CN1260131C - Synthesis of micron and nano zinc oxide fiber by alloy gas controllable evaporation method - Google Patents

Abstract

The present invention provides a method for synthesizing the micrometer fiber and the nanometer fiber of zinc oxide by an alloy gas controllable evaporation method. The method utilizes the mixed powder of copper and zinc, or brass ingots of commercial purity as a reactant, and zinc steam released from the fused reactant is directly oxidized in the air at high temperature. The synthesized micrometer fiber of the zinc oxide has the dimension of 0.1 to 0.6 micrometer and the single-needle length of 1 to 3 micrometer; the synthesized nanometer fiber of the zinc oxide has the dimension of 10 to 150 nanometer, and the length of 3 to 8 micrometer, and the dimension of most of the nanometer fiber is 50 to 100 nanometer.

Description

Synthesis of Micro and Nano ZnO Fibers by Controlled Evaporation of Alloy Gas

Technical field

The invention belongs to the synthesis method of zinc oxide micro and nano fibers.

Background technique

Zinc oxide fiber is widely used as reinforcement and toughening agent of composite materials, shock absorption, impact resistance and sound insulation materials, wear-resistant and anti-skid materials, coatings, antistatic materials, and wave-absorbing materials. It plays a huge role in national defense, electronics, chemical industry, transportation and other fields. At present, there are two main methods for synthesizing micron and nanometer zinc oxide fibers: mechanized pre-oxidation of zinc powder (oxidation roasting method) and direct oxidation roasting of metal zinc powder.

The former was developed by Matsushita Electric Corporation of Japan in the late 1980s. The principle process is: first mix the raw material zinc powder with deionized water in a certain proportion, activate it in a stamping or vortex cutting mill, and then place the activated material at a certain temperature After aging treatment in the water, a dense oxide film is formed on the surface of the zinc powder. When the oxide film on the surface of the zinc powder is too thin, needle-shaped zinc oxide whiskers cannot be obtained. This pre-oxidized zinc powder is used as a gasification oxidation after drying Raw materials, which are gasified and oxidized at high temperature in specific equipment for a certain period of time (heat treatment time is related to temperature) and post-treated to obtain zinc oxide whisker products. Among them, the mechanochemical pre-oxidation of zinc powder and the gasification and oxidation of pre-oxidized zinc powder Equipment is the key to the realization of the process. On this basis, Panasonic has successively realized the automatic control of the roasting gasification oxidation process, the continuous production of whiskers, the large size of whisker products and the direct recycling of non-whisker zinc oxide products The product yield is improved. The whiskers produced by the process are loose in appearance and low in density. The yield of needle-shaped zinc oxide whiskers is higher than 40% of the initial zinc powder quality, and can reach 80%-86% when it is better. The obtained zinc oxide fibers have different specifications and can be separated by grading. The disadvantage is that the mechanochemical pretreatment of zinc powder takes a long time and the process conditions are relatively complicated.

The latter was developed by Southwest Jiaotong University and Tsinghua University. The principle process is as follows: metal zinc powder is used as raw material, coke powder is used as solid reducing agent, and the two are mixed in proportion in an open resistance furnace, and then roasted and oxidized at high temperature to obtain zinc oxide whiskers. Since then "researchers have made many improvements to the shortcomings of its difficult atmosphere control and low yield, and realized the continuous production of zinc oxide whiskers. This process is simple and easy to implement, but there is a certain gap between the product quality and the products of Japan's Matsushita Electric Co. , and the yield is low, making it difficult to scale production.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of long-time pretreatment, complex process, low yield and difficulty in scale production in the production of zinc oxide fibers. The invention provides a simple, rapid and controllable method for synthesizing high-purity micron and nanometer zinc oxide fibers in large quantities. The method does not need complex mechanochemical pretreatment, and the process conditions are simple. The production process is fast, continuous and easy to form large-scale production.

In order to realize the purpose of the present invention, we propose the method for synthesizing zinc oxide micron and nanofibers by alloy gas controllable evaporation method,

Principle of the present invention: studies have shown that zinc oxide micron and nanofibers can be obtained by directly oxidizing metal zinc vapor at high temperature. Its morphology can be controlled by the oxygen bias in the reaction gas or metal zinc vapor. Usually, it is difficult to realize the oxygen bias in the reaction gas, which complicates the reaction process, prolongs the reaction time, and makes it difficult to achieve the continuity of the synthesis process. At present, there is no good solution for the control of the metal zinc vapor bias. However, here we propose a controllable vaporization method of the alloy gas to achieve the control of the metallic Zn vapor bias. The alloy gas controllable evaporation method is mainly to form a certain proportion of metal alloys through high melting point metals and low melting point metals. Raising the liquefaction temperature of the low-melting metal to the melting temperature of the alloy allows for a slow release of the resulting vapor bias. The alloy here is a broad concept, and this method is also applicable to the control of the vapor bias of non-metals. Specifically in the present invention, according to the copper-zinc binary alloy phase diagram (see Fig. 1), the melting point of the copper-zinc alloy increases with the increase of the copper component, and the release temperature of the zinc vapor in the alloy also improves, and due to the formation of alloy, which can release slowly at high temperature, and the vapor bias can be adjusted by the ratio of the alloy. At a suitable high temperature, the slowly and steadily released zinc vapor from the molten alloy gathers in the air to form zinc micron and nanometer multi-twin particles. The multi-twinned particles are oxidized in the air and absorb the zinc component in the atmosphere at the same time, each twinned particle grows outward to form an independent needle-like structure, and finally the entire multi-twinned particle develops into a multi-needle zinc oxide fiber structure (see Figure 2, which shows the process of multi-twins developing into multi-needle fiber structure). The size of ZnO fibers can be adjusted by the size of the formed multi-twin particles, which is controlled by the zinc vapor bias in the reaction atmosphere and ultimately determined by the ratio of copper to zinc in the starting reactants.

