scholarly journals Bonding Reactions of Dental Self-Adhesive Cements with Synthetic Hydroxyapatite as a Function of the Polymerization Protocol

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Roger Borges ◽  
Carlos Frederico de Oliveira Graeff ◽  
Juliana Marchi ◽  
Paulo Henrique Perlatti D'Alpino
Keyword(s):  
Binding Energy ◽  
Chemical Interaction ◽  
Chemical Elements ◽  
Light Exposure ◽  
Chemical Reactivity ◽  
Chemical Activation ◽  
Atomic Scale ◽  
Chemical Information ◽  
Calcium Salts ◽  
Synthetic Hydroxyapatite

Objectives. This study evaluated the influence of the cement composition and different polymerization protocols on the bonding chemical interaction of self-adhesive cements with synthetic hydroxyapatite. Materials and Methods. Two commercial self-adhesive resin cements (RelyX U200 and Maxcem Elite) were selected, manipulated, mixed with hydroxyapatite dry powder (HAp), dispensed into molds, and distributed into three groups according to polymerization protocols: immediate photoactivation (IP); delayed photoactivation, 10 min self-curing and light-curing (DP); and chemical activation (CA, no light exposure). The detailed chemical information, at atomic scale, on the surface and deeper into the bulk of self-adhesive cement/hydroxyapatite mixtures was evaluated with X-ray photoelectron spectroscopy (XPS). Results. Chemical elements were detected in both cements, such as Na, O, Ca, C, P, and Si. Other elements were detected in minor concentrations. RelyX U200 exhibited the most intense formation of calcium salts products when the cement/HAp mixtures were photoactivated (immediate or delayed). RelyX U200/HAp mixture under delayed photoactivation (DP) also exhibited higher binding energy between calcium moieties of the HAp and methacrylates in the cement. A higher energy difference in the interaction of HAp with the cement comparing the bulk and surface areas was observed when RelyX U200 underwent the delayed photoactivation protocol. Maxcem Elite exhibited an increased chemical reactivity when either chemically activated or immediately photoactivated and a higher binding energy of the carboxyl groups bonded to the calcium of HAp when chemically activated. Conclusions. The interaction of cements with hydroxyapatite is chemical in nature and leads to the formation of calcium salts, which may favor better integrity and longevity of adhesive restorations. The polymerization protocol affects the chemical interaction in mixtures of self-adhesive cements and hydroxyapatite, influencing the formation of these salts and the establishment of intermolecular interactions between the HAp and the cements.

Process-Dependent Electronic Structure at Metallized GaAs Contacts

1992 ◽  
Vol 260 ◽  
Author(s):  
L. J. Brillson ◽  
I. M. Vitomirov ◽  
A. Raisanen ◽  
S. Chang ◽  
R. E. Viturro ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Chemical Interaction ◽  
Deep Level ◽  
Multiple Roles ◽  
Atomic Scale ◽  
Photoemission Spectroscopy ◽  
Band Bending ◽  
Barrier Heights ◽  
Barrier Formation ◽  
Thermally Driven

ABSTRACTThe influence of metallization and processing on Schottky barrier formation provides the basis for one of several fruitful approaches for controlling junction electronic properties. Interface cathodo-and photoluminescence measurements reveal that electrically-active deep levels form on GaAs(100) surfaces and metal interfaces which depend on thermally-driven surface stoichiometry and reconstruction, chemical interaction, as well as surface misorientation and bulk crystal quality. These interface states are discrete and occur at multiple gap energies which can account for observed band bending. Characteristic trends in such deep level emission with interface processing provide guides for optimizing interface electronic behavior. Correspondingly, photoemission and internal photoemission spectroscopy measurements indicate self-consistent changes in barrier heights which may be heterogeneous and attributable to interface chemical reactions observed on a monolayer scale. These results highlight the multiple roles of atomic-scale structure in forming macroscopic electronic properties of compound semiconductor-metal junctions.

Computer simulation of polypropylene/organoclay nanocomposites: characterization of atomic scale structure and prediction of binding energy

Polymer ◽  
2004 ◽  
Vol 45 (23) ◽  
pp. 8075-8083 ◽  
Author(s):  
Radovan Toth ◽  
Alessandro Coslanich ◽  
Marco Ferrone ◽  
Maurizio Fermeglia ◽  
Sabrina Pricl ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Binding Energy ◽  
Scale Structure ◽  
Atomic Scale ◽  
Atomic Scale Structure

Investigation of the Structure and Distribution of Chemical Elements between the Phases of Hard Alloys of the Cr3C2-Ti System, Obtained at Various Modes of Explosive Compaction

