Influence of Co ion doping on the microstructure, magnetic and dielectric properties of Ni1-xCoxFe2O4 ceramics

Ni1-xCoxFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8) ceramics were prepared by chemical co-precipitation method and the effect of Co ion doping on the microstructure, magnetic and dielectric properties has been investigated. The results show that the synthesized ceramics display only spinel phase of Ni1-xCoxFe2O4, without other apparent impurities found. The lattice of Ni1-xCoxFe2O4 crystal structure was distorted as a result of the incorporation of Co ion, and the lattice parameters increase with the increase of Co ion content. The grain size decreases slightly with increasing the content of Co ion, indicating a change of particle size and morphology at higher doping content. The results of impedance analysis shows that the sample doped with 80 at.% Co possesses the maximal dielectric constant, while the pure NiFe2O4 sample shows the minimal value when the frequency is below 0.1 MHz. The M-H loops of these ceramics exhibit highly magnetic nature and the saturation magnetization. The remnant magnetization increases linearly with the increase of Co-concentration in nickel ferrite while the coercive field (Hc) shows non-monotonic variation with Co content. The minimal and maximal values of Hc can be obtained when the Co concentrations are 40 and 80 at.%, respectively. The highest value of the saturation magnetization is 63 emu/g obtained with 80 at.% Co doping while the lowest value is ∼31 emu/g for the pure NiFe2O4 ceramics. The abnormal magnetic behaviour is due to the A-B super exchange interaction when magnetic Co2+ ions are added

Surface characteristics and corrosion resistance of biodegradable magnesium alloy ZK60 modified by Fe ion implantation and deposition

The ZK60 magnesium alloy has been modified by Fe ion implantation and deposition with a metal vapor vacuum arc plasma source. The surface morphology, phase constituent and elemental distribution are determined by scanning electron microscopy, transmission electron microscopy, X-ray diffractometer and Auger electron spectroscopy. The results show that Fe thin film is deposited on ZK60 alloy and the corresponding thickness increases from 2.73 μm to 6.36 μm with increasing deposition time. A transition layer mainly composed of Mg, Fe and O elements is formed between Fe thin film and ZK60 substrate. The potentiodynamic polarization tests reveal that a high corrosion potential and a low corrosion current density are detected for the Fe deposited ZK60 alloy, indicating the improvement of corrosion resistance. The tensile deformation test indicates that the Fe deposited film on the ZK60 substrate can sustain 1% tensile strain without any cracks

High-performance brazing of single crystal superalloys with Ni-Cr-Ta filler material

High-performance joining especially brazing has been highly expected in the manufacture or maintenance of single crystal blades. In this paper, a Ni-40Cr-10Ta (at.%) alloy was developed as filler material for single crystal superalloys. High-performance brazing of DD5 superalloy was achieved. The joints brazed at 1260 °C contained an isothermal solidification zone (ISZ) with “γ + γ′” structure and an athermal solidification zone (ASZ) composed of γ, γ', γ/γ′-eutectics, TaCr2 and TaC. Unlike the conventional filler materials with melting point depressants of B and Si, the Ni-Cr-Ta filler material was free of B and Si, and thus the resulting joints contained no B-rich and Si-rich compounds and eutectics with low melting points, which enhanced the brazed joint performance. The tensile strength at 980 ℃ of the heat-treated joints reached 654 MPa, which is 88.5 % that of the base metal

Reconstruction of environmental changes using a multi-proxy approach in the Ulleung Basin (Sea of Japan) over the last 48 ka

National Natural Science Foundation of China [40906035, 40710069004]; Youth Foundation of the State Oceanic Administration People's Republic of China [2012301]; Basic Research Science Foundation in the First Institute of Oceanography, State Oceanic Administration [2010G24, 2007T09, 2012G31]Based on elemental geochemical data, we reconstructed the sediment provenance, surface productivity and bottom water redox conditions for the last 48 ka in the Ulleung Basin (Sea of Japan) and inferred the factors controlling them. Al2O3/TiO2 ratio and chemical index of alteration (CIA) suggest that sediment provenance changed during the glacial period (4818 ka) compared to the deglacial (ca. 1811 ka) and Holocene. Mass accumulation rates of total organic carbon (TOC), CaCO3, phosphorus, cadmium and excess barium reveal low paleoproductivity during low sea stand. During 1811 ka, productivity increased due to increasing inflow of nutrient-rich water masses the Oyashio and the East China Sea coastal water in tandem with the rising sea level. Maximum productivity occurred during Younger Dryas and Pre-boreal periods when sea level was at similar to-60?m and then gradually decreased as the Tsushima Warm Current inflow kicked off at ca. 9.3 ka, consistent with other paleoredox proxies, which reveal the presence of anoxic bottom water during ca. 129 ka. With the changes in paleoredox proxies and their ratios (TOC, Mo, U, Mn, C/S ratio and Uauthigenic and Mo contents), we hypothesized that the redox changes were mainly ventilation driven and were superimposed on the influence of circulation-induced productivity changes. The global climate and sea-level changes on a millennial timescale play a major role in enhancing paleoproductivity and restrict bottom water advection, subsequently driving the oxygenation of bottom water in the Ulleung Basin. Copyright (c) 2012 John Wiley & Sons, Ltd

SURFACE MODIFICATION OF PRINTED CARBON NANOTUBES AND ITS APPLICATION OF FIELD EMISSION

A surface-modified carbon nanotubes (CNTs), which shows an excellent electron field emission property was obtained in the present work. Conventional screen-printing technology was applied to prepare the CNT films. After hydrogen plasma surface treating process, the morphology of nanotubes surface were totally changed. Those modified CNTs exhibited low turn-on electron field of 0.98 V/μm, current density of 1 mA/cm2 at a field of 6.53 V/μm and a very high emission site density of about 106/cm2, which is three orders of magnitude higher than that of untreated CNT films. Diode-type prototype devices were obtained which proved the modified CNTs is suitable for field emission displays.Carbon nanotubes, field emission, screen-printing, surface modification

Effect of a Conditional Cash Transfer Program on Nutritional Knowledge and Food Practices among Caregivers of 3–5-Year-Old Left-Behind Children in the Rural Hunan Province

Left-behind children (LBC) are a unique population in China, whose numbers have increased dramatically in recent years. Most caregivers of left-behind children (CLBC) are grandparents who lack knowledge about proper nutrition and food practice, putting LBC at greater risk for malnutrition. A cluster randomized controlled trial was carried to assess the effectiveness of the conditional cash transfer (CCT) program. Forty rural villages from Fenghuang County and Pingjiang County of Hunan province were selected. The villages were randomized into the intervention and control groups. In the intervention group, caregivers received a cash transfer conditional on bimonthly health education attendance, bringing LBC in for vaccinations, and on-time annual health checks. The control group received routine health services only. Two rounds of questionnaire surveys were conducted in March 2015 and July 2016. Questionnaires and in-person interviews were used to assess the changes in nutritional knowledge and food practices among CLBC. Among 447 valid subjects, CLBC in the intervention group were significantly more likely to correctly understand the importance of children’s height and weight measurements, food variety, inclusion of eggs and dairy in the diet, and anemia identification and prevention. Intervention group CLBC were also significantly more likely to prepare dairy products and eggs for their children. Generalized liner mixed model (GLMM) analysis showed that CLBC nutrition knowledge was improved significantly in the intervention group (adjusted p value = 0.01), and there were also positive changes in their food practice (adjusted p value = 0.047). This CCT intervention turned to be effective with respect to rural caregivers’ nutritional knowledge and food practice behavior. The findings from this project could be helpful for future health strategies targeting rural children, in particular the LBC group