Crystal Volume Fraction Research Articles

Isothermal Solidification of an Al–Zn Alloy

In diffusion brazing, a brazing alloy layer thickness introduced into the gap between brazed parts is very small, which hinders the study of the isothermal solidification process. In this work, the isothermal solidification of an Al–Zn alloy is investigated at large volume and mass of the initial liquid that takes part in isothermal solidification. Zinc cylinders are caulked in the holes bored in aluminum cubes. The samples thus assembled are held at 500 ± 10°C for different times. The volume fraction of isothermal solidified crystals has been determined, and the growth rate of isothermal crystals is shown to decrease upon holding. The crystals formed during isothermal solidification width are up to 380 μm and length more than 1 mm. They are observed in the samples that are held more than 2 days. The zinc content in the isothermal solidified crystals corresponds to its mean content in the aluminum solid solution at 490–510°C, according to the Al–Zn phase diagram. The composition of the former liquid that surrounded the crystals during isothermal solidification coincides with the equilibrium composition of the liquid in the Al–Zn system at a temperature of 490–510°C.

In-situ tensile testing of ZrCu-based metallic glass composites

ZrCu-based bulk metallic glass composites (BMGCs) are well known for their plastic deformability, superior to traditional metallic glasses (MGs), which is attributed to a unique dual-phases structure, namely, the glassy matrix and unstable B2 phase. In the present study, in-situ tensile testing is used to trace the deformation process of a ZrCu-based BMGC. Three deformation stages of the BMGC, i.e., the elastic-elastic stage, the elastic-plastic stage, and the plastic-plastic stage are identified. In the elastic-elastic and elastic-plastic stages, the yield strength and elastic limit are major influenced by the volume fraction of the B2 crystals. In the plastic-plastic stage, the B2 phase stimulates the formation of multiple shear bands and deflects the direction of shear bands by disturbing the stress field in front of the crack tip. The deformation-induced martensitic transformation of the metastable B2 phase contributes to the plasticity and work hardening of the composite. This study highlights the formation and propagation of multiple shear bands and reveals the interactions of shear bands with structural heterogeneities in situ. Especially, the blocking of shear bands by crystals and the martensitic transformation of the B2 phase are critical for the mechanistic deformation process and illustrate the function of the B2 phase in the present BMGCs.

Microstructure of AZ31 Magnesium Alloy deformed by indentation-flattening compound deformation technology

Characteristic of indentation-flattening compound deformation technology (IFCDT) is discussed, and the parameters of IFCDT are defined. Performance of magnesium alloy AZ31 sheet deformed by IFCDT is researched. The effect of IFCDT coefficient, temperature and reduction ratio on the microstructure of magnesium alloy sheet is analyzed. The research results show that the volume fraction of the twin crystal decreases gradually and the average grain size increases with increasing of coefficient of IFCDT. With increase of the reduction ratio, the volume fraction of the twin crystal gradually increases, and the average grain size also increases. With increase of deformation temperature, the volume fraction of the twin crystal decreases gradually, and the twin crystal grain size increases.

Premature melt solidification during mold filling and its influence on the as-cast structure

Premature melt solidification is the solidification of a melt during mold filling. In this study, a numerical model is used to analyze the influence of the pouring process on the premature solidification. The numerical model considers three phases, namely, air, melt, and equiaxed crystals. The crystals are assumed to have originated from the heterogeneous nucleation in the undercooled melt resulting from the first contact of the melt with the cold mold during pouring. The transport of the crystals by the melt flow, in accordance with the socalled “big bang” theory, is considered. The crystals are assumed globular in morphology and capable of growing according to the local constitutional undercooling. These crystals can also be remelted by mixing with the superheated melt. As the modeling results, the evolutionary trends of the number density of the crystals and the volume fraction of the solid crystals in the melt during pouring are presented. The calculated number density of the crystals and the volume fraction of the solid crystals in the melt at the end of pouring are used as the initial conditions for the subsequent solidification simulation of the evolution of the as-cast structure. A five-phase volume-average model for mixed columnar-equiaxed solidification is used for the solidification simulation. An improved agreement between the simulation and experimental results is achieved by considering the effect of premature melt solidification during mold filling. Finally, the influences of pouring parameters, namely, pouring temperature, initial mold temperature, and pouring rate, on the premature melt solidification are discussed.

