of the superfine cementing material is less than or equal to 5 microns, preferably less than or equal to 2 microns;

the micron-sized filler is an inert filler or/and an active filler, and the average particle size is 5-100 microns;

the admixture is a solid-phase admixture or/and a liquid-phase admixture.

In the disclosure, micron-sized filler, superfine cementing material and silicate inorganic gel generated by hydrating the superfine cementing material are selected to form a solid framework of the millimeter-micron-nanometer hierarchical pore silicon-based material. Wherein, the millimeter-scale holes are prepared by a foaming agent by adopting a chemical foaming method. As the average grain diameter of the micron-sized filler is 5-100 microns, larger micron pores are formed among the grains. As the average grain diameter of the superfine cementing material is less than or equal to 5 micrometers (for example, 1-5 micrometers), smaller micropores are formed among the grains. Moreover, the superfine cementing material can be hydrated to generate silicate inorganic gel, and nano holes are further formed in the gaps of the particles. The final microscopic structure of the millimeter-micron-nanometer hierarchical porous silicon-based material is formed by three-dimensional lap joint of pores and a solid skeleton, wherein the pores comprise millimeter pores (millimeter-scale pores), micron pores (micron-scale pores) and nanometer pores (nanometer-scale pores), as shown in fig. 1.

Preferably, the micron-sized filler is at least one selected from quartz powder, wollastonite, limestone, slag, diatomite and concrete waste residue powder abrasive.

Preferably, the foaming agent is selected from at least one of hydrogen peroxide, aluminum powder and magnesium powder; the foam fixing agent is at least one of sodium stearate, calcium stearate and stearic acid.

Preferably, the additive is selected from at least one of an anionic surfactant, a neutral surfactant, a cationic surfactant, a polymer surfactant, a thickening agent and an infrared shielding agent.

Preferably, the anionic surfactant is at least one of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium fatty alcohol ether sulfate, sodium alpha-alkenyl sulfonate and alcohol acyl carboxylate; the cationic surfactant is at least one of cetyl trimethyl ammonium bromide, stearic acid amine hydrochloride and dodecyl dimethyl benzyl ammonium chloride; the neutral surfactant is at least one of Tween-20, OP-10, Span-80 and peregal; the polymer surfactant is at least one of polycarboxylic acid and salt thereof, melamine, wood calcium and polyvinyl alcohol; the thickening agent is at least one of sodium carboxymethylcellulose, polyacrylic acid, xanthan gum, guar gum, starch and bentonite; the infrared shielding agent is at least one of carbon black, titanium oxide, silicon carbide and zirconium silicate.

Preferably, the pore structure of the millimeter-micron-nanometer hierarchical pore silicon-based material comprises millimeter pores, micron pores and nanometer pores; the aperture range of the millimeter holes is 0.5-5 millimeters; the aperture range of the micropores is 1-100 micrometers; the pore diameter range of the nano-pores is 10-1000 nanometers.

Preferably, the density of the millimeter-micron-nanometer hierarchical pore silicon-based material is 0.1-0.5 g/cm³The compression strength is 0.1-3.0 MPa, and the room-temperature heat conductivity coefficient is 0.046-0.11W/m.K; the residual compressive strength of the millimeter-micron-nanometer hierarchical pore silicon-based material after being burned for 8 hours at 400 ℃ is not lower than 75% of the original strength.

In another aspect, the present invention provides a method for preparing the above-mentioned millimeter-micron-nanometer hierarchical porous silicon-based material, comprising:

(1) mixing a superfine cementing material, a micron-sized filler, a foam stabilizer and a solid-phase additive, adding water and a liquid-phase additive, and mixing to obtain slurry;

(2) heating the obtained slurry to 30-50 ℃, adding a foaming agent under a stirring state, continuously stirring for 2-60 seconds, pouring into a mold, and obtaining a biscuit after self-foaming is finished;

(3) standing and curing the obtained biscuit at 50-90 ℃ for 2-72 hours, and curing the biscuit to a specified age under the conditions of room temperature (for example, 15-35 ℃) and relative humidity not lower than 75% to obtain a finished blank;

(4) and drying the obtained blank at 100-150 ℃ for 2-48 hours to obtain the millimeter-micron-nanometer hierarchical pore silicon-based material product for heat preservation of the thermal pipeline.

