Abstract: An attempt to prepare Fe2VAl deposited film and the thermoelectric module using RF
sputtering has been made. Sputtering target has been prepared using mechanical alloying of
metallic powders and the subsequent pulse current sintering process. The obtained deposited film
has had a lack of aluminum content compared to the composition of the starting material.
Controlling of aluminum content for the preparation of Fe2VAl sputtering target has made it
possible to obtain the desired material composition. The film has had the experimental
thermoelectric force being similar to the one estimated from the measured thermoelectric data of the
materials. Fe2VAl thermoelectric module of eight pairs with a film thickness of 4 μm has had an
electric force of 31mV and 5.6μW.
Abstract: Creatures have evolved extremely intelligent and complex adaptive systems
for conducting their movements. They are protein motors with typical sizes of a few
tens of nanometers. Protein motors include three major protein families, myosin, kinesin
and dynein, which participate in a wide range of cellular processes, using energy from
the hydrolysis of adenosinetriphosphate ATP. To harness these protein motors to power
nanometer-scale devices, we have investigated effective and non-destructive methods
for immobilizing protein motors on surfaces and to arrange the output of these motors,
e.g. force and movement, to be in a defined direction. We found NEB-22 to be useful
for retaining the abilities of protein motors to support the movement of protein filaments.
We fabricated various patterns of tracks of NEB-22 on coverslips and protein motors
were introduced and immobilized on glass surface. The trajectories of protein polymers
were confined to these tracks. Simple patterns readily biased and guide polymer
movement confining it to be unidirectional. In addition, having used dynein c purified
from Chlamydomonas flagellar axoneme, we showed that microtubules driven by
surface-bound dynein were self-organized into dynamic streams through collisions
between the microtubules and their subsequent joining.
Abstract: Both bulk and thin film amorphous carbon were irradiated using a nitrogen
ion beam and changes in surface roughness and composition after ion beam irradiation
have been studied. Amorphous carbon thin films were prepared from toluene vapor
using plasma enhanced chemical vapor deposition. Ion irradiation was performed at
room temperature using a nitrogen ion beam and the ion beam energy was varied from
0.2 to 1.5 keV under the constant ion current density. Surface morphology was
observed with atomic force microscopy (AFM). Depth profiles of nitrogen in the
irradiated specimens were analyzed by X-ray photoelectron spectroscopy (XPS). AFM
observations reveal that after the ion beam irradiation the surface of the bulk amorphous
carbon becomes rough, while the surface of the amorphous carbon films becomes
smooth. However, the notable difference in the surface roughness is hardly observed
between low- and high-energy ion irradiation. From XPS studies, it is found that the
nitrogen concentration near the surface increases after the ion irradiation for both bulk
and thin films and irradiated nitrogen ions are combined with carbon, resulting in
formation of carbon nitride layers. Depth profiles of nitrogen show that for the bulk
specimen low-energy ion irradiation is more effective for the carbon nitride formation
than high-energy ion irradiation, while for the thin films high-energy ions are implanted
more deeply than low-energy ions.
Abstract: A new kind of nanocomposite rare-earth magnets of Nd2Fe14B/ α-Fe were prepared by
melt-spinning method. Effects of alloying element and processing parameter on the microstructure
and magnetic properties of nanocomposite materials have been investigated. Zr is effective to
enhance coercivity of alloys because of a refinement of grains, so that in alloy of Zr content with
1.0 at% (Zr1.0) has the smallest grain size of 17 nm and therefore causes the highest intrinsic
coercivity . Addition of Zr can also enhance the ability of amorphous-forming. The combination of
adding of Zr and using a smaller diameter of the nozzle in the melt-spinning method is effective for
the forming of amorphous structure.
According to the MFM study, the length of the magnetic contrast in the alloy is much larger
than the mean grain size. The large length corresponds to that of interaction domains(ID), which is
related to the exchange coupling effect.
Abstract: Ba8Al16Si30 type I clathrate was produced by arc melting and thermoelectric properties
were investigated. The phase transformation behavior of arc-melted type I Ba8Al16Si30 was
examined by thermogravimetric analysis, differential scanning calorimetry, hardness test, density
measurement, X-ray diffraction and scanning electron microscope analyses. Homogenization was
carried out to induce the transformation to a thermoelectric phase at 773K to 973K for 5 hours and
24 hours in the vacuum furnace. Thermoelectric properties in the temperature range between 300K
and 600K were measured and evaluated. Electrical conductivity was decreased and Seebeck
coefficient was increased with increasing homogenization temperature and time. The arc-melted
and the homogenized specimens represented n-type conduction at temperatures examined, and they
showed reliable thermoelectric behaviors with increasing homogenization temperature and time.
