The Experts below are selected from a list of 216 Experts worldwide ranked by ideXlab platform
G M Pharr - One of the best experts on this subject based on the ideXlab platform.
-
depth resolved residual Stress analysis of thin coatings by a new fib dic method
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011Co-Authors: Marco Sebastiani, C Eberl, Edoardo Bemporad, G M PharrAbstract:Abstract A new methodology for the measurement of depth sensitive residual Stress profiles of thin coatings with sub-micrometer resolution is presented. The two step method consists of incremental focused ion beam (FIB) ring-core milling, combined with high-resolution in situ SEM-FEG imaging of the relaxing surface and a full field strain analysis by digital image correlation (DIC). The through-thickness profile of the residual Stress can be obtained by comparison of the experimentally measured surface strain with finite element modeling using Schajer's integral method. In this work, a chromium nitride (CrN) CAE-PVD 3.0 μm coating on steel substrate, and a gold MS-PVD 1.5 μm on silicon were selected for the experimental implementation. Incremental FIB milling was conducted using an optimized milling strategy that produces minimum re-deposition over the sample surface. Results showed an average residual Stress of σ = −5.15 GPa in the CrN coating and σ = +194 MPa in the Au coating. These values are in reasonable agreement with estimates obtained by other conventional techniques. The depth profiles revealed an increasing residual Stress from surface to the coating/surface interface for both coatings. This observation is likely related to Stress relaxation during grain growth, which was observed in microstructural cross sections, as predicted by existing models for Structure–Stress evolution in PVD coatings. A correlation between the observed Stress gradients and the in-service mechanical behavior of the coatings is proposed. Finally, critical aspects of the technique and the influence of microStructure and elastic anisotropy on Stress analysis are analyzed and discussed.
Ibro Tabakovic - One of the best experts on this subject based on the ideXlab platform.
-
composition gradient Structure Stress roughness and magnetic properties of 5 500 nm thin nife films obtained by electrodeposition
Journal of Magnetism and Magnetic Materials, 2016Co-Authors: Jie Gong, Steve Riemer, Michael Christopher Kautzky, Ibro TabakovicAbstract:Abstract The composition gradients of 5–500 nm thin NiFe films on Cu and NiP substrates obtained by electrodeposition in stirred plating solutions at pH 3.0 on 8 in wafers were studied. It was found that the average elemental composition of the NiFe changes during electrodeposition with steep downturns of Fe-content, from 58 to 50 wt% Fe, in composition gradient zone near the substrate interface in the thickness range 5–250 nm depending on the electrode substrate (Cu and NiP). The increase of Fe-content in the composition gradient zone is accompanied by the increase of coercivity, H c , magnetic flux saturation, B s , saturation magnetostriction, λ s , increase of dimensionless roughness, ρ rms , and change of Stress, σ . The coercivity (easy and hard axis) follows the Neel's relation H c = ct − n ( t is thickness and c is a constant). The mechanisms related to the change of coercivity of the NiFe films deposited on different substrates (Cu and NiP) are discussed in terms of material properties of these films.
-
Structure and room temperature recrystallization of electrodeposited copper
Electrochemical and Solid State Letters, 2003Co-Authors: Vladyslav Alexandrovich Vasko, Ibro Tabakovic, Steven C RiemerAbstract:The 2 μm thick copper films have been electrodeposited onto sputtered copper seed layers from a sulfate-sulfuric acid bath (0.3 M CuSO0 4 + 1.8 M H 2 SO 4 + 70 ppm Cl - ) with 3-N,N-dimethylaminodithiocarbamoyl-l-propanesulfonic acid and polyethylene glycol (Mw 8000) organic additives. Crystal Structure, surface Structure, Stress, and resistivity of the films were characterized over four weeks. Room-temperature recrystallization occurs in the films, accompanied by a change in Stress, from compressive to slightly tensile, and a decrease in resistivity. The role of Stress-relieving recrystallization is linked to the increase in grain size and enhancement in (111) and especially (200) texture.
-
composition Structure Stress and coercivity of electrodeposited soft magnetic conife films thickness and substrate dependence
Journal of The Electrochemical Society, 2002Co-Authors: Ibro Tabakovic, Venkatesewara Inturi, Steve RiemerAbstract:The properties of soft magnetic CoNiFe films electrodeposited in the presence of saccharin and sodium lauryl sulfate additives were studied in terms of their thickness and substrate dependence. Auger depth profile analysis of the elemental composition in CoNife films electrodeposited over different substrates (Pd 00 Ni 10. 1.0 T NiFe.Cu) demonstrate that the average composition at the substrate interface and bulk deposited films remains constant. X-ray diffraction (XRD) measurements reveal the existence of mixed fcc + bcc phase with larger amounts of bcc crystallites near the substrate side of the films, i.e.,at the lower thickness. XRD and transmission electron microscopy measurements revealed a larger grain size at the CoNiFe/substrate interface. The measured average Stress is both substrate- and thickness-dependent. The easy-axis coercivity, H c , follows the Neel's relation H c = ct n (t is the thickness and c is a constant). It was found that the value of the exponent n is substrate dependent. Mechanisms related to the coercivity of CoNiFe films deposited ovar different substrates (1.0 T NiFe, Cu, Pd 90 Ni 10 , high magnetic moment CoNiFe) are discussed in terms of material properties of these magnetic films.
P Djemia - One of the best experts on this subject based on the ideXlab platform.