In the invention, firstly, the superfine cementing material, the micron-sized filler, the foam stabilizer and the solid-phase admixture (generally in a powder state) are mixed to obtain a dry material. And adding water and the liquid-phase admixture into the dry material and uniformly mixing to form slurry. And heating the obtained slurry to 30-50 ℃, adding a foaming agent under a stirring state, continuously stirring for 2-60 seconds, pouring into a mold, and obtaining a biscuit after self-foaming is finished. In the self-foaming process, millimeter holes with the hole diameter range of 0.5-5 millimeters are prepared by a chemical foaming method. Wherein the foaming mechanism is that hydrogen peroxide and the like generate gas under the action of a catalyst to generate a large number of foam holes in the slurry; and solidifying the slurry after the foam holes are generated to obtain the solid porous material. As the average grain diameter of the micron-sized filler is 5-100 microns, larger micron pores are formed among the grains, and the pore diameter range is 10-100 microns. The average grain size of the superfine cementing material is 1-5 microns, smaller micron pores are formed among the grains, and the pore diameter ranges from 1 micron to 10 microns. And (3) standing and curing the obtained biscuit at 50-90 ℃ for 2-72 hours, wherein the curing enables cement in the biscuit to be further hydrated to generate silicate gel and nano-pores, and meanwhile, certain strength is obtained, so that demolding is realized, and the turnover of a mold is facilitated. And (2) after standing and curing, curing the mixture to a specified age at room temperature (for example, 15-35 ℃) under the condition that the relative humidity is not lower than 75%, wherein the curing continuously performs hydration and hardening of cement and the cementing material in the material to further generate silicate gel to form nano holes, and the required final strength and other properties are obtained, so that the superfine cementing material is hydrated to generate the silicate gel, nano holes are formed among particles of the silicate gel, and the range of the hole diameter is 10-1000 nanometers. And finally, drying the formed blank at 100-150 ℃ for 2-48 hours to discharge water in a sample, wherein the water comprises pore water, adsorbed water and structural water in silicate gel to form a dry material so as to prevent the water from increasing the weight of the tube shell and subsequent corrosion of steel and the like, and finally obtaining the millimeter-micron-nanometer hierarchical pore silicon-based material for thermal insulation of the thermal power pipeline. That is, the selection of the raw materials such as cement, filler and admixture in the invention is carefully selected and designed: the grain diameter of the superfine gel material must be prepared in several micrometers, and the nanometer structure can be obtained through hydration; the grain diameter of the filler is required to be 5-100 micrometers, so that a micrometer channel can be formed through grain composition; and a foaming agent is selected to form the millimeter-sized pore channel.

Preferably, the time of the predetermined age is 3 to 28 days.

In another aspect, the invention also provides a thermal pipeline insulation shell prepared from the millimeter-micron-nanometer hierarchical pore silicon-based material.

Has the beneficial effects that:

(1) the invention has the outstanding characteristics that in the aspect of microstructure of the thermal pipeline insulation material, a unique millimeter-micron-nanometer three-level pore structure system is constructed, the density of the material can be greatly reduced by millimeter pores, and the micron pores and the nanometer pores with different scales can effectively isolate heat conduction caused by air convection and reduce the heat conductivity coefficient, so that the unique three-level pore structure material has the characteristics of low density, small heat conductivity coefficient and excellent heat insulation effect;

(2) the main material used by the thermal insulation material for the thermal pipeline is inorganic silicon-based materials such as silicate, quartz, wollastonite, diatomite and the like, has the characteristic of high temperature resistance, and can be used for various thermal pipelines for conveying high-temperature steam and media at the temperature of 400 ℃ for a long time;

