scholarly journals Mechanisms of antiwear tribofilm growth revealed in situ by single-asperity sliding contacts

Science ◽  
2015 ◽  
Vol 348 (6230) ◽  
pp. 102-106 ◽  
Author(s):  
N. N. Gosvami ◽  
J. A. Bares ◽  
F. Mangolini ◽  
A. R. Konicek ◽  
D. G. Yablon ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Critical Role ◽  
Force Microscopy ◽  
Thermally Activated ◽  
Single Asperity ◽  
Atomic Force ◽  
Sliding Interfaces ◽  
Lubricant Base Stock

Zinc dialkyldithiophosphates (ZDDPs) form antiwear tribofilms at sliding interfaces and are widely used as additives in automotive lubricants. The mechanisms governing the tribofilm growth are not well understood, which limits the development of replacements that offer better performance and are less likely to degrade automobile catalytic converters over time. Using atomic force microscopy in ZDDP-containing lubricant base stock at elevated temperatures, we monitored the growth and properties of the tribofilms in situ in well-defined single-asperity sliding nanocontacts. Surface-based nucleation, growth, and thickness saturation of patchy tribofilms were observed. The growth rate increased exponentially with either applied compressive stress or temperature, consistent with a thermally activated, stress-assisted reaction rate model. Although some models rely on the presence of iron to catalyze tribofilm growth, the films grew regardless of the presence of iron on either the tip or substrate, highlighting the critical role of stress and thermal activation.

scholarly journals All chemical YBa2Cu3O7 superconducting multilayers: Critical role of CeO2 cap layer flatness

2009 ◽  
Vol 24 (4) ◽  
pp. 1446-1455 ◽  
Author(s):  
M. Coll ◽  
J. Gàzquez ◽  
R. Huhne ◽  
B. Holzapfel ◽  
Y. Morilla ◽  
...  
Keyword(s):  
Critical Role ◽  
High Energy ◽  
Buffer Layers ◽  
Solution Deposition ◽  
Ybco Films ◽  
Force Microscopy ◽  
Atomic Force ◽  
Current Densities ◽  
Atomically Flat

New advances toward microstructural improvement of epitaxial CeO2 films grown by chemical solution deposition and their use as buffer layers for YBa2Cu3O7 (YBCO) films are presented. We demonstrate that the degree of epitaxy and the fraction of (001) atomically flat surface area are controlled by the incorporation of tetravalent (Zr4+) or trivalent (Gd3+) cations into the ceria lattice. The degree of epitaxy has been investigated by means of Rutherford backscattering spectroscopy-channeling and reflection high-energy electron diffraction, and a new methodology is also presented to quantify the fraction of (001) atomically flat area from atomic force microscopy images. Results are further correlated with the superconducting properties, microstructure, and texture of YBCO films grown by the trifluoroacetate route. A comparison with pulsed laser deposition and YBCO films grown on the same ceria layers is also presented. This growth procedure has allowed us to obtain all chemical multilayer films with controlled microstructure and critical current densities above 4 MA cm−2 at 77 K.

Probing Crystallization of Calcium Oxalate Monohydrate and the Role of Macromolecule Additives with in Situ Atomic Force Microscopy

Langmuir ◽  
2004 ◽  
Vol 20 (20) ◽  
pp. 8587-8596 ◽  
Author(s):  
Taesung Jung ◽  
Xiaoxia Sheng ◽  
Chang Kyun Choi ◽  
Woo-Sik Kim ◽  
Jeffrey A. Wesson ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Calcium Oxalate ◽  
Calcium Oxalate Monohydrate ◽  
Force Microscopy ◽  
Atomic Force

Multi-Scale Structure of the Pinctada Mother of Pearl: Demonstration of a Continuous and Oriented Organic Framework in a Natural Ceramic

2005 ◽  
Vol 284-286 ◽  
pp. 705-708 ◽  
Author(s):  
Marthe Rousseau ◽  
Xavier Bourrat ◽  
Philippe Stempflé ◽  
Marcel Brendlé ◽  
Evelyne Lopez
Keyword(s):  
Cross Sections ◽  
Organic Matrix ◽  
Phase Imaging ◽  
Force Microscopy ◽  
Multi Scale ◽  
Atomic Force ◽  
Intermittent Contact ◽  
Organic Framework

