Synthesis Of Microporous Amorphous Silica From ...

Log InSign Up

• Log In
• Sign Up
• more
• • About
  • Press
  • Papers
  • Terms
  • Privacy
  • Copyright
  • We're Hiring!
  • Help Center
  • less

Outline

keyboard_arrow_downTitleAbstractKey TakeawaysIntroductionExperimental ProceduresResults and DiscussionSummaryReferencesAll TopicsChemistryMaterials Chemistrydownload

Download Free PDF

Download Free PDFSynthesis of microporous amorphous silica from perhydropolysilazane chemically modified with alcohol derivativesMOHD NAZRI BIN MOHD SOKRI

2015, Journal of the Ceramic Society of Japan

https://doi.org/10.2109/JCERSJ2.123.292visibility

…

description

6 pages

descriptionSee full PDFdownloadDownload PDF bookmarkSave to LibraryshareShareclose

Sign up for access to the world's latest research

Sign up for freearrow_forwardcheckGet notified about relevant paperscheckSave papers to use in your researchcheckJoin the discussion with peerscheckTrack your impact

Abstract

Perhydropolysilazane (PHPS) was chemical modified with alcohol derivative (ROH, R = CH 3 , i-C 3 H 7 , n-C 5 H 11 , n-C 10 H 21) at the silicon (Si) of PHPS/ROH molar ratio of 4/1. The alkoxy group-functionalized PHPS was converted into amorphous silica powders by curing at 270°C to promote oxidative crosslinking, followed by pyrolysis at 600°C in air to complete the polymer/amorphous silica conversion. Thermogravimetric analysis in air of the 270°C-crosslinked PHPS showed an approximately 18% weight gain at 200 to 500°C. This weight gain was suppressed consistently with the number of carbon atoms of the alkoxy groups introduced to PHPS. Upon heating to 600°C, the PHPS modified with n-C 5 H 11 OH showed a total weight loss of 12%, and further weight loss of 31% was observed for the PHPS modified with n-C 10 H 21 OH. The nitrogen sorption analysis revealed that micropore volume of the polymer-derived amorphous silica increased consistently with the weight loss during the pyrolysis up to 600°C, and the amorphous silica derived from the PHPS modified with n-C 10 H 21 OH exhibited the highest micropore volume. Further increase in the micropore volume was achieved by increasing the Si/n-C 10 H 21 OH molar ratio from 4/1 to 2/1. The micropore volume and specific surface area of the resulting amorphous silica powders were 0.193 cm 3 /g and 370 m 2 /g, respectively.

... Read more

Key takeaways

AI

1. The study synthesizes microporous amorphous silica from perhydropolysilazane (PHPS) modified with alcohol derivatives.
2. Curing PHPS at 270°C and pyrolyzing at 600°C achieves conversion to silica with substantial micropore volume.
3. Micropore volume reaches 0.193 cm³/g and specific surface area is 370 m²/g at a Si/n-C₁₀H₂₁OH ratio of 2/1.
4. Weight gain during pyrolysis correlates with the number of carbon atoms in alkoxy groups.
5. FT-IR and NMR confirm alkoxy groups replace reactive SiH and NH groups in PHPS.

Related papers

Synthesis of Microporous Silica SpheresRobert Flatt

Journal of Colloid and Interface Science, 2000

Spherical microporous silica powders with a narrow size distribution have been prepared by a precipitation technique involving the hydrolysis reaction of a silicon alkoxide in ethanol. The formation of the important microporosity has been investigated following two templating methods: the co-hydrolysis and condensation of two alkoxides, one of which presents porogen function, and the adsorption of an organic compound (glycerol) as the porogen. In both processes, the organic porogen is removed by a simple calcination. In the first method, the addition of more than 20 mol% of the porogen alkoxide, necessary for generating enough microporosity, disturbs completely the condensation process resulting in microporous, nonuniform silica particles of large size distribution. The best result has been obtained with the glycerol method where submicrometersized silica spheres with a very narrow size distribution and about 40 vol% porosity have been synthesized. The presence of glycerol during the synthesis considerably affects the precipitation mechanism, resulting in a larger mean particle size. The use of an aggregative growth model has successfully been employed to explain the effect of the porogen during particle formation. The precipitation mechanism of silica involves the aggregation between particles of similar size until a critical size is reached, resulting in a uniform particle size distribution. In the presence of glycerol, it has been shown that a second aggregative growth between still-nucleating primary particles and large particles occurred with increasing reaction time. This second aggregative growth appears at an intermediate stage of the precipitation process and is due to both the precipitation of smaller primary particles and the destabilization of the colloidal stability of the system. This explains why the final particle size reached in this system is larger compared to silica particles synthesized without glycerol and shows how glycerol is incorporated in the silica particles. The synthesis of silica microporous spheres of narrow size distribution, by varying particle size and porosity, should yield a wide range of aqueous silica slurries for particular chemical mechanical polishing applications. C 2000 Academic Press

