An Empirical Formula for Sound Absorption of Fibrous Materials

The sound absorption coefficient(SAC)curves of the nonwovens,fabrics,and thick fibrous layers with the frequency in the range of 125-3 200 Hz and cavity distances of 5 cm,10 cm,20 cm,30 cm and 40 cm were measured.Based on analysis,it is found that the SAC is actually in direct proportion to the relative vibration amplitude of the sound wave,resulting in obtaining a mathematical expression showing that the SAC changes with the frequency for a given material.Additionally,a good corresponding relation between the maximal SAC and the permeability of the materials is discovered,thus an empirical formula is established.As a result,a complete SAC formula has been developed.In this formula,the SAC is solely a function of the sound wave frequency and permeability of the material.In comparison with sound absorption spectra of several materials,the calculated results and results measured with the formula coincide well with each other.

Recent Advances in Fibrous Materials for Hydroelectricity Generation

Depleting fossil energy sources and conventional polluting power generation pose a threat to sustainable development.Hydroelectricity generation from ubiquitous and spontaneous phase transitions between liquid and gaseous water has been considered a promising strategy for mitigating the energy crisis.Fibrous materials with unique flexibility,processability,multifunctionality,and practicability have been widely applied for fibrous materials-based hydroelectricity generation(FHG).In this review,the power generation mechanisms,design principles,and electricity enhancement factors of FHG are first introduced.Then,the fabrication strategies and characteristics of varied constructions including 1D fiber,1D yarn,2D fabric,2D membrane,3D fibrous framework,and 3D fibrous gel are demonstrated.Afterward,the advanced functions of FHG during water harvesting,proton dissociation,ion separation,and charge accumulation processes are analyzed in detail.Moreover,the potential applications including power supply,energy storage,electrical sensor,and information expression are also discussed.Finally,some existing challenges are considered and prospects for future development are sincerely proposed.

TiO2-PES Fibrous Composite Material for Ammonia Removal Using UV-A Photocatalyst

This study focused on the development and characterization of TiO2-PES composite fibers with varying TiO2 loading amounts using a phase inversion process. The resulting composite fibers exhibited a sponge-like structure with embedded TiO2 nanoparticles within a polymer matrix. Their photocatalytic performance for ammonia removal from aqueous solutions under UV-A light exposure was thoroughly investigated. The findings revealed that PeTi8 composite fibers displayed superior adsorption capacity compared to other samples. Moreover, the study explored the impact of pH, light intensity, and catalyst dosage on the photocatalytic degradation of ammonia. Adsorption equilibrium isotherms closely followed the Langmuir model, with the results indicating a correlation between qm values of 2.49 mg/g and the porous structure of the adsorbents. The research underscored the efficacy of TiO2 composite fibers in the photocatalytic removal of aqueous under UV-A light. Notably, increasing the distance between the photocatalyst and the light source resulted in de-creased hydroxyl radical concentration, influencing photocatalytic efficiency. These findings contribute to our understanding of TiO2 composite fibers as promising photocatalysts for ammonia removal in water treatment applications.

Recent Advances in Fibrous Materials for Interfacial Solar Steam Generation

The scarcity of fresh water resources has become a serious issue hindering the sustainable development of modern civilization.The interfacial solar steam generation(ISSG)system that produces heat on material surface through photothermal conversion for desalination has been demonstrated as a promising candidate for practical application.Fibrous materials with unique flexibility,durability,processability,practicability,and multifunctionality have attracted considerable attention in the ISSG field.In this review,the basics of fibrous materials,such as their classification,manufacturing methods and flexible fibrous structure,are firstly introduced.Afterward,the outstanding properties of fibrous materials on different dimensions are demonstrated,as well as the versatile morphologies and structures that allow fibrous materials to carry out different roles in ISSG.Moreover,the practicability and multifunctionality of fibrous materials are illustrated in detail by combining specific cases to show their promising potential in practical ISSG application.Finally,existing challenges and future opportunities of fibrous material-based ISSG systems are discussed.

