Li2CO3 Content Research Articles

Li2CO3 as a Modifier for PVA/PVP/PEG Blend Polymer Electrolytes: Effects on Structural Integrity, Electrical Performance, Thermal Behavior and Optical Properties

ABSTRACT The effects of incorporating lithium carbonate (Li2CO3) into a polyvinyl alcohol/polyvinyl pyrrolidone/polyethylene glycol (PVA/PVP/PEG) blend polymer electrolyte were investigated. Electrolytes were prepared via solution casting method, with Li2CO3 added at 10, 20, and 30 wt.% to the PVA/PVP/PEG blend (50/30/20 ratio). Fourier transform infrared spectroscopy analysis revealed interactions between the added salt and the polymer blend. The addition of both PEG and Li2CO3 resulted in increased ionic conductivity, reaching a maximum of 4.51 × 10− 5 S/cm at 30°C with 20 wt.% Li2CO3. Ionic conductivity also exhibited a positive temperature dependence. Optical analysis showed a decrease in the optical energy gap with the addition of PEG and Li2CO3. Differential thermal analysis indicated improved thermal stability with increasing Li2CO3 content, as evidenced by higher onset, endset, and midset temperatures. The enhanced properties of the modified electrolyte suggest its potential applicability in lithium-based electrochemical devices.

Molten-Salt-Mediated Chemical Looping Oxidative Dehydrogenation of Ethane with In-Situ Carbon Capture and Utilization.

The molten-salt-mediated oxidative dehydrogenation (MM-ODH) of ethane (C2H6) via a chemical looping scheme represents an effective carbon capture and utilization (CCU) method for the valorization of ethane-rich shale gas and concurrent mitigation of carbon dioxide (CO2) emissions. Here, stepwise experimentation with Li2CO3-Na2CO3-K2CO3 (LNK) ternary salts (i) assessed how each component of the LNK mixture impacted ethane MM-ODH performance and (ii) explored physicochemical and thermodynamic mechanisms behind melt-induced changes to ethylene (C2H4) and carbon monoxide (CO) yields. Of fifteen screened LNK compositions, nine exhibited ethylene yields greater than 50 % at 800 °C while maintaining C2H4 selectivities of 85 % or higher. LNK salts rich in Li2CO3 content yielded more ethylene and CO on average than their counterparts, and net CO2 capture per cycle reached a maximum of ~75 %. Extended MM-ODH cycling also demonstrated long-term stability of a high-performing LNK medium. Density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations suggested that the molten salt does not directly activate C2H6. Meanwhile, an empirical model informed by experimental data and reaction thermodynamics adequately predicted overall MM-ODH performance from LNK composition and provided insights into the system's primary drivers.

Optimizing the content of Li2CO3, Na2SO4 and TEA in fly ash–cement system by response surface methodology

With an optimized dosage, hardening accelerators become a vital means of modifying fly ash-cement system (FAC). This study comprehensively investigated the mechanical properties of FAC modified by Li2CO3, Na2SO4, and triethanolamine (TEA) under different dosages, and optimized the dosage of accelerators through the response surface method (RSM). The synergistic effect of accelerators on the hydration of FAC was characterized by thermogravimetric differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results demonstrated that the factors and response value followed a quadratic polynomial model. The regression coefficients R2 of the model were all greater than 0.9, indicating good agreement with the experimental data. The content of Li2CO3 and Na2SO4 had an extremely significant effect on the compressive strength of 1d and 3d, followed by TEA. The optimal mix ratio predicted by RSM was 0.12 % Li2CO3, 0.47 % Na2SO4, and 0.40 % TEA. Early hydration stages revealed that the combined action of these accelerators increased the formation of CH, CaCO3, and amorphous C-(A)-S-H gel. Microscopically, the surface of fly ash exhibited alkali-induced corrosion, thereby enhancing its pozzolanic reactivity.

