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91.
A qualitative model for the sequence of phase transforma-tions leading to perovskite phase formation in sol–gel-derived PZT thin films is presented. It is suggested that for sol–gel-derived Pb(Zrx Ti1–x )O3 (x = 0.4) thin films, prepared using the molecularly modified alkoxide precursors (MMAP) approach, complete (or partial) conversion of the originally amorphous film into a "pyrochlore" phase, although possible, may not be necessary. Differences between the sequence of phase formation encountered in the tradi-tional (oxide-mix) synthesis and that in chemically derived ceramics are discussed. The sequence of phase formation in these thin films also appears to be intertwined with the texture development in that a (111) PZT texture develop-ment appears to be controlled by nucleation of the perovs-kite phase, assisted by a solid-phase epitaxial effect, and the (100)/(001) texture appears to be growth controlled.x 相似文献
92.
C. Chandrasekhara Sastry P. Hariharan M. Pradeep Kumar 《Materials and Manufacturing Processes》2019,34(7):814-831
In this research work, an attempt has been carried out to examine (investigate) and study the dry, wet and cryogenic boring of AA 7075 alloy, which is predominantly used in transport applications in defense (aeronautical parts), oceanic and automaker industries. To ensure direct supply of the coolant, and real-time measurement of cutting temperature a modified boring bar is used (modification is carried out using EDM to accommodate placement of a thermocouple to obtain real-time measurement of temperature readings during the boring cycle). It is observed that during cryogenic boring of AA 7075 alloy there is a considerable reduction in the cutting force (Fc), cutting temperature (Tc) and surface roughness (Ra) by 56.16%, 84.70%, 58.98% compared to dry boring and 48.43%, 80.70%, 34.70% compared to wet boring, respectively. Decrease in Fc and Tc leads to a reduction in high stresses at localized points during machining and in turn curtail wear in workpiece and tool. Lubrication provided by cryogenic fluids also plays a sizable role in reduction of Fc and Tc. Reduction in lower Fc and Tc has a glaring effect on the surface characteristics of the hole produced during the boring process. Tool wear is reduced in cryogenic boring by 36.96% and 17.57% compared to dry and wet boring, respectively. Taguchi and ANOVA was carried out which helped in determining feed as an important parameter with respect to Fc and Ra during boring of AA 7075 under dry, wet and cryogenic conditions whereas speed as an important parameter in determining Tc in dry and wet conditions and feed for Tc in cryogenic boring condition. TOPSIS analysis highlighted speed of 770 rpm and feed of 0.055 mm/min as the most closest to ideal solution for all three different cutting conditions. Surface morphology study after boring of AA 7075 highlighted better surface characteristics in cryogenic bored surface compared to dry and wet boring. Roughness measured in AFM for tool used in boring highlighted a decrease in 86.79% and 66.01% in cryogenic boring in juxtaposition with dry and wet boring, respectively. A surge in compressive residual stress is observed in cryogenic bored surface by 10.41% and 3.5% in juxtaposition with dry and wet boring, respectively, highlighting an abatement in tensile residual stress and better workpiece integrity as compared to dry and wet boring conditions. 相似文献
93.
94.
Fei Chen Nikhil Gupta Rakesh K. Behera Pradeep K. Rohatgi 《JOM Journal of the Minerals, Metals and Materials Society》2018,70(6):837-845
Graphene-reinforced aluminum (Gr-Al) matrix nanocomposites (NCs) have attracted strong interest from both research and industry in high-performance weight-sensitive applications. Due to the vastly different bonding characteristics of the Al matrix (metallic) and graphene (in-plane covalent?+?inter-plane van der Waals), the graphene phase has a general tendency to agglomerate and phase separate in the metal matrix, which is detrimental for the mechanical and chemical properties of the composite. Thus, synthesis of Gr-Al NCs is extremely challenging. This review summarizes the different methods available to synthesize Gr-Al NCs and the resulting properties achieved in these NCs. Understanding the effect of processing parameters on the realized properties opens up the possibility of tailoring the synthesis methods to achieve the desired properties for a given application. 相似文献
95.
In the present study, hydroxyapatite (HAP) coating along with HAP/TiO2 coating has been deposited by high-velocity flame spray (HVFS) technique onto 316LSS. Titania was used as a bond coat and HAP as top coat in HAP/TiO2 coating. The main aim of the study is to investigate the corrosion behavior of thermal spray coating of HAP and HAP/TiO2 on steel. Electrochemical corrosion testing was carried out using potentiodynamic polarization test. The corrosion behavior of bare and as-sprayed specimens was analyzed in simulated body fluid known as Hank’s solution. As-sprayed specimens along with corroded specimens were further characterized by XRD, SEM/EDS, and x-ray mapping analysis. It was observed that the HAP/TiO2 coating possessed higher microhardness (280 Hv) as compared to HAP coating (254 Hv). Surface roughness also got enhanced in case of HAP/TiO2 coating (9.35 μm) as compared to pure HAP coating (7.37 μm). The porosity of the HAP coating was found to be higher than the bond coating. It was observed that the Ca/P ratio almost resembled that of the natural bone composition. The corrosion resistance of steel increased after the deposition of HAP and HAP/TiO2 coatings. The maximum corrosion resistance was exhibited by HAP/TiO2 coating. 相似文献
96.
