Comparative study of conventional and microwave heating of polyacrylonitrile-based fibres

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Guozhen Zhao ◽  
Jianhua Liu ◽  
Lei Xu ◽  
Shenghui Guo
Keyword(s):  
Microwave Heating ◽  
Surface Defects ◽  
Energy Dispersive Spectrometer ◽  
Xrd Analysis ◽  
Economic Benefits ◽  
Heating Time ◽  
Oxidation Temperature ◽  
Conventional Heating ◽  
Heating Method ◽  
Molecular Arrangement

Abstract The effects of the conventional heating method and the microwave heating method on polyacrylonitrile-based fibres in the temperature range of 180–280 °C were investigated. Fourier transform infrared spectroscopy, X-ray wide-angle scattering, Raman spectroscopy, energy-dispersive spectrometer, scanning electron microscopy and bulk density were used to characterise the properties of the samples. Results show that the microwave heating method can shorten the pre-oxidation time, reduce pre-oxidation temperature and reduce the number of surface defects. The pre-oxidised fibres obtained by the microwave heating method exhibit not only good crystallite size but also a smooth surface. Atomic morphology and molecular arrangement are orderly inside the fibre. The FT-IR spectrum shows that the oxidation reaction occurs at 220 °C, and the CI value of PAN fibers stabilised by microwave heating is the larger than the fibers stabilised by conventional heating. XRD analysis shows that fibers stabilised by microwave heating have low stack domains. The SEM and Raman spectra indicate that hydrogen peroxide can improve the surface finish of the fibers and reduce defects. Microwave heating can reduce the pre-oxidation temperature by about 20 °C and shorten the heating time. The economic benefits of using this method are significantly improved.

A high-yield microwave heating method for the preparation of (phthalocyaninato)bis(chloro)silicon(IV)

2001 ◽  
Vol 05 (04) ◽  
pp. 376-380 ◽  
Author(s):  
DOMINIC A. DAVIES ◽  
CHRISTINA SCHNIK ◽  
JACK SILVER ◽  
JOSE L. SOSA-SANCHEZ ◽  
PHILIP G. RIBY
Keyword(s):  
Reaction Time ◽  
Microwave Heating ◽  
Silicon Tetrachloride ◽  
Conventional Heating ◽  
High Yield ◽  
Thermal Heating ◽  
Heating Method ◽  
Purification Time

The microwave heating synthesis of (phthalocyaninato)bis(chloro)silicon(IV) prepared from diiminoisoindolene and silicon tetrachloride in quinoline has been shown to be rapid (5 min reaction time compared to 30 min with thermal heating) and results in a high yield (91% compared to 71% using thermal heating). A modified microwave ashing furnace was used to heat the reaction mixture. The high yield has led to a reduction in the purification time to 1 h (compared to 4 h or more using conventional heating).

Preparation of Perovskite Type SrNiO3 Photocatalyst Material by Microwave Heating Method

2013 ◽  
Vol 826 ◽  
pp. 211-214 ◽  
Author(s):  
Xin Wang
Keyword(s):  
Microwave Heating ◽  
Heating Time ◽  
X Ray Diffraction ◽  
Calcination Time ◽  
Heating Method ◽  
X Ray ◽  
Preparation Conditions ◽  
Simulated Fuel ◽  
Photocatalytic Material ◽  
Perovskite Type

A new microwave heating method for reparation of SrNiO3 photocatalyst material was described. The optimum preparation conditions are that the microwave power is 560W, the microwave heating time is 30min, the calcination temperature is 700°C and the calcination time is 5h.The compound was measured by X-ray diffraction. In visible light and under the conditions of simulated fuel waste water, the photocatalytic properties of the catalyst material have been studied. The results showed the photocatalytic material prepared by that microwave heating have a high photocatalytic performance of degradation, and the degeneration rate of the dye may reach 98%.

Synthesis of Nanosized Carbonated Hydroxyapatite under Microwave Irradiation

2007 ◽  
Vol 330-332 ◽  
pp. 303-306 ◽  
Author(s):  
Xu Ran ◽  
Ji Yong Chen ◽  
Jun Guo Ran ◽  
Li Guo ◽  
Xing Dong Zhang
Keyword(s):  
Microwave Irradiation ◽  
Microwave Heating ◽  
Power Level ◽  
Xrd Analysis ◽  
Sem Analysis ◽  
Conventional Heating ◽  
Precipitation Method ◽  
Crystallization Time ◽  
X Ray Diffraction ◽  
Ir Analysis

In order to solve the problems on synthesizing carbonated hydroxyapatites (CHA) by the conventional heating precipitation method, such as long reaction and large particle size, poor crystallinity of CHA etc, the nanosized CHA particles have been synthesized by microwave heating method using phosphoric acid (H3PO4), calcium hydroxide (Ca(OH)2) and calcium carbonate (CaCO3 ) as starting materials in the present paper. The influences of power level and time of microwave irradiation on synthesis of CHA have been investigated. The X-ray diffraction (XRD) analysis has indicated that microwave heating will reduce CHA crystallization time and improve crystallinity of CHA. Scanning electron microscope (SEM) analysis has showed that CHA particles are of rod like morphology with about 60nm width and 200nm length respectively. Infrared spectroscopy (IR) analysis has confirmed the B-type CHA precipitate can be formed under microwave irradiation. The microwave irradiation plays an important role to promote the reaction and the synthesis of nanosized CHA particles.

