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.
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, Volume:
68, Issue:
9-10
Journal Article
Peer reviewed
Open access
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.
Ultrastructure of adhesive bond is a significant indicator of the efficiency of the bond between material and dental tissue. Bonding between composite and hard dental tissue is also most commonly ...assessed by measuring bonding strength or by absence of marginal gap along restoration interface.
The aim of this investigation was to estimate ultrastructural features of the bond between composite materials and dentin after using two adhesive techniques.
Twenty Class V cavities on extracted teeth were prepared and restored for scanning electron microscope (SEM) analysis of composite bonding to dentin. Adhesion was achieved by Adper Single Bond 2-ASB/3M ESPE or by Adper Easy One-AEO/3M ESPE. Photopolymerization of adhesives and composite material Filtek Ultimate FU/3M ESPE was performed using halogen light (Elipar Highlight 3M ESPE). After vertical sections through crown of teeth and composite restorations, surfaces of sections were treated with 37% phosphoric acid-60s and 2% NaOH-60s to remove the smear layer and obtain a better view of adhesive bond.
SEM analysis of adhesive bond showed better micromorphological bonding of composite to dentin after etch and rinse adhesive technique (ASB/FU matherials) than after self-etch technique (AEO/FU materials). In etch and rinse technique, the ultrastructure of adhesive bond to dentin was composed of adhesive and hybrid layers, with resin processes in dentinal canals. In self-etch technique, apart from adhesive and hybrid layers, resin processes were rare or were not observed at all. Better ultastructural bonding of composite restoration to dentin was obtained with etch and rinse adhesive technique.
Ultrastruktura adhezivne veze je značajan pokazatelj efikasnosti pripoja materijala za zubna tkiva. Kvalitet veze kompozita za tvrda zubna tkiva takođe se procenjuje jačinom vezivanja ili odsustvom marginalne pukotine po obodu restauracija.
Cilj ovog rada bio je da se proceni ultrastruktura veze kompozitnih materijala za dentin nakon primene dve adhezivne tehnike.
Na ekstrahovanim zubima restaurisano je 20 kaviteta V klase za skenirajuću elektronsku mikroskopsku (SEM) analizu pripoja kompozita za dentin. Adhezija je obezbeđivana primenom Adper Single Bond2- ASB/3M ESPE, odnosno primenom Adper Easy One-AEO/3M ESPE. Svetlosna polimerizacija adheziva i kompozitnog materijala Filtek Ultimate-FU-/3M ESPE vršena je halogenim svetlom (Elipar Highlight 3M ESPE). Nakon vertikalnog presecanja krunica zuba kroz kompozitne restauracije i pripreme površine preseka (30% fosforna kiselina-30s i 2% NaOH-30s), vršena je SEM analiza adhezivne veze. Bolje mikromorfološko vezivanje kompozita za dentin SEM analiza adhezivne veze pokazala je kod adhezivne tehnike sa nagrizanjem i ispiranjem zubnih tkiva (ASB/FU materijali), u odnosu na tehniku samonagrizanja tkiva (AEO/FU materijali). Kod tehnike nagrizanja i ispiranja, ultrastruktura adhezivne veze za dentin sastojala se od hibridnog i adhezivnog sloja, kao i produžetaka smole u dentinskim kanalićima. Kod samonagrizajuće tehnike, pored adhezivnog i hibridnog sloja, retko su viđani ili uopšte nisu postojali produžeci smole u kanalićima.
Bolju ultrastrukturu veze kompozita za dentin obezbedila je primena adhezivne tehnike sa nagrizanjem i ispiranjem tkiva.
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