CN107473675B

CN107473675B - GO and nano mineral powder synergistically dispersed CNT modified nano building material and preparation method and application thereof

Info

Publication number: CN107473675B
Application number: CN201710656212.9A
Authority: CN
Inventors: 罗健林; 张春巍; 李秋义; 金祖权; 侯东帅; 张鹏; 张纪刚; 王鹏刚
Original assignee: Qingdao University of Technology
Current assignee: Qingdao University of Technology
Priority date: 2017-08-03
Filing date: 2017-08-03
Publication date: 2019-12-17
Anticipated expiration: 2037-08-03
Also published as: CN107473675A

Abstract

the invention belongs to the technical field of nano materials, and particularly relates to a GO and nano mineral powder synergistic dispersion CNT modified nano building material, and a preparation method and application thereof. The GO and nano mineral powder synergistically dispersed CNT modified nano building material comprises CNT powder or CNT dispersion liquid, GO powder or GO dispersion liquid, nano mineral powder, a high-efficiency water reducing agent, water, cement and a defoaming agent. The prepared nano building material can realize the effect of cooperatively dispersing CNT by GO and nano mineral powder, and solves the problem that GO is easy to deoxidize and agglomerate in an alkaline system. The prepared piezoresistive sensor based on the nano building material has good piezoresistive sensing efficiency, good mechanical toughness and strong compatibility with a concrete matrix, and has good application prospects in the fields of high-rise building frame shearing connecting beams, energy consumption nodes, high-strength/high-toughness splicing seams of traffic bridges and road surface structures and health monitoring sensors of large engineering structures.

Description

GO and nano mineral powder synergistically dispersed CNT modified nano building material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of nano materials, and particularly relates to a GO and nano mineral powder synergistic dispersion CNT modified nano building material, and a preparation method and application thereof.

Background

The cement-based composite material is the most widely used building material in the current infrastructure construction due to the advantages of convenient material acquisition, good slurry plasticity, high compression resistance of a hardened body, good durability and the like. However, it has disadvantages such as low tensile strength, poor fracture toughness, etc., and is liable to fail the corresponding structural system based on cement-based composite materials. The solution of the problems has very important application and economic value, and the application range of the solution is further widened. In the last century, people mainly improve the tensile strength, fracture toughness and other properties of cement-based materials by compounding micron-sized fibers such as steel fibers, glass fibers, carbon fibers, basalt fibers, aramid fibers, polyvinyl alcohol fibers and the like. A large number of scientific researches and engineering applications show that the microscopic fibers have good effect on inhibiting the propagation of the macroscopic cracks of the cement-based material, and the corresponding mechanical toughness is effectively improved. And meanwhile, the corresponding cement-based composite material also presents certain intelligent self-perception functional characteristics. However, since the C-S-H gel, the main hydration product of cement, contains a large number of gel pores and is in a nanometer scale, it is difficult to effectively bridge micropores by using microscopic fibers to inhibit the expansion of corresponding microcracks.

Carbon Nanotubes (CNTs) discovered in 1991 with SP²The hybrid structure has a length-diameter ratio of hundreds, has the characteristics of excellent chemical stability, mechanical property, thermal stability, good microwave absorption, thermal/electrical properties and the like, and further, various composite materials modified based on the CNT are continuously concerned. However, the excellent properties of CNTs on the nanoscale are often difficult to transfer to relevant properties on the macroscopic scale of relevant composites. This is because the inherent hydrophobicity of the CNT surface and the presence of strong intermolecular van der waals forces make CNTs highly susceptible to entanglement, agglomeration, and poor internal dispersibility in the cement matrix. Therefore, in order to effectively exert the enhanced modification effect of the CNT, the reasonable dispersion method is adopted to introduce the CNT into a cement-based material system, and the key point is that the excellent performance of the nanometer scale is transferred to the macro scale.

the covalent modification of the CNT by the oxidation of strong acid by professor Wangbei of Tongji university effectively improves the functional group on the surface of the CNT, improves the dispersibility of the CNT in water, improves the strength of the CNT cement-based composite material, realizes the function of bridging microcracks, but the covalent modification method can weaken the structure and electronic performance of the CNT. Chinese patents ZL200810064075.0, ZL200810064522.2, ZL200810064501.0 respectively attempt to disperse CNTs in a cement-based material by using a surfactant through ultrasonic, high-speed shearing, and electric field induction processes; however, the surfactant often has a large amount of air bubbles, which may affect cement hydration and weaken the bonding interface between the CNT and the cement; the high-speed shearing method may shear CNTs, on the one hand, and the sample throughput is low, on the other hand; the electric field induction method consumes a large amount of organic solvent on one hand, and the bonding surface of the corresponding CNT deposition layer and the cement-based layer is weak on the other hand. Chinese patents CN106007553A and CN105268339A respectively disclose that firstly CNT is uniformly dispersed in polyvinyl alcohol colloid and nano silica gel, then the prepared CNT/polyvinyl alcohol pre-polymerization solution and CNT/nano silica gel solution are doped into cement mortar as composite modifiers, the CNT is effectively prevented from agglomerating, the toughness and durability enhancement effects of the CNT, polyvinyl alcohol or nano silica gel in cement-based materials are fully exerted, the internal stress change of the base materials can be reflected through the internal resistance change, and a certain intelligent sensing effect is achieved; however, good dispersion of CNTs in polyvinyl alcohol colloids, nanosilica, and does not represent a good continued dispersion in cement matrices. International patent ZL200980125145.1 uses cement clinker as a substrate for anchoring transition metal nanoparticles, allowing continuous, large-scale synthetic growth of CNTs on cement clinker and grains, thereby forming subsequent CNT/cement clinker composites and structural products; however, this method still has difficulty in achieving sufficient dispersion of CNTs on a nano scale because cement clinker is of a micron scale. Chinese patent CN106277876A discloses that a polypyrrole conductive polymer with good conductivity and hydrophilicity is loaded on the surface of CNT by using an in-situ polymerization method, and is added into a cement matrix as a conductive filler to prepare a cement-based conductive composite material with good conductivity, self-sensing performance and mechanical properties; however, polypyrrole degrades in alkaline cement-based hydration systems and it is difficult to maintain its dispersibility continuously.

