Julian Wagner

Thermal-runaway experiments on consumer Li-ion batteries with metal-oxide and olivin-type cathodes

Li-ion batteries play an ever-increasing role in our daily life. Therefore, it is important to understand the potential risks involved with these devices. In this work we demonstrate the thermal runaway characteristics of three types of commercially available Li-ion batteries with the format 18650. The Li-ion batteries were deliberately driven into thermal runaway by overheating under controlled conditions. Cell temperatures up to 850 °C and a gas release of up to 0.27 mol were measured. The main gas components were quantified with gas-chromatography. The safety of Li-ion batteries is determined by their composition, size, energy content, design and quality. This work investigated the influence of different cathode-material chemistry on the safety of commercial graphite-based 18650 cells. The active cathode materials of the three tested cell types were (a) LiFePO4, (b) Li(Ni0.45Mn0.45Co0.10)O2 and (c) a blend of LiCoO2 and Li(Ni0.50Mn0.25Co0.25)O2.

Development of an Itraconazole-loaded nanostructured lipid carrier (NLC) formulation for pulmonary application

Itraconazole-loaded NLC for pulmonary application were developed. In Precirol ATO 5 and oleic acid Itraconazole had the highest solubility. The solid lipid and the oil were mixable in a ratio 9:1 possessing a melting point above body temperature. 0.4% Itraconazole was dissolved in this lipid blend. Eumulgin SLM 20 was the stabilizer with the highest affinity to the lipid blend used as particle matrix. 2.5% Eumulgin SLM 20 was sufficient to obtain NLC with a narrow particle size distribution and sufficient stability. The tonicity of the formulation was adjusted with glycerol. Sterility was obtained by autoclaving. Neither the addition of glycerol nor autoclaving had an influence on the particle size and the zeta potential of Itraconazole-loaded NLC. SEM images showed spherical particles confirming the particle size measured by light scattering techniques. An entrapment efficiency of 98.78% was achieved. Burst release of Itraconazole from the developed carrier system was found. Itraconazole-loaded NLC possessed good storage stability. Nebulizing Itraconazole-loaded NLC with a jet stream and an ultrasonic nebulizer had no influence on the particle size and the entrapment efficiency of Itraconazole in the particle matrix, being a precondition for pulmonary application.

Serial sectioning methods for 3D investigations in materials science

A variety of methods for the investigation and 3D representation of the inner structure of materials has been developed. In this paper, techniques based on slice and view using scanning microscopy for imaging are presented and compared. Three different methods of serial sectioning combined with either scanning electron or scanning ion microscopy or atomic force microscopy (AFM) were placed under scrutiny: serial block-face scanning electron microscopy, which facilitates an ultramicrotome built into the chamber of a variable pressure scanning electron microscope; three-dimensional (3D) AFM, which combines an (cryo-) ultramicrotome with an atomic force microscope, and 3D FIB, which delivers results by slicing with a focused ion beam. These three methods complement one another in many respects, e.g., in the type of materials that can be investigated, the resolution that can be obtained and the information that can be extracted from 3D reconstructions. A detailed review is given about preparation, the slice and view process itself, and the limitations of the methods and possible artifacts. Applications for each technique are also provided.

