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Low-cost and efficient multifunctional electrodes play an important part in promoting the practical application of energy conversion and storage. Herein, we report the facile synthesis of N-graphyne, with a novel structure, by one-step ball milling of CaC2 and pyrazine. The accurate doping of nitrogen atoms at the controllable sites of the molecular skeleton of γ-graphyne was achieved using the nitrogenous precursor (pyrazine) as a reactant. Various techniques were adopted for the investigation of the composition, structure, and morphology of the obtained samples. The electrochemical measurements demonstrated that N-graphyne can serve as an excellent electrode material for both electrocatalysis and supercapacitors. As an electrocatalyst, N-graphyne exhibited an overpotential of 280 mV at 100 mA cm-2 and a Tafel slope of 122 mV dec-1 for the oxygen evolution reaction with highly stable morphology and electrocatalytic performance. As a supercapacitor electrode, N-graphyne showed a maximum capacitance of 235 F g-1 at 1 A g-1, and capacitance retention of 87% after 3000 cycles. The superior electrochemical performance of N-graphyne is due to the nitrogen heteroatomic defects, large electrochemical active surface areas and fast electron migration. Our studies provide a facile synthesis of novel N-graphyne with controllable doping sites and promote its potential applications in electrocatalysis and supercapacitors.

A paradigm for material synthesis is demonstrated under the guidance of machine learning as well as the designed wet-lab experiments. This work begins with a series of well-tailored experiments, including the synthesis of C/N-codoped TiO2 nanoparticles with exposed anatase {001} facets and its photocatalytic performance evaluations. In advance of applying the machine learning, the underlying synergistic effects are revealed and expounded in detail purely based on wet-lab experiments. Then, the idea of active learning is adopted by implementing a multi-step workflow to iterate the experiments around preferred synthesis conditions, and unravel the optimum synthesis parameters with the assistance of machine learning. In this work, the prediction models are built on a solid physical and chemical understanding, rather than a ‘black box approach’. To this end, the designed experiments as well as the bootstrapping technique together guarantee a good prediction with less training. The compatibility of the artificial neural network and wet-lab experiment also endows the current strategy with several innate advantages. Moreover, controlled experiments with different starting materials were carried out. The results suggest that, in an effort to ensure more accurate predictions, further restrictions could be placed on data collection prior to the stage of introducing machine learning, and the design of wet-lab experiment plays a crucial role in facilitating machine learning. Lastly, the future prospect for machine learning-assisted material synthesis is briefly discussed based on the current work.

The development of efficient photocatalyst is critical for the practical application of photocatalysis. Herein, Ti3C2 MXenes, a kind of 2D-layered material, is successfully coupled with g-C3N4 sheets under ultrasound irradiation. A series of characterization methods are adopted for the investigation of the obtained samples. The consequences reflect that for the successful formation of 2D/2D schottky junction and a new Ti-N bond between g-C3N4 and Ti3C2. Moreover, photocatalytic measurements demonstrate Ti3C2 MXenes is an efficient activator for g-C3N4 to promote its photocatalytic reactivity. The photocatalytic fixation of N2 tests manifest that the optimized sample of TC-CN-1 (g-C3N4 with the 1 wt% Ti3C2 MXene loading) shows the highest generation yield of NH4+ (601 umol L-1·gcat-1·h-1), which is 3.64-fold higher than that of pristine g-C3N4 (203 umol L-1·gcat-1·h-1). Furthermore, the Ti3C2/g-C3N4 show superior photocatalytic conversion of CO2 to CO or CH4 yields than that of g-C3N4. Besides, the photocatalytic degradation measurements show that only 33.6% of levofloxacin can be decomposed by pristine g-C3N4, while the removal ratio of levofloxacin reaches 72% for g-C3N4 with 1 wt% loading of Ti3C2 MXene under visible light illumination for 30 min. The photocatalytic improvements are confirmed to benefit from the faster separation of photo-generated electrons and holes, higher light response ability, and more active sites. This study demonstrates that Ti3C2/g-C3N4 schottky junction is a promising photocatalyst for the photocatalytic nitrogen fixation, and antibiotics degradation.

