Al-Si/Al-Mn composites are commonly used in aluminum heat exchangers. Improving their corrosion resistance is the key for prolonging their service life and reducing their costs. In this paper, an ...artificial salt spray corrosion test was adopted in accordance with the ASTM G85 standard to evaluate the atmospheric corrosion resistance of Al-Si/Al-Mn composites. The corroded samples were tested with electrochemical impedance spectroscopy (EIS). Microstructure evolution and their corrosion mechanism were discussed after the use of OM, SEM, EPMA and XRD. The results showed two corrosion mechanisms, including the pitting-induction mechanism and intergranular-development mechanism: pitting is induced by the destruction of the passive film as Cl– is adsorbed at the defects, while the corrosive medium in the pitting pores expands along the grain boundaries where eutectic Si is enriched. A corrosion process can be divided into three periods: the pitting-induction period, pitting-propagation period and matrix-corrosion period. The equivalent circuit models established sequentially were consistent with the actual macroscopic and microscopic observations.
This study outlines the production of an electrically conductive clay-based composite containing the halloysite as clay mineral and poly(o-toluidine) (POT) as a conductive filler. In the study, ...conductive POT/halloysite composite was obtained by in situ oxidative polymerization of o-toluidine using ammonium persulphate (APS) as an oxidant between the halloysite layers. By changing the polymerization conditions such as polymerization time, o-toluidine concentration, APS, and the concentration of HCl solution used as the reaction medium, the composite with the highest conductivity (7.5×10-5 S.cm-1) was obtained. Structural and morphological changes and thermal behaviors that occurred after the composite formation was revealed using various characterization techniques such as FTIR, XRD, TGA, and SEM. The usability of the prepared POT/halloysite composite as humidity sensing material was tested in comparison with the pure POT component of the composite at a relative humidity (% RH) varied between 41-94 (%). Accordingly, it was found that the composite exhibited a fairly regular resistance change to varying relative humidity compared to pure POT polymer.
Bu çalışma, kil minerali olarak halloysit ve iletken bir dolgu maddesi olarak poli (o-toluidin) (POT) içeren elektriksel olarak iletken kil bazlı bir kompozitin üretimini özetlemektedir. Çalışmada, iletken POT / halloysit kompoziti, o-toluidinin, halloysit tabakaları arasında oksidant olarak amonyum persülfat (APS) kullanılarak in-situ oksidatif polimerizasyon yöntemi ile elde edildi. Polimerizasyon süresi, o-toluidin derişimi, APS ve reaksiyon ortamı olarak kullanılan HCl çözeltisi derişimi gibi polimerizasyon koşulları değiştirilerek en yüksek iletkenliğe sahip kompozit (7.5×10-5 Scm-1) elde edildi. Kompozit oluşumundan sonra meydana gelen yapısal ve morfolojik değişiklikler ve termal davranışlar FTIR, XRD, TGA ve SEM gibi çeşitli karakterizasyon teknikleri kullanılarak ortaya konuldu. Hazırlanan POT / halloysit kompozitin nem algılama malzemesi olarak kullanılabilirliği, 41-94 arasında değişen bir bağıl nemde (% RH) kompozitin saf POT bileşeni ile karşılaştırılarak test edilmiştir. Buna göre kompozitin, saf POT polimere kıyasla değişen bağıl neme karşı oldukça düzenli bir direnç değişikliği sergilediği bulundu.
We study theoretically the biaxial bending of symmetric, flat layered ceramic composites (laminates) due to external loading. We focus on three-layered alumina/zirconia laminates. We compare the ...principal stresses in the samples in the case of static and harmonic dynamic loading. The dynamic equation within the Kirchhoff theory for thin homogeneous plates is first generalized to the case of multilayered plates. It is solved numerically with the relaxation method, which we have developed for this purpose.
Primjena naprednih polimernih materijala Hrnjak-Murgić, Zlata; Peršić, Ana; Kratofil Krehula, Ljerka ...
