Moisture sensor based on evanescent wave light scattering by porous sol-gel silica coating

Science.gov (United States)

Tao, Shiquan; Singh, Jagdish P.; Winstead, Christopher B.

2006-05-02

An optical fiber moisture sensor that can be used to sense moisture present in gas phase in a wide range of concentrations is provided, as well techniques for making the same. The present invention includes a method that utilizes the light scattering phenomenon which occurs in a porous sol-gel silica by coating an optical fiber core with such silica. Thus, a porous sol-gel silica polymer coated on an optical fiber core forms the transducer of an optical fiber moisture sensor according to an embodiment. The resulting optical fiber sensor of the present invention can be used in various applications, including to sense moisture content in indoor/outdoor air, soil, concrete, and low/high temperature gas streams.

A silica sol-gel design strategy for nanostructured metallic materials

NARCIS (Netherlands)

Warren, S.C.; Perkins, M.R.; Adams, A.M.; Kamperman, M.M.G.

2012-01-01

Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol–gel process. The porous materials made by silica sol–gel chemistry are typically insulators, however, which has

HPLC-CUPRAC post-column derivatization method for the determination of antioxidants: a performance comparison between porous silica and core-shell column packing.

Science.gov (United States)

Haque, Syed A; Cañete, Socrates Jose P

2018-01-01

An HPLC method employing a post-column derivatization strategy using the cupric reducing antioxidant capacity reagent (CUPRAC reagent) for the determining antioxidants in plant-based materials leverages the separation capability of regular HPLC approaches while allowing for detection specificity for antioxidants. Three different column types, namely core-shell and porous silica including two chemically different core-shell materials (namely phenyl-hexyl and C18), were evaluated to assess potential improvements that could be attained by changing from a porous silica matrix to a core-shell matrix. Tea extracts were used as sample matrices for the evaluation specifically looking at catechin and epigallocatechin gallate (EGCG). Both the C18 and phenyl-hexyl core-shell columns showed better performance compared to the C18 porous silica one in terms of separation, peak shape, and retention time. Among the two core-shell materials, the phenyl-hexyl column showed better resolving power compared to the C18 column. The CUPRAC post-column derivatization method can be improved using core-shell columns and suitable for quantifying antioxidants, exemplified by catechin and EGCG, in tea samples.

Porous Silica Sol-Gel Glasses Containing Reactive V2O5 Groups

Science.gov (United States)

Stiegman, Albert E.

1995-01-01

Porous silica sol-gel glasses into which reactive vanadium oxide functional groups incorporated exhibit number of unique characteristics. Because they bind molecules of some species both reversibly and selectively, useful as chemical sensors or indicators or as scrubbers to remove toxic or hazardous contaminants. Materials also oxidize methane gas photochemically: suggests they're useful as catalysts for conversion of methane to alcohol and for oxidation of hydrocarbons in general. By incorporating various amounts of other metals into silica sol-gel glasses, possible to synthesize new materials with broad range of new characteristics.

Fullerenol-Capped Porous Silica Nanoparticles for pH-Responsive Drug Delivery

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Nikola Ž. Knežević

2015-01-01

Full Text Available Novel nanocomposite containing fullerenol nanoparticles (FNP and porous silica nanoparticles (PSNs was constructed and characterized. The capability of FNP to serve as a pore-capping agent and for entrapping 9-aminoacridine (9-AA inside the pores of the PSN material was also demonstrated. Nitrogen sorption measurements evidence the successful capping of the silica pores while thermogravimetric analysis of FNP loaded PSN indicates the existence of pore-loaded fullerenol molecules. Higher amount of the drug release was noted by exposing the material to weakly acidic conditions in comparison to physiological pH, which may find application in targeted treatment of weakly acidic tumor tissues.

The increase in pH during aging of porous sol-gel silica spheres

NARCIS (Netherlands)

Titulaer, M.K.; Kegel, W.K.; Jansen, J.B.H.; Geus, John W.

1994-01-01

The increase in pH in the hydrothermal fluid is studied after hydrothermal aging of porous silica gel spheres of 1–3 mm diameter. The porous silica spheres are formed by the sol-gel process from a supersaturated silica solution. The increase of the pH of the hydrothermal solution affects the silica

Influences of surface charge, size, and concentration of colloidal nanoparticles on fabrication of self-organized porous silica in film and particle forms.

Science.gov (United States)

Nandiyanto, Asep Bayu Dani; Suhendi, Asep; Arutanti, Osi; Ogi, Takashi; Okuyama, Kikuo

2013-05-28

Studies on preparation of porous material have attracted tremendous attention because existence of pores can provide material with excellent performances. However, current preparation reports described successful production of porous material with only partial information on charges, interactions, sizes, and compositions of the template and host materials. In this report, influences of self-assembly parameters (i.e., surface charge, size, and concentration of colloidal nanoparticles) on self-organized porous material fabrication were investigated. Silica nanoparticles (as a host material) and polystyrene (PS) spheres (as a template) were combined to produce self-assembly porous materials in film and particle forms. The experimental results showed that the porous structure and pore size were controllable and strongly depended on the self-assembly parameters. Materials containing highly ordered pores were effectively created only when process parameters fall within appropriate conditions (i.e., PS surface charge ≤ -30 mV; silica-to-PS size ratio ≤0.078; and silica-to-PS mass ratio of about 0.50). The investigation of the self-assembly parameter landscape was also completed using geometric considerations. Because optimization of these parameters provides significant information in regard to practical uses, results of this report could be relevant to other functional properties.

Effect of Synthesis Time on Morphology of Hollow Porous Silica Microspheres

Directory of Open Access Journals (Sweden)

Qian CHEN

2012-03-01

Full Text Available Hollow porous silica microspheres may be applicable as containers for the controlled release in drug delivery systems (DDS, foods, cosmetics, agrochemical, textile industry, and in other technological encapsulation use. In order to control the surface morphological properties of the silica microspheres, the effect of synthesis time on their formation was studied by a method of water-in-oil (W/O emulsion mediated sol-gel techniques. An aqueous phase of water, ammonium hydroxide and a surfactant Tween 20 was emulsified in an oil phase of 1-octanol with a stabilizer, hydroxypropyl cellulose (HPC, and a surfactant, sorbitan monooleate (Span 80 with low hydrophile-lipophile balance (HLB value. Tetraethyl orthosilicate (TEOS as a silica precursor was added to the emulsion. The resulting silica particles at different synthesis time 24, 48, and 72 hours were air-dried at room temperature and calcinated at 773 K for 3 hours. The morphology of the particles was characterized by scanning electron microscopy and the particle size distribution was measured by laser diffraction. The specific surface areas were studied by 1-point BET method, and pore sizes were measured by Image Tool Software. Both dense and porous silica microspheres were observed after all three syntheses. Hollow porous silica microspheres were formed at 24 and 48 hours synthesis time. Under base catalyzed sol-gel solution, the size of silica particles was in the range of 5.4 μm to 8.2 μm, and the particles had surface area of 111 m2/g – 380 m2/g. The longer synthesis time produced denser silica spheres with decreased pore sizes.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1344

Polyethyleneimine-loaded bimodal porous silica as low-cost and high-capacity sorbent for CO{sub 2} capture

Energy Technology Data Exchange (ETDEWEB)

Witoon, Thongthai, E-mail: fengttwi@ku.ac.th [National Center of Excellence for Petroleum, Petrochemicals and Advance Material, Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900 (Thailand); Center for Advanced Studies in Nanotechnology and Its Applications in Chemical Food and Agricultural Industries, Kasetsart University, Bangkok 10900 (Thailand)

2012-11-15

In this work, bimodal (meso-macro) porous silicas with different mesopore diameters synthesized by using rice husk ash as a low-cost silica source and chitosan as a natural template were used as a polyethyleneimine (PEI) support for CO{sub 2} capture. Unimodal porous silica supports with equivalent mesopore diameters to bimodal porous silica supports have been prepared for purpose of comparison. Effects of different PEI contents (10, 20, 30, 40 and 50 wt%) on CO{sub 2} sorption capacity have been systematically investigated. The porous silica supports and the PEI-loaded porous silica supports were characterized by N{sub 2}-sorption analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and thermal gravimetric analysis. CO{sub 2} sorption measurements of all PEI-loaded porous silica supports were performed at different adsorption temperatures (60, 75, 85, 90, 95 and 105 Degree-Sign C). At low PEI contents (10-20 wt%), the CO{sub 2} sorption of all adsorbents was found to decrease as a function of adsorption temperature, which was a characteristic of a thermodynamically-controlled regime. A transition from the thermodynamically-controlled regime to a kinetically-controlled regime was found when the PEI content was increased up to 30 wt% for PEI-loaded unimodal porous silicas and 40 wt% for PEI-loaded bimodal porous silicas. At high PEI contents (40-50 wt%), the CO{sub 2} capturing efficiency of the PEI-loaded bimodal porous silicas was found to be considerably greater than that of the PEI-loaded unimodal porous silicas, indicating that most of the amine groups of PEI molecules loaded on the unimodal porous silica supports was useless, and thus the appeared macroporosity of the bimodal porous silica supports could provide a higher effective amine density to adsorb CO{sub 2}. Highlights: Black-Right-Pointing-Pointer PEI-impregnated bimodal porous silica as low-cost sorbent for CO{sub 2} capture. Black-Right-Pointing-Pointer Macropores enhances

Preparation of porous materials for radionuclides capture

International Nuclear Information System (INIS)

Bajzikova, Anna; Smrcek, Stanislav; Kozempel, Jan; Vlk, Martin; Barta, Jan

2015-01-01

Porous materials showing promise for radionuclide capture from water at contaminated sites were prepared. Nanoporous materials (size of pores 1-100 nm) and some polymers are well suited to this purpose owing their affinity for selected radionuclides. Nanoporous metal oxides and silica gel with styrene-divinylbenzene-TODGA-modified surface were prepared, characterized and tested for radionuclide ( 227 Ac, 227 Th, 223 Ra) capture efficiency. (orig.)

Ordered mesoporous silica materials with complicated structures

KAUST Repository

Han, Yu

2012-05-01

Periodically ordered mesoporous silicas constitute one of the most important branches of porous materials that are extensively employed in various chemical engineering applications including adsorption, separation and catalysis. This short review gives an introduction to recently developed mesoporous silicas with emphasis on their complicated structures and synthesis mechanisms. In addition, two powerful techniques for solving complex mesoporous structures, electron crystallography and electron tomography, are compared to elucidate their respective strength and limitations. Some critical issues and challenges regarding the development of novel mesoporous structures as well as their applications are also discussed. © 2011 Elsevier Ltd.

Control the Morphologies and the Pore Architectures of Meso porous Silicas through a Dual-Templating Approach

International Nuclear Information System (INIS)

Wang, H.; Chen, H.; Xu, Z.; Wang, S.; Li, B.; Li, Y.

2012-01-01

Meso porous silica nanospheres were prepared using a chiral cationic low-molecular-weight amphiphile and organic solvents such as toluene, cyclohexane, and tetrachlorocarbon through a dual-templating approach. X-ray diffraction, nitrogen sorption, field emission scanning electron microscopy, and transmission electron microscopy techniques have been used to characterize the meso porous silicas. The volume ratio of toluene to water plays an important role in controlling the morphologies and the pore architectures of the meso porous silicas. It was also found that meso porous silica nano flakes can be prepared by adding tetrahydrofuran to the reaction mixtures.

Core-shell designs of photoluminescent nanodiamonds with porous silica coatings for bioimaging and drug delivery II: application.

Science.gov (United States)

Prabhakar, Neeraj; Näreoja, Tuomas; von Haartman, Eva; Karaman, Didem Şen; Jiang, Hua; Koho, Sami; Dolenko, Tatiana A; Hänninen, Pekka E; Vlasov, Denis I; Ralchenko, Victor G; Hosomi, Satoru; Vlasov, Igor I; Sahlgren, Cecilia; Rosenholm, Jessica M

2013-05-07

Recent advances within materials science and its interdisciplinary applications in biomedicine have emphasized the potential of using a single multifunctional composite material for concurrent drug delivery and biomedical imaging. Here we present a novel composite material consisting of a photoluminescent nanodiamond (ND) core with a porous silica (SiO2) shell. This novel multifunctional probe serves as an alternative nanomaterial to address the existing problems with delivery and subsequent tracing of the particles. Whereas the unique optical properties of ND allows for long-term live cell imaging and tracking of cellular processes, mesoporous silica nanoparticles (MSNs) have proven to be efficient drug carriers. The advantages of both ND and MSNs were hereby integrated in the new composite material, ND@MSN. The optical properties provided by the ND core rendered the nanocomposite suitable for microscopy imaging in fluorescence and reflectance mode, as well as super-resolution microscopy as a STED label; whereas the porous silica coating provided efficient intracellular delivery capacity, especially in surface-functionalized form. This study serves as a demonstration how this novel nanomaterial can be exploited for both bioimaging and drug delivery for future theranostic applications.

Microstructure investigation on micropore formation in microporous silica materials prepared via a catalytic sol-gel process by small angle X-ray scattering.

Science.gov (United States)

Shimizu, Wataru; Hokka, Junsuke; Sato, Takaaki; Usami, Hisanao; Murakami, Yasushi

2011-08-04

The so-called sol-gel technique has been shown to be a template-free, efficient way to create functional porous silica materials having uniform micropores. This appears to be closely linked with a postulation that the formation of weakly branched polymer-like aggregates in a precursor solution is a key to the uniform micropore generation. However, how such a polymer-like structure can precisely be controlled, and further, how the generated low-fractal dimension solution structure is imprinted on the solid silica materials still remain elusive. Here we present fabrication of microporous silica from tetramethyl orthosilicate (TMOS) using a recently developed catalytic sol-gel process based on a nonionic hydroxyacetone (HA) catalyst. Small angle X-ray scattering (SAXS), nitrogen adsorption porosimetry, and transmission electron microscope (TEM) allowed us to observe the whole structural evolution, ranging from polymer-like aggregates in the precursor solution to agglomeration with heat treatment and microporous morphology of silica powders after drying and hydrolysis. Using the HA catalyst with short chain monohydric alcohols (methanol or ethanol) in the precursor solution, polymer-like aggregates having microscopic correlation length (or mesh-size) micropores with diameters 2 nm) in the solid product due to apertures between the particle-like aggregates. The data demonstrate that the extremely fine porous silica architecture comes essentially from a gaussian polymer-like nature of the silica aggregates in the precursor having the microscopic mesh-size and their successful imprint on the solid product. The result offers a general but significantly efficient route to creating precisely designed fine porous silica materials under mild condition that serve as low refractive index and efficient thermal insulation materials in their practical applications.

Synthesis of Macroporous Silica Particles by Continuous Generation of Droplets for Insulating Materials.

Science.gov (United States)

Cho, Young-Sang; Lee, Dokyoung

2018-09-01

We report on the synthesis of porous silica particles by self-assembly routes in a continuous manner for application to thermal insulators. A continuous process was employed to produce tiny droplets containing precursor materials such as silica and organic templates for self-organization to fabricate particles with well defined pores. A rotating cylinder system or a spray drying process was adopted to form emulsions or aerosol droplets as micro-reactors for self-assembly, and the physical properties including the thermal conductivity of the resulting porous particles were compared between the two methods. The porous particles could be coated as a thick film by solution dripping, and the fluorination treatment using a silane coupling agent was performed to produce superhydrophobic surfaces of insulating layers by a lotus effect.

Preparation and characterization of monodisperse large-porous silica microspheres as the matrix for protein separation.

Science.gov (United States)

Xia, Hongjun; Wan, Guangping; Zhao, Junlong; Liu, Jiawei; Bai, Quan

2016-11-04

High performance liquid chromatography (HPLC) is a kind of efficient separation technology and has been used widely in many fields. Micro-sized porous silica microspheres as the most popular matrix have been used for fast separation and analysis in HPLC. In this paper, the monodisperse large-porous silica microspheres with controllable size and structure were successfully synthesized with polymer microspheres as the templates and characterized. First, the poly(glycidyl methacrylate-co-ethyleneglycol dimethacrylate) microspheres (P GMA-EDMA ) were functionalized with tetraethylenepentamine (TEPA) to generate amino groups which act as a catalyst in hydrolysis of tetraethyl orthosilicate (TEOS) to form Si-containing low molecular weight species. Then the low molecular weight species diffused into the functionalized P GMA-EDMA microspheres by induction force of the amino groups to form polymer/silica hybrid microspheres. Finally, the organic polymer templates were removed by calcination, and the large-porous silica microspheres were obtained. The compositions, morphology, size distribution, specific surface area and pore size distribution of the porous silica microspheres were characterized by infrared analyzer, scanning-electron microscopy, dynamic laser scattering, the mercury intrusion method and thermal gravimetric analysis, respectively. The results show that the agglomeration of the hybrid microspheres can be overcome when the templates were functionalized with TEPA as amination reagent, and the yield of 95.7% of the monodisperse large-porous silica microspheres can be achieved with high concentration of polymer templates. The resulting large-porous silica microspheres were modified with octadecyltrichlorosilane (ODS) and the chromatographic evaluation was performed by separating the proteins and the digest of BSA. The baseline separation of seven kinds of protein standards was achieved, and the column delivered a better performance when separating BSA digests

Hydrothermal synthesis of meso porous silica MCM-41 using commercial sodium silicate

International Nuclear Information System (INIS)

Melendez O, H. I.; Mercado S, A.; Garcia C, L. A.; Castruita, G.; Perera M, Y A.

2013-01-01

In this work, ordered meso porous silica MCM-41 was prepared by hydrothermal synthesis using industrial-grade sodium silicate (Na 2 SiO 3 ) as silica source, hexadecyltrimethyl-ammonium bromide (CTAB) as template agent and ethyl acetate as ph regulator. The influence of CTAB/SiO 2 molar ratio, reaction time, aging temperature, and co-surfactant type on the structural and morphological properties of the obtained silica was studied. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption isotherms. Ordered meso porous MCM-41 silica was obtained at 80 C by using a range of CTAB/SiO 2 molar ratio from 0.35 to 0.71 and reaction times up to 72 h and isopropanol (i-Pr OH) as co-surfactant. (Author)

Polymer-Silica Nanocomposites: A Versatile Platform for Multifunctional Materials

Science.gov (United States)

Chiu, Chi-Kai

was ground into two different sizes of powder followed by powder pressing, heat-treating and etching. A new robust porous silver foam was then successfully made. By combining the results from room temperature and high temperature processes, we further study the patterned silver nanoparticles arrays in order to examine how mobility of silver can be controlled on a quantifiable scale. Furthermore, we have identified a thiolcontaining sol-gel precursor to control the affinity between silver and silica matrix. Lastly, the effects of interfacial interactions between sol-gel silica and other nanocomposite components and the effect of thickness of the sol-gel layer on mechanical properties were investigated. These studies were applied to the biomimetic hydroxyapatite-gelatin system. We have found that by limiting the thickness while maintaining interfacial interactions of the sol-gel layer, a unique moldable property and short hardening time from these nanocomposites can be achieved without compromising its biocompatibility. Their biocompatibility has been proven based on the in vitro and in vivo testing of these materials. In conclusion, the present study has demonstrated that polymer-silica nanocomposite is a versatile platform to carry out applications in nanocrystal growth, nanoporous metals, metal-ceramic composites, nano-imprint thin film, and bone grafts. These important findings not only provide new insights into nanocomposites but also give new meanings to the previously functional-limited sol-gel materials.

Hydrothermal synthesis of meso porous silica MCM-41 using commercial sodium silicate

Energy Technology Data Exchange (ETDEWEB)

Melendez O, H. I.; Mercado S, A.; Garcia C, L. A.; Castruita, G.; Perera M, Y A., E-mail: ivan_melendez380@hotmail.com [Centro de Investigacion en Quimica Aplicada, Bldv. Enrique Reyna Hermosillo No. 140, Saltillo 25294, Coahuila (Mexico)

2013-08-01

In this work, ordered meso porous silica MCM-41 was prepared by hydrothermal synthesis using industrial-grade sodium silicate (Na{sub 2}SiO{sub 3}) as silica source, hexadecyltrimethyl-ammonium bromide (CTAB) as template agent and ethyl acetate as ph regulator. The influence of CTAB/SiO{sub 2} molar ratio, reaction time, aging temperature, and co-surfactant type on the structural and morphological properties of the obtained silica was studied. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption isotherms. Ordered meso porous MCM-41 silica was obtained at 80 C by using a range of CTAB/SiO{sub 2} molar ratio from 0.35 to 0.71 and reaction times up to 72 h and isopropanol (i-Pr OH) as co-surfactant. (Author)

One-pot pseudomorphic crystallization of mesoporous porous silica to hierarchical porous zeolites

Energy Technology Data Exchange (ETDEWEB)

Xing, Jun-Ling; Jiang, Shu-Hua; Pang, Jun-Ling; Yuan, En-Hui; Ma, Xiao-Jing [Shanghai Key Laboratory of Green Chemistry and Chemical Processes, College of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhongshan North Road, 200062 Shanghai (China); Lam, Koon-Fung [Department of Chemical Engineering, University College London, Torrington Place, London (United Kingdom); Xue, Qing-Song, E-mail: qsxue@chem.ecnu.edu.cn [Shanghai Key Laboratory of Green Chemistry and Chemical Processes, College of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhongshan North Road, 200062 Shanghai (China); Zhang, Kun, E-mail: kzhang@chem.ecnu.edu.cn [Shanghai Key Laboratory of Green Chemistry and Chemical Processes, College of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhongshan North Road, 200062 Shanghai (China)

2015-09-15

Hierarchically porous silica with mesopore and zeolitic micropore was synthesized via pseudomorphic crystallization under high-temperature hydrothermal treatment in the presence of cetyltrimethylammonium tosylate and tetrapropylammonium ions. A combined characterization using small-angle X-ray diffraction (XRD), nitrogen adsorption, high-resolution transmission electron microscopy (TEM), thermogravimetric analysis (TG), and elemental analysis showed that dual templates, CTA{sup +} and TPA{sup +} molecules, can work in a cooperative manner to synthesize mesoporous zeolite in a one-pot system by precisely tuning the reaction conditions, such as reaction time and temperature, and type and amount of heterometal atoms. It is found that the presence of Ti precursor is critical to the successful synthesis of such nanostructure. It not only retards the nucleation and growth of crystalline MFI domains, but also acts as nano-binder or nano-glue to favor the assembly of zeolite nanoblocks. - Graphical abstract: Display Omitted - Highlights: • A facile method to synthesize mesoporous zeolites with hierarchical porosity was presented. • It gives a new insight into keeping the balance between mesoscopic and molecular ordering in hierarchical porous materials. • A new understanding on the solid–solid transformation mechanism for the synthesis of titanosilicate zeolites was proposed.

Two-Stage Crystallizer Design for High Loading of Poorly Water-Soluble Pharmaceuticals in Porous Silica Matrices

Directory of Open Access Journals (Sweden)

Leia Dwyer

2017-05-01

Full Text Available While porous silica supports have been previously studied as carriers for nanocrystalline forms of poorly water-soluble active pharmaceutical ingredients (APIs, increasing the loading of API in these matrices is of great importance if these carriers are to be used in drug formulations. A dual-stage mixed-suspension, mixed-product removal (MSMPR crystallizer was designed in which the poorly soluble API fenofibrate was loaded into the porous matrices of pore sizes 35 nm–300 nm in the first stage, and then fed to a second stage in which the crystals were further grown in the pores. This resulted in high loadings of over 50 wt % while still producing nanocrystals confined to the pores without the formation of bulk-sized crystals on the surface of the porous silica. The principle was extended to another highly insoluble API, griseofulvin, to improve its loading in porous silica in a benchtop procedure. This work demonstrates a multi-step crystallization principle API in porous silica matrices with loadings high enough to produce final dosage forms of these poorly water-soluble APIs.

Selective porous gates made from colloidal silica nanoparticles

Directory of Open Access Journals (Sweden)

Roberto Nisticò

2015-11-01

Full Text Available Highly selective porous films were prepared by spin-coating deposition of colloidal silica nanoparticles on an appropriate macroporous substrate. Silica nanoparticles very homogenous in size were obtained by sol–gel reaction of a metal oxide silica precursor, tetraethyl orthosilicate (TEOS, and using polystyrene-block-poly(ethylene oxide (PS-b-PEO copolymers as soft-templating agents. Nanoparticles synthesis was carried out in a mixed solvent system. After spin-coating onto a macroporous silicon nitride support, silica nanoparticles were calcined under controlled conditions. An organized nanoporous layer was obtained characterized by a depth filter-like structure with internal porosity due to interparticle voids. Permeability and size-selectivity were studied by monitoring the diffusion of probe molecules under standard conditions and under the application of an external stimulus (i.e., electric field. Promising results were obtained, suggesting possible applications of these nanoporous films as selective gates for controlled transport of chemical species in solution.

Thermally induced structural modifications and O2 trapping in highly porous silica nanoparticles

International Nuclear Information System (INIS)

Alessi, A.; Agnello, S.; Iovino, G.; Buscarino, G.; Melodia, E.G.; Cannas, M.; Gelardi, F.M.

2014-01-01

In this work we investigate by Raman spectroscopy the effect of isochronal (2 h) thermal treatments in air in the temperature range 200–1000 °C of amorphous silicon dioxide porous nanoparticles with diameters ranging from 5 up to 15 nm and specific surface 590–690 m 2 /g. Our results indicate that the amorphous structure changes similarly to other porous systems previously investigated, in fact superficial SiOH groups are removed, Si–O–Si linkages are created and the ring statistic is modified, furthermore these data evidence that the three membered rings do not contribute significantly to the Raman signal detected at about 495 cm −1 . In addition, after annealing at 900 and 1000 °C we noted the appearance of the O 2 emission at 1272 nm, absent in the not treated samples. The measure of the O 2 emission has been combined with electron paramagnetic resonance measurements of the γ irradiation induced HO · 2 radicals to investigate the O 2 content per mass unit of thin layers of silica. Our data reveal that the porous nanoparticles have a much lower ability to trap O 2 molecules per mass units than nonporous silica supporting a model by which O 2 trapping inside a surface layer of about 1 nm of silica is always limited. - Highlights: • O 2 emission and HO · 2 electron paramagnetic resonance signals are investigated. • Silica surface ability to trap O 2 molecules is explored by thermal treatments. • Raman study of thermally induced structural changes in porous silica nanoparticles. • Raman signal attributable to the three membered rings in silica

Porous silicon based anode material formed using metal reduction

Science.gov (United States)

Anguchamy, Yogesh Kumar; Masarapu, Charan; Deng, Haixia; Han, Yongbong; Venkatachalam, Subramanian; Kumar, Sujeet; Lopez, Herman A.

2015-09-22

A porous silicon based material comprising porous crystalline elemental silicon formed by reducing silicon dioxide with a reducing metal in a heating process followed by acid etching is used to construct negative electrode used in lithium ion batteries. Gradual temperature heating ramp(s) with optional temperature steps can be used to perform the heating process. The porous silicon formed has a high surface area from about 10 m.sup.2/g to about 200 m.sup.2/g and is substantially free of carbon. The negative electrode formed can have a discharge specific capacity of at least 1800 mAh/g at rate of C/3 discharged from 1.5V to 0.005V against lithium with in some embodiments loading levels ranging from about 1.4 mg/cm.sup.2 to about 3.5 mg/cm.sup.2. In some embodiments, the porous silicon can be coated with a carbon coating or blended with carbon nanofibers or other conductive carbon material.

TiO2-Impregnated Porous Silica Tube and Its Application for Compact Air- and Water-Purification Units

Directory of Open Access Journals (Sweden)

Tsuyoshi Ochiai

2015-09-01

Full Text Available A simple, convenient, reusable, and inexpensive air- and water-purification unit including a one-end sealed porous amorphous-silica (a-silica tube coated with TiO2 photocatalyst layers has been developed. The porous a-silica layers were formed through outside vapor deposition (OVD. TiO2 photocatalyst layers were formed through impregnation and calcination onto a-silica layers. The resulting porous TiO2-impregnated a-silica tubes were evaluated for air-purification capacity using an acetaldehyde gas decomposition test. The tube (8.5 mm e.d. × 150 mm demonstrated a 93% removal rate for high concentrations (ca. 300 ppm of acetaldehyde gas at a single-pass condition with a 250 mL/min flow rate under UV irradiation. The tube also demonstrated a water purification capacity at a rate 2.0 times higher than a-silica tube without TiO2 impregnation. Therefore, the tubes have a great potential for developing compact and in-line VOC removal and water-purification units.

Differently-catalyzed silica-based precursors as functional additives for the epoxy-based hybrid materials

Czech Academy of Sciences Publication Activity Database

Perchacz, Magdalena; Beneš, Hynek; Zhigunov, Alexander; Serkis, Magdalena; Pavlova, Ewa

2016-01-01

Roč. 99, 2 September (2016), s. 434-446 ISSN 0032-3861 R&D Projects: GA ČR(CZ) GA14-05146S; GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : epoxy-silica hybrid material * solvent-free sol-gel process * silica-based precursor Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.684, year: 2016

TiO2 supported over porous silica photocatalysts for pesticide degradation using solar light: Part 2. Silica prepared using acrylic acid emulsion

International Nuclear Information System (INIS)

Phanikrishna Sharma, Mangalampalli V.; Durga Kumari, Valluri; Subrahmanyam, Machiraju

2010-01-01

An acrylic acid emulsion mixture is used for synthesis of novel porous silica (E-Si) material. The photocatalytic activity of TiO 2 under solar light irradiation for isoproturon (herbicide) degradation is drastically increased when dispersed over E-Si support using solid state dispersion (SSD) technique. The composite material is characterized by XRD, nitrogen adsorption-desorption isotherms, UV-vis DRS, SEM and TEM measurements. The photocatalytic activities of the composite catalysts are evaluated for different parameters. The 5 wt% TiO 2 /E-Si is found to be highly active for isoproturon degradation.

Soft-Templating Synthesis of Mesoporous Silica-Based Materials for Environmental Applications

Science.gov (United States)

Gunathilake, Chamila Asanka

Dissertation research is mainly focus on: 1) the development of mesoporous silica materials with organic pendant and bridging groups (isocyanurate, amidoxime, benzene) and incorporated metal (aluminum, zirconium, calcium, and magnesium) species for high temperature carbon dioxide (CO2) sorption, 2) phosphorous-hydroxy functionalized mesoporous silica materials for water treatment, and 3) amidoxime-modified ordered mesoporous silica materials for uranium sorption under seawater conditions. The goal is to design composite materials for environmental applications with desired porosity, surface area, and functionality by selecting proper metal oxide precursors, organosilanes, tetraethylorthosilicate, (TEOS), and block copolymer templates and by adjusting synthesis conditions. The first part of dissertation presents experimental studies on the merge of aluminum, zirconium, calcium, and magnesium oxides with mesoporous silica materials containing organic pendant (amidoxime) and bridging groups (isocyanurate, benzene) to obtain composite sorbents for CO2 sorption at ambient (0-25 °C) and elevated (60-120 °C) temperatures. These studies indicate that the aforementioned composite sorbents are fairly good for CO2 capture at 25 °C via physisorption mechanism and show a remarkably high affinity toward CO2 chemisorption at 60-120 °C. The second part of dissertation is devoted to silica-based materials with organic functionalities for removal of heavy metal ions such as lead from contaminated water and for recovery of metal ions such as uranium from seawater. First, ordered mesoporous organosilica (OMO) materials with diethylphosphatoethyl and hydroxyphosphatoethyl surface groups were examined for Pb2+ adsorption and showed unprecedented adsorption capacities up to 272 mg/g and 202 mg/g, respectively However, the amidoxime-modified OMO materials were explored for uranium extraction under seawater conditions and showed remarkable capacities reaching 57 mg of uranium per gram

Synthesis, Characterization and Application of Multiscale Porous Materials

Energy Technology Data Exchange (ETDEWEB)

Hussami, Linda

2010-07-01

This thesis work brings fresh insights and improved understanding of nano scale materials through introducing new hybrid composites, 2D hexagonal in MCM-41 and 3D random interconnected structures of different materials, and application relevance for developing fields of science, such as fuel cells and solar cells. New types of porous materials and organometallic crystals have been prepared and characterized in detail. The porous materials have been used in several studies: as hosts to encapsulate metal-organic complexes; as catalyst supports and electrode materials in devices for alternative energy production. The utility of the new porous materials arises from their unique structural and surface chemical characteristics as demonstrated here using various experimental and theoretical approaches. New single crystal structures and arene-ligand exchange properties of f-block elements coordinated to ligand arene and halogallates are described in Paper I. These compounds have been incorporated into ordered 2D-hexagonal MCM-41 and polyhedral silica nano foam (PNF-SiO{sub 2}) matrices without significant change to the original porous architectures as described in Paper II and III. The resulting inorganic/organic hybrids exhibited enhanced luminescence activity relative to the pure crystalline complexes. A series of novel polyhedral carbon nano foams (PNF-C's) and inverse foams were prepared by nano casting from PNF-SiO{sub 2}'s. These are discussed in Paper IV. The synthesis conditions of PNF-C's were systematically varied as a function of the filling ratio of carbon precursor and their structures compared using various characterization methods. The carbonaceous porous materials were further tested in Paper V and VI as possible catalysts and catalyst supports in counter- and working electrodes for solar- and fuel cell applications

Thermally induced structural modifications and O{sub 2} trapping in highly porous silica nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Alessi, A., E-mail: antonino.alessi@unipa.it; Agnello, S.; Iovino, G.; Buscarino, G.; Melodia, E.G.; Cannas, M.; Gelardi, F.M.

2014-12-15

In this work we investigate by Raman spectroscopy the effect of isochronal (2 h) thermal treatments in air in the temperature range 200–1000 °C of amorphous silicon dioxide porous nanoparticles with diameters ranging from 5 up to 15 nm and specific surface 590–690 m{sup 2}/g. Our results indicate that the amorphous structure changes similarly to other porous systems previously investigated, in fact superficial SiOH groups are removed, Si–O–Si linkages are created and the ring statistic is modified, furthermore these data evidence that the three membered rings do not contribute significantly to the Raman signal detected at about 495 cm{sup −1}. In addition, after annealing at 900 and 1000 °C we noted the appearance of the O{sub 2} emission at 1272 nm, absent in the not treated samples. The measure of the O{sub 2} emission has been combined with electron paramagnetic resonance measurements of the γ irradiation induced HO{sup ·}{sub 2} radicals to investigate the O{sub 2} content per mass unit of thin layers of silica. Our data reveal that the porous nanoparticles have a much lower ability to trap O{sub 2} molecules per mass units than nonporous silica supporting a model by which O{sub 2} trapping inside a surface layer of about 1 nm of silica is always limited. - Highlights: • O{sub 2} emission and HO{sup ·}{sub 2} electron paramagnetic resonance signals are investigated. • Silica surface ability to trap O{sub 2} molecules is explored by thermal treatments. • Raman study of thermally induced structural changes in porous silica nanoparticles. • Raman signal attributable to the three membered rings in silica.

TiO{sub 2} supported over porous silica photocatalysts for pesticide degradation using solar light: Part 2. Silica prepared using acrylic acid emulsion

Energy Technology Data Exchange (ETDEWEB)

Phanikrishna Sharma, Mangalampalli V.; Durga Kumari, Valluri [Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500607, Andhra Pradesh (India); Subrahmanyam, Machiraju, E-mail: subrahmanyam@iict.res.in [Inorganic and Physical Chemistry Division, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500607, Andhra Pradesh (India)

2010-03-15

An acrylic acid emulsion mixture is used for synthesis of novel porous silica (E-Si) material. The photocatalytic activity of TiO{sub 2} under solar light irradiation for isoproturon (herbicide) degradation is drastically increased when dispersed over E-Si support using solid state dispersion (SSD) technique. The composite material is characterized by XRD, nitrogen adsorption-desorption isotherms, UV-vis DRS, SEM and TEM measurements. The photocatalytic activities of the composite catalysts are evaluated for different parameters. The 5 wt% TiO{sub 2}/E-Si is found to be highly active for isoproturon degradation.

Tailored Porous Materials

Energy Technology Data Exchange (ETDEWEB)

BARTON,THOMAS J.; BULL,LUCY M.; KLEMPERER,WALTER G.; LOY,DOUGLAS A.; MCENANEY,BRIAN; MISONO,MAKOTO; MONSON,PETER A.; PEZ,GUIDO; SCHERER,GEORGE W.; VARTULI,JAMES C.; YAGHI,OMAR M.

1999-11-09

Tailoring of porous materials involves not only chemical synthetic techniques for tailoring microscopic properties such as pore size, pore shape, pore connectivity, and pore surface reactivity, but also materials processing techniques for tailoring the meso- and the macroscopic properties of bulk materials in the form of fibers, thin films and monoliths. These issues are addressed in the context of five specific classes of porous materials: oxide molecular sieves, porous coordination solids, porous carbons, sol-gel derived oxides, and porous heteropolyanion salts. Reviews of these specific areas are preceded by a presentation of background material and review of current theoretical approaches to adsorption phenomena. A concluding section outlines current research needs and opportunities.

Porous silica nanoparticles as carrier for curcumin delivery

Science.gov (United States)

Hartono, Sandy Budi; Hadisoewignyo, Lannie; Irawaty, Wenny; Trisna, Luciana; Wijaya, Robby

2018-04-01

Mesoporous silica nanoparticles (MSN) with large surface areas and pore volumes show great potential as drug and gene carriers. However, there are still some challenging issues hinders their clinical application. Many types of research in the use of mesoporous silica material for drug and gene delivery involving complex and rigorous procedures. A facile and reproducible procedure to prepare combined drug carrier is required. We investigated the effect of physiochemical parameters of mesoporous silica, including structural symmetry (cubic and hexagonal), particles size (micro size: 1-2 µm and nano size: 100 -300 nm), on the solubility and release profile of curcumin. Transmission Electron Microscopy, X-Ray Powder Diffraction, and Nitrogen sorption were used to confirm the synthesis of the mesoporous silica materials. Mesoporous silica materials with different mesostructures and size have been synthesized successfully. Curcumin has anti-oxidant, anti-inflammation and anti-virus properties which are beneficial to fight various diseases such as diabetic, cancer, allergic, arthritis and Alzheimer. Curcumin has low solubility which minimizes its therapeutic effect. The use of nanoporous material to carry and release the loaded molecules is expected to enhance curcumin solubility. Mesoporous silica materials with a cubic mesostructure had a higher release profile and curcumin solubility, while mesoporous silica materials with a particle size in the range of nano meter (100-300) nm also show better release profile and solubility.

Super-Hydrophobic/Icephobic Coatings Based on Silica Nanoparticles Modified by Self-Assembled Monolayers

Directory of Open Access Journals (Sweden)

Junpeng Liu

2016-12-01

Full Text Available A super-hydrophobic surface has been obtained from nanocomposite materials based on silica nanoparticles and self-assembled monolayers of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS using spin coating and chemical vapor deposition methods. Scanning electron microscope images reveal the porous structure of the silica nanoparticles, which can trap small-scale air pockets. An average water contact angle of 163° and bouncing off of incoming water droplets suggest that a super-hydrophobic surface has been obtained based on the silica nanoparticles and POTS coating. The monitored water droplet icing test results show that icing is significantly delayed by silica-based nano-coatings compared with bare substrates and commercial icephobic products. Ice adhesion test results show that the ice adhesion strength is reduced remarkably by silica-based nano-coatings. The bouncing phenomenon of water droplets, the icing delay performance and the lower ice adhesion strength suggest that the super-hydrophobic coatings based on a combination of silica and POTS also show icephobicity. An erosion test rig based on pressurized pneumatic water impinging impact was used to evaluate the durability of the super-hydrophobic/icephobic coatings. The results show that durable coatings have been obtained, although improvement will be needed in future work aiming for applications in aerospace.

On the improvement of mechanical properties of monolithic silica aerogels (for transparent insulating material); Silica aerogel (tomei dannetsu zairyo) kyodo no kaizen ni tsuite

Energy Technology Data Exchange (ETDEWEB)

Tajiri, K; Igarashi, K; Tanemura, S [National Industrial Research Institute of Nagoya, Nagoya (Japan)

1997-11-25

Study was made on improvement of the strength of silica aerogel as transparent insulating material. Silica aerogel is a low-density porous material with high heat insulation and transparency. To develop a insulating material with high transparency, monolithic silica aerogel was studied. For direct use of it for windows, its strength improvement was attempted. The aerogel was prepared by supercritical drying (alcohol or CO2) of silica wet gel obtained by hydrolysis and condensation of silicon alkoxide solution. To prepare the aerogel bonded on plate glass for strength improvement, the aerogel was bonded to alkoxide by exposing active silanol radical through F-etching of plate glass surface. However, to obtain the practical large-area bonded aerogel, shrinkage control of the aerogel in supercritical drying was necessary. Addition of Laponite into a silica network for strength improvement by polymer increased the bending strength by 50%. Although some reduction of its transparency was observed because of clouding, its heat insulation was stable. Further strength improvement is necessary for its practical use. 5 figs., 1 tab.

Positronium formation in porous materials for antihydrogen production

International Nuclear Information System (INIS)

Ferragut, R; Calloni, A; Dupasquier, A; Consolati, G; Giammarchi, M G; Quasso, F; Trezzi, D; Egger, W; Ravelli, L; Petkov, M P; Jones, S M; Wang, B; Yaghi, O M; Jasinska, B; Chiodini, N; Paleari, A

2010-01-01

Positronium (Ps) formation measurements in several porous materials as: Vycor, germanate Xerogel, Metal-Organic Frameworks MOF-177 and Aerogel with two densities (20 and 150 mg/cm 3 ), were performed by means of a variable energy positron beam provided with a Ge detector and a positron lifetime spectrometer. An efficient formation of cooled Ps atoms is a requisite for the production of antihydrogen, with the aim of a direct measurement of the Earth gravitational acceleration g of antimatter, which is a primary scientific goal of AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy). Porous materials are necessary to form a high yield of Ps atoms as well as to cool Ps through collisions with the inner walls of the pores. The different materials were characterized and produce Ps into the pores. Lifetime measurements give an estimation of the typical pores dimension of the substances. A comparative study of the positron lifetime and the Ps fraction values in the above mentioned materials indicates that silica Aerogel, with the appropriate density, is an excellent candidate for an efficient formation of cold Ps atoms for the AEGIS project.

Sedimentation behaviour and colloidal properties of porous, chemically modified silicas in non-aqueous solvents

NARCIS (Netherlands)

Vissers, J.P.C.; Laven, J.; Claessens, H.A.; Cramers, C.A.M.G.; Agterof, W.G.M.

1997-01-01

The sedimentation behaviour and colloidal properties of porous, chemically modified silicas dispersed in non-aqueous solvents have been studied. The free settling behaviour of non-aggregated silica suspensions could effectively be described with a modified Stokes equation that takes into account the

Organoclay hybrid materials as precursors of porous ZnO/silica-clay heterostructures for photocatalytic applications

Directory of Open Access Journals (Sweden)

Marwa Akkari

2016-12-01

Full Text Available In this study, ZnO/SiO2-clay heterostructures were successfully synthesized by a facile two-step process applied to two types of clays: montmorillonite layered silicate and sepiolite microfibrous clay mineral. In the first step, intermediate silica–organoclay hybrid heterostructures were prepared following a colloidal route based on the controlled hydrolysis of tetramethoxysilane in the presence of the starting organoclay. Later on, pre-formed ZnO nanoparticles (NP dispersed in 2-propanol were incorporated under ultrasound irradiation to the silica–organoclay hybrid heterostructures dispersed in 2-propanol, and finally, the resulting solids were calcinated to eliminate the organic matter and to produce ZnO nanoparticles (NP homogeneously assembled to the clay–SiO2 framework. In the case of montmorillonite the resulting materials were identified as delaminated clays of ZnO/SiO2-clay composition, whereas for sepiolite, the resulting heterostructure is constituted by the assembling of ZnO NP to the sepiolite–silica substrate only affecting the external surface of the clay. The structural and morphological features of the prepared heterostructures were characterized by diverse physico-chemical techniques (such as XRD, FTIR, TEM, FE-SEM. The efficiency of these new porous ZnO/SiO2-clay heterostructures as potential photocatalysts in the degradation of organic dyes and the removal of pharmaceutical drugs in water solution was tested using methylene blue and ibuprofen compounds, respectively, as model of pollutants.

Controlled release of phenytoin for epilepsy treatment from titania and silica based materials

International Nuclear Information System (INIS)

Lopez, Tessy; Ortiz, Emma; Meza, Doraliz; Basaldella, Elena; Bokhimi, Xim; Magana, Carlos; Sepulveda, Antonio; Rodriguez, Francisco; Ruiz, Javier

2011-01-01

Research highlights: → Template technique was used to obtain well ordered nanostructured materials: SBA-15 and titania tubes. → Phenytoin (PH), a drug used in epilepsy treatment, was loaded in these materials to used como PH release. → Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. → The load-release PH are faster in nanostructured TiO2 tubes than in mesoporous silica matrix. → There is an inverse effect of the surface area of the structured materials on the amount of released PH. - Abstract: Template technique was used to obtain well ordered nanostructured materials: mesoporous silica and nanostructured titania tubes. This technique permits the synthesis of solids with controlled mesoporosity, where a large variety of molecules that have therapeutic activity can be hosted and further released to specific sites. In this work phenytoin (PH), a drug used in epilepsy treatment, was loaded in ordered mesoporous silica (SBA 15) and nanostructured titania tubes (TiO 2 ). The pure materials and those containing PH were characterized by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N 2 adsorption-desorption at 77 K. In order to determine the loading capacity of the antiepileptic drug on these silica- and titania-based materials, the loading and release of PH was investigated using UV-vis spectroscopy. Tubular structures were found for the titania samples, for which the X-ray diffractograms showed to be formed by anatase and rutile phases. On the other hand, an amorphous phase was found in the silica sample. A highly ordered hexagonal structure of 1D cylindrical channels was also observed for this material. Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. The adsorption and desorption of PH are faster in nanostructured TiO 2 tubes than in mesoporous silica matrix.

Interphases, gelation, vitrification, porous glasses and the generalized Cauchy relation: epoxy/silica nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Philipp, M; Mueller, U; Jimenez Rioboo, R J; Baller, J; Sanctuary, R; Krueger, J K [Laboratoire de Physique des Materiaux, University of Luxembourg, 162A avenue de la Faiencerie, L-1511 Luxembourg (Luxembourg); Possart, W [Fachbereich Werkstoffwissenschaften, Universitaet des Saarlandes, D-66123 Saarbruecken (Germany)], E-mail: martine.philipp@uni.lu

2009-02-15

The generalized Cauchy relation (gCR) of epoxy/silica nano-composites does not show either the chemically induced sol-gel transition or the chemically induced glass transition in the course of polymerization. Astonishingly, by varying the silica nanoparticles' concentration between 0 and 25 vol% in the composites, the Cauchy parameter A of the gCR remains universal and can be determined from the pure epoxy's elastic moduli. Air-filled porous silica glasses are considered as models for percolated silica particles. A longitudinal modulus versus density representation evidences the aforementioned transition phenomena during polymerization of the epoxy/silica nanocomposites. The existence of optically and mechanically relevant interphases is discussed.

Interphases, gelation, vitrification, porous glasses and the generalized Cauchy relation: epoxy/silica nanocomposites

International Nuclear Information System (INIS)

Philipp, M; Mueller, U; Jimenez Rioboo, R J; Baller, J; Sanctuary, R; Krueger, J K; Possart, W

2009-01-01

The generalized Cauchy relation (gCR) of epoxy/silica nano-composites does not show either the chemically induced sol-gel transition or the chemically induced glass transition in the course of polymerization. Astonishingly, by varying the silica nanoparticles' concentration between 0 and 25 vol% in the composites, the Cauchy parameter A of the gCR remains universal and can be determined from the pure epoxy's elastic moduli. Air-filled porous silica glasses are considered as models for percolated silica particles. A longitudinal modulus versus density representation evidences the aforementioned transition phenomena during polymerization of the epoxy/silica nanocomposites. The existence of optically and mechanically relevant interphases is discussed.

Preparation and Photocatalytic Property of TiO2/Diatomite-Based Porous Ceramics Composite Materials

Directory of Open Access Journals (Sweden)

Shuilin Zheng

2012-01-01

Full Text Available The diatomite-based porous ceramics was made by low-temperature sintering. Then the nano-TiO2/diatomite-based porous ceramics composite materials were prepared by hydrolysis deposition method with titanium tetrachloride as the precursor of TiO2 and diatomite-based porous as the supporting body of the nano-TiO2. The structure and microscopic appearance of nano-TiO2/diatomite-based porous ceramics composite materials was characterized by XRD and SEM. The photocatalytic property of the composite was investigated by the degradation of malachite green. Results showed that, after calcination at 550°C, TiO2 thin film loaded on the diatomite-based porous ceramics is anatase TiO2 and average grain size of TiO2 is about 10 nm. The degradation ratio of the composite for 5 mg/L malachite green solution reached 86.2% after irradiation for 6 h under ultraviolet.

IR-spectroscopical investigations on the glass structure of porous and sintered compacts of colloidal silica gels

Science.gov (United States)

Clasen, Rolf; Hornfeck, M.; Theiss, Wolfgang

1991-08-01

The forming and sintering of fumed silica powders is an interesting route for the preparation of large, very pure or doped silica glasses with a precise geometry. The processing from the shaping of a porous compact to the sintering of transparent silica glass can be successfully investigated with optical spectroscopy. As only the dielectric function DF (a dielectric function is the square root of the complex refractive index) characterizes the material, the vibrational bands were calculated from reflectance measurements. In compacts of fine particles, the topology cannot be neglected. Therefore, the models describing topological effects are briefly reviewed. With these model calculations it could be proven that new bands in the compacts and the significant shifts in the reflectance spectra during sintering are mainly caused by topological effects and that changes in the glass structure play only a secondary role.

Manganese–Schiff base complex immobilized silica materials

Indian Academy of Sciences (India)

III)]+ and [Mn(salophen)]+: [N,N′-bis(salicylaldehyde)-1,2-phenylenediimino manganese(III)]+ were introduced into/onto the MCM-41 type silica spheres and used for the electrocatalytic reduction of oxygen. Synthesized materials were ...

