Coal gangue-based porous ceramic heat pipe wick and preparation method thereof
Patent Information
- Application Number
- CN202610947525.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-29
- Publication Date
- 2026-09-15
Smart Images
Figure CN122749166A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of coal gangue resource utilization technology, and relates to a coal gangue-based porous ceramic heat pipe liquid absorber core, its preparation method and application. Background Technology
[0002] Coal gangue is a large-scale industrial solid waste generated during coal mining and washing, with a huge annual emission volume in my country. Long-term stockpiling of coal gangue not only occupies vast amounts of land resources but also causes dust, water, and soil pollution, and can even spontaneously combust, releasing harmful gases, becoming a key bottleneck restricting the green development of the coal industry. Currently, the resource utilization of coal gangue is mainly concentrated in low-value-added areas such as building bricks, roadbed filling, and cement admixtures. The rich aluminosilicate mineral resources it contains have not been fully explored, resulting in extremely low high-value utilization rates.
[0003] Heat pipes, as highly efficient heat transfer elements, are widely used in electronic heat dissipation and industrial waste heat recovery due to their excellent thermal conductivity and isothermal properties. The capillary wick is the core functional component of a heat pipe, and its performance directly determines the heat transfer efficiency and service life of the heat pipe. Currently, commercially available wicks are mainly metal-based, which suffers from defects such as easy corrosion and poor high-temperature stability. While ceramic-based wicks offer excellent corrosion resistance, they often use high-purity powders such as alumina and silicon carbide as raw materials, resulting in high costs and complex manufacturing processes. They generally face a technical bottleneck where it is difficult to balance porosity and mechanical strength; high porosity often leads to insufficient strength, while pursuing strength sacrifices porosity and capillary performance. Summary of the Invention
[0004] In view of the defects and deficiencies in the existing technology, the purpose of this invention is to provide a porous ceramic heat pipe liquid absorber core based on coal gangue, which solves the problem of how to make high-value utilization of coal gangue, and at the same time solves the problems of high cost and difficulty in achieving both performance and efficiency of existing ceramic liquid absorber cores.
[0005] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:
[0006] A porous ceramic heat pipe wick based on coal gangue is made from raw materials comprising the following mass percentages: 44.8%~48.7% coal gangue, 34.0%~36.0% potassium feldspar, 9.0%~9.7% calcium-based bentonite, 0.9%~1.1% silicon carbide, and 6.5%~9.7% sodium bicarbonate, wherein sodium bicarbonate is used as a pore-forming agent, silicon carbide is used as a reinforcing phase, and calcium-based bentonite is used as a binder.
[0007] Preferably, the chemical composition of the coal gangue satisfies the following: SiO2 content 50%~55%, Al2O3 content 17%~20%, Fe2O3 content 3%~8%, CaO content 1%~3%, MgO content 0.5%~2%, and loss on ignition 14%~18%.
[0008] Preferably, the raw materials are: coal gangue 46.0%, potassium feldspar 35.0%, calcium-based bentonite 9.2%, silicon carbide 0.9%, and sodium bicarbonate 8.9% by mass.
[0009] Preferably, the porosity of the liquid-absorbing core is 50%~73%, and the compressive strength is 0.8MPa~2.2MPa.
[0010] A method for preparing a coal gangue-based porous ceramic heat pipe wick, as disclosed in this application, includes the following steps: S1 Ingredient Mixing: Weigh out coal gangue, potassium feldspar, calcium-based bentonite, silicon carbide and sodium bicarbonate by mass percentage, mix them evenly to obtain coal gangue-based porous ceramic precursor material; S2 Drying: Dry the precursor material to a moisture content of ≤2%; S3 molding: The dried precursor material is placed in the mold and cold-pressed. The pressure is held at 15~25MPa for 10~15min. After demolding, the green body is obtained. S4 sintering: Sintering the green body; The sintering process is as follows: first, the temperature is raised to 600℃ at a heating rate of 5℃ / min to 8℃ / min and held for 0.5h; then, the temperature is raised to 850℃ at a heating rate of 2℃ / min to 4℃ / min and held for 1h; and then cooled to room temperature with the furnace to obtain the liquid-absorbing core of the porous ceramic heat pipe based on coal gangue.
[0011] Preferably, in S1, the particle size of both coal gangue and potassium feldspar is ≤150μm; and the particle size of silicon carbide is ≤5μm.
[0012] Preferably, in S3, the cold pressing process specifically adopts a gradient pressurization mode: the pressure starts from 5MPa, increases to 15~25MPa at a rate of 2MPa / min, holds for 10~15min, and then depressurizes at a rate of 1MPa / min.
[0013] Preferably, in S4, the heating rate is: heating to 600°C at 6°C / min, and heating to 850°C at 3°C / min.