Ion Conductive High Li+ Transference Number Polymer Composites for Solid-State Batteries

Solid-state electrolytes are a promising field of study to improve the safety and energy density of lithium-based batteries. Composite solid electrolytes seek to leverage both the desirable mechanical properties of polymers and the high conductivity of active ceramic fillers; however, Li+ transport through the composite, and especially the extent of Li+ through the ceramic phase, remains an open question.1, 2 Simulations suggest that decreasing interfacial resistance between polymer and ceramic would promote transport through ceramic particles.1 Our work seeks to improve Li+ transport in the ceramic phase by engineering both polymer and ceramic materials that minimize the interfacial resistance between the two.Traditional polymer electrolytes have a low transference number (~0.15) compared to ceramics (~1), and when combined in composites this mismatch has been suggested as a major contributor to interfacial impedance.3 We explore the effect of the transference number mismatch by using a single-ion conducting polymer poly((trifluoromethane)sulfonamide lithium methacrylate) (PMTFSILi). The Li+ transport in a composite electrolyte with high transference number PMTFSILi is compared with that of a system utilizing a lithium salt.Contaminants on ceramic surface can also contribute to interfacial resistance. We consider how lithium carbonate (Li2CO3) content on the surface of LLZTO (Li6.4La3Zr2Ta0.6O12) affects Li+ transport. Accompanying this study is a detailed description of washing procedures used to clean the LLZTO surface. Titration Mass Spectrometry (TiMS) is used to quantify Li2CO3 content in our ceramic particles and assess the effectiveness of our cleaning procedures. Inductively-coupled plasma mass spectrometry (ICP-MS) data also assists in measuring the impact (Li+ exchange and transition metal dissolution) of various washing procedures (basic, acidic) on the LLZTO particles.Solid-state NMR has proven to be a useful tool in deconvoluting Li+ transport in different phases of composite electrolytes2 and is the primary technique we use to quantify transport in our system. These findings will provide a deeper understanding into the relationship between interfacial resistance and Li+ transport in composite electrolyte systems and shed light on how material choices can better utilize the highly conductive ceramic phase for Li+ transport. Kim, HK., Barai, P., Chavan, K. et al.Transport and mechanical behavior in PEO-LLZO composite electrolytes. J Solid State Electrochem 26, 2059–2075 (2022). https://doi.org/10.1007/s10008-022-05231-wZheng J., Hu, Y. New Insights into the Compositional Dependence of Li-Ion transport in polymer-ceramic composite electrolytes. ACS Appl. Mater. Interfaces, 10, 4, 4113–4120 (2018). https://doi.org/10.1021/acsami.7b17301Mehrotra A. et al. Quantifying Polarization Losses in an Organic Liquid Electrolyte/Single Ion Conductor Interface. Electrochem. Soc. 161 A1681 (2014). https://doi.org /10.1149/2.0721410jes

Revealing the Role of Lithium Carbonate at Lithium Metal Anodes Through Study of Gas-Reacted Interphases

A stable, ionically-conductive solid electrolyte interphase (SEI) is vital to lithium (Li) metal anodes, yet key properties of common SEI phases remain unknown. Among these, Li2CO3, central to foundational SEI models, has been difficult to probe given its metastability on Li. To address this, we adopted two approaches: (i) synthesis and study of model Li2CO3-based SEI and (ii) cycling and titration-based analysis of SEI from Li–Cu cells with or without additive CO2, with the aim of modulating Li2CO3 content natively. In (i), reductive instability of Li2CO3 led to co-formation of Li2O and Li2C2 in a multiphasic film with a Li+ conductivity (∼8 × 10−9 S cm−1) more than 4x higher than previously-measured Li2O or LiF films. Li2CO3 content in native interphases from (ii) was found to correlate with decreased inactive Li0 accumulation and improved Coulombic efficiency (CE) across diverse electrolytes having moderate CE. In high CE electrolytes, however, capacity losses become dominated by SEI formation rather than inactive Li0, and Li2CO3 enrichment had negligible impact. This work updates understanding of SEI Li2CO3 formed in modern electrolytes, reveals a leading mechanism by which Li2CO3 can boost CE despite its metastability, and indicates the potential and limitations of enriching this phase through electrolyte design.

