Tribological Performance of UHMWPE/GNPs Nanocomposite Coatings for Solid Lubrication in Bearing Applications

Ultra-high molecular weight polyethylene (UHMWPE)/ graphene nanoplatelets (GNPs) nanocomposite coatings were developed to reduce friction and wear in the absence of liquid lubrication. UHMWPE nanocomposite powders with different loadings (0.25, 1, and 2 wt.%) of GNPs were prepared and electrostatic spraying technique was then used to deposit the nanocomposite powders on aluminum alloy to form a thin coating. Friction and wear tests were conducted on the coatings against a flat-end pin, made of hardened tool steel to determine the best loading of GNPs. That was further tested to investigate the effect of sliding speed and contact pressure on its tribological properties and to establish coating operating limits. Results showed that UHMWPE nanocomposite coating reinforced with 1 wt.% GNPs showed the best tribological performance. It reduced wear rate by about 51% as compared to the pristine UHMWPE coating. The coating sustained a maximum sliding speed of 1 m/s at a contact pressure of 4 MPa equivalent to a pressure and velocity (PV) value of 4 MPa.m/s.     

Biobased composites prepared by compression molding with a novel thermoset resin from soybean oil and a natural‐fiber reinforcement

Biobased composites were manufactured with a compression‐molding technique. Novel thermoset resins from soybean oil were used as a matrix, and flax fibers were used as reinforcements. The air‐laid fibers were stacked randomly, the woven fabrics were stacked crosswise (0/90°), and impregnation was performed manually. The fiber/resin ratio was 60 : 40. The prepared biobased composites were characterized by impact and flexural testing. Scanning electron microscopy of knife‐cut cross sections of the specimens was also done to investigate the fiber–matrix interface. Thermogravimetric analysis of the composites was carried out to provide indications of thermal stability. Three resins from soybean oil [methacrylated soybean oil, methacrylic anhydride modified soybean oil (MMSO), and acetic anhydride modified soybean oil] were used as matrices. The impact strength of the composites with MMSO resin reinforced with air‐laid flax fibers was 24 kJ/m², whereas that of the MMSO resin reinforced with woven flax fabric was between 24 and 29 kJ/m². The flexural strength of the MMSO resin reinforced with air‐laid flax fibers was between 83 and 118 MPa, and the flexural modulus was between 4 and 6 GPa, whereas the flexural strength of the MMSO resin reinforced with woven fabric was between 90 and 110 MPa, and the flexural modulus was between 4.87 and 6.1 GPa. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The use of lipase (acetone powder) from Vernonia galamensis in the fatty acid analysis of seed oils

Examined in this study is a potential application of Vernonia galamensis lipase (acetone powder) in enzyme-catalyzed hydrolysis of seed oils, most especially of those containing reactive functionalities which are easily affected under drastic hydrolytic and methylating/transesterification conditions during fatty acid analysis. Eight seed oils from V. galamensis, Ximenia kaffra, castor, corn, soyabean, palm kernel, sunflower and olive were hydrolyzed by lipase (acetone powder) followed by methylation using diazomethane in ethyl ether. Results obtained showed that the lipolytic hydrolysis of triglycerides by V. galamensis lipase (acetone powder) was probably nonspecific and did not result in isomerization and as such hydrolyzed the triglycerides of the seed oil in a fashion that the resulting fatty acids were unaltered during hydrolysis. The fatty acids obtained were representative of the parent seed oils. Values reported for the various seed oils were similar to those of previous studies.     

Photoelastic analysis of practical mode I fracture test specimens

A photoelastic technique for the evaluation of the isochromatic fringe patterns of practical Mode I fracture test specimen is presented.The new procedure uncouples the expressions for the stress intensity factor $\text{K}$ and the non-singular stress term $\text{A}$ from the governing maximum shear expression by employing a line perpendicular to the crack-tip in a photoelastic specimen, (this line intersects the isochromatic fringes at the locus of points $\text{r}{}_{\mathrm{i}}$, $\text{θ}{}_{\mathrm{i}}\text{= π/2}$, $\text{i = 1,2,…, n}$, where $\text{n}$ is the maximum analizable fringe) in developing the least-squares technique employed in this research.The least-squares expressions developed required no assumption of initial values for the stress intensity factor $\text{K}$ and the non-singular stress term $\text{A}$. The accuracy of the approach is then demonstrated by obtaining the $\text{K}$ and $\text{A}$ values of some practical Mode I specimens under applied uniaxial and biaxial stresses.     

Quality assessment of laminated fillet blocks from blue whiting (Micromesistius poutassou)

Laminated fillet blocks made from blue whiting (Micromesistius poutassou) caught in February and April were assessed for quality. The total protein nitrogen value in February-caught fish was greater than the April-caught fish. The bone content, water content and pH values were consistently lower in the February fish than the April fish. Measurement of the acceptability of deep fried, breaded fingers made from the fish and compared with cod fingers produced from fish caught at the same time of year showed a consistent difference between the cod and blue whiting. In addition, the fish fingers from fish caught in February scored consistently higher than those caught in April. The implications of the findings are discussed.     

DFTMicroagg: a dual-level anonymization algorithm for smart grid data

International Journal of Information Security - The introduction of advanced metering infrastructure (AMI) smart meters has given rise to fine-grained electricity usage data at different levels of...     

Prediction of structural response to blast –induced vibration in Kopek Construction Quarry,Ikere – Ekiti,Ekiti State,Nigeria

The responses of adjoining structures to blast induced ground vibrations emanating from Kopek Construction Quarry, Ikere – Ekiti in Ekiti State were evaluated and predicted. Five off site receptors at predetermined distances from the blast source were chosen and the Peak Particle Velocity (PPV) at each receptor during blasting was estimated using the squared root scaled distance equation. The estimated PPVs were compared with the USBM – RI 8705 reference. The results showed that the blast induced vibrations from the quarry site were within the recommended limits and were insignificant to warrant concerns of causing structural damages to buildings in proximity to the quarry site with the given blast design parameters.     

Rapid transesterification and mass spectrometric approach to seed oil analysis

Fatty acid composition of seed oil is determined in less than one hr using a quantitative one-vial technique. The method of analysis requires alcoholic solutions of sodium methoxide mild enough for epoxy and polyunsaturated oils. Separation and characterization of component fatty acids were accomplished by high resolution gas chromatography-mass spectrometry. Using this method,Vernonia galamensis seed oil is shown to contain 79–80% vernolic (cis-12,13-epoxy-cis-9-octadecenoic) acid.Amaranthus cruentus, a West African vegetable crop, is shown to contain 17.3% palmitic acid, 3.2% stearic acid, 22.7% oleic acid, 54.7% linoleic acid and 2.1% linolenic acid.