(3) the invention is characterized in that the millimeter-scale pore canal of the thermal pipeline insulation material is constructed by adopting a chemical foaming technology. Compared with a physical foaming method, the method utilizes the chemical reaction of the foaming agent to generate the foam holes in the slurry in situ, so that the obtained millimeter-scale foam holes are more stable, the pore channels are more uniform, the pore walls are firmer, the density of the whole material is lower, and the strength is higher;

(4) the thermal pipeline heat-insulating material prepared by the technology has the characteristics of low density, high strength, small heat conductivity coefficient, high temperature resistance and the like, and the density of the material is as low as 0.17g/cm³The compression strength is as high as 2.94MPa, the heat conductivity coefficient at room temperature is as low as 0.046W/m.K, the product has no phenomena of cracking, peeling and the like after being burned for 8 hours at 400 ℃, and the residual compression strength is not lower than 75 percent of the original strength. The invention is applied to the heat-insulating shell of a high-temperature heating pipeline, and has strict requirements on the density, the strength, the heat conductivity coefficient and the long-term high temperature resistance of the material.

Drawings

FIG. 1 is a schematic view of the microstructure of a millimeter-micron-nanometer hierarchical porous silicon-based material prepared by the present invention, wherein 1-millimeter pores, 2-micron fillers, 3-ultrafine gelling materials, 4-hydrated silicate gels and nanopores;

FIG. 2 is a photograph of a sample specimen of a millimeter-micron-nanometer hierarchical porous silicon-based material prepared in example 1, showing the millimeter pores;

FIG. 3a is a SEM photo of a sample of the Si-based material with millimeter-micron-nano hierarchical pores prepared in example 1, wherein the sample has a structure of millimeter pores;

FIG. 3b is a SEM photograph of a sample of the Si-based millimeter-micron-nanoscale porous material prepared in example 1, wherein the sample has a micron pore structure;

FIG. 3c is a SEM photograph of a sample of the MMP-NMP Si-based material prepared in example 1, wherein the sample has a nanopore structure;

fig. 4 is a graph showing a distribution of pore sizes of a sample of the millimeter-micron-nanometer hierarchical porous si-based material prepared in example 1 measured by mercury intrusion.

Detailed Description

The present invention is further illustrated by the following examples, which are to be construed as merely illustrative, and not a limitation of the present invention.

In the present disclosure, the raw material composition of the millimeter-micron-nanometer hierarchical pore silicon-based material comprises: 5-40 wt% of an ultrafine cementing material; 10-42 wt% of micron-sized filler, 1-5 wt% of foaming agent, 1-5 wt% of foam stabilizer, 1-8 wt% of additive and 25-50 wt% of water, wherein the content of each component is 100 wt%. Wherein the superfine cementing material is selected from one or more of pure portland cement, ordinary portland cement, aluminate cement and sulphoaluminate cement. The average grain size of the superfine cementing material is less than or equal to 5 microns, and preferably, the average grain size is less than or equal to 2 microns. The micron-sized filler can be inert filler or/and active filler, and the average particle size is 5-100 micrometers. The admixture can be a solid-phase admixture or/and a liquid-phase admixture. The superfine cementing material, the micron-sized filler and silicate gel formed by hydrating the superfine cementing material are solid frameworks formed by main materials, and the hierarchical pore high-temperature pipeline heat-insulating material simultaneously has millimeter, micron and nanometer pore canals on the structure. That is, the microstructure of the millimeter-micron-nanometer hierarchical pore silicon-based material is formed by three-dimensional lap joint of pores and a solid framework.

The main materials of the millimeter-micron-nanometer hierarchical pore silicon-based material are silicon oxide and silicate. Wherein, the silicon oxide and the silicate are used as inorganic materials and have the outstanding characteristic of high temperature resistance. In the three-level micro-pore structure, the millimeter pores are realized by a chemical foaming technology, the micron pores are realized by micron-level inert or active fillers, and the nanometer pores are realized by hydration reaction of a superfine cementing material. The holes with three scales act synergistically to realize the effects of high strength, low density and low thermal conductivity of the heat-insulating material together.

