Growth Of Blisters Research Articles

Interfacial degradation of epoxy coated silicon nitride

Silicon (Si) wafers passivated with a nitride film, fabricated by low-pressure chemical vapor deposition (LPCVD) and coated with epoxy were used as test specimens to characterize the interfacial degradation. For the sample preparation, the surface was examined by x-ray photoelectron spectrometry (XPS) and contact angle measurement. The stress test conditions were 121/spl deg/C and 100% relative humidity. Optical microscopy was used to monitor the growth of damage as a function of time. Results of electron microscopy and XPS indicate that two different failure modes exist at the interface. One type of degradation is etching of the silicon nitride, Si/sub 3/N/sub 4/ (SiN) film, which appears in the early stages of aging. In more severely etched areas, the concentration of oxygen (O) is quite high and surface cracks develop. The other degradation mechanism is the nucleation and growth of blisters. Phenomenologically, their common characteristics were observed to be rapid growth initially followed by gradual maturing. When a blister became sufficiently large that it could no longer sustain its shape, it collapsed. Often additional blistering propagated subsequently. Blister growth can be accelerated by condensed water that oxidizes the SiN film. Adhesion failure, in the presence of oxygen, is propagated by the degradation of the epoxy silane and SiN film. Precipitate, consisting primarily of sodium (Na), carbon (C) and oxygen (O) with sodium being the main constituent, formed in many of the damage locations. XPS confirmed that a significant source of sodium was the epoxy. Depending on the environmental conditions, the morphology of the precipitate changed. The growth kinetics of the interfacial damage in terms of geometrical properties was observed and statistically analyzed. It was shown that a two-parameter Weibull cumulative distribution function (cdf) could be used to represent the blister growth at each time interval. Naturally, the total blister area increased as the total number of blisters increased. Furthermore, the mean blister area as a function of time was estimated quite well by a power function; however, the scatter about the mean was rather significant. In fact, the statistical variability was sufficiently high throughout that further investigations are warranted. Although progress has been made toward an understanding of the growth kinetics of interfacial damage, the complex processes that compromise the mechanical and electrical integrity require further study.

Thermodynamic model of hydrogen-induced silicon surface layer cleavage

A thermodynamic model of hydrogen-induced silicon surface layer splitting with the help of a bonded silicon wafer is proposed in this article. Wafer splitting is the result of lateral growth of hydrogen blisters in the entire hydrogen-implanted region during annealing. The blister growth rate depends on the effective activation energies of both hydrogen complex dissociation and hydrogen diffusion. The hydrogen blister radius was studied as a function of annealing time, annealing temperature, and implantation dose. The critical radius was obtained according to the Griffith energy condition. The time required for wafer splitting at the cut temperature was calculated in accordance with the growth of hydrogen blisters.

Thermal Stability of the HOPG/Liquid Electrolyte Interphase Studied by In Situ Electrochemical Atomic Force Microscopy

In situ atomic force microscopy (AFM) was used to follow temperature‐dependent morphological changes at a highly oriented pyrolytic graphite (HOPG)/electrolyte interface. Cyclic voltammetry was performed on an HOPG crystal covered with an electrolyte [, ethylene carbonate/β‐butyrolactone (EC/γ‐BL) 2:1] with a 0.5% water content. Water reduction was observed at 1.4 V vs. . A solid electrolyte interphase (SEI) formation occurred at 0.8 V, and lithium‐ion intercalation began at 0.2 V. In situ AFM measurements were made at 25, 40, 50, 60, and 70°C. Destruction or melting of the SEI layer, causing a growth of small blisters spread on the surface, could be detected at 50°C. At higher temperatures, reaction products concentrate at the HOPG edge planes. X‐ray photoelectron spectroscopy characterization of HOPG cells stored at 20 and 80°C support the in situ AFM observations. Graphite powder electrodes show similar thermal SEI breakdown behavior, generating a thick carbon‐oxygen layer on the electrode surface at temperatures above 60°C. The influence of the lithium salt (here, ), organic solvent and water are discussed. © 2000 The Electrochemical Society. All rights reserved.

Hydride-Related Degradation of Spent-Fuel Cladding Under Repository Conditions

This report summarizes results of an analysis of hydride-related degradation of commercial spent-nuclear-fuel cladding under repository conditions. Based on applicable laboratory data on critical stress intensity obtained under isothermal conditions, occurrence of delayed hydride cracking from the inner-diameter side of cladding is concluded to be extremely unlikely. The key process for potential initiation of delayed hydride cracking at the outer-diameter side is long-term microstructural evolution near the localized regions of concentrated hydrides, i.e., nucleation, growth, and cracking of hydride blisters. Such locally concentrated hydrides are, however, limited to some high-burnup cladding only, and the potential for crack initiation and propagation at the outer-diameter side is expected to be insignificant for most spent fuels. Some degree of hydride reorientation could occur in high-burnup spent-fuel cladding. However, even if hydride reorientation occurs, accompanying stress-rupture failure in spent-fuel cladding is unlikely to occur.