Controlled release of phenytoin for epilepsy treatment from titania and silica based materials

Energy Technology Data Exchange (ETDEWEB)

Lopez, Tessy, E-mail: tessy3@prodigy.net.mx [Universidad Autonoma Metropolitana-Xochimilco. Departamento de Microbiologia. Calzada del Hueso 1100, Col. Villa Quietud, Coyoacan, C.P. 04960, Mexico D.F. Mexico (Mexico); Instituto Nacional de Neurologia y Neurocirugia ' MVS' . Laboratorio de Nanotecnologia. Av. Insurgentes Sur 3877, Col. La Fama, Tlalpan, 14269, Mexico, D.F. Mexico (Mexico); Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118 (United States); Ortiz, Emma [Instituto Nacional de Neurologia y Neurocirugia ' MVS' . Laboratorio de Nanotecnologia. Av. Insurgentes Sur 3877, Col. La Fama, Tlalpan, 14269, Mexico, D.F. Mexico (Mexico); Meza, Doraliz [Universidad Autonoma Metropolitana-Iztapalapa, Departamento de Quimica, Av. San Rafael Atlixco 186, A.P. 55-534, Mexico D.F., C.P. 09340 (Mexico); Basaldella, Elena [CIC-CINDECA - Universidad Nacional de La Plata - Calle 47 No 257 - La Plata (Argentina); Bokhimi, Xim; Magana, Carlos [Instituto de fisica, UNAM. Circuito de la Investigacion s/n. C.U. Mexico D.F. 01000 (Mexico); Sepulveda, Antonio; Rodriguez, Francisco; Ruiz, Javier [Departamento de Quimica Inorganica, Universidad de Alicante. Apartado 99, E-03080 Alicante, Espana Spain (Spain)

2011-04-15

Research highlights: {yields} Template technique was used to obtain well ordered nanostructured materials: SBA-15 and titania tubes. {yields} Phenytoin (PH), a drug used in epilepsy treatment, was loaded in these materials to used como PH release. {yields} Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. {yields} The load-release PH are faster in nanostructured TiO2 tubes than in mesoporous silica matrix. {yields} There is an inverse effect of the surface area of the structured materials on the amount of released PH. - Abstract: Template technique was used to obtain well ordered nanostructured materials: mesoporous silica and nanostructured titania tubes. This technique permits the synthesis of solids with controlled mesoporosity, where a large variety of molecules that have therapeutic activity can be hosted and further released to specific sites. In this work phenytoin (PH), a drug used in epilepsy treatment, was loaded in ordered mesoporous silica (SBA 15) and nanostructured titania tubes (TiO{sub 2}). The pure materials and those containing PH were characterized by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N{sub 2} adsorption-desorption at 77 K. In order to determine the loading capacity of the antiepileptic drug on these silica- and titania-based materials, the loading and release of PH was investigated using UV-vis spectroscopy. Tubular structures were found for the titania samples, for which the X-ray diffractograms showed to be formed by anatase and rutile phases. On the other hand, an amorphous phase was found in the silica sample. A highly ordered hexagonal structure of 1D cylindrical channels was also observed for this material. Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. The adsorption and desorption of PH are faster in nanostructured TiO{sub 2} tubes than in mesoporous silica

Nanoscale assembly of lanthanum silica with dense and porous interfacial structures.

Science.gov (United States)

Ballinger, Benjamin; Motuzas, Julius; Miller, Christopher R; Smart, Simon; Diniz da Costa, João C

2015-02-03

This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)3) suggests the formation of La2O3 surrounded by lanthanum silicate.

Fluid Flow Programming in Paper-Derived Silica-Polymer Hybrids.

Science.gov (United States)

Dubois, Christelle; Herzog, Nicole; Rüttiger, Christian; Geißler, Andreas; Grange, Eléonor; Kunz, Ulrike; Kleebe, Hans-Joachim; Biesalski, Markus; Meckel, Tobias; Gutmann, Torsten; Gallei, Markus; Andrieu-Brunsen, Annette

2017-01-10

In paper-based devices, capillary fluid flow is based on length-scale selective functional control within a hierarchical porous system. The fluid flow can be tuned by altering the paper preparation process, which controls parameters such as the paper grammage. Interestingly, the fiber morphology and nanoporosity are often neglected. In this work, porous voids are incorporated into paper by the combination of dense or mesoporous ceramic silica coatings with hierarchically porous cotton linter paper. Varying the silica coating leads to significant changes in the fluid flow characteristics, up to the complete water exclusion without any further fiber surface hydrophobization, providing new approaches to control fluid flow. Additionally, functionalization with redox-responsive polymers leads to reversible, dynamic gating of fluid flow in these hybrid paper materials, demonstrating the potential of length scale specific, dynamic, and external transport control.

Silica sol as grouting material: a physio-chemical analysis.

Science.gov (United States)

Sögaard, Christian; Funehag, Johan; Abbas, Zareen

2018-01-01

At present there is a pressing need to find an environmentally friendly grouting material for the construction of tunnels. Silica nanoparticles hold great potential of replacing the organic molecule based grouting materials currently used for this purpose. Chemically, silica nanoparticles are similar to natural silicates which are essential components of rocks and soil. Moreover, suspensions of silica nanoparticles of different sizes and desired reactivity are commercially available. However, the use of silica nanoparticles as grouting material is at an early stage of its technological development. There are some critical parameters such as long term stability and functionality of grouted silica that need to be investigated in detail before silica nanoparticles can be considered as a reliable grouting material. In this review article we present the state of the art regarding the chemical properties of silica nanoparticles commercially available, as well as experience gained from the use of silica as grouting material. We give a detailed description of the mechanisms underlying the gelling of silica by different salt solutions such as NaCl and KCl and how factors such as particle size, pH, and temperature affect the gelling and gel strength development. Our focus in this review is on linking the chemical properties of silica nanoparticles to the mechanical properties to better understand their functionality and stability as grouting material. Along the way we point out areas which need further research.

Enantioselectively controlled release of chiral drug (metoprolol) using chiral mesoporous silica materials

Energy Technology Data Exchange (ETDEWEB)

Guo Zhen; Liu Xianbin; Ng, Siu-Choon; Chen Yuan; Yang Yanhui [School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459 (Singapore); Du Yu, E-mail: du_yu@jlu.edu.cn, E-mail: yhyang@ntu.edu.sg [College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China)

2010-04-23

Chiral porous materials have attracted burgeoning attention on account of their potential applications in many areas, such as enantioseparation, chiral catalysis, chemical sensors and drug delivery. In this report, chiral mesoporous silica (CMS) materials with various pore sizes and structures were prepared using conventional achiral templates (other than chiral surfactant) and a chiral cobalt complex as co-template. The synthesized CMS materials were characterized by x-ray diffraction, nitrogen physisorption, scanning electron microscope and transmission electron microscope. These CMS materials, as carriers, were demonstrated to be able to control the enantioselective release of a representative chiral drug (metoprolol). The release kinetics, as modeled by the power law equation, suggested that the release profiles of metoprolol were remarkably dependent on the pore diameter and pore structure of CMS materials. More importantly, R- and S-enantiomers of metoprolol exhibited different release kinetics on CMS compared to the corresponding achiral mesoporous silica (ACMS), attributable to the existence of local chirality on the pore wall surface of CMS materials. The chirality of CMS materials on a molecular level was further substantiated by vibrational circular dichroism measurements.

Enantioselectively controlled release of chiral drug (metoprolol) using chiral mesoporous silica materials

International Nuclear Information System (INIS)

Guo Zhen; Liu Xianbin; Ng, Siu-Choon; Chen Yuan; Yang Yanhui; Du Yu

2010-01-01

Chiral porous materials have attracted burgeoning attention on account of their potential applications in many areas, such as enantioseparation, chiral catalysis, chemical sensors and drug delivery. In this report, chiral mesoporous silica (CMS) materials with various pore sizes and structures were prepared using conventional achiral templates (other than chiral surfactant) and a chiral cobalt complex as co-template. The synthesized CMS materials were characterized by x-ray diffraction, nitrogen physisorption, scanning electron microscope and transmission electron microscope. These CMS materials, as carriers, were demonstrated to be able to control the enantioselective release of a representative chiral drug (metoprolol). The release kinetics, as modeled by the power law equation, suggested that the release profiles of metoprolol were remarkably dependent on the pore diameter and pore structure of CMS materials. More importantly, R- and S-enantiomers of metoprolol exhibited different release kinetics on CMS compared to the corresponding achiral mesoporous silica (ACMS), attributable to the existence of local chirality on the pore wall surface of CMS materials. The chirality of CMS materials on a molecular level was further substantiated by vibrational circular dichroism measurements.

Synthesis of Various Silica Nanoparticles for Foam Stability

International Nuclear Information System (INIS)

Yoon, Suk Bon; Yoon, Inho; Jung, Chonghun; Kim, Chorong; Choi, Wangkyu; Moon, Jeikwon

2013-01-01

The synthesis of the non-porous silica nanoparticles with uniform sizes has been reported through the Sto ber method, the synthesis of meso porous silica nanoparticles with a specific morphology such as core-shell, rod-like, and hexagonal shapes is not so common. As a synthetic strategy for controlling the particle size, shape, and porosity, the synthesis of core-shell silicas with meso porous shells formed on silica particle cores through the self-assembly of silica precursor and organic templates or spherical meso porous silicas using modified Sto ber method was also reported. Recently, in an effort to reduce the amount of radioactive waste and enhance the decontamination efficiency during the decontamination process of nuclear facilities contaminated with radionuclides, a few research for the preparation of the decontamination foam containing solid nanoparticles has been reported. In this work, the silica nanoparticles with various sizes, shapes, and structures were synthesized based on the previous literatures. The resulting silica nanoparticles were used to investigate the effect of the nanoparticles on the foam stability. In a study on the foam stability using various silica nanoparticles, the results showed that the foam volume and liquid volume in foam was enhanced when using a smaller size and lower density of the silica nanoparticles. Silica nanoparticles with various sizes, shapes, and structures such as a non-porous, meso porous core-shell, and meso porous silica were synthesized to investigate the effect of the foam stability. The sizes and structural properties of the silica nanoparticles were easily controlled by varying the amount of silica precursor, surfactant, and ammonia solution as a basic catalyst. The foam prepared using various silica nanoparticles showed that foam the volume and liquid volume in the foam were enhanced when using a smaller size and lower density of the silica nanoparticles

Construction and evaluation of controlled-release delivery system of Abamectin using porous silica nanoparticles as carriers.

Science.gov (United States)

Wang, Yan; Cui, Haixin; Sun, Changjiao; Zhao, Xiang; Cui, Bo

2014-12-01

Photolysis and poor solubility in water of Abamectin are key issues to be addressed, which causes low bioavailability and residual pollution. In this study, a novel hydrophilic delivery system through loading Abamectin with porous silica nanoparticles (Abam-PSNs) was developed in order to improve the chemical stability, dispersity, and the controlled release of Abamectin. These results suggest that Abam-PSNs can significantly improve the performance of controllable release, photostability, and water solubility of Abamectin by changing the porous structure of silica nanoparticles, which is favorable to improve the bioavailability and reduce the residues of pesticides.

Pore fabrication in various silica-based nanoparticles by controlled etching

KAUST Repository

Zhao, Lan

2010-07-20

A novel method based on controlled etching was developed to fabricate nanopores on preformed silica nanoparticles (<100 nm in diameter). The obtained monodisperse nanoporous particles could form highly stable homogeneous colloidal solution. Fluorescent silica nanoparticles and magnetic silica-coated γ-Fe 2O 3 nanoparticles were investigated as examples to illustrate that this strategy could be generally applied to various silica-based functional nanoparticles. The results indicated that this method was effective for generating pores on these nanoparticles without altering their original functionalities. The obtained multifunctional nanoparticles would be useful for many biological and biomedical applications. These porous nanoparticles could also serve as building blocks to fabricate three-dimensionally periodic structures that have the potential to be used as photonic crystals. © 2010 American Chemical Society.

Effects of confinement in meso-porous silica and carbon nano-structures

International Nuclear Information System (INIS)

Leon, V.

2006-07-01

Physico-chemical properties of materials can be strongly modified by confinement because of the quantum effects that appear at such small length scales and also because of the effects of the confinement itself. The aim of this thesis is to show that both the nature of the confining material and the size of the pores and cavities have a strong impact on the confined material. We first show the effect of the pore size of the host meso-porous silica on the temperature of the solid-solid phase transition of silver selenide, a semiconducting material with enhanced magnetoresistive properties under non-stoichiometric conditions. Narrowing the pores from 20 nm to 2 nm raises the phase transition temperature from 139 C to 146 C. This result can be explained by considering the interaction between the confining and confined materials as a driving force. The effects of confinement are also studied in the case of hydrogen and deuterium inside cavities of organized carbon nano-structures. The effects that appear in the adsorption/desorption cycles are much stronger with carbon nano-horns as the host material than with C60 pea-pods and single-walled carbon nano-tubes. (author)

Supercritical carbon dioxide behavior in porous silica aerogel

International Nuclear Information System (INIS)

Ciccariello, Salvino; Melnichenko, Yuri B.; He, Lilin

2011-01-01

Analysis of the tails of the small-angle neutron scattering (SANS) intensities relevant to samples formed by porous silica and carbon dioxide at pressures ranging from 0 to 20 MPa and at temperatures of 308 and 353 K confirms that the CO2 fluid must be treated as a two-phase system. The first of these phases is formed by the fluid closer to the silica wall than a suitable distance (delta) and the second by the fluid external to this shell. The sample scattering-length densities and shell thicknesses are determined by the Porod invariants and the oscillations observed in the Porod plots of the SANS intensities. The resulting matter densities of the shell regions (thickness 15-35 (angstrom)) are approximately equal, while those of the outer regions increase with pressure and become equal to the bulk CO2 at the higher pressures only in the low-temperature case.

Pretreatments of porous silica for improving the activity of a nickel-loaded catalyst

Energy Technology Data Exchange (ETDEWEB)

Arai, M.; Ikushima, Y.; Nishiyama, Y.

1986-02-01

Nickel catalysts supported on porous silicas treated with water, ethanol, and 1-butanol were found to be more active than that supported on untreated silica for ethane hydrogenolysis and furan hydrogenation. To elucidate the reason for the activation, some surface properties of the treated silicas were examined. The treatments decreased the surface area and increased the volume of the macropores, the surface density of hydroxyl groups, and the heat of immersion in water per unit surface area. The state of nickel on the support was examined by temperature programed desorption (TPD) of hydrogen, X-ray diffraction (XRD), and scanning electron microscopy/X-ray microanalysis. The dispersion measured by XRD was not appreciably altered by the treatments, but the TPD showed more hydrogen desorbed above 150/sup 0/C from nickel on the treated supports. The activation of nickel by pretreatment of the support was ascribed to the increase of those nickel atoms which dispersed finely over the support by the increased number of surface hydroxyl groups. This was based on the number of hydroxyl groups per unit surface area. The nickel catalyst supported on the pretreated silicas showed greater thermal stability. 16 references, 5 figures, 1 table.

Structure and thermal performance of poly(ethylene glycol) alkyl ether (Brij)/porous silica (MCM-41) composites as shape-stabilized phase change materials

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lingjian; Shi, Haifeng, E-mail: haifeng.shi@gmail.com; Li, Weiwei; Han, Xu; Zhang, Xingxiang, E-mail: zhangpolyu@gmail.com

2013-10-20

Graphical abstract: The maximum 50 wt% Brij58 is loaded into the porous MCM-41 networks, and a new peak at 18.8° in XRD patterns confirmed the changes of crystallization behavior of Brij58 against the bulk one. - Highlights: • Poly(ethylene glycol) hexadecyl ether and poly(ethylene glycol) octadecyl ether have the good thermal storage ability. • New peak at 18.8° proved the coexisted confined crystallization and nucleation-induced crystallization. • Poly(ethylene glycol) alkyl ether/MCM-41 PCMs exhibits the good thermal stability. - Abstract: A series of shape-stabilized phase change materials (PCMs), composed of poly(ethylene glycol) hexadecyl ether (Brij58) or poly(ethylene glycol) octadecyl ether (Brij76) and porous silica (MCM-41), were prepared by the physical mixing method. The structure, thermal stability, energy storage ability and crystallization behavior of these composites are deeply investigated and characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD) and thermogravimetric analysis (TGA). Obvious phase transition behavior and energy storage capability are observed for these Brij/MCM-41 composites, and the heat storage efficiency increased with the weight of Brij component. New peak at 18.8° demonstrated that the pore size and the surface adsorption ability of MCM-41 affect the crystallization behavior of Brij molecule. The crystalline structure and energy storage ability of these Brij/MCM-41 composites are discussed based on the crystallization process.

Formation of Micro and Mesoporous Amorphous Silica-Based Materials from Single Source Precursors

Directory of Open Access Journals (Sweden)

Mohd Nazri Mohd Sokri

2016-03-01

Full Text Available Polysilazanes functionalized with alkoxy groups were designed and synthesized as single source precursors for fabrication of micro and mesoporous amorphous silica-based materials. The pyrolytic behaviors during the polymer to ceramic conversion were studied by the simultaneous thermogravimetry-mass spectrometry (TG-MS analysis. The porosity of the resulting ceramics was characterized by the N2 adsorption/desorption isotherm measurements. The Fourier transform infrared spectroscopy (FT-IR and Raman spectroscopic analyses as well as elemental composition analysis were performed on the polymer-derived amorphous silica-based materials, and the role of the alkoxy group as a sacrificial template for the micro and mesopore formations was discussed from a viewpoint to establish novel micro and mesoporous structure controlling technologies through the polymer-derived ceramics (PDCs route.

Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment.

Science.gov (United States)

Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

2015-01-01

Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.

Heavy metals adsorption by novel EDTA-modified chitosan-silica hybrid materials.

Science.gov (United States)

Repo, Eveliina; Warchoł, Jolanta K; Bhatnagar, Amit; Sillanpää, Mika

2011-06-01

Novel adsorbents were synthesized by functionalizing chitosan-silica hybrid materials with (ethylenediaminetetraacetic acid) EDTA ligands. The synthesized adsorbents were found to combine the advantages of both silica gel (high surface area, porosity, rigid structure) and chitosan (surface functionality). The Adsorption potential of hybrid materials was investigated using Co(II), Ni(II), Cd(II), and Pb(II) as target metals by varying experimental conditions such as pH, contact time, and initial metal concentration. The kinetic results revealed that the pore diffusion process played a key role in adsorption kinetics, which might be attributed to the porous structure of synthesized adsorbents. The obtained maximum adsorption capacities of the hybrid materials for the metal ions ranged from 0.25 to 0.63 mmol/g under the studied experimental conditions. The adsorbent with the highest chitosan content showed the best adsorption efficiency. Bi-Langmuir and Sips isotherm model fitting to experimental data suggested the surface heterogeneity of the prepared adsorbents. In multimetal solutions, the hybrid adsorbents showed the highest affinity toward Pb(II). Copyright © 2011 Elsevier Inc. All rights reserved.

A tri-continuous mesoporous material with a silica pore wall following a hexagonal minimal surface

KAUST Repository

Han, Yu

2009-04-06

Ordered porous materials with unique pore structures and pore sizes in the mesoporous range (2-50nm) have many applications in catalysis, separation and drug delivery. Extensive research has resulted in mesoporous materials with one-dimensional, cage-like and bi-continuous pore structures. Three families of bi-continuous mesoporous materials have been made, with two interwoven but unconnected channels, corresponding to the liquid crystal phases used as templates. Here we report a three-dimensional hexagonal mesoporous silica, IBN-9, with a tri-continuous pore structure that is synthesized using a specially designed cationic surfactant template. IBN-9 consists of three identical continuous interpenetrating channels, which are separated by a silica wall that follows a hexagonal minimal surface. Such a tri-continuous mesostructure was predicted mathematically, but until now has not been observed in real materials. © 2009 Macmillan Publishers Limited. All rights reserved.

A tri-continuous mesoporous material with a silica pore wall following a hexagonal minimal surface

KAUST Repository

Han, Yu; Zhang, Daliang; Chng, Leng Leng; Sun, Junliang; Zhao, L. J.; Zou, Xiaodong; Ying, Jackie

2009-01-01

Ordered porous materials with unique pore structures and pore sizes in the mesoporous range (2-50nm) have many applications in catalysis, separation and drug delivery. Extensive research has resulted in mesoporous materials with one-dimensional, cage-like and bi-continuous pore structures. Three families of bi-continuous mesoporous materials have been made, with two interwoven but unconnected channels, corresponding to the liquid crystal phases used as templates. Here we report a three-dimensional hexagonal mesoporous silica, IBN-9, with a tri-continuous pore structure that is synthesized using a specially designed cationic surfactant template. IBN-9 consists of three identical continuous interpenetrating channels, which are separated by a silica wall that follows a hexagonal minimal surface. Such a tri-continuous mesostructure was predicted mathematically, but until now has not been observed in real materials. © 2009 Macmillan Publishers Limited. All rights reserved.

Development of pore interconnectivity/morphology in porous silica films investigated by cyclic voltammetry and slow positron annihilation spectroscopy

International Nuclear Information System (INIS)

Tang, Xiuqin; Xiong, Bangyun; Li, Qichao; Mao, Wenfeng; Xiao, Wei; Fang, Pengfei; He, Chunqing

2015-01-01

Highlights: •Porous silica films were studied by cyclic voltammetry and positron annihilation. •Highly interconnected pores were formed in the film fabricated with more CTAB. •Aligned nanochannels were observed in the porous flim prepared with 25 wt.% CTAB. •I − and Ps diffusion in the films was governed by pore interconnectivity/morphology. •Cyclic voltammetry is feasible to explore pore interconnectivity/morphology. -- Abstract: Cyclic voltammetry and positronium (Ps) 3γ-annihilation spectroscopy were applied to investigate pore interconnectivity/morphology of porous silica films fabricated with various loading of cetyltrimethyl ammonium bromide (CTAB). With increasing the ratio of CTAB up to 15 wt.%, the total charge Q, resulted from I − diffusion across the silica films, increased remarkably, indicative of formation of highly interconnected pores in the films prepared with more porogen. However, it decreased dramatically with further loading CTAB of 25 wt.%. Interestingly, 3γ-annihilation fraction I 3γ due to a triplet-state Ps (ortho-positronium, o-Ps) emission from the silica films showed a similar behavior as a function of CTAB loading. The abnormal decrement in Q and I 3γ in the film fabricated with 25 wt.% CTAB was well explained by formation of long nanochannels aligning parallel to the film surface. The results indicated that the total charge Q and Ps 3γ-annihilation fraction were closely associated with I − and Ps diffusion governed by the pore interconnectivity/morphology of the silica films, which made cyclic voltammetry possible to be a feasible tool to characterize pore interconnectivity/morphology of porous thin films

Metal-silica sol-gel materials

Science.gov (United States)

Stiegman, Albert E. (Inventor)

2002-01-01

The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

Fabrication and Properties of Silica Gel/Calcium Sulfate/Strontium-doped β-tricalcium Phosphate Composite Porous Scaffolds for Bone Tissue Engineering

Directory of Open Access Journals (Sweden)

QIN Xiao-su

2018-03-01

Full Text Available The calcium sulfate/strontium-doped β-tricalcium phosphate composite spherical pellets was fabricated, using the calcium sulfate/strontium-doped β-TCP as raw material, and through the stirring spray drying method, and then composite spherical pellets were combined with silica gel, porous silica gel/calcium sulfate/strontium-doped β-tricalcium phosphate scaffold was obtained by stacking aggregation method in the mould. The XRD, SEM and FT-IR, etc are employed to examine the chemical composition, composite morphology and structure characteristics, and the degradability, porosity, mechanical properties and cytotoxicity of the scaffolds materials were studied. The results reveal that the composite porous scaffolds have irregular pore structure with pore size between 0.2-1.0mm, and they have a large number of micropores on each of the composite spherical pellets, with the aperture between 50-200μm. Moreover, the porosity of the composite scaffolds is about 62%, which can meet the requirements of scaffolds for bone tissue engineering in porosity; the cytotoxicity tests show the composite scaffolds have no cytotoxic effect and it has good degradation. Therefore, it has good application prospect in bone tissue engineering of the bone defect repair of non-bearing site.

Design and evaluation of hybrid meso-porous silicas to uranium extraction from sulfuric media

International Nuclear Information System (INIS)

Charlot, Alexandre

2016-01-01

Nuclear industries are perpetually looking for technical, economic and environmental progresses. Important volumes of acidic waste are generated by nuclear plants of the front end. The extraction of uranium from these solutions is required to decontaminate effluents (decrease of the radioactivity) and value uranium (re-incorporation in the cycle). Uranium leaching is mostly achieved using sulfuric acid leading to the production of aqueous effluents that contain a large grade of sulfate complexes. In such conditions, uranyl sulfate complexes constitute the predominant uranium species in solution and its extraction represents a real scientific and technological challenge. Commonly, precipitation, solvent extraction or solid phase extraction are used. The last one is particularly adapted for low grade solutions due to it weak environmental footprint (no solvent are handling) and the facility of the process involved (i.e. fixed bed column). among the available solid-phase extraction candidates, hybrid meso-porous silicas get a crucial part. They develop a very high specific surface areas and a driven porosity which give them a high potential of extraction capacities. In this manuscript the tailoring and the evaluation of hybrid meso-porous silicas have been investigated. Firstly, the work focus on the organic part grafted by post-synthetic pathway, the N,N-dialkyl-carbamoyl-phosphonate based molecules have been identified to get interesting extraction properties. This study emphasizes that acid groups are required and that alkyl substituents get a real importance in the extraction efficiency. On the second hand, the role of pore size has been investigated. The results obtained disclosed that pores size diameters directly impact the grafting ratio as well as the homogeneity of the material: (1) materials with a pore size below 3 nm are heterogeneously functionalized due to steric issues, (2) a homogeneous organic monolayer grafted onto the silica skeleton occurs when

Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment

Science.gov (United States)

Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

2015-01-01

Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits. PMID:26322304

Effectiveness of silica based Sol-gel microencapsulation Method for odorants and flavours leading to sustainable Environment

Directory of Open Access Journals (Sweden)

Muhammad Aqeel eAshraf

2015-08-01

Full Text Available Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol–gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol–gel SiO2 is non-toxic and safe, whereas the sol–gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped actives, thereby broadening the practical utilization of chemically unstable essential oils. Reviewing progress in the fabrication of diverse odorant and flavoured sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.

Transport of Silica Colloid through Saturated Porous Media under Different Hydrogeochemical and Hydrodynamic Conditions Considering Managed Aquifer Recharge

Directory of Open Access Journals (Sweden)

Zhuo Wang

2016-11-01

Full Text Available Colloids may have an important role in regulating the structure and function of groundwater ecosystems, and may influence the migration of low solubility contaminants in groundwater. There is, however, a degree of uncertainty about how colloids behave under the variable hydrogeochemical and hydrodynamic conditions that occur during managed aquifer recharge. We used an online monitoring system to monitor the transport of silica colloid in saturated porous media under different hydrogeochemical conditions, including a range of pH values (5, 7, and 9, ionic strengths (<0.0005, 0.02, and 0.05 M, cation valences (Na+, Ca2+, flow rates (0.1, 0.2, and 0.4 mL/min. The results showed that silica colloid was more likely to deposit on the surface of porous media in acidic conditions (pH = 5 than in alkaline conditions (pH = 9, indicating that the risks of pollution from colloidal interactions would be higher when the pH of the recharge water was higher. Colloid deposition occurred when the ionic strength of the colloidal suspension increased, and bivalent cations had a greater effect than monovalent cations. This suggests that bivalent cation-rich recharge water might affect the porosity of the porous medium because of colloid deposition during the managed aquifer recharge process. As the flow rate increased, the migration ability of silica colloid increased. We simulated the migration of silica colloid in porous media with the COMSOL Multiphysics model.

On strength of porous material

DEFF Research Database (Denmark)

Nielsen, Lauge Fuglsang

1999-01-01

The question of non-destructive testing of porous materials has always been of interest for the engineering profession. A number of empirically based MOE-MOR relations between stiffness (Modulus Of Elasticity) and strength (Modulus OF Rupture) of materials have been established in order to control...

Environmentally-Friendly Dense and Porous Geopolymers Using Fly Ash and Rice Husk Ash as Raw Materials

Directory of Open Access Journals (Sweden)

Daniele Ziegler

2016-06-01

Full Text Available This paper assesses the feasibility of two industrial wastes, fly ash (FA and rice husk ash (RHA, as raw materials for the production of geopolymeric pastes. Three typologies of samples were thus produced: (i halloysite activated with potassium hydroxide and nanosilica, used as the reference sample (HL-S; (ii halloysite activated with rice husk ash dissolved into KOH solution (HL-R; (iii FA activated with the alkaline solution realized with the rice husk ash (FA-R. Dense and porous samples were produced and characterized in terms of mechanical properties and environmental impact. The flexural and compressive strength of HL-R reached about 9 and 43 MPa, respectively. On the contrary, the compressive strength of FA-R is significantly lower than the HL-R one, in spite of a comparable flexural strength being reached. However, when porous samples are concerned, FA-R shows comparable or even higher strength than HL-R. Thus, the current results show that RHA is a valuable alternative to silica nanopowder to prepare the activator solution, to be used either with calcined clay and fly ash feedstock materials. Finally, a preliminary evaluation of the global warming potential (GWP was performed for the three investigated formulations. With the mix containing FA and RHA-based silica solution, a reduction of about 90% of GWP was achieved with respect to the values obtained for the reference formulation.

A Short Overview on the Biomedical Applications of Silica, Alumina and Calcium Phosphate-based Nanostructured Materials.

Science.gov (United States)

Ellahioui, Younes; Prashar, Sanjiv; Gómez-Ruiz, Santiago

2016-01-01

This article reviews the use of silica, alumina and calcium phosphate-based nanostructured materials with biomedical applications. A short introduction on the use of the materials in Science, Nanotechnology and Health is included followed by a revision of each of the selected materials. A description of the principal synthetic methods used in the preparation of the materials in nanostructured form is included. The most widely used applications in biomedicine are reviewed including, for example drug-delivery, bone regeneration, imaging, sensoring amongst others. Finally, a short description of the toxicity and cytotoxicity associated with each of the materials of this revision is presented. This short literature revision serves to demonstrate the very promising future ahead of nanosystems based on silica, alumina and calcium phosphate for biological and biomedical applications.

Nano-Tomography of Porous Geological Materials Using Focused Ion Beam-Scanning Electron Microscopy

Directory of Open Access Journals (Sweden)

Yang Liu

2016-10-01

Full Text Available Tomographic analysis using focused ion beam-scanning electron microscopy (FIB-SEM provides three-dimensional information about solid materials with a resolution of a few nanometres and thus bridges the gap between X-ray and transmission electron microscopic tomography techniques. This contribution serves as an introduction and overview of FIB-SEM tomography applied to porous materials. Using two different porous Earth materials, a diatomite specimen, and an experimentally produced amorphous silica layer on olivine, we discuss the experimental setup of FIB-SEM tomography. We then focus on image processing procedures, including image alignment, correction, and segmentation to finally result in a three-dimensional, quantified pore network representation of the two example materials. To each image processing step we consider potential issues, such as imaging the back of pore walls, and the generation of image artefacts through the application of processing algorithms. We conclude that there is no single image processing recipe; processing steps need to be decided on a case-by-case study.

Effect of Steam Activation on Development of Light Weight Biomorphic Porous SiC from Pine Wood Precursor

Science.gov (United States)

Manocha, Satish M.; Patel, Hemang; Manocha, L. M.

2013-02-01

Biomorphic SiC materials with tailor-made microstructure and properties similar to ceramic materials manufactured by conventional method are a new class of materials derived from natural biopolymeric cellulose templates (wood). Porous silicon carbide (SiC) ceramics with wood-like microstructure have been prepared by carbothermal reduction of charcoal/silica composites at 1300-1600 °C in inert Ar atmosphere. The C/SiO2 composites were fabricated by infiltrating silica sol into porous activated biocarbon template. Silica in the charcoal/silica composite, preferentially in the cellular pores, was found to get transformed in forms of fibers and rods due to shrinkage during drying. The changes in the morphology of resulting porous SiC ceramics after heat treatment to 1600 °C, as well as the conversion mechanism of wood to activated carbon and then to porous SiC ceramic have been investigated using scanning electron microscope, x-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. Activation of carbon prior to silica infiltration has been found to enhance conversion of charcoal to SiC. The pore structure is found to be uniform in these materials than in those made from as-such charcoal/silica composites. This provides a low-cost and eco-friendly route to advanced ceramic materials, with near-net shape potential.

Computational materials chemistry for carbon capture using porous materials

International Nuclear Information System (INIS)

Sharma, Abhishek; Malani, Ateeque; Huang, Runhong; Babarao, Ravichandar

2017-01-01

Control over carbon dioxide (CO 2 ) release is extremely important to decrease its hazardous effects on the environment such as global warming, ocean acidification, etc. For CO 2 capture and storage at industrial point sources, nanoporous materials offer an energetically viable and economically feasible approach compared to chemisorption in amines. There is a growing need to design and synthesize new nanoporous materials with enhanced capability for carbon capture. Computational materials chemistry offers tools to screen and design cost-effective materials for CO 2 separation and storage, and it is less time consuming compared to trial and error experimental synthesis. It also provides a guide to synthesize new materials with better properties for real world applications. In this review, we briefly highlight the various carbon capture technologies and the need of computational materials design for carbon capture. This review discusses the commonly used computational chemistry-based simulation methods for structural characterization and prediction of thermodynamic properties of adsorbed gases in porous materials. Finally, simulation studies reported on various potential porous materials, such as zeolites, porous carbon, metal organic frameworks (MOFs) and covalent organic frameworks (COFs), for CO 2 capture are discussed. (topical review)

Hierarchical porous carbon materials derived from petroleum pitch for high-performance supercapacitors

Science.gov (United States)

Abudu, Patiman; Wang, Luxiang; Xu, Mengjiao; Jia, Dianzeng; Wang, Xingchao; Jia, Lixia

2018-06-01

In this work, a honeycomb-like carbon material derived from petroleum pitch was synthesized by a simple one-step carbonization/activation method using silica nanospheres as the hard templates. The obtained hierarchical porous carbon materials (HPCs) with a large specific surface area and uniform macropore distribution provide abundant active sites and sufficient ion migration channels. When used as an electrode material for supercapacitors, the HPCs exhibit a high specific capacitance of 341.0 F g-1 at 1 A g-1, excellent rate capability with a capacitance retention of 55.6% at 50 A g-1 (189.5 F g-1), and outstanding cycling performance in the three-electrode system.

Amine-oxide hybrid materials for acid gas separations

KAUST Repository

Bollini, Praveen; Didas, Stephanie A.; Jones, Christopher W.

2011-01-01

Organic-inorganic hybrid materials based on porous silica materials functionalized with amine-containing organic species are emerging as an important class of materials for the adsorptive separation of acid gases from dilute gas streams

Mesoporous silica materials modified with alumina polycations as catalysts for the synthesis of dimethyl ether from methanol

Energy Technology Data Exchange (ETDEWEB)

Macina, Daniel; Piwowarska, Zofia; Tarach, Karolina; Góra-Marek, Kinga [Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Kraków (Poland); Ryczkowski, Janusz [Maria Curie Skłodowska University, Faculty of Chemistry, Maria Curie-Skłodowska 2, 20-031 Lublin (Poland); Chmielarz, Lucjan, E-mail: chmielar@chemia.uj.edu.pl [Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Kraków (Poland)

2016-02-15

Highlights: • Deposition of alumina ologoctaions on mesoporous silicas modified with surface −SO{sub 3}H groups. • Alumina aggregates generated acid properties in the silica supports. • Alumina modified SBA-15 and MCF were active and selective catalysts in DME synthesis. - Abstract: Mesoporous silica materials (SBA-15 and MCF) were used as catalytic supports for the deposition of aggregated alumina species using the method consisting of the following steps: (i) anchoring 3-(mercaptopropyl)trimethoxysilane (MPTMS) on the silica surface followed by (ii) oxidation of −SH to−SO{sub 3}H groups and then (iii) deposition of aluminum Keggin oligocations by ion-exchange method and (iv) calcination. The obtained samples were tested as catalysts for synthesis of dimethyl ether from methanol. The modified silicas were characterized with respect to the ordering of their porous structure (XRD), textural properties (BET), chemical composition (EDS, CHNS), structure ({sup 27}Al NMR, FTIR) and location of alumina species (EDX-TEM), surface acidity (NH{sub 3}-TPD, Py-FTIR) and thermal stability (TGA). The obtained materials were found to be active and selective catalysts for methanol dehydration to dimethyl ether (DME) in the MTD process (methanol-to-dimethyl ether).

Study of silica sol-gel materials for sensor development

Science.gov (United States)

Lei, Qiong

Silica sol-gel is a transparent, highly porous silicon oxide glass made at room temperature by sol-gel process. The name of silica sol-gel comes from the observable physical phase transition from liquid sol to solid gel during its preparation. Silica sol-gel is chemically inert, thermally stable, and photostable, it can be fabricated into different desired shapes during or after gelation, and its porous structure allows encapsulation of guest molecules either before or after gelation while still retaining their functions and sensitivities to surrounding environments. All those distinctive features make silica sol-gel ideal for sensor development. Study of guest-host interactions in silica sol-gel is important for silica-based sensor development, because it helps to tailor local environments inside sol-gel matrix so that higher guest loading, longer shelf-life, higher sensitivity and faster response of silica gel based sensors could be achieved. We focused on pore surface modification of two different types of silica sol-gel by post-grafting method, and construction of stable silica hydrogel-like thin films for sensor development. By monitoring the mobility and photostability of rhodamine 6G (R6G) molecules in silica alcogel thin films through single molecule spectroscopy (SMS), the guest-host interactions altered by post-synthesis grafting were examined. While physical confinement remains the major factor that controls mobility in modified alcogels, both R6G mobility and photostability register discernable changes after surface charges are respectively reversed and neutralized by aminopropyltriethoxysilane (APTS) and methyltriethoxysilane (MTES) grafting. The change in R6G photostability was found to be more sensitive to surface grafting than that of mobility. In addition, silica film modification by 0.4% APTS is as efficient as that by pure MTES in lowering R6G photostability, which suggests that surface charge reversal is more effective than charge neutralization

Basalt fiber reinforced porous aggregates-geopolymer based cellular material

Science.gov (United States)

Luo, Xin; Xu, Jin-Yu; Li, Weimin

2015-09-01

Basalt fiber reinforced porous aggregates-geopolymer based cellular material (BFRPGCM) was prepared. The stress-strain curve has been worked out. The ideal energy-absorbing efficiency has been analyzed and the application prospect has been explored. The results show the following: fiber reinforced cellular material has successively sized pore structures; the stress-strain curve has two stages: elastic stage and yielding plateau stage; the greatest value of the ideal energy-absorbing efficiency of BFRPGCM is 89.11%, which suggests BFRPGCM has excellent energy-absorbing property. Thus, it can be seen that BFRPGCM is easy and simple to make, has high plasticity, low density and excellent energy-absorbing features. So, BFRPGCM is a promising energy-absorbing material used especially in civil defense engineering.

Quantitative analysis of silica aerogel-based thermal insulation coatings

DEFF Research Database (Denmark)

Kiil, Søren

2015-01-01

containing intact hollow glass or polymer spheres showed that silica aerogel particles are more efficient in an insulation coating than hollow spheres. In a practical (non-ideal) comparison, the ranking most likely cannot be generalized. A parameter study demonstrates how the model can be used, qualitatively......A mathematical heat transfer model for a silica aerogel-based thermal insulation coating was developed. The model can estimate the thermal conductivity of a two-component (binder-aerogel) coating with potential binder intrusion into the nano-porous aerogel structure. The latter is modelled using...... a so-called core–shell structure representation. Data from several previous experimental investigations with silica aerogels in various binder matrices were used for model validation. For some relevant cases with binder intrusion, it was possible to obtain a very good agreement between simulations...

Random-walk diffusion and drying of porous materials

Science.gov (United States)

Mehrafarin, M.; Faghihi, M.

2001-12-01

Based on random-walk diffusion, a microscopic model for drying is proposed to explain the characteristic features of the drying-rate curve of porous materials. The constant drying-rate period is considered as a normal diffusion process. The transition to the falling-rate regime is attributed to the fractal nature of porous materials which results in crossover to anomalous diffusion.

Porous titanium bases for osteochondral tissue engineering

Science.gov (United States)

Nover, Adam B.; Lee, Stephanie L.; Georgescu, Maria S.; Howard, Daniel R.; Saunders, Reuben A.; Yu, William T.; Klein, Robert W.; Napolitano, Anthony P.; Ateshian, Gerard A.

2015-01-01

Tissue engineering of osteochondral grafts may offer a cell-based alternative to native allografts, which are in short supply. Previous studies promote the fabrication of grafts consisting of a viable cell-seeded hydrogel integrated atop a porous, bone-like metal. Advantages of the manufacturing process have led to the evaluation of porous titanium as the bone-like base material. Here, porous titanium was shown to support the growth of cartilage to produce native levels of Young’s modulus, using a clinically relevant cell source. Mechanical and biochemical properties were similar or higher for the osteochondral constructs compared to chondral-only controls. Further investigation into the mechanical influence of the base on the composite material suggests that underlying pores may decrease interstitial fluid pressurization and applied strains, which may be overcome by alterations to the base structure. Future studies aim to optimize titanium-based tissue engineered osteochondral constructs to best match the structural architecture and strength of native grafts. Statement of Significance The studies described in this manuscript follow up on previous studies from our lab pertaining to the fabrication of osteochondral grafts that consist of a bone-like porous metal and a chondrocyte-seeded hydrogel. Here, tissue engineered osteochondral grafts were cultured to native stiffness using adult chondrocytes, a clinically relevant cell source, and a porous titanium base, a material currently used in clinical implants. This porous titanium is manufactured via selective laser melting, offering the advantages of precise control over shape, pore size, and orientation. Additionally, this manuscript describes the mechanical influence of the porous base, which may have applicability to porous bases derived from other materials. PMID:26320541

Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

International Nuclear Information System (INIS)

Alyoshina, Nonna A.; Parfenyuk, Elena V.

2013-01-01

A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N 2 adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption process of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica

Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials.

Science.gov (United States)

Hesemann, Peter; Nguyen, Thy Phung; Hankari, Samir El

2014-04-11

The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS) recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA), mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the "anionic templating" strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

Book Review [Surfaces of Nanoparticles and Porous Materials. Edited by James A. Schwarz and Cristian I. Contescu. 1 999. Marcel Dekker, New York, USA. ISBN: 0824719336

International Nuclear Information System (INIS)

Gonzalez, Richard D

1999-01-01

The volume is organized into three sections. The first section deals with the preparation, characterization and transport properties of this unique class of materials. A total of twelve contributions are included in this section, ten of which are full reviews and two are essentially short papers. The topics include: the synthesis of polysilazane coatings on the surface of silica gel; preparation of molecular sieves by the pillaring of synthetic clays; the acid/base behavior of surfaces of porous materials; electro-optical spectroscopy of colloid systems; NMR studies of colloidal oxides; polymer surface dynamics via contact angle measurements; collagen fibers; the role of diffusion on adsorption on oxide surfaces; transport processes in microemulsions; electrokinetic phenomena in porous media, and structural effects on diffusivity within colloidal zirconia. The remaining two sections deal with the fundamental and practical utilization of nanostructured materials in gaseous and liquid environments. The second section addresses the former case. A total of seven well documented contributions are included in this section. The papers address studies in diverse areas: energetically heterogeneous surfaces as studied using experimental adsorption isotherms; computer simulations of adsorbed surface layers; the effect of surface heterogeneity on adsorption equilibria and kinetics; single and multicomponent adsorption; surface properties of modified porous silicas; heats of adsorption of pure gases; and nanodimensional magnetic assembly of confined oxygen. The final section includes a total of ten reviews that address adsorption from the liquid phase. The following topics are covered: surface chemistry of activated carbon; charge regulation at the surface of porous solids; surface ionization and complexation; ionic adsorbates on hydrophobic surfaces; adsorption of metals on humic acid surfaces; hydrated metal oxides as adsorbents for heavy metals; adsorption of ions on alumina

Synthesis and characterization of titanium oxide supported silica materials

Science.gov (United States)

Schrijnemakers, Koen

2002-01-01

Titania-silica materials are interesting materials for use in catalysis, both as a catalyst support as well as a catalyst itself. Titania-silica materials combine the excellent support and photocatalytic properties of titania with the high thermal and mechanical stability of silica. Moreover, the interaction of titania with silica leads to new active sites, such as acid and redox sites, that are not found on the single oxides. In this Ph.D. two recently developed deposition methods were studied and evaluated for their use to create titanium oxide supported silica materials, the Chemical Surface Coating (CSC) and the Molecular Designed Dispersion (MDD). These methods were applied to two structurally different silica supports, an amorphous silica gel and the highly ordered MCM-48. Both methods are based on the specific interaction between a titanium source and the functional groups on the silica surface. With the CSC method high amounts of titanium can be obtained. However, clustering of the titania phase is observed in most cases. The MDD method allows much lower titanium amounts to be deposited without the formation of crystallites. Only at the highest Ti loading very small crystallites are formed after calcination. MCM-48 and silica gel are both pure SiO2 materials and therefore chemically similar to each other. However, they possess a different morphology and are synthesized in a different way. As such, some authors have reported that the MCM-48 surface would be more reactive than the surface of silica gel. In our experiments however no differences could be observed that confirmed this hypothesis. In the CSC method, the same reactions were observed and similar amounts of Ti and Cl were deposited. In the case of the MDD method, no difference in the reaction mechanism was observed. However, due to the lower thermal and hydrothermal stability of the MCM-48 structure compared to silica gel, partial incorporation of Ti atoms in the pore walls of MCM-48 took place

High-density oxidized porous silicon

International Nuclear Information System (INIS)

Gharbi, Ahmed; Souifi, Abdelkader; Remaki, Boudjemaa; Halimaoui, Aomar; Bensahel, Daniel

2012-01-01

We have studied oxidized porous silicon (OPS) properties using Fourier transform infraRed (FTIR) spectroscopy and capacitance–voltage C–V measurements. We report the first experimental determination of the optimum porosity allowing the elaboration of high-density OPS insulators. This is an important contribution to the research of thick integrated electrical insulators on porous silicon based on an optimized process ensuring dielectric quality (complete oxidation) and mechanical and chemical reliability (no residual pores or silicon crystallites). Through the measurement of the refractive indexes of the porous silicon (PS) layer before and after oxidation, one can determine the structural composition of the OPS material in silicon, air and silica. We have experimentally demonstrated that a porosity approaching 56% of the as-prepared PS layer is required to ensure a complete oxidation of PS without residual silicon crystallites and with minimum porosity. The effective dielectric constant values of OPS materials determined from capacitance–voltage C–V measurements are discussed and compared to FTIR results predictions. (paper)

Encapsulating Silica/Antimony into Porous Electrospun Carbon Nanofibers with Robust Structure Stability for High-Efficiency Lithium Storage.

Science.gov (United States)

Wang, Hongkang; Yang, Xuming; Wu, Qizhen; Zhang, Qiaobao; Chen, Huixin; Jing, Hongmei; Wang, Jinkai; Mi, Shao-Bo; Rogach, Andrey L; Niu, Chunming

2018-04-24

To address the volume-change-induced pulverization problems of electrode materials, we propose a "silica reinforcement" concept, following which silica-reinforced carbon nanofibers with encapsulated Sb nanoparticles (denoted as SiO 2 /Sb@CNFs) are fabricated via an electrospinning method. In this composite structure, insulating silica fillers not only reinforce the overall structure but also contribute to additional lithium storage capacity; encapsulation of Sb nanoparticles into the carbon-silica matrices efficiently buffers the volume changes during Li-Sb alloying-dealloying processes upon cycling and alleviates the mechanical stress; the porous carbon nanofiber framework allows for fast charge transfer and electrolyte diffusion. These advantageous characteristics synergistically contribute to the superior lithium storage performance of SiO 2 /Sb@CNF electrodes, which demonstrate excellent cycling stability and rate capability, delivering reversible discharge capacities of 700 mA h/g at 200 mA/g, 572 mA h/g at 500 mA/g, and 468 mA h/g at 1000 mA/g each after 400 cycles. Ex situ as well as in situ TEM measurements confirm that the structural integrity of silica-reinforced Sb@CNF electrodes can efficiently withstand the mechanical stress induced by the volume changes. Notably, the SiO 2 /Sb@CNF//LiCoO 2 full cell delivers high reversible capacities of ∼400 mA h/g after 800 cycles at 500 mA/g and ∼336 mA h/g after 500 cycles at 1000 mA/g.

Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

Energy Technology Data Exchange (ETDEWEB)

Alyoshina, Nonna A.; Parfenyuk, Elena V., E-mail: evp@iscras.ru

2013-09-15

A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N{sub 2} adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption process of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica.

Influence of geometry on mechanical properties of bio-inspired silica-based hierarchical materials

International Nuclear Information System (INIS)

Dimas, Leon S; Buehler, Markus J

2012-01-01

Diatoms, bone, nacre and deep-sea sponges are mineralized natural structures found abundantly in nature. They exhibit mechanical properties on par with advanced engineering materials, yet their fundamental building blocks are brittle and weak. An intriguing characteristic of these structures is their heterogeneous distribution of mechanical properties. Specifically, diatoms exhibit nanoscale porosity in specific geometrical configurations to create regions with distinct stress strain responses, notably based on a single and simple building block, silica. The study reported here, using models derived from first principles based full atomistic studies with the ReaxFF reactive force field, focuses on the mechanics and deformation mechanisms of silica-based nanocomposites inspired by mineralized structures. We examine single edged notched tensile specimens and analyze stress and strain fields under varied sample size in order to gain fundamental insights into the deformation mechanisms of structures with distinct ordered arrangements of soft and stiff phases. We find that hierarchical arrangements of silica nanostructures markedly change the stress and strain transfer in the samples. The combined action of strain transfer in the deformable phase, and stress transfer in the strong phase, acts synergistically to reduce the intensity of stress concentrations around a crack tip, and renders the resulting composites less sensitive to the presence of flaws, for certain geometrical configurations it even leads to stable crack propagation. A systematic study allows us to identify composite structures with superior fracture mechanical properties relative to their constituents, akin to many natural biomineralized materials that turn the weaknesses of building blocks into a strength of the overall system. (paper)

NMR of mercury in porous coal and silica gel

International Nuclear Information System (INIS)

Kasperovich, V.S.; Charnaya, E.V.; Tien, C.; Wur, C.S.

2003-01-01

Temperature dependences of the integral intensity and NMR signals Knight shift in 199 Hg nuclei are measured for liquid and solid mercury introduced into the porous coal and silica gel. The decrease in the crystallization completion temperature and small temperature hysteresis (from 4 up to 9 K) between melting and crystallization are identified. Mercury melting temperature in pores coincided with melting temperature of the bulk mercury. NMR signal from crystalline mercury under conditions of limited geometry was observed for the first time. It is ascertained that Knight shift for mercury in the pores both in liquid and crystalline phases is lesser than for the bulk mercury [ru

Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials

Directory of Open Access Journals (Sweden)

Peter Hesemann

2014-04-01

Full Text Available The synthesis of nanostructured anionic-surfactant-templated mesoporous silica (AMS recently appeared as a new strategy for the formation of nanostructured silica based materials. This method is based on the use of anionic surfactants together with a co-structure-directing agent (CSDA, mostly a silylated ammonium precursor. The presence of this CSDA is necessary in order to create ionic interactions between template and silica forming phases and to ensure sufficient affinity between the two phases. This synthetic strategy was for the first time applied in view of the synthesis of surface functionalized silica bearing ammonium groups and was then extended on the formation of materials functionalized with anionic carboxylate and bifunctional amine-carboxylate groups. In the field of silica hybrid materials, the “anionic templating” strategy has recently been applied for the synthesis of silica hybrid materials from cationic precursors. Starting from di- or oligosilylated imidazolium and ammonium precursors, only template directed hydrolysis-polycondensation reactions involving complementary anionic surfactants allowed accessing structured ionosilica hybrid materials. The mechanistic particularity of this approach resides in the formation of precursor-surfactant ion pairs in the hydrolysis-polycondensation mixture. This review gives a systematic overview over the various types of materials accessed from this cooperative ionic templating approach and highlights the high potential of this original strategy for the formation of nanostructured silica based materials which appears as a complementary strategy to conventional soft templating approaches.

