Md Julker Nine | University of Adelaide (original) (raw)

Papers by Md Julker Nine

Surface coatings to protect materials from mechanical abrasion, fire and microbial colonization a... more Surface coatings to protect materials from mechanical abrasion, fire and microbial colonization are associated with billion dollars of expenses across broad range of industrial, domestic and defence applications. Currently used protective coatings based on heavy metals, halogenated fire-retardation, and biocide agents have considerable environmental concerns due their toxicity, and lack of effectiveness with limited functionality. In this paper, we present engineering of new multifunctional coating based on graphene composites with the ability to provide " 3-in-1 " protective properties. These multiple func-tionalities were created with specially designed graphene composite by growing sodium metaborate (NaBO 2 $xH 2 O) crystals into graphene oxide (GO) layer during their reduction, which works synergisti-cally as a surface binder, a flame-retardant additive, and an antibacterial agent. The testing of protective coating performances revealed an outstanding mechanical robustness (ASTM-class 4B), and the reduction of bacterial colonization up to ~99.92%. The high flame retardant performance of the coated wood, and paper showed non-flammability, strong intumescent effect, and self-extinguishing ability during fire. These protective coatings based on graphene composites due the simplicity of their formulations, scal-ability, and outstanding performance offer a great potential for their industrial, structural, and environmental applications.

To address high fire risks of flamable cellulosic materials, that can trigger easy combustion, fl... more To address high fire risks of flamable cellulosic materials, that can trigger easy combustion, flame propagation, and release of toxic gases, we report a new fire-retardant approach using synergetic actions combining unique properties of reduced graphene oxide (rGO) and hydrated-sodium metaborates (SMB). The single-step treatment of cellulosic materials by a composite suspension of rGO/SMB was developed to create a barrier layer on sawdust surface providing highly effective fire retardant protection with multiple modes of action. These performances are designed considering synergy between properties of hydrated-SMB crystals working as chemical heat-sink to slow down the thermal degradation of the cellulosic particles and gas impermeable rGO layers that prevents access of oxygen and the release of toxic volatiles. The rGO outer layer also creates a thermal and physical barrier by donating carbon between the flame and unburnt wood particles. The fire-retardant performance of developed graphene-borate composite and mechanism of fire protection are demonstrated by testing of different forms of cellulosic materials such as pine sawdust, particle-board, and fiber-based structures. Results revealed their outstanding self-extinguishing behavior with significant resistance to release of toxic and flammable volatiles suggesting rGO/ SMB to be suitable alternative to the conventional toxic halogenated flame-retardant materials.

Adhesion behavior of superhydrophobic (SH) surfaces is an active research field related to variou... more Adhesion behavior of superhydrophobic (SH) surfaces is an active research field related to various engineering applications in controlled microdroplet transportation, self-cleaning, deicing, biochemical separation, tissue engineering, and water harvesting. Herein, we report a facile approach to control droplet adhesion, bouncing and rolling on properties of SH surfaces by tuning their air-gap and roughness-height by altering the concentrations of poly dimethyl-siloxane (PDMS). The optimal use of PDMS (4−16 wt %) in a dual-scale (nano-and microparticles) composite enables control of the specific surface area (SSA), pore volume, and roughness of matrices that result in a well-controlled adhesion between water droplets and SH surfaces. The sliding angles of these surfaces were tuned to be varied between 2 ± 1 and 87 ± 2°, which are attributed to the transformation of the contact type between droplet and surface from " point contact " to " area contact ". We further explored the effectiveness of these low and high adhesive SH surfaces in icing and deicing actions, which provides a new insight into design highly efficient and low-cost ice-release surface for cold temperature applications. Low adhesion (lotus effect) surface with higher pore-volume exhibited relatively excellent ice-release properties with significant icing delay ability principally attributed to the large air gap in the coating matrix than SH matrix with high adhesion (petal effect).

