scholarly journals Structure analysis and enhancement of creep resistance and thermal properties of eutectic Sn-Ag lead free solder alloy by Ti and Cd - addition

2017 ◽  
pp. 5092-5099
Author(s):  
Amal Mohamed Yassin ◽  
Berlent Abd El Hamed Khalifa ◽  
Reda Afify Ismail
Keyword(s):  
Thermal Properties ◽  
Solder Alloy ◽  
Creep Property ◽  
Axial Ratio ◽  
Tensile Creep ◽  
Creep Tests ◽  
X Ray ◽  
Temperature Range ◽  
Morphological Studies ◽  
Residual Strains

Eutectic (Sn-3.5wt.%Ag) solder alloy is used in electronic circuits in which the creep property of the solder joints is essential for their applications. The study of creep, structure and thermal properties of three solder alloys (Sn-3.5wt.%Ag,Sn-3.5wt.%Ag-0.27wt.%Ti and Sn-3.5wt.Ag-0.27wt.%Cd) is characterized by the presence of (Ag3Sn-IMC) beside the phase (β-Sn). The microstructure parameters obtained from the X-ray analysis represented by, lattice parameters (a, c), the axial ratio (c/a), the residual strains (Δa/a0, Δc/c0) and peak height intensities (hkl) of some crystallographic planes are given. All parameters were found to be sensitive to the additions of (Ti or Cd), applied stresses and working temperatures in the range (298-373K).The crystallite size of the (211) reflection was found to increase from (61-132nm) with the additions and to decrease from (115-79nm) with the working temperatures. The morphological studies show a remarkable decrease in the size of (β-Sn) grains with the addition of (Cd) content which confirms the X-ray data. The obtained results show a decrease in melting temperature with the additions. The creep properties are notably improved by the addition of either (Ti) or (Cd). In order to reveal the creep characteristics such as stress exponent (n) and activation energy (Q), the tensile creep tests were performed within the temperature range (298-373K) at constant applied stress (17.27MPa). Based on the obtained stress exponents and activation energies, it is explained that the dominant deformation mechanism is dislocation climb over all temperature range.  

scholarly journals Influence of Low Ti-Element Additions on The Microstructure, Melting Properties and Creep Behavior of Sn-Ag-Cu Lead Free Solders

2018 ◽  
Vol 14 (3) ◽  
pp. 5835-5850
Author(s):  
Amal Mohamed Yassin ◽  
Reda Ismail Afify ◽  
Berlent Khalifa
Keyword(s):  
Creep Behavior ◽  
Axial Ratio ◽  
Lead Free ◽  
Solder Alloys ◽  
Creep Tests ◽  
Scanning Calorimetry ◽  
Thermal Tests ◽  
X Ray ◽  
Morphological Studies ◽  
Residual Strains

Sn-3.5wt.%Ag-0.5wt.%Cu is one of the alloys considered for replacing SnPb solder alloys in electronic ambiance. In the present study, the effect of minor additions of Ti (0.25, 0.5, 1.0 wt.%) on the microstructure, creep and thermal properties of Sn-3.5wt.%Ag-0.5wt.%Cu lead free solder alloy are investigated by means of scanning electron microscopy (SEM), x-ray diffraction (XRD), creep tests and differential scanning calorimetry (DSC) thermal tests. Results showed that the addition of different wt.% of Ti refined the grain size of the solder alloys. The microstructure parameters obtained from x-ray analysis represented by lattice parameters (a,c), axial ratio (c/a), residual strains (?a/a? & ?c/c?), peak height intensities and crystallite size of some crystallographic planes were found to be sensitive to Ti - additions, applied stresses and working temperatures. The morphological studies using SEM showed refinements of Ag3Sn, Cu6Sn5 and Ti2Sn3 (IMCs) in ?-Sn matrix. Thermal analysis showed that Ti - additions slightly affect melting temperature and pastry range. In terms of creep behavior the addition of 1wt.%Ti gave the highest creep resistance with respect to the others, due to fine dispersion of IMCs. The stress exponents (n) and the activation energies (Q) indicated that the dominant creep mechanism is dislocation climb over all temperature ranges

Mechanical and thermal properties of the glassy semiconductor chlorinated Se0 997As0 003 used as an X-ray imaging material

1989 ◽  
Vol 67 (7) ◽  
pp. 686-693 ◽  
Author(s):  
S. O. Kasap ◽  
S. Yannacopoulos
Keyword(s):  
Thermal Properties ◽  
Structural Changes ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Mechanical And Thermal Properties ◽  
Debye Relaxation ◽  
X Ray ◽  
Temperature Range ◽  
Glass Transformation ◽  
X Ray Imaging

