Sensor Applications of Polyimides

Based on the “stable benzylic cation” theory, a novel borate ester with high hydrolytic stability was designed and synthesized. Its tribological properties as an additive in synthetic ester were evaluated using a four-ball tribometer. The results show that compared with ZDDP, the additive possesses outstanding loading-carrying and friction-reducing properties, and can improve the antiwear properties of the base oil dramatically. Moreover, its thermal stability, antioxidant performance, and hydrolytic stability were also evaluated, and indicated that the additive has excellent antioxidation performance, high hydrolytic stability, and high thermal stability. The worn surface of the steel ball was investigated by X-ray photoelectron spectroscopy (XPS) and the antiwear mechanism of the additive was preliminarily discussed.

Basalt waste fine powder deriving from ore processes was tested as raw solid aluminosilicate precursor for sustainable alkali activated materials (AAMs) with prospects for expanding sustainable alternatives to conventional structural and non-structural materials. Different formulations able to guarantee high consolidation degrees were explored, varying liquid-to-solid ratios (0.35-0.5), alkaline activators (sodium hydroxides and/or silicate solutions at different concentrations) and the amount of a secondary highly reactive precursor (metakaolin) as partial replacement of basalt waste (0%, 10%, 15% or 20% by weight). The formulations were screened, and the obtained materials were characterized in terms of microstructural features, density, water stability, pore size distribution, mechanical strength and thermal behavior up to 1000°C. Supplementary post-curing treatments by sodium silicate infiltrations were also explored, to optimize the water absorption and compressive strength of the obtained materials. The results highlighted that all the selected materials were characterized by a well reacted structure, with excellent thermal stability and tailorable pore size distribution in function of the basal-to-metakaolin relative amount and post-treatment steps. In particular, the basalt-only formulation activated with 8 M NaOH (B-H8) reached compressive strengths of 47.3 MPa, further increasing up to 63.7 MPa after silicate infiltration. The B/Mk formulation activated with sodium silicate (BMk-S) reached 29.1 MPa, increasing up to 59.2 MPa when using diluted silicate infiltration. Both systems exhibited low water absorption (≈ 10–15%) and high thermal stability up to 1000 °C . By modulating the composition and curing procedure, valuable materials were obtained even from the alkaline activation of basalt powder alone. These findings identify B-H8 and BMk-S (after infiltration) as the most performant formulations under the investigated processing conditions. This study demonstrates that basalt-based AAMs offer a sustainable alternative for structural materials, with preliminary assessments indicating low production costs jointly with good mechanical properties. • An effective route for the alkali activation of basalt dust was found • Good mechanical strengths were obtained without needing secondary precursors • All formulations exhibit good thermal resistance up to 1000 °C • Post-curing at 200 °C prevents efflorescence and improves the binders stability • Silicate infiltration significantly enhances strength and stiffness of the binders

