阅读说明：本技术 一种具有湿度敏感特性的碳化木质素/海藻酸钠复合薄膜的制备方法 (Preparation method of lignin carbide/sodium alginate composite film with humidity sensitivity characteristic ) 是由 闵斗勇 运晓静 罗斌 陈昌洲 王双飞 于 2020-05-25 设计创作，主要内容包括：本发明公开了一种具有湿度敏感特性的碳化木质素/海藻酸钠复合薄膜的制备方法,包括如下制备步骤：(1)在惰性气体氛围中,将木质素进行碳化,经过研磨和过筛后制得粉末状的碳化木质素；(2)将海藻酸钠分散于水中,制备海藻酸钠溶液,并将碳化木质素粉末分散于海藻酸钠溶液,搅拌均匀制备碳化木质素/海藻酸钠混合液；(3)将碳化木质素/海藻酸钠混合液烘干制得碳化木质素/海藻酸钠复合薄膜；(4)将碳化木质素/海藻酸钠复合薄膜浸泡于氯化钙溶液中一段时间后,烘干制得具有湿度敏感特性的碳化木质素/海藻酸钠复合薄膜。该材料对湿度具有超高的响应性,且原料丰富,成本低,制作工艺简单,便于产业化和长期使用。(The invention discloses a preparation method of a lignin carbide/sodium alginate composite film with humidity sensitivity, which comprises the following preparation steps: (1) carbonizing lignin in an inert gas atmosphere, and grinding and sieving to obtain powdery carbonized lignin; (2) dispersing sodium alginate in water to prepare a sodium alginate solution, dispersing carbonized lignin powder in the sodium alginate solution, and uniformly stirring to prepare a carbonized lignin/sodium alginate mixed solution; (3) drying the lignin carbide/sodium alginate mixed solution to prepare a lignin carbide/sodium alginate composite film; (4) and soaking the lignin carbide/sodium alginate composite film in a calcium chloride solution for a period of time, and drying to obtain the lignin carbide/sodium alginate composite film with the humidity sensitivity. The material has ultrahigh responsiveness to humidity, and has the advantages of abundant raw materials, low cost, simple manufacturing process, and convenience for industrialization and long-term use.)

1. A preparation method of a carbonized lignin/sodium alginate composite film with humidity sensitivity is characterized by comprising the following steps:

s1, carbonizing lignin, wherein the carbonizing conditions are as follows: under the protection of inert gas, heating to 500-1000 ℃ at the heating rate of 2-20 ℃/min, preserving the heat for 0.5-3.0h, then cooling to room temperature, and taking out to prepare the massive lignin carbide;

s2, crushing the blocky carbonized lignin prepared in the step S1, and collecting the powdery carbonized lignin through a 100-mesh and 300-mesh screen;

s3, dissolving sodium alginate in water to prepare a sodium alginate solution with the mass fraction of 1-3%;

s4, dispersing the powdery carbonized lignin prepared in the step S2 in the sodium alginate solution prepared in the step S3, and uniformly stirring to prepare a carbonized lignin/sodium alginate mixed solution;

s5, drying the carbonized lignin/sodium alginate mixed solution prepared in the step S4 in vacuum at the temperature of 40-80 ℃ to prepare a carbonized lignin/sodium alginate composite film;

s6, placing the carbonized lignin/sodium alginate composite film in a calcium chloride solution with the mass fraction of 1-10% to soak for 1-24h, and drying in vacuum at the temperature of 40-80 ℃ to obtain the carbonized lignin/sodium alginate composite film with the humidity sensitivity characteristic.

2. The method for preparing the carbonized lignin/sodium alginate composite film with the humidity sensitivity characteristic as claimed in claim 1, wherein the carbonization temperature of the lignin in the step S1 is 900 ℃, the heating rate is 10 ℃/min and the holding time is 2h under the inert gas atmosphere.

3. The method for preparing the carbonized lignin/sodium alginate composite film with the humidity sensitivity characteristic as claimed in claim 1, wherein the step S6 is to place the carbonized lignin/sodium alginate composite film in a calcium chloride solution with a mass fraction of 5% for soaking for 2h, and vacuum drying is carried out at 60 ℃.

4. The preparation method of the carbonized lignin/sodium alginate composite film with the humidity sensitivity characteristic as claimed in claim 1, wherein the mass ratio of the carbonized lignin to the sodium alginate in the carbonized lignin/sodium alginate mixed solution is 1: 1-3: 1.

5. The preparation method of the carbonized lignin/sodium alginate composite film with the humidity sensitivity characteristic as claimed in claim 4, wherein the mass ratio of the carbonized lignin to the sodium alginate in the carbonized lignin/sodium alginate mixed solution is 3: 1.

6. The application of the carbonized lignin/sodium alginate composite film with humidity sensitivity prepared by the preparation method of any one of claims 1 to 5 in preparing a humidity sensitive element of a humidity sensor.

Technical Field

The invention belongs to the technical field of humidity sensing, and particularly relates to a preparation method of a lignin carbide/sodium alginate composite film with humidity sensitivity.

