[Preparation and photocatalytic activity of boron doped CeO2/TiO2 mixed oxides].

PubMed

Tang, Xin-hu; Wei, Chao-hai; Liang, Jie-rong; Wang, Bo-guang

2006-07-01

Boron doped CeO2/TiO2 mixed oxides photocatalysts were prepared by adding boric acid and cerous nitrate during the hydrolyzation of titanium trichloride and tetrabutyl titanate. XRD, UV-Vis DRS and XPS techniques were used to characterize the crystalline structure, light absorbing ability and the chemical state of Boron element in the photocatalyst sample. The photocatalytic activities were evaluated by monitoring the degradation of acid red B under UV irradiation. These results indicate that the wavelengths at adsorbing edge are affected by the content of cerous nitrate and the maximum absorption wavelength is about 481 nm when the mole ratio of Ce/Ti is 1.0. For higher dosage of Cerium, the absorbance edge shifts to blue slightly. The prepared photocatalyst is composed of anatase TiO2 and cubic CeO2 when calcined at 500 degrees C. An increase in the calcination temperature transforms the crystalline structure of the titanium oxides from anatase to rutile, and has no obvious influence on crystalline structure of CeO2 but crystallites growth up. The absorbance edge decreases drastically with the increase of calcination temperature. With a view to the stability of photocatalyst and utilization of sun energy, 500 degrees C of calcination temperature is recommended. The XP spectrum for B1s exhibits that only a few boron ions dope into titania and ceria matrix, others exist in B2O3. The photocatalytic activity increases with increase of cerous nitrate dosage, and decreases drastically due to higher dosage (the mol ratio of Ce/Ti > 0.5). After 10 min UV irradiation, 96% of acid red B is degraded completely over photocatalyst under optimum reaction condition.

Towards understanding the electronic structure of Fe-doped CeO2 nanoparticles with X-ray spectroscopy.

PubMed

Wang, Wei-Cheng; Chen, Shih-Yun; Glans, Per-Anders; Guo, Jinghua; Chen, Ren-Jie; Fong, Kang-Wei; Chen, Chi-Liang; Gloter, Alexandre; Chang, Ching-Lin; Chan, Ting-Shan; Chen, Jin-Ming; Lee, Jyh-Fu; Dong, Chung-Li

2013-09-21

This study reports on the electronic structure of Fe-doped CeO2 nanoparticles (NPs), determined by coupled X-ray absorption spectroscopy and X-ray emission spectroscopy. A comparison of the local electronic structure around the Ce site with that around the Fe site indicates that the Fe substitutes for the Ce. The oxygen K-edge spectra that originated from the hybridization between cerium 4f and oxygen 2p states are sensitive to the oxidation state and depend strongly on the concentration of Fe doping. The Ce M(4,5)-edges and the Fe L(2,3)-edges reveal the variations of the charge states of Ce and Fe upon doping, respectively. The band gap is further obtained from the combined absorption-emission spectrum and decreased upon Fe doping, implying Fe doping introduces vacancies. The oxygen vacancies are induced by Fe doping and the spectrum reveals the charge transfer between Fe and Ce. Fe(3+) doping has two major effects on the formation of ferromagnetism in CeO2 nanoparticles. The first, at an Fe content of below 5%, is that the formation of Fe(3+)-Vo-Ce(3+) introduces oxygen deficiencies favoring ferromagnetism. The other, at an Fe content of over 5%, is the formation of Fe(3+)-Vo-Fe(3+), which favors antiferromagnetism, reducing the Ms. The defect structures Fe(3+)-Vo-Ce(3+) and Fe(3+)-Vo-Fe(3+) are crucial to the magnetism in these NPs and the change in Ms can be described as the effect of competitive interactions of magnetic polarons and paired ions.

Bioactivity of Y2O3 and CeO2 doped SiO2-SrO-Na2O glass-ceramics.

PubMed

Placek, L M; Keenan, T J; Wren, A W

2016-08-01

The bioactivity of yttrium and cerium are investigated when substituted for Sodium (Na) in a 0.52SiO2-0.24SrO-0.24-xNa2O-xMO glass-ceramics (where x = 0.08 and MO = Y2O3 or CeO2). Bioactivity is monitored through pH and inductively coupled plasma-optical emission spectrometry where pH of simulated body fluid ranged from 7.5 to 7.6 and increased between 8.2 and 10.0 after 14-day incubation with the glass-ceramic disks. Calcium (Ca) and phosphorus (P) levels in simulated body fluid after incubation with yttrium and cerium containing disks show a continual decline over the 14-day period. In contrast, Con disks (not containing yttrium or cerium) caused the elimination of Ca in solution after 1 day and throughout the incubation period, and initially showed a decline in P levels followed by an increase at 14 days. Scanning electron microscopy and energy dispersive spectroscopy confirmed the presence of Ca and P on the surface of the simulated body fluid-incubated disks and showed precipitates on Con and HCe (8 mol% cerium) samples. Cell viability of MC3T3 osteoblasts was not significantly affected at a 9% extract concentration. Optical microscopy after 24 h cell incubation with disks showed that Con samples do not support osteoblast or Schwann cell growth, while all yttrium and cerium containing disks have direct contact with osteoblasts spread across the wells. Schwann cells attached in all wells, but only showed spreading with the HY-S (8 mol% yttrium, heated to sintering temperature) and YCe (4 mol% yttrium and cerium) disks. Scanning electron microscopy of the compatible disks shows osteoblast and sNF96.2 Schwann cells attachment and spreading directly on the disk surfaces. © The Author(s) 2016.

Magnetism mediated by a majority of [Fe3+ + \\mathbf{V}_{\\mathbf{O}}^{\\mathbf{2-}} ] complexes in Fe-doped CeO2 nanoparticles

NASA Astrophysics Data System (ADS)

Paidi, V. K.; Ferreira, N. S.; Goltz, D.; van Lierop, J.

2015-08-01

We examine the role of Fe3+ and vacancies ({{V}\\text{O}} ) on the magnetism of Fe-doped CeO2 nanoparticles. Magnetic nanoparticles of Ce100-xFexO2 (x  =  0, 0.26, 1.82, 2.64, 5.26, 6.91, and 7.22) were prepared by a co-precipitation method, and their structural, compositional and magnetic properties were investigated. The CeO2 nanoparticles had a mixed valance of Ce4+ and Ce3+ ions, and doping introduced Fe3+ ions. The decrease in Ce3+ and increase in Fe3+ concentrations indicated the presence of more [Fe3+ +V\\text{O}2- ] complexes with Fe loading in the particles. Charge neutralization, Fe3+ + V\\text{O}2- + 2Ce4+ ≤ftrightarrow 2Ce3+ + Fe3+, identified the impact of {{V}\\text{O}} on the magnetism, where our results suggest that the Fe-doped CeO2 nanoparticle magnetism is mediated by a majority of [Fe3+ +V\\text{O}2- ]—Ce3+ —[Fe3+ +V\\text{O}2- ] complexes.

Effect of CeO2 and Y2O3 on microstructure, bioactivity and degradability of laser cladding CaO-SiO2 coating on titanium alloy.

PubMed

Li, H C; Wang, D G; Chen, C Z; Weng, F

2015-03-01

To solve the lack of strength of bulk biomaterials for load-bearing applications and improve the bioactivity of titanium alloy (Ti-6Al-4V), CaO-SiO2 coatings on titanium alloy were fabricated by laser cladding technique. The effect of CeO2 and Y2O3 on microstructure and properties of laser cladding coating was analyzed. The cross-section microstructure of ceramic layer from top to bottom gradually changes from cellular-dendrite structure to compact cellular crystal. The addition of CeO2 or Y2O3 refines the microstructure of the ceramic layer in the upper and middle regions. The refining effect on the grain is related to the kinds of additives and their content. The coating is mainly composed of CaTiO3, CaO, α-Ca2(SiO4), SiO2 and TiO2. Y2O3 inhibits the formation of CaO. After soaking in simulated body fluid (SBF), the calcium phosphate layer is formed on the coating surface, indicating the coating has bioactivity. After soaking in Tris-HCl solution, the samples doped with CeO2 or Y2O3 present a lower weight loss, indicating the addition of CeO2 or Y2O3 improves the degradability of laser cladding sample. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Doping on Surface Reactivity and Conduction Mechanism in Sm-doped CeO2 Thin Films

DOE PAGES

Yang, Nan; Belianinov, Alex; Strelcov, Evgheni; ...

2014-11-21

Scanning probe microscopy measurements show irreversible surface electrochemistry in Sm-doped CeO2 thin films, which depends on humidity, temperature and doping concentration. A systematic study by electrochemical strain microscopy (ESM) in samples with two different Sm content and in several working conditions allows disclosing the microscopic mechanism underlying the difference in water adsorption and splitting with subsequent proton liberation. We measure the behavior of the hysteresis loops by changing temperature and humidity, both in standard ESM configuration and using the first order reversal curve (FORC) method. Complementing our study with spectroscopic measurements by hard x-ray photoemission spectroscopy we find that watermore » incorporation is favored until the doping with Sm is too high to allow the presence of Ce3+. The influence of doping on the surface reactivity and conduction mechanism clearly emerges from all of our experimental results. We find that at lower Sm concentration proton conduction is prevalent, featured by lower activation energy and higher mobility. Defect concentrations determine the type of the prevalent charge carrier in a doping dependent manner.« less

Synthesis, characterization of CaF2 doped silicate glass-ceramics.

PubMed

Riaz, Madeeha; Zia, Rehana; Mirza, Ambreen; Hussain, Tousif; Bashir, Farooq; Anjum, Safia

2017-06-01

This paper reports the fabrication and characterization of silicate glass-ceramics doped with (0-12mol%) CaF 2 . TGA-DSC analysis was carried out to determine the crystallization temperature and stability of glass measured by two glass parameters; Hruby parameter K H =(T x -T g )/(T L -T x ) and Weinberg parameter K W =(T c -T g )/T L . It was found that with CaF 2 doping improved sinterability at low temperature and provided stability to the glass. The XRD pattern exhibits a single phase of combeite and doping of CaF 2 cause increase in crystallite size. Microstructure of samples was also improved with CaF 2 addition, pores were significantly reduced. After 15days immersion in simulated body fluid all samples developed apatite layer onto its surface. Hence, the addition of CaF 2 provided bioactive glass-ceramic material having a low processing temperature. Copyright © 2017 Elsevier B.V. All rights reserved.

Microstructure and dielectric properties of (Nb + In) co-doped rutile TiO2 ceramics

NASA Astrophysics Data System (ADS)

Li, Jinglei; Li, Fei; Zhuang, Yongyong; Jin, Li; Wang, Linghang; Wei, Xiaoyong; Xu, Zhuo; Zhang, Shujun

2014-08-01

The (Nb + In) co-doped TiO2 ceramics recently attracted considerable attention due to their colossal dielectric permittivity (CP) (˜100,000) and low dielectric loss (˜0.05). In this research, the 0.5 mol. % In-only, 0.5 mol. % Nb-only, and 0.5-7 mol. % (Nb + In) co-doped TiO2 ceramics were synthesized by standard conventional solid-state reaction method. Microstructure studies showed that all samples were in pure rutile phase. The Nb and In ions were homogeneously distributed in the grain and grain boundary. Impedance spectroscopy and I-V behavior analysis demonstrated that the ceramics may compose of semiconducting grains and insulating grain boundaries. The high conductivity of grain was associated with the reduction of Ti4+ ions to Ti3+ ions, while the migration of oxygen vacancy may account for the conductivity of grain boundary. The effects of annealing treatment and bias filed on electrical properties were investigated for co-doped TiO2 ceramics, where the electric behaviors of samples were found to be susceptible to the annealing treatment and bias field. The internal-barrier-layer-capacitance mechanism was used to explain the CP phenomenon, the effect of annealing treatment and nonlinear I-V behavior for co-doped rutile TiO2 ceramics. Compared with CaCu3Ti4O12 ceramics, the high activation energy of co-doped rutile TiO2 (3.05 eV for grain boundary) was thought to be responsible for the low dielectric loss.

Defect Complex Effect in Nb Doped TiO2 Ceramics with Colossal Permittivity

NASA Astrophysics Data System (ADS)

Li, Fuchao; Shang, Baoqiang; Liang, Pengfei; Wei, Lingling; Yang, Zupei

2016-10-01

Donor-doped Nb x Ti1- x O2 ( x = 1%, 2%, 4%, 6%, and 8%) ceramics with giant permittivity (>104) and a very low dielectric loss (˜0.05) were sintered under flowing N2 at 1400°C for 10 h. By increasing Nb doping concentration, two different dielectric responses were evidenced in the frequency dependence of dielectric properties of Nb doped TiO2 ceramics, which corresponded to the space charge polarization and the electron-pinned defect-dipoles effect, respectively. Especially, combined with the x-ray photoelectron spectroscopy results, the electron-pinned defect-dipoles induced by the 2({Nb}^{5 + } )_{{Ti}}^{ bullet } to 4({Ti}^{3 + } )^'_{{Ti}} leftarrow {V}_{{o}}^{ bullet bullet } defect complex were further confirmed to give rise to both their high ɛr and low tan δ in the high frequency range for the Nb x Ti1- x O2 ceramics with x > 4%.

The influence of co-sintering Bi2O3 on Yb0.2Ce0.8O2-δ ceramic SOFC

NASA Astrophysics Data System (ADS)

Budiana, B.; Suasmoro, S.

2017-01-01

Ceramic Yb-doped CeO2 were prepared through two ways. First, sintering of mixed 20 mol % Yb2O3 and 80 mol % CeO2 at 1350 °C for 20 h and second sintering of mixed 96 mol % calcined Yb-doped CeO2 with 4 mol % Bi2O3 as a co-sintering agent at 1100 °C for 8h. Phase identification revealed that for the first sample was a cubic phase (a=5,3939Å) while the second sample showed three phases, CeO2 (cubic a=5,4254Å), YbxCe1-xO2-δ (cubic a=5,3980Å) and Bi5Yb3O12 (cubic a=10,5343Å). Cole-cole plot of impedance revealed 3 semicircles as marked of grain, grain boundary and electrode responses for B1 while for B2 showed two semicircles as marked of grain, grain boundary+electrode responses. Plot of log (σt) versus 1/T for both samples possed 2 activation energy regime, for the Sample B1 at T>650 °C Ea grain =1,01±0,04 eV and T<650 °C Ea grain =0,76±0,06 eV while for the sample B2 at T>650 °C, Ea grain =0,99±0,03 eV and T<650 °C Ea grain=0,70±0,09 eV.

Research and Development of High Energy 2 - Micron Lasers Based on TM: Doped Ceramic Laser Gain Media and TM: Doped Optical Fibers

DTIC Science & Technology

2016-07-20

AFRL-AFOSR-VA-TR-2016-0257 RESEARCH AND DEVELOPMENT OF HIGH ENERGY 2 - MICRON LASERS BASED ON TM: DOPED CERAMIC LASER GAIN MEDIA AND TM: DOPED...2010 to 01/03/2016 4. TITLE AND SUBTITLE RESEARCH AND DEVELOPMENT OF HIGH ENERGY 2 - MICRON LASERS BASED ON TM: DOPED CERAMIC LASER GAIN MEDIA AND...NOTES 14. ABSTRACT Our research and development of 2-μm femtosecond lasers has included development of mode-locked Tm:fiber lasers , super-continuum

Tuning the hybridization and magnetic ground state of electron and hole doped CeOs2Al10 : An x-ray spectroscopy study

NASA Astrophysics Data System (ADS)

Chen, Kai; Sundermann, Martin; Strigari, Fabio; Kawabata, Jo; Takabatake, Toshiro; Tanaka, Arata; Bencok, Peter; Choueikani, Fadi; Severing, Andrea

2018-04-01

Here we present linear and circular polarized soft x-ray absorption spectroscopy (XAS) data at the Ce M4 ,5 edges of the electron (Ir) and hole-doped (Re) Kondo semiconductor CeOs2Al10 . Both substitutions have a strong impact on the unusual high Néel temperature TN=28.5 K, and also the direction of the ordered moment in case of Ir. The substitution dependence of the linear dichroism is weak thus validating the crystal-field description of CeOs2Al10 being representative for the Re and Ir substituted compounds. The impact of electron and hole doping on the hybridization between conduction and 4 f electrons is related to the amount of f0 in the ground state and reduction of x-ray magnetic circular dichroism. A relationship of c f -hybridization strength and enhanced TN is discussed. The direction and doping dependence of the circular dichroism strongly supports the idea of strong Kondo screening along the crystallographic a direction.

Third order nonlinear optical properties of Mn doped CeO2 nanostructures

NASA Astrophysics Data System (ADS)

Mani Rahulan, K.; Angeline Little Flower, N.; Annie Sujatha, R.; Mohana Priya, P.; Gopalakrishnan, C.

2018-05-01

Mn doped CeO2 nanoparticles with different ratios of Mn were synthesized by hydrothermal method and their structural properties were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). XRD patterns revealed that the peaks are highly crystalline structure with no segregation of Mn. The surface morphology from SEM reveals that particle size decreases with increase in Mn concentration. Nonlinear optical studies of the samples were measured by single-beam open aperture Z-scan technique using 5 ns laser pulses at 532 nm. The measured optical nonlinearity of all the samples exhibit typical third order nonlinear optical behavior including two-photon absorption (2 PA) and reverse saturable absorption (RSA). The experimental results show that the presence of RSA in these nanoparticles makes them a promising material for the fabrication of optical limiting devices. .

Effect of Ge-GeO2 co-doping on non-ohmic behaviour of TiO2-V2O5-Y2O3 varistor ceramics

NASA Astrophysics Data System (ADS)

Kunyong, Kang; Guoyou, Gan; Jikang, Yan; Jianhong, Yi; Jiamin, Zhang; Jinghong, Du; Wenchao, Zhao; Xuequan, Rong

2015-07-01

An investigation was made into the effect of doping with the elemental crystal Ge or/and GeO2 on the TiO2-V2O5-Y2O3 varistor ceramics. The result shows that as the doping contents of V2O5 and Y2O3 are 0.5 mol%, respectively, co-doping with 0.3 mol% Ge and 0.9 mol% GeO2 makes the highest α value (α = 12.8), the lowest breakdown voltage V1mA (V1mA = 15.8 V/mm) and the highest grain boundary barrier ΦB (ΦB = 1.48 eV), which is remarkably superior to the TiO2-V2O5-Y2O3 varistor ceramics undoped with Ge and GeO2 and mono-doped with Ge or GeO2. The TiO2-V2O5-Y2O3-Ge-GeO2 ceramic has the prospect of becoming a novel varistor ceramic with excellent electrical properties. Project supported by the National Natural Science Foundation of China (Nos. 51262017, 51362017).

Dielectric and piezoelectric properties of CeO2-added nonstoichiometric (Na0.5K0.5)0.97(Nb0.96Sb0.04)O3 ceramics for piezoelectric energy harvesting device applications.

PubMed

Oh, Youngkwang; Noh, Jungrae; Yoo, Juhyun; Kang, Jinhee; Hwang, Larkhoon; Hong, Jaeil

2011-09-01

In this study, nonstoichiometric (Na(0.5)K(0.5))(0.97)(Nb(0.96)Sb(0.04))O(3) ceramics were fabricated and their dielectric and piezoelectric properties were investigated according to the CeO(2) addition. In this ceramic composition, CeO(2) addition improved sinterability, electromechanical coupling factor k(p), mechanical quality factor Q(m), piezoelectric constant d(33), and g(33). At the sintering temperature of 1100°C, for the 0.2wt% CeO(2) added specimen, the optimum values of density = 4.359 g/cm(3), k(p) = 0.443, Q(m) = 588, ε(r) = 444, d(33) = 159 pC/N, and g(33) = 35 × 10(-3) V·m/N, were obtained. A piezoelectric energy harvesting device using 0.2 wt% CeO(2)- added lead-free (K(0.5)Na(0.5))(0.97)(Nb(0.96)Sb(0.04))O(3) ceramics and a rectifying circuit for energy harvesting were fabricated and their electrical characteristics were investigated. Under an external vibration acceleration of 0.7 g, when the mass, the frequency of vibration generator, and matching load resistance were 2.4 g, 70 Hz, and 721 Ω, respectively, output voltage and power of piezoelectric harvesting device indicated the optimum values of 24.6 mV(rms) and 0.839 μW, respectively-suitable for application as the electric power source of a ubiquitous sensor network (USN) sensor node.

Interplay of dopant, defects and electronic structure in driving ferromagnetism in Co-doped oxides: TiO(2), CeO(2) and ZnO.

PubMed

Ali, Bakhtyar; Shah, Lubna R; Ni, C; Xiao, J Q; Shah, S Ismat

2009-11-11

A comprehensive study of the defects and impurity (Co)-driven ferromagnetism is undertaken in the oxide semiconductors: TiO(2), ZnO and CeO(2). The effect of magnetic (Co(2+)) and non-magnetic (Cu(2+)) impurities in conjunction with defects, such as oxygen vacancies (V(o)), have been thoroughly investigated. Analyses of the x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) data reveal the incorporation of cobalt in the lattice, with no signature of cobalt segregation. It is shown that oxygen vacancies are necessary for the ferromagnetic coupling in the Co-doped oxides mentioned above. The possible exchange mechanisms responsible for the ferromagnetism are discussed in light of the energy levels of dopants in the host oxides. In addition, Co and Cu co-doped TiO(2) samples are studied in order to understand the role of point defects in establishing room temperature ferromagnetism. The parameters calculated from the bound magnetic polaron (BMP) and Jorgensen's optical electronegativity models offer a satisfactory explanation of the defect-driven ferromagnetism in the doped/co-doped samples.

Recent Progress in the Development of Neodymium Doped Ceramic Yttria

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Edwards, Chris; Trivedi, Sudhir B.; Kutcher, Susan; Wang, Chen-Chia; Kim, Joo-Soo; Hommerich, Uwe; Shukla, Vijay; Sadangi, Rajendra; Kear, Bernard

2007-01-01

Solid-state lasers play a significant role in providing the technology necessary for active remote sensing of the atmosphere. Neodymium doped yttria (Nd:Y2O3) is considered to be an attractive material due to its possible lasing wavelengths of aprrox.914 nm and approx.946 nm for ozone profiling. These wavelengths when frequency tripled can generate UV light at approx.305 nm and approx.315 nm, which is particularly useful for ozone sensing using differential absorption lidar technique. For practical realization of space based UV transmitter technology, ceramic Nd:Y2O3 material is considered to possess great potential. A plasma melting and quenching method has been developed to produce Nd3+ doped powders for consolidation into Nd:Y2O3 ceramic laser materials. This far-from-equilibrium processing methodology allows higher levels of rare earth doping than can be achieved by equilibrium methods. The method comprises of two main steps: (a) plasma melting and quenching to generate dense, and homogeneous doped metastable powders, (b) pressure assisted consolidation of these powders by hot isostatic pressing to make dense nanocomposite ceramics. Using this process, several 1" x 1" ceramic cylinders have been produced. The infrared transmission of undoped Y2O3 ceramics was as high as approx.75% without anti-reflection coating. In the case of Nd:Y2O3 ceramics infrared transmission values of approx.50% were achieved. Furthermore, Nd:Y2O3 samples with dopant concentrations of up to approx.2 at. % were prepared without significant emission quenching.

An insight into the dopant selection for CeO2-based resistive-switching memory system: a DFT and experimental study

NASA Astrophysics Data System (ADS)

Hussain, Fayyaz; Imran, Muhammad; Rana, Anwar Manzoor; Khalil, R. M. Arif; Khera, Ejaz Ahmad; Kiran, Saira; Javid, M. Arshad; Sattar, M. Atif; Ismail, Muhammad

2018-03-01

The aim of this study is to figure out better metal dopants for CeO2 for designing highly efficient non-volatile memory (NVM) devices. The present DFT work involves four different metals doped interstitially and substitutionally in CeO2 thin films. First principle calculations involve electron density of states (DOS) and partial density of states (PDOS), and isosurface charge densities are carried out within the plane-wave density functional theory using GGA and GGA + U approach by employing the Vienna ab initio simulation package VASP. Isosurface charge density plots confirmed that interstitial doping of Zr and Ti metals truly assists in generating conduction filaments (CFs), while substitutional doping of these metals cannot do so. Substitutional doping of W may contribute in generating CFs in CeO2 directly, but its interstitial doping improves conductivity of CeO2. However, Ni-dopant is capable of directly generating CFs both as substitutional and interstitial dopants in ceria. Such a capability of Ni appears acting as top electrode in Ni/CeO2/Pt memory devices, but its RS behavior is not so good. On inserting Zr layer to make Ni/Zr:CeO2/Pt memory stacks, Ni does not contribute in RS characteristics, but Zr plays a vital role in forming CFs by creating oxygen vacancies and forming ZrO2 interfacial layer. Therefore, Zr-doped devices exhibit high-resistance ratio of 104 and good endurance as compared to undoped devices suitable for RRAM applications.

ROS mediated malignancy cure performance of morphological, optical, and electrically tuned Sn doped CeO2 nanostructures

NASA Astrophysics Data System (ADS)

Abbas, Fazal; Iqbal, Javed; Maqbool, Qaisar; Jan, Tariq; Ullah, Muhammad Obaid; Nawaz, Bushra; Nazar, Mudassar; Naqvi, M. S. Hussain; Ahmad, Ishaq

2017-09-01

To grapple with cancer, implementation of differentially cytotoxic nanomedicines have gained prime attention of the researchers across the globe. Now, ceria (CeO2) at nanoscale has emerged as a cut out therapeutic agent for malignancy treatment. Keeping this in view, we have fabricated SnxCe1-xO2 nanostructures by facile, eco-friendly, and biocompatible hydrothermal method. Structural examinations via XRD and FT-IR spectroscopy have revealed single phase cubic-fluorite morphology while SEM analysis has depicted particle size ranging 30-50nm for pristine and doped nanostructures. UV-Vis spectroscopy investigation explored that Sn doping significantly tuned the band gap (eV) energies of SnxCe1-xO2 nanostructures which set up the base for tremendous cellular reactive oxygen species (ROS) generations involved in cancer cells' death. To observe cytotoxicity, synthesized nanostructures were found selectively more toxic to neuroblastoma cell lines as compared to HEK-293 healthy cells. This study anticipates that SnxCe1-xO2 nanostructures, in future, might be used as nanomedicine for safer cancer therapy.

Doped sesquioxide ceramic for eye-safe solid state laser materials

NASA Astrophysics Data System (ADS)

Kim, Woohong; Baker, Colin; Florea, Catalin; Frantz, Jesse; Villalobos, Guillermo; Shaw, Brandon; Bowman, Steve; O'Connor, Shawn; Sadowski, Bryan; Hunt, Michael; Aggalwar, Ishwar; Sanghera, Jasbinder

2013-03-01

In this paper, we present our recent results in the development of Ho3+ doped sesquioxides for eye-safe solid state lasers. We have synthesized optical quality Lu2O3 nanopowders doped with concentrations of 0.1, 1.0, 2.0, and 5% Ho3+. The powders were synthesized by a co-precipitation method beginning with nitrates of holmium and lutetium. The nanopowders were hot pressed into optical quality ceramic discs. The optical transmission of the ceramic discs is excellent, nearly approaching the theoretical limit. The optical, spectral and morphological properties as well as the lasing performance from highly transparent ceramics are presented.

Regulating the active species of Ni(OH)2 using CeO2: 3D CeO2/Ni(OH)2/carbon foam as an efficient electrode for the oxygen evolution reaction.

PubMed

Liu, Zhengqing; Li, Na; Zhao, Hongyang; Zhang, Yi; Huang, Yunhui; Yin, Zongyou; Du, Yaping

2017-04-01

Three dimensional (3D) N, O and S doped carbon foam (NOSCF) is prepared as a substrate for in situ vertically grown Ni(OH) 2 nanosheets. As designed Ni(OH) 2 /NOSCF possesses strong electrostatic interactions with OH - ions due to many C 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 O groups existing in NOSCF, which can facilitate the formation of crucial NiOOH intermediates during the OER process. CeO 2 nanoparticles (NPs) of ∼3.3 nm in size are decorated on Ni(OH) 2 nanosheets to design a highly efficient CeO 2 /Ni(OH) 2 /NOSCF electrocatalyst for the oxygen evolution reaction (OER). The CeO 2 NP decorated Ni(OH) 2 /NOSCF not only exhibits a remarkably improved OER performance with an onset potential of 240 mV, outperforming most reported non-noble metal based OER electrocatalysts, but also possesses a small Tafel slope of 57 mV dec -1 and

Colossal dielectric permittivity in (Al + Nb) co-doped rutile SnO2 ceramics with low loss at room temperature

NASA Astrophysics Data System (ADS)

Song, Yongli; Wang, Xianjie; Zhang, Xingquan; Qi, Xudong; Liu, Zhiguo; Zhang, Lingli; Zhang, Yu; Wang, Yang; Sui, Yu; Song, Bo

2016-10-01

The exploration of colossal dielectric permittivity (CP) materials with low dielectric loss in a wide range of frequencies/temperatures continues to attract considerable interest. In this paper, we report CP in (Al + Nb) co-doped rutile SnO2 ceramics with a low dielectric loss at room temperature. Al0.02Nb0.05Sn0.93O2 and Al0.03Nb0.05Sn0.92O2 ceramics exhibit high relative dielectric permittivities (above 103) and low dielectric losses (0.015 < tan δ < 0.1) in a wide range of frequencies and at temperatures from 140 to 400 K. Al doping can effectively modulate the dielectric behavior by increasing the grain and grain boundary resistances. The large differences in the resistance and conductive activation energy of the grains and grain boundaries suggest that the CP in co-doped SnO2 ceramics can be attributed to the internal barrier layer capacitor effect.

In vitro bioactivity behavior of modified multicomponent borate glasses containing dopants of Ag2O, CuO, CeO2 or V2O5

NASA Astrophysics Data System (ADS)

Marzouk, M. A.; ElBatal, F. H.; Ghoneim, N. A.

2018-02-01

Some multi-component borate glasses containing dopants of Ag2O, CuO, CeO2 or V2O5 were prepared. Multi-characterization techniques were carried out to investigate their bioactivity, corrosion weight loss after immersion in phosphate solution. Controlled thermal heat-treatment by two-step technique was done to convert the prepared glasses to their corresponding glass-ceramic derivatives. X-ray diffraction analysis was performed to identify the crystalline phases formed by thermal treatment. Infrared absorption of glasses and glass-ceramics reveal vibrational bands due to combined main triangular and tetrahedral borate groups in their specific wavenumbers besides some sharing of phosphate group. After immersion in the phosphate solution, two extra characteristic peaks are generated indicating the bioactivity of the studied glasses and glass-ceramics through the formation of calcium phosphate (hydroxyapatite). X-ray diffraction data indicate the formation of crystalline phases which are variable with the introduced dopants. The main crystalline phase identified is calcium borate together with some other phases some of which contain phosphate ions. These data indicate that the presence of CaO and P2O5 initiates phase separation and subsequent crystallization of the parent and doped glasses. Weight loss data indicate that glass-ceramics are obviously durable than the parent glasses. SEM micrographs of glass-ceramics before immersion show multiconstituent crystalline phases due to the basic chemical composition consisting of multicomponent mixed alkali and alkaline earth oxides beside P2O5 and with the main B2O3 constituent. After immersion, the crystalline phases are identified to be more distinct in different shapes because of the multi-composition involved.

Influence of rare earth doping on thermoelectric properties of SrTiO3 ceramics

NASA Astrophysics Data System (ADS)

Liu, J.; Wang, C. L.; Li, Y.; Su, W. B.; Zhu, Y. H.; Li, J. C.; Mei, L. M.

2013-12-01

Thermoelectric properties of SrTiO3 ceramics, doped with different rare earth elements, were investigated in this work. It's found that the ionic radius of doping elements plays an important role on thermoelectric properties: SrTiO3 ceramics doped with large rare earth ions (such as La, Nd, and Sm) exhibit large power factors, and those doped with small ions (such as Gd, Dy, Er, and Y) exhibit low thermal conductivities. Therefore, a simple approach for enhancing the thermoelectric performance of SrTiO3 ceramics is proposed: mainly doped with large ions to obtain a large power factor and, simultaneously, slightly co-doped with small ions to obtain a low thermal conductivity. Based on this rule, Sr0.8La0.18Yb0.02TiO3 ceramics were prepared, whose ZT value at 1 023 K reaches 0.31, increasing by a factor of 19% compared with the single-doped counterpart Sr0.8La0.2TiO3 (ZT = 0.26).

Design and characterization of Yb and Nd doped transparent ceramics for high power laser applications: recent advancements

NASA Astrophysics Data System (ADS)

Lapucci, A.; Vannini, M.; Ciofini, M.; Pirri, A.; Nikl, M.; Li, J.; Esposito, L.; Biasini, V.; Hostasa, J.; Goto, T.; Boulon, G.; Maksimov, R.; Gizzi, L.; Labate, L.; Toci, G.

2017-01-01

We report a review on our recent developments in Yttebium and Neodymium doped laser ceramics, along two main research lines. The first is the design and development of Yb:YAG ceramics with non uniform doping distribution, for the management of thermo-mechanical stresses and for the mitigation of ASE: layered structures have been produced by solid state reactive sintering, using different forming processes (spray drying and cold press of the homogenized powders, tape cast of the slurry); samples have been characterized and compared to FEM analysis. The second is the investigation of Lutetium based ceramics (such as mixed garnets LuYAG and Lu2O3); this interest is mainly motivated by the favorable thermal properties of these hosts under high doping. We recently obtained for the first time high efficiency laser emission from Yb doped LuYAG ceramics. The investigation on sesquioxides has been focused on Nddoped Lu2O3 ceramics, fabricated with the Spark Plasma Sintering method (SPS). We recently achieved the first laser emission above 1 W from Nd doped Lu2O3 ceramics fabricated by SPS.

Ceramic oxide reactions with V2O5 and SO3

NASA Technical Reports Server (NTRS)

Jones, R. L.; Williams, C. E.

1985-01-01

Ceramic oxides are not inert in combustion environments, but can react with, inter alia, SO3, and Na2SO4 to yield low melting mixed sulfate eutectics, and with vanadium compounds to produce vanadates. Assuming ceramic degradation to become severe only when molten phases are generated in the surface salt (as found for metallic hot corrosion), the reactivity of ceramic oxides can be quantified by determining the SO3 partial pressure necessary for molten mixed sulfate formation with Na2SO3. Vanadium pentoxide is an acidic oxide that reacts with Na2O, SO3, and the different ceramic oxides in a series of Lux-Flood type of acid-base displacement reactions. To elucidate the various possible vanadium compound-ceramic oxide interactions, a study was made of the reactions of a matrix involving, on the one axis, ceramix oxides of increasing acidity, and on the other axis, vanadium compounds of increasing acidity. Resistance to vanadium compound reaction increased as the oxide acidity increased. Oxides more acidic than ZrO2 displaced V2O5. Examination of Y2O3- and CeO2-stabilized ZrO2 sintered ceramics which were degraded in 700 C NaVO3 has shown good agreement with the reactions predicted above, except that the CeO2-ZrO2 ceramic appears to be inexplicably degraded by NaVO3.

High power density cell using nanostructured Sr-doped SmCoO3 and Sm-doped CeO2 composite powder synthesized by spray pyrolysis

NASA Astrophysics Data System (ADS)

Shimada, Hiroyuki; Yamaguchi, Toshiaki; Suzuki, Toshio; Sumi, Hirofumi; Hamamoto, Koichi; Fujishiro, Yoshinobu

2016-01-01

High power density solid oxide electrochemical cells were developed using nanostructure-controlled composite powder consisting of Sr-doped SmCoO3 (SSC) and Sm-doped CeO2 (SDC) for electrode material. The SSC-SDC nano-composite powder, which was synthesized by spray pyrolysis, had a narrow particle size distribution (D10, D50, and D90 of 0.59, 0.71, and 0.94 μm, respectively), and individual particles were spherical, composing of nano-size SSC and SDC fragments (approximately 10-15 nm). The application of the powder to a cathode for an anode-supported solid oxide fuel cell (SOFC) realized extremely fine cathode microstructure and excellent cell performance. The anode-supported SOFC with the SSC-SDC cathode achieved maximum power density of 3.65, 2.44, 1.43, and 0.76 W cm-2 at 800, 750, 700, and 650 °C, respectively, using humidified H2 as fuel and air as oxidant. This result could be explained by the extended electrochemically active region in the cathode induced by controlling the structure of the starting powder at the nano-order level.

Investigation of holmium-doped zirconium oxide ceramic phosphor as an ultraviolet wavelength-discriminating laser beam viewer

NASA Astrophysics Data System (ADS)

Yamanoi, Kohei; Hori, Tatsuhiro; Minami, Yuki; Empizo, Melvin John F.; Luong, Mui Viet; Shiro, Atsushi; Watanabe, Jun; Iwano, Keisuke; Iwasa, Yuki; Cadatal-Raduban, Marilou; Gabayno, Jacque Lynn; Shimizu, Toshihiko; Sarukura, Nobuhiko; Norimatsu, Takayoshi

2018-01-01

We report the fluorescence spectra of ZrO2 and trivalent Ho-doped ZrO2 ceramics under ultraviolet (UV) excitation at 213, 266, and 355 nm wavelengths. The Ho3+-doped ZrO2 ceramics exhibited varying fluorescence color tones depending on the excitation wavelength used. The different color tones match the fluorescence spectrum characteristics at each excitation wavelength. Our results demonstrate that Ho3+-doped ZrO2 ceramics can discriminate between UV light, specifically the third, fourth, and fifth harmonics of a Nd:YAG laser. It can potentially be used for developing UV laser beam viewers to aid laser alignment.

Down- and up-conversion emissions in Er-doped transparent fluorotellurite glass-ceramics

NASA Astrophysics Data System (ADS)

Miguel, A.; Morea, R.; Gonzalo, J.; Fernandez, J.; Balda, R.

2015-03-01

In this work, we report the near infrared and upconversion emissions of Er3+-doped transparent fluorotellurite glassceramics obtained by heat treatment of the precursor Er-doped TeO2-ZnO-ZnF2 glass. Structural analysis shows that ErF3 nanocrystals nucleated in the glass-ceramic sample are homogeneously distributed in the glass matrix with a typical size of 45±10 nm. The comparison of the fluorescence properties of Er3+-doped precursor glass and glass-ceramic confirms the successful incorporation of the rare-earth into the nanocrystals. An enhancement of the red upconversion emission due to 4F9/2→4I15/2 transition together with weak emission bands due to transitions from 2H9/2, 4F3/2,5/2, and 4F7/2 levels to the ground state are observed under excitation at 801 nm in the glass-ceramic sample. The temporal evolution of the red emission together with the excitation upconversion spectrum suggest that energy transfer processes are responsible for the enhancement of the red emission.

Effects of ion doping at different sites on electrical properties of multiferroic BiFeO3 ceramics

NASA Astrophysics Data System (ADS)

Yu, Benfang; Li, Meiya; Liu, Jun; Guo, Dongyun; Pei, Ling; Zhao, Xingzhong

2008-03-01

Pure, La3+ doped at A site, V5+ doped at B site, and La3+ and V5+ co-doped multiferroic BiFeO3 ceramics: BiFeO3 (BFO), Bi0.85La0.15FeO3 (BLF), BiFe0.97V0.03O3 (BFV), Bi0.85La0.15Fe0.97V0.03O3 (BLFV), etc were successfully prepared by a rapid liquid sintering technique. X-ray diffraction indicated that these ceramics were of polycrystalline perovskite structures, accompanied with a tiny residual Bi2O3 phase. It was found that, among these ceramics, BLFV ceramic exhibited the best electrical properties. The leakage current density of BLFV ceramic was only 2.1 × 10-6 A cm-2 at 10 kV cm-1, two and one orders of magnitude lower than those of the BLF and BFV ceramics, respectively. In the measuring frequency of 4 KHz-1 MHz, the dielectric constants and losses of this sample exhibited slight variation and the lowest loss tangent was 0.08. The sample had a relatively saturated ferroelectric hysteresis loop. These suggested that the co-doped BiFeO3 ceramic by La3+ and V5+ at A and B sites showed advantages in application over the pure BFO, doped BLF and BFV ceramics, respectively.

Dose-Dependent Effects of CeO2 on Microstructure and Antibacterial Property of Plasma-Sprayed TiO2 Coatings for Orthopedic Application

NASA Astrophysics Data System (ADS)

Zhao, Xiaobing; Liu, Gaopeng; Zheng, Hai; Cao, Huiliang; Liu, Xuanyong

2015-02-01

Titanium and its alloys have been used extensively for orthopedic and dental implants. Although these devices have achieved high rates of success, two major complications may be encountered: the lack of osseointegration and the biomaterial-related infection. Accordingly, cerium oxide (CeO2)-doped titanium oxide (TiO2) materials were coated on titanium by an atmospheric plasma spraying (APS) technique. The phase structures, morphologies, and surface chemical states of the obtained coatings were characterized by x-ray diffraction, scanning electron microscopy, and x-ray photoelectron spectroscopy techniques. The in vitro antibacterial and cytocompatibility of the materials were studied with Staphylococcus aureus ( S. aureus, ATCC25923) and osteoblast precursor cell line MC3T3-E1. The results indicated that the addition of CeO2 shifts slightly the diffraction peaks of TiO2 matrix to low angles but does not change its rutile phase structure. In addition, the CeO2/TiO2 composite coatings possess dose-dependent corrosion resistance and antimicrobial properties. And doping of 10 wt.% CeO2 exhibits the highest activity against S. aureus, improved corrosion resistance, and competitive cytocompatibility, which argues a promising option for balancing the osteogenetic and antibacterial properties of titanium implants.

Ultrafine Nanocrystalline CeO2@C-Containing NaAlH4 with Fast Kinetics and Good Reversibility for Hydrogen Storage.

PubMed

Zhang, Xin; Liu, Yongfeng; Wang, Ke; Li, You; Gao, Mingxia; Pan, Hongge

2015-12-21

A nanocrystalline CeO2@C-containing NaAlH4 composite is successfully synthesized in situ by hydrogenating a NaH-Al mixture doped with CeO2@C. Compared with NaAlH4 , the as-prepared CeO2@C-containing NaAlH4 composite, with a minor amount of excess Al, exhibits significantly improved hydrogen storage properties. The dehydrogenation onset temperature of the hydrogenated [NaH-Al-7 wt % CeO2@C]-0.04Al sample is 77 °C lower than that of the pristine sample because of a reduced kinetic barrier. More importantly, the dehydrogenated sample absorbs ∼4.7 wt % hydrogen within 35 min at 100°C and 10 MPa of hydrogen. Compositional and structural analyses reveal that CeO2 is converted to CeH2 during ball milling and that the newly formed CeH2 works with the excess of Al to synergistically improve the hydrogen storage properties of NaAlH4. Our findings will aid in the rational design of novel catalyst-doped complex hydride systems with low operating temperatures, fast kinetics, and long-term cyclability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New CeO2 nanoparticles-based topical formulations for the skin protection against organophosphates.

PubMed

Zenerino, Arnaud; Boutard, Tifenn; Bignon, Cécile; Amigoni, Sonia; Josse, Denis; Devers, Thierry; Guittard, Frédéric

2015-01-01

To reinforce skin protection against organophosphates (OPs), the development of new topical skin protectants (TSP) has received a great interest. Nanoparticles like cerium dioxide (CeO 2 ) known to adsorb and neutralize OPs are interesting candidates for TSP. However, NPs are difficult to disperse into formulations and they are suspected of toxicological issues. Thus, we want to study: (1) the effect of the addition of CeO 2 NPs in formulations for the skin protection (2) the impact of the doping of CeO 2 NPs by calcium; (3) the effect of two methods of dispersion of CeO 2 NPs: an O/W emulsion or a suspension of a fluorinated thickening polymer (HASE-F) grafted with these NPs. As a screening approach we used silicone membranes as a skin equivalent and Franz diffusion cells for permeation tests. The addition of pure CeO 2 NPs in both formulations permits the penetration to decrease by a 3-4-fold factor. The O/W emulsion allows is the best approach to obtain a film-forming coating with a good reproducibility of the penetration results; whereas the grafting of NPs to a thickener is the best way to obtain an efficient homogenous suspension of CeO 2 NPs with a decreased of toxicological impact but the coating is less film-forming which slightly impacts the reproducibility of the penetration results.

Eu-doped ZnO-HfO2 hybrid nanocrystal-embedded low-loss glass-ceramic waveguides

NASA Astrophysics Data System (ADS)

Ghosh, Subhabrata; N, Shivakiran Bhaktha B.

2016-03-01

We report on the sol-gel fabrication, using a dip-coating technique, of low-loss Eu-doped 70SiO2 -(30-x) HfO2-xZnO (x = 2, 5, 7 and 10 mol%) ternary glass-ceramic planar waveguides. Transmission electron microscopy and grazing incident x-ray diffraction experiments confirm the controlled growth of hybrid nanocrystals with an average size of 3 nm-25 nm, composed of ZnO encapsulated by a thin layer of nanocrystalline HfO2, with an increase of ZnO concentration from x = 2 mol% to 10 mol% in the SiO2-HfO2 composite matrix. The effect of crystallization on the local environment of Eu ions, doped in the ZnO-HfO2 hybrid nanocrystal-embedded glass-ceramic matrix, is studied using photoluminescence spectra, wherein an intense mixed-valence state (divalent as well as trivalent) emission of Eu ions is observed. The existence of Eu2+ and Eu3+ in the SiO2-HfO2-ZnO ternary matrix is confirmed by x-ray photoelectron spectroscopy. Importantly, the Eu{}2+,3+-doped ternary waveguides exhibit low propagation losses (0.3 ± 0.2 dB cm-1 at 632.8 nm) and optical transparency in the visible region of the electromagnetic spectrum, which makes ZnO-HfO2 nanocrystal-embedded SiO2-HfO2-ZnO waveguides a viable candidate for the development of on-chip, active, integrated optical devices.

Dielectric characteristics of Mn-doped LaTiO3+δ ceramics

NASA Astrophysics Data System (ADS)

Chen, Yan; Cui, Yimin

A series of ceramic composites of Mn-doped La1- x MnxTiO3+ δ and LaMnxTi1- x O3+ δ (x = 0.1, 0.2) were synthesized by conventional solid-state reaction method. The low-frequency complex dielectric properties of the composites were investigated as functions of temperature (77 K <= T <= 360 K) and frequency (100 Hz <= f <= 1 MHz), respectively. The dielectric constant of A-site doped samples is higher than that of B-site doped samples. The loss tangent of low doped samples is much less than that of high doped samples. The A-site doped composites exhibit intrinsic dielectric response with a dielectric constant of 40 in the temperature below 250 K. Interestingly, the dielectric constants of B-site doped ceramics increase slightly in the temperature range from 77 to 360 K. And it is clearly observed that extraordinarily high dielectric loss tangent ( 6) appear at low frequency (100 Hz) in LaMn0.2Ti0.8O3+ δ , which is 8 times larger than that of LaMn0.1Ti0.9O3+ δ , which indicates that the doped content can affect the intrinsic dielectric characteristics significantly.

Luminescent properties of Eu{sup 2+}-doped BaGdF{sub 5} glass ceramics a potential blue phosphor for ultra-violet light-emitting diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Weihuan; Zhang, Yuepin, E-mail: zhangyuepin@nbu.edu.cn; Ouyang, Shaoye

2015-01-14

Eu{sup 2+} doped transparent oxyfluoride glass ceramics containing BaGdF{sub 5} nanocrystals were successfully fabricated by melt-quenching technique under a reductive atmosphere. The structure of the glass and glass ceramics were investigated by differential scanning calorimetry, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The luminescent properties were investigated by transmission, excitation, and emission spectra. The decay time of the Gd{sup 3+} ions at 312 nm excited with 275 nm were also investigated. The results of XRD and TEM indicated the existence of BaGdF5 nanocrystals in the transparent glass ceramics. The excitation spectra of Eu{sup 2+} doped glass ceramics showed an excellent overlapmore » with the main emission region of an ultraviolet light-emitting diode (UV-LED). Compared with the as-made glass, the emission of glass ceramics is much stronger by a factor of increasing energy transfer efficiency from Gd{sup 3+} to Eu{sup 2+} ions, the energy transfer efficiency from Gd{sup 3+} to Eu{sup 2+} ions was discussed. In addition, the chromaticity coordinates of glass and glass ceramics specimens were also discussed, which indicated that the Eu{sup 2+} doped BaGdF{sub 5} glass ceramics may be used as a potential blue-emitting phosphor for UV-LED.« less

Synthesis, characterization, bioactivity and antibacterial studies of silver doped calcium borosilicate glass-ceramics

NASA Astrophysics Data System (ADS)

Kumar, Alesh; Mariappan, C. R.

