• Volume 25, Issue 1

February 2002,   pages  1-78

• Organization of copper nanoclusters in Langmuir–Blodgett films

Stable nanoclusters of Cu were synthesized using Langmuir–Blodgett films of octadecylsuccinic acid (ODSA) as template. The Langmuir–Blodgett films of ODSA formed from subphase containing copper ions were first subjected to sulphidation (S) using sodium sulphide and then hydrogenated (H) using hydrogen gas. Diffuse reflectance UV-visible spectroscopy (DIR-UV-vis), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) used to characterize these films indicated the formation of Cu(0) metallic clusters ranging in size from 3 ∼ 10 nm.

• Cell attachment on diamond-like carbon coating

Preliminary results of diamond-like carbon (DLC) coating with its novel properties with no toxicity have caused a strong interest of commercial manufacturers of surgical implants. DLC coatings were prepared on polymethylmethacrylate (PMMA) at room temperature using ion beam assisted deposition (IBAD). It could be shown by X-ray photoelectron spectroscopy, Auger electron spectroscopy, and Raman spectroscopy that DLC coating prepared by 800 eV CH𝑛+ beam bombardment possessed a higher fraction of 𝑠𝑝3 bonds in the structure of mixed 𝑠𝑝3 + 𝑠𝑝2 bonding, resulting in a higher hydrophobicity. The results of the cell attachment tests indicated that DLC coatings exhibited low macrophage attachment and provided desirable surface for the normal cellular growth and morphology of the fibroblasts. At the same time, the number of both neutral granulocytes and platelets adhering to DLC coatings decreased significantly. These findings showed that DLC was a better coating with desirable tissue and blood compatibility.

• Synthesis, microstructure and mechanical properties of ceria stabilized tetragonal zirconia prepared by spray drying technique

Ceria stabilized zirconia powders with ceria concentration varying from 6 to 16 mol% were synthesized using spray drying technique. Powders were characterized for their particle size distribution and specific surface area. The dense sintered ceramics fabricated using these powders were characterized for their microstructure, crystallite size and phase composition. The flexural strength, fracture toughness and microhardness of sintered ceramics were measured. High fracture toughness and flexural strength were obtained for sintered bodies with 12 mol% of CeO2. Flexural strength and fracture toughness were dependent on CeO2 concentration, crystallite size and phase composition of sintered bodies. Correlation of data has indicated that the transformable tetragonal phase is the key factor in controlling the fracture toughness and strength of ceramics. It has been demonstrated that the synthesis method is effective to prepare nanocrystalline tetragonal ceria stabilized zirconia powders with improved mechanical properties. Ce–ZrO2 with 20 wt% alumina was also prepared with flexural strength, 1200 MPa and fracture toughness, 9.2 MPa √m.

• Surface modification on PMMA : PVDF polyblend: hardening under chemical environment

The influence of chemical environment on polymers include the surface alteration as well as other deep modifications in surface layers. The surface hardening, as an effect of organic liquids on poly(methyl methacrylate): poly(vinylidene fluoride) (PMMA: PVDF), which is one of the few known miscible blends, has been detected using microhardness testing. Organic liquids like acetone, toluene, xylene and benzene were introduced on the surface of blend specimens for different durations. Vickers microhardness (𝐻v) was measured for treated and untreated specimens. The study reveals both hardening and plasticization of specimens at different exposure times. The degree of surface hardening is maximum under acetone treatment. All the specimens exhibit surface hardening at an exposure time of 1 h with all the four liquids. This feature is prominent with longer exposures for specimens with increasing content of PVDF. However, the degree of hardening decreases with the time of exposure in the respective environments. In general, acetone and toluene impart surface hardening, whereas, xylene and benzene soften the specimen. PMMA: PVDF (83 : 17) blend exhibits surface hardening under all the four treatments when compared with the respective untreated specimens.

• Mechanical and microstructure studies on the modification of CA film by blending with PS

Dried Musa paradiciaca (banana) stem and veins of the leaves, which were hitherto discarded as a waste, were collected and used as starting material for the preparation of cellulose and cellulose acetate. This cellulose acetate was mixed with polystyrene to form blend of cellulose acetate–polystyrene in order to provide enhanced stability and extended utility to the end products. The films of these composites or their individual partners were made separately and studied for their mechanical properties, chemical modification and morphological changes. We report here that banana stem is good source of cellulose and that cellulose completely undergoes modification upon esterification.

• Systematic hardness measurements on CsCl𝑥Br(1–x) and NH4Cl𝑥Br(1–x) mixed crystals

Vickers hardness measurements have been made on polycrystalline blanks of CsCl𝑥Br(1–x) and single crystals of NH4Cl𝑥Br(1–x). The composition dependence of hardness is highly nonlinear in both systems and follows an empirical model that includes a lattice contribution and a disorder contribution. The Gilman–Chin parameter (𝐻/𝐶44) has been calculated and its significance discussed.

• Dielectric properties of fly ash

This paper reports the dielectric properties of fly ash. The dielectric measurements were performed as a function of frequency and temperature. The sample of fly ash shows almost similar behaviour in the frequency and temperature range studied. The large value of dielectric constant in the typical frequency range is because of orientation polarization and tight binding force between the ions or atoms in the fly ash. The sample of fly ash is of great scientific and technological interest because of its high value of dielectric constant (104).

