Nickel-titanium (NiTi) shape memory alloys undergo relatively large recoverable inelastic deformations via a stress-induced martensitic phase transformation. The nanoindentation experimental results presented in this study are the first to show evidence of discrete forward and reverse stress-induced thermoelastic martensitic transformations in nanometer scaled volumes of material. Shape recovery due to indentation, followed by subsequent heating, is demonstrated for indents depths in the sub 10 nm range via atomic force microscopy. It is also shown that the local material structure can be utilized to modify transformation behavior at nanometer scales, yielding insight into the nature of stress-induced martensitic phase transformations at small scales and providing opportunity for the design of nanometer sized NiTi actuators.

To investigate the effects of partially substitution of lanthanum for bismuth in the BiScO3-PbTiO3 (BSPT) ceramics, the 0.38(Bi1−xLax)ScO3-0.62PbTiO3 (BLSPTx) ceramics were prepared by using conventional solid state process. It was found that the partial replacement of lanthanum for bismuth do not affects the crystalline structure of the BSPT ceramics. With increasing of the lanthanum content, the grains of BLSPTx ceramics grown much bigger than those of BSPT ceramics when BLSPTx and BSPT ceramics were sintered at the same temperature. The temperature dependence of dielectric permittivity of BLSPTx ceramics shows that the Curie temperature (Tc) shifts toward lower temperature with the increasing of lanthanum content, and the BLSPTx samples for x=0.02 show the highest value of the dielectric constant at Tc.

During attempts to roll Fe-18.7%Ga alloy (atomic%), an alloy of interest because single crystal samples exhibit magnetostriction of ∼400 ppm, cracks formed along grain boundaries and subsequently samples fractured during hot rolling such that the alloy was too brittle to make thin sheets. While variations to rolling schedules (temperatures, times, roll diameters, etc.) may improve rollability, in this paper we investigate the effect of boron addition on Fe-18.7% Ga alloy magnetostrictive and mechanical properties. Thin sheets of Fe-18.7%Ga alloy plus 0.5 and 1.0 at.%B were successfully fabricated to thickness of 0.35 mm using rolling processes. It was observed that the fracture surface of the B-free alloy clearly appeared as an intergranular fracture mode and that of the B-added alloys was changed to a transgranular fracture mode with grain refinement. The annealed sheets with boron content of 0.5 and 1.0 at.% exhibit the maximum magnetostriction values of 103 and 184 ppm, respectively. In the case of Fe-18.7%Ga plus 1.0 %B, Fe2B phase presents throughout the α-iron matrix in small amount.

Shape Memory Alloys (SMAs) are versatile functional materials with an I.Q of their own. This class of SMART Materials exhibit unique properties like superelasticity and shape memory effect (SME) which have made them suitable for potential applications. Although Ni-Ti SMAs have attracted attention ever since their inception in 1962, Cu based SMAs due to their ease in fabrication, cost effectiveness and high temperature properties are gaining immense popularity. This research aimed at the fabrication of Cu-14 Al-3.5 Ni (wt %) Shape Memory Alloy by a simple cost effective route and its characterization to correlate its structure and properties. The alloy of desired composition was melted in an Electric Resistance Furnace at 1473 K and cast in a metallic mould. Homogenization was carried out at 1123 K for twenty four hours followed by analysis of chemical composition by Optical Emission Spectroscopy. Transformation temperatures of the alloy were determined using Differential Scanning Calorimetry. Heat treatment operations were carried out at 1273 K for one hour followed by quenching in different media. Optical and SEM micrographs were taken at various magnifications and the formation of self accommodating martensite was observed which was further confirmed by X-Ray Diffraction technique. Further improvements in the mechanical properties of the alloy by quaternary additions of Mn and Ti have been cited. Finally, SME was observed in a rolled strip of the alloy, thus concreting the obtained results.

TiO2 anatase thin films with different thickness (100 – 1200 nm) have been deposited on glass, sapphire and Si(100) substrates using pulsed DC magnetron reactive sputtering. The thin films were exposed to carbon monoxide (CO) gas at different concentrations (20–100 ppm) in a nitrogen carrier, and the resistance was measured as a function of the CO concentration for films of different thicknesses for temperatures in the range of (100 - 300°C). The films with good crystalline order showed better response than amorphous films. The response increased monotonically with CO concentration. The thicker films showed higher sensitivity. The anatase films deposited on sapphire generally had a larger response than those deposited on glass or on silicon. The films on sapphire substrate showed good response at temperatures as high as 300°C, while those deposited on glass and silicon had good responses only to 200°C. Furthermore, the addition of different concentrations of O2 and H2 affected the response as expected. The response to CO in the presence of N2 showed good reversibility which is evidence that complete regeneration on turn off the CO does not require exposure to oxygen or air. The response and the recovery times are fast.

