جستجوی مقالات مرتبط با کلیدواژه "نانوسلولز" در نشریات گروه "جنگلداری"

Nanocellulosic aerogels are solid, porous materials with nanometeric pore size, which are formed by replacing liquid (hydrogel) with gas. The preparation of nanocellulosic aerogels consists of two main steps: preparation of hydrogel from a solution and removal of solvent through sublimation by freeze drying or supercritical method with solvent exchange. Due to desirable characteristics such as ultra-light density, porous structure, biodegradable and being environmental friendly, these materials have a wide range of applications in various industries, such as medicine, pharmaceutical, military, defense, etc. Despite the above advantages, they also have disadvantages such as flammability when exposed to heat or fire, which limits their use in many cases. Therefore, it seems necessary to modify cellulose nanofibers with flame retardants. To prepare of nanocellulose aerogels, 2% wt concentration nanocellulose gel was prepared from Nanonovin Polymer Company. In order to prepare of flame retarding nanocellulose aerogels, 20% wt of dry weight of nanocellulose gel, sodium bicarbonate was added. This suspension was placed on a magnetic stirrer at a speed of 1200 rpm for 30 minutes to form a uniform hydrogel. Then, control nanocellulose (CNF) and treated with sodium bicarbonate (CNF+SBC) hydrogels were poured into copper molds and placed in a refrigerator at 2°C for 24 hours. After that, the molds were taken out of the refrigerator and transferred directly to the liquid nitrogen bath for quick freezing. Immediately, they were placed in a freeze dryer for 48 hours, and control and treated nanocellulose aerogels with sodium bicarbonate were prepared. The results of the FTIR spectrum confirmed the presence of sodium bicarbonate in flame retarded aerogels structure. Also, based on SEM and BET observations, it was found that this substance in nanocellulosic aerogel reduced the porosity and specific surface area. In the study of the thermal characteristics of aerogels, control nanocellulose aerogels had lower thermal stability than flame retarded nanocellulose aerogels, and the residue of the treated samples was about 30% more than the control nanocellulosic aerogels. The flammability test also confirmed this claim, and the presence of carbon dioxide prevented aerogel from more burning by limiting the oxygen needed during the ignition process. The crystalline structure of cellulose in nanocellulose aerogels containing sodium bicarbonate remained unchanged compared to the control, and the compression strength and modulus of the treated aerogel decreased compared to control aerogels due to decrease of polymerization degree. For this product, we can imagine applications in the construction industry or thermal insulation in the oil and gas and textile industries, as well as energy storage and production tools.Conclusion In general, sodium bicarbonate treatment led to the production of lightweight and flame retarded nano cellulose aerogels, which are completely green and environmental friendly.

Due to its many applications in other industries, nanocelluloses have attracted the attention of governments and investors. The recognition and potential of nanocellulose has encouraged countries to invest in this green product. However, in Iran, Production of nanocellulose is still in the laboratory Scale due to unidentified challenges and thus, it has not yet reached the huge production. Therefore, the purpose of this research is to identify the strengths, weaknesses, opportunities, and risks of the proposed situation and the use of nanocellulose in Iran using the SWOT method.

The indicators affecting the state of supply and demand of nanocellulose were presented and completed and identified by 10 experts consisting of academic professors and private manufacturing and technology companies and knowledge-based in three stages (or three rounds) by Delphi questionnaire. Then, using the studies and opinions of the scientific professors of the related field and several member manufacturing companies, the internal factors (strengths and weaknesses) and external factors (opportunities and threats) affecting the supply and demand situation of nanocellulose were identified in the separate tables of the SWOT analysis.

In the strengths of 8 indicators (creating high added value to the raw material and nanocellulose products - diversity and availability of the raw material - biocompatibility and biodegradability of the nanocellulose product - the ability to produce a new generation of efficient products with nanocellulose - creating sustainable development with the commercialization of nanocellulose - The share of manpower with high local technical knowledge - the need for less space for the production of nanocellulose - the variety of nanocellulose products) and in the weak points of 9 indicators (the size change of nanocellulose during drying - the high cost of energy, operation, land and machinery - the need for High investment - high cost of drying nanocellulose - lack of investment by the government and banks - low production efficiency - lack of efficiency of the equipment in companies for use in nanocellulose - production in the form of nanocellulose gel (with water) - expensiveness of nanocellulose production method compared to competitors ) and the opportunity points of 7 indicators (use of nanocellulose in various fields - high innovation and virginity of the field of nanocellulose applications - attracting foreign investors and the private sector - suitable export markets in the region - the possibility of accessing the technical knowledge of other countries' production - the need for high research and development - Government support for the nanocellulose production industry - high acceleration of transformation in nanocellulose products in the world) and opportunity points of 8 indicators (raw materials and alternative products - customization of nanocellulose - low price of raw materials and competing products - expensiveness of nanocellulose - lack of special production machines and equipment - Managers' lack of risk-taking in using hi-tech and new products-difficulty introducing and promoting new products in the market) were identified, each of which affects the supply and demand of nanocellulose.

The indicators affecting the supply and demand of nanocellulose were identified by experts through the Delphi and SWOT methods, and these factors have a significant effect on it, and by applying the presented solutions, mass production and commercialization of nanocellulose can be achieved in Iran.

Nanocelluloses have attracted the attention of some countries due to their potential for economic growth. There are two approaches to obtain nanocellulose: bottom-up strategy (bacterial nanocellulose) and top-down strategy (plant-based nanocellulose).

