Particle Interlayer Research Articles

High dislocation-density silver particle interlayer for high-quality YSZ and Al2O3 joints

An Ag particle interlayer was adopted to join YSZ to Al2O3 ceramics in air directly. In comparison with the traditional Ag-CuO braze used in our previous work, the Ag particle interlayer prevented the formation of the brittle compound (CuAl2O4) layer along the ceramic interface. Sintering effect of particulate Ag and high-density dislocations in the interlayer are the major contributors to recrystallization of Ag and elemental interdiffusion. High Resolution Transmission Electron Microscope images confirmed that atomic bonding was achieved between the interlayer and Al2O3. Joining parameters, including temperatures and pressures, were optimized, resulting in the maximum shear strength of the joint (∼80 MPa) obtained at 950 °C/30 min with the external pressure of 0.9 MPa, which is 78 % higher than that of the joint brazed by Ag-CuO.

Interface enhancement mechanism of rolled Mg/Al clad plate with particle interface control

In this study, the cold-spraying process was utilized to deposit Al particles onto an Al slab, an Mg slab, and both Al and Mg slabs to form an ultra-thin interlayer, and then the clad slabs were rolled at 400 °C, developing three roll-bonding processes: the roll-bonding process with cold-sprayed Al powder on the Al slab (CS-Al), the roll-bonding process with cold-sprayed Al powder on the Mg slab (CS-Mg), and the roll-bonding process with cold-sprayed Al powder on both the Al slab and the Mg slab (CS-Both). The effects of three different cold-sprayed Al particle interlayer processes on the mechanical properties of rolled Mg/Al clad plates were investigated to improve the mechanical properties. The microstructure, texture evolution, intermetallic compound formation, mechanical properties, and mechanisms involved in the Mg/Al clad plate rolling were systematically investigated. The results showed that the pre-bonding between the particles and the substrates through cold-spraying had a significant impact on the bonding strength of the Mg/Al clad plates, and the CS-Both process can increase the average shear strength of the Mg/Al clad plates to 49.24 MPa at a medium reduction rate of 37.5 %, 2.5 times that of the conventional rolling process. The CS-Both process constructed more evident dual microscopic three-dimensional interfaces and promoted more thorough atomic diffusion at the interface through the double-sided cold-spraying process. Meanwhile, the dual cold-sprayed Al coatings on both the Mg slab and Al slab underwent dynamic recrystallization during rolling to form a homogeneous unit with no additional coating interfaces. Fine grain strengthening and dislocation strengthening were judged to be important mechanisms for improving the mechanical performance of the interfacial layer.

Micro-Ag particle interlayer with high dislocation density for sintered-joining of Al2O3 and AlN in air

A novel sintered-joining of Al2O3 and AlN is achieved for the first time using micro-Ag particle interlayers in air. In comparison with reactive air brazing, this method addresses the issue of reduced strength caused by air holes in brazed joints. Also, this sintered-joining method can be performed at a lower temperature (920 °C), improving the joint strength by relieving the residual stresses. The sintering effect of micro-Ag particles and their high density of dislocations promote the recovery and recrystallization of the Ag interlayer, as well as the interdiffusion of Ag and ceramic. Ag–O clusters formed at the interface can be embedded into oxygen vacancies on the ceramic surface, playing a key role in interfacial joining. By optimizing joining temperature, assembly pressure and holding time, a maximum joint shear strength of 85.2 MPa is achieved at 920 °C for 30 min with an assembly pressure of 1 MPa. This study successfully prepares Al2O3/AlN joints with excellent mechanical properties, providing a reliable foundation for the fabrication of power integrated circuits with efficient operation.

Propagation Behavior of P1-Wave Passing through Fluid-Saturated Porous Continuous Barrier in Layered Saturated Soil