Influence of glass insulation on the structure and magnetic properties of Co-Si-B microwires

ABSTRACTInvestigations of the effect of glass insulation on the structure of Co67,7Fe4,3Cr3B15Si10 glass-coated microwire are carried out. It is shown that in initial MW the average distance between metal atoms and the average number of Co neighbors are 0.253 nm and 10.2, respectively. Heat treatments influence considerably on the structural parameters of amorphous microwires. In microwires, an increase in the height of the first maximum of the structure factor is observed, but in glass-coating microwires this increasing is more significant. Such structure changes indicate the beginning of crystallization processes. The crystallization of amorphous microwires occurs in two stages. At the first stage of crystallization primary α-Co crystallites are formed in residual amorphous matrix at the temperature 495 – 498°C. At the second stage the residual B and Si enriched amorphous phase transforms into Co2Si phase and the metastable phase Co3B through eutectic crystallization in the temperature range 510–550°C. The mean grain size and crystallized volume fraction of α-Co crystals are 20 nm and 7%, respectively. Additional internal stresses arising from the presence of glass insulation accelerate the crystallization processes (crystallized volume fraction and the mean grain size of Co crystals increases up to 12%, and 30 nm, respectively). The nanocrystalline structure cased a decrease of coercivity from 130 A/m in initial state to 60 A/m at the annealing 495°C.

Crystallization kinetics of Li2O–Al2O3–GeO2–P2O5 glass–ceramics system

Lithium aluminum germanium phosphate glass–ceramics with NASICON structure find potential application in the field of energy storage device/solid-state battery. Two different glasses with nominal compositions (a) Li1.5Al0.5Ge1.5P2.9Si0.1O12 (LAGP1) and (b) Li1.5Al0.5Ge1.5P2.5Si0.5O12 (LAGP2) were prepared by standard melt-quench technique, and crystallization kinetics phenomenon in these systems was studied using differential thermal analysis technique (DTA). In addition to different conventional methods for crystallization kinetics analysis, model-free kinetics was also applied. The values obtained for activation energy of crystallization (E a) are compared and used for determination of crystallization index, n and m. The E a value obtained for LAGP1 is 375 ± 17 kJ mol−1 which is higher as compared to the E a value of LAGP2, 199 ± 22 kJ mol−1. LAGP2 with higher amount of Si(0.5) causes significant structural modification in the phosphate network and an early phase separation in the silico-phosphate glass. Thus, LAGP2 shows lower activation energy value as compared to LAGP1. The kinetic parameter, n, related to crystal nucleation, was evaluated from crystallized volume fraction (x) at a fixed temperature using predetermined E a value, and other parameter ‘m’ related to the crystal growth was determined using the modified Kissinger equation. The model-free kinetics was used to evaluate the variation of E a, m and n with temperature and suggests a dynamic nucleation and crystallization process with progressive change in kinetic parameters. In LAGP1 sample, an unusual increase in E a value was observed at x value > 0.2 and can be correlated with the existing ‘self-feeding’ process, which is observed in DTA plots. In both of these systems, the values of n and m are found to be equal and more than 3 which suggests three-dimensional growths of Li1.5Ge1.5Al0.5(PO4) crystals on a constant number of already grown nuclei. XRD and micro-Raman spectroscopy were used to identify the crystalline phase formed and various structural units present in the glass and glass–ceramics samples. Minor amount of LiAlPO4 was confirmed from XRD and Raman spectroscopy along with major Li1.5Ge1.5Al0.5(PO4) phase. In addition, using advanced kinetics and technology solution software non-isothermal data were simulated and the isothermal conversion data were extracted for various temperatures which are found to be very close to experimental isothermal data.

Relation between the Hardness and the Strength of Gray Cast Iron with Allowance for the Structural Parameters

The factors that affect the relation between ultimate tensile strength σu and hardness HB of gray cast iron with flaked graphite are studied. The scatter of the ultimate tensile strengths at a given hardness is shown to be caused by one of the primary structure parameters, namely, the volume fraction of primary austenite dendritic crystals. The dependences derived in this work can be used to increase the accuracy of a rapid estimation of the quality of cast iron ingots.

