Search

MgAlON transparent ceramic was prepared via pressureless sintering and post hot isostatic pressing. The in-line transmittance of MgAlON ceramic exceeds 80% in the range 0.39–4.67 μm, and the ceramic was fully dense with average grain sizes ∼55 μm. The mechanical properties at the grain boundary (GB) and the center of the grain (CG) of MgAlON ceramic was investigated by nanoindentation at forces of 1 × 102–3 × 105 μN. The results indicated that the hardness values of MgAlON ceramic were sensitive to the testing forces and measurements position. The hardness at GB zone was lower than that at CG zone, which was probably ascribed to weaker interatomic bonding force in GB area. The Meyer's index of the hardness in GB and CG regions is 1.87 and 1.82, respectively. There is a weaker ISE in GB area of MgAlON as a result of larger plasticity and smaller elasticity. The hardness values of GB and CG regions are ∼13.36 GPa and ∼13.58 GPa, respectively.

Sintering aid was very crucial to influence the microstructure and thus the optical property of the sintered optical ceramics. The purpose of this work was to explain the difference between the sintering aids of Li

Combining the advantages of high thermal conductivities and low graphene contents to fabricate polymer composites for applications in thermal management is still a great challenge due to the high defect degree of exfoliated graphene, the poor orientation of graphene in polymer matrices, and the horrible phonon scattering between graphene/graphene and graphene/polymer interfaces. Herein, mesoplasma chemical vapor deposition (CVD) technology was successfully employed to synthesize vertically aligned graphene nanowalls (GNWs), which are covalently bonded by high-quality CVD graphene nanosheets. The unique architecture leads to an excellent thermal enhancement capacity of the GNWs, and a corresponding composite film with a matrix of polyvinylidene fluoride (PVDF) presented a high through-plane thermal conductivity of 12.8 ± 0.77 W m

The stability of AlON powder in the aqueous system was studied during the gel-casting procedure of AlON ceramic. The pH value of AlON slurry, the phase assemblage and the morphology of AlON powder all suggested the excellent stability of untreated AlON powder even in hot water. Finally, highly-transparent AlON ceramic pellets (D = 110 mm and D = 22 mm) were fabricated by a feasible and easy aqueous gel-casting method. The polished AlON ceramics with 3.5 mm thickness possesses the highest inline transmittance above 86% at the wavelength of 2000 nm.

Diamond films prepared by chemical vapor deposition will exhibit different surface morphologies, which are determined by the texture and the structural perfection of the deposited diamond. In general, its surface morphology can be controlled by adjusting the deposition conditions. In the present work, textured diamond film was deposited on single crystalline silicon through pre-seeding by diamond nanosheets, rather than controlling the deposition conditions. The employed diamond nano-sheets were prepared by cleavage along a plane, exhibiting good crystallinity. Before chemical vapor deposition, the as-prepared diamond nano-sheets were pre-seeded on the surface of single crystalline silicon as nucleation sites for diamond growth. SEM and XRD results show that the prepared diamond films have a texture. FIB observation reveals that diamonds homogeneously grow on the pre-seeded diamond nano-sheets during chemical vapor deposition, achieving the diamond film with texture. Our work provides a new strategy to prepare textured diamond film.

Cubic polycrystalline LiAlON solid solution ceramics with differential transparencies were prepared by solid-state reaction sintering and post-HIP. The light transmission properties of the ceramics were studied via in-line transmittance (IT) and real in-line transmittance (RIT) measurements. The main scattering resources were characterized via SEM and EDS analysis. It was suggested that, composition inhomogeneity in the solid solution could contribute to strong light scattering with low RIT even though the IT is very high. LiAlON ceramic with high transparency (RIT up to 85.5%) was mainly benefited from the eliminations of composition inhomogeneity and residual pores.

MgAlON and AlON powders have been synthesized by carbothermal reduction and nitridation (CRN) from C–Al2O3–7.8 wt% MgO and C–Al2O3 systems, respectively. The phase and morphology of the systems were investigated under 1100–1750 °C via XRD, DTA, SEM and NMR. The results showed that, MgO could significantly effected the stabilization region and morphology of the (Mg)AlON products. The formation of spinel MgAl2O4s intermediate phase was key to obtain MgAlON at lower temperature with smaller particles than that of AlON. Under the optimized compositions, single-phase MgAlON and AlON were obtained at 1600 °C and 1720 °C, respectively. When sintered at 1850 °C for 24 h, the MgAlON sample was clear with highly transparency (82.5% at 3.7 μm), while AlON was opaque with lower transmittance (∼8.0% at 4.7 μm) due to lower sintering activity of the powder.

