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Selective laser melting (SLM) can effectively replace traditional processing methods to prepare parts with arbitrary complex shapes through layer-by-layer accumulation. However, SLM Ti-6Al-4V alloy typically exhibits low ductility and significant mechanical properties anisotropy due to the presence of acicular α′ martensite and columnar prior β grains. Post-heat treatment is frequently used to obtain superior mechanical properties by decomposing acicular α′ martensite into an equilibrium α + β phase. In this study, the microstructure and tensile properties of SLM Ti-6Al-4V alloy before and after various heat treatments were systematically investigated. The microstructure of the as-fabricated Ti-6Al-4V sample was composed of columnar prior β grains and acicular α′ martensite, which led to high strength (~1400 MPa) but low ductility (~5%) as well as significantly tensile anisotropy. The single heat treatment samples with lamellar α + β microstructure exhibited improved elongation to 6.8–13.1% with a sacrifice of strength of 100–200 MPa, while the tensile anisotropy was weakened. A trimodal microstructure was achieved through multi-step high-to-low-temperature (HLT) heat treatment, resulting in an excellent combination of strength (~1090 MPa) and ductility (~17%), while the tensile anisotropy was almost eliminated. The comprehensive mechanical properties of the HLT samples were superior to that of the conventional manufactured Ti-6Al-4V alloy. [ABSTRACT FROM AUTHOR]

Ceramic-based absorbing composite is irreplaceable in high-temperature conditions. This work has fabricated a novel biomass–derived porous SiCnw/SiC composite for structure–function integrated electromagnetic wave (EMW) absorption through selective laser sintering (SLS) 3D printing and carbothermal reduction. SLS processed the biomass-derived wood precursor with unique porous microstructures. The structure–function properties were controlled by changing the SiO carbothermal reduction temperatures, which facilitated the growth of SiC nanowires for effective EMW absorption. The 3D printed porous SiCnw/SiC composite shows efficient EMW absorption abilities with a minimum reflection loss of −49.01 dB and an effective absorption bandwidth of 5.1 GHz. The bulk density and flexural strength of porous SiCnw/SiC composite are respectively 0.73 ± 0.001 g/cm3 and 6.21 ± 0.66 MPa. Despite a high open porosity of 75.58 ± 0.31%, the porous SiCnw/SiC composite demonstrates excellent thermal conductivities of 3.21∼4.99 W/(m·K) and superior fire-resistant ability. The 3D printed SiCnw/SiC composite integrates structure and functions, indicating wide applications in specific harsh environments. [ABSTRACT FROM AUTHOR]

Given that spin and orbital angular momenta of photons have been widely investigated in optical communication and information processing systems, efficient decoding of optical vortex states using a single element is highly anticipated. In this work, a wavelength-independent holographic scheme has been proposed for total angular momentum sorting of both scalar and vector vortex states with a stationary broadband geometric-phase waveplate by means of reference-free shearing interferometry. The entangled spin and orbital angular momentum modes can be distinguished simultaneously based on the spin–orbit optical Hall effect in order to realize single-shot vortex detection. The viability of our scheme has also been demonstrated experimentally. [ABSTRACT FROM AUTHOR]

This paper presents a distributed output-feedback-based coordinated controller for Unmanned Container Transporter (UCT) platooning. To reduce the communication burden and the execution rate of actuator, event-triggered mechanisms (ETMs) are introduced to the position-heading information transmission and controller-to-actuator channel respectively. An event-triggered extended state observer (ET-ESO) with inter-sample output predictor is proposed to recover the position-heading and velocity information as well as to estimate model uncertainties and unknown disturbances. Kinematic and kinetic control laws are constructed to achieve formation control of the UCT platoon. The Input-to-State Stability (ISS) of the closed-loop system is analyzed via cascade theory. Furthermore, it is proved that the Zeno behavior is excluded from the proposed ETMs by the analysis on minimum inter-event time. Simulation results substantiate the effectiveness of the proposed distributed controller for UCT platooning. [ABSTRACT FROM AUTHOR]

Nonlinearity-induced asymmetric diffraction based on spatial self-phase modulation is demonstrated experimentally through the illumination of a focus Gaussian laser beam on azo-containing materials coupled together with an A/B structure. We report here that symmetry breaking occurs to the intensity distribution of the transmitted light with diffraction rings when the propagation direction of the pump light is reversed, where asymmetric diffraction excitation takes place. In certain cases, unidirectional diffraction excitation could be realized. In addition, as the light intensity is enhanced, the diameter of the diffraction pattern increases linearly and the linear coefficient is related to the propagation direction of the beam. The diffraction efficiency of the nth diffraction ring differs significantly between the two directions when incident light is set in some specific intensity range. The achievement of the symmetry breaking of light propagation is attributed to the different nonlinear optical response strength of the two azo-containing materials. [ABSTRACT FROM AUTHOR]

Photoisomerization of azobenzene spatially confined in silver nanoparticle (AgNP) aggregates and in ethanol solution was monitored by Raman spectroscopy inside optically clear colorimetric dishes. After ultraviolet irradiation, overall Raman intensity assigned to trans‐azobenzene of these two samples decreased, and notably, a cis peak appeared at 599 cm−1, assigned to C─N═N─C torsional mode. The Raman intensity at 1,007 cm−1, assigned to trans‐azobenzene, was recorded versus irradiation time for analyzing the trans‐to‐cis photoisomerization quantum yield (PQY). By combining our theoretical derivation and standard curve of Raman spectra, the trans‐to‐cis PQY of azobenzene in AgNP aggregates was roughly calculated to be 79.0% higher than that in ethanol solution. The enhancement mechanism was discussed in terms of the competition between enhanced local optical field from surface plasmon resonance and the accelerated nonradiative decay of excited azobenzene molecules together. [ABSTRACT FROM AUTHOR]

