Sintered (Ti,W)C carbides were prepared from (Ti,W)C solid solution powder at 1510 degrees C. The powder was produced by milling a mixture of carbon and oxides and then reducing it at 1200 degrees C for 1 h. The sintered (Ti,W)C carbides demonstrate full density, excellent hardness and fracture toughness values (rho: 98-100%, HVN: 19-21 GPa, K-IC: 6.4-7.7 MPa m(1/2)). These homogeneous (Ti,W)C carbides have considerable potential for use in structural applications. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Sintered (Ti,W)C carbides were prepared from (Ti,W)C solid solution powder at 1510degC. The powder was produced by milling a mixture of carbon and oxides and then reducing it at 1200degC for 1h. The sintered (Ti,W)C carbides demonstrate full density, excellent hardness and fracture toughness values ( rho: 98-100%, HVN: 19-21GPa, KIC: 6.4-7.7MPam 1/2). These homogeneous (Ti,W)C carbides have considerable potential for use in structural applications. [All rights reserved Elsevier]
Internal curing (IC) is an effective method for improving performance of low W/C – low permeability concretes because they require additional water to hydrate the cementitious materials. Conventional concretes, on the other hand, contain enough water to hydrate the cementitious materials, but are frequently not properly cured, allowing drying and compromising strength gain and durability. The aim of this investigation is to assess the effect of IC as a complement to traditional curing in relatively high W/C concretes (W/C above 0.42) under drying conditions. Degree of hydration, compressive strength, and permeability were measured in concretes with IC and without IC. Results show that even under drying conditions, mixtures with IC exhibit 16%higher hydration, 19%higher compressive strength, and 30%lower permeability than their counterparts with no IC. This suggests that IC can be very useful for improving performance in concrete mixtures with relatively high W/C under poor curing conditions.
Internal curing (IC) is an effective method for improving performance of low W/C - low permeability concretes because they require additional water to hydrate the cementitious materials. Conventional concretes, on the other hand, contain enough water to hydrate the cementitious materials, but are frequently not properly cured, allowing drying and compromising strength gain and durability. The aim of this investigation is to assess the effect of IC as a complement to traditional curing in relatively high W/C concretes (W/C above 0.42) under drying conditions. Degree of hydration, compressive strength, and permeability were measured in concretes with IC and without IC. Results show that even under drying conditions, mixtures with IC exhibit 16% higher hydration, 19% higher compressive strength, and 30% lower permeability than their counterparts with no IC. This suggests that IC can be very useful for improving performance in concrete mixtures with relatively high W/C under poor curing conditions. (C) 2010 Elsevier Ltd. All rights reserved.
Internal curing (IC) is an effective method for improving performance of low W/C - low permeability concretes because they require additional water to hydrate the cementitious materials. Conventional concretes, on the other hand, contain enough water to hydrate the cementitious materials, but are frequently not properly cured, allowing drying and compromising strength gain and durability. The aim of this investigation is to assess the effect of IC as a complement to traditional curing in relatively high W/C concretes (W/C above 0.42) under drying conditions. Degree of hydration, compressive strength, and permeability were measured in concretes with IC and without IC. Results show that even under drying conditions, mixtures with IC exhibit 16% higher hydration, 19% higher compressive strength, and 30% lower permeability than their counterparts with no IC. This suggests that IC can be very useful for improving performance in concrete mixtures with relatively high W/C under poor curing conditions. [All rights reserved Elsevier].
Tritium exposed samples, including doped graphite, SiC coated graphite, tungsten coatings fabricated by vacuum plasma spraying, and polycrystalline tungsten, were examined by beta-ray-induced X-ray spectrometry in an argon atmosphere. The changes in the X-ray spectra with time were followed for a maximum time of 100 h. The results indicated that the SiC coated graphite absorbed the most tritium and the polycrystalline tungsten the least. Preliminary computer simulations were performed to analyze the depth profiles of tritium in these materials. (C) 2010 Elsevier B.V. All rights reserved.
Abstract Given any compact, Hausdorff space K and 1 < p < ∞ , we compute the Szlenk and w ⁎ -dentability indices of the spaces C ( K ) and L p ( C ( K ) ) . We show that if K is compact, Hausdorff, scattered, C B ( K ) is the Cantor–Bendixson index of K , and ξ is the minimum ordinal such that C B ( K ) ⩽ ω ξ , then S z ( C ( K ) ) = ω ξ and D z ( C ( K ) ) = S z ( L p ( C ( K ) ) ) = ω 1 + ξ .
Zhongshi Yang
Q. Xu
Junqi Liao
Q. Li
G.-H. Lu
G.-N. Luo
By means of molecular dynamics simulations using bond-order potential (BOP), we have investigated the interactions between carbon (C) atoms and bcc tungsten (W). At finite temperature (T = 300 K) with incident energy of C atoms ranging from 0.5 to 100 eV at normal incidence, the projected range distribution as a function of incident energy and the average depth have been depicted. The properties of vacancy, vacancy migration, interstitial and substitutional C atoms in W have been determined. The most stable configuration for an interstitial C atom in W is in octahedral position and the lattice distortion around the C atom in octahedral interstitial configuration occurs along lang100rang and lang110rang directions. The mutual interaction between a vacancy and near interstitial C atom is also studied. [All rights reserved Elsevier].
The annealing behaviour of Ti(C 0.5N 0.05)-40wt.% W and Ti(C 0.5N 0.5) 0.6-40 wt.% W mechanically alloyed powders was investigated using XRD, TEM, SEM and DTA techniques. It was observed that the reaction start and finish temperatures between constituents were lower in the system that had higher residual lattice strains after milling. The compositions of the intermetallic compounds and solution phases formed were dependent of the milling conditions and the annealing temperature. Thermal alloying was observed during annealing of Ti(C 0.5N 0.05)-40wt.% W mechanically alloyed products, whereas de-mixing of W-rich phases from the metastable solid solution occurred during annealing of the Ti(C 0.5N 0.5)0.6-40wt.% W milled powders. [All rights reserved Elsevier].
The annealing behaviour of Ti(C(0.5)N(0.05))-40 wt.% W and Ti(C(0.5)N(0.5))(0.6)-40 wt.% W mechanically alloyed powders was investigated using XRD, TEM, SEM and DTA techniques. It was observed that the reaction start and finish temperatures between constituents were lower in the system that had higher residual lattice strains after milling. The compositions of the intermetallic compounds and solution phases formed were dependent of the milling conditions and the annealing temperature. Thermal alloying was observed during annealing of Ti(C(0.5)N(0.05))-40 wt.% W mechanically alloyed products, whereas de-mixing of W-rich phases from the metastable solid solution occurred during annealing of the Ti(C(0.5)N(0.5))(0.6)-40 wt.% W milled powders. (C) 2011 Elsevier Ltd. All rights reserved.
It is well known that the Diophantine equations x(4) + y(4) =3D z(4) + w(4) and x(4) + y(4) + z(4) =3D w(4) each have infinitely many rational solutions. It is also known for the equation x(6) + y(6) - z(6) =3D w(2). We extend the investigation to equations x(a) +/- y(b) =3D +/- z(c) +/- w(d), a, b, c, d is an element of Z, with 1/a + 1/b + 1/c + 1/d =3D 1. We show, with one possible exception, that if there is a solution of the equation in the reals, then the equation has infinitely many solutions in the integers. Of particular interest is the equation x(6) + y(6) + z(6) =3D w(2) because of its classical nature; but there seem to be no references in the literature.
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