Translucent, homogeneous, and monolithic gels of the (ZrO
2
)
0.92
(Y
2
O
3
)
0.08
1−x
(TiO
2
)
x
system, where x = 0, 0.05, 0.08, and x = 0.10 (mol), have been reliably obtained, for the first ...time, by a sol–gel route from zirconium (IV) n-propoxide (Zr(OPr
n
)
4
), yttrium acetate hydrate and titanium (IV) isopropoxide (Ti(OPr
i
)
4
). Chemical modification of both alkoxides, zirconium (IV) n-propoxide and titanium (IV) isopropoxide, by acetic acid allows us to change the hydrolysis and condensation behavior of them. Their modification implies the formation of chelating and bridging acetates avoiding the formation of precipitates. The line width and some shoulders in the FT-IR spectra of the solution, resulting of the mixture of the precursors and the catalysts, during the hydrolysis reaction suggest that both coordinations, chelating and bridging, should occur. Furthermore, the separation of the steps of hydrolysis and condensation allows to achieve conditions under which hydrolysis of the molecular precursor is slowed, whereas condensation is promoted under chemical reversibility to ensure a crystalline product at low calcination temperatures. In addition, the formation of metalloxane bondings (M–O–M’, M and M’ = Zr, Y, and Ti) has been confirmed by FT-IR throughout the sol–gel process. At about 630 °C, the crystallization of yttria stabilized zirconia (YSZ) for x = 0 or a titania-doped yttria stabilized zirconia solid solution (Ti-doped YSZ) for x = 0.05, 0.08, and 0.10 is detected by DTA-TG. By SEM-EDX and TEM-EDX the presence of Zr, Y, and Ti elements, in the adequate proportions according to the nominal compositions, has been proven in both dried and calcined gels.
•Dense YSZ has been obtained after sintering at 1350ºC in CO+N2/H2 or in CO2+air.•Reduced sample shows bands at 1298 and 1605 cm−1 corresponding to D and G bands of C, respectively.•ID/IG value is ...3.8 indicating a larger content of disordered carbon.•XPS showed that reduced samples contain N and C.•Sintering under CO2 +air causes a detrimental effect on YSZ conductivity.
Display omitted
Given the need to process anodes and composites based on nano-YSZ in reducing or in air containing additional CO2 atmospheres for the fabrication of solid oxide fuel cells (SOFCs), and solid oxide electrolysis cells (SOECs), we have studied the effect of the exposure to CO+N2/H2 or CO2+air mixtures during sintering of YSZ green pellets, prepared from commercial nanopowders, on their structure, microstructure, chemical composition and their electrical properties. The reduced sample shows Raman bands at 1298 and 1605 cm−1 that are assigned to the D and G bands of carbon, respectively. The bands intensity ratio ID/IG indicates a larger content of disordered carbon. X-ray photoelectron spectroscopy (XPS) shows that C is present in the reduced samples as reduced carbon. However, the samples sintered in CO2+air present C as carbonate-type. Impedance spectroscopy reveals that the highest total conductivity is for the reduced samples in the whole range of studied temperatures. In addition, sintering in CO2+air causes a detrimental effect on the grain boundary conductivity and therefore, on the total electrical conductivity of YSZ. It can be due to the presence of impurities such as carbonates and oxidised or even, polymerised carbonaceous species located at those areas.
In this work the colloidal behaviour of three different TiO
2 nanopowders in water is studied. A commercial powder of anatase and another of rutile were used for this study. For comparison purposes, ...a cryogel of anatase synthesised by a particulate sol–gel route and freeze-dried was also studied. All three powders were characterised by scanning electron microscopy, specific surface area measurements and X-ray diffraction. Diluted aqueous suspensions were prepared and characterised in terms of particle size distribution and zeta potential, using dynamic light scattering and laser Doppler velocimetry principles, respectively. All suspensions were prepared using an ultrasounds probe for mixing times ranging from 0 to 5
min. Colloidal stability was studied as a function of pH, type and concentration of dispersants (polyacrylic-based deflocculant and citric acid) and mixing time. Stable suspensions of commercial nanosized powders were obtained with polyelectrolyte contents of 1.0–1.5
wt.%. No stable suspensions of the cryogel were obtained with polyelectrolyte, requiring in this case the use of citric acid as deflocculant. It was observed that neither the size distribution nor the zeta potential values were affected by the sonication time.
