Graphene/chitosan/Ag+- doped hydroxyapatite triple composite fiber coatings on new generation hybrid titanium composite by electrospinning

In this work, The hybrid hydroxyapatite (HaP), chitosan (CH) and graphene nanosheets (GNS) mixtures were applied by electrospinning on the surface of GNS and Si3N4 (SN) binary powder reinforced hybrid titanium (Ti) metal composites surface to improve composite biosurface functionallity. The surfaces of coated materials were characterized and antibacterial tests were carried on for their suitability in the industry by performing artificial body fluid tests. The hybrid nano fiber coatings formed a homogeneous structure on the composite. According to bioactivity tests and microstructure analysis, it was seen that HaP, which has the best results in the change of pH (pH= 11.80) values. The lowest mass change (0.0005 g) was observed on the 10th day of pure titanium. The highest mass change (0.0210 g) was obtained as on the HaP coated hybrid titanium composite. According to the antibacterial test result the hybrid nanofiber containing silver (Ag+) doped HaP on Ti composites showed the best antibacterial property aganist the E.coli. The fabricated electrospin coated hybrid composites can be a potantial candidate for dental, orthopedic implant applications and tissue engineering.

Paraffin/polyacrylonitrile hybrid nanofibers for thermal hysteresis enhancement of paraffin actuators

Fast and facile one-step preparation of paraffin/polyacrylonitrile hybrid nanofibers via single needle (uniaxial) electrospinning system was studied. As-spun paraffin/polyacrylonitrile nanofibers were used for thermal hysteresis enhancement of paraffin actuators. Solid paraffin with the melting point of 32, 58, 89 and 114°C were employed for the preparation of the paraffin/polyacrylonitrile nanofibers. Differential scanning calorimetry measurements revealed that the melting point of the paraffin in paraffin/polyacrylonitrile hybrid nanofiber was clearly detectable and the melting entalpy coming from the paraffin part gradually increased from 9.6 to 101.5 J/g with the increase in the melting points of the added same amount of paraffins in paraffin/polyacrylonitrile nanofibers. When both calorimetric and weight loss measurements were considered, the paraffin which has the melting point of 32°C was found to be suitable to produce hybrid nanofibers paraffin actuator. Therefore, this hybrid nanofiber was selected for the application in paraffin actuators for e-vehicle battery cooling systems where the battery temperature must be kept between 15 and 35°C. Paraffin compound of the paraffin actuators was prepared with a mixture of pure paraffin and paraffin/polyacrylonitrile nanofiber with the wt.% of 2.5, 5, 7.5 and 10. In the hysteresis measurements, the hysteresis value at 3 mm stroke was successfully enhanced as 1.7, 3.4, 11.9 and 15.3% sequentially for the samples produced with the above ratios. Beyond hysteresis enhancement, the phenomena of thermal percolation threshold effect and thermal conductivity contrast ratio effect in nano scale were emprically exposed on opening and closing behavior of the paraffin actuator.