Crystal growth and concentration change of (Mn,Ni,Zn)-ferrite single crystals by the flame fusion method

Single crystals of (Mn,Ni,Zn)ferrite are grown by the flame fusion method. The chemical analysis of composition reveals that ZnO shows the largest change in concentration among the components, for example, from 26.7 mol% to 17.3 mol% in a crystal of 50 mm in length and 25 mm in diameter. This inhomogeneity is only observed along the growth direction and cannot be detected by analysis at this level of accuracy along the direction perpendicular to the growth direction, except at the periphery to a depth of 1 mm. This inhomogeneity may be explained as a result of the evaporation of Zn from the molten zone during growth. The equation $\text{C}{}_{\mathrm{o}}\text{C}\text{= 1 +}\text{K}\text{V}$ is derived (C /2b Zn concentration, V = crystal growth rate and C_o, K = const). Crystal free from cracks can be grown successfully by using an after-furnace made of SiC heater. A new apparatus to feed the crystal constantly with raw material powder is proposed, and by using this the change in concentration can be reduced to less than 1 mol% throughout the crystal of the above size. These crystals have also been investigated for the Micro-Vicker's hardness.     

Preparation of ultra-high-strength nylon-6 fibre by a multi-step zone-annealing method

A multi-step procedure to improve the zone-annealing method was attempted to prepare a high-modulus and high-strength nylon-6 fibre. By the adoption of this procedure, the dynamic storage modulus at room temperature was markedly increased and reached 15.7 × 10¹⁰ dyne cm⁻² which is 1.5 times that obtained by the previous zone-annealing method. Tensile properties, orientation, crystallinity and mechanical dispersion were also measured. Comparing the multi-step procedure with the previous one-step procedure, the excellent effects of the multi-step procedure on mechanical properties are discussed. Further, in order to prevent selective relaxation of amorphous molecular chains on removing the applied tension after zone-annealing, heat-setting at constant length was subsequently carried out on the as-zone-annealed fibre. The mechanical properties were further improved: for example, the dynamic storage modulus at room temperature of the resulting fibre was raised to 16.9 × 10¹⁰ dyne cm⁻², which was well beyond the highest modulus available in the literature, 14 × 10¹⁰ dyne cm⁻².     

Simulation of cyclic dynamics in isothermal gas-solid reaction systems effects of the frequency of sinusoidal perturbation in the bulk gas concentration

The dynamic responses of a gas-solid reaction system to a sinusoidal perturbation in the bulk gas concentration are analyzed. Effects of the frequency variations on the gas and solid concentration profiles and the solid conversion are comprehensively examined based on the volume reaction model under the isothermal condition. The results show that the solid conversion can be accelerated as much as 50% and retarded as much as 50% depending on the frequency and the amplitude of the perturbation. The relationships between the reactant concentrations at the surface and the center are elucidated by means of phase-plane plots.     

Single-Cycle Terahertz Pulse Generation from OH1 Crystal via Cherenkov Phase Matching

OH1 crystal is an organic nonlinear optical crystal with a large nonlinear optical constant. However, it has dispersion of refractive indices in the terahertz (THz) frequency. This limits the frequencies that satisfy the phase matching conditions for THz wave generation. In this study, we addressed the phase matching conditions for THz wave generation by combining an OH1 crystal with prism-coupled Cherenkov phase matching. We observed the generation of single-cycle THz pulses with a spectrum covering a frequency range of 3 THz. These results prove that combining prism-coupled Cherenkov phase matching with nonlinear optical crystals yields a THz wave generation method that is insusceptible to crystal dispersion.     

