Pore Shape Research Articles

Enhanced mechanical properties of alumina ceramics: Role of nanoscale C@Al2O3 core-shell particle

The introduction of pores to improve the toughness of alumina ceramics is considered to be a feasible strategy by using the inhibitory effect of pores on crack propagation. However, the mechanical properties of alumina ceramics are often reduced due to the uncontrollable pore shape. In this work, the nano-scale C@Al2O3 core-shell particles were fabricated and introduced into the alumina powder treated by dielectric barrier discharge plasma-assisted milling, and the alumina ceramics with closed pores of regular shape (approximate sphere) and small size (<1 μm) were prepared. Since the approximate spherical pore structure and small pore size eliminate the adverse effects of stress concentration, and the deflection and pinning effect of closed pores on cracks, the flexural strength and fracture toughness of the prepared samples were improved, increasing by 12.6 % and 18.8 % respectively.

Preparation and application of chromatographic stationary phase based on two-dimensional materials

The stationary phase is the heart of chromatographic separation technology and a critical contributor to the overall separation performance of a chromatographic separation technique. However, traditional silicon-based materials designed for this purpose usually feature complex preparation processes, suboptimal permeability, pronounced mass-transfer resistance, and limited pH-range compatibility. These limitations have spurred ongoing research efforts aimed at developing new chromatographic stationary phases characterized by higher separation efficiency, adaptable selectivity, and a broader scope of applicability. In this context, the scientific community has made significant strides toward the development of new-generation materials suitable for use as chromatographic stationary phases. These materials include carbon-based nanomaterial arrays, carbon quantum dots, and two-dimensional (2D) materials. 2D-materials are characterized by nanometer-scale thicknesses, extensive specific surface areas, distinctive layered structures, and outstanding mechanical properties under standard conditions. Thus, these materials demonstrate excellent utility in various applications, such as electrical and thermal conductivity enhancements, gas storage and separation solutions, membrane separation technologies, and catalysis. Graphene, which is arguably the most popular 2D-material used for chromatographic separation, consists of a 2D-lattice of carbon atoms arranged in a single layer, with a large specific surface area and efficient adsorption properties. Its widespread adoption in research and various industries is a testament to its versatility and effectiveness. In addition to graphene, the scientific community has developed various 2D-materials that mirror the layered structures of graphene, such as boron nitride, transition-metal sulfides, and 2D porous organic frameworks, all of which offer unique advantages. 2D porous organic frameworks, in particular, have received attention because of their nanosheet morphology, one-dimensional pores, and special interlayer forces; thus, these frameworks are considered promising candidate chromatographic stationary phase materials. Such recognition is especially true for 2D-metal organic frameworks (MOFs) and 2D-covalent organic frameworks (COFs), which exhibit low densities, high porosities, and substantial specific surface areas. The modifiability of these materials, in terms of pore size, shape, functional groups, and layer-stacking arrangements allows for excellent separation selectivity, highlighting their promising potential in chromatographic separation. Compared with their three-dimensional counterparts, 2D-MOFs feature a simple pore structure that offers reduced mass-transfer resistance and enhanced column efficiency. These attributes highlight the advantages of 2D-MOF nanosheets as chromatographic stationary phases. Similarly, 2D-COFs, given their high specific surface area and porosity, not only exhibit great thermal stability and chemical tolerance but also support a wide selection of solvents and operational conditions. Therefore, their role in the preparation of chromatographic stationary phases is considered highly promising. This review discusses the latest research developments in 2D porous organic framework materials in the context of gas- and liquid-chromatographic stationary phases. It introduces the synthesis methods for these novel materials, elucidates their retention mechanisms, and describes the applications of other 2D-materials, such as graphene, its derivatives, graphitic carbon nitride, and boron nitride, in chromatography. This review aims to shed light on the promising development prospects and future directions of 2D-materials in the field of chromatographic separation, offering valuable insights into the rational design and application of new 2D-materials in chromatography.