2018-04-01

Bioactive glass-ceramics 45.8 mol% SiO- 45.8 CaO - 8.4 B2O3 doped with Ag2O were synthesized by sol-gel method. The glass-ceramic nature of samples was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. Fourier transform infrared (FT-IR) spectra reveal the probable stretching and bending vibration modes of silicate and borate groups. UV-Visible spectra reveal the presence of Ag+ ions and metallic Ag in the glass matrix for Ag2O doped ceramic sample. Biocompatibility of the glass nature of samples was studied by soaking of samples in Dulbecco's Modified Eagle's Medium (DMEM) with subsequent XRD studies. It was found that bone-like apatite formation on the glasses after soaked in DMEM. Antibacterial studies of glass ceramics powder against gram positive and negative microorganisms were carried out.

Ytterbium-doped glass-ceramics for optical refrigeration.

PubMed

Filho, Elton Soares de Lima; Krishnaiah, Kummara Venkata; Ledemi, Yannick; Yu, Ye-Jin; Messaddeq, Younes; Nemova, Galina; Kashyap, Raman

2015-02-23

We report for the first time the characterization of glass-ceramics for optical refrigeration. Ytterbium-doped nanocrystallites were grown in an oxyfluoride glass matrix of composition 2YbF(3):30SiO(2)-15Al(2)O(3)-25CdF(2)-22PbF(2)-4YF(3), forming bulk glass-ceramics at three different crystalisation levels. The samples are compared with a corresponding uncrystalised (glass) sample, as well as a Yb:YAG sample which has presented optical cooling. The measured X-ray diffraction spectra, and thermal capacities of the samples are reported. We also report for the first time the use of Yb:YAG as a reference for absolute photometric quantum efficiency measurement, and use the same setup to characterize the glass and glass-ceramic samples. The cooling figure-of-merit was measured by optical calorimetry using a fiber Bragg grating and found to depend on the level of crystallization of the sample, and that samples with nanocrystallites result in higher quantum efficiency and lower background absorption than the pure-glass sample. In addition to laser-induced cooling, the glass-ceramics have the potential to serve as a reference for quantum efficiency measurements.

Rare-earth doped transparent ceramics for spectral filtering and quantum information processing

NASA Astrophysics Data System (ADS)

Kunkel, Nathalie; Ferrier, Alban; Thiel, Charles W.; Ramírez, Mariola O.; Bausá, Luisa E.; Cone, Rufus L.; Ikesue, Akio; Goldner, Philippe

2015-09-01

Homogeneous linewidths below 10 kHz are reported for the first time in high-quality Eu3+ doped Y 2O3 transparent ceramics. This result is obtained on the 7F0→5D0 transition in Eu3+ doped Y 2O3 ceramics and corresponds to an improvement of nearly one order of magnitude compared to previously reported values in transparent ceramics. Furthermore, we observed spectral hole lifetimes of ˜15 min that are long enough to enable efficient optical pumping of the nuclear hyperfine levels. Additionally, different Eu3+ concentrations (up to 1.0%) were studied, resulting in an increase of up to a factor of three in the peak absorption coefficient. These results suggest that transparent ceramics can be useful in applications where narrow and deep spectral holes can be burned into highly absorbing lines, such as quantum information processing and spectral filtering.

CoO-doped MgO-Al2O3-SiO2-colored transparent glass-ceramics with high crystallinity

NASA Astrophysics Data System (ADS)

Tang, Wufu; Zhang, Qian; Luo, Zhiwei; Yu, Jingbo; Gao, Xianglong; Li, Yunxing; Lu, Anxian

2018-02-01

To obtain CoO-doped MgO-Al2O3-SiO2 (MAS)-colored transparent glass-ceramics with high crystallinity, the glass with the composition 21MgO-21Al2O3-54SiO2-4B2O3-0.2CoO (in mol %) was prepared by conventional melt quenching technique and subsequently thermal treated at several temperatures. The crystallization behavior of the glass, the precipitated crystalline phases and crystallinity were analyzed by X-ray diffraction (XRD). The microstructure of the glass-ceramics was characterized by field emission scanning electron microscopy (FSEM). The transmittance of glass-ceramic was measured by UV spectrophotometer. The results show that a large amount of α-cordierite (indianite) with nano-size was precipitated from the glass matrix after treatment at 1020 °C for 3 h. The crystallinity of the transparent glass-ceramic reached up to 97%. Meanwhile, the transmittance of the glass-ceramic was 74% at 400 nm with a complex absorption band from 450 nm to 700 nm. In addition, this colored transparent glass-ceramic possessed lower density (2.469 g/cm3), lower thermal expansion coefficient (1.822 × 10-6 /℃), higher Vickers hardness (9.1 GPa) and higher bending strength (198 MPa) than parent glass.

Spectroscopic properties of Nd3+ doped transparent oxyfluoride glass ceramics.

PubMed

Yu, Yunlong; Chen, Daqin; Ma, En; Wang, Yuansheng; Hu, Zhongjian

2007-07-01

In this paper, the spectroscopic properties of Nd(3+) doped transparent oxyfluoride glass ceramics containing LaF(3) nano-crystals were systematically studied. The formation and distribution of LaF(3) nano-crystals in the glass matrix were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Based on Judd-Ofelt theory, the intensity parameters Omega(t) (t=2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency, width of the emission line and stimulated emission cross-section of Nd(3+) were evaluated. Particularly, the effect of Nd(3+) doping level on them was discussed. With the increase of Nd(3+) concentration in the glass ceramic, the experimental luminescence lifetime, radiative quantum efficiency and stimulated emission cross-section vary from 353.4 micros, 78.3% and 1.86 x 10(-20)cm(2) to 214.7 micros, 39.9% and 1.52 x 10(-20)cm(2), respectively. The comparative study of Nd(3+) spectroscopic parameters in different hosts suggests that the investigated glass ceramic system is potentially applicable as laser materials for 1.06 microm emission.

Ultra-broadband amplification properties of Ni2+-doped glass-ceramics amplifiers.

PubMed

Jiang, Chun

2009-04-13

The energy level, transition configuration and mathematical model of Ni(2+)-doped glass-ceramics amplifiers are presented for the first time, to the best of one's knowledge. A quasi-three-level system is employed to model the gain and noise characteristics of the doped system, and the rate and power propagation equations of the mathematical model are solved to analyze the effect of the active ion concentration, fiber length, pump power as well as thermal-quenching on the gain spectra. It is shown that our model is in agreement with experimental result, and when excited at longer wavelength, the center of gain spectra of the amplifier red shifts, the ultra-broad band room-temperature gain spectra can cover 1.25-1.65 microm range for amplification of signal in the low-loss windows of the all-wave fiber without absorption peak caused by OH group.

Laser and gain parameters at 2.7 μm of Er 3+-doped oxyfluoride transparent glass-ceramics

NASA Astrophysics Data System (ADS)

Tikhomirov, V. K.; Méndez-Ramos, J.; Rodríguez, V. D.; Furniss, D.; Seddon, A. B.

2006-07-01

The room temperature emission spectrum at about 2.7 μm corresponding to the laser transition 4I 11/2 → 4I 13/2 in Er 3+-doped nano-scaled transparent oxyfluoride glass-ceramic has been measured and stimulated emission cross-section for the transition has been calculated. The intensity of the transition has been found to be 40 times stronger and lifetime 50 times longer in the glass-ceramics compared to the precursor glass, which we show to be due to a change of frequency of the phonon involved in non-radiative de-excitation of the 4I 11/2 level from 900 cm -1 in the precursor glass to 240 cm -1 in the ensuing glass-ceramics. The absorption cross-section for the excited state absorption 4I 13/2 → 4I 11/2 has been calculated based on the experimental reciprocal emission spectrum and wavelength dependence of the gain cross-section for the lasing transition 4I 11/2 → 4I 13/2 vs population inversion has been derived. The lasing/optical amplification gain parameters, such as population inversion, pump saturation intensity and product of emission cross-section and fluorescence lifetime have been obtained at the 2.7 μm wavelength. A noteworthy result is that laser action at 2.7 μm is possible in these Er 3+-doped glass-ceramics, already not taking into account energy transfer or up-conversion processes, related to the 4I 13/2 level, which favour the population inversion.

Rare-earth doped transparent ceramics for spectral filtering and quantum information processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunkel, Nathalie, E-mail: nathalie.kunkel@chimie-paristech.fr; Goldner, Philippe, E-mail: philippe.goldner@chimie-paristech.fr; Ferrier, Alban

2015-09-01

Homogeneous linewidths below 10 kHz are reported for the first time in high-quality Eu{sup 3+} doped Y {sub 2}O{sub 3} transparent ceramics. This result is obtained on the {sup 7}F{sub 0}→{sup 5}D{sub 0} transition in Eu{sup 3+} doped Y {sub 2}O{sub 3} ceramics and corresponds to an improvement of nearly one order of magnitude compared to previously reported values in transparent ceramics. Furthermore, we observed spectral hole lifetimes of ∼15 min that are long enough to enable efficient optical pumping of the nuclear hyperfine levels. Additionally, different Eu{sup 3+} concentrations (up to 1.0%) were studied, resulting in an increase ofmore » up to a factor of three in the peak absorption coefficient. These results suggest that transparent ceramics can be useful in applications where narrow and deep spectral holes can be burned into highly absorbing lines, such as quantum information processing and spectral filtering.« less

Luminescence properties of Eu3+-doped SiO2-LiYF4 glass-ceramic microrods

NASA Astrophysics Data System (ADS)

Secu, C. E.; Secu, M.

2015-09-01

Photoluminescence properties of the glass-ceramics microrods containing Eu3+-doped LiYF4 nanocrystals have been studied and characterized. Judd-Ofelt parameters and quantum efficiency has been computed from luminescence spectra and discussed by comparison to the glass ceramic bulk and pellet. The radiative decay rate Arad is higher in the glass ceramic rods (221 s-1) than in the glass ceramic bulk (130 s-1) but the quantum efficiency computed is very low (21%) compared to the glass-ceramic bulk (97%). There are effective non-radiative decay channels that might be related to an influence of the dimensional constraints imposed by the membrane pores during xerogel formation and subsequent glass ceramization.

Optical properties of rare earth doped transparent oxyfluoride glass ceramics

NASA Astrophysics Data System (ADS)

Mendez-Ramos, J.; Lavin, V.; Martin, I. R.; Rodriguez-Mendoza, U. R.; Rodriguez, V. D.; Lozano-Gorrin, A. D.; Nunez, P.

2003-01-01

Optical properties of Eu3+ ions in oxyfluoride glasses and glass ceramics doped with low concentration (0.1 mol%) have been analysed and compared with previous results for high concentrated samples (2.5 mol%). The Eu3+ ions in the low dopant concentration glass ceramics are diluted into like crystalline environments with higher symmetry and lower coupled phonons energy than in the precursor glasses. Fluorescence line narrowing measurements indicate the presence of two main fluoride site distributions for the Eu3+ ions in these low concentrated glass ceramics.

Millimeter-wave irradiation heating for operation of doped CeO2 electrolyte-supported single solid oxide fuel cell

NASA Astrophysics Data System (ADS)

Che Abdullah, Salmie Suhana Binti; Teranishi, Takashi; Hayashi, Hidetaka; Kishimoto, Akira

2018-01-01

High operation temperature of solid oxide fuel cell (SOFC) results in high cell and operation cost, time consuming and fast cell degradation. Developing high performance SOFC that operates at lower temperature is required. Here we demonstrate 24 GHz microwave as a rapid heating source to replace conventional heating method for SOFC operation using 20 mol% Sm doped CeO2 electrolyte-supported single cell. The tested cell shows improvement of 62% in maximum power density at 630 °C under microwave heating. This improvement governs by bulk conductivity of the electrolyte. Investigation of ionic transference number reveals that the value is unchanged under microwave irradiation, confirming the charge carrier is dominated by oxygen ion species. This work shows a potential new concept of high performance as well as cost and energy effective SOFC.

Solid state speciation of uranium and its local structure in Sr2CeO4 using photoluminescence spectroscopy

NASA Astrophysics Data System (ADS)

Sahu, M.; Gupta, Santosh K.; Jain, D.; Saxena, M. K.; Kadam, R. M.

2018-04-01

An effort was taken to carry our speciation study of uranium ion in technologically important cerate host Sr2CeO4 using time resolved photoluminescence spectroscopy. Such studies are not relevant only to nuclear industry but can give rich insight into fundamentals of 5f electron chemistry in solid state systems. In this work both undoped and varied amount of uranium doped Sr2CeO4 compound is synthesized using complex polymerization method and is characterized systematically using X-ray diffraction (XRD), Raman spectroscopy, photoluminescence spectroscopy and scanning electron microscopy (SEM). Both XRD and Raman spectroscopy confirmed the formation of pure Sr2CeO4 which has tendency to decompose peritectically to SrCeO3 and SrO at higher temperature. Uranium doping is confirmed by XRD. Uranium exhibits a rich chemistry owing to its variable oxidation state from +3 to +6. Each of them exhibits distinct luminescence properties either due to f-f transitions or ligand to metal charge transfer (LMCT). We have taken Sr2CeO4 as a model host lattice to understand the photophysical characteristics of uranium ion in it. Emission spectroscopy revealed the stabilization of uranium as U (VI) in the form of UO66- (octahedral uranate) in Sr2CeO4. Emission kinetics study reflects that uranate ions are not homogeneously distributed in Sr2CeO4 and it has two different environments due to its stabilization at both Sr2+ as well as Ce4+ site. The lifetime population analysis interestingly pinpointed that majority of uranate ion resided at Ce4+ site. The critical energy-transfer distance between the uranate ion was determined based on which the concentration quenching mechanism was attributed to electric multipolar interaction. These studies are very important in designing Sr2CeO4 based optoelectronic material as well exploring it for actinides studies.

Solid state speciation of uranium and its local structure in Sr2CeO4 using photoluminescence spectroscopy.

PubMed

Sahu, M; Gupta, Santosh K; Jain, D; Saxena, M K; Kadam, R M

2018-04-15

An effort was taken to carry our speciation study of uranium ion in technologically important cerate host Sr 2 CeO 4 using time resolved photoluminescence spectroscopy. Such studies are not relevant only to nuclear industry but can give rich insight into fundamentals of 5f electron chemistry in solid state systems. In this work both undoped and varied amount of uranium doped Sr 2 CeO 4 compound is synthesized using complex polymerization method and is characterized systematically using X-ray diffraction (XRD), Raman spectroscopy, impedance spectroscopy and scanning electron microscopy (SEM). Both XRD and Raman spectroscopy confirmed the formation of pure Sr 2 CeO 4 which has tendency to decompose peritectically to SrCeO 3 and SrO at higher temperature. Uranium doping is confirmed by XRD. Uranium exhibits a rich chemistry owing to its variable oxidation state from +3 to +6. Each of them exhibits distinct luminescence properties either due to f-f transitions or ligand to metal charge transfer (LMCT). We have taken Sr 2 CeO 4 as a model host lattice to understand the photophysical characteristics of uranium ion in it. Emission spectroscopy revealed the stabilization of uranium as U (VI) in the form of UO 6 6- (octahedral uranate) in Sr 2 CeO 4 . Emission kinetics study reflects that uranate ions are not homogeneously distributed in Sr 2 CeO 4 and it has two different environments due to its stabilization at both Sr 2+ as well as Ce 4+ site. The lifetime population analysis interestingly pinpointed that majority of uranate ion resided at Ce 4+ site. The critical energy-transfer distance between the uranate ion was determined based on which the concentration quenching mechanism was attributed to electric multipolar interaction. These studies are very important in designing Sr 2 CeO 4 based optoelectronic material as well exploring it for actinides studies. Copyright © 2018 Elsevier B.V. All rights reserved.

Exceptional capability of nanosized CeO(2) materials to "dissolve" lanthanide oxides established by time-gated excitation and emission spectroscopy.

PubMed

Tiseanu, Carmen; Parvulescu, Vasile; Avram, Daniel; Cojocaru, Bogdan; Sanchez-Dominguez, Margarita

2014-05-28

The atomic scale homogeneity of Ce and Zr oxygen bonds represents the main reason for enhanced total oxygen storage capability of CeO2-ZrO2 (Ce/Zr = 1) as compared to that of CeO2. Here, we demonstrate that the addition of 10% Eu(3+) by wet impregnation on preformed nanosized CeO2-ZrO2 (Ce/Zr = 1) followed by calcination induces a remarkable homogeneity of 10% Eu(3+)-CeO2-ZrO2 solid solution. By use of time-resolved emission and excitation spectroscopies, the improvement of the nanoscale chemical and structural homogeneity of 10% Eu(3+)-CeO2-ZrO2 calcined at 1000 as compared to sample calcined at 750 °C is demonstrated. Based on the comparison of luminescence properties of 10% Eu(3+) impregnated on preformed nanosized CeO2-ZrO2 and CeO2, we also show that the presence of zirconium does not only preserve the ability of cerium oxide to "dissolve" lanthanide oxide, but also determines an important stabilization of defects (oxygen vacancies) generated upon Eu(3+) doping.

Dip-coating of nano-sized CeO2 on SiC membrane and its effect on thermal diffusivity.

PubMed

Park, Jihye; Jung, Miewon

2014-05-01

CeO2-SiC mixed composite membrane was fabricated with porous SiC ceramic and cerium oxide powder synthesized by sol-gel process. This CeO2-SiC membrane and SiC membrane which is made by the purified SiC ceramic were pressed and sintered in Ar atmosphere. And then, the SiC membrane was dip-coated by cerium oxide precursor sol solution and heat-treated in air. The surface morphology, particle size, porosity and structure analysis of the mixing and dip-coating SiC membrane were monitored by FE-SEM and X-ray diffraction analysis. Surface area, pore volume and pore diameter were determined by BET instrument. Thermal diffusivity was measured by laser flash method with increasing temperature. The relation between porosity and thermal diffusivity from different preparation process has been discussed on this study.

Influence of nanopowders sedimentation on characteristics of Yb-doped Y2O3 transparent ceramics

NASA Astrophysics Data System (ADS)

Aleksandrov, E. O.; Shitov, V. A.; Maksimov, R. N.; Basyrova, L. R.

2017-09-01

In this work we report on the effects induced by different conditions of nanopowders sedimentation on the microstructure features and optical properties of ytterbium-doped yttrium oxide (Yb:Y2O3) transparent ceramics sintered at 1780 °C for 20 h under a vacuum. The nanopowder of (Yb0.005Y0.995)2O3 co-doped with 5 at % ZrO2 was synthesized by laser ablation and used as the starting material for the fabrication of ceramics. The obtained nanoparticles were annealed at 1100 °C for 3 h in air in order to transform a metastable monoclinic phase into a main cubic phase. After sedimentation for 24 h in isopropyl alcohol the useful suspension was dried using a rotary evaporator operating at different temperatures and pressures. The use of lower evaporation temperature (37 °C) and higher vacuum level (10 mbar) lead to complete removal of organic species from the nanopowder and promote homogeneous densification of the powder compact. Under optimal treatment conditions the optical transmittance and the average content of the scattering centers were measured to be 77 % at a wavelength of 1080 nm and 0.25 ppm, respectively.

Enhancement of Dielectric Breakdown Strength and Energy Conversion Efficiency of Niobate Glass-Ceramics by Sc2O3 Doping

NASA Astrophysics Data System (ADS)

Xiao, Shi; Xiu, Shaomei; Yang, Ke; Shen, Bo; Zhai, Jiwei

2018-01-01

Niobate glass-ceramics K2O-SrO-Nb2O5-B2O3-Al2O3-SiO2 (KSN-BAS) doped with different amounts of Sc2O3 have been prepared through a melt quenching/controlled crystallization method, and the influence of the Sc2O3 content on their phase composition, microstructure, dielectric performance, and charge-discharge properties investigated. X-ray powder diffraction results showed that the peak positions of the KSr2Nb5O15 phase shifted to higher angle and the glass-ceramic microstructures were significantly improved by Sc2O3 addition. Based on these results, 0.5 mol.% Sc2O3 doping was found to achieve remarkable enhancement in energy storage density, which reached 9.63 ± 0.39 J/cm3 at dielectric breakdown strength of 1450.38 ± 29.01 kV/cm with high conversion efficiency of ˜ 92.1%. For pulsed power applications, discharge speed of 17 ns and power density of 0.48 MW/cm3 were obtained in the glass-ceramic with 0.5 mol.% Sc2O3. These results could provide a new design strategy for high-performance dielectric capacitors.

Influence of the sintering temperature on the electrical properties of Ce-doped WO3 ceramics prepared from nano-powders

NASA Astrophysics Data System (ADS)

Dong, Liang; Chen, Han-Jun; Wang, Yu; Li, De-Zhu; Li, Tong-Ye; Zhao, Yong

2007-04-01

Using a nm-level powder fabricated by a wet chemical method as precursor, the CeO2-doped WO3 ceramics were prepared by the conventional solid state reaction at sintering temperatures from 600 to 1100 °C. The x-ray diffraction analysis reveals the coexistence of different WO3 phases in the samples sintered at temperatures below 900 °C, whereas a single phase appears in the samples sintered above 1000 °C. No new Ce-W compound appears. As the sintering temperature increases, the electrical properties of the samples display an interesting transformation from linear to nonlinear behaviour. The measurements of scanning electron microscope, complex impedance and electrical stability indicate that a lot of grain boundary regions in the samples sintered at low temperatures strongly influences the electrical transportation. Therefore, the electrical nonlinearity is due to a basic process controlled by the back-to-back Schottky barriers at grain boundaries with suitable thickness as well as the coexistence of phases.

Evidences of grain boundary capacitance effect on the colossal dielectric permittivity in (Nb + In) co-doped TiO2 ceramics

PubMed Central

Li, Jinglei; Li, Fei; Li, Chao; Yang, Guang; Xu, Zhuo; Zhang, Shujun

2015-01-01

The (Nb + In) co-doped TiO2 ceramics were synthesized by conventional solid-state sintering (CSSS) and spark plasma sintering (SPS) methods. The phases and microstructures were studied by X-ray diffraction, Raman spectra, field-emission scanning electron microscopy and transmission electron microscopy, indicating that both samples were in pure rutile phase while showing significant difference in grain size. The dielectric and I–V behaviors of SPS and CSSS samples were investigated. Though both possess colossal permittivity (CP), the SPS samples exhibited much higher dielectric permittivity/loss factor and lower breakdown electric field when compared to their CSSS counterparts. To further explore the origin of CP in co-doped TiO2 ceramics, the I–V behavior was studied on single grain and grain boundary in CSSS sample. The nearly ohmic I–V behavior was observed in single grain, while GBs showed nonlinear behavior and much higher resistance. The higher dielectric permittivity and lower breakdown electric field in SPS samples, thus, were thought to be associated with the feature of SPS, by which reduced space charges and/or impurity segregation can be achieved at grain boundaries. The present results support that the grain boundary capacitance effect plays an important role in the CP and nonlinear I–V behavior of (Nb + In) co-doped TiO2 ceramics. PMID:25656713

Evidences of grain boundary capacitance effect on the colossal dielectric permittivity in (Nb + In) co-doped TiO2 ceramics

NASA Astrophysics Data System (ADS)

Li, Jinglei; Li, Fei; Li, Chao; Yang, Guang; Xu, Zhuo; Zhang, Shujun

2015-02-01

The (Nb + In) co-doped TiO2 ceramics were synthesized by conventional solid-state sintering (CSSS) and spark plasma sintering (SPS) methods. The phases and microstructures were studied by X-ray diffraction, Raman spectra, field-emission scanning electron microscopy and transmission electron microscopy, indicating that both samples were in pure rutile phase while showing significant difference in grain size. The dielectric and I-V behaviors of SPS and CSSS samples were investigated. Though both possess colossal permittivity (CP), the SPS samples exhibited much higher dielectric permittivity/loss factor and lower breakdown electric field when compared to their CSSS counterparts. To further explore the origin of CP in co-doped TiO2 ceramics, the I-V behavior was studied on single grain and grain boundary in CSSS sample. The nearly ohmic I-V behavior was observed in single grain, while GBs showed nonlinear behavior and much higher resistance. The higher dielectric permittivity and lower breakdown electric field in SPS samples, thus, were thought to be associated with the feature of SPS, by which reduced space charges and/or impurity segregation can be achieved at grain boundaries. The present results support that the grain boundary capacitance effect plays an important role in the CP and nonlinear I-V behavior of (Nb + In) co-doped TiO2 ceramics.

Evidences of grain boundary capacitance effect on the colossal dielectric permittivity in (Nb + In) co-doped TiO2 ceramics.

PubMed

Li, Jinglei; Li, Fei; Li, Chao; Yang, Guang; Xu, Zhuo; Zhang, Shujun

2015-02-06

The (Nb + In) co-doped TiO2 ceramics were synthesized by conventional solid-state sintering (CSSS) and spark plasma sintering (SPS) methods. The phases and microstructures were studied by X-ray diffraction, Raman spectra, field-emission scanning electron microscopy and transmission electron microscopy, indicating that both samples were in pure rutile phase while showing significant difference in grain size. The dielectric and I-V behaviors of SPS and CSSS samples were investigated. Though both possess colossal permittivity (CP), the SPS samples exhibited much higher dielectric permittivity/loss factor and lower breakdown electric field when compared to their CSSS counterparts. To further explore the origin of CP in co-doped TiO2 ceramics, the I-V behavior was studied on single grain and grain boundary in CSSS sample. The nearly ohmic I-V behavior was observed in single grain, while GBs showed nonlinear behavior and much higher resistance. The higher dielectric permittivity and lower breakdown electric field in SPS samples, thus, were thought to be associated with the feature of SPS, by which reduced space charges and/or impurity segregation can be achieved at grain boundaries. The present results support that the grain boundary capacitance effect plays an important role in the CP and nonlinear I-V behavior of (Nb + In) co-doped TiO2 ceramics.

Enhanced dielectric response of GeO{sub 2}-doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amaral, F.; School of Technology and Management of Oliveira do Hospital, Oliveira do Hospital, 3400-124 Oliveira; Rubinger, C. P. L.

2009-02-01

CaCu{sub 3}Ti{sub 4}O{sub 12} ceramic samples were prepared by solid state conventional route using stoichiometric amounts of CuO, TiO{sub 2}, and CaCO{sub 3}. Afterward the material was doped with GeO{sub 2} with concentrations up to 6% by weight and sintered at 1050 deg. C for 12 h. The influence of doping on the microstructure, vibrational modes, and dielectric properties of the material was investigated by x-ray diffraction, scanning electron microscopy coupled with an energy dispersive spectrometer, and infrared and dielectric measurements between 100 Hz and 30 MHz. The materials presented huge dielectric response, which increases with doping level relative tomore » undoped CaCu{sub 3}Ti{sub 4}O{sub 12}. The main effect of doping on the microstructure is the segregation of Cu-rich phase in the ceramic grain boundaries. Cole-Cole modeling correlates well the effects of this segregation with the relaxation parameters obtained. The intrinsic phonon contributions for the dielectric response were obtained and discussed together with the structural evolution of the system.« less

Fabrication of Ce3+ doped Gd3Ga3Al2O12 ceramics by reactive sintering method

NASA Astrophysics Data System (ADS)

Ye, Yong; Liu, Peng; Yan, Dongyue; Xu, Xiaodong; Zhang, Jian

2017-09-01

Ce3+ doped Gd3Ga3Al2O12 (Ce:GGAG) ceramics were fabricated by solid state reactive sintering method in this study. The ceramics were pre-sintered in normal muffle furnace in air at various temperature range from 1410 °C to 1550 °C for 10 h and post-treated by hot isostatic press at 1400 °C/2 h in 200 MPa Ar. The phase and microstructure evolution of Ce: GGAG samples during the densification process were investigated by X-ray diffraction and scanning electron microscope. Pure GGAG phase appeared with the temperature increased to 1200 °C. The fully dense and translucent GGAG ceramics were fabricated by pre-sintering at 1450 °C and followed by HIP treatment.

Dielectric spectroscopy of Dy2O3 doped (K0.5Na0.5)NbO3 piezoelectric ceramics

NASA Astrophysics Data System (ADS)

Mahesh, P.; Subhash, T.; Pamu, D.

2014-06-01

We report the dielectric properties of ( K 0.5 Na 0.5 ) NbO 3 ceramics doped with x wt% of Dy 2 O 3 (x= 0.0-1.5 wt%) using the broadband dielectric spectroscopy. The X-ray diffraction studies showed the formation of perovskite structure signifying that Dy 2 O 3 diffuse into the KNN lattice. Samples doped with x > 0.5 wt% exhibit smaller grain size and lower relative densities. The dielectric properties of KNN ceramics doped with Dy 2 O 3 are enhanced by increasing the Dy 3+ content; among the compositions studied, x = 0.5 wt% exhibited the highest dielectric constant and lowest loss at 1MHz over the temperature range of 30°C to 400°C. All the samples exhibit maximum dielectric constant at the Curie temperature (˜ 326°C) and a small peak in the dielectric constant at around 165°C is due to a structural phase transition. At the request of all authors, and by agreement with the Proceedings Editors, a corrected version of this article was published on 19 June 2014. The full text of the Corrigendum is attached to the corrected article PDF file.

Enhanced texture evolution and piezoelectric properties in CuO-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 grain-oriented ceramics

NASA Astrophysics Data System (ADS)

Chang, Yunfei; Watson, Beecher; Fanton, Mark; Meyer, Richard J.; Messing, Gary L.

2017-12-01

In this work, both crystallographic texture and doping engineering strategies were integrated to develop relaxor-PbTiO3 (PT) based ternary ferroelectric ceramics with enhanced texture evolution and superior electromechanical properties. CuO-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) piezoelectric ceramics with [001]c texture fraction ≥97% were synthesized by templated grain growth. The addition of CuO significantly promotes densification and oriented grain growth in the templated ceramics, leading to full texture development at dramatically reduced times and temperatures. Moreover, the CuO dopant remarkably enhances the piezoelectric properties of the textured ceramics while maintaining high phase transition temperatures and large coercive fields. Doping 0.125 wt. % CuO yields the electromechanical properties of d33 = 927 pC/N, d33* = 1510 pm/V, g33 = 43.2 × 10-3 Vm/N, Kp = 0.87, Ec=8.8 kV/cm, and tan δ = 1.3%, which are the best values reported so far in PIN-PMN-PT based ceramics. The high piezoelectric coefficient is mainly from the reversible piezoelectric response, with the irreversible contribution being on the order of 13.1%. We believe that this work not only facilitates closing the performance gap between ceramics and single crystals but also can expand relaxor-PT based piezoelectric application fields.

Laser ceramic materials for subpicosecond solid-state lasers using Nd3+-doped mixed scandium garnets.

PubMed

Okada, Hajime; Tanaka, Momoko; Kiriyama, Hiromitsu; Nakai, Yoshiki; Ochi, Yoshihiro; Sugiyama, Akira; Daido, Hiroyuki; Kimura, Toyoaki; Yanagitani, Takagimi; Yagi, Hideki; Meichin, Noriyuki

2010-09-15

We have successfully developed and demonstrated broadband emission Nd-doped mixed scandium garnets based on laser ceramic technology. The inhomogeneous broadening of Nd(3+) fluorescence lines results in a bandwidth above 5 nm that is significantly broader than that for Nd:YAG and enables subpicosecond mode-locked pulse durations. We have also found the emission cross section of 7.8 × 10(-20) cm(2) to be adequate for efficient energy extraction and thermal conductivity of 4.7 W/mK from these new Nd-doped laser ceramics. The new laser ceramics are good candidates for laser host material in a diode-pumped subpicosecond laser system with high efficiency and high repetition rate.

Influence of La doping on structural and dielectric properties of SrBi2Nb2O9 ceramics

NASA Astrophysics Data System (ADS)

Verma, Maya; Sreenivas, K.; Gupta, Vinay

2009-01-01

Lanthanum doped SrBi2Nb2O9 ceramics with the chemical formula SrBi2-xLaxNb2O9 (SBLN) (x =0-0.5) have been prepared through conventional solid state route. X-ray diffraction reveals the shrinkage of unit cell of strontium bismuth niobate with incorporation of La3+ dopant, having no lone pair electrons. Shifting of Raman phonon modes indicates the reduced rattling space of NbO6 octahedra with increase in La doping concentration. Further, the softening of lowest frequency phonon mode with increasing x in SBLN shows the transition from ferroelectric to paraelectric at room temperature. The dielectric properties for all the compositions are studied as a function of temperature (25 to 500 °C) over the frequency range of 10 kHz-1 MHz. With increase in lanthanum doping concentration the phase transition becomes diffused and transition temperature gets shifted toward lower temperature. A phase transition from normal ferroelectric to paraelectric has been observed via relaxor-type ferroelectrics with increase in x. The frequency dependence of transition temperature was studied in terms of Vogel-Fulcher relation for SBLN (x =0.4).

Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals for 2.7 μm emissions

PubMed Central

Jiang, Yiguang; Fan, Jintai; Jiang, Benxue; Mao, Xiaojian; Tang, Junzhou; Xu, Yinsheng; Dai, Shixun; Zhang, Long

2016-01-01

Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals were obtained by direct liquid-phase sintering of a mixture of SrF2 powders and precursor glass powders at 820 °C for 15 min. The appearance and microstructural evolution of the SrF2 crystals in the resulting glass ceramics were investigated using X-ray diffraction, field-emission scanning electron microscopy and transmission microscopy. The SrF2 crystals are ~15 μm in size and are uniformly distributed throughout the fluorophosphate glass matrix. The glass ceramics achieve an average transmittance of 75% in the visible region and more than 85% in the near-IR region. The high transmittance of the glass ceramics results from matching the refractive index of the SrF2 with that of the precursor glass. Energy dispersive spectroscopy, photoluminescence spectra, and photoluminescence lifetimes verified the incorporation of Er3+ into the micron-sized SrF2 crystals. Intense 2.7 μm emissions due to the 4I11/2 → 4I13/2 transition were observed upon excitation at 980 nm using a laser diode. The maximum value of the emission cross section of Er3+ around 2.7 μm is more than 1.2 × 10−20 cm2, which indicates the potential of using transparent glass ceramics containing micron-sized SrF2 crystals for efficient 2.7 μm lasers and amplifiers. PMID:27430595

Er(3+)-doped transparent glass ceramics containing micron-sized SrF2 crystals for 2.7 μm emissions.

PubMed

Jiang, Yiguang; Fan, Jintai; Jiang, Benxue; Mao, Xiaojian; Tang, Junzhou; Xu, Yinsheng; Dai, Shixun; Zhang, Long

2016-07-19

Er(3+)-doped transparent glass ceramics containing micron-sized SrF2 crystals were obtained by direct liquid-phase sintering of a mixture of SrF2 powders and precursor glass powders at 820 °C for 15 min. The appearance and microstructural evolution of the SrF2 crystals in the resulting glass ceramics were investigated using X-ray diffraction, field-emission scanning electron microscopy and transmission microscopy. The SrF2 crystals are ~15 μm in size and are uniformly distributed throughout the fluorophosphate glass matrix. The glass ceramics achieve an average transmittance of 75% in the visible region and more than 85% in the near-IR region. The high transmittance of the glass ceramics results from matching the refractive index of the SrF2 with that of the precursor glass. Energy dispersive spectroscopy, photoluminescence spectra, and photoluminescence lifetimes verified the incorporation of Er(3+) into the micron-sized SrF2 crystals. Intense 2.7 μm emissions due to the (4)I11/2 → (4)I13/2 transition were observed upon excitation at 980 nm using a laser diode. The maximum value of the emission cross section of Er(3+) around 2.7 μm is more than 1.2 × 10(-20) cm(2), which indicates the potential of using transparent glass ceramics containing micron-sized SrF2 crystals for efficient 2.7 μm lasers and amplifiers.

Effect of cerium oxide doping on the performance of CaO-based sorbents during calcium looping cycles.

PubMed

Wang, Shengping; Fan, Shasha; Fan, Lijing; Zhao, Yujun; Ma, Xinbin

2015-04-21

A series of CaO-based sorbents were synthesized through a sol-gel method and doped with different amounts of CeO2. The sorbent with a Ca/Ce molar ratio of 15:1 showed an excellent absorption capacity (0.59 gCO2/g sorbent) and a remarkable cycle durability (up to 18 cycles). The admirable capture performance of CaCe-15 was ascribed to its special morphology formed by the doping of CeO2 and the well-distributed CeO2 particles. The sorbents doped with CeO2 possessed a loose shell-connected cross-linking structure, which was beneficial for the contact between CaO and CO2. CaO and CeO2 were dispersed homogeneously, and the existence of CeO2 also decreased the grain size of CaO. The well-dispersed CeO2, which could act as a barrier, effectively prevented the CaO crystallite from growing and sintering, thus the sorbent exhibited outstanding stability. The doping of CeO2 also improved the carbonation rate of the sorbent, resulting in a high capacity in a short period of time.

[Optical and spectral parameters in Ce3+ -doped gadolinium gallium aluminum garnet glass-ceramics].

PubMed

Gong, Hua; Zhao, Xin; Yu, Xiao-bo; Setsuhisa, Tanabe; Lin, Hai

2010-01-01

The crystalline phases of Ce3+ -doped gadolinium gallium aluminum garnet (GGAG) glass-ceramics were investigated by X-ray diffraction, and the fluorescence spectra were recorded under the pumping of blue light-emitting diode (LED) using an integrating sphere of 10-inch in diameter, which connected to a CCD detector. The spectral power distribution of the glass-ceramics was obtained from the measured spectra first, and then the quantum yield was derived based on the photon distribution. The quantum yield of Ce3+ emission in GGAG glass-ceramics is 29.2%, meanwhile, the color coordinates and the correlated color temperature (CCT) of combined white light were proved to be x = 0.319, y = 0.349 and 6086 K, respectively. Although the quantum yield is a little smaller than the value in Ce3+ -doped YAG glass-ceramics, the CCT of the combined white light is much smaller than that in the latter. The optical behavior of GGAG glass-ceramics provides new vision for developing comfortable LED lighting devices.

White up-conversion emission in Ho3+/Tm3+/Yb3+ tri-doped glass ceramics embedding BaF2 nanocrystals

NASA Astrophysics Data System (ADS)

Li, Chenxia; Xu, Shiqing; Ye, Rengguang; Deng, Degang; Hua, Youjie; Zhao, Shilong; Zhuang, Songlin

2011-04-01

Ho3+/Tm3+/Yb3+ tri-doped glass ceramics with white light emitting have been developed and demonstrated. Pumped by 980 nm laser diode (LD), intensive red, green and blue up-conversions (UC) were obtained. The green emission is assigned to Ho3+ ion and the blue emission is assigned to Tm3+ ion, whereas the red emission is the combination contribution of the Ho3+ and Tm3+ ions. The RGB intensities could be adjusted by tuning the rare-earth ion concentration and pump power intensity. Thus, multicolor of the luminescence, including perfect white light with CIE-X=0.329 and CIE-Y=0.342 in the 1931 CIE chromaticity diagram can be obtained in 0.15 Ho3+/0.2Tm3+/3Yb3+ tri-doped glass ceramics embedding BaF2 nanocrystals pumped by a single infrared laser diode source of 980 nm at 500 mW. The up-conversion luminescence mechanism of Yb3+ sensitize Ho3+ and Tm3+ ions and the energy transfer from Ho3+ to Tm3+ in oxy-fluoride silicate glass ceramics were analyzed.

THE STUDY OF HIGH DIELECTRIC CONSTANT MECHANISM OF La-DOPED Ba0.67Sr0.33TiO3 CERAMICS

NASA Astrophysics Data System (ADS)

Xu, Jing; He, Bo; Liu, Han Xing

It is a common and effective method to enhance the dielectric properties of BST ceramics by adding rare-earth elements. In this paper, it is important to analyze the cause of the high dielectric constant behavior of La-doped BST ceramics. The results show that proper rare earth La dopant (0.2≤x≤0.7) may greatly increase the dielectric constant of BST ceramics, and also improve the temperature stability, evidently. According to the current-voltage (J-V) characteristics, the proper La-doped BST ceramics may reach the better semiconductivity, with the decrease and increase in La doping, the ceramics are insulators. By using the Schottky barrier model and electric microstructure model to find the surface or grain boundary potential barrier height, the width of the depletion layer and grain size do play an important role in impacting the dielectric constant.

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

PubMed Central

Mehdizadeh Dehkordi, Arash; Bhattacharya, Sriparna; Darroudi, Taghi; Zeng, Xiaoyu; Alshareef, Husam N.; Tritt, Terry M.

2015-01-01

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3. PMID:26327483

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties.

PubMed

Mehdizadeh Dehkordi, Arash; Bhattacharya, Sriparna; Darroudi, Taghi; Zeng, Xiaoyu; Alshareef, Husam N; Tritt, Terry M

2015-08-15

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

Chemical reaction mechanisms between Y2O3 stabilized ZrO2 and Gd doped CeO2 with PH3 in coal syngas

NASA Astrophysics Data System (ADS)

Chen, Gang; Kishimoto, Haruo; Yamaji, Katsuhiko; Kuramoto, Koji; Gong, Mingyang; Liu, Xingbo; Hackett, Gregory; Gerdes, Kirk; Horita, Teruhisa

2014-12-01

To clarify the chemical stability of the key materials exposed to coal syngas (CSG) containing PH3 contaminant atmosphere, exposure tests of Y2O3 8 mol.% stabilized ZrO2 (YSZ) and Gd doped CeO2 (GDC) are carried out in simulated CSG with different concentrations of PH3. Significant reaction between YSZ and 10 ppm PH3 in CSG atmosphere is confirmed, and no obvious reaction is detected on the surface of YSZ after exposed in CSG with 1 ppm PH3. YPO4, Zr2.25(PO4)3 and monoclinic Y partial stabilized ZrO2 (m-PSZ) are identified on the YSZ pellet surface after exposed in CSG with 10 ppm PH3. GDC reacted with PH3 even at 1 ppm concentration. A (Ce0.9Gd0.1)PO4 layer is formed on the surface of GDC pellet after exposure in CSG with 10 ppm PH3. Possible reaction mechanisms between YSZ and GDC with PH3 in CSG are clarified. Compared with GDC, YSZ exhibits sufficient phosphorus resistance for devices directly exposed to a coal syngas atmosphere containing low concentration of PH3.

Promotional effect of Al2O3 on WO3/CeO2-ZrO2 monolithic catalyst for selective catalytic reduction of nitrogen oxides with ammonia after hydrothermal aging treatment

NASA Astrophysics Data System (ADS)

Xu, Haidi; Liu, Shuang; Wang, Yun; Lin, Qingjin; Lin, Chenlu; Lan, Li; Wang, Qin; Chen, Yaoqiang

2018-01-01

Hydrothermal stability of catalysts for selective catalytic reduction of NOx with NH3 (NH3-SCR) has always been recognized as a challenge in development of candidate catalysts for applications in diesel engine emissions. In this study, Al2O3 was introduced into CeO2-ZrO2 to improve the NH3-SCR activity of WO3/CeO2-ZrO2 after hydrothermal aging (HA) treatment at 800 °C for 12 h. The activity results indicated that the NH3-SCR activity of WO3/CeO2-ZrO2-HA was obviously improved in the whole reaction temperature range after doping Al2O3 into CeO2-ZrO2, for example, the average and maximum NOx conversion were separately increased by ca. 20% and 25% after HA treatment. XRD, Raman, TEM and EDX results revealed that the introduction of Al2O3 inhibited the sintering and agglomeration of CeO2-ZrO2 and WO3 and the formation of Ce2(WO4)3 after HA treatment. Accordingly, WO3/CeO2-ZrO2-Al2O3-HA showed remarkably improved structural stability and reducibility, increased surface acidity, and facilitated the reactivity between adsorbed NH3 and nitrate species, which together contributed to its better catalytic performance after hydrothermal aging treatment.

Enhanced strain effect of aged acceptor-doped BaTiO3 ceramics with clamping domain structures

NASA Astrophysics Data System (ADS)

Wang, Lei; Zhou, Zhiyong; Zhao, Xiaobo; Liu, Zhen; Liang, Ruihong; Dong, Xianlin

2017-03-01

A clamping domain structure is proposed to improve the amount of non-180° domain switching in BaTiO3 based piezoelectric ceramics. Experimental results show a large unipolar strain of 0.23% at 5 kV/mm in aged 0.5 mol. % Mn doped BaTiO3 ceramics with clamping domain structures, and the normalized strain (d33*= Smax/Emax) reaches 600 pm/V at low electric fields of 2 or 3 kV/mm. In contrast, pure BaTiO3 ceramics with clamping domain structures exhibit no clear polarization constriction or strain enhancement at 3 kV/mm. Electron paramagnetic resonance spectra verify the existence of titanium vacancies, Mn2+ and Mn4+, in 0.5 mol. % Mn doped BaTiO3 ceramics. These results indicate that the enhanced strain effect can be attributed to the combined effect of the clamping domain structure and stabilization of defect dipoles. This method provides a general way to obtain large strain in ferroelectrics.

Microstructure and spectroscopic investigations of calcium zinc bismuth phosphate glass ceramics doped with manganese ions

NASA Astrophysics Data System (ADS)

Suneel Kumar, A.; Sambasiva Rao, M. V.; Chinna Ram, G.; Krishna Rao, D.

2018-01-01

Multi-component 10CaF2-20ZnO-(15 - x)Bi2O3-55P2O5:xMnO (0 ≤ x ≤ 2.5) glass ceramics were synthesised by melt quenching technique and heat treatment. The prepared glass ceramics were characterised by XRD, DTA, EDS and SEM. Spectroscopic studies such as optical absorption, EPR, FTIR and Raman were also carried out on these glass ceramics. The XRD and SEM studies have indicated that ceramic samples contain well defined and randomly distributed grains of different crystalline phases. The observed increase of enthalpy from DTA patterns up to 1 mol% of MnO indicates that the crystallisation starts initially from the surface of the material then gradually it is extended to the volume of the material and this influence is meagre at higher concentrations of MnO. The absorption spectra of manganese doped glass ceramics have exhibited two types of conventional bands; one due to Mn2+ ions and other due to Mn3+ ions. The EPR spectra of MnO doped glass ceramics showed a resonance signal around g2 = 2.023 with a six line hyperfine structure and another signal at about g1 = 4.314. The relative intensity and half-width of these two signals are observed to increase with the increase in the concentration of manganese ions up to 1 mol% beyond this concentration it is found to decrease. Such observation indicates the conversion of part of Mn2+ ions into Mn3+ ions in the glass ceramic matrix. The observed increase in the intensity of symmetrical structural units at the expense of asymmetrical structural units from the FTIR and Raman spectra at higher concentration of MnO indicating that Mn2+ ions occupy the network forming positions in the glass ceramic structure.

