Characterization of adsorbed polymer conformational response using spectroscopic ellipsometry
- Authors: Kim, Sungho , Palomino, Angelica , Podraza, Nikolas
- Date: 2012
- Type: Text , Conference paper
- Relation: GeoCongress 2012
- Full Text: false
- Reviewed:
- Description: This study applies a novel technique, multichannel spectroscopic ellipsometry (SE), to characterize adsorbed responsive polymer molecules on simulated clay mineral surfaces representing "tunable" clay-polymer nanocomposites (CPN). SE is a non-destructive, non-invasive, highly accurate technique that has commonly been used to characterize layered materials systems. Predicting conformational behavior of the polymer molecules in CPNs is critical, but not fully understood due to many factors simultaneously affecting the behavior of the clay-polymer system. Since the conformation of responsive polymer molecules varies with external environmental conditions, SE results can be used to predict clay fabric changes due to micro-scale conformational changes of adsorbed polymer molecules. The purpose of this study is to investigate pH- and time-dependent conformational behavior of a responsive polymer on a simulated clay mineral surface and to link the micro-scale conformational variations to the meso-scale swelling potential of tunable CPNs. Using in-situ real-time spectroscopic ellipsometry (RTSE), conformational behavior of the responsive polymer is characterized as functions of pH and time. Low swelling potential measured at pH 3 is likely due to contracted coil conformation of the polymer. On the other hand, high swelling potential measured at pH 11.5 is likely due to extended conformation, and the conformation may be further extended over time.
Conformational effects of adsorbed polymer on the swelling behavior of engineered clay minerals
- Authors: Kim, Sungho , Motyka, Michael , Palomino, Angelica , Podraza, Nikolas
- Date: 2012
- Type: Text , Journal article
- Relation: Clays and Clay Minerals Vol. 60, no. 4 (2012), p. 363-373
- Full Text: false
- Reviewed:
- Description: The conformational behavior of polymers in clay-polymer nanocomposites (CPN) is not fully understood because of the many factors involved. The purpose of the present study was to investigate the conformational behavior of a polymer at the micro- and meso-scales in order to predict the behavior of tunable CPN. The study used a pH-responsive polymer, polyacrylamide, which has time-dependent hydrolysis response properties, to examine micro-scale conformational behavior of the polymer adsorbed on representative clay-mineral surfaces, SiO2 and Al2O3. A nanocomposite and a microcomposite were used to link meso-scale CPN behavior to micro-scale polymer conformation. The conformational behavior was characterized using in situ, real-time spectroscopic ellipsometry. The contracted coil conformation of polyacrylamide was observed at pH = 3, while extended conformation was observed at pH = 11.5 on both SiO2 and Al2O3 surfaces. At pH = 11.5, the polymer conformation changed from expanded coil to extended conformation over time. The polymer conformation changed more rapidly with the Al2O3 surface due to mineral dissolution at pH = 3 and 11.5. Swelling tests were conducted as functions of pH and time to link the micro-scale phenomena to meso-scale CPN behavior. The results indicated that the swelling potential of CPN corresponded to the conformation of adsorbed polyacrylamide, which varied with pH and time. The swelling potential of CPN was maximized at pH = 11.5 and decreased with decreasing pH, corresponding to the observed micro-scale conformational behavior.
Controlling desiccation cracks in clay with fibre and enzyme
- Authors: Costa, Susanga , Kim, Sungho , Xue, Jianfeng , Xie, Yuekai , Zhou, Limin
- Date: 2017
- Type: Text , Conference paper
- Relation: 2nd Symposium on Coupled Phenomena in Environmental Geotechnics (CPEG2)
- Full Text: false
- Reviewed:
- Description: Desiccation cracking is a common, undesirable phenomenon in many geotechnical engineering applications, particularly in compacted clay liners as it causes significant changes to the hydraulic and mechanical properties of soils. This is one of the major concerns in design and construction of landfill clay liners in arid regions. This paper reports the findings of laboratory tests conducted to investigate the effects of adding nylon fibre, guar gum and organic enzyme to the soil to control desiccation cracks. Merri-Creek clay, a highly expansive soil from Victoria, Australia, was used in the tests. The additives were mixed with soil in different combinations and in varying proportions. Desiccation tests were conducted in thin, long moulds as in the free shrinkage tests. It was observed that very small quantities of these additives were sufficient to alter the properties of overall mixture. The results indicated that fibre – enzyme is the most effective combination to reduce desiccation cracks. This additive combination contained 0.3% percent of fibres by dry weight of soil and 0.35 g of enzyme per kg of dry soil. There was a modest improvement in dry density in the fibre -enzyme mixture compared to pure Merri-Creek clay. Fibre-enzyme combination also showed the ability to reduce the hydraulic conductivity. It was discovered that guar gum is not desirable to mix with clays in terms of reducing desiccation cracking or decreasing hydraulic conductivity.
