Journal articles: 'Microporous /Mesoporous Oxides'

1

Gounder, Rajamani. "Hydrophobic microporous and mesoporous oxides as Brønsted and Lewis acid catalysts for biomass conversion in liquid water." Catal. Sci. Technol. 4, no. 9 (2014): 2877–86. http://dx.doi.org/10.1039/c4cy00712c.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Skadtchenko, B. O., and D. M. Antonelli. "2005 Pure or Applied Inorganic Chemistry Award Lecture — Host–guest inclusion chemistry of electroactive, mesoporous transition metal oxides oxidation and 1-D confinement in one step and why amorphous is better." Canadian Journal of Chemistry 84, no. 3 (March 1, 2006): 371–83. http://dx.doi.org/10.1139/v06-021.

Full text

Abstract:

The flexible oxidation states of mesoporous Nb, Ta, and Ti oxides make them unique amongst porous materials allowing reaction pathways and cascades that are not possible for mesoporous silica or microporous materials such as zeolites. This electronic activity coupled with the 20–30 Å pores and the amorphous wall structure, which provides greater bandwidth (W) and hence an even greater range of redox potentials, leads to a rich variety of host–guest inclusion chemistry, which serves as an unprecedented 1-D analogue to layered 2-D host–guest inclusion reactions studied for decades. In this paper we survey a series of reactions between these mesoporous hosts and a wide variety of organic and organometallic guest species including alkali fullerides, cobaltocene, and other organometallic sandwhich species, and discuss the electronic and magnetic properties of the resulting composites.Key words: mesoporous materials, semiconductors, fullerides, superconductors, oxides, nanomaterials, metallocenes.

APA, Harvard, Vancouver, ISO, and other styles

3

Hu, Xin, Boris O. Skadtchenko, Michel Trudeau, and David M. Antonelli. "Hydrogen Storage in Chemically Reducible Mesoporous and Microporous Ti Oxides." Journal of the American Chemical Society 128, no. 36 (September 2006): 11740–41. http://dx.doi.org/10.1021/ja0639766.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Jiao, Feng, and Peter G. Bruce. "Two- and Three-Dimensional Mesoporous Iron Oxides with Microporous Walls." Angewandte Chemie International Edition 43, no. 44 (November 12, 2004): 5958–61. http://dx.doi.org/10.1002/anie.200460826.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Jiao, Feng, and Peter G. Bruce. "Two- and Three-Dimensional Mesoporous Iron Oxides with Microporous Walls." Angewandte Chemie 116, no. 44 (November 12, 2004): 6084–87. http://dx.doi.org/10.1002/ange.200460826.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Valentini, Antoninho, Neftalı́ L. V. Carreño, Luiz F. D. Probst, Edson R. Leite, and Elson Longo. "Synthesis of Ni nanoparticles in microporous and mesoporous Al and Mg oxides." Microporous and Mesoporous Materials 68, no. 1-3 (March 8, 2004): 151–57. http://dx.doi.org/10.1016/j.micromeso.2003.12.021.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Qin, Hong, Zhi Jia Tan, and Qing Wang. "Research on Adsorption of H₂S by Oil Shale Ash." Advanced Materials Research 463-464 (February 2012): 133–37. http://dx.doi.org/10.4028/www.scientific.net/amr.463-464.133.

Full text

Abstract:

The ash of Huadian oil shale is made to remove H2S in this experiment. XRD and nitrogen adsorption experiments are used to analyze the physical and chemical properties of the ash, the results show that the ash of oil shale has many metal and nonmetal oxides, and also has much microporous and mesoporous, all above is helpful to remove H2S. The sample is modified by different ways to see the change of adsorption capacity. the sample which is modified by alkali and sprinkler is the best adsorbent, but the sample which is modified by microwave does not increase the removal ability obviously.

APA, Harvard, Vancouver, ISO, and other styles

8

Li, Yongfeng, Jiaojiao Su, Guiping Li, and Xiufeng Meng. "Facile Synthesis of Super-Microporous Titania–Alumina with Tailored Framework Properties." Materials 13, no. 5 (March 3, 2020): 1126. http://dx.doi.org/10.3390/ma13051126.

Full text

Abstract:

Super-microporous material (pore size 1–2 nm) can bridge the pore size gap between the zeolites (<1 nm) and the mesoporous oxides (>2 nm). A series of super-microporous titania–alumina materials has been successfully prepared via a facile one-pot evaporation-induced self-assembly (EISA) strategy by different solvents using fatty alcohol polyoxyethylene ether (AEO-7) as the template. Moreover, no extra acid or base is added in our synthesis process. When titanium isopropylate is used as the titanium source, these materials exhibit high BET surface areas (from 275 to 396 m2/g) and pore volumes (from 0.14 to 0.18 cm3/g). The sample prepared using methanol as the solvent shows the largest Brunauer–Emmett–Teller (BET) surface area of 396 m2/g. When tetrabutyl titanate is used as the titanium source, these materials exhibit high BET surface areas (from 282 to 396 m2/g) and pore volumes (from 0.13 to 0.18 cm3/g). The sample prepared using ethanol as the solvent shows the largest BET surface area of 396 m2/g.

APA, Harvard, Vancouver, ISO, and other styles

9

Soler-Illia, Galo J. de A. A., Clément Sanchez, Bénédicte Lebeau, and Joël Patarin. "Chemical Strategies To Design Textured Materials: from Microporous and Mesoporous Oxides to Nanonetworks and Hierarchical Structures." Chemical Reviews 102, no. 11 (November 2002): 4093–138. http://dx.doi.org/10.1021/cr0200062.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Gong, Bo, Qing Peng, Jesse S. Jur, Christina K. Devine, Kyoungmi Lee, and Gregory N. Parsons. "Sequential Vapor Infiltration of Metal Oxides into Sacrificial Polyester Fibers: Shape Replication and Controlled Porosity of Microporous/Mesoporous Oxide Monoliths." Chemistry of Materials 23, no. 15 (August 9, 2011): 3476–85. http://dx.doi.org/10.1021/cm200694w.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Liu, Zhufang, Gretchen M. Crumbaugh, and Robert J. Davis. "Effect of Structure and Composition on Epoxidation of HexeneCatalyzed by Microporous and Mesoporous Ti–Si Mixed Oxides." Journal of Catalysis 159, no. 1 (March 1996): 83–89. http://dx.doi.org/10.1006/jcat.1996.0066.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Gounder, Rajamani. "ChemInform Abstract: Hydrophobic Microporous and Mesoporous Oxides as Bronsted and Lewis Acid Catalysts for Biomass Conversion in Liquid Water." ChemInform 45, no. 40 (September 18, 2014): no. http://dx.doi.org/10.1002/chin.201440290.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Khandaker, Tasmina, Muhammad Sarwar Hossain, Palash Kumar Dhar, Md Saifur Rahman, Md Ashraf Hossain, and Mohammad Boshir Ahmed. "Efficacies of Carbon-Based Adsorbents for Carbon Dioxide Capture." Processes 8, no. 6 (May 30, 2020): 654. http://dx.doi.org/10.3390/pr8060654.