Pb(Sc1/2Ta1/2)O3 (PST) relaxor ferroelectric ceramics were investigated widely in the past decades for their excellent pyroelectric, ferroelectric and dielectric properties and comprehensive applications in uncooled focal plane arrays infrared detectors and other electronic devices. However, some other ferroelectrics could be added into the PST ceramics to form the complex perovskite ferroelectrics with better electric properties. In this paper, (1-x)PST-xPZT(PSTZT) relaxor ferroelectric ceramics were prepared by wolframite precursor process (named two-step -sintering method, TSSM). The experiment results showed that the PSTZT ceramics with pure perovskite structure could be prepared by using TSSM. The temperature dependence of permittivity and dielectric loss of PSTZT ceramics were investigated in detail, which indicated that PSTZT ceramics showed partly diffusive phase transition with little frequency dispersion. The dielectric and pyroelectric properties of PSTZT ceramics were also investigated and discussed.

Calcium phosphate films were prepared on commercially pure titanium (CP-Ti) substrates by RF magnetron sputtering using β-tricalcium phosphate targets. XRD and FTIR analyses showed that the films consisted of amorphous calcium phosphate and oxyapatite phases. The (002) preferred orientation of the oxyapatite phase was observed depending on the oxygen gas concentration in the sputtering gas. The surface reactions of the calcium phosphate films were investigated in Hanks' solution and PBS(-). Apatite crystallites were detected on the films after immersion for 7 days. An active surface reaction was observed on the amorphous calcium phosphate films during immersion in PBS(-). The CP-Ti plates coated with the calcium phosphate films were placed on the mandible of male Japanese white rabbits. These results suggest that the calcium phosphate coating improves the biocompatibility of titanium implants with bone.

Giant magnetostrictive Fe-Pd and Fe-Ga thin films are expected as actuator/ sensor materials with high respective velocity and huge stress created by the magnetostriction. In order to develop magnetostrictive material induced by low magnetic field, we investigated bimorph-type magnetostrictive (positive magnetostriction / substrate / negative magnetostriction) thin films, that is, Fe-Pd(1, 3µm) or Fe-Ga(1, 3µm)/substlate /Ni(1, 3µm) by magnetron sputtering system. The substrate is Al(50µm) or kapton foil (125µm). Displacement of a upper part of these films was measured using an optical lever method. The displacement of the Fe70-Pd30(3µm )/ Al(50µm)/Ni(3µm)film ( length is 20 mm) was 280 μm under low DC magnetic field of 500 Oe and exhibits little hysteresis. These magnetostrictive properties are maintained under low alternating magnetic field. Moreover, the displacement of the film at the resonance frequency exhibits a peak and reached to 1.4 mm. The bimorph-type magnetostrictive thin film is useful for application in micro device as micro-pomp.

Over the past decade synthetic jets have emerged as a promising means of active flow control. They have the ability to introduce small amounts of energy locally to achieve non-local changes in the flow field. These devices have the potential of saving millions of dollars by increasing the efficiency and simplifying fluid related systems. A synthetic jet actuator consists of a cavity with an oscillating diaphragm. As the diaphragm oscillates, jets are formed through an orifice in the cavity. This paper focuses on piezoelectric synthetic jets formed using two types of active diaphragms, Thunder® and Lipca. Thunder® is composed of three layers; two metal layers, with a PZT-5A layer in between, bonded with a polyimide adhesive. Lipca is a Light WeIght Piezo Composite Actuator, formed of a number of carbon fiber prepreg layers and an active PZT-5A layer. As these diaphragms oscillate, pressure differences within the cavity as well as average maximum jet velocities are measured. These parameters are measured under load and no-load conditions by controlling pressure at the back of the actuator or the passive cavity. Results show that the average maximum jet velocities measured at the exit of the active cavity, follow a similar trend to the active pressures for both devices. Active pressure and jet velocity increase with passive pressure to a maximum, and then decrease. Active pressure and the jet velocity peaked at the same passive cavity pressure of 18kPa for both diaphragms indicating that the same level of pre-stresses is present in both actuators even though Lipca produces approximately 10% higher velocities than Thunder®.

