Due to the difference of thermal expansion coefficient between the components in the solid oxide fuel cell (SOFC), there are some residual thermal stresses in the cell in fabrication. Introducing the functional gradient layer is an effective technique to relieve the residual thermal stress in fabrication. The residual thermal stress and failure probability were calculated by a commercial package named ANSYS. The effects of gradient distribution factor n, sublayers number w in the gradient layer and gradient layer thickness H on the thermal residual stress and failure probability were investigated. The results show that the functional gradient layer can reduce the stress and failure probability in the cell. The increase of the number of sublayers w has little effect on the decrease of the stress and failure probability when the w number exceeds 2. The optimum w number of sublayers is 2. When the gradient distribution factor n is small, the anode failure probability decreases with the increase of gradient layer thickness. In addition, the gradient parameter for the composition functionally graded anode layer was also optimized.

Lithium cobalt oxide is a leading cathode material for 3C electronic products because of its high bulk energy density, excellent rate capacity and good cycle performance. The existing gram capacity of lithium cobalt oxide material in practical application is approximately 65% of the theoretical capacity, and this material has a potential for further development. In this paper, a lithium ion cobalt oxide cathode material was coated with lithium ion conductor material LiAlSiO₄ by a sol-gel method. The effects of LiAlSiO₄ and heat treatment temperature on the structure, morphology and electrochemical properties of the material were investigated. The results show that during the heat treatment, Al³⁺ enters the LiCoO₂ lattice to form a solid solution LiCo_1-xAl_xO₂, and an inert coating layer is formed on the surface of the lithium cobalt oxide particles LiAlSiO₄ coating, effectively improving the cycle and rate performance of the lithium cobalt oxide material at a high voltage. The optimum overall performance of the lithium cobalt oxide material coated with LiAlSiO₄ can be obtained at a heat treatment temperature of 600 ℃. In a voltage range of 2.75-4.55 V, the specific discharge capacity at room temperature at 0.5 C rate is 209.3 mA·h/g, and the discharge specific capacity after 50 cycles is 201.6 mA·h/g (at a capacity retention rate of 96.3%), and the specific capacity is 160.0 mA·h/g at 8 C.

Gradient anode is an effective way to improve the electrical performance of anode-supported solid oxide fuel cell (SOFC). However, the porosity is closely related to the thermomechanical properties and thermal stress distribution of the anode. It is thus important to investigate the comprehensive effect of porosity on the thermal stress and electrical performance of SOFC. A single planar SOFC model considering various porosity-dependent properties of the materials was proposed via multi-physics coupling based on the COMSOL Multiphysics simulation platform. The electrochemical performance and thermal stress distribution of the SOFC with a gradient-porosity-anode design at working stage were investigated. The results show that the gradient porosity-anode design effectively improves the thermomechanical matching of the positive-electrolyte-negative structure, while maintains the high electrochemical performance of the SOFC. Compared with the usual uniform porosity anode designed SOFC with a porosity of 0.4, the output power of SOFC is increased by 3.5%, while the maximum first principal stress of the electrolyte is reduced by 68.5%. The results of this study provide the theoretical and data supports for optimizing anode structure design of SOFC.

The infrared films with ultra-high reflection is the key and basic materials for the realization of low loss optical device, infrared stealth, etc.. According to the transmission matrix principle of multilayer optical films, the reflectance and transmittance expressions of one-dimensional photonic crystals were obtained, and the energy band structure of one-dimensional photonic crystals was analyzed. Using the principle of transmission matrix, we designed a 28-layer λ/4 one-dimensional photonic crystal structure with Ge and SiO₂ as dielectric materials. Also, the first and second band gaps of the photonic crystal calculated by the finite element method to be 2.01×10¹³~4.11×10¹³ Hz and 8.13×10¹³~1.02×10¹⁴ Hz, respectively. The optimized λ/4 one-dimensional photonic crystal structure has as low as 14 layers, thus achieving high reflections of 3~5 μm and 8~14 μm.

Nb₂O₅ has a variety of crystalline states. However, the intermediate process of forming a long-range ordered structure is still unclear. Nb₂O₅ precursor was prepared by a sol-gel method. The intermediate-state samples in the crystallization of amorphous Nb₂O₅ were obtained at 460 ℃-520 ℃. The crystal structure, morphology, pore structure and crystallization kinetics of the intermediate-state samples were investigated. The results show that the atomic ordering process of the sample is from 1.0 nm short-range order with an amorphous state, to 1.0 nm short-range order with a small amount of crystal and amorphous mixed state, to 1.5 nm medium-range order with a pseudo hexagonal and amorphous mixed state, and then to more than 2.0 nm long-range order with a pseudo hexagonal, orthorhombic and a small amount of amorphous mixed state. The crystallinity of the samples at >495 ℃ increases rapidly from 20% to 86%. The samples are formed due to the crisscross accumulation of massive flaky particles and a small amount of rod-shaped particles. From a short-range order to a long-range order, the growth process of flake particles is the main process, while the rod-shaped particles have little change. The particles are mesoporous, and the size of the main pore becomes 10 nm as the calcination temperature increases. The Avrami index (n) of the samples is 1-2, and the main nucleation mode is the surface nucleation. During the transformation from short program to medium program, there exists a crystallization incubation period. This study provides a working basis for the investigation of Nb₂O₅ crystallization intermediate state.

