Martin Nosko

Label-free detection of glycoproteins by the lectin biosensor down to attomolar level using gold nanoparticles

We present here an ultrasensitive electrochemical biosensor based on a lectin biorecognition capable to detect concentrations of glycoproteins down to attomolar (aM) level by investigation of changes in the charge transfer resistance (Rct) using electrochemical impedance spectroscopy (EIS). On polycrystalline gold modified by an aminoalkanethiol linker layer, gold nanoparticles were attached. A Sambucus nigra agglutinin was covalently immobilised on a mixed self-assembled monolayer formed on gold nanoparticles and finally, the biosensor surface was blocked by poly(vinyl alcohol). The lectin biosensor was applied for detection of sialic acid containing glycoproteins fetuin and asialofetuin. Building of a biosensing interface was carefully characterised by a broad range of techniques such as electrochemistry, EIS, atomic force microscopy, scanning electron microscopy and surface plasmon resonance with the best performance of the biosensor achieved by application of HS-(CH2)11-NH2 linker and gold nanoparticles with a diameter of 20 nm. The lectin biosensor responded to an addition of fetuin (8.7% of sialic acid) with sensitivity of (338 ± 11) Ω decade(-1) and to asialofetuin (≤ 0.5% of sialic acid) with sensitivity of (109 ± 10) Ω decade(-1) with a blank experiment with oxidised asialofetuin (without recognisable sialic acid) revealing sensitivity of detection of (79 ± 13) Ω decade(-1). These results suggest the lectin biosensor responded to changes in the glycan amount in a quantitative way with a successful validation by a lectin microarray. Such a biosensor device has a great potential to be employed in early biomedical diagnostics of diseases such as arthritis or cancer, which are connected to aberrant glycosylation of protein biomarkers in biological fluids.

Strain Rate Sensitivity, Work Hardening, and Fracture Behavior of an Al-Mg TiO 2 Nanocomposite Prepared by Friction Stir Processing

Annealed and wrought AA5052 aluminum alloy was subjected to friction stir processing (FSP) without and with 3 vol pct TiO2 nanoparticles. Microstructural studies by electron backscattered diffraction and transmission electron microscopy showed the formation of an ultra-fine-grained structure with fine distribution of TiO2 nanoparticles in the metal matrix. Nanometric Al3Ti and MgO particles were also observed, revealing in-situ solid-state reactions between Al and Mg with TiO2. Tensile testing at different strain rates determined that FSP decreased the strain rate sensitivity and work hardening of annealed Al-Mg alloy without and with TiO2 nanoparticles, while opposite results were obtained for the wrought alloy. Fractographic studies exhibited that the presence of hard reinforcement particles changed the fracture mode from ductile rupture to ductile-brittle fracture. Notably, the failure mechanism was also altered from shear to tensile rupture as the strain rate increased. Consequently, the fracture surface contained hemispherical equiaxed dimples instead of parabolic ones.

Influence of hard inclusions on microstructural characteristics and textural components during dissimilar friction-stir welding of an PM Al–Al2O3–SiC hybrid nanocomposite with AA1050 alloy

ABSTRACT Owing to the advantages of nanocomposites for structural applications, we present microstructural evolutions and texture development during dissimilar friction stir welding (DFSW) of an Al-matrix hybrid nanocomposite (Al-2 vol.-% Al2O3-2 vol.-% SiC) with AA1050. It is shown that DFSW can successfully be performed at a rotating speed of 1200 rev min−1 and a transverse speed of 50 mm min−1 while locating the nanocomposite at retreating side. Formation of macro-, micro-, and nano-mechanical interlocks between dissimilar base materials (BMs) as a result of FSW tool stirring action possessed an impact influence on the mechanical performance of dissimilar welds. Electron microscopy revealed formation of a three-modal grain structure from microscale (>1 µm) to nanoscale (<100 nm) range in the stir zone of the joint materials. Texture components included a mixture of shear elements and ideal random orientations, as compared to the completely random and Cu-P preferred textures for the aluminum and composite BMs.