A surface enhanced Raman spectroscopy (SERS) substrate with high sensitivity for the rapid determination of pesticide residues was developed by combining silver nanoparticles (AgNPs) and a fibrous swab. The SERS substrate was prepared simply by forming a SERS-active area on the section of fibrous swab and centrifuge tube with a soak-absorb approach. Rhodamine 6 G (R6G), a common SERS probe molecule, was used for performance characterization of the prepared SERS substrate that was shown to have high sensitivity, good stability and good reproducibility. Due to its good flexibility, the prepared SERS substrate was used to wipe contaminated surfaces for residue extraction. High sensitivity for detecting trace-level pesticides was verified for thiram. The limits of detection (LODs) for thiram on apple, grape and eggplant epidermis were calculated to be as low as 0.5313, 0.5768, and 0.5495 ng·cm−2, respectively, nearly 2 orders of magnitude below the maximum residue limit (MRL) for pesticide in food issued by the National Food Safety Standard of China. In addition, there was a linear relationship between the SERS intensity and the concentration of thiram in these three samples, indicating the good potential of this substrate for quantitative SERS analysis. [ABSTRACT FROM AUTHOR]

Phase-induced polarization modulation has been achieved experimentally by means of the all-optical holographic method. An extra spiral phase is added to a Gaussian beam and then a holographic grating is recorded through the interference of a Gaussian beam and the phase-vortex beam with the same linear polarization state in an azobenzene liquid-crystalline film. We report here that the polarization state of the diffraction light from the recorded grating is different from that of the incident light, while no polarization variation occurs for the holographic grating recorded by two Gaussian beams. The phase-induced polarization modulation is mainly attributed to the formation of birefringence in the film generated by phase vortex, which is investigated through the ripple patterns resulting from the competition between photoinduced torques and analysed by the Jones matrix. The experimental results could enrich the connotation between optical parameters and offer a method to realize polarization modulation through phase control. [ABSTRACT FROM AUTHOR]

• Fe 1-x S nanocrystals/ultra-thin carbon nano-lamellar structure is fabricated. • The uniform dispersion of Fe 1-x S nanocrystals on the ultra-thin carbon layer favours the rapid complete reconfiguration. • The rapid reconfiguration creates new actual catalytic active species of amorphous iron-based oxide. • The reconfigured catalyst shows high OER activity and good stability in alkaline conditions. The surface reconfiguration of electrocatalysts during oxygen evolution reaction (OER) is much more important to reveal the actual catalytic active species, thus realizing the optimization of electrocatalyst activity. Herein, we demonstrate a simple strategy to achieve the complete electrochemical reconfiguration of Fe 1-x S nanocrystals/ultra-thin carbon (Fe 1-x S NCs/@ UT-C) nano-lamellar structure during the OER process. The uniform dispersion of Fe 1-x S nanocrystals on the ultra-thin carbon layer favors the rapid complete reconfiguration. Such rapid reconfiguration creates new actual catalytic active species of amorphous iron-based oxide transformed from Fe 1-x S, which is coupled with an ultra-thin carbon layer to facilitate the charge transfer of OER. More detailed, partly graphitization of the ultra-thin carbon layer not only affords to overcome the ohmic losses but also enhances the overall electrical conductivity and OER activity of the material. The Fe 1-x S NCs/@UT-C as pre-catalyst shows high OER activity with a low overpotential of only 303 mV at 100 mA cm−2 and a Tafel slope of 55 mV/dec. In addition, the reconfigured catalyst has good stability for 168 h in alkaline conditions. This work is beneficial to understand the reconfiguration of electrocatalysts and design high-efficiency nonprecious metal-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Thermo-optical properties of push–pull azobenzene dyes doped nematic liquid crystals was investigated and experimentally demonstrated. The dynamical variations of transmission upon a CW Nd:YAG laser exposure at room temperature were determined by laser intensity, azobenzene dye concentration and sample temperature. Transmission behaviors at different temperatures were distinct, which resulted from oscillation transmittance performance of nematic liquid crystals with temperature variation and photoisomerization process of azobenzene dye. Our experimental results demonstrated that the dynamical thermo-optical change in azobenzene dye doped nematic liquid crystals could be a promising candidate for thermo-optical controller. [ABSTRACT FROM AUTHOR]

Bimetallic Au@Cu core–shell nanocrystals have been synthesized by a two-step seed-mediated growth method through controlled heteroepitaxial growth of Cu shells on Au nanorods serving as seeds. The final crystal structures have cubic morphology with edge lengths from 50 to 100 nm due to a strong affinity of hexadecylamine, which is a selective capping agent for the {100} facets of Cu. Various characterizations reveal that the epitaxial growth mechanism is based on block-type growth mode, rather than layer-by-layer growth mode, owing to the larger mismatch in the different lattice constants between Au core and Cu shell. Moreover, contrastive experiments using Au nanobipyramids as seeds were carried out to gain further insight into the heteroepitaxial growth mechanism. Combining first-principles density-functional theory with experimental results, the binding energies of Cu atoms at different sites on Au surfaces are explored to clarify the aspects of nanostructure formation. This study provides useful insights into the effective synthesis method and the further investigation of the proposed growth mechanism. [ABSTRACT FROM AUTHOR]

