Determination of Hydrocarbons Using Sapphire Fibers Coated with Poly(Dimethylsiloxane)

2003 ◽  
Vol 57 (4) ◽  
pp. 400-406 ◽  
Author(s):  
Rhona Howley ◽  
B. D. MacCraith ◽  
Kieran O'Dwyer ◽  
Hugh Masterson ◽  
P. Kirwan ◽  
...  
Keyword(s):  
Film Thickness ◽  
Diffusion Model ◽  
Diffusion Coefficients ◽  
Molecular Size ◽  
Infrared Region ◽  
Sensor Response ◽  
Fickian Diffusion ◽  
Prototype System ◽  
Pdms Film ◽  
Diffusion Behavior

A poly(dimethylsiloxane) (PDMS) coated sapphire fiber has been investigated as a sensor for hydrocarbons (HCs) in the mid-infrared region around 3000 cm−1. In order to optimize and predict sensor response, the diffusion behavior of the analytes into the PDMS preconcentration medium has been examined. A diffusion model based on Fickian diffusion was used to quantify diffusion. The model incorporated such factors as film thickness, refractive index of the polymer and the fiber core, and principal wavelength at which the analyte absorbs. A range of hydrocarbons, from hexane to pentadecane, was analyzed at 2930 cm−1 using both fiber-coupled Fourier transform infrared spectroscopy and a modular prototype system. Diffusion coefficients were determined for these compounds and diffusion behavior examined and related to factors such as analyte polarity and molecular size. The diffusion coefficients were found to range from 6.41 × 10−11 ± 5 × 10−12 to 5.25 × 10−11 ± 9 × 10−13 cm2 s−1 for hexane and pentadecane into a 2.9 μm PDMS film, respectively. The diffusion model was also used to examine the effect of changing system parameters such as film thickness in order to characterize sensor response.

The Deresination of Guayule: A Physical Model. Part II: A Two-Component Analog for Deresination

1984 ◽  
Vol 57 (2) ◽  
pp. 370-378
Author(s):  
S. Budiman ◽  
D. McIntyre
Keyword(s):  
Diffusion Coefficients ◽  
Abietic Acid ◽  
Additive Model ◽  
Molecular Size ◽  
Design Parameters ◽  
Model Compounds ◽  
Diffusion Behavior ◽  
Diffusion Studies ◽  
Two Component ◽  
Physical Geometry

Abstract Based on GPC, the worm resin can be separated into two distinct groups, large and small. To obtain the overall diffusion coefficients for the two groups that could be useful as commercial design parameters, the worms were converted into wet worm crepe. Diffusion studies with model compounds, abietic acid, and trilinolein, reveal that: (a) their diffusion coefficients for desorption into acetone are inversely proportional to their respective molecular size, (b) the diffusion behavior of the two model compounds in a mixture can be fitted to a simple additive model, and (c) their diffusion coefficients are quite similar to those of the two groups of resin constituents (large and small). It is, therefore, possible to model and optimize a commercial deresination process for guayule worms on the basis of the diffusion behavior of two model compounds linolein and abietic acid and the physical geometry.

Rutherford Backscattering Spectrometry Studies on Copper and Chromium Diffusion in Polyimide

1989 ◽  
Vol 153 ◽  
Author(s):  
Kyung W. Paik ◽  
Arthur L. Ruoff
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Room Temperature ◽  
Rutherford Backscattering Spectrometry ◽  
Annealing Treatment ◽  
Rutherford Backscattering ◽  
Fickian Diffusion ◽  
Chromium Diffusion ◽  
Diffusion Behavior ◽  
Slight Amount

AbstractDiffusion of Cu in polyimide(PI) film was observed after Cu evaporation on PI at room temperature. Annealing treatment significantly enhanced the diffusion of Cu. The diffusion coefficient measured at 200 and 400 C using the Fickian erfc solution are 3 × 10−14 and 1 × 10−13 cm2/sec, respectively. Cu shows the Fickian diffusion behavior. In contrast to Cu, no clearly measurable diffusion had occurred for an as-deposited Cr specimen and a specimen annealed at 400 C for 1 hour. However, for longer annealing times a slight amount of Cr diffused into PI because of the growth of the intermixed region. The diffusion coefficients of Cr at 200 and 400 C for less than 20 hours are 2 × 10−15 and 7 × 10−15 cm2/sec, respectively. The diffusion of Cr in PI shows non-Fickian behavior.