[0014] Preferably, in S4, sintering is carried out in an air atmosphere, the green blank is placed in a crucible, and high-temperature cotton is placed at the contact point between the green blank and the crucible, and then the crucible is placed in a muffle furnace.
[0015] The application of a coal gangue-based porous ceramic heat pipe wick in a heat pipe, wherein the coal gangue-based porous ceramic heat pipe wick is the coal gangue-based porous ceramic heat pipe wick disclosed in this application or a coal gangue-based porous ceramic heat pipe wick prepared by the preparation method disclosed in this application.
[0016] The above technical solution has the following beneficial effects: (1) It realizes the high-value utilization of solid waste and greatly reduces the cost of raw materials; using bulk industrial solid waste coal gangue as the main raw material to replace traditional high-purity chemical raw materials, it brings significant economic benefits while solving environmental pollution problems.
[0017] (2) The porosity and mechanical strength were synergistically optimized. Through the synergistic effect of specific raw materials (potassium feldspar flux, silicon carbide reinforcement, sodium bicarbonate pore-forming) and precise control of the segmented sintering process, the technical problem of balancing the porosity and strength of porous ceramics was successfully solved. The resulting liquid-absorbing core has both excellent capillary suction ability and structural stability.
[0018] (3) The one-step sintering method is adopted, which completes the decomposition of the pore-forming agent and the densification of the ceramic in the same heat treatment process. There is no need for complicated pre-firing and debinding or post-treatment. The process is short, the energy consumption is low, and it meets the requirements of green manufacturing.
[0019] (4) The obtained ceramic liquid absorber has excellent corrosion resistance and high temperature resistance. It can be used with a variety of working fluids such as water and alcohol. It can be widely used in various thermal management scenarios such as heat dissipation of electronic devices and industrial waste heat recovery. The product has wide applicability and good engineering application prospects. Attached Figure Description
[0020] Figure 1 This is a schematic flowchart illustrating the preparation of coal gangue-based liquid-absorbing cores using a pore-forming agent method according to the present invention.
[0021] Figure 2 SEM images of coal gangue-based liquid-absorbing cores with different raw material ratios according to the present invention.
[0022] Figure 3 This is the XRD pattern of the raw materials used in this invention.
[0023] Figure 4 The XRD patterns of the coal gangue-based liquid-absorbing cores under different raw material ratios according to the present invention are shown.
[0024] Figure 5 Images showing the water absorption performance and porosity of the coal gangue-based liquid-absorbing core under different raw material ratios according to the present invention.
[0025] Figure 6 Images showing the compressive strength of the coal gangue-based liquid-absorbing core under different raw material ratios according to the present invention.
[0026] Figure 7 This is a photograph of the liquid-absorbing core of the porous ceramic heat pipe based on coal gangue prepared in Example 1 of the present invention.
[0027] Figure 8 This is a photograph of the coal gangue-based porous ceramic heat pipe liquid-absorbing core prepared in Example 2 of the present invention.
[0028] Figure 9 This is a photograph of the coal gangue-based porous ceramic heat pipe liquid-absorbing core prepared in Example 3 of the present invention.
[0029] Figure 10 This is a photograph of the coal gangue-based porous ceramic heat pipe liquid-absorbing core prepared in Example 4 of the present invention.
[0030] Figure 11 This is a photograph of the coal gangue-based porous ceramic heat pipe liquid-absorbing core prepared in Example 5 of the present invention.
[0031] The specific content of the present invention will be further explained in detail below with reference to comparative examples. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0033] The raw materials used in the embodiments of this invention are all industrial-grade conventional raw materials, and their source and specifications have no special limitations on the implementation of this invention. Coal gangue needs to be crushed, ground, and sieved through a 100-mesh sieve before use, and dried to a moisture content ≤2%. Potassium feldspar is sieved through a 100-mesh sieve for later use. Silicon carbide is selected as micro powder with a particle size ≤5μm.
[0034] Example 1 This embodiment provides a coal gangue-based porous ceramic heat pipe wick, with the following raw material mass percentages: coal gangue 46.0%, potassium feldspar 35.0%, calcium-based bentonite 9.2%, silicon carbide 0.9%, and sodium bicarbonate 8.9%.