Suppressing Anodic Degradation of Lithium-Ion Batteries by Sinusoidal Waveform Charging Method

The effects of Constant current-Constant voltage charging and combined sinusoidal waveform charging methods on the internal structure of LiFePO4 battery have been discussed in detail in this study. Experimental results clearly indicated that after 600 cycles, the battery that utilized the charging method had retained about 94% of state of health. In the electrochemical impedance analysis and cyclic voltammetry tests, the portion of the SEI film impedance was increased about 0.08 mΩ. In the micro structured view, no significant SEI film formation was observed on the surface of the negative electrode that used the battery in the present charging method. Finally, in the analysis of the SEI film composition, it was found that the Li2CO3 and Li2O content in the Li element was only about 15.97% and 4.42% in the battery employing this charging method, and the battery component contents in the CC-CV charging method were 27.2% and 6.69% respectively.

The formation mechanism of NaLiTi3O7 and its effect on Li4Ti5O12 prepared by the NaCl molten salt flux method

Octahedral single-crystal Li4Ti5O12 materials with {111} crystalline surfaces exposed are prepared in NaCl flux, but the presence of NaLiTi3O7 in the product deteriorates the electrochemical performance of Li4Ti5O12 materials. Herein, the formation mechanism of NaLiTi3O7 in the product was discussed, and it was suggested that the impurity content is affected by the diffusion of the raw materials in the NaCl molten salt flux. The more NaCl is present, the more NaLiTi3O7 is generated. Because Li2O and TiO2 are separated by the salt, and both reactants should diffuse a much longer distance to react. Once the ratio of Li2O and TiO2 reaches 1:3, NaLiTi3O7 will form immediately; otherwise, if the ratio reaches 2:5, Li4Ti5O12 forms. Based on this hypothesis, NaLiTi3O7 will form because there is not enough Li2O to react with TiO2 to form Li4Ti5O12. Therefore, the content of Li2CO3 in the material preparation process was increased, allowing more Li2O to come into contact with TiO2 in the NaCl flux, thereby increasing the probability of Li4Ti5O12 formation and reducing the generation of NaLiTi3O7. Two modification strategies have been proposed to inhibit the generation of impurities. It was found that increasing the amount of Li2CO3 to 15 wt % in excess can reduce impurities of NaLiTi3O7, and further increasing its amount will cause the occurrence of new impurities. Adding a small amount of LiCl to the precursor mixtures can also inhibit NaLiTi3O7 generation in the prepared LTO materials and improve their electrochemical performances.

The Deep Eutectic Solvent in Used Batteries as an Electrolyte Additive for Potential Chitosan Solid Electrolyte Membrane

The electrolyte or ion conductor acts as a bridge to transfer the ions the electrodes generate. In general, electrolytes are in the form of liquids. However, liquid electrolytes have drawbacks, including needing to be more practical and leaking quickly. Therefore, people switch to solid matrix electrolytes as battery electrolytes. An ideal solid electrolyte membrane must have chemical stability, thermal stability, high ionic conductivity, high flexibility, low cost, and abundant material availability. Lithium extraction from used batteries using Deep Eutectic Solvent (DES) was found to be an intelligent solvent. Mixing the method with lithium salt on a chitosan membrane can increase conductivity. This study aims to determine the lowest resistance value and highest conductivity of solid polymer electrolytes using Li2CO3 from used batteries. After separating the Lithium-Cobalt component from the used battery, it was extracted with deep DES solvent and precipitated using Na2CO3 to produce the Li2CO3 compound. Polymer electrolyte was synthesized by mixing polyvinyl alcohol and adding 0.2 grams, 0.4 grams, 0.6 grams, 0.8 grams, and 1 gram of chitosan. Li2CO3 variables are 0.2 grams, 0.4 grams, 0.6 grams, 0.8 grams, and 1 gram. The results showed that the higher content of chitosan and Li2CO3 led to an increase in ionic conductivity. These results concluded that the best solid electrolyte membrane was obtained with a variation ratio of 0.2 grams of chitosan with the addition of 1 gram of Li2CO3.

Unveiling the parasitic-reaction-driven surface reconstruction in Ni-rich cathode and the electrochemical role of Li2CO3

Nickel-rich transition-metal oxides are widely regarded as promising cathode materials for high-energy-density lithium-ion batteries for emerging electric vehicles. However, achieving high energy density in Ni-rich cathodes is accompanied by substantial safety and cycle-life obstacles. The major issues of Ni-rich cathodes at high working potentials are originated from the unstable cathode-electrolyte interface, while the underlying mechanism of parasitic reactions towards surface reconstructions of cathode materials is not well understood. In this work, we controlled the Li2CO3 impurity content on LiNi0.83Mn0.1Co0.07O2 cathodes using air, tank-air, and O2 synthesis environments. Home-built high-precision leakage current and on-line electrochemical mass spectroscopy experiments verify that Li2CO3 impurity is a significant promoter of parasitic reactions on Ni-rich cathodes. The rate of parasitic reactions is strongly correlated to Li2CO3 content and severe performance deterioration of Ni83 cathodes. The post-mortem characterizations via high-resolution transition electron microscope and X-ray photoelectron spectroscopy depth profiles reveal that parasitic reactions promote more Ni reduction and O deficiency and even rock-salt phase transformation at the surface of cathode materials. Our observation suggests that surface reconstructions have a strong affiliation to parasitic reactions that create chemically acidic environment to etch away the lattice oxygen and offer the electrical charge to reduce the valence state of transition metal. Thus, this study advances our understanding on surface reconstructions of Ni-rich cathodes and prepares us for searching for rational strategies.

Study on mechanical and shrinkage properties of ES-UHPC

Some road and bridge projects to be repaired require materials that can quickly and easily obtain high mechanical properties. Added early strength agents are commonly used to improve the early strength of Ultra-high performance concrete (UHPC). Previous studies focused primarily on improving the early strength of UHPC, and few studies on how to reduce early age shrinkage of UHPC. This paper selected two inorganic early-strength agents, lithium carbonate (Li2CO3), nano-calcium carbonate (NC), and two organic early-strength agents, calcium formate(CF), triethanolamine(TEA),and an CaO expansion agent, which are commonly used. Experimental studies were carried out for single and compound early-strength agent systems in a cement-based UHPC system. The results showed three early-strength agents (NC, Li2CO3,CF) reduced the setting time and improved the early-strength of the UHPC. TEA had an adverse effect in the both single and compound systems. The 1-d compressive strength of the group(L0.15N3P10) reaches 84.5 MPa, with good workability and lower shrinkage. It can be used to prepare early strength ultra-high performance concrete (ES-UHPC) at room temperature. In terms of strength, shrinkage, and workability, it is suggested that the combination content of Li2CO3 is 0.15%, NC is 3%, and the expansion agent is 10% for fast repair and reinforcement projects.

Inhibiting Formation and Reduction of Li2 CO3 to LiCx at Grain Boundaries in Garnet Electrolytes to Prevent Li Penetration.

Poor ion and high electron transport at the grain boundaries (GBs) of ceramic electrolytes are the primary reasons for lithium filament infiltration and short-circuiting of all-solid-state lithium metal batteries (ASLMBs). Herein, it is discovered that Li2 CO3 at the GBs of Li7 La3 Zr2 O12 (LLZO) sheets is reduced to highly electron-conductive LiCx during cycling, resulting in lithium penetration of LLZO. The ionic and electronic conductivity of the GBs within LLZO can be simultaneously tuned using sintered Li3 AlF6 . The generated LiAlO2 (LAO) infusion and F-doping at the GBs of LLZO (LAO-LLZOF) significantly reduce the Li2 CO3 content and broaden the energy bandgap of LLZO, which decreases the electronic conductivity of LAO-LLZOF. LAO forms a 3D continuous ion transport network at the GB that significantly improves the total ionic conductivity. Lithium penetration within LLZO is suppressed and an all-solid-state LiFePO4 /LAO-LLZOF/Li battery stably cycled for 5500 cycles at 3C. This work reveals the chemistry of Li2 CO3 at the LLZO GBs during cycling, presents a novel lithium penetration mechanism within garnet electrolytes, and provides an innovative method to simultaneously regulate the ion and electron transport at the GBs in garnet electrodes for advanced ASLMBs.