A new technique, based on Optical Methods, has been tested for the evaluation of the lithium bromide (LiBr) concentration, a corrosive substance frequently used in heat pumps. Those solutions have large oxidizing capabilities. This technique avoids the direct contact between the electrodes and the LiBr aqueous solution within a thermodynamic absorption cycle. The viability of this technique in a potential commercial device, resides on its capability to detect working fluid concentrations within a temperature range from 25 °C up to 70 °C, those limiting temperature values correspond to the operating wavelengths of 1.33 μm and 1.55 μm, respectively. Our system determines the correlation among the signal and temperature data, for various concentrations, between 49 and 58 mass percentages. This function of two variables is represented as a surface with the transmittance, concentration and temperature as parameters and wavelength as reference. We discuss the adequate parameters characterization used in this technique.

This paper reports on the development of a smart sensor array consisting of selective gas sensing elements for use in disease diagnosis to monitor signaling gases. These are gases typically found in exhaled human breath that can serve as biomarkers for specific diseases. Utilizing the polymorphic selectivity of semiconducting metal oxides and by employing temperature modulation we have developed a smart gas selective sensor array able to identify and discriminate between isoprene, NOx, alcohols and amines/NH3. The sensing elements are thin films based on the various polymorphs of molybdenum trioxide. A breath analysis system based on our smart sensor array can be used for non-invasive monitoring and differential diagnosis of diseases.

Lithium sodium potassium niobate (Li, Na, K)NbO3 (LNKN) piezoelectric ceramics were prepared by using conventional solid state process. The phase structures of LNKN ceramics were characterized by x-ray diffraction (XRD). The dielectric properties of LNKN ceramics have been also studied at different temperature and frequency. It was found that LNKN ceramics have high Curie temperature Tc(about 460°C), and relatively high piezoelectric constant d33 (∼200pC/N) and high electromechanical coupling coefficient kp(∼0.40). Both of the piezoelectric constant d33 and electromechanical coupling coefficient kp of LNKN ceramics decreased with the increasing of sintering temperature. The piezoelectric property dependence of composition of LNKN ceramics has also been studied.

Fabrication of functional devices in fibers by thermal drawing requires a material identification scheme and challenging composite material processing. A macroscopic preform rod containing metallic, semiconducting and insulating constituents in a variety of geometries and close contact leads to kilometer-long novel optoelectronic, and thermal mesoscopic fiber devices. The preform-to-fiber approach yields spectrally tunable photodetectors and integrated self-monitoring fibers.

The normal physiologic response of vascular surgery is one of acute and intense inflammation and thrombosis. Research to date on improving outcomes after surgery has focused on drugs known to be active with the adrenergic system more specifically statins. Till date there has been no correlation between inflammation post surgery and the effect of perioperative anti-inflammatory drugs on improving surgical outcomes. The goal of this research is to characterize the role perioperative inflammation and thrombosis plays in determining outcomes after surgery. The goal of this particular application is to identify two specific pro-inflammatory protein markers namely C-reactive protein (CRP) and Myloperoxidase (MPO) associated with thrombosis from a wide range of serum samples. This is achieved by integrating the principles of fabrication associated with micro and nanotechnology to develop a sensor device comprising of nano ordered porous alumina membrane embedded in an elastomer (polydimethylsiloxane, PDMS) micro fluidic base. The nano porous membrane is selectively functionalized by a two level masking technique to the binding of CRP and MPO in selected areas. The binding event results in an electrochemical reaction that in turn produces a change in the surface charge. This in turn produces a measurable change to the electrical voltage. This is measured in an in-situ, non-invasive manner from selectively metalized areas of the nano membrane. Energy density analysis yielded unique electrical identifiers for each of the protein markers. Detection sensitivity of the order of 10 ppm was observed.

