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High-cycle fatigue tests of Pt–Al bond coated and bare single crystal superalloys were conducted at 700 °C and 800 °C, aiming at investigating the effect of bond coat on the high-cycle fatigue properties of a single crystal superalloy. The impact of bond coat was studied merely on the tensile and creep properties of this superalloy, but was not found on the high-cycle fatigue behavior of this alloy. The experimental results showed that the bond coat was found to be beneficial at 800 °C or under low stresses at 700 °C owing to the fact that cracks were retarded by the fine grains in the IDZ, the P-type rafted γ′ phases in the substrate or the coat/substrate interface, respectively. However, the bond coat was detrimental under high stresses at 700 °C owing to the rapid propagation of the early cracking and the brittle nature of bond coat. Moreover, EBSD results showed the all bond coat cracks mainly initiated at the surface of the coated specimens and started from grains with {123} slip system within bond coat. Fatigue tested samples at 800 °C showed a comparatively higher Schmid factor value than that at 700 °C. Following the fatigue test, TEM tests indicated that in the superalloy close to the bond coat, the dislocation networks formed due to the activity of various slip systems at 700 °C; under 450 MPa at 800 °C in this region, a special a0 superdislocation with two segments of compact core was observed in the rafted γ′ phases.

Topic Visual impairment (VI) and cognitive impairment (CIM) are prevalent age-related conditions that impose substantial burden on the society. Findings on the hypothesized bidirectional association of VI and CIM remains equivocal. Hence, we conducted a systematic review and meta-analysis to examine this bidirectional relationship. Clinical Relevance Sixty percent risk of CIM has not been well elucidated in the literature. A bidirectional relationship between VI and CIM may support the development of strategies for early detection and management of risk factors for both conditions in older people. Methods PubMed, Embase, and Cochrane Central registers were searched systematically for observational studies, published from inception until April 6, 2020, in adults 40 years of age or older reporting objectively measured VI and CIM assessment using clinically validated cognitive screening tests or diagnostic evaluation. Meta-analyses on cross-sectional and longitudinal associations between VI and CIM outcomes (any CIM assessed using screening tests and clinically diagnosed dementia) were examined. Random effect models were used to generate pooled odds ratios (ORs) and 95% confidence intervals (CIs). We also examined study quality, publication bias, and heterogeneity. Results Forty studies were included (n = 47 913 570). Meta-analyses confirmed that persons with VI were more likely to have CIM, with significantly higher odds of: (1) any CIM (cross-sectional: OR, 2.38 [95% CI, 1.84–3.07]; longitudinal: OR, 1.66 [95% CI, 1.46–1.89]) and (2) clinically diagnosed dementia (cross-sectional: OR, 2.43 [95% CI, 1.48–4.01]; longitudinal: OR, 2.09 [95% CI, 1.37–3.21]) compared with persons without VI. Significant heterogeneity was explained partially by differences in age, sex, and follow-up duration. Also, some evidence suggested that individuals with CIM, relative to cognitively intact persons, were more likely to have VI, with most articles (8/9 [89%]) reporting significantly positive associations; however, meta-analyses on this association could not be conducted because of insufficient data. Discussion Overall, our work suggests that VI is a risk factor of CIM, although further work is needed to confirm the association of CIM as a risk factor for VI. Strategies for early detection and management of both conditions in older people may minimize individual clinical and public health consequences.

Both surface and internal microstructures of a second-generation Ni-based single crystal (SX) superalloy were studied after creep and rejuvenation heat treatment (RHT). It is indicated that the microstructures, such as the dislocation network, the γ phase and the γ' phase, can be recovered to those after the standard heat treatment (SHT). It is found that RHT affected zone (RAZ) formed at the surface is composed of the γ'-free layer, the transition layer and the recrystallization (RX), which are less than 20 μm in depth totally. Such depth of the RAZ doesn’t affect the properties of the superalloy. The morphology of γ' phase at the RAZ is related to the composition of the elements. The average creep life after RHT is close to the average life after SHT. It is concluded that RHT could effectively repair SX parts and increase the total life of the sample after a damage by creep.

