A method for preparing magnesium titanate with controllable particle size

Abstract

The invention discloses a method for preparing magnesium titanate with controllable particle size, which belongs to the field of magnesium titanate preparation. The preparation process is as follows: after magnesium oxide and titanium dioxide are evenly mixed, deionized water is added for wet ball milling, a dispersant is added to the mixed slurry for continued ball milling, and then drying is performed, first placed in a sagger, and then pre-sintered and high-temperature sintered in a push plate kiln, and finally cooled and ball milled and sieved to obtain the final product, magnesium titanate powder. The present invention improves the existing preparation process, can be controlled at a certain micron scale, and synthesized magnesium titanate powder with uniform particle size is prepared, ball milling and sintering processes are used for processing, which greatly saves the process flow, the process is simpler and more convenient, the finished product quality control is more stable, the product particle size is smaller, the reflectivity is higher, it has better pigment performance, and the scope of application is wider.

Description

Technical Field

[0001] The invention relates to the technical field of magnesium titanate preparation, and in particular to a method for preparing magnesium titanate with controllable particle size. Background Art

[0002] Magnesium titanate has the characteristics of low dielectric loss, low dielectric constant, low resonant frequency, and low temperature coefficient. It is a very important microwave dielectric ceramic material used in low-loss microwave resonators, capacitors, filters, mobile phones, radars, broadcast satellites, and microwave frequency global positioning systems. In recent years, magnesium titanate has been more widely used in friction materials and other fields due to its controllable micron-level morphology. The commonly used synthesis methods of magnesium titanate are combustion method and chemical method. The combustion method synthesizes magnesium titanate by placing a mixture of corresponding soluble metal nitrates (oxidants) and organic fuels (such as urea or citric acid, etc.) in a certain temperature environment and igniting to induce a violent oxidation-reduction reaction. Once ignited, the reaction will be maintained automatically by the heat released by the oxidation-reduction reaction. The entire combustion process can be completed within a few minutes, and a large amount of gas escapes. The product is a loose foam-like solid. Therefore, this method is relatively difficult to operate in the preparation process, and the preparation process is unstable and highly dangerous; while the chemical method is to synthesize magnesium titanate by MgO and TiO 2 A solid-phase reaction occurs at high temperature to generate magnesium titanate. This method is characterized by a slow reaction rate and slow substrate diffusion. It usually needs to be carried out at high temperatures. Due to the limitations of preparation conditions, it is difficult to carry out large-scale industrial production.

[0003] In addition, in the existing preparation technology, magnesium titanate is prepared by combustion method or chemical method, but these two preparation methods cannot control the particle size of magnesium titanate through the preparation process conditions, and the preparation process requires high conditions and cannot meet the current technical requirements. At the same time, in the existing chemical preparation process, the firing equipment used cannot achieve stable heating and cooling effects on the product, resulting in a large span of particle size of the prepared magnesium titanate powder and uneven distribution, which cannot meet higher product quality requirements. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing magnesium titanate with controllable particle size within a certain scale, solve the problems existing in the solid-phase method for preparing magnesium titanate, and prepare magnesium titanate products with controllable particle size by a simpler, more environmentally friendly and lower-cost method. At the same time, the high-temperature firing equipment in the preparation process is structurally improved so that the product can be heated evenly and sufficiently at high temperature, and can be cooled at a uniform and rapid speed to solve the technical problems mentioned in the above-mentioned background technology.

[0005] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0006] The purpose of the present invention is to provide a method for preparing magnesium titanate with uniform particle size, and the specific steps are as follows:

[0007] (1) Mix magnesium oxide and titanium dioxide in a molecular formula molar ratio, put them into a ball mill, add deionized water and perform wet ball milling for 6-8 hours, and continue to add deionized water to obtain a mixed slurry;

[0008] (2) Add 5-10%wt dispersant to the mixed slurry and continue ball milling for 2-3h to obtain a mixed solution;

[0009] (3) placing the obtained mixed liquid into a dryer and drying it at 300°C to remove moisture and obtain a dry material;

[0010] (4) Place the dried material in a sagger and then place it in a push plate kiln for pre-sintering for 2-3 hours. Set the sintering curve of the push plate kiln to 700-900°C.

[0011] (5) Continue to increase the temperature of the push plate kiln for high-temperature sintering, the sintering temperature is 1250-1300℃, and keep warm for 2.5-3.5h;

[0012] (6) Cooling and ball milling the sintered material again for 6 hours to finally obtain a magnesium titanate powder with a particle size distribution of 1-5 μm.

