scholarly journals Measuring Open Porosity of Porous Materials Using THz-TDS and an Index-Matching Medium

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3120
Author(s):  
Mira Naftaly ◽  
Iliya Tikhomirov ◽  
Peter Hou ◽  
Daniel Markl
Keyword(s):  
Refractive Index ◽  
Porous Materials ◽  
Open Porosity ◽  
Pore Space ◽  
Total Porosity ◽  
Terahertz Time Domain Spectroscopy ◽  
Compression Pressure ◽  
Pharmaceutical Tablets ◽  
Index Matching ◽  
Scattering Losses

The porosity of porous materials is a critical quality attribute of many products ranging from catalysis and separation technologies to porous paper and pharmaceutical tablets. The open porosity in particular, which reflects the pore space accessible from the surface, is crucial for applications where a fluid needs to access the pores in order to fulfil the functionality of the product. This study presents a methodology that uses terahertz time-domain spectroscopy (THz-TDS) coupled with an index-matching medium to measure the open porosity and analyze scattering losses of powder compacts. The open porosity can be evaluated without the knowledge of the refractive index of the fully dense material. This method is demonstrated for pellets compressed of pharmaceutical-grade lactose powder. Powder was compressed at four different pressures and measured by THz-TDS before and after they were soaked in an index-matching medium, i.e., paraffin. Determining the change in refractive index of the dry and soaked samples enabled the calculation of the open porosity. The results reveal that the open porosity is consistently lower than the total porosity and it decreases with increasing compression pressure. The scattering losses reduce significantly for the soaked samples and the scattering centers (particle and/or pore sizes) are of the order of or somewhat smaller than the terahertz wavelength. This new method facilitates the development of a better understanding of the links between material properties (particles size), pellet properties (open porosity) and performance-related properties, e.g., disintegration and dissolution performance of pharmaceutical tablets.

scholarly journals Определение пористости микрочастиц диоксида кремния с помощью метода соответствия показателей преломления

2020 ◽  
Vol 128 (9) ◽  
pp. 1277
Author(s):  
А.А. Ахмадеев ◽  
А.Р. Гайнутдинов ◽  
М.А. Хамадеев ◽  
М.Х. Салахов
Keyword(s):  
Refractive Index ◽  
Silicon Dioxide ◽  
Incident Light ◽  
Total Porosity ◽  
Matching Methods ◽  
Index Matching ◽  
Refractive Index Matching

The porosity of silicon dioxide microparticles synthesized by the Stöber - Fink method has been determined by using the refractive index matching methods. The values of the total porosity of particles have been obtained for different wavelengths of the incident light. The limits of applicability of the method associated with the ratio of the wavelength of the radiation to the size of microparticles have been analyzed.

scholarly journals Refractive index matching applied to fecal smear clearing

2005 ◽  
Vol 47 (6) ◽  
pp. 347-350 ◽  
Author(s):  
Cláudio S. Ferreira
Keyword(s):  
Refractive Index ◽  
Sucrose Solution ◽  
Glycerol Solution ◽  
Human Feces ◽  
Microscope Slide ◽  
Helminth Eggs ◽  
Index Matching ◽  
Refractive Index Matching ◽  
Fecal Smear ◽  
Effect Of Light

Thick smears of human feces can be made adequate for identification of helminth eggs by means of refractive index matching. Although this effect can be obtained by simply spreading a fleck of feces on a microscope slide, a glycerol solution has been routinely used to this end. Aiming at practicability, a new quantitative technique has been developed. To enhance both sharpness and contrast of the images, a sucrose solution (refractive index = 1.49) is used, which reduces the effect of light-scattering particulates. To each slide a template-measured (38.5 mm³) fecal sample is transferred. Thus, egg counts and sensitivity evaluations are easily made.

scholarly journals Biological glass: structural determinants of eye lens transparency

2011 ◽  
Vol 366 (1568) ◽  
pp. 1250-1264 ◽  
Author(s):  
Steven Bassnett ◽  
Yanrong Shi ◽  
Gijs F. J. M. Vrensen
Keyword(s):  
Refractive Index ◽  
Cellular Level ◽  
Structural Determinants ◽  
Lens Transparency ◽  
Index Matching ◽  
Lens Fibre ◽  
Refractive Index Matching ◽  
Lens Membranes ◽  
Adhesive Proteins ◽  
Structural Adaptations

