共查询到20条相似文献,搜索用时 453 毫秒
1.
2.
3.
4.
沉积模拟是沉积学理论研究发展的一个重要方法,它分为数值模拟和物理模拟。沉积物理模拟是对自然界中沉积的过程在室内进行的动态模拟,具有更加真实、形象、直观的特点。它为油田进行油气勘探开发、建立沉积学理论知识提供了基本参数与依据。 相似文献
5.
针对循环流化床铁矿粉烧结技术中的关键问题,首次用直接数值模拟方法对不同密度床料颗粒在床内的分布进行了数值模拟。数值模拟将气相场和离散颗粒场分别用欧拉方法和拉格朗日方法进行处理,在每一时间步长内对气相场和离散颗粒场的相互作用进行耦合,得出了焦炭和铁矿粉混合床料在循环流化床内的分离规律。数值模拟结果与国外相同研究的实验结果进行了对比,验证结果表明本文所给出的直接数值模拟方法具有较高的准确性。 相似文献
6.
7.
化学气相渗透(CVI)工艺被广泛应用于制备碳基及碳化硅(SiC)基复合材料,CVI工艺是实现制备高纯度和高晶粒度SiC基体的SiCf/SiC复合材料最佳方案。为了优化CVI制备SiC基体的工艺参数,本文主要研究了CVI工艺沉积SiC的动力学机理及数值模拟。对于CVI工艺SiC沉积的动力学,本文提出了SiC沉积过程的反应动力学机理模型,并通过耦合反应器内的流场和浓度场,模拟了甲基三氯硅烷(MTS)在CVI过程中的SiC沉积实验。通过对样品在CVI致密化过程中孔隙率的实验结果与模拟结果比较,表明该SiC沉积动力学模型的合理性。通过模拟获得了在反应器内的速度场和各组分(MTS, CH3,SiCl3)的浓度场分布情况,以及预制体致密化过程的密度分布情况。以上SiC的CVI工艺动力学模拟,对未来优化SiCf/SiC复合材料CVI工艺具有重要的指导意义。 相似文献
8.
结合沉积坯的实际沉积过程,利用跟踪计算沉积坯表面轮廓线坐标而建立沉积坯形状的预测模型,模拟结果与实验基本吻合,表明该方法可以获得较合理外形的沉积坯;使用有限元分析方法,对沉积坯动态凝固过程做出了表征,并对其温度场做出数值模拟,结果表明,利用数值模拟方法可以理解喷射沉积动态凝固过程,有效优化沉积工艺,对获得优质沉积材料具有一定指导意义. 相似文献
9.
利用双放电腔微波等离子体源全方位离子注入设备,分别采用等离子体增强化学气相沉积技术、等离子体源离子注入和等离子体增强化学气相沉积复合技术两种工艺对医用3161,不锈钢进行类会刚石薄膜表面改性。利用电化学阻抗谱法考察了两种工艺制备的类金刚石薄膜在模拟体液中的抗腐蚀性能。结果表明:与采用等离子体增强化学气相沉积技术制备的类金刚石薄膜相比,在72h的浸泡时间内,采用等离子体源离子注入和等离子体增强化学气相沉积复合技术制备的类金刚石薄膜防腐蚀性能明显增高,腐蚀阻抗较高,碳注入层可有效抑制溶液渗入薄膜和基体之间的界面,起到了腐蚀防护层的作用。动电位极化测试表明:采用复合技术制备的类金刚石薄膜在模拟体液中的腐蚀倾向性更低,钝态稳定性更好。 相似文献
10.
通过对加氢空冷系统NH4HS结晶沉积机理的分析,结合物性仿真计算得到典型工况下NH4HS结晶反应的起始温度。采用HTRI软件获得空冷器管束不同位置的温度分布情况,确定开始发生NH4HS结晶反应的具体位置。通过数值模拟获得流动场、温度场和浓度场作用下的NH4HS结晶沉积规律。研究结果表明:典型工况下加氢空冷系统中发生NH4HS结晶反应的起始位置在第5/6排管束距入口5.9 m处;结晶反应速率最大值位于气相中且靠近气液界面,生成的铵盐颗粒在气相空间靠近上壁面处扩散速率最快,且易沉积于管束顶端;仿真得到最大铵盐沉积量的区域为距出口3.32 m处,与现场检测数据相吻合。研究结果可为后续铵盐沉积腐蚀的定量分析提供依据。 相似文献
11.
综述纳米线的主要制备方法:激光烧蚀法、化学气相沉积法、热气相沉积法、横板法、水热法等,以及目前纳米线的研究进展。 相似文献
12.