graphene (GNP) is the thinnest and hardest nano material in the modern society, has excellent mechanical, electrical and thermal properties, and is widely applied to various base materials as a novel nano material. Graphene Oxide (GO) is an intermediate product for preparing GNP by a redox method, and as a derivative of GNP, GO has a two-dimensional structure similar to that of GNP, a huge specific surface area and excellent performance, and contains a large number of oxygen-containing functional groups such as hydroxyl, epoxy, carboxyl and the like on the surface. The unique structure of GO enables GO to have good hydrophilicity, is beneficial to being uniformly dispersed in a cement-based water-based system, guarantees good interface bonding strength between the GO and a cement matrix, and finally improves rheological property and mechanical strength of a cement-based composite material, which can be seen from relevant reports of Chinese patents ZL201310098136.6, CN104628294A, CN105801047A and the like.

Nano mineral powder (nano SiO)₂Superfine silica fume, SiO-containing₂And Al₂O₃Of nano-clay, SiO-containing₂and Al₂O₃Superfine mineral powder or nano Fe₂O₃Micropowder) is a nano powder material which is industrially produced on a large scale at present. The surface of the nano mineral powder has larger specific surface area, contains a large amount of unsaturated silica, aluminum oxide or titanium oxide residual bonds and hydroxyl groups in different bonding states, deviates from a stable bond structure due to surface oxygen deficiency, and therefore, the nano mineral powder can well mix with Ca-containing cement concrete hydration slurry system²⁺、Mg²⁺、Al³⁺、Fe³⁺、OH^-the plasma generates chemical bonding and has high reaction activity.

However, little research is done on the synergistic modification of the cement-based composite material by mixing the CNT and GO, and no report is found on whether the GO which is in the molecular scale of DNA together with a concrete water reducing agent can synergistically disperse the CNT. Meanwhile, the problem that GO is easy to deoxidize and agglomerate in an alkaline cement paste system is still not effectively solved. These problems will greatly limit its widespread use in a wide range of cementitious concrete materials.

Disclosure of Invention

The invention provides a GO and nano mineral powder synergistic dispersion CNT modified nano building material, a preparation method and application thereof in order to overcome the defects.

The theoretical basis of the invention is as follows:

in one aspect, a six-membered ring aromatic SP in which GO is not oxidized is utilized²Hybrid region and oxidized aliphatic chain SP³Amphiphilic structural features of the GO³the hybridization region ensures that GO has good hydrophilicity and is easy to be uniformly dispersed in a water-based system, and the SP of GO²SP of hybrid region and CNT²The hybrid region can be combined through pi-pi supermolecule acting force, so that the GO can form a good L-B film on the surface of an aqueous system like a surfactant, and the CNT can be effectively dispersed under the action of the good amphiphilic molecules of the GO, so that the cement-based composite material is synergistically enhanced.

On the other hand, aiming at the problem that GO is rapidly deoxidized under a strong alkaline environment at normal temperature to cause re-agglomeration of GO and further to be unfavorable for effective dispersion of CNT and GO in an alkaline cement slurry system, on one hand, the hydration products Ca (OH) formed in early stage of cement hydration slurry are effectively consumed by utilizing high-activity nano mineral powder₂(C-H), the alkalinity of the GO is reduced, and the deoxidation agglomeration of the GO is effectively avoided; on the other hand, the nano mineral powder is utilized to promote the CNT and GO to be further dispersed in a cement-based system, more hydrated calcium silicate (C-S-H), hydrated calcium aluminosilicate (C-A-S-H), hydrated calcium ferrite (C-F-H) gel and hydrated calcium aluminate (C-A-H) crystals can be generated, anchoring points are formed on the surfaces of the CNT and GO, and the bonding strength between the CNT and the cement matrix interface is effectively improved.

On the other hand, the high belite sulphoaluminate cement with high setting speed, high early strength and low hydration alkalinity is selected as the corresponding cement cementing material. Because the minerals of the sulphoaluminate cement clinker are mainly anhydrous calcium sulphoaluminate (C)₄A₃S) and dicalcium silicate (C)₂S) and corresponding hydration products mainly comprise hydrated calcium sulphoaluminate and hydrated calcium silicate, and almost no alkaline CH exists, so that the hydration slurry system is low in alkalinity, high in coagulation speed and high in early strength, and the problem of GO deoxidation in a strong alkaline hydration gelation environment can be further avoided. Also, portland cements (such as slag cement, pozzolana cement, fly ash cement, composite cement, etc.) of magnesium phosphate cement or high mineral admixtures may be used, wherein the magnesium phosphate cement hydration product is mainly mgo₂.H₂o, almost no alkaline CH exists, a corresponding hydrated slurry system is close to neutrality, the setting speed is high, and the early strength is high; whereas the portland cement hydration product of a high mineral admixture contains onlyAnd a small amount of CH is provided, so that the problem of deoxidation of GO in a strong alkali hydration gelation environment can be effectively avoided.

