Wyniki wyszukiwania - BazTech

1

Morphology Control of One-Dimensional Gallium Nitride Nanostructures by Modulating the Crystallinity of Sacrificial Gallium Oxide Templates

Ko Yun Taek, Park Mijeong, Park Jingyeong, Moon Jaeyun, Choa Yong-Ho, Lee Young-In

Archives of Metallurgy and Materials

|

2021

|

Vol. 66, iss. 3

709--712

EN

In this study, we demonstrated a method of controllably synthesizing one-dimensional nanostructures having a dense or a hollow structure using fibrous sacrificial templates with tunable crystallinity. The fibrous Ga2O3 templates were prepared by calcining the polymer/gallium precursor nanofiber synthesized by an electrospinning process, and their crystallinity was varied by controlling the calcination temperature from 500°C to 900°C. GaN nanostructures were transformed by nitriding the Ga2O3 nanofibers using NH3 gas. All of the transformed GaN nanostructures maintained a one-dimensional structure well and exhibited a diameter of about 50 nm, but their morphology was clearly distinguished according to the crystallinity of the templates. When the templates having a relatively low crystallinity were used, the transformed GaN showed a hollow nanostructure, and as the crystallinity increased, GaN was converted into a denser nanostructure. This morphological difference can be explained as being caused by the difference in the diffusion rate of Ga depending on the crystallinity of Ga2O3 during the conversion from Ga2O3 to GaN. It is expected that this technique will make possible the tubular nanostructure synthesis of nitride functional nanomaterials.

2

Electrostatic fabrication of polymer nanofibers

Czapka Tomasz, Kopaniarz Tomasz, Woś Angelika

Przegląd Elektrotechniczny

|

2020

|

R. 96, nr 2

174--177

EN

Fabrication process of nanofibers from the liquid polymer solution using electrospinning is described in the paper. In the experiments, polyvinylidene fluoride (PVDF) and dimethylformamide (DMF) were used as a polymeric material and a solvent, respectively. Additionally, the results of the measurements of diameters of obtained fibers, current-voltage characteristics of the process and calculation of resistivity of liquid polymer are presented.

PL

W pracy przedstawiono proces elektrostatycznego wytwarzania nanowłókien z roztworu ciekłego polimeru. W procesie elektroprzędzenia w roli polimeru i rozpuszczalnika użyto odpowiednio polifluorek winylidenu (PVDF) i dimetyloformamid (DMF). Dodatkowo badania obejmowały pomiary średnic otrzymanych włókien, charakterystyk prądowo-napięciowych procesu oraz wyznaczenie rezystywności ciekłego polimeru.

3

Innovations in poly(vinyl alcohol) derived nanomaterials

Kausar A.

Advances in Materials Science

|

2020

|

Vol. 20, nr 3(65)

5--22

EN

Poly(vinyl alcohol) (PVA) has been considered as an important commercial synthetic thermoplastic polymer. PVA is a low cost, reasonably processable, optically transmitting, heat stable, and mechanically robust plastic. PVA-based nanomaterials usually comprise of the nanocomposites (PVA/graphene, PVA/carbon nanotube, PVA/nanodiamond, PVA/metal nanoparticle) and nanofibers. The structural, optical, mechanical, and electrical properties of the PVA-based nanomaterials have been enhanced with nanofiller addition or nanostructuring. This review offers fundamentals and advanced aspects of poly(vinyl alcohol) and the derived nanomaterials. It highlights recent advances in PVA nanocomposites and nanofibers for potential applications. The PVA-based nanomaterials have been successfully employed in fuel cells, sensors, batteries, membranes, electronics, and drug delivery relevances. The challenges and opportunities to strengthen the research fields of PVA-based nanomaterials have also been presented.

