On the design of aluminum-based complex hydride systems for chemical hydrogen storage

The present study focuses on the development of Al-based systems and their examination as a medium for reversible hydrogen uptake. The first part of this thesis is dedicated to the chemistry and properties of Al-N-based materials. The synthesis, characterization, and detailed thermal decomposition studies of several aminoalanes have been described. As a result, single-crystal X-ray diffraction analyses revealed two new crystal structures of piperidinoalanes. The perspective approach employing activated aluminum and piperidine for reversible hydrogen uptake has been established. The second part of this work was focused on the modification of the properties of NaAlH4-based systems in order to generate the material with the high dissociation pressure suitable for high-pressure tank technologies. Considerable progress has been achieved in improving the hydrogen sorption properties by adding the extra aluminum powder to the Ti-catalysed NaAlH4-based system. Thus, the present study contributes to the understanding of the hydrogen sorption behavior of Al-based systems with perspectives being applicable to other related materials.:DECLARATION ACKNOWLEDGEMENTS DEFINITIONS AND ABBREVIATIONS ABSTRACT CONTENTS LIST OF TABLES LIST OF FIGURES MOTIVATION AND GOALS 1 INTRODUCTION 1.1 The prospects for hydrogen-based energy systems 1.2 Requirements for the hydrogen storage system 1.3 An overview of hydrogen storage strategies 1.4 Complex hydrides as a promising hydrogen storage materials 1.4.1 Metal borohydride systems 1.4.2 Alanate-based systems 1.4.3 Nitrogen-containing complex hydrides 1.5 Summary 2 GENERAL CHARACTERIZATION METHODS 2.1 X-ray crystallography 2.1.1 X-ray powder diffraction (XRPD) 2.1.2 Single-crystal structure analysis 2.2 Thermal analysis 2.3 Quantitative chemical analysis 2.3.1 Elemental analysis 2.3.2 Inductively coupled plasma optical emission spectrometry (ICP-OES) 2.4 Nuclear magnetic resonance spectroscopy (NMR) 3 LIQUID-STATE HYDROGEN STORAGE 3.1 State of the art 3.1.1 Liquid-state hydrogen storage materials 3.1.2 Al-N-based compounds as potential materials for hydrogen storage 3.1.3 Summary 3.2 Materials preparation and experimental details 3.2.1 Chemicals and sample handling 3.2.2 Synthesis of aminoalane in diethyl ether solution with aluminum hydride 3.2.3 Preparation of activated aluminum 3.2.4 Direct hydrogenation of activated aluminum supported by amine 3.3 Results and discussion 3.3.1 Is the solid-state hydrogen storage in aminoalanes possible? 3.3.2 Optimization of the direct hydrogenation of activated aluminum supported by amine 3.3.2.1 Synthesis and characterization of triethylenediamine alane complex 3.3.2.2 Synthesis of aminoalanes via direct hydrogenation of activated aluminum and N-heterocyclic amine 3.3.3 Investigation of piperidinoalanes for reversible hydrogen uptake 3.3.3.1 Crystal structure determination of piperidinoalanes 3.3.3.2 Influence of the initial reaction parameters on the piperidinoalane formation 3.3.3.3 Reversible hydrogenation in piperidinoalane system 3.3.4 Conclusions 4 SOLID-STATE HYDROGEN STORAGE 4.1 State of the art 4.1.1 Thermodynamic tuning of the hydrides 4.1.2 Features of the sodium alanate system 4.1.3 Catalytic enhancement of reversible hydrogenation in sodium alanate 4.1.4 The relevance of the Al-TM species in doped sodium alanate 4.1.5 Summary 4.2 Materials preparation and experimental details 4.2.1 Chemicals and purification procedure 4.2.2 Activation procedure of sodium alanate via mechanochemical treatment 4.2.3 Pressure-composition-isotherm measurements with a Sieverts-apparatus 4.2.4 High-pressure differential scanning calorimetry investigation of sodium alanate samples 4.3 Results and discussion 4.3.1 Tailoring the properties of sodium alanate-based system with the help of Ti-additive 4.3.2 Influence of the aluminum addition on the sorption behavior of Ti-doped sodium alanate 4.3.3 High-pressure DSC study of hydrogen sorption properties of doped sodium alanate system 4.3.4 Conclusions 5 SUMMARY AND CONCLUSIONS RECOMMENDATIONS AND OUTLOOK REFERENCES SUPPORTING INFORMATION Appendix A Appendix B Appendix C Publication

Everyday struggle - Gender Equal Working Conditions for Females in Cambodia?