The scheme for realizing the object of the present invention is: a method for synthesizing zinc oxide micron and nanofibers by the controllable evaporation method of alloy gas, the steps of the method are:

(1) Using copper-zinc mixed powder or directly using commercially pure brass block as the reactant raw material, the copper content in the reactant raw material is 10wt%-95wt%;

(2) Put the reactants in an open high-temperature silicon-molybdenum rod programmed temperature-controlled reaction furnace at a reaction temperature of 1100°C-1450°C to oxidize and melt to release metal zinc vapor by itself, and the reaction time is 5-15min;

(3) The product zinc oxide synthesized by the reaction is directly collected in the downwind direction of the airflow and near the reactants. The dimension of the collected synthetic zinc oxide micron fibers is 0.1 μm-0.6 μm, and the length of a single needle is 1 μm-3 μm. The dimension of the zinc oxide nanowire fiber is 10-150 nm, and the length is 3-8 μm.

In the above reaction, the copper-zinc mixed powder or the brass as the reactant preferably has a copper content of 40wt%-70wt%.

In the above reaction, the preferred reaction temperature is 1200°C-1300°C.

In the above reaction, the remaining product of the reactant is brass with low content, which can be recycled and reused.

The beneficial effect of the invention is that the shape and dimension of the product are controllable, the production process is fast and simple, and it is easy to realize large-scale continuous production.

Description of drawings

Figure 1 is a binary phase diagram of a copper-zinc alloy.

Figure 2 is a transmission electron microscope picture of the growth process of zinc oxide multi-twins to multi-acicular fibers.

Fig. 3 is a fiber scanning electron microscope picture of zinc oxide synthesized with copper-zinc weight ratio of 50% mixed powder as a reactant.

Figure 4 is a scanning and transmission electron microscope image of zinc oxide nanofibers synthesized using commercial grade brass blocks as reactants.

Detailed ways

Example 1: In an open high-temperature silicon-molybdenum rod program temperature-controlled reaction furnace (GWDL-1KY, Luoyang Weida High Temperature Instrument Co., Ltd.), at 1250 ° C, copper-zinc mixed powder with a copper-zinc weight ratio of 50% was mixed in the air Put it in the reaction temperature zone, and the reaction ends in 10 minutes. A large amount of white flocculent product can be received in the downwind direction.

XRD diffraction analysis shows that the white floc product is zinc oxide with excellent crystallization degree, and no other phases of copper or copper oxide appear. The resulting zinc oxide was observed by a scanning electron microscope (SEM) to be uniform three-needle or four-needle fibers (see FIG. 3 ). The dimensions of a single needle are 100nm and the length is 1.5um.

Embodiment 2: In the open high-temperature silicon-molybdenum rod programmed temperature control reaction furnace, at 1250 ° C, a commercially pure brass block (copper content 50wt%-65wt%) is placed in the reaction temperature zone in the air, and reacted for 15 minutes Finish. A large amount of white flocculent product can be received in the downwind direction.

XRD diffraction analysis shows that the white floc product is zinc oxide with excellent crystallization degree, and no other phases of copper or copper oxide appear. The resulting zinc oxide was observed as a one-dimensional nano-dimensional linear product with a scanning electron microscope (SEM) (Fig. 4a) and a transmission electron microscope (TEM) (Fig. 4b). The dimensions of zinc oxide nanowires vary from 10-150nm, but most of them have dimensions of 50-100nm, the distribution of dimensions is relatively uniform, and the length is 3-8um.

The leftovers after the reaction of the above reactants are low-content brass alloys, which can be directly recycled.

Claims (2)

1, the method for a kind of alloy gas controlled evaporation method synthesizing zinc oxide micron and nanofiber is characterized in that synthesis step is:

(1) with copper zinc mixed powder or brass ingot as reactant feed, copper content is 40wt%-70wt% in its reactant feed.Place opening high temperature silicon molybdenum bar temperature programmed control Reaktionsofen under greater than 1200 ℃ of-1450 ℃ of temperature of reaction reactant, make its own oxidation fusion discharge the metallic zinc steam, the reaction times is 5-15min;

(2) near the following wind direction of air-flow and reactant, directly collect reaction synthetic product zinc oxide, the dimension of collected synthesizing zinc oxide micrometer fibers is 0.1 μ m-0.6 μ m, single needle length is 1 μ m-3 μ m, the dimension of collected synthesizing zinc oxide nano wire fiber is 10-150nm, and length is 3-8 μ m.

2, the method for claim 1 is characterized in that described temperature of reaction is greater than 1200 ℃-1300 ℃.

Images