[0035] Table 1. Chemical composition of raw materials (wt.%)
[0036] The preparation method of this embodiment includes the following steps: S1 Ingredient Mixing: Weigh each raw material according to the above mass percentage, put them into a planetary ball mill, use zirconia balls as the grinding medium (ball-to-material ratio 3:1), dry mix at 900 r / min for 3 h to obtain a uniformly mixed coal gangue-based porous ceramic precursor material; S2 Drying: The precursor material was placed in a 50℃ forced-air drying oven and dried for 10 hours. The moisture content of the material after drying was 1.8%, which meets the requirement of ≤2%. S3 molding: The dried precursor material is injected into a special mold for heat pipe liquid absorbing core with an inner diameter of 10mm and a length of 100mm. The gradient pressure cold pressing molding process is adopted: the pressure starts from 5MPa, increases to 20MPa at a rate of 2MPa / min, holds the pressure for 12min, and then slowly releases the pressure at a rate of 1MPa / min. The molded green blank is obtained without cracks or deformation, and the dimensional accuracy error of the green blank is ≤±0.2mm. S4 sintering: The green body is placed in a corundum crucible, and a 1 mm thick layer of high-temperature ceramic fiber cotton is laid at the contact point between the green body and the crucible. Then the crucible is placed in a muffle furnace and sintered in sections under an air atmosphere: first, the temperature is raised to 600℃ at a heating rate of 6℃ / min and held for 0.5 h; then the temperature is raised to 850℃ at a heating rate of 3℃ / min and held for 1 h; after the holding period, the furnace is allowed to cool naturally to room temperature. After the furnace is removed, the high-temperature cotton fiber attached to the surface is removed to obtain the liquid absorber core of the porous ceramic heat pipe based on coal gangue.
[0037] Performance test results: like Figure 2 As shown, the microstructure of the sample's pores was observed using scanning electron microscopy. Detailed SEM images are attached. Figure 2 (a), 2(b), 2(c); Figure 2 (a) shows the high-magnification microstructure, where a large number of interconnected open pores are formed inside the sample, the particles are tightly bonded together, and the pore walls are intact without obvious cracks or collapse. Figure 2 (b) is a medium magnification overall view, showing a uniform overall pore distribution without localized dense agglomerates, and excellent pore connectivity. The overall microstructure balances fluid flow capacity and material mechanical strength. Figure 2 (c) shows the low-magnification overall morphology. Under the large field of view, the microstructure of the sample is uniform, with no pore-rich areas or dense islands, and a complete three-dimensional interconnected pore network that runs through the matrix is constructed.
[0038] like Figure 3 As shown, Figure 3 XRD diffraction patterns of three raw materials: coal gangue, potassium feldspar, and calcium-based bentonite. The diffraction curve of coal gangue shows that its main phases are kaolinite and highly crystalline quartz. Kaolinite can react at high temperatures to form mullite, ensuring the mechanical properties of the ceramic, while quartz acts as a rigid framework phase to improve sintering stability. The characteristic diffraction peaks of potassium feldspar correspond to sodium feldspar and microcline. This feldspar system can generate a liquid phase during the intermediate-temperature sintering stage, acting as a flux and binder. Calcium-based bentonite shows characteristic diffraction peaks of montmorillonite at 2θ≈10°, with a small amount of associated quartz impurity peaks having low intensity. The mineral components of the three raw materials are complementary in function, and there are no harmful impurity crystalline phases. Using them together can balance the plasticity of the green body, low-temperature sintering performance, and post-firing mechanical strength, making them suitable for porous ceramic preparation systems.
[0039] like Figure 4As shown in the spectrum, albite (peak 2) has the highest diffraction intensity, while aluminosilicate (peak 3) has the weakest diffraction signal. The data indicate that the high proportion of feldspar flux in the system demonstrates strong low-temperature liquid-phase generation capability, which can reduce sintering temperature and save energy consumption. The moderate intensity of the quartz peak indicates a harmonious ratio between the rigid framework and the liquid-phase binder, making the green body less prone to cracking during sintering. However, the low mullite formation suggests room for improvement in the material's mechanical properties and high-temperature resistance.
[0040] like Figure 5 As shown, the Archimedes drainage method was used to test the porosity of the sample, and the total porosity was measured to be 56.25%. like Figure 6 The room temperature compressive strength of the sample was determined using a universal pressure testing machine. The maximum compressive strength of the sample was 2.167 MPa. As shown in Table 3, the maximum load on the sample was 2.655 kN.
[0041] The technical advantages of this sample lie in its well-connected open-pore structure, uniform pore distribution, intact and robust pore walls, and tight particle bonding, which simultaneously ensures efficient fluid flow and structural mechanical strength. The complementary advantages of the raw material mineral components result in excellent green body formability, outstanding low-temperature sintering capability, effectively reduced production energy consumption, and reduced cracking issues during sintering, leading to superior overall performance.
[0042] Example 2 This embodiment provides a coal gangue-based porous ceramic heat pipe wick, with the following raw material mass percentages: coal gangue 44.8%, potassium feldspar 35.5%, calcium-based bentonite 9.0%, silicon carbide 1.0%, and sodium bicarbonate 9.7%.
