The economic significance and damage caused by counterfeit products has been evident in industry and society for a long time. In addition to the loss in sales and image damage for the original manufacturers, plagiarism in security-relevant components can also have disastrous consequences for the customer. Manufacturers use technical features to identify their products. The aim of these features is to make them most difficult to copy or to find. None of these features are completely safe from being copied. SMA-components can be treated to be used as a new kind of identification elements for products. In this paper a new method for coding information based on annealing of SMA-wires is presented. The focus is the development of a heat treatment that provides different annealing temperatures in small adjacent areas along the wire. As the annealing temperature has effects on the thermal resistance behavior of the SMA, a combined behavior of different annealing temperatures leads from a curved to a stepped resistance behavior when heated from martensite to austenite.

The functional properties of Nitinol (NiTi) are set by composition, production process, and post-production heat treatment and cold working. Post-production heat treating is dependent on two main parameters: anneal temperature and aging time. Most heat-treating processes performed by researchers generally consist of simple temperature soaks at specified aging times. However, there are drawbacks to this method. More complex heat treatments can result in performance improvements, but they are difficult to implement and often proprietary to manufacturers and therefore not widely used by researchers. By designing a Continuously-Fed heat treatment System (CFS), this work demystifies this complex heat-treatment process by rapidly heat-treating NiTi wire samples across a range of annealing temperatures, soak times, and tensions with little human intervention. This automated process ensures samples are created in a consistent manner and results in a much more consistent end-product when compared to conventional heat-treating methods. Using the CFS, a gamut of samples with varying annealing temperatures (400–550°C) and aging times (1–3 minutes) were created with 0.25mm diameter high-temperature actuator wire initially in the ‘as-drawn’ condition. Differential Scanning Calorimetry (DSC) analysis was performed to determine how the transition temperature(s) change with the various heat-treating parameters and the mechanical properties of the wire were determined utilizing a tensile test. The experimental results demonstrate the benefits of the CFS and are compared to those of a more conventional heat treatment process. Experimental results show that high-performance Nitinol actuator behavior can consistently be achieved using the CFS. Optimal heat treatment processes can be determined quickly experimentally.

Large stable ferroelectricity in hafnium zirconium oxide (HZO) solid solution ultrathin films (including pure zirconia (ZrO 2 ) and hafnia (HfO 2 )) and ZrO 2 /HfO 2 bilayer ultrathin films of thickness ranging from 5–12 nm, prepared by thermal atomic layer deposition or remote plasma atomic layer deposition (RP-ALD) has been demonstrated. Ferroelectric crystallization of the ZrO 2 ultrathin film with high-pressure orthorhombic ( o ) space group Pbc 2 1 could be achieved without post-annealing due to the plasma-induced thermal stresses experienced by the film during the RP-ALD process. In contrast, for the ZrO 2 /HfO 2 bilayer ultrathin film, due to the high crystallization temperature of HfO 2 , post-annealing was needed to achieve sufficient confinement of the sandwiched HfO 2 layer by the ZrO 2 top layer and Si bottom substrate to promote the high-pressure ferroelectric o -phase in HfO 2 . The ferroelectric properties of the HZO ultrathin films prepared by RP-ALD were highly dependent on the Hf-to-Zr ratio — an increasing amount of HfO 2 has been found to be detrimental to the ferroelectricity, mainly due to the high crystallization temperature of HfO 2 . Without post-annealing, the ferroelectricity of the HZO ultrathin films was governed by the relative amounts of the amorphous phase and the ferroelectric o -phase induced by the plasma treatment. While with post-annealing, the ferroelectricity was governed by the relative amounts of the ferroelectric o -phase and the non-ferroelectric monoclinic ( m ) phase.