In situ growth of hollow gold-silver nanoshells within porous silica offers tunable plasmonic extinctions and enhanced colloidal stability.

Science.gov (United States)

Li, Chien-Hung; Jamison, Andrew C; Rittikulsittichai, Supparesk; Lee, Tai-Chou; Lee, T Randall

2014-11-26

Porous silica-coated hollow gold-silver nanoshells were successfully synthesized utilizing a procedure where the porous silica shell was produced prior to the transformation of the metallic core, providing enhanced control over the structure/composition of the bimetallic hollow core. By varying the reaction time and the precise amount of gold salt solution added to a porous silica-coated silver-core template solution, composite nanoparticles were tailored to reveal a readily tunable surface plasmon resonance that could be centered across the visible and near-IR spectral regions (∼445-800 nm). Characterization by X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy revealed that the synthetic methodology afforded particles having uniform composition, size, and shape. The optical properties were evaluated by absorption/extinction spectroscopy. The stability of colloidal solutions of our composite nanoparticles as a function of pH was also investigated, revealing that the nanoshells remain intact over a wide range of conditions (i.e., pH 2-10). The facile tunability, enhanced stability, and relatively small diameter of these composite particles (∼110 nm) makes them promising candidates for use in tumor ablation or as photothermal drug-delivery agents.

The role of positron annihilation lifetime studies and nuclear sensors for characterising porous materials

International Nuclear Information System (INIS)

Mume, E; Smith, S V; Uedono, A; Mizunaga, G; Lynch, D E

2011-01-01

A series of nuclear sensors were designed to assess the chemistry within the nanopores of a porous material. The nuclear sensors of varying size, charge, and hydrophobicity were exposed to hollow silica shells (HSS) at varying pH. Uptake and release kinetics were studied over a 24 h period at room temperature. Preliminary study indicate positively charged nuclear sensors were selectively and rapidly (within 10 min) absorbed by the HSS at pH 7 to 9. PALS showed there were two types of pores (1.7 and 0.7 nm) present. The data suggest the nuclear sensors sit within the larger pore of the HSS. Both PALS and nuclear sensors are required to obtain an accurate insight into the nanoporosity of the hollow silica shells.

The measurement of pore size in porous and microporous materials using resonant ion beam backscattering

International Nuclear Information System (INIS)

Armitage, B.H.; Ramsay, J.D.F.; Brady, F.P.

1978-01-01

Established methods for measuring the size of pores in porous materials include those of mercury porosimetry and gas adsorption. A disadvantage of these methods is that only one determination can be made for each prepared specimen. A property of the ion beam backscattering method is that each specimen can be probed over the surface and also as a function of depth. Furthermore for microporous samples (pore width less than 2 nm) mercury penetration methods cannot be used because the high pressures involved make unreasonable demands in terms of mechanical strength. At the same time gas adsoption techniques are considerably restricted because capillary condensation is no longer possible because of the small size of the pores. A description is given of the methods of calculation of pore size from resonant ion beam backscattering data, with various assumptions for the pore and interpore path length distributions. Examples are shown of results obtained with highly porous silica gels where good agreement with gas adsoption has been achieved. Finally, some results obtained by scanning silica gels of lower porosity are also given. (Auth.)

Two-Stage Crystallizer Design for High Loading of Poorly Water-Soluble Pharmaceuticals in Porous Silica Matrices

OpenAIRE

Leia Dwyer; Samir Kulkarni; Luzdary Ruelas; Allan Myerson

2017-01-01

While porous silica supports have been previously studied as carriers for nanocrystalline forms of poorly water-soluble active pharmaceutical ingredients (APIs), increasing the loading of API in these matrices is of great importance if these carriers are to be used in drug formulations. A dual-stage mixed-suspension, mixed-product removal (MSMPR) crystallizer was designed in which the poorly soluble API fenofibrate was loaded into the porous matrices of pore sizes 35 nm-300 nm in the first st...

Porous material neutron detector

Science.gov (United States)

Diawara, Yacouba [Oak Ridge, TN; Kocsis, Menyhert [Venon, FR

2012-04-10

A neutron detector employs a porous material layer including pores between nanoparticles. The composition of the nanoparticles is selected to cause emission of electrons upon detection of a neutron. The nanoparticles have a maximum dimension that is in the range from 0.1 micron to 1 millimeter, and can be sintered with pores thereamongst. A passing radiation generates electrons at one or more nanoparticles, some of which are scattered into a pore and directed toward a direction opposite to the applied electrical field. These electrons travel through the pore and collide with additional nanoparticles, which generate more electrons. The electrons are amplified in a cascade reaction that occurs along the pores behind the initial detection point. An electron amplification device may be placed behind the porous material layer to further amplify the electrons exiting the porous material layer.

One pot synthesized Li, Zr doped porous silica nanoparticle for low temperature CO2 adsorption

Directory of Open Access Journals (Sweden)

Mani Ganesh

2017-05-01

Full Text Available Li, Zr doped porous silica was synthesized in one pot and investigated for low temperature CO2 adsorption. The synthesized nanoparticle was characterized by X-ray diffraction (XRD, N2 adsorption–desorption measurement, thermogravimetric analysis (TGA and scanning electron microscopy (SEM. The specific surface area, average pore diameter and pore volume were determined to be 962 m2/g, 2.3 nm and 0.56 cm3/g respectively. ICP-AES analysis revealed a metal content of 4 wt.% (Zr and 3.42 wt.% (Li. Their CO2 adsorption capacity was tested at room temperature and atmospheric pressure. An uptake of about 5 wt.% was observed and regenerable at a low temperature of 200 °C. This adsorption and desorption temperature of the sorbent is lower than the reported lithium silicate. The CO2 adsorption–desorption cyclic performance studies illustrated that Li, Zr doped porous silica is a recyclable, selective and potential sorbent for CO2 adsorption.

Characterization of Lignocellulosic Biomass as Raw Material for the Production of Porous Carbon-based Materials

Directory of Open Access Journals (Sweden)

Saptadi Darmawan

2016-02-01

Full Text Available Lignocellulosic biomass is a potential raw material that can be used in the synthesis (manufacture of porous carbon stuffs. The properties of such porous carbon products are affected by the species of the raw material and the manufacturing process, among other things. This paper scrutinizes the related characteristics of lignocellulosic raw materials that indicate potential for the production of porous carbon. Three species were used: pine (Pinus merkusii wood, mangium (Acacia mangium wood, and candlenut (Aleurites moluccana shells, representing softwoods, hardwoods, and non-wood stuffs, respectively. Analyses of their chemical compounds and proximate contents were carried out. Additionally, nano scale scrutiny of the lignocellulosic biomass was also conducted using the nano capable instruments, which consisted of SEM, EDS, XRD, FTIR, and DSC. Results revealed that pine wood had the most potential to produce porous carbon. Morphologically, pine wood afforded the best permeability, whereby at the structure of monoclinic cellulose crystals, there were cellulose-I(alpha structures, which contained less cellulose-I(beta structures. Furthermore, pine wood exhibited greater volatile matter content, as confirmed through the FTIR, which greatly assisted the forming of porosity inside its corresponding carbon.

Enthalpy-based equation of state for highly porous materials employing modified soft sphere fluid model

Science.gov (United States)

Nayak, Bishnupriya; Menon, S. V. G.

2018-01-01

Enthalpy-based equation of state based on a modified soft sphere model for the fluid phase, which includes vaporization and ionization effects, is formulated for highly porous materials. Earlier developments and applications of enthalpy-based approach had not accounted for the fact that shocked states of materials with high porosity (e.g., porosity more than two for Cu) are in the expanded fluid region. We supplement the well known soft sphere model with a generalized Lennard-Jones formula for the zero temperature isotherm, with parameters determined from cohesive energy, specific volume and bulk modulus of the solid at normal condition. Specific heats at constant pressure, ionic and electronic enthalpy parameters and thermal excitation effects are calculated using the modified approach and used in the enthalpy-based equation of state. We also incorporate energy loss from the shock due to expansion of shocked material in calculating porous Hugoniot. Results obtained for Cu, even up to initial porosities ten, show good agreement with experimental data.

Mannose-functionalized porous silica-coated magnetic nanoparticles for two-photon imaging or PDT of cancer cells

International Nuclear Information System (INIS)

Perrier, Marine; Gary-Bobo, Magali; Lartigue, Lenaïc; Brevet, David; Morère, Alain; Garcia, Marcel; Maillard, Philippe; Raehm, Laurence; Guari, Yannick; Larionova, Joulia; Durand, Jean-Olivier; Mongin, Olivier; Blanchard-Desce, Mireille

2013-01-01

An original fluorophore engineered for two-photon excitation or a porphyrin derivative were entrapped in the silica shell of magnetic porous silica nanoparticles during the synthesis of the silica moiety without damaging the structure of the organic part. The mild conditions involved allowed obtaining microporous or mesoporous silica magnetic nanoparticles, respectively. Mannose was grafted on the surface of the nanoparticles to target MCF-7 breast cancer cells. The studies of magnetic properties of these hybrid nanoparticles show that they present a blocking temperature at 190 K. The nano-objects designed with the two-photon fluorophore were efficient for two-photon imaging of MCF-7 cancer cells, whereas the nano-objects with the photosensitizer efficiently killed cancer cells. The presence of the mannose moiety was demonstrated to improve both imaging and therapy properties.

Mannose-functionalized porous silica-coated magnetic nanoparticles for two-photon imaging or PDT of cancer cells

Energy Technology Data Exchange (ETDEWEB)

Perrier, Marine [UMR 5253 CNRS-UM2-ENSCM-UM1, Institut Charles Gerhardt Montpellier (France); Gary-Bobo, Magali [Faculte de Pharmacie, Universite Montpellier 1, Universite Montpellier 2, Institut des Biomolecules Max Mousseron UMR 5247 CNRS (France); Lartigue, Lenaiec; Brevet, David [UMR 5253 CNRS-UM2-ENSCM-UM1, Institut Charles Gerhardt Montpellier (France); Morere, Alain; Garcia, Marcel [Faculte de Pharmacie, Universite Montpellier 1, Universite Montpellier 2, Institut des Biomolecules Max Mousseron UMR 5247 CNRS (France); Maillard, Philippe [Universite Paris-Sud, UMR 176 CNRS, Institut Curie (France); Raehm, Laurence; Guari, Yannick, E-mail: yannick.guari@um2.fr; Larionova, Joulia; Durand, Jean-Olivier, E-mail: durand@univ-montp2.fr [UMR 5253 CNRS-UM2-ENSCM-UM1, Institut Charles Gerhardt Montpellier (France); Mongin, Olivier [Universite de Rennes 1, Institut des Sciences Chimiques de Rennes, CNRS UMR 6226 (France); Blanchard-Desce, Mireille [Universite Bordeaux, Institut des Sciences Moleculaires, UMR CNRS 5255 (France)

2013-05-15

An original fluorophore engineered for two-photon excitation or a porphyrin derivative were entrapped in the silica shell of magnetic porous silica nanoparticles during the synthesis of the silica moiety without damaging the structure of the organic part. The mild conditions involved allowed obtaining microporous or mesoporous silica magnetic nanoparticles, respectively. Mannose was grafted on the surface of the nanoparticles to target MCF-7 breast cancer cells. The studies of magnetic properties of these hybrid nanoparticles show that they present a blocking temperature at 190 K. The nano-objects designed with the two-photon fluorophore were efficient for two-photon imaging of MCF-7 cancer cells, whereas the nano-objects with the photosensitizer efficiently killed cancer cells. The presence of the mannose moiety was demonstrated to improve both imaging and therapy properties.

Hybrid silica luminescent materials based on lanthanide-containing lyotropic liquid crystal with polarized emission

Energy Technology Data Exchange (ETDEWEB)

Selivanova, N.M., E-mail: natsel@mail.ru [Kazan National Research Technological University, 68 Karl Marx Str., Kazan 420015 (Russian Federation); Vandyukov, A.E.; Gubaidullin, A.T. [A.E. Arbuzov Institute of Organic and Physical Chemistry of the Kazan Scientific Center of the Russian Academy of Sciences, 8 Acad. Arbuzov Str., Kazan 420088 (Russian Federation); Galyametdinov, Y.G. [Kazan National Research Technological University, 68 Karl Marx Str., Kazan 420015 (Russian Federation)

2014-11-14

This paper represents the template method for synthesis of hybrid silica films based on Ln-containing lyotropic liquid crystal and characterized by efficient luminescence. Luminescence films were prepared in situ by the sol–gel processes. Lyotropic liquid crystal (LLC) mesophases C{sub 12}H{sub 25}O(CH{sub 2}CH{sub 2}O){sub 10}H/Ln(NO{sub 3}){sub 3}·6H{sub 2}O/H{sub 2}O containing Ln (III) ions (Dy, Tb, Eu) were used as template. Polarized optical microscopy, X-ray powder diffraction, and FT-IR-spectroscopy were used for characterization of liquid crystal mesophases and hybrid films. The morphology of composite films was studied by the atomic force microscopy method (AFM). The optical properties of the resulting materials were evaluated. It was found that hybrid silica films demonstrate significant increase of their lifetime in comparison with an LLC system. New effects of linearly polarized emission revealed for Ln-containing hybrid silica films. Polarization in lanthanide-containing hybrid composites indicates that silica precursor causes orientation of emitting ions. - Highlights: • We suggest a new simple approach for creating luminescence hybrid silica films. • Ln-containing hybrid silica films demonstrate yellow, green and red emissions. • Tb(III)-containing hybrid film have a high lifetime. • We report effects of linearly polarized emission in hybrid film.

Functional Biomass Carbons with Hierarchical Porous Structure for Supercapacitor Electrode Materials

International Nuclear Information System (INIS)

Chen, Hao; Liu, Duo; Shen, Zhehong; Bao, Binfu; Zhao, Shuyan; Wu, Limin

2015-01-01

Highlights: • We successfully prepared bamboo-derived porous carbon with B and N co-doping. • This novel carbon exhibits significantly enhanced specific capacitance and energy density. • The highest specific capacitance exceeds those of most similar carbon materials. • Asymmetric supercapacitor based on this carbon shows satisfactory capacitive performance. - Abstract: This paper presents nitrogen and boron co-doped KOH-activated bamboo-derived carbon as a porous biomass carbon with utility as a supercapacitor electrode material. Owing to the high electrochemical activity promoted by the hierarchical porous structure and further endowed by boron and nitrogen co-doping, electrodes based on the as-obtained material exhibit significantly enhanced specific capacitance and energy density relative to those based on most similar materials. An asymmetric supercapacitor based on this novel carbon material demonstrated satisfactory energy density and electrochemical cycling stability.

The carbonaceous sorbent based on the secondary silica-containing material from oil extraction industry

Science.gov (United States)

Starostina, I. V.; Stolyarov, D. V.; Anichina, Ya N.; Porozhnyuk, E. V.

2018-01-01

The object of research in this work is the silica-containing waste of oil extraction industry - the waste kieselghur (diatomite) sludge from precoat filtering units, used for the purification of vegetable oils from organic impurities. As a result of the thermal modification of the sludge, which contains up to 70% of organic impurities, a finely-dispersed low-porous carbonaceous mineral sorption material is formed. The modification of the sludge particles surface causes the substantial alteration of its physical, chemical, adsorption and structural properties - the organic matter is charred, the particle size is reduced, and on the surface of diatomite particles a carbon layer is formed, which deposits in macropores and partially occludes them. The amount of mesopores is increased, along with the specific surface of the obtained product. The optimal temperature of sludge modification is 500°C. The synthesized carbonaceous material can be used as an adsorbing agent for the purification of wastewater from heavy metal ions. The sorption capacity of Cu2+ ions amounted to 14.2 mg·g-1 and for Ni2+ ions - 17.0 mg·g-1. The obtained values exceed the sorption capacity values of the initial kieselghur, used as a filtering charge, for the researched metal ions.

Syntheses of carbon porous materials with varied pore sizes and their performances as catalyst supports during methanol oxidation reaction

International Nuclear Information System (INIS)

Lo, An-Ya; Hung, Chin-Te; Yu, Ningya; Kuo, Cheng-Tzu; Liu, Shang-Bin

2012-01-01

Highlights: ► CPMs with varied pore sizes (1–400 nm) were replicated from various porous silicas by CVI method. ► MOR activities of Pt/CPM electrocatalysts increase with increasing pore size of CPM support. ► Microporous CPMs are favorable supports for Pt in terms of catalytic performance and CO-tolerance. -- Abstract: Carbon porous materials (CPMs) with extended ranges of pore size and morphology were replicated using various porous silicas, such as zeolites, mesoporous silicas, and photonic crystals, as templates by means of chemical vapor infiltration (CVI) method. The micro-, meso-, and macro-porous carbons so fabricated were adopted as supports for the metal (Pt) catalyst for direct methanol fuel cells (DMFCs), and the supported Pt/CPM electrocatalysts were characterized by a variety of different spectroscopic/analytical techniques, viz. transmission electron microscopy (TEM), Raman, X-ray photoelectron spectroscopy (XPS), gas physisorption/chemisorption analyses, and cyclic voltammetry (CV). That these Pt/CPMs were found to exhibit superior electrocatalytic activities compared to the commercial Pt/XC-72 with a comparable Pt loading during methanol oxidation reaction (MOR) is attributed to the presence of Pt nanoparticles (NPs; typically 1–3 nm in size) that are highly dispersed in the CPMs, facilitating an improved tolerance for CO poisoning. While the MOR activity observed for various Pt/CPMs tend to increase with increasing pore size of the carbon supports, Pt catalyst supported on carbon substrates possessing microporosities was found to have superior stability in terms of tolerance for CO poisoning than those with greater pore size or having meso- and macroporosities.

Microporous Silica Based Membranes for Desalination

Directory of Open Access Journals (Sweden)

João C. Diniz da Costa

2012-09-01

Full Text Available This review provides a global overview of microporous silica based membranes for desalination via pervaporation with a focus on membrane synthesis and processing, transport mechanisms and current state of the art membrane performance. Most importantly, the recent development and novel concepts for improving the hydro-stability and separating performance of silica membranes for desalination are critically examined. Research into silica based membranes for desalination has focussed on three primary methods for improving the hydro-stability. These include incorporating carbon templates into the microporous silica both as surfactants and hybrid organic-inorganic structures and incorporation of metal oxide nanoparticles into the silica matrix. The literature examined identified that only metal oxide silica membranes have demonstrated high salt rejections under a variety of feed concentrations, reasonable fluxes and unaltered performance over long-term operation. As this is an embryonic field of research several target areas for researchers were discussed including further improvement of the membrane materials, but also regarding the necessity of integrating waste or solar heat sources into the final process design to ensure cost competitiveness with conventional reverse osmosis processes.

A polyacrylonitrile copolymer-silica template for three-dimensional hierarchical porous carbon as a Pt catalyst support for the oxygen reduction reaction.

Science.gov (United States)

Liu, Minmin; Li, Jian; Cai, Chao; Zhou, Ziwei; Ling, Yun; Liu, Rui

2017-08-01

Herein, we report a novel route to construct a hierarchical three-dimensional porous carbon (3DC) through a copolymer-silica assembly. In the synthesis, silica acts as a hard template and leads to the formation of an interconnected 3D macropore, whereas styrene-co-acrylonitrile polymer has been used as both a carbon source and a soft template for micro- and meso-pores. The obtained 3DC materials possess a large surface area (∼550.5 m 2 g -1 ), which facilitates high dispersion of Pt nanoparticles on the carbon support. The 3DC-supported Pt electrocatalyst shows excellent performance in the oxygen reduction reaction (ORR). The easy processing ability along with the characteristics of hierarchical porosity offers a new strategy for the preparation of carbon nanomaterials for energy application.

Geometry and topology of porous materials

International Nuclear Information System (INIS)

Cohen, M.H.

1985-01-01

A very general definition of porous materials is given. The method of Lin and Cohen for the simple but exact description of the topology of porous materials is reviewed. The method leads to a precise definition of chambers, channels, and throats in the pore space. The power and utility of the method is illustrated via a discussion of the remarkable morphological features of porous rocks. These are enumerated and explained

Silica- and silylated europium-based luminescent hybrids: new analysis tools for biological environments

International Nuclear Information System (INIS)

Pereira Duarte, Adriana

2012-01-01

The association of the very interesting luminescence properties of the lanthanide chelates with the physicochemical properties of inorganic matrix such as silica is a promising way to obtain new probes or luminescent markers for biology analyses. In this idea, this work focuses on the preparation of new hybrid materials based on the grafting of new europium(III) complexes on silica nanoparticles. These europium complexes were developed in our group using bifunctional ligands containing both complexing and grafting sites. Intrinsic characteristic of the ligands gives us the ability to make a covalent bond between the material surface and the complex. Two different methodologies were used; the first one is the direct grafting reaction involving the complex and silica nanoparticles (i.e. dense or meso-porous particles). The second one is the Stoeber reaction, where the SiO 2 nanoparticles were prepared in presence of the europium complex. The last methodology has an additional difficult, because of the presence of silylated europium complex, it needs a closer control of the physicochemical conditions. The new organic-inorganic hybrid materials, obtained in this work, present an interesting luminescence behavior and this one is depending on the localization of the europium complex, i.e. on the surface or within the nanoparticles. In addition, the obtained hybrids present the nano-metric dimension and the complex is not leachable. Analyses were realized to describe the luminescence properties, beyond surface and structural characteristics. Initial results show that the new hybrids are promising candidates for luminescent bio-markers, particularly for the time-resolved analysis. (author) [fr

Novel sponge-like molecularly imprinted mesoporous silica material for selective isolation of bisphenol A and its analogues from sediment extracts

International Nuclear Information System (INIS)

Yang, Jiajia; Li, Yun; Wang, Jincheng; Sun, Xiaoli; Shah, Syed Mazhar; Cao, Rong; Chen, Jiping

2015-01-01

Highlights: • Novel sponge-like molecularly imprinted mesoporous silica was synthesized. • Extraordinarily large specific surface area and highly interconnected 3-D porous network. • High specific adsorption capacity and fast adsorption kinetics for BPA. • Good class-selectivity and clean-up effect for bisphenols in sediment under SPE mode. • Good recoveries and sensitivity for bisphenols using the MISMS–SPE coupled with HPLC–DAD method. - Abstract: Bisphenol A (BPA) imprinted sponge mesoporous silica was synthesized using a combination of semi-covalent molecular imprinting and simple self-assembly process. The molecularly imprinted sponge mesoporous silica (MISMS) material obtained was characterized by FT-IR, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption measurements. The results show that the MISMS possessed a large specific surface area (850.55 m 2 g −1 ) and a highly interconnected 3-D porous network. As a result, the MISMS demonstrated a superior specific adsorption capacity of 169.22 μmol g −1 and fast adsorption kinetics (reaching equilibrium within 3 min) for BPA. Good class selectivity for BPA and its analogues (bisphenol F, bisphenol B, bisphenol E and bisphenol AF) was also demonstrated by the sorption experiment. The MISMS as solid-phase extraction (SPE) material was then evaluated for isolation and clean-up of these bisphenols (BPs) from sediment samples. An accurate and sensitive analytical method based on the MISMS–SPE coupled with HPLC–DAD has been successfully established for simultaneous determination of five BPs in river sediments with detection limits of 0.43–0.71 ng g −1 dry weight (dw). The recoveries of BPs for lyophilizated sediment samples at two spiking levels (50 and 500 ng g −1 dw for each BP) were in the range of 75.5–105.5% with RSD values below 7.5%

Novel sponge-like molecularly imprinted mesoporous silica material for selective isolation of bisphenol A and its analogues from sediment extracts

Energy Technology Data Exchange (ETDEWEB)

Yang, Jiajia [Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Li, Yun; Wang, Jincheng [Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023 (China); Sun, Xiaoli [Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Shah, Syed Mazhar [Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023 (China); Cao, Rong [Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Chen, Jiping, E-mail: chenjp@dicp.ac.cn [Key Laboratory of Separation Sciences for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023 (China)

2015-01-01

Highlights: • Novel sponge-like molecularly imprinted mesoporous silica was synthesized. • Extraordinarily large specific surface area and highly interconnected 3-D porous network. • High specific adsorption capacity and fast adsorption kinetics for BPA. • Good class-selectivity and clean-up effect for bisphenols in sediment under SPE mode. • Good recoveries and sensitivity for bisphenols using the MISMS–SPE coupled with HPLC–DAD method. - Abstract: Bisphenol A (BPA) imprinted sponge mesoporous silica was synthesized using a combination of semi-covalent molecular imprinting and simple self-assembly process. The molecularly imprinted sponge mesoporous silica (MISMS) material obtained was characterized by FT-IR, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption measurements. The results show that the MISMS possessed a large specific surface area (850.55 m{sup 2} g{sup −1}) and a highly interconnected 3-D porous network. As a result, the MISMS demonstrated a superior specific adsorption capacity of 169.22 μmol g{sup −1} and fast adsorption kinetics (reaching equilibrium within 3 min) for BPA. Good class selectivity for BPA and its analogues (bisphenol F, bisphenol B, bisphenol E and bisphenol AF) was also demonstrated by the sorption experiment. The MISMS as solid-phase extraction (SPE) material was then evaluated for isolation and clean-up of these bisphenols (BPs) from sediment samples. An accurate and sensitive analytical method based on the MISMS–SPE coupled with HPLC–DAD has been successfully established for simultaneous determination of five BPs in river sediments with detection limits of 0.43–0.71 ng g{sup −1} dry weight (dw). The recoveries of BPs for lyophilizated sediment samples at two spiking levels (50 and 500 ng g{sup −1} dw for each BP) were in the range of 75.5–105.5% with RSD values below 7.5%.

Porous materials based on foaming solutions obtained from industrial waste

Science.gov (United States)

Starostina, I. V.; Antipova, A. N.; Ovcharova, I. V.; Starostina, Yu L.

2018-03-01

This study analyzes foam concrete production efficiency. Research has shown the possibility of using a newly-designed protein-based foaming agent to produce porous materials using gypsum and cement binders. The protein foaming agent is obtained by alkaline hydrolysis of a raw mixture consisting of industrial waste in an electromagnetic field. The mixture consists of spent biomass of the Aspergillus niger fungus and dust from burning furnaces used in cement production. Varying the content of the foaming agent allows obtaining gypsum binder-based foam concretes with the density of 200-500 kg/m3 and compressive strength of 0.1-1.0 MPa, which can be used for thermal and sound insulation of building interiors. Cement binders were used to obtain structural and thermal insulation materials with the density of 300-950 kg/m3 and compressive strength of 0.9-9.0 MPa. The maximum operating temperature of cement-based foam concretes is 500°C because it provides the shrinkage of less than 2%.

A new porous hybrid material derived from silica fume and alginate for sustainable pollutants reduction

Science.gov (United States)

Zanoletti, Alessandra; Vassura, Ivano; Venturini, Elisa; Monai, Matteo; Montini, Tiziano; Federici, Stefania; Zacco, Annalisa; Treccani, Laura; Bontempi, Elza

2018-03-01

In this work a new mesoporous adsorbent material obtained from a natural, high abundant raw material and a high volume industrial by-product is presented. The material is consolidated by the gelling properties of alginate and by decomposition of sodium-bicarbonate controlled porosity at low temperatures (70-80°C) at different scale lengths. The structural, thermal, and morphological characterization shows that the material is a mesoporous organic-inorganic hybrid. The material is tested as adsorbent, showing high performances. Methylene blue, used as model pollutant, can be adsorbed and removed from aqueous solutions even at a high concentration with efficiency up to 94%. By coating the material with a 100 nm thin film of titania, good photodegradation performance (more than 20%) can be imparted. Based on embodied energy and carbon footprint of its primary production, the sustainability of the new obtained material is evaluated and quantified in respect to activated carbon as well. It is shown that the new proposed material has an embodied energy lower than one order of magnitude in respect to the one of activated carbon, which represents the gold standards. The versatility of the new material is also demonstrated in terms of its design and manufacturing possibilities. In addition, this material can be printed in 3D. Finally, preliminary results about its ability to capture diesel exhaust particulate matter are reported. The sample exposed to diesel contains a large amount of carbon in its surface. At the best of our knowledge this is the first time that hybrid porous materials are proposed as a new class of sustainable materials, produced to reduce pollutants in the wastewaters and in the atmosphere.

Granulation study of porous silica particles for MA recovery process

International Nuclear Information System (INIS)

Goto, Ichiro; Kofuji, Hirohide; Oriuchi, Akio; Watanabe, Sou; Takeuchi, Masayuki

2017-01-01

JAEA has been working on partition of MA from HLLW generated in the reprocessing by extraction chromatography technology. This technology utilizes 50 μm porous silica particles coated by styrene-divinylbenzene copolymer in which an extractant for MA recovery is impregnated as adsorbent. In this study, spray drying granulating experiments with various operating conditions and with different experimental apparatuses were carried out to find an appropriate condition to control the size of the particle and the pore. The target average sizes of the particle and pore are more than 50 μm and 600 nm respectively. Suspension containing fine silica particles were supplied to the spray drying devices, and small droplets generated through the spray nozzle were dried inside the drying chamber. In this study, viscosity of the feed solution and some granulation conditions were parametrically changed, and two different types of the spray nozzles were used. An air atomizing nozzle and a rotary disk nozzle were equipped at different chambers respectively. Then, performance of the product particle was evaluated by particle and pore size distributions and adsorption experiment after the polymer coating and an extractant impregnation. The particle size of the product depended on the atomizing pressure and viscosity of the feed solution, and the size increased with decrease in the pressure and in the viscosity. The maximum size obtained in this study was about 40 μm. Large viscosity of the feed solution lead poor recovery ratio and uniformity in the size distribution of the product powder. The pore size of the resultant particle was 550-800 nm as expected. As the type of the nozzle changed from the air atomizing nozzle to the rotary disk nozzle and size of the drying chamber became large, the average particle size and the particle size distribution became large and sharp, respectively. Rotation speed of the nozzle also influenced on the particle size, and targeted average size of the

Rhodamine 6G impregnated porous silica: A photoluminescence study

Energy Technology Data Exchange (ETDEWEB)

Anedda, A. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Canada) (Italy); Carbonaro, C.M. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Canada) (Italy)]. E-mail: cm.carbonaro@dsf.unica.it; Clemente, F. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Ca) (Italy); Corpino, R. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Ca) (Italy); Ricci, P.C. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Ca) (Italy); Rossini, S. [Dipartimento di Fisica, Universita degli Studi di Cagliari and INMF UdR Cagliari, SP no8, Km 0700, 09042, Monserrato (Ca) (Italy)

2005-12-15

The optical properties of rhodamine 6G dye confined in porous silica are reported. Photoluminescence properties of embedded chromophores in mesoporous hosts can be affected by the surrounding matrices: shifts in emission spectra and variations of photoluminescence quantum yield are found as compared to dye solutions. Host-guest interactions are studied here by varying both SiO{sub 2} xerogels porosity and the dye concentration. Comparing samples obtained by impregnating matrices with 5.4 and 18.2 nm pores with solutions having concentrations in the rhodamine 6G high laser gain, matrices with 5.4 nm pores impregnated with a dye concentration of 5 x 10{sup -4} M are found to be the most stable and efficient in the examined range.

Transport of oxidized multi-walled carbon nanotubes through silica based porous media: influences of aquatic chemistry, surface chemistry, and natural organic matter.

Science.gov (United States)

Yang, Jin; Bitter, Julie L; Smith, Billy A; Fairbrother, D Howard; Ball, William P

2013-12-17

This paper provides results from studies of the transport of oxidized multi-walled carbon nanotubes (O-MWCNTs) of varying surface oxygen concentrations under a range of aquatic conditions and through uniform silica glass bead media. In the presence of Na(+), the required ionic strength (IS) for maximum particle attachment efficiency (i.e., the critical deposition concentration, or CDC) increased as the surface oxygen concentration of the O-MWCNTs or pH increased, following qualitative tenets of theories based on electrostatic interactions. In the presence of Ca(2+), CDC values were lower than those with Na(+) present, but were no longer sensitive to surface oxygen content, suggesting that Ca(2+) impacts the interactions between O-MWCNTs and glass beads by mechanisms other than electrostatic alone. The presence of Suwannee River natural organic matter (SRNOM) decreased the attachment efficiency of O-MWCNTs in the presence of either Na(+) or Ca(2+), but with more pronounced effects when Na(+) was present. Nevertheless, low concentrations of SRNOM (organic carbon) were sufficient to mobilize all O-MWCNTs studied at CaCl2 concentrations as high as 10 mM. Overall, this study reveals that NOM content, pH, and cation type show more importance than surface chemistry in affecting O-MWCNTs deposition during transport through silica-based porous media.

Fractal dimensions of silica gels generated using reactive molecular dynamics simulations

International Nuclear Information System (INIS)

Bhattacharya, Sudin; Kieffer, John

2005-01-01

We have used molecular dynamics simulations based on a three-body potential with charge transfer to generate nanoporous silica aerogels. Care was taken to reproduce the sol-gel condensation reaction that forms the gel backbone as realistically as possible and to thereby produce credible gel structures. The self-similarity of aerogel structures was investigated by evaluating their fractal dimension from geometric correlations. For comparison, we have also generated porous silica glasses by rupturing dense silica and computed their fractal dimension. The fractal dimension of the porous silica structures was found to be process dependent. Finally, we have determined that the effect of supercritical drying on the fractal nature of condensed silica gels is not appreciable

A study of luminescence from silicon-rich silica fabricated by plasma enhanced chemical vapour deposition

International Nuclear Information System (INIS)

Trwoga, P.F.

1998-01-01

Silicon is the most studied electronic material known to man and dominates the electronics industry in its use as a semiconductors for nearly all integrated electronics. However, optoelectronics is almost entirely based on III-V materials. This technology is used because silicon is a very inefficient light source, whereas the III-V band structure can lend itself to efficient light emission by electron injection. However, due to the overwhelming dominance of silicon based electronics it is still a highly desirable goal to generate light efficiently from silicon based materials. Recently, studies have demonstrated that efficient visible luminescence can be obtained from certain novel forms of silicon. These materials include porous silicon, hydrogenated amorphous silicon, and silicon-rich silica (SiO x x x is studied in detail; in addition, electroluminescence and rare-earth doping of silicon-rich silica is also addressed. (author)

Fabrication of Porous Ceramic-Geopolymer Based Material to Improve Water Absorption and Retention in Construction Materials: A Review

Science.gov (United States)

Jamil, N. H.; Ibrahim, W. M. A. W.; Abdullah, M. M. A. B.; Sandu, A. V.; Tahir, M. F. M.

2017-06-01

Porous ceramic nowadays has been investigated for a variety of its application such as filters, lightweight structural component and others due to their specific properties such as high surface area, stability and permeability. Besides, it has the properties of low thermal conductivity. Various formation techniques making these porous ceramic properties can be tailored or further fine-tuned to obtain the optimum characteristic. Porous materials also one of the good candidate for absorption properties. Conventional construction materials are not design to have good water absorption and retention that lead to the poor performance on these criteria. Temperature is a major driving force for moisture movement and influences sorption characteristics of many constructions materials. The effect of elevated temperatures on the water absorption coefficient and retention remain as critical issue that need to be investigated. Therefore, this paper will review the process parameters in fabricating porous ceramic for absorption properties.

Study of water radiolysis in porous media

International Nuclear Information System (INIS)

Rotureau, Patricia

2001-08-01

The understanding of the production of H 2 in the radiolysis of water confined into pores of concrete is important for the disposal of radioactive waste. In order to describe the mechanisms of water radiolysis in such heterogeneous porous systems we have studied the behaviour under gamma radiation of water confined in porous silica glasses with pores going from 8 to 300 nm of diameter and meso-porous molecular sieves (MCM-41). The radiolytic yields of hydroxyl radicals, hydrated electron and dihydrogen, have been determined with respect to the pore size of materials. The increase of these radiolytic yields compared to those of free water allowed us to show a charge transfer from silica to confined water. On the other hand the kinetics of hydrated electron reactions measured by pulse radiolysis are not modified. (author) [fr

Constitutive model for porous materials

International Nuclear Information System (INIS)

Weston, A.M.; Lee, E.L.

1982-01-01

A simple pressure versus porosity compaction model is developed to calculate the response of granular porous bed materials to shock impact. The model provides a scheme for calculating compaction behavior when relatively limited material data are available. While the model was developed to study porous explosives and propellants, it has been applied to a much wider range of materials. The early development of porous material models, such as that of Hermann, required empirical dynamic compaction data. Erkman and Edwards successfully applied the early theory to unreacted porous high explosives using a Gruneisen equation of state without yield behavior and without trapped gas in the pores. Butcher included viscoelastic rate dependance in pore collapse. The theoretical treatment of Carroll and Holt is centered on the collapse of a circular pore and includes radial inertia terms and a complex set of stress, strain and strain rate constitutive parameters. Unfortunately data required for these parameters are generally not available. The model described here is also centered on the collapse of a circular pore, but utilizes a simpler elastic-plastic static equilibrium pore collapse mechanism without strain rate dependence, or radial inertia terms. It does include trapped gas inside the pore, a solid material flow stress that creates both a yield point and a variation in solid material pressure with radius. The solid is described by a Mie-Gruneisen type EOS. Comparisons show that this model will accurately estimate major mechanical features which have been observed in compaction experiments

Functionalized silica materials for electrocatalysis

Indian Academy of Sciences (India)

To increase the efficiency of the electrocatalytic process and to increase the electrochemical accessibility of the immobilized electrocatalysts, functionalized and non-functionalized mesoporous organo-silica (MCM41-type-materials) are used in this study. These materials possess several suitable properties to be durable ...

Recent Advances in Porous Carbon Materials for Electrochemical Energy Storage.

Science.gov (United States)

Wang, Libin; Hu, Xianluo

2018-06-18

Climate change and the energy crisis have promoted the rapid development of electrochemical energy-storage devices. Owing to many intriguing physicochemical properties, such as excellent chemical stability, high electronic conductivity, and a large specific surface area, porous carbon materials have always been considering as a promising candidate for electrochemical energy storage. To date, a wide variety of porous carbon materials based upon molecular design, pore control, and compositional tailoring have been proposed for energy-storage applications. This focus review summarizes recent advances in the synthesis of various porous carbon materials from the view of energy storage, particularly in the past three years. Their applications in representative electrochemical energy-storage devices, such as lithium-ion batteries, supercapacitors, and lithium-ion hybrid capacitors, are discussed in this review, with a look forward to offer some inspiration and guidelines for the exploitation of advanced carbon-based energy-storage materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electroactive Properties of 1-propyl-3-methylimidazolium Ionic Liquid Covalently Bonded on Mesoporous Silica Surface: Development of an Electrochemical Sensor Probed for NADH, Dopamine and Uric Acid Detection

International Nuclear Information System (INIS)

Maroneze, Camila M.; Rahim, Abdur; Fattori, Natália; Costa, Luiz P. da; Sigoli, Fernando A.; Mazali, Italo O.; Custodio, Rogério; Gushikem, Yoshitaka

2014-01-01

Graphical abstract: - Abstract: A hybrid organic-inorganic porous material was successfully prepared through chemical modification of a non-ordered mesoporous silica, obtained by the sol-gel process, with 1-propyl-3-methylimidazolium groups. The porous material was evaluated as a platform for the development of electrochemical sensors, here probed toward the electrooxidation of NADH (β-nicotinamide adenine dinucleotide), uric acid (UA) and dopamine (DA). The presence of cationic imidazolium groups on the surface of the hybrid silica-based material allowed the electrochemical detection of these biomolecules without any other electron mediator or biomolecular recognition component. Such behavior highlights the potentiality of this material to be applied in the development of new electrochemical sensing devices. Theoretical calculations based on density functional theory emphasizes that the cationic character of imidazolium group provides better oxidation conditions if the solvent effect is minimized

Effect of porous material heating on the drag force of a cylinder with gas-permeable porous inserts in a supersonic flow

Science.gov (United States)

Mironov, S. G.; Poplavskaya, T. V.; Kirilovskiy, S. V.

2017-10-01

The paper presents the results of an experimental investigation of supersonic flow around a solid cylinder with a gas-permeable porous insert on its front end and of supersonic flow around a hollow cylinder with internal porous inserts in the presence of heating of the porous material. The experiments were performed in a supersonic wind tunnel with Mach number 4.85 and 7 with porous inserts of cellular-porous nickel. The results of measurements on the filtration stand of the air filtration rate through the cellular-porous nickel when it is heated are also shown. For a number of experiments, numerical modeling based on the skeletal model of a cellular-porous material was carried out.

High-average-power laser medium based on silica glass

Science.gov (United States)

Fujimoto, Yasushi; Nakatsuka, Masahiro

2000-01-01

Silica glass is one of the most attractive materials for a high-average-power laser. We have developed a new laser material base don silica glass with zeolite method which is effective for uniform dispersion of rare earth ions in silica glass. High quality medium, which is bubbleless and quite low refractive index distortion, must be required for realization of laser action. As the main reason of bubbling is due to hydroxy species remained in the gelation same, we carefully choose colloidal silica particles, pH value of hydrochloric acid for hydrolysis of tetraethylorthosilicate on sol-gel process, and temperature and atmosphere control during sintering process, and then we get a bubble less transparent rare earth doped silica glass. The refractive index distortion of the sample also discussed.

A new surface catalytic model for silica-based thermal protection material for hypersonic vehicles

Directory of Open Access Journals (Sweden)

Li Kai

2015-10-01

Full Text Available Silica-based materials are widely employed in the thermal protection system for hypersonic vehicles, and the investigation of their catalytic characteristics is crucially important for accurate aerothermal heating prediction. By analyzing the disadvantages of Norman’s high and low temperature models, this paper combines the two models and proposes an eight-reaction combined surface catalytic model to describe the catalysis between oxygen and silica surface. Given proper evaluation of the parameters according to many references, the recombination coefficient obtained shows good agreement with experimental data. The catalytic mechanisms between oxygen and silica surface are then analyzed. Results show that with the increase of the wall temperature, the dominant reaction contributing to catalytic coefficient varies from Langmuir–Hinshelwood (LH recombination (TW  1350 K. The surface coverage of chemisorption areas varies evidently with the dominant reactions in the high temperature (HT range, while the surface coverage of physisorption areas varies within quite low temperature (LT range (TW < 250 K. Recommended evaluation of partial parameters is also given.

The Effect of Using Sewage Sludge Ash with and without Nano Silica Particles on Properties of Self-compacting Cement Based Materials

Directory of Open Access Journals (Sweden)

Amin Khoshravesh

2014-10-01

Full Text Available Nowadays using pozzolanic materials is crucial as a replacement of needed cement, improving properties of cement based materials and saving costs. On the other hand sewage sludge is harmful to the environment and human health. So in this research the sewage sludge ash has been used as an artificial pozzolan to produce self compacting cement based materials which could be evaluated as a revolution in the concrete industry. The objective of this research was to accelerate the performance of sewage sludge ash by utilizing nano silica particles. This research includes 10 mix designs for self compacting mortar and concrete made up of binary and ternary cementitious blends of sewage sludge ash (0%,5%,10%,15%,20% and nano silica (0%,1%. The results showed that by adding the sewage sludge ash, rheological and mechanical properties of the samples were reduced and for small percentages of sewage sludge ash, the durability characteristics were improved. The results also showed that adding nano silica improved the mechanical and durability properties of self compacting mortar and concrete. Finally in presence of nano silica, the reactivity of the sewage sludge ash was increased and its performance was improved.

FACADE SYSTEM MADE OF POROUS MATERIALS

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Zhukov Aleksey Dmitrievich

2012-10-01

Full Text Available The proposed multi-component façade system is made of porous concretes employed both as bearing structures and for heat insulation and fireproofing purposes. The authors also provide their recommendations in respect of the mounting of the proposed façade system. The façade system considered in the article is composed of wall foam concrete blocks reinforced by basalt fibers (bearing elements of the structure, cellular concrete polystyrene (thermal insulation, and porous concrete (fireproofing and thermal insulation. Retained shuttering (in the fireproofing sections represents chrysolite cement sheets attached to the structures composed of glass-fiber plastic elements. The application of insulating porous concrete as a fireproofing material is based on the principle of adjustable stress-strained states of materials in the environment of variable pressure. This technology was developed at Moscow State University of Civil Engineering, and it was initially designated for the manufacturing of tailor-made products. The above concrete is also designated for retained shuttering and modified cavity masonry walls. Porous concrete that expands inside the fireproofing cavity ensures a tight contact both with the basic material and thermal insulation plates. The use of materials of the same origin (Portland cement means the formation of strong transition zones connecting the system components in the course of its hardening and further operation. The results of the thermotechnical calculation demonstrate that the thermal resistance registered on the surface of the wall that is 3 meters high (that has a 0.4 m fireproofing cavity is equal to 3.98 sq. m. C/Wt. The value of the coefficient of thermotechnical heterogeneity (r is equal to 0.86 with account for the thickness and thermal conductivity of point and linear elements. If the thermotechnical heterogeneity is taken into consideration, the thermal resistance of the proposed wall is equal to 3.42 m2 С/Wt.

Method for Waterproofing Ceramic Materials

Science.gov (United States)

Cagliostro, Domenick E. (Inventor); Hsu, Ming-Ta S. (Inventor)

1998-01-01

Hygroscopic ceramic materials which are difficult to waterproof with a silane, substituted silane or silazane waterproofing agent, such as an alumina containing fibrous, flexible and porous, fibrous ceramic insulation used on a reentry space vehicle, are rendered easy to waterproof if the interior porous surface of the ceramic is first coated with a thin coating of silica. The silica coating is achieved by coating the interior surface of the ceramic with a silica precursor converting the precursor to silica either in-situ or by oxidative pyrolysis and then applying the waterproofing agent to the silica coated ceramic. The silica precursor comprises almost any suitable silicon containing material such as a silane, silicone, siloxane, silazane and the like applied by solution, vapor deposition and the like. If the waterproofing is removed by e.g., burning, the silica remains and the ceramic is easily rewaterproofed. An alumina containing TABI insulation which absorbs more that five times its weight of water, absorbs less than 10 wt. % water after being waterproofed according to the method of the invention.

1.9 μm superficially porous packing material with radially oriented pores and tailored pore size for ultra-fast separation of small molecules and biomolecules.

Science.gov (United States)

Min, Yi; Jiang, Bo; Wu, Ci; Xia, Simin; Zhang, Xiaodan; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

2014-08-22

In this work, 1.9 μm reversed-phase packing materials with superficially porous structure were prepared to achieve the rapid and high efficient separation of peptides and proteins. The silica particles were synthesized via three steps, nonporous silica particle preparation by a modified seeded growth method, mesoporous shell formation by a one pot templated dissolution and redeposition strategy, and pore size expansion via acid-refluxing. By such a method, 1.9 μm superficially porous materials with 0.18 μm shell thickness and tailored pore diameter (10 nm, 15 nm) were obtained. After pore enlargement, the formerly dense arrays of mesoporous structure changed, the radially oriented pores dominated the superficially porous structure. The chromatographic performance of such particles was investigated after C18 derivatization. For packing materials with 1.9 μm diameter and 10 nm pore size, the column efficiency could reach 211,300 plates per m for naphthalene. To achieve the high resolution separation of peptides and proteins, particles with pore diameter of 15 nm were tailored, by which the baseline separation of 5 peptides and 5 intact proteins could be respectively achieved within 1 min, demonstrating the superiority in the high efficiency and high throughput analysis of biomolecules. Furthermore, BSA digests were well separated with peak capacity of 120 in 30 min on a 15 cm-long column. Finally, we compared our columns with a 1.7 μm Kinetex C18 column under the same conditions, our particles with 10nm pore size demonstrated similar performance for separation of the large intact proteins. Moreover, the particles with 15 nm pore size showed more symmetrical peaks for the separation of large proteins (BSA, OVA and IgG) and provided rapid separation of protein extracts from Escherichia coli in 5 min. All these results indicated that the synthesized 1.9 μm superficially porous silica packing materials would be promising in the ultra-fast and high

New Porous Material Made from Industrial and Municipal Waste for Building Application

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Diana BAJARE

2014-09-01

Full Text Available The aim of this study was to find a new method for usage of the hazardous waste coming from recycling industry. Two hazardous wastes – aluminium recycling final dross or non-metallic product (NMP and lead – silica glass (LSG were investigated. It is generally considered that NMP is a process waste and subject to disposal after residual metal has been recovered from primary dross. NMP is impurities which are removed from the molten metal in dross recycling process and it could be defined as a hazardous waste product in aluminium recycling industry. LSG comes from fluorescence lamp recycling plant and could be classified as hazardous waste due to high amount of lead in the composition and re-melting problems. The new alkali activated material, which can be defined as porous building material, was created. Composition of this material consisted of aluminium recycling waste, recycled fluorescent lamp LSG, sintered kaolin clay as well as commercially available alkali flakes (NaOH and liquid glass (Na2SiO3 + nH2O. Physical and mechanical properties of the obtained material were tested. Density of the obtained material was from (460 – 550 kg/m3 and the total porosity was from 82 % – 83 %. The compressive strength of the material was in range from 1.1 MPa to 2.3 MPa. The thermal conductivity was determined. The pore microstructure was investigated and the mineralogical composition of porous material was determined. DOI: http://dx.doi.org/10.5755/j01.ms.20.3.4330

Enhanced microcontact printing of proteins on nanoporous silica surface

Energy Technology Data Exchange (ETDEWEB)

Blinka, Ellen; Hu Ye; Gopal, Ashwini; Hoshino, Kazunori; Lin, Kevin; Zhang, John X J [Department of Biomedical Engineering, University of Texas at Austin, Austin, TX 78758 (United States); Loeffler, Kathryn; Liu Xuewu; Ferrari, Mauro, E-mail: John.Zhang@engr.utexas.edu [Department of Nanomedicine and Biomedical Engineering, University of Texas Health Science Service, Houston, TX 77031 (United States)

2010-10-15

We demonstrate porous silica surface modification, combined with microcontact printing, as an effective method for enhanced protein patterning and adsorption on arbitrary surfaces. Compared to conventional chemical treatments, this approach offers scalability and long-term device stability without requiring complex chemical activation. Two chemical surface treatments using functionalization with the commonly used 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) were compared with the nanoporous silica surface on the basis of protein adsorption. The deposited thickness and uniformity of porous silica films were evaluated for fluorescein isothiocyanate (FITC)-labeled rabbit immunoglobulin G (R-IgG) protein printed onto the substrates via patterned polydimethlysiloxane (PDMS) stamps. A more complete transfer of proteins was observed on porous silica substrates compared to chemically functionalized substrates. A comparison of different pore sizes (4-6 nm) and porous silica thicknesses (96-200 nm) indicates that porous silica with 4 nm diameter, 57% porosity and a thickness of 96 nm provided a suitable environment for complete transfer of R-IgG proteins. Both fluorescence microscopy and atomic force microscopy (AFM) were used for protein layer characterizations. A porous silica layer is biocompatible, providing a favorable transfer medium with minimal damage to the proteins. A patterned immunoassay microchip was developed to demonstrate the retained protein function after printing on nanoporous surfaces, which enables printable and robust immunoassay detection for point-of-care applications.

