Fracture toughness (K1C) and tensile properties of as-cast and age-hardened aluminium (6063)–silicon carbide particulate composites

AbstractThe tensile and fracture behavior of as-cast and age-hardened aluminium (6063), silicon carbide particulate composites produced, using borax additive and a two step stir casting method, was investigated. Al (6063), SiCp composites having 3, 6, 9, and 12 volume percent of SiC were produced, and sample representatives of each composition were subjected to age-hardening treatment at 1800 °C for 3 hours. Tensile and Circumferential Notched Tensile (CNT) specimens were utilized for tension testing to evaluate, respectively, the tensile properties and fracture toughness of the composites. Experimental results show that the ageing treatment resulted in little improvement in the tensile strength of the composites. The tensile strength and yield strength increased to almost the same magnitude with an increase in SiC volume percent for both as-cast and age-hardened conditions. The increase was, however, more significant for the 9 and 12 volume percent SiC reinforcement. The strain to fracture was less sensitive to volume percent SiC reinforcement and ageing treatment, with values less than 12% strain to fracture observed in all cases. The fracture toughness, however, improved significantly with ageing treatment (as-cast K1C=6.63−6.71MPam1/2; ageing treatment K1C=7.57−8.2MPam1/2)

Mechanical behaviour of Al-Mg-Si matrix composites reinforced with alumina and bamboo leaf ash

The mechanical behaviour of Al-Mg-Si alloy matrix composites reinforced with alumina and bamboo leaf ash (BLA) has been investigated. Alumina (Al2O3) particulates complemented with 0, 2, 3, and 4 wt% BLA were utilized to prepare 10 wt% of reinforcement in Al-Mg-Si alloy matrix using double stir casting method. Micro-hardness measurement, tensile testing, fracture toughness evaluation, optical and scanning electron microscopy were used to characterize the composites. It was observed that 4.7, 9.32, and 14.3 % reduction in tensile strength was obtained for the composites containing 2, 3, and 4 wt % BLA, respectively. Although there was still a decrease in specific strength and hardness with increase in BLA content, the reductions are less than 9 % for a 40 % reduction of alumina as obtained in the hybrid composite containing 6wt % alumina - 4 wt % BLA. The hybrid composites containing 2 and 3 wt % BLA exhibited a superior elongation in comparison to the single reinforced Al-Mg-Si/ 10 wt % alumina composite, while all hybrid composite compositions exhibited a superior fracture toughness compared to the single alumina reinforced composite

Corrosion inhibitory properties of elephant grass (Pennisetum purpureum) extract: Effect on mild steel corrosion in 1M HCl solution

AbstractCorrosion inhibition and adsorption characteristics of elephant grass extracts on mild steel in 1M HCl solution were investigated. Mass loss, corrosion rate measurements, inhibition efficiency, atomic adsorption spectroscopy (AAS), FT-IR spectroscopy and scanning electron spectroscopic analysis were used to assess the inhibitory properties of the extract in the acid solution. The results show that the steel dissolution rate in the acidic solution was sensitive to the extract concentration as mass loss and corrosion rates were observed to decrease with increase in the extract concentration. The inhibition efficiencies were averagely above 95% at room temperature increasing with increase in concentration of the extract but decreases with increasing temperature. FTIR results showed that the inhibition was essentially by absorption through the functional groups present in the extract while the activation energies and Langmuir adsorption isotherms confirm the mechanism to be physical adsorption. The SEM images of the corroded substrates confirmed pitting as the primary corrosion mechanism which was substantially mitigated with the use of the extract. Overall, the elephant grass extract was found to be efficient for corrosion inhibition of mild steel in HCl environment

Pharmacokineticosf biliary excretion of N-nitrosodimethylaminein ratsf ed dietsc ontainingle velso f protein

Albino Wistar rats (Rattus nomegius) fed semi-purified diets ssnf qini n g 3.5 Vo, 8 Vo, 27 Vo, and 64 Vo casein, respectively, as the protein source, were poisoned with an intraperitoneal dose of 20mg N-nitrosodimethylamine (NDMA/kg, following cannulation of the bile duct, in vitro, under urethane anaesthesia Bile exudates was collected at designated time intervals and analysed for unchangetl NDMA using thin layer chromatography and gas liquid chromatography methods. Rats on 64Vo htgh protein diet (HpD) were the highest excretors of NDMA, followed by rats on the 3.SVo kwashiorkorigenic diet (KWD), 8Vo low protein diet (LpD) and,27Von ormal protein diet (NDP) as the leaste xcretors,i n that order. The corresponding values for culmulative excretionso f NDMA were4 .38Vo2, .74Vo,2.96Vaon d4. .ll7o, and, for elimination rate contents they were 54.05Kh", 23.01Kh-', 23.76Kh" and 48.88Kh'', while the respective elimination half-life values were 0.013h, 0.031h, 0.029h and 0.014h. The toxicological and pharmacological implication of the pharmacokinetic findings are discusse

Fracture toughness and tribological wear behaviour of micro alloyed pearlitic- ferritic ductile cast iron

