Blisters

About: Blisters is a research topic. Over the lifetime, 980 publications have been published within this topic receiving 16229 citations.

A Mechanism for Blistering of Carbon Fiber Composites

Abstract: : Blisters containing fluid with a high pH were induced in a carbon fiber vinyl ester polymer matrix composite by cathodic polarization in a sodium chloride solution. The oxygen content of the solution was varied in order to determine the effect of oxygen on the blister process. It was found that increasing the oxygen content in solution decreased the time for blister initiation, indicating that the reduction of oxygen to form hydroxyl ions was an important reaction. Calculations indicated that a similar cumulative charge density was required for blister initiation for the different oxygen contents, confirming the importance of oxygen to the blister process. A mechanism for blister formation dependent upon oxygen reduction to hydroxyl ions and the subsequent formation of an osmotic cell is outlined from the results of this study

Dielectric Coating Thermal Stabilization During GaAs-Based Laser Fabrication for Improved Device Yield

Abstract: The quality and yield of GaAs-based ridge waveguide devices fabricated at MIT Lincoln Laboratory were negatively impacted by the random lot-to-lot appearance of blisters in the front-side contact metal. The blisters signaled compromised adhesion between the front-side contact metal, underlying SiO2 dielectric coating, and semiconductor surface. A thermal-anneal procedure developed for the fabrication of GaAs slab coupled optical waveguide (SCOW) ridge waveguide devices stabilizes the SiO2 dielectric coating by means of outgassing and stress reduction. This process eliminates a primary source of adhesion loss, as well as blister generation, and thereby significantly improves device yield. Stoney’s equation was used to analyze stress-induced bow in device wafers fabricated using this stabilization procedure. This analysis suggests that changes in wafer bow contribute to the incidence of metal blisters in SCOW devices.

Comparative Evaluation of the Shear Adhesion Strength of Ice on PTFE Solid Lubricant

Abstract: The development of a durable and green icephobic coating plays a vital role in the aviation industry due to the adverse impact of ice formation on aircraft performance. The lack of study into how temperature and surface roughness impact icephobicity is the main problem with present icephobic coatings. This study aims to qualitatively evaluate the icephobicity performance of a polytetrafluoroethylene (PTFE) solid lubricant film, as an environmentally friendly solution, with a custom-built push-off test device in different icing conditions utilizing a wind tunnel. The ice-adhesion reduction factor (ARF) of the film has been assessed in comparison to a bare aluminium substrate (Al 6061). The impact of surface energy was investigated by comparing the water contact angle (WCA), the contact angle hysteresis (CAH), and the pull-off force of the PTFE solid lubricant and Al with an atomic force microscope (AFM). The results of ice shear adhesion on the PTFE solid lubricant film showed a significant reduction in the ice adhesion force at various substrate temperatures and surface roughness compared to the bare aluminium substrate. The difference in the ice adhesion between the solid lubricant and aluminium alloy was attributed to the differences in the detachment mechanism. For the PTFE-based solid lubricant, the interfacial detachment mechanism was based on the formation of interfacial blisters towards the centre of the ice. Consequently, upon continued application of the shear force, most of the energy injected would be distributed throughout the blisters, ultimately causing detachment. In the comparison of ice adhesion on PTFE solid lubricant and bare aluminium, the film showed minimal ice adhesion at −6 °C with an adhesion force of 40 N (ARF 3.41). For temperature ranges between −2 °C and −10 °C, the ice adhesion for bare aluminium was measured at roughly 150 N.

Inverted Pyramidal Texturing of Silicon Through Blisters in Silicon Nitride

Abstract: We have demonstrated a novel process for the fabrication of inverted pyramidal structures on silicon. The proposed technique uses no photolithography step and is instead replaced by a thin-film deposition step and thermal annealing. In this paper, inductively coupled plasma CVD (ICP-CVD) silicon nitride was used as the thin film. Blisters were formed on the silicon nitride film upon annealing at 800 $^{\circ}$ C. The silicon nitride film remaining on the surface of the wafer acts as an etch mask for the texturization process, which is carried out in an alkaline solution. It was observed that only open blisters participated in the etch process, while closed blisters were resistant to the etching solution. It was observed that the gas flow ratio, annealing time, and temperature played an important role in determining the shape, size, and areal density of the blisters. By integrating an argon plasma pretreatment in the silicon nitride deposition process, surface coverage of 51% was obtained for lower annealing temperatures of 550 $^{\circ}$ C. Upon etching the sample in an alkaline solution, a weighted average reflectance of 17.3% was obtained, indicating the potential of this process.

Study of hydrogen embrittlement of iron by internal-friction methods

Abstract: Note presenting the effects of electrolytic charging on the properties of relatively pure iron and tempered 4340 steel investigated metallographically and by observing internal-friction behavior from -196 to 430 degrees Celsius. Electrolytic charging caused severe structural damage to both iron and steel, consisting of blisters and internal cracks.