The fluid-saturated porous continuous barrier has a better vibration isolation effect than the single-phase solid continuous barrier, and layer-forming saturated soils will have an impact on the vibration isolation effect of the barriers due to their irregular layer-forming distribution. Based on Biot’s theory of saturated porous media and Snell’s law, a dynamic model of a fluid-saturated porous continuous barrier in layered saturated soil is established in this study. By introducing the potential function and using the continuous boundary condition of the interface between the saturated soil and the barrier, the analytical solution of the inverse transmission amplitude ratio of a P1-wave passing through the fluid-saturated porous continuous barrier in stratified saturated soil is obtained. The rationality of the proposed method is verified by comparing the solution of the P-wave model at the interface between the elastic medium and the saturated coarse particle interlayer. The differences in the propagation characteristics of fluid-saturated porous continuous barriers in layered saturated soils, homogeneous saturated soils, and layered single-phase soils are analyzed via numerical examples, and the influence of changes in the physical and mechanical parameters of the fluid-saturated porous continuous barriers on the reflectance amplitude ratios under the conditions of a layered saturated soil foundation are also analyzed. The results show that the presence of fluid in the stratified saturated soil model changes the trend of the reflection amplitude ratio with the incidence angle. The reflection amplitude ratio of the P2-wave and the SV-wave increases first and then decreases with the increase in the incident angle, while the reflection amplitude ratio of P1-wave decreases first and then increases. Barrier thickness and porosity change the energy distribution relationship at the interface; a relatively thicker barrier thickness and a higher porosity would result in a higher amplitude of barrier reflections.

A new process for preparing rolled Mg/Al clad plates assisted by cold spraying ultra-thin Al particle interlayer

A novel process, "cold spraying interlayer + roll-bonding" (CSIR), was proposed for the preparation of Mg/Al clad plates. The microstructural evolution of interfaces and mechanical properties of Mg/Al clad plates were investigated. The results showed that the CSIR process produced microscopic three-dimensional mechanical interlocking at the interface and promoted atomic diffusion. The CSIR process collaborated microscopic three-dimensional mechanical bonding with metallurgical bonding, resulting in a shear strength of 1.5 times that of conventional rolling at a reduction rate of 37.5% and reaching 40.02 MPa after annealing at 200 °C for 1 h.

X-ray study on crystalline morphology in iPP/MMT nanocomposite fibers

Nanocomposite fibers based on isotactic polypropylene (iPP) and an organically modified montmorillonite (MMT), Cloisite 15A, were formed from the melt at different take-up velocity. The studies were performed for pure iPP fibers and fibers containing three different concentrations of MMT. The supermolecular structures of the fibers at the crystallographic and lamellar levels were examined by means of X-ray scattering methods (WAXS and SAXS). It was found that the dominant crystal form of iPP is α modification. The increase of take-up velocity induces the orientation of iPP crystals parallel to the fiber axis. The cross-hatching crystallization of iPP was also observed in the tested fibers. Only for the gravity spun fibers containing MMT, the β modification of iPP was observed. Assuming that nucleation does not occur on the surfaces of clay platelets but rather in the interlayers of MMT particles, a probable β-phase nucleation mechanism has been suggested. This mechanism was confirmed by the isothermal crystallization experiment. During heating, the β crystalline form transformed into α-form. The degree of transformation depended on the annealing temperature. The studies also revealed that lamellar stacks of iPP are perpendicular to the MMT layers surfaces.

Temperature-Dependent Sheet and Contact Resistivity Measurements on Ag and Ag-Ni Circuit Pastes

The metal circuits and brazes used in electronic, energy conversion, and/or energy storage devices often have difficulty wetting and adhering to ceramic and/or ceramic-passivated metal substrates. Here, a novel Particle Interlayer Directed Wetting and Spreading (PIDWAS) technique is demonstrated that utilizes screen printing, the low wetting angle of silver on nickel, and the high work of adhesion between nickel and various ceramics to produce well-adhered, self-assembled silver patterns on ceramic and/or stainless-steel substrates not normally wet by silver. The resulting Ag-Ni circuits have higher sapphire adhesion strengths (up to 30 MPa on sapphire), higher densities (>97% on sapphire), and similar high-temperature electronic resistivities to those made using commercially-available Heraeus C8710 or DAD-87 silver circuit pastes. Similarly, Ag-Ni brazes between a variety of ceramic and/or stainless-steel substrates have better microstructural stability with rapid thermal cycling, reduction-oxidation cycling, and dual atmosphere isothermal aging than conventional Ag-CuO brazes. In addition, the residual Ni in these Ag-Ni circuits and brazes can be used to chemically getter surface segregated Al, ensuring low contact resistances on a variety of chromia- and/or alumina-passivated stainless steels.Reference:[1] Hu G, Zhou Q, Bhatlawande A, Park J, Termuhlen R, Ma Y, Bieler TR, Yu HC, Qi Y, Hogan T & Nicholas JD. Patterned Nickel Interlayers for Enhanced Silver Wetting, Spreading and Adhesion on Ceramic Substrates. Scripta Materialia, 2021; 196, 113767. 10.1016/j.scriptamat.2021.113767[2] Park J, Phongpreecha T, Nicholas JD & Qi Y. Enhanced Liquid Metal Wetting on Oxide Surfaces via Patterned Particles. Acta Materialia, 2020; 199, 551-560. 10.1016/j.actamat.2020.08.037

