Experimental Investigation of Tool Wear and Machining Quality of BTA Deep-Hole Drilling in Low-Carbon Alloy Steel SA-5083.

Nuclear power tube plates are made from the high-strength, low-carbon alloy steel SA-5083, which has high values of toughness and plasticity, though it is forged with poor consistency and entails serious work hardening. It requires a large number of deep holes with a high machining accuracy and high surface quality to be processed. However, the quality of the processed holes is often not up to the standard of the Boring and Trepanning Association (BTA) for the deep-hole drilling of tube plates; this has led to deep-hole processing becoming a bottleneck in the manufacture of steam generators for the main equipment of nuclear power islands. The variation laws of the diameter, roundness, perpendicularity, roughness, microhardness, and residual stress in relation to the feed, speed, and drilling depth are explored in the macro- and micro-dimensions; also explored is the wear morphology of BTA drills. The internal influence mechanisms between them are revealed in order to provide a scientific basis for the control of surface quality and machining accuracy as well as the optimization of process parameters. Our research results indicate that the guide block wear is mainly concentrated at the top 1-2 mm and that the drilling depth and feed have a great influence on the machining diameter. The hole wall roughness is between 0.3 and 0.6 µm, the maximum microhardness is about 2.15 times the hardness of the matrix material, and the residual stress is compressive stress. With increases in the feed and drilling depth, the hole diameter and the roughness increase. With an increase in the speed, the roughness decreases and the compressive stress of the BTA deep-hole drilling wall increases.

Assembly and Manipulation of a Prototypical N-Heterocyclic Carbene with a Metalloporphyrin Pedestal on a Solid Surface.

The controlled arrangement of N-heterocyclic carbenes (NHCs) on solid surfaces is a current challenge of surface functionalization. We introduce a strategy of using Ru porphyrins in order to control both the orientation and lateral arrangement of NHCs on a planar surface. The coupling of the NHC to the Ru porphyrin is a facile process which takes place on the interface: we apply NHCs as functional, robust pillars on well-defined, preassembled Ru porphyrin monolayers on silver and characterize these interfaces with atomic precision via a battery of experimental techniques and theoretical considerations. The NHCs assemble at room temperature modularly and reversibly on the Ru porphyrin arrays. We demonstrate a selective and complete functionalization of the Ru centers. With its binding, the NHC modifies the interaction of the Ru porphyrin with the Ag surface, displacing the Ru atom by 1 Å away from the surface. This arrangement of NHCs allows us to address individual ligands by controlled manipulation with the tip of a scanning tunneling microscope, creating patterned structures on the nanometer scale.

Interaction of cyclosporin A molecules with alkali and transition metal atoms on Cu(111).

The structure of a cyclic peptide with important biological functionalities, cyclosporin A (CsA), is investigated at the single molecule level. Its adsorption on Cu(111) under ultra-high vacuum is characterised with scanning tunnelling microscopy (STM) and density functional theory. With STM investigations, we demonstrate element specific on-surface coordination schemes of CsA with coadsorbed K, Co and Fe atoms. Thus, clear insights emerge in the behaviour of cyclic peptides at interfaces and their interactions with different metal atoms, providing control of the adsorption structure and assembly and paving the way for the integration of cyclic peptides in functional metal-organic nanostructures on surfaces.

A Fast Estimation Method for Direction of Arrival Using Tripole Vector Antenna.

The tripole vector antenna comprises three orthogonal dipole antennas, so it could completely capture all the electric field of the incident electromagnetic (EM) wave. Then, the electric field information could be used to estimate the direction of arrival (DOA) of the EM wave if two conditions are satisfied. One is that there exists only one single EM wave in space. The other is that the EM wave is elliptically or circularly polarized. The new estimation method obtains two snapshot vectors through the output of a tripole antenna and computes their cross-product vector. Furthermore, the direction of the cross-product vector is used to estimate the DOA of the EM wave directly. We analyze the statistical characteristics of the DOA estimation error to prove that the new scheme is an asymptotic unbiased estimation. Furthermore, unlike the existing Multiple Signal Classification (MUSIC)-based algorithms, the proposed approach only need one tripole vector antenna instead of an antenna array. Meanwhile, the new method also outperforms existing MUSIC-based algorithms in the term of computational complexity. Finally, the performance and advantages of the proposed method are verified by numerical simulations.

Snapshots of Dynamic Adaptation: Two-Dimensional Molecular Architectonics with Linear Bis-Hydroxamic Acid Modules.

Linear modules equipped with two terminal hydroxamic acid groups act as the building block of diverse two-dimensional supramolecular motifs and patterns with room-temperature stability on the close-packed single-crystal surfaces of silver and gold, revealing a complex self-assembly scenario. By combining multiple investigation techniques (scanning tunneling microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and density functional theory calculations), we analyze the characteristics of the ordered assemblies which range from close-packed structures to polyporous networks featuring an exceptionally extended primitive unit cell with a side length exceeding 7 nm. The polyporous network shows potential for hosting and promoting the formation of chiral supramolecules, whereas a transition from 1D chiral randomness to an ordered racemate is discovered in a different porous phase. We correlate the observed structural changes to the adaptivity of the building block and surface-induced changes in the chemical state of the hydroxamic acid functional group.

The self-assembly and metal adatom coordination of a linear bis-tetrazole ligand on Ag(111).