A process using a thermal reduction for producing the battery grade lithium hydroxide from wasted black powder generated by cathode active materials manufacturing

Recent lithium consumption is doubled in a decade due to the Li-ion battery (LIB) demand for electric vehicles, the energy storage system, etc. The LIBs market capacity is expected to be in strong demand due to the political drive by many nations. Wasted black powders (WBP) are generated from the manufacturing of the cathode active material and spent LIBs. The recycling market capacity is also expected to expand rapidly. This study is to propose a thermal reduction technique for recovering Li selectively. The WBP, containing 7.4 % Li, 62.1 % Ni, 4.5 % Co, and 0.3 % Al, was reduced in a vertical tube furnace using a 10 % H2 gas as a reducing agent at 750 ºC for 1 h, and 94.3 % of Li was recovered from a water leaching, while other metal values, including Ni and Co remained in the residue. A leach solution was treated in a series of crystallisations, filtering, and washing. An intermediate product was produced and re-dissolved in hot water at 80 ºC for 0.5 h to minimise Li2CO3 content into a solution. A final solution was crystallised repeatedly to produce the final product. A 99.5 % of LiOH·H2O was characterised and passed the impurity specification by the manufacturer as a marketable product. The proposed process is relatively simple to utilise to scale up for bulk production, and it can also be contributed to the battery recycling industry as the spent LIBs are expected to overabundance within the near future. A brief cost evaluation confirms the process feasibility, particularly, for the company that produces cathode active material (CAM) and generates WBP in their own supply chain.

Predicting Compressive Strength and Hydration Products of Calcium Aluminate Cement Using Data-Driven Approach

Calcium aluminate cement (CAC) has been explored as a sustainable alternative to Portland cement, the most widely used type of cement. However, the hydration reaction and mechanical properties of CAC can be influenced by various factors such as water content, Li2CO3 content, and age. Due to the complex interactions between the precursors in CAC, traditional analytical models have struggled to predict CAC binders' compressive strength and porosity accurately. To overcome this limitation, this study utilizes machine learning (ML) to predict the properties of CAC. The study begins by using thermodynamic simulations to determine the phase assemblages of CAC at different ages. The XGBoost model is then used to predict the compressive strength, porosity, and hydration products of CAC based on the mixture design and age. The XGBoost model is also used to evaluate the influence of input parameters on the compressive strength and porosity of CAC. Based on the results of this analysis, a closed-form analytical model is developed to predict the compressive strength and porosity of CAC accurately. Overall, the study demonstrates that ML can be effectively used to predict the properties of CAC binders, providing a valuable tool for researchers and practitioners in the field of cement science.

In situ experimental study on the solubility and crystallization of zabuyelite (Li2CO3) in aqueous solution under igneous conditions

Zabuyelite (Li2CO3) was discovered in sedimentary environments, but it can form in igneous environments (e.g., rare-element pegmatites). This experiment extends the solubility and crystallization behaviors of Li2CO3 in an aqueous solution to igneous conditions (up to 783 °C and 8.24 kbar) from sedimentary conditions using a Bassett-type hydrothermal diamond-anvil cell. The solubility of Li2CO3 in an aqueous solution increases with temperature and pressure above the vapor-liquid critical pressure–temperature (P–T) condition. This is in contrast to its negative temperature coefficient in vapor-saturated water. The solubility data are fitted with the eq. R × T × lnxLi2CO3 = −3.0328 × 104–16.6486 × T + 3.3252 × 103 × P (r2 = 0.9643), where xLi2CO3 is the mole fraction (mol/mol) of Li2CO3, 714 ≤ T (K) ≤ 1056, 3.28 ≤ P (kbar) ≤ 8.24, and R is the gas constant. Zabuyelite grows quickly when nucleated from complete Li2CO3-dissolved aqueous solutions during cooling (at average rates of 0.2–3.0 μm2/s), especially in the initial exponential growth stage with approximately 18.7–34.2 μm2/s. This is orders of magnitude faster than other pegmatite minerals (e.g., spodumene), forming tabular crystals with the pseudo-hexagonal outlines of monoclinic systems in an aqueous solution. Nevertheless, zabuyelite forms microcrystals in Li2CO3 melt. In addition, zabuyelite crystallization (exhibiting significant temperature dependence) dominantly occurs at ~450–600 °C. The aforementioned crystallization features are identical with the features of zabuyelite contained in crystal-rich fluid inclusions from pegmatite, proving the zabuyelite's daughter-mineral nature in the fluid inclusions, hence indicating the primary origin of the crystal-rich inclusions in pegmatite. In the future, the solubility model of Li2CO3 in an aqueous solution can infer pegmatite formation conditions based on the analysis of the Li2CO3 content dissolved in the pegmatite crystallization media.

