Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 75
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Carbohydr Polym ; 212: 21-29, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30832849

RESUMO

Synthetic polymers are easy to process and have excellent mechanical properties but low wettability and poor cell compatibility limit their applications in tissue scaffolding. In this study, a facile procedure was established to regenerate cellulose and calcium lactate (CaL) into a polycaprolactone (PCL) nanofibrous scaffold for tissue engineering applications. Briefly, varying amounts of lactic acid (LA) was mixed with the blend of PCL and cellulose acetate (CA) solutions and electrospun to fabricate an optimal composite PCL/CA/LA fibrous membrane. Later on, as-prepared membranes were treated with calcium hydroxide solution. This process simultaneously converted CA and LA contents into Cellulose and CaL, respectively. In situ regeneration of Cellulose and CaL into the composite fiber remarkably enhanced the biological and physicochemical properties of the composite fiber. This work provides a novel dual-channel strategy for simultaneous regeneration of biopolymer and bioactive molecule into the PCL nanofiber for regenerative medicine and tissue engineering applications.


Assuntos
Materiais Biocompatíveis/síntese química , Compostos de Cálcio/síntese química , Celulose/síntese química , Química Farmacêutica/métodos , Lactatos/síntese química , Nanofibras/química , Poliésteres/síntese química , Materiais Biocompatíveis/farmacologia , Compostos de Cálcio/farmacologia , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/fisiologia , Celulose/farmacologia , Humanos , Lactatos/farmacologia , Nanofibras/administração & dosagem , Poliésteres/farmacologia
2.
Ecotoxicol Environ Saf ; 168: 35-44, 2019 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-30384165

RESUMO

The LaFeO3 perovskite oxide decorated active carbon fibers (LFO-ACFs) based on cotton fabric waste were successfully synthesized through sol-gel loading and thermal treatment. LaFeO3 perovskite and cotton fabric waste were combined to an eco-friendly and cheap adsorbent, which could reuse the leftover materials of textile industry and realize their functional modification. The structural, morphology/microstructure and functional groups were investigated through X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Fourier Transform Infrared spectroscopy (FTIR), respectively. The XRD pattern suggested the cotton fabric matrix didn't influence the structure of LaFeO3 perovskite oxide. In SEM studies, LFO-ACFs still maintained fibrous shape of the raw cotton fibers, and the EDX analysis showed that the main elements of the prepared LFO-ACFs were La, Fe, O and C. The synthesized LFO-ACF was employed for adsorption of cational dye of Rhodamine B (RhB), and the effects of adsorption parameters, i.e. pH, contact time, solution temperature and initial concentration of dye, on adsorption behavior were investigated. Results suggested the adsorption performance of LFO-ACF for RhB was nearly not affected by solution pH and its maximum adsorption capacity fitted by the Langmuir isothermal model could attain 182.6 mg/g at 293 K. The adsorption kinetics followed the pseudo-second-order equation and the regeneration of LFO-ACF could be well realized through an easy pyrolysis method.


Assuntos
Compostos de Cálcio/síntese química , Óxidos/síntese química , Rodaminas/química , Adsorção , Carvão Vegetal/química , Concentração de Íons de Hidrogênio , Cinética , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Indústria Têxtil , Titânio , Eliminação de Resíduos Líquidos , Águas Residuárias/química , Poluentes Químicos da Água/química , Difração de Raios X
3.
Carbohydr Polym ; 199: 244-255, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-30143127

RESUMO

Scaffolds are crucial for bone tissue engineering since their compositions and properties could significantly affect the seeded cells' behavior. In this study, we developed an interpenetrating network hydrogel by utilizing Ca2+ from calcium silicate (CS) to simultaneously crosslink silk fibroin (SF) and sodium alginate (SA). Afterwards, the hydrogels were lyophilized to obtain scaffolds and systematically evaluated by physical characterizations, in vitro cytocompatibility and alkaline phosphatase (ALP) assay. We found that CS inside the porous structure of SF/CS/SA scaffolds could remarkably enhance hydrophilicity, degradation, compression resistance, bioactivity and pH of SF/CS/SA scaffolds. Scaffolds with CS concentrations of 25% and 12% (25/CS and 12/CS) could dominantly stimulate proliferation of bone marrow stromal cells (BMSCs). Besides, BMSCs cultured with 25/CS and 12/CS scaffolds showed high ALP activity, respectively. Consequently, this study suggested SF/CS/SA scaffolds possess potential in non-loading bone tissue engineering application.


