Fabrication and thermo-mechanical behavior of ultra-fine porous copper

The Application Value of Spiral CT Lung Densitometry Software in the Diagnosis of Radiation-Induced Lung Injury

In order to study the application value of spiral CT lung density measurement software in the diagnosis of radioactive lung injury, the average CT values of lung apex, hilum, and diaphragm were measured by Pulmo automatic evaluation software of 16-slice spiral CT in 96 patients with different types of radiation lung injury diagnosed by conventional CT and 80 healthy subjects. The radiation lung injury on CT slices was classified, and the lung density was measured. In 96 patients with different types of radiation lung injury, 56 patients had different degrees of increase in average lung density, which was most obvious in the type of air insufficiency and chronic fibrosis. CT values of lung density in the ground glass stage and patch stage of acute radiation pneumonia had little influence due to the range and time of exposure. The lung density of 35 patients with radiation injury was measured in the normal range. There was a significant difference between normal lung density and abnormal lung density in different types of radiation lung injury (X ² = 56.718, P < 0.001). The mean lung density of 68 cases was normal and that of 12 cases was abnormal. There was a significant difference in lung density between the lung injury group and the normal group (X ² = 18.027, P < 0.001). Spiral CT lung density measurement can accurately evaluate the lung density values of different types of radiation lung injury and judge the correlation between lung density and different types of radiation lung injury. It is of great value to diagnose, locate, and master the radiation dose of different types of radiation lung injury.

Influence of Metallic Powder Characteristics on Extruded Feedstock Performance for Indirect Additive Manufacturing

Material extrusion (MEX) of metallic powder-based filaments has shown great potential as an additive manufacturing (AM) technology. MEX provides an easy solution as an alternative to direct additive manufacturing technologies (e.g., Selective Laser Melting, Electron Beam Melting, Direct Energy Deposition) for problematic metallic powders such as copper, essential due to its reflectivity and thermal conductivity. MEX, an indirect AM technology, consists of five steps—optimisation of mixing of metal powder, binder, and additives (feedstock); filament production; shaping from strands; debinding; sintering. The great challenge in MEX is, undoubtedly, filament manufacturing for optimal green density, and consequently the best sintered properties. The filament, to be extrudable, must accomplish at optimal powder volume concentration (CPVC) with good rheological performance, flexibility, and stiffness. In this study, a feedstock composition (similar binder, additives, and CPVC; 61 vol. %) of copper powder with three different particle powder characteristics was selected in order to highlight their role in the final product. The quality of the filaments, strands, and 3D objects was analysed by micro-CT, highlighting the influence of the different powder characteristics on the homogeneity and defects of the greens; sintered quality was also analysed regarding microstructure and hardness. The filament based on particles powder with D₅₀ close to 11 µm, and straight distribution of particles size showed the best homogeneity and the lowest defects.

Synthesis and characterizations of (Mg, Co, Ni, Cu, Zn)O high-entropy oxides

High-temperature structural ceramic materials require stability in terms of thermal and mechanical properties. High entropy oxides (HEOs) are among the emerging novel family of advanced ceramic materials with peculiar functional properties. However, their thermal stabilities and mechanical properties are not well investigated. In this work, HEO systems were synthesized from binary oxides of MgO, CoO, NiO, CuO, and ZnO using solid-state reaction method at high temperature, after obtaining the individual oxides through co-precipitation methods. The phase purity of as-synthesized and sintered samples was characterized using X-ray powder diffraction, while the microstructural investigation was performed using Scanning electron microscopy. Mechanical property of the sintered samples at different sintering times and temperatures was investigated and the sample sintered at a sintering temperature of 1200 °C for 15 h sintering time showed a maximum Vickers hardness of about 16 GPa. This result is comparable with some of the hard ceramic materials, and therefore the materials could be a potential candidate for structural applications.

