scholarly journals Structural Factors Inducing Cracking of Brass Fittings

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3255
Author(s):  
Lenka Kunčická ◽  
Michal Jambor ◽  
Adam Weiser ◽  
Jiří Dvořák
Keyword(s):  
Chemical Composition ◽  
Plastic Flow ◽  
Beta Phase ◽  
Alpha Phase ◽  
Structural Factors ◽  
Transmission Electron ◽  
Medical Gas ◽  
Hot Die Forging ◽  
Multiple Step

Cu–Zn–Pb brasses are popular materials, from which numerous industrially and commercially used components are fabricated. These alloys are typically subjected to multiple-step processing—involving casting, extrusion, hot forming, and machining—which can introduce various defects to the final product. The present study focuses on the detailed characterization of the structure of a brass fitting—i.e., a pre-shaped medical gas valve, produced by hot die forging—and attempts to assess the factors beyond local cracking occurring during processing. The analyses involved characterization of plastic flow via optical microscopy, and investigations of the phenomena in the vicinity of the crack, for which we used scanning and transmission electron microscopy. Numerical simulation was implemented not only to characterize the plastic flow more in detail, but primarily to investigate the probability of the occurrence of cracking based on the presence of stress. Last, but not least, microhardness in specific locations of the fitting were examined. The results reveal that the cracking occurring in the location with the highest probability of the occurrence of defects was most likely induced by differences in the chemical composition; the location the crack in which developed exhibited local changes not only in chemical composition—which manifested as the presence of brittle precipitates—but also in beta phase depletion. Moreover, as a result of the presence of oxidic precipitates and the hard and brittle alpha phase, the vicinity of the crack exhibited an increase in microhardness, which contributed to local brittleness.

scholarly journals Structural characterization of liquid phase sintered silicon carbide by high-resolution X-ray diffractometry

Cerâmica ◽  
2005 ◽  
Vol 51 (318) ◽  
pp. 168-172 ◽  
Author(s):  
C. A. Kelly ◽  
P. A. Suzuki ◽  
S. Ribeiro ◽  
S. Kycia
Keyword(s):  
Silicon Carbide ◽  
High Resolution ◽  
Mixed Oxide ◽  
Beta Phase ◽  
Alpha Phase ◽  
X Ray Diffraction ◽  
Solid Solution Formation ◽  
X Ray ◽  
Synchrotron Light

Silicon carbide (SiC) was sintered using two different additives: AlN-Y2O3 or AlN-CRE2O3. CRE2O3 is a mixed oxide formed by Y2O3 and rare-earth oxides. The crystalline structures of the phases were analyzed by high-resolution X-ray diffraction using synchrotron light source. The results of the Rietveld refinement of the mixed oxide show a solid solution formation. In both silicon carbide samples prepared using AlN-Y2O3 or AlN-CRE2O3 3C (beta-phase) and 6H (alpha-phase) polytypes were found. The structural and microstructural results for both samples were similar. This is an indication of the viability of the use of CRE2O3 in substitution for Y2O3 as additive to obtain dense materials.

The Characterization Of Organic Charge Transfer Superconductors By Microreflectance Spectroscopy

1990 ◽  
Vol 48 (2) ◽  
pp. 272-273
Author(s):  
S. L. Hill ◽  
K. Krishnan ◽  
J. R. Ferraro
Keyword(s):  
Charge Transfer ◽  
Single Crystal ◽  
Beta Phase ◽  
Alpha Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Crystallography ◽  
A Value ◽  
Charge Transfer Salts

Certain classes of organic charge-transfer salts demonstrate superconducting behavior at liquid helium temperatures. Single crystal x-ray diffraction and infrared microreflectance analysis have been performed on several conducting systems to associate the nature of the crystalline structure with the electrical conductivity. The infrared spectrum for a single crystal salt exhibits absorptions which correlate with superconducting behavior.Discussion Williams and coworkers have performed x-ray Crystallography experiments to demonstrate the presence of an anion cavity between radical cation stacks- of bis(ethylenedithio)- tetrathiafulvalene (ET). The sulfur…sulfur interstack distance in a beta or kappa phase salt assumes a value less than the Vanderwaals distance and exhibit a superconducting (two dimensional) metal behavior (verified by Fermi surface calculations) at 1-20K. The structures of alpha and beta phase ET2I3 suggest the potential for several potential intermolecular interaction modes. It may be observed that the beta phase permits both interstack as well as H … X anionic interactions, whereas these interactions are less likely to occur in the alpha phase.

