High-precision and high-strength ink-jet 3D printing cement-based material as well as preparation method and use method thereof

Abstract

The invention discloses a high-precision high-strength ink-jet 3D printing cement-based material and a preparation method and a use method thereof, the material comprises a powder material and ink, the powder material comprises, by weight, 10-50 parts of dead burned MgO powder, 5-30 parts of phosphate powder, 10-20 parts of polymer powder, 10-30 parts of nanometer filling powder, and 30-100 parts of precision strength improving components; and the precision strength improving component is composed of citric acid powder and sodium silicate powder, and the citric acid powder and the sodium silicate powder have a synergistic effect, so that common insufficient strength and forming precision deviation in ink-jet 3D printing can be improved. The polymer powder comprises polyvinyl alcohol powder and ethylene-vinyl acetate rubber powder, and the polyvinyl alcohol powder and the ethylene-vinyl acetate rubber powder have a synergistic effect to improve the interlayer bonding quality and reduce the size error, so that the forming precision and the performance stability of an ink-jet 3D printed part are improved. The nano-scale particles effectively fill pores of the cement-based material, so that the micro-scale density is improved. Through cooperation of all the components in the powder material and the ink formula, the forming precision and the mechanical strength of a 3D printing test piece are finally effectively improved.

Description

Technical Field

[0001] This invention relates to the field of inkjet 3D printing cement-based materials technology, specifically to high-precision and high-strength inkjet 3D printing cement-based materials, their preparation methods, and usage methods. The cement-based materials are used for the fabrication and research of complex components and for applications in decorative products. Background Technology

[0002] With the widespread application of 3D printing technology in architecture, landscape, and integrated structural components, inkjet 3D printing, an advanced additive manufacturing process, has the following core process: First, a layer of powder material is evenly laid on the printing platform. Next, based on the pre-designed 3D model information, binder is precisely sprayed onto specific locations within the powder layer. The sprayed binder causes the contacting powder particles to bond together and gradually harden, forming a thin layer of the model. Subsequently, the printing platform is lowered to a certain height, and a new layer of powder is laid, repeating the binder spraying process. This layer-by-layer stacking process ultimately constructs the desired 3D object. Traditional silicate cement, due to its long setting time, low early strength, and large shrinkage, cannot meet the requirements of inkjet 3D printing for rapid curing, high early strength, and dimensional stability. The development of powder and binder materials is crucial for promoting the application of BJ3DP technology in practical engineering projects. Currently, gypsum powder is the most widely used material in inkjet 3D printing technology. For example, Chinese patent CN104230289A mentions a method for preparing gypsum powder inkjet 3D printing materials. However, gypsum-printed products generally suffer from low strength and poor printing accuracy, which severely limits their application range. Typically, resin materials are selected as binders in BJ3DP (Brush-Jet 3D Printing) to bond sand grains to create sand molds or components. Chinese patent CN120228242A discloses silica sand for 3D printing of casting sand molds and its preparation method. However, traditional silica sand suffers from performance defects, reliance on imports, and binder contamination, limiting its application in high-precision casting sand mold 3D printing. Furthermore, its high cost and limited durability make it difficult to apply in the construction engineering field. Chinese patent CN118084436A mentions a method for preparing high-toughness, fast-hardening sulfoaluminate cement-based materials. While this method produces high-strength 3D-printed specimens, it suffers from poor dimensional accuracy. Magnesium phosphate cement (MPC), due to its rapid setting, high early strength, and room-temperature curing properties, can reach high strength within hours, making it ideal for 3D printing and enabling rapid construction. This has become a research hotspot in 3D printing cement-based materials. Chinese patent CN112759298A discloses a 3D printing material prepared from magnesium phosphate cement powder where precision and strength are contradictory. Improving precision requires low viscosity and good spreadability, while improving strength requires high solid ink content and strong setting and hardening ability. These requirements mutually constrain the material formulation and inkjet printing conditions, making it difficult to simultaneously achieve both in practical processes. Existing materials exhibit high exothermic hydration, easily leading to microcracks and reduced structural uniformity. Therefore, developing a high-strength and high-precision magnesium phosphate cement-based inkjet 3D printing material that can simultaneously address these issues is crucial for advancing the construction industry. Summary of the Invention

[0003] The purpose of this invention is to provide a high-precision, high-strength inkjet 3D printing cement-based material, its preparation method, and its application method. This cement-based material can improve the precision of 3D printing cement-based materials, optimize the material's mechanical properties, and increase printing efficiency, achieving all three effects simultaneously and showing good application prospects.

[0004] To achieve the above objectives, the present invention provides a high-precision and high-strength inkjet 3D printing cement-based material, characterized in that the material comprises powder material and ink, wherein the powder material, by relative weight ratio, comprises 10-50 parts of reburned MgO powder, 5-30 parts of phosphate powder, 10-20 parts of polymer powder, 10-30 parts of nano-filler powder, and 30-100 parts of precision and strength improving components. The particle size range of the recalcined MgO powder is 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. The phosphate powder has a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. The polymer powder includes polyvinyl alcohol powder and ethylene-vinyl acetate powder, with a weight ratio of 2-3:1, a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. The nanofiller material includes nano-silica and nano-titanium dioxide powder, and the weight ratio of nano-silica to nano-titanium dioxide powder is 1.8-3:1; the particle size range of nano-silica is 0.07-0.15 nm, and the particle size range of nano-titanium dioxide is 0.1-0.25 nm. The precision and strength improvement components include citric acid powder and sodium silicate powder, wherein the weight ratio of citric acid powder to sodium silicate powder is 1.1-1.5:1, the particle size range is 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. The raw materials for preparing the ink include 3-10 parts viscosity modifier, 0.5-2.5 parts solubilizer and stabilizer, 0.1-0.8 parts surface tension modifier, 0.01-0.1 parts defoamer, 3-6 parts humectant, and 80-97 parts deionized water; the viscosity of the ink is 3-15 mPa•s, and the surface tension is 35-55 mN / m.

