scholarly journals Preparation, Stabilization and Carbonization of a Novel Polyacrylonitrile-Based Carbon Fiber Precursor

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1150 ◽  
Author(s):  
Huichao Liu ◽  
Shuo Zhang ◽  
Jinglong Yang ◽  
Muwei Ji ◽  
Jiali Yu ◽  
...  
Keyword(s):  
Carbon Nanofibers ◽  
Carbon Fibers ◽  
High Performance ◽  
Great Influence ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Electrospinning Method ◽  
Lower Heat ◽  
Group 2

The quality of polyacrylonitrile (PAN) precursor has a great influence on the properties of the resultant carbon fibers. In this paper, a novel comonomer containing the sulfonic group, 2-acrtlamido-2-methylpropane acid (AMPS), was introduced to prepare P(AN-co-AMPS) copolymers using itaconic acid (IA) as the control. The nanofibers of PAN, P(AN-co-IA), and P(AN-co-AMPS) were prepared using the electrospinning method. The effect of AMPS comonomer on the carbon nanofibers was studied using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Raman spectrum. The structural evolutions of PAN-based nanofibers were quantitatively tracked by FTIR and XRD during the thermal oxidative stabilization (TOS) process. The results suggested that P(AN-co-AMPS) nanofibers had the lower heat release rate (ΔH/ΔT = 26.9 J g−1 °C−1), the less activation energy of cyclization (Ea1 = 26.6 kcal/mol and Ea2 = 27.5 kcal/mol), and the higher extent of stabilization (Es and SI) during TOS process, which demonstrated that the AMPS comonomer improved the efficiency of the TOS process. The P(AN-co-AMPS) nanofibers had the better thermal stable structures. Moreover, the carbon nanofibers derived from P(AN-co-AMPS) precursor nanofibers had the better graphite-like structures (XG = 46.889). Therefore, the AMPS is a promising candidate comonomer to produce high performance carbon fibers.

scholarly journals Thermal Analysis and Crystal Structure of Poly(Acrylonitrile-Co-Itaconic Acid) Copolymers Synthesized in Water

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 221
Author(s):  
Hailong Zhang ◽  
Ling Quan ◽  
Aijun Gao ◽  
Yuping Tong ◽  
Fengjun Shi ◽  
...  
Keyword(s):  
Carbon Fibers ◽  
High Performance ◽  
Thermal Stabilization ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Air Atmosphere ◽  
Composition And Structure ◽  
Average Size ◽  
Dsc Curves

The composition and structure of polyacrylonitrile (PAN) precursors play an important role during thermal stabilization, which influences the properties of the resulting carbon fibers. In this paper, PAN homopolymer and PAN-itaconic (IA) copolymers with different IA contents were synthesized by aqueous phase precipitation polymerization. The effects of IA content on the structure and thermal properties were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The morphology of PAN polymers showed that the average size of the PAN particles increased with the increase of IA content in the feed. The content of the IA comonomer on the copolymers was quantitatively characterized by the relative absorbance intensity (A1735/A2243) in FTIR spectrum. With the increase of IA content in the feed, PAN-IA copolymers exhibited lower degree of crystallinity and crystal size than the control PAN homopolymer. The results from DSC curves indicated that PAN-IA1.0 copolymers had lower initial exothermic temperature (192.4 °C) and velocity of evolving heat (6.33 J g−1 °C−1) in comparison with PAN homopolymer (Ti = 238.1 °C and ΔH/ΔT = 34.6 J g−1 °C−1) in an air atmosphere. TGA results suggested that PAN-IA1.0 copolymers had higher thermal stability than PAN homopolymer, which can form a ladder structure easier during thermal processing. Therefore, PAN-IA1.0 copolymers would be a suitable candidate for preparing high performance PAN based carbon fibers.