In conclusion, the synergistic dispersion of the CO and the nano mineral powder to the CNT can be effectively realized through the three measures, so that the CNT still has good dispersion stability in a nano building material system.

The technical scheme adopted by the invention is as follows:

the GO and nano mineral powder synergistically dispersed CNT modified nano building material comprises the following components in parts by mass:

0.00005-0.05 part of CNT powder or dispersion liquid directly containing 0.00005-0.05 part of CNT, 0.00001-0.001 part of GO powder or dispersion liquid directly containing 0.00001-0.001 part of GO, 0-0.05 part of nano mineral powder, 0-0.02 part of high efficiency water reducing agent, 0.25-0.5 part of water, 1 part of cement and 0-0.01 part of defoaming agent.

The GO and the nano mineral powder synergistically disperse the CNT modified nano building material, and further comprises 1.5-3 parts of fine sand.

The CNT powder is pure CNT, carboxylated CNT, aminated CNT or sulfonated CNT; the CNT dispersion is a CNT aqueous dispersion, and can be obtained in an aqueous system through surfactant ultrasonic dispersion and covalent modification of CNT powder or directly purchased.

The CNT powder is single-wall CNT or multi-wall CNT, the diameter is 1-50nm, and the length is 2-50 μm; the CNT dispersion is a multi-wall CNT aqueous dispersion with the concentration of 2 wt% and the mass of more than or equal to 95%.

The GO powder or GO dispersion can be synthesized or purchased by a Brodie method, Staudenmaier method, Hummers method or electrochemical method; preferably selecting GO dispersion liquid, wherein the concentration of the GO dispersion liquid is 1mg/mL, the oxygen content is 20%, and the sheet diameter is 1-500 nm.

The nano mineral powder is nano SiO₂SiO-containing₂and Al₂O₃Of nano-clay, SiO-containing₂and Al₂O₃Superfine mineral powder or nano Fe₂O₃One or two of the micro powders; preferably nano SiO₂The diameter is 50-200 nm.

The high-efficiency water reducing agent is one of polycarboxylic acids, naphthalene sulfonate, aliphatic series, sulfamate and melamine resin; graft block copolymerization type polycarboxylic acids are preferable.

The water is deionized water or distilled water, and the water used for dispersing the CNT and GO is the same water as the water in the CNT dispersion and the GO dispersion.

the cement is one of sulphoaluminate cement, magnesium phosphate cement and silicate cement (such as slag cement, volcanic ash cement, fly ash cement, composite cement and the like) of high-mineral admixture, and preferably the high belite sulphoaluminate cement with low alkalinity, high setting speed and high early strength of a hydrated slurry system is selected.

The fine sand is ultra-fine sand with a fineness modulus of 0.7-1.5, preferably siliceous fine sand with the maximum grain diameter and the minimum grain diameter of 0.25mm and 0.12mm respectively and the cumulative screen residue rate of a 0.60mm sieve of not more than 5 percent.

the defoaming agent is one or more of polydimethylsiloxane, a high-alcohol fatty acid ester compound, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether and emulsified silicone oil defoaming agent; polydimethylsiloxane-type defoaming agents are preferred.

The preparation method of the GO and nano mineral powder synergistically dispersed CNT modified nano building material comprises the following steps:

(1) Preparation of GO co-dispersed CNT suspensions

step 1: sequentially adding the GO dispersion liquid, the CNT powder or the CNT dispersion liquid into a high-efficiency water reducing agent aqueous solution, and obtaining the optimal dispersion effect of GO/CNT in the high-efficiency water reducing agent by the UV absorbance of the GO/CNT/water reducing agent mixed solution under the UV spectral characteristic peaks of GO and CNT under the condition of different ultrasonic energy input quantities, thereby finally obtaining a GO/CNT dispersion mother solution;

Step 2: diluting the printing ink-shaped GO/CNT dispersion liquid into 3/4 of the required total water amount according to the water-to-gel ratio, and further obtaining GO/CNT dispersion sub-liquids for different material mixing ratios by adopting the same surfactant ultrasonic process as the first step;

(2) Preparation of GO and nano mineral powder synergistically dispersed CNT modified nano building material

Step 1: sequentially adding the GO/CNT dispersion sub-solution and the nano mineral powder into a shearing and emulsifying container, and performing high-speed shearing treatment to obtain uniform GO/CNT/nano mineral powder mixed slurry for later use;

Step 2: uniformly stirring cement, fine sand (if needed) and residual 1/4 water which is determined according to the water-to-gel ratio and contains a high-efficiency water reducing agent in a mortar stirring pot, adding GO/CNT/nano mineral powder mixed slurry, continuously stirring uniformly, and adding a defoaming agent to prepare GO and nano mineral powder synergistic dispersed CNT modified nano building material slurry;

and 3, step 3: and (3) putting the GO and the nano mineral powder cooperated with the dispersed CNT modified nano building material slurry into a steel mould which is placed in advance and coated with a release agent, vibrating to compact and trowel, and pouring or compacting to form.