Structural Heterogenity of Intraluminal Content of The Prostate: A Histochemical and Ultrastructural Study

2015 ◽  
Vol 21 (2) ◽  
pp. 368-376 ◽  
Author(s):  
Paula Badea ◽  
Amelia Petrescu ◽  
Lucia Moldovan ◽  
Otilia Zarnescu
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Chemical Composition ◽  
Radical Prostatectomy ◽  
Ultrastructural Observation ◽  
Corpora Amylacea ◽  
Histochemical Methods ◽  
Transmission Electron ◽  
Malignant Prostate

AbstractIntraluminal contents of benign and malignant prostatic tissue are associated with varying forms of acellular structures. These include corpora amylacea, prostatic calculi, and prostatic crystalloids. There are relatively few microscopy studies about the characterization of intraluminal structures from benign and malignant prostatic glands and little is known about their chemical composition. In the present study, we used a combination of special histochemical methods, immunohistochemistry, and transmission electron microscopy to characterize intraluminal contents of benign and malignant prostate glands. The study was done on 33 radical prostatectomy and four transurethral resections of prostate specimens. Histochemical methods such as von Kossa, autometallography (AMG), as well as PSA immunohistochemistry and transmission electron microscopy were performed to characterize intraluminal contents of benign and malignant prostate glands. Von Kossa staining was observed in acellular structures, corpora amylacea, prostatic calculi, and calcified blood vessels. AMG staining was observed in the lumen of small glands, in the epithelium lining prostate glands, and corpora amylacea. PSA staining showed prostatic glands with both positive and negative corpora amylacea and epithelial cells. Ultrastructural observation revealed the presence of a variety of highly heterogeneous aggregates composed of fibrillar elements that were similar to those of amyloid.

Synthesis and Characterization of Silica-Lead Sulfide Core Shell Nanospheres For Applications in Optoelectronic Devices

2021 ◽  
Author(s):  
Anderson Klay Romero-Jaime ◽  
Milka del Carmen Acosta-Enríquez ◽  
Diana Vargas-Hernández ◽  
Judith Celina Tánori-Córdova ◽  
Horacio Antolín Pineda-León ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Lead Sulfide ◽  
Photoelectron Spectroscopy ◽  
Core Shell ◽  
Shell System ◽  
Quantum Confinement Effects ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Spectrum Shift

Abstract Nanoscale miniaturization of chalcogenides semiconductors, such as lead sulfide (galena), can generate interesting quantum confinement effects in the field of optoelectronic applications. At this work, a process in order to obtain SiO2 nanospheres coated with Galena, as the denominated core-shell system, is developed, this process it is based in Stöber’s method, where only the magnetic stirring was replaced by an ultrasonic bath, to achieve well rounded, and highly stable silica nanoparticles with diameters average of 70 nm. The PbS shell cover presents a thickness of 10 nm around. Nanostructures chemical composition, morphology and optical properties were determined by Transmission Electron Microscopy and UV-Vis spectroscopy, respectively. As a result, the nano shells correspond to cubic PbS, presenting some interplanar distances of 2.95 Å and 3.41 Å; this nano shell also shown a toward blue optical spectrum shift and a remarkable increase in its band gap, 3.75 eV, was obtained, compared with the PbS bulk value. The chemical composition it is studied by energy scattering spectroscopy, and X-ray photoelectron spectroscopy analyzes.