Assuntos
Alginatos/farmacologia , Materiais Biocompatíveis/farmacologia , Compostos de Cálcio/química , Fibroínas/farmacologia , Células-Tronco Mesenquimais/efeitos dos fármacos , Silicatos/química , Tecidos Suporte/química , Alginatos/síntese química , Alginatos/química , Alginatos/metabolismo , Fosfatase Alcalina/metabolismo , Animais , Materiais Biocompatíveis/síntese química , Materiais Biocompatíveis/química , Materiais Biocompatíveis/metabolismo , Compostos de Cálcio/síntese química , Compostos de Cálcio/metabolismo , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Reagentes para Ligações Cruzadas/síntese química , Reagentes para Ligações Cruzadas/química , Reagentes para Ligações Cruzadas/metabolismo , Fibroínas/síntese química , Fibroínas/química , Fibroínas/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Fenômenos Mecânicos , Osteogênese/efeitos dos fármacos , Porosidade , Ratos , Silicatos/síntese química , Silicatos/metabolismo , Engenharia Tecidual/métodos
4.
Dent Mater ; 34(8): e214-e223, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29789161

RESUMO

OBJECTIVE: To synthetize calcium aluminate (C3A) and silver-containing C3A particles (C3A+Ag) testing their effects on the properties of a MTA-based endodontic sealer in comparison to an epoxy resin- and a calcium silicate-based sealer. METHODS: Pure C3A and C3A+Ag particles were synthesized by a chemical method and characterized using XRD to identify crystalline phases. SEM/EDS analysis investigated morphology, particle size, and elemental composition of particles. Setting time, flow, radiopacity, water sorption and solubility of commercial and modified sealers were evaluated according to ISO 6876/2012. The pH and ions release were measured using a pHmeter and a microwave induced plasma optical emission spectrometer. The inhibition of biofilm growth was evaluated by confocal laser scanning microscopy (CLSM). Data were rank transformed and analyzed by ANOVA and Tukey test (P<0.05). RESULTS: The C3A particles showed an irregular grain agglomerated structure with voids and pores. In C3A+Ag particles, Ag modified the material morphology, confirming the deposition of Ag. The physicochemical properties of the modified MTA-based sealer were similar to the commercial material, except for the significant increase in Ca+2 release. However, there was no Ag release. Setting time, flow, radiopacity, water sorption and solubility were adequate for all materials. All the materials showed alkaline pH. Antibiofilm effect was improved in the presence of C3A particles, while the biofilm inhibition was lower in the presence of Ag. SIGNIFICANCE: The modified sealer presented improved antibiofilm properties and calcium release, without dramatic effects on the other characteristics. It is expected a positive effect in its antimicrobial behavior.


Assuntos
Compostos de Alumínio/química , Compostos de Alumínio/síntese química , Compostos de Cálcio/química , Compostos de Cálcio/síntese química , Óxidos/química , Materiais Restauradores do Canal Radicular/síntese química , Silicatos/química , Prata/química , Biofilmes/efeitos dos fármacos , Combinação de Medicamentos , Resinas Epóxi/química , Concentração de Íons de Hidrogênio , Teste de Materiais , Microscopia Eletrônica de Varredura , Tamanho da Partícula , Solubilidade , Espectrometria por Raios X , Difração de Raios X
5.
J Endod ; 43(3): 425-432, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28231981

