Surface treatmet of sillimanite-based microspheres for strength enhancement of high-temperature lightweight cement composites

The compressive strength of high-temperature lightweight cementing materials containing sillimanite-based hollow microspheres as a filler can be improved by treating the surfaces of the microspheres with a calcium hydroxide-saturated solution at temperatures up to 200° C. The precipitation of an epitaxial layer formed by an interaction between the hot calcium hydroxide solution end the surface of the sphere played an essential role in developing favourable bonding characteristics at the interfaces and in promoting the hydration of the cement matrix. Bonding is associated with the formation of an intermediate layer of aluminium-rich calcium silicate hydrate, produced by an interfacial reaction of the cement paste with the epitaxy under the hydrothermal environment at 300° C. A dense intermediate layer consisting of a rim structure of 4m thickness acts in cross-linking and coupling functions that serve to connect the cement matrix and spheres, thereby improving the interfacial bond strength. The presence of the epitaxial layer on the treated sphere surfaces leads to the formation of a well-crystallized tobermorite matrix phase, which is responsible for the development of strength in autoclaved lightweight cements.     

Hydraulic cement-type fillers for hydrothermally stable polymer concretes

Hydraulic cement fillers, which can prevent the hydrothermal decomposition of vinyl-type polymer concrete (PC) containing carboxylate groups in the polymer molecule, have been developed. Experiments were performed in which a co-polymer was used in combination with an aggregate containing various commercial cements such as Portland type I, III, and V cements, slag cement (IS), and a Class H oil-well cement. It was observed for Class H cement-filled PC that a strong interaction occurred between the cement grains and the CH₂ groups in the main chain of the co-polymer. The other cements exhibited lesser interactions. It was observed that after exposure to a 25% brine at 240° C, ionic bonding of carboxylate anions in the co-polymer with Ca²⁺ ions from the Class H cement and the hydration products of Class H cement had a significant effect on the strength. This improvement is believed to result from a reductive effect on the molecular mobility of the co-polymer chains. Fillers having a-dicalcium silicate (C₂S)/Class H cement ratio from 0.7 to 1.5 made the greatest contribution to the hydrothermal stability of the vinyl-type PCs.     

Binocular open-view Shack-Hartmann wavefront sensor with consecutive measurements of near triad and spherical aberration

We have developed a binocular open-view Shack-Hartmann wavefront sensor for measuring time variation of binocular accommodation, vergence, pupil sizes (i.e., the binocular near triad), and monochromatic aberrations. The device measures these values16 times per second for up to 1 min. Our purpose is to introduce the new instrument. We have confirmed the accuracy of the device. Refractions for a 4 mm pupil were accurate across the range of measurements of model eyes and normal human eyes. We measured binocular dynamics of accommodation, vergence, and spherical aberrations.     

Interaction mechanisms between poly(methyl methacrylate) and tricalcium silicate (C3S)

Interaction mechanisms between poly(methyl methacrylate) (PMMA) molecules and tricalcium silicate (C₃S) occurring in a C₃S-filled PMMA molecular structure before and after exposure to a simulated 25% geothermal brine solution at 240°C have been investigated by use of thermal analysis, infrared spectroscopy analysis, scanning electron microscopy, and compressive strength tests. For C₃S-filled PMMA samples before exposure to hot brine, it was observed that an interaction between the C₃S filler and the CH₂ groups in the main chain of the PMMA occurred. After exposure to the hydrothermal environment, indications were that the brine solution induced ionic bonding between the carboxylate anion (? COO^?) groups in the PMMA and the Ca²⁺ ions from the C₃S. The reaction contributed to improvements in the thermal stability of the PMMA.     

Corrosion protection of steel and bond durability at polyphenylene sulfide-to-anhydrous zinc phosphate interfaces

To enhance the performance of high-temperature polyphenylene sulfide (PPS) coating in protecting steels from corrosion, the cold-rolled steel surfaces were prepared with anhydrous zinc phosphate (Zn · Ph) conversion coatings containing poly(acid) anhydride as an interfacial tailoring material. The factors contributing to the formation of a good bond at the PPS/Zn · Ph joints were as follows: (1) the chemical reaction of PPS with Fe₂O₃ in the Zn · Ph layers, (2) PPS-to-poly(acid) anhydride interaction, and (3) the mechanical interlocking between PPS and the rough Zn · Ph crystal surfaces. Although such interfacial bond structures provide a superior durability of PPS/Zn · Ph joints against a hot H₂SO₄ solution, the cathodic reaction, H₂O + ½O₂ + 2e^? = 2OH^?, occurring at any defect in the PPS/Zn · Ph joint system when NaCl is present will lead to the delamination of the PPS film from the phosphated steel. This cathodic delamination was due mainly to alkali-induced dissolution of Zn · Ph layers. However, the rate of delamination for the PPS/Zn · Ph systems was considerably lower compared with that for the PPS/steel system in the absence of Zn · Ph.     

