A novel four-layer structured Cr–Al–O tandem nano-multilayer composite coating has been prepared by cathodic arc ion plating for solar selective absorbing. The four-layer structured coating consists ...of pure chromium layer, low oxygen content Cr–Al–O layer (LOCL), middle oxygen content Cr–Al–O layer (MOCL) and high oxygen content Cr–Al–O layer (HOCL). The composition, structure, and surface morphology of the coating were characterized using SEM, EDS, XPS, TEM, and AFM. The optical performances of the coating were measured by spectrophotometer, while the thermal stability of the coating was evaluated by Raman spectroscopy. Results showed that LOCL and MOCL, in which amorphous Cr–Al–Ox nanolayers and composite Cr–Al–Ox nanolayers embedded with Cr2Al nanograins alternated with each other, were the main absorbers, while HOCL acted as an antireflection layer. The coating exhibited a relatively high absorptance of 0.924 and a relatively low emittance of 0.21, as well as an outstanding thermal stability with a selectivity of 0.919/0.225 even after annealing at 700°C for 2h in air, which properties rendered the four-layer structured Cr–Al–O tandem coating a potential material for photo-thermal conversion at high temperatures.
•A Cr–Al–O tandem nanomultilayer composite coating was fabricated by arc ion plating under O2 ambient.•Amorphous Cr–Al–Ox nanolayers and Cr–Al–Ox nanolayers containing Cr2Al nanograins alternated with each other in absorbing layers.•The coating exhibited outstanding thermal stability annealing at 700°C for 2h in air.
In this work, a Ni-Al layered double hydroxide/graphene (NiAl-LDH/RGO) nanocomposite which was synthesized by introducing NiAl-LDH on the surface of graphene oxide (GO) and simultaneously reducing ...graphene oxide without any additional reducing agents was utilized as the support for Au nanoparticles. Raman spectroscopy and XPS analysis revealed that the NiAl-LDH/RGO composite had both defect sites and oxygenic functional groups in RGO to control the directional growth of Au nanoparticles and lead to a small particle size. Compared to an Au catalyst supported on single GO and RGO or NiAl-LDH, this composite-supported Au catalyst (Au/NiAl-LDH/RGO) exhibited superior catalytic activity and stability in the selective oxidation of benzyl alcohol using molecular oxygen under low pressure. Improved activity was mainly ascribed to the small Au particle size effect caused by RGO and the contribution of basic sites in NiAl-LDH. Moreover, the preferable catalytic stability of the Au/NiAl-LDH/RGO catalyst was attributed to the defect sites and oxygenic functional groups in RGO which anchored the Au NPs and prevented the agglomeration, meanwhile, the agglomeration of RGO was inhibited by the introduction of NiAl-LDH.
A NiAl-LDH/RGO composite-supported Au catalyst was synthesized and exhibited high activity and stability in the selective oxidation of benzyl alcohol.
A comprehensive study of a series four‐coordinate boron compounds with the general formula of BPh2(N,N), where N,N are bidentate chelate ligands containing both neutral and negatively charged ...nitrogen donor atoms has been conducted. The structures of the boron complexes were examined via single‐crystal X‐ray diffraction. The series of molecules display bright luminescence with emission maxima λmax ranging from blue to red, depending on the nature of the N,N chelate ligand. The electronic effects and their consequences on the luminescent properties of the complexes due to the CH replacement of the chelate ligand by a nitrogen atom, the increase of conjugation, or the change of substituents on the chelate ligand have been examined using electrochemical analysis, UV‐visible, and fluorescence spectroscopic methods, and by molecular orbital calculations (Gaussian 98). Experimental data and MO calculation results established that the emission of this class of compounds is caused by π–π* transitions centered on the chelate ligand. Furthermore, the experimental and theoretical results consistently and conclusively established that electron withdrawing groups on the negatively charged N‐donor portion of the chelate ligand causes a decrease in the highest occupied molecular orbital (HOMO) energy level, thus increasing the energy gap. The CH replacement by a nitrogen atom on the negatively charged portion of the chelate ligand causes a dramatic decrease of the HOMO energy level, and the increase of conjugation in the chelate ligand significantly decreases the energy gap. Blue and red electroluminescent (EL) devices were fabricated successfully using two representative boron compounds from the series. The new boron compounds have been found to be able to function as both emitters and electron transport materials in EL devices.