Outstanding enhancements in stability of LiNi0.8Mn0.1Co0.1O2 cathode by AlPO4/ACB double coating: Insights into surface structure and chemistry

Ni-rich layered cathode materials are highly attractive for high energy density lithiumion batteries, which however are facing serious surface issues. The effects of various coating materials on surface stability have been investigated, which mostly focus on exterior coating structure and properties. Herein, we focus on the surface variations of the cathode induced by the AlPO4/acetylene carbon black double coatings. It is the first time to discover that the AlPO4 coating greatly promotes crystallinity and lattice bonded oxygen near the surface of LiNi0.8Mn0.1Co0.1O2, which lead to decrease of Li/Ni disordering. The low ratio of Ni ions mixed in Li slab further prevents the serious Ni ions’ dissolution in electrolyte at high potential. Nevertheless, the discontinuous AlPO4 coating layer is unable to suppress the formation of Li2CO3 on surface. Additional carbon coating provides better coverage to effectively isolate the moisture and CO2 in air, and the content of surface Li2CO3 remarkably decreases. Eventually, the AlPO4/acetylene carbon black double coated LiNi0.8Mn0.1Co0.1O2 exhibits greatly enhanced charge/discharge stability at both 25℃ and 55℃.

Low sintering temperature, large strain and reduced strain hysteresis of BiFeO3–BaTiO3 ceramics for piezoelectric multilayer actuator applications

BiFeO3–BaTiO3 solid solutions with pseudo-cubic phase have received a lot of attention because of their large strain for potential piezoelectric multilayer actuator applications. However, the high sintering temperature, large dielectric loss and severe strain hysteresis hindered their real applications. In this work, Li2CO3 sintering aid modified 0.64BiFeO3-0.36BaTiO3 (BF-BT-L) ceramics were prepared by the high-temperature sintering method, and their phase structure, microstructure, electric properties as well as strain were investigated. With the increase of Li2CO3 content, the sintering temperature decreases down to 900 °C, and the relative density increases up to 96%. Of particular importance is that the dielectric loss and strain hysteresis of BF-BT-L ceramics are reduced by 40% and 47%, respectively, while BF-BT-L ceramics shows a large strain of 0.3% (60 kV/cm). The sintering temperature, relative density, strain, large-signal d33* and strain hysteresis of BF-BT-L ceramics are 900 °C, 96.5%, 0.3%, 500 pm/V, and 25% respectively. The reduced dielectric loss and strain hysteresis result from the enhanced relative density, decreased concentration of defects and partial phase transition from partial pseudo-cubic to rhombohedral one by Li2CO3 additions. Furthermore, BF-BT-L ceramics show positive temperature dependent strain, with large d33* and strain hysteresis of 675 pm/V and 15% at 200 °C respectively. The simple composition, low sintering temperature, large strain and reduced strain hysteresis of BF-BT-L ceramics indicate that they are promising candidates for high-performance and lead-free piezoelectric multilayer actuator applications.

