Microstructure and properties of WC-12Co composite coatings prepared by laser cladding

A comprehensive study of the phase composition, microstructure evolution, microhardness and wear performance of WC-12 Co composite coatings fabricated by laser cladding using coaxial powder-feed mode was presented. It was shown that a combination of high scan speed and high laser energy density made WC on the edge of WC-12 Co composite powders partially melt in liquid Co and 304 stainless steel matrix, and then new carbides consisting of lamellar WC and herringbone M3 W3 C(M=Fe,Co) were formed. Meanwhile, WC-12 Co composite coatings with no porosity, cracks and drawbacks like decarburization were obtained, showing high densification and good metallurgical bonding with the substrate. Furthermore, a considerably high microhardness of HV0.3 1500-1600, low coefficient of friction of 0.55 and wear rate of(2.15±0.31)×10-7 mm3/(N·m) were achieved owing to the synergistic effect of excellent metallurgical bonding and fine microstructures of composite coating under laser power of 1500 W.

Biological Stimuli-responsive Polymer Systems:Design,Construction and Controlled Self-assembly

Biological stimuli-responsive polymers have increasingly attracted attention in recent years because it can satisfy many requirements of applications related with human body while traditional systems do not meet.Due to the importance of this burgeoning field,great efforts have been devoted and,up to now,polymer chemists have made a remarkable success in this prospective research topic.In this review,we systematically generalize the present state of biological stimuli-responsive polymer systems.We highlight several representative examples to specify the current problems and look ahead a clear sense of direction in this area.

Optimization of Supercritical Fluid Extraction and Rapid Resolution LC-MS/ESI Identification of Chromones from Saposhnikoviae Radix through Orthogonal Array Design

Objective To establish a rapid and effective supercritical fluid extraction（SFE） and rapid resolution liquid chromatography method coupled with diode-array detector（RRLC-DAD） to quantify the chromones in a species. Methods The effects of four parameters including ethanol concentration（50%-90%）, pressure（25-45 MPa）, temperature（40-60 ℃）, and time（30-90 min） on the chromones yields, namely prim-O-glucosylcimifugin, cimifugin, 5-O-methylvisammioside, and sec-O-glucosylhamaudol, were investigated using SFE system with orthogonal array design（OAD）. Furthermore, the extracts were analyzed using rapid resolution liquid chromatography coupled with diode-array detector（RRLC-DAD） system to confirm the results. Results Under the optimized conditions, i.e., 35 MPa of pressure, 60 ℃ of temperature, 70% ethanol, and 60 min of time, the yields of prim-O-glucosylcimifugin, cimifugin, 5-O-methylvisammioside, sec-O-glucosylhamaudol, and total chromones were 3.514, 0.132, 6.242, 0.342, and 10.231 mg/g, respectively. In comparison with ultrasonic assisted extraction（UAE）, SFE was able to yield a 20.7% increase in the total chromones from Saposhnikoviae Radix. Conclusion SFE is an alternative and promising method to extract chromones from this species, and the established RRLC-DAD method could serve as a rapid and effective method for the identification of chromones from Saposhnikoviae Radix.