Effect of the interlayer on soil temperature and the transformation between phreatic water and soil water under laboratory freeze-thaw action

To reveal the effect of interlayer on the temperature of freeze-thaw soil and the transformation between phreatic water and soil water in shallow groundwater areas, a freeze-thaw test was conducted with a groundwater table depth of 0.5 m under laboratory freeze-thaw action. The soil temperature and the transformation between phreatic water and soil water of sand columns under constant freezing temperature at −20°C lasted for 20 days, and the thawing process lasted for 15 days were monitored. The interlayers with a particle size of 0.1–0.5 mm (d50 = 0.3 mm) and a thickness of 5 cm were set at 5, 15, 20, and 25 cm away from the surface and these sand columns were marked as D5, D15, D20, and D25, which were compared with a homogeneous sand column (Ch) with a particle size of 0.5–1.5 mm (d50 = 1.0 mm). The results showed that the fine particle interlayer had thermal insulation on the soil profile and that it effectively inhibited upward migration of phreatic water to soil water during the freezing process. A sand column that had a near-surface interlayer had a better thermal insulation, a stronger inhibition effect on upward migration amount of phreatic water to soil water (UMA) and a larger cumulative downward movement amount of soil water to phreatic water (DMA). The cumulative UMA of D5, D15, D20, and D25 was 61%–84% of Ch during the freezing stage, and the cumulative DMA of D5, D15, D20, and D25 was 29%–57% of Ch during the thawing stage. The inefficient loss of groundwater increased exponentially with the depth of interlayer, the sand column with an interlayer that was farther away from the surface consumed more groundwater and stored more water in the unsaturated zone, and its DMA reached almost zero earlier. These research results were significant for the scientific evaluation of water resources in shallow groundwater areas.

Microstructural evolutions and mechanical characteristics of roll-bonding Mg/Al clad plate regulated by cold spraying micron particle interlayer

A new process of “cold spraying interlayer + roll-bonding” (CSIR) was put forward for the preparation of Mg/Al clad plates. First, the micron Ni and Al powders (including some Zn particles) were cold sprayed to form an ultrathin coating on Al or Mg substrate slabs. Then roll-bonding was performed at 400 °C. The influence of cold sprayed coating on slab surfaces, interfacial microstructures, texture evolutions, mechanical properties and the related mechanism were systematically investigated. The results show that the average shear strength of the as-rolled Mg/Al clad plate assisted by cold spraying Al and Ni micron powders interlayer on the substrate slabs was nearly twice (35.58 MPa) than that of conventional rolling under the same conditions (single pass, reduction ratio was 35%). For as-rolled Mg/Al clad plates, almost no reaction diffusion layers are generated, and the mechanical interlocking between cold sprayed coatings and substrate slabs is the main mechanism for improving the shear strength. The interface between the Al coating and the Ni coating is weakest of the as-rolled Mg/Al clad plates. As the reduction rate increases from 27.5% to 47.5%, the function of the mechanical interlocking of cold sprayed coatings will first increase and then weaken. After annealing at 400 °C for 1 h, the interface between the Al coating and the Mg substrate slab will form thick mixed brittle intermetallic compounds, including Al3Mg2, Mg17Al12, MgZn2 and AlMg4Zn11, and cause local gaps, holes, and cracks around the Zn-rich Ni coating. The fracture path after annealing starts from the vicinity of the defective Ni particles, and eventually enlarges along the mixed intermetallic compounds layer between the Al coating and the Mg substrate slab. The research indicates that the CSIR process has great potential in cooperating the metallurgical bonding with the mechanical interlocking of clad plates.