Conversion of Lignin-Nanofibers to CNFs

NANO ◽  
2015 ◽  
Vol 10 (06) ◽  
pp. 1550092 ◽  
Author(s):  
Aili Ma ◽  
Li Zhou ◽  
Jie Chang
Keyword(s):  
Carbon Nanofibers ◽  
Carbon Fibers ◽  
Carbonization Temperature ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Compact Structure ◽  
Graphitization Degree ◽  
Novel Method ◽  
Thermal Stability Of

In this study, a novel method, electrospinning, was used to prepare lignin-based carbon nanofibers. The major material was lignin. The chemical and thermal properties of different lignins were characterized to determine their suitability for partial incorporation of polyacrylonitrile (PAN). Then the precursor fibers were carbonized at a temperature from 600°C to 1000°C, respectively to prepare biomass-based carbon nanofibers. The influences of carbonization temperature on prepared carbon nanofibers were investigated by X-ray diffraction (XRD), Raman, thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results indicated that the diameter of prepared precursor fibers and carbon fibers were about 200nm and 100nm, respectively. The increase of temperature has little influence on the carbon fiber graphitization degree. The D band of the carbon fibers carbonized at 900°C is lowest. The thermal stability of the carbon fibers changes little with rising temperature when carbonized temperature exceeds 900°C, and carbon fibers carbonized under 900°C have most compact structure. Therefore, the above conclusions make clearly that 900°C is the optimal carbonization temperature for preparing lignin-based carbon nanofibers in this technique. Meanwhile, the study is a doubled-edged enterprise that aims to recycle the waste from pulping industry as well as to turn it into a valuable material.

scholarly journals Enhanced Water Solubility and Oral Bioavailability of Paclitaxel Crystal Powders through an Innovative Antisolvent Precipitation Process: Antisolvent Crystallization Using Ionic Liquids as Solvent

Pharmaceutics ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1008 ◽  
Author(s):  
Qilei Yang ◽  
Chang Zu ◽  
Wengang Li ◽  
Weiwei Wu ◽  
Yunlong Ge ◽  
...  
Keyword(s):  
Oral Bioavailability ◽  
High Performance ◽  
Water Solubility ◽  
Water Soluble ◽  
Precipitation Process ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Antisolvent Precipitation ◽  
Antisolvent Crystallization ◽  
Artificial Gastric Juice

Paclitaxel (PTX) is a poor water-soluble antineoplastic drug with significant antitumor activity. However, its low bioavailability is a major obstacle for its biomedical applications. Thus, this experiment is designed to prepare PTX crystal powders through an antisolvent precipitation process using 1-hexyl-3-methylimidazolium bromide (HMImBr) as solvent and water as an antisolvent. The factors influencing saturation solubility of PTX crystal powders in water in water were optimized using a single-factor design. The optimum conditions for the antisolvent precipitation process were as follows: 50 mg/mL concentration of the PTX solution, 25 °C temperature, and 1:7 solvent-to-antisolvent ratio. The PTX crystal powders were characterized via scanning electron microscopy, Fourier transform infrared spectroscopy, high-performance liquid chromatography–mass spectrometry, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, Raman spectroscopy, solid-state nuclear magnetic resonance, and dissolution and oral bioavailability studies. Results showed that the chemical structure of PTX crystal powders were unchanged; however, precipitation of the crystalline structure changed. The dissolution test showed that the dissolution rate and solubility of PTX crystal powders were nearly 3.21-folds higher compared to raw PTX in water, and 1.27 times higher in artificial gastric juice. Meanwhile, the bioavailability of PTX crystal increased 10.88 times than raw PTX. These results suggested that PTX crystal powders might have potential value to become a new oral PTX formulation with high bioavailability.

Properties of Carbon Nanofibers Prepared from Polyacrylonitrile/Poly(methyl Methacrylate) Blend

2009 ◽  
Vol 79-82 ◽  
pp. 353-356
Author(s):  
Wei Pan ◽  
Yan Chen ◽  
Xiao Wei He
Keyword(s):  
Methyl Methacrylate ◽  
Carbon Nanofibers ◽  
Carbon Fibers ◽  
Nitrogen Atmosphere ◽  
Wet Spinning ◽  
X Ray Diffraction ◽  
X Ray ◽  
Poly Methyl Methacrylate ◽  
Graphite Crystallite ◽  
Raman Microspectrometry