Abstract: Fracture toughness and wear behaviour of micro alloyed ductile iron were investigated. Hardness, fracture, fracture toughness and wear tests were carried out on the ductile irons samples (D1, D2, D3, D4 and D5), containing micro alloyed nickel, molybdenum, copper and chromium in an amount of 0.2 % or less. They were characterized using optical metallurgical microscope and they contained pearlitic- ferritic matrix structure. They were subjected to wear test at room temperature based on pin-on-disk operation. Fracture surfaces and the wear track were studied using scanning electron microscope and found that the fracture surfaces majorly consist of fibrous with little cleavage fracture pattern in some samples. Wear mechanism is delamination with adhesive wear behavior. The specific wear rate was found to decrease with increasing hardness of the material and coefficient of friction of the ductile irons during test

MICROSTRUCTURAL CHARACTERISTICS, MECHANICAL AND WEAR BEHAVIOUR OF ALUMINIUM-ALLOYED DUCTILE IRONS SUBJECTED TO TWO AUSTEMPERING PROCESSES

The effect of aluminium addition and austempering processes on the microstructures, mechanical and wear properties of rotary melting furnace processed ductile irons was investigated. Ductile irons containing 1−4 wt.% Al were produced and subjected to single and two-step austempering processes. Optical microscopy was used to characterize the graphite features and estimate the volume fraction of the matrix phases present, while the x-ray diffractogram was also carried out to analyse the samples. Mechanical and wear properties of the alloys were equally evaluated. From the results, it was observed that both the as-cast and austempered ductile iron microstructures contained nodular graphite, and the matrix structure for the as-cast ductile irons consisted predominantly of pearlite and ferrite, while that of the austempered grades, contained principally, ausferrite. The microstructure and intermetallic compound obtained played dominant role on the properties of the alloys. The aluminium addition and austempering processes had a significant influence on the mechanical properties and wear resistance of the alloys. The austempered ductile irons exhibited superior strength and wear resistance compared to the as-cast samples, albeit ductility values were lower in the composition group. Austempering increased the strength by over 100% while the addition of Al further enhanced the strength. The improved properties were linked to the refined microstructure, increased proportion of ausferrite phase and intermetallic compound formed. For all properties evaluated, the two-step austempering yielded better properties combination than the single step process. The rotary melting furnace processing adopted was found viable for ductile iron production

Corrosion inhibition of mild steel in acidic solution by cow dung extract as an eco-friendly inhibitor

Abstract: The anti corrosion potential of cow dung was assessed using weight loss, Electrochemical techniques, Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) along with Energy dispersive spectroscopy (EDS), and Atomic absorption spectroscopy (AAS). The results show that cow dung extract (CDE) possesses good inhibition properties. The inhibition efficiency was found to increase with concentration but decrease with temperature. The highest inhibition efficiency obtained was 91% at 303K. Potentiodynamic polarization result suggests that CDE functioned as a mixed-type inhibitor. The AAS analysis shows that the concentration of Fe2+ in the electrolyte decreases with increase in the extract concentration. The adsorption of extract on the metal surface followed both Langmuir and Freundlich adsorption isotherms though Langmuir model better explained the adsorption process involved

Challenges of Finance and the Performance of Small and Medium Enterprises (SMES) in Lagos State

This study examined the challenges of finance as is experienced by business operators classified into micro, small and medium scale (MSMEs), and how this affects their financial performance. The study evaluated the efficiency of the different sources of funds available for the SMEs as well as other non financial factors responsible for the poor performance of SMEs in Nigeria. Given some of the government interventions to solving the issue of credit to SMEs, the operations of the micro finance banks were also evaluated to determine their capacity toward closing the funding gap for SMEs. This study became imperative given the conflicting reasons adduced to why small scale enterprises perform poorly in developing economies including Nigeria There was a need to find out if the major challenge of SMEs is indeed credit using the five divisions in Lagos State as the study area. The useable sample size consisted of 222 returned copies of questionnaire out of the 250 distributed representing 88.8% response rates. Quota sampling as well as stratified random sampling technique was applied in the choice of the five divisions under study and the distribution of the sampling frame; while convenience sampling technique was used to get to the individual respondents. Correlation and one sample t-test was used to test the hypotheses. The study indicated significant statistical difference for sources of funds and in the efficiency of the various sources. The challenge of funds still ranked highest followed by unstable power supply, while micro finance banks were expected to do more to assist the SMEs. Keywords: Challenges, Finance, Lagos State, MSMEs, Nigeria, SMEs

Valuating hydrocarbon pipeline facility service beyond 20–25 year economic life: Accounting for residual value

The 20–25 years economic life for hydrocarbon pipelines in the investment decision model is at wide variance with historical statistical records of more than 90-percent world-wide. Opinions diverge, from service type to the product quality, and materials resilience as basis for this premise. While, financial experts consider time to fully depreciate a capital investment, irrespective of the rate of returns, engineers consider operational availability and reliability duration. The risk is that actual residue values of pipelines worldwide are erroneously omitted in every project’s economics Cash-flow computation, thus eroding the investment decision quality. Statistics showed that more than 60-percent of pipelines worldwide have already exceeded the 25 years economic life, while more than 40-percent have operated more than 30-years and above. This theoretical appraisal identified a gap in the economic model in handling multi-criteria risk management uncertainties like hedging, weighting, etc., and highlighted the exigency to craft and assign numeric residue values for pipelines in the investment Cash-flow models