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In this paper, using only high alumina fly ash as raw material and MoO 3 as additive agent, the high-strength porous mullite ceramics were achieved by in situ mullite whisker growth via a calcination method. The influence of MoO 3 addition on pore structure and mechanical properties of as-prepared mullite ceramics was investigated. The mechanism of MoO 3 promoting the formation of mullite whiskers and improving the strength of matrix was elucidated. The porous mullite ceramic reached its best performance with a high porosity of 49.4% and an improved compressive strength of 13.03 MPa with 10 wt% MoO 3 addition calcinated at 1300 °C. Specifically, MoO 3 facilitated the mullite whisks growth mainly by reducing melting point of amorphous SiO 2 /quartz and changing crystal structure of Al 2 O 3. The larger aspect ratio of mullite grain at 1300 °C was easier to form an interlocking structure, which enhanced the strength of mullite ceramic while maintaining high porosity. [ABSTRACT FROM AUTHOR]

In this paper, the ceramics with composition of (0.98- x)(K 0.5 Na 0.5)(Nb 0.96 Sb 0.04)O 3 -0.02(Bi 0.5 Na 0.5)(Zr 0.8 Ti 0.2)O 3- x CaZrO 3 (abbreviated as (0.98- x)KNNS-0.02BNZT- x CZ, x = 0, 0.01, 0.015, 0.02, 0.025, 0.03) were prepared by a traditional solid-state reaction method. The effect of the additional amount of CaZrO 3 on the phase structure, microstructure, dispersion index, domain structure and piezoelectric properties of ceramics was systematically studied. Finally, the piezoelectric properties and thermal stability of ceramics could be controlled by adding different amounts of CaZrO 3. The addition of CaZrO 3 transferred the phase structure of the ceramics from orthogonal-tetragonal (O-T) coexistence phase to rhombohedral-orthogonal (R–O) coexistence phase, which could be demonstrated by XRD test, temperature-dependent Raman spectra and ε r ‐ T plot analysis. And when x = 0.02, the ceramics possessed the best piezoelectric and dielectric properties (d 33 = 253 pC/N, ε r = 1185, tan δ = 0.044). Such excellent electrical properties could be originated from the heterogeneous domain structure and small-size nano-domains of the ceramics. Moreover, with the increase of CaZrO 3 doping amount, the dispersion index of ceramics gradually increased from 1.404 to 1.871, which showed more obvious dispersion phase transition characteristics and improved the thermal stability of ceramics. Particularly, when x = 0.02, after annealing at a high temperature of 220 °C (close to its Curie temperature), the d 33 tested at room temperature remained above 85% of that without annealing. The results indicated that (0.98- x)KNNS-0.02BNZT- x CZ ceramic was a promising lead-free piezoelectric ceramic system. [ABSTRACT FROM AUTHOR]

The effect of CaF 2 addition (15.4, 20.4, 27.4 and 35.4 wt%) on the crystallisation ability and preparation of transparent glass ceramics (TGCs) containing CaF 2 nanocrystals was studied. It was found that samples with 15.4, 20.4, and 35.4 wt% CaF 2 are crystallised with multiple crystal phases, making the TGCs opaque. Only when the amount of CaF 2 added is increased to 27.4 wt%, TGCs with only CaF 2 nanocrystals can be successfully prepared by heat treatment at 630 and 730 °C for 2 h. The crystallisation activation energy of the sample with 27.4 wt% CaF 2 is 247.07 kJ mol−1, and the crystallisation energy barrier to be overcome corresponds to the formation of CaF 2 nanocrystals rather than the formation of aluminosilicates, whose size and distribution easily make the glass opaque. Similarly, the FT-IR and XPS results indicate that as the amount of CaF 2 added is increased to 27.4 wt%, the polymerisation degree of the sample is more suitable for the diffusion of calcium and fluorine atoms to form only CaF 2 nanocrystals; therein, the corresponding mole fractions of the bridging oxygen (Oo), non-bridging oxygen (O−), and free oxygen (O2−) are approximately about 0.12, 0.77 and 0.11, respectively. [ABSTRACT FROM AUTHOR]

Good dual electrochromic-capacitive performances and long life are both important for an electrochromo-pseudocapacitor. In this paper, a novel heterostructure, which is fabricated using well-oriented hexagonal WO 3 nanorod arrays as the core and amorphous WO 3− x as the shell, has been proved to possess excellent electrochromic and pseudocapacitive properties. The annealing temperatures for coating the shell take great influence on its microstructure, especially the crystallinity, thus on the comprehensive properties of the heterostructure. Results show that the heterostructure reaches the optimal state at 250 °C with short response times (14, 10.5 s) and high specific capacitance (716.8 F·g−1) while maintaining good stability. Bifunctional well-oriented hexagonal/amorphous tungsten oxide core/shell nanorod arrays (h@a-WNRAs) on FTO substrates possess excellent electrochromic and pseudocapacitive properties. Unlabelled Image [ABSTRACT FROM AUTHOR]

