Current Commercial Materials Research Articles

Strategically designed metal-free deep-ultraviolet birefringent crystals with superior optical properties.

Finding new birefringent materials with deep-ultraviolet (DUV, λ < 200 nm) transparency is urgent, as current commercial materials cannot meet the rapidly growing demands in related application fields. Herein, three guanidinium-based compounds, C(NH2)3CH3SO3, β-C(NH2)3Cl, and γ-C(NH2)3Cl, all featuring [C(NH2)3·X]∞ (X = CH3SO3 and Cl) pseudo layers, were designed through structural motif tailoring. Theoretical calculations indicate that these metal-free compounds all possess broad bandgaps (6.49-6.71 eV, HSE06) and remarkable birefringence (cal. 0.166-0.211 @ 1064 nm). Centimeter-sized C(NH2)3CH3SO3 crystals have been grown using a feasible aqua-solution method. Subsequently, to further optimize the properties, β/γ-C(NH2)3Cl was remolded by further tailoring the [C(NH2)3]+ cationic unit and the acceptor Cl- anion, and then the fourth compound NH2COF was theoretically constructed. Interestingly, NH2COF exhibits the desired coexistence of a wider bandgap (7.87 eV, HSE06) and giant birefringence (cal. 0.241 @ 1064 nm) attributed to its higher density of well-aligned birefringence-active groups (BAGs). Furthermore, among these four designed compounds, C(NH2)3CH3SO3 has been experimentally synthesized and exhibits a short UV cutoff edge. Centimeter-sized crystals have been grown using a feasible aqueous solution method. This study provides an effective strategy to optimize the density of BAGs for large birefringence and offers valuable insights into the strategic design of metal-free DUV birefringent crystals.

Influence of knot strength on the mechanical performance of a biodegradable gillnet

Ghost fishing is a global issue that can be addressed using fishing gear materials that do not persist in the marine environment. However, for these alternatives to be widely adopted, they must meet the same mechanical specifications as current commercial materials while degrading without any negative impact. The objective of this study was to compare a conventional gillnet made of polyamide 6 (PA6) with an alternative made of poly(butylene succinate-co-adipate-co-terephthalate) (PBSAT) at three different scales: monofilament, knot, and net. While the PBSAT monofilament’s strength was half that of the conventional PA6 net, knot and net losses were even more significant. This indicates a greater sensitivity of the material to the knot. Since the results between the knot and net scales were coherent, testing whole net panels is not necessary. Studying the curvature and the behaviour of the knot revealed its complex geometry and mechanical behaviour. Testing the weaver’s knot is a good indicator for studying the relevance of an alternative to conventional fishing gear materials. This should be considered when developing biodegradable nets in order to reduce ghost fishing at sea.

Roll-to-roll solvent-free manufactured electrodes for fast-charging batteries

Roll-to-roll solvent-free manufactured electrodes for fast-charging batteries

Development of Ti–Al–V alloys for usage as single-axis knee prostheses: evaluation of mechanical, corrosion, and tribocorrosion behaviors

Single-axis knee prosthesis is an artificial biomechanical device that provides motion to amputees without the need for assistance appliances. Besides it is mainly composed of metallic materials, the current commercial materials did not group adequate properties for long-term usage or accessible cost. This study produced and characterized Ti-(10 −x)Al-xV (x = 0, 2, and 4 wt.%) alloys for potential use as single-axis knee prostheses. The samples exhibited a gradual decrease in the density values, with proper chemical mixing of the alloying elements on the micro-scale. The phase composition exhibited a primary α phase with a minor α′ + β phase for the Ti-8Al-2V and Ti-6Al-4V samples. Due to their different atomic radius compared to Ti, the addition of alloying elements changed the cell parameters. Their selected mechanical properties (Young’s modulus, Vickers microhardness, and damping factor) performed better values than the CP-Ti grade 4. The samples also exhibited good corrosion properties against the simulated marine solution. The tribocorrosion resistance of the samples was better than the reference material, with the wear tracks composed of some tribolayers and grooves resulting from adhesive and abrasive wear. The Ti-10Al alloy displayed the best properties and estimated low cost to be used as single-axis knee prostheses.

Particle Surface Cracking Is Correlated with Gas Evolution in High-Ni Li-Ion Cathode Materials.

