CN111118667A

CN111118667A - Method for preparing SiC fibers by using highly oxidized silicon waste

Info

Publication number: CN111118667A
Application number: CN202010054799.8A
Authority: CN
Inventors: 李翔; 张广清; 唐凯; 吉恒松; 李振强; 张梅; 夏燏杰; 彭海涛
Original assignee: Taizhou Haichuang New Energy Research Institute Co ltd
Current assignee: Taizhou Haichuang New Energy Research Institute Co ltd
Priority date: 2020-01-17
Filing date: 2020-01-17
Publication date: 2020-05-08

Abstract

The invention relates to a method for preparing SiC fibers by utilizing highly oxidized silicon waste, in particular to a method for preparing SiC fibers by utilizing highly oxidized diamond wire cutting silicon chip waste in the photovoltaic industry, the used raw materials have wide sources and low price, and do not contain toxic and harmful substances, organic matters in the silicon chip waste are removed by alcohol washing and water washing, and the obtained waste mainly comprises Si and SiO₂Can react at high temperature to generate gaseous SiO and CH introduced₄Reaction to form SiC fibers, followed by H at high temperature₂And (3) roasting in the atmosphere to remove the surplus free carbon in the fiber, and cooling to collect the high-quality SiC fiber with low carbon content.

Description

Method for preparing SiC fibers by using highly oxidized silicon waste

Technical Field

The invention relates to the technical field of SiC fiber materials, in particular to a method for preparing low-carbon-content SiC fibers by utilizing highly-oxidized diamond wire cutting silicon waste.

Background

At present, when a crystalline silicon solar cell is prepared, a polycrystalline silicon ingot or a monocrystalline silicon rod must be cut into silicon wafers by adopting a diamond wire multi-wire cutting technology. Because the diameter of the diamond wire is very close to the thickness of the silicon wafer, at least more than 40% of the crystal silicon is cut and ground into silicon powder. The fresh waste material has a major component of Si, with small amounts of C and metallic impurities. These waste materials are essentially in an idle or low value use state. Therefore, the waste materials are often left in the open air for a long time and are easily autoxidized in a hot and humid air environment, and the oxidation degree can exceed 50%. This further increases the difficulty of recycling the waste. Therefore, how to effectively utilize the highly oxidized diamond wire-cut silicon waste becomes a problem to be solved urgently by the photovoltaic industry.

The invention provides a method for preparing low-carbon-content SiC fibers by using highly-oxidized diamond wire cutting silicon waste. The SiC fiber and the composite material product thereof have the characteristics of excellent high temperature resistance, oxidation resistance, wave absorption stealth and the like, well meet the requirements and development of high-tech industries, are widely applied in the military and civil fields, and have high added value.

Disclosure of Invention

The invention discloses a method for preparing SiC fibers by using highly oxidized silicon waste, which is a method for preparing SiC fibers by using diamond wire cutting silicon wafer waste in the photovoltaic industry. Organic matters in the silicon chip waste are removed through alcohol washing and water washing. Then the mixture is put into a high-temperature reactor to generate gas-phase SiO and the introduced CH₄And reacting to generate the SiC fiber. Followed by H at elevated temperature₂And (4) roasting in the atmosphere to remove the residual free carbon in the fiber. And cooling to obtain the high-quality SiC fiber with low carbon content.

A method for preparing high-quality SiC fibers with low carbon content by utilizing highly oxidized silicon waste comprises the following specific steps:

(1) cleaning the silicon waste materials of diamond wire cutting: rinsing the silicon wafer cutting waste materials for several times by using ethanol and deionized water, and filtering and drying to obtain cleaner waste silicon powder;

(2) preparing SiC fibers: pouring a certain amount of the waste silicon powder obtained in the step (1) into an alumina crucible, and filling the alumina crucible into an alumina reactor. Introducing Ar-H into an alumina reactor at normal pressure₂-CH₄And (4) mixing the gases. The alumina reactor was slowly inserted into a preheated high temperature furnace, the temperature of the furnace was set at 1600 ℃ and the temperature was maintained for 60 min. The highly oxidized waste silicon powder in the crucible contains Si and SiO₂Can react at high temperature to generate gaseous SiO, and then reacts with CH in the reaction gas₄And reacting to generate SiC fibers. The chemical reaction formula involved in the process is as follows:

