In the field of advanced ceramic materials, silicon nitride (Si3N4) has attracted much attention for its excellent mechanical strength, chemical stability and high temperature properties. However, the thermal conductivity of silicon nitride ceramics, as one of the key factors affecting its wide application, has been an important subject in materials science research. This paper aims to investigate the heat transfer mechanism of silicon nitride ceramics, especially the lattice vibration and scattering phenomenon during phonon conduction, and focus on the unique role of carbon additives in the sintering process of silicon nitride and the mechanism of improving the thermal conductivity. Through the comprehensive analysis of experimental data and theoretical models, this paper aims to provide new ideas and strategies for the preparation of silicon nitride substrate with high thermal conductivity.
Reunderstanding of heat transfer mechanism
As a typical covalent bonded ceramic material, the heat transfer mechanism of silicon nitride mainly depends on lattice vibration and phonon conduction. The nonlinear propagation and collision between phonons in the lattice are not only restricted by the lattice structure itself, but also influenced by the microstructure characteristics such as internal defects, impurities and grain boundaries. In particular, lattice oxygen is the main scattering source, and its content is directly related to the mean free path of phonons, which affects the thermal conductivity of silicon nitride. Therefore, reducing the lattice oxygen content becomes one of the key ways to improve the thermal conductivity of silicon nitride.
Discussion on the introduction and mechanism of carbon additives
In recent years, the research of carbon as a sintering additive for non-oxide ceramics has attracted extensive attention. In the silicon nitride system, carbon is introduced not only to remove the oxide impurities on the surface of the oxide powder, but more importantly, it can play a significant reduction role in the nitriding and post-sintering process. Specifically, carbon can reduce the partial pressure of SiO and promote the reduction of oxygen-containing impurities such as SiO2, thus reducing the content of lattice oxygen. This process not only purified the lattice environment, but also promoted the growth of silicon nitride grains and the optimization of structure.
Effect of carbon additives on thermal conductivity of silicon nitride ceramics
The experimental results show that the thermal conductivity of silicon nitride ceramics can be significantly improved by adding proper amount of carbon. Specifically, the reduction of carbon increases the secondary N/O atomic ratio between silicon nitride grains, forming a bimodal microstructure conducive to heat conduction. This structural feature is characterized by the coexistence of large grains and elongated grains, which provide efficient heat conduction channels, while elongated grains help to reduce phonon scattering, and jointly improve the thermal conductivity of silicon nitride ceramics.
In addition, the use of carbon additives also reduces the strict requirements for the oxygen content of raw materials and the selection of sintering additives. Traditionally, in order to obtain high thermal conductivity silicon nitride ceramics, it is often necessary to choose raw material powder with low oxygen content and high performance sintering additives, which undoubtedly increases the preparation cost. The introduction of carbon additives alleviates this problem to a certain extent, so that silicon nitride ceramics with excellent thermal conductivity can be prepared in a wider range of raw materials and additives.
Industrial application prospect
With the continuous progress of technology and the continuous optimization of cost, the method of carbon additive-assisted sintering to prepare high thermal conductivity silicon nitride ceramics is expected to be widely used in industrial production. This method not only improves the thermal conductivity of silicon nitride ceramics, but also reduces the preparation cost, providing a more economical and efficient solution for high-performance electronic packaging, aerospace and energy conversion fields. In the future, we look forward to further promoting the innovative application and development of silicon nitride substrate materials in more fields through more in-depth research and process optimization.
In summary, carbon addition-assisted sintering, as an innovative preparation technology for silicon nitride ceramics, optimizes the microstructure of the material through its unique reduction effect and significantly improves the thermal conductivity of silicon nitride ceramics. This discovery not only opens up a new way for the preparation of high-performance silicon nitride ceramics, but also provides a more economical and efficient solution for the development of electronic packaging, aerospace and energy conversion. With the continuous deepening of research and continuous progress of technology, we have reason to believe that silicon nitride ceramics will show its unique charm and wide application prospects in more fields. At the same time, this will also encourage us to continue to explore new material preparation technology, and promote the progress and development of materials science.