Holographic gratings in nematic liquid crystals doped with Disperse Red 1 (DR1) were investigated using a linearly polarised He–Ne laser. Although the electric transitions of the samples were almost off-resonant, the diffraction of the transient holographic grating was found to exhibit a sinusoidal feature with changing the polarisation of recording beams, and the diffraction intensities and response time of the gratings were strongly dependent on DR1 concentration. The results revealed that the diffraction of holographic grating depends on the rate of trans–cis isomerisation of DR1 molecules. Moreover, the temperature dependence of diffraction indicated that the grating formation mechanism was attributed to photoinduced reorientation of photoisomerisation effect. [ABSTRACT FROM AUTHOR]

Polarization holographic recordings in an azobenzene copolymer were performed by using the interference of two linearly orthogonally polarized beams. The first order diffraction efficiency of the recorded gratings was modulated by the polarization direction of the probe beam as a consequence of the spatial modulation of the linear and circular photoinduced birefringence. The polarization of the diffractive wave was also strongly dependent on the polarization of the readout wave. The value of the photoinduced linear and circular birefringence was evaluated through Jones matrix calculations, and the obtained values were experimentally confirmed to be valid by single beam excitation measurements. [ABSTRACT FROM AUTHOR]

Abstract: Nonlinear optical absorption properties of two chiral polybinaphthyls with the same backbone but different electron acceptor hydroxyl and octoxy were studied in tetrahydrofuran solution. When excited by 100 fs 800 nm laser pulses, the up-converted fluorescence were observed and the intensities related to the different input irradiances were measured to confirm the two-photon excited fluorescence. The two-photon absorption coefficients were obtained as 4.82 cm GW−1 and 12.36 cm GW−1 with 100 fs pulses at 800 nm for two polymers, respectively. Under the excitation of 532 nm 38 ps pulse, it was found that the polymer with the side-chain of hydroxyl showed saturable absorption while the polymer with the side-chain of octoxy presented reverse saturable absorption. Their different nonlinear absorption behavior resulted from the fact that the ground-state absorption cross-section in the latter polymer was about 10 times larger than that of the former polymer while the excited-state absorption cross-section represented similar. [Copyright &y& Elsevier]

Highlights: [•] Timing of phenological events is not necessarily delayed as elevation increases. [•] Changes in timing of phenological events are inconsistent as elevation increases. [•] Individual reproductive components have independent responses to climate change. [•] Duration of reproduction stage is dependent on timing of phenological events. [•] Response of phenological events to climate change is species-specific. [Copyright &y& Elsevier]

Abstract: The ultrafast third-order nonlinear optical properties of an azobenzene-containing ionic liquid crystalline polymer were investigated by optical Kerr effect (OKE) and pump–probe techniques with femtosecond pulses. The third-order nonlinear optical susceptibility of the sample solution was obtained to be 2.1×10−14 esu at a concentration of 2×10−3 M. The temporal response of the sample solution was decomposed into two components, which could be explained by the relaxation of different singlet excited states. The polymer thin film exhibited strong ultrafast nonlinear optical response of 8.26×10−10 esu and show its potential applications for further nonlinear optical devices. [Copyright &y& Elsevier]

Abstract: The nonlinear optical properties of a series of azobenzene liquid-crystalline materials, which have different side-chain lengths in their molecular structure from one to another, were investigated using Z-scan method under picosecond pulse laser at 532nm, 1064nm and CW 488nm excitation. The mechanism accounting for the process of nonlinear refraction was discussed under different laser excitations. The polymer films possess very large nonlinear refraction at all the three different laser excitations. Especially, the nonlinear refractive index becomes larger as the length of side-chain, where azobenzene group is contained, increases under pulse excitation at 1064nm. [Copyright &y& Elsevier]

Abstract: The nonlinear optical properties of an azo-based dye were investigated using Z-scan technique employing 38ps pulses at 532 and 1064nm, and 6ns laser pulses at 532nm. Large nonlinear absorption and nonlinear refraction were observed at both ps and ns 532nm in the azoic dye. When excited at ps 1064nm, this dye displayed a large two-photon absorption cross-section (σ 2=1810GM). Meanwhile, the optical nonlinearity mechanism was discussed in terms of molecular structure, excitation wavelength, and pulse width. [ABSTRACT FROM AUTHOR]

Abstract: The nonlinear absorption of an azo-containing ion liquid crystal polymer, in dimethylformamide solution or solid thin film, has been investigated using Z-scan technique. Under the excitation of nanosecond or picosecond pulses at 532nm, the film presents large saturable absorption (SA), while the solution shows reverse saturable absorption. The alteration of nonlinear absorption behavior is due to the change of excited state cross-section and the time of intersystem crossing in solution and film. Irradiated by a continuous wave laser, SA is observed in both solution and film due to the low excitation optical intensity and thermal effect. [ABSTRACT FROM AUTHOR]

Abstract: Study on reduction of Au(III) and Ag(I) and the formation of Au and Ag nanostructures was performed on the gels of metal precursor and PVP polymer mixture. Some comparing samples were prepared for better understanding the role of reactants on the reduction of metal ions and further growth of nanocrystals. The results suggest that, in addition to its function of generating stable colloids, PVP not only has a reducing effect on metal ions, but also acts as a crystal growth modifier. At low temperatures, the reducing effect of PVP is strong on Ag(I) ions in AgNO3, while the reduction of complex Au(III) ions in HAuCl4 is slow, involving two steps of Au(III)→Au(I)→Au. In the study of temperature disturbance on crystal growth, Au nanoplates of new and well-defined star shape were observed. The differences in the size and shape of nanoparticles are discussed from the colloid chemistry. [Copyright &y& Elsevier]

