Stefano De La Pierre

This study investigates the soldering process for joining silicon nitride (Si ₃ N ₄ ), a commonly used ceramic, to Invar42, a low thermal expansion alloy. The focus lies on analyzing interfacial reactions and evaluating the bonding performance of the Si ₃ N ₄ —Invar42 joint. Field emission scanning electron microscopy (FESEM) and energy‐dispersive X‐ray spectroscopy (EDS) were employed to examine the microstructure, elemental distribution, and chemical composition of the interfacial region. The results underscore the critical role of interfacial reaction layers in the soldering process. Mechanical testing (single lap offset, SLO, lap shear tests) was conducted to assess the bonding strength and mechanical integrity of the soldered joints. Furthermore, the thermal stability and reliability of these joints were evaluated through SLO tests at 300°C. This study contributes to the advancement of a user‐friendly, pressureless, localized heating and field‐deployable technique for soldering Si ₃ N ₄ to Invar42, thereby facilitating the fabrication of advanced engineering systems in industrial environments.

This study investigates the impact of exposure to aggressive environments, specifically saline conditions per ASTM B117 standard, on the shear strength of adhesive‐bonded joints, crucial for ensuring structural integrity in various industrial applications like automotive, aerospace, and construction. Using an epoxy‐based adhesive to bond AISI304 steel, specimens undergo 14‐ and 28‐day salt spray treatments to simulate harsh working conditions. Torsional shear strength assessment of steel‐to‐steel adhesive joints is conducted using a torsion test methodology, with an analytical approach used to extrapolate adhesive joint shear strength. This research contributes to understanding adhesively bonded joint performance in challenging environmental conditions, and how the shear strength of the bonded joints changes in relatively small amount of time, offering valuable insights for robust structural designs across industrial sectors.

Nowadays adhesive joints are more and more used; therefore, a precise and reliable shear strength measurement of these joints is necessary to design and predict a final components’ performance. This work aimed to assess the shear strength value of adhesively joined ceramics (SiC, Si3N4) and steel in the case of an elasto-plastic (ductile) joining material (Loctite EA 9321 AERO) by an experimental campaign and associated analytical modelling. The joined samples were tested using a single lap offset test in compression (SLO), an asymmetrical 4-point bending test (A4PB, ASTM C1469), and by torsion on fully joined hourglass shaped samples (THG). A simple model based on the elastic-plastic response in shear was proposed to fit the torque-rotation curve measured in the torsion tests. The results showed that, with the adopted test methods and conditions, and by using the model, consistent values of shear strength could be obtained by torsion tests.

The integration of oxygen transport membranes in industrial processes can lead to energy and economic advantages, but proof of concept membrane modules are highly necessary to demonstrate the feasibility of this technology. In this work, we describe the development of a lab-scale module through a comprehensive study that takes into consideration all the relevant technological aspects to achieve a prototype ready to be operated in industrial environment. We employed scalable techniques to manufacture planar La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ membrane components suitable for the application in both 3- and 4-end mode, designed with a geometry that guarantees a failure probability under real operating conditions as low as 2.2 × 10⁻⁶. The asymmetric membranes that act as separation layers showed a permeation of approx. 3 NmL/min/cm² at 900 °C in air/He gradient, with a remarkable stability up to 720 h, and we used permeation results to develop a CFD model that describes the influence of the working conditions on the module performance. The housing of the membrane component is an Inconel 625 case joined to the membrane component by means of a custom-developed glass–ceramic sealant that exhibited a remarkable thermo-chemical compatibility both with metal and ceramic, despite the appearance of chemical strain in LSCF at high temperature. The multi-disciplinary approach followed in this work is suitable to be adapted to other module concepts based on membrane components with different dimensions, layouts or materials.

A summary and update of the research on the design, process, and testing of glass and glass‐ceramic to metal seals for solid oxide cells (SOC) conducted during the last 13 years at the Politecnico di Torino, Italy, within our research group and with several international collaborations, is presented and discussed. Glass and glass‐ceramic‐based materials play a key role in SOC performance and durability as well as in the sealing and joining of metallic interconnects. The sinter‐crystallization method is a powerful technique that is used to obtain dense and reliable glass‐ceramics capable of providing hermetic joining and seals. The issues, learned from our experience, that have an impact on the lifetime behavior of glass and glass‐ceramic to metal seals are briefly reviewed in terms of challenges and working conditions. The mechanical characterization of glass‐to‐metal seal materials has a crucial impact on the overall performance, as the metal–glass interface plays a key role on the final joining strength and reliability. Several glass compositions are presented along with results on their characterization and behavior as joining materials for metallic interconnects, with a focus on their potential use as SOC seals.