downloadDownload free PDFView PDFchevron_rightAmorphous Micro and Nano Silica Extracted from Rice Husks and Obtained by Acidic Prehydrolysis and Calcination: Preparation Route and CharacterizationEduardo Roque Budemberg

The Great World of Nanotechnology Vol II

O conteúdo deste livro está licenciado sob uma Licença de Atribuição Creative Commons Atribuição-Não-Comercial NãoDerivativos 4.0 Internacional (CC BY-NC-ND 4.0). Direitos para esta edição cedidos à Editora Artemis pelos autores. Permitido o download da obra e o compartilhamento, desde que sejam atribuídos créditos aos autores, e sem a possibilidade de alterá-la de nenhuma forma ou utilizá-la para fins comercial. A responsabilidade pelo conteúdo dos artigos e seus dados, em sua forma, correção e confiabilidade é exclusiva dos autores. A Editora Artemis, em seu compromisso de manter e aperfeiçoar a qualidade e confiabilidade dos trabalhos que publica, conduz a avaliação cega pelos pares de todos manuscritos publicados, com base em critérios de neutralidade e imparcialidade acadêmica.

downloadDownload free PDFView PDFchevron_rightSynthesis and characterization of nanosized-silica gels formed under controlled conditionsNuchanaporn Pijarn

Powder Technology, 2010

Silica gel has been synthesized by the refluxing of rice husk ash with 1 M NaOH and subsequently adjusting the pH using 1 M H 2 SO 4. The high purity of the silica gel has been found to be dependent on: (i) reflux time, (ii) water loading by addition of boiling DI water to the silica gel prior to titration with 1 M H 2 SO 4 and (iii) rinse time on removal of impurities prior to drying. The surface area, pore size and volume of the silica gel were measured; XRD peaks of Na 2 SO 4 impurity were absent after rinsing N 4 times. FTIR spectra showed that all the silica gels made by different schedules had a similar functional composition. The advantages of the present synthesis route are (i) a cost reduction due to the absence of pre-treatment for the rice husks before calcination below 700°C, and (ii) the formation of a pure high surface area mesoporous amorphous silica gel.

downloadDownload free PDFView PDFchevron_rightSynthesis and Structure of Composites of Nanosize Silica Particles Modified with Glass MicrospheresVladimir Ogenko

Russian Journal of Applied Chemistry, 2005

A method for production of porous composites from pyrogenic silicas, whose surface is preliminarily modified with methyl and trimethyl siloxane groups, was developed. In order to diminish shrinkage, glass microspheres and organosilicon compounds were used as modifiers. The total porosity of the composites obtained was 0.28 30.55.

downloadDownload free PDFView PDFchevron_rightA Novel Method To Synthesize Amorphous Silica−Alumina Materials with Mesoporous Distribution without Using Templates and Pore-Regulating AgentsMingyuan He

