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1.
Small Bus Econ (Dordr) ; 59(2): 627-643, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-38624928

RESUMO

Despite the proliferation of innovative technologies during the Fourth Industrial Revolution (4IR), there is a severe lack of quantitative and empirical studies that deal with the effectiveness of recently emerging technologies. This study examines the impact of employing core technologies of the 4IR on small and medium enterprises (SMEs). We used the firm-level cross-sectional data on Korean manufacturing SMEs, including the information on technology utilization. The stochastic production frontier estimation with selectivity correction is employed, besides matching technique to obtain unbiased estimates on technology efficiency. The empirical analysis finds that adopting emerging technologies enhances the productivity of SMEs. After observed and unobserved factors are controlled, the technical efficiency of adopters is higher by more than 26% on average, compared to non-adopters. Moreover, if the gap among production frontiers is considered, the difference in productivity would rise further. Additionally, a strategic alliance is a crucial route for SMEs to accept new technologies.

2.
Am Econ Rev ; 106(10): 3064-3103, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-28781375

RESUMO

This research explores the origins of observed differences in time preference across countries and regions. Exploiting a natural experiment associated with the expansion of suitable crops for cultivation in the course of the Columbian Exchange, the research establishes that pre-industrial agro-climatic characteristics that were conducive to higher return to agricultural investment, triggered selection, adaptation and learning processes that generated a persistent positive effect on the prevalence of long-term orientation in the contemporary era. Furthermore, the research establishes that these agro-climatic characteristics have had a culturally embodied impact on economic behavior such as technological adoption, education, saving, and smoking.


Assuntos
Agricultura , Desenvolvimento Econômico/estatística & dados numéricos , Tempo , Agricultura/história , Produtos Agrícolas , Emigração e Imigração , Europa (Continente) , História do Século XV , História do Século XVI , Humanos , Fumar , Estados Unidos
3.
Q J Econ ; 139(1): 575-635, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38859982

RESUMO

This article examines the consequences and causes of low enrollment of Black patients in clinical trials. We develop a simple model of similarity-based extrapolation that predicts that evidence is more relevant for decision-making by physicians and patients when it is more representative of the group being treated. This generates the key result that the perceived benefit of a medicine for a group depends not only on the average benefit from a trial but also on the share of patients from that group who were enrolled in the trial. In survey experiments, we find that physicians who care for Black patients are more willing to prescribe drugs tested in representative samples, an effect substantial enough to close observed gaps in the prescribing rates of new medicines. Black patients update more on drug efficacy when the sample that the drug is tested on is more representative, reducing Black-white patient gaps in beliefs about whether the drug will work as described. Despite these benefits of representative data, our framework and evidence suggest that those who have benefited more from past medical breakthroughs are less costly to enroll in the present, leading to persistence in who is represented in the evidence base.

4.
Adv Sci (Weinh) ; 11(14): e2307223, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38311586

RESUMO

Electrochromic smart windows are promising for building energy savings due to their dynamic regulation of the solar spectrum. Restricted by materials or traditional complementary device configuration, precisely and independently controlling of visible (VIS) and near-infrared (NIR) light is still on the drawing board. Herein, a novel Zn2+ electrochemically active Ce4W9O33 electrode is reported, which demonstrates three distinct states, including VIS and NIR transparent "bright and warm" state, VIS and NIR opaque "dark and cool" state, VIS transparent and NIR opaque "bright and cool" state. A dual-operation mode electrochromic platform is also presented by integrating Ce4W9O33/NiO complementary device and Zn anode-based electrochromic device (Ce4W9O33/Zn/NiO device). Such a platform enables an added VIS opaque and NIR transparent "dark and warm" state, thus realizing four color states through individually controlling Ce4W9O33 and NiO electrodes, respectively. These results present an effective approach for facilitating electrochromic windows more intelligent to weather/season conditions and personal preferences.

5.
Heliyon ; 10(17): e36621, 2024 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-39263108

RESUMO

This study compares hindering and fostering factors for SMEs in China and Sri Lanka in their internationalization efforts through e-commerce. The study uses qualitative research methods to examine how SMEs in both countries utilize e-commerce platforms for global expansion. Narrative and thematic analysis techniques focus on manufacturing sector SMEs actively engaged in global expansion through e-commerce. Purposive sampling is used to select participants. The findings reveal shared patterns and distinctive characteristics in the digital transformation of SMEs. Chinese SMEs benefit from product popularity and advanced technologies, while Sri Lankan SMEs face challenges accessing financial resources and advanced technologies. Perspectives on innovation and regulatory/cross-cultural considerations vary. Supportive government policies and infrastructure are crucial for SME internationalization. The research provides insights for policymakers, researchers, and practitioners to enhance SME development and promote cross-national collaborations in the digital era.

