Literatura científica selecionada sobre o tema "EHLA process fabrication"

Constructing ingenious microstructures, such as core–shell, laminate, microcapsule and porous microstructures, is an efficient strategy for tuning the combustion behaviors and thermal stability of energetic materials (EMs). Electrohydrodynamic atomization (EHDA), which includes electrospray and electrospinning, is a facile and versatile technique that can be used to process bulk materials into particles, fibers, films and three-dimensional (3D) structures with nanoscale feature sizes. However, the application of EHDA in preparing EMs is still in its initial development. This review summarizes the progress of research on EMs prepared by EHDA over the last decade. The morphology and internal structure of the produced materials can be easily altered by varying the operation and precursor parameters. The prepared EMs composed of zero-dimensional (0D) particles, one-dimensional (1D) fibers and two-dimensional (2D) films possess precise microstructures with large surface areas, uniformly dispersed components and narrow size distributions and show superior energy release rates and combustion performances. We also explore the reasons why the fabrication of 3D EM structures by EHDA is still lacking. Finally, we discuss development challenges that impede this field from moving out of the laboratory and into practical application.

In this nanotechnology era, nanostructures play a crucial role in the investigation of novel functional nanomaterials. Complex nanostructures and their corresponding fabrication techniques provide powerful tools for the development of high-performance functional materials. In this study, advanced micro-nanomanufacturing technologies and composite micro-nanostructures were applied to the development of a new type of pharmaceutical formulation, aiming to achieve rapid hemostasis, pain relief, and antimicrobial properties. Briefly, an approach combining a electrohydrodynamic atomization (EHDA) technique and reversed-phase solvent was employed to fabricate a novel beaded nanofiber structure (BNS), consisting of micrometer-sized particles distributed on a nanoscale fiber matrix. Firstly, Zein-loaded Yunnan Baiyao (YB) particles were prepared using the solution electrospraying process. Subsequently, these particles were suspended in a co-solvent solution containing ciprofloxacin (CIP) and hydrophilic polymer polyvinylpyrrolidone (PVP) and electrospun into hybrid structural microfibers using a handheld electrospinning device, forming the EHDA product E3. The fiber-beaded composite morphology of E3 was confirmed through scanning electron microscopy (SEM) images. Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis revealed the amorphous state of CIP in the BNS membrane due to the good compatibility between CIP and PVP. The rapid dissolution experiment revealed that E3 exhibits fast disintegration properties and promotes the dissolution of CIP. Moreover, in vitro drug release study demonstrated the complete release of CIP within 1 min. Antibacterial assays showed a significant reduction in the number of adhered bacteria on the BNS, indicating excellent antibacterial performance. Compared with the traditional YB powders consisting of Chinese herbs, the BNS showed a series of advantages for potential wound dressing. These advantages include an improved antibacterial effect, a sustained release of active ingredients from YB, and a convenient wound covering application, which were resulted from the integration of Chinese herbs and Western medicine. This study provides valuable insights for the development of novel multiscale functional micro-/nano-composite materials and pioneers the developments of new types of medicines from the combination of herbal medicines and Western medicines.

AbstractAdditive manufacturing (AM) enables the production of high value and high performance components with applications from aerospace to biomedical fields. We report here on the fabrication of poly(3-hexylthiophene): phenyl-C61-butyric acid methyl ester (P3HT:PCBM) thin films through the electrohydrodynamic atomization (EHDA) process and its integration as absorber layer for organic solar cells. Prior to the film fabrication, the optimization of the process was carried out by developing the operating envelope for the P3HT:PCBM ink to determine the optimal flow rate and the appropriate applied voltage to achieve a stable-cone deposition mode. The EHDA printed thin-film’s topography, morphology and optical properties were systematically analyzed. The root-mean-square roughness was found to vary significantly with the annealing temperature and the flow rate and ranged from 1.938 to 3.345 nm. The estimated film mass and thickness were found between 3.235 and 23.471 mg and 597.5 nm to 1.60 µm, respectively. The films exhibited a broad visible absorption spectrum ranging from ~ 340 to ~ 600 nm, with a maximum peak λmax located at ~ 500 nm. As the annealing temperature and the flow rate were increased, discernible alterations in the PCBM clusters were consequently observed in the blends of the film and the size of the PCBM clusters has decreased by 3% while the distance between them was highly reduced by as much as 82%.