Luminescence Properties of Y(P,V)O4 Synthesized by Microwave Heating

2009 ◽  
Vol 421-422 ◽  
pp. 356-359
Author(s):  
Ayano Toda ◽  
Kenji Toda ◽  
Tadashi Ishigaki ◽  
Kazuyuki Uematsu ◽  
Mineo Sato
Keyword(s):  
Microwave Heating ◽  
Single Mode ◽  
Heating Time ◽  
Microwave Oven ◽  
Homogeneous Distribution ◽  
Sintering Behavior ◽  
Heating Method ◽  
Red Emission ◽  
Multi Mode ◽  
Uv Excitation

Eu3+ doped and undoped Y(P,V)O4 phosphors were prepared using multi-mode and single-mode microwave oven operated at 2.45 GHz. In the case of the microwave heating method, the phosphor particles were non-aggregated. A homogeneous distribution of Eu ion was observed in the microwave synthesis. No sintering behavior found in the microwave heating may be attributed to a quite shorter heating time. The Eu3+ doped sample synthesized by microwave heating showed intense red emission under UV excitation.

Activation of kaolin with minimum solvent consumption by microwave heating

Clay Minerals ◽  
2014 ◽  
Vol 49 (5) ◽  
pp. 667-681 ◽  
Author(s):  
R. Z. Al Bakain ◽  
Y. S. Al-Degs ◽  
A. A. Issa ◽  
S. Abdul Jawad ◽  
K. A. Abu Safieh ◽  
...  
Keyword(s):  
Microwave Heating ◽  
Chemical Properties ◽  
Heating Time ◽  
Input Power ◽  
Conventional Heating ◽  
Tangent Loss ◽  
Experimental Conditions ◽  
Solid Ratio ◽  
Physicochemical Changes ◽  
High Dielectric

AbstractA kaolin clay was activated with 1.0 M H2SO4 solution at minimum liquid to solid ratio (L/S) using microwave heating. The optimum experimental conditions for activation were L/S ratio 3.0 mL 1 M H2SO4 per gram kaolin, microwave input power 500–600 W, and heating time 5–10 min. Activation at L/S < 3.0 mL/g using 1.0 M H2SO4 was not efficient, indicating the influence of solvent for absorbing microwaves more intensively and thus improving activation. Significant physicochemical changes were observed by the proposed procedure with smaller volumes of activator compared to the conventional heating method. Microwave input power and heating time have a strong influence on the quality of the final material; activation at high input power (>700 W) and longer heating times (>10 min.) are not recommended since they cause dissolution of kaolinite structure. Microwave-heated kaolin manifested better adsorption for tartrazine dye due to improvements in textural and chemical properties of kaolinite. Moreover, irradiation of used kaolinite has significantly improved dye desorption, increasing the importance of microwaves in regeneration/recycling studies. Detailed dielectric measurements of kaolin-acid mixtures recorded at frequencies much lower than 2.45 GHz revealed that absorption of radiation is highly dependent on the activator solution in the mixture. For 3.0 mL/g mixtures, high dielectric constant ε’ 5223, dielectric loss factor ε” 5083, tangent loss tan d 1.30, penetration depth dp 0.57 cm at (103 Hz), and AC-conductivity σ 0.032 Om–1 were determined at 105 Hz. Filling the pores of kaolin by acid solution increased the microwave absorption and hence de-alumination of kaolinite.

Rare Earth Doped Y2O3:RE3+ (RE= Eu, Tm and Tb) Powder Phosphors Prepared by Microwave Heating Technique

2006 ◽  
Vol 517 ◽  
pp. 227-231 ◽  
Author(s):  
Izdihar Ishak ◽  
Alias Daud
Keyword(s):  
Microwave Heating ◽  
Conventional Method ◽  
Blue Emission ◽  
Green Emission ◽  
Heating System ◽  
Heating Time ◽  
Conventional Heating ◽  
X Ray Diffraction ◽  
Powder Samples ◽  
Suitable Technique

A simple microwave heating system was designed for firing phosphor samples. An 800W magnetron operating at 2.45 GHz was used. The system is capable of reaching 1200oC in less than three minutes with the help of SiC succeptor. The synthesis technique prior to the microwave heating is described. The results indicate that the samples start to crystallize after 5 minutes. The X-Ray diffraction (XRD) data indicates that the sample is polycrystalline and acquires the host structure. The Photoluminescence (PL) and Photoluminescence Excitation (PLE) spectra for the powder phosphor prepared show similar results as those prepared using the conventional method. The Y2O3 powder samples doped with Eu show strong red emission at 630nm, the Tb doped samples show a strong green emission at 550nm and Tm doped samples shows blue emission at 460nm. The Scanning Electron microscope (SEM) picture taken show that the crystal size of the microwave irradiated samples was smaller in comparison to those prepared using the conventional method. This may be due to shorter heating time. These results indicate that the microwave heating technique is a reliable, fast and suitable technique to produce these powder phosphors. The characteristics of the phosphors are as good as those prepared using the conventional heating technique.

