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An in-depth evaluation of the mechanical and metallurgical properties of NiTi instruments is fundamental to assess their performance and to compare recently introduced instrument with widespread ones. According to this, since there are no data on this topic, the aim of the study was to mechanically and metallurgically evaluate an instrument recently introduced into the market (ZenFlex (ZF)), by comparing it with two well-known instruments with similar characteristics: Vortex Blue (VB) and EdgeSequel Sapphire (EES). According to this, 195 instruments were selected: 65 ZF, 65 VB and 65 EES. Each group was divided in subgroups according to the mechanical tests (i.e., cyclic fatigue resistance, torsional resistance and bending ability; (n = 20)) and the metallurgical test (differential scanning calorimetry (n = 5)). A scanning electron microscopy was performed to verify the causes of fracture after mechanical tests (cyclic fatigue and torsional tests). According to results, VB showed the highest flexibility and cyclic fatigue resistance in comparison to the other instruments, with a statistically significant difference (p < 0.05). Regarding torsional resistance, EES showed the lowest value of torque at fracture, with a statistically significant difference, whilst the comparison between ZF and VB showed no statistically significant difference (p > 0.05). DSC analysis pointed out that VB had the highest austenite start and finish temperatures, followed by ESS and then ZF. ESS sample showed the highest martensite start and finish temperatures followed by VB and ZF. Considering the results, it can be concluded that VB showed the best mechanical performance during static tests in comparison to ESS and ZF. This is fundamentally due to the interaction of parameters such as instrument design and heat-treatments that are able to enhance its mechanical performance.

Lithium-ion batteries (LIBs) are employed when high energy and power density are required. However, under electrical, mechanical, or thermal abuse conditions a thermal runaway can occur resulting in an uncontrollable increase in pressure and temperature that can lead to fire and/or explosion, and projection of fragments. In this work, the behavior of LIBs under thermal abuse conditions is analyzed. To this purpose, tests on NCA 18,650 cells are performed in a cone calorimeter by changing the radiative heat flux of the conical heater and the State of Charge (SoC) of the cells from full charge to deep discharge. The dependence of SoC and radiative heat flux on the thermal runaway onset is clearly revealed. In particular, a deep discharge determines an earlier thermal runaway of the cell with respect to those at 50% and 100% of SoC when exposed to high radiative heat flux (50 kW/m2). This is due to a mechanism such as an electrical abuse. Cell components before and after tests are investigated using Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy—Energy Dispersive X-ray Spectroscopy (SEM-EDS) and X-ray Diffraction (XRD) to determine the structural, morphological, and compositional changes. It results that the first reaction (423–443 K) that occurs at the anode involves the decomposition of the electrolyte. This reaction justifies the observed earlier venting and thermal runaway of fully charged cells with respect to half-charged ones due to a greater availability of lithium which allows a faster kinetics of the reaction. In the cathode residues, metallic nickel and NO are found, given by decomposition of metal oxide by the rock-salt phase cathode.

Thermal abuse of lithium-ion batteries (LIBs) leads to the emission of gases, solids, fires and/or explosions. Therefore, it is essential to define the temperatures at which key events occur (i.e., CID activation, venting, and thermal runaway (TR)) and to identify the related emissions for identifying the hazards to which people and especially rescue teams are exposed. For this purpose, thermal abuse tests were performed on commercial lithium nickel cobalt aluminum oxide (NCA) 18650 cells at 50% state of charge in a reactor connected to an FT-IR spectrometer by varying test conditions (feed gas of N2 or air; heating rates of 5 or 10 °C/min until 300 °C). In particular, the concentrations of the gases and the composition of the condensed-phase emissions were estimated. As regards gases, a high concentration (1695 ppmv) of hydrofluoric acid (HF) was measured, while the emissions of condensed matter consisted of organic compounds such as polyethylene oxide and paraffin oil, and inorganic compounds containing Li (0.173 mg/m3) and Al (0.344 mg/m3). The main safety concerns were caused by the temperatures (564 ± 85 °C) reached by the cell during TR, by the HF concentration which exceeded the toxicity limits of 30 ppm, the IDLH defined by the NIOSH, and the diameter of the particles (1.54 ± 0.69 µm) that rose the PM2.5 concentration. These results are also useful for identifying personal protection equipment for rescue teams.

Differential scanning calorimetry (DSC) was used as an efficient and rapid tool in studying the conformational transitions between the folded and unfolded structures of cellulolytic enzymes. The thermal properties of two crude hydrolytic enzyme cocktails containing extracellular cellulases from Trichoderma longibrachiatum DIBAF-10 were analyzed and compared with three commercial cellulase preparations. Differences in the thermal behavior of fungal cellulases in the liquid phase, freeze-dried state, liquid formulations in sodium citrate buffer (pH 4.8), and contact with cellulose, carboxymethyl cellulose, and cellobiose were evaluated. DSC profiles of cellulases from the DIBAF-10 strain provided important thermodynamic information about the thermal stability of the included proteins. Crude enzyme cocktails underwent a reproducible and irreversible exothermic aggregation phenomenon at 52.45 ± 0.90 °C like commercial β-glucosidase. Freeze-dried and resuspended in a sodium citrate buffer, cellulases from T. longibrachiatum showed an endothermic peak dependent on buffer and enzyme concentration. In the enzyme-substrates systems, a shift of the same peak was recorded for all substrates tested. The thermal analysis of freeze-dried cellulase samples in the range of 20–150 °C gave information on the denaturation process. In conclusion, we demonstrated that DSC is a cost-effective tool for obtaining "conformational fingerprinting" of crude fungal cellulase preparations. Graphical abstract