Synthesis of SiC Based Fibers with Continuous Pore Structure by Melt- Spinning and Controlled Curing Method

Silicon carbide (SiC) based fibers with continuous pore structures were synthesized by the precursor method using a polycarbosilane (PCS) and polymethylhydrosiloxane (PMHS) polymer blends. The pore formation process can be explained by hydrogen gas dissolution in the polymer melt and desaturation process of the dissolved gas during the fiber spinning. We investigated the effect of PMHS additives with different chemical and physical natures on the obtained pore structures, because PMHS decomposition process played a role of hydrogen gas source. The individual polymer melts were characterized by viscosity measurement, gas chromatograph analysis and thermogravimetric (TG) analysis in order to obtain details of pore structure control.

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Effect of Pozzolanic Additive on Pore Structure of Cement Mortar

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.923.89 ◽

2014 ◽

Vol 923 ◽

pp. 89-92 ◽

Cited By ~ 2

Author(s):

Radka Pernicová ◽

Daniel Dobiáš

Keyword(s):

Pore Structure ◽

Cement Mortar ◽

Positive Impact ◽

Sodium Sulphate ◽

Sulphate Solution ◽

Clay Brick ◽

Clay Bricks ◽

Pore Structures ◽

The Individual

In this paper are explored the changes of pore structures of mortar with pozzolanic admixture exposed to aggressive environments, namely 5% wt. sodium sulphate solution. Influence of non-flowing sulphate solution on the test specimens were determined in dependence on the different type of cement and used minced clay brick as pozzolanic admixture. Attention is also paid to the properties of the individual components of the mortar. From the results obtained follows that the additive of minced clay bricks has positive impact on the sulphate resistance.

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Effect of Non-equilibrium Pulsed Ejection of Si Species into Background Gas on the Formation of Si Nanocrystallite and Nanocrystal-film

MRS Proceedings ◽

10.1557/opl.2011.87 ◽

2011 ◽

Vol 1305 ◽

Author(s):

Ikurou Umezu ◽

Shunto Okubo ◽

Akira Sugimura

Keyword(s):

Laser Ablation ◽

Film Growth ◽

Pulsed Laser ◽

Pulsed Laser Ablation ◽

Hydrogen Gas ◽

Gas Pressure ◽

Spatial Confinement ◽

The Individual ◽

Background Gas ◽

Non Equilibrium

ABSTRACTThe Si nanocrystal-films are prepared by pulsed laser ablation of Si target in a mixture of helium and hydrogen gas. The total gas pressure and hydrogen partial gas pressure were varied to control structure of nanocrystal-film. The surface of Si nanocrystallite was hydrogenated and degree of hydrogenation increased with increasing hydrogen partial gas pressure. The aggregate structure of nanocrystal-film depended on both the total gas pressure and the hydrogen partial gas pressure. The former and the latter alter spatial confinement of Si species during deposition and the surface hydrogenation of individual nanocrystal, respectively. Spatial confinement increases probability of collision between nanocrystals in the plume. While, surface hydrogenation prevents coalescence of nanocrystals. The individual or aggregated nanocrystals formed in the plume reach the substrate and the nanocrystal-film is deposited on the substrate. The non-equilibrium growth processes during pulsed laser ablation are essential for the formation of the surface structure and the subsequent nanocrystal-film growth. Our results indicate that the structure of nanocrystal-film depends on the probabilities of collision and coalescence between nanocrystals in the plume. These probabilities can be varied by controlling the total gas pressure and the hydrogen partial gas pressure.

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Deformation of Ordered Mesoporous Silica Structures on Exposure to High Temperatures

Journal of Nanomaterials ◽

10.1155/2014/754076 ◽

2014 ◽

Vol 2014 ◽

pp. 1-13 ◽

Cited By ~ 5

Author(s):

John B. Lowe ◽

Richard T. Baker

Keyword(s):