In an optional embodiment, the foaming agent is selected from hydrogen peroxide, aluminum powder, magnesium powder and the like. The foam stabilizer is one or more of sodium stearate, calcium stearate, commercial foam stabilizers (such as foaming cement foam stabilizer and foam stabilizer). The micron-sized filler comprises one or more of quartz powder, wollastonite, slag, diatomite and concrete waste residue powder abrasive. The additive is one or more of anionic surfactant, neutral surfactant, cationic surfactant, polymer surfactant, thickener, infrared shielding agent, etc. The water may be tap water.

Further preferably, the anionic surfactant may be sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, or the like. The cationic surfactant may be cetyltrimethylammonium bromide. The amphoteric surfactant can be tween-20, OP-10, Span-80, etc. The polymeric surfactant may be polycarboxylic acids and salts thereof, melamine, calcium lignosulfonate, and the like. The thickener can be sodium carboxymethylcellulose, polyacrylic acid, xanthan gum, etc. The infrared shielding agent can be carbon black, titanium oxide, silicon carbide, zirconium silicate and the like.

In one embodiment of the invention, the heat insulation material for the thermal pipeline, which takes the inorganic silicon material as the main material and has a millimeter-micron-nanometer multilevel pore channel structure, is constructed by combining the chemical foaming technology with the superfine cement. The obtained material has the characteristics of low density, high strength, small heat conductivity coefficient, high temperature resistance and the like, and is widely applied to hard heat-preservation occasions such as various steam pipelines, hot water/hot oil pipelines and the like. The following is an exemplary description of a method for preparing a millimeter-micron-nanoscale porous silicon-based material.

And (4) preparing slurry. Accurately weighing the ultrafine cementing material, the micron-sized filler, the foam stabilizer and the solid-phase admixture in specified weight, and uniformly mixing in a stirrer to form a dry material. Accurately weighing water and liquid-phase admixture with specified weight, and uniformly mixing in another stirrer to form wet material. And pouring the wet material into the dry material, and mixing and stirring for 1-20 minutes to form slurry (or called slurry). In an alternative embodiment, the particle size of the ultrafine cementing material is generally between 10 and 80 μm, and still special grinding treatment is required to ensure that the particle size reaches the specified average particle size. Wherein, the grinding treatment mode includes but not limited to ball milling treatment and the like, and only needs to enable the superfine cementing material to reach corresponding fineness.

And (5) molding. Accurately weighing foaming agent with specified weight, heating the prepared slurry to 30-50 ℃ (if the temperature can not be increased in summer), adding the foaming agent into the slurry under stirring, continuously stirring for 2-60 seconds, and quickly pouring into a prepared mold. And (4) finishing self-foaming of the slurry in a mold to form a biscuit. Wherein, the time of self-foaming is adjusted according to the added raw materials, and can be generally 0.2-3 minutes.

And (5) demolding and maintaining. And (3) placing the obtained biscuit in a baking oven or a drying room at the temperature of 50-90 ℃ for standing and curing for 2-72 hours, so that cement is hydrated, and the biscuit obtains a certain demolding strength. And then curing the mixture to a specified age at room temperature (for example, 15-35 ℃) under the condition that the relative humidity is not lower than 75% to obtain a blank.

And (5) drying. And drying the obtained blank to obtain the final millimeter-micron-nanometer hierarchical pore silicon-based material. The drying can be performed in a kiln at 100-150 ℃ for 2-48 hours to discharge water in the sample, including pore water, adsorbed water and structural water in silicate gel, to form a dry material, so that the phenomenon that the water in the sample increases the weight of the product and causes corrosion of reinforcing steel bars is avoided.