Structural and Chemical Characterization of Al(Ga)N/GaN Quantum Well Structures Grown by Plasma Assisted Molecular Beam Epitaxy

2012 ◽  
Vol 186 ◽  
pp. 70-73 ◽  
Author(s):  
Jolanta Borysiuk ◽  
Piotr Dłużewski ◽  
Zbigniew Zytkiewicz ◽  
Marta Sobańska ◽  
Kamil Kłosek ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Molecular Beam Epitaxy ◽  
Scanning Transmission Electron Microscopy ◽  
Molecular Beam ◽  
Chemical Characterization ◽  
Quantum Well Structures ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

Growth of high quality GaN/AlN heterostructures by plasma assisted molecular beam epitaxy (PAMBE) is possible with excess of Ga on the surface. During growth of AlN this additional Ga acts as surfactant and improves mobility of the Al adatoms on the growing surface, at the possible cost of Ga segregation and creation of mixed AlGaN interlayer. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) were used to determine chemical composition of high crystallographic quality GaN-AlN multilayer structure. It was shown that segregation occurs at AlN-GaN heterointerfaces, while GaN-AlN interfaces have abrupt stepwise change of the chemical composition. HRTEM results show creation of trench defects at the periphery of growing AlN islands in the case of nonoptimized growth.

Characterization of small inclusions: SEM vs TEM, or is it even worth considering Sem?

1996 ◽  
Vol 54 ◽  
pp. 498-499
Author(s):  
Carl Blais ◽  
Gilles L’Espérance ◽  
Éric Baril ◽  
Clément Forget
Keyword(s):  
Chemical Composition ◽  
X Rays ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Diffraction Patterns ◽  
Micro Alloyed Steel ◽  
Steel Welds ◽  
Scanning Electron Microscopes

Inclusions of technological importance are often in the size range from 0.1 to 1 μm, These inclusions are generally too thick for EEL-spectrometry and require the use of EDS to characterize their chemical composition. Recent Monte Carlo simulations indicated that scanning electron microscopes (SEM’s) equiped with a field emission gun (FEG) might challenge transmission electron microscopes (TEM’s) for the charaterization of small inclusions, In the light of these results, we investigated the possibility of using a FEGSEM to characterize inclusions found in micro-alloyed steel welds used for arctic applications. The main setbacks of using EDS for such a task are due to the presence of small phases of unknown thicknesses, non-homogeneity of the X-ray generation volumes, variation in absorption along the path length of the X-rays, etc., Even though these problems are encoutered in both the SEM and the TEM, the relative ease of imaging the very small inclusions in TEM confers a definite advantage to this technique. Furthermore, TEM allows to obtain convergent-bearn electron diffraction patterns (CBED) which complement the chemical composition characterization, thereby allowing the unambiguous identification of the phases present (chemistry and crystal structure).

Preparation and Characterization of High Purity β-SiC Powder

2012 ◽  
Vol 512-515 ◽  
pp. 3-6 ◽  
Author(s):  
Eun Jin Jung ◽  
Yoon Joo Lee ◽  
Soo Ryong Kim ◽  
Woo Teck Kwon ◽  
Se Young Choi ◽  
...  
Keyword(s):  
Reaction Time ◽  
Beta Phase ◽  
Alpha Phase ◽  
Carbon Powder ◽  
X Ray Diffraction ◽  
Synthetic Temperature ◽  
Diffraction Peaks ◽  
Lower Temperature ◽  
Metallic Impurities

SiC powder can be produced generally through the Acheson process and it is required long carbothermic reaction time of SiO2 with carbon powder around 2200 °C ~ 2400 °C. Due to the high reaction temperature and long reaction time of the process, the powders produced have a large particle size and consist of mostly alpha phase SiC. Synthetic temperature of beta phase SiC powder is known to produce at 1700 °C ~ 1900 °C which is lower temperature than that of alpha phase SiC powder. We prepared β-SiC powder by heating precursor derived from the mixture of phenolic resin and tetraethyl orthosilicate. The precursor was heated at 1800 °C for 4 h in an Ar atmosphere. In order to examine the pyrolysis residue after the heat treatment, the SiC powder was analyzed with XRD and SEM. The X-ray diffraction result of the SiC powder shows the diffraction peaks around 35°, 60°, and 73° corresponded to the beta SiC phase. β-SiC powder prepared in this study contains lower metallic impurities compare than that of α-SiC powder prepared from Acheson method and is able to use as a good starting material for SiC single crystal growing.

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