Kang Guan Yong Gao Qingfeng Zeng Xingang Luan Yi Zhang Laifei Cheng Jianqing Wu Zhenya Lu 《中国化学工程学报》2020,28(6):1733-1743
The development of functional relationships between the observed deposition rate and the experimental conditions is an important step toward understanding and optimizing low-pressure chemical vapor deposition (LPCVD) or low-pressure chemical vapor infiltration (LPCVI). In the field of ceramic matrix composites (CMCs), methyltrichlorosilane (CH3SiCl3, MTS) is the most widely used source gas system for SiC, because stoichiometric SiC deposit can be facilitated at 900℃-1300℃. However, the reliability and accuracy of existing numerical models for these processing conditions are rarely reported. In this study, a comprehensive transport model was coupled with gas-phase and surface kinetics. The resulting gas-phase kinetics was confirmed via the measured concentration of gaseous species. The relationship between deposition rate and 24 gaseous species has been effectively evaluated by combining the special superiority of the novel extreme machine learning method and the conventional sticking coefficient method. Surface kinetics were then proposed and shown to reproduce the experimental results. The proposed simulation strategy can be used for different material systems. 相似文献
13.
O.K. Mohammed HafizAnugrah Singh 《Chemical Engineering Research and Design》2011,89(6):593-602
The modified chemical vapor deposition (MCVD) process is one of the most widely used processes to manufacture the optical fiber preforms. There have been several experimental and numerical studies to establish that thermophoresis is the dominant mechanism for the transport of silica particles to the preform wall. There also exists several modification of this process to increase the deposition efficiency in the MCVD process. In this work we have carried out computational fluid dynamics simulation of the coupled equations of mass, momentum, energy and species transport in the laser enhanced thermophoretic deposition process using the conservative finite volume scheme. The effect of laser heating on different parameters such as thermophoresis, conversion rate and deposition efficiency is examined in this study. The presence of laser heating alters the velocity and temperature profile that leads to increase in the conversion and deposition efficiency due to high thermophoresis. The results of numerical simulations are in support of experimental and analytical studies. Our numerical simulations using the conservative finite volume scheme show that deposition efficiency increases with increasing power of the laser. 相似文献
14.
15.
流化床-化学气相沉积(FB-CVD)技术是一种多学科交叉的材料制备技术,兼有流化床传热传质性能良好以及化学气相沉积均匀、产物单一等优点,在工业生产中有着广泛的应用,但因其属于交叉学科,散见于各种研究,没有进行专门的进展评述。本文拟对FB-CVD的工业应用进行专题综述,分析其发展和研究趋势。首先探讨了FB-CVD的基本原理,分别综述了其在颗粒包覆、一维纳米材料、多晶硅制备、颗粒表面改性及粉体制备等方面的应用,介绍了FB-CVD的过程模拟及反应器结构优化方面的研究进展。通过以上讨论,梳理了FB-CVD研究的科学内涵。可以看出,该过程具有明显的多尺度特征,即材料制备的微观层次、颗粒流化均匀性的介观层次以及反应器结构设计的宏观尺度。总结得出:FB-CVD技术的未来发展取决于3个尺度的耦合分析,其研究重点也应关注尺度间的相互影响效应,如材料制备的均相成核、非均相成核和颗粒流化及运动规律的相互耦合等。 相似文献
16.
17.
18.
19.
A thermodynamic analysis of the doping of silica glass with nitrogen by the chemical vapor deposition methods has been carried
out. The fundamental differences are revealed between the plasma chemical vapor deposition and modified chemical vapor deposition
methods. The basic parameters of nitrogen introduction into silica glass are determined by thermodynamic calculations. It
is found that the main factor that ensures doping of silica glass with nitrogen by the modified chemical vapor deposition
is an extremely low partial oxygen pressure in the reaction zone. The results of theoretical analysis are used in practice
for nitrogenizing silica glass by modified chemical vapor deposition. The increment in the refractive index is equal to 0.0015. 相似文献
20.
A thermodynamic analysis of the doping of silica glass with nitrogen by the chemical vapor deposition methods has been carried
out. The fundamental differences are revealed between the plasma chemical vapor deposition and modified chemical vapor deposition
methods. The basic parameters of nitrogen introduction into silica glass are determined by thermodynamic calculations. It
is found that the main factor that ensures doping of silica glass with nitrogen by the modified chemical vapor deposition
is an extremely low partial oxygen pressure in the reaction zone. The results of theoretical analysis are used in practice
for nitrogenizing silica glass by modified chemical vapor deposition. The increment in the refractive index is equal to 0.0015. 相似文献