Chemistry of Materials, 2002

In this study, a novel sol-gel method is used to synthesize amorphous silica-alumina materials with a narrow mesoporous distribution and various Si/Al molar ratios without using any templates and pore-regulating agents. During the preparation procedure, only inexpensive inorganic salts were used as raw materials, instead of expensive and harmful alkoxides. The precursor sol was dried at room temperature in a vacuum box kept at 60 mmHg until it began to form the gel. The results of a nitrogen sorption experiment indicate that the synthesized materials with different Si/Al molar ratios have similar mesoporous distributions (within 2-12 nm). Moreover, it was found that the material's pore size distribution remains at a similar value during the heat treatment from room temperature to 550°C. On the basis of the nitrogen sorption, TEM, and AFM characterization results, a formation mechanism of mesopores which accounts for the experimental data is also suggested. This suggested mechanism involves rearrangement of the primary particles during the drying process to form the precursors of the similarly sized mesopores. The synthesized materials were characterized by XRD, thermal analysis (TG/DTA), 27 Al and 29 Si MAS NMR spectroscopy, SEM, TEM, and AFM. The results of 27 Al and 29 Si MAS NMR indicate that the distribution of silicon and aluminum in the synthesized materials is more uniform and homogeneous than that in the mixed oxides prepared via the traditional sol-gel method even at high alumina contents. The type and density of the acid sites were studied using pyridine adsorption-desorption FTIR spectroscopy. It was shown that the acidity of the synthesized materials is higher than that of the silica-alumina materials prepared by conventional methods.

downloadDownload free PDFView PDFchevron_rightSynthesis and Microstucture of Silica ParticlesAnkita Sharma

Silica particle powder was prepared using tetraethylorthosilicate as silica source by taking different reaction time. The powder samples were characterized by transmission electron microscope (TEM) and X-ray powder diffraction (XRD). Mean particle size is estimated by sampling more than 50 particles from TEM images. The TEM measurements show that the average size of silica particles do not change during different reaction time.

downloadDownload free PDFView PDFchevron_rightPreparation of crystalline silica (quartz, cristobalite, and tridymite) and amorphous silica powder (one step)marwa nabil

Journal of Physics and Chemistry of Solids, 2018

Silica nanoparticles (SiO 2 NPs) have found applications in many advanced areas. In this study, we report a powder technology route as a low cost, simple and safe method for the fabrication of SiO 2 NPs. It is a promising method as it has high throughput (91.7%) for different applications. The SiO 2 NPs were prepared by an ultra-sonication technique and an alkali wet chemical etching process (one step), starting from commercial silicon powder. The main factors that affect the production of crystalline (quartz, cristobalite, and tridymite) and amorphous SiO 2 NPs from crystalline silicon are the etching solution (KOH) concentration and the sonication time. The particle size of the SiO 2 NPs is inversely related to the sonication time for 3 wt % KOH but directly proportional to the sonication time for 6 wt % KOH. The synthesized nanoparticles were systematically characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy and scanning electron microscopy.

downloadDownload free PDFView PDFchevron_rightPreparation of Nanometer Silica by Freeze-Drying Chemical Precipitation Methodxuehui rui

2018

Nanometer SiO2 with different sizes and shapes is synthesized by coprecipitation technique using sodium silicane as Si source, ammonium chloride as precipitant, ethanol as dispersant, CTAB as regulator. Nanometer SiO2 is obtained from the titration precipitation method and reverse titration precipitation method, respectively．Morphology size distribution and structure of SiO2 particles is characterized by laser particle size analyzer ,microscope and FTIR.The results show that the optimum condition of synthesizing nanometer SiO2 were as follows, the concentration of sodium silicane was 0.4 mol/L, volume ratio of ethanol to water was1:8,pH value was 8.5, concentration of CTAB was 6mmol/l.Spherical silica particles ranging from 3 to 6nm are prepared by the method of reverse titration precipitation and freeze-drying.

downloadDownload free PDFView PDFchevron_rightMesoporous silica obtained by polycondensation of octahydridooctasilsesquioxaneMirosław Handke

Journal of Materials Science, 2013

Mesoporous silica, due to its porosity and morphological features, have been considered a fascinating material for many technological applications. In this report, we describe the preparation of a structurally stable mesoporous silica material using octahydridooctasilsesquioxane (T 8 H ). The structure and properties of final samples were determined by XRD, FT-IR, and TEM methods. Structural analysis has shown that the siliceous material is amorphous but mesoporous. BET surface area, pore volumes, and pore size distribution were measured using nitrogen sorption methods-data were collected from the adsorption branch using BJH method for mesopores and t-plot method for micropores. It was found that the cage-type structure of T 8 H molecules and the process conditions determine the specific morphology of the cross-linked products. Completely inorganic, mesoporous silica of a narrow pore distribution was obtained. It was found that the materials have large surface area and pores in the meso range (2-5 nm). The amount of mesopores and the characteristic surface area of the prepared samples strongly depended on the reaction conditions.