[0013] Preferably, the magnesium oxide is micron-sized magnesium oxide powder.

[0014] Preferably, the titanium dioxide is rutile titanium dioxide.

[0015] Preferably, in step (1), the concentration of the mixed slurry is 60-80% solid content.

[0016] Preferably, the dispersant is a polymer dispersant selected from polycarboxylic acid ammonium salt, acrylic resin, acrylic acid ammonium salt or PVA polyvinyl alcohol. In the technical solution of the present invention, the function of the dispersant is to allow the raw materials magnesium oxide and titanium dioxide to be fully dispersed in the dispersant to improve the grinding effect, and at the same time, in the subsequent heating process, the two materials can fully react to improve the reaction efficiency of the product.

[0017] Preferably, the push-plate kiln heating in step (4) and step (5) is performed at a heating rate of 10°C / min.

[0018] Preferably, another object of the present invention is to disclose a push plate kiln in a method for preparing magnesium titanate with controllable particle size, comprising a furnace body, a heating system, a propulsion device and a control system; the furnace body is divided into three areas: a preheating zone, a heating zone and a cooling zone; the top of the preheating zone is located above the furnace body and a preheating device is installed; the top of the heating zone is located above the furnace body and a heating device is installed; a heating chamber is provided in the furnace body;

[0019] The furnace body feed port is located at a position where tracks are installed on both sides of the feed port, and the other side of the track passes through the furnace body and extends from the furnace body discharge port; a push plate is provided between the two tracks located in the heating chamber, and the push plate slides in the track through a slider; two stacked saggers are placed on the push plate; a propulsion device is installed on the track at the furnace body feed port, and the propulsion device is used to push the push plate into the heating chamber in sequence;

[0020] Two support seats are installed at the bottom of the furnace body; a bottom plate is installed between the two support seats; and evenly arranged inlets are opened on the bottom plate;

[0021] A cooling box is installed on the furnace body on the right side of the heating device, and a gas cooling device is installed in the cooling box;

[0022] Three circulation bins are installed under the bottom plate, namely the first circulation bin, the second circulation bin and the third circulation bin, and air pumps are installed in the three circulation bins;

[0023] The first circulation chamber is aligned with the preheating device and connected through a connecting pipe; the second circulation chamber is aligned with the heating device and connected through a connecting pipe; the third circulation chamber is aligned with the cooling device and connected through a connecting pipe;

[0024] A transverse groove is provided on the furnace body below the preheating device, the heating device and the cooling box;

[0025] The position of the furnace body feed port is fixedly installed with an inclined plate;

[0026] The push plates are each provided with an auxiliary structure, and the auxiliary structure is used to assist the materials in preheating, sintering and cooling.

[0027] Preferably, the auxiliary structure comprises a rectangular groove;

[0028] The push plate surface is provided with two mutually parallel rectangular grooves, and the rectangular grooves penetrate the push plate and are perpendicular to the sliding block;

[0029] Baffles are slidably connected in the two rectangular grooves. When the baffles slide into the heating chamber, the baffles fit the top and two side surfaces of the heating chamber. The length of the baffles is greater than the length of the inlet opening on the bottom plate.

[0030] On the opposite sides of the two baffles, a limit plate is installed on the top of the baffle. In the initial state, the baffle is located below the push plate, and the bottom surface of the limit plate is in contact with the top surface of the push plate.

[0031] Between the two baffles, two connecting plates are fixedly connected at the bottom of the baffles.

[0032] Preferably, two extrusion plates are fixedly connected to the end surfaces on opposite sides of the two baffles, and the tops of the extrusion plates are both rounded;

[0033] The two rectangular grooves are provided with notches on the push plate at one side opposite to each other, and the extrusion plates slide in the notches;

[0034] A supporting plate is fixedly connected between two extrusion plates on the same baffle; a mounting plate is fixedly connected to one side of the upper sagger close to the supporting plate, and the mounting plate and the supporting plate are arranged alternately.

[0035] More preferably, air grooves are provided in the inner walls of the two baffles, and the air grooves extend through the top of the baffles;

[0036] The end surfaces of the two baffles on one side opposite to each other are both provided with evenly arranged air holes, and the air holes are all inclined downward.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. Add special dispersant for ball milling, formulate sintering curve, and perform program heating and segmented sintering to solve the shortcomings of existing solid-state synthetic magnesium titanate such as uneven particle size and uneven dispersion;

[0039] 2. The present invention improves the existing preparation process and can prepare magnesium titanate powder with uniform synthetic particle size under a certain micron scale.