Effect of Alumina Reactivity on the Densification and Properties of Al2O3–Cr2O3 Refractories
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Mithun Nath Vakiti Pradeep Reddy Somnath Sinhamahapatra Kausik Dana Arup Ghosh Himansu Sekhar Tripathi 《International Journal of Applied Ceramic Technology》2015,12(3):608-613
Alumina‐chrome (Al2O3–Cr2O3) refractories with Al2O3:Cr2O3 molar ratio 1:1 were synthesized in the temperature range of 1400–1700°C by conventional solid–oxide reaction route. The effect of different aluminas (viz., hydrated and calcined) on the densification, microstructure, and properties of Al2O3–Cr2O3 refractories was investigated without changing the Cr2O3 source. The starting materials were analyzed to determine the chemical composition, mineralogy, density, surface area, and particle size. Sintered materials were characterized in terms of densification, phase assemblage, and mechanical strength at room temperature and at higher temperatures. Microstructural evolution at different sintering temperature was correlated with sintering characteristics. It can be concluded that the Al2O3–Cr2O3 refractories prepared with hydrated alumina as Al2O3 source show better densification and hot mechanical strength than corresponding calcined variety. 相似文献
97.
Yong-Chul Jang Pradeep Jain Thabet Tolaymat Brajesh Dubey Shrawan Singh 《The Science of the total environment》2010,408(8):1878-1887
The chemical characterization of sediments accumulated in catch basins and stormwater ponds provides important information for assessing risks associated with management of these residuals upon removal of accumulated deposits in stormwater systems. In this study, over a period of 15 months, more than 150 residual samples were collected from 77 catch basin units and 22 stormwater ponds from 16 municipalities throughout the state of Florida. Concentrations (mg/kg) of metals and metalloids (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, and zinc) and trace organics (volatile organics, semi-volatile organics, herbicides, and pesticides) in the sediments were measured. In addition, the synthetic precipitation leaching procedure (SPLP) was utilized to evaluate pollutant leachability risk for a subset of the samples collected. Measured pollutant concentrations were compared to corresponding risk-based guidelines in Florida (i.e., Florida soil cleanup target levels) to assess potential human health risks of beneficial use of these residuals through land application. Leached concentrations were compared to risk-based water quality guidelines (i.e., Florida groundwater cleanup target levels) to examine the potential for groundwater contamination. Although several metals (arsenic, barium, chromium, copper, nickel, lead, and zinc) were routinely detected in the catch basin and stormwater pond sediments, their concentrations were generally lower than the Florida's risk-based cleanup target levels for soils. A small number of organochlorine compounds (e.g., 4,4′-DDE, 4,4′-DDT) were detected, but only in a limited number of the samples (less than 10%); leaching of trace organic pollutants above the Florida risk-based groundwater thresholds was rare. The results suggest that when land-applied or beneficially used, these residuals are not expected to pose a significant threat to human health or the environment and the results of this research will provide stormwater managers and environmental management authorities with a useful resource to examine proper disposal and beneficial use of catch basin and stormwater pond sediments. 相似文献
98.
Prashant Singh Pradeep Kumar Anju Katyal Rashmi Kalra Sujata K. Dass Satya Prakash Ramesh Chandra 《Catalysis Letters》2010,134(3-4):303-308
In this present work, we report that phosphotungstic acid provides a simple, efficient and environmentally benign route is a two-component one-pot domino Knoevenagel-type condensation/Michael reaction between 4-coumarin derivative and an aldehyde in water as a solvent in shorter duration with high yields. 相似文献
99.
A Simple Conceptual Model of Sediment Yield 总被引:2,自引:0,他引:2
Pradeep Kumar Bhunya S. K. Jain P. K. Singh S. K. Mishra 《Water Resources Management》2010,24(8):1697-1716
The sediment graphs (time distribution of sediment yield) are very essential if the sediment transports the pollutants that
are toxic at high concentrations, requiring determination of peak, rather than average sediment flow rate. In this paper,
an effort has been made to develop a simple conceptual model of sediment yield based on Soil Conservation Service Curve Number
(SCS-CN) method, instantaneous unit sediment graph (IUSG) method, and Power law and the performance is tested using real field
data of Chaukhutia watershed of Ramganga river catchment (area = 452.25 km2). The proposed model is found to provide realistic estimates of temporal variation of sediment yield as well as total sediment
yield during a storm event. The model is found to be most sensitive to parameter β followed by k,
\upalpha\upalpha, A, and ns. A comparison is made with the existing IUSG based models of Kumar and Rastogi (J Hydrol 95:155–163, 1987) and Raghuwanshi et al. (J Hydraul Eng ASCE 120(4):495–503, 1994) for developing sediment graphs. 相似文献
100.
Pradeep Ilayaperumal Praveena Chelladurai Karthik Vairan Pooja Anilkumar Balajothi Balagurusamy 《大分子材料与工程》2023,308(4):2200553
Synthetic polymer materials have been surged to the forefront of research in the fields of tissue engineering, drug delivery, and biomonitoring in recent years. Biodegradable synthetic polymers are increasingly needed as transient substrates for tissue regeneration and medicine delivery. In contrast to commonly used polymers including polyesters, polylactones, polyanhydrides, poly(propylene fumarates), polyorthoesters, and polyurethanes, biodegradable polyphosphazenes (PPZs) hold great potential for the purposes indicated above. PPZ's versatility in the synthetic process has enabled the production of a variety of polymers with various physico-chemical, and biological properties have been produced, making them appropriate for biomedical applications. Biocompatible PPZs are often used as scaffolds in the regeneration of skeleton, bones, and other tissues. PPZs have also received special attention as potential drug vehicles of high-value biopharmaceuticals such as anticancer drugs. Additionally, by incorporating fluorophores into the PPZ backbone to produce photoluminescent biodegradable PPZs, the utility of polyphosphazenes is further expanded as they are used in tracking the regeneration of the target tissue as well as the fate of PPZ based scaffolds or drug delivery vehicles. This review provides a summary of the evolution of PPZ applications in the fields of tissue engineering, drug delivery, and bioimaging in recent 5 years. 相似文献