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Improved oxidation and hot corrosion resistance of the NiSiAlY alloy at 750 degrees C
No full textThe oxidation and hot corrosion behaviors of the NiAlY alloy, NiCrAlY alloy and NiSiAlY alloys with different Si content (1, 3 and 5 wt%) were investigated at 750 degrees C. With the addition of Si, the oxidation resistance of the NiSiAlY alloys was significantly improved compared to the undoped NiAlY alloy. The doped Si promoted the formation of the protective oxide scales. Moreover, the NiSiAlY alloys exhibited enhanced resistance to the NaClinduced hot corrosion in both dry and humid environments. Si played a beneficial role in restraining the internal corrosion and consumption of Al. In addition, the oxidation and hot corrosion mechanisms of the tested alloys were also discussed
Understanding the CO2/CH4/N-2 Separation Performance of Nanoporous Amorphous N-Doped Carbon Combined Hybrid Monte Carlo with Machine Learning
No full textAmorphous carbon (aC) is widely used as the adsorbent in the purification of industrial gas. Introducing nitrogen dopant can regulate the morphology and improve the adsorption capacity of specific species. Due to the amorphous structure, it is difficult to understand the relationship between structural features and adsorption performance through atom-based simulation. Here, a series of nitrogen-doped amorphous carbon (N-aC) models is built through reverse Monte Carlo method. The uptakes of three common gases, i.e., CO2, CH4, and N-2 are estimated in each constructed framework by using grand canonical Monte Carlo (GCMC). Deep neural network is trained based on the simulated adsorption capacity with nitrogen content, surface area, pore size, atomic charge, and other factors. Through the data-driven approaches, the adsorption capacity and the selectivity of three gases are predicted. The simulation in this study shows that the nitrogen content has less influence on the capacity and selectivity than the structural parameters, while nitrogen doping may improve CO2 loading and separation selectivity in the nanopores with pore size close to gas molecules. This work is helpful in constructing amorphous carbon structures for further simulation and understanding the influence of various features on gas separation
Self-compatibilization effect of phosphonate with cyano group on flame retardancy and mechanical properties of epoxy
No full textA phosphonate flame retardant containing cyano group (CPDPO) was synthesized by using diphenylphosphinyl chloride and 4-cyanophenol and used to modify the flame retardancy epoxy (EP). The curing process, flame retardant performance and mechanism of EP/CPDPO were investigated. The cyano is a strong electron withdrawing group which makes some CPDPO to react with EP via transesterification, thus about 17% diphenyl phosphine oxide (DPO) and 4-cyanophenol group will be grafted onto the chain of EP. Therefore CPDPO plays a self-compatibilization role in the system. The EP with 6 wt% CPDPO achieves the UL-94 V0 rating and a LOI value of 36.6%. The peak of heat release rate and total heat release of EP with 6 wt% CPDPO are decreased by 47% and 24% compared with EP, respectively. The DPO grafted on the EP network tends to work in the condensed phase, while the free CPDPO is easy to work in the gas phase. The latter is far more than the former. Therefore, the effect of gas phase is obviously greater than that of condensed phase, which matches the structure of EP which has good charring ability itself. Moreover, the EP/CPDPO has better mechanical properties than that of EP and transparency equivalent to itself. This work suggests that the phosphonate containing strong electron-withdrawing group not only has self-compatibilization effect, but also regulates the properties and flame retardant mechanism
Study on anti-corrosion performance and mechanism of epoxy coatings based on basalt flake loaded aniline trimer
