Conventional and new lead-free radiation shielding materials for radiation protection in nuclear medicine: A review

https://backend.orbit.dtu.dk/ws/files/145410334/Tusek_et_al_2018.pdf

Elastocaloric effect vs fatigue life: Exploring the durability limits of Ni-Ti plates under pre-strain conditions for elastocaloric cooling

Journal of Optoelectronics and Advanced Materials: Introduction

Geopolymer foam concrete (GFC) has attracted significant research interest in various fields, thanks to their porous structure which brings the inherent merits of lightweight, acoustic and thermal insulation, and fire resistance. This review is focussed on three primary functional properties of GFC, namely mechanical properties (compression and flexural strengths), serviceability (thermal conductivity, sound absorption, and fire resistance), and durability. The functional properties depend on the fundamental fresh and hardened properties (rheology, stability, density, porosity and pore morphology), and all these properties are decided by the materials, foaming methods, curing conditions, and additives. A clear insight to these relationships and the ways of optimising the performance as a construction material are therefore presented. Also, the challenges towards the large-scale production and real-world application of GFC are discussed. The identified research needs include studies on fresh properties, durability, processing techniques to attract industrial applications, and developing 3D printable GFC.

Progress, current thinking and challenges in geopolymer foam concrete technology

Study on gamma shielding polymer composites reinforced with different sizes and proportions of tungsten particles using MCNP code

This paper presents the mechanical properties of a lightweight geopolymer concrete synthesized by the alkali-activation of a fly ash source (FA) produced by mixing a paste of geopolymer with foam produced by using NCT Foam Generator. Two curing conditions are used, curing at room temperature and curing in an oven with a constant temperature which is 60 oC. Bulk density showed that fly ash-based geopolymer lightweight concrete is light with the density of 1225 kg/m3 - 1667 kg/m3 with an acceptable compressive strength of 17.60 MPa for the density of 1667 kg/m3.

Fly Ash Based Lightweight Geopolymer Concrete Using Foaming Agent Technology

When we use effectively shape memory alloys require knowledge of operational behavior at the thermal stresses and mechanical variables. Measurements performed on a CuZnAl alloy, revealed fatigue properties by considering the size of the maximum load deformation corresponding recovered memory. It requires knowledge in design fatigue behavior of shape memory alloy components after education, fatigue strength by performing partial memory loss or physical destruction. The properties of memory shape alloys recommend their use for complex mechanical applications in domains as follows medicine, robotics, aeronautics, electric contacts, actuators. Shape memory metal alloys in the construction of such installations are subject to mechanical stress, and the thermal stresses, so their inclusion in a computing system fatigue involves consideration of the function performed.

On the Fatigue of Shape Memory Alloys

The paper aims the determination of the friction force by means of external friction stress, at the severe plastic deformation processing using cyclic closed-die forging method. It is known that the total force used at the severe plastic deformation by the method of multiaxial forging is being composed by the deformation force itself and the friction force between the semi-product and the deformation tools. Once the friction stresses known, for a certain material, one can determine the friction force corresponding for a given deformation of a semi-product of a particular shape and sizes. By means of the flowing curve of the semi-product material one can determine the deformation force, which together with the friction force give the total necessary force for a deformation and so one can choose the necessary equipment for the processing of the material by severe plastic deformation. For this purpose it has been severely plastic deformed by the method of multiaxial forging, a semi-product having the sizes 10x10x20 mm, the finished part having the same sizes and shape. It has been measured the deformation force and the extraction force of the finished part from the cavity of the active plate, the late being used for the determination of the friction stress between the semi-product and the active plate.

The Experimental Determination of the Friction Stress between the Semi-Product and the Active Plate at the Multiaxial Forging of Copper

Lead metal proved to be toxic. Its lethal effect became eminent. Many developed countries have banned lead usage in various applications. Seeking alternative material to replace lead is a crucial goal. As density concerns, tungsten-brass composite is a good candidate for lead replacement. In this study the radiation shielding effects of tungsten-brass composites were evaluated. To attain this goal, four tungsten-brass sets were prepared. The tungsten (W) wt. % in these specimens was ranged from 50 to 80, the balance is brass. The specimens were sintered at 10500C in alumina tube furnace under protective environment. To evaluate the radiation shielding performance of these specimens, two gamma ray sources, 137Cs and 60Co were utilized. The photon energy levels for these sources were of o.662MeV and 1.25MeV respectively. The measurements were performed using gamma spectrometer contains NaI (Tl) detector. The anti-radiation performance of the tungsten-brass was correlated to that of lead under similar conditions. Vickers micro hardness, relative sintered density, micro structural characterisation and linear attenuation coefficient (μ) were carried out. Samples with the highest Weight percentage of W has the highest hardness value while the one with the lowest Weight percentage of W. The linear attenuation coefficients of the specimens were significantly improved by increasing the W wt. % of the specimen. The linear attenuation coefficients of the tested specimens ranged from 0.85±0.010cm-1 to 1.12±0.049cm-1for 60Co and0.73±0.012 cm-1 to 0.97±0.027 cm-1 for 137Cs. This result indicates that W-brass composites are suitable material for lead replacement as a shielding barrier.Keywords: Attenuation coefficient, radiation shielding, lead, tungsten-brass composites, NaI (Tl).

Replacement of Lead by Green Tungsten-Brass Composites as a Radiation Shielding Material

European Union faces challenge in the waste management practices. Despite the economic downturn and the decrease in consumption at European Union level the waste generation stays stable, and the recycling disposal stagnates. Since the level of the recycling and recovery is set at 70% for the year 2020 for the construction and demolition waste for achieving the proposed level practical possibilities for recycling of large quantities are necessary. The paper presents cementitious composites using recycled waste which might represent practical solution for increasing the rate of recycling of construction and demolition waste and of textile industry waste. Mechanical characteristics of two different composites using recycled wastes are presented. The first cementitious composition incorporates recycled aggregates substituting new, non-renewable natural aggregates, while the second composition – beside the recycled aggregates – contains also textile industrial waste. The mechanical characteristics of the obtained compositions are comparable with the ones of the road concrete, in the same time fulfilling also the norm requirements for composites used for road concrete. The proposed cementitious composites represent significant potential for recycling, and as consequence, potential for achieving the targeted rate of the recycling.

Andrei Victor Sandhu

Papers

Fly Ash Based Lightweight Geopolymer Concrete Using Foaming Agent Technology

On the Fatigue of Shape Memory Alloys

The Experimental Determination of the Friction Stress between the Semi-Product and the Active Plate at the Multiaxial Forging of Copper

Replacement of Lead by Green Tungsten-Brass Composites as a Radiation Shielding Material

Cementitious Composites Using Recycled Waste