A simple, fast and low-cost test method for determining the incipient melting point of ceramic materials

Abstract

This invention discloses a simple, rapid, and low-cost method for determining the initial melting point of ceramic materials, comprising the following steps: preparing a powder for molding; filling the powder into a metal mold, simultaneously inserting high-temperature wires into both ends of the deposited powder to prepare a test sample with wires embedded at both ends of the green body; placing the test sample inside the furnace chamber of a high-temperature electric furnace, leading the wires connected to both ends of the green body to the outer wall of the high-temperature electric furnace, and then connecting the connected high-temperature wires to a multimeter to form a complete circuit; starting the high-temperature electric furnace program, and the data acquisition system connected to the multimeter records the measured high-temperature resistance in real time; plotting a temperature-resistance curve based on the data recorded by the data acquisition system, and the temperature of the first abrupt change point corresponding to the curve is the initial melting point of the ceramic material. This testing method is not limited by predicting the temperature and high-temperature resistance of the target material, and the detection method has the characteristics of low cost, high accuracy, and simple and rapid testing.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, specifically to a simple, rapid, and low-cost test method for determining the initial melting point of ceramic materials. Background Technology

[0002] In the production of architectural ceramics, clearly defining the initial melting point of ceramic materials is crucial for setting the firing regime and designing the formula. During high-temperature firing, ceramic materials ideally possess a high initial melting point and a wide firing temperature range, which facilitates control of the firing process. A suitable initial melting point helps control surface defects. If the initial melting point is too low, gases may escape from the glaze during firing, creating voids that the glaze cannot fill, ultimately resulting in pinholes or glaze shrinkage. Conversely, if the initial melting point is too high, it can lead to underfiring, preventing the ceramic material from achieving a dense structure and resulting in lower body strength. A low liquid phase content in the glaze can also result in low surface stain resistance, and in some cases, a large amount of gas may be trapped in the high-temperature liquid phase, causing surface blemishes. Furthermore, the glaze's abrasion resistance will decrease, affecting the performance of the ceramic product.

[0003] Currently, there are two main methods for testing the initial melting point of ceramic materials. One method is the thermometric triangular pyramid method, which involves preparing ceramic powder into a triangular pyramid shape using appropriate molding processes (typically 30mm high, 8mm at the base, and 2mm at the top, as described in *Ceramic Technology*, edited by Ma Tiecheng, China Light Industry Press, 2nd edition, January 2011, page 39). The initial melting point is determined by heating the thermometric cone at a certain rate in a high-temperature environment until the cone softens and bends at the top to the bottom plane. However, this method suffers from poor accuracy and a certain degree of lag. When the material reaches its initial melting point, it needs to descend further under gravity until it contacts the bottom plane, during which time the temperature has already changed, resulting in a lag in the measured initial melting point. The other method uses a visual high-temperature deformation analyzer to determine the initial melting point. Visual high-temperature deformation analyzers heat samples in a high-temperature electric furnace, and high-temperature microscopes are used to observe and record the deformation of materials at high temperatures in real time, providing important data support for the study and optimization of the sintering process. However, this equipment is expensive, has a long testing cycle, and the highest testing temperature is often below 1800℃. Currently, most ceramic companies use the first method to determine the initial melting point of ceramic materials. Therefore, it is of great significance to find a simple, fast, widely applicable, and low-cost method for testing the initial melting point of ceramic materials. Summary of the Invention

[0004] This invention provides a simple, rapid, and low-cost method for determining the initial melting point of ceramic materials, aiming to solve the problems of insufficient testing accuracy or high testing costs associated with existing methods. The method of this invention is simple, rapid, and cost-effective, and can withstand testing temperatures above 1800℃.

[0005] This invention provides a simple, rapid, and low-cost method for determining the initial melting point of ceramic materials, characterized by the following steps:

[0006] A simple, rapid, and low-cost method for determining the initial melting point of ceramic materials, characterized by the following steps:

[0007] (1) Prepare powder, wherein the powder is used to prepare ceramic blank;

[0008] (2) Fill the metal mold with the powder prepared in step (1), embed the high temperature wires into both ends of the metal mold filled with powder, and then prepare a ceramic green body from the powder in the metal mold. The ceramic green body is a ceramic green body test sample, and the two ends of the ceramic green body test sample are embedded with wires.

