The thermal conductivity of polymethylsilsesquioxane aerogels and xerogels with varied pore sizes for practical application as thermal superinsulators

2014 ◽  
Vol 2 (18) ◽  
pp. 6525-6531 ◽  
Author(s):  
G. Hayase ◽  
K. Kugimiya ◽  
M. Ogawa ◽  
Y. Kodera ◽  
K. Kanamori ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Pore Size ◽  
Gas Pressure ◽  
Practical Application ◽  
Practical Applications ◽  
Pore Sizes ◽  
The Relationship

The relationship between the thermal conductivity, gas pressure and pore size of polymethylsilsesquioxane aerogels and xerogels has been investigated for practical applications.

scholarly journals Mineral compositional controls on the porosity of black shales from the Wufeng and Longmaxi Formations (Southern Sichuan Basin and its surroundings) and insights into shale diagenesis

2018 ◽  
Vol 36 (4) ◽  
pp. 665-685
Author(s):  
Mei Han ◽  
Chao Han ◽  
Zuozhen Han ◽  
Zhigang Song ◽  
Wenjian Zhong ◽  
...  
Keyword(s):  
Organic Matter ◽  
Pore Size ◽  
Pore Volume ◽  
Total Pore Volume ◽  
Black Shales ◽  
Carbonate Content ◽  
Pore Sizes ◽  
Pore Size Distributions ◽  
Shale Composition ◽  
The Relationship

The effects of brittle minerals in shale diagenesis on shale pores remain controversial and it is difficult to quantify directly. However, the relationship between brittle minerals and shale pores could provide indirect guidance regarding diagenesis processes in post-mature marine shales. In this study, the pore size distribution was determined, and the relationship between pore volume and shale composition was examined in shale samples with different total organic carbon contents from the Wufeng and Longmaxi Formations, with the objective of distinguishing pore size ranges in organic matter and inorganic minerals, respectively, and studying shale diagenesis. The samples of the Wufeng and Longmaxi shales are composed of clay minerals, calcite, dolomite, quartz, feldspar, and some minor components. The pore size distributions, which were determined using nitrogen adsorption isotherm analysis of shale and kerogen, show similar trends for pore sizes less than approx. 6.5 nm but different trends for larger pore sizes. Mercury injection saturation shows that macropores account for 14.4–22% of the total pore volume. Based on a series of crossplots describing the relationships between shale composition and pore volume or porosity associated with different pore sizes as well as on scanning electron microscopy observations, organic matter pores were found to comprise most of the micro-mesopores (pore diameters < 6.5 nm). Organic matter pores and intraparticle pores associated with carbonate constitute the majority of mesopores (pore diameters 6.5–50 nm). Finally, interparticle pores associated with quartz comprise the majority of the macropores. The mesopores associated with carbonate were formed by dissolution during diagenesis, whereas the macropores associated with quartz are the remainders of the original interparticle pores. Mesopore volumes increase with increasing carbonate content while macropore volumes decrease due to the ‘pore size controlled solubility’ effect, which causes dissolved calcium carbonate to precipitate in larger macropores.

scholarly journals Thermal conductivity analysis of a new sub-micron sized polystyrene foam

2020 ◽  
pp. 0021955X2094310
Author(s):  
FA Almeida ◽  
H Beyrichen ◽  
N Dodamani ◽  
R Caps ◽  
A Müller ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Conductivity ◽  
Pore Structure ◽  
Gas Pressure ◽  
Polystyrene Foam ◽  
Influence Of Temperature ◽  
Pore Sizes ◽  
Vacuum Insulation ◽  
First Results ◽  
Thermal Conductivity Λ

New polystyrene (PS) foams with submicron pore sizes and open pore structure are introduced as potential cores for vacuum insulation panels (VIPs). Measurements of the thermal conductivity λ of the air-filled and evacuated PS foams, the influence of temperature T, opacifiers as well as gas pressure p on the thermal conductivity λ are presented. First results of the foam microstructures, as visualized by electron microscopy, confirm that pore sizes below 1 µm can be achieved. Thermal conductivity values of advanced samples in vacuum of about 7 mW/(m·K) were measured.

scholarly journals Utilization of Air Permeability in Predicting the Thermal Conductivity

2004 ◽  
Vol os-13 (2) ◽  
pp. 1558925004os-13
Author(s):  
Pamela Banks-Lee ◽  
Massoud Mohammadi ◽  
Parviz Ghadimi
Keyword(s):  
Thermal Conductivity ◽  
Linear Regression ◽  
Pore Size ◽  
Effective Thermal Conductivity ◽  
Regression Models ◽  
Temperature Drop ◽  
Air Permeability ◽  
Linear Regression Models ◽  
Fabric Weight ◽  
The Relationship