Fabrication and characterization of millimeter-scale translucent La{sub 2}O{sub 3}-doped Al{sub 2}O{sub 3} ceramic hollow spheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Haoting; Liao, Qilong, E-mail: liaoqilong@swust.edu.cn; Dai, Yunya

2016-04-15

Highlights: • Millimeter-scale translucent La{sub 2}O{sub 3}-doped Al{sub 2}O{sub 3} hollow spheres have been prepared. • The diameters of the prepared hollow spheres are 500–1300μm. • The degree of sphericity for the prepared hollow spheres is above 98%. • The mechanisms of transparency are discussed. - Abstract: Millimeter-scale translucent La{sub 2}O{sub 3}-doped Al{sub 2}O{sub 3} ceramic hollow spheres have been successfully prepared using the oil-in-water (paraffin-in-alumina sol) droplets as precursors made by self-made T-shape micro-emulsion device. The main crystalline phase of the obtained hollow sphere is alpha alumina. The prepared translucent La{sub 2}O{sub 3}-containing Al{sub 2}O{sub 3} ceramic hollow spheresmore » have diameters of 500–1300 μm, wall thickness of about 23 μm and the degree of sphericity of above 98%. With the increase of the La{sub 2}O{sub 3} content, grains and grain-boundaries of the alumina spherical shell for the prepared millimeter-scale hollow spheres become regular and clear gradually. When the La{sub 2}O{sub 3} content is 0.1 wt.%, the crystal surface of the obtained Al{sub 2}O{sub 3} spherical shell shows optimal grains and few pores, and its transmittance reaches 42% at 532 nm laser light. This method provides a promising technique of preparing millimeter-scale translucent ceramic hollow spheres for laser inertial confined fusion.« less

Improved dielectric and ferroelectric properties of Mn doped barium zirconium titanate (BZT) ceramics for energy storage applications

NASA Astrophysics Data System (ADS)

Sangwan, Kanta Maan; Ahlawat, Neetu; Kundu, R. S.; Rani, Suman; Rani, Sunita; Ahlawat, Navneet; Murugavel, Sevi

2018-06-01

Lead free Mn doped barium zirconium titanate ceramic of composition BaZr0.045 (MnxTi1-x)0.955O3 (x = 0.00, 0.01, 0.02) were prepared by solid state reaction method. Tetragonal perovskite structure was confirmed by Rietveld refinement of X-ray diffraction pattern. Analysis of Scanning electron microscope (SEM) micrographs revealed that addition of Mn up to a certain limit accelerates grain growth of BZT ceramic. Static dielectric constant was successfully extended up to high frequencies with an appreciable decrease in dielectric loss about 70% for Mn doped BZT ceramics. The experimental data fitted with Curie Weiss Law and Power Law confirmed first order transition and diffusive behavior of the investigated system. The shifting of Curie temperature (Tc) from 387 K to 402 K indicated tendency for sustained ferroelectricity in doped BZMT ceramics. High value of percentage temperature coefficient of capacitance TCC >10% near Tc was observed for all the compositions and increases with Mn content in pure BZT. At room temperature, BZT modified ceramic corresponding to x = 0.01 composition shows better values of remnant polarization (Pr = 5.718 μC/cm2), saturation polarization (Ps = 14.410 μC/cm2), low coercive field (Ec = 0.612 kV/cm), and highest value of Pr/Ps = 0.396.

Laser Demonstration of Diode-Pumped Nd3+-Doped Fluorapatite Anisotropic Ceramics

NASA Astrophysics Data System (ADS)

Akiyama, Jun; Sato, Yoichi; Taira, Takunori

2011-02-01

We report the first demonstration of a diode-pumped anisotropic ceramic laser that uses microdomain-controlled neodymium-doped hexagonal fluorapatite [Nd3+:Ca10(PO4)6F2, Nd:FAP] polycrystalline ceramics as the gain medium, which were fabricated by the rare-earth-assisted magnetic grain-orientation control method, as a step toward achieving giant micro photonics. The laser delivers 1063.10 and 1063.22 nm output beams when pumped with a central wavelength of 807.5 nm and a 2 nm bandwidth diode laser operating in quasi-continuous-wave (QCW) mode. We obtained a maximum QCW peak power of 255 mW with an uncoated 2 at. % Nd:FAP material.

Down-shifting in Ce3+-Tb3+ co-doped SiO2-LaF3 nano-glass-ceramics for photon conversion in solar cells

NASA Astrophysics Data System (ADS)

Velázquez, J. J.; Rodríguez, V. D.; Yanes, A. C.; del-Castillo, J.; Méndez-Ramos, J.

2012-10-01

95SiO2-5LaF3 sol-gel derived nano-glass-ceramics single doped with Ce3+ or Tb3+ and co-doped with Ce3+-Tb3+ were synthesized by thermal treatment of precursor glasses. Precipitation of LaF3 nanocrystals during ceramming process was confirmed by X-ray diffraction with mean size ranging from 12 to 15 nm. An exhaustive spectroscopic analysis has been carried out. As a result, it was found that the green emission of Tb3+ ions was greatly enhanced through down shifting process, due to efficient energy transfer from Ce3+ to Tb3+ ions in the glass-ceramics, which is favored by the reduction of the interionic distances when the dopant ions are partitioned into LaF3 nanocrystals. These results suggest the use of these materials to improve the efficiency of solar cells.

Piezoelectric properties and temperature stability of Mn-doped Pb(Mg1/3Nb2/3)-PbZrO3-PbTiO3 textured ceramics

NASA Astrophysics Data System (ADS)

Yan, Yongke; Cho, Kyung-Hoon; Priya, Shashank

2012-03-01

In this letter, we report the electromechanical properties of textured 0.4Pb(Mg1/3Nb2/3)O3-0.25PbZrO3-0.35PbTiO3 (PMN-PZT) composition which has relatively high rhombohedral to tetragonal (R-T) transition temperature (TR-T of 160 °C) and Curie temperature (TC of 234 °C) and explore the effect of Mn-doping on this composition. It was found that MnO2-doped textured PMN-PZT ceramics with 5 vol. % BaTiO3 template (T-5BT) exhibited inferior temperature stability. The coupling factor (k31) of T-5BT ceramic started to degrade from 75 °C while the random counterpart showed a very stable tendency up to 180 °C. This degradation was associated with the "interface region" formed in the vicinity of BT template. MnO2 doped PMN-PZT ceramics textured with 3 vol. % BT and subsequently poled at 140 °C (T-3BT140) exhibited very stable and high k31 (>0.53) in a wide temperature range from room temperature to 130 °C through reduction in the interface region volume. Further, the T-3BT140 ceramic exhibited excellent hard and soft combinatory piezoelectric properties of d33 = 720 pC/N, k31 = 0.53, Qm = 403, tan δ = 0.3% which are very promising for high power and magnetoelectric applications.

Thermoelectric properties of the yttrium-doped ceramic oxide SrTiO3

NASA Astrophysics Data System (ADS)

Khan, Tamal Tahsin; Ur, Soon-Chul

2017-01-01

The doping dependence of the thermoelectric figure of merit, ZT, of the ceramic oxide SrTiO3 at high temperature has been studied. In this study, yttrium was used as the doping element. A conventional solid-state reaction method was used for the preparation of Y-doped SrTiO3. The doping level in SrTiO3 was controlled to be in the doping range of 2 - 10 mole%. Almost all the yttrium atoms incorporated into the SrTiO3 provided charge carriers, as was observed by using X-ray diffraction pattern. The relative densities of all the samples varied from 98.53% to 99.45%. The thermoelectric properties, including the electrical conductivity σ, Seebeck coefficient S, thermal conductivity k, and the figure of merit, ZT, were investigated at medium temperatures. The ZT value showed an obvious doping level dependence, in which a value as high as 0.18 is realized at 773 K for a doping of 8 mole%.

SO2 Adsorption on CeO2(100) and CeO2(111)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mullins, David R.

2016-09-13

The adsorption and reaction of sulfur dioxide, SO2, was studied on oxidized and reduced CeOX(100) and compared to previous results on CeOX(111). SO2 adsorbs on oxidized CeO2(100) as sulfite, SO32-, at 200 K and sulfite is the only adsorbate observed on the surface at any temperature. The sulfite desorbs monotonically from 200 to 700 K. The adsorption and desorption of SO2 does not result in any change in the Ce4+ oxidation state. SO2 also adsorbs as sulfite on reduced CeO1.7(100) at 200 K. There is also a small amount of elemental sulfur, S0, formed. As the sample is heated themore » sulfite decomposes into sulfide, S2-. Roughly 25 % of the adsorbed S either desorbs or diffuses into the bulk of the reduced ceria. The decomposition, and resulting formation of S2- and O2-, re-oxidize some of the Ce3+ to Ce4+. Unlike what has been observed following the adsorption and reaction of many other molecules, the adsorption and reaction of SO2 is virtually identical on CeOX(100) and CeOX(111).« less

Spectroscopic properties of Eu3+/Nd3+ co-doped phosphate glasses and opaque glass-ceramics

NASA Astrophysics Data System (ADS)

Narro-García, R.; Desirena, H.; López-Luke, T.; Guerrero-Contreras, J.; Jayasankar, C. K.; Quintero-Torres, R.; De la Rosa, E.

2015-08-01

This paper reports the fabrication and characterization of Eu3+/Nd3+ co-doped phosphate (PNE) glasses and glass-ceramics as a function of Eu3+ concentration. The precursor glasses were prepared by the conventional melt quenching technique and the opaque glass-ceramics were obtained by heating the precursor glasses at 450 °C for 30 h. The structural and optical properties of the glass and glass-ceramics were analyzed by means of X-ray diffraction, Raman spectroscopy, UV-VIS-IR absorption spectroscopy, photoluminescence spectra and lifetimes. The amorphous and crystalline structures of the precursor glass and opaque glass-ceramic were confirmed by X-ray diffraction respectively. The Raman spectra showed that the maximum phonon energy decreased from 1317 cm-1 to 1277 cm-1 with the thermal treatment. The luminescence spectra of the glass and glass-ceramic samples were studied under 396 nm and 806 nm excitation. The emission intensity of the bands observed in opaque glass-ceramic is stronger than that of the precursor glass. The luminescence spectra show strong dependence on the Eu3+ ion concentration in the Nd3+ ion photoluminescence (PL) intensity, which suggest the presence of energy transfer (ET) and cross-relaxation (CR) processes. The lifetimes of the 4F3/2 state of Nd3+ ion in Eu3+/Nd3+ co-doped phosphate glasses and glass-ceramics under 806 nm excitation were measured. It was observed that the lifetimes of the 4F3/2 level of Nd3+ of both glasses and glass-ceramics decrease with the increasing Eu3+ concentration. However in the case of opaque glass-ceramics the lifetimes decrease only 16%.

Electrical and dielectric properties of ZnO and CeO{sub 2} doped ZrTi{sub 2}O{sub 6} ceramic

DOE Office of Scientific and Technical Information (OSTI.GOV)

George, Aneesh; Thomas, Jijimon K.; John, Annamma

2014-01-28

Zirconium oxide (ZrO{sub 2}) and titanium dioxide (TiO{sub 2}) are the important catalyst supports, since it has acidic and basic properties. The intermediate phase zirconium titanate ZrTi{sub 2}O{sub 6}, which is a solid solution with Zr:Ti ratio 1:2 has outstanding dielectric properties. The effects of doping of ZnO and CeO{sub 2} on the dielectric and electrical properties of ZrTi{sub 2}O{sub 6} ceramic are investigated. On adding 0.5 wt% ZnO, the dielectric constant is increased but, on adding CeO{sub 2}, the dielectric constant is decreased. The bulk density of pure sample sintered at 1530 °C is 91% of theoretical density whilemore » that of the doped samples sintered at 1450 °C is more than 94% of theoretical density. Scanning electron micrographs reveal that the samples are well sintered with minimum porosity. The semicircle behavior in the Cole-Cole plots at room temperature reveals that the samples are good ionic conductor. The induced impedance is reduced for doped samples and this can be used as a material for electrolyte in Solid Oxide Fuel Cell.« less

Fabrication and microstructure of cerium doped lutetium aluminum garnet (Ce:LuAG) transparent ceramics by solid-state reaction method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Junlang, E-mail: lijunlangx@163.com; Xu, Jian, E-mail: xu.jian.57z@st.kyoto-u.ac.jp; Graduate School of Human and Environmental Studies, Division of Materials Function, Kyoto University, Kyoto 606-8501

2014-07-01

Highlights: • We fabricate Ce doped lutetium aluminum garnet ceramics by solid-state method. • The raw materials include Lu{sub 2}O{sub 3} nanopowders synthesized by co-precipitation method. • The density of the transparent ceramics reach 99.7% of the theoretical value. • The optical transmittance of the bulk ceramic at 550 nm was 57.48%. • Some scattering centers decrease the optical characteristic of the ceramic. - Abstract: Polycrystalline Ce{sup 3+} doped lutetium aluminum garnet (Ce:LuAG) transparent ceramics fabricated by one step solid-state reaction method using synthetic nano-sized Lu{sub 2}O{sub 3}, commercial α-Al{sub 2}O{sub 3} and CeO{sub 2} powders were investigated in thismore » paper. The green compacts shaped by the mixed powders were successfully densified into Ce:LuAG transparent ceramics after vacuum sintering at 1750 °C for 10 h. The in-line optical transmittance of the Ce:LuAG ceramic made by home-made Lu{sub 2}O{sub 3} powders could reach 57.48% at 550 nm, which was higher than that of the ceramic made by commercial Lu{sub 2}O{sub 3} powders (22.96%). The microstructure observation showed that light scattering centers caused by micro-pores, aluminum segregation and refraction index inhomogeneities induced the decrease of optical transparency of the Ce:LuAG ceramics, which should be removed and optimized in the future work.« less

Microstructure evolution and electrical characterization of Lanthanum doped Barium Titanate (BaTiO{sub 3}) ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Billah, Masum, E-mail: masum.buet09@gmail.com; Ahmed, A., E-mail: jhinukbuetmme@gmail.com; Rahman, Md. Miftaur, E-mail: miftaurrahman@mme.buet.ac.bd

2016-07-12

In the current work, we investigated the structural and dielectric properties of Lanthanum oxide (La{sub 2}O{sub 3}) doped Barium Titanate (BaTiO{sub 3}) ceramics and established a correlation between them. Solid state sintering method was used to dope BaTiO{sub 3} with 0.3, 0.5 and 0.7 mole% La{sub 2}O{sub 3} under different sintering parameters. The raw materials used were La{sub 2}O{sub 3} nano powder of ~80 nm grain size and 99.995% purity and BaTiO{sub 3} nano powder of 100 nm grain size and 99.99% purity. Grain size distribution and morphology of fracture surface of sintered pellets were examined by Field Emission Scanningmore » Electron Microscope and X-Ray Diffraction analysis was conducted to confirm the formation of desired crystal structure. The research result reveal that grain size and electrical properties of BaTiO{sub 3} ceramic significantly enhanced for small amount of doping (up to 0.5 mole% La{sub 2}O{sub 3}) and then decreased with increasing doping concentration. Desired grain growth (0.80-1.3 µm) and high densification (<90% theoretical density) were found by proper combination of temperature, sintering parameters and doping concentration. We found the resultant stable value of dielectric constant was 10000-12000 at 100-300 Hz in the temperature range of 30°-50° C for 0.5 mole% La{sub 2}O{sub 3} with corresponding shift of curie temperature around 30° C. So overall this research showed that proper La{sup 3+} concentration can control the grain size, increase density, lower curie temperature and hence significantly improve the electrical properties of BaTiO{sub 3} ceramics.« less

Aerosol Physics Considerations for Using Cerium Oxide CeO 2 as a Surrogate for Plutonium Oxide PuO 2 in Airborne Release Fraction Measurements for Storage Container Investigations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, Murray E.; Tao, Yong

Cerium oxide (CeO2) dust is recommended as a surrogate for plutonium oxide (PuO2) in airborne release fraction experiments. The total range of applicable particle sizes for PuO2 extends from 0.0032 μm (the diameter of a single PuO2 molecule) to 10 μm (the defined upper boundary for respirable particles). For particulates with a physical particle diameter of 1.0 μm, the corresponding aerodynamic diameters for CeO2 and PuO2 are 2.7 μm and 3.4 μm, respectively. Cascade impactor air samplers are capable of measuring the size distributions of CeO2 or PuO2 particulates. In this document, the aerodynamic diameters for CeO2 and PuO2 weremore » calculated for seven different physical diameters (0.0032, 0.02, 0.11, 0.27, 1.0, 3.2, and 10 μm). For cascade impactor measurements, CeO2 and PuO2 particulates with the same physical diameter would be collected onto the same or adjacent collection substrates. The difference between the aerodynamic diameter of CeO2 and PuO2 particles (that have the same physical diameter) is 39% of the resolution of a twelve-stage MSP Inc. 125 cascade impactor, and 34% for an eight-stage Andersen impactor. An approach is given to calculate the committed effective dose (CED) coefficient for PuO2 aerosol particles, compared to a corresponding aerodynamic diameter of CeO2 particles. With this approach, use of CeO2 as a surrogate for PuO2 material would follow a direct conversion based on a molar equivalent. In addition to the analytical information developed for this document, several US national labs have published articles about the use of CeO2 as a PuO2 surrogate. Different physical and chemical aspects were considered by these investigators, including thermal properties, ceramic formulations, cold pressing, sintering, molecular reactions, and mass loss in high temperature gas flows. All of those US national lab studies recommended the use of CeO2 as a surrogate material for PuO2.« less

Phase segregation and dielectric, ferroelectric, and piezoelectric properties of MgO-doped NBT-BT lead-free ferroelecric ceramics

NASA Astrophysics Data System (ADS)

Liu, Gang; Wang, Ziyang; Zhang, Leiyang; Shi, Wenjing; Jing, Jiayi; Chen, Yi; Liu, Hongbo; Yan, Yan

2018-03-01

MgO doped NBT-BT ceramics were prepared by the conventional electroceramic processing. The effects of MgO on the phase, microstructures and electrical properties of NBT-BT ceramics were systematically investigated. When doping content is more than 1%, a second phase appeared, which has great effect on dielectric, ferroelectric, and piezoelectric properties, such as the T F-R peak weakened, moved to the higher temperature, and eventually disappeared. When the doping content is above 1.5%, the ceramic samples show a strong relaxation. The detailed analysis and discussion can be found within this study.

Photocatalytic activity of binary metal oxide nanocomposites of CeO2/CdO nanospheres: Investigation of optical and antimicrobial activity.

PubMed

Magdalane, C Maria; Kaviyarasu, K; Vijaya, J Judith; Siddhardha, Busi; Jeyaraj, B

2016-10-01

We report the synthesis of high quality CeO2-CdO binary metal oxide nanocomposites were synthesized by a simple chemical precipitation and hydrothermal method. Cerium nitrate and cadmium nitrate were used as precursors. Composition, structure and morphology of the nanocomposites were analyzed by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). XRD pattern proves that the final product has cubic phase and the particle size diameter of the nanocomposites are 27nm, XRD results also indicated that the crystalline properties of the nanocomposite were improved without affecting the parent lattice, FESEM analysis indicates that the product is composed of spherical particles in clusters. The morphological and optical properties of CeO2-CdO nanosamples were characterized by HRTEM and DRS spectroscopy. The IR results showed high purity of products and indicated that the nanocomposites are made up of CeO2 and CdO bonds. Absorption spectra exhibited an upward shift in characteristic peaks caused by the addition of transition metal oxide, suggesting that crystallinity of both the metal oxide is improved due to specific doping level. TGA plots further confirmed the purity and stability of nanomaterials prepared. Hence the nanocomposite has cubic crystal lattice and form a homogeneous solid structure. From the result, Cd(2+) ions are embedded in the cubic crystal lattice of ceria. The growth rate increases which are ascribed to the cationic doping with a lower valence cation. Ce-Cd binary metal oxide nanocomposites showed antibacterial activity, it showed the better growth inhibition towards p.aeruginosa. Exploit of photodegradation and photocatalytic activity of large scale synthesis of CeO2-CdO binary metal oxide nanocomposites was reported. Copyright © 2016 Elsevier B.V. All rights reserved.

Robust Hydrophobic Surfaces from Suspension HVOF Thermal Sprayed Rare-Earth Oxide Ceramics Coatings.

PubMed

Bai, M; Kazi, H; Zhang, X; Liu, J; Hussain, T

2018-05-03

This study has presented an efficient coating method, namely suspension high velocity oxy-fuel (SHVOF) thermal spraying, to produce large super-hydrophobic ceramic surfaces with a unique micro- and nano-scale hierarchical structures to mimic natural super-hydrophobic surfaces. CeO 2 was selected as coatings material, one of a group of rare-earth oxide (REO) ceramics that have recently been found to exhibit intrinsic hydrophobicity, even after exposure to high temperatures and abrasive wear. Robust hydrophobic REO ceramic surfaces were obtained from the deposition of thin CeO 2 coatings (3-5 μm) using an aqueous suspension with a solid concentration of 30 wt.% sub-micron CeO 2 particles (50-200 nm) on a selection of metallic substrates. It was found that the coatings' hydrophobicity, microstructure, surface morphology, and deposition efficiency were all determined by the metallic substrates underneath. More importantly, it was demonstrated that the near super-hydrophobicity of SHVOF sprayed CeO 2 coatings was achieved not only by the intrinsic hydrophobicity of REO but also their unique hierarchically structure. In addition, the coatings' surface hydrophobicity was sensitive to the O/Ce ratio, which could explain the 'delayed' hydrophobicity of REO coatings.

Transparent layered YAG ceramics with structured Yb doping produced via tape casting

NASA Astrophysics Data System (ADS)

Hostaša, Jan; Piancastelli, Andreana; Toci, Guido; Vannini, Matteo; Biasini, Valentina

2017-03-01

The flexibility of the ceramic production process, in particular in terms of shaping and spatial control of distribution of active ions, is one of the strong points in favor of transparent ceramics. In high power lasers in particular, where thermal management is a critical issue, the finely controlled design of spatial distribution of the doping ions within the laser gain media can reduce undesired thermally induced effects and large temperature gradients, and thus enhance the efficiency and laser beam quality especially under increased thermal load. In the present work transparent structured YAG ceramics with Yb doping were produced by tape casting followed by thermal compression of assembled tapes and sintered under high vacuum. The thermal compression of variously doped tape cast layers is a very promising method because it allows a high precision and good control over dopant distribution in the sintered material. After sintering, the distribution of Yb across the layers was characterized by SEM-EDX and the thickness of Yb diffusion zones between the layers with different Yb content was measured. Optical homogeneity was assessed by means of optical transmittance mapping of the samples and by 2D scanning of laser output. The effect of structured dopant distribution on laser performance was measured in quasi-CW and CW regime with different duty factors. Slope efficiency values higher than 50% were measured both in quasi-CW and in CW lasing conditions. The results are in good agreement with previously calculated predictions, confirming the beneficial effect of structured doping on laser performances and enlightening the impact of the residual scattering losses. Compared to other processing methods, such as the pressing of granulated powders, tape casting followed by thermal compression leads to straight and narrow interfaces between layers with different composition and allows to build structures composed of extremely thin layers with defined dopant content.

Multi-susceptibile Single-Phased Ceramics with Both Considerable Magnetic and Dielectric Properties by Selectively Doping

PubMed Central

Liu, Chuyang; Zhang, Yujing; Jia, Jingguo; Sui, Qiang; Ma, Ning; Du, Piyi

2015-01-01

Multiferroic ceramics with extraordinary susceptibilities coexisting are vitally important for the multi-functionality and integration of electronic devices. However, multiferroic composites, as the most potential candidates, will introduce inevitable interface deficiencies and thus dielectric loss from dissimilar phases. In this study, single-phased ferrite ceramics with considerable magnetic and dielectric performances appearing simultaneously were fabricated by doping target ions in higher valence than that of Fe3+, such as Ti4+, Nb5+ and Zr4+, into BaFe12O19. In terms of charge balance, Fe3+/Fe2+ pair dipoles are produced through the substitution of Fe3+ by high-valenced ions. The electron hopping between Fe3+ and Fe2+ ions results in colossal permittivity. Whilst the single-phased ceramics doped by target ions exhibit low dielectric loss naturally due to the diminishment of interfacial polarization and still maintain typical magnetic properties. This study provides a convenient method to attain practicable materials with both outstanding magnetic and dielectric properties, which may be of interest to integration and multi-functionality of electronic devices. PMID:25835175

Multi-susceptibile single-phased ceramics with both considerable magnetic and dielectric properties by selectively doping.

PubMed

Liu, Chuyang; Zhang, Yujing; Jia, Jingguo; Sui, Qiang; Ma, Ning; Du, Piyi

2015-04-02

Multiferroic ceramics with extraordinary susceptibilities coexisting are vitally important for the multi-functionality and integration of electronic devices. However, multiferroic composites, as the most potential candidates, will introduce inevitable interface deficiencies and thus dielectric loss from dissimilar phases. In this study, single-phased ferrite ceramics with considerable magnetic and dielectric performances appearing simultaneously were fabricated by doping target ions in higher valence than that of Fe(3+), such as Ti(4+), Nb(5+) and Zr(4+), into BaFe12O19. In terms of charge balance, Fe(3+)/Fe(2+) pair dipoles are produced through the substitution of Fe(3+) by high-valenced ions. The electron hopping between Fe(3+) and Fe(2+) ions results in colossal permittivity. Whilst the single-phased ceramics doped by target ions exhibit low dielectric loss naturally due to the diminishment of interfacial polarization and still maintain typical magnetic properties. This study provides a convenient method to attain practicable materials with both outstanding magnetic and dielectric properties, which may be of interest to integration and multi-functionality of electronic devices.

Multi-susceptibile Single-Phased Ceramics with Both Considerable Magnetic and Dielectric Properties by Selectively Doping

NASA Astrophysics Data System (ADS)

Liu, Chuyang; Zhang, Yujing; Jia, Jingguo; Sui, Qiang; Ma, Ning; Du, Piyi

2015-04-01

Multiferroic ceramics with extraordinary susceptibilities coexisting are vitally important for the multi-functionality and integration of electronic devices. However, multiferroic composites, as the most potential candidates, will introduce inevitable interface deficiencies and thus dielectric loss from dissimilar phases. In this study, single-phased ferrite ceramics with considerable magnetic and dielectric performances appearing simultaneously were fabricated by doping target ions in higher valence than that of Fe3+, such as Ti4+, Nb5+ and Zr4+, into BaFe12O19. In terms of charge balance, Fe3+/Fe2+ pair dipoles are produced through the substitution of Fe3+ by high-valenced ions. The electron hopping between Fe3+ and Fe2+ ions results in colossal permittivity. Whilst the single-phased ceramics doped by target ions exhibit low dielectric loss naturally due to the diminishment of interfacial polarization and still maintain typical magnetic properties. This study provides a convenient method to attain practicable materials with both outstanding magnetic and dielectric properties, which may be of interest to integration and multi-functionality of electronic devices.

The effect of micro-structure on upconversion luminescence of Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glass-ceramics

NASA Astrophysics Data System (ADS)

Zhang, Minghui; Wen, Haiqin; Pan, Xiuhong; Yu, Jianding; Jiang, Meng; Yu, Huimei; Tang, Meibo; Gai, Lijun; Ai, Fei

2018-03-01

Nd3+/Yb3+ co-doped La2O3-TiO2-ZrO2 glasses have been prepared by aerodynamic levitation method. The glasses show high refractive index of 2.28 and Abbe number of 18.3. Glass-ceramics heated at 880 °C for 50 min perform the strongest upconversion luminescence. X-ray diffraction patterns of glass-ceramics with different depths indicate that rare earth ions restrain crystallization. Body crystallization mechanism mixed with surface crystallization is confirmed in the heat treatment. Surface crystals achieve priority to grow, resulting in important effects on upconversion luminescence. The results of atomic force microscope and scanning electron microscope indicate that crystal particles with uniform size distribute densely and homogenously on the surface and large amount of glass matrix exists in the glass ceramics heated at 880 °C for 50 min. Crystals in the glass-ceramics present dense structure and strong boundaries, which can reduce the mutual nonradiative relaxation rate among rare earth ions and then improve upconversion luminescence effectively. Based on micro-structural study, the mechanism that upconversion luminescence can be improved by heat treatment has been revealed. The results of micro-structural analysis agree well with the spectra.

Transparent athermal glass-ceramics in Li2O-Al2O3-SiO2 system

NASA Astrophysics Data System (ADS)

Himei, Yusuke; Nagakane, Tomohiro; Sakamoto, Akihiko; Kitamura, Naoyuki; Fukumi, Kohei; Nishii, Junji; Hirao, Kazuyuki

2005-04-01

An attempt has been conducted to develop multicomponent transparent glass-ceramics which have athermal property better than silica glass. Transparent Li2O-Al2O3-SiO2 (LAS) glass-ceramics with small thermal expansion coefficient was chosen as a candidate. Athermal property of the glass-ceramics was improved by the independent control of temperature coefficients of electronic polarizability and thermal expansion coefficient, both of which govern the temperature coefficient of optical path length. It was found that temperature coefficient of electronic polarizability and thermal expansion coefficient of the LAS glass-ceramics were controllable by the additives and crystallization conditions. The doping of B2O3 and the crystallization under a hydrostatic pressure of 196 MPa were very effective to reduce temperature coefficient of electronic polarizability without a remarkable increase in thermal expansion coefficient. It was deduced that the reduction in temperature coefficient of electronic polarizability by the crystallization under 196 MPa resulted from the inhibition of the precipitation of beta-spodumene solid solution. The relative temperature coefficients of optical path length of B2O3-doped glass-ceramic crystallized under 196 MPa was 11.7 x 10-6/°C, which was slightly larger than that of silica glass. Nevertheless, the thermal expansion coefficient of this glass-ceramic was smaller than that of silica glass.

Homogeneously dispersed CeO2 nanoparticles on exfoliated hexaniobate nanosheets

NASA Astrophysics Data System (ADS)

Marques, Thalles M. F.; Strayer, Megan E.; Ghosh, Anupama; Silva, Alexandre; Ferreira, Odair P.; Fujisawa, Kazunori; Alves da Cunha, Jose R.; Abreu, Guilherme J. P.; Terrones, Mauricio; Mallouk, Thomas E.; Viana, Bartolomeu C.

2017-12-01

Hexaniobate nanosheets derived from the parent compound K4Nb6O17 have been decorated with CeO2 nanoparticles by ion exchange with aqueous cerium (IV) solution. Very homogeneous CeO2 nanoparticle decoration of the hexaniobate sheets can be achieved by this method and the resulting composites may absorb visible light. HRTEM images show that ∼3.0 nm diameter CeO2 nanoparticles adhere to hexaniobate nanosheets that are exfoliated and then restacked prior to Ce deposition. The interfacial interaction between CeO2 nanoparticles and nanosheets would be due to an electrostatic attraction mechanism. Raman and XRD measurements have given strong evidence that CeO2 nanoparticles have fluorite structure. EDS, FTIR and XPS results suggest almost complete exchange of TBA+ and K+ by Ce4+. Cerium ion exchange on the acid exchanged parent compound, H2.9K1.1Nb6O17, revealed that the extent of Ce ion exchange is much greater in case of nanosheets, which may be rationalized by the larger surface area available after exfoliation. XPS measurements show that the ratio of Ce4+/Ce3+ is around 4.4, in agreement with the formation of fluorite structure (CeO2). Thus, these CeO2 nanoparticle/nanosheet composites may be useful for catalytic processes.

Rare-earth doped transparent nano-glass-ceramics: a new generation of photonic integrated devices

NASA Astrophysics Data System (ADS)

Rodríguez-Armas, Vicente Daniel; Tikhomirov, Victor K.; Méndez-Ramos, Jorge; Yanes, Angel C.; Del-Castillo, Javier; Furniss, David; Seddon, Angela B.

2007-05-01

We report on optical properties and prospect applications on rare-earth doped oxyfluoride precursor glass and ensuing nano-glass-ceramics. We find out the spectral optical gain of the nano-glass-ceramics and show that its flatness and breadth are advantageous as compared to contemporary used erbium doped optical amplifiers. We present the possibility of flat gain cross-section erbium doped waveguide amplifiers as short 'chip', all-optical, devices capable of dense wavelength division multiplexing, including the potential for direct writing of these devices inside bulk glasses for three-dimensional photonic integration. We carried out a comparative study of the up-conversion luminescence in Er 3+-doped and Yb 3+-Er 3+-Tm 3+ co-doped samples, which indicates that these materials can be used as green/red tuneable up-conversion phosphors and white light simulation respectively. Observed changes in the spectra of the up-conversion luminescence provide a tool for tuning the colour opening the way for producing 3-dimensional optical recording.

Enhanced ferromagnetic properties in Nd and Gd co-doped BiFeO3 ceramics

NASA Astrophysics Data System (ADS)

Jena, A. K.; Chelvane, J. Arout; Mohanty, J.

2018-05-01

Structural, optical and magnetic properties of Nd3+ and Gd3+ doped BiFeO3 were studied. X-ray diffraction studies confirmed that all the co-doped Bi1-x-yNdxGdyFeO3 samples are polycrystalline in nature crystallizing in rhombohedral type structure (Space group: R3c). In addition to this presence of residual phases like Bi2Fe4O9, Bi25FeO40 were also observed. Raman spectra confirms the structural distortion in co-doped ceramics. Band gap of samples decrease from 2.08eV to 1.95eV with increase in Gd concentration. Room temperature magnetization measurement indicated enhancement of magnetic properties with increase in Gd concentration.

Microstructural analysis and thermoelectric properties of Sn-Al co-doped ZnO ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoemke, Joshua, E-mail: jhoemke@sigma.t.u-tokyo.ac.jp; Tochigi, Eita; Shibata, Naoya

2016-08-26

Sn-Al co-doped polycrystalline ZnO ceramics were prepared by sintering in air. Phase and microstructure analysis was performed by X-ray diffraction and SEM-EDS and thermoelectric properties were measured. XRD analysis showed a ZnO primary phase as well as secondary phase peaks due to the formation of a Zn{sub 2}SnO{sub 4} spinel phase or SnO{sub 2}(ZnO:Sn-Al){sub m} intergrowth phase. SEM analysis revealed a dense microstructure with a small number of nanometric pores, consistent with the measured density of 5.48 g/cm{sup 3}. An activated electrical conductivity characteristic of a semiconducting material was observed as well as a negative Seebeck coefficient with both valuesmore » increasing in absolute value from RT to 730 °C. The power factor had a maximum value of 3.73×10{sup −4} W m{sup −1} K{sup −2} at 730 °C. Thermal conductivity measurements showed a significant reduction over the measured temperature range compared to undoped ZnO. This could be attributed to grain size reduction, the formation of a nanoscale secondary phase or a reduction in crystallinity caused by Sn-Al co-doping. A maximum ZT of 0.06 was obtained at 750 °C for the Sn-Al co-doped ZnO ceramics.« less

Structural, optical and magnetic investigation of Gd implanted CeO2 nanocrystals

NASA Astrophysics Data System (ADS)

Kaviyarasu, K.; Murmu, P. P.; Kennedy, J.; Thema, F. T.; Letsholathebe, Douglas; Kotsedi, L.; Maaza, M.

2017-10-01

Gadolinium implanted cerium oxide (Gd-CeO2) nanocomposites is an important candidate which have unique hexagonal structure and high K- dielectric constant. Gd-CeO2 nanoparticles were synthesized using hydrothermal method. X-ray diffraction (XRD) results showed that the peaks are consistent with pure phase cubic structure the XRD pattern also confirmed crystallinity and phase purity of the sample. Nanocrystals sizes were found to be up to 25 nm as revealed by XRD and SEM. It is suggested that Gd gives an affirmative effect on the ion influence behavior of Gd-CeO2. XRD patterns showed formation of new phases and SEM micrographs revealed hexagonal structure. Photoluminescence measurement (PL) reveals the systematic shift of the emission band towards lower wavelength thereby ascertaining the quantum confinement effect (QCE). The PL spectrum has wider broad peak ranging from 390 nm to 770 nm and a sharp one centered on at 451.30 nm which is in tune with Gd ions. In the Raman spectra showed intense band observed between 460 cm-1 and 470 cm-1 which is attributed to oxygen ions into CeO2. Room temperature ferromagnetism was observed in un-doped and Gd implanted and annealed CeO2 nanocrystals. In the recent studies, ceria based materials have been considered as one of the most promising electrolytes for reduced temperature SOFC (solid oxide fuel cell) system due to their high ionic conductivities allowing its use in stainless steel supported fuel cells. CeO2 having an optical bandgap 3.3 eV and n-type carrier density which make it a promising candidate for various technological application such as buffer layer on silicon on insulator devices.

Contrastive Study on the Structure and the Ultraviolet Absorption Property of Multiple-Doped and Element-Doped ZnO Thin Films

NASA Astrophysics Data System (ADS)

Xu, Yunyun; Zhang, Tao; Lin, Zhenrong; Tian, Yanfeng; Zhou, Shandan

Sb2O3- and CeO2-doped ZnO thin films were prepared by RF magnetron sputtering technique. The influence of Sb2O3 and CeO2 on the structure and ultraviolet (UV) absorption properties was studied by X-ray diffraction and UV-Vis spectrophotometry. Results show that multiple doping of films had a prominent effect on the development of crystal grains and the UV absorption property. Ce and Sb exist in many forms in the ZnO film. The multiple-doped films also show enhanced UVA absorption, and the UV absorption peak widens and the absorption intensity increases. Sb plays a dominant role on the structure and UV absorption of ZnO thin films, which are enhanced by Ce.

Hydrodeoxygenation of p -Cresol over Pt/Al 2 O 3 Catalyst Promoted by ZrO 2 , CeO 2 , and CeO 2 –ZrO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Weiyan; Wu, Kui; Liu, Pengli

2016-07-20

ZrO 2-Al 2O 3 and CeO 2-Al 2O 3 were prepared by a co-precipitation method and selected as supports for Pt catalysts. The effects of CeO 2 and ZrO 2 on the surface area and Brønsted acidity of Pt/Al 2O 3 were studied. In the hydrodeoxygenation (HDO) of p-cresol, the addition of ZrO 2 promoted the direct deoxygenation activity on Pt/ZrOO 2-Al 2O 3 via Caromatic-O bond scission without benzene ring saturation. Pt/CeOO 2-Al 2O 3 exhibited higher deoxygenation extent than Pt/Al 2O 3 due to the fact that Brønsted acid sites on the catalyst surface favored the adsorption ofmore » p-cresol. With the advantages of CeO 2 and ZrO 2 taken into consideration, CeO 2-ZrOO 2-Al 2O 3 was prepared, leading to the highest HDO activity of Pt/CeO 2-ZrOO 2-Al 2O 3. The deoxygenation extent for Pt/CeO 2-ZrOO 2-Al 2O 3 was 48.4% and 14.5% higher than that for Pt/ZrO2O 2-Al 2O 3 and Pt/CeOO 2-Al 2O 3, respectively.« less

Nd3+-doped TeO2-Bi2O3-ZnO transparent glass ceramics for laser application at 1.06 μm

NASA Astrophysics Data System (ADS)

Hu, Xiaolin; Luo, Zhiwei; Liu, Taoyong; Lu, Anxian

2017-04-01

The high crystallinity transparent glass ceramics based on Nd3+-doped 70TeO2-15Bi2O3-15ZnO (TBZ) compositions were successfully prepared by two-step heat treatment process. The effects of Nd2O3 content on the thermal, structural, mechanical, and optical properties of TBZ glass ceramics were studied. The incorporation of Nd2O3 enhanced the crystallization tendency in the matrix glass composition. The crystal phase and morphology of Bi2Te4O11 in the glass ceramics were confirmed by X-ray diffraction and field emission scanning electron microscopy. Due to precipitate more crystal phase, the hardness values increased from 3.21 to 3.66 GPa. Eight absorption peaks were observed from 400 to 900 nm and three emission bands appeared in the range of 850-1400 nm. With the increasing of Nd2O3 content from 0.5 to 2.5 wt%, the intensity of absorption peaks enhanced and the emission intensity increased up to 1.0 wt% and then fell down for further dopant concentration. The fluorescence decay lifetime decreased rapidly starting from 1.5 wt% Nd2O3 content due to the obvious energy migration among Nd3+. According to the extreme strong emission band around 1062 nm and the optimum Nd2O3 content (1.0 wt%), N10 glass ceramic was considered as a potential material for 1.06 μm laser applications.

Development of Ceramic Solid-State Laser Host Material

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Trivedi, Sudhir; Kutcher, Susan; Wang, Chen-Chia; Kim, Joo-Soo; Hommerich, Uwe; Shukla, Vijay; Sadangi, Rajendra

2009-01-01

Polycrystalline ceramic laser materials are gaining importance in the development of novel diode-pumped solid-state lasers. Compared to single-crystals, ceramic laser materials offer advantages in terms of ease of fabrication, shape, size, and control of dopant concentrations. Recently, we have developed Neodymium doped Yttria (Nd:Y2O3) as a solid-state ceramic laser material. A scalable production method was utilized to make spherical non agglomerated and monodisperse metastable ceramic powders of compositions that were used to fabricate polycrystalline ceramic material components. This processing technique allowed for higher doping concentrations without the segregation problems that are normally encountered in single crystalline growth. We have successfully fabricated undoped and Neodymium doped Yttria material up to 2" in diameter, Ytterbium doped Yttria, and erbium doped Yttria. We are also in the process of developing other sesquioxides such as scandium Oxide (Sc2O3) and Lutesium Oxide (Lu2O3) doped with Ytterbium, erbium and thulium dopants. In this paper, we present our initial results on the material, optical, and spectroscopic properties of the doped and undoped sesquioxide materials. Polycrystalline ceramic lasers have enormous potential applications including remote sensing, chem.-bio detection, and space exploration research. It is also potentially much less expensive to produce ceramic laser materials compared to their single crystalline counterparts because of the shorter fabrication time and the potential for mass production in large sizes.

Room temperature magnetic and dielectric properties of cobalt doped CaCu3Ti4O12 ceramics

NASA Astrophysics Data System (ADS)

Mu, Chunhong; Song, Yuanqiang; Wang, Haibin; Wang, Xiaoning

2015-05-01

CaCu3Ti4-xCoxO12 (x = 0, 0.2, 0.4) ceramics were prepared by a conventional solid state reaction, and the effects of cobalt doping on the room temperature magnetic and dielectric properties were investigated. Both X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the presence of Cu and Co rich phase at grain boundaries of Co-doped ceramics. Scanning electron microscopy micrographs of Co-doped samples showed a striking change from regular polyhedral particle type in pure CaCu3Ti4O12 (CCTO) to sheet-like grains with certain growth orientation. Undoped CaCu3Ti4O12 is well known for its colossal dielectric constant in a broad temperature and frequency range. The dielectric constant value was slightly changed by 5 at. % and 10 at. % Co doping, whereas the second relaxation process was clearly separated in low frequency region at room temperature. A multirelaxation mechanism was proposed to be the origin of the colossal dielectric constant. In addition, the permeability spectra measurements indicated Co-doped CCTO with good magnetic properties, showing the initial permeability (μ') as high as 5.5 and low magnetic loss (μ″ < 0.2) below 3 MHz. And the interesting ferromagnetic superexchange coupling in Co-doped CaCu3Ti4O12 was discussed.

Microstructure and dielectric properties of BaTiO{sub 3} ceramic doped with yttrium, magnesium, gallium and silicon for AC capacitor application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Min-Jia; Yang, Hui; Zhejiang California International NanoSystems Institute, Hangzhou 310029

2014-12-15

Graphical abstract: Core–shell structure can be obtained in BaTiO{sub 3} ceramics co-doped with Y–Mg-Ga-Si. Y-Mg-Ga-Si co-dopant can obviously reduce dielectric loss, improve AC breakdown voltage and flatten temperature dependence of capacitance curve. - Highlights: • Y-Mg-Ga-Si co-doped BaTiO{sub 3} ceramics with core-shell structure were prepared. • Y{sup 3+}, Mg{sup 2+}, and Ga{sup 3+} dissolved in the lattice BaTiO{sub 3} replacing Ba{sup 2+} site or Ti{sup 4+} site. • Y{sup 3+} and Ga{sup 3+} tended to remain close to the grain boundaries as a shell maker. • Y-Mg-Ga-Si co-doped BaTiO{sub 3} ceramics show high AC breakdown voltage and low tanδ. -more » Abstract: The microstructures and dielectric properties of Y-Mg-Ga-Si co-doped barium titanate ceramics were investigated. Y{sup 3+} dissolved in the lattice of BaTiO{sub 3} replacing both Ba{sup 2+} site and Ti{sup 4+} site, and Mg{sup 2+} replaced Ti{sup 4+} site. The replacements of Y{sup 3+} and Mg{sup 2+} inhibit the grain growth, cause tetragonal-to-pseudocubic phase transition, reduce the dielectric loss, and flatten the temperature dependence of capacitance curve. The incorporation of Ga{sup 3+} can improve sintering and increase permittivity. Y{sup 3+} and Ga{sup 3+} tended to remain close to the grain boundaries, and play an important role as a shell maker in the formation of the core–shell structure in the co-doped BaTiO{sub 3} ceramics. Excellent dielectric properties: ϵ{sub r} = ∼2487, tanδ = ∼0.7% (at 1 kHz), ΔC/C{sub 25} < ∼6.56% (from −55 °C to 125 °C) and alternating current breakdown voltage E < ∼4.02 kV/mm can be achieved in the BaTiO{sub 3}–0.02Y{sub 2}O{sub 3}–0.03MgO–0.01Ga{sub 2}O{sub 3}–0.005SiO{sub 2} ceramics sintered at 1380 °C. This material has a potential application in alternating current multilayer ceramic capacitor.« less

Green chemical approach towards the synthesis of CeO2 doped with seashell and its bacterial applications intermediated with fruit extracts.

PubMed

Arasu, Mariadas Valan; Thirumamagal, R; Srinivasan, M P; Al-Dhabi, Naif Abdullah; Ayeshamariam, A; Saravana Kumar, D; Punithavelan, N; Jayachandran, M

2017-08-01

Nanomaterials of CeO 2 with A. vera were synthesized by using simple chemical method. Grapes drops are used as an oxidizing agent. Structural and morphological studies of nanomaterials of cerium oxide (CeO 2 ), were studied for combustion method of preparation. The precursor solution was initialized by a hydrothermal reaction. Cerium hydroxyl carbonate precursors which involves cerium (III) nitrate Ce(NO 3 ) 3 . 6 H 2 O with (1.0M) of seashell powder, 3% A. vera, extracts, grapes and pomegranate drops and this complex solution was used to produce the CeO 2 powder particles. We have prepared another sample with 5% of Aloe vera extract and found that 3% Aloe vera extract has lesser grain size and enhanced band gap values, so the article explained the sample analysis of combination with 3% extract of Aloe vera. The product has the rod pattern which was the unusual features appear to originate from the unique crystal chemistry aspects. From the optical absorption spectrum, it has been shown that the CeO 2 rods have 3.847eV of direct band gap energy. The minimum inhibitory concentration (MIC) values of the synthesized compounds exhibited activity towards various microbial pathogens such as B. subtilis (15μg/mL), S. aureus (50μg/mL), S. epidermidis (20μg/mL), E. faecalis (25μg/mL) and towards E. coli (100μg/mL), K. pneumoniae (50μg/mL) and P. aeruginosa (75μg/mL) respectively. The tests on bacterial activities confirmed that the CeO 2 rods are suitable hand for the biological applications. The seashell structure and the phytochemical contents of A. vera might enhance its bacterial activities. Copyright © 2017 Elsevier B.V. All rights reserved.

Synthesis of CeO2 nanoparticles: Photocatalytic and antibacterial activities

NASA Astrophysics Data System (ADS)

Reddy Yadav, L. S.; Lingaraju, K.; Daruka Prasad, B.; Kavitha, C.; Banuprakash, G.; Nagaraju, G.

2017-05-01

We have successfully synthesized CeO2 nanoparticles (Nps) via the solution combustion method using sugarcane juice as a novel combustible fuel. The structural features, optical properties and morphology of the nanoparticles were characterized using XRD, FTIR, and Raman spectroscopy, UV-Vis, SEM and TEM. Structural characterization of the product shows cubic phase CeO2 . FTIR and Raman spectrum show characteristic peaks due to the presence of Ce-O vibration. SEM images show a porous structure and, from TEM images, the size of the nanoparticles were found to be ˜ 50 nm. The photocatalytic degradation of the methylene blue (MB) dye was examined using CeO2 Nps under solar irradiation as well as UV light irradiation and we studied the effect of p H, catalytic load and concentration on the degradation of the MB dye. Furthermore, the antibacterial properties of CeO2 Nps were investigated against Gram+ve and Gram- ve pathogenic bacterial strains using the agar well diffusion method.

