scholarly journals Influence of the Base Element on the Thermal Properties of Non- Ferrous Chromium-Rich TaC-Containing Alloys Elaborated by Conventional Casting: Part 3: Surface and Cross-Sectional Metallographic Characterization of the Oxidized Alloys

2019 ◽  
Vol 6 ◽  
Author(s):  
Jean-Paul K. Gomis ◽  
Patrice Berthod ◽  
Erwann Etienne
Keyword(s):  
Thermal Properties ◽  
Isothermal Oxidation ◽  
Population Characteristics ◽  
Cross Sectional ◽  
Base Element ◽  
Free Zone ◽  
The Matrix ◽  
Oxide Spallation ◽  
First Time

The six alloys the thermal properties of which and the tendency to oxide spallation of which were studied in the first two parts of this work, were here characterized after oxidation for 70 hours at 1250°C. The external chromia scale, and also the CrTaO4 subsurface oxide, formed for all the alloys, almost independently of the Co and Ni proportions in the base element content. But, because of the formation of more CrTaO4 for the nickel-richest alloys probably due to the higher availability of Ta in the matrix and its easier diffusion towards the neighbourhood of the oxidation front, the adherence of chromia was weakened and spallation, suggested by the thermogravimetric curves in the second part of this work, is here really observed and the denuded part of alloys clearly seen. The degradation of the subsurface, which can be in a first time summarized by the development of a carbide-free zone and a {Cr, Ta}-depleted zone, depends on the Co and Ni proportions. The microstructure of the bulk is differently affected by long exposure at elevated temperature. The changes in carbide population characteristics are stronger for the nickel-based alloys than for the cobalt-based ones. Finally, the isothermal oxidation behaviour is best for the nickel-richest alloys but the oxide spallation behaviour and the potential mechanical properties are the best for the cobalt-richest alloys.

Graphite/UPE Nanocomposite: Transport, Thermal, Mechanical and Viscoelastic Properties

2019 ◽  
Vol 23 ◽  
pp. 201-212
Author(s):  
Shivkumari Panda ◽  
Dibakar Behera ◽  
Tapan Kumar Bastia
Keyword(s):  
Transport Properties ◽  
Unsaturated Polyester ◽  
Homogeneous Distribution ◽  
Thermo Gravimetric ◽  
New Class ◽  
The Matrix ◽  
Novel Method ◽  
Water Transport Properties ◽  
First Time

This chapter presents the preparation and characterization of some unique properties of nanocomposites by dispersing graphite flakes in commercial unsaturated polyester (UPE) matrix. The composite was prepared by a novel method with the use of solvent swelling technique. Three different specimens of UPE/graphite nanocomposites were fabricated with addition of 1, 2 and 3 wt% of graphite flakes. Except mechanical, viscoelastic and thermo gravimetric properties, transport properties like electrical conductivity, thermal conductivity and water transport properties were studied for the first time. Graphite flakes propose enhanced properties to the composites suggesting homogeneous distribution of the nanofiller in the matrix and strong interaction with the matrix. 2wt% nanofiller loading showed superior essential characteristics and after that the properties reduced may be due to the nucleating tendency of the nanofiller particles. The XRD pattern showed the compatibility of the graphite flakes by introducing a peak around 26.550 in the nanocomposites. SEM Properties are also in agreement with the compatibility. Nanocomposite with 2wt% graphite also showed remarkable enhancement in transport, mechanical, viscoelastic and thermo gravimetric properties. So by introduction of a small quantity of graphite endow the new class of multiphase nanocomposites with inimitable structure and tremendous application.

scholarly journals Mechanical and Fractographical Characterization of Extruded Al-Mg-Si-Zr Alloys

2018 ◽  
Vol 188 ◽  
pp. 02017
Author(s):  
Fulya Kahrıman ◽  
Muzaffer Zeren
Keyword(s):  
Fracture Behavior ◽  
Direct Chill ◽  
Grain Structure ◽  
Tensile Fracture ◽  
Casting Method ◽  
Cross Sectional ◽  
Fracture Surfaces ◽  
The Matrix ◽  
Zr Alloys

