In this paper, we focus on the recent advances on the physical chemistry of lignin. Emerging trends of incorporating lignin in promising future applications such as controlled release, saccharification of lignocelluloses, bioplastics, composites, nanoparticles, adsorbents and dispersants, in electro-chemical applications and carbon fibers, are also reviewed. We briefly describe the complexity of the lignin structure that influences the solution behavior, both as a macromolecule and a colloid, as well as the potential of being a renewable precursor in the development of high-value applications. Special attention is paid on summarizing the present knowledge on lignin colloidal stability and surface chemistry.

Lignin: Recent advances and emerging applications

Heteroatom-doped porous carbon materials (HPCMs) have found extensive applications in adsorption/separation, organic catalysis, sensing, and energy conversion/storage. The judicious choice of carbon precursors is crucial for the manufacture of HPCMs with specific usages and maximization of their functions. In this regard, polymers as precursors have demonstrated great promise because of their versatile molecular and nanoscale structures, modulatable chemical composition, and rich processing techniques to generate textures that, in combination with proper solid-state chemistry, can be maintained throughout carbonization. This Review comprehensively surveys the progress in polymer-derived functional HPCMs in terms of how to produce and control their porosities, heteroatom doping effects, and morphologies and their related use. First, we summarize and discuss synthetic approaches, including hard and soft templating methods as well as direct synthesis strategies employing polymers to control the pores and/or heteroatoms in HPCMs. Second, we summarize the heteroatom doping effects on the thermal stability, electronic and optical properties, and surface chemistry of HPCMs. Specifically, the heteroatom doping effect, which involves both single-type heteroatom doping and codoping of two or more types of heteroatoms into the carbon network, is discussed. Considering the significance of the morphologies of HPCMs in their application spectrum, potential choices of suitable polymeric precursors and strategies to precisely regulate the morphologies of HPCMs are presented. Finally, we provide our perspective on how to predefine the structures of HPCMs by using polymers to realize their potential applications in the current fields of energy generation/conversion and environmental remediation. We believe that these analyses and deductions are valuable for a systematic understanding of polymer-derived carbon materials and will serve as a source of inspiration for the design of future HPCMs.

Polymer-Derived Heteroatom-Doped Porous Carbon Materials.

This paper reviews the research and development works conducted over the past few decades on carbon fiber reinforced metal matrix composites (CFR-MMC). The structure and composition of carbon fiber and its bonding to metal matrix have an impact on the properties of the resulting CFR-MMC remarkably. The research efforts on process optimization and utilizing of carbon fibers are discussed in this review. The effect of carbon fiber on structural, physical and mechanical properties of metal matrix composite are studied as well. This review also provide an overview of the research to date on various fabrication methods that is used for production of CFR-MMC.

Carbon fiber reinforced metal matrix composites: Fabrication processes and properties

Graphene fiber: a new trend in carbon fibers

Motivated by their unique structure and excellent properties, significant progress has been made in recent years in the development of graphene-based fibers (GBFs). Potential applications of GBFs can be found, for instance, in conducting wires, energy storage and conversion devices, actuators, field emitters, solid-phase microextraction, springs, and catalysis. In contrast to graphene-based aerogels (GBAs) and membranes (GBMs), GBFs demonstrate remarkable mechanical and electrical properties and can be bent, knotted, or woven into flexible electronic textiles. In this review, the state-of-the-art of GBFs is summarized, focusing on their synthesis, performance, and applications. Future directions of GBF research are also proposed.

Graphene‐Based Fibers: A Review

This Review gives an overview of precursor systems, their processing, and the final precursor-dependent structure of carbon fibers (CFs) including new developments in precursor systems for low-cost CFs. The following CF precursor systems are discussed: poly(acrylonitrile)-based copolymers, pitch, cellulose, lignin, poly(ethylene), and new synthetic polymeric precursors for high-end CFs. In addition, structure-property relationships and the different models for describing both the structure and morphology of CFs will be presented.

