Wave propagation in multi-phase porous media is a significant research topic. There are a series of studies about porous media saturated with a single fluid, a solid and a fluid, two fluids, and three fluids. Some gas hydrate-bearing sediments are typical multiphase porous media saturated with a solid(gas hydrates) and two fluids(water and gas). Based on existing theories of porous media, we develop a theory and give a comprehensive analysis of wave propagation in a poroelastic medium saturated with two fluids and a solid. Initially, we establish the constitutive relations and equations of motion. Based on Biot's approach for describing the equations of motion in fluid-saturated porous media at the macroscale,the kinetic energy density, potential energy density, and dissipative energy density are derived. After deriving the equations of motion, a plane wave analysis predicts the existence of four compressional waves, denoted P1, P2, P3, and P4 waves,and two shear waves, denoted S1 and S2 waves. Numerical examples are presented to demonstrate how velocities and attenuations of various waves behave with gas saturation, gas hydrate saturation, and frequency. A model degradation to porous media saturated with a single fluid supports the validity of the theory, which enriches the theory of multiphase porous media and provides a foundation for the evaluation of gas hydrate-bearing sediments.
The bioinert nature of polyether ether ketone(PEEK)material limits the widespread clinical application of PEEK implants.Although the porous structure is considered to improve osseointegration of PEEK implants,it is hardly used due to its mechanical properties.This study investigated the combined influence of the porous structure and in vivo mechanical stimulation on implantation safety and bone growth based on finite element analysis of the biomechanical behavior of the implantation system.The combined control of pore size and screw preloads allows the porous PEEK implant to achieve good osseointegration while maintaining a relatively high safety level.A pore size of 600μm and a preload of 0.05 N·m are the optimal combination for the long-term stability of the implant,with which the safety factor of the implant is>2,and the predicted percentage of effective bone growth area of the bone-implant interface reaches 97%.For further clinical application,PEEK implants were fabricated with fused filament fabrication(FFF)three-dimensional(3D)printing,and clinical outcomes demonstrated better bone repair efficacy and long-term stability of porous PEEK implants compared to solid PEEK implants.Moreover,good osteointegration performance of 3D-printed porous PEEK implants was observed,with an average bone volume fraction>40%three months after implantation.In conclusion,3D-printed porous PEEK implants have great potential for clinical application,with validated implantation safety and good osseointegration.
The complex stresses experienced by medical-grade porous metals in the physiological environment following implantation as bone repair materials necessitate a comprehensive understanding of their mechanical behavior.This paper investigates the efects of pore structure and matrix composition on the corrosion behavior and mechanical properties of pure Zn.Porous Zn alloys with varying pore sizes were prepared via vacuum infltration casting.The results showed that addition of Mg elements and an increase in pore size were observed to enhance the strength and elastic modulus of the porous Zn alloy(41.34±0.113 MPa and 0.58±0.02 GPa of the C-Z3AM).However,corrosion tests indicated that specimens with smaller pores and the addition of Mg elements exhibited accelerated corrosion of porous Zn alloys in Hank’s solution.Electrochemical test results show the corrosion resistance rank in order of C-Z5A>C-Z3AM>N-Z5A>N-Z3AM.Additionally,the mechanical retention of porous Zn alloys in simulated body fuids was found to be signifcantly reduced by the incorporation of Mg elements and smaller pore sizes,the yield strength declines rates of C-Z5A,C-Z3AM and N-Z3AM after 30 days of immersion were 16.7%,63.7%and 78.2%,respectively.The objective is to establish the role of the material-structurecorrosion-mechanics relationship,which can provide a theoretical and experimental basis for the design and evaluation of Zn and its alloy implanted devices.
Xiaotong LuPingyun YuanZhengquan WangXiaocheng LiHanyuan LiuWenhao ZhouKun SunYongliang Mu
With the impact of energy crisis and environmental problems,it is urgent to develop green sustainable energy.Osmotic energy stored in the salinity difference between seawater and river water is one of the sustainable,abundant,and renewable energy.However,the membranes used to capture osmotic energy by reverse electrodialysis (RED) always suffer from low ion selectivity,low stability and low power.Hydrogels with three-dimensional (3D) networks have shown great potential for ion transportation and energy conversion.In this work,based on the homogeneity and porosity characteristics of acrylamide(AM) hydrogel,as well as the remarkable stability and abundant negative charge of 3-sulfopropyl acrylate potassium salt (SPAK),a high-performance AM/SPAK cation-selective hydrogel membrane was successfully developed for harvesting osmotic energy.Compared to AM hydrogels,utilizing AM/SPAK as a monomer mixture greatly facilitated the preparation of homogeneous polymers,exhibiting a porous structure,exceptional ion selectivity,and remarkable stability.A maximum output power density of 13.73 W/m^(2)was achieved at a 50-fold NaCl concentration gradient,exceeding the commercial requirement of 5 W/m^(2).This work broadens the idea for the construction and application of composite hydrogel in high efficiency osmotic energy conversion.
Guilong LiWenbo MaJialing ZhouCaiqin WuChenling YaoHuan ZengJian Wang
Propane dehydrogenation(PDH)is a vital industrial process for producing propene,utilizing primarily Cr-based or Pt-based catalysts.These catalysts often suffer from challenges such as the toxicity of Cr,the high costs of noble metals like Pt,and deactivation issues due to sintering or coke formation at elevated temperatures.We introduce an exceptional Ru-based catalyst,Ru nanoparticles anchored on a nitrogendoped carbon matrix(Ru@NC),which achieves a propane conversion rate of 32.2%and a propene selectivity of 93.1%at 550°C,with minimal coke deposition and a low deactivation rate of 0.0065 h^(-1).Characterizations using techniques like TEM and XPS,along with carefully-designed controlled experiments,reveal that the notable performance of Ru@NC stems from the modified electronic state of Ru by nitrogen dopant and the microporous nature of the matrix,positioning it as a top contender among state-of-the-art PDH catalysts.
MXene is an emerging class of two-dimensional(2D)layered transition metal carbides or nitrides.Due to the highly tunable components and surface functional groups,it holds great potential in electrocatalytic hydrogen evolution reaction(HER).However,MXene nanosheet suffers from a strong tendency to restack and a lack of active edge sites.In this work,the porous Ti_(3)C_(2)T_(x)was synthesized by an oxidation and etching two-step strategy and then characterized by a series of spectroscopic techniques.The obtained porous Ti_(3)C_(2)T_(x)possesses a large number of in-plane pores.This not only creates abundant active edge sites but also enhances the mass transfer and increases the accessibility of the active sites.Compared with Ti_(3)C_(2)T_(x),in a 0.5 mol/L H_(2)SO_(4)electrolyte,the porous Ti_(3)C_(2)T_(x)shows a 65.6%higher electrochemical surface area(ECSA)(440 mF/cm^(2)),a 95.2%lower charge transfer resistance(12.8Ω),and a 69.8%lower Tafel slope(144 mV/dec),and thus exhibits lower overpotential with good stability at a current density of 10 mA/cm^(2).At the same time,the HER performance of the porous Ti_(3)C_(2)T_(x)can be further enhanced by near-infrared laser irradiation based on the localized surface plasmon resonance effect.
Porous spherical MnCo_(2)S_(4) was synthesized by a simple solvothermal method.Thanks to the well-designedbimetallic composition and the unique porous spherical structure,the MnCo_(2)S_(4) electrode exhibited an exceptionalspecific capacitance of 190.8 mAh·g^(-1)at 1 A·g^(-1),greatly higher than the corresponding monometallic sulfides MnS(31.7 mAh·g^(-1))and Co_(3)S_(4)(86.7 mAh·g^(-1)).Impressively,the as-assembled MnCo_(2)S_(4)||porous carbon(PC)hybridsupercapacitor(HSC),showed an outstanding energy density of 76.88 Wh·kg^(-1)at a power density of 374.5 W·kg^(-1),remarkable cyclic performance with a capacity retention of 86.8% after 10000 charge-discharge cycles at 5 A·g^(-1),and excellent Coulombic efficiency of 99.7%.
LUO MinWANG XiaonanZHANG YaqinPANG TianLI FuzhiSHI Pu