Superhydrophobic surfaces for self-cleaning applications often suffer from mechanical instability... more Superhydrophobic surfaces for self-cleaning applications often suffer from mechanical instability and do not function well after abrasion/scratching. To address this problem, we present a method to prepare graphene-based superhydrophobic composite coatings with robust mechanical strength, self-cleaning, and barrier properties. A suspension has been formulated that contains a mixture of reduced graphene oxide (rGO) and diatomaceous earth (DE) modified with polydimethylsiloxane (PDMS) that can be applied on any surface using common coating methods such as spraying, brush painting, and dip coating. Inclusion of TiO2 nanoparticles to the formulation shows further increase in water contact angle (WCA) from 159 ± 2° to 170 ± 2° due to the structural improvement with hierarchical surface roughness. Mechanical stability and durability of the coatings has been achieved by using a commercial adhesive to bond the superhydrophobic “paint” to various substrates. Excellent retention of superhydrophobicity was observed even after sandpaper abrasion and crosscut scratching. A potentiodynamic polarization study revealed excellent corrosion resistance (96.78%) properties, and an acid was used to provide further insight into coating barrier properties. The ease of application and remarkable properties of this graphene-based composite coating show considerable potential for broad application as a self-cleaning and protective layer.

Dye-sensitized solar cells (DSSCs) have received significant attention from the scientific commun... more Dye-sensitized solar cells (DSSCs) have received significant attention from the scientific community since their discovery in 1991. However, the high cost and scarcity of platinum has motivated researchers to seek other suitable materials for the counter electrode of DSSCs. Owing to their exceptional properties such as high conductivity, good electrochemical activity, and low cost, carbon nanotubes (CNTs) have been considered as promising alternatives to expensive platinum (Pt) in the counter electrode of DSSCs. Herein, we provide a Minireview of the CNTs use in the counter electrode of DSSCs. A brief overview of Pt-based counter electrodes is also discussed. Particular attention is given to the recent advances of counter electrodes with CNT-based composite structures.

Graphene based materials have attracted great interest in the development of new and advanced pro... more Graphene based materials have attracted great interest in the development of new and advanced protective coatings due to their excellent chemical resistance, impermeability to gases, adsorption capacity, anti-bacterial properties, mechanical strength, lubricity and thermal stability. This review presents current progress and discusses the major challenges and future potential of graphene in the field of protective coatings. This review specifically focuses on the most recent advances in the application of graphene for corrosion resistant coatings, flame retardant coatings, wear/scratch resistant coatings, anti-fouling coatings, pollutant adsorption coatings and anti-septic coatings.

Nanofluid is a colloidal suspension which has received great attention over the past two decades,... more Nanofluid is a colloidal suspension which has received great attention over the past two decades, but its limited heat transfer enhancement is a matter of concern for industrial applications. We demonstrate an improvement in the thermal conductivity of TiO2 nanofluids with an addition of negligible amounts of modified silver “Ag” nanoparticles. In this work, the surface/shape of newly synthesized “Ag” nanoparticles is modified by planetary ball milling. Then, to enhance the thermal conductivity of TiO2 nanofluids, the flattened “Ag” particles are incorporated with the combination of small (15 nm) and large (300 nm) TiO2 nanoparticles in an aqueous solution. The thermal conductivities of Ag/TiO2–water nanofluids with various weight concentrations are measured at temperatures ranging from 15 to 40 °C. As a result, the present study confirms that the thermal conductivity of TiO2 based solution can be improved by introducing the flattened “Ag” particles.

Elsevier, Apr 16, 2014

The oscillations of liquid slugs and vapor plugs inside an oscillating heat pipe (OHP) are captur... more The oscillations of liquid slugs and vapor plugs inside an oscillating heat pipe (OHP) are captured and shown in terms of pressure frequency spectrum. Pressure fluctuation inside a single loop OHP between the evaporative and the condensing sections is analyzed to evaluate thermal performance. De-Ionized (DI) water and Cu/water nanofluid with different mass fractions (0.5 wt%, 1 wt%, 2 wt% and 3 wt%) are studied subjected to the evaporative heat load of 20–120 W. Swirling, bubble creation and bubble growth phenomena are observed inside OHP integrated with circulation and oscillating motion of vapor plug and liquid slug. Furthermore, deposition of nanoparticles is found on the surface of the evaporative section of OHP when charged with nanofluid. Experimental results show that Cu/Water nanofluid containing 2 wt% of Cu nanoparticles facilitates lowest thermal resistance and highest magnitude of pressure fluctuation inside OHP. Maximum 22% efficiency is achieved by Cu/Water nanofluid with 2 wt% of Cu nanoparticles at 80 W of evaporative power input. However, thermal performance is found significantly interrelated with inside pressure fluctuation of OHP. Cu/water nanofluid is found to promote circulation and oscillation of the liquid slug and the vapor plug rather than reinforcing bubble formation and bubble growth inside OHP.