Bestimmung der Haftzugfestigkeit dichter Beschichtungen / Determination of bond strength of impermeable polymer coatings

Abstract In many cases there is a risk for the formation of blisters if impermeable polymer coatings are applied on porous substrates. On covers of courses in sport stadiums formation of blisters has been observed recently. In this contribution a method is described which can be used to investigate the causes of blister formation in a given system. Blisters are artificially created by the application of a gas pressure in the interface between coating and substrate. In this way the growth of blisters can be varied under controlled conditions. The theoretical background of this method is outlined. In this way it is possible to estimate the necessary pressure under the cover to create blisters of the observed size.

塗り床のふくれ発生に及ぼす下地コンクリートの影響

Effect of property of substrate concrete on blistering of floor coatings is studied from the two view points such as property of concrete itself and surface characteristics. The concrete specimens of various water cement ratios, on which floor coatings is applied, were exposed in the accelerated condition for reproducing blistering, and growth of blisters were observed for a few months. After the test, adhesive strength was measured and the concrete surface was observed through a microscope. It was found out that blistering is much influenced by the water flux property induced by semi-permeability of concrete, and the distribution of adhesive strength caused by exposed materials on surface such as cement paste, aggregates and laitance.

Styrenics materials and cyclopentane: problems and perspectives

The use of chlorofluorocarbons (CFC) and hydrochlorofluorocarbons (HCFC) has been greatly limited in recent years because of their high ozone depletion potential (ODP) (Montreal protocol). The manufacturers of refrigerators have tried various new blowing agents for polyurethane (PU) foams used as insulating panels, and currently the chosen organic compound in Europe seems to be cyclopentane (CP), due to its acceptable insulating power and null ODP and toxicity. Unfortunately the interaction of CP with high impact polystyrene (HIPS) panels of the refrigerators produces blisters and can possibly induce environmental stress cracking (ESC). The aim of this work is, then, to explain the growth of blisters with a theoretical calculation and also to investigate the mechanical behaviour of HIPS in contact with gaseous and liquid CP, in comparison with usually used Freon® 11 (F11).

Probabilistic techniques for the assessment of pressure tube hydride blistering in CANDU reactor cores

The integrity of pressure tubes in CANDU reactors can be threatened if there is contact with the surrounding calandria tube and hydride blisters form in the pressure tube. In order to assess the state of a reactor core in which such contacts can occur, a probabilistic assessment technique based upon Monte Carlo methods has been developed. This approach was required due to the distributed nature of many of the factors required for such an assessment. The computer code embodies the results of an extensive research program into the growth and fracture characteristics of hydride blisters in pressure tube material. A single assessment generates distributions of the times to first blister formation and first blister cracking in the reactor core as well as the expected number of blistered tubes as a function of time. Multiple assessments can be used to explore the dependence of the assessment on variation in input assumptions. The result is a powerful tool for making key decisions on reactor maintenance requirements.

Formation of Hydride Blisters in Zirconium Alloy Pressure Tubes

AbstractThe fracture of the Zircaloy-2 pressure tube in the Pickering Unit 2 power reactor was associated with the growth of hydride blisters at points of contact between the pressure tube and the cooler calandria tube surrounding it. Similar blisters have been observed in a Zr-2.5 wt %Nb pressure tube in WR-l, an organic-cooled research reactor. These hydride blisters were formed and grew as a result of the thermal diffusion of hydrogen in the zirconium, a mechanism whereby hydrogen diffuses down a temperature gradient. If the terminal solid solubility of hydrogen is exceeded in the cooler regions, hydride will precipitate. In this paper, the time required to grow these hydride blisters will be estimated from the blister size and the hydrogen distribution in its neighborhood, by using simple equations derived from thermal diffusion theory.

Formation of Hydride Blisters in Zirconium Alloy Pressure Tubes

The fracture of the Zircaloy-2 pressure tube in the Pickering Unit 2 power reactor was associated with the growth of hydride blisters at points of contact between the pressure tube and the cooler calandria tube surrounding it. Similar blisters have been observed in a Zr-2.5 wt %Nb pressure tube in WR-l, an organic-cooled research reactor. These hydride blisters were formed and grew as a result of the thermal diffusion of hydrogen in the zirconium, a mechanism whereby hydrogen diffuses down a temperature gradient. If the terminal solid solubility of hydrogen is exceeded in the cooler regions, hydride will precipitate. In this paper, the time required to grow these hydride blisters will be estimated from the blister size and the hydrogen distribution in its neighborhood, by using simple equations derived from thermal diffusion theory.