[0009] (3) Place the test sample prepared in step 2 into the furnace chamber of the high-temperature electric furnace, lead the wires connected at both ends to the outer wall of the high-temperature electric furnace, and then connect the high-temperature wires to the multimeter to form a complete circuit.

[0010] (4) Start the high-temperature electric furnace program and the data acquisition system connected to the multimeter records the measured high-temperature resistance in real time;

[0011] (5) Plot a temperature-resistance curve based on the data recorded by the data acquisition system in step (4). The temperature of the first abrupt change point on the curve is the initial melting point of the ceramic material.

[0012] Preferably, in the test method, the ceramic green body in step (1) is prepared by dry pressing; the thickness of the ceramic green body is maintained within 1.5 to 2.0 mm, the length of the ceramic green body is less than 30 mm, and the width is less than 15 mm.

[0013] Preferably, in the testing method, in step (2), connecting wires are embedded at both ends of the prepared ceramic green body. The material of the wires can be one or more of refractory metals such as tungsten, molybdenum, tantalum, niobium, and chromium. The diameter of the wires is controlled between 0.5 and 1.0 mm.

[0014] Preferably, in the test method, the wires connected to both ends of the ceramic green body in step (3) are guided from both ends to the outer wall of the high-temperature electric furnace, and the wires and the opening of the electric furnace are wrapped with high-temperature resistant insulating ceramic fibers.

[0015] Preferably, in the test method, the ceramic green body in step (3) is placed on the surface of the alumina pad, and the thickness of the alumina pad is 1-2 mm.

[0016] Preferably, the test method can test the resistance value of the sample at temperatures above 1800°C.

[0017] During the heating process, especially at high temperatures, a liquid phase is generated within the material structure. The amount of liquid phase increases gradually with rising temperature. The liquid phase generated at high temperatures contains alkali metal and alkaline earth metal ions (K...). + Na + Ca 2+ Mg 2+ The diffusion of ions creates an electric field within the material structure, resulting in a change in resistance. Therefore, the change in the material's initial melting point can be characterized by measuring the resistance at high temperatures. Before the initial melting point, the material does not produce a liquid phase, while after the initial melting point, the amount of liquid phase gradually increases. When no liquid phase is formed, the ion diffusion barrier is high, leading to a low ion diffusion rate and thus high resistance; when a liquid phase is formed, the ion diffusion rate accelerates, resulting in low resistance. In other words, the initial melting point is accompanied by the emergence of a liquid phase, representing a sudden change in the electric field resistance. Therefore, the initial melting point of the material can be characterized by the temperature corresponding to this change in resistance.

[0018] Therefore, this embodiment of the invention predicts the initial melting point of the target material based on the resistance change law, providing data support for industrial production and improving the stability of material preparation.

[0019] The present invention has the following beneficial effects:

[0020] (1) The detection method disclosed in this invention can not only measure the high-temperature resistance value in the temperature range with a maximum temperature of 1800℃, but is also not limited by the detection equipment. In order to ensure that the maximum test temperature is above 1800℃, the high-temperature wire selected in this invention is one or more of refractory metals such as tungsten, molybdenum, tantalum, niobium, and chromium. This ensures that the temperature resistance of the test wire and the performance change of the wire in the high-temperature stage have little impact on the resistance. The diameter of the wire is controlled at 0.5 to 1.0 mm, which is also to control the performance change of the wire in the high-temperature stage so as not to affect the value change of the measured high-temperature resistance. The blank prepared by the dry pressing process has a length of less than 30 mm, a width of less than 15 mm, and a thickness of 1.5 to 2.0 mm. This is mainly because the size of the blank will affect the accuracy of the test. Since the blank relies on heat conduction to heat the test sample in the high-temperature electric furnace test environment, when the test sample is larger, there is a large temperature difference between the surface and the internal structure of the sample. This causes the surface and the interior to be tested at different temperatures during the test, which seriously affects the accuracy of the test.

[0021] (2) The detection method disclosed in this invention has the characteristics of low cost and simple and quick operation. The metal molds, presses, high-temperature electric furnaces, multimeters, and high-temperature resistant metal wires used for dry pressing are all common materials or equipment, which are far lower than the cost of using a high-temperature visual deformation analyzer. It is expected to popularize this testing method in ceramic enterprises and guide the industrial production of ceramics.

