Towards bridging the structure gap in heterogeneous catalysis: the impact of defects in dissociative chemisorption of methane on Ir surfaces

2021 ◽  
Vol 23 (7) ◽  
pp. 4376-4385
Author(s):  
Xueyao Zhou ◽  
Yaolong Zhang ◽  
Hua Guo ◽  
Bin Jiang
Keyword(s):  
Heterogeneous Catalysis ◽  
Surface Defects ◽  
Dissociative Chemisorption ◽  
The Impact

The negatively activated region in CH4 dissociation is attributed to a precursor-mediated mechanism involving surface defects.

scholarly journals The Role of Thin-Film Vacuum-Plasma Coatings and Their Influence on the Efficiency of Ceramic Cutting Inserts

Coatings ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 287 ◽  
Author(s):  
Marina Volosova ◽  
Sergey Grigoriev ◽  
Alexander Metel ◽  
Alexander Shein
Keyword(s):  
Bending Strength ◽  
Surface Defects ◽  
Cutting Tools ◽  
High Energy ◽  
Radius Of Curvature ◽  
Sic Ceramic ◽  
Operational Tests ◽  
Mechanical Fastening ◽  
Cutting Inserts ◽  
The Impact

The main problem with ceramics used in cutting tools is related to the unpredictable failures caused by the brittle fracturing of ceramic inserts, which is critical for the intermittent milling of cyclic loading. A 125-mm-diameter eight-toothed end mill, with a mechanical fastening of ceramic inserts, was used as a cutting tool for milling hardened steel (102Cr6). For the experiments, square inserts of the Al2O3 + SiC ceramic were used and compared with the samples made of Al2O3 + TiC to confirm the obtained results. The samples were coated with diamond-like coating (DLC), TiZrN, and TiCrAlN coatings, and their bending strength and adhesion were investigated. Investigations into the friction coefficient of the samples and operational tests were also carried out. The effect of smoothing the microroughness and surface defects in comparison with uncoated inserts, which are characteristic of the abrasive processing of ceramics, was investigated and analyzed. The process developed by the authors of the coating process allows for the cleaning and activation of the surface of ceramic inserts using high-energy gas atoms. The impact of these particles on the cutting edge of the insert ensures its sharpening and reduces the radius of curvature of its cutting edges.

scholarly journals Effect of CeO2-ZnO Nanocomposite for Photocatalytic and Antibacterial Activities

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 817
Author(s):  
Asad Syed ◽  
Lakshmi Sagar Reddy Yadav ◽  
Ali H. Bahkali ◽  
Abdallah M. Elgorban ◽  
Deshmukh Abdul Hakeem ◽  
...  
Keyword(s):  
Surface Defects ◽  
Uv Light ◽  
Antibacterial Properties ◽  
Combustion Method ◽  
Antibacterial Activities ◽  
Cubic Phase ◽  
Solution Combustion ◽  
Tem Analysis ◽  
Bet Specific Surface Area ◽  
The Impact

The impact of a CeO2-ZnO nanocomposite on the photocatalytic and antibacterial properties compared to bare ZnO was investigated. A CeO2-ZnO nanocomposite was synthesized using Acacia nilotica fruit extract as a novel fuel by a simple solution combustion method. The obtained CeO2-ZnO nanocomposite was confirmed structurally by XRD, FTIR, Raman and UV-DRS and morphologically by SEM/TEM analysis. The XRD pattern indicates the presence of both hexagonal Wurtzite-structured ZnO (major) and cubic-phase CeO2 (minor). FTIR shows the presence of a Ce-O-Ce vibration at 468 cm−1 and Zn-O vibration at 445 cm−1. The existence of a band at 460 cm−1 confirmed the F2g Raman-active mode of the fluorite cubic crystalline structure for CeO2. Diffused reflectance spectroscopy was used to estimate the bandgap (Eg) from Kubelka–Munk (K–M) theory which was found to be 3.4 eV. TEM analysis shows almost spherical-shaped particles, at a size of about 10–15 nm. The CeO2-ZnO nanocomposite shows a good BET specific surface area of 30 m2g−1. The surface defects and porosity of the CeO2-ZnO nanocomposite caused methylene blue (MB) dye to degrade under sunlight (88%) and UV light (92%). The CeO2-ZnO nanocomposite also exhibited considerable antibacterial activity against a pathogenic bacterial strain.

