NOVEL SiOx / CARBON NANOFIBER AND METHOD FOR PRODUCING THE SAME

Abstract

To provide a method for producing SiOx and carbon composite structure nanofibers observed as a material replaced with the conventional SiC fiber material.SOLUTION: A method for producing SiOx / carbon nanofibers sequentially implementes reactions of: cleaning a Si substrate 1 to insert the Si substrate into a thermal CVD device and forming a phosphorus thin film layer 2 on the Si substrate while atomizing a phosphorus / ethanol mixed liquid in a temperature range of 900-1000°C by a nebulizer device (I); causing a fusion reaction with Si to form a phosphorus-Si mixed liquid layer 3 (II); and rapidly forming the surface of the Si-phosphorus fusion liquid layer in a supersaturation state and depositing and growing SiOx / carbon nano fibers through the oxidation reaction of Si+O2→SiOx and depositing even an amorphous carbon layer 4 simultaneously deposited from ethanol on the outside of a SiOx core 5 (III).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a novel SiO x / This relates to carbon nanofibers and their manufacturing method. [Background technology]

[0002] The global ceramic matrix composites (CMC-SiC fiber) and carbon matrix composites (CAMC) market refers to advanced materials made of ceramic or carbon fibers embedded in a ceramic or carbon matrix. These materials are known for their high strength, stiffness, and heat resistance and are used in a variety of applications across aerospace, defense, energy, automotive, and industrial.

[0003] Although conventional SiC fibers have many advantages as high-performance materials, they also have some disadvantages. For example, 1. High price: Compared to alloy materials, the manufacturing cost is high and the manufacturing process is complicated, which limits the wide range of applications to some extent. 2. Brittleness problem: It is easily broken in high temperature and pressure environments. 3. High thermal expansion rate: It has a significantly different thermal expansion rate compared to other materials. 4: Although it has high strength, it lacks toughness and is prone to cracks at some stress concentration points.

[0004] This is because in existing SiC fiber structures, the Si and C elements are normally strongly bonded and do not react with most chemicals, resulting in high strength but lacking toughness. However, they react with oxygen under high temperature and pressure to produce oxides, which destroy the structure and performance of the fiber material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2012-511492 Summary of the Invention [Problem to be solved by the invention]

[0006] In contrast, SiO x Nanofibers made of carbon and a composite structure are an ideal material, with high strength, high heat resistance, high impact resistance, insulation properties, high acid resistance and chemical stability.

[0007] This is SiO x In the composite structure of SiOx and carbon nanofibers, the intervention of O atoms allows the formation of Si-O and CO bonds with Si and C elements, reducing the formation of oxides and improving the oxidation resistance of the nanofiber material; and the intervention of O atoms allows the Si and C elements to form stronger Si-O and CO bonds, strengthening the bond strength and improving the heat resistance of SiOx / carbon nanofibers.

[0008] Therefore, the present invention proposes a new material, SiO x The objective of this project is to focus on nanofibers with a composite structure of carbon and to develop a manufacturing method for them. [Means for solving the problem]

[0009] In the manufacturing method according to the present invention, a Si substrate is inserted into a thermal CVD apparatus, and a phosphorus / alcohol mixed liquid is atomized by a nebulizer device at a temperature range of 950 to 1050°C, preferably 900 to 1000°C, to cause a reaction on the Si substrate for a certain period of time.

[0010] The phosphorus used in the present invention may be any phosphorus allotrope such as red phosphorus, white phosphorus, or yellow phosphorus, with red phosphorus being preferred.

[0011] The alcohol used is a lower alcohol such as methanol or ethanol, which allows the phosphorus-alcohol mixture to be nebulized using a nebulizer device, and is preferably ethanol.

[0012] The reaction time is about 1 hour.

[0013] This reaction first forms a thin film layer of phosphorus on the Si substrate, then a fusion reaction with Si occurs, forming a phosphorus-Si mixed liquid layer, and finally the surface of the Si-phosphorus fused liquid layer rapidly becomes supersaturated, resulting in the reaction Si+O2→SiO x Through the oxidation reaction of SiO x The carbon nanofibers precipitate and continue to grow, and at the same time, the amorphous carbon layer precipitated from the alcohol also turns into SiO x Core-shell SiO deposited on the outside of the core x / Carbon nanofibers are obtained.

[0014] This core-shell SiO x / Carbon nanofibers contain SiO x As a nanofiber material with a very large specific surface area, consisting of a core and an amorphous carbon layer in the shell, it is expected to have high performance such as high heat resistance, high toughness, high strength, and high elastic modulus in harsh environments. x The combination of hard and soft qualities of SiO and C provides the perfect combination of toughness and rigidity. x / The overall mechanical performance of carbon nanofibers can be improved.

[0015] The applications of nanofibers that take advantage of their excellent properties are expanding to various fields, including as additives or replacements for innovative materials such as aircraft gas turbine engines, antifriction materials (automobile brakes), heat exchangers (high-temperature parts), and Kevlar® fibers, as shown below.

