Treating Fibrous Insulation to Reduce Thermal Conductivity

A chemical treatment reduces the convective and radiative contributions to the effective thermal conductivity of porous fibrous thermal-insulation tile. The net effect of the treatment is to coat the surfaces of fibers with a mixture of transition-metal oxides (TMOs) without filling the pores. The TMO coats reduce the cross-sectional areas available for convection while absorbing and scattering thermal radiation in the pores, thereby rendering the tile largely opaque to thermal radiation. The treatment involves a sol-gel process: A solution containing a mixture of transition-metal-oxide-precursor salts plus a gelling agent (e.g., tetraethylorthosilicate) is partially cured, then, before it visibly gels, is used to impregnate the tile. The solution in the tile is gelled, then dried, and then the tile is fired to convert the precursor salts to the desired mixed TMO phases. The amounts of the various TMOs ultimately incorporated into the tile can be tailored via the concentrations of salts in the solution, and the impregnation depth can be tailored via the viscosity of the solution and/or the volume of the solution relative to that of the tile. The amounts of the TMOs determine the absorption and scattering spectra

Hardness of Alumina/Silicon Carbide Nanocomposites at Various Silicon Carbide Volume Percentages

Presented at the 37th International Conference and Expo on Advanced Ceramics and Composites (ICACC'13), Daytona Beach, Florida.Vickers indentation was employed to measure the microhardness of monolithic alumina and six alumina-based nanocomposites consisting of variable silicon carbide nanoparticle volume percentages of 0.3% to 20%. Indentation tests were performed over a broad range of loads from 0.5N to 40N. The resultant hardness-load curves exhibit cumulative increases in the apparent hardness based on the silicon carbide content and reveal each sample suffers from a prominent indentation size effect (ISE). Herein, we present a comprehensive analysis of this data using Meyer’s Law, the proportional specimen resistance model (PSR) and the modified proportional specimen resistance model (MPSR) and employ TEM imagery to detail potential mechanisms by which silicon carbide nano-reinforcements influence the “true hardness” and the ISE

Prehistoric polymer engineering : a study of rubber technology in the Americas

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003.Includes bibliographical references (p. 135-139).by Michael J. Tarkanian.S.M

In vitro biomechanical evaluation and comparison of a new prototype locking plate and a limited-contact self compression plate for equine fracture repair

OBJECTIVE: To determine if the mechanical properties (strength and stiffness) of a new prototype 4.5 mm broad locking plate (NP-LP) are comparable with those of a traditional 4.5 mm broad limited-contact self compression plate (LC-SCP), and to compare the bending and torsional properties of the NP-LP and LC-SCP when used in osteotomized equine third metacarpal bones (MC3). METHODS: The plates alone were tested in four-point bending single cycle to failure. The MC3-plate constructs were created with mid-diaphyseal osteotomies with a 1 cm gap. Constructs were tested in four-point bending single cycle to failure, four-point bending cyclic fatigue, and torsion single cycle to failure. RESULTS: There were not any significant differences in bending strength and stiffness found between the two implants. The MC3-NP-LP construct was significantly stiffer than the MC3-LC-SCP in bending. No other biomechanical differences were found in bending, yield load in torsion, or mean composite rigidity. Mean cycles to failure for bending fatigue testing were similar for both constructs. CLINICAL SIGNIFICANCE: The NP-LP was comparable to the LC-SCP in intrinsic, as well as structural properties. The NP-LP construct was more rigid than the LC-SCP construct under four-point bending, and both constructs behaved similarly under four-point bending cyclic fatigue testing and torsion single cycle to failure. The new NP-LP implant fixation is biomechanically comparable to the LC-SCP in a simulated MC3 fracture