An evaluation was conducted on the impact of a Pt–Al bond coat on the creep behaviours of a second-generation Ni-based single crystal superalloy at 750 °C/820 MPa, 850 °C/630 MPa, 1038 °C/137 MPa and 1100 °C/112 MPa, respectively. As revealed by the creep results, the creep behaviours of the coated superalloy were inferior to those of the bare superalloy to some extent under all testing conditions. The maximum deterioration in the strain-to-fracture and time-to-rupture was observed at 1100 °C/112 MPa (7.3%) and 750 °C/820 MPa (74.7 h), respectively. Following the creep test, deconvolution calculations were performed, which indicated that the creep stress for all core superalloys was as low as approximately 1.7–1.9% of the applied stress while the bond coat stress was 4.0–10.4% that at the minimum creep rate. Moreover, TEM analyses revealed that within the superalloy substrate adjacent to the bond coat, there were fewer stacking faults and an abundance of dislocation debris observed within γ′-Ni3Al at 750 °C/820 MPa. The misfit of the γ/γ′ phase was insignificant and the dislocation networks became irregular at 1100 °C/112 MPa. With an increase in temperature from 750 °C to 1100 °C, the fracture mechanism of both the substrate and bond-coat was found to shift from quasi-cleavage to micro-void coalescence. The quasi-cleavage cracks occurring within the bond coat increased the number of connections with creep cracks to cause spreading from the interior of the samples, thus resulting in premature failure at 750 °C/820 MPa and 850 °C/630 MPa. However, the degradation at 1038 °C/137 MPa and 1100 °C/112 MPa was ascribed to the increasing thickness of the inter-diffusion zone, as well as the volume of the blocky γ′-Ni3Al phase inside the bond coat and topologically close-packed phases in the superalloy near the bond coat.

An investigation was conducted into the influence of applying Pt Al bond-coat on the tensile deformation and fracture behavior of second-generation single crystal superalloy substrate with the temperature ranging between room temperature RT and 1100 °C. In the meantime, the development of a two-layer Pt Al bond-coat, consisting of an outer layer of single-phase β-(Ni,Pt)Al and an inter-diffusion zone of refractory metal precipitates, has also been discussed. As revealed by the results, the application of Pt Al bond-coat contributed to a noticeable deterioration in both yield strength and ultimate tensile strength of the superalloy substrate at elevated temperatures. Nevertheless, the elongation of coated superalloy was shown to be 17.2% (at RT) and 10.4% (at 750 °C) lower and 9.6% (at 1100 °C) higher compared to uncoated samples. Following tensile test, the TEM analyses indicated that there were onsets of various slip systems, the traditional superlattice stacking faults were retarded at intermediate temperature and the dislocation debris could be increased to develop dislocation networks at higher temperature in the region of superalloy near the bond-coat. As the temperature was on the rise, the fracture mechanism of coated superalloy shifted from tearing ridges and dimples to quasi-cleavage and then to micro-void coalescence. While that of Pt Al bond-coat was transformed from brittle to ductile rupture. Within the temperature range from RT up to 750 °C, a combination of long crack lengths and greater crack penetration depths into bond-coat caused more deterioration in the tensile properties of superalloy. When the temperature rose above 750 °C, the application of Pt Al bond-coat improved the ductility of the substrate, as a result of the ductile failure in the bond-coat which hindered the development of through-thickness cracks.

SnS2 is a layered semiconductor with a van der Waals gap separating the covalently bonded layers. In this study, post-synthesis intercalation of donor organic amine molecules, such as ethylenediamine (en), into tin disulfide and secondary intercalation of p-phenylenediamine (PPD) and 1, 5-naphthalenediamine (NDA) into SnS2_en have been verified with X-ray diffraction. PPD and NDA did not intercalate directly even during prolonged annealing but replaced en readily if en was already present in the van der Waals gap. The c-lattice dilation is proportional to the intercalant size. Unit cell lattices of intercalated products were determined from the positions of the X-ray diffraction peaks. Optical images taken during the intercalation showed that intercalation progressed from the periphery towards the interior of the crystal. TEM diffraction patterns in the [0 0 1] direction of SnS2 after intercalation revealed defects and stacking mismatches among the SnS2 layers caused by the intercalation. UV–Vis absorption studies showed a red shift in the band edge of the SnS2 material after intercalation. The band edge was 2.2 eV for pristine SnS2; after intercalation with en or PPD, the absorbance spectra band edges shifted to approximately 0.7 eV or 0.5 eV, respectively.

The feasibility of estimating total solar radiation on a horizontal plane through sunshine hours and other meteorological factors is examined with analyses of data from Singapore. No empirical relationships appear to give consistent estimates over different periods of time. The use of a weather indicator is suggested for improvement of solar radiation estimation. A set of charts are prepared for convenient estimation of radiation on tilted planes.