Fabrication and Characterization of Chitosan-Silk Fibroin/Hydroxyapatite Composites via in situ Precipitation for Bone Tissue Engineering

Homogeneous chitosan-silk fibroin/hydroxyapatite （CS-SF/HA） composites were prepared by in situ precipitation method driven by a multiple-order template. The morphology of the composites was investigated by scanning electron microscope （SEM） and transmission electron microscope （TEM）. The compositional analysis was carried out by X-ray diffraction analysis （XRD） and Fourier transformed infrared spectroscopy （FTIR）. The mechanical properties and biocompatibility of the composites were also determined. The results indicated that the inorganic particles of uniform size （50 nm） were well-dispersed among the CS-SF matrices. The compressive modulus of the CS-SF/HA composites was enhanced with the increasing amount of SF. The in vitro results suggested that the MC3T3-E1 osteoblast-like cells on CS-SF/HA composite disks displayed strong bonding and spreading, and the cell proliferation cultured on each composite disk increased throughout the culture period for up to 7 days. Especially, the samples with higher content of SF had much better biological properties. The evidences proved that the CS-SF/HA composites possessed excellent biocompatibility. By using the freeze-drying technique, hierarchical porous scaffolds with pores ranging from 50 μm to 200 μm were obtained. This work presented the advantages of in situ precipitation method to prepare the organic/inorganic composites, and a multiple-order template was introduced in the system to improve the properties of the composites by combining the merits of each organic template.

Highly enhanced thermoelectric and mechanical performance of copper sulfides via natural mineral in-situ phase separation

In situ phase separation precipitates play an important role in enhancing the thermoelectric properties of copper sulfides by suppressing phonon transmission.In this study,Cu1.8S composites were fabricated by melting reactions and spark plasma sintering.The complex structures,namely,micron-PbS,Sb_(2)S_(3),nano-FeS,and multiscale pores,originate from the introduction of FePb_(4)Sb_(6)S_(14)into the Cu1.8S matrix.Using effective element(Fe)doping and multiscale precipitates,the Cu_(1.8)S+0.5 wt%FePb_(4)Sb_(6)S_(14)bulk composite reached a high dimensionless figure of merit(ZT)value of 1.1 at 773 K.Furthermore,the modulus obtained for this sample was approximately 40.27 GPa,which was higher than that of the pristine sample.This study provides a novel strategy for realizing heterovalent doping while forming various precipitates via in situ phase separation by natural minerals,which has been proven to be effective in improving the thermoelectric and mechanical performance of copper sulfides and is worth promoting in other thermoelectric systems.

Microstructure and magnetocaloric properties of partially crystallized Gd_(60)Co_(30)Fe_(10)amorphous alloy prepared by different solidification cooling rates

The Gd_(60)Co_(30)Fe_(10)alloy ribbons with different solidification cooling rates were prepared by modifying the melt-spinning speed of 6.0,12.5,25.0 and 50.0 m·s^(-1)·With cooling rate decreasing,the(Fe,Co)5 Gd and hcp-Gd nanocrystalline was in situ precipitated among the amorphous matrix,which resulted in the composition change of the amorphous phase.Because of the only slight amount of crystalline phase in Gd_(60)Co_(30)Fe_(10)alloys,the magnetic and magnetocaloric properties mainly depend on the amorphous phase,and all the magnetic entropy change versus temperature(|Δ|SMI-T)curves are table-like,indicating the suitability for Ericsson cycle.The magnetic transition temperature of the Gd_(60)Co_(30)Fe_(10)alloy at a melt-spinning speed of 6.0 m·s^(-1) shifted obviously to the lower value with the applied magnetic fields increasing.The peak value of magnetic entropy change(|ΔSMpk|)is 2.19 J·kg^(-1)·K^(-1)at217 K under the magnetic field change of 0-2 T,and the table-like region is 200-230 K.It was proved that the moderate reduction of the cooling rate will not deteriorate the magnetocaloric performance of the Gd_(60)Co_(30)Fe_(10)ribbons seriously.