No full textThe main protection mechanism of anti-corrosion coatings was to shield and hinder corrosive media. When inorganic flake fillers were added to improve the anti-corrosion performance of the coatings, it was necessary to solve the problem of inorganic-organic compatibility. This paper combined the barrier properties of flaky and chemically inert basalt scales with the corrosion inhibition of aniline trimers, and prepared aniline trimers modified basalt scales to improve the anticorrosion performance of the coatings. Aniline trimer was conducive to the compatibility and dispersion of basalt flakes in epoxy resin. The enhancement of shielding and anti-corrosion performance of the coatings was attributed to the dispersed distribution of basalt flakes, which reduced the water content and diffusion rate in coatings. Aniline trimer acted as the corrosion inhibitor. When corrosive media penetrated the coatings, it adsorbed on the metal surface and formed protective films, thereby enhancing the corrosion resistance of the coatings. The aniline trimer modified basalt flakes increased the anti-corrosion resistance of epoxy coatings by two orders of magnitude, and its optimal mass content was about 10%
Microstructural and optical characterization of polymer nanotemplates with different morphologies
No full textThe block copolymer (BCP) templates with nanoscale structures and diverse morphologies have attracted much attention for nanofabrication in photonic and plasmonic research fields. Herein, PS-b-PMMA BCP nanotemplates with different morphologies, including the patterns of hexagonal hole arrays, fingerprint stripes, and their mixture, are successfully prepared for in-depth microstructural and optical characterizations. Apart from direct microstructure observations and component characterization, ellipsometric measurements are mainly applied to characterize structural and optical evolution of these BCP nanotemplates undergoing different preparation stages. Interestingly, among different BCP nanotemplates, two typical reflectance peaks in the ultraviolet region (200-250 nm) are distinctly different from each other, due to their PS- and thickness-dependent optical behaviors. With the preparation proceeding, there are synchronous diminution in the intensity of the two peaks, accompanying with an obvious blue-shift for the shorter wavelength peak. In addition, the variation of refractive index and ellipsometric parameters greatly demonstrates morphology-dependent optical behaviors among different BCP nanotemplates. Finally, Au-covered BCP nanotemplates present the distinct template-morphologydependent visible-light responses, demonstrating different light-matter interactions occurred in their plasmonic Au nanostructures
Effects of thin cladding layer and annealing treatments on mechanical properties of AISI4340 steel
No full textIn this study, a NiCrFeBSi alloy layer with a thickness of about 140 mu m was cladded on the AISI4340 steel and then annealed at 700 degrees C, and the influences of cladding and annealing on tensile and fatigue damage mechanisms of the AISI4340 steel were investigated. The fatigue stress ranges were set from 0 to 0.30-0.75 of the yield strength, and the fatigue deformation and cracking morphologies after different cycles were in-situ compared to reveal the dynamic damage mechanisms. The results reveal that the yield strength of the substrate shows little change after cladding, while the tensile fracture strain and fatigue life decrease significantly due to the high cracking susceptibility of the cladding layer. After the annealing treatment, the yield strength decreases obviously, while the fracture strain and fatigue life recover somewhat. For the original AISI4340 steel specimen, a few fatigue cracks initiate around the stress concentration region at relative high stress level, and the crack initiation cycles are high. After cladding, more fatigue cracks initiate along the cladding track boundaries at a stress far lower than the yield strength, resulted by the residual stress and microdefects, and some of the microcracks propagate into the substrate, makes the crack initiation cycle decreases sharply. For the annealed specimen, fewer fatigue cracks appear and the main crack initiates at the edge of the cladding layer, and the crack initiation and propagation cycles recover. All the fatigue fracture surfaces are composed of a flat area, a radial area and a fibrous area, and the fracture mode transforms from quasi-cleavage to microporous polymerization with crack propagation
Microwave-assisted synthesis of Zr-based metal-organic framework (Zr-fum-fcu-MOF) for gas adsorption separation
No full textA reliable strategy of Zr-based metal-organic framework (Zr-fum-fcu-MOF) was successfully achieved by microwave-assisted synthesis. Well-shaped and octahedral Zr-fum-fcu-MOF particles were obtained at 100 degrees C for 1.0 h with 150 equivalents of FA per ZrOCl2 center dot 8H(2)O. A clear difference for the adsorption behavior of iso-C4H10 (1.11 mmol/g) and n-C4H10 (3.56 mmol/g) was observed at 25 degrees C and 1.0 bar. Moreover, 3.16 mmol/g CO2 uptake was also obtained at 0 degrees C and 1.0 bar while the adsorption capacity of CH4 and N-2 is 0.85 mmol/g and 0.21 mmol/g, respectively. This indicates that Zr-fum-fcu-MOF is a promising candidate for CO2 capture