RESUMO

INTRODUCTION: The aim of this article was to analyze biocompatibility and bioactivity of new endodontic materials on the basis of nanosynthesized calcium silicates (ALBO-MPCA1 and ALBO-MPCA2) combined with different radiopacifiers in comparison with MTA+. METHODS: Morphology of the samples was studied by scanning electron microscopy, and the pH and ion release analysis were also assessed. Biocompatibility of materials' eluates (24-hour, 7-day, and 21-day) was conducted by using MTT test. Twelve New Zealand white rabbits were used for intraosseous implantation. Four calvarial defects per animal were created and filled with freshly prepared investigated materials. RESULTS: Samples mostly consisted of agglomerates built up from nanoparticles, preferably spherical and rod-like. There was no significant difference among pH values of materials' eluates after 24 hours (P > .05). The amount of calcium and aluminum ion release decreased, whereas the amount of magnesium and bismuth (ALBO-MPCA1, MTA+) and barium (ALBO-MPCA2) increased during 21-day period. The metabolic activity of cells increased after the extraction time, except in case of undiluted elutes of ALBO-MPCA2 and ALBO-MPCA1 (21-day). Histologic analysis of the samples revealed newly formed bone tissue with moderate inflammation for all investigated materials, which subsided during 90-day period to mild. Both MTA+ and ALBO-MPCA1 were in direct contact with the newly formed bone tissue. After 90 days, statistically significant difference in hard tissue formation was observed in comparison of MTA+ and ALBO-MPCA1 with control group (P < .05). CONCLUSIONS: Experimental materials ALBO-MPCA1 and ALBO-MPCA2 possess both biocompatibility and bioactivity. Because ALBO-MPCA1 provokes favorable biological response, it is especially good candidate for further clinical investigations.


Assuntos
Materiais Biocompatíveis , Osso e Ossos/efeitos dos fármacos , Compostos de Cálcio , Teste de Materiais , Silicatos , Compostos de Alumínio , Animais , Osso e Ossos/patologia , Compostos de Cálcio/síntese química , Compostos de Cálcio/química , Células Cultivadas , Implantação Dentária Endo-Óssea , Combinação de Medicamentos , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Nanopartículas , Óxidos , Coelhos , Materiais Restauradores do Canal Radicular/síntese química , Materiais Restauradores do Canal Radicular/química , Silicatos/síntese química , Silicatos/química , Difração de Raios X
6.
Top Curr Chem (Cham) ; 374(5): 59, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27573501

RESUMO

In recent years, a good number of methods have become available for the preparation of an important group of photoactive materials for applications in photocatalysis and solar cells. Nevertheless, the benefits derived from preparing those materials through unconventional approaches are very attractive from the green chemistry point of view. This critical review work is focused on sonication as one of these promising new synthetic procedures that allow control over size, morphology, nanostructure and tuning of catalytic properties. Ultrasound-based procedures offer a facile, versatile synthetic tool for the preparation of light-activated materials often inaccessible through conventional methods.


Assuntos
Nanoestruturas/química , Energia Solar , Compostos de Cálcio/síntese química , Compostos de Cálcio/química , Catálise , Óxidos/síntese química , Óxidos/química , Pirólise , Pontos Quânticos/química , Titânio/química , Raios Ultravioleta
7.
Sci Adv ; 2(7): e1600427, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27453945

RESUMO

The physical and chemical properties of Earth's mantle, as well as its dynamics and evolution, heavily depend on the phase composition of the region. On the basis of experiments in laser-heated diamond anvil cells, we demonstrate that Fe,Al-bearing bridgmanite (magnesium silicate perovskite) is stable to pressures over 120 GPa and temperatures above 3000 K. Ferric iron stabilizes Fe-rich bridgmanite such that we were able to synthesize pure iron bridgmanite at pressures between ~45 and 110 GPa. The compressibility of ferric iron-bearing bridgmanite is significantly different from any known bridgmanite, which has direct implications for the interpretation of seismic tomography data.


Assuntos
Alumínio/química , Compostos de Cálcio/química , Ferro/química , Silicatos de Magnésio/química , Óxidos/química , Titânio/química , Compostos de Cálcio/síntese química , Silicatos de Magnésio/síntese química , Óxidos/síntese química , Pressão , Temperatura , Difração de Raios X
8.
J Nanosci Nanotechnol ; 16(1): 844-50, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27398534

