Master of Philosophy (M.Phil.)
http://dl.lib.uom.lk/handle/123/18725
2024-03-29T01:31:32ZDevelopment of coir fiber based insulative composite material to reduce thermal heat in buildings
http://dl.lib.uom.lk/handle/123/21397
Development of coir fiber based insulative composite material to reduce thermal heat in buildings
Chamath LG
Energy consumption is a critical factor in building design. Maintaining a comfortable
indoor temperature consumes high energy than other necessities such as lighting and
cooking. The building envelope is the main component of the building that transfers
heat between indoor and outdoor environments. During the daytime, a proper
ventilation system or an air conditioning system can control the heat in a building.
Insulation layers are also used under the roofing sheets to control the heat transfer
through the roof because a building’s roof contributes to a significant heat gain in
tropical countries.
Sustainable insulation materials have been more attractive in the last two decades due
to biodegradability, low embodied energy, availability, and non-toxicity. Sustainable
insulation materials are primarily fabricated using lignocellulose fiber (natural plant
fibers). Then it is mandatory to add binder material to adhere to fibers and the material
formulated as a composite material, and an air void should be introduced to the
combination of fiber and binder to increase insulation properties. Now the whole
material can be identified as a three-phase composite material. Thus, the volume
fraction of each phase (fiber, binder, and air void) is the most critical factor which
controls these composites’ insulation properties.
The insulation properties of the material can be analysed using experimental,
analytical, and numerical methods. Analytical and numerical methods are more
attractive than experimental methods. However, there are limited number of studies on
the effect of volume fraction with insulation properties in a three-phase composite. In
this study, the effective thermal conductivity (K
eff
) of the composite was analysed
through the analytical and numerical models and validated through the experimental
results. The results concluded that the experimental results agreed with the numerical
and analytical results. Furthermore, a novel mathematical model has been proposed to
find the K
eff
of the three-phase composite using the analytical and numerical methods.
The proposed model shows better agreement with the experimental result. Therefore,
it can be used to develop this research area further.
2022-01-01T00:00:00ZSynthesis of porous graphene from Sri Lankan graphite for supercapacitor applications
http://dl.lib.uom.lk/handle/123/21395
Synthesis of porous graphene from Sri Lankan graphite for supercapacitor applications
Sandaruwani MKA
A feasible process to synthesize porous graphene with ultra-high surface area is
presented in this thesis. Graphene oxide (GO) was synthesized from Sri Lankan
graphite via the modified hummers method. Then, GO was subjected to a chemical
activation process to produce graphene with a mesoporous structure, where KOH was
used as the activation agent. The influence of the critical activation process parameters
on the specific surface area of graphene was studied. In this study, activation time at
60 min, activation temperature at 800 ℃ and KOH/GO mass ratio at 4 were identified
as the optimum activation parameters for high surface area. As an alternative route to
find the specific surface area (SSA), a dye adsorption based SSA calculation method
was followed, and the methylene blue adsorption kinetics were studied for that. Second
order kinetic model and Langmuir isotherms were the most suitable kinetic models for
the methylene blue adsorption onto porous graphene which were produced from Sri
Lankan vein graphite. A combined mathematical model of methylene blue number
(MBN) and iodine number (IN) was used to calculate the SSA for high accuracy. The
obtained optimum activated graphene sample showed a high specific surface area of
768.15 m
2
/g as measured from the dye adsorption method and it was verified by BET
analysis. Furthermore, methylene blue and Iodine adsorption methods are studied as a
low-cost and feasible method for surface area determination of porous graphene. The
high surface area of the obtained graphene would make it a promising material for
supercapacitor applications. The present study mainly focuses on the value addition to
Sri Lankan vein graphite trough the utilization of vein graphite as an electrode material
in electrochemical double layer capacitor (EDLC).
