Bradley Richards

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n air plasma spray process has been used to deposit tri-layer environmental barrier coatings consisting of a silicon bond coat, a mullite interiffusion barrier, and a Yb2SiO5 top coat on SiC substrates. Solidified droplets in as-deposited Yb2SiO5 and mullite layers were discovered to be epleted in silicon. This led to the formation of an Yb2SiO5 + Yb2O3(More)
An air plasma spray process has been used to apply a model tri-layer Yb2SiO5/Al6Si2O13/Si environmental barrier coating system on SiC test coupons. Significant differences in the thermal expansion of the component layers resulted in periodically spaced mud cracks in the Yb2SiO5 and Al6Si2O13 layers. Upon thermal cycling between 1316°C and 110°C in a 90%(More)
Article history: Received 22 October 2015 Revised 15 December 2015 Accepted in revised form 16 December 2015 Available online 14 January 2016 The reactions betweenmolten calcium aluminummagnesium silicates (CMAS) at 1300 °C and atmospheric plasma spray (APS) deposited environmental barrier coatings on SiC substrates have been investigated. The tri-layer(More)
Environmental barrier coatings (EBCs) are needed to protect SiC structures exposed to high temperatures in water vapor-rich environments. Recent studies of a tri-layer EBC system consisting of a silicon layer attached to the SiC, a mullite diffusion barrier and a lowsteam volatility ytterbium silicate topcoat have shown some promise for use at temperatures(More)
A preliminary study of a promising bi-layer environmental barrier coating (EBC) designed to reduce the susceptibility of SiC composites to hot water vapor erosion is reported. The EBC system consisted of a silicon bond coat and a pore-free ytterbium disilicate (YbDS; Yb2Si2O7) topcoat. Both layers were deposited on a-SiC substrates using a recently(More)
Workforce projections indicate a potential shortage of up to 31,000 adult primary care providers by the year 2025. Approximately 80 % of internal medicine residents and nearly two-thirds of primary care internal medicine residents do not plan to have a career in primary care or general internal medicine. We aimed to explore contextual and programmatic(More)
Whereas the major satellite fraction in mouse extends its domain from the centromere to the distal end of the pericentric heterochromatin, the minor satellite DNA is present specifically in the centromere or primary constriction. We hybridized the biotinylated minor satellite sequence to L929 cells of mouse origin. The sequence hybridized to all(More)
I am grateful to Bradley Richards and J. H. Taylor for their thoughtful critiques and for the chance to clarify and re-think the main line of argument in ‘‘The Grain of Vision and the Grain of Attention’’ (Block 2013). My article concerned peripheral vision. Much of normal vision is peripheral. The fovea is the central area of the retina that is needed for(More)
A recently optimized air plasma spray process has been used to deposit a model tri-layer Yb2SiO5/ Al6Si2O13/Si environmental barrier coating (EBC) system on a-SiC substrates using low power deposition parameters to reduce silicon losses, improve interface adherence and decrease defect concentrations. During cooling, tensile stresses developed in the(More)