Surface chemistry, rheology and microstructure of as-received SHCa-1 hectorite gels

Clay Minerals ◽  
2019 ◽  
Vol 54 (3) ◽  
pp. 269-275 ◽  
Author(s):  
Pek-Ing Au ◽  
Mingyong Du ◽  
Jishan Liu ◽  
Md. Bashirul Haq ◽  
Yee-Kwong Leong
Keyword(s):  
Zeta Potential ◽  
Yield Stress ◽  
Maximum Yield ◽  
Ageing Behaviour ◽  
Cellular Microstructure ◽  
Ageing Model ◽  
Yield Stress Increase ◽  
Ph Range ◽  
Stress Behaviour ◽  
The Relationship

AbstractThe zeta potential and yield-stress behaviour of gels prepared from as-received SHCa-1 hectorite (Ht) containing 50 wt.% impurities, mainly of calcite, dolomite and quartz, were characterized. The zeta potential is negative in the pH range 4–12. At pH <5, reaction of CaCO3 producing CO2 and Ca2+ increased the solution conductivity significantly and reduced the zeta potential. The buffering effect due to this chemical reaction was also observed in the yield stress–pH characterization below pH 8. Low yield stress was observed below pH 6 and above pH 12. The yield stress peaked at pH ~8, where Ht displayed a zeta potential of –20 mV. The relationship between maximum yield stress and Ht content (wt.%) was linear and was not affected by impurities. The ageing behaviour was characterized by an initial phase of rapid yield-stress increase and then by a phase of gradual increase. The Leong model performed better than the two-parameter glassy polymer ageing model in describing this ageing behaviour. However, the empirical power law model was more accurate. The timescale of the ageing process is long, lasting several days. An open cellular microstructure was observed to form in the gels. Impurities appeared not to interact with or bind to the Ht platelets.

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.

scholarly journals Comparison of the Effects of Conching Parameters on the Contents of Three Dominant Flavan3-ols, Rheological Properties and Sensory Quality in Chocolate Milk Mass Based on Liquor from Unroasted Cocoa Beans

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2502
Author(s):  
Bogumiła Urbańska ◽  
Hanna Kowalska ◽  
Karolina Szulc ◽  
Małgorzata Ziarno ◽  
Irina Pochitskaya ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Yield Stress ◽  
Sensory Quality ◽  
Raw Material ◽  
Antioxidant Compounds ◽  
Chocolate Milk ◽  
Cocoa Beans ◽  
Variable Parameters ◽  
The Relationship ◽  
Manufacturing Parameters

The content of polyphenols in chocolate depends on many factors related to the properties of raw material and manufacturing parameters. The trend toward developing chocolates made from unroasted cocoa beans encourages research in this area. In addition, modern customers attach great importance to how the food they consume benefits their bodies. One such benefit that consumers value is the preservation of natural antioxidant compounds in food products (e.g., polyphenols). Therefore, in our study we attempted to determine the relationship between variable parameters at the conching stage (i.e., temperature and time of) and the content of dominant polyphenols (i.e.,catechins, epicatechins, and procyanidin B2) in chocolate milk mass (CMM) obtained from unroasted cocoa beans. Increasing the conching temperature from 50 to 60 °C decreased the content of three basic flavan-3-ols. The highest number of these compounds was determined when the process was carried out at 50 °C. However, the time that caused the least degradation of these compounds differed. For catechin, it was 2 h; for epicatechin it was 1 h; and for procyanidin it was 3 h. The influence of both the temperature and conching time on the rheological properties of chocolate milk mass was demonstrated. At 50 °C, the viscosity and the yield stress of the conched mass showed its highest value.

Adsorption of Benzene from Aqueous Solution Using Base Modified Expanded Perlite

2012 ◽  
Vol 622-623 ◽  
pp. 1779-1783
Author(s):  
Richard Appiah-Ntiamoah ◽  
Xuan Thang Mai ◽  
Francis W.Y. Momade ◽  
Hern Kim
Keyword(s):  
Zeta Potential ◽  
Adsorption Capacity ◽  
Linear Regression Analysis ◽  
Basic Medium ◽  
Maximum Adsorption Capacity ◽  
Hydroxyl Groups ◽  
Expanded Perlite ◽  
Oh Groups ◽  
Base Solution ◽  
Ph Range

