RU2795956C1 - Device for manufacturing silicon carbide powder - Google Patents

Abstract

FIELD: inorganic chemistry.

SUBSTANCE: invention relates to the production of compounds with carbon and can be used to obtain tantalum carbide powder. The device contains a graphite cathode in the form of a vertically located cup, to which a dielectric holder is attached, a screw is inserted into the threaded hole of which above the cathode connected to one end of the graphite anode in the form of a rod, and the free end of the anode is located coaxially with the cathode with the possibility of longitudinal movement in its cavity, while the anode and cathode are connected to a direct current source. At the same time, a second graphite cup is inserted into the specified graphite cup, which is covered with a graphite cover and is designed to place an equimolar powder mixture of carbon and tantalum on its bottom. The second cup is concentrically fixed inside the first cup by evenly placed graphite spacers between the inner surface of the first cup and the outer surface of the second cup. Moreover, the inner diameter of the first cup is 1.25 times greater than the outer diameter of the second cup, and the height of the first cup is 1.5–2 times greater than the height of the second cup, and the free end of the anode is located coaxially to the second cup with the possibility of moving until it comes into contact with the outer surface of its cover.

EFFECT: obtaining powder of tantalum carbide with a cubic face-centered lattice.

1 cl, 2 dwg

Description

The invention relates to inorganic chemistry, namely to the production of compounds with carbon and can be used to obtain tantalum carbide powder.

A device for producing powder of tantalum carbide [A.Ya. Pak, PS Grinchuk, AA Gumovskaya, Yu.Z. Vassilyeva. Synthesis of transition metal carbides and high-entropy carbide TiZrNbHfTaC ₅ in self-shielding DC arc discharge plasma. https://doi.Org/10.1016/j.ceramint.2021.10.165], taken as a prototype, which contains cylindrical anode and cathode made of graphite, which are connected to a direct current source. The cathode is made in the form of a vertically located glass, to which a dielectric holder is attached. A screw connected to one end of the anode in the form of a rod is inserted into the threaded hole of the dielectric holder above the cathode. The free end of the anode is located coaxially to the cathode with the possibility of longitudinal movement in the cathode cavity until it comes into contact with a powder mixture of carbon and tantalum dioxide placed at the bottom of the cathode, containing 1 mass part of carbon and 1 mass part of tantalum dioxide.

The preparation of tantalum carbide powder using this device is carried out in air under normal atmospheric conditions. However, the resulting tantalum carbide powder is contaminated with graphite, which is caused by the ingress of carbon eroded from the anode into the synthesis product. The presence of electrical connections between the graphite cathode heated to high temperatures and the metal power wire, as well as the dielectric holder, require maintenance after each operating cycle of the device and limit its service life.

The technical result of the proposed invention is the production of tantalum carbide powder with a cubic face-centered lattice.

The device for producing tantalum carbide powder contains a graphite cathode in the form of a vertically located cup, to which a dielectric holder is attached, a screw is inserted into the threaded hole of which above the cathode, connected to one end of the graphite anode in the form of a rod, and the free end of the anode is located coaxially with the cathode with the possibility of longitudinal movement in its cavity, while the anode and cathode are connected to a direct current source.

According to the invention, the second graphite cup is inserted into the specified graphite cup of the cathode, which is covered with a graphite cover and is designed to place an equimolar powder mixture of carbon and tantalum on its bottom. The second cup is concentrically fixed inside the first cup by evenly spaced graphite spacers between the inner surface of the first cup and the outer surface of the second cup. The inner diameter of the first glass is 1.25 more than the outer diameter of the second glass. The height of the first glass is 1.5-2 times the height of the second glass. The free end of the anode is located coaxially to the second glass with the possibility of moving until it comes into contact with the outer surface of its cover.

The proposed device makes it possible to implement the synthesis of tantalum carbide powder in the plasma of a DC arc discharge initiated in an open air environment. The resulting tantalum carbide powder is not contaminated with graphite. In this case, there is no connection between the graphite cup, in which tantalum carbide is synthesized, and the dielectric anode holder, as well as the current-carrying line for connecting to the power source. When a direct current arc discharge occurs, the temperature of the internal graphite cup rises to 1500°C - 1700°C, as a result of which conditions arise for the synthesis of tantalum carbide. In the cavity of the first graphite cup, when the arc discharge burns, gaseous carbon monoxide CO is generated, which prevents oxidation of the surface of the second graphite cup and the resulting powder by atmospheric oxygen.