Full text

Abstract:

Carbon dioxide (CO2), a major greenhouse gas, capture has recently become a crucial technological solution to reduce atmospheric emissions from fossil fuel burning. Thereafter, many efforts have been put forwarded to reduce the burden on climate change by capturing and separating CO2, especially from larger power plants and from the air through the utilization of different technologies (e.g., membrane, absorption, microbial, cryogenic, chemical looping, and so on). Those technologies have often suffered from high operating costs and huge energy consumption. On the right side, physical process, such as adsorption, is a cost-effective process, which has been widely used to adsorb different contaminants, including CO2. Henceforth, this review covered the overall efficacies of CO2 adsorption from air at 196 K to 343 K and different pressures by the carbon-based materials (CBMs). Subsequently, we also addressed the associated challenges and future opportunities for CBMs. According to this review, the efficacies of various CBMs for CO2 adsorption have followed the order of carbon nanomaterials (i.e., graphene, graphene oxides, carbon nanotubes, and their composites) < mesoporous -microporous or hierarchical porous carbons < biochar and activated biochar < activated carbons.

APA, Harvard, Vancouver, ISO, and other styles

14

Dziuba, M., L. Mushinskii, R. Brovko, and V. Doluda. "Surface Characterization of Zn-modified H-ZSM-5 Zeolites." Bulletin of Science and Practice 6, no. 6 (June 15, 2020): 48–54. http://dx.doi.org/10.33619/2414-2948/55/06.

Full text

Abstract:

The surface properties of microporous aluminosilicates are of primary importance in chemical technology and catalysis. The determination of the surface area, pore volume, and pore size and size distribution for microporous aluminosilicates is a complex scientific and technical problem related to both accurate measurements and the correct choice of a mathematical model that adequately describes the physicochemical processes occurring on the test surface. Currently, t-plot, as-plot, Dubinin-Radushkevich model, Dillimore model and Horvath-Kawazoe model are frequently used, each of which has certain advantages and certain disadvantages, to determine micropores in the material. It should be noted that t-plot model found the most frequent use. This is a consequence of the good correlation of volumes and pore areas obtained with its help with theoretically calculated values for various materials. In this point, the article provides a calculation of Zn-modified zeolite H-ZSM-5 surface properties using the t-plot model, for which nitrogen adsorption isotherms were originally obtained. The nitrogen adsorption isotherms of the initial zeolite H-ZSM-5 can be attributed to the first type of isotherms, and the modified samples to the fourth type of isotherms according to Brunauer’s classification. It was found that the initial zeolite is a typical microporous zeolite of H-ZSM-5 type, while the modified samples are micro- and mesoporous materials. Calculation of nitrogen adsorption isotherms using the t-plot model allows to determine the volume of micro and mesopores, which varied in the range of 0.11–0.14 cm3/g for micropores and 0.04–0.07 cm3/g for mesopores. Based on the obtained data, it can be concluded that when zeolite is modified with zinc at a zinc concentration less than 15 wt.%, micropores are not filled with zinc, while mesopores are predominantly filled and an additional surface of zinc oxide is formed on the external surface of the zeolite.

APA, Harvard, Vancouver, ISO, and other styles

15

Sadek, Renata, Karolina A. Chalupka, Pawel Mierczynski, Waldemar Maniukiewicz, Jacek Rynkowski, Jacek Gurgul, Magdalena Lasoń-Rydel, Sandra Casale, Dalil Brouri, and Stanislaw Dzwigaj. "The Catalytic Performance of Ni-Co/Beta Zeolite Catalysts in Fischer-Tropsch Synthesis." Catalysts 10, no. 1 (January 13, 2020): 112. http://dx.doi.org/10.3390/catal10010112.

Full text

Abstract:

The influence of nickel introduction on the catalytic performance of cobalt micro- and mesoporous Beta zeolite catalysts in Fischer–Tropsch Synthesis was studied. Catalysts containing 3 wt% of nickel and 10 wt% of cobalt were prepared by co-impregnation and sequential impregnation and comprehensively characterized by XRD, XPS, NH3-TPD, TPR-H2 and TEM EDX techniques. Neither the dealumination of Beta zeolite nor the incorporation of Co and Ni affected its structure, as shown by XRD and BET investigations. The presence of nickel results in the decrease in the temperature of the cobalt oxide reduction, evidenced by TPR-H2 and the increase of CO conversion. Among all the tested catalysts, the best catalytic properties in FTS showed that based on microporous dealuminated zeolites with a very high CO conversion, near 100%, and selectivity to liquid products of about 75%. In case of dealuminated samples, the presence of Ni decreased the selectivity to liquid products. All catalysts under study showed high resistance to deactivation during the whole time of synthesis (24 h). The very high stability of nickel-cobalt based Beta catalysts was probably due to the hydrogen spillover from metallic nickel particles to cobalt oxides, which decreased re-oxidation of the active phase, sintering and the creation of the carbon on the catalyst surface. Moreover, the presence of Ni on the surface of cobalt-based Beta catalysts could obstruct the formation of graphitic carbon and, in consequence, delay the deactivation of the catalyst.

APA, Harvard, Vancouver, ISO, and other styles

16

López-Hernández, Irene, Jesús Mengual, and Antonio Eduardo Palomares. "The Influence of the Support on the Activity of Mn–Fe Catalysts Used for the Selective Catalytic Reduction of NOx with Ammonia." Catalysts 10, no. 1 (January 1, 2020): 63. http://dx.doi.org/10.3390/catal10010063.

Full text

Abstract:

Mono and bimetallic Mn–Fe catalysts supported on different materials were prepared and their catalytic performance in the NH3–SCR of NOx was investigated. It was shown that Mn and Fe have a synergic effect that enhances the activity at low temperature. Nevertheless, the activity of the bimetallic catalysts depends very much on the support selected. The influence of the support on the catalyst activity has been studied using materials with different textural and acid–base properties. Microporous (BEA-zeolite), mesoporous (SBA15 and MCM41) and bulk (metallic oxides) materials with different acidity have been used as supports for the Mn–Fe catalysts. It has been shown that the activity depends on the acidity of the support and on the surface area. Acid sites are necessary for ammonia adsorption and high surface area produces a better dispersion of the active sites resulting in improved redox properties. The best results have been obtained with the catalysts supported on alumina and on beta zeolite. The first one is the most active at low temperatures but it presents some reversible deactivation in the presence of water. The Mn–Fe catalyst supported on beta zeolite is the most active at temperatures higher than 350 °C, without any deactivation in the presence of water and with a 100% selectivity towards nitrogen.

APA, Harvard, Vancouver, ISO, and other styles

17

Han, Guodong, Xin Wang, Jia Yao, Mi Zhang, and Juan Wang. "The Application of Indium Oxide@CPM-5-C-600 Composite Material Derived from MOF in Cathode Material of Lithium Sulfur Batteries." Nanomaterials 10, no. 1 (January 20, 2020): 177. http://dx.doi.org/10.3390/nano10010177.

