Abstract: Sol-enhanced Zn-Ni-Al2O3 nanocomposite coatings
were electroplated on mild steel by our newly developed solenhanced
electroplating method. In this method, transparent Al2O3 sol
was added into the acidic Zn-Ni bath to produced Zn-Ni-Al2O3nanocomposite
coatings. The chemical composition, microstructure and
mechanical properties of the composite and alloy coatings deposited
at two different agitation speed were investigated. The structure of all
coatings was single γ-Ni5Zn21 phase. The composite coatings possess
refined crystals with higher microhardness compared to Zn-Ni alloy
coatings. The wear resistance of Zn-Ni coatings was improved
significantly by incorporation of alumina nano particles into the
coatings. Higher agitation speed provided more uniform coatings
with smaller grain sized and slightly higher microhardness.
Considering composite coatings, high agitation speeds may facilitate
co-deposition of alumina in the coatings.
Abstract: Pt/γ-Al2O3 membrane catalysts were prepared via an
evaporative-crystallization deposition method. The obtained Pt/γ-
Al2O3 catalyst activity was tested after characterization (SEM-EDAX
observation, BET measurement, permeability assessment) in the
catalytic oxidation of selected volatile organic compound (VOC) i.e.
propane, fed in mixture of oxygen. The VOC conversion (nearly
90%) obtained by varying the operating temperature showed that
flow-through membrane reactor might do better in the abatement of
VOCs.
Abstract: Nanofibers of PVA /nickel nitrate/silica/alumina
izopropoxide/boric acid composite were prepared by using sol-gel
processing and electrospinning technique. By high temperature
calcinations of the above precursor fibers, nanofibers of
NiO/Al2O3/B2O3/SiO2 composite with diameters about 500 nm
could be successfully obtained. The fibers were characterized by
XRD and SEM analyses.
Abstract: The objective of this work is to study the effect of two
key factors - external magnetic field and applied current density
during template-based electrodeposition of nickel nanowires using an
electrode distance of 20 mm. Morphology, length, crystallite size and
crystallographic characterization of the grown nickel nanowires at an
electrode distance of 20mm are presented. For this electrode distance
of 20 mm, these two key electrodeposition factors when coupled was
found to reduce crystallite size with a higher growth length and
preferred orientation of Ni crystals. These observed changes can be
inferred to be due to coupled interaction forces induced by the
intensity of applied electric field (current density) and external
magnetic field known as magnetohydrodynamic (MHD) effect during
the electrodeposition process.
Abstract: The effect of transition metal doping on Pt/Al2O3
catalyst used in propane dehydrogenation reaction at 500°C was
studied. The preparation methods investigated were sequential
impregnation (Pt followed by the 2nd metal or the 2nd metal followed
by Pt) and co-impregnation. The metal contents of these catalysts
were fixed as the weight ratio of Pt per the 2nd metal of around 0.075.
These catalysts were characterized by N2-physisorption, TPR, COchemisorption
and NH3-TPD. It was found that the impregnated 2nd
metal had an effect upon reducibility of Pt due to its interaction with
transition metal-containing structure. This was in agreement with the
CO-chemisorption result that the presence of Pt metal, which is a
result from Pt species reduction, was decreased. The total acidity of
bimetallic catalysts is decreased but the strong acidity is slightly
increased. It was found that the stability of bimetallic catalysts
prepared by co-impregnation and sequential impregnation where the
2nd metal was impregnated before Pt were better than that of
monometallic catalyst (undoped Pt one) due to the forming of Pt sites
located on the transition metal-oxide modified surface. Among all
preparation methods, the sequential impregnation method- having Pt
impregnated before the 2nd metal gave the worst stability because this
catalyst lacked the modified Pt sites and some fraction of Pt sites was
covered by the 2nd metal.
Abstract: The development of active and stable catalysts
without noble metals for low temperature oxidation of exhaust gases
remains a significant challenge. The purpose of this study is to
determine the influence of the preparation method on the catalytic
activity of the supported copper-manganese mixed oxides in terms of
VOCs oxidation. The catalysts were prepared by impregnation of γ-
Al2O3 with copper and manganese nitrates and acetates and the
possibilities for CO, CH3OH and dimethyl ether (DME) oxidation
were evaluated using continuous flow equipment with a four-channel
isothermal stainless steel reactor. Effect of the support, Cu/Mn mole
ratio, heat treatment of the precursor and active component loading
were investigated. Highly active alumina supported Cu-Mn catalysts
for CO and VOCs oxidation were synthesized. The effect of
preparation conditions on the activity behavior of the catalysts was
discussed.