Four‐coordinate boron compounds with the general formula of BPh2(L) (L is the N,N′‐chelate ligand) and emission colors that cover the entire visible spectra are achieved and their uses in electroluminescent devices are demonstrated. The Figure shows the photoluminescence spectra of representative boron compounds.
In this study, nanoporous silver with tunable porosity was fabricated by chemically dealloying Ag-based metallic glasses in HCl solution. By systematically investigating the dynamic change in pore ...characteristics of the nanoporous silver with dealloying condition, the correlation between ligament size and dealloying parameter was successfully established. It was also found that the evolution behavior of the ligament size can be well described by a diffusion based growth kinetic model. In addition, our study of the capacitive performance of the nanoporous silver shows that these newly developed materials are promising for applications as electrode/substrate materials in electrochemical supercapacitors.
Formation mechanism of forming nanoporous silver with tunable porosity by chemically dealloying metallic glasses was proposed. The evolution behavior of the ligament size can be well described by a diffusion based growth kinetic model. In addition, the capacitive performance data indicated that our newly developed nanoporous silver is promising for applications as electrode/substrate materials in electrochemical supercapacitors. Display omitted
W–Ni alloy parts were produced with selective laser melting (SLM) and the influence of the Ni content on the microstructure evolution and microhardness was investigated methodically. The resultant ...microstructure of the SLM specimens with a Ni content of 10wt.%, 20wt.% and 40wt.% exhibited bar-shaped structures, dendrites and honeycomb structures respectively. It was found that a higher Ni content decreased the melt viscosity and increased the densities of W–Ni parts. The microhardness decreased on the other hand with increasing Ni content. The microstructure formed in the SLM process was characterized by a mixture of typical liquid phase sintering (LPS) microstructure and W dendritic structure. This revealed that the forming mechanism of the SLM process on W–Ni particles was a combination of LPS and partial melting of W particles. The microstructure showed that SLM process improved the bonding ability of the powder particles and therefore enhancing the mechanical properties.
•Different Ni content W–Ni parts were produced via selective laser melting.•The influence of Ni content on the microstructure evolution was studied.•The micro hardness variation of as-built parts was investigated methodically.•The forming mechanism on SLM of W–Ni particles was studied and explained.
The bottom-up fabrication of molecular nanodevices will require precise (photo)-control over self-assembled interfacial structures. Here, the self-assembly and photopolymerization behaviors of six ...diacetylenic acid derivatives on highly oriented pyrolytic graphite (HOPG) surfaces are studied by using scanning tunneling microscope (STM). The van der Waals interaction among alkyl chains is the predominant driving force for determining the varied assembly structure. Diacetylenic acid derivatives with the diacetylene moiety directly connected to the carboxyl group (2,4-heptadecadiynoic acid (C
17
H
26
O
2
), 2,4-nonadecadiynoic acid (C
19
H
30
O
2
) and 2,4-heneicosadiynoic acid (C
21
H
34
O
2
)) assemble to form surface monolayers with lamella-like structures where the alkyl chains interdigitate. Moreover, diacetylenic acid derivatives with the diacetylene group located in the middle of the side chains and far from the carboxyl group (10,12-tricosadiynoic acid (C
23
H
38
O
2
), 10,12-pentacosadiynoic acid (C
25
H
42
O
2
) and 10,12-heptacosadiynoic acid (C
27
H
46
O
2
)) tend to assemble into paralleled structures with the alkyl chains adopting a tail-to-tail assembly mode. This work thus elucidates in detail the structure-function relationships for photo-modifiable self-assembled interfacial nanostructures based on diacetylenic acid.
The effect of UV illumination time on the polymerization efficiency and the structural change of DA-25.
