High Relative Density Research Articles

Influence of Contrast Materials on Dose Accuracy of MR-Linac in Patients with SBRT Liver Cancer

Objective: Intravenous injection of contrast agent during CT scanning can improve the accuracy of target area contouring, however the contrast agent will cause dose bias due to the high relative electron density. This study aims to explore the influence of contrast agent on the accuracy of dose calculation of the planning system during SBRT based on MRI-Linac for liver cancer treatment. Methods: In this study, 20 patients undergoing stereotactic body radiation therapy (SBRT) for liver cancer were selected, and their complete unenhanced CT, contrast-enhanced CT, and corresponding structures were imported into Monaco V.5.4. The target and organs at risk (OARs) in the unenhanced CT and contrast-enhanced CT were additionally contoured according to the target contouring guidelines and OARs were ranked. The average relative electron densities of OARs (lung, spinal cord, heart, rib, etc.) were calculated with Monaco TPS. The reference plan is based on unenhanced CT for plan calculation (plan1). To compare the dosimetry errors caused by the synthetic CT, the average relative electron density of all structures in unenhanced CT was forced and the plans were recalculated (plan2). To investigate dosimetric differences caused by the changes of relative electron density due to the contrast agent, the average relative electron density of all structures in contrast-enhanced CT was forced and the plans were recalculated(plan3). The dosimetric differences in groups A (plan 1 and plan2), B (plan 1 and plan3), and C (plan2 and plan3) were compared, respectively. There were not significant difference between three groups in the affected lung, heart, liver, blood, all within 3%. However, differences were significantly different in the group B. The maximum deviation of spinal cord Dmax reached 4.78%. In addition, the deviation of the dose parameters in the target area was small, except that the maximum deviation of the CI value in group B was 3.23%. For SBRT planning of liver cancer based on magnetic resonance accelerator, synthetic CT has little influence on the calculation of planned dose. The dose difference caused by contrast materials is also relatively small, although the deviation of the CI value of the target area exceeds 3%, which is also within the clinical acceptance range. However, the deviation of the maximum value of the spinal cord is relatively large, exceeding the clinically acceptable range. Therefore, when optimizing the SBRT plan for liver cancer, attention should be paid to important organs such as the spinal cord, and should be avoided as far as possible when setting the fields.

Collaborative improvement of strength and ductility over Mo composites enabled by WC and La2O3

The low ductility of refractory Mo-based materials limits their further processing and wide applications. To address this challenge, a composite strengthening and toughening strategy was proposed by the simultaneous addition of WC and La2O3. And a collaborative improvement of strength and ductility is achieved over the as-sintered Mo-WC-La2O3, exhibiting a total elongation (TE) of 33.63% and an ultimate tensile strength (UTS) of 611.33 MPa, about 50.27% and 24.76% larger than those of pure Mo, respectively. Furthermore, the corresponding microstructural features and tensile fracture behavior were also discussed to explore the improvement mechanism. And it is found that the enhancement should be attributed to the high relative density, grain refinement, generated substructures and secondary phase particle refinement. Moreover, the additional toughening mechanisms of crack deflection, particles pull-out and crack halt can also prevent crack extension, which helps to give full play to the potential ductility of Mo composites. This work provides a new pathway for manufacturing advanced Mo-based products with excellent strength-ductility balance.

Passive Soil Arching Effect in Aeolian Sand Backfills for Grillage Foundation.

The passive soil arching effect exists in many soil-grille interaction systems. Increasing mental grillage foundations are used for transmission lines in aeolian sand areas; thus, exploring the evolution mechanism of passive soil arching is crucial. This study investigates the evolution and influencing factors of passive soil arching through a series of tests using a trapdoor device and particle image velocimetry (PIV). The test results show that the evolution of the arching structure causes the aeolian sand deformation to gradually extend to the backfill surface and stationary zone, generating two triangular arching surfaces between the movable beams and sliding surface at the junction of the active and stationary zones. Cracks in the arching and sliding surfaces were connected to form a W-shaped shear band. The development of the soil pressure was divided into four arching structure stages. The different stages of the inner and outer arches of the bearing characteristics had strong differences. Taking the appearance of the first arch surface as the time point, the soil pressure changes abruptly and the inner and outer arches alternate to bear the as a major role. The beam spacing significantly affected the arching evolution. A smaller beam spacing formed an initial bending configuration with an inconspicuous arching structure and incomplete shear band. As the beam spacing increased, the arching shape changed from triangular to parabolic, sudden changes in the soil pressure were more pronounced, and the arch height increased. The relative density and water content had little impact on the arch shape and shear zone but significantly affected the arching strength, soil pressure transfer, and arching height. The medium and high relative densities and low water contents resulted in a stronger arching structure and greater arching height, while low relative densities and high water contents weakened the soil pressure transfer. The range values for the optimum beam spacing, relative density, and water contents are given based on the variation characteristics of the evaluated parameters (E, n) under different conditions.

Analysis of the high cracking resistance of a Co Ni superalloy during laser additive manufacturing

A newly developed CoNi-based superalloy is demonstrated to be tolerant of a wide range of laser powder bed fusion print conditions, with limited defect content and high relative densities. These promising traits motivated investigation of the structural uniformity in samples printed at the upper end of the scan velocity processing window (>▪). A new misorientation metric, starting reference orientation deviation (SROD), was calculated from ▪-scale 3D microstructure information to examine structure evolution during epitaxial growth of columnar grains. Misorientations of >20° were observed within the large columnar grains that grew through multiple build layers. The SROD observations highlight the CoNi superalloy's ability to plastically deform to high levels, as evidenced by misorientation gradients, across the range of temperatures experienced in laser additive manufacturing. Misorientation gradients within the columnar grain structure are high relative to Ni base superalloys, allowing for strengthening with high volume fractions of L12 precipitates.

Fast and low-temperature densification of highly conductive Li7La3Zr2O12 ceramic electrolytes for solid-state batteries

Garnet-type electrolyte like Li7La3Zr2O12 (LLZO) is a promising candidate for solid-state batteries (SSBs) due to its high Li + conductivity. Obtaining a dense microstructure for their practical use typically requires 1200 °C, which often lead to structural issues in addition to concerns on the scale up at industrial level.In this study, we propose a two-step process to fabricate LLZO electrolytes with a high relative density under low temperature. During the first step, a high quasi-isostatic pressure of 5.5 GPa was applied at temperatures below 500 °C (high pressure and low temperature, HPLT), reaching a density of over 97% with absence of grain growth. Then, a brief treatment at moderate temperature below 800 °C was applied to promote grain growth, leading to an ionic conductivity of 3·10−4 S cm−1. A relationship between the microstructure obtained under key parameters: temperature, pressure, and time; and the ionic transport of LLZO electrolytes has been established. Besides the high ionic conductivity obtained via HPLT, stripping and plating of lithium in a symmetric cell demonstrated the practical application.This work provides guidelines on the control of the microstructure of LLZO from processing parameters and contributes to the understanding of the correlations between microstructure and conductivity.

Thermodynamics aided design of hBN-capsulated diboride powders from novel nitrate precursors for high entropy ceramics

Hexagonal BN-coated powders have been widely used in various engineering sectors, however, their productions are restricted by the complexity of gas-solid reactions. In this study, guided by thermodynamics, a novel approach to synthesize Layer-structured hexagonal BN (hBN)-coated high entropy diboride powders in vacuum was developed, using metal salt Zr(NO3)4·5H2O, HfCl4, NbCl5, TaCl5, C16H36O4Ti, boric acid, and sucrose as raw materials. By adjusting the ratio of carbon to metal source (C/M), powders only consisting of two boride solid solutions and hBN were finally obtained, under an optimal processing condition of C/M = 5.5 and synthesis temperature of 1400 °C. Parts of hBN were found to coat on high-entropy metal diborides ceramic (HEB) particles, corresponding formation mechanism for core-shell structured powders was investigated, together with the liquid precursor assisted boro/carbothermal reduction process. Starting from as-synthesized core-shell powders, (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2–11 vol% hBN ceramics were densified at 1900 °C under 50 MPa without holding, with a high relative density of 97.3%.

Preparation and properties of K0.48Na0.52NbO3 ceramics for bone scaffolds via digital light processing

Lead-free piezoelectric ceramics are expected to be used for artificial bone scaffolds since they can generate electrical signals and promote recovery, but it is still difficult to fabricate piezoelectric scaffolds with complex structures. In this work, digital light processing (DLP) technology was used to fabricate potassium sodium niobate (K0.48Na0.52NbO3, KNN) bone scaffolds with gyroid triply periodic minimal surface. Suspension was first optimized to ensure both high solid loading (42 vol%) and high cure depth (>50 μm). KNN porous scaffolds (porosity: 60%) and other samples for tests were printed successfully. Then, influences of sintering temperature on microstructure, relative density and mechanical properties were discussed. Results showed that when sintered at 1090 °C, printed KNN ceramics had the highest relative density (90.11%) and lowest open porosity (5.75%), and exhibited the most satisfying mechanical properties (compressive strength: 33.85 MPa, elastic modulus: 1.87 GPa, flexural strength: 35.40 MPa, hardness: 2.39 GPa), which can meet the requirements of cancellous bone. Finally, the electric properties of samples at room temperature were verified. With d33 being 113.67 ± 2.49 pC/N and Pr being 19.94 μC/cm2, printed KNN ceramics showed comparable piezoelectric and ferroelectric performances with traditionally dry-pressed samples. These results indicated that DLP technology is competitive in preparing KNN piezoelectric bone scaffolds for implantation.

The compression characteristics and lateral earth pressure coefficient of sand–HDPE mixtures

In recent decades, considerable attempts through geotechnical study have been made to reduce plastic waste by recycling and reuse. The aim of this study was to reuse waste plastic mixed with sand for geotechnical application. To this end, large-scale oedometer experiments were carried out to examine the compressibility of Bandar-e Anzali sands stabilised with plastic-waste-originated high-density polyethylene (HDPE). Bandar-e Anzali is a populated coastal city in the vicinity of the Caspian Sea (northern Iran). Large-scale oedometer and direct shear tests were performed to study the applicability of HDPE chips mixed with sand at various HDPE contents (0, 2, 4, 6 and 8%). Based on the experimental tests, the addition of plastic waste to the soil improved the soil's strength, significantly raised its compressibility and decreased the undrained elasticity modulus. By adding 8% HDPE, the constrained compression modulus decreased to 50% at a pressure of 300 kPa due to the elastic deformability of HDPEs. However, at higher relative density, adding HDPE by more than 4% did not affect the coefficient of lateral earth pressure at rest.

Crystal structure, Raman spectra, and microwave dielectric properties of a novel temperature-stable LiY9Si6O26 ceramic with hexagonal structure

This study presents a comprehensive investigation into the dielectric properties of LiY9Si6O26 ceramics, which were prepared for the first time using the solid-state method. XRD patterns and Rietveld refinement analysis conclusively demonstrate that LiY9Si6O26 adopts a hexagonal crystal structure with space group P63/m (176). Furthermore, Raman spectroscopy reveals a significant correlation between the quality factor and the FWHM of the A1g(O) mode at 879 cm−1. Transmission electron microscopy (TEM) was employed to verify the ordered layered structure inherent in the hexagonal LiY9Si6O26 ceramics. The microstructure of the ceramic grains was analysed using scanning electron microscopy (SEM), which revealed a remarkably high relative density of 96.4% for the LiY9Si6O26 ceramic. The Si–O bond valences (VSi–O) were found to be closely associated with the τf in LiY9Si6O26 ceramics. Remarkably, the microwave dielectric properties of LiY9Si6O26 ceramics sintered at 1425 °C were ascertained to be εr = 10.54, Q × f = 25,579 GHz (f = 10.3 GHz), and τf = 2.64 ppm/°C. These outstanding properties position LiY9Si6O26 ceramics as promising candidates for high-performance dielectric materials.

Laser powder bed fusion (LPBF) of commercially pure titanium and alloy development for the LPBF process.

Laser powder bed fusion (LPBF) of titanium or titanium alloys allows fabrication of geometrically more complex and, possibly, individualized implants or osteosynthesis products and could thus improve the outcome of medical treatments considerably. However, insufficient LPBF process parameters can result in substantial porosity, decreasing mechanical properties and requiring post-treatment. Furthermore, texturized parts with anisotropic properties are usually obtained after LPBF processing, limiting their usage in medical applications. The present study addresses both: first, a design of experiments is used in order to establish a set of optimized process parameters and a process window for LPBF printing of small commercially pure (CP) titanium parts with minimized volume porosity. Afterward, the first results on the development of a biocompatible titanium alloy designed for LPBF processing of medical implants with improved solidification and more isotropic properties are presented on the basis of conventionally melted alloys. This development was performed on the basis of Ti-0.44O-0.5Fe-0.08C-0.4Si-0.1Au, a near-α alloy presented by the authors for medical applications and conventional manufacturing, with yttrium and boron additions as additional growth restriction solutes. In terms of LPBF processing of CP titanium grade 1 powder, a high relative density of approximately 99.9% was obtained in the as-printed state of the volume of a small cubical sample by using optimized laser power, scanning speed, and hatch distance in combination with a rotating scanning pattern. Moreover, tensile specimens processed with these volume settings and tested in the as-printed milled state exhibited a high average yield and ultimate tensile strength of approximately 663 and 747N/mm2, respectively, combined with a high average ductility of approximately 24%. X-ray diffraction results suggest anisotropic mechanical properties, which are, however, less pronounced in terms of the tested specimens. Regarding alloy development, the results show that yttrium additions lead to a considerable microstructure refinement but have to be limited due to the occurrence of a large amount of precipitations and a supposed higher propensity for the formation of long columnar prior β-grains. However, phase/texture and microstructure analyses indicate that Ti-0.44O-0.5Fe-0.08C-0.4Si-0.1Au-0.1B-0.1Y is a promising candidate to achieve lower anisotropy during LPBF processing, but further investigations on LPBF printing and Y2O3 formation are necessary.

Achieving high relative density and low resistivity in indium tin oxide targets via Bi2O3-CeO2 additive

Indium tin oxide (ITO) target, an important raw material of ITO films, is difficultly prepared by traditional sintering due to the volatilization and partial dissociation at high sintering temperature. In this work, the high-density and low-resistivity ITO targets were prepared with Bi2O3-CeO2 additive at low sintering temperature. The effects of Bi2O3-CeO2 content and sintering temperature on the densification, phase composition, microstructure, mechanical properties and electrical resistivity of ITO targets were systematically investigated. The results revealed that the Bi2O3-CeO2 addition reduced sintering temperature by 50 ℃, and the ITO target with 1.0 wt% Bi2O3-1.0 wt% CeO2 had the maximum relative density of 99.57%, surpassing additive-free ITO target. The dense microstructure at low sintering temperature was attributed that Bi2O3 could convert solid phase sintering into liquid phase sintering. Notably, the ITO target with 1.0 wt% Bi2O3-1.0 wt% CeO2 also had the minimum resistivity of 1.82 × 10−4 Ω·cm, which was due to more free electrons generated by CeO2 doping and the dense microstructure. In addition, the grain growth kinetics was applied to calculate corresponding diffusion data, namely, the grain growth exponent (n = 7.4), growth rate constant (k = 4.211 × 1023) and growth activation energy (Q = 394.79 kJ/mol). This work provides a strategy to prepare high-quality ITO targets and presents great potential for the low-temperature sintering on other ceramic materials.

Water-assisted densification and broadband dielectric response of cold-sintered CaCu3Ti4O12-SnF2 composites

Miniaturization of electronic devices is one of the great challenges faced by the scientific and engineering community; hence extensive research has focused on novel materials, devices and technologies to implement the same. Calcium copper titanate (CCTO), a unique electro-ceramic material with a complex perovskite structure and reasonably high temperature-stable relative permittivity, is a potential candidate for the miniaturization of capacitors. In the present work, cold sintering is used to synthesize xCCTO–(1 – x)SnF2 (x = 0.5–0.8 vol fraction) composites at ultra-low temperature (<150 °C) in 30 min at a pressure of 500 MPa, which has not been reported earlier. The effect of the liquid phase (water) on the densification and microstructure of these composites is also investigated. X-ray diffraction (XRD) analysis confirms the co-existence of CCTO and SnF2 phases in the composites. As the volume fraction of SnF2 increases in the presence of the liquid phase, an evolution of microstructure showing the enhancement in densification is observed. A high relative density (>90%) is obtained for SnF2-based, cold-sintered systems, which can be due to the melting of SnF2, thus forming a liquid phase during cold sintering that enhances the dissolution-precipitation mechanism. Microstructural studies reveal that a certain amount of SnF2 and water enhances the densification in the composite through dissolution–precipitation followed by melting of SnF2. The relative permittivity (εr), dielectric loss (tan δ) and micro-hardness of the xCCTO-(1 – x) SnF2 composite increase from 21.6 to 25.3, from 0.026 to 0.039 and from 3.6 to 5.1 GPa, respectively, with increasing SnF2 content. Further, a comparison of sintering temperature, relative permittivity, dielectric loss and micro-hardness of this system reveals that the 0.8CCTO–0.2SnF2 composite cold-sintered at 150 °C achieves moderate relative permittivity (25.3 at 950 MHz), low dielectric loss (0.039 at 950 MHz) and good micro-hardness (3.6 GPa).

Comparative performance evaluation of microarchitected lattices processed via SLS, MJ, and DLP 3D printing methods: Experimental investigation and modelling

Additively manufactured mechanical metamaterials are gaining prominence in lightweight energy-absorption applications due to their exceptional mass-specific properties. Herein, we examine the energy absorption characteristics of micro-architected truss-, shell- and plate-lattice structures, namely, Octet, Kelvin, Gyroid, SC, BCC and FCC over a range of relative densities under quasi-static compression via both experiments and finite element analysis (FEA). Employing different 3D printing methods, namely, Digital Light Processing, Selective Laser Sintering and Material Jetting, the lattices were fabricated using PlasGray™ (photo-resin based plastic), PA12 (Nylon) and VeroWhite (photo-resin based rigid plastic) respectively. Our results indicate that the SC lattice structure outperforms in terms of stiffness and strength, while the Gyroid lattice outperforms in terms of energy absorption efficiency (η). At lower relative densities (<0.3), η reaches up to 61% for the Gyroid lattices made of PlasGray, while only at high relative densities the Octet truss lattices compete with the Gyroid lattices. For Gyroid lattices made of PA12 with a relative density of 0.23, an energy absorption efficiency of 68% was observed. Design maps are presented for all lattice structures processed and tested herein, to demonstrate their relative merits. Moreover, a two-step FEA was executed on a chosen array of lattices to thoroughly investigate the extensive design possibilities, utilising the elastic-plastic, Drucker-Prager, and concrete damage plasticity material models for PlasGray, PA12, and VeroWhite, respectively, with calibration based on experimental results. The results highlight that the tailored design of Gyroid lattices enabled by AM positions them as promising candidates for lightweight energy-absorbing applications.

Strong and ductile Al–Mn–Mg–Sc–Zr alloy achieved in fabrication-rate enhanced laser powder bed fusion

ABSTRACT The high cost of laser powder bed fusion (LPBF) fabricated high-strength Sc containing aluminium alloy hinders its applications. To reduce the cost, we reported a LPBF fabricated strong and ductile Al–Mn–Mg–Sc–Zr alloy using large layer thicknesses to improve the fabrication efficiency on coarse powder particles. A high relative density exceeding 99.2% was achieved at layer thicknesses up to 120 μm. In post-process heat-treated specimens, the yield strength only had a slight 6% decrease from layer thickness of 30 to 120 μm; such a decrease in strength was attributed to the larger grain size resulted from the adopted larger layer thickness. The fabricated sample at layer thickness of 120 μm still exhibited high tensile yield strength of 472 MPa and fracture strain of ∼10%. This work showed a successful application of improving the LPBF fabrication efficiency of high-strength Al–Mn–Mg–Sc–Zr alloy using large layer thickness in LPBF process.

Thermally Stable Ceramic-Salt Electrolytes for Li Metal Batteries Produced from Cold Sintering Using DMF/Water Mixture Solvents.

The cold sintering process (CSP) for synthesizing oxide-based electrolytes, which uses water transient solvents and uniaxial pressure, is a promising alternative to the conventional high temperature sintering process due to its low temperature (<200 °C) and short processing time (<2 h). However, the formation of amorphous secondary phases in the intergranular regions, which results in poor ionic conductivity (σ), remains a challenge. In this study, we introduced high-boiling solvents of dimethylformamide (DMF, b.p.: 153 °C) and dimethyl sulfoxide (DMSO, b.p.: 189 °C) as transient solvents to develop composite electrolytes of Li1.5Al0.5Ge1.5(PO4)3 (LAGP) with bis(trifluoromethane)sulfonimide lithium salt (LiTFSI). Our results show that composite electrolytes processed with the DMF/water mixture (CSP LAGP-LiTFSI DMF/H2O) yield a high σ of 10-4 S cm-1 at room temperature and high relative densities of >87%. Furthermore, the composite electrolytes exhibit good thermal stability; the σ maintains its initial value after heat treatment. In contrast, the composite electrolytes processed with the DMSO/water mixture and water alone show thermal degradation. The CSP LAGP-LiTFSI DMF/H2O composite electrolytes exhibit long-term stability, showing no signs of short circuiting after 350 h at 0.1 mAh cm-2 in Li symmetric cells. Our work highlights the importance of selecting appropriate transient solvents for producing efficient and stable composite electrolytes using CSP.

Influence of B-site rare-earth Yb cation on the crystal structure and microwave dielectric properties of Ca3Yb2Ge3O12 garnet ceramics

In this work, garnet structured Ca3Yb2Ge3O12 ceramics with a space group of Ia-3d were synthesized by a solid-state reaction method. Rietveld refinement analysis demonstrated that Yb3+with small ionic radius and large electronegativity entered the B-sites and shortened the bond length of B–O and Ge–O. The bond valence and P-V-L theory analysis results showed that Ca cations with a weakened rattling effect exerted a critical effect on the dielectric constant, and the Ge–O bond was the main factor that influenced dielectric loss. Ca3Yb2Ge3O12 with a high relative density (98.2%) and excellent microwave dielectric properties (εr= 10.2, Q × f = 98,400 GHz, τf = -48 ppm/°C) was obtained at 1360 °C for 4 h. Furthermore, the intrinsic dielectric constant and dielectric loss (εr =10.12, Q × f = 101,900 GHz) of Ca3Yb2Ge3O12 were obtained by infrared reflectivity spectroscopy.

Enhancing high frequency magneto-dielectric performance with exchange-coupled garnet/spinel ferrite (Y3Fe5O12/Mg0.4Cd0.4Co0.2Fe2O4) composites

Yttrium iron garnet ferrite (YIG), with good magnetic and dielectric properties, was mixed with doped magnesium spinel ferrite (Y3Fe5O12(x)/Mg0.4Cd0.4Co0.2Fe2O4(1-x) (x = 0.3, 0.6, 0.9)) to attain high permittivity and permeability with low magneto-dielectric losses. We have reported the synthesis and enhanced structural, magnetic and magnetodielectric properties of composites for miniaturized antenna applications. The X-ray diffraction (XRD) patterns of all the composites were analysed using the Rietveld method, which confirmed that they exhibited a crystalline structure with a cubic spinel and cubic garnet phase. XRD spectra confirm that the spinel ferrite phase dominates over the garnet ferrite phase in the x = 0.3 composite, whereas it is the opposite for the other composites. In contrast to the parent ferrites, it has been observed that the composites (x = 0.3, 0.6, 0.9) exhibit a higher value of the crystallite size ‘D’ and a lower value of the lattice constant ‘a’. The composite with the x = 0.3 composition has the least porosity and a high relative density. From field emission scanning electron microscopy (FESEM), it has been ascertained that the materials possess a grain size ranging from 0.57 to 0.8μm, with a larger grain size for the x = 0.9 composite, while the x = 0.3 composite has the smallest grain size. Transmission electron microscopy (TEM) scans have corroborated the FESEM micrographs’ findings, indicating that the grains within the composites’ structure exhibit agglomeration. The calculated values of inter-planar spacing of the samples using high-resolution TEM (HR-TEM) matches well with the XRD results. A magnetic study reveals that the composite with x = 0.3 has a good exchange-coupling, the highest coercivity value of 99.2 Oe and a magnetization value of 41 emu/g. The composite with x = 0.3 also has the highest permittivity value of ∼19.5, a permeability value of ∼2.8, but low dielectric and magnetic losses of ∼0.009 and ∼0.002, respectively. These low losses and a high miniaturization factor of ∼7.2 at high frequency (14 GHz) make it a potential candidate for high-speed satellite antenna applications.