[0005] Furthermore, this invention provides a method for preparing high-precision, high-strength inkjet 3D printed cement-based materials. This method is used to prepare the high-precision, high-strength inkjet 3D printed cement-based materials as described above, and specifically includes the following steps: Step 1: Preparation of powder materials Add 10-50 parts of recalcined MgO powder, 5-30 parts of phosphate powder, 10-20 parts of polymer powder and 10-30 parts of nanofiller to a planetary mixer and stir for 5-10 min; then add 50-100 parts of precision strength improving component and continue stirring for 10-15 min to obtain the powder material. Step 2: Prepare ink (1) Mixing binder: Add 3-10 parts of viscosity modifier to 0.5-2.5 parts of solubilizer stabilizer, stir for 10-15 minutes to obtain the first mixed solution; (2) Add 0.1-0.8 parts of surface tension modifier, 0.01-0.1 parts of defoamer, 3-6 parts of humectant, and 80-97 parts of deionized water to the No. 1 mixed solution, and then use an ultrasonic disperser with a frequency of 50 Hz to ultrasonically disperse for 5-10 min to obtain the No. 2 mixed solution. (3) The No. 2 mixed solution was vacuum filtered sequentially using PP material filter membranes of 15 μm, 10 μm and 0.5 μm, with a filtration negative pressure of 0.7-0.8 MPa; (4) The filtered No. 2 mixed solution is degassed sequentially using a vacuum degassing tank and a vacuum degassing mold to obtain the ink.

[0006] Furthermore, the present invention provides a method for using a high-precision, high-strength inkjet 3D printing cement-based material, characterized in that the high-precision, high-strength inkjet 3D printing cement-based material is the high-precision, high-strength inkjet 3D printing cement-based material as described above or obtained by the preparation method described above, and the specific method of use is as follows: High-precision, high-strength inkjet 3D printing cement-based material powder is added to the powder feed hopper of the inkjet 3D printer. High-precision, high-strength inkjet 3D printing cement-based material ink is added to the primary ink cartridge of the ink supply system. The printing program and printing parameters are set. The inkjet 3D printer is started. The powder spreader, according to the system settings of the inkjet 3D printer, evenly and flatly lays the first layer of powder material on the printing plate. The print head sprays ink onto the first layer of powder material laid by the powder spreader according to the set path. The ink reacts with the powder material and quickly bonds and hardens. After the first layer of the set path of the print head is printed, the printing platform descends by one printing layer thickness. The steps of powder spreading by the powder spreader, ink spraying by the print head, and descent of the printing platform are repeated until the printing is completed, and the model printing is finished. The printer parameters are as follows: printhead movement speed is 300 mm / s, powder roller speed is 350 r / min, printing speed is 3 L / h, and printing layer thickness is 0.125 mm; the unit volume weight ratio of ink ejected by the printhead to powder material in the model is 0.2-0.4:1.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The precision-strength improvement component of this invention consists of citric acid powder and sodium silicate powder. Citric acid, by adsorbing onto the surface of cement particles, regulates the surface charge of the particles, reduces agglomeration behavior, and significantly improves the dispersibility and flowability of the powder; at the same time, its retarding effect can prolong the induction period of magnesium phosphate cement, making the capillary penetration and diffusion of the binder in the powder bed more sufficient and uniform, thereby reducing dimensional deviations and improving forming stability. The regulation of reaction kinetics by citric acid can make the hydration products more compact, effectively improving the shrinkage cracking problem caused by rapid reaction, and improving the bending strength and Z-axis mechanical properties of the specimen. However, citric acid is highly hygroscopic, which is not conducive to the long-term dryness and stability of the powder. The addition of sodium silicate powder can enhance the dry stability of the powder, improve agglomeration and spreading performance, and avoid premature local solidification that would lead to damage during the powder spreading process; the SiO2 gel formed after it is exposed to water can also enhance the interlayer interface adhesion. The synergistic effect of the two can simultaneously improve the common insufficient strength and forming precision deviation in inkjet 3D printing, and realize the integrated printing of high strength and high precision of the model.

[0008] (2) The polymer powder of the present invention includes polyvinyl alcohol (PVA) powder and ethylene-vinyl acetate (EVA) powder. PVA can quickly dissolve after the binder is sprayed to form a high-viscosity polymer film, which enhances the adhesion between particles and limits the excessive penetration of the binder, thereby significantly improving the printing accuracy. However, its polymer film will inhibit droplet penetration to a certain extent, affecting local strength. EVA powder can improve the powder packing density and flowability. When it comes into contact with water, it forms an elastic mesh film, fills the pores, improves the density and toughness, effectively relieves shrinkage and internal stress, and at the same time compensates for the local penetration restriction caused by the PVA film, reducing interlayer misalignment and warping. The synergistic effect of the two can improve the interlayer bonding quality and reduce dimensional errors, thereby improving the forming accuracy and performance stability of inkjet 3D printed parts.

[0009] (3) This invention uses nano-silica and nano-titanium dioxide as nanofiller materials (particle size 0.07–0.125 mm). Nanoscale particles can effectively fill the pores of cement-based materials and improve microscale density. Hydrophobic nano-silica can be adsorbed on the surface of MPC particles to form a "ball effect", which significantly improves powder flowability and powder spreading smoothness, reduces interlayer defects, and thus improves printing accuracy; its rigid skeleton can also inhibit the excessive growth of reaction product crystals, reduce shrinkage and warping, make the microstructure more uniform, and enhance the compressive strength, flexural strength and durability of the material. The filling effect of nanomaterials can improve the interlayer interface bonding quality and further improve the overall performance. An appropriate amount of nano-titanium dioxide can maintain particle morphology and flowability for a long time in a slightly alkaline environment, supporting repeated batch recycling of powder without reducing printing accuracy.