[0043] The preparation method of this embodiment includes the following steps: S1 Ingredient Mixing: Weigh each raw material according to the above mass percentage, place them in a mixing device and dry mix for 4 hours until uniformly mixed to obtain coal gangue-based porous ceramic precursor material; S2 Drying: The precursor material was placed in an air drying oven and dried at 60℃ for 8 hours. The moisture content of the dried material was 1.5%, which meets the requirement of ≤2%. S3 molding: The dried precursor material is injected into a special mold for the heat pipe wick, and a cold pressing process is used. The material is held under 15MPa pressure for 15 minutes and then demolded to obtain a green blank. S4 sintering: The green body is placed in a corundum crucible, and high-temperature cotton is laid at the contact point between the green body and the crucible. Then the crucible is placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min and held for 0.5h. Then the temperature is increased to 850°C at a heating rate of 2°C / min and held for 1h. The furnace is then cooled to room temperature to obtain a coal gangue-based porous ceramic heat pipe liquid absorber core.
[0044] Performance test results: like Figure 2 As shown, the microstructure of the sample's pores was observed using scanning electron microscopy. Detailed SEM images are attached. Figure 2 (d), 2(e), 2(f); Figure 2 (d) shows the high-magnification microstructure, where the raw material particles are sintered to form a continuous bonding phase, the particle interface is firmly bonded, and multi-level interconnected pores are generated inside the matrix. The pore walls are regular and complete, without structural defects such as cracks or collapsed pores. Figure 2 (e) shows the cross-sectional morphology under medium magnification. The sample contains both small micropores and medium-sized pores, with a gradient distribution of pore size, no local accumulation or blockage of pores, and a high degree of cross-connection of pores. Figure 2 (f) shows the low-magnification overall morphology. The cross-section of the sample is uniformly dense, with no large-area dense agglomerates, and a continuous and interconnected three-dimensional pore network is formed throughout the entire area.
[0045] like Figure 4 As shown, clear diffraction peaks were observed in all three crystal phases of this sample: quartz, albite, and aluminosilicate. The test data indicates that the high-temperature transformation reaction of kaolinite to mullite was more complete under this formulation, increasing the formation of high-strength aluminosilicate crystal phases, which enhances the matrix's mechanical support capacity. The moderate intensity of the feldspar diffraction peaks provides a binding liquid phase, ensuring strong interparticle bonding.
[0046] like Figure 5 As shown, the Archimedes drainage method was used to test the porosity of the sample, and the total porosity was measured to be 64.32%. like Figure 6 The compressive strength at room temperature was determined using a universal pressure testing machine, and the maximum compressive strength of the sample was 1.732 MPa. As shown in Table 3, the maximum load on the sample was 2.123 kN.
[0047] The technical advantages of this sample are its well-developed and uniformly distributed pores, good internal channel connectivity, excellent air permeability, heat insulation, and sound insulation capabilities, stable particle bonding, and strong structural reliability. The raw material composition is rationally matched, resulting in good low-temperature sintering performance, low production energy consumption, and resistance to cracking during sintering, achieving a good balance between porous functionality and structural stability.
[0048] Example 3 This embodiment provides a coal gangue-based porous ceramic heat pipe wick, with the following raw material mass percentages: coal gangue 48.7%, potassium feldspar 34.0%, calcium-based bentonite 9.7%, silicon carbide 1.1%, and sodium bicarbonate 6.5%.
[0049] The preparation method of this embodiment includes the following steps: S1 Ingredient Mixing: Weigh each raw material according to the above mass percentage, place them in a mixing device and dry mix for 2 hours until uniformly mixed to obtain coal gangue-based porous ceramic precursor material; S2 Drying: The precursor material was placed in an air drying oven and dried at 55℃ for 9 hours. The moisture content of the material after drying was 1.9%, which meets the requirement of ≤2%. S3 molding: The dried precursor material is injected into a special mold for the heat pipe wick, and a cold pressing process is used. The material is held under pressure of 25MPa for 10 minutes and then demolded to obtain a green blank. S4 sintering: The green body is placed in a corundum crucible, and high-temperature cotton is laid at the contact point between the green body and the crucible. Then the crucible is placed in a muffle furnace and heated to 600°C at a heating rate of 8°C / min and held for 0.5 h. Then the temperature is increased to 850°C at a heating rate of 4°C / min and held for 1 h. The furnace is then cooled to room temperature to obtain a coal gangue-based porous ceramic heat pipe liquid absorber core.
