Characterization and Applications of Metal Ferrite Nanocomposites

In recent years, nanosized spinel-type ferrites emerged as an important class of nanomaterials due to their high electrical resistivity, low eddy current loss, structural stability, large permeability at high frequency, high coercivity, high cubic magnetocrystalline anisotropy, good mechanical hardness, and chemical stability [...]

Compositionally Disordered Doped with Cerium Crystalline Garnet Type Materials for Brighter and Faster Scintillations

Ce-doped tetracationic garnets (Gd, M)3Al2Ga3O12(M = Y, Lu) form a family of new multipurpose promising scintillation materials. The aim of this work was to evaluate the scintillation yield in the materials of quaternary garnets activated by cerium ions with partial isovalent substitution of the matrix-forming gadolinium ions by yttrium or lutetium ions.Materials were obtained in the form of polycrystalline ceramic samples, and the best results were shown by samples obtained from the raw materials produced by the coprecipitation method. It was found that ceramics obtained from coprecipitated raw materials ensure a uniform distribution of activator ions in the multi-cationic matrices, which enables the high light yield and fast scintillation kinetics of the scintillation. It was demonstrated that the superstoichiometric content of lutetium/gadolinium in the material is an effective method to suppress phosphorescence accompanied scintillation. For ceramics with the composition (Gd, Lu)3Al2Ga3O12 , a scintillation yield of more than 50.000 ph/MeV was achieved. The scintillation kinetics was measured to be close to the kinetics with a decay constant of 50 ns.In terms of the set of the parameters, the developed scintillation materials are close to the recently developed alkali halide materials LaBr3:Ce, GdBr3:Ce. Moreover, they have high mechanical hardness, are characterized by the absence of hygroscopicity, and are better adapted to the manufacture of pixel detectors used in modern devices for medical diagnostics.

Hardness and Texture of Electrolytic Copper Processed by ECAP at Ambient and Warm Temperature

Among several severe plastic deformation (SPD) methods, the Equal Channel Angular Pressing (ECAP) process is one of the most popular. This process's main characteristic is producing materials with ultra-fine or nanometric grains. Due to these microstructural changes, it is possible to improve mechanical properties such as strength and ductility. In this perspective, the aim of the present work was to evaluate the variations of the mechanical hardness property associated with microstructural and textural changes of pure copper as a function of its processing by SPD via ECAP. For this, the material was submitted to four passes through routes A (the sample is repetitively pressed without any rotation between each pass) and Bc (the sample is rotated in the same sense by 90° between each pass) at cold and warm temperatures. Through the obtained result, it was verified that the ambient temperature of the Bc route was the one that promoted greater homogeneity in the microstructure and weakening of the texture after the fourth pass. On the other hand, warm processing of copper by ECAP promoted a softening of the samples and a homogeneous distribution of hardness in both routes.

First-principles calculations of high-pressure physical properties anisotropy for magnesite

The first-principles calculations based on density functional theory with projector-augmented wave are used to study the anisotropy of elastic modulus, mechanical hardness, minimum thermal conductivity, acoustic velocity and thermal expansion of magnesite(MgCO3) under deep mantle pressure. The calculation results of the phase transition pressure, equation of state, elastic constants, elastic moduli, elastic wave velocities and thermal expansion coefficient are consistent with those determined experimentally. The research results show that the elastic moduli have strong anisotropy, the mechanical hardness gradually softens with increasing pressure, the conduction velocity of heat in the [100] direction is faster than that in the [001] direction, the plane wave velocity anisotropy first increases and then gradually decreases with increasing pressure, and the shear wave velocity anisotropy increases with the increase of pressure, the thermal expansion in the [100] direction is greater than that in the [001] direction. The research results are of great significance to people's understanding of the high-pressure physical properties of carbonates in the deep mantle.

Bioactive Glass—An Extensive Study of the Preparation and Coating Methods

Diseases or complications that are caused by bone tissue damage affect millions of patients every year. Orthopedic and dental implants have become important treatment options for replacing and repairing missing or damaged parts of bones and teeth. In order to use a material in the manufacture of implants, the material must meet several requirements, such as mechanical stability, elasticity, biocompatibility, hydrophilicity, corrosion resistance, and non-toxicity. In the 1970s, a biocompatible glassy material called bioactive glass was discovered. At a later time, several glass materials with similar properties were developed. This material has a big potential to be used in formulating medical devices, but its fragility is an important disadvantage. The use of bioactive glasses in the form of coatings on metal substrates allows the combination of the mechanical hardness of the metal and the biocompatibility of the bioactive glass. In this review, an extensive study of the literature was conducted regarding the preparation methods of bioactive glass and the different techniques of coating on various substrates, such as stainless steel, titanium, and their alloys. Furthermore, the main doping agents that can be used to impart special properties to the bioactive glass coatings are described.

Mechanical Reliability and Modeling of Hydroxyapatite Acaffold

Significant contributions on the improvement of the mechanical properties of hydroxyapatite (HAp) have been widely reported. However, failure analysis (mechanical reliability) and modeling are missing. This article filled the gap by conducting Two-parameter Weibull distribution assisted by modeling to investigate the mechanical reliability of HAp. The employed HAp was characterized under SEM/EDS analysis. The results revealed the characteristics of HAp and also the nature of the synthesis route employed through its irregular morphology. The Two-parameter Weibull distribution analysis was conducted on the hardness and compressive strength of HAp scaffold. The characteristic hardness and compressive strength, coupled with their corresponding bounds, failure rates, and correlation coefficients were been presented. The Weibull analysis with the assistance of modeling revealed HAp fabricated under 10 KN compaction load and sintered at 1100 oC as the most reliable sample under hardness condition, while HAp fabricated under 15 KN compaction load and sintered at 1000 oC gave the most reliable characteristic under compression. However, 15 KN compaction load and 1100 oC sintering temperature showed the best reliability on the overall mechanical (hardness and compressive strength) reliability. Future study is recommended on the reliability of HAp scaffolds considering other mechanical properties that are essential for biomedical application.

Rate and Temperature Effect in Nanoindentation Testing on Hardness in SLM IN718

The microstructure and mechanical hardness of Inconel 718 (INC718) hexagonal honeycomb cellular structure manufactured by Selective Laser Melting (SLM) was studied in this work. Non-heat-treated SLM-produced samples with cell wall thicknesses of 0.4, 0.6 and 0.8 mm were studied. The hardness was measured using MTS Nanoindenter. For room temperature, continuous hardness measurements over penetration depths up to 2 µm under three different strain rates of 0.02, 0.05 and 0.08 s−1 was performed. For the 100 and 200°C, single hardness measurements at eight different depths were performed. The grain size was found to change considerably as the cell wall thickness changed from 0.6 mm to 0.4 mm compared to the change from 0.8 mm to 0.6 mm. similar trend in mechanical hardness reduction and strain rate sensitivity changes were observed between the three samples. The microstructure and hardness showed anisotropy between the planes parallel and perpendicular to the build planes as well. Temperature and strain rate indentation size effect model developed by the second author was modified and used to evaluate the intrinsic material length scale used in gradient plasticity theory.