Elsevier, May 30, 2014

A pre- and post experimental analysis of copper–water and silver–water nanofluids are conducted t... more A pre- and post experimental analysis of copper–water and silver–water nanofluids are conducted to investigate minimal changes in quality of nanofluids before and after an effective heat transfer. A single loop oscillating heat pipe (OHP) having inner diameter of 2.4 mm is charged with aforementioned nanofluids at 60% filling ratio for end to end heat transfer. Post experimental analysis of both nanofluids raises questions to the physical, chemical and thermal stability of such suspension for hazardless uses in the field of heat transfer. The color, deposition, dispersibility, propensity to be oxidized, disintegration, agglomeration and thermal conductivity of metal nanofluids are found to be strictly affected by heat transfer process and vice versa. Such degradation in quality of basic properties of metal nanofluids implies its challenges in practical application even for short-term heat transfer operations at oxidative environment as nano-sized metal particles are chemically more unstable than its bulk material. The use of the solid/liquid suspension containing metal nanoparticles in any heat exchanger as heat carrier might be detrimental to the whole system.

Wear debris, of deferent sizes, shapes and quantities, generated in artificial hip and knees is l... more Wear debris, of deferent sizes, shapes and quantities, generated in artificial hip and knees is largely confined to the bone and joint interface. This debris interacts with periprosthetic tissue and may cause aseptic loosening. The purpose of this review is to summarize and collate findings of the recent demonstrations on debris characterization and their biological response that influences the occurrence in implant migration. A systematic review of peer-reviewed literature is performed, based on inclusion and exclusion criteria addressing mainly debris isolation, characterization, and biologic responses. Results show that debris characterization largely depends on their appropriate and accurate isolation protocol. The particles are found to be non-uniform in size and non-homogeneously distributed into the periprosthetic tissues. In addition, the sizes, shapes, and volumes of the particles are influenced by the types of joints, bearing geometry, material combination, and lubricant. Phagocytosis of wear debris is size dependent; high doses of submicron-sized particles induce significant level of secretion of bone resorbing factors. However, articles on wear debris from engineered surfaces (patterned and coated) are lacking. The findings suggest considering debris morphology as an important parameter to evaluate joint simulator and newly developed implant materials.

IOP science, Feb 1, 2014

Coatings such as diamond-like carbon (DLC) and titanium nitride (TiN) are employed in joint impla... more Coatings such as diamond-like carbon (DLC) and titanium nitride (TiN) are employed in joint implants due to their excellent tribological properties. Recently, graphite-like carbon (GLC) and tantalum (Ta) have been proven to have good potential as coating as they possess mechanical properties similar to bones—high hardness and high flexibility. The purpose of this systematic literature review is to summarize the coating techniques of these four materials in order to compare their mechanical properties and tribological outcomes. Eighteen studies published between January 2000 and February 2013 have met the inclusion criteria for this review. Details of their fabrication parameters, material and mechanical properties along with the tribological outcomes, such as friction and wear rate, were identified and are presented in a systematic way. Although experiment conditions varied, we conclude that Ta has the lowest wear rate compared to DLC, GLC and TiN because it has a lower wear rate with high contact pressure as well as higher hardness to elasticity ratio. However, a further tribology test is needed in an environment which replicates artificial joints to confirm the acceptability of these findings.