The synergetic interaction between copper and manganese species
increases the activity for complete oxidation over mixed catalysts.
Type of support, calcination temperature and active component
loading along with catalyst composition are important factors,
determining catalytic activity. Cu/Mn molar ratio of 1:5, heat
treatment at 450oC and 20 % active component loading are the best
compromise for production of active catalyst for simultaneous
combustion of CO, CH3OH and DME.
Abstract: Catalytic combustion of methane is imperative due to
stability of methane at low temperature. Methane (CH4), therefore,
remains unconverted in vehicle exhausts thereby causing greenhouse
gas GHG emission problem. In this study, heterogeneous catalysts of
palladium with bio-char (2 wt% Pd/Bc) and Al2O3 (2wt% Pd/ Al2O3)
supports were prepared by incipient wetness impregnation and then
subsequently tested for catalytic combustion of CH4. Support-porous
heterogeneous catalytic combustion (HCC) material were selected
based on factors such as surface area, porosity, thermal stability,
thermal conductivity, reactivity with reactants or products, chemical
stability, catalytic activity, and catalyst life. Sustainable and
renewable support-material of bio-mass char derived from palm shell
waste material was compared with those from the conventional
support-porous materials. Kinetic rate of reaction was determined for
combustion of methane on Palladium (Pd) based catalyst with Al2O3
support and bio-char (Bc). Material characterization was done using
TGA, SEM, and BET surface area. The performance test was
accomplished using tubular quartz reactor with gas mixture ratio of
3% methane and 97% air. The methane porous-HCC conversion was
carried out using online gas analyzer connected to the reactor that
performed porous-HCC. BET surface area for prepared 2 wt% Pd/Bc
is smaller than prepared 2wt% Pd/ Al2O3 due to its low porosity
between particles. The order of catalyst activity based on kinetic rate
on reaction of catalysts in low temperature was 2wt%
Pd/Bc>calcined 2wt% Pd/ Al2O3> 2wt% Pd/ Al2O3>calcined 2wt%
Pd/Bc. Hence agro waste material can successfully be utilized as an
inexpensive catalyst support material for enhanced CH4 catalytic
combustion.
Abstract: In this paper, effects of using Alumina-water
nanofluid on the rate of heat transfer have been investigated
numerically. Physical model is a square enclosure with insulated top
and bottom horizontal walls, while the vertical walls are kept at
different constant temperatures. Two appropriate models are used to
evaluate the viscosity and thermal conductivity of nanofluid. The
governing stream-vorticity equations are solved using a second order
central finite difference scheme, coupled to the conservation of mass
and energy. The study has been carried out for the Richardson
number 0.1 to 10 and the solid volume fraction 0 to 0.04. Results are
presented by isotherms lines, average Nusselt number and normalized
Nusselt number in different range of φ and Ri for forced, combined
and natural convection dominated regime. It is found that higher heat
transfer rate is predicted when the effects of nanoparticle is taken into
account.
Abstract: The borate glasses are known by their structural
characterized by existence of unit’s structural composed by triangles
and tetrahedrons boron in different configurations depending on the
percentage of B2O3 in the glass chemical composition. In this paper,
effect of lithium oxide addition on the thermal and physical
properties of an alumina borate glass, was investigated. It was found
that the boron abnormality has a significant effect in the change of
glass properties according to the addition rate of lithium oxide.
Abstract: In this paper, two options of anodic alumina barrier
layer thinning have been demonstrated. The approaches varied with
the duration of the voltage step. It was found that too long step of the
barrier layer thinning process leads to chemical etching of the
nanopores on their top. At the bottoms pores are not fully opened
what is disadvantageous for further applications in nanofabrication.
On the other hand, while the duration of the voltage step is controlled
by the current density (value of the current density cannot exceed
75% of the value recorded during previous voltage step) the pores are
fully opened. However, pores at the bottom obtained with this
procedure have smaller diameter, nevertheless this procedure
provides electric contact between the bare aluminum (substrate) and
electrolyte, what is suitable for template assisted electrodeposition,
one of the most cost-efficient synthesis method in nanotechnology.
Abstract: In this research the effects of adding silica and
alumina nanoparticles on flow ability and compressive strength of
cementitious composites based on Portland cement were investigated.
In the first stage, the rheological behavior of different samples
containing nanosilica, nanoalumina and polypropylene, polyvinyl
alcohol and polyethylene fibers were evaluated. With increasing of
nanoparticles in fresh samples, the slump flow diameter reduced.
