Characterizations of MWCNTs nanofluids on the effect of surface oxidative treatments

In this study, multi-walled carbon nanotubes (MWCNTs) were chemically modified using three acid treatment methods to introduce the surface oxygen functional group (SOFG). The presence of SOFG on the MWCNTs has been characterized by Fourier Transform Infrared (FTIR) spectroscopy. Morphology, structural and thermal properties were performed using Field Emission Scanning Electron Microscopy (FESEM), Raman spectroscopy, and Thermogravimetric analysis (TGA), respectively. The result shows that the modification with acid treatment significantly affects the degree of defects and surface group functionality of surface oxidized MWCNTs from method B. The preparation of nanofluids using MWCNTs produced from method B (MWCNT-MB) was prepared using two different parameters: with and without polyvinylpyrrolidone (PVP) as surfactant. The experiment was conducted by setting variable carbon particle concentration from 0.1 wt.% to 1.0 wt.%, and the amount of PVP is 10% of carbon particles at different temperatures (6 ◦C, 25 ◦C, 40 ◦C). Based on visual observation, the dispersion of carbon particles was enhanced by the presence of PVP as the stabilizing agent. The thermal conductivity performance of nanofluids revealed that the surface oxidized MWCNTs with PVP show enhanced thermal conductivity compared to the nanofluid containing MWCNTs without PVP. The improvement contributes to this in terms of stability and homogenization of nanoparticles. Hence the improved distribution of MWCNTs in water-based media improves thermal conductivity. These promising properties of MWCNTs in water-based fluids would enable the nanofluids to be used in heat transfer fluid and cooling applications

Immobilization of mutant phosphotriesterase on fuller’s earth enhanced the stability of the enzyme

Immobilization is a method for making an enzyme more robust in the environment, especially in terms of its stability and reusability. A mutant phosphotriesterase (YT PTE) isolated from Pseudomonas dimunita has been reported to have high proficiency in hydrolyzing the Sp and Rp-enantiomers of organophosphate chromophoric analogs and therefore has great potential as a decontamination agent and biosensor. This work aims to investigate the feasibility of using Fuller’s earth (FE) as a YT PTE immobilization support and characterize its biochemical features after immobilization. The immobilized YT PTE was found to show improvement in thermal stability with a half-life of 24 h compared to that of the free enzyme, which was only 8 h. The stability of the immobilized YT PTE allowed storage for up to 4 months and reuse for up to 6 times. The immobilized YT PTE showed high tolerance against all tested metal ions, Tween 40 and 80 surfactants and inorganic solvents. These findings showed that the immobilized YT PTE became more robust for use especially with regards to its stability and reusability. These features would enhance the future applicability of this enzyme as a decontamination agent and its use in other suitable industrial applications

Surface-oxidised carbon nanofibre-based nanofluids: Structural, morphological, stability and thermal properties

The reputation of nanofluids as a convenient heat transfer media has grown in recent years. The synthesis of nanofluids is often challenging, particularly carbon-based nanofluids, due to the rapid agglomeration of the nanoparticles and the instability of the nanofluids. In this regard, surface modification and surfactant addition are potential approaches to improve the physical and thermal properties of carbon-based nanofluids that have been studied and the structural, morpho-logical, and thermal characteristics of surface-oxidised carbon nanofibre (CNF)-based nanofluids has been characterised. Commercial CNF was first subjected to three different acid treatments to introduce surface oxygen functional groups on the CNF surface. Following the physical and thermal characterisation of the three surface-oxidised CNFs (CNF-MA, CNF-MB, and CNF-MC), including Raman spectroscopy, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM), the CNF-MB was selected as the best method to synthesise the surface-oxidised CNF-based nanofluid. A total of 40 mL of ultrapure water was used as a pure base fluid and mixed with the surface-oxidised CNF at a concentration range of 0.1– 1.0 wt.%, with a fixed of 10 wt.% amount of polyvinylpyrrolidone (PVP). The thermal conductivity of CNF-based nanofluid was then characterised at different temperatures (6, 25, and 40 °C). Based on the results, surface oxidation via Method B significantly affected the extent of surface defects and effectively enhanced the group functionality on the CNF surface. Aside from the partially defective and rough surface of CNF-MB surfaces from the FESEM analysis, the presence of surface oxygen functional groups on the CNF wall was confirmed via the Raman analysis, TGA curve, and FTIR analysis. The visual sedimentation observation also showed that the surface-oxidised CNF particles remained dispersed in the nanofluid due to the weakened van der Waals interaction. The dispersion of CNF particles was improved by the presence of PVP, which further stabilised the CNF-based nanofluids. Ultimately, the thermal conductivity of the surface-oxidised CNF-based nanofluid with PVP was significantly improved with the highest enhancement percentage of 18.50, 16.84, and 19.83% at 6, 25, and 40 °C, respectively, at an optimum CNF concentration of 0.7 wt.%