Sheet nacre is a promising natural bioceramic, which consists on the internal lustrous “mother of pearl” layer of many molluscan shells, e.g. Pinctada, our model. The aim of this work is to study the structure of the flat polygonal tablets of nacre, in order to understand the multi-scale organization of this composite material and the role of the organic template during the growth of the biocrystal. We studied the organic matrix, in situ with techniques such as darkfield transmission electronic microscopy (TEM) on small cross-sections of nacre of Pinctada maxima, or intermittent-contact atomic force microscopy coupled with phase imaging on samples of nacre of Pinctada margaritifera polished parallel to the surface of the tablets. In this study, we demonstrate the continuity of the organic framework and the crystallographic orientation in the biocrystal at 2 relevant levels : nano- and micro-scale.

scholarly journals Temperature Effects on the HOPG Intercalation Process

2019 ◽  
Vol 4 (1) ◽  
pp. 23 ◽  
Author(s):  
Gianlorenzo Bussetti ◽  
Rossella Yivlialin ◽  
Claudio Goletti ◽  
Maurizio Zani ◽  
Lamberto Duò
Keyword(s):  
Common Procedure ◽  
Force Microscopy ◽  
Carbon Dissolution ◽  
Atomic Force ◽  
Defect Sites ◽  
Graphite Intercalation ◽  
Increasing Temperature ◽  
Chemical Strategies

Graphite intercalation via chemical strategies is a common procedure to delaminate stratified crystals and obtain a suspension of graphene flakes. The intercalation mechanism at the molecular level is still under investigation in view of enhancing graphene production and reducing damage to the original pristine crystal. The latter, in particular, can undergo surface detriment due to both blister evolution and carbon dissolution. The role of the electrolyte temperature in this process has never been investigated. Here, by using an in-situ atomic force microscopy (AFM) apparatus, we explore surface morphology changes after the application of fast cyclic-voltammetries at 343 K, in view of de-coupling the crystal swelling phenomenon from the other electrochemical processes. We find that blisters do not evolve as a consequence of the increasing temperature, while the quality of the graphite surface becomes significantly worse, due to the formation of some adsorbates on possible defect sites of the electrode surface. Our results suggest that the chemical baths used in graphite delamination must be carefully monitored in temperature for avoiding undesired electrode detriment.

In Situ Atomic Force Microscopy of Pt/Ti film morphology changes on a microelectronic gas sensor operating at elevated temperatures

1995 ◽  
Vol 53 ◽  
pp. 254-255
Author(s):  
M. DiBattista ◽  
S. V. Patel ◽  
J. F. Mansfield ◽  
J. L. Gland ◽  
J. W. Schwank
Keyword(s):  
Atomic Force Microscopy ◽  
Elevated Temperatures ◽  
Film Surface ◽  
Film Structure ◽  
Film Morphology ◽  
Force Microscopy ◽  
Atomic Force ◽  
Morphology Changes ◽  
Ti Films

Thin film electronic devices that employ resistance change responses of Pt / Ti films to detect gas species have been microfabricated at the University of Michigan. Atomic force microscopy (AFM) is used to investigate morphology of the Pt / Ti sensing films deposited on the microfabricated device. These Pt / Ti sensing films are strongly influenced by many factors, making it difficult to determine the exact relationship between film structure, chemical sensitivity, and selectivity. In-situ AFM investigations of Pt / Ti films on this device at elevated temperatures provides the opportunity for real time observation of film morphology changes under controlled conditions, testing sensing film stability during device operation, and correlating film structure to resistance.Observation of the Pt / Ti film surface and in-situ resistance measurements at elevated temperatures are possible due to the construction of the sensing device. The sensors are based on chemically active thin films deposited on a micromachined silicon window, supported by a 300 μn thick silicon rim.