The effect of textural characteristics and the degree of surface protonation of the pore wall on water uptake and proton conductivity in micro- and mesoporous SiO2 membranes, prepared by colloidal ...sol–gel route, has been studied. For that, some aspects of the pore structure of the xerogels have been modified by the control of the size and the packing process of the nanoparticles in the sol. In addition, the modification of the pH before gelation changes the degree of the surface protonation of the pore wall for the resulting xerogels. Pore volume (Pv), pore size (Ps), and specific surface area (SSA) have been evaluated with nitrogen sorption techniques. Water content and water adsorption isotherms were calculated using data from DTA-TG analysis. In addition, proton conductivity was measured using impedance spectroscopy under controlled temperature and relative humidity (RH).
At a given RH, membranes with the same water content showed differences in proton conductivity, then, water content is not the predominant variable controlling proton conductivity.
For instance, at low and intermediate RH values (33 and 58%), the membranes with the highest proton conductivity were the membranes with the largest water contents, the smallest average pore sizes, and the highest specific surface area/pore volume (SSA/Pv) ratio. In particular, the membranes with the smallest average pore size (2.2 nm), i.e., the xerogels obtained from sols adjusted to pH 5.0 showed proton conductivity values of more than two orders of magnitude than those with the largest pore sizes. At high RH (75, 81, and 97%) the xerogels with the highest proton conductivity were the xerogels with the largest water content, the largest average pore sizes, the lowest SSA/Pv ratio, and the highest connectivity. Xerogels adjusted to pH 6.0 and 8.0 present all of those characteristics and both have the same water content at those RH; however, the membranes adjusted to pH 6.0 present the highest proton conductivity. That membrane has the highest degree of surface protonation and the highest connectivity value, if we compare both. It is clear that the features of the pore network influence the structure of the pore water that consequently affects the mobility of the protons. It seems that the SSA/Pv ratio, the average pore size, and the connectivity are the textural properties of these materials, within those studied in this work, having the most influence on proton conductivity. Furthermore, the degree of surface protonation of the pore wall seems to have also an important influence on proton conductivity, at least at high RH. The highest value of proton conductivity found was 2.01 × 10−2 Scm−1 at 80 °C and 81% RH and corresponds to the membrane prepared from the sol adjusted to pH 6.0. In addition, proton conductivity showed an Arrhenius-like dependence on temperature in all cases and according to the activation energy values, proton migration is dominated by the Grotthuss mechanism at low and intermediate RH. At high RH the vehicle mechanism also occurs for the xerogels adjusted to pH 6.0 and 8.0 according to the low activation energy values found (0.08–0.13 eV).
The effect of textural characteristics and the degree of surface protonation of the pore wall on water uptake and proton conductivity in micro- and mesoporous SiO2 membranes, prepared by colloidal sol–gel route, has been studied. The figure shows the proton conductivity at 70 °C and the number of water molecules adsorbed per nm2 as a function of RH for the SiO2 membranes prepared. The dependence of the water adsorption uptake and the conductivity have a sigmoidal trend for both micro- and mesoporous materials, and according to the classification of proton conductors as a function of the water vapor partial pressure, the behavior of the silica xerogels is somewhere between an intrinsic (bulk conductor) and a surface conductor.
