ABSTRACT
In order to increase the performance of tool or mold/die, there are a lot of micro features on the surface to provide special functions, such as anti-adhesion or lubrication. The MPB (Micro Particle Bombarding) process provides a powerful technology to enhance the surface quality without damaging the micro features. The effect of MPB parameters were investigated by bombarding the surface with extremely small particles (20~200 µm in diameter) at a high velocity and pressure to obtain a better surface integrity. -The MPB has two functions, one is micro blasting for cleaning purposes and the other is micro shot peening for surface strengthening. The regression relationship between particle bombarding time and micro hardness is established to predict the surface hardness after MPB process. The experimental results reveal that the surface hardness of cermet is increased 14~66% (HV2167~HV3163) by micro particle bombarding. The micro shot peening provides a good surface integrity due to thebetter surface roughness of 0.1 µmRa and higher compress residual stress of -1393.7 MPa, which is up to 26% enhancement compared with the base material cermet. After micro shot peening, the surface hardness of the SKD11 tool steel increased from HV 686 to HV 739~985. The surface roughness of SKD 11 after micro shot peening was 0.31-0.48 µmRa, while the surface roughness after micro blasting was 0.77-1.15 µmRa. It is useful to predict the residual stress for micro blasting by surface roughness, and to estimate the residual stress after micro shot peening by surface hardness by applying the MPB process in industry in the case of SKD 11 tool steel.
ABSTRACT
This study demonstrates a novel package design to store colloidal quantum dots in liquid format and integrate them with a standard LED. The high efficiency and high quality color performance at a neutral white correlated color temperature is demonstrated. The experimental results indicate that the liquid-type quantum dot white light-emitting diode (LQD WLED) is highly efficient and reliable. The luminous efficiency and color rendering index (CRI) of the LQD WLED can reach 271 lm Wop(-1) and 95, respectively. Moreover, a glass box is employed to prevent humidity and oxygen erosion. With this encapsulation design, our quantum dot box can survive over 1000 hours of storage time.
ABSTRACT
Atomically thin heterostructures of transition-metal dichalcogenides (TMDs) with various geometrical and energy band alignments are the key materials for next generation flexible nanoelectronics. The individual TMD monolayers can be adjoined laterally to construct in-plane heterostructures, which are difficult to reach with the laborious pick-up-and-transfer method of the exfoliated flakes. The ability to produce copious amounts of high quality layered heterostructures on diverse surfaces is highly desirable but it has remained a challenging issue. Here, we have achieved a direct synthesis of lateral heterostructures of monolayer TMDs: MoS(2)-WS(2) and MoSe(2)-WSe(2). The synthesis was performed using ambient-pressure chemical vapor deposition (CVD) with aromatic molecules as seeding promoters. We discuss possible growth behaviors, and we examine the symmetry and the interface of these heterostructures using second-harmonic generation and atomic-resolution scanning TEM. We found that the one-dimensinal (1D) interface of the lateral heterostructures picks the zigzag direction of the lattice instead of the armchair direction. Our method offers a controllable synthesis to obtain high-quality in-plane heterostructures of TMD atomic layers with 1D interface geometry.
