Lignocresol was synthesized from Hinoki cypress (Chamaecyparis obtusa) through the phase-separation system with p-cresol and 72% sulfuric acid. Molecular responses of lignocresol for heating were observed at around 160°C. These behaviors were caused by molecular rearrangement associated with the cleavages of benzyl aryl ether linkages. By the alkaline treatment under ordinary pressure at room temperature, benzyl aryl ether linkages with phenolic units are cleaved, and then low molecular lignin fractions are formed. After the alkaline treatment, thermal stability of lignocresol was improved. The glass-transition temperature (Tg) of lignocresol was shifted up by removing the low molecular weight units. The solid-liquid transition temperature was also shifted. These results indicated that the low molecular weight fractions released from lignocresol work as plasticizer. Lignophenols are bio-based thermo plastics, self-providing plasticizer through molecular rearrangement under high energy condition.
The underwater shock wave selectively destroys the tracheid of the conifer by the effect of the spalling destruction, and forms the extraction road of an internal tree sap. The shock wave that is the instantaneous high pressure reaches the entire cell, and the effects are expected more than usual static pressures. As for the essential oil obtained by steaming distilling Hiba (Thujopsis dolabrata var. hondae) sawn wood, a variety of physiology revitalizations like the antibacterial activity and the effect etc. of insecticide of Hinokitiol that is the principal ingredient are admitted. As a preprocessing, treating the underwater shock wave to Hiba sawn wood, the essential oil is expected to be able to be extracted more highly effective than a usual steam distillation. In this research, the increasing of the amount of Hinokitiol included in the essential oil by the shock wave loading is reported.
The fabrication of ferroelectric nanocrystal materials such as Pb(Zr,Ti)O3 has been widely researched because of the development of high capacity ferroelectric random access memory devices (FeRAM) and ferroelectric domain physics at the nano scale. The ultra flat surface of electrically conductive materials such as Pt is required for the deposition of the ferroelectric nanocrystal substrate. In this paper, Pt deposition was performed using our newly developed sputtering method (low angle incidence sputtering) on an atomically flat sapphire substrate. Due to Volmer-Waber growth, the sputtered Pt grew into island crystals at the normal deposition rate. However, lateral growth of Pt occurred at a very low rate, and the ultra thin atomically flat Pt layer could be obtained on the atomically flat sapphire surface. The Pt thin layer was also evaluated using electrically conductive atomic force microscope (C-AFM) measurement, confirming electric conduction of the atomically flat Pt layer. The obtained atomically flat Pt layer is expected to be utilized for electrical evaluation of PbTiO3 nanocrystal array.
The electronic structure at surface of Y-doped BaCeO3 (BaCe1-xYxO3-δ) has been studied by soft-X-ray spectroscopy. The conduction band and valence band are mainly composed of Ce 4f state and the O 2p state hybridized with the Ce 4f state, respectively. The energy gap of BaCeO3, which corresponds to the energy separation between the top of the valence band and the bottom of the conduction band, is approximately 3.0 eV. The Fermi level in the surface state shifts to the valence band side with y concentration. The valence band consists of the mixed valence states of 4f0 (Ce4+) and 4f1L. (Ce3+). The Ce4+ and Ce3+ states decrease with Y concentration. The existence of Ce3+ state disappears above x=0.08.
The electronic structure of La0.6Sr0.4FeO3 thin film on MgO substrate has been studied using resonant soft-X-ray emission spectroscopy (SXES) and X-ray absorption spectroscopy (XAS). The thin film has the mixed valence states of Fe2+ and Fe3+ in the ground state. The valence band is mainly composed of O 2p state hybridized with t2g and eg states of Fe 3d. The conduction band is composed of t2g and eg states of Fe 3d. and hole-induced state created by Sr doping. These findings accord with the result of electronic structure expected by tight-binding calculation that included the effect of electron-electron interaction.
