Study on Air Void Characteristics and Hydraulic Characteristics of Porous Asphalt Concrete Based on Image Processing Technology

The appearance of porous asphalt (PA) pavement is to solve the problem of road ponding in rainy days. The internal air voids in PA pavement are the main functional structure that determines its drainage performance. It is of great practical significance to find out the relationship between void drainage capacity and air voids. This paper is aimed at researching the relationship between three-dimensional (3D) pore structures and drainage performance of PA concrete. Four samples were formed and scanned by CT equipment to obtain the internal cross-sectional CT images. Image dodging algorithm and OTSU method were conducted to deal with these CT images for segmenting them into three subimages (void image, asphalt mortar image, and aggregate image) according to the three components of PA concrete. The voids on void images were identified and classified into three groups according to the three kind of pores (interconnected pore, semi-interconnected pore, and closed pore) and reshaped them into 3D pore structures according to the overlapping principle. Then, the volume and size distribution of the pores was analyzed. Besides, this research mainly focused on the influence of several parameters obtained from interconnected pores on the drainage performance of PA concrete at last. The permeability coefficient of PA concrete samples was tested, and equations between permeability coefficient and void content were fitted linearly. The distribution of hydraulic radius and cross-sectional area ratio was calculated and researched by statistical methods. A new parameter, perimeter variation coefficient, is proposed to study the influence of boundary wall roughness on the drainage performance. At last, equivalent drainage channel was drawn to reflect the drainage capacity of PA concrete.

Textiles for Noise Control

This chapter includes the mechanism of sound absorption and the classes of sound absorbing material to control the noise. The basic phenomena related to the reduction of sound by allowing it to soak in and dissipate also were introduced first, which, can be realised by viscous effects, heat conduction effects, and internal molecular energy interchanges. Porous absorbers are materials where sound propagates through an interconnected pore network resulting in sound energy dissipation. They are only effective at the mid-to-high frequency range, which is most sensitive to the human ear. The applications of different textile fibres and their various forms were identified later in the chapter. Finally, specific discussions are given to sound parameters, noise absorption coefficient, and its measurement technique. The chapter also deals with various factors influencing sound absorption.

Nickel Wick by Continuous Freeze-Casting: Influences of the Particle Size on the Capillarity and Mechanical Properties

The aim of this work was to study the effect of the particle size range, the freeze casting temperature and sintering temperature on the capillarity performance and mechanical properties of Ni wicks manufactured by freeze-casting. The use of Ni/camphene-polystyrene suspensions creates wicks with an open porosity above 80% and average pore sizes of 38 μm to 17 μm by tailoring the particle size ranges and freezing temperatures employed. The incorporation of PS and the use of a continuous freeze-casting process reduces the particle sedimentation and generates a highly interconnected pore structure with regular pore sizes across the sample. The capillarity performances exhibit a fast and complete water adsorption, especially in Ni wicks freeze-casted at 10 °C and sintered at 800 °C, but only when the smaller particle size range is used do Ni wicks achieve sufficient mechanical strength.

Novel Biodegradable Polyurethanes Reinforced With Green Nanofibers for Applications in Tissue Engineering

New class of green biocomposites were designed and synthesized for tissue engineering applications. These newly introduced non-cytotoxic, biodegradable polyurethane composites had different compositions (i.e., ratio of hard to soft segments) of the linear, aliphatic hexamethylene diisocyanate and polycaprolactone diol. The porosity was introduced in the polyurethane matrix using a combination of salt leaching and thermally induced phase separation (TIPS). The resulting interconnected pore size was characterized using Scanning Electron Microscope (SEM) to be between 125-355 μm. Porosity was determined using liquid displacement and found to be between 70-75% for non-reinforced matrices, 64-70% for reinforcement with 5 wt% biocellulose nanofiber (BCNF), 59-69% for 10 wt% BCNF, and 57-69% for 15 wt% BCNF biocomposite samples. Dependent on the composition, compressive strength showed up to a little less than two-fold increase (85%) for green BCNF reinforcement of 5 wt% and more than two-fold increase (120%) for 10 wt%. The tensile strength also increased up to almost two-fold (114%) for reinforcement with 5 wt% BCNF and to more than two-fold (140%) for 10 wt% reinforcement. Higher degrees of reinforcement showed a detrimental effect on both properties. Properties demonstrate that this novel class of nanostructured biocomposite holds potential to be utilized as scaffolds for tissue regeneration.