[0016] 1. Aircraft gas turbine engines SiC fiber and nickel alloy have been used in aircraft gas turbine engines, but SiOx / carbon nanofiber is a high-performance, lightweight material that can replace SiC fiber and nickel alloy.

[0017] 2. Anti-friction materials (automobile brakes) S iOx / carbon nanofibers have high temperature stability: They have a high melting point and are much more thermally stable than conventional alloy materials.

[0018] 3. Heat exchanger (high temperature part) The application of SiOx / carbon nanofiber in the high temperature part of the heat exchanger is mainly to manufacture the radiator core material of the high temperature plate heat exchanger, which has excellent performance in high temperature and high corrosive environment, and can greatly improve the service life and heat exchange efficiency of the heat exchanger.

[0019] 4. Use as an alternative to Kevlar® fiber Kevlar (registered trademark) fiber, a type of aramid fiber, is used in materials such as bulletproof vests, and SiOx / carbon nanofiber is used as a type of high-performance bulletproof material and can be used to manufacture bulletproof vests. High hardness: The hardness is much higher than conventional bulletproof materials such as resin and glass, effectively preventing the penetration of bullets and shell fragments. Lightweight: Compared to conventional bulletproof materials, it has a smaller specific gravity, so it does not put excessive strain on the body and is lightweight and comfortable to wear. Impact resistance: In addition to hardness and lightness, it also has high impact resistance, which can effectively absorb impact energy and reduce damage to the human body. Effect of the Invention

[0020] In summary, according to the present invention, SiO 2 can be expected to be used as a material for aircraft gas turbine engines, antifriction materials (automobile brakes), heat exchangers (high-temperature parts), bulletproof vests, etc. x / We can provide carbon nanofibers. [Brief description of the drawings]

[0021] [Figure 1] Schematic diagram of a thermal CVD apparatus equipped with a nebulizer [Diagram 2] Schematic of the growth mechanism of core-shell SiOx / carbon nanofibers [Diagram 3] SEM images of the synthesized core-shell SiOx / carbon nanofibers [Figure 4] Elemental analysis mapping of the synthesized core-shell SiOx / carbon nanofibers [Diagram 5]Raman spectrum of the synthesized core-shell SiOx / carbon nanofibers [Figure 6] X-ray photoelectron spectroscopy (XPS) diagram of the synthesized core-shell SiOx / carbon nanofibers [Figure 7] Cross-section of the synthesized core-shell SiOx / carbon nanofiber [Figure 8] Process diagram of the synthesized core-shell SiOx / carbon nanofibers DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The Si substrate is washed and inserted into a thermal CVD apparatus. A phosphorus / ethanol mixed liquid is atomized by a nebulizer at a temperature range of 900-1000°C for about 1 hour to react with the mixture. Core-shell SiO x / SiO2 characterized by precipitating and growing carbon nanofibers x / Method of manufacturing carbon nanofibers EXAMPLES

[0023] FIG. 1 is a schematic diagram of an apparatus used in the method of the present invention. The method of the present invention will be described with reference to the apparatus of FIG. 1, but the apparatus used in the method of the present invention is not limited to this. The thermal CVD apparatus has three main parts: an electric furnace (6), a nebulizer device (9), and a nitrogen gas canister (8). In FIG. 1, the electric furnace (6), the nebulizer device (9), and the nitrogen gas canister (8) are arranged in that order from left to right.

[0024] (1) Red phosphorus / ethanol mixture and SiO x / A method for synthesizing carbon nanofibers, in which a Si substrate is first washed in order with acetone, a methanol solution, and ultrapure water using an ultrasonic cleaning device, and then the remaining ultrapure water on the Si substrate (1) is removed using a nitrogen gun. (2) The red phosphorus described in (1) is (Phosphorus Powder, Kojundo Chemical Laboratory, 99.5%). (3) The cleaned Si substrate (1) is placed in the electric furnace (6) of the thermal CVD equipment, the nitrogen valve (7) is opened, and the nitrogen flow rate is set to 0.1 L / min for about 10 minutes. Turn on the electric furnace (6) of the thermal CVD equipment and let it flow for about 1000 minutes. o Heat to C, wait another 10 minutes, and then turn on the nebulizer device (9). The nebulizer device (9) (1.65 MHz, Atom Medical Corp., Model 303) described in (4)(3) is a key device in the thermal CVD apparatus of the present invention, and can atomize the phosphorus / ethanol mixed liquid (3) and deliver it via nitrogen gas to the surface of the Si substrate (1) in the thermal CVD apparatus for synthesis. (5) The proportions of the red phosphorus / ethanol mixed liquid (3) described in (1) are 10 wt% and 100 ml, respectively. (6) The reaction time was about 1 hour, and when the experiment was completed, the power to the electric furnace (6) of the thermal CVD apparatus was turned off, and the temperature of the electric furnace (6) was allowed to drop to room temperature before removing the Si substrate (1).