Bacterial prostatitis is a challenging condition to treat with traditional dosage forms. Physicians often prescribe a variety of dosage forms with different administration methods, which fail to provide an efficient and convenient mode of drug delivery. The aim of this work was to develop a new type of hybrid material incorporating both electrosprayed core-shell microparticles and electrospun nanofibers. A traditional Chinese medicine (Ningmitai, NMT) and a Western medicine (ciprofloxacin, CIP) were co-encapsulated within this material and were designed to be released in a separately controlled manner. Utilizing polyvinylpyrrolidone (PVP) as a hydrophilic filament-forming polymer and pH-sensitive Eudragit® S100 (ES100) as the particulate polymeric matrix, a combined electrohydrodynamic atomization (EHDA) method comprising coaxial electrospraying and blending electrospinning, was used to create the hybrids in a single-step and straightforward manner. A series of characterization methods were conducted to analyze both the working process and its final products. Scanning electron microscopy and transmission electron microscopy revealed that the EHDA hybrids comprised of both CIP-PVP nanofibers and NMT-ES100 core-shell microparticles. Multiple methods confirmed the rapid release of CIP and the sustained release of NMT. The antibacterial experiments indicated that the hybrids exhibited a more potent antibacterial effect against Escherichia coli dh5α and Bacillus subtilis Wb800 than either the separate nanofibers or microparticles. The amalgamation of fibrous nanomedicine and particulate micromedicine can expand the horizon of new types of medicines. The integration of electrospinning and coaxial electrospraying provides a straightforward approach to fabrication. By combining hydrophilic soluble polymers and pH-sensitive polymers in the hybrids, we can ensure the separate sequential controlled release of CIP and NMT for a potential synergistic and convenient therapy for bacterial prostatitis.

La pollution de l’air est une préoccupation grandissante et les règlementations évoluent rapidement. Les émissions de particules au freinage des véhicules notamment, sont particulièrement dangereuses pour les voies respiratoires des populations. Dans cette thèse, des revêtements à base d’acier austénitique, ferritique (316L et 430L), de carbure (WC) et de cermets (NbCFeCr, TiCFeCr) sont mis en œuvre par procédé EHLA (Extreme High Speed Laser Material deposition) sur des disques de frein en fonte à graphite lamellaire. La nature, la proportion, la morphologie et la distribution des poudres utilisées, sont caractérisées dans le but d’optimiser un revêtement capable de répondre aux exigences de la future réglementation européenne. L’utilisation de poudres cermets sous forme d’agrégats, permet l’obtention de revêtements, pour lesquels la répartition des carbures est homogène. Grâce à un taux de cermet optimisé dans la matrice métallique, le comportement tribologique du disque revêtu est performant, notamment en termes d’usure. En effet, les différentes caractérisations sur bancs tribologiques, ont révélé une faible usure du disque revêtu et l’absence de défauts de type fissures traversantes jusqu’au substrat. Une étude de la nature et de la morphologie des particules émises lors des essais a été réalisée pour tenter d’identifier l’origine de ces particules. Finalement, le disque revêtu et la plaquette de frein émettent des particules fines sous une forme oxydée. Cependant, les revêtements à base de cermets NbCFeCr et TiCFeCr dans une matrice d’acier inoxydable, permettent une réduction des émissions de 75%, avec une plaquette de frein optimisée, par rapport à un disque non revêtu
Air pollution is a growing concern and regulations are changing. Particle emissions from braking vehicle are particularly dangerous for people's respiratory tracts. In this thesis, coatings based on austenitic, ferritic steels (316L and 430L), carbides (WC) and cermets (NbC FeCr, TiC FeCr) are developped by EHLA process (Extreme High Speed Laser Material deposition) on brake discs in lamellar graphite cast iron. The nature, proportion, morphology, and distribution of the powders used are characterized with the aim of optimizing a coating able to reach the requirements of future European regulations. The use of cermet powders in the form of aggregates makes it possible to obtain coatings for which the distribution of carbides is homogeneous. Thanks to an optimized rate of cermet in the metal matrix, the tribological behavior of the coated disc is efficient, particularly in terms of wear. Indeed, the various characterizations on tribological benches revealed low wear of the coated disc and the absence of defects such as cracks crossing down to the substrate. A study of the nature and morphology of the particles emitted during the tests was carried out to identify the origin of these particles. Eventually, the coated disc and brake pad emit fine particles in an oxidized form. However, coatings based on NbCFeCr and TiCFeCr cermets incorporated in a steel matrix, allow a reduction in emissions of 75%, with an optimized brake pad, compared to an uncoated disc