Rutherford Backscattering Spectrometry Studies on Copper and Chromium Diffusion in Polyimide

1989 ◽  
Vol 154 ◽  
Author(s):  
Kyung W. Paik ◽  
Arthur L. Ruoff
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Room Temperature ◽  
Rutherford Backscattering Spectrometry ◽  
Annealing Treatment ◽  
Rutherford Backscattering ◽  
Fickian Diffusion ◽  
Chromium Diffusion ◽  
Diffusion Behavior ◽  
Slight Amount

AbstractDiffusion of Cu in polyimide(PI) film was observed after Cu evaporation on PI at room temperature. Annealing treatment significantly enhanced the diffusion of Cu. The diffusion coefficient measured at 200 and 400 C using the Fickian erfc solution are 3 × 10−14 and 1 × 10−13 cm2/sec, respectively. Cu shows the Fickian diffusion behavior. In contrast to Cu, no clearly measurable diffusion had occurred for an as-deposited Cr specimen and a specimen annealed at 400 C for 1 hour. However, for longer annealing times a slight amount of Cr diffused into PI because of the growth of the intermixed region. The diffusion coefficients of Cr at 200 and 400 C for less than 20 hours are 2 × 10−15 and 7 × 10−15 cm2/sec, respectively. The diffusion of Cr in PI shows non-Fickian behavior.

scholarly journals Influence of Hydrostatic Pressure and Cationic Type on the Diffusion Behavior of Chloride in Concrete

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2851
Author(s):  
Huanqiang Liu ◽  
Linhua Jiang
Keyword(s):  
Diffusion Coefficient ◽  
Hydrostatic Pressure ◽  
Diffusion Model ◽  
Coupling Effect ◽  
Experimental Results ◽  
Chloride Diffusion ◽  
Concrete Durability ◽  
Chloride Diffusion Coefficient ◽  
Diffusion Behavior ◽  
Diffusion Source

The durability of the concrete in underground and marine engineering is affected by the underground and ocean environment. Chloride diffusion coefficient under hydrostatic pressure is a key parameter of concrete durability design under corresponding conditions. Therefore, this paper studies the diffusion behavior of chloride in different diffusion source solutions by experiment and simulation. Based on the experimental results, this paper proposes a new chloride diffusion model under the coupling effect of diffusion and convection. The interaction of ions and compounds in the diffusion source solutions, concrete pore fluid, and concrete material are considered in the new chloride diffusion model. The experimental results show that chloride diffusion rate is significantly affected by hydrostatic pressure, which increases with the increase of hydrostatic pressure. The chloride diffusion coefficient shows a certain difference in difference diffusion source solutions. The chloride diffusion coefficient in divalent cationic diffusion source solutions is the largest, the chloride diffusion coefficient in the divalent and monovalent cationic compound ones is in the middle, and the chloride diffusion coefficient in the monovalent cationic ones is the smallest. There is a linear relationship between the chloride diffusion coefficient and the hydrostatic pressure whether in single or combined cationic diffusion source solutions.

An Improved Multicomponent Diffusion Model for Compositional Simulation of Fractured Unconventional Reservoirs

SPE Journal ◽  
2021 ◽  
pp. 1-26
Author(s):  
Ye Tian ◽  
Chi Zhang ◽  
Zhengdong Lei ◽  
Xiaolong Yin ◽  
Hossein Kazemi ◽  
...  
Keyword(s):  
Diffusion Model ◽  
Fractured Reservoirs ◽  
Multicomponent Diffusion ◽  
Unconventional Reservoirs ◽  
Fickian Diffusion ◽  
Minor Effect ◽  
Matrix Interface ◽  
Fine Grid ◽  
Soaking Time ◽  
Fluid Saturation

Summary Most simulators currently use the advection/diffusion model (ADM), where the total flux comprises Darcian advection and Fickian diffusion. However, significant errors can arise, especially for modeling diffusion processes in fractured unconventional reservoirs, if diffusion is modeled by the conventional Fick’s law using molar concentration. Hence, we propose an improved multicomponent diffusion model for fractured reservoirs to better quantify the multiphase multicomponent transport across the fracture/matrix interface. We first give a modified formulation of the Maxwell-Stefan (MS) equation to model the multicomponent diffusion driven by the chemical potential gradients. A physics-based modification is proposed for the ADM in fractured reservoirs, where fracture, matrix, and their interface are represented by three different yet interconnected flow domains to honor the flux continuity at the fracture/matrix interface. The added interface using a more representative fluid saturation and composition of the interface can hence better capture the transient mass fluxes between fracture and matrix. The proposed approach is also implemented in an in-house compositional simulator. The multicomponent diffusion model is validated with both intraphase and interphase diffusion experiments. Then, the improved model for fracture/matrix interaction is compared with a fine-grid model. The proposed multiple interacting continua (MINC) model with three continua (MINC3) can better match the fine-grid model’s result than the double-porosity (DP) model, which only obtains a fair match at an early time. Then, we simulate a gas huff ‘n’ puff (HnP) well in the Permian Basin to investigate the effect of diffusion within the fractured tight oil reservoir. The simulation reveals that diffusion has a minor effect on the performance of depletion when oil is the dominant phase. For gas HnP, the simulation neglecting diffusion will underestimate the oil recovery factor (RF) but overestimate the gas rate. The DP approach tends to overestimate the RF of heavy components but leads to a similar cumulative oil RF compared with MINC3. With the diffusion included in the simulation, gas HnP performance becomes more sensitive to the soaking time than the model without diffusion. Although increasing the soaking time will lead to a higher RF after considering diffusion, the incremental oil is not sufficiently large to justify a prolonged soaking time.

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