Full text

Abstract:

Due to the “shuttle effect”, the cycle performance of lithium sulfur (Li-S) battery is poor and the capacity decays rapidly. Replacing lithium-ion battery is the maximum problem to be overcome. In order to solve this problem, we use a cage like microporous MOF(CPM-5) as a carbon source, which is carbonized at high temperature to get a micro-mesoporous carbon composite material. In addition, indium oxide particles formed during carbonization are deposited on CPM-5 structure, forming a simple core-shell structure CPM-5-C-600. When it is used as the cathode of Li-S battery, the small molecule sulfide can be confined in the micropores, while the existence of large pore size mesopores can provide a channel for the transmission of lithium ions, so as to improve the conductivity of the material and the rate performance of the battery. After 100 cycles, the specific capacity of the battery can be still maintained at 650 mA h·g−1 and the Coulombic efficiency is close to 100%. When the rate goes up to 2 C, the first discharge capacity not only can reach 1400 mA h·g−1, but also still provides 500 mA h·g−1 after 200 cycles, showing excellent rate performance.

APA, Harvard, Vancouver, ISO, and other styles

18

Lin, Cunlong, Deping Wang, and Song Ye. "Synthesis of micro-mesoporous glass-analcime composite structure with soda–lime–silica glass as raw material." Functional Materials Letters 12, no. 03 (May 16, 2019): 1950021. http://dx.doi.org/10.1142/s1793604719500218.

Full text

Abstract:

The micro-mesoporous composite phase structure of the analcime and the glass phase was successfully synthesized at 200∘C by using hydrothermal method, in which the soda–lime–silica glass was used as the silica source and the sodium hydroxide and aluminum oxide were used as additive. The TEM and SEM results showed that the obtained rod-shaped analcime was growing on the surface of glass particles. Thermogravimetric analysis indicated that they are stable and the adsorption isotherm shape indicated the coexistence of micropores and mesopores.

APA, Harvard, Vancouver, ISO, and other styles

19

Cao, Yingze, Wentao Zhai, Xiang Zhang, Shuxi Li, Lin Feng, and Yen Wei. "Mesoporous SiO2-Supported Pt Nanoparticles for Catalytic Application." ISRN Nanomaterials 2013 (March 10, 2013): 1–7. http://dx.doi.org/10.1155/2013/745397.

Full text

Abstract:

SiO2 nanoparticles have been synthesized by combining Stober’s method and nonsurfactant process. The diameters and pore sizes can be controlled by altering the template and its concentration. Mesoporous SiO2 obtained this way has extremely large surface area compared with most oxide supports, which benefits the catalytic performance. Pt nanoparticles were in situ grown on and in mesoporous SiO2 nanoparticles with low amount of the metal and high load ratio. Furthermore, we firstly developed a novel route, called “one-pot” method, to prepare Pt/SiO2 catalyst where mesoporous silica preparing and Pt loading occurred in one step. This method is more efficient in saving reagent, since it can prevent Pt loss. In the meantime, it enables the template to reduce agent. The catalytic activity of Pt/SiO2 samples was measured by CO oxidation. It is indicated that the supporting silica with mesopores is more active than silica with micropores.

APA, Harvard, Vancouver, ISO, and other styles

20

Li, Jiangbo, Feifei Zhang, Lukuan Zong, Xiangyu Wang, and Huijuan Wei. "Improved Catalytic Propylene Epoxidation for Extruded Micrometer TS-1: Introducing Mesopores and Macropores Insides the Crystals." Catalysts 11, no. 1 (January 14, 2021): 113. http://dx.doi.org/10.3390/catal11010113.

Full text

Abstract:

In the paper, mesopores and macropores are introduced inside the crystals of micrometer microporous titanium silicate-1 (TS-1) to solve the problem of active site coverage and mass transfer during extrusion. Hierarchically porous titanium silicalite-1 (HPTS-1) was acquired by treating micrometer microporous TS-1 with TPABr and ethanolamine. Extruded HPTS-1 maintained greatly superior catalytic performance and possessed high mechanical strength. Characterization results showed that extruded HPTS-1 possessed macroporous, mesoporous structure inside the crystals. These abundant pores are not only beneficial for diffusion reactants, but also make Ti-peroxo species (η2), active oxidation sites in TS-1/H2O2 system become much more reactive. The formula of extruded HPTS-1 was optimized using an orthogonal experiment. The maximum strength of extruded HPTS-1 was up to 200 N/cm, the highest yield of propylene oxide was 92.5% and the specific rate was up to 41.9%. The research provides a scientific basis for producing extruded catalysts with excellent catalytic performance and high mechanical strength in industrial applications.

APA, Harvard, Vancouver, ISO, and other styles

21

Vendange, V., and Ph Colomban. "How to tailor the porous structure of alumina and aluminosilicate gels and glasses." Journal of Materials Research 11, no. 2 (February 1996): 518–28. http://dx.doi.org/10.1557/jmr.1996.0062.

Full text

Abstract:

Optically clear monolithic (OCM) gels of mesoporous aluminosilicates (average pore diameter 3.6 nm) and alumina (6 nm) have been prepared by slow hydrolysis-polycondensation of alkoxides and converted into OCM mesoporous glasses by heating. In order to change the properties, different ways of modifying the pore size and structure are proposed. We show that addition of boron oxide reduces the average pore diameter. A higher effect can be obtained by addition of a surfactant. In this case the mesoporous matrix becomes microporous (d < 2 nm). Another way of modifying the pore structure consists of introducing nanoprecipitates inside the porosity by an impregnation process. Modifications of the porous structure are different in alumina and aluminosilicates.

APA, Harvard, Vancouver, ISO, and other styles

22

Liu, Liang, David K. Wang, Peter Kappen, Dana L. Martens, Simon Smart, and João C. Diniz da Costa. "Hydrothermal stability investigation of micro- and mesoporous silica containing long-range ordered cobalt oxide clusters by XAS." Physical Chemistry Chemical Physics 17, no. 29 (2015): 19500–19506. http://dx.doi.org/10.1039/c5cp02309b.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Díaz, Isabel, Verónica González-Peña, Carlos Márquez-Alvarez, and Joaquín Pérez-Pariente. "Transmission Electron Microscopy Study of the Porous Structure of Aluminas Synthesized by Non-Ionic Surfactant Templating Route." Collection of Czechoslovak Chemical Communications 68, no. 10 (2003): 1937–48. http://dx.doi.org/10.1135/cccc20031937.