Creep due to chemical alteration of rocks - A Case study in brown coal
- Authors: Mackay, Rae , Wight, B. J. , Kim, Sungho
- Date: 2014
- Type: Text , Conference paper
- Relation: AusRock 2014: Third Australasian Ground Control in Mining Conference p. 61-64
- Full Text: false
- Reviewed:
Deformation of "tunable" clay-polymer composites
- Authors: Bishop, Matthew , Kim, Sungho , Palomino, Angelica , Lee, Jong-Sub
- Date: 2014
- Type: Text , Journal article
- Relation: Applied Clay Science Vol. 101, no. (2014), p. 265-271
- Full Text: false
- Reviewed:
- Description: Responsive clay-polymer composites are the next step in the development of polymer-modified clay materials. It has been shown at the micro-scale that these materials respond to the surrounding pore fluid environment, resulting in an alteration in fabric. The purpose of this study is to investigate the impact of the responsive nature of these materials on the consolidation properties. Two composite types were selected to highlight the differences based on modified interparticle and interparticle/interlayer spacings: one made from a kaolinite and one from a montmorillonite. Each composite was made with polyacrylamide as the polymer. The clay-polymer composites were subjected to 1-D consolidation tests during which shear wave velocity was also measured. The pH of the saturating fluid was varied to promote composite response. Results show that the compressibility, compression index, and swelling index of the composite materials are greater than the untreated clay materials. Furthermore, these properties are pH-dependent for both types of composite materials and are consistent with the long-term conformational behavior of PAM. This apparent observation confirms that the behavior of the clay-PAM composites is controlled by the behavior of PAM. On the other hand, the shear wave velocities between the control and composite samples were not significantly different. © 2014 Elsevier B.V.
Double protection drilling fluid : Optimization for sandstone-like uranium formation
- Authors: Hao, Shu-Qing , Kim, Sungho , Qin, Yong , Fu, Xue-Hai
- Date: 2014
- Type: Text , Journal article
- Relation: Applied Clay Science Vol. 88-89, no. (2014), p. 233-238
- Full Text: false
- Reviewed:
- Description: Nuclear energy, an alternative for fossil fuel, is accompanied by the excavation of uranium ores and in turn the use of drilling fluids. Thus, the objective of this study was to optimize the formula of drilling fluid for sandstone-like uranium formation representing the Xinjiang's Yili Basin uranium formation in China. Additives such as Na2CO3, potassium humate (KHM), sodium carboxymethyl cellulose (Na-CMC), and vegetable gum (VG) were introduced to montmorillonite (Mt) slurry to maximize the performance of drilling fluid in terms of rheological behavior and filtration characteristics. Orthogonal testing, soaking test, and pressure-bearing test were conducted to find the optimum formula of drilling fluid. The maximized performance was achieved with a drilling fluid consisting of 4% Mt, 1.6% Na2CO3, 0.1% KHM, 1.5% Na-CMC, and 0.5% VG. The lowest density and water loss, with a sufficiently high viscosity were achieved with this concentration combination of each additive. Soaking and pressure-bearing tests exhibited no visual changes of a specimen treated with the drilling fluid, which confirmed the result of optimization. © 2013 Elsevier B.V.
Effects of CaCO3 on kaolin: Fabric, shear strength, and deformation
- Authors: Kim, Sungho , Palomino, Angelica
- Date: 2012
- Type: Text , Conference paper
- Relation: Conference: Experimental Micromechanics for Geomaterials - Joint workshop of the ISSMGE TC101-TC105
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Enhanced CO2 gas storage in coal
- Authors: Hao, Shu-Qing , Kim, Sungho , Qin, Yong , Fu, Xue-Hai
- Date: 2013
- Type: Text , Journal article
- Relation: Industrial and Engineering Chemistry Research Vol. 52, no. 51 (2013), p. 18492-18497
- Full Text: false
- Reviewed:
- Description: We investigate coal's performance for storing carbon dioxide (CO 2) gas molecules in the form of CO2 hydrates when the in situ hydrates-forming method is applied with the use of promoters. Sodium dodecyl sulfate (SDS) and pressure augmentation were adopted as a promoter for the hydrate formation in coal. The use of SDS considerably increased the rate of hydrates-forming reaction in coal. The calculated rates of the reaction in the presence of SDS reached 143.70 cm3/min at 3 MPa, and 50% of the maximum gas storage capacity was attained within 2 h. Pressure also controlled the final gas storage capacity of coal. The maximum gas storage capacity of coal under 3 MPa was 188.65 volume of CO2 gas at standard temperature (273.15 K) and pressure (100 kPa) condition per unit volume of coal, as compared to 136.30 under 2.3 MPa. © 2013 American Chemical Society.
