In this work, (Ba_0.75Sr_0.25) (Ti_0.95Co_0.05) O₃ perovskite nanostructured material, denoted subsequently as Co-doped BaSrTiO₃, was synthesized in a one-step process in hydrothermal conditions. The obtained powder was heat-treated at 800 °C and 1000 °C, respectively, in order to study nanostructured powder behavior during thermal treatment. The Co-doped BaSrTiO₃ powder was pressed into pellets of 5.08 cm (2 inches) then used for thin film deposition onto commercial Al₂O₃ substrates by RF sputtering method. The microstructural, thermal, and gas sensing properties were investigated. The electrical and thermodynamic characterization allowed the evaluation of thermodynamic stability and the correlation of structural features with the sensing properties revealed under real operating conditions. The sensing behavior with respect to the temperature range between 23 and 400 °C, for a fixed CO₂ concentration of 3000 ppm, highlighted specific differences between Co-doped BaSrTiO₃ treated at 800 °C compared to that treated at 1000 °C. The influence of the relative humidity level on the CO₂ concentrations and the other potential interfering gases was also analyzed. Two possible mechanisms for CO₂ interaction were then proposed. The simple and low-cost technology, together with the high sensitivity when operating at room temperature corresponding to low power consumption, suggests that Co-doped BaSrTiO₃ has a good potential for use in developing portable CO₂ detectors.

Microencapsulation of sodium nitrate (NaNO₃) as phase change material for high temperature thermal energy storage aims to reduce costs related to metal corrosion in storage tanks. The goal of this work was to test in a prototype thermal energy storage tank (16.7 L internal volume) the thermal properties of NaNO₃ microencapsulated in zinc oxide shells, and estimate the potential of NaNO₃–ZnO microcapsules for thermal storage applications. A fast and scalable microencapsulation procedure was developed, a flow calorimetry method was adapted, and a template document created to perform tank thermal transfer simulation by the finite element method (FEM) was set in Microsoft Excel. Differential scanning calorimetry (DSC) and transient plane source (TPS) methods were used to measure, in small samples, the temperature dependency of melting/solidification heat, specific heat, and thermal conductivity of the NaNO₃–ZnO microcapsules. Scanning electron microscopy (SEM) and chemical analysis demonstrated the stability of microcapsules over multiple tank charge–discharge cycles. The energy stored as latent heat is available for a temperature interval from 303 to 285 °C, corresponding to onset–offset for NaNO₃ solidification. Charge–self-discharge experiments on the pilot tank showed that the amount of thermal energy stored in this interval largely corresponds to the NaNO₃ content of the microcapsules; the high temperature energy density of microcapsules is estimated in the range from 145 to 179 MJ/m³. Comparison between real tank experiments and FEM simulations demonstrated that DSC and TPS laboratory measurements on microcapsule thermal properties may reliably be used to design applications for thermal energy storage.

Barium titanate (BT) and barium strontium titanate (BST) are one of the most studied ferroelectric materials with excellent piezoelectric properties, which can be used to stimulate bone formation by applying an electrical field. It is known that this ceramic is biocompatible and can be used for medical applications. New hybrid materials based on BT and collagen and BST and collagen, with potential applications in bone reconstruction, are presented, emphasizing the potential of fabricating 3D structures by integrating hydrothermal synthesis with additive manufacturing. Designing such structures may take advantage of rheological characterization at single-molecule level for some elastic biopolymers like titin and collagen and their molecular dissection into structural motifs that independently contribute to the protein viscoelasticity. Atomic force spectroscopy measurements on synthetic polypeptides showed that a polypeptide chain containing Ig domain modules is protected against rupture at high stretch by Ig domain unfolding, an important mechanism for stress relaxation in titin molecules. This property may be exploited to enhance the tensile strength of a 3D structure by adding specific synthetic polypeptides to the composition of the printing paste.