[0040] 3. The present invention adopts ball milling and sintering processes for processing, which greatly saves the process flow, makes the process simpler, the operation more convenient, the cost lower, and the quality control of the finished product more stable.

[0041] 4. The magnesium titanate product obtained by the present invention has an ideal particle size distribution, with a particle size D50 between 1 and 5 microns. The product has a smaller particle size, a higher reflectivity, better pigment properties, and a wider range of applications.

[0042] 5. The high temperature firing equipment in the present invention, the push plate kiln, can realize internal gas flow through the preheating or heating device, in conjunction with the cooling box, to accelerate the heating and cooling effects of the materials, so that the materials can be heated and cooled more fully, the heating or cooling effects can be more uniform, and the effects can be better, which not only meets the quality requirements of the magnesium titanate product of the present invention, but also can achieve the purpose of energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a 5μm SEM electron microscope image of the magnesium titanate powder product prepared in Example 8.

[0044] Figure 2 This is a 1 μm SEM electron microscope image of the magnesium titanate powder product prepared in Example 8.

[0045] Figure 3 It is a stereoscopic diagram of a push plate kiln, a high temperature heating device in the preparation method of the present invention;

[0046] Figure 4 It is the internal structure diagram of the push plate kiln of the present invention;

[0047] Figure 5 It is a schematic diagram of the push plate, auxiliary structure and sagger before entering the furnace body in the present invention;

[0048] Figure 6 It is a schematic diagram of the push plate, auxiliary structure and sagger entering the furnace body in the present invention;

[0049] Figure 7 It is a structural diagram of the push plate, auxiliary structure and sagger in the present invention;

[0050] Figure 8 It is a top view of the push plate kiln of the present invention;

[0051] Fig. 9 The present invention Figure 8 Sectional view at AA;

[0052] Fig.10 The present invention Fig. 9 A partial enlarged view of point B in the middle;

[0053] Fig.11 The present invention Fig. 9 A partial enlarged view of point C in the middle.

[0054] In the figure: 1. furnace body; 11. preheating device; 12. heating device; 13. track; 14. push plate; 15. slider; 16. sagger; 17. cooling box; 2. support seat; 21. bottom plate; 22. inlet; 23. first circulation bin; 24. second circulation bin; 25. third circulation bin; 26. transverse groove; 27. inclined plate; 28. connecting pipe; 3. rectangular groove; 31. baffle; 32. limit plate; 33. connecting plate; 34. extrusion plate; 35. missing groove; 36. support plate; 37. mounting plate; 38. air groove; 39. air hole. DETAILED DESCRIPTION

[0055] The following is a combination of multiple embodiments and comparative examples to verify the preparation process of the catalyst of the present invention and the influencing factors of the preparation parameters, and then further illustrate the technical solution of the invention.

[0056] Example 1

[0057] (1) Mixing micron-sized magnesium oxide and rutile titanium dioxide in an equal molar ratio, placing the mixture in a ball mill, adding deionized water and performing wet ball milling for 6 hours to obtain a mixed slurry;

[0058] (2) Add 5%wt dispersant-acrylic resin to the mixed slurry and continue ball milling for 2h to obtain a mixed solution;

[0059] (3) placing the obtained mixed liquid into a dryer and drying it at 300°C to remove moisture and obtain a dry material;

[0060] (4) The dried material is placed in a sagger and then placed in a push plate kiln for pre-sintering for 3 hours. The sintering curve of the push plate kiln is set to 700°C, and the heating temperature is increased at a heating rate of 10°C / min.

[0061] (5) Continue to increase the temperature of the push plate kiln for high-temperature sintering. The sintering temperature is 1280°C and kept warm for 3 hours. The heating rate is 10°C / min.

[0062] (6) Cooling and ball milling the sintered material again for 6 h to obtain the final product, magnesium titanate powder.

[0063] The particle size distribution of the obtained magnesium titanate powder was 4-5 microns as measured by a laser particle size analyzer.

[0064] Example 2

[0065] Compared with Example 1, Example 2 of the present invention is different in that the proportion of the dispersant in the preparation process (2) is 7.5wt%, and the particle size distribution of the obtained magnesium titanate powder is 3-4 microns.

[0066] Example 3

[0067] Compared with Example 1, Example 3 of the present invention is different in that the proportion of the dispersant in the preparation process (2) is 10 wt %, and the particle size distribution of the obtained magnesium titanate powder is 2-3 μm.

