Co evolutions for WC-Co with different Co contents during pretreatment and HFCVD diamond film growth processes

Systematical researches were accomplished on WC-Co with different Co contents(6%,10%and 12%,mass fraction).Based on the XPS and EDX,from orthogonal pretreatment experiments,it is indicated that the acid concentration,the time of the acid pretreatment and the original Co content have significant influences on the Co-removal depth(D).Moreover,the specimen temperature,original Co content and Co-removal depth dependences of the Co evolution in nucleation,heating(in pure H2 atmosphere)and growth experiments were discussed,and mechanisms of Co evolutions were summarized,providing sufficient theoretical bases for the deposition of high-quality diamond films on WC-Co substrates,especially Co-rich WC-Co substrates.It is proven that the Co-rich substrate often presents rapid Co diffusion.The high substrate temperature can promote the Co diffusion in the pretreated substrate,while acts as a Co-etching process for the untreated substrates.It is finally found that the appropriate Co-removal depth for the WC-12%Co substrate is 8-9μm.

Approach for Polishing Diamond Coated Complicated Cutting Tool: Abrasive Flow Machining(AFM)

Lower surface roughness and sharper cutting edge are beneficial for improving the machining quality of the cut?ting tool, while coatings often deteriorate them. Focusing on the diamond coated WC?Co milling cutter, the abrasive flow machining(AFM) is selected for reducing the surface roughness and sharpening the cutting edge. Comparative cutting tests are conducted on di erent types of coated cutters before and after AFM, as well as uncoated WC?Co one, demonstrating that the boron?doped microcrystalline and undoped fine?grained composite diamond coated cutter after the AFM(AFM?BDM?UFGCD) is a good choice for the finish milling of the 6063 Al alloy in the present case, because it shows favorable machining quality close to the uncoated one, but much prolonged tool lifetime. Besides, compared with the micro?sized diamond films, it is much more convenient and e cient to finish the BDM?UFGCD coated cutter covered by nano?sized diamond grains, and resharpen its cutting edge by the AFM, owing to the lower initial surface roughness and hardness. Moreover, the boron incorporation and micro?sized grains in the underly?ing layer can enhance the film?substrate adhesion, avoid the rapid film removal in the machining process, and thus maximize the tool life(1040 m, four times more than the uncoated one). In general, the AFM is firstly proposed and discussed for post?processing the diamond coated complicated cutting tools, which is proved to be feasible for improving the cutting performance

Fabrication and application of nano/microcrystalline composite diamond coated drawing dies using alternative carbon sources

Nano/microcrystalline composite diamond films were deposited on the holes of WC-6%Co drawing dies by a two-step procedure using alternative carbon sources, i.e., methane for the microcrystalline diamond（MCD） layer and acetone for the nanocrystalline diamond（NCD） layer. Moreover, the monolayer methane-MCD and acetone-NCD coated drawing dies were fabricated as comparisons. The adhesion and wear rates of the diamond coated drawing dies were also tested by an inner hole polishing apparatus. Compared with mono-layer diamond coated drawing die, the composite diamond coated one exhibits better comprehensive performance, including higher adhesive strength and better wear resistance than the NCD one, and smoother surface（Ra=65.3 nm） than the MCD one（Ra=95.6 nm） after polishing at the same time. Compared with the NCD coated drawing die, the working lifetime of the composite diamond coated one is increased by nearly 20 times.

Revealing unconventional host-guest complexation at nanostructured interface by surface-enhanced Raman spectroscopy

Interfacial host–guest complexation offers a versatile way to functionalize nanomaterials.However,the complicated interfacial environment and trace amounts of components present at the interface make the study of interfacial complexation very difficult.Herein,taking the advantages of near-single-molecule level sensitivity and molecular fingerprint of surface-enhanced Raman spectroscopy(SERS),we reveal that a cooperative effect between cucurbit[7]uril(CB[7])and methyl viologen(MV^(2+)2^(I−))in aggregating Au NPs originates from the cooperative adsorption of halide counter anions I^(−),MV^(2+),and CB[7]on Au NPs surface.Moreover,similar SERS peak shifts in the control experiments using CB[n]s but with smaller cavity sizes suggested the occurrence of the same guest complexations among CB[5],CB[6],and CB[7]with MV2+.Hence,an unconventional exclusive complexation model is proposed between CB[7]and MV^(2+)on the surface of Au NPs,distinct from the well-known 1:1 inclusion complexation model in aqueous solutions.In summary,new insights into the fundamental understanding of host–guest interactions at nanostructured interfaces were obtained by SERS,which might be useful for applications related to host–guest chemistry in engineered nanomaterials.

Research on the underlying mechanism behind abrasive flow machining on micro-slit structures and simulation of viscoelastic media

In this study,the machining mechanism of abrasive flow machining(AFM)microstructures was analyzed in depth according to the transmission morphology and rheological behaviors of the abrasive media.The transmission morphology demonstrated the excellent combination of the polymer melt with abrasive grains at the interface,indicating that the polymer melt,combined with the uniform distribution of the polymer chains,could exert a harmonious axial force on the abrasive grains.Based on the rheological behavior analysis of the abrasive media,for example,the stress relaxation and moduli of storage and loss,a machining mechanism model was established incorporating the effect of microplastic deformation and continuous viscous flow,which was further verified by the grooves along the flow direction.In addition,the PhanThien-Tanner(PTT)model combined with a wall slipping model was employed to simulate the machining process for the first time here.The value of the simulated pressure(1.3 MPa)was similar to the measured pressure(1.45 MPa),as well as the simulated volumetric rate(0.0114 mL/s)to the measured volumetric rate(0.067 mL/s),which further proved the validity of the simulation results.The flow duration(21 s)derived from a velocity of 1.2 mm/s further confirmed the residual stretched state of the polymer chains,which favored the elasticity of the abrasive media on the grains.Meanwhile,the roughly uniform distribution of the shear rate at the main machining region exhibited the advantages of evenly spread storage and loss moduli,contributing to the even extension of indentation caused by the grains on the target surface,which agreed with the mechanism model and machined surface morphology.