Dense Material Research Articles

Optimization design of Ta2O5-doped calcium hexaaluminate with improved sintering densification and properties for metallurgical application

In view of the application limitation caused by poor densification and mechanical properties of calcium hexaaluminate, achieving the optimization design of the calcium hexaaluminate materials with improved sintering densification and comprehensive properties is highly required. Therefore, the present work looked at the effect of the Ta2O5 on the sintering densification, microstructure evolution, thermal shock resistance and slag resistance of the CA6 materials. Studies showed that the Ta2O5 was incorporated into the CA6 grains during the sintering process at high temperatures by substituting Al3+, greatly promoting the CA6 grain to grow along the direction perpendicular to the basal plane (c-axes), which was responsible for a more equiaxed morphology and highly dense microstructure. The in-situ formation of the Ca(TaO3)2 was able to infiltrate the pores inside the sample and resulted in the reduction of the apparent porosity. The improvement in sintering densification and decrease of porosity greatly enhanced the cold compressive strength, thermal shock resistance and slag resistance of the CA6 materials. Consequently, it can be considered that the introduction of Ta2O5 is expected to produce dense CA6 materials with improved mechanical properties, thermal shock resistance and slag resistance for the better application in metallurgical field.

Artificial intelligence for improved fitting of trajectories of elementary particles in dense materials immersed in a magnetic field

Particle track fitting is crucial for understanding particle kinematics. In this article, we use artificial intelligence algorithms to show how to enhance the resolution of the elementary particle track fitting in dense detectors, such as plastic scintillators. We use deep learning to replace more traditional Bayesian filtering methods, drastically improving the reconstruction of the interacting particle kinematics. We show that a specific form of neural network, inherited from the field of natural language processing, is very close to the concept of a Bayesian filter that adopts a hyper-informative prior. Such a paradigm change can influence the design of future particle physics experiments and their data exploitation.

Cerium-modified single perovskite CaMnO3: structural, dielectric, and transport properties

ABSTRACT In this communication, the synthesis (solid-state reaction) and characterization (structural, dielectric, and transport) of the CaMn0.9Ce0.1O3 ceramic (named, CMCO) are discussed. The CMCO has an orthorhombic crystal symmetry with an average crystallite size of 108.7 nm and lattice strain of 0.00375 respectively. The grains are distributed uniformly in a very compact manner so that highly dense material is formed and the ratio of average grain size to average crystallite size is about 21, which may be a possible reason for a better dielectric and conductivity mechanism. Raman's study confirms the presence of all constituent elements. The analysis of the dielectric properties suggests the presence of the Maxwell-Wagner type of dispersion. The study of impedance spectroscopy reveals how grains and grain boundaries play an important role to define conductivity mechanism and hence prove a non-Debye type of relaxation. The analysis of the resistance versus temperature plots supports NTC thermistor character.

3D-Printed Carbons with Improved Properties and Oxidation Resistance

In this paper, we show the preparation and characteristics of new 3D-printed porous carbons obtained by stereolithography (SLA) of a precursor resin followed by heat treatment. Their physical and textural properties can be tuned by using chemically modified biobased aromatic precursors as monomers. Thus, vanillin and polyflavonoids such as mimosa tannins can be used together as building blocks for SLA materials when functionalized with methacrylate groups by a solvent-free technique and mixed with a photosensitive resin. Adjusting the photosensitive formulations led to high thermal stability and an increase in carbon yield of up to 27%. The corresponding dense porous carbon materials showed outstanding mechanical properties, far exceeding those of other SLA-printed carbons and carbon foams, and a very low surface area, which improves their oxidation resistance compared to acrylate–tannin-derived carbon or activated carbons. This new approach to architecturally engineered carbons with tailored properties can therefore be used for the promising design of catalyst supports or sodium-ion batteries.