Adiponectin-coated nanoparticles for enhanced imaging of atherosclerotic plaques

Background: Atherosclerosis is a leading cause of mortality in the Western world, and plaque diagnosis is still a challenge in cardiovascular medicine. The main focus of this study was to make atherosclerotic plaques visible using targeted nanoparticles for improved imaging. Today various biomarkers are known to be involved in the pathophysiologic scenario of atherosclerotic plaques. One promising new candidate is the globular domain of the adipocytokine adiponectin (gAd), which was used as a targeting sequence in this study. Methods: gAd was coupled to two different types of nanoparticles, namely protamine-oligonucleotide nanoparticles, known as proticles, and sterically stabilized liposomes. Both gAd-targeted nanoparticles were investigated for their potency to characterize critical scenarios within early and advanced atherosclerotic plaque lesions using an atherosclerotic mouse model. Aortic tissue from wild type and apolipoprotein E-deficient mice, both fed a high-fat diet, were stained with either fluorescent-labeled gAd or gAd-coupled nanoparticles. Ex vivo imaging was performed using confocal laser scanning microscopy. Results: gAd-targeted sterically stabilized liposomes generated a strong signal by accumulating at the surface of atherosclerotic plaques, while gAd-targeted proticles became internalized and showed more spotted plaque staining. Conclusion: Our results offer a promising perspective for enhanced in vivo imaging using gAd-targeted nanoparticles. By means of nanoparticles, a higher payload of signal emitting molecules could be transported to atherosclerotic plaques. Additionally, the opportunity is opened up to visualize different regions in the plaque scenario, depending on the nature of the nanoparticle used.

A method to measure the total scattering cross section and effective beam gas path length in a low-vacuum SEM.

A method is presented to determine the total scattering cross section of imaging gases used in low-vacuum scanning electron microscopy or environmental scanning electron microscopy. Experimental results are presented for water vapor, nitrogen gas and ambient air for primary beam electron energies between 5 and 30 keV. The measured results are compared and discussed with calculated values. This method allows the effective beam gas path length (BGPL) to be determined. The variations of the effective BGPL with varying chamber pressure are presented.

A potential tailor-made hyaluronic acid buccal delivery system comprising rotigotine for Parkinson's disease?

AIMS Parkinsons disease (PD) affects over 10 million people around the world. Dysphagia is one of its main problems. Therefore, mucosal delivery is beneficial for patient compliance. This study aimed to synthesize mucoadhesive hyaluronic acid (HA) comprising rotigotine for the treatment of PD. MATERIALS & METHODS HA - a biocompatible, naturally occurring polysaccharide - was chemically modified with the thiol-bearing ligand cysteine ethyl ester via amide bond formation (HAC). HAC was evaluated in terms of stability, cytotoxicity, permeation enhancement, controlled drug release and mucoadhesiveness. RESULTS HAC showed 1.49-fold higher stability, 3.47-fold improved swelling capacity and 12.16-fold augmentation in mucoadhesion. Additionally, HAC exhibited 1.18-fold permeation enhancement over HA. DISCUSSION Taking the findings into consideration, HAC represents a pillar of mucosal buccal delivery in the treatment of PD.

Thinking continuously: a microreactor for the production and scale-up of biodegradable, self-assembled nanoparticles

Scale-up of nanoparticle batch productions continues to be a major challenge in the pharmaceutical nanotechnology. Continuously operating microreactors have great potential to circumvent the scale-up difficulties. In this work a passive microreactor was used for the first time for the electrostatic self-assembly of biodegradable, mucoadhesive thiomer–protamine nanoparticles for drug delivery. The influence of three different parameters (the overall flow rate, the educt mass ratio and the molecular weight of the thiomer) on the particle characteristics was tested for the microreactor production and compared to the results of a successful 1 ml-batch reaction. As the flow rate increased (2, 5, 9, 16 ml min−1), the particle sizes and the polydispersity indexes decreased. In addition, the protamine : 5 kDa thiomer binding ratio and hence the zeta potential, as a measure of the suspensions stability, increased to >+40 mV due to better mixing during the microreactor production at a flow rate of 16 ml min−1. Producing nanoparticles from different mass ratios of 5 kDa thiomer : protamine (1 : 1, 1 : 3, 1 : 5) in the microreactor at this flow rate resulted in smaller particles with more distinct zeta potentials than those prepared by the 1 ml-batch reaction. Using a higher molecular weight thiomer (30 kDa) for the microreactor production at a flow rate of 16 ml min−1 led to slightly increased mean particle sizes (125.0 nm) compared to those produced by the 1 ml-batch reaction (102.9 nm). However, there was still a decrease in the width of the particle size distributions. In addition to the experimental work, a numerical model based on the population balance equation was developed. The results presented in this paper are in agreement with the experimental findings, especially with regard to the trends of decreased particle size and polydispersity with the increasing flow rate. The model results confirm that mixing effects to a great extent determine the particle size distribution of the resulting nanoparticles and show that spatial inhomogeneity of the mixing process must be taken into account. The unprecedented use of a passive microreactor for the production of biodegradable thiomer–protamine nanoparticles by electrostatic self-assembly was a success. Due to the reactors continuous way of operation, not only were the scale-up problems of batch reactions overcome, but particle characteristics were also improved because of a better mixing effect.

