Theoretical analysis and experimental research on thermal focal length of a YVO_4/Nd:YVO_4 composite crystal

This paper investigates the temperature field distribution and thermal focal length within a laser diode array （LDA） end-pumped YVO4/Nd：YVO4 rectangular composite crystal. A general expression of the temperature field distribution within the Nd：YVO4 rectangular crystal was obtained by analysing the characteristics of the Nd：YVO4 crystal and solving the Poisson equation with boundary conditions. The temperature field distributions in the Nd：YVO4 rectangular crystal for the YVO4/Nd：YVO4 composite crystal and the Nd：YVO4 single crystal are researched respectively. Calculating the thermal focal length within the Nd：YVO4 rectangular crystal was done by an analysis of the additional optical path differences （OPD） caused by heat, which was very identical with experimental results in this paper. Research results show that the maximum relative temperature on the rear face of the Nd：YVO4 crystal in the composite crystal is 150 K and the thermal focal length is 35.7mm when the output power of the LDA is 22 W. In the same circumstances, the experimental value of the thermal focal length is 37.4 mm. So the relative error between the theoretical analysis and the experimental result is only 4.5%. With the same conditions, the thermal focal length of the Nd：YVO4 single crystal is 18.5 mm. So the relative rate of the thermal focal length between the YVO4/Nd：YVO4 crystal and the Nd：YVO4 crystal is 93%. So, the thermal stability of the output power and the beam quality of the YVO4/Nd：YVO4 laser is more advantageous than the laser with Nd：YVO4 single crystal.

Crystallization characteristics of Ni-W-P composite coatings reinforced by CeO_2 and SiO_2 nano-particles

Ni-W-P composite coatings reinforced by Ce O2 and Si O2 nano-particles on the surface of common carbon steels, were prepared by double pulse electrodeposition. The crystallization course was characterized by phase structures, crystallinity, grain sizes and microstructures. The results indicate that as-deposited composite coating is amorphous. Whereas it turns into the crystalline structure with 98.25% crystallinity, and Ni3 P, Ni2 P and Ni5P2 alloy phases precipitate from structures at 400 °C. Thereafter, Ni2 P and Ni5P2 metastable alloy phases turn into Ni3 P stable alloy phase at 500 °C. The crystallization course of the composite coating has finished when being heat-treated at 700 °C. The average sizes of Ni grains increase with the rise of heat treatment temperature from400 °C to 700 °C. Ce O2 and Si O2 nano-particles deposited into Ni-W-P alloys can delay the crystallization course and habit the growth of alloy phases.

Effective Anisotropic Dielectric Properties of Crystal Composites

Transformation fieM method （TFM） is developed to estimate the anisotropic dielectric properties of crystal composites having arbitrary shapes and dielectric properties of crystal inclusions, whose principal dielectric axis are different from those of anisotropic crystal matrix. The complicated boundary-value problem caused by inclusion shapes is circumvented by introducing a transformation electric field into the crystal composites regions, and the effective anisotropic dielectric responses are formulated in terms of the transformation field. Furthermore, the numerical results show that the effective anisotropie dielectric responses of crystal composites periodically vary as a function of the rotating angle between the principal dielectric axes of inclusion and matrix crystal materials. It is found that at larger inclusion volume fraction the inclusion shapes induce profound effect on the effective anisotropic dielectric responses.

Carbon fiber reinforced liquid crystalline elastomer composites:a dual exploration in strength augmentation and transformation flexibility through 4D printing

Liquid Crystal Elastomers(LCEs)are renowned for their reversible deformation capabilities.Yet,enhancing their mechanical strength while retaining such flexibility has posed a considerable challenge.To overcome this,we utilized 4D printing to develop an innovative composite of LCE with carbon fiber fabric(LCEC).This approach has notably increased the tensile strength of LCE by eightfold,all the while maintaining its exceptional capacity for reversible deforma-tion.By adjusting the alignment angle between carbon fiber and the LCE printing direction from 0°to 90°,the LCEC demonstrates an array of new deformation patterns,including bending,twisting,wrapping,and S-shaped transformations,which are distinct from pure LCE materials.Our study unveils that LCE composites exhibit deformation processes markedly different from their pure material counterparts,with the ability of pure LCE to sustain tensile strains exceeding 1900%.These findings,previously undocumented and unexplored,represent a substantial contribution to the field of smart materials.Employing finite element analysis,we explored the carbon fiber and LcE matrix dynamics,revealing bending mechanics in LCECs.This combined experimental and simulation approach yields crucial insights for crafting durable,high-strength LCECs with diverse deformational properties,advancing smart material technology.