The preparation method of the GO and nano mineral powder synergistically dispersed CNT modified nano building material further comprises the following steps:

And after casting or compacting and forming, covering a plastic film, standing for 3-24 hours at room temperature in a sealed environment, demolding the GO and the nano mineral powder synergistically dispersed CNT modified nano building material test piece, and performing standard curing and solidification to a preset age.

And the piezoresistive sensor is prepared by the GO and the nano mineral powder cooperatively dispersing the CNT modified nano building material.

The preparation method of the piezoresistive sensor prepared by the CNT modified nano building material through the synergy dispersion of GO and nano mineral powder comprises the following steps:

The method comprises the steps of compression molding GO and nano mineral powder synergistically dispersing CNT modified nano building material blocks or sheets, embedding a pair of stainless steel electrodes into the side faces of a mold in advance, leading out a lead by using an aviation plug after drying, and spraying polyether spray to form an insulating and moisture-proof packaging thin layer around the GO and nano mineral powder synergistically dispersing CNT modified nano building material blocks or sheets so as to form a compact packaging layer.

The piezoresistive sensor can regularly change due to the change of the CNT physical overlap resistance or the macroscopic quantum tunneling carrier current density in a cement or mortar system through the electrical signal of a nano building material test block or a test block under the condition of an external load, thereby realizing the piezoresistive sensing capability of the sensor.

the piezoresistive sensor made by the GO prepared by the preparation method and the nano mineral powder synergistically dispersed CNT modified nano building material can be in the shape of a concrete coarse aggregate block or a compacted round sheet; the size of the sensor can be adjusted according to actual requirements.

compared with the prior art, the invention has the following excellent technical effects:

The method aims at the problems that whether the GO which is at the molecular scale of DNA and a concrete water reducing agent can also synergistically disperse CNT and that the GO is easy to deoxidize and aggregate in an alkaline cement slurry system. The invention adopts the following comprehensive means: firstly, the good amphiphilic molecular effect of GO is utilized to effectively disperse CNT; secondly, on one hand, the C-H formed in the early stage of cement hydration slurry can be effectively consumed by utilizing the high-activity nano mineral powder, the alkalinity of the cement hydration slurry is reduced, and the deoxidation and agglomeration of GO are effectively avoided; on the other hand, the nano mineral powder is utilized to promote the CNT and GO to be further dispersed in a cement-based system, more C-S-H, C-A-S-H, C-F-H gel and C-A-H crystal can be generated, anchoring points are formed on the surfaces of the CNT and GO, and the bonding strength between the CNT and the interface of the cement matrix is effectively improved; and thirdly, the problems of deoxidation of GO in a strong alkaline hydration gelation environment can be effectively avoided by selecting sulphoaluminate cement, magnesium phosphate cement or high-mineral admixture portland cement with a low hydration slurry system alkalinity, a high setting speed and a high early strength.

The piezoresistive sensor of the nano building material can regularly change to realize the piezoresistive sensing efficiency under the condition that an electrical signal of the piezoresistive sensor is subjected to external load due to the physical overlap resistance of the CNT fiber or the current density change of a macroscopic quantum tunneling carrier. The sensor prepared by the GO and the nano mineral powder synergistically dispersed CNT modified nano building material has the characteristics of strong compatibility with a concrete matrix, good durability and the like, has excellent mechanical toughness and good piezoresistive sensing characteristics, and has good application prospects in the fields of high-rise building frame shear coupling beams, high-strength/high-toughness splicing seams of energy-consuming node traffic bridges and road surface structures and health monitoring sensors of large engineering structures.

Drawings

FIG. 1 is a schematic diagram of a system of GO and nano mineral powder synergistically dispersing CNT in cement hydration products;

The reference symbols shown in the figures are:

1. GO; 2. a CNT; 3. nano mineral powder particles; 4. an additive; 5. c- (A) -S (F) -H.

Detailed Description

the invention is further explained below with reference to the figures and examples:

Example 1

The preparation steps of the GO and nano mineral powder synergistically dispersed CNT modified nano building material are as follows:

(1) Preparation of GO co-dispersed CNT suspensions

step 1: adding 0.1g of GO dispersion liquid with 30 percent of oxygen content into 300mL of water dissolved with 5g of polycarboxylic acid high-efficiency water reducing agent, adding 1g of CNT powder with the diameter of 10-20nm and the length of 5-15 mu m, and then carrying out ultrasonic treatment, wherein the corresponding process is that the stop time is 1s per 10s of ultrasonic treatment; the optimal ultrasonic treatment energy of 60KJ is obtained through comprehensive balance by testing the UV absorbance of the GO/CNT/water reducing agent mixed solution under the UV spectral characteristic peaks (230nm and 220nm) of GO and CNT under the ultrasonic treatment energy of 0KJ to 100KJ (step by step of 10KJ) and combining the consumed ultrasonic energy and the absorbance peak value. And finally preparing the printing ink-like GO/CNT dispersion mother liquor for later use by adopting an optimized ultrasonic energy treatment process.

Step 2: setting the water-to-gel ratio to be 0.5, taking 50mL of the prepared printing ink-like GO/CNT dispersion mother liquor, adding 2g of polycarboxylic acid high-efficiency water reducing agent, adding distilled water, diluting into 300mL of GO/CNT suspension, and then carrying out ultrasonic treatment, wherein the corresponding process is also that the stop time is 1s per 10s of ultrasonic treatment; by testing the UV absorbance of the GO/CNT suspension under the UV spectral characteristic peaks of GO and CNT under the ultrasonic treatment energy of 0KJ to 50KJ (5 KJ is taken in a step), and combining the consumed ultrasonic energy and the absorbance peak value, the optimal ultrasonic treatment energy is 15KJ through comprehensive balance. And finally preparing GO/CNT dispersion sub-solution which can be directly used for different material mixing ratios by adopting an optimized ultrasonic energy treatment process.

