Binder jetting has emerged as a compelling approach for processing lunar regolith, as it is well-suited for low-energy environments and requires lower amounts of organic binder, compared to the competitive technologies. This study investigates the feasibility of binder jetting lunar regolith simulants from micrometric particles, focusing on the interplay between sintering conditions, especially atmosphere and temperature, and the resulting microstructural and mechanical properties. Sintering was explored across a range of conditions to elucidate the evolution of porosity and phase composition. Microstructural characterization revealed void morphologies varying due to progressive coalescence, while energy-dispersive x-ray (EDX) and x-ray diffraction (XRD) identified the primary presence of bytownite with other minor oxides, partially subjected to redistribution and reduction as in the case of ilmenite and pyroxene. Mechanical testing revealed the influence of sintering conditions on mechanical properties. While the compression samples, sintered at 1150 degrees C, yielded 228.7 +/- 100.9 MPa of strength, the performance of the samples sintered at 1200 degrees C in air degraded down to 180.6 +/- 53.7 MPa.

Binder jetting of potassium sodium niobate (K0.5Na0.5NbO3) offers potential for generating shape-dependent responses with high industrial output. However, the printing stage relies heavily on the properties of the dry feedstock, making its performance optimization crucial. In this regard, morphological functionalization through granulation can be a useful methodology.This study characterizes two powders in dry and wet states to develop colloidal suspensions for spray drying granulation. Particle size, shape, and ζ-potential are measured to stabilize them in an aqueous slurry. Granule morphology and flowability are assessed and compared with the original feedstock. Disk-shaped specimens are then printed and sintered.Spray drying granulation successfully produces spherical and fine feedstocks compatible with the typical layer thickness (50 μm) of binder jetting. Densified parts displayed significant residual porosity (20–40 %) along the building direction, affecting piezoelectric performance: strain coefficients were reduced, but increased voltage coefficients yielded high figures-of-merit.

The development of interpenetrating phase composites via binder jetting offers a promising route for fabricating architected ceramic-based systems with tailored microstructures and multifunctional properties. This study investigates the influence of multimodal particle size distributions of spheroidized alumina powders on the formation, sintering behaviour, and copper infiltration performance of porous ceramic preforms. Six distinct feedstocks with varying multimodality were characterized in terms of flowability, spreadability, and packing efficiency. The resulting green and sintered preforms were evaluated for porosity morphology and densification kinetics by geometrical measurements and computed tomography, revealing feedstock-dependent voids architectures. These networks control capillary-driven infiltration dynamics and the formation of complex copper-alumina oxide phases, including spinel and delafossite with twinning mechanisms. CALPHAD simulations corroborated the experimental findings, elucidating the thermodynamic pathways of phase evolution under varying oxygen activities. Mechanical testing demonstrated that composites derived from sintered preforms exhibit superior hardness and wear resistance with a reduction of the friction coefficient of similar to 25 % compared to those produced from green preforms, attributed to enhanced alumina content and refined oxide phase distribution. These results underscore the pivotal role of powder multimodality and preform processing in dictating the hierarchical structure and performance of printed ceramic-based composites, offering new insights for the design of advanced materials with tunable properties and complex geometries.

Inkjet printing is a versatile and cheap technique for the fabrication of films, offering unique advantages in terms of scalability, precision, and customization. In recent years, there has been a growing interest in utilizing inkjet printing technology for the deposition of magnetic films with tailored properties. Cobalt ferrite (CoFe2O4) stands out due to its exceptional magnetic properties, including high coercivity, saturation magnetization, and excellent chemical stability. This paper presents a comprehensive study on the inkjet printing of cobalt ferrite magnetic films, focusing on the manufacturing process, especially on the different factors that could lead to stable multilayer depositions to achieve high thicknesses: ink solid loading, drop spacing, substrate temperature, and interlayers drying. Finally, the microstructure of the samples is investigated to identify the occurring defects after sintering between 800 and 1000 °C. The magnetic properties of the films are determined, revealing a maximum coercivity of 1.98 kOe and a magnetic saturation of 78.25 emu cm−3.