Numerical analysis of mineral crystals on mechanical properties of mineralized collagen fibers

AbstractBone, with excellent mechanical properties, can adapt to a variety of external forces through adjust its complex hierarchical structure. The basis of the hierarchical structure is mineralized collagen fibers, which consist of mineral crystals and collagen fibers. To better understand the mechanical properties of mineralized collagen fibers, we establish a series of representative volume element models of mineralized collagen fibers based on the different arrangement of mineral crystals in the collagen fibers. The effects of crystal aspect ratio, volume fraction, and crystal defect on the effective elastic modulus and Poisson's ratio of mineralized collagen fibers are calculated by combining the homogenization theory with the finite element method. Results show that the elastic modulus of mineralized collagen fibers can be regulated effectively by adjusting the aspect ratio and volume fraction of crystals. This research explains the mechanical advantages of mineralized collagen fibers in the structure, provides a basis for the calculation of high level structure of bone and offers insight into the design of bionic composite materials.

Relationship between Dendritic Structure of Grey Cast Iron and Mechanical Properties of Castings

The relationship between tensile strength σВ and Brinell hardness HB of different grey cast irons was investigated. It was found that at the same hardness values the tensile strength of different specimens may differ by almost two times. It was shown that the mentioned above tensile strength scatter is caused by the different volume fraction of dendritic crystals of a primary austenite fdc. The quantitative relationships between σB and fdc for in situ tensile strength assessment were established. The comparison of σB values calculated through Brinell hardness HB and through volume fraction of dendritic crystals fdc shows that the latter method developed in the present paper provides more reliable results.

The mechanics of shallow magma reservoir outgassing

AbstractMagma degassing fundamentally controls the Earth's volatile cycles. The large amount of gas expelled into the atmosphere during volcanic eruptions (i.e., volcanic outgassing) is the most obvious display of magmatic volatile release. However, owing to the large intrusive:extrusive ratio, and considering the paucity of volatiles left in intrusive rocks after final solidification, volcanic outgassing likely constitutes only a small fraction of the overall mass of magmatic volatiles released to the Earth's surface. Therefore, as most magmas stall on their way to the surface, outgassing of uneruptible, crystal‐rich magma storage regions will play a dominant role in closing the balance of volatile element cycling between the mantle and the surface. We use a numerical approach to study the migration of a magmatic volatile phase (MVP) in crystal‐rich magma bodies (“mush zones”) at the pore scale. Our results suggest that buoyancy‐driven outgassing is efficient over crystal volume fractions between 0.4 and 0.7 (for mm‐sized crystals). We parameterize our pore‐scale results for MVP migration in a thermomechanical magma reservoir model to study outgassing under dynamical conditions where cooling controls the evolution of the proportion of crystal, gas, and melt phases and to investigate the role of the reservoir size and the temperature‐dependent viscoelastic response of the crust on outgassing efficiency. We find that buoyancy‐driven outgassing allows for a maximum of 40–50% volatiles to leave the reservoir over the 0.4–0.7 crystal volume fractions, implying that a significant amount of outgassing must occur at high crystal content (>0.7) through veining and/or capillary fracturing.

On the kinematics and dynamics of crystal‐rich systems

AbstractPartially molten rocks, often called a mush, are examples of a hydrogranular mixture where the dynamics are controlled by both fluid and crystal‐crystal interactions. An obstacle to progress in understanding high‐temperature hydrogranular systems has been the lack of adequate levels of description of microphysical processes. Here we rationalize the hydrogranular kinematic and dynamic states by applying the concept of particle (crystal) force chains. We exemplify this with discrete‐element computational fluid dynamic simulations of the intrusion of a basaltic melt into an olivine‐basalt mush, where crystal‐scale force chains, crystal transport, and melt mixing are resolved. To describe the microscale kinematics of the system, we introduce the coordination number and the fabric tensors of particle contacts and forces. We quantify the changing contact and force fabric anisotropy, coaxiality, and the connectedness of the mush, under dynamic conditions. To describe the dynamics, particle and fluid characteristic response times are derived. These are used to define local and bulk Stokes numbers, and viscous and inertia numbers, which quantify the multiphase coupling under crystal‐rich conditions. We employ the Sommerfeld number, which describes the importance of crystal‐melt lubrication, with a viscous number to illustrate the dynamic regimes of crystal‐rich magmas. We show that the notion of mechanical “lock up” is not uniquely identified with a particular crystal volume fraction and that distinct mechanical behaviors can emerge simultaneously within a crystal‐rich system. We also posit that this framework describes magmatic fabrics and processes which “unlock” a crystal mush prior to eruption or mixing.