Influence of spatial distribution of fine sand layers on the mechanical behavior of coral reef sand

Fine coral sand commonly distributes in coral sand artificial foundation due to the effect of gravity sorting during hydraulic process and the particle breakage of coarse particle. Considering that the significant impact of the distribution form of fine sand on the strength and deformation properties of coral sand foundation, the effect of spatial distribution of fine sand layers on the mechanical behavior of coral sand was studied. The mechanical behavior of coral sand in the consolidated undrained (CU) shear tests were simulated by discrete element models (DEM) analysis method, and the impact mechanism of fine sand interlayers on mechanical strength was analyzed. The effect of thickness and number of fine sand interlayer on the mechanical behavior and shear deformation of coral sand specimens were analyzed based on the proposed uniformity degree, a parameter that quantify the spatial distribution of fine particle interlayers. The results show that the mechanical behavior of coral sand was simulated well by DEM based on particle scanning results. Under the condition of constant fine particle content, the average coordination number of particles increased and the minimum contact force between particles decreased when fine particles were distributed in the form of interlayer. It indicates that the fine particle interlayer has a diffusion effect on stress transfer, which revealed the mechanism of the macro increasing strength of 10%–20% under the same confining pressure. A linear relationship was found between the proposed parameter uniformity and the peak deviator stress of specimens, and the impact of uniformity on the strength was particularly significant under high confining pressures.

Silver particle interlayer with high dislocation density for improving the joining of BaZr0.1Ce0.7Y0.1Yb0.1O3-δ electrolyte and AISI 441 interconnect

One of the critical challenges for the protonic ceramic fuel cell stack is sealing electrolytes and interconnects. However, the traditional AgCuO sealant will aggravate the oxidation along the interconnect surface and result in brittle compound layers at the BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) electrolyte interface. The present work demonstrates that a silver particle interlayer with high dislocation density can be adopted to join BZCYYb electrolyte to the interconnect (AISI 441 stainless) in air instead of traditional AgCuO sealant. Elevating temperatures result in a sufficient bonding at the Ag/BZCYYb interface, and a defect-free joint is obtained at 950 °C. Atomic bonding at Ag/BZCYYb interface is confirmed by TEM. Also, a dense and thin oxide layer (2–3 μm) is formed along the AISI 441 interface. Ag particles in the interlayer provide the main driving force for the sintering joining. The massive dislocations promote the recovery and recrystallization of the Ag interlayer, as well as the interdiffusion of BZCYYb/Ag. After aging in the wet oxidizing atmosphere at 600 °C for 300 h, joints remain intact and dense, indicating superior oxidation resistance and aging performance. Besides, the joint shear strength (25.3 MPa) is 59 % higher than that of the joint brazed by traditional AgCuO.

Roll-Bonding of Mg and Al Plates Assisted by Cold Spraying Micro Particle Interlayer

Roll-Bonding of Mg and Al Plates Assisted by Cold Spraying Micro Particle Interlayer

Joining 3YSZ Electrolyte to AISI 441 Interconnect Using the Ag Particle Interlayer: Enhanced Mechanical and Aging Properties

Reactive air brazing has been widely used in fabricating solid oxide fuel/electrolysis cell (SOFC/SOEC) stacks. However, the conventional Ag–CuO braze can lead to (I) over oxidation at the steel interconnect interface caused by its adverse reactions with the CuO and (II) many voids caused by the hydrogen-induced decomposition of CuO. The present work demonstrates that the Ag particle interlayer can be used to join yttria-stabilized zirconia (YSZ) electrolytes to AISI 441 interconnect in air instead of Ag–CuO braze. Reliable joining between YSZ and AISI 441 can be realized at 920 °C. A dense and thin oxide layer (~2 μm) is formed at the AISI 441 interface. Additionally, an interatomic joining at the YSZ/Ag interface was observed by TEM. Obtained joints displayed a shear strength of ~86.1 MPa, 161% higher than that of the joints brazed by Ag–CuO braze (~33 MPa). After aging in reducing and oxidizing atmospheres (800 °C/300 h), joints remained tight and dense, indicating a better aging performance. This technique eliminates the CuO-induced issues, which may extend lifetimes for SOFC/SOEC stacks and other ceramic/metal joining applications.

