scholarly journals 2D Rigid Benzoxazole-Linked Covalent Organic Framework Films with High-Strength, High-Modulus Mechanical Behavior

2020 ◽  
Author(s):  
Kristen Miller ◽  
Lawrence B. Alemany ◽  
Edwin L. Thomas ◽  
Eilaf Egap
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Single Step ◽  
Two Dimensions ◽  
Free Standing ◽  
Step Process ◽  
Axial Tensile ◽  
Solution Cast ◽  
One Step ◽  
Rigid Rod

<p>Two-dimensional (2D) benzoxazole-linked covalent organic frameworks (COFs) provide an opportunity to incorporate the strength and modulus of corresponding 1D rigid-rod polymers into multiple directions by extending covalent bonding into two dimensions while simultaneously reducing density. Thus far, this potential has been elusive because of the challenge of producing high-quality COF films, particularly those with irreversible, rigid benzazole linkages. The majority of COF syntheses use a single-step process approach where polymerization occurs faster than crystallization and typically result in a poorly ordered and insoluble powder. Here, we present a one-step synthesis and two-step process that allows the deposition of a uniform intermediate film via reversible, non-covalent interactions. This network then undergoes an annealing step that facilitates the irreversible conversion to 2D covalently-bonded polymer product. The resulting films are semi-crystalline with platelet-like crystals embedded in an amorphous matrix with sharp crystal-amorphous interfaces. By this approach, we achieve free-standing films for which we demonstrate the first example of mechanical testing of benzazole-linked COFs. These initial films have promising mechanical properties with an in-plane ultimate tensile strength of nearly 50 MPa and axial tensile and transverse compressive elastic moduli on the scale of several GPa. These mechanical properties already rival the performance of solution-cast films of 1D polybenzoxazole (PBO).<i></i></p>

scholarly journals 2D Rigid Benzoxazole-Linked Covalent Organic Framework Films with High-Strength, High-Modulus Mechanical Behavior

2020 ◽  
Author(s):  
Kristen Miller ◽  
Lawrence B. Alemany ◽  
Edwin L. Thomas ◽  
Eilaf Egap
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Single Step ◽  
Two Dimensions ◽  
Free Standing ◽  
Step Process ◽  
Axial Tensile ◽  
Solution Cast ◽  
One Step ◽  
Rigid Rod

<p>Two-dimensional (2D) benzoxazole-linked covalent organic frameworks (COFs) provide an opportunity to incorporate the strength and modulus of corresponding 1D rigid-rod polymers into multiple directions by extending covalent bonding into two dimensions while simultaneously reducing density. Thus far, this potential has been elusive because of the challenge of producing high-quality COF films, particularly those with irreversible, rigid benzazole linkages. The majority of COF syntheses use a single-step process approach where polymerization occurs faster than crystallization and typically result in a poorly ordered and insoluble powder. Here, we present a one-step synthesis and two-step process that allows the deposition of a uniform intermediate film via reversible, non-covalent interactions. This network then undergoes an annealing step that facilitates the irreversible conversion to 2D covalently-bonded polymer product. The resulting films are semi-crystalline with platelet-like crystals embedded in an amorphous matrix with sharp crystal-amorphous interfaces. By this approach, we achieve free-standing films for which we demonstrate the first example of mechanical testing of benzazole-linked COFs. These initial films have promising mechanical properties with an in-plane ultimate tensile strength of nearly 50 MPa and axial tensile and transverse compressive elastic moduli on the scale of several GPa. These mechanical properties already rival the performance of solution-cast films of 1D polybenzoxazole (PBO).<i></i></p>

Improving the Mechanical Properties of AZ31 Mg Alloy by High Ratio Extrusion

2006 ◽  
Vol 503-504 ◽  
pp. 865-870 ◽  
Author(s):  
Yongjun Chen ◽  
Qu Dong Wang ◽  
Jianguo Peng ◽  
Chun Quan Zhai
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
High Ratio ◽  
Extrusion Ratio ◽  
Mg Alloy ◽  
Fine Grained ◽  
Az31 Mg Alloy ◽  
Industry Applications ◽  
One Step ◽  
The One

