13 research outputs found
Aerogel insulation materials for industrial installation : properties and structure of new factory-made products
In this article the comparisons of two new
factory-made Chinese aerogel products with the Pyrogel®
product, all available on the market, are presented. The
aerogel products are in a flexible blanket form and all
products are dedicated for high temperature applications.
The properties of the samples such as their dimension stability,
water vapour transmission and water absorption are
also described. Additionally the microstructure and chemical
composition of the products are analysed using SEM/
EDS (scanning electron microscopy coupled with X-ray
energy-dispersive spectroscopy). The differences in the
maximum service temperature are presented. The internal
self-heating of the aerogel samples is described and is
compared to a similar effect observed in mineral wool
samples. The results in the change of the thermal properties
in a wide range of temperatures (+ 10–600°C) are shown.
The obtained results are correlated with the mineral wool
data. The correlation shows an advantage in a highefficiency
thermal performance of aerogel products compared
to other insulation materials at high temperatures
Energy transfer study on Tb3+/Eu3+ Co-activated sol-gel glass-ceramic materials containing MF3 (M = Y, La) nanocrystals for NUV optoelectronic devices
In the present work, the Tb3+/Eu3+ co-activated sol-gel glass-ceramic materials (GCs)
containing MF3 (M = Y, La) nanocrystals were fabricated during controlled heat-treatment of silicate
xerogels at 350 C. The studies of Tb3+ ! Eu3+ energy transfer process (ET) were performed by
excitation and emission spectra along with luminescence decay analysis. The co-activated xerogels
and GCs exhibit multicolor emission originated from 4fn–4fn optical transitions of Tb3+ (5D4 !7FJ,
J = 6–3) as well as Eu3+ ions (5D0 ! 7FJ, J = 0–4). Based on recorded decay curves, it was found
that there is a significant prolongation in luminescence lifetimes of the 5D4 (Tb3+) and the 5D0 (Eu3+)
levels after the controlled heat-treatment of xerogels. Moreover, for both types of prepared GCs,
an increase in ET e ciency was also observed (from ET 16% for xerogels up to ET = 37.3% for
SiO2-YF3 GCs and ET = 60.8% for SiO2-LaF3 GCs). The changes in photoluminescence behavior
of rare-earth (RE3+) dopants clearly evidenced their partial segregation inside low-phonon energy
fluoride environment. The obtained results suggest that prepared SiO2-MF3:Tb3+, Eu3+ GC materials
could be considered for use as optical elements in RGB-lighting optoelectronic devices operating
under near-ultraviolet (NUV) excitation
Reddish-Orange Luminescence from BaF2:Eu3+ Fluoride Nanocrystals Dispersed in Sol-Gel Materials
Nanocrystalline transparent BaF2:Eu3+ glass-ceramic materials emitting reddish-orange
light were fabricated using a low-temperature sol-gel method. Several experimental techniques were
used to verify structural transformation from precursor xerogels to sol-gel glass-ceramic materials
containing fluoride nanocrystals. Thermal degradation of xerogels was analyzed by thermogravimetric
analysis (TG) and di erential scanning calorimetry method (DSC). The presence of BaF2 nanocrystals
dispersed in sol-gel materials was confirmed by the X-ray di raction (XRD) analysis and transmission
electron microscopy (TEM). In order to detect structural changes in silica network during annealing
process, the infrared spectroscopy (IR-ATR) was carried out. In particular, luminescence spectra
of Eu3+ and their decays were examined in detail. Some spectroscopic parameters of Eu3+ ions in
