Isolation and characterization of cellulose nanowhiskers from Acacia caesia plant

Acacia caesia (L.) Willd (soap bark) fiber is an abundant natural resource, that is rich in cellulose. The study reports the effective utilization of underutilized Acacia caesia fiber for the isolation of nanocellulose whiskers. The nanocellulose whiskers were isolated successfully from Acacia caesia fibers by following alkali, bleaching, and sulfuric acid treatment. The obtained nanocellulose whiskers were carefully investigated for its chemical composition, structure, morphology, crystallinity, and thermal stability. The chemical composition and Fourier transform infrared spectra of nanocellulose whiskers showed the elimination of the non-cellulosic parts present in the raw Acacia caesia fibers. The X-ray diffraction analysis showed an upsurge in the crystallinity of the cellulose fibers after the chemical treatments. The isolation of nanocellulose whiskers from Acacia caesia raw fiber was confirmed by electron microscopy analysis. The thermogravimetric analysis showed remarkably high char residue for the nanocellulose whiskers compared to raw fibers. Based on the properties of nanocellulose whiskers, it can be concluded that the nanocellulose whiskers produced from Acacia caesia raw fibers are potential reinforcing material for developing high-performance green composites.     

铋对SAC305−xBi/Cu焊接接头显微组织、热性能、力学性能和界面行为的影响

通过添加1％ 和2％(质量分数)的Bi提高SAC305焊接接头的性能,并研究Bi掺杂对SAC305?xBi/Cu焊接接头显微组织、热性能和力学性能的影响.Bi掺杂通过细化初始β-Sn和共晶相改善焊接接头的显微组织.当Bi含量低于2％ 时,Bi溶解到β-Sn基体中形成固溶体;而当Bi含量等于或高于2％时,β-Sn基体中形...     

Influence of surface treatment on properties of Cocos nucifera L. Var typica fiber reinforced polymer composites

Natural fibers are a powerful competitor in the polymer composite market due to their availability, sustainability, obtainability, cost, and biodegradability. The surface of natural fibers was changed to increase mechanical qualities, hydrophobicity, and bonding with polymer matrix. This study exposes the influence of several surface treatments of coconut tree peduncle fibers (CTPFs) on the thermomechanical and water absorption properties of CTPF-reinforced polymer composites. The CTPFs were treated with sodium hydroxide, benzoyl peroxide, potassium permanganate and stearic acid at a constant 40 wt% and individually reinforced in an unsaturated polyester resin matrix containing 60 wt% CTPFs. Chemically treated CTPFs improved reinforcement-matrix adhesion and enhanced composite mechanical characteristics. In addition, the scanning electron microscope fractographical study of stressed composite specimens shows improved reinforcement-matrix bonding. Moreover, the treated CTPFs have a higher cellulose wt%, which improves the composites crystalline nature, hydrophobicity and thermal stability. The potassium permanganate treated CTPF composite's maximum tensile strength of 128 MPa, flexural strength of 119 MPa, impact strength of 9.9 J/cm², hardness value of 99 HRRW and thermal stability up to 193°C make them appropriate for lightweight mobility and structural applications.     

Comparative Evaluation of Hot-Air and Superheated-Steam Impinging Stream Drying as Novel Alternatives for Paddy Drying

An investigation was conducted on impinging stream drying of moist paddy using hot air and superheated steam as the drying media. Drying experiments were divided into two parts: namely, one-pass and two-pass drying. The volumetric water evaporation rate, volumetric heat transfer coefficient, and specific energy consumption of the drying system at various conditions were assessed; in the case of superheated-steam drying, the effect of steam recycle was also assessed. The quality of dried paddy was evaluated in terms of color, head rice yield, and degree of starch gelatinization. In the case of one-pass drying, an increase in the drying temperature led to a significant increase in the volumetric water evaporation rate and volumetric heat transfer coefficient. On the other hand, in the case of two-pass drying, an increase in the drying temperature led to a significant decrease in the volumetric heat transfer coefficient; the volumetric water evaporation rate was not significantly affected, however. The specific energy consumption decreased with an increase in the drying temperature. At the same temperature, using superheated steam as the drying medium led to lower specific energy consumption; higher level of steam recycle also led to more energy conservation. The color of the dried paddy was not affected by the change in the drying temperature; superheated-steam-dried paddy was redder and more yellow than the hot-air-dried paddy. An increase in the drying temperature led to decreased percentage of head rice yield. Superheated-steam drying helped enhance the level of starch gelatinization in comparison with hot-air drying at the same temperature. Nevertheless, drying at the highest tested temperature led to a lower level of starch gelatinization.     