CsPbX₃ (X=Cl, Br, I) perovskite quantum dots embedded glass-ceramics (GCs) are a composite material with the steady physical and chemical properties of glass matrix phase and the superior optical performance of CsPbX₃ quantum dot phase. These materials are used in optical data storage, random laser, X-ray image, lighting and display, solar cells, photocatalysis, etc.. Recent advances on the preparation and the corresponding performance/application were introduced, i.e., the use of fs laser to form CsPbX₃ in selected zone to serve as optical data storage, thereby showing the regular pattern of these materials' composition-structure-performance relationship. Nevertheless, these are some challenges of investigating for these materials, i.e., the in-situ formation of CsPbX₃ in glass matrix is entirely unclear. And the studies on CsPbX₃ precursors' occurrence state, neighbor structure and morphological distribution could further help to understand the formation mechanism of CsPbX₃ in glass, providing a guide to obtain the better CsPbX₃ perovskite quantum dots embedded GCs.

As-S sulfide glasses with a high optical quality were prepared via purification of high-purity elemental raw materials and chemical distillation of the glass melt. Based on the glasses, a multimode step-index optical fiber was drawn by a rod-in-tube technique. The transmission loss of the fiber was measured, its performance of transmitting high-power mid-infrared laser was characterized, and the laser damage mechanism was analyzed. The results show that the fabricated fiber with a core diameter of~200 μm and a numerical aperture of ~0.35 has transmission losses of ~0.25 dB/m and ~0.35 dB/m at 2 μm and 4.6 μm, respectively. Under effective cooling condition, the fiber can withstand ~120 W incident power of 2 μm continuous wave laser, and deliver transmitted power of ~63 W. According to the theoretical analysis, the damage of the fiber at a high laser power is related to the distribution of nano-sized heterophase inclusions (NHPI) in the core glass. The heat accumulation could occur in the region at a high concentration of NHPI, resulting in the thermal damage of the fiber.

Glasses doped with quantum dots (QDs) are intensively investigated in recent years due to the tunable absorption and photoluminescence in a wide wavelength range induced by the quantum confinement effects. Since lead chalcogenide semiconductors have narrow energy bandgaps and large Borh radius, the QDs made of lead chalcogenide compounds have widespread technological applications in optoelectronics. The QD-doped glasses with good chemical and thermal stability offer a possibility to make the all-solid and compact devices. To achieve the desirable optical properties, recent efforts are devoted to tune the bandgap of QDs and improve the quantum efficiency. This review summarized recent research progress on the tuning methods of optical properties of PbS and PbSe QDs in glasses. In addition, the problems and future research directions of IV-VI QDs-doped glasses for applications were also emphasized.

Yb³⁺-doped silica fiber is a key component of high power fiber laser and its core material is Yb³⁺-doped silica glass. The performance of Yb³⁺-doped silica fiber is closely related to the properties of core material. This paper reviews our research progress on Yb³⁺-doped silica glass co-doped with Al, P, F, B and Ce fabricated by a sol-gel method and subsequent high-temperature sintering and effect of co-doping elements on the optical, spectroscopic and structural properties of Yb³⁺-doped silica glass, to provide a reference for optimizing the laser performance of Yb³⁺-doped silica fiber. More researches should focus on the relationship between properties of optical fiber and structure of Yb³⁺-doped silica glass in the future.

Phosphor in glass (PiG) is widely used as a fluorescent conversion material for light emitting diode (LED) device packaging. However, for the PiG with a single refractive index (SRIN) structure, the optical loss is large when light transmits from air through PiG to the packaging material due to large refractive index difference between the interfaces. In addition, the sintering temperature of PiG is high, thus reducing the light conversion efficiency of phosphor. To address the problems above, lead-free B₂O₃-ZnO-SiO₂ matrix glass with gradient refractive index structure matching with yellow phosphor was prepared. Also, B₂O₃-ZnO-SiO₂ system fluorescent glass (phosphor in matrix glass with gradient refractive index structure) was prepared via multi-layer screen printing and low-temperature sintering process. The glass was used in LED packaging to improve the optical performance of LED devices.