Heat is often lost unused in industry, commerce and households and is considered a waste product — while there is a lot of energy potential in waste heat. As part of the project “Theasmart”, scientists and companies are exploring just these potentials to find out how the waste product heat can be used for further purposes through the use of an innovative smart materials technology. The goal of the project is the further qualification of shape memory alloys with special focus on thin hysteresis applications for energy harvesting. In certain applications, these metals can be used as a thermal drive, for example for thermal valves or as thermal air flow regulators. Energy efficiency in processes in industrial companies or households could be improved by their use of waste heat. By 2020, the development of thermally driven generators, so-called “energy harvesters”, and the identification of other areas of application is planned. This publication focuses on first steps towards a process tool which can be actuated by waste heat of a thermal annealing sub-process directly, or used as mechanical energy charging device combined with a releasing mechanism.

In this study, we demonstrate the electric and magnetic manipulation of nanoscale M-type Barium Hexaferrite (nBF) in polydimethylsiloxane (PDMS) to engineer a multifunctional nanocomposite with improved dielectric and magnetic properties. First, we synthesized the single crystal nBF via the hydrothermal synthesis route. The hydrothermal temperature, duration, and surfactant conditions were optimized to improve the magnetic properties of the nBFs, with further improvement achieved by post-annealing. The annealed nBFs were aligned dielectrophoretically (DEP) in the polymer matrices by applying an AC electric field. Under the influence of this electric field, nBFs were observed to rotate, align and form chains within the polymer matrix. Optical microscopy (OM) imaging was used to determine the electrical alignment conditions (duration, magnitude, and frequency) and these parameters were used to fabricate the composites. A Teflon setup with Indium Tin Oxide (ITO) coated Polyethylene Terephthalate (PET) was used, where the ITO coatings act as electrodes for the electric field-manipulation. To simultaneously apply the magnetic field, this Teflon setup is placed between two permanent magnets capable of generating a 0.6 T external magnetic field. Along with electric and magnetic fields, concurrent heating was applied to cure the PDMS and freeze the microstructure formed due to electric and magnetic fields. Upon completion of the curing step, parallel chain formation is observed under OM. The X-Ray Diffraction (XRD) results also confirm that the particles are magnetically oriented in the direction of the magnetic field within the chain. Vibrating Sample Magnetometry (VSM) measurements and dielectric spectroscopy are used to characterize the extent of anisotropy and improvement in dielectric and magnetic properties compared to random composites. We find that simultaneous electric and magnetic field alignment improves the dielectric properties by 12% compared to just magnetic alignment. We also observe 19% improved squareness ratio when both fields are applied. The possibility of simultaneous electrical and magnetic alignment of magnetic nanoparticles will open up new doors to manipulate and design particle-modified polymers for various applications.

Recently, carbon fiber-reinforced thermoplastics (CFRTPs) have become popular choices in desktop-based additive manufacturing, but there is limited information on their effective usage. In Fused Deposition Modeling (FDM), a structure is created by layers of extruded beads. The degree of bonding between beads, bead orientation, degree of interlayer bonding, type of infill and the type of material, determines overall mechanical performance. The presence of chopped fibers in thermoplastics increases melt viscosity, changes coefficients of thermal expansion, may have layer adhesion issues, and causes increased wear on nozzles, which makes FDM fabrication of thermoplastic composites somewhat different from neat thermoplastics. In the current work, best practices and the effect of annealing and infill patterns on the mechanical performance of FDM-fabricated composite parts were investigated. Materials included commercially available PLA, CF-PLA, ABS, CF-ABS, PETG, and CF-PETG. Two sets of ASTM D638 tensile and ASTM D790 flexural test specimens with 3 different infill patterns and each material were fabricated, one set annealed, and all tested. Anisotropic behavior was observed as a function of infill pattern. As expected, strength and stiffness were higher when the beads were oriented in the direction of the load, even for neat resins. All fiber-filled tensile results showed an increase in stiffness, but surprisingly, not in strength (likely due to very short fiber lengths). Tests of annealed specimens resulted in clear improvements in tensile strength, tensile stiffness and flexural strength for PLA, CF-PLA, and PETG, CF-PETG but a reduction in flexural stiffness. Also, annealing resulted in mixed improvements for ABS and CF-ABS and is only useful in certain infill patterns. This work also establishes ‘Best Practices’ of FDM-type fabrication of thermoplastic composite structures and documents the minimum critical fiber lengths and fiber fractions of several CF-filled FDM filaments.

