Rapid bonding of Pyrex glass microchips

A newly developed vacuum hot press system has been specially designed for the thermal bonding of glass substrates in the fabrication process of Pyrex glass microchemical chips. This system includes a vacuum chamber equipped with a high-pressure piston cylinder and carbon plate heaters. A temperature of up to 900 degrees C and a force of as much as 9800 N could be applied to the substrates in a vacuum atmosphere. The Pyrex substrates bonded with this system under different temperatures, pressures, and heating times were evaluated by tensile strength tests, by measurements of thickness, and by observations of the cross-sectional shapes of the microchannels. The optimal bonding conditions of the Pyrex glass substrates were 570 degrees C for 10 min under 4.7 N/mm(2) of applied pressure. Whereas more than 16 h is required for thermal bonding with a conventional furnace, the new system could complete the whole bonding processes within just 79 min, including heating and cooling periods. Such improvements should considerably enhance the production rate of Pyrex glass microchemical chips. Whereas flat and dust-free surfaces are required for conventional thermal bonding, especially without long and repeated heating periods, our hot press system could press a fine dust into glass substrates so that even the areas around the dust were bonded. Using this capability, we were able to successfully integrate Pt/Ti thin film electrodes into a Pyrex glass microchip.     

Protolytic behavior of hydroxylated Pyrex glass surfaces in NaCl media

Adsorption of hydrogen ions from aqueous NaCl solutions at the Pyrex glass-water interface was investigated by acid-base titration (glass electrode) at 25 degrees C and at the ionic strengths 0.010, 0.030, 0.10, 1.0, and 3.0 mol dm(-3). The pH values ranged from 2 to 7. The Pyrex samples had a specific surface area of 19.2x10(3) m(2)kg(-1) and a porous structure (pores 2.4 nm thick, 280 nm long). The reactions were found to be extremely slow but showed good reversibility. The potentiometric data, due to the small effect of ionic strength on the equilibria, were fitted with a simple nonelectrostatic model based on strong specific interactions of medium ions with deprotonated silanol, >SiO(-), and boranol, >BO(-), as well as with protonated sites. The acid-base properties are described by the reactions and equilibrium constants at the infinite dilution reference state: >SiONa + H(+) <==> >SiOHNa(+), logbeta110Si=3.1+/-0.2; >SiONa + 2H(+) + Cl(-) <==> >SiOH(2)Cl + Na(+), logbeta201Si=6.75+/-0.15; >SiONa + H(+) <==> >SiOH + Na(+), logbeta100Si=1.8+/-0.2, >BONa + H(+) <==>BOH + Na(+), logbeta100B=6.4+/-0.2; >BONa + H(+) <==> >BOHNa(+), logbeta110B=6.6+/-0.2; >BONa + 2H(+) <==> >BOH(+)(2) + Na(+), logbeta200B=11.56+/-0.15.     

纳米复合体中Mn^2＋的研究

通过对ＺｎＳ：Ｍｎ＾２＋纳米晶钠硼硅玻璃复合体的发光和激发光谱研究发现Ｍｎ＾２＋有闰（Ｍｎ＾２＋）ｓｕｂ和间隙（Ｍｎ＾２＋）ｉｎｔ两种格位态。在进一步的电子顺磁共振实验中,证实了Ｍｎ＾２＋的替位和间隙两种格位态的存在,并观测到由于强偶极－偶极相互作用而产生的Ｍｎ团簇。／     

Characterization of TiO2 thin film immobilized on glass tube and its application to PCE photocatalytic destruction

TiO₂ was immobilized on to the surface of a pyrex glass tube through a dip coating process, and a pyrex glass tube with TiO₂ thin film was used as a batch reactor and continuous flow reactor for the photocatalytic destruction of PCE in water. TiO₂ could be successfully immobilized with a thickness of 0.3 μm in the pyrex glass tube. The TiO₂-immobilized pyrex glass tube itself showed high photocatalytic activity for the destruction of PCE in water.     

