JP-2026075981-A - Method for manufacturing porous silicon, porous silicon

Abstract

[Problem] To manufacture porous silicon with a high pore count. [Solution] The method includes the steps of contacting a raw material containing at least one silicon oxide selected from the group consisting of SiO and SiO2 with an alkaline earth metal gas under conditions of furnace pressure of 15 Pa or less, and contacting the raw material that has been contacted with the alkaline earth metal gas with an acid. [Selection Diagram] None

Inventors

• 内山 貴之
• 野瀬 雅文

Assignees

• トヨタ自動車株式会社

Dates

Publication Date

20260511

Application Date

20241023

Claims (6)

1. A process of contacting a raw material containing at least one silicon dioxide selected from the group consisting of SiO and SiO2 with an alkaline earth metal gas under conditions of furnace pressure of 15 Pa or less, A step of bringing the raw material that has been in contact with the aforementioned alkaline earth metal gas into contact with an acid, A method for producing porous silicon containing [the specified material].
2. The method for producing porous silicon according to claim 1, wherein in the step of contacting the raw material with the alkaline earth metal gas, the heating rate in the furnace is less than 21.6°C/min.
3. The method for producing porous silicon according to claim 1, wherein the alkaline earth metal gas is magnesium gas.
4. The method for producing porous silicon according to claim 1, wherein in the step of contacting the raw material with the alkaline earth metal gas, the temperature inside the furnace is raised to 550°C to 750°C.
5. Porous silicon exhibiting two peaks at different pore diameter positions in its log differential pore volume distribution measured by the Barrett-Joyner-Halenda method (BJH method), with the peak representing the larger pore diameter existing in the pore diameter range of 100 nm to 200 nm.
6. The porous silicon according to claim 5, manufactured by the method for manufacturing porous silicon described in any one of claims 1 to 4.

Description

This disclosure relates to a method for producing porous silicon and to porous silicon itself. The method for producing porous silicon disclosed in Non-Patent Document 1 comprises a reduction step and a washing step. The reduction step is a step in which an intermediate product containing Si and MgO is produced by reducing SiO2 contained in porous diatomaceous earth using Mg vapor generated by heating metallic Mg. The washing step is a step in which porous silicon is obtained by washing the intermediate product with acid to remove MgO. Patent Document 3 discloses a method for producing porous silicon described above, which aims to reduce the material without generating Mg₂Si and SiO₂ , and includes a reduction step to obtain an intermediate product containing Si and MgO by contacting a raw material containing SiO₂ with Mg vapor under reduced pressure and Mg vapor pressure below the equilibrium pressure of the reaction equation (Mg₂Si⇔2Mg(g)+Si), and a washing step to remove MgO from the intermediate product. Nature 2007, 446, 172-175 Japanese Patent Publication No. 2023-76283 This is a schematic diagram of the vacuum furnace used for the reduction process.This characteristic diagram shows the cumulative pore volume distribution measured for the porous silicon of the example and the porous silicon of the comparative example.This characteristic diagram shows the log differential pore volume distribution measured for the porous silicon of the example and the porous silicon of the comparative example. The following describes embodiments of this disclosure. These descriptions are illustrative and do not limit the scope of this disclosure. In this specification, numerical ranges indicated using "~" represent a range that includes the numbers listed before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise within this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described within this specification, the upper or lower limit of that range may be replaced with the values shown in the examples. In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that their intended purpose is achieved. In this specification, when embodiments are described with reference to the drawings, the configuration of the embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the components are not limited thereto. The method for producing porous silicon according to this disclosure includes the steps of contacting a raw material containing at least one silicon oxide selected from the group consisting of SiO and SiO2 with an alkaline earth metal gas under conditions of furnace pressure of 15 Pa or less, and contacting the raw material that has been contacted with the alkaline earth metal gas with an acid. According to the method for producing porous silicon according to this disclosure, the silicon oxide contained in the raw material can be sufficiently contacted with the alkaline earth metal gas, and as a result, porous silicon with a large amount of pores can be produced. In the following description, the step of contacting the raw material with an alkaline earth metal gas will be referred to as the reduction step, and the step of contacting the raw material with an acid will be referred to as the washing step. <Reduction Process> The reduction step is a process in which an intermediate product containing Si and MgO is obtained by a reduction reaction in which an alkaline earth metal gas is brought into contact with a raw material containing at least one type of silicon oxide selected from the group consisting of SiO and SiO2 (hereinafter referred to as the Si raw material) to reduce the silicon oxide. In the method for producing porous silicon of this disclosure, the reduction step is carried out in a furnace with an internal pressure of 15 Pa or less, but the lower the internal pressure, the better, and it is particularly preferable to set the internal pressure to 10 Pa or less, and more preferably to 8 Pa or less. By setting the internal pressure within this range, it is possible to prevent the alkaline earth metal gas from being discharged outside the furnace and to bring the alkaline earth metal gas into sufficient contact with the Si raw material. As a result, according to the method for producing porous silicon of this disclosure, it is possible to produce porous silicon with a large amount of pores. Here, the furnace is not particularly limited, but the vacuum furnace 13 shown in Figure 1 can be given as an example. The vacuum furnace 13 shown in Figure 1 includes, for example, a stainless steel reaction