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Recently, laser cladding has been widely investigated for the preparation of Co-based coatings for high-temperature applications. However, there is a highly cracking tendency in Co-based alloys due to the reinforcing hard phases. In this work, a single layer of CoCrMoSi coating was prepared with laser cladding on 304 stainless steel. By proper preheating, cracking was avoided during deposition. The high-temperature wear behaviors of the coating were evaluated by ball-on-disk test. In terms of morphology and chemical composition, the coating exhibited a gradient microstructure across the section. From the interface with the substrate to the top surface, the structure was characterized with three types of morphology in sequence, i.e., coarse cellular crystals in the interdiffusion zone, nanosized lamellar eutectic and Laves-phase dendrites embedded within nanosized lamellar eutectic. The surface hardness of the coating is 835HV0.3, which was mainly attributed to the Laves phase. Compared with the 304 stainless steel, the volume loss of the coating decreased by 76.5%at 400°C. The wear mechanisms of the coating were oxidation wear and abrasive wear. The excellent coating wear resistance at high-temperature can be traced to the microstructure of Laves phase embedded within the nanosized eutectic.

Hierarchical nano-sized ZSM-5 aggregates were successfully synthesized via a seed-assisted method in the presence of cetyltrimethylammonium bromide (CTAB) through a facile one-step crystallization process. Commercial ZSM-5 zeolites with a SiO2/Al2O3 ratio comparable to that of ZSM-5 products were treated with alkali and used as the seed particles. The influences of crystallization conditions were investigated, and the possible synthesis mechanism was proposed. ZSM-5 zeolites with different amounts of CTAB added were characterized using many techniques and evaluated in toluene alkylation with methanol. The results showed that a trace amount of CTAB significantly promoted the crystallization of ZSM-5 zeolite, with the morphology changing from hexagonal-shape crystals to uniform spherical aggregates. CTAB may act as the structure-directing agent and assemble the primary crystallites to generate hierarchical ZSM-5 aggregates. The ZSM-5 zeolite with the smallest primary particles of 50–80 nm exhibited large specific surface area, abundant mesopores, and the greatest microporosity. The hierarchical nano-sized ZSM-5 aggregate showed higher toluene conversion and a longer lifetime without compromising the selectivity to xylene and p-xylene in toluene alkylation with methanol.

Thermal spraying has been widely used to obtain functional surface coatings against wear or corrosion in various industrial fields. However, pores and low bonding strength are the two inevitable drawbacks for thermal-sprayed coatings. In this study, a hybrid process combining thermal spraying with laser beam irradiation was employed to solve the drawbacks. A Cr3C2-NiCr cermet coating was processed successively by high-velocity oxygen-fuel spraying and laser remelting. A fully dense remelt layer without any cracks was successfully obtained. The remelt layer was composed of fused steel base metallurgically bonded with cermet coating, showing a transverse gradient microstructure in aspects of chemical composition and grain shapes. On the top surface, chemical composition and phases from the original coating were preserved, contributing to the enhanced properties of electrochemical corrosion and wear resistance. The improvement was discussed in terms of structure densifying and homogenization. The enhanced properties by the HVOF/laser hybrid process indicate promising application in industrial fields.

Laser shock peening (LSP) is a competitive surface strengthening technology for post-weld treatment. In this work, tungsten inert gas (TIG) welded joints of Alloy 600 were treated by LSP to enhance the mechanical properties. The results showed that the tensile residual stress in weld surface was transformed into the compressive stress state after LSP. LSP treatment caused a significant improvement in microhardness and dislocation density in the weld surface. The tensile strength and yield strength of joints after peening on the full gauge part of tensile samples were increased by 10% and 75%, respectively. However, the fatigue life could be improved much more by only peening on the fusion zone and heat affected zone than that of samples peened on the full gauge part. The peening region played a crucial role on the difference of tensile and fatigue properties due to the residual stress distribution, dislocation strengthening and work hardening induced by LSP.

