Alumina substrate

FD C lakes were first approved for use ia 1959. Today, they are the most widely used type of lake. To make a lake, an alumina substrate is first prepared by adding sodium carbonate or sodium hydroxide to a solution of aluminum sulfate. Next, a solution of certified colorant is added to the resulting slurry, then aluminum chloride is added to convert the colorant to an aluminum salt, which then adsorbs onto the surface of the alumina. The slurry is then filtered, and the cake is washed, dried, and ground to an appropriate fineness, typically 0.1—4.0 p.m. 

The extent to which small particles of Pd and Pt show evidence of oxidation after exposure to air Is also highly variable. It Is difficult to confirm the evidence of X-ray diffraction and EXAFS (25) that most particles In the 15-20A size range consist entirely of oxide. We have found that such particles usually give single crystal patterns attributable to the metals. There Is, however, considerable evidence that, in the case of Pt on alumina, the Pt crystals have a well-defined epitaxial relationship with the crystallites (20-50A diameter) of the nominally "amorphous" alumina substrate. 

Li Y.S., Vo-Dinh T., Stokes D.L., Yu W., Surface-enhanced Raman analysis of p-nitroaniline on vacuum evaporation and chemically deposited silver-coated alumina substrates,Appl. Spectrosc 1992 46 1354-1357. 

Li Y.S., Wang Y., Chemically prepared silver alumina substrate for surface- enhanced Raman-scattering, 4/ /)/. Spectrosc 1992 46 142-146. 

Figure 5.15. ESCA depth profile of Cu diffusion through an alumina substrate following oxidation at 200°C. The sample is etched from the alumina edge (i), towards the alumina/Cu interface is- (After Gai et al Nature 348 430.)...

Nitrobenzene (1 mmol) dissolved in minimum amount of dichloromethane, adsorbed over the neutral alumina (substrate alumina=l 2, w/w), dried and mixed with feiTous sulfate (1.2 mmol) and sodium hydrogen phosphite (5 mmol). It was transfered into a test tube and subjected to microwave irradiation (BPL make, BMO 700T, 650 W, power 80%). Reaction was monitored by TLC (hexane-ethyl acetate, 70 30). After completion of the reaction (50 s), it was leached with di-... 

A cross-section schematic drawing of the newly-developed thick film oxygen sensor is shown in Figure 2. The platinum film heater is embedded in the alumina substrate. Electrical resistance of the heater is about 6 ohms at room temperature. 

Arranged in layered fashion on the alumina substrate are the zirconia underlayer, the platinum reference electrode, the zirconia solid electrolyte stabilized with 5.1 mole % Y2O3, the platinum measurement electrode, and finally,the protective spinel (A203 Mg0) layer. The zirconia layer is Umm long, 1+mm wide and 30pm thick. 

This activation energy is close to the 24 kj mol-1 reported by Mezaki and Inoue for the methane oxidation at a platinum catalyst on an alumina substrate at temperatures above 350°C. 

Fig. 4.5 Film devices and circuits (a) thin-film resistors on glass and steatite substrates (b) thick-film resistor networks on snapstrate alumina substrate (c) various thick-film resistors (d) hybrid microcircuits. (Components kindly supplied by General Hybrid, C-MAC and...

Fig. 4.49 Twin tin oxide-based sensors for monitoring N02 and CO in automobile passenger compartments. NB alumina substrate size approximately 2x2.6x0.254 mm. (Adapted from Oto, K. et al. (2001), Sensors and Actuators, B77, 525-8.)...

The substrates carrying the circuits shown in Fig. 4.5 are a 95-96% alumina. This ceramic has been adopted for its combination of physical and chemical characteristics and, importantly, low cost. It offers a combination of mechanical, thermal and electrical properties which meet the in-service requirements, and compositional and microstructural characteristics suited to thick film printing (see Section 4.2.2). Alumina substrates are manufactured on a very large scale making the unit costs a small fraction of the total circuit cost. 

An alumina substrate of dimensions 1 cmx 1 cmx 0.5 mm carries a device dissipating 20 W. If the substrate is bonded to a metallic heat sink, estimate the steady state difference in temperatures between the surface carrying the device and the heat sink. The thermal conductivity of alumina may be taken to be 35 Wm-1 K-1. [Answer 3°C]... 

Fig. 10.6. Schematic diagrams of a microband electrode prepared by screen-printing gold onto an alumina substrate, over-printing with an insulator and then snapping to expose a fresh line electrode (Reference [33]). Substrate (1) 500 p.m thick gold (2) 10 im thick insulator (3) 20 p.m thick, (a) Cross section showing the different layers (b) cross-section of the exposed surface at the snap line (c) scheme of oscillation.

Figure 9. Extent of reaction for space velocities of 1000 hr 1 (O) and 5000 hr 1 (A) for catalyst MBS (1% Pt on a spherical alumina substrate). S03 S02 +...

ETES films could not be obtained on alumina substrates by retraction. Retraction did not occur from solutions of the triethoxysilane even up to concentrations of 5%, and adsorption times of many days. This was the case using both air-dried and flamed alumina and for a-chloro-naphthalene or isopropylbicyclohexyl as the solvent. 

Because pressed alkali carbonates are often hygroscopic and tend to sublimate a combination of alkali carbonates and a stable alkali ion conductor like -> Nasi-con, - fi -alumina or [5"-alumina as an electrolyte are used (Fig. 6, middle) [x]. The /1-alumina can be formed as a thin layer on a a-alumina substrate [xi]. 

Commercial hydroisomerization catalysts have both a noble metal based hydrogenating function and an acid function (Table 7.3). Traditionally, the acid component is provided by (i) a zeolite or by (ii) a chlorinated alumina substrate or by (iii) a sulfated zirconia carrier, the latter both being extremely intolerant of sulfur, water, and other feed contaminants. The zeolite is generally a mordenite and not a Y-zeolite. However, catalysts based on zeolite omega have been shown to be superior to mordenite-based catalysts, but no up-scale to commercial use has been reported for omega zeolite containing hydroisomerization catalysts (see below). 

Figure 13 is an SEM SE plan-view image of another PEVD sample, where the Pt thick film coverage at the sink side of the sample is not entirely continuous. After PEVD, the product (Na2C03) only formed in area (A), where the Pt thick film of the working electrode is continuous and connected to the external circuit. No PEVD product formed in area (B), where the Pt thick film is discontinuous appearing as individual islands (white spots in the figure) on the Na -P"-alumina substrate. 

In the present investigation, the interaction ot vanadium oxide with dif-ferent alumina phases (7, 6-6, and a) is examined with Raman spectroscopy. Comparison ot the Raman spectra ot the supported vanadium oxide catalysts with those obtained -from vanadium oxide reference compounds allows for the structural assignment of these supported species. The present Raman data demonstrate that the molecular structures of the surface vanadium oxide phases are significantly influenced by the presence of surface impurities on the alumina supports and this overshadows the influence, if any, of the alumina substrate phase. 

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