Characterization of amide and ester functionalized multiwalled carbon nanotubes

Multi-walled carbon nanotubes (MWCNT) were functionalized by different functional group via amidation and esterification process. The MWCNT were treated with H2SO4/HNO3 first to introduce carboxylic acid functional group on the surface of MWCNT. This carboxylic group was used as reaction precursor in the functionalization. There are two functionalizing reactant were used which is dodecylamine, CH3(CH2)11NH2 and 1-octadecanol, CH(CH)17OH. Electron microscopy revealed that the morphology of amide and ester functionalized MWCNT exhibit decrease in their diameter size due to insertion of amide and ester functional group. Raman measurements showed that G-band (graphitic structure) of amide and ester functionalized MWCNT slightly shifted downfield about 6-8 cm–1 due to presence of new functional group on the surface of MWCNT. Multi-walled carbon nanotubes attached to organofunctional element have greater flexibility for further usage in various application fields such as nanocomposite material, biology and chemical sensor and environmental monitoring

Predictors of travel motivations: The case of domestic tourists to island destinations in northwest of Malaysia

This paper examines the role of key socio demographic attributes and trip characteristics in travel motivations of domestic tourists to island destinations.A total of 1780 useful survey responses were collected over a period of 6 months via an assisted survey.Analysis using independent sample t-test and one-way ANOVA revealed that only the “travel companionship status” in respondents' trip characteristics significantly influences the travel motivations of domestic tourists. Particularly, family and friends were found to be a major influence on the travel motivations of domestic tourists.The study concludes that the travel motivations of domestic tourists are more influenced by who individuals choose to travel with, therefore reflecting the issue of local conditions. The findings support Gilbert's (1991, Progress in tourism, recreation and hospitality management. London: Belhaven) theory of family influence in travel decisions. However, it adds that where the population is relatively young, friends can also be a major influence.Theoretical and managerial implications are then discussed

Shopping orientation and purchase behaviour of Malaysian consumers towards green products

Over the past decades, concern about the environment has become not only a significant public issue but also a crucial topic in academic research.Concern about environmental sustainability and climate change has increased dramatically in the past and is affecting the way consumers behave.This change has lead to a greater focus on green consumerism.This study aimed to identify the profile of green consumers in Malaysia and the factors that contribute to green purchase behaviour.This study is correlational in nature, with the intention to obtain a good grasp of the consumer purchasing behavior of green products. This study is a cross-sectional where data was gathered once. A survey was carried out to acquire data from 616 respondents at ten main hypermarkets in Malaysia, utilizing a series of mall intercept method.From the responses gathered, only 186 respondents can be categorized as green consumers.Data were analyzed using descriptive statistics, t-test, anova, correlation and path analysis. The result indicated that level of green purchase behavior among Malaysian consumers were not encouraging.They tend to have low level of purchase on environmentally products as their shopping items.Respondents overall reported moderate levels of environmental knowledge and environmental attitudes.The findings suggest that environmental knowledge and subjective norms significantly influence environmental attitudes.Results from the path analysis revealed that environmental attitudes, environmental knowledge, subjective norms and perceived behavioural control contributed significantly to green purchase behavior.This study provides valuable insight into consumer behavior literature regarding the profile and purchase behavior of green products. Results are compared with earlier findings and implications for future research are discussed

Surface modification of multi-walled carbon nanotube using double-chained quaternary ammonium bromide

Modification of multi-walled carbon nanotube (MWCNT) plays an important role to produce MWCNT crossbreeds that may be useful for exploration of new materials. In this report, characterization of dimethyl dioctadecylammonium bromide (DDOAB) modified multi-walled carbon nanotube (Mo-MWCNT) using Fourier Transform Infrared (FTIR) spectroscopy and Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) is described. FTIR shows the presence of both aliphatic (CH stretching and CH bending) and ammonium (CN stretching) groups from DDOAB and the existence of C=C aromatic functional group from the structure of MWCNT in Mo-MWCNT spectra. This result was supported by TGA result which suggests that there are weight losses due to the degradation of DDOAB (between 250 °C to 500 °C) in the product. In addition, XRD pattern remain after modification suggesting attachment of MWCNT and DDOAB occurs at the surface of MWCNT