Experiments were conducted both to evaluate the potential for grain refinement, the subsequent mechanical properties at room temperature in samples of AZ31 Mg alloy and also to investigate the relationship between one-step and two-step high ratio extrusion (HRE). The one-step HRE was undertaken using a high extrusion ratio of 70:1 at 250, 300 and 350°C. And the two-step HRE was conducted with an extrusion ratio of 7 for the first step at 250, 300 and 350°C, followed by a second-step extrusion with an extrusion ratio of 10 at 250, 300 and 350°C. The initial grain size in the AZ31 ingot was 100μm and that after one-step HRE became similar to 5μm, after two-step HRE at 250, 300 and 350°C were 2, 4, 7μm, respectively, resulting in superior mechanical properties at ambient temperature. The microstructure of two-step HRE was finer and uniformer than that of one-step HRE and the strength of one-step and two-step HRE were similar, moreover, the elongation of one-step HRE was improved markedly than that of two-step HRE. Dynamic recrystallization and adjacent grain broking during HRE is introduced to explain the effects of one-step and two-step HRE on the microstructure and mechanical properties of AZ31 Mg alloy. The current results imply that the simple HRE method might be a feasible processing method for industry applications, and the multiply steps extrusion are effective to fabricate high strength of fine grained hcp metals.

Free-standing three-dimensional hollow bacterial cellulose structures with controlled geometry via patterned superhydrophobic–hydrophilic surfaces

Soft Matter ◽  
2018 ◽  
Vol 14 (19) ◽  
pp. 3955-3962 ◽  
Author(s):  
Anna Laromaine ◽  
Tina Tronser ◽  
Ivana Pini ◽  
Sebastià Parets ◽  
Pavel A. Levkin ◽  
...  
Keyword(s):  
Bacterial Cellulose ◽  
Three Dimensional ◽  
Advanced Materials ◽  
Free Standing ◽  
Step Process ◽  
Hydrophilic Surfaces ◽  
One Step ◽  
Cellulose Structures

Biosynthesis of multiple shapes of 3D self-standing BC structures in a static one-step process to fabricate advanced materials.

Progress in One-Pot Synthesis of Methyl Isobutyl Ketone Using Multifunctional Layered Based Catalysts

2013 ◽  
Vol 571 ◽  
pp. 169-196
Author(s):  
Nigamananda Das
Keyword(s):  
Methyl Isobutyl Ketone ◽  
Single Step ◽  
Methyl Isobutyl ◽  
Isobutyl Ketone ◽  
One Pot ◽  
Catalytic Systems ◽  
Step Process ◽  
One Pot Synthesis ◽  
Multifunctional Catalysts ◽  
One Step

Methyl isobutyl ketone (MIBK) is one of the most widely produced and used aliphatic ketones worldwide. The one-step MIBK process with no intermediate separation steps using multifunctional catalysts is an important development towards greener organic synthesis and generates tremendous interest among the researcher across the globe. The single step process is facile and more economically viable and has provided opportunity to develop new and improved catalyst systems capable of operating under mild conditions. A widely variety of catalytic systems have been used in one-step process during last three to four decades. The progress in one-pot synthesis of MIBK using different multifunctional catalysts with special reference to layered based catalysts was critically reviewed in this article.

