Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(12)00115-1.pdf

Recent advances in bone tissue engineering scaffolds.

Macroporous ceramics with pore sizes from 400 nm to 4 mm and porosity within the range 20%–97% have been produced for a number of well-established and emerging applications, such as molten metal filtration, catalysis, refractory insulation, and hot gas filtration. These applications take advantage of the unique properties achieved through the incorporation of macropores into solid ceramics. In this article, we review the main processing routes that can be used for the fabrication of macroporous ceramics with tailored microstructure and chemical composition. Emphasis is given to versatile and simple approaches that allow one to control the microstructural features that ultimately determine the properties of the macroporous material. Replica, sacrificial template, and direct foaming techniques are described and compared in terms of microstructures and mechanical properties that can be achieved. Finally, directions to future investigations on the processing of macroporous ceramics are proposed.

/pdf/processing-routes-to-macroporous-ceramics-a-review-1urld578zq.pdf

Processing Routes to Macroporous Ceramics: A Review

Preceramic polymers were proposed over 30 years ago as precursors for the fabrication of mainly Si-based advanced ceramics, generally denoted as polymer-derived ceramics (PDCs). The polymer to ceramic transformation process enabled significant technological breakthroughs in ceramic science and technology, such as the development of ceramic fibers, coatings, or ceramics stable at ultrahigh temperatures (up to 2000°C) with respect to decomposition, crystallization, phase separation, and creep. In recent years, several important advances have been achieved such as the discovery of a variety of functional properties associated with PDCs. Moreover, novel insights into their structure at the nanoscale level have contributed to the fundamental understanding of the various useful and unique features of PDCs related to their high chemical durability or high creep resistance or semiconducting behavior. From the processing point of view, preceramic polymers have been used as reactive binders to produce technical ceramics, they have been manipulated to allow for the formation of ordered pores in the meso-range, they have been tested for joining advanced ceramic components, and have been processed into bulk or macroporous components. Consequently, possible fields of applications of PDCs have been extended significantly by the recent research and development activities. Several key engineering fields suitable for application of PDCs include high-temperature-resistant materials (energy materials, automotive, aerospace, etc.), hard materials, chemical engineering (catalyst support, food- and biotechnology, etc.), or functional materials in electrical engineering as well as in micro/nanoelectronics. The science and technological development of PDCs are highly interdisciplinary, at the forefront of micro- and nanoscience and technology, with expertise provided by chemists, physicists, mineralogists, and materials scientists, and engineers. Moreover, several specialized industries have already commercialized components based on PDCs, and the production and availability of the precursors used has dramatically increased over the past few years. In this feature article, we highlight the following scientific issues related to advanced PDCs research: (1) General synthesis procedures to produce silicon-based preceramic polymers.
(2) Special microstructural features of PDCs.
(3) Unusual materials properties of PDCs, that are related to their unique nanosized microstructure that makes preceramic polymers of great and topical interest to researchers across a wide spectrum of disciplines.
(4) Processing strategies to fabricate ceramic components from preceramic polymers.
(5) Discussion and presentation of several examples of possible real-life applications that take advantage of the special characteristics of preceramic polymers. Note: In the past, a wide range of specialized international symposia have been devoted to PDCs, in particular organized by the American Ceramic Society, the European Materials Society, and the Materials Research Society. Most of the reviews available on PDCs are either not up to date or deal with only a subset of preceramic polymers and ceramics (e.g., silazanes to produce SiCN-based ceramics). Thus, this review is focused on a large number of novel data and developments, and contains materials from the literature but also from sources that are not widely available.

Polymer-Derived Ceramics: 40 Years of Research and Innovation in Advanced Ceramics

Functional materials by electrospinning of polymers

A novel method of selecting solvents for polymer electrospinning

A simple method was developed to produce silicon carbide foams using polysilane polymeric precursors Polyurethane foams were immersed in polysilane precursor solutions to prepare pre-foams Subsequently, these were heated in nitrogen at different temperatures in the range of 900°C to 1300°C The silicon carbide foams produced in this manner showed well-defined open-cell structures and the struts in the foams were free of voids The shrinkage which accompanies pyrolysis of the pre-foams was reduced with increasing the concentration of the polymeric precursor solutions

Preparation of silicon carbide foams using polymeric precursor solutions

A new method of forming silicon carbide–silicon nitride composite foams is presented. These are prepared by immersing a polyurethane foam in a polysilane precursor solution mixed with Si3N4 powder to form a pre-foam followed by heating it in nitrogen at >900°C. X-ray diffraction patterns indicate that a SiC–Si3N4 composite was formed after sintering the ceramic foam at >1500°C. Micrographs show that most of these foams have well-defined open-cell structures and macro-defect free struts. The shrinkage is reduced considerably due to the addition of Si3N4 particles.

Preparation of silicon carbide-silicon nitride composite foams from pre-ceramic polymers

Two types of polymeric precursors for silicon carbide (SiC) were dissolved in dichloromethane. Subsequently, between 10–80 wt% of silicon nitride (Si3N4) and titanium carbide (TiC) powder were added separately into the solutions to make SiC-Si3N4 and SiC-TiC suspensions. Cubes of polyurethane (PU) foams were soaked in precursor solution and suspensions and pyrolyzed in flowing nitrogen to produce SiC, SiC-Si3N4 and SiC-TiC composite foams. Some foams were heated further in nitrogen to 1600°C. Shrinkage observed after pyrolysis and further heating the foams was measured and can be reduced by varying the concentration of polymeric precursor, Si3N4 and TiC content. The foams produced have porosities in the range 85–96%. The average compressive strength of the foams is in the range of 1.1–1.6 MPa.

Porosity and Strength of Silicon Carbide Foams Prepared Using Preceramic Polymers

In this work, using multiple co-flows we demonstrate in-situ encapsulation of nano-particles, liquids and/or gases in different structural morphologies, which can also be deposited in a designated pattern by a direct write method and surface modification can be controlled to release encapsulated material. The range of possibilities offered by exposing a material solution to an applied electric field can result in a plethora of structures which can accommodate a whole host of biomedical applications from microfluidic devices (microchannels, loaded with various materials), printed 3D structures and patterns, lab-on-a-chip devices to encapsulated materials (capsules, tubes, fibres, dense multi-layered fibrous networks) for drug delivery and tissue engineering. The structures obtained in this way can vary in size from micrometer to the nanometer range and the processing is viable for all states of matter. The work shown demonstrates some novel structures and methodologies for processing a biomaterial.

M. Nangrejo

Papers

A novel method of selecting solvents for polymer electrospinning

Preparation of silicon carbide foams using polymeric precursor solutions

Preparation of silicon carbide-silicon nitride composite foams from pre-ceramic polymers

Porosity and Strength of Silicon Carbide Foams Prepared Using Preceramic Polymers

Engineering a material for biomedical applications with electric field assisted processing