General linear regression models were used to determine the relationship between thermal conductivity and specific air permeability of 48 heterogeneous, needlepunched, nonwoven samples that were made from ceramic and glass webs. Parameters analyzed included number of needle barbs, fabric weight, thickness, and porosity. Other factors considered were fabric layering structure, temperature drop across the fabric and specific air permeability. Of the linear regression models examined, three models were found to be significant at greater than 95% confidence. These models had r2 values of greater than 97%. Factors that proved to be greater than 95% significant in predicting the effective thermal conductivity of the samples tested were fabric thickness and weight, fabric porosity, fabric mean pore size, and specific air permeability.

Pore Size and Air Permeability of Four Nonwoven Fabrics

2000 ◽  
Vol os-9 (2) ◽  
pp. 1558925000OS-90 ◽  
Author(s):  
Helen H. Epps ◽  
Karen K. Leonas
Keyword(s):  
Pore Size ◽  
Air Permeability ◽  
Mean Flow ◽  
Pore Sizes ◽  
Nonwoven Fabrics ◽  
Maximum Pore Size ◽  
Highly Correlated ◽  
Fabric Weight ◽  
The Relationship

The relationship between pore size and air permeability in two spunlaced fabrics and two spunbonded/meltblown/spunbonded (SMS) fabrics were investigated. Minimum, maximum and mean flow pore sizes were determined using liquid porosimetry. The influence of fabric weight and thickness on air permeability and pore sizes was also evaluated. For the spunlaced fabrics, air permeability was most highly correlated with mean flow pore size, while there was a significant correlation between air permeability and maximum pore size for the SMS fabrics. Liquid porosimetry is a useful technique in assessing pore sizes of nonwoven fabrics and can also aid in understanding the mechanism of air permeability.

The Effects of Density on Thermal Conductivity of Al2O3 Fiber Composite Papers

2012 ◽  
Vol 512-515 ◽  
pp. 543-546
Author(s):  
Shi Chao Zhang ◽  
Yu Feng Chen ◽  
Xing Shi ◽  
Wei Wu ◽  
Hao Ran Sun ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Pore Size ◽  
Fiber Composite ◽  
Pressure Filtration ◽  
Optimum Density ◽  
Al2o3 Fiber ◽  
The Relationship ◽  
Thermal Conductivity Λ ◽  
Thermal Conductivities ◽  
Effects Of Density

In this study, Al2O3 fiber composite papers with a certain strength and flexibility were prepared by pressure filtration. Microstructure and pore size of the composite papers with different density were investigated and thermal conductivities were measured by plane table thermo-conductivity meter at 600°C to 1200°C. Then the relationship between density ρ and thermal conductivity λ was studied, and the optimum density of Al2O3 fiber composite papers at different temperature was determined.

Fabrication and Thermal Conductivity Characterization of Polyetherimide Nanofoam

2012 ◽  
Author(s):  
Sriharsha S. Sundarram ◽  
Wei Jiang ◽  
Wei Li
Keyword(s):  
Thermal Conductivity ◽  
Pore Size ◽  
Effective Thermal Conductivity ◽  
Saturation Pressure ◽  
Effective Porosity ◽  
Analytical Models ◽  
Pore Sizes ◽  
Foaming Process ◽  
The Individual ◽  
Foaming Temperature

A number of analytical models exist to predict the thermal conductivity of foams; however, they do not consider the effect of pore size on the effective thermal conductivity. It is speculated that foams with smaller pore sizes would have much lower thermal conductivity owing to the Knudsen effect. This study aims at fabricating polymer nanofoams with pore sizes on the level of nanometers and to characterize their thermal conductivity. Polyetherimide (PEI) foams were fabricated using solid state foaming. Process parameters such as saturation pressure and duration, desorption time and foaming temperature were varied to obtain foams with pore sizes ranging from a few hundred nanometers to two microns. The microstructures of the samples were characterized using scanning electron microscopy. Throughout the cross section of the foams, there exist regions with varying pore size and porosity. The effective porosity and thermal conductivity of the individual regions were determined based on a series model for effective thermal conductivity. It is confirmed that as the pore size is reduced while maintaining a fixed porosity, the thermal conductivity also decreases.