Si(s)+SiO2(s) ＝ 2SiO(g)

SiO(g)+2CH₄(g) = SiC(s)+CO(g)+4H₂(g)

CH₄(g) = C(s) + 2 H₂(g)

(3) removing the surplus free carbon in the fiber: the reaction gas is switched to pure H₂The temperature of the reaction furnace was set to 1600 ℃ and maintained for 20 min. The gas feed was then stopped and the alumina reactor was slowly lifted out of the high temperature furnace. And after the mixture is sufficiently cooled, taking out the alumina crucible from the alumina reactor to obtain the SiC fiber with low carbon content in the crucible. The chemical reaction formula involved in the process is as follows:

C(s) + 2 H₂(g) = CH₄(g)

further, the highly oxidized silicon scrap for diamond wire cutting in the step (1) comprises the following components in percentage by mass: 24 to 40% of SiO₂: 59-75%, C: 0 to 1.5 percent.

Further, Ar-H in the step (2)₂-CH₄Mixed gas, CH₄Content of (2 vol%), H₂The content of (3) was 68vol%, and the content of Ar was 30 vol%.

Further, the low-carbon content SiC fibers obtained in the step (3) have the diameter of 0.2-0.6 μm, the length of 10-100 μm and the free carbon content of less than 1.5%.

The invention has the beneficial effects that:

1. the method solves the problem caused by recycling of the diamond wire-electrode cutting silicon wafer waste in the prior art, and can be widely popularized in the fields of silicon powder waste recycling and the like.

2. The invention is through H₂And (3) roasting in the atmosphere, effectively removing the surplus free carbon in the fiber, obtaining the SiC fiber with excellent performance and low carbon content, and improving the densification degree and the high temperature resistance of the fiber.

Drawings

Table 1 shows the chemical composition of the highly oxidized diamond wire-cut silicon wafer scrap of example 1.

FIG. 1 is a schematic view of the structure of an alumina reactor according to the present invention.

Figure 2 is an XRD diffractogram of the SiC fiber described in example 1.

Fig. 3 is an SEM picture of the SiC fiber described in example 1.

Fig. 4 is a TEM picture of the SiC fiber described in example 1.

Detailed Description

The following detailed description of the embodiments of the present invention is provided in connection with the accompanying drawings, so that the related technical solutions in the embodiments of the present invention are more clear and complete, and the embodiments of the present invention are only a part of the embodiments of the present invention, but not all of the embodiments of the present invention, and the scope of the present invention is not limited to the contents.

Example 1

(1) Cleaning the silicon waste materials of diamond wire cutting: and taking 25g of highly oxidized diamond wire-electrode cutting silicon chip waste, rinsing the silicon chip waste for 10 minutes by using ethanol, and rinsing the silicon chip waste for 2 times by using deionized water after suction filtration. And (3) carrying out suction filtration and drying to obtain clean waste silicon powder, wherein the chemical components are shown in table 1, and the main components comprise Si: 40.31% and contains SiO₂: 58.42%, C: 1.03 percent;

(2) preparing SiC fibers: 10g of waste silicon powder obtained in the step (1) is weighed, poured into an alumina crucible and loaded into an alumina reactor as shown in figure 1. Introducing Ar-H into an alumina reactor at normal pressure₂-CH₄Mixed gas (Ar 30 vol%, H)₂68vol%, CH ₄2 vol%), the gas flow was set at 2L/min. Slowly inserting the alumina reactor into the pre-feedingIn the hot high-temperature furnace, the temperature of the reaction furnace is set to 1600 ℃, and the temperature is kept for 60 min.

