Preparation method of densified wood-based graphene conductive composite material

文档序号：1654311 发布日期：2019-12-27 浏览：30次中文

阅读说明：本技术 一种密实化木基石墨烯导电复合材料的制备方法 (Preparation method of densified wood-based graphene conductive composite material ) 是由王丽张晓涛武静单晓飞王喜明于 2019-11-25 设计创作，主要内容包括：本发明提供了一种密实化木基石墨烯导电复合材料的制备方法,该方法包括在不影响木材原有力学性能强度的前提下提高木材内部渗透性的预处理,木材与氧化石墨烯均匀高度有机结合,分布于木材内部的氧化石墨烯最大程度还原释放出具有导电性石墨烯的三个过程,最终获得赋予木材导电、提高木材原有尺寸稳定性、密度及力学性能的优良绿色导电功能型复合材料。本发明具有原材料来源广泛,绿色可再生,制备工艺简单,无二次污染等优点,在半导体领域及木材领域都具有广阔的应用范围。(The invention provides a preparation method of a densified wood-based graphene conductive composite material, which comprises three processes of improving the internal permeability of wood on the premise of not influencing the original mechanical property strength of the wood, uniformly and highly organically combining the wood and graphene oxide, and reducing and releasing the graphene oxide distributed in the wood to the maximum extent to obtain the excellent green conductive functional composite material which endows the wood with conductivity and improves the original dimensional stability, density and mechanical property of the wood. The invention has the advantages of wide raw material source, green and renewable property, simple preparation process, no secondary pollution and the like, and has wide application range in the semiconductor field and the wood field.)

1. A preparation method of a densified wood-based graphene conductive composite material specifically comprises the following 3 steps:

(1) wood pretreatment:

boiling the wood with deionized water, taking out the wood, and freezing, wherein the above steps are repeated for 3-5 times until the residual liquid after the water boiling is clear and transparent; then, on the premise of ensuring that the wood is not cracked, drying treatment is carried out to reach the moisture content of the wood below 10%;

(2) wood and graphene oxide are uniformly and highly organically combined:

soaking the graphene oxide dispersion liquid with the concentration of 1-5mg/mL into the wood treated in the step (1) under a pulse type vacuum condition, and drying at 45-60 ℃ until the water content of the wood is 20 +/-5%;

the vacuum condition is that the vacuum degree is 0.5-0.8MPa, and the impregnation: firstly, vacuum impregnation is carried out for 10-30 minutes, then the impregnation is carried out for 3-10 minutes under normal pressure, and then the vacuum impregnation is carried out for 5-15 minutes;

the drying treatment is carried out in the following mode in sequence:

(3) graphene oxide distributed in the wood is reduced to the maximum extent to release conductive graphene:

and (3) placing the wood-based graphene oxide composite material prepared in the step (2) in a flat plate hot press for hot-pressing reduction treatment, wherein the temperature of the press is 180-200 ℃, the treatment time is 30-75min, and the compression rate of a test piece is 30-60%, so that the densified wood-based graphene conductive composite material is obtained.

2. The preparation method of the densified wood-based graphene conductive composite material according to claim 1, wherein the preparation method comprises the following steps:

in the step (1), the temperature of deionized water is 70-100 ℃, preferably 80 ℃, the boiling time is 0.5-2 hours, preferably 0.5 hour, the freezing treatment time is 2-7 days, the freezing temperature is ~ -25 ℃ at minus 15 ℃, preferably 2-3 days, and the processes are repeated for 3-5 times until the residual liquid after the final boiling treatment is clear and transparent;

the drying treatment in the step (1) is carried out in sequence according to the following modes: drying at 103 deg.C for 0.5-2 hr; preferably 1 h; drying at 80 deg.C for 3-6h, preferably 4 h; drying under 0.2MPa vacuum at 60 deg.C for 1-4 hr, preferably 2 hr.

