CN1377832A - Process for synthesizing different crystal form one-dimensional single crystal mangnesium dioxide nano wire - Google Patents

Abstract

The present invention relates to the preparation of nano material. One-dimensional monocrystalline nano manganese dioxide wire of different crystal form is synthesized selectively via controlling the temperature, period and material control of the hydrothermal reaction of two-valent manganese salt and ammohnium persulfate as raw material and ammonium sulfate as additive at 100-220 deg.c inside one sealed reactor. The process may be widely used in basic theory research in lithium ion cell, molecular sieve and relevant fields.

Description

Method for synthesizing manganese dioxide one-dimensional single crystal nanowires with different crystal forms

Technical Field

The invention relates to a preparation method of a nano material, in particular to a synthesis method of one-dimensional single crystal nanowires with different crystal forms. The preparation of the one-dimensional single crystal nanowire belongs to the leading-edge subject of the international research on nano materials at present, and has good application prospect.

Background

The existing method for synthesizing manganese dioxide can not control crystal form and is only limited to generating block materials, the preparation of layered manganese dioxide by an ion exchange method is reported in the United kingdom, Nature, 1996, volume 381 and 500, the preparation of layered manganese dioxide by pyrolysis of sodium permanganate is reported in 1995, volume 120 and 70 of the United kingdom, the preparation of α type manganese dioxide by pyrolysis is reported in the Journal of solid Chemistry, 1999, volume 144 and 136 of the Journal, the preparation of gamma type manganese dioxide nanocrystals by pyrolysis is reported, 2001, volume 159 and 94 of the Journal of the solid Chemistry, the preparation of α type manganese dioxide by an ozone oxidation method is reported, and in related domestic researches, only single crystal form manganese dioxide can be prepared, the appearance of products is block or nanocrystalline, and selective control of the synthesis of manganese dioxide single-dimensional single-crystal nanowires is not reported in both China and abroad.

Disclosure of Invention

The invention aims to provide a method for selectively synthesizing manganese dioxide one-dimensional single crystal nanowires with different crystal forms, which realizes the selective control of the preparation of the manganese dioxide one-dimensional single crystal nanowires with different crystal forms on the same test device so as to fill the blank in the preparation of the manganese dioxide one-dimensional single crystal nano material.

A method for synthesizing manganese dioxide one-dimensional single crystal nanowires with different crystal forms is characterized in that divalent manganese salt is used as a reducing agent, ammonium persulfate or sodium hypochlorite is used as an oxidizing agent, ammonium sulfate is used as a raw material additive, and the reaction is carried out in a closed reactor, wherein the synthesis method comprises the following steps:

(1) adding a divalent manganese salt reducing agent and equimolar ammonium persulfate or sodium hypochlorite oxidizing agent into deionized water, and stirring to form a uniform solution;

(2) putting the solution into a closed reaction kettle, reacting for 6-12 hours at the temperature of 100-220 ℃, then cooling to room temperature, filtering and washing to prepare β type manganese dioxide one-dimensional single crystal nanowires;

(3) adding an ammonium sulfate additive in the step (1), and preparing α type manganese dioxide one-dimensional single crystal nanowires under the same reaction conditions as the step (2);

a method for synthesizing manganese dioxide one-dimensional single crystal nanowires with different crystal forms is characterized by comprising the following steps: the method takes manganous salt as a reducing agent and potassium permanganate as an oxidizing agent to react in a closed reactor, and comprises the following steps:

(1) adding divalent manganese salt and potassium permanganate into deionized water according to the molar ratio of 3: 2, stirring to form a uniform solution, reacting for 6-12 hours at the temperature of 100-220 ℃, cooling to room temperature, filtering and washing to prepare β type manganese dioxide one-dimensional single crystal nanowires;

(2) reacting divalent manganese salt and potassium permanganate according to the molar ratio of 1: 1.5-3 under the same reaction conditions (1) to obtain the α type manganese dioxide one-dimensional single crystal nanowire.