[0010] (4) The pyrrolidone solubilizer and stabilizer added to the ink components of this invention can work synergistically with PVA or PVP to prevent component precipitation under high binder content, avoid nozzle clogging, and ensure continuous and stable jetting process. The added glycerol or 1,2-propanediol, as a humectant, can inhibit rapid evaporation of moisture, prevent nozzle clogging due to dryness, and achieve jetting stability for long-term printing. The defoamer in the formula can reduce bubble formation and prevent bubbles from clogging the nozzles; the surface tension modifier improves the ink's ability to wet and penetrate powder, making jetting more uniform and thus improving forming accuracy. The ink of this invention has comprehensive advantages of anti-precipitation, anti-clogging, moisturizing stability, anti-bubble and excellent wettability, which can significantly improve the accuracy, stability and reliability of inkjet 3D printing, and also has cost and environmental advantages.

[0011] The synergistic combination of the components in the powder material and the ink formulation of this invention effectively improves the forming accuracy and mechanical strength of 3D printed specimens, and has a wide range of applications in inkjet 3D printing technology. Attached Figure Description

[0012] Figure 1 This is an image of the powder material of the high-precision and high-strength inkjet 3D printed cement-based material obtained in Embodiment 1 of the present invention spreading on the printing substrate during inkjet 3D printing.

[0013] Figure 2 This is an image of the powder material of the 3D printed cement-based material obtained in Comparative Example 1 of the present invention spreading on the printing substrate during inkjet 3D printing.

[0014] Figure 3 This is an image of the powder material of the 3D printed cement-based material obtained in Comparative Example 3 of the present invention spreading on the printing substrate during inkjet 3D printing.

[0015] Figure 4 This is an image of the powder material of the 3D printed cement-based material obtained in Comparative Example 5 of the present invention spreading on the printing substrate during inkjet 3D printing.

[0016] Figure 5 The model is obtained by 3D printing using the high-precision and high-strength inkjet 3D printing cement-based material obtained in Example 1 of this invention.

[0017] Figure 6 This is a model obtained by 3D printing the cement-based material obtained in Comparative Example 1 of this invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. The parts of components mentioned in the embodiments refer to relative weight proportions.

[0019] This invention provides a high-precision and high-strength inkjet 3D printing cement-based material, which includes powder material and ink. The powder material, by relative weight ratio, includes 10-50 parts of reburned MgO powder, 5-30 parts of phosphate powder, 10-20 parts of polymer powder, 10-30 parts of nano-filler powder, and 30-100 parts of precision and strength improving components. The particle size range of the recalcined MgO powder is 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution.

[0020] The phosphate powder has a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution.

[0021] The recalcined MgO powder is prepared by calcining magnesite in a high-temperature furnace at 1600-1960℃ for 30-120 min, followed by ball milling at 1400-1800 r / min for 15-35 min, and then sieving through sieves of different mesh sizes (usually 120-200 mesh) to separate particles with a diameter range of 0.075-0.125 mm. Finally, the particles with a diameter range of 0.075-0.125 mm are mixed according to a normal distribution of volume proportions of different particle sizes to obtain the recalcined MgO powder with a bulk density of 1.8-2.0 g / cm³. 3 Specific surface area is 230-287 m² 2 / kg.

[0022] The phosphate powder is one or more of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and sodium dihydrogen phosphate powder. The phosphate material with a purity of 96% or higher is ball-milled at 1400-1800 r / min for 15-35 min, then sieved through sieves of different mesh sizes (usually 120-200 mesh) to separate particles with a diameter range of 0.075-0.125 mm. Finally, the powders with a diameter range of 0.075-0.125 mm are mixed according to a normal distribution of volume proportions for different particle sizes to obtain the phosphate powder. The phosphate material is at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and sodium dihydrogen phosphate.

[0023] The polymer powder includes polyvinyl alcohol (PVA) powder and ethylene-vinyl acetate (EVA) powder, with a weight ratio of 2-3:1. The PVA powder is one or more of the following types: 1780, 1788, 1792, and K30, with a purity greater than 98%, a molecular weight of 30,000-100,000, a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. It is obtained by sieving with sieves of different mesh sizes and then mixing according to the volume percentage. The ethylene-vinyl acetate (EVA) powder is one or more of the following types: SWF-05, Elvax 150, Elvax 205W, and Elvax 210W, with a purity greater than 98%, a water content less than 0.2%, a molecular weight distribution less than 22,000, a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. It is obtained by sieving with sieves of different mesh sizes and then mixing according to the volume percentage.

[0024] The nanofiller material includes nano-silica and nano-titanium dioxide powder, and the weight ratio of nano-silica to nano-titanium dioxide powder is 1.8-3:1; the particle size range of nano-silica is 0.07-0.15 nm, and the particle size range of nano-titanium dioxide is 0.1-0.25 nm. The precision and strength improving component includes citric acid powder and sodium silicate powder, wherein the weight ratio of citric acid powder to sodium silicate powder is 1.1-1.5:1; the citric acid powder is at least one of anhydrous citric acid and citric acid monohydrate, with a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution; as an example, the anhydrous citric acid and / or citric acid monohydrate are first ball-milled, then sieved using sieves of different mesh sizes, and then mixed according to the volume percentage. The sodium silicate powder is anhydrous sodium silicate, with a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution, and is obtained by sieving using sieves of different mesh sizes and then mixing according to the volume percentage.

[0025] The raw materials for preparing the ink include 3-10 parts of viscosity modifier, 0.5-2.5 parts of solubilizer and stabilizer, 0.1-0.8 parts of surface tension modifier, 0.01-0.1 parts of defoamer, 3-6 parts of humectant, and 80-97 parts of deionized water; the above parts are relative weight parts.