Lithium bis(oxalato) borate (LiBoB) is promising lithium salt for electrolyte solutions of lithium-ion and lithium batteries because of high thermal and hydrolytic stability as well as high electrochemical stability of BoB- anion in wide potential range [1,2]. Sulfones are promising solvents and co-solvents for high-voltage batteries [3-7]. Sulfolane (tetramethylene sulfone) is the most known representative of sulfones. It has high dielectric permittivity (43.3 at 30 °C), high oxidizing stability (≥5 V vs. Li/Li+), high flash point (> 166 °C [8]) and low toxicity [3-5]. This work summarizes the results of studies on the conductivity, viscosity, electrochemical and thermal stability of LiBoB solutions in sulfolane with concentration range of 6·10-4 – 1.1 mol L-1. The maximum of specific conductivity is 1,7·10-3 S·cm-1 at 30 ºС and corresponds to ~0.8 mol L-1 (Fig. a). Activation energy of conductivity of 1M LiBoB in sulfolane is 23.3±0.5 kJ mol-1. Solutions of LiBoB in sulfolane are viscous (Fig. b). Activation energy of viscous flow for 1M LiBoB in sulfolane is 29.4±0.5 kJ mol-1. Association constant and limiting molar conductivity (λ0) of LiBoB in sulfolane are 6 mol-1·L and 8·10-4 S·m2·mol-1, correspondingly. The decomposition temperature (temperature at the initial decomposition) of 1M LiBoB in sulfolane is 286 °C, estimated by DSC method (Fig. c), and 260 °C, estimated by DTA method (Fig. d). Anodic stability of 1M LiBoB in sulfolane is ~5.8 V vs. Li/Li+, estimated at Pt working electrode. Therefore, lithium bis(oxalato) borate dissociates well in sulfolane, its solution has moderate conductivity, high thermal and electrochemical stability. Figure. Isotherms of specific conductivity (a) and dynamic viscosity (b) of LiBoB solutions in sulfolane; DSC (c) and DTA (d) of 1M LiBoB in sulfolane. This work was performed as part of a Government Order to Ufa Institute of Chemistry of the Russian Academy of Sciences by the Ministry of Science and Higher Education of the Russian Federation (Theme No. AAAA-A17-117011910031-7). References R. Younesi, G. M. Veith, P. Johansson, K. Edstrӧm, T. Vegge // Energy Environ. Sci., 2015, 8, pp. 1905-1922.Z. Liu, J. Chai, G. Xu, Q. Wang, G. Cui //Coordination Chemistry Reviews, 2015, 292, pp. 56-73.K. Xu // Chemical Reviews, 2004, 104 (10), pp. 4303-4417.A. Abouimrane, I. Belharouak, K. Amine // Electrochemistry Communications, 2009, 11, pp. 1073-1076.N. Shao, X.-G. Sun, S. Dai, D. Jiang // J. Phys. Chem. B., 2011, 115, pp. 12120-12125.S. Li, W. Zhao, C. Xiaoling, Y. Zhao, B. Li, H. Zhang, Y. Li, G. Li, X. Ye, Y. Luo // Electrochimica Acta, 2013, 91, pp. 282-292.F. Wu, H. Zhou, Y. Bai, H. Wang, C. Wu // ACS Appl. Mater. Interfaces, 2015, 7 (27), pp. 15098-15107.Electrolytes for Lithium and Lithium-Ion Batteries / Editors T. R. Jow, K. Xu, O. Borodin, M. Ue. // Modern Aspects of Electrochemistry, Springer, 2014, V. 58, 476 p. DOI: 10.1007/978-1-4939-0302-3. Figure 1

The interest is rapidly growing to use green and renewable polymers for engineering applications. Herein, biopolymers have shown great potential as environmentally friendly alternatives. Lignin is one of the most abundant biopolymers obtained from lignocellulosic biomass. Lignin constitutes approximately 15–35% of the lignocellulosic biomass. It has unique properties, such as high carbon content, high thermal stability, adhesive properties, biodegradability, biocompatibility and biological activities. Lignin has also the benefit of cost-effective processing with low energy requirements as a by-product of agricultural, paper and pulp industries. Taking account of these properties, a significant amount of research has been carried out toward the fabrication of advanced lignin-based materials with functional properties to be evaluated in several industrial applications for the last few decades. In recent years, lignin composites have gained popularity in the biomedical applications including tissue engineering scaffolds, wound dressing materials, drug delivery carriers and other medical applications. The studies have shown the suitability of lignin composites for multiple biomedical proposes. The present chapter presents a widespread overview of current achievements, limitations and future perspectives of lignin composites in biomedical field. In this chapter, recent advances in the fabrication, characterization and potential biomedical applications of lignin-based composites will be analyzed and discussed in detail.

