The current work provides an overview of the state-of-the-art in polymer and metal additive manufacturing and provides a progress report on the science and technology behind gradient metal alloys produced through laser deposition. The research discusses a road map for creating gradient metals using additive manufacturing, demonstrates basic science results obtainable through the methodology, shows examples of prototype gradient hardware, and suggests that Compositionally Graded Metals is an emerging field of metallurgy research.

The process of laser-induced brazing constitutes a potential option for connecting several ceramic components (n- and p-type ceramic bars and ceramic substrate) of a thermoelectric generator (TEG) unit. For the construction of the TEGs, TiOx and BxC were used as thermoelectric bars and AlN was used as substrate material. The required process time for joining is well below that of conventional furnace brazing processes and, furthermore, establishes the possibility of using a uniform filler system for all contacting points within the thermoelectric unit. In the work reported here, the application-specific optimization of the laser-joining process is presented as well as the adapted design of the thermoelectric modules. The properties of the produced bonding were characterized by using fatigue strength and microstructural investigations. Furthermore, the operational reliability of the modules was verified.

Nanoindentation experiments have been carried on Arabidopsis thaliana using spherical tungsten tips. Load–displacement plots obtained from experiments suggest that there is an optimum diameter of tip size which can be used to safely penetrate the tip through the cell wall. Based on the exact tip size used in the experiments and the measured load–displacement response, the failure stress was calculated using the experimental data in conjunction with a computational model. The value of failure stress was investigated in hypertonic (plasmolyzed), isotonic, and hypotonic (turgid) samples.

The nature of morphological instabilities in sputtered titanium and niobium nitride thin films grown on amorphous borosilicate glass and single-crystal Si (311) substrates is investigated. All the films were grown by RF magnetron sputtering at constant power and pressure but with thickness varying from 40 to 400 nm and substrate temperatures of 250–300 °C. The surfaces of the thin films can be divided into two areas: one in which the morphology is smooth with densely packed grains and the other in which there are morphological instabilities. A closer observation of the morphological instabilities reveals the coexistence of elastic strain-induced Asaro–Tiller–Grinfeld (ATG) type of instability and dendritic and snowflake structures due to diffusion-limited aggregation (DLA). The ATG instabilities extend over lengths of several tens of micrometers, whereas the DLA structures are confined to lengths of less than 10 μm in the same film. At low thickness (40–100 nm) only the elastic strain-induced instabilities emerge. High growth rates and a thickness of 150 nm are required to cause DLA and coexistence of the two kinds of instabilities. It has also been found that crystallization is not a prerequisite for the formation of dendritic structures.

In this work, we report an experimental technique with nanometer resolution to reveal the microstructural mechanism for electric fatigue in ferroelectrics. The electric field in situ transmission electron microscopy (TEM) was used to directly visualize the domain evolution during the fatigue process in a 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 ceramic. The structure–property relationship was well demonstrated by combining the microscopic observations with corresponding dielectric, piezoelectric, and ferroelectric properties measured on bulk specimens. It was found that the domain switching capability was substantially suppressed after 103 cycles of bipolar fields, leading to an immobilized domain configuration thereafter. Correspondingly, a pronounced degradation of the functionality of the ceramic was manifested, accompanying with a coercive field bumping and polarization current density peak broadening. The reduction of the polarization, dielectric constant, and piezoelectric coefficient were found to follow a power-law relation. Seed inhibition mechanism was suggested to be responsible for the observed fatigue behaviors.

Materials and processes used for medical applications should have specific attributes. For bone repair and reconstruction, controlled open porosity and osteoconductivity are essential apart from mechanical strength and biocompatibility. Several forms of calcium phosphates are often used for these applications, considering properties similar to bone minerals, but often in combinations with other biopolymers. Polymethyl methacrylate (PMMA) and β-tricalcium phosphate (β-TCP) are identified as a suitable combination for the current research, considering specific properties both individually and in combinations, when processed by different means for specific medical applications. Specific responses of the biocomposite material formed by mechanically mixing the two materials in the powder form to selective laser sintering (SLS) under varying conditions are investigated. The results indicate the suitability of the material system for SLS, while controlled porosity and mechanical property combinations are possible by optimizing material composition and process parameters.