2020 ◽  
Vol 992 ◽  
pp. 487-492
Author(s):  
V.O. Kharlamov ◽  
Aleksandr Vasilevich Krokhalev ◽  
S.V. Kuz’min ◽  
V.I. Lysak
Keyword(s):  
Phase Composition ◽  
Powder Mixture ◽  
Chemical Interaction ◽  
Chemical Elements ◽  
Equilibrium Phase ◽  
Hard Alloys ◽  
Explosive Compaction ◽  
Thermo Calc Software ◽  
Equilibrium Phases ◽  
Explosive Pressing

The Article presents the findings of the studies of the microstructure, chemical and phase composition of the Cr3C2-Ti system alloys obtained by the explosion. Scanning electron microscopy, energy dispersive and x-ray diffraction analyses were used. The program Thermo-Calc software was used to calculate the equilibrium phases. The phase composition of the compact was shown to fully correspond to that of the initial powder mixture during explosive pressing in the modes of heating from 300 ̊С to 600 ̊С. When heated above 600 ̊С, the chemical interaction of the initial components begins with the formation of new boundary phases. Meanwhile, there is a change in the sample destruction nature and a significant increase in hardness, which points to the hard alloy consolidation. The increase in the powder mixture heating in shock waves to 1000 ̊С leads to intensive macrochemical interaction of the powder mixture components and to formation of an equilibrium phase composition. The established temperature limits determine the most appropriate parameters of shock-wave loading when producing hard alloys by explosive pressing.

scholarly journals A Nanoscale Investigation of Carlin-Type Gold Deposits: An Atom-Scale Elemental and Isotopic Perspective

2019 ◽  
Vol 114 (6) ◽  
pp. 1123-1133 ◽  
Author(s):  
Phillip Gopon ◽  
James O. Douglas ◽  
Maria A. Auger ◽  
Lars Hansen ◽  
Jon Wade ◽  
...  
Keyword(s):  
Gold Mineralization ◽  
Sulfur Isotopes ◽  
Atom Probe ◽  
Gold Deposits ◽  
Atomic Scale ◽  
Chemical Information ◽  
Arsenian Pyrite ◽  
Turquoise Ridge ◽  
Dispersed Gold ◽  
Carlin Type Gold Deposits

Abstract Carlin-type gold deposits are one of the most important gold mineralization styles in the world. Despite their economic importance and the large volume of work that has been published, there remain crucial questions regarding their metallogenesis. Much of this uncertainty is due to the cryptic nature of the gold occurrence, with gold occurring as dispersed nanoscale inclusions within host pyrite rims that formed on earlier formed barren pyrite cores. The small size of the gold inclusions has made determining their nature within the host sulfides and the mechanisms by which they precipitated from the ore fluids particularly problematic. This study combines high-resolution electron probe microanalysis (EPMA) with atom probe tomography (APT) to constrain whether the gold occurs as nanospheres or is dispersed within the Carlin pyrites. APT offers the unique capability of obtaining major, minor, trace, and isotopic chemical information at near-atomic spatial resolution. We use this capability to investigate the atomic-scale distribution of trace elements within Carlin-type pyrite rims, as well as the relative differences of sulfur isotopes within the rim and core of gold-hosting pyrite. We show that gold within a sample from the Turquoise Ridge deposit (Nevada) occurs within arsenian pyrite overgrowth (rims) that formed on a pyrite core. Furthermore, this As-rich rim does not contain nanonuggets of gold and instead contains dispersed lattice-bound Au within the pyrite crystal structure. The spatial correlation of gold and arsenic within our samples is consistent with increased local arsenic concentrations that enhanced the ability of arsenian pyrite to host dispersed gold (Kusebauch et al., 2019). We hypothesize that point defects in the lattice induced by the addition of arsenic to the pyrite structure facilitate the dissemination of gold. The lack of gold nanospheres in our study is consistent with previous work showing that dispersed gold in arsenian pyrite can occur in concentrations up to ~1:200 (gold/arsenic). We also report a method for determining the sulfur isotope ratios from atom probe data sets of pyrite (±As) that illustrates a relative change between the pyrite core and its Au and arsenian pyrite rim. This spatial variation confirms that the observed pyrite core-rim structure is due to two-stage growth involving a sedimentary or magmatic-hydrothermal core and hydrothermal rim, as opposed to precipitation from an evolving hydrothermal fluid.

