Effect of interstitial carbon on the evolution of early-stage irradiation damage in equi-atomic FeMnNiCoCr high-entropy alloys

Owing to their excellent radiation tolerance, some of the high-entropy alloys (HEAs) are considered as potential candidates for structural materials in extreme conditions. In order to shed light on the early-stage irradiation damage in HEAs, we performed positron annihilation spectroscopy on hydrogen implanted equiatomic FeMnNiCoCr and interstitial carbon-containing FeMnNiCoCr HEAs. We reveal primary damage as monovacancies in low dose irradiated HEAs. The enhancement of Frenkel pair recombination by C addition is observed in C-containing HEAs. In addition, the C interstitials suppress the vacancy cluster formation in high dose irradiated HEAs.Peer reviewe

Irradiation Damage Independent Deuterium Retention in WMoTaNbV

High entropy alloys are a promising new class of metal alloys with outstanding radiation resistance and thermal stability. The interaction with hydrogen might, however, have desired (H storage) or undesired effects, such as hydrogen-induced embrittlement or tritium retention in the fusion reactor wall. High entropy alloy WMoTaNbV and bulk W samples were used to study the quantity of irradiation-induced trapping sites and properties of D retention by employing thermal desorption spectrometry, secondary ion mass spectrometry, and elastic recoil detection analysis. The D implantation was not found to create additional hydrogen traps in WMoTaNbV as it does in W, while 90 at% of implanted D is retained in WMoTaNbV, in contrast to 35 at% in W. Implantation created damage predicted by SRIM is 0.24 dpa in WMoTaNbV, calculated with a density of 6.044×1022 atoms/cm3. The depth of the maximum damage was 90 nm. An effective trapping energy for D in WMoTaNbV was found to be about 1.7 eV, and the D emission temperature was close to 700 °C

An Energy Balanced and Lifetime Extended Routing Protocol for Underwater Sensor Networks

Energy limitation is an adverse problem in designing routing protocols for underwater sensor networks (UWSNs). To prolong the network lifetime with limited battery power, an energy balanced and efficient routing protocol, called energy balanced and lifetime extended routing protocol (EBLE), is proposed in this paper. The proposed EBLE not only balances traffic loads according to the residual energy, but also optimizes data transmissions by selecting low-cost paths. Two phases are operated in the EBLE data transmission process: (1) candidate forwarding set selection phase and (2) data transmission phase. In candidate forwarding set selection phase, nodes update candidate forwarding nodes by broadcasting the position and residual energy level information. The cost value of available nodes is calculated and stored in each sensor node. Then in data transmission phase, high residual energy and relatively low-cost paths are selected based on the cost function and residual energy level information. We also introduce detailed analysis of optimal energy consumption in UWSNs. Numerical simulation results on a variety of node distributions and data load distributions prove that EBLE outperforms other routing protocols (BTM, BEAR and direct transmission) in terms of network lifetime and energy efficiency

Enhancement of vacancy diffusion by C and N interstitials in the equiatomic FeMnNiCoCr high entropy alloy

We present evidence of homogenization of atomic diffusion properties caused by C and N interstitials in an equiatomic single-phase high entropy alloy (FeMnNiCoCr). This phenomenon is manifested by an unexpected interstitial-induced reduction and narrowing of the directly experimentally determined migration barrier distribution of mono-vacancy defects introduced by particle irradiation. Our observation by positron annihilation spectroscopy is explained by state-of-the-art theoretical calculations that predict preferential localization of C/N interstitials in regions rich in Mn and Cr, leading to a narrowing and reduction of the mono-vacancy size distribution in the random alloy. This phenomenon is likely to have a significant impact on the mechanical behavior under irradiation, as the local variations in elemental motion have a profound effect on the solute strengthening in high entropy alloys. (C) 2021 The Authors. Published by Elsevier Ltd on behalf of Acta Materialia Inc.Peer reviewe

Hydrogen Effects in Equiatomic CrFeNiMn Alloy Fabricated by Laser Powder Bed Fusion

This study investigates the effects of laser powder bed fusion (LPBF) on the hydrogen uptake of the face-centered cubic (FCC) equiatomic CrFeNiMn multicomponent alloy after cathodic hydrogen charging (HC). Hydrogen desorption was evaluated using thermal desorption spectroscopy (TDS), and microstructural changes after the TDS test were examined. Results reveal that the amount of hydrogen absorbed by LPBF CrFeNiMn alloy was significantly higher than that in pulsed electric current sintered (PECS) CrFeNiMn alloy or in conventional 316L austenitic stainless steel. The observations are ascribed to the differences in the amount of hydrogen absorbed by the multicomponent lattice, dislocation densities, width of segregation range at cell walls created by the rapid cooling in LBPF, and vacancies remaining after cooling to room temperature. A hydrogen-charged LBPF transmission electron microscope (TEM) specimen was also characterized. Stacking faults and cracks along the (111)-planes of austenite were observed. Scanning electron microscopy (SEM) of the surface of the TDS-tested samples also indicated hydrogen-induced cracks and hydrogen-induced submicron pits at the grain boundary inclusions