Fabrication of Fibrous Mullite-alumina Ceramic with High Strength and Low Thermal Conductivity

Optimizing highly porous fibrous ceramics, like bird’s nest structure, were obtained by vacuum impregnation method with mullite fibers and alumina sol as raw material. The influences of impregnation cycles on the property of the sample, such as porosity, compressive strength and room-temperature thermal conductivity were explored. The experimental results show that the 3D skeleton structure of the sample was constructed by the randomly arranged mullite fibers and inorganic particles. The content of alumina can be adjusted effectively by impregnation times and it increases with increasing impregnation cycles. The thermal conductivity and compressive strength can also be controlled via tailored impregnation cycles. The compressive strength of fibrous ceramic ranged from 1.03 MPa to 5.31 MPa, while the porosity decrease slightly from 85.3% to 73.8%. In the same time, the thermal conductivity increase from 0.037 W/(m·K) to 0.217 W/(m·K), indicating that the fibrous ceramic with high impressive and low thermal conductivity can be fabricated by impregnation method.

Textile electronics for wearable applications

Textile electronics have become an indispensable part of wearable applications because of their large flexibility,light-weight,comfort and electronic functionality upon the merge of textiles and microelectronics.As a result,the fabrication of functional fibrous materials and the integration of textile electronic devices have attracted increasing interest in the wearable electronic community.Challenges are encountered in the development of textile electronics in a way that is electrically reliable and durable,without compromising on the deformability and comfort of a garment,including processing multiple materials with great mismatches in mechanical,thermal,and electrical properties and assembling various structures with the disparity in dimensional scales and surface roughness.Equal challenges lie in high-quality and cost-effective processes facilitated by high-level digital technology enabled design and manufacturing methods.This work reviews the manufacturing of textile-shaped electronics via the processing of functional fibrous materials from the perspective of hierarchical architectures,and discusses the heterogeneous integration of microelectronics into normal textiles upon the fabric circuit board and adapted electrical connections,broadly covering both conventional and advanced textile electronic production processes.We summarize the applications and obstacles of textile electronics explored so far in sensors,actuators,thermal management,energy fields,and displays.Finally,the main conclusions and outlook are provided while the remaining challenges of the fabrication and application of textile electronics are emphasized.

An Elastic Absorber Theory for a Thin Fabric Sheet

The current sound absorption theory which is based on Rayleigh model believes that fibrous material absorb sound by the fluid frictional energy dissipation between the air and the solid fibers. However, Rayleigh model is only useful for a quanlitative understanding of effects In a porous material but not for calculation of the acoustical properties of real absorbent. In this paper, a new vibration sound absorption theory which is totally different from classical theory was put forward. The specific acoustic impedance of fiber layers have been derived from the membrane vibration equation and the sound absorption coefficient calculated agree with test results. The new theory can explaIn the phenomenon that thIn fiber layers exhibit less sound absorption coefficient when it was as the cover fabric of sound absorber, but it is more efficient to sound absorption when it was hang as the curtains or have back cavity behind it.

Anisotropic Structure of Glass Wool Determined by Air Permeability and Thermal Conductivity Measurements

We want to conclude on the interest of the “crimping” process used to produce the glass wool and to make a comparison for anisotropic factor obtained from structural property (air permeability) as well as thermal property (thermal conductivity and diffusivity). The main structural (densities, porosity, specific surface, air permeability) and the thermal (conductivity, diffusivity, heat capacity) characteristics of this glass wool are presented. Thermal results are determined by using several methods (Hot disc (HD), Heat Flow Meter (HFM) and Guarded Hot Plate).