downloadDownload free PDFView PDFchevron_rightChromatographic characterization of macroporous monolithic silica prepared via sol-gel processHiroyoshi Minakuchi, Kazuki Nakanishi

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2001

A continuous porous silica monolith prepared by the sol-gel process including phase separation was aged in a basic solvent making use of hydrolysis of urea to prepare extended mesopore structures for chromatographic applications. The dissolution-reprecipitation kinetics at the interfaces between wet gel skeletons and an external solvent affected the size and volume of pores formed within the skeletons. At above 200°C, the pore size attained the macropore dimensions (\50 nm). The results of chromatography indicate that the monolithic silica column with wide mesopore could reduce the separation time compared to the conventional column packed with 5 mm silica particle.

downloadDownload free PDFView PDFchevron_rightSee full PDFdownloadDownload PDF

Loading Preview

Sorry, preview is currently unavailable. You can download the paper by clicking the button above.

References (18)

1. R. W. Rice, Am. Ceram. Soc. Bull., 62, 889892 (1983).
2. K. J. Wynne and R. W. Rice, Annu. Rev. Mater. Sci., 14, 297 334 (1984).
3. R. Riedel and W. Dressler, Ceram. Int., 22, 233239 (1996).
4. D. Seyferth, C. Strohmann, N. R. Dando and A. Perrotta, J. Chem. Mater., 7, 20582066 (1995).
5. E. Kroke, Y.-L. Li, C. Konetschny, E. Lecomte, C. Fasel and R. Riedel, Mater. Sci. Eng., R, 26, 97199 (2000).
6. O. Funayama, M. Arai, Y. Tashiro, H. Aoki, T. Suzuki, K. Tamura, H. Kaya, H. Nishii and T. Isoda, J. Ceram. Soc. Japan, 98, 104107 (1990).
7. Funayama, T. Kato, Y. Tashiro and T. Isoda, J. Am. Ceram. Soc., 76, 717723 (1993).
8. O. Funayama, Y. Tashiro, T. Aoki and T. Isoda, J. Ceram. Soc. Japan, 102, 908912 (1994).
9. Y. Iwamoto, K. Kikuta and S. Hirano, J. Mater. Res., 13, 353 361 (1998).
10. Y. Iwamoto, K. Kikuta and S. Hirano, J. Ceram. Soc. Japan, 108, 350356 (2000).
11. T. Kubo and H. Kozuka, J. Ceram. Soc. Japan, 114, 517523 (2006).
12. Y. Iwamoto, K. Sato, T. Kato, T. Inada and Y. Kubo, J. Eur. Ceram. Soc., 25, 257264 (2005).
13. Y. Iwamoto, J. Ceram. Soc. Japan, 115, 947954 (2007).
14. D. F. Shiver and M. A. Drezdzon, "The manipulation of air sensitive compounds", 2nd Edition, John Wiley & Sons, Inc. (1986) pp. 3044.
15. A. Saito and H. C. Foley, AIChE J., 37, 429436 (1991).
16. P. Barrett, L. G. Joyner and P. H. Halenda, J. Am. Chem. Soc., 73, 373380 (1951).
17. D. Seyferth, G. Wiseman and C. Prud'homme, J. Am. Ceram. Soc., 66, C-13C-14 (1983).
18. R. M. Silverstein, G. C. Bassler and T. C. Morrill, "Spectro- metric Identification of Organic Compounds", 5th Edition, John Wiley & Sons, Inc. (1991).

View morearrow_downward

Related papers

Synthesis and Characterization of Large Specific Surface Area Nanostructured Amorphous Silica Materials Using a modification of the Stober-Fink-Bohn method modified, silicas of specific surface area up to 1,600 m2/g were syntehsizedRolando Roque-Malherbe

Journal of Nanoscience and Nanotechnology, 2006

Large specific surface area materials attract wide attention because of their applications in adsorption, catalysis, and nanotechnology. In the present study, we describe the synthesis and characterization of nanostructured amorphous silica materials. These materials were obtained by means of a modification of the Stobe-Fink-Bohn (SFB) method. The morphology and essential features of the synthesized materials have been studied using an automated surface area and pore size analyzer and scanning electron microscopy. The existence of a micro/mesoporous structure in the obtained materials has been established. It was also found that the obtained particle packing materials show large specific surface area up to 1,600 m2/g. (To our best knowledge, there is no any reported amorphous silica material with such a higher specific surface area.) The obtained materials could be useful in the manufacture of adsorbents, catalyst supports, and other nanotechnological applications.