Microstructure and mechanical properties of nucleant-free Li2O-CaO-SiO2 glass-ceramics

An attractive characteristic of the Li2O-CaO-SiO2 glass-forming system is the possibility of obtaining internally nucleated crystal phases – CaSiO3 and Li2SiO3 – having elongated morphologies that can potentially lead to tough glass-ceramics. Another great advantage of this system is that it does not need a nucleating agent to crystallize internally. In this research work, three glasses with systematic compositional variations within the range of 30–50 mol% CaSiO3/70-50 mol% Li2SiO3 were prepared, heat-treated and their microstructures and mechanical properties evaluated. Heating cycles were applied in two-stage treatments. The temperatures were selected based on previous DSC analyses. The crystallized samples were characterized by XRD and SEM to examine the nature, size and morphology of their crystals. The effect of microstructure on the Vickers hardness (Hv) and indentation fracture toughness (Kc) of the glass-ceramics was determined. Elastic modulus (E), biaxial strength (σm) and fracture toughness (KDTIC) were determined from nanoindentation, ball-on-three-balls and double torsion tests, respectively. The level of internal residual stresses was evaluated by X-rays diffraction. The best mechanical properties were exhibited by a composition containing 44 mol% CaSiO3 heat-treated at 498 °C for 24 h for nucleation and at 700 °C for 2 h for crystal growth. This composition resulted in a glass-ceramic with the following microstructural features and properties: average Li2SiO3 (LS) crystal size of 8.5 μm, wollastonite (CS) phase surrounding the LS crystals with approximately 50% LS crystallized volume fraction, KDTIC = 2.3 ± 0.5 MPa m1/2, σm = 270 ± 20 MPa, HV = 8.4 ± 0.7 GPa and E = 146 ± 8 GPa. These are exciting mechanical properties for glass-ceramics intended for load bearing applications.

The effect of Ni addition on microstructure and soft magnetic properties of FeCoZrBCu nanocrystalline alloys

(Fe0.7Co0.3-xNix)88Zr7B4Cu1 nanocrystalline alloys were developed with the aim of improving the magnetic properties while keeping high Curie temperature (TC). It was revealed that Ni addition inhibited the precipitation of metastable fcc-(Fe,Co,Ni) phase hence increased thermal stability. Although the saturation magnetic flux density (Bs) showed a slight decrease, uniform nanostructure with small grain size and high volume fraction of crystals was formed with increasing Ni addition. As a result, the (Fe0.7Co0.3-xNix)88Zr7B4Cu1 nanocrystalline alloys exhibited excellent magnetic properties with a high Bs of 1.54-1.79 T, low coercivity (Hc) of 17-20 A/m and low core loss of 9.1-11.1 W/kg at 1 T and 400 Hz. The combination of high TC of 747-972 °C, low core loss as well as low material cost promised this FeCoNiZrBCu alloys broad application prospect at high temperature.

Crystallization and soft magnetic properties of metalloid-free Fe89Hf7Al3Zr1 amorphous alloy

A new high iron content metalloid-free Fe-based amorphous alloy with the nominal composition of Fe89Hf7Al3Zr1 was fabricated by melt-spinning technique. The alloy shows good soft magnetic properties, such as saturation induction Bs up to 1.60T and coercivity Hc as low as 4.3A/m. Crystallization was investigated in non-isothermal conditions using DSC measurements. It was shown that the observed DSC peaks may be attributed to precipitation of α-Fe phase and Fe2Hf(Zr) compound, respectively. The apparent activation enthalpy Ep of both the exothermic peaks was determined by Kissinger and Ozawa models. The local activation enthalpy E(x) decreases gradually with crystallized volume fraction x indicating that crystallization process of the second step becomes easier. After annealing at different temperatures, the Bs maintains a trend of increase in each crystallization process. The optimized annealing process is established at 798K (close to Tp1) for 0.5h with maximum Bs of 1.75(±0.01) T.

Local melting to design strong and plastically deformable bulk metallic glass composites

Recently, CuZr-based bulk metallic glass (BMG) composites reinforced by the TRIP (transformation-induced plasticity) effect have been explored in attempt to accomplish an optimal of trade-off between strength and ductility. However, the design of such BMG composites with advanced mechanical properties still remains a big challenge for materials engineering. In this work, we proposed a technique of instantaneously and locally arc-melting BMG plate to artificially induce the precipitation of B2 crystals in the glassy matrix and then to tune mechanical properties. Through adjusting local melting process parameters (i.e. input powers, local melting positions, and distances between the electrode and amorphous plate), the size, volume fraction, and distribution of B2 crystals were well tailored and the corresponding formation mechanism was clearly clarified. The resultant BMG composites exhibit large compressive plasticity and high strength together with obvious work-hardening ability. This compelling approach could be of great significance for the steady development of metastable CuZr-based alloys with excellent mechanical properties.