In the present work, highly-transparent aluminum oxynitride (AlON) ceramic has been fabricated by hot isostatic pressing sintering method. SiO2 was used for the first time as a sintering additive for producing highly-transparent AlON ceramics where it plays an effective role to promote the densification during hot isostatic pressing sintering. Furthermore, the optical property of the AlON ceramic is not sensitive to the change of additive concentration when SiO2 was used. All the 3.5 mm thick samples doped with 0.15 wt% ∼0.55 wt% SiO2 showed a high inline transmittance above 86% at 2000 nm. The effects of SiO2 on the phase, lattice parameter, microstructures and hardness of AlON have been investigated in details.

Shock impedance matching between transparent ceramic windows and shock-loaded metal materials is the fundamental requirement for constructing a highly confident equation of state (EOS) for samples testing. The new ZnxMg1-xAl2O4 spinel system has a wide range of shock impedance and a high pressure range transparency. In this paper, the shock impedance of ZnxMg1-xAl2O4 spinel was designed by density functional theory (DFT). The results show that the ZnxMg1-xAl2O4 system has good transparency in the test range of

In the biological world, due to the body’s microstructure can interfere with light in an orderly manner, many animals produce different colors after receiving environmental stimuli which is vital to the species’ survival. Researchers have discovered that beautiful colors are not produced by pigments, but by an ordered arrangement of dots or thin lines. In this chapter, we introduced the development and imitation of variable structural colors, by learning from nature, we prepared and characterized the bionic colloidal crystal coatings. We also introduced the photochromic mechanism in bionic colloidal crystals coatings. This project will be of major significance to broaden the application of colloidal crystals, improve the property of current coatings, provide the design reference for future coatings, and reduce the pollution in traditional paint or dye productions.

Highly transparent MgAlON ceramics were fabricated by pressureless presintering and hot isostatic pressing. The deformation, hardness and fracture toughness of MgAlON transparent ceramics have been studied by nanoindentation technique. The indentation tests were performed with applied loads of 2–400 mN to investigate the variation in mechanical behaviors. It was found that the plastic deformation component dominated MgAlON ceramics at the applied loads from 2 mN to 200 mN. The resistance to plastic deformation decreased when the applied load increased. However, the micro-cracks induced by nanoindentation have been observed at the load above 200 mN. In addition, the true hardness (∼13.5 GPa) was determined based on the proportional sample resistance (PSR). Furthermore, the fracture toughness (2.2–2.7 MPa m1/2) was evaluated using Laugier's equation. This study lends credible the realization of mechanical properties of the MgAlON transparent ceramics in the design and practical applications.

Using the co-precipitated Nd:YAG and YAG powders as raw materials, the Nd:YAG/YAG composite ceramics (Ф 50 mm × 5 mm) were prepared by vacuum sintering (1790 °C 50 h), followed by hot isostatic pressing (HIP) post treatment (1700 °C 2 h, 200 MPa Ar atmosphere) and air annealing (1250 °C 100 h). The optical properties of Nd:YAG/YAG samples were improved markedly by HIP post-treatment, mainly due to the elimination of residual pores in the samples. The composite sample showed a perfect bonding interface from Nd:YAG to YAG regions without obvious grain size difference, pores or other defects. This structure should be responsible for the thermal conductivity larger than that of non-composite sample. The composite sample revealed good optical properties with transmittance up to 83.9% at 1064 nm and 80.8% at 400 nm, and a maximum laser output power of 1.38 KW with the slope efficiency of 36.7% was obtained.

