scholarly journals A Comparative Study on the Characterization of Nanofibers with Cellulose I, I/II, and II Polymorphs from Wood

Polymers ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 153 ◽  
Author(s):  
Haiying Wang ◽  
Suiyi Li ◽  
Tiantian Wu ◽  
Xiaoxuan Wang ◽  
Xudong Cheng ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Comparative Study ◽  
Coefficient Of Thermal Expansion ◽  
Cellulose Nanofibers ◽  
High Yield ◽  
Chemical Extraction ◽  
Cellulose Content ◽  
Cellulose I ◽  
Aspect Ratios

Polymorphic changes in cellulose nanofibers (CNFs) are closely related to their properties and applications, and it is of interest to investigate how polymorphic changes influence their properties. A comparative study on the properties of CNFs with cellulose I, I/II, and II polymorphs from wood was conducted herein. CNFs were obtained by chemical extraction combined with a simple and efficient mechanical treatment (one pass through a grinder). This process resulted in a relatively high yield of 80–85% after a simple grinding treatment. The polymorphic changes in the CNFs and the chemical composition, morphology, tensile performances, and thermal properties were systematically characterized and compared. The X-ray diffraction and FTIR analyses verified the existence of three types of purified pulps and CNFs with cellulose I, cellulose I/II, and cellulose II polymorphs (CNF-I, CNF-I/II, CNF-II). Morphological observations presented that these three types of CNFs all exhibited high aspect ratios and entangled structures. Tensile testing showed that the CNF films all exhibited high tensile strengths, and the fracture strains of the CNF-I/II (11.8%) and CNF-II (13.0%) films were noticeably increased compared to those of the CNF-I film (6.0%). If CNF-II is used as reinforcing material, its larger fracture strain can improve the mechanical performance of the CNF composites, such as fracture toughness and impact strength. In addition, CNF-I, CNF-I/II, and CNF-II films showed very low thermal expansion in the range 20–150 °C, with the coefficient of thermal expansion values of 9.4, 17.1, and 17.3 ppm/K, respectively. Thermogravimetric analysis (TGA) revealed that the degradation temperature of CNF-I and CNF-II was greater than that of CNF-I/II, which was likely due to increased α-cellulose content. This comparative study of the characterization of CNF-I, CNF-I/II, and CNF-II provides a theoretical basis for the application of CNFs with different polymorphs and could broaden the applications of CNFs.

scholarly journals Synthesis and Characterization of a High Flux Nanocellulose–Cellulose Acetate Nanocomposite Membrane

Membranes ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 70 ◽  
Author(s):  
Nancy Li ◽  
Jackie Zheng ◽  
Pejman Hadi ◽  
Mengying Yang ◽  
Xiangyu Huang ◽  
...  
Keyword(s):  
Polymer Matrix ◽  
Energy Requirement ◽  
Cellulose Nanofibers ◽  
Membrane Resistance ◽  
High Energy ◽  
Sem Images ◽  
Membrane Performance ◽  
Aspect Ratios ◽  
Membrane Flux

Despite the advantages of membrane processes, their high energy requirement remains a major challenge. Fabrication of nanocomposite membranes by incorporating various nanomaterials in the polymer matrix has shown promise for enhancing membrane flux. In this study, we embed functionalized cellulose nanofibers (CNFs) with high aspect ratios in the polymer matrix to create hydrophilic nanochannels that reduce membrane resistance and facilitate the facile transport of water molecules through the membrane. The results showed that the incorporation of 0.1 wt % CNF into the polymer matrix did not change the membrane flux (~15 L · m − 2 · h − 1 ) and Bovine Serum Albumin (BSA) Fraction V rejection, while increasing the CNF content to 0.3 wt % significantly enhanced the flux by seven times to ~100 L · m − 2 · h − 1 , but the rejection was decreased to 60–70%. Such a change in membrane performance was due to the formation of hydrophilic nanochannels by the incorporation of CNF (corroborated by the SEM images), decreasing the membrane resistance, and thus enhancing the flux. When the concentration of the CNF in the membrane matrix was further increased to 0.6 wt %, no further increase in the membrane flux was observed, however, the BSA rejection was found to increase to 85%. Such an increase in the rejection was related to the electrostatic repulsion between the negatively-charged CNF-loaded nanochannels and the BSA, as demonstrated by zeta potential measurements. SEM images showed the bridging effect of the CNF in the nanochannels with high CNF contents.

