Multiscale Tomographic Analysis for Micron-Sized Particulate Samples

Three-Dimensional Characterization of Dry Particle Coating Structures Originating from the Mechano-fusion Process

Dry particle coating processes are of key importance for creating functionalized materials. By a change in surface structure, initiated during coating, a surface property change and thus functionalization can be achieved. This study introduces an innovative approach employing 3D X-ray micro-computed tomography (micro-CT) to characterize coated particles, consisting of spherical alumina particles (d50 = 45.64 μm), called hosts, surrounded by spherical polystyrene particles (d50 = 3.5 μm), called guests. The formed structures, hetero-aggregates, are generated by dry particle coating using mechano-fusion (MF). A deeper understanding of the influence of MF process parameters on the coating structures is a crucial step toward tailoring of coating structure, resulting surface property and functionalization. Therefore, the influence of rotational speed, process time, and total mechanical energy input during MF is explored. Leveraging micro-CT data, acquired of coated particles, enables non-stereologically biased and quantitative coating structure analysis. The guest's coating thickness is analyzed using the maximum inscribed sphere and ray method, two different local thickness measurement approaches. Particle-discrete information of the coating structure are available after a proper image processing workflow is implemented. Coating efficiency and guest's neighboring relations (nearest neighbor distance and number of neighbors inside search radius) are evaluated.

Novel Wet Electrospinning Inside a Reactive Pre-Ceramic Gel to Yield Advanced Nanofiber-Reinforced Geopolymer Composites

Electrospinning is a versatile approach to generate nanofibers in situ. Yet, recently, wet electrospinning has been introduced as a more efficient way to deposit isolated fibers inside bulk materials. In wet electrospinning, a liquid bath is adopted, instead of a solid collector, for fiber collection. However, despite several studies focused on wet electrospinning to yield polymer composites, few studies have investigated wet electrospinning to yield ceramic composites. In this paper, we propose a novel in-situ fabrication approach for nanofiber-reinforced ceramic composites based on an enhanced wet-electrospinning method. Our method uses electrospinning to draw polymer nanofibers directly into a reactive pre-ceramic gel, which is later activated to yield advanced nanofiber-reinforced ceramic composites. We demonstrate our method by investigating wet electrospun Polyacrylonitrile and Poly(ethylene oxide) fiber-reinforced geopolymer composites, with fiber weight fractions in the range 0.1–1.0 wt%. Wet electrospinning preserves the amorphous structure of geopolymer while changing the molecular arrangement. Wet electrospinning leads to an increase in both the fraction of mesopores and the overall porosity of geopolymer composites. The indentation modulus is in the range 6.76–8.90 GPa and the fracture toughness is in the range 0.49–0.76 MPam with a clear stiffening and toughening effect observed for Poly(ethylene oxide)-reinforced geopolymer composites. This work demonstrates the viability of wet electrospinning to fabricate multifunctional nanofiber-reinforced composites.

Real-Time Modeling of Volume and Form Dependent Nanoparticle Fractionation in Tubular Centrifuges

A dynamic process model for the simulation of nanoparticle fractionation in tubular centrifuges is presented. Established state-of-the-art methods are further developed to incorporate multi-dimensional particle properties (traits). The separation outcome is quantified based on a discrete distribution of particle volume, elongation and flatness. The simulation algorithm solves a mass balance between interconnected compartments which represent the separation zone. Grade efficiencies are calculated by a short-cut model involving material functions and higher dimensional particle trait distributions. For the one dimensional classification of fumed silica nanoparticles, the numerical solution is validated experimentally. A creation and characterization of a virtual particle system provides an additional three dimensional input dataset. Following a three dimensional fractionation case study, the tubular centrifuge model underlines the fact that a precise fractionation according to particle form is extremely difficult. In light of this, the paper discusses particle elongation and flatness as impacting traits during fractionation in tubular centrifuges. Furthermore, communications on separation performance and outcome are possible and facilitated by the three dimensional visualization of grade efficiency data. Future research in nanoparticle characterization will further enhance the models use in real-time separation process simulation.

PARROT: A Pilot Study on the Open Access Provision of Particle-Discrete Tomographic Datasets

In the present paper, as part of an interdisciplinary research project (Priority Programme SPP2045), we propose a possible way to design an open access archive for particle-discrete tomographic datasets: the PARROT database (https://parrot.tu-freiberg.de). This archive is the result of a pilot study in the field of particle technology and three use cases are presented for illustrative purposes. Instead of providing a detailed instruction manual, we focus on the methodologies of such an archive. The presented use cases stem from our working group and are intended to demonstrate the advantage of using such an archive with concise and consistent data for potential and ongoing studies. Data and metadata merely serve as examples and need to be adapted for disciplines not concerned here. Since all datasets within the PARROT database and its source code are freely accessible, this study represents a starting point for similar projects.

Usefulness of microfocus computed tomography in life science research: preliminary study using murine micro-hepatic tumor models

PURPOSE

Microfocus computed tomography (micro-CT) has not been widely used at high radiation intensity (industrial micro-CT) in life science fields. In this preliminary study, we investigated its potential value in the detection of micro-hepatic tumors in a mouse model.

METHODS

The liver with micro-hepatic tumors was surgically resected en-bloc from mice, and examined with industrial micro-CT and lower intensity micro-CT (small animal micro-CT). The number of hepatic tumors was manually counted on serial images. Then, the accuracy of each technique was determined by preparing matching liver sections and comparing the number of tumors identified in a conventional pathological examination.

RESULTS

The number of hepatic tumors evaluated with industrial micro-CT showed high concordance with the results of the pathological examinations (intraclass correlation coefficient [ICC]: 0.984; 95% confidence interval [CI] 0.959-0.994). On the other hand, the number of hepatic tumors evaluated with the small animal micro-CT showed low concordance with the number identified in the pathological examinations (ICC: 0.533; 95% CI 0.181-0.815).

CONCLUSION

Industrial micro-CT improved the detection of small structures in resected specimens, and might be a promising solution for life science research.