| 1. |
- Deng, Yin, et al.
(författare)
-
Effects of Zr/(Sc plus Zr) microalloying on dynamic recrystallization, dislocation density and hot workability of Al-Mg alloys during hot compression deformation
- 2023
-
Ingår i: Transactions of Nonferrous Metals Society of China. - : ELSEVIER. - 1003-6326 .- 2210-3384. ; 33:3, s. 668-682
-
Tidskriftsartikel (refereegranskat)abstract
- The deformation behavior and microstructure characteristics of Al-6.00Mg, Al-6.00Mg-0.10Zr and Al-6.00Mg-0.25Sc-0.10Zr (wt.%) alloys were investigated by hot compression tests and electron microscopy methods. The results show that after deforming under the maximum processing efficiency condition (673 K, 0.01 s-1), dislocation densities of Al-6.00Mg, Al-6.00Mg-0.10Zr and Al-6.00Mg-0.25Sc-0.10Zr alloys are 2.68x1016, 8.93x1016 and 6.1x1017 m-2, respectively. Their dynamic recrystallization fractions are 19.8%, 15.0% and 12.7%, respectively. Kernel average misorientation (KAM) analyses indicate that dislocation accumulation near grain boundaries is enhanced by adding Zr or Sc+Zr. Besides, the established hot processing maps, based on the dynamic material model (DMM), reveal that the addition of Zr or Sc+Zr can reduce the range of low-temperature unstable domain but expand the unstable domain at high temperatures and high strains. The experimental results further verify that under the testing deformation condition, only the Al-6.00Mg-0.25Sc-0.10Zr alloy cracks at 773 K and 1 s-1.
|
|
| 2. |
- Zhu, Xin-wen, et al.
(författare)
-
Effects of Al3(Sc1-xZrx) nano-particles on microstructure and mechanical properties of friction-stir-welded Al-Mg-Mn alloys
- 2023
-
Ingår i: Transactions of Nonferrous Metals Society of China. - : Elsevier. - 1003-6326 .- 2210-3384. ; 33:1, s. 25-35
-
Tidskriftsartikel (refereegranskat)abstract
- Microstructure and mechanical properties of friction-stir-welded Al-5.50Mg-0.45Mn and Al-5.50Mg- 0.45Mn-0.25Sc-0.10Zr (wt.%) alloys were investigated by tensile tests and microscopy methods. The results show that the yield strength, ultimate tensile strength and elongation of the Al-Mg-Mn joint are (191 +/- 3) MPa, (315 +/- 1) MPa and (4.8 +/- 1.9)%, respectively. The corresponding values of the Al-Mg-Mn-Sc-Zr joint are (288 +/- 5) MPa, (391 +/- 2) MPa and (3.4 +/- 1.0)%. The Al-Mg-Mn-Sc-Zr joint has smaller grain size, lower average misorientation angle and higher low-angle grain boundary fraction than the Al-Mg-Mn joint. Both the two joints fracture at the weld nugget zone (WNZ), and Al3(Sc1-xZrx) nano-particles with a mean size of (9.92 +/- 2.69) nm still remain in this "weakest zone". Theoretical calculation indicates that nano-particles can provide Orowan and grain boundary strengthening in WNZ, increasing the yield strength of the Al-Mg-Mn joint by 97 MPa.
|
|
| 3. |
- Yao, Huadong, 1982, et al.
(författare)
-
Computation of Turbulence-Generated Noise by Large-Eddy Simulation
- 2009
-
Ingår i: New Trends in Fluid Mechanics Research Proceedings of the Fifth International Conference on Fluid Mechanics. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 9783540759959 ; , s. 83-86
-
Konferensbidrag (refereegranskat)abstract
- The hybrid method of large eddy simulation (LES) and the Lighthill analogy is being developed to compute the sound radiated from turbulent flows. The results obtained from the hybrid method are often contaminated by the absence of small scales in LES, since the energy level of sound is much smaller than that of turbulent flows. Previous researches investigate the effects of subgrid sacle (SGS) eddies on the frequency spectra of sound radiated by isotropic turbulence and suggest an SGS noise model to represent the SGS contributions to the frequency spectra. Their investigations are conducted in physical space and are unavoidably influenced by boundary conditions. In this paper, we propose to perform such calculations in Fourier space so that the effects of boundary conditions can be correctly treated. Posteriori tests are carried out to investigate the SGS contribution to the sound. The results obtained recover the -7/2 law within certain wave-number ranges, but under-estimate the amplitudes of the frequency spectra. The reason for the underestimation is also discussed.
|
|
| 4. |
- Yang, Xin, et al.