Quasi-zero-dimensional cobalt-doped CeO2 dots on Pd catalysts for alcohol electro-oxidation with enhanced poisoning-tolerance.

PubMed

Tan, Qiang; Zhu, Haiyan; Guo, Shengwu; Chen, Yuanzhen; Jiang, Tao; Shu, Chengyong; Chong, Shaokun; Hultman, Benjamin; Liu, Yongning; Wu, Gang

2017-08-31

Deactivation of an anode catalyst resulting from the poisoning of CO ad -like intermediates is one of the major problems for methanol and ethanol electro-oxidation reactions (MOR & EOR), and remains a grand challenge towards achieving high performance for direct alcohol fuel cells (DAFCs). Herein, we report a new approach for the preparation of ultrafine cobalt-doped CeO 2 dots (Co-CeO 2 , d = 3.6 nm), which can be an effective anti-poisoning promoter for Pd catalysts towards MOR and EOR in alkaline media. Compared to Pd/CeO 2 and pure Pd, the hybrid Pd/Co-CeO 2 nanocomposite catalyst exhibited a much enhanced activity and remarkable anti-poisoning ability for both MOR and EOR. The nanocomposite catalyst showed much higher mass activity (4×) than a state-of-the-art PtRu catalyst. The promotional mechanism was elucidated using extensive characterization and density-functional theory (DFT). A bifunctional effect of the Co-CeO 2 dots was discovered to be due to (i) an enhanced electronic interaction between Co-CeO 2 and Pd dots and (ii) the increased oxygen storage capacity of Co-CeO 2 dots to facilitate the oxidation of CO ad . Therefore, the Pd/Co-CeO 2 nanocomposite appears to be a promising catalyst for advanced DAFCs with low cost and high performance.

Synthesis, characterization and potential utility of doped ceramics based catalysts

NASA Astrophysics Data System (ADS)

Sharma, Ritika; Yadav, Deepshikha; Singh, G. P.; Vyas, G.; Bhojak, N.

2018-05-01

Excessive utilization of petrol, diesel and other fossil fuels, continuous increase in their prices, and the big problem of carbon dioxide mission have encouraged scientists and technologist to find either new sources of energy or to develop technologies for the sustainable utilization of fuel. Biofuels are the only energy technologies that can resolve the problem of carbon dioxide emission in the atmosphere as well as reduce the amount of fossil fuel burned. Bio ethanol and biodiesel are the most common types of biofuel which are being used at present. Biodiesel has become more interesting for all the researchers in present scenario. Various feedstock viz. edible, nonedible oils, waste cooking oil, animal fat, algae etc, are using for the production of biodiesel worldwide according to their availability. Selection of efficient heterogeneous catalysts for biodiesel preparation still needs more attention of researchers. The present investigation deals with determination of synthesis, characterization and applications of doped ceramic based materials in different medium. Two of doped ceramic based catalysts which has been potentially used for the production of biodiesel. The Engine performance of biodiesel samples, made from industrial waste oils and ceramic based catalyst, have also been investigated and found up to satisfactory levels.

Scintillation and storage luminescence properties of MgF2 transparent ceramics doped with Ce3+

NASA Astrophysics Data System (ADS)

Nakamura, Fumiya; Kato, Takumi; Okada, Go; Kawaguchi, Noriaki; Fukuda, Kentaro; Yanagida, Takayuki

2017-10-01

In this paper, we report basic optical properties and scintillation and storage luminescence properties of MgF2:Ce transparent ceramics with different doping concentrations of Ce (0.01, 0.1 and 1%) synthesized by spark plasma sintering (SPS). In scintillation, thermally-stimulated luminescence (TSL) and optically-stimulated luminescence (OSL), the dominant emissions were due to the 5d-4f transitions of Ce3+ which appeared in the near-UV region peaking around 320 and 360 nm. The scintillation was evaluated by X-ray irradiation while OSL was observed under 540 nm stimulation. In particular, the TSL sensitivity was high and showed a good linearity from 0.1 mGy to 1000 mGy.

Structure and up-conversion luminescence in sol-gel derived Er 3+-Yb 3+ co-doped SiO 2:PbF 2 nano-glass-ceramics

NASA Astrophysics Data System (ADS)

del-Castillo, J.; Yanes, A. C.; Méndez-Ramos, J.; Tikhomirov, V. K.; Rodríguez, V. D.

2009-11-01

Transparent oxyfluoride nano-glass-ceramics 90(SiO 2)10(PbF 2) co-doped with 0.3 Yb 3+ and 0.1 Er 3+ (mol%) have been prepared by thermal treatment of precursor sol-gel glasses. X-ray diffraction and high resolution transmission electron microscopy analysis pointed out a precipitation of cubic β-PbF 2 nanocrystals of certain diameter in nano-glass-ceramics varying from 10 to 20 nm depending on heat treatment conditions. The incorporation of Yb 3+ and Er 3+ dopants in these nanocrystals has been confirmed by signatures of luminescence spectroscopy. Up-conversion luminescence pumped at 980 nm has been detected. Colour tuneability of up-conversion luminescence varying pump power has been analyzed in terms of standard chromaticity diagram. This tuneability opens applications for up-conversion phosphors and three-dimensional optical recording.

Temperature-controlled down-conversion luminescence behavior of Eu3+ -doped transparent MF2 (M = Ba, Ca, Sr) glass ceramics.

PubMed

Zhou, B; E, C Q; Bu, Y Y; Meng, L; Yan, X H; Wang, X F

2017-03-01

Eu 3 + -doped transparent glass ceramics containing MF 2 (M = Ba, Ca, Sr) nanocrystals were fabricated using a melt-quenching method, and the resulting structures were studied using X-ray diffraction. Levels 5 D 1 and 5 D 0 of Eu 3 + ions were verified as thermally coupled levels using the fluorescence intensity ratio method. The fluorescence intensity ratios, optical temperature sensitivity and thermal quenching ratios of the transparent glass ceramics were studied as a function of temperature. With an increase in temperature, the relative sensitivity (S R ) decreased sharply at first, then slowly increased, before finally decreasing. The minimum S R values of GCBaF 2 (GCB), GCCaF 2 (GCC) and GCSrF 2 (GCS) were 2.8 × 10 -4 , 0.8 × 10 -4 and 1.9 × 10 - 4  K -1 at 360, 269 and 319 K, respectively. Glass ceramics with an intense emission intensity can be used to convert the measured spectrum into temperature and may have an important role in temperature detectors. Copyright © 2016 John Wiley & Sons, Ltd.

Cubic to tetragonal phase transition of Tm{sup 3+} doped nanocrystals in oxyfluoride glass ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yiming; Fu, Yuting; Shi, Yahui

2016-02-15

Tm{sup 3+} ions doped β-PbF{sub 2} nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm{sup 3+} doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an O{sub h} to D{sub 4h} site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm{sup 3+} doped nanocrystals at 800more » nm was modulated by the phase transition of the surrounding crystal field.« less

αTCP ceramic doped with dicalcium silicate for bone regeneration applications prepared by powder metallurgy method: in vitro and in vivo studies.

PubMed

Velasquez, Pablo; Luklinska, Zofia B; Meseguer-Olmo, Luis; Mate-Sanchez de Val, Jose E; Delgado-Ruiz, Rafael A; Calvo-Guirado, Jose L; Ramirez-Fernandez, Ma P; de Aza, Piedad N

2013-07-01

This study reports on the in vitro and in vivo behavior of α-tricalcium phosphate (αTCP) and also αTCP doped with either 1.5 or 3.0 wt % of dicalcium silicate (C2 S). The ceramics were successfully prepared by powder metallurgy method combined with homogenization and heat treatment procedures. All materials were composed of a single-phase, αTCP in the case of a pure material, or solid solution of C2 S in αTCP for the doped αTCP, which were stable at room temperature. The ceramics were tested for bioactivity in simulated body fluid, cell culture medium containing adult mesenchymal stem cells of human origin, and in animals. Analytical scanning electron microscopy combined with chemical elemental analysis was used and Fourier transform infrared and conventional histology methods. The in vivo behavior of the ceramics matched the in vitro results, independently of the C2 S content in αTCP. Carbonated hydroxyapatite (CHA) layer was formed on the surface and within the inner parts of the specimens in all cases. A fully mineralized new bone growing in direct contact with the implants was found under the in vivo conditions. The bioactivity and biocompatibility of the implants increased with the C2 S content in αTCP. The C2 S doped ceramics also favoured a phase transformation of αTCP into CHA, important for full implant integration during the natural bone healing processes. αTCP ceramic doped with 3.0 wt % C2 S showed the best bioactive in vitro and in vivo properties of all the compositions and hence could be of interest in specific applications for bone restorative purposes. Copyright © 2012 Wiley Periodicals, Inc.

Colossal permittivity and the polarization mechanism of (Mg, Mn) co-doped LaGaO3 ceramics

NASA Astrophysics Data System (ADS)

Luo, Tingting; Liu, Zhifu; Zhang, Faqiang; Li, Yongxiang

2018-03-01

Mg and Mn co-doped LaGa0.7-xMgxMn0.3O3 (x = 0, 0.05, 0.10, 0.15) ceramics were prepared by a solid-state reaction method. The electrical properties of the LaGa0.7-xMgxMn0.3O3 ceramics were studied in detail by dielectric spectra, impedance spectra, and I-V characteristic analysis. Colossal permittivity up to 104 could be obtained across the frequency range up to 104 Hz. The impedance analysis of the co-doped LaGaO3 ceramics indicated that the Mott's variable range hopping (VRH) polarization should be the main origin of colossal permittivity. Mg and Mn co-doping suppressed the formation of Mn3+ and enhanced the VRH polarization, resulting in increased permittivity. Partial localization of electrons by Mg reduced the long-range electron hopping and led to the decrease in dielectric loss.

Designed synthesis of multi-functional PEGylated Yb2O3:Gd@SiO2@CeO2 islands core@shell nanostructure.

PubMed

Li, Junqi; Yao, Shuang; Song, Shuyan; Wang, Xiao; Wang, Yinghui; Ding, Xing; Wang, Fan; Zhang, Hongjie

2016-07-28

Nanomaterials that can restrain or reduce the production of excessive reactive oxygen species such as H2O2 to defend and treat against Alzheimer's disease (AD) have attracted much attention. In this paper, we adopt the strategy of layer-by-layer deposition; namely, first synthesizing available gadolinium-doped ytterbia nanoparticles (Yb2O3:Gd NPs) as cores, and then coating them with silica via the classical Stöber method to prevent leakage and act as a carrier for subsequent ceria deposition and PEGylation, and finally obtain the expected core@shell-structured nanocomposite of PEGylated Yb2O3:Gd@SiO2@CeO2 islands. The nanomaterial has proved not only to be a high-performance dual-modal contrast agent for use in MRI and CT, but also to exhibit excellent catalase mimetic activity, which may help the prognosis, diagnosis and treatment of AD in the future. In addition, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy characterization have revealed the successful design and synthesis of the cores with remarkable size uniformity, with well-distributed CeO2 islands decorated on the surface of SiO2 shells, and tightly immobilized PEG.

Intense red photoluminescence from Mn2+-doped (Na+; Zn2+) sulfophosphate glasses and glass ceramics as LED converters.

PubMed

Da, Ning; Peng, Mingying; Krolikowski, Sebastian; Wondraczek, Lothar

2010-02-01

We report on intense red fluorescence from Mn(2+)-doped sulfophosphate glasses and glass ceramics of the type ZnO-Na(2)O-SO(3)-P(2)O(5). As a hypothesis, controlled internal crystallization of as-melted glasses is achieved on the basis of thermally-induced bimodal separation of an SO(3)-rich phase. Crystal formation is then confined to the relict structure of phase separation. The whole synthesis procedure is performed in air at 2+) species are incorporated on Zn(2+) sites with increasingly ionic character for increasing concentration. Correspondingly, in the glasses, increasing MnO content results in decreasing network polymerization. Stable glasses and continuously increasing emission intensity are observed for relatively high dopant concentration of up to 3 mol.%. Recrystallization of the glass results in strongly increasing emission intensity. Dynamic emission spectroscopy reveals only on type of emission centers in the glassy material, whereas three different centers are observed in the glass ceramic. These are attributed to octahedrally coordinated Mn(2+) in the residual glass phase and in crystalline phosphate and sulfate lattices, respectively. Relatively low crystal field strength results in almost ideal red emission, peaking around 625 nm. Excitation bands lie in the blue-to-green spectral range and exhibit strong overlap. The optimum excitation range matches the emission properties of GaN- and InGaN-based light emitting devices.

Electrical properties of palladium-doped CaCu3Ti4O12 ceramics

NASA Astrophysics Data System (ADS)

Singh, Arashdeep; Md Mursalin, Sk.; Rana, P.; Sen, Shrabanee

2015-09-01

The effect of doping palladium (Pd) at the Cu site of CaCu3Ti4O12 powders (CCPTO) synthesized by sol-gel technique on electrical properties was studied. XRD analysis revealed the formation of CCTO and CCPTO ceramics with some minor quantities of impurities. SEM micrographs revealed that the grain size decreased with Pd doping. TEM micrographs of CCPTO powder showed the formation of irregular-shaped particles of ~40 nm. The dielectric constant and dielectric loss showed a significant enhancement with Pd doping. A significant decrease in grain-boundary resistance with Pd doping was ascertained by impedance spectroscopy study.

Hexagonal CeO2 nanostructures: an efficient electrode material for supercapacitors.

PubMed

Maheswari, Nallappan; Muralidharan, Gopalan

2016-09-28

Cerium oxide (CeO2) has emerged as a new and promising pseudocapacitive material due to its prominent valance states and extensive applications in various fields. In the present study, hexagonal CeO2 nanostructures have been prepared via the hydrothermal method employing cationic surfactant cetyl trimethyl ammonium bromide (CTAB). CTAB ensures a slow rate of hydrolysis to form small sized CeO2 nanostructures. The role of calcination temperature on the morphological, structural, electrochemical properties and cyclic stability has been assessed for supercapacitor applications. The mesoscopic hexagonal architecture endows the CeO2 with not only a higher specific capacity, but also with an excellent rate capability and cyclability. When the charge/discharge current density is increased from 2 to 10 A g(-1) the reversible charge capacity decreased from 927 F g(-1) to 475 F g(-1) while 100% capacity retention at a high current density of 20 A g(-1) even after 1500 cycles could be achieved. Furthermore, the asymmetric supercapacitor based on CeO2 exhibited a significantly higher energy density of 45.6 W h kg(-1) at a power density of 187.5 W kg(-1) with good cyclic stability. The electrochemical richness of the CeO2 nanostructure makes it a suitable electrode material for supercapacitor applications.

Toxicity of CeO2 nanoparticles - the effect of nanoparticle properties.

PubMed

Leung, Yu Hang; Yung, Mana M N; Ng, Alan M C; Ma, Angel P Y; Wong, Stella W Y; Chan, Charis M N; Ng, Yip Hang; Djurišić, Aleksandra B; Guo, Muyao; Wong, Mabel Ting; Leung, Frederick C C; Chan, Wai Kin; Leung, Kenneth M Y; Lee, Hung Kay

2015-04-01

Conflicting reports on the toxicity of CeO2 nanomaterials have been published in recent years, with some studies finding CeO2 nanoparticles to be toxic, while others found it to have protective effects against oxidative stress. To investigate the possible reasons for this, we have performed a comprehensive study on the physical and chemical properties of nanosized CeO2 from three different suppliers as well as CeO2 synthesized by us, and tested their toxicity. For toxicity tests, we have studied the effects of CeO2 nanoparticles on a Gram-negative bacterium Escherichia coli in the dark, under ambient and UV illuminations. We have also performed toxicity tests on the marine diatom Skeletonema costatum under ambient and UV illuminations. We found that the CeO2 nanoparticle samples exhibited significantly different toxicity, which could likely be attributed to the differences in interactions with cells, and possibly to differences in nanoparticle compositions. Our results also suggest that toxicity tests on bacteria may not be suitable for predicting the ecotoxicity of nanomaterials. The relationship between the toxicity and physicochemical properties of the nanoparticles is explicitly discussed in the light of the current results. Copyright © 2015 Elsevier B.V. All rights reserved.

Diffuse Phase Transitions and Giant Electrostrictive Coefficients in Lead-Free Fe3+-Doped 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 Ferroelectric Ceramics.

PubMed

Jin, Li; Huo, Renjie; Guo, Runping; Li, Fei; Wang, Dawei; Tian, Ye; Hu, Qingyuan; Wei, Xiaoyong; He, Zhanbing; Yan, Yan; Liu, Gang

2016-11-16

The electrostrictive effect has some advantages over the piezoelectric effect, including temperature stability and hysteresis-free character. In the present work, we report the diffuse phase transitions and electrostrictive properties in lead-free Fe 3+ -doped 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (BZT-0.5BCT) ferroelectric ceramics. The doping concentration was set from 0.25 to 2 mol %. It is found that by introducing Fe 3+ ion into BZT-0.5BCT, the temperature corresponding to permittivity maximum T m was shifted toward lower temperature monotonically by 37 °C per mol % Fe 3+ ion. Simultaneously, the phase transitions gradually changed from classical ferroelectric-to-paraelectric phase transitions into diffuse phase transitions with a weak relaxor characteristic. Purely electrostrictive responses with giant electrostrictive coefficient Q 33 between 0.04 and 0.05 m 4 /C 2 are observed from 25 to 100 °C for the compositions doped with 1-2 mol % Fe 3+ ion. The Q 33 of Fe 3+ -doped BZT-0.5BCT ceramics is almost twice the Q 33 of other ferroelectric ceramics. These observations suggest that the present system can be considered as a potential lead-free material for the applications in electrostrictive area and that BT-based ferroelectric ceramics would have giant electrostrictive coefficient over other ferroelectric systems.

Transport Properties of La- doped SrTiO3 Ceramics Prepared Using Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Mehdizadeh Dehkordi, Arash; Bhattacharya, Sriparna; Tritt, Terry M.; Alshareef, Husam N.

2012-02-01

In this work, thermoelectric transport properties of La-doped SrTiO3 ceramics prepared using conventional solid state reaction and spark plasma sintering have been investigated. Room temperature power factor of single crystal strontium titanate (SrTiO3), comparable to that of Bi2Te3, has brought new attention to this perovskite-type transition metal-oxide as a potential n-type thermoelectric for high temperature applications. Electronic properties of this model complex oxide, SrTiO3 (ABO3), can be tuned in a wide range through different doping mechanisms. In addition to A site (La-doped) or B site (Nb-doped) substitutional doping, introducing oxygen vacancies plays an important role in electrical and thermal properties of these structures. Having multiple doping mechanisms makes the transport properties of these perovskites more dependent on preparation parameters. The effect of these synthesis parameters and consolidation conditions on the transport properties of these materials has been studied.

Ni-CeO2 spherical nanostructures for magnetic and electrochemical supercapacitor applications.

PubMed

Murugan, Ramachandran; Ravi, Ganesan; Vijayaprasath, Gandhi; Rajendran, Somasundharam; Thaiyan, Mahalingam; Nallappan, Maheswari; Gopalan, Muralidharan; Hayakawa, Yasuhiro

2017-02-08

The synthesis of nanoparticles has great control over the structural and functional characteristics of materials. In this study, CeO 2 and Ni-CeO 2 spherical nanoparticles were prepared using a microwave-assisted method. The prepared nanoparticles were characterized via thermogravimetry, X-ray diffraction (XRD), Raman, FTIR, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM) and cyclic voltammetry (CV). The pure CeO 2 sample exhibited a flake-like morphology, whereas Ni-doped CeO 2 showed spherical morphology with uniform shapes. Spherical morphologies for the Ni-doped samples were further confirmed via TEM micrographs. Thermogravimetric analyses revealed that decomposition varies with Ni-doping in CeO 2 . XRD revealed that the peak shifts towards lower angles for the Ni-doped samples. Furthermore, a diamagnetic to ferromagnetic transition was observed in Ni-doped CeO 2 . The ferromagnetic property was attributed to the introduction of oxygen vacancies in the CeO 2 lattice upon doping with Ni, which were confirmed by Raman and XPS. The pseudo-capacitive properties of pure and Ni-doped CeO 2 samples were evaluated via cyclic voltammetry and galvanostatic charge-discharge studies, wherein 1 M KOH was used as the electrolyte. The specific capacitances were 235, 351, 382, 577 and 417 F g -1 corresponding to the pure 1%, 3%, 5% and 7% of Ni doped samples at the current density of 2 A g -1 , respectively. The 5% Ni-doped sample showed an excellent cyclic stability and maintained 94% of its maximum specific capacitance after 1000 cycles.

Investigation of high dielectric constant ceramics and films with improved temperature stability of doped and undoped lead indium niobate:lead magnesium niobate

NASA Astrophysics Data System (ADS)

Tai, Cheuk Wai

Complex perovskite-structured relaxor ferroelectric ceramics of (x)Pb(In 1/2Nb1/2)O3:(1-x)Pb(Mg 1/3Nb2/3)O3 with x = 0.1 to 0.9 were studied extensively during the project. The ceramics were fabricated by conventional mixed oxide route of the two-step method. Measurements of their dielectric properties and ferroelectric hysteresis were performed to explore their potential for capacitor applications. The results show many features common to the relaxor behavior, including slim ferroelectric hysteresis loop and frequency dispersions in plots of relative permittivity. In addition, the ceramics with x = 0.3 to 0.7 show relative permittivity that is highly stable over the temperature range -30°C to 125°C. In order to explore structural alterations and their subsequent influence on dielectric properties, a variety of dopants were added to (0.3)Pb(In 1/2Nb1/2)O3:(0.7)Pb(Mg1/3Nb2/3 )O3 ceramics. The additives were Ba2+, Sr 2+, La3+, Na+, Ti4+ and Yb4+ obtained from different raw materials of oxides or carbonates. The modified ceramics were also fabricated by the two-step method. Fourteen ceramics samples doped with 2 or 5 mole % of the above elements, 5 mole % Na + 2 mole % Ti and 5 mole % Na + 5 mole % Ti doped were characterized in total. The measured dielectric properties of these ceramics were different to those of the parent ceramics and some of these meet the EIA-standard for industrial ceramic capacitor applications. An exploratory fabrication and study of thin films of the (0.4)Pb(In 1/2Nb1/2)O3:(0.6)Pb(Mg1/3Nb2/3 )O3 and two doped (0.3)Pb(In1/2Nb1/2)O 3: (0.7)Pb(Mg1/3Nb2/3)O3 compositions were carried out to demonstrate their potential for MEMS or other micro- or nano-scale systems. The epitaxial films were grown successfully by pulsed laser deposition (PLD). Prior to deposition of the films, La0.7Sr 0.3MnO3 (LSMO) bottom electrode was first grown on LaAlO 3 substrate. The orientation relationship between film, electrode and substrate was characterized by x

Morphology of size-selected Ptn clusters on CeO2(111)

NASA Astrophysics Data System (ADS)

Shahed, Syed Mohammad Fakruddin; Beniya, Atsushi; Hirata, Hirohito; Watanabe, Yoshihide

2018-03-01

Supported Pt catalysts and ceria are well known for their application in automotive exhaust catalysts. Size-selected Pt clusters supported on a CeO2(111) surface exhibit distinct physical and chemical properties. We investigated the morphology of the size-selected Ptn (n = 5-13) clusters on a CeO2(111) surface using scanning tunneling microscopy at room temperature. Ptn clusters prefer a two-dimensional morphology for n = 5 and a three-dimensional (3D) morphology for n ≥ 6. We further observed the preference for a 3D tri-layer structure when n ≥ 10. For each cluster size, we quantitatively estimated the relative fraction of the clusters for each type of morphology. Size-dependent morphology of the Ptn clusters on the CeO2(111) surface was attributed to the Pt-Pt interaction in the cluster and the Pt-O interaction between the cluster and CeO2(111) surface. The results obtained herein provide a clear understanding of the size-dependent morphology of the Ptn clusters on a CeO2(111) surface.

Morphology of size-selected Ptn clusters on CeO2(111).

PubMed

Shahed, Syed Mohammad Fakruddin; Beniya, Atsushi; Hirata, Hirohito; Watanabe, Yoshihide

2018-03-21

Supported Pt catalysts and ceria are well known for their application in automotive exhaust catalysts. Size-selected Pt clusters supported on a CeO 2 (111) surface exhibit distinct physical and chemical properties. We investigated the morphology of the size-selected Pt n (n = 5-13) clusters on a CeO 2 (111) surface using scanning tunneling microscopy at room temperature. Pt n clusters prefer a two-dimensional morphology for n = 5 and a three-dimensional (3D) morphology for n ≥ 6. We further observed the preference for a 3D tri-layer structure when n ≥ 10. For each cluster size, we quantitatively estimated the relative fraction of the clusters for each type of morphology. Size-dependent morphology of the Pt n clusters on the CeO 2 (111) surface was attributed to the Pt-Pt interaction in the cluster and the Pt-O interaction between the cluster and CeO 2 (111) surface. The results obtained herein provide a clear understanding of the size-dependent morphology of the Pt n clusters on a CeO 2 (111) surface.

Giant strain with low cycling degradation in Ta-doped [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}]TiO{sub 3} lead-free ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xiaoming; Tan, Xiaoli, E-mail: xtan@iastate.edu

2016-07-21

Non-textured polycrystalline [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}](Ti{sub 1−x}Ta{sub x})O{sub 3} ceramics are fabricated and their microstructures and electrical properties are characterized. Transmission electron microscopy reveals the coexistence of the rhombohedral R3c and tetragonal P4bm phases in the form of nanometer-sized domains in [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}]TiO{sub 3} with low Ta concentration. When the composition is x = 0.015, the electrostrain is found to be highly asymmetric under bipolar fields of ±50 kV/cm. A very large value of 0.62% is observed in this ceramic, corresponding to a large-signal piezoelectric coefficient d{sub 33}* of 1240 pm/V (1120 pm/V under unipolar loading). These values are greater thanmore » most previously reported lead-free polycrystalline ceramics and can even be compared with some lead-free piezoelectric single crystals. Additionally, this ceramic displays low cycling degradation; its electrostrain remains above 0.55% even after undergoing 10 000 cycles of ±50 kV/cm bipolar fields at 2 Hz. Therefore, Ta-doped [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}]TiO{sub 3} ceramics show great potential for large displacement devices.« less

Characterization and spectroscopic studies of multi-component calcium zinc bismuth phosphate glass ceramics doped with iron ions

NASA Astrophysics Data System (ADS)

Kumar, A. Suneel; Narendrudu, T.; Suresh, S.; Ram, G. Chinna; Rao, M. V. Sambasiva; Tirupataiah, Ch.; Rao, D. Krishna

2018-04-01

Glass ceramics with the composition 10CaF2-20ZnO-(15-x)Bi2O3-55P2O5:x Fe2O3(0≤x≤2.5) were synthesized by melt-quenching technique and heat treatment. These glass ceramics were characterized by XRD and SEM. Spectroscopic studies such as optical absorption, EPR were also carried out on these glass ceramics. From the absorption spectra the observed bands around 438 and 660nm are the octahedral transitions of Fe3+ (d5) ions and another band at about 536 nm is the tetrahedral transition of Fe3+ (d5) ions. The absorption spectrum also consist of a band around 991 nm and is attributed to the octahedral transition of Fe2+ ions. The EPR spectra of the prepared glass ceramics have exhibited two resonance signals one at g1=4.32 and another signal at g2=2.008. The observed decrease in band gap energy up to 2 mol% Fe2O3 doped glass ceramics is an evidence for the change of environment around iron ions and ligands from more covalent to less covalent (ionic) and induces higher concentration of NBOs which causes the depolymerization of the glass ceramic network.

Density functional analysis of fluorite-structured (Ce, Zr)O 2/CeO 2 interfaces [Density functional analysis of fluorite-structured (Ce, Zr)O 2/CeO 2 interfaces: Implications for catalysis and energy applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weck, Philippe F.; Juan, Pierre -Alexandre; Dingreville, Remi

The structures and properties of Ce 1–xZr xO 2 (x = 0–1) solid solutions, selected Ce 1–xZr xO 2 surfaces, and Ce 1–xZr xO 2/CeO 2 interfaces were computed within the framework of density functional theory corrected for strong electron correlation (DFT+ U). The calculated Debye temperature increases steadily with Zr content in (Ce, Zr)O 2 phases, indicating a significant rise in microhardness from CeO 2 to ZrO 2, without appreciable loss in ductility as the interfacial stoichiometry changes. Surface energy calculations for the low-index CeO 2(111) and (110) surfaces show limited sensitivity to strong 4f-electron correlation. The fracture energymore » of Ce 1–xZr xO 2(111)/CeO 2(111) increases markedly with Zr content, with a significant decrease in energy for thicker Ce 1–xZr xO 2 films. These findings suggest the crucial role of Zr acting as a binder at the Ce 1–xZr xO 2/CeO 2 interfaces, due to the more covalent character of Zr–O bonds compared to Ce–O. Finally, the impact of surface relaxation upon interface cracking was assessed and found to reach a maximum for Ce 0.25Zr 0.75O 2/CeO 2 interfaces.« less

Density functional analysis of fluorite-structured (Ce, Zr)O 2/CeO 2 interfaces [Density functional analysis of fluorite-structured (Ce, Zr)O 2/CeO 2 interfaces: Implications for catalysis and energy applications

DOE PAGES

Weck, Philippe F.; Juan, Pierre -Alexandre; Dingreville, Remi; ...

2017-06-21

The structures and properties of Ce 1–xZr xO 2 (x = 0–1) solid solutions, selected Ce 1–xZr xO 2 surfaces, and Ce 1–xZr xO 2/CeO 2 interfaces were computed within the framework of density functional theory corrected for strong electron correlation (DFT+ U). The calculated Debye temperature increases steadily with Zr content in (Ce, Zr)O 2 phases, indicating a significant rise in microhardness from CeO 2 to ZrO 2, without appreciable loss in ductility as the interfacial stoichiometry changes. Surface energy calculations for the low-index CeO 2(111) and (110) surfaces show limited sensitivity to strong 4f-electron correlation. The fracture energymore » of Ce 1–xZr xO 2(111)/CeO 2(111) increases markedly with Zr content, with a significant decrease in energy for thicker Ce 1–xZr xO 2 films. These findings suggest the crucial role of Zr acting as a binder at the Ce 1–xZr xO 2/CeO 2 interfaces, due to the more covalent character of Zr–O bonds compared to Ce–O. Finally, the impact of surface relaxation upon interface cracking was assessed and found to reach a maximum for Ce 0.25Zr 0.75O 2/CeO 2 interfaces.« less

Yb3+-Er3+-Tm3+ co-doped nano-glass-ceramics tuneable up-conversion phosphor

NASA Astrophysics Data System (ADS)

Méndez-Ramos, J.; Rodriguez, V. D.; Tikhomirov, V. K.; Del-Castillo, J.; Yanes, A. C.

2008-08-01

Transparent Yb3+-Er3+-Tm3+ co-doped nano-glass-ceramics have been prepared, 32(SiO{2}) 9(AlO{1.5}) 31.5(CdF{2}) 18.5(PbF{2}) 5.5(ZnF{2}): 3.5(Yb-Er-TmF{3}) mol%, where the co-dopants partition mostly to the fluoride PbF{2}-based nano-crystals. A comparative study of the up-conversion luminescence in nano-glass-ceramics and its precursor glass indicates that these materials can be used as blue/green/red tuneable up-conversion phosphor, in particular for white light generation. A ratio between blue, green and red emission bands of the Tm3+ and Er3+ can be widely varied with nano-ceramming of the precursor glass and with changing a pump power of luminescence. The change in the ratio between the blue, green and red emission bands is explained to be due to substantial lowering phonon energy and shortening of inter-dopant distances with nano-ceramming of the precursor glass and due to change in the ratio of 2- and 3-photon up-conversion processes with pump power.

Effect of BiFeO3 doping on the structural, dielectric and electrical properties of CaCu3Ti4O12 ceramics

NASA Astrophysics Data System (ADS)

Dai, Haiyang; Liu, Dewei; Chen, Jing; Xue, Renzhong; Li, Tao; Xiang, Huiwen; Chen, Zhenping; Liu, Haizeng

2015-04-01

(1 - x)CaCu3Ti4O12- xBiFeO3 ( x = 0, 0.003, 0.006, 0.010 and 0.015) ceramics have been fabricated by the solid-state reaction method. The effects of BiFeO3 (BFO) doping on the microstructure, dielectric and electrical properties of CaCu3Ti4O12 (CCTO) ceramics were investigated. It is found that BFO doping can affect the microstructure of the CCTO ceramics, and some properties of CCTO ceramics can hence be improved by BFO doping. The XRD and Raman results show that no phase transition has occurred in the doping content range, but BFO doping induces the crystal structure distortion. Analysis of microstructure indicates that the grain morphology varies significantly with increasing BFO content, and an appropriate amount of BFO can promote the grain growth. Impedance spectroscopy results show that the dielectric constant and loss of the BFO-doped CCTO samples are stable with frequency. The dielectric constant and nonohmic properties can be enhanced markedly in an appropriate doping content. The dielectric loss of all BFO-doped samples was lower than that of undoped CCTO sample in low frequencies. The related mechanism is also discussed in the paper.

Research on up- and down-conversion emissions of Er3+/Yb3+ co-doped phosphate glass ceramic

NASA Astrophysics Data System (ADS)

Ming, Chengguo; Song, Feng; An, Liqun; Ren, Xiaobin; Yuan, Yize; Cao, Yang; Wang, Gangzhi

2012-12-01

By high-temperature melting method and thermal treatment technology, Er3+/Yb3+ co-doped phosphate glass and glass ceramic samples were prepared. The luminescence spectra of the glass and glass ceramic samples were studied under 975 nm excitation. In visible and near-infrared bands, the emission intensity of the glass ceramic is stronger than that of the glass. The glass ceramic can comprehensively improve the luminous characters of the precursor glass. The phosphate glass ceramic will be valuable luminescence materials.

CW and tunable performances of Yb3+:LuAG transparent ceramics with different doping concentrations

NASA Astrophysics Data System (ADS)

Ma, Chaoyang; Zhu, Jiangfeng; Liu, Kai; Wen, Zicheng; Ma, Ran; Long, Jiaqi; Yuan, Xuanyi; Cao, Yongge

2017-07-01

We report the CW laser operation and wavelength tunability of 10 at%, 15 at% and 20 at% Yb3+-doping LuAG ceramics pumped at 970 nm. The absorption saturation effects were taken into account herein. For 10 at% Yb3+-doping sample, the maximum slop efficiency and output power was 60.7% and 1.8 W, respectively. Furthermore, the slop efficiencies of 52.3% (15 at%) and 46.5% (20 at%) were reported. What's more, the maximum optical-to-optical efficiency for our samples was determined to be 40.1%, 36.8%, and 33.1% at the incident pump power of 4 W, respectively. The round-trip cavity loss of the laser system based on our Yb3+:LuAG ceramics were evaluated. The tuning curve of a 20 at% Yb3+:LuAG ceramic extended from 1018 nm up to 1062 nm, and that of 10 at% and 15 at% samples became much more broader, making Yb3+:LuAG ceramics possible candidates for ultrashort pulse generation.

Silver ion doped ceramic nano-powder coated nails prevent infection in open fractures: In vivo study.

PubMed

Kose, Nusret; Çaylak, Remzi; Pekşen, Ceren; Kiremitçi, Abdurrahman; Burukoglu, Dilek; Koparal, Savaş; Doğan, Aydın

2016-02-01

Despite improvement in operative techniques and antibiotic therapy, septic complications still occur in open fractures. We developed silver ion containing ceramic nano powder for implant coating to provide not only biocompatibility but also antibacterial activity to the orthopaedic implants. We hypothesised silver ion doped calcium phosphate based ceramic nano-powder coated titanium nails may prevents bacterial colonisation and infection in open fractures as compared with uncoated nails. 33 rabbits divided into three groups. In the first group uncoated, in the second group hydroxyapatite coated, and in the third group silver doped hydroxyapatite coated titanium nails were inserted left femurs of animals from knee regions with retrograde fashion. Before implantation of nails 50 μl solution containing 10(6)CFU/ml methicillin resistance Staphylococcus aureus (MRSA) injected intramedullary canal. Rabbits were monitored for 10 weeks. Blood was taken from rabbits before surgery and on 2nd, 6th and 10th weeks. Blood was analysed for biochemical parameters, blood count, C-reactive protein and silver levels. At the end of the 10 weeks animals were sacrificed and rods were extracted in a sterile fashion. Swab cultures were taken from intramedullary canal. Bacteria on titanium rods were counted. Liver, heart, spleen, kidney and central nervous tissues samples were taken for determining silver levels. Histopathological evaluation of bone surrounding implants was also performed. No significant difference was detected between the groups from hematologic, biochemical, and toxicological aspect. Microbiological results showed that less bacterial growth was detected with the use of silver doped ceramic coated implants compared to the other two groups (p=0.003). Accumulation of silver was not detected. No cellular inflammation was observed around the silver coated prostheses. No toxic effect of silver on bone cells was seen. Silver ion doped calcium phosphate based ceramic nano

Preparation and characterization of TiO2 and Si-doped octacalcium phosphate composite coatings on zirconia ceramics (Y-TZP) for dental implant applications

NASA Astrophysics Data System (ADS)

Bao, Lei; Liu, Jingxiao; Shi, Fei; Jiang, Yanyan; Liu, Guishan

2014-01-01

In order to prevent the low temperature degradation and improve the bioactivity of zirconia ceramic implants, TiO2 and Si-doped octacalcium phosphate composite coating was prepared on zirconia substrate. The preventive effect on low temperature degradation and surface morphology of the TiO2 layer were studied. Meanwhile, the structure and property changes of the bioactive coating after doping Si were discussed. The results indicate that the dense TiO2 layer, in spite of some microcracks, inhibited the direct contact of the water vapor with the sample's surface and thus prevented the low temperature degradation of zirconia substrates. The acceleration aging test shows that the ratio of the monoclinic phase transition decreased from 10% for the original zirconia substrate to 4% for the TiO2-coated substrate. As to the Si-doped octacalcium phosphate coating prepared by biomimetic method, the main phase composition of the coating was octacalcium phosphate. The morphology of the coating was lamellar-like, and the surface was uniform and continuous with no cracks being observed. It is suggested that Si was added into the coating both through substituting for PO43- and doping as NaSiO3.

[Preparation of porous ceramics based on waste ceramics and its Ni2+ adsorption characteristics].

PubMed

Zhang, Yong-Li; Wang, Cheng-Zhi; Shi, Ce; Shang, Ling-Ling; Ma, Rui; Dong, Wan-Li

2013-07-01

The preparation conditions of porous ceramics were determined by SEM, XRD and FT-IR characterizations as well as the nickel removal ability of porous ceramics to be: the mass fraction w of sesbania powder doped was 4%, and the calcination temperature was 800 degrees C. SEM and pore structure characterization illustrated that calcination caused changes in the structure and morphology of waste ceramics. With the increase of calcination temperature, the specific surface area and pore volume decreased, while the aperture increased. EDS analyses showed that the main elements of both the original waste porcelain powder and the porous ceramics were Si, Al and O. The SEM, XRD and FT-IR characterization of porous ceramics illustrated that the structure of porous ceramics was stable before and after adsorption. The series of experiments of Ni2+ adsorption using these porous ceramics showed that when the dosage of porous ceramics was 10 g x L(-1), the adsorption time was 60 min, the pH value was 6.32, and the concentration of nickel-containing wastewater was below 100 mg x L(-1), the Ni2+ removal of wastewater reached 89.7%. Besides, the porous ceramics showed higher removal efficiency on nickel in the wastewater. The Ni(2+)-containing wastewater was processed by the porous ceramics prepared, and the adsorption dynamics and adsorption isotherms of Ni2+ in wastewater by porous ceramics were investigated. The research results showed that the Ni2+ adsorption process of porous ceramics was in accordance with the quasi second-order kinetic model (R2 = 0.999 9), with Q(e) of 9.09 mg x g(-1). The adsorption process can be described by the Freundlich equation and Langmuir equation, and when the temperature increased from 20 degrees C to 40 degrees C, the maximum adsorption capacity Q(m) increased from 14.49 mg x g(-1) to 15.38 mg x g(-1).

Multifold polar states in Zn-doped Sr0.9Ba0.1TiO3 ceramics

NASA Astrophysics Data System (ADS)

Guo, Yan-Yan; Guo, Yun-Jun; Wei, Tong; Liu, Jun-Ming

2015-12-01

We investigate the effect of Zn doping on the dielectricity and ferroelectricity of a series of polycrystalline Sr0.9-xZnxBa0.1TiO3 (0.0% ≤ x ≤ 5.0%) ceramics. It is surprisingly observed that the Zn doping will produce the multifold polar states, i.e., the Zn-doped ceramic will convert a reduced polar state into an enhanced polar state, and eventually into a stabilized polar state with increasing the doping level x. It is revealed that in the background of quantum fluctuations, the competition between the Zn-doping-induced lattice contraction and the Ba-doping-induced lattice expansion is responsible for both the reduced polar state and the enhanced polar state coming into being. Also, the addition of the antiferrodistortive effect, which is the antipolar interaction originating from the opposite tilted-TiO6 octahedra rotation, represents the core physics behind the stabilized polar state. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304158, 51431006, 51102277, and 11104118), the Scientific Research Foundation of Nanjing University of Posts and Telecommunications, China (Grant No. NY213020), and the Qing Lan Project of Jiangsu Province, China.

Comprehensive studies of the Ag+ effect on borosilicate glass ceramics containing Ag nanoparticles and Er-doped hexagonal NaYF4 nanocrystals: morphology, structure, and 2.7 μm emission

NASA Astrophysics Data System (ADS)

Liu, Qunhuo; Tian, Ying; Tang, Wenhua; Jing, Xufeng; Zhang, Junjie; Xu, Shiqing

2018-05-01

In this work, we have performed a comprehensive investigation of the Ag+ concentration effect on the morphological, thermal, structural, and mid-infrared emission properties of novel oxyfluoride borosilicate glasses and glass ceramics containing both Ag nanoparticles and erbium-doped hexagonal NaYF4 nanocrystals. The effect of Ag+ ions on the glass forming and crystallization processes was discussed in detail by glass structural analysis. It was found that the Ag+ concentration can affect the distribution of Na+ ion and bridge oxygen in boron-rich and silicon-rich phases, which induced the transformation between BO3 triangles and BO4 tetrahedra during crystallization process. In addition, there was a turning point when the doped Ag+ ion concentration reached its solubility in the borosilicate glass. Furthermore, the enhancement of the 2.7 μm emission and the reduction of the lifetime of the 4I13/2 level were observed both in glasses and in glass ceramics, and its origin was revealed by qualitative and quantitative analyses of the Er3+-Ag nanoparticles (localized electric field enhancement) and Er3+-Er3+ (nonradiative resonance energy transfer) interactions within glasses and glass ceramics. Moreover, the high lifetime of the 4I11/2 level (2.12 ms) and the peak emission cross section in 2.7 μm (6.8×10-21 cm2) suggested that the prepared glass ceramics have promising mid-infrared laser applications.

Magnetic properties of Y3+ doped Bi4-xTi2FeO12 aurivillius phase ceramics

NASA Astrophysics Data System (ADS)

Tirupathi, Patri; Reddy, H. Satish Kumar; Babu, P. D.

2018-05-01

In the present paper reports a comprehensive investigation of structural, microstructural and magnetic phase transition in Y3+ doped BITF Aurivillius phase compounds. The study of surface morphology by scanning electron microscope reveals the growth of plate-like grains and further the grain size increase with increasing Y3+ composition. Low temperature magnetic studies reveals enhanced magnetic property with doping of Y3+ in BITF. It was explained by considering exchange interaction between the neighboring Fe+3 ions via electron trapped electrons at oxygen vacancies. Temperature dependent dc-magnetic studies exhibit a magnetic transitions TC = 750 K for x=0.0 TC ˜ 674 K for x=1.0 & TC ˜ 645 K for x=1.50 ceramics respectively in high temperature magnetization studies

Neuroprotective Effect of CeO2@PAA-LXW7 Against H2O2-Induced Cytotoxicity in NGF-Differentiated PC12 Cells.

PubMed

Jia, Jingjing; Zhang, Ting; Chi, Jieshan; Liu, Xiaoma; Sun, Jingjing; Xie, Qizhi; Peng, Sijia; Li, Changyan; Yi, Li

2018-06-07

CeO 2 nanoparticles (nanoceria) have been used in many studies as a powerful free radical scavenger, and LXW7, a small-molecule peptide, can specifically target the integrin αvβ3, whose neuroprotective effects have also been demonstrated. The objective of this study is to observe the neuroprotective effect and potential mechanism of CeO 2 @PAA-LXW7, a new compound that couples CeO 2 @PAA (nanoceria modified with the functional group of polyacrylic acid) with LXW7 via a series of chemical reactions, in H 2 O 2 -induced NGF-differentiated PC12 cells. We examined the effects of LXW7, CeO 2 @PAA, and CeO 2 @PAA-LXW7 on the viability of primary hippocampal neurons and found that there was no significant difference under control conditions, but increased cellular viability was observed in the case of H 2 O 2 -induced injury. We used H 2 O 2 -induced NGF-differentiated PC12 cells as the classical injury model to investigate the neuroprotective effect of CeO 2 @PAA-LXW7. In this study, LXW7, CeO 2 @PAA, and CeO 2 @PAA-LXW7 inhibit H 2 O 2 -induced oxidative stress by reducing the production of reactive oxygen species (ROS) and regulating Bax/Bcl-2, cleaved caspase-3 and mitochondrial cytochrome C (cyto C) in the apoptotic signaling pathways. We found that the levels of phosphorylation of focal adhesion kinase (FAK) and of signal transducer and activator of transcription 3 (STAT3) increased significantly in H 2 O 2 -induced NGF-differentiated PC12 cells, whereas LXW7, CeO 2 @PAA, and CeO 2 @PAA-LXW7 suppressed the increase to different degrees. Among the abovementioned changes, the inhibitory effect of CeO 2 @PAA-LXW7 on H 2 O 2 -induced changes, including the increases in the levels of p-FAK and p-STAT3, is more obvious than that of LXW7 or CeO 2 @PAA alone. In summary, these results suggest that integrin signaling participates in the regulation of apoptosis via the regulation of ROS and of the apoptosis pathway in H 2 O 2 -induced NGF-differentiated PC12 cells. LXW7, CeO

Synthesis of monodisperse CeO 2-ZrO 2 particles exhibiting cyclic superelasticity over hundreds of cycles

DOE PAGES

Du, Zehui; Ye, Pengcheng; Zeng, Xiao Mei; ...