[0026] The ink has a viscosity of 3-15 mPa•s and a surface tension of 35-55 mN / m; the weight ratio of the ink to the powder material is 0.2-0.4. The viscosity modifier is at least one of PVA, polyvinylpyrrolidone, or xanthan gum; The solubilizing stabilizer is at least one of 2-pyrrolidone, sodium pyrrolidone carboxylate, and diethylene glycol; The surface tension modifier is a nonionic surfactant, at least one of Surfynol 465, polyether-modified silicone oil, and ethylene glycol monobutyl ether; The defoamer is an organosilicon defoamer with a pH of 3-14. The moisturizer is at least one of glycerin, 1,2-propanediol, and sorbitol.

[0027] Furthermore, this invention provides a method for preparing high-precision, high-strength inkjet 3D printed cement-based materials. This method is used to prepare the high-precision, high-strength inkjet 3D printed cement-based materials as described above, and specifically includes the following steps: Step 1: Preparation of powder materials Add 10-50 parts of recalcined MgO powder, 5-30 parts of phosphate powder, 10-20 parts of polymer powder and 10-30 parts of nanofiller to a planetary mixer and stir for 5-10 minutes; then add 50-100 parts of precision strength improving component and continue stirring for 10-15 minutes to obtain the powder material.

[0028] Step 2: Prepare ink (1) Mixing binder: Add 3-10 parts of viscosity modifier to 0.5-2.5 parts of solubilizer stabilizer, stir for 10-15 minutes to obtain the first mixed solution; (2) Add 0.1-0.8 parts of surface tension modifier, 0.01-0.1 parts of defoamer, 3-6 parts of humectant, and 80-97 parts of deionized water to the No. 1 mixed solution, and then use an ultrasonic disperser with a frequency of 50 Hz to ultrasonically disperse for 5-10 min to obtain the No. 2 mixed solution. (3) The No. 2 mixed solution was vacuum filtered sequentially using PP material filter membranes of 15 μm, 10 μm and 0.5 μm, with a filtration negative pressure of 0.7-0.8 MPa; (4) The filtered No. 2 mixed solution is degassed sequentially using a vacuum degassing tank and a vacuum degassing mold to obtain the ink.

[0029] Furthermore, the present invention provides a method for using a high-precision, high-strength inkjet 3D printing cement-based material. This high-precision, high-strength inkjet 3D printing cement-based material is either the high-precision, high-strength inkjet 3D printing cement-based material described above or obtained by the above preparation method. The specific method of use is as follows: High-precision, high-strength inkjet 3D printing cement-based material powder is added to the powder feed hopper of the inkjet 3D printer. High-precision, high-strength inkjet 3D printing cement-based material ink is added to the primary ink cartridge of the ink supply system. The printing program and printing parameters are set. The inkjet 3D printer is started. The powder spreader, according to the system settings of the inkjet 3D printer, evenly and flatly lays the first layer of powder material on the printing plate. The print head sprays ink onto the first layer of powder material laid by the powder spreader according to the set path. The ink reacts with the powder material and quickly bonds and hardens. After the first layer of the set path of the print head is printed, the printing platform descends by one printing layer thickness. The steps of powder spreading by the powder spreader, ink spraying by the print head, and descent of the printing platform are repeated until the printing is completed, and the model printing is finished.

[0030] The printer parameters are: printhead travel speed of 300 mm / s, toner roller speed of 350 r / min, printing speed of 3 L / h, layer thickness of 0.125 mm, and printing time of approximately 30 s per layer. The ink-to-powder material weight ratio per unit volume in the model is 0.2-0.4:1. After printing, immediately remove the printed model from the powder bed, gently brush off any loose powder from the surface of the sample with a brush, and place it in a sealed box to cure indoors for 24 hours to obtain a high-precision, high-strength printed model.

[0031] Example 1 This embodiment provides a high-precision, high-strength inkjet 3D printing cement-based material, its preparation method, and its application method. The preparation method is as follows: Step 1: Preparation of powder materials 50 parts of reburned MgO powder, 30 parts of phosphate powder, 20 parts of polymer material powder, and 30 parts of nanofiller were added to a planetary mixer and stirred for 10 min. Then, 100 parts of a precision and strength improving component were added, and stirring was continued for 15 min to obtain the powder material. The polymer material component included 5 parts of polyvinyl alcohol (PVA) powder and 15 parts of ethylene-vinyl acetate (EVA) powder. The PVA was of type K30 with a purity of 98%, and the EVA was of type SWF-05 with a water content of 0.15%. The precision and strength improving component included 60 parts of citric acid powder and 40 parts of sodium silicate powder. The nanofiller included 21.5 parts of nano-silica and 7.5 parts of nano-titanium dioxide powder. The particle size range of the recalcined MgO powder is 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution.

[0032] The phosphate powder has a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution.

[0033] Polyvinyl alcohol (PVA) powder has a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. Ethylene-vinyl acetate (EVA) powder has a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution.

[0034] The sodium silicate powder is anhydrous sodium silicate with a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution.

[0035] The citric acid powder is at least one of anhydrous citric acid and citric acid monohydrate, with a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution.

[0036] The particle size range of nano-silica is 0.07-0.15 nm, and the particle size range of nano-titanium dioxide is 0.1-0.25 nm.

[0037] Step 2: Prepare ink (1) Mixing adhesive: Add 8% PVA to 1.2% 2-pyrrolidone and stir for 10 min to obtain the first mixed solution; (2) Add 0.5 parts of nonionic surfactant Surfynol 465, 0.05 parts of silicone defoamer, 4 parts of 1,2-propanediol, and 90 parts of deionized water to the first mixed solution, and then ultrasonically disperse it for 8 min using an ultrasonic disperser at a frequency of 50 Hz to obtain the second mixed solution; the effective ingredient content of Surfynol 465 is greater than 99%; the effective ingredient content of silicone defoamer is greater than 98%, and the pH is 3-14; (3) The No. 2 mixed solution was vacuum filtered sequentially using PP material filter membranes of 15 μm, 10 μm and 0.5 μm, with a filtration negative pressure of 0.7 MPa. (4) The filtered No. 2 mixed solution is degassed sequentially using a vacuum degassing tank and a vacuum degassing mold to obtain the ink.