Cu-infiltrated (Nb,W)C solid solution carbides

Binderless NbC with 0–25 wt% WC powder mixtures were pressureless sintered in vacuum at 1330, 1390 or 1450 °C to generate open porosity (Nb,W)C skeletons. The formation of residual minor amounts of W2C and WC was discussed as a function of WC addition and compared with thermodynamic predictions. The structures with 15–25 wt% WC addition with 16–35% open porosity were used as a skeleton for Cu infiltration at 1390 °C in H2. The microstructure of the as-sintered homogeneous (Nb,W)C grains in the skeleton changed into a core-rim structured grains after Cu infiltration due to the partial dissolution of Nb into the liquid Cu phase. The fracture toughness, hardness, Young's modulus, electrical conductivity and flexural strength of the as-sintered porous and near fully dense Cu-infiltrated materials were assessed and discussed.

Corrosion behavior and mechanism of 4004/Al-Mn-Cu-Mg-Si/4004 aluminum brazing sheet in sea water acidified accelerated test

The microstructure and corrosion properties of a novel 4004/Al-Mn-Cu-Mg-Si/4004 aluminum brazing sheet were investigated in comparison with the traditional 4004/3003/4004. It revealed that, the microstructure after brazing of two aluminum brazing sheets from outer to center were both residual Al-Si eutectic, precipitate-free zone (PFZ), band of dense precipitates (BDP) and core material, respectively. However, the alloying element distribution and the types and amounts of second phases were quite different. The sea water acidified accelerated test showed that 4004/Al-Mn-Cu-Mg-Si/4004 exhibited typical exfoliation corrosion, while the corrosion quickly spread deep into the core material of 4004/3003/4004. The formation of Cu concentration gradient and the strip distribution of Al-Mg-Cu-Si precipitates in the BDP region contributed to the exfoliation corrosion of 4004/Al-Mn-Cu-Mg-Si/4004. The corrosion behaviors of Al-Mn-Cu-Mg-Si and AA3003 core materials are both in form of intergranular corrosion (IGC)，and the later was more severe than the former. For Al-Mn-Cu-Mg-Si core material, high-density fine dispersed cathodic α-Al(Mn, Cu)Si precipitates promoted the formation of a profusion of micro-galvanic cells in the Al matrix, which would retard any effects between the grain boundary precipitations and the adjacent relatively PFZs. Hence, the IGC susceptibility of Al-Mn-Cu-Mg-Si core material was decreased. Besides, less large-sized α-AlFeMn(Cu)Si phases in core material also reduced the localized corrosion attack. At last, the corrosion in depth direction of 4004/Al-Mn-Cu-Mg-Si/4004 was retarded, compared to its counterpart.

Synthesis and Rapid Sintering of Ultra Fine TiB2-ZrO2 Composite

TiB2 is considered candidate materials for ultra-high temperature ceramics and cutting tools because of its a high thermal conductivity, a low coefficient of thermal expansion, a high hardness and high melting temperature. Despite these attractive properties, TiB2 applications are limited because it has a low fracture toughness below the brittle-ductile transition temperature. To improve on its mechanical properties, the approach universally utilized has been to add secondary materials to form a composite and to fabricate an ultra - fine material. A dense ultra - fine TiB2- ZrO2 composite was rapidly sintered using pulsed high current activated heating (PHCAH) methods within 3 min in one step from the mechanically synthesized the powders of TiB2 and ZrO2 . Consolidation was reached using an effective combination of mechanical pressure and the pulsed high current. A highly dense TiB2-ZrO2 material with relative density of 97.2% was made by the simultaneous application of 75 MPa pressure and a pulsed 2500 A current. The grain sizes of TiB2 and ZrO2 in the composite were 135 nm and 84 nm, respectively. The fracture toughness and hardness of the TiB2 -ZrO2 composite were 11.2 MPa.m1/2 and 957 kg/mm2 , respectively. The fracture toughness of the TiB2 -ZrO2 composite was three times higher than that of monolithic TiB2 .