glass-ceramics containing BaF2 nanocrystals were determined and compared to the values obtained
for precursor xerogels. It was observed, that the intensities of two main red and orange emission bands
corresponding to the 5D0!7F2 electric-dipole transition (ED) and the 5D0!7F1 magnetic-dipole (MD)
transition are changed significantly during transformation from xerogels to nanocrystalline BaF2:Eu3+
glass-ceramic materials. The luminescence decay analysis clearly indicates that the measured lifetime
5D0 (Eu3+) considerably enhanced in nanocrystalline BaF2:Eu3+ glass-ceramic materials compared
to precursor xerogels. The evident changes in luminescence spectra and their decays suggest the
successful migration of Eu3+ ions from amorphous silica network to low-phonon BaF2 nanocrystals
Fabrication of fluoride nanocrystals and their spectroscopic properties
In this work, the fabrication of glass-ceramic materials containing MF3:Eu3+ (M = La, Gd) nanocrystals
dispersed in silica sol-gel hosts has been presented. The transformation from liquid sols towards
bulk samples was also examined based on IR measurements. The crystallization temperatures and
formation of MF3 phases were verified based on TG/DSC analysis and XRD measurements. The optical
properties of prepared Eu3+-doped samples were evaluated based on PLE and PL as well as
luminescence decay analysis of the 5D0 excited state. Obtained samples exhibit a series of the
5D0 → 7FJ (J = 1–4) emission bands, which were recorded within the reddish-orange spectral area
under near-UV illumination (λexc = 393 nm). Recorded luminescence spectra and double-exponential
character of decay curves for prepared glass-ceramic samples indicated the successful migration
of Eu3+ dopant ions from amorphous silica framework to low-phonon energy MF3 nanocrystal
phases
Sol-Gel Glass-Ceramic Materials Containing CaF2:Eu3+ Fluoride Nanocrystals for Reddish-Orange Photoluminescence Applications
CaF2:Eu3+ glass-ceramic sol-gel materials have been examined for reddish-orange
photoluminescence applications. The transformation from precursor xerogels to glass-ceramic materials
with dispersed fluoride nanocrystals was verified using several experimental methods: di erential
scanning calorimetry (DSC), thermogravimetric analysis (TG), X-ray di raction (XRD), transmission
electron microscopy (TEM), infrared spectroscopy (IR-ATR), energy dispersive X-ray spectroscopy
(EDS) and photoluminescence measurements. Based on luminescence spectra and their decays,
the optical behavior of Eu3+ ions in fabricated glass-ceramics were characterized and compared to
those of precursor xerogels. In particular, the determined luminescence lifetime of the 5D0 excited
state of Eu3+ ions in nanocrystalline CaF2:Eu3+ glass-ceramic materials is significantly prolonged
in comparison with prepared xerogels. The integrated intensities of emission bands associated
to the 5D0 ! 7F2 electric-dipole transition (ED) and the 5D0 !7F1 magnetic-dipole transition
(MD) are changed drastically during controlled ceramization process of xerogels. This implies the
e cient migration of Eu3+ ions from amorphous silicate sol-gel network into low-phonon energy
CaF2 nanocrystals
Studies of sol-gel evolution and distribution of Eu3+ ions in glassceramics containing LaF3 nanocrystals depending on initial sols composition
In this work, we performed a systematic analysis of the impact of selected chemical reagents
used in sol-gel synthesis (i.e., N,N-dimethylformamide) and different catalyst agents (i.e.,
CH3COOH, HNO3) on the formation and luminescence of Eu3+-doped SiO2–LaF3 nano-glass–ceramics.
