Observation of the wetting angle of aluminum and magnesium molten solutions using the sessile drop method in a sealed chamber with extremely low oxygen partial pressure

Abstract

The present invention relates to an extremely low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts. First, an extremely low oxygen partial pressure quartz sealed chamber that does not exchange gas with the vacuum chamber of the heating furnace is constructed in a low vacuum heating furnace, and then the aluminum and magnesium metals in the sealed chamber are heated to melt, so as to achieve the observation and measurement of the wetting angles of the aluminum and magnesium melts and ceramic test pieces in the sealed chamber. The sealed chamber constructed by the present invention at a relatively low heating temperature has extremely low oxygen partial pressure and nitrogen partial pressure, which can eliminate the constraints of the oxide film on the surface of aluminum and magnesium on the droplets, and achieve the observation and measurement of the wetting angle of the molten metal on the surface of the ceramic test piece at high temperature. This method greatly reduces the stringent requirements for the vacuum degree required for the observation equipment, and has the advantages of accurate and reliable observation results, convenient operation and low cost.

Description

Technical Field

[0001] The present invention relates to a technology in the field of composite materials, in particular to a method for observing the wetting angle of aluminum and magnesium melts by obtaining an extremely low oxygen partial pressure sealed chamber. Background Art

[0002] Composite materials composed of metal and ceramics, whether metal-based composite materials or ceramic-based composite materials, have a wide range of uses in modern industry, and their application areas are still expanding. Metal-based composite materials composed of light metals such as aluminum, magnesium, and titanium and ceramic reinforcements have the characteristics of light weight and high strength, and have special advantages in the field of lightweight transportation, including aerospace. Ceramic-based composite materials represented by cemented carbide are also indispensable in modern industry due to their high hardness and high modulus.

[0003] The wetting behavior of molten metal and solid ceramics is of great significance in the preparation, processing and connection of composite materials, and this wetting behavior is described and characterized by the sessile drop method, which measures the wetting angle formed after the metal melts on the ceramic surface. When observing the wettability of metal droplets by the sessile drop method, low-pressure vacuum is the most basic gas phase environment, and the oxygen partial pressure therein is very important. The oxide film they form on the solid metal and subsequent droplet surfaces strongly affects the wetting behavior of the droplets. For metals such as aluminum and magnesium, which are extremely easy to oxidize, the surface oxide films formed are extremely difficult to remove. These oxide films not only affect the accuracy of the droplet wetting angle observation results, but can even make it difficult for metal droplets to form.

[0004] The surface of aluminum is covered with a solid Al2O3 oxide film with a melting point of up to 2050°C. The chemical properties of this dense oxide film are extremely stable. Even at a high temperature of 1000°C, it takes only 10 -30 Pa oxygen partial pressure is possible to decompose, and this extremely low oxygen partial pressure vacuum is not achievable by existing technology.

[0005] Magnesium is also an extremely active metal. Its surface is also covered with an oxide film with extremely stable chemical properties and a melting point of up to 2852°C. The loose nature of this oxide film allows its thickness to continue to increase with increasing temperature and time in a vacuum with very low oxygen partial pressure. In addition, the high saturated vapor pressure of metallic magnesium and the volatilization produced under high temperature and vacuum conditions make it very difficult to observe its wetting angle.

[0006] In order to eliminate the constraints of Al2O3 and MgO surface films on aluminum and magnesium droplets, the prior art uses an improved sessile drop method, which allows the aluminum or magnesium melt to be pressed out from a small hole and drip onto the surface of the ceramic test piece to tear off the oxide film on the melt surface. This process and subsequent observations still require the environment to be maintained in a very low oxygen partial pressure gas phase environment. For aluminum, this gas phase environment is often vacuum, and for magnesium, an inert gas with a certain pressure is used to prevent magnesium from evaporating.

[0007] The above existing technologies use the dripping method to improve the sessile drop method. Although it can tear off the surface oxide film of active metals to obtain droplets, the kinetic energy of the molten metal dripping will affect the accuracy of the obtained wetting angle. Moreover, this technology still needs to be used in a very low oxygen partial pressure environment. For aluminum, only when the thermodynamic conditions that the aluminum melt and Al2O3 can react to generate gaseous Al2O at high temperature can the regeneration of the Al2O3 oxide film be prevented. This reaction requires a vacuum environment with an oxygen partial pressure as low as 10 -6 Pa. For magnesium, the inert gas filled to prevent metal volatilization and the formation and thickening of the surface MgO film also requires a very low oxygen partial pressure. Due to these stringent low oxygen partial pressure vacuum environment requirements, the improved sessile drop method of the prior art still has the disadvantage of being difficult to promote. Summary of the invention

[0008] In view of the shortcomings of the prior art in that it is difficult to remove the oxide film on the surface of aluminum and magnesium melts and prevent the droplets from being oxidized again, as well as the deviation of the wetting angle caused by the kinetic energy of the molten liquid dripping, the present invention proposes a sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts. This method constructs a transparent quartz sealed chamber with an extremely low oxygen partial pressure in a heating furnace with a relatively low vacuum degree, so that the metal in the sealed chamber melts on the surface of a ceramic test piece to form droplets, thereby realizing the observation and measurement of the wetting angle of the droplets.