[0038] The method of use is as follows: High-precision, high-strength inkjet 3D printing cement-based material powder is added to the powder feed hopper of the inkjet 3D printer. High-precision, high-strength inkjet 3D printing cement-based material ink is added to the primary ink cartridge of the ink supply system. The printing program and printing parameters are set. The inkjet 3D printer is started. The powder spreader, according to the system settings of the inkjet 3D printer, evenly and flatly lays the first layer of powder material on the printing plate. The print head sprays ink onto the first layer of powder material laid by the powder spreader according to the set path. The ink reacts with the powder material and quickly bonds and hardens. After the first layer of the set path of the print head is printed, the printing platform descends by one printing layer thickness. The steps of powder spreading by the powder spreader, ink spraying by the print head, and descent of the printing platform are repeated until the printing is completed, and the model printing is finished.

[0039] The printer parameters are as follows: printhead travel speed 300 mm / s, toner roller speed 350 r / min, printing speed 3 L / h, layer thickness 0.125 mm, and printing time per layer approximately 30 s. The ink-to-powder material weight ratio per unit volume in the model is 0.3:1.

[0040] In the model, ink acts as a binder between powder material layers. Its amount can be determined based on the printing speed (i.e., ink jet velocity - ink jet volume per unit time) and printing time. The printing time can be determined by planning the printing path and the printhead moving speed. The amount of powder material can be determined based on the volume of the model and the density of the powder material.

[0041] After printing, immediately remove the printed model from the powder bed, gently brush off any loose powder from the surface of the sample with a brush, and place it in a sealed box to cure indoors for 24 hours to obtain a high-precision, high-strength printed model.

[0042] Multiple specimens were printed using the above method, and high-precision, high-strength printed specimens were obtained by curing them indoors for 24 hours. After curing them under natural conditions for 7 days, their diffusion error and 7-day compressive strength were tested.

[0043] The high-precision, high-strength inkjet 3D printing cement-based material obtained in this embodiment was used for 3D printing to obtain a printed structure. The printing process proceeded smoothly without cracking, and the printed structure exhibited good integrity and precision.

[0044] Example 2 This embodiment provides a high-precision, high-strength inkjet 3D printing cement-based material, its preparation method, and its application method. Compared to Embodiment 1, this embodiment differs in that 50 parts of recalcined MgO powder and 30 parts of phosphate powder are replaced with 30 parts of recalcined MgO powder and 20 parts of phosphate powder; 20 parts of polymer material powder are replaced with 18 parts of polymer material powder; 30 parts of nano-filler material are replaced with 28 parts of nano-filler material; and 100 parts of precision and strength improving components are replaced with 84 parts of precision and strength improving components. Using the high-precision, high-strength inkjet 3D printing cement-based material obtained in this embodiment, a 3D printing structure is obtained. The printing process proceeds smoothly, and the printed structure exhibits good integrity and precision, with a minimum printable precision of 0.20 mm, and no cracking occurs.

[0045] Example 3 This embodiment provides a high-precision, high-strength inkjet 3D printing cement-based material, its preparation method, and its application method. Compared to Embodiment 1, this embodiment differs in that 50 parts of recalcined MgO powder and 30 parts of phosphate powder are replaced with 25 parts of recalcined MgO powder and 15 parts of phosphate powder; 20 parts of polymer material powder are replaced with 13 parts of polymer material powder; 30 parts of nano-filler material are replaced with 21 parts of nano-filler material; and 100 parts of precision and strength improving components are replaced with 77 parts of precision and strength improving components. Using the high-precision, high-strength inkjet 3D printing cement-based material obtained in this embodiment, 3D printing is performed to obtain a printed structure. The printing process proceeded smoothly, and the printed structure exhibited good integrity and precision, with a minimum printable precision of 0.21 mm, and no cracking occurred.

[0046] Example 4 This embodiment provides a high-precision, high-strength inkjet 3D printing cement-based material, its preparation method, and its application method. Compared to Embodiment 1, this embodiment differs in that 50 parts of recalcined MgO powder and 30 parts of phosphate powder are replaced with 10 parts of recalcined MgO powder and 5 parts of phosphate powder; 20 parts of polymer material powder are replaced with 10 parts of polymer material powder; 30 parts of nano-filler material are replaced with 10 parts of nano-filler material; and 100 parts of precision and strength improving components are replaced with 30 parts of precision and strength improving components. Using the high-precision, high-strength inkjet 3D printing cement-based material obtained in this embodiment, 3D printing is performed to obtain a printed structure. The printing process proceeded smoothly, and the printed structure exhibited good integrity and precision, with a minimum printable precision of 0.18 mm, and no cracking occurred.

[0047] Comparative Example 1 This comparative example provides a 3D printing cement-based material, its preparation method, and its usage. The difference between this comparative example and Example 1 is that the recalcined MgO powder in Example 1 is changed to 5 parts, and the 30 parts of phosphate powder is changed to 40 parts. When using the 3D printing cement-based material obtained in this comparative example for 3D printing, it was found that due to the excessive amount of phosphate added in the comparative example, the powder system solidified too quickly, the heat release was concentrated, the specimen cracked, and it was difficult to meet the printing requirements.

[0048] Comparative Example 2 This comparative example provides a 3D printing cement-based material, its preparation method, and its usage. The difference between this comparative example and Example 1 is that the recalcined MgO powder in Example 1 is changed to 60 parts, and the 30 parts of phosphate powder is changed to 20 parts. When using the 3D printing cement-based material obtained in this comparative example for 3D printing, it was found that due to the excessive amount of magnesium oxide and insufficient amount of phosphate in the comparative example, the powder system solidified slowly, and the powder-coated specimen was cracked, making it difficult to meet the printing requirements.