Step 1: transferring the 300mLGO/CNT dispersion liquid into a shearing emulsification container, and adding 80g of nano SiO₂and (3) shearing the mineral powder at a high speed of 5000rpm for 10min to prepare GO/CNT/nano mineral powder mixed slurry for later use.

step 2: sequentially adding 800g of sulphoaluminate cement, 1200g of fine sand and 100mL of distilled water dissolved with 1g of polycarboxylic acid high-efficiency water reducing agent into a JJ-5 type glue and sand stirring pot, and stirring for 30s at a low speed (120 rpm);

And 3, step 3: adding the GO/CNT/nano mineral powder mixed slurry prepared in the step 1, stirring at a high speed (300rpm) for 2min, adding 1g of polydimethylsiloxane defoaming agent, and stirring at a low speed (120rpm) for 1min to prepare GO and nano mineral powder synergetic dispersed CNT modified nano building material slurry;

Step 4; putting the mixture into a steel cuboid type triple (40mm multiplied by 160mm) mould coated with a release agent in 2 batches, sequentially vibrating for 10s and 50s, leveling, pouring or compacting and forming to prepare a GO and nano mineral powder synergetic dispersed CNT modified nano building material sample; then covering with a plastic film, placing in a sealed environment at room temperature for 6 hours, and then demolding, curing and curing to 7d age.

the preparation method of the piezoresistive sensor by using the GO and the nano mineral powder to synergistically disperse the CNT modified nano building material comprises the following steps:

The GO and nano mineral powder synergetic dispersion CNT modified nano building material slurry is loaded into a cylindrical mold with the height of 20mm and the diameter of 40mm, wherein a mesh-shaped counter stainless steel electrode is placed in advance in 2 batches, the counter electrode spacing is 10mm, the vibration is carried out for 10s and 50s in sequence, the GO and nano mineral powder synergetic dispersion CNT modified nano building material cylindrical block or sheet is subjected to compression molding, a shielding lead is led out by an aviation plug after the counter electrode spacing is 10mm and the counter electrode spacing is cured to 7d, and then a polyether spray is sprayed around the nano building material block or sheet to form an insulating and moisture-proof packaging thin layer to form a compact packaging layer. The specification of the piezoresistive sensor can be adjusted according to the actual application requirement.

Determining the uniform dispersion and stable state of 300mL of GO/CNT/water reducing agent mixed solution and CNT and GO in GO/CNT suspension under different ultrasonic energy treatment conditions by using characterization methods such as an ultraviolet-visible spectrophotometer and a solution conductivity method; respectively diluting 0.1mL of GO/CNT/water reducing agent mixed solution and GO/CNT suspension to 10mL, respectively comparing absorbance values at characteristic peaks with wavelengths of 230nm and 220nm, and optimizing that the optimal ultrasonic treatment energy is 60KJ and 15KJ respectively; the solution conductivity was 13.17S/cm, 2.38S/cm.

The fluidity of the GO and the nano mineral powder synergistic dispersion CNT modified nano building material is tested to be 126 +/-5 mm by using an electric jump table, and the initial setting time and the final setting time of the GO and the nano mineral powder synergistic dispersion CNT modified nano building material are respectively tested to be 23 +/-2 min and 187 +/-4 min by using a mortar setting time tester. This also shows that the incorporation of CNTs, GO and nanopowder significantly reduced the fluidity of the nanostrucrure slurry, but had substantially no effect on the setting time of the slurry. The flexural strength and the compressive strength of a 7d test piece of the GO and nano mineral powder synergistically dispersed CNT modified nano building material measured by using a universal material testing machine are respectively 15.3 +/-1.58 MPa and 71.6 +/-5.24 MPa; fracture toughness K measured by notch three-point bending method_ICIs 14.92MPa.m^1/2(ii) a The impact toughness of the steel is measured by a drop hammer method, and the initial cracking times and the final cracking times are respectively 15 times and 22 times. And (3) connecting the mesh counter electrode by using an LCR digital bridge, and testing that the alternating current impedance value of the piezoresistive sensor prepared by GO and nano mineral powder in cooperation with the dispersed CNT modified nano building material is 2.08k omega at the frequency of 20 kHz. Under a universal material experiment machine, the piezoresistive sensor is obtained in a structural frequency-encountering cyclic elastic strain range (0-600 mu epsilon) by combining a dynamic data acquisition and processing technology, the impedance change rate of the piezoresistive sensor is 57.3 percent, the corresponding sensitivity coefficient and linearity of the strain perception to the structure are respectively 95.5/mu epsilon and 2.13 percent, and the piezoresistive sensor is far superior to a common strain gauge and a similar cement basic characteristic sensor.

