Assistant professor：Sayaka Yanagida
Glasses are very beautiful materials which have been made for more than 6,000 years and have widely utilised as window glasses and tableware. Nowadays, optical communication system and displays for TV, PC and smartphone are not able to fabricate without fine glass materials. We mainly investigates the high performance glass and ceramic materials which are applicable to solve various problems on natural resources, environment and energy, and additionally, to help chemical-bio sensing and medical treatment.
In various oxide glasses, silicate glasses of which main component is silica (SiO2) are excellent materials because of their optical, thermal and mechanical properties, high chemical durability and easy forming ability. The glasses are also good as “host” materials because they can contain functional substances (“guest”) and enhance their performances. For example, transition metal ion doped glasses show beautiful colours and such glasses can make their practicability and artistic points go together.
Nowadays, the global problems in energy, environment and natural resources are matters of great urgency. For the solutions to such problems, one of the important materials is a light emitted diode (LED). The LEDs have good performance of not only energy saving but also small and lightweight, so that the LED lighting system has rapidly spread and become common. However, it is still necessary to increase their performance in order to improve their light emitting power, colour rendition and light diffusing ability.
We investigate various glasses containing transition metal ions or appropriate phosphors as luminous materials for a LED lighting system. For example, we studies cupper ion doped glasses which can emit warm incandescent colour without using rare and/or hazardous elements. Another is RGB phosphors containing glasses which can show high rendering light emission.
Titania (TiO2) is a typical semiconductor which shows excellent photocatalytic reaction well known as Honda-Fujishima effect. Nowadays, various materials have been developed and practically utilized, which show self-cleaning, antibacterial and sterilization, and photo-decomposition of pollutants by photocatalytic reactions induced by titania This unique reaction and technique originated in Japan is widely spreading all-over the world.
We now challenge to prepare high photocatalytic functional materials. The target applications are photo-decomposition of pollutants, photo-machining of material surfaces, and sensing of hydrogen, organic substances or bio molecules by combination of semiconductor photocatalyst, glasses and other functional materials.
For example, we investigate the composite materials which consist of titania, porous adsorbents and transparent glass substrate or fibres in order to adsorb interior hazardous substances such as volatile organic compounds and ammonia in a short time, and to decompose them by photocatalytic reaction. On the other hand, we also try to utilize photocatalytic reaction for chemical-bio sensing. We combine titania thin film or porous material with noble metal nano particles such as platinum, palladium and gold in order to prepare a combustion type gas sensor and chemical-bio sensors utilizing localized surface plasmon resonance (LSPR).
Generally, glasses do not show electro conductivity and ferromagnetic. However, when the glass is combined with semiconductor and/or magnetic materials, the obtained composite can show such properties. Particularly, a magnetic semiconductor which has both electro conductivity and ferromagnetic property show various interesting properties: those are change of electro conductivity by magnetic field and heat generation by high frequency magnetic field.
We prepare magnetic composite materials having high function and low environment load by combining silicate glasses with ferrite which does not contain rare elements. The combination of ferrite with glass enable protection of ferrite from oxidation and/or chemical attacks, particular shape forming such as needle, glazing on ceramics. We also utilize the forming of manometer scale texture and crystallization by using phase separation phenomenon of glass to realize the functional materials.
For example, we select magnetite and Mn-Zn ferrite as ferromagnetic materials and combine them with silicate glasses. The obtained composite materials show both electro conductivity and ferromagnetic. These materials are expected to be applicable to magnetic sensing under severe condition such as high temperature and/or high humidity. Another targeting property is heat generation under high frequency magnetic field which are applicable to ceramics for IH cooker and hyperthermia for cancer treatment.