Influence of hydrogen on magnetic properties of soft magnetic amorphous alloys
The influence of electrolytic hydrogenation on the magnetic properties of three different kinds of amorphous alloys has been investigated. The alloys studied were Fe/sub 83.3/Si/sub 3.5/B/sub 11.2/C/sub 2/, Fe/sub 38/Ni/sub 38/Mo/sub 2/Si/sub 8/B/sub 14/, and (Co/sub 86/Fe/sub 5/Cr/sub 9/)/sub 75/Si/sub 10/B/sub 15/. The experimental results showed that after hydrogenation the samples became very brittle and the soft magnetic properties degraded dramatically, but saturation magnetization sigma /sub s/ and average hyperfine field increased markedly. As hydrogen evolved from the charged samples which were placed in air at room temperature, the magnetic properties, toughness, and average hyperfine field were gradually recovered. >
Site occupancies and stoichiometries in hydrides of intermetallic compounds: Geometric considerations
Abstract Hole sizes and intersite distances were calculated at various hydrogen concentrations for the interstices in hydrides of TiCr 1.8 , ZrTi 2 , ZrV 2 , ZrCr 2 , ZrFe 2 , HfV 2 and TaV 2 with the cubic MgCu 2 C15 structure and of ZrMn 2 and ErMn 2 with the hexagonal MgZn 2 C14 structure. From a survey of other metallic hydrides, empirical criteria were chosen for the minimum hole size (0.40 A) and the minimum H-H distance (2.1 A) for hydrogen atom occupancy in stable hydrides. With these criteria, a model was developed for predicting which sites and how many of them could be occupied by hydrogen atoms in each of the intermetallic compounds listed. The resulting stoichiometries were determined by experimentally filling the interstices of model lattices constructed of Friauf polyhedra without violating either of the adopted geometric criteria. For each of the compounds rationales are presented to explain the experimental observations reported by other researchers.
Inference and Evidence in Archaeology: A Discussion of the Conceptual Problems
Publisher Summary This chapter dicsusses the general features of scientific inference and explains the way inference has been discussed by archaeologists. It presents an explication of current problems in the various areas: (1) the justification of archaeological conclusions, (2) the concepts of archaeological evidence, and (3) the undeveloped relations between archaeological theory and archaeological evidence. The chapter defines these problems and explains the way to resolve them. To resolve many of the problems surrounding uncertain links between inference and evidence, archaeologists should develop a rigorous model that specifies the way information about the past is transmitted to the present via material remains. The chapter presents the structure of such a model. However, establishing relevant data to support conclusions about past phenomena is only part of the overall process of generating archaeological knowledge. Some of the processes responsible for producing the material remains that archaeologists manipulate in assembling evidence to support claims about past phenomena are described in the chapter.