A novel technique of laser measurement for the surface roughness

This paper describes a non-contact system for the surface roughness measurement without damage. It is suitable for various materials.     

FOURIER TRANSFORM INFRARED STUDIES OF POLY (ETHYLENE TEREPHTHALATE) FILM IN THE GLASS TRANSITION REGION

Three specimens from a solution-cast poly (ethylene terephthalate) (PET) film, one being liquid-N_2 quenched from 92℃(Q), one being slowly cooled from 92℃(SC) and one being quenched and sub-T_g annealed at 67℃(AN), have been studied by specimen difference spectra Q-SC and AN-Q and temperature difference spectra T-70 and T_2-T_1 for every 2℃steps on heating to 90℃at 2℃/min. SC and AN showed more gauche conformers than Q. That means that the PET chain has more trans conformers at higher temperatures and some of these are frozen during quenching through T_g. A band at 1340 cm~(-1) has been found to be complex containing overlapping bands reflecting trans in crystalline regions and trans in amorphous regions. The temperature difference spectra on heating through T_g showed that the spectral changes in Q are gradual while a rather abrupt change occurs in AN at 80—82℃for the bands at 1340, 1042 and 1020 cm~(-1). No new conformational structure or new vibrational mode is involved. A kind of locking mechanism is suggested which hinders the molecular vibrational changes in AN below T_g until a sudden release occurs at T_g. These locking sites can be nothing else than sites of tighter local packing of chain segments. Consequently it is believed that inter-chain van der Waals attraction energy plays a dominating role in the volume relaxation and sub-T_g annealing of quenched amorphous polymers.     

Initial crystallization mechanism of isotactic polystyrene from different States

The isothermal crystallization processes of isotactic polystyrene at 160 degrees C from different initial states (quenched glassy state and melt state), i.e., cold- and melt-crystallization processes, have been investigated by infrared (IR) and generalized two-dimensional (2D) IR correlation spectroscopy. It has been found that not only the crystallization kinetics and crystallinity but also the sequential changes of the amorphous and crystalline sensitive bands are quite different for the cold- and melt-crystallization processes. This leads to the conclusion that the physical origins for spinodal decomposition prior to polymer crystallization may be different for different crystallization processes.     

Pre-intercalation of Ammonium Ions in Layered δ-MnO2 Nanosheets for High-Performance Aqueous Zinc-Ion Batteries

Layered manganese dioxide is a promising cathode candidate for aqueous Zn-ion batteries. However, the narrow interlayer spacing, inferior intrinsic electronic conductivity and poor structural stability still limit its practical application. Herein, we report a two-step strategy to incorporate ammonium ions into manganese dioxide (named as AMO) nanosheets as a cathode for boosted Zn ion storage. K⁺-intercalated δ-MnO₂ nanosheets (KMO) grown on carbon cloth are chosen as the self-involved precursor. Of note, ammonium ions could replace K⁺ ions via a facile hydrothermal reaction to enlarge the lattice space and form hydrogen-bond networks. Compared with KMO, the structural stability and the ion transfer kinetics of the layered AMO are enhanced. As expected, the obtained AMO cathode exhibits remarkable electrochemical properties in terms of high reversible capacity, decent rate performance and superior cycling stability over 10000 cycles.     

Epitaxial crystallization of isotactic poly(methyl methacrylate) on highly oriented polyethylene

The annealing behavior of amorphous i-PMMA thin films on highly oriented HDPE substrates was studied by transmission infrared spectroscopy and electron diffraction. The i-PMMA thin film on highly oriented HDPE exhibits a much faster crystallization rate than usual, providing not only a good method for the preparation of crystalline i-PMMA thin and ultrathin film, but also the convenience to observe the crystallization process by infrared spectroscopy in situ. The overall crystallization kinetics of the i-PMMA thin film on the highly oriented HDPE layer was also explored in this work, and an Avrami exponent of about 2 was obtained. The accelerated crystallization behavior indicates a special interaction between HDPE and i-PMMA, which favors the nucleation and crystallization of i-PMMA. This special interaction leads also to an oriented alignment of i-PMMA on the HDPE substrate with both polymer chains parallel, i.e., the occurrence of heteroepitaxy, which could be verified by the polarized infrared spectra and electron diffraction pattern. Electron diffraction analysis further demonstrated that the contact planes of this epitaxial system are (100) lattice planes of both polymers. This can be explained in terms of a two-dimensional lattice matching.     