High-Ni layered oxide cathode materials (LiNixTM(1-x)O2, where x > 0.8) are of great interest because they offer increased capacity compared to current commercial materials within a narrow voltage range. However, recent studies have shown that these materials in their current form suffer from capacity fading when an upper cutoff voltage above 4.3 V vs Li/Li+ is used. While many studies have focused on the H2 → H3 transition as the primary cause of capacity fading, gas evolution studies show that degradation processes cannot be attributed to the H2 → H3 transition alone. In this work, differential electrochemical mass spectrometry (DEMS) is combined with titration mass spectrometry (TiMS) to measure gases evolved in a lithium half-cell during cycling as well as surface species which evolve gas upon addition of strong acid to an extracted cathode. Along with qualitative observations of particle cracking by scanning electron microscopy (SEM), these results reveal correlations between particle cracking, electrolyte reactivity, and carbonate oxidation and deposition on the cathode surface during the first charge of high-Ni cathode materials.

The Role of Gas Evolution in Particle Surface Cracking in Nickel-Rich Lithium-Ion Cathode Materials

Nickel-rich layered oxide cathode materials (LiNixTM(1-x)O2 where x > 0.8) are of great interest because they offer increased capacity compared to current commercial materials while maintaining compatibility with supply chain and production processes already in place. However, recent studies have shown that these materials in their current form are unsuitable for commercial applications due to the accelerated degradation caused by replacing more stable transition metals with the relatively unstable nickel. While various strategies have already been proposed to mitigate this issue, the fundamental degradation mechanism still needs to be better understood to inform the design of the next generation of nickel-rich cathode materials. In this work, differential electrochemical mass spectrometry (DEMS) is combined with titration mass spectrometry (TiMS) to measure gases evolved in a lithium half-cell during cycling as well as surface species which evolve gas upon addition of strong acid to an extracted cathode. Along with qualitative observations of particle cracking by scanning electron microscopy (SEM), these results reveal correlations between particle cracking, electrolyte reactivity, and carbonate oxidation and deposition on the changing cathode surface in nickel-rich cathode materials.

Energy efficient ethylene purification in a commercially viable ethane-selective MOF

• Cu(BDC)(DMF) using BDC as a cheap ligand was prepared using a simple and easy-to-scale up method. • Cu(BDC) simultaneously meets the requirements of high C 2 H 6 uptake and excellent ethane/ethylene separation selectivity. • Cu(BDC) exhibits excellent thermal stability and could be stored at room temperature for>1 year. • Cu(BDC) shows excellent separation ability with superior regeneration capability. Separating ethane (C 2 H 6 ) from ethylene (C 2 H 4 ) using ethane-selective adsorbents to replace energy-intensive cryogenic distillation technology is an important energy-saving method in the petrochemical industry to obtain high purity C 2 H 4 . Limited to the low separation efficiency in current commercial materials, it is very urgent and promising to fabricate such alkane selective adsorbents using cheap ligands and simple synthesis methods, which have characteristics such as stable structure, high C 2 H 6 uptake, and adsorption selectivity. In this work, we have used one of the cheapest ligands (terephthalic acid, H 2 BDC) to prepare Cu(BDC)(DMF) via a simple and easy-to-scale up solvothermal method. The activated Cu(BDC) exposed diamond-shaped one-dimensional pores form a stronger affinity with C 2 H 6 than C 2 H 4 through the double function of C-H∙∙∙π interactions and C-H∙∙∙O hydrogen bonds. Benefiting from the difference in these interactions, Cu(BDC) exhibited a higher adsorption capacity of C 2 H 6 (51.5 cm 3 /g) compared to C 2 H 4 (45.1 cm 3 /g) at 1 bar and 298 K, which resulted in high adsorption selectivity (2.0) for the C 2 H 6 /C 2 H 4 mixture (50/50, v/v). Breakthrough experiments indicated that Cu(BDC) successfully achieved the removal of C 2 H 6 from C 2 H 6 /C 2 H 4 (50/50 and 10/90, v/v) mixtures to obtain high purity C 2 H 4 (> 99.99%) using a one-step separation process. When compared with the benchmark materials, Fe 2 (O 2 )(dobdc) and NIIC-20, Cu(BDC) had the advantages of much lower preparation cost and enhanced structural stability. These comprehensive properties indicated that Cu(BDC) with a commercially viable price and synthesis process, could be potentially used for the C 2 H 6 removal step during the production of high purity C 2 H 4 .

Stable, Ductile and Strong Ultrafine HT-9 Steels via Large Strain Machining.