In vitro and in vivo degradation profile, biocompatibility of poly-L-lactic acid porous microspheres

The objective of this study is to evaluate the in vitro and in vivo degradation profile and biocompatibility of poly-L-lactic acid (PLLA) porous microspheres (PMs) for their potential application as injectable microcarrier or micro-scaffolds materials in the research and clinical use of craniofacial cartilage repair. In this study, PLLA PMs prepared exhibited spherical shape and uniform surface pores followed by 24-week evaluations for degradation behavior and biocompatibility. In vitro degradation analysis encompassed morphological examination, pH monitoring, molecular weight analysis, thermodynamic assessment, and chemical structure analysis. After 12 weeks of in vitro degradation, PMs maintained a regular porous spherical structure. Molecular weight and glass transition temperature of PLLA PMs decreased over time, accompanying with an initial increase and subsequent decrease in crystallinity. Enzymatic degradation caused morphological changes and accelerated degradation in the in vitro studies. Finally, in vivo evaluations involved subcutaneous implantation of PLLA PMs in rats, demonstrating biocompatibility by enhancing type I and type III collagen regeneration as observed in histological analysis. The results demonstrated that PLLA PMs were able to maintain their spherical structure for 12 weeks, promoting the generation of collagen at the implantation site, meeting the time requirements for craniofacial cartilage repair.

Fabrication of 3D chitosan/polyvinyl alcohol/brushite nanofibrous scaffold for bone tissue engineering by electrospinning using a novel falling film collector

Despite its advantages, electrospinning has limited effectiveness in 3D scaffolding due to the high density of fibers it produces. In this research, a novel electrospinning collector was developed to overcome this constraint. An aqueous suspension containing chitosan/polyvinyl alcohol nanofibers was prepared employing a unique falling film collector. Suspension molding by freeze-drying resulted in a 3D nanofibrous scaffold (3D-NF). The mineralized scaffold was obtained by brushite deposition on 3D-NF using wet chemical mineralization by new sodium tripolyphosphate and calcium chloride dihydrate precursors. The 3D-NF was optimized and compared with the conventional electrospun 2D nanofibrous scaffold (2D-NF) and the 3D freeze-dried scaffold (3D-FD). Both minor fibrous and major freeze-dried pore shapes were present in 3D-NFs with sizes of 16.11–24.32 μm and 97.64–234.41 μm, respectively. The scaffolds' porosity increased by 53 % to 73 % compared to 2D-NFs. Besides thermal stability, mineralization improved the 3D-NF's ultimate strength and elastic modulus by 2.2 and 4.7 times, respectively. In vitro cell studies using rat bone marrow mesenchymal cells confirmed cell infiltration up to 290 μm and scaffold biocompatibility. The 3D-NFs given nanofibers and brushite inclusion exhibited considerable osteoinductivity. Therefore, falling film collectors can potentially be applied to prepare 3D-NFs from electrospinning without post-processing.

Robust Photocatalytic MICROSCAFS® with Interconnected Macropores for Sustainable Solar-Driven Water Purification.

Advanced oxidation processes, including photocatalysis, have been proven effective at organic dye degradation. Tailored porous materials with regulated pore size, shape, and morphology offer a sustainable solution to the water pollution problem by acting as support materials to grafted photocatalytic nanoparticles (NPs). This research investigated the influence of pore and particle sizes of photocatalytic MICROSCAFS® on the degradation of methyl orange (MO) in aqueous solution (10 mg/L). Photocatalytic MICROSCAFS® are made of binder-less supported P25 TiO2 NPs within MICROSCAFS®, which are silica-titania microspheres with a controlled size and interconnected macroporosity, synthesized by an adapted sol-gel method that involves a polymerization-induced phase separation process. Photocatalytic experiments were performed both in batch and flow reactors, with this latter one targeting a proof of concept for continuous transformation processes and real-life conditions. Photocatalytic degradation of 87% in 2 h (batch) was achieved, using a calibrated solar light simulator (1 sun) and a photocatalyst/pollutant mass ratio of 23. This study introduces a novel flow kinetic model which provides the modeling and simulation of the photocatalytic MICROSCAFS® performance. A scavenger study was performed, enabling an in-depth mechanistic understanding. Finally, the transformation products resulting from the MO photocatalytic degradation were elucidated by high-resolution mass spectrometry experiments and subjected to an in silico toxicity assessment.