In this study, the chemical composition of Al-0.8Mg-0.8Si alloys was modified with the addition of 0.1 and 0.2 wt.-% Zr. The billets were manufactured by direct chill casting method, homogenized at 560 °C for 6h and then extruded in order to obtain profiles having hollow and circular sections. Recrystallization layer (shell) became narrower due to the addition of Zr. This was attributed to the formation of very fine precipitates (Al3Zr) within the matrix. The mechanical properties showed that both yield and tensile strengths increased as a function of Zr content. Tensile fracture surfaces were examined by scanning electron microscope and the fractographs reflected the effect of grain structure on the fracture behavior of studied alloys. All fracture surfaces indicated typical dimple ruptures, however, the size of dimples were observed as finer structures as a function of Zr content. As seen in cross-sectional graphs, as the Zr content increased the grain structure was refined due to Al3Zr precipitates. These fine precipitates caused the formation of fine and shallow dimples under loading.

Preparation and characterization of poly(3-glycidoxypropyltrimethoxysilane) nanocomposite using organophilic montmorillonite clay (Mag-cetyltrimethylammonium)

2019 ◽  
Vol 53 (28-30) ◽  
pp. 4313-4322 ◽  
Author(s):  
Nadia Embarek ◽  
Nabahat Sahli ◽  
Mohammed Belbachir
Keyword(s):  
Thermal Properties ◽  
Preparation Method ◽  
X Ray Diffraction ◽  
Scanning Electronic Microscopy ◽  
X Ray ◽  
The Matrix ◽  
Organophilic Clay ◽  
Linear Poly ◽  
Organophilic Montmorillonite

Nanocomposites of linear poly(3-glycidoxypropyltrimethoxysilane) based on Algerian natural organophilic clay: montmorillonite–cetyltrimethylammonium named Maghnite-CTA were prepared by enhancing the dispersion of the matrix polymer in sheets of the organoclay. The effect of the organoclay, used with different amounts (3, 5, and 7% by weight) and the preparation method were studied in order to determine and evaluate their structural, morphological and thermal properties. X-ray diffraction analysis of obtained nanocomposites showed a significant change in the distance interlayer of montmorillonite–cetyltrimethylammonium. Therefore, interlayer expansion and exfoliation of linear poly(3-glycidoxypropyltrimethoxysilane) between layers of montmorillonite–cetyltrimethylammonium were observed. The thermal properties of the prepared nanocomposites were given by thermogravimetric analysis. The structure and morphology of the obtained materials were determined respectively by Fourier transform infrared spectroscopy and scanning electronic microscopy. The results obtained have approved the privilege of the intercalation of linear poly(3-glycidoxypropyltrimethoxysilane) in the interface of montmorillonite–cetyltrimethylammonium and the best quantity of organoclay required to prepare nanocomposite with a high thermal stability is 5% (by weight).

Synthesis and Characterization of Microcellular Injection Molded Polyolefin/Polycaprolactone Composites

2021 ◽  
Vol 1041 ◽  
pp. 11-15
Author(s):  
Shyh Shin Hwang ◽  
Shia Chung Chen ◽  
Chiu Lan Yang
Keyword(s):  
Tensile Strength ◽  
Thermal Properties ◽  
Cell Size ◽  
Cell Density ◽  
Synthesis And Characterization ◽  
Degradation Temperature ◽  
The Matrix ◽  
Filler Dispersion ◽  
Injection Molded

This study investigated the effect of polycaprolactone (PCL) loading (0.5, 1, and 3 wt%) on the morphology, tensile strength, and thermal properties of microcellular injection molded PP/PCL and PPgMA/PCL composites. We used the filler, PCL, that is micro-material in size. Results showed that 0.5 wt% loading of PCL on foamed PP has the largest tensile strength. However, tensile strength was almost similar to that of PPgMA composites. Tensile strength depends on the filler dispersion in the matrix and cell size present on the foamed composites. Good dispersion resulted in good tensile strength. The elongation decreased on PP but increased on PPgMA composites. The highest degradation temperature for PP/PCL and PPgMA/PCL was noted for 3.0 wt% PCL loading and neat PPgMA respectively. Cell size decreased and cell density increased with the addition of PCL into the PP and PPgMA matrix.

scholarly journals Characterizing the Brain Structural Adaptations Across the Motherhood Transition