[0050] Performance test results: like Figure 2 As shown, the microstructure of the sample's pores was observed using scanning electron microscopy. Detailed SEM images are attached. Figure 2 (g), 2(h), 2(i); Figure 2 (g) has a high magnification microstructure, the powder particles are highly integrated by sintering, the matrix has abundant interconnected pores, the pore walls are dense without obvious microcracks, the pore boundaries are regular, and there is no local structural collapse. Figure 2 (h) shows the medium magnification cross-sectional morphology, with uniform pore distribution, no continuous large closed pores, a high proportion of open through-holes, and a stable and reliable particle-supported skeleton. Figure 2 (i) Low magnification overall morphology, the microstructure of the material is uniform and consistent under a large field of view, the pore network runs through the entire observation section, and there are no local dense non-porous areas.
[0051] like Figure 4 As shown, the diffraction peaks of the quartz, albite, and aluminosilicate phases in this sample are balanced and clear, with no single phase diffraction peak being excessively prominent or missing. The test data indicates that this formulation can simultaneously exert the triple effects of quartz framework stabilization, albite low-temperature fluxing, and aluminosilicate matrix strengthening. The crystalline phase composition is rationally matched, and the material's mechanical properties and sintering processing performance are well-suited.
[0052] like Figure 5 As shown, the Archimedes drainage method was used to test the porosity of the sample, and the total porosity was measured to be 50.31%. like Figure 6 The compressive strength at room temperature was determined using a universal pressure testing machine, and the maximum compressive strength of the sample was 1.036 MPa. As shown in Table 3, the maximum load on the sample was 1.270 kN.
[0053] The technical advantages of this sample include a dense and regular pore structure, outstanding impermeability and waterproofing, and adaptability to humid environments. It also exhibits excellent synergy between raw materials, resulting in superior molding performance, strong sintering stability, effectively reducing production defects, a robust overall structure, and good long-term stability.
[0054] Example 4 This embodiment provides a coal gangue-based porous ceramic heat pipe wick, with the following raw material mass percentages: coal gangue 46.0%, potassium feldspar 35.0%, calcium-based bentonite 9.0%, silicon carbide 0.9%, and sodium bicarbonate 9.1%. Other preparation methods are completely consistent with Example 1.
[0055] like Figure 2 As shown, the microstructure of the sample's pores was observed using scanning electron microscopy. Detailed SEM images are attached. Figure 2 (j), 2(k), 2(l); Figure 2 (j) shows the high-magnification microstructure. After sintering, the interparticle bonding layer is continuous and complete, and a large number of interconnected open channels are formed inside. The pore wall structure is complete and there are no defects such as cracking, collapse, or pore collapse. Figure 2 (k) is the medium magnification section morphology, with a wide range of pore sizes, alternating distribution of large and small pores, uniform pore dispersion, no local dense areas of particle agglomeration, and good connectivity of open pores; Figure 2 (l) is a low-magnification overall morphology. The microstructure of the overall cross section of the sample has no obvious partitions. The three-dimensional through-holes are evenly spread inside the matrix, and the skeleton is continuous without large-area fracture defects.
[0056] like Figure 4 As shown, the intensity of the characteristic diffraction peaks of aluminosilicate in this sample was further enhanced, while the diffraction signal of albite was moderately weakened. The test data indicate that the mullite crystalline phase content in the system continued to increase, fully demonstrating the excellent high-temperature resistance and thermal shock resistance properties of mullite; the quartz diffraction peaks showed no abnormal increase, indicating that particle bonding could be achieved without increasing the sintering temperature, and the suitable sintering process temperature range was wider.
[0057] like Figure 5 As shown, the Archimedes drainage method was used to test the porosity of the sample, and the total porosity was measured to be 72.39%. like Figure 6 The compressive strength at room temperature was determined using a universal pressure testing machine, and the maximum compressive strength of the sample was 0.857 MPa. As shown in Table 3, the maximum load on the sample was 1.05 kN.
[0058] The technical advantages of this sample are its highly developed pore structure, excellent pore connectivity, and outstanding fluid throughput, heat preservation, and filtration performance. The raw material has a significant fluxing effect, reducing sintering energy consumption, minimizing cracking during the molding process, and exhibiting prominent lightweight and porous characteristics, resulting in significant functional application advantages.
[0059] Example 5 This embodiment provides a coal gangue-based porous ceramic heat pipe wick, with the following raw material mass percentages: coal gangue 46.8%, potassium feldspar 36.0%, calcium-based bentonite 9.5%, silicon carbide 1.0%, and sodium bicarbonate 6.7%. Other preparation methods are completely consistent with Example 1.
