Influences of defects and defect formation on the wet grinding limit

缺陷和缺陷形成对湿磨极限的影响

• 批准号: 178858354
• 负责人: Professor Dr.-Ing. Wolfgang Peukert
• 金额: --
• 依托单位: Lehrstuhl für Feststoff- und Grenzflächenverfahrenstechnik (LFG)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/178858354?language=en
• 关键词: Influences; defects; defect; formation; wet

Top-down processing by wet comminution in stirred media mills is a rather simple, easily scalable yet versatile process towards large scale production of nanoparticles. Fundamental processes leading on the one hand to fracture of particles even in the nanometer size range and on the other hand to a limiting particle size are not yet understood.Within the first funding period of this project significant progress in the understanding of deformation and fracture of submicron spherical model particles as well as a microstructural interpretation of the grinding limit has been achieved: a strong structure-property relation between crosslinking of the underlying silica structure and the mechanical properties has been shown. The brittle-to-ductile transition for this material system was found at a particle size slightly below 1 µm; however, crack formation was still observed. For CaF2, SnO2, ZrO2, and Al2O3 a connection between the observed grinding limit and the particle size dependent capabilities to create and store defects within the particle volume could be shown. To this end, X-ray diffraction, electron microscopy, gas adsorption and molecular dynamic calculations were used. Additionally, a size effect was shown by molecular dynamic calculations for metal nanoparticles: below a limiting particle size of 30 nm a decrease of the elastic properties is observed. Scaling occurs in a linear fashion with the total number of atoms for a given particle size. The underlying reason is seen in the significantly lowered coordination number of the surface near atoms and their increasing influence with decreasing particle size. Further hints pointing towards the commonly underestimated role of the freshly broken surface and its interaction with the surrounding solvent was found for TiO2, SiO2 and a complex glass composition (45S55 Bioglass®): dependent on the used solvent fusion of individual particles, changes in the chemical composition and overall structure, as well as an increasing hydroxylation was found.In addition to breakage and structural changes during comminution, interactions of the solid with the surrounding solvent shall be investigated as an additional aspect during processing. Conditions of true breakage, as observable by in-situ electron microscopy techniques, shall be separated from mainly solvent influenced breakage conditions. By thorough analysis of the solid phase and the surrounding liquid with respect to dissolved species, a mechanistic understanding of the surface mediated interaction between the mechanically stressed solid and the surrounding liquid phase shall be derived. Furthermore, the size dependent true breakage of submicron particles shall be characterized, below the brittle-ductile transition by (multiple) stressing in-situ in a SEM and a TEM. To approach anisotropic fracture fragments, as expected during wet grinding, a stepwise variation of particle microstructure and particle morphology will be performed.

通过在搅拌介质米尔斯中的湿粉碎的自上而下的加工是一种相当简单、易于规模化但多用途的用于大规模生产纳米颗粒的方法。导致颗粒断裂的基本过程，一方面甚至在纳米尺寸范围内，另一方面导致极限颗粒尺寸，目前还不清楚。在该项目的第一个资助期内，在理解亚微米球形模型颗粒的变形和断裂以及对研磨极限的微观结构解释方面取得了重大进展：已经显示了在下面的二氧化硅结构的交联和机械性能之间的强的结构-性能关系。在颗粒尺寸略低于1 µm时，发现该材料系统的脆韧性转变;然而，仍观察到裂纹形成。对于CaF 2、SnO 2、ZrO 2和Al 2 O3，可以显示出观察到的研磨极限与在颗粒体积内产生和储存缺陷的颗粒尺寸相关能力之间的联系。为此，X射线衍射，电子显微镜，气体吸附和分子动力学计算。此外，金属纳米颗粒的分子动力学计算显示出尺寸效应：低于30 nm的极限粒径，观察到弹性性能的降低。对于给定的颗粒尺寸，缩放以线性方式与原子总数发生。其根本原因在于表面原子附近的配位数显著降低，并且随着粒径的减小，配位数的影响越来越大。对于TiO 2、SiO 2和复杂的玻璃组合物，发现了指向通常被低估的新破碎表面及其与周围溶剂的相互作用的进一步提示（45S55 Bioglass®）：取决于单个颗粒的所用溶剂熔融，化学组成和整体结构的变化，除了粉碎过程中的破碎和结构变化之外，在加工过程中，固体与周围溶剂的相互作用也应该作为另一个方面进行研究。通过原位电子显微镜技术观察到的真正断裂条件应与主要受溶剂影响的断裂条件分开。通过对固相和周围液体中溶解物质的全面分析，应得出对机械应力固体和周围液相之间表面介导相互作用的机械理解。此外，亚微米颗粒的尺寸依赖性真实断裂应通过SEM和TEM中的（多重）原位应力表征，低于脆-韧性转变。为了接近各向异性断裂碎片，如湿磨期间所预期的，将进行颗粒微观结构和颗粒形态的逐步变化。

项目成果

Mechanochemical aspects in wet stirred media milling

• DOI: 10.1016/j.minpro.2016.05.018
• 发表时间: 2016-11
• 期刊: International Journal of Mineral Processing
• 作者: Stefan Romeis;Jochen Schmidt;W. Peukert

Enhancing In Vitro Bioactivity of Melt‐Derived 45S5 Bioglass® by Comminution in a Stirred Media Mill

• DOI: 10.1111/jace.12615
• 发表时间: 2014
• 期刊: Journal of the American Ceramic Society
• 影响因子: 3.9
• 作者: Stefan Romeis;A. Hoppe;C. Eisermann;N. Schneider;A. Boccaccini;Jochen Schmidt;W. Peukert

Local densification of a single micron sized silica sphere by uniaxial compression

• DOI: 10.1016/j.scriptamat.2015.06.023
• 发表时间: 2015-11
• 期刊: Scripta Materialia
• 影响因子: 6
• 作者: Stefan Romeis;Jonas Paul;P. Herre;D. Ligny;Jochen Schmidt;W. Peukert

Correlation of Enhanced Strength and Internal Structure for Heat‐Treated Submicron Stöber Silica Particles

热处理亚微米二氧化硅颗粒的增强强度与内部结构的相关性

• DOI: 10.1002/ppsc.201300306
• 发表时间: 2014
• 期刊: Particle & Particle Systems Characterization
• 影响因子: 2.7
• 作者: S. Romeis;J. Paul;M. Hanisch;V.R.R. Marthala;M. Hartmann;R.N. Klupp Taylor;J. Schmidt
• 通讯作者: J. Schmidt

In situ cracking of silica beads in the SEM and TEM — Effect of particle size on structure–property correlations

• DOI: 10.1016/j.powtec.2014.10.026
• 发表时间: 2015
• 期刊: Powder Technology
• 影响因子: 5.2
• 作者: Jonas Paul;Stefan Romeis;M. Mačković;V. Marthala;P. Herre;T. Przybilla;M. Hartmann;E. Spiecker;Jochen Schmidt;W. Peukert