The reducing agent is manganese sulfate, manganese nitrate, manganese carbonate or manganese chloride.

The above reaction is expressed by the following chemical equation:

the α and β type manganese dioxide single crystal nanowires are prepared by adopting cheap divalent manganese salt reducing agents, oxidants such as ammonium persulfate and the like and ammonium sulfate as raw materials and adopting lower temperature conditions and the same experimental device.

Drawings

FIG. 1 is an X-ray diffraction pattern of β -type manganese dioxide powder obtained in example 1.

FIG. 2 is a TEM micrograph of β type manganese dioxide prepared in example 1.

FIG. 3 is an X-ray diffraction pattern of α -type manganese dioxide powder obtained in example 2.

FIG. 4 is a TEM image of α type manganese dioxide prepared in example 2

Detailed Description

The following are examples of α and β manganese dioxide one-dimensional single crystal nanowires prepared by the method of the present invention.

In the process, the concentration optimization conditions of reducing agents such as manganese sulfate and the like and ammonium persulfate (potassium permanganate and sodium hypochlorite) are controlled to be 0.1-0.3 mol/l, and the concentration of an ammonium sulfate additive is controlled to be 0.5-0.7 mol/l.

Example 1:

weighing 1.3g of analytically pure manganese sulfate and 1.8g of ammonium persulfate, placing the weighed materials in a 40ml stainless steel pressure-resistant reaction kettle, adding deionized water, stirring to form a uniform solution, sealing the reaction kettle, reacting at 140 ℃ for 12 hours, cooling to room temperature, opening the reaction kettle, performing suction filtration by using a distributed funnel, washing by using deionized water to obtain black powder, identifying a product as β type manganese dioxide through X-ray powder diffraction, detecting the product appearance by using a TEM (transmission electron microscope), controlling the reaction temperature to be 100-100 nanometers in diameter and 2.5-4.0 micrometers in length, verifying that the product is a single crystal through single nanowire electron diffraction, controlling the reaction temperature to be 100, 160 and 220 ℃ under the same conditions, and obtaining the β type one-dimensional single-crystal manganese dioxide nanowires by using manganese chloride or manganese carbonate, wherein the length-diameter ratio of the products is slightly different according to different preparation temperature.

Example 2:

weighing 1.3g of analytically pure manganese sulfate, 1.8g of ammonium persulfate and 3g of ammonium sulfate, placing the weighed materials in a 40ml stainless steel pressure-resistant reaction kettle, adding deionized water, stirring to form a uniform solution, sealing the reaction kettle, reacting at 120 ℃ for 12 hours, cooling to room temperature, opening the reaction kettle, pumping by a distributed funnel, washing by deionized water to obtain black powder, identifying a product as α type manganese dioxide by X-ray powder diffraction, detecting the product appearance by a TEM (transmission electron microscope), controlling the reaction temperature at 100, 160 and 220 ℃ under the same conditions, and obtaining α type one-dimensional single-crystal nanowires by using manganese chloride or manganese carbonate and the like as divalent manganese salt, wherein the length-diameter ratio of the product is slightly different according to different preparation conditions.

Example 3:

weighing 0.3g of analytically pure manganese sulfate and 0.5g of potassium permanganate, placing the weighed materials in a 40ml stainless steel pressure-resistant reaction kettle, adding deionized water, stirring to form a uniform solution, reacting in the sealed reaction kettle at 180 ℃ for 6h, then cooling to room temperature, opening the reaction kettle, pumping by a distributed funnel, washing by deionized water to obtain black powder, wherein the divalent manganese salt can adopt manganese chloride or manganese carbonate, the reaction can be carried out at 100 ℃, 160 ℃ and 220 ℃, and the obtained product is detected to be α type manganese dioxide nanorods.

