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Cryolite has been considered as an appropriate host for up-conversion materials due to its low phonon energy, wide light transmission range, easy to form waveguide and stable structure. In this paper, a series of up-conversion materials Cs 3 YF 6 : Er3+, Yb3+ with cryolite structure were prepared by high-temperature solid-phase method. The structure, morphology, element composition and up-conversion luminescence properties of as-prepared samples were characterized. In addition, the number of photons absorbed during the up-conversion process and the possible up-conversion luminescence mechanism are analyzed in detail. Under the excitation of 980 ​nm, the Cs 3 YF 6 : Er3+, Yb3+ sample emits strong green light visible to the naked eye. Simultaneously, the maximum absolute sensitivity (S a) and relative sensitivity (S r) were calculated. All the results indicated that Cs 3 YF 6 : Er3+, Yb3+ has potential applications in the fields of green light display and temperature sensing. Up-conversion materials Cs 3 YF 6 : Er3+, Yb3+ with cryolite structure has potential applications in the fields of green light display and temperature sensing. [Display omitted] • Single-phase up-conversion luminescent materials Cs 3 YF 6 : Er3+,Yb3+ with cryolite structure were obtained for the first time. • The up-conversion luminescence properties and mechanism of the as-prepared samples were analyzed under excitation of 980 ​nm. • Two-phonon up-conversion phenomenon was confirmed. • High color purity green luminescence was achieved under 980 ​nm excitation. • Temperature sensing properties of novel up-conversion luminescent materials Cs 3 YF 6 : Er3+,Yb3+ were investigated. [ABSTRACT FROM AUTHOR]

• Durability of porous perlite geopolymer was investigated in hot and humid environment. • The simulation of extremity of environment temperature and humidity on samples was conducted. • The durability effects of porous perlite geopolymer was analyzed. • The improvement of durability of porous perlite geopolymer was proposed. Porous geopolymers can be potentially applied in building thermal insulation. In this work, we investigated the durability of porous perlite geopolymer by long-term aging experiments under high temperature (50 ℃) and relative humidity (98%). Samples were characterized by digital photo analyses, scanning electron microscope (SEM), X-Ray Fluorescence Spectroscopy (XRF), X-Ray Diffractometer (XRD), Fourier Transform Infrared Spectrum (FT-IR), Solid-State Nuclear Magnetic Resonance (SS NMR), compressive strength measurements and thermal conductivity analyses. Results show that Na+ has great influence on the stability of porous perlite geopolymer. The hydrated Na+ in the pore reacts with CO 2 to form Na 2 CO 3 ·H 2 O, and part of Na+ enters and breaks geopolymer gel network, resulting in the deterioration of physical properties. When soaked in HCl or CaCl 2 solution, the geopolymerization is improved; at the same time, Na+ in the pore reacts with Cl– to form NaCl, and Ca2+ reacts with Cl– and OH– to form CaClOH, which jointly prevents Na+ from entering and breaking gel network and results in the improvement of durability of porous perlite geopolymer. Aging process promotes further polymerization in porous perlite geopolymer, which might also contribute to physical property variations of porous perlite geopolymer. This paper not only clarifies the mechanism of performance variation of porous perlite geopolymer in hot and humid environment, but also offers guidelines for the design and durability research of other porous geopolymers. [ABSTRACT FROM AUTHOR]

Carbon/carbon composites were prepared by thermal gradient chemical vapor infiltration with kerosene as precursor. The microstructure and electrical resistivity were examined by polarized light microscopy and low-resistance instrument, respectively. The effects of processing parameters on microstructure as well as the influences of sample density, processing parameters, and needle punch on electrical resistivity of carbon/carbon composites were analyzed. The results show that besides rough laminar, smooth laminar and isotropic pyrocarbon occur at temperatures of 1000°C and 1200°C, respectively. The graphitization degree of composites increases from 16.28% to 63.95% as the heat treatment temperature increases from 2100°C to 2500°C. The electrical resistivity of carbon/carbon composites decreases with increasing heat treatment temperature and sample density but increases as the texture of pyrocarbon varies from rough laminar to smooth laminar. The main mechanism for influencing the electrical resistivity of carbon/carbon composites can be changing carrier concentration, altering grain scattering, or both actions. [ABSTRACT FROM PUBLISHER]