RESUMO

Organometal trihalide perovskite based solar cells have attracted great attention worldwide since their power conversion efficiency (PCE) have risen to over 15% within only 3 years of development. Comparing with other types of perovskite solar cells, mesostructured perovskite solar cells based on CH3NH3Pbl3 as light harvesting material have already demonstrated remarkable advance in performance and reproducibility. Here, we reported a mesoscopic TiO2/CH3NH3Pbl3 heterojunction solar cell with uniform perovskite thin film prepared via solvent-assisted solution processing method. The best performing device delivered photocurrent density of 20.11 mA cm⁻², open-circuit voltage of 1.02 V, and fill factor of 0.70, leading to a PCE of 14.41%. A small anomalous hysteresis in the J-V curves was observed, where the PCE at forward scan was measured to be 84% of the PCE at reverse scan. Based on a statistical analysis, the perovskite solar cells prepared by the reported method exhibited reproducible and high PCE, indicating its promising application in the fabrication of low-cost and high-efficiency perovskite solar cells.


Assuntos
Compostos de Cálcio/química , Compostos de Cálcio/síntese química , Óxidos/química , Óxidos/síntese química , Energia Solar , Titânio/química , Porosidade
9.
J Nanosci Nanotechnol ; 16(4): 3973-6, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-27451749

RESUMO

Novel warm-white emitting phosphors CaIn2O4:Dy3+ co-doped with Gd3+, Zn2+, or Al3+ ions were prepared by solid state reaction. In this paper, a strategy of co-doping with different ions was used with the aim of affecting the luminescence properties of CaIn204:0.6%Dy3+ under NUV excitation. The luminescence intensities of CaIn2O4:0.6%Dy3+ were enhanced by 0.2% Gd3+ or 0.2% Zn2+ ions co-doping under 367 nm excitation, but lowered by co-doping with 0.2% Al3+ ions. Furthermore, the chromaticity coordinates of CaIn2O4:0.6%Dy3+ can be tuned from the cold-white region to warm-white region with Gd3+ or Zn2+ ions co-doping. These findings show that CaIn2O4:0.6%Dy3+,0.2% Gd3+, and CaIn2O4:0.6%Dy3+,0.2% Zn2+ have potential application value as new warm-white LED phosphors.


Assuntos
Compostos de Cálcio/síntese química , Medições Luminescentes/métodos , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Cristalização/métodos , Luz , Luminescência , Teste de Materiais , Tamanho da Partícula
10.
J Nanosci Nanotechnol ; 16(2): 1676-9, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27433645

RESUMO

A solution combustion process for the synthesis of perovskite (CaTiO3) powders is described. Perovskite is one of the crystalline host matrics for the disposal of high-level radioactive wastes (HLW) because it immobilizes Sr and Lns elements by forming solid solutions. Solution combustion synthesis, which is a self-sustaining oxi-reduction reaction between nitrate and organic fuel, the exothermic reaction, and the heat evolved convert the precursors into their corresponding oxide products above 1100 degrees C in air. To investigate the effects of amino acid on the combustion reaction, various types of fuels were used; a glycine, amine and carboxylic ligand mixture. Sr, La and Gd-nitrate with equivalent amounts of up to 20% of CaTiO3 were mixed with Ca and Ti nitrate and amino acid. X-ray diffraction analysis, SEM and TEM were conducted to confirm the formed phases and morphologies. While powders with an uncontrolled shape are obtained through a general oxide-route process, Ca(Sr, Lns)TiO3 powders with micro-sized soft agglomerates consisting of nano-sized primary particles can be prepared using this method.


Assuntos
Compostos de Cálcio , Cerâmica , Óxidos , Resíduos Radioativos , Estrôncio/química , Titânio , Compostos de Cálcio/síntese química , Compostos de Cálcio/química , Cerâmica/síntese química , Cerâmica/química , Óxidos/síntese química , Óxidos/química , Titânio/química
12.
Molecules ; 21(4): 542, 2016 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-27120590

RESUMO

UNLABELLED: In this work, we describe the role of the different layers in perovskite solar cells to achieve reproducible, ~16% efficient perovskite solar cells. We used a planar device architecture with PEDOT: PSS on the bottom, followed by the perovskite layer and an evaporated C60 layer before deposition of the top electrode. No high temperature annealing step is needed, which also allows processing on flexible plastic substrates. Only the optimization of all of these layers leads to highly efficient and reproducible results. In this work, we describe the effects of different processing conditions, especially the influence of the C60 top layer on the device performance.


Assuntos
Compostos de Cálcio/síntese química , Óxidos/síntese química , Compostos de Cálcio/química , Temperatura Baixa , Óxidos/química , Plásticos/química , Energia Solar , Titânio/química
13.
Langmuir ; 32(13): 3226-33, 2016 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-27010624

RESUMO

Bone regeneration and scaffold degradation do not usually follow the same rate, representing a daunting challenge in bone repair. Toward this end, we propose to use an external field such as light (in particular, a tissue-penetrating near-infrared light) to precisely monitor the degradation of the mineralized scaffold (demineralization) and the formation of apatite mineral (mineralization). Herein, CaTiO3:Yb(3+),Er(3+)@bioactive glass (CaTiO3:Yb(3+),Er(3+)@BG) nanofibers with upconversion (UC) photoluminescence (PL) were synthesized. Such nanofibers are biocompatible and can emit green and red light under 980 nm excitation. The UC PL intensity is quenched during the bone-like apatite formation on the surface of the nanofibers in simulated body fluid; more mineral formation on the nanofibers induces more rapid optical quenching of the UC PL. Furthermore, the quenched UC PL can recover back to its original magnitude when the apatite on the nanofibers is degraded. Our work suggests that it is possible to optically monitor the apatite mineralization and demineralization on the surface of nanofibers used in bone repair.


Assuntos
Materiais Biocompatíveis/efeitos da radiação , Nanofibras/efeitos da radiação , Materiais Biocompatíveis/síntese química , Materiais Biocompatíveis/toxicidade , Materiais Biomiméticos , Compostos de Cálcio/síntese química , Compostos de Cálcio/efeitos da radiação , Compostos de Cálcio/toxicidade , Células Cultivadas , Érbio/química , Érbio/efeitos da radiação , Érbio/toxicidade , Luminescência , Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/efeitos dos fármacos , Nanofibras/química , Nanofibras/toxicidade , Óxidos/síntese química , Óxidos/efeitos da radiação , Óxidos/toxicidade , Titânio/efeitos da radiação , Titânio/toxicidade , Itérbio/química , Itérbio/efeitos da radiação , Itérbio/toxicidade
14.
J Am Chem Soc ; 138(11): 3687-93, 2016 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-26974387

RESUMO

We have designed a nitroaromatic photochemical protecting group that absorbs visible light in the violet-blue range. The chromophore is a dinitro derivative of bisstyrylthiophene (or BIST) that absorbs light very effectively (ε440 = 66,000 M(-1) cm(-1) and two-photon cross section of 350 GM at 775 nm). We developed a "caged calcium" molecule by conjugation of BIST to a Ca(2+) chelator that upon laser flash photolysis rapidly releases Ca(2+) in <0.2 ms. Using the patch-clamp method the optical probe, loaded with Ca(2+), was delivered into acutely isolated mouse cardiac myocytes, where either one- and two-photon uncaging of Ca(2+) induced highly local or cell-wide physiological Ca(2+) signaling events.


Assuntos
Compostos de Cálcio/química , Tiofenos/química , Compostos de Cálcio/síntese química , Quelantes/química , Ácido Egtázico/química , Luz , Processos Fotoquímicos , Tiofenos/síntese química
15.
ACS Appl Mater Interfaces ; 8(13): 8608-19, 2016 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-26998964

RESUMO

We envision that CaWO4 (CWO) nanocrystals have the potential for use in biomedical imaging and therapy because of the unique ways this material interacts with high-energy radiation. These applications, however, require development of nanoparticle (NP) formulations that are suitable for in vivo applications; primarily, the formulated nanoparticles should be sufficiently small, chemically and biologically inert, and stable against aggregation under physiological conditions. The present study demonstrates one such method of formulation, in which CWO nanoparticles are encapsulated in bioinert block copolymer (BCP) micelles. For this demonstration, we prepared three different CWO nanocrystal samples having different sizes (3, 10, and 70 nm in diameter) and shapes (elongated vs truncated rhombic). Depending on the specific synthesis method used, the as-synthesized CWO NPs contain different surfactant materials (citric acid or cetyltrimethylammonium bromide or a mixture of oleic acid and oleylamine) in the coating layers. Regardless of the type of surfactant, the original surfactant coating can be replaced with a new enclosure formed by BCP materials using a solvent-exchange method. Two types of BCPs have been tested: poly(ethylene glycol-block-n-butyl acrylate) (PEG-PnBA) and poly(ethylene glycol-block-D,L-lactic acid) (PEG-PLA). Both BCPs are able to produce fully PEGylated CWO NPs that are stable against aggregation under physiological salt conditions for very long periods of time (at least three months). The optical and radio luminescence properties of both BCP-encapsulated and surfactant-coated CWO NPs were extensively characterized. The study confirms that the BCP coating structure does not influence the luminescence properties of CWO NPs.