In the invention, the density of the millimeter-micron-nanometer hierarchical pore silicon-based material tested by the method specified in GB/T5486 can be 0.1-0.5 g/cm³. The room temperature thermal conductivity coefficient of the millimeter-micron-nanometer hierarchical pore silicon-based material tested by the method specified in GB/T10294 can be 0.046-0.11W/m.K, and is preferably 0.046-0.08W/m.K.

In the invention, the compression strength of the millimeter-micron-nanometer hierarchical pore silicon-based material tested by the method specified in GB/T5486 can be 0.1-3.0 MPa. The residual compressive strength of the millimeter-micron-nanometer hierarchical pore silicon-based material after uniform temperature ignition (400 ℃) can be more than 75% of that of an unburned sample after the uniform temperature ignition is tested by adopting the methods specified in GB/T5486 and GB/T10699.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that insubstantial modifications and adaptations of the invention by those skilled in the art based on the foregoing description are intended to be included within the scope of the invention. The specific process parameters and the like of the following examples are also merely one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1

(1) Selecting materials: selecting ordinary portland cement (manufacturer: Shanghai sea snail cement Co., Ltd., P.O52.5) with an average particle size of 2 microns, grinding the ordinary portland cement to an average particle size of 2 microns by itself, wherein the components of the ordinary portland cement are the same as those of the existing product, but grinding treatment is carried out to meet the fineness requirement, and the original fineness of the ordinary portland cement is generally 45 microns) as an ultrafine cementing material, 350-mesh quartz sand as a micron-sized filler, hydrogen peroxide as a foaming agent, calcium stearate as a foam fixing agent, sodium dodecyl benzene sulfonate and tween 20 as surfactants, sodium carboxymethylcellulose as a thickening agent, and titanium oxide as an infrared shielding agent;

(2) preparing slurry: accurately weighing 120 g of superfine cementing material, 80 g of micron-sized filler, 2g of foam fixing agent, 0.3 g of sodium dodecyl benzene sulfonate, 0.2 g of sodium carboxymethyl cellulose and 5g of titanium oxide, and uniformly mixing in a stirrer to form a dry material; accurately weighing 90 g of water and 200.2 g of Tween, and uniformly mixing in another stirrer to form a wet material; pouring the wet material into the dry material, and stirring for 5 minutes to form slurry;

(3) molding: heating the slurry prepared in the step (2) to 45 ℃, accurately weighing 9g of hydrogen peroxide, adding the slurry in a stirring state, continuously stirring for 10 seconds, quickly pouring the mixture into a prepared mould, and automatically foaming the slurry after 15 minutes to form a biscuit;

(4) demolding and maintaining: placing the biscuit obtained in the step (3) in a 60 ℃ oven for standing and curing for 24 hours, and curing for 7 days at room temperature and relative humidity of 95% to obtain a finished blank;

(5) drying: and (5) drying the blank obtained in the step (4) in a kiln at 120 ℃ for 24 hours to obtain the hierarchical porous silicon-based material.

The density of the hierarchical porous silicon-based material prepared in example 1 was 0.17g/cm³The compression strength is 0.28MPa, and the heat conductivity coefficient at room temperature is 0.046W/m.K measured by adopting a transient plane heat source method. The sample is placed in a muffle furnace at 400 ℃ to be burnt for 8 hours, the surface does not crack or peel obviously, and the residual compressive strength is 0.22 MPa.

As can be seen from fig. 2 and fig. 3a-3c, the material has a distribution of millipores, millipores and nanopores at the millimeter, micron and nanometer scales. As can be seen from the mercury intrusion pore size distribution plot of fig. 4, the material has nanopores on the ten to one hundred nanometer scale and micropores in the 30 to 300 micrometer range.