Mesoporous silica-coated NaYF4:Yb3+, Er3+ particles for drug release

NaYF₄:Yb³⁺, Er³⁺ nanoparticles were successfully prepared by a polyol process using diethyleneglycol (DEG) as solvent. These NaYF₄:Yb³⁺, Er³⁺ nanoparticles can be coated with mesoporous silica using nonionic triblock copolymer EO₂₀PO₇₀EO₂₀ (P 123) as structure-directing agent and other materials. The composites can load ibuprofen and release the drug in the phosphate buffer solution (PBS). The composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen absorption/desorption isotherms, fluorescence spectra, and UV/Vis absorption spectra, respectively. The composites have the mesoporous structure. In addition, the composites emit red fluorescence (from Er³⁺) under 980 nm near infrared laser excitation, which can be used as fluorescent probes in the drug-delivery system.     

NiMn‐Based Bimetal–Organic Framework Nanosheets Supported on Multi‐Channel Carbon Fibers for Efficient Oxygen Electrocatalysis

Developing noble‐metal‐free bifunctional oxygen electrocatalysts is of great significance for energy conversion and storage systems. Herein, we have developed a transformation method for growing NiMn‐based bimetal–organic framework (NiMn‐MOF) nanosheets on multi‐channel carbon fibers (MCCF) as a bifunctional oxygen electrocatalyst. Owing to the desired components and architecture, the MCCF/NiMn‐MOFs manifest comparable electrocatalytic performance towards oxygen reduction reaction (ORR) with the commercial Pt/C electrocatalyst and superior performance towards oxygen evolution reaction (OER) to the benchmark RuO₂ electrocatalyst. X‐ray absorption fine structure (XAFS) spectroscopy and density functional theory (DFT) calculations reveal that the strong synergetic effect of adjacent Ni and Mn nodes within MCCF/NiMn‐MOFs effectively promotes the thermodynamic formation of key *O and *OOH intermediates over active NiO₆ centers towards fast ORR and OER kinetics.     

Co3O4 Hollow Nanoparticles Embedded in Mesoporous Walls of Carbon Nanoboxes for Efficient Lithium Storage

Confining nanostructured electrode materials in porous carbon represents an effective strategy for improving the electrochemical performance of lithium-ion batteries. Herein, we report the design and synthesis of hybrid hollow nanostructures composed of highly dispersed Co₃O₄ hollow nanoparticles (sub-20 nm) embedded in the mesoporous walls of carbon nanoboxes (denoted as H-Co₃O₄@MCNBs) as an anode material for lithium-ion batteries. The facile metal–organic framework (MOF)-engaged strategy for the synthesis of H-Co₃O₄@MCNBs involves chemical etching-coordination and subsequent two-step annealing treatments. Owing to the unique structural merits including more active interfacial sites, effectively alleviated volume variation, good and stable electrical contact, and easy access of Li⁺ ions, the H-Co₃O₄@MCNBs exhibit excellent lithium-storage performance in terms of high specific capacity, excellent rate capability, and cycling stability.     

Ab-initio molecular dynamics simulation on nano-system under external pressure

A new constant-pressure molecular dynamics (MD) method is developed to simulate the dynamic behavior and structure transition of finite system under external pressure. In this method, no artificial parameter is introduced and the computation overheads are very small. As an application, a hard-soft transition of single wall carbon nanotube     

Hydrogen bonding in polyamide 66/clay nanocomposite

Hydrogen bonding in polyamide 66/clay nanocomposite (PA66CN) was first investigated with temperature Fourier transform infrared (FTIR), the results of which were compared with that of pristine polyamide 66 (PA66) with the same thermal history. FTIR spectra at room temperature revealed that there is essentially 100% hydrogen bonding in both PA66CN and PA66, and the difference in hydrogen‐bonding status between them is tiny. Additionally, DSC showed that the crystalline degrees and melting temperatures of PA66CN and PA66 prepared by melt quenching are similar. However, the changes of hydrogen bonding with temperature in PA66CN and PA66 are different. As the temperature rose, the hydrogen bonding in PA66CN attenuated and dissociated considerably at a smaller rate than PA66. According to transmission electron microscopic morphology of PA66CN, we analyzed the effect of nanodispersion clay layers on the motion of a polymer chain and the thermal expansion of crystalline lamella for interpreting the observed phenomenon. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2313–2321, 2003