Mechanical and thermal properties of a typical X-ray imaging material amorphous Se0.997As0.003, chlorinated in the ppm range were investigated using thermal microhardness analysis (TμHA) and differential scanning calorimetry (DSC). The experiments were carried out over a temperature range encompassing the glass transformation to study the nature of structural changes controlling the mechanical and thermal properties. It is shown that the mechanical property microhardness when examined on an Itoh–Shishokin plot of log Vickers hardness number (VHN) vs. temperature (T) exhibits a hardness transition temperature, Tg*, in the glass transformation region. The rates of relaxation of the mechanical and thermal properties in the glass transformation region were studied by investigating the heating rate dependence of the glass transition temperatures, Tg* and Tg, defined empirically on the log VHN vs. T behavior and the DSC glass transformation endotherm, respectively. By applying the present thermoanalytical methods, it has proved possible to identify a typical Vogel–Tammann–Fulcher type of behavior in the mechanical and thermal relaxation times that correlates remarkably well with the viscosity–temperature data of M. Cukierman and D. R. Uhlmann (J. Non-Cryst. Solids, 12, 199 (1973)) as well as the dielectric loss experiments of M. Abkowitz, D. F. Pochan, and J. M. Pochan (J. Appl. Phys. 51, 1539 (1980)). The latter had previously exposed a Williams–Landel–Ferry relation for the Debye relaxation times in a-Se and a-Se: 1% As. It is therefore concluded that the behavior of mechanical, thermal, and dielectric properties of a-Se0997As0003 in the glass transformation region is inversely proportional to the viscosity, which in turn can be adequately described over a temperature range above ~30 °C by a Vogel expression.

Microstructure and Tensile Creep Behavior of Mg-Nd-RE-Ca Casting Alloys

2007 ◽  
Vol 345-346 ◽  
pp. 557-560 ◽  
Author(s):  
Joong Hwan Jun ◽  
Bong Koo Park ◽  
Jeong Min Kim ◽  
Ki Tae Kim ◽  
Woon Jae Jung
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Tensile Creep ◽  
Secondary Creep ◽  
Creep Tests ◽  
X Ray ◽  
Casting Alloys ◽  
High Temperature Mechanical Properties ◽  
Ca Addition ◽  
Average Size

Influences of Ca addition on microstructures and mechanical properties at room and elevated temperatures have been investigated for Mg-1.5%Nd-1.0%RE-0.5%Zn-(0~1.0)%Ca casting alloys, on basis of experimental results from X-ray diffractometry (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), tensile and creep tests. Microstructures of the alloys are characterized by dendritic α-(Mg) grains surrounded by Mg12Nd-Zn-(Ca) eutectic network phase. The average size of α grains decreases gradually with an increase in Ca content. At room temperature, yield strength (YS) is enhanced with increasing Ca content with a decrease in ultimate tensile strength (UTS) and elongation to fracture, whereas the Ca addition leads to greater YS and UTS at 175oC. The tensile creep strain and secondary creep rate, measured at 150 and 200oC under 100MPa for 100hrs, become lower with the increase in Ca content. The obtained tensile properties at elevated temperature demonstrate that the addition of Ca plays a role in improving high temperature mechanical properties including creep resistance for the Mg-Nd-RE-Zn-(Ca) alloys. In view of microstructural evolution, this would be attributed to the refined primary α grains and higher thermal stability of the Mg12Nd-Zn-Ca eutectic strengthening phase.

Polygonal profiles of ferritin molecules

1983 ◽  
Vol 41 ◽  
pp. 600-601
Author(s):  
William H. Massover
Keyword(s):  
Axial Ratio ◽  
X Ray Diffraction ◽  
Rhombic Dodecahedron ◽  
Apparent Contradiction ◽  
Iron Storage ◽  
X Ray ◽  
Hexagonal Shape ◽  
Axes Of Symmetry ◽  
Apparent Conflict ◽  
Iron Storage Protein

The molecular structure of the iron-storage protein, ferritin, is becoming known in ever finer detail. The 24 apoferritin subunits (MW ca. 20,000) have a 2:1 axial ratio and are polymerized with 4:3:2 symmetry to form an outer shell surrounding a variable amount of microcrystalline iron, Recent x-ray diffraction results indicate that the projected outline of the native molecule has a quasi-hexagonal shape when viewed down the 3-fold axes of symmetry, and a quasi-square shape when looking down the 4-fold axes. To date, no electron microscope study has reported observing anything other than circular profiles, which would indicate that ferritin is strictly spherical. The apparent conflict between the "hollow sphere" of electron microscopy (E.M.) and the "truncated rhombic dodecahedron" of x-ray diffraction could reflect the poorer effective resolution of E.M. coming from radiation damage, staining, drying, etc. The present study investigates the detailed shape of individual ferritin molecules in order to search for the predicted aspherical profiles and to interpret the nature of this apparent contradiction.

