γ-Alumina: a single-crystal X-ray diffraction study

The structure of γ-alumina (Al21+1/3◊2+2/3O32) crystals obtained as a product of a corrosion reaction between β-sialon and steel was refined in the space group Fd-3m. The oxygen sublattice is fully occupied. The refined occupancy parameters are 0.83(3), 0.818(13), 0.066(14) and 0.044(18) for Al ions in 8a, 16d, 16c and 48f positions, respectively. The Al ions are distributed over octahedral and tetrahedral sites ina 63:37 ratio, with 6% of all Al ions occupying non-spinelpositions

Corrosion and oxidation behaviour of B-SiAlON via different processing route

The corrosion resistance of B-SiAlON based advanced ceramic materials in molten aluminum, equimolar NaCl-KCl melt and also in the melted mixture of NaF and AlF3 (molar ratio: 1:1.163) were investigated. two kinds of B-SiAlON were tested: B-SiAlON prepared from powder precursor produced by carbothermal reduction and nitridation (CRN) of pyrophyllite and B-SiAlON made from commercila powders (AlN, Al2O3 and Si3N4). Corrosion tests were realized at 760?C for 7, 36 and 72 h under nitrogen atmosphere by dip finger test method. All types of B-SiAlON have great corrosion resistance against molten aluminium and NaCl-KCl melt at these conditions. The results of corrosion test were different for the B-SiAlONs in the in molten fluorides. While the corroded zone was only 100?m deep after 72 h corrosion test in reference B-SiAlON prepared from synthetic powders /SiAlON-R), in sample prepared from CNR pyrophyllite (SiAlON-P) it was almost 230 ?m thick. Additionally, the oxidation resistance of B-SiAlON was tested. The results showed that both SiAlON-P and reference SiAlON-R have comparable good oxidation resistance

Imaging of Metabolic Bone Diseases:The Spine View, Part II

Metabolic bone diseases comprise a wide spectrum. Osteoporosis, the most frequent, characteristically involves the spine, with a high impact on health care systems and on the morbidity of patients due to the occurrence of vertebral fractures (VFs).Part II of this review completes an overview of state-of-the-art techniques on the imaging of metabolic bone diseases of the spine, focusing on specific populations and future perspectives. We address the relevance of diagnosis and current status on VF assessment and quantification. We also analyze the diagnostic techniques in the pediatric population and then review the assessment of body composition around the spine and its potential application. We conclude with a discussion of the future of osteoporosis screening, through opportunistic diagnosis and the application of artificial intelligence

Imaging of Metabolic Bone Diseases:The Spine View, Part I

Metabolic bone diseases comprise a wide spectrum. Of them, osteoporosis is the most frequent and the most commonly found in the spine, with a high impact on health care systems and on morbidity due to vertebral fractures (VFs).This article discusses state-of-the-art techniques on the imaging of metabolic bone diseases in the spine, from the well-established methods to the latest improvements, recent developments, and future perspectives.We review the classical features of involvement of metabolic conditions involving the spine. Then we analyze the different imaging techniques for the diagnosis, characterization, and monitoring of metabolic bone disease: dual-energy X-ray absorptiometry (DXA) and DXA-based fracture risk assessment applications or indexes, such as the geometric parameters, Bone Strain Index, and Trabecular Bone Score; quantitative computed tomography; and magnetic resonance and ultrasonography-based techniques, such as radiofrequency echographic multi spectrometry. We also describe the current possibilities of imaging to guide the treatment of VFs secondary to metabolic bone disease