@article{rabiei_thomas_neville_lee_cuomo_2007, title={A novel technique for processing functionally graded HA coatings}, volume={27}, ISSN={["0928-4931"]}, DOI={10.1016/j.msec.2006.05.037}, abstractNote={Hydroxyapatite (HA) films were deposited using dual ion beam sputtering. Deposition was carried out with an in situ heat treatment at three temperature settings during deposition. X-ray diffraction of the films at the surface revealed that the deposited film is composed of hydroxyapatite crystalline and amorphous phases. Cross-sectional transmission electron microscopy analysis displayed that the films have a graded crystal structure with the crystalline layer near the substrate and the amorphous layer at the top surface. Compositional analysis was performed using SEM-EDX at the top surface as well as STEM-EDX at the cross-section of the film. The average calcium to phosphorous ratio at the surface is 1.46, obtained by SEM-EDX. The Ca/P ratios in the crystalline and amorphous layers of the film are 1.6 to 1.7, close to the ratio of 1.67 for HA.}, number={3}, journal={MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS}, author={Rabiei, A. and Thomas, B. and Neville, B. and Lee, J. W. and Cuomo, J.}, year={2007}, month={Apr}, pages={523–528} }
 @article{rabiei_blalock_thomas_cuomo_yang_ong_2007, title={Microstructure, mechanical properties, and biological response to functionally graded HA coatings}, volume={27}, ISSN={["0928-4931"]}, DOI={10.1016/j.msec.2006.05.036}, abstractNote={Hydroxyapatite (HA) [Ca10(PO4)6(OH)2] is the primary mineral content, representing 43% by weight, of bone. Applying a thin layer of HA, to the surface of a metal implant, can promote osseointegration and increase the mechanical stability of the implant. In this study, a biocompatible coating comprising an HA film with functionally graded crystallinity is being deposited on a heated substrate in an Ion Beam Assisted Deposition (IBAD) system. The microstructure of the film was studied using Transmission Electron Microscopy techniques. Finally, initial cell adhesion and cell differentiation on the coating was evaluated using ATCC CRL 1486 human embryonic palatal mesenchymal cell, an osteoblast precursor cell line. The results have shown superior mechanical properties and biological response to the functionally graded HA film.}, number={3}, journal={MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS}, author={Rabiei, Afsaneh and Blalock, Travis and Thomas, Brent and Cuomo, Jerry and Yang, Y. and Ong, Joo}, year={2007}, month={Apr}, pages={529–533} }
 @article{rabiei_thomas_jin_narayan_cuomo_yang_ong_2006, title={A study on functionally graded HA coatings processed using ion beam assisted deposition with in situ heat treatment}, volume={200}, ISSN={["0257-8972"]}, DOI={10.1016/j.surfcoat.2005.09.027}, abstractNote={A new generation of calcium phosphate coatings with less than 1 μm thickness and graded crystallinity through the thickness of the film has been processed using ion beam assisted deposition (IBAD) and in situ heat treatment. Microstructural analysis of the film confirmed a gradual decrease of the grain size and crystallinity towards the surface, leading to nano-scale grains and eventually amorphous layer at the surface. The mechanical properties and adhesion bonding of the film have been evaluated using microscratch and nanoindentation tests and, in general, functionally graded HA films deposited using our IBAD system together with in situ heat treatment demonstrated higher modulus and hardness values than sputter-deposited films with the same thickness as well as those appearing in the literature for sintered HA. Scratch test results of both sets of samples revealed that crack formation is more common in sputter-deposited HA film than in the functionally graded HA film deposited using IBAD and in situ heat treatment. We anticipate that the functionally graded hydroxyapatite films will provide improved tissue–implant interfaces for orthopedic and dental implants.}, number={20-21}, journal={SURFACE & COATINGS TECHNOLOGY}, author={Rabiei, A and Thomas, B and Jin, C and Narayan, R and Cuomo, J and Yang, Y and Ong, JL}, year={2006}, month={May}, pages={6111–6116} }