An Experimental Investigation on Thermal Conductivity and Viscosity of Graphene doped CNTs /TiO2 Nanofluid

2020 ◽  
Vol 17 (3) ◽  
Author(s):  
A.M. Zetty Akhtar ◽  
M.M. Rahman ◽  
K. Kadirgama ◽  
M.A. Maleque
Keyword(s):  
Thermal Conductivity ◽  
Zeta Potential ◽  
Base Fluid ◽  
Minimum Quantity Lubrication ◽  
Cutting Fluid ◽  
Cutting Zone ◽  
Observation Method ◽  
The Stability ◽  
The Relationship ◽  
Zeta Potential Analysis

This paper presents the findings of the stability, thermal conductivity and viscosity of CNTs (doped with 10 wt% graphene)- TiO2 hybrid nanofluids under various concentrations. While the usage of cutting fluid in machining operation is necessary for removing the heat generated at the cutting zone, the excessive use of it could lead to environmental and health issue to the operators. Therefore, the minimum quantity lubrication (MQL) to replace the conventional flooding was introduced. The MQL method minimises the usage of cutting fluid as a step to achieve a cleaner environment and sustainable machining. However, the low thermal conductivity of the base fluid in the MQL system caused the insufficient removal of heat generated in the cutting zone. Addition of nanoparticles to the base fluid was then introduced to enhance the performance of cutting fluids. The ethylene glycol used as the base fluid, titanium dioxide (TiO2) and carbon nanotubes (CNTs) nanoparticle mixed to produce nanofluids with concentrations of 0.02 to 0.1 wt.% with an interval of 0.02 wt%. The mixing ratio of TiO2: CNTs was 90:10 and ratio of SDBS (surfactant): CNTs was 10:1. The stability of nanofluid checked using observation method and zeta potential analysis. The thermal conductivity and viscosity of suspension were measured at a temperature range between 30˚C to 70˚C (with increment of 10˚C) to determine the relationship between concentration and temperature on nanofluid’s thermal physical properties. Based on the results obtained, zeta potential value for nanofluid range from -50 to -70 mV indicates a good stability of the suspension. Thermal conductivity of nanofluid increases as an increase of temperature and enhancement ratio is within the range of 1.51 to 4.53 compared to the base fluid. Meanwhile, the viscosity of nanofluid shows decrements with an increase of the temperature remarks significant advantage in pumping power. The developed nanofluid in this study found to be stable with enhanced thermal conductivity and decrease in viscosity, which at once make it possible to be use as nanolubricant in machining operation.

Petrographic and Petrophysical Characteristics of the Upper Devonian Three Forks Formation, Southern Nesson Anticline, North Dakota

2017 ◽  
Vol 54 (3) ◽  
pp. 181-201
Author(s):  
Rebecca Johnson ◽  
Mark Longman ◽  
Brian Ruskin
Keyword(s):  
Relaxation Time ◽  
Pore Size ◽  
Water Saturation ◽  
Average Pore Size ◽  
Total Porosity ◽  
Average Pore ◽  
Pore Sizes ◽  
Three Forks Formation ◽  
Three Forks ◽  
Intercrystalline Pores

