Pinhole measurement

As an additional antifoulant measure, SHEs have been coated with a phenolic hning. This provides some degree of corrosion protection as well, but this is not guaranteed due to pinholes in the lining process. 

The Gurley number is used to characterize membranes because the measurement is accurate and easy to make, and deviations from specified values are a good indication of problems. A higher Gurley value than specified can indicate the membrane has surface damage a lower value than specified can indicate pinholes. 

Figure 8.14 (a) Values of as a function of corresponding diffusion times (observation times) for each CdTe quantum dot. Four sets of measurements for one sample were conducted with diferent sized pinholes and different solvent as follows (1) 25 Xm pinhole, in water (2) 25 Xm pinhole, in deuterated water (3) 50 Xm pinhole. 

Supersonic molecular beam (SMB) mass spectrometry (SMB-MS) measures the mass spectrum of vibra-tionally cold molecules (cold El). Supersonic molecular beams [43] are formed by the co-expansion of an atmospheric pressure helium or hydrogen carrier gas, seeded with heavier sample organic molecules, through a simple pinhole (ca. 100 p,m i.d.) into a 10 5-mbar vacuum with flow-rates of 200 ml. rn in. In SMB, molecular ionisation is obtained either through improved electron impact ionisation, or through hyperthermal surface ionisation... 

Ch - chopper disc, Fhl - filter holder, D - iris diaphragm and interchangeable pinholes of various sizes, Sch - sample chamber, S - sample holder, ID - iris diaphragm, L2 - receiver lens, Ph2 - detector photomultiplier, A - measuring arm, Fh 2 - filter holder, Phi - detector photomultiplier... 

Hydrogen gas would effuse through a pinhole 3.728 times as fast as nitrogen gas. The answer is reasonable, since the lower the molecular mass, the faster the gas is moving. Sometimes we measure the effusion rates of a known gas and an unknown gas, and use Graham s law to calculate the molecular mass of the unknown gas. 

More often the passive layer is broken down locally and then the steel is said to be attacked by localized corrosion, the most important forms being pitting, crevice corrosion, and corrosion cracking. Most often the localized corrosion is caused by halogen ions such as chloride, bromide, and iodide. Pitting or pitting corrosion is seen as small pinholes on the surface of the steel. This section describes electrochemical instrumental methods to investigate and measure this form of corrosion attack. 

Such a pinhole density test was performed on the AZ/PMMA two-layer deep-UV PCM system (26). The result is shown in Table IX where a pinhole density of 8 and 6 per cm was obtained for the capped (A) and uncapped (B) systems. Because only three wafers were used for each test, the result should be taken only qualitatively and the numerical difference between 6 and 8 pinholes/cm should be taken as being indicative of measurement fluctuations only. It should not be attributed to the use of different developers or O2 plasma because in the subsequent tests of batches C and D in which the DUV exposure was omitted, the numbers were 0 and 1 pinhole/cm with the capped system giving the smaller pinhole density. The low pinhole density in batch E in which the AZ development step was omitted suggests that the pinholes arise during the development of the AZ layer. Presumably, a small portion of the AZ base resin molecules were not linked up with the photoactive compound and therefore still exhibited their intrinsic high solubility in the AZ developer. After development, these high solubility spots became pinholes. These pinholes are apparently larger than the diffraction - limited sizes so that they can be transferred into the PMMA film by deep-UV exposure. 

SAMFETs have also been used in chemical sensing. The a-substituted quincpiethiophene SAMFETs were covered with a 10-nm pinhole-riddled iron tetraphenylporphyrin chloride layer, that acts as a receptor to nitric oxide (NO), an important biomarker [74]. The threshold voltage, measured by the FET transfer characteristics with the porphyrin receptor shifts upon increased exposure to NO. Annealing the monolayer FET in vacuum restores the initial FET behavior. Also, in the single monolayer HBC assembled FETs between metallic SWCNT source and drain electrodes increased current levels were measured in /d-Fds and Aj-Fg characteristics (Fig. 9) upon exposure to solutions of the electron acceptor TCNQ [68]. While the mechanism of response is not known, TCNQ has an affinity for coronene, and likely gives rise to charge transfer between electron-deficient TCNQ... 

AFM (cp-AFM). This specific measurement detects highly local and isolated penetration spots caused by either static pinholes or local blocking of a thiol terminal group at the SAM/vacuum interface due to some local disorder in the SAM. 

Two-photon excitation can be used for the fluorescence up-conversion microscope, and high axial resolution was achieved without a pinhole in this case. Figure 3.5 shows the up-converted fluorescence from a coumarin 522B solution at a fluorescence wavelength of 520 nm observed in the same manner of Figure 3.4d without pinhole. In this measurement, a fundamental laser pulse at 800 nm was used for excitation. The axial resolution with two-photon excitation was evaluated to be 0.97 pm (FWHM) by fitting for the first derivative of the obtained data. This result indicates... 

Pinhole density was Indirectly assessed by measuring shorts In a series of crossovers of first and second metal with Intervening polylmlde. For 1.2 y thick PI2545, the probability of a short was estimated at 1 In 133,333 crossovers. 

A 3/8 inch diameter aluminum or titanium-tungsten dot pattern WLs fabricated on top of the cured polyimide film to make electrical leakage to substrate measurements for pinhole density estimation. An etch decoration technique was used to visually determine pinhole densities in polyimide films. The polyimide film was cast on substrates comprised of a layer of 200 nm thick alumimmi on blue colored field oxide with a grid pattern for area computation. Replicate holes were etched in the aluminum by a hot phosphoric acid solution. With the polyimide film removed, a good visual contrast was achieved for pinhole density counting. 

Fig. 61. Schematics of pressure-induced and applied-potential-induced BLM deformations. Application of hydrostatic pressure (by lowering a piston into the aqueous solution bathing the cis side of the BLM) displaces the BLM from position 1 to position 2. The displacement involves both translational (lateral) motion (Ft) and curvature increase (Fc). As indicated, deformation of the BLM is accompanied by a change in its torus (Plateau-Gibbs border). 2R and 2Rm represent the diameters of the aperture of the pinhole in the Tefzel film and that of the membrane (excluding the torus). The object laser beam, incident upon the trans side of the BLM and reflected by it at 45° at a shortened wavelength produces concentric optical interference fringes with the reference laser beam. Ag/AgCl electrodes, placed in the cis and trans sides of the BLM, allow for continuous electrical measurements [413]...

Bilayer lipid membranes (BLMs) 2D, 3D 30- to 50- Painting of the surfactant (or A-thick, 1- to 2- lipid), dissolved in a hydrocarbon mm-diameter mem- solvent, across a teflon pinhole brane, supported which separates two by a solvent compartments of aqueous solution surfactant reservoir the Plateau-Gibbs border or torus) and separating two aqueous solutions macroscopically Hours Convenient system for fundamental studies as simultaneous electrical and spectroscopic measurements were possible 385, 387... 

---