Research On The Technology Of Preparing Nickel-based Ceramic Composite Powder By Fluidized Crystallization Granulation-hydrogen Reductio

Ceramic materials have the characteristics of high strength and wear resistance,but their application is limited due to their brittleness.Metal ceramic composites can improve the disadvantages of ceramic materials and make them have the characteristics of high strength,ductility and conductivity of metals.They are widely used in military,aviation,aerospace,chemical industry,medicine and other fields.Due to the poor coating and purity of the composite powder materials prepared by the existing methods,the requirements for preparation conditions are high,which greatly limits the application range of nickel based ceramic composite powder.With the rapid development of industrial technology,it is particularly important to break through the existing technical methods,explore,establish and optimize new process routes,and prepare nickel series ceramic composite powder in a more green and environment-friendly way.This thesis proposes a new process route of fluidized crystallization granulation-hydrogen reduction for the preparation of nickel-based ceramic composite powders,focusing on the research on the technology of fluidized crystallization granulation hydrogen reduction to prepare composite powder.Taking Al₂O₃,SiO₂ and TiC ceramic matrix particles as the research object,this paper systematically studies the process feasibility,nickel concentration,nucleation mode,particle dehydration mode,hydraulic retention time,dosing ratio,dosing flow the preparation parameters of nickel coated powder and nickel coated powder were determined successfully.The main conclusions of the study are as follows:（1）With the Al₂O₃ substrate as the research object,and the reduced nickel concentration,heterogeneous nucleation,and natural air-drying of precursor particles are beneficial to the formation of the complete and uniform cladding layer,and the increased hydraulic residence time can improve the thickness of the cladding layer,and the optimal process is:nickel concentration of 50 mg/L,the hydraulic residence time of 75 h,ensuring heterogeneous nucleation,two-step hydrogen reduction of precursor particles to obtain Ni/Al₂O₃ cladding layer is complete and uniform,and the nickel content of the powder surface reaches 59.5%.（2）With irregular SiO₂ as matrix,based on the above process,the optimized process parameters are:nickel concentration of 100 mg/L,feed ratio of 1.5,the feed flow rate of 5m L/min,the hydraulic retention time of 50 h,and one-step hydrogen reduction of precursors for 2 h.The Ni/SiO₂ composite powder surface nickel content was 50.8%,and Ni/Si increase in the feed rate leads to a faster crystallization rate and a lower density,and a lower feed ratio reduces the crack generation and strengthens the bonding between the cladding layer and the substrate surface.（3）With irregular TiC as matrix,determine the process conditions:nickel concentration of100 mg/L,feed ratio of 1.5,feed flow rate of 5 m L/min,the hydrodynamic residence time of50 h for the precursor powder,static hydrogen reduction at 500°C for 2 h.The nickel content of the powder surface was 33.4%,and the Ni/Ti ratio was 0.646.Nickel content.Dynamic hydrogen reduction can destroy the plating effect and reduce the nickel content of the powder surface.The pilot scale-up device can prepare precursor particles with good coating and similar nickel content on the powder surface,improve the coating efficiency and lay a certain foundation for industrial application.