Compared to other East Asian countries, Cambodia has relatively high female labor force participation rates. More than 75 percent of women are working, compared to the regional average of 60% (World Bank 2018). However, the educational background of many people, especially females coming from rural areas, is still poor in Cambodia, Therefore, the garment industry and the construction sector offer low-threshold job possibilities for less educated females in order to gain a stable income. Whereas the garment industry is defined as dominated by females, the construction sector is still characterized as typical male sector. The study aims to ask to what extend less educated females, coming from poor areas of Cambodia can enjoy and benefit from their work lives. In addition, gender stereotypes and gender inequality concerning the female workforce in garment and construction are presented. As previous research has focused on quantitative analysis, this study tried to explore perceptions of females working in the garment and construction sector by using the qualitative method of focus group discussions

Co-Constructing Crises – To what extend does digitalization contribute to a professionalization of social, person-related services?

This paper addresses the impact of experiences with digital teaching and digital advising processes in social, person-centered studies courses and fields of work such as Early Childhood Education, Social Work and Nursing. The central point of reference is the fact, that social, person-centered services are very young professions, characterized by speficic professional criteria that are closely linked to personal negotiation and communication processes between professionals and clients. By taking a closer look at the effects of online teaching and learning and the need to establish alternative exchange formats in the fields of work, the question is addressed to which competencies students at universities should be taught in the future in order to be able to meet the challenges and changes in their fields of work as professionals

Malaysia and Its Transition Process Towards More Gender Equality at the Labor Market

The promotion of labor market opportunities for females in Malaysia has been part of several quantitative studies. Although the empirical data stresses the existence of gender-related constraints females are facing when trying to access labor market, the reasons remain mainly unexplored. Thus, this qualitative study tried to identify major constraints and challenges females are facing when entering the Malaysian labor market. Focus group discussions with different groups of females aged 16 to 50 have been conducted, as well as with employers and HR Managers of global players. The study identifies local disparities between rural and urban living as major consequences for female labor market access and the achievable employment situation. The analysis of the focus groups also highlights that two groups of women – females living in Projek Perumahan Rakyat (PPR) or “People ́s Housing Project” areas and Single Mothers – are strongly affected from often being no constant part of labor market but trapped in side-jobs or non-satisfying microbusinesses. The solidification of social inequality by an absence of support structures and empowerment programs can be seen as the most important reason. Policy recommendations, based on the empirical results, are therefore discussed in order to stimulate a discussion on gender equality

Family Day Care in Germany – the gap between vision and reality

In Germany, family day care has dominated for a long time as a more or less informal provision of childcare. With massive legal changes in the system of Early Childhood Education and Care (ECEC) since 2006, family day care became a part of the formal ECEC system and has now the same comprehensive legal tasks of education and care. This leads both to profound changes and to challenges for the system of family day care. This report provides an overview of current developments in family day care in Germany and the perspectives of its enhancement. In addition to considering the quantitative development, it mainly deals with the paradigms of a qualitative upgrading, which in particular emphasizes the current structures of the public support for family day care such as an adequate advisory system or qualification. We have based this overview mainly on qualitative and quantitative data from research at the German Youth Institute within the last five years. There is still a gap between the development of day care and its legal equality in the ECEC system on the one hand and the conditions condition and everyday structures on the other hand. The quantitative development of family day care does not yet involve a necessary qualitative upgrading of this day care system yet

Forced Degradation Testing as Complementary Tool for Biosimilarity Assessment

Oxidation of monoclonal antibodies (mAbs) can impact their efficacy and may therefore represent critical quality attributes (CQA) that require evaluation. To complement classical CQA, bevacizumab and infliximab were subjected to oxidative stress by H2O2 for 24, 48, or 72 h to probe their oxidation susceptibility. For investigation, a middle-up approach was used utilizing liquid chromatography hyphenated with mass spectrometry (LC-QTOF-MS). In both mAbs, the Fc/2 subunit was completely oxidized. Additional oxidations were found in the light chain (LC) and in the Fd’ subunit of infliximab, but not in bevacizumab. By direct comparison of methionine positions, the oxidized residues in infliximab were assigned to M55 in LC and M18 in Fd’. The forced oxidation approach was further exploited for comparison of respective biosimilar products. Both for bevacizumab and infliximab, comparison of posttranslational modification profiles demonstrated high similarity of the unstressed reference product (RP) and the biosimilar (BS). However, for bevacizumab, comparison after forced oxidation revealed a higher susceptibility of the BS compared to the RP. It may thus be considered a useful tool for biopharmaceutical engineering, biosimilarity assessment, as well as for quality control of protein drugs