[0049] Comparative Example 3 This comparative example provides a 3D printing cement-based material, its preparation method, and its application method. The difference between this comparative example and Example 1 is that the 20 parts of polymer powder in Example 1 are replaced with 1 part of polyvinyl alcohol (PVA) powder and 19 parts of ethylene-vinyl acetate (EVA) powder. Using the 3D printing cement-based material obtained in this comparative example, 3D printing was performed. During the printing process, it was found that due to the insufficient amount of PVA powder in the comparative example, the effective film-forming component in the powder system was insufficient, which significantly increased the penetration and lateral diffusion of ink in the powder material, easily leading to structural defects such as pores and collapses. The resulting specimens had poor overall forming quality, blurred boundaries, large dimensional deviations, and printing accuracy that was difficult to meet requirements.

[0050] Comparative Example 4 This comparative example provides a 3D printing cement-based material, its preparation method, and its application method. The difference between this comparative example and Example 1 is that the 20 parts of polymer powder in Example 1 are replaced with 15 parts of polyvinyl alcohol (PVA) powder and 5 parts of ethylene-vinyl acetate (EVA) powder. Using the 3D printing cement-based material obtained in this comparative example, 3D printing was performed. During the printing process, it was found that due to the excessive amount of PVA powder in the comparative example, a dense water-blocking layer easily formed on the surface of the powder bed, making it difficult for the ink to fully penetrate the lower powder layers. This resulted in insufficient interlayer bonding and obvious weak interlayer surfaces, leading to a decrease in forming accuracy. Furthermore, due to the low amount of ethylene-vinyl acetate (EVA) powder, the components that provide flexible film-forming properties in the system were reduced, resulting in weaker overall powder bonding performance. In addition, the low EVA content resulted in insufficient regulation of the cement reaction, lower early matrix density, and increased ink penetration and diffusion in the powder, ultimately leading to poor overall specimen forming quality and difficulty in meeting printing accuracy requirements.

[0051] Comparative Example 5 This comparative example provides a 3D printing cement-based material, its preparation method, and its application method. The difference between this comparative example and Example 1 is that the 30 parts of nano-filler material in Example 1 are replaced with 10 parts of nano-silica and 20 parts of nano-titanium dioxide powder. Using the 3D printing cement-based material obtained in this comparative example, 3D printing was performed. During the printing process, it was found that due to the insufficient incorporation of nano-silica in the comparative example, the effective filling components for refining pores and enhancing adhesion were insufficient, leading to increased ink penetration depth in the powder material, more pronounced lateral diffusion, and defects such as blurring and collapse at the edges and corners, resulting in a significant decrease in the overall forming accuracy of the specimen. Simultaneously, the nano-silica was insufficient to effectively improve the early gelling and structural density of the matrix, affecting the compressive strength of the specimen. The compressive strength of the obtained specimen was affected, decreasing by approximately 18% compared to Example 1, and the forming quality was significantly deteriorated. Because nano-titanium dioxide has a large specific surface area and high surface activity, excessive addition will significantly increase the moisture adsorption capacity of the powder system, resulting in uneven distribution of local bonding points. This leads to abnormal wetting and spreading behavior of the ink in the powder, such as reduced penetration depth and limited bonding range, causing defects such as edge deformation of printed parts, increased surface roughness, and excessive micropores.

[0052] Comparative Example 6 This comparative example provides a 3D printing cement-based material, its preparation method, and its application method. The difference between this comparative example and Example 1 is that the 30 parts of nanofiller material in Example 1 are replaced with 28 parts of nano-silica and 2 parts of nano-titanium dioxide powder. Using the 3D printing cement-based material obtained in this comparative example, 3D printing was performed. During the printing process, it was found that due to the high nano-silica content in the comparative example, nanoparticles in the system were prone to agglomeration, resulting in decreased powder bed uniformity, increased interlayer packing differences, and uneven interlayer bonding with significant interlayer effects. Conversely, the low nano-titanium dioxide content failed to fully exert its effect of reducing static electricity and inhibiting powder agglomeration, resulting in significant agglomeration during powder spreading. Ultimately, this led to varying degrees of decrease in the forming accuracy and mechanical strength of the specimens.

[0053] Comparative Example 7 This comparative example provides a 3D printing cement-based material, its preparation method, and its application method. The difference between this comparative example and Example 1 is that the 90 parts of the precision and strength improvement component in Example 1 are replaced with 10 parts of citric acid powder and 80 parts of sodium silicate powder. Using the 3D printing cement-based material obtained in this comparative example, 3D printing was performed. During the printing process, it was found that due to the low content of citric acid powder in the comparative example, its dispersion regulation and particle surface complexation effects on the powder system were insufficient, leading to an increase in agglomerates in the powder, a decrease in powder uniformity, significant differences in interlayer packing, and a noticeable interlayer effect. Simultaneously, the excessively high content of sodium silicate powder resulted in excessively strong early alkalinity of the system, causing the initial bonding reaction between powders to be too rapid and uneven, easily leading to localized hardening and uneven pore structure. Ultimately, this resulted in a decrease in the forming precision of the specimen, insufficient mechanical properties, and an increase in the number of defects.

[0054] Comparative Example 8 This comparative example provides a 3D printing cement-based material, its preparation method, and its application method. The difference between this comparative example and Example 1 is that the 90 parts of the precision and strength-improving component in Example 1 are replaced with 70 parts of citric acid powder and 20 parts of sodium silicate powder. Using the 3D printing cement-based material obtained in this comparative example, 3D printing was performed. During the printing process, it was found that due to the excessive amount of citric acid powder in the comparative example, its complexing and adsorption effects on the powder particle surface were enhanced, leading to a significant increase in agglomerates in the powder system and reduced powder uniformity. Furthermore, the excessive amount of citric acid powder significantly retarded the cement system, delaying the early hydration process and causing a lag in matrix structure formation, further exacerbating the insufficient early strength and poor interlayer bonding of the specimens. Simultaneously, due to the low amount of sodium silicate powder, its effect on improving the early setting and bonding properties of the system was insufficient, making it difficult to form a stable initial skeleton structure, resulting in insufficient local density of the specimens and a decrease in forming accuracy and mechanical properties.