Beyond the current commercial materials, refining the grain size is among the proposed strategies to manufacture resilient materials for industrial applications demanding high resistance to severe environments. Here, large strain machining (LSM) was used to manufacture nanostructured HT-9 steel with enhanced thermal stability, mechanical properties, and ductility. Nanocrystalline HT-9 steels with different aspect rations are achieved. In-situ transmission electron microscopy annealing experiments demonstrated that the nanocrystalline grains have excellent thermal stability up to 700 °C with no additional elemental segregation on the grain boundaries other than the initial carbides, attributing the thermal stability of the LSM materials to the low dislocation densities and strains in the final microstructure. Nano-indentation and micro-tensile testing performed on the LSM material pre- and post-annealing demonstrated the possibility of tuning the material’s strength and ductility. The results expound on the possibility of manufacturing controlled nanocrystalline materials via a scalable and cost-effective method, albeit with additional fundamental understanding of the resultant morphology dependence on the LSM conditions.

Peering into Batteries: Electrochemical Insight Through In Situ and Operando Methods over Multiple Length Scales

Summary In order to overcome the limitations of static and destructive characterizations of Li-ion battery materials and components, comprehensive investigation peering into batteries over various length and time scales is essential. In this regard, emerging in situ and operando characterization methodologies focusing on multiple size domains become a powerful approach to resolve current challenges and navigate future directions. This perspective provides a series of illustrative examples of in situ and operando characterizations over atomic, crystallite/particle, electrode, and battery system length scales with a focus on two electrode material classes: insertion and conversion materials. The operating principles, features, analysis methods, and information gained from each characterization method are discussed. Herein, we present the necessity and opportunity for in situ and operando characterization of electrochemical energy storage materials and systems. Further, we suggest future directions to gain the insight needed to tackle currently intractable issues on Li-ion battery application, failure, and emerging design concepts.

Perovskite vulnerability uncovered

Methylammonium lead halide perovskites (CH3NH3PbI3) show great promise for solar-cell materials because they are more efficient at converting sunlight into electricity than current commercial materials are. Perovskite efficiencies can reach 22%, while those of commercial materials are about 15%. However, these perovskites suffer from a serious drawback: They degrade rapidly upon exposure to oxygen and light. A group including M. Saiful Islam at the University of Bath and Saif A. Haque of Imperial College London now reports experimental and theoretical evidence for the mechanism behind this degradation (Nat. Commun. 2017, DOI: 10.1038/ncomms15218). Their findings have led them to a way to protect these promising materials. The team previously determined that when light excites these crystals, it creates electrons, which can react with O2 to make reactive superoxide species. These superoxides then wreak havoc on the perovskite crystal structure, breaking it down to PbI2, methylamine, and water. In the new work,

Filler characteristics of modern dental resin composites and their influence on physico-mechanical properties

ObjectiveThe mechanical properties of dental resin-based composites (RBCs) are highly dependent on filler characteristics (size, content, geometry, composition). Most current commercial materials are marketed as “nanohybrids” (i.e. filler size <1μm). In the present study, filler characteristics of a selection of RBCs were described, aiming at identifying correlations with physico-mechanical properties and testing the relevance of the current classification. MethodsMicron/sub-micron particles (> or <500nm) were isolated from 17 commercial RBCs and analyzed by laser diffractrometry and/or electron microscopy. Filler and silane content were evaluated by thermogravimetric analysis and a sedimentation technique. The flexural modulus (Eflex) and strength (σflex) and micro-hardness were determined by three-point bending or with a Vickers indenter, respectively. Sorption was also determined. All experiments were carried out after one week of incubation in water or 75/25 ethanol/water. ResultsAverage size for micron-sized fillers was almost always higher than 1μm. Ranges for mechanical properties were: 3.7<Eflexwater<16.3GPa, 86<σflexwater<161MPa and 23.7<hardnesswater<108.3HV0.2/30. Values generally decreased after storage in ethanol/water (Δmax=86%). High inorganic filler contents (>75wt%) were associated with the highest mechanical properties (Eflex and σflex>12GPa and 130MPa, respectively) and lowest solvent sorption (∼0.3%). SignificanceMechanical properties and filler characteristics significantly vary among modern RBCs and the current classification does not accurately illustrate either. Further, the chemical stability of RBCs differed, highlighting differences in resin and silane composition. Since Eflex and sorption were well correlated to the filler content, a simple and unambiguous classification based on such characteristic is suggested, with three levels (ultra-low fill, low-fill and compact resin composites).

