热喷涂涂层中残余应力分析和检测研究进展

综述热喷涂涂层中残余应力研究进展．主要内容有：对残余应力产生的最新认识，残余应 力分布实验测试技术、理论分析模型及其对热喷涂材料界面结合强度影响等领域的研究进展．最后 对该领域几个学术界和工程界关注的研究方向进行了展望．

Film Thickness and Surface Plasmon Tune the Contribution of SFG Signals from Buried Interface and Air Surface

Sum frequency generation vibrational spectroscopy(SFG-VS)is a powerful technique for determining molecular structures at both buried interface and air surface.Distinguishing the contribution of SFG signals from buried interface and air surface is crucial to the applications in devices such as microelectronics and bio-tips.Here we demonstrate that the SFG spectra from buried interface and air surface can be differentiated by controlling the film thickness and employment of surface-plasmon enhancement.Using substrate-supported PMMA(poly(methyl methacrylate))films as a model,we have visualized the variations in the contribution of SFG signals from buried interface and air surface.By monitoring carbonyl and C-H stretching groups,we found that SFG signals are dominated by the moieties(-CH2,-CH3,-OCH3 and C=O)segregated at the PMMA/air surface for the thin films while they are mainly contributed by the groups(-OCH3 and C=O)at the substrate/PMMA buried interface for the thick films.At the buried interface,the tilt angle of C=O decreases from65°to 43°as the film preparation concentration increases;in contrast,the angles at the air surface fall in the range from 38°to 21°.Surface plasmon generated by gold nanorods can largely enhance SFG signals,particularly the signals from the buried interface.

On-site building of a Zn^(2+)-conductive interfacial layer via short-circuit energization for stable Zn anode

Aqueous zinc ion batteries(ZIBs)show great potential in large-scale energy storage systems for their advantages of high safety,low cost,high capacity,and environmental friendliness.However,the poor performance of Zn metal anode seriously hinders the application of ZIBs.Herein,we use the zinc-ion intercalatable V_(2)O_(5)nH_(2)O(VO)as the interface modification material,for the first time,to on-site build a Zn^(2+)-conductive ZnxV_(2)O_(5)nH_(2)O(ZnVO)interfacial layer via the spontaneous short-circuit reaction between the pre-fabricated VO film and Zn metal foil.Compared with the bare Zn,the ZnVO-coated Zn anode exhibits better electrochemical performances with dendrite-free Zn deposits,lower polarization,higher coulombic efficiency over 99%after long cycles and 10 times higher cycle life,which is confirmed by constructing Zn symmetrical cell and Zn|ZnSO_(4)+Li_(2)SO_(4)|LiFePO_(4) full cell.

Computational Investigation of Blade slotting on a High-Load Low-Pressure Turbine Profile at various Reynolds Numbers:Part Ⅰ——Slotting Scheme's Verification

Boundary layer separation and reattachment is often an unavoidable feature of low pressure (LP) turbine,one of the main causes of this phenomenon is the high altitude low Reynolds number experienced by the modern LP turbine stage in aero-engine.Although an excellent turbine airfoil design can avoid flow separation on certain extent,but within flight envelope,LP turbine's characteristic Reynolds number may varied greatly,so it will be still under the risk of the presence of separation bubble.In this two parts paper a new concept of slotted-blade was raised to testify the gain of the blade slotting.A high aerodynamic loading LP turbine blade IET-LPTA was under investigated with different Reynolds number.Computational results reveal that the blade slotting could be a way of choice to suppress separation bubble and reduce profile loss under the condition of low Reynolds number,although its position and geometry need to be further investigated.

Experimental study on the interfacial delamination in a thermal barrier coating system at elevated temperatures

The failure mode and adhesion of thermal barrier coating (TBC) 8YSZ (ZrO2+8% (w/w) Y2O3) deposited on NiCoCrAlTaY bond coat by atmospheric plasma spraying were investigated. A grooved modified three-point bending specimen that can generate a single interface crack to facilitate the control of crack growth was adopted for testing, which was conducted at the ambient temperature of 100 °C. The morphology and composition of fractured surfaces were examined by means of a scanning electron microscopy (SEM) and an energy disperse spectroscopy (EDS). Images and spectrum show that cracks are initiated and propagated exclusively within YSZ layer adjacent to top/bond coat interface. The load-displacement curves obtained exhibit similar shapes that indicate two distinct stages in crack initiation and stable crack growth. Finite element analyses were performed to extract the adhesion strength of the TBCs. The delamination toughness of the plasma-sprayed 8YSZ coatings at 100 °C, in terms of critical strain energy release rate Gc, can be reliably obtained from an analytical solution.

Contracted interlayer distance in graphene/sapphire heterostructure

Direct growth of graphene on insulators is expected to yield significant improvements in performance of graphene-based electronic and spintronic devices. In this study, we successfully reveal the atomic arrangement and electronic properties of a coherent heterostructure of single-layer graphene and α-Al2O3（0001）. The analysis of the atomic arrangement of single-layer graphene on α-Al2O3（0001） revealed an apparentcontradiction. The in-plane analysis shows that single-layer graphene grows not in a single-crystalline epitaxial manner, but rather in polycrystalline form, with two strongly pronounced preferred orientations. This suggests relatively weak interfacial interactions are operative. However, we demonstrate that unusually strong physical interactions between graphene and α-Al2O3（0001） exist, as evidenced by the small separation between the graphene and the α-Al2O3（0001） surface. The interfacial interaction is shown to be dominated by the electrostatic forces involved in the graphene n-system and the unsaturated electrons of the topmost O layer of α-Al2O3（0001）, rather than the van der Waals interactions. Such features causes graphene hole doping and enable the graphene to slide on the α-Al2O3（0001） surface with only a small energy barrier despite the strong interfacial interactions.