Investigations on physical,mechanical, morphological and water absorption properties of ramie/hemp/kevlar reinforced vinyl ester hybrid composites

Structural uses in the vehicle, aerospace, and sporting goods industries are being supplanted by hybrid composites that utilized natural fibers as reinforcements. The main focus of this work is to fabricate and characterize the ramie, hemp, and kevlar fabric reinforced hybrid vinyl ester composites. The composite laminates were fabricated via economically feasible and flexible hand lay-up technique. Overall six composites were prepared by varying the stacking sequence, including both hybrid and non-hybrid composites. The prepared composites were subjected to physical analysis (density, void fraction), mechanical tests (tensile, flexural, interlaminar shear, and impact test), morphological analysis (scanning electron microscopy), and water absorption test. The hybrid composites exhibited lesser void percentage than the non-hybrid composites. The mechanical properties were maximum for kevlar fabric skinned with core natural fabric reinforced composites (L-5, L-6) due to hybridization of highly strengthened kevlar fabrics. Moreover, the number fabric layers reinforced to achieve the standard thickness also affected the mechanical properties. All composite morphologies exhibited the same failure characteristics, including transverse interlaminar shear cracking, microbuckling, and fiber rip. The texture of the Kevlar yarns is uniform, but the texture of the natural fabric yarns is relatively less uniform. In comparison to the salt water medium, the percentage of water absorbed by composites in normal and distilled water was greater. This is due to the presence and accumulation of salt particles on the surface of the materials, which inhibits the action of water molecules, resulting in a drop in the proportion.     

Effects of antimony on the microstructure,thermal properties,mechanical performance,and interfacial behavior of Sn–0.7Cu–0.05Ni–xSb/Cu solder joints

Journal of Materials Science: Materials in Electronics - We investigated a new, lead-free solder alloy to replace traditional lead-based solder alloys. A Sn–0.7Cu–0.05Ni solder alloy...     

Processing and characterization analysis of pyrolyzed oil rubber (from waste tires)‐epoxy polymer blend composite for lightweight structures and coatings applications

In this experimental investigation, the authors have fabricated and characterized composites made from pyrolysis oil rubber and epoxy resin. As the dumping of waste scrap tires poses a serious environmental threat, the pyrolysis oil rubber was extracted from these waste tires only. The prepared blend having pyrolysis oil with various weight percentages (wt%) was examined on the basis of various physical, microstructural, mechanical, and thermal tests. The microstructural tests (scanning electron microscopy and X‐ray diffraction) analysis complemented with the mechanical tests (tensile, compression, flexural, hardness, and impact) results and confirmed that the 4.4 wt% of pyrolysis oil in epoxy resin sample exhibited the best results in toughening of the polymer network. Furthermore, the thermal analysis (differential thermal analysis and thermogravimetric analysis), electrical conductivity, density, water absorption, gas chromatography–mass spectroscopy, and Fourier‐transform infrared tests for the composites were also performed. Low density and high tensile strength than neat epoxy resin makes this composite a potential candidate for fabricating lightweight structures and in polymer coatings for automotive industries. POLYM. ENG. SCI., 59:2041–2051, 2019. © 2019 Society of Plastics Engineers     

Antibacterial and thermomechanical properties of composites of polylactic acid modified with capsicum oleoresin-impregnated nanoporous silica

Biodegradable composite films of poly(lactic acid) (PLA) modified with varying amounts of capsicum oleoresin (CO)-impregnated nanoporous silica (SiCO) were prepared. The antimicrobial and thermomechanical properties of the PLA composites were carefully investigated. The Gram-positive pathogenic bacteria (Staphylococcus aureus and Bacillus) and the Gram-negative pathogenic bacteria (Escherichia coli and Salmonella enterica) tests established excellent antimicrobial properties of the composites even at small concentrations of SiCO. The microscopic (scanning electron micrograph) and spectroscopic (energy-dispersive X-ray) investigations manifested the uniformity of particle distribution. Although the addition of CO slightly decreased the thermal stability of the composite films, it marginally enhanced the mechanical properties and crystallinity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47825.     

Comparing phenanthrene degradation by alginate‐encapsulated and free Pseudomonas sp. UG14Lr cells in heavy metal contaminated soils

BACKGROUND: Many polycyclic aromatic hydrocarbon (PAH) contaminated sites also contain high levels of toxic heavy metals. The presence of heavy metals can adversely affect PAH biodegradation. Encapsulation of bacterial cells has been shown to improve survival and activity of cells under various environmental stresses. This study examined if encapsulation of a phenanthrene‐mineralizing bacterial strain could improve its survival and phenanthrene degradation in heavy metal contaminated soils. RESULTS: Alginate encapsulation did not improve survival and phenanthrene degradation by Pseudomonas sp. UG14Lr in heavy metal contaminated soil. Phenanthrene degradation by, and survival of, free cells and alginate‐encapsulated cells were similar in soil contaminated with 5 mg kg^?1 dry soil of As, Cd, or Pb. The number of UG14Lr cells decreased to undetectable level when the concentration of each heavy metal was increased to 100 mg kg^?1 dry soil. UG14Lr, when inoculated as free cells, survived the best and they were detected over 60 days of incubation in soil. Cells in both wet and dry alginate beads survived less well than free cells at the higher metal concentrations. Correspondingly, phenanthrene degradation in soil inoculated with free UG14Lr was better than that in soil inoculated with alginate‐encapsulated cells. CONCLUSION: Alginate encapsulation adversely affected the survival and phenanthrene degradation ability of UG14Lr cells in heavy metal contaminated soil. It is postulated that alginate may have concentrated the metals which in turn increased the toxicity to UG14Lr cells. The results are of interest to those interested in the use of encapsulation technology to formulate microbial cells for bioremediation purposes. Copyright © 2009 Society of Chemical Industry