Low Temperature and High-Pressure Study of Bending L-Leucinium Hydrogen Maleate Crystals

The polymorphism of molecular crystals is a well-known phenomenon, resulting in modifications of physicochemical properties of solid phases. Low temperatures and high pressures are widely used to find phase transitions and quench new solid forms. In this study, L-Leucinium hydrogen maleate (LLHM), the first molecular crystal that preserves its anomalous plasticity at cryogenic temperatures, is studied at extreme conditions using Raman spectroscopy and optical microscopy. LLHM was cooled down to 11 K without any phase transition, while high pressure impact leads to perceptible changes in crystal structure in the interval of 0.0–1.35 GPa using pentane-isopentane media. Surprisingly, pressure transmitting media (PTM) play a significant role in the behavior of the LLHM system at extreme conditions—we did not find any phase change up to 3.05 GPa using paraffin as PTM. A phase transition of LLHM to amorphous form or solid–solid phase transition(s) that results in crystal fracture is reported at high pressures. LLHM stability at low temperatures suggests an alluring idea to prove LLHM preserves plasticity below 77 K.

Fracture Energy Measurement of Prismatic Plane and Σ2 Boundary in Cemented Carbide

The grain boundary network of WC in WC-Co is important, as cracks often travel intergranularly. This motivates the present work, where we experimentally measure the fracture energy of Σ2 twist grain boundaries between WC crystals using a double cantilever beam opened with a wedge under displacement control in a WC-10wt%Co sample. The fracture energy of this boundary type was compared with cleaving {$$10\overline{1}0$$ 10 1 ¯ 0 } prismatic planes in a WC single crystal. Fracture energies of 7.04 ± 0.36 Jm−2 and 3.57 ± 0.28 Jm−2 were measured for {$$10\overline{1}0$$ 10 1 ¯ 0 } plane and Σ2 twist boundaries, respectively.

Preliminary Exploration on the Preparation of LYSO:Ce Single Crystal Using Verneuil Method

LYSO:Ce single crystal was widely manufactured by Czochralski method. Considering its high cost and the pollution of the crucible, we tried to prepare the crystal by Verneuil method. Unlike Czochralski method, the Verneuil method need the powders with excellent fluidity and high purity. By comparing the powders annealed at 1100°C,1200°C,1300°C,1400°C and 1500°C, we can obtained the needed powders at 1500°C. We also increased the content of silica to satisfy the volatilization in crystal growth process. The single crystal was prepared by changing the growth parameter. We investigated the phase and the microstructure of the powders and observed the microstucture of the crystal fracture. We discussed the improved method of the process of crystal growth.

Failure Analysis of Cathode Materials for Energy Storage Batteries in Overcharge Test

The micro-analysis of energy storage batteries in overcharge test at 20°C temperature was investigated. The results showed as follows: (1) Compared with the normal battery charge at room temperature scanning microscope maps of battery overcharge, the crystal was fractured of the positive surface when the battery was overcharging, and with the increase of experimental time, the crystal fracture is more serious, this is to say that the battery electrolyte decomposition or battery material structure could change by overcharge test. (2) Based on the XRD maps, the characteristic peak position of overcharge test of cathode materials were changed, this showed that the content of cathode material elemental has been destroyed and changed in overcharge test.

Fracture Behavior of High-Frequency Welded Joints of GH4169 Alloy

The CTOD test was performed on Instron8801 servo hydraulic testing machine according to the GB/T 2358-94 standard at room temperature. Scanning microscopy was used for observation of the fracture surface of the test specimens and compared with general TIG welded joint. The results show that the average CTOD for high frequency TIG welded joints is lower than the average CTOD for TIG welded joints because of the decrease of the plastic portion of CTOD. The fracture characteristic of high frequency TIG welded joints is dendritic crystal fracture.