In order to further improve the performance of 0.94[(Bi0.5Na0.5)TiO3]-0.06BaTiO(3)/ polyvinylidene fluoride (NBT-BT/PVDF) flexible composite films prepared by the hot-pressing method, the effect of surface modification of the NBT-BT particles on the structure and properties of the films was investigated. Two coupling agents, namely, (3-aminopropyl)triethoxysilane (APTES) and dodecyl triethoxysilane (DDTES) were added to enhance dispersion and interfacial adhesion of the active phase powder with the polymer matrix. The highest amount of the electroactive PVDF ss-phase was formed in APTES-modified samples while in DDTES samples mainly.-phase was formed as shown by Fourier-transform infrared spectroscopy analysis. Differential scanning calorimetry measurements indicated that the addition of filler particles reduced the total crystallinity degree of the PVDF. Dielectric permittivity values as well as dielectric losses decreased for silanized samples due to reduced tension at the interface between particles and polymer. Strong intermolecular interaction between the PVDF chains and the APTES-modified particles led to enhanced breakdown strength of these samples. The highest level of agglomeration in the DDTES-modified samples induced the deterioration of ferroelectric properties. The highest voltage output of .15 V and 225 mu W of power was obtained for the APTES-modified harvester, evidencing their potential for energy harvesting applications. Highlights .Surface of NBT-BT particles was successfully modified by the silanization method. . NBT-BT-PVDF flexible lead-free composite films were prepared by hot pressing. . APTES coupling agent enabled the transformation of PVDF a-phase into electro-active ss. . APTES-modified samples showed the highest breakdown strength. . Notable properties for energy harvesting application found, up to 225 mu W of generated power.

Binder Jetting (BJT) is a non-fusion-based Additive Manufacturing (AM) technique. It consists of the selective deposition of a liquid binder to join powder particles, thereby enabling the creation of near-net-shaped parts.In this study, the main printing parameters correlated to the binder distribution and infiltration (binder saturation, binder set time, drying time, and target bed temperature) were optimised to improve the precision of green parts printed with potassium sodium niobate (KNN) powder. The optimisation procedure was conducted using the Taguchi statistical method. An L9 orthogonal array with four factors of control at three levels each was employed. The analysis showed that the drying time had the greatest influence on the precision of green parts, followed by binder saturation and target bed temperature. Binder set time did not seem to affect the results.Dimensional analysis, microstructural and piezoelectric characterisation of parts densified by pressureless sintering were conducted. The highest average relative density exceeded 80% for the specimens printed with the lower binder saturation. Piezoelectric properties exhibit more complex behaviour. The prolonged infiltration of larger binder volumes is correlated to higher g33, thus FOMh and FOM33, and lower values for ε33T. On the other hand, d33 does not display a specific dependence on density or printing parameters.The results of this study indicate that BJT can be used to fabricate high-precision KNN components with good piezoelectric properties. The optimisation of printing parameters is essential to achieve the desired results.

Interest towards fabrication and post-processing of thermoelectric micro-sized devices has increased in recent years. The coupling of inexpensive deposition technologies and fast laser treatments on “as-deposited” films is an attractive solution for industrial scalability. In this work, we propose an approach never reported before in literature: the utilization of a ns-pulsed active fibre laser to directly densify p-type bismuth telluride-based thick films deposited on silicon. A feasibility study was conducted on the material to determine optimal laser parameters: the treated products were characterized, and it was concluded that a value of laser fluence as low as 4.5 mJ cm−2 is sufficient for densification. The material resulted cracked after the laser treatment, and it was demonstrated by SEM and profilometric analyses that shrinking occurs and sintering necks are formed; further, the arising of second phases after annealing was excluded by means of XRD analysis. Envisioning an industrial large area process with linear diode arrays source, a prediction of the laser power requirements to irradiate 1 mm2 films in selected conditions is presented. More extensive studies will be performed to determine a narrower parameters window and determine a relationship between the film thickness and laser parameters for future applications to as-deposited films.

