Interfacial thermoelectric and mechanical properties of indigenously prepared Ni–Cr–Cu/Co4Sb12 skutterudite thermoelectric joints

Thermoelectric and mechanical properties of indigenously prepared Ni–Cr–Cu/Co4Sb12 skutterudite thermoelectric joints are reported. Co4Sb12 based skutterudite compounds are highly enticing mid-temperature thermoelectric materials for waste-heat harvesting. Ni–Cr–Cu electrode powder is prepared by ball milling, and a one-step sintering route is adopted to fabricate the Ni–Cr–Cu electrode/n-type Dy0.4Co3.2Ni0.8Sb12 thermoelectric joints. The processed Ni–Cr–Cu/skutterudite joint interface is continuous without having any crack and has low contact resistance (<12 μΩ cm2). The contact resistance at the interface of the joints decreases to 7 μΩ cm2 under thermal ageing at 823 K for 15 days in a vacuum. The mechanical properties of the joints are not degraded even after ageing at 823 K for 15 days. The theoretical lifetime of the skutterudite device using the Ni–Cr–Cu/Dy0.4Co3.2 Ni0.8Sb12 joints is calculated to be 11 years while maintaining the hot side temperature of the device at 773 K. Our results demonstrate that indigenously prepared Ni–Cr–Cu/Co4Sb12 thermoelectric joints can be effectively used for skutterudite module fabrication

Bioengineered Three-Dimensional Physiological Model of Colonic Longitudinal Smooth Muscle In Vitro

Background: The objective of this study was to develop a physiological model of longitudinal smooth muscle tissue from isolated longitudinal smooth muscle cells arranged in the longitudinal axis. Methods: Longitudinal smooth muscle cells from rabbit sigmoid colon were isolated and expanded in culture. Cells were seeded at high densities onto laminin-coated Sylgard surfaces with defined wavy microtopographies. A highly aligned cell sheet was formed, to which addition of fibrin resulted in delamination. Results: (1) Acetylcholine (ACh) induced a dose-dependent, rapid, and sustained force generation. (2) Absence of extracellular calcium attenuated the magnitude and sustainability of ACh-induced force by 50% and 60%, respectively. (3) Vasoactive intestinal peptide also attenuated the magnitude and sustainability of ACh-induced force by 40% and 60%, respectively. These data were similar to force generated by longitudinal tissue. (4) Bioengineered constructs also maintained smooth muscle phenotype and calcium-dependence characteristics. Summary: This is a novel physiologically relevant in vitro three-dimensional model of colonic longitudinal smooth muscle tissue. Bioengineered three-dimensional longitudinal smooth muscle presents the ability to generate force, and respond to contractile agonists and relaxant peptides similar to native longitudinal tissue. This model has potential applications to investigate the underlying pathophysiology of dysfunctional colonic motility. It also presents as a readily implantable band-aid colonic longitudinal muscle tissue.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85093/1/ten_tec_2009_0394.pd

Modeling of Laser-Tempering Process for Hyper-Eutectoid Steels

Laser surface tempering causes reduction in the surface hardness without affecting the bulk material hardness. The tempering behavior can be advantageous in advanced manufacturing processes that require controlled softening of the surface layers of through-hardened high-strength steels. This paper presents a computational phase change kinetics-based model for selecting the laser parameters that temper the surface layers of a through-hardened hyper-eutectoid steel (AISI 52100) over a known depth. First, a three-dimensional analytical thermal model is used to evaluate the temperature field produced in the material due to thermal cycles produced by laser scanning of the surface. The computed temperature histories are then fed to the phase-change model to predict the surface and subsurface hardness for the chosen laser-processing conditions. Microstructural analysis of the laser-treated AISI 52100 workpiece surface is presented for different laser-processing conditions. It is shown that good agreement is achieved between the predicted and measured surface hardness. © 2014 The Minerals, Metals &amp; Materials Society and ASM International.