The Impact of Nanoscience in Heterogeneous Catalysis

2015 ◽  
pp. 405-430 ◽  
Author(s):  
Sharifah Bee Abd Hamid ◽  
Robert Schlögl
Keyword(s):  
Heterogeneous Catalysis ◽  
The Impact

scholarly journals Effect of pulsed soft X-ray radiation on the surface topography of some metals

2021 ◽  
Vol 2064 (1) ◽  
pp. 012092
Author(s):  
A E Ligachev ◽  
M V Zhidkov ◽  
S A Sorokin ◽  
G V Potemkin ◽  
Yu R Kolobov
Keyword(s):  
Surface Topography ◽  
Surface Defects ◽  
Radiation Energy ◽  
High Current ◽  
Radiation Energy Density ◽  
Near Surface ◽  
Ion Flow ◽  
X Ray ◽  
Irradiation Energy ◽  
The Impact

Abstract Effect of the pulsed soft X-ray fluxes (PSXF) on the surface topography of metals (Mg and Cu) has been investigated. Soft pulse X-ray irradiation (energy quanta of 0.1-1.0 keV) were carried out on a high-current MIG generator. The sample of magnesium was located at a distance of 10 cm from the X-ray source. Since the distance to the sample significantly exceeded the size of the X-ray beam, it can be assumed that the density of the X-ray radiation flow to the magnesium sample was uniform. The duration of the radiation pulse was 100 ns, and the radiation energy density in the pulse varied from 13 to 19 J/cm2. As a result of melting under the action of PSXF of the near-surface layer of metals and subsequent solidification, a wavy relief is formed on their surface. Defects in the form of craters, which usually occur after the impact of a powerful pulsed ion flow on metals, were not detected.

scholarly journals Molecular Dynamics Simulations on Influence of Defect on Thermal Conductivity of Silicon Nanowires

2021 ◽  
Vol 9 ◽  
Author(s):  
Hao Li ◽  
Qiancheng Rui ◽  
Xiwen Wang ◽  
Wei Yu
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Nanowires ◽  
Surface Defects ◽  
Low Frequency ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Impact

A non-equilibrium molecular dynamics simulation method is conducted to study the thermal conductivity (TC) of silicon nanowires (SiNWs) with different types of defects. The impacts of defect position, porosity, temperature, and length on the TC of SiNWs are analyzed. The numerical results indicate that SiNWs with surface defects have higher TC than SiNWs with inner defects, the TC of SiNWs gradually decreases with the increase of porosity and temperature, and the impact of temperature on the TC of SiNWs with defects is weaker than the impact on the TC of SiNWs with no defects. The TC of SiNWs increases as their length increases. SiNWs with no defects have the highest corresponding frequency of low-frequency peaks of phonon density of states; however, when SiNWs have inner defects, the lowest frequency is observed. Under the same porosity, the average phonon participation of SiNWs with surface defects is higher than that of SiNWs with inner defects.

scholarly journals Effect of benzophenone on the physicochemical properties of N-CNTs synthesized from 1-ferrocenylmethyl (2-methylimidazole) catalyst

2020 ◽  
pp. 205-217
Author(s):  
Ayomide Labulo ◽  
Elijah Temitope Adesuji ◽  
Charles Ojiefoh Oseghale ◽  
Elias Emeka Elemike ◽  
Akinola Kehinde Akinola ◽  
...  
Keyword(s):  
Oxygen Concentration ◽  
Photoelectron Spectroscopy ◽  
Surface Defects ◽  
Molecular Nitrogen ◽  
Chemical Vapour ◽  
Morphological Difference ◽  
Effective Control ◽  
Fe Catalyst ◽  
Nitrogen Doped Carbon ◽  
The Impact

Vertically-aligned nitrogen-doped carbon nanotubes (v-N-CNTs) were synthesized \textit{via} the chemical vapour deposition (CVD) technique. 1-ferrocenylmethyl(2-methylimidazole) was employed as the source of the Fe catalyst and was dissolved in different ratios of acetonitrile/benzophenone feedstock which served as both the carbon, nitrogen, and oxygen sources. The morphological difference in N-CNTs was as a result of increased oxygen concentration in the reaction mix and not due to water vapour formation as observed in the oxygen-free experiment, indicating specifically, the impact of oxygen. Raman and X-ray photoelectron spectroscopy (XPS) revealed surface defects and grafting of oxygen functional groups on the sidewall of N-CNTs. The FTIR data showed little or no effect as oxygen concentration increases. XPS analysis detected the type of nitrogen species (\textit{i.e.} pyridinic, pyrrolic, graphitic, or molecular nitrogen forms) incorporated in the N-CNT samples. Pyrrolic nitrogen was dominant and increased (from 8.6 to 11.8 at.\%) as oxygen concentration increases in the reaction precursor. An increase in N content was observed with the introduction of a lower concentration of oxygen, followed by a gradual decrease at higher oxygen concentration. Our result suggested that effective control of the reactant mixtures can manipulate the morphology of N-CNTs.

