Increase In Co Concentration Research Articles

The Impact of Exhaust Louvres and Emission Rates on The Effectiveness of Parking Lot Ventilation

Abstract This research investigated a couple of aspects of CO emissions from car vehicles. Firstly, it explored the influence of varying the number of vehicles in operation. Secondly, it analysed the significance of exhaust vents affecting the concentration of CO through parking space lots. The conducted analysis relied on simulation data obtained using ANSYS-Software, as opposed to experimental data. The accuracy of the natural ventilation model was validated. The impact of various running vehicles was examined, including those with half, partially, and fully-loaded. The objective was to determine the correlation between the number of running vehicles and the increase in CO concentration. In addition, several configurations of exhaust vents were examined for the fully loaded scenario. As a result, it was shown that the architectural layout has an impact on the natural ventilation system, which may not be suitable for human health, especially when dealing with greater car emission rates.

Temperature-dependent dielectric and electromechanical properties of co-modified calcium bismuth titanate (CaBi4Ti4O15) ceramics

Bismuth layer-structured ferroelectrics (BLSFs), Aurivillius-type ceramics, are of great interest primarily due to their exceptionally high Curie temperature (Tc), rendering them invaluable in various applications such as sensors, actuators, transducers, and micro-electro-mechanical systems designed for elevated temperature operations, including ferroelectric Random-Access Memory applications. This study delves into the dielectric and electromechanical properties of Cobalt-modified Calcium Bismuth Titanate (CaBi4Ti4O15, CBT) (CBT-xCo, with x = 2, 4, and 6 mol%) prepared using a conventional solid-state route followed by sintering. By incorporation of Co, insignificant structural changes were observed, disclosed by X-ray Diffraction analysis. Scanning Electron Microscope micrographs unveiled highly anisotropic grains. The sintered density measured by Archimedes method was maximum for x = 6 mol% with value of 99.1 %. A temperature-dependent dielectric study disclosed that the Curie temperature of the CBT ceramics improved with the increase in Co concentration. Notably, CBT-4Co exhibited the lowest dielectric loss of 0.0967 at 1 MHz and the highest resistivity value of 0.1975 × 105 (Ω cm) at a temperature of 775 °C. Moreover, the electromechanical coupling (kp) and mechanical quality factor (Qm) measured at elevated temperatures unveiled distinctive properties, asserting the potential of the ceramics for high-temperature piezoelectric applications up to 450 °C. CBT-4Co demonstrated the highest kp, with a negligible variation at high temperature, although Qm declined. Results confirmed that CBT-4Co stands distinguished showcasing high Tc, minimal dielectric loss, and consistent electromechanical properties making it the prime candidate for electromechanical applications spanning the gamut from room temperature to elevated temperatures.

Introduction of Co atoms into CdS thin films for improving photovoltaic properties

This paper represents a systematic work on the fabrication of chemical bath-grown CdS films with and without Co atoms and their photovoltaic performances in hybrid solar cells. Structural properties showed 1% Co-doping promoted crystal quality of CdS films. However, a poor crystal quality was developed above 3% Co concentrations. A reduction in sphere size of CdS samples was observed for 1% Co-doping which was ascribed to slow growth of film. Optical examination demonstrated CdS films with 1% Co-doping displayed the highest transparency of 85% in the visible and near-infrared regions, which were explained by the improvement of crystal quality. A maximum band gap of 2.43 eV was found for 1% Co-doped CdS films, whereas an increase in Co concentration to 7% led to a decline in the band gap of CdS that was attributed to sp-d exchange interaction. Photoluminescence data showed Co-doped CdS films had lower PL peak intensity than that of CdS, demonstrating a decrease in the number of intrinsic defects. Photovoltaic measurements displayed that the best efficiency of 0.488% was achieved for CdS-based device including 1% Co atoms, which were almost a seven-fold boost in overall efficiency compared to bare CdS-based device. The enhancement in power conversion efficiency originated from an increase in short-circuit current density of 1% Co-doped CdS-based photovoltaic cell.

Unraveling the physical and mechanical properties of 4 O modulated martensite in Ni-Co-Mn-Sb magnetic shape memory alloys

Ni-Mn-Sb alloy has attracted much attention due to its low cost and excellent magnetic properties. To enhance the magnetic moment difference of the alloy, the fractional substitution of Co for Ni in Ni-Mn-Sb alloys is an effective strategy. And there is little research on modulated martensite closely related to excellent magnetic properties. Therefore, we systematically investigated the influences of Co-doping on the physical and mechanical properties of four-layered orthorhombic modulated martensite (4 O) in Ni24-xCoxMn18Sb6 (x = 0, 1, 2, 3, 4, 5, 6) alloys by the first principles calculations. Key results demonstrate that the phase stability of 4 O phase decreases with the increase of Co concentration. At the same time, the phase transition temperature from austenite (A) to 4 O phase significantly decreases. The sensitivity of the phase transition temperature from A to 4 O phase to the components is not as high as the phase transition temperature from A to non-modulated martensite (NM) phase. The magnetic moment difference between A and 4 O increases sharply at x = 6. In terms of mechanical properties, Co-doping helps to enhance the mechanical stability and the anisotropy of 4 O phase. The origin of the above phenomena was explained through the density of states. The above results can provide useful information for optimizing the performance of multivariate shape memory alloys.

Association Between Air Pollution and Cardiovascular Disease Hospitalizations in Lanzhou City, 2013-2020: A Time Series Analysis.

Extensive evidence has shown that air pollution increases the risk of cardiovascular disease (CVD) admissions. We aimed to explore the short-term effect of air pollution on CVD admissions in Lanzhou residents and their lag effects. Meteorological data, air pollution data, and a total of 309,561 daily hospitalizations for CVD among urban residents in Lanzhou were collected from 2013 to 2020. Distributed lag non-linear model was used to analyze the relationship between air pollutants and CVD admissions, stratified by gender, age, and season. PM2.5, NO2, and CO have the strongest harmful effects at lag03, while SO2 at lag3. The relative risks of CVD admissions were 1.0013(95% CI: 1.0003, 1.0023), 1.0032(95% CI: 1.0008, 1.0056), and 1.0040(95% CI: 1.0024, 1.0057) when PM2.5, SO2, and NO2 concentrations were increased by 10μg/m³, respectively. Each 1mg/m3 increase in CO concentration was associated with a relative risk of cardiovascular hospitalization of risk was 1.0909(95% CI: 1.0367, 1.1479). We observed a relative risk of 0.9981(95% CI: 0.9972, 0.9991) for each 10μg/m³ increase in O3 for CVD admissions at lag06. We found a significant lag effects of air pollutants on CVD admissions. NO2 and CO pose a greater risk of hospitalization for women, while PM2.5 and SO2 have a greater impact on men. PM2.5, NO2, and CO have a greater impact on CVD admissions in individuals aged <65years, whereas SO2 affects those aged ≥65years. Our research indicates a possible short-term impact of air pollution on CVD. Local public health and environmental policies should take these preliminary findings into account.

Association Between Air Pollution and Coronary Heart Disease Hospitalizations in Lanzhou City, 2013-2020: a Time Series Analysis.

Coronary heart disease (CHD) is one of the most serious public health problems. However, few studies have focused on the effects of exposure to particulate matter and gaseous air pollutants on CHD. This study aimed to explore the relationship between air pollutants and the number of hospitalized patients with CHD in Lanzhou, and we collected daily data on the number of hospitalized patients with CHD, daily air pollutants, and meteorological factors from 2013 to 2020. A distributed lag nonlinear model (DLNM) combined with a quasi-Poisson regression model was applied to evaluate the relationship between air pollutants and the number of hospitalized patients with CHD. The results indicated that the hysteresis effect of all pollutants except O38h reached its maximum at lag3, and the relative risk of coronary heart disease admission was 1.0014 (95%CI: 1.0004, 1.0023), 1.0003 (95%CI: 1.0000, 1.0006), 1.0020 (95%CI: 1.0004, 1.0035), and 1.0053 (95%CI: 1.0026, 1.0080) when PM2.5, PM10, NO2, and SO2 concentrations were increased by 10 μg/m3, respectively. Each 1 mg/m3 increase in CO concentration was associated with a relative risk of coronary heart disease; hospitalization risk was 1.1076 (95%CI: 1.0530, 1.1650). We observed a relative risk of 0.9991 (95%CI: 0.9986, 0.9999) for each 10 μg/m3 increase in O38h for coronary heart disease admission at lag1. Women and elderly were more susceptible to the impact of air pollution, and the impact was greater during cold seasons. Our results indicate that air pollution increased the risk of hospitalization for CHD in a short term. The research findings can provide strategic insights into the impact of current and future air pollution on CHD.

Experimental and theoretical studies on the reactivity and reaction mechanism of LaMnO3 with CO in chemical looping combustion

LaMnO3 perovskite was developed as a promising oxygen carrier in chemical looping combustion due to its abundant oxygen amounts and excellent thermal stability. The reactivity and reaction mechanism of LaMnO3 with CO were systemically studied based on thermogravimetric experiments and density functional theory calculations. The results indicate that LaMnO3 is reduced to Mn3O4 and La2O3 at 707 °C, and finally to MnO. The weight loss of LaMnO3 is 8.67% during the whole reduction process. The reaction rate of LaMnO3 at low temperature can be improved with the increase of CO concentration. The maximal reaction rate of LaMnO3 with CO increases as the heating rate rises. The higher reaction temperature leads to the complete reduction of LaMnO3. Besides, SEM analysis reveals that LaMnO3 has no sintering-agglomeration phenomenon and exhibits good sintering resistance. Density functional theory calculations indicate that the Mn–O bridge sites are the most favorable for CO adsorption on the LaMnO3 surface. The adsorbed CO reacts with a bridging surface lattice O to generate CO2 precursor, revealing the key intermediate for CO oxidation. CO2 precursor will break through the energy barrier of 56.03 kJ/mol to generate free CO2 molecule.

Association between short-term exposure to ambient air pollution and outpatient visits for pulpitis in Hefei, China: a time series study.

Evidence suggests a possible association between ambient air pollutants and oral diseases. Nevertheless, information regarding the relationship between air pollutants and pulpitis is scarce and inconclusive. In view of this, the present study aimed to investigate the relationship between short-term exposure to air pollution and outpatient visits for pulpitis. Daily data on outpatient visits for pulpitis, air pollutants, and meteorological data in Hefei, China, was collected from January 1, 2015 to December 31, 2021. The association between exposure to air pollutants and pulpitis outpatient visits was evaluated using distributed lag non-linear model (DLNM) and a generalized linear model (GLM). Furthermore, stratified analyses were performed by gender, age and season. A total of 93,324 records of outpatient visits for pulpitis were included in this study. The results showed that exposure to NO2, PM2.5, and CO were positively correlated with an increased risk of pulpitis outpatient visits. Each 10 μg/m3 increase in NO2 and PM2.5 concentration, at lag 0-2 day, was associated with a 2.4% (relative risk (RR) = 1.024, 95% confidence interval (CI): 1.014-1.035) and 0.5% (RR = 1.005, 95% CI: 1.000-1.010) increase in pulpitis outpatient visits, respectively. With a 1 mg/m3 increase in CO concentration, the risk of pulpitis outpatient visits increased by 9.1% (RR = 1.091, 95% CI: 1.031-1.154, lag 0-1 day). Intriguingly, exposure to O3 was associated with a decreased risk of pulpitis outpatient visits (RR = 0.990, 95% CI: 0.984-0.995, lag 0-5 day). Subgroup analysis revealed that in the warm season, exposure to PM2.5, O3, and CO was related with a significantly higher outpatient risk of pulpitis than in the cold season. Additionally, the influence of PM2.5 and CO exposure at age < 65 years was significantly stronger than at age ≥ 65 years. In conclusion, exposure to ambient NO2, PM2.5, and CO is associated with an increase in pulpitis outpatient visits in Hefei, China. Conversely, exposure to O3 reduces the risk of outpatient visits for pulpitis. Age and season are effect modifiers of these associations.

Effects of ammonia on combustion of coal in stoichiometric premixed methane–air flames

NH3 has long been considered a promising alternative fuel·NH3 from renewables can be used for energy storage·NH3 is a zero-carbon molecule and can be burned directly and used as a hydrogen carrier. Compared with hydrocarbon fuels, NH3 has several drawbacks, such as an inferior flammability limit, flame temperature, and flame burning velocity, resulting in a lower reactivity rate and the production of pollutants.Therefore, cofiring coal with NH3 is an approach that has been growing in popularity. This study investigated the combustion of coal cofired with NH3 and conducted two-color pyrometry to measure the temperature profiles of coal particles in hybrid flames, that is, methane–coal–air and methane–NH3–coal–air premixed flames. The axial temperature distribution at the center of the flame was measured using two-color pyrometry and a thermocouple. The temperature values obtained were not identical but exhibited similar trends. The results indicated that the temperature at the origin significantly decreased upon ammonia addition, but as the measuring height increased, the final temperatures approached similarity.In addition, the emissions of pollutants such as CO and NOx were also measured. The results indicate that the addition of coal particles without ammonia gas leads to an increase in CO concentration due to the pyrolysis of the pulverized coal. However, there was no significant impact on NOx emissions.In contrast, the addition of coal particles under CH4 − NH3 gas combustion conditions results in a significant decrease in both CO and NOx concentrations. Specifically, under the 80 %CH4 + 20 %NH3 condition and with a coal particle feeding rate increasing from 0 to 0.24 g/min, there was a reduction of approximately 34% in CO concentration and 35% in NOx concentration.In order to confirm the coal consumption rate, coal particles were captured before and after flame sheet using a metal grid, and the particle projected area was determined based on scanning electron microscopy (SEM) images. These results provided evidence that the addition of NH3 to the CH4 − air flame enhances coal combustion, as indicated by a decrease in the particle shrinkage rate and sampling density.

Tuning magnetic properties of FePtCo ternary alloy thin films for magnetic storage device application

FePtCo ternary alloy films have been grown on Si-substrate by co-sputtering of Co with FePt under three conditions i.e., as-deposited, in-situ annealed, and with Cu-underlayer using a DC magnetron sputtering. The film surface roughness, crystal structure, and magnetic properties of these films were investigated. The average surface roughness (Sa and Ra) of these films deposited under three deposition conditions slightly varies in the range of 0.41–2.48 nm with the increase of Co content. The XRD results show that all the films crystallize in a close-packed FCC structure. The lattice parameters and average crystallite size decrease with an increase in Co concentration for all deposited conditions. The magnetic measurement indicates that the as-deposited films exhibit low coercivity and excellent in-plane magnetic anisotropy with a large effective anisotropy energy in the range of 1.22×106−1.88×107 erg/cc. The increase of Co content in as-deposited FePtCo films leads to a reduction in the saturation magnetization (MS) and Keff by promoting antiferromagnetic interaction with FePt sublattice. However, the annealing and insertion of a 2 nm Cu-underlayer further help to enhance the ferromagnetic nature and as a result, the value of MS and Keff is enhanced with an increase of Co content.

Excellent microwave absorption performances of cobalt-doped SrFe12O19 hexaferrite with varying incident angles

The rapid development of electronic technology and wireless communication for electronic equipment is crucial for civilian and military fields nowadays. However, it has been generating electromagnetic (EM) radiation pollution, which has recently gained more attention. Cobalt-doped SrFe12O19 (Co-SrM) samples, which were predicted to be excellent microwave-absorbing materials (MAMs), were successfully prepared using a ball milling method followed by heat treatment. Samples were formed into polygonal shapes with a crystallite size of ∼24 nm and an average grain size of 160−200 nm. The saturation magnetization (Ms) increased with the increase in Co concentration, whereas coercivity (Hc) showed an inverse tendency. The doping also resulted in variations and fluctuations in EM properties, which affected their microwave absorption properties. All Co-SrM-epoxied samples showed good microwave absorption performances in the frequency and thickness ranges of 12−18 GHz (Ku band) and 4−6 mm, respectively. The best value of reflection loss (RL) was −30.7 dB, meaning that ∼99.9% of the incident wave was absorbed. The excellent microwave absorption performance could be attributed to impedance matching, natural resonance, eddy current effects, and dielectric relaxation loss. In both transverse electric and magnetic polarization modes, Co-SrM-epoxied samples maintained (even improved) the RL values with the large incident angle of 0−60° for the Ku band. In addition, Co-SrM-epoxied samples also enhanced the microwave absorption performance in the C and X bands (4 −12 GHz) with an incident angle of 80−89°. These results proved that Co-SrM epoxied samples could be applied as promising MAMs for practical applications.

Study on the Increase of Co Concentration and the Purification of La–Co Cosubstituted M-Type Sr Ferrite by Oxygen Partial Pressure Control

Study on the Increase of Co Concentration and the Purification of La–Co Cosubstituted M-Type Sr Ferrite by Oxygen Partial Pressure Control

Magnetization Dynamics in FexCo1-x in Presence of Chemical Disorder

In this paper, we present a theoretical formulation of magnetization dynamics in disordered binary alloys, based on the Kubo linear response theory, interfaced with a seamless combination of three approaches: density functional-based tight-binding linear muffin-tin orbitals, generalized recursion and augmented space formalism. We applied this method to study the magnetization dynamics in chemically disordered FexCo1−x (x = 0.2, 0.5, 0.8) alloys. We found that the magnon energies decreased with an increase in Co concentration. Significant magnon softening was observed in Fe20Co80 at the Brillouin zone boundary. Magnon–electron scattering increased with increasing Co content, which in turn modified the hybridization between the Fe and Co atoms. This reduced the exchange energy between the atoms and softened down the magnon energy. The lowest magnon lifetime was found in Fe50Co50, where disorder was at a maximum. This clearly indicated that the damping of magnon energies in FexCo1−x was governed by hybridization between Fe and Co, whereas the magnon lifetime was controlled by disorder configuration. Our atomistic spin dynamics simulations show reasonable agreement with our theoretical approach in magnon dispersion for different alloy compositions.

Risk and economic cost of hospitalization due to atrial fibrillation caused by air pollution: a multi-city time series analysis

BackgroundAtrial fibrillation (AF) is the most common arrhythmia, resulting in serious cardiovascular diseases. Air pollution may cause heart rate disturbance, but there is no clear or consistent evidence that short-term exposure to air pollution leads to an increased risk of hospitalisation for symptomatic episodes of AF. This study aimed to assess the impact of short-term exposure to air pollution on inpatient numbers.MethodsThe inpatient records of AF cases in nine cities of the Sichuan Province, China and air pollution and meteorological data from 183 monitoring stations from 2017 to 2018 were collected. The impact of short-term exposure to air pollution on AF inpatients was evaluated using a time-stratified crossover case study design. The economic burden of AF attributable to air pollution was also estimated.ResultsA total of 5,958 patients with AF from 123 medical institutions were included in the analysis. Air pollutants had a significant impact on the number of patients with AF. The number increased by 2.5% (95% confidence interval [CI] = 1.006 to 1.044) and 1.8% (95% CI = 1.003–1.033) for every 10 µg/m3 increase in PM2.5, PM10, concentration, respectively. Moreover, the number increased by 12.7% (95% CI = 1.006 to 1.262) for every 10 µg/m3 increase of SO2 concentration. For every 0.1 μg/m3 increase in CO concentration, the number of inpatients with AF increased by 3.9% (95% CI = 1.010–1.070). People aged 65 years or older and women were more likely to be affected by air pollutants. The AF in 430 and 209 inpatients were attributable to PM2.5 and PM10, respectively. The total hospitalization expenses attributed to excessive exposure to PM2.5 and PM10 were 13.98 million CNY and 6.68 million CNY, respectively. Furthermore, the out-of-pocket expenses were 6.81 million CNY and 3.28 million CNY, respectively.ConclusionsThis study showed a strong correlation between air pollution and AF. Hence, there is a need to reduce air pollution to control health risks.

Effect of cobalt content on point defects and local structure in activated Ca3(VO4)2 single-crystal solid solutions

Doping-induced structural changes of Co-activated calcium orthovanadate Ca3(VO4)2 (CVO) single crystals and specific local behavior of cobalt ions depending on the dopant content are presented in this paper. CVO is activated with over-stoichiometric Co3O4 of different concentration (CVO:xCo; x ​= ​0.1, 0.5, 1.0, 1.5, 2.0 ​wt %) during the Czochralski growth. Single-crystal synchrotron X-ray diffraction study shows gradual increase in the number of Ca crystallographic sites occupied by cobalt ions with increasing dopant concentration: from Ca3 site for CVO:0.1Co to additionally Ca2 and Ca4 sites for CVO:0.5–1.5Co, and also to Ca1 site for CVO:2.0Co. Vacancies in the tetrahedral vanadium V2 site are detected for all samples, and those in the tetrahedral V1 site are additionally found for CVO:2.0Co. Disordering of O1, O4, O7 oxygen sites is observed in all structures. Combined results of X-ray diffraction analysis and X-ray absorption spectroscopy showed that the formal charge of Co ions is mixed between 2+ and 3+ with the prevalence of 2+. A trend towards a decrease in formal charge with an increase in Co concentration is observed. The coordination number of Co(2+δ)+ ions is found to be 4.6 and polyhedron is intermediate between tetrahedral and octahedral.

Ambient Air Pollution and Acute Ischemic Stroke-Effect Modification by Atrial Fibrillation.

Acute ischemic strokes (AIS) are closely linked with air pollution, and there is some evidence that traditional cardiovascular risk factors may alter the relationship between air pollution and strokes. We investigated the effect of atrial fibrillation (AF) on the association of AIS with air pollutants. This was a nationwide, population-based, case-only study that included all AIS treated in public healthcare institutions in Singapore from 2009 to 2018. Using multivariable logistic regression, adjusted for time-varying meteorological effects, we examined how AF modified the association between AIS and air pollutant exposure. A total of 51,673 episodes of AIS were included, with 10,722 (20.7%) having AF. The odds of AIS in patients with AF is higher than those without AF for every 1 µg/m3 increase in O3 concentration (adjusted OR [aOR]: 1.005, 95% CI 1.003–1.007) and every 1 mg/m3 increase in CO concentration (aOR: 1.193, 95% CI 1.050–1.356). However, the odds of AIS in patients with AF is lower than those without AF for every 1 µg/m3 increase in SO2 concentration (aOR: 0.993, 95% CI 0.990–0.997). Higher odds of AIS among AF patients as O3− and CO concentrations increase are also observed in patients aged ≥65 years and non-smokers. The results suggest that AF plays an important role in exacerbating the risk of AIS as the levels of O3 and CO increase.

Study on the Increase of Co Concentration and the Purification of La-Co Cosubstituted M-type Sr Ferrite by Oxygen Partial Pressure Control

Study on the Increase of Co Concentration and the Purification of La-Co Cosubstituted M-type Sr Ferrite by Oxygen Partial Pressure Control

