阅读说明：本技术 一种碳纤维基SiO2气凝胶发泡水泥及其制备方法 (Carbon fiber based SiO2Aerogel foam cement and preparation method thereof ) 是由 王玉镯 高英 黄颖 任丽 李雪玲 赵彦彦 房其娟 刘伟 刘媛媛 于 2020-11-27 设计创作，主要内容包括：本发明属于建筑材料应用技术领域,涉及发泡水泥,尤其涉及一种碳纤维基SiO2气凝胶发泡水泥及其制备方法。按照重量份数包括以下有效成份：水泥60份～80份；碳纤维基SiO2气凝胶10份～20份；多孔陶瓷粉末10份～20份；双氧水发泡剂5份～8份；发泡催化剂0.3份～0.5份；促凝剂5份～8份；稳泡剂2份～4份；余量为水其中,所述碳纤维基SiO2气凝胶为权利要求1所提供的碳纤维基SiO2气凝胶,水的添加量按照水灰比0.46进行添加。本发明利用碳纤维增强发泡水泥的强度,同时,利用碳纤维基SiO2气凝胶所形成的纳米气孔填补双氧水作为发泡剂导致的气泡扁平、模具底部气泡小、顶部气泡大,气泡分布不均匀及气泡壁有大量微裂纹,闭孔率低的技术问题。(The invention belongs to the technical field of building material application, relates to foaming cement, and particularly relates to carbon fiber based SiO2 aerogel foaming cement and a preparation method thereof. The composition comprises the following effective components in parts by weight: 60-80 parts of cement; 10-20 parts of carbon fiber-based SiO2 aerogel; 10-20 parts of porous ceramic powder; 5-8 parts of hydrogen peroxide foaming agent; 0.3 to 0.5 portion of foaming catalyst; 5-8 parts of a coagulant; 2-4 parts of a foam stabilizer; the balance of water, wherein the carbon fiber based SiO2 aerogel is the carbon fiber based SiO2 aerogel provided by claim 1, and the addition amount of water is added according to the water-cement ratio of 0.46. According to the invention, the strength of the foamed cement is enhanced by using the carbon fibers, and meanwhile, the technical problems of flat bubbles, small bubbles at the bottom of the mold, large bubbles at the top, uneven bubble distribution, a large amount of microcracks on the bubble wall and low hole closing rate caused by using hydrogen peroxide as a foaming agent are solved by using nano-pores formed by carbon fiber-based SiO2 aerogel.)

1. A preparation method of carbon fiber-based SiO2 aerogel is characterized by comprising the following effective steps:

a. adding carbon fiber into dimethyl sulfoxide, keeping the temperature at 30 ℃, heating and stirring until the carbon fiber is uniformly dispersed, and stirring uniformly;

b. after being stirred uniformly, the methyltrimethoxysilane and the oxalic acid are respectively added into the mixture and stirred for 30min at the temperature of 30 ℃;

c. after stirring, adding a certain amount of mixed solution of ammonia water and dimethyl sulfoxide, and continuously stirring for 15min to obtain silicon dioxide sol;

d. stopping stirring, and keeping the environment at 50 ℃ until the gel is finished;

e. soaking the obtained gel in ethanol, washing for 24 hr, and replacing ethanol for 3 times;

f. after the dimethyl sulfoxide is completely washed by the ethanol, drying for 3 hours at 40 ℃ under 10MPa by adopting a supercritical drying technology to obtain the carbon fiber-based SiO₂An aerogel.

2. The carbon fiber-based SiO2 aerogel foam cement is characterized by comprising the following effective components in parts by weight:

wherein the carbon fiber based SiO2 aerogel is the carbon fiber based SiO2 aerogel provided by claim 1, and the addition amount of water is added according to the water-cement ratio of 0.46.

3. The carbon fiber-based SiO2 aerogel foam cement as claimed in claim 2, wherein the cement is portland cement.

4. The carbon fiber-based SiO2 aerogel foam cement according to claim 3, wherein the foaming catalyst is manganese oxide.

5. The carbon fiber-based SiO2 aerogel foam cement as claimed in claim 4, wherein the foam stabilizer is calcium stearate modified by nano-intercalation technology.

6. The carbon fiber-based SiO2 aerogel foam cement as claimed in claim 5, wherein the coagulant is a composite of sodium carbonate and triethanolamine, wherein the mass ratio of sodium carbonate to triethanolamine is 10: 1.