Transient and Residual Stresses and Displacements in Self-Curing Bone Cement—Part I: Characterization of Relevant Volumetric Behavior of Bone Cement

1982 ◽  
Vol 104 (1) ◽  
pp. 21-27 ◽  
Author(s):  
A. M. Ahmed ◽  
W. Pak ◽  
D. L. Burke ◽  
J. Miller
Keyword(s):  
Thermal Expansion ◽  
Residual Stresses ◽  
Bone Cement ◽  
Coefficient Of Thermal Expansion ◽  
Stress Generation ◽  
Curing Process ◽  
Cooling Phase ◽  
Volumetric Behavior ◽  
Fixation System

In this first part of a two-part report, some aspects of the volumetric behavior of bone cement during its curing process are examined as a prelude to an analysis for the transient and residual stresses and displacements in stem fixation systems. Experiments show that stress generation in the cement is associated with its temperature while curing and that during the cooling phase, the stresses are mainly due to thermal as opposed to bulk shrinkage. The appropriate coefficient of thermal expansion of bone cement has been evaluated from measurements in a simulated fixation system in conjunction with a thermoelastic analysis.

Synthesis of Ca-Al-Si-O Compounds from Local Wastes

2009 ◽  
Vol 620-622 ◽  
pp. 121-124
Author(s):  
U.Sangwanna Sanewirush ◽  
P. Saewong
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Rice Husk Ash ◽  
Coefficient Of Thermal Expansion ◽  
Ternary Diagram ◽  
Alumina Ceramics ◽  
Calcium Aluminosilicate ◽  
Pulp Production ◽  
Aluminum Anodizing

The local wastes, which are sources of SiO2, Al2O3 and CaO, are rice husk ash, waste sediment from aluminum anodizing process and dreg from pulp production, respectively. The wastes are mixed in three different compositions in ranges of 20-50 SiO2, 20-35 CaO and 20-45 Al2O3, wet milled, slip casted and then fired at 1,100 °C. Characterization of the fired bodies reveals the formation of calcium-aluminosilicate compounds: gehlenite and anorthite as major phases, in accordance with the SiO2-CaO-Al2O3 ternary diagram. Their bulk densities and % water absorption lies between 0.95-1.42 g/cm3 and 37.40-67.95%, respectively. While flexural strength and coefficient of thermal expansion are between 4.09-9.56 MPa and 6.14 - 10.1 x 10-6 °C-1, respectively. By simple thermal conductivity comparison, the materials themselves have thermal conductivity comparable to alumina ceramics. These wastes, therefore, may be used as precursors for the production of some insulating refractory members, in place of minerals from natural resources.

Characterization of Epoxy-Functionalized Silsesquioxanes as Potential Underfill Encapsulants

1998 ◽  
Vol 519 ◽  
Author(s):  
E. K. Lin ◽  
C. R. Snyder ◽  
F. I. Mopsik ◽  
W. E. Wallace ◽  
W. L. Wu ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Flip Chip ◽  
Coefficient Of Thermal Expansion ◽  
Silica Particles ◽  
Critical Parameters ◽  
Organic Hybrid ◽  
Solder Bumps ◽  
The Difference ◽  
Electronics Packages

AbstractIn electronics packaging, underfill encapsulants are needed to improve package reliability in flip-chip devices. The underfill generally consists of an epoxy resin highly filled with silica particles and is designed to reduce the stress arising from the difference in the thermal expansion between the solder bumps and the substrate. Currently, concerns about the flow of the silica particles and surface phenomena are arising as electronics packages reduce in size. Newly developed epoxy-functionalized octameric silsesquioxanes provide an intriguing alternative to current formulations. These single-phase inorganic/organic hybrid materials may have properties similar to filled materials without the complications from the rheology of filled materials. The physical properties of the functionalized silsesquioxanes are measured with respect to the critical parameters for underfill materials. Measurements of properties such as the coefficient of thermal expansion and density are performed to evaluate the suitability of these materials as potential underfill encapsulants.