[0022] (3) Compared with the high temperature visualization deformation analyzer, the absolute deviation of the test results obtained by the detection method disclosed in this invention is controlled within 3℃, and the test data is accurate. Attached Figure Description

[0023] Figure 1 Schematic diagram of the initial melting point test experiment for ceramic materials;

[0024] Figure 2 Example 1: Temperature-resistance curve of ceramic green body;

[0025] Figure 3 Example 2: Temperature-resistance curve of ceramic green body;

[0026] Figure 4 Example 3: Temperature-resistance curve of ceramic green body;

[0027] Figure 5 Example 4: Temperature-resistance curve of ceramic green body;

[0028] Figure 6 The left image shows the green body of ceramic powder after room temperature drying in Example 1; the right image shows the green body at 1172℃.

[0029] Figure 7 The left image shows the green body of ceramic powder after room temperature drying in Example 2; the right image shows the green body at 1177℃.

[0030] Figure 8 The left image shows the green body of ceramic powder after room temperature drying in Example 3; the right image shows the green body at 1162℃.

[0031] Figure 9 The left image shows the green body after the ceramic powder in Example 4 has been dried at room temperature; the right image shows the green body at 1167℃. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that the step numbers in this document are only for the convenience of explaining the specific embodiments and are not intended to limit the order in which the steps are performed.

[0034] Throughout this specification, the materials described herein refer to blanks or billets required for ceramics, glass, and other inorganic non-metallic materials produced through firing. The firing temperature refers to the temperature required for sintering the blanks or billets into a firing vessel.

[0035] Implementation Example 1

[0036] (1) Prepare powder for ceramic body forming. The chemical composition of the powder is as follows: silicon oxide 48.34 wt.%, aluminum oxide 18.02 wt.%, iron oxide 0.30 wt.%, titanium oxide 0.16 wt.%, calcium oxide 14.07 wt.%, magnesium oxide 2.23 wt.%, potassium oxide 0.87 wt.%, sodium oxide 2.63 wt.%, and the remainder is loss on ignition.

[0037] (2) Fill the metal mold with the powder prepared in step (1), embed a high temperature wire with a diameter of 0.5 mm into the powder, and use dry pressing to prepare a green body with a length of 25 mm, a width of 12 mm and a thickness of 2 mm.

[0038] (3) Place the green billet inside the furnace chamber of the high-temperature electric furnace. The wires connected to both ends of the green billet are led from both ends to the outer wall of the high-temperature electric furnace. Then connect the high-temperature wires to the multimeter to form a complete circuit. The wires are wrapped with high-temperature resistant insulating ceramic fiber at the furnace door opening to prevent the wires from contacting the metal outer wall of the furnace and causing a short circuit.

[0039] (4) Start the high-temperature electric furnace program and the data acquisition system connected to the multimeter records the measured resistance in real time;

[0040] (5) Plot the temperature-resistance curve based on the data recorded by the data acquisition system in step (4). Figure 2 The temperature of the first abrupt change point on the curve, 1171℃, is the initial melting point of the ceramic material.

[0041] Implementation Example 2

[0042] (1) Prepare powder for ceramic body forming. The chemical composition of the powder is as follows: silicon oxide 48.07wt%, aluminum oxide 18.46wt%, iron oxide 0.27wt%, titanium oxide 0.15wt%, calcium oxide 12.47wt%, magnesium oxide 2.54wt%, potassium oxide 1.12wt%, sodium oxide 2.75wt%, and the remainder is loss on ignition.

[0043] (2) Fill the metal mold with the powder prepared in step (1), embed a high temperature wire with a diameter of 1 mm into the powder, and prepare a green body with a length of 20 mm, a width of 10 mm and a thickness of 1.5 mm by dry pressing process.

[0044] (3) Place the green billet inside the furnace chamber of the high-temperature electric furnace. The wires connected to both ends of the green billet are led from both ends to the outer wall of the high-temperature electric furnace. Then connect the high-temperature wires to the multimeter to form a complete circuit. The wires are wrapped with high-temperature resistant insulating ceramic fiber at the furnace door opening to prevent the wires from contacting the metal outer wall of the furnace and causing a short circuit.