Uniaxial Compression Tests of Metallic Foams: A Recipe

In case of metallic foams the stress-strain curve observed during uniaxial compression is often not smooth, expecting plateau is often missing, and the curve instead of slowly increasing stress before final densification takes place often exhibit a lot of peaks with even local stress drops. It is generally accepted that the origin of this behavior is linked to the heterogeneity and/or anisotropy of foams, ductility or brittleness of used matrix alloy and the presence of surface skin. This contribution is designed as a recipe for metal foam investigator how to handle the uniaxial compression test results on metallic foams. Aim of this contribution is to introduce engineers and researchers also to the unusual events that can occur during foam compression test.

Novel Ultrafine-Grained Aluminium Metal Matrix Composites Prepared from Fine Atomized Al Powders

The paper reviews the developments to date of novel ultrafine-grained (UFG) Al metal matrix composites (MMCs) reinforced and stabilized with nanometric Al2O3 phase produced in situ by compaction of fine gas-atomized Al powders. This is followed by a discussion of the recent developments of the novel UFG Al-AlN MMCs produced by partial nitridation of fine gasatomised Al powders. The paper summarizes previously published data with an addition of the new unpublished results.

EBSD investigation of Al/(Al13Fe4+Al2O3) nanocomposites fabricated by mechanical milling and friction stir processing

The application of ball‐milling for reactant powders (Fe2O3+Al) to form in situ nanosized reaction products in the stir zone of 1050 aluminium alloy was examined and the evolution of microstructure, grain boundaries and microtexture of the fabricated Al/(Al13Fe4+Al2O3) nanocomposite was investigated. The mean matrix grain size of the fabricated nanocomposites by the combination of ball milling and friction stir processing were found to be ∼3.2, 3.1 and 2.1 μm for 1, 2 and 3 h milled powder mixtures, respectively. The fraction of high‐angle grain boundaries increased markedly in the stir zone indicating the occurrence of dynamic restoration of the aluminium matrix. This was also associated with increasing of the fraction of low ∑CSL boundaries. In addition, the fraction of high‐angle grain boundaries increased as the reaction product increased. The developed textures were compared with the most important deformation and recrystallisation texture components of cubic close packed structure. Some of the main texture components formed due to the restoration of aluminium in the stir zone of the material with no powder addition were CubeND {001}<310>, BR {236}<385> and R (or retained S{123} <634>); these are usually found in the rolled materials. However, the presence of nanosized reaction products in the fabricated nanocomposite changed the texture components to the dominant Goss {011}<100>, P {011}<122> and R{124}<211> textures.

Dynamic restoration and crystallographic texture of a friction-stir processed Al–Mg–SiC surface nanocomposite

ABSTRACT In this study, SiC nanoparticles (∼50 nm, 3 vol%) are homogenously incorporated within an Al–Mg alloy metal matrix during multi-step friction-stir processing (FSP) to fabricate an Al-matrix surface nanocomposite. A fundamental understanding is developed, correlating microstructural features and crystallographic textural components in the context of the material flow pattern and operative dynamic restoration phenomena using electron backscattering diffraction and high resolution-transmission electron microscopy analysis. The annealed base metal does not contain any preferred orientation and its texture is completely random. Incorporation of SiC nanoparticles via FSP results in significant grain structural refinement down to the size of ∼1.4 µm and changing the textural component towards the Goss/Cubic and P1/P2 dominant fibre components in the centre of stirred zone.

