This work presents a fabrication process for the conformal growth of vertically aligned BaTiO 3 films on 3-dimensionally patterned silicon waters. The conformal growth is performed through a two-step hydrothermal reaction that enables the direct growth of piezoelectric films on nonplanar architectures while utilizing relatively low synthesis temperatures. Scanning electron microscopy (SEM) is used to show the controllable conversion of TiO 2 nanowires to BaTiO 3 films and x-ray diffraction (XRD) is used to validate the crystal structures. Tested by a refined piezoresponse force microscopy (PFM) method, the conformal films exhibited a piezoelectric coupling coefficient as high as 100 pm/V. With superior piezoelectric properties and the capability to grow on design specific surfaces, the BaTiO 3 conformal films demonstrate high potential for sensors, random access memory, and other micro-electromechanical systems.

Traditionally, sensors to be integrated into a structural component are attached to or mounted on the component after the component has been fabricated. This tends to result in unsecured sensor attachment and/or serious offset between the sensor reading and the actual status of the structure, leading to performance degradation of the host structure. This paper describes a novel extrusion-based additive manufacturing process that has been developed to enable embedment of sensors in ceramic components during the part fabrication. In this process, an aqueous paste of ceramic particles with a very low amount of binder content (< 1 vol%) is extruded through a moving nozzle to build the part layer-by-layer. In the case of sensor embedment, the fabrication process is halted after a certain number of layers have been deposited. The sensors are placed in their predetermined locations, and the remaining layers are deposited until the part fabrication is completed. Because the sensors are embedded during the fabrication process, they are fully integrated with the part and the aforementioned problems of traditional sensor embedment can be eliminated. The sensors used in this study were made of sapphire optical fibers of 125 and 250 micro-meters diameter and can withstand temperatures up to 1600 °C. After the parts were built, two different drying processes (freeze drying and humid drying) were investigated to dry the parts. The dried parts were then sintered to achieve near theoretical density. Scanning electron microscopy was used to observe the embedded sensors and to detect any possible flaws in the part or embedded sensor. Attenuation of the sensors was measured in near-infrared region (1500–1600 nm wavelength) with a tunable laser source. Raman spectroscopy was performed on the samples to measure the residual stresses caused by shrinkage of the part and its slippage on the fibers during sintering and mismatch between the coefficients of thermal expansion of the fiber and host material. Standard test methods were employed to examine the effect of embedded fibers on the strength and hardness of the parts. The result indicated that the sapphire fiber sensors with diameters smaller than 250 micrometers are able to endure the freeform extrusion fabrication process and also the post-processing without compromising the part properties.

This study investigates the evolution of filler particle networks using electrical and rheological property measurements. Polyvinylediene Flouride (PVDF) was used as the matrix thermoplastic polymer which was reinforced with multiwall carbon nanotubes (MWNT) as the filler phase using high shear twin screw extrusion mixing. Electrical conductivity and dielectric constant measurements were done using impedance spectroscopy. Viscosity and storage modulus measurements were performed using a dynamic rheometer. Morphologies of the composites were observed using scanning electron microscopy. The percolation behavior in electrical conductivity was determined to be 1.3 wt% MWNT content in PVDF. This is in contrast to the nanocomposite viscosity percolation threshold which occurred at 1.9 wt%.

In this study, the electrochemical performance of Multi-walled Carbon nanotubes (MWCNT) and polyaniline (PANI) composite (PANI/MWCNT) as supercapacitor electrode material was investigated. An improvement in capacitive performance due to the combination of pseudo capacitance and double layer capacitance was observed. A nano-composite was fabricated by polymerizing pseudo-capacitive polyaniline onto the MWCNT surface through the in-situ chemical polymerization approach. Ammonium persulphate (APS) was used as oxidant to polymerize PANI and HCl was used as dopant. Stainless steel thin foil was used as a current collector as well as a flexible back bone. Graphite conductive ink as binder was used to form a conductive paste. Different composition is varied by varying the PANI concentration from 0.1M, 0.3M, and 0.5M to 1M molar concentration. For material characterization, Scanning Electron Microscopy (SEM) was used to characterize surface morphology of the composite. Cyclic Voltammetry and Electrochemical Impedance Spectrometry in three electrodes set up found that 0.1M PANI/MWCNT yields the best electrochemical performance. Two electrodes setup evaluation on 0.1M PANI/MWCNT reviews promising characteristic suitable for device application. The improved electroactivity of the PANI/MWCNT composite is discussed in detail.