2017-05-09

Nano- and microscale CeO 2–ZrO 2 (CZ) shape memory ceramics are promising materials for smart micro-electro-mechanical systems (MEMS), sensing, actuation and energy damping applications, but the processing science for scalable production of such small volume ceramics has not yet been established. Herein, we report a modified sol-gel method to synthesize highly monodisperse spherical CZ particles with diameters in the range of ~0.8-3.0 μm. Synchrotron X-ray micro-diffraction (μSXRD) confirmed that most of the particles are single crystal after annealing at 1450°C. Having a monocrystalline structure and a small specimen length scale, the particles exhibit significantly enhanced shape memory and superelasticity propertiesmore » with up to ~4.7% compression being completely recoverable. Highly reproducible superelasticity through over five hundred strain cycles, with dissipated energy up to ~40 MJ/m 3 per cycle, is achieved in the CZ particles containing 16 mol% ceria. This cycling capability is enhanced by ten times compared with our first demonstration using micropillars (only 50 cycles in Lai et al, Science, 2013, 341, 1505). Furthermore, the effects of cycling and testing temperature (in 25°C-400°C) on superelasticity have been investigated.« less

Fabrication and Sintering Behavior of Er:SrF2 Transparent Ceramics using Chemically Derived Powder

PubMed Central

Liu, Jun; Liu, Peng; Wang, Jun; Xu, Xiaodong; Li, Dongzhen; Zhang, Jian; Nie, Xinming

2018-01-01

In this paper, we report the fabrication of high-quality 5 at. % Er3+ ions doped SrF2 transparent ceramics, the potential candidate materials for a mid-infrared laser-gain medium by hot-pressing at 700 °C for 40 h using a chemically-derived powder. The phase structure, densification, and microstructure evolution of the Er:SrF2 ceramics were systematically investigated. In addition, the grain growth kinetic mechanism of Er:SrF2 was clarified. The results showed lattice diffusion to be the grain growth mechanism in the Er:SrF2 transparent ceramic of which highest in-line transmittance reached 92% at 2000 nm, i.e., very close to the theoretical transmittance value of SrF2 single crystal. Furthermore, the emission spectra showed that the strongest emission band was located at 2735 nm. This means that it is possible to achieve a laser output of approximately 2.7 μm in the 5 at. % Er3+ ions doped SrF2 transparent ceramics. PMID:29565322

Effect of Fe doping on structural and impedance properties of PZTFN ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Arvind, E-mail: arvindmse07311209.in@gmail.com; Pal, Vijayeta; Mishra, S. K.

2016-05-06

An attempts have been made to synthesis the ceramics Pb{sub 1-3x/2} Fe{sub x}(Zr{sub 0.52}Ti{sub 0.48}){sub 1-5y/4} NbyO{sub 3} abbreviated as (PFZTN) for x = 1-6 mol% and y = 5.5 mol% by a semi-wet route. In the present paper, we have investigated the effect of Fe doping on structural and electrical properties of the PFZTN ceramics. X-ray diffraction (XRD) patterns reveal that PFZTN ceramics are single phase in nature. However, for x = 0.05 and 0.06, a secondary phase appears as discernible from the XRD profiles. Rietveld analysis of the powder diffraction data shows the presence of coexistence of tetragonal (P4mm spacemore » group) and rhombohedral phases (R3c space group) occurs near the morphotropic phase boundary (MPB) at x ≥ = 0.05. The log-log plots show that the conductivity increases with increase of temperature. The ac conductivity becomes sensitive at high frequency region and shifted towards higher frequency side with increasing temperature. It is observed that the activation energy (Ea) decreases with increasing frequency. This complex perovskite structure can be used as a multilayer ceramic capacitors and electromechanical transducers.« less

A comparative study of CeO2-Al2O3 support prepared with different methods and its application on MoO3/CeO2-Al2O3 catalyst for sulfur-resistant methanation

NASA Astrophysics Data System (ADS)

Jiang, Minhong; Wang, Baowei; Yao, Yuqin; Li, Zhenhua; Ma, Xinbin; Qin, Shaodong; Sun, Qi

2013-11-01

The CeO2-Al2O3 supports prepared with impregnation (IM), deposition precipitation (DP), and solution combustion (SC) methods for MoO3/CeO2-Al2O3 catalyst were investigated in the sulfur-resistant methanation. The supports and catalysts were characterized by N2-physisorption, transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and temperature-programmed reduction (TPR). The N2-physisorption results indicated that the DP method was favorable for obtaining better textural properties. The TEM and RS results suggested that there is a CeO2 layer on the surface of the support prepared with DP method. This CeO2 layer not only prevented the interaction between MoO3 and γ-Al2O3 to form Al2(MoO4)3 species, but also improved the dispersion of MoO3 in the catalyst. Accordingly, the catalysts whose supports were prepared with DP method exhibited the best catalytic activity. The catalysts whose supports were prepared with SC method had the worst catalytic activity. This was caused by the formation of Al2(MoO4)3 and crystalline MoO3. Additionally, the CeO2 layer resulted in the instability of catalysts in reaction process. The increasing of calcination temperature of supports reduced the catalytic activity of all catalysts. The decrease extent of the catalysts whose supports were prepared with DP method was the lowest as the CeO2 layer prevented the interaction between MoO3 and γ-Al2O3.

Doped Calcium Silicate Ceramics: A New Class of Candidates for Synthetic Bone Substitutes

PubMed Central

No, Young Jung; Li, Jiao Jiao; Zreiqat, Hala

2017-01-01

Doped calcium silicate ceramics (DCSCs) have recently gained immense interest as a new class of candidates for the treatment of bone defects. Although calcium phosphates and bioactive glasses have remained the mainstream of ceramic bone substitutes, their clinical use is limited by suboptimal mechanical properties. DCSCs are a class of calcium silicate ceramics which are developed through the ionic substitution of calcium ions, the incorporation of metal oxides into the base binary xCaO–ySiO2 system, or a combination of both. Due to their unique compositions and ability to release bioactive ions, DCSCs exhibit enhanced mechanical and biological properties. Such characteristics offer significant advantages over existing ceramic bone substitutes, and underline the future potential of adopting DCSCs for clinical use in bone reconstruction to produce improved outcomes. This review will discuss the effects of different dopant elements and oxides on the characteristics of DCSCs for applications in bone repair, including mechanical properties, degradation and ion release characteristics, radiopacity, and biological activity (in vitro and in vivo). Recent advances in the development of DCSCs for broader clinical applications will also be discussed, including DCSC composites, coated DCSC scaffolds and DCSC-coated metal implants. PMID:28772513

Nanocrystalline CeO2-δ coated β-MnO2 nanorods with enhanced oxygen transfer property

NASA Astrophysics Data System (ADS)

Huang, Xiubing; Zhao, Guixia; Chang, Yueqi; Wang, Ge; Irvine, John T. S.

2018-05-01

In this research, β-MnO2 nanorods were synthesized by a hydrothermal method, followed by a facile precipitation method to obtain nanocrystalline CeO2-δ coated β-MnO2 nanorods. The as-prepared samples were characterized by XRD, HRTEM, FESEM, XPS and in-situ high-temperature XRD. The HRTEM results show that well dispersed CeO2-δ nanocrystals sized about 5 nm were coated on the surface of β-MnO2 nanorods. The oxygen storage and transfer property of as-synthesized materials were evaluated using TGA under various atmospheres (air, pure N2, and 5%H2/95%Ar). The TGA results indicate that CeO2-δ modification could favour the reduction of Mn4+ to Mn3+ and/or Mn2+ at lower temperature as compared with pure β-MnO2 nanorods and the physically mixed CeO2-δ-β-MnO2 under low oxygen partial pressure conditions (i.e., pure N2, 5%H2/95%Ar). Specifically, CeO2-δ@β-MnO2 sample can exhibit 7.5 wt% weight loss between 100 and 400 °C under flowing N2 and 11.4 wt% weight loss between 100 and 350 °C under flowing 5%H2/95%Ar. During the reduction process under pure N2 or 5%H2/95%Ar condition, the oxygen ions in β-MnO2 nanorods are expected to be released to the surroundings in the form of O2 or H2O with the coated CeO2-δ nanocrystals acting as mediator as inferred from the synergistic effect between the well-interacted CeO2-δ nanocrystals and β-MnO2 nanorods.

The effect of zirconium doping of cerium dioxide nanoparticles on pulmonary and cardiovascular toxicity and biodistribution in mice after inhalation.

PubMed

Dekkers, Susan; Miller, Mark R; Schins, Roel P F; Römer, Isabella; Russ, Mike; Vandebriel, Rob J; Lynch, Iseult; Belinga-Desaunay, Marie-France; Valsami-Jones, Eugenia; Connell, Shea P; Smith, Ian P; Duffin, Rodger; Boere, John A F; Heusinkveld, Harm J; Albrecht, Catrin; de Jong, Wim H; Cassee, Flemming R

2017-08-01

Development and manufacture of nanomaterials is growing at an exponential rate, despite an incomplete understanding of how their physicochemical characteristics affect their potential toxicity. Redox activity has been suggested to be an important physicochemical property of nanomaterials to predict their biological activity. This study assessed the influence of redox activity by modification of cerium dioxide nanoparticles (CeO 2 NPs) via zirconium (Zr) doping on the biodistribution, pulmonary and cardiovascular effects in mice following inhalation. Healthy mice (C57BL/6 J), mice prone to cardiovascular disease (ApoE -/- , western-diet fed) and a mouse model of neurological disease (5 × FAD) were exposed via nose-only inhalation to CeO 2 NPs with varying amounts of Zr-doping (0%, 27% or 78% Zr), or clean air, over a four-week period (4 mg/m 3 for 3 h/day, 5 days/week). Effects were assessed four weeks post-exposure. In all three mouse models CeO 2 NP exposure had no major toxicological effects apart from some modest inflammatory histopathology in the lung, which was not related to the amount of Zr-doping. In ApoE -/- mice CeO 2 did not change the size of atherosclerotic plaques, but there was a trend towards increased inflammatory cell content in relation to the Zr content of the CeO 2 NPs. These findings show that subacute inhalation of CeO 2 NPs causes minimal pulmonary and cardiovascular effect four weeks post-exposure and that Zr-doping of CeO 2 NPs has limited effect on these responses. Further studies with nanomaterials with a higher inherent toxicity or a broader range of redox activities are needed to fully assess the influence of redox activity on the toxicity of nanomaterials.

Formation of qualified BaHfO3 doped Y0.5Gd0.5Ba2Cu3O7-δ film on CeO2 buffered IBAD-MgO tape by self-seeding pulsed laser deposition

NASA Astrophysics Data System (ADS)

Liu, Linfei; Wang, Wei; Yao, Yanjie; Wu, Xiang; Lu, Saidan; Li, Yijie

2018-05-01

Improvement in the in-filed transport properties of REBa2Cu3O7-δ (RE = rare earth elements, REBCO) coated conductor is needed to meet the performance requirements for various practical applications, which can be accomplished by introducing artificial pinning centers (APCs), such as second phase dopant. However, with increasing dopant level the critical current density Jc at 77 K in zero applied magnetic field decreases. In this paper, in order to improve Jc we propose a seed layer technique. 5 mol% BaHfO3 (BHO) doped Y0.5Gd0.5Ba2Cu3O7-δ (YGBCO) epilayer with an inserted seed layer was grown on CeO2 buffered ion beam assisted deposition MgO (IBAD-MgO) tape by pulsed laser deposition. The effect of the conditions employed to prepare the seed layer, including tape moving speed and chemical composition, on the quality of 5 mol% BHO doped YGBCO epilayer was systematically investigated by X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM) observations. It was found that all the samples with seed layer have higher Jc (77 K, self-field) than the 5 mol% BHO doped YGBCO film without seed layer. The seed layer could inhibit deterioration of the Jc at 77 K and self-filed. Especially, the self-seed layer (5 mol% BHO doped YGBCO seed layer) was more effective in improving the crystal quality, surface morphology and superconducting performance. At 4.2 K, the 5 mol% BHO doped YGBCO film with 4 nm thick self-seed layer had a very high flux pinning force density Fp of 860 GN/m3 for B//c under a 9 T field, and more importantly, the peak of the Fp curve was not observed.

A Facile Method for Loading CeO2 Nanoparticles on Anodic TiO2 Nanotube Arrays.

PubMed

Liao, Yulong; Yuan, Botao; Zhang, Dainan; Wang, Xiaoyi; Li, Yuanxun; Wen, Qiye; Zhang, Huaiwu; Zhong, Zhiyong

2018-04-03

In this paper, a facile method was proposed to load CeO 2 nanoparticles (NPs) on anodic TiO 2 nanotube (NT) arrays, which leads to a formation of CeO 2 /TiO 2 heterojunctions. Highly ordered anatase phase TiO 2 NT arrays were fabricated by using anodic oxidation method, then these individual TiO 2 NTs were used as tiny "nano-containers" to load a small amount of Ce(NO 3 ) 3 solutions. The loaded anodic TiO 2 NTs were baked and heated to a high temperature of 450 °C, under which the Ce(NO 3 ) 3 would be thermally decomposed inside those nano-containers. After the thermal decomposition of Ce(NO 3 ) 3 , cubic crystal CeO 2 NPs were obtained and successfully loaded into the anodic TiO 2 NT arrays. The prepared CeO 2 /TiO 2 heterojunction structures were characterized by a variety of analytical technologies, including XRD, SEM, and Raman spectra. This study provides a facile approach to prepare CeO 2 /TiO 2 films, which could be very useful for environmental and energy-related areas.

Room temperature magnetic and dielectric properties of cobalt doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mu, Chunhong; Song, Yuanqiang, E-mail: yuanqiangsong@uestc.edu.cn; Wang, Xiaoning

2015-05-07

CaCu{sub 3}Ti{sub 4−x}Co{sub x}O{sub 12} (x = 0, 0.2, 0.4) ceramics were prepared by a conventional solid state reaction, and the effects of cobalt doping on the room temperature magnetic and dielectric properties were investigated. Both X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the presence of Cu and Co rich phase at grain boundaries of Co-doped ceramics. Scanning electron microscopy micrographs of Co-doped samples showed a striking change from regular polyhedral particle type in pure CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) to sheet-like grains with certain growth orientation. Undoped CaCu{sub 3}Ti{sub 4}O{sub 12} is well known for its colossal dielectric constant inmore » a broad temperature and frequency range. The dielectric constant value was slightly changed by 5 at. % and 10 at. % Co doping, whereas the second relaxation process was clearly separated in low frequency region at room temperature. A multirelaxation mechanism was proposed to be the origin of the colossal dielectric constant. In addition, the permeability spectra measurements indicated Co-doped CCTO with good magnetic properties, showing the initial permeability (μ′) as high as 5.5 and low magnetic loss (μ″ < 0.2) below 3 MHz. And the interesting ferromagnetic superexchange coupling in Co-doped CaCu{sub 3}Ti{sub 4}O{sub 12} was discussed.« less

The structure of Er3+-doped oxy-fluoride transparent glass-ceramics studied by Raman scattering

NASA Astrophysics Data System (ADS)

Tikhomirov, V. K.; Seddon, A. B.; Ferrari, M.; Montagna, M.; Santos, L. F.; Almeida, R. M.

2003-11-01

We show that the structure of transparent oxy-fluoride glass-ceramics formed by heat treatment of glasses of typical composition 32(SiO2):9(AlO1.5):31.5(CdF2):18.5(PbF2): 5.5(ZnF2):3.5(ErF3) mol% consists of ~ 12 nm diameter, Er3+-doped, β-PbF2 nano-crystals embedded in a silica-based glass network and connected to it via non-bridging O and F anions, or fluorine linkages such as Pb-F-Cd and Pb-F-Zn. It is proposed that the glass network structure is mostly chain-like and dominated by Si(O,F)4 tetrahedra with two bridging O and two non-bridging O and/or F atoms (Q2 units). SiO4 tetrahedra with zero and one bridging O (Q0 and Q1 units, respectively) are also present in the glass structure, in the approximate proportion Q0:Q1:Q2 = 1:1:3, a characteristic which appears to be of primary importance. The flexible, chain-like glass-network, with many broken bonds, results in easy accommodation of the Er3+-doped PbF2 nano-crystals, which are grown by heat-treatment of the precursor glass. The boson peak in the Raman spectrum of the precursor glass decreases in intensity upon ceramming and is partly converted to narrow crystalline peaks at lower frequency, consistent with the precipitation of PbF2 crystalline nano-particles. It is suggested that the boson peak involves localized vibrations of broken or stretched Pb-F bonds. The mean free path for these vibrations increases with ceramming, which involves partial crystallization of the glass network, resulting in a shift of the boson peak vibrations to lower-frequency crystalline peaks.

Template-assisted formation of microsized nanocrystalline CeO2 tubes and their catalytic performance in the carboxylation of methanol

PubMed Central

Naumann, Meike; Schäfer, Christian; Brandner, Armin; Hofmann, Heiko J; Claus, Peter

2011-01-01

Summary Polymethylmethacrylate (PMMA)/ceria composite fibres were synthesized by using a sequential combination of polymer electrospinning, spray-coating with a sol, and a final calcination step to yield microstructured ceria tubes, which are composed of nanocrystalline ceria particles. The PMMA template is removed from the organic/inorganic hybrid material by radio frequency (rf) plasma etching followed by calcination of the ceramic green-body fibres. Microsized ceria (CeO2) tubes, with a diameter of ca. 0.75 µm, composed of nanocrystalline agglomerated ceria particles were thus obtained. The 1-D ceramic ceria material was characterized by X-ray diffraction, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV–vis and photoluminescence spectroscopy (PL), as well as thermogravimetric analysis (TGA). Its catalytic performance was studied in the direct carboxylation of methanol with carbon dioxide leading to dimethyl carbonate [(CH3O)2CO, DMC], which is widely employed as a phosgene and dimethyl sulfate substitute, and as well as a fuel additive. PMID:22259761

Mechanical, lattice dynamical and electronic properties of CeO2 at high pressure: First-principles studies

NASA Astrophysics Data System (ADS)

Li, Mei; Jia, Huiling; Li, Xueyan; Liu, Xuejie

2016-01-01

The elastic constants (Cij), bulk modulus (B), shear modulus (G) and elastic modulus (E) of cubic fluorite CeO2 under high pressure have been studied using the plane-wave pseudopotential method based on density functional theory. The calculated results show that the mechanical properties (Cij, B, G and E) of CeO2 increase with increasing pressure, and the phase transition of CeO2 occurs beyond the pressure of 130 GPa. From the calculated phonon spectrum using Parlinsk-Li-Kawasoe method, we found that CeO2 appears imaginary frequency at 140 GPa, which indicates phase transition. The energy band, density of states and charge density of CeO2 under high pressure are calculated using GGA+U method. It is found that the high pressure makes the electron delocalization and Ce-O covalent bonding enhanced. As pressure increases, the band gap between O2p and Ce4f states near the Fermi level increases, and CeO2 nonmetallic nature promotes. The present research results in a better understanding of how CeO2 responds to compression.

Spectroscopic properties in Er3+-doped germanotellurite glasses and glass ceramics for mid-infrared laser materials.

PubMed

Kang, Shiliang; Xiao, Xiudi; Pan, Qiwen; Chen, Dongdan; Qiu, Jianrong; Dong, Guoping

2017-03-07

Transparent Er 3+ -doped germanotellurite glass ceramics (GCs) with variable Te/Ge ratio were prepared by controllable heat-treated process. X-ray diffraction (XRD) and transmission electron microscope (TEM) confirmed the formation of nanocrystals in glass matrix. Raman spectra were used to investigate the evolution of glass structure and photon energy. Fourier transform infrared (FTIR) spectra were introduced to characterize the change of hydroxyl group (OH - ) content. Enhanced 2.7 μm emission was achieved from Er 3+ -doped GCs upon excitation with a 980 nm laser diode (LD), and the influence of GeO 2 concentration and heat-treated temperature on the spectroscopic properties were also discussed in detail. It is found that the present Er 3+ -doped GC possesses large stimulated emission cross section at around 2.7 μm (0.85 × 10 -20  cm 2 ). The advantageous spectroscopic characteristics suggest that the obtained GC may be a promising material for mid-infrared fiber lasers.

Spectroscopic properties in Er3+-doped germanotellurite glasses and glass ceramics for mid-infrared laser materials

PubMed Central

Kang, Shiliang; Xiao, Xiudi; Pan, Qiwen; Chen, Dongdan; Qiu, Jianrong; Dong, Guoping

2017-01-01

Transparent Er3+-doped germanotellurite glass ceramics (GCs) with variable Te/Ge ratio were prepared by controllable heat-treated process. X-ray diffraction (XRD) and transmission electron microscope (TEM) confirmed the formation of nanocrystals in glass matrix. Raman spectra were used to investigate the evolution of glass structure and photon energy. Fourier transform infrared (FTIR) spectra were introduced to characterize the change of hydroxyl group (OH−) content. Enhanced 2.7 μm emission was achieved from Er3+-doped GCs upon excitation with a 980 nm laser diode (LD), and the influence of GeO2 concentration and heat-treated temperature on the spectroscopic properties were also discussed in detail. It is found that the present Er3+-doped GC possesses large stimulated emission cross section at around 2.7 μm (0.85 × 10−20 cm2). The advantageous spectroscopic characteristics suggest that the obtained GC may be a promising material for mid-infrared fiber lasers. PMID:28266570

Low-Temperature Sintering Li3Mg1.8Ca0.2NbO6 Microwave Dielectric Ceramics with LMZBS Glass

NASA Astrophysics Data System (ADS)

Wang, Gang; Zhang, Huaiwu; Liu, Cheng; Su, Hua; Jia, Lijun; Li, Jie; Huang, Xin; Gan, Gongwen

2018-05-01

Li3Mg1.8Ca0.2NbO6 ceramics doped with Li2O-MgO-ZnO-B2O3-SiO2 glass (LMZBS) were prepared via a solid-state route. The LMZBS glass effectively reduced the sintering temperature of Li3Mg1.8Ca0.2NbO6 ceramics to 950°C. The effects of the LMZBS glass on the sintering behavior, microstructures and microwave dielectric properties of Li3Mg1.8Ca0.2NbO6 ceramics are discussed in detail. Among all the LMZBS doped Li3Mg1.8Ca0.2NbO6 ceramics, the sample with 1 wt.% of LMZBS glass sintered at 950°C for 4 h exhibited good dielectric properties: ɛ r = 16.7, Q × f = 31,000 GHz (9.92 GHz), τ f = - 1.3 ppm/°C. The Li3Mg1.8Ca0.2NbO6 ceramics possessed excellent chemical compatibility with Ag electrodes, and could be applied in low temperature co-fired ceramics (LTCC) applications.

CeO2 nanoparticles alter the outcome of species interactions.

PubMed

Peng, Cheng; Chen, Ying; Pu, Zhichao; Zhao, Qing; Tong, Xin; Chen, Yongsheng; Jiang, Lin

2017-06-01

Despite considerable research on the environmental impacts of nanomaterials, we know little about how they influence interactions between species. Here, we investigated the acute (12 d) and chronic (64 d) toxicities of cerium oxide nanoparticles (CeO 2 NPs) and bulk particles (0-200 mg/L) to three ciliated protist species (Loxocephalus sp., Paramecium aurelia, and Tetrahymena pyriformis) in single-, bi-, and multispecies microcosms. The results show that CeO 2 NPs strongly affected the interactions between ciliated protozoan species. When exposed to the highest CeO 2 NPs (200 mg/L), the intrinsic growth rates of Loxocephalus and Paramecium were significantly decreased by 18.87% and 88.27%, respectively, while their carrying capacities declined by more than 90%. However, CeO 2 NP exposure made it difficult to predict outcomes of interspecific competition between species. At higher NP exposure (100 and 200 mg/L), competition led to the extinction of both species in the Loxocephalus and Paramecium microcosms that survived in the absence of competitors or CeO 2 NPs. Further, the presence of potential competitors improved the survival of Loxocephalus to hundreds of individuals per milliliter in microcosms with Tetrahymena where Loxocephalus would otherwise not be able to tolerate high levels of NP exposure. This result could be attributed to weakened NP adsorption on the cell surface due to competitor-caused reduction of NP surface charge (from -18.52 to -25.17 mV) and intensified NP aggregation via phagocytosis of NPs by ciliate cells. Our results emphasize the need to explicitly consider species interactions for a more comprehensive understanding of the ecological consequences of NP exposure.

First-principles characterization of formate and carboxyl adsorption on the stoichiometric CeO2(111) and CeO2(110) surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mei, Donghai

2013-05-20

Molecular adsorption of formate and carboxyl on the stoichiometric CeO2(111) and CeO2(110) surfaces was studied using periodic density functional theory (DFT+U) calculations. Two distinguishable adsorption modes (strong and weak) of formate are identified. The bidentate configuration is more stable than the monodentate adsorption configuration. Both formate and carboxyl bind at the more open CeO2(110) surface are stronger. The calculated vibrational frequencies of two adsorbed species are consistent with experimental measurements. Finally, the effects of U parameters on the adsorption of formate and carboxyl over both CeO2 surfaces were investigated. We found that the geometrical configurations of two adsorbed species aremore » not affected by using different U parameters (U=0, 5, and 7). However, the calculated adsorption energy of carboxyl pronouncedly increases with the U value while the adsorption energy of formate only slightly changes (<0.2 eV). The Bader charge analysis shows the opposite charge transfer occurs for formate and carboxyl adsorption where the adsorbed formate is negatively charge whiled the adsorbed carboxyl is positively charged. Interestingly, with the increasing U parameter, the amount of charge is also increased. This work was supported by the Laboratory Directed Research and Development (LDRD) project of the Pacific Northwest National Laboratory (PNNL) and by a Cooperative Research and Development Agreement (CRADA) with General Motors. The computations were performed using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), which is a U.S. Department of Energy national scientific user facility located at PNNL in Richland, Washington. Part of the computing time was also granted by the National Energy Research Scientific Computing Center (NERSC)« less

Morphology, structure and optical properties of hydrothermally synthesized CeO2/CdS nanocomposites

NASA Astrophysics Data System (ADS)

Mohanty, Biswajyoti; Nayak, J.

2018-04-01

CeO2/CdS nanocomposites were synthesized using a two-step hydrothermal technique. The effects of precursor concentration on the optical and structural properties of the CeO2/CdS nanoparticles were systematically studied. The morphology, composition and the structure of the CeO2/CdS nanocomposite powder were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectrum analysis (EDXA) and X-ray diffraction (XRD), respectively. The optical properties of CeO2/CdS nanocomposites were studied by UV-vis absorption and photoluminescence (PL) spectroscopy. The optical band gaps of the CeO2/CdS nanopowders ranged from 2.34 eV to 2.39 eV as estimated from the UV-vis absorption. In the room temperature photoluminescence spectrum of CeO2/CdS nanopowder, a strong blue emission band was observed at 400 nm. Since the powder shows strong visible luminescence, it may be used as a blue phosphor in future. The original article published with this DOI was submitted in error. The correct article was inadvertently left out of the original submission. This has been rectified and the correct article was published online on 16 April 2018.

Biochemical effects of six TiO2 and four CeO2 nanomaterials in HepG2 cells

EPA Science Inventory

Biochemical effects of six TiO2 and four CeO2 nanomaterials in HepG2 cellsBecause of their growing number of uses, nanoparticles composed of CeO2 (cosmetics, polishing materials and automotive fuel additives) and TiO2 (pigments, sunscreens and photocatalysts) are of particular to...

Zr doped anatase supported reticulated ceramic foams for photocatalytic water purification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plesch, G., E-mail: plesch@fns.uniba.sk; Vargová, M.; Vogt, U.F.

2012-07-15

Highlights: ► Thick photocatalytic anatase films on macroporous reticulated ceramic foams. ► Alumina and alumina–mullite macroporous reticulated foams as photocatalyst support. ► Zr doping significantly improves the TiO{sub 2} film activity in phenol photomineralization. ► Comparison of photocatalytic activity of thick films and powder suspensions. -- Abstract: Titanium dioxide films were deposited on macroporous reticulated Al{sub 2}O{sub 3} and alumina–mullite foams with pore sizes of 15 ppi (pores per inch). Coatings were prepared from suspensions of precursor powders of Aeroxide{sup ®} P25 nanopowder and precipitated TiO{sub 2} by using a dip coating process. The TiO{sub 2} forms films with amore » thickness of ∼2–20 μm. The photocatalytic activity was characterized as the mineralization rate of an aqueous phenol solution under UVA irradiation by the TOC technique. Precipitated TiO{sub 2} films have nearly the same photocatalytic activity as a titania suspension, in which powder aggregates have a size comparable with the thickness of the films. Samples made of Aeroxide{sup ®} P25 nanopowder, in which the size of aggregates is ∼0.1 μm show higher efficiency of photodecomposition in suspensions with films. The doping of precipitated anatase with Zr(IV) in the atomic ratio Zr/Ti = 0.008 significantly improves the photocatalytic activity of the foam supported titania. Zr doped anatase films show better performance as the films prepared only from Aeroxide{sup ®} P25 nanopowder.« less

Characterization and synergetic antibacterial properties of ZnO and CeO2 supported by halloysite

NASA Astrophysics Data System (ADS)

Shu, Zhan; Zhang, Yi; Ouyang, Jing; Yang, Huaming

2017-10-01

A novel antibacterial nanocomposite, CeO2-ZnO/HNTs was prepared by a homogeneous co-precipitation method in ethanol solution. ZnO and CeO2 nanoparticles with sizes of approximately 8 and 4 nm, respectively, were dispersively precipitated onto the surface of halloysite nanotubes (HNTs). HNTs served as a template for reducing the agglomeration of ZnO nanoparticles and improving the interface reactions between the nanocomposite and bacteria cells. CeO2 nanoparticles were introduced to suppress the recombination of electron-hole pairs, and narrow the energy gap of ZnO nanoparticles. The synergistic effects of ZnO, CeO2 nanoparticles and HNTs led to the superior antibacterial activity of the CeO2-ZnO/HNTs nanocomposite against gram-negative Escherichia coli.

Irradiation effects in UO2 and CeO2

NASA Astrophysics Data System (ADS)

Ye, Bei; Oaks, Aaron; Kirk, Mark; Yun, Di; Chen, Wei-Ying; Holtzman, Benjamin; Stubbins, James F.

2013-10-01

Single crystal CeO2, as a surrogate material to UO2, was irradiated with 500 keV xenon ions at 800 °C while being observed using in situ transmission electron microscopy (TEM). Experimental results show the formation and growth of defect clusters including dislocation loops and cavities as a function of increasing atomic displacement dose. At high dose, the dislocation loop structure evolves into an extended dislocation line structure, which appears to remain stable to the high dose levels examined in this study. A high concentration of cavities was also present in the microstructure. Despite high atomic displacement doses, the specimen remained crystalline to a cumulated dose of 5 × 1015 ions/cm2, which is consistent with the known stability of the fluorite structure under high dose irradiation. Kinetic Monte Carlo calculations show that oxygen mobility is substantially higher in hypo-stoichiometric UO2/CeO2 than hyper-stoichiometric systems. This result is consistent with the ability of irradiation damage to recover even at intermediate irradiation temperatures.

Molecular dynamics simulation of fast particle irradiation to the Gd2O3-doped CeO2

NASA Astrophysics Data System (ADS)

Sasajima, Y.; Ajima, N.; Osada, T.; Ishikawa, N.; Iwase, A.

2013-12-01

The structural relaxation caused by the high-energy-ion irradiation of CeO2 with Gd2O3 addition was simulated by the molecular dynamics method. The amount of Gd2O3 was changed from 0 to 25 mol% by 5 mol%. As the initial condition, high thermal energy was supplied to the individual atoms within a cylindrical region of nanometer-order radius located in the center of the specimen. The potential proposed by Inaba et al. was utilized to calculate interaction between atoms [H. Inaba, R. Sagawa, H. Hayashi, K. Kawamura, Solid State Ionics 122 (1999) 95-103]. The supplied thermal energy was first spent to change the crystal structure into an amorphous one within a short period of about 0.3 ps, then it dissipated in the specimen. By increasing the concentration of Gd2O3, more structural disorder was observed in the sample, which is consistent to the actual experiment.

High thermal stability of La 2O 3 and CeO 2-stabilized tetragonal ZrO 2

DOE PAGES

Wang, Shichao; Xie, Hong; Lin, Yuyuan; ...

2016-02-15

Catalyst support materials of tetragonal ZrO 2, stabilized by either La 2O 3 (La 2O 3-ZrO 2) or CeO 2 (CeO 2-ZrO 2), were synthesized under hydrothermal conditions at 200 °C with NH 4OH or tetramethylammonium hydroxide as the mineralizer. From In Situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La 2O 3-ZrO 2 and CeO 2-ZrO 2 supports were nonporous nanocrystallites that exhibited rectangular shapes with thermal stability up to 1000 °C in air. These supports had an average size of ~10 nm and a surface area of 59-97 m 2/g. The catalysts Pt/La 2Omore » 3-ZrO 2 and Pt/CeO 2-ZrO 2 were prepared by using atomic layer deposition with varying Pt loadings from 6.3-12.4 wt %. Mono-dispersed Pt nanoparticles of ~3 nm were obtained for these catalysts. As a result, the incorporation of La 2O 3 and CeO 2 into the t-ZrO 2 structure did not affect the nature of the active sites for the Pt/ZrO 2 catalysts for the water-gas-shift (WGS) reaction.« less

Formation of nanostructures in Eu3+ doped glass-ceramics: an XAS study.

PubMed

Pellicer-Porres, J; Segura, A; Martínez-Criado, G; Rodríguez-Mendoza, U R; Lavín, V

2013-01-16

We describe the results of x-ray absorption experiments carried out to deduce structural and chemical information in Eu(3+) doped, transparent, oxyfluoride glass and nanostructured glass-ceramic samples. The spectra were measured at the Pb and Eu-L(III) edges. The Eu environment in the glass samples is observed to be similar to that of EuF(3). Complementary x-ray diffraction experiments show that thermal annealing creates β-PbF(2) type nanocrystals. X-ray absorption indicates that Eu ions act as seeds in the nanocrystal formation. There is evidence of interstitial fluorine atoms around Eu ions as well as Eu dimers. X-ray absorption at the Pb-L(III) edge shows that after the thermal treatment most lead atoms form a PbO amorphous phase and that only 10% of the lead atoms remain available to form β-PbF(2) type nanocrystals. Both x-ray diffraction and absorption point to a high Eu content in the nanocrystals. Our study suggests new approaches to the oxyfluoride glass-ceramic synthesis in order to further improve their properties.

Temperature Dependence Discontinuity in the Stability of Manganese doped Ceria Nanocrystals

DOE PAGES

Wu, Longjia; Dholabhai, Pratik; Uberuaga, Blas P.; ...

2017-01-05

CeO 2 has strong potential for chemical-looping water splitting. It has been shown that manganese doping decreases interface energies of CeO 2, allowing increased stability of high surface areas in this oxygen carrier oxide. The phenomenon is related to the segregation of Mn3+ at interfaces, which causes a measurable decrease in excess energy. Here in the present work, it is shown that, despite the stability of nanocrystals of manganese-doped CeO 2 with relation to undoped CeO 2, the effect is strongly dependent on the oxidation state of manganese, i.e., on the temperature. At temperatures below 800 °C, Mn is inmore » the 3+ valence state, and coarsening is hindered by the reduced interface energetics, showing smaller crystal sizes with increasing Mn content. At temperatures above 800 °C, Mn is reduced to its 2+ valence state, and coarsening is enhanced with increasing Mn content. Atomistic simulations show the segregation of Mn to grain boundaries is relatively insensitive to the charge state of the dopant. However, point defect modeling finds that the reduced state causes a decrease in cation vacancy concentration and an increase in cation interstitials, reducing drag forces for grain boundary mobility and increasing growth rates.« less

Fundamentals and Catalytic Applications of CeO2-Based Materials.

PubMed

Montini, Tiziano; Melchionna, Michele; Monai, Matteo; Fornasiero, Paolo

2016-05-25

Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40(th) anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are deepening our understanding of these materials, helping us to predict their behavior and application potential. This review has a wide view on all those aspects related to ceria which promise to produce an important impact on our life, encompassing fundamental knowledge of CeO2 and its properties, characterization toolbox, emerging features, theoretical studies, and all the catalytic applications, organized by their degree of establishment on the market.

Ferroelectric relaxor behaviour and impedance spectroscopy of Bi2O3-doped barium zirconium titanate ceramics

NASA Astrophysics Data System (ADS)

Mahajan, Sandeep; Thakur, O P; Bhattacharya, D K; Sreenivas, K

2009-03-01

Bi2O3-doped barium zirconate titanate ceramics, Ba1-xBix(Zr0.05Ti0.95)O3, have been prepared by the conventional solid-state reaction method. The ferroelectric relaxor behaviour and dielectric properties have been investigated in detail. By XRD analysis, it is suggested that up to x = 0.04, Bi3+ substitutes A-site ion, and thereafter with higher Bi3+ content, it enters the B-site sub lattice. Substitution of Bi3+ ions induces ferroelectric relaxor behaviour and the degree of relaxation behaviour increases with bismuth concentration. The remanent polarization and strain behaviour show a slight increase with the substitution level. The degree of hysteresis (strain versus electric field) also reduces from 21.4% to 4.6% with bismuth substitution. Impedance measurements were made on the prepared sample over a wide range of temperatures (300-723 K) and frequencies (40 Hz-1 MHz), which show the presence of both bulk and grain boundary effects in the material. The bulk and grain boundary conductivities determined from impedance study indicate the Arrhenius-type thermally activated process. Impedance spectroscopy is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries to the complex impedance of a ceramic system, accurately estimating its electrical conductivity as well as its corresponding activation energies and drawing conclusions on its structural properties.

Dielectric and nonlinear current-voltage characteristics of rare-earth doped CaCu3Ti4O12 ceramics

NASA Astrophysics Data System (ADS)

Liu, Laijun; Fang, Liang; Huang, Yanmin; Li, Yunhua; Shi, Danping; Zheng, Shaoying; Wu, Shuangshuang; Hu, Changzheng

2011-11-01

CaCu3Ti4O12 (CCTO) ceramics doped with rare earth (RE) oxides, including Y2O3, La2O3, Eu2O3, and Gd2O3, were prepared by the traditional solid-state reaction method in order to investigate the effect of RE oxide dopants on the electrical properties as a varistor. The phase identification and morphology of the ceramics were investigated by x-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. A high voltage measuring unit and precision impedance analyzer were used to determine the nonohmic (J-E) behaviors and measure the dielectric properties and impedance spectroscopy of the ceramics, respectively. The results showed that RE oxides enhanced greatly the breakdown electric flied but reduced the nonlinear coefficient and the mean grain size of CCTO ceramics. There was a good linear relationship between ln J and E1/2, which demonstrated that the Schottky barrier should exist at the grain boundary. A double Schottky barrier model composed of a depletion layer and a negative charge sheet was proposed, analogous to the barrier model for ZnO varistors. The depletion layer width determined by diffusion distance of RE ions and the effective surface states played important roles on the electrical properties of the ceramics.

A neutron scintillator based on transparent nanocrystalline CaF{sub 2}:Eu glass ceramic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Struebing, Christian; Kang, Zhitao, E-mail: zhitao.kang@gtri.gatech.edu; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332

2016-04-11

There are no efficient Eu{sup 2+} doped glass neutron scintillators reported due to low doping concentrations of Eu{sup 2+} and the amorphous nature of the glass matrix. In this work, an efficient CaF{sub 2}:Eu glass ceramic neutron scintillator was prepared by forming CaF{sub 2}:Eu nanocrystals in a {sup 6}Li-containing glass matrix. Through appropriate thermal treatments, the scintillation light yield of the transparent glass ceramic was increased by a factor of at least 46 compared to the as-cast amorphous glass. This improvement was attributed to more efficient energy transfer from the CaF{sub 2} crystals to the Eu{sup 2+} emitting centers. Furthermore » light yield improvement is expected if the refractive index of the glass matrix can be matched to the CaF{sub 2} crystal.« less

(U) Equation of State and Compaction Modeling for CeO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fredenburg, David A.; Chisolm, Eric D.

2014-10-20

Recent efforts have focused on developing a solid-liquid and three-phase equation of state (EOS) for CeO 2, while parallel experimental efforts have focused on obtaining high-fidelity Hugoniot measurements on CeO 2 in the porous state. The current work examines the robustness of two CeO 2 SESAME equations of state, a solid-liquid EOS, 96170, and a three-phase EOS, 96171, by validating the EOS against a suite of high-pressure shock compression experiments on initially porous CeO 2. At lower pressures compaction is considered by incorporating a two-term exponential form of the P-compaction model, using three separate definitions for α(P). Simulations are executedmore » spanning the partially compacted and fully compacted EOS regimes over the pressure range 0.5 - 109 GPa. Comparison of calculated Hugoniot results with those obtained experimentally indicate good agreement for all definitions of α(P) with both the solid-liquid and three-phase EOS in the low-pressure compaction regime. At higher pressures the three-phase EOS does a better job at predicting the measured Hugoniot response, though at the highest pressures EOS 96171 predicts a less compliant response than is observed experimentally. Measured material velocity profiles of the shock-wave after it has transmitted through the powder are also compared with those simulated using with solid-liquid and three-phase EOS. Profiles lend insight into limits of the current experimental design, as well as the threshold conditions for the shock-induced phase transition in CeO 2.« less

Enhanced Colloidal Stability of CeO2 Nanoparticles by Ferrous Ions: Adsorption, Redox Reaction, and Surface Precipitation.

PubMed

Liu, Xuyang; Ray, Jessica R; Neil, Chelsea W; Li, Qingyun; Jun, Young-Shin

2015-05-05

Due to the toxicity of cerium oxide (CeO2) nanoparticles (NPs), a better understanding of the redox reaction-induced surface property changes of CeO2 NPs and their transport in natural and engineered aqueous systems is needed. This study investigates the impact of redox reactions with ferrous ions (Fe2+) on the colloidal stability of CeO2 NPs. We demonstrated that under anaerobic conditions, suspended CeO2 NPs in a 3 mM FeCl2 solution at pH 4.8 were much more stable against sedimentation than those in the absence of Fe2+. Redox reactions between CeO2 NPs and Fe2+ lead to the formation of 6-line ferrihydrite on the CeO2 surfaces, which enhanced the colloidal stability by increasing the zeta potential and hydrophilicity of CeO2 NPs. These redox reactions can affect the toxicity of CeO2 NPs by increasing cerium dissolution, and by creating new Fe(III) (hydr)oxide reactive surface layers. Thus, these findings have significant implications for elucidating the phase transformation and transport of redox reactive NPs in the environment.

A comparative investigation of SO2 oxidative transfer over CuO with a CeO2 surface

NASA Astrophysics Data System (ADS)

Liu, Yifeng; Shen, Benxian; Pi, Zhipeng; Chen, Hua; Zhao, Jigang

2017-04-01

To further improve the catalytic desulfurization function of the Mg-Al spinel sulfur transfer agent in a fluid catalytic cracking (FCC) unit, the reaction paths of SO2 oxidation by O2 over the metal oxide surface of CuO (111) and CeO2 (111) were investigated. In reference to the fact that SO2 reacting with O2 over CuO was a Mars-van Krevelen cycle, a similar reaction law for SO2 oxidation over CeO2 was also verified by characterization methods (e.g., IR, XPS). Meanwhile, the molecular simulation results indicated that the rate-control step of SO2 oxidation over CeO2 (111) and CuO (111) was a SO3 desorption step. The lower energy barrier in the rate-control step corresponded to better catalytic performance; hence, it could explain the reason that CeO2 had a better sulfur oxidization transfer performance than CuO.

Plasma-assisted adsorption of elemental mercury on CeO2/TiO2 at low temperatures

NASA Astrophysics Data System (ADS)

Liu, Lu; Zheng, Chenghang; Gao, Xiang

2017-11-01

Mercury is a kind of pollutants contained in flue gas which is hazardous for human beings. In this work, CeO2 was packed in the discharge zone of a plasma reactor to adsorb elemental mercury at low temperatures. Plasma-catalyst reactor can remove Hg0 efficiently with CeO2/TiO2 catalysts packed in the discharge zone. The Hg0 concentration continued to decrease gradually when the plasma was turned on, but not sank rapidly. This tendency was different with other catalysts. The treatment of plasma to CeO2/TiO2 catalysts has a promotion effect on the adsorption of Hg0. Plasma has the effect of changing the surface properties of the catalysts and the changes would restitute if the condition changed. The long-running test demonstrated that this method is an effective way to remove Hg0. The removal efficiency remained at above 99% throughout 12 hours when plasma had been turned on (15kV, 0.5 g packed CeO2/TiO2).

Nb-doped SrTiO3 glass-ceramics as high temperature stable n-type oxide thermoelectrics

NASA Astrophysics Data System (ADS)

Lingner, Julian; Jakob, Gerhard; Letz, Martin

2012-06-01

Niobium doped SrTiO3 is known for its high potential as an oxide thermoelectric material and is one of the possible candidates for the n-type site in an oxidic thermoelectric module. The high thermal conductivity [1] and the lack of high-temperature stability of the oxygen vacancies [2] limit its properties in the ceramic systems. Glass-ceramics are intrinsic nano-structured systems and provide crystal phases densely embedded in a glass matrix which prevents the material from detoriation at high temperatures. In particular, the glass-matrix prevents an uncontrolled reoxidization as well as an uncontrolled grain growth therefore retaining the nano-structure even at high temperatures. Here, measurements and results of first glass-ceramic systems are presented, which show a low thermal conductivity due to the residue glass phase. Furthermore a stable thermal cycling up to 650 °C is demonstrated.

Identification of Cr valence states in Cr and Nd co-doped Lu3Al5O12 laser ceramics

NASA Astrophysics Data System (ADS)

Zhang, Pande; Jiang, Benxue; Fan, Jintai; Mao, Xiaojian; Zhang, Long

2017-09-01

Cr and Nd co-doped laser ceramics, as the potential gain materials in inertial confinement fusion (ICF), have been widely investigated. And the study on valence states of chromium ions is important. The effects of sintering additives and annealing atmosphere on the valence state of chromium were studied in detail, and the results shown that the Cr valence states were demonstrated to be Cr2+ and Cr3+ ions in HIP-sintered Cr(0.2 at.%), Nd(0.8 at.%): LuAG laser ceramics. And the intensity of the near-infrared absorption band caused by Cr2+ ions was attenuated with the decreasing SiO2 concentration and increasing MgO amount. The near-infrared absorption could be eliminated by annealing in air. And the transformation of valence states of Cr ions in the Cr,Nd:LuAG ceramics were also confirmed by electron paramagnetic resonance and X-ray photoelectron spectroscopy.

Development of Nano-crystalline Doped-Ceramic Enabled Fiber Sensors for High Temperature In-Situ Monitoring of Fossil Fuel Gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Hai; Dong, Junhang; Lin, Jerry

2012-03-01

This is a final technical report for the first project year from July 1, 2005 to Jan 31, 2012 for DoE/NETL funded project DE-FC26-05NT42439: Development of Nanocrystalline Doped-Ceramic Enabled Fiber Sensors for High Temperature In-Situ Monitoring of Fossil Fuel Gases. This report summarizes the technical progresses and achievements towards the development of novel nanocrystalline doped ceramic material-enabled optical fiber sensors for in situ and real time monitoring the gas composition of flue or hot gas streams involved in fossil-fuel based power generation and hydrogen production.

Catalytic hydrolysis of COS over CeO2 (110) surface: A density functional theory study

NASA Astrophysics Data System (ADS)

Song, Xin; Ning, Ping; Wang, Chi; Li, Kai; Tang, Lihong; Sun, Xin

2017-08-01

Density functional theory (DFT) calculations were performed to investigate the reaction pathways for catalytic hydrolysis of COS over CeO2 (110) surface using Dmol3 model. The thermodynamic stability analysis for the suggested routes of COS hydrolysis to CO2 and H2S was evaluated. The absolute values of adsorption energy of H2O-CeO2 are higher than that of COS-CeO2. Meanwhile, the adsorption energy and geometries show that H2O is easier adsorbed on the surface of CeO2 (110) than COS. H2O plays a role as a bridge in the process of joint adsorption. H2O forms more Cesbnd Osbnd H groups on the CeO2 (110) surface. CeO2 decreases the maximum energy barrier by 76.15 kcal/mol. The migration of H from H2O to COS is the key for the hydrolysis reaction. Csbnd O channel is easier to occur than Csbnd S channel. Experimental result shows that adding of CeO2 can increase COS removal rate and prolong the 100% COS removal rate from 180 min to 210 min. The difference between Fe2O3 and CeO2 for the hydrolysis of COS is characterized in the atomic charge transfer and the formation of Hsbnd O bond and Hsbnd S bond. The transfer effect of H in H2O to S in COS over CeO2 decreases the energy barriers of hydrolysis reaction, and enhances the reaction activity of COS hydrolysis.

