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1.
Vladimír Zivica 《Bulletin of Materials Science》2003,26(6):605-608
Reinforced concrete structures during their exploitation may be exposed to the common action of carbonation and chlorides
causing corrosion of steel reinforcement. Therefore, the related data seem to be interesting and important when the evaluation
of the service life of the structures is the object of interest. This fact was a motivation for the present experimental study
on the sequence of action of chloride solutions and carbonation of the embedding concrete. The results obtained show that
carbonation of concrete foregoing the action of chloride solutions may intensify the process of corrosion of steel reinforcement
in comparison to the converse sequence of the action of mentioned media. At the same time the natrium chloride solution has
been shown as a more aggressive medium opposite to the calcium and magnesium chloride solutions. 相似文献
2.
In this study, the electrical and optical properties of Zn doped tin oxide films prepared using sol-gel spin coating process
have been investigated. The SnO2 : Zn multi-coating films were deposited at optimum deposition conditions using a hydroalcoholic solution consisting of stannous
chloride and zinc chloride. Films with Zn doping levels from 0–10 wt% in solution are developed. The results of electrical
measurements indicate that the sheet resistance of the deposited films increases with increasing Zn doping concentration and
several superimposed coatings are necessary to reach expected low sheet resistance. Films with three coatings show minimum
sheet resistance of 1–479 kΩ/ in the case of undoped SnO2 and 77 kΩ/ for 5 wt% Zn doped SnO2 when coated on glass substrate. In the case of single layer SnO2 film, absorption edge is 3.57 eV and when doped with Zn absorption edge shifts towards lower energies (longer wavelengths).
The absorption edge lies in the range of 3.489-3.557 eV depending upon the Zn doping concentration. The direct and indirect
transitions and their dependence on dopant concentration and number of coatings are presented. 相似文献
3.
In the present work, tracking phenomena has been studied with the ethylene propylene diene monomer (EPDM) material under the
a.c. and d.c. voltages, with ammonium chloride/acid rain solution as the contaminant. It is noticed that the tracking time
depends on the conductivity and flow rate of the contaminant. The physico-chemical analyses viz. wide angle X-ray diffraction
(WAXD), thermo-gravimetric differential thermal analysis (TG-DTA) and the differential scanning calorimetry (DSC) studies,
were carried out and it was concluded that the tracking process is a surface degradation process. The tracking time is different
for a.c. and d.c. voltages. 相似文献
4.
Ujjal K. Ghosh Narayan C. Pradhan Basudam Adhikari 《Bulletin of Materials Science》2006,29(3):225-231
Hydroxyterminated polybutadiene (HTPB) based porous polyurethaneurea (PUU) membranes were prepared. The porosity was developed
by incorporation of lithium chloride into polymer matrix with subsequent leaching of the same in hot water. Scanning electron
microscopic analysis of the prepared membrane surfaces was performed. The pervaporation performance of the synthesized membrane
was studied with aqueous 4-nitrophenol solution as feed. The effects of various parameters on 4-nitrophenol separation factor
and total as well as 4-nitrophenol flux were studied. Polyurethaneurea membrane was found to permeate 4-nitrophenol selectively
with high separation factors for the organic component. Pore size and number of pores on the surface of the membrane were
calculated from SEM image of the membranes. Effects of pore size and porosity on pervaporation flux were also investigated. 相似文献
5.
Nano-crystal embedded PbO-P2O5 glass has been prepared and characterized by XRD and TEM measurements. The ultrasonic velocity and attenuation measured within
the temperature range 80–300 K show significant structure and interesting feature with the presence of nano-crystalline region.
The glass samples were prepared by melt-quench method and nano-crystals of different sizes were produced by heat treatment
of the glasses for different durations of heating. All the processes were carried out at or above glass transition temperature.
A theoretical model that takes account of the effects of thermally activated relaxation, anharmonicity as well as microscopic
elastic inhomogeneities arising out of fluctuations has been successfully applied to interpret the variation of ultrasonic
velocity and attenuation data. An interesting outcome of this application has been to propose a method for the determination
of the size of nano-crystals from the ultrasonic attenuation data. 相似文献
6.
Effect of zirconium addition on the recrystallization behaviour of a commercial Al-Cu-Mg alloy 总被引:3,自引:0,他引:3
K. T. Kashyap 《Bulletin of Materials Science》2001,24(6):643-648
It is well known that the second phase particles have an effect on recrystallization and grain growth behaviour of an alloy.
Particularly the bimodal distribution of second phase particles has an effect which is opposite in sense where coarse second
phase particles (> 1 μm) stimulate nucleation while fine particles exhibit Zener drag.