Mesoporous Silica ◽

Pore Structure ◽

High Temperatures ◽

Elevated Temperatures ◽

Ordered Mesoporous Silica ◽

Large Cage ◽

Pore Structures ◽

Ordered Mesoporous ◽

Pore Size Distributions ◽

Wide Range

Ordered mesoporous silica materials are of interest for a wide range of applications. In many of these, elevated temperatures are used either in the preparation of the material or during its use. Therefore, an understanding of the effect of high temperature treatments on these materials is desirable. In this work, a detailed structural study is performed on silicas with three representative pore structures: a 2-D hexagonal pore arrangement (SBA-15), a continuous 3D cubic bimodal pore structure (KIT-6), and a 3D large cage pore structure (FDU-12). Each silica is studied as prepared and after treatment at a series of temperatures between 300 and 900°C. Pore structures are imaged using Transmission Electron Microscopy. This technique is used in conjunction with Small-Angle X-ray Diffraction, gas physisorption, and29Si solid state Nuclear Magnetic Resonance. Using these techniques, the pore size distributions, the unit cell dimensions of the mesoporous structures, and the relative occupancy of the distinct chemical environments of Si within them are cross correlated for the three silicas and their evolution with treatment temperature is elucidated. The physical and chemical properties before, during, and after collapse of these structures at high temperatures are described as are the differences in behavior between the three silica structures.

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Pore structure control in Ni/SiO2 catalysts with both macropores and mesopores

Microporous and Mesoporous Materials ◽

10.1016/j.micromeso.2006.08.027 ◽

2007 ◽

Vol 98 (1-3) ◽

pp. 107-114 ◽

Cited By ~ 17

Author(s):

Ryoji Takahashi ◽

Satoshi Sato ◽

Satoshi Tomiyama ◽

Tomoya Ohashi ◽

Norifumi Nakamura

Keyword(s):

Pore Structure ◽

Structure Control ◽

Pore Structure Control

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Characterization of Micro-Pore Structure in Novel Cement Matrices

MRS Proceedings ◽

10.1557/opl.2014.908 ◽

2014 ◽

Vol 1712 ◽

Author(s):

Seyoon Yoon ◽

Isabel Galan ◽

Kemal Celik ◽

Fredrik P. Glasser ◽

Mohammed S. Imbabi

Keyword(s):

Portland Cement ◽

Pore Structure ◽

Engineering Properties ◽

Calcium Sulfoaluminate ◽

Pore Structures ◽

Porosity And Permeability ◽

Experimental Protocols ◽

Novel Processing ◽

Main Component

ABSTRACTCalcium sulfoaluminate (CSA) cements are being developed using a novel processing method having as its objective lowering specific CO2 emissions by ∼50% relative to a Portland cement benchmark. We need to be able to measure the properties of the products. Porosity and permeability measurements help define the engineering properties but their quantification is influenced by the choice of experimental protocols. In the present study we used ordinary Portland cement (PC) paste as a benchmark and hydrated ye’elimite, which is a main component of CSA cements, to understand its pore structure. We report on the use of synchrotron-sourced radiation for µCT (Computerized Tomography) and 3D image re-construction of the internal micro-pore structure of PC and ye’elimite-gypsum pastes. As a comparison, porosity and permeability measurements were traditionally obtained using Mercury Intrusion Porosimetry (MIP). The Mori-Tanaka method and the polynomial statistical model were used to analyze the effects of different 3-D micro-pore structures on mechanical properties. The results show that e micro-pore structures differ considerably between PC and ye’elimite pastes and their bulk modulus is significantly affected by the shapes of their micro-pore structures.

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Computer simulation of steady polymer melt spinning

Polymer Engineering & Science ◽

10.1002/pen.760211307 ◽

1981 ◽

Vol 21 (13) ◽

pp. 844-853 ◽

Cited By ~ 47

Author(s):

Del Kenneth Gagon ◽

Morton M. Denn

Keyword(s):

Computer Simulation ◽

Melt Spinning ◽

Polymer Melt

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Identification of Oil Reservoir Meeting Atypical Archie Phenomenon

The Open Petroleum Engineering Journal ◽

10.2174/1874834101508010354 ◽

2015 ◽

Vol 8 (1) ◽

pp. 354-357

Author(s):

Shixiong Yuan ◽

Haimin Guo ◽

Yu Ding ◽

Rui Deng

Keyword(s):

Pore Structure ◽

Water Saturation ◽

Saturation Index ◽

Oil Reservoir ◽

Formation Water ◽

Core Data ◽

Hydrocarbon Reservoir ◽

Pore Structures ◽

Structure Index ◽

Very High

According to core data, this paper studies variation of resistivity in different pore structures and wettability conditions. The results show that with the increase of pore structure index m, the resistivity will increase significantly when the saturation is constant. Similarly, with increasing saturation index n, the resistivity will also increase even with the same saturation. With fixed m and n, the calculated formation water saturation will be very high, resulting in hydrocarbon reservoir being ignored. This variation characteristic is significant for the identification of hidden reservoir with atypical Archie formula.

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