 @article{lee_thomas_rabiei_2006, title={Microstructural study of titanium-palladium-nickel base thin film shape memory alloys}, volume={500}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2005.11.027}, abstractNote={Abstract A new generation of thin film shape memory alloys has been developed with 1.65 μm thickness for micro-actuator applications. In this work, the microstructure of thin film Titanium–Palladium–Nickel (TiPdNi) shape memory alloys deposited using ion beam assisted deposition from a Ti50Pd30Ni20 target is studied. The TiPdNi thin films were deposited with and without substrate heating during deposition. As-deposited films without substrate heating were found to be amorphous. Deposition on heated substrate produced a dense, columnar crystalline structure. Microstructures of bulk TiPdNi thin films as well as the interfacial region between the film and substrate were characterized by various techniques including transmission electron microscope, scanning transmission electron microscope, scanning electron microscope-energy dispersive X-ray spectroscopy and scanning transmission electron microscope-energy dispersive X-ray spectroscopy. A transition layer with 70 nm thickness is observed at the interface between the bulk film and silicon substrate. It is composed of three layers; two amorphous layers above the silicon substrate and a 50 nm thick twin absent layer, which was identified as B2 austenite phase by Fourier spectra analysis. In the bulk film, nano-scale grains in the range of 80–200 nm were observed. The width of twin band of the film was very narrower in the range of ∼5 nm.}, number={1-2}, journal={THIN SOLID FILMS}, author={Lee, JW and Thomas, B and Rabiei, A}, year={2006}, month={Apr}, pages={309–315} }
 @article{baldwin_thomas_lee_rabiei_2006, title={Residual stresses in TiPdNi base thin film shape memory alloys}, volume={434}, ISSN={["0921-5093"]}, DOI={10.1016/j.msea.2006.06.123}, abstractNote={TiPdNi thin films with less than 2 μm thickness were produced using ion beam assisted deposition (IBAD) on heated and unheated substrates. Films deposited on unheated substrates were found to be amorphous, and subsequently annealed to induce crystallization. Residual stresses in the films were evaluated using the Stoney equation after deposition, and after annealing. Films deposited using IBAD on unheated substrates were found to have slight compressive stress (−22.4 MPa) while films deposited on heated substrates had a moderate tensile stress (176.2 MPa). Annealed films experienced extensive tensile stress (598.3 MPa), resulting in film failure.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Baldwin, E. and Thomas, B. and Lee, J. W. and Rabiei, A.}, year={2006}, month={Oct}, pages={124–130} }
 @article{baldwin_thomas_lee_rabiei_2005, title={Processing TiPdNi base thin-film shape memory alloys using ion beam assisted deposition}, volume={200}, ISSN={["0257-8972"]}, DOI={10.1016/j.surfcoat.2004.08.172}, abstractNote={A new generation of thin-film shape memory alloys (SMA) has been developed with less than 2 μm thickness for MEMS microactuator applications. In this study, thin-film TiPdNi SMA was processed using ion beam assisted deposition (IBAD) with and without in situ heat treatment. As-deposited films were found to be amorphous. Postdeposition annealing lead to bulk diffusion of palladium to the substrate interface and silicon into the bulk film, creating a porous cross section. Various forms of tensile failures were observed including decohesion and delamination as a result of postdeposition annealing. Effect of heating and cooling rates was studied as well as in situ heat treatment during deposition. Deposition using the IBAD technique with in situ heat treatment was successful in producing fully martensitic films 1.5 μm thick and with reduced grain size and film defects, compared to the other sputter deposited films and IBAD deposited followed by postdeposition heat treatment. The effects of various processing parameters, and heat treatment conditions, on film properties have been studied.}, number={7}, journal={SURFACE & COATINGS TECHNOLOGY}, author={Baldwin, E and Thomas, B and Lee, JW and Rabiei, A}, year={2005}, month={Dec}, pages={2571–2579} }