[0068] Example 4

[0069] Compared with Example 1, Example 4 of the present invention is different in that the pre-sintering temperature in the preparation process (4) is 800° C., the sintering time is 2.5 h, and the particle size distribution of the obtained magnesium titanate powder is 2-3 μm.

[0070] Example 5

[0071] Compared with Example 1, Example 5 of the present invention is different in that the pre-sintering temperature in the preparation process (4) is 900° C., the sintering time is 2 h, and the particle size distribution of the obtained magnesium titanate powder is 1.5-2.5 μm.

[0072] Example 6

[0073] Compared with Example 1, Example 6 of the present invention is different in that the sintering temperature in the preparation process (5) is 1250° C., the sintering time is 3.5 h, and the particle size distribution of the obtained magnesium titanate powder is 3-4 μm.

[0074] Example 7

[0075] Compared with Example 1, Example 7 of the present invention is different in that the sintering temperature in the preparation process (5) is 1280° C., the sintering time is 2.5 h, and the particle size distribution of the obtained magnesium titanate powder is 4-5 μm.

[0076] Example 8

[0077] Compared with Example 1, Example 8 of the present invention is different in that the proportion of the dispersant in the preparation process (2) is 7.5wt%; the pre-sintering temperature in the preparation process (4) is 900°C and the sintering time is 2h; the sintering temperature in the preparation process (5) is 1250°C and the sintering time is 3.5h, and the particle size distribution of the obtained magnesium titanate powder is 1-2 microns.

[0078] Comparative Example 1

[0079] Compared with Example 1, Comparative Example 1 of the present invention is different in that in the preparation process (2), the proportion of the dispersant is 0, and the particle size of the obtained magnesium titanate product is 8-12 microns.

[0080] Comparative Example 2

[0081] The difference between Comparative Example 2 of the present invention and Example 1 is that in the preparation process (2), the proportion of the dispersant is 15wt%, and the particle size of the obtained magnesium titanate product is 8-10 microns.

[0082] Comparative Example 3

[0083] The difference between Comparative Example 3 of the present invention and Example 1 is that in the preparation process (4), the pre-sintering temperature is 600° C., and the particle size of the obtained magnesium titanate product is 7-10 μm.

[0084] Comparative Example 4

[0085] The difference between Comparative Example 4 of the present invention and Example 1 is that in the preparation process (4), the pre-sintering temperature is 1000° C., and the particle size of the obtained magnesium titanate product is 8-11 μm.

[0086] Comparative Example 5

[0087] Compared with Example 1, Comparative Example 5 of the present invention is different in that in the preparation process (4), the sintering temperature is 1230° C., and the particle size of the obtained magnesium titanate product is 8-10 μm.

[0088] Comparative Example 6

[0089] Compared with Example 1, Comparative Example 6 of the present invention is different in that in the preparation process (4), the sintering temperature is 1330° C., and the particle size of the obtained magnesium titanate product is 9-12 μm.

[0090] It can be seen from the results of Examples 1-8 and Comparative Examples 1-6 that the particle size of the magnesium titanate prepared by the present invention is related to the dispersant, the pre-sintering temperature and the sintering temperature. When the proportion of the dispersant in the 5-10%wt range is smaller, the pre-sintering temperature in the 700-900°C range is lower, and the sintering temperature in the 1250-1300°C range is higher, the particle size of the final magnesium titanate product is larger; conversely, when the proportion of the dispersant in the 5-10%wt range is larger, the pre-sintering temperature in the 700-900°C range is higher, and the sintering temperature in the 1250-1300°C range is lower, the particle size of the final magnesium titanate product is smaller.

[0091] It can be seen from Comparative Examples 1-6 that if no dispersant is added during the preparation process or the proportion of the dispersant is high, the particle size of the magnesium titanate is significantly increased, and the range of the particle size is wider. This is because in the absence of the condensation effect of the dispersant, the titanium dioxide and magnesium oxide molecules cannot be well aggregated and combined. Due to the aggregation effect between the molecules, the magnesium titanate molecules generated during the reaction sintering reaction are also larger in particle size; and if the proportion of the dispersant is too large, the amount of dispersant between the titanium dioxide and magnesium oxide molecules is large, so the particle size of the magnesium titanate molecules generated during the sintering process is also larger.