2021 ◽  
Vol 2 ◽  
Author(s):  
Magdalena Martínez-García ◽  
María Paternina-Die ◽  
Manuel Desco ◽  
Oscar Vilarroya ◽  
Susanna Carmona
Keyword(s):  
Early Years ◽  
Cross Sectional ◽  
Confounding Variables ◽  
Physiological Adaptations ◽  
Current Article ◽  
Brain Changes ◽  
Magnetic Resonance Imaging Mri ◽  
First Time ◽  
Structural Adaptations

Women that become mothers face notable physiological adaptations during this life-period. Neuroimaging studies of the last decade have provided grounded evidence that women's brains structurally change across the transition into motherhood. The characterization of this brain remodeling is currently in its early years of research. The current article reviews this scientific field by focusing on our longitudinal (pre-to-post pregnancy) Magnetic Resonance Imaging (MRI) studies in first-time parents and other longitudinal and cross-sectional studies of parents. We present the questions that are currently being answered by the parental brain literature and point out those that have not yet been explored. We also highlight potential confounding variables that need to be considered when analyzing and interpreting brain changes observed during motherhood.

scholarly journals Extraction and characterization of the tissue forms of collagen types II and IX from bovine vitreous

1994 ◽  
Vol 299 (2) ◽  
pp. 497-505 ◽  
Author(s):  
P N Bishop ◽  
M V Crossman ◽  
D McLeod ◽  
S Ayad
Keyword(s):  
Chondroitin Sulphate ◽  
Minor Component ◽  
Type Ii Collagen ◽  
Type Ii ◽  
Collagen Types ◽  
The Matrix ◽  
Type V ◽  
Chain Lengths ◽  
First Time

We report for the first time that, after centrifugation of adult bovine vitreous, the hyaluronan-rich supernatant contains collagens which can be isolated in their intact forms by precipitation with 4.5 M NaCl. This precipitate constituted approx. 4% of the total vitreous collagen and comprised collagen types IX and II (in the approximate ratio of 4:1) with negligible amounts of type-V/XI collagen. Type-II collagen was present partly in a pro-alpha 1(II) form, suggesting that there is active synthesis of type-II collagen into the matrix of adult bovine vitreous. Type-IX collagen was purified (2-2.5 mg/l of vitreous) and its glycosaminoglycan chain composition was analysed. Bovine vitreous type-IX collagen always possessed a glycosaminoglycan chain of comparatively low M(r) that was predominantly 4-sulphated, with chondroitin 6-sulphate representing a more minor component. By contrast, chick vitreous has been shown to contain type-IX collagen which always possesses a high-M(r) chondroitin sulphate chain that is predominantly 6-sulphated. The functional significance of these different glycosaminoglycan chain lengths and sulphation patterns is discussed.

AEM characterization of SiC fiber/AIN composites

1994 ◽  
Vol 52 ◽  
pp. 630-631
Author(s):  
K. Park ◽  
C. Sung
Keyword(s):  
Liquid Phase ◽  
Grain Boundaries ◽  
Creep Tests ◽  
Cross Sectional ◽  
Sintering Aid ◽  
Sic Fiber ◽  
Vacuum Atmosphere ◽  
The Matrix ◽  
Convergent Beam

SiC fiber (15 vol. %)/AlN composites were fabricated by hot pressing at 1650°C and 17.6 MPa using a 4Ca(OH)2·Al2O3 sintering aid under vacuum atmosphere. Creep tests for the composites were conducted at compressive stress of 50 MPa and at 1120°C for 48 hours under oxygen atmosphere. Cross-sectional TEM samples were analyzed using a Philips EM400T TEM and a Noran ultrathin window Micro-Z detector. Selected area diffraction (SAD), convergent beam electron diffraction (CBED), and energy dispersive X-ray spectroscopy (EDXS) were used to identify the microstructure and microchemistry of the matrix, fiber, and matrix/fiber interface of the composites.Generally, the AIN matrix contained a liquid phase at grain boundaries and a high density of dislocations within the grains (Fig. 1(a)). Most of the additives were present at the grain boundaries. Fig. 1(b) shows a SAD pattern from the liquid phase at the grain boundaries. The liquid phase was identified as Ca12Al14O33 with a cubic structure (a = 1.198 nm).

scholarly journals Characterization of Refractive Errors in a Population of Children from 2 to 14 Years of Age in Bogotá, Colombia*