Influence of CNTs decomposition during reactive friction-stir processing of an Al-Mg alloy on the correlation between microstructural characteristics and microtextural components: INFLUENCE OF CNTS DECOMPOSITION DURING REACTIVE FRICTION-STIR PROCESSING OF AN AL-MG ALLOY

Multipass friction‐stir processing was employed to uniformly disperse multiwalled carbon nanotubes (MW‐CNTs) within an Al–Mg alloy metal matrix. Decomposition of MW‐CNTs occurs in situ as a result of solid‐state chemical reactions, forming fullerene (C60) and aluminium carbide (Al4C3) phases during reactive high temperature severe plastic processing. The effects of this decomposition on the microstructural features, dynamic restoration mechanisms and crystallographic microtextural developments are studied for the first time by using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) analysis. The formation of an equiaxed grain structure with an average size of ∼1.5 μm occurs within the stirred zone (SZ) under the influence of inclusions which hinder grain boundary migration via Zener‐Smith pinning mechanisms during the discontinuous dynamic recrystallisation (DDRX). Formation of two strong Cubic and Brass microtextural components in the heat affected zone (HAZ) and thermomechanical affected zone (TMAZ) was noted as compared to the completely random and Cube components found in the base and SZ regions, respectively. The microstructural modification led to hardening and tensile strength improvement for the processed nanocomposite by ∼55% and 110%, respectively with respect to the annealed Al–Mg base alloy.

Electron backscattered diffraction analysis of friction stir processed nanocomposites produced via spark plasma sintering: ELECTRON BACKSCATTERED DIFFRACTION ANALYSIS OF FRICTION

In the present study, Spark Plasma Sintered (SPSed) aluminium matrix composites were severely deformed through Friction stir processing (FSP). Pure aluminium powders and bimodal sized Al2O3 particles (80 nm and 25 μ m) were firstly mixed by ball milling and then consolidated by spark plasma sintering. The effect of the heat input as well the bimodal particle size of the alumina on the materials’ microstructure and texture development was evaluated by electron back scattered diffraction (EBSD) analysis. The EBSD analysis clearly showed that the SPSed nanocomposites possessed bimodal aluminium matrix grain structure as well as a crystallography characterised by random texture. In addition, microstructural examination revealed that the partial recrystallisation occurred during SPS for all the nanocomposites. Also, it is revealed that the Zener pinning effect of Al2O3 nanoparticles retarded recrystallised grain growth following recrystallisation during FSP and then leading to grain refinement of the aluminium. The results revealed that the heat generated during FSP has a remarkable effect on the grain distribution as well as on the crystallographic orientation. Also, a mixture of {112} <110> shear elements and an ideal strong B/ B¯ component were observed. The microstructural changes, occurred during FSP in the stir zone region for Al‐Al2O3 nanocomposites, were attributed to both the discontinuous along with the continuous recrystallisation (DDRX/CDRX). It should be pointed out that with increasing the heat input, recrystallised grains portion increased.

Applications of Nanocomposite-Enhanced Phase-Change Materials for Heat Storage

The development of efficient materials for heat storage has become recently a popular research topic as amount of energy gained from solar power depends significantly on day and night cycle. Thats why the right choice of material for heat storage directly affects the utilization efficiency of solar thermal energy. Research on heat storage materials nowadays focuses on phase change materials (PCMs) enabling repeatedly utilize the latent heat of the phase transition between the solid and liquid phase. Most currently used PCMs have low thermal conductivity, which prevents them from overcoming problem of rapid load changes in the charging and discharging processes. To overcome this obstacle and to obtain excellent heat storage possibility, various techniques have been proposed for enhancing the thermal conductivity of PCMs, such as adding metallic or nonmetallic particles, in-corporating of porous or expanded materials, fibrous materials, macro-, micro-, or nanocapsules, etc.The authors of this study report particularly the huge potential of oxide nanoadditives, such as titania (TiO2), alumina (Al2O3), silica (SiO2) and zinc oxide (ZnO), that are even in small quantities (up to 3 wt.%) able significantly to enhance the heat storage characteristics of conventional PCMs. Moreover, the microstructure of the granules produced by recycling of aluminum scrap refers to the possibility of their utilizing for the purpose of low cost solutions enabling to increase the thermal conductivity of PCMs. The above mentioned technical solutions are therefore the important keys to successful commercialization of materials for latent heat storage in future building industry.