Characterization of hydroxyapatite-tantalum pentoxide nanocomposite coating applied by electrophoretic deposition on Nitinol superelastic alloy

In this study, natural hydroxyapatite (nHA) and nHA-20?wt.%Ta₂O₅ nanocomposite coatings were deposited via electrophoretic deposition (EPD) on the NiTi substrate. The suspensions of nHA and nHA-Ta₂O₅ nanoparticles were prepared in n-butanol as a medium with different contents (0, 4, 8, 12, 16, and 20?mL/L) of triethanolamine (TEA) as a dispersant. The most stable suspensions of nHA and nHA-Ta₂O₅ nanoparticles were achieved with 16?mL/L TEA according to the sedimentation test and zeta potential measurement results. The enhanced colloidal stability of nanoparticles in n-butanol by TEA addition was investigated by FTIR analysis. The highest in-situ EPD kinetics were accomplished from suspensions containing an optimum concentration of dispersant. The phase compositions and microstructures of the coatings, before and after sintering under 1.4?×?10^?6?mbar vacuum at 800?°C for 1?h, were perused using XRD and FESEM, respectively. The results of the nano-scratch analysis showed the highest critical distance of delamination (0.38?mm), normal load before failure (133?mN) as well as the critical contact pressure (7.12?GPa) for nHA-Ta₂O₅ coating on the NiTi. The concentration of the released Ni ions from passivated-NiTi with nHA coating in PBS after 30 days of immersion reduced from 45.72 to 5.62 μg/Lcm² by introducing Ta₂O₅ in nHA matrix. On the other hand, the improved corrosion behavior of passivated-NiTi with nHA-Ta₂O₅ coating in comparison to that of with nHA deposit was explained with the lower amount of open porosities in the microstructure. The biocompatibility of the nHA and nHA-Ta₂O₅ surfaces were studied by osteoblast cell attachment during 7 days of culturing.     

Anticorrosion epoxy coating enriched with hybrid nanozinc dust and halloysite nanotubes

In this study, the performance of an epoxy coating with hybrid nanozinc dust and halloysite nanotube (HNT) fillers on the corrosion protection of a carbon steel substrate was investigated. The epoxy resin was mixed with a constant amount of nanozinc dust (1%) and different contents of HNTs (0, 0.5, 1, and 1.5%) with a high speed mixer. Fourier transform infrared spectroscopy and thermogravimetric analysis were used to analyze the interactions between the components in the coating material and the thermal stability of the epoxy coating, respectively. Open‐circuit potential, salt spray testing, and microscopy were also used to assess the corrosion resistance of the carbon steel substrate coated with these coating materials. The incorporation of nanozinc in the epoxy coating enhanced the corrosion protection of the carbon steel substrate compared with the pure coating. Furthermore, HNTs further enhanced the corrosion protection. The best protection was achieved when 1% nanozinc and 1% HNT were used. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 955‐960, 2013     

Real-time absorption and scattering characterization of slab-shaped turbid samples obtained by a combination of angular and spatially resolved measurements

We present a fast and accurate method for real-time determination of the absorption coefficient, the scattering coefficient, and the anisotropy factor of thin turbid samples by using simple continuous-wave noncoherent light sources. The three optical properties are extracted from recordings of angularly resolved transmittance in addition to spatially resolved diffuse reflectance and transmittance. The applied multivariate calibration and prediction techniques are based on multiple polynomial regression in combination with a Newton--Raphson algorithm. The numerical test results based on Monte Carlo simulations showed mean prediction errors of approximately 0.5% for all three optical properties within ranges typical for biological media. Preliminary experimental results are also presented yielding errors of approximately 5%. Thus the presented methods show a substantial potential for simultaneous absorption and scattering characterization of turbid media.     

Enhancing water swelling ability and mechanical properties of water‐swellable rubber by PAA/SBS nanofiber mats

Investigation of the potential use of nanofibers to reinforce composites has gained significance in many applications. In this article, the nanofiber mats of poly(acrylic acid) (PAA) and styrene–butadiene–styrene (SBS) triblock copolymer with composites structure were interweaved by double needle electrospinning process. The multiple nanofiber mats were added to conventional water‐swellable rubber (WSR). Improved mechanical and physical properties of WSR were obtained. Enhancement of the swellability of WSR + PAA/SBS nanofiber mats was derived from the PAA constituent absorbing water from the surface into the bulk and introducing random internal water channels between discontinuous superabsorbent polymers. The role of SBS nanofibers in the composite of WSR + PAA/SBS nanofiber mats was more related to the mechanical properties, where the breaking force of the composite increased to twice that of the conventional WSR. Interestingly, after immersion of the WSR + PAA/SBS nanofiber mats in water for 1 week, there was only a slight decrease in their mechanical properties of less than 5% compared to the dry state. The mechanisms and effects of the nanofiber mats in enhancing the mechanical and water swelling properties of WSR are also discussed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44213.     

Allocating fixed resources and setting targets using a common-weights DEA approach

Data envelopment analysis (DEA) is a data-driven non-parametric approach for measuring the efficiency of a set of decision making units (DMUs) using multiple inputs to generate multiple outputs. Conventionally, DEA is used in ex post evaluation of actual performance, estimating an empirical best-practice frontier using minimal assumptions about the shape of the production space. However, DEA may also be used prospectively or normatively to allocate resources, costs and revenues in a given organization. Such approaches have theoretical foundations in economic theory and provide a consistent integration of the endowment-evaluation-incentive cycle in organizational management. The normative use, e.g. allocation of resources or target setting, in DEA can be based on different principles, ranging from maximization of the joint profit (score), combinations of individual scores or game-theoretical settings. In this paper, we propose an allocation mechanism that is based on a common dual weights approach. Compared to alternative approaches, our model can be interpreted as providing equal endogenous valuations of the inputs and outputs in the reference set. Given that a normative use implicitly assumes that there exists a centralized decision-maker in the organization evaluated, we claim that this approach assures a consistent and equitable internal allocation. Two numerical examples are presented to illustrate the applicability of the proposed method and to contrast it with earlier work.