Artificial muscle systems have the potential to impact many technologies ranging from advanced prosthesis to miniature robotics. Recently, it has been shown that twisting drawn polymer fibers such as nylon can result in torsional or tensile actuators depending on the final fiber configuration. The actuation phenomenon relies on the anisotropic nature of the fibers moduli and thermal expansion. They have high axial stiffness, low shear stiffness, and expand more radially when heated than axially. If a polymer fiber is twisted but not coiled, these characteristics result in a torsional actuator that will untwist when heated. During the fabrication process, these twisted polymers can be configured helically before annealing. In this configuration, the untwisting that occurs in a straight twisted fiber results in a contraction or extension depending on relative directions of twist and coiling. In these ways, these materials can be used to create both torsional or axial actuators with extremely high specific work capabilities. To date, the focus of research on twisted polymer actuators (TPAs) and twisted-coiled polymer actuators (TCPAs) has been actuator characterization that demonstrates the technologies capabilities. Our work focuses here on applying a 2D analysis of individual layers of the TPAs to predict thermally induced twisting angle and fiber length based on virgin (untwisted) material properties and actuator parameters like fiber length and inserted twist. A multi-axis rheometer with a controlled thermal environmental chamber was used to twist, anneal, and test thermally induced actuation. Experimentally measured angle of untwist and axial contraction after heating are compare the the model. In comparing the experimental results with the two dimensional model, it appears that the difference between the 2D model and experimental results can be explained by the longitudinal stresses that develop inside the material. Future work will aim to include these effects in the model in order to be able to use this model in the design of TPAs.

Effect of annealing time on the micro structure and electromechanical properties PVDF TrFE CTFE terpolymer with 7.8 mol % CTFE was investigated to better understand structure-property relationships in these polymers. DSC results show that the 9 hr-annealing time gives the maximum enthalpy of melting which suggests the crystallinity of the polymer is increased. WAXS results show that annealing increases the proportion of the γ-phase with the ratio of the intensity of γ-phase to α-phase increases with more annealing time. Dielectric spectroscopic study of 9hr-annealed film also suggests that the film shows complete relaxor ferroelectric behavior with a maximum electrostrictive strain up to 4.4 % compared to 4.1 % for the 2.5 hr-annealed film. Finally, annealing time higher than 9 hrs result in a decrease in the electrostrictive strain.

The development of self-powered wireless microelectromechanical (MEMS) sensors hinges on the ability to harvest adequate energy from the environment. When solar energy is not available, mechanical energy from ambient vibrations, which are typically low frequency, is of particular interest. Here, higher power levels were approached by better coupling mechanical energy into the harvester, using improved piezoelectric layers, and efficiently extracting energy through the use of low voltage rectifiers. Most of the available research on piezoelectric energy harvesters reports Pb(Zr,Ti)O 3 (PZT) or AlN thin films on Si substrates, which are well-utilized for microfabrication. However, to be highly reliable under large vibrations and impacts, flexible passive layers such as metal foil with high fracture strength would be more desirable than brittle Si substrates for MEMS energy harvesting. In addition, metallic substrates readily enable tuning the resonant frequency down by adding proof masses. In order to extract the maximum power from such a device, a high level of (001) film orientation enables an increase in the energy harvesting figures of merit due to the coupling of strong piezoelectricity and low dielectric permittivity. Strongly {001} oriented PZT could be deposited by chemical solution deposition or RF magnetron sputtering and ex situ annealing on (100) oriented LaNiO 3 / HfO 2 / Ni foils. The comparatively high thermal expansion coefficient of the Ni facilitates development of a strong out-of-plane polarization. 31 mode cantilever beam energy harvesters were fabricated using strongly {001} textured 1∼3 μm thick PZT films on Ni foils with dielectric permittivity of ∼ 350 and low loss tangent (<2%) at 100 Hz. The resonance frequency of the cantilevers (50∼75 Hz) was tuned by changing the beam size and proof mass. A cantilever beam with 3 μm thickness of PZT film and 0.4 g proof mass exhibited a maximum output power of 64.5 μW under 1 g acceleration vibration with a 100 kΩ load resistance after poling at 50 V (E C ∼ 16 V) for 10 min at room temperature. Under 0.3g acceleration, the average power of the device is 9 μW at a resonance frequency of ∼70 Hz. Excellent agreement between the measured and modeled data was obtained using a linear analytical model for an energy harvesting system, using an Euler-Bernoulli beam model. It was also demonstrated that up to an order of magnitude more power could be harvested by more efficiently utilizing the available strain using a parabolic mode shape for the vibrating structure. Additionally, voltage rectifying electronics in the form of ZnO thin film transistors are deposited directly on the cantilever. This relieves the role of voltage rectification from the interfacing circuitry and provides a technique improved harvesting relative to solid state diode rectification because the turn-on bias can be reduced to zero.

