Síntese e caracterização de alfa-fosfato de zircônio(IV) contendo agregados de cobre metálico

The alpha-zirconium (IV) hydrogenphosphate (alpha-ZrP) has received great attention in the last years due to its properties like ion exchange, intercalation, ionic conductivity and catalytic activity. This work reports a method to produce metallic copper clusters on alpha-ZrP to be used as catalysts in petrochemical processes. It was found that the solids were non-crystalline regardless of the uptake of copper and the reduction. The specific surface area increased as a consequence of the increase of the interlayer distance to accept the copper ions between the layers. During the reduction, big clusters of copper (0,5-11µ) with different sizes and shapes were produced.

Aspectos estruturais relacionados ao processo de troca iônica no niobato lamelar K4Nb6O17

The niobate with formula K4Nb6O17 has a layered structure formed by stacked negative sheets and exchangeable cations in the interlayer region. In this study we discuss some structural aspects related to the ion exchange in layered hexaniobate based on X-ray diffractometry and vibrational Raman spectroscopy data. Hexaniobate has two distinct interlayer regions and the potassium ions of one interlayer in particular are preferably exchanged by other cations, leading to an interstratified material.

Microwave Slot Transmission Line Filled with Ferroelectric and Ferromagnetic Layers

Now when the technology is fast developing it is very important to investigate new hybrid structures. One way is to use ferrite ferroelectric layered structures. Theoretical and experimental investigation of such structures was made. These structures have advantages of both layers and it is possible to tune the behavior of this structure by external electric and magnetic field. But these structures have some disadvantages connected with presence of thick ferroelectric layer. One way to overcome this problem is to use slotline. So this is another new way to create hybrid ferrite ferroelectric structures, but it is needed to create new theory and find experimental proof that the behavior of these structures can be tuned with external magnetic and electric fields.

Nanocompósitos eletroativos de poli-o-metoxianilina e polissacarídeos naturais

In this work we take advantage of the polyelectrolyte character of some Brazilian native gums to fabricate electrically conductive, nanostructured films. The gums Sterculia urens, (caraia), Sterculia striata (chicha) or Anadenanthera macrocarpa Benth were assembled in conjunction with poly(o-methoxyaniline) (POMA) in the form of layered nanostructured films using the layer-by-layer (LbL) technique. All the LbL films displayed a well-defined electroactivity, as confirmed via cyclic voltammetry. In comparison to POMA LbL films fabricated with conventional polyelectrolytes (viz. poly(vinyl sulfonic acid)-PVS), the presence of the gums in the LbL films increased remarkably the electrochemical stability of the films.

Hidróxidos duplos lamelares: nanopartículas inorgânicas para armazenamento e liberação de espécies de interesse biológico e terapêutico

Studies about the inorganic nanoparticles applying for non-viral release of biological and therapeutic species have been intensified nowadays. This work reviews the preparation strategies and application of layered double hydroxides (LDH) as carriers for storing, carrying and control delivery of intercalated species as drugs and DNA for gene therapy. LDH show low toxicity, biocompatibility, high anion exchange capacity, surface sites for functionalization, and a suitable equilibrium between chemical stability and biodegradability. LDH can increase the intercalated species stability and promote its sub-cellular uptake for biomedical purposes. Concerning the healthy field, LDH have been evaluated for clinical diagnosis as a biosensor component.

Catalisadores heterogêneos para a produção de monoésteres graxos (biodiesel)

The recent increase in the world biodiesel demand, along with the need to reduce costs while improving the environmental sustainability of the entire biodiesel production chain, have led to the search for heterogeneous catalysts that would be efficient and highly amenable to recycling. Many classes of materials have been tested for these purposes. Among these are zeolites, ion-exchange resins, inorganic oxides, guanidines, metal complexes, layered compounds and ionic liquids. This review article describes the structure, properties, synthesis and performance of compounds that are catalytic active in both esterification and transesterification reactions.

Adsorção de arsênio(V) pelo compósito magnético hidrotalcita: óxido de ferro

In this work, hydrotalcite, a layered double hydroxide, had its adsorption and ion exchange properties combined with the magnetic properties of iron oxide to produce a magnetic adsorbent, HT-Fe. The removal of As(V) by a HT-Fe adsorbent was evaluated under various conditions. The Kinetic process was well described by a pseudo-second order rate model. The maximum adsorption capacity, calculated with the Langmuir model showed to be dependent on pH, reaching values of 24.09, 10.19 and 7.44 mg g-1, respectively, for pH values of 4.0, 7.0 and 9.0. The inhibition by competition of anions is dependent on the type of ionic species.

Remoção dos hormônios 17β-estradiol e 17α-etinilestradiol de soluções aquosas empregando turfa decomposta como material adsorvente

This paper describes the adsorption of 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) from aqueous solution by decomposed peat. The peat presented a good adsorption process, close to 76.2% for E2 removal and approximately 55.0% for EE2. Moreover, the results indicated a probable multi-layered process. Adsorption isotherms were well fitted by Freundlich model. The data were evaluated considering the pseudo-first-order and pseudo-second-order approaches, being the second more significant mechanism in the rate-controlling step. Thermodynamic data revealed that hormones adsorption onto peat is spontaneous under the employed experimental conditions. The results confirmed the potential of this adsorbent to be employed for effluents treatment.

Hidróxidos duplos lamelares à base de escória de alto forno

Hydrotalcite like compounds (HT) were prepared by co-precipitation (Mg/Al = 3.5), using an acid solution with blast furnace slag and MgCl2.6H2O and aqueous solutions of NaOH. The following synthesis variables were investigated: temperature (30 and 45 ºC) and pH (9 and 12). Depending of the temperature two systems were observed: Mg-Al-CO3 (T = 30 ºC); Mg-Al-Cl-CO3 (T = 45 ºC). An increase in the pH of synthesis and Mg2+ concentration produced HTs well-crystallized and with greater values of all cell parameters. The study showed the potentiality of BFS in the synthesis of well-crystallized LDHs without the presence of other crystalline phases.