3. The preparation method of the densified wood-based graphene conductive composite material according to claim 1, wherein the preparation method comprises the following steps:

the wood and the graphene oxide are uniformly and highly organically combined:

soaking the graphene oxide dispersion liquid with the concentration of 3mg/mL into the wood treated in the step (1) under a pulse type vacuum condition, and drying at 50 ℃ until the water content of the wood is 20 +/-5%;

the vacuum condition is that the vacuum degree is 0.6MPa, and the impregnation: firstly, vacuum impregnation is carried out for 10 minutes, then the impregnation is carried out for 3 minutes under normal pressure, and then the vacuum impregnation is carried out for 5 minutes;

the drying treatment is carried out in the following mode in sequence:

drying at 50 ℃ for 10h in a vacuum drying oven, drying at 50 ℃ for 6h in a forced air drying oven, drying at 50 ℃ for 1h in the vacuum drying oven under the vacuum condition of 0.04MPa, and forced air drying at 50 ℃ for 10h in the forced air drying oven to obtain the wood-based graphene oxide composite material.

4. The preparation method of the densified wood-based graphene conductive composite material according to claim 1, wherein the preparation method comprises the following steps:

and (3) the graphene oxide distributed in the wood is reduced to the maximum extent to release the conductive graphene:

and (3) placing the wood-based graphene oxide composite material prepared in the step (2) into a flat plate hot press for hot-pressing reduction treatment, wherein the temperature of the press is 200 ℃, the treatment time is 45min, the compression ratio of a test piece is 45%, and after the hot pressing is finished, the water content is controlled to be 3-10%, so that the densified wood-based graphene conductive composite material is obtained.

5. The preparation method of the densified wood-based graphene conductive composite material according to any one of claims 1 to 4, wherein: the wood comprises one of poplar, eucalyptus, fir, pinus sylvestris and larch.

Technical Field

The invention belongs to the technical field of wood functionalization treatment, and particularly relates to a preparation method of a densified wood-based graphene conductive composite material.

Background

In 2014, the wood consumption of China is about 69,572 ten thousand cubic meters, and the total quantity of imported wood is up to 2,565.56 billion cubic meters. Meanwhile, the total wood consumption of China reaches 5.57 billions of cubic meters by 2020. In order to effectively protect natural forest resources and relieve the supply contradiction of natural forests, artificial fast-growing forests are widely planted in China. The eighth national forest resource clearing result shows that the artificial forest in China rapidly develops from 2009 to 2013. Wherein the area of the artificial forest is increased from 6169 to 6933 trillions, and the accumulation of the artificial forest is increased from 19.61 to 24.83 billion cubic meters. The artificial fast-growing forest has the advantages of short growing time, high yield and the like, but because the growing period is short, for example, the growing time of fast-growing poplar which is most widely distributed is 5-6 years, most fast-growing forests have the defects of low density, soft wood, poor physical and mechanical strength, high water content, uneven distribution, easiness in generating dry shrinkage deformation and the like, so that the application range of fast-growing forest varieties is limited, and the application in the high-value-added processing field is less. Therefore, the high added value utilization of the artificial fast-growing forest is vigorously developed, so that the demand of the national people on wood materials is met, and the method has important significance for solving the unreasonable structure of forest resources and the economic development of forestry industry in China.

The prior functional treatment of fast growing wood mainly comprises densification treatment and chemical modification treatment. The densification technology can well improve the mechanical property and the mechanical property of the material, and can change low-density wood with low density, abundant resources and low price into wood with high density and high strength. For example, the wood prepared by the ultrahigh-temperature hot-pressing surface carbonization method disclosed in patent 201410479233.4 has the advantages of no warpage, no cracking, good hydrophobic effect and better maintenance of the original mechanical properties of the wood. The densified wood prepared by the thermocompression bonding integral spray method disclosed in patent 201710108674.7 can be used to obtain high strength and high density wood. But the compression deformation of the wood after the densification treatment is unstable and easy to deform and recover, the mechanical support of the wood is mainly improved, the defect that the wood is easy to deform is overcome, and the additional value of the wood can be further improved by combining the chemical modification technology for research.