7. The carbon fiber-based SiO2 aerogel foam cement of claim 6, wherein the particle size of the porous ceramic powder is 325 mesh.

8. Method for preparing the carbon fiber based SiO2 aerogel foam cement according to claim 7, characterized in that it comprises the following effective steps:

A. firstly, weighing raw materials according to corresponding parts by weight;

B. adding the weighed cement, the porous ceramic powder and the foam stabilizer into a stirring kettle for dry mixing uniformly

C. After the mixture is uniformly stirred, adding water into the stirring kettle, and continuously stirring;

D. quickly adding the foaming catalyst into hydrogen peroxide, quickly stirring, quickly adding into a stirring kettle, and continuously stirring at the stirring speed of 1000 r/min;

E. after 1 minute, adding the carbon fiber-based SiO2 aerogel and the coagulant into the stirring kettle, and continuing stirring;

F. and after stirring, injecting the stirred slurry into a mold, curing and molding, and obtaining the carbon fiber-based SiO2 aerogel foam cement after curing and molding.

Technical Field

The invention belongs to the technical field of building material application, relates to foaming cement, and particularly relates to carbon fiber based SiO2 aerogel foaming cement and a preparation method thereof.

Background

In recent years, the market share and the usage amount of the organic heat-insulating material are obviously reduced along with the increasingly obvious defects of easy cracking, poor durability, flammability, toxic gas generation by combustion and the like of the organic heat-insulating material. As an ideal substitute, inorganic heat insulating materials are favored because of their outstanding advantage of high safety. The foamed cement as one kind of inorganic heat insulating material has the advantages of light weight, small heat conductivity, sound absorption, sound insulation, long service life, no toxicity, etc. Therefore, the foamed cement is expected to be widely applied to the building heat preservation industry.

According to the current standards and literature reports, the dry apparent density of the foamed cement is generally greater than 200kg/m³The thermal conductivity is generally greater than 0.06 W.m^-1K^-1The water absorption rate is generally not more than 10%, and although the fireproof material has excellent fireproof performance, the thermal performance and the mechanical performance of the fireproof material are further improved compared with those of an organic heat-insulating material, so that the requirement of building energy conservation is met.

Meanwhile, the existing foaming cement mainly comprises five materials: the foaming agent mainly comprises a physical foaming agent and a chemical foaming agent at present, wherein substances which can chemically react with substances in cement slurry and generate gas can be regarded as the chemical foaming agent. Many substances can be used as chemical foaming agents, such as aluminum powder, hydrogen peroxide, calcium carbide and the like, wherein the most widely applied and mature process is the aluminum powder and the hydrogen peroxide. The foaming cement is prepared by using aluminum powder as a foaming agent and by utilizing the reaction of the aluminum powder and an alkaline substance in cement slurry to generate hydrogen bubbles in the cement slurry. However, the aluminum powder generates explosive gas-hydrogen in the reaction process, which causes certain potential safety hazard. Hydrogen peroxide is used as a foaming agent, and oxygen is generated by utilizing the disproportionation reaction of hydrogen peroxide in an alkaline medium. The hydrogen peroxide is easy to be uniformly dispersed in the cement slurry, the gas generation rate is controllable, and harmful substances such as calcium carbide and the like are not generated. However, hydrogen peroxide foaming has the defects of flat bubbles, small bubbles at the bottom of the mold, large bubbles at the top, uneven bubble distribution, a large number of microcracks on the bubble wall, low closed porosity and the like, so that the prepared foamed cement wall thermal insulation material has the defects of low strength, large heat conductivity coefficient, poor thermal insulation performance and the like.

Disclosure of Invention

Aiming at the technical problems that the thermal performance and the mechanical performance of the existing foaming cement need to be further improved and bubbles exist, the invention provides the carbon fiber-based SiO2 aerogel foaming cement which is reasonable in formula, convenient to process and capable of effectively improving the thermal performance and the mechanical performance of the foaming cement and the preparation method thereof.

In order to achieve the above purpose, the invention adopts a technical scheme that the invention provides a preparation method of carbon fiber based SiO2 aerogel, which comprises the following effective steps:

a. adding carbon fiber into dimethyl sulfoxide, keeping the temperature at 30 ℃, heating and stirring until the carbon fiber is uniformly dispersed, and stirring uniformly;

b. after being stirred uniformly, the methyltrimethoxysilane and the oxalic acid are respectively added into the mixture and stirred for 30min at the temperature of 30 ℃;

c. after stirring, adding a certain amount of mixed solution of ammonia water and dimethyl sulfoxide, and continuously stirring for 15min to obtain silicon dioxide sol;

d. stopping stirring, and keeping the environment at 50 ℃ until the gel is finished;

e. soaking the obtained gel in ethanol, washing for 24 hr, and replacing ethanol for 3 times;

f. and after the dimethyl sulfoxide is completely washed by the ethanol, drying for 3 hours at 40 ℃ under 10MPa by adopting a supercritical drying technology to obtain the carbon fiber-based SiO2 aerogel.

