Composition-dependent phase segregation and cocrystallization behaviors of blends of metallocene-catalyzed octene-LLDPE(D) and LDPE(H)

The morphological structures of slowly cooled blends of deuterated metallocene-catalyzed octene linear low-density polyethylene (O-mLLDPE(D)), and hydrogenous low-density polyethylene (LDPE(H)) were studied by using small angle neutron scattering in combination with complementary small angle X-ray scattering and differential scanning calorimetry. The phase segregation, which is more nanoscale than macroscale, and cocrystallization behaviors were found to vary with the blend composition. Phase-segregated O-mLLDPE(D) lamellae are predominantly formed in LDPE(H)-rich compositions. In contrast, few segregated O-mLLDPE(D) lamellae form in O-mLLDPE(D)-rich compositions, and instead O-mLLDPE(D) lamellar stacks are extensively cocrystallized with LDPE(H) mostly in the interlamellar amorphous region.     

Abnormal Grain Growth of Alumina

Abnormal grain growth (AGG) is not one of the intrinsic properties of alumina but rather is an extrinsic property that is controlled by certain impurities that are introduced during powder synthesis, processing, or sintering. When small amounts of glass-forming impurities are introduced, some portion beyond their solubility limits will accumulate at grain boundaries at the final stage of densification, form thin intergranular glass films of thermodynamically stable thickness, and induce the sudden appearance of abnormal grains by increasing the rate of grain-boundary migration abruptly. The proposition has been tested experimentally with small, but varying, amounts of silica in ultrapure alumina (99.999%) that has been sintered in a contamination-free condition. Average grain sizes for the appearance of AGG are inversely related to the doping concentration of silica. The thickness of intergranular silicate glass films at the onset of AGG in alumina is constant and estimated to be }3.7 nm.     

Self‐Powered,Room‐Temperature Electronic Nose Based on Triboelectrification and Heterogeneous Catalytic Reaction

Herein, a self‐powered electronic nose strategy with highly selective gas detection is described. The electronic nose is a two‐dimensional microarray based on the triboelectrification between ZnO nanowires and the dielectric layers, and the heterogeneous catalytic reaction occurring on the nanowires and on the NiO nanoparticles. These electronic noses show the ability to distinguish between four volatile organic compound (VOC) gases (methanol, ethanol, acetone, and toluene) with a detection limit of 0.1% at room temperature using no external power source.     

An Atomistic Tomographic Study of Oxygen and Hydrogen Atoms and their Molecules in CVD Grown Graphene

The properties and growth processes of graphene are greatly influenced by the elemental distributions of impurity atoms and their functional groups within or on the hexagonal carbon lattice. Oxygen and hydrogen atoms and their functional molecules (OH, CO, and CO₂) positions' and chemical identities are tomographically mapped in three dimensions in a graphene monolayer film grown on a copper substrate, at the atomic part‐per‐million (atomic ppm) detection level, employing laser assisted atom‐probe tomography. The atomistic plan and cross‐sectional views of graphene indicate that oxygen, hydrogen, and their co‐functionalities, OH, CO, and CO₂, which are locally clustered under or within the graphene lattice. The experimental 3D atomistic portrait of the chemistry is combined with computational density‐functional theory (DFT) calculations to enhance the understanding of the surface state of graphene, the positions of the chemical functional groups, their interactions with the underlying Cu substrate, and their influences on the growth of graphene.     

Three‐Dimensional Branched Nanowire Heterostructures as Efficient Light‐Extraction Layer in Light‐Emitting Diodes

A facile method to fabricate three‐dimensional branched ZnO/MgO nanowire heterostructures and their application as the efficient light‐extraction layer in light‐emitting diodes are reported. The branched MgO nanowires are produced on the hydrothermally‐grown ZnO nanowires with a small tapering angle towards the tip (≈6°), by the oblique angle flux incidence of MgO. The structural evolution during the growth verifies the formation of the MgO nanoscale islands with strong (111) preferred orientation on very thin (5–7 nm) MgO (110) layer. The MgO nanobranches, then grown on the islands, are polycrystalline consisting of many grains oriented in specific directions of <200> and <220>, supported by the nucleation theory. The LEDs with the branched ZnO/MgO nanowire arrays show a remarkable enhancement in the light output power by 21% compared with that of LEDs with pristine ZnO nanowires. Theoretical calculations using a finite‐difference time‐domain method reveal that the nanostructure is very effective in breaking the wave‐guiding mode inside the ZnO nanowires, extracting more light especially in radial direction through the MgO nanobranches.     

Synthesis and electrochemical characterization of LixCoO2 for lithium-ion batteries

The cathode material Li_xCoO₂ was synthesized by preliminary mechanochemical activation of precursor oxide mixture powders, followed by thermal treatment at 800 °C for 5 h. The effects of the molar ratio of Li/Co on the electrochemical behavior were examined. The Li_xCoO₂ at Li/Co=1.07 showed superior cycling stability to the Li/Co=1.0 sample. This is attributed to the disappearance of a phase transition related to monoclinic distortion and the relatively lowered transport resistance in Li/Co=1.07 sample.