APPLICATION OF ION SCATTERING TO ALLOY SURFACE ANALYSIS

1996 ◽  
Vol 03 (05n06) ◽  
pp. 1847-1856 ◽  
Author(s):  
D. J. O’CONNOR ◽  
Y. G. SHEN ◽  
E. ZUR MUHLEN ◽  
L. ZHU ◽  
R. J. MACDONALD
Keyword(s):  
Chemical Interaction ◽  
Bulk Composition ◽  
Atomic Layer ◽  
Surface Concentration ◽  
Real Space ◽  
Alloy Surface ◽  
Ion Scattering ◽  
Composition And Structure ◽  
Physical And Chemical ◽  
Bulk Alloys

The physical and chemical interaction of an alloy with its environment is dictated not by its bulk composition but by the surface concentration of different elements and their physical arrangement. Of the tools developed to measure these properties, ion scattering (with energies of 0.1–100 keV) has the capacity to measure composition with atomic layer sensitivity and short range order in real space. These advantages have been used to investigate the surface structure, composition and oxidation of bulk alloys and surface alloys. The composition and structure have also been used as probes of order-disorder transitions. In this presentation a review will be undertaken of the information so far delivered by ion scattering, and some of the potential directions will be outlined. Examples of work recently published or currently under investigation will be used to demonstrate the special applications of LEIS to alloy surface studies.

LOW ENERGY ION SCATTERING

2007 ◽  
Vol 14 (01) ◽  
pp. 31-41 ◽  
Author(s):  
FERIDOUN SAMAVAT ◽  
BRUCE V. KING ◽  
D. JOHN O'CONNOR
Keyword(s):  
Surface Analysis ◽  
Atomic Layer ◽  
Low Energy ◽  
Surface Atom ◽  
Ion Scattering ◽  
Low Energy Ion Scattering ◽  
Composition And Structure ◽  
Extreme Sensitivity ◽  
Low Energy Ions

Low energy ion scattering (LEIS) is the study of the composition and structure of a surface by the detection of low energy ions with energies ranging from 100 eV to 10 keV elastically scattered off the surface. The extreme sensitivity to the outermost atomic layer makes it as a unique tool for surface analysis. In this paper, concepts of shadowing, blocking, and also polar and azimuthal scans have been described. Surface order and surface atom spacings are revealed by using these concepts and measuring the intensity of backscattered projectiles as a function of the incident and azimuthal angles.

scholarly journals Bimetallic Nanocrystals: Structure, Controllable Synthesis and Applications in Catalysis, Energy and Sensing

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1926
Author(s):  
Gaojie Li ◽  
Wenshuang Zhang ◽  
Na Luo ◽  
Zhenggang Xue ◽  
Qingmin Hu ◽  
...  
Keyword(s):  
Gas Sensing ◽  
Chemical Properties ◽  
Research Progress ◽  
Synthesis Methods ◽  
Controlled Synthesis ◽  
Controllable Synthesis ◽  
Composition And Structure ◽  
Bimetallic Nanocrystals ◽  
Physical And Chemical ◽  
And Chemical Properties

In recent years, bimetallic nanocrystals have attracted great interest from many researchers. Bimetallic nanocrystals are expected to exhibit improved physical and chemical properties due to the synergistic effect between the two metals, not just a combination of two monometallic properties. More importantly, the properties of bimetallic nanocrystals are significantly affected by their morphology, structure, and atomic arrangement. Reasonable regulation of these parameters of nanocrystals can effectively control their properties and enhance their practicality in a given application. This review summarizes some recent research progress in the controlled synthesis of shape, composition and structure, as well as some important applications of bimetallic nanocrystals. We first give a brief introduction to the development of bimetals, followed by the architectural diversity of bimetallic nanocrystals. The most commonly used and typical synthesis methods are also summarized, and the possible morphologies under different conditions are also discussed. Finally, we discuss the composition-dependent and shape-dependent properties of bimetals in terms of highlighting applications such as catalysis, energy conversion, gas sensing and bio-detection applications.