Development of experimental resin modified glass ionomer cements (RMGICs) with reduced water uptake and dimensional change

ObjectiveTo investigate water uptake, desorption, diffusion coefficient, solubility and dimensional changes of four experimental RMGICs in deionized water (DW) and artificial saliva (AS), and compare with two commercial RMGICs and control home liquids based on the two commercial materials used. MethodsTwo commercial RMGICs, RelyX Luting (RX, 3M ESPE) and Fuji Plus (FP, GC), two control home liquids and four new liquid compositions (F1, F2, R1, R2) comprising different percentages of the monomer THFM (tetrahydrofurfuryl-methacrylate) with the original monomer HEMA (2-hydroxyethyl-methacrylate) were used in this study. Home and experimental liquids were mixed with the corresponding commercial powder. Disk-shaped specimens (16mm diameter 1mm thickness) were immersed in DW/AS at 37°C (n=6) and weighed at regular time intervals. Percentage weight change with time was recorded. At 24 weeks, disks were desorbed in an oven at 37°C to minimum weight. ResultsAll new compositions showed lower water uptake and dimensional (volume) changes than the commercial products in both DW and AS. On desorption, FP showed higher weight loss compared to materials in the same group in both solutions (p<0.0001), with the exception of F2 in DW (p=0.283). RX had higher weight loss compared to R1 and R2 in DW and AS (p<0.0001). Fickian diffusion was confirmed for all materials immersed in DW and AS. SignificanceThe experimental compositions in this study have shown promising results when tested in both DW and AS with lower water uptakes and volume changes than commercial materials. This may lead to wider applications than current commercial materials.

Enhanced transparent-conducting fluorine-doped tin oxide films formed by Aerosol-Assisted Chemical Vapour Deposition

We report a systematic study into the importance of carrier solvent on the Aerosol-Assisted Chemical Vapour Deposition (AACVD) of fluorine-doped tin oxide (FTO) films. In particular, the resultant effects on both the optical transparency and electrical conductivity properties are reported with optimised films showing figures-of merit significantly beyond commercial products. Depositions were carried out at substrate temperatures of 500, 550 and 600 °C using either N2 or air as the carrier gas. The carrier solvent was found to have a marked effect on film quality and performance characteristics. Hall Effect results indicate that use of propan-2-ol as carrier solvent and air as carrier gas gave the best performing n-type FTO thin films overall that exhibited high optical transparency (>80% at 550 nm) and resistivity values of 4 × 10−4 Ω cm, with charge carrier density and carrier mobility values of 4 × 1020 cm−3 and 39 cm2 V−1 s−1 respectively, in addition to haze values of 10–15%. Such parameters are ideal for thin film solar cell applications and have significantly higher figures of merit compared to current commercial materials. Success of this method of deposition is attributed, in part, to a halide transfer reaction in which part fluorine substitution of the tin precursor occurs in the solvent resulting in a direct tin–fluorine bond. The work shows the key role carrier solvents play in AACVD in directing the system chemistry.

ChemInform Abstract: Nonlinear Optical Materials

The current state of materials development in nonlinear optics is summarized, and the promise of these materials is critically evaluated. Properties and important materials constants of current commercial materials and of new, promising, inorganic and organic molecular and polymeric materials with potential in second- and third-order nonlinear optical applications are presented.

Microstructure and mechanical properties of commercial, bronze-bond, diamond-abrasive tool materials

Bronze-matrix, diamond-particle composites are commonly employed as tool materials in grinding applications, in particular for precision grinding of optical materials. However, while tool selection and performance is often rationalized in terms of changes in tool “modulus/stiffness” or “hardness,” neither the range and variability of the mechanical properties nor the fundamental microstructural parameters controlling them are well understood. This has hindered quality control and prevented the accumulation of the industrial property-performance data essential to the development of improved tool materials and processes. In this study, bronze-bond diamond-abrasive composite tool materials, with systematic differences in their diamond sizes and concentrations, were obtained from different commercial vendors, characterized mechanically and microstructurally, and the results statistically analyzed. Microstructurally, a size dependent diamond distribution and relatively high levels of porosity (~10 vol%) were observed. The mechanical properties exhibited a high degree of variability, with statistically significant differences occurring based on the vendor and diamond concentration, but not diamond size. Porosity was shown to be the key microstructural parameter controlling mechanical properties. Porosity depended on vendor, diamond size, and diamond concentration, but large, nonsystematic variations were also observed, indicating that it is not consistently controlled in current commercial materials. Finally, the porosity and mechanical properties were shown to correlate strongly with ultrasonic wave speed over a wide range of tool materials, demonstrating a practical nondestructive method for tool characterization.

