碳化表面的温度依赖氧化行为:反应分子动力学模拟
Qing Xie1,2, Xiao Liu2, Shuguang Zhou2
1State Key Laboratory of Environment-friendly Energy Materials, Southwest University of Science and Technology, Mianyang 621010, China.
ACS applied materials & interfaces
|October 3, 2024
概括
碳化 (SiC) 的高温氧化遵循一种被动机制,氧化速率受到反应动力学和氧气通过层扩散的限制. 这种理解是飞机热保护系统的关键.
科学领域:
- 材料科学 材料科学 材料科学
- 化学工程是化学工程的重要组成部分.
- 航空航天工程 航空航天工程
背景情况:
- 碳化 (SiC) 对于高温应用至关重要,特别是在飞机的热保护系统中.
- 了解SiC在高温下氧化机制对于材料设计和性能至关重要.
- 关于控制SiC氧化过程的原子级过程,现有的知识差距仍然存在.
研究的目的:
- 为了研究碳化 (SiC) 表面和接口的高温氧化机制.
- 分析温度和氧气对二氧化 (SiO2) 增长和氧化动态的影响.
- 阐明涉及SiC氧化中的原子级化学反应过程和扩散机制.
主要方法:
- 使用反应分子动力学模拟来建模SiC氧化.
- 模拟涵盖了300-2300 K的温度范围.
- 分析的重点是的生长,氧化阶段和氧气扩散.
主要成果:
- 氧化遵循一种被动机制,其特点是逐渐增长的层.
- 确定了三个不同的氧化过程:初始吸附,快速Si/C氧化和接口氧化.
- 氧化速率受到氧气通过二氧化层的扩散屏障的阻碍,在后期阶段激活能量增加.
结论:
- 这项研究为SiC的热氧化行为提供了原子规模的见解.
- 氧化动力学受到反应速率和氧气扩散系数的影响.
- 发现有助于设计用于热保护应用的先进陶材料.
更多相关视频
13:58Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics
Published on: September 28, 2016
08:02Rendering SiO2/Si Surfaces Omniphobic by Carving Gas-Entrapping Microtextures Comprising Reentrant and Doubly Reentrant Cavities or Pillars
Published on: February 11, 2020
相关概念视频
01:24Redox Reactions
Oxidation-reduction or redox reactions involve the transfer of electrons from one molecule or atom to another. When an atom gains an electron, another atom must lose an electron, meaning oxidation and reduction must occur together. Since the redox occurs in pairs, the atom that gets oxidized is also called the reducing agent or reductant, and the atom that is reduced is also called the oxidizing agent or oxidant. A straightforward way to remember the definitions of oxidation and reduction is...
02:55Temperature Dependence on Reaction Rate
The Collision Theory
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates.
The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates.
The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
03:06Reaction Mechanisms
Chemical reactions often occur in a stepwise fashion, involving two or more distinct reactions taking place in a sequence. A balanced equation indicates the reacting species and the product species, but it reveals no details about how the reaction occurs at the molecular level. The reaction mechanism (or reaction path) provides details regarding the precise, step-by-step process by which a reaction occurs.
For instance, the decomposition of ozone appears to follow a mechanism with two steps:
For instance, the decomposition of ozone appears to follow a mechanism with two steps:
01:24Thermodynamics: Activity Coefficient
Activity is the measure of the effective concentration of the species in solution. It can be expressed as the product of the molar concentration of the species and its activity coefficient. The activity coefficient is a dimensionless quantity and depends on the total ionic strength of the solution.
The activity coefficient is a measure of the deviation from ideal behavior. When the ionic strength of the solution is minimal, the activity coefficient of an ionic species is close to unity, making...
The activity coefficient is a measure of the deviation from ideal behavior. When the ionic strength of the solution is minimal, the activity coefficient of an ionic species is close to unity, making...
01:24The Kinetic Model of Gases
The kinetic model of gases explains the properties of a perfect gas using three main assumptions: molecules move in ceaseless random motion, their size is negligible compared to the distances between them, and they do not interact except during perfectly elastic collisions. The total energy of a gas is the sum of the kinetic energies of all its constituent molecules. The pressure exerted by the gas arises from the continual bombardment of the container walls by billions of colliding molecules.
01:22Heterogeneous Catalysis
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...