Due to the characteristic nature of intra-configurational electronic transitions of Eu3+ ions within
the 4f6 manifold (5D0 → 7FJ, J = 0–4), they are frequently used as a spectral probe. Thus, the changes
in the photoluminescence profile of Eu3+ ions could identify the general tendency of rare earth materials
to segregate inside low-phonon energy fluoride nanocrystals, which allows us to assess their
application potential in optoelectronics. Fabricated sol-gel materials, from sols to gels and xerogels
to nano-glass–ceramics, were examined using several experimental techniques: X-ray diffraction
(XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR), and luminescence
measurements. It was found that the distribution of Eu3+ ions between the amorphous silicate solgel
host and LaF3 nanocrystals is strictly dependent on the initial composition of the obtained sols,
and the lack of N,N-dimethylformamide significantly promotes the segregation of Eu3+ ions inside
LaF3 nanocrystals. As a result, we detected long-lived luminescence from the 5D0 excited state equal
to 6.21 ms, which predisposes the obtained glass–ceramic material for use as an optical element in
reddish-orange emitting devices
Structural and photoluminescence investigations of Tb3+/Eu3+ codoped silicate sol-gel glass-ceramics containing CaF2 nanocrystals
In this work, the series of Tb3+/Eu3+ co-doped xerogels and derivative glass-ceramics
containing CaF2 nanocrystals were prepared and characterized. The in situ formation of fluoride
crystals was verified by an X-ray diffraction technique (XRD) and transmission electron microscopy
(TEM). The studies of the Tb3+/Eu3+ energy transfer (ET) process were performed based on excitation
and emission spectra along with luminescence decay analysis. According to emission spectra
recorded under near-ultraviolet (NUV) excitation (351 nm, 7F6 ! 5L9 transition of Tb3+), the mutual
coexistence of the 5D4 ! 7FJ (J = 6–3) (Tb3+) and the 5D0 ! 7FJ (J = 0–4) (Eu3+) luminescence bands
was clearly observed. The co-doping also resulted in gradual shortening of a lifetime from the
5D4 state of Tb3+ ions, and the ET efficiencies were varied from ET = 11.9% (Tb3+:Eu3+ = 1:0.5)
to ET = 22.9% (Tb3+:Eu3+ = 1:2) for xerogels, and from ET = 25.7% (Tb3+:Eu3+ = 1:0.5) up to
ET = 67.4% (Tb3+:Eu3+ = 1:2) for glass-ceramics. Performed decay analysis from the 5D0 (Eu3+) and
the 5D4 (Tb3+) state revealed a correlation with the change in Tb3+–Eu3+ and Eu3+–Eu3+ interionic
distances resulting from both the variable Tb3+:Eu3+ molar ratio and their partial segregation in CaF2
nanophase
Luminescence of SiO2-BaF2:Tb3+, Eu3+ nano-glass-ceramics made from sol-gel method at low temperature
The synthesis and characterization of multicolor light-emitting nanomaterials based on rare
earths (RE3+) are of great importance due to their possible use in optoelectronic devices, such as LEDs
or displays. In the present work, oxyfluoride glass-ceramics containing BaF2 nanocrystals co-doped
with Tb3+, Eu3+ ions were fabricated from amorphous xerogels at 350 C. The analysis of the thermal
behavior of fabricated xerogels was performed using TG/DSC measurements (thermogravimetry
(TG), differential scanning calorimetry (DSC)). The crystallization of BaF2 phase at the nanoscale was
confirmed by X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM),
and the changes in silicate sol–gel host were determined by attenuated total reflectance infrared
(ATR-IR) spectroscopy. The luminescent characterization of prepared sol–gel materials was carried
out by excitation and emission spectra along with decay analysis from the 5D4 level of Tb3+. As
a result, the visible light according to the electronic transitions of Tb3+ (5D4 ! 7FJ (J = 6–3)) and
Eu3+ (5D0 ! 7FJ (J = 0–4)) was recorded. It was also observed that co-doping with Eu3+ caused the
shortening in decay times of the 5D4 state from 1.11 ms to 0.88 ms (for xerogels) and from 6.56 ms
to 4.06 ms (for glass-ceramics). Thus, based on lifetime values, the Tb3+/Eu3+ energy transfer (ET)
efficiencies were estimated to be almost 21% for xerogels and 38% for nano-glass-ceramics. Therefore,
such materials could be successfully predisposed for laser technologies, spectral converters, and
three-dimensional displays
Long-lived emission from Eu3+:PbF2 nanocrystals distributed into sol-gel silica glass
This paper reports an optical investigation of Eu3+:PbF2 nanocrystals distributed into silica glasses fabricated by sol–gel methods. The sample microstructure was investigated using scanning transmission electron microscopy. The β-cubic PbF2 crystalline phase was identified using X-ray diffraction analysis. The observed emission bands correspond to 5D0 → 7FJ (J = 0–4) transitions of Eu3+. The spectroscopic parameters for Eu3+ ions were determined based on excitation and emission measurements as well as luminescence decay analysis. Emission originating from 5D0 state of Eu3+ ions in sample containing PbF2 nanocrystals is long-lived in comparison to precursor sol–gel silica glasses