Study of interactions at water-soluble polymer/Ca(OH)2 or gibbsite interfaces by XPS

In an attempt to better understand interactions occuring at hydrated cement/organic polymer interfaces, the reaction mechanism and products formed at the interfaces between poly(acrylic acid), p(AA) or poly(acrylamide), p(AM), and Ca(OH)₂ or gibbsite, Al₂O₃·3H₂O, were explored using x-ray photoelectron spectroscopy (XPS). It was estimated that at p(AA)/Ca(OH)₂ interfaces, a Ca-complexed carboxylate interfacial reaction product was formed by an ionic reaction between the COOH in p(AA) and Ca²⁺ ions from Ca(OH)₂. A similar reaction product was formed at p(AM)/Ca(OH)₂ interfaces as a result of an inter-facial transformation of amide in p(AM) into carboxylic acid, caused by the alkali-catalyzed hydrolysis of the amide. The proton-accepting hydroxyl groups existing at the outermost surface sites of Al₂O₂·3H₂O react favorably with proton-donating COOH groups in p(AA). This acidbase interaction at the p(AA)/Al₂O₃·3H₂O joint formed hydrogen bonds. Whereas, when the p(AM) was applied on Al₂O₃·3H₂O surfaces, interfacial electrostatic bonds were formed through charge-transferring reaction mechanisms in which the charge density was transferred from the Al in Al₂O₃·3H₂O to the C=0 oxygen in p(AM).     

Hydrothermal stability of vinyl-type polymer concrete containing tricalcium silicate (C3S)

Infrared analysis (IR) studies and measurements of the mechanical and physical properties of vinyl-type polymer concrete (PC) containing tricalcium silicate (C₃S) as a constituent of the inorganic phase were performed after exposure of the composite to a 25% simulated geothermal brine at 240°C. The purpose of the study was to determine the physical effects and the chemical reaction mechanism produced by the apparent interactions between the vinyl-type polymers, C₃S, and the hydration products of C₃S. Infrared analysis indicated that ionic bonding between carboxylate anion (?COO^θ) groups in the polymer produced by the hydrothermal reaction and Ca²⁺ ions of C₃S occurred. The addition of silica flour, calcium carbonate, and calcium hydroxide to the filler system did not produce results similar to those produced by the C₃S.     

Polyphenylenesulphide-sealed Ni–Al coatings for protecting steel from corrosion and oxidation in geothermal environments

Polyphenylenesulphide (PPS) polymer was applied as a sealing material to flame-sprayed nickel–aluminium (Ni–Al) coatings to protect the interior surfaces at the ends where the mild carbon steel (MCS) heat-exchanger tubes are jointed to the tubesheet. The aim of applying PPS is to prevent their corrosion, oxidation and abrasive wear, in a low pH, hypersaline brine geothermal environment at 200°C under a hydrothermal pressure of 1.6 MPa. Although the Ni–Al coatings had an excellent thermal conductivity and a good wear-resistance, the inherent open structure of these coatings allowed the hot brine to permeate them easily under such pressure, causing the development of corrosion-induced stress cracks in the MCS. Furthermore, under these conditions, the coatings underwent oxidation with the formulation of Al₂O₃ as the major scale compound and NiO as the minor one. PPS sealant was used to solve these problems. However, one major drawback of PPS was its susceptibility to oxidation reaction with hot brine. This reaction not only incorporated more oxygen into the PPS, generating a sulphide sulphone transformation within PPS, but also it caused the decomposition of PPS, yielding polychloroaryl compound, and sodium sulphate, and also evolving SO₂ gases. The SO₂ gases had a chemical affinity for oxide scales in Ni–Al, forming water-soluble Al₂(SO₄)₃ and NiSO₄ salt reaction products at the PPS/Ni–Al interfaces. Despite the occurrence of such oxidation damage in PPS, an exposure for 14 days showed that there was no development of corrosion-caused cracks at the interfaces between the underlying steel and Ni–Al, nor was a striking oxidation of the sealed coating panels.     

AC detection of directivity of fluorescence from a minute particle using TAS chip incorporated with radially arranged light-waveguides

Microsystem Technologies - In this paper, we attempt to drastically improve the S/N ratio of detected fluorescence signals from the resin-based optical TAS chip by applying AC-modulated laser power...     

Flexible humidity sensor in a sandwich configuration with a hydrophilic porous membrane

We constructed a wearable and flexible humidity sensor (thickness: 80 μm) in a sandwich configuration, with a hydrophilic poly-tetrafluoroethylene membrane placed between two gold deposited layers, using soft-MEMS techniques. The device was used to measure humidity level, via its electrical conductivity, using a multi-frequency LCR-meter at frequencies ranging from 100 Hz to 100 kHz. The device was calibrated at 100 Hz against moist air over the range of 30–85% RH, which includes normal humidity levels in the atmosphere and physiological air such as breath and evaporating sweat. The response sensitivity of the humidity device was extremely high, even for recovery to dry air; for example response time was less than 1 s for a conductivity shift between humid air of 80% RH and dry air of −60 °C dew point. The sensor performance was reproducible over multiple measurements, with a coefficient of variation of 1.77% (n = 5). The sensor was appropriate for physiological applications, and was successfully used in two non-invasive approaches: to monitor breath air at the mouth, and to measure sweat moisture from the nostrils.