Construction of attapulgite decorated cetylpyridinium bromide/cellulose acetate composite beads for removal of Cr (VI) ions with emphasis on mechanistic insights

Eco-friendly and renewable composite beads were constructed for efficient adsorptive removal of Cr (VI) ions. Attapulgite (ATP) clay decorated with cetylpyridinium bromide (CPBr) was impregnated into cellulose acetate (CA) beads, which were formulated through a simple and cost-effective solvent-exchange approach. FTIR, XRD, SEM, Zeta potential, and XPS characterization tools verified the successful formation of ATP–CPBr@CA beads. The composite beads displayed a spherical and porous shape with a positively charged surface (26.6 mV) at pH 2. In addition, higher adsorption performance was accomplished by ATP–CPBr@CA composite beads with ease of separation compared to their components. Meanwhile, equilibrium isotherms pointed out that the Langmuir model was optimal for describing the adsorption process of Cr (VI) with a maximal adsorption capacity of 302 mg/g. Moreover, the D–R isotherm model verified the physical adsorption process, while adsorption data obeyed the pseudo-second-order kinetic model. Further, XPS results hypothesized that the removal mechanism involves adsorption via electrostatic interactions, redox reaction, and co-precipitation. Interestingly, the ATP–CPBr@CA composite beads reserved tolerable adsorption characteristics with a maximum removal present exceeding 70% after reuse for seven successive cycles, proposing its feasible applicability as a reusable and easy-separable candidate for removing heavy metals from aquatic bodies.

Physical Characteristics of Immobilized Cells Acetobacter xylinum of Various Concentrations of Na-alginate

Immobilization of Acetobacter xylinum cells by trapping technique is considered one way to maintain cell viability and can be used repeatedly. The purpose of this study was to determine the physical characteristics of immobilized cells in different concentrations of Na-alginate and apply them to the manufacture of nata de coco, as well as to see the surface and pore shape of immobilized cells after fermentation. This study used a descriptive method with visual observation. This study used one factor, namely various concentrations of Na-alginate, namely 2%, 3%, 4%, and 5% w/v. The immobilized cells applied to the manufacture of nata de coco had only a Na-alginate concentration of 3% resulting in a nata fiber layer close to that of a control. Immobilized cells with a Na-alginate concentration of 2% have a cracked, slightly pore surface with a size of 60.37 μm, while a Na-alginate concentration of 5%, have a smooth surface, many pores, with a size of 10.55 μm. Thus, the concentration affects the characteristics of immobilized cells. Application of immobilized cells with a Na-alginate concentration of 3% produces nata de coco with a fairly thick and stable fiber layer characteristic (close to control).

Porous shape memory NiTi-entangled material with incredible recoverable strain for downhole sand control in oil/gas production

Porous shape memory NiTi-entangled material with incredible recoverable strain for downhole sand control in oil/gas production

Pore characteristics and microscopic damage mechanism of disintegrated carbonaceous mudstone exposed to dry-wet cycles

Disintegrated carbonaceous mudstone (DCM), derived from pre-disintegration treatments of waste carbonaceous mudstone, is utilized as filler for highway embankments with the aim of conserving resources. However, the mechanical behavior of DCM is greatly influenced by its microstructure, particularly pore characteristics. The aim of this study is to investigate the pore characteristics and microscopic damage mechanisms of DCM subjected to dry-wet cycles. Triaxial tests, along with microscopic observations using scanning electron microscopy and mercury intrusion porosimetry, were performed. Three-dimensional pore models were reconstructed from the microscopic test results via the Markov chain-Monte Carlo method. Subsequently, a finite element method that accounts for the anisotropy of porosity was proposed based on these pore models. Finally, numerical triaxial tests were performed to analyze stress changes in DCM under triaxial loading using the proposed method. The results show that the shear strength and cohesion of the DCM decrease with an increase in dry-wet cycles, stabilizing notably after four cycles. Meanwhile, the porosity and the number of slender pores in the specimen increase, leading to intricate alterations in pore shape and distribution. A comparison between numerical and laboratory triaxial tests demonstrates closely aligned results, with distinct stress concentration behavior related to porosity anisotropy. It is revealed that dry-wet cycles cause an increase in porosity and the occurrence of more irregular-shaped pores, subsequently leading to a decrease in the cohesion. This microscopic mechanism is responsible for the shear strength damage of DCM.