scholarly journals Change in Microwave-Absorbing Characteristics during the Oxidation Processes of an Ilmenite Concentrate

2017 ◽  
Vol 36 (8) ◽  
pp. 779-787
Author(s):  
Wei Li ◽  
Binfang Meng ◽  
Xinying Wang ◽  
Yuqi Liu ◽  
Libo Zhang
Keyword(s):  
Particle Size ◽  
Microwave Heating ◽  
Oxidation Time ◽  
Oxidation Temperature ◽  
Conventional Heating ◽  
Microwave Cavity ◽  
Substantial Impact ◽  
Oxidation Processes ◽  
Ilmenite Concentrate ◽  
Microwave Absorbing

AbstractMicrowave-absorbing characteristics of the oxidized ilmenite concentrate were measured by the method of microwave cavity perturbation. The effects of particle size, oxidation temperature and oxidation time on the microwave-absorbing characteristics were investigated. The particle size, oxidation temperature and oxidation time have substantial impact on the microwave-absorbing characteristics of the sample and therefore the microwave heating performance during the oxidation processes of the ilmenite concentrate. Results indicated that at the same oxidation time, the microwave absorbing characteristics decreased as the oxidation temperature increased, and at a constant temperature, the microwave absorbing characteristics of the sample decreased as the oxidation time increased. The microwave absorbing characteristics of the ilmenite concentrate with 80–120 mesh particle size was stronger than that of 200 mesh particle size. The microwave absorbing characteristics of products oxidized at 900 °C for 30 min were slightly weaker than those treated at 800 °C for 30 min and 900 °C for 20 min. The sample becomes less efficient in absorbing microwave energy as the oxidation proceeds. It is therefore recommended strong microwave absorbing materials or conventional heating be applied at the late stage of oxidation to aid microwave heating.

Synthesis of 20nm Colloidal Gold by Microwave Heating Method

2011 ◽  
Vol 204-210 ◽  
pp. 2045-2048
Author(s):  
Jing Jing Feng ◽  
Yang Zhao ◽  
Xiang Yu Yang ◽  
Hai Feng Zhao ◽  
He Huang
Keyword(s):  
Microwave Heating ◽  
Colloidal Gold ◽  
Small Diameter ◽  
Heating Time ◽  
Measurement Sensitivity ◽  
Immunochromatographic Strip ◽  
Heating Method ◽  
Gold Particles ◽  
Sterically Hinder ◽  
Colloidal Gold Immunochromatographic Strip

Colloidal gold immunochromatographic strip is a simple and convenient method for detecting harmful substances, such as Morphine and CLB. For the purpose of reducing sterically hinder and enhancing the measurement sensitivity, 20nm colloidal gold was choosed. Therefor, in this paper, the microwave heating method was improved to synthesize the 20nm collidal gold, the addtion of reductantan and the heating time were explored. We use transmission electron microscope and UV-vis spectroscope to character the size of series particles. The result showed that when 1ml reduces was added and the heating time was more than 2min, the gold particles were close to 20nm and much more uniform. In conclusion, the improved microwave method was more suitable for preparation of small diameter gold particles.

scholarly journals Microwaves and Heterogeneous Catalysis: A Review on Selected Catalytic Processes

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 246 ◽  
Author(s):  
Vincenzo Palma ◽  
Daniela Barba ◽  
Marta Cortese ◽  
Marco Martino ◽  
Simona Renda ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
Energy Saving ◽  
Microwave Heating ◽  
Microwave Radiation ◽  
Heterogeneous Catalysts ◽  
Conventional Heating ◽  
Specific Effects ◽  
Natural Choice ◽  
Future Challenges ◽  
Catalyzed Reactions

Since the late 1980s, the scientific community has been attracted to microwave energy as an alternative method of heating, due to the advantages that this technology offers over conventional heating technologies. In fact, differently from these, the microwave heating mechanism is a volumetric process in which heat is generated within the material itself, and, consequently, it can be very rapid and selective. In this way, the microwave-susceptible material can absorb the energy embodied in the microwaves. Application of the microwave heating technique to a chemical process can lead to both a reduction in processing time as well as an increase in the production rate, which is obtained by enhancing the chemical reactions and results in energy saving. The synthesis and sintering of materials by means of microwave radiation has been used for more than 20 years, while, future challenges will be, among others, the development of processes that achieve lower greenhouse gas (e.g., CO2) emissions and discover novel energy-saving catalyzed reactions. A natural choice in such efforts would be the combination of catalysis and microwave radiation. The main aim of this review is to give an overview of microwave applications in the heterogeneous catalysis, including the preparation of catalysts, as well as explore some selected microwave assisted catalytic reactions. The review is divided into three principal topics: (i) introduction to microwave chemistry and microwave materials processing; (ii) description of the loss mechanisms and microwave-specific effects in heterogeneous catalysis; and (iii) applications of microwaves in some selected chemical processes, including the preparation of heterogeneous catalysts.

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