Sulfonated polyetherketone （SPEK-C） films investigated by positron annihilation lifetime spectroscopy and atomic force microscopy

The characterization of sulfonated polyetherketone （SPEK-C） films was investigated by using positron annihilation lifetime spectroscopy （PALS） and atomic force microscopy （AFM）. It was found that free volume radius and intensity depend on the variation of sulfonation degree and solvent evaporation time of the films. Pore size and distribution determined from PALS and AFM measurements showed reasonable agreement.     

Effect of pH and ionic strength on phospholipid nanomechanics and on deposition process onto hydrophilic surfaces measured by AFM

The effect of ion-binding on a zwitterionic phospholipid such as 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) has been studied by measuring the zeta potential value of the unilamellar liposomes present in solution while varying the pH and the ionic strength in independent experiments. We have experimentally confirmed that DMPC binds cations, resulting in an increase of the zeta potential value. The liposome surface charge has been proved to have a strong effect on the supported bilayer formation on hydrophilic, negatively charged surfaces such as mica and silicon oxide as atomic force microscopy images reveal. Furthermore, thanks to force spectroscopy measurements we have proved that ion-binding also affects the nanomechanical response of the system, since it increases the force that has to be exerted on the membrane in order to puncture it. Last but not least, the nanomechanics of the bilayer does not depend on the substrate, thus implying that membrane properties are not influenced by the supporting material.     

Thermal conductivity of bulk ZnO after different thermal treatments

Thermal conductivities (κ) of melt-grown bulk ZnO samples thermally treated under different conditions were measured using scanning thermal microscopy. Samples annealed in air at 1050°C for 3 h and treated with N-plasma at 750°C for 1 min. exhibited κ=1.35±0.08 W/cm-K and κ=1.47±0.08 W/cm-K, respectively. These are the highest values reported for ZnO. Atomic force microscopy (AFM) and conductive-AFM measurements revealed that surface carrier concentration as well as surface morphology affected the thermal conductivity.     

Surface film morphology (AFM) and chemical features (XPS) of cycled V2O5 thin films in lithium microbatteries

Sputtered vanadium pentoxide thin films have been used as positive electrode in lithium microbatteries and extensively studied after cycling over the 31st galvanostatic cycles by two complementary techniques, especially well-adapted for thin films analysis: X-ray photoelectron spectroscopy and atomic force microscopy. This study is mainly focussed on the characterization of the surface film (solid electrolyte interface-type) which is formed during subsequent discharges and charges and especially on its composition and its morphology that are changing during cycling. First, the growth of a surface layer between the positive electrode and the liquid electrolyte has been evidenced upon the discharge as well as its partial dissolution upon the charge. Secondly, the chemical and topographic changes of this interfacial layer at various stages of cycling are discussed in correlation with the evolution of the discharge capacity over cycles.     

Electron holography and AFM studies on styrenic block copolymers and a high impact polystyrene

Many of the artifacts of conventional electron microscopy can be avoided if the unstained polymers are studied by electron holography and atomic force microscopy (AFM). Holograms of thin sections (50–70 nm) of organic block copolymers were recorded, and the corresponding phase images were reconstructed. In this way, typical structures such as lamellae and cylinders could be imaged without any staining. In addition, we successfully recorded holograms and performed Lorentz microscopy of an impact‐modified polystyrene (high‐impact polystyrene). The results were compared with the tapping mode AFM phase images. Electron holography and AFM have been demonstrated as suitable tools to image unstained heterogeneous polymers, leading to the understanding of their structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1573–1583, 2005     

Enhanced corrosioon resistance by sol‐gel‐based ZrO2‐CeO2 coatings on magnesium alloys

The physical, chemical and mechanical properties of magnesium alloys make them attractive materials for automotive and aerospace applications. However, these materials are susceptible to corrosion and wear. This work discusses the potential of using sol‐gel based coatings consisting of ZrO₂ and 15 wt.% of CeO₂. The CeO₂ component provides enhanced corrosion protection, while ZrO₂ impart corrosion as well as wear resistance. Coating deposition was performed by the dip coating technique on two magnesium alloy substrates with different surface finishes: AZ91D (as‐casted, sand‐blasted, and machined) and AZ31 (rolled and machined). All as‐deposited coatings (xerogel coatings) were then subjected to 10 h annealilng: a temperature of 180°C was applied to the AZ91D alloy and 140°C to the AZ31 alloy. Morphological and structural properties of the annealed coatings were investigated by scanning electron microscopy, atomic force microscopy and transmission electron microscopy. Coating composition was examined using energy dispersive X‐ray analysis. Adhesion of the annealed ZrO₂‐CeO₂ coatings on the substrates, assessed by scratch tests, showed critical loads indicative of coating perforation of up to 32 N. Hardness and elasticity, measured using depth‐sensing nanoindentation tests, gave a hardness and elastic modulus of 4.5 GPa and 98 GPa, respectively. Salt spray corrosion tests performed on these coatings showed superior corrosion resistance for AZ91D (as‐casted and machined) and AZ31 (machined), while severe corrosion was observed for the AZ31 (rolled) and AZ91D (sand‐blasted) magnesium alloy substrates.     

