A review of natural convection and heat transfer in attic-shaped space

This paper presents a review of studies on natural convection heat transfer in the triangular enclosure namely, in attic-shaped space. Much research activity has been devoted to this topic over the last three decades with a view to providing thermal comfort to the occupants in attic-shaped buildings and to minimising the energy costs associated with heating and air-conditioning. Two basic thermal boundary conditions of attic are considered to represent hot and cold climates or day and night time. This paper also reports on a significant number of studies which have been performed recently on other topics related to the attic space, for example, attics subject to localized heating and attics filled with porous media.     

TC4钛合金负泊松比人工骨微结构的力学性能匹配研究

设计不同变形机制、不同孔隙率下的负泊松比多孔骨结构材料,借助选区激光融化成型技术制备医用Ti6Al4V负泊松比多孔植入物样件,进行微观材料表征和可制造性评测,并通过压缩试验揭示强度、弹性模量等力学性能与胞元结构类型、结构参数间的影响规律,评测不同结构与人骨力学性能的匹配程度。结果表明:各结构都具有较高的可制造性,成型质量与结构特征和孔隙率相关;负泊松比结构力学性能高度依赖于结构设计及孔隙率;所设计的负泊松比结构通过改变支柱直径能够将实体金属弹性模量降低至与人体骨骼相近的范围内,并有望通过调整结构参数进一步实现植入体力学性能的广跨度调控。     

Structure and oil retaining capacity of gasar copper fabricated by radial solidification with a combined crystallizer

Porous copper with elongated pores was fabricated by a radial solidification method. The process was carried out in a combined crystallizer under high pressure of a mixture of hydrogen and argon. Pore size, pore length, pore density and porosity of the porous copper were characterized. Furthermore, the oil retaining capacity including oil content and oil efficiency was also evaluated. It is found that porous copper solidified with water-circulated chiller through a thick graphite jacket possesses a gradient structure with increasing pore size, and thus pore density decreases. Also pore length and pore aspect ratio decrease from lateral inwardly, while its porosity is almost uniform. The results show that the porous copper with radial pores has a good oil retaining capacity.     

Thermal conductivity estimates of intumescent chars by direct numerical simulation

The effective thermal conductivity of fully expanded intumescent chars is estimated numerically using the finite element method. Digital images are used in conjunction with information regarding total porosity from bulk and helium density measurements to construct the FE model, where one pixel of the image corresponds to one element in the model. In order to account for micro-porous inclusions (at resolutions below the digital images), a thermal conductivity sub-model is employed. This is necessary in order to restrict the number of elements in the model to a reasonable size (∼10⁷ or fewer). Corrections to account for assumed 3D structure from the observed 2D image and also radiation augmentation across pores are also used in order to obtain better estimates of effective thermal conductivity. Calculations are compared to experimental values for a wide range of temperatures and surprisingly good agreement is found, given the severe assumptions adopted in the model.     

Numerical Simulation of the Mechanical Properties of Sintered and Bonded Perforated Hollow Sphere Structures (PHSS)

This paper investigated the uniaxial mechanical properties of a new type of hollow sphere structures. For this new type, the sphere shell was perforated by several holes in order to open the inner sphere volume and surface. The mechanical properties, i.e. elastic properties and initial yield stress of perforated hollow sphere structures (PHSS) in a primitive cubic arrangement were numerically evaluated for different hole diameters and different joining techniques of the hollow spheres. The results are compa...     

Comparative study of porous anodic alumina: effects of aluminium deposition methods

This article reports on the comparative study of the fabrication of porous anodic alumina films by anodisation of the aluminium films on glass substrates which were deposited by direct current sputtering and electron beam evaporation methods. The relationship between surface morphology of the deposited aluminum films and porous anodic alumina films was investigated. A more uniform and ordered porous anodic alumina was obtained by fabricating from electron beam evaporation deposited aluminium film with smaller and compact grains. Two-step anodisation was used to further improve the quality of porous anodic alumina compared to one-step anodisation. The optical transmittance spectra within wavelength of 370–800 nm were obtained and the optical properties were studied.     