Oxide nanoparticles of Bi-Ti-O system were fabricated in TiO2 host material by ion beam irradiation. The implanted nanoparticles were evaluated by high-energy X-ray diffraction. The irradiated Bi ions were implanted in the TiO2 as Bi2O3. The implanted Bi2O3 were changed to Bi2Ti2O7 through heating process. The host TiO2 was not damaged seriously by the Bi-ion irradiation owing to its diffuse crystal system. This technique can be used to make the ferroelectric nanoparticle in the paraelectric host material and realize the structure of magnetostrictive material similar to SmFe2.
The electronic structure in the bulk state of SrTiO3-δ single crystal has studied by X-ray absorption spectroscopy (XAS) and soft-X-ray emission spectroscopy (SXES). The SrTiO3-σ exhibits the electrical conductivity in semiconducting region. The Ti 3d DOS is created in the band gap energy region by substituting oxygen vacancies. The SXES spectra exhibit the soft-X-ray Raman scattering structures, which correspond to d-d transition from occupied Ti 3d state to unoccupied Ti 3d state. The peak position of the Raman scattering reflects the half on-site Coulomb energy (Udd/2).
The indicatrix rotation in domains far from the 90° domain wall in the tetragonal phase was theoretically discussed on the basis of the Ginzburg-Landau free energy. It is pointed out that the Lagrangian strain tensor guaranteeing the total rotational invariance of the elastic energy should be used to reproduce the indicatrix rotation and to estimate the domain wall thickness in ferroelectric materials.
We have performed first-principles tensile tests of silica glass to investigate effects of the local structure on the intrinsic mechanical properties. We found that the bond-network flexibility with the rotation of SiO4 tetrahedra plays an important role for the relief of local strain and that strained ring structures such as three-membered rings are hard to be rearranged. The less flexibility near strained ring structures results in the larger elastic constant and higher tensile strength.
Bi88Sb12 was prepared by mechanical grinding (MG) followed by hot pressing. The disks were cut and then deformed using high pressure torsion (HPT) at 373 K under a pressure of 6.0 GPa. The number of turns in the HPT process was either one or five. Metallurgical and structural characterizations were performed using scanning electron microscopy, differential thermal analysis, X-ray diffraction, and Vickers microhardness measurements. The thermoelectric properties were estimated by measuring the thermal and electrical conductivities, and the Hall and Seebeck coefficients. The HPT samples prepared using one turn were homogeneous and finely grained; those prepared using five turns were coarse grained. The results indicated that grain growth occurred after HPT deformation, which was consistent with the microhardness results. The thermal conductivity of the as-sintered MG sample was 2.83 W m−1 K−1 at room temperature, which was lower than values previously reported for samples prepared by mechanical alloying (MA). The power factors of the HPT samples were almost the same as that of the as-sintered MG sample.
Asbestos is a biopersistent fiber made mainly of silica, which has been widely used in industry and engineering. This broad use of asbestos is due to its unique physicochemical properties and low cost. However, inhalation of asbestos is now clearly linked with development of lung cancer and malignant mesothelioma. Malignant mesothelioma is a cancer arising from mesothelial cells that are the lining cells of somatic cavities, such as pleura, peritoneum and pericardium. The mechanism of mesotheliomagenesis is still unclear, and thus how dimension (long/thin), shape (straight/tangled) and constituents (iron) of fibers are contributing to cancer development is yet to be answered. The investigation of the carcinogenic mechanism is now becoming more and more important because we now welcome a new type of biopersistent fibers, carbon nanotubes. Although there are many differences between carbon nanotubes and asbestos, there is an important similarity in needle-like structure and durability. In order to avoid the case that carbon nanotubes would bring about similar environmental health problems as asbestos, we should hasten to elucidate how biopersistent fibers can be oncogenic. Here we summarize classical hypotheses of mesotheliomagenesis and recent advances in fiber toxicology.