[0060] like Figure 2 As shown, the microstructure of the sample's pores was observed using scanning electron microscopy. Detailed SEM images are attached. Figure 2 (m), 2(n), 2(o); Figure 2 (m) shows the high-magnification microstructure, with the powder particles tightly bonded by sintering. A large number of continuous interconnected pores are generated inside the matrix, with smooth and complete pore walls, and no structural defects such as microcracks, pore collapse, or interface peeling. Figure 2 (n) is the medium magnification cross-sectional morphology, with micron-level open pores uniformly distributed throughout the entire area, the pores interpenetrating and interconnected, without local dense agglomerates blocking the channels, and the particle support skeleton is complete. Figure 2 (o) shows the low-magnification overall morphology. Under the large field of view, the material cross-section has a uniform structure, and the three-dimensional through-hole network is continuous and complete, with no local dense, non-porous island areas.
[0061] like Figure 4 The diffraction peaks of aluminosilicate in this sample are the strongest among all samples in this group, while the diffraction peak signal of albite is the weakest, with only a small number of quartz diffraction peaks present. The test data indicate that mullite is the dominant crystalline phase in this sample. Mullite crystals have strong bonding and high-temperature structural stability, which can endow the sample with optimal compressive strength and long-term high-temperature service performance. No low-melting-point harmful impurities were detected in the spectra, and the phase structure is not prone to phase transformation and deterioration under high-temperature conditions.
[0062] like Figure 5 As shown, the Archimedes drainage method was used to test the porosity of the sample, and the total porosity was measured to be 65.26%. like Figure 6 The compressive strength at room temperature was determined using a universal pressure testing machine, and the maximum compressive strength of the sample was 1.526 MPa. As shown in Table 3, the maximum load on the sample was 1.87 kN.
[0063] Table 3. Compressive strength of coal gangue-based liquid absorbent cores with different raw material ratios
[0064] The technical advantages of this sample are its uniform micropore distribution, intact pore walls, tight particle bonding, and balanced performance across various aspects. The raw material system exhibits excellent molding and sintering properties, good energy consumption control, and the finished product is less prone to cracking. It is suitable for a variety of applications and possesses strong overall practicality.
[0065] Example 6 This embodiment aims to evaluate the core performance potential of the wicking core of the present invention in heat pipe applications and verify its practical advantages as a heat pipe wicking core. The coal gangue-based porous ceramic wicking core prepared by the present invention has a well-developed and interconnected open-pore structure with uniformly distributed capillary channels, exhibiting excellent water absorption performance and capillary suction capability. It can effectively achieve rapid wetting and stable reflux of the working fluid, providing a fundamental guarantee for efficient heat transfer in heat pipes. Compared with commercial copper-based wicking cores and high-purity alumina-based ceramic wicking cores, the wicking core of the present invention, while possessing excellent water absorption and capillary performance, also has advantages such as high temperature resistance, corrosion resistance, and structural stability. Moreover, using industrial solid waste coal gangue as the main raw material, the preparation cost is significantly reduced, showing good application prospects and practical value in the field of heat pipe heat transfer.
[0066] Comparative Example Comparative examples are the core evidence to prove the inventiveness of this invention. They need to be designed using the principle of a single variable and make a precise comparison with the technical solution of this invention to prove that the technical features of this invention are not a simple combination of existing technologies and have achieved unexpected technical effects. They solve the technical pain points of existing technologies that have long existed, such as the difficulty in balancing porosity and mechanical strength, high raw material costs, and low solid waste utilization.
[0067] 1. Comparative examples of missing / replaced key components Potassium feldspar was missing; the missing potassium feldspar was replaced with an equal amount of coal gangue, otherwise the results were the same as in Example 1. The sintering liquid phase of the sample was insufficient, resulting in severe cracking of the green body and poor pore connectivity. In the comparative example (without silicon carbide), there was no silicon carbide, and the missing silicon carbide was replaced with an equal amount of potassium feldspar. The rest was the same as in Example 1. The results are shown in Table 2. The porosity of the sample was 78.87%, the water absorption was 39.97%, the high temperature thermal shock resistance and corrosion resistance of the sample were significantly deteriorated, and the compressive strength decreased significantly. The sample was missing sodium bicarbonate and was replaced with an equal amount of silicon carbide. The rest was the same as in Example 1. The sample could not be sintered into a block and was in powder form after sintering.
[0068] 2. Component content exceeds the range (comparative example) In the comparative example (10% coal gangue), the coal gangue content was 10% (lower than the lower limit of 44.8% in claim 1), and the remaining components were adjusted proportionally. As shown in Table 2, the porosity of this comparative example sample was significantly lower. Although the water absorption rate was low, the porous characteristics were greatly weakened, resulting in insufficient thermal insulation, sound insulation, and fluid permeability. It could not meet the core functional requirements of this patent for porous ceramics, and its overall adaptability was poor.
[0069] Table 2. Properties of foamed ceramics with different raw material ratios
[0070] In the comparative example (10% potassium feldspar), the potassium feldspar content was 10% (lower than the lower limit of 34.0% in claim 1), and the remaining components were adjusted proportionally. As shown in Table 2, although this comparative example sample has a high porosity, its raw material ratio deviates from the range defined in this patent, resulting in insufficient overall mechanical properties and long-term stability. It is difficult to ensure sufficient structural strength while maintaining high porosity, thus limiting its practical application scenarios.