In this study, the adsorption capacity of expanded perlite (EP) for benzene at low concentrations in water was investigated after EP was treated with sodium hydroxide (NaOH). IR spectra used to characterize the modified EP showed that there was no bonding between NaOH and the hydroxyl groups on the surface of EP. However, the NaOH provided a basic medium for negatively charged surface oxide ions (-SO-) to form on EP. This fact was corroborated by pH readings of the modification solution. This reduced in pH from 10 to 9 at the end of the reaction which indicated that the hydroxyl OH- groups on the EP underwent deprotonation and hence releases H+ into the solution, and also positive sites on EP adsorbed OH- ions from the base solution. Mahir et al. in their paper Zeta potential of unexpanded and expanded perlite samples in various electrolyte media confirmed that EP has no isoelectric point and exhibits negative zeta potential in the pH range of 2-11. The surface oxides (-SO-) were believed to have given EP it adsorptive potential. Adsorption isotherm values correlated reasonably well with the Langmuir isotherm model and it parameters (qo and K) were obtained using linear regression analysis. A maximum adsorption capacity (qo) value of 19.42 mg/g was achieved.

scholarly journals Ageing simulation of a hydraulic engine mount: A data-informed finite element approach

2018 ◽  
Vol 233 (10) ◽  
pp. 2432-2442 ◽  
Author(s):  
Payam Soltani ◽  
Christophe Pinna ◽  
David J Wagg ◽  
Roly Whear
Keyword(s):  
Finite Element ◽  
Mechanical Response ◽  
Element Model ◽  
Experimental Results ◽  
Softening Effect ◽  
Engine Mounts ◽  
Ageing Behaviour ◽  
Ageing Model ◽  
Engine Mount ◽  
Vehicle Suspension System

Hydraulic engine mounts are key elements in an automotive vehicle suspension system that typically experience a change of their designed function during their working lifetime due to progressive material ageing, primarily from the elastomeric component. Ageing of the engine mount, resulting from severe and continuous mechanical and thermal loads, can have a detrimental impact on the ride and comfort and long-term customer satisfaction. This paper introduces a new practical methodology for simulating the ageing behaviour of engine mounts resulting from the change in properties of their elastomeric main spring component. To achieve this, a set of dynamic mechanical thermal analysis tests were conducted on elastomeric coupons taken from a set of engine mounts with different service and ageing conditions. These experimental results were used to characterise the change in mechanical response of the elastomer and to build up an empirical elastomer ageing model. Then a finite element model of the main spring was developed that used the elastomer ageing model so that the ageing behaviour of the engine mount could be simulated. The resulting ageing model was verified by using experimental results from a second batch of ex-service engine mounts. The results show an increasing trend of the vertical static stiffness of the engine mounts with distance travelled (or age) up to a certain distance (approximately 95,000 km). The trend is then reversed and a softening effect is observed. Moreover, the results reveal that both the maximum stiffness value and the distance travelled at the peak stiffness decrease as the temperature increases.

scholarly journals Maximum yield stress in reinforced concrete frames

1969 ◽  
Vol 2 (3) ◽  
pp. 267-269
Author(s):  
D. S. Mackenzie
Keyword(s):  
Reinforced Concrete ◽  
Yield Stress ◽  
Maximum Stress ◽  
Maximum Yield ◽  
Reinforcing Bars ◽  
Concrete Frames ◽  
Standard Specification ◽  
The Past ◽  
Moment Resisting ◽  
Earthquake Moment

In the past steelmakers have tried to ensure that the yield stress of their reinforcing bars has always been above the specified minimum. It now appears that for earthquake moment resisting frames it should always be below some known maximum stress. Such a stress could with justification be included in the Standard Specification for the reinforcing concerned.

Investigation on the recycling of sulfuric acid from pretreatment of cellulose for nanocellulose preparation

TAPPI Journal ◽  
2020 ◽  
Vol 19 (2) ◽  
pp. 103-111
Author(s):  
CHAOYU DUAN ◽  
YANGYANG PENG ◽  
SHIYU FU ◽  
LUCIAN LUCIA
Keyword(s):  
Thermal Stability ◽  
Sulfuric Acid ◽  
Zeta Potential ◽  
Surface Properties ◽  
Value Chain ◽  
Solid Residue ◽  
Number Of Cycles ◽  
The Relationship

Sulfuric acid is often used to pretreat cellulose prior to homogenization and conversion to nanocellulose. It would be economically significant to reuse the acid to close the overall value chain loop. The target of this work was to investigate the effect of recovery and recycling frequency of sulfuric acid from the pretreatments on the pretreatment yield of water-insoluble cellulose solid residue, and to explore the relationship between the nanocellulose size prepared by recovery of acid and number of cycles. The surface properties of the nanocelluloses were measured, including content of sulfate groups, absolute zeta potential, crystallinity, and thermal stability.

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