Received 4 February 2023DOI:https://doi.org/10.1103/PhysRevB.107.099902©2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasStructural propertiesPhysical SystemsAntiferroelectricsFerroelectricsTechniquesX-ray diffractionCondensed Matter, Materials & Applied Physics

The coexistence of several lattice instabilities in Zr-rich Pb(Zr,Ti)O3 leads to the possibility of condensing them successively to trigger a sequence of phase transitions, instead of reaching directly the AFE phase, as in pure PbZrO3. This is especially noticeable in compositions near the antiferroelectric morphotropic phase boundary and the tricritical point around room temperature, as PZT 95/5, where three phases are energetically available. To check the thermal development of these different phases, differential scanning calorimetry, dielectric spectroscopy and Raman scattering experiments were carried on antiferroelectric morphotropic-adjacent ceramics PZT 96/4 and 95/5. They revealed a complicated and hysteretic thermal behavior due to the complex microstructure and the coexistence of regions with different phases within the samples. On heating and cooling the ceramics show two intermediate polar phases between the cubic paraelectric and the low temperature antiferroelectric phase, which are attained under different experimental conditions and specific pre-history. Our results suggest that ceramics with composition near PZT 95/5 are potential materials for novel room temperature device applications. An innovative approach of phase-control is proposed, based on the thermal behaviour of the intermediate polar states observed and using small temperature gradients by appropriate heating-cooling cycles.

Solid-state energy conversion has been established as one of the most promising solutions to address the issues related to conventional energy generation. Thermoelectric materials allow direct energy conversion without moving parts and being deprived of greenhouse gases emission, employing lightweight and quiet devices. Current applications, main thermoelectric material classes, and manufacturing methods are the topics of this work; the discussion revolves around the crucial need for highly performing materials in the mid-temperature range, and around the development of more scalable fabrication technologies. The different manufacturing methods for thermoelectric bulk materials and films are also discussed. Small-scale technologies are generating increasing interest in research; the high potential of aerosol jet printing is highlighted, stressing the many advantages of this technology. A promising approach to scale the production of miniaturized thermoelectric devices that combines high energy ball milling and aerosol jet printing is proposed in the conclusion.

9/65/35 PLZT relaxor was studied under a bias electric field using the acoustic emission method. It was established that the temperature of smeared dielectric constant maximum exhibits the V-shape, lying fully within the ergodic phase, as well as that the threshold electric field is found to be approximately the same as in both PMN-0.24PT and PFN-0.02PT relaxors. A reason of the latter phenomena is discussed from the viewpoint of incorporated ions properties.

9/65/35 PLZT relaxor was studied under a bias electric field using the acoustic emission method. It was established that the temperature of smeared dielectric constant maximum exhibits the V-shape, lying fully within the ergodic phase, as well as that the threshold electric field is found to be approximately the same as in both PMN-0.24PT and PFN-0.02PT relaxors. A reason of the latter phenomena is discussed from the viewpoint of incorporated ions properties.

In the last years, ultrasound energy harvesting has emerged as the most promising technique for wireless power supply of implanted medical devices. These devices require flexible piezoelectric materials with high piezoelectric response in the ultrasonic range. Here we report on bio-compatible NBT-BT/PVDF flexible composites, with variable filler content up to 50 vol%, prepared by a properly designed and optimized process, which incorporates in a complex connectivity pattern fully sintered NBT-BT crystalline powders in a PVDF matrix. The dielectric constant of the flexible composites increased from 10 of pure PVDF polymer to 110 of composite films with 50 vol% NBT-BT content, while the high frequency piezoelectric d33 constant increased from 0.2 pC/N to 33 pC/N for the same samples. The composite with 50 vol% NBT-BT exhibits the figure of merit for the harvested ultrasound energy d33g33 approximately equal to 1.54 x 10-12 m3/J, which is comparable to the figure of merit for the NBT-BT piezoelectric ceramic (1.8 x 10-12 m3/J) and higher than other reported results for random composites. Based on these results, this study provides an easy method to fabricate random flexible piezoelectric composites with enhanced high frequency piezoelectric response and high energy density harvested from an ultrasound source.