[0025] Figure 2 shows the core-shell SiO x / Schematic diagram of the carbon nanofiber growth mechanism. First, a phosphorus coating is applied onto a Si substrate (1) using a nebulizer device (9), and the nitrogen valve (7) of a nitrogen gas canister (8) is turned on, allowing nitrogen gas to flow from the supply gas inlet (10) to the exhaust outlet (11). As shown in Figure 2 (I), a thin phosphorus layer (2) is formed. As shown in Figure 2 (II), a fusion reaction occurs between Si and phosphorus, forming a phosphorus-Si mixed liquid layer (3). Finally, as shown in Figure 2 (III), the surface of the Si-phosphorus fusion liquid layer (3) quickly becomes supersaturated, and Si+O2→SiO x Through the oxidation reaction of SiO x Carbon nanofibers precipitate and continue to grow. At the same time, the amorphous carbon layer (4) precipitated from the ethanol also turns into SiO x It was deposited on the outside of the core (5).

[0026] Figure 3 shows a typical SEM image of nanofibers synthesized at a synthesis temperature of approximately 1000°C, where high-density nanofibers with diameters of 200 to 300 nm are observed.

[0027] Figure 4 shows a typical TEM image and the corresponding energy dispersive X-ray spectroscopy (EDS) mapping and spectrum spectroscopy. The TEM image in Figure 4(a) shows that the diameter of the fibers is about 300 nm. TEM observation also shows that these nanofibers have a neat core (spot (i)). Amorphous carbon structures were also observed outside the core (spot (ii)). Figure 4(b)-(d) show the elemental mapping and energy filter images of the nanofibers, and the fiber components are mainly composed of carbon, oxygen, and silicon atoms. Si and O atoms are mainly present in the core of the nanofibers, while C atoms are mainly present in the shell. EDS characterization reveals the percentages of C: 95.54%, O: 2.11%, and Si: 1.40%. The EDS spectrum of the nanofibers (Figure 3(f)) displays three clear peaks of C, O, and Si, but part of the C peak is represented by the C thin film supporting on the TEM grid.

[0028] Figure 5 shows the Raman spectrum obtained using a laser with an excitation wavelength of 532 nm. C shows two common features in the Raman spectrum, 1580–1620 cm -1 G peak near 1350cm -1 The D peak of the nanofibers is observed to be higher than the G peak. The D peak is caused by the amorphous structure, whereas the G peak is caused by the sp 2 This is caused by the elongation of carbon atoms. The Raman spectrum has a strong D peak, suggesting an amorphous carbon structure due to graphitic distortion, vacancies, and strain. This feature is common to basic amorphous carbon nanofibers.

[0029] Figure 6 shows the X-ray photoelectron spectroscopy (XPS spectrum) of the nanofibers. The XPS spectrum (Figure 6(a)) clearly shows the presence of C, O and Si in the nanofibers. In Figure 6(b), two C1s peaks are located at 284.4 and 285.6 eV, respectively, which correspond to sp 2 andsp 3 This corresponds to an atomic layer. The recombination peak of Si and C is at 282-283 eV, so this is not SiC. In Fig. 6(c), the XPS peaks at 102.25 and 103.65 eV are clearly observed, indicating a low Si oxide composition (Si 3+ As shown in Figure 6(c), the nanofibers are made of SiO x The x-dependent XPS peaks in the SiO / C composite are evident. x It has ingredients.

[0030] Figure 7 shows low density SiO x Cross-sectional SEM images of carbon nanofibers are shown. x / The SiOx core and carbon shell of the carbon nanofiber are visible.

[0031] Figure 8 shows the SiO x The following SEM images show the synthesis process of carbon nanofibers. x / It can be clearly seen that carbon nanofibers are grown from the Si substrate at high temperatures of approximately 1000°C. [Industrial Applicability]

[0032] In summary, according to the present invention, SiO 2 can be expected to be used as a material for aircraft gas turbine engines, antifriction materials (automobile brakes), heat exchangers (high-temperature parts), bulletproof vests, etc. x / Carbon nanofibers can be provided. [Explanation of symbols]

[0033] 1.…………Si substrate 2. Phosphorus thin film layer 3: Phosphorus-Si mixed liquid layer 4………………Amorphous carbon layer 5.…………SiO x Core 6………………Electric furnace 7………………Nitrogen valve 8………………Nitrogen gas canister 9. Nebulizer device 10... Gas supply port 11………………Exhaust port 1.…………Si substrate 2. Phosphorus thin film layer 3: Phosphorus-Si mixed liquid layer 4………………Amorphous carbon layer 5.…………SiO x Core 6………………Electric furnace 7………………Nitrogen valve 8………………Nitrogen gas

Claims

【Request 1】 The Si substrate is washed and inserted into a thermal CVD device. A phosphorus / alcohol mixture is atomized by a nebulizer device at a temperature range of 950-1050°C for a certain period of time to react with the substrate. x / SiO2 characterized by precipitating and growing carbon nanofibers x / Method of manufacturing carbon nanofibers. 【Request 2】 SiO x Core-shell SiO with an amorphous carbon layer around the core x / Carbon nanofiber. 【Request 3】 The core-shell SiO 2 according to claim 2 is used as a material for a heat exchanger in an aircraft gas turbine engine, an automobile brake, a high-temperature part, or a bulletproof vest. x / Carbon nanofiber.

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