CrO2 is a ferromagnetic half metal with 100% polarization of conduction electrons, and BaTiO3 has been known as to be ferroelectric at room temperature. We prepared the multi-ferroic granular junctions from the mixture of CrO2 and BaTiO3. If the BaTiO3 forms a good tunneling barrier for conduction electrons, the enhancement of magneto-resistance ratio (MRR) can be expected. The field dependences of resistivity of (BaTiO3)x(CrO2)1-x showed that the | MRR | becomes maximum at x=0.5.
We assayed biologically significant isoprenoids for antibacterial and antifungal activities. Isoprenoids varied widely with respect to their growth inhibitory activities towards Gram-positive and Gram-negative bacteria and fungal species. Of particular interest was the finding that geraniol acted as a broad spectrum of antibiotic, and significantly inhibited the growth of Gram-positive Staphylococcus aureus 209P and methicillin resistant S. aureus 834, Gram-negative Escherichia coli IFO-3806, and Shigella sonnei, as well as the fungus Trichopyton sp. Farnesol inhibited S. aureus strains 209P and 834 to a greater extent than did geraniol, but did not detectably inhibit Gram-negative bacteria.
Experiments on plasma irradiation to ionic liquids (ILs) have been initiated. Despite lower density and kinetic energy of ions, discoloration of ILs is still observed. Spectrometric and calorimetric measurements show that once the visible change in color of ILs happens, spectra of both the crystallization temperature and the melting point completely disappear, suggesting decompositions of a part of components of ILs by plasma irradiation.
Electrochemical sensors based on electrolysis of chlorine (Cl2) and phosgene (COCl2) gas have been developed by using gas permeable membrane modified by ion irradiation technique. An expanded polytetrafluoroethylene (ePTFE) membrane is a chemically stable substance and has high permeability of gases without permeation of electrolytic solutions. In this study, gas permeable membrane of ePTFE has been made of ion irradiation of Ne+ with a fluence of 1×1015 ions/cm2. After ion-irradiation into ePTFE, Ag was coated by a vacuum evaporation method, which was used as a working electrode to construct the electrochemical gas sensors for Cl2 and COCl2. The sensitivity for Cl2 and COCl2 of the sensors used the ion-irradiated ePTFE membrane showed significant enhancement, which was more than 3.8 and 1.3 times higher than that of non ion-irradiated one. Morphology change of ePTFE by ion irradiation was observed by scanning electron microscopy. The enhancement of the sensitivity by the ion irradiation is due to changing of active nature of the Ag electrode and increase of the effective surface area.
The departure process of residual Ga in diamond-like carbon (DLC) film synthesized by focused-ion-beam chemical vapor deposition (FIB-CVD) was investigated by measuring Rutherford backscattering (RBS) spectra of FIB-CVD DLC films after heat treatment in various conditions. The annealing temperature and annealing time were varied in the range of 473-973 K and 0-64 h, respectively. The decrease in Ga concentration and transfer of Ga in the FIB-CVD DLC film were not observed due to heat treatment at less than 573 K. The transfer of residual Ga from inside the film to the surface, and the formation of Ga spheres, which were surrounded by a graphite shell, were observed after heat treatment at 673 K, but Ga concentration did not vary much. When the annealing temperature was higher than 773 K, a decrease in the Ga concentration was observed. The depth profile of Ga in the DLC film in the RBS spectra was observed to divide into two peaks when treated with heat at temperatures higher than 673 K. This splitting can be interpreted as the difference in the desorption rate of Ga in the DLC, graphite shell, and Si substrate.