Binder jetting is an emerging indirect additive manufacturing technique for ceramic materials, which could be employed to produce application-oriented designed components impossible to achieve with traditional processes and featuring enhanced performances. In our study, niobium-doped lead zirconate titanate (PZT-N) powder, usually processed through the standard press-and-sinter route, was employed as the raw material. First, the powder was characterized in terms of granulometry and flowability to assess its suitability for the printing process. Then, shaping by binder jetting was studied, and the effect of three levels of binder saturation (75–90–105%) on the green bodies was assessed. Finally, the microstructure of the sintered samples was studied using SEM, to investigate the effect of thermal treatments on the grain size distribution and residual porosity (~40%). The piezoelectric properties were measured and compared to those of conventionally processed material. The piezoelectric charge and voltage constants (d33 and g33) were evaluated to determine the possible use of printed parts as porous piezoelectric components to be exploited in hydrophones in the direct mode.

The hexagonal Z-type ferrite Sr3Co2Fe24O41 (SrZ) was first synthesised in 2001 and reported as being a room temperature multiferroic material in 2010, with subsequent investigations into its multiferroic properties, but little into high frequency and microwave properties, and ferromagnetic resonance frequency (FMR), which determines its ability as an electromagnetic (EM) absorber and radar absorbing (RAM) stealth material. It was shown that SrZ existed as a majority or single phase after heating in a narrow temperature range between 1170 and 1190 degrees C using X-ray diffraction (XRD) and measurement of magnetic hysteresis loops, with the sample appearing to be single phase SrZ at 1190 degrees C. We measured complex permeability and permittivity of a single phase polycrystalline ceramic sample of SrZ between 500 MHz and 8 GHz (X-band). The sample had a relatively high permittivity >17 over this entire frequency range, and it showed a strong ferromagnetic resonance (FMR) at 2.3 GHz. This FMR could also be tuned by the effect of an external magnetic field, by moving a simple bar magnet progressively closer to a toroidal sample. This incurred a very slight shift in the peak up to 2.48 GHz at distances of 2.5-10 cm from the sample - a tuning of similar to 5-6% with applied magnetic fields estimated to be 0.11-0.23 T, which is not insignificant. At a close distance of 0.5 mm we got a high degree of tuning of FMR to 3.4 GHz, a large change of 1.07 GHz (= 46% increase) with an applied magnetic field estimated to be 0.40 T. Despite this, the applied field had no significant effect on permittivity over 0.5-8 GHz. Such results have never been reported before, and are significant, as this would enable tuning of the FMR via simple physical/mechanical movement of a bulk alloy magnet, effectively creating a tuneable microwave filter or absorber.

Motivated by the goal of developing ultralow power, smart and multifunctional nano (micro) electronic devices, research has shown unwavering interest in synthesis methods, architectures and interphase connectivity of composites containing magnetostrictive and piezoelectric phases, known as magnetoelectric (ME) materials. Herein we report on CoFe 2 O 4 / 0.92 Bi 0.5 Na 0.5 TiO 3 – 0.08 BaTiO 3 biphasic ME composites, obtained by sol-gel chemistry, by mixing the precursor sols of the two phases into one precursor sol and further transforming it into gel, with the goal of obtaining homogeneous nanocomposites with magnetoelectric properties. The structural properties, the temperature dependance of dielectric properties, the magnetic and magnetoelectric properties of these biphasic mixtures, with various molar ratios CoFe 2 O 4 /BNT–BT 0.08 = 0.5:1, 1:1 and 1.5:1, are investigated. It is observed that the amount of CoFe 2 O 4 and the synthesis in situ of these composites influences their macroscopic properties showing a high difficulty of carrying out an efficient poling resulting in small piezoelectric and magnetoelectric response. It was concluded that the synthesis procedure, the type of architecture and the interphase connectivity are of outmost importance for magnetoelectric properties based on lead-free materials.