Gaseous Nanocarving‐Mediated Carbon Framework with Spontaneous Metal Assembly for Structure‐Tunable Metal/Carbon Nanofibers

Vapor phase carbon (C)‐reduction‐based syntheses of C nanotubes and graphene, which are highly functional solid C nanomaterials, have received extensive attention in the field of materials science. This study suggests a revolutionary method for precisely controlling the C structures by oxidizing solid C nanomaterials into gaseous products in the opposite manner of the conventional approach. This gaseous nanocarving enables the modulation of inherent metal assembly in metal/C hybrid nanomaterials because of the promoted C oxidation at the metal/C interface, which produces inner pores inside C nanomaterials. This phenomenon is revealed by investigating the aspects of structure formation with selective C oxidation in the metal/C nanofibers, and density functional theory calculation. Interestingly, the tendency of C oxidation and calculated oxygen binding energy at the metal surface plane is coincident with the order Co > Ni > Cu > Pt. The customizable control of the structural factors of metal/C nanomaterials through thermodynamic‐calculation‐derived processing parameters is reported for the first time in this work. This approach can open a new class of gas–solid reaction‐based synthetic routes that dramatically broaden the structure‐design range of metal/C hybrid nanomaterials. It represents an advancement toward overcoming the limitations of intrinsic activities in various applications.     

抽水蓄能电站巴氏合金上导轴瓦损坏原因分析

由于冷却油供油路中出油不均匀,使得油槽中存在大量漩涡或空气,造成轴瓦上半部分的油膜无法形成或形成不均匀,从而在运行过程中产生了油膜压力波动。同时,由于轴瓦轴向摆动的灵活性较差,轴瓦上半部分与滑转子间隙较小,轴瓦只有上半部分与滑转子接触,致使轴瓦表面单位面积受力过大。上述两种原因造成的瓦面上半部分应力幅值增加,使轴瓦产生了疲劳破坏。为此,利用光学显微镜和直读光谱仪对轴瓦巴氏合金的组织和成分进行了分析,在此基础上,提出了适宜的改进措施。实践表明,轴瓦金相组织中再无区域性偏析、聚集和组织分层现象出现,Cu6Sn5分布均匀,Sn Sb未发生区域性偏析,组织形貌与两种硬相Sn Sb和Cu6Sn5的总量符合要求。通过对轴瓦衬垫结构进行改进,使得轴瓦摆动的灵活性加大,轴瓦和滑转子之间形成了稳定的油膜,从而使轴瓦受力均匀,运行平稳。     

Special features of pulsed arc welding of titanium

The special features of pulsed arc welding of titanium are described.     

Micropyretic Synthesis of Refractory Metal Intermetallic Compounds

Abstract

The processing of refractory metal intermetallic compounds by micropyretic synthesis has been discussed in this article. The advantages of this process have been elaborated with the synthesis of intermetallic compounds in view. Microstructures of the synthesized alloys have been examined in detail and compared with the conventionally produced microstructure. The effect of different process parameters on the process and on the synthesized microstructure has been described. Special emphasis is given on the synthesis of aluminides of Nb and Ti and NiTi. The mechanism of micropyretic synthesis of the aforementioned intermetallic compounds from elemental powders has been studied by arresting the synthesis process midway. This has resulted in preservation of the unsynthesized material on one side, the fully synthesized material on the other and intermediate stages of synthesis frozen in between. A detailed microstructural characterization has been carried out around the arrested synthesis front in order to establish the sequence of synthesis.     

A videogrammetric as-built data collection method for digital fabrication of sheet metal roof panels

A roofing contractor typically needs to acquire as-built dimensions of a roof structure several times over the course of its build because a structure is never built to the exact drawing dimensions. In the construction phase and in order to digitally fabricate sheet metal roof panels, the contractor has to measure end-to-end dimensions of boundaries of every roof plane with a certain level of accuracy (i.e., errors less than ±2 cm). This is necessary to be able to cut sheet metal coil such that different pieces perfectly fit together. Obtaining these measurements using the exiting roof surveying methods could be costly in terms of equipment, labor, and/or worker exposure to safety hazards. This paper presents a video-based surveying framework as an alternative method which is simple to use, automated, less expensive, and safe. When using this framework, the contractor collects video streams with a calibrated stereo camera set. The captured data is processed to automatically generate a 3D wire-diagram of the target roof. Measurements from the wire-diagram are saved in a digital file (XML format) which could be loaded into an on-site sheet metal folding and cutting machine. Experimental analyses demonstrate applicability of the proposed framework.     

