2D-Co 3 O 4 and 3D-Co 3 O 4 catalysts were prepared by the hard template method, and nano-Co 3 O 4 was synthesized by precipitation method. The catalytic activity for the oxidation of formaldehyde over various types of catalysts was investigated. The 3D-Co 3 O 4 catalyst attained a 100% conversion rate of formaldehyde at 130 °C with a space velocity of 30,000 mL/(g h), while the 2D-Co 3 O 4 catalyst oxidized formaldehyde completely at 150 °C in the same space velocity conditions. The difference in activity is due to the clear channel structure of the mesoporous Co 3 O 4 prepared by the hard template method, which has large specific surface area and surface active species that allows the reactant to diffuse and undergo surface reactions. The 3D-Co 3 O 4 had the best performance of formaldehyde oxidation due to the three-dimensional porous channel structure, larger specific surface area, abundant active surface oxygen species and active Co 3+ cationic species on the exposed (2 2 0) crystal face. Complete conversion of formaldehyde had remained the same after 3D-Co 3 O 4 was observed for 160 h. Therefore, the 3D-Co 3 O 4 catalyst has the best catalytic activity and stability for formaldehyde, which might be a non-noble catalyst for catalytic removal of formaldehyde in practical application.

Comparison of the performance for oxidation of formaldehyde on nano-Co3O4, 2D-Co3O4, and 3D-Co3O4 catalysts

Hierarchical Co3O4@Ni(OH)2 core-shell nanosheet arrays for isolated all-solid state supercapacitor electrodes with superior electrochemical performance

A highly dispersed nickel supported catalyst for dry reforming of methane

A simple method to prepare highly active and dispersed Ni/MCM-41 catalysts by co-impregnation

Three-dimensional branched single-crystal β-Co(OH)2 nanowire array and its application for supercapacitor with excellent electrochemical property

A novel, simple, and general method for preparing a highly dispersed supported metal catalyst was developed by modification of a silica surface with ethylene glycol (EG) before the impregnation of cobalt precursors. The modified surface of the silica support significantly improved the dispersion of supported cobalt oxide and formed more Co3+ species on the surface of Co3O4 particles, resulting in very high catalytic activity in CO oxidation. The obtained catalysts were characterized by XRD, TEM, and XPS.

A Simple Method for Preparing the Highly Dispersed Supported Co3O4 on Silica Support

LEDs are widely used in medicine, navigation and landscape lighting. The development of high-power LED is a severe challenge to LED heat dissipation. In this review, packaging technology and packaging structure are reviewed in terms of the thermal performance of LED packaging, and related technologies that promote heat dissipation in LED packaging are introduced. The design of three components to enhance heat dissipation in LED packaging is described: substrate, lens and phosphor layer. By conducting a summary of the technology and structure of the package, the defects of LED package technology and structure are deeply investigated, and the package is prospected. This has reference value for the heat dissipation design of the LED package and helps to improve the design and manufacture of the LED package.

/pdf/development-of-led-package-heat-dissipation-research-1xn9d8l6.pdf

Development of LED Package Heat Dissipation Research

With the increase of power level and integration in electric vehicle controllers, the heat flux of the key silicon-based IGBT (Insulated Gate Bipolar Transistor) device has reached its physical limit. At present, third-generation semiconductor devices including SiC MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor) are gradually replacing the dominant IGBT module. The hybrid IGBT module consists of both and can improve the performance and reduce the cost of controllers. Limits due to the installation space, location, and other conditions in the car make it difficult to meet the requirements of controllers with an air-cooled heatsink due to their large size and limited heat dissipation capacity. A smaller and more powerful water-cooled heatsink case is required to ensure the heat dissipation of the IGBT in the controller. Based on previous experience in finite element numerical simulation, hydrodynamics calculation, and heat transfer calculation, ANSYS Workbench finite element software was used to analyze the thermal resistance of each structure inside the module and the heatsink structure. The fluid characteristics and heat transfer performance of three different flow channel structures were analyzed, and the design of the cooling flow fin was improved to provide a reference for the heat dissipation of the hybrid IGBT module.

/pdf/heat-dissipation-characteristics-of-igbt-module-based-on-23pzxbei.pdf

Heat Dissipation Characteristics of IGBT Module Based on Flow-Solid Coupling

Gallium nitride (GaN) power devices have many benefits, including high power density, small footprint, high operating voltage, and excellent power gain capability. However, in contrast to silicon carbide (SiC), its performance and reliability can be negatively impacted by its low thermal conductivity, which can cause overheating. Hence, it is necessary to provide a reliable and workable thermal management model. In this paper, a model of a flip-chip packing (FCP) GaN chip was established, and it was assigned to the Ag sinter paste structure. The different solder bumps and under bump metallurgy (UBM) were considered. The results indicated that the FCP GaN chip with underfill was a promising method because it not only reduced the size of the package model but also reduced thermal stress. When the chip was in operation, the thermal stress was about 79 MPa, only 38.77% of the Ag sinter paste structure, lower than any of the GaN chip packaging methods currently in use. Moreover, the thermal condition of the module often has little to do with the material of the UBM. Additionally, nano-silver was found to be the most suitable bump material for FCP GaN chip. Temperature shock experiments were also conducted with different UBM materials when nano-silver was used as bump. It was found that Al as UBM is a more reliable option.

/pdf/reliability-analysis-of-flip-chip-packaging-gan-chip-with-wgnxznuk.pdf

Li Tan

Papers

A Simple Method for Preparing the Highly Dispersed Supported Co3O4 on Silica Support

Development of LED Package Heat Dissipation Research

Heat Dissipation Characteristics of IGBT Module Based on Flow-Solid Coupling

Reliability Analysis of Flip-Chip Packaging GaN Chip with Nano-Silver Solder BUMP