Transverse thermoelectric generators (TTEG) enable conversion of thermal into electrical energy with perpendicular directions of the applied temperature gradient and the induced thermoelectric voltage. We report on the fabrication of transverse multilayer thermoelectric generators (TMLTEG) based on p-type Ca3Co4O9 (CCO) ceramic tapes and printed silver which were conventionally sintered (CS) in air at 920 degrees C or using pressure-assisted sintering (PAS) at 920 degrees C and 1.5 MPa. The thermoelectric performance of TMLTEGs was evaluated using analytical calculations and simulations. The transverse thermoelectric power factor PFtr and thermoelectric figure-of-merit ZTtr of an artificial layered structure composed of CCO and silver were calculated and simulated as functions of layers tilt angle phi and metal-to-ceramic thickness ratio nu t. TMLTEG devices with various CCO layer thicknesses of 150 & micro;m, 100 & micro;m, or 33 & micro;m were fabricated and cofired at 920 degrees C in air, which exhibit power outputs of 2.3 mW, 3.2 mW, and 4.1 mW at Delta T = 160 K, respectively. TMLTEGs which were cofired using PAS show a higher power density of 16.4 mW/cm(3) at Delta T = 225 K. This enhancement in power (approximate to 80%) is crucial for thermoelectric modules comprising multiple TMLTEG devices. The device measurements were compared with 3D simulations.
Vinylene-linked two-dimensional (2D) conjugated covalent organic frameworks, or 2D poly(arylene vinylene)s (2D PAVs), are promising polymer semiconductors for (opto-)electronics, photocatalysis and electrochemistry. However, conventional solvothermal synthesis often produces 2D PAVs that are poorly crystalline or difficult to access. Here we introduce a Mannich-elimination strategy that converts 8 2D imine-covalent organic frameworks into 11 highly crystalline 2D PAVs though a reversible C=C bond formation mechanism enabling precise crystallization control. This versatile approach affords robust 2D PAVs with honeycomb, square or kagome lattices, specific surface area up to ∼2,000 m2 g−1 and lattice-mismatch tolerance up to 3.5 Two-dimensional poly(arylene vinylene) frameworks are promising polymer semiconductors, yet obtaining highly crystalline materials is a major challenge. Now a series of 11 highly crystalline or single-crystalline 2D poly(arylene vinylene)s have been prepared—from 2D imine-linked covalent organic frameworks through a Mannich-elimination strategy—with diverse lattices, enhanced conjugation and specific surface areas up to 2,000 m2 g−1.
This research systematically evaluates the biodegradation and corrosion behavior of a novel class of composite coatings for bone implants based on chitosan (CS) and two bioactive components (Hydroxyapatite (HA) and Bioactive glass (BG)) in simulated physiological conditions through a comparative approach. Chitosan (CS)based composite coatings (HACS and BGCS) were deposited on Ti6Al4V substrates via electrophoretic deposition (EPD) using unified processing parameters. Initially, the primary materials, relevant suspensions, and final coatings were studied and compared by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Zetasizer, and X-ray diffractometer (XRD) methods. While positive ZPs for both HACS (55.44 f 2.43 mV) and BGCS (35.62 f 2.95 mV) suspensions were aligned with cathodic deposition of coatings, a large difference between recorded current densities during EPD for HACS (6.98 f 0.38 mA center dot cm- 2) and BGCS (56.14 f 3.99 mA center dot cm- 2) were noteworthy. The in-vitro degradation of BGCS and HACS coatings in DMEM solution was assessed not only under a conventional static condition but also within a fluid-dynamic degradation setup. The mass and pH evolution, surface morphology, compositional changes, and release of metallic ions were investigated over the degradation period by gravimetric, optical microscope, SEM, FTIR, and ICP-MS techniques, respectively. While the majority of BGCS degradation (above 3 mg center dot cm- 2) occurred only after 8 h of immersion, a maximum mass loss of about 2 mg center dot cm- 2 happened for HACS coatings on day 10 of the test. Electrochemical corrosion studies of coated samples compared to plain substrates in DMEM solution were carried out using open circuit potential (OCP), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests, and the equivalent circuit was defined to model the experimental data. Interestingly, the corrosion rate of the uncoated sample (9.13E-05 mm center dot year- 1) was about three times and ten times less than HACS and BGCS samples, respectively. It was revealed that the surface pretreatment (polishing) method can have a decisive effect on the corrosion protection behavior of Ti6Al4V samples, coated with CS-based EPD coatings.
Zn-reclaimed WC-Co-Cr powders are strongly agglomerated, requiring additional milling to achieve homogeneous particle size distribution and adequate compaction behavior. As milling time (i.e. milling energy) increases, both powder specific surface area and oxygen content increase. A limiting milling time has been identified, beyond which the finest and more oxidized powders tend to re-agglomerate. Solid state shrinkage during sintering, fully inhibited in un-milled Zn-reclaimed materials, is strongly activated as milling time increases up to the point at which powder re-agglomeration occurs. Activation energies, derived from shrinkage rate values assuming viscous flow-like behavior, confirm a transition between at least two diffusion-controlled regimes around 980-1000 degrees C. At lower temperatures, the "effective" viscosity of compacts during shrinkage decreases with milling time, except for the case of re-agglomeration. Nevertheless, at elevated temperatures, all materials show similar activation energies, suggesting that the lattice defects induced by milling-which promote solid state diffusion-are progressively annihilated through annealing.
Correction for ‘Characterizing nanoplastic suspensions of increasing complexity: inter-laboratory comparison of size measurements using dynamic light scattering’ by Korinna Altmann et al. , Environ. Sci.: Nano , 2025, 12 , 5242–5256, https://doi.org/10.1039/D5EN00645G.