Pure single-crystalline bismuth (III) sulfide (Bi2S3) nanowires with lengths of the long and short axes being 1.58–1.75 μm and 40 nm were prepared by a simple surfactant-assisted reflux method in the presence of thioacetamide, which served as both the sulfur source and a “soft template” in the formation of bismuth sulfide nanostructures. The effects of different surfactant, surfactant molecular weight, solvent medium, and sulfur source on the morphology, structure, and phase composition of the as-prepared Bi2S3 products were discussed. The formation of long Bi2S3 nanowires was probably via the mechanism of pyrolysis of bismuth (III) sulfide complexes dimer and continuous growth of crystalline nuclei along rod-shaped micelles originated from “soft-template” of polyethylene glycol (PEG-800). Besides, ultraviolet–visible spectroscopic (UV-Vis), and photoluminescent (PL) Bi2S3 band features indicated that the nanowires have excellent optical properties, in the optical field of potential applications.

Utilization of PbZrxTi1−xO3 (PZT) nanofibers as functional flexible fillers in sensing and energy harvesting applications requires uniform, submicrometer fibers with a large aspect ratio. Previous studies concentrated on the rheological effects on the fiber's diameter and morphology. However, reports on the effect of electric field on these fiber properties are still scarce. In this paper, the effects of surface charge and electric field on the fiber branching are decoupled. We show unequivocally that the external electric field governs this phenomenon. Low viscosity (∼0.12 Pa s) PZT sols yielded a sharp step-like transition from a large to a small diameter regime at electric fields above 0.8 kV/cm. On the other hand, high viscosity sols (∼0.74 Pa s) yielded a transition from a single to a bimodal distribution at the same electric field, due to the branching effect. An ability to obtain a single or bimodal diameter distribution in the range of 100–800 nm was demonstrated.

Oxide composites are a class of materials with potential uses for nuclear, space, and coating applications. Exploiting their promise, however, requires a detailed understanding of their interfacial structure and chemistry. Using analytical microscopy, we have examined the radiation damage behavior at the interface of a model oxide bilayer, SrTiO3/MgO. The as-synthesized SrTiO3 thin film contained both (100) and (110) oriented domains. We found that after ion beam implantation the (110) domains amorphized at a lower radiation fluence than the (100) domains. Further, a persistent crystalline layer of SrTiO3 forms at the interface even as the rest of the SrTiO3 film amorphizes. We hypothesize that the enhanced amorphization susceptibility of the (110) domains is a consequence of how charged irradiation-induced defects at the interfaces interact with the charged planes of the (110) domains. These results demonstrate the complex relationship between interfacial structure and radiation damage evolution at oxide interfaces.

Additive manufacturing (AM) opens new possibilities for functionalization and miniaturization of components in many application fields. Different technologies are known to produce single- or multimaterial components from polymer ceramic or metal. Our new approach – thermoplastic 3D printing – makes it possible to produce metal–ceramic composites. High-filled metal and ceramic suspensions based on thermoplastic binder systems were used as they solidify by cooling. Hence, the portfolio of applicable materials is not limited. Paraffin-based thermoplastic feedstocks with stainless steel powder (17-4PH) and zirconia powder (TZ-3Y-E) were developed with an adapted powder content of 47 vol% steel and 45 vol% zirconia. As compared to other AM technologies, the suspensions were only applied at particular points and areas and not on the whole layer. The printed samples were conventionally debinded and sintered. FESEM studies of the cross-section of the sintered samples showed a homogenous, dense microstructure and a very good connection between the different materials and layers.