Dielectric properties of woven fabric glass fiber reinforced polymer-matrix composites in the THz frequency range

Electromagnetic wave transmittances of plain woven fabric glass fiber reinforced epoxy matrix composite (PW-GFRP) and eight-harness-stain fabric glass fiber reinforced polyimide matrix composite (8H-GFRP) with 1.0 mm thickness were measured in a terahertz (THz) frequency range. The transmittance values for both composites are nearly zero at a frequency of 1.0 THz. The real parts of the complex dielectric constant, ε′(ω) are 4.45 and 3.87 for PW-GFRP and 8H-GFRP, respectively, in the frequency range from 0.2 to 1.0 THz, and they are almost frequency independent. Conversely, the imaginary parts of the dielectric constant, ε′′(ω) for both composites linearly increases with increase of the frequency from 0.13 to 0.37 for PW-GFRP, and from 0.12 to 0.33 for 8H-GFRP.     

Fail-safe light transmitting SiC fiber-reinforced spinel matrix optomechanical composite

A light transmitting Optomechanical Composite was fabricated by incorporating SiC (SCS-6) fibers into optically transparent MgAl₂O₄ ceramics. The fibers were aligned unidirectionally in the matrix with a spacing of 1 to 4 mm to allow light transmittance between the fibers: resulting fiber volume content was from 0.75 to 0.19 vol%. The total and in-line light transmittance of the matrix and the composite was measured in the visible/near-IR wavelength region. The light transmittance of the composite was found to be decreasing with increasing fiber volume fraction, however, even the composite with the highest fiber volume fraction has a light transmittance of 25–50% in the visible wavelength region. Although the optical transparency of the matrix becomes slightly lower by the incorporation of the opaque fibers, its catastrophic failure is prevented by the bridging effect of the intact fibers, introducing the fail-safe nature to the brittle ceramic material. To obtain this fail-safe mechanism, the minimum fiber volume fraction was 0.37 vol% in the present material system.     

Discrete correlation processor as a building core of a digital optical computing system: architecture and optoelectronic embodiment

In this paper we present a general-purpose discrete correlation processor (DCP) expected to be the building core block of a digital optical computing system. The DCP-1 is embodied by optoelectronic devices such as a VCSEL and a complementary metal-oxide silicon photodetector. The application targets of the DCP-1 are optical interconnection and various types of digital optical computing. It is expected that digital optical computing techniques coupled with the optoelectronic technology will provide large capability and flexibility in information processing. Introduction of a processing scheme of optical array logic enlarges the applicable field of the DCP-1 as well as its processing capability. With the experimental DCP-1 a bit error rate smaller than 10(-9) was obtained for A . B? operation under a 500-kHz clock rate.     

Finite element iterative techniques for determining the interface boundary between Laplace and Poisson domains—characteristic analysis of a field effect transistor

Two kinds of techniques for solving a shape determination problem are proposed. The determination of the interface boundary between two domains governed by Poisson and Laplace equations under the compatible and constraint condition is considered. Influence coefficient and inverse variational approaches are examined by using the iterative finite element procedure. A two-dimensional model of a junction-type field effect transistor is a test example. The determination of its interface boundary and the prediction of the potential distribution and static characteristic are demonstrated.     

Characterization of the chemical conversion films that form on Mg−Al alloy in colloidal silica solution

Chemical conversion treatment of Mg−Al alloy (AZ91) using colloidal silica as an alternative to chromate conversion was investigated as a function of solution pH, temperature, solution conditions, and treatment time. The solution used for the colloidal silica coating consisted of colloidal silica, titanium sulfate, and cobalt ions to maintain good anti-corrosion and adhesion properties. Adding CoSO₄ to the colloidal silica solution enhanced the adhesion force between the silica film and magnesium substrate. The optimum conditions for the chemical conversion treatment solution were pH 2, 90-sec treatment, and 25°C.     