The polyacrylonitrile(PAN)/poly (methyl methacrylate)(PMMA) blend fibers were prepared by wet-spinning technique and carbonized over the temperature range of 400-1000°C in nitrogen atmosphere. After carbonization of the blend fibers, the PMMA component removed and the PAN component left in the form of carbon nanofibers. Morphology of the carbon nanofibers were investigated via scanning electron microscopy (SEM), and the carbonization behavior of the fibers were examined via x-ray diffraction (XRD), Raman microspectrometry. The optimal condition made carbon fibers with great L/D ratio and diameter less than 200 nm. XRD and Raman spectra shows that the PAN/PMMA blend fibers treated at 600°C produced some graphite crystallite.

scholarly journals Improved Model of Scheduling Algorithm

2018 ◽  
pp. 104-106
Author(s):  
Artur Vardanyan
Keyword(s):  
High Performance ◽  
Cluster Computing ◽  
Scheduling Algorithm ◽  
Great Influence ◽  
Cluster Management ◽  
Task Scheduling Algorithm ◽  
Long Time ◽  
Improved Model ◽  
First In First Out

Cluster computing is becoming increasingly practical for high performance computing research and development. A computer cluster is a set of connected computers that work together so that, they can be viewed as a single system. Clusters offer a scalable means of linking computers together to provide an expansive environment for hosting enterprise applications. As the number of nodes in cluster configurations grows, the cluster administration becomes more challenging. We need to study the challenges of cluster management and to provide a solution. To have an effective cluster management we need to have an effective task scheduling algorithm. With the explosive growth of information, the demand on computing is sharply increasing. Due to a large number of computing tasks, the scheduling algorithm is an important part of cluster computing and has a great influence on the quality of claster service. In cluster computing, some large tasks may occupy too many resources and some small tasks may wait for a long time based on First-In-First-Out (FIFO) scheduling algorithm. This paper provides an overview of an improved scheduling algorithm that shortens the execution time of tasks and increases the resource utilization.

Optimization of Structure of Soft Block for Design of Adaptive Polyurethanes

2020 ◽  
Vol 869 ◽  
pp. 273-279
Author(s):  
Marina A. Gorbunova ◽  
Denis V. Anokhin ◽  
Valentina A. Lesnichaya ◽  
Alexander A. Grishchuk ◽  
Elmira R. Badamshina
Keyword(s):  
Mutual Influence ◽  
Glycol Adipate ◽  
Mass Ratio ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Crystallization Conditions ◽  
Crystalline Domains ◽  
Kinetics Of

A synthesis of new di-and triblock polyurethane thermoplastic copolymers containing different mass ratio of two crystallizing blocks - poly (1,4-butylene glycol) adipate and poly-ε-caprolactone diols was developed. Using combination of danamometric analysis, IR-spectroscopy, differential scanning calorimetry and X-ray diffraction, the effect of the soft block composition and crystallization conditions on crystal structure and thermal behavior of the obtained polymers have been studied. For the triblock copolymers we have shown a possibility of control the kinetics of material hardening and final mechanical characteristics due to the mutual influence of polydiols during crystallization. In the result, the second crystallizing component allows to control amount, structure and quality of crystalline domains in polyurethanes by variation of crystallization conditions.

Stretching-Induced Orientation for Improving the Mechanical Properties of Electrospun Polyacrylonitrile Nanofiber Sheet

2008 ◽  
Vol 47-50 ◽  
pp. 1169-1172 ◽  
Author(s):  
Si Zhu Wu ◽  
Feng Zhang ◽  
Xiao Xiao Hou ◽  
Xiao Ping Yang
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanofibers ◽  
Molecular Orientation ◽  
High Performance ◽  
Carbon Composites ◽  
X Ray Diffraction ◽  
Fiber Alignment ◽  
X Ray ◽  
N2 Atmosphere ◽  
Potential Precursor

Partially aligned and oriented polyacrylonitrile(PAN)-based nanofibers were electrospun from PAN and CNTs/PAN in the solution of dimethylformamide(DMF) to manufacture the carbon nanofibers. The as-spun nanofibers were hot-stretched in a temperature controlled oven to enhance its crystallinity and molecular orientation. Therefore it were stabilized at 250 ( under a stress, and carbonized at 1000 ( in N2 atmosphere by fixing the length of the stabilized nanofiber to convert them into carbon nanofibers. With the hot-stretched process and with the content of CNTs, the mechanical properties will be enhanced correspondingly. The crystallinity of the stretched fibers confirmed by X-ray diffraction has also increased. For PAN nanofibers, the improved fiber alignment and crystallinity resulted in the increased mechanical properties, such as the modulus and tensile strength of the nanofibers. It was concluded that the hot-stretched nanofiber and the CNTs/PAN nanofibers can be used as a potential precursor to produce high-performance carbon composites.