Time Resolved Actinometric Study of Pulsed RF Oxygen Discharge

The dissociation efficiency of a pulsed RF discharge (with duty cycle 1:1 and discharge duration 0.2, 1, 5, and 20 ms) in oxygen at pressures from 1 to 5 torr and effective discharge currents from 50 to 210 mA has been studied. For monitoring of the atomic oxygen density the method of actinometry has been used. In order to evaluate the absolute dissociation degree, a numerical model has been developed and actinometric coefficients were calculated. Maximal degree of the dissociation reached value of 0.05. A saturation of the dissociation degree at higher pressures was observed and discussed.     

Quantification of the adsorption of methyl viologen on pyrex glass using a renewable perfluorosulfonated ionomer carbon paste electrode

Square wave voltammograms of methyl viologen (MV²⁺) were recorded at a renewable Nafion-loaded carbon paste electrode immersed in 20 mL of phosphate buffer solution (pH 7.4) contained in a beaker-type electrochemical cell (Pyrex glass; contact area = 33 cm²). From the calibration plot obtained in the concentration range 0.01–2.4 μM, it could be concluded that the maximum surface excess of MV²⁺ adsorbed on Pyrex glass (0.24 nmol cm⁻²) was reached at concentrations above 1.4 μM. The adsorption isotherm presented a sigmoidal shape characteristic of attractive interaction. From this plot, it was evaluated that the maximum depletion of MV²⁺ in solution (28%) did not occur at the lowest concentrations, but in nearly micromolar solutions. This result emphasizes the unavoidable and random errors which are involved when MV²⁺ solutions are purposely diluted in Pyrex glassware. The MV²⁺ adsorption proceeds to a less extent on Duran borosilicate glass and/or in acid or alkaline medium.     

Thermal conductivity measurements using the flash method

Thermal diffusivity is the speed with which heat propagates through a material. It has a multitude of direct applications, such as determining heat transfer through brake pads at the moment of contact, etc., but more often it is used to derive thermal conductivity from the fundamental relationship tying it with specific heat capacity and density. Using a new multi-sample configuration system, and testing a reference sample adjacent to the unknown, specific heat capacity can be obtained parallel with thermal diffusivity. Thus, a single test yields thermal diffusivity and thermal conductivity with prior knowledge of density. The method is fast and produces results with high accuracy and very good repeatability. The sample size, 12 to 30 mm diameter and 2 to 5 mm thickness, is easy to handle and is well suited for a broad range of materials, even for composites, often a problem for other methods. Typical data on two polymers, Pyrex glass and Pyroceram 9606 are presented. This revised version was published online in July 2006 with corrections to the Cover Date.     

An eco-friendly efficient extractor

A microscale solid-liquid Pyrex extractor is described. The extractor has a novel detachable extraction vessel (H) containing a filter paper cylinder (C) over the reservoir. A filter paper cylinder (C) is firmly placed in the socket (E) with a plug (G) on which the cylinder has been placed. The sample is directly weighed in the extraction vessel (H) and the vessel is clamped (F) to the body (B). Contents in the extraction reservoir (H) are stirred (I) with a magnetic stirrer (J) and heated sufficiently (e.g. at 84.8 °C in using water) by the solvent vapor (D). Easy filtration (C) and continuous outflow (D) of the filtrates out of the reservoir (H) keeps a stable boiling condition (K), rather than batchwise conditions operative in a Soxhlet; this results in rapid and exhaustive extraction. The present extractor (8.0 mL extraction reservoir (H) capacity) equipped with a 25 mL solvent flask (K) was applied to fat extraction from powdered peanut by using 18 mL of ether. The extraction was complete in 30-60 min depending on reflux rate; in contrast, extraction with a commercial micro-Soxhlet device (23.9 mL extraction reservoir capacity) equipped with a 25 mL flask by using 34 mL of the solvent was incomplete in 120 min. Unlike filter paper thimbles used in Soxhlet devices, filter paper cylinder (C) in the new extractor could be reused many times and results in significant savings of the filter paper cylinders. Small reservoir and flask capacities of the new extractor minimize the use of organic solvents. The present apparatus permits fast and efficient extraction, sharply reduces waste, minimizes solvent consumption, and thus should find wide use aiming at the Green Solutions to Global Problems.