Enhanced methane hydrate storage using sodium dodecyl sulfate and coal
- Authors: Hao, Shu-Qing , Kim, Sungho , Qin, Yong , Fu, Xue-Hai
- Date: 2014
- Type: Text , Journal article
- Relation: Environmental Chemistry Letters Vol. 12, no. 2 (2014), p. 341-346
- Full Text: false
- Reviewed:
- Description: A potential solution to reduce global warming is to store greenhouse gases. Greenhouse gas storage has been recently improved using several materials and techniques. However, the actual storage capacity is slow, limited, and costly. Here, we tested the use of an accelerating agent, sodium dodecyl sulfate, and coal to produce methane hydrate for methane storage. Experiments of storing methane gas in coal samples have been carried out under high pressures, 4 or 6 MPa, and low temperature of 273.15 K. Results reveal that sodium dodecyl sulfate improved the rate up to 58.26 cm3/min and the capacity up to 179.97 volume at standard temperature and pressure per unit volume of coal. This finding shows that sodium dodecyl sulfate is efficient to accelerate the formation of methane hydrate. We also found that storage capacity increased with pressure. We conclude that our method allows a gas storage capacity higher than any other medium materials reported previously. © 2013 Springer-Verlag Berlin Heidelberg.
Factors influencing the synthesis of tunable clay-polymer nanocomposites using bentonite and polyacrylamide
- Authors: Kim, Sungho , Palomino, Angelica
- Date: 2011
- Type: Text , Journal article
- Relation: Applied Clay Science Vol. 51, no. 4 (2011), p. 491-498
- Full Text: false
- Reviewed:
- Description: Although clay-polymer nanocomposites have been successfully produced in the material science field, they are typically utilized as static structures. That is, no further structural modification is expected due to the irreversible interaction of the polymer and clay particles. Yet, polymer-intercalated clay nanocomposites may be produced with environmentally-responsive polymers such that the final nanocomposites are "tunable". The conformation of responsive polymers varies with external environmental conditions such as pH, ionic concentration, temperature, and electric field. The purpose of this study is to develop an optimized procedure for synthesizing tunable clay-polymer nanocomposites using an expansive clay mineral (bentonite) and a responsive polymer for the future production of "tunable" clay soils. The nanocomposites were produced using a solution intercalation technique. Variables investigated include synthesizing temperature, clay content, polymer molecular weight, pH, and clay-to-polymer volume ratio. Changes in the basal spacing of montmorillonite were characterized using X-ray diffraction. Intercalation was not found to vary with mixing and drying temperature. The polymer solution pH variation did not cause significant mineral dissolution, evidenced by nuclear magnetic resonance as well as X-ray diffraction. Optimum conditions for the greatest quantity of intercalated structure were at clay content of 0.001, synthesis with a low molecular weight polymer, and clay-to-polymer volume ratio of 2. Measured total specific surface area implies that the interlayer distances of synthesized nanocomposites vary with pH. © 2011 Elsevier B.V.
Liquid limit and hydraulic conductivity of brown coal composites
- Authors: Stipcevich, Jack , Kim, Sungho , Xue, Jianfeng
- Date: 2016
- Type: Text , Journal article
- Relation: Environmental Geotechnics Vol. 3, no. 6 (2016), p. 364-371
- Full Text: false
- Reviewed:
- Description: Adequate waste disposal is currently under high demand in Australia, due to a rapid growth in population. Australia’s scarcity and cost for the use of clays (most commonly used landfill liner material) have resulted in a search for alternative materials to achieve satisfactory performance in landfill design. This study explored liquid limit and hydraulic conductivity (HC) of coal composites for potential landfill liner use. Brown coal (lignite) was mixed with polyacrylamide (PAM) or sodium bentonite (Bt) to investigate liquid limits (LL), HC, and swelling behaviour. Each additive was subject to distilled water and sodium chloride solution (50 g/l) to investigate the effects of pore fluid chemistry. The addition of 2 wt% PAM resulted in approximately 82 percentage point (pp) increase in the LL of lignite with distilled water and 76 pp increase with 50 g/l sodium chloride (NaCl) solution. The HC of lignite also decreased by more than two orders of magnitude as the PAM content increased. The swell index of lignite composites increased with the addition of PAM. This exploratory study has found the unique property of brown coal and its composites that the LL, HC and swell index do not deteriorate significantly in the presence of highly concentrated electrolyte solution (50 g/l NaCl). Such distinct properties will be beneficial over currently used landfill liner materials.