[0009] The present invention is achieved through the following technical solutions:

[0010] A very low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts. First, an extremely low oxygen partial pressure quartz sealed chamber that does not exchange gas with the vacuum chamber of the heating furnace is constructed in a low vacuum heating furnace. Then, the aluminum and magnesium metals in the sealed chamber are heated to melt, so as to observe and measure the wetting angle of the aluminum and magnesium melts and ceramic test pieces in the sealed chamber.

[0011] Furthermore, the specific method of constructing an extremely low oxygen partial pressure quartz sealed chamber in a low vacuum heating furnace that does not produce gas exchange with the vacuum chamber of the heating furnace is: a quartz cup is inverted on a metal or ceramic base with a groove, an indium tin alloy is placed in the groove, the vacuum chamber of the heating furnace is evacuated, and an inert gas is filled into it, and the indium tin alloy in the groove is heated to melt to achieve sealing of the space inside the quartz cup, thereby obtaining a sealed chamber that does not produce gas exchange with the vacuum chamber of the heating furnace.

[0012] Furthermore, a ceramic test piece is pre-placed on the metal or ceramic base with the groove, and a test block of aluminum or magnesium, or their respective alloys, is placed on the ceramic test piece.

[0013] Furthermore, a small weight for generating pressure is provided on the outer top of the inverted quartz cup.

[0014] Furthermore, the vacuum degree in the vacuum chamber of the heating furnace is evacuated to 10 -1 Pa.

[0015] Furthermore, aluminum powder is placed in the quartz cup to further reduce the oxygen and nitrogen partial pressures in the sealed chamber, so as to consume the residual oxygen and nitrogen in the sealed chamber.

[0016] Furthermore, the metal or ceramic base is made of one of steel, quartz and alumina which can be wetted by indium tin alloy.

[0017] Furthermore, the indium content in the indium-tin alloy is 30-60%, and a melting temperature of 120-180° C. is obtained, and the sealing of the sealing chamber can be achieved within this temperature range.

[0018] Furthermore, the aluminum or magnesium test block includes pure aluminum or pure magnesium or various alloys based on them; the ceramic test piece adopts ceramics of aluminum oxide, aluminum nitride or silicon nitride.

[0019] Furthermore, the inert gas filled is a gas that does not chemically react with aluminum and magnesium, and the pressure range is 50-500Pa.

[0020] The beneficial effects of the present invention are:

[0021] Compared with the existing sessile drop method and the improved sessile drop method that can make the melt drip, which require very high vacuum equipment and have the disadvantage that the melt dripping will produce unstable data, the present invention can construct a transparent sealed chamber with a very low oxygen partial pressure vacuum environment in a commonly used low vacuum heating furnace, and the sealed chamber formed at a lower temperature below 180°C of the present invention has the effect of preventing the thickening of the surface oxide film of aluminum and magnesium test blocks before melting, and the advantage of preventing the oxidation of the droplets during the spreading process, and can realize the direct observation and measurement of the wetting angle between the droplet and the surface of the ceramic test piece and its changes with temperature and time. The method has the advantages of convenience, accuracy, high efficiency and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of a device for achieving sealing according to the present invention;

[0023] In the figure: 1-base, 2-indium tin alloy, 3-quartz cup, 4-small weight, 5-aluminum powder, 6-ceramic test piece, 7-metal test block. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] Embodiment 1:

[0026] like Figure 1 As shown, this embodiment is based on an extremely low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts, and observing the wettability of pure aluminum on the Al2O3 ceramic surface. A quartz cup 3 with a flat mouth is used, which is inverted on a base 1 with a groove, an indium tin alloy 2 is placed in the groove, a small weight 4 is pressed on the top of the quartz cup, aluminum powder 5 for absorbing oxygen and nitrogen is placed on the base inside the quartz cup, and a ceramic test piece 6 (Al2O3) for testing is also placed, and a metal test block 7 (pure aluminum) to be tested is placed on the ceramic test piece 6.

[0027] The assembly is placed in a low vacuum heating furnace with an observation hole, and the vacuum chamber of the heating furnace is evacuated to 10 - 1 Pa, heated until the indium tin alloy melts (~150°C), the quartz cup is immersed in the molten indium tin alloy liquid under the pressure of a small weight to seal the internal space of the quartz cup, and obtain a quartz sealed chamber that does not exchange gas with the vacuum chamber of the heating furnace. Continue to heat the sealed chamber to a certain temperature after the aluminum melts, and observe and measure the wetting angle of the aluminum droplet on the alumina test piece at this temperature and its change over time through the observation hole of the heating furnace and the transparent quartz cup.