The invention also provides carbon fiber-based SiO2 aerogel foam cement which comprises the following effective components in parts by weight:

the carbon fiber-based SiO2 aerogel is the carbon fiber-based SiO2 aerogel obtained by the preparation method of the carbon fiber-based SiO2 aerogel, and the addition amount of water is added according to the water-cement ratio of 0.46.

Preferably, the cement is portland cement.

Preferably, the blowing catalyst is manganese oxide.

Preferably, the foam stabilizer is calcium stearate modified by a nano intercalation technology.

Preferably, the coagulant is a compound of sodium carbonate and triethanolamine, wherein the mass ratio of the sodium carbonate to the triethanolamine is 10: 1.

Preferably, the porous ceramic powder has a particle size of 325 mesh.

The invention also provides a method for preparing the carbon fiber-based SiO2 aerogel foam cement, which comprises the following effective steps:

A. firstly, weighing raw materials according to corresponding parts by weight;

B. adding the weighed cement, the porous ceramic powder and the foam stabilizer into a stirring kettle for dry mixing uniformly

C. After the mixture is uniformly stirred, adding water into the stirring kettle, and continuously stirring;

D. quickly adding the foaming catalyst into hydrogen peroxide, quickly stirring, quickly adding into a stirring kettle, and continuously stirring at the stirring speed of 1000 r/min;

E. after 1 minute, adding the carbon fiber-based SiO2 aerogel and the coagulant into the stirring kettle, and continuing stirring;

F. and after stirring, injecting the stirred slurry into a mold, curing and molding, and obtaining the carbon fiber-based SiO2 aerogel foam cement after curing and molding.

Compared with the prior art, the invention has the advantages and positive effects that,

1. the invention provides carbon fiber-based SiO2 aerogel foamed cement and a preparation method thereof, which utilize carbon fibers to enhance the strength of the foamed cement, and simultaneously utilize nano-pores formed by carbon fiber-based SiO2 aerogel to fill up the technical problems of flat bubbles, small bubbles at the bottom of a mold, large bubbles at the top, uneven bubble distribution, a large number of microcracks on bubble walls and low closed pore rate caused by using hydrogen peroxide as a foaming agent.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.

FIG. 1 is a cross-sectional view of a carbon fiber-based SiO2 aerogel foam cement provided in example 1;

fig. 2 is a SEM image of the carbon fiber-based SiO2 aerogel foamed cement 7d provided in example 1.

Detailed Description

In order that the above objects, features and advantages of the present invention can be more clearly understood, the present invention will be further described with reference to the accompanying drawings and examples. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and thus the present invention is not limited to the specific embodiments of the present disclosure.

Example 1, this example provides a carbon fiber based SiO2 aerogel foam cement

Aerogels are also known as xerogels. When most of the solvent is removed from the gel, the liquid content in the gel is much less than the solid content, or the space network structure of the gel is filled with gas, and the appearance is solid, namely xerogel, also called aerogel.

In this embodiment, at first prepare carbon fiber based SiO2 aerogel, add carbon fiber and keep 30 ℃ heating stirring to homodisperse in dimethyl sulfoxide, the stirring, the addition of carbon fiber is 20% of the aerogel weight that forms, in this embodiment, add carbon fiber to the main purpose of aerogel and be the intensity that improves whole aerogel, and dimethyl sulfoxide is as the existence of the solvent that the aerogel produced.

After the mixture is stirred uniformly, the methyltrimethoxysilane and the oxalic acid are respectively added into the mixture and stirred for 30min at the temperature of 30 ℃. The addition of oxalic acid can obtain aerogel with a network structure stacked by relatively compact nano particles. After stirring is finished, adding a certain amount of mixed solution of ammonia water and dimethyl sulfoxide, and continuously stirring for 15min to obtain silicon dioxide sol, wherein the main purpose of adding ammonia water is to accelerate gelation. After stopping stirring, the environment at 50 ℃ is maintained until the gel is finished. Soaking the obtained gel in ethanol, washing for 24 hr, and replacing ethanol for 3 times; and after the dimethyl sulfoxide is completely washed by the ethanol, drying for 3 hours at 40 ℃ under 10MPa by adopting a supercritical drying technology to obtain the carbon fiber-based SiO2 aerogel.