High-performance red phosphorus/carbon nanofibers/graphene free-standing paper anode for sodium ion batteries

2018 ◽  
Vol 6 (4) ◽  
pp. 1574-1581 ◽  
Author(s):  
Xiaoxin Ma ◽  
Long Chen ◽  
Xiaohua Ren ◽  
Guangmei Hou ◽  
Lina Chen ◽  
...  
Keyword(s):  
Electrochemical Performance ◽  
Carbon Nanofibers ◽  
High Performance ◽  
Sodium Ion ◽  
Sodium Ion Batteries ◽  
Red Phosphorus ◽  
Free Standing ◽  
Graphene Electrode ◽  
Excellent Electrochemical Performance ◽  
Electrospinning Method

A novel flexible P/carbon nanofibers@graphene electrode, which exhibits an excellent electrochemical performance, is fabricated via a vapor-redistribution and electrospinning method.

Hierarchical porous Fe/N doped carbon nanofibers as host materials for high sulfur loading Li–S batteries

Nanoscale ◽  
2019 ◽  
Vol 11 (32) ◽  
pp. 15156-15165 ◽  
Author(s):  
Mao Jiang ◽  
Ruxing Wang ◽  
Kangli Wang ◽  
Shu Gao ◽  
Jing Han ◽  
...  
Keyword(s):  
Carbon Nanofibers ◽  
Carbon Fibers ◽  
High Performance ◽  
Porous Structures ◽  
Host Materials ◽  
Hierarchical Porous ◽  
High Sulfur Loading

Self-supporting carbon fibers with unique hierarchical porous structures and abundant Fe/N adsorption–nucleation centers enable the construction of high performance Li–S batteries.

scholarly journals Toward an Understanding of the Formation and Desolvation of Methanol Solvate, and Structure of Methanolysis Product: A Case Study of Nicosulfuron

Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 157
Author(s):  
Huaxiang Zhu ◽  
Bei Zhang ◽  
Di Wu ◽  
Xiaowei Cheng ◽  
Guiping Li ◽  
...  
Keyword(s):  
Solid Phase ◽  
Great Influence ◽  
Acid Methyl Ester ◽  
Analytical Techniques ◽  
Systematic Investigation ◽  
Herbicidal Activity ◽  
Carbamic Acid ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

Nicosulfuron (NS) is a widely used sulfonylurea herbicide because of its high selectivity, broad spectrum of herbicide activity, and excellent performance. In this work, nicosulfuron methanol solvate (NS-MeOH) and [[3-[(Dimethylamino)carbonyl]-2-pyridinyl]sulfonyl]carbamic acid methyl ester (PCM) as a product of methanolysis of NS were obtained. Both of their structures were determined by a single crystal X-ray diffraction. A broad range of analytical techniques was applied to characterize the NS-MeOH, such as Powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and hot stage microscopy (HSM). Combined with the analysis of the Independent gradient model (IGM), Atom-in-molecules (AIM), and Hirshfeld surface (HS), direct insights into the role of solvent played in the formation of NS-MeOH and the mechanism of solid-to-solid phase transformation of NS-MeOH could be obtained. In addition, the aqueous solubility of NS was improved through the formation of NS-MeOH. A systematic investigation of herbicidal activity of NS and PCM was carried out. It was found that NS and NS-MeOH had similar herbicidal activities at the experimental concentrations while PCM exhibited significantly lower activity. It was suggested that methanolysis of the sulfonylurea bridge in the NS molecule exerted a great influence on the herbicidal activity.

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