Photoluminescence Enhancement of CdS Nanocrystals Fabricated on Dithiocarbamate Functionalized PET Substrates

2012 ◽  
Vol 512-515 ◽  
pp. 1511-1515
Author(s):  
Chun Lin Zhao ◽  
Li Xing ◽  
Xiao Hong Liang ◽  
Jun Hui Xiang ◽  
Fu Shi Zhang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Hexagonal Structure ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
Visible Absorption ◽  
X Ray ◽  
Cds Nanocrystals ◽  
Morphological Studies ◽  
Transmission Electron

Cadmium sulfide (CdS) nanocrystals (NCs) were self-assembled and in-situ immobilized on the dithiocarbamate (DTCs)-functionalized polyethylene glycol terephthalate (PET) substrates between the organic (carbon disulfide diffused in n-hexane) –aqueous (ethylenediamine and Cd2+ dissolved in water) interface at room temperature. Powder X-ray diffraction measurement revealed the hexagonal structure of CdS nanocrystals. Morphological studies performed by scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) showed the island-like structure of CdS nanocrystals on PET substrates, as well as energy-dispersive X-ray spectroscopy (EDS) confirmed the stoichiometries of CdS nanocrystals. The optical properties of DTCs modified CdS nanocrystals were thoroughly investigated by ultraviolet-visible absorption spectroscopy (UV-vis) and fluorescence spectroscopy. The as-prepared DTCs present intrinsic hydrophobicity and strong affinity for CdS nanocrystals.

scholarly journals Y3+ substituted Sr-hexaferrites: sol-gel synthesis, structural, magnetic and electrical characterization

Cerâmica ◽  
2019 ◽  
Vol 65 (374) ◽  
pp. 274-281 ◽  
Author(s):  
S. S. Satpute ◽  
S. R. Wadgane ◽  
S. R. Kadam ◽  
D. R. Mane ◽  
R. H. Kadam
Keyword(s):  
Electron Microscopy ◽  
Sol Gel ◽  
Electrical Characterization ◽  
Combustion Method ◽  
Hexagonal Structure ◽  
Strontium Hexaferrite ◽  
X Ray Diffraction ◽  
X Ray ◽  
Morphological Studies ◽  
Auto Combustion

Abstract Y3+ substituted strontium hexaferrites having chemical composition SrYxFe12-xO19 (x= 0.0, 0.5, 1.0, 1.5) were successfully synthesized by sol-gel auto-combustion method. The structural and morphological studies of prepared samples were investigated by using X-ray diffraction technique, energy dispersive X-ray spectroscopy, field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy. The X-ray diffraction pattern confirmed the single-phase hexagonal structure of yttrium substituted strontium ferrite and the lattice parameters a and c increased with the substitution of Y3+ ions. The crystallite size also varied with x content from 60 to 80 nm. The morphology was studied by FE-SEM, and the grain size of nanoparticles ranged from 44 to 130 nm. The magnetic properties were investigated by using vibrating sample magnetometer. The value of saturation magnetization decreased from 49.60 to 35.40 emu/g. The dielectric constant decreased non-linearly whereas the electrical dc resistivity increased with the yttrium concentration in strontium hexaferrite.

scholarly journals Inverse Design of Fe-Based Bulk Metallic Glasses Using Machine Learning

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 729
Author(s):  
Junhyub Jeon ◽  
Namhyuk Seo ◽  
Hwi-Jun Kim ◽  
Min-Ha Lee ◽  
Hyun-Kyu Lim ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Metallic Glasses ◽  
Alloy Composition ◽  
Relevant Literature ◽  
Bulk Metallic Glasses ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ann Models ◽  
Wide Scale ◽  
Artificial Neural Network Ann

Fe-based bulk metallic glasses (BMGs) are a unique class of materials that are attracting attention in a wide variety of applications owing to their physical properties. Several studies have investigated and designed the relationships between alloy composition and thermal properties of BMGs using an artificial neural network (ANN). The limitation of the wide-scale use of these models is that the required composition is yet to be found despite numerous case studies. To address this issue, we trained an ANN to design Fe-based BMGs that predict the thermal properties. Models were trained using only the composition of the alloy as input and were created from a database of more than 150 experimental data of Fe-based BMGs from relevant literature. We adopted these ANN models to design BMGs with thermal properties to satisfy the intended purpose using particle swarm optimization. A melt spinner was employed to fabricate the designed alloys. X-ray diffraction and differential thermal analysis tests were used to evaluate the specimens.

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