Synthesis of silica nanoparticles for the manufacture of porous carbon membrane and particle size analysis by sedimentation field-flow fractionation

Energy Technology Data Exchange (ETDEWEB)

Lee, Seung Ho; Eum, Chul; Hun; Choi, Seong Ho; Kim, Woon Jung [Dept. of Chemistry, Hannam University, Daejeon (Korea, Republic of)

2016-11-15

Silica nanoparticles were synthesized by emulsion polymerization by mixing ethanol, ammonium hydroxide, water, and tetraethyl orthosilicate. An apparatus was designed and assembled for a large-scale synthesis of silica nanospheres, which was aimed for uniform mixing of the reactants. Then sedimentation field-flow fractionation (SdFFF) was used to determine the size distribution of the silica nanoparticles. SdFFF provided mass-based separation where the retention time increased with the particle size, thus the size distribution of silica nanoparticles obtained from SdFFF appeared more accurate than that from dynamic light scattering, particularly for those having broad and multimodal size distributions. A disk-shaped porous carbon membrane (PCM) was manufactured for application as an adsorbent by pressurizing the silica particles, followed by calcination. Results showed that PCM manufactured in this study has relatively high surface area and temperature stability. The PCM surface was modified by attaching a carboxyl group (PCM-COOH) and then by incorporating silver (PCM-COOH-Ag). The amount of COOH group on PCM was measured electrochemically by cyclic voltammetry, and the surface area, pore size, pore volume of PCM-COOH-Ag by Brunauer–Emmet–Teller measurement. The surface area was 40.65 and reduced to 13.02 after loading a COOH group then increased up to 30.37 after incorporating Ag.

Study of association of Eu(III) β-diketonato-1,10-phenanthroline complexes in silica-based hybrid materials

Energy Technology Data Exchange (ETDEWEB)

Fadieiev, Yevhen M.; Smola, Sergii S. [A.V. Bogatsky Physico-chemical Institute, National Academy of Sciences of Ukraine, 86, Lustdorfskaya doroga, 65080 Odessa (Ukraine); Malinka, Elena V. [Odessa National Academy of Food Technology, 112, Kanatna Street, 65039 Odessa (Ukraine); Rusakova, Nataliia V., E-mail: lanthachem@ukr.net [A.V. Bogatsky Physico-chemical Institute, National Academy of Sciences of Ukraine, 86, Lustdorfskaya doroga, 65080 Odessa (Ukraine)

2017-03-15

Hybrid organic-inorganic materials based on silica and mixed-ligand complexes of Eu(III) with β-diketones and 1,10-phenanthroline with covalent and non-covalent attachment to matrix were obtained by a sol-gel route. Luminescent study of obtained systems allowed to propose spectral criteria for estimation of the uniformity of complex distribution in amorphous silica matrix. Thus, such criteria are the broadening of Eu(III) 4f-luminescence bands, emission decay and the shape of plot of the emission intensity vs. concentration of complex in the materials. Full width of {sup 5}D{sub 0}→{sup 7}F{sub 2} band at its half maximum and the ratio of the {sup 5}D{sub 0}→{sup 7}F{sub 2} and {sup 5}D{sub 0}→{sup 7}F{sub 1} bands intensities were used as quantitative measures of spectral changes and the bands broadening in Eu(III) emission spectra. - Highlights: • Modification of Eu(III) β-diketonates by an anchor fragments was carried out. • The degree of association of molecules was estimated based on emission spectra. • Covalent anchoring of complexes promotes their uniform distribution in matrix. • Non-covalently grafted complexes are prone to association in amorphous silica.

Numerical modelling of porous cement-based materials by superabsorbent polymers

DEFF Research Database (Denmark)

Viejo, Ismael; Esteves, Luis Pedro; Laspalas, Manuel

2016-01-01

The development of new cementitious materials raises new challenges with regard to structural design. One of the potential applications of superabsorbent polymers (SAP) is to deliver well-defined porosity to cement systems. This is particularly interesting for the development of porous cement...

Novel bioactive materials: silica aerogel and hybrid silica aerogel/pseudowollastonite

Directory of Open Access Journals (Sweden)

Reséndiz-Hernández, P. J.

2014-10-01

Full Text Available Silica aerogel and hybrid silica aerogel/pseudowollastonite materials were synthesized by controlled hydrolysis of tetraethoxysilane (TEOS using also methanol (MeOH and pseudowollastonite particles. The gels obtained were dried using a novel process based on an ambient pressure drying. Hexane and hexamethyl-disilazane (HMDZ were the solvents used to chemically modify the surface. In order to assess bioactivity, aerogels, without and with pseudowollastonite particles, were immersed in simulated body fluid (SBF for 7 and 14 days. The hybrid silica aerogel/pseudowollastonite showed a higher bioactivity than that observed for the single silica aerogel. However, as in both cases a lower bioactivity was observed, a biomimetic method was also used to improve it. In this particular method, samples of both materials were immersed in SBF for 7 days followed by their immersion in a more concentrated solution (1.5 SBF for 14 days. A thick and homogeneous bonelike apatite layer was formed on the biomimetically treated materials. Thus, bioactivity was successfully improved even on the aerogel with no pseudowollastonite particles. As expected, the hybrid silica aerogel/pseudowollastonite particles showed a higher bioactivity.Se sintetizaron aerogel de sílice y aerogel híbrido de sílice/partículas de pseudowollastonita por hidrólisis controlada de tetraetoxisilano (TEOS usando metanol (MeOH y partículas de pseudowollastonita. Los geles obtenidos se secaron utilizando un novedoso proceso basado en una presión de secado ambiental. Hexano y hexametil-disilazano fueron los solventes usados para modificar químicamente la superficie. Para evaluar la bioactividad, los aerogeles con y sin partículas de pseudowollastonita se sumergieron en un fluido fisiológico simulado (SBF por 7 y 14 días. El aerogel híbrido de sílice/partículas de pseudowollastonita mostró más alta bioactividad que la observada por el aerogel solo. Sin embargo, en ambos casos, se

Polymer-filler interactions in polyether based thermoplastic polyureathane/silica nanocomposites

OpenAIRE

Heinz, Özge; Heinz, Ozge

2013-01-01

Thermoplastic polyurethaneureas (TPU) are a unique class of materials that are used in a broad range of applications due to their tailorable chemistry and morphology that allow engineering materials with targeted properties. The central theme of this dissertation is to develop an understanding on polymer-filler interfacial interactions and related reinforcing mechanism of silica nanoparticles in polyether based TPU/silica nanocomposites. Prior to our investigation on nanocomposite materials, ...

Impact of Micro Silica Surface Hydroxyl Groups on the Properties of Calcium Silicate Products

DEFF Research Database (Denmark)

Haastrup, Sonja; Jørgensen, Bianca; Yu, Donghong

2017-01-01

Porous calcium silicates are widely used in insulating systems for high temperature applications. In the production of porous calcium silicates, quicklime and micro silica have been utilized as key raw materials. In the reaction between SiO2 and CaO, the dissolution of SiO2 has been proven...

Ordered silica particles made by nonionic surfactant for VOCs sorption

Energy Technology Data Exchange (ETDEWEB)

Difallah, Oumaima; Hamaizi, Hadj, E-mail: hamaizimizou@yahoo.fr [University of Oran, OranMenaouer (Algeria); Amate, Maria Dolores Urena; Socias-Viciana, Maria Del Mar [University of Almeria (Spain)

2017-07-15

Adsorption of light organic compounds such acetone, 1-propanol and carbon dioxide was tested by using mesoporous silica materials made from non ionic surfactant with long chain and silica sources as tetraethyl orthosilicate TEOS and modified Na-X and Li-A Zeolites. X-ray powder diffraction (XRD), nitrogen adsorption-desorption analysis and scanning electron microscopy (SEM) were applied to characterize the silica particles of a variety prepared samples. Acetone, 1-propanol and CO{sub 2} adsorption at 298K was evaluated by a volumetric method and indicate a high sorption capacity of organic compounds depending essentially on the porous texture of adsorbents. An adsorption kinetic model was proposed to describe the adsorption of VOCs over template-free mesoporous silica materials. A good agreement with experimental data was found. (author)

Synthesis And Characterization Of Pure-Silica- Zeolite-Beta Membrane

Directory of Open Access Journals (Sweden)

Yeong Yin Fong

2017-11-01

Full Text Available The semiconductor industry needs low dielectric constant (low k-value materials to more advance microprocessor and chips by reducing the size of the device features. In fabricate this context, a new material with lower k value than conventional silica ( k = 3.9 - 4.2 is needed in order to improve the circuit performance. As per the recent International Semiconductor Technology plan, a low-k material with a k = 1.6 will be needed by 2010. The choice of the inorganic zeolite membrane is an attractive option for low k material and suitable for microprocess application.  In the present study, a pure silica zeolite beta membrane coated on the non-porous stainless steel support was synthesized using in situ crystallization of a gel with the composition of  SiO2 : 0.6 TEAOH : 0.6 HF : 10.1 H2O. The crystallization was carried in the presence of tetraethylammonium hydroxide TEA(OH as structure directing agent, fumed silica, HF and deionized water at pH value of 9. The crystallization under hydrothermal conditions at 130oC was carried out for the time period of 14 days. The membrane was characterized by X-Ray Diffraction ( XRD ,  Thermogravimetric Analysis ( TGA , Nitrogen Adsorption and Scanning Electron Microscope ( SEM .   SEM micrographs show highly crystalline, truncated square bipyramidal morphology of pure silica zeolite beta was coated on the non-porous stainless steel support. The membrane dielectric constant, k-value was measured as 2.64 which makes it suitable for the microprocessor applications.

Effect of silica fiber on the mechanical and chemical behavior of alumina-based ceramic core material

OpenAIRE

Weiguo Jiang; Kaiwen Li; Jiuhan Xiao; Langhong Lou

2017-01-01

In order to improve the chemical leachability, the alumina-based ceramic core material with the silica fiber was injected and sintered at 1100 °C/4 h, 1200 °C/4 h, 1300 °C/4 h and 1400 °C/4 h, respectively. The micrographs of ceramic core materials at sintered and leached state were characterized by scanning electron microscopy (SEM). The phase composition of ceramic core material after sintering and the leaching product after leaching were detected by X-ray diffraction (XRD). The porosity, r...

Methods for removing contaminant matter from a porous material

Science.gov (United States)

Fox, Robert V [Idaho Falls, ID; Avci, Recep [Bozeman, MT; Groenewold, Gary S [Idaho Falls, ID

2010-11-16

Methods of removing contaminant matter from porous materials include applying a polymer material to a contaminated surface, irradiating the contaminated surface to cause redistribution of contaminant matter, and removing at least a portion of the polymer material from the surface. Systems for decontaminating a contaminated structure comprising porous material include a radiation device configured to emit electromagnetic radiation toward a surface of a structure, and at least one spray device configured to apply a capture material onto the surface of the structure. Polymer materials that can be used in such methods and systems include polyphosphazine-based polymer materials having polyphosphazine backbone segments and side chain groups that include selected functional groups. The selected functional groups may include iminos, oximes, carboxylates, sulfonates, .beta.-diketones, phosphine sulfides, phosphates, phosphites, phosphonates, phosphinates, phosphine oxides, monothio phosphinic acids, and dithio phosphinic acids.

Optical Fiber Chemical Sensor with Sol-Gel Derived Refractive Material as Transducer for High Temperature Gas Sensing in Clean Coal Technology

Energy Technology Data Exchange (ETDEWEB)

Shiquan Tao

2006-12-31

The chemistry of sol-gel derived silica and refractive metal oxide has been systematically studied. Sol-gel processes have been developed for preparing porous silica and semiconductor metal oxide materials. Micelle/reversed micelle techniques have been developed for preparing nanometer sized semiconductor metal oxides and noble metal particles. Techniques for doping metal ions, metal oxides and nanosized metal particles into porous sol-gel material have also been developed. Optical properties of sol-gel derived materials in ambient and high temperature gases have been studied by using fiber optic spectroscopic techniques, such as fiber optic ultraviolet/visible absorption spectrometry, fiber optic near infrared absorption spectrometry and fiber optic fluorescence spectrometry. Fiber optic spectrometric techniques have been developed for investigating the optical properties of these sol-gel derived materials prepared as porous optical fibers or as coatings on the surface of silica optical fibers. Optical and electron microscopic techniques have been used to observe the microstructure, such as pore size, pore shape, sensing agent distribution, of sol-gel derived material, as well as the size and morphology of nanometer metal particle doped in sol-gel derived porous silica, the nature of coating of sol-gel derived materials on silica optical fiber surface. In addition, the chemical reactions of metal ion, nanostructured semiconductor metal oxides and nanometer sized metal particles with gas components at room temperature and high temperatures have also been investigated with fiber optic spectrometric methods. Three classes of fiber optic sensors have been developed based on the thorough investigation of sol-gel chemistry and sol-gel derived materials. The first group of fiber optic sensors uses porous silica optical fibers doped with metal ions or metal oxide as transducers for sensing trace NH{sub 3} and H{sub 2}S in high temperature gas samples. The second group of

Study of the radiolysis of water in porous media

International Nuclear Information System (INIS)

Rotureau, P.

2004-01-01

The understanding of the production of H 2 in the radiolysis of water confined into pores of concrete is important for the disposal of radioactive waste. In order to describe the mechanisms of water radiolysis in such heterogeneous porous systems we have studied the behaviour under gamma radiation of water confined in porous silica glasses with pores going from 8 to 300 nm of diameter and meso-porous molecular sieves (MCM-41). The radiolytic yields of hydroxyl radicals, hydrated electron and dihydrogen, have been determined with respect to the pore size of materials. The increase of these radiolytic yields compared to those of free water allowed us to show a charge transfer from silica to confined water. On the other hand the kinetics of hydrated electron reactions measured by pulse radiolysis are not modified. (author) [fr

Simplified method to solve sound transmission through structures lined with elastic porous material.

Science.gov (United States)

Lee, J H; Kim, J

2001-11-01

An approximate analysis method is developed to calculate sound transmission through structures lined with porous material. Because the porous material has both the solid phase and fluid phase, three wave components exist in the material, which makes the related analysis very complicated. The main idea in developing the approximate method is very simple: modeling the porous material using only the strongest of the three waves, which in effect idealizes the material as an equivalent fluid. The analysis procedure has to be conducted in two steps. In the first step, sound transmission through a flat double panel with a porous liner of infinite extents, which has the same cross sectional construction as the actual structure, is solved based on the full theory and the strongest wave component is identified. In the second step sound transmission through the actual structure is solved modeling the porous material as an equivalent fluid while using the actual geometry of the structure. The development and validation of the method are discussed in detail. As an application example, the transmission loss through double walled cylindrical shells with a porous core is calculated utilizing the simplified method.

Statistical Inference for Porous Materials using Persistent Homology.

Energy Technology Data Exchange (ETDEWEB)

Moon, Chul [Univ. of Georgia, Athens, GA (United States); Heath, Jason E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mitchell, Scott A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-12-01

We propose a porous materials analysis pipeline using persistent homology. We rst compute persistent homology of binarized 3D images of sampled material subvolumes. For each image we compute sets of homology intervals, which are represented as summary graphics called persistence diagrams. We convert persistence diagrams into image vectors in order to analyze the similarity of the homology of the material images using the mature tools for image analysis. Each image is treated as a vector and we compute its principal components to extract features. We t a statistical model using the loadings of principal components to estimate material porosity, permeability, anisotropy, and tortuosity. We also propose an adaptive version of the structural similarity index (SSIM), a similarity metric for images, as a measure to determine the statistical representative elementary volumes (sREV) for persistence homology. Thus we provide a capability for making a statistical inference of the uid ow and transport properties of porous materials based on their geometry and connectivity.

New strategy for surface functionalization of periodic mesoporous silica based on meso-HSiO1.5.

Science.gov (United States)

Xie, Zhuoying; Bai, Ling; Huang, Suwen; Zhu, Cun; Zhao, Yuanjin; Gu, Zhong-Ze

2014-01-29

Organic functionalization of periodic mesoporous silicas (PMSs) offers a way to improve their excellent properties and wide applications owing to their structural superiority. In this study, a new strategy for organic functionalization of PMSs is demonstrated by hydrosilylation of the recently discovered "impossible" periodic mesoporous hydridosilica, meso-HSiO1.5. This method overcomes the disadvantages of present pathways for organic functionalization of PMSs with organosilica. Moreover, compared to the traditional functionalization on the surface of porous silicon by hydrosilylation, the template-synthesized meso-HSiO1.5 is more flexible to access functional-groups-loaded PMSs with adjustable microstructures. The new method and materials will have wider applications based on both the structure and surface superiorities.

Improved Optical and Morphological Properties of Vinyl-Substituted Hybrid Silica Materials Incorporating a Zn-Metalloporphyrin

Directory of Open Access Journals (Sweden)

Zoltán Dudás

2018-04-01

Full Text Available This work is focused on a novel class of hybrid materials exhibiting enhanced optical properties and high surface areas that combine the morphology offered by the vinyl substituted silica host, and the excellent absorption and emission properties of 5,10,15,20-tetrakis(N-methyl-4-pyridylporphyrin-Zn(II tetrachloride as a water soluble guest molecule. In order to optimize the synthesis procedure and the performance of the immobilized porphyrin, silica precursor mixtures of different compositions were used. To achieve the requirements regarding the hydrophobicity and the porous structure of the gels for the successful incorporation of porphyrin, the content of vinyltriacetoxysilane was systematically changed and thoroughly investigated. Substitution of the silica gels with organic groups is a viable way to provide new properties to the support. An exhaustive characterization of the synthesized silica samples was realised by complementary physicochemical methods, such as infrared spectroscopy (FT-IR, absorption spectroscopy (UV-Vis and photoluminescence, nuclear magnetic resonance spectroscopy (29Si-MAS-NMR transmission and scanning electron microscopy (TEM and SEM, nitrogen absorption (BET, contact angle (CA, small angle X ray and neutron scattering (SAXS and SANS. All hybrids showed an increase in emission intensity in the wide region from 575 to 725 nm (Q bands in comparison with bare porphyrin. By simply tuning the vinyltriacetoxysilane content, the hydrophilic/hydrophobic profile of the hybrid materials was changed, while maintaining a high surface area. Good control of hydrophobicity is important to enhance properties such as dispersion, stability behaviour, and resistance to water, in order to achieve highly dispersible systems in water for biomedical applications.

Development and characterization of silica and titania based nano structured materials for the removal of indoor and outdoor air pollutants

Science.gov (United States)

Peiris, Thelge Manindu Nirasha

Solar energy driven catalytic systems have gained popularity in environmental remediation recently. Various photocatalytic systems have been reported in this regard and most of the photocatalysts are based on well-known semiconducting material, Titanium Dioxide, while some are based on other materials such as Silicon Dioxide and various Zeolites. However, in titania based photocatalysts, titania is actively involved in the catalytic mechanism by absorbing light and generating exitons. Because of this vast popularity of titania in the field of photocatalysis it is believed that photocatalysis mainly occurs via non-localized mechanisms and semiconductors are extremely important. Even though it is still rare, photocatalysis could be localized and possible without use of a semiconductor as well. Thus, to support localized photocatalytic systems, and to compare the activity to titania based systems, degradation of organic air pollutants by nanostructured silica, titania and mixed silica titania systems were studied. New materials were prepared using two different approaches, precipitation technique (xerogel) and aerogel preparation technique. The prepared xerogel samples were doped with both metal (silver) and non-metals (carbon and sulfur) and aerogel samples were loaded with Chromium, Cobalt and Vanadium separately, in order to achieve visible light photocatalytic activity. Characterization studies of the materials were carried out using Nova BET analysis, DR UV-vis spectrometry, powder X-ray diffraction, X-ray photoelectron Spectroscopy, FT-IR spectroscopy, Transmission Electron Microscopy, etc. Kinetics of the catalytic activities was studied using a Shimadzu GCMS-QP 5000 instrument using a closed glass reactor. All the experiments were carried out in gaseous phase using acetaldehyde as the model pollutant. Kinetic results suggest that chromium doped silica systems are good UV and visible light active photocatalysts. This is a good example for a localized

C,N-bipyrazole receptor grafted onto a porous silica surface as a novel adsorbent based polymer hybrid.

Science.gov (United States)

Radi, Smaail; Attayibat, Ahmed; El-Massaoudi, Mohamed; Bacquet, Maryse; Jodeh, Shehdeh; Warad, Ismail; Al-Showiman, Salim S; Mabkhot, Yahia N

2015-10-01

A simple heterogeneous synthesis of pure adsorbent based polymer hybrid made by condensing a functionalized C,N-bipyrazole with a 3-glycidoxypropyl-trimethoxysilane silylant agent, previously anchored on a silica surface was developed. The formed material (SG2P) was characterized through elemental analysis, FT-IR spectroscopy, (13)C NMR of solid state, scanning electron microscope (SEM), and was studied and evaluated by determination of the surface area using the BET equation, the adsorption and desorption capability using the isotherm of nitrogen and B.J.H. pore sizes. The new material exhibits good thermal stability determined by thermogravimetry curves and good chemical stability was examined in various acidic and buffer solutions (pH 1-7). The binding and adsorption abilities of SG2P were investigated for Hg(2+), Cd(2+), Pb(2+), Zn(2+), K(+), Na(+) and Li(+) cations and compared to the results of classical liquid-liquid extraction with the unbound C,N-bipyrazole compound. The grafting at the surface of silica does not affect complexing properties of the ligand and the SG2P exhibits a high selectivity toward Hg(2+) ion with no complexation being observed towards zinc and alkali metals. The extracted and the complexing cation percentages were determined by atomic absorption measurements. Copyright © 2015 Elsevier B.V. All rights reserved.

Preparation and characterization of hydrated salts/silica composite as shape-stabilized phase change material via sol–gel process

International Nuclear Information System (INIS)

Wu, Yuping; Wang, Tao

2014-01-01

Highlights: • A mixture of hydrated salts were adopted as phase change materials. • Phase segregation of the hydrated salts was inhibited. • Subcooling was slightly mitigated. • Thermal cycling performance was greatly improved after PVP coating. - Abstract: A novel shape-stabilized phase change material composite was prepared by impregnating the mixture of hydrated salts (Na 2 SO 4 ·10H 2 O–Na 2 HPO 4 ·12H 2 O) into porous silica matrix obtained by sol–gel process and further coated with polyvinylpyrrolidone (PVP) to improve the thermal cycling performance. The chemical compatibility, morphology and phase change properties were investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), hot-stage polarizing optical microscope (HS-POM) and differential scanning calorimetry (DSC). Confined in the silica matrix, phase segregation of the hydrated salts was inhibited and subcooling was slightly mitigated. No leakage was observed during the solid–liquid phase transition even when the mass ratio of hydrated salts to silica was as high as 70:30. Results showed that the melting enthalpy of the composite can reach 106.2 kJ/kg with the melting temperature at 30.13 °C and there was no significant enthalpy loss after 30 thermal cycles

Drug delivery via porous silicon: a focused patent review.

Science.gov (United States)

Kulyavtsev, Paulina A; Spencer, Roxanne P

2017-03-01

Although silicon is more commonly associated with computer chips than with drug delivery, with the discovery that porous silicon is a viable biocompatible material, mesoporous silicon with pores between 2 and 50 nm has been loaded with small molecule and biomolecule therapeutics and safely implanted for controlled release. As porous silicon is readily oxidized, porous silica must also be considered for drug delivery applications. Since 2010, only a limited number of US patents have been granted, primarily for ophthalmologic and immunotherapy applications, in contrast to the growing body of technical literature in this area.

Metal Oxide Thin Films Grafted on Silica Gel Surfaces: Recent Advances on the Analytical Application of these Materials

Directory of Open Access Journals (Sweden)

Gushikem Yoshitaka

2001-01-01

Full Text Available In the highly dispersed MxOy monolayer film on a porous SiO2 surface, denoted as SiO2/MxOy, the Si-O-M covalent bond formed on the SiO2 surface restricts the mobility of the attached oxide resulting in coordinatively unsaturated metal oxides (LAS in addition to the Brønsted acid sites (BAS. The BAS arise from the MOH and SiOH groups, the latter due to the unreacted silanol groups. As the attached oxides are strongly immobilized on the surface, they are also thermally very stable. The amphoteric character of most of the attached oxides allows the immobilization of various chemical species, acid or bases, resulting in a wide application of these surface modified materials. In this work many of the recent applications of these MxOy coated silica surfaces are described, such as selective adsorbents, in preconcentration processes, as new packing material for use in HPLC, support for immobilization of enzymes, amperometric electrodes, sensors and biosensors

Hydrogen storage by physisorption on porous materials

Energy Technology Data Exchange (ETDEWEB)

Panella, B

2006-09-13

A great challenge for commercializing hydrogen powered vehicles is on-board hydrogen storage using economic and secure systems. A possible solution is hydrogen storage in light-weight solid materials. Here three principle storage mechanisms can be distinguished: i) absorption of hydrogen in metals ii) formation of compounds with ionic character, like complex hydrides and iii) physisorption (or physical adsorption) of hydrogen molecules on porous materials. Physical adsorption exhibits several advantages over chemical hydrogen storage as for example the complete reversibility and the fast kinetics. Two classes of porous materials were investigated for physical hydrogen storage, i.e. different carbon nanostructures and crystalline metal-organic frameworks possessing extremely high specific surface area. Hydrogen adsorption isotherms were measured using a Sieverts' apparatus both at room temperature and at 77 K at pressures up to the saturation regime. Additionally, the adsorption sites of hydrogen in these porous materials were identified using thermal desorption spectroscopy extended to very low temperatures (down to 20 K). Furthermore, the adsorbed hydrogen phase was studied in various materials using Raman spectroscopy at different pressures and temperatures. The results show that the maximum hydrogen storage capacity of porous materials correlates linearly with the specific surface area and is independent of structure and composition. In addition the pore structure of the adsorbent plays an important role for hydrogen storage since the adsorption sites for H2 could be assigned to pores possessing different dimensions. Accordingly it was shown that small pores are necessary to reach high storage capacities already at low pressures. This new understanding may help to tailor and optimize new porous materials for hydrogen storage. (orig.)

Hydrogen storage by physisorption on porous materials

Energy Technology Data Exchange (ETDEWEB)

Panella, B.

2006-09-13

A great challenge for commercializing hydrogen powered vehicles is on-board hydrogen storage using economic and secure systems. A possible solution is hydrogen storage in light-weight solid materials. Here three principle storage mechanisms can be distinguished: i) absorption of hydrogen in metals ii) formation of compounds with ionic character, like complex hydrides and iii) physisorption (or physical adsorption) of hydrogen molecules on porous materials. Physical adsorption exhibits several advantages over chemical hydrogen storage as for example the complete reversibility and the fast kinetics. Two classes of porous materials were investigated for physical hydrogen storage, i.e. different carbon nanostructures and crystalline metal-organic frameworks possessing extremely high specific surface area. Hydrogen adsorption isotherms were measured using a Sieverts' apparatus both at room temperature and at 77 K at pressures up to the saturation regime. Additionally, the adsorption sites of hydrogen in these porous materials were identified using thermal desorption spectroscopy extended to very low temperatures (down to 20 K). Furthermore, the adsorbed hydrogen phase was studied in various materials using Raman spectroscopy at different pressures and temperatures. The results show that the maximum hydrogen storage capacity of porous materials correlates linearly with the specific surface area and is independent of structure and composition. In addition the pore structure of the adsorbent plays an important role for hydrogen storage since the adsorption sites for H2 could be assigned to pores possessing different dimensions. Accordingly it was shown that small pores are necessary to reach high storage capacities already at low pressures. This new understanding may help to tailor and optimize new porous materials for hydrogen storage. (orig.)

Mesoporous Silica Molecular Sieve based Nanocarriers: Transpiring Drug Dissolution Research.

Science.gov (United States)

Pattnaik, Satyanarayan; Pathak, Kamla

2017-01-01

Improvement of oral bioavailability through enhancement of dissolution for poorly soluble drugs has been a very promising approach. Recently, mesoporous silica based molecular sieves have demonstrated excellent properties to enhance the dissolution velocity of poorly water-soluble drugs. Current research in this area is focused on investigating the factors influencing the drug release from these carriers, the kinetics of drug release and manufacturing approaches to scale-up production for commercial manufacture. This comprehensive review provides an overview of different methods adopted for synthesis of mesoporous materials, influence of processing factors on properties of these materials and drug loading methods. The drug release kinetics from mesoporous silica systems, the manufacturability and stability of these formulations are reviewed. Finally, the safety and biocompatibility issues related to these silica based materials are discussed. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Three-dimensional printing of transparent fused silica glass

Science.gov (United States)

Kotz, Frederik; Arnold, Karl; Bauer, Werner; Schild, Dieter; Keller, Nico; Sachsenheimer, Kai; Nargang, Tobias M.; Richter, Christiane; Helmer, Dorothea; Rapp, Bastian E.

2017-04-01

Glass is one of the most important high-performance materials used for scientific research, in industry and in society, mainly owing to its unmatched optical transparency, outstanding mechanical, chemical and thermal resistance as well as its thermal and electrical insulating properties. However, glasses and especially high-purity glasses such as fused silica glass are notoriously difficult to shape, requiring high-temperature melting and casting processes for macroscopic objects or hazardous chemicals for microscopic features. These drawbacks have made glasses inaccessible to modern manufacturing technologies such as three-dimensional printing (3D printing). Using a casting nanocomposite, here we create transparent fused silica glass components using stereolithography 3D printers at resolutions of a few tens of micrometres. The process uses a photocurable silica nanocomposite that is 3D printed and converted to high-quality fused silica glass via heat treatment. The printed fused silica glass is non-porous, with the optical transparency of commercial fused silica glass, and has a smooth surface with a roughness of a few nanometres. By doping with metal salts, coloured glasses can be created. This work widens the choice of materials for 3D printing, enabling the creation of arbitrary macro- and microstructures in fused silica glass for many applications in both industry and academia.

Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica

DEFF Research Database (Denmark)

Wu, Qiong; Andersson, Richard L.; Holgate, Tim

2014-01-01

This article presents a novel type of flame-retardant biohybrid foam with good insulation properties based on wheat gluten and silica, the latter polymerized in situ from hydrolysed tetraethyl orthosilicate (TEOS). This led to the formation of intimately mixed wheat gluten and silica phases, wher...... with a vacuum treatment to remove the largest air bubbles. X-ray photoelectron and infrared spectroscopy showed that silicon was present mainly as SiO2....

Double-Layer Surface Modification of Polyamide Denture Base Material by Functionalized Sol-Gel Based Silica for Adhesion Improvement.

Science.gov (United States)

Hafezeqoran, Ali; Koodaryan, Roodabeh

2017-09-21

Limited surface treatments have been proposed to improve the bond strength between autopolymerizing resin and polyamide denture base materials. Still, the bond strength of autopolymerizing resins to nylon polymer is not strong enough to repair the fractured denture effectively. This study aimed to introduce a novel method to improve the adhesion of autopolymerizing resin to polyamide polymer by a double layer deposition of sol-gel silica and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS). The silica sol was synthesized by acid-catalyzed hydrolysis of tetraethylorthosilicate (TEOS) as silica precursors. Polyamide specimens were dipped in TEOS-derived sol (TS group, n = 28), and exposed to ultraviolet (UV) light under O 2 flow for 30 minutes. UV-treated specimens were immersed in AE-APTMS solution and left for 24 hours at room temperature. The other specimens were either immersed in AE-APTMS solution (AP group, n = 28) or left untreated (NT group, n = 28). Surface characterization was investigated by fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Two autopolymerizing resins (subgroups G and T, n = 14) were bonded to the specimens, thermocycled, and then tested for shear bond strength with a universal testing machine. Data were analyzed with one-way ANOVA followed by Tukey's HSD (α = 0.05). FTIR spectra of treated surfaces confirmed the chemical modification and appearance of functional groups on the polymer. One-way ANOVA revealed significant differences in shear bond strength among the study groups. Tukey's HSD showed that TS T and TS G groups had significantly higher shear bond strength than control groups (p = 0.001 and p < 0.001, respectively). Moreover, bond strength values of AP T were statistically significant compared to controls (p = 0.017). Amino functionalized TEOS-derived silica coating is a simple and cost-effective method for improving the bond strength between the autopolymerizing resin and polyamide

Molecular dynamics study of shock compression in porous silica glass

Science.gov (United States)

Jones, Keith; Lane, J. Matthew D.; Vogler, Tracy J.

2017-06-01

The shock response of porous amorphous silica is investigated using classical molecular dynamics, over a range of porosity ranging from fully dense (2.21 g/cc) down to 0.14 g/cc. We observe an enhanced densification in the Hugoniot response at initial porosities above 50 %, and the effect increases with increasing porosity. In the lowest initial densities, after an initial compression response, the systems expand with increased pressure. These results show good agreement with experiments. Mechanisms leading to enhanced densification will be explored, which appear to differ from mechanisms observed in similar studies in silicon. Sandia National Laboratories is a multi mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Disorder-induced stiffness degradation of highly disordered porous materials

Science.gov (United States)

Laubie, Hadrien; Monfared, Siavash; Radjaï, Farhang; Pellenq, Roland; Ulm, Franz-Josef

2017-09-01

The effective mechanical behavior of multiphase solid materials is generally modeled by means of homogenization techniques that account for phase volume fractions and elastic moduli without considering the spatial distribution of the different phases. By means of extensive numerical simulations of randomly generated porous materials using the lattice element method, the role of local textural properties on the effective elastic properties of disordered porous materials is investigated and compared with different continuum micromechanics-based models. It is found that the pronounced disorder-induced stiffness degradation originates from stress concentrations around pore clusters in highly disordered porous materials. We identify a single disorder parameter, φsa, which combines a measure of the spatial disorder of pores (the clustering index, sa) with the pore volume fraction (the porosity, φ) to scale the disorder-induced stiffness degradation. Thus, we conclude that the classical continuum micromechanics models with one spherical pore phase, due to their underlying homogeneity assumption fall short of addressing the clustering effect, unless additional texture information is introduced, e.g. in form of the shift of the percolation threshold with disorder, or other functional relations between volume fractions and spatial disorder; as illustrated herein for a differential scheme model representative of a two-phase (solid-pore) composite model material.

Kinetics Study of Gas Pollutant Adsorption and Thermal Desorption on Silica Gel

Directory of Open Access Journals (Sweden)

Rong A

2017-06-01

Full Text Available Silica gel is a typical porous desiccant material. Its adsorption performance for gaseous air pollutants was investigated to determine its potential contribution to reducing such pollutants. Three gaseous air pollutants, toluene, carbon dioxide, and methane, were investigated in this paper. A thermogravimetric analyzer was used to obtain the equilibrium adsorption capacity of gases on single silica gel particles. The silica gel adsorption capacity for toluene is much higher than that for carbon dioxide and methane. To understand gas pollutant thermal desorption from silica gel, the thermogravimetric analysis of toluene desorption was conducted with 609 ppm toluene vapor at 313 K, 323 K, and 333 K. The overall regeneration rate of silica gel was strongly dependent on temperature and the enthalpy of desorption. The gas pollutant adsorption performance and thermal desorption on silica gel material may be used to estimate the operating and design parameters for gas pollutant adsorption by desiccant wheels.

Preparation of Silica Nanoparticles and Its Beneficial Role in Cementitious Materials

Directory of Open Access Journals (Sweden)

S. Ahalawat

2011-07-01

Full Text Available Spherical silica nanoparticles (n‐SiO2 with controllable size have been synthesized using tetraethoxysilane as starting material and ethanol as solvent by sol‐gel method. Morphology and size of the particles was controlled through surfactants. Sorbitan monolaurate, sorbitain monopalmitate and sorbitain monostearate produced silica nanoparticles of varying sizes (80‐150 nm, indicating the effect of chain length of the surfactant. Increase in chain length of non‐ionic surfactant resulted in decreasing particle size of silica nanoparticles. Further, the size of silica particles was also controlled using NH3 as base catalyst. These silica nanoparticles were incorporated into cement paste and their role in accelerating the cementitious reactions was investigated. Addition of silica nanoparticles into cement paste improved the microstructure of the paste and calcium leaching is significantly reduced as n‐SiO2 reacts with calcium hydroxide and form additional calcium‐ silicate‐hydrate (C‐S‐H gel. It was found that calcium hydroxide content in silica nanoparticles incorporated cement paste reduced ~89% at 1 day and up to ~60% at 28 days of hydration process. Synthesized silica particles and cement paste samples were characterized using scanning electron microscopy (SEM, powder X‐ray diffraction (XRD, infrared spectroscopy (IR and thermogravimetric analysis (TGA.

Response to Extreme Temperatures of Mesoporous Silica MCM-41: Porous Structure Transformation Simulation and Modification of Gas Adsorption Properties.

Science.gov (United States)

Zhang, Shenli; Perez-Page, Maria; Guan, Kelly; Yu, Erick; Tringe, Joseph; Castro, Ricardo H R; Faller, Roland; Stroeve, Pieter

2016-11-08

Molecular dynamics (MD) and Monte Carlo (MC) simulations were applied together for the first time to reveal the porous structure transformation mechanisms of mesoporous silica MCM-41 subjected to temperatures up to 2885 K. Silica was experimentally characterized to inform the models and enable prediction of changes in gas adsorption/separation properties. MD simulations suggest that the pore closure process is activated by a collective diffusion of matrix atoms into the porous region, accompanied by bond reformation at the surface. Degradation is kinetically limited, such that complete pore closure is postponed at high heating rates. We experimentally observe decreased gas adsorption with increasing temperature in mesoporous silica heated at fixed rates, due to pore closure and structural degradation consistent with simulation predictions. Applying the Kissinger equation, we find a strong correlation between the simulated pore collapse temperatures and the experimental values which implies an activation energy of 416 ± 17 kJ/mol for pore closure. MC simulations give the adsorption and selectivity for thermally treated MCM-41, for N 2 , Ar, Kr, and Xe at room temperature within the 1-10 000 kPa pressure range. Relative to pristine MCM-41, we observe that increased surface roughness due to decreasing pore size amplifies the difference of the absolute adsorption amount differently for different adsorbate molecules. In particular, we find that adsorption of strongly interacting molecules can be enhanced in the low-pressure region while adsorption of weakly interacting molecules is inhibited. This then results in higher selectivity in binary mixture adsorption in mesoporous silica.

Impact of water mobility in some porous media on migration of radio isotopes to the geosphere

International Nuclear Information System (INIS)

AL-Hajji, E.

2011-07-01

The aim of this work is to study the behavior of the water state (bound /free water) in porous materials such as illite and bentonite. These materials are widely used in the storage of radioactive waste. The study was carried out using proton nuclear magnetic resonance technique (NMR). That permits to understand the mechanism of leakage of radioactive elements from these porous materials to the surrounding environment. Such a leakage may have very serious consequences like the contamination of groundwater. In addition, other porous materials like silica and alumina, the two main composite of bentonite, have been studied as well.(author)

Characterization of porous materials by small-angle scattering

Indian Academy of Sciences (India)

With the availability of ultra small-angle scattering instruments, one can investigate porous materials in the sub-micron length scale. Because of the increased accessible length scale vis-a-vis the multiple scattering effect, conventional data analysis procedures based on single scattering approximation quite often fail.

On strength of porous material - simple systems and densified systems

DEFF Research Database (Denmark)

Nielsen, Lauge Fuglsang

1997-01-01

The question of non-destructive testing of porous materials has always been of interest for the engineering profession. A number of empirically based MOE-MOR relations between stiffness (Modulus Of Elasticity) and strength (Modulus Of Rupture) of materials have been established in order to control...

Immobilization of Bacillus subtilis lipase on a Cu-BTC based hierarchically porous metal-organic framework material: a biocatalyst for esterification.

Science.gov (United States)

Cao, Yu; Wu, Zhuofu; Wang, Tao; Xiao, Yu; Huo, Qisheng; Liu, Yunling

2016-04-28

Bacillus subtilis lipase (BSL2) has been successfully immobilized into a Cu-BTC based hierarchically porous metal-organic framework material for the first time. The Cu-BTC hierarchically porous MOF material with large mesopore apertures is prepared conveniently by using a template-free strategy under mild conditions. The immobilized BSL2 presents high enzymatic activity and perfect reusability during the esterification reaction. After 10 cycles, the immobilized BSL2 still exhibits 90.7% of its initial enzymatic activity and 99.6% of its initial conversion.

l-Cysteine-modified silver-functionalized silica-based material as an efficient solid-phase extraction adsorbent for the determination of bisphenol A.

Science.gov (United States)

Li, Yuanyuan; Zhu, Nan; Li, Bingxiang; Chen, Tong; Ma, Yulong; Li, Qiang

2018-02-01

A new silver-functionalized silica-based material with a core-shell structure based on silver nanoparticle-coated silica spheres was synthesized, and silver nanoparticles were modified using strongly bound l-cysteine. l-Cysteine-silver@silica was characterized by scanning electron microscopy and FTIR spectroscopy. Then, a solid-phase extraction method based on l-cysteine-silver@silica was developed and successfully used for bisphenol A determination prior to HPLC analysis. The results showed that the l-cysteine-silver@silica as an adsorbent exhibited good enrichment capability for bisphenol A, and the maximum adsorption saturation was 20.93 mg/g. Moreover, a short adsorption equilibrium time was obtained due to the presence of silver nanoparticles on the surface of the silica. The extraction efficiencies were then optimized by varying the eluents and pH. Under the optimized conditions, good linearity for bisphenol A was obtained in the range from 0.4 to 4.0 μM (R 2  > 0.99) with a low limit of detection (1.15 ng/mL). The spiked recoveries from tap water and milk samples were satisfactory (85-102%) with relative standard deviations below 5.2% (n = 3), which indicated that the method was suitable for the analysis of bisphenol A in complex samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison of the surface ion density of silica gel evaluated via spectral induced polarization versus acid-base titration

Science.gov (United States)

Hao, Na; Moysey, Stephen M. J.; Powell, Brian A.; Ntarlagiannis, Dimitrios

2016-12-01

Surface complexation models are widely used with batch adsorption experiments to characterize and predict surface geochemical processes in porous media. In contrast, the spectral induced polarization (SIP) method has recently been used to non-invasively monitor in situ subsurface chemical reactions in porous media, such as ion adsorption processes on mineral surfaces. Here we compare these tools for investigating surface site density changes during pH-dependent sodium adsorption on a silica gel. Continuous SIP measurements were conducted using a lab scale column packed with silica gel. A constant inflow of 0.05 M NaCl solution was introduced to the column while the influent pH was changed from 7.0 to 10.0 over the course of the experiment. The SIP measurements indicate that the pH change caused a 38.49 ± 0.30 μS cm- 1 increase in the imaginary conductivity of the silica gel. This increase is thought to result from deprotonation of silanol groups on the silica gel surface caused by the rise in pH, followed by sorption of Na+ cations. Fitting the SIP data using the mechanistic model of Leroy et al. (Leroyet al., 2008), which is based on the triple layer model of a mineral surface, we estimated an increase in the silica gel surface site density of 26.9 × 1016 sites m- 2. We independently used a potentiometric acid-base titration data for the silica gel to calibrate the triple layer model using the software FITEQL and observed a total increase in the surface site density for sodium sorption of 11.2 × 1016 sites m- 2, which is approximately 2.4 times smaller than the value estimated using the SIP model. By simulating the SIP response based on the calibrated surface complexation model, we found a moderate association between the measured and estimated imaginary conductivity (R2 = 0.65). These results suggest that the surface complexation model used here does not capture all mechanisms contributing to polarization of the silica gel captured by the SIP data.

Measurement of Emissivity of Porous Ceramic Materials

OpenAIRE

BÜYÜKALACA, Orhan

1998-01-01

In this study, measurements of spectral and total emissivities of seven different porous ceramic materials and one ceramic fibre material are reported. Measurements were made for wavelength range from 1.2 µm to 20 µm and temperature range from 200 °C to 700 °C. It was found that total emissivity increases with increase of pore size but decreases with increase of temperature. The results showed all the porous ceramic materials tested to be much better than ceramic fibre in terms of total em...

Faraday rotation measurements in maghemite-silica aerogels

International Nuclear Information System (INIS)

Taboada, E.; Real, R.P. del; Gich, M.; Roig, A.; Molins, E.

2006-01-01

Faraday rotation measurements have been performed on γ-Fe 2 O 3 /SiO 2 nanocomposite aerogels which are light, porous and transparent magnetic materials. The materials have been prepared by sol-gel polymerization of a silicon alkoxide, impregnation of the intermediate silica gel with a ferrous salt and supercritical drying of the gels. During supercritical evacuation of the solvent, spherical nanoparticles of iron oxide, with a mean particle diameter of 8.1±2.0 nm, are formed and are found to be homogenously distributed within the silica matrix. The specific Faraday rotation of the composite was measured at 0.6 T using polarized light of 810 nm, being 29.6 deg./cm. The changes in the plane of polarization of the transmitted light and the magnetization of the material present similar magnetic field dependencies and are characteristic of a superparamagnetic system

High-performance supercapacitors of Cu-based porous coordination polymer nanowires and the derived porous CuO nanotubes.

Science.gov (United States)

Wu, Meng-Ke; Zhou, Jiao-Jiao; Yi, Fei-Yan; Chen, Chen; Li, Yan-Li; Li, Qin; Tao, Kai; Han, Lei

2017-12-12

Electrode materials for supercapacitors with one-dimensional porous nanostructures, such as nanowires and nanotubes, are very attractive for high-efficiency storage of electrochemical energy. Herein, ultralong Cu-based porous coordination polymer nanowires (copper-l-aspartic acid) were used as the electrode material for supercapacitors, for the first time. The as-prepared material exhibits a high specific capacitance of 367 F g -1 at 0.6 A g -1 and excellent cycling stability (94% retention over 1000 cycles). Moreover, porous CuO nanotubes were successfully fabricated by the thermal decomposition of this nanowire precursor. The CuO nanotube exhibits good electrochemical performance with high rate capacity (77% retention at 12.5 A g -1 ) and long-term stability (96% retention over 1000 cycles). The strategy developed here for the synthesis of porous nanowires and nanotubes can be extended to the construction of other electrode materials for more efficient energy storage.

Transient Infrared Measurement of Laser Absorption Properties of Porous Materials

Directory of Open Access Journals (Sweden)

Marynowicz Andrzej

2016-06-01

Full Text Available The infrared thermography measurements of porous building materials have become more frequent in recent years. Many accompanying techniques for the thermal field generation have been developed, including one based on laser radiation. This work presents a simple optimization technique for estimation of the laser beam absorption for selected porous building materials, namely clinker brick and cement mortar. The transient temperature measurements were performed with the use of infrared camera during laser-induced heating-up of the samples’ surfaces. As the results, the absorbed fractions of the incident laser beam together with its shape parameter are reported.

Transient Infrared Measurement of Laser Absorption Properties of Porous Materials

Science.gov (United States)

Marynowicz, Andrzej

2016-06-01

The infrared thermography measurements of porous building materials have become more frequent in recent years. Many accompanying techniques for the thermal field generation have been developed, including one based on laser radiation. This work presents a simple optimization technique for estimation of the laser beam absorption for selected porous building materials, namely clinker brick and cement mortar. The transient temperature measurements were performed with the use of infrared camera during laser-induced heating-up of the samples' surfaces. As the results, the absorbed fractions of the incident laser beam together with its shape parameter are reported.

Analytical and numerical models of transport in porous cementitious materials

International Nuclear Information System (INIS)

Garboczi, E.J.; Bentz, D.P.

1990-01-01

Most chemical and physical processes that degrade cementitious materials are dependent on an external source of either water or ions or both. Understanding the rates of these processes at the microstructural level is necessary in order to develop a sound scientific basis for the prediction and control of the service life of cement-based materials, especially for radioactive-waste containment materials that are required to have service lives on the order of hundreds of years. An important step in developing this knowledge is to understand how transport coefficients, such as diffusivity and permeability, depend on the pore structure. Fluid flow under applied pressure gradients and ionic diffusion under applied concentration gradients are important transport mechanisms that take place in the pore space of cementitious materials. This paper describes: (1) a new analytical percolation-theory-based equation for calculating the permeability of porous materials, (2) new computational methods for computing effective diffusivities of microstructural models or digitized images of actual porous materials, and (3) a new digitized-image mercury intrusion simulation technique

Immobilization of Lactobacillus rhamnosus in mesoporous silica-based material: An efficiency continuous cell-recycle fermentation system for lactic acid production.

Science.gov (United States)

Zhao, Zijian; Xie, Xiaona; Wang, Zhi; Tao, Yanchun; Niu, Xuedun; Huang, Xuri; Liu, Li; Li, Zhengqiang

2016-06-01

Lactic acid bacteria immobilization methods have been widely used for lactic acid production. Until now, the most common immobilization matrix used is calcium alginate. However, Ca-alginate gel disintegrated during lactic acid fermentation. To overcome this deficiency, we developed an immobilization method in which Lactobacillus rhamnosus cells were successfully encapsulated into an ordered mesoporous silica-based material under mild conditions with a high immobilization efficiency of 78.77% by using elemental analysis. We also optimized the cultivation conditions of the immobilized L. rhamnosus and obtained a high glucose conversion yield of 92.4%. Furthermore, L. rhamnosus encapsulated in mesoporous silica-based material exhibited operational stability during repeated fermentation processes and no decrease in lactic acid production up to 8 repeated batches. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Fabrication of polystyrene porous films with gradient pore structures

International Nuclear Information System (INIS)

Yan Hongwei; Zhang Lin; Li Bo; Yin Qiang

2010-01-01

Silica opals and multilayer heterostructures were fabricated by vertical deposition technique. Polystyrene inverse opals and gradient porous structures were obtained by colloidal templating, in order to control the pore microstructure of polymer porous materials. As shown in the scanning electron microscopy images, the polystyrene porous structures are precise replicas of inverse structures of the original templates. After being infiltrated with the polystyrene, the photonic stop-band position of the opal composite is redshifted compared with the original template, and it is blueshifted after the opal template being removed. The filling ratio of polystyrene was calculated according to the Bragg formula. (authors)

Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction.

Science.gov (United States)

Ma, Hao; Zheng, Xiaoyang; Luo, Xuan; Yi, Yong; Yang, Fan

2018-01-30

Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM) method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress) of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future.

Simulation and Analysis of Mechanical Properties of Silica Aerogels: From Rationalization to Prediction

Directory of Open Access Journals (Sweden)

Hao Ma

2018-01-01

Full Text Available Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM method to calculate the mechanical properties of silica aerogels with different geometric properties such as particle size, pore size, ligament diameter, etc. The FVM simulation results show that a power law correlation existing between relative density and mechanical properties (elastic modulus and yield stress of silica aerogels, which are consistent with experimental and literature studies. In addition, depending on the relative densities, different strategies are proposed in order to synthesize silica aerogels with better mechanical performance by adjusting the distribution of pore size and ligament diameter of aerogels. Finally, the results suggest that it is possible to synthesize silica aerogels with ultra-low density as well as high strength and stiffness as long as the textural features are well controlled. It is believed that the FVM simulation methodology could be a valuable tool to study mechanical performance of silica aerogel based materials in the future.