MgAlON transparent ceramics are fabricated by pressureless sintering using the carbothermal raw powder. The obtained MgAlON powder is well crystallined and exhibits a spinel structure. It shows a bimodal particle size distribution (PSD) at 0.3 μm and 0.9 μm. An investigation on the microstructural sintering evolution indicates the stages of significant densification at the intermediate temperature regions (1600–1700 °C) and rapid grain growth at higher temperature (1750–1850 °C). Additional holds at the intermediate temperature are effective to controlling the microstructure with reduced porosity, which in turns, improving the transmittance. The sample with hold at 1700 °C for 2 h followed by 1850 °C for 20 h exhibits excellent transmittance from the visible to middle infrared (IR) regions, achieving 86.59% at 3.70 μm and 82.37% at 0.60 μm.

Highly transparent MgAlON ceramic was prepared by hot isostatic pressing (HIP) of the presintered compact using the MgAlON powder synthesized by carbothermal reduction and nitridation (CRN) method. Fine and low agglomerated MgAlON powder was synthesized at a relatively low temperature (1600 °C) for 2 h under N2 atmosphere. The MgAlON powder showed high sinterability with a bimodal particle size distribution at 0.3 µm and 0.7 µm. MgAlON ceramics were fabricated by pressureless presintering at 1840 °C for 10 h in N2 atmosphere and HIP at 1880 °C for 2 h in 190 MPa Ar gas. The HIPed ceramic was fully dense with average grain sizes ~ 50 µm. The in-line transmittance of the HIPed sample reached ~ 81.2% at 400 nm and ~ 84.1% at 2500 nm, respectively. The Vickers hardness and flexural strength of highly transparent MgAlON ceramic were 13.74 ± 0.15 GPa and 268 ± 7 MPa, respectively. The results demonstrate that our method has a promising future in transparent MgAlON ceramic production.

Three-dimensional ordered macroporous (3DOM) materials based on fullerenes (C60) were prepared by using silica (SiO2) colloidal crystals as templates. The silica colloids were deposited in an orderly manner onto the gold surface, followed with the infiltration of the C60 nanoparticles into the interspaces of the colloids. The as-formed SiO2/C60 hybrid colloidal crystals were subsequently immersed in hydrofluoric acid to remove the silica components fully to obtain 3DOM C60 frameworks. The control of the C60 infiltration solution concentration is the key to obtaining a high quality 3DOM structure of C60. The band gaps of the SiO2 colloidal crystal, SiO2/C60 hybrid colloidal crystal and 3DOM C60 were measured by UV-Vis reflection spectrometry, calculated using Bragg's law, and simulated by Band SOLVE, respectively. It was demonstrated that the 3DOM C60 possesses electrochemical activity and can be used in detecting dopamine with a detection limit of 1.3 × 10−9 mol L−1. Having a three-dimensional ordered macroporous structure with a greater surface area, the 3DOM C60 modified electrode performed better than an unordered C60 modified electrode and a bare gold electrode.

The test section of Changzhou North Railway Station of Rail Transit Line 1 is taken as the engineering background. It is before the shield tunnel passes through the Beijing-Shanghai high-speed railway. With software of PLAXIS 3D, the numerical simulation on surface deformation is conducted considering the influence of shield tunnelling, based on the M-C. HS and HSS model. The calculated results of the three models are compared with the monitoring data. It is shown that the HSS model is optimal. In addition, the applicability of 0.5% and 0.8% for the loss rate of shield tunnelling in Changzhou is studied. It is reasonable to adopt 0.5% stratum loss rate for general shield tunnel conditions. But, sometimes in order to consider the special conditions such as deviation rectification construction, stratum loss rate should be set at 0.8%.

In this paper, we reported an effective microfluidic-based method for fast continuous synthesis of monodisperse PEG/SiO2 hybrid microspheres. The T-junction microfluidic chip equipped with rounded channels and the online photopolymerization system were applied for the microspheres microfabrication. The size of the microspheres was well controlled by the rounded channels and flow rate ratios of immiscrible fluids. We can obtain porous PEG microspheres when the hybrid microspheres were corroded by hydrofluoric acid. What's more, the interpenetrating polymer network structures of SiO2 microspheres were obtained after the hybrid microspheres treated via a calcination process.

Fe3O4-nanoparticles/polystyrene (Fe3O4-NPs/PS) composite microspheres were synthesized using a modified dispersion polymerization method. The distribution and content of Fe3O4-NPs in the microspheres were studied. Using the Fe3O4-NPs/PS microspheres as templates, Fe3O4-NPs/SiO2 core-shell hollow microspheres with excellent magnetic property and large cubage were synthesized facilely. The obtained Fe3O4-NPs/SiO2 core-shell hollow microspheres had a potential application in detoxification extraction and rapid waste removal with a very simple procedure.