PREPARATION, EVALUATION AND OPTIMIZATION OF MUCOADHESIVE MINI TABLETS OF TELMISARTAN BY USING SINGLE UNIT ENCAPSULATION SYSTEM

INDIAN DRUGS ◽  
2019 ◽  
pp. 64-67
Author(s):  
Indrajeet S. Patil ◽  
Omkar A. Patil ◽  
Rohankumar R. Chavan ◽  
Dheeraj S. Randive ◽  
Mangesh A. Bhutkar ◽  
...  
Keyword(s):  
Drug Release ◽  
Single Unit ◽  
Chemical Interaction ◽  
Extended Period ◽  
Controlled Drug Release ◽  
Wet Granulation ◽  
Dissolution Study ◽  
Capsule Shell ◽  
Physical And Chemical

The objective of the present study was to develop and optimize capsule filled oral mucoadhesive minitablets of telmisartan. Wet granulation method was employed for the development of minitablets. All the formulations (F1- F13) exhibited more than 21% drug release at 4h and at the end of 12h it showed drug release more than 90%. During the dissolution study it was observed that the capsule shell in which the minitablets were filled got completely dissolved in the first 5 min. FTIR and UV study showed absence of any significant physical and chemical interaction between drug and polymers. Formulation F 10 was found to possess higher drug release at 4h and 12 h. Combination of HPMC and Carbopol was found to be suitable for formulation of mucoadhesive minitablets, showed promising mucoadhesive strength and exhibited controlled drug release over an extended period of time.

scholarly journals Adhesion and Stability of Nanocellulose Coatings on Flat Polymer Films and Textiles

2020 ◽  
Author(s):  
Raha Saremi ◽  
Nikolay Borodinov ◽  
Amine Mohamed Laradji ◽  
Suraj Sharma ◽  
Igor Luzinov ◽  
...  
Keyword(s):  
Polymer Films ◽  
Food Packaging ◽  
Mechanical Stability ◽  
Polymer Coatings ◽  
High Specific Surface Area ◽  
Force Microscopy ◽  
Polycarboxylic Acids ◽  
Composition And Structure ◽  
Filtration Properties ◽  
Physical And Chemical

Renewable nanocellulose materials received increased attention owing to their small dimensions, high specific surface area, high mechanical characteristics, biocompatibility, and compostability. Nanocellulose coatings are among many interesting applications of these materials to functionalize different by composition and structure surfaces, including plastics, polymer coatings, and textiles with broader applications from food packaging to smart textiles. Variations in porosity and thickness of nanocellulose coatings are used to adjust a load of functional molecules and particles into the coatings, their permeability, and filtration properties. Mechanical stability of nanocellulose coatings in a wet and dry state are critical characteristics for many applications. In this work, nanofibrillated and nanocrystalline cellulose coatings deposited on the surface of polymer films and textiles made of cellulose, polyester, and nylon are studied using atomic force microscopy, ellipsometry, and T-peel adhesion tests. Methods to improve coatings adhesion and stability using physical and chemical cross-linking with added polymers and polycarboxylic acids are analyzed in this study. The paper reports on the effect of the substrate structure and ability of nanocellulose particles to intercalate into the substrate on the coating adhesion.

scholarly journals Medidas de adesão entre agregado e ligante asfáltico

TRANSPORTES ◽  
2008 ◽  
Vol 16 (1) ◽  
Author(s):  
Kamilla Lima Vasconcelos ◽  
Amit Bhasin ◽  
Dallas N. Little ◽  
Jorge Barbosa Soares
Keyword(s):  
Chemical Interaction ◽  
Asphalt Binder ◽  
Fatigue Cracking ◽  
Adhesion Measurement ◽  
Materials Used ◽  
Enthalpy Of Immersion ◽  
Physical And Chemical ◽  
Energy Components

<p>A adesão entre agregado e ligante asfáltico vem sendo apontada como uma propriedade de grande importância para a causa de defeitos encontrados em pavimentos asfálticos, tais como trincas por fadiga, e dano por umidade. Diferentes mecanismos existem na literatura para explicar a adesão entre os dois materiais, porém, estes mecanismos podem ser resumidos em três grandes grupos: inter- travamento mecânico, adesão física, e interação química. A ocorrência de mais de um mecanismo simultaneamente parece ser o fenô- meno mais provável, sendo a relevância de cada um dependente das características físicas e químicas do agregado e do ligante asfálti- co. No presente trabalho, dois procedimentos foram utilizados para acessar a adesão entre agregado e ligante. O primeiro constou do cálculo do trabalho de adesão através da energia livre de superfície dos materiais envolvidos e o segundo, da determinação da entalpia de imersão quando soluções de asfalto são postas em contato com o agregado. Todos os materiais usados foram provenientes da biblio- teca de referência do SHRP sendo um pedregulho como agregado, e três diferentes ligantes asfálticos. Os resultados mostraram a capa- cidade do microcalorímetro em detectar possíveis interações químicas na adesão entre agregado e ligante asfáltico, em conjunto com adesão física. A presença de grupos funcionais mais fortemente adsorvidos pela superfície dos agregados justificou os maiores valores de entalpia de imersão para as combinações onde esses grupos se encontravam presentes.</p><p><em><strong>Abstract</strong> Adhesion between the asphalt binder and the aggregate is critical to the performance and durability of asphalt mixtures. According to the literature, distresses mechanisms such as fatigue cracking and moisture induced damage are correlated to the nature and quality of adhesion between these two materials. Different mechanisms already exist to explain adhesion, but they can be summa- rized in three main groups: mechanical interlocking, physical adhesion and chemical interaction. Although discussions of isolated theo- ries and mechanisms help to clarify the understanding of adhesion, they can rarely be separated completely to each other. The physical and chemical characteristics of asphalt and aggregate will in fact determine the relevance of each of these mechanisms. This study presents the results of two procedures for adhesion measurement: (i) an indirect method based on the surface free energy components of asphalt binder and aggregate; and (ii) the determination of the enthalpy of immersion through the use of a microcalorimeter. The materials used, a gravel as aggregate and three different neat asphalts, were provided by the Strategic Highway Research Program's Material Reference Library. The results showed the capacity of the microcalorimeter in detecting possible chemical reactions together with physical adhesion. The presence of functional groups more strongly adsorbed by the aggregate surface justified the higher values of the heat of immersion. </em></p>