The Three Forks Formation, which is about 230 ft thick along the southern Nesson Anticline (McKenzie County, ND), has four “benches” with distinct petrographic and petrophysical characteristics that impact reservoir quality. These relatively clean benches are separated by slightly more illitic (higher gamma-ray) intervals that range in thickness from 10 to 20 ft. Here we compare pore sizes observed in scanning electron microscope (SEM) images of the benches to the total porosity calculated from binned precession decay times from a suite of 13 nuclear magnetic resonance (NMR) logs in the study area as well as the logarithmic mean of the relaxation decay time (T2 Log Mean) from these NMR logs. The results show that the NMR log is a valid tool for quantifying pore sizes and pore size distributions in the Three Forks Formation and that the T2 Log Mean can be correlated to a range of pore sizes within each bench of the Three Forks Formation. The first (shallowest) bench of the Three Forks is about 35 ft thick and consists of tan to green silty and shaly laminated dolomite mudstones. It has good reservoir characteristics in part because it was affected by organic acids and received the highest oil charge from the overlying lower Bakken black shale source rocks. The 13 NMR logs from the study area show that it has an average of 7.5% total porosity (compared to 8% measured core porosity), and ranges from 5% to 10%. SEM study shows that both intercrystalline pores and secondary moldic pores formed by selective partial dissolution of some grains are present. The intercrystalline pores are typically triangular and occur between euhedral dolomite rhombs that range in size from 10 to 20 microns. The dolomite crystals have distinct iron-rich (ferroan) rims. Many of the intercrystalline pores are partly filled with fibrous authigenic illite, but overall pore size typically ranges from 1 to 5 microns. As expected, the first bench has the highest oil saturations in the Three Forks Formation, averaging 50% with a range from 30% to 70%. The second bench is also about 35 ft thick and consists of silty and shaly dolomite mudstones and rip-up clast breccias with euhedral dolomite crystals that range in size from 10 to 25 microns. Its color is quite variable, ranging from green to tan to red. The reservoir quality of the second bench data set appears to change based on proximity to the Nesson anticline. In the wells off the southeast flank of the Nesson anticline, the water saturation averages 75%, ranging from 64% to 91%. On the crest of the Nesson anticline, the water saturation averages 55%, ranging from 40% to 70%. NMR porosity is consistent across the entire area of interest - averaging 7.3% and ranging from 5% to 9%. Porosity observed from samples collected on the southeast flank of the Nesson Anticline is mainly as intercrystalline pores that have been extensively filled with chlorite clay platelets. In the water saturated southeastern Nesson Anticline, this bench contains few or no secondary pores and the iron-rich rims on the dolomite crystals are less developed than those in the first bench. The chlorite platelets in the intercrystalline pores reduce average pore size to 500 to 800 nanometers. The third bench is about 55 ft thick and is the most calcareous of the Three Forks benches with 20 to 40% calcite and a proportionate reduction in dolomite content near its top. It is also quite silty and shaly with a distinct reddish color. Its dolomite crystals are 20 to 50 microns in size and partly abraded and dissolved. Ferroan dolomite rims are absent. This interval averages 7.1% porosity and ranges from 5% to 9%, but the pores average just 200 nanometers in size and occur mainly as microinterparticle pores between illite flakes in intracrystalline pores in the dolomite crystals. This interval has little or no oil saturation on the southern Nesson Anticline. Unlike other porosity tools, the NMR tool is a lithology independent measurement. The alignment of hydrogen nuclei to the applied magnetic field and the subsequent return to incoherence are described by two decay time constants, longitudinal relaxation time (T1) and transverse relaxation time (T2). T2 is essentially the rate at which hydrogen nuclei lose alignment to the external magnetic field. The logarithmic mean of T2 (T2 Log Mean) has been correlated to pore-size distribution. In this study, we show that the assumption that T2 Log Mean can be used as a proxy for pore-size distribution changes is valid in the Three Forks Formation. While the NMR total porosity from T2 remains relatively consistent in the three benches of the Three Forks, there are significant changes in the T2 Log Mean from bench to bench. There is a positive correlation between changes in T2 Log Mean and average pore size measured on SEM samples. Study of a “type” well, QEP’s Ernie 7-2-11 BHD (Sec. 11, T149N, R95W, McKenzie County), shows that the 1- to 5-micron pores in the first bench have a T2 Log Mean relaxation time of 10.2 msec, whereas the 500- to 800-nanometer pores in the chlorite-filled intercrystalline pores in the second bench have a T2 Log Mean of 4.96 msec. This compares with a T2 Log Mean of 2.86 msec in 3rd bench where pores average just 200 nanometers in size. These data suggest that the NMR log is a useful tool for quantifying average pore size in the various benches of the Three Forks Formation.

scholarly journals Effect of microstructure on the properties of polystyrene microporous foaming material

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 103-110
Author(s):  
Anfu Guo ◽  
Hui Li ◽  
Jie Xu ◽  
Jianfeng Li ◽  
Fangyi Li
Keyword(s):  
Thermal Conductivity ◽  
Compression Modulus ◽  
Cell Diameter ◽  
Compressive Property ◽  
Strength Increase ◽  
Compression Performance ◽  
Negative Linear Correlation ◽  
Sample Density ◽  
Foaming Temperature ◽  
The Relationship

AbstractThe performance of Polystyrene microporous foaming (PS-MCF) materials is influenced by their microstructures. Therefore, it is essential for industrializing them to investigate the relationship between their microstructure and material properties. In this study, the relationship between the microstructure, compressive property, and thermal conductivity of the PS-MCF materials was studied systematically. The results show that the ideal foaming pressure of PS-MCF materials, obtaining compression performance, is around 20 MPa. In addition, the increase of temperature causes the decrease of sample density. It effects that the compression modulus and strength increase with the decrease of foaming temperature. Because the expansion rate and cell diameter of the PS-MCF materials reduce the thickness of cell wall, they are also negatively correlated with their mechanical properties. Moreover, there is a negative linear correlation between the thermal conductivity and cell rate, whereas the cell diameter is positively correlated with the thermal conductivity.

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