A nanocomposite of Multi-walled Carbon nanotubes (MWCNT) and Polypolypyrrole (PPy) is fabricated and characterized for supercapacitor application. PPy is uniformly coated on the MWCNT surface by mean of in-situ chemical polymerization. MWCNT content is varied to control the thickness of deposited Pyrrole layer. Ferric chloride solution (FeCl 3. 6H 2 O) is used as oxidant to polymerize Pyrrole. Highly conductive nickel foam is used as a current collector for the electrode. Scanning Electron Microscopy (SEM) and Transmission Electron (TE) imaging were used in characterizing composite surface morphology. Electrochemical behavior is studied by mean of Cyclic Voltammetry (CV) and AC Impedance Spectrometry. The effect of varying monomer to MWCNT weight ratio in composite electrical properties was studied in this paper.

Direct write (DW) technology offers a simple method of rapid manufacturing technology for printing electronic, optoelectronic devices, and complex functional devices. The key component of DW technology is the functional inks, which are colloidal suspensions of functional nanoparticles in various solvents such as aerosol or liquid form. With a DW approach, patterns or structures can be easily deposited on flexible substrates such as paper, plastics, and composites, once the solvent volatilizes or is driven off via conventional, laser, or microwave sintering. In this work, polymer-assisted silver (Ag) nanoinks were synthesized by silver salt and polymer in the water solution at relatively high silver precursor concentrations and relatively low concentration of polymers. The silver nanoparticle dispersion and morphology was examined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The results showed that the size of Ag nanoparticles was in nanoscale (∼20 nm) with a narrow distribution of Ag nanoparticle sizes. The viscosity and thermal properties of synthesized silver nanoinks were characterized to determine their applicability and the lifetime. It has been shown that the synthesized silver nanoink can be printed on a flexible plastic substrate or glass substrate. The morphology of the Ag nanoink line printed on the substrate was observed by optical microscopy and scanning electron microscopy (SEM) to understand the relationship between the microstructure and wettability. Uniaxial tension tests of silver nanoink line on a Kapton film indicate that the ink can be stretched ∼20% without failure. The resistance of silver nanoink line printed on the Kapton films was also measured by four probe conductivity measurement system to assess the electrical performance. The resistivity is about 7.5 × 10 −5 Ω-cm by thermal treatment at 250°C for 30 min, which is about half that of bulk silver (1.6 × 10 −6 Ω-cm). Overall, the performance of the synthesized silver nanoink is comparable to a commercially available ink with lower Ag weight content at relatively low cost.

This study seeks to assess the morphology of Nafion nanofiber membranes produced by electrospinning technology. The effects of solution concentration, electrode separation and applied voltage on diameter are investigated. The morphology of Nafion nanofibers measurements for different concentration and operating conditions are acquired by scanning electron microscopy (SEM). The thermal performance is also analyzed by TGA and DSC. Results show that the bead-free nanofibers are electrospun from 0.3 wt%∼0.7 wt% PEO in 5 wt% Nafion solution at the electrode separation of 16 cm ∼ 20 cm, an applied voltage of 20 kV ∼ 50 kV and an electrode bar rotation rate of 0.9 rpm. The mean dimeters of Nafion increase with increasing PEO content and electrode separation. The mean dimeters of Nafion decrease with increasing applied voltage. The formation of continuous smooth nanofiber is related to solution viscosity and electrospinning conditions. In addition, glass transition temperature of the Nafion nanofibers increases with increasing PEO concentration and Nafion nanofibers show a good thermal stability.

Carbon-based flow sensors can be made by embedding carbon nanotubes (CNT) into a polymeric substrate. Specifically, when a conductive aqueous solution flows over the surface of the exposed CNT, a flow-dependent voltage is generated. The carbonaceous flow sensors fabricated in our work were all tested in salt water (5% NaCl). In order to measure the surface coverage of the CNT coated sensors, the electrical resistance across the surface of each sample was measured. Electrical Impedance Spectroscopy (EIS) measurements were also carried out in order to understand the electrical relationship between the sensor and the salt water. In order to study the surface topology and morphology of the flow sensors, scanning electron microscopy (SEM) was used. Voltage measurements of sensors with different levels of resistance were tested in varying fluid velocities. The least resistive sensor showed small, but detectable changes in voltages, while higher resistance sensors showed less response. On the other hand, the average current did not change with varying flow conditions for any of the sensors.