Then, 60 to 80 parts of cement is added; 10-20 parts of carbon fiber-based SiO2 aerogel; 10-20 parts of porous ceramic powder; 5-8 parts of hydrogen peroxide foaming agent; 0.3 to 0.5 portion of manganese oxide foaming catalyst; 5-8 parts of coagulant of a compound of sodium carbonate and triethanolamine, wherein the mass ratio of the sodium carbonate to the triethanolamine is 10: 1; 2-4 parts of a foam stabilizer of calcium stearate modified by a nano intercalation technology; the balance of water, and the cement is Portland cement. The porous ceramic powder is particles processed by the existing waste porous ceramics into particles with the particle size of 325 meshes, and the mesh size is the common particle size of the existing portland cement, and of course, the particle size can be larger, and the maximum particle size does not exceed 180 meshes. The balance of water, the water-cement ratio is 0.46.

The method comprises the steps of adding weighed cement, porous ceramic powder and a foam stabilizer into a stirring kettle, and performing dry mixing uniformly, wherein the purpose of the dry mixing uniformly is to fully mix the cement, the porous ceramic powder and the foam stabilizer, calcium stearate modified by a nano intercalation technology is selected as the foam stabilizer, and the stability of bubbles is a key factor related to the preparation process and performance of the foamed cement in the process of growing the bubbles. Microscopically, in the porous material, a liquid film (i.e., a liquid film generated by cement slurry) plays a role in separating bubbles, and the destruction of the bubbles is the rupture of the liquid film around the bubbles. The instability of the bubbles is also manifested by the growth of the bubbles through fusion with each other. The stability of the bubbles is mainly affected by surface tension and cement paste viscosity. The change in surface tension causes a change in the size of the bubbles, and thus the surface tension affects the stability of the bubbles. In the early stage of mixing cement slurry, friction between internal fluid layers is quite complex, the formed slurry has low plastic viscosity and high flow rate, and bubbles are easy to fuse or break. For this purpose, in this example, the cement, the porous ceramic powder and the foam stabilizer are added to the stirring kettle and mixed uniformly.

The porous ceramic powder particles are mainly added in a flake structure rather than a particle structure, the smoothness of bubbles can be improved mainly because the porous ceramic powder particles do not react and are filled in gaps, and as shown in figure 2, the addition of the flake porous ceramic powder particles provides an early strength effect for the foamed cement to form a good network-shaped framework structure.

After the mixture is uniformly stirred, water is added into the stirring kettle, the stirring is continued, the water-cement ratio is about 0.46, the existing research shows that the microbial foaming agent contains a large amount of water, and therefore, the integral ratio of the microbial foaming agent to the water reaches 0.46.

Then quickly adding the manganese oxide foaming catalyst into hydrogen peroxide, quickly stirring, quickly adding into a stirring kettle, continuously stirring, wherein the stirring speed is 1000r/minIn the embodiment, the main effect of adding the catalyst is to enable hydrogen peroxide to react quickly, and similarly, the stirring rotating speed is the same purpose, so that hydrogen peroxide can react within 10-20S, therefore, when the foamed cement is prepared, the slurry can be condensed and hardened within 10 minutes, the reaction speed and the stirring speed are increased, bubbles can be prevented from rising, no bubbles exist at the bottom of a mould, more bubbles exist at the upper part, uniform distribution of bubbles is ensured, and meanwhile, the carbon fiber-based SiO can be convenient₂Addition of aerogel, as shown in figure 1.

After 1 minute, the carbon fiber-based SiO was then applied₂Aerogel and coagulant are added to the stirred tank and stirring is continued, in this example, carbon fiber based SiO₂The addition of aerogel can seal a large amount of microcracks and improve the closed porosity, as shown in FIG. 2, the carbon fiber based SiO which can not react₂The aerogel can be used as a supplement to bond cement and porous ceramic powder particles together to form a good network-like framework structure.

The effect of adding the coagulant at this time is to prevent the slurry from rapidly solidifying, and the coagulant is carbon fiber-based SiO₂The aerogel is ineffective, and in the embodiment, the coagulant mixed by sodium carbonate and triethanolamine according to the mass ratio of 10:1 is adopted, and the sodium carbonate is mainly capable of reducing the loss of later strength and further improving the early strength of the cement.