Effects of void geometry on two-dimensional monolithic porous phononic crystals

Phononic crystals are renowned for their distinctive wave propagation characteristics, notably bandgaps that offer precise control over vibration phenomena, positioning them as a critical material in advanced vibro-elastic engineering and design. We investigate how pore shapes influence the bandgap in continuum two-dimensional phononic crystals made from a single material. Using the square lattice and unit cells with fourfold symmetry, our numerical analyses reveal that the normalized gap size is highly dependent on the minimum ligament width in the structure. Additionally, we find that fine geometric features represented by higher-order Fourier coefficients decrease the gap size. This study offers insight into the design of phononic crystals and vibro-elastic metamaterials for precise wave control through void patterning.

Rheological Properties and 3D Printing Behavior of PCL and DMSO2 Composites for Bio-Scaffold.

The significance of rheology in the context of bio three-dimensional (3D) printing lies in its impact on the printing behavior, which shapes material flow and the layer-by-layer stacking process. The objective of this study is to evaluate the rheological and printing behaviors of polycaprolactone (PCL) and dimethyl sulfone (DMSO2) composites. The rheological properties were examined using a rotational rheometer, employing a frequency sweep test. Simultaneously, the printing behavior was investigated using a material extrusion 3D printer, encompassing varying printing temperatures and pressures. Across the temperature range of 120-140 °C, both PCL and PCL/DMSO2 composites demonstrated liquid-like behavior, with a higher loss modulus than storage modulus. This behavior exhibited shear-thinning characteristics. The addition of DMSO2 10, 20, and 30 wt% into the PCL matrix reduced a zero-shear viscosity of 33, 46, and 74% compared to PCL, respectively. The materials exhibited extrusion velocities spanning from 0.0850 to 6.58 mm/s, with velocity being governed by the reciprocal of viscosity. A significant alteration in viscosity by temperature change directly led to a pronounced fluctuation in extrusion velocity. Extrusion velocities below 0.21 mm/s led to the production of unstable printed lines. The presence of distinct viscosities altered extrusion velocity, flow rate, and strut diameter. This phenomenon allowed the categorization of pore shape into three zones: irregular, normal, and no-pore zones. It underscored the importance of comprehending the rheological aspects of biomaterials in enhancing the overall quality of bio-scaffolds during the 3D printing process.

Tailorable Multi-Modular Pore-Space-Partitioned Vanadium Metal-Organic Frameworks for Gas Separation.

Currently, few porous vanadium metal-organic frameworks (V-MOFs) are known and even fewer are obtainable as single crystals, resulting in limited information on their structures and properties. Here this work demonstrates remarkable promise of V-MOFs by presenting an extensible family of V-MOFs with tailorable pore geometry and properties. The synthesis leverages inter-modular synergy on a tri-modular pore-partitioned platform. New V-MOFs show a broad range of structural features and sorption properties suitable for gas storage and separation applications for C2H2/CO2, C2H6/C2H4, and C3H8/C3H6. The c/a ratio of the hexagonal cell, a measure of pore shape, is tunable from 0.612 to 1.258. Other tunable properties include pore size from 5.0 to 10.9 Å and surface area from 820 to 2964 m2 g-1. With C2H2/CO2 selectivity from 3.3 to 11 and high uptake capacity for C2H2 from 65.2 to 182 cm3 g-1 (298K, 1bar), an efficient separation is confirmed by breakthrough experiments. The near-record high uptake for C2H6 (166.8 cm3 g-1) contributes to the promise for C2H6-selective separation of C2H6/C2H4. The multi-module pore expansion enables transition from C3H6-selective to more desirable C3H8-selective separation with extraordinarily high C3H8 uptake (254.9 cm3 g-1) and high separation potential (1.25mmol g-1) for C3H8/C3H6 (50:50 v/v) mixture.

Characterization of Porous β-Type Tricalcium Phosphate Ceramics Formed via Physical Foaming with Freeze-Drying.