Abstract: The nonlinear optical properties and photoinduced anisotropy of an azobenzene ionic liquid–crystalline polymer were investigated. The single beam Z-scan measurement showed the polymer film possessed a value of nonlinear refractive index n 2 =−1.07×10−9 cm2/W under a picosecond 532nm excitation. Photoinduced anisotropy in the polymer was studied through dichroism and photoinduced birefringence. A photoinduced birefringence value Δn ∼10−2 was achieved in the polymer film. The mechanism for the nonlinear optical response and the physical process of photoinduced anisotropy in the polymer were discussed. [Copyright &y& Elsevier]

The nonlinear optical properties and photoinduced anisotropy of a novel stilbene-containing fluorinated polyimide were investigated. Large macroscopic second-order optical nonlinearity (d 33 =35.4pm/V) was obtained in a poled thin film using the Maker fringe method. A nonlinear absorption coefficient (β) of 0.65×10−5 cm/W and third-order nonlinear refractive index (n 2) of −1.13×10−10 cm2/W were determined by Z-scan measurements. Photoinduced birefringence (Δn) of 1.02×10−2 was observed using a continuous Nd:YAG laser at 532nm as pump light and a continuous diode laser at 650nm as probe light. [Copyright &y& Elsevier]

Abstract: Colloidal Au and colloidal Ag were prepared by chemical reaction method and the nonlinear optical properties of Au and Ag nanoparticles doped polyvinylpyrrolidone (PVP) composite films were investigated using Z-scan technique with 38 ps pulses at 532 nm. Open aperture Z-scan measurements indicated that both the Au/PVP and Ag/PVP composite films exhibited reverse saturable absorption. Nonlinear absorption coefficients and third-order nonlinear refractive indices were determined. The mechanisms accounting for the process of nonlinear refractions were analyzed and the figures of merit W and T of the Au/PVP and Ag/PVP composite films were evaluated. [Copyright &y& Elsevier]

The nonlinear optical properties of p-aminoazobenzene (PAAB), methyl orange (MO) and p-dimethylamino benzene arsenic acid (PDBAA) were investigated by a single beam Z-scan technique, respectively. Their solution samples all exhibited large nonlinear refractive indices under the excitation of a 633 nm laser. Among the three azo dyes, PDBAA showed the largest value of nonlinear refractive index. Moreover, the process of nonlinear refraction induced by the laser thermal effect was also analyzed in this paper. [ABSTRACT FROM AUTHOR]

Abstract: The nonlinear refraction and photoinduced birefringence of chlorophosphonazo I (CPA I ) doped PVA thin films were investigated. The single-beam Z-scan measurement showed that CPA I doped PVA thin film possessed a large value of nonlinear refractive index (n 2=1.82×10−12 cm2/W) under a pulse 532nm excitation, and the mechanism accounting for the process of nonlinear refraction was discussed in term of resonant electronic effect. Moreover, fast and stable molecular reorientation was observed when investigating the photoinduced birefringence of CPA I doped PVA thin film with a CW 532nm laser as pump light and a CW 650nm laser as probe light. [Copyright &y& Elsevier]

Abstract: The nonlinear optical properties of Sudan I were investigated by a single beam Z-scan technique. The Sudan I ethanol solution exhibited large nonlinear refractive indices under both CW and pulse laser excitations. The nonlinear refractive indices of Sudan I were in the order of −10−8 cm2/W under CW 633nm excitation and −10−6 cm2/W under CW 488nm excitation, respectively. Under the excitation of a pulse 532nm laser, the nonlinear refractive index n 2 was calculated to be 1.19×10−14 cm2/W. It was discussed that the mechanism accounting for the process of nonlinear refraction was attributed to the laser heating for the CW laser excitation and the electronic effect for the pulse excitation. Moreover, the second hyperpolarizability of Sudan I was also estimated in this paper. [Copyright &y& Elsevier]

Abstract: Patterning SiO2 thin film on the Si (100) surface was demonstrated by synchrotron radiation (SR) stimulated etching with a contact cobalt mask. The reaction gas was a mixture of SF6 and O2. The contact cobalt mask was fabricated by sputtering cobalt films on a photolithography resist pattern and lift-off technique. The thickness of the mask was about 145nm. The SR irradiation with flowing SF6 and O2 could effectively etch the silicon dioxide and the etching process stopped at the SiO2/Si interface. The etching rate at room temperature was about 2.7nm per 100mAmin. The etched pattern was evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and step profile meter. Area-selective and anisotropy etching were achieved and the roughness (Ra) with a line profile on the etched surface was about 0.05nm. [Copyright &y& Elsevier]

• Periodically distributed refractive index and photoinduced birefringence. • Polarization modulation is realized with stable diffraction efficiency. • Different grating structures can be recorded in the same double-layer film. • The 2D diffraction device is angle-sensitive. A two-dimensional diffraction device with the properties of polarization modulation, angular sensitivity, polarization-independent diffraction efficiency and repeatable recording has been designed and fabricated in an azopolymer-silver double-layer film by means of two-step holographic exposure. A silver pattern is formed in the light field with the sinusoidally distributed intensity, and then a polarization holographic grating is recorded in the azobenzene liquid-crystalline layer through the interference of two orthogonally linearly polarized lasers. We report here that the polarization states of the diffraction beams from the recorded two-dimensional grating are orthogonally modulated; the diffraction efficiency is related to the incident angle of the probe light and the rotation angle between the two-step recording, while independent on the incident polarization state. Furthermore, the experimental results are analyzed through the scalar diffraction theory and Jones matrices. [ABSTRACT FROM AUTHOR]