Thermally activated phenomena observed by atomic force microscopy

2003 ◽  
Vol 790 ◽  
Author(s):  
Enrico Gnecco ◽  
Elisa Riedo ◽  
Roland Bennewitz ◽  
Ernst Meyer ◽  
Harald Brune
Keyword(s):  
Thermal Effects ◽  
Thermal Activation ◽  
Velocity Dependence ◽  
Stick Slip ◽  
Force Microscopy ◽  
Thermally Activated ◽  
Atomic Force ◽  
Stick Slip Motion ◽  
Thermal Vibrations

ABSTRACTThermal effects may affect the velocity dependence of friction on the nanoscale in different ways. In a dry environment the stick-slip motion of a nanotip sliding across a crystalline surface is modified by thermal vibrations, which leads to a logarithmic increase of friction with the sliding velocity at very low speeds (v < 10 μm/s). At higher speeds the role of thermal activation is negligible, and friction becomes velocity-independent. An analytical expression, which explains both regimes of friction vs. velocity, is introduced. In a humid environment the situation is complicated by water capillaries formed between tip and surface, which act as obstacles for thermally activated jumps. Depending on the wettability of the surface, different tendencies in the velocity dependence are observed.

Formation Two Dimensional Negative Islands At High Rate Cooling Of Ultra-Flat Surface Si(111)

2016 ◽  
Vol 11 (1) ◽  
pp. 94-99
Author(s):  
Sergey Sitnikov ◽  
Sergey Kosolobov ◽  
Aleksandr Latyshev
Keyword(s):  
Elevated Temperatures ◽  
High Rate ◽  
Ex Situ ◽  
Two Dimensional ◽  
Island Nucleation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Atomic Mechanism ◽  
Negative Islands

In situ ultrahigh vacuum reflection electron and ex situ atomic force microscopy have been applied to investigate morphology transformations of the ultra-flat stepped Si(111) surface with wide (20–50 µm in diameter) singular terraces during sublimation and quenching from elevated temperatures. The formation of two dimensional negative (vacancy) islands has been observed on the wide terraces after the quenching from temperatures above 1 200°C. The increasing of the critical terrace size for the two-dimensional negative island nucleation has been explained by the changing of the atomic mechanism of mass transport on silicon surface.

scholarly journals DJ-1 Acts as a Scavenger of α-Synuclein Oligomers and Restores Monomeric Glycated α-Synuclein

Biomolecules ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1466
Author(s):  
Tamr B. Atieh ◽  
Jonathan Roth ◽  
Xue Yang ◽  
Cody L. Hoop ◽  
Jean Baum
Keyword(s):  
Critical Role ◽  
Force Microscopy ◽  
Oligomer Formation ◽  
Atomic Force ◽  
Glycation End Products ◽  
Catalytic Cysteine ◽  
Solution Nuclear Magnetic Resonance ◽  
Integrate Solution ◽  
Toxic Oligomer

Glycation of α-synuclein (αSyn), as occurs with aging, has been linked to the progression of Parkinson’s disease (PD) through the promotion of advanced glycation end-products and the formation of toxic oligomers that cannot be properly cleared from neurons. DJ-1, an antioxidative protein that plays a critical role in PD pathology, has been proposed to repair glycation in proteins, yet a mechanism has not been elucidated. In this study, we integrate solution nuclear magnetic resonance (NMR) spectroscopy and liquid atomic force microscopy (AFM) techniques to characterize glycated N-terminally acetylated-αSyn (glyc-ac-αSyn) and its interaction with DJ-1. Glycation of ac-αSyn by methylglyoxal increases oligomer formation, as visualized by AFM in solution, resulting in decreased dynamics of the monomer amide backbone around the Lys residues, as measured using NMR. Upon addition of DJ-1, this NMR signature of glyc-ac-αSyn monomers reverts to a native ac-αSyn-like character. This phenomenon is reversible upon removal of DJ-1 from the solution. Using relaxation-based NMR, we have identified the binding site on DJ-1 for glycated and native ac-αSyn as the catalytic pocket and established that the oxidation state of the catalytic cysteine is imperative for binding. Based on our results, we propose a novel mechanism by which DJ-1 scavenges glyc-ac-αSyn oligomers without chemical deglycation, suppresses glyc-ac-αSyn monomer–oligomer interactions, and releases free glyc-ac-αSyn monomers in solution. The interference of DJ-1 with ac-αSyn oligomers may promote free ac-αSyn monomer in solution and suppress the propagation of toxic oligomer and fibril species. These results expand the understanding of the role of DJ-1 in PD pathology by acting as a scavenger for aggregated αSyn.

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