The excellent piezoresistive sensing performance also shows that the CNT subjected to synergistic dispersion of GO and the nano mineral powder is fully dispersed in the cement matrix, and a corresponding synergistic dispersion mechanism is schematically shown in figure 1, wherein the schematic diagram comprises graphene oxide GO1, CNT2, nano mineral powder particles 3, an additive 4 and a cement hydration product C- (A) -S (F) -H5. Firstly, CNTs 2 are effectively dispersed with GO1, which possesses good amphiphilic molecular properties; secondly, on one hand, C-H formed in the early stage of cement hydration slurry can be effectively consumed by utilizing the nano mineral powder particles 3, the alkalinity of the cement hydration slurry is reduced, and the deoxidation and agglomeration of GO1 are effectively avoided; on the other hand, the nano mineral powder particles 3 are utilized to promote further dispersion of GO1 and CNT2 in C- (A) -S (F) -H5, more C- (A) -S (F) -H5 can be generated, anchor points are formed on the surfaces of GO1 and CNT2, and the bonding strength of the GO1 and the C- (A) -S (F) -H5 interface is effectively improved; and thirdly, the sulphoaluminate cement with low alkalinity, high setting speed and high early strength of a hydration slurry system is selected, so that the problem of deoxidation of GO1 in a strong alkali hydration gel environment can be effectively avoided.

Example 2

(1) Preparation of GO co-dispersed CNT suspensions

Step 1: adding 0.1g of GO dispersion liquid with 30% oxygen content into 300mL of water dissolved with 5g of naphthalene sulfonate superplasticizer FDN, adding 50g of CNT dispersion liquid with the concentration of 2 wt%, and then carrying out ultrasonic treatment, wherein the corresponding process is that the stop time is 1s per 10s of ultrasonic treatment; the optimal ultrasonic treatment energy of 60KJ is obtained through comprehensive balance by testing the UV absorbance of the GO/CNT/water reducing agent mixed solution under the UV spectral characteristic peaks (230nm and 220nm) of GO and CNT under the ultrasonic treatment energy of 0KJ to 100KJ (step by step of 10KJ) and combining the consumed ultrasonic energy and the absorbance peak value. And finally preparing the printing ink-like GO/CNT dispersion mother liquor for later use by adopting an optimized ultrasonic energy treatment process.

Step 2: setting the water-to-gel ratio to be 0.5, taking 50mL of the prepared printing ink-like GO/CNT dispersion mother liquor, adding 2g of naphthalene sulfonate type high-efficiency water reducing agent FDN, adding distilled water, diluting into 300mL of GO/CNT suspension, and then carrying out ultrasonic treatment, wherein the corresponding process is also 10s of stop time per ultrasonic treatment for 1 s; by testing the UV absorbance of the GO/CNT suspension under the UV spectral characteristic peaks of GO and CNT under the ultrasonic treatment energy of 0KJ to 50KJ (5 KJ is taken in a step), and combining the consumed ultrasonic energy and the absorbance peak value, the optimal ultrasonic treatment energy is 15KJ through comprehensive balance. And finally preparing GO/CNT dispersion sub-solution which can be directly used for different material mixing ratios by adopting an optimized ultrasonic energy treatment process.

Step 1: the 300mLGO/CNT dispersion prepared above was transferred to a shear emulsification vessel and 64g of SiO-containing dispersion was added₂And Al₂O₃The nano clay is subjected to high-speed shearing treatment for 5-30min at the rotation speed of 5000-5500rpm to prepare GO/CNT/nano mineral powder mixed slurry for later use.

Step 2: sequentially adding 800g of magnesium phosphate cement, 1200g of fine sand and 100mL of distilled water dissolved with 1g of naphthalene sulfonate superplasticizer FDN into a JJ-5 type mortar stirring pot, and stirring for 30s at a low speed (120 rpm);

Step 4; putting the mixture into a steel cuboid type triple (40mm multiplied by 160mm) mould coated with a release agent in 2 batches, sequentially vibrating for 10s and 50s, leveling, pouring or compacting and forming to prepare a GO and nano mineral powder synergetic dispersed CNT modified nano building material sample; then covering a plastic film, placing the plastic film in a sealed environment at room temperature for 3 hours, and then demolding, curing and curing to 7d of age.

The GO and nano mineral powder synergetic dispersion CNT modified nano building material slurry is loaded into a cylindrical mold with the height of 20mm and the diameter of 40mm, wherein a mesh counter stainless steel electrode is placed in advance, the counter electrode distance is 10mm, the vibration is carried out for 10s and 50s in sequence, the GO and nano mineral powder synergetic dispersion CNT modified nano building material cylindrical block or sheet is subjected to compression molding, the pressure is 15MPa, the pressure maintaining time is 15-90min, a shielding lead is led out by an aviation plug after demolding, curing and 7d age, and then a thin insulating and moisture-proof packaging layer is sprayed around the nano building material block or sheet by a polyether spray to form a compact packaging layer. The specification of the piezoresistive sensor can be adjusted according to the actual application requirement.

test with electric diving tableThe fluidity of the GO and the nano mineral powder synergistically dispersed CNT modified nano building material is 119 +/-4 mm, and the initial setting time and the final setting time of the GO and the nano mineral powder are respectively 25 +/-1 min and 57 +/-3 min measured by a sand gel setting time tester. The results also show that the fluidity of the nano building material slurry is reduced by the doping of the CNT, GO and nano clay admixtures, but the fluidity of the nano building material slurry is basically not influenced on the setting time of the magnesium phosphate cement slurry, and the flexural strength and the compressive strength of a GO and nano mineral powder synergistically dispersed CNT modified nano building material test piece 7d measured by using an universal material testing machine are respectively 12.7 +/-2.02 MPa and 62.8 +/-4.3 MPa; fracture toughness K measured by notch three-point bending method_ICis 12.75MPa.m^1/2(ii) a The impact toughness of the steel is measured by a drop hammer method, and the initial cracking times and the final cracking times are respectively 13 times and 20 times. And (3) connecting the mesh counter electrode by using an LCR digital bridge, and testing that the alternating current impedance value of the pressure-resistant sensor made of the nano building material modified by the GO subjected to compression molding and the nano mineral powder in cooperation with the dispersed CNT is 4.15k omega at the frequency of 20 kHz. Under a universal material experiment machine, the piezoresistive sensor is obtained in a structural frequency-encountering cyclic elastic strain range (0-600 mu epsilon) by combining a dynamic data acquisition and processing technology, the impedance change rate of the piezoresistive sensor is 46.1 percent, and the corresponding sensitivity coefficient and linearity to the strain borne by the structure are respectively 76.8/mu epsilon and 4.73 percent, which are superior to those of a common strain gauge and a CNT modified cement basic characteristic sensor prepared by a common dispersion process.