We employ a linear linker molecule consisting of a benzene functionalised with two tetrazole moieties at para positions. Its self-assembly and coordination with the native silver adatoms and codeposited Fe adatoms on a Ag(111) surface under ultra high vacuum conditions are investigated by means of scanning tunnelling microscopy and X-ray photoelectron spectroscopy. We discover a rich spectrum of room-temperature stable Ag and Fe2+ coordination nodes depending on the formation temperature.

Tuning the ease of formation of on-surface metal-adatom coordination polymers featuring diketones.

We use pyrene-4,5,9,10-tetraketone molecules with substituents of varying bulkiness in the 2,7 positions to probe the generality and versatility of the previously reported on-surface coordination of two diketones with a single metal atom, leading to one-dimensional coordination polymers. Three different low index surfaces of group 11 metals (Cu, Ag and Au) are used to provide both the support and the metal atoms for metal-organic coordination. By real space visualisation with single molecule resolution employing scanning tunnelling microscopy we investigate the molecular self-assembly and show how this can be substantiated with the formation of metal-organic linear and cyclic oligomers, depending on the employed substrate.

N-Heterocyclic carbenes on close-packed coinage metal surfaces: bis-carbene metal adatom bonding scheme of monolayer films on Au, Ag and Cu.

By means of scanning tunnelling microscopy (STM), complementary density functional theory (DFT) and X-ray photoelectron spectroscopy (XPS) we investigate the binding and self-assembly of a saturated molecular layer of model N-heterocyclic carbene (NHC) on Cu(111), Ag(111) and Au(111) surfaces under ultra-high vacuum (UHV) conditions. XPS reveals that at room temperature, coverages up to a monolayer exist, with the molecules engaged in metal carbene bonds. On all three surfaces, we resolve similar arrangements, which can be interpreted only in terms of mononuclear M(NHC)2 (M = Cu, Ag, Au) complexes, reminiscent of the paired bonding of thiols to surface gold adatoms. Theoretical investigations for the case of Au unravel the charge distribution of a Au(111) surface covered by Au(NHC)2 and reveal that this is the energetically preferential adsorption configuration.

Ionic liquids as plasticizers for polyelectrolyte complexes.

Uptake of salts by insoluble polyelectrolyte complexes (PECs) leads to plasticization, and here it is shown that ionic liquids (ILs) are more effective plasticizers than simple organic salts such as NaCl. The PEC uptake of IL cation was monitored by solution (1)H NMR, and the mechanical impacts of plasticization were tracked by dynamic mechanical analysis (DMA). PECs prepared with polystyrene sulfonate (PSS) and poly(diallyldimethylammonium chloride) (PDDA) under charge stoichiometric conditions were immersed in aqueous solutions of 1-butyl-3-methylimidazolium chloride [BMIM][Cl] to cause IL uptake, which could be controlled by the solution's IL concentration: higher concentration leads to higher uptake which leads to greater plasticization. The effectiveness of plasticization was assessed through the position and height of a DMA tan(δ) peak ascribed to a glassy-to-rubbery PEC transition. Consistent with greater PEC uptake, isothermal titration calorimetry demonstrated that solution binding by PSS of [BMIM](+) was much stronger than binding of Na(+).

Synthesis of hollow Ag-Au bimetallic nanoparticles in polyelectrolyte multilayers.

Ag nanoparticles of ~20 nm size and rather uniform size distribution were synthesized in polyelectrolyte multilayers (PEMs) via an ion-exchange/reduction process in two stages (seeding and growth), which were used as sacrificial templates to fabricate Ag-Au bimetallic hollow nanoparticles via galvanic replacement reaction. The reaction process was monitored by UV-vis spectroscopy. The morphology and structure of the nanoparticles were characterized by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy, which confirmed the formation of hollow Ag-Au bimetallic nanoparticles. UV-vis absorbance spectroscopy and TEM results indicated that both size and optical properties of the Ag nanoparticles in the PEM can be controlled by manipulating ion content in the PEM and the number of the ion-exchange/reduction cycle, whereas that of Ag-Au bimetallic nanoparticles were dependent on size of the Ag templates and the replacement reaction kinetics. The hollow Ag-Au bimetallic nanoparticles exhibited a significant red shift in the surface plasmon resonance to the near-infrared region. The strategy enables facile preparation of hollow bimetallic nanoparticles in situ in polymer matrixes.

In vivo osteogenic properties of the composite of periosteal-derived osteoblast and collagen- coated true bone ceramics.

OBJECTIVE: To contrive new ways for repairing bone defects on the basis of the observation of the osteogenic properties of implanted composite made from periosteal-derived osteoblasts (POB) and true bone ceramics (TBC) coated with collagen (TBCc). METHODS: Bovine cancellous bone was calcined and coated with collagen before being mixed with cultured rabbit osteoblast suspension to prepare the composite, which was respectively implanted subcutaneously on the right of the back of BALB/c nude mice and in the muscle pouches in similar sites of rabbits. The control was established by implantation of TBCc in the contralateral sites corresponding to the former implants in both of animals. Samples were obtained from the implant sites 4 weeks later in mice and 8 weeks later in rabbits respectively, and light and electron microscopic observation was performed routinely. RESULTS: A large number of osteoblasts were seen to grow and proliferate within the TBCc-POB composite where cartilage and bone tissues also generated, which was no observed in the control group. CONCLUSION: The osteoblasts in the implanted TBCc-POB composite can survive and develop into cartilage and bone tissues.