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The shaping of the green body before the molding and sintering of ceramic materials has a direct impact on the properties of the final product. To improve the uniformity of the green body and its density after dry pressing, the shaping characteristics of the powder are particularly important. Spray granulation technology is widely used to prepare advanced ceramic powders. In addition to meeting certain particle size requirements, the powder obtained through spray granulation also needs to: (1) be blended according to various composition requirements; (2) possess good flowability, formability, and chemical homogeneity, especially when used for continuous automatic molding. Due to the differences in particle size, density, dispersibility, and so on of various components or additives, strict control over the wet chemical processes and conditions during mixing is necessary to ensure uniform dispersion of all components within the mixture. If a simple mixing-drying-sieving-granulation process is used, it will be difficult to ensure the quality of the powder. In this paper, pressure spray granulation is used to granulate SiC powder, and the effects of process conditions and slurry additives during spray granulation on the properties of the powder are investigated. 1 Experiment 1.1 Preparation of the slurry: Sub-micron SiC powder and anhydrous ethanol were placed in a hard plastic container. Organic additives used as binders, plasticizers, and lubricants—phenolic resin, sucrose lipids, and oleic acid—were added in appropriate proportions. The mixture was then subjected to wet ball milling for 1 hour; after that, a certain amount of HT resin was added and further ball milling was carried out for 0.5 hour to obtain a stable slurry. The viscosity of the slurry was measured using an NDJ-1 rotary viscometer in order to determine the appropriate solid content of the slurry and the amount of organic additives to be used. 1.2 Granulation and powder property testing During spray granulation, a magnetic stirrer is used to mix the slurry while feeding it in, in order to maintain its uniformity. The slurry is atomized through low-pressure spray nozzles, mixed with hot air in a mixed-flow manner, and dried to form granular powder. The key process parameters controlled during the drying process include the solid content of the slurry, the amount of binder, the inlet and outlet temperatures, pressure, and feed rate. The properties of the powder are determined by using a flowability and bulk density tester to measure its flowability and bulk density; for each sample, 3 measurements are taken and the average value is used. The particle morphology was observed and analyzed using a scanning electron microscope (Shimadzu SS-550). 1.3 Properties of the spray-dried powder The bulk density of the solid-sintered silicon carbide ceramic powder prepared by spray drying is 0.91 g/cm3, with a flowability of 20 seconds (sample weight: 30 g). Observations under a scanning electron microscope show that the approximate distribution of particle sizes is as follows: 60%–70% of the powder particles have a size of 50 μm; they are solid spherical in shape with smooth surfaces. The powder exhibits good flowability, which meets the requirements for compression molding. After dry pressing of the powder, it is fired at 2,150 °C, resulting in a density of 3.14 g/cm3. 2 Results and Discussion 2.1 Influence of inlet and outlet temperatures on SiC granulated powder During the drying process, the inlet and outlet temperatures have a significant impact on the drying efficiency as well as the properties of the powder after drying. Excessively high inlet temperature can overheat the hot air at the top of the tower; when the mist droplets rise to higher levels and come into contact with this overheated air, it reduces the effectiveness of the binder, ultimately affecting the compressibility of the powder. If the exit temperature is too high, the mist droplets dry out quickly, which can result in particles that are too fine and have a high bulk density; it can also lead to clogging of the nozzles. At too low temperatures, the solvent in the fog droplets evaporates slowly, leading to sticking to the walls; moreover, the strength of the powder particles is insufficient, resulting in many broken particles and poor flowability. The tests also showed that the outlet temperature has a significant impact on particle morphology; however, since it is not possible to control the outlet temperature by adjusting the heating system of the equipment, it must be controlled by adjusting the feed rate and the solid content of the slurry. The final temperature conditions are: inlet temperature of 110–125 °C, and outlet temperature of 70–80 °C. 2.2 Effect of spray pressure and feed rate on SiC granulated powder: During spray granulation, the slurry is atomized into droplets through a pressure nozzle; hot air enters the drying tower from the top, and the droplets mix with the hot air first in counterflow and then in co-current flow, thereby enabling rapid drying. The