And after stirring is finished, injecting the stirred slurry into a mold, curing and molding, and obtaining the foamed cement after curing and molding. The curing process adopts the existing mature process.

And (3) testing: in this example, tests were conducted on the mechanical properties, dry density, thermal conductivity, and pore structure of the formed foamed cement block.

Wherein, the mechanical properties comprise compressive strength and flexural strength. Firstly, the molded test block is maintained to the age, and is respectively cut into the sizes of 100mm multiplied by 100mm and 40mm multiplied by 160mm, after being dried, a CMT5504 type microcomputer control electronic universal tester is used for testing according to the GB/T5486 test method for inorganic hard heat insulation products, and the loading speed is adjusted to be (10 +/-1) mm/min.

And (3) putting the test block into an air drying oven, drying the test block to constant weight at the temperature of 60 +/-5 ℃, namely, weighing the test block with the mass change rate within 0.2 percent within 3 hours, and weighing the test block with the mass G. The length, width and height of the steel bar are measured by a steel ruler, the volume V1 is calculated, and the dry density calculation formula is as follows:

where ρ is the dry density of the test piece (kg/m 3).

The thermal conductivity was tested according to the method of GB/T10294.

The dry density of the test block is 253kg/m³The 28d flexural strength reaches 0.23MPa, the 28d compressive strength is 0.65MPa, the flexibility coefficient is 2.82, the thermal conductivity coefficient is 0.077w/(m.k), the thermal performance and the mechanical performance of the material are obviously improved, and the water absorption rate is 36%.

Example 2, this example provides a carbon fiber based SiO2 aerogel foam cement

In this example, compared with example 1, the main points are the addition of raw materials, and in this example, 80 parts of cement; 20 parts of carbon fiber-based SiO2 aerogel; 20 parts of porous ceramic powder; 8 parts of hydrogen peroxide foaming agent; 0.5 part of manganese oxide foaming catalyst; 8 parts of coagulant of a compound of sodium carbonate and triethanolamine, wherein the mass ratio of the sodium carbonate to the triethanolamine is 10: 1; 4 parts of a foam stabilizer of calcium stearate modified by a nano intercalation technology; the balance of water, and the cement is Portland cement. The porous ceramic powder is particles processed by the existing waste porous ceramics into particles with the particle size of 325 meshes, and the mesh size is the common particle size of the existing portland cement, and of course, the particle size can be larger, and the maximum particle size does not exceed 180 meshes. The balance of water, the water-cement ratio is 0.46.

The dry density of the test block is 258kg/m³The 28d flexural strength reaches 0.22MPa, the 28d compressive strength is 0.62MPa, the flexibility coefficient is 2.81, the heat conductivity coefficient is 0.078w/(m.k), the thermal performance and the mechanical performance of the material are obviously improved, and the water absorption rate is 35%.

Example 3, this example provides a carbon fiber based SiO2 aerogel foam cement

Compared with the example 1, the main points of the present example are the addition of raw materials, and in the present example, 70 parts of cement; 15 parts of carbon fiber-based SiO2 aerogel; 15 parts of porous ceramic powder; 6 parts of hydrogen peroxide foaming agent; 0.4 part of manganese oxide foaming catalyst; 6 parts of coagulant of a compound of sodium carbonate and triethanolamine, wherein the mass ratio of the sodium carbonate to the triethanolamine is 10: 1; 3 parts of a foam stabilizer of calcium stearate modified by a nano intercalation technology; the balance of water, and the cement is Portland cement. The porous ceramic powder is particles processed by the existing waste porous ceramics into particles with the particle size of 325 meshes, and the mesh size is the common particle size of the existing portland cement, and of course, the particle size can be larger, and the maximum particle size does not exceed 180 meshes. The balance of water, the water-cement ratio is 0.46.

The dry density of the test block is 256kg/m³The 28d flexural strength reaches 0.24MPa, the 28d compressive strength is 0.66MPa, the flexibility coefficient is 2.83, the thermal conductivity coefficient is 0.076w/(m.k), the thermal performance and the mechanical performance of the material are obviously improved, and the water absorption rate is 36%.

The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention in other forms, and any person skilled in the art may apply the above modifications or changes to the equivalent embodiments with equivalent changes, without departing from the technical spirit of the present invention, and any simple modification, equivalent change and change made to the above embodiments according to the technical spirit of the present invention still belong to the protection scope of the technical spirit of the present invention.