Full text

Abstract:

Organized mesoporous and microporous aluminas have been synthesized by a sol-gel route in non-aqueous media using poly(oxyethylene) block polymers as directing agents. Gel compositions adjusted to obtain direct micelles (in 1,4-dioxane solution) and reverse micelles (in cyclohexane solution) were tested. The influence of synthesis conditions, such as temperature, solvent, use of additives or chemical modification of the precursor, on the alumina porous structure has been analysed by transmission electron microscopy (TEM). Mesoporous aluminas with a pore structure originated by the cross-linking of corrugated oxide-hydroxide platelets of nanometric size were obtained using aluminum sec-butoxide as precursor. The addition of ammonium fluoride or amines to the synthesis gel, as well as higher calcination temperatures, caused a decrease in the surface area due to the condensation of the crystallites into a dense porous structure composed of small polycrystalline agglomerates. Microporous aluminas with higher density and a disordered but isotropic porous structure were obtained by chemical modification of the alkoxide precursor with chelating agents such as ethyl acetoacetate or triethanolamine.

APA, Harvard, Vancouver, ISO, and other styles

24

Ali, A. A., F. A. Al-Sagheer, and M. I. Zaki. "Surface Texture of Microcrystalline Tunnel-Structured Manganese(IV) Oxides: Nitrogen Sorptiometry and Electron Microscopy Studies." Adsorption Science & Technology 20, no. 7 (September 2002): 619–32. http://dx.doi.org/10.1260/02636170260504314.

Full text

Abstract:

Three different modifications of manganese(IV) oxide, viz. cryptomelane, nsutite and todorokite-like, were synthesized by hydrothermal methods. The bulk chemical composition, phase composition, crystalline structure and particle morphology of the resulting materials were determined by thermogravimetry, atomic absorption spectroscopy, X-ray diffractometry, infrared spectroscopy and scanning electron microscopy. The surface chemical composition, texture and structure were assessed using X-ray photoelectron microscopy, nitrogen sorptiometry and high-resolution electron microscopy. The results highlighted the hydrothermal conditions under which such tunnel-structured modifications of manganese(IV) oxide can be successfully synthesized. Moreover, they revealed that (i) the bulk was microcrystalline, (ii) the crystallites were either fibrils (cryptomelane and nsutite) or rod-like (todorokite) with low-index exposed facets, (iii) the surface chemical composition mostly reflected that of the bulk and (iv) the surface texture was linked with high specific areas, slit-shaped mesopores associated with particle interstices and micropores which allowed surface accessibility to the bulk tunnels of the test oxides. The application of such test oxides as shape-selective oxidation catalysts appears worthy of investigation.

APA, Harvard, Vancouver, ISO, and other styles

25

Catlow, C. R. A., S. A. French, A. A. Sokol, and J. M. Thomas. "Computational approaches to the determination of active site structures and reaction mechanisms in heterogeneous catalysts." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 363, no. 1829 (April 15, 2005): 913–36. http://dx.doi.org/10.1098/rsta.2004.1529.

Full text

Abstract:

We apply quantum chemical methods to the study of active site structures and reaction mechanisms in mesoporous silica and metal oxide catalysts. Our approach is based on the use of both molecular cluster and embedded cluster (QM/MM) techniques, where the active site and molecular complex are described using density functional theory (DFT) and the embedding matrix simulated by shell model potentials. We consider three case studies: alkene epoxidation over the microporous TS-1 catalyst; methanol synthesis on ZnO and Cu/ZnO and C–H bond activation over Li-doped MgO.

APA, Harvard, Vancouver, ISO, and other styles

26

Kevan, Larry, and Martin Hartmann. "ChemInform Abstract: Pulsed ESR of Microporous and Mesoporous Oxide Materials." ChemInform 30, no. 22 (June 15, 2010): no. http://dx.doi.org/10.1002/chin.199922312.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Sun, Lu, and Jun Tang. "Welding partially reduced graphene oxides by MOFs into micro–mesoporous hybrids for high-performance oil absorption." RSC Advances 11, no. 49 (2021): 30980–89. http://dx.doi.org/10.1039/d1ra05644a.

Full text

Abstract:

PRGOs were interlocked by UiO-66-NH2 nanoparticles into PRGO@UiO-66-NH2, in which MOFs provide micropores and PRGOs skeletons provide mesopores. The PRGO@UiO-66-NH2-laden MFs exhibit the high absorption selectivity of oil over water.

APA, Harvard, Vancouver, ISO, and other styles

28

MARINOIU, Adriana, Radu ANDREI, Irina VAGNER, Violeta NICULESCU, Felicia BUCURA, Marius CONSTANTINESCU, and Elena CARCADEA. "One Step Synthesis of Au Nanoparticles Supported on Graphene Oxide Using an Eco-Friendly Microwave-Assisted Process." Materials Science 26, no. 3 (February 27, 2020): 249–54. http://dx.doi.org/10.5755/j01.ms.26.3.21857.

Full text

Abstract:

Microwave (MW) assisted processes become more and more used in the synthesis and alteration of graphene materials. This technique brings some various advantages compare to the classical ones because it is a green, low-cost, environmentally-friendly process. Moreover, no toxic solvent is necessary for the production of high-quality graphene-based materials. This eco-friendly process has recently received important attention as uniform, fast, energy efficient and scalable approach to synthesis noble metals supported on graphene oxide. A facile, rapid, low cost and efficient method to prepare gold supported on reduced graphene oxide (Au/rGO) is presented in this paper. The Au/rGO samples were produced using the microwave power of 800 W and two temperatures, 60 and 80°C, for 30 minutes only. The physical characterization showed that the Au nanoparticles were grafting on the graphene surface. Additionally, the nitrogen adsorption–desorption isotherms show a high pore volume and specific surface suggesting that a larger mesoporous volume have been achieved. The presence of interconnections between micropores and mesopores is beneficial to the mass transport process in PEMFC by creating a facile access of the reactants. Moreover, the accelerated stability tests (AST) of the catalysts showed that the catalysts are stable and no remarkable change in the shape of the voltammetry curve could be observed after 200 cycles.

APA, Harvard, Vancouver, ISO, and other styles

29

Masoumifard, Nima, Kyoungsoo Kim, Serge Kaliaguine, Pablo M. Arnal, and Freddy Kleitz. "Synthesis of microporous/mesoporous core–shell materials with crystalline zeolitic shell and supported metal oxide silica core." CrystEngComm 18, no. 23 (2016): 4452–64. http://dx.doi.org/10.1039/c6ce00286b.

Full text

Abstract:

Engineered silica@zeolite core–shell composites, possessing a hierarchical porosity in a shape selective manner, were synthesised by deposition of silicalite-1 nanocrystals over various mesoporous silica spheres, in either pure form or loaded with metal guest species.

APA, Harvard, Vancouver, ISO, and other styles

30

Tan, Xiaoying, Pingping Dong, Hongping Min, Jinxue Luo, Wenhai Huang, Xiaodong Wang, Qingqing Li, and Qile Fang. "“Sea Anemone”-like CeFe Oxides for High-Efficient Phosphate Removal." Water 14, no. 15 (August 7, 2022): 2445. http://dx.doi.org/10.3390/w14152445.

