The electrospun nanofibers membranes (ENMs) have gained great attention due to their superior performance. However, the low mechanical strength of ENMs, such as the rigidity and low strength, limits their applications in many aspects which need adequate strength, such as water filtration. This work investigates the impact of electrospinning parameters on the properties of ENMs fabricated from polyacrylonitrile (PAN) solved in N, N-Dimethylformamide (DMF). The studied electrospinning parameters were polymer concentration, solution flow rate, collector rotating speed, and the distance between the needle and collector. The fabricated ENMs were characterized using scanning electron microscopy (SEM) to understand the surface morphology and estimate the average fiber sizes. The membrane porosity percentage was measured using the dry-wet weight method. Also, a dynamic mechanical analyzer was used to determine the mechanical strength properties (tensile strength and Young's modulus) (DMA). The obtained results revealed that the polymer concentration and flow rate mainly affect the porosity and fiber size in ENMs. Increasing the polymer concentration improves the strength and flexibility, while the flow rate did not show a clear effect on the mechanical strength of ENMs. Both fibers collecting speed and spinning distance did not clearly impact the membrane morphology. ENMs flexibility significantly increased with increasing the collector speed and decreasing the spinning distance. Strong and flexible ENMs with small fibers can be fabricated using 10% PAN/DMF at a flow rate of 1 mL/h, collector speed of 140 rpm, and spinning distance of 13 cm.
من نحن ؟ التحديات التي تواجه الهوية الامريكية
Anger is one of the problems of scientific importance that psychologists and education scientists are interested in, especially societies and educational environments, because if a child’s anger continues to develop into violence, then it becomes an unusual behavior, and an indication of the child's lack of adaptation to his family and his environment (Moses, 2013: 4) &n
... Show Moreتصنيع الطابوق الحراري الثقيل من خامات محلية
اتخذت الهند موقفاً محايداً من الحرب الروسية الأوكرانية، لما له من أبعاد سياسية واقتصادية وعسكرية مع أطراف الصراع في الحرب، وقناعتها بعدم قدرتها على التأثير فيها. فهي تربطها علاقات استراتيجية تاريخية مع روسيا، الداعمة لها سياسياً في مجلس الأمن والوسيط ضد خصومها الصين وباكستان. لذلك الهند مقتنعة بأن أوكرانيا تُعدّ مجالاً للنفوذ الروسي الذي عمل حلف شمال الأطلسي على التوسع به رغم التحذيرات الروسية. لذا أيقنت ا
... Show MoreEtude de I' espace dans un extrait de Les sequestres d' Altona de Jean
The current research tries to study the reasons for lying since its
inception, as it is interesting to a child's moral growth, which can benefit from
the results of this research by institutions of socialization, parents and
teachers in the treatment and care of children.
The objective of this research is to highlight the reasons for lying to the
children from the viewpoint of teachers and the answer to the paragraphs of
research designed research instrument (questionnaire) was distributed to a
sample of teachers was clear from the analysis that the reasons lie that
received a high percentage of members of the sample are: -
- The fear of severe punishment
- Child rid himself of a specific problem
- To sat
The study of Terracotta in Mesopotamia is one of the important
technical topics that gave us valuable information ،whether from a
technical or cultural point of view
The research deals with a modern concept in its applications and the studies it deals with, as the concept of urban densification is one of the most recent sustainable development strategies for cities.
Studies looking at the relationship between condensation and viability show mixed results. This study sheds light on how the built environment of dense urban areas affects the perceived quality of life of the population. How to enhance acceptance of dense life is an important question to investigate.
Adopting the concept of urban densification in city planning policies to be more sustainable and livable is of great importance by achieving efficient use of urban land and limiting urban sprawl, as well as reducing the
... Show MoreThe importance of this research is to clarify the nature and the relationship between the indicators of financial policy and banking stability in Iraq, as well as to find a composite index reflects the state of banking stability in Iraq in order to provide an appropriate means to help policymakers in making appropriate decisions before the occurrence of financial crises.
Hence, the problem of research is that the fiscal policy has implications for the macro economy and does not rule out its impact on banking stability. Moreover, the central bank does not possess a single indicator that reflects the stability of the banking system, rather than the scattered indicators that depend o
... Show MoreThe Turkish intervention in the Libyan crisis in the recent period was a trigger for more tension than a solution - as Turkey claims - as Turkey seeks to quickly set a welcome military footing in Libya to prevent the reconciliation government from falling and planning to start exploration for gas and oil in Libya to solve the Turkish energy crisis, that is, the energy exchange for security and trying to exploit the situation to establish a new gathering of proTurkish political Islam, as for the Iranian position on the Libyan crisis, it does not exceed a logistical role and provide Turkey with expertise in circumventing international sanctions and assisting it in transporting fighters and weapons to Libya, Iran has also deliberately added so
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