Template-Free Hydrothermal Synthesis, Mechanism, and Photocatalytic Properties of Core-Shell CeO2 Nanospheres

NASA Astrophysics Data System (ADS)

Li, Huijie; Meng, Fanming; Gong, Jinfeng; Fan, Zhenghua; Qin, Rui

2018-03-01

CeO2 nanospheres with the core-shell nanostructure have been successfully synthesized by a template-free hydrothermal method. The structures, morphologies and optical properties of core-shell CeO2 nanospheres were analyzed by X-ray diffraction (XRD), TG, Fourier transform infrared spectroscopy, XRD, EDS, SAED, scanning electron microscopy and transmission electron microscopy, UV-Vis diffuse reflectance spectra, Raman analyses. The degradation efficiencies of core-shell CeO2 nanospheres for methyl orange were as high as 93.49, 95.67 and 98.28% within 160 min, and the rates of photo degradation of methyl orange by core-shell CeO2 nanospheres under UV-light were 0.01693, 0.01782 and 0.02375 min-1. Methyl orange was degraded in photocatalytic oxidation processes, which mainly gave the credit to a large number of reactive species including h+, surface superoxide species ·O2 -, and ·OH radicals. The core-shell structure, small crystallite size and the conversion between Ce3+ and Ce4+ of CeO2 nanospheres were of importance for its catalytic activity. These results demonstrated the possibility of improving the efficient catalysts of the earth abundant CeO2 catalysts.

Indentation Behavior and Mechanical Properties of Tungsten/Chromium co-Doped Bismuth Titanate Ceramics Sintered at Different Temperatures

PubMed Central

Xu, Jiageng; Chen, Yu; Tan, Zhi; Nie, Rui; Wang, Qingyuan; Zhu, Jianguo

2018-01-01

A sort of tungsten/chromium(W/Cr) co-doped bismuth titanate (BIT) ceramics (Bi4Ti2.95W0.05O12.05 + 0.2 wt % Cr2O3, abbreviate to BTWC) are ordinarily sintered between 1050 and 1150 °C, and the indentation behavior and mechanical properties of ceramics sintered at different temperatures have been investigated by both nanoindentation and microindentation technology. Firstly, more or less Bi2Ti2O7 grains as the second phase were found in BTWC ceramics, and the grain size of ceramics increased with increase of sintering temperatures. A nanoindentation test for BTWC ceramics reveals that the testing hardness of ceramics decreased with increase of sintering temperatures, which could be explained by the Hall–Petch equation, and the true hardness could be calculated according to the pressure-state-response (PSR) model considering the indentation size effect, where the value of hardness depends on the magnitude of load. While, under the application of microsized Vickers, the sample sintered at a lower temperature (1050 °C) gained four linearly propagating cracks, however, they were observed to shorten in the sample sintered at a higher temperature (1125 °C). Moreover, both the crack deflection and the crack branching existed in the latter. The hardness and the fracture toughness of BTWC ceramics presented a contrary variational tendency with increase of sintering temperatures. A high sintering tends to get a lower hardness and a higher fracture toughness, which could be attributed to the easier plastic deformation and the stronger crack inhibition of coarse grains, respectively, as well as the toughening effect coming from the second phase. PMID:29584677

Structural, magnetic and electronic structural properties of Mn doped CeO2 nanoparticles

NASA Astrophysics Data System (ADS)

Kumari, Kavita; Vij, Ankush; Hashim, Mohd.; Chae, K. H.; Kumar, Shalendra

2018-05-01

Nanoparticles of Ce1-xMnxO2, (x=0.0, 0.01, and 0.05) have been synthesized by using co-precipitation method, and then characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), near edge x-ray absorption fine structure (NEXAFS) spectroscopy and dc magnetization measurements. XRD results clearly showed that the all the samples have single phase nature and exclude the presence of any secondary phase. The average particle size calculated using XRD TEM measurements found to decrease with increase in Mn doping in the range of 4.0 - 9.0 nm. The structural parameters such as strain, interplaner distance and lattice parameter is observed to decrease with increase in doping. The morphology of Ce1-xMnxO2 nanoparticles measured using TEM micrographs indicate that nanoparticle have spherical shape morphology. Magnetic hysteresis curve for Ce1-xMnxO2, (x = 0.0, 0.01, and 0.05) confirms the ferromagnetic ordering room temperature. The value of saturation magnetization is observed to decrease with increase in temperature from 10 K to 300 K. The NEXAFS spectra measured at Ce M4,5 edge reveals that Ce-ions are in +4 valance state.

Magnetism mediated by a majority of [Fe³⁺ + VO²⁻] complexes in Fe-doped CeO₂ nanoparticles.

PubMed

Paidi, V K; Ferreira, N S; Goltz, D; van Lierop, J

2015-08-26

We examine the role of Fe(3+) and vacancies (V(O)) on the magnetism of Fe-doped CeO2 nanoparticles. Magnetic nanoparticles of Ce(100-x)Fe(x)O2 (x  =  0, 0.26, 1.82, 2.64, 5.26, 6.91, and 7.22) were prepared by a co-precipitation method, and their structural, compositional and magnetic properties were investigated. The CeO2 nanoparticles had a mixed valance of Ce(4+) and Ce(3+) ions, and doping introduced Fe(3+) ions. The decrease in Ce(3+) and increase in Fe(3+) concentrations indicated the presence of more [Fe(3+) + V(O)(2-)] complexes with Fe loading in the particles. Charge neutralization, Fe(3+) + V(O)(2-) + 2Ce(4+) ↔ 2Ce(3+) + Fe(3+), identified the impact of V(O) on the magnetism, where our results suggest that the Fe-doped CeO2 nanoparticle magnetism is mediated by a majority of [Fe(3+) + V(O)(2-)]-Ce(3+) -[Fe(3+) + V(O)(2-)] complexes.

CO2 methanation on the catalyst of Ni/MCM-41 promoted with CeO2.

PubMed

Wang, Xiaoliu; Zhu, Lingjun; Liu, Yincong; Wang, Shurong

2018-06-01

CO 2 as a raw feed combined with renewable hydrogen for the production of useful chemicals and alternative energy products is one of the solutions to environmental and energy problems. In this study, a series of Ni-xCeO 2 /MCM-41 catalysts with a nickel content of 20wt% were prepared through deposition precipitation method for CO 2 methanation. Different characterization methods, including BET, XRD, TEM, SEM, H 2 -TPR and H 2 -TPD were applied to help explore the influence mechanism of CeO 2 on Ni/MCM-41 in CO 2 methanation. It was found that all CeO 2 -promoted catalysts exhibited enhanced catalytic activity when compared to Ni/MCM-41. The catalyst modified with 20wt% CeO 2 showed the best catalytic performance, with CO 2 conversion and CH 4 selectivity of 85.6% and 99.8%, respectively, at the temperature of 380°C under atmospheric pressure. The synergetic effects among Ni 0 active sites, the promoter and the support, including nickel dispersion improvement and increased CO 2 adsorption sites due to the addition of CeO 2 , were considered as important factors for high reactivity of the promoted catalysts. The stability test showed that the promoted catalyst maintained its high reactivity after 30h. Copyright © 2017 Elsevier B.V. All rights reserved.

Dielectric and varistor properties of rare-earth-doped ZnO and CaCu3Ti4O12 composite ceramics

NASA Astrophysics Data System (ADS)

Lu, Huafei; Lin, Yuanhua; Yuan, Jiancong; Nan, Cewen; Chen, Kexin

2013-02-01

To investigate the multi-functional ceramics with both high permittivity and large nonlinear coefficient, we have prepared rare-earth Tb-and-Co doped ZnO and TiO2-rich CaCu3Ti4O12 (TCCTO) powders by chemical co-precipitation and sol-gel methods respectively, and then obtained the TCCTO/ZnO composite ceramics, sintered at 1100°C for 3 h in air. Analyzing the composite ceramics of the microstructure and phase composition indicated that the composite ceramics were composed of the main phases of ZnO and CaCu3Ti4O12 (CCTO). Our results revealed that the TCCTO/ZnO composite ceramics showed both high dielectric and good nonlinear electrical behaviors. The composite ceramic of TCCTO: ZnO = 0.3 exhibited a high dielectric constant of 210(1 kHz) with a nonlinear coefficient of 11. The dielectric behavior of TCCTO/ZnO composite could be explained by the mixture rule. With the high dielectric permittivity and tunable varistor behaviors, the composite ceramics has a potential application for the higher voltage transportation devices.

Luminescence of Er/Yb and Tm/Yb doped FAp nanoparticles and ceramics

NASA Astrophysics Data System (ADS)

Grigorjeva, L.; Smits, K.; Millers, D.; Jankoviča, Dz

2015-03-01

The nanoparticles of hydroxiapatite and fluorapatite doped with Er/Yb and Tm/Yb were synthesized and characterized by FTIR, XRD, SEM and TEM methods. The results of up-conversion luminescence studies were presented for the samples as prepared, annealed at 500°C and at 900-1000 °C. At annealing above 800°C the ceramic state was formed. It is shown that fluorapatite host is more appropriate than hydroxiapatite host for rare ions luminescence and up-conversion processes. The post preparing annealing of nanarticles significantly enhanced the luminescence intensity. The Tm/Yb doped fluorapatite shows intense up-conversion luminescence in 790-800 nm spectral region and is potentially useful for biomedical applications.

X-Ray Absorption Spectroscopy Studies of the Atomic Structure of Zirconium-Doped Lithium Silicate Glasses and Glass-Ceramics, Zirconium-Doped Lithium Borate Glasses, and Vitreous Rare-Earth Phosphates

NASA Astrophysics Data System (ADS)

Yoo, Changhyeon

In the first part of this work, the atomic-scale structure around rare-earth (RE = Pr, Nd, Eu, Dy, and Er) cations (RE3+) in rare-earth sodium ultraphosphate (REUP) glasses were investigated using RE LIII -edge (RE = Nd, Er, Dy, and Eu) and K-edge (RE = Pr and Dy) Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. (RE2O 3)x(Na2O)y(P2O5) 1-x-y glasses in the compositional range 0 ≤ x ≤ 0.14 and 0.3 ≤ x + y ≤ 0.4 were studied. For the nearest oxygen shell, the RE-oxygen (RE-O) coordination number decreases from 10.8 to 6.5 with increasing RE content for Pr-, Nd-, Dy-, and Er-doped sodium ultraphosphate glasses. For Eu-doped samples, the Eu-O coordination number was between 7.5 and 8.8. Also, the RE-O mean distance ranges were between 2.43-2.45 A, 2.40-2.43 A, 2.36-2.38 A, 2.30-2.35 A, and 2.28-2.30 A for Pr-, Nd-, Eu-, Dy-, and Er-doped samples, respectively. In the second part, a series of Zr-doped (3-10 mol%) lithium silicate (ZRLS) glass-ceramics and their parent glasses and a series of Zr-doped (2-6 mol% ZrO2) lithium borate (ZRLB) glasses were investigated using Zr K-edge EXAFS and X-ray Absorption Near Edge Structure (XANES) spectroscopy. Immediate coordination environments of all ZRLS glasses are remarkably similar for different compositions. For the nearest oxygen shell, the Zr-O coordination number ranges were between 6.1 and 6.3 for nucleated and crystallized samples, respectively. Also, the Zr-O mean distance remains similar around 2.10 A. For these glasses, the composition dependence of structural parameters was small. Small changes in the coordination environment were observed for ZRLS glass-ceramics after thermal treatments. In contrast, Zr coordination environment in ZRLB glasses appear to depend appreciably on the Zr concentration. For the nearest oxygen shell, the Zr-O coordination number increased from 6.1 to 6.8 and the Zr-O distance decreased from 2.18 A to 2.14 A with decreasing ZrO2 content.

Ceramic Laser Materials

PubMed Central

Sanghera, Jasbinder; Kim, Woohong; Villalobos, Guillermo; Shaw, Brandon; Baker, Colin; Frantz, Jesse; Sadowski, Bryan; Aggarwal, Ishwar

2012-01-01

Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements. PMID:28817044

Luminescence and scintillation properties of BaF2sbnd Ce transparent ceramic

NASA Astrophysics Data System (ADS)

Luo, Junming; Sahi, Sunil; Groza, Michael; Wang, Zhiqiang; Ma, Lun; Chen, Wei; Burger, Arnold; Kenarangui, Rasool; Sham, Tsun-Kong; Selim, Farida A.

2016-08-01

Cerium doped Barium Fluoride (BaF2sbnd Ce) transparent ceramic was fabricated and its luminescence and scintillation properties were studied. The photoluminescence shows the emission peaks at 310 nm and 323 nm and is related to the 5d-4f transitions in Ce3+ ion. Photo peak at 511 keV and 1274 keV were obtained with BaF2sbnd Ce transparent ceramic for Na-22 radioisotopes. Energy resolution of 13.5% at 662 keV is calculated for the BaF2sbnd Ce transparent ceramic. Light yield of 5100 photons/MeV was recorded for BaF2sbnd Ce(0.2%) ceramic and is comparable to its single crystal counterpart. Scintillation decay time measurements shows fast component of 58 ns and a relatively slow component of 434 ns under 662 keV gamma excitation. The slower component in BaF2sbnd Ce(0.2%) ceramic is about 200 ns faster than the STE emission in BaF2 host and is associated with the dipole-dipole energy transfer from the host matrix to Ce3+ luminescence center.

The influence of different alkaline earth oxides on the structural and optical properties of undoped, Ce-doped, Sm-doped, and Sm/Ce co-doped lithium alumino-phosphate glasses

NASA Astrophysics Data System (ADS)

Othman, H. A.; Arzumanyan, G. M.; Möncke, D.

2016-12-01

Undoped, singly Sm doped, Ce doped, and Sm/Ce co-doped lithium alumino-phosphate glasses with different alkaline earth modifiers were prepared by melt quenching. The structure of the prepared glasses was investigated by FT-IR and Raman, as well as by optical spectroscopy. The effect of the optical basicity of the host glass matrix on the added active dopants was studied, as was the effect doping had on the phosphate structural units. The optical edge shifts toward higher wavelengths with an increase in the optical basicity due to the increased polarizability of the glass matrix, but also with increasing CeO2 concentration as a result of Ce3+/Ce4+ inter valence charge transfer (IV-CT) absorption. The optical band gap for direct and indirect allowed transitions was calculated for the undoped glasses. The glass sample containing Mg2+ modifier ions is found to have the highest value (4.16 eV) for the optical band gap while Ba2+ has the lowest value (3.61 eV). The change in the optical band gap arises from the structural changes and the overall polarizability (optical basicity). Refractive index, molar refractivity Rm and molar polarizability αm values increase with increasing optical basicity of the glasses. The characteristic absorption peaks of Sm3+ were also investigated. For Sm/Ce co-doped glasses, especially at high concentration of CeO2, the absorption of Ce3+ hinders the high energy absorption of Sm3+ and this effect becomes more obvious with increasing optical basicity.

Low toxicity of HfO2, SiO2, Al2O3 and CeO2 nanoparticles to the yeast, Saccharomyces cerevisiae.

PubMed

García-Saucedo, Citlali; Field, James A; Otero-Gonzalez, Lila; Sierra-Álvarez, Reyes

2011-09-15

Increasing use of nanomaterials necessitates an improved understanding of their potential impact on environment health. This study evaluated the cytotoxicity of nanosized HfO(2), SiO(2), Al(2)O(3) and CeO(2) towards the eukaryotic model organism Saccharomyces cerevisiae, and characterized their state of dispersion in bioassay medium. Nanotoxicity was assessed by monitoring oxygen consumption in batch cultures and by analysis of cell membrane integrity. CeO(2), Al(2)O(3), and HfO(2) nanoparticles were highly unstable in yeast medium and formed micron-sized, settleable agglomerates. A non-toxic polyacrylate dispersant (Dispex A40) was used to improve nanoparticle stability and determine the impact of enhanced dispersion on toxicity. None of the NPs tested without dispersant inhibited O(2) uptake by yeast at concentrations as high as 1000 mg/L. Dispersant supplementation only enhanced the toxicity of CeO(2) (47% at 1000 mg/L). Dispersed SiO(2) and Al(2)O(3) (1000 mg/L) caused cell membrane damage, whereas dispersed HfO(2) and CeO(2) did not cause significant disruption of membrane integrity at the same concentration. These results suggest that the O(2) uptake inhibition observed with dispersed CeO(2) NPs was not due to reduced cell viability. This is the first study evaluating toxicity of nanoscale HfO(2), SiO(2), Al(2)O(3) and CeO(2) to S. cerevisiae. Overall the results obtained demonstrate that these nanomaterials display low or no toxicity to yeast. Copyright © 2011 Elsevier B.V. All rights reserved.

In vitro skin decontamination of the organophosphorus pesticide Paraoxon with nanometric cerium oxide CeO2.

PubMed

Salerno, Alicia; Devers, Thierry; Bolzinger, Marie-Alexandrine; Pelletier, Jocelyne; Josse, Denis; Briançon, Stéphanie

2017-04-01

Organophosphorus compounds (OP), which mainly penetrate via the percutaneous pathway, represent a threat for both military and civilians. Body surface decontamination is vital to prevent victims poisoning. The development of a cost-effective formulation, which could be efficient and easy to handle in case of mass contamination, is therefore crucial. Metal oxides nanoparticles, due their large surface areas and the large amount of highly reactive sites, present high reactivity towards OP. First, this study aimed at evaluating the reaction of CeO 2 nanoparticles, synthetized by microwave path and calcined at 500 or 600 °C, with Paraoxon (POX) in aqueous solution. Results showed that both nanoparticles degraded 60%-70% of POX. CeO 2 calcined at 500 °C, owing to its larger specific area, was the most effective. Moreover, the degradation was significantly increased under Ultra-Violet irradiation (initial degradation rate doubled). Then, skin decontamination was studied in vitro using the Franz cell method with pig-ear skin samples. CeO 2 powder and an aqueous suspension of CeO 2 (CeO 2 -W) were applied 1 h after POX exposure. The efficiency of decontamination, including removal and/or degradation of POX, was compared to Fuller's earth (FE) and RSDL lotion which are, currently, the most efficient systems for skin decontamination. CeO 2 -W and RSDL were the most efficient to remove POX from the skin surface and decrease skin absorption by 6.4 compared to the control not decontaminated. FE reduced significantly (twice) the absorbed fraction of POX, contrarily to CeO 2 powder. Considering only the degradation rate of POX, the products ranged in the order CeO 2  > RSDL > CeO 2 -W > FE (no degradation). This study showed that CeO 2 nanoparticles are a promising material for skin decontamination of OP if formulated as a dispersion able to remove POX like CeO 2 -W and to degrade it as CeO 2 powder. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Synthesis and characterization of cerium containing iron phosphate based glass-ceramics

NASA Astrophysics Data System (ADS)

Deng, Yi; Liao, Qilong; Wang, Fu; Zhu, Hanzhen

2018-02-01

The structure and properties of xCeO2-(100-x)(40Fe2O3-60P2O5), where x = 0, 2, 4, 6 and 8 mol%, glass-ceramics prepared by melting and slow cooling method have been investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA) and the Product Consistency Test (PCT). The results show that the 40Fe2O3-60P2O5 sample is homogeneously amorphous and the sample containing 2 mol% CeO2 has a small amount of FePO4 phase embedded. For the sample containing up to 4 mol% CeO2, monazite CePO4 and a small amount of FePO4 appear. Spectra analysis show that the structure networks of the glass-ceramics mainly consist of orthophosphate, along with pyrophosphate and a small amount of metaphosphate units. Moreover, the leaching rates of Fe and Ce are about 3.5 × 10-5 g m-2 d-1 and 5.0 × 10-5 g m-2 d-1 respectively after immersion in deionized water at 90 °C for 56 days, indicating their good chemical durability. The conclusions imply that the prepared method may be a promising process to immobilize nuclear waste into glass-ceramic matrix.

Fabrication and magnetic properties of Fe and Co co-doped ZrO2

NASA Astrophysics Data System (ADS)

Okabayashi, J.; Kono, S.; Yamada, Y.; Nomura, K.

2011-12-01

We investigate the effects of Fe and Co co-doping on the magnetic and electronic properties of ZrO2 ceramics prepared by a sol-gel method, and study their dependence on the annealing temperature. Dilute Fe and Co co-doping into ZrO2 exhibits ferromagnetic behavior at room temperature for annealing temperatures above 900 °C, accompanying the phase transition from tetragonal to monoclinic structure in ZrO2. The electronic structures are studied by x-ray absorption spectroscopy and Mössbauer spectroscopy, which suggest that the Fe3+ and Co2+/Co3+ mixing states are dominant in Fe and Co co-doped ZrO2.

Fundamental Understanding of the Interaction of Acid Gases with CeO 2 : From Surface Science to Practical Catalysis

DOE PAGES

Tumuluri, Uma; Rother, Gernot; Wu, Zili

2016-03-21

Acid gases including CO 2, SO 2, and NO x are ubiquitous in large-scale energy applications including heterogeneous catalysis. The adverse environmental and health effects of these acid gases have resulted in high interest in the research and development of technologies to remove or convert these acid gases. The main challenge for the development of these technologies is to develop catalysts that are highly efficient, stable, and cost-effective, and many catalysts have been reported in this regard. CeO 2 and CeO 2-based catalysts have gained prominence in the removal and conversion of CO 2, SO 2, and NO x becausemore » of their structural robustness and redox and acid–base properties. In this article, we provide a brief overview of the application of CeO 2 and CeO 2-based catalysts for the removal of CO 2, SO 2, and NO x gases with an emphasis on the fundamental understanding of the interactions of these acid gases with CeO 2. The studies summarized in this review range from surface science using single crystals and thin films with precise crystallographic planes to practical catalysis applications of nanocrystalline and polycrystalline CeO 2 materials with defects and dopants. After an introduction to the properties of CeO 2 surfaces, their catalytic properties for conversions of different acid gases are reviewed and discussed. Lastly, we find that the surface atomic structure, oxygen vacancies, and surface acid–base properties of CeO 2 play vital roles in the surface chemistry and structure evolution during the interactions of acid gases with CeO 2 and CeO 2-based catalysts.« less

Fundamental Understanding of the Interaction of Acid Gases with CeO 2 : From Surface Science to Practical Catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tumuluri, Uma; Rother, Gernot; Wu, Zili

Acid gases including CO 2, SO 2, and NO x are ubiquitous in large-scale energy applications including heterogeneous catalysis. The adverse environmental and health effects of these acid gases have resulted in high interest in the research and development of technologies to remove or convert these acid gases. The main challenge for the development of these technologies is to develop catalysts that are highly efficient, stable, and cost-effective, and many catalysts have been reported in this regard. CeO 2 and CeO 2-based catalysts have gained prominence in the removal and conversion of CO 2, SO 2, and NO x becausemore » of their structural robustness and redox and acid–base properties. In this article, we provide a brief overview of the application of CeO 2 and CeO 2-based catalysts for the removal of CO 2, SO 2, and NO x gases with an emphasis on the fundamental understanding of the interactions of these acid gases with CeO 2. The studies summarized in this review range from surface science using single crystals and thin films with precise crystallographic planes to practical catalysis applications of nanocrystalline and polycrystalline CeO 2 materials with defects and dopants. After an introduction to the properties of CeO 2 surfaces, their catalytic properties for conversions of different acid gases are reviewed and discussed. Lastly, we find that the surface atomic structure, oxygen vacancies, and surface acid–base properties of CeO 2 play vital roles in the surface chemistry and structure evolution during the interactions of acid gases with CeO 2 and CeO 2-based catalysts.« less

Lutetium oxide-based transparent ceramic scintillators

DOEpatents

Seeley, Zachary; Cherepy, Nerine; Kuntz, Joshua; Payne, Stephen A.

2016-01-19

In one embodiment, a transparent ceramic of sintered nanoparticles includes gadolinium lutetium oxide doped with europium having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YEu.sub.YO.sub.3, where X is any value within a range from about 0.05 to about 0.45 and Y is any value within a range from about 0.01 to about 0.2, and where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm. In another embodiment, a transparent ceramic scintillator of sintered nanoparticles, includes a body of sintered nanoparticles including gadolinium lutetium oxide doped with a rare earth activator (RE) having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YRE.sub.YO.sub.3, where RE is selected from the group consisting of: Sm, Eu, Tb, and Dy, where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm.

An Investigation of Dielectric, Piezoelectric Properties and Microstructures of Bi0.5Na0.5TiO3-BaTiO3-Bi0.5K0.5TiO3 Lead-Free Piezoelectric Ceramics Doped with K2AlNbO5 Compound

NASA Astrophysics Data System (ADS)

Liu, Gang; Jiang, Wentao; Liu, Kaihua; Liu, Xiaokui; Song, Chunlin; Yan, Yan; Jin, Li

2017-08-01

The effect of K2AlNbO5 compound acting as both donor and accepter on the phase, microstructures and electrical properties of the 0.9362(Bi0.5Na0.5)TiO3-0.0637BaTiO3-0.02(Bi0.5K0.5)TiO3 [(1- x)(0.9163BNT-0.0637BT-0.02BKT)- x(K2AlNbO5)] (BNKBT-1000 xKAN) ternary lead-free piezoelectric ceramics was systematically investigated. When doping content of K2AlNbO5 was varied from 0 to 0.009, the BNKBT-1000 xKAN ceramics showed a single perovskite structure, and the phase structure transferred from a rhombohedral-tetragonal coexistent morphotropic phase boundaries zone to a tetragonal zone. The x-ray photoelectron spectroscopy analysis indicated that the chemical valence of the Nb and Al element are 5+ and 3+, respectively. Strong relaxor characteristics were revealed by the temperature-dependent dielectric properties of the ceramics. Typical square polarization-electric field ( P- E) hysteresis loops were observed in the samples with doping content lower than 0.005. However, with further increasing the doping content ( x = 0.007 and 0.009), round P- E hysteresis loops were observed due to the high conductivity of these samples. Moreover, when the doping content was less than 0.005, the ceramic samples exhibited good piezoelectric properties. Specially, when the doping content was 0.001, the piezoelectric constant d 33 and electromechanical coupling coefficient k p of the sample were 197 pC/N and 22%, respectively. However, further addition would deteriorate both the dielectric and piezoelectric properties.

The CEO Speaks.

ERIC Educational Resources Information Center

Isherwood, Geoffrey B.; And Others

1984-01-01

Reports results of a 1982-83 survey of 37 Canadian chief executive school officers (CEOs) regarding their effectiveness. Presents findings and analysis regarding CEO relationships and effectiveness with community groups and school board members, community expectations of CEOs, CEO roles as mediators and policy makers, and reasons for…

Enhancement of photocatalytic activity of combustion-synthesized CeO2/C3N4 nanoparticles

NASA Astrophysics Data System (ADS)

Li, Dong-Feng; Yang, Ke; Wang, Xiao-qin; Ma, Ya-Li; Huang, Gui-Fang; Huang, Wei-Qing

2015-09-01

Nanocrystalline CeO2/C3N4 was synthesized via a one-step solution combustion method using urea as fuel for the first time. The effects of the molar ratio of urea to cerium chloride on the photocatalytic activity of the synthesized samples were investigated. The synthesized nanocrystalline CeO2/C3N4 shows small size and large surface exposure area. Photocatalytic degradation of methylene blue demonstrates that the synthesized nanocrystalline CeO2/C3N4 possesses enhanced photocatalytic activity. It is proposed that the enhanced photocatalytic activity might be related to the favorable morphology and structure, and the effective charge separation between C3N4 and CeO2 in the photocatalytic process.

The Interaction of Carbon Monoxide with Rhodium on Potassium-Modified CeO 2(111)

DOE PAGES

Mullins, David R.

2016-02-03

The adsorption and reactions of CO adsorbed on Rh particles deposited on K-covered CeO 2(111) were studied by temperature programmed desorption and photoelectron spectroscopy. K deposited on CeO 2(111) forms a KO X over-layer by extracting O from the ceria and partially reducing some of the Ce 4+ to Ce 3+. CO does not adsorb on the KO X / CeO 2-X(111) surface in the absence of Rh particles. CO adsorbed on Rh / K / CeO 2(111) adsorbs molecularly on the Rh at 200 K. As the surface is heated the CO spills-over and reacts with the KOX tomore » form carbonate. The carbonate decomposes at elevated temperature to produce CO and CO 2. The carbonate stabilizes the KO X so that K desorbs at a higher temperature than it would in the absence of CO. When the Rh and K deposition are reversed so that K is deposited on both the Rh and the CeO 2(111), CO adsorbs as CO 2- at 200 K. The CO 2- decomposes below 350 K to produce gas phase CO and adsorbed CO3 2- and CO. The CO is stabilized by the K on the Rh and desorbs above 540 K. The carbonate decomposes into gas phase CO and CO 2.« less

Transparent Oxyfluoride Nano-Glass-Ceramics Doped with Pr3+ and Pr3+-Yb3+ for NIR Emission

NASA Astrophysics Data System (ADS)

Gorni, Giulio; Cosci, Alessandro; Pelli, Stefano; Pascual, Laura; Durán, Alicia; Pascual, M. J.

2016-12-01

Pr3+-Yb3+ co-doped oxyfluoride glasses and glass-ceramics (GC) containing LaF3 nanocrystals have been prepared to obtain NIR emission of Yb3+ ions upon Pr3+ excitation in the blue region of the visible spectrum. Two different compositions have been tested 0.1-0.5 Pr-Yb and 0.5-1 Pr-Yb, in addition to Pr3+ singly doped samples. The crystallization mechanism of the nano-glass-ceramics was studied by DTA revealing that it occurs from a constant number of nuclei, the crystal growth being limited by diffusion. HR-TEM demonstrated that phase separation acts as precursor for LaF3 crystallization and a detailed analysis of the chemical composition (EDXS) revealed the enrichment in RE3+ ions inside the initial phase separated droplets, from which the LaF3 crystals are formed. The RE3+ ions incorporation inside LaF3 crystals was also proved by photoluminescence measurements showing Stark splitting of the RE3+ ions energy levels in the glass-ceramic samples. Lifetimes measurements showed the existence of a better energy transfer process between Pr3+ and Yb3+ ions in the glass-ceramics compared to the as made glass, and the highest value of energy transfer efficiency is 59% and the highest theoretical quantum efficiency is 159%, obtained for glass-ceramics GC0.1-0.5 Pr-Yb treated at 620 ºC-40 h.

CeO2 /Bi2 WO6 Heterostructured Microsphere with Excellent Visible-light-driven Photocatalytic Performance for Degradation of Tetracycline Hydrochloride.

PubMed

Zhang, Fengjun; Zou, Shuang; Wang, Tianye; Shi, Yuxi; Liu, Peng

2017-10-01

CeO 2 /Bi 2 WO 6 heterostructured microsphere with excellent and stable photocatalytic activity for degradation tetracyclines was successfully synthesized via a facile solvothermal route. The photocatalytic experiments indicated that CeO 2 /Bi 2 WO 6 heterostructured microspheres exhibited enhanced photocatalytic activity compared to pure Bi 2 WO 6 in both the degradation of tetracycline hydrochloride (TCH) and rhodamine B (RhB) under visible-light irradiation. The 1CeO 2 /2Bi 2 WO 6 exhibited the best photocatalytic activity for degradation of TCH, reaching 91% after 60 min reaction. The results suggested that the particular morphological conformation of the microspheres resulted in smaller size and more uniform morphology so as to increase the specific surface area. Meanwhile, the heterojunction was formed by coupling CeO 2 and Bi 2 WO 6 in the as-prepared microspheres, so that the separation efficiency of photogenerated electrons and holes was dramatically improved and the lifetimes of charge carriers were prolonged. Hence, introduction of CeO 2 could significantly enhance the photocatalytic activity of CeO 2 /Bi 2 WO 6 heterostructured microspheres and facilitate the degradation of TCH. This work provided not only a principle method to synthesize CeO 2 /Bi 2 WO 6 with the excellent photocatalytic performance for actual produce, but also a excellent property of the photocatalyst for potential application in photocatalytic treatment of tetracyclines wastewater from pharmaceutical factory. © 2017 The American Society of Photobiology.

Hydrophilic CeO2 nanocubes protect pancreatic β-cell line INS-1 from H2O2-induced oxidative stress

NASA Astrophysics Data System (ADS)

Lyu, Guang-Ming; Wang, Yan-Jie; Huang, Xue; Zhang, Huai-Yuan; Sun, Ling-Dong; Liu, Yan-Jun; Yan, Chun-Hua

2016-04-01

Oxidative stress plays a key role in the occurrence and development of diabetes. With their unique redox properties, CeO2 nanoparticles (nanoceria) exhibit promising potential for the treatment of diabetes resulting from oxidative stress. Here, we develop a novel preparation of hydrophilic CeO2 nanocubes (NCs) with two different sizes (5 nm and 25 nm) via an acetate assisted hydrothermal method. Dynamic light scattering, zeta potential measurements and thermogravimetric analyses were utilized to investigate the changes in the physico-chemical characteristics of CeO2 NCs when exposed to in vitro cell culture conditions. CCK-8 assays revealed that the CeO2 NCs did not impair cell proliferation in the pancreatic β-cell line INS-1 at the highest dose of 200 μg mL-1 over the time scale of 72 h, while being able to protect INS-1 cells from H2O2-induced cytotoxicity even after protein adsorption. It is also noteworthy that nanoceria with a smaller hydrodynamic radius exhibit stronger antioxidant and anti-apoptotic effects, which is consistent with their H2O2 quenching capability in biological systems. These findings suggest that nanoceria can be used as an excellent antioxidant for controlling oxidative stress-induced pancreatic β-cell damage.Oxidative stress plays a key role in the occurrence and development of diabetes. With their unique redox properties, CeO2 nanoparticles (nanoceria) exhibit promising potential for the treatment of diabetes resulting from oxidative stress. Here, we develop a novel preparation of hydrophilic CeO2 nanocubes (NCs) with two different sizes (5 nm and 25 nm) via an acetate assisted hydrothermal method. Dynamic light scattering, zeta potential measurements and thermogravimetric analyses were utilized to investigate the changes in the physico-chemical characteristics of CeO2 NCs when exposed to in vitro cell culture conditions. CCK-8 assays revealed that the CeO2 NCs did not impair cell proliferation in the pancreatic β-cell line INS-1 at

UV-Resistant and Thermally Stable Superhydrophobic CeO2 Nanotubes with High Water Adhesion.

PubMed

Li, Xue-Ping; Sun, Ya-Li; Xu, Yao-Yi; Chao, Zi-Sheng

2018-06-03

A novel type of sticky superhydrophobic cerium dioxide (CeO 2 ) nanotube material is prepared by hydrothermal treatment without any chemical modification. A water droplet on the material surface shows a static water contact angle of about 157° but the water droplet is pinned on the material surface even when the material surface is turned upside down. Interestingly, the as-prepared CeO 2 nanotube material displays durable superhydrophobicity and enhanced adhesion to water under ultraviolet (UV) light irradiation. Importantly, this change in water adhesion can be reversed by heat treatment to restore the original adhesive value of 20 µL. Further, the maximum volume of the water droplet adhered on the material surface of CeO 2 nanotubes can be regulated without loss of superhydrophobicity during the heating treatment/UV-irradiation cycling. Meanwhile, the superhydrophobic CeO 2 nanotube material shows remarkable thermal stability even at temperatures as high as 450 °C, long-term durability in chemical environment, and air-storage and good resistance to oily contaminant. Finally, the potential application in no-loss water transportation of this sticky superhydrophobic CeO 2 material is demonstrated. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of feather-like CeO2 microstructures and enzymatic electrochemical catalysis for trichloroacetic acid

NASA Astrophysics Data System (ADS)

Xiao, Xin; Zhang, Dong En; Zhang, Fan; Gong, Jun Yan; Zhang, Xiao Bo; Wang, Yi Hui; Ma, Juan Juan; Tong, Zhi Wei

Novel feather-like CeO2 microstructures were achieved by a thermal decomposition approach of Ce(OH)CO3 precursor. The Ce(OH)CO3 was obtained from a solvothermal method employing Ce(NO3)3.6H2O with C6H12N4 and C16H33(CH3)3NBr (CTAB) at 190∘C in a water-PEG-200 mixed solution. The feather-like CeO2 dendrite was obtained by thermal conversion of the feather-like Ce(OH)CO3 at 650∘C in air. A reasonable growth mechanism was proposed with the soft-template effect of PEG-200. The electrochemical behavior and enzyme activity of myoglobin (Mb) immobilized on CeO2-Nafion modified glassy carbon electrode (GCE) are demonstrated by cyclic voltammetric measurements. The results indicate that CeO2 can obviously promote the direct electron transfer between the Mb redox centers and the electrode. The Mb on CeO2-Nafion behaves as an elegant performance on the electrochemical reduction of trichloroacetic acid (TCA) from 0.32μM to 2.28μM. The detection limit is estimated to be 0.08μM.

Effects of doping on photocatalytic activity for water splitting of metal oxides and nitride

NASA Astrophysics Data System (ADS)

Arai, Naoki; Saito, Nobuo; Nishiyama, Hiroshi; Kadowaki, Haruhiko; Kobayashi, Hisayoshi; Sato, Kazunori; Inoue, Yasunobu

2007-09-01

The effects of metal-ion doping or replacement on the photocatalytic performance for water splitting of d 10 and d 0 metal oxides and d 10 metal nitride were studied. The photocatalysts examined were (1) α-Ga 2-2xIn 2xO 3 and ZnGa 2-2xIn 2xO 4 in which In 3+ was added to Ga IIO 3 and ZnGa IIO 4, respectively, (2) Y xIn 2-xO 3 being a solid solution of In IIO 3 and Y IIO 3, (3) metal ion doped CeO II, and (4) metal ion doped GaN. The photocatalytic activity of 1 wt % RuO II-loaded α-Ga 2-2xIn 2xO 3 increased sharply with increasing x, reached a maximum at around x=0.02, and considerably decreased with further increase in x. The DFT calculation showed that the band structures of α-Ga 2-2xIn 2xO 3 had the contribution of In 4d orbital to the valence band and of In5s orbital to the conduction band. Similar effects were observed for ZnGa 2-2xIn 2xO 4. RuO II-dispersed Y xIn 2-xO 3 had a capability of producing H II and O II in the range x=1.0-1.5 in which the highest activity was obtained at x=1.3. The structures of both InO 6 and YO 6 octahedra were deformed in the solid solution,, and the hybridization of In5s5p and Y4d orbitals in the conduction band was enhanced. Undoped CeO II was photocatalytically inactive, but metal ion-doped CeO II showed a considerable photocatalytic activity. The activation occurred in the case that metal ions doped had larger ion sizes than that of Ce 4+. The small amount doping of divalent metal ions (Zn 2+ and Mg 2+) converted photocatalytically inactive GaN to an efficient photocatalyst. The doping was shown to produce p-type GaN which had the large concentration and high mobility of holes. The roles of metal ion doping and replacement in the photocatalytic properties are discussed.

Rational design of octahedron and nanowire CeO2@MnO2 core-shell heterostructures with outstanding rate capability for asymmetric supercapacitors.

PubMed

Zhu, Shi Jin; Jia, Jia Qi; Wang, Tian; Zhao, Dong; Yang, Jian; Dong, Fan; Shang, Zheng Guo; Zhang, Yu Xin

2015-10-14

Two kinds of novel CeO2@MnO2 nanostructures have been synthesized via a self-assembly strategy. The as-prepared CeO2 nanowire@MnO2 nanostructures exhibited unprecedented pseudocapacitance performance (255 F g(-1)) with outstanding rate capability. A new mechanism based on the synergistic effect between CeO2 and MnO2 was proposed to interpret this phenomenon. When assembled as an asymmetric supercapacitor, an energy density of 27.5 W h kg(-1) with a maximum power density of 1.6 kW kg(-1) was achieved for CeO2 nanowire@MnO2 nanostructures.

Dielectric properties of Y and Nb co-doped TiO2 ceramics.

PubMed

Wang, Xianwei; Zhang, Bihui; Xu, Linhai; Wang, Xiaoer; Hu, Yanchun; Shen, Gaohang; Sun, Lingyun

2017-08-17

In this work, the (Y 0.5 Nb 0.5 ) x Ti 1-x O 2 (x = 0.001, 0.01, 0.02, 0.04, 0.06 and 0.1) ceramics (as called YNTO) were fabricated by synthesized through a standard solid-state reaction. As revealed by the X-ray diffraction (XRD) spectra, the YNTOs exhibit tetragonal rutile structure. Meanwhile, the grain size of YNTO ceramics increased and then decreased with the increase of x value, and the largest value reached when x = 0.02. All the YNTO samples display colossal permittivity (~10 2 -10 5 ) over a wide temperature and frequency range. Moreover, the optimal ceramic, (Y 0.5 Nb 0.5 ) 0.02 Ti 0.98 O 2 , exhibits high performance over a broad temperature range from 20 °C to 180 °C; specifically, at 1 kHz, the dielectric constant and dielectric loss are 6.55 × 10 4 and 0.22 at room temperature, and they are 1.03 × 10 5 and 0.11 at 180 °C, respectively.

Mixedness determination of rare earth-doped ceramics

NASA Astrophysics Data System (ADS)

Czerepinski, Jennifer H.

The lack of chemical uniformity in a powder mixture, such as clustering of a minor component, can lead to deterioration of materials properties. A method to determine powder mixture quality is to correlate the chemical homogeneity of a multi-component mixture with its particle size distribution and mixing method. This is applicable to rare earth-doped ceramics, which require at least 1-2 nm dopant ion spacing to optimize optical properties. Mixedness simulations were conducted for random heterogeneous mixtures of Nd-doped LaF3 mixtures using the Concentric Shell Model of Mixedness (CSMM). Results indicate that when the host to dopant particle size ratio is 100, multi-scale concentration variance is optimized. In order to verify results from the model, experimental methods that probe a mixture at the micro, meso, and macro scales are needed. To directly compare CSMM results experimentally, an image processing method was developed to calculate variance profiles from electron images. An in-lens (IL) secondary electron image is subtracted from the corresponding Everhart-Thornley (ET) secondary electron image in a Field-Emission Scanning Electron Microscope (FESEM) to produce two phases and pores that can be quantified with 50 nm spatial resolution. A macro was developed to quickly analyze multi-scale compositional variance from these images. Results for a 50:50 mixture of NdF3 and LaF3 agree with the computational model. The method has proven to be applicable only for mixtures with major components and specific particle morphologies, but the macro is useful for any type of imaging that produces excellent phase contrast, such as confocal microscopy. Fluorescence spectroscopy was used as an indirect method to confirm computational results for Nd-doped LaF3 mixtures. Fluorescence lifetime can be used as a quantitative method to indirectly measure chemical homogeneity when the limits of electron microscopy have been reached. Fluorescence lifetime represents the

Enhance D. C. resistivity of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} ceramic by acceptor (Mn) doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Hakikat, E-mail: sharmahakikat@yahoo.in; Arya, G. S.; Pramar, Kusum

2015-05-15

In the present work, we prepared Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Mn (2 and 3 at % on Ti site) doped Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} ceramic by sol- gel method. The samples were characterized by X-ray diffraction (XRD). The XRD patterns reveled that Mn ions did not change the perovskite structure of BST (70/30). The dielectric measurements proved that dielectric constant decreased with Mn doping. The dc resistivity was studied by using I-V measurements. The dc resistivity of the BST increased with Mn doping, which suppressed the leakage current.

Fate and Phytotoxicity of CeO2 Nanoparticles on Lettuce Cultured in the Potting Soil Environment

PubMed Central

Gui, Xin; Zhang, Zhiyong; Liu, Shutong; Ma, Yuhui; Zhang, Peng; He, Xiao; Li, Yuanyuan; Zhang, Jing; Li, Huafen; Rui, Yukui; Liu, Liming; Cao, Weidong

2015-01-01

Cerium oxide nanoparticles (CeO2 NPs) have been shown to have significant interactions in plants. Previous study reported the specific-species phytotoxicity of CeO2 NPs by lettuce (Lactuca sativa), but their physiological impacts and vivo biotransformation are not yet well understood, especially in relative realistic environment. Butterhead lettuce were germinated and grown in potting soil for 30 days cultivation with treatments of 0, 50, 100, 1000 mg CeO2 NPs per kg soil. Results showed that lettuce in 100 mg·kg-1 treated groups grew significantly faster than others, but significantly increased nitrate content. The lower concentrations treatment had no impact on plant growth, compared with the control. However, the higher concentration treatment significantly deterred plant growth and biomass production. The stress response of lettuce plants, such as Superoxide dismutase (SOD), Peroxidase (POD), Malondialdehyde(MDA) activity was disrupted by 1000 mg·kg-1 CeO2 NPs treatment. In addition, the presence of Ce (III) in the roots of butterhead lettuce explained the reason of CeO2 NPs phytotoxicity. These findings demonstrate CeO2 NPs modification of nutritional quality, antioxidant defense system, the possible transfer into the food chain and biotransformation in vivo. PMID:26317617

Fate and Phytotoxicity of CeO2 Nanoparticles on Lettuce Cultured in the Potting Soil Environment.

PubMed

Gui, Xin; Zhang, Zhiyong; Liu, Shutong; Ma, Yuhui; Zhang, Peng; He, Xiao; Li, Yuanyuan; Zhang, Jing; Li, Huafen; Rui, Yukui; Liu, Liming; Cao, Weidong

2015-01-01

Cerium oxide nanoparticles (CeO2 NPs) have been shown to have significant interactions in plants. Previous study reported the specific-species phytotoxicity of CeO2 NPs by lettuce (Lactuca sativa), but their physiological impacts and vivo biotransformation are not yet well understood, especially in relative realistic environment. Butterhead lettuce were germinated and grown in potting soil for 30 days cultivation with treatments of 0, 50, 100, 1000 mg CeO2 NPs per kg soil. Results showed that lettuce in 100 mg·kg-1 treated groups grew significantly faster than others, but significantly increased nitrate content. The lower concentrations treatment had no impact on plant growth, compared with the control. However, the higher concentration treatment significantly deterred plant growth and biomass production. The stress response of lettuce plants, such as Superoxide dismutase (SOD), Peroxidase (POD), Malondialdehyde(MDA) activity was disrupted by 1000 mg·kg-1 CeO2 NPs treatment. In addition, the presence of Ce (III) in the roots of butterhead lettuce explained the reason of CeO2 NPs phytotoxicity. These findings demonstrate CeO2 NPs modification of nutritional quality, antioxidant defense system, the possible transfer into the food chain and biotransformation in vivo.

CEO performance appraisal: review and recommendations.

PubMed

Newman, J F; Tyler, L; Dunbar, D M

2001-01-01

CEO performance appraisal (PA) is very valuable to an organization, but the chances of obtaining a PA of high quality decrease as executive responsibility increases. The realities of CEO PA are that it: (1) is inevitable; (2) is creative and complex; (3) involves politics; and (4) has a significant effect on the organization and the executive. PA is conducted for legal and social requirements, to enhance communication, to provide opportunities for improvement, and to relate performance to compensation. This article discusses several problems with chief executive officer (CEO) PA and the contemporary approaches that seek to improve it. Three fundamental areas for evaluation are identified: (1) organizational success; (2) areawide health status; and (3) professional role fulfillment. These provide an outline for successful healthcare PA. In addition to a discussion of the strategic considerations behind a successful CEO PA system, several recommendations are offered for the implementation of the annual evaluation process. The final goal of CEO PA is to link its results to CEO incentive compensation. It is strongly recommended that some portion of the CEO's salary directly hinge on his performance in two critical areas: organizational effectiveness and community health status.

Luminescence of Er 3+-doped nanostructured SiO 2-LaF 3 glass-ceramics prepared by the sol-gel method

NASA Astrophysics Data System (ADS)

Rodríguez, V. D.; Del Castillo, J.; Yanes, A. C.; Méndez-Ramos, J.; Torres, M.; Peraza, J.