Example 4:

weighing 0.6g of analytically pure manganese sulfate and 0.4g of potassium permanganate, placing the weighed materials into a 40ml stainless steel pressure-resistant reaction kettle, adding deionized water, stirring to form a uniform solution, reacting the solution in the sealed reaction kettle at 200 ℃ for 6 hours, then cooling to room temperature, opening the reaction kettle, pumping through a distributed funnel, washing with the deionized water to obtain black powder, wherein the divalent manganese salt can adopt manganese chloride or manganese carbonate, the reaction can be carried out at 100 ℃, 160 ℃ and 220 ℃, and the black powder is detected to be β type manganese dioxide nanorods.

Example 5:

weighing 0.6g of analytically pure manganese sulfate, measuring 5ml of 20% sodium hypochlorite solution, placing the solution in a 40ml stainless steel pressure-resistant reaction kettle, adding deionized water, sealing the reaction kettle, reacting at 200 ℃ for 6h, cooling to room temperature, opening the reaction kettle, filtering by a distributed funnel, washing by deionized water to obtain black powder, wherein the divalent manganese salt can adopt manganese chloride or manganese carbonate, the reaction can be carried out at 100 ℃, 160 ℃ and 220 ℃, and the detected manganese dioxide nano-rod is β type manganese dioxide.

Example 6:

weighing 0.6g of analytically pure manganese sulfate and 3g of ammonium sulfate, measuring 5ml of 20% sodium hypochlorite solution, placing the solution in a 40ml stainless steel pressure-resistant reaction kettle, adding deionized water, sealing the reaction kettle, reacting at 200 ℃ for 6h, cooling to room temperature, opening the reaction kettle, pumping through a distributed funnel, washing with deionized water to obtain black powder, wherein the divalent manganese salt can adopt manganese chloride or manganese carbonate, the reaction can be carried out at 100 ℃, 160 ℃ and 220 ℃, and the black powder is detected to be α type manganese dioxide nanorods.

Claims (3)

1. A method for synthesizing manganese dioxide one-dimensional single crystal nanowires with different crystal forms is characterized in that divalent manganese salt is used as a reducing agent, ammonium persulfate or sodium hypochlorite is used as an oxidizing agent, ammonium sulfate is used as a raw material additive, and the reaction is carried out in a closed reactor, wherein the steps are carried out in the following order:

(1) adding a divalent manganese salt reducing agent and equimolar ammonium persulfate or sodium hypochlorite oxidizing agent into deionized water, and stirring to form a uniform solution;

(2) putting the solution into a closed reaction kettle, reacting for 6-12 hours at the temperature of 100-220 ℃, then cooling to room temperature, filtering and washing to prepare β type manganese dioxide one-dimensional single crystal nanowires;

(3) adding an ammonium sulfate additive in the step (1), and preparing α type manganese dioxide one-dimensional single crystal nanowires under the same reaction conditions as the step (2);

2. a method for synthesizing manganese dioxide one-dimensional single crystal nanowires with different crystal forms is characterized by comprising the following steps: the method comprises the following steps of taking divalent manganese salt as a reducing agent and potassium permanganate as an oxidizing agent to react in a closed reactor:

(1) adding divalent manganese salt and potassium permanganate into deionized water according to the molar ratio of 3: 2, stirring to form a uniform solution, reacting for 6-12 hours at the temperature of 100-220 ℃, cooling to room temperature, filtering and washing to prepare β type manganese dioxide one-dimensional single crystal nanowires;

(2) reacting divalent manganese salt and potassium permanganate according to the molar ratio of 1: 1.5-3 under the same reaction conditions (1) to obtain the α type manganese dioxide one-dimensional single crystal nanowire.

3. The method for synthesizing the manganese dioxide one-dimensional single crystal nanowires with different crystal forms according to claim 1 or 2, which is characterized in that: the reducing agent is manganese sulfate, manganese nitrate, manganese carbonate or manganese chloride.

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