Influence of Boron on Mechanical Properties and Microstructures of Hot-Rolled Interstitial Free Steel

2005 ◽  
Vol 495-497 ◽  
pp. 537-542 ◽  
Author(s):  
S.I. Kim ◽  
Shi Hoon Choi ◽  
Yeon Chul Yoo
Keyword(s):  
Mechanical Properties ◽  
High Strength ◽  
Recrystallization Temperature ◽  
Interstitial Free ◽  
If Steel ◽  
Softening Behavior ◽  
Axial Tensile ◽  
Dynamic Softening ◽  
Work Hardening Rate ◽  
Hot Rolled

This paper examines an effect of boron (B) on dynamic softening behavior, mechanical properties and microstructures for Nb-Ti added high strength interstitial free (IF) steel. For this purpose, IF steels containing 0ppm B, 5ppm B and 30ppm B were chosen. Continuous cooling compression test was performed to investigate dynamic softening behavior. Mechanical properties and microstructures of pilot hot-rolled IF steel sheet were analyzed by uni-axial tensile test and electron back-scattered diffraction (EBSD). It was found that no-dynamic recrystallization temperature (Tndrx) which can be determined from the relationship between flow stress and temperature is a constant of 955oC for all IF steels. However, an addition of B into IF steels increases work hardening rate at the temperature below Tndrx. It was also verified that B retards phase transformation of austenite into ferrite. EBSD analysis revealed that absence of B induces fine ferrite grain size and many high angle grain boundaries.

Synergistic Toughening Effects of Nano-CaCO3 and POE on Ternary-Phase Polypropylene Nanocomposites

2007 ◽  
Vol 334-335 ◽  
pp. 553-556 ◽  
Author(s):  
Min Zhi Rong ◽  
Ming Qiu Zhang ◽  
Chuan Guo Ma
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Synergistic Effect ◽  
Ternary Phase ◽  
Binary Blends ◽  
Step Process ◽  
Phase Structures ◽  
Polypropylene Nanocomposites ◽  
One Step ◽  
The One

Microstructure and mechanical properties of ternary PP/POE/nano-CaCO3 composites were investigated. Two different phase structures were obtained mainly by adjusting processing sequence. The one-step process led to the isolated distribution of elastomer and CaCO3 particles in PP matrix, while the two-step one attained an encapsulated microstructure. In comparison with binary blends of PP/POE or pure PP, toughness of the ternary composites was significantly increased. Meanwhile, their stiffness and tensile strength kept nearly unchanged or slightly enhanced, implying that there is a synergistic effect between nano-CaCO3 and POE components.

Pigment printing of polyester fabric using a single step synthesized PDMS-modified polyurethane-acrylic/pigment hybrid emulsion

2021 ◽  
pp. 004051752110185
Author(s):  
Ziwen Xie ◽  
Xiaofei Yan ◽  
Jiawei Li ◽  
Chenkai Zhu ◽  
Dongming Qi
Keyword(s):  
Mechanical Properties ◽  
Miniemulsion Polymerization ◽  
Polyester Fabric ◽  
Air Permeability ◽  
Single Step ◽  
Thermal And Mechanical Properties ◽  
Color Strength ◽  
Latex Particles ◽  
One Step ◽  
Hybrid Latex

A novel, waterborne polydimethylsiloxane (PDMS)-modified polyurethane-acrylic (Si-PUA)/pigment hybrid emulsion was synthesized by one-step miniemulsion polymerization for the pigment printing of polyester fabric. The phase structure, hydrophobicity, and thermal and mechanical properties of the formed films with different PDMS contents from the hybrid emulsion were investigated. The results indicated that the pigment particles were uniformly distributed in the homogeneous phase polymer substrate without phase separation occurring between the PDMS phase and polyurethane-acrylic. The hydrophobicity and toughness of the Si-PUA/pigment hybrid latex films gradually increased with the increase of PDMS content. Moreover, the obtained hybrid emulsion was used as a self-curable hybrid pigment that was applied to polyethylene terephthalate fabric for pigment printing. This showed that the Si-PUA/pigment hybrid latex particles yielded similarly good values in terms of color strength, and dry- and wet-rubbing fastness to the PDMS-free hybrid latex particles. Furthermore, use of the Si-PUA/pigment hybrid latex avoided certain problems related to printed fabric, such as poor air permeability and softness.