We develop a stoichiometric silicon nitride (SiN) membrane-based electromechanical system, in which the spring constant of the mechanical resonator can be dynamically controlled via piezoelectric actuation. The degenerate parametric amplifier is studied in this configuration. We observe the splitting of mechanical mode in the response spectra of a phase-sensitive parametric amplifier. In addition, we demonstrate that the quality factor Q of the membrane oscillator can be significantly enhanced by more than two orders of magnitude due to the coherent amplification, reaching an effective Q factor of ∼3 × 108 at room temperature. The nonlinear effect on the parametric amplification is also investigated, as well as the thermomechanical noise squeezing. This system offers the possibility to integrate electrical, optical and mechanical degrees of freedom without compromising the exceptional material properties of SiN membranes, and can be a useful platform for studying cavity optoelectromechanics.

Composites with enhanced refractive index have been synthesised through a sol–gel process. A refractive index of approximately 1.70 has been achieved at a concentration of 75 wt% TiO2. The refractive index increases with the concentration of TiO2. The influence of the concentration of TiO2 on the mechanical properties has been studied. The potential application of these materials in photonics area has been demonstrated by fabricating multi-layer spherical voids in them through a femtosecond laser-driven micro-explosion method.

A single-monomer acrylate resin (SR348, Sartomer) with an aromatic ketone photoinitiator (Irgacure 369, Ciba) has been developed to produce photonic crystal structures by two-photon photopolymerisation. Compared with more complex acrylate-based resins, this one-component resin is easily prepared. The material is homogeneous before and after photocuring and has a high photosensitivity. SR348 (ethoxylated (2) bisphenol A dimethacrylate) is a difunctional monomer, which generates an insoluble crosslinked network by free radical polymerisation. The polymerised material is thermally stable up to 300 °C. Its refractive index jumps from 1.54 to 1.59 upon polymerisation. Scanning electron microscopy images of photonic crystal structures reveal a minimum structural element size of approximately 300 nm. The photonic crystals were fabricated in a 40 layer woodpile structure at a layer-spacing of 500 nm and an in-plane rod spacing of 1.5 μm. Fundamental stop gaps were observed in the stacking direction at wavelengths of 1.9–2.3 μm dependent on the rod size. Suppression of infrared light transmission of as much as 40% in the stop gap region and gap/midgap ratios of up to 0.15 demonstrate the high degree of correlation of structural elements in three dimensions.

In this paper we report on the application of polarisation encoding in three-dimensional (3D) bit data storage within azo dye doped polymer. Two letters are encoded in the same region of the medium by the two-photon-induced birefringence.

In this paper we report on two-photon-excited bit by bit data storage within a photorefractive polymer composed of 53.9 weight percents of PVK (poly(N-vinylecarbazole)), 30wt% of DMNPAA (2,5-dimethyl-4-(p-nitrophenylazo)anisole), 16wt% of ECZ (N-ethylcarbazole) and 0.1 wt% of CdS quantum dots as a sensitizer. Multi-layer data sets with a layer spacing 20 mu are recorded using a pulsed ultrashort laser at a wavelength of 780 nm

We demonstrate the formation of complete pieces of high refractive-index three-dimensional inverse woodpile photonic crystals by a simple and inexpensive sol-gel process. A mixture of the titanium dioxide precursor and the silica dioxide precursor was infiltrated multiple times into a polymeric template produced by two-photon polymerization to improve the mechanical properties of the inverse structure. After removal of the polymer template, transparent inverse photonic crystals with a refractive index of approximately 2.2 were achieved. The spectroscopic characterization reveals a stop gap in the near-infrared wavelength range, agreeing with the theoretical prediction.

We report a rewritable polarization-encoded multilayer data storage method with a polymer film doped with the azo dye DMNPAA (2,5-dimethyl-4-(p-nitrophenylazo)anisole). It is found that under two-photon excitation by a linearly polarized femtosecond laser beam at wavelength 780 nm the optical axis of DMNPAA molecules can be oriented to the perpendicular direction of the beam via a trans-cis-trans isomerization process. As a result, multilayer polarization-encoded optical data storage is demonstrated by recording two letters of a bit spacing of 4 microm in the same region of a given layer. It is shown that erasing and rewriting a particular layer is possible.

As a promising candidate for the next generation communication and information systems, photonic crystals (PCs) have received intensive research interests in the past few years. To explore the advanced functionalities of PCs, three-dimensional (3D) structures with a complete bandgap are crucial. To this end, materials of high refractive index contrast have to be employed to fabricate 3D PCs.