Novel ultra nanoindentation method with extremely low thermal drift: Principle and experimental results

Despite active development over the past 15 years, contemporary nanoindentation methods still suffer serious drawbacks, particularly long thermal stabilization and thermal drift, which limit the duration of the measurements to only a short period of time. The presented work introduces a novel ultra nanoindentation method that uses loads from the μN range up to 50 mN, is capable of performing long-term stable measurements, and has negligible frame compliance. The method is based on a novel patented design, which uses an active top referencing system. Several materials were used to demonstrate the performance of the method. The measurements with hold at maximum load confirm extremely low levels of instrument thermal drift. The presented Ultra Nanoindentation Tester opens new possibilities for testing thin films and long-term testing, including creep of polymers at high resolution without the need of long thermal stabilizatio

Influence of load on the dry frictional performance of alkyl acrylate copolymer elastomers coated with diamond-like carbon films

In this work, the influence of applied load on the frictional behavior of alkyl acrylate copolymer elastomers coated with diamond- like carbon films is studied at dry conditions. The performance of two coatings with very different microstructure (patched vs. continuous film) is compared with the uncoated substrate. A wide range of applied loads is explored, from 1mN to 1 N, which is achieved by using a specific tribometer. The variation of 3 orders of magnitude in the applied load leads to a strong variation of the observed frictional phenomena. The different behavior of both samples at various loads is explained using a model that considers two contributions to the friction coefficient, namely, an adhesive and a rubber hysteresis part. The constraints and applicability of such model are critically evaluated. (C) 2015 AIP Publishing LLC

Multiple receptor tyrosine kinases are expressed in adult rat retinal ganglion cells as revealed by single-cell degenerate primer polymerase chain reaction

BACKGROUND: To achieve a better understanding of the repertoire of receptor tyrosine kinases (RTKs) in adult retinal ganglion cells (RGCs) we performed polymerase chain reaction (PCR), using degenerate primers directed towards conserved sequences in the tyrosine kinase domain, on cDNA from isolated single RGCs univocally identified by retrograde tracing from the superior colliculi.RESULTS: All the PCR-amplified fragments of the expected sizes were sequenced, and 25% of them contained a tyrosine kinase domain. These were: Axl, Csf-1R, Eph A4, Pdgfrbeta, Ptk7, Ret, Ros, Sky, TrkB, TrkC, Vegfr-2, and Vegfr-3. Non-RTK sequences were Jak1 and 2. Retinal expression of Axl, Csf-1R, Pdgfrbeta, Ret, Sky, TrkB, TrkC, Vegfr-2, and Vegfr-3, as well as Jak1 and 2, was confirmed by PCR on total retina cDNA. Immunodetection of Csf-1R, Pdgfralpha/beta, Ret, Sky, TrkB, and Vegfr-2 on retrogradely traced retinas demonstrated that they were expressed by RGCs. Co-localization of Vegfr-2 and Csf-1R, of Vegfr-2 and TrkB, and of Csf-1R and Ret in retrogradely labelled RGCs was shown. The effect of optic nerve transection on the mRNA level of Pdgfrbeta, Csf-1R, Vegfr-2, Sky, and Axl, and of the Axl ligands Gas6 and ProteinS, was analysed. These analyses show transection-induced changes in Axl and ProteinS mRNA levels.CONCLUSIONS: The repertoire of RTKs expressed by RGCs is more extensive than previously anticipated. Several of the receptors found in this study, including Pdgfrbeta, Csf-1R, Vegfr-2, Sky, and Axl, and their ligands, have not previously been primarily associated with retinal ganglion cells

New ultra low load indentation device with extremely low thermal drift: principle and experimental results

Nanoindentation has become an indispensable method for measuring the mechanical properties of small volumes of materials. It has gained importance in several domains such as thin film science, electronics and materials research. Despite continuous evolution of the nanoindentation technique over the past fifteen years, contemporary methods still suffer serious drawbacks, particularly long thermal stabilization and thermal drift which limit the duration of the measurements to only a short period of time. The presented paper introduces a novel ultra nanoindentation method that utilizes loads from the μN range up to 50 mN, is capable of performing long term stable measurements and has negligible frame compliance. The method is based on a novel patented design which uses an active top referencing system and components made from Zerodur$^{\circledR}$ glass. Several materials including fused silica, DLC and selected polymers were used to show the performance of the method. The tests were performed mainly at low loads to demonstrate the low load and displacement capabilities of the instrument. A large number of tests were performed with a hold at the maximum indentation load to observe the instrument thermal drift. It was proved that indentations with maximum loads in μN range and penetration depth of a few nm can be easily performed with this method. The measurements with hold at maximum load confirm extremely low levels of instrument thermal drift. The presented Ultra Nanoindentation Tester opens new possibilities for testing thin films and long term testing including creep of polymers at very high resolution without the need of long thermal stabilization

A Numerical Investigation of the Effect of Cubic Crystals Orientation on the Indentation Modulus

The elastic finite element computations of the indentation process with the Berkovich indenter are performed to examine the effect of cubic crystal and indenter orientation on indentation moduli of anisotropic material. Three metals with a cubic crystal lattice and various degree of elastic anisotropy from 1 to 9 are studied: tungsten, AISI 304 steel and β -brass. Differences in anisotropy ratios expressed by the Young moduli on the one side and by the indentation moduli on the other side are quantified

Characterisation of strain-induced martensite in a metastable austenitic stainless steel by nanoindentation

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Interesting aspects of indentation and scratch methods for characterization of thermally-sprayed coatings

In order to improve the knowledge on the use and significance of instrumented indentation and scratchtesting on thermally-sprayed materials, a wide range of tests was performed on thermally-sprayed ceramic,cermet and metal coatings. A scale-dependent behavior of hardness was observed as a function ofindentation depth for all coatings: at low penetration depths, the hardness value depends on theintralamellar material properties, whereas at larger depths it reflects the long-range cohesive strength of thecoating. In all cases, hardness becomes independent of the indentation depth above a threshold value of~2000 nm. The elastic modulus is also scale-dependent, but it never stabilizes to a depth-independent value,probably on account of crack opening/closing mechanisms. Scratch test on the cross-section has been deeplyinvestigated and identified as a comparative method to quantify the cohesion of the coatings

Plasma spraying of a novel material with amorphous and nanocrystalline microstructure

A novel material has been used for plasma spraying by WSP\uae. The material is composed of three main phases, namely corundum (aluminum oxide), baddeleyite (zirconium oxide), and glassy phase (silicon oxide). The material is a refractory and exhibits very high hardness, extremely high abrasion resistance, and chemical resistance. Conventionally, the material is fabricated by melt casting and machining. Cast tiles of the material were ground and sieved to obtain the right powder cut size for plasma spraying by water stabilized plasma torch (WSP\uae). Both dense coatings and free standing parts were successfully produced from the new material by WSP\uae. Spraying parameters were varied and molten particles were monitored in flight by DPV 2000. The coatings exhibit very low porosity and high hardness. The as-sprayed material is mostly amorphous with some nanocrystalline grains of aluminum and zirconium oxide present. The phase composition of the as-sprayed material is thus different from that of the feedstock material, which is mostly crystalline with a small faction of amorphous silica glass. The micro-structure of the newly sprayed material was studied by electron microscopy (SEM, TEM) and is very complex. Upon annealing, the as-sprayed material crystallizes around 950\ub0C. This result and other thermal properties were obtained by TMA and DTA measurement. The ease of plasma spraying and the coating properties make this material a suitable candidate for many industrial applications.Peer reviewed: NoNRC publication: Ye

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