[0092] During the sintering process, if the pre-sintering temperature is lower, the reaction between the raw materials will be milder and the generated magnesium carbonate structural network will be larger; and the higher the sintering temperature, the polymer dispersant in the magnesium carbonate material will be carbonized and then generate gas to leave, forming regular pores in the magnesium carbonate material. The higher the temperature, the larger the pores, the smaller the single pore volume, and the larger the particle size of the material obtained through ball milling.

[0093] In order to further verify the particle size distribution, solubility and tinting strength of the magnesium titanate product of the present invention, the magnesium titanate products prepared in Examples 1-8 were tested. The particle size is the result of the laser particle size analyzer test, and the reflectivity curve is the result of the Agilent Cary 5000 test. The obtained test data are shown in Table 1:

[0094] Table 1 Test data of examples and comparative examples

[0095]

[0096] It can be seen from the data of Examples 1-8 in Table 1 that the magnesium titanate prepared by the method of the present invention has a particle size distribution between 1 and 5 microns, and there is negligible large-particle magnesium titanate powder in the prepared product. The smaller the particle size of the magnesium titanate powder, the greater its solubility and the stronger its tinting power.

[0097] In order to further ensure the quality of the magnesium titanate product of the present invention and solve the problems of uneven heating of the product during high-temperature heating, as well as slow and uneven cooling, in the preparation method of the product, it is necessary to improve the push plate kiln used in the firing process of magnesium titanate to meet the preparation requirements of the product.

[0098] like Figures 3 to 11 As shown, the push plate kiln of the present invention includes a furnace body 1, a heating system, a propulsion device and a control system. The furnace body 1 is divided into three areas: a preheating zone, a heating zone and a cooling zone. A preheating device 11 is installed at the top of the preheating zone above the furnace body 1, and a heating device 12 is installed at the top of the heating zone above the furnace body 1. A heating chamber is provided in the furnace body 1.

[0099] In an embodiment of the present invention, a track 13 is installed at the feed port position of the furnace body 1 and on both sides of the feed port, and the other side of the track 13 passes through the furnace body 1 and extends from the discharge port position of the furnace body 1; a push plate 14 is provided between the two tracks 13 located in the heating chamber, and the push plate 14 slides in the track 13 through a slider 15, and two stacked saggers 16 are placed on the push plate 14; a propulsion device is installed on the track 13 at the feed port position of the furnace body 1, and the propulsion device is used to push the push plate 14 to enter the heating chamber in sequence.

[0100] In the embodiment of the present invention, two support seats 2 are installed at the bottom of the furnace body 1 , a bottom plate 21 is installed between the two support seats 2 , and evenly arranged inlets 22 are opened on the bottom plate 21 .

[0101] In the embodiment of the present invention, a cooling box 17 is installed on the furnace body 1 at the right side of the heating device 12 , and a gas cooling device is installed in the cooling box 17 .

[0102] In an embodiment of the present invention, three circulation chambers are installed under the bottom plate 21, namely the first circulation chamber 23, the second circulation chamber 24 and the third circulation chamber 25, and air pumps are installed in the three circulation chambers; the first circulation chamber 23 is aligned with the preheating device 11 and is connected through a connecting pipe 28; the second circulation chamber 24 is aligned with the heating device 12 and is connected through a connecting pipe 28; the third circulation chamber 25 is aligned with the cooling device and is connected through a connecting pipe 28.

[0103] A transverse groove 26 is provided on the furnace body 1 below the preheating device 11 , the heating device 12 and the cooling box 17 , and an inclined plate 27 is fixedly installed at the position of the feed port of the furnace body 1 .

[0104] The push plates 14 are each provided with an auxiliary structure, and the auxiliary structure is used to assist the material in preheating, sintering and cooling.

[0105] As a further embodiment of the present invention, the auxiliary structure includes a rectangular groove 3, two parallel rectangular grooves 3 are opened on the surface of the push plate 14, and the rectangular groove 3 passes through the push plate 14 and is perpendicular to the slider 15; baffles 31 are slidably connected in the two rectangular grooves 3, and when the baffles 31 slide into the heating chamber, the baffles 31 fit the top and two side surfaces of the heating chamber; the length of the baffle 31 is greater than the length of the inlet 22 opened on the bottom plate 21.