Example 3

(1) Preparation of GO co-dispersed CNT suspensions

Step 1: adding 25mL of GO dispersion liquid with the concentration of 4mg/mL and the oxygen content of 41-50% into 300mL of water in which 5g of aliphatic high-efficiency water reducing agent is dissolved, adding 1g of single-wall CNT powder with the diameter of 1-2nm and the length of 2-8 mu m, and then carrying out ultrasonic treatment, wherein the corresponding process is that the stop time is 1s per 10s of ultrasonic treatment; the optimal ultrasonic treatment energy of 60KJ is obtained through comprehensive balance by testing the UV absorbance of the GO/CNT/water reducing agent mixed solution under the UV spectral characteristic peaks (230nm and 220nm) of GO and CNT under the ultrasonic treatment energy of 0KJ to 100KJ (step by step of 10KJ) and combining the consumed ultrasonic energy and the absorbance peak value. And finally preparing the printing ink-like GO/CNT dispersion mother liquor for later use by adopting an optimized ultrasonic energy treatment process.

Step 2: setting the water-to-gel ratio to be 0.5, taking 50mL of the prepared printing ink-like GO/CNT dispersion mother liquor, adding 2g of aliphatic high-efficiency water reducing agent, adding distilled water, diluting into 300mL of GO/CNT suspension, and then carrying out ultrasonic treatment, wherein the corresponding process is also 10s of pause per ultrasonic time for 1 s; by testing the UV absorbance of the GO/CNT suspension under the UV spectral characteristic peaks of GO and CNT under the ultrasonic treatment energy of 0KJ to 50KJ (5 KJ is taken in a step), and combining the consumed ultrasonic energy and the absorbance peak value, the optimal ultrasonic treatment energy is 15KJ through comprehensive balance. And finally preparing GO/CNT dispersion sub-solution which can be directly used for different material mixing ratios by adopting an optimized ultrasonic energy treatment process.

Step 1: transferring the 300mLGO/CNT dispersion liquid into a shearing emulsification container, and adding 64g of nano Fe₂O₃And carrying out high-speed shearing treatment at the rotation speed of 5000-5500rpm for 5-30min to prepare GO/CNT/nano mineral powder mixed slurry for later use.

Step 2: sequentially adding 800g of high-mineral admixture portland cement (fly ash portland cement), 1200g of fine sand and 100mL of distilled water dissolved with 1g of aliphatic high-efficiency water reducing agent into a JJ-5 type mortar stirring pot, and stirring for 30s at a low speed (120 rpm);

And 3, step 3: adding the GO/CNT/nano mineral powder mixed slurry prepared in the step 1, stirring at a high speed (300rpm) for 2min, adding 1.6g of polyoxypropylene polyoxyethylene glycerol ether, and stirring at a low speed (120rpm) for 1min to prepare GO and nano mineral powder synergistic dispersion CNT modified nano building material slurry;

Step 4; putting the mixture into a steel cuboid type triple (40mm multiplied by 160mm) mould coated with a release agent in 2 batches, sequentially vibrating for 10s and 50s, leveling, pouring or compacting and forming to prepare a GO and nano mineral powder synergetic dispersed CNT modified nano building material sample; then covering with a plastic film, placing in a sealed environment at room temperature for 6 hours, and then demolding, curing and curing to 28d age.

The fluidity of the GO and the nano mineral powder synergistic dispersion CNT modified nano building material is tested to be 137 +/-3 mm by using an electric jump table, and the initial setting time and the final setting time of the GO and the nano mineral powder synergistic dispersion CNT modified nano building material are respectively tested to be 161 +/-3 min and 378 +/-5 min by using a mortar setting time tester. This also indicates that CNT, GO and nano Fe₂O₃The fluidity of the corresponding nano building material slurry is not obviously reduced by adding the fly ash cement slurry, and the initial setting time and the final setting time of the corresponding cement slurry are basically not influenced. The flexural strength and the compressive strength of the GO and nano mineral powder synergistic dispersed CNT modified nano building material test piece 28d which are measured by a universal material testing machine are respectively 11.9 +/-1.16 MPa and 58.4 +/-4.95 MPa; fracture toughness K measured by notch three-point bending method_ICis 10.83MPa.m^1/2(ii) a The impact toughness of the steel is measured by a drop hammer method, and the initial cracking times and the final cracking times are respectively 11 times and 19 times. And (3) connecting the mesh counter electrode by using an LCR digital bridge, and testing that the alternating current impedance value of the pressure-resistance type sensor made of the nano building material modified by the GO and the nano mineral powder which are subjected to compression molding and dispersed with the CNT is 5.21k omega at the frequency of 20 kHz. Under a universal material experiment machine, the piezoresistive sensor is obtained in a structural frequency-encountering cyclic elastic strain range (0-600 mu epsilon) by combining a dynamic data acquisition and processing technology, the impedance change rate of the piezoresistive sensor is 49.7 percent, the corresponding sensitivity coefficient and linearity to the strain borne by the structure are 82.8/mu epsilon and 4.54 percent respectively, and the piezoresistive sensor is superior to a common strain gauge and CNT modified cement basic cement prepared by adopting a common dispersion processa characterization sensor.