The periodic oscillation of the optical transmittance in the nematic liquid crystals (5CB) doped with azobenzene compound (DR1) between two crossed polarizers has been demonstrated and investigated by monitoring the signal intensity variation of the transmitted light in different conditions of the light irradiation and environment temperature. It is found that the oscillation of the transmittance lasts more than 4 periods before the nematic–isotropic phase transition when the dye doped liquid crystal sample is heated from 20 to 40 °C. The oscillation is attributed to the continuous decrease of the birefringence of the dye doped liquid crystals with the temperature increasing. The oscillation curve shifts forward significantly when the sample is exposed to the pump light irradiation, which indicates that the pump light irradiation induces an additional decrease of the birefringence. A more accurate and comprehensive way for estimating the magnitude of the birefringence of the anisotropic materials is proposed based on the transmittance oscillation phenomenon. The switchable properties and the potential applications of the transmittance oscillation are discussed. [ABSTRACT FROM AUTHOR]

Area-selective deposition of self-assembled monolayers (SAMs) has been demonstrated on patterns of SiO2/Si(100). The pattern was fabricated by synchrotron radiation stimulated etching of SiO2 thin films on Si substrate. Several kinds of the patterns were obtained with different types of masks. A dodecene SAM was deposited on Si surface and an octadecyltrichlorosilane SAM was deposited on SiO2 surface. The deposited SAMs were densely packed and well ordered characterized by infrared spectroscopy, ellipsometry, and water contact angle measurements. [ABSTRACT FROM AUTHOR]

A nano-pattern of SiO2 on a Si (100) surface has been demonstrated by synchrotron-radiation-stimulated etching with a tungsten nano-pillar mask. The reaction gas was a mixture of SF6 and O2. The mask was fabricated using a focused ion beam with W(CO)6 as the source gas. The width and height of the tungsten nano-pillar were ∼80 nm and 160 nm, respectively. Synchrotron radiation irradiation with flowing SF6 and O2 effectively etches the silicon dioxide, and the etching process followed the surface photochemical reaction. The etched surface was very flat, and no undercutting occurred during the etching process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent progress in thermal debinding (TD) for stereolithography additive manufacturing (SLAM) of advanced ceramic parts are comprehensively reviewed. • Two key problems for TD of SLAM-printed advanced ceramic parts are undesired numerous defects and unacceptable long period. • Materials, processes, and applications that affect TD scheme design for SLAM-printed advanced ceramic parts are summarized. • Challenges and future prospects of TD for SLAM of advanced ceramic parts are presented. Stereolithography additive manufacturing (SLAM) has exhibited great potential for fabricating advanced ceramic objects with geometrically complicated structures for use in diverse fields owing to its excellent feature resolution and high surface quality. However, it is difficult to fabricate advanced ceramic parts with desired performance for structural and functional applications using this technology, because numerous binders used in ceramic SLAM must be removed by thermal debinding (TD), resulting in various defects generation and long processing period. In this review, we first focus on the raw materials used to create photocurable ceramic suspensions that greatly affect the TD process. We then highlight three important issues related to the TD process: TD mechanism, characterization method, and TD procedure design. Besides, this review summarizes the basis and principles for designing reasonable TD profiles for various practical applications. Finally, this review presents the challenges and future perspective for TD of ceramic SLAM. This review provides an overview of the crucial TD process for advanced ceramic components fabricated using SLAM approach, thus providing valuable reference information and helping readers grasp the theoretical foundation for the targeted design of TD schemes to stimulate the development of advanced ceramic parts manufactured by SLAM in both academia and industry. [ABSTRACT FROM AUTHOR]

Hybrid organic–inorganic metal halides have emerged as highly promising materials for a wide range of applications in optoelectronics. Incorporating chiral organic molecules into metal halides enables the extension of their unique optical and electronic properties to chiral optics. By using chiral (R)‐ or (S)‐methylbenzylamine (R‐/S‐MBA) as the organic component, we synthesized chiral hybrid copper halides, (R‐/S‐MBA)2CuCl4, and investigated their optical activity. Thin films of this material showed a record anisotropic g‐factor as high as approximately 0.06. We discuss the origin of the giant optical activity observed in (R‐/S‐MBA)2CuCl4 by theoretical modeling based on density functional theory (DFT) and demonstrate highly efficient second harmonic generation (SHG) in these samples. Our study provides insight into the design of chiral materials by structural engineering, creating a new platform for chiral and nonlinear photonic device applications of the chiral hybrid copper halides. [ABSTRACT FROM AUTHOR]