Helium implantation of an Fe-Ni-Mo-B amorphous alloy: I. Experimental data on bubble growth and blistering during 5 keV He + implantation in the temperature range 200–600 K

The formation and growth of helium bubbles and blisters under 5 keV He + implantation has been studied for the amorphous alloy Metglas 2826 MB in the implantation temperature range 200–600 K and dose range 5 × 10 20 He +/ m 2−10 22 He +/ m 2. For all implantation temperatures bubbles are observed in the above-mentioned dose range and they grow with increasing dose. At a dose lower than the critical dose for blistering (~ 8 × 10 21 He +/ m 2) a second population of bubbles starts to grow, resulting in a class of larger bubbles. There is good evidence that these larger bubbles are the intermediate stages between the smaller-sized bubbles and the final blisters. It is suggested that the mechanism for blister formation is different for implantations below room temperature from that for implantations at or above room temperature. This suggestion is based on the variation of mechanical properties of the amorphous alloy with temperature.

複合処理鋼板の耐食性におよぼす下地処理の影響について

The effect of pretreatment on the corrosion resistance of zinc-rich painted steel sheets was evaluated by salt spray tests and the corrosion behavior was investigated electrochemically and by ESCA. The results obtained were as follows, (1) Steel sheet with 6-7μm composite coating containing about 70wt% zinc powder showed excellent formability. (2) Cold-rolled steel sheet with composite coating had poor corrosion resistance, indicating the importance of the pretreatment. (3) Pretreatment by Zn-Co-Mo electrodeposition produced superior corrosion resistance to that produced by Zn plating. (4) The excellent corrosion resistance of composite coated sheet pretreated by Zn-Co- Mo electrodepositi on depended on two factors, a) the corrosion products of Co and/or Mo controlled the increase in the anodic and cathodic reaction rates, which decreased the dissolution of Zn in the plated layer and prevented the growth of blisters; and b) most of the Zn in the composite coating and in the plated layer remained as a corrosion product on the surface, protecting the steel sheet substrate.

Use of long-term automatic time-lapse photography to measure the growth of frost blisters

The use of automatic time-lapse camera systems, taking daily photographs at solar noon between 26 September 1977 and 3 May 1978, has made it possible to determine the time and rate of growth of frost blisters at Bear Rock near Fort Norman, N.W.T. The daily negatives have been printed and refilmed to produce a time-lapse motion picture covering the full 220 day observation period. The use of paired cameras allowed production and viewing of daily stereo pairs.

A transmission electron microscopy study of molybdenum irradiated with helium ions

Abstract The paper describes the application of transmission electron microscopy to investigate the structure developed in the surface layers of molybdenum samples during irradiations with helium ions in the range 18 to 60 keV. Specimen temperatures were varied over a wide range from 20° C to above 1000°C and both dynamic and post-irradiation analytical techniques were utilised to provide information on the separate contributions of interstitials, vacancies and the helium gas to the formation of the damage structures. The interstitials formed dislocation loops, with subsequent growth to a dislocation network, while the combination of vacancies and gas resulted in a very high density (≈10 19 cm −3 ) of small helium bubbles over a wide temperature range (20–700°C). The helium bubbles were frequently found to be aligned in a body-centred-cubic lattice which produced extra reflections in electron diffraction patterns. Measured [110] bubble lattice spacings varied between 32 A and 50 A but showed no significant temperature dependence up to 700°C. At high helium doses (≈5 × 10 17 ions cm −2 ) blisters were clearly seen, together with the small bubbles, thus indicating the rapid growth of blisters rather than the slow coalescence and growth of the bubbles. At high temperatures larger helium bubbles were present. The insensitivity of the bubble parameters to vacancy mobility, the role of interstitials in creating surface stresses, and other aspects, are discussed particularly in relation to mechanisms of blistering. Although no definite conclusions are reached, it is clear that TEM evidence is important and that any proposed mechanism of blister formation must take this evidence into account.

亜鉛ダイカストメッキ面のフクレについて

Studies were made on the blisters which appear on the plated surface of zinc alloy die castings after several months more since the plating. The processes for accelerating the appearance of these blisters were also discussed. The following results were obtained(1) Each blister had a circular gap of 30-40μ in dia. at its centre, from which cracks radiated.(2) Growth of blisters was due to the corrosion of the substratum of zinc alloy.(3) For accelerating the appearance of blisters, it was found to be most effective to immerse the castings in the solution of about 3% of NH4Cl in boiling.(4) The blisters appeared in the above test were considered to be the same in nature as that in practice. Accordingly, the above test would be most available for detecting the surface defects for blistering source.