Electrodes borosilicate

Figure 9-2 shows the discharge curve of borosilicate electrode versus the standard carbon electrode of the H-Tec fuel cell. The load across the fuel cell for this test is 10 Q, resulting in a discharge of 100 mA cm. The cermet electrode demonstrates minimal increases of impedance over the discharge period and the higher overall voltage. The maximum developed by borosihcate substrate is 0.3489 V. This demonstrates that Ag metallization with a platinum/ruthenium catalyst can be developed as a cathode structure in DMFCs. 

As indicated in Fig. 21.3, for both atomic absorption spectroscopy and atomic fluorescence spectroscopy a resonance line source is required, and the most important of these is the hollow cathode lamp which is shown diagrammatically in Fig. 21.8. For any given determination the hollow cathode lamp used has an emitting cathode of the same element as that being studied in the flame. The cathode is in the form of a cylinder, and the electrodes are enclosed in a borosilicate or quartz envelope which contains an inert gas (neon or argon) at a pressure of approximately 5 torr. The application of a high potential across the electrodes causes a discharge which creates ions of the noble gas. These ions are accelerated to the cathode and, on collision, excite the cathode element to emission. Multi-element lamps are available in which the cathodes are made from alloys, but in these lamps the resonance line intensities of individual elements are somewhat reduced. 

The lamp is filled under reduced pressure with an inert gas such as argon or neon. The open end of the cathode faces the window of the lamp, which is constructed of borosilicate glass or quartz the latter window must be used if ultraviolet radiation is measured. A sufficient potential is applied across the electrodes to cause a current of from 1 to 50 mamp to flow. The inert gas is positively ionized at the... 

Fig. 3.22. Arrangement of the leads inside the conductivity cell shown in Fig. 3.23. Cu copper wire, Sd soldered joint, W tungsten wire, SW spot-weld, Pt platinum wire, S soda glass sleeve, SS silver-soldered joint, P borosilicate glass arm fused to the cell, PtP platinum plate electrodes held together with lead glass beads L.

Fig. 3.25. The Pask-Nuyken device for measuring simultaneously the conductivity and the UV spectrum of a reaction mixture. A mixing chamber, B conductivity cell with jacket, C graded-seal borosilicate glass-soda glass, D jacketed quartz cell, E copper leads to platinum electrodes Pt, F graded-seal borosilicate glass-quartz.

For use over a wide temperature range, it is necessary to match the thermal expansion coefficients of electrode and insulation sheath. RRDEs of glassy carbon embedded in borosilicate glass for use up to 450° C [123] and gold sputtered on to a chromium or titanium substrate on a Macor ceramic cylinder for use up to at least 125°C [124] are examples. 

Six conductance cells, LC-1 through LC-7, each constructed of borosilicate glass with platinized platinum electrodes, are shown in Figure 5 (LC-7 is similar to LC-5 and... 

Since the 1970s, patch-clamp electrodes (electrodes placed inside a borosilicate glass pipet that is then heated and pulled, with its contents, to submicron-size diameters) have been used as micron-sized probes in elec-trophysiology experiments. Since 2000, single-walled and multiple-walled carbon nanotubes have been used as nanoelectrodes. 

The conductivity cell is modified from a conventional type. It is made of borosilicate glass, which resists the attack of anhydrous chlorine and bromine trifluorides, and is equipped with two smooth platinum electrodes to minimize electrode corrosive effects. These electrodes are approximately 12x25 mm. in size, held 1.5 mm. apart with borosilicate glass spacers. The arrangement of electrodes and leads is shown in Figure 1. An internal thermocouple well leads from the top of the cell to a point near the electrodes and contains a copper constantan thermocouple. The cell constant is determined by measuring the cell resistance... 

The following procedure was followed for all copper titrations at 25°C and constant pH. The three electrodes were first preconditioned for 30 min in a solution at pH 8 containing 0.1 M Tris base, 0.05 M HCl and sufficient CUSO4 to achieve a pCu of 13.0 to 13.5. The electrodes were then rinsed several times with distilled water and placed for 30 min in a portion of the solution to be titrated. The electrodes were then placed in a fresh 70 mX-portion of the same solution contained in a 100 mJl borosilicate glass beaker and titrated with CUSO4. Sufficient time was allowed for the electrodes to reach steady state potentials after each copper addition. At no copper addition, 60 min was allowed. For copper concentrations 10 M and > 10"7 m, measurements were made 30-60 min and 20-30 min, respectively, after each qopper addition. After reaching steady state, pCu and pH values were... 

To diminish electrode pore flooding, McHenry and Winnick [106] studied new membrane formulations which included borosilicate glass and zeolites. These showed improved electrolyte retention and polarization behavior as compared with MgO-based membranes. The reduction in flooding allowed the cell to handle three times the current for the same applied overpotential. The same authors [107] also found that Lao,8Sro.2Co03 electrodes reacted with the molten pyrosulfate electrolyte. Lithium-doped nickel oxide replacement electrodes, however, were not degraded. 

The capacity of the cell is 450 cc. It is constructed of silica, the adsorption of water on borosilicate glass being too troublesome. The electrodes are made of platinized platinum and have been calibrated with an aqueous solution of potassium chloride O.OIN at 0°C. Introduction of alkali metal and ammonia is made in a similar way to that used in kinetic studies. The formation reaction of the alkali amides is catalyzed by the electrodes. Various concentrations are studied with the same preparation of alkali amide. After ammonia has been removed, the alkali amide is hydrolyzed in the cell. The amounts of alkali ammonium hydroxides are determined by conductimetric titration. 

FIG. 7.4. Seals made with tungsten wire and borosilicate glass, (a) A prepared wire with sleeves and button, (b) Building up the button witli tliin rod. (c) and (d) show two electrodes with this type of seal. 

A standard Welsbach ozonator dielectric comprising a 3-inch borosilicate glass tube with a wrinkled open end was used. An internal conductive coating of metallic aluminum served as an inner electrode. Electrical contact was established bv means... 

The more recent models are distinguished from the older models (prior to 1930) by a central electrode of stainless steel instead of aluminum, dielectrics of borosilicate glass instead of ordinary glass, an improved method of fixing the dielectric tubes into the end plates, and a change in the exterior shape of the housings for the units. 

A much smaller micropipette silver electrode was prepared for chloride measurements by Kerkut and Meech (37). They introduced a concentrated ammoniac silver nitrate solution into borosilicate glass micropipettes and kept the micropipettes for 10 hours in 20% formaldehyde solution. The formaldehyde diffusing into the narrow opening reduced the silver and formed a metallic silver plug inside the tip of the micropipette. Silver chloride-coated silver wire was used as inner reference electrode in the silver nitrate internal filling solution. 

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