Consideration of residual stress and geometry during heat treatment to decrease shaft bending

In automotive industry, heat treatment of components is implicitly related to distortion. This phenomenon is particularly obvious in the case of gearbox parts because of their typical geometry and precise requirements. Even if distortion can be anticipated to an extent by experience, it remains complex to comprehend. Scientific literature and industrial experience show that the whole manufacturing process chain has an influence on final heat treatment distortions. This paper presents an approach to estimate the influence of some factors on the distortion, based on the idea of a distortion potential taking into account not only geometry but also the manufacturing process history. Then the idea is developed through experiments on an industrial manufacturing process to understand the impact of residual stress due to machining on shaft bending and teeth distortion during heat treatment. Instead of being measured, residual stress is being neutralized. By comparing lots between each other, connections between gear teeth geometry and manufacturing steps before heat treatment are obtained. As a consequence, geometrical nonconformities roots can be determined more easily thanks to this diagnosis tool, and corrective actions can be applied. Secondly, the influence of product geometry on bending is experimentally considered. Moreover, metallurgical observations enable to explain the influence of workpieces geometry on shaft bending. Thanks to the obtained results, process and product recommendations to decrease shafts bending are proposed.     

MgH2 with different morphologies synthesized by thermal hydrogenolysis method for enhanced hydrogen sorption

Magnesium hydride (MgH₂) with a range of morphologies has been synthesized via a simple hydrogenolysis route involving the decomposition of di-n-butylmagnesium. As the synthetic medium evolved from an inert atmosphere of argon to hydrogen pressure, the morphology shifted from rod like to small particles (25–170 nm). In cyclohexane, a solvent relative inert toward magnesium, smaller particles (15–50 nm) were formed. However in diethyl ether, which is more reactive toward magnesium, flakes organized in large microstructures were obtained. Remarkably in all cases β-MgH₂ was readily obtained with some residual carbon contamination. Hydrogen release from these structures occurred at a relatively low temperature (300 °C), with desorption kinetics faster or equivalent to that of ball milled magnesium. In particular, hydrogen desorption from the smallest particles of MgH₂ produced via the hydrogenolysis of di-n-butylmagnesium under hydrogen pressure or cyclohexane was impressive with the full desorption achieved in less than 10 min without any catalyst. These remarkable hydrogen storage properties are believed to result from an appropriate stabilization of the nanoparticles generated.     

Ba1−xPrxCo1−yFeyO3−δ as cathode materials for low temperature solid oxide fuel cells

Ba_1−xPr_xCo_1−yFe_yO_3−δ (BPCF) perovskite oxides have been synthesized and investigated as cathode materials for low temperature solid oxide fuel cells (LT-SOFCs). Compared with those of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) and Sm_0.5Sr_0.5CoO₃ (SSCo) cathode materials, BPCF has a lower polarization resistance at decreased temperatures. In particular, Ba_0.5Pr_0.5Co_0.8Fe_0.2O_3−δ showed the lowest polarization loss among the different compositions as a cathode material for LT-SOFCs. The area specific resistance (ASR) of Ba_0.5Pr_0.5Co_0.8Fe_0.2O_3−δ as a cathode material is 0.70 and 0.185 Ω cm² at 500 °C and 550 °C, respectively. The maximum power density of the cell BPCF/SDC/Ni-SDC with humidified hydrogen as fuel and air as oxidant reaches 860 mW cm⁻² at 650 °C.     

Modeling of non-equilibrium transport effects in Fully-Depleted GeOI-MOSFETs

Germanium is investigated as basic semiconductor for advanced CMOS nodes. A mobility model at low fields for Ge devices is developed starting from the CVT model, whose parameters are calibrated by comparison with experiments. TCAD simulations of Fully-Depleted (FD) Germanium-On-Insulator (GeOI) n- and p-MOSFETs are presented using both the drift-diffusion and the energy balance transport models. Effects due to non-equilibrium transport in small devices are estimated by varying the energy-relaxation time of the Ge material and by analyzing the phenomenon of velocity overshoot in the channel. It is found that GeOI MOSFETs furnish robust performance improvements when short device lengths are considered due to the influence of non-local effects.     

Design,Properties, and In Vivo Behavior of Super­paramagnetic Persistent Luminescence Nanohybrids

With the fast development of noninvasive diagnosis, the design of multimodal imaging probes has become a promising challenge. If many monofunctional nanocarriers have already proven their efficiency, only few multifunctional nanoprobes have been able to combine the advantages of diverse imaging modalities. An innovative nanoprobe called mesoporous persistent luminescence magnetic nanohybrids (MPNHs) is described that shows both optical and magnetic resonance imaging (MRI) properties intended for in vivo multimodal imaging in small animals. MPNHs are based on the assembly of chromium‐doped zinc gallate oxide and ultrasmall superparamagnetic iron oxide nanoparticles embedded in a mesoporous silica shell. MPNHs combine the optical advantages of persistent luminescence, such as real time imaging with highly sensitive and photostable detection, and MRI negative contrast properties that ensure in vivo imaging with rather high spatial resolution. In addition to their imaging capabilities, these MPNHs can be motioned in vitro with a magnet, which opens multiple perspectives in magnetic vectorization and cell therapy research.     

Peptidic Ligands to Control the Three‐Dimensional Self‐Assembly of Quantum Rods in Aqueous Media

The use of peptidic ligands is validated as a generic chemical platform allowing one to finely control the organization in solid phase of semiconductor nanorods originally dispersed in an aqueous media. An original method to generate, on a macroscopic scale and with the desired geometry, three‐dimensional supracrystals composed of quantum rods is introduced. In a first step, nanorods are transferred in an aqueous phase thanks to the substitution of the original capping layer by peptidic ligands. Infrared and nuclear magnetic resonance spectroscopy data prove that the exchange is complete; fluorescence spectroscopy demonstrates that the emitter optical properties are not significantly altered; electrophoresis and dynamic light scattering experiments assess the good colloidal stability of the resulting aqueous suspension. In a second step, water evaporation in a microstructured environment yields superstructures with a chosen geometry and in which nanorods obey a smectic B arrangement, as shown by electron microscopy. Incidentally, bulk drying in a capillary tube generates a similar local order, as evidenced by small angle X‐ray scattering.     

High Temperature Co-Electrolysis as a Key Technology for CO2 Emission Mitigation – A Model-Based Assessment of CDA and CCU

The mitigation of CO₂ emissions is a major challenge for modern society. While the mitigation of energy-related emissions can be achieved comparatively easy by switching to renewable energy sources, reduction of process-related industrial emissions is considerably more challenging. To reduce industrial CO₂ emissions, two basic routes are available: carbon direct avoidance (CDA) and carbon capture and utilization (CCU). It is shown that in terms of efficiency, CDA is to be favored when applicable. However, for applications where emissions cannot be avoided, CCU can be a viable approach allowing for emission mitigation.     

Development of a Novel High-Performance Thin Layer Chromatography–Based Method for the Simultaneous Quantification of Clinically Relevant Lipids from Cells and Tissue Extracts

Lipids such as cholesterol, triacylglycerols, and fatty acids play important roles in the regulation of cellular metabolism and cellular signaling pathways and, as a consequence, in the development of various diseases. It is therefore important to understand how their metabolism is regulated to better define the components involved in the development of various human diseases. In the present work, we describe the development and validation of a high-performance thin layer chromatography (HPTLC) method allowing the separation and quantification of free cholesterol, cholesteryl esters, nonesterified fatty acids, and triacylglycerols. This method will be of interest as the quantification of these lipids in one single assay is difficult to perform.