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排序方式: 共有1423条查询结果,搜索用时 15 毫秒
71.
Darothi Bairagi Venkataramana Munukuti Pallabi Bhuyan Rajib Saha Sumantra Mandal 《工业材料与腐蚀》2021,72(5):829-838
The influence of cementite spheroidization on the impact toughness and electrochemical properties of a high-carbon steel has been thoroughly investigated in this study. Heavy warm rolling, followed by 2 h of annealing, has resulted in near-complete spheroidization, leading to a microstructure consisting of nano-cementite globules dispersed in the ultrafine-grained ferritic matrix. The Charpy impact test exhibited superior impact toughness with increased spheroidization. It is validated by the presence of abundant dimples in the fractographs of spheroidized specimens, in contrast to the as-received one that experienced a brittle failure due to its lamellar pearlitic structure. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) carried out in a 3.5% NaCl solution revealed that the corrosion resistance of the alloy gets improved with the increase in the degree of spheroidization. This is attributed to the lower susceptibility of the spheroidized specimen to microgalvanic corrosion owing to the minimum area of contact between nano-spheroidized cementite and ferrite, as elucidated with the help of EIS results aided by equivalent electrical circuit model. 相似文献
72.
Siddhartha Sankar Mandal K. S. Ghosh 《International Journal of Cast Metals Research》2018,31(3):177-192
Destabilisation of as-cast chromium white iron with 16 wt-% chromium are performed by continuous destabilisation treatment for 4 h and short duration (0.66 h) cyclic destabilisation treatment at 900, 950, 1000, 1050, and 1100 °C. Continuous destabilisation causes secondary carbides precipitation from austenite which on slow cooling transforms to pearlite matrix. Cyclic destabilisation treatment causes similar precipitation of finer secondary carbides following shorter period austenitisation and a matrix containing martensite and retained austenite on forced-air cooling. After continuous destabilisation, hardness falls below the as-cast value (HV622); whereas it rises to HV950 after cyclic destabilisation treatment. The as-cast notched impact toughness (4.0 J) increases to 8.5 J or more after both continuous and cyclic destabilisation at 1050 and 1100 °C. Abrasive wear resistance after continuous destabilisation improves only at higher wear load (49.0 N), while after cyclic destabilisation it supersedes the as-cast and Ni-Hard IV performance at both low (19.6 N) and high (49.9 N) wear load. 相似文献
73.
Shammya Afroze Nico Torino Md Sumon Reza Nikdalila Radenahmad Quentin Cheok Paul F. Henry Abul K. Azad 《Ceramics International》2021,47(1):541-546
The structural and electrochemical properties of the double perovskite-type oxide, PrBaMnMoO6-δ, was investigated using neutron diffraction with in-situ conductivity measurement under a dry Argon atmosphere from 25 °C to 700 °C. A Rietveld refinement of the neutron diffraction data confirmed monoclinic symmetry in the P21/n space group. Rietveld refinement also confirms the unit cell parameters of a = 5.6567 (1) Å, b = 5.6065 (2) Å, c = 7.9344 (1) Å and β = 84.43° with reliable atomic positions and refinement factors (R-factors). Neutron diffraction data refinement shows two minor phases (<5%), an orthorhombic AB2O5 type phase of PrMn2O5 in the Pbam (No. 32) space group with unit cell parameters, a = 7.9672 (1) Å, b = 8.9043 (2) Å and c = 5.8540 (1) Å and a scheelite phase of BaMoO4 in the tetragonal I41/a (88) space group with the unit cell parameters, a = b = 5.9522 (1) Å, and c = 12.3211 (2) Å. Morphological images revealed a porous and intertwined microstructure. In-situ conductivity measurement shows that the total conductivity of this material was 130.84 Scm?1 at 700 °C. 相似文献
74.
S.K. Mandal M.M. Singh 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2009,24(1):22-36
Damage or overbreak not only endangers safety of structure but also increases cost of construction and time of completion. Drilling and blasting being cost-effective for excavation of any underground structure should strictly adhere into specialized controlled blasting pattern to minimize the unacceptable impact on peripheral in situ rock mass. The paper reveals that in addition to geo-technical properties of rock mass, in situ stress condition plays an important role in enhancing the magnitude of overbreak. Implementation of same blast pattern throughout the length of tunnel results into different magnitudes of overbreak and the magnitude increases in highly stressed zone. Furthermore, implementation of same controlled perimeter blast pattern along the tunnel cross-section may result into different magnitudes of overbreak. Different magnitude of overbreak along the tunnel cross-section i.e., in left and right wall and crown has been observed even with implementation of same controlled blast pattern throughout the tunnel cross-section. Feasibility and compatibility of drilling equipment with respect to tunnel cross-section also adds to the quality and magnitude of overbreak. Undersize drilling equipment leads to angular drilling on either walls or crown and enhances the magnitude of overbreak. The paper with the help of statistical and graphical analysis revealed that blast pattern for peripheral rock mass should consider geo-technical properties and in situ stress condition of rock mass to minimize the magnitude of overbreak. The authors also emphasized that to contain magnitude of overbreak within allowable limit; the implemented blast pattern should be different for different sections viz., right wall, left wall and crown of tunnel. Furthermore, in poor rock mass condition or in highly stressed zone, drivage of tunnel should be carried out in small sections and in different phases until the excavation reaches the required excavation profile in that area. Excavation in small sections and in different phases would lead to proper excavated profile and minimize overbreak and damage of peripheral rock mass. 相似文献
75.