scholarly journals Mechanical Properties of Architectured Gelatin-Based Hydrogels on Different Hierarchical Levels

MRS Advances ◽  
2016 ◽  
Vol 1 (27) ◽  
pp. 1995-2001 ◽  
Author(s):  
Radovan Vukićević ◽  
Axel T. Neffe ◽  
Tim Gebauer ◽  
Oliver Frank ◽  
Michael Schossig ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Ethyl Ester ◽  
Tensile Tests ◽  
Step Process ◽  
Afm Indentation ◽  
Opposite Trend ◽  
Hierarchical Levels ◽  
One Step ◽  
Micro Level ◽  
Porous Biomaterials

ABSTRACTPreparation of three-dimensionally architectured porous biomaterials can be achieved in a one-step process by stabilizing gelatin with L-lysine diisocyanate ethyl ester (LDI) in water. The reaction of gelatin with LDI in presence of water leads to the formation of oligourea bridges between gelatin molecules and oligourea chains grafted on gelatin. The number and the length of the bridges, as well as of the grafted chains strongly depend on the concentration of the LDI used for the stabilization, and this has huge influence on the mechanical properties of the material on different hierarchical levels. Higher LDI concentrations yield materials with increased deformation resistance in tensile tests due to the higher number of covalent and physical netpoints in the material. However, mechanical properties determined on the micro-level by AFM indentation showed the opposite trend, i.e. a decrease of Young’s modulus with increasing LDI content. This was interpreted by a decreasing number of shorter oligourea bridges between gelatin chains with decreasing LDI content.

scholarly journals Transport Properties of One-Step Compression Molded Epoxy Nanocomposite Foams

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 756 ◽  
Author(s):  
Mario Martin-Gallego ◽  
Emil Lopez-Hernandez ◽  
Javier Pinto ◽  
Miguel A. Rodriguez-Perez ◽  
Miguel A. Lopez-Manchado ◽  
...  
Keyword(s):  
Transport Properties ◽  
High Strength ◽  
Single Step ◽  
Environmental Stability ◽  
Syntactic Foams ◽  
Molding Process ◽  
Polymeric Microspheres ◽  
Nanocomposite Foams ◽  
One Step ◽  
Strength And Stiffness

Owing to their high strength and stiffness, thermal and environmental stability, lower shrinkage, and water resistance, epoxy resins have been the preferred matrix for the development of syntactic foams using hollow glass microspheres. Although these foams are exploited in multiple applications, one of their issues is the possibility of breakage of the glass hollow microspheres during processing. Here, we present a straightforward and single-step foaming protocol using expandable polymeric microspheres based on the well-established compression molding process. We demonstrate the viability of the protocol producing two sets of nanocomposite foams filled with carbon-based nanoparticles with improved transport properties.

A One-Step Method to Fabricate PLLA Scaffolds With Deposition of Bioactive Hydroxyapatite and Collagen Using Ice-Based Microporogens

2009 ◽  
Author(s):  
Yun Chen ◽  
Jiashen Li ◽  
Rocky S. Tuan ◽  
Arthur F. T. Mak
Keyword(s):  
Tissue Engineering ◽  
Single Step ◽  
Step Method ◽  
Step Process ◽  
Collagen Coating ◽  
One Step ◽  
Bioactive Agents

Scaffolding is an essential issue in tissue engineering. We have recently developed an approach to generate HA/collagen coated poly(lactic-glycolic acids) scaffolds using a porogen-leaching method [1]. The approach involves a two-step process with coating first on the paraffin microspheres and then using the coated microspheres both as the porogens and the vehicles to transfer the bioactive apatite/collagen coating. In this study, we describe an advancement of the porogen-based technology using ice-based microporogens to deposit multiple bioactive agents into the desired scaffold in a single step.

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