Abstract: Aluminosilicate-reinforced carbon foams have been prepared by chemical foaming with phenolic resin as matrix precursor and aluminosilicate as the additive. The effects of the amount of aluminosilicate used on the microstructure, mechanical properties and oxidation resistance of the carbon foams have been investigated by scanning electronic microscopy, mechanical testing, and oxidation weight loss, respectively. The results show that the amount of aluminosilicate added has a significant influence on the surface roughness and the structure uniformity of carbon foams. The compressive strengths are usually higher than that of the pure carbon foam sample by as much as 60%. The percentage of weight loss of the carbon foams drops with increasing aluminosilicate content up to 11wt%, but then increases. [Copyright &y& Elsevier]

Cryolite was considered to be an ideal up-conversion host material due to its low phonon energy, which can effectively suppress the radiation-free transition process of excited state energy levels. In the present paper, a novel up-conversion material K 3 YF 6 :Ho3+, Yb3+ with cryolite structure was prepared successfully using a high-temperature solid state method. The up-conversion luminescence properties of K 3 YF 6 doped with different Ho3+/Yb3+ doping ratio were investigated and the optimal doping ratio were confirmed in this system. Under 980 nm excitation, Ho3+/Yb3+ co-doped K 3 YF 6 revealed a strong green emission at the 541 nm, 549 nm and a weak red emission peaking at 666 nm, corresponding to the 5F 4 , 5S 2 →5I 8 and 5F 5 →5I 8 transitions of Ho3+, respectively. All the red and green up-conversion emission of K 3 YF 6 :Ho3+, Yb3+ belong to two-photon process and energy transfer from Yb3+ to Ho3+ simultaneously. Additionally, to understand the energy transfer and electronic transition process of the red and green light emitted, the possible luminescence mechanism were also analyzed in this paper. All the results indicate that Ho3+/Yb3+ co-doped K 3 YF 6 have potential application value in green up-conversion luminescent materials. • Single-phase up-conversion luminescent materials K 3 YF 6 : Ho3+,Yb3+ with cryolite structure were obtained for the first time. • The up-conversion luminescence properties and mechanism of the as-prepared samples were analyzed under excitation of 980 nm. • Two-phonon up-conversion phenomenon was confirmed. [ABSTRACT FROM AUTHOR]

The Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ powder phosphor with apatite structure has been successfully synthesized via a facile route of sol-combustion technique. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) spectroscopy were used to characterize the as-prepared samples. Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ phosphor was composed of particles with average sizes range about 300 nm. The phosphor exhibited an absorption ranging from 220 to 390 nm in ultraviolet range and a broad blue-violet emission band peaked at 403 nm with a CIE coordinates of (0.167, 0.028). The concentration quenching mechanism was also determined to be dipole–dipole interaction. [ABSTRACT FROM AUTHOR]

In this paper, K 3 ScF 6 :Er3+,Yb3+ up-conversion luminescent materials with cryolite structure were synthesized via solid-state method. The X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL) under the excitation of a 980 nm laser with different power density were used to investigate the phase structure, elemental composition, and up-conversion luminescence properties of K 3 ScF 6 :Er3+,Yb3+. The quenching concentrations of Yb3+ and Er3+ were confirmed to 0.15 and 0.05 (mol concentration) in this system, respectively. Upon 980 nm excitation, the K 3 ScF 6 :Er3+,Yb3+ showed a typical transition of Er3+ which contains two main bands in the visible region that green and red. According to the fitting result of the pump power dependence of up-conversion intensity, all the green and red up-conversion emission of K 3 ScF 6 :0.05Er3+,0.15 Yb3+ belong to the two-photon process. To better understand the origin of radiation and energy transfer mechanism of the red and green up-conversion, the possible mechanism and electron transition process were also discussed. Single-phase Er3+/Yb3+ co-doped K 3 ScF 6 with cryolite structure were synthesized. Image 1 • Single-phase Er3+/Yb3+ co-doped K 3 ScF 6 with cryolite structure was synthesized. • Structural and up-conversion properties of K 3 ScF 6 :Er3+, Yb3+ were studied. • Mechanism of up-conversion was analyzed. [ABSTRACT FROM AUTHOR]