Improved photocatalytic performance of acetaldehyde degradation via crystal plane regulation on truncated octahedral CeO_(2)

In this study,the truncated octahedral CeO_(2)(CeO_(2)-to)with special morphology was prepared by the solvothermal method with oleic acid(OA)and oleamine(OM)as the morphology-directing agents.High-resolution transmission electron microscopy(HRTEM)results show that CeO_(2)-to exposes composite{100}and{111}facets,while CeO_(2)cubic(CeO_(2)-c)and CeO_(2)octahedral(CeO_(2)-o)only expose single crystal facets of{100}plane and{111}plane,respectively.Interestingly,this CeO_(2)-to photocatalyst exhibits remarkable photooxidation performance of gaseous acetaldehyde(CH_(3)CHO)degradation,in which CO_(2)generation value reaches 1.78 and 7.97-times greater than that of CeO_(2)-c and CeO_(2)-o,respectively.In addition,the active species trapping experiment signifies that superoxide(·O_(2)^(-))and holes(h^(+))are the main reactive substances during the CH_(3)CHO degradation process,and the electron paramagnetic resonance(EPR)spectra indicates that the former is the major contributor.Notably,the electron transfer mechanism between CeO_(2)-to{100}and{111}facets and the surface oxygen adsorption ability are revealed via density functional theory(DFT)calculations.It is also confirmed that{100}facets are more conducive to the absorption of acetaldehyde than{111}facets.Finally,a reasonable mechanism for improved photocatalytic CH_(3)CHO degradation on CeO_(2)-to is proposed based on relevant experiments and DFT calculations.This study demonstrates that the systematic development of surface homojunction structured photocatalysts can efficiently increase the degradation activity for volatile organic compounds(VOCs).It also offers additional direction for optimizing the photocatalytic activity of other ceriumbased photocatalysts.

Programming Shape-Morphing Behavior of Zwitterionic Polymer/Liquid Crystal Composite with Humidity-responsive Self-healing Performance

In this study,a zwitterionic polymer/liquid crystals composite film with programming shape-morphing behavior and humidityresponsive self-healing performance was prepared by blending a zwitterionic polymer and liquid crystalline azobenzene compound in solution,followed by film-forming in a mold without tedious or multistep synthetic route.The as-obtained zwitterionic polymer/liquid crystal composite film exhibited programming shape-morphing behavior under different stimuli.In this process,the temporary shape of the composite film was memorized after the removal of the stimuli.Such characteristics would fit the requirements of intelligence and energy-saving for stimuliresponsive shape-changing materials.Moreover,the composite film showed humidity-responsive self-healing performances under wet conditions at room temperature.In summary,the simple design and preparation route of the zwitterionic polymer/liquid crystal composite film with programming shape-morphing behavior and mild condition-responsive self-healing performance look promising for the fabrication and practical application of novel photo-driven devices and soft robotics.

A Luminescent Dicyanodistyrylbenzene-based Liquid Crystal Polymer Network for Photochemically Patterned Photonic Composite Film

A novel photonic composite film based on a luminescent dicyanodistyrylbenzene-based liquid crystal polymer network（LCN） was fabricated by using a silica colloidal crystal as a template. The upper part of inverse opal structure and the luminescence characteristics of dicyanodistyrylbenzene-based moiety endowed the resulting bilayer photonic film with structural color arising from coherent Bragg reflection and fluorescence properties, respectively. A fluorescence enhancement phenomenon was observed in the photonic film due to the overlap between the reflection band and emission band of the fluorescent LCN. More importantly, the photo-induced irreversible Z/E photoisomerization of dicyanodistyrylbenzene-based moiety in the photonic film led to both a reflection spectral shift and an observable fluorescence variation. On the basis of this effective phototuning process, microscopic patterning of photonic film was developed under both fluorescence mode and reflection mode. The work demonstrated here provides a new route to construct photo-responsive photonic film.

Pulsed-Laser Annealing of NiTi Shape Memory Alloy Thin Film

Local annealing of amorphous NiTi thin films was performed by using an Nd：YAG 1064 nm wavelength pulsed laser beam. Raw samples produced by simultaneous sputter deposition from elemental Ni and Ti targets onto unheated Si （100） and Silica （111） substrates were used for annealing. Delicate treatment with 15.92 W/mm^2 power density resulted in crystallization of small spots; while 16.52 and 17.51 W/mm^2 power densities caused ablation of the amorphous layer. Optical microscopy, scanning electron microscopy, X-ray diffraction and atomic force microscopy were performed to characterize the microstructure and surface morphology of the amorphous/crystallized spot patterns.

Long-range ordering of composites for organic electronics:TIPS-pentacene single crystals with incorporated nano-fibers

Multi-component active materials are widely used for organic electronic devices, with every component contributing complementary and synergistic optoelectronic functions. Mixing these components generally leads to lowered crystallinity and weakened charge transport. Therefore, preparing the active materials without substantially disrupting the crystalline lattice is highly desired. Here, we show that crystallization of TIPS-pentacene from solutions in the presence of fluorescent nanofibers of a perylene bisimide derivative （PBI） leads to formation of composites with nanoflber guest incorporated in the crystal host. In spite of the binary composite structure, the TIPS-pentacene maintains the single- crystalline nature. As a result, the incorporation of the PB1 guest introduces additional fluorescence function but does not significantly reduce the charge transport property of the TIPS-pentacene host, exhibiting field-effect mobility as high as 3.34 cm^2 V^-1 s^-1 even though 26.4% of the channel area is taken over by the guest. As such, this work provides a facile approach toward high-performance multifunctional organic electronic materials.

Hexagonal trumpet-like flowers growth induced by a colloidal crystal composite film

Hexagonal trumpet-like sodium hexafluorosilicate （SFS） flowers, grown on an ordered porous polystyrene film （OPPF）, were prepared via a synchronous dissolution/regrowth process. Their formation process can be divided into several steps： first, the dissolution of the silica spheres induced the crystallization of SFS onto the OPPF; second, some pores emerged on the closely packed bumps when being blown by the SiF4 gas; third, when the crystal was blown by continuous gas from the pores, the span of the top became larger than that of the bottom.