Powder metallurgy as a perfect technique for preparation of Cu–TiO2 composite by identifying their microstructure and optical properties

Powder metallurgy (PM) is a technique that involves the manufacturing of metal powders and their consolidation into finished products or components. This process involves the mixing of metal powders with other materials such as ceramics or polymers, followed by the application of heat and pressure to produce a solid, dense material. The use of PM has several advantages over traditional manufacturing techniques, including the ability to create complex shapes and the production of materials with improved properties. Cu–TiO2 composite materials are of great interest due to their unique properties, such as high electrical conductivity, improved mechanical strength, and enhanced catalytic activity. The synthesis of Cu–TiO2 composites using the PM technique has been gaining popularity in recent years due to its simplicity, cost-effectiveness, and ability to produce materials with excellent homogeneity. The novelty of using the PM technique for the preparation of Cu–TiO2 composite lies in the fact that it enables the production of materials with controlled microstructures and optical properties. The microstructure of the composite can be fine-tuned by controlling the particle size and distribution of the starting powders, as well as the processing parameters such as temperature, pressure, and sintering time. The optical properties of the composite can also be tailored by adjusting the size and distribution of the TiO2 particles, which can be used to control the absorption and scattering of light. This makes Cu–TiO2 composites particularly useful for applications such as photocatalysis and solar energy conversion. In summary, the use of Powder Metallurgy for the preparation of Cu–TiO2 composite is a novel and effective technique for producing materials with controlled microstructures and optical properties. The unique properties of Cu–TiO2 composites make them attractive for a wide range of applications in various fields, including energy, catalysis, and electronics.

Neural Network Aided Homogenization Approach for Predicting Effective Thermal Conductivity of Composite Construction Materials.

Thermal conductivity is a fundamental material parameter involved in various infrastructure design guides around the world. This paper developed an innovative neural network (NN) aided homogenization approach for predicting the effective thermal conductivity of various composite construction materials. The 2-D meso-structures of dense graded asphalt mixture, porous asphalt mixture, and cement concrete were generated and divided into 2n × 2n square elements with specific thermal conductivity values. A two-layer feed-forward neural network with sigmoid hidden neurons and linear output neurons was built to predict the effective thermal conductivity of the 2 × 2 block. The Levenberg-Marquardt backpropagation algorithm was used to train the network. By repeatedly using the neural network, the effective thermal conductivities of 2-D meso-structures were calculated. The accuracy of the above NN aided homogenization approach was validated with experiment, and various factors affecting the effective thermal conductivity were analyzed. The analysis results show that the accuracy of the NN aided approach is acceptable with relative errors of 1.92~4.34% for the dense graded asphalt mixture, 1.10~6.85% for the porous asphalt mixture, and 1.13~3.14% for the cement concrete. The relative errors for all the materials are lower than 5% when the heterogeneous structures are divided into 512 × 512 elements. Ignoring the actual material meso-structures may lead to significant errors (134.01%) in predicting the effective thermal conductivity of materials with high heterogeneity such as porous asphalt mixture. While proper simplification is acceptable for dense construction composite materials. The effective thermal conductivity of composite cement-asphalt mixtures increases with higher saturation of grouted material. However, the improvement effect of the high-conductive cement paste on the composite cement-asphalt mixtures could be significantly reduced when the cement paste concentrates at the bottom of the mixture. Cracked aggregates and segregation of material components tend to decrease the effective thermal conductivity of construction materials. The NN aided homogenization approach presented in this paper is useful for selecting the effective thermal conductivity of construction materials.