[0071] 3. Process parameters out of range (comparison sample) At a sintering temperature of 700℃, and otherwise consistent with Example 5, the sample could not be sintered into a block and remained in powder form. In the comparative example (Example 5 raw material) sample sintered at -925℃, with the sintering temperature at 925℃ and otherwise consistent with Example 5, the results are shown in Table 2. The porosity of the sample was 46.47%, and the water absorption rate was 12.8%. The porosity decreased to a certain extent, and the water absorption rate decreased significantly. 4. Comparison of Existing Technologies Existing technologies employ heat pipe enhanced heat transfer technology using Al2O3 nanoparticles combined with acetone and deionized water-based liquid to prepare heat pipe wicks, coupled with traditional high-temperature sintering processes, to produce heat pipe wicks with an inner diameter of 10 mm and a length of 100 mm. Example 1 of this invention uses a composite raw material system mainly composed of coal gangue, potassium feldspar, and calcium-based bentonite, combined with silicon carbide and sodium bicarbonate. Through planetary ball milling, low-temperature drying, gradient cold pressing, and segmented low-temperature sintering processes, porous ceramic heat pipe wicks of the same specifications (inner diameter 10 mm, length 100 mm) are prepared. The two types of wicks are now compared and analyzed from five dimensions: raw material cost, sintering temperature, porosity, compressive strength, and corrosion resistance.
[0072] Raw material cost comparison: Existing technologies use high-purity Al2O3 powder as the core raw material. Alumina powder is difficult to purify and has a high market price, resulting in high raw material procurement and pretreatment costs. The raw material formula (mass fraction) in this embodiment is: coal gangue 46.0%, potassium feldspar 35.0%, calcium-based bentonite 9.2%, silicon carbide 0.9%, and sodium bicarbonate 8.9%. Coal gangue is industrial solid waste and can be utilized at low cost. Potassium feldspar and calcium-based bentonite are both readily available and inexpensive non-metallic minerals, with only trace amounts of functional additives added. Compared to Al2O3-based ceramic absorbent cores, the overall raw material cost of this invention is reduced by more than 42%, demonstrating significant advantages in resource utilization and economics.
[0073] Sintering Temperature Comparison: Existing Al2O3 ceramic liquid absorber sintering processes require stringent conditions, with conventional sintering temperatures generally reaching 1200℃ or higher. High-temperature operation not only consumes enormous amounts of energy but also places high demands on sintering equipment and furnace materials. Example 1 employs a segmented low-temperature sintering process: first, the temperature is increased to 600℃ at a rate of 6℃ / min and held for 0.5 hours; then, the temperature is increased to 850℃ at a rate of 3℃ / min and held for 1 hour; finally, the furnace is allowed to cool naturally. This invention achieves a maximum sintering temperature that is more than 350℃ lower than that of the Al2O3-based liquid absorber core, significantly reducing sintering energy consumption, lowering investment and maintenance costs for production equipment, and making the production process easier to implement and mass-produce.
[0074] Porosity Comparison: Porosity is a core indicator of heat pipe wicks, directly affecting the transport efficiency of Al2O3 nanofluids and the overall heat transfer performance of the heat pipe. Existing dense Al2O3 ceramic wicks have low porosity, generally below 60%, with limited pore connectivity. The porous ceramic wick prepared in this invention achieves a porosity of 65.26%, with well-developed internal pores and a high proportion of interconnected channels. The porosity of this invention is significantly superior to that of Al2O3-based ceramic wicks, ensuring rapid and stable flow of acetone-based and water-based Al2O3 nanofluids within the wick, perfectly suited for the two-phase flow heat transfer conditions of parallel flat plate heat pipes.
[0075] Compressive strength comparison: Compressive strength determines the structural stability and service life of the wick under assembly, vibration, and temperature alternation conditions. In this embodiment, the finished product has a compressive strength of 1.526 MPa, the dimensional error of the green body after molding is ≤±0.2 mm, and the finished product is free of cracks and deformation, exhibiting good structural integrity. Existing Al2O3 ceramic wicks of the same specifications have a compressive strength range of 1.4~1.6 MPa. The compressive strength of this invention is comparable to that of Al2O3-based wicks, fully meeting the mechanical requirements for heat pipe assembly and long-term service, and effectively preventing cracking and collapse during use.