In the literature, the effect of zirconium addition to aluminium alloys has been well documented in order to produce superplasticity
by giving ultra fine grain size to the alloy. Addition of zirconium produces Al
3
Zr particles which pin the grain boundaries during recrystallization and grain growth.
In the present work, zirconium was added to a commercial Al-Cu-Mg alloy and by heat treatment Al
3
Zr particles were precipitated and after forging, the grain size was an order of magnitude lower than the alloy without zirconium.
Transmission electron microscopy was employed to characterize the second phase particles, i.e. Al
3
Zr particles and found to be rod shaped and identified to be cubic ordered
L
1
2
phase with a lattice parameter of 0.408 nm. Further, it was observed that fine (100 nm) Al
3
Zr particles promote only continuous recrystallization which is polygonization of subgrains and subgrain growth.
It was found that the fine dispersion of Al
3
Zr particles inhibits both recrystallization and grain growth in the commercial Al-Cu-Mg alloy. 相似文献
7.
A. Venkataraman Vijay A. Hiremath S. K. Date S. D. Kulkarni 《Bulletin of Materials Science》2001,24(6):617-621
A new combustion route for the synthesis of γ-Fe
2
O
3
is reported by employing purified a-Fe
2
O
3
as a precursor in the present investigation. This synthesis which is similar to a self propagation combustion reaction, involves
fewer steps, a shorter overall processing time, is a low energy reaction without the need of any explosives, and also the
reaction is completed in a single step yielding magnetic iron oxide i.e. γ-Fe
2
O
3
.The as synthesized γ-Fe
2
O
3
is characterized employing thermal, XRD, SEM, magnetic hysteresis, and density measurements. The effect of ball-milling on
magnetic properties is also presented. 相似文献
8.
The theory of photoelasticity is used to study analytically the effects of T-stress on the fringe patterns around the crack tip in mode II crack specimens. The locus of an isochromatic fringe determined
by taking into account the T-stress is compared with the locus of a fringe with no T-stress. It is shown for mode II cracks that in the presence of T-stress, the fringe loops are neither symmetric nor continuous. Asymmetric and discontinuous fringe patterns predicted in
this paper are consistent with the experimental results observed previously in photoelasticity tests. 相似文献
9.
External stimuli response on a novel chitosan hydrogel crosslinked with formaldehyde 总被引:1,自引:0,他引:1
Keeping in mind the significance of hydrogels as an external stimuli sensitive super absorbing material, some transparent
covalent hydrogels of chitosan were prepared by crosslinking with varying amounts of formaldehyde solution used as crosslinking
agent. The characteristics of hydrogels were investigated by Fourier transform infrared (FT-IR) spectroscopy and swelling
experiments. The effect of crosslinking agent on water absorbency has been investigated. The hydrogels exhibited a relatively
higher swelling ratio in the range of 2066–3306% and equilibrium water content (EWC) in the range of 95-38–97 06% at pH 7
and 35°C temperature. The influence of external stimuli such as pH, temperature, and ionic strength of the swelling media
on equilibrium swelling properties has been observed. Hydrogels showed a typical pH and temperature responsive behaviour such
as low pH and high temperature has maximum swelling while high pH and low temperature show minimum swelling. An increase in
the ionic strength of swelling media caused a continuous decrease in the swelling of hydrogels at both acidic and basic pH. 相似文献
10.
Stoichiometric hydroxyapatite with Ca/P molar ratio, 1.67, was synthesized using hen’s eggshell as calcium source and phosphoric
acid by precipitation method. Conventional EDTA titration and gravimetric methods were adopted to estimate the amount of calcium
and phosphorous, respectively. Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD) techniques were employed to
investigate the formation of the HAP phase. Thermal analysis (TG-DTA) was carried out to investigate the thermal stability
of HAP powder. FT-IR spectra show the characteristic peaks for phosphate and hydroxyl groups. XRD results reveal that the
major characteristic peaks of HAP appear in the region of approximately 26°, 28°, 29°, 30–35°, 39°, 46°, 49° and 50° (2θ)
and also indicate that there are no occurrences of secondary phases during HAP formation. TG-DTA result depicts that the synthesized
HAP was stable up to 1300°C. 相似文献
11.
P. N. Vishwakarma V. Prasad S. V. Subramanyam V. Ganesan 《Bulletin of Materials Science》2005,28(6):609-615
Amorphous conducting carbon films deposited over quartz substrates were analysed using X-ray diffraction and AFM technique.