Example 2

(1) Selecting materials: selecting pure Portland cement (P.O52.5, self-grinding) with average particle size of 5 microns as superfine cementing material, 400-mesh quartz sand as micron filler, hydrogen peroxide as foaming agent, calcium stearate as foam-fixing agent, sodium dodecyl sulfate, OP-10 as surfactant, sodium polyacrylate as thickener and silicon carbide as infrared shielding agent;

(2) preparing slurry: accurately weighing 180 g of superfine cementing material, 45 g of micron-sized filler, 2g of foam fixing agent, 0.15 g of sodium dodecyl sulfate, 0.2 g of sodium polyacrylate and 25 g of silicon carbide, and uniformly mixing in a stirrer to form a dry material; accurately weighing 80 g of water and 100.2 g of OP, and uniformly mixing in another stirrer to form a wet material; pouring the wet material into the dry material, and stirring for 5 minutes to form slurry;

(3) molding: heating the slurry prepared in the step (2) to 45 ℃, accurately weighing 7.5 g of hydrogen peroxide, adding the slurry in a stirring state, continuously stirring for 10 seconds, quickly pouring the slurry into a prepared mould, and finishing self foaming after 15 minutes to form a biscuit;

(4) demolding and maintaining: placing the biscuit obtained in the step (3) in an oven at 80 ℃ for standing and curing for 24 hours, and curing for 14 days at room temperature and relative humidity of 95% to obtain a finished blank;

(5) and (3) drying: and (5) drying the blank obtained in the step (4) in a kiln at 120 ℃ for 24 hours to obtain the hierarchical porous silicon-based material.

The density of the hierarchical porous silicon-based material prepared in the example 2 is 0.38g/cm³The compression strength is 2.94MPa, and the heat conductivity coefficient at room temperature is 0.11W/m.K measured by adopting a transient plane heat source method. The sample is placed in a 400 ℃ muffle furnace to be burnt for 8 hours, the surface does not crack or peel obviously, and the residual compressive strength is 2.28 MPa.

Example 3

(1) Selecting materials: selecting pure silicate cement (P.O52.5, self-grinding) with average particle size of 2 micrometers as an ultrafine cementing material, 400-mesh quartz sand as a micron filler, aluminum powder as a foaming agent, sodium stearate as a foam fixing agent, hexadecyl trimethyl ammonium bromide and tween-20 as surfactants, sodium carboxymethylcellulose as a thickening agent, and silicon carbide as an infrared shielding agent;

(2) preparing slurry: accurately weighing 160 g of superfine cementing material, 60 g of micron filler, 2g of foam fixing agent, 0.2 g of hexadecyl trimethyl ammonium bromide, 0.2 g of carboxymethyl cellulose and 5g of silicon carbide, and uniformly mixing in a stirrer to form a dry material; accurately weighing 120 g of water and 0.3 g of Tween 20, and uniformly mixing in another stirrer to form a wet material; pouring the wet material into the dry material, and stirring for 5 minutes to form slurry;

(3) molding: heating the slurry prepared in the step (2) to 48 ℃, accurately weighing 12 g of aluminum powder, adding the slurry in a stirring state, continuously stirring for 10 seconds, quickly pouring the slurry into a prepared die, and finishing self-foaming after 15 minutes of the slurry to form a biscuit;

(4) demolding and maintaining: standing and curing the biscuit obtained in the step (3) in a 70 ℃ oven for 48 hours, and curing for 14 days at room temperature and relative humidity of 90% to obtain a finished blank;

(5) and (3) drying: and (5) drying the blank obtained in the step (4) in a kiln at 150 ℃ for 24 hours to obtain the hierarchical porous silicon-based material.

The density of the hierarchical porous silicon-based material prepared in the example 3 is 0.22g/cm³The compression strength is 0.69MPa, and the heat conductivity coefficient at room temperature is 0.052W/m.K measured by a transient plane heat source method. The sample is placed in a 400 ℃ muffle furnace to be burnt for 8 hours, the surface does not crack or peel obviously, and the residual compressive strength is 0.56 MPa.