Ultra-low hysteresis electrostrictive strain with high thermal stability in Bi(Li0.5Nb0.5)O3-modified BaTiO3 lead-free ferroelectrics

Polyimide (PI) film is an insulator and has been commonly used as a dielectric layer of a flexible printed circuit board (FPCB) due to its high thermal stability, well mechanical strength and excellent chemical resistance. For FPCB fabrication, the dielectric layer surface, PI surface, has to be metallized. Herein, we proposed an all-wet process to fabricate a copper diffusion barrier layer, avoiding Cu diffusion into the PI and a conducting layer, that is, a reduced graphene oxide (rGO) grafted on the PI surface. For a copper diffusion barrier layer, rGO has great electrical and thermal properties, and easy process than Ni barrier deposited by electroless plating. Owing to graphene oxide has a lot of carboxyl functional groups that forms carboxylate anions, it can ligand with the cations on the PI surface after the PI went through a chemical grafting process step. In this work, we successfully utilized rGO as a conducting layer on the PI surface, which can conduct copper plating on the PI surface. Furthermore, we demonstrated that rGO changed PI surface roughness by using an atomic force microscope (AFM). Keywords Reduced Graphene Oxide, Polyimide, Copper Electroplating References [1] Wei-Ping Dow, Guo-Liang Liao, Shang-En Huang and Sinn-Wen Chen, “Modification of Cu nanoparticles with a disulfide for polyimide metallization”, J. Mater. Chem. (2010) 20, 3600-3609 [2] T. Osaka, S. Wakatsuki, T. Masuda, M. Yoshino, N. Yamachika, J. Sasano, I. Matsuda, Y. Okinaka, “A Wet Process for Forming an Adhesive Copper Layer on Polyimide Film”, Electrochemistry, 76, 191 (2008). [3] Songfeng Pei, Hui-Ming Cheng, “The Reduction of Graphene oxide”, Carbon, 2012, 50, 3210-3228

Controllable growth of porous morphology in low dielectric polyimides via thermal-driven spontaneous phase separation

Evaluation of basic sites of ZIFs metal organic frameworks in the Knoevenagel condensation reaction

Global demand for lithium-ion secondary batteries have been increasing due to new market growth from electric vehicles and power storage systems. Lithium-ion batteries possess high power density, energy density and long cycle life without memory effect and little self-discharge, and have been primary energy storage system for commercial electronics. However, recent accidents regarding battery safety, such as Samsung Note 7 issue, has raised doubt among public about lithium-ion batteries as option for energy storage. Separator is one of the primary component for lithium-ion battery safety. Commercial separators like PE or PP not only possess outstanding mechanical and electrochemical performance, but also have thermal shutdown function that provide safety measure by pore—blocking with melted polyolefin materials. Nevertheless, polyolefin materials suffered serious shrinkage at elevated temperature, which cause internal short-circuited of batteries ; also, polyolefin materials have relatively low electrolyte uptake, and could be major obstacle for future lithium-ion battery application. Hence it’s necessary to design new type of separator that guarantee battery safety and demonstrate better electrochemical performance In this study, we proposed a brand-new method to design composite separator with high thermal stability, electrolyte uptake ability and thermal shutdown function. Polyimide(PI) nanofiber film was used as substrate and produced by electrospinning technique, and ultra-thin Low-Density-Polyethylene(LDPE) layer was laid upon PI by simple spin-coating method. Spin-coating method provided unique advantages such as ultra thin coating layer (less than 1 micron), uniform coating structure and simple process, and was yet been applied for construction of composite film as lithium-ion battery separator. Coating parameter was tuned to obtain the optimized composite separator. Field-emission scanning electron microscope (FE-SEM) was used to investigate morphologies of separators ; Contact angle measurement was conducted to verify electrolyte affinity of different separators ; A.C. impedance method was used to measure conductivities and verify thermal shutdown of separators, and electrolyte uptake of different separators were measured by electrolyte soaking method in an argon-filled glovebox. The composite film had sub-micron average pore size, and possessed excellent physical properties, for instance, high porosity(73%), electrolyte uptake(1300%), ion conductivity(4.3*10-4 S/cm), air permeability(gurley value=0), and thermal stability(no shrink up to 150。C). Thermal shutdown function of composite film was also confirmed by impedance measurement at elevated temperature. It was noticed that physical properties between pristine PI and composite film were similar owning to ultra-thin coating layer, which mitigate performance loss from LDPE coating. Afterward, full cell battery tests were conducted with CR2032 type coin cell (Cathode : LFP, anode : MCMB, electrolyte : 1 M LiPF6 in EC/EMC/DMC=1:1:1+1%VC, 1C=2.4mAh/g). The first cycle charge-discharge curves, rate capability and cyclic performance were conducted. The composite film showed flatter first cycle charge-discharge plateau, better capacity retention at higher C-rate (Composite film :102 mAh/g at 1C, 79% retention, Celgard 2500 : 73 mAh/g, 51% retention , w.r.t. 0.1C), and higher discharge capacity at 0.5C 50th cyclic test. The higher porosity and electrolyte uptake of composite film facilitated ion conduction and were the main cause for enhanced battery performance. With enhanced thermal stability and electrochemical performance, we expected this type of composite separator to be promising for future lithium-ion battery application. Figure 1