Fundamentals of X-ray Spectrometric Analysis Using Low-Energy Electron Excitation

1990 ◽  
Vol 34 ◽  
pp. 105-121 ◽  
Author(s):  
K. J. Romand ◽  
F. Gaillard ◽  
M. Charbonnier ◽  
D. S. Urch
Keyword(s):  
Analytical Techniques ◽  
Atomic Layer ◽  
Mean Free Path ◽  
Electron Excitation ◽  
Spectrometric Analysis ◽  
Ion Scattering ◽  
X Ray ◽  
Secondary Ions ◽  
Information Depth ◽  
Wide Range

In the field of material analysis and characterization interest has considerably shifted over the last few decades from bulk to surface and very thin film problems. At the present state a wide range of surface analytical techniques - such as x-ray photoelectron (XPS), Auger electron (AES), secondary ion mass (SIMS), ion scattering (ISS) spectroscopies - have become available but every one of them exhibits specific analytical features and information content. Within the context of this paper the main parameter to be considered is the information depth i.e the layer thickness from which the majority of information-bearing particles escape and hence are detected. For XPS and AES, this parameter is associated with the mean-free path of photoelectrans or Auger electrons and typically is in the range from 0.5 to 4 nm. In SIMS the ejected secondary ions are emitted from the outer 2 or 3 atomic layers (i.e. from about 1 nm) while the single-collision binary process occuring in ISS is restricted to atoms from the top most atomic layer (0.2-0.3 nm).

X-ray photoelectron and ion scattering spectroscopic surface analyses of amorphous and crystalline calcium phosphate nanoparticles with different chemical histories

2020 ◽  
Vol 22 (10) ◽  
pp. 5531-5547 ◽  
Author(s):  
Vuk Uskoković
Keyword(s):  
Calcium Phosphate ◽  
Atomic Layer ◽  
Hydroxyapatite Nanoparticles ◽  
Ion Scattering ◽  
Amorphous Precursor ◽  
X Ray ◽  
History Of ◽  
Calcium Phosphate Nanoparticles ◽  
History Of Formation

The surface of hydroxyapatite nanoparticles is enriched in the topmost atomic layer with calcium and depleted of it elsewhere, alongside being dependent on the history of formation of hydroxyapatite from the amorphous precursor.

scholarly journals Synthesis of 1,2,3-Triazole Derivatives and Its Evaluation as Corrosion Inhibitors for Carbon Steel

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Gabriel O. Resende ◽  
Sara F. Teixeira ◽  
Igor F. Figueiredo ◽  
Alexandre A. Godoy ◽  
Dafne Júlia F. Lougon ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Heterocyclic Compounds ◽  
Steel Surface ◽  
Corrosion Inhibitors ◽  
Inhibition Efficiency ◽  
Chemical Interaction ◽  
Synthetic Route ◽  
Acid Media ◽  
Carbon Steel Surface ◽  
Physical And Chemical

Heterocyclic compounds containing the 1,2,3-triazole moiety can be synthesized through click-chemistry, which is rapid reactions with good yields allowing the synthesis of great derivatives diversity by making minor changes in the reagents. The products were obtained with good yields through a synthetic route which uses ready available nonexpensive commercial reagents and without any further purification of any product or intermediate. The carbon steel anticorrosive activity was tested through weight loss and electrochemical assays in acid media. It was observed relevant inhibition efficiency (> 90%) for inhibitors 1 and 2. From Langmuir isotherm, it was hypothesized the adsorption of inhibitors on the carbon steel surface might occur by physical and chemical interaction; however, the activation energy raised suggests a physisorption process for the interaction of the inhibitor on the carbon steel surface.

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