According to the World Health Organization, noise pollution is second only to air pollution in its impact on health and the environment. Fiber-based sound-absorbing structures have great application potential in the field of sound absorption and noise reduction because they can provide a wider sound absorption range than traditional porous fiber materials, and at the same time have the advantages of light weight, low cost and strong processability. Consequently, significant research interest in the field of noise control has been directed into the study of composite sound-absorbing materials based on porous fiber materials. In this review, we have summarized manifold theoretical structures based on fiber materials, such as multilayer structure, porous micro/nano structure, membrane sound-absorbing structure and perforated resonance structure of fiber-based sound-absorbing structures, aiming to illustrate that the structure must affect the sound absorption performance of the material. The focus is on the research and development of the design concepts, and preparation methods of fiber-based acoustic structures are reviewed. Finally, this review concludes with the prospects and outlook for fiber-based acoustic structures. We hope that this article which reviews the structure design principle and preparation method of fiber-based sound-absorbing structures can give inspirations for readers.
Biosynthesis of metal-oxide nanoparticles using plant extracts has been attracting increasing interest. In this study, we focused on the green synthesis of zinc oxide (ZnO) nanomaterials using zinc acetate as a precursor and mulberry fruit extract as a green reducing agent and determined the antioxidant activity. Powder X-ray diffraction and UV-Vis and Fourier Transform Infra-Red (FT-IR) spectroscopy were used for structure elucidation and to determine the crystallinity of the synthesized product. The morphology of samples was determined using Scanning Electron Microscopy (SEM). Our results indicated the successful synthesis of ZnO nanoparticles. SEM findings revealed the nanoparticles to be spherical; they were found to agglomerate and showed a narrow space between particles, which could be indicative of improved activity. The antioxidant activity of ZnO nanoparticles was determined using a 2,2-Diphenyl-1-Picryl-Hydrazyl (DPPH) free-radical scavenging assay taking into account time and concentration. Our results indicated that ZnO nanoparticles with mulberry fruit extract that were synthesized using green chemistry could effectively scavenge the free DPPH radicals, thereby confirming their superior antioxidant activity.
In the structural design of sound-absorbing materials, how to combine the merits of porous materials with acoustic functional fillers with special structures to improve the sound-absorbing performance of porous materials at low-medium frequencies is a challenging problem. Herein, a directionally antagonistic acoustic textile is proposed as a sound absorber fabricated via single-sided coating. It is found that the sound absorber presents a double gradient structure by controlling the distribution of filler on the porous material frame. Considering the incident plane of acoustic waves, two different paths are defined, namely A–B and B–A (A, coated side; B, uncoated side), under which the sound absorber shows remarkable anisotropic sound absorption. The peak frequency is from 5559 Hz of bare fabric to 3455 Hz of the A–B NWIII (coated nonwoven when sound waves propagate along A–B) sound absorber, showing a significant tendency to move to the lower frequencies. The peak value of sound absorption coefficient of the A–B NWIII is 0.94, indicating a high sound absorptivity. In addition, by adjusting the acoustic functional filler and weaving structure and thickness of the base fabric, the sound absorber exhibits the expected anisotropic sound absorption. The novel sound absorber can be fit for lightweight sound-absorbing applications because of the characteristics of light, soft, high efficiency and broadband sound absorption.
Indigo is one of the most widely used dyes in history, but its application is currently greatly limited due to the lack of clean and efficient reduction methods. Aimed at the long-term consumption of traditional bio-reduction of indigo and the ecological problems existing in the application of chemical reducing agents, a high-efficiency indigo dyeing method based on pH-controlled bio-reduction of Saccharomyces cerevisiae under an aerobic environment at normal temperature was constructed. The results showed that the reduction ability of the bio-reduction system and its effect on dye reduction was closely related to the growth and metabolism of cells and the pH of the system. It is worth noting that a suitable alkaline environment is a key to improving the reduction capacity and shortening the reduction time. Under the dyeing pH condition of 10, the K/S of the fabric could reach 6.2 and exhibited the greatest color strength with good fastness after dyeing for 4 days. A pH-controlled bio-reduction strategy with whole-cell biotransformation was designed to construct an indigo green dyeing system with high efficiency and less environmental pollution.
Oak Ridge, TN 37831-6038 1.Research Objective: Laser-ablation based decontamination is a new and effective approach for simultaneous removal and characterization of contaminants from surfaces (e.g., building walls, ground floors, etc.). The scientific objectives of this research are to: (1) characterize particles generated during laser decontamination, (2) develop a technique for simultaneous cleaning and verification, and (3) develop a model for predicting particle generation. The research will provide fundamental data regarding the particle generation mechanisms, and a model for prediction of particle generation such that an effective control strategy can be devised to facilitate worker protection. 2.Research Progress and Implications: This report summarizes work performed from FY02-04. A technique for simultaneous surface cleaning using laser plasma and contaminant verification using the plasma emissions has been developed. The effects of laser treatment (ablation) on surface decontamination were systematically examined. The decontamination technique does not produce a large quantity of highly contaminated secondary liquid waste that could be produced when an alternative technique such as a wet scrubbing method is employed. The new technique will save both time and cost by preventing removal of an unnecessarily large quantity of material during building decommission and decontamination of DOE facilities. The new technique will save a significant amount of analytical cost because it can characterize the effectiveness of surface decontamination in real time; thus, it does not create a latent and undesired waiting period for decision making and material transport off-site.Over the past three years, a large volume of experimental data has been collected at the Laboratories of Aerosol Science and Technology (ASTL) at ORNL for cement, stainless steel, contaminant-added cement, and alumina. The first three materials are commonly found in the DOE complex, while the last material was included for fundamental research purposes. It will possibly take another year to fully analyze the data. However, previous analysis indicates that the particles produced during the decontamination/ablation process are ultrafine (dp < 100 nm) and fine particles (dp < 1,000 nm). Rarely, particles greater than 1 micrometer were found. These facts are unequivocal for all the materials tested. Instrumentation data from a commercial scanning mobility particle sizer, a research-grade nano-aerosol sizer, and TEM are consistent and all indicate that no supermicron particles were generated. A TEM image (Fig. 1) of the particles generated from alumina and the energy dispersive spectrum (EDS) of the particles (Fig. 2) are shown below. The main circle (~ 100 nm in diameter) was likely formed by condensation of Al vapor onto nuclei, because the particle surface appears to be coated with Al as indicated in the EDS.
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