• Synthesis and characterization of tetraethylammonium tetrachlorocobaltate crystals

Single crystals of tetraethylammonium tetrachlorocobaltate were grown by solution method and characterized through single crystal X-ray diffraction, thermogravimetric analysis (TGA), differential scanning calorimetric studies (DSC) and infrared spectroscopic technique (IR). The crystals were bright, transparent and blue coloured. The unit cell parameters were found to be 𝑎 = 𝑏 = 9.0363 Å and 𝑐 = 14.9879 Å and 𝛼 = 𝛽 = 𝛾 = 90°, showing tetragonal lattice from the XRD data. Thermogravimetric analysis showed a loss of weight at 683 K from which the decomposition reaction was formulated. Thermal anomalies were found for this crystal at temperatures 200 K, 220 K in the cooling cycle and at temperatures 200 K, 240 K in the heating cycle, respectively which showed that this crystal was associated with first order phase transition. All the vibrational frequencies corresponding to (TEA)+ ions and CoCl$^{2-}_4$ ions were assigned from the IR spectral data of this crystal.

• Stress corrosion cracking of AISI 321 stainless steel in acidic chloride solution

The stress corrosion cracking (SCC) of AISI 321 stainless steel in acidic chloride solution was studied by slow strain rate (SSR) technique and fracture mechanics method. The fractured surface was characterized by cleavage fracture. In order to clarify the SCC mechanism, the effects of inhibitor KI on SCC behaviour were also included in this paper. A study showed that the inhibition effects of KI on SCC were mainly attributed to the anodic reaction of the corrosion process. The results of strain distribution in front of the crack tip of the fatigue pre-cracked plate specimens in air, in the blank solution (acidic chloride solution without inhibitor KI) and in the solution added with KI measured by speckle interferometry (SPI) support the unified mechanism of SCC and corrosion fatigue cracking (CFC).

• Cast iron deterioration with time in various aqueous salt solutions

The changes with time in the corrosion rate and corrosion current density on a cast iron electrode in various aqueous salt solutions have been carried out using total immersion test and potentiostatic polarization curves. The concentration of salts taken is expected to be present in potable water. The relative behaviour of these salts towards corrosion has also been studied, which is found to be different from previous studies. The total immersion test parameters viz. weight loss, corrosion rate as well as potentiostatic parameters, open circuit potential, 𝐼corr, Tafel slopes, corrosion rate, have been calculated by standard methods. Besides these the relative increase in corrosion rate with time as well as the percentage to which corrosion rate should be decreased so as to provide protection towards corrosion have also been calculated. It was found that KCl and NaCl are major contributors than MnSO4, Pb(NO3)2, KI and KBr. The relative increase in corrosion is high in KBr, KI, NaNO3, CaCl2, and less in Pb(NO3)2, NaHCO3 and CaCO3 test solutions. For the reliability of results the data has been statistically analysed.

• Effect of thermomechanical treatment on mechanical properties and electrical conductivity of a CuCrZr alloy

The CuCrZr alloy undergoes processes of precipitation during ageing. Besides precipitation hardening the strength is affected by cold deformation which is performed before and after ageing.

The cold deformation (𝐷1) before ageing accelerates the process of strength hardening, since it induces higher rate of precipitation from the saturated 𝛼-solid solution. Cold deformation (𝐷2) after ageing primarily affects the alloy strength.

In this paper the results of the effect of thermomechanical treatment on mechanical properties and electrical conductivity of a CuCrZr alloy are presented. The aim of the paper was to evaluate the most suitable combination of thermomechanical treatment and alloy properties.

• Volume variation of Gruneisen parameters of fcc transition metals

The volume variation of the Gruneisen parameters of ten fcc transition metals, up to 40% compression, has been studied on the basis of a model approach proposed by Antonov et al. The results are reasonably good for six metals except for Rh, Ag, Au and Ni when compared with available experimental and other theoretical values. The model requires an appropriate modification for Rh, Ag, Au and Ni.

• Spectroscopic studies of Cu2+ ions in sol–gel derived silica matrix

The Cu2+ ion doped silica gel matrices in monolithic shape were prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS). The absorption, transmittance and fluorescence spectra of the gel matrices heat treated at different temperatures were monitored. The loss of water and hydroxyl group from silica network changes the optical properties of the Cu2+ ions in the host, noted by the change in colour of monolith and spectral characteristics. The pronounced blue shift observed (700–900 nm to 600–850 nm) for the broad band of the absorption spectra of the samples heated up to 700°C is attributed to the ligand field splitting and partial removal of hydroxyl group from the silica matrices. The results indicate broadband filtering effects of the samples in the wavelength region 400–600 nm. Absorption and fluorescence spectra of the glass matrices heated to 1000°C confirms the conversion of Cu2+ ion to Cu+ ion.

• Infrared spectra of zinc doped lead borate glasses

The infrared spectra of zinc-doped lead borate glasses (10–30 mol% ZnO) were measured over a continuous spectral range (400–4000 cm–1) in an attempt to study their structure systematically. No boroxol ring formation was observed in the structure of these glasses. The formation of Zn in tetrahedral coordination was not observed. The conversion of three-fold to four-fold coordinated boron took place.

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Posted on July 25, 2019