Macro electrochemical milling and its hybrid variants

Macro electromechanical milling has recently attracted increasing attention because numerous large thin-walled structures composed of difficult-to-cut materials are employed in the aerospace field.This paper reviews recent developments in state-of-the-art macro electromechanical milling.The fundamental aspects of material removal mechanisms,such as the generation and breakdown behaviors of passive oxide films of typical difficult-to-cut materials,were discussed.Rapid methods for breaking down passive films are summarized,and simulation methods for the machining process coupling multiple physical fields are introduced.Specific electrochemical milling methods,including fly mode electrochemical milling and sink electrochemical milling,are classified.Efforts made to improve process performance,such as the material removal rate,surface quality,and machining accuracy,are discussed.In addition,the main hybrid electrochemical milling methods,including electrochemical discharge milling,mechano-electrochemical milling,and electrochemical mill grinding,are also presented.

Detector-integrated vertical-cavity surfaceemitting laser with a movable high-contrast grating mirror

In this paper, we present a detector-integrated vertical-cavity surface-emitting laser(VCSEL) with a movable high-contrast grating(HCG) mirror in an n-i-p-i-n manner. The detector-integrated VCSEL with a movable HCG can achieve three functions, including wavelength tuning, power monitoring, and resonant-cavity-enhanced(RCE)photon detection. Currently, the device can achieve a wavelength tuning range of 27 nm at room temperature when the suspended HCG is driven by the reverse-bias voltage. The n-i-p structure located at the upper part of the device can serve as an intra-cavity photodiode to monitor the output power due to the defect absorption. The RCE photon detection function of the detector-integrated VCSEL with a movable HCG is measured, and it has a peak responsivity at about 926 nm. This detector-integrated VCSEL with a movable HCG will be useful for sensing and imaging.

Single-fundamental-mode cryogenic(3.6 K)850-nm oxideconfined VCSEL

Cryogenic oxide-confined vertical-cavity surface-emitting laser(VCSEL)has promising application in cryogenic optical interconnect for cryogenic computing.In this paper,we demonstrate a cryogenic 850-nm oxide-confined VCSEL at around 4 K.The cryogenic VCSEL with an optical oxide aperture of 6.5μm in diameter can operate in single fundamental mode with a side-mode suppression-ratio of 36 dB at 3.6 K,and the fiber-coupled output power reaches 1 mW at 5 mA.The small signal modulation measurements at 298 and 292 K show the fabricated VCSEL has the potential to achieve a high modulation bandwidth at cryogenic temperature.

Simultaneously improved actuated performance and mechanical strength of silicone elastomer by reduced graphene oxide encapsulated silicon dioxide

Herein,graphene oxide(GO)-encapsulated silica(SiO 2)hybrids(GO@SiO 2)were prepared via electrostatic self-assembly of the 3-aminopropyltriethoxysilane(APS)-modified SiO_(2) and GO.The as-prepared GO@SiO 2 was introduced into polydimethyl-siloxane(PDMS)elastomer to simultaneously increase the dielectric constant(k)and mechanical properties of PDMS.Then,the in situ thermal reduction of GO@SiO_(2)/PDMS composites was conducted at 180℃ for 2 h to increase the interfacial polariz-ability of GO@SiO_(2).As a result,the values of k at 1000 Hz are largely improved from 3.2 for PDMS to 13.3 for the reduced GO@SiO_(2)(RGO@SiO_(2))/PDMS elastomer.Meanwhile,the dielectric loss of the composites remains low(<0.2 at 1000 Hz).More importantly,the actuated strain at low electric field(5 kV/mm)obviously increases from 0.3%for pure PDMS to 2.59%for the composites with 60 phr of RGO@SiO_(2),an eightfold increase in the actuated strain.In addition,both the tensile strength and elastic modulus are obviously improved by adding 60 phr of RGO@SiO_(2),indicating a good reinforcing effect of RGO@SiO_(2) on PDMS.Our goal is to develop a simple and effective way to improve the actuated performance and mechanical strength of the PDMS dielectric elastomer for its wider application.

Improving performance of macro electrolyte jet machining of TC4 titanium alloy:Experimental and numerical studies

Electrolyte jet machining(EJM)is a promising method for shaping titanium alloys due to its lack of tool wear,thermal and residual stress,and cracks and burrs.Recently,macro-EJM has attracted increasing attention for its high efficiency in machining wide grooves or planes.However,macro-EJM generates large amounts of electrolytic products,thereby increasing the difficulty of rapid product removal with a standard tool and reducing the surface quality.Therefore,for enhanced product transport,a novel tool with a back inclined end face was proposed for macroEJM of TC4 titanium alloy.For comparison,also proposed were ones with a standard flat end face,a front inclined end face,and both front and back inclined end faces.The flow field distributions of all proposed tools were simulated numerically,and experiments were also conducted to validate the simulation results.The results show that one with a 5°back inclined end face can decrease the lowvelocity flow zone in the machining area and increase the high-velocity flow zone at the back end of tool,thereby promoting rapid product removal.A relatively smooth bright-white groove surface was obtained.The same tool also resulted in the highest machining depth and material removal rate among the tested ones.In addition,rapid product removal was beneficial to the subsequent processing.Because of its rapid product removal,the machining depth and material removal rate during deep groove machining using the tool with a 5°back inclined end face were respectively 7%and14%higher than those produced using a standard one.Moreover,the lowest bottom height difference of 0.027 mm can be obtained when the step-over value was 8.2 mm,and a plane with a depth of0.285 mm and a bottom height difference of 0.03 mm was fabricated using the tool with a 5°back inclined end face.