Fibers reduced the flow ability of the samples and viscosity
increased. With increasing of the micro silica particles to cement
ratio from 2/1 to 2/2, the slump flow diameter increased. By adding
silica and alumina nanoparticles up to 3% and 2% respectively, the
compressive strength increased and after decreased. Samples
containing silica nanoparticles and fibers had the highest compressive
strength.
Abstract: Violet Sr–Al–O:Eu2+ phosphor particles were
synthesized from a metal–ethylenediaminetetraacetic acid (EDTA)
solution of Sr, Al, Eu, and particulate alumina via spray drying and
sintering in a reducing atmosphere. The crystal structures and emission
properties at 85–300 K were investigated. The composition of the
violet Sr–Al–O:Eu2+ phosphor particles was determined from various
Sr–Al–O:Eu2+ phosphors by their emission properties’ dependence
on temperature. The highly crystalline SrAl12O19:Eu2+ emission phases
were confirmed by their crystallite sizes and the activation energies for
the 4f5d–8S7/2 transition of the Eu2+ ion. These results showed that the
material identification for the violet Sr–Al–O:Eu2+ phosphor was
accomplished by the low-temperature luminescence measurements.
Abstract: The aluminum impregnated catalysts of Al-alumina (Al-Al2O3), Al-montmorillonite (Al-Mmn) and Al-activated charcoal (Al-AC) of various percent loadings were prepared by wet impregnation method and characterized by SEM, XRD and N2 adsorption/desorption (BET). The catalytic properties were investigated in the degradation of waste polystyrene (WPS). The results of catalytic degradation of Al metal, 20% Al-Al2O3, 5% Al-Mmn and 20% Al-AC were compared with each other for optimum conditions. Among the catalyst used 20% Al-Al2O3 was found the most effective catalyst. The BET surface area of 20% Al-Al2O3 determined was 70.2 m2/g. The SEM data revealed the catalyst with porous structure throughout the frame work with small nanosized crystallites. The yield of liquid products with 20% Al-Al2O3 (91.53 ± 2.27 wt%) was the same as compared to Al metal (91.20 ± 0.35 wt%) but the selectivity of hydrocarbons and yield of styrene monomer (56.32 wt%) was higher with 20% Al-Al2O3 catalyst.
Abstract: The production of aluminum alloys and ingots –
starting from the processing of alumina to aluminum, and the final
cast product – was studied using a Life Cycle Assessment (LCA)
approach. The studied aluminum supply chain consisted of a carbon
plant, a reduction plant, a casting plant, and a power plant. In the
LCA model, the environmental loads of the different plants for the
production of 1 ton of aluminum metal were investigated. The impact
of the aluminum production was assessed in eight impact categories.
The results showed that for all of the impact categories the power
plant had the highest impact only in the cases of Human Toxicity
Potential (HTP) the reduction plant had the highest impact and in the
Marine Aquatic Eco-Toxicity Potential (MAETP) the carbon plant
had the highest impact. Furthermore, the impact of the carbon plant
and the reduction plant combined was almost the same as the impact
of the power plant in the case of the Acidification Potential (AP). The
carbon plant had a positive impact on the environment when it come
to the Eutrophication Potential (EP) due to the production of clean
water in the process. The natural gas based power plant used in the
case study had 8.4 times less negative impact on the environment
when compared to the heavy fuel based power plant and 10.7 times
less negative impact when compared to the hard coal based power
plant.
Abstract: Palm kernel shell is an important bioenergy resource
in Thailand. However, due to elevated alkali content in biomass ash,
this oil palm residue shows high tendency to bed agglomeration in a
fluidized-bed combustion system using conventional bed material
(silica sand). In this study, palm kernel shell was burned in the
conical fluidized-bed combustor (FBC) using alumina and dolomite
as alternative bed materials to prevent bed agglomeration. For each
bed material, the combustion tests were performed at 45kg/h fuel feed
rate with excess air within 20–80%. Experimental results revealed
rather weak effects of the bed material type but substantial influence
of excess air on the behavior of temperature, O2, CO, CxHy, and NO
inside the reactor, as well as on the combustion efficiency and major
gaseous emissions of the conical FBC. The optimal level of excess air
ensuring high combustion efficiency (about 98.5%) and acceptable
level of the emissions was found to be about 40% when using
alumina and 60% with dolomite. By using these alternative bed
materials, bed agglomeration can be prevented when burning the
shell in the proposed conical FBC. However, both bed materials
exhibited significant changes in their morphological, physical and
chemical properties in the course of the time.
Abstract: Endothelium proliferation is an important process in cardiovascular homeostasis and can be regulated by extracellular environment, as cells can actively sense mechanical environment. In this study, we evaluated endothelial cell proliferation on PDMS/alumina (Al2O3) composites and pure PDMS. The substrates were prepared from pure PDMS and its composites with 5% and 10% Al2O3 at curing temperature 50˚C for 4h and then characterized by mechanical, structural and morphological analyses. Higher stiffness was found in the composites compared to the pure PDMS substrate. Cell proliferation of the cultured bovine aortic endothelial cells on substrate materials were evaluated via Resazurin assay and 1, 1’-Dioctadecyl-1, 3, 3, 3’, 3’-Tetramethylindocarbocyanine Perchlorate-Acetylated LDL (Dil-Ac-LDL) cell staining, respectively. The results revealed that stiffer substrates promote more endothelial cells proliferation to the less stiff substrates. Therefore, this study firmly hypothesizes that the stiffness elevates endothelial cells proliferation.
Abstract: Several review papers exist in literature related to the concrete containing mineral admixtures; however this paper reviews the durability characteristics of the concrete containing fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS), metakaolin (MK) and rice husk ash (RHA). Durability related properties reviewed include permeability, resistance to sulfate attack, alkali-silica reaction (ASR), carbonation, chloride ion penetration, freezing and thawing, abrasion, fire, acid and efflorescence. From review of existing literature, it is found that permeability of concrete depends upon the content of alumina in mineral admixtures, i.e. higher the alumina content, lesser the permeability which results higher resistance to sulfate and chloride ion penetration. Highly reactive mineral admixtures prevent more ASR and reduce efflorescence. The carbonation increases with the mineral admixtures because higher water binder ratio and lesser content of portlandite in concrete due to pozzolanic reaction. Mineral admixtures require air entrainment except MK and RHA for better resistance to freezing and thawing.
Abstract: The coal utilization in thermal power plants in Malaysia has increased significantly which produces an enormous amount of coal combustion by-product (CCBP) or coal ash and poses severe disposal problem. As each coal ash is distinct, this study presents the geochemistry of the coal ash, in particular fly ash, produced from the combustion of local coal from Kuching Sarawak, Malaysia. The geochemical composition of the ash showed a high amount of silica, alumina, iron oxides and alkalies which was found to be a convenient starting material for the hydrothermal synthesis of zeolites with the higher Na2O percentage being a positive factor for its alkaline activation; while the mineral phases are mainly quartz, mullite, calcium oxide, silica, and iron oxide hydrate. The geochemical changes upon alkali activation that can be predicted in a similar type of ash have been described in this paper. The result shows that this particular ash has a good potential for a high value industrial product like zeolites upon alkali activation.
Abstract: The tribological outcomes of micro dent are found to be outstanding in many engineering and natural surfaces. Ceramic (Al2O3) is considered one of the most potential material to bearing surfaces particularly, artificial hip or knee implant. A well-defined micro dent on alumina oxide interface could further decrease friction and wear rate, thus increase their stability and durability. In this study we fabricated circular micro dent surface profiles (Dia: 400µm, Depth 20µm, P: 1.5mm; Dia: 400µm, Depth 20µm, P: 2mm) on pure Al2O3 (99.6%) substrate by using a micro tool machines. A preliminary tribological experiment was carried out to compare friction coefficient of these fabricated dent surfaces with that of non-textured surfaces. The experiment was carried on well know pin-on-disk specimens while other experimental parameters such as hertz pressure, speed, lubrication, and temperature were maintained to standard of simulated hip joints condition. The experiment results revealed that micro dent surface texture reduced 15%, 8% and 4% friction coefficient under 0.132,0.162, 0.187 GPa contact pressure respectively. Since this is a preliminary tribological study, we will pursue further experiments considering higher ranges of dent profiles and longer run experiments. However, the preliminary results confirmed the suitability of fabricating dent profile to ceramic surfaces by using micro tooling, and also their improved tribological performance in simulated hip joints.
Abstract: In the present work the internal sulfate attack on
pastes made from pure clinker phases was studied. Two binders were
produced: (a) a binder with 2% C3A and 18% C4AF content; (b) a
binder with 10% C3A and C4AF content each. Gypsum was used as
the sulfate bearing compound, while calcium carbonate added to
differentiate the binders produced. The phases formed were identified
by XRD analysis. The results showed that ettringite was the
deterioration phase detected in the case of the low C3A content
binder. Carbonation occurred in the specimen without calcium
carbonate addition, while portlandite was observed in the one
containing calcium carbonate. In the case of the high C3A content
binder, traces of thaumasite were detected when calcium carbonate
was not incorporated in the binder. A solid solution of thaumasite and
ettringite was found when calcium carbonate was added. The amount
of C3A had not fully reacted with sulfates, since its corresponding
peaks were detected.