Background

The environmental humidity is closely related to human life, industrial and agricultural production. With the increasing requirements of people on the quality of life and the quality of industrial and agricultural products, how to measure and control the environmental humidity more accurately becomes one of the research hotspots of people. The humidity sensor is a chemical sensor which expresses the environmental humidity in an electric signal form, and the main working principle is that materials capable of adsorbing water molecules are utilized, different characteristics (resistance and capacitance) are generated by the difference of the content of the adsorbed water molecules under different humidity conditions, and the electric signal is output by connecting with an external circuit. The traditional humidity sensing materials are metals and semiconductors, and the daily life of people is gradually faded due to the characteristics of low sensitivity, toughness, narrow strain range and the like. At present, the novel humidity sensing materials include metal oxides and nano materials mainly comprising graphene, carbon nanotubes and the like. Chinese patent publication No. CN104569074A discloses a nano-composite humidity sensitive material, a resistance-type humidity sensor and a preparation method thereof, wherein the humidity sensitive material is polypyrrole and TiO₂And graphene. Chinese patent publication No. CN 102495106A discloses a humidity sensitive material for a flexible humidity sensor and a preparation method thereof, wherein the humidity sensitive material is a composite material consisting of multi-wall carbon nano tubes and organic silicon. The humidity sensitive materials in the above two patents have good flexibility and humidity sensing performance, but the preparation processes of graphene and carbon nanotubes are complex, expensive, and high in production cost, and are not conducive to industrial continuous production. Therefore, the research and development of a novel material with cheap raw materials, simple preparation process and good humidity response performance is of great significance.

Disclosure of Invention

The invention aims to provide a preparation method of a carbonized lignin/sodium alginate composite film with humidity sensitivity, which has ultrahigh response, low hysteresis and stability to humidity.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a preparation method of a carbonized lignin/sodium alginate composite film with humidity sensitivity comprises the following steps:

s1, carbonizing lignin, wherein the carbonizing conditions are as follows: under the protection of inert gas, heating to 500-1000 ℃ at the heating rate of 2-20 ℃/min, preserving the heat for 0.5-3.0h, then cooling to room temperature, and taking out to prepare the massive lignin carbide;

s2, crushing the blocky carbonized lignin prepared in the step S1, and collecting the powdery carbonized lignin through a 100-mesh and 300-mesh screen;

s3, dissolving sodium alginate in water to prepare a sodium alginate solution with the mass fraction of 1-3%;

s4, dispersing the powdery carbonized lignin prepared in the step S2 in the sodium alginate solution prepared in the step S3 and with the mass fraction of 1-3%, and uniformly stirring to prepare a carbonized lignin/sodium alginate mixed solution;

s5, drying the carbonized lignin/sodium alginate mixed solution prepared in the step S4 in vacuum at the temperature of 40-80 ℃ to prepare a carbonized lignin/sodium alginate composite film;

s6, placing the carbonized lignin/sodium alginate composite film in a calcium chloride solution with the mass fraction of 1-10% to soak for 1-24h, and drying in vacuum at the temperature of 40-80 ℃ to obtain the carbonized lignin/sodium alginate composite film with the humidity sensitivity characteristic.

Preferably, in the step S1, the carbonization temperature of the lignin is 900 ℃, the heating rate is 10 ℃/min, and the holding time is 2h under the inert gas atmosphere.

Preferably, in the step S6, the carbonized lignin/sodium alginate composite film is placed in a calcium chloride solution with a mass fraction of 5% to be soaked for 2 hours, and is dried in vacuum at 60 ℃.

Preferably, the mass ratio of the carbonized lignin to the sodium alginate in the carbonized lignin/sodium alginate mixed solution is 1: 1-3: 1.

More preferably, the mass ratio of the carbonized lignin to the sodium alginate in the carbonized lignin/sodium alginate mixed solution is 3: 1.

The lignin carbide/sodium alginate composite film with the humidity sensitivity characteristic can be used for preparing a humidity sensitive element of a humidity sensor, and the humidity sensor prepared by the composite film has the characteristics of ultrahigh sensitivity, low hysteresis, stability and flexibility.

Compared with the prior art, the invention has the following beneficial effects:

(1) the lignin carbide/sodium alginate composite film prepared by the method has ultrahigh humidity responsiveness, low hysteresis and stability.

(2) The raw materials adopted by the invention are rich in sources, the lignin sources can be lignin in papermaking black liquor, enzymatic hydrolysis lignin, sodium lignosulfonate, organic solvent extraction lignin and the like, and the lignin is cheap and easily available, biodegradable and meets the requirement of green production.

(3) The preparation method has the advantages of simple preparation process, convenient operation, low production cost and convenient industrialization.

Drawings

FIG. 1 shows the actual resistance change of the composite film of carbonized lignin and sodium alginate prepared in example 1 of the present invention under different humidity conditions.

FIG. 2 is a response-recovery curve of the carbonized lignin/sodium alginate composite film prepared in example 1 of the present invention.

FIG. 3 is a graph showing the stability of the carbonized lignin/sodium alginate composite film prepared in example 1 of the present invention at different humidities.

Detailed Description

The process of the present invention is further illustrated by the following examples. The embodiments described herein are presently preferred embodiments of the invention, are provided for the purpose of illustration and explanation only and are not intended to be limiting of the invention.