Monodisperse silica microspheres have drawn much attention for having important applications in many areas. In this paper, a series of monodisperse silica (SiO2) microspheres was synthesized successfully using a modified Stober method in which tetraethyl orthosilicate (TEOS) was continuously supplied into the reaction system by a syringe pump. By changing the supply rate of TEOS, the diameters of the obtained SiO2 microspheres were controlled very well from 1 μm to 3 μm. Detailed characterization of the silica particles was performed using scanning electron microscopy (SEM).

The oxidation behavior of AlON translucent ceramic was investigated both in non-isothermal (from room temperature to 1573 K) and isothermal (at 1373 and 1473 K) conditions. The mass gains, phase compositions and micromorphology of oxidized samples were examined by thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. The results suggest that in non-isothermal environment the oxidation reaction starts at about 1173 K for both AlON bulk sample and powder. In isothermal condition, the mass gain indicates the two-stage reaction mechanism which starts with chemical reaction, followed by diffusion controlled stage. XRD patterns suggest that AlON is thermodynamically unstable and it partly decomposes into corundum phase Al2O3 and AlN during the oxidation process. SEM results indicate that different micromorphology is obtained at different temperatures in the oxidation process. The estimated apparent activation energy for the diffusion rate controlled stage from isothermal experiment is about 245.2 kJ/mol.

Using micro-sized aluminum powder (11 wt.%) and nano-sized Al2O3 powder (89 wt.%) with five different phase compositions, AlON powders were synthesized at different temperatures in flowing-nitrogen atmosphere. Our results suggest that for starting materials with low γ-Al2O3/total Al2O3 ratio R (0 and 0.15), a calcination temperature of 1 750 °C is required to obtain single-phase AlON. This temperature is about 50 °C higher than for other batches starting with larger R values (0.5, 0.85, and 1.0). The AlON powders fabricated from reactants with a high R value in this work show narrower particle size distribution and better particle homogeneity than those prepared from batches with lower R values.

Spinel aluminium oxynitride (γ-AlON), as a kind of transparent ceramic material expectable, is studied using the ab initio density functional method, in terms of electronic, elastic, thermodynamic properties and structure disorder. The results show that γ-AlON exhibits strong ionicity, as quantitatively expressed by ( Al O 2.43 + ) 15 ( Al T 2.41 + ) 8 ( O 1.64 - ) 27 ( N 2.27 - ) 5 from our reassessment of the ionic character. We summarize and speculate that the considered oxynitride single-crystals exhibit highly elastic anisotropy. The interpretation of the thermodynamic properties of γ-AlON according to quasi-harmonic Debye model confirm the available experiments and are extended to a wider temperature/pressure range. This material holds high elastic strength under extreme environments, where dB/dT absolute value is less than 0.03 GPa/K, independent of the pressure. Finally, we study the O/N structure disorder character of γ-AlON solid solution by investigating nine possible crystal structures. It is found that γ-AlON should be partially disordered, and in fact, the O/N ordering has a significant effect on the properties.

Monodisperse microsphere has drawn more and more attention in the past two decades. In order to synthesize it, an efficient procedure was employed by combining dispersion and seeding polymerizations together. The polymerization can be divided into two processes: nucleation and growth. Monodisperse polystyrene seed colloids with a diameter of 2 μm were synthesized in the nucleation process using dispersion polymerization, and then the seed colloids were swollen by monomer and further polymerized in the growth process. Finally, monodisperse polymer microspheres with an average diameter of 10 μm were obtained.

Superwettability of substrates has had a profound influence on the production of novel and advanced colloidal assemblies in recent decades owing to its effect on the spreading area, evaporation rate, and the resultant assembly structure. In this paper, we investigated in detail the influence of the superwettability of a transfer/template substrate on the colloidal assembly from a hybrid top-down/bottom-up strategy. By taking advantage of a superhydrophilic flat transfer substrate and a superhydrophobic groove-structured silicon template, the patterned colloidal microsphere assembly was formed including linear and mesh-, cyclic-, and multistopband assembly arrays of microspheres, and the optic-waveguide of a circular colloidal structure was demonstrated. We believed this liquid top-down/bottom-up strategy would open an efficient avenue for assembling/integrating microspheres building blocks into device applications in a low-cost manner.

