scholarly journals Recent Strategies in Preparation of Cellulose Nanocrystals and Cellulose Nanofibrils Derived from Raw Cellulose Materials

2018 ◽  
Vol 2018 ◽  
pp. 1-25 ◽  
Author(s):  
Hongxiang Xie ◽  
Haishun Du ◽  
Xianghao Yang ◽  
Chuanling Si
Keyword(s):  
Cellulose Nanocrystals ◽  
Biomedical Engineering ◽  
Cellulose Nanofibrils ◽  
Low Density ◽  
High Tensile Strength ◽  
Low Thermal Expansion ◽  
Strength And Stiffness ◽  
Biological Methods ◽  
Food Sensor ◽  
Cellulose Materials

The recent strategies in preparation of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) were described. CNCs and CNFs are two types of nanocelluloses (NCs), and they possess various superior properties, such as large specific surface area, high tensile strength and stiffness, low density, and low thermal expansion coefficient. Due to various applications in biomedical engineering, food, sensor, packaging, and so on, there are many studies conducted on CNCs and CNFs. In this review, various methods of preparation of CNCs and CNFs are summarized, including mechanical, chemical, and biological methods. The methods of pretreatment of cellulose are described in view of the benefits to fibrillation.

Factors affecting microstructural scale in liquid crystalline polymers

1990 ◽  
Vol 48 (4) ◽  
pp. 220-221
Author(s):  
Christine M. Dannels ◽  
Christopher Viney
Keyword(s):  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Factors Affecting ◽  
Crystalline Polymers ◽  
Thermal Expansion Coefficients ◽  
Low Thermal Expansion ◽  
Lower Viscosity ◽  
Fine Microstructure ◽  
Planar Orientation ◽  
Strength And Stiffness

Processing polymers from the liquid crystalline state offers several advantages compared to processing from conventional fluids. These include: better axial strength and stiffness in fibers, better planar orientation in films, lower viscosity during processing, low solidification shrinkage of injection moldings (thermotropic processing), and low thermal expansion coefficients. However, the compressive strength of the solid is disappointing. Previous efforts to improve this property have focussed on synthesizing stiffer molecules. The effect of microstructural scale has been overlooked, even though its relevance to the mechanical and physical properties of more traditional materials is well established. By analogy with the behavior of metals and ceramics, one would expect a fine microstructure (i..e. a high density of orientational defects) to be desirable.Also, because much microstructural detail in liquid crystalline polymers occurs on a scale close to the wavelength of light, light is scattered on passing through these materials.

scholarly journals Biomimetic Composites with Enhanced Toughening Using Silk Inspired Triblock Proteins and Aligned Nanocellulose Reinforcements

2019 ◽  
Author(s):  
Pezhman Mohammadi ◽  
A. Sesilja Aranko ◽  
Christopher P. Landowski ◽  
Olli Ikkala ◽  
Kristaps Jaudzems ◽  
...  
Keyword(s):  
Spider Silk ◽  
Cellulose Nanofibrils ◽  
High Strength ◽  
Beta Sheets ◽  
Conformational Switching ◽  
Multiple Length Scales ◽  
The Matrix ◽  
Strength And Stiffness ◽  
Flow Alignment

Silk and cellulose are biopolymers that show a high potential as future sustainable materials.They also have complementary properties, suitable for combination in composite materials where cellulose would form the reinforcing component and silk the tough matrix. Therein, a major challenge concerns balancing structure and properties in the assembly process. We used recombinant proteins with triblock architecture combining structurally modified spider silk with terminal cellulose affinity modules. Flow-alignment of cellulose nanofibrils and triblock protein allowed a continuous fiber production.The protein assembly involved phase separation into concentrated coacervates, with subsequent conformational switching from disordered structures to beta sheets. This gave the matrix a tough adhesiveness, forming a new composite material with high strength and stiffness combined with increased toughness. We show that versatile design possibilities in protein engineering enable new fully biological materials, and emphasize the key role of controlled assembly at multiple length scales for realization.<br>

scholarly journals All-cellulose Materials Adhered with Cellulose Nanofibrils

2018 ◽  
Vol 72 (9) ◽  
pp. 1050-1058 ◽  
Author(s):  
Junji Nemoto ◽  
Shota Fukushima ◽  
Atsushi Kobayashi ◽  
Minami Tagawa ◽  
Tsuguyuki Saito ◽  
...  
Keyword(s):  
Cellulose Nanofibrils ◽  
Cellulose Materials