4

Preparation of ceramic nanofibers of iron vanadate using electrospinning method

Khaksarfard Yasaman, Ziyadi Hakimeh, Heydari Akbar

Materials Science Poland

|

2019

|

Vol. 37, No. 4

645--651

EN

Because of special characteristics of vanadate compound, such as its sustainability, magneticity, high selectivity in reactions and catalytic character, this study aimed to preparation and analyzing novel ceramic iron vanadate (FeVO4) nanofibers. The ceramic nanofibers of iron vanadate were made by the combination of sol-gel and electrospinning methods. First, polyvinyl alcohol (PVA), as a matrix polymer, was mixed separately with ammonium metavanadate (NH4VO3) and iron (III) nitrate (Fe(NO3)3). As a result, the spinnable polymeric gel was obtained from the controlled mixture of these two precursors of ceramic material. Electrospinning of PVA/iron (III) nitrate/ammonium vanadate solution was done using an Electroris setup that enabled preparation of polymeric template nanofiber. Finally, iron vanadate nanofiber was obtained by calcination of polymer nanofiber at controlled temperature. The products were characterized with scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM) and Brunauer-Emmett-Teller (BET) surface area analysis.

5

Fabrication and characterization of Zn doped CuO nanofiber using newly designed nanofiber generator for the photodegradation of methylene blue from textile effluent

Sethuraman R. G., Venkatachalam T., Kirupha S. D.

Materials Science Poland

|

2018

|

Vol. 36, No. 3

520--529

EN

High aspect ratio, Zn doped copper oxide (Zn-CuO) nanofibers have been fabricated employing a newly designed electrospun coating unit using copper acetate, sodium hydroxide and polyethylene glycol in aqueous state. The prepared Zn doped copper oxide (Zn-CuO) nanofibers were sintered at 400 °C, 500 °C and 600 °C separately and characterized using X-ray diffraction XRD, Fourier transformation infrared spectroscopy FT-IR, scanning electron microscopy SEM, energy dispersive spectroscopy EDS. The average crystallite size was in the range of 28 nm to 30 nm. Optical properties of Zn-CuO nanofibers were analyzed using UV-DRS studies which showed a blue shift in the absorption band. An increase in band gap with the increase in postannealing temperature was observed due to the blue shift in absorption edge of CuO causing enhanced photodegradation. The catalytic properties of the CuO nanofibers were tested using methylene blue in aqueous medium. The influences of parameters responsible for high photodegradation were optimized and the rate of the photodegradation process was calculated using photodegradation kinetics. The reusability test was conducted to find the stability of the fabricated Zn-CuO nanofibers.

6

X Preparation and Characterization of Carbon-Based Composite Nanofibers for Supercapacitor

Gao D., Wang L., Wang C., Chang Y., Ma P.

Autex Research Journal

|

2017

|

Vol. 17, no. 2

129--134

EN

Polyacrylonitrile (PAN)/Co(OAc)2/carbon nanotubes (CNTs) composite nanofibers were fabricated via electrospinning with N,N-dimethylformamide (DMF) as solvent, and by carbonization and activation of the above precursor nanofibers, porous carbon composite nanofibers were successfully obtained. Scanning electron microscope, X-ray diffraction, ASAP 2020, and Solartron 1470 were used to characterize the surface morphology, the phase composition, specific surface area, and electrochemical property of the nanofibers, respectively. The result showed that some of the fibers were broken after sintering, and the surface area and pore volume of the porous C/Cu/CNTs were 771 m2/g and 0.347 cm3/g, respectively. The specific capacitance of the composite nanofibers reached up to 210 F/g at the current density of 1.0 A/g. Its energy density and power density were 3.1 Wh/Kg and 2,337 W/Kg, respectively, at the current of 0.5 and 5 mA.

7

Kształtowanie i dobór przegród filtracyjnych do powietrza wlotowego silników spalinowych pojazdów mechanicznych

Dziubak T.

Logistyka

|

2015

|

nr 3

1206--1216, CD 1

PL

W artykule przeanalizowano zalecenia dotyczące kryteriów oceny ryzyka dla prac w przemyśle off-shore wprowadzonych przez administracje państw mających największy udział w badaniach i wydobyciu morskich złóż naturalnych. Podano główne czynniki ryzyka dla obiektów prowadzących prace wydobywcze w warunkach morskich oraz metody jego określenia i przyjęte granice akceptacji. Wsparto się danymi statystycznymi zebranymi w ogólnoświatowej bazie danych sporządzonej przez Norweskie Towarzystwo Klasyfikacyjne DNV - Worldwide Offshore Accident Databank - WOAD obejmującej wypadki w sektorze off-shore od roku 1970 do 2014. W szczególności analizie poddane zostało ryzyko występujące na obszarach polskiej strefy ekonomicznej w związku z intensywnym rozwojem polskiego przemysłu badawczo wydobywczego.