The wood is a green renewable material with micron-to-nano-scale multi-scale channels, has sound insulation, temperature and humidity regulation and decoration performances, can be used as a matrix template of other materials in a natural framework form, is rich in a large number of active sites (carbon free radicals C) and groups (free hydroxyl-OH, carboxyl-COOH and the like) on the surface of a porous channel, and can perform a series of physical and chemical reactions. Among them, the function of imparting conductivity to wood is attracting attention to broaden its application fields.

The preparation of the conductive wood at home and abroad mainly combines wood as a mechanical template with a conductive material and mainly adopts a surface coating method, a wood filling method, a carbonization crystallization method and a nano material compounding method. Most of wood-based conductive composite materials are made of metal and wood, the environment pollution is serious, part of the wood-based conductive composite materials only depend on surface conduction, the production process is complex, the cost is high, and meanwhile, the environment pollution is serious by using a chemical reduction mode, so that the search for a green and renewable wood-based conductive material with good conductivity is urgent. For example, patent 201710716619.6 discloses that a 3-layer eucalyptus plywood prepared by using bismuth oxide coated nano-magnesium oxide and glass fiber as fillers and modified bean gum and carbon powder modified silica sol as adhesives has good bonding strength and water resistance after hot pressing treatment, and also has a certain electromagnetic shielding function. The patent 201510434482.6 discloses that nickel salt is chemically plated on the surface of wood to obtain a corrosion-resistant high-conductivity wood electromagnetic shielding material, which can be used in the fields of electronics, aviation, medicine and the like. But the environmental problems caused by the chemically obtained conductive material are serious.

Graphene is a carbon atom in sp²The hybridized and connected monoatomic layer structure has excellent crystallography and physical and chemical properties and super-high performanceStrong thermal, electrical and strength. It has a resistivity lower than that of silver or copper, only about 10^-6Omega cm, the material with the lowest resistivity in the world. The carbon atoms in graphene are arranged very closely and neatly, and the crystal structure of the graphene is a two-dimensional hexagon which is a basic composition unit of all carbon materials. Since graphene has special mechanical properties, it is used as an additive for novel composite materials, thereby improving mechanical strength.

Therefore, if the graphene is compounded with the wood, excellent conductive performance can be endowed to the wood. Meanwhile, the original natural performance of the wood can be further optimized by combining a hot-pressing densification technology, the method has important theoretical research and application values, the application range of the wood can be further expanded, and the environment-friendly densified wood-based graphene conductive composite material with a promising prospect can be prepared.

Disclosure of Invention

The invention aims to provide a preparation method of a densified wood-based graphene conductive composite material, which endows wood with conductive performance in the densification process, improves the mechanical property of the wood, and effectively solves the technical problems of moisture absorption, easy deformation, easy corrosion and the like of the wood.

In order to achieve the above object, the present invention comprises the steps of:

a preparation method of a densified wood-based graphene conductive composite material specifically comprises the following 3 steps:

(1) wood pretreatment:

(2) wood and graphene oxide are uniformly and highly organically combined:

soaking the graphene oxide dispersion liquid with the concentration of 1-5mg/mL in a pulse type vacuum condition, allowing the graphene oxide dispersion liquid to enter the wood treated in the step (1), and performing drying treatment at the temperature of 45-60 ℃ (in an experimental process, if the drying temperature in the step is higher than 60 ℃, chemical change occurs, graphene oxide distributed in a wood body forms a film and becomes black, and the later-stage hot-pressing reduction is influenced); the water content of the wood is up to 20% +/-5%; (after a plurality of tests, the moisture range is an important condition for ensuring that the graphene oxide dispersion liquid realizes stable impregnation and does not influence hot-pressing reduction in the later period and wood does not crack);

the drying treatment is carried out in the following mode in sequence:

drying at 45-60 ℃ for 8-12h in a vacuum drying oven, drying at 45-60 ℃ for 5-7h in an air-blast drying oven, drying at 45-60 ℃ for 1-3h under the vacuum condition of 0.02-0.06MPa of vacuum degree in the vacuum drying oven, and air-blast drying at 45-60 ℃ for 8-12h in the air-blast drying oven to obtain the wood-based graphene oxide composite material; (the segmented drying process of the step is determined by a plurality of tests, so that the cracking of the wood can be avoided, the moisture can be fully removed, the later hot-pressing reduction is facilitated, if the moisture is too high, the graphene in the wood can be extruded, and if the moisture is too low, the wood can crack)

