Water sapphire

Picosecond time-resolved total internal reflection fluorescence spectroscopy was applied to analyze the proton-transfer reaction of INpOH in water-sapphire interface layers [206], The rate constant of the proton-transfer reaction from excited neutral species became slow in the interface layer as compared with that in the bulk aqueous solution and decreased smoothly with increasing penetration depth in the interfacial layer up to 100 nm. The anomaly was interpreted in terms of rotational fluctuations of water aggregates in the interface layer. 

Diamond behaves somewhat differently in that n is low in air, about 0.1. It is dependent, however, on which crystal face is involved, and rises severalfold in vacuum (after heating) [1,2,25]. The behavior of sapphire is similar [24]. Diamond surfaces, incidentally, can have an oxide layer. Naturally occurring ones may be hydrophilic or hydrophobic, depending on whether they are found in formations exposed to air and water. The relation between surface wettability and friction seems not to have been studied. 

Figure B2.1.6 Femtosecond spectrometer for transient hole-burning spectroscopy with a continuum probe. Symbols used bs, 10% reflecting beamsplitter p, polarizer. The continuum generator consists of a focusing lens, a cell containing flowing water or ethylene glycol or, alternatively, a sapphire crystal and a recollimating lens.

Eigure 3.56 depicts LEIS spectra for two completely different types of AI2O3 sample, i. e. a-alumina (sapphire) and y-alumina (a powder with high specific surface area) which show very similar results in both cases after thermal treatment at 400 °C [3.142]. Reduction of the A1 signal in y-alumina was ascribed to shielding by hydroxyl groups formed by water molecules, which are typical adsorbates on y-alu-mina. 

The reactor assembly was heated by electric heaters. The maximum operating temperature Is determined by the window construction. Sapphire windows (from EIMAC), brazed into Kovar sleeves, were used the sleeves were then welded directly into the stainless steel reactor housing. We found that the cell so constructed was capable of trouble-free, continuous operation at 450°C operations at somewhat higher temperatures are probably still possible but were not explored. Sapphire was chosen as a window material because it is insensitive to water vapor and is transparent in tljie wave number range of our interest (about 2400 cm to 2000 cm in these experiments). Moreover, the thermal expansion characteristics of the reactor were found to match well with those of the window fixture. 

Examples are water for the calibration of viscometers, sapphire as a heat-capacity calibrant in calorimetry, and solutions used for calibration in chemical analysis... 

The underwater sensor platform is derived from the Fido explosives vapor sensor, originally developed under the Defense Advanced Research Projects Agency (DARPA) Dog s Nose Program. The vapor sensor, whose operation is discussed in Chapters 7 and 9 and in other publications [7-9], was developed for the task of landmine detection. The underwater adaptation of the sensor is very similar to the vapor sensor. In the underwater implementation of the sensor, thin films of polymers are deposited onto glass or sapphire substrates. The emission intensity of these films is monitored as water (rather than air) flows past the substrate. If the concentration of TNT in the water beings to rise, the polymer will exhibit a measurable reduction in fluorescence intensity. The reduction in emission intensity is proportional to the concentration of target analyte in the water. Because the sensor is small, lightweight, and consumes little power, it proved to be ideal for deployment on autonomous platforms. 

Occurs in nature in abundance the principal forms are bauxites and lat-erites. The mineral corundum is used to produce precious gems, such as ruhy and sapphire. Activated aluminas are used extensively as adsorbents because of their affinity for water and other polar molecules and as catalysts because of their large surface area and appropriate pore sturcture. As adsorbents, they are used for drying gases and liquids and in adsorption chromatography. Catalytic properties may be attributed to the presence of surface active sites (primarily OFT, 02, and AF+ ions). Such catalytic applications include sulfur recovery from H2S (Clauss catalysis) dehydration of alcohols, isomerization of olefins and as a catalyst support in petroleum refining. 

The material for an acoustic lens should have a low attenuation, and a high velocity to minimize aberrations. Sapphire is an excellent material in both these respects. But the high velocity has a less desirable consequence. An acoustic impedance can be defined, which is equal to the product of the velocity and the density. The impedance of sapphire for longitudinal waves travelling parallel to the c-axis is thus 44.3 Mrayl, compared with the impedance of water which at room temperature is about 1.5 Mrayl, rising to 1.525 Mrayl at 60°C. When sound is transmitted across an interface between two materials of different impedance, the stress amplitude transmission coefficient is ( 6.4.1 Auld 1973 Brekhovskikh and Godin 1990)... 

Kushibiki, J., Sannomiya, T., and Chubachi, N. (1980). Performance of sputtered Si02 film as an acoustic antireflection coating at sapphire/water interface. Electron. Lett. 16, 737-8. [57]... 

The EPS experiments were carried out according to the procedure described in Ref. [20], The sample, used in experiments, was a 0.6 M solution of HDO molecules in heavy water at room temperature (maximal OD-O.6). The solution was pumped through a sapphire nozzle to form 100-pm thick, free-standing jet, that was positioned at the intersection of the laser beams. Use of the free-standing jet instead of a sample cell allowed us to avoid unwanted complications such as temporal broadening of the ultrashort pulses, their adverse scattering, and cross-phase modulation. The excitation pulses were -70 fs in duration and centered around -3 tm [19]. The excitation pulse spectra and the absorption spectrum of the OH-stretch vibration of HDO molecules in D2O are shown in the inset to Fig.lb. 

Femtosecond Ti-Sapphire oscillator (CDP, TiF50, 100 fs, 80 MHz, 0.3 W, 800 run) pumped with diode pumped solid state laser (Coherent, Verdi) was used to excite the system. The time- and spectral-resolved fluorescence spectra of C522 were measured by using up-conversion set-up (CDP, FOG100). The p-cyclodextrin, C42H70O35, and coumarin C522, C14H12F3NO2, used in these experiments were produced by Cyclolab and Radiant Dyes Chemie, respectively. All experiments were performed at room temperature and used water was twice deionised. 

A hydrate nucleating agent (precipitated amorphous silica) and a quiescent surface inhibitor (sodium dodecyl sulfate) were used in an attempt to initiate hydrates in the bulk phase. While the induction time (for detectable hydrate formation) was not predictable, in every case hydrate was initiated at a surface—usually at the vapor-water interface, but infrequently along the sides of the sapphire tube in the gas phase, and at the metal end-plate below the liquid phase. 

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