In recent years, single crystal TiO 2 nanorod arrays (TNRAs) with fewer grain boundaries for photo-generated electron transport and ordered channel structures for perovskite filling have been employed as electron transport layers for efficient perovskite solar cells (PSCs). However, further improvements in TNRA-based PSC performance are urgently needed because defects in the perovskite layer seriously hinder device efficiency and stability. In this study, with TNRAs as the electron transport layer, CH 3 NH 3 PbI 3 (MAPbI 3) perovskite films were prepared in air by a two-step spin coating method. The grain boundary defects and surface defects of the MAPbI 3 layer are co-passivated by octyl ammonium iodide (CH 3 (CH 2) 7 NH 3 I, OAI) and choline chloride (HOCH 2 CH 2 N(CH 3) 3 Cl, Ch), respectively, and the effects of the two passive materials on the power conversion efficiency (PCE) and stability of TNRA-based PSCs are systematically investigated. The results reveal that the introduction of OAI facilitates the formation of intermolecular valence bonds between crystalline MAPbI 3 to enhance its structural stability, while Ch passivates the Pb–I antisite substitution defect and I− vacancy defect on the perovskite film surface. Compared with the pristine device, the optimal PCE of the passivated device increases from 18.86% to 20.08%, and the thermal, humid and long-term stability of the device is also improved. [ABSTRACT FROM AUTHOR]

Traditional piezoelectric materials cause serious environmental and health issues because of their lead–containing substances, and thus lead–free piezoelectric ceramics would have many applications. In this study, we successfully prepared the lead–free ceramics (1- x) (K 0 · 48 Na 0 · 48 Li 0.04) (Nb 0 · 975 Sb 0.025)O 3 – x (Bi 0 · 5 Na 0.5) (Zr 0 · 8 Ti 0.2)O 3 ((1- x)KNLNS– x BNZT, x = 0, 0.005, 0.0075, 0.01, 0.015, 0.02 and 0.03) with rhombohedral–tetragonal (R–T) phase coexistence near room temperature, employing con–entional solid sintering. The minimum cell volume of the ceramics and R–T phase coexistence in them were achieved at a doping amount x = 0.01, which facilitated the optimal performance of the ceramics (d 33 ∼467 pC/N ± 14 pC/N, T c∼272 °C, ε r ∼1676, k p ∼0.42, where d 33 : piezoelectric constant; T c: Curie temperature; ε r : dielectric constant; k p : electromechanical coefficient). The ceramics exhibited microstructures with high density and low porosity and had a maximum relative density of 95.68 %. At x = 0.01, the ceramics exhibited a uniformly distributed small domain structures with nanodomains, accounting for their high-voltage electrical properties. Because these stable and reliable piezoelectric (1- x)KNLNS– x BNZT ceramics exhibit excellent electrical performance, they can replace lead–based materials. The direct solid–phase sintering method provides prospects for the large–scale application of the lead–free piezoelectric ceramics. The 0.99(K 0 · 48 Na 0 · 48 Li 0.04)(Nb 0 · 975 Sb 0.025)O 3 –0.01(Bi 0 · 5 Na 0.5)(Zr 0 · 8 Ti 0.2)O 3 ceramics exhibit excellent piezoelectric properties owing to their nanodomain structures, rhombohedral–tetragonal coexistence phase boundaries at room temperature (25°C ± 5°C) and dense microstructures. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Transparent glass ceramics containing CaF 2 nanocrystals were synthesized using a conventional melting and heat treatment process. The mechanism associated with the maintenance of the high transparency of the as-prepared glass ceramics was further clarified. The maximum light transmittance of the as-obtained transparent glass ceramics was approximately 85%, with microhardness value that reaches 761.62 ± 7.93 HV. To obtain transparent glass ceramics, in addition to controlling the CaF 2 nanocrystal size to be smaller than the wavelength of visible light, the average grain spacing (or concentration) of the CaF 2 is also a key factor. CaF 2 transparent glass ceramics were prepared following heat-treatment at a temperature between 630 °C and 700 °C for a period of 1–4 h; herein, the CaF 2 grain size was approximately 10–25 nm. The transmission electron microscopy (TEM) results showed that the CaF 2 grains were evenly distributed within the glass phase and that the average grain spacing was greater than 5.64 nm. The Raman analysis results indicate that at 730 °C, there was a significant increase in the degree of polymerization and an obvious increase in the concentration of CaF 2 grains. The average grain spacing was much lower than 5 nm, and therefore, light energy was constantly reflected between the grains and eventually consumed, resulting in the observed opacity. [ABSTRACT FROM AUTHOR]