At a given RH, membranes with the same water content showed differences in proton conductivity, then, water content is not the predominant variable controlling proton conductivity. It seems that the SSA/Pv ratio, the average pore size, and the connectivity are the textural properties of these materials, within those studied in this work, having the most influence on proton conductivity. Furthermore, the degree of surface protonation of the pore wall seems to have also an important influence on proton conductivity, at least at high RH. Display omitted
•Effect of pore structure on water uptake and conductivity in SiO2 was studied.•The water content is not the prevailing variable controlling proton conductivity.•Network structure influences pore water structure that affects the proton mobility.•Surface protonation influences pore water structure that affects the proton mobility.•Proton conductivity showed an Arrhenius-like dependence on temperature in all cases.
Introduction
In hoarding disorder the patient has a strong tendency to collect and accumulate objects with or without value and great difficulty in destroying them.
In this case, a 58-year-old woman ...diagnosed with a hoarding disorder 5 years ago, came to a psychiatry clinic due to frequent auditory hallucinations related to episodes of acute stress. She received treatment in an outpatient mental health unit which consisted of psychopharmaceuticals and cognitive behavioural therapy. The patient achieved a partial remission of the hallucinations and a clinical improvement of the accumulation symptoms.
Objectives
The main objective of this study is to describe the psychiatric and psychological treatment of this patient. We also performed a review of the available literature on comorbidity of the symptoms of Diogenes syndrome and psychotic symptoms.
Methods
A close follow-up of the psychopathology of this patient was carried out and we did a database search in PubMed to document the case, with the keywords: “hoarding disorder”, “psychotic disorder”, “comorbidity”, “hallucination”, with the inclusion criteria: In the last ten years, Spanish and English language.
Results
The patient, who was being treated with sertraline 100 mg, started treatment with olanzapine 10 mg and with a psychotherapeutic plan with different objectives: stabilization of symptoms, reduction of hoarding behaviours, letting go of objects, as well as coping with stressful situations. Cognitive behavioural techniques such as psychoeducation, exposure with response prevention and cognitive therapy were included in the psychological treatment.
After one year of treatment the hallucinatory symptoms have remitted and the patient’s daily functioning has improved. The most resistant symptoms are those of accumulation that are slowly decreasing but the patient has stopped collecting objects from the street.
Conclusions
More studies of the treatment of hoarding disorder and more investigation of its possible comorbidities are needed.
Disclosure of Interest
None Declared
Tb-doped TiO2 hollow spheres (HSs) in the range 0.0–2.0 at.% have been synthesized by the first time to the best of our knowledge. The HSs are compared with nanoparticles (NPs) to evaluate the impact ...of morphology on their physicochemical and photoluminescence (PL) behavior upon increasing calcination temperature. After calcination at 550 °C, the particles are anatase with a primary average size of 10.0 ± 0.2 nm for the NPs and 12.0 ± 0.2 nm for those that form the micron sized hollow spheres of 1.8 ± 0.2 μm diameter and ca. 64 nm shell thickness. The temperature of the anatase–rutile transition is found to be strongly dependent on the presence of Tb as well as on morphology. Contrarily to the usual stabilization of anatase when doping with trivalent rare-earth ions, the transition temperature is reduced when doping with Tb. The rutile phase is further favored for the HSs compared to the NPs probably related to the low density of the HSs and/or a more efficient packing density and/or a bigger crystal size of the nanoparticles that form those spheres with respect to the packing and the size of the NPs and/or the crystal size of the nanoparticles of the HSs with respect to the size of the NPs. Only a slight unit-cell volume increase for the anatase structure is observed upon Tb doping, in both the NPs and in the HSs, contrary to the expected increment due to the larger ionic radius of Tb3+ compared to Ti4+. In addition, the intensity of the characteristic f-f Tb3+ emission bands is extremely weak both in the anatase and rutile phases. The transition is accompanied with the emergence of an infrared emission band centered at 810 nm related to the formation of defects during the structural transformation providing deep levels in the gap that partly quench the f-f emissions in the rutile phase. The results are consistent with the presence of Tb in both +3 and +4 valence states. XPS measurements confirmed the presence of Tb3+ as well as of Tb4+ in both HSs and NPs. The large fraction of Tb4+ present in the samples originates the weak f-f emission intensity, an only slight increase of the cell parameters and the destabilization of the anatase phase.