2007-07-01

Transparent glass ceramics with composition of 95SiO2-5LaF3 doped with 0.1 mol% of Er3+ were synthesized by thermal treatment of precursor sol-gel glasses. Segregated LaF3 nanocrystals in the glass were confirmed from a structural analysis performed by X-ray diffraction. Blue, green and red efficient up-conversion emissions were observed under 980 nm excitation at room temperature. Under this excitation near infrared down-conversion at 1.55 μm is also observed. These results could be attributed to the precipitation of LaF3 nanocrystals and the incorporation of most Er3+ ions in these nanocrystals. The mechanisms involved in the up-conversion emissions could be ascribed to two and three photon processes.

Different heat treatment of CeO2 nanoparticle composited with ZnO to enhance photocatalytic performance

NASA Astrophysics Data System (ADS)

Taufik, A.; Shabrany, H.; Saleh, R.

2017-04-01

In this study, ZnO/CeO2 nanocomposites were prepared with four variations of the molar ratio of ZnO to CeO2 nanoparticles. Both ZnO and CeO2 nanoparticles were synthesized using the sol-gel method at low temperature, followed by different heat treatments for CeO2 nanoparticles. Thermal phase transformation studies of the CeO2 nanoparticles were observed at annealing temperatures of 400-800°C. The complete crystalline structure of CeO2 nanoparticles was obtained at an annealing temperature of 800°C. The structural and optical properties of all samples were observed using several characterization techniques, such as X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy, and Brunauer, Emmett, and Teller (BET) surface area analysis. The structural characterization results revealed that the prepared CeO2 nanoparticles were quite crystalline, with a cubic structure. The photocatalytic activities of all samples were tested under visible irradiation. The obtained results showed that ZnO/CeO2 nanocomposites with a molar ratio 1:0.3 exhibited the highest photocatalytic activity. Further understanding of the role of primary active species underlying the reaction mechanism involved in photocatalytic activity were carried out in controlled experiments by adding several scavengers. The detailed mechanism and its correlation with the properties of ZnO/CeO2 nanocomposites were discuss.

Structural, topographical and electrical properties of cerium doped strontium barium niobate (Ce:SBN60) ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raj, S. Gokul; Mathivanan, V.; Mohan, R.

2016-05-06

Tungsten bronze type cerium doped strontium barium niobate (Ce:SBN - Sr{sub 0.6}B{sub 0.4}Nb{sub 2}O{sub 6}) ceramics were synthesized by solid state process. Cerium was used as dopant to improve its electrical properties. Influence of Ce{sup +} ions on the photoluminescence properties was investigated in detail. The grain size topographical behavior of SBN powders and their associated abnormal grain growth (AGG) were completely analyzed through SEM studies. Finally dielectric, measurement discusses about the broad phase transition observed due to cerium dopant The results were discussed in detail.

Synthesis of novel CeO2-BiVO4/FAC composites with enhanced visible-light photocatalytic properties.

PubMed

Zhang, Jin; Wang, Bing; Li, Chuang; Cui, Hao; Zhai, Jianping; Li, Qin

2014-09-01

To utilize visible light more effectively in photocatalytic reactions, a fly ash cenosphere (FAC)-supported CeO2-BiVO4 (CeO2-BiVO4/FAC) composite photocatalyst was prepared by modified metalorganic decomposition and impregnation methods. The physical and photophysical properties of the composite have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and UV-Visible diffuse reflectance spectra. The XRD patterns exhibited characteristic diffraction peaks of both BiVO4 and CeO2 crystalline phases. The XPS results showed that Ce was present as both Ce(4+) and Ce(3+) oxidation states in CeO2 and dispersed on the surface of BiVO4 to constitute a p-n heterojunction composite. The absorption threshold of the CeO2-BiVO4/FAC composite shifted to a longer wavelength in the UV-Vis absorption spectrum compared to the pure CeO2 and pure BiVO4. The composites exhibited enhanced photocatalytic activity for Methylene Blue (MB) degradation under visible light irradiation. It was found that the 7.5wt.% CeO2-BiVO4/FAC composite showed the highest photocatalytic activity for MB dye wastewater treatment. Copyright © 2014. Published by Elsevier B.V.

Highly transparent cerium doped gadolinium gallium aluminum garnet ceramic prepared with precursors fabricated by ultrasonic enhanced chemical co-precipitation.

PubMed

Zhang, Ji-Yun; Luo, Zhao-Hua; Jiang, Hao-Chuan; Jiang, Jun; Chen, Chun-Hua; Zhang, Jing-Xian; Gui, Zhen-Zhen; Xiao, Na

2017-11-01

Cerium doped gadolinium gallium aluminum garnet (GGAG:Ce) ceramic precursors have been synthesized with an ultrasonic chemical co-precipitation method (UCC) and for comparison with a traditional chemical co-precipitation method (TCC). The effect of ultra-sonication on the morphology of powders and the transmittance of GGAG:Ce ceramics are studied. The results indicate that the UCC method can effectively improve the homogenization and sinterability of GGAG:Ce powders, which contribute to obtain high transparent GGAG ceramic with the highest transmittance of 81%. Copyright © 2017 Elsevier B.V. All rights reserved.

Electric modulation of conduction in multiferroic Ni-doped GaFeO3 ceramics

NASA Astrophysics Data System (ADS)

Ghani, Awais; Yang, Sen; Rajput, S. S.; Ahmed, S.; Murtaza, Adil; Zhou, Chao; Yu, Zhonghai; Zhang, Yin; Song, Xiaoping; Ren, Xiaobing

2018-06-01

In this work, the effects of Ni substitution on the electrical leakage and multiferroic properties of GaFeO3 were examined. Structural analysis of grown ceramics using x-ray diffraction and Raman shows that all ceramics have pure phases with an orthorhombic structure and space group. Ni substitutions slightly modify lattice parameters and induce lattice distortion within the same crystalline structure. It is observed that with increasing Ni-content up to 0.10, the magnetic transition temperature () increases from 196 K to 407 K. Ni-doped samples showed better ferroelectric properties and a drastic reduction in leakage current (~three orders of magnitude) at room temperature. Enhanced characteristics behavior is observed for 10% Ni substitution (GaFe0.9Ni0.1O3) and higher substitution leads to deterioration of properties with a larger leakage current. It is proposed that the role of Ni substitution can reduce hopping between Fe+3 and Fe+2 as well as suppressing the oxygen vacancies. This work would open new possibilities for integrating polycrystalline GaFeO3 at room temperature for magnetoelectric applications.

Stress response and tolerance of Zea mays to CeO2 nanoparticles: cross talk among H2O2, heat shock protein, and lipid peroxidation.

PubMed

Zhao, Lijuan; Peng, Bo; Hernandez-Viezcas, Jose A; Rico, Cyren; Sun, Youping; Peralta-Videa, Jose R; Tang, Xiaolei; Niu, Genhua; Jin, Lixin; Varela-Ramirez, Armando; Zhang, Jian-ying; Gardea-Torresdey, Jorge L

2012-11-27

The rapid development of nanotechnology will inevitably release nanoparticles (NPs) into the environment with unidentified consequences. In addition, the potential toxicity of CeO(2) NPs to plants and the possible transfer into the food chain are still unknown. Corn plants (Zea mays) were germinated and grown in soil treated with CeO(2) NPs at 400 or 800 mg/kg. Stress-related parameters, such as H(2)O(2), catalase (CAT), and ascorbate peroxidase (APX) activity, heat shock protein 70 (HSP70), lipid peroxidation, cell death, and leaf gas exchange were analyzed at 10, 15, and 20 days post-germination. Confocal laser scanning microscopy was used to image H(2)O(2) distribution in corn leaves. Results showed that the CeO(2) NP treatments increased accumulation of H(2)O(2), up to day 15, in phloem, xylem, bundle sheath cells and epidermal cells of shoots. The CAT and APX activities were also increased in the corn shoot, concomitant with the H(2)O(2) levels. Both 400 and 800 mg/kg CeO(2) NPs triggered the up-regulation of the HSP70 in roots, indicating a systemic stress response. None of the CeO(2) NPs increased the level of thiobarbituric acid reacting substances, indicating that no lipid peroxidation occurred. CeO(2) NPs, at both concentrations, did not induce ion leakage in either roots or shoots, suggesting that membrane integrity was not compromised. Leaf net photosynthetic rate, transpiration, and stomatal conductance were not affected by CeO(2) NPs. Our results suggest that the CAT, APX, and HSP70 might help the plants defend against CeO(2) NP-induced oxidative injury and survive NP exposure.

Stress Response and Tolerance of Zea mays to CeO2 Nanoparticles: Cross Talk among H2O2, Heat Shock Protein and Lipid Peroxidation

PubMed Central

Zhao, Lijuan; Peng, Bo; Hernandez-Viezcas, Jose A.; Rico, Cyren; Sun, Youping; Peralta-Videa, Jose R.; Tang, Xiaolei; Niu, Genhua; Jin, Lixin; Varela-Ramirez, Armando; Zhang, Jian-ying; Gardea-Torresdey, Jorge L.

2014-01-01

The rapid development of nanotechnology will inevitably release nanoparticles (NPs) into the environment with unidentified consequences. In addition, the potential toxicity of CeO2 NPs to plants, and the possible transfer into the food chain, are still unknown. Corn plants (Zea mays) were germinated and grown in soil treated with CeO2 NPs at 400 or 800 mg/kg. Stress related parameters, such as: H2O2, catalase (CAT) and ascorbate peroxidase (APX) activity, heat shock protein 70 (HSP 70), lipid peroxidation, cell death and leaf gas exchange were analyzed at 10, 15, and 20 days post germination. Confocal laser scanning microscopy was used to image H2O2 distribution in corn leaves. Results showed that the CeO2 NP treatments increased accumulation of H2O2, up to day 15, in phloem, xylem, bundle sheath cells, and epidermal cells of shoots. The CAT and APX activities were also increased in the corn shoot, concomitant with the H2O2 levels. Both 400 and 800 mg/kg CeO2 NPs triggered the up regulation of the HSP 70 in roots, indicating a systemic stress response. None of the CeO2 NPs increased the level of thiobarbituric acid reacting substances, indicating that no lipid peroxidation occurred. CeO2 NPs, at both concentrations, did not induce ion leakage in either roots or shoots, suggesting membrane integrity was not compromised. Leaf net photosynthetic rate, transpiration, and stomatal conductance were not affected by CeO2 NPs. Our results suggest that the CAT, APX and HSP 70 might help the plants defend against CeO2 NPs induced oxidative injury and survive NP exposure. PMID:23050848

Study of the growth of CeO2 nanoparticles onto titanate nanotubes

NASA Astrophysics Data System (ADS)

Marques, Thalles M. F.; Ferreira, Odair P.; da Costa, Jose A. P.; Fujisawa, Kazunori; Terrones, Mauricio; Viana, Bartolomeu C.

2015-12-01

We report the study of the growth of CeO2 nanoparticles on the external walls and Ce4+ intercalation within the titanate nanotubes. The materials were fully characterized by multiple techniques, such as: Raman spectroscopy, infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The ion exchange processes in the titanate nanotubes were carried out using different concentrations of Ce4+ in aqueous solution. Our results indicate that the growth of CeO2 nanoparticles grown mediated by the hydrolysis in the colloidal species of Ce and the attachment onto the titanate nanotubes happened and get it strongly anchored to the titanate nanotube surface by a simple electrostatic interaction between the nanoparticles and titanate nanotubes, which can explain the small size and even distribution of nanoparticles on titanate supports. It was demonstrated that it is possible to control the amount and size of CeO2 nanoparticles onto the nanotube surface, the species of the Ce ions intercalated between the layers of titanate nanotubes, and the materials could be tuned for using in specific catalysis in according with the amount of CeO2 nanoparticles, their oxygen vacancies/defects and the types of Ce species (Ce4+ or Ce3+) present into the nanotubes.

Physical properties of nanostructured CeO2 thin films grown by SILAR method

NASA Astrophysics Data System (ADS)

Khan, Ishaque Ahmed; Belkhedkar, M. R.; Salodkar, R. V.; Ubale, A. U.

2018-05-01

Nanostructured CeO2 thin films have been deposited by Successive Ionic Layer Adsorption and Reaction (SILAR) method onto glass substrate using (CeNO3)3 6H2O and NaOH as cationic and anionic precursors respectively. The structural and morphological characterizations were carried out by means of X-ray diffraction, FTIR, FESEM and EDX studies. The highly resistive (1010 Ω cm) semiconducting CeO2 film exhibits 2.95 eV optical band gap.

Microstructural effects on fracture toughness of polycrystalline ceramics in combined mode I and mode II loading

NASA Technical Reports Server (NTRS)

Singh, D.; Shetty, D. K.

1988-01-01

Fracture toughness of polycrystalline alumina and ceria partially-stabilized tetragonal zirconia (CeO2-TZP) ceramics were assessed in combined mode I and mode II loading using precracked disk specimens in diametral compression. Stress states ranging from pure mode I, combined mode I and mode II, and pure mode II were obtained by aligning the center crack at specific angles relative to the loading diameter. The resulting mixed-mode fracture toughness envelope showed significant deviation to higher fracture toughness in mode II relative to the predictions of the linear elastic fracture mechanics theory. Critical comparison with corresponding results on soda-lime glass and fracture surface observations showed that crack surface resistance arising from grain interlocking and abrasion was the main source of the increased fracture toughness in mode II loading of the polycrystalline ceramics. The normalized fracture toughness for pure mode II loading, (KII/KIc), increased with increasing grain size for the CeO2-TZP ceramics. Quantitative fractography confirmed an increased percentage of transgranular fracture of the grains in mode II loading.

Electron paramagnetic resonance of Nb-doped BaTiO3 ceramics with positive temperature coefficient of resistivity

NASA Astrophysics Data System (ADS)

Jida, Shin'suke; Miki, Toshikatsu

1996-11-01

Paramagnetic centers in Nb-doped BaTiO3 ceramics are measured at 77-500 K by electron paramagnetic resonance (EPR) for investigating the role of the centers on the well-known positive temperature coefficient of resistivity (PTCR) effect (PTCR at the Curie temperature). EPR detects four signals; an anisotropically broad singlet signal at g=2.005, a sextet signal due to Mn2+, a Cr3+ signal, and a Ti3+ signal. The former two signals arise in the rhombohedral and cubic phases, but disappear in the tetragonal and orthorhombic phases. The Cr3+ signal appears in all of the phases, while the Ti3+ signal is detected only at low temperatures. The singlet signal also arises in undoped, barium-deficient BaTiO3 ceramics, therefore the signal is attributable to barium-vacancy-associated centers rather than Nb4+ ions or Fe3+ ions proposed by several authors. In this article, we propose that the singlet signal is due to vacancy-pairs of VBa-F+ type, i.e., the vacancy pair of VBa-VO capturing one electron. The electrical resistivity data show a polaronic character of low-temperature conduction and a high resistivity jump around the Curie temperature. The low-temperature polaronic conduction is explained in terms of electron-hopping between Ti4+ and Ti3+ ions. The resistivity jump at the Curie temperature occurs along with the EPR intensity increase of the singlet signal, the Mn2+ signal and the Cr3+ signal. We conclude that the PTCR of Nb-doped BaTiO3 ceramics is strongly associated with the trap activation of the VBa-VO vacancy-pairs and manganese centers at the tetragonal-to-cubic transition.

Frequency stabilization of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hitachi, K., E-mail: hitachi.kenichi@lab.ntt.co.jp; Ishizawa, A.; Mashiko, H.

2015-06-08

We report the stabilization of the carrier-envelope offset (CEO) frequency of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer. The interferometer is implemented by a dual-pitch periodically poled lithium niobate ridge waveguide with two different quasi-phase matching pitch sizes. We obtain a 52-dB signal-to-noise ratio in the 100-kHz resolution bandwidth of a heterodyne beat signal, which is sufficient for frequency stabilization. We also demonstrate that the collinear geometry is robust against environmental perturbation by comparing in-loop and out-of-loop Allan deviations when the in-loop CEO frequency is stabilized with a phase-locked loop circuit.

Laser and thermal properties of Nd:YGd2Sc2Al2GaO12 garnet ceramic Laser and thermal properties of Nd:YSGG garnet ceramic

NASA Astrophysics Data System (ADS)

Brenier, A.; Alombert-Goget, G.; Guyot, Y.; Boulon, G.

2012-10-01

The absorption and fluorescence properties of the Nd-doped YGd2Sc2Al2GaO12 mixed garnet ceramics have been measured at different temperatures. Under laser diode pumping an efficient laser emission has been demonstrated with 45% slope efficiency. The emission is constituted by two lines at 1058.6 and 1061.3 nm, subjected to a red shift and a variable relative intensity versus pump power. The role of the temperature has been investigated playing with the cavity parameters. The thermal conductivity of the 1% Nd-doped material has been determined (3.2 W/m/K) measuring the radial temperature distribution of the exit face of the sample including the axial heat flow in the analysis. The M2 beam quality factor and the dioptric power of the thermal lens have been investigated versus the pump power. The thermo-optic coefficient χ was determined as 44.4×10-6 K-1.

Strong emission in Yb3+/Er3+ co-doped phosphate glass ceramics

NASA Astrophysics Data System (ADS)

Liu, Yanling; Song, Feng; Jia, Guozhi; Zhang, Yanbang; Tang, Yi

Yb3+/Er3+ co-doped phosphate glass and glass ceramics were prepared by high-temperature melting method. The X-ray diffraction, transmission electron micrographs, up-conversion and infrared emissions, photothermal conversion properties of the samples have been measured. The results showed the annealing time had a great impact on the microstructure and luminous performance of the phosphate glass. At the beginning of annealing, the metaphosphate crystals were firstly dissolved out. The metaphosphate crystals gradually turned into the orthophosphate with the increasing of annealing time. The emission intensity of the sample was obviously improved after the precursor glass was annealed. The up-conversion and infrared emissions of the sample annealed at 600 °C for 24 h, reached the maximum intensity. Compared with the photothermal properties of glass, the lower photothermal conversion efficiency of the glass ceramics testified the strong emission.

Ionic liquid-assisted sonochemical preparation of CeO 2 nanoparticles for CO oxidation

DOE PAGES

Alammar, Tarek; Noei, Heshmat; Wang, Yuemin; ...

2014-10-10

CeO 2 nanoparticles were synthesized via a one-step ultrasound synthesis in different kinds of ionic liquids based on bis(trifluoromethanesulfonylamide, [Tf 2N] –, in combination with various cations including 1-butyl-3-methylimidazolium ([C 4mim] +), 1-ethyl-2,3-dimethylimidazolium ([Edimim] +), butyl-pyridinium([Py 4] +), 1-butyl-1-methyl-pyrrolidinium ([Pyrr 14] +), and 2-hydroxyethyl-trimethylammonium ([N 1112OH] +). Depending on synthetic parameters, such as ionic liquid, Ce(IV) precursor, heating method, and precipitator, formed ceria exhibits different morphologies, varying from nanospheres, nanorods, nanoribbons, and nanoflowers. The morphology, crystallinity, and chemical composition of the obtained materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-raymore » spectroscopy (EDX), Raman spectroscopy, and N2 adsorption. The structural and electronic properties of the as-prepared CeO 2 samples were probed by CO adsorption using IR spectroscopy under ultrahigh vacuum conditions. The catalytic activities of CeO 2 nanoparticles were investigated in the oxidation of CO. CeO 2 nanospheres obtained sonochemically in [C 4mim][Tf 2N] exhibit the best performance for low-temperature CO oxidation. As a result, the superior catalytic performance of this material can be related to its mesoporous structure, small particle size, large surface area, and high number of surface oxygen vacancy sites.« less

Investigation of trimethylacetic acid adsorption on stoichiometric and oxygen-deficient CeO 2 (111) surfaces

DOE PAGES

Sanghavi, Shail; Wang, Weina; Nandasiri, Manjula I.; ...

2016-05-12

We studied the interactions between the carboxylate anchoring group from trimethylacetic acid (TMAA) and CeO 2(111) surfaces as a function of oxygen stoichiometry using in situ X-ray photoelectron spectroscopy (XPS). The stoichiometric CeO 2(111) surface was obtained by annealing the thin film under 2.0 × 10 –5 Torr of oxygen at ~550 °C for 30 min. In order to reduce the CeO 2(111) surface, the thin film was annealed under ~5.0 × 10 –10 Torr vacuum conditions at 550 °C, 650 °C, 750 °C and 850 °C for 30 min to progressively increase the oxygen defect concentration on the surface.more » The saturated TMAA coverage on the CeO 2(111) surface determined from XPS elemental composition is found to increase with increasing oxygen defect concentration. This is attributed to the increase of under-coordinated cerium sites on the surface with the increase in the oxygen defect concentrations. Furthermore, XPS results were in agreement with periodic density functional theory (DFT) calculations and indicate a stronger binding between the carboxylate group from TMAA and the oxygen deficient CeO 2–δ(111) surface through dissociative adsorption.« less

Wavelength tunability of laser based on Yb-doped YGAG ceramics

NASA Astrophysics Data System (ADS)

Šulc, Jan; Jelínková, Helena; Jambunathan, Venkatesan; Miura, Taisuke; Endo, Akira; Lucianetti, Antonio; Mocek, TomáÅ.¡

2015-02-01

The wavelength tunability of diode pumped laser based on Yb-doped mixed garnet Y3Ga2Al3O12 (Yb:YGAG) ceramics was investigated. The tested Yb:YGAG sample (10% Yb/Y) was in the form of 2mm thick plane-parallel face-polished plate (without AR coatings). A fiber (core diameter 100 μm, NA= 0.22) coupled laser diode (LIMO, LIMO35-F100-DL980-FG-E) with emission at wavelength 969 nm, was used for longitudinal Yb:YGAG pumping. The laser diode was operating in the pulsed regime (2 ms pulse length, 10 Hz repetition rate). The duty-cycle 2% ensured a low thermal load even under the maximum diode pumping power amplitude 20W (ceramics sample was only air-cooled). The 145mm long semi-hemispherical laser resonator consisted of a flat pumping mirror (HR @ 1.01 - 1.09 μm, HT @ 0.97 μm) and curved (r = 150mm) output coupler with a reflectivity of ˜ 97% @ 1.01 - 1.09 μm. Wavelength tuning of the ytterbium laser was accomplished by using a birefringent filter (single 1.5mm thick quartz plate) placed inside the optical resonator at the Brewster angle between the output coupler and the laser active medium. The laser was continuously tunable over ˜ 58nm (from 1022nm to 1080 nm) and the tuning band was mostly limited by the free spectral range of used birefringent filter. The maximum output power amplitude 3W was obtained at wavelength 1046nm for absorbed pump power amplitude 10.6W. The laser slope efficiency was 34%.

Cell uptake, intracellular distribution, fate and reactive oxygen species generation of polymer brush engineered CeO2-x NPs

NASA Astrophysics Data System (ADS)

Qiu, Yuan; Rojas, Elena; Murray, Richard A.; Irigoyen, Joseba; Gregurec, Danijela; Castro-Hartmann, Pablo; Fledderman, Jana; Estrela-Lopis, Irina; Donath, Edwin; Moya, Sergio E.

2015-04-01

Cerium Oxide nanoparticles (CeO2-x NPs) are modified with polymer brushes of negatively charged poly (3-sulfopropylmethacrylate) (PSPM) and positively charged poly (2-(methacryloyloxy)ethyl-trimethylammonium chloride) (PMETAC) by Atom Transfer Radical Polymerisation (ATRP). CeO2-x NPs are fluorescently labelled by covalently attaching Alexa Fluor® 488/Fluorescein isothiocyanate to the NP surface prior to polymerisation. Cell uptake, intracellular distribution and the impact on the generation of intracellular Reactive Oxygen Species (ROS) with respect to CeO2-x NPs are studied by means of Raman Confocal Microscopy (CRM), Transmission Electron Microscopy (TEM) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). PSPM and PMETAC coated CeO2-x NPs show slower and less uptake compared to uncoated Brush modified NPs display a higher degree of co-localisation with cell endosomes and lysosomes after 24 h of incubation. They also show higher co-localisation with lipid bodies when compared to unmodified CeO2-x NPs. The brush coating does not prevent CeO2-x NPs from displaying antioxidant properties.Cerium Oxide nanoparticles (CeO2-x NPs) are modified with polymer brushes of negatively charged poly (3-sulfopropylmethacrylate) (PSPM) and positively charged poly (2-(methacryloyloxy)ethyl-trimethylammonium chloride) (PMETAC) by Atom Transfer Radical Polymerisation (ATRP). CeO2-x NPs are fluorescently labelled by covalently attaching Alexa Fluor® 488/Fluorescein isothiocyanate to the NP surface prior to polymerisation. Cell uptake, intracellular distribution and the impact on the generation of intracellular Reactive Oxygen Species (ROS) with respect to CeO2-x NPs are studied by means of Raman Confocal Microscopy (CRM), Transmission Electron Microscopy (TEM) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). PSPM and PMETAC coated CeO2-x NPs show slower and less uptake compared to uncoated Brush modified NPs display a higher degree of co-localisation with cell

Confined NaAlH4 nanoparticles inside CeO2 hollow nanotubes towards enhanced hydrogen storage.

PubMed

Gao, Qili; Xia, Guanglin; Yu, Xuebin

2017-10-05

NaAlH 4 has been widely regarded as a potential hydrogen storage material due to its favorable thermodynamics and high energy density. The high activation energy barrier and high dehydrogenation temperature, however, significantly hinder its practical application. In this paper, CeO 2 hollow nanotubes (HNTs) prepared by a simple electrospinning technique are adopted as functional scaffolds to support NaAlH 4 nanoparticles (NPs) towards advanced hydrogen storage performance. The nanoconfined NaAlH 4 inside CeO 2 HNTs, synthesized via the infiltration of molten NaAlH 4 into the CeO 2 HNTs under high hydrogen pressure, exhibited significantly improved dehydrogenation properties compared with both bulk and ball-milled CeO 2 HNTs-catalyzed NaAlH 4 . The onset dehydrogenation temperature of the NaAlH 4 @CeO 2 composite was reduced to below 100 °C, with only one main dehydrogenation peak appearing at 130 °C, which is 120 °C and 50 °C lower than for its bulk counterpart and for the ball-milled CeO 2 HNTs-catalyzed NaAlH 4 , respectively. Moreover, ∼5.09 wt% hydrogen could be released within 30 min at 180 °C, while only 1.6 wt% hydrogen was desorbed from the ball-milled NaAlH 4 under the same conditions. This significant improvement is mainly attributed to the synergistic effects contributed by the CeO 2 HNTs, which could act as not only a structural scaffold to fabricate and confine the NaAlH 4 NPs, but also as an effective catalyst to enhance the hydrogen storage performance of NaAlH 4 .

Ga2O3 doping and vacancy effect in KNN—LT lead-free piezoceramics

NASA Astrophysics Data System (ADS)

Tan, Zhi; Xing, Jie; Jiang, Laiming; Zhu, Jianguo; Wu, Bo

2017-12-01

Ga2O3 was doped into 0.95(K0.48Na0.52)NbO3—0.05LiTaO3 (KNN—LT) ceramics and its influences on the sintering behavior, phase structure and electrical properties of ceramics were studied. Firstly, SEM observation exhibits that more and more glass phase appears in ceramics with the gradual addition of Ga2O3, which determines the continuous decrease in sintering temperatures. And the addition of Ga2O3 is also found to increase the orthorhombic—tetragonal transition temperature ( T O—T) of system to a higher level. Secondly, both the density and the coercive field ( E C) of ceramics increase firstly and then decrease with increasing the Ga2O3 content, and the KNN—LT— xGa sample at x = 0.004 shows a pinched P— E hysteresis loop. Finally, the impedance characteristics of KNN—LT— xGa ceramics were investigated at different temperatures, revealing a typical vacancy related conduction mechanism. This work demonstrates that Ga2O3 is a good sintering aid for KNN-based ceramics, and the vacancy plays an important role in the sintering and electrical behaviors of ceramics.

Investigation on charge transfer bands of Ce 4+ in Sr 2CeO 4 blue phosphor

NASA Astrophysics Data System (ADS)

Li, Ling; Zhou, Shihong; Zhang, Siyuan

2008-03-01

Bulk and nano-materials Sr2CeO4 were prepared by solid-state reaction and sol-gel technique, respectively. Photoluminescence shows that luminescence has the characteristic of a ligand-to-metal charge transfer (CT) emission. Compared with bulk Sr2CeO4, the nano-material exhibits stronger emission intensity, longer decay time, and higher CT excitation energy. Three CT excitation peaks were observed in both bulk and nano samples. Based on the theoretical calculations of the average energy gap of the chemical bond using the dielectric theory of complex crystal, the highest and the lowest energy CT bands were assigned to the transitions O1 → Ce4+ and O2 → Ce4+, respectively. The middle bands were due to the superposition of the transitions Ce-O1 and Ce-O2.

A facile method of fabricating mechanical durable anti-icing coatings based on CeO2 microparticles

NASA Astrophysics Data System (ADS)

Wang, Pengren; Peng, Chaoyi; Wu, Binrui; Yuan, Zhiqing; Yang, Fubiao; Zeng, Jingcheng

2015-07-01

Compromising between hydrophobicity and mechanical durability may be a feasible approach to fabricating usable anti-icing coatings. This work improves the contact angle of current commercial anti-icing coatings applied to wind turbine blades dramatically and keeps relatively high mechanical durability. CeO2 microparticles and diluent were mixed with fluorocarbon resin to fabricate high hydrophobic coatings on the glass fiber reinforced epoxy composite substrates. The proportion of CeO2 microparticles and diluent influences the contact angles significantly. The optimum mass ratio of fluorocarbon resin to CeO2 microparticles to diluent is 1:1.5:1, which leads to the highest contact angle close to 140°. The microscopy analysis shows that the CeO2 microparticles form nano/microscale hierarchical structure on the surface of the coatings.

The role of scattering and absorption on the optical properties of birefringent polycrystalline ceramics: Modeling and experiments on ruby (Cr:Al2O3)

NASA Astrophysics Data System (ADS)

Penilla, E. H.; Hardin, C. L.; Kodera, Y.; Basun, S. A.; Evans, D. R.; Garay, J. E.

2016-01-01

Light scattering due to birefringence has prevented the use of polycrystalline ceramics with anisotropic optical properties in applications such as laser gain media. However, continued development of processing technology has allowed for very low porosity and fine grains, significantly improving transparency and is paving the way for polycrystalline ceramics to be used in demanding optical applications. We present a method for producing highly transparent Cr3+ doped Al2O3 (ruby) using current activated pressure assisted densification. The one-step doping/densification process produces fine grained ceramics with well integrated (doped) Cr, resulting in good absorption and emission. In order to explain the light transmission properties, we extend the analytical model based on the Rayleigh-Gans-Debye approximation that has been previously used for undoped alumina to include absorption. The model presented captures reflection, scattering, and absorption phenomena in the ceramics. Comparison with measured transmission confirms that the model adequately describes the properties of polycrystalline ruby. In addition the measured emission spectra and emission lifetime are found to be similar to single crystals, confirming the high optical quality of the ceramics.

Modifications of the structure and magnetic properties of ceramic YCrO3 with Fe/Ni doping

NASA Astrophysics Data System (ADS)

Mall, Ashish Kumar; Garg, Ashish; Gupta, Rajeev

2017-07-01

In this manuscript, we have investigated the effect of Fe and Ni doping on the structure and magnetic properties of YCr1-x M x O3 ceramics (M  =  Fe, Ni and x  =  0, 0.1). X-ray diffraction analysis of the samples accompanied with, Rietveld refinement suggested no change in the structure upon doping, with structure of the samples being orthorhombic (space group: Pnma). Raman spectroscopic analysis of the samples revealed that doping induced disorder leads to broadening of the certain Raman modes of the system. While, both B 3g(5) and B 1g(3) modes are broadened in Ni and Fe doped samples, in addition Fe doped samples also show broadening of B 1g(4) mode. In doped samples a new mode, A 1g(3) appears due to the induced lattice disorder. Temperature dependent magnetic measurements suggested a negative value of Curie-Weiss temperature (θ cw) indicating that all the samples are antiferromagnetic. However, the Neel temperature (T N) increased for Fe doping and decreased with Ni doping. These changes in the Neel temperature upon doping can be correlated to the changes in the nearest neighbor and next nearest neighbor exchange interactions.

Optoenergy storage and random walks assisted broadband amplification in Er3+-doped (Pb,La)(Zr,Ti)O3 disordered ceramics.

PubMed

Xu, Long; Zhao, Hua; Xu, Caixia; Zhang, Siqi; Zou, Yingyin K; Zhang, Jingwen

2014-02-01

A broadband optical amplification was observed and investigated in Er3+-doped electrostrictive ceramics of lanthanum-modified lead zirconate titanate under a corona atmosphere. The ceramic structure change caused by UV light, electric field, and random walks originated from the diffusive process in intrinsically disordered materials may all contribute to the optical amplification and the associated energy storage. Discussion based on optical energy storage and diffusive equations was given to explain the findings. Those experiments performed made it possible to study random walks and optical amplification in transparent ceramics materials.

Crystal Structure, Piezoelectric and Dielectric Properties of (Li, Ce)4+, Nb5+ and Mn2+ Co-doped CaBi4Ti4O15 High-Temperature Ceramics

NASA Astrophysics Data System (ADS)

Xin, Deqiong; Chen, Qiang; Wu, Jiagang; Bao, Shaoming; Zhang, Wen; Xiao, Dingquan; Zhu, Jianguo

2016-07-01

Bismuth-layered structured ceramics Ca0.85(Li,Ce)0.075Bi4Ti4- x Nb x O15-0.01MnCO3 were prepared by the conventional solid-state reaction method. The evolution of microstructure and corresponding electrical properties were studied. All the samples presented a single bismuth layered-structural phase with m = 4, indicating that (Li, Ce)4+, Nb5+ and Mn2+ adequately enter into the pseudo-perovskite structure and form solid solutions. It was found that Ca0.85(Li,Ce)0.075Bi4Ti3.98Nb0.02O15-0.01MnCO3 (CBTLCM-0.02Nb) ceramics possess the optimum electrical properties. The piezoelectric coefficient d 33, dielectric constant ɛ r, loss tan δ, planar electromechanical coupling factor k p and Curie-temperature T C of CBTLCM-0.02Nb ceramics were found to be ˜19.6 pC/N, 160, 0.16%, 8.1% and 767°C, respectively. Furthermore, the thermal depoling behavior demonstrates that the d 33 value of x = 0.02 content remains at 16.8 pC/N after annealing at 500°C. These results suggest that the (Li, Ce)4+-, Nb5+- and Mn2+-doped CBT-based ceramics are promising candidates for high-temperature piezoelectric applications.

The translocation and distribution of CeO2 nanoparticles in plants (Soybeans, Chili, Eggplant and Tomato)

NASA Astrophysics Data System (ADS)

Li, Teng; Dai, Yanhui

2018-02-01

Intensive production of CeO2 nanoparticles (NPs) would lead to their release into the environment. While their use in commercial goods is constantly increasing, location of NPs in plant is still poorly documented. In this study we determined the translocation of CeO2-NPs in four plants (Soybeans, Tomato, Chili and Eggplant) grown in natural conditions. The plants were digged out 1/4 roots into 2000 mg/L CeO2-NPs solution during the blossoming period. After being exposed for one month, the contents of Ce in plant tissues were measured by inductively coupled plasma mass spectrometry (ICP-MS). There was more Ce in the leaf of treated plants than in control plants. The contents of Ce in leaf tissues was different. This research offers vital information about the translocation and distribution of CeO2-NPs in higher plants.

Dielectric properties and nonlinear I-V electrical behavior of (Li1+, Al3+) co-doped CaCu3Ti4O12 ceramics

NASA Astrophysics Data System (ADS)

Sun, Li; Ni, Qing; Guo, Jianqin; Cao, Ensi; Hao, Wentao; Zhang, Yongjia; Ju, Lin

2018-06-01

(Li1+, Al3+) co-doped CaCu3Ti4O12 ceramics (CaCu3-2 x Li x Al x Ti4O12, x = 0.05, 0.1, 0.15) were prepared by a sol-gel method and were sintered at 1020-1080 °C for 8 h to improve the geometric microstructure, dielectric and nonlinear I-V electrical properties. Notably, very high dielectric constant of 1 × 105 with good dielectric-frequency as well as dielectric-temperature stability can be achieved in CaCu2.8Li0.1Al0.1Ti4O12 ceramic sintered at 1060 °C. The average grain sizes, resistivity and the non-Ohmic properties are also improved compared to pure CaCu3Ti4O12. These results indicate that (Li1+, Al3+) co-doping at the Cu2+ site can improve the dielectric properties of CaCu3Ti4O12, supporting the internal barrier layer capacitance effect of Schottky barriers at grain boundaries.

[Preparation and photoluminescence study of Er3+ : Y2O3 transparent ceramics].

PubMed

Luo, Jun-ming; Li, Yong-xiu; Deng, Li-ping

2008-10-01

Y2O3 acted as the matrix material, which was doped with different concentrations of Er3+, Er3+ : Y2O3 nanocrystalline powder was prepared by co-precipitation method, and Er3+ : Y2O3 transparent ceramics was fabricated by vacuum sintering at 1700 degrees C, 1 x 10(-3) Pa for 8 h. By using the X-ray diffraction (D/MAX-RB), transmission electron microscopy(Philips EM420), automatic logging spectrophotometer(DMR-22), fluorescence analyzer (F-4500) and 980 nm diode laser, the structural, morphological and luminescence properties of the sample were investigated. The results show that Er3+ dissolved completely in the Y2O3 cubic phase, the precursor was amorphous, weak diffraction peaks appeared after calcination at 400 degrees C, and if calcined at 700 degrees C, the precursor turned to pure cubic phase. With increasing the calcining temperature, the diffraction peaks became sharp quickly, and when the calcining temperature reached 1100 degrees C, the diffraction peaks became very sharp, indicating that the grains were very large. The particles of Er+ : Y2O3 is homogeneous and nearly spherical, the average diameter of the particles is in the range of 40-60 nm after being calcined at 1000 degrees C for 2 h. The relative density of Er3+ : Y2O3 transparent ceramics is 99.8%, the transmittance of the Er2+ : Y2O3 transparent ceramics is markedly lower than the single crystal at the short wavelength, but the transmittance is improved noticeably with increasing the wavelength, and the transmittance exceeds 60% at the wavelength of 1200 nm. Excited under the 980 nm diode laser, there are two main up-conversion emission bands, green emission centers at 562 nm and red emission centers at 660 nm, which correspond to (4)S(3/2) / (2)H(11/2) - (4)I(15/2) and (4)F(9/2) - (4)I(15/2) radiative transitions respectively. By changing the doping concentrations of Er3+, the color of up-conversion luminescence can be tuned from green to red gradually. The luminescence intensity is not reinforce

Fabrication of CeO2–MOx (M = Cu, Co, Ni) composite yolk–shell nanospheres with enhanced catalytic properties for CO oxidation

PubMed Central

Shi, Jingjing; Cao, Hongxia; Wang, Ruiyu

2017-01-01

CeO2–MOx (M = Cu, Co, Ni) composite yolk–shell nanospheres with uniform size were fabricated by a general wet-chemical approach. It involved a non-equilibrium heat-treatment of Ce coordination polymer colloidal spheres (Ce-CPCSs) with a proper heating rate to produce CeO2 yolk–shell nanospheres, followed by a solvothermal treatment of as-synthesized CeO2 with M(CH3COO)2 in ethanol solution. During the solvothermal process, highly dispersed MOx species were decorated on the surface of CeO2 yolk–shell nanospheres to form CeO2–MOx composites. As a CO oxidation catalyst, the CeO2–MOx composite yolk–shell nanospheres showed strikingly higher catalytic activity than naked CeO2 due to the strong synergistic interaction at the interface sites between MOx and CeO2. Cycling tests demonstrate the good cycle stability of these yolk–shell nanospheres. The initial concentration of M(CH3COO)2·xH2O in the synthesis process played a significant role in catalytic performance for CO oxidation. Impressively, complete CO conversion as reached at a relatively low temperature of 145 °C over the CeO2–CuOx-2 sample. Furthermore, the CeO2–CuOx catalyst is more active than the CeO2–CoOx and CeO2–NiO catalysts, indicating that the catalytic activity is correlates with the metal oxide. Additionally, this versatile synthesis approach can be expected to create other ceria-based composite oxide systems with various structures for a broad range of technical applications. PMID:29234577

Antimicrobial potential of green synthesized CeO2 nanoparticles from Olea europaea leaf extract.

PubMed

Maqbool, Qaisar; Nazar, Mudassar; Naz, Sania; Hussain, Talib; Jabeen, Nyla; Kausar, Rizwan; Anwaar, Sadaf; Abbas, Fazal; Jan, Tariq

This article reports the green fabrication of cerium oxide nanoparticles (CeO 2 NPs) using Olea europaea leaf extract and their applications as effective antimicrobial agents. O. europaea leaf extract functions as a chelating agent for reduction of cerium nitrate. The resulting CeO 2 NPs exhibit pure single-face cubic structure, which is examined by X-ray diffraction, with a uniform spherical shape and a mean size 24 nm observed through scanning electron microscopy and transmission electron microscopy. Ultraviolet-visible spectroscopy confirms the characteristic absorption peak of CeO 2 NPs at 315 nm. Fourier transform infrared spectroscopy reflects stretching frequencies at 459 cm -1 , showing utilization of natural components for the production of NPs. Thermal gravimetric analysis predicts the successful capping of CeO 2 NPs by bioactive molecules present in the plant extract. The antimicrobial studies show significant zone of inhibition against bacterial and fungal strains. The higher activities shown by the green synthesized NPs than the plant extract lead to the conclusion that they can be effectively used in biomedical application. Furthermore, reduction of cerium salt by plant extract will reduce environmental impact over chemical synthesis.

Antimicrobial potential of green synthesized CeO2 nanoparticles from Olea europaea leaf extract

PubMed Central

Maqbool, Qaisar; Nazar, Mudassar; Naz, Sania; Hussain, Talib; Jabeen, Nyla; Kausar, Rizwan; Anwaar, Sadaf; Abbas, Fazal; Jan, Tariq

2016-01-01

This article reports the green fabrication of cerium oxide nanoparticles (CeO2 NPs) using Olea europaea leaf extract and their applications as effective antimicrobial agents. O. europaea leaf extract functions as a chelating agent for reduction of cerium nitrate. The resulting CeO2 NPs exhibit pure single-face cubic structure, which is examined by X-ray diffraction, with a uniform spherical shape and a mean size 24 nm observed through scanning electron microscopy and transmission electron microscopy. Ultraviolet-visible spectroscopy confirms the characteristic absorption peak of CeO2 NPs at 315 nm. Fourier transform infrared spectroscopy reflects stretching frequencies at 459 cm−1, showing utilization of natural components for the production of NPs. Thermal gravimetric analysis predicts the successful capping of CeO2 NPs by bioactive molecules present in the plant extract. The antimicrobial studies show significant zone of inhibition against bacterial and fungal strains. The higher activities shown by the green synthesized NPs than the plant extract lead to the conclusion that they can be effectively used in biomedical application. Furthermore, reduction of cerium salt by plant extract will reduce environmental impact over chemical synthesis. PMID:27785011

[Effect of three kinds of rare earth oxides on chromaticity and mechanical properties of zirconia ceramic].

PubMed

Huang, Hui; Zhang, Fu-qiang; Sun, Jing; Gao, Lian

2006-06-01

To evaluate the colouration of zirconia ceramic by adding three kinds of rare earth oxides. The influence of the pigments concentration on the mechanical properties and the microstructure was also analyzed. Added different concentrations of CeO(2), Er(2)O(3) and Pr(6)O(11) in tetragonal zirconia poly crystals stabilized with 3 mol% yttria (3Y-T2P) powder, compacted at 200 MPa using cold isostatic pressure, and sintered to 1 400 degrees C. The heating rate was 150 degrees C/h and the dwelling time was 2 hours. The chromaticity of sintered bodies was measured with chroma meter. The relative density, hardness, flexure strength and fracture toughness were investigated as well. The phase stability of the colorized and pure zirconia was evaluated by X-ray diffraction (XRD) using an automated diffractometer. The microstructures of the specimens were evaluated by scanning electron microscope (SEM). Several kinds of color achieved by the different pigments praseodym oxide, cerium oxide and erbium oxide were presented in the CIELab system. The a* value increased with the added amount of Er(2)O(3), while b* value rose with the increasing amount of CeO(2) and Pr(6)O(11). However, three pigments failed to decrease L* value and the sintered body appeared too bright. Adding three pigments influenced flexure strength of zirconia ceramic significantly, but had little influence on the hardness and fracture toughness. Microscopy revealed the relationship between the porosity and shapes of grains was correlated to strength of the diphase ceramics. No additional phase could be detected by XRD, except t-ZrO(2) in all colorized samples after sintering at 1 400 degrees C for 120 min. Zirconia ceramic can be colorized by CeO(2), Er(2)O(3), and Pr(6)O(11). Pigments even in a small amount influence the mechanical properties of the colorized zirconia material, which necessitates further investigation.

Nearly full-dense and fine-grained AZO:Y ceramics sintered from the corresponding nanoparticles

PubMed Central

2012-01-01

Aluminum-doped zinc oxide ceramics with yttria doping (AZO:Y) ranging from 0 to 0.2 wt.% were fabricated by pressureless sintering yttria-modified nanoparticles in air at 1,300°C. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, a physical property measurement system, and a densimeter were employed to characterize the precursor nanoparticles and the sintered AZO ceramics. It was shown that a small amount of yttria doping can remarkably retard the growth of the as-received precursor nanoparticles, further improve the microstructure, refine the grain size, and enhance the density for the sintered ceramic. Increasing the yttria doping to 0.2 wt.%, the AZO:Y nanoparticles synthetized by a coprecipitation process have a nearly sphere-shaped morphology and a mean particle diameter of 15.1 nm. Using the same amount of yttria, a fully dense AZO ceramic (99.98% of theoretical density) with a grain size of 2.2 μm and a bulk resistivity of 4.6 × 10−3 Ω·cm can be achieved. This kind of AZO:Y ceramic has a potential to be used as a high-quality sputtering target to deposit ZnO-based transparent conductive films with better optical and electrical properties. PMID:22929049

Magnetic ordered mesoporous Fe3O4/CeO2 composites with synergy of adsorption and Fenton catalysis

NASA Astrophysics Data System (ADS)

Li, Keyan; Zhao, Yongqin; Song, Chunshan; Guo, Xinwen

2017-12-01

Magnetic Fe3O4/CeO2 composites with highly ordered mesoporous structure and large surface area were synthesized by impregnation-calcination method, and the mesoporous CeO2 as support was synthesized via the hard template approach. The composition, morphology and physicochemical properties of the materials were characterized by XRD, SEM, TEM, XPS, Raman spectra and N2 adsorption/desorption analysis. The mesoporous Fe3O4/CeO2 composite played a dual-function role as both adsorbent and Fenton-like catalyst for removal of organic dye. The methylene blue (MB) removal efficiency of mesoporous Fe3O4/CeO2 was much higher than that of irregular porous Fe3O4/CeO2. The superior adsorption ability of mesoporous materials was attributed to the abundant oxygen vacancies on the surface of CeO2, high surface area and ordered mesoporous channels. The good oxidative degradation resulted from high Ce3+ content and the synergistic effect between Fe and Ce. The mesoporous Fe3O4/CeO2 composite presented low metal leaching (iron 0.22 mg L-1 and cerium 0.63 mg L-1), which could be ascribed to the strong metal-support interactions for dispersion and stabilization of Fe species. In addition, the composite can be easily separated from reaction solution with an external magnetic field due to its magnetic property, which is important to its practical applications.