[0106] On the opposite sides of the two baffles 31, a limit plate 32 is installed on the top of the baffle 31. In the initial state, the baffle 31 is located below the push plate 14, and the bottom surface of the limit plate 32 is in contact with the top surface of the push plate 14; between the two baffles 31, there are two connecting plates 33 fixedly connected at the bottom of the baffle 31;

[0107] Specifically, when the material needs to be sintered, the material is first placed in the sagger 16, and then the sagger 16 is placed on the push plate 14, and two saggers 16 are stacked on each push plate 14, and then the push plate 14 with the sagger 16 placed is transferred to the track 13, and the push plate kiln is started, and then the propulsion device is controlled to work, and the propulsion device will push the push plate 14 with the sagger 16 placed into the furnace body 1 along the track 13 in sequence. When the push plate 14 is gradually pushed into the furnace body 1, the baffle 31 originally located under the push plate 14 will gradually contact with the inclined plate 27. When the push plate 14 and the inclined plate 27 are contacted, the push plate 14 and the inclined plate 27 are contacted. After the two baffles 31 are in contact with each other, and the propulsion device continues to push the push plate 14 to move, the baffle 31 will move along the inclined plate 27, and the inclined plate 27 will gradually push the baffle 31 to slide upward in the rectangular groove 3. Since the two baffles 31 are connected by the connecting plate 33, the two baffles 31 will move upward at the same time. When the baffle 31 moves to the position of the bottom plate 21, the bottom of the baffle 31 will continue to slide along the bottom plate 21, and the baffle 31 will move up to the limit position, and the top of the baffle 31 will fit with the top of the heating chamber, and the side wall of the baffle 31 will also fit with the side wall of the heating chamber.

[0108] More specifically, during the operation of the propulsion device, the push plate 14 will be pushed into the furnace body 1 in sequence. When the push plate 14 enters the furnace body 1, the baffles 31 on the push plate 14 will move upward under the guidance of the inclined plate 27, and the baffles 31 will fit the inner cavity of the heating chamber. At the same time, when the push plates 14 enter the furnace body 1 in sequence, the push plates 14 entering the furnace body 1 will contact the push plates 14 that have entered the furnace body 1 first, and push the push plates 14 that have entered the furnace body 1 first to move. At the same time, the limit plates 32 on adjacent baffles 31 on different push plates 14 will fit each other, and the tops of the limit plates 32 will fit together. When the push plates 14 are moved to the preheating zone, the push plates 14 are located just below the transverse groove 26 below the preheating device 11. Then, the heat generated by the preheating device 11 acts on the sagger 16 placed on the push plates 14 through the transverse groove 26, so that the material in the sagger 16 can be preheated. Since the limiting plates 32 on the adjacent baffles 31 are fitted to each other, and the baffles 31 are fitted to the heating chamber, the heat generated by the preheating device 11 enters between the two baffles 31, so that the material in the sagger 16 between the two baffles 31 can be preheated.

[0109] As a further embodiment of the present invention, when the preheating of the material in the sagger 16 on the push plate 14 is completed, the propulsion device will continue to push the push plate 14 to move, and the moving push plate 14 will gradually move to the bottom of the heating device 12. When the push plate 14 moves to the position below the heating device 12, the heat generated by the heating device 12 will pass through the horizontal groove 26 below and sinter the material below. Since the limiting plates 32 on the adjacent baffles 31 fit each other, and the baffles 31 fit the heating chamber, the heat generated by the heating device 12 will directly enter between the two adjacent baffles 31, so that the material in the sagger 16 between the two baffles 31 can be sintered. When the material is sintered, the propulsion device will continue to push the push plate 14 to move. When the push plate 14 moves to the bottom of the cooling box 17, the cooling device can cool the material.

[0110] As a further embodiment of the present invention, since air pumps are installed in the three circulation bins, the air pumps in the three circulation bins will work during the process of preheating, sintering and cooling the materials, so that the gas above the three circulation bins can be first drawn into the three circulation bins through the inlet 22, and then the gas in the three circulation bins is respectively introduced into the preheating device 11, the heating device 12, and the cooling box 17 through the connecting pipe 28, so that the gas passing through the preheating zone, the heating zone and the cooling zone can be circulated. The gas circulating in the preheating device 11 and the first circulation bin 23 can circulate to preheat the materials, thereby reducing heat loss and improving the preheating effect of the materials. The gas circulating in the heating device 12 and the second circulation bin 24 can circulate to sinter the materials, thereby reducing heat loss and improving the sintering effect of the materials. The gas circulating in the cooling box 17 and the third circulation bin 25 can take away the heat in the materials, and then cool the materials again after being cooled by the gas cooling device, thereby improving the cooling efficiency of the materials.