Surface damage/modification of n-GaN by Xe plasma etching has been investigated for a variety of gas pressures and etching times, using an experiment and a simulation. The result has been compared with that for the Kr plasma etching. The surface morphology etched by the Xe plasma is dependent on gas pressure and etching time. At a low gas pressure (10 mTorr), where there is no UV light emission from the plasma, the surface morphology is observed to be as smooth as that of the as-grown surface, and is independent of etching time. At a high gas pressure (50 mTorr), where there is the UV radiation emission resulting from XeII, there are defects on the etched surface when the etching time increases (200 min), which would probably result from synergy effect of the Xe plasma ions and UV radiations. This result is significantly different from that etched by the Kr plasma which does not change from that of the as-grown surface. The simulation also shows that the Ga/N ratio at the surface etched by the Xe plasma is lower than that by the Kr plasma, which would be related to the difference between the surface morphologies by these two plasmas.
We have searched for an optimum condition to form a specific defect center called NV-N (nitrogen-vacancy-nitrogen) in a diamond, which is of interest, because of the possibility of a NOT system in a quantum computer. It is composed of one NV center made of a substitutional nitrogen (N) coupled with an adjacent vacancy (V) and an associated N atom. The second N is located at a mean distance (RN-N) of ～ 2 nm. Considering the cohesive potentials we performed an empirical molecular dynamic simulation for the low-energy N2 beam implantation into a diamond. The identification of a NV center was performed by a crystallographic analysis called the pixel-mapping (PM) method based on crystallography. We found that impact energy E0 could be decisive for the mean distance RN-N, while temperature T was decisive for the formation of NV centers. The optimum set of conditions to form an NV-N center is a compromising choice of (E0,T). The formation probability of the NV center exceeded 20 % when using (E0,T) = (200 (eV/atom), 1000 K), however, the mean value ＜RN-N＞ was below 1.5 nm. A little higher energy than 200 (eV/atom) will be necessary for ideal NV-N centers.
Surface damage of gold-ion implanted Co-WC micro-punch tools during press processing was evaluated by using a novel die system to monitor changes in the tool surface after each punch. A previously developed micro device fabrication system using micro press forming system was used to fabricate the tools. Despite the advantage of micro scale forming processes in downsizing production, the relative toughness of the formed tools is a serious problem. The lifespan of the tools, particularly punch tools, is too short for manufacturing use. Punch holes are typically smaller than 100 mm, and the fracture toughness is equal to the stress. The lifespan of punch tools can be increased by using the ion implantation method that we previously developed, involving gold ion implantation with post thermal annealing. However the lifespan of ion implanted punch is not enough for manufacturing, we try for clear a reason of this achievement and try to increasing lifespan. In this current study, we used a novel die system to monitor the surface damage of a punch after each punch. Results revealed that adhesion of work material on the punch surface differed between the ion implanted and un-implanted surfaces of the punch tools. The surface modification decreased the adhesion of the sheet metals, thus increasing the lifespan of the punch tool.
Fundamental study on sterilizing polymeric film by ion bombardment is carried out. The sterilization isachieved by physical reaction of high energy ions with Bacillus subtilis spores which are attached to the polymeric film surface, although in usual “plasma sterilizations” the sterilization is achieved by plasma-enhanced chemical reaction of toxic molecules with the spores. The plasma-based ion implantation (PBII) is utilized in order to implant ions into insulated material without electric charging problems. Microwave plasma is generated in magnetic field with nitrogen gas. Spores of Bacillus subtilis on a polymeric film are bombarded by nitrogen ions with the energy of up to 10 keV. Since the ion bombardment is carried out with pulse mode of 0.5 % in duty cycle, the film temperature can be kept low enough to avoid heat damage to the polymeric film. Thedependencies of ion energy and ion fluence on the sterilization rates are obtained. The technique is expected to be further developed and applied to treating polymer bottles in future.