Electrochemical Fabrication of Metallic Nanowires and Metal Oxide Nanopores

A nuclear track etched polycarbonate membrane filter with numerous cylindrical nanopores was applied as a nanoporous template for growing metallic nanowires. Nickel, cobalt, and iron nanowires were electrodeposited into the cylindrical nanopores. Cathodic polarization curves were measured to determine an optimum condition for growing nanowires. The shape of nanowires was observed using scanning electron microscope (SEM) and the crystal structure was analyzed using transmission electron microscopy (TEM). Diameter and length of nanowires corresponded to those of nanopores and each nanowire was composed of a single crystal. Anodized aluminum oxide films were also fabricated as a novel nanoporous template. The pore length and diameter was controlled changing anodizing conditions. Ordering behavior of nanopores array in an anodized aluminum oxide film was also investigated to make a novel nanoporous template with a highly ordered honeycomb array of nanopores.     

The effect of polyimide surface chemistry and morphology on critical stress intensity factor

The increasingly severe demands of concurrently increasing die size while reducing the package size have made the mechanical stability of IC packaging technologies a grave concern. The dominant failure is caused at the interface between dissimilar materials. To investigate the effect of polyimide surface morphology and chemistry on the epoxy molding compound adhesion, the polyimide samples were characterized by X-ray photoemission spectroscopy, atomic force microscopy, attenuated total reflection and interfacial adhesion tests. The results of the characterization and an explanation of the primary factors affecting interfacial adhesion are presented in this paper.     

Fatigue crack propagation behavior in four-points bending specimens with multiple parallel edge notches at regular intervals

Fatigue crack propagation tests were performed using specimens with multiple parallel edge notches at regular intervals. Fatigue pre-cracks of uniform length were successfully introduced by eccentric tension-compression loading. Fatigue crack propagation tests were carried out under four-points bending loading. Obtained crack propagation behavior was simulated by using newly developed stress intensity factor equations for multiple parallel edge cracks with alternately different lengths. Simulated results showed a good agreement with the experiment for specimens with relatively broad crack intervals, while for specimens with narrow crack intervals showed a different tendency from the experiment when crack lengths became long.     

Coal liquefaction mechanism using a tritium tracer method

To determine the behavior of hydrogen in tetralin, the reaction of tetralin with tritiated gaseous hydrogen was studied in a flow reactor at 400–450°C, 2.5–9.8 MPa for various residence times. The amount of hydrogen exchange between tetralin and tritiated hydrogen was estimated from the balance of hydrogen and tritium. Although yields of methylindan and naphthalene, and the hydrogen-exchange ratio (HER) of tetralin increased monotonously with residence time, these values were scarcely influenced by the reaction pressure at every temperature. It was thought that the formation of tetralyl radicals in this system would be the rate-determining step for both the conversions of tetralin into methylindan and naphthalene, and the hydrogen exchange of tetralin. Conversions of tetralin into methylindan and naphthalene, and the hydrogen-exchange reaction using the autoclave were very close to those using the flow reactor.     

Ultrafine particles of the ZrO2-SiO2 system prepared by the spray-ICP technique

Ultrafine powders of the ZrO₂-SiO₂ system prepared by spraying aqueous mixed solutions of ZrO(NO₃)₂·2H₂O and silicone oil into an ultrahigh temperature inductively coupled plasma (the spray-ICP technique) have been investigated in connection with particle growth and phase change caused by heat treatment. The prepared powders were composed of roundish ultrafine particles 10 to 20 nm in size, and their components were tetragonal ZrO₂ (t-ZrO₂) and amorphous SiO₂ (a-SiO₂).a-SiO₂ alone did not crystallize below 1400° C, though the particles grew above 900° C.t-ZrO₂ converted to monoclinic ZrO₂ (m-ZrO₂) above 400° C, also followed by particle growth. On the other hand composite powders oft-ZrO₂ anda-SiO₂ exhibited no particle growth below 1200° C. Above 1200° Ct-ZrO₂ converted tom-ZrO₂, and its amount decreased with an increase in SiO₂ content. At 1400° C particle growth occurred, and the round particles of ZrO₂ were dispersed in ana-SiO₂ glass medium. These results indicate that ZrO₂ and SiO₂ mutually block particle growth, and that SiO₂ contributes to the quenching oft-ZrO₂ by keeping the particles of ZrO₂ within the critical particle size oft-ZrO₂.