[0076] Corrosion Resistance Comparison: This liquid absorber is applied to an Al2O3 nanofluid parallel flat plate heat pipe, which is in long-term contact with working fluids such as acetone and deionized water, and is subjected to alternating temperature environments, thus requiring high corrosion resistance. While existing pure Al2O3 ceramics are chemically stable, the single alumina material is prone to interfacial micro-deterioration under long-term immersion in organic working fluids; the matrix of this invention is SiO2. The Al2O3 composite aluminosilicate system, combined with silicon carbide modification, exhibits enhanced resistance to water and acetone corrosion, as well as outstanding anti-aging and anti-corrosion properties. This invention demonstrates superior corrosion resistance compared to traditional Al2O3 ceramic wicks, effectively preventing pore blockage and material pulverization, thus ensuring long-term stable operation of the heat pipe.
[0077] The above-described embodiments are merely preferred embodiments of the present invention and are not limited to the present invention. The coal gangue-based porous ceramic heat pipe liquid-absorbing core and its preparation method of the present invention are not limited to the above-described specific embodiments. The present invention can be used as a low-infrared emissivity material for infrared stealth, a photocatalytic material, etc. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention that do not depart from the technology of the present invention and are applied to any field constitute an infringement of the protection scope of the present invention and are included within the protection scope of the present invention.
Claims
1. A coal gangue-based porous ceramic heat pipe wick, characterized in that, Made from raw materials comprising the following percentages by weight: The composition includes 44.8%~48.7% coal gangue, 34.0%~36.0% potassium feldspar, 9.0%~9.7% calcium-based bentonite, 0.9%~1.1% silicon carbide, and 6.5%~9.7% sodium bicarbonate, wherein the sodium bicarbonate is used as a pore-forming agent, the silicon carbide is used as a reinforcing phase, and the calcium-based bentonite is used as a binder.
2. The coal gangue-based porous ceramic heat pipe liquid absorber core according to claim 1, characterized in that, The chemical composition of the coal gangue is as follows: SiO2 content 50%~55%, Al2O3 content 17%~20%, Fe2O3 content 3%~8%, CaO content 1%~3%, MgO content 0.5%~2%, and loss on ignition 14%~18%.
3. The coal gangue-based porous ceramic heat pipe liquid absorber core according to claim 1 or 2, characterized in that, The raw materials are as follows by mass percentage: coal gangue 46.0%, potassium feldspar 35.0%, calcium-based bentonite 9.2%, silicon carbide 0.9%, and sodium bicarbonate 8.9%.
4. The coal gangue-based porous ceramic heat pipe liquid absorber core according to claim 1 or 2, characterized in that, The liquid-absorbing core has a porosity of 50% to 73% and a compressive strength of 0.8 MPa to 2.2 MPa.
5. A method for preparing a coal gangue-based porous ceramic heat pipe wick as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1 Ingredient Mixing: Weigh out coal gangue, potassium feldspar, calcium-based bentonite, silicon carbide and sodium bicarbonate by mass percentage, mix them evenly to obtain coal gangue-based porous ceramic precursor material; S2 Drying: Dry the precursor material to a moisture content of ≤2%; S3 molding: The dried precursor material is placed in the mold and cold-pressed. The pressure is held at 15~25MPa for 10~15min. After demolding, the green body is obtained. S4 sintering: The green blank is sintered; The sintering process is as follows: first, the temperature is raised to 600℃ at a heating rate of 5℃ / min to 8℃ / min and held for 0.5h; then, the temperature is raised to 850℃ at a heating rate of 2℃ / min to 4℃ / min and held for 1h; and then cooled to room temperature in the furnace to obtain the coal gangue-based porous ceramic heat pipe liquid absorber core.
6. The preparation method according to claim 5, characterized in that, In S1, the particle size of the coal gangue and potassium feldspar is ≤150μm; the particle size of the silicon carbide is ≤5μm.
7. The preparation method according to claim 5, characterized in that, In S3, the cold pressing process specifically adopts a gradient pressurization mode: the pressure starts from 5MPa, increases to 15~25MPa at a rate of 2MPa / min, holds for 10~15min, and then depressurizes at a rate of 1MPa / min.
8. The preparation method according to claim 5, characterized in that, In S4, the heating rate is: heating to 600°C at 6°C / min, and heating to 850°C at 3°C / min.
9. The preparation method according to claim 5, characterized in that, In S4, the sintering is carried out in an air atmosphere. The green blank is placed in a crucible, and high-temperature cotton is placed at the contact point between the green blank and the crucible. Then the crucible is placed in a muffle furnace.
10. The application of a coal gangue-based porous ceramic heat pipe wick in a heat pipe, wherein the coal gangue-based porous ceramic heat pipe wick is the coal gangue-based porous ceramic heat pipe wick as described in any one of claims 1 to 4 or the coal gangue-based porous ceramic heat pipe wick prepared by the preparation method described in any one of claims 5 to 9.