Creep of Sylramic-iBN Fiber Tows at Elevated Temperature in Air and in Silicic Acid-Saturated Steam

Stressed oxidation experiments on Sylramic-iBN fiber tows were performed to evaluate the novel fiber\u27s mechanical performance, creep behavior, and creep mechanisms. This research effort investigated creep response of Sylramic-iBN fiber tows at elevated temperatures in both air and in silicic acid-saturated steam environments. Creep experiments were conducted at creep stresses ranging from 127 to 762 MPa at 400°C and 500°C in order to examine the mechanical behavior of the Sylramic-iBN fiber tows at temperatures below and above the melting point of boria (450°C). Sylramic-iBN fibers are known to have excellent creep resistance, better than most other non-oxide fibers and significantly better than oxide fibers. These fibers have a near-stoichiometric SiC composition, so they are a strong candidate for use in advanced aerospace CMCs. This research effort is a pilot program on the study of the effects of steam on Sylramic-iBN fibers. Previous attempts to study creep of SiC fiber tows in steam at elevated temperatures at the Air Force Institute of Technology\u27s (AFIT) Mechanics of Advanced Aerospace Materials Research Laboratory have yielded inconclusive results. Prior work at AFIT showed that the steam extracted silicon from the fiber tow and became saturated with silicic acid (Si[OH]4) . As the steam traveled along the SiC fiber, it also chemically altered the fiber surface producing inconsistent chemical compositions along the length of the fiber tow specimen. Along the fiber portion exposed to the unsaturated steam, the fiber experienced a chemical change leading to material loss, while the fiber portion exposed to the saturated steam experienced a silica scale growth along the fiber surface. A new test facility had to be designed to accurately evaluate the effects of steam on SiC fibers. The facility design incorporated an apparatus for saturating steam with silicic acid prior to entering the test chamber

Dutchwoman Butte Revisted

The Rangelands archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform March 202

Preparation and Characterization of Rare Earth Doped Fluoride Nanoparticles

This paper reviews the synthesis, structure and applications of metal fluoride nanoparticles, with particular focus on rare earth (RE) doped fluoride nanoparticles obtained by our research group. Nanoparticles were produced by precipitation methods using the ligand ammonium di-n-octadecyldithiophosphate (ADDP) that allows the growth of shells around a core particle while simultaneously avoiding particle aggregation. Nanoparticles were characterized on their structure, morphology, and luminescent properties. We discuss the synthesis, properties, and application of heavy metal fluorides; specifically LaF3:RE and PbF2, and group IIA fluorides. Particular attention is given to the synthesis of core/shell nanoparticles, including selectively RE-doped LaF3/LaF3, and CaF2/CaF2 core/(multi-)shell nanoparticles, and the CaF2-LaF3 system

Antigen specificity of clonally expanded and receptor edited cerebrospinal fluid B cells from patients with relapsing remitting MS

We re-engineered the immunoglobulin rearrangements from clonally expanded CSF B cells of three Multiple Sclerosis patients as Fab fragments, and used three methods to test for their antigen (Ag) specificity. Nine out of ten Fab fragments were reactive to Myelin Basic Protein (MBP). The one Fab that did not react to MBP was a product of receptor editing. Two of the nine MBP reactive Fabs were also reactive to GFAP and CNPase, indicating that these clones were polyreactive. Targeting the mechanisms that allow these self-reactive B cells to reside in the CSF of MS patients may prove to be a potent immunotherapeutic strategy.</p