The sorption of monovalent cations onto norway spruce: Model studies using wood flour and LiCl solution

The transport of chemicals in a porous material such as wood is very complex and involves several processes: the diffusion of chemicals in the cell pores (lumen and pit pores), through the cell walls at certain conditions, and sorption of wood tissue. In the present study, batch sorption experiments were performed to examine the sorption of Li⁺ ions from an aqueous LiCl solution onto Norway spruce wood flour samples. The experimental methodology employed is suitable for differentiating the amount of ions sorbed onto the wood tissue and dissolved in the solution in wood pores. The apparent equilibrium sorption data were analyzed using two widely applied isotherm models: Langmuir and Freundlich. The results suggest that the sorption was spontaneous, and for the experimental conditions studied, probably involved several interaction types between the different functional groups of the wood and the Li⁺/Cl^? ions.     

Layer-by-layer assembly of long-afterglow self-supporting thin films with dual-stimuli-responsive phosphorescence and antiforgery applications

The assembly of thin films (TFs) having long-lasting luminescence can be expected to play an important role in the development of new-generation smart sensors,anti-counterfeiting materials,and information-encryption systems.However,such films are limited compared with their powder and solution counterparts.In this study,by exploiting the self-organization of phosphors in the two-dimensional (2D) galleries between clay nanosheets,we developed a method for the ordered assembly of long-afterglow TFs by utilizing a hydrogen-bonding layer-by-layer (LBL) process.Compared with the pristine powder,the TFs exhibit high polarization and up-conversion room-temperature phosphorescence (RTP),as well as enhanced quantum yields and luminescence lifetimes,allowing them to be used as room-temperature phosphorescent sensors for humidity and oxygen.Moreover,modified day-based hybrids with multicolor RTP can serve as anti-counterfeiting marks and triple-mode 2D barcode displays.We anticipate that the LBL assembly process can be extended to the fabrication of other inorganic-organic room-temperature phosphorescent hybrids with smart luminescent sensor and antiforgery applications.     

Stabilization of heavy metals in biochar pyrolyzed from phytoremediated giant reed (Arundo donax) biomass

The pyrolysis of phytoremediated giant reed (Arundo donax) biomass could cause secondary pollution of heavy metals. The stabilization of heavy metals in the pyrolysis process with external materials such as Al₂O₃, CaCO₃, FeCl₃ and NaOH, was studied. The results showed that 37% As and 97% Cd in biochar were stabilized when giant reed powder was pyrolyzed at 250 °C with 5% Al₂O₃ for 2 h. Furthermore, 59% Pb in biochar was stabilized at 400 °C with 5% CaCO₃ for 1 h. Under biochar produced in optimized pyrolysis conditions, Cd mainly existed in a residual fraction, while Pb and As mainly existed in oxidizable fraction in BCR analysis. In XRD analysis, As was only found in Ca₂As₂O₇; Cd in biochar mainly existed in Cd (AlCl₄)₂, CdPbO₃ or CdSO₃; and Pb mainly existed as Pb₃O₂SO₄.     

Transition metal oxides on organic semiconductors

Transition metal oxides (TMOs) on organic semiconductors (OSs) structure has been widely used in inverted organic optoelectronic devices, including inverted organic light-emitting diodes (OLEDs) and inverted organic solar cells (OSCs), which can improve the stability of such devices as a result of improved protection of air sensitive cathode. However, most of these reports are focused on the anode modification effect of TMO and the nature of TMO-on-OS is not fully understood. Here we show that the OS on TMO forms a two-layer structure, where the interface mixing is minimized, while for TMO-on-OS, due to the obvious diffusion of TMO into the OS, a doping-layer structure is formed. This is evidenced by a series of optical and electrical studies. By studying the TMO diffusion depth in different OS, we found that this process is governed by the thermal property of the OS. The TMO tends to diffuse deeper into the OS with a lower evaporation temperature. It is shown that the TMO can diffuse more than 20 nm into the OS, depending on the thermal property of the OS. We also show that the TMO-on-OS structure can replace the commonly used OS with TMO doping structure, which is a big step toward in simplifying the fabrication process of the organic optoelectronic devices.