atomization pressure is inversely proportional to the size of the droplets, while the feed rate is directly proportional to droplet size. At lower pressures and higher feed rates, the droplets produced are larger; the solvent does not have enough time to evaporate, resulting in powder particles that are large but have a high moisture content and poor flowability. When the pressure is too high and the feed rate is low, the droplets are ejected at a higher height, where they come into contact with the hot air at the top, causing the solvent to evaporate rapidly and leading to particle fragmentation, thus preventing the formation of powder with an ideal particle size. Experiments have shown that a pressure range of 0.08–0.1 MPa and a feed rate of 100 mL/min are appropriate. 2.3 Effects of solid content and binder content on SiC granulated powder: The solid content and binder content of the slurry have a significant impact on the flowability of the powder as well as on the shape of its particles. A high solid content can significantly increase the amount of spherical coarse particles; a low solid content leads to the formation of numerous hollow particles, which reduces the fluidity of the powder. At the same time, the solid content and binder content are the main factors affecting the viscosity of the slurry. The higher the solid content, the greater the viscosity; a sharp increase in viscosity occurs when the solid content is between 55% and 60%, as shown in Figure 1. Meanwhile, when the solid content is fixed, increasing the amount of binder also leads to an increase in the viscosity of the slurry. When the solid content and viscosity of the slurry are too low, the proportion of fine powder is high, the strength of the particles is poor, and most of them fail to form complete spherical particles, resulting in very poor flowability of the powder. The viscosity is too high, resulting in easy clogging of the nozzle and severe sticking to the walls; however, the yield of coarse particles is high. Tests have shown that an optimal feeding condition is achieved when the viscosity of the slurry is between 2,400 and 2,800 MP·s. When the binder content is below 2.5%, the particle strength increases while the mutual adhesion force decreases, which facilitates flow. However, larger particles result in larger voids when piled up, reducing the density of the filled powder. Under the influence of these two opposing factors, and taking into account the viscosity limitations of the slurry, the powder produced from a slurry with a binder content of 2.5%–5% and a solid content of 55% has a bulk density of 0.91 g/cm3 and a flow time of 20 seconds (with a sample weight of 30 g). Time has little effect on the viscosity of the slurry, and it contributes to the stability of the slurry. As the binder content and slurry concentration increase, the bulk density of the powder also increases accordingly. When the binder content exceeds 5%, no further increase in bulk density is observed, but well-fluidized spherical particles are formed; the morphology of these particles is shown in Figure 2. Generally, the larger the size of the aggregate particles and the greater their strength, the weaker the mutual adhesion forces between them, which facilitates flow. However, larger sizes result in larger voids when they are piled up, thereby reducing the density of the filled powder. Under the influence of these two opposing factors, and taking into account the viscosity limitations of the slurry, the powder produced from a slurry with a binder content of 2.5%–5% and a solid content of 55% has a bulk density of 0.91 g/cm3 and a flow time of 20 seconds (with a sample weight of 30 g). 3 Conclusion During the spray drying process, the solid content and viscosity of the slurry, as well as the amount of binder, along with the temperature and pressure during spraying, have a significant impact on the flowability of the powder and the morphology of its particles. Through experiments, the process conditions for preparing solid-sintered SiC ceramic powder were determined: ethanol was used as the solvent, with 2.5%–5% phenolic resin serving as the binder, to produce a slurry with a solid content of over 55% and a viscosity of 2,400–2,800 MPa·s. During spray granulation, the inlet temperature was set at 110–125 °C, the outlet temperature at 70–80 °C, the pressure at 0.08–0.1 MPa, and the feed rate at 100 mL/min. This resulted in spherical, solid particles with a loose density of 0.91 g/cm3, a flowability of 20 seconds (for a sample weight of 30 g), and an average particle diameter of 50 μm; the particles exhibited good formability. References: Fan Zengzhao, Chen Kungang, Xu Xiaohé. Preparation of ceramic powders by spray drying. Acta Silicologica Sinica, 1989, 17(3): 278-282. Fan Zengzhao, Gu Zhonghua, Chen Kungang, et al. Preparation of high-performance β-Al2O3 ceramic compacting powders. Acta Materialia Inorganica, 1999, 14(1): 36-42. Zhu Guihua, Chen Yuhong. Process control for spray granulation of silicon carbide via liquid-phase sintering. Chemical New Materials, 2006, 34(8): 65-67.