[0111] Since the limiting plates 32 on adjacent baffles 31 on different push plates 14 fit together, and the baffles 31 fit together with the heating chamber, the heat generated by the preheating device 11 or the heating device 12 will enter between the two baffles 31 through the transverse groove 26, so that the material in the sagger 16 between the two baffles 31 can be preheated or sintered. The presence of the baffle 31 can limit the flow direction of the hot air to prevent the hot air from diffusing in the furnace body 1, thereby causing uneven temperatures in the preheating zone and heating zone areas in the furnace body 1, thereby causing uneven heating of the material, thereby reducing the preheating or sintering efficiency of the material. At the same time, the gas circulating in the cooling box 17 can continuously take away the heat from the material, thereby accelerating the cooling effect of the material.

[0112] As another embodiment of the push plate kiln of the present invention

[0113] Two extrusion plates 34 are fixedly connected to the opposite end faces of the two baffles 31 , and the tops of the extrusion plates 34 are rounded; the opposite sides of the two rectangular grooves 3 are provided with notches 35 on the push plate 14 , and the extrusion plates 34 slide in the notches 35 .

[0114] A support plate 36 is fixedly connected between two extrusion plates 34 on the same baffle 31 ; a mounting plate 37 is fixedly connected to one side of the sagger 16 located above and close to the support plate 36 , and the mounting plate 37 and the support plate 36 are arranged alternately.

[0115] In this embodiment, air grooves 38 are formed in the inner walls of the two baffles 31 , and the air grooves 38 extend to the top of the baffles 31 ; and air holes 39 are evenly arranged on the opposite side end surfaces of the two baffles 31 , and the air holes 39 are inclined downward.

[0116] In the above embodiment, the specific working principle is that when the baffle plate 31 gradually moves upward, the baffle plate 31 will also drive the extrusion plate 34 to move upward. Since the top of the extrusion plate 34 is designed with rounded corners, if the sagger 16 placed on the push plate 14 is not in the middle position of the push plate 14, the upward extrusion plate 34 will push the sagger 16 located between the two baffle plates 31 to move. When the sagger 16 is pushed to the middle position of the push plate 14, the upward extrusion plate 34 no longer pushes the sagger 16 to move. When the push plate 14 moves upward to the limit position, the sagger 16 is just between the opposite extrusion plates 34. At this time, the extrusion plate 34 can limit the sagger 16, thereby preventing the sagger 16 from tipping over in the process of following the movement of the push plate 14.

[0117] More specifically, since the support plate 36 is fixedly connected between the two extrusion plates 34 located on the same baffle 31, the support plate 36 will be driven to move upward during the upward movement of the extrusion plate 34. When the support plate 36 moves to the position of the mounting plate 37, the mounting plate 37 will be driven to move upward. At the same time, the mounting plate 37 will drive the upper sagger 16 to move upward, thereby separating the upper and lower saggers 16, thereby increasing the distance between the two saggers 16. When the gas circulates, the gas can easily enter the position between the two saggers 16, thereby enabling the flowing gas to better preheat, sinter or cool the material in the lower sagger 16.

[0118] Since the gas groove 38 opened in the inner wall of the baffle 31 penetrates the baffle 31 to the top of the baffle 31, the gas flowing out from the transverse groove 26 will enter the gas groove 38, and the gas entering the gas groove 38 will flow out through the evenly arranged air holes 39. Therefore, the outflowing gas can act on the side of the sagger 16, so that the material in the sagger 16 can be preheated, sintered or cooled evenly.