Covalent triazine frameworks composite membrane (CdS/CTF-1) with enhanced photocatalytic in-situ cleaning and disinfection properties for sustainable separation
No full textPhoto-assisted catalysis is proposed to be an effective approach to deal with the membrane fouling issue, which restricts the broad application of burgeoning 2D covalent organic frameworks (COF) membranes in sustainable separation process. In this work, a new type of [0D + 2D] composite membrane was developed via covalent triazine frameworks (CTF-1) nanosheets with built-in CdS quantum dots (QDs). The regular skeleton of 2D-CTF-1 facilitated the uniform growth of CdS QDs (3 nm) on the planar nanosheets. CdS/CTF-1 composite membrane exhibits high water flux (>170 L m- 2 h-1, 0.1 MPa) and high dyes rejection (>94%) via manipulating transportation channels. More importantly, the built-in [0D + 2D]-heterojunction significantly improves the photocatalytic in-situ cleaning and disinfection performance of CdS/CTF-1 membrane, allowing for regenerating permeability (>95%) with the assist of H2O2 during multiple operations. Thus, we provide a prospective strategy to resolve the membrane fouling issues and enable the practical application of 2D membranes for continuous separation
Observation of Atomic-Order Engineered Martensitic Transformation in Ni45Co5Mn37In13 Metamagnetic Shape Memory Alloys
No full textEngineering the martensite-austenite transformation interval (Delta T (i)) is important for optimizing the functionalities of metamagnetic shape memory alloys. Although it has been revealed that both doping and thermal annealing can influence Delta T (i), the underlying mechanisms remain largely unexplored. Herein, a direct observation of the martensitic transformation process in Ni45Co5Mn37In13 alloys with distinct Delta T (i)s is made. In contrast to the typical burst-like martensitic transition, it is revealed that the alloy with a large Delta T (i) exhibits discretely distributed martensitic and austenite phases that evolve slowly with varying temperature. The unusual properties are found to be mainly correlated with atomic disorder rather than lattice distortions. The results indicate the great potential of atomistic engineering in manipulating the martensitic transformation for applications
Design of High-Barrier and Environmentally Degradable FDCA-Based Copolyesters: Experimental and Theoretical Investigation
No full textThe 2,5-furandicarboxylic acid (FDCA)-based aliphatic-aromatic copolyester is an intensively researched area of bio-based polymers with high gas barrier and mechanical properties. However, the contradiction between the barrier and degradation performance still remains a huge challenge and severely limits their applications. Here, we combine branched neopentyl glycol, hydrophilic diglycolic acid, and FDCA to prepare poly(neopentyl glycol diglycolate/furandicarboxylate) (PNDF) copolyesters. With poor crystallization capability, PNDF40 and 50 (content of NF units) display low modulus (58 vs 108 MPa) but elastomeric behavior. Their tensile broken samples can even rapidly restore the original length, which might be derived from the physical crosslinking networks. It was interesting to find that even when more than 50% of the NF units were replaced by ND units, the PNDF copolyesters still retained high gas barrier. The introduction of diglycolic acid improved the hydrolysis rate, showing potential degradability under environmental conditions. However, enzymatic degradation using Candida antarctica lipase B (CALB) revealed that the branched neopentyl glycol decreased the biodegradation rate when compared with other linear diols. Furthermore, the hydrolytic pathway of PNDF was explored by density functional theory (DFT) calculation. Through Fukui function analysis, we identified the most active sites of PNDF for hydrolysis. Additionally, the calculated energy barrier indicated that hydrolysis of the polymer chain became easier with the increase in the number of ND units. Molecular dynamics (MD) simulations of PNDF-CALB illustrated that Val154 and Gln157 of CALB located at catalytic entrance formed noncovalent interaction with PNDF, which would sterically hinder the carbonyl carbon from reaching an ideal distance for nucleophilic attack and decrease the tendency to enter a pre-reaction state