Kemija u industriji; časopis kemičara i tehnologa Jugoslavije,
10/2019, Letnik:
68, Številka:
9-10
Journal Article
Recenzirano
Odprti dostop
Sve intenzivniji razvoj naprednih polimernih materijala kao što su polimerne mješavine i (nano)kompoziti nude brojna inovativna rješenja za različitu upotrebu, što ima velik ekonomski značaj za ...plastičnu industriju i područja u kojima se primjenjuju. Napredne tehnike modificiranja polimera razvile su se gotovo do krajnjih granica, a znatno su poboljšale omjer troškova i svojstava nastalih modifikacijom strukture polimera. Miješanje različitih polimera, priprema (nano)kompozita te stvaranje višeslojnih materijala, laminata neke su od najznačajnijih tehnika modifikacije. Pri tome postoje sinergistička djelovanja između komponenti, kako bi se postigli izvrsni učinci koji su prilagođeni specifičnim primjenama, kao npr. antimikrobno djelovanje, blokiranje ultraljubičastog svjetla, smanjenje gorivosti, fotokatalitičko djelovanje, a u radu su prikazani rezultati ispitivanja polimernih nanokompozita s ciljem modifikacije navedenih svojstava.
The intense development of advanced polymer materials, such as polymer blends and (nano)composites, offers a number of innovative solutions for different applications, which is of great economic importance for the plastics industry and the fields in which they are applied. Advanced polymer modification techniques have pushed the limit, and have significantly improved the cost/properties ratio engendered by manipulating the structure of polymers. Blending dissimilar polymers, preparing composites where polymer matrix is modified by fillers, and creating multilayer structures and laminates are some of the most significant polymer modification techniques. In such modification, synergistic effects between the components are required in order to achieve excellent performances tailored to specific applications, such as antimicrobial activity, blocking ultraviolet light, reducing flammability, photocatalytic activity. This paper presents the results of the research on polymer nanocomposites aimed at the modification of the aforementioned properties.
In this study, copper alloy matrix composites reinforced with tungsten carbide (WC) particles with the addition of different Ni contents (0, 3, 5, 7, and 10 wt.%) were prepared by the spontaneous ...infiltration process. Image analysis was used to quantify the microstructural parameters, such as the particle size and distribution, area fraction, binder mean free path, and pore size. The effect of Ni addition on the microstructure, density and hardness are discussed. The results show that a small addition of Ni improves the densification of the infiltrated composites. The highest density value of 11.84 g/cm3 with a hardness of 327 HV was obtained for the infiltrated composite with the addition of 3 wt.% of Ni. The quantitative analysis results are in good agreement with the microstructure properties and hardness results.
nema
Novel ultrafine grain composites of Cu matrix reinforced with 2-50 wt. % of Ti48Cu39.5Ni10Co2.5 and Ti48Cu39.5Zr10Co2.5 (at. %) amorphous-nanocrystalline alloy particles have been fabricated by ...powder metallurgy. The composites showed a homogeneous structure. The characterization of composites was performed by optical and scanning electron microscopy (SEM), X-ray powder diffraction (XRD), micro- and macrohardness, as well as density measurements. After hot-pressing the crystallite size of Cu was smaller than 200 nm and nanocrystalline phases of reinforcing powder were 5-35 nm. Densities of 97-76 % relative to calculated values of consolidated composites were obtained, depending on the reinforcing weight fraction. Additionally, the mechanical properties and electrical resistivity of composites have been investigated. The results reveal that the 0.2% offset compressive yield strength of composites increases by two and five times, with respect to pure Cu matrix, for the composites reinforced with 2 and 50 wt. % of reinforcing particles, respectively. Electrical resistivity increases continuously, with higher values after 30 wt. % of addition. Changes in mechanical and electrical properties were produced by the increase of amorphous-nanocrystalline additive.
nema
Opisan je višenamjenski diferencijalni toplinski konduktometar za tekstilne kompozite i odjeću koji može mjeriti kontaktni otpor prolasku topline kroz tekstilne plošne tvorevine, tekstilne kompozite ...ili dijelove odjeće, pri čemu može mjeriti debljine navedenih ispitnih uzoraka, kompresibilnost, toplinsku vodljivost pri različitim specifičnim tlakovima i gradijente pada temperature unutar slojeva kompozita ili odjeće.
This study examined the effects of wood pulp fiber length (short, medium, and long), and fiber loading (27%,
37%, 47%, and 0% non-reinforced PP) with 3% maleic anhydride-grafted polypropylene on the ...mechanical properties
of wood-plastic composites (WPCs). Polypropylene and fibers were compounded into pellets using a counter-rotating
twin-screw extruder and test specimens were prepared by injection molding. The results show that increases in fiber
length and fiber loading significantly increased (P < 0.05) the mechanical properties of the WPCs (MOE and tensile
modulus). The behavior of the composites against MOR and impact strength varied according to fiber length and loading
level. In general, the tensile strength was observed to be the same.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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