Volume expansion of amorphous silicon electrodes during potentiostatic lithiation of Li-ion batteries

Large volume modifications during electrochemical cycling of electrodes in Li-ion batteries often limit successful applications due to stress formation, electrode fracture and delamination from the current collector. In this study, we carried out investigations on the volume changes taking place during potentiostatic lithiation of the high capacity electrode material amorphous silicon. Thin film electrodes were investigated at potentials of 0.45, 0.28, 0.19 und 0.06 V vs Li/Li+ during lithiation using in-operando neutron reflectometry. We found a strongly non-linear correlation between volume and state-of-charge for each potential applied in strong contrast to the results of galvanostatic lithiation. A possible explanation might be that for high current densities occurring at the beginning of each potentiostatic lithiation step free volumes are created in the electrode material leading to disproportionate volume expansion

Correlation of electrical properties and acoustic loss in single crystalline lithium niobate-tantalate solid solutions at elevated temperatures

Electrical conductivity and acoustic loss Q−1 of single crystalline Li(Nb,Ta)O3 solid solutions (LNT) are studied as a function of temperature by means of impedance spectroscopy and resonant piezoelectric spectroscopy, respectively. For this purpose, bulk acoustic wave resonators with two different Nb/Ta ratios are investigated. The obtained results are compared to those previously reported for congruent LiNbO3. The temperature dependent electrical conductivity of LNT and LiNbO3 show similar behavior in air at high temperatures from 400 to 700 °C. Therefore, it is concluded that the dominant transport mechanism in LNT is the same as in LN, which is the Li transport via Li vacancies. Further, it is shown that losses in LNT strongly increase above about 500 °C, which is interpreted to originate from conductivity-related relaxation mechanism. Finally, it is shown that LNT bulk acoustic resonators exhibit significantly lower loss, comparing to that of LiNbO3

Achieving Energy Efficiency in Accordance with Bioclimatic Architecture Principles

By using our natural resources, and through inefficient use of energy, we produce much waste that can be recycled as a useful resource, which further contributes to climate change. This study aims to address energy effective bioclimatic architecture principles, by which we can achieve a potential energy savings, estimated at thirty-three per cent, mainly through environmentally affordable reconstruction, resulting in low negative impact on the environment. The study presented in this paper investigated the Ulpiana neighbourhood of Prishtina City, focusing on urban design challenges, energy efficiency and air pollution issues. The research methods consist of empirical observations through the urban spatial area using a comparative method, in order to receive clearer data and information research is conducted within Ulpiana’s urban blocks, shapes of architectural structures, with the objective focusing on bioclimatic features in terms of the morphology and microclimate of Ulpiana. Energy supply plays a key role in the economic development of any country, hence, bioclimatic design principles for sustainable architecture and energy efficiency, present an evolutive integrated strategy for achieving efficiency and healthier conditions for Kosovar communities. Conceptual findings indicate that with the integrated design strategy: energy efficiency, and passive bioclimatic principles will result in a bond of complex interrelation between nature, architecture, and community. The aim of this study is to promote structured organized actions to be taken in Prishtina, and Kosovo, which will result in improved energy efficiency in all sectors, and particularly in the residential housing sector

2. The Concept of “Modelarium” and its Impact on Creativity And Artistic Education

Students and Teachers are an epic symbiosis in process of direct learning and academic advancement. Nowadays, this interaction is more bonded and interdependent with technology and equipment‟s, which in a whole system expands learning horizons. The digital era has introduced in the education system new modes of learning, a new way of life and style in schooling. This phenomenon changed the methods of teaching in universities, where lectures were accompanied with concrete explanations of works in modeling, in structural and conceptual sense. The relationship between a student of architecture and teachers broadened with introduction of computer aided modeling and simulation tools to construct those ideas into the reality. The study presented in this paper investigates conceptual methods in art, architecture, creativity and innovation in academic education, focusing on interactive teaching issues, and methods. The research methods consist of empirical observation carried out during 25 years of experience in academia, and direct observation of teaching methods. The purpose of this paper is to examine the evolutive process in teaching relations between architectural students and teachers, with the focus in educational competencies and communication skills. Findings indicate that through artistic concepts of “Modelarium” as an unconventional learning space, a tool and space that enables the partnership. An informal meeting place for artistic interaction, but, concurrently it is a formal part of the educational system in architectural studies, a strategy by which we can bring more: time, conceptual awareness of space and interactive teaching in architecture, which bonds multidimensional threads between students and teachers; thus, fostering a powerful sense of partnership, avoiding boredom and passive learning, while facing the challenges, associated with the development of technology, life style, real issues and global world trends. Research suggests that uniform and/or partially new strategy, cannot respond to all specific issues faced by students in day to day basis. Therefore, new teaching strategies must involve new partnerships, a brand new and a redefined role as a holistic symbiosis, as an response to a less functional and/or conventional academic system. Partnership, a new working symbiosis between students and teachers is an answer to the needs of working together simultaneously towards continuous improvement of academia processes

Correlation of Electrical Properties and Acoustic Loss in Single Crystalline Lithium Niobate-Tantalate Solid Solutions at Elevated Temperatures

Electrical conductivity and acoustic loss Q−1 of single crystalline Li(Nb,Ta)O3 solid solutions (LNT) are studied as a function of temperature by means of impedance spectroscopy and resonant piezoelectric spectroscopy, respectively. For this purpose, bulk acoustic wave resonators with two different Nb/Ta ratios are investigated. The obtained results are compared to those previously reported for congruent LiNbO3. The temperature dependent electrical conductivity of LNT and LiNbO3 show similar behavior in air at high temperatures from 400 to 700 °C. Therefore, it is concluded that the dominant transport mechanism in LNT is the same as in LN, which is the Li transport via Li vacancies. Further, it is shown that losses in LNT strongly increase above about 500 °C, which is interpreted to originate from conductivity-related relaxation mechanism. Finally, it is shown that LNT bulk acoustic resonators exhibit significantly lower loss, comparing to that of LiNbO3