Phase equilibria and thermodynamic modeling of ethane and propane hydrates in porous silica gels.

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Seo, Yongwon; Lee, Seungmin; Cha, Inuk; Lee, Ju Dong; Lee, Huen

2009-04-23

In the present study, we examined the active role of porous silica gels when used as natural gas storage and transportation media. We adopted the dispersed water in silica gel pores to substantially enhance active surface for contacting and encaging gas molecules. We measured the three-phase hydrate (H)-water-rich liquid (L(W))-vapor (V) equilibria of C(2)H(6) and C(3)H(8) hydrates in 6.0, 15.0, 30.0, and 100.0 nm silica gel pores to investigate the effect of geometrical constraints on gas hydrate phase equilibria. At specified temperatures, the hydrate stability region is shifted to a higher pressure region depending on pore size when compared with those of bulk hydrates. Through application of the Gibbs-Thomson relationship to the experimental data, we determined the values for the C(2)H(6) hydrate-water and C(3)H(8) hydrate-water interfacial tensions to be 39 +/- 2 and 45 +/- 1 mJ/m(2), respectively. By using these values, the calculation values were in good agreement with the experimental ones. The overall results given in this study could also be quite useful in various fields, such as exploitation of natural gas hydrate in marine sediments and sequestration of carbon dioxide into the deep ocean.

Capillary condensation of adsorbates in porous materials.

Science.gov (United States)

Horikawa, Toshihide; Do, D D; Nicholson, D

2011-11-14

Hysteresis in capillary condensation is important for the fundamental study and application of porous materials, and yet experiments on porous materials are sometimes difficult to interpret because of the many interactions and complex solid structures involved in the condensation and evaporation processes. Here we make an overview of the significant progress in understanding capillary condensation and hysteresis phenomena in mesopores that have followed from experiment and simulation applied to highly ordered mesoporous materials such as MCM-41 and SBA-15 over the last few decades. Copyright © 2011 Elsevier B.V. All rights reserved.

Supercritical carbon dioxide versus toluene as reaction media in silica functionalisation: Synthesis and characterisation of bonded aminopropyl silica intermediate.

Science.gov (United States)

Ashu-Arrah, Benjamin A; Glennon, Jeremy D

2017-06-09

This research reports supercritical carbon dioxide versus toluene as reaction media in silica functionalisation for use in liquid chromatography. Bonded aminopropyl silica (APS) intermediates were prepared when porous silica particles (Exsil-pure, 3μm) were reacted with 3-aminopropyltriethoxysilane (3-APTES) or N,N-dimethylaminopropyltrimethoxysilane (DMAPTMS) using supercritical carbon dioxide (sc-CO 2 ) and toluene as reaction media. Covalent bonding to silica was confirmed using elemental microanalysis (CHN), thermogravimetric analysis (TGA), zeta potential (ξ), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, scanning electron microscopy (SEM) and solid-state nuclear magnetic resonance (CP/MAS NMR) spectroscopy. The results demonstrate that under sc-CO 2 conditions of 100°C/414bar in a substantial reduced time of 3h, the surface coverage of APS (evaluated from%C obtained from elemental analysis) prepared with APTES (%C: 8.03, 5.26μmol/m -2 ) or DMAPTES (%C: 5.12, 4.58μmol/m 2 ) is somewhat higher when compared to organic based reactions under reflux in toluene at a temperature of 110°C in 24h with APTES (%C: 7.33, 4.71μmol/m 2 ) and DMAPTMS (%C: 4.93, 4.38μmol/m 2 ). Zeta potential measurements revealed a change in electrostatic surface charge from negative values for bare Exsil-pure silica to positive for functionalised APS materials indicating successful immobilization of the aminosilane onto the surface of silica. Copyright © 2017 Elsevier B.V. All rights reserved.

Core-shell microspheres with porous nanostructured shells for liquid chromatography.

Science.gov (United States)

Ahmed, Adham; Skinley, Kevin; Herodotou, Stephanie; Zhang, Haifei

2018-01-01

The development of new stationary phases has been the key aspect for fast and efficient high-performance liquid chromatography separation with relatively low backpressure. Core-shell particles, with a solid core and porous shell, have been extensively investigated and commercially manufactured in the last decade. The excellent performance of core-shell particles columns has been recorded for a wide range of analytes, covering small and large molecules, neutral and ionic (acidic and basic), biomolecules and metabolites. In this review, we first introduce the advance and advantages of core-shell particles (or more widely known as superficially porous particles) against non-porous particles and fully porous particles. This is followed by the detailed description of various methods used to fabricate core-shell particles. We then discuss the applications of common silica core-shell particles (mostly commercially manufactured), spheres-on-sphere particles and core-shell particles with a non-silica shell. This review concludes with a summary and perspective on the development of stationary phase materials for high-performance liquid chromatography applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication and application of advanced functional materials from lignincellulosic biomass

Science.gov (United States)

Hu, Sixiao

This dissertation explored the conversion of lignocellulosic biomass into advanced functional materials and their potential applications. Lignocellulosic biomass represents an as-of-yet underutilized renewable source for not only biofuel production but also functional materials fabrication. This renewable source is a great alternative for fossil fuel based chemicals, which could be one of the solutions to energy crisis. In this work, it was demonstrated a variety of advanced materials including functional carbons, metal and silica nanoparticles could be derived from lignocellulosic biomass. Chapter 1 provided overall reviewed of the lignin structures, productions and its utilizations as plastics, absorbents and carbons, as well as the preparation of nano-structured silver, silica and silicon carbide/nitride from biomass. Chapter 2, 3 and 4 discussed the fabrication of highly porous carbons from isolated lignin, and their applications as electric supercapacitors for energy storage. In chapter 2, ultrafine porous carbon fibers were prepared via electrospinning followed by simultaneous carbonization and activation. Chapter 3 covered the fabrication of supercapacitor based on the porous carbon fibers and the investigation of their electrochemical performances. In chapter 4, porous carbon particulates with layered carbon nano plates structures were produced by simple oven-drying followed by simultaneous carbonization and activation. The effects of heat processing parameters on the resulting carbon structures and their electrochemical properties were discussed in details. Chapter 5 and 6 addressed the preparation of silver nanoparticles using lignin. Chapter 5 reported the synthesis, underlying kinetics and mechanism of monodispersed silver nanospheres with diameter less than 25 nm in aqueous solutions using lignin as dual reducing and capping agents. Chapter 6 covered the preparation of silver nanoparticles on electrospun celluloses ultrafine fibers using lignin as both

Nano-silica as the go material on heat resistant tunnel lining

Science.gov (United States)

Omar, Faizah; Osman, S. A.; Mutalib, A.

2018-04-01

This paper is concerned with passive fire protection method of protective concrete mix that is made up of fly ash, polypropylene fibre, and nano-silica. Nano-silica is focused on as the innovative material to be used in the composition of the protective concrete mix. The previous experimental studies which analyse the performance of passive fire protection on tunnels are discussed. This paper also discusses passive fire protection. The fire protection materials and behaviour analyses of tunnel structure are also presented. At the end of the paper, the recommendation of the optimum composition concrete material with fly ash, polypropylene fibre and nano-silica as tunnel lining fire protective materials is proposed.

General Theory of Absorption in Porous Materials: Restricted Multilayer Theory.

Science.gov (United States)

Aduenko, Alexander A; Murray, Andy; Mendoza-Cortes, Jose L

2018-04-18

In this article, we present an approach for the generalization of adsorption of light gases in porous materials. This new theory goes beyond Langmuir and Brunauer-Emmett-Teller theories, which are the standard approaches that have a limited application to crystalline porous materials by their unphysical assumptions on the amount of possible adsorption layers. The derivation of a more general equation for any crystalline porous framework is presented, restricted multilayer theory. Our approach allows the determination of gas uptake considering only geometrical constraints of the porous framework and the interaction energy of the guest molecule with the framework. On the basis of this theory, we calculated optimal values for the adsorption enthalpy at different temperatures and pressures. We also present the use of this theory to determine the optimal linker length for a topologically equivalent framework series. We validate this theoretical approach by applying it to metal-organic frameworks (MOFs) and show that it reproduces the experimental results for seven different reported materials. We obtained the universal equation for the optimal linker length, given the topology of a porous framework. This work applied the general equation to MOFs and H 2 to create energy-storage materials; however, this theory can be applied to other crystalline porous materials and light gases, which opens the possibility of designing the next generations of energy-storage materials by first considering only the geometrical constraints of the porous materials.

Properties of porous netted materials

International Nuclear Information System (INIS)

Daragan, V.D.; Drozdov, B.G.; Kotov, A.Yu.; Mel'nikov, G.N.; Pustogarov, A.V.

1987-01-01

Hydraulic and strength characteristics, efficient heat conduction and inner heat exchange coefficient are experimentally studied for porous netted materials on the base of the brass nets as dependent on porosity, cell size and method of net laying. Results of the studies are presented. It is shown that due to anisotropy of the material properties the hydraulic resistance in the direction parallel to the nets plane is 1.3-1.6 times higher than in the perpendicular one. Values of the effective heat conduction in the direction perpendicular to the nets plane at Π>0.45 agree with the data from literature, at Π<0.45 a deviation from the calculated values is marked in the direction of the heat conduction decrease

Fabrication of keratin-silica hydrogel for biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Kakkar, Prachi; Madhan, Balaraman, E-mail: bmadhan76@yahoo.co.in

2016-09-01

In the recent past, keratin has been fabricated into different forms of biomaterials like scaffold, gel, sponge, film etc. In lieu of the myriad advantages of the hydrogels for biomedical applications, a keratin-silica hydrogel was fabricated using tetraethyl orthosilicate (TEOS). Textural analysis shed light on the physical properties of the fabricated hydrogel, inturn enabling the optimization of the hydrogel. The optimized keratin-silica hydrogel was found to exhibit instant springiness, optimum hardness, with ease of spreadability. Moreover, the hydrogel showed excellent swelling with highly porous microarchitecture. MTT assay and DAPI staining revealed that keratin-silica hydrogel was biocompatible with fibroblast cells. Collectively, these properties make the fabricated keratin-silica hydrogel, a suitable dressing material for biomedical applications. - Highlights: • Keratin-silica hydrogel has been fabricated using sol–gel technique. • The hydrogel shows appropriate textural properties. • The hydrogel promotes fibroblast cells proliferation. • The hydrogel has potential soft tissue engineering applications like wound healing.

Light scattering in porous materials: Geometrical optics and stereological approach

International Nuclear Information System (INIS)

Malinka, Aleksey V.

2014-01-01

Porous material has been considered from the point of view of stereology (geometrical statistics), as a two-phase random mixture of solid material and air. Considered are the materials having the refractive index with the real part that differs notably from unit and the imaginary part much less than unit. Light scattering in such materials has been described using geometrical optics. These two – the geometrical optics laws and the stereological approach – allow one to obtain the inherent optical properties of such a porous material, which are basic in the radiative transfer theory: the photon survival probability, the scattering phase function, and the polarization properties (Mueller matrix). In this work these characteristics are expressed through the refractive index of the material and the random chord length distribution. The obtained results are compared with the traditional approach, modeling the porous material as a pack of particles of different shapes. - Highlights: • Porous material has been considered from the point of view of stereology. • Properties of a two-phase random mixture of solid material and air are considered. • Light scattering in such materials has been described using geometrical optics. • The inherent optical properties of such a porous material have been obtained

Rare Earth-Activated Silica-Based Nanocomposites

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C. Armellini

2007-01-01

Full Text Available Two different kinds of rare earth-activated glass-based nanocomposite photonic materials, which allow to tailor the spectroscopic properties of rare-earth ions: (i Er3+-activated SiO2-HfO2 waveguide glass ceramic, and (ii core-shell-like structures of Er3+-activated silica spheres obtained by a seed growth method, are presented.

Elaboration of porous gehlenite and anorthite based ceramics using low price raw materials

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F. Zenikheri

Full Text Available Abstract Porous ceramics of good quality cost a lot in the world market, which has limited their use in developing countries. This is why this work was mainly devoted to prepare low-cost and good quality ceramics, using kaolin (DD2 type and calcite (CaCO3 available in abundance in Algeria. Based on previous results, 28 wt% CaCO3 ceramic was selected. The presence of CaCO3 favors to achieve porous samples characterized by a high percentage of porosity due to the CO2 release and CaO formation during its calcination at about 700 °C. The choice of these raw materials is based on their natural abundance (low price. It has been found that the samples had interesting characteristics: average pore size between 2.87 and 6.50 μm and porosity between 53 and 57%. It has also been found that the manufactured membrane supports are mainly constituted of gehlenite and anorthite phases. Moreover, the pore size distribution was mono-modal type. The surface and cross-section morphologies observed through a scanning electron microscope were also homogeneous and do not present any possible macro-defects (cracks, etc..

Porous Silicon–Carbon Composite Materials Engineered by Simultaneous Alkaline Etching for High-Capacity Lithium Storage Anodes

International Nuclear Information System (INIS)

Sohn, Myungbeom; Kim, Dae Sik; Park, Hyeong-Il; Kim, Jae-Hun; Kim, Hansu

2016-01-01

Highlights: • A porous Si–C anode is obtained by alkaline etching of a non-porous Si–C composite. • The pores in the carbon frame are created by simultaneous etching of Si and carbon. • The cycle life is greatly improved after the alkaline treatment. • The porous Si–C composite electrode shows high dimensional stability during cycling. - Abstract: Porous silicon–carbon (Si–C) composite materials have attracted a great deal of attention as high-performance anode materials for Li-ion batteries (LIBs), but their use suffers from the complex and limited synthetic routes for their preparation. Herein we demonstrate a scalable and nontoxic method to synthesize porous Si–C composite materials by means of simultaneous chemical etching of Si and carbon phases using alkaline solution. The resulting porous Si–C composite material showed greatly improved cycle performance, good rate capability, and high dimensional stability during cycling. Porous Si–C electrode showed an expansion of the height by about 22% after the first lithiation and only 16% after the first cycle. The material synthesis concept and scalable simultaneous etching approach presented here represent a means of improving the electrochemical properties of Si-based porous anode materials for use in commercial LIBs.

Systems and strippable coatings for decontaminating structures that include porous material

Science.gov (United States)

Fox, Robert V [Idaho Falls, ID; Avci, Recep [Bozeman, MT; Groenewold, Gary S [Idaho Falls, ID

2011-12-06

Methods of removing contaminant matter from porous materials include applying a polymer material to a contaminated surface, irradiating the contaminated surface to cause redistribution of contaminant matter, and removing at least a portion of the polymer material from the surface. Systems for decontaminating a contaminated structure comprising porous material include a radiation device configured to emit electromagnetic radiation toward a surface of a structure, and at least one spray device configured to apply a capture material onto the surface of the structure. Polymer materials that can be used in such methods and systems include polyphosphazine-based polymer materials having polyphosphazine backbone segments and side chain groups that include selected functional groups. The selected functional groups may include iminos, oximes, carboxylates, sulfonates, .beta.-diketones, phosphine sulfides, phosphates, phosphites, phosphonates, phosphinates, phosphine oxides, monothio phosphinic acids, and dithio phosphinic acids.

Application of porous material to reduce aerodynamic sound from bluff bodies

International Nuclear Information System (INIS)

Sueki, Takeshi; Takaishi, Takehisa; Ikeda, Mitsuru; Arai, Norio

2010-01-01

Aerodynamic sound derived from bluff bodies can be considerably reduced by flow control. In this paper, the authors propose a new method in which porous material covers a body surface as one of the flow control methods. From wind tunnel tests on flows around a bare cylinder and a cylinder with porous material, it has been clarified that the application of porous materials is effective in reducing aerodynamic sound. Correlation between aerodynamic sound and aerodynamic force fluctuation, and a surface pressure distribution of cylinders are measured to investigate a mechanism of aerodynamic sound reduction. As a result, the correlation between aerodynamic sound and aerodynamic force fluctuation exists in the flow around the bare cylinder and disappears in the flow around the cylinder with porous material. Moreover, the aerodynamic force fluctuation of the cylinder with porous material is less than that of the bare cylinder. The surface pressure distribution of the cylinder with porous material is quite different from that of the bare cylinder. These facts indicate that aerodynamic sound is reduced by suppressing the motion of vortices because aerodynamic sound is induced by the unstable motion of vortices. In addition, an instantaneous flow field in the wake of the cylinder is measured by application of the PIV technique. Vortices that are shed alternately from the bare cylinder disappear by application of porous material, and the region of zero velocity spreads widely behind the cylinder with porous material. Shear layers between the stationary region and the uniform flow become thin and stable. These results suggest that porous material mainly affects the flow field adjacent to bluff bodies and reduces aerodynamic sound by depriving momentum of the wake and suppressing the unsteady motion of vortices. (invited paper)

Synthesis of hierarchical porous materials with ZSM-5 structures via template-free sol–gel method

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Wei Han et al

2007-01-01

Full Text Available Interests are focused on preparation of hierarchical porous materials with zeolite structures by using soft or rigid templates in order to solve diffusion and mass transfer limitations resulting from the small pore sizes of zeolites. Here we develop a convenient template-free sol–gel method to synthesize hierarchical porous materials with ZSM-5 structures. This method involves hydrothermal recrystallization of the xerogel converted from uniform ZSM-5 sol by a vacuum drying process. By utilizing this method we can manipulate the size of zeolite nanocrystals as building units of porous structures based on controlling temperature of recrystallization, consequently obtain hierarchical porous materials with different intercrystalline pore sizes and ZSM-5 structures.

Biodiesel production from transesterification of palm oil with methanol over CaO supported on bimodal meso-macroporous silica catalyst.

Science.gov (United States)

Witoon, Thongthai; Bumrungsalee, Sittisut; Vathavanichkul, Peerawut; Palitsakun, Supaphorn; Saisriyoot, Maythee; Faungnawakij, Kajornsak

2014-03-01

Calcium oxide-loaded porous materials have shown promise as catalysts in transesterification. However, the slow diffusion of bulky triglycerides through the pores limited the activity of calcium oxide (CaO). In this work, bimodal meso-macroporous silica was used as a support to enhance the accessibility of the CaO dispersed inside the pores. Unimodal porous silica having the identical mesopore diameter was employed for the purpose of comparison. Effects of CaO content and catalyst pellet size on the yield of fatty acid methyl esters (FAME) were investigated. The basic strength was found to increase with increasing the CaO content. The CaO-loaded bimodal porous silica catalyst with the pellet size of 325μm achieved a high %FAME of 94.15 in the first cycle, and retained an excellent %FAME of 88.87 after five consecutive cycles. Copyright © 2014 Elsevier Ltd. All rights reserved.

Preparation of porous bio-char and activated carbon from rice husk by leaching ash and chemical activation.

Science.gov (United States)

Ahiduzzaman, Md; Sadrul Islam, A K M

2016-01-01

Preparation porous bio-char and activated carbon from rice husk char study has been conducted in this study. Rice husk char contains high amount silica that retards the porousness of bio-char. Porousness of rice husk char could be enhanced by removing the silica from char and applying heat at high temperature. Furthermore, the char is activated by using chemical activation under high temperature. In this study no inert media is used. The study is conducted at low oxygen environment by applying biomass for consuming oxygen inside reactor and double crucible method (one crucible inside another) is applied to prevent intrusion of oxygen into the char. The study results shows that porous carbon is prepared successfully without using any inert media. The adsorption capacity of material increased due to removal of silica and due to the activation with zinc chloride compared to using raw rice husk char. The surface area of porous carbon and activated carbon are found to be 28, 331 and 645 m(2) g(-1) for raw rice husk char, silica removed rice husk char and zinc chloride activated rice husk char, respectively. It is concluded from this study that porous bio-char and activated carbon could be prepared in normal environmental conditions instead of inert media. This study shows a method and possibility of activated carbon from agro-waste, and it could be scaled up for commercial production.

Effect of Pressing Parameters on the Structure of Porous Materials Based on Cobalt and Nickel Powders

Science.gov (United States)

Shustov, V. S.; Rubtsov, N. M.; Alymov, M. I.; Ankudinov, A. B.; Evstratov, E. V.; Zelensky, V. A.

2018-03-01

Porous materials with a bulk porosity of more than 68% were synthesized by powder metallurgy methods from a cobalt-nickel mixture. The effect of the ratio of nickel and cobalt powders used in the synthesis of this porous material (including cases when either nickel or cobalt alone was applied) and the conditions of their compaction on structural parameters, such as open and closed porosities and pose size, was established.

A diffusivity model for predicting VOC diffusion in porous building materials based on fractal theory

International Nuclear Information System (INIS)

Liu, Yanfeng; Zhou, Xiaojun; Wang, Dengjia; Song, Cong; Liu, Jiaping

2015-01-01

Highlights: • Fractal theory is introduced into the prediction of VOC diffusion coefficient. • MSFC model of the diffusion coefficient is developed for porous building materials. • The MSFC model contains detailed pore structure parameters. • The accuracy of the MSFC model is verified by independent experiments. - Abstract: Most building materials are porous media, and the internal diffusion coefficients of such materials have an important influences on the emission characteristics of volatile organic compounds (VOCs). The pore structure of porous building materials has a significant impact on the diffusion coefficient. However, the complex structural characteristics bring great difficulties to the model development. The existing prediction models of the diffusion coefficient are flawed and need to be improved. Using scanning electron microscope (SEM) observations and mercury intrusion porosimetry (MIP) tests of typical porous building materials, this study developed a new diffusivity model: the multistage series-connection fractal capillary-bundle (MSFC) model. The model considers the variable-diameter capillaries formed by macropores connected in series as the main mass transfer paths, and the diameter distribution of the capillary bundles obeys a fractal power law in the cross section. In addition, the tortuosity of the macrocapillary segments with different diameters is obtained by the fractal theory. Mesopores serve as the connections between the macrocapillary segments rather than as the main mass transfer paths. The theoretical results obtained using the MSFC model yielded a highly accurate prediction of the diffusion coefficients and were in a good agreement with the VOC concentration measurements in the environmental test chamber.

Physical Characteristics of Chitosan Based Film Modified With Silica and Polyethylene Glycol

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F. Widhi Mahatmanti

2014-07-01

Full Text Available Recently, development of film materials is focused on finding the films with high chemical and physical stabilities. Organic based material such as chitosan produces films with low physical stability, and hence addition of inorganic materials necessary. In this research, the effect of silica and polyethylene glycol (PEG addition on the properties of chitosan based films has been investigated. Precursors used to produce films included chitosan with the deacetylation degree of 83% and sodium silicate solution as the silica source. A simple synthesis in a one-pot process was carried out by mixing 1%(w of chitosan solution in 2%(v/v acetate acid and sodium silicate solution (27% SiO2 in various composition ratios and casting the solution on a glass dish. The tensile strength and percentage of elongation decrease with increasing the silica content. The tensile strength tends to decline with addition of PEG, but the elongation percentage of the film increases. Hydrophilicity of the film decreases with the addition of silica and increases with the addition of PEG. The addition of silica and PEG does not change significantly the morphology of the film and functional groups indicating the domination of physical interaction among active sites in the film components.

Hybrid silica materials for detection of toxic species and clinical diagnosis

OpenAIRE

Pascual Vidal, Lluís

2017-01-01

The present PhD thesis entitled "Silica Hybrid Materials for detection of toxic species and clinical diagnosis" is focused on the design and synthesis of new hybrid materials, using different silica supports as inorganic scaffolds, with applications in recognition, sensing and diagnostic protocols. The first chapter of the PhD thesis is devoted to the definition and classification of hybrid materials, relying on concepts of Nanotechnology, Supramolecular and Materials Chemistry. State o...

Assessment of porous material anisotropy and its effect on gas permeability

Science.gov (United States)

Wałowski, Grzegorz

2017-10-01

The results of experimental research upon the assessment of porous material anisotropy and its effect on gas permeability of porous materials with respect to the gas flow. The conducted research applied to natural materials with an anisotropic gap-porous structure and - for comparative purposes - to model materials such as coke, pumice and polyamide agglomerates. The research was conducted with the use of a special test stand that enables measuring the gas permeability with respect to three flow orientations compared with symmetric cubic-shaped samples. The research results show an explicit impact of the flow direction on the permeability of materials porous, which results from their anisotropic internal structures. The anisotropy coefficient and permeability effective coefficient of such materials was determined and an experimental evaluation of the value of this coefficient was conducted with respect to the gas stream and the total pressure drop across the porous deposit. The process of gas permeability was considered in the category of hydrodynamics of gas flow through porous deposits. It is important to broaden the knowledge of gas hydrodynamics assessment in porous media so far unrecognised for the development of a new generation of clean energy sources, especially in the context of biogas or raw gas production.

Molecular imprinting at walls of silica nanotubes for TNT recognition.

Science.gov (United States)

Xie, Chenggen; Liu, Bianhua; Wang, Zhenyang; Gao, Daming; Guan, Guijian; Zhang, Zhongping

2008-01-15

This paper reports the molecular imprinting at the walls of highly uniform silica nanotubes for the recognition of 2,4,6-trinitrotoluene (TNT). It has been demonstrated that TNT templates were efficiently imprinted into the matrix of silica through the strong acid-base pairing interaction between TNT and 3-aminopropyltriethoxysilane (APTS). TNT-imprinted silica nanotubes were synthesized by the gelation reaction between APTS and tetraethylorthosilicate (TEOS), selectively occurring at the porous walls of APTS-modified alumina membranes. The removal of the original TNT templates leaves the imprinted cavities with covalently anchored amine groups at the cavity walls. A high density of recognition sites with molecular selectivity to the TNT analyte was created at the wall of silica nanotubes. Furthermore, most of these recognition sites are situated at the inside and outside surfaces of tubular walls and in the proximity of the two surfaces due to the ultrathin wall thickness of only 15 nm, providing a better site accessibility and lower mass-transfer resistance. Therefore, greater capacity and faster kinetics of uptaking target species were achieved. The silica nanotube reported herein is an ideal form of material for imprinting various organic or biological molecules toward applications in chemical/biological sensors and bioassay.

Polymer-silica hybrids for separation of CO2 and catalysis of organic reactions

Science.gov (United States)

Silva Mojica, Ernesto

Porous materials comprising polymeric and inorganic segments have attracted interest from the scientific community due to their unique properties and functionalities. The physical and chemical characteristics of these materials can be effectively exploited for adsorption applications. This dissertation covers the experimental techniques for fabrication of poly(vinyl alcohol) (PVA) and silica (SiO2) porous supports, and their functionalization with polyamines for developing adsorbents with potential applications in separation of CO2 and catalysis of organic reactions. The supports were synthesized by processes involving (i) covalent cross-linking of PVA, (ii) hydrolysis and poly-condensation of silica precursors (i,e,. sol-gel synthesis), and formation of porous structures via (iii) direct templating and (iv) phase inversion techniques. Their physical structure was controlled by the proper combination of the preparation procedures, which resulted in micro-structured porous materials in the form of micro-particles, membranes, and pellets. Their adsorption characteristics were tailored by functionalization with polyethyleneimine (PEI), and their physicochemical properties were characterized by vibrational spectroscopy (FTIR, UV-vis), microscopy (SEM), calorimetry (TGA, DSC), and adsorption techniques (BET, step-switch adsorption). Spectroscopic investigations of the interfacial cross-linking reactions of PEI and PVA with glutaraldehyde (GA) revealed that PEI catalyzes the cross-linking reactions of PVA in absence of external acid catalysts. In-situ IR spectroscopy coupled with a focal plane array (FPA) image detector allowed the characterization of a gradient interface on a PEI/PVA composite membrane and the investigation of the cross-linking reactions as a function of time and position. The results served as a basis to postulate possible intermediates, and propose the reaction mechanisms. The formulation of amine-functionalized CO2 capture sorbents was based on the

Reactive silica transport in fractured porous media: Analytical solutions for a system of parallel fractures

Science.gov (United States)

Yang, Jianwen

2012-04-01

A general analytical solution is derived by using the Laplace transformation to describe transient reactive silica transport in a conceptualized 2-D system involving a set of parallel fractures embedded in an impermeable host rock matrix, taking into account of hydrodynamic dispersion and advection of silica transport along the fractures, molecular diffusion from each fracture to the intervening rock matrix, and dissolution of quartz. A special analytical solution is also developed by ignoring the longitudinal hydrodynamic dispersion term but remaining other conditions the same. The general and special solutions are in the form of a double infinite integral and a single infinite integral, respectively, and can be evaluated using Gauss-Legendre quadrature technique. A simple criterion is developed to determine under what conditions the general analytical solution can be approximated by the special analytical solution. It is proved analytically that the general solution always lags behind the special solution, unless a dimensionless parameter is less than a critical value. Several illustrative calculations are undertaken to demonstrate the effect of fracture spacing, fracture aperture and fluid flow rate on silica transport. The analytical solutions developed here can serve as a benchmark to validate numerical models that simulate reactive mass transport in fractured porous media.

Synthesis and Characterization of Meso porous Material Functionalized with Different Silylating Agent and Their Capability to Remove Cu2+

International Nuclear Information System (INIS)

Zaini Hamzah; Norhidayu Narawi; Hamizah Mohd Rasid; Amira Nazirah Mohd Yusoff

2012-01-01

Meso porous material MCM-41 with uniform hexagonally ordered pores in range of 2-10 nm was synthesized through hydrothermal method. The synthesis started from highly pure silica source known as Ludox which act as an active source of silica in the presence of organic surfactant (CTABr) as structure-directing agent. MCM-41 has been functionalized with the organic group known as 3-aminopropyltriethoxysilane (APTES), 3-mercaptopropyltrimethoxysilane (MPTMS), and chloropropyl triethoxysilane (CPTES) by co-condensation method in order to enhance the surface hydrophobicity of MCM-41. The increasing hydrophobicity will lead to efficient reaction specifically for organic reaction in organic solvent. The resulting materials were characterized with various techniques which are PXRD, FTIR, NMR, Elemental Analysis and AAS. The formation of uniform hexagonal framework of synthesized materials was shown in PXRD result. The functionalized groups of modified MCM-41 can be characterized via FTIR and 13 C-NMR results. The Elemental Analysis shows the percentage of nitrogen, carbon, hydrogen and sulphur in MCM-41 and functionalized MCM-41. From AAS, MCM-41 MPTMS has high capability for removal of Cu (II) in aqueous solution compared with others. (author)

Porous materials produced from incineration ash using thermal plasma technology.

Science.gov (United States)

Yang, Sheng-Fu; Chiu, Wen-Tung; Wang, To-Mai; Chen, Ching-Ting; Tzeng, Chin-Ching

2014-06-01

This study presents a novel thermal plasma melting technique for neutralizing and recycling municipal solid waste incinerator (MSWI) ash residues. MSWI ash residues were converted into water-quenched vitrified slag using plasma vitrification, which is environmentally benign. Slag is adopted as a raw material in producing porous materials for architectural and decorative applications, eliminating the problem of its disposal. Porous materials are produced using water-quenched vitrified slag with Portland cement and foaming agent. The true density, bulk density, porosity and water absorption ratio of the foamed specimens are studied here by varying the size of the slag particles, the water-to-solid ratio, and the ratio of the weights of the core materials, including the water-quenched vitrified slag and cement. The thermal conductivity and flexural strength of porous panels are also determined. The experimental results show the bulk density and the porosity of the porous materials are 0.9-1.2 g cm(-3) and 50-60%, respectively, and the pore structure has a closed form. The thermal conductivity of the porous material is 0.1946 W m(-1) K(-1). Therefore, the slag composite materials are lightweight and thermal insulators having considerable potential for building applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

Random laser emission from a Rhodamine B-doped GPTS/TEOS-derived organic/silica monolithic xerogel

Science.gov (United States)

Abegão, Luis M. G.; Manoel, D. S.; Otuka, A. J. G.; Ferreira, P. H. D.; Vollet, D. R.; Donatti, D. A.; De Boni, L.; Mendonça, C. R.; De Vicente, F. S.; Rodrigues, J. J., Jr.; Alencar, M. A. R. C.

2017-06-01

A Rhodamine B-doped 3-glycidoxypropyltrimethoxysilane (GPTS)/tetraethyl orthosilicate (TEOS)-derived organic/silica monolithic xerogel with excellent optical properties was prepared and its potential as a random laser host investigated. This hybrid material has a non-porous organic/inorganic morphology with silica-rich nanoparticles of less than 10 nm in diameter homogeneously dispersed within the matrix. Random laser emission with incoherent feedback, centered at 618 nm, was observed from Rhodamine B incorporated into the monolithic xerogel when excited by a 532 nm pulsed laser. This hybrid system is shown to be very promising for the development of a new class of random laser-based integrated devices, with applications ranging from optical bio-imaging to sensing.

Bone tissue engineering using silica-based mesoporous nanobiomaterials:Recent progress.

Science.gov (United States)

Shadjou, Nasrin; Hasanzadeh, Mohammad

2015-10-01

Bone disorders are of significant concern due to increase in the median age of our population. It is in this context that tissue engineering has been emerging as a valid approach to the current therapies for bone regeneration/substitution. Tissue-engineered bone constructs have the potential to alleviate the demand arising from the shortage of suitable autograft and allograft materials for augmenting bone healing. Silica based mesostructured nanomaterials possessing pore sizes in the range 2-50 nm and surface reactive functionalities have elicited immense interest due to their exciting prospects in bone tissue engineering. In this review we describe application of silica-based mesoporous nanomaterials for bone tissue engineering. We summarize the preparation methods, the effect of mesopore templates and composition on the mesopore-structure characteristics, and different forms of these materials, including particles, fibers, spheres, scaffolds and composites. Also, the effect of structural and textural properties of mesoporous materials on development of new biomaterials for production of bone implants and bone cements was discussed. Also, application of different mesoporous materials on construction of manufacture 3-dimensional scaffolds for bone tissue engineering was discussed. It begins by giving the reader a brief background on tissue engineering, followed by a comprehensive description of all the relevant components of silica-based mesoporous biomaterials on bone tissue engineering, going from materials to scaffolds and from cells to tissue engineering strategies that will lead to "engineered" bone. Copyright © 2015 Elsevier B.V. All rights reserved.

Electrokinetic desalination of porous building materials

NARCIS (Netherlands)

Kamran, K.

2012-01-01

The deterioration of porous building materials and structures by the crystallization of water soluble salts is a well known phenomenon. The threats posed by salts to building materials can be minimized either by controlling the environment or by removing the salts from the deteriorated zone. In

Porous glass with high silica content for nuclear waste storage : preparation, characterization and leaching

International Nuclear Information System (INIS)

Aegerter, M.A.; Santos, D.I. dos; Ventura, P.C.S.

1984-01-01

Aqueous solutions simulating radioactive nuclear wastes (like Savanah River Laboratory) were incorporated in porous glass matrix with high silica content prepared by decomposition of borosilicate glass like Na 2 O - B 2 O 3 - SiO 2 . After sintering, the samples were submitted, during 28 days, to standard leaching tests MCC1, MCC5 (Soxhlet) and stagnating. The total weight loss, ph, as well as the integral and differential leaching rates and the accumulated concentrations in the leach of Si, Na, B, Ca, Mn, Al, Fe and Ni. The results are compared with the results from reference borosilicate glass, made by fusion, ceramic, synroc, concrets, etc... (E.G.) [pt

Porous polymeric materials for hydrogen storage

Science.gov (United States)

Yu, Luping; Liu, Di-Jia; Yuan, Shengwen; Yang, Junbing

2013-04-02

A porous polymer, poly-9,9'-spirobifluorene and its derivatives for storage of H.sub.2 are prepared through a chemical synthesis method. The porous polymers have high specific surface area and narrow pore size distribution. Hydrogen uptake measurements conducted for these polymers determined a higher hydrogen storage capacity at the ambient temperature over that of the benchmark materials. The method of preparing such polymers, includes oxidatively activating solids by CO.sub.2/steam oxidation and supercritical water treatment.

Omega-3 PUFA concentration by a novel PVDF nano-composite membrane filled with nano-porous silica particles.

Science.gov (United States)

Ghasemian, Samaneh; Sahari, Mohammad Ali; Barzegar, Mohsen; Ahmadi Gavlighi, Hasan

2017-09-01

In this study, polyvinylidene fluoride (PVDF) and nano-porous silica particle were used to fabricate an asymmetric nano-composite membrane. Silica particles enhanced the thermal stability of PVDF/SiO 2 membranes; increasing the decomposition temperature from 371°C to 408°C. Cross sectional morphology showed that silica particles were dispersed in polymer matrix uniformly. However, particle agglomeration was found at higher loading of silica (i.e., 20 by weight%). The separation performance of nano-composite membranes was also evaluated using the omega-3 polyunsaturated fatty acids (PUFA) concentration at a temperature and pressure of 30°C and 4bar, respectively. Silica particle increased the omega-3PUFA concentration from 34.8 by weight% in neat PVDF to 53.9 by weight% in PVDF with 15 by weight% of silica. Moreover, PVDF/SiO 2 nano-composite membranes exhibited enhanced anti-fouling property compared to neat PVDF membrane. Fouling mechanism analysis revealed that complete pore blocking was the predominant mechanism occurring in oil filtration. The concentration of omega-3 polyunsaturated fatty acids (PUFA) is important in the oil industries. While the current methods demand high energy consumptions in concentrating the omega-3, membrane separation technology offers noticeable advantages in producing pure omega-3 PUFA. Moreover, concentrating omega-3 via membrane separation produces products in the triacylglycerol form which possess better oxidative stability. In this work, the detailed mechanisms of fouling which limits the performance of membrane separation were investigated. Incorporating silica particles to polymeric membrane resulted in the formation of mixed matrix membrane with improved anti-fouling behaviour compared to the neat polymeric membrane. Hence, the industrial potential of membrane processing to concentrate omega-3 fatty acids is enhanced. Copyright © 2017. Published by Elsevier Ltd.

Porous glasses as a matrix for incorporation of photonic materials. Pore determination by positron annihilation lifetime spectroscopy

Science.gov (United States)

Reisfeld, Pore determination by positron annihilation lifetime spectroscopy R.; Saraidarov, T.; Jasinska, B.

2004-07-01

Porous glasses prepared by the sol-gel technique have a variety of applications when incorporated by photonic materials: tunable lasers, sensors, luminescence solar concentrators, semiconductor quantum dots, biological markers. The known methods of pore size determinations, the nitrogen adsorption and mercury porosimetry allow to determine the sizes of open pores. Positron annihilation lifetime spectroscopy (PALS) allows to determine pore sizes also of closed pores. As an example we have performed measurements of non-doped zirconia-silica-polyurethane (ZSUR) ormocer glasses and the same glasses doped with lead sulfide quantum dots. The pore radii range between 0.25-0.38 nm, total surface area 15.5-23.8 m 2/g.

Modelling critical degrees of saturation of porous building materials subjected to freezing

DEFF Research Database (Denmark)

Hansen, Ernst Jan De Place

1996-01-01

of SCR based on fracture mechanics and phase geometry of two-phase materials has been developed.The degradation is modelled as being caused by different eigenstrains of the pore phase and the solid phase when freezing, leading to stress concentrations and crack propagation. Simplifications are made......Frost resistance of porous materials can be characterized by the critical degree of saturation, SCR, and the actual degree of saturation, SACT. An experimental determination of SCR is very laborious and therefore only seldom used when testing frost resistance. A theoretical model for prediction...... to describe the development of stresses and the pore structure, because a mathematical description of the physical theories explaining the process of freezing of water in porous materials is lacking.Calculations are based on porosity, modulus of elasticity and tensile strength, and parameters characterizing...

Supercapacitive characteristics of electrochemically active porous materials

Directory of Open Access Journals (Sweden)

VLADIMIR V. PANIC

2008-06-01

Full Text Available The results of an investigation of the capacitive characteristics of sol–gel-processed titanium- and carbon-supported electrochemically active noble metal oxides, as representatives of porous electrode materials, are presented in the lecture. The capacitive properties of these materials were correlated to their composition, the preparation conditions of the oxides and coatings, the properties of the carbon support and to the composition of the electrolyte. The results of the electrochemical test methods, cyclic voltammetry and electrochemical impedance spectroscopy, were employed to resolve the possible physical structures of the mentioned porous materials, which are governed by the controlled conditions of the preparation of the oxide by the sol–gel process.

Chemical Stability of Cd(II and Cu(II Ionic Imprinted Amino-Silica Hybrid Material in Solution Media

Directory of Open Access Journals (Sweden)

Buhani Buhani

2012-02-01

Full Text Available Chemical stability of Cd(II and Cu(II ionic imprinted amino-silica (HAS material of (i-Cd-HAS and i-Cu-HAS derived from silica modification with active compound (3-aminopropyl-trimethoxysilane (3-APTMS has been studied in solution media.  Stability test was performed with HNO3 0.1 M (pH 1.35 to investigate material stability at low pH condition, acetat buffer at pH 5.22 for adsorption process optimum pH condition, and in the water (pH 9.34 for base condition.  Material characteristics were carried out with infrared spectrophotometer (IR and atomic absorption spectrophotometer (AAS.  At interaction time of 4 days in acid and neutral condition, i-Cd-HAS is more stable than i-Cu-HAS with % Si left in material 95.89 % (acid media, 43.82 % (close to neutral, and 9.39 % (base media.Keywords: chemical stability, amino-silica hybrid, ionic imprinting technique.

Solid phase characterization and gas transfers through unsaturated porous media: experimental study and modeling applied diffusion of hydrogen through cement-based materials

International Nuclear Information System (INIS)

Vu, T.H.

2009-10-01

This thesis documents the relationship between the porous microstructure of cement based materials and theirs gaseous diffusivity properties relative to the aqueous phase location and the global saturation level of the material. The materials studied are cement pastes and mortars. To meet the thesis objective, the materials are characterized in detail by means of several experimental methods: mercury intrusion porosimetry, water porosimetry, thermo-poro-metry, nitrogen sorption and water desorption. In addition, diffusion tests realized on materials maintained in controlled humidity chambers allow obtaining the effective hydrogen diffusivity as function of the microstructure and the saturation state of material with a gas chromatography. The experimental results are then used as a data base that is compared to a modeling approach. The model developed consists of a combination of ordinary diffusion (Fick regime) and Knudsen diffusion of hydrogen. The model also accounts for the effects of the liquid curtains, the impact of tortuosity on gas diffusion, and the saturation level of the porous system. (author)

Hyperpolarized Porous Silicon Nanoparticles: Potential Theragnostic Material for ²⁹Si Magnetic Resonance Imaging.

Science.gov (United States)

Seo, Hyeonglim; Choi, Ikjang; Whiting, Nicholas; Hu, Jingzhe; Luu, Quy Son; Pudakalakatti, Shivanand; McCowan, Caitlin; Kim, Yaewon; Zacharias, Niki; Lee, Seunghyun; Bhattacharya, Pratip; Lee, Youngbok

2018-05-20

Porous silicon nanoparticles have recently garnered attention as potentially-promising biomedical platforms for drug delivery and medical diagnostics. Here, we demonstrate porous silicon nanoparticles as contrast agents for ²⁹Si magnetic resonance imaging. Size-controlled porous silicon nanoparticles were synthesized by magnesiothermic reduction of silica nanoparticles and were surface activated for further functionalization. Particles were hyperpolarized via dynamic nuclear polarization to enhance their ²⁹Si MR signals; the particles demonstrated long ²⁹Si spin-lattice relaxation (T₁) times (~ 25 mins), which suggests potential applicability for medical imaging. Furthermore, ²⁹Si hyperpolarization levels were sufficient to allow ²⁹Si MRI in phantoms. These results underscore the potential of porous silicon nanoparticles that, when combined with hyperpolarized magnetic resonance imaging, can be a powerful theragnostic deep tissue imaging platform to interrogate various biomolecular processes in vivo. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Global sensitivity analysis of multiscale properties of porous materials

Science.gov (United States)

Um, Kimoon; Zhang, Xuan; Katsoulakis, Markos; Plechac, Petr; Tartakovsky, Daniel M.

2018-02-01

Ubiquitous uncertainty about pore geometry inevitably undermines the veracity of pore- and multi-scale simulations of transport phenomena in porous media. It raises two fundamental issues: sensitivity of effective material properties to pore-scale parameters and statistical parameterization of Darcy-scale models that accounts for pore-scale uncertainty. Homogenization-based maps of pore-scale parameters onto their Darcy-scale counterparts facilitate both sensitivity analysis (SA) and uncertainty quantification. We treat uncertain geometric characteristics of a hierarchical porous medium as random variables to conduct global SA and to derive probabilistic descriptors of effective diffusion coefficients and effective sorption rate. Our analysis is formulated in terms of solute transport diffusing through a fluid-filled pore space, while sorbing to the solid matrix. Yet it is sufficiently general to be applied to other multiscale porous media phenomena that are amenable to homogenization.

Fabrication of 3-Dimensional Porous Graphene Materials for Lithium Ion Batteries

International Nuclear Information System (INIS)

Jiang, Yu; Jiang, Zhong-Jie; Cheng, Shuang; Liu, Meilin

2014-01-01

A simple two-step procedure involving hydrothermal reaction and subsequent calcination has been employed to synthesis porous graphene material, which exhibits significantly high electrochemical performance when used as the anode in lithium ion batteries. - Highlights: • A PGM been synthesized by a simple two-step process involving hydrothermal reaction and subsequent calcination. • The PGM exhibits exhibit a significantly high specific surface area. • The PGM can deliver large capacities and excellent cycling performance when used in LIBs. • The high electrochemical performance of the PGM is attributed to its unique porous structure with more disordered carbon atoms. - Abstract: A 3-dimensional porous graphene material (PGM) has been synthesized using a simple two-step process: hydrothermal reaction and calcination. Hydrothermal reaction of graphene oxide (GO) in the presence of resorcinol and glutaraldehyde leads to covalent grafting of partially reduced GO with glutaraldehyde and the deposition of phenolic resin. Subsequent calcination of the composite consisting of phenolic resin deposited on partially reduced GO in the presence of KOH produces structurally stable, highly porous graphene material with a specific surface area of ∼1,066 ± 2 m 2 g −1 . When used as an active electrode material in a lithium battery, the PGM exhibits an initial discharge capacity of ∼1,538 mAh g −1 , which is significantly higher than those of graphite and other carbonaceous materials reported previously. More importantly, when cycled at higher discharge/charge rates, the PGM-based electrodes still deliver large capacities and excellent cycling performance, demonstrating great potential for high-performance lithium-ion batteries. The attractive electrochemical performance of the PGM is attributed to its unique porous structure with large specific surface area and the presence of more disordered carbon atoms produced by the KOH activation

Efficiently mapping structure-property relationships of gas adsorption in porous materials: application to Xe adsorption.

Science.gov (United States)

Kaija, A R; Wilmer, C E

2017-09-08

Designing better porous materials for gas storage or separations applications frequently leverages known structure-property relationships. Reliable structure-property relationships, however, only reveal themselves when adsorption data on many porous materials are aggregated and compared. Gathering enough data experimentally is prohibitively time consuming, and even approaches based on large-scale computer simulations face challenges. Brute force computational screening approaches that do not efficiently sample the space of porous materials may be ineffective when the number of possible materials is too large. Here we describe a general and efficient computational method for mapping structure-property spaces of porous materials that can be useful for adsorption related applications. We describe an algorithm that generates random porous "pseudomaterials", for which we calculate structural characteristics (e.g., surface area, pore size and void fraction) and also gas adsorption properties via molecular simulations. Here we chose to focus on void fraction and Xe adsorption at 1 bar, 5 bar, and 10 bar. The algorithm then identifies pseudomaterials with rare combinations of void fraction and Xe adsorption and mutates them to generate new pseudomaterials, thereby selectively adding data only to those parts of the structure-property map that are the least explored. Use of this method can help guide the design of new porous materials for gas storage and separations applications in the future.

Preparation and characterization of micro-cell membrane chromatographic column with N-hydroxysuccinimide group-modified silica-based porous layer open tubular capillary.

Science.gov (United States)

Xu, Liang; Xu, Bei; Zhao, Zhi-Yu; Yang, Hui-Ping; Tang, Cheng; Dong, Lin-Yi; Liu, Kun; Fu, Li; Wang, Xian-Hua

2017-09-22

Cell membrane chromatography (CMC) is an effective tool in screening active compounds from natural products and studying membrane protein interactions. Nevertheless, it always consumes a large amount of cells (e.g. 10 7 -10 8 ) for column preparation. To overcome this, micro-CMC (mCMC), that employs a silica capillary as membrane carrier, was developed. However, both CMC and mCMC suffer from short column life span (e.g. 3days), mainly due to the falling-off of cellular membranes (CMs). This has greatly limited further application of CMC and mCMC, especially when the cells are hard to obtain. To solve this, N-hydroxysuccinimide (NHS)-modified silica-based porous layer open tubular capillary was first prepared for mCMC. The NHS groups can easily react with amino groups on CMs to form a stable covalent bond under a mild condition. So, CMs immobilized on the NHS-modified capillary are less likely to fall off. To verify this, SKBR3/mCMC (Her2 positive) and BALL1/mCMC (CD20 positive) columns were prepared. Two monoclonal antibody drugs, trastuzumab (anti-Her2) and rituximab (anti-CD20), were selected as analytes to characterize the columns. As a result, NHS-modified column for mCMC can afford higher chromatographic retention than non-modified column. Besides, the column life span was significantly improved to more than 16days for SKBR3/mCMC and 14days for BALL1/mCMC, while the compared column showed a sharp decline in retention factor in first 3days. Copyright © 2017 Elsevier B.V. All rights reserved.

The evaluation of hydroxyapatite (HA) coated and uncoated porous tantalum for biomedical material applications

International Nuclear Information System (INIS)

Safuan, Nadia; Sukmana, Irza; Kadir, Mohammed Rafiq Abdul; Noviana, Deni

2014-01-01

Porous tantalum has been used as an orthopedic implant for bone defects as it has a good corrosion resistance and fatigue behaviour properties. However, there are some reports on the rejection of porous Ta after the implantation. Those clinical cases refer to the less bioactivity of metallic-based materials. This study aims to evaluate hydroxyapatite coated and uncoated porous Tantalum in order to improve the biocompatibility of porous tantalum implant and osseointegration. Porous tantalum was used as metallic-base substrate and hydroxyapatite coating has been done using plasma-spraying technique. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) techniques were utilizes to investigate the coating characteristics while Confocal Raman Microscopy to investigate the interface and image. The effect of coating to the corrosion behaviour was assessed by employing potentiodynamic polarization tests in simulated body fluid at 37±1 °C. Based on SEM and FESEM results, the morphologies as well the weight element consists in the uncoated and hydroxyapatite coated porous tantalum were revealed. The results indicated that the decrease in corrosion current density for HA coated porous Ta compared to the uncoated porous Ta. This study concluded that by coating porous tantalum with HA supports to decrease the corrosion rate of pure porous.