EN

The basic rules shaping of filtration paper, and rules of selecting main dimensions of the cylindrical and panel filter cartridge are shown. Types of paper filters cartridge to the engine intake air filters of cars and trucks are presented. Shaping of traditional filters cartridges and modern design of filters, which is characteristic of the axial flow of air and low flow resistance are shown. Ways to prevent contact between the pleats of filter cartridge are presented. The criteria of selection of filtration papers to filter cartridges of intake air filters of engine are discusses. It has been shown that the selection of the active surface of paper according to maximum filtration velocity criterion is necessary, but not sufficient. It has been shown the need to have of many experimental data, which are characterized by a concrete type of paper, and the dust absorption coefficient.

8

Systemy uwalniania leków oparte na nanowłóknach

Nakielski P.

IPPT Reports on Fundamental Technological Research

|

2015

|

nr 1

2--215

PL

W pracy podjęto się zadania stworzenia systemu uwalniania leków opartego na zastosowaniu biodegradowalnych materiałów polimerowych wytworzonych z nanowłókien otrzymywanych metodą elektroprzędzenia. Bezpośrednim celem tej pracy było stworzenie aktywnego opatrunku wspomagającego operacje neurochirurgiczne. Praca zawiera eksperymentalną i numeryczną analizę procesu uwalniania i transportu leku do typowego płynu buforowego oraz analogu tkanki mającą na celu znalezienie optymalnych warunków kontrolowania w czasie i przestrzeni rozkładu stężenia leku. Uwalnianie leku w zaproponowanym modelu matematycznym opisano za pomocą równań adsorpcji-desorpcji, zaś transport w porowatym materiale z wykorzystaniem równania dyfuzji. Przedstawiona analiza parametrów materiałów z nanowłókien mających wpływ na szybkość uwalniania leków, opis matematyczny procesu lokalnego uwalniania leków z materiałów polimerowych, jak również transportu substancji aktywnych w organizmie w szczególności w tkance mózgowej, pozwoliły na zbudowanie modelu numerycznego umożliwiającego parametryczną ocenę wpływu czynników geometrycznych, struktury materiału, metody enkapsulacji leku we włóknach, jak i własności nanowłókien na profile uwalniania leków. W rezultacie przeprowadzonych badań stworzono materiały do operacji chirurgicznych oparte na trzech lekach neuroprotektycznych: lipofilowego alfa-tokoferolu, oraz hydrofilowych czynników wzrostu NGF (Nerve Growth Factor) i BDNF (Brain Derived Neurotrophic Factor). Jako nośników leków użyto biodegradowalnych i biokompatybilnych polimerów poli(L-laktydu-co-kaprolaktonu) PLC, poli(L-laktydu) PLLA, poli(DL-laktydu-co-glikolidu) PDLG. Przeprowadzone we współpracy z Instytutem Medycyny Doświadczalnej i Klinicznej PAN operacje neurochirurgiczne wykonane na modelu zwierzęcym potwierdziły pozytywny wpływ wytworzonych z nanowłókien materiałów na proces regeneracji tkanki nerwowej, zapobiegając jednocześnie szkodliwemu dla tego procesu bliznowaceniu tkanki.