With the rapid development of wireless remote sensor systems, battery is becoming the limiting factor in the lifetime of the device and miniaturization. As a way to eliminate battery in the system, the conversion of ambient vibration energy has been addressed. The piezoelectric cantilever beam with a proof mass was exploited for energy conversion since it can generate large strain and power density. The design of cantilever beams was optimized through numerical analysis and FEM simulation at higher acceleration condition. The investigated parameters influencing the output energy of piezoelectric bimorph cantilevers include dimensions of cantilever beam and proof mass. The resonant frequency and robustness of cantilever structure were also considered for enhancing power conversion efficiency and implementing devices at high acceleration condition. The power density generated by the optimized piezoelectric device was high enough (> 1200 μW/cm3) to operate microsensor systems. However, high stress near clamping area of cantilever beam could lead to the fracture at high acceleration condition.

We evaluate the performance capabilities and limitations of high voltage 4H-SiC based Bipolar Junction Transistors (BJTs). Experimental forward characteristics of a 4kV BJT are studied and simulations are employed to determine the factors behind the higher than expected specific on-resistance (Ron,sp) for the device. The impact of material (minority carrier lifetimes), processing (surface recombination velocity) and design (p contact spacing from the emitter mesa) parameters on the forward active performance of this device are discussed and ways to lower Ron,sp, below the unipolar level, and increase the gain (β) are examined. A correlation between the open base blocking behavior (forward blocking) and the current gain (forward active) for 4H-SiC based high-voltage BJTs with lightly doped collector regions is presented and experimental device characteristics are utilized to verify our numerical analysis.

Ti-Ni shape memory alloy is used for bio-medical and industrial fields even if Ni is a substance which has strong allergic nature and carcinogenicity to a human body, then, Ti-Ni alloy system is in a prohibition tendency in the medical field in Europe in recent years. Therefore, Ni-free shape memory alloy is desired in the near future medical field. In this research, we pay our attention to the Ti-Nb alloy which has shape memory as well as superelastic effects. The Ti-Nb fiber was fabricated by using the ark melting and nozzelless rapid solidification method. The fiber samples were used to investigate the following characteristics relating with shape memory effect, that is to say, (1) cross sectional microstructure observation, (2) DSC(phase transformation temperature changes), (3) temperature-shape recovery relationship. Moreover, heat-treated effect on shape recovery phenomena was observed in comparison with the starting bulk material. Finally, the fundamental discussion to correlate the rapid-solidification process condition with the characteristic of Ti-Nb shape memory alloy for bio-medical engineering application was conducted.

An electroactive polymer-ceramic hybrid actuation system (HYBAS) has been developed at NASA Langley Research Center. The system demonstrates significantly-enhanced electromechanical performance by cooperatively utilizing advantages of a combination of electromechanical responses of an electroative polymer (EAP), and an electroactive ceramic single crystal, PZN-PT single crystal. The electroactive elements are driven by a single power source. Recently, a modification of HYBAS has been made to increase the capability of air driving for synthetic jet devices (SJ) used in aerodynamic control technologies. The dependence of the air driving capability of the modified HYBAS on the configuration of the actuating device has been investigated. For this particular application, the modified HYBAS demonstrated a 50% increase in the volume change in the synthetic jet air chamber, as compared with that of the HYBAS without the modification. The theoretical modeling of the performances of the HYBAS is in good agreement with experimental observation. The consistence between the theoretical modeling and experimental test make the design concept an effective route for the development of high performance actuating devices for many applications. The theoretical modeling, fabrication of the HYBAS and the initial experimental results will be presented and discussed.

This project investigates the magnetomechanical sensing behavior of iron-gallium alloys in response to applied bending loads to identify the relevant design criteria for novel magnetostrictive sensor applications. A series of experiments are conducted on the magnetic induction response of cantilevered beams to dynamic bending loads. Analytic models of the system are formulated from both the constitutive magnetostriction equations and a free energy derivation. Both the experimental and analytical results show a change of as much as 0.3 T of induction can be measured in the samples in response to relatively small applied forces, with the output magnetic signal appearing at twice the frequency of beam vibration.

‘Nanoparticle route’ has been utilized to fabricate a ‘new generation’ of switchable mirrors in which the switching properties can be tuned by controlling the nanoparticle size in the underlying Gd layer or Pd over layer. Better color neutrality, faster response time, improved optical contrast, and an enhanced stability has been observed in Gd nanoparticle layer as a direct consequence of the size-induced blue shift in the optical band gap and enhanced surface area. The improvements in optical and electrical switching characteristics are directly related to the large change in H concentration during loading-deloading cycles in Gd nanoparticle layers. It has also been observed that a uniformly deposited Pd nanoparticle over layer also plays a crucial role for improving hydrogen recovery time.