The Evaluation of Hydroxyapatite (HA) Coated and Uncoated Porous Tantalum for Biomedical Material Applications

Science.gov (United States)

Safuan, Nadia; Sukmana, Irza; Kadir, Mohammed Rafiq Abdul; Noviana, Deni

2014-04-01

Porous tantalum has been used as an orthopedic implant for bone defects as it has a good corrosion resistance and fatigue behaviour properties. However, there are some reports on the rejection of porous Ta after the implantation. Those clinical cases refer to the less bioactivity of metallic-based materials. This study aims to evaluate hydroxyapatite coated and uncoated porous Tantalum in order to improve the biocompatibility of porous tantalum implant and osseointegration. Porous tantalum was used as metallic-base substrate and hydroxyapatite coating has been done using plasma-spraying technique. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FESEM) techniques were utilizes to investigate the coating characteristics while Confocal Raman Microscopy to investigate the interface and image. The effect of coating to the corrosion behaviour was assessed by employing potentiodynamic polarization tests in simulated body fluid at 37±1 °C. Based on SEM and FESEM results, the morphologies as well the weight element consists in the uncoated and hydroxyapatite coated porous tantalum were revealed. The results indicated that the decrease in corrosion current density for HA coated porous Ta compared to the uncoated porous Ta. This study concluded that by coating porous tantalum with HA supports to decrease the corrosion rate of pure porous.

Porous Materials - Structure and Properties

DEFF Research Database (Denmark)

Nielsen, Anders

1997-01-01

The paper presents some viewpoints on the description of the pore structure and the modelling of the properties of the porous building materials. Two examples are given , where it has been possible to connect the pore structure to the properties: Shrinkage of autoclaved aerated concrete...

Reflectance Spectra Diversity of Silica-Rich Materials: Sensitivity to Environment and Implications for Detections on Mars

Science.gov (United States)

Rice, M. S.; Cloutis, E. A.; Bell, J. F., III; Bish, D. L.; Horgan, B. H.; Mertzman, S. A.; Craig, M. A.; Renault, R. W.; Gautason, B.; Mountain, B.

2013-01-01

Hydrated silica-rich materials have recently been discovered on the surface of Mars by the Mars Exploration Rover (MER) Spirit, the Mars Reconnaissance Orbiter (MRO) Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), and the Mars Express Observatoire pour la Mineralogie, l'Eau, les Glaces, et l'Activite'(OMEGA) in several locations. Having been interpreted as hydrothermal deposits and aqueous alteration products, these materials have important implications for the history of water on the martian surface. Spectral detections of these materials in visible to near infrared (Vis NIR) wavelengths have been based on a H2O absorption feature in the 934-1009 nm region seen with Spirit s Pancam instrument, and on SiOH absorption features in the 2.21-2.26 micron range seen with CRISM. Our work aims to determine how the spectral reflectance properties of silica-rich materials in Vis NIR wavelengths vary as a function of environmental conditions and formation. Here we present laboratory reflectance spectra of a diverse suite of silica-rich materials (chert, opal, quartz, natural sinters and synthetic silica) under a range of grain sizes and temperature, pressure, and humidity conditions. We find that the H2O content and form of H2O/OH present in silica-rich materials can have significant effects on their Vis NIR spectra. Our main findings are that the position of the approx.1.4 microns OH feature and the symmetry of the approx.1.9 microns feature can be used to discern between various forms of silica-rich materials, and that the ratio of the approx.2.2 microns (SiOH) and approx.1.9 microns (H2O) band depths can aid in distinguishing between silica phases (opal-A vs. opal-CT) and formation conditions (low vs. high temperature). In a case study of hydrated silica outcrops in Valles Marineris, we show that careful application of a modified version of these spectral parameters to orbital near-infrared spectra (e.g., from CRISM and OMEGA) can aid in characterizing the

Dendritic silica nanomaterials (KCC-1) with fibrous pore structure possess high DNA adsorption capacity and effectively deliver genes in vitro.

Science.gov (United States)

Huang, Xiaoxi; Tao, Zhimin; Praskavich, John C; Goswami, Anandarup; Al-Sharab, Jafar F; Minko, Tamara; Polshettiwar, Vivek; Asefa, Tewodros

2014-09-16

The pore size and pore structure of nanoporous materials can affect the materials' physical properties, as well as potential applications in different areas, including catalysis, drug delivery, and biomolecular therapeutics. KCC-1, one of the newest members of silica nanomaterials, possesses fibrous, large pore, dendritic pore networks with wide pore entrances, large pore size distribution, spacious pore volume and large surface area--structural features that are conducive for adsorption and release of large guest molecules and biomacromolecules (e.g., proteins and DNAs). Here, we report the results of our comparative studies of adsorption of salmon DNA in a series of KCC-1-based nanomaterials that are functionalized with different organoamine groups on different parts of their surfaces (channel walls, external surfaces or both). For comparison the results of our studies of adsorption of salmon DNA in similarly functionalized, MCM-41 mesoporous silica nanomaterials with cylindrical pores, some of the most studied silica nanomaterials for drug/gene delivery, are also included. Our results indicate that, despite their relatively lower specific surface area, the KCC-1-based nanomaterials show high adsorption capacity for DNA than the corresponding MCM-41-based nanomaterials, most likely because of KCC-1's large pores, wide pore mouths, fibrous pore network, and thereby more accessible and amenable structure for DNA molecules to diffuse through. Conversely, the MCM-41-based nanomaterials adsorb much less DNA, presumably because their outer surfaces/cylindrical channel pore entrances can get blocked by the DNA molecules, making the inner parts of the materials inaccessible. Moreover, experiments involving fluorescent dye-tagged DNAs suggest that the amine-grafted KCC-1 materials are better suited for delivering the DNAs adsorbed on their surfaces into cellular environments than their MCM-41 counterparts. Finally, cellular toxicity tests show that the KCC-1-based

Acoustic properties of a porous glass (vycor) at hypersonic frequencies

International Nuclear Information System (INIS)

Levelut, C; Pelous, J

2007-01-01

Brillouin scattering experiments have been performed from 5 to 1600 K in vycor, a porous silica glass. The acoustic velocity and attenuation at hypersonic frequencies are compared to those of bulk silica and others porous silica samples. The experimental evidence for the influence of porosity on the scattering by acoustic waves is compared to calculations. The correlation between internal friction and thermal conductivity at low temperature is discussed

A diffusivity model for predicting VOC diffusion in porous building materials based on fractal theory.

Science.gov (United States)

Liu, Yanfeng; Zhou, Xiaojun; Wang, Dengjia; Song, Cong; Liu, Jiaping

2015-12-15

Most building materials are porous media, and the internal diffusion coefficients of such materials have an important influences on the emission characteristics of volatile organic compounds (VOCs). The pore structure of porous building materials has a significant impact on the diffusion coefficient. However, the complex structural characteristics bring great difficulties to the model development. The existing prediction models of the diffusion coefficient are flawed and need to be improved. Using scanning electron microscope (SEM) observations and mercury intrusion porosimetry (MIP) tests of typical porous building materials, this study developed a new diffusivity model: the multistage series-connection fractal capillary-bundle (MSFC) model. The model considers the variable-diameter capillaries formed by macropores connected in series as the main mass transfer paths, and the diameter distribution of the capillary bundles obeys a fractal power law in the cross section. In addition, the tortuosity of the macrocapillary segments with different diameters is obtained by the fractal theory. Mesopores serve as the connections between the macrocapillary segments rather than as the main mass transfer paths. The theoretical results obtained using the MSFC model yielded a highly accurate prediction of the diffusion coefficients and were in a good agreement with the VOC concentration measurements in the environmental test chamber. Copyright © 2015 Elsevier B.V. All rights reserved.

Testing of porous materials using ion beam techniques

International Nuclear Information System (INIS)

Szilagyi, E.; Asrama, M.; Paszti, F.; Battistig, G.; Hajnal, Z.

1999-01-01

Porous materials were examined by backscattering spectrometry and oxygen resonance measurements. The material was a porous silicon (PS) sample. The BS data were evaluated by simulation, using the RBX program, and a comparison was made with measured data. The PS sample was also investigated using the 16 O(α,α) 16 O reaction, and the resonance spectra were evaluated. The data yielded useful information on porosity, mean pore diameter, mean pore distance, and structure ordering. (R.P.)

ELECTROKINETIC DEVICE AND METHOD FOR CONSOLIDATING POROUS MATERIALS

DEFF Research Database (Denmark)

2017-01-01

The invention relates to a device and an associated electrokinetic method which allows the pores (superficial and deep) of a porous material to be filled, by forcing the precipitation therein of a product of low solubility in water by creating an electric field which will mobilise the cations...... and anions supplied by previously selected solutions. This method comprises two phases. In the first phase, the pores located at a specified distance from the surface of contact between the porous material and the anodic or cathodic compartment are plugged. In a second phase, the rest of the pores, mainly...... those which are on the surface level, are collapsed. As a result of the designed device and the plugging system contained therein, the porous material is not affected at any moment by chemical alteration processes caused by contact with extreme pH values. This device allows the treatment to be applied...

Optimized manufacturable porous materials

DEFF Research Database (Denmark)

Andreassen, Erik; Andreasen, Casper Schousboe; Jensen, Jakob Søndergaard

Topology optimization has been used to design two-dimensional material structures with specific elastic properties, but optimized designs of three-dimensional material structures are more scarsely seen. Partly because it requires more computational power, and partly because it is a major challenge...... to include manufacturing constraints in the optimization. This work focuses on incorporating the manufacturability into the optimization procedure, allowing the resulting material structure to be manufactured directly using rapid manufacturing techniques, such as selective laser melting/sintering (SLM....../S). The available manufacturing methods are best suited for porous materials (one constituent and void), but the optimization procedure can easily include more constituents. The elasticity tensor is found from one unit cell using the homogenization method together with a standard finite element (FE) discretization...

Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

KAUST Repository

Munirasu, Selvaraj

2014-07-22

A new kind of asymmetric organic-inorganic porous structure has been proposed. Asymmetric lattices of polymer grafted silica nanoparticles were manufactured by casting and phase inversion in water. Silica nanoparticles were first functionalized with 3-(dimethylethoxysilyl)propyl-2-bromoisobutyrate, followed by grafting of poly(methylmethacrylate) (PMMA) segments, performed by atom-transfer radical polymerization. Mechanically stable self-standing films were prepared by casting a dispersion of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO2 hybrid material in acetone or acetone/dioxane led to the best-assembled structures. Porous asymmetric membranes were prepared by adding free PMMA and PMMA terminated with hydrophilic hydroxyl group. Nitrogen flow of 2800 L m-2 h -1 was measured at 1.3 bar demonstrating the porosity and potential application for membrane technology. © 2014 Springer Science+Business Media New York.

Mesoporous Carbon Produced from Tri-constituent Mesoporous Carbon-silica Composite for Water Purification

KAUST Repository

Yu, Yanjie

2012-01-01

Highly ordered mesoporous carbon-silica nanocomposites with interpenetrating carbon and silica networks were synthesized by the evaporation-induced tri-constituent co- assembly approach. The removal of silica by concentrated NaOH solution produced mesoporous carbons, which contained not only the primary large pores, but also the secondary mesopores in the carbon walls. The thus synthesized mesoporous carbon was further activated by using ZnCl2. The activated mesoporous carbon showed an improved surface area and pore volume. The synthesized mesoporous carbon was tested for diuron removal from water and the results showed that the carbon gave a fast diuron adsorption kinetics and a high diuron removal capacity, which was attributable to the primary mesopore channels being the highway for mass transfer, which led to short diffusion path length and easy accessibility of the interpenetrated secondary mesopores. The optimal adsorption capacity of the porous carbon was determined to be 390 mg/g, the highest values ever reported for diuron adsorption on carbon-based materials.

Mesoporous Carbon Produced from Tri-constituent Mesoporous Carbon-silica Composite for Water Purification

KAUST Repository

Yu, Yanjie

2012-05-01

Highly ordered mesoporous carbon-silica nanocomposites with interpenetrating carbon and silica networks were synthesized by the evaporation-induced tri-constituent co- assembly approach. The removal of silica by concentrated NaOH solution produced mesoporous carbons, which contained not only the primary large pores, but also the secondary mesopores in the carbon walls. The thus synthesized mesoporous carbon was further activated by using ZnCl2. The activated mesoporous carbon showed an improved surface area and pore volume. The synthesized mesoporous carbon was tested for diuron removal from water and the results showed that the carbon gave a fast diuron adsorption kinetics and a high diuron removal capacity, which was attributable to the primary mesopore channels being the highway for mass transfer, which led to short diffusion path length and easy accessibility of the interpenetrated secondary mesopores. The optimal adsorption capacity of the porous carbon was determined to be 390 mg/g, the highest values ever reported for diuron adsorption on carbon-based materials.

Review on recent and advanced applications of monoliths and related porous polymer gels in micro-fluidic devices

International Nuclear Information System (INIS)

Vazquez, Mercedes; Paull, Brett

2010-01-01

This review critically summarises recent novel and advanced achievements in the application of monolithic materials and related porous polymer gels in micro-fluidic devices appearing within the literature over the period of the last 5 years (2005-2010). The range of monolithic materials has developed rapidly over the past decade, with a diverse and highly versatile class of materials now available, with each exhibiting distinct porosities, pore sizes, and a wide variety of surface functionalities. A major advantage of these materials is their ease of preparation in micro-fluidic channels by in situ polymerisation, leading to monolithic materials being increasingly utilised for a larger variety of purposes in micro-fluidic platforms. Applications of porous polymer monoliths, silica-based monoliths and related homogeneous porous polymer gels in the preparation of separation columns, ion-permeable membranes, preconcentrators, extractors, electrospray emitters, micro-valves, electrokinetic pumps, micro-reactors and micro-mixers in micro-fluidic devices are discussed herein. Procedures used in the preparation of monolithic materials in micro-channels, as well as some practical aspects of the micro-fluidic chip fabrication are addressed. Recent analytical/bioanalytical and catalytic applications of the final micro-fluidic devices incorporating monolithic materials are also reviewed.

Porous Materials for Hydrolytic Dehydrogenation of Ammonia Borane

Directory of Open Access Journals (Sweden)

Tetsuo Umegaki

2015-07-01

Full Text Available Hydrogen storage is still one of the most significant issues hindering the development of a “hydrogen energy economy”. Ammonia borane is notable for its high hydrogen densities. For the material, one of the main challenges is to release efficiently the maximum amount of the stored hydrogen. Hydrolysis reaction is a promising process by which hydrogen can be easily generated from this compound. High purity hydrogen from this compound can be evolved in the presence of solid acid or metal based catalyst. The reaction performance depends on the morphology and/or structure of these materials. In this review, we survey the research on nanostructured materials, especially porous materials for hydrogen generation from hydrolysis of ammonia borane.

Porous Materials for Hydrolytic Dehydrogenation of Ammonia Borane.

Science.gov (United States)

Umegaki, Tetsuo; Xu, Qiang; Kojima, Yoshiyuki

2015-07-21

Hydrogen storage is still one of the most significant issues hindering the development of a "hydrogen energy economy". Ammonia borane is notable for its high hydrogen densities. For the material, one of the main challenges is to release efficiently the maximum amount of the stored hydrogen. Hydrolysis reaction is a promising process by which hydrogen can be easily generated from this compound. High purity hydrogen from this compound can be evolved in the presence of solid acid or metal based catalyst. The reaction performance depends on the morphology and/or structure of these materials. In this review, we survey the research on nanostructured materials, especially porous materials for hydrogen generation from hydrolysis of ammonia borane.

Transport and abatement of fluorescent silica nanoparticle (SiO_2 NP) in granular filtration: effect of porous media and ionic strength

International Nuclear Information System (INIS)

Zeng, Chao; Shadman, Farhang; Sierra-Alvarez, Reyes

2017-01-01

The extensive production and application of engineered silica nanoparticles (SiO_2 NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO_2 NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO_2 NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO_2 filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO_2 NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO_2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO_2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO_2 NP filtration.

Transport and abatement of fluorescent silica nanoparticle (SiO2 NP) in granular filtration: effect of porous media and ionic strength

Science.gov (United States)

Zeng, Chao; Shadman, Farhang; Sierra-Alvarez, Reyes

2017-03-01

The extensive production and application of engineered silica nanoparticles (SiO2 NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO2 NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO2 NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO2 filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO2 NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO2 NP filtration.

Zirconia-hydroxyapatite composite material with micro porous structure.

Science.gov (United States)

Matsumoto, Takuya Junior; An, Sang-Hyun; Ishimoto, Takuya; Nakano, Takayoshi; Matsumoto, Takuya; Imazato, Satoshi

2011-11-01

Titanium plates and apatite blocks are commonly used for restoring large osseous defects in dental and orthopedic surgery. However, several cases of allergies against titanium have been recently reported. Also, sintered apatite block does not possess sufficient mechanical strength. In this study, we attempted to fabricate a composite material that has mechanical properties similar to biocortical bone and high bioaffinity by compounding hydroxyapatite (HAp) with the base material zirconia (ZrO(2)), which possesses high mechanical properties and low toxicity toward living organisms. After mixing the raw material powders at several different ZrO(2)/HAp mixing ratios, the material was compressed in a metal mold (8 mm in diameter) at 5 MPa. Subsequently, it was sintered for 5 h at 1500°C to obtain the ZrO(2)/HAp composite. The mechanical property and biocompatibility of materials were investigated. Furthermore, osteoconductivity of materials was investigated by animal studies. A composite material with a minute porous structure was successfully created using ZrO(2)/HAp powders, having different particle sizes, as the starting material. The material also showed high protein adsorption and a favorable cellular affinity. When the mixing ratio was ZrO(2)/HAp=70/30, the strength was equal to cortical bone. Furthermore, in vivo experiments confirmed its high osteoconductivity. The composite material had strength similar to biocortical bones with high cell and tissue affinities by compounding ZrO(2) and HAp. The ZrO(2)/HAp composite material having micro porous structure would be a promising bone restorative material. Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Multi-template synthesis of hierarchically porous carbon spheres with potential application in supercapacitors

NARCIS (Netherlands)

Zhou, Weizheng; Lin, Zhixing; Tong, Gangsheng; Stoyanov, Simeon D.; Yan, Deyue; Mai, Yiyong; Zhu, Xinyuan

2016-01-01

A new and simple multi-template approach towards hierarchical porous carbon (HPC) materials was reported. HPC spheres were prepared by using hierarchical silica capsules (HSCs) as the hard template and triblock copolymer Pluronic P123 as the soft template. Three types of pores were tunably

Preparation of resveratrol-loaded nanoporous silica materials with different structures

International Nuclear Information System (INIS)

Popova, Margarita; Szegedi, Agnes; Mavrodinova, Vesselina; Novak Tušar, Natasa; Mihály, Judith; Klébert, Szilvia; Benbassat, Niko; Yoncheva, Krassimira

2014-01-01

Solid, nanoporous silica-based spherical mesoporous MCM-41 and KIL-2 with interparticle mesoporosity as well as nanosized zeolite BEA materials differing in morphology and pore size distribution, were used as carriers for the preparation of resveratrol-loaded delivery systems. Two preparation methods have been applied: (i) loading by mixing of resveratrol and mesoporous carrier in solid state and (ii) deposition in ethanol solution. The parent and the resveratrol loaded carriers were characterized by XRD, TEM, N2 physisorption, thermal analysis, and FT-IR spectroscopy. The influence of the support structure on the adsorption capacity and the release kinetics of this poorly soluble compound were investigated. Our results indicated that the chosen nanoporous silica supports are suitable for stabilization of trans-resveratrol and reveal controlled release and ability to protect the supported compound against degradation regardless of loading method. The solid-state dry mixing appears very effective for preparation of drug formulations composed of poorly soluble compound. - Graphical abstract: trans-Resveratrol was stabilized in the pores of BEA zeolite, MCM-41and KIL2 mesoporous silicas. - Highlights: • BEA, KIL-2 and MCM-41 materials were used as carriers for resveratrol loading. • Resveratrol encapsulation in ethanol solution and solid state procedure were applied. • The solid-state preparation appears very effective for stabilization of trans-resveratrol

Preparation of resveratrol-loaded nanoporous silica materials with different structures

Energy Technology Data Exchange (ETDEWEB)

Popova, Margarita, E-mail: mpopova@orgchem.bas.bg [Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Szegedi, Agnes [Research Centre for Natural Sciences, Institute of Materials and Environmental Chemistry, Hungarian Academy of Sciences, 1117 Budapest, Magyar tudósok körútja 2. (Hungary); Mavrodinova, Vesselina [Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Novak Tušar, Natasa [National Institute of Chemistry, Ljubljana (Slovenia); Mihály, Judith; Klébert, Szilvia [Research Centre for Natural Sciences, Institute of Materials and Environmental Chemistry, Hungarian Academy of Sciences, 1117 Budapest, Magyar tudósok körútja 2. (Hungary); Benbassat, Niko; Yoncheva, Krassimira [Faculty of Pharmacy, 2 Dunav Str., 1000 Sofia (Bulgaria)

2014-11-15

Solid, nanoporous silica-based spherical mesoporous MCM-41 and KIL-2 with interparticle mesoporosity as well as nanosized zeolite BEA materials differing in morphology and pore size distribution, were used as carriers for the preparation of resveratrol-loaded delivery systems. Two preparation methods have been applied: (i) loading by mixing of resveratrol and mesoporous carrier in solid state and (ii) deposition in ethanol solution. The parent and the resveratrol loaded carriers were characterized by XRD, TEM, N2 physisorption, thermal analysis, and FT-IR spectroscopy. The influence of the support structure on the adsorption capacity and the release kinetics of this poorly soluble compound were investigated. Our results indicated that the chosen nanoporous silica supports are suitable for stabilization of trans-resveratrol and reveal controlled release and ability to protect the supported compound against degradation regardless of loading method. The solid-state dry mixing appears very effective for preparation of drug formulations composed of poorly soluble compound. - Graphical abstract: trans-Resveratrol was stabilized in the pores of BEA zeolite, MCM-41and KIL2 mesoporous silicas. - Highlights: • BEA, KIL-2 and MCM-41 materials were used as carriers for resveratrol loading. • Resveratrol encapsulation in ethanol solution and solid state procedure were applied. • The solid-state preparation appears very effective for stabilization of trans-resveratrol.

A statistical method for predicting sound absorbing property of porous metal materials by using quartet structure generation set

International Nuclear Information System (INIS)

Guan, Dong; Wu, Jiu Hui; Jing, Li

2015-01-01

Highlights: • A random internal morphology and structure generation-growth method, termed as the quartet structure generation set (QSGS), has been utilized based on the stochastic cluster growth theory for numerical generating the various microstructures of porous metal materials. • Effects of different parameters such as thickness and porosity on sound absorption performance of the generated structures are studied by the present method, and the obtained results are validated by an empirical model as well. • This method could be utilized to guide the design and fabrication of the sound-absorption porous metal materials. - Abstract: In this paper, a statistical method for predicting sound absorption properties of porous metal materials is presented. To reflect the stochastic distribution characteristics of the porous metal materials, a random internal morphology and structure generation-growth method, termed as the quartet structure generation set (QSGS), has been utilized based on the stochastic cluster growth theory for numerical generating the various microstructures of porous metal materials. Then by using the transfer-function approach along with the QSGS tool, we investigate the sound absorbing performance of porous metal materials with complex stochastic geometries. The statistical method has been validated by the good agreement among the numerical results for metal rubber from this method and a previous empirical model and the corresponding experimental data. Furthermore, the effects of different parameters such as thickness and porosity on sound absorption performance of the generated structures are studied by the present method, and the obtained results are validated by an empirical model as well. Therefore, the present method is a reliable and robust method for predicting the sound absorption performance of porous metal materials, and could be utilized to guide the design and fabrication of the sound-absorption porous metal materials

Small-angle and surface scattering from porous and fractal materials.

Energy Technology Data Exchange (ETDEWEB)

Sinha, S. K.

1998-09-18

We review the basic theoretical methods used to treat small-angle scattering from porous materials, treated as general two-phase systems, and also the basic experimental techniques for carrying out such experiments. We discuss the special forms of the scattering when the materials exhibit mass or surface fractal behavior, and review the results of recent experiments on several types of porous media and also SANS experiments probing the phase behavior of binary fluid mixtures or polymer solutions confined in porous materials. Finally, we discuss the analogous technique of off-specular scattering from surfaces and interfaces which is used to study surface roughness of various kinds.

Biobased, Internally pH-Sensitive Materials: Immobilized Yellow Fluorescent Protein as an Optical Sensor for Spatiotemporal Mapping of pH Inside Porous Matrices.

Science.gov (United States)

Consolati, Tanja; Bolivar, Juan M; Petrasek, Zdenek; Berenguer, Jose; Hidalgo, Aurelio; Guisán, Jose M; Nidetzky, Bernd

2018-02-28

The pH is fundamental to biological function and its measurement therefore crucial across all biosciences. Unlike homogenous bulk solution, solids often feature internal pH gradients due to partition effects and confined biochemical reactions. Thus, a full spatiotemporal mapping for pH characterization in solid materials with biological systems embedded in them is essential. In here, therefore, a fully biocompatible methodology for real-time optical sensing of pH within porous materials is presented. A genetically encoded ratiometric pH sensor, the enhanced superfolder yellow fluorescent protein (sYFP), is used to functionalize the internal surface of different materials, including natural and synthetic organic polymers as well as silica frameworks. By using controlled, tailor-made immobilization, sYFP is homogenously distributed within these materials and so enables, via self-referenced imaging analysis, pH measurements in high accuracy and with useful spatiotemporal resolution. Evolution of internal pH is monitored in consequence of a proton-releasing enzymatic reaction, the hydrolysis of penicillin by a penicillin acylase, taking place in solution or confined to the solid surface of the porous matrix. Unlike optochemical pH sensors, which often interfere with biological function, labeling with sYFP enables pH sensing without altering the immobilized enzyme's properties in any of the materials used. Fast response of sYFP to pH change permits evaluation of biochemical kinetics within the solid materials. Thus, pH sensing based on immobilized sYFP represents a broadly applicable technique to the study of biology confined to the internally heterogeneous environment of solid matrices.

Impact of surface impurity on phase transitions in amorphous micro silica

DEFF Research Database (Denmark)

Haastrup, Sonja; Yu, Donghong; Yue, Yuanzheng

2016-01-01

In this work we study three types of spherically shaped micron and submicron sized amorphous micro silica (MS) as common raw material for production of porous calcium silicate products used for insulation, which are selected on basis of chemical composition and production method. Two of them have...... silica content of 96% (from silicon production) and one has that of 92% (from ferro-silicon production). In order to achieve high quality calcium silicate products, which strongly depends on the characteristics of the raw MS, it is crucial to study the chemical and physical properties of the raw MS...

STUDY ON SILICA INFUSED RECYCLED AGGREGATE CONCRETE USING DESIGN OF EXPERIMENTS

Directory of Open Access Journals (Sweden)

P. M. MRUDUL

2017-04-01

Full Text Available Recycled Aggregate (RA generated from the construction industry is used as a material for sustainable construction. The old mortar attached to these aggregates makes it porous and are generally used for low-grade applications. However, by infusing with silica fumes, the properties of recycled aggregate concrete (RAC can be improved, as the silica fumes get infused into the pores of old mortar attached to it. In this study, the optimum percentage of recycled aggregate that can be used in fresh concrete for higher grade applications was found out. Design of experiments (DoE was used to optimize percentage of silica fumes and recycled aggregate to achieve optimum properties of concrete. Equations to predict the properties of concrete were also modelled using regression analysis.

Comparison of two silica-based extraction methods for DNA isolation from bones.

Science.gov (United States)

Rothe, Jessica; Nagy, Marion

2016-09-01

One of the most demanding DNA extractions is from bones and teeth due to the robustness of the material and the relatively low DNA content. The greatest challenge is due to the manifold nature of the material, which is defined by various factors, including age, storage, environmental conditions, and contamination with inhibitors. However, most published protocols do not distinguish between different types or qualities of bone material, but are described as being generally applicable. Our laboratory works with two different extraction methods based on silica membranes or the use of silica beads. We compared the amplification success of the two methods from bone samples with different qualities and in the presence of inhibitors. We found that the DNA extraction using the silica membrane method results an in higher DNA yield but also in a higher risk of co-extracting impurities, which can act as inhibitors. In contrast the silica beads method shows decreased co-extraction of inhibitors but also less DNA yield. Related to our own experiences it has to be considered that each bone material should be reviewed independently regarding the analysis and extraction method. Therefore, the most ambitious task is determining the quality of the bone material, which requires substantial experience. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Fabrication of Porous Materials from Natural/Synthetic Biopolymers and Their Composites

Directory of Open Access Journals (Sweden)

Udeni Gunathilake T.M. Sampath

2016-12-01

Full Text Available Biopolymers and their applications have been widely studied in recent years. Replacing the oil based polymer materials with biopolymers in a sustainable manner might give not only a competitive advantage but, in addition, they possess unique properties which cannot be emulated by conventional polymers. This review covers the fabrication of porous materials from natural biopolymers (cellulose, chitosan, collagen, synthetic biopolymers (poly(lactic acid, poly(lactic-co-glycolic acid and their composite materials. Properties of biopolymers strongly depend on the polymer structure and are of great importance when fabricating the polymer into intended applications. Biopolymers find a large spectrum of application in the medical field. Other fields such as packaging, technical, environmental, agricultural and food are also gaining importance. The introduction of porosity into a biomaterial broadens the scope of applications. There are many techniques used to fabricate porous polymers. Fabrication methods, including the basic and conventional techniques to the more recent ones, are reviewed. Advantages and limitations of each method are discussed in detail. Special emphasis is placed on the pore characteristics of biomaterials used for various applications. This review can aid in furthering our understanding of the fabrication methods and about controlling the porosity and microarchitecture of porous biopolymer materials.

Fabrication of Porous Materials from Natural/Synthetic Biopolymers and Their Composites.

Science.gov (United States)

Sampath, Udeni Gunathilake T M; Ching, Yern Chee; Chuah, Cheng Hock; Sabariah, Johari J; Lin, Pai-Chen

2016-12-07

Biopolymers and their applications have been widely studied in recent years. Replacing the oil based polymer materials with biopolymers in a sustainable manner might give not only a competitive advantage but, in addition, they possess unique properties which cannot be emulated by conventional polymers. This review covers the fabrication of porous materials from natural biopolymers (cellulose, chitosan, collagen), synthetic biopolymers (poly(lactic acid), poly(lactic- co -glycolic acid)) and their composite materials. Properties of biopolymers strongly depend on the polymer structure and are of great importance when fabricating the polymer into intended applications. Biopolymers find a large spectrum of application in the medical field. Other fields such as packaging, technical, environmental, agricultural and food are also gaining importance. The introduction of porosity into a biomaterial broadens the scope of applications. There are many techniques used to fabricate porous polymers. Fabrication methods, including the basic and conventional techniques to the more recent ones, are reviewed. Advantages and limitations of each method are discussed in detail. Special emphasis is placed on the pore characteristics of biomaterials used for various applications. This review can aid in furthering our understanding of the fabrication methods and about controlling the porosity and microarchitecture of porous biopolymer materials.

Multifunctional nanomedicine with silica: Role of silica in nanoparticles for theranostic, imaging, and drug monitoring.

Science.gov (United States)

Chen, Fang; Hableel, Ghanim; Zhao, Eric Ruike; Jokerst, Jesse V

2018-07-01

The idea of multifunctional nanomedicine that enters the human body to diagnose and treat disease without major surgery is a long-standing dream of nanomaterials scientists. Nanomaterials show incredible properties that are not found in bulk materials, but achieving multi-functionality on a single material remains challenging. Integrating several types of materials at the nano-scale is critical to the success of multifunctional nanomedicine device. Here, we describe the advantages of silica nanoparticles as a tool for multifunctional nano-devices. Silica nanoparticles have been intensively studied in drug delivery due to their biocompatibility, degradability, tunable morphology, and ease of modification. Moreover, silica nanoparticles can be integrated with other materials to obtain more features and achieve theranostic capabilities and multimodality for imaging applications. In this review, we will first compare the properties of silica nanoparticles with other well-known nanomaterials for bio-applications and describe typical routes to synthesize and integrate silica nanoparticles. We will then highlight theranostic and multimodal imaging application that use silica-based nanoparticles with a particular interest in real-time monitoring of therapeutic molecules. Finally, we will present the challenges and perspective on future work with silica-based nanoparticles in medicine. Copyright © 2018 Elsevier Inc. All rights reserved.

Development of porous materials for hydrogen storage

Energy Technology Data Exchange (ETDEWEB)

Shinji Oshima; Osamu Kato; Takeshi Kataoka; Yoshihiro Kobori; Michiaki Adachi [Hydrogen and New Energy Research Laboratory Nippon Oil Corporation 8, Chidoricho, Naka-ku, Yokohama, 231-0815 (Japan)

2006-07-01

To achieve hydrogen storage of more than 5 mass%, we are focusing on porous materials that consist of light elements. At WHEC 15, we reported that KOH-activated bamboo charcoal showed 0.79 mass% hydrogen uptake at 9.5 MPa and 303 K. After examining various carbon materials, we found that carbonized and KOH-activated polyacrylonitrile fibers showed 1.0 mass% hydrogen uptake at 9.5 MPa and 303 K. When the pressure was raised to 35 MPa, this material showed 1.5 mass% hydrogen uptake at 303 K. Besides porous carbon, other materials, such as coordination polymers, were examined. Since these materials contain elements other than carbon, different adsorption phenomena may be expected. Although the values of their hydrogen uptakes are still lower than those of carbon materials, a coordination polymer which showed 0.38 mass% hydrogen uptake at 9.5 MPa and 303 K was revealed to give an adsorption density of 47 kg/m{sup 3} at 0.1 MPa and 77 K, the highest value reported for a coordination polymer. (authors)

Electrohydrodynamic bubbling: an alternative route to fabricate porous structures of silk fibroin based materials.

Science.gov (United States)

Ekemen, Zeynep; Ahmad, Zeeshan; Stride, Eleanor; Kaplan, David; Edirisinghe, Mohan

2013-05-13

Conventional fabrication techniques and structures employed in the design of silk fibroin (SF) based porous materials provide only limited control over pore size and require several processing stages. In this study, it is shown that, by utilizing electrohydrodynamic bubbling, not only can new hollow spherical structures of SF be formed in a single step by means of bubbles, but the resulting bubbles can serve as pore generators when dehydrated. The bubble characteristics can be controlled through simple adjustments to the processing parameters. Bubbles with diameters in the range of 240-1000 μm were fabricated in controlled fashion. FT-IR characterization confirmed that the rate of air infused during processing enhanced β-sheet packing in SF at higher flow rates. Dynamic mechanical analysis also demonstrated a correlation between air flow rate and film tensile strength. Results indicate that electrohydrodynamically generated SF and their composite bubbles can be employed as new tools to generate porous structures in a controlled manner with a range of potential applications in biocoatings and tissue engineering scaffolds.

Development of high-average-power-laser medium based on silica glass

International Nuclear Information System (INIS)

Fujimoto, Yasushi; Nakatsuka, Masahiro

2000-01-01

We have developed a high-average-power laser material based on silica glass. A new method using Zeolite X is effective for homogeneously dispersing rare earth ions in silica glass to get a high quantum yield. High quality medium, which is bubbleless and quite low refractive index distortion, must be required for realization of laser action, and therefore, we have carefully to treat the gelation and sintering processes, such as, selection of colloidal silica, pH value of for hydrolysis of tetraethylorthosilicate, and sintering history. The quality of the sintered sample and the applications are discussed. (author)

Influence of corn flour as pore forming agent on porous ceramic material based mullite: Morphology and mechanical properties

Directory of Open Access Journals (Sweden)

Ayala-Landeros J.G.

2016-01-01

Full Text Available Porous material was processed by the mixing, molding and pressing the ceramic material, afterward burnout and sintering; through the forming porous, using corn flour at different concentration (10, 15 and 20 wt.% as a pore forming agent; in order to determinate the influence of porous on the mechanical, morphological and structural properties. The effect of the volume fraction of corn flour in the mullite matrix, at various sintering temperature from 1100, 1200, 1300 and 1500°C were tested by Diffraction X ray, showing changes in crystalline phases of mullite (3Al2O3-2SiO2, as result of sintered temperatures. Presence of talcum powder in formula, also cause the formation of the cordierite and cristobalite crystalline phases, giving stability and adhesion to the structure of ceramic material. When sintering at temperatures between 1300 to 1500°C, and it was used the concentration of corn flour 15-20 wt.% as forming agent porous, it was found the better mechanical properties. The scanning electron microscopy analysis shows the presence of open porosity and anisotropy.

Construction of Silica-Based Micro/Nanoplatforms for Ultrasound Theranostic Biomedicine.

Science.gov (United States)

Zhou, Yang; Han, Xiaoxia; Jing, Xiangxiang; Chen, Yu

2017-09-01

Ultrasound (US)-based biomedicine has been extensively explored for its applications in both diagnostic imaging and disease therapy. The fast development of theranostic nanomedicine significantly promotes the development of US-based biomedicine. This progress report summarizes and discusses the recent developments of rational design and fabrication of silica-based micro/nanoparticles for versatile US-based biomedical applications. The synthetic strategies and surface-engineering approaches of silica-based micro/nanoparticles are initially discussed, followed by detailed introduction on their US-based theranostic applications. They have been extensively explored in contrast-enhanced US imaging, US-based multi-modality imaging, synergistic high-intensity focused US (HIFU) ablation, sonosensitizer-enhanced sonodynamic therapy (SDT), as well as US-triggered chemotherapy. Their biological effects and biosafety have been briefly discussed to guarantee further clinical translation. Based on the high biocompatibility, versatile composition/structure and high performance in US-based theranostic biomedicine, these silica-based theranostic agents are expected to pave a new way for achieving efficient US-based theranostics of disease by taking the specific advantages of material science, nanotechnology and US-based biomedicine. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cu(II) recognition materials: Fluorophores grafted on mesoporous silica supports

International Nuclear Information System (INIS)

Kledzik, Krzysztof; Orlowska, Maja; Patralska, Dorota; Gwiazda, Marcin; Jezierska, Julia; Pikus, Stanislaw; Ostaszewski, Ryszard; Klonkowski, Andrzej M.

2007-01-01

There were designed and synthesized naphthalene and pyrene derivatives consisting of fluorophore group and of receptor fragment with donor N and O atoms. These fluorosensors were covalently attached by grafting carboxyl group to surfaces of silica xerogel or mesoporous silicas (MCM-41 and MCM-48) functionalized either with 3-aminopropyl or 3-glycidoxypropyl groups. The pyrene derivatives 2 and 3 covalently grafted on MCM-48 silica functionalized with 3-aminopropyl groups are potential recognition elements of a fluorescence chemical sensor. Fluorescence emission of the prepared recognition materials is quenched specifically owing to photoinduced electron transfer (PET) effect after coordination reactions with Cu(II) ions. Moreover, both the materials exhibit selectivity for Cu(II) ions in aqueous solutions in presence of such metal ions as: alkali, alkaline earth and transition. During UV irradiation the studied recognition elements undergo slowly photochemical degradation

Structural control in the synthesis of inorganic porous materials

Science.gov (United States)

Holland, Brian Thomas

Mesoporous (2.0--50.0 nm pore diameter) and macroporous (50.0 nm on up) materials have been the basis of my studies. These materials, for many years, possessed large pore size distributions. Recently, however, it has been possible to synthesize both mesoporous and macroporous materials that possess highly ordered uniform pores throughout the material. Workers at Mobil Corporation in 1992 discovered a hexagonally arrayed mesoporous material, designated MCM-41, which exhibited uniform pores ranging from 2.0--10.0 nm in diameter. In my work MCM-41 was used as a host for the incorporation of meso-tetrakis(5-trimethylammoniumpentyl)porphyrin (TMAP-Cl) and as a model for the synthesis of mesoporous alumino- and galloaluminophosphates which were created using cluster precursors of the type MO4Al 12(OH)24(H2O)12 7+, M = Al or Ga. Macroporous materials with uniform pore sizes have been synthesized by our group with frameworks consisting of a variety of metal oxides, metals, organosilanes, aluminophosphates and bimodal pores. These materials are synthesized from the addition of metal precursors to preordered polystyrene spheres. Removal of the spheres results in the formation of macropores with highly uniform pores extending microns in length. Porous materials with uniform and adjustable pore sizes in the mesoporous and macroporous size regimes offer distinct advantages over non-ordered materials for numerous reasons. First, catalysis reactions that are based on the ability of the porous materials to impose size and shape restrictions on the substrate are of considerable interest in the petroleum and petrochemical industries. As pore diameters increase larger molecules can be incorporated into the pores, i.e., biological molecules, dyes, etc. For the macroporous materials synthesized by our group it has been envisioned that these structures may not only be used for catalysis because of increased efficiencies of flow but for more advanced applications, e.g., photonic crystals

Transport and abatement of fluorescent silica nanoparticle (SiO{sub 2} NP) in granular filtration: effect of porous media and ionic strength

Energy Technology Data Exchange (ETDEWEB)

Zeng, Chao, E-mail: chaozeng@email.arizona.edu; Shadman, Farhang; Sierra-Alvarez, Reyes [University of Arizona, Department of Chemical and Environmental Engineering (United States)

2017-03-15

The extensive production and application of engineered silica nanoparticles (SiO{sub 2} NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO{sub 2} NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO{sub 2} NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO{sub 2} filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO{sub 2} NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO{sub 2} NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO{sub 2} NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO{sub 2} NP filtration.

Silica-scavenging effects in ceria-based solid electrolytes

Directory of Open Access Journals (Sweden)

Ivanova, D.

2008-08-01

Full Text Available Composite materials based on gadolinium doped ceria (CGO with additions of silica, with both silica and lanthanum oxide, and with lanthanum silicate, were prepared by the conventional ceramic route, to assess the silica scavenging role of lanthanum oxide additions. Structural, microstructural and electrical characterization of these samples confirmed the formation of one apatite type lanthanum silicate-based phase from reaction of silica with lanthanum oxide. The formation of this phase occurred in parallel with a significant enhancement of the grain boundary conductivity of these composite materials. Further interaction between constituents, involving diffusion of La to CGO, and Ce and Gd to the apatite phase, had no significant consequences on the electrical performance of these materials. Overall, lanthanum oxide was shown to remove the siliceous phases from the grain boundaries of CGO.

Se prepararon materiales compuestos basados en óxido de cerio dopado con gadolinio (TGO con adicciones de sílice, con sílice y óxido de lantano y silicato del lantano, mediante procesamiento cerámico convencional con objeto de confirmar el papel secuestrante de sílice de las adicciones. La caracterización estructural, microestructural y eléctrica de las muestras confirmó la formación de una fase tipo apatito basada en silicato de lantano a partir de la reacción de la sílice con el óxido de lantano. La formación de esta fase ocurre en paralelo con un incremento significativo de la conductividad a través del borde de grano de estos materiales. La interacción entre los constituyentes, incluyendo la difusión del La al CGO, y el Ce y el Gd a la fase apatito, no tiene consecuencias significativas sobre el comportamiento eléctrico de estos materiales. Resumiendo, el óxido de lantano es capaz de eliminar las fases silicias del borde de grano del CGO.

Improvements in or relating to method of preparing porous material/synthetic polymer composites

International Nuclear Information System (INIS)

Hills, P.R.; McGahan, D.J.

1976-01-01

A method for preparing a composite material is described comprising polymerising a monoethylenically unsaturated monomer of a mixture of copolymerisable monoethylenically unsaturated monomers in a porous material, excluding a porous natural cellulosic fibre material, the polymerisable liquid being admixed in the porous material with a saturated aliphatic hydrocarbon or a halogen derivative thereof. It is preferable that the polymerisable liquid and the hydrocarbon or halogen derivative are present in the porous material. Impregnation may be carried out by a vacuum technique or by simple immersion. The monomers that may be used are listed, but a mixture of styrene and acrylonitrile is preferred in the proportions 60 : 40 by volume. Polymerisation may be effected by irradiation, preferably with 60 Co γ-radiation. Suitable porous materials include concrete, stone, and fibreboard. If concrete is used the composite material may be used for pressure pipes and other articles normally made of steel. Examples of the application of the process are given. (U.K.)

Molecular simulation strategy for mechanical modeling of amorphous/porous low-dielectric constant materials

NARCIS (Netherlands)

Yuan, C.A.; Sluis, van der O.; Zhang, G.Q.; Ernst, L.J.; Driel, van W.D.; Flower, A.E.; Silfhout, van R.B.R.

2008-01-01

We propose an amorphous/porous molecular connection network generation algorithm for simulating the material stiffness of a low-k material (SiOC:H). Based on a given concentration of the basic building blocks, this algorithm will generate an approximate and large amorphous network. The molecular

Corundum ceramic materials modified with silica nanopowders: structure and mechanical properties

International Nuclear Information System (INIS)

Kostytsyn, M. A.; Muratov, D. S.; Lysov, D. V.; Chuprunov, K. O.; Yudin, A. G.; Leybo, D. V.

2016-01-01

Filtering elements are often used in the metallurgy of rare earth metals. Corundum ceramic is one of the most suitable materials for this purpose. The process of formation and the properties of nanomodified ceramic materials, which are proposed as filtering materials with tunable effective porosity, are described. A silica nanopowder is used as a porosity-increasing agent. Vortex layer apparatus is used for mixing of precursor materials. The obtained results show that nanomodification with the vortex layer apparatus using 0.04 wt. % silica nanopowder as a modifying agent leads to an increase in the compression strength of corundum ceramic by the factor of 1.5. (paper)

Toughening Mechanisms in Silica-Filled Epoxy Nanocomposites

Science.gov (United States)

Patel, Binay S.

Epoxies are widely used as underfill resins throughout the microelectronics industry to mechanically couple and protect various components of flip-chip assemblies. Generally rigid materials largely surround underfill resins. Improving the mechanical and thermal properties of epoxy resins to better match those of their rigid counterparts can help extend the service lifetime of flip-chip assemblies. Recently, researchers have demonstrated that silica nanoparticles are effective toughening agents for lightly-crosslinked epoxies. Improvements in the fracture toughness of silica-filled epoxy nanocomposites have primarily been attributed to two toughening mechanisms: particle debonding with subsequent void growth and matrix shear banding. Various attempts have been made to model the contribution of these toughening mechanisms to the overall fracture energy observed in silica-filled epoxy nanocomposites. However, disparities still exist between experimental and modeled fracture energy results. In this dissertation, the thermal, rheological and mechanical behavior of eight different types of silica-filled epoxy nanocomposites was investigated. Each nanocomposite consisted of up to 10 vol% of silica nanoparticles with particle sizes ranging from 20 nm to 200 nm, with a variety of surface treatments and particle structures. Fractographical analysis was conducted with new experimental approaches in order to accurately identify morphological evidence for each proposed toughening mechanism. Overall, three major insights into the fracture behavior of real world silica-filled epoxy nanocomposites were established. First, microcracking was observed as an essential toughening mechanism in silica-filled epoxy nanocomposites. Microcracking was observed on the surface and subsurface of fractured samples in each type of silica-filled epoxy nanocomposite. The additional toughening contribution of microcracking to overall fracture energy yielded excellent agreement between experimental

A Novel FCC Catalyst Based on a Porous Composite Material Synthesized via an In Situ Technique

Directory of Open Access Journals (Sweden)

Shu-Qin Zheng

2015-11-01

Full Text Available To overcome diffusion limitations and improve transport in microporous zeolite, the materials with a wide-pore structure have been developed. In this paper, composite microspheres with hierarchical porous structure were synthesized by an in situ technique using sepiolite, kaolin and pseudoboehmite as raw material. A novel fluid catalytic cracking (FCC catalyst for maximizing light oil yield was prepared based on the composite materials. The catalyst was characterized by XRD, FT-IR, SEM, nitrogen adsorption-desorption techniques and tested in a bench FCC unit. The results indicated that the catalyst had more meso- and macropores and more acid sites than the reference catalyst, and thus can increase light oil yield by 1.31 %, while exhibiting better gasoline and coke selectivity.

Thermodynamic Damping in Porous Materials with Spherical Cavities

Directory of Open Access Journals (Sweden)

Sofia D. Panteliou

1997-01-01

Full Text Available When a material is subjected to an alternating stress field, there are temperature fluctuations throughout its volume due to the thermoelastic effect. The resulting irreversible heat conduction leads to entropy production that in turn is the cause of thermoelastic damping. An analytical investigation of the entropy produced during a vibration cycle due to the reciprocity of temperature rise and strain yielded the change of the material damping factor as a function of the porosity of the material. A homogeneous, isotropic, elastic bar of cylindrical shape is considered with uniformly distributed spherical cavities under alternating uniform axial stress. The analytical calculation of the dynamic characteristics of the porous structure yielded the damping factor of the bar and the material damping factor. Exsperimental results on porous metals are in good correlation with an analysis.

A Mathematical Model of Repeated Impregnation of Porous Bodies with Solutions of Polymers

Directory of Open Access Journals (Sweden)

I. V. Glebov

2015-01-01

Full Text Available The paper describes basic methods of impregnating porous bodies with solutions of polymers and their use to manufacture prepregs. It also describes the existing methods of manufacturing multilayer prepregs to produce aerospace coating of the spacecraft "Soyuz". It is shown that these prepregs have to meet high requirements for the content of the polymer, as compared with other composite materials, about 35 - 40% of the mass. Methods used for their manufacturing are long-term and non-controllable. The assumption is made that using the vacuum impregnation technology of a woven material will allow to accelerate the manufacturing process of these prepregs and improve their quality.In reviewing the technical literature have been found works on modeling the processes of impregnation, but they are aimed only at studying the speed of the woven material impregnation by various fluids and determining the time of impregnation. There were no models found to define prepreg parameters during the process of multiple impregnations. The aim of this work is to develop the simple mathematical model, which enables us to predict the polymer content of volatile products in the prepreg after each cycle of multiple impregnation of woven material with a solution of the polymer.To consider the vacuum impregnation method are used the prepregs based on silica and silica-nylon stitch-bonding fabric and bakelite varnish LBS-4 containing 50 - 60% of phenol resin and the solvent with minor impurities of pure phenol and water, as an example. To describe the process of vacuum impregnation of the porous work-piece is developed a mathematical description of the process of filling the porous space of the material with a varnish. It is assumed that the varnish components fill the porous space of the material in the same proportion as they are contained in the varnish.It is shown that a single impregnation cannot ensure the content of phenol resin in the prepreg over 32%, which does

Effect of various structure directing agents on the physicochemical properties of the silica aerogels prepared at an ambient pressure

KAUST Repository

Sarawade, Pradip

2013-12-01

We studied the effects of various surfactants on the textural properties (BET surface area, pore size, and pore volume) of the silica aerogels prepared at an ambient pressure. A simple surface modification of silica gel prepared at an ambient pressure through hydrolysis and polycondensation of TEOS as asilica precursor was conducted using various structure directing agents. The treatment was found to induce a significant difference in the porosity of the silica aerogel. Highly porous silica aerogels with bimodal porous structures were prepared by modifying the surface of the silica wet-gel (alcogel) with trimethylchlorosilane (TMCS) in order to preserve its porosity. The samples were analyzed by small-angle X-ray scattering and nitrogen adsorption. In this work, a possible new type of highly porous hydrophobic silica aerogel with a bimodal porous structure is presented. A hydrophilic extremely porous (high surface area and large pore volume) silica aerogel was obtained by heating the as-synthesized hydrophobic silica aerogel at 400°C for 1 h. There was a significant effect of structure directing agent on the textural properties, such as specific surface area, pore size distribution and cumulative pore volume of the silicaaerogels. © 2013 Elsevier B.V. All rights reserved.

