43 research outputs found
Developing a friction-stir welding window for joining the dissimilar aluminum alloys AA6351 and AA5083
Abstract: In this study a welding window was constructed for the relatively new welding process of friction-stir welding (FSW) to join the 6-mm-thick dissimilar aluminium alloys AA5083-H111 and AA6351-T6. The dissimilar joints were fabricated using different combinations of tool rotational speeds and welding speeds. The effect of the process parameters on the macrostructure of the joints was analysed and reported. Established along with the macrostructural analysis, a welding window was made. These windows will act as reference maps for selecting the appropriate FSW process parameters to produce defect-free welds of dissimilar aluminium alloys
Studies on thermal hysteresis of KNO3 by thermo-Raman spectroscopy
[[abstract]]In this work, the polymorphic phase transformations of KNO3were studied by thermo-Raman spectroscopy in a dynamical thermal process with a heating rate of 5°C min−1 from 30°C to 170°C and then cooling down to 30°C at the same rate. Three distinct phase transformations were detected. The characteristic spectrum for each phase was identified. The nature of each phase transformation was investigated in detail through the studies on spectral variation, intensity, intensity variation and shift in band position. In addition, the intensity variation of the ν1 mode at 1042 cm−1 clearly revealed thermal hysteresis involved in the phase transformation of KNO3. Furthermore, the thermal hysteresis of each phase was also obtained from the ν3 mode in the range from 1341 to 1354 cm−1
Influence of distillation on performance, emission, and combustion of a DI diesel engine, using tyre pyrolysis oil diesel blends
Fast lithium ion conduction in garnet-type Li<sub>7</sub>La <sub>3</sub>Zr<sub>2</sub>O<sub>12</sub>
(Figure Presented) Low activation energy and fast lithium ion conduction have been observed for the new compound Li7La3Zr 2O12. Relative to previously reported lithium garnets, the solid electrolyte shows a larger cubic lattice constant, higher lithium ion concentration, lower degree of chemical interaction between the Li+ ions and the other lattice constituents, and higher densification.</p
Effect of Simultaneous Substitution of Y and Ta on the Stabilization of Cubic Phase, Microstructure, and Li<sup>+</sup> Conductivity of Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> Lithium Garnet
Garnet-type
lithium stuffed oxide Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> (LLZ) in the cubic phase has received significant
attention because of its high Li<sup>+</sup> conductivity at room
temperature and excellent stability against lithium metal anodes.
In addition to the high Li<sup>+</sup> conductivity, the dense microstructure
is also a critical issue for the successful application of LLZ as
a solid electrolyte membrane in all-solid-state lithium and lithium–air
batteries. The stabilization of LLZ in the cubic phase with dopants
indicated a reduction in sintering temperature with La<sup>3+</sup> site doping and improved conductivity by doping the Zr<sup>4+</sup> site. However, there are only a few reports regarding the simultaneous
substitution
on the La<sup>3+</sup> and on the Zr<sup>4+</sup> site in LLZ. In
the present study, systematic investigations have been carried out
on Li<sub>7–<i>x</i></sub>La<sub>3–<i>y</i></sub>Y<sub><i>y</i></sub>Zr<sub>2–<i>x</i></sub>Ta<sub><i>x</i></sub>O<sub>12</sub> (<i>x</i> = 0.4, <i>y =</i> 0, 0.125, 0.25,
and 0.5) to understand the effect of simultaneous substitution of
Y<sup>3+</sup> for La<sup>3+</sup> and Ta<sup>5+</sup> for Zr<sup>4+</sup> in LLZ on the stabilization of the high conductive cubic
phase, microstructure, and Li<sup>+</sup> conduction behavior. Powder
X-ray diffraction (PXRD) revealed the stabilization of a
cubic-like garnet structure for the entire selected compositional
range of Li<sub>7–<i>x</i></sub>La<sub>3–<i>y</i></sub>Y<sub><i>y</i></sub>Zr<sub>2–<i>x</i></sub>Ta<sub><i>x</i></sub>O<sub>12</sub> (<i>x</i> = 0.4, <i>y</i> = 0, 0.125, 0.25,
and 0.5) samples sintered at 750 °C. However, the Raman spectra
revealed that the cubic phase stabilized at around
750 °C for the Li<sub>7–<i>x</i></sub>La<sub>3–<i>y</i></sub>Y<sub><i>y</i></sub>Zr<sub>2–<i>x</i></sub>Ta<sub><i>x</i></sub>O<sub>12</sub> (<i>x</i> = 0.4, <i>y</i> = 0, 0.125,
0.25,
and 0.5) samples is different from the high Li<sup>+</sup> conductive
cubic phase (<i>Ia</i>3̅<i>d</i>), and the
transformation to the high Li<sup>+</sup> conductive cubic phase with
a distorted lithium sublattice (<i>Ia</i>3̅<i>d</i>) is observed only
for the samples sintered at elevated temperature. Preliminary thermogravimetric
(TG), Raman, and Fourier transform infrared (FTIR) studies indicated
that the observed low temperature cubic phase of the investigated
samples sintered at 750 °C might result from insertion of water
vapor
from the humid atmosphere into the crystal lattice and subsequent
replacement of the lithium ions by protons to form O–H bonds.
The AC impedance analysis indicated that the optimal Y substitution
in Li<sub>7–<i>x</i></sub>La<sub>3–<i>y</i></sub>Y<sub><i>y</i></sub>Zr<sub>2–<i>x</i></sub>Ta<sub><i>x</i></sub>O<sub>12</sub> (<i>x</i> = 0.4, <i>y</i> = 0.125 and 0.25)
helps to reduce the grain boundary resistance in a major way and also
helps to reduce the bulk resistance slightly. Among the investigated
compositions, Li<sub>6.6</sub>La<sub>2.75</sub>Y<sub>0.25</sub>Zr<sub>1.6</sub>Ta<sub>0.4</sub>O<sub>12</sub> sintered at 1200 °C
exhibits a maximized room temperature total (bulk + grain boundary)
Li<sup>+</sup> conductivity of 4.36 × 10<sup>–4</sup> S
cm<sup>–1</sup> along with the improved ceramic density