downloadDownload free PDFView PDFchevron_rightSol–Gel Synthesis of Microporous Amorphous Silica from Purely Inorganic Precursorsmiguel gregorkiewitz

Journal of Colloid and Interface Science, 1997

the microporous material is deposited as a thin layer on the Aqueous sodium silicate solutions and hydrochloric acid were top of a porous support which consists generally of a similar used to prepare silica gels without any additives. In order to estabmaterial with a coarser pore structure. lish the optimum conditions for the preparation of microporous Amorphous silica, which can be obtained with one of the and monodisperse gels, the sol-gel reaction has been studied as highest known degrees of dispersion (700 m 2 /g, (1)), is a a function of pH, concentration of silicate, time, and temperature. promising candidate to be used as a microporous top layer. From 29 Si NMR spectroscopy it was found that polycondensation First studies in this direction have recently been reported sets on immediately after mixing the reagents, with a continuous and show that a silica top layer could be formed either by increase of the fraction of 4-connected silicate tetrahedra (Q 4) at deposition from the gaseous phase (2-4) or by sol-gel the expense of Q 1 and Q 2. Polycondensation continues beyond the gelation point for 1 £ pH £ 7, but not for 7 £ pH £ 10. Two techniques, the latter using either organic (5, 6) or inorganic mechanisms were also observed for the gelation kinetics which is (7-9) precursors for the polycondensation. However, the about second order with respect to [Si] for pH £ 7, whereas for resulting membranes had so far a poor definition with regard pH ú 7, the order increases rapidly with pH. Gels formed at pH to cracks, thickness, and pore size distribution, and almost ú 7 had an electrostatic nature and redissolved in water, whereas nothing is known about their temperature resistance. In the for pH £ 7, gelation was irreversible as expected for a gel where sol-gel techniques, these problems are obviously related individual colloid particles are linked by chemical (GSi{O{ to organic compounds (unavoidably present in the case of SiG) bonds. From nitrogen adsorption, it is found that the pore organosiloxane precursors, and so far always employed as size depends mainly upon pH, the finest pores being obtained for additives in the case of inorganic precursors) which can pH 2-3 (BET surface area 650-700 m 2 /g, porosity 35%, pore be expected to introduce important structural uncertainties radius 5-11 Å). ᭧ 1997 Academic Press during the drying and eventual calcination of the gel.

downloadDownload free PDFView PDFchevron_rightEffects of process variable on synthesis and characterization of amorphous silica nanoparticles using sodium silicate solutions as precursor by sol–gel methodSEGUN M ABEGUNDE

Nano-Structures & Nano-Objects

The recent rapid urban growth has resulted into high demand for virgin materials thus causing more accumulation of solid wastes (urban mines). As a result, efforts are now geared towards urban mining approach based on re-using and recycling in order to ensure sustainability and environmental protection. In this regard, the present work synthesized pure amorphous silica nanoparticles using sodium silicate solutions produced from recycled glass powder under varying process parameter. In this work, the process variable used was NaOH concentration (3.0, 4.0 and 5.0 mol/L). 20 g of glass powder was reacted with 160 ml of 3.0, 4.0 and 5.0 mol/L NaOH solutions respectively in a 250 ml Erlenmeyer flask placed on a heating plate connected with a reflux condenser to maintain the volume of the mixture and stirred continuously at a speed of 60 rpm for 180 mins under reaction temperature of 200 • C. The solutions were filtered to obtain a sodium silicate solution (SSLS) samples. Hydrochloric acid (3 mol/L) was added gently into the respective SSLS while continuously stirred to obtain a white gel mixture. The gel was left to age for 18 h at room temperature (25 • C), then filtered and washed repeatedly using deionized water until a neutral pH is reached; then dried in an electric-powered oven at 80 • C for 12 h to obtain highly pure white silica powder. The results showed that the nano-size range between 0.025 µm (25 nm) to 0.067 µm (67 nm).

downloadDownload free PDFView PDFchevron_rightA facile synthesis of amorphous silica nanoparticles by simple thermal treatment routeAli M U S T A P H A Alibe