Synthesis and physical properties of estolides from lesquerella and castor fatty acid esters

Biodegradable, vegetable oil-based lubricants must have better low temperature properties as well as comparable cost to petroleum oils before they can become widely acceptable in the marketplace. The low temperature property usually measured is the pour point (pp), the minimum temperature at which the material will still pour. Viscosity and viscosity index also provide information about a fluid's properties where a high viscosity index denotes that a fluid has little viscosity change over a wide temperature range. Lesquerella oil is a good candidate for its development into a biodegradable lubricant as it is being developed as an alternative crop for the southwestern U.S. The hydroxy site on the fatty acid (FA) makes it a suitable site for esterification to yield estolides. Castor and lesquerella FA esters were combined with different types of saturated, unsaturated, and branched FAs to produce estolides. Castor and lesquerella estolide esters had the best cold temperature properties when capped with oleic (pp = −54 °C for castor and pp = −48 °C for lesquerella) or capped with a branched material, 2-ethylhexanoic acid (pp = −51 °C for castor and pp = −54 °C for lesquerella). As the saturation was increased in the estolide, pour and cloud points also increased. The increased saturation such as in stearic capped estolides allowed for sufficient alkyl stacking of these long saturated chains producing higher pour points. Oxidative stability of the estolides was compared between the oleic-castor estolide 2-ethylhexyl ester and the coco-castor estolide 2-ethylhexyl ester by the rotating bomb oxidation test (RBOT). The RBOT times for both estolides were low with a similar time of about 15 min. However, when the antioxidant package (3.5 wt.%) was added, the RBOT times increased to 403 min for the coco-castor estolide 2-ethylhexyl ester while still retaining its outstanding cold temperature properties, (pp = −36 °C and cp = −30 °C). The viscosity index ranged from 164 to 200 for these new hydroxy FA derived estolide 2-ethylhexyl esters. These oleic-castor and lesquerella estolide esters have displayed far superior low temperature properties (pp = −54 °C) than any other estolides reported to date. Due to the lack of solvent and catalysts, the cost of these estolides should be reasonable and more suitable as a base stock for biodegradable lubricants and functional fluids than current commercial materials.

Physical properties of saturated estolides and their 2-ethylhexyl esters

Biodegradable, vegetable oil-based lubricants must have better low temperature properties before they can become widely acceptable in the marketplace. These low temperature properties are usually measured as the material's pour point, the minimum temperature at which a material will still pour. Viscosity and viscosity index also provide information about a fluid's properties where a high viscosity index denotes that a fluid has little viscosity change over a wide temperature range. Oleic acid and a series of saturated fatty acids, butyric through stearic, were treated with 0.4 equivalents of perchloric acid at either 45 or 55 °C to produce complex estolides, dimers and tetramers of fatty acids linked through the double bond and carbonyl group. Yields varied between 45 and 65% after Kugelrohr distillation. The estolide number (EN), the average number of fatty acid units added to a base fatty acid, varied with reaction temperature as well as with the change in saturated fatty acids. The saturate-capped, oleic estolides were esterified with 2-ethylhexanol to obtain high yields of the corresponding ester. As the chain length of saturate capping material increased from C-4 to C-10, the low temperature performance of the estolide 2-ethylhexyl esters, namely pour point, decreased to −39 °C. The other mid-chain, saturated estolide 2-ethylhexyl esters C-6 through C-14 also had superior low temperature properties compared with their competitors; i.e. soy-based, synthetic-based and petroleum-based oils. The amount of oligomerization (EN) had an important role with the viscosities. Viscosity increased with higher oligomerization and the free acid estolides were generally several hundred centistokes (cSt) more viscous than the corresponding esters. The viscosity index ranged from 122 to 155 for the free acids estolides while the estolide 2-ethylhexyl esters had slightly higher indices which ranged from 172 to 196. These new estolide esters displayed far superior low temperature properties, and were more suitable as a base stock for biodegradable lubricants and functional fluids than current commercial materials.

Nonlinear Optical Materials

The current state of materials development in nonlinear optics is summarized, and the promise of these materials is critically evaluated. Properties and important materials constants of current commercial materials and of new, promising, inorganic and organic molecular and polymeric materials with potential in second- and third-order nonlinear optical applications are presented.

A metallurgical evaluation of a new tungsten product

An experimental program was conducted to evaluate a new form of granule tungsten produced via the hydrogen reduction of tungsten hexafluoride. The as-produced granule tungsten is characterized by both an unusually high purity and a very fine grain size. These characteristics can be retained in massive forms of the metal by consolidation of the granules with a gas-pressure bonding process. Consolidation by this method also offers close control over both dimensional tolerances and the degree of densification. Sheet bars thus prepared were rolled to sheet using practices commensurate with those being applied to current commercial materials. Sheet evaluation studies in comparison with commercial tungsten sheet included softening and recrystallization behavior, bend transition temperature, and intermediateto high-temperature tensile properties. The granule sheet showed superior resistance to recrystallization and lower transition temperatures; it also showed improved tensile strength, especially after high-temperature thermal cycling.