A novel technique to grow carbon nanotubes (CNTs) on the surface of carbon fibers in a controlled fashion using simple lab set up is developed. Growing CNTs on the surface of carbon fibers will eliminate the problem of dispersion of CNTs in polymeric matrices. The employed synthesis technique retains the attractive feature of uniform distribution of the grown CNTs, low temperature of CNTs’ formation, i.e. 550 °C, via cheap and safe synthesis setup and catalysts. A protective thermal shield of thin ceramic layer and subsequently nickel catalytic particles are deposited on the surface of the carbon fiber yarns using magnetron sputtering. A simple tube furnace setup utilizing nitrogen, hydrogen and ethylene (C 2 H 4 ) were used to grow CNTs on the carbon fiber yarns. Scanning electron microscopy revealed a uniform areal growth over the carbon fibers where the catalytic particles had been sputtered. The structure of the grown multiwall carbon nanotubes was characterized with the aid of transmission electron microscopy (TEM). Dynamical mechanical analysis (DMA) was employed to measure the loss and storage moduli of the hybrid composite together with the reference raw carbon fiber composite and the composite for which only ceramic and nickel substrates had been deposited on. The DMA tests were conducted over a frequency range of 1–40 Hz. Although the storage modulus remained almost unchanged over the frequency range for all samples, the loss modulus showed a frequency dependent behavior. The hybrid composite obtained the highest loss modulus among other samples with an average increase of approximately 25% and 55% compared to composites of the raw and ceramic/nickel coated carbon fibers, respectively. This improvement occurred while the average storage modulus of the hybrid composite declined by almost 9% and 15% compared to the composites of reference and ceramic/nickel coated samples, respectively. The ultimate strength and elastic moduli of the samples were measured using standard ASTM tensile test. Results of this study show that while the addition of the ceramic layer protects the fibers from mechanical degradation it abolishes the mechanisms by which the composite dissipates energy. On the other hand, with almost no compromise in weight, the hybrid composites are good potential candidate for damping applications. Furthermore, the addition of CNTs could contribute to improving other mechanical, electrical and thermal properties of the hybrid composite.

High dielectric polymer nanocomposites are promising candidates for energy storage applications. The main criteria of focus are high dielectric breakdown strength, high dielectric constant and low dielectric loss. In this study, we investigate the effect of the addition of TiO 2 particles to PVDF matrix on the dielectric constant, breakdown and energy density of the system. The dispersion of the particles is qualified by scanning electron microscopy (SEM). The morphology of the composites is characterized by polarized light microscopy, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The dielectric properties are measured by a Novocontrol system with an Alpha analyzer. Finally, the breakdown measurements are carried out by a QuadTech hipot tester.

Aqueous magnetorheological (MR) suspensions of composite carbonyl iron particles (CCIPs) were prepared with carbonyl iron particles and an organic reagent coating (N-polyether, N, N, N,-acetyloxy) 2, 6-aminion-1, 3, 4-thiadiazole dimer (EAMTD). The properties of the CCIPs, including morphology, structure, and magnetic behaviors, were characterized using scanning electron microscopy (SEM) and a vibrating sample magnetometer (VSM). The MR properties of the aqueous MR suspensions were analyzed via a strain-controlled parallel disk rheometer equipped with a magnetic field source. The results show that the stability and redispersibility of the aqueous MR suspensions were greatly improved, and the yield stress is influenced by the EAMTD coating layer of the CCIPs.

This paper deals with the study of different structuring methods for high temperature nickel alloys, which are used for compressor and turbine blades in aeroengines. The ideal structured surface combines high oxidation resistance with low drag in a hot gas flow. The effect of drag reduction due to riblet structured surfaces was originally inspired by the shark scales, which have a drag reducing riblet structure. Riblets were successfully produced on a NiCoCrAlY coating by picosecond laser treatment. This method is suitable for larger structures within the range of some tens of micrometers. Furthermore, experiments were performed by depositing different materials through polymer and metal masks via electrodeposition and physical vapor deposition. All fabricated structures were oxidized at 900–1100°C for up to 100 h to simulate the temperature conditions in an aeroengine. The resulting shape of the riblets was characterized using scanning electron microscopy. The most accurate structures were obtained by using photolithography with a subsequent electrodeposition of nickel. This method is suited for single digit micrometer structures. The reduction of the wall shear stress was measured in an oil channel. The riblet structures prior to oxidation showed a reduction of the wall shear stress of up to 4.9%.

In the present work, apart from developing a processing method for multi-scale laminates, characterization efforts are focused on finding longitudinal, transverse and in-plane shear modulus using flexure and in-plane shear testing of unidirectional, [0°] 10 , and multidirectional, [±45°] 2s , laminates. A comparison of the above mentioned macroscale properties is presented for three types of composites, i.e., composites embedded with functionalized nanotubes, un-functionalized or pristine nanotubes and base composite without nanotubes. Classical laminate theory is used to model a representative laminate system. Transverse and longitudinal properties are presented and compared with experimental observations. Transmission and scanning electron microscopy is performed to study the nanotube dispersion and the morphology of fracture surfaces at different length scales.