Molecular and Crystal Deformation in Poly(aryl ether ether ketone) Fibers

Preparation of hydroxyapatite-titanium particle hierarchical filled polyetheretherketone functional gradient biocomposites

Functional gradient biomaterials have been widely applied in the biomedical field due to their designable structure and performance. In this paper, hydroxyapatite-titanium particles hierarchical filled polyetheretherketone functional gradient biocomposites [(HA-Ti)/PEEK FGBm] were successfully fabricated through combination of a layer-by-layer casting method and hot pressing technology. The microstructure and morphology of the FGBm were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), energy dispersive X-ray analysis spectrometry (EDS) and scanning electron microscopy (SEM). The results of XRD and EDS verified that the components of the FGBm consist of HA, Ti and PEEK. FTIR and SEM studies showed that the existence of TiO2 thin film on the surface of Ti particles was beneficial to improve the wettability of Ti particles to the PEEK matrix, thus increasing the interfacial bonding strength between Ti particles and PEEK matrix. The SEM observation revealed that the size of HA particles in (HA-Ti)/PEEK FGBm was on the nano-scale and that of Ti particles was on the micron-scale. Furthermore, several typical microstructures such as micro-pores, dimple-like, and encapsulated-like morphologies in (HA-Ti)/PEEK FGBm were observed by SEM. With the rise of Ti and HA particle content in PEEK matrix, the distribution of them in PEEK matrix becomes more and more inhomogeneous and they tend to agglomerate.

In situ study on atomic mechanism of melting and freezing of single bismuth nanoparticles

Experimental study of the atomic mechanism in melting and freezing processes remains a formidable challenge. We report herein on a unique material system that allows for in situ growth of bismuth nanoparticles from the precursor compound SrBi₂Ta₂O₉ under an electron beam within a high-resolution transmission electron microscope (HRTEM). Simultaneously, the melting and freezing processes within the nanoparticles are triggered and imaged in real time by the HRTEM. The images show atomic-scale evidence for point defect induced melting, and a freezing mechanism mediated by crystallization of an intermediate ordered liquid. During the melting and freezing, the formation of nucleation precursors, nucleation and growth, and the relaxation of the system, are directly observed. Based on these observations, an interaction-relaxation model is developed towards understanding the microscopic mechanism of the phase transitions, highlighting the importance of cooperative multiscale processes.

Deformation-induced structure evolution of poly(butylene terephthalate)/poly(carbonate) blends during uniaxial stretching

Phase separation occurs during deformation for all the PBT/PC samples. At large strains, microfibril slippage plays a leading role in the macroscopic strain.