2022-01-01T00:00:00ZCorrelation between the degree of corrosion and the ultrasonic parameters in steel
http://dl.lib.uom.lk/handle/123/16961
Correlation between the degree of corrosion and the ultrasonic parameters in steel
Piyathilake SAKVM
In metallurgical engineering, corrosion is considered as one of the main reasons for the failure of metallic components. The main reason for this is that, the corrosion is a phenomenon which is mainly influenced by the nature itself. It is very important to eliminate or reduce corrosion since it can lead to major disasters which can negatively affect the human lives and properties. Inaccurate estimations, inaccessibility of the areas of corrosion, limitations for the destructive tests can be identified as some of the main reasons for the wrong and misleading preliminary corrosion investigations, which lead to catastrophic failures. Conventionally, the degree of corrosion is determined using destructive testing methods. Also, most of the research work in this area has focused on the uniform corrosion/general attack faced by steels across a range of atmospheres. With those methods, the real degree of corrosion cannot be revealed since it is difficult to address regarding the corrosion penetrations or pits. Therefore, those are inaccurate up to some extent. In contrast to that, Ultrasonic testing methods would be more effective and convenient to overcome above limitations and would be able to open a new area of estimating the degree of corrosion accurately. Also this study sought to contribute to this field by examining whether the penetration of corrosion beyond the general attack has a significant effect on the load-bearing capacity of mild steel. Also,in some cases such as in bridges and pipelines ultrasonic non-destructive method would be really advantageous since it is not only non-destructive but also it will allow reaching inaccessible locations easily. Further,an Ultrasonic wave can easily propagate through steel and its attenuation would provide a measurable reading to express the degree of corrosion including every minor detail. The research work is basically focused on measuring the degree of corrosion accurately using ultrasound attenuation. The selected steel materials were subjected to corrosion in a standard accelerated environment for a defined period of time. Then after a set of experiments, the degree of corrosion has been represented by the weight loss per unit
iii
area, corrosion rate and the corrosion penetration depth in to the material. Furthermore,
the research work was able to cover the area of the mechanical property deterioration.
The tensile samples were also corroded in the same standard accelerated environment as
mentioned above, and subjected to periodic tensile testing and corrosion weight loss
analyses. Further, the corroded samples were examined under optical and scanning
electron microscopy to observe the penetration behavior of corrosion in to the material.
The results showed that the actual breaking loads deviated negatively from the expected
load-bearing capacity, which was determined through conventional methods. This
deviation showed a close correlation to the increase of penetration of corrosion with
time.
Meanwhile, the ultrasound attenuation related to each of those corroded samples was
measured simultaneously. Finally, all the data were analyzed through mathematical
software such as MATLAB and SPSS to generate final correlations. Thereby, a
nondestructive method through ultrasound attenuation was developed to determine the
accurate degree of corrosion and to predict the remaining load bearing capacity of
corroded structures.
2020-01-01T00:00:00ZPrediction of corrosion behavior of mild steel in different Sri Lankan atmospheric conditions
http://dl.lib.uom.lk/handle/123/14651
Prediction of corrosion behavior of mild steel in different Sri Lankan atmospheric conditions
Adikari, AAMT
Corrosion is defined as the deterioration of materials due to the reaction with its
environment. According to the physical nature of environment, corrosion can be
categorized as 'corrosion in atmosphere', 'corrosion in water', 'corrosion in sea',
'corrosion in soil' etc. Among them, corrosion of steel in atmosphere is identified as one
of most important type of corrosion. Because studies show that corrosion cost of a
country may vary between 1 to5% of their GDP and about one half of that cost is due to
atmospheric corrosion.
Corrosion problem cannot be completely eliminated but it is possible to control by
methods known as 'corrosion management systems'. Corrosion model is a one of the best
tool that can be used for atmospheric corrosion management. Use of a corrosion model
as a tool for corrosion prevention is the common practice in many other countries, but
using this method is not a popular practice in Sri Lanka due to non availability of such
model. Therefore, this project was carried out for the formulation of an atmospheric
corrosion model that can be applicable in Sri Lankan atmosphere.
For this purpose, by reviewing internationally published literature a model structure was
proposed. Then field exposure programs were conducted to obtain data required for
model calibration. The model was calibrated with the obtained data and test has been
done for goodness of fit and the model shows considerably acceptable goodness of fit
with more than 80% of data are within the ±10% deviation from actual value. Finally, a
completely different set of samples were placed in different locations and data gathered
were used to find out the validity and forecasting capability of the model,. The model
shows a good performance in forecasting capability with acceptable deviations.