6.
J Quant Econ ; 21(1): 235-264, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36686615

RESUMO

Income inequality in developing countries remains a major concern. It has been established that higher inequality makes a greater proportion of the population vulnerable to poverty. This paper aimed to analyse the effect of the interaction between ICTs and human capital on income inequality in developing countries. Covering 89 developing countries for the period 2000 to 2015 and based on panel fixed effects instrumental variables technique, this study finds that the interaction between ICTs and human capital reduces overall income inequality on the one hand, and on the other, leads to an increase in the income shares of the poorest, and in particular relative to the richest in developing countries. Furthermore, the interaction between ICTs and human capital reinforces the impact of ICTs on income inequality in developing countries. These results suggest that prioritizing the acquisition of human capital by the poorest, as well as promoting access to and use of ICTs for the benefit of the poorest would significantly contribute to reduce overall income inequality and increase income shares of the poorest in developing countries.

7.
Materials (Basel) ; 16(20)2023 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-37895616

RESUMO

Understanding the infiltration and solidification processes of liquid 5083Al alloy into Al2O3 three-dimensional reticulated porous ceramic (Al2O3(3D) RPC) is essential for optimizing the microstructure and properties of Al2O3(3D)/5083Al interpenetrating phase composites (IPCs) prepared by low-pressure infiltration process (LPIP). This study employs ProCAST software to simulate the infiltration and solidification processes of liquid 5083Al with pouring velocities (PV) of 0.4 m/s infiltrating into Al2O3(3D) RPC preforms with varying porosities at different pouring temperatures (PT) to prepare Al2O3(3D)/5083Al IPCs using LPIP. The results demonstrate that pore diameter of Al2O3(3D) RPC preforms and PT of liquid 5083Al significantly influence the of the infiltration. Solidification process analysis reveals that the Al2O3(3D) RPC preform with smaller pore diameters allows the lower pouring velocity of 5083Al to solidify faster compared to the preform with larger pore diameters. Al2O3(3D)/5083Al IPCs were prepared successfully from Al2O3(3D) RPC porosity of 15 PPI with liquid 5083Al at PV 0.4 m/s and PT 800 °C using LPIP, resulting in nearly fully dense composites, where both Al2O3(3D) RPCs and 5083Al interpenetrate throughout the microstructure. The infiltration and solidification defects were reduced under air pressure of 0.3 MPa (corresponding to PV of 0.4 m/s) during LPIP. Finite volume method simulations are in good agreement with experimental data, validating the suitability of the simplified model for Al2O3(3D) RPCs in the infiltration simulation.

8.
Materials (Basel) ; 16(5)2023 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-36902934

RESUMO

Niobates are very promising anode materials for Li+-storage rooted in their good safety and high capacities. However, the exploration of niobate anode materials is still insufficient. In this work, we explore ~1 wt% carbon-coated CuNb13O33 microparticles (C-CuNb13O33) with a stable shear ReO3 structure as a new anode material to store Li+. C-CuNb13O33 delivers a safe operation potential (~1.54 V), high reversible capacity of 244 mAh g-1, and high initial-cycle Coulombic efficiency of 90.4% at 0.1C. Its fast Li+ transport is systematically confirmed through galvanostatic intermittent titration technique and cyclic voltammetry, which reveal an ultra-high average Li+ diffusion coefficient (~5 × 10-11 cm2 s-1), significantly contributing to its excellent rate capability with capacity retention of 69.4%/59.9% at 10C/20C relative to 0.5C. An in-situ XRD test is performed to analyze crystal-structural evolutions of C-CuNb13O33 during lithiation/delithiation, demonstrating its intercalation-type Li+-storage mechanism with small unit-cell-volume variations, which results in its capacity retention of 86.2%/92.3% at 10C/20C after 3000 cycles. These comprehensively good electrochemical properties indicate that C-CuNb13O33 is a practical anode material for high-performance energy-storage applications.

9.
Front Artif Intell ; 5: 832736, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35620279

RESUMO

Recent years have seen impressive advances in artificial intelligence (AI) and this has stoked renewed concern about the impact of technological progress on the labor market, including on worker displacement. This paper looks at the possible links between AI and employment in a cross-country context. It adapts the AI occupational impact measure developed by Felten, Raj and Seamans-an indicator measuring the degree to which occupations rely on abilities in which AI has made the most progress-and extends it to 23 OECD countries. Overall, there appears to be no clear relationship between AI exposure and employment growth. However, in occupations where computer use is high, greater exposure to AI is linked to higher employment growth. The paper also finds suggestive evidence of a negative relationship between AI exposure and growth in average hours worked among occupations where computer use is low. One possible explanation is that partial automation by AI increases productivity directly as well as by shifting the task composition of occupations toward higher value-added tasks. This increase in labor productivity and output counteracts the direct displacement effect of automation through AI for workers with good digital skills, who may find it easier to use AI effectively and shift to non-automatable, higher-value added tasks within their occupations. The opposite could be true for workers with poor digital skills, who may not be able to interact efficiently with AI and thus reap all potential benefits of the technology.

10.
Econ Disaster Clim Chang ; 6(2): 393-416, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35071973

RESUMO

If economists have largely failed to predict or prevent the Global Financial Crisis in 2008, and the more disastrous economic collapse associated with the pandemic of 2020, what else is the profession missing? This is the question that motivates this survey. Specifically, we want to highlight four catastrophic risks - i.e., risks that can potentially result in global catastrophes of a much larger magnitude than either of the 2008 or 2020 events. The four risks we examine here are: Space weather and solar flares, super-volcanic eruptions, high-mortality pandemics, and misaligned artificial intelligence. All four have a non-trivial probability of occurring and all four can lead to a catastrophe, possibly not very different from human extinction. Inevitably, and fortunately, these catastrophic events have not yet occurred, so the literature investigating them is by necessity more speculative and less grounded in empirical observations. Nevertheless, that does not make these risks any less real. This survey is motivated by the belief that economists can and should be thinking about these risks more systematically, so that we can devise the appropriate ways to prevent them or ameliorate their potential impacts.

11.
Am Econ J Econ Policy ; 14(2): 1-33, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35992019

RESUMO

Pharmaceutical companies market to physicians through individual detailing accompanied by monetary or in-kind transfers. Large compensation payments to a small number of physicians account for most of this promotional spending. Studying US promotional payments and prescriptions for anticoagulant drugs, we investigate how peer influence broadens the payments' reach. Following a compensation payment, prescriptions for the marketed drug increase by both the paid physician and the paid physician's peers. Payments increase prescriptions to both recommended and contraindicated patients. Over three years, marketed anticoagulant prescriptions rose 23 percent due to payments, with peer spillovers contributing a quarter of the increase.

12.
Materials (Basel) ; 16(1)2022 Dec 22.
Artigo em Inglês | MEDLINE | ID: mdl-36614427

RESUMO

In this study, an Al2O33D/5083 Al composite was fabricated by infiltrating a molten 5083 Al alloy into a three-dimensional alumina reticulated porosity ceramics skeleton preform (Al2O33D) using a pressureless infiltration method. The corrosion resistance of 5083 Al alloy and Al2O33D/5083 Al in NaCl solution were compared via electrochemical impedance spectroscopy (EIS), dynamic polarization potential (PDP), and neutral salt spray (NSS) tests. The microstructure of the two materials were investigated by 3D X-ray microscope and scanning electron microscopy aiming at understanding the corrosion mechanisms. Results show that an Al2O33D/5083 Al composite consists of interpenetrating structure of 3D-continuous matrices of continuous networks 5083 Al alloy and Al2O33D phase. A large area of strong interfaces of 5083 Al and Al2O33D exist in the Al2O33D/5083 Al composite. The corrosion development process can be divided into the initial period, the development period, and the stability period. Al2O33D used as reinforcement in Al2O33D/5083 Al composite improves the corrosion resistance of Al2O33D/5083 Al composite via electrochemistry tests. Thus, the corrosion resistance of Al2O33D/5083 Al is higher than that of 5083 Al alloy. The NSS test results indicate that the corrosion resistance of Al2O33D/5083 Al was lower than that of 5083 Al alloy during the initial period, higher than that of 5083 Al alloy during the development period, and there was no obvious difference in corrosion resistance during the stability period. It is considered that the elements in 5083 Al alloy infiltrated into the Al2O33D/5083 Al composite are segregated, and the uniform distribution of the segregated elements leads to galvanic corrosion during the corrosion initial period. The perfect combination of interfaces of Al2O33D and the 5083 Al alloy matrix promotes excellent corrosion resistance during the stability period.

13.
Materials (Basel) ; 15(3)2022 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-35160794

RESUMO

In this study, we address the effect of vacuum heat treatment on the morphology of Al2O3-3wt.%TiO2 coating, element diffusion behavior, coating hardness, and corrosion resistance. The pores, cracks, and non-liquefied particles on the as-heat treated coating surface of the vacuum-heat-treated coating were observed and compared with the as-sprayed coating using a scanning electron microscope. The diffusion behavior of the elements in the coating was demonstrated by using a line scanning of a cross-section of the coating. Hardness and corrosion-resistance test results were used to judge the effect of a vacuum heat treatment on the coating. The research results show that compared with atmospheric heat treatment, the vacuum heat treatment had less effect on the pores, cracks, and non-liquefied particles on the surface of the coating. However, in the absence of new oxide formation, the pores and cracks in the cross-section of the coating were significantly improved by the vacuum heat treatment. The surface hardness and corrosion resistance of the coating were significantly improved. The crack defects were eliminated, and the uniformity of TiO2 distribution was improved, which are the main factors that improved the coating performance after vacuum heat treatment. The combination of the coating and the substrate is strengthened, and an Al2O3 and TiO2 interdiffusion zone is formed when the coating undergoes vacuum heat treatment, which is the main mechanism improving the performance of the AT3 coating.

14.
Chemosphere ; 273: 128581, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33082000

RESUMO

In the present study, heterogeneous electro-Fenton (EF) process was applied to remove the sulfasalazine (SU) pharmaceutical from aqueous solutions. In the first part, 3D graphene loaded with Fe@Fe2O3 core-shell nanowires (Fe@Fe2O3/3D-GO) was used as a cathode electrode in the EF process. Graphene oxide (GO) was synthesized for the synthesis of 3D graphene nanocomposites using the improved Hummers' method and subsequently 3D graphene synthesized by the hydrothermal method using glycine. Finally, Fe@Fe2O3/3D-GO composite was synthesized and its properties were assessed by Scanning electron microscopy, Atomic force microscopy, Brunauer-Emmett-Teller, Fourier-transform infrared spectroscopy and X-ray diffraction methods. Then, the cathode electrode was prepared using the resulting composite and its performance was evaluated using Cyclic Voltammetry analysis. In the final part of this work, the Fe@Fe2O3/3D-GO electrode was used as the cathode electrode in the heterogeneous EF process to remove SU from aqueous solutions. The effect of operating parameters such as applied current (mA), initial pH of solution, initial pharmaceutical concentration (mg L-1) and process time (min) on pharmaceutical removal efficiency under heterogeneous EF process was investigated by response surface methodology. The results showed that the optimum values for applied current, pH, initial pharmaceutical concentration and electrolysis time were respectively 300 mA, 7, 30 mg L-1 and 100 min, resulting 99.60% of SU removal. Finally, the intermediates of SU degradation were determined by Gas chromatography-mass spectrometry analysis and the amount of mineralization was determined by total organic carbon analysis. About 5.2% drop in the SU removal efficiency was observed within 8 operational runs.


Assuntos
Grafite , Poluentes Químicos da Água , Eletrodos , Peróxido de Hidrogênio , Sulfassalazina
15.
Materials (Basel) ; 14(5)2021 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-33806687

RESUMO

In order to evaluate the elevated temperature creep performance of the ABOw/Al-12Si composite as a prospective piston crown material, the tensile creep behaviors and creep fracture mechanisms have been investigated in the temperatures range from 250 to 400 °C and the stress range from 50 to 230 MPa using a uniaxial tensile creep test. The creep experimental data can be explained by the creep constitutive equation with stress exponents of 4.03-6.02 and an apparent activation energy of 148.75 kJ/mol. The creep resistance of the ABOw/Al-12Si composite is immensely improved by three orders of magnitude, compared with the unreinforced alloy. The analysis of the ABOw/Al-12Si composite creep data revealed that dislocation climb is the main creep deformation mechanism. The values of the threshold stresses are 37.41, 25.85, and 17.36 at elevated temperatures of 300, 350 and 400 °C, respectively. A load transfer model was introduced to interpret the effect of whiskers on the creep rate of this composite. The creep test data are very close to the predicted values of the model. Finally, the fractographs of the specimens were analyzed by Scanning Electron Microscope (SEM), the fracture mechanisms of the composites at different temperatures were investigated. The results showed that the fracture characteristic of the ABOw/Al-12Si composite exhibited a macroscale brittle feature range from 300 to 400 °C, but a microscopically ductile fracture was observed at 400 °C. Additionally, at a low tensile creep temperature (300 °C), the plastic flow capacity of the matrix was poor, and the whisker was easy to crack and fracture. However, during tensile creep at a higher temperature (400 °C), the matrix was so softened that the whiskers were easily pulled out and interfacial debonding appeared.

16.
J Agric Econ ; 71(1): 1-21, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-32406423

RESUMO

Drought Tolerant Maize Varieties (DTMV) and Rainfall Index Insurance (RII) are potential complements, though with limited empirical basis. We employ a multivariate spatial framework to investigate the potential for bundling DTMV with a simulated multi-site and multi-environment RII, designed to insure against mild, moderate and severe drought risk. We use yield data from on-farm trials conducted by the International Maize and Wheat Improvement Center (CIMMYT) and partners over 49 locations in Eastern and Southern Africa spanning 8 countries and 5 mega-environments (dry lowland, dry mid altitude, wet lower mid altitude, low wetland and wet upper mid altitude) in which 19 different improved maize varieties including DTMV were tested at each location. Spatially correlated daily rainfall data are generated from a first-order two-state Markov chain process and used to calibrate the index and predict yields with a hierarchical Bayes multivariate spatial model. Results show high variation in the performance and benefits of different bundles which depend on the maize variety, the risk layer insured, and the type of environment, with high chances of selecting a sub-optimal and unattractive contract. We find that complementing RII with a specific DTMV produces contracts with lower premiums and higher guaranteed returns especially in dry lowland increasing the chances of scaling up RII within this environment.

17.
Heliyon ; 5(5): e01808, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31193906

RESUMO

The aim of this work was to investigate the effect of free oxygen radicals and free electrons in a Ca12Al14O33 (C12A7) cement structure on the optical, electronic and antibacterial activity of this material. Ca12Al14O33 was successfully fabricated via rapid heating to high temperatures by high frequency electromagnetic induction. Ca12Al14O33 cement samples were characterized using XRD and UV-Vis-DRS spectroscopy. The morphology and chemical composition of the samples were also investigated using SEM and EDS techniques. The presence of free oxygen radicals (O2 -ions) in the insulating structure of Ca12Al14O33 was confirmed using Raman spectroscopy showing a spectrum peak at 1067 cm-1. The excitation of free electrons in the Ca12Al14O33 cement was indicated by UV-Vis absorption spectra at 2.8 eV and an optical energy gap of 3.5 eV, which is consistent with the first-principles calculations for the band energy level. The effects of free oxygen radicals and free electrons in the Ca12Al14O33 structure as antibacterial agents against Escherichia Coli (E. coli) and Staphylococcus Aureus (S. aureus) were investigated using an agar disk-diffusion method. The presence of O2 - anions as a reactive oxygen species (ROS) at the surface of Ca12Al14O33 caused inhibition of E. coli and S. aureus cells. The free electrons in the conducting C12A7 reacted with O2 gas to produce ROS, specifically super oxides (O2 -), superoxide radicals (O2 •-), hydroxyl radicals (OH•) and hydrogen peroxide (H2O2), which exhibited antibacterial properties. Both mechanisms were active against bacteria without effects from nano-particle sized materials and photocatalytic activity. The experimental results showed that the production of ROS from free electrons was greater than that of the free O2 - anions in the structure of Ca12Al14O33. The antibacterial actions for insulating and conducting Ca12Al14O33 were different for E. coli and S. aureus. Thus, Ca12Al14O33 cement has antibacterial properties that do not require the presence of nano-particle sizes materials or photocatalysis.

18.
J Med Econ ; 21(11): 1131-1138, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30130990

RESUMO

AIMS: Hormonal imbalances can affect a woman's physical and mental condition, impacting her daily life and productivity. A mobile application, "Karada-no-kimochi", predicts the menstrual cycle based on recorded data, and provides the information regarding menstruation. This study investigates the effectiveness of the application from health condition and labor productivity loss perspectives, and evaluates its cost-effectiveness for employed women in Japan. MATERIALS AND METHODS: A randomized controlled trial (RCT) was performed to compare the use of the application and non-intervention in female workers (20-45 years) based on an online survey. A discrete-event model based on the RCT data, published literature, and claims data was used for the cost-effectiveness analysis. RESULTS: The intervention and non-intervention groups comprised 612 and 914 women, respectively. In the intervention group, the incidences of depression (0.16%) and dysmenorrhea (0.33%) were significantly lower than those of the non-intervention group (0.77% and 1.31%, respectively) in the third month. While labor productivity and absenteeism varied, presenteeism showed almost no change across groups. The quality-adjusted life year in the intervention group was 6.84 (0.07 higher than that in the non-intervention group). By analyzing medical expenses and making assumptions regarding productivity, we estimated that the aggregate of medical expenses, productivity loss, and application fee for the intervention group could be lower than that of the non-intervention group by over JPY 130,000 (USD 1,170, as of December 2017) per individual. LIMITATIONS: The subjects included were willing or relatively willing to use the application. Because all outcomes were based on online surveys, the results depended on the objectivity and preciseness of the reports provided by users, and those with severe symptoms might not provide reports. CONCLUSIONS: The results suggest that using the application is cost-effective and might reduce the incidence of dysmenorrhea and depression.


Assuntos
Depressão/terapia , Dismenorreia/terapia , Aplicativos Móveis/economia , Mulheres Trabalhadoras , Absenteísmo , Adulto , Análise Custo-Benefício , Depressão/economia , Dismenorreia/economia , Eficiência , Feminino , Humanos , Japão , Menstruação/fisiologia , Menstruação/psicologia , Pessoa de Meia-Idade , Modelos Econométricos , Adulto Jovem
19.
Front Chem ; 6: 69, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29616215

RESUMO

The dual-functional Ca12Al14O33: Tb3+ and Ca12Al14O33: Sm3+ materials were prepared by the Self-Propagating Combustion Synthesis (SPCS) technology. The structure, morphology and light absorption property were investigated by XRD, FT-IR, UV-Vis DRS and SEM etc. The doping of Tb3+ and Sm3+ ions had not changed cubic structure of Ca12Al14O33 but leaded to the slight lattice dilatation and the red-shifts of absorption peaks/edges. The excitation and emission spectra indicated that Ca12Al14O33: Tb3+ and Ca12Al14O33: Sm3+ are superior green and red luminescent materials, respectively, and it displayed the distinctly refined structure characteristics which had importantly reference value for the energy level investigation of Tb3+ and Sm3+ ions. Meanwhile, Ca12Al14O33: Tb3+ and Ca12Al14O33: Sm3+ also exhibited the improved photocatalytic degradation for removing dye MB compared with bare Ca12Al14O33.

20.
Materials (Basel) ; 12(1)2018 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-30591643

RESUMO

Ca12Al14O33 (C12A7 or Mayenite) is a material whose caged clathrate structure and occluded anionic species leads to significant functionality. The creation of occluded anionic vacancies leads to the injection of localized electrons at the center of the cage, converting the wide band gap insulator to a semi- or metallic conducting material. The conversion to the electride historically requires the synthesis of oxy-C12A7, consolidation, and then reduction to introduce anionic vacancies. This report develops and characterizes an electride formation procedure from three starting points: unconsolidated oxy-C12A7, heterogenous solid-state reactants (CaCO3 and Al2O3), and homogenous non-carbonaceous polymer assisted sol-gel reactants. Electride-C12A7 formation is observed in a vacuum furnace where the reactants are in direct contact with a carbon source. Process time and temperature-dependent structural characterization provides insight into the source of high temperature C12A7 stability, the mechanism of anionic vacancy formation, and the magnitude of ultimate conductivity that cannot be explained by current reduction theories. A new theory is presented where mixed O- and C-occupied cages lead to high temperature stability, oxidation of C species creates anionic vacancies, and an equilibrium between the reducing power of the electride-C12A7 and of the C species leads to the ultimate conductivity achieved by the process. This represents a shift in understanding of the carbonaceous reduction process and the first report of high purity electride-C12A7 formation from heterogenous solid-state reactants and homogenous non-carbonaceous polymer assisted sol-gel reactants.

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