Claims

1. A method for preparing magnesium titanate with controllable particle size, characterized in that: The specific preparation steps are as follows: (1) Mixing magnesium oxide and rutile titanium dioxide in a molecular formula molar ratio uniformly, placing in a ball mill, adding deionized water for wet ball milling for 6-8 hours, and continuously adding to obtain a mixed slurry, wherein the concentration of the mixed slurry is 60-80% solid content; (2) Add 5-10%wt dispersant to the mixed slurry and continue ball milling for 2-3h to obtain a mixed solution; (3) placing the obtained mixed liquid into a dryer and drying it at 300°C to remove moisture and obtain a dry material; (4) Place the dried material in a sagger and then place it in a push plate kiln for pre-sintering for 2-3 hours. Set the sintering curve of the push plate kiln to 700-900°C. (5) Continue to increase the temperature of the push plate kiln for high-temperature sintering, the sintering temperature is 1250-1300℃, and keep warm for 2.5-3.5h; (6) Cooling and ball milling the sintered material again for 6 hours to finally obtain a magnesium titanate powder with a particle size distribution of 1-5 μm; The push plate kiln in step (4) comprises a furnace body (1), a heating system, a propulsion device and a control system; the furnace body (1) is divided into three areas: a preheating zone, a heating zone and a cooling zone; the top of the preheating zone is located above the furnace body (1) and is equipped with a preheating device (11); the top of the heating zone is located above the furnace body (1) and is equipped with a heating device (12); a heating chamber is provided in the furnace body (1); The furnace body (1) has rails (13) installed on both sides of the feed inlet, and the other side of the rail (13) passes through the furnace body (1) and extends from the discharge port of the furnace body (1); a push plate (14) is provided between the two rails (13) located in the heating chamber, and the push plate (14) slides in the rail (13) through a slider (15); two stacked saggers (16) are placed on the push plate (14); a propulsion device is installed on the rail (13) at the feed inlet of the furnace body (1), and the propulsion device is used to push the push plates (14) into the heating chamber in sequence; Two support seats (2) are installed at the bottom of the furnace body (1); a bottom plate (21) is installed between the two support seats (2); and evenly arranged inlets (22) are provided on the bottom plate (21); A cooling box (17) is installed on the furnace body (1) on the right side of the heating device (12), and a gas cooling device is installed in the cooling box (17); Three circulation chambers are installed below the bottom plate (21), namely a first circulation chamber (23), a second circulation chamber (24) and a third circulation chamber (25), and air pumps are installed in the three circulation chambers; The first circulation chamber (23) is aligned with the preheating device (11) and is in communication with the preheating device (11) via a connecting pipe (28); the second circulation chamber (24) is aligned with the heating device (12) and is in communication with the preheating device (11) via a connecting pipe (28); and the third circulation chamber (25) is aligned with the cooling device and is in communication with the preheating device via a connecting pipe (28); A transverse groove (26) is provided on the furnace body (1) below the preheating device (11), the heating device (12) and the cooling box (17); An inclined plate (27) is fixedly installed at the position of the feed inlet of the furnace body (1); The push plate (14) is provided with an auxiliary structure, and the auxiliary structure is used to assist the material in preheating, sintering and cooling; The auxiliary structure comprises a rectangular groove (3); The push plate (14) has two mutually parallel rectangular grooves (3) formed on its surface, and the rectangular grooves (3) penetrate the push plate (14) and are perpendicular to the slider (15); Baffles (31) are slidably connected to the two rectangular grooves (3); when the baffles (31) slide into the heating chamber, the baffles (31) fit the top and two side surfaces of the heating chamber; the length of the baffles (31) is greater than the length of the inlet (22) opened on the bottom plate (21); On opposite sides of the two baffles (31), a limiting plate (32) is installed on the top of each baffle (31); in an initial state, the baffle (31) is located below the push plate (14), and the bottom surface of the limiting plate (32) is in contact with the top surface of the push plate (14); Between the two baffles (31), two connecting plates (33) are fixedly connected to the bottom of the baffles (31).

2. The method for preparing magnesium titanate with controllable particle size according to claim 1, characterized in that: The magnesium oxide is micron-sized magnesium oxide powder.

3. The method for preparing magnesium titanate with controllable particle size according to claim 1, characterized in that: The dispersant is a polymer dispersant selected from polycarboxylic acid ammonium salt, acrylic resin, acrylic acid ammonium salt or PVA polyvinyl alcohol.

4. The method for preparing magnesium titanate with controllable particle size according to claim 1, characterized in that: The push plate kiln heating in step (4) and step (5) is carried out at a heating rate of 10°C / min.

5. The method for preparing magnesium titanate with controllable particle size according to claim 4, characterized in that: Two extrusion plates (34) are fixedly connected to the end surfaces of the two baffles (31) on opposite sides, and the tops of the extrusion plates (34) are both rounded; A notch (35) is provided on the push plate (14) at one side opposite to the two rectangular grooves (3), and the extrusion plates (34) slide in the notch (35); A support plate (36) is fixedly connected between the two extrusion plates (34) located on the same baffle (31); a mounting plate (37) is fixedly connected to one side of the sagger (16) located above and close to the support plate (36), and the mounting plate (37) and the support plate (36) are arranged in an alternating manner.

6. The method for preparing magnesium titanate with controllable particle size according to claim 5, characterized in that: An air groove (38) is provided in the inner wall of each of the two baffles (31), and the air groove (38) penetrates to the top of the baffle (31); The end surfaces of the two baffles (31) on one side opposite to each other are provided with evenly arranged air holes (39), and the air holes (39) are all inclined downward.

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