Hybrid organic–inorganic metal halides have emerged as highly promising materials for a wide range of applications in optoelectronics. Incorporating chiral organic molecules into metal halides enables the extension of their unique optical and electronic properties to chiral optics. By using chiral (R)‐ or (S)‐methylbenzylamine (R‐/S‐MBA) as the organic component, we synthesized chiral hybrid copper halides, (R‐/S‐MBA)2CuCl4, and investigated their optical activity. Thin films of this material showed a record anisotropic g‐factor as high as approximately 0.06. We discuss the origin of the giant optical activity observed in (R‐/S‐MBA)2CuCl4 by theoretical modeling based on density functional theory (DFT) and demonstrate highly efficient second harmonic generation (SHG) in these samples. Our study provides insight into the design of chiral materials by structural engineering, creating a new platform for chiral and nonlinear photonic device applications of the chiral hybrid copper halides. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SiC/Al composites was fabricated by LPBF combined with VPI. • The particle size distribution significantly affect the properties of the SiC/Al composites. • The pre-oxidation is beneficial for preventing the lamellar cracking. • The experimental data were in good agreement with the predicted values based on Kerner's model. A novel method has been developed to fabricate SiC/Al composites by the combination of laser powder bed fusion (LPBF) and vacuum-pressure infiltration. The effects of the SiC particle size distribution and pre-oxidation on the microstructure and properties of SiC/Al composites were investigated. A new phenomenon of severe lamellar cracking was observed in SiC/Al composites without pre-oxidation treatment, which can be explained in terms of the mechanism of interlayer bonding. The results showed that the residual porosity of the sample without pre-oxidation treatment s was higher than 3 %, with a maximum of (8.16±0.57) %, which was much higher than that of the pre-oxidised samples(1 % – 2%). The bulk density of the powders was significantly improved by designing the material system with mono-, bi-, and tri-modal particle size distributions and the density of final SiC/Al samples gradually increases from 2.804±0.009 to 2.871±0.008 g/cm3, and the volume fraction of SiC increases from 36.7 vol% to 50.1 vol%. As a result, the coefficients of thermal expansion (CTE) of SiC/Al composites varies consistently with the volume fraction of SiC, decreasing from 13.72 to 10.84×10−6 °C−1. Our study shows that this method has the potential for great applications. [ABSTRACT FROM AUTHOR]

SiC ceramic lattice structures (CLSs) via additive manufacturing (AM) have been recognized as potential candidates in engineering fields owing to their various merits. Compared with traditional SiC CLSs, SiC triply periodic minimal surface (TPMS) CLSs could possess more outstanding properties, making them more promising for wider applications. Since SiC CLSs are hard to be fabricated through stereolithography techniques because of inferior light performance, the laser powder bed fusion (LPBF) process via selective sintering is an effective method to prepare near‐net‐shaped SiC TPMS lattices. As the mechanical performances of lattice structures are the foundation for future practical applications, it is of great significance to optimize the preparation process, thus improving the mechanical properties of SiC TPMS structures. In this work, the optimal printing parameters of the LPBF and liquid silicon infiltration process for SiC ceramic TPMS CLSs with three different volume fractions were systematically illustrated and analyzed. The effects of the printing parameters and carbon densities on the fabrication accuracy, microstructure, and mechanical performance of SiC TPMS CLSs were defined. The mechanism of the reactive sintering process for the SiC TPMS lattice structure was revealed. The results reveal that Si/SiC TPMS CLSs with optimum preparation have superior manufacturing accuracy (most less than 6%), relatively high bulk densities (about 2.75 g/cm3), low residual Si content (6.01%), and excellent mechanical properties (5.67, 15.4, and 44.0 MPa for Si/SiC TPMS CLSs with 25%, 40%, and 55% volume fractions, respectively). [ABSTRACT FROM AUTHOR]

Manufacturing abrasion‐resistant superhydrophobic matters is challenging due to the fragile feature of the introduced micro‐/nanoscale surface roughness. Besides the long‐term durability, large scale at meter level, and 3D complex structures are of great importance for the superhydrophobic objects used across diverse industries. Here it is shown that abrasion‐resistant, half‐a‐meter scaled superhydrophobic objects can be one‐step realized by the selective laser sintering (SLS) 3D printing technology using hydrophobic‐fumed‐silica (HFS)/polymer composite grains. The HFS grains serve as the hydrophobic guests while the sintered polymeric network provides the mechanical strength, leading to low‐adhesion, intrinsic superhydrophobic objects with desired 3D structures. It is found that as‐printed structures remained anti‐wetting capabilities even after undergoing different abrasion tests, including knife cutting test, rude file grinding test, 1000 cycles of sandpaper friction test, tape test and quicksand impacting test, illustrating their abrasion‐resistant superhydrophobic stability. This strategy is applied to manufacture a shell of the unmanned aerial vehicle and an abrasion‐resistant superhydrophobic shoe, showing the industrial customization of large‐scale superhydrophobic objects. The findings thus provide insight for designing intrinsic superhydrophobic objects via the SLS 3D printing strategy that might find use in drag‐reduce, anti‐fouling, or other industrial fields in harsh operating environments. [ABSTRACT FROM AUTHOR]

The nonlinear absorption and optical limiting properties of a chiral polymer were investigated by employing Z-scan technique in femtosecond regime. Reverse saturable absorption was observed in the polymer at 800 nm and the nonlinear absorption coefficient of 5.97 cm/GW was obtained at the irradiance of 2.75 GW/cm2. The nonlinear absorption coefficient versus the input irradiance was measured to meet a linear increasing function, giving evidence of two-photon induced excited-state absorption existing. Particularly, the chiral polymer was shown to possess a large ratio (∼251) of excited-state to ground-state absorption cross-section and a remarkable optical limiting behavior was achieved in it. [ABSTRACT FROM AUTHOR]