EN

In this work the task of preparation of drug release system based on the biodegradable polymeric materials made from nanofibers obtained by electrospinning is presented. The main goal of this work was to create an active dressing for the use in neurosurgery. The work includes experimental and numerical analysis of the release process and transport of the drug to the typical buffer fluid and tissue simulator aimed at finding the optimal conditions to control in time and space the drug concentration distribution. The drug release in proposed mathematical model was described by the adsorption-desorption equation while transport in the porous material by the diffusion equation. Presented analysis of nanofibrous material parameters affecting drug release rate, the mathematical description of the process of local drug release from polymeric materials as well as the transport of active substances in the body, in particular in brain tissue, enabled the construction of a numerical model allowing a parametric evaluation of geometric factors, structure of the material, the drug encapsulation in the fibers, as well as the properties of nanofibers on the drug release profiles. In order to calibrate and validate the numerical model, the experimental system have been proposed to assess transport of the drug analog (rhodamine B and the protein BSA) from the material located in a tissue simulating medium. As a result materials for surgical operations based on three neuroprotective drugs: lipophilic alpha-tocopherol and hydrophilic growth factors NGF (Nerve Growth Factor) and BDNF (Brain Derived Neurotrophic Factor) were developed. As a drug carriers biocompatible biodegradable polymers poly(L-lactideco-caprolactone) PLCL, poly(L-lactide) PLLA, poly(DL-lactide-co-glycolide) PDLG were used. Conducted in collaboration with the Mossakowski Medical Research Centre PAS neurosurgeries performed on an animal model confirmed positive impact of nanofibrous materials on the process of regeneration of nerve tissue, preventing at the same time improper process of tissue scarring.

9

Polyaniline/CaTi0.8Fe0.2O3 composites for humidity sensors

Łańcucki Ł., Pasierb P.

Composites Theory and Practice

|

2015

|

R. 15, nr 4

233-242

EN

Polyaniline (PANI) is a conductive polymer material with a huge potential for constructing different electrochemical devices. Different strategies can be used to modify and optimize polymer properties from the point of certain applications, e.g. for the construction of gas sensors. Among those strategies, the formation of composite materials comprising PANI as the base material and ceramic powder material as a modifier is a promising approach. In this work the results concerning the influence of CaTi0.8Fe0.2O3 (CTFO) powders on some physicochemical properties of polyaniline (PANI) were presented and discussed. The materials were obtained by the polymerization of an aniline solution where CTFO powder, prepared by the sol-gel method was added. The microstructures of the materials were characterized using Scanning Electron Microscopy (SEM), the structure and phase composition was tested by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The electrical properties of the developed PANI-CTFO composites were determined using Electrochemical Impedance Spectroscopy (EIS). The gas sensing properties of the constructed sensor devices in the presence of water vapor were tested by measurements of DC electrical conductivity changes as a function of water vapor partial pressure. The current-voltage (I-U) characteristics were also used to characterize the influence of CTFO material on PANI electrical properties. It was found that the introduction of CTFO into the PANI host material leads to substantial changes in the material properties comparing to unmodified PANI. The discussion concerning the influence of the used modifiers on the structure, microstructure and electrical and sensing properties of the developed materials and observed correlation is also presented. The mechanism of the observed influence of CTFO on PANI properties is also proposed. The dominating role of the PANI-CTFO interface on the material properties is postulated.

PL

Polianilina (PANI) należy do grupy polimerów przewodzących posiadających ogromny potencjał z punktu widzenia możliwości budowy różnych urządzeń elektrochemicznych. W celu optymalizacji właściwości polimeru pod kątem określonego zastosowania, np. do konstrukcji czujników gazowych, stosuje się różne strategie modyfikacji. Wśród nich obiecującym podejściem jest utworzenie materiałów kompozytowych zawierających jako materiał bazowy PANI i jako modyfikator proszkowy materiał ceramiczny. W pracy przedstawiono wyniki dotyczące wpływu proszków CaTi0.8 Fe0.2O3 (CTFO) na niektóre właściwości fizykochemiczne polianiliny (PANI). Materiały zostały uzyskane przez polimeryzację roztworu aniliny, do których dodano proszku CTFO przygotowanego metodą zol-żel. Mikrostruktura materiałów została określona przy użyciu skaningowej mikroskopii elektronowej (SEM), strukturę i skład fazy zbadano przez dyfrakcję promieniowania X (XRD) i spektroskopii w podczerwieni z transformacją Fouriera (FTIR). Właściwości elektryczne opracowanych kompozytów PANI-CTFO wyznaczono za pomocą pomiarów metodą elektrochemicznej spektroskopii impedancyjnej (EIS). Charakterystyki sensorowe na obecność pary wodnej prototypowych czujników budowanych z otrzymanych materiałów były testowane poprzez pomiar zmian przewodnictwa elektrycznego w funkcji ciśnienia cząstkowego pary wodnej. Wykonano także pomiary charakterystyk prąd-napięcie (I-U), które wykorzystano do dodatkowego scharakteryzowania wpływ materiału CTFO na właściwości elektryczne PANI. Stwierdzono, że wprowadzenie CTFO do materiału bazowego PANI prowadzi do znacznych zmian właściwości materiału w porównaniu do niezmodyfikowanej polianiliny PANI. Przeprowadzono dyskusję dotyczącą wpływu stosowanych modyfikatorów CTFO na strukturę, mikrostrukturę i właściwości elekftryczne badanych materiałów na bazie PANI oraz określono wzajemne korelacje. Uzyskane wyniki wskazują na dominującą rolę granic faz CTFO-PANI na właściwości elektryczne badanych materiałów.