M2 high speed steel (HSS) samples were produced by an additive manufacturing (AM) process, selective laser melting (SLM). The observed microstructure from SEM and FIB was characterised by a ...continuous and homogeneous network of dendrites within two different phases. These phases were characterised to be bcc single crystals and fcc/bcc polycrystals from TEM-SADP. EBSD results also indicated that the bcc grains were randomly orientated. In addition, the lattice constants from two different SADPs of bcc crystal were calculated to be 2.892Å and 2.905Å, larger than high purity iron bcc structure of lattice constant 2.867Å. The elements V, Cr, Mo, W and Si were detected in the iron matrix with TEM-EDS. These elements were responsible for the enlargement of the lattice constant. TEM-EDS results also indicated that the network of dendrites were carbides. These results gave insights on the rapid solidification phenomenon in SLM.
•Microstructure of SLM M2 high speed steel was investigated through TEM.•A continuous and homogeneous network of carbide dendrites was observed.•Two distinct phases of bcc single crystals and fcc/bcc polycrystals were observed.•The iron bcc lattice constant calculated from TEM-SADP was larger.•Alloying elements V, Cr, Mo, W and Si were detected in the iron matrix by TEM-EDS.
ABSTRACT
The follow-up timing observations were carried out for 24 pulsars discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in Commensal Radio Astronomy FAST Survey. ...We report their phase-connected timing ephemeris, polarization pulse profiles, and Faraday rotation measurements. With their spin periods spanning from 2.995 ms to 4.34 s, their period derivatives were determined to spread between 7.996(8) × 10−21 and 9.83(3) × 10−15 s s−1, which imply that they have characteristic ages from 1.97 × 106 to 5.93 × 109 yr. It is inferred that PSRs J0211+4235 and J0518+2431 are beyond the ‘traditional death line’. PSR J0211+4235 is beyond the ‘death valley’. The death line model of Zhang et al. also cannot explain the radio presence of PSR J0211+4235. This suggests that radiation theory needs to be improved. Besides, ten of the 22 canonical pulsars show nulling phenomena. Moreover, PSR J1617+1123 exhibits variation of emission and J0540+4542 shows subpulse drifting. The DM of five pulsars is larger than the estimated by the YMW16 electron density model, which could suggest that electron density models need updates for higher Galactic latitude regions. PSRs J0447+2447 and J1928−0548 are isolated millisecond pulsars. With their flux densities spanning from 5(1)–553(106) μJy, some of these new pulsars found by FAST are distant, dim, and low-$\dot{E}$ ones and are suitable for testing pulsar emission theories.
Hypertension results from the interaction of genetic and acquired factors. IgG occurs in the form of different subclasses, of which the effector functions show significant variation. The detailed ...differences between the glycosylation profiles of the individual IgG subclasses may be lost in a profiling method for total IgG N-glycosylation. In this study, subclass-specific IgG Fc glycosylation profile was investigated in the four northwestern Chinese minority populations, namely, Uygur (UIG), Kazak (KZK), Kirgiz (KGZ), and Tajik (TJK), composed of 274 hypertensive patients and 356 healthy controls. The results showed that ten directly measured IgG N-glycan traits (i.e., IgG1G0F, IgG2G0F, IgG2G1FN, IgG2G1FS, IgG2G2S, IgG4G0F, IgG4G1FS, IgG4G1S, IgG4G2FS, and IgG4G2N) representing galactosylation and sialylation are significantly associated with hypertension, with IgG4 consistently showing weaker associations of its sialylation, across the four ethnic groups. We observed a modest improvement on the AUC of ROC curve when the IgG Fc N-glycan traits are added into the glycan-based model (difference between AUCs, 0.044, 95% CI: 0.016-0.072, P = 0.002). The AUC of the diagnostic model indicated that the subclass-specific IgG Fc N-glycan profiles provide more information reinforcing current models utilizing age, gender, BMI, and ethnicity, and demonstrate the potential of subclass-specific IgG Fc N-glycosylation profiles to serve as a biomarker for hypertension. Further research is however required to determine the additive value of subclass-specific IgG Fc N-glycosylation on top of biomarkers, which are currently used.
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