Seeing the whole picture: Methods for getting the most from micro X-ray computed tomography of TRISO nuclear fuel particles

Tristructural isotropic (TRISO) coated fuel particles are a nuclear fuel form under extensive study for use in advanced nuclear reactor concepts. TRISO fuels are subjected to high temperature neutron irradiations and then examined to assess their performance by determining fission product retention and studying morphological changes. Micro X-ray computed tomography is one method of nondestructively studying the effects of TRISO performance. This work addresses the need for image processing to remove X-ray tomographic reconstruction artifacts that prevent the study of TRISO features, as the TRISO particles’ high Z kernel can introduce metal artifacts that degrade the image quality in the surrounding low Z coating layers. These metal artifacts were reduced by imaging the TRISO particles with both high- and low-energy X-rays and applying a mask to the radiographs obtained with low-energy X-rays to digitally remove the dense fuel kernel region. These masked radiographs were then used to produce a tomographic reconstruction which was combined with the tomographic reconstruction of the high-energy data. This enabled the relatively-low-density TRISO buffer layer to be examined in more detail, providing information on irradiation induced dimensional changes of the coatings. This methodology, which helps see the full picture of a TRISO particle, is not limited to nuclear fuels but can be applied to systems that contain highly attenuating material surrounded by less dense materials.

Synthesis and study of dense materials in the Zr–Al–C system

The initial powders Zr, Al, C and Zr, Al, Sc were used for the synthesis of MAX phases of the composition Zr2AlC and Zr3AlC2. The highest content (50.4 vol%) of the MAX phase Zr3AlC2 was obtained using the initial powders Zr/Al/Zr in the ratio of components 1:1.5:2 with the addition of 5 vol% Al. The optimal temperature for the synthesis of a material based on the MAX phase Zr2AlC is 1525° C, a material based on Zr3AlC2 is 1575°C. The structure of the synthesized MAX materials obtained includes elongated grains of the composition Zr2AlC and Zr3AlC2, which determines their high strength. Zirconium carbide, as an intermediate phase, is always present in the final products. Due to the large evaporation of aluminum, the ZrO2 phase is also present in the synthesis products. Excess aluminum contributes to the greatest formation of Zr2AlC and Zr3AlC2 phases during synthesis.

INVESTIGATION OF CELL AGGREGATE SIZE AND POTENTIAL BONE GROWTH WITH BONE CELL LINE AND HUMAN MESENCHYMAL STEM CELLS

Our previous research has demonstrated that minor adjustments to in vitro cellular aggregation parameters, i.e. alterations to aggregate size, can influence temporal and spatial mineral depositions within maturing bone cell nodules. What remains unclear, however, is how aggregate size might affect mineralisation within said nodules over long-term in vivo culture.In this study, we used an osteoblast cell line, MLO-A5, and a primary cell culture, mesenchymal stem cells (MSC), to compare small (approximately 80 µm) with large (approximately 220 µm) cellular aggregates for potential bone nodule development after 8 weeks of culturing in a mouse model (n = 4 each group). In total, 30 chambers were implanted into the intra-peritoneal cavity of 20 male, immunocompromised mice (MF1-Nu/Nu, 4 – 5 weeks old). Nine small or three large aggregates were used per chamber. Neoveil mesh was seeded directly with 2 × 103 cells for monolayer control. At 8 weeks, the animals were euthanised and chambers fixed with formalin. Aggregate integrity and extracellular material growth were assessed via light microscopy and the potential mineralisation was assessed via micro-CT.Many large aggregates appeared to disintegrate, whilst the small aggregates maintained their form and produced additional extracellular material with increased sizes. Both MLO-A5 cells and MSC cells saw similar results. Interestingly, however, the MSCs were also seen to produce a significantly higher volume of dense material compared to the MLO-A5 cells from micro-CT analysis.Overall, a critical cell aggregate size appeared to exist balancing optimal tissue growth with oxygen diffusion, and cell source may influence differentiation pathway despite similar experimental parameters. The MSCs, for example, were likely producing bone via the endochondral ossification pathway, whilst the matured bone cells, MLO-A5 cells, were likely producing bone via the intramembranous ossification pathway.

Where can the low dielectric constant go in dense inorganic materials?

Where can the low dielectric constant go in dense inorganic materials?