10

Surface effects on the wave propagation in composites with random dispersive parallel cylindrical nanofibers

Kong Z., Qiang F. W., Wei P. J., Tang Q.

Archives of Mechanics

|

2015

|

Vol. 67, nr 5

355--370

EN

The propagation of elastic waves in composites with randomly distributed parallel cylindrical nanofibers is studied. The non-classical boundary conditions on the surface of nanofibers are derived by using the surface elasticity theory. The scattering waves from an individual nanofiber are obtained by the plane-wave expansion method. These scattering waves from all nanofibers are summed up to obtain the multiple-scattering waves. The effective propagation constants (speed and attenuation) of coherent waves and the associated effective dynamical moduli of composites are evaluated numerically. Based on these numerical results, the influences of the surface effects on the effective dynamical properties of composites are discussed.

11

Manufacturing and characterisation of PMMA-graphene oxide (GO) nanocomposite sandwich films with electrospun nano-fibre core

Upadhyay J, Das R., Rao S., Liu D., Bhattacharyya D

Journal of Achievements in Materials and Manufacturing Engineering

|

2012

|

Vol. 55, nr 2

835--840

EN

Purpose: Nanocomposite materials, comprising of polymer matrices and nano-sized reinforcements, exhibit significantly enhanced mechanical and functional properties at extremely low filler loading. In recent years, graphene oxide (GO) has emerged as a new class of low cost nano-filler with high mechanical strength and stiffness, and alterable electrical properties. For nano-fillers with layered structure like GO, complete exfoliation and uniform dispersion of filler in the polymer matrices is essential to enhance the matrix-filler interaction and in turn the mechanical and/or functional property improvement. Conventional nanocomposite manufacturing methods including in-situ polymerisation and solvent processing encounter the problem of agglomeration of GO films. Additionally, its low bulk density presents difficulties in handling, and the energy requirement for mechanical mixing and extrusion processes is very high. In this work, we report manufacturing of poly(methyl methacrylate)-graphene oxide (PMMA-GO) nano-fibre mat using relatively novel approach of employing electrospinning technique. The manufactured electrospun core was inserted between plain polymer layers to prepare a robust and easy to handle sandwich film. Morphology and structure of the PMMA-GO nano-fibre cores was evaluated with scanning and transmission electron microscopy and X-ray diffractometry. The manufactured nano-fibre mat samples exhibited uniform diameter and dispersion. The functional parameters including thermal stability and gas barrier were evaluated with differential scanning calorimetry and oxygen permeation testing, and these functional properties were observed to be superior to that of monolithic polymer counterparts.

12

Conceptual study on a new generation of the high-innovative advanced porous and composite nanostructural functional materials with nanofibers

Dobrzański L. A., Pawlyta M., Hudecki A.

Journal of Achievements in Materials and Manufacturing Engineering

|

2011

|

Vol. 49, nr 2

550--565

EN

Purpose: The purpose of the paper is to analyse theoretically the possibilities of the development of a new generation of the high-innovative advanced porous and composite nanostructural functional materials with nanofibers and to study into the material science grounds of synthesis and/or production and formulation of such materials’ structure and properties and to characterise and model their structure and properties depending on the compositional, phase and chemical composition and the applied synthesis and/or production and/or processing processes, without the attitude towards any direct practical application or use, but with confirming the highly probable future application areas, using the unexpected effects of formulating such materials’ functional properties. Design/methodology/approach: In general, the study is of priority cognitive importance as theoretical considerations and the author’s initial analyses related to technology foresight concerning this group of issues as well as sporadical results of research provided in the literature, usually in its incipient phase, indicating a great need to intensify scientific research, to develop the new groups of materials with quite unexpected predictable effects, resulting from the use of nanofibers for fabricating super advanced composite and porous materials. Findings: The description of the state of the art for the subject of the study has been limited to the issues initially selected with an analysis with the method of weighted scores. Practical implications: The outcoming materials may have direct influence on the development of electronics and photonics, medicine and pharmacy, environmental protection, automotive industry, space industry, machine industry, textile and clothing industry, cosmetic industry, agriculture and food sector. Originality/value: The value of this paper lies in the fact that it proposes a new generation of the high-innovative advanced porous and composite nanostructural functional materials with nanofibers.