Display omitted
•Tb-doped TiO2 hollow spheres (HSs) have been synthesized by the first time.•The impact of Tb4+ and morphology on thermal evolution and photoluminescence properties are evaluated.•The temperature of the anatase–rutile transition is found to be strongly dependent on Tb as well as on morphology.•The transition is accompanied with emergence of deep levels that partly quench the f-f emissions.•The intensity of the f-f Tb3+ bands is consistent with the presence of Tb3+ and Tb4+.
In this study, a facile, cheap, scalable, and environmentally friendly method has been developed to prepare nanostructured TiO
2
coatings with a high catalytic activity. In addition, a protocol to ...characterize the prepared films in order to obtain consistent results between their texture, their structure, their microstructure, and their catalytic behavior has been established. For that, two types of TiO
2
coatings have been fabricated by applying once TiO
2
aqueous suspensions, prepared from commercial nanopowders, by immersion followed by an adequate thermal treatment. The first type of films is constituted by coatings with anatase as single phase, and the second one by films with a rutile molar fraction of
X
R
= 0.07 ± 0.02, determined from grazing incidence X-ray diffraction (GI-XRD) data. High spatial resolution chemical imaging, obtained by confocal Raman microscopy (CRM), of the surface and of the cross section for the films showed a good distribution of rutile without any segregation of this phase. Furthermore, high resolution electron microscopy (HREM) confirmed the presence of anatase/rutile biphasic domains in those areas in which both phases were previously found together by CRM. In addition, the catalytic data fit to a first-order kinetic model with high catalytic reaction constants (
k
′), especially when rutile is present. Furthermore, consistent results have been found in this study between the textural, structural, and microstructural studied features with the catalytic properties for the prepared TiO
2
films.
Nanoporous anatase thin films (see Figure) have been prepared via particulate sol–gel processes. The proton conductivity shows a sigmoidal dependence on relative humidity (RH). The highest value of ...proton conductivity was 3.78 × 10–2 S cm–1 at 80 °C and 81% RH. The comparable proton conductivity, lower cost, and higher hydrophilicity of these thin films make them potential substitutes for Nafion membranes in proton‐exchange membrane fuel cells.
Taking advantage of the fact that TiO
2 additions to 8YSZ cause not only the formation of a titania-doped YSZ solid solution but also a titania-doped YTZP solid solution, composite materials based on ...both solutions were prepared by solid state reaction. In particular, additions of 15
mol% of TiO
2 give rise to composite materials constituted by 0.51
mol fraction titania-doped yttria tetragonal zirconia polycrystalline and 0.49
mol fraction titania-doped yttria stabilized zirconia (0.51TiYTZP/0.49TiYSZ). Furthermore, Y
2(Ti
1−
y
Zr
y
)
2O
7 pyrochlore is present as an impurity phase with
y close to 1, according to FT-Raman results. Lower and higher additions of titania than that of 15
mol%, i.e.,
x=0, 5, 10, 20, 25 and 30
mol% were considered to study the evolution of 8YSZ phase as a function of the TiO
2 content. Furthermore, zirconium titanate phase (ZrTiO
4) is detected when the titania content is equal or higher than 20
mol% and this phase admits Y
2O
3 in solid solution according to FE-SEM-EDX.
The 0.51TiYTZP/0.49TiYSZ duplex material was selected in this study to establish the mechanism of its electronic conduction under low oxygen partial pressures. In the
pO
2 range from 0.21 to 10
−7.5
atm. the conductivity is predominantly ionic and constant over the range and its value is 0.01
S/cm. The ionic plus electronic conductivity is 0.02
S/cm at 1000
°C and 10
−12.3
atm. Furthermore, the onset of electronic conductivity under reducing conditions exhibits a −1/4
pO
2 dependence. Therefore, it is concluded that the n-type electronic conduction in the duplex material can be due to a small polaron-hopping between Ti
3+ and Ti
4+.