Correlated Electronic and Opto-magnetic Properties of Cobalt Doped GaN

The effect of cobalt doping on the electronic, magnetic and optical properties of GaN has been investigated using density functional theory (DFT) first-principles calculations within the framework of generalized gradient approximation suggested by Perdew-Burke Ernzerhof and ultrasoft pseudopotential. The electronic band structure of cobalt (Co) doped GaN turns into half metallic rather than semiconducting in its pure form and reduces significantly too. The values of magnetic moment at Co and nitrogen (N) sites are 0.8 μB and 0.12 μB, respectively. The effect of the increase in Co concentration results in reduced spin-polarization and the Co magnetic moment itself. According to phenomenological band structure model, the p-d repulsion increases with increasing Co concentration, which subsequently lowers the spin-polarization and hence the d-d coupling increases due to possible charge transfer between Co t2d and ed states. The Co d-Dos diagram for various doping concentrations exhibits more broadened t2d levels, thus predicting the increase in stability with increase in dopant concentration. The coupling between Co atoms is ferromagnetic, mediated through neighboring Ga and N atoms. The absorption edge of Co-doped GaN manifests a red shift with the increase in doping concentration. These findings are in good agreement with the experimental results. We predict that a lower concentration of cobalt-doped GaN is appropriate for spintronic applications.

Microstructure, coercivity and thermal stability of nanostructured (Nd,Ce)-(Fe,Co)-B hot-compacted permanent magnets

We report on microstructure, hard magnetic properties and thermal stability of nanocrystalline (Nd0.85Ce0.15)15(Fe1-xCox)78B7 (x = 0 – 1) hot-compacted permanent magnets. At lower Co concentrations (x < 0.3), the substitution of Fe by Co changes the composition of grain boundary phase from non-magnetic (Nd,Ce)2Fe1 to magnetic (Nd,Ce)1(Fe,Co)2, leading to the degrading of the coercivity. At x ≥ 0.6, the grain boundary phase is no longer observed between the nanocrystalline grains, resulting in strong magnetic coupling of constituent phases. With the further increase of Co concentration (x>0.6), additional RE(Fe,Co)2, RE(Fe,Co)4B and RECo5 phases are gradually formed in the magnets. A new type of microstructure with nanograins of RE2(Fe,Co)14B phase, RE(Fe,Co)2 phase and RE(Fe,Co)4B phase, with partial or without grain boundary phase shows good thermal stability (x = 0.4 and 0.6). In (Nd0.85Ce0.15)15(Fe0.4Co0.6)78B7 magnets, the absolute values of temperature coefficient of coercivity |β| can reach 0.3 %/K within the temperature range of 300 K - 500 K, and it exceeds 0.23 %/K for the temperature range of 300 K - 650 K, indicating a promising method for designing highly thermal stable permanent magnets.

Synthesis and Blue Emission Properties of Co-Doped CdS Semiconductor Nanoparticles

Background: Cadmium sulfide (CdS) based semiconductors are of great interest for different high-end applications because they pose a direct bandgap (2.42 eV). CdS are used as the main constituent material in many applications, namely solar cells, electroluminescent, and quantum dot light-emitting diodes. Transition metal-doped CdS revealed considerable influence in the bandgap, photoluminescence properties and peak energy upon increasing the metal content. Objective: In this work, we study the single-phase cubic structure of CdS. Photoluminescence spectra revealed a strong blue emission peak located at about 445 nm. Methods: We investigate the Co-doping CdS semiconductor nanoparticles prepared via the chemical co-precipitation method using thiophenol as template, 300 °C/2h in vacuum optimum temperature and period of annealing to yield nanosized particles. Morphology and structural studies of the particles were using XRD, and TEM, respectively. Results: XRD and TEM studies for the calcined samples revealed a cubic structure. The crystalline size was in the range of 10-17 nm. Thermogravimetric analysis (TGA) was employed to stabilize the temperature of annealing for the samples. The blue shift in the spectra and the band gap value of Codoped CdS nanoparticles were estimated using UV-vis absorption spectra. Photoluminescence spectra revealed a strong blue emission peak around 445 nm indicating the presence of surface states within the bandgap region, which is a characteristic feature of nanoparticles. Conclusion: XRD analysis indicated zinc blend structure and the intensity decreased with increasing Co content. TEM images show that the particles are spherical in shape with average sizes around 13 nm. Luminescence of the synthesized nanoparticles exhibited blue emission between 400 – 500 nm with the peak located at about 445 nm. The emission intensity increased with the increase in Co concentration.