The complex compositions and structural features of low-rank coal obstruct its wide use in materials applications directly. Graphene nanocarbon hydrosol with uniform particle size and containing nanodiamond structures were prepared from long-flame coal by a simple H 2 O 2 oxidation, achieving the highest extraction rate of 30.86%, and the depolymerization degree was 80.21% when the temperature was 80 °C. The average diameter of the carbon nanoparticles was 1.86 ± 0.62 nm with 2–3 graphite flake layers, and these graphite flake layers were derived from the stable crystalline domains in the raw coal. Carbon nanoparticles exhibited good excitation wavelength-dependent and concentration-dependent fluorescence, which can be tunable from blue to green fluorescence by adjusting the concentration (0.19–1.5 g/L) and excitation wavelength (340–460 nm), the reason may be due to the combined effect of the relative intensity changes of various types of oxygenous groups, low-lying effects resulting from n(OH)→π*(CO) interactions between the hydroxyl groups and carbonyl groups, and the aggregation of particle. The post-reaction residue has a similar structural composition to that of humic acid and could be used for developing functional materials and agricultural restoration. Therefore, preparing carbon nanoparticles and humic acid by mild oxidation of hydrogen peroxide for the high-value utilization of long-flame coal has good application prospects. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorescence carbon dots were directly prepared by alkaline hydrothermal method from low-rank coals. • Carbon dots had an average size of 1.36 nm with graphitic structure and fewer functional groups. • Carbon dots exhibit high emission intensity at both long and low excitation wavelengths. • Low fluorescence emission is caused by quantum size effects while the long one is resulted from functional groups. • The carbon dots shows excellent trace detection of Fe3+ or Cu2+ ion with detection limit of ∼ 0.04 μM. The intricate composition and structural of low-rank coal have hindered its broad utilization in the field of material science. The study utilized an alkaline hydrothermal method to enhance the depolymerization of long-flame coal and achieve the purification of fluorescent carbon dots for the first time, which were then being employed for the trace detection of Cu2+ or Fe3+ ions. The carbon extraction efficiency reached 58 %, with the carbon dots averaging size of 1.36 ± 0.42 nm, the sp2 hybridized structure of the carbon dots indicated successfully purification under alkaline conditions. After reduction with sodium borohydride, defects in the core region of the carbon dots were repaired, and the C = O functional groups were transformed into O–H groups, leading to an increase in fluorescence intensity. At a concentration of 0.25 g/L of carbon dots, demonstrated high emission intensity at both long and low emission wavelengths, which can be used as LED luminescent material. Furthermore, the application of these carbon dots in detecting heavy metal ions (Cu2+, Fe3+) in aqueous solutions was explored, showing as low as detection limit of ∼ 0.04 μM. This study achieved higher depolymerization of coal and purification of fluorescent carbon dots for use in probe-based detection, providing fresh perspectives on the high-value utilization of low-rank coal. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ceramsite was prepared by low-activity circulating fluidized bed fly ash (CFBFA) with 73% utilization. • The ceramsite was non-fired without pretreating CFBFA. • The ceramsite behaved the strength of 5.5 MPa and porosity of 51.86 % synchronously. • Both quicklime and desulfurized gypsum can promote the formation of C S H in the system. • The preparation process is simple, green and energy-saving. The combustion of low calorific value coal in circulating fluidized bed boilers produces a large amount of fly ash with low activity and utilization. In this paper, the lightweight high strength ceramsite was prepared by a non-fired method using low-activity circulating fluidized bed fly ash (CFBFA) as raw material. And the effects of reinforcing agent and foaming agent on the properties of ceramsite were studied. The dosages of cement, quicklime, desulfurization gypsum and hydrogen peroxide were 15.0 wt%, 6.0 wt%, 6.0 wt% and 2.0 wt%, respectively. The hydration reaction in the system can be maximized by steam curing at 70 ℃ for 12 h. The bulk density and cylinder compressive strength of the obtained ceramsite were 695.34 kg/m3 and 5.5 MPa, respectively, which belonged to 700 grade high strength fly ash ceramsite. The corresponding apparent density and apparent porosity of the products were 1091.88 kg/m3 and 51.86 %, respectively. The admixture of cement, quicklime and desulfurization gypsum can all promote the hydration reaction in the system to produce denser needle-like and flocculent C S H. In addition, the admixture of hydrogen peroxide only enhanced the porosity of ceramsite and had no effect on the phase. The experimental process was simple, green and energy saving. In particular, the total solid waste utilization was up to 79 %. [ABSTRACT FROM AUTHOR]