Full text

Abstract:

The excessive release of phosphorus is a prime culprit for eutrophication and algal bloom in the aquatic environment, and there is always an urgent need to develop effective methods to deal with phosphorus pollution. Ce-based oxide is a type of compelling adsorbent for phosphate removal, and a self-templating strategy is used to construct high-performance Ce-based oxides for phosphate adsorption in this study. A “sea anemone”-like CeFe cyanometallate (CM) with a 3D microstructure is fabricated to provide a precursor for synthesizing CeFe-based oxides (CeFe-CM-T) by high-temperature pyrolysis. The as-prepared CeFe-CM-T maintains the “sea anemone” morphology well and has abundant micropores/mesopores, which render its superior phosphate adsorption capacity 1~2 orders of magnitude higher than that of the commercial CeO2 and Fe3O4 materials. Moreover, CeFe-CM-T shows high selectivity for phosphate removal when it co-exists with other anions and natural organic matter and exhibits excellent recycling performance. It demonstrates that both Ce3+ and Ce4+ are reserved in the oxides, where Ce3+ serves as the main active site for phosphate capture, which forms stable Ce-PO4 compounds via a ligand-exchange mechanism. Thus, the self-templating strategy using CM as a precursor is a potential method for synthesizing porous Ce-based oxides for phosphate removal.

APA, Harvard, Vancouver, ISO, and other styles

31

Khalil, L. B., M. N. Alaya, N. Sh Petro, and R. M. M. Abo Elenein. "Changes in the Porous Texture of Hydrous Ferric Oxide on Adsorption of Transition Metal Ions: Adsorption Mechanism." Adsorption Science & Technology 20, no. 5 (June 2002): 501–9. http://dx.doi.org/10.1260/026361702320644789.

Full text

Abstract:

In general, it was found that loading hydrous ferric oxide (HFO) with transition metal ions led to a decrease in both the internal surface and external surface area. The micropore volume in the microporous samples (obtained by heating the oxide at 50°C and 200°C) and the total pore volume in both samples and in the mesoporous sample (obtained by heating the oxide at 400°C) also decreased. The mean pore radius, however, appeared to be little altered in all the samples. The observed effects cannot be interpreted on the basis of the adsorption of unhydrated transition metal ions, nor by assuming precipitation of these ions as hydroxides inside the pores. The only other possibility was the assumption that the adsorption of these ions was accompanied by the adsorption of relatively more strongly adsorbed water (not removed during evacuation of the samples) and/or the transformation of water already present in the oxide to strongly adsorbed water. This conclusion was confirmed by comparing the water loss at 100°C and 200°C in the original and metal-loaded HFO samples.

APA, Harvard, Vancouver, ISO, and other styles

32

Liu, Zi Yu, Yue Qi, Ying Xu Wei, Zong Bin Wu, and Zhong Min Liu. "Synthesis of Mesoporous Zr-P-Al Materials with High BET Specific Surface Area without Calcination." Advanced Materials Research 287-290 (July 2011): 2094–101. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.2094.

Full text

Abstract:

A mesostructured zirconium oxide was synthesized hydrothermally using cetyltrimethylammonium bromide (CTAB) as the structure-directing agent and ZrSO4. 4H2O as the reactant. Subsequent post-synthetic treatment with H3PO4followed by the treatment with AlCl3solutions resulted in mesoporous Zr-P-Al materials, which exhibited high BET specific surface area before calcination. The phosphoric acid concentrationaffected the textual data of the resulting Zr-P and Zr-P-Al materials greatly. 0.1-0.5 M H3PO4increased obviously the long-range order of the as-synthesized Zr-P materials while 0.76 M H3PO4decreased it. After calcination at 773 K, the Zr-P materials turned to nonporous materials except the one synthesized by 0.5 M H3PO4, which showed micropores with a BET specific surface area of 147 m2/g. Further treating the Zr-P materials (synthesized from different concentration of phosphoric acid) with the same amount of AlCl3solution resulted in mesoporous Zr-P-Al materials, but the long-range order of which decreased when the H3PO4concentration increased. Similarly, the BET specific surface area of the above-mentioned Zr-P-Al materials decreased from 462 m2/g for 0.25 M H3PO4to 394 m2/g for 0.5 M H3PO4and finally to 332 m2/g for 0.76 M H3PO4after calcination at 773 K, while the pore size increased gradually from 3.0 to 3.5 nm. It was found that about 90% of the CTAB had been removed during the AlCl3treatment and that the as-synthesized Zr-P-Al materials exhibited high BET specific surface area as well as mesopores. The AlCl3amount is another factor affecting the textual data of the uncalcined Zr-P-Al materials besides the H3PO4concentration. With the phosphoric acid concentration of 0.25 M, the BET specific surface area of the as-synthesized Zr-P-Al materials increased from 477 m2/g to as high as 734 m2/g with the increasing AlCl3amount before it decreased from then on.

APA, Harvard, Vancouver, ISO, and other styles

33

Liang, Xinhua, Miao Yu, Jianhua Li, Ying-Bing Jiang, and Alan W. Weimer. "Ultra-thin microporous–mesoporous metal oxide films prepared by molecular layer deposition (MLD)." Chemical Communications, no. 46 (2009): 7140. http://dx.doi.org/10.1039/b911888h.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Bellmann, Andrea, Christine Rautenberg, Ursula Bentrup, and Angelika Brückner. "Determining the Location of Co2+ in Zeolites by UV-Vis Diffuse Reflection Spectroscopy: A Critical View." Catalysts 10, no. 1 (January 15, 2020): 123. http://dx.doi.org/10.3390/catal10010123.

Full text

Abstract:

UV–Vis spectroscopy as well as in situ FTIR spectroscopy of pyridine and CO adsorption were applied to determine the nature of Co species in microporous, mesoporous, and mixed oxide materials like Co–ZSM-5, Co/Na–ZSM-5, Co/Al–SBA-15, and Co/Al2O3–SiO2. Because all sample types show comparable UV–Vis spectra with a characteristic band triplet, the former described UV–Vis band deconvolution method for determination and quantification of individual cationic sites in the zeolite appears doubtful. This is also confirmed by results of pyridine and CO adsorption revealing that all Co–zeolite samples contain two types of Co2+ species located at exchange positions as well as in oxide-like clusters independent of the Co content, while in Co/Al–SBA-15 and Co/Al2O3–SiO2 only Co2+ species in oxide-like clusters occur. Consequently, the measured UV–Vis spectra represent not exclusively isolated Co2+ species, and the characteristic triplet band is not only related to γ-, β-, and α-type Co2+ sites in the zeolite but also to those dispersed on the surface of different oxide supports. The study demonstrates that for proper characterization of the formed Co species, the use of complementary methods is required.

APA, Harvard, Vancouver, ISO, and other styles

35

Dugkhuntod, Pannida, and Chularat Wattanakit. "A Comprehensive Review of the Applications of Hierarchical Zeolite Nanosheets and Nanoparticle Assemblies in Light Olefin Production." Catalysts 10, no. 2 (February 18, 2020): 245. http://dx.doi.org/10.3390/catal10020245.