scholarly journals Impact of Pulse Length on the Accuracy of Defect Depth Measurements in Pulse Thermography

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
James Pierce ◽  
Nathan B. Crane
Keyword(s):  
Surface Defects ◽  
Pulse Length ◽  
Input Pulse ◽  
Three Dimensional ◽  
Acrylonitrile Butadiene Styrene ◽  
Test Method ◽  
Defect Depth ◽  
Pulse Thermography ◽  
Energy Pulse ◽  
The Impact

Pulse thermography (PT) is a nondestructive testing method in which an energy pulse is applied to a surface while the surface temperature evolution is measured to detect sub surface defects and estimate their depth. This nondestructive test method was developed on the assumption of instantaneous surface heating, but recent work has shown that relatively long pulses can be used to accurately determine defect depth in polymers. This paper examines the impact of varying input pulse length on the accuracy of defect depth quantification as a function of the material properties. Simulations using both thermoplastics and metals show that measurement error is dependent on a nondimensionalized pulse length. The simulation results agree with experimental results for three-dimensional (3D) printed acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) components. Analysis and experiments show that defects can be accurately detected with minor modification to the standard methods as long as the pulse ends before the characteristic defect signal is detected.

scholarly journals Impact of machining-induced surface defects on the edge formability of commercially pure titanium sheet at room temperature

2020 ◽  
Vol 2 (12) ◽  
Author(s):  
J. S. Kwame ◽  
E. Yakushina ◽  
P. Blackwell
Keyword(s):  
Room Temperature ◽  
Surface Defects ◽  
Pure Titanium ◽  
Commercially Pure Titanium ◽  
Hole Expansion ◽  
Expansion Test ◽  
Hole Expansion Test ◽  
Edge Surface ◽  
Cp Ti ◽  
The Impact

AbstractDespite the good properties of titanium, which have drawn the interest of various industries over the years, one of the major drawbacks of this material is its poor machinability. This has largely been attributed to its low thermal conductivity and elastic modulus. The ability to attain the optimum sheet edge performance during forming is dependent on the quality of the edges produced. Also, the demanding nature of aerospace part design has provoked the interest of both industry and academia to continually explore avenues tailored at enhancing part performance. The sort of edge surface integrity produced for aerospace part fabrication thus becomes a vital consideration in the quest to ensuring prime performance of components. This work seeks to study the influence of different machining-induced surface defects on the sheet edge performance of CP-Ti (grade 2) at room temperature. Hole expansion test was used to assess the edge surface formability of CP-Ti with different machining-induced edge defects. The research found that machining-induced surface defects act as stress concentration sites during the hole expansion test and have a major impact on the material flow. Electro-discharge machined edges were observed to exhibit high edge formability compared to laser and abrasive water jet cut edges due to the impact of machining-induced microstructural changes.

In Situ Spectroscopic Ellipsometry for Real Time Composition Control of Hg1−xcdx Te Grown by Molecular Beam Epitaxy

1997 ◽  
Vol 487 ◽  
Author(s):  
R. Dat ◽  
F. Aqariden ◽  
W. M. Duncan ◽  
D. Chandra ◽  
H. D. Shih
Keyword(s):  
Experimental Data ◽  
Molecular Beam Epitaxy ◽  
Surface Topography ◽  
Spectroscopic Ellipsometry ◽  
Molecular Beam ◽  
Surface Defects ◽  
Spectral Ellipsometry ◽  
Composition Control ◽  
The Impact

AbstractSpectral ellipsometry (SE) was applied to in situ composition control of Hg1−xCdxTe grown by molecular beam epitaxy (MBE), and the impact of surface topography of the Hg1−xCdxTe layers on the accuracy of SE was investigated. Of particular importance is the presence of surface defects, such as voids in MBE- Hg1−xCdx.Te layers. While dislocations do not have any significant impact on the dielectric functions, the experimental data in this work show that MBE- Hg1−xCdxTe samples having the same composition, but different void densities, have different effective dielectric functions.

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