Porous β-tricalcium phosphate (Ca3(PO4)2; β-TCP) was prepared via freeze-drying and the effects of this process on pore shapes and sizes were investigated. Various samples were prepared by freezing β-TCP slurries above a liquid nitrogen surface at -180 °C with subsequent immersion in liquid nitrogen at -196 °C. These materials were then dried under reduced pressure in a freeze-dryer, after which they were sintered with heating. Compared with conventional heat-based drying, the resulting pores were more spherical, which increased both the mechanical strength and porosity of the β-TCP. These materials had a wide range of pore sizes from 50 to 200 µm, with the mean and median values both approximately 100 µm regardless of the freeze-drying conditions. Mercury porosimetry data showed that the samples contained small, interconnected pores with sizes of 1.24 ± 0.25 µm and macroscopic, interconnected pores of 25.8 ± 4.7 µm in size. The effects of nonionic surfactants having different hydrophilic/lipophilic balance (HLB) values on foaming and pore size were also investigated. Materials made with surfactants having lower HLB values exhibited smaller pores and lower porosity, whereas higher HLB surfactants gave higher porosity and slightly larger macropores. Even so, the pore diameter could not be readily controlled solely by adjusting the HLB value. The findings of this work indicated that high porosity (>75%) and good compressive strength (>2 MPa) can both be obtained in the same porous material and that foaming agents with HLB values between 12.0 and 13.5 were optimal.

Topology Prediction of Gas-Separating Metal-Organic Frameworks with Low Symmetry Vertices.

Topology serves as a blueprint for the construction of reticular structures such as metal-organic frameworks, especially for those based on building blocks with highly symmetrical shapes. However, it remains a challenge to predict the topology of the frameworks from less symmetrical units, because their corresponding vertex figures are largely deformed from the perfect geometries with no "default" net embedding. Furthermore, vertices involving flexible units may have multiple shape choices, and the competition among their designated topologies makes the structure prediction in large uncertainty. Herein, the deformation index is proposed to characterize the symmetry loss of the vertex figure by comparing it with its ideal geometry. The mathematical index is employed to predict the shapes of two in situ formed Co-based metalloligands (pseudo-tetrahedron and pseudo-square), which further dictate the framework topology (flu and scu) when they are joined with the [Zr6O8]-based cuboid units. The two frameworks with very similar constituents provide an ideal platform to investigate how the pore shapes and interconnectivity influence the gas separation. The net with cylindrical channels outperforms the other with discreate cages in C3H8/C2H6/CH4 separation, benefiting from the facile accessibility of its interaction sites to the guests imposed by the specific framework topology.

Capture of carbonyl sulfide trace from natural gas by adsorption on zeolitic Nanostructure: Monte Carlo molecular simulation

The economic and environmental challenge for the oil and gas industries is to eliminate carbonyl sulfide (COS) from natural gas selectively. This compound can lead to corrosion and environmental damage, even when it is present in small amounts. The zeolites have been known as the appropriate adsorbent for COS. Grand Canonical Monte Carlo (GCMC) simulation has been used to explore the suitability of zeolite frameworks with different topologies on the adsorption and separation properties of mixtures containing industrial concentrations of COS in order to overcome the experimental tests that are difficult to handle. The adsorption isotherms for pure COS and COS/methane mixture on purely siliceous zeolites such as BEA, FAU, LTL, MFI, and MOR have been recorded at 298 K within a pressure range of 0–100 kPa. MFI zeolite, with its high adsorption capacity and isosteric heat, has been identified as the most suitable candidate for COS adsorption due to its ideal pore size and shape. Examining the density distribution snapshots reveals the preferred locations of zeolites for the COS adsorption. The findings could be systematically used in various case studies, thereby providing insights into selecting the best zeolitic nanostructure for the industrial removal processes of COS.

Adsorption Study of Methylene Blue and Methyl Red on Activated Carbon from Silver Composite Using the Extract of Spent Coffee Grounds

The activated carbon was prepared from silver composite via an extract of spent coffee grounds with phosphoric acid activation. The activated carbon was used to study the removal of methylene blue and methyl red from an aqueous medium. Fourier-transform infrared spectroscopy (FTIR) spectra confirmed the functional group of O–P–O that can interact with dye molecules and the reduction process of Ag+ to Ag0. Field Emission Scanning Electron Microscopy (FESEM) morphology suggests a porous and irregular polygonal shape. The efficiency removal and adsorption capacity of methylene blue reached 98.73% and 9.87 mg/g at pH 9, while methyl red reached 98.55% and 9.86 mg/g at pH 4. The kinetics adsorption study followed the pseudo-first order. The isotherm adsorption study followed the Langmuir model. Based on the kinetics and isotherm study, the adsorption study of methylene blue and methyl red is chemical sorption.