(författare)
-
Tribo-corrosion resistance of Ti-Nb-Cr-Mo-Al refractory high-entropy alloys in molten aluminum
- 2023
-
Ingår i: Corrosion Science. - 0010-938X. ; 224
-
Tidskriftsartikel (refereegranskat)abstract
- Ti40Nb25Cr15Mo10Al10 and Ti40Nb20Cr20Mo10Al10 refractory high-entropy alloys (RHEAs) were designed and fabricated, aiming at investigating their mechanical properties, corrosion and tribo-corrosion behavior in molten aluminum. Compared with H13 steel, these RHEAs exhibit significantly better combinations of high-temperature mechanical properties, corrosion and tribo-corrosion resistance. Low solubility of constituent elements in molten aluminum along with slow diffusion of Al atoms in RHEAs’ matrices, are responsible for the outstanding corrosion resistance of RHEAs. Exceptional tribo-corrosion resistance of RHEAs derives from their outstanding combinations of corrosion resistance and high-temperature mechanical properties. Additionally, higher content of Cr in RHEAs would lead to worse tribo-corrosion resistance.
|
|
| 5. |
- Kapilashrami, Mukes, et al.
(författare)
-
Understanding the magnetic interaction between intrinsic defects and impurity ions in room-temperature ferromagnetic Mg1-xFexO thin films
- 2016
-
Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 28:15
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the nature and characteristics of the intrinsic defects and impurities in the dielectric barrier separating the ferromagnetic electrodes in a magnetic tunneling junction is of great importance for understanding the often observed 'barrier-breakdown' therein. In this connection, we present herein systematic experimental (SQUID and synchrotron-radiation-based x-ray absorption spectroscopy) and computational studies on the electronic and magnetic properties of Mg1-xFexO thin films. Our studies reveal: (i) defect aggregates comprised of basic and trimer units (Fe impurity coupled to 1 or 2 Mg vacancies) and (ii) existence of two competing magnetic orders, defect- and dopant-induced, with spin densities aligning anti-parallel if the trimer is present in the oxide matrix. These findings open up new avenues for designing tunneling barriers with high endurance and tunneling effect upon tuning the concentration/distribution of the two magnetic orders.
|
|
| 6. |
- Liang, Yusen, et al.
(författare)
-
Migrating photon avalanche in different emitters at the nanoscale enables 46th-order optical nonlinearity
- 2022
-
Ingår i: Nature Nanotechnology. - : Springer Nature. - 1748-3387 .- 1748-3395. ; 17:5, s. 524-530
-
Tidskriftsartikel (refereegranskat)abstract
- A photon avalanche (PA) effect that occurs in lanthanide-doped solids gives rise to a giant nonlinear response in the luminescence intensity to the excitation light intensity. As a result, much weaker lasers are needed to evoke such PAs than for other nonlinear optical processes. Photon avalanches are mostly restricted to bulk materials and conventionally rely on sophisticated excitation schemes, specific for each individual system. Here we show a universal strategy, based on a migrating photon avalanche (MPA) mechanism, to generate huge optical nonlinearities from various lanthanide emitters located in multilayer core/shell nanostructrues. The core of the MPA nanoparticle, composed of Yb3+ and Pr3+ ions, activates avalanche looping cycles, where PAs are synchronously achieved for both Yb3+ and Pr3+ ions under 852 nm laser excitation. These nanocrystals exhibit a 26th-order nonlinearity and a clear pumping threshold of 60 kW cm−2. In addition, we demonstrate that the avalanching Yb3+ ions can migrate their optical nonlinear response to other emitters (for example, Ho3+ and Tm3+) located in the outer shell layer, resulting in an even higher-order nonlinearity (up to the 46th for Tm3+) due to further cascading multiplicative effects. Our strategy therefore provides a facile route to achieve giant optical nonlinearity in different emitters. Finally, we also demonstrate applicability of MPA emitters to bioimaging, achieving a lateral resolution of ~62 nm using one low-power 852 nm continuous-wave laser beam.
|
|
| 7. |
- Zhang, Xiaoyu, et al.