[0055] Table 1. Raw material ratios for the preparation of powder materials in Examples 1-4 and Comparative Examples 1-8

[0056] The spreading test results of each component material are shown in Table 2.

[0057] Table 2. Printing effects of 3D printed cement-based materials obtained in Examples 1-4 and Comparative Examples 1-8

[0058] The dimensional errors and mechanical property test results of each group of printed specimens are shown in Table 3: Table 3 shows the performance of the printed structures obtained in Examples 1-4 and Comparative Examples 1-8.

[0059] The X-axis represents the powder spreader movement direction, the Y-axis represents the printing nozzle movement direction, and the Z-axis represents the powder stacking direction. The compressive strength of the binder-jet 3D printed specimens exhibits significant directional anisotropy. The mechanical properties of the specimens show obvious anisotropic characteristics; there are obvious interlayer interface textures in the X and Y directions, with poor structural continuity, while the Z direction exhibits the highest compressive strength. Dimensional errors also show anisotropy.

[0060] In this embodiment, a precision and strength-enhancing component with well-distributed particle size was added. Ions adsorbed onto the surface of magnesium oxide particles, forming a negatively charged layer that hinders agglomeration with positively charged particles. Uniform dispersion between particles is achieved, thus increasing powder spreadability with increasing content. The precision and strength-enhancing component slows down the conversion of free water to bound water, reducing cracking caused by early exothermic reactions and promoting more uniform exothermic reactions, thereby improving the overall performance of the printed product. This prevents cracking of magnesium phosphate cement due to excessively rapid water evaporation and allows more water to participate in subsequent reactions. The retarding effect makes the hydration process of magnesium phosphate cement smoother and more complete. The heat of hydration is dispersed and released, reducing the generation of internal microcracks. Simultaneously, the retarding effect allows the reaction products more time to grow and crystallize, resulting in a more uniform and regular morphology and a denser and more uniform microstructure. This not only improves later strength but also enhances the interfacial bonding strength between layers.

[0061] Sodium silicate powder can inhibit certain unfavorable crystal transformations in cement-based materials, reducing later strength decay. Sodium silicate can also improve powder agglomeration, thereby improving powder bed spreading performance and ultimately optimizing printing accuracy. Polyvinyl alcohol powder can effectively control the penetration and diffusion of binders in the powder bed, significantly improving printing accuracy. Ethylene-vinyl acetate (EVA) powder, through microsphere treatment and other methods, can improve powder bulk density and flowability, reduce friction between cement particles, and form a network film to fill micropores and cracks in the matrix, promoting structural densification and improving the overall toughness of the material. Nanofillers improve the density of cement-based materials by filling pores, thereby enhancing their compressive and flexural strength, reducing the intrusion of moisture and harmful substances, and improving material durability. Nanofillers can also improve the interlayer bond strength of cement-based materials, reduce interlayer interface defects, and thus improve the overall performance of printed objects.

[0062] In Example 1, 100 parts of a precision and strength improvement component with good particle size distribution were added. The particle size and volume distribution needed to meet the requirement of an approximately normal distribution. The specimen showed the best performance in terms of printing precision, with diffusion errors of 0.20 mm in the X direction, 0.21 mm in the Y direction, and 0.12 mm in the Z direction. The compressive strength in the Z direction reached 29.89 MPa, which meets the performance requirements of high printing precision and high strength cement-based materials for inkjet 3D printing.

[0063] Ultimately, the dimensional errors of the specimen in all three directions can be controlled within 0.2mm, achieving higher printing accuracy while ensuring high strength (24-30Mpa). The dimensional errors in the X, Y, and Z directions are all controlled to around 0.2mm, with the Z-direction dimensional error preferably controlled to around 0.2mm.

[0064] This application effectively controls printing accuracy by controlling the content of precision strength improvement components and powder bed temperature. Furthermore, by adding polymer powder, nanofiller materials, and precision strength improvement components, it achieves the dual requirements of improving accuracy and strength, which is a significant advancement.

[0065] To more intuitively illustrate the innovation of the aforementioned high-precision material, this invention uses the material parameters from Example 1 and Comparative Example 1 to print a complex model with a diameter of 5 cm under the same external conditions. Figure 5 .

[0066] The experimental results clearly show that, within the scope of this application, compared with traditional construction methods and cement-based 3D printing technologies, this invention offers advantages such as high printing precision while ensuring high strength, thus expanding the application range of inkjet 3D printing of cement-based materials. The embodiments described in this invention are easy to understand, and those skilled in the art can normally prepare and use inkjet 3D printing of high-precision and high-strength cement-based materials, facilitating implementation and enabling its widespread use in the field of new materials technology.

[0067] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0068] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A high-precision, high-strength inkjet 3D printing cement-based material, characterized in that, The material comprises powder material and ink, wherein the powder material, by relative weight ratio, comprises 10-50 parts of reburned MgO powder, 5-30 parts of phosphate powder, 10-20 parts of polymer powder, 10-30 parts of nano-filler powder, and 30-100 parts of precision and strength improving components. The particle size range of the recalcined MgO powder is 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. The phosphate powder has a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. The polymer powder includes polyvinyl alcohol powder and ethylene-vinyl acetate powder, with a weight ratio of 2-3:1, a particle size range of 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. The nanofiller material includes nano-silica and nano-titanium dioxide powder, and the weight ratio of nano-silica to nano-titanium dioxide powder is 1.8-3:1; the particle size range of nano-silica is 0.07-0.15 nm, and the particle size range of nano-titanium dioxide is 0.1-0.25 nm. The precision and strength improvement components include citric acid powder and sodium silicate powder, wherein the weight ratio of citric acid powder to sodium silicate powder is 1.1-1.5:1, the particle size range is 0.075-0.125 mm, and the volume percentage of different particle sizes follows a normal distribution. The raw materials for preparing the ink include 3-10 parts viscosity modifier, 0.5-2.5 parts solubilizer and stabilizer, 0.1-0.8 parts surface tension modifier, 0.01-0.1 parts defoamer, 3-6 parts humectant, and 80-97 parts deionized water; the viscosity of the ink is 3-15 mPa•s, and the surface tension is 35-55 mN / m.