Claims

1. The GO and nano mineral powder synergistically dispersed CNT modified nano building material is characterized by comprising the following components in parts by mass:

0.00005-0.05 part of CNT powder or a dispersion liquid directly containing 0.00005-0.05 part of CNT, 0.00001-0.001 part of GO powder or a dispersion liquid directly containing 0.00001-0.001 part of GO, more than 0 and less than or equal to 0.05 part of nano mineral powder, 0-0.02 part of high efficiency water reducing agent, 0.25-0.5 part of water, 1 part of cement and 0-0.01 part of defoaming agent;

The nano mineral powder is nano SiO₂SiO-containing₂And Al₂O₃Of nano-clay, SiO-containing₂And Al₂O₃superfine mineral powder or nano Fe₂O₃One or two of the micro powders, nano SiO₂The diameter of (A) is 50-200 nm;

(1) Preparation of GO co-dispersed CNT suspensions

step 2: diluting the printing ink-shaped GO/CNT dispersion liquid into 3/4 water with the required total water consumption according to the water-to-gel ratio, and further obtaining GO/CNT dispersion sub-liquids for different material mixing ratios by adopting the same surfactant ultrasonic process as the step 1;

step 2: uniformly stirring cement and residual 1/4 water which is determined according to a water-cement ratio and contains a high-efficiency water reducing agent in a mortar stirring pot, adding GO/CNT/nano mineral powder mixed slurry, continuously stirring uniformly, and adding a defoaming agent to prepare GO and nano mineral powder synergistic dispersed CNT modified nano building material slurry;

2. The GO and nano mineral powder synergistically dispersed CNT-modified nano building material of claim 1, further comprising 1.5-3 parts of fine sand.

3. The GO and nano mineral powder synergistically dispersed CNT modified nano building material of claim 1 or 2, wherein the CNT powder is pure CNT, carboxylated CNT, aminated CNT or sulfonated CNT, and the CNT dispersion is a CNT aqueous dispersion obtained by surfactant ultrasonic dispersion and covalent modification of CNT powder in an aqueous system or purchased directly; the CNT powder is single-wall CNT or multi-wall CNT, the diameter is 1-50nm, the length is 2-50 μm, and the CNT dispersion is multi-wall CNT aqueous dispersion with the concentration of 2 wt% and the mass of more than or equal to 95%.

4. The GO and nanopowder cooperative dispersion CNT modified nanomaterials of claim 1 or 2, wherein the GO powder or GO dispersion is synthesized or purchased by a Brodie method, Staudenmaier method, Hummers method or electrochemical method; the concentration of the GO dispersion liquid is 1mg/mL, the oxygen content is 20%, and the sheet diameter is 1-500 nm.

5. the GO and nano mineral powder synergistically dispersed CNT modified nano building material of claim 1 or 2, wherein the superplasticizer is one of polycarboxylic acids, naphthalene sulfonates, aliphatic series, sulfamates and melamine resins; the cement is one of sulphoaluminate cement, magnesium phosphate cement and high-mineral admixture portland cement; the defoaming agent is one or more of polydimethylsiloxane, a high-alcohol fatty acid ester compound, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether and emulsified silicone oil defoaming agent; the water is deionized water or distilled water, and the water used for dispersing the CNT and GO is the same water as the water in the CNT dispersion and the GO dispersion.

6. The GO and nanopowder cooperative dispersed CNT modified nano building material of claim 5, wherein the nanopowder is SiO nanopowder₂The diameter is 50-200 nm; the high-efficiency water reducing agent is graft block copolymerization type polycarboxylic acid; the cement is high belite sulphoaluminate cement; the defoaming agent is a polydimethylsiloxane defoaming agent.

7. the GO and nano mineral powder synergistically dispersed CNT modified nano building material of claim 2, wherein the fine sand is extra-fine sand with a fineness modulus of 0.7-1.5.

8. the GO and nanopowder cooperative dispersion CNT modified nanostructural material of claim 7, wherein the maximum particle size and the minimum particle size of the fine sand are 0.25mm and 0.12mm respectively, and the cumulative screen residue rate of a 0.60mm sieve is not more than 5% of siliceous fine sand.

9. The method for preparing the GO and nano mineral powder synergistically dispersed CNT modified nano building material according to any one of claims 1 to 8, is characterized by comprising the following steps of:

(1) Preparation of GO co-dispersed CNT suspensions

10. the method for preparing the GO and nano mineral powder synergistically dispersed CNT modified nano building material of claim 9, further comprising the following steps:

11. a piezoresistive sensor prepared by the GO and nano mineral powder synergistic dispersion CNT modified nano building material as claimed in any one of claims 1 to 8.

12. The method for preparing a piezoresistive sensor prepared by the GO and nano mineral powder synergistically dispersed CNT modified nano building material according to claim 11, wherein the method comprises the following steps: