In this paper, anisotropic transparent ceramics of 2 at.% Nd3+ doped Sr5(PO4)3F (Nd:S-FAP) was fabricated using the synthesized Nd:Sr5(PO4)3F particles as reaction materials by a simple sintering ...route of hot-pressing method for the first time. XRD results proved that the nanoparticles sizes of the synthesized powder were 23 nm. Dense microstructure of transparent ceramic and the maximum relative density was obtained by sintering temperature of 1200 °C for 1 h. The transmittance of the ceramic at the wavelength of 400 nm and 1200 nm were 45% and 50%, respectively. SEM images proved that the grain size of the fabricated ceramics was 1 μm. Spectra properties of Nd:Sr5(PO4)3F transparent ceramics were also investigated.
•2 at.% Nd:Sr5(PO4)3F nanopowders with the grain size of 23 nm was prepared by co-precipitation method.•Transparent and pore-free Nd:Sr5(PO4)3F ceramics was successfully fabricated by HP method at 1200 °C for the first time.•The fabricated ceramics had the obvious advantage in fluorescence lifetime compared to the other matrixes.
Under the current requirements of environmental protection, carbon peaking and carbon neutrality goals, the capacity of the new energy interconnection network is increasing day by day. The thermal ...power unit requires the ability of rapid load adjustment to meet the requirements of real-time power balance. However, when the unit is in a variable load condition, the denitrification system is inefficient or even inoperable. The NOx emission is large, which makes it difficult to meet environmental protection requirements. In this study, a new method for predicting reductive products in the preheating process is proposed, introducing the gasification mechanism into the pulverized coal preheating process. The effects of air coefficient on combustion temperature, velocity, O2, CO2, CO, CH4, and H2, volatile matter and NOx emission are investigated by numerical simulation. It is demonstrated that the gasification mechanism is applicable to predict the reduction products and NOx during preheating. Internal combustion burners can stabilize the precipitation of volatile matter, CH4, CO, and H2. The burner outlet temperature and flow rate decrease with decreasing air coefficient. The local maximum concentration of volatile matter and CH4 are 8.3 vol.% and 2.54 vol.%, respectively. The CO concentration increases with decreasing air coefficient under the effect of CO2 gasification reaction. When the air coefficient is 0.33, the NOx concentration at the burner outlet is 2.8 mg/Nm3 (at 6% O2).
Surfactant-free microemulsions (SFMEs) have shown great potential in many aspects such as chemical reactions and material preparation. Ionic liquid (IL)-based SFME is a promising member in this ...family. However, switchable phase separation of nonaqueous IL SFMEs has not been reported up to now although it is of great importance for the separation of products and recycling of the systems. Herein, a new kind of CO2-responsive SFMEs composed of quaternary ammonium IL, dimethyl sulfoxide, and ethyl acetate has been developed. It is worth noting that the microemulsion can be reversibly switched between emulsification and complete phase separation upon alternative CO2 and N2 bubbling at atmospheric pressure. The microstructures and phase behavior of the systems before and after CO2 bubbling have been systematically studied by phase diagrams, electrical conductivity, dynamic light scattering, optical microscopy, and atomic force microscopy, respectively. Mechanism studies verify that the reversible switching is attributed to the generation and restoration of more hydrophilic carbamate salts from the reaction of CO2 with IL anions, which results in poor solubility of ILs in the nonaqueous microemulsions and thus reversible breaking and rebuilding of the microemulsions. Based on this unique phase behavior, the CO2-switchable SFMEs are used as a microreactor for room temperature synthesis of Zn-based metal–organic frameworks, and effective reaction and microemulsion recycling have been achieved. This study may provide a new strategy for the integration of reaction, separation, and recycling procedures to obtain sustainable chemical processes.
•Transparent SrF2/Nd:SrF2/SrF2 composite ceramic was fabricated by HP sintering.•The composite ceramic maintained a sandwich-like laminar configuration.•The transmittance at 500 nm and 1200 nm are ...about 49.6 % and 62.3 %, respectively.•Thermal conductivity of the composite ceramic at room temperature is 6.07 W/m.K.
A novel transparent SrF2/Nd:SrF2/SrF2 composite ceramic with sandwich-like laminar configuration was designed and successfully fabricated by the hot-pressed sintering method. The composite ceramic possesses an apparent transition interfacial (about 200 μm in thickness) between SrF2 and Nd:SrF2 layers, formed by non-uniform distribution of raw powders and the diffusion of Nd ions during the high temperature sintering. The average grain sizes of SrF2 and Nd:SrF2 layers are about 262.1 μm and 28.6 μm, respectively. For a 2-mm thick transparent SrF2/Nd:SrF2/SrF2 composite ceramic hot-pressed at 900 °C for 2 h, the transmittance at 500 nm and 1200 nm are about 49.6 % and 62.3 %, respectively. The microstructure, emission spectra and thermal conductivities of ceramics are also detected and studied.
Pr, La:SrF2 ceramics co-doped with various amounts of LaF3 were fabricated by hot-pressing (HP) sintering in a vacuum environment. The transmittance of the Pr, La:SrF2 ceramics was gradually improved ...with the increase in sintering temperature, and the sintering temperature of 1000 °C was adequate to fabricate highly transparent ceramics without rapid grain growth. Residual pores and undissolved PrF3/LaF3 fluorides were identified as light scattering defects within the ceramic sintered at 830 °C. The effect of LaF3 on the microstructural, transmittance, and spectroscopic characteristics of ceramics was studied systematically. The luminescence intensity of the Pr, La:SrF2 ceramics was drastically enhanced through LaF3 co-doping, while the optical transmittance first slightly increased and then decreased. The ceramic sample co-doped with 1 wt% LaF3 exhibits the highest transmittance with the smallest grain size of 43.4 μm, and the transmittance reaches 87.8% at 400 nm and 87.2% at 1100 nm.