The influence of rhenium addition on the distribution of vacancy-type defects in tungsten

To investigate the influence of transmutation rhenium on the irradiation-induced defects in tungsten, H+ and He+ irradiation of 50 keV with a fixed fluence of 1 x 10(16) atoms cm(-2) were conducted on WxRe (x =0, 3, 5 and 25 wt.%) alloys, respectively. Doppler Broadening Spectroscopy and Coincidence Doppler Broadening Spectroscopy both based on slow positron beam were employed in the current work to characterize the depth distribution and the chemical surroundings of the irradiation-induced defects. The results showed that under 723K irradiation, Re addition suppressed the accumulation of vacancy-type defects compared with pure W. This suppression was enhanced by increasing Re content in W. An obvious Re-related peak from (7-28) x 10(-3) m(0)c was observed in CDB spectra of well-annealed W-Re alloys. The irradiation effect led to the height deviation of Re-related peak. The decrease of the Re-related peak could be attributed to the formation of irradiation-induced defects in irradiated samples, and the reduction of positron annihilation fraction with core electrons of Re. (C) 2021 Elsevier B.V. All rights reserved.Peer reviewe

Clinical Study for Safety Evaluation of GXN Tablets Combined with Aspirin in Long-Term Treatment of Coronary Heart Disease

Background. GXN tablets are composed of Danshen and Chuanxiong, with the functions of activating blood circulation, removing blood stasis, invigorating the pulse, and nourishing the heart, which are used for CHD patients with stable exertional angina Grade I or II (according to traditional Chinese medicine, it is a syndrome of heart and blood stasis with chest pain and dark purple lips and tongue). Clinical trials have shown satisfactory effects on coronary heart disease (CHD). 90.6% of Chinese patients with CHD use both Western medicine and Chinese medicine with the latter being thought to promote blood circulation and remove blood stasis. Some researchers doubt that the combination of Chinese medicine increases the risk of bleeding. The main objective of this study is to observe the safety of long-term use of Guanxinning (hereafter referred to as GXN) tablets combined with aspirin. Methods. The study population is patients with CHD after percutaneous coronary intervention (PCI). Randomization was performed for patients with stable CHD who received dual antiplatelet therapy (DAPT) with aspirin plus clopidogrel or ticagrelor for more than 12 months and then switched to the treatment with aspirin alone for 1 month. This study includes a total of 3,595 subjects in 63 hospitals. The experimental group took aspirin orally (100 mg, 1 time/day) + GXN tablets (0–6 months: 4 tablets/time, 3 times/day; 7–12 months, 4 tablets/time, 2 times/day), and the control group received oral aspirin (100 mg, 1 time/day). Major observation indicators are the incidence of bleeding events, adverse events (AEs), and adverse reactions. The primary endpoint indicators are the incidence of major adverse cardiovascular and cerebrovascular events (MACCE) and the MACCE composite endpoint. Results. A total of 31 cases of symptomatic bleeding were found in the two groups, including 21 cases (0.98%) in the experimental group and 10 cases (0.86%) in the control group; the difference between the two groups was not statistically significant. There were 29 cases (1.35%) of bleeding not reaching BARC type 1 in the experimental group. No attention was paid to the laboratory indicators in the control group during the trial process, so the bleeding as a laboratory indicator between the two groups was not comparable. For BARC type 3–5 bleeding events, there were 3 cases in the experimental group (0.139%) and 2 cases in the control group (0.172%); the difference between the two groups was not statistically significant and not clinically significant. During the trial period, there were a total of 255 cases of adverse reactions in 208 subjects with an incidence of 6.57% (141/2146) in the experimental group and 5.77% (67/1161) in the control group, and the P value was 0.5021; the difference between the two groups was not statistically significant. According to the analysis, the adverse reactions with a statistically significant difference between the two groups were gastrointestinal diseases, with the incidence in the experimental group being higher than that in the control group, and the main manifestations were gastrointestinal symptoms. There was no statistical difference in other types of adverse reactions between the two groups. In the trial period, there were 10 cases of serious adverse reactions, including 5 cases in the experimental group (5/2146, 0.23%) and 5 cases in the control group (5/ 1161, 0.43%), the P value was 0.3351; the difference in the incidence between the two groups was not statistically significant. Conclusion. For CHD patients with heart-blood stasis syndrome, the combination of aspirin and GXN tablets in the experimental group did not increase the incidence of bleeding events, nor did it increase the risk of bleeding of types 3–5 defined by BARC. Except for the increase in gastrointestinal symptoms, there was no increase in other adverse reactions in the experimental group. This trial is registered with Registration no. ChiCTR-IIR-17010688