A Comparative Study of the Structural, Optical, and Electrochemical Properties of Squarate-Based Coordination Frameworks

2013 ◽  
Vol 66 (4) ◽  
pp. 429 ◽  
Author(s):  
Pavel M. Usov ◽  
Tony D. Keene ◽  
Deanna M. D'Alessandro
Keyword(s):  
Thermal Expansion ◽  
Comparative Study ◽  
Electrochemical Properties ◽  
Near Infrared ◽  
Coefficient Of Thermal Expansion ◽  
Redox Properties ◽  
Electrochemical Measurements ◽  
Positive Coefficient ◽  
Trigonal Structure ◽  
Coordination Frameworks

Systematic studies of the thermal expansion, optical, and redox properties of a series of six squarate-based frameworks, [MII(C4O4)(H2O)2] (MII = MnII, FeII, CoII, NiII, ZnII, CdII) have revealed that five members of the series exhibit cubic structures in which the squarate ligands are configured in an ‘eclipsed’ phase, while the CdII analogue exhibits a trigonal structure with a ‘staggered’ orientation of the ligands. The ‘eclipsed’ structures are characterised by a positive coefficient of thermal expansion, while the CdII analogue exhibits zero thermal expansion. Ultraviolet-visible-near infrared (UV-Vis-NIR) spectra and electrochemical measurements indicate that electron delocalisation across the dianionic squarate bridge is absent.

Processing, Microstructure, and Thermal Expansion Measurements for High Temperature Ru-Al-Cr B2 Alloys

2008 ◽  
Vol 1128 ◽  
Author(s):  
Yutaka Hashimoto ◽  
Norihiko L. Okamoto ◽  
Manuel Acosta ◽  
David R Johnson ◽  
Haruyuki Inui
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Room Temperature ◽  
Coefficient Of Thermal Expansion ◽  
Directionally Solidified ◽  
Average Value ◽  
Heat Treated ◽  
Structural Applications ◽  
Cr System

AbstractThe B2 intermetallic compound RuAl has a melting temperature above 2000 °C and is a candidate for high temperature structural applications. A large extension of the B2 phase field is found in the Ru-Al-Cr system as was documented by the characterization of arc-melted and heat treated alloys. Two compositions consisting of Ru-35Al-19Cr and Ru-20Al-38Cr (at. %) were directionally solidified in an optical floating zone furnace. Depending upon the processing conditions, single phase, polycrystalline, B2 microstructures could be produced. The coefficient of thermal expansion (CTE) was measured from room temperature to 1250 °C for the Ru-20Al-38Cr alloy, and an average value of 11×10-6 K-1 was found. Additionally, the thermal conductivity was measured as 27 W/mK at room temperature for the Ru-20Al-38Cr B2 alloy and as 89 W/mK for binary RuAl.

Direct CTE Measurement Technique for the MEMS Materials

2006 ◽  
Vol 326-328 ◽  
pp. 199-202 ◽  
Author(s):  
Chung Seog Oh ◽  
Sung Hoon Choa ◽  
Chang Seung Lee ◽  
Hak Joo Lee
Keyword(s):  
Thin Films ◽  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Test System ◽  
Test Method ◽  
Linear Coefficient ◽  
Aln Film ◽  
Certified Value ◽  
Plane Displacement

The accurate characterization of linear coefficient of thermal expansion (CTE) of thin films is vital for predicting the thermal stress, which often results in warpage and failure of a MEMS structure. In this paper, special emphasis is placed on the development of novel test method to extend an ISDG (Interferometric Strain/Displacement Gage) technique to the direct and accurate CTE measurement of MEMS materials, AlN and Au. The freestanding AlN and Au films are 1 μm thick and 5 mm wide. Strain is directly measured by a brand-new digital type ISDG with two Cr lines deposited on the specimen while heating a specimen in a furnace. The whole test system is verified first by measuring the CTE for the NIST’s SRM (Standard Reference Material) 736 (Cu) block. The measured CTE is 17.3 με/oC up to 167 oC, which agrees well with the NIST’s certified value. The CTE of Au is 25.4 ± 1.15 με/oC and that of AlN film is 3.77 ± 0.12 με/oC. The in-plane displacement resolution is about 5 nm at the best circumstances.

Sign in / Sign up

Export Citation Format

Share Document