The effects of cryogenic treatment on the toughness and tribological behaviors of eutectoid steel

Cryogenic treatment is a supplementary heat treatment usually applied after quenching. Its effects are permanent and this process affects the entire section. There have been many studies related to cryogenic treatment, most of which have been focused on tool steels. In the current study, a high-speed-train railway material was investigated, and different heat treatment processes were applied to the eutectoid steel. The effects of quenching and cryogenic treatment were investigated on the mechanical properties (toughness, hardness and wear). Four different structures were obtained with different heat treatment cycles: Pearlitic, tempered martensite, 12 hour cryo-treated tempered and 36 hour cryo-treated tempered. As a result of Charpy v-notch tests and hardness tests, cryogenic treatment was found to improve the toughness and hardness of quenched samples. The results of the ball-on-disc wear tests showed that the cryo-treated samples have better wear resistance than pearlitic and martensitic samples.     

Stress relaxation in carbon black loaded butyl rubber

The dependence of equilibrium force (F^*) on the strain ratio (α) of carbon black loaded butyl rubber was studied. The relation between elastic constant and volume fraction of carbon black was found in good agreement with that obtained by Guth and Gold relation at low concentrations using the shape factor (f = 6.5). The relaxation time and viscosity (η) were calculated by using stress relaxation of these samples at different compression strains. The same agreement was observed in the relation between viscosity and volume fraction of carbon black concentration. The results are discussed according to the dispersion mechanism of carbon black in rubber. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1067–1076, 2000     

Influence of hydrostatic pressure on the electrical properties of unvulcanized FEF-loaded SBR

Styrene butadience rubber (SBR-1502) loaded with different concentrations of FEF carbon black was tested to find out the effect of pressure on its electrical properties during vulcanization. Using the thermodynamically calculated values of the pressure coefficient (K), the thermoelastic coefficient (L = ?T/?P) was also estimated and compared with that obtained by other workers. The thermoelastic coefficient was found to be strongly dependent on the carbon black concentration.     

Condensation of 4-phenyl-3,5-dicarboethoxycyclopentane-1,2-dione with primary amines

Condensation of the title compound ( 1 ) with primary aromatic amines gave the dianilides ( 2 ), which cyclized to cyclopenta[1,2-c:4,3-c′]diquinolines ( 3 ). Treatment of 1 with o-phenylenediamine or 2,3-diaminopyridine afforded cyclopenta[2,1-b:3,4- b ′]bis[1,5]benzodiazepine ( 4 ) and bis[1,5]pyrido[b]diazepine derivative ( 5 ), respectively. Whereas, with o-aminophenol a mixture of 2c and cyclopenta[2,1- b :3,4- b ′]bis[1,5]benzoxazepine ( 7 ) was obtained. Pechmann reaction of 1 with m-cresol gave the bis[1]benzopyrane ( 9 ). Mannich reaction of 1 with benzylamine afforded the 3-azabicyclo[3.2.1]octane system ( 10 ).     

Removal of heavy‐metal ions by magnetic beads containing triazole chelating groups

The aim of this study was to prepare magnetic beads that could be used for the removal of heavy‐metal ions from synthetic solutions. Magnetic poly(ethylene glycol dimethacrylate–1‐vinyl‐1,2,4‐triazole) [m‐poly(EGDMA–VTAZ)] beads were produced by suspension polymerization in the presence of a magnetite Fe₃O₄ nanopowder. The specific surface area of the m‐poly(EGDMA–VTAZ) beads was 74.8 m²/g with a diameter range of 150–200 μm, and the swelling ratio was 84%. The average Fe₃O₄ content of the resulting m‐poly(EGDMA–VTAZ) beads was 14.8%. The maximum binding capacities of the m‐poly(EGDMA–VTAZ) beads from aquous solution were 284.3 mg/g for Hg²⁺, 193.8 mg/g for Pb²⁺, 151.5 mg/g for Cu²⁺, 128.1 mg/g for Cd²⁺, and 99.4 mg/g for Zn²⁺. The affinity order on a mass basis was Hg²⁺ > Pb²⁺ > Cu²⁺ > Cd²⁺> Zn²⁺. The binding capacities from synthetic waste water were 178.1 mg/g for Hg²⁺, 132.4 mg/g for Pb²⁺, 83.5 mg/g for Cu²⁺, 54.1 mg/g for Cd²⁺, and 32.4 mg/g for Zn²⁺. The magnetic beads could be regenerated (up to ca. 97%) by a treatment with 0.1M HNO₃. These features make m‐poly(EGDMA–VTAZ) beads potential supports for heavy‐metal removal under a magnetic field. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermally Pretreated 46% Pt/Vulcan XC72: Characterisation by TGA/DSC/TEM and Cyclic Voltammetry