Full text

Abstract:

Light olefins including ethylene, propylene and butylene are important building blocks in petrochemical industries to produce various chemicals such as polyethylene, polypropylene, ethylene oxide and cumene. Traditionally, light olefins are produced via a steam cracking process operated at an extremely high temperature. The catalytic conversion, in which zeolites have been widely used, is an alternative pathway using a lower temperature. However, conventional zeolites, composed of a pure microporous structure, restrict the diffusion of large molecules into the framework, resulting in coke formation and further side reactions. To overcome these problems, hierarchical zeolites composed of additional mesoporous and/or macroporous structures have been widely researched over the past decade. In this review, the recent development of hierarchical zeolite nanosheets and nanoparticle assemblies together with opening up their applications in various light olefin productions such as catalytic cracking, ethanol dehydration to ethylene, methanol to olefins (MTO) and other reactions will be presented.

APA, Harvard, Vancouver, ISO, and other styles

36

NINNESS, BRIAN J., LUKE D. DOUCETTE, BEN MCCOOL, and CARL P. TRIPP. "DEVELOPMENT OF MATERIALS AND SAMPLING METHODS FOR IR-BASED DETECTION OF TOXIC COMPOUNDS IN WATER." International Journal of High Speed Electronics and Systems 17, no. 04 (December 2007): 697–708. http://dx.doi.org/10.1142/s0129156407004904.

Full text

Abstract:

A detection approach based on the principles of Fourier Transform Infrared Spectroscopy (FTIR) is presented for the trace level detection of toxic compounds in water. The main advantages of this approach are that it operates in heterogeneous aqueous environments, provides fast detection (< 10 min), and exhibits high sensitivity/selectivity to nonvolatile toxic materials with minimal false alarms. The key enablers to using FTIR for aqueous-based detection is the development of a selective and robust sampling protocol coupled to a miniaturized portable FTIR unit. The sampling approaches involve synthesizing and tailoring microporous, mesoporous, and nonporous metal oxide powders/films that are amenable for in situ FTIR measurements. In this paper we provide an overview of the material synthesis and surface modification strategies, and present results obtained using these materials for the low level detection of the organophosphate pesticide phosmet. Phosmet is used as a surrogate for the nerve agent VX.

APA, Harvard, Vancouver, ISO, and other styles

37

Allwar, Allwar, Asih Setyani, Ulul Sugesti, and Khusna Afifah Fauzani. "Physical-chemical Characterization of Nano-Zinc Oxide/Activated Carbon Composite for Phenol Removal from Aqueous Solution." Bulletin of Chemical Reaction Engineering & Catalysis 16, no. 1 (March 23, 2021): 136–47. http://dx.doi.org/10.9767/bcrec.16.1.10282.136-147.

Full text

Abstract:

Oil palm shell was used as a precursor for preparation of activated carbon using different chemical activations (potassium hydroxide (KOH), zinc chloride (ZNCl2), and phosphoric acid (H3PO4)). Each activated carbons (AC) was mixed with nano-zinc oxide to form a composite. From the gas sorption analyzer, it is showed that nitrogen adsorption isotherms show Type II for ZnO/AC-KOH and ZnO/AC-ZnCl2 corresponding to the micro- and mesoporous structures, respectively. However, the nitrogen adsorption isotherm of ZnO/AC-H3PO4 exhibits the Type I with predominantly microporous structures. The SEM micrographs produced unsmooth surface and different pore sizes. The XRD patterns at 2θ of 25.06° and 26.75° were come from amorphous activated carbon. The peak intensity of ZnO was weak due to low concentration of zinc precursor. However, the ZnO of ZnO/AC-ZnCl2 showed strongly peak intensity. The effectiveness of the composites was examined for phenol removal determined by UV-Vis Spectrophotometer method. The equilibrium adsorption follows the Langmuir and Freundlich models according to the best correlation coefficient (R2). The kinetic model was only obtained for the pseudo-second-order with the best linearity of the correlation coefficient (R2). The results of this study showed that the oil palm shell has a great potential for ZnO/AC with excellent adsorptive property. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

APA, Harvard, Vancouver, ISO, and other styles

38

Krisnandi, Yuni Krisyuningsih, Dita Arifa Nurani, Anastasia Agnes, Ralentri Pertiwi, Noer Fadlina Antra, Alika Rizki Anggraeni, Anya Prilla Azaria, and Russell Francis Howe. "Hierarchical MnOx/ZSM-5 as Heterogeneous Catalysts in Conversion of Delignified Rice Husk to Levulinic Acid." Indonesian Journal of Chemistry 19, no. 1 (January 29, 2019): 115. http://dx.doi.org/10.22146/ijc.28332.

Full text

Abstract:

Hierarchical ZSM-5 zeolite was synthesized using a double template method using TPAOH and PDDA as templates, while microporous ZSM-5 was also prepared using only TPAOH as a template. The syntheses then were followed by impregnation with Mn(II) c.a. 2 wt.% and calcination at 550 °C to obtain MnOx/ZSM-5 zeolite catalysts. Extensive characterization of the zeolite catalysts was performed using XRD, SEM, AAS, EDX, FTIR and BET measurement. The characterization showed that hierarchical or mainly mesoporous ZSM-5 was successfully synthesized, having added features compared to the microporous counterpart. The catalysts then were used in conversion reaction of delignified rice husk to levulinic acid, a platform chemical. As a comparison, a certain amount of MnCl2.4H2O was used as a homogeneous catalyst in a similar reaction. The product of the reaction was separated and analyzed with HPLC. It showed that 8 h was the optimum condition for the conversion, with hierarchical MnOx/hi_ZSM-5 catalyst gave the highest amount of levulinic acid (%Y of 15.83%), followed by microporous MnOx/mi_ZSM-5 (%Y of 10%). The % yield of levulinic acid using homogeneous Mn(II) catalyst (%Y of 8.86%) gave more charcoal as a product. Meanwhile, the stability of the zeolite catalysts after the reaction has also been investigated, mainly by analyzing the FTIR spectra and EDX data of the used catalysts after separated and calcined at 550 °C. From the analysis, some of the silica and alumina are leached from the framework, as well as the manganese oxide due to acidic condition at the beginning of the reaction. Nevertheless, it can be concluded that the conversion took place as the interaction between the cellulose and either MnOx in zeolites or Mn2+ ions in the solution, with the support of porous ZSM-5 framework. Hierarchical system somehow assists the ZSM-5 structure stays intact.

APA, Harvard, Vancouver, ISO, and other styles

39

Li, Hui, Yutian Fu, Jinglong Liang, and Yu Yang. "Effect of Cathode Physical Properties on the Preparation of Fe3Si0.7Al0.3 Intermetallic Compounds by Molten Salt Electrode Deoxidation." Materials 15, no. 21 (October 31, 2022): 7646. http://dx.doi.org/10.3390/ma15217646.