Kinetics study on non-isothermal crystallization of Cu50Zr50 metallic glass

In this paper, the crystallization kinetics of melt-spun Cu50Zr50 amorphous alloy ribbons has been investigated using differential scanning calorimetry. Moreover, the Kissinger, Ozawa and isoconversional approaches have been used to obtain the crystallization kinetic parameters. As shown in the results, the onset crystallization activation energy E x is less than crystallization peak activation energy E p. The local activation energy E α increases at the crystallized volume fraction α 0.2). The nucleation activation energy E nucleation is greater than grain growth activation energy E growth, indicating that the nucleation is harder than growth. In terms of the local Avrami exponent n(α), it lies between 1.27 and 8, which means that crystallization mechanism in the non-isothermal crystallization is interface-controlled one- two- or three-dimensional growth with different nucleation rates.

Crystallization kinetics of new heavy metal oxide glasses within the Sb2O3-Na2O-WO3-PbO system

Crystallization kinetic studies of new quaternary antimonite glasses within the Sb2O3-Na2O-WO3-PbO system were performed by non-isothermal methods using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The kinetic parameters n and m which determine crystallization reaction mechanism in glasses were obtained using experimental values of the crystallized volume fraction, χ, by applying Ozawa method. Values of n and m were found as 1 indicating surface crystallization which was confirmed by SEM investigations. The values of crystallization activation energy were calculated in the range of 234–272kJ/mol by using seven different theoretical models. The calculated crystallization activation energy values were associated with the crystallization of cubic crystalline senarmontite phase of Sb2O3.

Crystallization kinetics of the Cu50Zr50 metallic glass under isothermal conditions

Amorphous structure of the melt-spun Cu50Zr50 amorphous alloy ribbons were confirmed by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). Isothermal crystallization kinetics of these alloy ribbons were investigated using differential scanning calorimetry (DSC). Besides, Arrhenius and Johnson-Mehl-Avrami (JMA) equations were utilized to obtain the isothermal crystallization kinetic parameters. As shown in the results, the local activation energy Eα decreases by a large margin at the crystallized volume fraction α<0.1, which proves that crystallization process is increasingly easy. In addition, the local activation energy Eα is basically constant at 0.1<α<0.9. Therefore, it turns out that the unchanged barrier is overcome in the crystallization process. Finally, Eα rapidly decreases at 0.9<α<1, implying that crystallization becomes easier and easier to proceed. Nucleation activation energy Enucleation is greater than growth activation energy Egrowth, so nucleation is harder than growth in isothermal process. In terms of the local Avrami exponent n(α), it ranges 1.1–7.4, revealing that isothermal crystallization mechanism is interface-controlled one- two- or three-dimensional growth with different nucleation rates.

Electrochemical Characteristics of the Composite Electrodes of Li4Ti5O12 Crystals/Li3BO3 Glass and Li4Ti5O12 Crystals/Li3BO3-Li6.75La3Zr1.75Nb0.25O12 Hybrid Solid Electrolyte System for All-Solid-State Lithium-Ion Secondary Battery