M. A. Kalam H. H. Masjuki M. Redzuan T. M. I. Mahlia M. A. Fuad M. Mohibah K. H. Halim A. Ishak M. Khair A. Shahrir A. Yusoff 《Sadhana》2009,34(3):467-481
This paper presents characteristics of a new catalytic converter (catco) to be used for natural gas fuelled engine. The catco were developed based on catalyst materials consisting of metal oxides such as titanium dioxide (TiO2) and cobalt oxide (CoO) with wire mesh substrate. Both of the catalyst materials (such as TiO2 and CoO) are inexpensive in comparison with conventional catalysts (noble metals) such as palladium or platinum. In addition, the noble metals such as platinum group metals are now identified as human health risk due to their rapid emissions in the environment from various resources like conventional catalytic converter, jewelers and other medical usages. It can be mentioned that the TiO2/CoO based catalytic converter and a new natural gas engine such as compressed natural gas (CNG) direct injection (DI) engine were developed under a research collaboration program. The original engine manufacture catalytic conveter (OEM catco) was tested for comparison purposes. The OEM catco was based on noble metal catalyst with honeycomb ceramic substrate. It is experimentally found that the conversion efficiencies of TiO2/CoO based catalytic converter are 93%, 89% and 82% for NOx, CO and HC emissions respectively. It is calculated that the TiO2/CoO based catalytic converter reduces 24%, 41% and 40% higher NOx, CO and HC emissions in comparison to OEM catco respectively. The objective of this paper is to develop a low-cost three way catalytic converter to be used with the newly developed CNG-DI engine. Detailed review on catalytic converter, low-cost catalytic converter development characteristics and CNGDI engine test results have been presented with discussions. 相似文献
76.
Abul Fazal M. Arif 《Journal of Mechanical Science and Technology》2009,23(10):2603-2611
Laser shock processing (LSP) involves high-energy laser radiation combined with suitable overlays to generate high-pressure
pulses on the surface of the metal. The stress wave generated due to high pressure pulses propagates into the material causing
the surface layer to yield and plastically deform, and thereby, develop a significant residual compressive stress in the surface
region of the substrate material. The developed compressive stress field is beneficial to improve surface properties such
as fatigue, wear, and corrosion. To improve the understanding of the shock hardening process, investigation into the physical
processes involved is necessary. In the first part of this paper, the temporal variation in the pressure intensity and spot
size is calculated by using a two-dimensional recoil pressure prediction model. Using an explicit non-linear FEA code, ANSYS
LS-DYNA, the deformation behavior and residual stresses in the substrate material are predicted. In the second part, a probabilistic
approach to the modeling and analysis of LSP is presented in this paper. Various factors that affect the probabilistic performance
of the LSP are grouped into categories and a select number of factors known to be significant, for which the variability could
be assessed, are modeled as random variables (such as recoil pressure, laser beam spot size, substrate material properties
and others). The potential of the probabilistic approach in predicting the structural integrity of the laser-shocked components
is addressed. 相似文献
77.
The potential of CaSnO3 for application as a capacitor component possessing a small temperature coefficient of capacitance has been examined by ac small-signal measurements at elevated temperatures (25–300°C) in the frequency range 5–13 MHz. The samples were synthesized by a novel technique called self-heat-sustained (SHS) reaction. The ac data were acquired for the CaSnO3 samples sintered at various temperatures with varying soak temperatures, T, and some times, t (1200°C T 1600°C 2 h t 48 h). An analysis of the electrical data in more than one complex-plane formalism indicated relaxation processes. The resistance of these sintered samples was dominated by the grain boundaries, and the capacitance exhibited near-linear behavior at elevated temperature for several decades of measurement frequency. The electrical behavior has been correlated with the evolved microstructure in these samples in conjunction with the results obtained in a previous study for solid-state reaction (SSR) derived sintered bodies. The multi-plane analytical criteria provided a meaning for the lumped equivalent circuit representation including the origin and purpose of the contributing elements extracted from each complex plane formalism. 相似文献
78.
Effect of environmental pollutants on the C-reactive protein of a freshwater major carp, Catla catla
C-reactive proteins (CRP) have been affinity purified to electrophoretic homogeneity from the sera of major carp, Catla catla before and after exposure to environmental pollutants. Exposure to these pollutants elevate the levels of circulating CRPs to 2.8-3.5 times the normal values. Kinetic studies of metal intoxication indicate that a unique molecular variant of CRP is present in the serum at the peak level of acute phase induction, and this variant coexists with normal CRPs. Carbohydrate analysis and lectin binding reveals that these CRPs are glycoproteins differing significantly in total carbohydrate contents. Their electrophoretic mobilities in native gel are different but become identical on desialylation and deglycosylation implying that the molecular variants vary in the glycan parts. All these forms of CRP contain two nonidentical subunits of Mr 22 and 29 kDa. Examination of their immunological crossreactivity demonstrate their similarity in overall molecular topology but their differences in the quantitative extent of binding are reflected. 相似文献
79.
J. B. Mandal B. Bandyopadhyay B. Ghosh H. Rajagopal A. Sequeira J. V. Yakhmi 《Journal of Superconductivity and Novel Magnetism》1996,9(2):253-257
Rietveld analysis of powder neutron diffraction pattern recorded on Sr-based 1201-phase superconductor (T c =53 K), (Hg0.7Cr0.3)Sr2CuO4+δ shows that the oxygen atoms at O(3) site are disordered atx=y=0.3712. This fourfold split site has a total combined occupancy of ~80% and is the only occupied site in the (Hg, Cr)O plane. 相似文献
80.
A template synthesis technique of encapsulating DNA molecules inside polypyrrole (PPy) nanotubes, termed as DNA-PPy nanocapsule, has been described here. The insertion of DNA molecules inside polypyrrole nanotubes is spontaneous in nature. The structural characterizations and possible applications of DNA-PPy nanocapsule in bio-sensing devices have been discussed. 相似文献