Example 4

(1) Selecting materials: aluminate cement (duck brand aluminate cement, CA-80, automatically ground) with the average grain diameter of 2 microns is selected as a superfine cementing material, quartz sand with 400 meshes is a micron-sized filler, hydrogen peroxide is a foaming agent, sodium stearate is a foam fixing agent, Tween-20 is a surfactant, sodium carboxymethylcellulose is a thickening agent, and titanium oxide is an infrared shielding agent;

(2) preparing slurry: accurately weighing 60 g of superfine cementing material, 120 g of micron-sized filler, 2g of foam fixing agent, 0.2 g of carboxymethyl cellulose and 5g of titanium oxide, and uniformly mixing in a stirrer to form a dry material; accurately weighing 120 g of water and 2g of Tween 20, and uniformly mixing in another stirrer to form a wet material; pouring the wet material into the dry material, and stirring for 5 minutes to form slurry;

(3) molding: heating the slurry prepared in the step (2) to 48 ℃, accurately weighing 12 g of hydrogen peroxide, adding the slurry in a stirring state, continuously stirring for 10 seconds, quickly pouring the slurry into a prepared mould, and finishing self foaming after 15 minutes to form a biscuit;

(4) demolding and maintaining: placing the biscuit obtained in the step (3) in a 70 ℃ oven for standing and curing for 24 hours, and curing for 7 days at room temperature and relative humidity of 90% to obtain a finished blank;

(5) and (3) drying: and (5) drying the blank obtained in the step (4) in a 135 ℃ drying kiln for 48 hours to obtain the hierarchical porous silicon-based material.

The density of the hierarchical porous silicon-based material prepared in the example 4 is 0.19g/cm³The compression strength is 1.2MPa, and the heat conductivity coefficient at room temperature is 0.078W/m.K when the transient plane heat source method is adopted. After the sample is placed in a muffle furnace at 400 ℃ and burned for 8 hours, the surface has no obvious cracking or peeling, and the residual compressive strength is 1.05 MPa.

Example 5

In this example 5, the process for preparing the silicon-based material with millimeter-micron-nanometer hierarchical pores is as shown in example 1, which is different from the following: the superfine cementing material is sulphoaluminate cement with the average grain size of 2 microns (the manufacturer: Shanghai double crane special cement Co., Ltd., super-early-40, self-grinding). The density of the obtained hierarchical porous silicon-based material is 0.21g/cm³The compression strength is 0.35MPa, and the heat conductivity coefficient at room temperature is 0.058W/m.K measured by adopting a transient plane heat source method. The sample is placed in a muffle furnace at 400 ℃ to be burned for 8 hours, the surface has no obvious cracking or peeling, and the residual compressive strength is 0.27 MPa.

Comparative example 1

The preparation of the hierarchical porous silicon-based material in this comparative example 1 is described in example 1, with the following differences: no ultra-fine gel material was added. In fact, the silicon-based material cannot be foamed without adding the superfine gel material, and the millimeter-micron-nanometer hierarchical pore silicon-based material cannot be obtained.

Comparative example 2

For the preparation of the hierarchical porous si-based material in this comparative example 2, reference is made to example 1, with the following differences: the average particle size of the silica sand was 2 μm. The adoption of quartz sand with the particle size of 2 microns can not form larger micropores, can not form the millimeter-micron-nanometer hierarchical pore structure of the invention, and the cost is increased too much.

Comparative example 3

The raw materials and preparation process of the hierarchical porous silicon-based material in the comparative example 3 are shown in example 1, and the difference is that: 200 g of ultrafine cementing material, 20 g of micron filler and the other components are the same as the embodiment 1. After foaming and forming, the hydration heat is greatly improved due to the excessive use amount of the superfine cementing material, and the crack development is not limited due to the reduction of the micron-sized filler, so that the biscuit is greatly shrunk in the curing process, a large amount of cracks or fissures are generated on the surface and the edge of a sample, and a product with application value cannot be obtained.