Assuntos
Compostos de Cálcio/química , Sistemas de Liberação de Medicamentos , Nanopartículas/química , Tensoativos/química , Compostos de Tungstênio/química , Compostos de Cálcio/síntese química , Compostos de Cálcio/uso terapêutico , Cetrimônio , Compostos de Cetrimônio/química , Química Farmacêutica , Humanos , Lactatos/síntese química , Lactatos/química , Lactatos/uso terapêutico , Micelas , Nanopartículas/uso terapêutico , Tamanho da Partícula , Polietilenoglicóis/síntese química , Polietilenoglicóis/química , Polietilenoglicóis/uso terapêutico , Radiação , Tensoativos/síntese química , Tensoativos/uso terapêutico , Compostos de Tungstênio/síntese química , Compostos de Tungstênio/uso terapêutico
16.
J Hazard Mater ; 295: 119-26, 2015 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-25897693

RESUMO

This work reported on the synthesis of a series of nitrogen doped Ca2Nb2O7 with tunable nitrogen content that were found to be efficient and green noble-metal-free catalysts toward catalytic reduction of p-nitrophenol. XPS and ESR results indicated that the introduction of nitrogen in Ca2Nb2O7 gave rise to a large number of defective nitrogen and oxygen species. Defective nitrogen and oxygen species were found to play synergetic roles in the reduction of p-nitrophenol. The underlying mechanism is completely different from those reported for metallic nanoparticles. Moreover, the more negative conduction band edge potential enabled nitrogen doped Ca2Nb2O7 to show photo-synergistic effects that could accelerate the reduction rate toward p-nitrophenol under UV light irradiation. This work may provide a strategy for tuning the catalytic performance by modulating the chemical composition, electronic structure as well as surface defect chemistry.


Assuntos
Compostos de Cálcio/síntese química , Nióbio/química , Nitrofenóis/química , Catálise , Nitrogênio/química
17.
ACS Comb Sci ; 16(11): 614-23, 2014 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-25321326

RESUMO

A fast parallel screening method based on combinatorial chemistry (combichem) has been developed and applied in the screening tests of perovskite-based oxide (PBO) catalysts for NO oxidation to hit a promising PBO formulation for the oxidation of NO to NO2. This new method involves three consecutive steps: oxidation of NO to NO2 over a PBO catalyst, adsorption of NOx onto the PBO and K2O/Al2O3, and colorimetric assay of the NOx adsorbed thereon. The combichem experimental data have been used for determining the oxidation activity of NO over PBO catalysts as well as three critical parameters, such as the adsorption efficiency of K2O/Al2O3 for NO2 (α) and NO (ß), and the time-average fraction of NO included in the NOx feed stream (ξ). The results demonstrated that the amounts of NO2 produced over PBO catalysts by the combichem method under transient conditions correlate well with those from a conventional packed-bed reactor under steady-state conditions. Among the PBO formulations examined, La0.5Ag0.5MnO3 has been identified as the best chemical formulation for oxidation of NO to NO2 by the present combichem method and also confirmed by the conventional packed-bed reactor tests. The superior efficiency of the combichem method for high-throughput catalyst screening test validated in this study is particularly suitable for saving the time and resources required in developing a new formulation of PBO catalyst whose chemical composition may have an enormous number of possible variations.


Assuntos
Compostos de Cálcio/química , Técnicas de Química Combinatória/métodos , Óxido Nítrico/química , Óxidos/química , Titânio/química , Adsorção , Compostos de Cálcio/síntese química , Catálise , Técnicas de Química Combinatória/economia , Técnicas de Química Combinatória/instrumentação , Desenho de Equipamento , Dióxido de Nitrogênio/química , Oxirredução , Óxidos/síntese química
18.
J Hazard Mater ; 280: 478-86, 2014 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-25199504

RESUMO

Betafite of composition [(Ca,U)2(Ti,Nb,Ta)2O7] was prepared via a solid state synthesis route. The synthesis was shown to be sensitive to initial reactant ratios, the atmosphere used (oxidising, neutral, reducing) and time. The optimum conditions for the synthesis of betafite were found to be heating the reactants required at 1150°C for 48 h under an inert gas atmosphere. XRD characterisation revealed that the synthesised betafite contained minor impurities. EPMA analysis of a sectioned surface showed very small regions of Ca-free betafite on grain boundaries as well as minor rutile impurities. Some heterogeneity between the Nb:Ta ratio was observed by quantitative EPMA but was generally within the nomenclature requirements stated for betafite. SEM analysis revealed the synthesised betafite was comprised mostly of hexaoctohedral crystals of ∼ 3 µm in diameter. XPS analysis of the sample showed that the uranium in the synthesised betafite was predominately present in the U(5+) oxidation state. A minor amount of U(6+) was also detected which was possibly due to surface oxidation.


Assuntos
Compostos de Cálcio/síntese química , Nióbio/química , Óxidos/síntese química , Resíduos Radioativos , Urânio/química , Espectroscopia Fotoeletrônica , Tantálio/química , Titânio/química
19.
Waste Manag Res ; 32(12): 1178-85, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25012303

RESUMO

This work explored several synthesis routes to obtain calcium silicates from different calcium-rich and silica-rich industrial residues. Larnite, wollastonite and calcium silicate chloride were successfully synthesised with moderate heat treatments below standard temperatures. These procedures help to not only conserve natural resources, but also to reduce the energy requirements and CO2 emissions. In addition, these silicates have been successfully tested as carbon dioxide sequesters, to enhance the viability of CO2 mineral sequestration technologies using calcium-rich industrial by-products as sequestration agents. Two different carbon sequestration experiments were performed under ambient conditions. Static experiments revealed carbonation efficiencies close to 100% and real-time resolved experiments characterised the dynamic behaviour and ability of these samples to reduce the CO2 concentration within a mixture of gases. The CO2 concentration was reduced up to 70%, with a carbon fixation dynamic ratio of 3.2 mg CO2 per g of sequestration agent and minute. Our results confirm the suitability of the proposed synthesis routes to synthesise different calcium silicates recycling industrial residues, being therefore energetically more efficient and environmentally friendly procedures for the cement industry.


Assuntos
Compostos de Cálcio/síntese química , Dióxido de Carbono/química , Sequestro de Carbono , Resíduos Industriais/análise , Reciclagem/métodos , Silicatos/síntese química , Cálcio/química , Compostos de Cálcio/química , Silicatos/química
20.
Inorg Chem ; 53(14): 7089-91, 2014 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-25000156

RESUMO

A novel perovskite oxide, CaCu3Rh4O12, has been synthesized under high-pressure and high-temperature conditions (15 GPa and 1273 K). Rietveld refinement of synchrotron X-ray powder diffraction data indicates that this compound crystallizes in a cubic AA'3B4O12-type perovskite structure. Synchrotron X-ray absorption and photoemission spectroscopy measurements reveal that the Cu and Rh valences are nearly trivalent. The spectroscopic analysis based on calculations suggests that the appropriate ionic model of this compound is Ca(2+)Cu(∼2.8+)3Rh(∼3.4+)4O12, as opposed to the conventional Ca(2+)Cu(2+)3Rh(4+)4O12. The uncommon valence state of this compound is attributed to the relative energy levels of the Cu 3d and Rh 4d orbitals, in which the large crystal-field splitting energy of the Rh 4d orbitals is substantial.


Assuntos
Compostos de Cálcio/síntese química , Óxidos/química , Compostos de Cálcio/química , Temperatura Alta , Óxidos/síntese química , Difração de Pó , Pressão , Titânio/química , Espectroscopia por Absorção de Raios X
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA