Void Formation Research Articles

Deposition of a low-activity type cobalt-modified aluminide coating by slurry aluminizing of a pre-Co-electroplated Ni-based superalloy (IN738LC)

Incorporating the Co element into the β-NiAl phase as a third element enhances the hot corrosion and oxidation properties of aluminide coatings. The deposition of Co-modified aluminide coatings is limited to co-deposition by the pack cementation method or a two-step pack cementation process of Co and Al, so far. This study investigates the possibility of depositing a low-activity type of Co-modified aluminide coating by combining the electroplating process with the slurry aluminizing method. To accomplish this objective, different thicknesses of Co-electroplated layers, deposited by a Watts bath, ranging from 5 to 20 μm are slurry aluminized using a slurry consisting of Al particles as the Al source and a PVA aqueous solution as the binder at 1100 °C for 2 h. Formation mechanisms are discussed through slurry aluminizing of 5, 10, and 20 μm thick Co-electroplated layers at the temperature range of 700–1100 °C with 100 °C intervals at zero time. FE-SEM surface morphology, BSE-SEM cross-sectional observation, surface XRD characterization, and EDS elemental analysis are utilized to characterize the coatings. Results show a critical thickness of the Co layer is required to deposit a defect-free low-activity type of Co-modified aluminide coating, which is determined to be ∼10 μm in this study. The final aluminide coating thickness decreases from ∼140 to ∼65 μm by increasing the Co-electroplated layer thickness from 5 to 20 μm. The identified phases on the surface differ from β-NiAl to β-CoAl by increasing the Co-electroplated layer thickness up to critical value. The Void formation occurs by the Kirkendall effect in coatings with more Co-electroplated layer thickness than the critical value, segregating the coatings within the β-CoAl phase.

Nanoscale Kirkendall effect induced void formation in Au–Ag nanostructures and their application as SERS substrate

Triangular-shaped silver nanostructures were synthesized via a seed-mediated two-step method. A galvanic replacement reaction coupled with the Kirkendall effect was employed to transform Ag nanostructures into porous Au–Ag structures having voids at the nanoscale. Compared with previous reports, the medium and the binding agent used in the synthesis of silver nanoparticles employed as templates play a vital role in determining the extent of nanoscale voids formed due to the Kirkendall effect. Raman activity of these porous structures was tested with crystal violet as the probe molecule, and it was found that the Raman enhancement factor varies with cathode concentration.

Effect of Dispensing Type On Void Formation Using Convolutional Neural Network

Abstract Underfilling in flip chip packages is a critical component of reliability. This study utilized I-type, L-type, and U-type dispensing methods to address the issue namely voiding that creates empty spaces which compromises reliability. An automated solution using Convolutional Neural Network (CNN) is propose for void detection in chip images to replace the conventional manual inspection approach. The CNN model built on MobileNetV2, attains a mean average precision of 0.533. This method calculates void percentage, adhering to IPC standards, to determine product acceptance or rejection, offering an efficient solution for quality control in flip-chip package manufacturing.

The role of printing parameters on the short beam strength of 3D-printed continuous carbon fibre reinforced epoxy-PETG composites

It is well known that printing parameters strongly affect the mechanical performance of 3D printed parts. This work explores the role of i) extruder temperature, ii) print speed, and iii) layer height on the interlaminar strength of 3D-printed continuous fibre-reinforced composites. The carbon fibre-reinforced thermoset filament is printed concomitantly with polyethylene terephthalate glycol (PETG) thermoplastic filament in a single nozzle, characterising a continuous fibre co-extrusion (CFC) process. There is a significant variation in the short beam strength for composites printed with different parameters. The load–displacement curves have a similar pattern, with clear load peaks followed by a plastic zone. Optical micrographs and computed tomography (CT) scans reveal that the microstructure is dependent on the printing parameters. Image analysis elucidates the various mechanisms of void formation. Following the application of a three-way ANOVA and statistical tests to quantify the effects and interactions among variables, the analysis concludes that the extruder temperature has the highest influence, followed by print speed and layer height. When considering all possible interactions between the factors, the interaction between print speed and layer height is the most impactful.

Garnet-Based Solid-State Li Batteries with High-Surface-Area Porous LLZO Membranes.

Rechargeable garnet-based solid-state Li batteries hold immense promise as nonflammable, nontoxic, and high energy density energy storage systems, employing Li7La3Zr2O12 (LLZO) with a garnet-type structure as the solid-state electrolyte. Despite substantial progress in this field, the advancement and eventual commercialization of garnet-based solid-state Li batteries are impeded by void formation at the LLZO/Li interface at practical current densities and areal capacities beyond 1 mA cm-2 and 1 mAh cm-2, respectively, resulting in limited cycling stability and the emergence of Li dendrites. Additionally, developing a fabrication approach for thin LLZO electrolytes to achieve high energy density remains paramount. To address these critical challenges, herein, we present a facile methodology for fabricating self-standing, 50 μm thick, porous LLZO membranes with a small pore size of ca. 2.3 μm and an average porosity of 51%, resulting in a specific surface area of 1.3 μm-1, the highest reported to date. The use of such LLZO membranes significantly increases the Li/LLZO contact area, effectively mitigating void formation. This methodology combines two key elements: (i) the use of small pore formers of ca. 1.5 μm and (ii) the use of ultrafast sintering, which circumvents ceramics overdensification using rapid heating/cooling rates of ca. 50 °C per second. The fabricated porous LLZO membranes demonstrate exceptional cycling stability in a symmetrical Li/LLZO/Li cell configuration, exceeding 600 h of continuous operation at a current density of 0.1 mA cm-2.

A solid-state lithium-ion battery with micron-sized silicon anode operating free from external pressure

Applying high stack pressure (often up to tens of megapascals) to solid-state Li-ion batteries is primarily done to address the issues of internal voids formation and subsequent Li-ion transport blockage within the solid electrode due to volume changes. Whereas, redundant pressurizing devices lower the energy density of batteries and raise the cost. Herein, a mechanical optimization strategy involving elastic electrolyte is proposed for SSBs operating without external pressurizing, but relying solely on the built-in pressure of cells. We combine soft-rigid dual monomer copolymer with deep eutectic mixture to design an elastic solid electrolyte, which exhibits not only high stretchability and deformation recovery capability but also high room-temperature Li-ion conductivity of 2×10−3 S cm−1 and nonflammability. The micron-sized Si anode without additional stack pressure, paired with the elastic electrolyte, exhibits exceptional stability for 300 cycles with 90.8% capacity retention. Furthermore, the solid Li/elastic electrolyte/LiFePO4 battery delivers 143.3 mAh g−1 after 400 cycles. Finally, the micron-sized Si/elastic electrolyte/LiFePO4 full cell operates stably for 100 cycles in the absence of any additional pressure, maintaining a capacity retention rate of 98.3%. This significantly advances the practical applications of solid-state batteries.

Effect of in situ thermal treatment on interlayer adhesion of 3D printed polyetherimide (PEI) parts produced by fused deposition modeling (FDM)

Polyetherimide (PEI) possesses remarkable mechanical and thermal properties that make it a promising high-performance material for a wide range of applications. In addition to its simple processability, adhesive properties, and minimal smoke emission when heated, PEI is a suitable material for additive manufacturing. Because of its low cost and straightforward method, fused deposition modeling, or FDM, is a popular additive manufacturing technique for extruding thermoplastic filaments. Parts printed with the FDM approach, on the other hand, have common drawbacks such as low mechanical strength, shape inaccuracy, high porosity, void formation, interlayer adhesion problems, and anisotropic properties. The purpose of this study was to evaluate the effect of the thermal process during printing on the interlayer adhesion strength and the mechanical performances of PEI. The thermal treatment was done on a radiant heating system at 390 °C with a printing speed of 35 mm/s. In this study, parts printed with and without radiant heating system were characterized and analyzed with scanning electron microscopy (SEM), optical microscopy (OM), X-ray microtomography (µ-CT), optical profilometry (OP), atomic force microscopy (AFM), dynamic mechanical analysis (DMA), and tensile tests. The results revealed that the treated specimen exhibited better interlayer adhesion between printed layers. The interfacial voids were less visible in treated specimens. Furthermore, the treated specimen had lower porosity (5%) than the untreated one (8%). Moreover, increases of 183% in tensile strength, 22% in elastic modulus, and 190% in elongation at break were observed for treated specimens when compared to untreated ones.

Processing–microstructure–fracture toughness relationships in PP/EPDM/SiO2 blend‐nanocomposites: Effect of mixing sequence

AbstractThis study investigates the mechanical properties and fracture behavior of polypropylene (PP)‐based blend‐nanocomposites comprising 30 wt.% ethylene–propylene–diene monomer (EPDM) and 5 wt.% SiO2 nanoparticles. Different mixing sequences were employed to prepare the nanocomposites, and the resulting morphology development and dispersion states of modifiers were analyzed. Mechanical performance of the nanocomposites was evaluated through quasi‐static and high‐speed dynamic fracture tests. The dispersion and distribution of SiO2 nanoparticles within the nanocomposites were significantly influenced by the mixing protocol. In impact fracture tests, the presence of nanoparticles exhibited a beneficial efffect on fracture energy, demonstrating a synergistic toughening effect of the soft EPDM and rigid SiO2 particles. Conversely, adverse effects were observed in quasi‐static tests. Essential work of fracture (EWF) parameters indicated an increase in the yielding component and a decrease in the necking‐to‐tearing component with SiO2 incorporation into the PP/EPDM blends. During impact loadings, the highest improvement in crack propagation resistance was observed in nanocomposites with nanoparticles localized around the rubbery domains forming a network‐like structure of EPDM/SiO2‐nanoparticles. Morphologies where rubber domains and nanoparticles were separately distributed in the PP matrix resulted in the lowest fracture parameters. Energy dissipation mechanisms were elucidated, revealing multiple void formation followed by matrix shear yielding as the primary source under both quasi‐static and impact fracture conditions. In the latter case, stress‐concentrating percolated structures in the PP matrix facilitated the nucleation of dilatational bands evolving into highly stretched void‐fibrillar structures upon further loading. These findings contribute valuable insights into tailoring nanocomposite morphologies for enhanced mechanical performance in different loading scenarios.Highlights Fracture behavior of PP/EPDM/SiO2 ternary systems was evaluated by EWF methodology and Izod impact test. Rubber particles surrounded by silica nanoparticles led to a percolated morphology and as a result to superior impact resistance. EWF parameters were mostly controlled by the tearing‐related parts regardless of phase morphology. The impact toughness was mainly controlled by the dispersion and distribution characteristics of the SiO2 nanoparticles.

Exploring a novel chamfered tool design for short duration refill friction stir spot welds of high strength aluminium

This work investigates refill friction stir spot welded joints of AA2024-T3 aluminium alloy, produced with short welding times between 3 s and 0.75 s. A novel tool geometry that incorporates a chamfer on the inner edge of the shoulder tip is investigated as a means of improving joint quality at short welding times by easing material flow during the refill stage. The influence of shoulder design on weld microstructure, defect formation, material flow, and mechanical properties was assessed. When compared with a standard shoulder geometry, it was found that the introduction of a chamfer on the inner tip edge improved material flow during the refill stage and led to improved material mixing at the weld periphery. The formation of voids in the region of the weld periphery was eliminated and tensile lap-shear strength of the welded joints was increased by 19% to 7.2 kN, and 27% to 8.16 kN, for 0.75 s and 1.5 s duration welds, respectively.

Microscale underfill dynamics and void formation of high-density flip-chip packaging: Experiments and simulations

This research focuses on developing high-fidelity experimental and numerical models to analyze microscale underfill dynamics and void formation in high-density flip-chip packaging. Three underfilling scenarios are investigated, namely, point type, I-shaped line type, and L-type line type. The point-type underfilling validates the numerical model against experimental results, while the I-shaped and L-type line-type underfilling explore grid independence, void formation, and critical parameters such as filling position, contact angle, and liquid viscosity. Results indicate that contact angle and viscosity significantly influence filling efficiency and interface evolution. A smaller contact angle accelerates the process, reducing interface jumping motions. Viscous effects are quantified, revealing dimensionless filling time convergence. The use of low-viscosity surrogate fluids enhances numerical simulation efficiency. Sub-bump-sized, bump-sized, and sup-bump-sized voids are observed, identifying three void formation scenarios representing different underfilling flow mechanisms. This study provides insight into microscale flip-chip underfill physics and establishes validated models for next-generation high-density flip-chip products. These models can be further refined and integrated into optimization tools for automated process design, contributing to improved assembly yield and reliability of emerging electronic packages through physics-based understanding and modeling.

Trapped O2 and the origin of voltage fade in layered Li-rich cathodes

Oxygen redox cathodes, such as Li1.2Ni0.13Co0.13Mn0.54O2, deliver higher energy densities than those based on transition metal redox alone. However, they commonly exhibit voltage fade, a gradually diminishing discharge voltage on extended cycling. Recent research has shown that, on the first charge, oxidation of O2− ions forms O2 molecules trapped in nano-sized voids within the structure, which can be fully reduced to O2− on the subsequent discharge. Here we show that the loss of O-redox capacity on cycling and therefore voltage fade arises from a combination of a reduction in the reversibility of the O2−/O2 redox process and O2 loss. The closed voids that trap O2 grow on cycling, rendering more of the trapped O2 electrochemically inactive. The size and density of voids leads to cracking of the particles and open voids at the surfaces, releasing O2. Our findings implicate the thermodynamic driving force to form O2 as the root cause of transition metal migration, void formation and consequently voltage fade in Li-rich cathodes.

Effective Utilization of Bio and Industry Wastes to Produce Thermal Insulation Concrete: A Novel Solution for Energy-Saving Buildings

The research addressed the effective and sustainable ways to enhance the thermal insulation properties of concrete without compromising its structural integrity. Traditional methods of enhancing thermal insulation in buildings, such as using thick layers of insulation materials, can be costly and may not always be practical in certain settings. Additionally, the disposal of waste materials such as date palm fiber, shopping plastic bags, and thermocol beads presents an environmental challenge. Therefore, this study aims to investigate the potential use of these waste materials as additives in concrete to improve its thermal insulation properties while also providing a sustainable solution for waste disposal. Date palm fiber is a natural material that is widely available in the Gulf region. Plastic bags are a huge waste from the shops every day, and from the packing materials, this thermocol is a huge waste product. We have to recycle it very efficiently to protect the environment. Three types of special materials, such as thermocol beads (30%), date palm fiber (3%) & shopping plastic bag fiber (3%), were tested in this research. Thermocol beads, when used, reduce their strength and increase the thermal resistance of concrete, while date palm fiber and shopping bag waste fiber, when used, increase the strength of concrete and also increase the thermal resistance of concrete, so it is an excellent reinforcing material and thermal barrier for shopping plastic bags fiber and date palm fiber. Based on this research result, when thermocol beads are used, they prevent heat by 42 percent, while when added with date palm fiber and plastic fiber, they also block heat by an average of 30% percent; thus, all three ingredients are considered excellent thermal insulation material. The reduction in thermal conductivity was attributed to the formation of air voids and the low thermal conductivity of the waste materials. The density of the concrete decreased with the addition of the waste materials. The study suggests that the incorporation of date palm fiber, shopping bag waste fiber, and thermocol beads can be an effective way to enhance the thermal insulation properties of concrete while also providing an environmentally sustainable solution for waste disposal. It will boost green energy technology in the construction industry.

Merging polymers of intrinsic microporosity and porous carbon-based zinc oxide composites in novel mixed matrix membranes for efficient gas separation

Mixed matrix membranes (MMMs) have demonstrated significant promise in energy-intensive gas separations by amalgamating the unique properties of fillers with the facile processability of polymers. However, achieving a simultaneous enhancement of permeability and selectivity remains a formidable challenge, due to the difficulty of achieving an optimal match between polymers and fillers. In this study, we incorporate a porous carbon-based zinc oxide composite (C@ZnO) into high-permeability polymers of intrinsic microporosity (PIMs) to fabricate MMMs. The dipole–dipole interaction between C@ZnO and PIMs ensures their exceptional compatibility, mitigating the formation of non-selective voids in the resulting MMMs. Concurrently, C@ZnO with abundant interconnected pores can provide additional low-resistance pathways for gas transport in MMMs. As a result, the CO2 permeability of the optimized C@ZnO/PIM-1 MMMs is elevated to 13,215 barrer, while the CO2/N2 and CO2/CH4 selectivity reached 21.5 and 14.4, respectively, substantially surpassing the 2008 Robeson upper bound. Additionally, molecular simulation results further corroborate that the augmented membrane gas selectivity is attributed to the superior CO2 affinity of C@ZnO. In summary, we believe that this work not only expands the application of MMMs for gas separation but also heralds a paradigm shift in the application of porous carbon materials.

Property of Cu and PbSrZrTiO3 multilayer actuator fabricated by cofiring with wet reduction

Traditional co-firing processes involving noble metals are costly, thereby prompting a shift to base metals, such as Cu, to reduce manufacturing expenses. This study explored the use of Cu as an internal electrode for fabricating piezoelectric multilayer devices using a Pb0.98Sr0.02(Zr0.48Ti0.52)O3 (PSZT) ceramic material. The compatibility of Cu with PSZT in ambient air and the subsequent wet-reduction was investigated. The addition of polyvinylidene fluoride (PVDF) to the Cu electrode expedited the reduction process; however, this prompted void formation. Thus, epoxy resin was injected to post-reduction to enhance its mechanical property and address this issue. The impact of the PVDF content on the reduction rates, microstructure, and electrical/mechanical properties was analyzed. The experimental results highlighted the successful fabrication of Cu/PSZT devices with performances comparable to those of traditional noble metal (AgPd) counterparts. The polarization and strain of the Cu/PSZT device with 10% PVDF were comparable to those of the AgPd/PSZT. Subsequently, the incorporation of epoxy resin and Cu electroplating greatly improved the mechanical strength of Cu/PSZT to values comparable to that of AgPd/PSZT, as confirmed by the successful fabrication of a piezoelectric ultrasonic device and vibration measurement at 60 kHz. Therefore, this proposed process is a viable alternative for fabricating low-cost and stable multilayer ceramic devices.

Effects of beam scanning modes on ion-irradiated iron microstructure

Neutron induced damage in future nuclear materials can be studied using heavy ion beams only if the differences in the microstructure evolution are well understood. Large variations in the damage dose rate, caused by scanning of the ion beam, can alter the microstructure compared to steady-state irradiation. We study the effect of scanning on the microstructure by irradiating pure iron with a 10 MeV Fe ion beam to a dose of 0.2 dpa. The beam is scanned in one direction with frequencies of 200 Hz and 10 kHz. Different shapes of the beam are also used to study the effect of dose variation. All of the irradiations are conducted at room temperature using the DiFU chamber at RBI. TEM analysis shows differences between the narrow beam and defocused irradiation modes, including unusual void formation observed at 10 kHz. A wider beam reduces the effect of scanning speed and no voids are found in this scanning case.

Gold Coated Silver Bonding Wire and Its Consistent Reliability Performances

Thermal aging of gold coated silver bonded ball with aluminium bond pads exhibited a stable interface without Kirkendall voids until 4000h at 200°C for an un-molded device tested under vacuum. Ball and stitch pull remains in strength and remained constant until 4000 hours of aging. The growth of aluminides at the bond interface is about 4.5µm for 4000 hours of aging. The electrical resistance of the bonded ball remains the same until 4000 hours at 175°C for an epoxy molded device, molded with 5 to 7 pH green epoxy molding compound containing low chlorine and sulfur. Interestingly, the bonded ball interface of epoxy molded device has sustained 480h on biased Highly Accelerated Stress Test (bHAST) at +20V bias, 130°C, 85%RH. The bonded ball interface is stable until 1000 hours on unbiased HAST (uHAST) at 130°C, 85% RH as well. Cross-sectional ovservations of the bonded balls revealed the presence of intermetallic phases at the bond interface. However, formation of Kirkendall voids or crack propagatioon due to galvanic corrosions are absent.

Formation and persistence of glaciovolcanic voids explored with analytical and numerical models

Abstract One fifth of Earth's volcanoes are covered by snow or ice and many have active geothermal systems that interact with the overlying ice. These glaciovolcanic interactions can melt voids into glaciers, and are subject to controls exerted by ice dynamics and geothermal heat output. Glaciovolcanic voids have been observed to form prior to volcanic eruptions, which raised concerns when such features were discovered within Job Glacier on Qw̓elqw̓elústen (Mount Meager Volcanic Complex), British Columbia, Canada. In this study we model the formation, evolution, and steady-state morphology of glaciovolcanic voids using analytical and numerical models. Analytical steady-state void geometries show cave height limited to one quarter of the ice thickness, while numerical model results suggest the void height h scales with ice thickness H and geothermal heat flux $\dot {Q}$ as $h/H = a H^b \dot {Q}^c$ , with exponents b = −n/2 and c = 1/2 where n is the creep exponent. Applying this scaling to the glaciovolcanic voids within Job Glacier suggests the potential for total geothermal heat flux in excess of 10 MW. Our results show that relative changes in ice thickness are more influential in glaciovolcanic void formation and evolution than relative changes in geothermal heat flux.

Utilization of waste cooking oil as a substitute for plasticizers in the production of carrageenan/cornstarch bioplastic

In the current investigation, to develop a carrageenan/cornstarch bioplastic production technique suitable for commercial-scale production, an alternative method to the commonly used solvent-casting technique was implemented through a hot-melt extrusion process. Moreover, to enhance the water resistance of the bioplastic and reduce production costs, waste cooking oil (WCO) was used as a substitute for glycerol plasticizer. Various weight ratios of WCO to glycerol (w/w) were used in formulations. All the material ingredients were compounded using a double-screw extruder at 115°C. Subsequently, the resulting extrudate was then cut into resin pellets, followed by hot compression to produce bioplastic film samples. The film samples underwent testing for mechanical properties, water resistance, biodegradability, chemical structure and morphology. The overall results showed that the addition of WCO improved the tensile properties and water resistance and accelerated biodegradation. These findings were attributed to the presence of ester groups in the polymer structure, the intrinsic hydrophobic nature of WCO and the formation of voids within the film structure, as revealed by Fourier transform infrared spectroscopy and scanning electron microscopy analyses. Based on the findings, the utilization of WCO in carrageenan/cornstarch-based bioplastic production offers potential advantages for commercial applications.

Prediction of transverse permeability in representative volume elements with closely arranged fibers through the application of delaunay-triangulation and electrical-circuit analogy

The distribution of fibers in composite manufacturing significantly affects fiber bundle permeability, a crucial factor for resin impregnation and void formation, which determines final product quality. However, as the industry increasingly seeks composite materials characterized by high fiber volume fractions, the existing numerical analysis methodologies employed for predicting permeability require a considerable computational cost. In this study, the permeability prediction model was developed using a fluid domain simplification technique based on Delaunay triangulation. The inter-fiber flow was approximated using a lubrication model, and continuity was ensured using a circuit analogy. This model can explain stochastic permeability characteristics according to fiber distribution and accurately predicts the permeability regardless of the distance between fibers. Additionally, compared to existing computational fluid dynamics simulations, it achieved an incredible accuracy of 97.74% and reduced computational costs by an average of 1,700 times.

Investigation on mechanical properties of the green synthesis bamboo fiber/eggshell/coconut shell powder-based hybrid biocomposites under NaOH conditions

Abstract This research delves into the effects of different alkalization treatment approaches on the mechanical characteristics of epoxy matrix composites that are reinforced with natural bamboo fibers and enriched with egg and coconut shell powders as fillers. Various weight ratios of fibers and fillers were investigated, specifically at 5%, 10%, 15%, 20%, 25%, and 30%. The study assessed mechanical properties such as tensile strength, flexural behavior, microhardness, and impact resilience. Findings indicate that composites with alkali-treated fibers demonstrate superior mechanical performance (49.28 MPa of tensile, 57.33 MPa of flexural 89 HV of hardness, and 1.3 kJ·m−2 of impact) compared to untreated counterparts. Particularly noteworthy is the significant improvement in fracture toughness observed with the inclusion of 20% hybrid laminates, surpassing the performance of existing biomaterial-based composites. This heightened toughness is attributed to the optimized composition of fibers and enhanced water absorption capabilities. Conversely, the incorporation of 25% and 30% hybrid composites led to a decrease in mechanical strength (38.65 MPa of tensile, 46.7 MPa of flexural, 72 HV of hardness, and 1.19 kJ·m−2 of impact) due to the formation of additional interfacial contacts, pores, and voids within the polymeric matrix.