A series of γ-graphyne/TiO2 nanotube array heterostructures are first synthesized by a facile and environmental-friendly drop-coating method. The prepared heterostructures is completely investigated by a collection of characterizations. Interestingly, the unique C-O-Ti linkage between γ-graphyne and TiO2 nanotube arrays is verified by both X-ray photoelectron spectroscopy and Fourier transform infrared analysis. After modification of γ-graphyne, the maximum transient photo-current and photo-potential of TiO2 nanotube arrays are improved by 2.2 and 1.3 folds, respectively. Moreover, a maximum of 3.64 and 1.35 folds enhancements are severally verified for the photoelectrocatalytic degradation of levofloxacin and rhodamine B over the heterostructures compared to that of TiO2 nanotube arrays. Furtherly, the heterostructures also show superior photoelectrocatalytic performance on nitrogen fixation and oxygen evolution than TiO2 nanotube arrays. The crystal, morphological, photoelectrochemical, and photoelectrocatalytic stability of the heterostructures are confirmed. This work sheds light on designing γ-graphyne modified composites for photoelectrochemical and photoelectrocatalytic application.

Polyhedral oligomeric silsesquioxane (POSS) was grafted onto carbon fiber surface using poly(amidoamine) (PAMAM) as a novel coupling agent at mild reaction conditions. Firstly, the reinforcement was designed with propagation of PAMAM on the fiber surface by in situ polymerization to improve the surface activities of carbon fiber. Secondly, the POSS further grafted on the fiber could significantly enhance fiber surface energy and wettability, which would greatly increase the interfacial strength of fiber-matrix. The microstructure and mechanical properties of carbon fiber and the resulting composites were investigated. The results indicated that PAMAM and POSS, which could significantly increase the surface roughness and wettability of carbon fiber, were successfully grafted on the fiber surface. Compared with the desized fiber composites, the interlaminar shear strength and the interfacial shear strength of the modified carbon fiber composites increased by 48% and 89%, respectively.

A thin-film piezoelectric-on-silicon (TPoS) structured Lame mode resonator is experimentally reported in this work. The resonator is of a ring shape design and fabricated on the in-house AlN-on-SOI (silicon-on-insulator) platform. The thickness of the AlN layer and the device layer of the SOI is $1 \mu \mathrm{m}$ and $5 \mu \mathrm{m}$, respectively. Experimental results show that the Lame mode can be excited at 60.6MHz, with loaded Q factors of 3617 in air and 4708 in vacuum, demonstrating great potential for the reported resonator for applications such as timing and inertial measurement.

A Wafer Level Chip Scale Packaging (WLCSP) solution with CuPd wire in epoxy mold compound (EMC) as through mold interconnection (TMI) was proposed for the capacitive MEMS such as accelerometer packaging. The size of fabricated WLCSP is 2 mm × 2 mm × 0.83 mm. Silicon cap was designed as 1 mm × 2 mm × 0.1 mm. Device wafer and cap wafer was bonded with wafer level Al/Ge eutectic bonding process. Vertical CuPd wire with diameter of 2 mils embedded in the EMC was used as the TMI. Dummy ASIC die with the size of 1 mm × 1 mm × 0.15 mm can be mounted on the UBM above the RDL of the WLCSP with micro-bumps. MSL1, -40 oC to 125 oC thermal cycling (TC), unbiased highly accelerated stress test (HAST) and 150 oC high temperature storage (HST) testing was conducted on the fabricated dummy test vehicle samples. Testing results show that the fabricated test vehicle can pass the tests without electrical failure. The WLCSP with CuPd wire in EMC as TMI has been successfully demonstrated, which provides the confidence for the next step fabrication of WLCSP with functional accelerometer.

This paper presents the development of Al-Ge eutectic bonding for wafer level chip scale packaging of MEMS sensors. Al is sputtered on the MEMS wafer while an Al/Ti/Ge stack is sputtered on the cap wafer. The bonding temperature and bonding time are 430°C and 30min, respectively. A CMOS compatible Ti/Ni stack was deposited as getter on the cap wafer to maintain the vacuum level inside the cavity. A silicon pirani gauge was used as hermeticity indicator to evaluate the vacuum level of the bonding. The operational dynamic range of the pirani gauge is 100mTorr-76Torr. The experimental results over three wafers show that the achieved vacuum level of the bonding is less than 200mTorr with yield more than 90%, 1000 rapid thermal cycles from -50°C to 150°C with 1 hour for each cycle were conducted, and the related vacuum level were recorded at 150th, 400th, 650th, 800th, 1000th cycle. The normalized vacuum degradation percentage are about 1.6%, 2.05%, 2.25%, 2.54%, 2.78%, 2.82%, respectively. The results also show the vacuum level trends to be stable from the 650th cycle.