Effect of various structure directing agents on the physicochemical properties of the silica aerogels prepared at an ambient pressure

KAUST Repository

Sarawade, Pradip; Shao, Godlistennamwel; Quang, Dangviet; Kim, Heetaik

2013-01-01

We studied the effects of various surfactants on the textural properties (BET surface area, pore size, and pore volume) of the silica aerogels prepared at an ambient pressure. A simple surface modification of silica gel prepared at an ambient pressure through hydrolysis and polycondensation of TEOS as asilica precursor was conducted using various structure directing agents. The treatment was found to induce a significant difference in the porosity of the silica aerogel. Highly porous silica aerogels with bimodal porous structures were prepared by modifying the surface of the silica wet-gel (alcogel) with trimethylchlorosilane (TMCS) in order to preserve its porosity. The samples were analyzed by small-angle X-ray scattering and nitrogen adsorption. In this work, a possible new type of highly porous hydrophobic silica aerogel with a bimodal porous structure is presented. A hydrophilic extremely porous (high surface area and large pore volume) silica aerogel was obtained by heating the as-synthesized hydrophobic silica aerogel at 400°C for 1 h. There was a significant effect of structure directing agent on the textural properties, such as specific surface area, pore size distribution and cumulative pore volume of the silicaaerogels. © 2013 Elsevier B.V. All rights reserved.

An environmentally benign route for the development of compressible, thermally insulating and fire retardant aerogels through self-assembling the silk fibroin biopolymer inside the silica structure - An approach towards 3D printing of aerogels.

Science.gov (United States)

Maleki, Hajar; Montes, Susan; Hayati-Roodbari, Nastaran; Putz, Florian; Huesing, Nicola

2018-06-04

Thanks to the exceptional materials properties of silica aerogels, this fascinating highly porous material has found high performance and real-life applications in various modern industries. However, a requirement for a broadening of these applications is based on the further improvement of their properties especially with regard to mechanical strength and post-synthesis processability with minimum compromise to the other physical properties. Here, we report an entirely novel, simple and aqueous based synthesis approach to prepare mechanically robust aerogel hybrids by co-gelation of silk fibroin (SF) biopolymer, extracted from silkworm cocoons. The synthesis is based on a one-step sequential processes of acid catalysis (physical) crosslinking of the SF biopolymer and simultaneous polycondensation of tetramethyl orthosilicate (TMOS), in the presence of 5-(trimethoxysilyl)pentanoic acid (TMSPA) as a coupling agent and subsequent solvent exchange and supercritical drying. Extensive characterizations by solid-state 1H-NMR, 29Si-NMR, and 2D 1H-29Si heteronuclear correlation (HETCOR) MAS NMR spectroscopy as well as various microscopic techniques (SEM, TEM) and mechanical assessment, confirmed the molecular-level homogeneity of the hybrid nanostructure. The developed silica-SF aerogel hybrids contained an improved set of material properties, such as low density (ρb, average = 0.11 - 0.2 g cm-3), high porosity (~90%), high specific surface area (~ 400-800 m2 g-1), excellent flexibility in compression (up to 80% of strain) with three-order of magnitude improvement in the Young's modulus over that of pristine silica aerogels. In addition, the silica-SF hybrid aerogels are fire retardant and demonstrated excellent thermal insulation performance with thermal conductivities (λ) of (0.033-0.039 Wm-1 K-1). As a further advantage, the formulated hybrid silica-SF aerogel showed an excellent printability in the wet state using a micro-extrusion based 3D printing approach. The

Shear bond strengths of an indirect composite layering material to a tribochemically silica-coated zirconia framework material.

Science.gov (United States)

Iwasaki, Taro; Komine, Futoshi; Fushiki, Ryosuke; Kubochi, Kei; Shinohara, Mitsuyo; Matsumura, Hideo

2016-01-01

This study evaluated shear bond strengths of a layering indirect composite material to a zirconia framework material treated with tribochemical silica coating. Zirconia disks were divided into two groups: ZR-PRE (airborne-particle abrasion) and ZR-PLU (tribochemical silica coating). Indirect composite was bonded to zirconia treated with one of the following primers: Clearfil Ceramic Primer (CCP), Clearfil Mega Bond Primer with Clearfil Porcelain Bond Activator (MGP+Act), ESPE-Sil (SIL), Estenia Opaque Primer, MR. Bond, Super-Bond PZ Primer Liquid A with Liquid B (PZA+PZB), and Super-Bond PZ Primer Liquid B (PZB), or no treatment. Shear bond testing was performed at 0 and 20,000 thermocycles. Post-thermocycling shear bond strengths of ZR-PLU were higher than those of ZR-PRE in CCP, MGP+Act, SIL, PZA+PZB, and PZB groups. Application of silane yielded better durable bond strengths of a layering indirect composite material to a tribochemically silica-coated zirconia framework material.

Novel Fe-Pd/SiO2 catalytic materials for degradation of chlorinated organic compounds in water

Science.gov (United States)

Novel reactive materials for catalytic degradation of chlorinated organic compounds in water at ambient conditions have been prepared on the basis of silica-supported Pd-Fe nanoparticles. Nanoscale Fe-Pd particles were synthesized inside porous silica supports using (NH4

Thiol-functionalized silica colloids, grains, and membranes for irreversible adsorption of metal(oxide) nanoparticles

NARCIS (Netherlands)

Claesson, E.M.; Philipse, A.P.

2007-01-01

Thiol-functionalization is described for silica surfaces from diverging origin, including commercial silica nanoparticles and St¨ober silica as well as silica structures provided by porous glasses and novel polymer-templated silica membranes. The functionalization allows in all cases for the

Characteristics, distribution, origin, and significance of opaline silica observed by the Spirit rover in Gusev crater, Mars

Science.gov (United States)

Ruff, S.W.; Farmer, J.D.; Calvin, W.M.; Herkenhoff, K. E.; Johnson, J. R.; Morris, R.V.; Rice, M.S.; Arvidson, R. E.; Bell, J.F.; Christensen, P.R.; Squyres, S. W.

2011-01-01

The presence of outcrops and soil (regolith) rich in opaline silica (???65-92 wt % SiO2) in association with volcanic materials adjacent to the "Home Plate" feature in Gusev crater is evidence for hydrothermal conditions. The Spirit rover has supplied a diverse set of observations that are used here to better understand the formation of silica and the activity, abundance, and fate of water in the first hydrothermal system to be explored in situ on Mars. We apply spectral, chemical, morphological, textural, and stratigraphic observations to assess whether the silica was produced by acid sulfate leaching of precursor rocks, by precipitation from silica-rich solutions, or by some combination. The apparent lack of S enrichment and the relatively low oxidation state of the Home Plate silica-rich materials appear inconsistent with the originally proposed Hawaiian analog for fumarolic acid sulfate leaching. The stratiform distribution of the silica-rich outcrops and their porous and brecciated microtextures are consistent with sinter produced by silica precipitation. There is no evidence for crystalline quartz phases among the silica occurrences, an indication of the lack of diagenetic maturation following the production of the amorphous opaline phase. Copyright ?? 2011 by the American Geophysical Union.

The structural coloration of textile materials using self-assembled silica nanoparticles.

Science.gov (United States)

Gao, Weihong; Rigout, Muriel; Owens, Huw

2017-01-01

The work presented investigates how to produce structural colours on textile materials by applying a surface coating of silica nanoparticles (SNPs). Uniform SNPs with particle diameters in a controlled micron size range (207-350 nm) were synthesized using a Stöber-based solvent varying (SV) method which has been reported previously. Photonic crystals (PCs) were formed on the surface of a piece of textile fabric through a process of natural sedimentation self-assembly of the colloidal suspension containing uniform SNPs. Due to the uniformity and a particular diameter range of the prepared SNPs, structural colours were observed from the fabric surface due to the Bragg diffraction of white light with the ordered structure of the silica PCs. By varying the mean particle diameter, a wide range of spectral colours from red to blue were obtained. The comparison of structural colours on fabrics and on glasses suggests that a smooth substrate is critical when producing materials with high colour intensity and spatial uniformity. This work suggested a promising approach to colour textile materials without the need for traditional dyes and/or pigments. Graphical abstract.

Sound Transmission Through Multi-Panel Structures Lined with Elastic Porous Materials

Science.gov (United States)

Bolton, J. S.; Shiau, N.-M.; Kang, Y. J.

1996-04-01

Theory and measurements related to sound transmission through double panels lined with elastic porous media are presented. The information has application to the design of noise control barriers and to the optimization of aircraft fuselage transmission loss, for example. The major difference between the work described here and earlier research in this field relates to the treatment of the porous material that is used to line the cavity between the two panels of the double panel structure. Here we have used the porous material theory proposed by Biot since it takes explicit account of all the wave types known to propagate in elastic porous materials. As a result, it is possible to use the theory presented here to calculate the transmission loss of lined double panels at arbitrary angles of incidence; results calculated over a range of incidence angles may then be combined to yield the random incidence transmission loss. In this paper, the equations governing wave propagation in an elastic porous material are first considered briefly and then the general forms for the stresses and displacements within the porous material are given. Those solutions are expressed in terms of a number of constants that can be determined by application of appropriate boundary conditions. The boundary conditions required to model double panels having linings that are either directly attached to the facing panels or separated?!from them by air gaps are presented and discussed. Measurements of the random incidence transmission loss of aluminium double-panel structures lined with polyurethane foam are presented and have been found to be in good agreement with theoretical predictions. Both the theoretical predictions and the measured results have shown that the method by which an elastic porous lining material is attached to the facing panels can have a profound influence on the transmission loss of the panel system. It has been found, for example, that treatments in which the lining material

Supramolecular structures on silica surfaces and their adsorptive properties.

Science.gov (United States)

Belyakov, Vladimir N; Belyakova, Lyudmila A; Varvarin, Anatoly M; Khora, Olexandra V; Vasilyuk, Sergei L; Kazdobin, Konstantin A; Maltseva, Tetyana V; Kotvitskyy, Alexey G; Danil de Namor, Angela F

2005-05-01

The study of adsorptive and chemical immobilization of beta-cyclodextrin on a surface of hydroxylated silicas with various porous structure is described. Using IR spectroscopy, thermal gravimetrical analysis with a programmed heating, and chemical analysis of the silica surface, it is shown that the process of adsorption-desorption of beta-cyclodextrin depends on the porous structure of the silica. The reaction of esterification was used for chemical grafting of beta-cyclodextrin on the surface of hydroxylated silicas. Hydrolytic stability of silicas chemically modified by beta-cyclodextrin apparently is explained by simultaneous formation of chemical and hydrogen bonds between surface silanol groups and hydroxyl groups of beta-cyclodextrin. The uptake of the cations Cu(II), Cd(II), and Pb(II) and the anions Cr(VI) and As(V) by silicas modified with beta-cyclodextrin is investigated as a function of equilibrium ion concentrations. The increase of ion uptake and selectivity of ion extraction in comparison with starting silicas is established. It is due to the formation of surface inclusion complexes of the "host-guest" type in which one molecule of beta-cyclodextrin interacts simultaneously with several ions.

Production of a calcium silicate cement material from alginate impression material.

Science.gov (United States)

Washizawa, Norimasa; Narusawa, Hideaki; Tamaki, Yukimichi; Miyazaki, Takashi

2012-01-01

The purpose of this study was to synthesize biomaterials from daily dental waste. Since alginate impression material contains silica and calcium salts, we aimed to synthesize calcium silicate cement from alginate impression material. Gypsum-based investment material was also investigated as control. X-ray diffraction analyses revealed that although firing the set gypsum-based and modified investment materials at 1,200°C produced calcium silicates, firing the set alginate impression material did not. However, we succeeded when firing the set blend of pre-fired set alginate impression material and gypsum at 1,200°C. SEM observations of the powder revealed that the featured porous structures of diatomite as an alginate impression material component appeared useful for synthesizing calcium silicates. Experimentally fabricated calcium silicate powder was successfully mixed with phosphoric acid solution and set by depositing the brushite. Therefore, we conclude that the production of calcium silicate cement material is possible from waste alginate impression material.

High-Throughput Characterization of Porous Materials Using Graphics Processing Units

Energy Technology Data Exchange (ETDEWEB)

Kim, Jihan; Martin, Richard L.; Rübel, Oliver; Haranczyk, Maciej; Smit, Berend

2012-05-08

We have developed a high-throughput graphics processing units (GPU) code that can characterize a large database of crystalline porous materials. In our algorithm, the GPU is utilized to accelerate energy grid calculations where the grid values represent interactions (i.e., Lennard-Jones + Coulomb potentials) between gas molecules (i.e., CH$_{4}$ and CO$_{2}$) and material's framework atoms. Using a parallel flood fill CPU algorithm, inaccessible regions inside the framework structures are identified and blocked based on their energy profiles. Finally, we compute the Henry coefficients and heats of adsorption through statistical Widom insertion Monte Carlo moves in the domain restricted to the accessible space. The code offers significant speedup over a single core CPU code and allows us to characterize a set of porous materials at least an order of magnitude larger than ones considered in earlier studies. For structures selected from such a prescreening algorithm, full adsorption isotherms can be calculated by conducting multiple grand canonical Monte Carlo simulations concurrently within the GPU.

Morphological characterization of shocked porous material

International Nuclear Information System (INIS)

Xu Aiguo; Zhang Guangcai; Pan, X F; Zhang Ping; Zhu Jianshi

2009-01-01

Morphological measures are introduced to probe the complex procedure of shock wave reaction on porous material. They characterize the geometry and the topology of the pixelized map of a state variable like temperature. The relevance to thermodynamical properties of a material is revealed and various experimental conditions are simulated. Numerical results indicate that the shock wave reaction results in a complicated sequence of compressions and rarefactions in porous material. The increasing rate of the total fractional white area A roughly gives the velocity D of a compressive-wave series. When a velocity D is mentioned, the corresponding threshold contour level of the state variable, such as temperature, should also be stated. When the threshold contour level increases, D becomes smaller. The area A increases parabolically with time t during the initial period. The A(t) curve goes back to being linear in the following three cases: (i) when the porosity δ approaches 1, (ii) when the initial shock becomes stronger and (iii) when the contour level approaches the minimum value of the state variable. The area with high temperature may continue to increase even after the early compressive waves have arrived at the downstream free surface and some rarefactive waves have come back into the target body. In the case of energetic material needing a higher temperature for initiation, a higher porosity is preferred and the material may be initiated after the precursory compressive waves have scanned the entire target body. In some cases we need scattered hot spots, but in others we need connected ones. One may desire the fabrication of a porous body and choose the appropriate shock strength according to what is needed. With the Minkowski measures, the dependence on experimental conditions is reflected simply by a few coefficients. They may be used as order parameters to classify the maps of physical variables in a similar way to thermodynamic phase transitions.

Strength degradation and failure limits of dense and porous ceramic membrane materials

DEFF Research Database (Denmark)

Pećanac, G.; Foghmoes, Søren Preben Vagn; Lipińska-Chwałek, M.

2013-01-01

Thin dense membrane layers, mechanically supported by porous substrates, are considered as the most efficient designs for oxygen supply units used in Oxy-fuel processes and membrane reactors. Based on the favorable permeation properties and chemical stability, several materials were suggested...

Investigating the binding properties of porous drug delivery systems using nuclear sensors (radiotracers) and positron annihilation lifetime spectroscopy--predicting conditions for optimum performance.

Science.gov (United States)

Mume, Eskender; Lynch, Daniel E; Uedono, Akira; Smith, Suzanne V

2011-06-21

Understanding how the size, charge and number of available pores in porous material influences the uptake and release properties is important for optimising their design and ultimately their application. Unfortunately there are no standard methods for screening porous materials in solution and therefore formulations must be developed for each encapsulated agent. This study investigates the potential of a library of radiotracers (nuclear sensors) for assessing the binding properties of hollow silica shell materials. Uptake and release of Cu(2+) and Co(2+) and their respective complexes with polyazacarboxylate macrocycles (dota and teta) and a series of hexa aza cages (diamsar, sarar and bis-(p-aminobenzyl)-diamsar) from the hollow silica shells was monitored using their radioisotopic analogues. Coordination chemistry of the metal (M) species, subtle alterations in the molecular architecture of ligands (Ligand) and their resultant complexes (M-Ligand) were found to significantly influence their uptake over pH 3 to 9 at room temperature. Positively charged species were selectively and rapidly (within 10 min) absorbed at pH 7 to 9. Negatively charged species were preferentially absorbed at low pH (3 to 5). Rates of release varied for each nuclear sensor, and time to establish equilibrium varied from minutes to days. The subtle changes in design of the nuclear sensors proved to be a valuable tool for determining the binding properties of porous materials. The data support the development of a library of nuclear sensors for screening porous materials for use in optimising the design of porous materials and the potential of nuclear sensors for high through-put screening of materials.

Silica nanoparticles produced by DC arc plasma from a solid raw materials

Science.gov (United States)

Kosmachev, P. V.; Vlasov, V. A.; Skripnikova, N. K.

2017-05-01

Plasma synthesis of SiO2 nanoparticles in experimental atmospheric pressure plasma reactor on the basis of DC arc plasma generator was presented in this paper. Solid high-silica raw materials such as diatomite from Kamyshlovskoye deposit in Russia, quartzite from Chupinskoye deposit in Russia and milled window glass were used. The obtained nanoparticles were characterized based on their morphology, chemical composition and size distribution. Scanning electron microscopy, laser diffractometry, nitrogen absorption (Brunauer-Emmett-Teller method), X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy were used to characterize the synthesized products. The obtained silica nanoparticles are agglomerated, have spherical shape and primary diameters between 10-300 nm. All samples of synthesized nanopowders were compared with commercial nanopowders.

Amperometric xanthine biosensors using glassy carbon electrodes modified with electrografted porous silica nanomaterials loaded with xanthine oxidase

International Nuclear Information System (INIS)

Saadaoui, Maroua; Sánchez, Alfredo; Díez, Paula; Raouafi, Noureddine; Pingarrón, José M.; Villalonga, Reynaldo

2016-01-01

Glassy carbon electrodes were modified with silica materials such as silica nanoparticles, mesoporous silica nanoparticles and mesoporous silica thin films with the aim to introduce scaffolds suitable for the immobilization of enzymes. Xanthine oxidase was selected as a model enzyme, and xanthine as the target analyte. A comparison of the modified electrodes showed the biosensor prepared with mesoporous silica nanoparticles to perform best. By using the respective biosensor, xanthine can be amperometrically determined (via measurement of enzymatically formed hydrogen peroxide) at a working voltage of 0.7 V (vs. Ag/AgCl) with a 0.28 μM detection limit. The biosensor was evaluated in terms of potential interferences, reproducibility and stability, and applied to the determination of fish freshness via sensing of xanthine. (author)

Synthesis and structural evaluation of freeze-cast porous alumina

Energy Technology Data Exchange (ETDEWEB)

Souza, Douglas F., E-mail: souzadf@outlook.com [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Nunes, Eduardo H.M., E-mail: eduardohmn@gmail.com [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Pimenta, Daiana S.; Vasconcelos, Daniela C.L. [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil); Nascimento, Jailton F.; Grava, Wilson [Petrobras/CENPES, Avenida Horácio Macedo 950, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ CEP:21941-915 (Brazil); Houmard, Manuel [Department of Materials Engineering and Civil Construction, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 1, sala 3304 (Brazil); Vasconcelos, Wander L., E-mail: wlv@demet.ufmg.br [Department of Metallurgical and Materials Engineering, Federal University of Minas Gerais — UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG CEP: 31270-901, Escola de Engenharia, bloco 2, sala 2230 (Brazil)

2014-10-15

In this work we fabricated alumina samples by the freeze-casting technique using tert-butanol as the solvent. The prepared materials were examined by scanning electron microscopy and X-ray microtomography. Next, they were coated with sol–gel silica films by dip-coating. Permeability tests were carried out in order to assess the permeation behavior of the materials processed in this study. We observed that the sintering time and alumina loading showed a remarkable effect on both the structural properties and flexural strength of the freeze-cast samples. Nitrogen adsorption tests revealed that the silica prepared in this study exhibited a microporous structure. It was observed that the presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance by about one order of magnitude. Because of the similar kinetic diameters of nitrogen and carbon dioxide, the CO{sub 2}/N{sub 2} system showed a separation efficiency that was lower than that observed for the He/CO{sub 2} and He/N{sub 2} systems. We noticed that increasing the feed pressure improved the separation capacity of the obtained materials. - Highlights: • Porous alumina samples obtained by the freeze-casting technique • Microporous silica coating prepared by a simple sol–gel dip-coating methodology • Samples examined by SEM, μ-CT, and nitrogen sorption tests • Mechanical tests were carried out in the freeze-cast samples. • The presence of silica coatings on the alumina surface decreased the CO{sub 2} permeance.

Polyphosphazine-based polymer materials

Science.gov (United States)

Fox, Robert V.; Avci, Recep; Groenewold, Gary S.

2010-05-25

Methods of removing contaminant matter from porous materials include applying a polymer material to a contaminated surface, irradiating the contaminated surface to cause redistribution of contaminant matter, and removing at least a portion of the polymer material from the surface. Systems for decontaminating a contaminated structure comprising porous material include a radiation device configured to emit electromagnetic radiation toward a surface of a structure, and at least one spray device configured to apply a capture material onto the surface of the structure. Polymer materials that can be used in such methods and systems include polyphosphazine-based polymer materials having polyphosphazine backbone segments and side chain groups that include selected functional groups. The selected functional groups may include iminos, oximes, carboxylates, sulfonates, .beta.-diketones, phosphine sulfides, phosphates, phosphites, phosphonates, phosphinates, phosphine oxides, monothio phosphinic acids, and dithio phosphinic acids.

Positron and positronium annihilation in silica-based thin films studied by a pulsed positron beam

International Nuclear Information System (INIS)

Suzuki, R.; Ohdaira, T.; Kobayashi, Y.; Ito, K.; Shioya, Y.; Ishimaru, T.

2003-01-01

Positron and positronium annihilation in silica-based thin films has been investigated by means of measurement techniques with a monoenergetic pulsed positron beam. The age-momentum correlation study revealed that positron annihilation in thermally grown SiO 2 is basically the same as that in bulk amorphous SiO 2 while o-Ps in the PECVD grown SiCOH film predominantly annihilate with electrons of C and H at the microvoid surfaces. We also discuss time-dependent three-gamma annihilation in porous low-k films by two-dimensional positron annihilation lifetime spectroscopy

Thermal conductivity of highly porous mullite material

International Nuclear Information System (INIS)

Barea, Rafael; Osendi, Maria Isabel; Ferreira, Jose M.F.; Miranzo, Pilar

2005-01-01

The thermal diffusivity of highly porous mullite materials (35-60 vol.% porosity) has been measured up to 1000 deg C by the laser flash method. These materials were fabricated by a direct consolidation method based on the swelling properties of starch granules in concentrated aqueous suspensions and showed mainly spherical shaped pores of about 30 μm in diameter. From the point of view of heat conduction, they behave as a bi-phase material of voids dispersed in the continuous mullite matrix. The temperature dependence of thermal conductivity for the different porosities was modeled by a simple equation that considers the contribution to heat conduction of the mullite matrix and the gas inside the pores, as well as the radiation. The thermal conductivity of the matrix was taken from the measurements done in a dense mullite while the conductivity in the voids was assumed to be that of the testing atmosphere

Highly Porous Silicon Embedded in a Ceramic Matrix: A Stable High-Capacity Electrode for Li-Ion Batteries.

Science.gov (United States)

Vrankovic, Dragoljub; Graczyk-Zajac, Magdalena; Kalcher, Constanze; Rohrer, Jochen; Becker, Malin; Stabler, Christina; Trykowski, Grzegorz; Albe, Karsten; Riedel, Ralf

2017-11-28

We demonstrate a cost-effective synthesis route that provides Si-based anode materials with capacities between 2000 and 3000 mAh·g Si -1 (400 and 600 mAh·g composite -1 ), Coulombic efficiencies above 99.5%, and almost 100% capacity retention over more than 100 cycles. The Si-based composite is prepared from highly porous silicon (obtained by reduction of silica) by encapsulation in an organic carbon and polymer-derived silicon oxycarbide (C/SiOC) matrix. Molecular dynamics simulations show that the highly porous silicon morphology delivers free volume for the accommodation of strain leading to no macroscopic changes during initial Li-Si alloying. In addition, a carbon layer provides an electrical contact, whereas the SiOC matrix significantly diminishes the interface between the electrolyte and the electrode material and thus suppresses the formation of a solid-electrolyte interphase on Si. Electrochemical tests of the micrometer-sized, glass-fiber-derived silicon demonstrate the up-scaling potential of the presented approach.

The solid-liquid extraction separation of lithium isotopes by porous composite materials doped with ionic liquids and 2,2'-binaphthyldiyl-17-crown-5

International Nuclear Information System (INIS)

Xiao-Li Sun; Ling Gu; Dan Qiu; Dong-Hong Ren; Zaijun Li; Zhi-Guo Gu; Jiangnan University, Wuxi

2015-01-01

A green and efficient solid-liquid extraction method of lithium isotopes separation by porous composite materials doped with imidazolium ionic liquids and 2,2'-binaphthyldiyl-17-crown-5 has been reported in this paper. The composite materials of mesoporous silica and impregnated resin were synthesized by sol-gel and direct impregnation process, respectively. Various extraction parameters such as the concentration of lithium salt, anion of lithium salt, initial pH, time and temperature were investigated. Under optimized conditions, the maximum single-stage separation factor of 6 Li/ 7 Li was 1.048 ± 0.002, the maximum extraction efficiency was 15.86 %. The sorbents can be regenerated easily with HCl solution and reused repeatedly. (author)

Investigations on the homogeneity of silica glass and on the order of X-amorphous silica by luminescence measurements

International Nuclear Information System (INIS)

Boden, G.

1982-08-01

Silica glasses melted from crystalline SiO 2 were exposed to ionizing radiation. At room temperature the spatial intensity distribution of the emitted luminescent radiation has been recorded by means of photographic or autoradiographic materials. Thereby schlieren and inhomogeneities are made visible and information is obtained on the melting process of the crystalline SiO 2 . Synthetic fused silica made from SiCl 4 shows no luminescent radiation. Depending on the penetration depth of the ionizing radiation the bulk or the surface of the sample can be studied. The decay curves of the integral luminescence intensity yield data on inhomogeneities in the silica glass leading to conclusions on order state and structure. The luminescence intensity and its half-life are a measure for the inhomogeneity of the silica glass and the existence of so-called 'preordered states'. This connection between luminescence intensity and the order state is found also with other X-amorphous SiO 2 modifications: silica gel, precipitated silicic acids, porous SiO 2 glasses, aerosil, thin SiO 2 layers, mechanically activated quartz: whereas no luminescence phenomena occur in disordered nearly ideally amorphous SiO 2 species, the luminescence increases with increasing order degree of the SiO 2 network and attains a high intensity in the case of the crystalline SiO 2 modifications quartz and cristobalite

Effects of confinement in meso-porous silica and carbon nano-structures; Etude des effets de confinement dans la silice mesoporeuse et dans certaines nanostructures carbonees

Energy Technology Data Exchange (ETDEWEB)

Leon, V

2006-07-15

Physico-chemical properties of materials can be strongly modified by confinement because of the quantum effects that appear at such small length scales and also because of the effects of the confinement itself. The aim of this thesis is to show that both the nature of the confining material and the size of the pores and cavities have a strong impact on the confined material. We first show the effect of the pore size of the host meso-porous silica on the temperature of the solid-solid phase transition of silver selenide, a semiconducting material with enhanced magnetoresistive properties under non-stoichiometric conditions. Narrowing the pores from 20 nm to 2 nm raises the phase transition temperature from 139 C to 146 C. This result can be explained by considering the interaction between the confining and confined materials as a driving force. The effects of confinement are also studied in the case of hydrogen and deuterium inside cavities of organized carbon nano-structures. The effects that appear in the adsorption/desorption cycles are much stronger with carbon nano-horns as the host material than with C60 pea-pods and single-walled carbon nano-tubes. (author)

SEM and Raman studies of CNT films on porous Si

Science.gov (United States)

Belka, R.; Keczkowska, J.; Suchańska, M.; Firek, P.; Wronka, H.; Kozłowski, M.; Radomska, J.; Czerwosz, E.; Craciunoiu, F.

2017-08-01

Carbon nanotube (CNT) films deposited on different porous silica substrates were studied by Scanning Electron Microscopy (SEM) and Raman Spectroscopy (RS). The films samples were prepared by a two-step method consisting of PVD and CVD processes. In the first step the nanocomposite Ni-C film was obtained by evaporation in dynamic vacuum from two separated sources of fullerenes and nickel acetate. Those films were deposited on porous silica and DLC/porous silica substrates. Analysis of SEM imaging showed that the obtained film are composed of carbon nanotubes, the distribution, size and quality of which depend on the type of substrate. The CNT films were studied by RS method to determine the influence of the substrate type on disordering of carbonaceous structure and quality of CNT in deposited films.

SCDAP/RELAP5 Modeling of Movement of Melted Material Through Porous Debris in Lower Head

International Nuclear Information System (INIS)

Siefken, L. J.

1998-01-01

Designs are described for implementing models for calculating the movement of melted material through the interstices in a matrix of porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head during a severe accident in a Light Water Reactor. Currently, the COUPLE model has no capability to model the movement of material that melts within a matrix of porous material. The COUPLE model also does not have the capability to model the movement of liquefied core plate material that slumps onto a porous debris bed in the lower head. In order to advance beyond the assumption the liquefied material always remains stationary, designs are developed for calculations of the movement of liquefied material through the interstices in a matrix of porous material. Correlations are identified for calculating the permeability of the porous debris and for calculating the rate of flow of liquefied material through the interstices in the debris bed. Correlations are also identified for calculating the relocation of solid debris that has a large amount of cavities due to the flowing away of melted material. Equations are defined for calculating the effect on the temperature distribution in the debris bed of heat transported by moving material and for changes in effective thermal conductivity and heat capacity due to the movement of material. The implementation of these models is expected to improve the calculation of the material distribution and temperature distribution of debris in the lower head for cases in which the debris is porous and liquefied material is present within the porous debris

Numerical investigation of porous materials composites reinforced with natural fibers

Science.gov (United States)

Chikhi, M.; Metidji, N.; Mokhtari, F.; Merzouk, N. k.

2018-05-01

The present article tends to predict the effective thermal properties of porous biocomposites materials. The composites matrix consists on porous materials namely gypsum and the reinforcement is a natural fiber as date palm fibers. The numerical study is done using Comsol software resolving the heat transfer equation. The results are fitted with theoretical model and experimental results. The results of this study indicate that the porosity has an effect on the Effective thermal conductivity biocompoites.

Fluorescent Functionalized Mesoporous Silica for Radioactive Material Extraction

International Nuclear Information System (INIS)

Li, Juan; Zhu, Kake; Shang, Jianying; Wang, Donghai; Nie, Zimin; Guo, Ruisong; Liu, Chongxuan; Wang, Zheming; Li, Xiaolin; Liu, Jun

2012-01-01

Mesoporous silica with covalently bound salicylic acid molecules incorporated in the structure was synthesized with a one-pot, co-condensation reaction at room temperature. The as-synthesized material has a large surface area, uniform particle size, and an ordered pore structure as determined by characterization with transmission electron microscopy, thermal gravimetric analysis, and infrared spectra, etc. Using the strong fluorescence and metal coordination capability of salicylic acid, functionalized mesoporous silica (FMS) was developed to track and extract radionuclide contaminants, such as uranyl (U(VI)) ions encountered in subsurface environments. Adsorption measurements showed a strong affinity of the FMS toward U(VI) with a Kd value of 105 mL/g, which is four orders of magnitude higher than the adsorption of U(VI) onto most of the sediments in natural environments. The new materials have a potential for synergistic environmental monitoring and remediation of the radionuclide U(VI) from contaminated subsurface environments.

Poly(NIPAM-co-MPS-grafted multimodal porous silica nanoparticles as reverse thermoresponsive drug delivery system

Directory of Open Access Journals (Sweden)

Sushilkumar A. Jadhav

2017-05-01

Full Text Available Hybrid drug delivery systems (DDS have been prepared by grafting poly(NIPAM-co-MPS chains on multimodal porous silica nanoparticles having an inner mesoporous structure and an outer thin layer of micropores. The hybrid thermoresponsive DDS were fully characterized and loaded with a model drug. The in vitro drug release tests are carried out at below and above the lower critical solution temperature (LCST of the copolymer. The results have revealed that due to the presence of small diameter (~1.3 nm micropores at the periphery of the particles, the collapsed globules of the thermoresponsive copolymer above its LCST hinders the complete release of the drug which resulted in a reverse thermoresponsive drug release profile by the hybrid DDS.

Porous magnesium-based scaffolds for tissue engineering

International Nuclear Information System (INIS)

Yazdimamaghani, Mostafa; Razavi, Mehdi; Vashaee, Daryoosh; Moharamzadeh, Keyvan; Boccaccini, Aldo R.; Tayebi, Lobat

2017-01-01

Significant amount of research efforts have been dedicated to the development of scaffolds for tissue engineering. Although at present most of the studies are focused on non-load bearing scaffolds, many scaffolds have also been investigated for hard tissue repair. In particular, metallic scaffolds are being studied for hard tissue engineering due to their suitable mechanical properties. Several biocompatible metallic materials such as stainless steels, cobalt alloys, titanium alloys, tantalum, nitinol and magnesium alloys have been commonly employed as implants in orthopedic and dental treatments. They are often used to replace and regenerate the damaged bones or to provide structural support for healing bone defects. Among the common metallic biomaterials, magnesium (Mg) and a number of its alloys are effective because of their mechanical properties close to those of human bone, their natural ionic content that may have important functional roles in physiological systems, and their in vivo biodegradation characteristics in body fluids. Due to such collective properties, Mg based alloys can be employed as biocompatible, bioactive, and biodegradable scaffolds for load-bearing applications. Recently, porous Mg and Mg alloys have been specially suggested as metallic scaffolds for bone tissue engineering. With further optimization of the fabrication techniques, porous Mg is expected to make a promising hard substitute scaffold. The present review covers research conducted on the fabrication techniques, surface modifications, properties and biological characteristics of Mg alloys based scaffolds. Furthermore, the potential applications, challenges and future trends of such degradable metallic scaffolds are discussed in detail. - Highlights: • A porous 3D material provides the required pathways for cells to grow, proliferate, and differentiate • Porous magnesium and Mg alloys could be used as load-bearing scaffolds • Porous magnesium and Mg alloys are good

Porous magnesium-based scaffolds for tissue engineering

Energy Technology Data Exchange (ETDEWEB)

Yazdimamaghani, Mostafa [School of Chemical Engineering, Oklahoma State University, Stillwater, OK 74078 (United States); Razavi, Mehdi [Department of Radiology, School of Medicine, Stanford University, Palo Alto, CA 94304 (United States); Vashaee, Daryoosh [Electrical and Computer Engineering Department, North Carolina State University, Raleigh, NC 27606 (United States); Moharamzadeh, Keyvan [School of Clinical Dentistry, University of Sheffield, Claremont Crescent, Sheffield (United Kingdom); Marquette University School of Dentistry, Milwaukee, WI 53233 (United States); Boccaccini, Aldo R. [Institute of Biomaterials, University of Erlangen-Nuremberg, Cauerstrasse 6, 91058 Erlangen (Germany); Tayebi, Lobat, E-mail: lobat.tayebi@marquette.edu [Marquette University School of Dentistry, Milwaukee, WI 53233 (United States)

2017-02-01

Significant amount of research efforts have been dedicated to the development of scaffolds for tissue engineering. Although at present most of the studies are focused on non-load bearing scaffolds, many scaffolds have also been investigated for hard tissue repair. In particular, metallic scaffolds are being studied for hard tissue engineering due to their suitable mechanical properties. Several biocompatible metallic materials such as stainless steels, cobalt alloys, titanium alloys, tantalum, nitinol and magnesium alloys have been commonly employed as implants in orthopedic and dental treatments. They are often used to replace and regenerate the damaged bones or to provide structural support for healing bone defects. Among the common metallic biomaterials, magnesium (Mg) and a number of its alloys are effective because of their mechanical properties close to those of human bone, their natural ionic content that may have important functional roles in physiological systems, and their in vivo biodegradation characteristics in body fluids. Due to such collective properties, Mg based alloys can be employed as biocompatible, bioactive, and biodegradable scaffolds for load-bearing applications. Recently, porous Mg and Mg alloys have been specially suggested as metallic scaffolds for bone tissue engineering. With further optimization of the fabrication techniques, porous Mg is expected to make a promising hard substitute scaffold. The present review covers research conducted on the fabrication techniques, surface modifications, properties and biological characteristics of Mg alloys based scaffolds. Furthermore, the potential applications, challenges and future trends of such degradable metallic scaffolds are discussed in detail. - Highlights: • A porous 3D material provides the required pathways for cells to grow, proliferate, and differentiate • Porous magnesium and Mg alloys could be used as load-bearing scaffolds • Porous magnesium and Mg alloys are good

Metal-binding silica materials for wastewater cleanup

Energy Technology Data Exchange (ETDEWEB)

Kroh, F.O. [TPL, Inc., Albuquerque, NM (United States)

1997-10-01

In this Phase I Small Business Innovation Research program, TPL, Inc. is developing two series of high-efficiency covalently modified silica materials for removing heavy metal ions from wastewater. These materials have metal ion capacities greatly exceeding those of commercial ion exchange resins. One series, containing thiol groups, has high capacity for {open_quotes}soft{close_quotes} heavy metal ions such as Hg, Pb, Ag, and Cd; the other, containing quaternary ammonium groups, has high capacity for anionic metal ions such as pertechnetate, arsenate, selenite, and chromate. These materials have high selectivity for the contaminant metals and will function well in harsh systems that inactivate other systems.

A new equation of state for porous materials with ultra-low densities

CERN Document Server

Geng Hua Yun; Wu Qiang

2002-01-01

A thermodynamic equation of state is derived which is appropriate for investigating the thermodynamic variations along isobaric paths to predict compression behaviours of porous materials. This equation-of-state model is tested on porous iron, copper, lead and tungsten with different initial densities. The calculated Hugoniots are in good agreement with the corresponding experimental data published previously. This shows that this model can satisfactorily predict the Hugoniots of porous materials with wide porosity and pressure ranges.

Vibro-acoustics of porous materials - waveguide modeling approach

DEFF Research Database (Denmark)

Darula, Radoslav; Sorokin, Sergey V.

2016-01-01

The porous material is considered as a compound multi-layered waveguide (i.e. a fluid layer surrounded with elastic layers) with traction free boundary conditions. The attenuation of the vibro-acoustic waves in such a material is assessed. This approach is compared with a conventional Biot's mode...

Nanostructural Organization of Naturally Occurring Composites—Part I: Silica-Collagen-Based Biocomposites

Directory of Open Access Journals (Sweden)

Hermann Ehrlich

2008-01-01

Full Text Available Glass sponges, as examples of natural biocomposites, inspire investigations aiming at both a better understanding of biomineralization mechanisms and novel developments in the synthesis of nanostructured biomimetic materials. Different representatives of marine glass sponges of the class Hexactinellida (Porifera are remarkable because of their highly flexible basal anchoring spicules. Therefore, investigations of the biochemical compositions and the micro- and nanostructure of the spicules as examples of naturally structured biomaterials are of fundamental scientific relevance. Here we present a detailed study of the structural and biochemical properties of the basal spicules of the marine glass sponge Monorhaphis chuni. The results show unambiguously that in this glass sponge a fibrillar protein of collagenous nature is the template for the silica mineralization in all silica-containing structural layers of the spicule. The structural similarity and homology of collagens derived from M. chuni spicules to other sponge and vertebrate collagens have been confirmed by us using FTIR, amino acid analysis and mass spectrometric sequencing techniques. We suggest that nanomorphology of silica formed on proteinous structures could be determined as an example of biodirected epitaxial nanodistribution of amorphous silica phase on oriented fibrillar collagen templates. Finally, the present work includes a discussion relating to silica-collagen-based hybrid materials for practical applications as biomaterials.

Anticancer Applications of Nanostructured Silica-Based Materials Functionalized with Titanocene Derivatives: Induction of Cell Death Mechanism through TNFR1 Modulation

Directory of Open Access Journals (Sweden)

Santiago Gómez-Ruiz

2018-01-01

Full Text Available A series of cytotoxic titanocene derivatives have been immobilized onto nanostructured silica-based materials using two different synthetic routes, namely, (i a simple grafting protocol via protonolysis of the Ti–Cl bond; and (ii a tethering method by elimination of ethanol using triethoxysilyl moieties of thiolato ligands attached to titanium. The resulting nanostructured systems have been characterized by different techniques such as XRD, XRF, DR-UV, BET, SEM, and TEM, observing the incorporation of the titanocene derivatives onto the nanostructured silica and slight changes in the textural features of the materials after functionalization with the metallodrugs. A complete biological study has been carried out using the synthesized materials exhibiting moderate cytotoxicity in vitro against three human hepatic carcinoma (HepG2, SK-Hep-1, Hep3B and three human colon carcinomas (DLD-1, HT-29, COLO320 and very low cytotoxicity against normal cell lines. In addition, the cells’ metabolic activity was modified by a 24-h exposure in a dose-dependent manner. Despite not having a significant effect on TNFα or the proinflammatory interleukin 1α secretion, the materials strongly modulated tumor necrosis factor (TNF signaling, even at sub-cytotoxic concentrations. This is achieved mainly by upregulation of the TNFR1 receptor production, something which has not previously been observed for these systems.

Progress in the Development of SERS-Active Substrates Based on Metal-Coated Porous Silicon.

Science.gov (United States)

Bandarenka, Hanna V; Girel, Kseniya V; Zavatski, Sergey A; Panarin, Andrei; Terekhov, Sergei N

2018-05-21

The present work gives an overview of the developments in surface-enhanced Raman scattering (SERS) with metal-coated porous silicon used as an active substrate. We focused this review on the research referenced to SERS-active materials based on porous silicon, beginning from the patent application in 2002 and enclosing the studies of this year. Porous silicon and metal deposition technologies are discussed. Since the earliest studies, a number of fundamentally different plasmonic nanostructures including metallic dendrites, quasi-ordered arrays of metallic nanoparticles (NPs), and metallic nanovoids have been grown on porous silicon, defined by the morphology of this host material. SERS-active substrates based on porous silicon have been found to combine a high and well-reproducible signal level, storage stability, cost-effective technology and handy use. They make it possible to identify and study many compounds including biomolecules with a detection limit varying from milli- to femtomolar concentrations. The progress reviewed here demonstrates the great prospects for the extensive use of the metal-coated porous silicon for bioanalysis by SERS-spectroscopy.

Progress in the Development of SERS-Active Substrates Based on Metal-Coated Porous Silicon

Directory of Open Access Journals (Sweden)

Hanna V. Bandarenka

2018-05-01

Full Text Available The present work gives an overview of the developments in surface-enhanced Raman scattering (SERS with metal-coated porous silicon used as an active substrate. We focused this review on the research referenced to SERS-active materials based on porous silicon, beginning from the patent application in 2002 and enclosing the studies of this year. Porous silicon and metal deposition technologies are discussed. Since the earliest studies, a number of fundamentally different plasmonic nanostructures including metallic dendrites, quasi-ordered arrays of metallic nanoparticles (NPs, and metallic nanovoids have been grown on porous silicon, defined by the morphology of this host material. SERS-active substrates based on porous silicon have been found to combine a high and well-reproducible signal level, storage stability, cost-effective technology and handy use. They make it possible to identify and study many compounds including biomolecules with a detection limit varying from milli- to femtomolar concentrations. The progress reviewed here demonstrates the great prospects for the extensive use of the metal-coated porous silicon for bioanalysis by SERS-spectroscopy.

Applicability of a geometrical model coupled to computed tomography to characterize the transport properties of porous materials: comparison with through diffusion experiments

International Nuclear Information System (INIS)

Chagneau, Aurelie; Claret, Francis; Made, Benoit; Tuckermann, Juergen; Enzmann, Frieder; Schaefer, Thorsten

2012-01-01

they contain a heavy element (Sr) that can easily be differentiated from the lighter matrix elements (Si, Al) by tomography. The diffusion columns used consist of two reservoirs, one containing the strontium and radiotracer and the other the sulfate or carbonate stock solutions, one at each end of a 5 cm long column. Before any precipitation experiments, the De and porosity of the materials are characterized by realizing diffusion profiles of tritiated water (HTO), and the results are compared to a geometrical model of the material based on computed tomography observations. For this purpose, the images obtained by CT are reconstructed in three dimensions and then processed by separating the porous material and the pore network. The 3D reconstruction of the pore network is directly implemented into a geometrical model, GeoDict, to calculate the different properties of the material (e.g. porosity, tortuosity, diffusivity). The results obtained by the two different experimental approaches compare fairly well. For example, the connected porosity of a column filled with silica beads of 40 to 70 μm particle size was estimated at 0.39 by HTO diffusion and at 0.40 to 0.45 by computed tomography coupled to GeoDict. Computed tomography is a simple yet efficient method, when coupled to a geometrical model, to record the evolution of porosity with time, and to accurately estimate the impact of clogging on the diffusion properties of porous materials, without disturbing the system. To this characterization method will be added in further steps post mortem analyses by microscopic methods, microprobe and synchrotron μ-tomography. In parallel, experiments in the presence of trivalent actinides are planned to compare the chemical speciation during secondary phase formation in compacted systems with data already available obtained in batch-type and mixed flow reactor (MFR) experiments. (authors)

Porous silicon and diatoms micro-shells: an example of inverse biomimetic

Science.gov (United States)

De Tommasi, Edoardo; Rea, Ilaria; Rendina, Ivo; De Stefano, Luca

2011-05-01

Porous silicon (PSi) is by far a very useful technological platform for optical monitoring of chemical and biological substances and due to its peculiar physical and morphological properties it is worldwide used in sensing experiments. On the other hand, we have discovered a natural material, the micro-shells of marine diatoms, ubiquitous unicellular algae, which are made of hydrated amorphous silica, but, most of all, show geometrical structures made of complex patterns of pores which are surprisingly similar to those of porous silicon. Moreover, under laser irradiation, this material is photoluminescent and the photoluminescence is very sensitive to the surrounding atmosphere, which means that the material can act as a transducer. Starting from our experience on PSi devices, we explore the optical and photonic properties of marine diatoms micro-shells in a sort of inverse biomimicry.

Pseudocapacitive and hierarchically ordered porous electrode materials supercapacitors

Science.gov (United States)

Saruhan, B.; Gönüllü, Y.; Arndt, B.

2013-05-01

Commercially available double layer capacitors store energy in an electrostatic field. This forms in the form of a double layer by charged particles arranged on two electrodes consisting mostly of active carbon. Such double layer capacitors exhibit a low energy density, so that components with large capacity according to large electrode areas are required. Our research focuses on the development of new electrode materials to realize the production of electrical energy storage systems with high energy density and high power density. Metal oxide based electrodes increase the energy density and the capacitance by addition of pseudo capacitance to the static capacitance present by the double layer super-capacitor electrodes. The so-called hybrid asymmetric cell capacitors combine both types of energy storage in a single component. In this work, the production routes followed in our laboratories for synthesis of nano-porous and aligned metal oxide electrodes using the electrochemical and sputter deposition as well as anodization methods will be described. Our characterisation studies concentrate on electrodes having redox metal-oxides (e.g. MnOx and WOx) and hierarchically aligned nano-porous Li-doped TiO2-NTs. The material specific and electrochemical properties achieved with these electrodes will be presented.

Preparation of resveratrol-loaded nanoporous silica materials with different structures

Science.gov (United States)

Popova, Margarita; Szegedi, Agnes; Mavrodinova, Vesselina; Novak Tušar, Natasa; Mihály, Judith; Klébert, Szilvia; Benbassat, Niko; Yoncheva, Krassimira

2014-11-01

Solid, nanoporous silica-based spherical mesoporous MCM-41 and KIL-2 with interparticle mesoporosity as well as nanosized zeolite BEA materials differing in morphology and pore size distribution, were used as carriers for the preparation of resveratrol-loaded delivery systems. Two preparation methods have been applied: (i) loading by mixing of resveratrol and mesoporous carrier in solid state and (ii) deposition in ethanol solution. The parent and the resveratrol loaded carriers were characterized by XRD, TEM, N2 physisorption, thermal analysis, and FT-IR spectroscopy. The influence of the support structure on the adsorption capacity and the release kinetics of this poorly soluble compound were investigated. Our results indicated that the chosen nanoporous silica supports are suitable for stabilization of trans-resveratrol and reveal controlled release and ability to protect the supported compound against degradation regardless of loading method. The solid-state dry mixing appears very effective for preparation of drug formulations composed of poorly soluble compound.

Fluorescent silica hybrid materials containing benzimidazole dyes obtained by sol-gel method and high pressure processing

International Nuclear Information System (INIS)

Hoffmann, Helena Sofia; Stefani, Valter; Benvenutti, Edilson Valmir; Costa, Tania Maria Haas; Gallas, Marcia Russman

2011-01-01

Research highlights: → Sol-gel technique was used to obtain silica based hybrid materials containing benzimidazole dyes. → The sol-gel catalysts, HF and NaF, produce xerogels with different optical and textural characteristics. → High pressure technique (6.0 GPa) was used to produce fluorescent and transparent silica compacts with the dyes entrapped in closed pores, maintaining their optical properties. → The excited state intramolecular proton transfer (ESIPT) mechanism of benzimidazole dyes was studied by steady-state fluorescence spectroscopy for the monoliths, powders, and compacts. - Abstract: New silica hybrid materials were obtained by incorporation of two benzimidazole dyes in the silica network by sol-gel technique, using tetraethylorthosilicate (TEOS) as inorganic precursor. Several syntheses were performed with two catalysts (HF and NaF) producing powders and monoliths with different characteristics. The dye 2-(2'-hydroxy-5'-aminophenyl)benzimidazole was dispersed and physically adsorbed in the matrix, and the dye 2'(5'-N-(3-triethoxysilyl)propylurea-2'-hydroxyphenyl)benzimidazole was silylated, becoming chemically bonded to the silica network. High pressure technique was used to produce fluorescent and transparent silica compacts with the silylated and incorporated dye, at 6.0 GPa and room temperature. The excited state intramolecular proton transfer (ESIPT) mechanism of benzimidazole dyes was studied by steady-state fluorescence spectroscopy for the monoliths, powders, and compacts. The influence of the syntheses conditions was investigated by textural analysis using nitrogen adsorption isotherms.