Novel Biodegradable Polyurethanes Reinforced With Green Nanofibers for Applications in Tissue Engineering

New class of green biocomposites were designed and synthesized for tissue engineering applications. These newly introduced non-cytotoxic, biodegradable polyurethane composites had different compositions (i.e., ratio of hard to soft segments) of the linear, aliphatic hexamethylene diisocyanate and polycaprolactone diol. The porosity was introduced in the polyurethane matrix using a combination of salt leaching and thermally induced phase separation (TIPS). The resulting interconnected pore size was characterized using Scanning Electron Microscope (SEM) to be between 125-355 μm. Porosity was determined using liquid displacement and found to be between 70-75% for non-reinforced matrices, 64-70% for reinforcement with 5 wt% biocellulose nanofiber (BCNF), 59-69% for 10 wt% BCNF, and 57-69% for 15 wt% BCNF biocomposite samples. Dependent on the composition, compressive strength showed up to a little less than two-fold increase (85%) for green BCNF reinforcement of 5 wt% and more than two-fold increase (120%) for 10 wt%. The tensile strength also increased up to almost two-fold (114%) for reinforcement with 5 wt% BCNF and to more than two-fold (140%) for 10 wt% reinforcement. Higher degrees of reinforcement showed a detrimental effect on both properties. Properties demonstrate that this novel class of nanostructured biocomposite holds potential to be utilized as scaffolds for tissue regeneration.

High molecular weight polyethylenimine encapsulated into porous polymer monolithic by one-step polymerization for CO2 capture

A novel porous solid amine adsorbent (PEI@polyHIPE) with highly interconnected pore network was prepared by high inner phase emulsion polymerization (HIPE) of styrene and divinylbenzene, and was simultaneously functionalized with...

Formation of Free-Standing Inverse Opals with Gradient Pores

We demonstrate the fabrication of free-standing inverse opals with gradient pores via a combination of electrophoresis and electroplating techniques. Our processing scheme starts with the preparation of multilayer colloidal crystals by conducting sequential electrophoresis with polystyrene (PS) microspheres in different sizes (300, 600, and 1000 nm). The critical factors affecting the stacking of individual colloidal crystals are discussed and relevant electrophoresis parameters are identified so the larger PS microspheres are assembled successively atop of smaller ones in an orderly manner. In total, we construct multilayer colloidal crystals with vertical stacking of microspheres in 300/600, 300/1000, and 300/600/1000 nm sequences. The inverse opals with gradient pores are produced by galvanostatic plating of Ni, followed by the selective removal of colloidal template. Images from scanning electron microscopy exhibit ideal multilayer close-packed structures with well-defined boundaries among different layers. Results from porometer analysis reveal the size of bottlenecks consistent with those of interconnected pore channels from inverse opals of smallest PS microspheres. Mechanical properties determined by nanoindentation tests indicate significant improvements for multilayer inverse opals as compared to those of conventional single-layer inverse opals.

Leachable Poly(Trimethylene Carbonate)/CaCO3 Composites for Additive Manufacturing of Microporous Vascular Structures

The aim of this work was to fabricate microporous poly(trimethylene carbonate) (PTMC) vascular structures by stereolithography (SLA) for applications in tissue engineering and organ models. Leachable CaCO3 particles with an average size of 0.56 μm were used as porogens. Composites of photocrosslinkable PTMC and CaCO3 particles were cast on glass plates, crosslinked by ultraviolet light treatment and leached in watery HCl solutions. In order to obtain interconnected pore structures, the PTMC/CaCO3 composites had to contain at least 30 vol % CaCO3. Leached PTMC films had porosities ranging from 33% to 71% and a pore size of around 0.5 μm. The mechanical properties of the microporous PTMC films matched with those of natural blood vessels. Resins based on PTMC/CaCO3 composites with 45 vol % CaCO3 particles were formulated and successfully used to build vascular structures of various shapes and sizes by SLA. The intrinsic permeabilities of the microporous PTMC films and vascular structures were at least one order of magnitude higher than reported for the extracellular matrix, indicating no mass transfer limitations in the case of cell seeding.

Multilayer-structured fibrous membrane with directional moisture transportability and thermal radiation for high-performance air filtration

The demand of high-performance filter media for the face masks is urgent nowadays due to the severe air pollution. Herein, a highly breathable and thermal comfort membrane that combines the asymmetrically superwettable skin layer with the nanofibrous membrane has been fabricated via successive electrospinning and electrospraying technologies. Thanks to high porosity, interconnected pore structure, and across-thickness wettability gradient, the composite membrane with a low basis weight of 3.0 g m−2 exhibits a good air permeability of 278 mm s−1, a comparable water vapor permeability difference of 3.61 kg m−2 d−1, a high filtration efficiency of 99.3%, a low pressure drop of 64 Pa, and a favorable quality factor of 0.1089 Pa−1, which are better than those of the commercial polypropylene. Moreover, the multilayer-structured membrane displays a modest infrared transmittance of 92.1% that can keep the human face cool and comfort. This composite fibrous medium is expected to protect humans from PM2.5 and keep them comfortable even in a hygrothermal environment.