Fabrication of zirconium-pillared montmorillonite porous ceramic as adsorbents for Cr3+ removal and recycling

A novel zirconium-pillared montmorillonite (Zr-Mt) porous ceramic (P-ZMt) for Cr³⁺ removal was developed by gelcasting. P-ZMt was characterized by XRD, SEM, XPS, TEM, BET. The influence of pH value, contact time, temperature and initial concentration on the adsorption efficiency was investigated. The results revealed that the P-ZMt has a high removal efficiency of Cr³⁺ over a broad range of pH value. The pseudo-second-order kinetic model fitted our acquired Cr³⁺ adsorption data best, in comparison with the pseudo-first-order kinetic model. The Langmuir model was applied to fit the adsorption process better than that of the Freundlich model. The thermodynamic parameters (∆H, ∆G and ∆S) were also determined, which revealed that the Cr³⁺ adsorption process was spontaneous in nature. The present developed P-ZMt could be recovered and reused for more than 6 times. The novel developed P-ZMt is an inexpensive, effective and long-life-cycle adsorbent for Cr³⁺ removal from water solution.     

Fabrication and Characterization of Nanopillar-Like HA Coating on Porous Ti6Al4V Scaffold by a Combination of Alkali–Acid-Heat and Hydrothermal Treatments

Porous titanium scaffold with suitable porous architecture exhibits enormous potentials for bone defect repairs. However,insufficient osteointegration and osteoinduction still remain to open as one of the major problems to achieve satisfactory therapeutic effect. To solve this problem, many studies have been carried out to improve the bioactivity of porous titanium scaff old by surface modifications. In this study, porous Ti6Al4V scaff olds were fabricated using additive manufacturing technique. Porous architectures were built up based on a diamond pore structure unit. Alkali–acid-heat(AH) treatment was applied to create a TiO_2 layer on the porous Ti6Al4V scaff old(AH-porous Ti6Al4V). Subsequently, a hydrothermal treatment was employed to enable the formation of HA coating with nanopillar-like morphology on the alkali–acid-heat-treated surface(HT/AH-porous Ti6Al4V). The effects of surface modifications on apatite-forming ability, protein adsorption,cell attachment, cell proliferation and osteogenic gene expression were studied using apatite-forming ability test, protein adsorption assay and in vitro cell culture assay. It was found that the HT/AH-porous Ti6Al4V exhibited the highest apatite formation ability and best affinity to fibronectin and vitronectin. In vitro studies indicated that the mesenchymal stem cells(MSCs) cultured on the HT/AH-porous Ti6Al4V presented improved adhesion and differentiation compared with the porous Ti6Al4V and AH-porous Ti6Al4V.     

载Cu2+系列多孔非金属矿抗菌剂的制备及应用

对以多孔非金属矿为载体，用离子交换法制备铜型系列抗菌剂进行了试验研究，重点探索了载体种类、交换离子浓度、时间对载铜量及抗菌效果的影响，在此基础上，对抗菌剂在PP中的添加量与PP抗菌塑料物理性能及抗菌性能的关系也进行了初步的试研究。     

Porous TiO2/rGO nanocomposites prepared by cold sintering as efficient electrocatalyst for nitrogen reduction reaction under ambient conditions

Haber–Bosch process as the current dominant artificial NH₃ production process in industry, requires relatively high temperature (350–550 °C) and pressure (150–350 atm). Electrocatalytic nitrogen reduction reaction (NRR) as a green and sustainable strategy for ammonia production has raised intensive research interest in recent years but still remains a significant challenge because of the lack of high performance electrocatalysts. In this work, porous TiO₂-reduced graphene oxide (TiO₂/rGO) nanocomposite as self-supporting efficient electrocatalyst for NRR under ambient conditions were prepared by cold sintering associated with sacrificial template method. The porous TiO₂/rGO nanocomposite with grain size of ～40 nm were prepared by cold sintering process at 220 °C and 147 MPa. Given the 220 °C as cold sintering temperature, anatase TiO₂ were preserved as the final phase which exhibit much better NRR electrocatalytic performance than the rutile phase. The oxygen vacancy densities in the nanocomposites were also tuned by heat treatment at 450 °C under different atmosphere, while samples heat treated under H₂/Ar atmosphere gave the best electrocatalytic NRR performance with a FE of 8.88 % and an NH₃ yield of 7.75 μg h^?1 cm^?2 at ambient conditions. Experiments also shows that the addition of rGO significantly improved the electrocatalytic NRR performance especially the conductivity. This work not only designed a framework of ceramic nanocomposites based self-supporting and durable electrocatalysts system but also paves a feasible way towards preparing electrocatalysts that are sensitive to high temperature fabrication process.