Nano cellulose with Challenges in part production and Consumption is had encounter. That with using of Delphi method criterions and sub criterions very important effective on production and Consumption those were become Identify And 10 questionnaire according Delphi method with gamut likert design that this questionnaire contain criterion and sub criterion be and which of options contain 6 criterion to give scoring very low, low, middle, high and very high, is having. and to aces among professors university expert and Production companies and Private technology and knowledge base in 3 step or (rank) presentation and to has completed. Until position production and Consumption Nano cellulose with using of Delphi technical check and analysis its be made.

According to the results, in the criterion (raw materials and product), 2 sub-criteria (development of approach - access to raw materials inside and outside the province) with an average of less than 3 were removed from the 11 important sub-criteria in the first round, and 9 sub-criteria remained in the second and third rounds. In the criterion (economic and sales marketing) 4 sub-criteria (customer satisfaction - sales system - export opportunities - transportation costs) with an average of less than 3 were removed from 13 important sub-criteria in the first round, and 9 sub-criteria remained in the second and third rounds. In the criterion (competitive and infrastructure), 2 sub-criteria (purchasing power of nanocellulose suppliers - discount power of nanocellulose suppliers) with an average of less than 3 were removed from 9 important sub-criteria in the first round, and 7 sub-criteria remained in the second and third rounds, and 3 sub-criteria (existence of educational, university, technical-professional centers - living and welfare facilities of human resources - human resource management) with an average of less than 3 in the criterion (technical-human) were removed from 10 important sub-criteria in the first round, and 7 sub-criteria remained in second and third rounds. The reliability Cronbach's Alpha of the first round is 0.825, the second round is 0.815 and the third round is 0.845.

Indicators effective on production and Consumption Nano cellulose in 3 step questionnaire be full by aces trend dissection and analysis contain be meaning and too in research coordination coefficient kendal in rank second and third 0.57 is having. that a sign of been effective this factories on production and Consumption Nano cellulose in iran is having that in process production and marketing and supply the products Nano cellulose this factories important and effective must at looking.

The aim of this study was to investigate the possibility of increasing the germination traits (germination and rate percentage) and vegetation characteristics of 3-month-old seedlings of Betula pendula (plumule and radicle length, collar diameter, fresh and dry weight of root, leaf area) by applying nano-priming and magnetic field. Seeds were collected from the Siah- Marzkouh area, 18 km from Gorgan-Golestan, Iran and after disinfection they were primed (soaked)  in a 1% solution of nano-chitin, nano-chitosan and nano-cellulose, and then sown. Magnetic treatment was applied to the seeds at three levels of 20, 30 and 40 mT at 1, 10 and 20 minutes and were sown immediately. A number of seeds were primed with all 3 nanomaterials after being exposed to the magnetic field (with the previous dose and time) and then planted. The results showed that among all the applied treatments, 1 min magnetism in 30 mT and then 2 hour seed priming with 1% solution of nanocellulose, were the best, In a way that increased the germination percentage (1.58 times), germination rate (1.9 times), number of leaves (1.2 times), leaf area (1.84 times) and root length (1.4 times) compared to the control (no treatment). The 20-minute magnetic treatment of seeds at 30 mT intensity and then the two-hour seed priming with 1% nanocellulose gave similar results. Two seed treatments (10 and 20 minute) in 30 mT (without nanopriming) are also recommended after these two treatments.

Converting biomass waste such as bagasse as an abundant lignocellulosic resource available for producing biofuels can be a viable alternative to fossil fuel and environmental pollutants. The purpose of the present study was to produce biofuel briquettes from two dimensional classes of shredded bagasse and grinded bagasse. Nanometer lignocellulose binders including nanolignocellulose (LCNF) and nanocellulose (CNF) at three levels of 3, 6 and 9% were used to enhance and improve the thermal and technical parameters. The briquettes were produced by cylinder and piston press at 150 MPa and 100 °C. The results showed a positive effect of nanometer lignocellulosic binders on the thermal and strength properties. Thus, nano-lignocellulose was more effective on the physical and mechanical properties of nanocellulose binder in both dimensional classes. Also, in terms of thermal properties of nano-lignocellulose binder, better results were obtained in biofuel briquettes. Consequently, nanolignocellulose may be a more suitable binder, since its production costs are lower than nanocellulose and the calorific value of briquette is higher due to the low lignin content in the compound. As a result, at 9% level of usage, calorific value and compressive strength of shredded and grinded bagasse were 34.37 N.mm, 19.85 MJ/Kg and 19.85 Nmm 29.45 MJ/Kg, respectively.

Layer-by-Layer self-assembly technique is a novel method in nanothechnology for the modification of the surface properties of solid materials. This paper compares the influence of modification of cotton linter fibers external surfaces via alternate adsorption of positive and negative (chitosan/Cellulose nanofibers) polyelectrolytes. The adsorption of materials on cellulose fibers was analyzed via polyelectrolyte titration. The bonding ability of fibers was improved by polyelectrolyte multilayering (PEM) on the fiber surface visualized using Field-Emission Scanning Electron Microscopy (FESEM). The results showed that apparent density and also bonding ability were significantly improved at second layer، whereas the apparent density and tensile index of the sheet increased by 10% and 76% respectively compared to those of untreated fibers at second layer.