(3) Removing the surplus free carbon in the fiber: after the heat preservation in the step (2) is finished, the reaction gas is switched to pure H₂The temperature of the high temperature furnace is maintained at 1600 ℃ for 20 min. The gas feed was then stopped and the alumina reactor was slowly lifted out of the high temperature furnace. After sufficient cooling, the alumina crucible was taken out from the alumina reactor to obtain SiC fibers in the crucible.

(4) And (3) detection and test, wherein the crystal form of the SiC fiber obtained in the step (3) is β -SiC, as shown in figure 2, the length of the SiC fiber is 20-100 mu m, the diameter of the SiC fiber is 0.2-0.6 mu m, as shown in figures 3 and 4, and the content of free carbon in the SiC fiber is averagely 1.41% when an infrared carbon-sulfur analyzer (the temperature is set to 940 ℃).

Example 2

The procedure is the same as example 1, except that the used silicon wafer scrap for high-grade diamond oxide wire-electrode cutting contains 24.08% Si and SiO in the main components by mass percentage after being cleaned₂75.02% and contains C0.87%. The SiC fiber prepared by using the raw material has the length of 15-90 mu m, the diameter of 0.3-0.5 mu m and the average content of free carbon of 1.32 percent.

Example 3

The procedure is the same as example 1, except that the used silicon wafer scrap for high-grade diamond oxide wire-electrode cutting contains 30.36% Si and SiO in the main components by mass percentage₂68.37% and contains C0.98%. The SiC fiber prepared by using the raw material has the length of 10-100 mu m, the diameter of 0.3-0.6 mu m and the average content of free carbon of 1.29 percent.

The present invention is not limited to the above-described embodiments, and any obvious improvements, substitutions or modifications can be made by those skilled in the art without departing from the spirit of the present invention.

TABLE 1 chemical composition of Diamond wire-cut silicon wafer scrap

Element(s)	Si	SiO₂	C	Ca	Ni	K	Na	Mg	Al	Fe
											Content (wt%)	40.31	58.42	1.03	0.0612	0.0724	0.0035	0.0118	0.0606	0.0181	0.0152

Claims

1. A method for preparing SiC fiber from highly oxidized silicon waste comprises removing organic substances from silicon wafer waste by alcohol washing and water washing to obtain waste with main components of Si and SiO₂Can react at high temperature to generate gaseous SiO and CH introduced₄Reaction to form SiC fibers, followed by H at high temperature₂The method is characterized by comprising the following steps of roasting in the atmosphere to remove the surplus free carbon in the fiber, cooling and collecting the high-quality SiC fiber with low carbon content:

(2) preparing SiC fibers: pouring a certain amount of SiO precursor obtained in the step (1) into an alumina crucible, putting the alumina crucible into an alumina reactor, and introducing Ar-H into the alumina reactor at normal pressure₂-CH₄Mixing the gas, slowly inserting the alumina reactor into a preheated high temperature furnace, setting the temperature of the reaction furnace at 1600 ℃, preserving the temperature for 60min, reacting the silicon powder and the quartz powder in the crucible to generate gaseous SiO, and then reacting with CH in the reaction gas₄Reacting to generate SiC fibers;

(3) removing the surplus free carbon in the fiber: the reaction gas is switched to pure H₂And setting the temperature of the reaction furnace to 1600 ℃ and keeping the temperature for 20min, then stopping introducing gas, slowly lifting the alumina reactor out of the high-temperature furnace, fully cooling, and taking out the alumina crucible from the alumina reactor to obtain the SiC fibers with low carbon content in the crucible.

2. The method of claim 1, wherein: the highly oxidized silicon waste for diamond wire cutting in the step (1) comprises the following components in percentage by mass: 24 to 40% of SiO₂: 59-75%, C: 0 to 1.5 percent.

3. The method of claim 1, wherein: Ar-H in the step (2)₂-CH₄Mixed gas, CH₄Content of (2 vol%), H₂Has a content of 68vol% and Ar content was 30 vol%.

4. The method of claim 1, wherein: the low-carbon content SiC fibers obtained in the step (3) have the diameter of 0.2-0.6 mu m, the length of 10-100 mu m and the free carbon content of less than 1.5%.