Density, Molar Volume and IR Studies of Lithium Doped Bismuth Lead Borate Glasses

Structural analysis of 15Bi2O3-(50-x)PbO-35B2O3-xLi2CO3, x = 0,5,10,15 and 20) of lithium doped bismuth lead borate glass system (BPBL) using density, molar volume, and IR absorption spectra has been carried out for These glasses were prepared by the most reliable conventional melt quenching technique. Densities and molar volumes have been measured as a function of Li2CO3 content. Almost linear variation in the density and the molar volume has been observed in the present glasses and is attributed to the role of Li+ in these glasses. IR spectra of these glasses exhibit characteristic vibrations due to the borate network. The band at 400 cm−1-600 cm−1 due to absorption refers to metallic and cationic vibrations of metallic cations of Bi3+ and Li+.

Effect of Li2CO3 on the properties of Portland cement paste

In order to increase the application of CO2 in cementitious materials and to develop new additives for cement-based materials, the effect of lithium carbonate (Li2CO3) on the properties of Portland cement (PC) paste was investigated. The hydration heat of fresh paste was tested and the hydration products were characterized using XRD, TG–DTA, SEM and MIP. The results showed that both the initial and final setting time of the PC paste was prolonged with increasing Li2CO3 content. While, the compressive strength of the hardened PC paste at 1 day, 7 days and 28 days increased initially and then decreased. When the content of Li2CO3 was 0.09wt%, the initial and final setting time was increased by 19.8% and 27.7%, and the compressive strength at the age of 1 day, 7 days and 28 days was increased by 47.6%, 21.2% and 14.0%, respectively. Hydration heat, TG–DTA, XRD, SEM, pore structure and other tests showed that Li2CO3 promoted the formation of AFt, and prolonged the arrival time of hydrated calcium silicate peak, but increased the formation of hydrated calcium silicate. Especially when the Li2CO3 content was below 0.09wt%, the pore structure was also optimized. Based on the above results, when the content of Li2CO3 is not greater than 0.09wt%, not only the setting of the Portland cement paste can be retarded, but also the early strength can be enhanced. This can provide a good reference for the use of Li2CO3 in the preparation of new Portland cement-based material admixtures.

Solubility of CO2 in molten Li2Co3-LiCl

Solubility of CO2 in molten Li2CO3-LiCl was measured by a pressure differential method, and the enthalpy change of the solution was calculated on that basis. The relationships between the solubility and the enthalpy change, and the temperature and the composition of the melts were discussed. The results showed that when the temperature was 873?923 K and the Li2CO3 content was 10?50 mol%, the solubility of CO2 increased with decreasing temperature and/or increasing Li2CO3 content. The maximum solubility was 3.965 ? 10?7gCO2/gmelt at 873 K when the content of Li2CO3 was 50 mol%. The solution of CO2 was exothermic. With increasing temperature and Li2CO3 content, more enthalpy was needed for CO2 solution.

Hierarchical microstructure and two-stage corrosion behavior of a high-performance near-eutectic Zn-Li alloy

In order to improve mechanical and corrosion properties of biodegradable pure Zn, a knowledge-based microstructure design is performed on Zn-Li alloy system composed of hard β-LiZn4 and soft Zn phases. Precipitation and multi-modal grain structure are designed to toughen β-LiZn4 while strengthen Zn, resulting in high strength and high ductility for both the phases. Needle-like secondary Zn precipitates form in β-LiZn4, while fine-scale networks of string-like β-LiZn4 precipitates form in Zn with a tri-modal grain structure. As a result, near-eutectic Zn-0.48Li alloy with an outstanding combination of high strength and high ductility has been fabricated through hot-warm rolling, a novel fabrication process to realize the microstructure design. The as-rolled alloy has yield strength (YS) of 246 MPa, the ultimate tensile strength (UTS) of 395 MPa and elongation to failure (EL) of 47 %. Immersion test in simulated body fluid (SBF) for 30 days reveals that Li-rich products form preferentially at initial stage, followed by Zn-rich products with prolonged time. Aqueous insoluble Li2CO3 forms a protective passivation film on the alloy surface, which suppresses the average corrosion rate from 81.2 μm/year at day one down dramatically to 18.2 μm/year at day five. Afterwards, the average corrosion rate increases slightly with decrease of Li2CO3 content, which undulates around the clinical requirements on corrosion resistance (i.e., 20 μm/year) claimed for biodegradable metal stents.