Description of the PM Process by Using Ishikawa-Analysis

2013 ◽  
Vol 752 ◽  
pp. 48-56
Author(s):  
Andrea Simon ◽  
Károly Kovács ◽  
C. Hakan Gür ◽  
Tadeusz Pieczonka ◽  
Zoltán Gácsi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Powder Metallurgy ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
High Strength ◽  
Manufacturing Technology ◽  
Low Density ◽  
Composite Manufacturing ◽  
Low Thermal Expansion

Composites are special material which can provide individual properties such as high strength with low density or good thermal conductivity with low thermal expansion coefficient. Composites conform to the constantly evolving and more complex expectations. In order to make a product with good quality, it is important to choose suitable materials and technology. In this research powder metallurgy (PM), as one of the most common composite manufacturing technology, was examined -which factors and mechanisms influence mostly the properties of the product. Ishikawa method was used to reveal these correlations.

Advanced Oxidation Protection System for Carbon-Carbon Composites

1989 ◽  
Author(s):  
D. A. Eitman ◽  
R. W. Kidd ◽  
R. B. Dirling
Keyword(s):  
Advanced Oxidation ◽  
High Strength ◽  
Carbon Composite ◽  
Protection System ◽  
Carbon Composites ◽  
Oxidation Protection ◽  
Low Thermal Expansion ◽  
The Matrix ◽  
Strength And Stiffness ◽  
Orthotropic Properties

Carbon-carbon composites possess a number of desirable attributes including low density, high strength and stiffness at temperatures well beyond the capabilities of refractory alloys, low thermal expansion coefficient, tailorable orthotropic properties, absence of strategic materials, and resistance to thermal shock, fatigue, and brittle failures. However, for many applications of interest (such as aircraft and aerospace vehicle structure and engines) resistance to oxidation in high-temperature air or engine exhaust streams is a requirement which is not satisfied by unprotected carbon-carbon composites. The elements of an advanced oxidation protection system for carbon-carbon composites are described in this paper. The system is comprised of both an oxidation resistant coating intended to provide the primary barrier to oxygen ingress and inhibitors added to the matrix of the carbon-carbon composite to increase its oxidation resistance without significant losses in mechanical properties. The composite inhibition system is designed to be complementary to the coating and to enhance its long-term performance. A description of the principal elements of the system is presented along with recent test data and current research directions.

Production with a High Yield of Bacterial Cellulose Nanocrystals by Enzymatic Hydrolysis

2019 ◽  
Vol 19 (03) ◽  
pp. 1950015
Author(s):  
Ricardo Brandes ◽  
Leticia de Souza ◽  
Claudimir Carminatti ◽  
Derce Recouvreux
Keyword(s):  
Enzymatic Hydrolysis ◽  
Bacterial Cellulose ◽  
Cellulose Nanocrystals ◽  
Primary Objective ◽  
High Yield ◽  
Low Density ◽  
Enzymatic Method ◽  
Citrate Buffer ◽  
Cellulose Hydrogel ◽  
Time Required