Improving the Mechanical properties of 6061 and 5083 welded joint using Friction stir lap welding

Joining of metal is very important operation in every manufacturing activity. Conventional welding of Al alloys by Tungsten inert gas welding, Metal inert gas welding and Resistance spot welding was reported to produce poor quality weld joints, as the inherent characteristics of the base metal affected the weld properties. Friction stir welding, identified as one of the best alternative is employed to join Al 5083 and Al 6061 in this study. Aluminum alloys, Al 5083 and Al 6061 are welded in lap joint configuration, with SiC nano particles interlayer. The process parameters such as welding speed tool, rotational speed and volume percentage of Nano-powder were optimized by utilizing Response surface methodology, RSM. The joints welded without the SiC nano particle interlayer were observed to possess low mechanical strength at the best welding conditions determined by the RSM.

Patterned nickel interlayers for enhanced silver wetting, spreading and adhesion on ceramic substrates

The metal current collectors used in electronic, energy conversion, and energy storage devices often have difficulty wetting and adhering to ceramic substrates. Here, a novel Particle Interlayer Directed Wetting and Spreading (PIDWAS) technique is demonstrated that utilizes 1) the low wetting angle of silver on nickel and 2) the high work of adhesion between nickel and various ceramics to produce well-adhered, self-assembled silver patterns on ceramics not normally wet by silver. This is achieved by partially sintering nickel patterns and melt infiltrating either 1) locally-applied silver or 2) silver that simultaneously dewets the bare ceramic and laterally spreads through the porous nickel network. The resulting Ag-Ni patterns have higher ceramic adhesion strengths, higher densities, and similar electronic resistivities to those made using commercially-available silver circuit pastes. Further, these dense Ag-Ni patterns can be produced without externally-applied pressure, making them desirable for circuit, sealing, die-attach, joining and other applications.

Synergistic impacts of Cu2+ on simultaneous removal of tetracycline and tetracycline resistance genes by PSF/TPU/UiO forward osmosis membrane

Cu2+, tetracycline (TC), and corresponding tetracycline resistance genes (TRGs) are common micropollutants in aquaculture wastewater, which have great impact on environment and human health. In this study, we developed a thin-film nanocomposite (TFN) forward osmosis (FO) membrane with an electrospinning thermoplastic polyurethane/polysulfone (PSF/TPU) substrate and a UiO-66-NH2 particle interlayer modified active layer. The effects of Cu2+ concentration on the synergetic removal of TC and TRGs (e.g., tetA/M/X/O/C, int1, and 16 S rRNA gene) were analyzed to determine the role of Cu2+ in FO process. The rejection mechanism was also analyzed in depth. Results demonstrated that the rejection of TC and Cu2+ was 99.53% and 97.99%. The rejection of TRGs exceeded 90% (specifically, over 99% for tetC) at a Cu2+ concentration of 500 μg/L when 0.5 M (NH4)2HPO4 was used as draw solution. Complexation reaction between Cu2+ and TC, electrostatic interaction, and the adsorption of Cu2+ on membrane surface were the main contributing factors for the high rejection efficiencies. Altogether, the as-prepared FO membrane holds great potential for simultaneously removing heavy metals, antibiotics, and resistance genes in real wastewater.

Investigating Adsorption of Naphthalene to Organo-Modified Montmorillonites and Influencing Factors

There are many sites contaminated by polycyclic aromatic hydrocarbons (PAHs) or combined PAHs-heavy metal in China, which pose serious health-risks to local people and environments. Dissipative quartz crystal microbalance (QCM-D) was applied to investigate the adsorption of naphthalene to two organic-modified smectite clays (cetyltrimethyl ammonium bromide modified montmorillonite, CTAB-SMF, and 3-mercapto propyl trimethoxy silane modified montmorillonite, TMSP-SMF) and original SMF, together with batch adsorption experiments. The results, based on in-situ online QCM-D experiments, showed that the adsorption sites of CTAB-SMF on naphthalene were mainly CTAB grouped between the interlayers of clay particles, while TMSP-SMF's were TMSP grouped on the surfaces of clay particles. The isotherms of naphthalene adsorption to CTAB-SMF fitted well (R2>0.92) with the Freundlich model, while the adsorption isotherms to TMSP-SMF and SMF fitted well with the Langmuir model (R2>0.96). The parameters of CTAB-SMF (n>1) indicated that the adsorption sites of naphthalene to CTAB-SMF were heterogeneous and the adsorption increases at higher equilibrium concentration. The adsorption capacity qmax of TMSP-SMF is significantly greater than that of SMF (P<0.05). Based on the calculation, the value of ΔHobs for these three clays (CTAB-SMF, TMSP-SMF, and SMF) were within the range of -30 to -10 kJ·mol-1, which indicated that it was a spontaneous exothermic physical process. The solution ionic strength could decrease the adsorption of naphthalene to SMF, but had limited effects on naphthalene adsorption to the two organo-modified clay particles. The existence of Cu2+ in the solution could enhance naphthalene adsorption to the three particles, and naphthalene could improve Cu2+ adsorption to these two modified clays. The results of this study show that QCM-D is a useful technique to indicate the changes of clay film during the process of adsorption, and the two organo-modified clay particles have the potential to be remediation materials to remediate PAHs or PAHs-heavy metal-contaminated sites.