2018 ◽  
Vol 59 (1) ◽  
Author(s):  
Isabella Lince-Rivera ◽  
Gabriel Eduardo Camacho Flórez ◽  
Alexa Kunzel Gallo
Keyword(s):  
Visual Acuity ◽  
Cross Sectional Study ◽  
Population Characteristics ◽  
Ocular Motility ◽  
Refractive Errors ◽  
Sectional Study ◽  
Cross Sectional ◽  
The City

<p><strong>Introduction</strong>: Refractive errors can have important repercussions in the performance of an individual, especially in the pediatric community. <strong>Objective</strong>: To determine the prevalence of refractive errors within a sample of 112 children between the ages of 2 and 14 from the Colegio La Candelaria in the city of Bogotá. <strong>Methods</strong>: Cross-sectional study that evaluated through visual acuity, ocular motility, ophthalmoscopy, retinoscopy, and subjective exam, the visual capacity of the children in question. <strong>Results</strong>: We found a prevalence of refractive errors of 18.8% where 13.4% represented astigmatism, 3.6% hypermetropia and 1.8% myopia. <strong>Discussion</strong>: These results were compared with those exposed on a thesis performed in 1973 by which patients with similar conditions were tested. In this study, the refractive errors were of 30.48%, a difference that can be explained by variations in population characteristics. Lastly, it arises the need of screening in other communities.</p>

Microstructural characterization of CoPtCr/Cr thin film disks by cross-section TEM and elongated probe micro-diffraction

1991 ◽  
Vol 49 ◽  
pp. 762-763
Author(s):  
M.A. Parker ◽  
K.E. Johnson ◽  
C. Hwang ◽  
A. Bermea
Keyword(s):  
Magnetic Recording ◽  
Electron Probe ◽  
Microstructural Characterization ◽  
Crystallographic Structure ◽  
Recording Media ◽  
Layer By Layer ◽  
Cross Sectional ◽  
New Techniques ◽  
Polished Side

We have reported the dependence of the magnetic and recording properties of CoPtCr recording media on the thickness of the Cr underlayer. It was inferred from XRD data that grain-to-grain epitaxy of the Cr with the CoPtCr was responsible for the interaction observed between these layers. However, no cross-sectional TEM (XTEM) work was performed to confirm this inference. In this paper, we report the application of new techniques for preparing XTEM specimens from actual magnetic recording disks, and for layer-by-layer micro-diffraction with an electron probe elongated parallel to the surface of the deposited structure which elucidate the effect of the crystallographic structure of the Cr on that of the CoPtCr.XTEM specimens were prepared from magnetic recording disks by modifying a technique used to prepare semiconductor specimens. After 3mm disks were prepared per the standard XTEM procedure, these disks were then lapped using a tripod polishing device. A grid with a single 1mmx2mm hole was then glued with M-bond 610 to the polished side of the disk.

TEM characterization of reaction zone in a SiC fiber-reinforced titanium alloy

1988 ◽  
Vol 46 ◽  
pp. 738-739
Author(s):  
G. Das ◽  
R. E. Omlor
Keyword(s):  
Titanium Alloys ◽  
Reaction Zone ◽  
Carbon Layer ◽  
Fiber Reinforced ◽  
Reaction Products ◽  
Sic Fibers ◽  
Sic Fiber ◽  
The Matrix ◽  
Immense Potential

Fiber reinforced titanium alloys hold immense potential for applications in the aerospace industry. However, chemical reaction between the fibers and the titanium alloys at fabrication temperatures leads to the formation of brittle reaction products which limits their development. In the present study, coated SiC fibers have been used to evaluate the effects of surface coating on the reaction zone in the SiC/IMI829 system.IMI829 (Ti-5.5A1-3.5Sn-3.0Zr-0.3Mo-1Nb-0.3Si), a near alpha alloy, in the form of PREP powder (-35 mesh), was used a茸 the matrix. CVD grown AVCO SCS-6 SiC fibers were used as discontinuous reinforcements. These fibers of 142μm diameter contained an overlayer with high Si/C ratio on top of an amorphous carbon layer, the thickness of the coating being ∽ 1μm. SCS-6 fibers, broken into ∽ 2mm lengths, were mixed with IMI829 powder (representing < 0.1vol%) and the mixture was consolidated by HIP'ing at 871°C/0. 28GPa/4h.

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