(författare)
-
Effect of thiophene in bithiazole-bridged sensitizers on the performance of dye-sensitized solar cells
- 2014
-
Ingår i: Nano. - 1793-2920. ; 9:5, s. 1440009-
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we have designed and synthesized four bithiazole-bridged sensitizers (BT-T2, TBT-T2, BT-T3 and TBT-T3) with triphenylamine and indoline as the donor segment and applied them to dye-sensitized solar cells (DSSCs). For triphenylamine-based sensitizers as BT-T2 and TBT-T2, adding one thiophene unit between triphenylamine donor and bithiazole moiety not only led to bathochromic shift of the maximum absorption and increase of molar extinction coefficient, but also enhanced the photovoltaic conversion efficiency from 7.12% of BT-T2 to 7.51% of TBT-T2. But for indoline-based sensitizers as BT-T3 and TBT-T3, adding one thiophene unit between indoline donor and bithiazole moiety resulted in hypochromatic shift instead of bathochromic shift. We employed the density functional theory (DFT) calculations to further investigate the influence of the thiophene unit on their optical and electronic properties and photovoltaic performance of corresponding DSSC devices. Given the results, a reasonable explanation is the introduction of thiophene unit suppressed the intramolecular charge transfer and charge separation in the conjugation system of indoline-based sensitizer, which led to the hypochromatic shift of the maximum absorption wavelength and finally the low J(sc). Since the J(sc) dropped sharply from 15.26mAcm(-2) to 4.52mAcm(-2), the photovoltaic conversion efficiency decreased dramatically from 7.86% to 1.93%.
|
|
| 8. |
- Fan, Qunping, 1989, et al.
(författare)
-
A Non-Conjugated Polymer Acceptor for Efficient and Thermally Stable All-Polymer Solar Cells
- 2020
-
Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 59:45, s. 19835-19840
-
Tidskriftsartikel (refereegranskat)abstract
- A non-conjugated polymer acceptor PF1-TS4 was firstly synthesized by embedding a thioalkyl segment in the mainchain, which shows excellent photophysical properties on par with a fully conjugated polymer, with a low optical band gap of 1.58 eV and a high absorption coefficient >105 cm−1, a high LUMO level of −3.89 eV, and suitable crystallinity. Matched with the polymer donor PM6, the PF1-TS4-based all-PSC achieved a power conversion efficiency (PCE) of 8.63 %, which is ≈45 % higher than that of a device based on the small molecule acceptor counterpart IDIC16. Moreover, the PF1-TS4-based all-PSC has good thermal stability with ≈70 % of its initial PCE retained after being stored at 85 °C for 180 h, while the IDIC16-based device only retained ≈50 % of its initial PCE when stored at 85 °C for only 18 h. Our work provides a new strategy to develop efficient polymer acceptor materials by linkage of conjugated units with non-conjugated thioalkyl segments.
|
|
| 9. |
- Guo, Xin, et al.
(författare)
-
Machinability study on dry machining of white cast iron by polycrystalline cubic boron nitride inserts
- 2022
-
Ingår i: Machining Science and Technology. - : Informa UK Limited. - 1091-0344 .- 1532-2483. ; 26:2, s. 137-159
-
Tidskriftsartikel (refereegranskat)abstract
- The polycrystalline cubic boron nitride (PCBN) insert has been widely used in machining high chromium white cast iron (HCCI), which has the high hardness and abrasiveness. The aim of this article is to reveal that micro-mechanical properties play an essential role in assessing the machinability of high chromium cast iron. Grid nanoindentation is applied to measure the micro-hardness distribution. Based on grid nanoindentation results, the micro-hardness distribution is proposed to study the machinability. After the machining test of HCCI by the PCBN insert, the cutting force, tool wear, surface roughness, and chip formation showed that the micro-hardness distribution of materials has the better results than macro-hardness in machinability evaluation, and abrasive wear occurred on the rake and flank face of the cutting tool. The abrasiveness index that is related with the micro-hardness distribution and the abrasive wear effect in machining, for the most of high abrasion materials, has the possible to evaluate the dynamic cutting process and tool life in dry machining by using the PCBN insert. The micro-hardness distribution imported into the machinability model may propose a new way to improve the data exchange capability in the modern manufacturing process.
|
|
| 10. |
- Guo, Yu, et al.
(författare)
-
Localization of prostate cancer based on fuzzy fusion of multispectral MRI
- 2013
-
Ingår i: IFMBE Proceedings. - Berlin, Heidelberg : Springer. - 9783642293047 ; , s. 1844-1846
-
Konferensbidrag (refereegranskat)abstract
- Accurate prostate cancer localization with noninvasive imaging can be used to guide biopsy, radiotherapy and surgery as well as to monitor disease progression [1]. Published studies have shown multispectral magnetic resonance imaging (MRI), i.e., a combination of multiple types of MR images, as a promising noninvasive imaging technique for the localization of prostate cancer.
|
|