• A bifunctional hierarchical porous geopolymer with kaolinite was prepared. • Great thermal insulation and sound insulation performances. • The density is 0.086 g·cm−3 and compressive strength is high (0.27 MPa). • The pore diameter can be adjusted from 0.20 to 2.48 mm. Thermal and sound insulation materials are crucial for reducing the energy consumption and noise pollution of building, but these two types of materials are generally developed independently. Here, a new type of bifunctional hierarchical porous geopolymer which can effectively reduce heat transfer and noise sound is proposed and it is synthesized with inexpensive kaolinite as main raw material through an energy-saving method. The optimal porous geopolymer products show high porosity (93.80%) and extremely low density (0.086 g·cm−3) but relatively high compressive strength (0.27 MPa). More importantly, they have low thermal conductivity (0.040 W·m−1·K−1) but high sound absorption coefficient (0.539 at 5000 Hz; 0.809 at 500 Hz with gap of 50 mm) and sound reduction index (38.6 dB at 2000 Hz). Therefore, this hierarchical porous geopolymer can be potentially used as a new type of bifunctional building material to reduce the energy consumption and noise pollution of building at the same time. [ABSTRACT FROM AUTHOR]

In this paper, K 3 ScF 6 :Yb3+, Tm3+ phosphor with a cubic cryolite phase were prepared by means of high-temperature solid-state method. The crystal structure and up-conversion luminescence properties of Tm3+ and Yb3+ co-doped K 3 ScF 6 were investigated in detail. Scanning electron microscope (SEM), energy disperse spectroscopy (EDS), elemental mapping and X-ray photoelectron spectroscopy (XPS) were used to analyze the elements composition, elemental distribution and valence states of samples. Under an excitation wavelength at 980 nm, all the samples displayed blue and red emission. When gradually increasing the concentration of Tm3+ in K 3 ScF 6 :0.2 Yb3+, Tm3+ and Yb3+ in K 3 ScF 6 : 0.01 Tm3+, Yb3+, the emission intensity of the samples appeared obviously concentration quenching effect, and the optimum concentration of Tm3+ and Yb3+ were confirmed to 0.01 and 0.20 mol%. Additionally, the effect of pump power on up-conversion emission intensity and the energy transfer mechanism between the Tm3+ and Yb3+ in these samples were analyzed in detail. • Single-phase Tm3+/Yb3+ co-doped K 3 ScF 6 with cryolite structure were synthesized for the first time. • Up-conversion properties of K 3 ScF 6 : Yb3+, Tm3+ were studied. • Mechanism of up-conversion was analyzed. [ABSTRACT FROM AUTHOR]

Design and preparation of nanostructured conducting polymers (CPs) is a very important research direction for high performance CPs-based supercapacitors (SCs). With hollow structure, high surface area, tunable surface properties and abundant resources, natural halloysite is a promising template agent for preparing new nanotubular-structure CPs. Here, nanotubular-structure polyaniline was successfully synthesized using natural tubular halloysite as hard template. The obtained tubular polyaniline presents high specific capacitance at various current density as electrode material for supercapacitors. After a facile carbon coating, the carbon coated tubular polyaniline shows high specific capacitance of 654 F g−1 at the current density of 1 A g−1 and excellent electrochemical stability with capacitance retentions ∼87% after 10000 cycles. This work may prove the feasibility of preparing high performance CPs-based nanostructure electrode materials for SCs application based on inexpensive natural clay minerals. [ABSTRACT FROM AUTHOR]

A new kind of multicolor phosphor Ba 2 La 3 (SiO 4) 3 Cl:0.15Tb3+, x Eu3+ (BLSOCl:0.15Tb3+, x Eu3+) has been acquired through the traditional high temperature solid phase synthesis method. The structure information of the phosphor was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rietveld refinement. The optical properties of the phosphor have also been studied in detail, including photoluminescence spectra (PL), photoluminescence excitation spectra (PLE), fluorescence decay curves, energy transfer mechanism and thermal quenching spectra. The CIE values have also been studied. All the properties are good and can contribute to the promotion from the laboratory to practical application for the phosphor. Image 1 [ABSTRACT FROM AUTHOR]

Ca9La(PO4)5 (SiO4)F2:Dy3+ is prepared by solid state reaction of stoichiometric quantities of CaCO3, (NH4)2HPO4, SiO2, Dy2O3, and excess NH4HF2 as a flux ( 5% H2/N2 reducing atmosphere, alumina crucible, 1450 °C, 5 h). [ABSTRACT FROM AUTHOR]