[0028] Embodiment 2:

[0029] like Figure 1As shown, this embodiment is based on an extremely low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts, and observing the wettability of pure magnesium on the Al2O3 ceramic surface. A quartz cup 3 with a flat mouth is used, which is inverted on a base 1 with a groove, an indium tin alloy 2 is placed in the groove, a small weight 4 is pressed on the top of the quartz cup, aluminum powder 5 for absorbing oxygen and nitrogen is placed on the base inside the quartz cup, and a ceramic test piece 6 (Al2O3) for testing is also placed, and a metal test block 7 (pure magnesium) to be tested is placed on the ceramic test piece.

[0030] The assembly is placed in a low vacuum heating furnace with an observation hole, and the vacuum chamber of the heating furnace is evacuated to 10 - 1 Pa, filled with 100Pa of argon and heated until the indium tin alloy melts (~150℃), the quartz cup is immersed in the molten indium tin alloy liquid under the pressure of a small weight to achieve the sealing of the internal space of the quartz cup, and obtain a quartz sealed chamber that does not exchange gas with the vacuum chamber of the heating furnace. The oxygen partial pressure in the sealed chamber is extremely low and the partial pressure of argon is maintained at 100Pa, which can prevent the volatilization of magnesium. Continue to heat the sealed chamber to a certain temperature after the magnesium melts, and observe and measure the wetting angle of the magnesium droplet on the alumina test piece at this temperature and its change over time through the observation hole of the heating furnace and the transparent quartz cup.

[0031] In the above implementation:

[0032] Preferably, a small weight for generating pressure is provided on the outer top of the quartz cup.

[0033] Preferably, the metal or ceramic base is one of steel, quartz and alumina which can be wetted by indium tin alloy.

[0034] Preferably, the indium content in the indium-tin alloy is 30-60%, and a melting temperature of 120-180° C. is obtained, and the sealing of the sealing chamber can be achieved within this temperature range.

[0035] Preferably, the aluminum or magnesium test block comprises pure aluminum or pure magnesium or various alloys based thereon.

[0036] Preferably, the ceramic test piece is made of various ceramics such as alumina, aluminum nitride or silicon nitride.

[0037] Preferably, the inert gas filled is a gas that does not chemically react with aluminum and magnesium, and the pressure range is 50-500Pa.

[0038] The above specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and is not limited to the above specific embodiments. Each implementation scheme within its scope is subject to the constraints of the present invention.

Claims

1. An extremely low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts, characterized in that: First, a very low oxygen partial pressure quartz sealed chamber that does not exchange gas with the vacuum chamber of the heating furnace is constructed in a low vacuum heating furnace, and then the aluminum and magnesium metals in the sealed chamber are heated to melt, so as to observe and measure the wetting angle between the aluminum and magnesium melts in the sealed chamber and the ceramic test piece; the specific method of constructing the very low oxygen partial pressure quartz sealed chamber that does not exchange gas with the vacuum chamber of the heating furnace in the low vacuum heating furnace is: a quartz cup is inverted on a metal or ceramic base with a groove, an indium tin alloy is placed in the groove, and a small weight for generating pressure is provided on the outer top of the quartz cup; the vacuum chamber of the heating furnace is evacuated and filled with inert gas, and after heating until the indium tin alloy in the groove is melted, the quartz cup is immersed in the molten indium tin alloy liquid under the pressure of the small weight to achieve sealing of the space inside the quartz cup, so as to obtain a sealed chamber that does not exchange gas with the vacuum chamber of the heating furnace; aluminum powder for further reducing the oxygen and nitrogen partial pressures in the sealed chamber is placed in the quartz cup to consume the residual oxygen and nitrogen in the sealed chamber.

2. The extremely low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts according to claim 1, characterized in that: A ceramic test piece is placed on the metal or ceramic base with the grooves in advance, and a test block of aluminum or magnesium or an alloy based on the aluminum or magnesium is placed on the ceramic test piece.

3. The extremely low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts according to claim 1, characterized in that: The vacuum degree in the vacuum chamber of the heating furnace is evacuated to 10 -1 Pa.

4. The extremely low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts according to claim 1, characterized in that: The metal or ceramic base is made of one of steel, quartz and alumina which can be wetted by indium tin alloy.

5. The extremely low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts according to claim 1, characterized in that: The indium content of the indium-tin alloy is 30-60%, and a melting temperature of 120-180° C. is obtained, and the sealing of the sealing chamber can be achieved within this temperature range.

6. The extremely low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts according to claim 1, characterized in that: The aluminum or magnesium test block includes pure aluminum or pure magnesium and various alloys based on them; the ceramic test piece adopts ceramics of aluminum oxide, aluminum nitride or silicon nitride.

7. The extremely low oxygen partial pressure sealed chamber sessile drop method for observing the wetting angle of aluminum and magnesium melts according to claim 1, characterized in that: The inert gas filled is a gas that does not produce chemical reaction with aluminum and magnesium, and the pressure range is 50-500Pa.

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