Superhydrophobic fluoride conversion coating on bioresorbable magnesium alloy——fabrication,characterization,degradation and cytocompatibility with BMSCs

A micro-nano structure CaF_(2)chemical conversion layer was prepared on fluoride-treated AZ31 alloy,then the composite fluoride conversion film(CaF_(2)/MgF_(2))was modified by stearic acid(SA)and fabricated a superhydrophobic surface.The fluoride-treated magnesium,fluoride conversion film and superhydrophobic coating were characterized by SEM,EDS,XRD and FTIR.The properties of coatings1 adhesion and corrosion resistance were evaluated via tape test and electrochemical measurement.The cytocompatibility of the MgF_(2),CaF_(2)and superhydrophobic CaF_(2)/SA surface was investigated with bone marrow-derived mesenchymal stem cells(BMSCs)by direct culture for 24 h.The results showed that the superhydrophobic fluoride conversion coating composed of inner MgF_(2)layer and the outer CaF_(2)/SA composite layer had an average water contact angle of 152°.SA infiltrated into the micro-nano structure CaF_(2)layer and formed a strong adhesion with CaF_(2)layer.Furthermore,the super-hydrophobic coating showed higher barrier properties and corrosion resistance compared with the fluoride conversion film and fluoride-treated AZ31 alloy.The BMSC adhesion test results demonstrated MgF_(2)CaF_(2)and CaF_(2)/SA coatings were all nontoxic to BMSC.At the condition of in direct contact with cells,MgF_(2)showed higher cell density and enhanced the BMSCs proliferation,while CaF_(2)and CaF_(2)/SA coating showed no statistically difference in cell density compared with glass reference but the CaF_(2)and CaF_(2)/SA coating were not conducive to BMSCs adhesion.

Synthesis of tungsten ditelluride thin films and highly crystalline nanobelts from pre-deposited reactants

Tungsten ditelluride(WTe_(2))is a layered transition metal dichalcogenide(TMD)that has attracted increasing research inter-est in recent years.WTe_(2) has demonstrated large non-saturating magnetoresistance,potential for spintronic applications and promise as a type-II Weyl semimetal.The majority of works on WTe_(2) have relied on mechanically exfoliated flakes from chemical vapour transport(CVT)-grown crystals for their investigations.While producing high-quality samples,this method is hindered by several disadvantages including long synthesis time,high-temperature annealing and an inherent lack of scalability.In this work,a synthesis method is demonstrated that allows the production of large-area polycrystalline films of WTe_(2).This is achieved by the reaction of pre-deposited films of W and Te at a relatively low temperature of 550℃.Sputter X-ray photoelectron spectroscopy reveals the rapid but self-limiting nature of the oxidation of these WTe_(2) films in ambient conditions.The WTe_(2) films are composed of areas of micrometre-sized nanobelts that can be isolated and offer potential as an alternative to CVT-grown samples.These nanobelts are highly crystalline with low defect densities indicated by transmission electron microscopy and show promising initial electrical results.