Search

In this work, the single-layered amorphous NbMoTaW and multilayered amorphous NbMoTaW/TiVCr high entropy alloys were prepared to investigate the diffusion barrier performance. The microstructure and thermal stability of these samples were analyzed by X-ray diffraction, transmission electron microscope, and four-point probe method after annealing at different temperatures. In the single-layered structure, Cu silicide formed after annealing at 600 °C. The reason is that the amorphous NbMoTaW layer crystallizes during annealing, which causes the interdiffusion between Cu and Si through grain boundaries (GBs). However, the multilayered structure still maintains effective barrier performance as the annealing temperature is below 800 °C. Amorphous structure without GBs diffusion path, severe lattice distortion, and the high dense layer interface are responsible for the improved barrier property in the multilayered system.

A feeding trial A as conducted at the farm of Qinghai Academy of Animal and Veterinary Science, Xining, China during 1996 - 1997 with three dry yak cows (initial body weight 163 - 197 kg, age 5 - 6 years) by using 3 x 3 Latin Square Design to determine the effect of levels of feed intake on digestion, nitrogen balance and purine derivative excretion in urine of yak cows. The animals were fed oat hay (nitrogen 13.5 g/kg dry matter (DM), metabolisable energy 8.3 MJ/kg DM), i.e., 0.3, 0.6 and 0.9 of voluntary intake (VI). Each intake treatment lasted for 17 days and the samples (feeds, faeces and urine) were collected during last 7 days of each period. The results indicate that digestibility of dietary DM, OM, NDF and ash declined when intake levels increased from 0.3 to 0.9 VI [DM, from 66.1% to 59.1% (P < 0.05); OM, from 68.1% to 59.9% (P < 0.05); NDF, from 62.1% to 54.3% (P < 0.05); and ash, from 33.9% to 11.8% (P < 0.05)]. Around 0.10 g N/kg W-0.75 was deficient daily in yak cows at 0.3 VI, and positive N balances were observed at 0.6 and 0.9 VI. Intake levels significantly (P < 0.05) affected total PD excretion in yak urine. The proportion of allantoin increased (P < 0.05) and uric acid decreased (P < 0.05) as intake level of feed increased. (C) 2004 Elsevier B.V. All rights reserved.