On the thermal expansion of composite materials and cross-property connection between thermal expansion and thermal conductivity

The paper focuses on the quantitative characterization of heterogeneous microstructures from the point of view of the material’s thermal expansion. First, we derive expression for the second rank thermal expansion contribution tensor of an inhomogeneity and specify it for various inhomogeneity shapes. Case of a spheroidal inhomogeneity in an isotropic material is discussed in detail. Thermal expansion contribution tensor is used as a basic building block to calculate effective thermal expansion of a heterogeneous material and to derive explicit cross-property connection between thermal expansion and thermal resistivity of a composite. We compare our results with experimental data available in literature and with other approaches.     

Physicochemical and biological properties of composite bone cement based on octacalcium phosphate and tricalcium silicate

Biocompatible tricalcium silicate (C₃S) bone cement is widely used as dental and bone repair material; however, its long setting time, poor injectability and low initial mechanical properties limit clinical applications. In order to improve C₃S silicate bone cement and its derivatives to play a more important role in tooth restoration, bone defect repair, implant coating and tissue engineering scaffolds, a novel C₃S and octacalcium phosphate (OCP) composite bone cement (OCP/C₃S) was prepared and evaluated for setting time, injectability, anti-flocculation, pH, microstructure, bioactivity and cytotoxicity. The setting time of the OCP/C₃S composite bone cement was controlled within the clinically operable time range (8.3–13.7 min); the cement exhibited good compressive strength, injectability (93.54%), and anti-collapse performance. The 20% OCP/C₃S composite bone cement had a compressive strength of 28.94 MPa, 93% stronger than pure C₃S (14.98 MPa). An in vitro immersion test showed that the composite bone cement had excellent hydroxyapatite forming ability, proper degradation rate, and a low pH value. Cellular experiments confirmed the low cytotoxicity of the composite bone cement and its great capacity for cell proliferation. These results indicate that 20% OCP/C₃S composite bone cement is a promising biomaterial.     

Controlled synthesis of W–Co3S4@Co3O4 as an environmentally friendly and low cost electrocatalyst for overall water splitting

Electrochemistry splitting of water is considered to be one of the most fascinating methods to replace traditional chemical fuels. Here, we design a new method to exploit W–Co₃S₄@Co₃O₄ heterostructures. The W–Co₃S₄@Co₃O₄ material was first prepared and grown in situ on nickel foam by a typical hydrothermal and calcination approach. Based on the principle of electronic regulation, the synergistic effect of W and Co metal ions can increase the charge transfer of the electrode, thus significantly prompting the catalytic activity of the electrode. The W–Co₃S₄@Co₃O₄ material present superior catalytic performance for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), and the overpotential at 10 mA cm⁻² is 260 mV and 140 mV, respectively. Notably, W–Co₃S₄@Co₃O₄ catalyst showed excellent water splitting performance under alkaline conditions (cell voltage of 1.63V @10 mA cm⁻²). Density functional theory calculation shows that the existence of the Co₃O₄ material accelerates the rate of hydrogen production reaction, and the existence of the W–Co₃S₄ material promotes the conductivity of the W–Co₃S₄@Co₃O₄ electrode. The synergistic effect of W–Co₃S₄ and Co₃O₄ materials is beneficial to the improvement of the catalytic activity of the electrode. This study provides a novel view for the development of electrodes synthesis and a novel paradigm for the development of robust, better and relatively non-toxic bifunctional catalysts.     

Preparation of FeNi-based nanoporous amorphous alloy films and their electrocatalytic oxygen evolution properties

The progress of this research is the preparation of FeNi alloy thin films by magnetron sputtering. Each step of the experimental process is based on the electrocatalytic performance of the sample, and characterized by many characterizations means such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray energy spectrometry (EDS) and step gauge thickness test for morphology, structure and elemental composition, etc. The analysis of the characterization results is used as a support for the experimental process. Adjustment of various preparation process parameters for material growth and subsequent processing include doping of non-metallic elements and construction of nanostructures. Doping of C elements can make FeNi based alloy films further amorphous. Zn element is used as a pore-forming agent. The two processes of doping and high-temperature vacuum dealloying can make the film obtain a nanoporous structure, which greatly increases the specific surface area. These two strategies reduce the overpotential (η10) of oxygen evolution reaction (OER) of FeNi alloy thin films to 393 mV and 314 mV, which are reduced by 47 mV and 79 mV step by step. The electrochemical properties of the finally obtained alloy film are: overpotential of 314 mV, Tafel slope of 61.8 mV/dec and the stability of only 10% decay at a current density of 10 mA/cm2 for 12 h. In this study, low-cost transition metals were used as the main materials to design OER catalysts, and the catalytic efficiency was comparable to that of commercial noble metal catalysts. The physical preparation methods made each sample have good reproducibility. It provides the experimental basis and theoretical basis for the design and synthesis of new catalytic materials at a higher level.     

Novel carbon-ceramic composite membranes with high cation exchange properties for use in microbial fuel cell and electricity generation

Actually, there are different configurations used in microbial fuel cells (MFCs) with presence or absence of an ion exchange membrane between their electrodes. Specifically, MFCs that use membranes have the objective of avoiding the diffusion of oxygen and substrate between the anodic and cathodic compartment, and to achieve a correct transfer of protons from one chamber to another. In this regard, the current study seeks to prepare and characterize new composite membranes using as precursors three types of carbonaceous materials such as bone char, coconut shell activated carbon and bituminous activated carbon and natural clay. The composite membranes of bituminous activated carbon and clay showed more promising specific conductivity (42%) than the one made with pure clay. The physicochemical properties of the membranes and their precursors were elucidated by SEM/EDX analysis, IR spectroscopy, nitrogen adsorption isotherms at 77 K and optical microscopy. Further, membranes performance was assessed using microbial fuel cells (MFCs) where the composite membranes prepared with clay-bituminous carbon reached the highest voltage values (0.95–1.02 V) in open circuits, while that reached a maximum power density of 0.699 W/m³ at a current density of 4.012 A/m³ in closed circuit. This behavior is associated with the high content of silicon and aluminum in bituminous activated carbon, which favored the proper functioning of membranes in the MFCs. Specifically, with this type of cells, energy recovery of 0.0057 kWh/m³ and 0.1322 kWh/kg chemical oxygen demand (COD) removed, which indicates an extra economic income of the order of $0.0025/kg COD. Finally, the produced power was demonstrated in prototypes to power LED and four digital clocks. This novel clay-bituminous activated carbon showed promising cost-effectiveness and sustainable energy generation, which may be suitable for wastewater treatment.     

pH-based one pot synthesis of biocompatible olive shaped inorganic particles

A novel, single-step, one-pot method for preparation of inorganic hollow particles is introduced. The concept is grounded on the classical theory of nucleation of growth and can be carried out entirely at room temperature. Starting from an appropriate solution, precipitation and selective dissolution of inorganic nanoparticles are triggered by continuous addition of a salt while carefully controlling the pH. The approach is demonstrated on the example of hollow calcium phosphate particles using calcium carbonate solid nanoparticles as a template. The proposed synthesis procedure is simple and cheap and can be extended to other biocompatible compounds. It also can be upgraded with an additional in situ step.     

Application of a thin intermediate cathode layer prepared by inkjet printing for SOFCs

The application of an inkjet printing process for fabricating solid oxide fuel cell (SOFC) cathodes was investigated. Stably-dispersed LSCF–GDC inks were prepared by ball milling, and the composition was easily controlled by the preparation process. Fabrication of an LSCF–GDC layer was successfully carried out by depositing dots and the thickness was easily controlled by repeating printing process. A planar SOFC single cell with a double-layered cathode (comprised of a paste painted cathode layer and an inkjet printed interlayer) achieved a maximum power density of 0.71 W/cm² at 600 °C. This is the preliminary work for fabricating the cathode layer of a SOFC single cell via inkjet printing.     

Advanced combustion,cooling and refrigeration,waste gas treatment,heat integrated separation and case studies

This is an overview of a Special Issue that has been dedicated to the 8th conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction – PRES’05. Twelve papers from the conference have been selected and peer-reviewed and cover various subjects of advanced combustion, cooling and refrigeration and waste gas treatment. These have been supplemented with heat integrated separation and case studies.     

Selective separation of salicylic acid from aqueous solutions using molecularly imprinted nano-polymer on wollastonite synthesized by oil-in-water microemulsion method

Highly effective molecularly imprinted nano-polymer on wollastonite (nano-WMIP) was prepared by imprinting technique using oil-in-water emulsion polymerization in the presence of salicylic acid (SA) as template. The adsorption behavior of nano-WMIP including adsorption kinetic, isotherms, selective adsorption, recognition, and effects of initial pH, ionic strength, initial concentration, adsorption temperature, and amount of adsorbents were investigated in detail. Moreover, the selective recognition of nano-WMIP was further investigated by HPLC toward analogs of SA. The relative selectivity coefficients for p-HB, MS, and MP were 113.4, 8.049, and 6.239, respectively, showing that much higher selectivity of SA on nano-WMIP was obtained than that of wollastonite-based non-imprinted polymer (nano-WNIP).