High purity pressurised hydrogen production from syngas by the steam-iron process

The production of hydrogen in a fixed bed reactor at a maximum pressure of 50 bar by oxidising an oxygen carrier (Fe2O3/Al2O3/CeO2) with 0.06 g min−1 of steam at 1023 K is discussed. Reductions were performed with synthesis gas at ambient pressure and 1023 K for 90 minutes. The influences of the elevated system pressure on the carbon contamination, the quantification of the contaminations in the produced hydrogen and the oxygen carrier conversion are analysed. The results show that small amounts of carbon depositions are formed during the reduction, which are re-oxidised with steam leading to the contamination of the hydrogen. The hydrogen purity obtained in the experiments is within the range of 99.958% to 99.999% with CO as the main impurity. The amount of contaminations as a result of the oxidation of the solid carbon is not influenced by the elevated system pressure, which confirms the suitability of the reformer steam-iron process in a fixed bed to produce pressurised hydrogen directly from a hydrocarbon feed. The oxygen carrier conversion displays an initial drop followed by a slightly linear decrease. Air-oxidations revealed a regeneration effect on the oxygen carrier conversion, which reversed a part of the conversion losses.

Automated X-Ray Elemental Analysis in Three Dimensions Using a Dual Beam-Focused Ion Beam System

Investigation and analysis of inhomogeneous microstructures in three dimensions is very important for developing highly structured materials such as functionally ceramics or semiconducting devices successfully. A focused ion beam microscope (FIB) offers one way to investigate fine subsurface details by using the ion beam selectively removing material and exposing underlying structures [1]. A dual Beam FIB consists of both, an ion and an electron source (dual beam FIB) equipped with an X-ray detector is capable of elemental analysis also into the third dimension. By sequentially milling the sample with the ion beam and subsequently analyzing the produced cross-section by using the electron beam for scanning electron microscopy (SEM) images [2,3]. A series of images created this way can be used to virtually reconstruct a 3D volume model, provided the spatial distance between the milling steps (further called ‘slices’) is well known [4,5,6]. Monitoring and interrupting the slicing process then allows detailed analytical investigations of defects by energy dispersive X-ray spectroscopy (EDXS). Additionally, if EDXS information is gathered for each slice, a 3D reconstruction of elemental information (3D-EDXS) becomes also possible, as recently shown [7]. Performing such an investigative analysis method by manually cutting the slices and starting the EDXS acquisition is a time consuming task, which puts a practical limitation to this method. In this work we thus demonstrate the first fully automated longterm slice-view-&-map experiment with subsequent 3D-EDXS reconstruction of a large volume (2000 μm 3 ) with high spatial resolution.

Experimental determination of the total scattering cross section of water vapour and of the effective beam gas path length in a low vacuum scanning electron microscope.

Low Vacuum Electron Microscopy enables the investigation of non-conductive samples without special preparation procedures. The imaging gas inside the specimen chamber is responsible for the contrast formation by gas amplification and the generated positive gas ions suppress charging of the sample. But the gaseous environment inside the chamber is limiting the capability of the microscope by elastic and inelastic collisions of the primary beam electrons (PEs) with the gas molecules. This so called skirt effect degrades the signal to noise ratio by generating gaseous secondary electrons (SEs) as well as SEs from regions far away from the focused probe. Therefore the primary beam loses exponentially electrons to a broadly dispersed skirt along the beam gas path length (BGPL) (1).