2. The high-precision, high-strength inkjet 3D printing cement-based material according to claim 1, characterized in that, The viscosity modifier is at least one of PVA, polyvinylpyrrolidone, or xanthan gum.

3. The high-precision, high-strength inkjet 3D printing cement-based material according to claim 1, characterized in that, The solubilizing stabilizer is at least one of 2-pyrrolidone, sodium pyrrolidone carboxylate, and diethylene glycol.

4. The high-precision, high-strength inkjet 3D printing cement-based material according to claim 1, characterized in that, The surface tension modifier is a nonionic surfactant, at least one of Surfynol 465, polyether-modified silicone oil, and ethylene glycol monobutyl ether.

5. The high-precision, high-strength inkjet 3D printing cement-based material according to claim 1, characterized in that, The defoamer is an organosilicon defoamer with a pH of 3-14.

6. The high-precision, high-strength inkjet 3D printing cement-based material according to claim 1, characterized in that, The moisturizer is at least one of glycerin, 1,2-propanediol, and sorbitol.

7. The high-precision, high-strength inkjet 3D printing cement-based material according to claim 1, characterized in that, The recalcined MgO powder is prepared by calcining magnesite in a high-temperature furnace at 1600-1960℃ for 30-120 min, then ball-milling it at 1400-1800 r / min for 15-35 min, followed by sieving through sieves of different mesh sizes to separate particles with a diameter range of 0.075-0.125 mm. Finally, the particles with a diameter range of 0.075-0.125 mm are mixed according to a normal distribution of their different particle sizes to obtain the recalcined MgO powder with a bulk density of 1.8-2.0 g / cm³. 3 Specific surface area is 230-287 m² 2 / kg.

8. The high-precision, high-strength inkjet 3D printing cement-based material according to claim 1, characterized in that, The phosphate powder is one or more of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and sodium dihydrogen phosphate powder. The phosphate material with a purity of 96% or higher is ball-milled at 1400-1800 r / min for 15-35 min, then sieved through sieves of different mesh sizes to separate particles with a diameter range of 0.075-0.125 mm. Finally, the powders with a diameter range of 0.075-0.125 mm are mixed according to a normal distribution of volume proportions for different particle sizes to obtain the phosphate powder. The phosphate material is at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and sodium dihydrogen phosphate. The polyvinyl alcohol powder is one or more of the following types: 1780, 1788, 1792, and K30, with a purity greater than 98% and a molecular weight of 30,000 to 100,000; the ethylene-vinyl acetate powder is one or more of the following types: SWF-05, Elvax 150, Elvax 205W, and Elvax 210W, with a purity greater than 98% and a molecular weight distribution of less than 22,000.

9. A method for preparing high-precision, high-strength inkjet 3D printing cement-based materials, characterized in that, This method is used to prepare high-precision, high-strength inkjet 3D printing cement-based materials as described in any one of claims 1-8, and specifically includes the following steps: Step 1: Preparation of powder materials Add 10-50 parts of recalcined MgO powder, 5-30 parts of phosphate powder, 10-20 parts of polymer powder and 10-30 parts of nanofiller to a planetary mixer and stir for 5-10 min; then add 50-100 parts of precision strength improving component and continue stirring for 10-15 min to obtain the powder material. Step 2: Prepare ink (1) Mixing binder: Add 3-10 parts of viscosity modifier to 0.5-2.5 parts of solubilizer stabilizer, stir for 10-15 min to obtain the first mixed solution; (2) Add 0.1-0.8 parts of surface tension modifier, 0.01-0.1 parts of defoamer, 3-6 parts of humectant, and 80-97 parts of deionized water to the No. 1 mixed solution, and then use an ultrasonic disperser with a frequency of 50 Hz to ultrasonically disperse for 5-10 min to obtain the No. 2 mixed solution. (3) The No. 2 mixed solution was vacuum filtered sequentially using PP material filter membranes of 15 μm, 10 μm and 0.5 μm, with a filtration negative pressure of 0.7-0.8 MPa; (4) The filtered No. 2 mixed solution is degassed sequentially using a vacuum degassing tank and a vacuum degassing mold to obtain the ink.

10. A method for using a high-precision, high-strength inkjet 3D printing cement-based material, characterized in that, The high-precision, high-strength inkjet 3D printing cement-based material is the high-precision, high-strength inkjet 3D printing cement-based material as described in any one of claims 1-8, or is obtained by the preparation method described in claim 9. The specific method of use is as follows: High-precision, high-strength inkjet 3D printing cement-based material powder is added to the powder feed hopper of the inkjet 3D printer. High-precision, high-strength inkjet 3D printing cement-based material ink is added to the primary ink cartridge of the ink supply system. The printing program and printing parameters are set. The inkjet 3D printer is started. The powder spreader, according to the system settings of the inkjet 3D printer, evenly and flatly lays the first layer of powder material on the printing plate. The print head sprays ink onto the first layer of powder material laid by the powder spreader according to the set path. The ink reacts with the powder material and quickly bonds and hardens. After the first layer of the set path of the print head is printed, the printing platform descends by one printing layer thickness. The steps of powder spreading by the powder spreader, ink spraying by the print head, and descent of the printing platform are repeated until the printing is completed, and the model printing is finished. The printer parameters are as follows: printhead movement speed is 300 mm / s, powder spreading wheel speed is 350 r / min, printing speed is 3L / h, and printing layer thickness is 0.125 mm; the unit volume weight ratio of ink ejected from the printhead to powder material in the model is 0.2-0.4:1.

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