Elsevier, Jan 1, 2014

The article reports a comparative study of macro and micro type artificial roughness in convectiv... more The article reports a comparative study of macro and micro type artificial roughness in convective heat transfer performance under laminar and low turbulent regime. Circular ribs with different rib height to channel height ratios (e/H = 0.05, 0.1, 0.15) fabricated on copper substrate are introduced as macro type roughness whereas copper (Cu) nano-porous layer (avg. thickness about 5 μm) is considered as micro roughness. Surface heat transfer and friction characteristics are investigated under different scale roughnesses on one principle wall of a rectangular channel having an aspect ratio (AR) of 7.5. Result shows that the average turbulence intensity between two ribs decreases with decreasing roughness height. On the other hand, nano-porous layer provides significant heat transfer efficiency (about maximum 42% more than bare copper plate) under laminar and low turbulent region without inducing significant turbulence into the channel. Nano-porous layer less than 5 μm is found to increase heat transfer surface area significantly that influences the dynamic behaviors of working fluids in the vicinity of heat transfer wall.

American Scientific Publishers, Dec 1, 2013

The article reveals heat transfer performance of multi loops Oscillating Heat Pipe (MLOHP) in ter... more The article reveals heat transfer performance of multi loops Oscillating Heat Pipe (MLOHP) in terms of thermal resistance and inside pressure characteristics at different angular orientation. Aqueous alumina (Al2O3) and a combination of Al2O3 with multi-walled carbon nanotubes (MWCNTs) particles in a ratio of 90:10 of weight percentages were charged individually into OHP at 60% filling ratio to investigate thermal performance. The influences of aqueous Al2O3 of 0.9 wt% as well as the Al2O3/MWCNTs of same weight concentration on thermal resistance and inside pressure distribution were investigated. The investigation of pressure characteristics inside OHP and optimization of installation angle among 0°, 30°, 60°, 90° with a variation of working fluids were significant in this study. Experimental results showed that thermal characteristics are significantly inter-related with pressure distribution and strongly depend upon the number of pressure fluctuations inside oscillating heat pipe (OHP) per unit time. A little inclusion of MWCNTs into aqueous Al2O3 facilitated the system to achieve highest number of pressure fluctuation and low thermal resistance at OHPs operational angle of 30° and 60°. Thermal resistance decreased with increasing evaporative power input at any orientation for any working fluids employed in this experiment.

Heat transfer efficiency can be improved by increasing the thermal conductivity of the working fl... more Heat transfer efficiency can be improved by increasing the thermal conductivity of the working fluids. Commonly used heat transfer fluids have relatively low thermal conductivities, when compared to the thermal conductivity of metals or metal oxides. High thermal conductivity of fluids can be increased by adding small amount of metals or metal oxide particles to that fluid. In this research, colloidal suspension alumina nanofluids were prepared by dispersing alumina nanoparticles in DI water as base fluid. Thermal conductivity of alumina nanofluids was then measured by means of hot wire technique using a LAMBDA system. The results reviled that the thermal conductivity enhancement was from 2.29% to 3.06% with 5 wt% alumina nanofluids at temperatures ranging from 15 to 40 °C. An enhancement of 37% average local convective heat transfer was achieved with 5 wt% alumina nanofluids at Re. 1100. The numerical data of convective heat transfer by CFD analysis using mixture model has also shown a good and satisfactory agreement with the experimental data. The present research is helpful to understand the thermal characteristics of low weight fraction alumina nanofluids under Laminar flow regime.

"The article reports a simple, economical and highly productive synthesis process of cuprous oxid... more "The article reports a simple, economical and highly productive synthesis process of cuprous oxide (Cu2O)
and copper/cuprous oxide (Cu/Cu2O) nanoparticles with an average size of below 30 nm. A hydrolysis of
copper (Cu) particles (200 nm or even microsize) employing low energy ball milling in aqueous
circumstance results a controlled synthesis of Cu2O and cermets of Cu/Cu2O nanoparticles. Ground
particles are found both in nanobar and spherical shape with cluster nano-clouds into aqueous solution.
X-ray diffraction patterns of the sample powder conﬁrm Cu2O nanoparticles and Cu/Cu2O cermets
synthesized by complete and incomplete oxidation of Cu particles, respectively. The process is accom-
plished at room temperature in presence of de-ionized (DI) water and controlled by changing milling
period and ball sizes. Enhanced thermal conductivity of Cu2Oewater and Cu/Cu2Oewater nanoﬂuids are
recorded and compared with non-ground Cuewater nanoﬂuids."

Hybrid nanofluids of CNTs and Al2O3 have been introduced in this study.Multiphase mixture model i... more Hybrid nanofluids of CNTs and Al2O3 have been introduced in this study.Multiphase mixture model is employed to investigate convective heat transfer.Effect of base fluids on performance (water and ethylene glycol) is investigated.Combination of CNTs into Al2O3 provides significant enhancement in heat transfer.Ethylene Glycol base fluid gives better heat transfer enhancement than water.Two-phase mixture model has been chosen to study forced convective heat transfer of nanofluid introducing a new concept of heat transfer enhancement in this article. Two different base fluids are individually employed to investigate the effect of base fluids on convective heat transfer mixing Al2O3 nanoparticles. The computational method has been successfully validated in case of Al2O3/water Nanofluids using available experimental data reported in the literature. The results show that Ethylene Glycol base fluid gives better heat transfer enhancement than that of water. Mixture of Al2O3 nanoparticles into CNTs/water Nanofluids is considered as a new concept of combined/hybrid nanofluids that can successfully enhance convective heat transfer. The computational model for CNTs/water nanofluid has been validated comparing the results with experimental data reported in literature. Then the validated method was used to simulate new concept of combined nanofluids. Combination of CNTs and Al2O3 nanoparticles into water base fluid tends to enhance the convective heat transfer performance significantly. It happens because CNTs nanofluid shows higher shear thinning behavior which causes the boundary layer thinner; in these regions the significant convective heat transfer enhancement takes place.

For the purpose of increasing the dispersibility and thermal conductivity of fluid containing nan... more For the purpose of increasing the dispersibility and thermal conductivity of fluid containing nanoparticles, raw multi-walled carbon nanotubes (MWCNTs) were treated by strong acids. The purified structures were dispersed into aqueous solution by using wet grinding conditions at various rotation speeds (300–600 rpm) merged with ultrasonication. The particle size analyzer reveals that the agglomerated size of ground particles at rotation speed of 300 rpm was 39.811 μm. Nevertheless, the agglomerated size of particles significantly decreased to 11.482 μm after grinding at rotation speed of 600 rpm. The maximum absorbance (4.0 abs at wavelength of 300 nm) and highest thermal conductivity (0.6074 W/mk at 30 °C) of the suspension corresponds to the grinding speed of 600 rpm assisted by ultrasonication dispersion. From the overall results, grinding method with high rotation speed plays can be significantly increased both the dispersibility and thermal conductivity of MWCNTs in aqueous solution.► Purification of MWCNT removes the impurities and agglomerations of raw material. ► Grinding is effective method for reducing the agglomeration and particle size of MWCNTs. ► Dispersibility and thermal conductivity was increased with increasing the grinding speed.

Aqueous solution of Al 2 O 3 nanoparticles is dispersed and thermally characterized. Effect of ul... more Aqueous solution of Al 2 O 3 nanoparticles is dispersed and thermally characterized. Effect of ultrasonic period of action on dispersibility and particle size has been investigated over the concentration of 0.5 vol.% to 1.5 vol.%. Thermal conductivity and convective heat transfer performance of nanoparticle solution have been experimentally studied at different concentrations. Results show the agglomeration of nanoparticles into dilute solution is time dependent and mean diameter of dispersed particle into solution decreases with increasing ultrasonication period. Thermal conductivity linearly increases with increasing the concentration of nanofluids and it was strongly temperature dependent. The enhancement of local convective heat transfer has been achieved about from 27% to 37% by the concentration of 1.5 vol.% of Al 2 O 3 nanofluids where the maximum thermal conductivity was about 5.33% under same concentration.

The article reports a nanocomposite (graphene and tungsten (GN–W)) successfully used as an altern... more The article reports a nanocomposite (graphene and tungsten (GN–W)) successfully used as an alternative to a conventional Pt counter electrode in dye-sensitised solar cells (DSSCs). The dispersibility of the GN structure in ethanol was enhanced by acid oxidation and planetary ball milling. Raw, purified and purified and ground GN structures were spin coated onto fluorine-doped tin oxide (FTO) glass substrates and examined as catalytic films on the counter electrodes of DSSCs. Purified and ground GNs exhibited the best photovoltaic performance (4.55%) among these structures. The grinding method was found effective for upgrading the dispersibility of GNs in a base fluid and the photovoltaic efficiency results. Based on the photovoltaic efficiency results of the DSSCs with different GN structures, the purified and ground GN structure was selected and incorporated with tungsten. A composite film of GN–W was used as a catalytic film on the counter electrode of a DSSC. The DSSC fabricated with the GN–W composite counter electrode achieved a photovoltaic efficiency of 5.88%. This performance is comparable to that of a DSSC with a standard Pt counter electrode (5.92%).Graphene, tungsten and graphene–tungsten composite counter electrode structures were employed for Pt-free dye-sensitised solar cell. We found that the low cost composite structure of GN–tungsten can be a potential material for replacing the conventional, expensive Pt in a DSSC.► Dispersibility of GN solution is improved by acid oxidation and grinding approaches. ► Photovoltaic performance of DSSC with GN was improved after planetary ball milling. ► DSSC with GN, tungsten and GN–tungsten composite counter electrodes are fabricated. ► DSSC with GN–tungsten composite counter electrode recorded an efficiency of 5.88%. ► GN–tungsten composite can be potential material for replacing expensive Pt in DSSC.

The current paper presents a new approach of attaining the optimum grinding condition of a planet... more The current paper presents a new approach of attaining the optimum grinding condition of a planetary ball mill and simple method for purifying multi-walled carbon nanotubes (MWCNTs) to investigate the dispersion characteristics of MWCNTs. This work was conducted under dry and wet grinding conditions at various rotation speeds (200 rpm–500 rpm), and the dispersion characteristics of MWCNTs in aqueous solutions with and without surfactant were studied. The results were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle-size analysis (PSA), UV-spectrophotometry and zeta potential (ζ) measurements. The purification results show that the structures of amorphous carbon and carbon particles of MWCNTs were completely eliminated and the tips of nanotubes opened. Moreover, both dry and wet grinding caused the lengths of the MWCNTs to be shortened with increasing rotation speed. The maximum absorbance of nanofluid was revealed to be 2.485 abs at wavelength of 253 nm for the best dispersion. The best dispersion characteristics were observed for wet grinding at a rotation speed of 500 rpm assisted by the ultrasonication dispersion of CNTs in aqueous solutions with surfactant.The grinding effects of the planetary-ball milling of MWCNTs with changing rotation speeds were investigated to improve the dispersibilities of MWCNTs in aqueous solutions. The best dispersion characteristics were observed for wet grinding at a rotation speed of 500 rpm assisted by the ultrasonication dispersion of CNTs in aqueous solutions with surfactant.► Dry and wet ball milling approaches are compared on dispersibility of CNT nanofluid. ► Grinding is effective method for reducing the agglomerated particle size of CNTs. ► SDS molecule can exert an “unzippering force” to disperse CNTs in base fluid. ► Best dispersibility of nanofluid is obtained for purified and wet ground MWCNTs.

Elsevier, Apr 16, 2014

Elsevier, May 30, 2014

IOP science, Feb 1, 2014

Elsevier, Jan 1, 2014

American Scientific Publishers, Dec 1, 2013

The article provides an in-depth understanding of self-assembly concepts for the preparation of g... more The article provides an in-depth understanding of self-assembly concepts for the preparation of graphene-based composites for broad range of applications. This starts with a brief introduction of graphene oxide and reduced graphene oxide followed by the description of interlayer interactions and molecular bonds principally responsible for initiating self-assembly of graphene sheets and creating complex structures with one-, two-, and three-dimensional morphologies. Numerous self-assembly methods and self-assembled superstructures including fibers, thin films, spheres, crumpled particles, aerogel/hydrogels, honeycomb, and nacre-like structures have been discussed. Besides the structural merits, the useful properties and novel functionalities of these versatile nanoscale building blocks have been outlined. A brief overview of the recent progress of these self-assembled structures in the field of environmental remediation, sensing, energy, and drug delivery/tissue engineering is finally presented followed by the conclusion and future perspectives.