2016

A facile thermal treatment route was for the first time used to successfully synthesize amorphous silica nanoparticles. Various techniques were employed to study the structural, phase and elemental composition of the material at different calcination temperature between 500-750oC. The XRD analysis confirms the formation silica to be in an amorphous state and further revealed that the material remained in amorphous state even when calcined at 750oC. The FT-IR spectra shows that the calcination process has enable the removal of organic source from PVP and formation of amorphous silica nanoparticles. The average particle size of the material estimated from the TEM images shows that the particle were <10nm. The optical absorbance exhibited in the UV region reveals amorphous silica nanoparticles possess a wide band gap ranging from 3.803-4.126eV calcined between 500 to 750oC. The EDX analysis has confirmed the presence of Si and O as the only elements in the material formed, which imp...

downloadDownload free PDFView PDFchevron_rightHighly pure amorphous silica nano-disks from rice strawYou-Lo Hsieh

Powder Technology, 2012

White ash, containing majority of SiO 2 with trace amounts of Al 2 O 3 , CaO, MgO, K 2 O, P 2 O 5 , etc., was successfully produced by heating rice straw at 10°C/min and holding at 250, 325 and 575°C to facilitate decomposition and gasification of the organics while avoiding auto-ignition. Highly pure amorphous silica was derived from the resultant rice straw ash by a base dissolution and acid precipitation process at a 90.8% yield (or 11.47% from rice straw). The SiO 2 chemical composition was confirmed by EDS and FTIR and the amorphous nature by XRD. Freeze-drying of silica gel produced mesoporous silica powders with a 5.8 nm average pore size (2 to 22 nm pore size distribution) and very high specific surface (509.5 m 2 /g BET and 637.0 m 2 /g BJH) and pore volume (0.925 cm 3 /g). These silica powders were dispersible in water and shown to consist of nano-disks with an average 172 nm diameter and 3.09 nm thickness as measured by TEM and AFM, respectively.

downloadDownload free PDFView PDFchevron_rightAmorphous and nanostructured silica and aluminosilicate spray-dried microspheresFlaviu Turcu, B. Frentiu, Oana Ponta

Journal of Molecular Structure, 2011

Amorphous silica and aluminosilicate microspheres with diameters in the 0.1-20 lm range were produced by spray drying method. SEM, TEM and AFM images showed the spherical shape of the obtained particles. Based on thermal analysis data, several heat treatments have been applied on the as-prepared samples in order to check the amorphous state stability of the microspheres and to develop nanosized crystalline phases. As-prepared microspheres remain amorphous up to 1400°C. By calcination at 1400°C, cristobalite type nanocrystals are developed on silica sample, while in aluminosilicate sample first are developed mullite type nanocrystals and only after prolonged treatment are developed also cristobalite type nanocrystals. 29 Si and 27 Al MAS NMR results show that the local order around aluminum and silicon atoms strongly depend on the thermal history of the microspheres.

downloadDownload free PDFView PDFchevron_rightSol-gel synthesis of amorphous SiOC nanoparticles from BS290 silicone precursorBehzad Niroumand

Ceramics International, 2017

In this study, a facile method was employed for synthesis of amorphous ceramic nanoparticles from the commercially available BS290 polymer. The polymer precursor was found to be a silane compound using gas chromatography technique. The polymer was processed by sol-gel and pyrolysis methods and the product was characterized by FESEM, BET, FTIR, XRD and TG techniques. The synthesized particles were found to be amorphous silicon oxycarbide (SiOC). Particles of the ammonia derived powder were nano-size and the surface area of the powder was 191 m 2 /g. It was found that the synthesized powders in the base medium were finer (nano-size) as compared to that produced in the ethanol medium.

downloadDownload free PDFView PDFchevron_rightStructure and Properties of Amorphous Silica and Its Related Materials: Recent Developments and Future DirectionsTakashi Uchino

Journal of the Ceramic Society of Japan, 2005

Amorphous silica and related silicabased materials have been widely developed in optoelectronics and optical telecommunications technology. Despite comprehensive research for over the decades, the subject of amorphous silica continues to excite the interest of researchers in the field of chemistry, physics, and geology. This paper reviews some of the recent experimental and theoretical developments in the field, including mediumrange ord er, structural changes under pressures, vibrational and thermodynamic anomalies, and photoluminescence properties.

