A mass spectrometric investigation of the plasma polymerization of methyltrimethoxysilane in an r.f. discharge

Quadrupole mass spectrometry was used to determine the chemical species present during r.f. discharges in methyltrimethoxysilane (MTMOS) and in MTMOS-Ar and MTMOS-O₂ mixtures. Hydrogen, low molecular weight (C₁-C₃) hydrocarbons, aldehydes and alcohols and silicon-containing fragments arising from MTMOS decomposition were observed in discharges in MTMOS and in MTMOS-Ar mixtures. The major components of discharges in MTMOS-O₂ mixtures were found to be H₂, OH, H₂O, CO, CO₂ and residual oxygen.Discharges in MTMOS or in MTMOS-Ar mixtures deposited polyalkoxysiloxane films. Similar discharges in MTMOS-O₂ mixtures deposited oxygen-deficient vitreous silica films. All of these films had large internal stresses resulting from the plasma polymerization process. The use of argon as a carrier gas for MTMOS in the production of polyalkoxysiloxane coatings reduced this stress significantly.     

Angiotensin-converting enzyme inhibitory activity of hydrolysates generated from whey protein fortified with salal fruits (Galtheria shallon) by enzymatic treatment with Pronase from Streptomyces griseus

Whey proteins mixed with salal fruits extract (0–20% w/w) were hydrolysed with Pronase E from Streptomyces griseus for a period of 8 h. The angiotensin-converting enzyme (ACE) inhibitory activity of the hydrolysates was highest (IC₅₀: 0.087 mg mL⁻¹) for samples fortified with the highest extract concentration (20%). Peptides (>7 amino acids) with documented ACE inhibitory activity (DAQSAPLRVY, ALPMHIR, DKVGINY, LHLPLPL, YPFPGPI, YPFPGPIPN, VYPFPGPIPN) were identified bv LC-MS/MS data analysis using a database search approach. Fluorescence spectra of the whey proteins mixed with salal fruits extract indicates fluorescence quenching for α-lactalbumin. SDS-PAGE analysis suggests that α-lactalbumin is less susceptible to proteolysis when the extract is included in the formula. Data indicate that α-lactalbumin may be interacting with phenolic compounds naturally present in salal fruits. These interactions and the formation of complexes between a-Lac and phenolic compounds may affect the hydrolysis pattern of whey protein and the release of peptides with ACE-inhibitory activity.     

AR-aging as a new approach for enhanced results

MAR-aging steels have earned a niche in the metal market arena, especially where aerospace and outerspace applications are concerned. MAR-aging steels owe their high strength, excellent fracture toughness, and good ductility to a precipitation-hardening (aging) mechanism that has been debated by scientists for several years. Because of today’s trend toward more demanding design requirements and a continuing need to better understand the MAR-aging family of materials, six different alloys (C-200, C-250, C-300, C-350, T-250, and T-300) were selected for study using a singular processing treatment: a hot-wall zone-gradient furnace. These alloys were evaluated for the effects of a specific thermal gradient (°C/cm) from 1231 °C (2250 °F) at the hot-wall limit to about 260 °C (500 °F) at the opposite end, the cold wall. All six alloys were evaluated in terms of their microstructure, microhardness, composition, and associated properties as a result of this specific thermal processing method. In this paper, detailed observations on the C-350 alloy are presented, and the results are interpreted in terms of a new heat treatment cycle called AR-aging.     

Effects of {VIM+EBCHR} Refining for IN-738 Alloy

Alloy IN-738 has gained acceptance as a durable turbine blade material for the gas turbine power industry. Typically, IN-738 material is a vacuum-cast, precipitation-hardened nickel-base alloy exhibiting excellent high-temperature creep-stress rupture strengths for extended service in a harsh thermal environment. This alloy also demonstrates an outstanding hot-corrosion resistance superior to that of other high-strength superalloys containing lower chromium content. Normally, IN-738 is vacuum-melted and investment-cast where typical casting conditions are problematic. For example, melts are superheated above the lower-liquidus temperature to about 1454 °C (2650 °F) and casting molds are preheated to temperatures of 981 °C (1800 °F) or higher. For an alloy, which exhibits a melting range of (1231-1315) °C (2250-2400) °F, this abusive melt practice leads to an excessively large dendritic crystals and gross coring of the microstructure with associated defects and deleterious phases. The intent of this article is to show that modern-day refining by {VIM+EBCHR} methods can be used to create a better alloy 738 for turbine blade applications. Cross-comparisons of selected properties for both investment-cast and ingot-cast test samples are here given.