Physical characteristics of Cu2Te are poorly investigated due to limited Te sources available and unclear atomic positions of crystal structure. Herein, hexagonal Cu2Te microdisks are successfully prepared via chemical vapor deposition procedure using GaTe as Te source. The epitaxial growth mechanism of the Cu2Te hexagonal structures with the orthorhombic phase is rationalized by proposed layer‐over‐layer growth model. The photoluminescence (PL) spectrum of Cu2Te microdisks shows a new red emission band in addition to usual infrared light emission due to Cu deficiency. Single Cu2Te microdisk operates as an optical microcavity supporting whispering gallery modes for red lasing around 627.5 nm. This Cu2Te microdisk microcavity exhibits a high quality factor of 1568 and a low lasing threshold of 125 kW cm−2 at room temperature. Meanwhile, Cu2Te microdisks have been exhibited as an ideal platform for surface enhanced Raman scattering (SERS) eliminating drawbacks of noble metal substrates with detection limitation to nanomolar level and an enhancement factor of ≈1.95 × 105. Hexagonal Cu2Te microdisks turn out to be an efficient microcavity for red lasing and low‐cost nonmetallic SERS substrates, opening potential applications in photonics and biological detection of aromatic molecules.
In this study, a novel finishing method, entitled clustered magnetorheological finish (CMRF), was proposed to improve surface finish of the silicon nitride ( Si 3 N 4 ) balls with ultra fine precision. The effects of different polishing parameters including rotation speeds, eccentricities and the machining gaps on surface finish of Si 3 N 4 balls were investigated by analyzing the roughness, sphericity and the micro morphology of the machined surface. The experimental results showed that the polishing parameters significantly influenced the surface finish. The best surface finish was obtained by using the polishing parameters: the machining gap of 0.8 mm, the eccentricity of 10 mm and the rotation ratio of 3/4. To further investigate the influence of the polishing parameters on the surface finish, an analytical model was also developed to analyze the kinematics of the ceramic ball during CMRF process. The resulting surface finish, as a function of different polishing parameters employed, was evaluated by analyzing the visualized finishing trace and the distribution of the contact points. The simulative results showed that the distribution and trace of the contact points changed with different polishing parameters, which was in accordance with the results of experiments.
As an important parameter of HIPIMS, pulse frequency has significant influence on the microstructure and mechanical properties of the deposited coatings, especially for the multi-component coatings deposited by using a spliced target with different metal sputtering yields. In this study, a single Al67Ti33-V-Cu spliced target was designed to prepare Al-Ti-V-Cu-N coatings by using high power impulse magnetron sputtering (HIPIMS). The results showed that the peak target current density decreased from 0.75 to 0.24 A•cm −2 as the pulse frequency increased, along with the microstructure transferred from dense structure to coarse column structure. The pulse frequency has significant influence on chemical compositions of Al-Ti-V-Cu-N coatings, especially for Cu content increasing from 6.2 to 11.7 at.%. All the coatings exhibited a single solid-solution phase of Ti-Al-V-N, and the preferred orientation changed from (111) to (220) when the pulse frequency increased above 200 Hz. The decrease in peak target current density at high pulse frequencies resulted in a sharp decrease in the coating hardness from 35.2 to 16.4 GPa, whereas the relaxation of compressive residual stress contributed to an improvement in adhesion strength from 43.3 to 79.6 N.
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