[0045] (4) Start the high-temperature electric furnace program and the data acquisition system connected to the multimeter records the measured resistance in real time;

[0046] (5) Plot the temperature-resistance curve based on the data recorded by the data acquisition system in step (4). Figure 3 The temperature of the first abrupt change point on the curve, 1176℃, is the initial melting point of the ceramic material.

[0047] Implementation Example 3

[0048] (1) Prepare powder for ceramic body forming. The chemical composition of the powder is as follows: silicon oxide 49.27wt%, aluminum oxide 13.32wt%, iron oxide 0.30wt%, titanium oxide 0.11wt%, calcium oxide 6.44wt%, magnesium oxide 4.42wt%, potassium oxide 1.21wt%, sodium oxide 3.52wt%, and the remainder is loss on ignition.

[0049] (2) Fill the metal mold with the powder prepared in step (1), embed a high temperature wire with a diameter of 0.5 mm into the powder, and prepare a green blank with a length of 25 mm, a width of 10 mm and a thickness of 1.5 mm by dry pressing process.

[0050] (3) Place the green billet inside the furnace chamber of the high-temperature electric furnace. The wires connected to both ends of the green billet are led from both ends to the outer wall of the high-temperature electric furnace. Then connect the high-temperature wires to the multimeter to form a complete circuit. The wires are wrapped with high-temperature resistant insulating ceramic fiber at the furnace door opening to prevent the wires from contacting the metal outer wall of the furnace and causing a short circuit.

[0051] (4) Start the high-temperature electric furnace program and the data acquisition system connected to the multimeter records the measured resistance in real time;

[0052] (5) Plot the temperature-resistance curve based on the data recorded by the data acquisition system in step (4). Figure 4 The temperature of the first abrupt change point on the curve, 1160℃, is the initial melting point of the ceramic material.

[0053] Implementation Example 4

[0054] (1) Prepare powder for ceramic body forming. The chemical composition of the powder is as follows: silicon oxide 46.84wt%, aluminum oxide 16.08wt%, iron oxide 0.19wt%, titanium oxide 0.16wt%, calcium oxide 5.19wt%, magnesium oxide 4.53wt%, potassium oxide 2.20wt%, sodium oxide 2.71wt%, and the remainder is loss on ignition.

[0055] (2) Fill the metal mold with the powder prepared in step (1), embed a high temperature wire with a diameter of 0.5 mm into the powder, and prepare a green blank with a length of 25 mm, a width of 8 mm and a thickness of 1.5 mm by dry pressing process.

[0056] (3) Place the green billet inside the furnace chamber of the high-temperature electric furnace. The wires connected to both ends of the green billet are led from both ends to the outer wall of the high-temperature electric furnace. Then connect the high-temperature wires to the multimeter to form a complete circuit. The wires are wrapped with high-temperature resistant insulating ceramic fiber at the furnace door opening to prevent the wires from contacting the metal outer wall of the furnace and causing a short circuit.

[0057] (4) Start the high-temperature electric furnace program and the data acquisition system connected to the multimeter records the measured resistance in real time;

[0058] (5) Plot the temperature-resistance curve based on the data recorded by the data acquisition system in step (4). Figure 5 The temperature of the first abrupt change point on the curve, 1170℃, is the initial melting point of the ceramic material.

[0059] Comparative Example 1

[0060] The first type of ceramic green body powder was dry-pressed into a column shape with a diameter of 5 mm and a height of 3 mm. The initial melting point was determined by a high-temperature visual deformation analyzer.

[0061] The initial melting point measured by the high-temperature visual deformation analyzer (Tianjin Zhonghuan Electric Furnace Co., Ltd., TA-1601) was 1172℃. Figure 6 The image, taken with a high-temperature microscope, shows rounded corners on a columnar billet at 1172℃, indicating the onset of melting.

[0062] Comparative Example 2

[0063] The second type of ceramic green body powder was dry-pressed into a column shape with a diameter of 5 mm and a height of 3 mm. The initial melting point was determined by a high-temperature visual deformation analyzer.

[0064] The initial melting point measured by the high-temperature visual deformation analyzer (Tianjin Zhonghuan Electric Furnace Co., Ltd., TA-1601) was 1177℃. Figure 7 The image, taken with a high-temperature microscope, shows that the cylindrical blank at 1177℃ has rounded corners, indicating the onset of melting.