13

Epoxy resin/SiC nanocomposites. Synthesis and characterization

Poornima V., Thomas S., Huczko A.

Kompozyty

|

2010

|

R. 10, nr 1

11-14

EN

The sulicon carbide (SiC) nanofibers were produced by self-propagating high-temperature synthesis (SHS). Silicon and polytetrafluoroethylene (TEFLON™) powdered mixture was used as starting reactants. The raw product was chemically processed to isolate and purify SiC nanofibers, several nm in diameter and a length in a micron range. The nanomaterial was used to reinforce epoxy thermosets. Epoxy resin/SiC nanocomposites were prepared by using either ultrasonication or high shear mixing procedures. The dispersion and flexural properties of the nanocomposites prepared by two methods were evaluated and compared. Ultrasonication, in comparison to shear mixing method, yielded superior nanoscale dispersion according to scanning electron microscopy (SEM). As a result of the improvements in nanoscale dispersion, the corresponding improvements in flexural strength and modulus of produced composites were achieved. The better dispersion of SiC nanofibers and properties were obtained with nanocomposite containing 0.25 Phr (parts per hundred epoxy resin) nanomaterial. Thus, even such a low content of 1-D nanomaterial distinctly improves the properties of a composite.

PL

Otrzymywano nanowłókna węglika krzemu (SiC) na drodze samorozprzestrzeniającej się syntezy wysokotemperaturowej. Reagentem była mieszanina proszków krzemu oraz politetrafluoroetenu (Teflon ™). Otrzymany produkt poddano obróbce chemicznej w celu izolacji i oczyszczenia nanowłókien SiC, mających średnice rzędu kilkunastu-kilkudziesięciu nanometrów i długość kilku mikronów. Otrzymany nanomateriał zastosowano w celu modyfikacji - wzmocnienia termoutwardzalnej żywicy epoksydowej. Syntezowano nanokompozyty, stosując mieszanie ultradźwiekowe bądź wysoko wydajne mieszanie ścinające. Określono i porównano uzyskany stopień dyspersji oraz giętkości otrzymanych nanokompozytów. Badania mikroskopowe (SEM) wykazały, że mieszanie ultradźwiękowe jest znacznie efektywniejsze, jeśli chodzi o uzyskany stopień dyspersji nanowłókien. W wyniku podwyższenia dyspersji w nanoskali uzyskane nanokompozyty wykazały poprawę właściwości wytrzymałościowych. Najwyższy stopień dyspersji i najlepsze właściwości wykazały nanokompozyty zawierające nanowłókna SiC zmieszane z żywicą epoksydową w stosunku 0,25/100. Tak więc nawet tak niski dodatek jednowymiarowego materiału istotnie polepsza właściwości kompozytu.

14

Simulation of the electrospinning process

Karra S., Srinivasa A. R.

International Journal of Applied Mechanics and Engineering

|

2009

|

Vol. 14, no 1

175-188

EN

The electrospinning process is modeled and the bending instability of a slender viscoelastic jet is simulated. This is accomplished by modifying the discrete bead model by Reneker et al. (2000). Specifically, the force due to surface tension is incorporated using the expression suggested by Kowalewski et al. (2005) (see Eq.(7)). The results obtained by the use of this modification seem to be in accord with the experimental observations reported in Reneker et al. (2000) (Fig.2). An attempt is also made to simulate the effect of a secondary electric field which could be used to control the electrospinning process and whipping instability. It is observed that the external secondary field considered here, unwinds the jet spirals, reduces the whipping instability and increases the tension in the fiber.