Keep it Simple: Ceramic Kelvin Cells via Liquid Crystal Display‐Stereolithography Printing

Additive manufacturing is the state‐of‐the‐art method for producing complex ceramic parts. For cellular materials, the freedom of design is particularly advantageous, as pore networks and shapes can be tailored. Herein, the direct printing of complex parts with high porosity using the cost‐effective manufacturing method of Liquid Crystal Display‐based stereolithography on low‐cost printers is determined. It is investigated how the architecture of the alumina Kelvin cells topology, their fabrication process, the printing parameters, and the microstructure affect the accuracy and mechanical properties of the printed samples. A notable reduction to a strut thickness of Kelvin cells down to 0.20 mm is achieved corresponding to a reduction of 1.5 compared with the state‐of‐the‐art literature (min. 0.35 mm). Ultrahigh porosities between 89.5% and 97.2% and a maximum compressive strength of 1.84 ± 0.17 MPa are reached due to the dense struts of the structure. Low‐cost and simple vat ceramic photopolymerization with high accuracy printing proves to be a promising candidate for the rapid and cost‐effective fabrication of highly porous and complex ceramic structures.

Effects of microscopic pore-throat structure on gas–liquid relative permeability: Porous media construction and pore-scale simulation

The porous media structure of the oil/gas reservoir changes greatly after long-term development, which subsequently influences the macroscopic relative permeability. To clarify the effects of microscopic pore-throat structure on macroscopic relative permeability, we first proposed a method to generate two-dimensional porous media images with adjustable structure parameters. The method is based on Delaunay triangulation and is similar to the pore-network generation process, which can provide binary images for direct numerical simulation of flow through porous media. Then, we established the single component multiphase Shan–Chen lattice Boltzmann method coupling the real gas equation of state. Finally, we discussed the effect of pore radius, coordination number, pore-throat ratio, pore shape, and wettability on the gas–liquid relative permeability curve using the lattice Boltzmann simulation. This study provides an effective method to generate porous media and explain the mechanism of relative permeability change at the pore scale.

Comprehensive experimental assessment of Samanea saman wood and leaves waste combustion in the aspect of ash-related problem

This research focuses on a comprehensive investigation of the combustion characteristics of Samanea saman wood and leaves, especially addressing ash-related problems. The evaluation consisted of theoretical calculations, experimental combustion, and ash analysis using scanning electron microscope (SEM) and x-ray diffraction (XRD). The slagging and fouling tendencies are similar in both biomass samples. However, S. saman wood has cleaner probe in slagging area than the other probe samples. This finding is in line with SEM and XRD analysis which, showing that S. saman wood ash is characterized by a porous angular shape and fine particles which are dominated by calcite 38.79 wt% and 29.22 wt% in slagging and fouling probe, respectively. On the other hand, S. saman leaves contain albite 62.94 wt% and 53.33 wt% in slagging and fouling probe respectively. In addition, S. saman wood demonstrates comparable combustion characteristics to other solid fuels, suggesting its potential for broader utilization as a biomass fuel.

Synergetic enhancement of ultimate strength and damping properties by pore structure in novel porous Cu-Al-Mn shape memory alloy

To meet the higher device vibration reduction requirements, novel porous Cu71Al18Mn11 shape memory alloys (SMAs) with controllable porosity were prepared using Cu, Al, and Mn elemental powders as raw materials. To further enhance the strength and damping performance of SMAs, a low-temperature reactive synthesis combined with spark plasma sintering (LTRS+SPS) process was used. In this paper, the effects of LTRS+SPS process on pore structure and texture, compressive strength, and damping properties of porous Cu71Al18Mn11 alloy were studied. The outcomes indicated that LTRS+SPS process can effectively improve both compressive strength and damping properties. The associated closed pore structure caused by this process and the second phase γ2 phase formed by element diffusion result in a variety in compressive strength from 324.6 MPa to 617.9 MPa, which were 3.9 times that of the comparable porosity alloy with alloy powder as raw material by vacuum sintering. Meanwhile, the damping value changed from 0.27 to 0.10, which was 4.5 times that of the homogeneous dense alloy. The increase in damping property is caused by the increase of motionable interfaces in the matrix for the introduction of pores, which leads to the increase of energy dissipation. Besides. the interaction between the second phase γ2 and dislocation contributes to the improvement of damping, as well as the compressive strength. These findings in this paper provide new insights and references for the structural design and microstructure design of high-performance Cu-based alloys.