[0065] Comparative Example 3

[0066] The third type of ceramic green body powder was dry-pressed into a column shape with a diameter of 5 mm and a height of 3 mm. The initial melting point was determined by a high-temperature visual deformation analyzer.

[0067] The initial melting point measured by the high-temperature visual deformation analyzer (Tianjin Zhonghuan Electric Furnace Co., Ltd., TA-1601) was 1162℃. Figure 8 The image, taken with a high-temperature microscope, shows rounded corners on a columnar billet at 1162℃, indicating the onset of melting.

[0068] Comparative Example 4

[0069] The fourth type of ceramic green body powder was dry-pressed into a column shape with a diameter of 5 mm and a height of 3 mm. The initial melting point was determined by a high-temperature visual deformation analyzer.

[0070] The initial melting point measured by the high-temperature visual deformation analyzer (Tianjin Zhonghuan Electric Furnace Co., Ltd., TA-1601) was 1167℃. Figure 9 The image, taken with a high-temperature microscope, shows rounded corners on a columnar billet at 1167℃, indicating the onset of melting.

[0071] Table 1 Comparison of the detection method of the present invention and the test results of the visual high-temperature deformation analyzer.

[0072]

[0073] Table 1 compares the test results of the detection method of this invention with those of the visual high-temperature deformation analyzer. The high-temperature visual deformation analyzer serves as a representative characterization device and method for the initial melting point of test materials. Comparing the test results of the detection method of this invention with those of the visual high-temperature deformation analyzer reveals that, compared with the high-temperature visual deformation analyzer, the absolute deviation of the experimental results obtained by the detection method disclosed in this invention is controlled within 3℃, indicating accurate test data.

[0074] The detection method disclosed in this invention is characterized by low cost and simple and quick operation. The metal molds used in dry pressing, presses, high-temperature electric furnaces, multimeters, and high-temperature resistant metal wires are all common materials or equipment, with costs far lower than those of high-temperature visual deformation analyzers. This method is expected to be widely adopted in ceramic enterprises, guiding industrialized ceramic production.

[0075] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A simple, rapid, and low-cost method for determining the initial melting point of ceramic materials, characterized in that, Includes the following steps: (1) Prepare powder, wherein the powder is used to prepare ceramic blank; (2) Fill the metal mold with the powder prepared in step (1), embed the high temperature wires into both ends of the metal mold filled with powder, and then prepare a ceramic green body from the powder in the metal mold. The ceramic green body is a ceramic green body test sample, and the two ends of the ceramic green body test sample are embedded with wires. (3) Place the test sample prepared in step 2 into the furnace chamber of the high-temperature electric furnace, lead the wires connected at both ends to the outer wall of the high-temperature electric furnace, and then connect the high-temperature wires to the multimeter to form a complete circuit. (4) Start the high-temperature electric furnace program and the data acquisition system connected to the multimeter records the measured high-temperature resistance in real time; (5) Plot a temperature-resistance curve based on the data recorded by the data acquisition system in step (4). The temperature of the first abrupt change point on the curve is the initial melting point of the ceramic material.

2. The test method according to claim 1, characterized in that, The ceramic green body described in step (1) is prepared by dry pressing. The thickness of the ceramic green body is kept within 1.5 to 2.0 mm, the length of the ceramic green body is less than 30 mm, and the width is less than 15 mm.

3. The test method according to claim 2, characterized in that, In step (2), connecting wires are embedded at both ends of the ceramic green body. The material of the wires can be one or more of refractory metals such as tungsten, molybdenum, tantalum, niobium, and chromium. The diameter of the wires is controlled between 0.5 and 1.0 mm.

4. The test method according to claim 1, characterized in that, In step (3), the wires connected to both ends of the ceramic green body are guided from both ends to the outer wall of the high-temperature electric furnace, and the wires and the opening of the electric furnace are wrapped with high-temperature resistant insulating ceramic fibers.

5. The test method according to claim 1, characterized in that, In step (3), the ceramic green body is placed on the surface of the alumina pad, and the thickness of the alumina pad is 1-2 mm.

6. The test method according to claim 1, characterized in that, It can test the resistance value of a sample at temperatures above 1800℃.

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