(3) Graphene oxide distributed in the wood is reduced to the maximum extent to release conductive graphene:

and (3) placing the wood-based graphene oxide composite material prepared in the step (2) in a flat plate hot press for hot-pressing reduction treatment, wherein the temperature of the press is 180-200 ℃, the treatment time is 30-75min, and the compression ratio of a test piece is 30-60%, so that the densified wood-based graphene conductive composite material is obtained.

In the step (1), the temperature of deionized water is 70-100 ℃, preferably 80 ℃, the boiling time is 0.5-2 hours, preferably 0.5 hour, the freezing treatment time is 2-7 days, the freezing temperature is-15 ℃, ~ -25 ℃, preferably 2-3 days, and the processes are repeated for 3-5 times until the residual liquid after the final boiling treatment is clear and transparent;

Moreover, the (2) wood is uniformly and highly organically combined with the graphene oxide:

the drying treatment is carried out in the following mode in sequence:

drying at 50 ℃ for 10h in a vacuum drying oven, drying at 50 ℃ for 6h in a forced air drying oven, drying at 50 ℃ for 1h in the vacuum drying oven under the vacuum condition of 0.04MPa of vacuum degree, and forced air drying at 50 ℃ for 10h in the forced air drying oven to obtain the wood-based graphene oxide composite material;

and, the (3) graphene oxide distributed in the wood is reduced to the maximum extent to release the graphene with conductivity:

Further, the wood includes one of poplar, eucalyptus, fir, pinus sylvestris and larch.

Compared with the prior art, the technical scheme of the invention has the following advantages:

(1) the processing method of the invention endows the wood with the conductive capability and expands the application field of the wood. In order to ensure that the graphene precursor-graphene oxide lamellar structure smoothly enters the wood body, the method provided by the invention adopts a water circulation wood pretreatment mode to achieve the purpose of improving the porosity of the wood on the premise of reducing the strength loss of the wood as much as possible as shown in figure 1. In addition, through reasonable control of vacuum and high-pressure conditions, the graphene oxide is guaranteed to be uniformly dispersed in the wood body and reduced into graphene to the maximum extent, and therefore excellent conductivity is given to the wood. As can be seen from fig. 2, after the graphene oxide is processed by the method, the graphene oxide is uniformly distributed in the wood matrix, the hydrophilic group on the graphene oxide plane structure is organically combined with the active groups such as hydroxyl and carboxyl in the wood body, and then the oxygen-containing group on the graphene oxide lamella in the wood body is reduced by using a flat plate hot pressing method to release the conductivity, so that the composite material which not only has the conductivity, but also weakens the moisture absorption and easy deformation of the wood and improves the mechanical properties of the wood is obtained.

(2) According to the invention, wood is subjected to internal permeability treatment, the graphene oxide dispersion liquid is soaked in a pulse vacuum method and is chemically and physically combined with the wood, the graphene oxide is fully reduced in a wood body by utilizing hot-pressing reduction treatment, and the reductive graphene oxide fully spread in the wood endows the wood with uniform electric conductivity, the mechanical property and the crystallinity of the wood are obviously improved, free hydroxyl groups are fixed in a rivet mode, the moisture absorption and water absorption properties of the wood are obviously weakened, and the use performance of the wood is improved.

(3) The whole process of the invention adopts a physical treatment method, does not add any chemical additive, modifier and the like, is green and pollution-free, and has good application value and wide application prospect.