Graphical abstractAn ultrathin α-Ta (5nm)/graded Ta(N) (1.5nm)/TaN (2.5nm) multilayer film covered by Cu film was deposited on the Si substrate using reactive magnetron sputtering in N2/Ar ambient. The film stacks of Cu/α-Ta/graded Ta(N)/TaN/Si were then annealed in a vacuum chamber at 400-700?C for 1h. X-ray diffraction (XRD), scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (XTEM), and energy-dispersive spectrometer (EDS) line scans were employed to investigate the microstructure evolution and the diffusion behavior of the film stacks. The results show that the α-Ta/graded Ta(N)/TaN multilayer film as a diffusion barrier had sufficient interface stability, which was attributed to a relative stable amorphous layer forming at the interface of Cu and α-Ta layer, to prevent Cu atom diffusion at elevated temperatures up to 700?C. The relationship between the interface stability and the microstructure of the multilayer barrier were also constructed.Display Omitted Highlights? An ultrathin α-Ta/graded Ta(N)/TaN multilayer film was prepared. ? The reliability of Ta/TaN film is sensitive to variation of Ta phase structure. ? An amorphous interlayer can improve the properties of the diffusion barrier. ? The α-Ta/graded Ta(N)/TaN multilayer could block Cu diffusion at 700?C. An ultrathin α-Ta (5nm)/graded Ta(N) (1.5nm)/TaN (2.5nm) multilayer film coated with Cu film was deposited on the Si substrate using reactive magnetron sputtering in N2/Ar ambient. The film stacks of Cu/α-Ta/graded Ta(N)/TaN/Si were then annealed in a vacuum chamber at 400-700?C for 1h. X-ray diffraction (XRD), scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (XTEM), and energy-dispersive spectrometer (EDS) line scans were employed to investigate the microstructure evolution and the diffusion behavior of the film stacks, respectively. The results show that the α-Ta/graded Ta(N)/TaN multilayer film as a diffusion barrier had sufficient interface stability, which could be attributed to a relative stable amorphous layer forming at the interface of Cu and α-Ta layer, to prevent Cu atom diffusion at elevated temperatures up to 700?C. The relationship between the interface stability and the microstructure of the multilayer barrier were also investigated.

Nd:YAG ceramic samples with different transmittances were fabricated by vacuum sintering with 10 °C/min or 2 °C/min heating rate. SEM measurements revealed that the average pore size of samples was around 0.18 μm while the porosity ranged from 0.0053% to 0.0022%. Mie scattering theory was applied to calculate the scattering coefficients as a function of the ratio between pore size and incident wavelength, pore size and porosity. The results showed that the simulated transmittances were in good agreement with the experimental values. The scattering loss was extremely low when the porosity was lower than 0.001% or the pore size was below 0.01 μm. A novel approach, to synergetically control the parameters of sizes and densities of the pores quantitatively for low scattering loss Nd:YAG ceramics, was presented. This quantitative insight into the pore scattering effects of Nd:YAG ceramics would allow a more targeted experimental optimization of this laser material.

The single-phase aluminum oxynitride (AlON) powder used in this experiment was obtained at relatively low temperature by the solid-state-reaction method with nanosized AlN powder and nanosized alumina powder. The obtained powder was ground by ball milling and doped with Y2O3; then, it was shaped into pellets. Transparent ceramics sintering was carried out at 2153 K (1880 °C) for 5, 10, and 20 hours. Obtained samples for three duration times are all are transparent, and the light transmittance of samples increases with increasing the holding time at the sintering temperature. The transmittance of the sample with 20 hours holding time is 55 pct at near 5 μm. X-ray diffraction (XRD) measurement shows that all samples were single-phase AlON. The fracture surfaces of samples from scanning electron microscopy (SEM) analysis shows that with increasing the holding time, the grain size grows slightly, while the pore size and porosity decrease apparently, which bring about the transmittance increase. The pore size and the porosity are the main factors affecting the light transmitting properties of samples.