This work deals with the development of a non-contact torque sensor system prototype made from rolled and textured Galfenol, a magnetostrictive alloy of Iron and Gallium. It is already known that this smart material exhibits a linear response to strain in the presence of appropriate biasing magnets. The response of a sensor system built from it follows commercially available strain gages. In this research, the magnetic change in Galfenol due to shear strain experienced by the shaft in torque will be monitored using Hall effect sensors to derive the torque information. Factors affecting the performance of this Wireless Magneto-Elastic Torque Sensor System (WIMETs) such as annealing, rolling process and strain transfer of adhesives shall be explored. The ability to provide real-time measurements with minimal signal conditioning requirements make a well-designed torque system attractive for applications such as condition based maintenance. Factors such as being non-contact and passive to the shaft, compact and easy to install, accurate, sensitive and cost effective are highly desired for any torque measurement system. A rate-of-change torque sensor that demonstrates both a sensitivity and time resolution high enough to not only recognize failing machinery, but to specifically identify the failing part is also a critical feature. These characteristics have been incorporated in the current design of WIMETs. A mathematical model for the magneto-elastic coupling along with simulations from COMSOL shall be presented. Results from static tests for various torques and dynamic tests for various torques at different RPMs will be discussed. It will be shown that the WiMET sensor system setup in a clamshell is reliable and exhibits sensitivity of up to 10mV/in-lb. over a wide range of torque (0–150 lb.-in). Its performance will be compared with a commercial torque sensor and results for detection of eccentric loads on the shaft will also be furnished.

Shape memory alloys (SMA) are well-known for their ability to transform into an imprinted shape by means of thermal activation (pseudoplasticity) or after a mechanical deformation (pseudoelasticity). The thermal effects can be used in a wide range of industrial applications like valves, unlocking devices or comfort applications in the field of automotive mechatronics. While there are many ideas concerning shape memory actuators, only few thoughts have been spent on service applications around these unique actuators. At present, product-related services are usually considered as an add-on to the actual product. But in future, industrialized countries are subject to a structural change toward service societies. For this reason, new concepts and methods which enable the companies to design the potential services in an optimal way are necessary already during the development of a product. This is a paradigm shift from the separated consideration of products and services to a new product understanding consisting of integrated products and services. In the case of shape memory technology, recycling processes present an interesting field for such integrated services. Starting with general ideas towards recycling concepts for and with shape memory components, this paper focuses on refresh-annealing as an example of an interesting recycling process. Finally, the paper is summed up by an outlook on future works on development methods for generic shape memory actuators and their service systems. The aim of this study is to show the possibilities and the importance of services in the field of shape memory technology. As a result, new applications and markets for SMA can be developed.

The effect of adding surface-functionally treated TiO 2 nanoparticles on dielectric properties of PVDF matrix was investigated. Porosity of the nanocomposite films showed to have an impact on dielectric permittivity results. Thermal annealing was proposed as an effective way to overcome the porosity problem. By combination of surface treatment of particles and thermal annealing of nanocomposite films, considerable enhancement in dielectric permittivity of TiO 2 -PVDF nanocomposites was achieved. The experimental results were far higher than theoretical values based on Maxwell model, indicating the presence of an active interphase with high dielectric constant in the system.