The purpose of the lens is to project a sharply focused, undistorted image of the visual surround onto the neural retina. The first pre-requisite, therefore, is that the tissue should be transparent. Despite the presence of remarkably high levels of protein, the lens cytosol remains transparent as a result of short-range-order interactions between the proteins. At a cellular level, the programmed elimination of nuclei and other light-scattering organelles from cells located within the pupillary space contributes directly to tissue transparency. Scattering at the cell borders is minimized by the close apposition of lens fibre cells facilitated by a plethora of adhesive proteins, some expressed only in the lens. Similarly, refractive index matching between lens membranes and cytosol is believed to minimize scatter. Refractive index matching between the cytoplasm of adjacent cells is achieved through the formation of cellular fusions that allow the intermingling of proteins. Together, these structural adaptations serve to minimize light scatter and enable this living, cellular structure to function as ‘biological glass’.

scholarly journals Kilowatt-level direct-‘refractive index matching liquid’-cooled Nd:YLF thin disk laser resonator

2016 ◽  
Vol 24 (2) ◽  
pp. 1758 ◽  
Author(s):  
Zhibin Ye ◽  
Chong Liu ◽  
Bo Tu ◽  
Ke Wang ◽  
Qingsong Gao ◽  
...  
Keyword(s):  
Refractive Index ◽  
Thin Disk ◽  
Laser Resonator ◽  
Disk Laser ◽  
Index Matching ◽  
Refractive Index Matching ◽  
Thin Disk Laser

Numerical analysis of soil microstructure reveals conditions for natural attenuation in aged tar oil contaminated soil

2021 ◽  
Author(s):  
Pavel Ivanov ◽  
Karin Eusterhues ◽  
Kai Uwe Totsche
Keyword(s):  
Soil Solution ◽  
Contaminated Soil ◽  
Natural Attenuation ◽  
Pore Space ◽  
Total Porosity ◽  
Control Soil ◽  
Soil Microstructure ◽  
Cell Counts ◽  
Good Protection ◽  
Tar Oil

<p>Understanding of ongoing biogeochemical processes (natural attenuation) within contaminated soils is crucial for the development of plausible remediation strategies. We studied a tar oil contaminated soil with weak grass vegetation at a former manufactured gas plant site in Germany. Despite of the apparent toxicity (the soil contained up to 120 g kg<sup>-1</sup> petroleum hydrocarbons, 26 g kg<sup>-1</sup> toxic metals, and 100 mg kg<sup>-1</sup> polycyclic aromatic hydrocarbons), the contaminated layers have 3-5 times as much cell counts as an uncontaminated control soil nearby. To test, if the geometry of the pore space provides favourable living space for microorganisms, we applied scanning electron microscopy to the thin sections and calculated on sets of 15 images per layer three specific Minkowski functionals, connected to soil total porosity, interface, and hydraulic parameters.</p><p>Our investigation showed that the uncontaminated control soil has a relatively low porosity of 15-20 %, of which 50-70 % is comprised of small (< 15 µm) pores. These pores are poorly connected and show high distances between them (mean distance to the next pore 10 µm). The dominating habitats in the control soil are therefore created by small pores. They provide good protection from predators and desiccation, but input of dissolved organic C and removal of metabolic products are diffusion limited. Coarser pores (>15 µm) provide less space (< 50 % of total porosity) and solid surface area (< 20 %), are prone to desiccation and offer less protection from predators. However, they serve as preferential flow paths for the soil solution (input of nutrients) and are well aerated, therefore we expect the microbial activity in them to appear in “hot moments”, i.e. after rain events.</p><p>All layers of the contaminated profile have higher porosities (20-70 %) than the control. Coarse pores comprise 83-90 % of total pore area and create 34-52 % of total interface. Pores are also more connected and tortuous than in the control soil, which implies a better aeration and circulation of soil solution. The loops of pore channels may retain soil solution and be therefore preferably populated with microorganisms. The small (< 15 µm) pores comprise less than 17 % of total porosity but represent a substantial proportion of the interface (48-66 % vs 82-91 % in control). In the uppermost layer of the contaminated profile, such pores occur in plant residues, are close to the largest pores (mean distance to the next pore 4 µm) and therefore, along with good protection, are supplied with air, water, and non-tar C. In the middle of the profile, the small pores, presumably constantly filled with water, are located within dense tar pieces remote from the neighbouring pores (mean distance to the next pore 22 µm), and therefore, with hindered aeration and no supply of non-tar C, may create anaerobic domains of tar attenuation.</p><p>Our results show that the contaminated soil offers more favourable conditions for microorganisms than the control soil, probably because the hydrocarbons provide suitable energy and nutrition sources and a beneficial pore space geometry.</p>

Sign in / Sign up

Export Citation Format

Share Document