(4) The invention provides a preparation method of a densified wood-based graphene conductive composite material, which comprises three processes of improving the internal permeability of wood on the premise of not influencing the original mechanical property strength of the wood, uniformly and highly organically combining the wood and graphene oxide, and reducing and releasing the graphene oxide distributed in the wood to the maximum extent to obtain the excellent green conductive functional composite material which endows the wood with conductivity and improves the original dimensional stability, density and mechanical property of the wood. The volume resistivity of the poplar material is 5.973 multiplied by 10 before any treatment¹⁴Ω · cm, is an insulator. Adding graphene oxide and platingAfter the reduction is carried out by hot pressing, the reduction effect of the graphene oxide is the best, the lowest graphene oxide can reach 3.927 omega cm, and the graphene oxide has better conductivity.

Drawings

Fig. 1 is a macro topography during wood treatment process treated in the manner of example 3 (a is untreated wood, b is wood treated in step (1), c is wood-based graphene oxide composite, d is densified wood-based graphene conductive composite);

fig. 2 is a macro topography diagram of the densified wood-based graphene conductive composite material after being cut open;

fig. 3 is a diagram of a macroscopic conductive path of the densified wood-based graphene conductive composite material of example 3;

FIG. 4 is a graphene SEM scan;

FIG. 5 is an enlarged view of a radial section of the densified pure wood prepared in comparative example 3 and the corresponding position thereof;

fig. 6 is an enlarged structure view of a radial section and a corresponding position of the densified wood-based graphene conductive composite material prepared in example 3;

fig. 7 is a cross-sectional view of the densified pure wood prepared in comparative example 3 at the left, and a cross-sectional view of the densified wood-based graphene conductive composite prepared in example 3 at the right;

fig. 8 is a scanning electron micrograph of the densified pure wood prepared in comparative example 3 on the left and a scanning electron micrograph of the densified wood-based graphene conductive composite prepared in example 3 on the right;

fig. 9 is XPS full spectra of densified pure wood and densified wood-based graphene conductive composites prepared in comparative example 3 and example 3, respectively;

fig. 10 is a pore size diagram of densified pure wood and densified wood-based graphene conductive composite material prepared in comparative example 3 and example 3, respectively;

fig. 11 is an XRD crystallinity diagram of densified pure wood and densified wood-based graphene conductive composite material prepared in comparative example 3 and example 3, respectively;

fig. 12 is a comparison graph of infrared spectra of densified pure wood and densified wood-based graphene conductive composite materials prepared in comparative example 3 and example 3, respectively;

fig. 13 is a TG graph of densified pure wood and densified wood-based graphene conductive composite prepared in comparative example 3 and example 3, respectively;

fig. 14 is a DSC graph of densified pure wood and densified wood-based graphene conductive composite prepared in comparative example 3 and example 3, respectively;

fig. 15 is a curved line of static bending strength of densified pure wood and densified wood-based graphene conductive composite respectively prepared in comparative example 3 and example 3;

fig. 16 is a line graph of the elastic modulus of pure wood and the densified wood-based graphene conductive composite prepared in example 3;

fig. 17 is a line graph of linear hygroscopical expansion coefficients of pure wood and the densified wood-based graphene conductive composite prepared in example 3;

fig. 18 is a histogram of plot volume expansion ratio of pure wood and densified wood-based graphene conductive composite material prepared in example 3;

FIG. 19 is a plot of GO concentration single factor experimental sheet resistivity versus bulk resistivity;

FIG. 20 is a plot of compressibility single factor experimental sheet resistivity versus bulk resistivity;

FIG. 21 is a line graph of hot pressing temperature single factor experimental sheet resistivity and bulk resistivity;

FIG. 22 is a line graph of hot pressing time single factor experimental sheet resistivity versus bulk resistivity;

in the figure: in fig. 9 to 14, the wood-based graphene composite represents the densified wood-based graphene conductive composite prepared in example 3.

Detailed Description

In order that the objects and advantages of the invention will be more clearly understood, the invention is further described in detail below with reference to examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The volume resistivity: is the resistance per unit cubic volume of the material, in Ω · cm.

Apparent resistivity: the ratio of the potential gradient parallel to the direction of current flow through the surface of the material to the current per unit width of the surface is expressed in ohms omega.

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