Salinity effect on the liquid limit of soils

Previous studies stated that, with increasing salinity, the decreased liquid limit for expansive soils was attributed to the shrinkage of diffuse double layer, while the increased liquid limit for non-expansive soils was explained by the growing particle flocculation. These two mechanisms seem to be controversial and it is difficult to understand how an increasing salinity can promote soil flocculation. This study aims at clarifying the mechanism controlling liquid limit by conducting cone penetration test, sedimentation and rheological tests on MX80 Na-bentonite and silty soil. Results showed that the liquid limit and yield stress of MX80 increased then decreased with increasing salinity, while they increased slightly for the silty soil. In sedimentation test, faster settling rate and smaller sediment volume were identified for MX80 and silt suspensions in NaCl solution, evidencing the shrinkage of diffuse double layer and the formation of denser aggregated structure. This suggested that the change of liquid limit is the result of two mechanisms in competition, which depend on the compression rate of diffuse double layer: (1) the water storage in nano-fissures which correspond to the nanoscale spaces among interlayers of clay particles resulting from the slight shrinkage of diffuse double layer, and (2) the water expulsion into larger pores with significant shrinkage of diffuse double layer. For the MX80 at low salinity and for the silt soil, the first mechanism prevailed and the increasing liquid limit was attributed to the requirement of more water to fill the nano-fissures. In contrast, for MX80 at high salinity, the second mechanism prevailed—the diffuse double layer was compressed significantly, changing the double-layer water to free water and giving rise to the decrease in liquid limit.

Patterned Nickel Interlayers for Enhanced Silver Wetting, Spreading and Adhesion on Ceramic Substrates

The metal current collectors used in electronic, energy conversion, and energy storage devices often have difficulty wetting and adhering to ceramic substrates. Here, a novel Particle Interlayer Directed Wetting and Spreading (PIDWAS) technique is demonstrated that utilizes 1) the low wetting angle of silver on nickel and 2) the high work of adhesion between nickel and various ceramics to produce well-adhered, self-assembled silver patterns on ceramics not normally wet by silver. This is achieved by partially sintering nickel patterns and melt infiltrating either 1) locally-applied silver or 2) silver that simultaneously dewets the ceramic and laterally spreads through the porous nickel network. The resulting Ag-Ni patterns have higher sapphire adhesion strengths, higher densities, and similar electronic resistivities to those made using commercially-available silver circuit pastes. Further, these dense Ag-Ni patterns can be produced without the need for externally-applied pressure, making them desirable for circuit, sealing, die-attach, joining and other applications.

Joint formation in ultrasonic spot welding of aluminum to copper and the effect of particle interlayer

Ultrasonic spot welded Al/Cu joints with and without Al2219 particle interlayer are successfully achieved. For the Al/Cu joints, as the welding energy increases, the T-peel failure load increases up to the maximum value at the welding energy of 1500 J, and then decreases; the hardness at the center of the cross-section is lower than that of the base metal; micro-joints expand until a strong interface bonding is established, excessive welding energy promotes the formation of sonotrode tip sticking. Under the action of Al2219 particle interlayer, significant mechanical interlocking and swirl-like flow are generated at the weld interface. The maximum T-peel failure load (336.8 N) of Al/Al2219/Cu joint is 32.3 % higher than that (254.6 N) of Al/Cu joint.