Ceo2 Based Catalysts for the Treatment of Propylene in Motorcycle’s Exhaust Gases

PubMed Central

Pham, Phuong Thi Mai; Le Minh, Thang; Nguyen, Tien The; Van Driessche, Isabel

2014-01-01

In this work, the catalytic activities of several single metallic oxides were studied for the treatment of propylene, a component in motorcycles’ exhaust gases, under oxygen deficient conditions. Amongst them, CeO2 is one of the materials that exhibit the highest activity for the oxidation of C3H6. Therefore, several mixtures of CeO2 with other oxides (SnO2, ZrO2, Co3O4) were tested to investigate the changes in catalytic activity (both propylene conversion and CO2 selectivity). Ce0.9Zr0.1O2, Ce0.8Zr0.2O2 solid solutions and the mixtures of CeO2 and Co3O4 was shown to exhibit the highest propylene conversion and CO2 selectivity. They also exhibited good activities when tested under oxygen sufficient and excess conditions and with the presence of co-existing gases (CO, H2O). PMID:28788253

Enhanced NIR downconversion luminescence by precipitating nano Ca5(PO4)3F crystals in Eu2+-Yb3+ co-doped glass

NASA Astrophysics Data System (ADS)

Li, Chen; Song, Zhiguo; Li, Yongjin; Lou, Kai; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi; Wang, Xue; Wang, Qi; Wan, Ronghua

2013-10-01

Eu2+-Yb3+ co-doped transparent glass-ceramic containing nano-Ca5(PO4)3F (FAP) was prepared in reducing atmosphere. XRD and TEM analysis indicated that nano-FAP about 40 nm precipitated homogeneously in glass matrix after heat treatment. Confirmed by spectroscopy measurements, the crystal-like absorption and emission of Eu2+ indicated the partition of Eu2+ into FAP nanocrystals in glass ceramic. NIR emission due to the transition 2F→2F of Yb3+ ions (about 980-1100 nm) was observed from glasses under ultraviolet excitation, ascribed to downconversion from Eu2+ to Yb3+, which can be enhanced by precipitating nano-FAP crystals. The results indicated that Eu2+-Yb3+ co-doped glass-ceramic embedding with nano-FAP is a promising candidate as downconversion materials for enhancing conversion efficiency of solar cells.

Immunomodulation and T Helper TH1/TH2 Response Polarization by CeO2 and TiO2 Nanoparticles

PubMed Central

Schanen, Brian C.; Das, Soumen; Reilly, Christopher M.; Warren, William L.; Self, William T.; Seal, Sudipta; Drake, Donald R.

2013-01-01

Immunomodulation by nanoparticles, especially as related to the biochemical properties of these unique materials, has scarcely been explored. In an in vitro model of human immunity, we demonstrate two catalytic nanoparticles, TiO2 (oxidant) and CeO2 (antioxidant), have nearly opposite effects on human dendritic cells and T helper (TH) cells. For example, whereas TiO2 nanoparticles potentiated DC maturation that led towards TH1-biased responses, treatment with antioxidant CeO2 nanoparticles induced APCs to secrete the anti-inflammatory cytokine, IL-10, and induce a TH2-dominated T cell profile. In subsequent studies, we demonstrate these results are likely explained by the disparate capacities of the nanoparticles to modulate ROS, since TiO2, but not CeO2 NPs, induced inflammatory responses through an ROS/inflammasome/IL-1β pathway. This novel capacity of metallic NPs to regulate innate and adaptive immunity in profoundly different directions via their ability to modulate dendritic cell function has strong implications for human health since unintentional exposure to these materials is common in modern societies. PMID:23667525

Phase Transformation and Lattice Parameter Changes of Non-trivalent Rare Earth-Doped YSZ as a Function of Temperature

NASA Astrophysics Data System (ADS)

Jiang, Shengli; Huang, Xiao; He, Zhang; Buyers, Andrew

2018-01-01

To examine the effect of doping/co-doping on high-temperature phase compositions of YSZ, stand-alone YSZ and CeO2 and Nb2O5 co-doped YSZ samples were prepared using mechanical alloy and high-temperature sintering. XRD analysis was performed on these samples from room temperature to 1100 °C. The results show that the structure for the co-doped samples tends to be thermally stable when the test temperature is higher than a critical value. Monoclinic phase was dominant in Nb2O5 co-doped YSZ at temperatures lower than 600 °C, while for the YSZ and CeO2 co-doped YSZ, cubic/tetragonal phase was dominant in the whole test temperature range. The lattice parameters for all the samples increase with increasing test temperature generally. The lattice parameters for the two non-trivalent rare earth oxides co-doped YSZ show that the lattice parameter a for the cubic phase of the Ce4+ co-doped YSZ is consistently greater than that of 7YSZ which is related to the presence of larger radius of Ce4+ in the matrix. The lattice parameters a, b, c for the monoclinic phase of Ce4+ co-doped YSZ are much closer to each other than that of the Nb5+ co-doped YSZ, indicating the former has better tendency to form cubic/tetragonal phase, which is desired for vast engineering applications.

Phase Transformation and Lattice Parameter Changes of Non-trivalent Rare Earth-Doped YSZ as a Function of Temperature

NASA Astrophysics Data System (ADS)

Jiang, Shengli; Huang, Xiao; He, Zhang; Buyers, Andrew

2018-05-01

To examine the effect of doping/co-doping on high-temperature phase compositions of YSZ, stand-alone YSZ and CeO2 and Nb2O5 co-doped YSZ samples were prepared using mechanical alloy and high-temperature sintering. XRD analysis was performed on these samples from room temperature to 1100 °C. The results show that the structure for the co-doped samples tends to be thermally stable when the test temperature is higher than a critical value. Monoclinic phase was dominant in Nb2O5 co-doped YSZ at temperatures lower than 600 °C, while for the YSZ and CeO2 co-doped YSZ, cubic/tetragonal phase was dominant in the whole test temperature range. The lattice parameters for all the samples increase with increasing test temperature generally. The lattice parameters for the two non-trivalent rare earth oxides co-doped YSZ show that the lattice parameter a for the cubic phase of the Ce4+ co-doped YSZ is consistently greater than that of 7YSZ which is related to the presence of larger radius of Ce4+ in the matrix. The lattice parameters a, b, c for the monoclinic phase of Ce4+ co-doped YSZ are much closer to each other than that of the Nb5+ co-doped YSZ, indicating the former has better tendency to form cubic/tetragonal phase, which is desired for vast engineering applications.

Perceptions of hospital CEOs about the effects of CEO turnover.

PubMed

Khaliq, Amir A; Thompson, David M; Walston, Stephen L

2006-01-01

Empirical evidence is scarce on chief executive officer (CEO) turnover in U.S. hospitals, with potentially serious implications for many of these organizations. This study, based on a nationwide survey of CEOs at non-federal general surgical and medical community hospitals conducted in the spring of 2004, reports the perceptions of hospital CEOs regarding the circumstances and impact of CEO turnover on U.S. hospitals. In the opinion of the respondents, the impact includes competitors taking advantage of turnover by luring employees and physicians away from the target hospital, significantly increasing the likelihood of other senior executives leaving the hospital, and many of the important strategic activities being delayed or cancelled altogether. Interestingly, the perceptions of CEOs regarding the effects of turnover do not seem to differ regardless of voluntary or involuntary circumstances of turnover. However, there is a notable bias in emphasizing the perceived negative implications of respondents' own departures and allegedly positive effects of their predecessors' departures.

The CEO's real legacy.

PubMed

Freeman, Kenneth W

2004-11-01

The literature on CEO succession planning is nearly unanimous in its advice: Begin early, look first inside your company for exceptional talent, see that candidates gain experience in all aspects of the business, and help them develop the skills they will need in the top job. It all makes sense and sounds pretty straightforward. Nevertheless, the list of CEOs who last no more than a few years on the job continues to grow. Implicit in many, if not all, of these unceremonious departures is the absence of an effective CEO succession plan. The problem is, most boards simply don't want to talk about CEO succession: Why rock the boat when things are going well? Why risk offending the current CEO? Meanwhile, most CEOs can't imagine that anyone could adequately replace them. In this article, Kenneth W. Freeman, the retired CEO of Quest Diagnostics, discusses his own recent handoff experience (Surya N. Mohapatra became chief executive in May 2004) and offers his approach to succession planning. He says it falls squarely on the incumbent CEO to put ego aside and initiate and actively manage the process of selecting and grooming a successor. Aggressive succession planning is one of the best ways for CEOs to ensure the long-term health of the company, he says. Plus, thinking early and often about a successor will likely improve the chief executive's performance during his tenure. Freeman advocates the textbook rules for succession planning but adds to that list a few more that apply specifically to the incumbent CEO: Insist that the board become engaged in succession planning, look for a successor who is different from you, and make the successor's success your own. After all, Freeman argues, the CEO's true legacy is determined by what happens after he leaves the corner office.

Improve electrochemical performance of CeO2 surface modification LiNi0.80Co0.15Al0.05O2 cathode material

NASA Astrophysics Data System (ADS)

Xia, Shubiao; Zhang, Yingjie; Dong, Peng; Zhang, Yannan

2014-06-01

Lithium ion battery cathode material LiNi0.8Co0.15Al0.05O2 cathode has successfully prepared by co-precipitation. CeO2 surface modification has improved LiNi0.80Co0.15Al0.05O2 electrochemical performance use sol-gel method and subsequent heat treatment at 600 °C for 5 h. Different to other conventional coating material, CeO2 coating layer can not only inhibit the reaction of the electrode and the electrolyte, but also can reduce the impedance of electron transfer due to its high conductivity, and inhibit the production of Ni2+ because of its high oxidation. The surface-modified and pristine LiNi0.80Co0.15Al0.05O2 powders are characterized by XRD, SEM, TEM, XPS, CV and DSC. When CeO2 coating is 0.02% (mole ratio), contrast to pristine NCA, the CeO2-coated NCA cathode exhibits no decrease in its initial specific capacity of 184 mAh g -1 (at 0.2 C) and excellent capacity retention (86% of its initial capacity at 1 C) between 2.75 and 4.3 V after 100 cycles. The results indicate that the CeO2 surface treatment should be an effective way to improve cycle properties due to CeO2 inhibit the electrodes and the electrolyte side effects.

Investigation of the thermoelectric properties of Nb and oxygen vacancy co-doped SrTiO3 ceramics

NASA Astrophysics Data System (ADS)

Gong, Jing; Yuan, Zhanhui; Xu, Shikui; Li, Zhuangzhi; Xu, Jingzhou; Tang, Guide

2017-05-01

High quality Nb doped SrTi1-x Nb x O3 polycrystalline ceramics were fabricated using a conventional solid state reaction method. By annealing in a reducing atmosphere at an elevated temperature, a series of Nb and oxygen vacancy co-doped SrTi1-x Nb x O3-δ (0  ⩽  x  ⩽  0.2) samples was obtained. The thermoelectric properties of the samples were measured in the temperature range from 15 K to 380 K. These measurements showed that the transport behavior of these samples is consistent with the small polaron conduction mechanism for the temperature range from room temperature to 380 K. Furthermore, after annealing, samples with a lower Nb doping were found to give a relative higher ZT value, while excess Nb led to a reduced ZT value. The x  =  0.02 sample gave the optimal thermoelectric properties, with a ZT value of 0.023 at 300 K, and 0.028 at 380 K.

Synthesis and dc electrical conductivity of Cr-doped CeO2 nanoparticles by solution combustion method

NASA Astrophysics Data System (ADS)

Harish, B. M.; Avinash, B. S.; Chaturmukha, V. S.; Jayanna, H. S.; Suresh, S.; Naveen, C. S.; Lamani, Ashok R.

2018-04-01

NPs of Ce1-xCrxO2 (x=0, 0.04, 0.08, 0.12) have been synthesized by solution combustion method using glycine as fuel. The effect of chromium on structural and dc electrical conductivity of cerium oxide nanoparticles were investigated. The obtained powder is characterized by UV-visible spectrometer, X-ray diffractometer (XRD), Scanning electron microscope (SEM) and Energy dispersive X-Ray analysis (EDS). X-ray diffraction analysis carried out on calcined samples reveals that successful incorporation of Cr2+ in CeO2 lattice where as SEM studies confirms the porous morphological structure of the prepared sample. The Keithley source meter is used to measure the dc conductivity of samples in the temperature range from 303K to 623K. The conductivity was found to be increases with increase of temperature as well as the Cr concentration due to semiconducting behavior of material and change in the charge carrier concentration. The activation energy decreases with increasing chromium concentration. The present work deals with the effect of chromium additive on structural and the D.C electrical properties Ce1-xCrxO2 NPs.

Structure and photoluminescence studies of CeO2·CuAlO2 mixed metal oxide fabricated by co-precipitation method

NASA Astrophysics Data System (ADS)

Subhan, Md Abdus; Ahmed, Tanzir; Awal, M. R.; Kim, B. Moon

2015-01-01

A novel mixed metal oxide, CeO2·CuAlO2 was fabricated by co-precipitation method in aqueous medium. CeO2·CuAlO2 was characterized by XRD, SEM, EDS, TEM, FTIR and PL spectra. The optical properties of the nanoparticles were studied by photoluminescence (PL) spectra. PL spectra at different excitations were recorded. The composite showed emission in UV, visible and NIR region depending on the excitation wavelength. The special spectral feature observed for this composite is that it showed six emission bands at 364, 409, 434, 448, 465 and 481 nm when excited at 298 nm. The green and red emissions observed at 512 and 669 nm are originated from cubic CeO2 phase when excited at 450 nm. The PL spectra were found to be dependent on excitation wavelength violating Kasha's rule. The X-ray diffraction reveals a cubic CeO2 phase and hexagonal CuAlO2 phase. EDS spectra revealed the presence of cerium (Ce), copper (Cu), aluminum (Al) and oxygen (O) elements. The particle size of the CeO2·CuAlO2 mixed oxide was estimated using Scherrer's formula, which was found to be in the range of 17.2-34.2 nm. The TEM image showed particles are almost uniform size of approximately 15-50 nm with spherical morphology.

Photoemission properties of Eu-doped Zr1- x Ce x O2 (x = 0-0.2) nanoparticles prepared by hydrothermal method

NASA Astrophysics Data System (ADS)

Ozawa, Masakuni; Matsumoto, Masashi; Hattori, Masatomo

2018-01-01

Photoluminescent Eu-doped ZrO2 and Zr1- x Ce x O2 (x = 0-0.2) nanoparticles were prepared by a hydrothermal method. X-ray diffraction and Raman spectra indicated the formation of tetragonal crystals of ZrO2 and its solid solutions with a grain size of less than 10 nm diameter after heat treatment at 400 °C. The photoemission spectra of Zr1- x Ce x O2:Eu3+ nanocrystalline samples showed the typical emission of Eu3+ ions assigned to 5D0 → 7F1 (590 nm) and 5D0 → 7F2 (610 nm) transitions and additional emissions of 5D0 → 7F J with higher J of 3-5. Increasing the CeO2 concentration reduced the emission intensity, and the emission peak shift was affected by a local lattice distortion, i.e., CeO2 concentration. The present study provided fundamental knowledge that is expected to enable the fabrication of ZrO2-based nanocrystal phosphor materials and a measure for controlling the emission peak shift and intensity in oxide fluorite-based phosphor.

Evaluation of Pd Nanoparticle-Decorated CeO2-MWCNT Nanocomposite as an Electrocatalyst for Formic Acid Fuel Cells

NASA Astrophysics Data System (ADS)

Saleem, Junaid; Safdar Hossain, SK.; Al-Ahmed, Amir; Rahman, Ateequr; McKay, Gordon; Hossain, Mohammed M.

2018-04-01

In this work, CeO2-modified Pd/CeO2-carbon nanotube (CNT) electrocatalyst for the electro-oxidation of formic acid has been investigated. The support CNT was first modified with different amounts (5-30 wt.%) of CeO2 using a precipitation-deposition method. The electrocatalysts were developed by dispersing Pd on the CeO2-CNT supports using the borohydride reduction method. The synthesized electrocatalysts were analyzed for composition, morphology and electronic structure using x-ray diffraction (XRD), scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) techniques. The formation of Pd nanoparticles on the CeO2-CNT support was confirmed using TEM. The activity of Pd/CeO2-CNT and of Pd-CNT samples upon oxidation of formic acid was evaluated by using carbon monoxide stripping voltammetry, cyclic voltammetry, and chronoamperometry. The addition of moderate amounts of cerium oxide (up to 10 wt.%) significantly improved the activity of Pd/CeO2-CNT compared to the unmodified Pd-CNT. Pd/10 wt.% CeO2-CNT showed a current density of 2 A mg-1, which is ten times higher than that of the unmodified Pd-CNT (0.2 A mg-1). Similarly, the power density obtained for Pd/10 wt.% CeO2-CNT in an air-breathing formic acid fuel cell was 6.8 mW/cm2 which is two times higher than Pd-CNT (3.2 mW/cm2), thus exhibiting the promotional effects of CeO2 to Pd/CeO2-CNT. A plausible justification for the improved catalytic performance and stability is provided in the light of the physical characterization results.

Effect of ZrO(2) additions on the crystallization, mechanical and biological properties of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics.

PubMed

Li, H C; Wang, D G; Meng, X G; Chen, C Z

2014-06-01

A series of ZrO(2) doped MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics were obtained by sintering method. The crystallization behavior, phase composition, morphology and structure of glass-ceramics were characterized. The bending strength, elastic modulus, fracture toughness, micro-hardness and thermal expansion coefficient (TEC) of glass-ceramics were investigated. The in vitro bioactivity and cytotoxicity tests were used to evaluate the bioactivity and biocompatibility of glass-ceramics. The sedimentation mechanism and growth process of apatites on sample surface were discussed. The results showed that the mainly crystalline phases of glass-ceramics were Ca(5)(PO4)3F (fluorapatite) and β-CaSiO(3). (β-wollastonite). m-ZrO(2) (monoclinic zirconia) declined the crystallization temperatures of glasses. t-ZrO(2) (tetragonal zirconia) increased the crystallization temperature of Ca(5)(PO4)(3)F and declined the crystallization temperature of β-CaSiO(3). t-ZrO(2) greatly increased the fracture toughness, bending strength and micro-hardness of glass-ceramics. The nanometer apatites were induced on the surface of glass-ceramic after soaking 28 days in SBF (simulated body fluid), indicating the glass-ceramic has good bioactivity. The in vitro cytotoxicity test demonstrated the glass-ceramic has no toxicity to cell. Copyright © 2014 Elsevier B.V. All rights reserved.

Voluntary transition of the CEO: owner CEOs' sense of self before, during and after transition

PubMed Central

Byrnes, Randy T.; Taylor, Scott N.

2015-01-01

This inductive study explores how former business owner chief executive officers (CEOs) experience sense of self during voluntary separation and transition from their company. Our inquiry engaged 16 CEOs who ran companies ranging in size from 15 to 500 employees as they detailed their stories of walking away from roles as owner CEOs. We developed a coding scheme to analyze themes manifested in the narratives. We also analyzed the former CEOs' narratives using a stage and valence model depicting both the continuum of the separation experience and the characterization of each stage as a positive or negative state of being. The diverse yet synchronous stories resulted in three implications for current owner CEOs, professionals who advise CEOs, and future research on CEOs' careers. First, the CEOs often failed to allocate sufficient time and effort to prepare for an identity shift following the sale of their company or transition into retirement. Second, the CEOs experienced a diminished sense of self and dissatisfaction with the exit event. Third, the majority of the CEOs demonstrated an ability to work through the adverse and unanticipated states of being into a positive sense of self. PMID:26579018

Voluntary transition of the CEO: owner CEOs' sense of self before, during and after transition.

PubMed

Byrnes, Randy T; Taylor, Scott N

2015-01-01

This inductive study explores how former business owner chief executive officers (CEOs) experience sense of self during voluntary separation and transition from their company. Our inquiry engaged 16 CEOs who ran companies ranging in size from 15 to 500 employees as they detailed their stories of walking away from roles as owner CEOs. We developed a coding scheme to analyze themes manifested in the narratives. We also analyzed the former CEOs' narratives using a stage and valence model depicting both the continuum of the separation experience and the characterization of each stage as a positive or negative state of being. The diverse yet synchronous stories resulted in three implications for current owner CEOs, professionals who advise CEOs, and future research on CEOs' careers. First, the CEOs often failed to allocate sufficient time and effort to prepare for an identity shift following the sale of their company or transition into retirement. Second, the CEOs experienced a diminished sense of self and dissatisfaction with the exit event. Third, the majority of the CEOs demonstrated an ability to work through the adverse and unanticipated states of being into a positive sense of self.

Low-frequency zone boundary phonons in Li doped ZnO ceramics

NASA Astrophysics Data System (ADS)

Yadav, Harish Kumar; Sreenivas, K.; Gupta, Vinay; Katiyar, R. S.

2008-09-01

Room temperature Raman spectra of Li doped ZnO (Zn1-xLixO) ceramics with varying Li concentrations (x =0.0, 0.05, 0.10, and 0.15) are investigated in this study. Four peaks were identified at 96.6, 127, 157, and 194 cm-1 in the Li doped samples. The peaks at 127, 157, and 194 cm-1 are assigned to zone boundary phonons in ZnO [J. M. Calleja and M. Cardona, Phys. Rev. B 16, 3753 (1977)], and appear due to disorder in ZnO lattice with Li incorporation. Lithium, owing to its smaller radius, adjusts itself anywhere in the ZnO lattice and breaks the crystal translational symmetry to a large extent, compared to other dopants. Disorder in the lattice is seen to be finely modulated with varying Li content. The peak at 96.6 cm-1 is hypothesized to be a projection of the vibrational motion of Li atoms at lower frequencies, which contributes in a major fashion at higher frequencies, due to its lighter mass than Zn or O atoms.

Influence of fluoride additions on biological and mechanical properties of Na2O-CaO-SiO2-P2O5 glass-ceramics.

PubMed

Li, H C; Wang, D G; Hu, J H; Chen, C Z

2014-02-01

Two series of Na2O-CaO-SiO2-P2O5 glass-ceramics doped with NH4HF2 (G-NH4HF2) or CaF2 (G-CaF2) have been prepared by sol-gel method. The glass-ceramic phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The mechanical properties and thermal expansion coefficient were measured by a microhardness tester, an electronic tensile machine and a thermal expansion coefficient tester. The structure difference between these two glass-ceramics was investigated by Fourier transform infrared spectroscopy (FTIR), and the in vitro bioactivity of the glass-ceramics was determined by in vitro simulated body fluid (SBF) immersion test. The hemolysis test, in vitro cytotoxicity test, systemic toxicity test and the implanted experiment in animals were used to evaluate the biocompatibility of the glass-ceramics. The mechanical properties of sample G-NH4HF2 are lower than that of sample G-CaF2, and the bioactivity of sample G-NH4HF2 is better than that of sample G-CaF2. The thermal expansion coefficients of these two glass-ceramics are all closer to that of Ti6Al4V. After 7 days of SBF immersion, apatites were induced on glass-ceramic surface, indicating that the glass-ceramics have bioactivity. The hemolysis test, in vitro cytotoxicity test and systemic toxicity test demonstrate that the glass-ceramics do not cause hemolysis reaction, and have no toxicity to cell and living animal. The implanted experiment in animals shows that bone tissue can form a good osseointegration with the implant after implantation for two months, indicating that the glass-ceramics are safe to serve as implants. Copyright © 2013 Elsevier B.V. All rights reserved.

Improving the Efficiency of DASC by Adding CeO2/CuO Hybrid Nanoparticles in Water

NASA Astrophysics Data System (ADS)

Midhun Mohan, V.; Sajeeb, A. M.

Solar energy is the abundantly available source of renewable energy with least impact on environment. Direct absorption solar collector (DASC) is the commonly used device to absorb heat directly from sun and make use of it for different heating applications. In the past, many experiments have been done to increase the efficiency of DASC using nanofluids. In this paper, an examination of solar collector efficiency for hybrid CeO2/CuO-water (0.1% by volume) nanofluid under various flow rates and proportions of CeO2/CuO nanoparticles is investigated. The experiments were conducted at flow rates spanning from 20cc/min to 100cc/min and with CeO2/CuO nanoparticles proportions of 1:0, 1:0.5, 1:1, 0.5:1 and 0:1. The efficiency increases from 16.5% to 51.6% when the flow rate is increased from 20cc/min to 100cc/min for hybrid CeO2/CuO (1:1)-water nanofluid. The results also showed an increase in efficiency of 13.8%, 18.1%, 24.3%, 24.9% and 26.1% with hybrid combination of CeO2/CuO at ratios 1:0, 1:0.5, 1:1, 0.5:1 and 0:1, respectively, in comparison with water at a flow rate of 100cc/min.

Interfacial interactions of semiconductor with graphene and reduced graphene oxide: CeO2 as a case study.

PubMed

Xu, Liang; Huang, Wei-Qing; Wang, Ling-Ling; Huang, Gui-Fang

2014-11-26

The pursuit of superb building blocks of light harvesting systems has stimulated increasing efforts to develop graphene (GR)-based semiconductor composites for solar cells and photocatalysts. One critical issue for GR-based composites is understanding the interaction between their components, a problem that remains unresolved after intense experimental investigation. Here, we use cerium dioxide (CeO2) as a model semiconductor to systematically explore the interaction of semiconductor with GR and reduced graphene oxide (RGO) with large-scale ab initio calculations. The amount of charge transferred at the interfaces increases with the concentration of O atoms, demonstrating that the interaction between CeO2 and RGO is much stronger than that between CeO2 and GR due to the decrease of the average equilibrium distance between the interfaces. The stronger interaction between semiconductor and RGO is expected to be general, as evidenced by the results of two paradigms of TiO2 and Ag3PO4 coupled with RGO. The interfacial interaction can tune the band structure: the CeO2(111)/GR interface is a type-I heterojunction, while a type-II staggered band alignment exists between the CeO2(111) surface and RGO. The smaller band gap, type-II heterojunction, and negatively charged O atoms on the RGO as active sites are responsible for the enhanced photoactivity of CeO2/RGO composite. These findings can rationalize the available experimental reports and enrich our understanding of the interaction of GR-based composites for developing high-performance photocatalysts and solar cells.

Synthesis and Characterization of CeO2 Nanoparticles via Solution Combustion Method for Photocatalytic and Antibacterial Activity Studies

PubMed Central

Ravishankar, Thammadihalli Nanjundaiah; Ramakrishnappa, Thippeswamy; Nagaraju, Ganganagappa; Rajanaika, Hanumanaika

2015-01-01

CeO2 nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO2 nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450 °C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO2 having crystallite size of 35 nm. The infrared spectrum shows a strong band below 700 cm−1 due to the Ce−O−Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302 nm. The photoluminescence spectrum shows characteristic peaks of CeO2 nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42 nm. CeO2 nanoparticles exhibit photocatalytic activity against trypan blue at pH 10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO2 nanoparticles also reduce CrVI to CrIII and show antibacterial activity against Pseudomonas aeruginosa. PMID:25969812

Structure and photoluminescence studies of CeO2·CuAlO2 mixed metal oxide fabricated by co-precipitation method.

PubMed

Subhan, Md Abdus; Ahmed, Tanzir; Awal, M R; Kim, B Moon

2015-01-25

A novel mixed metal oxide, CeO2·CuAlO2 was fabricated by co-precipitation method in aqueous medium. CeO2·CuAlO2 was characterized by XRD, SEM, EDS, TEM, FTIR and PL spectra. The optical properties of the nanoparticles were studied by photoluminescence (PL) spectra. PL spectra at different excitations were recorded. The composite showed emission in UV, visible and NIR region depending on the excitation wavelength. The special spectral feature observed for this composite is that it showed six emission bands at 364, 409, 434, 448, 465 and 481 nm when excited at 298 nm. The green and red emissions observed at 512 and 669 nm are originated from cubic CeO2 phase when excited at 450 nm. The PL spectra were found to be dependent on excitation wavelength violating Kasha's rule. The X-ray diffraction reveals a cubic CeO2 phase and hexagonal CuAlO2 phase. EDS spectra revealed the presence of cerium (Ce), copper (Cu), aluminum (Al) and oxygen (O) elements. The particle size of the CeO2·CuAlO2 mixed oxide was estimated using Scherrer's formula, which was found to be in the range of 17.2-34.2 nm. The TEM image showed particles are almost uniform size of approximately 15-50 nm with spherical morphology. Copyright © 2014 Elsevier B.V. All rights reserved.

[Coloration of mica glass ceramic for use in dental CAD/CAM system].

PubMed

Sun, Ying; Wang, Zhong-yi; Tian, Jie-mo; Cao, Xiao-gang

2003-03-01

An intrinsically colored machinable glass-ceramic containing tetrasilicic fluormica as the predominant crystal phase was studied, which was used in molar crown in dental CAD/CAM system. Orthogonal design analysis was used to select appropriate base formula, coloration and heat treatment process. Factors influencing the color appearance of mica glass ceramic were nucleation agent and the ratio of Mg(2+) to K(+) in base formula; Cerium oxide (CeO(2)) was used as the main coloration; The preferred heat treatment was 650 degrees C for 1 h and 1,000 degrees C or 1,050 degrees C for 3 h - 4 h. This mica glass-ceramic could provide 4 to 5 color appearance for dental use, it showed excellent machinability which was eminently suitable for use in dental CAD/CAM system.

Significant enhancement in thermoelectric properties of polycrystalline Pr-doped SrTiO3-δ ceramics originating from nonuniform distribution of Pr dopants

NASA Astrophysics Data System (ADS)

Dehkordi, Arash Mehdizadeh; Bhattacharya, Sriparna; He, Jian; Alshareef, Husam N.; Tritt, Terry M.

2014-05-01

Recently, we have reported a significant enhancement (>70% at 500 °C) in the thermoelectric power factor (PF) of bulk polycrystalline Pr-doped SrTiO3 ceramics employing a novel synthesis strategy which led to the highest ever reported values of PF among doped polycrystalline SrTiO3. It was found that the formation of Pr-rich grain boundary regions gives rise to an enhancement in carrier mobility. In this Letter, we investigate the electronic and thermal transport in Sr1-xPrxTiO3 ceramics in order to determine the optimum doping concentration and to evaluate the overall thermoelectric performance. Simultaneous enhancement in the thermoelectric power factor and reduction in thermal conductivity in these samples resulted in more than 30% improvement in the dimensionless thermoelectric figure of merit (ZT) for the whole temperature range over all previously reported maximum values. Maximum ZT value of 0.35 was obtained at 500 °C.

Effect of CeO2 on TiC Morphology in Ni-Based Composite Coating

NASA Astrophysics Data System (ADS)

Cai, Yangchuan; Luo, Zhen; Chen, Yao

2018-03-01

The TiC/Ni composite coating with different content of CeO2 was fabricated on the Cr12MoV steel by laser cladding. The microstructure of cladding layers with the different content of CeO2 from the bottom to the surface is columnar crystal, cellular crystal, and equiaxed crystal. When the content of CeO2 is 0 %, the cladding layer has a coarse and nonuniform microstructure and TiC particles gathering in the cladding layer, and then the wear resistance was reduced. Appropriate rare-earth elements refined and homogenised the microstructure and enhanced the content of carbides, precipitated TiC particles and original TiC particles were spheroidised and refined, the wear resistance of the cladding layer was improved significantly. Excessive rare-earth elements polluted the grain boundaries and made the excessive burning loss of TiC particles that reduced the wear resistance of the cladding layer.

Crystal phase analysis of SnO{sub 2}-based varistor ceramic using the Rietveld method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreira, M.L.; Pianaro, S.A.; Andrade, A.V.C.

2006-09-15

A second addition of l mol% of CoO to a pre calcined SnO{sub 2}-based ceramic doped with 1.0 mol% of CoO, 0.05 mol% of Nb{sub 2}O{sub 5} and 0.05 mol% of Cr{sub 2}O{sub 3} promotes the appearance of a secondary phase, Co{sub 2}SnO{sub 4}, besides the SnO{sub 2} cassiterite phase, when the ceramic was sintered at 1350 deg. C/2 h. This was observed using X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray techniques. Rietveld refinement was carried out to quantify the phases present in the ceramic system. The results of the quantitative analysis were 97 wt.% SnO{sub 2}more » and 3 wt.% Co{sub 2}SnO{sub 4}. The microstructural analysis showed that a certain amount of cobalt ion remains into cassiterite grains.« less

Low temperature destruction of PCDD/Fs over V2O5-CeO2/TiO2 catalyst with ozone.

PubMed

Yu, Ming-Feng; Lin, Xiao-Qing; Yan, Mi; Li, Xiao-Dong; Chen, Tong; Yan, Jian-Hua

2016-09-01

Catalytic destruction of PCDD/Fs (polychlorinated dibenzo-p-dioxins and furans) over V2O5-CeO2/TiO2 catalyst was investigated at a low temperature range of 140-180 °C, in the absence and presence of ozone (200 ppm). Nano-TiO2 support was used to prepare the catalyst by step impregnation method. A stable PCDD/Fs-generating system was established to support the catalytic destruction tests. In the presence of ozone alone, destruction efficiencies of PCDD/Fs are between 32.2 and 43.1 % with temperature increasing from 140 to 180 °C. The activity of V2O5-CeO2/TiO2 catalyst alone on PCDD/Fs destruction is also studied. The increase of temperature from 140 to 180 °C enhances the activity of catalyst with destruction efficiencies increasing from 54.7 to 73.4 %. However, ozone addition greatly enhances the catalytic activity of V2O5-CeO2/TiO2 catalyst on PCDD/Fs decomposition. At 180 °C, the destruction efficiency of PCDD/Fs achieved with V2O5-CeO2/TiO2 catalyst and ozone is above 86.0 %. It indicates that the combined use of ozone and catalyst reduces the reaction temperature of PCDD/Fs oxidation and offers a new method to destroy PCDD/Fs with high destruction efficiency at a low temperature. Furthermore, the destruction efficiencies of 17 toxic PCDD/F congeners, achieved with ozone alone, catalyst alone, and catalyst/ozone are analyzed.

Blue emission of Eu 2+-doped translucent alumina

DOE PAGES

Yang, Yan; Zhang, Lihua; Kisslinger, Kim; ...

2015-08-21

Inorganic scintillators are very important in medical and industrial measuring systems in the detection and measurement of ionizing radiation. In addition to Ce 3+, a widely used dopant ion in oxide scintillators, divalent Europium (Eu 2+) has shown promise as a high-luminescence, fast-response luminescence center useful in the detection of ionizing radiation. In this research, aluminum oxide (Al 2O 3) was studied as a host material for the divalent europium ion. Polycrystalline samples of Eu 2+-doped translucent Al 2O 3 were fabricated, and room temperature luminescence behavior was observed. Al 2O 3 ceramics doped with 0.1 at% Eu 2+ weremore » fabricated with a relative density of 99.75% theoretical density and in-line transmittance of 22% at a wavelength of 800 nm. The ceramics were processed by a gel-casting method, followed by sintering under high vacuum. The gelling agent, a copolymer of isobutylene and maleic anhydride, is marketed under the commercial name ISOBAM, and has the advantage of simultaneously acting as both a gelling agent and as a dispersant. The microstructure and composition of the vacuum-sintered Eu 2+:Al 2O 3 were characterized by Scanning Electric Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy-dispersive X-ray spectroscopy (EDS). The phase composition was determined by X-ray diffraction measurements (XRD) combined with Rietveld analysis. The photoluminescence behavior of the Eu 2+:Al 2O 3 was characterized using UV light as the excitation source, which emitted blue emission at 440 nm. The radio-luminescence of Eu 2+:Al 2O 3 was investigated by illumination with X-ray radiation, showing three emission bands at 376 nm, 575 nm and 698 nm. Furthermore, multiple level traps at different depths were detected in the Eu 2+:Al 2O 3 by employing thermoluminescence measurements.« less

Environmentally friendly synthesis of CeO2 nanoparticles for the catalytic oxidation of benzyl alcohol to benzaldehyde and selective detection of nitrite

NASA Astrophysics Data System (ADS)

Tamizhdurai, P.; Sakthinathan, Subramanian; Chen, Shen-Ming; Shanthi, K.; Sivasanker, S.; Sangeetha, P.

2017-04-01

Cerium oxide nanoparticles (CeO2 NPs) are favorable in nanotechnology based on some remarkable properties. In this study, the crystalline CeO2 NPs are successfully prepared by an efficient microwave combustion (MCM) and conventional route sol-gel (CRSGM) methods. The structural morphology of the as-prepared CeO2 NPs was investigated by various spectroscopic and analytical techniques. Moreover, the XRD pattern confirmed the formation of CeO2 NPs as a face centered cubic structure. The magnetometer studies indicated the low saturation magnetization (23.96 emu/g) of CeO2 NPs for weak paramagnetic and high saturation magnetization (32.13 emu/g) of CeO2 NPs for super paramagnetic. After that, the oxidation effect of benzyl alcohol was investigated which reveals good conversion and selectivity. Besides, the CeO2 NPs modified glassy carbon electrode (GCE) used for the detection of nitrite with linear concentration range (0.02-1200 μM), low limit of detection (0.21 μM) and higher sensitivity (1.7238 μAμM-1 cm-2). However, the CeO2 NPs modified electrode has the fast response, high sensitivity and good selectivity. In addition, the fabricated electrode is applied for the determination of nitrite in various water samples. Eventually, the CeO2 NPs can be regarded as an effective way to enhance the catalytic activity towards the benzyl alcohol and nitrite.

Environmentally friendly synthesis of CeO2 nanoparticles for the catalytic oxidation of benzyl alcohol to benzaldehyde and selective detection of nitrite

PubMed Central

Tamizhdurai, P.; Sakthinathan, Subramanian; Chen, Shen-Ming; Shanthi, K.; Sivasanker, S.; Sangeetha, P.

2017-01-01

Cerium oxide nanoparticles (CeO2 NPs) are favorable in nanotechnology based on some remarkable properties. In this study, the crystalline CeO2 NPs are successfully prepared by an efficient microwave combustion (MCM) and conventional route sol-gel (CRSGM) methods. The structural morphology of the as-prepared CeO2 NPs was investigated by various spectroscopic and analytical techniques. Moreover, the XRD pattern confirmed the formation of CeO2 NPs as a face centered cubic structure. The magnetometer studies indicated the low saturation magnetization (23.96 emu/g) of CeO2 NPs for weak paramagnetic and high saturation magnetization (32.13 emu/g) of CeO2 NPs for super paramagnetic. After that, the oxidation effect of benzyl alcohol was investigated which reveals good conversion and selectivity. Besides, the CeO2 NPs modified glassy carbon electrode (GCE) used for the detection of nitrite with linear concentration range (0.02–1200 μM), low limit of detection (0.21 μM) and higher sensitivity (1.7238 μAμM−1 cm−2). However, the CeO2 NPs modified electrode has the fast response, high sensitivity and good selectivity. In addition, the fabricated electrode is applied for the determination of nitrite in various water samples. Eventually, the CeO2 NPs can be regarded as an effective way to enhance the catalytic activity towards the benzyl alcohol and nitrite. PMID:28406231

Origin of colossal dielectric response in (In + Nb) co-doped TiO2 rutile ceramics: a potential electrothermal material.

PubMed

Ke, Shanming; Li, Tao; Ye, Mao; Lin, Peng; Yuan, Wenxiang; Zeng, Xierong; Chen, Lang; Huang, Haitao

2017-08-31

(In + Nb) co-doped TiO 2 (TINO) rutile is an emerging material with a colossal dielectric permittivity (CP) and a low dielectric loss over wide temperature and frequency ranges. The electrical inhomogeneous nature of TINO ceramics is demonstrated by direct local current probing with high-resolution conductive atomic force microscopy (cAFM). The CP response in TINO is found to originate from the electron-pinned defect dipole induced conductive cluster effect and the electrode effect. Two types of dielectric relaxations are simultaneously observed due to these two effects. With the given synthesis condition, we found TINO shows a highly leaky feature that impairs its application as a dielectric material. However, the fast-temperature-rising phenomenon found in this work may open a new door for TINO to be applied as a potential electrothermal material with high efficiency, oxidation-proof, high temperature stability, and energy saving.

Role of CeO2 promoter in NiO/α-Al2O3 catalyst for dry reforming of methane

NASA Astrophysics Data System (ADS)

Loc, Luu Cam; Phuong, Phan Hong; Tri, Nguyen

2017-09-01

A series of Ni/α-Al2O3 (NiAl) catalysts promoted by CeO2 was prepared by co-impregnation methods with content of (NiO+CeO2) being in the range of 10-30 wt%. The NiO:CeO2 weight ratio was fluctuated at 1:1, 1:2 and 1:3. Several techniques, including X-ray powder diffraction (XRD), Hydrogen temperature-programmed reduction (H2-TPR), and transmission electron microscopy (TEM) were used to investigate catalysts' physico-chemical properties. The activity of these catalysts in dry reforming of CH4 was investigated at temperature range of 550-800 °C. The results revealed that the most suitable CeO2 promoted Ni catalyst contained 20 wt% of (NiO+CeO2) and NiO:CeO2 weight ratio of 1:2. The best catalytic performance of catalyst [20(1Ni2Ce)Al] due to a better reducibility resulted in a higher amount of free small particle NiO. At 700 °C and CH4:CO2 molar ratio of 1:1, the conversion of CH4 and CO2 on the most suitable CeO2 promoted Ni catalyst reached 86% and 67%, respectively; H2 and CO selectivity of 90% and H2:CO molar ratio of 1.15 were obtained. Being similar to MgO [1], promoter CeO2 could improve catalytic activity of Ni/α-Al2O3 catalyst at a lower range of temperature. Besides, both MgO and CeO2 had a great impact on improving coke resistance of Ni catalysts. At higher temperature, the role of CeO2 as well as MgO in preventing coke formation on catalyst was clarified by temperature-programmed oxidation (TPO) technique. Coke amount formed after 30-h TOS on 20(1Ni2Ce) catalyst was found to be 22.18 mgC/gcat, being less than on non-promoted catalyst (36.75 mgC/gcat), but more than on 20(1Ni2Mg)Al one (5.25 mgC/gcat).

Effects of rare earth ionic doping on microstructures and electrical properties of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xue, Renzhong; Department of Technology and Physics, Zhengzhou University of Light Industry, Zhengzhou 450002; Chen, Zhenping, E-mail: xrzbotao@163.com

2015-06-15

Graphical abstract: The dielectric constant decreases monotonically with reduced RE doping ion radius and is more frequency independent compared with that of pure CCTO sample. - Highlights: • The mean grain sizes decrease monotonically with reduced RE doping ionic radius. • Doping gives rise to the monotonic decrease of ϵ{sub r} with reduced RE ionic radius. • The nonlinear coefficient and breakdown field increase with RE ionic doping. • α of all the samples is associated with the potential barrier width rather than Φ{sub b}. - Abstract: Ca{sub 1–x}R{sub x}Cu{sub 3}Ti{sub 4}O{sub 12}(R = La, Nd, Eu, Gd, Er; xmore » = 0 and 0.005) ceramics were prepared by the conventional solid-state method. The influences of rare earth (RE) ion doping on the microstructure, dielectric and electrical properties of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics were investigated systematically. Single-phase formation is confirmed by XRD analyses. The mean grain size decreases monotonically with reduced RE ion radius. The EDS results reveal that RE ionic doping reduces Cu-rich phase segregation at the grain boundaries (GBs). Doping gives rise to the monotonic decrease of dielectric constant with reduced RE ionic radius but significantly improves stability with frequency. The lower dielectric loss of doped samples is obtained due to the increase of GB resistance. In addition, the nonlinear coefficient and breakdown field increase with RE ionic doping. Both the fine grains and the enhancement of potential barrier at GBs are responsible for the improvement of the nonlinear current–voltage properties in doped CCTO samples.« less

CeO2 nanoparticles induce no changes in phenanthrene toxicity to the soil organisms Porcellionides pruinosus and Folsomia candida.

PubMed

Tourinho, Paula S; Waalewijn-Kool, Pauline L; Zantkuijl, Irene; Jurkschat, Kerstin; Svendsen, Claus; Soares, Amadeu M V M; Loureiro, Susana; van Gestel, Cornelis A M

2015-03-01

Cerium oxide nanoparticles (CeO2 NPs) are used as diesel fuel additives to catalyze oxidation. Phenanthrene is a major component of diesel exhaust particles and one of the most common pollutants in the environment. This study aimed at determining the effect of CeO2 NPs on the toxicity of phenanthrene in Lufa 2.2 standard soil for the isopod Porcellionides pruinosus and the springtail Folsomia candida. Toxicity tests were performed in the presence of CeO2 concentrations of 10, 100 or 1000mg Ce/kg dry soil and compared with results in the absence of CeO2 NPs. CeO2 NPs had no adverse effects on isopod survival and growth or springtail survival and reproduction. For the isopods, LC50s for the effect of phenanthrene ranged from 110 to 143mg/kg dry soil, and EC50s from 17.6 to 31.6mg/kg dry soil. For the springtails, LC50s ranged between 61.5 and 88.3mg/kg dry soil and EC50s from 52.2 to 76.7mg/kg dry soil. From this study it may be concluded that CeO2 NPs have a low toxicity and do not affect toxicity of phenanthrene to isopods and springtails. Copyright © 2014 Elsevier Inc. All rights reserved.

Efficient lasing in Yb:(YLa){sub 2}O{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Snetkov, I L; Mukhin, I B; Palashov, O V

2015-02-28

A high-optical-quality sample of Yb{sub 0.1}Y{sub 1.7}La{sub 0.2}O{sub 3} ceramics is prepared using a recently developed technique of selfpropagating high-temperature synthesis of rare-earth-doped yttrium oxide nanopowder from acetate – nitrates of metals. Its optical and spectral characteristics are studied, and quasi-cw lasing at a wavelength of 1033 nm is achieved with a power of 7 W and a slope efficiency of 25%. (lasers)

Nanoparticle Precipitation in Irradiated and Annealed Ceria Doped with Metals for Emulation of Spent Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Weilin; Conroy, Michele A.; Kruska, Karen

Epsilon alloy precipitates have been observed with varied compositions and sizes in spent nuclear fuels, such as UO2. Presence of the inclusions, along with other oxide precipitates, gas bubbles and irradiation-induced structural defects, can significantly degrade the physical properties of the fuel. To predict fuel performance, a fundamental study of the precipitation processes is needed. This study uses ceria (CeO2) as a surrogate for UO2. Polycrystalline CeO2 films doped with Mo, Ru, Rh, Pd and Re (surrogate for Tc) were grown at 823 K using pulsed laser deposition, irradiated at 673 K with He+ ions, and subsequently annealed at highermore » temperatures. A number of methods, including transmission electron microscopy and atom probe tomography, were applied to characterize the samples. The results indicate that there is a uniform distribution of the doped metals in the as-grown CeO2 film. Pd particles of ~3 nm in size appear near dislocation edges after He+ ion irradiation to ~13 dpa. Thermal annealing at 1073 K in air leads to formation of precipitates with Mo and Pd around grain boundaries. Further annealing at 1373 K produces 70 nm sized precipitates with small grains at cavities.« less

In situ DRIFTS investigation of NH3-SCR reaction over CeO2/zirconium phosphate catalyst

NASA Astrophysics Data System (ADS)

Zhang, Qiulin; Fan, Jie; Ning, Ping; Song, Zhongxian; Liu, Xin; Wang, Lanying; Wang, Jing; Wang, Huimin; Long, Kaixian

2018-03-01

A series of ceria modified zirconium phosphate catalysts were synthesized for selective catalytic reduction of NO with ammonia (NH3-SCR). Over 98% NOx conversion and 98% N2 selectivity were obtained by the CeO2/ZrP catalyst with 20 wt.% CeO2 loading at 250-425 °C. The interaction between CeO2 and zirconium phosphate enhanced the redox abilities and surface acidities of the catalysts, resulting in the improvement of NH3-SCR activity. The in situ DRIFTS results indicated that the NH3-SCR reaction over the catalysts followed both Eley-Rideal and Langmuir-Hinshelwood mechanisms. The amide (sbnd NH2) groups and the NH4+ bonded to Brønsted acid sites were the important intermediates of Eley-Rideal mechanism.

The effect of fission-energy Xe ion irradiation on the structural integrity and dissolution of the CeO2 matrix