•High transparency Pr, La:SrF2 ceramics were fabricated by HP sintering.•Residual pores and PrF3/LaF3 phases as light scattering defects were identified.•The luminescence intensity was drastically enhanced through LaF3 co-doping.•The quantum efficiency of the ceramics was increased from 4.94% to 10.53%.
Highly transparent Nd‐doped calcium fluoride (Nd: CaF2) ceramics with different Nd‐doped concentrations were fabricated by hot‐pressed method using Nd: CaF2 nanopowders synthesized by coprecipitation ...method. SEM observations indicated that the average grain size of nanopowders was about 16–30 nm and the average grain size of the ceramics was between 200 nm and 1 μm. The grain boundaries of the ceramics were clean and no pores or impurities were detected. For 2‐mm‐thickness sample, the transmittance of the as‐fabricated 5 at.% Nd: CaF2 ceramic at 1200 nm was about 85%. The absorption coefficient and emission intensity of the Nd: CaF2 ceramics were measured and discussed. From the Nd: CaF2 ceramics fluorescent spectra and the decay curves, it was found that the fluorescent quenching effect became more evident with the increase in the Nd3+ ions‐doped concentration.
Microbial fouling of heat exchangers causes serious issues including increased fuel consumption, flow resistance, and maintenance cost expenditure. Composite Ni‐P‐nanoTiO2 coatings were prepared for ...inhibiting and mitigating the heat exchanger microbial fouling deposition. The surface energy components and wall adhesion work of microbial fouling medium had a significant effect on the microbial fouling deposition process. Compared with carbon steel coupons, the microbial fouling deposition on Ni‐P‐nanoTiO2 coatings was reduced by about 90 % and the wall adhesion work and microbial fouling deposition rate of these coatings were less. The Ni‐P‐nanoTiO2 coatings might not only be advantageous for controlling the initial microbial adhesion, but also effective for reducing the fouling deposition rate.
The microbial fouling inhibition performance of composite Ni‐P‐nanoTiO2 coatings was investigated experimentally. The prepared Ni‐P‐nanoTiO2 surfaces reduced the microbial fouling adhesion by ∼ 90 %. The effect of surface energy components and wall adhesion work on microbial fouling process was discussed. This surface technology could be practical for fouling inhibition and mitigation.
Abstract
Microbial fouling of heat exchangers causes serious issues including increased fuel consumption, flow resistance, and maintenance cost expenditure. Composite Ni‐P‐nanoTiO
2
coatings were ...prepared for inhibiting and mitigating the heat exchanger microbial fouling deposition. The surface energy components and wall adhesion work of microbial fouling medium had a significant effect on the microbial fouling deposition process. Compared with carbon steel coupons, the microbial fouling deposition on Ni‐P‐nanoTiO
2
coatings was reduced by about 90 % and the wall adhesion work and microbial fouling deposition rate of these coatings were less. The Ni‐P‐nanoTiO
2
coatings might not only be advantageous for controlling the initial microbial adhesion, but also effective for reducing the fouling deposition rate.
Erbium doped strontium fluoride (Er:SrF2) ceramics were fabricated by the hot-pressed (HP) sintering method without any sintering aids, and the densification and microstructure evolution of Er:SrF2 ...ceramics were investigated. The microstructure of Er:SrF2 ceramics was analyzed by SEM, and light scattering defects, including residual pores and un-dissolved ErF3 compound, were identified. The Er:SrF2 ceramic hot-pressed at 900 °C for 2 h exhibited the highest transmittance, and its transmittance at 500 nm and 1200 nm are 90.4% and 91.7%, respectively. In addition, it was clarified that the grain growth kinetic mechanism of Er:SrF2 ceramics at the final stage of sintering is related to the solute drag.
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•The densification of Er:SrF2 ceramic was realized within 2 h.•The highest transmittance reaches 90.4% at 500 nm and 91.7% at 1200 nm.•Residual pores and ErF3 phases as light scattering defects were identified.•A solute drag grain growth kinetic mechanism at the final stage was clarified.
In this study, high concentration (5 mol%) of cerium doped barium fluoride transparent ceramic was fabricated by hot pressing method t a temperature of 1200 °C under 30 MPa. XRD (X-ray Diffraction), ...SEM (Scanning Electron Microscope), PLE (Photoluminescence Emission) measurements was used to investigate the phase composition, microstructure as well as photoluminescence properties of Ce3+: BaF2. XEL (X-ray Excited Luminescence) and pulse height spectrum were used to investigate the scintillation properties of this ceramic. The phase composition and microstructure analyses showed that the Ce3+: BaF2precursor nanoparticles prepared by the co-precipitation method were uniform and have a average size of 25 nm. The highest transmittance of the ceramic was 77% at the wavelength of 2300 nm. The PL (photoluminescence) spectrum showed that the 5d–4f transition of Ce3+: BaF2 transparent ceramic is located at 340 nm. X-ray excited luminescence exhibited only one violet peak at 392 nm. Scintillation decay time measurements showed only a slow component of 437 ns under 662 keV gamma excitation.
•Highly transparent Ce3+: BaF2 ceramics was successfully fabricated by hotpressing method.•For a 2 mm thickness sample, the highest transmittance of the sample reached 77% n the wavelength from 250 nm to 2500 nm.•The SEM micrograph of the ceramics indicated that there still exists many pores inside the ceramics.•When doped with 5 at% Ce3+, the emission spectrum exhibited broad emission peaks from 340 nm to 365 nm.•X-ray excited luminescence exhibits one peak at 392 nm. Scintillation decay time measurements show only a slow component of 437 ns under 662 keV gamma excitation.