The Effelsberg survey of FU Orionis and EX Lupi objects

Context. FU Orionis (FUor) and EX Lupi (EXor) type objects represent two small but rather spectacular groups of low-mass, young, eruptive stars. In both cases, outbursts of several magnitudes are observed, which are attributed to enhanced mass accretion from the circumstellar disc onto the central protostar. Although these objects are well studied at optical and near-infrared wavelengths, their host molecular environments are poorly explored because of the scarcity of systematic molecular line observations. Aims. We aim to carry out the first dedicated survey of the molecular environments of a large sample of FUors and EXors, observing a total of 51 sources, including some Gaia alerts, to study the ammonia (NH3) emission in their host environments. Methods. We observed the ammonia (J, K) = (1,1), (2,2), and (3,3) inversion transitions at ~23.7 GHz in position-switching mode using the Effelsberg 100-m radio telescope. For 19 of the 51 sources in our sample, we derived H2 column densities and dust temperatures using archival Herschel/SPIRE data at 250 µm, 300 µm, and 500 µm. Results. We detected the NH3 (1,1) transition toward 28 sources and the (2,2) transition toward 12 sources, while the (3,3) transition was detected towards only two sources in our sample. We find kinetic temperatures between ~12 K and 21 K, ammonia column densities from 5.2 × 1013 cm−2 to 3.2 × 1015 cm−2, and fractional ammonia abundances with respect to H2 from 4.7 × 10−9 to 1.5 × 10−7. These results are comparable to those found in infrared dark clouds (IRDCs). Our kinematic analysis suggests that most of the eruptive stars in our sample reside in rather quiescent (sonic or transonic) host environments. Conclusions. Our NH3 observations and analysis of the SPIRE dust-based H2 column density maps confirm the presence of dense material towards seven sources in our sample; additional sources might also harbour dense gas based on their NH2 (2,2) detections, potentially indicating an earlier phase than originally classified. Based on our results, we suggest that observations targeting additional molecular lines would help to refine the evolutionary classification of eruptive stars.

Synthesis and Study of Dense Materials in the Zr–Al–C System

Synthesis and Study of Dense Materials in the Zr–Al–C System

Proton and gamma irradiation of novel tungsten boride and carbide candidate shielding materials

Low-activation cWC and RSBs show considerable promise as broad-spectrum radiation-dense materials suitable for use in compact spherical tokamaks (cSTs). The radiation response of novel radiation dense materials cemented tungsten carbide (cWC) and reactive sintered borides (RSBs) at ambient and non-ambient temperatures is investigated for the first time in this work.Sample irradiation consisted of 1.5 MeV protons at 408 K and at 873 K and 60Co gamma irradiation at 293 K and 77 K. Evaluation of radiation-induced damage via electron backscatter diffraction (EBSD) and TEM observed that cWCs have greater radiation attenuation than RSBs but RSBs have more diffuse dislocation distributions. Temperature at irradiation was observed to have a significant impact on dislocation presence with more diffuse dislocation presence in RSBs at 873K but with a well-defined damage front in cWCs as determined by changes in band contrast and indexing in EBSD and by dislocation presence in TEM. Dislocation presence observed to be significantly phase-dependant, particularly for cWC where the WC phase acts to absorb the bulk of radiation-induced dislocations. Both cWC and RSBs demonstrated significant γ-ray attenuation at 77 K with most radiation-induced changes confined to the top 25 µm from the incident face.

Durability of GGBS based alkali-activated binder treated peat through wetting-drying cycle

This research is aimed at investigating the effect of wetting-drying (NWD) cycles on pH, electrical conductivity, unconfined compressive strength (UCS), and mass loss of ground granulated blast furnace slag (GGBS)-NaOH stabilised sapric, fibric, and haemic peat. The ordinary Portland cement stabilised peats were selected as control samples for comparison. The microstructure of GGBS-NaOH stabilised peats before and after NWD cycles were analysed through X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and Fourier transform infrared spectroscopy (FTIR). The pH, electrical conductivity decrease with increasing NWD cycles. The GGBS-NaOH-treated peats exhibits higher UCS values of 3.1, 4.2, and 1.2 times more than cement-treated sapric, fibric, and haemic peats respectively. The FESEM micrographs reveal the presence of smooth and dense cementitious materials before NWD cycles, and the presence of microcracks after NWD cycles. Further, the FTIR confirms the presence of physical water in cavities of treated peats after NWD cycles.