Optimising Surface Roughness and Density in Titanium Fabrication via Laser Powder Bed Fusion.

The Ti6Al4V alloy has many advantages, such as being lightweight, formal, and resistant to corrosion. This makes it highly desirable for various applications, especially in the aerospace industry. Laser Powder Bed Fusion (LPBF) is a technique that allows for the production of detailed and unique parts with great flexibility in design. However, there are challenges when it comes to achieving high-quality surfaces and porosity formation in the material, which limits the wider use of LPBF. To tackle these challenges, this study uses statistical techniques called Design of Experiments (DoE) and Analysis of Variance (ANOVA) to investigate and optimise the process parameters of LPBF for making Ti6Al4V components with improved density and surface finish. The parameters examined in this study are laser power, laser scan speed, and hatch space. The optimisation study results show that using specific laser settings, like a laser power of 175 W, a laser scan speed of 1914 mm/s, and a hatch space of 53 µm, produces Ti6Al4V parts with a high relative density of 99.54% and low top and side surface roughness of 2.6 µm and 4.3 µm, respectively. This promising outcome demonstrates the practicality of optimising Ti6Al4V and other metal materials for a wide range of applications, thereby overcoming existing limitations and further expanding the potential of LPBF while minimising inherent process issues.

Characterization of Na2Zn2TeO6 ceramic solid electrolyte densified by hot pressing

AbstractIn this work, we applied hot pressing (HP) for the densification of Na2Zn2TeO6 (NZTO) at lower temperature than conventional furnace sintering (FS). Calcined NZTO powder was densified by HP at 700°C for 1 h under uniaxial pressure of 20 and 60 MPa using a graphite mold. By increasing the uniaxial pressure to 60 MPa for HP, high relative density above 90% was obtained. As‐prepared NZTO by HP showed total (bulk + grain‐boundary) ionic conductivity of 0.29 mS cm−1 at room temperature, which is lower than NZTO prepared by FS at 800°C (=0.4 mS cm−1) with lower relative density (&lt;85%). It was found that the contribution of grain‐boundary resistance in as‐prepared NZTO by HP is larger than NZTO by FS. We confirmed that the grain‐boundary resistance was significantly reduced by post‐annealing. Consequently, total conductivity at room temperature was improved to 0.42 and 0.56 mS cm−1 by annealing at 700 and 800°C for 2 h, respectively. X‐ray photoelectron spectroscopy analysis indicated that the residual carbon‐contained secondary phases were reduced by post‐annealing. These secondary phases could be formed by the carbon contamination from a graphite mold used for HP, and their removal by post‐annealing results in the improvement of ionic conduction at grain‐boundary.

A study of selective laser melting process for pure zinc and Zn10mg alloy on process parameters and mechanical properties

PurposeThe selective laser melting (SLM) technique, as a typical additive manufacturing process, is widely used for the fabrication of metallic biomedical components. In terms of biodegradability, zinc and its alloys represent an emerging generation of metallic materials for biomedical implants. The purpose of this paper is to obtain the Zn and Zn10Mg alloys with high mechanical properties using the SLM technology. The relationship between the processing parameters and the porosity of pure Zn and Zn10Mg alloy samples was investigated.Design/methodology/approachThe samples were fabricated using SLM technology working in an inert gas closed chamber. Preliminary experiments were conducted to analyze the laser power and gas flow on evaporation, single track form and porosity. To evaluate the influence of factors on relative density, the response surface methodology was applied.FindingsThe satisfactory results of the proposed method were achieved, in which the relative density of the components reached up to 99.63%, and compression strength reached 214 ± 13 MPa under optimal processing conditions.Originality/valueZinc is categorized by its low melting and boiling point, which leads to the high porosity of the components. It is difficult to prepare the Zn alloy samples with high relative density using SLM technology. This work successfully achieved dense Zn and Zn10Mg samples and investigated their microstructure, mechanical properties and corrosion behavior.