Bacterial cellulose nanocrystals are highly crystalline structures with nanoscopic scale dimensions that have received increased attention in the nanocomposites area. Its properties, such as large surface area, low density, mechanical strength and ease of modification, are attractive to the preparation many kinds of nanomaterials applied multifunctional in various fields. Besides, the cellulose nanocrystals are from abundant and renewable sources that are biodegradable. An altemative method is to obtain bacterial cellulose nanocrystal by enzymatic hydrolysis because it is, less expensive, it does not use chemicals and it requires much less energy. In this sense, the primary objective of this study was to produce bacterial cellulose using glycerol as a carbon source and isolate nanocrystals from bacterial cellulose using the enzymatic hydrolysis. This study also investigated the yield of nanocrystals depending on the weight of the bacterial cellulose hydrogel, keeping constant some enzymes. The study shows us that the enzymatic method has the best performance when using cellulose hydrogel 2[Formula: see text]g to 40[Formula: see text][Formula: see text]L cellulase enzyme (endoglucanase) and 1[Formula: see text]mL of citrate buffer. Also, it was observed that the yield of nanocrystals decrease with increasing time required for the hydrolysis.

Online determination of anisotropy during cellulose nanofibril assembly in a flow focusing device

RSC Advances ◽  
2015 ◽  
Vol 5 (24) ◽  
pp. 18601-18608 ◽  
Author(s):  
Karl M. O. Håkansson
Keyword(s):  
Cellulose Nanofibrils ◽  
High Strength ◽  
Cellulose Nanofibril ◽  
Flow Focusing ◽  
Strength And Stiffness

In order to utilize the high strength and stiffness of cellulose nanofibrils in a macroscopic material or composite, the structure of the elongated fibrils in the material must be controlled.

Synthesis, Characterization and Mechanical Properties of Silicon Carbide Nanowires

2010 ◽  
Author(s):  
Huan Zhang ◽  
Weiqiang Ding ◽  
Daryush Aidun
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Silicon Carbide ◽  
Physical And Mechanical Properties ◽  
High Hardness ◽  
High Strength ◽  
Harsh Environments ◽  
Low Density ◽  
Low Thermal Expansion ◽  
Oxidation And Corrosion

Silicon carbide (SiC) material has many outstanding physical and mechanical properties such as high strength, high hardness, low density, high thermal conductivity, low thermal expansion coefficient, large band-gap, and excellent oxidation and corrosion resistances [1–3]. It is a leading material for components and devices operating at high temperature, high power and under harsh environments [4–5]. Micro-sized SiC particles and whiskers are commonly used as reinforcement materials for ceramics, metals and alloys in various structural and tribological applications [6–7].

Low-Temperature Synthesis of Cordierite Using Magnesite

2014 ◽  
Vol 608 ◽  
pp. 122-126
Author(s):  
Jae Hwan Pee ◽  
Geun Hee Kim ◽  
Na Ri Lee ◽  
Hyung Tea Kim ◽  
Lada Punsukumtana
Keyword(s):  
Particle Size ◽  
Magnesium Content ◽  
Low Density ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Mean Particle Size ◽  
Synthetic Rate ◽  
Low Thermal Expansion ◽  
Wide Range ◽  
The Mean

Cordierite (2MgO·2Al2O3·5SiO2) has a low density of 2.2 g/cm3 due to its high magnesium content. Because of its low thermal expansion coefficient of 1~2 x10-6 /°C, many studies are being conducted on the synthesis of cordierite with the expensive petalite as a replacement for lithium alumina silicate-based heat-resistant materials. The cordierite can be synthesized over a wide range: SiO2 at 50~70%, Al2O3 at 20~40%, and MgO at 10~30%. In this study, the range of chemical composition and temperature of cordierite synthesis is thoroughly investigated. In particular, we use natural materials (magnesite, kaolin and clay) to examine how thermal properties are affected by changes in crystal phase arising from the varying composition of MgO, SiO2 and Al2O3. We focused on factors leading to an increase in the rate of cordierite synthesis at temperatures below 1280 °C. From observing the synthetic rate over 1250~1280 °C, the sintered body at 1280 °C had a high synthetic rate greater than 80%. Magnesite was ball milled at constant intervals, and mean particle size was controlled to improve the synthetic rate of cordierite. As a result, the cordierite synthetic rate increased by more than 15% with decreasing the mean particle size of magnesite.

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