We report a study of thermal stability and impact of thermal pretreatment procedures for 46% Pt/Vulcan XC72 (Tanaka) fuel cell catalyst. Stability in air and in inert gas (nitrogen, argon, helium) has been investigated by thermal gravimetric analysis (TGA), TGA‐mass spectrometry (TGA‐MS) and differential scanning calorimetry (DSC). Two distinct low temperature mass loss processes (100–200 and 285–300 °C) were observed, each exhibiting unique pretreatment temperature dependencies. TGA‐MS data in helium show fragment ions that suggest the thermal degradation processes are associated with decomposition of materials such as processing aids. Transmission electron microscopy (TEM) reveals a modest increase in average Pt nanoparticle size upon thermal pretreatment. After a pretreatment protocol based on TEM and thermal characterisation (300 °C/15 min, N₂), the electrochemically active surface area did not increase. At the kinetically controlled potential region (E >0.8 V) there was a small drop in current density for treated 46% Pt/C in comparison with as‐received catalyst. The slowing in ORR kinetics is significant. Apparently, the removal of organic components, which would improve mass transport, is negated by increased nanoparticle size.     

Material Parameters for Creep Rupture of Austenitic Stainless Steel Foils

Creep rupture properties of austenitic stainless steel foil, 347SS, used in compact recuperators have been evaluated at 700 °C in the stress range of 54-221 MPa to establish the baseline behavior for its extended use. Creep curves of the foil show that the primary creep stage is brief and creep life is dominated by tertiary creep deformation with rupture lives in the range of 10-2000 h. Results are compared with properties of bulk specimens tested at 98 and 162 MPa. Thin foil 347SS specimens were found to have higher creep rates and higher rupture ductility than their bulk specimen counterparts. Power law relationship was obtained between the minimum creep rate and the applied stress with stress exponent value, n = 5.7. The value of the stress exponent is indicative of the rate-controlling deformation mechanism associated with dislocation creep. Nucleation of voids mainly occurred at second-phase particles (chromium-rich M₂₃C₆ carbides) that are present in the metal matrix by decohesion of the particle-matrix interface. The improvement in strength is attributed to the precipitation of fine niobium carbides in the matrix that act as obstacles to the movement of dislocations.     

大塑性变形技术制备块状超细晶TiNi基形状记忆合金研究进展

详细介绍了块状超细晶TiNi基形状记忆合金的研究进展,包括其制备工艺与显微组织、马氏体相变行为、力学性能和形状记忆特性以及超弹性性能,并介绍了其在医学和工程领域的实际应用,最后探讨了块状超细晶TiNi基形状记忆合金今后的研究发展方向。     

Effect of Boronizing on Operating Stability of Steel AISI 304L under Erosion Impact of Hard Particles

Metal Science and Heat Treatment - The effect of solid boronizing at 950°C for 2 and 4 h on the phase composition, microstructure, hardness and abrasive wear of steel AISI 304L is studied...     

Polyethylene–Carbon Nanotube Composite Film Deposited by Cold Spray Technique

Carbon nanotubes (CNTs) are high-performance materials because of their superior electrical conductivity, thermal conductivity, and self-lubrication, and they have been studied for application to polymer composite materials as fillers. However, the methods of fabricating polymer composites with CNTs, such as injection molding, are too complicated for industrial applications. We propose a simple cold spray (CS) technique to obtain a polymer composite of polyethylene (PE) and CNTs. The composite films were deposited by CS on polypropylene and nano-porous structured aluminum substrates. The maximum thickness of the composite film was approximately 1 mm. Peaks at G and D bands were observed in the Raman spectra of the films. Scanning electron microscopy images of the film surface revealed that PE particles were melted by the acceleration gas and CNTs were attached with melted PE. The PE particles solidified after contact with the substrate. These results indicate that PE–CNT composite films were successfully deposited on polypropylene and nano-porous structured aluminum substrates by CS.