Porous 3D graphene-based bulk materials with exceptional high surface area and excellent conductivity for supercapacitors

Science.gov (United States)

Zhang, Long; Zhang, Fan; Yang, Xi; Long, Guankui; Wu, Yingpeng; Zhang, Tengfei; Leng, Kai; Huang, Yi; Ma, Yanfeng; Yu, Ao; Chen, Yongsheng

2013-01-01

Until now, few sp2 carbon materials simultaneously exhibit superior performance for specific surface area (SSA) and electrical conductivity at bulk state. Thus, it is extremely important to make such materials at bulk scale with those two outstanding properties combined together. Here, we present a simple and green but very efficient approach using two standard and simple industry steps to make such three-dimensional graphene-based porous materials at the bulk scale, with ultrahigh SSA (3523 m2/g) and excellent bulk conductivity. We conclude that these materials consist of mainly defected/wrinkled single layer graphene sheets in the dimensional size of a few nanometers, with at least some covalent bond between each other. The outstanding properties of these materials are demonstrated by their superior supercapacitor performance in ionic liquid with specific capacitance and energy density of 231 F/g and 98 Wh/kg, respectively, so far the best reported capacitance performance for all bulk carbon materials. PMID:23474952

Chemical Stability of Cd(II and Cu(II Ionic Imprinted Amino-Silica Hybrid Material in Solution Media

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Buhani, Narsito, Nuryono, Eko Sri Kunarti

2015-12-01

Full Text Available Chemical stability of Cd(II and Cu(II ionic imprinted hybrid material of (i-Cd-HAS and i-Cu-HAS derived from silica modification with active compound (3-aminopropyl-trimethoxysilane (3-APTMS has been studied in solution media. Stability test was performed with HNO3 0.1 M (pH 1.35 to investigate material stability at low pH condition, CH3COONa 0.1 M (pH 5.22 for adsorption process optimum pH condition, and in the water (pH 9.34 for base condition. Material characteristics were carried out with infrared spectrophotometer (IR and atomic absorption spectrophotometer (AAS. At interaction time of 4 days in acid and neutral condition, i-Cd-HAS is more stable than i-Cu-HAS with % Si left in material 95.89 % (acid media, 43.82 % (close to neutral, and 9.39 % (base media.Keywords: chemical stability, amino-silica hybrid, ionic imprinting technique

Research on the Ordered Mesoporous Silica for Tobacco Harm Reduction

Science.gov (United States)

Wang, Y.; Y Li, Z.; Ding, J. X.; Hu, Z. J.; Liu, Z.; Zhou, G.; Huang, T. H.

2017-12-01

For reducting tobacco harm, this paper prepared an ordered mesoporous silica by using triblock copolymer Pluronic P123 as template. The property of this material was characterized by the X-ray scattering spectrum(XRD), Transmission electron microscopy(TEM), Scanning electron microscopy (SEM) and Nitrogen adsorption/desorption. Then this ordered mesoporous silica was added into the cigarette filter in order to researching its effect of cigarette harm index. The result shows that the feature of SBA-15 was grain morphology, ordered arrangement, tubular porous 2-D hexagonal structure. The application of SBA-15 in cigarette filter can selectively reduce harmful components in cigarette smoke such as crotonaldehyde, hydrogen cyanide, benzo pyrene and tar. The synthesized SBA-15 could properly reduce cigarette harm index.

Examining porous bio-active glass as a potential osteo-odonto-keratoprosthetic skirt material.

Science.gov (United States)

Huhtinen, Reeta; Sandeman, Susan; Rose, Susanna; Fok, Elsie; Howell, Carol; Fröberg, Linda; Moritz, Niko; Hupa, Leena; Lloyd, Andrew

2013-05-01

Bio-active glass has been developed for use as a bone substitute with strong osteo-inductive capacity and the ability to form strong bonds with soft and hard tissue. The ability of this material to enhance tissue in-growth suggests its potential use as a substitute for the dental laminate of an osteo-odonto-keratoprosthesis. A preliminary in vitro investigation of porous bio-active glass as an OOKP skirt material was carried out. Porous glass structures were manufactured from bio-active glasses 1-98 and 28-04 containing varying oxide formulation (1-98, 28-04) and particle size range (250-315 μm for 1-98 and 28-04a, 315-500 μm for 28-04b). Dissolution of the porous glass structure and its effect on pH was measured. Structural 2D and 3D analysis of porous structures were performed. Cell culture experiments were carried out to study keratocyte adhesion and the inflammatory response induced by the porous glass materials. The dissolution results suggested that the porous structure made out of 1-98 dissolves faster than the structures made from glass 28-04. pH experiments showed that the dissolution of the porous glass increased the pH of the surrounding solution. The cell culture results showed that keratocytes adhered onto the surface of each of the porous glass structures, but cell adhesion and spreading was greatest for the 98a bio-glass. Cytokine production by all porous glass samples was similar to that of the negative control indicating that the glasses do not induce a cytokine driven inflammatory response. Cell culture results support the potential use of synthetic porous bio-glass as an OOKP skirt material in terms of limited inflammatory potential and capacity to induce and support tissue ingrowth.

An agent-based method for simulating porous fluid-saturated structures with indistinguishable components

Science.gov (United States)

Kashani, Jamal; Pettet, Graeme John; Gu, YuanTong; Zhang, Lihai; Oloyede, Adekunle

2017-10-01

Single-phase porous materials contain multiple components that intermingle up to the ultramicroscopic level. Although the structures of the porous materials have been simulated with agent-based methods, the results of the available methods continue to provide patterns of distinguishable solid and fluid agents which do not represent materials with indistinguishable phases. This paper introduces a new agent (hybrid agent) and category of rules (intra-agent rule) that can be used to create emergent structures that would more accurately represent single-phase structures and materials. The novel hybrid agent carries the characteristics of system's elements and it is capable of changing within itself, while also responding to its neighbours as they also change. As an example, the hybrid agent under one-dimensional cellular automata formalism in a two-dimensional domain is used to generate patterns that demonstrate the striking morphological and characteristic similarities with the porous saturated single-phase structures where each agent of the ;structure; carries semi-permeability property and consists of both fluid and solid in space and at all times. We conclude that the ability of the hybrid agent to change locally provides an enhanced protocol to simulate complex porous structures such as biological tissues which could facilitate models for agent-based techniques and numerical methods.

Silica nanoparticles as vehicles for therapy delivery in neurological injury

Science.gov (United States)

Schenk, Desiree

Acrolein, a very reactive aldehyde, is a culprit in the biochemical cascade after primary, mechanical spinal cord injury (SCI), which leads to the destruction of tissue initially unharmed, referred to as "secondary injury". Additionally, in models of multiple sclerosis (MS) and some clinical research, acrolein levels are significantly increased. This aldehyde overwhelms the natural anti-oxidant system, reacts freely with proteins, and releases during lipid peroxidation (LPO), effectively regenerating its self. Due to its ability to make more copies of itself in the presence of tissue via lipid peroxidation, researchers believe that acrolein plays a role in the increased destruction of the central nervous system in both SCI and MS. Hydralazine, an FDA-approved hypertension drug, has been shown to scavenge acrolein, but its side effects and short half life at the appropriate dose for acrolein scavenging must be improved for beneficial clinical translation. Due to the inefficient delivery of therapeutic drugs, nanoparticles have become a major field of exploration for medical applications. Based on their material properties, they can help treat disease by delivering drugs to specific tissues, enhancing detection methods, or a mixture of both. Nanoparticles made from silica provide distinct advantages. They form porous networks that can carry therapeutic molecules throughout the body. Therefore, a nanomedical approach has been designed using silica nanoparticles as a porous delivery vehicle hydralazine. The silica nanoparticles are formed in a one-step method that incorporates poly(ethylene) glycol (PEG), a stealth molecule, directly onto the nanoparticles. As an additional avenue for study, a natural product in green tea, epigallocatechin gallate (EGCG), has been explored for its ability to react with acrolein, disabling its reactive capabilities. Upon demonstration of attenuating acrolein, EGCG's delivery may also be improved using the nanomedical approach. The

Damage and failure modeling of lotus-type porous material subjected to low-cycle fatigue

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J. Kramberger

2016-01-01

Full Text Available The investigation of low-cycle fatigue behaviour of lotus-type porous material is presented in this paper. Porous materials exhibit some unique features which are useful for a number of various applications. This paper evaluates a numerical approach for determining of damage initiation and evolution of lotus-type porous material with computational simulations, where the considered computational models have different pore topology patterns. The low-cycle fatigue analysis was performed by using a damage evolution law. The damage state was calculated and updated based on the inelastic hysteresis energy for stabilized cycle. Degradation of the elastic stifness was modeled using scalar damage variable. In order to examine crack propagation path finite elements with severe damage were deleted and removed from the mesh during simulation. The direct cyclic analysis capability in Abaqus/Standard was used for low-cycle fatigue analysis to obtain the stabilized response of a model subjected to the periodic loading. The computational results show a qualitative understanding of pores topology influence on low-cycle fatigue under transversal loading conditions in relation to pore orientation.

Modeling of heat transfer within porous multi-constituent materials

International Nuclear Information System (INIS)

Niezgoda, M.

2012-01-01

The CEA works a great deal with porous materials - carbon composites, ceramics - and aims to optimize their properties for specific uses. These materials can be composed of several constituents and generally has a complex structure with pore size of several tens of micrometers. It is used in large-scale systems that are bigger than its own characteristic scale in which they are considered as equivalent to a homogeneous medium for the simulation of its behavior in its using environment without taking into account its local morphology. We are especially interested in the effective thermal diffusivity of heterogeneous materials that we estimate as a function of temperature with the help of an inverse method by considering they are homogeneous. The identification of the diffusivity of porous and/or semi-transparent materials is made difficult because of the strong conducto-radiative coupling can quickly occur when the temperature increases. We have thus modeled the coupled conductive and radiative heat transfer as a function of the temperature within porous multi-constituent materials from their morphology discretized into a set of homogeneous voxels. We have developed a methodology that consists in starting from a 3D-microstructure of the studied materials obtained by tomography. The microstructures constitute the numerical support to this modeling that renders it possible, on the one hand, to simulate any kind of numerical thermal experiments, especially the flash method whose the results render it possible to estimate the thermal diffusivity, and on the other hand, to reproduce the thermal behavior of our materials in their using conditions. (author) [fr

Contribution to research on the elastic and elastoplastic behavior of porous materials

International Nuclear Information System (INIS)

Frappier, J.-C.

1979-11-01

This three-part study concerns the mechanical behavior of porous materials. Part one, a bibliographical survey on the mechanical properties of porous materials, deals in turn with the following subjects: elastic properties, elasto-plastic boundary, plastic flow laws, fracture behavior and characterization methods. Part two is devoted to elastic behavior, giving the results of an experimental study on the elastic properties of a sintered nickel within a wide porosity range (5% to 55%) and establishing a theoretical law for the prediction of such characteristics; apart from the total porosity fraction and the elastic properties of the matrix this law can integrate parameters which represent the morphology of the material and may be determined empirically or by a modelisation, also proposed, of the structure of the material. Part three describes elastoplastic, behavior and includes experimental results obtained on sintered nickel in cases of simple mechanical stress, the demonstration - based on energy considerations of a theoretical plasticity criterion accounting for the substance, a theoretical definition of the plastic Poisson's ratio and the establishment of flow laws associated with this criterion [fr

Identification and Purification of Nyalo River Silica Sand as Raw Material for the Synthesis of Sodium Silicate

Science.gov (United States)

Aini, S.; Nizar, U. K.; NST, A. Amelia; Efendi, J.

2018-04-01

This research is on identification and purification of silica sand from Nyalo River. It will be used as a raw material for synthesis of sodium silicate. Silica sand was separated from clay by washing it with water, and then the existing alumina and iron oxide were removed by soaking the silica sand with 1 M HNO3 solution. Qualitative and quantitative analysis of the silica sand with X-ray diffraction and X-ray fluorescence revealed that, silica sand existed in quartz form and contained a small amount of impurity oxide such as Al2O3, K2O, MgO, CaO, Fe2O3 with percentage below the minimum threshold. The percentages of silica were 80.59% before purification. After three purificationsteps the silica percentage become 98.38%. It exceedsthe minimum threshold of silica percentage for industry.So, the silica sand from Nyalo River has high potency as a raw material for sodium silicate synthesizing.

Aerogels of 1D Coordination Polymers: From a Non-Porous Metal-Organic Crystal Structure to a Highly Porous Material

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Adrián Angulo-Ibáñez

2016-01-01

Full Text Available The processing of an originally non-porous 1D coordination polymer as monolithic gel, xerogel and aerogel is reported as an alternative method to obtain novel metal-organic porous materials, conceptually different to conventional crystalline porous coordination polymer (PCPs or metal-organic frameworks (MOFs. Although the work herein reported is focused upon a particular kind of coordination polymer ([M(μ-ox(4-apy2]n, M: Co(II, Ni(II, the results are of interest in the field of porous materials and of MOFs, as the employed synthetic approach implies that any coordination polymer could be processable as a mesoporous material. The polymerization conditions were fixed to obtain stiff gels at the synthesis stage. Gels were dried at ambient pressure and at supercritical conditions to render well shaped monolithic xerogels and aerogels, respectively. The monolithic shape of the synthesis product is another remarkable result, as it does not require a post-processing or the use of additives or binders. The aerogels of the 1D coordination polymers are featured by exhibiting high pore volumes and diameters ranging in the mesoporous/macroporous regions which endow to these materials the ability to deal with large-sized molecules. The aerogel monoliths present markedly low densities (0.082–0.311 g·cm−3, an aspect of interest for applications that persecute light materials.

Hydrothermal assisted synthesis of iron oxide-based magnetic silica spheres and their performance in magnetophoretic water purification

Energy Technology Data Exchange (ETDEWEB)

Caparros, C., E-mail: ccaparros@fisica.uminho.pt [Centro de Fisica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Benelmekki, M.; Martins, P.M. [Centro de Fisica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Xuriguera, E. [Facultat de Quimica, Universitat de Barcelona, 08028 Barcelona (Spain); Silva, C.J.R. [Departamento de Quimica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Martinez, Ll.M. [Sepmag Technologies, Parc Tecnologic del Valles, 08290 Barcelona (Spain); Lanceros-Mendez, S. [Centro de Fisica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal)

2012-08-15

Porous Magnetic Silica (PMS) spheres of about 400 nm diameter were synthesised by one-pot process using the classical Stber method combined with hydrothermal treatment. Maghemite nanoparticles ({gamma}-Fe{sub 2}O{sub 3}) were used as fillers and cetyltrimethylammonium bromide (CTAB) was used as templating agent. The application of the hydrothermal process (120 Degree-Sign C during 48 h) before the calcination leads to the formation of homogeneous and narrow size distribution PMS spheres. X-ray diffraction patterns (XRD), Infrared measurements (FTIR) and Transmission Electron microscopy (TEM) methods were used to determine the composition and morphology of the obtained PMS spheres. The results show a homogeneous distribution of the {gamma}-Fe{sub 2}O{sub 3} nanoparticles in the silica matrix with a 'hollow-like' morphology. Magnetophoresis measurements at 60 T m{sup -1} show a total separation time of the PMS spheres suspension of about 16 min. By using this synthesis method, the limitation of the formation of silica spheres without incorporation of magnetic nanoparticles is overcome. These achievements make this procedure interesting for industrial up scaling. The obtained PMS spheres were evaluated as adsorbents for Ni{sup 2+} in aqueous solution. Their adsorption capacity was compared with the adsorption capacity of magnetic silica spheres obtained without hydrothermal treatment before calcination process. PMS spheres show an increase of the adsorption capacity of about 15% of the initial dissolution of Ni{sup 2+} without the need to functionalize the silica surface. Highlights: Black-Right-Pointing-Pointer Homogeneous and controlled size porous magnetic silica spheres were obtained. Black-Right-Pointing-Pointer Magnetophoretic removing of Ni{sup 2+} processes was successfully preformed at HLGMF. Black-Right-Pointing-Pointer PMS show higher Ni{sup 2+} removing capacity than spheres without hydrothermal treatment. Black-Right-Pointing-Pointer PMS can be

Controlled generation of silver nanocolloid in amorphous silica materials

International Nuclear Information System (INIS)

Gil, C.; Garcia-Heras, M.; Carmona, N.; Villages, M. A.

2004-01-01

Amorphous silica-based materials bulk and superficially doped with silver nano colloids were prepared. Bulk doped glasses were obtained by conventional melting and doped monolithic slabs by sol-gel. Superficially doped glasses were obtained by ion-exchange and doped coatings by sol-gel. The samples were characterised by TEM and UV-VIS spectrometry. Depending on the composition, the silver incorporation process, and the thermal treatments, several colourings were obtained. By controlling these parameters, metallic silver nano colloids can be generated in the matrices studied. Colloids aggregation and growing up depends on the matrix nature and on the experimental process carried out. (Author) 10 refs

Biological Applications and Transmission Electron Microscopy Investigations of Mesoporous Silica Nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Trewyn, Brian G. [Iowa State Univ., Ames, IA (United States)

2006-01-01

The research presented and discussed within involves the development of novel biological applications of mesoporous silica nanoparticles (MSN) and an investigation of mesoporous material by transmission electron microscopy (TEM). Mesoporous silica nanoparticles organically functionalized shown to undergo endocytosis in cancer cells and drug release from the pores was controlled intracellularly and intercellularly. Transmission electron microscopy investigations demonstrated the variety of morphologies produced in this field of mesoporous silica nanomaterial synthesis. A series of room-temperature ionic liquid (RTIL) containing mesoporous silica nanoparticle (MSN) materials with various particle morphologies, including spheres, ellipsoids, rods, and tubes, were synthesized. By changing the RTIL template, the pore morphology was tuned from the MCM-41 type of hexagonal mesopores to rotational moire type of helical channels, and to wormhole-like porous structures. These materials were used as controlled release delivery nanodevices to deliver antibacterial ionic liquids against Escherichia coli K12. The involvement of a specific organosiloxane function group, covalently attached to the exterior of fluorescein doped mesoporous silica nanoparticles (FITC-MSN), on the degree and kinetics of endocytosis in cancer and plant cells was investigated. The kinetics of endocystosis of TEG coated FITC-MSN is significantly quicker than FITC-MSN as determined by flow cytometry experiments. The fluorescence confocal microscopy investigation showed the endocytosis of TEG coated-FITC MSN triethylene glycol grafted fluorescein doped MSN (TEG coated-FITC MSN) into both KeLa cells and Tobacco root protoplasts. Once the synthesis of a controlled-release delivery system based on MCM-41-type mesoporous silica nanorods capped by disulfide bonds with superparamagnetic iron oxide nanoparticles was completed. The material was characterized by general methods and the dosage and kinetics of the

Porous chromatographic materials as substrates for preparing synthetic nuclear explosion debris particles

International Nuclear Information System (INIS)

Harvey, S.D.; Carman, A.J.; Martin Liezers; Antolick, K.C.; Garcia, B.J.; Eiden, G.C.; Sweet, L.E.

2013-01-01

Several porous chromatographic materials were investigated as synthetic substrates for preparing surrogate nuclear explosion debris particles. Eighteen metals, including some of forensic interest, were loaded onto materials by immersing them in metal solutions (556 mg/L of each metal) to fill the pores, applying gentle heat (110 deg C) to drive off water, and then treating them at high temperatures (up to 800 deg C) in air to form less soluble metal species. High-boiling-point metals were uniformly loaded on spherical controlled-pore glass to emulate early fallout, whereas low-boiling-point metals were loaded on core-shell silica to represent coated particles formed later in the nuclear fallout-formation process. Analytical studies characterized material balance and the formation of recalcitrant species. Metal loading was 1.5-3 times higher than expected from the pore volume alone, a result attributed to surface coating. Most metals were passively loaded; that is, solutions filled the pores without active metal discrimination. However, niobium and tin concentrations were lower in solutions after pore filling, and were found in elevated concentrations in the final products, indicating selective loading. High-temperature treatments caused reduced solubility of several metals, and the loss of some volatile species (rhenium and tellurium). Sample preparation reproducibility was high (the inter- and intra-batch relative standard deviations were 7.8 and 0.84 %, respectively) indicating suitability for use as a working standard for analytical methods development. We anticipate future standardized radionuclide-loaded materials will find use in radioanalytical methods development and/or serve as a starting material for the synthesis of more complex nuclear explosion debris forms (e.g., Trinitite). (author)

Fabrication of hierarchical porous N-doping carbon membrane by using ;confined nanospace deposition; method for supercapacitor

Science.gov (United States)

Wang, Guoxu; Liu, Meng; Du, Juan; Liu, Lei; Yu, Yifeng; Sha, Jitong; Chen, Aibing

2018-03-01

The membrane carbon materials with hierarchical porous architecture are attractive because they can provide more channels for ion transport and shorten the ions transport path. Herein, we develop a facile way based on "confined nanospace deposition" to fabricate N-dopi-ng three dimensional hierarchical porous membrane carbon material (N-THPMC) via coating the nickel nitrate, silicate oligomers and triblock copolymer P123 on the branches of commercial polyamide membrane (PAM). During high temperature treatment, the mesoporous silica layer and Ni species serve as a "confined nanospace" and catalyst respectively, which are indispensable elements for formation of carbon framework, and the gas-phase carbon precursors which derive from the decomposition of PAM are deposited into the "confined nanospace" forming carbon framework. The N-THPMC with hierarchical macro/meso/microporous structure, N-doping (2.9%) and large specific surface area (994m2 g-1) well inherits the membrane morphology and hierarchical porous structure of PAM. The N-THPMC as electrode without binder exhibits a specific capacitance of 252 F g-1 at the current density of 1 A g-1 in 6 M KOH electrolyte and excellent cycling stability of 92.7% even after 5000 cycles.

Testing Silica Fume-Based Concrete Composites under Chemical and Microbiological Sulfate Attacks

Directory of Open Access Journals (Sweden)

Adriana Estokova

2016-04-01

Full Text Available Current design practices based on descriptive approaches to concrete specification may not be appropriate for the management of aggressive environments. In this study, the durability of cement-based materials with and without the addition of silica fume, subjected to conditions that leach calcium and silicon, were investigated. Chemical corrosion was simulated by employing various H2SO4 and MgSO4 solutions, and biological corrosion was simulated using Acidithiobacillus sp. bacterial inoculation, leading to disrupted and damaged surfaces; the samples’ mass changes were studied following both chemical and biological attacks. Different leaching trends were observed via X-ray fluorescence when comparing chemical with biological leaching. Lower leaching rates were found for concrete samples fortified with silica fume than those without silica fume. X-ray diffraction and scanning electron microscopy confirmed a massive sulfate precipitate formation on the concrete surface due to bacterial exposure.

Microporous silica prepared by organic templating: relationship between the molecular template and pore structure

International Nuclear Information System (INIS)

Brinker, C. Jeffrey; Cao, Guozhong; Kale, Rahul P.; Lopez, Gabriel P.; Lu, Yunfeng; Prabakar, S.

1999-01-01

Microporous silica materials with a controlled pore size and a narrow pore size distribution have been prepared by sol-gel processing using an organic-templating approach. Microporous networks were formed by pyrolytic removal of organic ligands (methacryloxypropyl groups) from organic/inorganic hybrid materials synthesized by copolymerization of 3-methacryloxypropylsilane (MPS) and tetraethoxysilane (TEOS). Molecular simulations and experimental measurements were conducted to examine the relationship between the microstructural characteristics of the porous silica (e.g., pore size, total pore volume, and pore connectivity) and the size and amount of organic template ligands added. Adsorption measurements suggest that the final porosity of the microporous silica is due to both primary pores (those present in the hybrid materials prior to pyrolysis) and secondary pores (those created by pyrolytic removal of organic templates). Primary pores were inaccessible to N(sub 2) at 77 K but accessible to CO(sub 2) at 195 K; secondary pores were accessible to both N(sub 2) (at 77 K) and CO(sub 2) (at 195 K) in adsorption measurements. Primary porosity decreases with the amount of organic ligands added because of the enhanced densification of MPS/TEOS hybrid materials as the mole fraction of trifunctional MPS moieties increases. pore volumes measured by nitrogen adsorption experiments at 77 K suggest that the secondary (template-derived) porosity exhibits a percolation behavior as the template concentration is increased. Gas permeation experiments indicate that the secondary pores are approximately 5(angstrom) in diameter, consistent with predictions based on molecular simulations

Structural effect of monomer type on properties of copolyimides and copolyimide-silica hybrid materials

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Kizilkaya Canan

2015-01-01

Full Text Available In this work, the effect of two different diamine monomers, containing phosphine oxide, on thermal, mechanical and morphological properties of copolyimides and their hybrid materials was investigated. Gas separation properties of the synthesized copolyimides were also analysed. Two different diamine monomers with phosphine oxide were bis(3-aminophenyl phenylphosphine oxide (BAPPO and bis(3-aminophenoxy-4-phenyl phenylphosphine oxide (m-BAPPO. In the synthesis of copolyimides 3,3’-diamino-diphenyl sulfone (DDS was also used as the diamine, as well as 2,2’-bis(3,4-dicarboxyphenylhexafluoropropane dianhydride (6FDA. Copolyimide films were prepared by thermal imidization. Hybrid materials containing 5 % SiO2 were synthesised further by sol-gel technique. The Fourier-transform infrared spectroscopy (FTIR, Nuclear magnetic resonance spectroscopy (NMR confirmed the expected structure. Dynamic mechanical analysis (DMA demonstrated that m-BAPPO based copolyimides had lower glass transition temperatures (Tg than BAPPO based copolyimides. m-BAPPO containing copolyimide without silica shifted the thermal decomposition temperature to a higher value. The moduli and strength values of BAPPO diamine containing copolyimide and its hybrid were higher than those of m-BAPPO containing materials. The contact angle measurements showed the hydrophobicity. Scanning electron microscope (SEM analysis exhibited the silica particles dispersion in the copolyimides. These copolyimides may be used in the coating industry. The CO2 permeability and the permselectivity were the highest among the other values in this study, when m-BAPPO containing copolyimide in the absence of silica was used. The gas permeabilities obtained from this work were in this decreasing order: PCO2 > PO2 > PN2.

Capillary condensation in porous materials. Hysteresis and interaction mechanism without pore blocking/percolation process.

Science.gov (United States)

Grosman, Annie; Ortega, Camille

2008-04-15

We have performed measurements of boundary hysteresis loops, reversal curves, and subloops in p+-type porous silicon, a porous material composed of straight non-interconnected pores. These data show that a strong interaction mechanism exists between the pores. The pores of porous silicon are non-independent, whereas they are not interconnected. This hysteretic behavior is very similar to that observed in porous glass, which consists of cavities connected to each other by constrictions. This questions the so-called pore blocking/percolation model developed to explain the behavior of fluid in porous glass. More generally, if we disregard the shape of the boundary hysteresis loops which depends on the porous material (H1 for MCM-41 and SBA-15, H2 for porous glass and p+-type porous silicon), the hysteretic features inside the main loop are qualitatively the same for all these porous systems. This shows that none of these systems are composed of independent pores. A coupling between the pores is always present whether they are interconnected or not and whatever the shape of the main loop is.

Synthesis of eccentric titania-silica core-shell and composite particles

NARCIS (Netherlands)

Demirors, A.F.; van Blaaderen, A.; Imhof, A.

2009-01-01

We describe a novel method to synthesize colloidal particles with an eccentric core-shell structure. Titania-silica core-shell particles were synthesized by silica coating of porous titania particles under Sto¨ber (Sto¨ber et al. J. Colloid Interface Sci. 1968, 26, 62) conditions. We can control

Cellular membrane trafficking of mesoporous silica nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Fang, I-Ju [Iowa State Univ., Ames, IA (United States)

2012-01-01

the specific organelle that mesoporous silica nanoparticles could approach via the identification of harvested proteins from exocytosis process. Based on the study of endo- and exocytosis behavior of mesoporous silica nanoparticle materials, we can design smarter drug delivery vehicles for cancer therapy that can be effectively controlled. The destination, uptake efficiency and the cellular distribution of mesoporous silica nanoparticle materials can be programmable. As a result, release mechanism and release rate of drug delivery systems can be a well-controlled process. The deep investigation of an endo- and exocytosis study of mesoporous silica nanoparticle materials promotes the development of drug delivery applications.

Monitoring Phase Behavior of Sub- and Supercritical CO2 Confined in Porous Fractal Silica with 85% Porosity

International Nuclear Information System (INIS)

Melnichenko, Yuri B.; Mayama, Hiroyuki; Cheng, Gang; Cheng, Gang; Blach, Tomasz P.

2010-01-01

Phase behavior of CO 2 confined in porous fractal silica with volume fraction of SiO 2 φ 5 = 0.15 was investigated using small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) techniques. The range of fluid densities (0 CO2 ) bulk 3 ) and temperatures (T = 22 C, 35 and 60 C) corresponded to gaseous, liquid, near critical and supercritical conditions of the bulk fluid. The results revealed formation of a dense adsorbed phase in small pores with sizes D CO2 ) bulk 3 ) the average fluid density in pores may exceed the density of bulk fluid by a factor up to 6.5 at T = 22 C. This 'enrichment factor' gradually decreases with temperature, however significant fluid densification in small pores still exists at temperature T = 60 C, i.e., far above the liquid?gas critical temperature of bulk CO 2 (T c = 31.1 C). Larger pores are only partially filled with liquid-like adsorbed layer which coexists with unadsorbed fluid in the pore core. With increasing pressure, all pores become uniformly filled with the fluid, showing no measurable enrichment or depletion of the porous matrix with CO 2 .

Thermal insulator made of ultra fine particles of silica. Chobiryushi silica kei dannetsuzai

Energy Technology Data Exchange (ETDEWEB)

Eguchi, T.

1991-05-30

An overview was presented of properties and applications of thermal insulator made of ultra fine powder of silica, MICROTHERM. The thermal conductivity of MICROTHERM is as low as (1/3) - (1/4) of that of conventional thermal insulator, because it is mainly composed of fumed silica or aero gel and formed into porous structure. In addition, metal oxide of special particle size is added to it in order to reject the radiative heat. The thermal insulation property and the mechanical strength of MICROTHERM is not affected by a sudden change in temperature and moisture. The standard type of MICROTHERM can be used at a temperature up to 950 {degree}C, while the high temperature type MICROTHERM can stand a high temperature up to 1025 {degree}C for long period of time. The thickness of insulator can be reduced markedly by using MICROTHERM as compared with the use of conventional insulating materials. Many new products in which MICROTHERM is used came into market. New type kilt, Semi-cylindrical block, Super high temperature MICROTHERM are just a few examples. Variety of application and energy saving effect are attracting public attention. 11 figs.

Electrokinetic salt removal from porous building materials using ion exchange membranes

NARCIS (Netherlands)

Kamran, K.; Van Soestbergen, M.; Pel, L.

The removal of salt from porous building materials under the influence of an applied voltage gradient normally results in high pH gradients due to the formation of protons and hydroxyl ions at the electrodes. The formed acidic and alkaline regions not only lead to disintegration of the porous

Electrokinetic salt removal from porous building materials using ion exchange membranes

NARCIS (Netherlands)

Kamran, K.; Soestbergen, van M.; Pel, L.

2012-01-01

The removal of salt from porous building materials under the influence of an applied voltage gradient normally results in high pH gradients due to the formation of protons and hydroxyl ions at the electrodes. The formed acidic and alkaline regions not only lead to disintegration of the porous

Pore radius fine tuning of a silica matrix (MCM-41) based on the synthesis of alumina nanolayers with different thicknesses by atomic layer deposition

International Nuclear Information System (INIS)

Zemtsova, Elena G.; Arbenin, Andrei Yu.; Plotnikov, Alexander F.; Smirnov, Vladimir M.

2015-01-01

The authors investigated a new approach to modify the surface of the mesoporous silica matrix MCM-41. This approach is based on manipulating the chemical composition of the porous surface layer and also on fine tuning the pore radius by applying the atomic layer deposition (ALD) technique. The synthesis of alumina nanolayers was performed on the planar and the porous matrix (MCM-41) by the ALD technique using aluminum tri-sec-butoxide and water as precursors. The authors show that one cycle on silicon, using aluminum tri-sec-butoxide and water as precursors, results in a 1–1.2 Å increase in alumina nanolayer thickness. This is comparable to the increase in thickness per cycle for other precursors such as trimethylaluminum and aluminum chloride. The authors show that the synthesis of an Al 2 O 3 nanolayer on the pore surface of the mesoporous silica matrix MCM-41 by the ALD technique results in a regular change in the porous structure of the samples. The specific porosity (ml/g) of the MCM-41 was 0.95 and that of MCM-41 after 5 ALD cycles was 0.39. The pore diameter (nm) of MCM-41 was 3.3 and that of MCM-41 after 5 ALD cycles was 2.3

Optimization of Preparation Program for Biomass Based Porous Active Carbon by Response Surface Methodology Based on Adsorptive Property

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ZHANG Hao

2017-06-01

Full Text Available With waste walnut shell as raw material, biomass based porous active carbon was made by microwave oven method. The effects of microwave power, activation time and mass fraction of phosphoric acid on adsorptive property of biomass based porous active carbon in the process of physical activation of active carbon precursor were studied by response surface method and numerical simulation method, the preparation plan of biomass based porous active carbon was optimized, and the optimal biomass based porous active carbon property was characterized. The results show that three factors affect the adsorptive property of biomass based porous active carbon, but the effect of microwave power is obviously more significant than that of mass fraction of phosphoric acid, and the effect of mass fraction of phosphoric acid is more significant than that of activation time. The optimized preparation conditions are:microwave power is 746W, activation time is 11.2min and mass fraction of phosphoric acid is 85.9% in the process of physical activation of activated carbon precursor by microwave heating method. For the optimal biomass based porous active carbon, the adsorption value of iodine is 1074.57mg/g, adsorption value of methylene blue is 294.4mL/g and gain rate is 52.1%.

Gas Separation through Bilayer Silica, the Thinnest Possible Silica Membrane.

Science.gov (United States)

Yao, Bowen; Mandrà, Salvatore; Curry, John O; Shaikhutdinov, Shamil; Freund, Hans-Joachim; Schrier, Joshua

2017-12-13

Membrane-based gas separation processes can address key challenges in energy and environment, but for many applications the permeance and selectivity of bulk membranes is insufficient for economical use. Theory and experiment indicate that permeance and selectivity can be increased by using two-dimensional materials with subnanometer pores as membranes. Motivated by experiments showing selective permeation of H 2 /CO mixtures through amorphous silica bilayers, here we perform a theoretical study of gas separation through silica bilayers. Using density functional theory calculations, we obtain geometries of crystalline free-standing silica bilayers (comprised of six-membered rings), as well as the seven-, eight-, and nine-membered rings that are observed in glassy silica bilayers, which arise due to Stone-Wales defects and vacancies. We then compute the potential energy barriers for gas passage through these various pore types for He, Ne, Ar, Kr, H 2 , N 2 , CO, and CO 2 gases, and use the data to assess their capability for selective gas separation. Our calculations indicate that crystalline bilayer silica, which is less than a nanometer thick, can be a high-selectivity and high-permeance membrane material for 3 He/ 4 He, He/natural gas, and H 2 /CO separations.

Self-diffusion of charged colloidal tracer spheres in transparent porous glass media: Effect of ionic strength and pore size

Science.gov (United States)

Kluijtmans, Sebastiaan G. J. M.; de Hoog, Els H. A.; Philipse, Albert P.

1998-05-01

The influence of charge on diffusion in porous media was studied for fluorescent colloidal silica spheres diffusing in a porous glass medium. The bicontinuous porous silica glasses were optically matched with an organic solvent mixture in which both glass and tracers are negatively charged. Using fluorescence recovery after photobleaching, the long-time self-diffusion coefficient DSL of the confined silica particles was monitored in situ as a function of the ionic strength and particle to pore size ratio. At high salt concentration DSL reaches a relatively high plateau value, which depends on the particle to pore size ratio. This plateau value is unexpectedly higher than the value found for uncharged silica spheres in these porous glasses, but still significantly smaller than the free particle bulk diffusion coefficient of the silica spheres. At low salt concentration DSL reduces markedly, up to the point where colloids are nearly immobilized. This peculiar retardation probably originates from potential traps and barriers at pore intersections due to deviations from cylinder symmetry in the double layer interactions between tracers and pore walls. This indicates that diffusion of charged particles in tortuous porous media may be very different from transport in long capillaries without such intersections.

Silica functionalized Cu(II) acetylacetonate Schiff base complex: An efficient catalyst for the oxidative condensation reaction of benzyl alcohol with amines

Science.gov (United States)

Anbarasu, G.; Malathy, M.; Karthikeyan, P.; Rajavel, R.

2017-09-01

Silica functionalized Cu(II) acetylacetonate Schiff base complex via the one pot reaction of silica functionalized 3-aminopropyltriethoxysilane with acetyl acetone and copper acetate has been reported. The synthesized material was well characterized by analytical techniques such as FT-IR, UV-DRS, XRD, SEM-EDX, HR-TEM, EPR, ICP-AES and BET analysis. The characterization results confirmed the grafting of Cu(II) Schiff base complex on the silica surface. The catalytic activity of synthesized silica functionalized Cu(II) acetylacetonate Schiff base complex was evaluated through the oxidative condensation reaction of benzyl alcohol to imine.

Three-Dimensional Porous Si and SiO2 with In Situ Decorated Carbon Nanotubes As Anode Materials for Li-ion Batteries.

Science.gov (United States)

Su, Junming; Zhao, Jiayue; Li, Liangyu; Zhang, Congcong; Chen, Chunguang; Huang, Tao; Yu, Aishui

2017-05-31

A high-capacity Si anode is always accompanied by very large volume expansion and structural collapse during the lithium-ion insertion/extraction process. To stabilize the structure of the Si anode, magnesium vapor thermal reduction has been used to synthesize porous Si and SiO 2 (pSS) particles, followed by in situ growth of carbon nanotubes (CNTs) in pSS pores through a chemical vapor deposition (CVD) process. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy have shown that the final product (pSS/CNTs) possesses adequate void space intertwined by uniformly distributed CNTs and inactive silica in particle form. pSS/CNTs with such an elaborate structural design deliver improved electrochemical performance, with better coulombic efficiency (70% at the first cycle), cycling capability (1200 mAh g -1 at 0.5 A g -1 after 200 cycles), and rate capability (1984, 1654, 1385, 1072, and 800 mAh g -1 at current densities of 0.1, 0.2, 0.5, 1, and 2 A g -1 , respectively), compared to pSS and porous Si/CNTs. These merits of pSS/CNTs are attributed to the capability of void space to absorb the volume changes and that of the silica to confine the excessive lithiation expansion of the Si anode. In addition, CNTs have interwound the particles, leading to significant enhancement of electronic conductivity before and after Si-anode pulverization. This simple and scalable strategy makes it easy to expand the application to manufacturing other alloy anode materials.

Mesoscopic objects, porous layers and nanocomposites-Possibilities of sol-gel chemistry

International Nuclear Information System (INIS)

Piwonski, Ireneusz

2009-01-01

The goal of this study was to prepare mesoscopic objects, thin porous films and nanocomposite coatings with the use of sol-gel technique. Silica nanotubes, titania nanoparticles, porous titania and zirconia coatings as well as titania nanocomposites were successfully synthesized by changing the type of sol-gel precursor, sol composition and applying dip-coating deposition procedure in order to obtain thin films or coatings. All materials were visualized and characterized by the Atomic Force Microcscopy (AFM) technique. Moreover, characterization of titania nanocomposites was extended to the tribological tests performed by means of microtribometer operating in normal loads range of 30-100 mN. The AFM analysis of mesoscopic objects and nanoparticles showed that the diameter of synthesized silica nanotubes was 60-70 nm and the size of titania nanoparticles was 43 nm. In case of porous layers the pore size in titania and zirconia coatings oscillated between 100 and 240 nm, however their shape and distribution were irregular. Microtribological studies of nanocomposites revealed the moderate decrease of the coefficient of friction for samples containing 5, 15 and 5 wt.% of zirconia nanoparticles in titania coatings annealed at 100, 500 and 1000 deg. C respectively. An enhancement of antiwear properties was already observed for 1 wt.% of nanophase content, except the sample annealed at 500 deg. C. It was also found that the annealing at high temperatures is a primary factor which affects the reduction of friction and wear of titania coatings while the presence of nanoparticles has secondary effect. Investigations in this study carried out with the use of the AFM technique highlighted the potential and flexibility of sol-gel approach in designing of various types of advanced materials in a form of mesoscopic objects, porous coatings and composite layers. Results collected in this study clearly demonstrated that sol-gel technique can be applied effectively in preparation of

Porous Structures in Stacked, Crumpled and Pillared Graphene-Based 3D Materials.

Science.gov (United States)

Guo, Fei; Creighton, Megan; Chen, Yantao; Hurt, Robert; Külaots, Indrek

2014-01-01

Graphene, an atomically thin material with the theoretical surface area of 2600 m 2 g -1 , has great potential in the fields of catalysis, separation, and gas storage if properly assembled into functional 3D materials at large scale. In ideal non-interacting ensembles of non-porous multilayer graphene plates, the surface area can be adequately estimated using the simple geometric law ~ 2600 m 2 g -1 /N, where N is the number of graphene sheets per plate. Some processing operations, however, lead to secondary plate-plate stacking, folding, crumpling or pillaring, which give rise to more complex structures. Here we show that bulk samples of multilayer graphene plates stack in an irregular fashion that preserves the 2600/N surface area and creates regular slot-like pores with sizes that are multiples of the unit plate thickness. In contrast, graphene oxide deposits into films with massive area loss (2600 to 40 m 2 g -1 ) due to nearly perfect alignment and stacking during the drying process. Pillaring graphene oxide sheets by co-deposition of colloidal-phase particle-based spacers has the potential to partially restore the large monolayer surface. Surface areas as high as 1000 m 2 g -1 are demonstrated here through colloidal-phase deposition of graphene oxide with water-dispersible aryl-sulfonated ultrafine carbon black as a pillaring agent.

Quasi-optic millimeter-wave device application of liquid crystal material by using porous PMMA matrix

Science.gov (United States)

Nose, T.; Watanabe, Y.; Kon, A.; Ito, R.; Honma, M.

2018-02-01

Recently, millimeter-waves (MMWs) have become indispensable for application in next-generation high-speed wireless communication i.e., 5G, in addition to conventional applications such as in automobile collision avoidance radars and airport security inspection systems. Some manageable devices to control MMW propagation will be necessary with the development of this new technology field. We believe that liquid crystal (LC) devices are one of the major candidates for such applications because it is known that LC materials are excellent electro-optic materials. However, as the wavelength of MMWs is extremely longer than the optics region, extremely thick LC layers are necessary if we choose the quasioptic approach to attain LC MMW control devices. Therefore, we adopt a PDLC structure to attain the extremely thick LC layers by using porous (polymethyl methacrylate) PMMA materials, which can be easily obtained using a solvent consisting of a mixture of ethanol/water and a little heating. In this work, we focus on Fresnel lens, which is an important quasi-optic device for MMW application, to introduce a tunable property by using LC materials. Here, we adopt the thin film deposition method to obtain a porous PMMA matrix with the aim of obtaining final composite structure based on the Fresnel substrate. First, the fundamental material properties of porous PMMA are investigated to control the microscopic porous structure. Then, the LC-MMW Fresnel lens substrate is prepared using a 3D printer, and the fundamental MMW focusing properties of the prototype composite Fresnel structure are investigated.

Structural properties of porous materials and powders used in different fields of science and technology

CERN Document Server

Volfkovich, Yury Mironovich; Bagotsky, Vladimir Sergeevich

2014-01-01

This book provides a comprehensive and concise description of most important aspects of experimental and theoretical investigations of porous materials and powders, with the use and application of these materials in different fields of science, technology, national economy and environment. It allows the reader to understand the basic regularities of heat and mass transfer and adsorption occurring in qualitatively different porous materials and products, and allows the reader to optimize the functional properties of porous and powdered products and materials. Written in an straightforward and transparent manner, this book is accessible to both experts and those without specialist knowledge, and it is further elucidated by drawings, schemes and photographs. Porous materials and powders with different pore sizes are used in many areas of industry, geology, agriculture and science. These areas include (i) a variety of devices and supplies; (ii) thermal insulation and building materials; (iii) oil-bearing geologic...

Obtaining of dense and highly porous ceramic materials from metallurgical slag

OpenAIRE

Fidancevska E.; Mangutova B.; Milosevski D.; Milosevski M.; Bossert J.

2003-01-01

Glass-ceramics in a dense and highly porous form can be obtained from metallurgical slag and waste glass of TV monitors. Using polyurethane foam as pore creator, a highly porous system with porosity of 65 ± 5 %, E-modulus and flexural strength of 8 ± 3 GPa and 13 ± 3.5 MPa respectively can be obtained. This porous material had durability (mass loss) of 0.03 % in 0.1 M HCl that is identical with the durability of a dense composite.

Development of vapor deposited silica sol-gel particles for use as a bioactive materials system.

Science.gov (United States)

Snyder, Katherine L; Holmes, Hallie R; VanWagner, Michael J; Hartman, Natalie J; Rajachar, Rupak M

2013-06-01

Silica-based sol-gel and bioglass materials are used in a variety of biomedical applications including the surface modification of orthopedic implants and tissue engineering scaffolds. In this work, a simple system for vapor depositing silica sol-gel nano- and micro-particles onto substrates using nebulizer technology has been developed and characterized. Particle morphology, size distribution, and degradation can easily be controlled through key formulation and manufacturing parameters including water:alkoxide molar ratio, pH, deposition time, and substrate character. These particles can be used as a means to rapidly modify substrate surface properties, including surface hydrophobicity (contact angle changes >15°) and roughness (RMS roughness changes of up to 300 nm), creating unique surface topography. Ions (calcium and phosphate) were successfully incorporated into particles, and induced apatitie-like mineral formation upon exposure to simulated body fluid Preosteoblasts (MC3T3) cultured with these particles showed up to twice the adhesivity within 48 h when compared to controls, potentially indicating an increase in cell proliferation, with the effect likely due to both the modified substrate properties as well as the release of silica ions. This novel method has the potential to be used with implants and tissue engineering materials to influence cell behavior including attachment, proliferation, and differentiation via cell-material interactions to promote osteogenesis. Copyright © 2012 Wiley Periodicals, Inc.

Morphology and properties of silica/novolac hybrid xerogels synthesized using sol–gel polymerization at solvent vapor-saturated atmosphere

International Nuclear Information System (INIS)

Seraji, Mohamad Mehdi; Seifi, Azadeh; Bahramian, Ahmad Reza

2015-01-01

Highlights: • Sol–gel polymerization in vapor of solvent saturated atmosphere is developed. • Highly porous novolac–silica hybrid xerogels are successfully synthesized. • Novolac–silica hybrid gel was dried in ambient condition with low shrinkage. • Required time for preparation of gel reduced from 5 days to about 5 h. • By incorporation of silica into the novolac xerogel structure, the pore size decreases. - Abstract: Highly porous novolac–silica hybrid xerogels were successfully synthesized via the novel method of sol–gel polymerization in solvent vapor-saturated atmosphere. This method removes the need for supercritical drying and yields the hybrid xerogels with reduced shrinkage in comparison with conventional sol–gel process. Tetraethoxysilane (TEOS) was used as the precursor of silica-based inorganic phase. The chemical and structural characterization of the prepared hybrid xerogels were performed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis, respectively. Thermal and mechanical properties of the hybrid samples were investigated by differential scanning calorimetry (DSC), and compressive strength analysis. The resultant hybrid xerogels show a nanostructured colloidal hybrid network with high porosity (above 80%) and low density (below 0.25 g cm −3 ). Si mapping images shows the good distribution of silica phase throughout the hybrid structure

Novel polymeric nanocomposites and porous materials prepared using organogels

International Nuclear Information System (INIS)

Lai, Wei-Chi; Tseng, Shen-Chen

2009-01-01

We propose a new method for preparing polymeric nanocomposites and porous materials using self-assembled templates formed by 1,3:2,4-dibenzylidene sorbitol (DBS) organogels. DBS is capable of self-assembling into a 3D nanofibrillar network at relatively low concentrations in some organic solvents to produce organogels. In this study, we induced the formation of such physical cross-linked networks in styrene. Subsequently, we polymerized the styrene in the presence of chemical cross-linkers, divinyl benzene (DVB), with different amounts of DBS using thermal-initiated polymerization. The resulting materials were transparent, homogeneous polystyrene (PS) nanocomposites with both physical and chemical cross-links. The porous polymeric materials were obtained by solvent extraction of the DBS nanofibrils from the PS. Brunauer-Emmett-Teller (BET) measurements show that the amounts of DBS and DVB influenced the specific surface area after the removal of the DBS fibrils.

Novel polymeric nanocomposites and porous materials prepared using organogels

Energy Technology Data Exchange (ETDEWEB)

Lai, Wei-Chi; Tseng, Shen-Chen, E-mail: wclai@mail.tku.edu.t [Department of Chemical and Materials Engineering, Tamkang University, 151 Ying-chuan Road, Tamsui, Taipei 25137, Taiwan (China)

2009-11-25

We propose a new method for preparing polymeric nanocomposites and porous materials using self-assembled templates formed by 1,3:2,4-dibenzylidene sorbitol (DBS) organogels. DBS is capable of self-assembling into a 3D nanofibrillar network at relatively low concentrations in some organic solvents to produce organogels. In this study, we induced the formation of such physical cross-linked networks in styrene. Subsequently, we polymerized the styrene in the presence of chemical cross-linkers, divinyl benzene (DVB), with different amounts of DBS using thermal-initiated polymerization. The resulting materials were transparent, homogeneous polystyrene (PS) nanocomposites with both physical and chemical cross-links. The porous polymeric materials were obtained by solvent extraction of the DBS nanofibrils from the PS. Brunauer-Emmett-Teller (BET) measurements show that the amounts of DBS and DVB influenced the specific surface area after the removal of the DBS fibrils.

Acid-base equilibria inside amine-functionalized mesoporous silica.

Science.gov (United States)

Yamaguchi, Akira; Namekawa, Manato; Kamijo, Toshio; Itoh, Tetsuji; Teramae, Norio

2011-04-15

Acid-base equilibria and effective proton concentration inside a silica mesopore modified with a trimethyl ammonium (TMAP) layer were studied by steady-state fluorescence experiments. The mesoporous silica with a dense TMAP layer (1.4 molecules/nm(2)) was prepared by a post grafting of N-trimethoxysilylpropyl-N,N,N-trimethylammonium at surfactant-templated mesoporous silica (diameter of silica framework =3.1 nm). The resulting TMAP-modified mesoporous silica strongly adsorbed of anionic fluorescence indicator dyes (8-hydroxypyrene-1,3,6-trisulfonate (pyranine), 8-aminopyrene-1,3,6-trisulfonate (APTS), 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid disulfuric acid (TPPS), 2-naphthol-3,6-disulfonate (2NT)) and fluorescence excitation spectra of these dyes within TMAP-modified mesoporous silica were measured by varying the solution pH. The fluorescence experiments revealed that the acid-base equilibrium reactions of all pH indicator dyes within the TMAP-modified silica mesopore were quite different from those in bulk water. From the analysis of the acid-base equilibrium of pyranine, the following relationships between solution pH (pH(bulk)) and the effective proton concentration inside the pore (pH(pore)) were obtained: (1) shift of pH(pore) was 1.8 (ΔpH(pore)=1.8) for the pH(bulk) change from 2.1 to 9.1 (ΔpH(bulk)=7.0); (2) pH(pore) was not simply proportional to pH(bulk); (3) the inside of the TMAP-modified silica mesopore was suggested to be in a weak acidic or neutral condition when pH(bulk) was changed from 2.0 to 9.1. Since these relationships between pH(bulk) and pH(pore) could explain the acid-base equilibria of other pH indicator dyes (APTS, TPPS, 2NT), these relationships were inferred to describe the effective proton concentration inside the TMAP-modified silica mesopore. © 2011 American Chemical Society