Full text

Abstract:

As a new process, molten salt electrolysis is widely used in the preparation of metal materials by in situ reduction in solid cathodes. Therefore, it is meaningful to study the influence of the physical properties of solid cathodes on electrolysis products. In this paper, mixed oxides of Fe2O3-Al2O3-SiO2 were selected as raw materials, and their particle size distribution, pore size distribution, specific surface area, and other physical properties were investigated by mechanical ball milling at different times. The CaCl2–NaCl molten salt system was selected to electrolyze the sintered cathode solid at 800 °C and a voltage of 3.2 V. The experimental results show that with the prolongation of ball-milling time, the particle size of mixed oxide raw materials gradually decreases, the specific surface area gradually increases, the distribution of micropores increases, and the distribution of mesopores decreases. After sintering at 800 °C for 4 h, the volume and particle size of the solid cathode increased, the impedance value gradually decreased, and the pores first increased and then decreased. The electrolysis results showed that the prolongation of the ball-milling time hindered the electrolysis process.

APA, Harvard, Vancouver, ISO, and other styles

40

Yuan, Jikang, Kate Laubernds, Qiuhua Zhang, and Steven L. Suib. "Self-Assembly of Microporous Manganese Oxide Octahedral Molecular Sieve Hexagonal Flakes into Mesoporous Hollow Nanospheres." Journal of the American Chemical Society 125, no. 17 (April 2003): 4966–67. http://dx.doi.org/10.1021/ja0294459.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Schmuhl, Riaan, Wietze Nijdam, Jelena Sekulić, Sankhanilay Roy Chowdhury, Cees J. M. van Rijn, Albert van den Berg, Johan E. ten Elshof, and Dave H. A. Blank. "Si-Supported Mesoporous and Microporous Oxide Interconnects as Electrophoretic Gates for Application in Microfluidic Devices." Analytical Chemistry 77, no. 1 (January 2005): 178–84. http://dx.doi.org/10.1021/ac049219c.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Choudhary, Nisha, Virendra Kumar Yadav, Huma Ali, Daoud Ali, Bader O. Almutairi, Simona Cavalu, and Ashish Patel. "Remediation of Methylene Blue Dye from Wastewater by Using Zinc Oxide Nanoparticles Loaded on Nanoclay." Water 15, no. 7 (April 6, 2023): 1427. http://dx.doi.org/10.3390/w15071427.

Full text

Abstract:

Dyes are one of the major environmental pollutants throughout the world, leading to pollution and numerous diseases. Though several techniques have been applied for the remediation of dyes, most of them are ineffective. The authors developed a halloysite clay/zinc oxide nanocomposite (HC/ZnONC) via a chemical route in the present study. The nanocomposite and its constituents, i.e., raw halloysite clay (HC) and zinc oxide nanoparticles (ZnONPs) (synthesized using the same chemical method) were analyzed for their detailed properties by sophisticated instruments. The field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) analysis showed spherical-shaped ZnONPs with an average size of 54.9 nm and tube-like shapes of HC with a diameter ranging from 40–200 nm and a length at the micron scale, while the nanocomposite had incorporated ZnONPs in their tube-like structures. Ultraviolet-Diffuse Reflectance Spectroscopic (UV-DRS) study revealed the photocatalytic ability of the nanocomposite with a band of 3.08 eV. A high surface area of 60.25 m2/g and the microporous and mesoporous nature of the nanocomposite were confirmed by the Brunauer–Emmet–Teller (BET) surface area analyzer. Finally, the developed nanocomposite was used for the remediation of methylene blue from the aqueous solutions, and the efficiency of removal varied from 90 to 97%.

APA, Harvard, Vancouver, ISO, and other styles

43

Mao, Haiyan, Jing Tang, Jun Chen, Jiayu Wan, Kaipeng Hou, Yucan Peng, David M. Halat, et al. "Designing hierarchical nanoporous membranes for highly efficient gas adsorption and storage." Science Advances 6, no. 41 (October 2020): eabb0694. http://dx.doi.org/10.1126/sciadv.abb0694.

Full text

Abstract:

Nanoporous membranes with two-dimensional materials such as graphene oxide have attracted attention in volatile organic compounds (VOCs) and H2 adsorption because of their unique molecular sieving properties and operational simplicity. However, agglomeration of graphene sheets and low efficiency remain challenging. Therefore, we designed hierarchical nanoporous membranes (HNMs), a class of nanocomposites combined with a carbon sphere and graphene oxide. Hierarchical carbon spheres, prepared following Murray’s law using chemical activation incorporating microwave heating, act as spacers and adsorbents. Hierarchical carbon spheres preclude the agglomeration of graphene oxide, while graphene oxide sheets physically disperse, ensuring structural stability. The obtained HNMs contain micropores that are dominated by a combination of ultramicropores and mesopores, resulting in high VOCs/H2 adsorption capacity, up to 235 and 352 mg/g at 200 ppmv and 3.3 weight % (77 K and 1.2 bar), respectively. Our work substantially expands the potential for HNMs applications in the environmental and energy fields.

APA, Harvard, Vancouver, ISO, and other styles

44

Vinogradov, Kirill Yurievich, Roman Vladimirovich Shafigulin, Elena Olegovna Tokranova, Sergey Vladimirovich Vostrikov, Evgeniya Andreevna Martynenko, Vladimir Vladimirovich Podlipnov, Pavel Vladimirovich Kazakevich, Artem Anatolevich Sheldaisov-Meshcheryakov, Nikolai Aleksandrovich Vinogradov, and Andzhela Vladimirovna Bulanova. "Catalysts for ORR Based on Silver-Modified Graphene Oxide and Carbon Nanotubes." Energies 16, no. 3 (February 3, 2023): 1526. http://dx.doi.org/10.3390/en16031526.

Full text

Abstract:

The main obstacle to the widespread dissemination of fuel cells is the high cost, so researchers are actively searching for ways to replace the expensive platinum catalyst with cheaper analogs. In this paper we studied the Ag- and Pd-containing carbon catalysts based on carbon nanotubes and graphene oxide. The study of the textural characteristics of the catalysts showed that the greatest specific surface area has a catalyst based on MWCNT containing 10% silver, all synthesized catalysts are mainly mesoporous, and the content of micropores is insignificant. Raman spectroscopy and SEM data indicate a significant change in the structure of the modified carriers compared to pure MWCNT and GO. An electrochemical experiment was performed and linear voltammetric diagrams were obtained and compared with the voltammetric diagrams obtained on the platinum catalyst. GO_Ag 10% and MWCNT_Ag 10% Pd 10% are closest in the values of kinetic parameters in both kinetic and diffusion regions. GO_Ag 10% has the highest initial potential Eonset = −0.145 V and MWCNT_Ag 10% Pd 10% has the highest half-wave potential E½ = −0.23 V. The studied catalysts have characteristics comparable to those presented in the literature.