X-ray diffraction data reveal disorder and roughness in the plane of graphene sheet as compared to that of graphite. This
roughness increases with decrease in preparation temperature. The AFM data shows surface roughness of carbon films depending
on preparation temperatures. The surface roughness increases with decrease in preparation temperature. Also some nucleating
islands were seen on the samples prepared at 900°C, which are not present on the films prepared at 700°C. Detailed analysis
of these islands reveals distorted graphitic lattice arrangement. So we believe these islands to be nucleating graphitic.
Power spectrum density (PSD) analysis of the carbon surface indicates a transition from the nonlinear growth mode to linear
surface-diffusion dominated growth mode resulting in a relatively smoother surface as one moves from low preparation temperature
to high preparation temperature. The amorphous carbon films deposited over a rough quartz substrate reveal nucleating diamond
like structures. The density of these nucleating diamond like structures was found to be independent of substrate temperature
(700–900° C). 相似文献
12.
Microstresses developed in the crystallites of polymeric material due to irradiation of high-energy particle causes peak broadening
and shifting of X-ray diffraction lines to lower angle. Neutron irradiation significantly changes the material properties
by displacement of lattice atoms and the generation of helium and hydrogen by nuclear transmutation. Another important aspect
of neutron irradiation is that the fast neutron can produce dense ionization at deep levels in the materials. The polyethylene
terephthalate (PET) fibre of raw denier value, 78.2, were irradiated by fast neutron of energy, 4.44 MeV, at different fluences
ranging from 1×109 n/cm2 to 1 × 1012 n/cm2. In the present work, the radiation heating microstresses developed in PET micro-crystallites was investigated applying X’Pert-MPD
Philips Analytical X-ray diffractometer and the effects of microstresses in tensile strength of fibre measured by Instron
have also been reported. The shift of 0.45 cm−1 in the Raman peak position of 1614.65 cm{−1} to a higher value confirmed the development of microstresses due to neutron irradiation using micro-Raman technique. The
defects due to irradiation were observed by SEM micrographs of single fibre for virgin and all irradiated samples. 相似文献
13.
A series of calcium substituted polycrystalline ferrite ceramics with magnetoplumbite structures were synthesized using perfect
stoichiometric mixtures of oxides with chemical composition, CaAlxCoxFe12−2xO19 (x = 2−5), by standard ceramic technique. The variation in the values ofH
candM
s,which depends on the additive content and the temperature, was studied by means of a vibration magnetometer. The strong variation
observed in coercivity, saturation magnetization and Curie temperature with chemical composition give rise to the possibility
of controlling these properties and hence applying these compounds in the millimeter— microwave range. 相似文献
14.
Sm-Ru intermetallic surface alloy films were prepared by vacuum deposition and annealing of rare earth Sm on single crystal
Ru(0001) surface. The Ru 3
d
and Sm 3
d
core level spectra clearly show the formation of surface alloy layers. XPS measurements on surface alloy film revealed an
induced peak in the Ru 3
d
region at lower binding energy by 1 eV compared to the bulk Ru (elemental) suggesting an electronic effect of alloying and
Sm-Ru bond formation. The Sm 3
d
5/2
photoemission peak of Sm film consists of strong features characteristic of Sm(II) with electron configuration 4
f
6
(5
d
6
s
)
2
and Sm(III) with electron configuration 4
f
5
(5
d
6
s
)
3
.It is observed that the Sm(II) feature decreases in intensity upon alloy formation with surface Ru atoms. Oxidation of these
films with carbon monoxide indicates alloy breakdown due to the oxidation of Sm atoms selectively. Alloy oxidation also shows
a clear shift of Sm 3
d
5/2
feature. 相似文献
15.
Single crystals of ternary mixed compounds of group IV-VI in the form of a series, SnSxSe1-x (wherex = 0, 0.25, 0.50, 0.75 and 1), have been grown using direct vapour transport technique. The grown crystals were characterized
by the X-ray diffraction analysis for their structural parameter determination. All the grown crystals were found to be orthorhombic.
The microstructure analysis of the grown crystals reveals their layered type growth mechanism. From the Hall effect measurements
Hall mobility, Hall coefficient and carrier concentration were calculated with all crystals showingp-type nature. The d.c. electrical resistivity measurements perpendicular toc-axis (i.e. along the basal plane) in the temperature range 303–453 K were carried out for grown crystals using four-probe
method. The d.c. electrical resistivity measurements parallel to c-axis (i.e. perpendicular to basal plane) in the temperature
range 303–453 K were carried out for the same crystals. The electrical resistivity measurements showed an anisotropic behaviour
of electrical resistivity for the grown crystals. The anisotropic behaviour and the effect of change in stoichiometric proportion
of S and Se content on the electrical properties of single crystals of the series, SnSxSe1-x (wherex = 0, 0.25, 0.50, 0.75 and 1), is presented systematically. 相似文献
16.
B. Eraiah 《Bulletin of Materials Science》2006,29(4):375-378
Glasses with the composition, (Sm2
O
3)
x
(ZnO)(40-x)(TeO
2)(60), were prepared by conventional melt quenching method. The density, molar volume, and optical energy band gap of these glasses
have been measured. The refractive index, molar refraction and polarizability of oxide ion have been calculated by using Lorentz-Lorentz
relations. Optical absorption spectra of these glasses were recorded in the range 300–700 nm at room temperature. The oxide
ion polarizabilities deduced from two different quantities, viz. refractive index and optical energy band gap, agree well
compared with other glasses. The nonlinear variation of the above optical parameters with respect to samarium dopant has been
explained. 相似文献
17.
A. Vadivel Murugan A. B. Gaikwad V. Samuel V. Ravi 《Bulletin of Materials Science》2006,29(3):221-223
An aqueous mixture of ammonium oxalate and ammonium hydroxide was used to coprecipitate barium and strontium ions as oxalates
and niobium ions as hydroxide under basic conditions. This precursor on calcining at 750°C yielded Sr0.5Ba0.5Nb2O6 phase. This is a much lower temperature than that prepared by traditional solid state method (1000°C) as reported for the
formation of Sr0.5Ba0.5Nb206 (SBN). Transmission electron microscopic (TEM) investigations revealed that the average particle size was 80 nm for the calcined
powders. The room temperature dielectric constant at 1 kHz was found to be 1100. The ferroelectric hysteresis loop parameters
of these samples were also studied. 相似文献
18.
A. Basumajumdar A. K. Das N. Bandyopadhyay S. Maitra 《Bulletin of Materials Science》2005,28(2):131-136
The reaction between fly ash (FA) and lime is extensively exploited for the manufacture of building bricks, blocks and aggregates.
To get a better idea of this reaction, FA from different sources were mixed in different ratios with lime and compacted. The
compacts were treated both by ordinary water and hydrothermal curing to promote lime bearing hydrate bond formation e.g. CaO-
SiO2-H2O (C-S-H), CaO-Al2O3-H2O (C-A-H) etc. The decrease in free lime content in these compacts was measured as a function of curing time and curing process.
This drop in this content was correlated to the chemical composition of the fly ashes. The mathematical relationships between
free lime remaining in the compacts after its maximum decrease in concentration and lime binding modulus (a ratio between
the amount of added lime and the total amount of lime binding constituents present in FA) for both types of curing were developed.
Further, the rate of decrease in free CaO content under both types of curing conditions was compared from kinetic study. From
this study the orders of the reactions and rate constants were found out. 相似文献
19.
C. Yürdü S. Işçi C. Ünlü O. Atici Ö. I. Ece N. Güngör 《Bulletin of Materials Science》2005,28(6):623-628
In this study, the rheologic and colloidal characterizations of sodium montmorillonite (NaMMT) were examined. Hexadecylamine
(CH3(CH2)15NH2, HDA) was added to the bentonite water dispersion (2%, w/w) in different concentrations in the range 5.6 × 10−4−9.4 × 10−3 mmol/l. The rheological and electrokinetic behaviour of aqueous montmorillonite dispersions was investigated as a function
of solid content and HDA concentration. The basal spacings of the HDA/NaMMT composites were studied by X-ray diffraction.
The FTIR spectra were obtained from the modified bentonite products, which revealed the characteristic absorbances after treatment
with HDA. 相似文献
20.
Vijay Kumar 《Bulletin of Materials Science》2003,26(1):109-114
We review recent findings of metal (M) encapsulated caged clusters of Si and Ge obtained from computer experiments based on
an
ab initio pseudopotential method. It is shown that one M atom changes drastically the properties of Si and Ge clusters and that depending
upon the size of the M atom, cages of 14, 15, and 16 Si as well as Ge atoms are formed. In particular M@Si16 silicon fullerene has been obtained for M= Zr and Hf, while a Frank-Kasper polyhedron has been obtained for M@X16, X = Si and Ge. These clusters show high stability and large highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO)
gaps which are likely to make these species strongly abundant. A regular icosahedral M@X12 cluster has also been obtained for X = Ge and Sn by doping a divalent M atom. Interactions between clusters are rather weak.
This is attractive for developing self-assembled cluster materials. 相似文献