Cosmic-Ray Tomography for Border Security

A key task for customs workers is the interception of hazardous, illegal and counterfeit items in order to protect the health and safety of citizens. However, it is estimated that only a small fraction of cargo is inspected and an even smaller fraction of trafficked goods are detected. Today, the most widely used technology for scanning vehicles, ranging from vans and trucks to railcars, is γ ray and X-ray radiography. New technologies are required to overcome current technological shortcomings, such as the inability to detect the target material composition, the usage of harmful ionising radiation sources and the resultant low throughput. Cosmic ray tomography (CRT) is a promising technology for cargo screening. Cosmic ray muons have average energies of around 10,000 times larger than a typical X-ray and therefore can penetrate relatively large and dense materials. By analysing muon scattering, it is possible to identify materials hidden inside shielding that is too thick or deep for other imaging methods. CRT is also completely passive, exploiting naturally occurring secondary cosmic radiation, and is therefore safe for humans and animals. Contrary to conventional X-ray- or γ-ray-based imaging techniques, CRT also allows material differentiation and anomaly localisation within the cargo or vehicle through the provision of 3D images. This article reviews the current state-of-the-art technology in CRT, critically assessing the strengths and weaknesses of the method, and suggesting further directions for development.

An Investigation into the Potential of Turning Induced Deformation Technique for Developing Porous Magnesium and Mg-SiO2 Nanocomposite

A new and novel method of synthesising porous Mg materials has been explored utilising a variant of a processing method previously used for the synthesis of dense Mg materials, namely the turning-induced deformation (TID) method combined with sintering. It was found that the Mg materials synthesised possessed comparable properties to previously-synthesised porous Mg materials in the literature while subsequent sintering resulted in a more consistent mechanical response, with microwave sintering showing the most promise. The materials were also found to possess mechanical response within the range of the human cancellous bone, and when reinforced with biocompatible silica nanoparticles, presented the most optimal combination of mechanical properties for potential use as biodegradable implants due to most similarity with cancellous bone properties.

Scalable Manufacturing of Environmentally Stable All-Solid-State Plant Protein-Based Supercapacitors with Optimal Balance of Capacitive Performance and Mechanically Robust.

The development of advanced biomaterial with mechanically robust and high energy density is critical for flexible electronics, such as batteries and supercapacitors. Plant proteins are ideal candidates for making flexible electronics due to their renewable and eco-friendly natures. However, due to the weak intermolecular interactions and abundant hydrophilic groups of protein chains, the mechanical properties of protein-based materials, especially in bulk materials, are largely constrained, which hinders their performance in practical applications. Here, a green and scalable method is shown for the fabrication of advanced film biomaterials with high mechanical strength (36.3MPa), toughness (21.25MJm-3 ), and extraordinary fatigue-resistance (213000 times) by incorporating tailor-made core-double-shell structured nanoparticles. Subsequently, the film biomaterials combine to construct an ordered, dense bulk material by stacking-up and hot-pressing techniques. Surprisingly, the solid-state supercapacitor based on compacted bulk material shows an ultrahigh energy density of 25.8Whkg-1 , which is much higher than those previously reported advanced materials. Notably, the bulk material also demonstrates long-term cycling stability, which can be maintained under ambient condition or immersed in H2 SO4 electrolyte for more than 120 days. Thus, this research improves the competitiveness of protein-based materials for real-world applications such as flexible electronics and solid-state supercapacitors.