What determines the critical size for phase separation in LiFePO4 in lithium ion batteries?

LiFePO4 characteristically shows a plateau voltage due to a two-phase (LiFePO4/FePO4) separation during the charge/discharge process in Li ion batteries. In this study, we clearly show that monodispersed nano-sized (about 10 nm) LiFePO4 particles exhibit a complete single-phase reaction without showing any plateau voltage. Since the elastic strain due to lattice mismatch between LiFePO4 and FePO4 would be easily released near the surface, elastic effects are usually expected to weaken, but, in contrast to this expectation, phase separation does not occur experimentally in such small nanoparticles. Consideration on the basis of only static thermodynamics is insufficient to explain why such a single-phase reaction occurs in nano-sized particles. In contrast, the mechanism of the single-phase reaction can be naturally understood, when we consider a kinetics concept based on the preferred wavelength for stable growth of the spinodal wave under such an elastic constraint

Preclinical evaluation of the effect of periodontal regeneration by carbonate apatite in a canine one-wall intrabony defect model

Objective: This study aimed to histologically compare periodontal regeneration of one-wall intrabony defects treated with open flap debridement, β-tricalcium phosphate (β-TCP), and carbonate apatite (CO3Ap) in dogs. Methods: The mandibular third premolars of four beagle dogs were extracted. Twelve weeks after the extraction, a one-wall bone defect of 4 mm × 5 mm (mesio-distal width × depth) was created on the distal side of the mandibular second premolar and mesial side of the fourth premolar. Each defect was randomly allocated to open flap debridement (control group), periodontal regeneration utilizing β-TCP, or CO3Ap. Eight weeks after the surgery, histologic and histometric analyses were performed. Results: No ankylosis, infection, or acute inflammation was observed at any of the experimental sites. Newly formed bone and cementum were observed in all experimental groups. The mineral apposition rate of the alveolar bone crest was higher in the CO3Ap group than in the control and β-TCP groups. The ratio of the new bone area was significantly higher in the CO3Ap group than in the control group (P < 0.05). The bone contact percentage of the residual granules was significantly higher in the CO3Ap group than in the β-TCP group (P < 0.05). Conclusion: Although this study has limitations, the findings revealed the safety and efficacy of CO3Ap for periodontal regeneration in one-wall intrabony defects in dogs, and CO3Ap has a better ability to integrate with bone than β-TCP