Compared with the prototype, the initial mixture of carbon and tantalum is in an equimolar ratio and completely fills the second graphite cup, it does not get carbon eroded from the anode, which settles on the lid of the second graphite cup. The dielectric holder and the metal power wire are connected to the first graphite cup, the temperature of which is significantly lower than the temperature of the second graphite cup, which ensures structural integrity and no need to revise these two connections after each operating cycle of the device.

In FIG. 1 shows a diagram of a device for producing tantalum carbide powder.

In FIG. 2 shows an X-ray diffraction pattern of the resulting tantalum carbide powder.

The device for producing tantalum carbide powder contains a graphite cathode, consisting of the first graphite vertically located cup 1, in which the second graphite cup 2 of smaller diameter is concentrically installed, designed to be filled with an equimolar mixture of carbon and tantalum 3. The second graphite cup 2 is covered with a graphite cover 4. Between The inner surface of the first cup 1 and the outer surface of the second cup 2 are equipped with three graphite spacers 5, evenly spaced along the circumference of the second graphite cup 2. A dielectric holder 7 is attached to the wall of the first graphite cup 1. A screw 8 is inserted into the threaded hole of the dielectric holder 7, connected to the end of the graphite anode 9 in the form of a rod, the other, the free end of which is located coaxially with the second graphite cup 2 with the possibility of longitudinal movement in the cavity of the first cup 1 until it comes into contact with the cover 4. The anode 9 and the first graphite cup 1 are connected to a direct current source 10 (IPT) power wires 11.

When you turn on the DC source 10 (IPT) between the graphite anode 9 and cover 4 of the second graphite glass 2 there is a potential difference. By rotating the screw 8, the anode 9 is moved inside the cavity of the first graphite cup 1 until it comes into contact with the cover 4 of the second graphite cup 2. The arc discharge 6 is ignited by short-term contact of the anode 9 with the cover 4 of the second graphite cup 2. After the start of current flow, the anode 9 is taken vertically upwards with a screw 8, forming a space for burning an arc discharge. After burning the arc discharge for a predetermined amount of time, the direct current source 10 (DCS) is turned off. After cooling the anode 9 and the second graphite cup 2, the anode 9 is moved upwards from the cavity of the first graphite cup 1, the cover 4 is removed and the tantalum carbide powder is removed from the cavity of the second graphite cup 2.

When using a powder mixture of carbon and tantalum, consisting of tantalum (with a cubic lattice) with a purity of 99.5% and carbon (graphite structure) with a purity of 99.5% at an atomic ratio of 1: 1, the outer dimensions of the buckets: a large graphite bucket with a height of 40 mm and diameter 30 mm; a small graphite cup 20 mm high and 20 mm in diameter, exposed to an arc discharge for 45 seconds at a current of 200 A, tantalum carbide powder TaC with a cubic face-centered lattice was obtained.

As a result of X-ray phase analysis of the resulting powder, five diffraction maxima were identified, corresponding to the cubic modification of tantalum carbide TaC, while the X-ray diffraction pattern did not reveal the maxima of other crystalline phases, and in particular, the maxima of graphite, tantalum, tantalum oxide were not detected (Fig. 2).

Claims (1)

A device for producing tantalum carbide powder, containing a graphite cathode in the form of a vertically located cup, to which a dielectric holder is attached, a screw is inserted into the threaded hole of which above the cathode, connected to one end of the graphite anode in the form of a rod, and the free end of the anode is located coaxially with the cathode with the possibility longitudinal movement in its cavity, while the anode and cathode are connected to a direct current source, characterized in that a second graphite cup is inserted into the specified graphite cup, which is covered with a graphite cover and is designed to place an equimolar powder mixture of carbon and tantalum on its bottom, the second cup concentrically fixed inside the first cup by evenly spaced graphite spacers between the inner surface of the first cup and the outer surface of the second cup, the inner diameter of the first cup being 1.25 times greater than the outer diameter of the second cup, and the height of the first cup being 1.5-2 times greater than the height of the second glass, while the free end of the anode is located coaxially to the second glass with the ability to move until it comes into contact with the outer surface of its cover.

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