Cu2S has wide-ranging applications in the energy field, particularly as electrode materials and components of energy storage devices. However, the migration of copper ions is prone to component segregation and copper precipitation, impairing long-term thermal stability and service performance. Ce2S3 not only possesses the unique 4f electron layer structure of Ce but also has high thermal stability and chemical inertness. Here, we report for the first time that the thermal stability and mechanical properties of Cu2S can be significantly enhanced by introducing the dispersed phase Ce2S3. Thermogravimetry—differential scanning calorimetry (TG-DSC) results show that the addition of 6 wt% Ce2S3 improves the thermal stability of Cu2S sintered at 400 °C. X-ray diffraction (XRD) results indicate that the crystal structure of Cu2S gradually transforms to tetragonal Cu1.96S and orthorhombic Cu1.8S phase at 400 °C with the increase of Ce2S3 addition. Scanning electron microscopy (SEM) results show that the particle size gradually decreased with the increase of Ce2S3 amount, indicating that the Ce2S3 addition increased the reactivity. The Ce content in Cu2S increased gradually with the increase of Ce2S3 amount at 400–600 °C. The 7 wt% Ce2S3-Cu2S exhibits paramagnetic behavior with a saturation magnetization of 1.2 µB/Ce. UV-Vis analysis indicates that the addition of Ce2S3 can reduce the optical energy gap and enrich the band structure of Cu2S. With increasing addition of Ce2S3 and rising sintering temperature, the density of Ce2S3-Cu2S gradually increases, and the hardness of Ce2S3-Cu2S increases by 52.5% at 400 °C and by 34.2% at 600 °C. The friction test results show that an appropriate addition amount of Ce2S3 can increase the friction coefficients of Cu2S. Ce2S3 modification offers a novel strategy to simultaneously enhance the structural and service stability of Cu2S by regulating Cu ion diffusion and suppressing compositional fluctuations.

7 - Polyimides

Polyimide (PI) has been widely used for insulation in motors, integrated circuits, electric wire, cable, and so on, due to its high mechanical strength, thermal stability, chemical stability, and radiation resistance. We have examined the degradation of API (all-aromatic polyimide) and TPI (thermoplastic polyimide) soaked in H/sub 2/O or KOH by measuring recovery voltage. The peak value of the recovery voltage was found to depend on the soaking time. We have developed a theoretical equation of recovery voltage, and have found that the peak value of recovery voltage is a function of the dielectric constant. By measuring the recovery voltage, it is possible to diagnose the degradation of API and TPI.

11 - Dielectric Polymer Materials with High Thermal Stability

Preparation of functionalized halloysite reinforced polyimide composite aerogels with excellent thermal insulation properties

High-temperature energy storage polyimide dielectric materials: polymer multiple-structure design