Coating of die steel substrates with DLC/Ti bi-layered films by magnetron DC sputtering was examined, in order to improve not only both the surface hardness and the wear resistance at the same time but also the adhesion between the deposited film and the substrate by relaxing the stress concentrated at the interface between them. The deposition of DLC/Ti bi-layered films onto the substrates was carried out in the atmosphere of argon. by sputtering of a titanium target followed by sputtering a carbon one. Under visual observation, the obtained DLC/Ti bi-layered films appeared to be adhesive while the DLC monolithic films deposited directly onto the substrates peeled off partly. Thus it was found that the DLC/Ti bi-layered films were more adhesive to the die steel than the DLC monolithic films. According to indentation hardness measurements, it was found that the surface hardness of the die steel could be improved by coating it with the DLC/Ti bi-layered films. Under optical microscopy, it was assumed that the deposited film could cover most of fine pits which had originally existed on the surface the die steel substrate. Furthermore, according to friction tests, it was found that the tribological property of the die steel could be also considerably improved by coating it with the DLC/Ti bi-layered films.
We have prepared water-repellent thin films on polycarbonate substrates by inductively coupled C2H2F2/Ar plasma CVD method for hydrophobic nature of automobile plastic window. The adhesion of water-repellent film is investigated by an ion-assist effect. Main plasma was produced by inductive discharge. C2H2F2 and Ar mixture gases were introduced into the vacuum chamber at a fixed each other pressure of 20Pa. As the source gas includes fluorine atoms, negative ions are formed in the deposition area. Thus, in order to achieve the ion assist effect to the deposition due to the negative ions, the substrates was biased by positively pulsed voltage. The adhesion of a deposition film was estimated by the hardness of the pencil. It is obtained that the hardness pencil of the prepared film at substrate bias frequency of 500 Hz and pulsed bias voltage of 300V is the highest in various conditions. A water contact angle of the prepared film is attained at about 100 degree.
We have investigated dual-frequency sputtering plasma for higher deposition rates of aluminum nitride thin films. Main plasma was produced by inductively coupled discharge where an internal antenna with 100 mm in diameter was input by RF power of 13.56 MHz. The aluminum sputtering target was biased by not magnetron discharge voltage but a self–biased voltage of 1 MHz because of the uniform erosion of the target. Influence of external parameters such as target voltage Vt, target-antenna distance d and gas pressure p on the deposition rate of aluminum thin films was examined. The antenna-substrate distance was fixed at 20 mm. The highest deposition rate of aluminum thin film with 21 nm/min was obtained at Vt = -800 V, d = 50 mm and p = 70mTorr in the proposed dual frequency sputtering plasma source.
We have observed secondary electron microscope (SEM) images of the surfaces of Si with native oxide layers and highly oriented pyrolytic graphite (HOPG) irradiated with highly charged ions (HCIs, Ar11+) produced by an electron beam ion source at the fluence in the order of 1013～1014 /cm2. The contrast of SEM image changes brighter at irradiated areas for graphite surfaces, while the contrast for the Si surface become darken at irradiated areas. The SEM contrast between irradiated and unirradiated areas is understood in terms of the voltage contrast mechanism in the interpretation of SEM images. When the strength of the contrasts is roughly compared with the sample irradiated with singly charged ions (SCIs), HCI has 100 times higher efficiency for the production of SEM contrast than SCI. The high efficiency reflects the nature of interaction between HCI and surface.
The research results of the cubic carbon nanosized particle synthesis during short pulse ion beam implantation to silicon target are presented. The experiments are carried out using the high power ion beam accelerator “TEMP”. The beam parameters are as follows: the ion energy is 250-300 keV, the pulse duration is 80 ns, the elemental composition of beam is carbon ions and protons, and the ion current density is 20-25 A/cm2. The formation of SiC nanosized particles and nanodiamonds in the surface layer of silicon is found out under sequential action of more than 100-500 pulses.
This paper presents an experimental study on Mn diffusion in the icosahedral quasicrystal Al69.9Pd20.5Mn9.6. The diffusion was measured by depositing Mn on the surface and measuring the rate of change in surface composition as a function of temperature by Low Energy Ions Scattering (LEIS), followed an Arrhenius relation from which an activation energy for the diffusion could be derived. The surface composition was monitored over the temperature range of 355K to 575K. Activation energy (0.20 ±0.01) eV has been measured for self diffusion of Mn in icosahedral Al-Pd-Mn. No deviation from Arrhenius behavior was detected in the temperature range covered by the present experiment.
Thermal evolution of Co precipitates in sapphire implanted with 5∙1017 Co+ ions/cm2 at 120 keV is studied. XRD measurements show that Co precipitates formed directly after implantation have average size of about 10 nm and grow in size to about 30 nm after annealing at 800 -1200℃ by means of monotonous Ostwald ripening process. In the final state they assume cubic form aligned with the sapphire lattice.
Ion beam at energy lower than tens of keV has been found to have significant biological effects on living materials. The finding has led to applications of ion-beam induced mutation and gene transfer. From the theoretical point of view, the low-energy ion beam effects on biology are difficult to understand with the knowledge of high-energy ion irradiation of biological matter since the ion range is so short that the ions can hardly directly interact with the key biological molecules for the changes. This paper introduces interesting aspects of low-energy ion beam biology, including basis of ion beam biotechnology and recent developments achieved in Chiang Mai University in relevant applications such as mutation and gene transfer and investigation on mechanisms involved in the low-energy ion interaction with biological matter such as eV-keV ion beam bombardments of naked DNA and the cell envelopes.
Swift heavy ion (SHI) beam (120 MeV Au, 1013 ions/cm2) irradiation of Zr/Si multilayers, deposited on Si substrates at room temperature, resulted in complete mixing of the structure, transforming it directly into a single layer of purely crystalline ZrSi2 (C49 type structure) on the substrate. As-deposited and SHI irradiated samples were analyzed by specular x-ray reflectivity and grazing incidence x-ray diffraction. The generation of this refractory silicide, known to be vital to integrated device processing, directly on Si and without annealing is a technologically useful result. Dynamics of the process was attributed to electron-phonon energy transfer and interdiffusion at the interface during transient melt phase, through application of thermal spike model. Within the framework of this model, the present work establishes an experimentally observed threshold for electronic excitation (Se) of Zr (24.4 keV/nm), leading to mixing in the Zr/Si system. However, this value is lower than the reported threshold for defect/track creation by electronic energy loss in Zr (28 keV/nm). Since it is known that SHI induced mixing takes place across the interface when Se exceeds this threshold, the results obtained through this study signify in effect, the greater sensitivity of Zr to swift heavy ion induced radiation damage.
The introduction of vacancies in palladium (Pd) was found to be effective for an increase in the initial hydrogen absorption reaction rate in a previous study. And it also has been reported that the initial hydrogen absorption reaction rate depends strongly on the surface conditions of metals. For the surface modification of materials, ion irradiation is known to be a quite useful method. Especially, heavy ions with keV ranges can create severe damage and high densities of vacancy near the surface of materials. As is further known, the formation of hydride phases can be facilitated by the presence of vacancy since vacancy acts as hydrogen trapping site to form hydrides. Therefore, the hydrogen absorption characteristics of Pd could be heavy ions with an energy range of keV such as chromium (Cr) ions. The Pd sample was irradiated with these ions at room temperature at TIARA (Takasaki Ion Accelerators for Advanced Radiation Application) of JAEA (Japan Atomic Energy Agency). The initial hydrogen absorption reaction rate of Pd was investigated before/after ion irradiations using an electrochemical method at room temperature. As a result, the initial hydrogen absorption reaction rate increase due to ion irradiation and the value became 3 ～ 10 times higher than un-irradiated Pd sample by ion irradiations. In order to obtain the information on electric charge of the hydriding process, the work function (contact potential) was also measured at several spots on the surface of Pd samples before/after ion irradiations by use of Kelvin probe. In this paper, the correlation among ion irradiation conditions, work function and initial hydrogen absorption reaction rate of Pd are reported.