Quartz metal-coated

SERS Substrates Based on Metal-Coated Quartz Posts... 

Figure 13 shows a photocell used recently for work-function measurements (43). A metal coating inside the cell serves as the anode, and B is the cathode, which may be a metal foil or a film previously evaporated from a filament at C. Also provided at C are a W emitter for bombarding the cathode surface and a Pt electrode for thermally dissociating gas molecules. The monochromatic light which passes through the quartz window Q strikes the cathode B, and its energy can be measured by a calibrated photocell. 

The electrochemical quartz crystal microbalance (EQCM) has emerged as a very powerful in situ technique to complement electrochemical experiments [3-5]. Nomura and Okuhara [15] first used the quartz crystal microbalance (QCM) to detect mass changes at a metal coated quartz resonator immersed in electrolyte during electrochemical experiments. 

Materials. Biaxially oriented polypropylene (PP) films of 50 um thickness were obtained from 3M and have been described (2). PMDA-ODA (PI) was Kapton H polyimide from Dupont. Copper-plated PTFE films were obtained from Spire Corporation (Bedford, MA). They were prepared using the Ion Beam Enhanced Deposition (IBED) process in which a 100 nm thick Cu film was vapor-deposited onto a PTFE substrate in the presence of a beam of 400 eV Ar+ ions of 25 uA/cm2 (IQ). Shortly before SIMS analysis, the Cu film was removed slowly by peeling at 90° in ambient conditions. Metal-coated PI films were prepared by sputtering 50 nm Cr and 1 um Cu onto a 50 um thick Kapton film on both sides. Thermal annealing was performed in a vacuum chamber at 2xl0 6 torr using a quartz lamp as the heating source. The samples were held for 15 min at the desired temperature and then cooled down to ambient temperature inside the chamber for about 2 hours. Just prior to SIMS analysis, the metal films were peeled slowly at 90° and then immediately introduced into the vacuum chamber of the instrument. 

In results reported here we used a metal coated eeramic foam 45 ppi a-A1203 monolith 10 mm thick and 18 mm in diameter sealed in a quartz tube reactor as sketched in figure 1. 

Fused quartz has often been used to date either as a reflecting surface or as a substrate for a metal coating, e.g. Hastings et al (1978) on SPEAR and Helliwell et al (1982a, 1986b), Brammer et al (1988) on the SRS. 

G.( Barchan states that he observed both in natural articulation, such as bone joints with sinovial liquid, mucous coating on fish scales, blood vessels and blood, as well as various organic compounds and LCs on quartz, metal and alloys, that effective lubrication was observed when the compounds were in... 

The most common detector is the photomultiplier tube (PMT). A PMT is a sealed, evacuated transparent envelope (quartz or glass) containing a photoemissive cathode, an anode, and several additional electrodes called dynodes. The photoemissive cathode is a metal coated with an alkali metal or a mixture of elements (e.g., Na/K/Cs/Sb or Ga/As) that emits electrons when struck by photons. The PMT is a more sophisticated version of a vacuum phototube (Fig. 5.17), which contained only a photoemissive cathode and an anode the photocurrent was hmited to the electrons ejected from the cathode. In the PMT (Fig. 5.18), the additional dynodes multiply the available electrons. The ejected electrons are attracted to a dynode that is maintained at a positive... 

Figure 12.8. (a) Schematic top and edge views of an EQCM original, (b) The outline of quartz crystal with a metallic coating (adapted from reference [83]). (c) Response of crystal frequency during polymerization of aniline. [87]... 

The active element of the electrochemical quartz crystal microbalance (EQCM) was a gold-coated quartz crystal whose oscillation frequency was equal to 5 or 6 MHz. It was plated in a similar way, but the metal coatings were thinner (0.2-0.4pm). The constant relating the variations in quartz crystal mass with its oscillation frequency was determined by special calibration using EQCM data obtained in acid CuSO solutions at a controlled current density. 

Silica. SiHca (qv) comes in various forms including quartz [14808-60-7]. It has found wide use as an abrasive in the past, particularly as an inexpensive coated abrasive for woodworking. The term sandpaper is stiU used as a generic term for coated abrasives in many quarters although the use of sand in coated abrasives has been almost entirely elkninated because of the hazard of siHcosis to the user and its inferior grinding properties (especially for metals). 

Acoustic Wave Sensors. Another emerging physical transduction technique involves the use of acoustic waves to detect the accumulation of species in or on a chemically sensitive film. This technique originated with the use of quartz resonators excited into thickness-shear resonance to monitor vacuum deposition of metals (11). The device is operated in an oscillator configuration. Changes in resonant frequency are simply related to the areal mass density accumulated on the crystal face. These sensors, often referred to as quartz crystal microbalances (QCMs), have been coated with chemically sensitive films to produce gas and vapor detectors (12), and have been operated in solution as Hquid-phase microbalances (13). A dual QCM that has one smooth surface and one textured surface can be used to measure both the density and viscosity of many Hquids in real time (14). 

Lighting. An important appHcation of clear fused quartz is as envelop material for mercury vapor lamps (228). In addition to resistance to deformation at operating temperatures and pressures, fused quartz offers ultraviolet transmission to permit color correction. Color is corrected by coating the iaside of the outer envelope of the mercury vapor lamp with phosphor (see Luminescent materials). Ultraviolet light from the arc passes through the fused quartz envelope and excites the phosphor, produciag a color nearer the red end of the spectmm (229). A more recent improvement is the iacorporation of metal haHdes ia the lamp (230,231). 

Hardness It is not possible to obtain a reliable figure for the hardness of anodic coatings with either the indentation or scratch methods, because of the influence of the relatively soft metal beneath the anodic film, and the presence of a soft outer layer on thick films. On Moh s Scale, the hardness of normal anodic films lies between 7 and 8, i.e. between quartz and topaz. 

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