-
Structure phase stability and elastic properties in the ti1 xzrxn thin film system experimental and computational studies
Acta Materialia, 2012Co-Authors: G Abadias, V I Ivashchenko, Laurent Belliard, P DjemiaAbstract:Abstract The composition-dependence of the Structure and elastic properties of ternary Ti 1– x Zr x N alloys is systematically investigated by combining thin film growth and ab initio calculations. Single-phase Ti 1– x Zr x N thin films (0 ⩽ x ⩽ 1) with a rocksalt Structure have been deposited using dc reactive magnetron sputtering at T s = 300 °C in Ar/N 2 plasma discharges. The Structure, Stress state and phase stability upon thermal annealing were studied by X-ray diffraction (XRD), while the acoustic and elastic properties were measured using Brillouin light spectroscopy, picosecond ultrasonics and nanoindentation. First-principles pseudopotential calculations of the total energy, lattice constants, bulk modulus, and single-crystal elastic constants C ij for several cubic ordered Structures of Ti 1– x Zr x N alloys were also carried out. The positive values of the computed formation energies indicate that the homogeneous Ti 1– x Zr x N alloys can be only stabilized at high temperatures. However, the magnetron-sputtered thin films were found to retain their as-grown single-phase cubic Structure during post-deposition annealing at 850 °C for 3 h. The calculated equilibrium lattice parameters are in good agreement with the Stress-free lattice parameters a 0 determined experimentally from XRD using the sin 2 ψ method: they both exhibit a positive deviation from Vegard-like linear interpolation. The calculated bulk modulus, elastic constants and Poisson’s ratio gradually decrease from TiN to ZrN. These computed values were used to interpret the experimentally derived elastic constants and Young’s modulus as functions of composition.
Lubna Sheikh - One of the best experts on this subject based on the ideXlab platform.
-
traversing the profile of biomimetically nanoengineered iron substituted hydroxyapatite synthesis characterization property evaluation and drug release modeling
RSC Advances, 2018Co-Authors: Lubna Sheikh, Shivendra Sinha, Y N Singhababu, Vineeta Verma, Sucheta TripathyAbstract:Even though ion substituted hydroxyapatite nanoparticles are associated with promising features for biomedical applications, green synthesis with precise control of size and shape to produce uniform nanoparticles remains elusive. To overcome this, we herein propose a room temperature, biomimetic approach to synthesize iron substituted nano-hydroxyapatite (m-HA) along with thorough physicochemical and biological evaluation. The study revealed that 10% iron could be isomorphously doped into hydroxyapatite crystal Structure. Stress, strain, energy density and atomic occupancy, as a result of substitution, have been ascertained by Williamson-Hall and Rietveld analysis using X-ray diffraction data. X-Ray photoelectron spectroscopy has been employed to confirm the elemental composition, chemical state and environment of m-HA. In addition, vibrating sample magnetometer of m-HA shows a trend towards superparamagnetic behaviour. Further, fluorescence assisted cell sorting and scanning electron microscope studies confirmed increase in the cell density with increasing iron concentration. Excellent antibacterial property, enhanced biocompatibility and bioactivity have also been interestingly observed. More controlled and sustained drug release has been observed with the inclusion of iron. A mathematical model developed to elucidate drug diffusion coefficient reveals Fickian mechanism to govern the release profile up to 8 hours followed by a non-Fickian transport. With these distinct features, this versatile material holds immense potential as bone repair material for osteoporosis where targeted delivery of calcium is required, as a heating mediator in cancer treatment and as a vehicle for site specific delivery of drug.
Sucheta Tripathy - One of the best experts on this subject based on the ideXlab platform.
-
traversing the profile of biomimetically nanoengineered iron substituted hydroxyapatite synthesis characterization property evaluation and drug release modeling
RSC Advances, 2018Co-Authors: Lubna Sheikh, Shivendra Sinha, Y N Singhababu, Vineeta Verma, Sucheta TripathyAbstract:Even though ion substituted hydroxyapatite nanoparticles are associated with promising features for biomedical applications, green synthesis with precise control of size and shape to produce uniform nanoparticles remains elusive. To overcome this, we herein propose a room temperature, biomimetic approach to synthesize iron substituted nano-hydroxyapatite (m-HA) along with thorough physicochemical and biological evaluation. The study revealed that 10% iron could be isomorphously doped into hydroxyapatite crystal Structure. Stress, strain, energy density and atomic occupancy, as a result of substitution, have been ascertained by Williamson-Hall and Rietveld analysis using X-ray diffraction data. X-Ray photoelectron spectroscopy has been employed to confirm the elemental composition, chemical state and environment of m-HA. In addition, vibrating sample magnetometer of m-HA shows a trend towards superparamagnetic behaviour. Further, fluorescence assisted cell sorting and scanning electron microscope studies confirmed increase in the cell density with increasing iron concentration. Excellent antibacterial property, enhanced biocompatibility and bioactivity have also been interestingly observed. More controlled and sustained drug release has been observed with the inclusion of iron. A mathematical model developed to elucidate drug diffusion coefficient reveals Fickian mechanism to govern the release profile up to 8 hours followed by a non-Fickian transport. With these distinct features, this versatile material holds immense potential as bone repair material for osteoporosis where targeted delivery of calcium is required, as a heating mediator in cancer treatment and as a vehicle for site specific delivery of drug.