Metal Overlayers on Self-Organized Molecular Assemblies: X-ray Photoelectron Spectroscopy of CR/CM and NI/CM on 12-Nercaptododecanenitrile

1993 ◽  
Vol 304 ◽  
Author(s):  
D. R. Jung ◽  
A. W. Czanderna
Keyword(s):  
Binding Energy ◽  
Photoelectron Spectroscopy ◽  
Chemical Interaction ◽  
Molecular Assemblies ◽  
X Ray ◽  
Self Organized ◽  
Deposited Metal ◽  
Show Evidence ◽  
Metal Overlayers ◽  
End Group

AbstractOverlayers of Cr and Ni deposited at 22 °C and at -100 °C onto self-organized molecular assemblies of HS(CH2 )11 CN on Au have been studied by X-ray photoelectron spectroscopy (XPS). For the lowest overlayer coverages, the C ls and N is core levels show evidence for a chemical interaction between the deposited metal and the CN end-group. At 22 °C and for coverages of 0.6 nm or more, Cr/CN shows a C ls low binding energy, carbide-like shoulder. The degree of metal penetration is assessed based on the attenuation of the C ls and Au 4f intensities, and on the positions of the Cr and Ni 2p levels. In general, the least penetration and the largest binding energy shifts of the C, N, and the Cr or Ni core levels are observed for Cr/CN, while and Ni/CN shows smaller shifts and greater penetration.

scholarly journals Local atomic structure determination using focused electron beams

2014 ◽  
Vol 70 (a1) ◽  
pp. C26-C26
Author(s):  
Joanne Etheridge
Keyword(s):  
Quantum Wells ◽  
Atomic Structure ◽  
Structural Information ◽  
Electron Beams ◽  
Focal Point ◽  
Local Atomic Structure ◽  
Atomic Scale ◽  
Chemical Information ◽  
Diffraction Patterns

This talk will give an overview of methods for solving the atomic structure of nanostructured materials using focused electron beams. It will illustrate these methods with a range of applications, such as the determination of the atomic structure and stability of nanoparticle facets [1]; the local atomic structure of "chessboard' nanostructures in lithium-based titanate perovskites; and the measurement of local polarity, dopant concentration and atomic-scale morphology in semiconducting nanowire quantum wells. These methods take advantage of the fact that electron wavefields can be brought to a focal point smaller than an Ångström in diameter, enabling small volumes of matter to be probed and characterized. The wealth of information contained in the resulting diffraction patterns can be interrogated selectively to isolate and `image' specific structural information. Several methods using small focused electron beams will be described in this talk, including; (i) An approach for the determination of centrosymmetric structures from the direct observation of structure factor phases by inspection of features in convergent beam electron diffraction patterns [2]. The method can achieve high resolution from just a few phase observations and no intensity measurements or iterative refinements are required; (ii) Methods for the quantitative interpretation of the intensity in atomic resolution imaging and diffraction data for the measurement of local atomic and electronic structure; (iii) Pseudo-confocal scanning transmission electron microscopy methods for obtaining depth and chemical information which record the scattered intensity in a plane conjugate to the specimen (as opposed to the diffraction plane) [3].

scholarly journals THE ROLE OF PH IN HEAVY METAL CONTAMINATION OF URBAN SOIL

2014 ◽  
Vol 22 (4) ◽  
pp. 311-318 ◽  
Author(s):  
Asta KAZLAUSKAITĖ-JADZEVIČĖ ◽  
Jonas VOLUNGEVIČIUS ◽  
Virginija GREGORAUSKIENĖ ◽  
Saulius MARCINKONIS
Keyword(s):  
Heavy Metals ◽  
Soil Ph ◽  
Urban Soil ◽  
Heavy Metal Contamination ◽  
Agricultural Soils ◽  
Chemical Elements ◽  
Chemical Reactivity ◽  
Atomic Emission ◽  
Parent Material ◽  
Ph Level

The aim of this study to assess interdependence between urban soil pH and its accumulation of heavy metals. The article meant to be a contribution to a better knowledge of peculiarities and diagnostics of urban soil and its anthropogenic transformation. The hypothesis assumes that relationship between urban soil pH and its accumulation of heavy metals may be determined by the origin and age of parent material as well as the nature and degree of the anthropogenic impact. The spatial variability of topsoil pH level was performed in 100 points in eldership of Šnipiškės of the city Vilnius. Laboratory analysis was based on ISO 10390:2005. Samples were collected from 20 cm topsoil layer in the same sampling points where have been analysed concentrations of topsoil chemical elements using optical atomic emission spectrophotometry. The contamination of urban soils exhibits somewhat different compared to agricultural soils. In contradiction to earlier studies in Lithuanian agricultural soils where strong correlation between soil pH and Cr, Cd, Pb, Ni, Cu and Zd found, the conducted analysis shows a statistically reliable, but very weak (<0.3) correlation between the soil pH and concentration of contaminants. The proof to this correlation is provided by an existing relationship between pH and the concentration of copper (r = 0.20), mercury (r = 0.15), strontium (r = –0.12) and the overall contamination index (r = 0.12). The applied statistical analysis, however, failed to reveal the nature of interdependence between the soil pH and its contamination with studied heavy metals there concentration of contaminant chemical elements depends on the pH range of the soil and, conversely, the chemical reactivity of the soil changes affect on the concentration of studied chemical elements.

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