FE-SEM micrograph of a polished and thermal etched surface of a Ti-doped YTZP/Ti-doped YSZ composite material.
Display omitted
► Ti-doped YTZP/Ti-doped YSZ composite materials are mixed conductors under low partial pressures. ► From 5
mol% of TiO
2, Y
2(Ti
1−
y
,Zr
y
)
2O
7 pyrochlore is present as a minor phase, being
y close to 1 according to FT-Raman studies. ► The onset of the electronic conductivity under reducing conditions exhibit a −1/4
pO
2 dependence. The n-type electronic conduction is due to a small polaron-hopping between Ti
3+ and Ti
4+.
For the first time, mesoporous acid-free hematite ceramic membranes have been studied as proton conductors. These ceramic membranes were prepared via a sol–gel process assisted by microwaves. The ...xerogels after calcination at 300°C for 1h were mesoporous, as is mentioned above, with a BET surface area of 130±2m2g−1, an average pore diameter of 3.8nm and a pore volume of 0.149±0.001cm3g−1. The proton conductivity and the water uptake of the membranes were measured as a function of both temperature and relative humidity (RH). A sigmoidal dependence of the conductivity and the water uptake with the RH at a constant temperature was observed with the greatest increase detected between 58 and 81% RH. The conductivity of the ceramic membranes increased linearly with temperature (from room temperature to 90°C) for all relative humidities studied. The highest value of proton conductivity was found to be 2.76×10−3Scm−1 at 90°C and 81% RH. According to the activation energy values, proton migration in this kind of materials could be dominated by the Grotthuss mechanism in the whole range of RH. Although the values of the proton conductivity of the mesoporous hematite ceramic membranes are slightly lower than those of Nafion, the lower cost and higher hydrophilicity of these ceramic membranes make them potential substitutes for perfluorosulfonic polymeric membranes in proton exchange membrane (PEMFCs). In addition, the hematite ceramic membranes are not susceptible to deformation under sorption, desorption and, permeation of water unlike organic membranes. Furthermore, the ceramic membranes can be easily obtained as thinner as it is needed, whereas Nafion® 111 membranes, the thinnest ones, are about 25–50μm thick. Therefore, the actual ohmic resistance of such thin films would be lower in a given device. In addition, since hydrogen permeability values are in the range of 10−9 to 10−10mol(cmsPa)−1, in order to fabricate oxide-based PEMs that are capable of keeping streams of H2 and O2 from mixing, a separation layer with pore sizes <2nm whose pores are filled with water will be needed. Display omitted
► Mesoporous acid-free hematite ceramic membranes have been studied as proton conductors. ► The highest value of proton conductivity (Grotthuss mechanism) was found to be 2.76×10−3Scm−1 at 90°C and 81% RH. ► The lower cost and higher hydrophilicity of these ceramic membranes make them potential substitutes for perfluorosulfonic polymeric membranes in PEMFCs.
For the first time, mesoporous acid-free hematite ceramic membranes have been studied as proton conductors. The xerogels after calcination at 300°C for 1h were mesoporous, as is mentioned above, with a BET surface area of 130±2m2g−1, an average pore diameter of 3.8nm and a pore volume of 0.149±0.001ccg−1. A sigmoidal dependence of the conductivity and the water uptake with the RH at a constant temperature was observed. The conductivity of the ceramic membranes increased linearly with temperature for all relative humidities studied. The highest value of proton conductivity was found to be 2.76×10−3Scm−1 at 90°C and 81% RH. According to the activation energy values, proton migration in this kind of materials could be dominated by the Grotthuss mechanism in the whole range of RH. The low cost and high hydrophilicity of these ceramic membranes make them potential substitutes for perfluorosulfonic polymeric membranes in proton exchange membrane (PEMFCs). In addition, since hydrogen permeability values are in the range of 10−9 to 10−10molcm−1sPa, in order to fabricate oxide-based PEMs that are capable of keeping streams of H2 and O2 from mixing, a separation layer with pore sizes <2nm whose pores are filled with water will be needed.
PDF
