Yasumitsu Tanaka

Synthesis of spinel Li4Mn5O12 with an aid of mechanochemical treatment

Abstract A mechanochemically assisted method for synthesizing spinel Li 4 Mn 5 O 12 has been proposed in this paper. The method involves grinding a mixture of LiOH·H 2 O and γ-MnO 2 in ambient air, followed by heating the ground product. The grinding of the mixture was conducted by using a planetary ball mill, causing their structural changes into amorphous state, which is lithium manganese oxides hydrated (Li–Mn–O· n H 2 O). The ground product can be crystallized into lithium manganese oxide by heating at about 400 °C or more. Heating the ground product at around 600 °C for 12 h results in the formation of pure phase of the spinel. Temperature in the heating stage is an important factor in crystallization of the spinel from the amorphous mixture, and heating up to about 600 °C is suitable for the formation of pure phase spinel. The product synthesized is very fine powder with mean grain size of 100 nm.

Plannar light source using a phosphor screen with single-walled carbon nanotubes as field emitters

We developed and successfully fabricated a plannar light source device using a phosphor screen with single-walled carbon nanotubes (SWCNTs) as field emitters in a simple diode structure composed of the cathode containing the highly purified and crystalline SWCNTs dispersed into an organic In2O3-SnO2 precursor solution and a non-ionic surfactant. The cathode was activated by scratching process with sandpaper to obtain a large field emission current with low power consumption. The nicks by scratching were treated with Fourier analysis to determine the periodicity of the surface morphology and designed with controlling the count number of sandpapers. The anode, on the other hand, was made with phosphor deliberately optimized by coverage of ITO nanoparticles and assembled together with the cathode by the new stable assembling process resulting to stand-alone flat plane-emission panel. The device in a diode structure has a low driving voltage and good brightness homogeneity in that plane. Furthermore, field emission current fluctuation, which is an important factor in comparing luminance devices too, has a good stability in a simple diode panel. The flat plane-emission device employing the highly purified and crystalline SWCNTs has the potential to provide a new approach to lighting in our life style.

Mechanochemical approaches to employ silicon as a lithium-ion battery anode

Silicon is essential as an active material in lithium-ion batteries because it provides both high-charge and optimal cycle characteristics. The authors attempted to realize a composite by a simple mechanochemical grinding approach of individual silicon (Si) particles and copper monoxide (CuO) particles to serve as an active material in the anode and optimize the charge-discharge characteristics of a lithium-ion battery. The composite with Si and CuO allowed for a homogenous dispersion with nano-scale Si grains, nano-scale copper-silicon alloy grains and silicon monoxide oxidized the oxide from CuO. The authors successfully achieved the synthesis of an active composite unites the structural features of an active material based on silicon composite as an anode in Li-ion battery with high capacity and cyclic reversible charge properties of 3256 mAh g−1 after 200 cycles.

Performance Test of Desiccant Heating, Ventilating and Air-Conditioning System by Using Multiple Tracer Gas Dilution Method

The desiccant-based air-conditioning system consists of many heat and mass transfer components operating together with air fans. The performance test using the multiple tracer gas dilution method is important for knowing the internal and external flow rates, including the air leakages. The results of the test show the actual internal air flow rates and the sources of air leakage, and also show the interaction of air in the air-conditioned lecture room and in the mechanical room. The performance test using the multiple tracer gas dilution method in air flow and air leakages is important for a detailed evaluation of any air-conditioning system such as this desiccant-based one.

Controlling the electrical properties of ZnO films by forming zinc and oxide bridges by a plasma and electron-assisted process

A new method to produce electrically steady ZnO films without any heating process has been developed by using plasma and electron beams to facilitate bonding between the metallic component and the oxygen on coated ZnO films. Both plasma atmosphere and electron beams can function as sources of nonequilibrium bonding energy, forming bridges between the zinc present in the zinc complex and the oxygen in the ZnO particles to construct a zinc-oxide thin film. Our results confirm that it is possible to achieve low conductive characteristics by controlling the acceleration voltage of electrons used to irradiate the ZnO coating. The electrically steady films fabricated have various potential applications, being particularly well-suited to electrical devices on a plastic medium.

In-Situ Performance Evaluation of the Desiccant Heating, Ventilating, and Air-Conditioning System Using Multiple Tracer Gas Dilution Method

The desiccant heating, ventilating and air-conditioning system (DHVAC) consists of many heat and mass transfer components operating together with air fans. The performance test using the multiple tracer gas dilution method is important for knowing the internal and external flow rates, including the air leakages. The results of the test show the actual internal air flow rates and the sources of air leakage, and also show the interaction of air in the air-conditioned lecture room and in the mechanical room. The performance test using the multiple tracer gas dilution method in air flow and air leakages is important for a detailed evaluation of DHVAC.

Background on Energy and Resources Strategy

This chapter sets the scene for the series of lectures on energy and resources provided as part of the environmental leader course. Many of the individual lectures (chapters in this book) focus on specific resource or energy issues or technical challenges but these have also to be seen as part of an overall picture, where human activities have reached a scale which can no longer be supported in a sustainable way. This chapter provides some of the background to placing these individual fields in this wider perspective by looking at some of the history of environmental problems in Japan, as well as some key current international issues including global warming and climate change, social issues including poverty, threats to biodiversity and sustainability’s limits and balances.

Nurturing Environmental Leaders Among Science and Engineering Researchers—Tohoku University Approach

This chapter sets the scene for the book by explaining the background reasons why Japan decided to support a range of environmental leader programs. Current trends in growth of both population and economy are placing demands on the Earth’s ability to supply resources or absorb the wastes. This is widely recognized but the current socio-economic system is currently not adapting and exhibits system failures in prioritizing growth over sustainability. Japan’s environmental leader programs are designed to nurture human resources who can help lead society towards a transition to a more sustainable socio-economic system. Tohoku University’s environmental leader program is described in this chapter and the background to the course materials on which this book is based introduced.

Environmental Leadership Training—Effects on Students’ Future Environmental Leadership

This book is based on the experience of developing and applying environmental leadership education and training at Tohoku University, where learners are masters and doctorate researchers in sciences, engineering and humanities. This book’s focus is on a range of issues in energy and resources, but is just one part of the wider curriculum outlined in Chap. 1 aiming to strengthen motivation and provide the necessary knowledge and personal skills to support environmental leadership in the student’s future workplace. This final chapter thus assesses how far we have achieved that role based on student feedback, their decisions in selection of future jobs, and limited feedback from their employment after graduating. This is set against a theoretical framework of leadership in sustainable development.

Technology Development Towards Localised Small-scale Electricity Generation and Its Use in Smart Buildings

Technological development is required for systems which will allow current centralised energy systems to be replaced by more dispersed and multiple low-energy sources. Such a system poses challenges both in maximising possible sources of small energy and also in developing the batteries necessary to deal with their intermittent supply. This chapter describes development of systems which run on limited sources of DC energy, and the interaction between the supply sources and the batteries to provide systems which are resilient to blackouts from natural disasters. It also describes work at Tohoku University on micro-scale generation from activities in everyday life and the first stages towards harnessing local marine energy and biomass sources. This development was tested by the disaster of the Great East Japan Earthquake and Tsunami on March 11, 2011 after which a black out and complete cessation of utilities lasted from a few days to several weeks, emphasising the critical importance of resilient energy sources.