Synthesis of statistical PET/PEN random block copolymers and their crystallizability in the bulk and at the surface

A series of PET/PEN copolyesters were synthesized by molten transesterification. The degree of randomness and the sequence length of the copolymers were determined by ¹H NMR spectroscopy, and the changes in the bulk glass transition temperature (T_gB), bulk crystallization temperature (T_cB), and bulk melting temperature (T_mB) were observed by DSC. A clear relationship was obtained between the observed enthalpy of melting (ΔH_m) and degree of randomness (B), and T_mB was suppressed for the midcompositions. As with their homopolymer counterparts, there was significant depression in crystallization temperature at the surface (T_cS) of the random/block copolymers compared with the bulk, and so surface‐localized crystallization could be induced in spin‐coated thick films (thickness ranging from ca. 400 to 700 nm) by annealing at a temperature in which the surface region is mobile, but the bulk is not. The formation of these clear surface crystals allows the morphology to be directly imaged by AFM, and we observed that the crystallizability and the lamellar morphology of the surface crystals deviated from those of the original homopolymers, depending on the mixing ratio of PET/PEN and degree of randomness. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46515.     

Can breath isoprene be measured by ozone chemiluminescence?

Isoprene, involved in the biosynthetic pathway to cholesterol, is the prevalent hydrocarbon in breath. Breath isoprene measurement is of great interest as a measure of basal cholesterol production rate. We investigated the merits and pitfalls of isoprene measurement via its chemiluminescence (CL) reaction with ozone. For many subjects, apparent concentrations measured are higher than those obtained by a gas chromatography (GC) reference method that can be traced to ozone-induced CL with simultaneously present lower olefins and sulfur compounds. A warm column preconcentration method eliminates the lower olefins and greatly improves sensitivity while a silver-form, ion-exchange resin can remove the sulfur gases. The breath sample is captured on a miniature synthetic carbon sorbent column maintained at 55 degrees C, under which conditions ethylene, propylene, and water vapor are not significantly captured while the preconcentration process greatly improves the limit of detection for isoprene to 0.6 ppbv (S/N=3). The captured isoprene is released by heating the column to 150 degrees C. Breath samples from different subjects were collected both before and after meals and analyzed in a double-blind fashion in two laboratories, with the second laboratory performing quantitation by cryofocusing GC-flame ionization detection with parallel measurement by mass spectrometry to provide identity confirmation. For all individuals studied, the CL and the GC results agreed when both warm column preconcentration and passage through Ag+-form cation-exchange resin, which removes divalent sulfur gases, were implemented prior to CL measurement. The intensity of CL from the reaction with ozone can be much higher for some sulfur gases than for isoprene. Even though present at lower concentrations than isoprene, unless removed prior to CL measurement, for some individuals sulfur gases can cause unacceptably large (up to 500%) errors, making the sulfur gas removal step critical.     

Glass Substrates for OLED Lighting with High Out-coupling Efficiency

Glass substrates which realize high out-coupling efficiency OLEDs （organic light emitting diodes） were developed. A scattering layer whose matrix was made of high refractive index glass was formed on a glass substrate, and pores in the glass matrix work as scattering centers. The out-coupling efficiency of an OLED using this substrate is 1.8 times higher compared with an OLED using an untreated glass substrate. Furthermore angular dependency of the color and color variation between panels can be successfully suppressed.     

Nanoscale liquid droplet deposition using the ultrasmall aperture on a dynamic mode AFM tip

We have developed a novel method for nanometer-sized droplet deposition of electrically conductive liquids based on the dynamic mode atomic force microscopy (AFM). We succeeded in depositing liquid droplets with a volume of ten zeptoliters or smaller and in making arrays of the droplets with a spacing of several tens of nanometers using the AFM cantilever with a small aperture fabricated by a focused ion beam. The liquid droplets were deposited through the aperture by applying an electric field between the liquid and a conductive surface.     

Styryl silsesquioxane photoresist

There is a substantial need for photopattern‐able, heat resistant, and transparent materials that are applicable to electronic devices, such as imaging or display elements. Styryl silsesquioxane based photoresist forms thin micro patterns after i‐line exposure and alkaline development, and the resulting transparent film shows remarkable heat resistance. Radicals generated from a photoinitiator induce polymerization of styryl functionality in the photoresist film to form the micropatterns. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41459.