Naturally ventilated urban vehicular tunnels with multiple roof openings have increased in China. Unnecessary gas (polluted air or fire smoke) are expected to be exhausted out through openings. Whether its safety standards can be satisfied or not still needs to be verified. In this paper, a safe CO concentration was firstly discussed, and a heat risk level of very high to extreme up to 46 °C was given. Secondly, a real 1410 m tunnel was proposed, and a 1/10 scale model tunnel was reproduced. Ambient winds of 0.95 m/s in prototype and 0.3 m/s in model were considered. Under normal traffic test, a track circuit was constructed with model vehicles moving on it to form traffic wind, and once the air velocity was larger than 0.31 m/s, the airflows were found to be not relevant to the Reynolds number. The traffic winds were weakened by openings. For three of all tested traffic, the actual air velocities were larger than the required ones, so its air qualities were satisfied. In firing test, two sets of burning experiments were conducted with which the heat release rates (HRR) were 8.35 kW and 13.7 kW. Large amounts of smoke were exhausted out of openings, and the high-temperature was not significant. Full-scale numerical simulations were carried out to verify the experimental results respectively using Fluent 6.0 for normal traffic and FDS 4.07 for firing. The simulations were compared well with the experiments. Further FDS simulations show that the openings’ mass flow rates are influenced little by ambient temperature; with the increasing length of the buried section, much smoke accumulate inside leading to a high temperature; having 4–5 openings in one shaft group is oversize in the actual engineering design. [ABSTRACT FROM AUTHOR]

High-volume-fraction SiC/Al (HVF-SiC/Al) composites have a wide range of applications in aerospace, optics, automotive and electronic packaging. However, because the hardness, brittleness and wear resistance increase with the increase in the volume fraction, it is difficult for traditional methods such as machining, to process HVF-SiC/Al composites to complex components. Therefore, in this paper, a novel method of the hybrid additive manufacturing is proposed to fabricate complex-structures SiC/Al composite parts. The effect of polymer infiltration and pyrolysis (PIP) on microstructure and properties of HVF-SiC/Al composites is investigated. The results show that the mechanical properties of the SiC preforms can be effctively enhanced by the PIP process, and this enhancement makes the SiC preforms meet the conditions for subsequent vacuum-pressure infiltration. The mechanical property of HVF-SiC/Al composites show a huge increase when in creasing the volume fraction of SiC. In particular, the flexural strength of HVF-SiC/Al composites increased from 202.28 MPa to 380.87 MPa, and the coefficient of thermal expansion (CTE) has also been reduced from 11.80 to 6.28 × 10−6/K, when the volume fraction of SiC increases from 42 to 80 vol%. For optimise the PIP process in the future, three theoretical models are used to predict the relationship between the CTE and the volume fraction of SiC. The results show that the experimental data are more consistent with the predicted values based on the Kerner's model, but deviate from the Rule-of-mixture (ROM) and Turner's models. Importantly, the complex-structures SiC/Al composite parts was successfully fabricated by this hybrid additive manufacturing. [ABSTRACT FROM AUTHOR]

Doping is known as an effective approach to extend the knowledge of structures and properties of clusters. Herein, Ge-doped boron clusters and their anions GeBn0/− with n = 6–20 are systematically investigated by using a spin-polarized density functional theory method to understand their structural evolution and electronic properties. The lowest-energy structures of GeBn and GeBn− clusters are globally searched with genetic algorithm. The doping of a Ge atom has significantly affected the growth behaviors of GeBn0/− clusters, leading to a structural evolution from three-dimensional configuration with a hypercoordinated Ge atom to planar or qusi-planar geometry and finally endohedral cage, in which Ge atom prefers the peripheral site or off-center position. Relative stability analysis identifies that GeB8, GeB10, GeB18, GeB7−, GeB9−, and GeB17− are magic clusters. The magnetic moments of GeBn and GeBn− clusters exhibit an evident odd–even oscillation behavior with cluster size, which is closely related to the interaction between the electronic states of Ge and B atoms. The simulated photoelectron spectra for GeBn− clusters can provide a valuable guidance for further experimental and theoretical research. [ABSTRACT FROM AUTHOR]

The nonlinear optical properties of an azobenzene-containing ionic liquid crystalline polymer were investigated by a single beam Z-scan technique employing 38 ps and 6 ns laser pulses at 532 nm. The polymer film exhibited large nonlinear refraction and negligible nonlinear absorption under both ps and ns pulses excitation. The nonlinear refractive indices of the polymer were in the order of $$10^{-11} \hbox {cm}^{2}/\hbox {W}$$ under ps excitation and $$10^{-8}\hbox {cm}^{2}/\hbox {W}$$ under ns excitation, respectively. The mechanism accounting for the process of nonlinear refraction was discussed in terms of photoinduced trans-cis transformation and thermal effect. [ABSTRACT FROM AUTHOR]

Abstract: Two-photon absorption and photoinduced anistropy of a methyl orange/Au nanoparticles composite system were investigated. Open aperture Z-scan measurements demonstrated that the absorption cross section of methyl orange in an Au colloid solution can increase 42-fold compared to purified that of a methyl orange aqueous solution. Meanwhile, a 2.6-fold enhancement of the photoinduced birefringence of methyl orange in the presence of Au was also observed. The mechanism accounting for the enhancement of two-photon absorption coefficient and photoinduced birefringence was discussed in terms of the localized field effect via surface plasmon resonance of Au nanoparticles, which was further confirmed using the fluorescence spectrum technique. [Copyright &y& Elsevier]