Table 1 shows the performance parameters of the hierarchical porous si-based materials prepared according to the present invention:

	density (g/cm)³)	Thermal conductivity at room temperature (W/m. K)	Compressive strength/MPa	Residual compressive strength/MPa
					Example 1	0.17	0.046	0.28	0.22
Example 2	0.38	0.11	2.94	2.28
					Example 3	0.22	0.052	0.69	0.56
Example 4	0.19	0.078	1.2	1.05
					Example 5	0.21	0.058	0.35	0.27

。

Claims

1. The preparation method of the millimeter-micron-nanometer hierarchical pore silicon-based material is characterized in that the raw material composition of the millimeter-micron-nanometer hierarchical pore silicon-based material comprises the following steps: 5-55 wt% of superfine cementing material; 10-42 wt% of micron-sized filler, 1-5 wt% of foaming agent, 0.1-5 wt% of foam fixing agent, 1-8 wt% of additive and 25-50 wt% of water, wherein the sum of the contents of all the components is 100 wt%;

the superfine cementing material is selected from at least one of pure portland cement, ordinary portland cement, aluminate cement and sulphoaluminate cement, and the average grain size of the superfine cementing material is less than or equal to 5 microns;

the admixture is a solid-phase admixture or/and a liquid-phase admixture; the additive comprises a surfactant, a thickening agent and an infrared shielding agent;

the pore structure of the millimeter-micron-nanometer hierarchical pore silicon-based material comprises a millimeter pore, a micron pore and a nanometer pore; the aperture range of the millimeter holes is 0.5-5 millimeters; the aperture range of the micropores is 1-100 micrometers; the pore diameter range of the nano-pores is 10-1000 nanometers;

the density of the millimeter-micron-nanometer hierarchical pore silicon-based material is 0.1-0.5 g/cm³The compression strength is 0.1-3.0 MPa, and the room-temperature heat conductivity coefficient is 0.046-0.11W/m.K; the residual compressive strength of the millimeter-micron-nanometer hierarchical pore silicon-based material after being burned for 8 hours at 400 ℃ is not lower than 75% of the original strength;

the preparation method of the millimeter-micron-nanometer hierarchical pore silicon-based material comprises the following steps:

(3) standing and curing the obtained biscuit at 50-90 ℃ for 2-72 hours, and curing to a specified age under the conditions of room temperature and relative humidity of not less than 75% to obtain a finished biscuit;

(4) and drying the obtained blank at 100-150 ℃ for 2-48 hours to obtain the millimeter-micron-nanometer hierarchical pore silicon-based material.

2. The method according to claim 1, wherein the average particle size of the ultra-fine cementitious material is less than or equal to 2 μm.

3. The method according to claim 1, wherein the micron-sized filler is at least one selected from the group consisting of quartz powder, wollastonite, limestone, slag, diatomaceous earth and concrete waste powder abrasive.

4. The preparation method of claim 1, wherein the foaming agent is at least one selected from hydrogen peroxide, aluminum powder and magnesium powder; the foam fixing agent is at least one of sodium stearate, calcium stearate and stearic acid.

5. The production method according to claim 1, wherein the surfactant comprises at least one of an anionic surfactant, a neutral surfactant, a cationic surfactant, or a polymer surfactant; the anionic surfactant is at least one of sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, fatty alcohol ether sodium sulfate, alpha-alkenyl sodium sulfonate and alcohol acyl carboxylate; the cationic surfactant is at least one of cetyl trimethyl ammonium bromide, stearic acid amine hydrochloride and dodecyl dimethyl benzyl ammonium chloride; the neutral surfactant is at least one of Tween-20, OP-10, Span-80 and peregal; the polymer surfactant is at least one of polycarboxylic acid and salt thereof, melamine, calcium lignosulphonate and polyvinyl alcohol; the thickening agent is at least one of sodium carboxymethylcellulose, polyacrylic acid, xanthan gum, guar gum, starch and bentonite; the infrared shielding agent is at least one of carbon black, titanium oxide, silicon carbide and zirconium silicate.

6. The method according to claim 1, wherein the specified age is 3 to 28 days.

7. A thermal pipe insulation shell made of the millimeter-micron-nanometer hierarchical pore silica-based material of claim 1.