Low energy oblique ion beam sputtering induced surface engineering of polyethylene terephthalate

ABSTRACT

In the present work, the self-organized pattern formation with simultaneous surface smoothing of Polyethylene terephthalate (PET) by 40 keV Ar+ ions irradiation has been discussed. The effect of most important experimental parameter i.e. ion beam incidence that control these processes has been discussed by varying off normal incidences from 30⁰ to 50⁰. The changes in surface topography have been studied using Atomic Force Microscopy (AFM). It has been investigated from AFM analysis that oblique ion beam induced sputtering significantly reduced the surface roughness with simultaneous formation of some hillock and hole like structures.     

Measurement of the Length and Strength of Adhesive Interactions in a Nanoscale Silicon–Diamond Interface

The adhesive interactions between nanoscale silicon atomic force microscope (AFM) probes and a diamond substrate are characterized using in situ adhesion tests inside of a transmission electron microscope (TEM). In particular, measurements are presented both for the strength of the adhesion acting between the two materials (characterized by the intrinsic work of adhesion W_adh,int) and for the length scale of the interaction (described by the range of adhesion z₀). These values are calculated using a novel analysis technique that requires measurement of the AFM probe geometry, the adhesive force, and the position where the snap‐in instability occurs. Values of W_adh = 0.66 J m⁻² and z₀ = 0.25 nm are extracted using this technique. This value of work of adhesion is 70% higher than the work of adhesion calculated if one uses a conventional paraboloidal asperity model. Comparing to literature, the work of adhesion obtained using the new method is significantly higher than most experimental and simulation values for similar material pairs. The discrepancy is attributed to nanoscale roughness, which was not accounted for previously. Furthermore, the value of the range of adhesion is comparable to previously reported values, but is significantly larger than the commonly assumed value of the interatomic spacing.     

Controlled nanodot fabrication by rippling polycarbonate surface using an AFM diamond tip

The single scratching test of polymer polycarbonate (PC) sample surface using an atomic force microscope (AFM) diamond tip for fabricating ripple patterns has been studied with the focus on the evaluation of the effect of the tip scratching angle on the pattern formation. The experimental results indicated that the different oriented ripples can be easily machined by controlling the scratching angles of the AFM. And, the effects of the normal load and the feed on the ripples formation and their periods were also studied. Based on the ripple pattern formation, we firstly proposed a two-step scratching method to fabricate controllable and oriented complex three-dimensional (3D) nanodot arrays. These typical ripple formations can be described via a stick-slip and crack formation process.     

Nonisothermal crystallization behavior and mechanical properties of PEEK/SCF/nano-SiO2 composites

Nonisothermal crystallization of hybrid PEEK composites reinforced with short carbon fibers (SCF) and nano-SiO₂ (1, 1.5 and 2 wt%) was investigated using DSC. Composites were fabricated by melt-mixing process at 400 °C. The Size of the nanoparticles was 13 nm. Samples were cooled from 410 °C to 25 °C with cooling rates of 10, 30, 50 and 70 °C min⁻¹. The onset, peak and end crystallization temperatures were investigated as well as absolute crystallization percentage and crystallization time. Avrami, Ozawa and Ozawa–Avrami equations were fitted to the data in order to investigate the crystallization kinetics. Mechanical behaviors of the composites were examined using nanoindentation and nanoscratching. DSC results revealed that absolute crystallization percentage increases in PEEK/SCF/1%SiO₂ and PEEK/SCF/1.5%SiO₂ samples compared to PEEK/SCF, however it decreases by adding more nano-SiO₂. Ozawa–Avrami is proved to be the best model for describing crystallization behavior of the composites while Avrami equation was suitable for describing a part of the crystallization process. The Avrami and Ozawa–Avrami constants were calculated. Besides, adding SCFs and nano-SiO₂ into PEEK results in a significant decrease in plasticity index, while increases the resistance to plastic deformation of the composite.