Abstract: A new type of core–shell nanostructure consisting of Au nanoparticles embedded in shells of Ag nanoparticles-filled polymer has been fabricated in a two-step procedure, in which Ag nanoparticles served as initial reductive agent for Au3+ ions with the existence of poly(vinylpyrrolidone). Upon ultrasonic irradiation, solidification and spherulite growth of the polymer was induced around the as-formed Au nanoparticles such that very small Ag nanoparticles were embedded in the crystalline polymer spherulites. UV/vis optical spectroscopy, transmission electron microscopy and high-resolution transmission electron microscopy have been used for structural characterization of these materials at various stages of the sonochemical synthesis. The growth mechanism was proposed for the composite nanostructure of Aucore/Ag-PVPshell. [Copyright &y& Elsevier]

Abstract: Photoinduced anisotropy in an azobenzene ionic liquid–crystalline polymer was investigated through dichroism, birefringence and polarization holography. A dichroism degree of 1.58 and a birefringence value Δn ∼10−2 were achieved in the polymer film at room temperature, and the polymer film was found to possess the characteristics of reversible and long-term optical storage. Particularly the stored birefringence could be enhanced to Δn ∼10−1 by annealing the film, and it is attributed to the thermal self-organization of the molecules. Furthermore, linear- and circular-polarization holographic recordings were accomplished in the polymer film and pure polarization gratings were produced. [Copyright &y& Elsevier]

Chirality, circular dichroism, hybrid copper halides, nonlinear optics, second harmonic generation Keywords: chirality; circular dichroism; hybrid copper halides; nonlinear optics; second harmonic generation EN chirality circular dichroism hybrid copper halides nonlinear optics second harmonic generation 21094 21094 1 09/16/21 20210920 NES 210920 Because the interference is not considered, formula (4) in this Communication is not really applicable for the I d SB eff sb i estimation of the hybrid metal halide thin film. [Extracted from the article]

Keywords: chirality; circular dichroism; hybrid copper halides; nonlinear optics; second harmonic generation EN chirality circular dichroism hybrid copper halides nonlinear optics second harmonic generation 21262 21262 1 09/16/21 20210920 NES 210920 Because the interference is not considered, formula (4) in this Communication is not really applicable for the I d SB eff sb i estimation of the hybrid metal halide thin film. Chirality, circular dichroism, hybrid copper halides, nonlinear optics, second harmonic generation. [Extracted from the article]

Two new azo-dye chromophores containing different electron-acceptor groups were synthesized and characterized by 1H NMR, FT-IR and UV-vis spectra, respectively. The second-order nonlinearity of azo-dyes doped films in poly (methylmethacrylate) and the first hyperpolarizability of the azo molecules were investigated by the Maker Fringe method and the solvatochromic method, respectively. Experimental results showed that both of the two dyes exhibited large second-order nonlinearity (d33 > 30 pm/v) and the stronger electron-acceptor groups in dye molecules would induce larger second-order nonlinearity. This was confirmed by the measurement of the first hyperpolarizability. [ABSTRACT FROM AUTHOR]

Plasmonic nanostructures exhibiting interior nanopores have found increasing applications in the fields of sensors and surface-enhanced Raman scattering due to controllable optical properties and built-in hotspots. Nonetheless, precise control over density of the nanopores in three-dimensional nanostructures remains a great challenge. In this study, we propose an effective synthesis strategy for porous Au–Ag alloy nanorods (P-AuAgNRs) by dealloying of Ag atoms from solid Au–Ag alloy nanorods in the presence of Fe(NO3)3. The strategy produced P-AuAgNRs with various degrees of porosity, which demonstrated a facile plasmonic tunability across visible to near-IR regions (indicated by longitudinal surface plasmon resonance peaks). Furthermore, experimental observations and theoretical finite-difference time-domain simulations indicated that P-AuAgNRs exhibit numerous internal hotspots which favor highly sensitive surface-enhanced Raman scattering (SERS) detection for rhodamine 6G and 4-nitrothiophenol. The enhanced SERS performance was remarkably maintained under oxidative environments. Overall, we demonstrated the reliability of the proposed strategy for synthesizing P-AuAgNRs with controlled nanopores and internal hotspots. Thus, we recommend the adoption of this strategy for the preparation of other porous nanoparticles exhibiting intrinsic hotspots for SERS-based analytical sensors and imaging application. [ABSTRACT FROM AUTHOR]

Background and aims: Dissolved organic nitrogen (DON) has been increasingly recognized as a crucial component of the terrestrial nitrogen (N) cycle that regulates the ecosystem feedback to climate change. Yet, little information is available about the factors that control soil DON in the alpine ecosystems of the Tibetan Plateau, a region that is extremely sensitive to climate change. Methods: Here, we examined the relationship between DON and climate, plant, and soil attributes along a precipitation gradient in five alpine ecosystems (alpine wetland, alpine meadow, alpine shrub, alpine steppe, and alpine desert) across 20 sites that were up to 4000 km apart on the Tibetan Plateau. Results: Results showed that soil DON concentration varied significantly across these alpine ecosystems, and had a positive relationship with mean annual precipitation. Belowground biomass, soil moisture, micro biomass carbon (MBC), and soil total phosphorus (TP) explained 84% of the variation in DON concentrations. The percentage of DON in soil total dissolved N (TDN) varied with vegetation type, with the lowest percentage observed in the alpine meadow (52%) and the highest in the alpine desert (77%), indicating the slow turnover of DON into inorganic N in systems with low litter input and microbial activity. Conclusions: Precipitation and plant biomass input determine the concentration and turnover of soil DON on the Tibetan Plateau. A warmer and wetter climate that has been predicted for the Tibetan grasslands may lead to a larger and more active DON pool. [ABSTRACT FROM AUTHOR]