APA, Harvard, Vancouver, ISO, and other styles

45

Ganesh, Suganthiny, Charitha Thambiliyagodage, S. V. T. Janaka Perera, and R. K. N. D. Rajapakse. "Influence of Laboratory Synthesized Graphene Oxide on the Morphology and Properties of Cement Mortar." Nanomaterials 13, no. 1 (December 21, 2022): 18. http://dx.doi.org/10.3390/nano13010018.

Full text

Abstract:

The introduction of Graphene Oxide (GO), a nanomaterial, has shown considerable promise in improving the mechanical properties of cement composites. However, the reasons for this improvement are not yet fully understood and demand further research. This study aims to understand the effect of laboratory-produced GO, using Tour’s method, on the mechanical properties and morphology of cement mortar containing GO. The GO was characterized using Fourier-transform infrared spectroscopy, X-ray Photoelectron Spectroscopy (XRD), X-ray powder diffraction, and Raman spectroscopy alongside Scanning electron microscopy (SEM). This study adopted a cement mortar with GO percentages of 0.02, 0.025, 0.03, 0.035, and 0.04 with respect to the weight of the cement. The presence of GO in cement mortar increased the density and decreased the consistency and setting times. At the optimum of 0.03% GO viscous suspension, the mechanical properties such as the 28-day compressive strength, splitting tensile strength, and flexural strength were enhanced by 41%, 83%, and 43%, respectively. In addition, Brunauer–Emmett–Teller analysis indicates an increase in surface area and volume of micropores of GO cement mortar, resulting in a decreased volume of mesopores. The improvement in properties was due to increased nucleation sites, calcium silicate hydrate (CSH) density, and a decreased volume of mesopores.

APA, Harvard, Vancouver, ISO, and other styles

46

Reddy Marthala, V. R., J. Frey, and M. Hunger. "Accessibility and Interaction of Surface OH Groups in Microporous and Mesoporous Catalysts Applied for Vapor-Phase Beckmann Rearrangement of Oximes." Catalysis Letters 135, no. 1-2 (February 2, 2010): 91–97. http://dx.doi.org/10.1007/s10562-010-0274-7.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Contarini, S., P. A. W. van der Heide, A. M. Prakash, and Larry Kevan. "Titanium coordination in microporous and mesoporous oxide materials by monochromated X-ray photoelectron spectroscopy and X-ray Auger electron spectroscopy." Journal of Electron Spectroscopy and Related Phenomena 125, no. 1 (August 2002): 25–33. http://dx.doi.org/10.1016/s0368-2048(02)00041-5.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Memetova, A. E., E. A. Neskoromnaya, A. D. Zelenin, A. V. Babkin, N. R. Memetov, and A. V. Gerasimova. "Accumulation of Natural Gas with a Prospective Material Based on Graphene Aerogel." Vestnik Tambovskogo gosudarstvennogo tehnicheskogo universiteta 27, no. 4 (2021): 636–46. http://dx.doi.org/10.17277/vestnik.2021.04.pp.636-646.

Full text

Abstract:

The assessment of the possibility of effective use of graphene aerogels for the adsorption storage and transportation of methane is given. For the study, an aerogel based on reduced graphene oxide was synthesized using supercritical methods for processing a hydrogel in an isopropyl alcohol medium. A narrow distribution of micropores with a maximum at 0.8 nm, a narrow distribution of mesopores with a maximum at about 4.5 and 6.5 nm were revealed. The obtained graphene aerogel (GA) was used to study the adsorption of methane at pressures up to 10 MPa and temperatures of 298, 303, 313 K. The maximum gravimetric absorption of methane reaches 0.86 g/g (37 cm3 (STP)/cm3) and 2.6 g/g (109 m3 (STP)/m3) at corresponding pressures of 35 and 100 bar and a temperature of 298 K, which is the highest recorded value for porous carbon previously reported.

APA, Harvard, Vancouver, ISO, and other styles

49

Guo, Xingzhong, Jiaqi Shan, Wei Lei, Ronghua Ding, Yun Zhang, and Hui Yang. "Facile Synthesis of Methylsilsesquioxane Aerogels with Uniform Mesopores by Microwave Drying." Polymers 11, no. 2 (February 20, 2019): 375. http://dx.doi.org/10.3390/polym11020375.

Full text

Abstract:

Methylsilsesquioxane (MSQ) aerogels with uniform mesopores were facilely prepared via a sol–gel process followed by microwave drying with methyltrimethoxysilane (MTMS) as a precursor, hydrochloric acid (HCl) as a catalyst, water and methanol as solvents, hexadecyltrimethylammonium chloride (CTAC) as a surfactant and template, and propylene oxide (PO) as a gelation agent. The microstructure, chemical composition, and pore structures of the resultant MSQ aerogels were investigated in detail to achieve controllable preparation of MSQ aerogels, and the thermal stability of MSQ aerogels was also analyzed. The gelation agent, catalyst, solvent, and microwave power have important roles related to the pore structures of MSQ aerogels. Meanwhile, the microwave drying method was found to not only have a remarkable effect on improving production efficiency, but also to be conducive to avoiding the collapse of pore structure (especially micropores) during drying. The resulting MSQ aerogel microwave-dried at 500 W possessed a specific surface area up to 821 m2/g and a mesopore size of 20 nm, and displayed good thermal stability.

APA, Harvard, Vancouver, ISO, and other styles

50

Delgado, A. V., S. Ahualli, M. M. Fernández, M. A. González, G. R. Iglesias, J. F. Vivo-Vilches, and M. L. Jiménez. "Geometrical properties of materials for energy production by salinity exchange." Environmental Chemistry 14, no. 5 (2017): 279. http://dx.doi.org/10.1071/en16210.

Full text

Abstract:

Environmental contextOceans and seas have the potential to play a significant role in providing renewable and clean energy. In particular, salinity difference energy aims to extract the enormous amount of energy that is released when fresh water rivers flow into the oceans. Capmix methods are focused on this challenge by using capacitive carbon electrodes whose optimisation will certainly help in developing salinity difference energy. AbstractOne of the most powerful marine renewable resources is salinity difference energy, also termed blue energy. Numerous techniques have been investigated to harvest this energy but, recently, the capmix proposal has increased in importance due to its easy implementation and use of low cost materials, very often activated carbon. Two methods based on this principle are tested in this work, namely CDLE (energy production by double layer expansion in bare electrodes) and SE (the electrodes are made ‘soft’ by polyelectrolyte coating). The characteristics of the carbon materials play a central role in capmix energy production. In this work, we focus on understanding the required pore structure that might be demanded from carbon samples. The balance between micro- and mesopores, the wettability of the material and its electrical resistance are explored by using hierarchical carbons, and their combination with graphene oxide and carbon nanotubes. It is found that the CDLE technique requires a large fraction of mesopores for easy solution exchange, while SE performance improves with a large amount of micropores. The addition of carbon nanotubes to the activated carbon reduces the capmix cycle duration, increasing the extracted power. In the case of electrodes containing graphene the internal resistance decreases, but the hydrophobicity of graphene oxide works against the improvement in energy extraction.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Microporous /Mesoporous Oxides'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles