Crystal orientation of β-phase isotactic polypropylene induced by magnetic orientation of N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide

Melt crystallization of isotactic polypropylene (iPP), containing crystallites of N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide (DCNDCA) as a nucleating agent of the the β-phase iPP crystal, is carried out under a magnetic field (6 T) to obtain the alignment of the iPP crystal induced by magnetic alignment of DCNDCA. In a previous paper, DCNDCA was reported to undergo magnetic alignment in a liquid suspension. The obtained iPP sample exhibits alignment of the β-phase crystal with the c-axis aligned perpendicular to the magnetic field. The comparison of this alignment of iPP with the reported magnetic alignment of DCNDCA indicates that the β-phase crystal grows epitaxially on the DCNDCA crystal. The (330)_β plane of the iPP crystal lies on the bc-plane of the DCNDCA crystal in which the direction of the c-axis of the iPP coincides with the direction of the b-axis of the DCNDCA crystal.     

Influences of perforation ratio in characteristics of capacitive micromachined ultrasonic transducers in air

Capacitive micromachined ultrasonic transducers (CMUTs) with a perforated membrane have been fabricated and characterized in air. Two types of CMUT device have been fabricated having perforation ratio (area ratio of holes = AR) of 10% and 20%, and analyzed about electrical and mechanical characteristics. The perforation ratio (AR) of membrane substantially influences on the electrostatic force and mechanical restoring force of the device since it leads to the area variation of electrode and membrane, it subsequently influences on the sensitivity and frequency response of the CMUT device. The electrostatic force and mechanical restoring force were improved by decreasing the AR and increasing the DC bias voltage. The open-circuit sensitivity of a CMUT having AR 10% membrane, 8.45 μV/Pa, is larger than that of AR 20%, 4.07 μV/Pa at DC 15 V. Furthermore, the resonance behaviors were observed in the range of 60-80 kHz, and the resonance frequency could be changed by varying the applied DC voltage and AR.     

Performance enhancement of partially and fully depleted strained-SOI MOSFETs

The authors have developed short-channel strained-silicon-on-insulator (strained-SOI) MOSFETs on silicon-germanium (SiGe)-on-insulator (SGOI) substrates fabricated by the Ge condensation technique. 35-nm-gate-length strained-SOI MOSFETs were successfully fabricated. The strain in Si channel is still maintained for the gate length of 35 nm. The performance enhancement of over 15% was obtained in 70-nm-gate-length strained-SOI n-MOSFETs. Fully depleted strained-SOI MOSFETs with back gate were successfully fabricated on SGOI substrate with SiGe layers as thin as 25 nm. The back-gate bias control successfully operated and the higher current drive was obtained by a combination of the low doping channel and the back-gate control.     

Effect of toughness distribution in the thickness direction on long brittle crack propagation/arrest behaviour of heavy gauge shipbuilding steel

ABSTRACT

Brittle crack arrestability of the heavy gauge steel plates for shipbuilding is now an important issue for the recent mega container ships. In the present work, the brittle crack arrestability of the steel plate with different toughness distributions in thickness is examined in ultra-wide duplex ESSO tests. It is examined whether a running long brittle crack arrests or not in flat temperature condition in ultra-wide duplex ESSO test that are harder mechanical conditions similar to an actual ship hull condition. Test temperatures are selected at which arrest toughness, Kca, evaluated by temperature gradient type standard ESSO test is the same for two test plates. The steel plate with higher toughness in mid-thickness (t/2) than that in quarter thickness (t/4) could arrest a running long brittle crack although the plate with lower toughness in mid-thickness than that in quarter thickness could not arrest it. The typical split-nail shape appeared at the arrested crack front in the plate with higher toughness in mid-thickness than that in quarter thickness. The numerical analyses also demonstrate that the local stress intensity factor at the arrested crack tip is changing sensitively to the crack front shape. It suggests that the higher brittle crack arrestability appears due to the split-nail shape of the arrested crack front enhanced by the inhomogeneous toughness in thickness.     

Porous Titania Ceramic Prepared by Mimicking Silicified Wood

A porous titania ceramic with a woodlike microstructure that was analogous to silicified wood was prepared. The production of "titanified wood" was performed using the following process: (i) introduction of titanium tetraisopropoxide into wood materials via vacuum infiltration, (ii) hydrolysis of the titanium tetraisopropoxide in the cell structure to form a titania gel, and (iii) firing at a temperature of 600°–1400°C in air. The resulting titania ceramic had the same external and internal forms of the original wood.     

Study of nanoscale structural changes in isolated bamboo constituents using multiscale instrumental analyses

To reveal morphological changes in bamboo constituents induced by delignification and hemicelluloses removal processes, changes in chemical composition and dynamics were examined at molecular‐ to nano‐scales, using scanning electron microscopy images, attenuated total reflection infrared spectra, solid state nuclear magnetic resonance spectra, and relaxation time analysis at multiple hierarchical levels. Boiling removed spherical particles from the parenchymal cells of bamboo, leaving the cells containing water that had infiltrated into the nanostructure composed of carbohydrates and lignin. Treatment of the boiled bamboo with NaClO₂ solution removed most of lignin, leaving hemicellulose chains that made the parenchymal cells stretch. In contrast, treatment of the boiled bamboo with NaOH solution removed both hemicellulose and lignin, with the result that parenchymal cells shrank in the cross‐section direction. Furthermore, treatment of the delignified bamboo with NaOH solution demolished the parenchymal cells due to complete removal of hemicellulose and lignin. A nanostructural model proposed on the basis of molecular‐ to nano‐scale analyses was consistent with the changes of vascular bundles and parenchymal cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40243.     

The degradation of TDDB characteristics of Si02/Si3N4/Si02 stacked films caused by surfaceroughness of Si3N4 films [DRAMs]

The effect of surface roughness of Si₃N₄ films on time-dependent dielectric breakdown (TDDB) characteristics of SiO₂/Si₃N₄/SiO₂ (ONO) stacked films was investigated. The surface roughness of Si₃N ₄ films-was found to become higher with increasing deposition temperature and to cause the degradation of TDDB characteristics of ONO films in DRAMs. A local thinning of ONO films, evaluated from the TDDB characteristics, agreed with the surface roughness measured by atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM). Dependence of time to breakdown of ONO films on the deposition conditions was interpreted by electric field intensification due to the surface roughness of Si₃N₄ films     

High-Performance Uniaxially Strained SiGe-on-Insulator pMOSFETs Fabricated by Lateral-Strain-Relaxation Technique

Novel uniaxially strained SiGe-on-insulator (SGOI) pMOSFETs with Ge content of 20% have been successfully fabricated by utilizing lateral (uniaxial) strain-relaxation process on globally (biaxially) strained SGOI substrates. Drastic increase of drain current (80%) caused by the change of strain from biaxial to uniaxial and the mobility enhancement of about 100% against the control Si-on-insulator pMOSFETs are observed in SGOI pMOSFET. This high mobility enhancement is maintained in high vertical effective fields as well as in short-channel devices. As a result, significant I_ON enhancement of 80% is demonstrated in 40-nm gate-length uniaxially strained SGOI pMOSFET     

Studies on bamboo for sustainable and advanced utilization

Relationship between thermal-softening properties and deformation appearing after heating and cooling processes with loading was investigated. In the heating process, an obvious decrease in relative relaxation modulus due to thermal-softening of lignin was found at around 60 °C. After the cooling process, around 70% of residual deformation was measured. Also, the residual set depended on the maximum temperature reached in the heating process and the unloaded temperature in the cooling process. It was thought that these results suggest that the glass transition of lignin from the rubbery to glassy state is important to fix the deformation.     

Improvement in tool life of electroplated diamond tools by Ni-based carbon nanotube composite coatings

Ni-based CNT composite (Ni-CNT) coatings were applied for improving the grain bonding strength of electroplated diamond tools. Further, since it is extremely important for the coatings to have good surface roughness for applications to micro-electroplated diamond tools, ultrasonic-vibration stirring was employed for improving the surface roughness of the coatings. The effects of the amount of CNTs in the plating bath on the hardness and grain bonding strength of Ni-CNT coatings were evaluated. Finally, we evaluated the tool life of microelectroplated diamond tools comprising Ni-CNT coatings as the topcoat layers by conducting experiments involving side machining and hole-drilling. The Vickers hardness of Ni-CNT coatings electroplated in a bath that contained more than 1-g/l CNTs exceeded 500 HV. The grain bonding strength can be improved by codepositing CNTs in Ni coatings and was almost 1.3 times in our estimations. In the case of the side machining of glass plates, electroplated diamond tools composed of the Ni-CNT coatings had a tool life approximately eight times longer than that of normal tools. Moreover, micro electroplated diamond tools also had a longer tool life for drilling holes in fused quartz glass. This represents the first experimental verification of the efficacy of Ni-CNT coatings in improving the grain bonding strength. In this manner, we have demonstrated that Ni-CNT coatings are extremely effective for improving the grain bonding strength of electroplated diamond tools.