Rotation magnetic beacons magnetic field strength is very important to drill parallel horizontal twin wells in steam assisted gravity drainage (SAGD). This paper analyzes a small magnet with a diameter of 25.4 mm. At each end, there is a length of 12.6 mm with permanent magnet, and in the middle, there is a length of 78mm with magnetic materials. The magnetic field strength generated by the magnetic material of 1J12, 1J50, and 1J79 is analyzed, respectively. ANSOFT software is used to simulate the magnetic field strength generated by different magnetic materials above, which also be tested through experimental methods. The comparison of the simulation and experimental results show that experimental and simulation results are basically consistent, and the results can meet the specific requirements of engineering applications.

To understand the responses of fish production to both fishing pressure and climate variability in the northern South China Sea (NSCS), catch time series are partitioned into interannual trends and variations. These are separately related to growth in fishing effort and physical variables. Catches of the fishery underwent dome-shaped trends corresponding to a monotonic growth in fishing effort, first in the inshore and then in the offshore demersal fishes, while total catch and catches of the low-trophic species showed a rising trend until 1990, and eventually experienced a decline under high fishing pressure. After accounting for the trends from the growth in fishing pressure, variations in catches were lag correlated with land precipitation, monsoon wind speeds, and a proposed index of tropical cyclone influence. The linkage suggests that river runoff, monsoon circulation and tropical cyclone impacts are the physical forcing factors dominating the catch variations, and the effects are largely through controlling the nutrient supply for biological production. Runoff provides nutrients to the inshore waters, while monsoons and tropical cyclones control the distribution and availability of nutrients. The winter monsoon increases primary production and hence fish production by offshore diffusion of the nitrogen-rich riverine water masses and by enhancing vertical mixing. In contrast, the summer monsoon reduces availability of nutrients for biological production by confining the distribution of the riverine water masses and strengthening water column stratification. Tropical cyclones are a strong forcing factor that has a positive effect on production of fishes. Tropical cyclones mobilize nutrient elements and enhance biological production by increasing water circulation, wind mixing and upwelling, and by inducing heavy rainfall and territory runoff. Based on the suggested physical forcing factors and their controlling mechanisms, the analysis predicts that increasing anthropogenic nutrient inputs and future climate changes are likely to result in an increase in fish production in the NSCS; this may be associated with even larger interannual and interdecadal fluctuations in fish production.

Anisotropic polystyrene (PS) particles with single cavity structures were synthesized using a modified dispersion polymerization method with divinylbenzene (DVB) as a crosslinker. Using the PS cave particles as templates, anisotropic titanium dioxide (TiO2) hollow microspheres were fabricated facilely. Due to possessing excellent photocatalytic activities, the obtained anisotropic TiO2 hollow spheres have potential applications in detoxification extraction and waste removal with very simple and efficient procedures.

A one-step strategy of magnetron sputtering deposition with dynamic regulation of sputtering atmosphere was developed to prepare α-Ta/graded Ta(N)/TaN multilayer films on the Si substrate. The evolution of Ta clusters shows a significant effect on the crystal structure of the Ta film. The experimental results validate that the formation of α-Ta was attributed to the nucleation of larger Ta clusters. After being annealed at 600 °C, the α-Ta/graded Ta(N)/TaN multilayer film can still effectively block the diffusion of Cu. The mechanisms of the forming of the α-Ta and the thermal stability of the film stacks are characterized in detail.

The transmission properties of aluminium oxynitride (AlON) ceramics were studied. AlON samples with different transmittances were prepared. SEM detected two types of pores with a different range of diameters in the samples; the porosity was obtained by counting the number of pores in a certain area. Mie theory was applied to illuminate the effects of pores on the transmittances. The calculated transmittances were compared with the experiments. The existence of pores with sizes in the 1.1–1.6 µm range and porosities above 10−4 accounted for the degradation of the transmittance spectra at 2.5 µm. Discrepancies of the spectra between the samples were caused mainly by different densities of the A-type pores with sizes above 1 µm. The concepts of critical size and critical concentration were proposed and were quantitatively characterized by critical curves, which divided the regions of translucency and transparency into three parts: R1, R2 and R3 depending on porosity. New approaches on how to control the pore sizes and porosities quantitatively for transparent ceramics design were presented.