Dynamic flow resistivity based model for sound absorption of multi-layer sintered fibrous metals

The sound absorbing performance of the sintered fibrous metallic materials is investigated by employing a dynamic flow resistivity based model,in which the porous material is modeled as randomly distributed parallel fibers specified by two basic physical parameters:fiber diameter and porosity.A self-consistent Brinkman approach is applied to the calculation of the dynamic resistivity of flow perpendicular to the cylindrical fibers.Based on the solved flow resistivity,the sound absorption of single layer fibrous material can be obtained by adopting the available empirical equations.Moreover,the recursion formulas of surface impedance are applied to the calculation of the sound absorption coefficient of multi-layer fibrous materials.Experimental measurements are conducted to validate the proposed model,with good agreement achieved between model predictions and tested data.Numerical calculations with the proposed model are subsequently performed to quantify the influences of fiber diameter,porosity and backed air gap on sound absorption of uniform(single-layer)fibrous materials.Results show that the sound absorption increases with porosity at higher frequencies but decreases with porosity at lower frequencies.The sound absorption also decreases with fiber diameter at higher frequencies but increases at lower frequencies.The sound absorption resonance is shifted to lower frequencies with air gap.For multi-layer fibrous materials,gradient distributions of both fiber diameter and porosity are introduced and their effects on sound absorption are assessed.It is found that increasing the porosity and fiber diameter variation improves sound absorption in the low frequency range.The model provides the possibility to tailor the sound absorption capability of the sintered fibrous materials by optimizing the gradient distributions of key physical parameters.

Structural and Interfacial Effects on Drug Release Kinetics of Liquid‑Based Fibrous Catheter

Catheterization is indispensable in the field of modern medicine.However,catheter-related thrombosis and infections almost inevitably occur during the process,and as drugs can only be administered at the end of catheter,auxiliary strategies are required for successful implantation.Considering these intractable limitations,a type of self-adaptive,anti-coagulate liquidbased fibrous catheter has been developed.More importantly,it has positional drug release property that traditional catheters desperately need but couldn’t attain.Although enlightening,the feasibility and performance of the positional drug release have only been demonstrated by fluorescents,the specific drug release kinetics remains unknown for adaptation to application scenarios.Therefore,we systematically investigate the structural and interfacial effects of drug molecules and fibrous matrixes on drug release kinetics in a liquid-based fibrous catheter.Theoretical calculations and experiments demonstrate that oleophilic and hydrophilic molecules release slowly due to a dissolution-diffusion mechanism.Amphipathic molecules,however,will significantly affect the gating performance by affecting the interfacial stability,hence they release quickly with emulsifying the gating liquid.Besides the significant impact of molecular properties and interfacial effects,matrix pore size also has a slight influence that molecules release faster in bigger pores.Through this study,the liquid-based fibrous catheter may step further toward practical applications including chemotherapy,haemodialysis,angiography,etc.to overcome the existing catheter-related limitations.

Synthesis,Characteristics and Applications of Fibrous Composites with Immobilized Nanomolecular Layers of Ferrocyanides and Phosphates of Some d-Elements

1 Results The general principle of the synthesis of fibrous inorganic ion-exchanging composites, containing the combination of polymer analogous conversion reactions of the fibres and cycles of ion-molecular layering is advanced. Synthesis of thin nanomolecular layers of the acid Ti(Ⅳ) and Zr(Ⅳ) phosphates on surface of the cotton fibres and Cu(Ⅱ) and Fe(Ⅲ) ferrocyanides-on polyacrylonitrile fibres was performed on the basis of this principle. By the method of X-ray analysis it was stated that the forme...

Experimental determination of effective light transport properties in fully anisotropic media

Structurally anisotropic materials are ubiquitous in several application fields,yet their accurate optical characterization remains challenging due to the lack of general models linking their scattering coefficients to the macroscopic transport observables and the need to combine multiple measurements to retrieve their direction-dependent values.Here,we present an improved method for the experimental determination of light-transport tensor coefficients from the diffusive rates measured along all three directions,based on transient transmittance measurements and a generalized Monte Carlo model.We apply our method to the characterization of light-transport properties in two common anisotropic materials—polytetrafluoroethylene tape and paper—highlighting the magnitude of systematic deviations that are typically incurred when neglecting anisotropy.