The surface-energy-induced selective grain growth with a specific plane can be governed in polycrystalline Fe-Ga-B alloys doped with sulfur. The segregated sulfur during texture annealing played an important role in controlling the surface energy to induce the selective growth of {100} or {110} grains, corresponding to maximum magnetostrictive performance, along <001> orientation with respect to rolling direction. The results show that sulfur diffuses (adsorbs) from bulk interior (sulfur atmosphere) then segregates on the surface. The amount of segregated sulfur increases with an increase of annealing time at the temperature of 1200°C. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) data on the surface as well as selective development of {100}<001> and {110}<001> preferred textures are presented in this work. The XPS fitted peaks of S 2p 3/2 at binding energy of 161.2 and 163.2 eV for annealed Fe-Ga-B doped with sulfur represent the presence of stoichiometric FeS and FeS n (polysulfide), respectively. For all of the sulfur-free Fe-Ga-B sheets annealed in the ampoule with sulfur element, XPS indicated contributions centered at approximately 161.7 (S 2p) that has been assigned to iron sulfide as well. The presence of FeS was clearly confirmed by XRD patterns and XPS fitted peak positions at 161.5 eV (S 2p 3/2 ) and 710.2 eV (Fe 2p 3/2 ). The segregation of sulfur and boron during annealing were also confirmed by AES depth profile results, which exhibited peak concentrations of 10 at.%S and 20 at.%B at the surface, respectively. The peak magnetostriction of 201 ppm was obtained at annealed (Fe 81.3 Ga 18.7 ) 99 B 1 alloy with near {100}<001> orientation under sulfur atmosphere containing the amounts of 6.4 mg S. On the other hand, the texture of sulfur-free Fe-Ga-B alloy was close to {110}<001> after annealing at 1200°C for 6h under flowing argon, corresponding to the magnetostriction of 160 ppm.

The recent discovery of Iron-Gallium alloy (Galfenol) as a “large” magnetostrictive material (as high as 400 ppm) offers a particularly promising transducer material that combines largely desirable mechanical attributes with superior magnetic properties [1]. The high permeability of this material makes it easy to magnetize, however it also causes a relatively low cutoff frequency in dynamic applications, above which eddy currents form and introduce significant power losses. To reduce the eddy current losses, magnetostrictive drivers used in dynamic applications are commonly laminated. A second transducer design consideration is the introduction of an initial alignment of domains inside of the material to maximize the magnetostriction performance. It is common to achieve this by imposing an external compressive prestress to align magnetic moments perpendicular to the direction of actuation. An alternative to the application of an external prestress is to build-in a uniaxial magnetic anisotropy through stress annealing [2]. Stress annealing is a high temperature process with simultaneous application of an external load and subsequent cooling under load in which the magnetic moment alignment developed at temperature is retained upon removal from the stress annealing fixture. The external load needed to build in a useful uniaxial magnetic anisotropy in Galfenol is greater than the buckling load for Galfenol laminae sized for use in high frequency dynamic applications. In this study, prior work on stress annealing of solid rods of single and polycrystalline samples of Galfenol is successfully extended to thin laminae of Galfenol by introducing fixtures to avoid buckling of the laminae under compression during the heat treatment process. Values of the uniaxial anisotropy, cubic anisotropy, saturation magnetic induction, and saturation magnetostriction were obtained from measurements of the magnetization and magnetostriction of stress-annealed Galfenol strip as a function of compressive and tensile stress. These values were derived from fitting magnetization and magnetostriction curves to the energy expression formula [3]. Data are presented that demonstrate the magnetic uniaxial anisotropy developed by stress annealing of laminated Galfenol rods. An annealing temperature of 500 °C and a compressive stress of 200 MPa produced a uniaxial anisotropy of 11.3 kJ/m 3 in this study.