Abstract: In this research, we investigated the fabrication conditions of Ti-Ni alloy powder by MA
process and the shape memory characteristics of the sintered alloy by a pulse-current sintering
equipment using mechanically alloyed powder (MA powder). The microstructure of the sintered
alloy of the MA powder was more homogeneous than that of the alloy of the elemental powders.
The application of the MA powder makes the width between transformation temperatures of the
shape memory treated alloy of the MA powder became narrower, that is, it improves the
temperature response of the compact. The tensile strength and elongation of the shape memory
compact of the MA powder were approximately 780 MPa and 7.5 %, respectively. This is one of
the superior tensile properties of SMA compact fabricated by powder metallurgy process. The
superelastic behavior took place in the alloy of the MA powder. Thus, the MA process in short
process time resulted in lower contamination of the MA powder and the application of the MA
powder resulted in superior shape memory characteristics of the sintered alloy.
Abstract: The electromechanical properties of a newly proposed 3-dimensional piezoelectric
transformer have been investigated. Especially, the effects of 3-dimensional geometry on the
maximum tip displacement were carefully investigated. As a result, it was found that the maximum
strain of the 3-dimensional piezoelectric device was significantly enhanced up to 4.5 times higher
than that of a disk shape device. This data were in good agreement with the finite element model
analysis of strains and vibration modes. Moreover, a very high voltage step-up ratio of 290 (10
times higher than the Rosen type), sustaining efficiency more than 96%, were achieved.
Abstract: CuAlNi shape memory alloy with Cu-13.5Al-4.5Ni(wt%) composition was prepared by
cross-rolling method and the aging effect, phase transformation characteristics, microstructural
variation were investigated. Transformation temperature was greatly increased in aged specimens at
250°C. Transformation temperature was not changed after the second reversed transformation, and
Ms point was same in most specimens with third reversed transformation cycle. The variation of Ms
point was not seen with aging at 100°C, but it was decreased with aging at 250°C. Transformation
temperatures appear to be constant, to an measurable extent, in specimens prepared by both hotrolling
and cross-rolling at 900°C. Plate shaped-specimen with the thickness of about 1mm was
prepared by cross-rolling treatment at 350°C. The transformation temperatures did not change after
the second transformation-reverse transformation cycling, and specially transformation start
temperature was the same in most specimens experiencing third thermal cycle and thereafter.
Undesirable tweed-like structure was observed in 250°C-aged specimen after a cross-rolling at
350°C. On aging the specimen prepared by cross-rolling, G.P zone was formed easier than that of γ2
phase. This phase was transformed to plate-like θ phase during aging.
Abstract: Stored energy plays a crucial role in recrystallization process. One can distinguish two
contributions to this energy. The first one is the elastic energy, connected with residual
stresses, i.e., with grain-grain interaction. Another part of the stored energy is due to
dislocation density, which is mainly localized inside grains. The latter one is considered as a
main driving force of recrystallization. However, the stored energy connected with residual
stresses can also have some influence on this process. Both types of energy can be determined
experimentally and predicted by deformation models. Taking into account both types of the
stored energy, some features of recrystallization textures can be explained.
Abstract: Crystallographic texture has an important effect on the magnetic quality of electrical steel: a specific
texture parameter A is defined and used to estimate the magnetic quality of texture components. It is
shown that obtaining the best possible texture in non oriented electrical steel can reduce the losses
with 1,5 W/kg. Two production schemes for high silicon electrical steel are described: a
conventional processing through hot and cold rolling with adequate temperatures and cooling rates
and an immersion-diffusion process by hot dipping in a Si- and Al-rich bath followed by diffusion
annealing. The texture evolution in these experimental materials is under study and first results are
reported for conventional alloys (rolling procedure) and for immersion-diffusion alloys, which are
annealed after dipping in order to obtain a controlled concentration gradient with high Si and/or Al at
the surface or a homogeneous Si and/or Al-content over the thickness.