Edible films and coatings: a review.

SUMMARY A new generalized FEM is introduced for solving problems with discontinuous gradient fields. The method relies on enrichment functions associated with generalized degrees of freedom at the nodes generated from the intersection of the phase interface with element edges. The proposed approach has several advantages over conventional generalized FEM formulations, such as a lower computational cost, easier implementation, and straightforward handling of Dirichlet boundary conditions. A detailed convergence study of the proposed method and a comparison with the standard FEM are presented for heat transfer problems. The method achieves the optimal rate of convergence using meshes that do not conform to the interfaces present in the domain while achieving a level of accuracy comparable to that of the standard FEM with conforming meshes. Various application problems are presented, including the conjugate heat transfer problem encountered in microvascular materials. Copyright © 2011 John Wiley & Sons, Ltd.

An interface-enriched generalized FEM for problems with discontinuous gradient fields

In this study, Al–Al2O3–Ag coated graphene hybrid nanocomposites was fabricated by Electroless coating and powder metallurgy. Electro-less deposition was used to coat graphene nanosheets (GNs) with a thin layer (~5 nm) of Ag. We studied the impact of GNs content on the structural, microhardness and wear properties of the manufactured hybrid nanocomposites. The energy dispersive X-ray (EDX) mapping images reveal that the Al2O3 and GNs reinforcements particles were homogeneously distributed into the Al matrix. The relative density decreased with increasing the weight fraction of GNs contents. The results showed that hardness and wear properties were improved with increasing GNs mass fraction. Vickers microhardness tests results showed that the highest hardness value of 130.5 HV is attributed to the sample containing 1% of GNs, much higher than the hardness value of the Al-5% Al2O3 composite of 48 HV. The wear test results showed that the composite with higher GNs content 1 wt.% showed the best wear resistance. The high strength and self lubricant properties of GNs and the grain size reduction due to electroless deposition were the main reason for properties improvement. Additionally, the increased efficient transfer of stresses due to the curled structure of GNs helps for properties improvement.

Experimental study on properties of Al–Al2O3 nanocomposite hybridized by graphene nanosheets

An innovative and simplified method of electroless pure‑nickel coating was plated on graphene nanoplatelets (GNPs). The nickel-coated graphene nanoplatelets (NiGNPs) were uniformly dispersed in Inconel 625 (IN625) powder with the ratio of 1:9 by ball milling. Then laser cladding was used to fabricate the NiGNPs reinforced IN625 composite coatings. The survivability of NiGNPs, morphology of precipitated phase, microhardness through transverse section and wear resistance at room and elevated temperatures were studied. The results indicated that the NiGNPs were successfully incorporated into IN625 coatings by laser cladding. Part of them were deduced to be damaged or dissolved into molten pool, which benefited the formation of NbC, but most of them could be observed as exposed GNPs and well-distributed welded GNPs. Compared to laser cladded IN625 coating, the composite coating showed higher hardness at bottom region of cladded coating and smaller size of HAZ due to the improvement of thermal conductivity by additional NiGNPs. Furthermore, comparative wear test demonstrated that friction coefficient (COF) and wear rate were decreased at both room and elevated temperatures. Combined with wrinkled, tiled and rolled GNPs observed on the worn surface, it was revealed that the wear properties were efficiently benefited from superior lubrication between interlayers of GNPs.

Enhanced wear resistance of laser cladded graphene nanoplatelets reinforced Inconel 625 superalloy composite coating

Fabrication and characterization of novel layered materials produced by electroless plating and hot pressing

Vibrations transmitted into the machine tool structure made of cast iron cause chattering and develop positional errors between the components during machining operations, causing dimensional inacc...

Dynamic analysis on fabricated mineral cast lathe bed

Nickel-based multiwalled carbon nanotube (Ni–MWCNT) composite coatings were electrodeposited over the inner groove of an aluminim alloy rotor with Zn–Ni interlayer. The surface of the composite coating was investigated by X-ray diffraction and scanning electron microscopy. The hardness of the coating was determined by Vicker's method. It was revealed that Ni–MWCNT composite coating has uniformity in thickness over the surface of the aluminim groove and also better particle distribution over the area. It was found that there was a significant improvement in the microhardness values of Ni–MWCNT composite coating than uncoated aluminum alloy rotor. In addition, the wear resistance of the composite coated increased nine times than the uncoated substrate. Thus, Ni–MWCNT composite coated aluminum alloy rotor can enhance the performance and life-time of the rotor in the textile industries.

Nickel–multiwalled carbon nanotube composite coating on aluminum alloy rotor for textile industries

NiP–multiwall carbon nanotube composite coatings were deposited on a textile component at ∼14 µm thickness through electroless plating route. The composites were prepared by depositing four different concentrations of multiwall carbon nanotube (i.e. 100, 200, 300 and 400 mg L–1) in an electroless bath over four NiP substrates. The NiP–multiwall carbon nanotube composite coating was observed to have a remarkably lower surface roughness and higher micro-hardness – by about 50% in both cases – in comparison with the NiP electroless plated substrate without the incorporation of multiwall carbon nanotube. In addition to that, there was a 14% reduction in yarn to metal friction between the investigated cases. This particular enhancement was adduced to the addition of surfactant to the electrolytic bath. The superior homogeneity in the distribution of multiwall carbon nanotube in the nickel matrix and the formation of the Ni–C bond were also identified to drive the multiwall carbon nanotube towards much improved...

Electroless NiP–MWCNT composite coating for textile industry application

Thermal conductivity is a thermophysical property that represents the rate at which heat energy can be transported through the material. For any alternate material chosen for machine tool structures, the study of its thermal characteristics is imminent. Thermal conductivity is one major characteristic to be analysed. Mineral cast structures made of epoxy-granite are found to exhibit good mechanical properties, such as high stiffness and damping ratio. The material also has lesser weight, compared to conventional materials used for machine tool structures. Hence, these materials are emerging as an alternate to conventional cast iron machine tool structures. This study attempts to determine the effective thermal conductivity of epoxy granite material using steady-state and transient plane source (TPS) methods. The results obtained using the experimental methods are compared with geometrical models and the suitability of the methods is evaluated. It is observed that both methods are suitable for measuring effective thermal conductivity of two-phase materials. Compared to TPS method, the steady-state method is a slow and material-consuming technique but provides more accurate results. The effective thermal conductivity of the developed material is compared with some commercial polymer composites and observed that the developed material has greater thermal conductivity.

Evaluation of Effective Thermal Conductivity for Mineral Cast Structural Materials Using Steady-State and Transient Methods

Conventionally, cast iron is the material used for high speed machine tool structures. As an alternate material to improve the structural properties, composite materials are being used, which are known to exhibit excellent thermal and mechanical properties. While selecting an alternate material, thermal conductivity is an important thermo physical property of the material that should be studied. A resin composite material has a lesser thermal conductivity and its thermal properties vary with the composition of the mixture. A material with lower thermal conductivity will have higher heat concentration within the structure, which may result in structural deformation. In this analysis, epoxy granite, a material which is tested to exhibit excellent mechanical properties has been selected to study its thermal properties. Tests are carried out using Transient Plane Source (TPS) method, on eight samples with varying volume fraction of epoxy content in the range 10-24%. It is observed that, the effective thermal conductivity decreases with an increase in epoxy resin content in the mixture because the resin content increases interfacial resistance between particles. Hence, lower epoxy content in the mixture that maximizes the effective thermal conductivity while maintaining good mechanical properties is to be selected.

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A. Selvakumar

Papers

Dynamic analysis on fabricated mineral cast lathe bed

Nickel–multiwalled carbon nanotube composite coating on aluminum alloy rotor for textile industries

Electroless NiP–MWCNT composite coating for textile industry application

Evaluation of Effective Thermal Conductivity for Mineral Cast Structural Materials Using Steady-State and Transient Methods

Analysis of effective thermal conductivity for mineral cast material structures with varying epoxy content using TPS method