Comparação estrutural entre amostras de materiais tipo hidrotalcita obtidas a partir de diferentes rotas de síntese

Three samples of hydrotalcite-like materials (HTC) were synthesized and their structural characteristics were compared with two HTCs obtained commercially. Thermal analyses, FT-IR, PXRD and textural analyses were used to investigate the structural differences between commercial and synthetic samples. Particularly, the memory effect was observed at temperature higher than 600 ºC. The Rietveld refinements were obtained with expressive accuracy and the statistical parameters of goodness of fit are quite satisfactory. In conclusion, the procedures adopted in synthesis of HTC produced crystalline materials with high surface area materials.

Remoção de cromo (VI) de soluções aquosas utilizando o compósito magnético calcinado hidrotalcita-óxido de ferro: estudo cinético e de equilíbrio termodinâmico

In this work, hydrotalcite, a layered double hydroxide, had its ion exchange properties combined with the magnetic properties of iron oxide to produce a magnetic adsorbent, HT-Fe 500. These magnetic composites can be used as adsorbents for anionic contaminants in water and subsequently removed from the medium by a simple magnetic process. Removal of chromium (VI) from aqueous solutions using HT-Fe 500 was achieved using batch adsorption experiments. The adsorption capacity, calculated with the Langmuir-Freundlich model showed to be dependent on temperature, reaching values of 25.93 and 48.31 mg g-1, respectively, for temperatures of 25 and 30 ºC.

Síntese e caracterização de nanocompósitos de poliestireno/hidroxissal lamelar

Polystyrene/layered hydroxide salt (LHS) modified with sodium dodecyl sulfate was synthesized by in situ polymerization. The materials synthesized were characterized by gravimetry, X-ray diffraction (XRD), thermogravimetry analyses (TGA), differential scanning calorimetry (DSC) and the flammability test (FT). XRD demonstrated that synthesized nanocomposites in all compositions studied showed poor global dispersion of LHS in polystyrene. TGA showed a slight decrease in thermal stability. DSC curves showed that the glass transition temperature of polystyrene and nanocomposites were similar. The FT showed that the nanocomposite with low load of LHS exhibited good results.

Dissulfeto de molibdênio, um material multifuncional e surpreendente: doze anos depois

In 2002, a review article was published in which molybdenum disulfide properties were discussed. The last sentence of the article read as follows: "Based on that described above, we can conclude that in spite of the vast applications of molybdenum disulfide in several industrial branches, many of the potential applications need to be investigated in the future". Since 2002, novel properties of molybdenum disulfide have been described which promise to revolutionize science. The objective of the present review paper was to provide an overview of the processes of 2H-MoS2 exfoliation and properties of the single layers, reported mainly in the last decade.

ESTERIFICAÇÃO E TRANSESTERIFICAÇÃO SIMULTÂNEAS DE ÓLEOS ÁCIDOS UTILIZANDO CARBOXILATOS LAMELARES DE ZINCO COMO CATALISADORES BIFUNCIONAIS

Palm oil containing 40% fatty acids was converted to methyl esters using zinc carboxylates as the esterification/transesterification catalyst. The reaction was optimized using a factorial design in which the effects of the alcohol:fatty acids molar ratio (MRAG) and the catalyst concentration (CAT) were assessed. The best conversion was achieved with CAT at 4 wt% and MRAG at 4:1. However, the solid catalyst presented significant structural changes after use. For instance, laurate anions were replaced by carboxylates of higher molecular mass, leading to the formation of a new catalytically active layered structure. Also, the glycerin obtained as a co-product contained 86 wt% glycerol.

Java-kieleen perustuvien www-sovellusten suorituskyvyn testaus ja parantaminen

Testauksesta on tullut oleellinen, yhä tärkeämpi sovelluskehitysprojektien osa. Sovelluksilta vaaditaan luotettavuutta kaikilla niiden toiminnan osa-alueilla. Suorituskykyyn liittyvät asiat ovat keskeinen osa näitä vaatimuksia erityisesti, kun kyse on Internetissä toimivista www-sovelluksista. Aluksi työssä esitellään erilaisia sovellusten testausmenetelmiä. Siinä kerrotaan yleisimmistä menetelmistä, joiden avulla pyritään sovelluksista löytämään vääränlaiset toimintatavat suhteessa niiden määriteltyihin toimintatapoihin. Testauksen tulosten avulla pystytään keskittymään oikeisiin kohtiin sovellusten toiminnan korjaamisessa. Työssä analysoidaan www-sovellusten rakennetta yleisen kerrosarkkitehtuurin eri kerrosten ominaisuuksia ja niihin sisältyviä keskeisimpiä sovellusten suorituskykyyn vaikuttavia tekijöitä kuvaillen. Näiden, www-sovellusten eri osien suorituskykyyn vaikuttavien ominaisuuksien perusteella esitellään esimerkkejä, kuinka Java-kieleen perustuvien www-sovellusten suorituskykyä voidaan parantaa. Lisäksi työssä kuvataan, kuinka erityisesti ilmaisella Apache JMeter-sovelluksella voidaan Java-kieleen perustuvien www-sovellusten suorituskykyä mitata. Työn tuloksena esitellään lopuksi suorituskyvyn testaus- ja parannusprosessi. Sen tarkoitus on selkeyttää erityisesti Java-kieleen perustuvien www-sovellusten suorituskyvyn testauksessa ja parannuksessa huomioon otettavia asioita.