Evaluation of Demineralized Bone Matrix Particles Delivered by Alginate Hydrogel for a Bone Graft Substitute: An Animal Experimental Study

BACKGROUND Our objective was to explore a synthetic alginate hydrogel delivery system for the delivery of demineralized bone matrix (DBM) particles for bone graft substitutes. MATERIAL AND METHODS The physiochemical properties of surface morphology, porosity measurements, in vitro degradation, equilibrium swelling, and mechanical testing of combined DBM powder and alginate in amounts of 0 mg/1 mL, 25 mg/1 mL, 50 mg/1 mL, and 100 mg/1 mL were detected. In vitro cell culture and in vivo studies using Sprague-Dawley rats were performed to evaluate the biocompatibility and osteoinductivity of DBM-alginate (ADBM) composites. RESULTS DBM particles were uniformly scattered in all composites, and macro-scale pores were omnipresent. All composites showed a similar low degradation rate, with approximately 85% of weight remaining after 15 days. As the concentration of DBM particles in composites increased, degradation in collagenase and elastic modulus increased and the pore area and swelling ratio significantly decreased. No cytotoxicity of ADBM or alginate on mesenchymal stem cells (MSCs) was observed. Cell cultivation with ADBM showed greater osteogenic potential, evidenced by the upregulation of alkaline phosphatase and alizarin red staining activity and the mRNA expression level of marker genes RUNX2, OCN, OPN, and collagen I compared with the cells grown in alginate. Evaluation of ectopic bone formation revealed the osteoinductivity of the ADBM composites was significantly greater than that of DBM particles. Osteoinduction of the composites was demonstrated by a cranial defect model study. CONCLUSIONS The delivery of DBM particles using a synthetic alginate hydrogel carrier may be a promising approach in bone tissue engineering for bone defects.

High Temperature Flow Behavior of Ultra-Strong Nanoporous Au assessed by Spherical Nanoindentation

Nanoporous metals have attracted attention in various research fields in the past years since their unique microstructures make them favorable for catalytic, sensory or microelectronic applications. Moreover, the refinement of the ligaments down to the nanoscale leads to an exceptionally high strength. To guarantee a smooth implementation of nanoporous metals into modern devices their thermo-mechanical behavior must be properly understood. Within this study the mechanical flow properties of nanoporous Au were investigated at elevated temperatures up to 300 °C. In contrast to the conventional synthesis by dealloying of AuAg precursors, the present foam was fabricated via severe plastic deformation of an AuFe nanocomposite and subsequent selective etching of iron, resulting in Au ligaments consisting of nanocrystalline grains, while remaining Fe impurities excessively stabilize the microstructure. A recently developed spherical nanoindentation protocol was used to extract the stress-strain curves of nanoporous Au. A tremendous increase of yield strength due to ligament and grain refinement was observed, which is largely maintained at high temperatures. Reviewing literature will evidence that the combined nanocrystalline and nanoporous structure leads to remarkable mechanical properties. Furthermore, comparison to a previous Berkovich nanoindentation study outlines the conformity of different indentation techniques.

Advanced Nanoindentation Testing for Studying Strain-Rate Sensitivity and Activation Volume

Nanoindentation became a versatile tool for testing local mechanical properties beyond hardness and modulus. By adapting standard nanoindentation test methods, simple protocols capable of probing thermally activated deformation processes can be accomplished. Abrupt strain-rate changes within one indentation allow determining the strain-rate dependency of hardness at various indentation depths. For probing lower strain-rates and excluding thermal drift influences, long-term creep experiments can be performed by using the dynamic contact stiffness for determining the true contact area. From both procedures hardness and strain-rate, and consequently strain-rate sensitivity and activation volume can be reliably deducted within one indentation, permitting information on the locally acting thermally activated deformation mechanism. This review will first discuss various testing protocols including possible challenges and improvements. Second, it will focus on different examples showing the direct influence of crystal structure and/or microstructure on the underlying deformation behavior in pure and highly alloyed material systems.

Thermally Activated Deformation Behavior of ufg-Au: Environmental Issues During Long-Term and High-Temperature Nanoindentation Testing

For testing time-dependent material properties by nanoindentation, in particular for long-term creep or relaxation experiments, thermal drift influences on the displacement signal are of prime concern. To address this at room and elevated temperatures, we tested fused quartz at various contact depths at room temperature and ultra-fine grained (ufg) Au at various temperatures. We found that the raw data for fused quartz are strongly affected by thermal drift, but corrected by use of dynamic stiffness measurements all the datasets collapse. The situation for the ufg Au shows again that the data are only useful with drift correction, but with this applied it turns out that there is a significant change of elastic and plastic properties when exceeding 200°C, which is also reflected by an increasing strain rate sensitivity.