Introduction All-solid-state lithium ion rechargeable batteries (LIBs) have been desired for higher energy density, long term durability and safety. A great challenge of all-solid-state LIBs for practical use is reduction of the interfacial resistance. Effective interface modification techniques have been proposed, however, the interfacial resistance is still large because the charge transfer resistance at the active material/ solid electrolyte interface would be strongly affected by interfacial contact condition. On the basis of these backgrounds, we have proposed a new route to prepare smart interfaces for all-solid-state lithium ion batteries through the growth of highly-faceted active material crystals in molten Li ion conductive glass as a flux. In facts, we reported the growth of LiCoO2 crystals with well-defined facets from molten Li3BO3 glass. High-resolution TEM and SEM-EDS revealed that the no voids and defects were formed at the interface between LiCoO2 and Li3BO3, suggesting that the homogeneous nucleation and following growth and liquid-phase sintering of the LiCoO2 crystal promoted the formation of highly sintered segregated particle in molten Li3BO3 flux resulted in the formation of tightly connected interface at atomic level with wide dimension. We have further extended this concept to hybrid electrolyte system composed of Li3BO3 and Li6.75La3Zr1.75Nb0.25O12, exhibiting total Li+ conductivity of 4.7×10-5 S·cm-1 at room temperature. And composite electrodes of LiCoO2 crystals/ Li3BO3 glass-Li6.75La3Zr1.75Nb0.25O12 crystals with volumetric ratio of 50 % exhibited 1.1×10-4 S·cm-1 at room temperature. In this work, in order to extend our concept to making anode electrodes, we demonstrate the fabrication of Li4Ti5O12 crystals/ Li3BO3 glass and Li4Ti5O12 crystals/ Li3BO3 glass-Li6.75La3Zr1.75Nb0.25O12 crystals composite electrodes as well as the characterization of their electrochemical properties by using electrochemical impedance spectroscopy. Experimental Anatase-phase TiO2, Li2CO3, and Li3BO3 were used as a starting materials for Li4Ti5O12 crystal growth in Li3BO3 glass matrix. The volume fraction of Li4Ti5O12 crystal was controlled from 50 to 90% to Li3BO3. The mixed powders was heated at 900oC for 10 h. Subsequently the powders were cooled to 100°C under temperature controlled conditions. The products were pulverized and heated again at 900 oC for 10 h after pelleting. The as obtained composites were structurally characterized by XRD, SEM-EDS, XRD, and TEM. Electrical conductivity measurements of the sintered pellets were performed using Li+ blocking Au-electrodes with area of 0.5 cm2 in the frequency range from 7 MHz to 0.1 Hz using an impedance analyzer at room temperature. Results and Discussions Primary single crystals with well-developed facets with 5 μm diameter were formed from a molten Li3BO3. Powdered XRD patter was good agreement with reference data of ICDD PDF 049-0207, indicating that the crystals formed spinel structure crystallized into Fd-3m cubic system. There are no any other diffraction lines were observed, suggesting that Li3BO3 formed amorphous phase. SEM-EDS revealed the idiomorphic Li4Ti5O12 crystals were homogeneously dispersed in the Li3BO3 glass matrix. Furthermore, Ti element was homogeneously dispersed in the all crystals, indicating that no Li+-rich phase, such as Li2TiO3 phase was formed at the interface. TEM observation revealed that the interface was atomically connected without any sub-phases formation, suggesting that the interfaces potentially provide efficient Li+ transport pathways. We will further discuss the effect of mixing ratio on the densification and the lithium ion conductivity of both Li4Ti5O12 crystals/ Li3BO3 glass and Li4Ti5O12 crystals/ Li3BO3 glass-Li6.75La3Zr1.75Nb0.25O12 crystals composite electrodes at PRiME 2016. Acknowledgments This research is partially supported by JST-ALCA and JST-CREST.

Variance-Based Sensitivity of Localized Sulphation to Microporous Separator Properties Using a Distributed Parameter Model of a Valve-Regulated Lead-Acid Battery

Progressive sulphation of the negative electrode in a lead-acid battery under high-rate operation remains a serious problem. This study investigates how healthier end-of-discharge conditions, in a valve-regulated lead-acid battery with an immobilized electrolyte, can be achieved by calculated changes in the separator’s porosity, thickness and tortuosity. The solubility, volume fraction and geometry factor of local PbSO4 crystals are modeled using a distributed parameter model and observed during a high-rate discharge in simulation. A variance-based sensitivity analysis, consisting of a Monte Carlo experiment and Jansen’s formulae for variance decomposition, is performed to quantify the effects of separator design on localized sulphation. The concentration profile across different regions of the cell is also briefly examined by means of a statistical equation for the concentration non-uniformity. The results indicate that the separator thickness has the greatest effect on the PbSO4 crystals at the negative electrode because it severely influences the concentration profile in this region. The simulation results also indicate that separator design with the aim of manipulating the concentration profile, and enabling faster homogenization within a lead-acid cell, can be achieved. We conclude that it is possible to design a microporous separator that improves the dissolution, during recharge, of the PbSO4 crystals on the negative electrode that initially formed during a high-rate discharge. The quantitative approach we have followed can be used to quickly evaluate thousands of different separator designs and determine a suitable starting point for experimental work.