Carbon Fibers: Precursor Systems, Processing, Structure, and Properties

Different softwood lignin O-acyl derivatives, i.e., methacrylated, hexanoylated, benzoylated, methoxybenzoylated, and cinnamoylated lignin are synthesized and subjected to melt spinning. In the presence of spinning aids such as vanillin and ethylene glycol dimethacrylate, multifilament melt spinning is accomplished with spinning speeds up to 500 m min−1, which allowed for realizing uniform precursor fibers 17 μm in diameter. Out of all acyl-derivatives of softwood lignin investigated, cinnamoylated softwood lignin (CL) turned out to be superior in terms of processability. CL-derived precursor fibers are oxidatively thermostabilized and then carbonized applying carbonization temperatures up to 2200 °C. Carbon fiber structure formation is followed in detail by wide-angle X-ray scattering and Raman spectroscopy. An orientation ≤53% and a d 002 spacing of 0.353 nm is achieved. According to small angle X-ray scattering, carbon fibers have a porosity of ≈38%. CL-derived carbon fibers are also characterized in terms of mechanical properties. Tensile strengths up to 0.93 GPa (average 0.75 GPa) are obtained and follow Weibull statistics. Elastic moduli are ≤66.5 GPa (average 41.1 GPa).

Carbon Fibers Prepared from Melt Spun Peracylated Softwood Lignin: an Integrated Approach

Dieser Aufsatz gibt einen Uberblick uber Prakursorsysteme, deren Verarbeitung und die resultierenden Eigenschaften der Carbonfasern (CF) in Abhangigkeit des Prakursors und berucksichtigt dabei die neuesten Entwicklungen auf dem Gebiet der alternativen Prakursoren fur die Herstellung von preisgunstigeren CF. Es werden folgende Prakursoren behandelt: Polyacrylnitril-basierte Copolymere, Pech, Cellulose, Lignin, Polyethylen und neue synthetische Polymerprakursoren fur hochwertige CF. Auserdem werden Zusammenhange zwischen Struktur und Eigenschaften aufgezeigt, und es werden verschiedene Modelle vorgestellt, die sowohl die Struktur als auch die Morphologie von CF beschreiben.

Carbonfasern: Präkursor‐Systeme, Verarbeitung, Struktur und Eigenschaften

Precursor-Fasern von Lignin-basierten Carbonfasern mit einem Gehalt an schmelzbarem modifiziertem Lignin, wobei das modifizierte Lignin durch die Formel L-O-CO-Rx (I), Formel L-O-Ry (II) und/oder Formel L-O-Rz (III)dargestellt ist, worin bedeuten L-O in den Formeln (I) und (II) einen veresterten oder veretherten Lignin-Rest, der Rest -CO-Rx in der Formel (I) einen Acyl-Rest, der Rest Rx und Ry einen aliphatischen und/oder aromatischen Rest und der Rest Rz in der Formel (III) durch einen Sulfonat-, Phosphat-, Phosphonat-, Phosphit-, Phosphonit- und/oder Phosphinit-Rest besetzt ist, bei deren Definition das Sauerstoffatom vom L-O einbezogen ist, das modifizierte Lignin einen Erweichungspunkt zwischen 80°C und 220°C aufweist und die Precursor-Fasern enthalten 1. ein Spinnadditiv (A) mit Weichmacherfunktion in Form einer aromatischen Verbindung sowie 2. ein einen Erweichungspunkt zwischen 130°C und 220°C aufweisendes Hilfspolymer (B) mit Vernetzer- und/oder Weichmacherfunktion. Ferner betrifft die Erfindung ein vorteilhaftes Verfahren zur Herstellung dieser Precursor-Fasern sowie deren Verwendung zur Herstellung von Carbonfasern, gegebenenfalls mit anschliesender Graphitisierung.

Lisa M. Steudle

Papers

Carbon Fibers: Precursor Systems, Processing, Structure, and Properties

Carbon Fibers: Precursor Systems, Processing, Structure, and Properties

Carbon Fibers Prepared from Melt Spun Peracylated Softwood Lignin: an Integrated Approach

Carbonfasern: Präkursor‐Systeme, Verarbeitung, Struktur und Eigenschaften

Precursor-Fasern von Lignin-basierten Carbonfasern, deren Herstellung und Verwendung