downloadDownload free PDFView PDFchevron_rightSynthesis of monolithic mesoporous silica with a regular structure (SBA-15) and macropores in neutral aqueous solution at room temperatureLi-Jen Chen

Colloid Journal, 2013

A monolithic biporous silica material of SBA 15 type has been synthesized by the sol gel method in a neutral aqueous solution in the presence of glycerol without heating. Synthesis has been performed using P123 triblock copolymer and a novel silica precursor containing ethylene glycol residues.

downloadDownload free PDFView PDFchevron_rightPorous Silica Matrix Obtained from Pyrex Glass by Hydrothermal Treatment: Characterization and Nature of the PorosityMarcus Giotto

Journal of The American Ceramic Society, 2003

A novel porous silica matrix has been prepared from Pyrex glass, using hydrothermal treatment under saturated-steam condition. This process makes it possible to obtain, in one step, a silica support formed of a homogeneously distributed and interconnected macropore microstructure. The new matrix contains silanol groups that can be used in reactions of surface modification to provide a hybrid material and a selective macrofiltration membrane, and also it can improve chemical inertness. The porous matrix is noncrystalline as obtained and, after thermal treatment at temperatures higher than 950°C, exhibits an X-ray pattern characteristic of α-cristobalite and low volume contraction. The present samples were characterized by scanning electron microscopy, mercury intrusion porosimetry, nitrogen adsorption-desorption isotherms, infrared spectroscopy, X-ray powder diffractometry, atomic absorption, and high-resolution solid-state nuclear magnetic resonance. The results present a new way of producing a macroporous silica matrix.

downloadDownload free PDFView PDFchevron_rightkeyboard_arrow_downView more papers

Related topics

Materials EngineeringaddFollow

Mechanical EngineeringaddFollow

Ceramics (Art History)addFollow

Porous MaterialsaddFollow

Porous ceramicsaddFollow

Microporous MaterialsaddFollow

Cited by

Tailored Oxidation Barrier Coatings for Mo-Hf-B and Mo-Zr-B AlloysIryna Smokovych

Materials, 2019

The cyclic oxidation response of Mo-14Hf-23B and Mo-14.8Zr-26B (compositions in at. %) was investigated in air at 800 °C, which is a critical temperature for Mo-based alloys because of the pesting phenomenon. Rapid oxidation was observed for the unprotected samples, and an oxidation protection coating was developed based on a preceramic polymer with silicon and boron as particulate fillers. Cyclic oxidation tests of the coated samples showed excellent oxidation protection: no Mo, Hf or Zr oxides were found after testing and a small mass gain in the initial stage of oxidation indicated the formation of a glassy protection layer on the alloys surfaces after exposure to air at 800 °C.

downloadDownload free PDFView PDFchevron_rightNew‐Type Oxidation Barrier Coatings for Titanium AlloysIryna Smokovych

Advanced Engineering Materials, 2020

In the present study, the complete mitogenome of Cryptococcus sp. were sequenced and assembled. The complete mitogenome of Cryptococcus sp. was composed of circular DNA molecules, with a total length of 30,029 bp. The base composition of this mitochondrial genome is as follows: A (31.94%), T (34.89%), G (15.97%), and C (17.21%). The mitogenome contains 20 protein-coding genes, 2 ribosomal RNA genes (rRNA), and 22 transfer RNA (tRNA) genes. Phylogenetic analysis showed that the mitogenome of the Cryptococcus sp. exhibited a closest relationship with Cryptococcus gattii.

downloadDownload free PDFView PDFchevron_rightFormation of Micro and Mesoporous Amorphous Silica-Based Materials from Single Source PrecursorsYuji Iwamoto

Inorganics, 2016

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 N 2 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.

downloadDownload free PDFView PDFchevron_right

• Explore
• Papers
• Topics

• Features
• Mentions
• Analytics
• PDF Packages
• Advanced Search
• Search Alerts

• Journals
• Academia.edu Journals
• My submissions
• Reviewer Hub
• Why publish with us
• Testimonials

• Company
• About
• Careers
• Press
• Help Center
• Terms
• Privacy
• Copyright
• Content Policy

580 California St., Suite 400San Francisco, CA, 94104© 2026 Academia. All rights reserved