Cryogenic Treatment of Polymer/MWCNT Nano-Composites for Mechanical and Tribological Applications

2019 ◽  
pp. 103-161 ◽  
Author(s):  
Swamini Chopra ◽  
S. Sreya ◽  
Rohit V. Babhulkar ◽  
Swaksha P. Halde ◽  
Kavita A. Deshmukh ◽  
...  
Keyword(s):  
Polymer Matrix ◽  
Structural Changes ◽  
Cryogenic Treatment ◽  
Treatment Temperature ◽  
Nano Composites ◽  
Crystallographic Structure ◽  
Nano Composite ◽  
Structural Modifications ◽  
Mechanical And Tribological Properties ◽  
Crystallinity Changes

The cryogenic treatment of material has been known to motivate structural stability by rearranging its crystallographic structure in metals and by promoting intermolecular as well as intramolecular rearrangements in polymers. Additionally, in case of polymers reinforced with micro fillers, the structural changes brought about by cryogenic treatment are still largely governed by the polymer matrix itself. Thus, when investigated for their mechanical and tribological properties, the response of polymer/MWCNT nano-composites after cryogenic treatment was found to be depending on the cryo-structural modifications in the polymer matrix, followed by the MWCNT interaction to some extent. The enhancement in the mechanical properties of the polymer/MWCNT nano-composites is attributed to the increasing % crystallinity, changes in crystal structure, conversion of less stable phases into more stable phases, change in the nature of bonding and strengthening of interphase between polymer and MWCNT. Thus, for the cryogenic treatment temperature of -185 °C, the optimum soaking period for PA and PA/MWCNT nano-composite was 24 hrs, whereas for PBT and PBT/MWCNT nano-composite it was 12 hrs and 16 hrs, respectively. This agrees well with the popular claim that each polymer has a specific functional group and/or structural characteristic that readily responds to the cryogenic treatments conditions (irrespective of the filler type, content and/or interaction), thereby, modifying the structure and giving superior properties, which makes cryogenic treatment a material specific process.

Structural modifications of disordered mesocarbon microbeads with lower temperatures of heat treatment

1998 ◽  
Vol 13 (7) ◽  
pp. 2015-2022 ◽  
Author(s):  
Prathap Haridoss ◽  
Francisco A. Uribe ◽  
Fernando H. Garzon ◽  
Thomas A. Zawodzinski
Keyword(s):  
Heat Treatment ◽  
Heat Treatment Temperature ◽  
Structural Changes ◽  
Electronic Conductivity ◽  
Average Crystallite Size ◽  
Treatment Temperature ◽  
Rechargeable Lithium Batteries ◽  
Structural Modifications ◽  
Mesocarbon Microbeads ◽  
Organic Fractions

We describe the variation of structural and physical properties of mesocarbon microbeads, a potential anode material for rechargeable lithium batteries, as a function of heat-treatment temperature in the range 400–1100 °C. Scanning electron microscopy (SEM) studies indicated changes in the morphology of the mesocarbons with heat treatment. X-ray studies show that average crystallite size varies considerably with heat treatment. The d002 spacing decreases with increasing heat-treatment temperatures. The electronic conductivity of the mesocarbon microbeads also increases substantially with increasing heat-treatment temperature. Based on thermogravimetric analysis (TGA) and other measurements, we find that organic fractions volatilizes out of these carbons in two distinct stages. The observed weight loss correlates with the structural changes observed. We suggest that these observations are consistent with two types of hydrogenated fractions present in the “green” mesocarbons.

scholarly journals Temperature effect in physicochemical and bioactive behavior of biogenic hydroxyapatite obtained from porcine bones

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
P. A. Forero-Sossa ◽  
J. D. Salazar-Martínez ◽  
A. L. Giraldo-Betancur ◽  
B. Segura-Giraldo ◽  
E. Restrepo-Parra
Keyword(s):  
Structural Changes ◽  
Biological Fluid ◽  
Treatment Temperature ◽  
Mineral Phase ◽  
Calcination Temperatures ◽  
Bioactive Properties ◽  
Temperature Ranges ◽  
Compositional Changes ◽  
Type Substitution ◽  
Biogenic Hydroxyapatite

AbstractBiogenic hydroxyapatite (BHAp) is a widely used material in the biomedical area due to its similarities with the bone tissue mineral phase. Several works have been spotlighted on the thermal behavior of bone. However, little research has focused on determining the influence of calcination temperature in the physicochemical and bioactive properties of BHAp. In this work, a study of the physicochemical properties’ changes and bioactive response of BHAp produced from porcine femur bones using calcination temperatures between 900 to 1200 °C was conducted. The samples’ structural, morphological, and compositional changes were determined using XRD, SEM, and FTIR techniques. XRD results identified three temperature ranges, in which there are structural changes in BHAp samples and the presence of additional phases. Moreover, FTIR results corroborated that B-type substitution is promoted by increasing the heat treatment temperature. Likewise, samples were immersed in a simulated biological fluid (SBF), following the methodology described by Kokubo and using ISO 23317:2014 standard, for 3 and 7 days. FTIR and SEM results determined that the highest reaction velocity was reached for samples above 1000 °C, due to intensity increasing of phosphate and carbonate bands and bone-like apatite morphologies, compared to other temperatures evaluated.

scholarly journals Structure-Activity Relationships of Sandalwood Odorants: Synthesis of a New Campholene Derivative

2010 ◽  
Vol 5 (9) ◽  
pp. 1934578X1000500
Author(s):  
Iris Stappen ◽  
Joris Höfinghoff ◽  
Gerhard Buchbauer ◽  
Peter Wolschann
Keyword(s):  
Structural Changes ◽  
Great Influence ◽  
Complete Loss ◽  
Side Chain ◽  
Side Chains ◽  
Quaternary Carbon ◽  
Structural Modifications ◽  
Structure Activity ◽  
Highly Sensitive ◽  
Sandalwood Odorants

Structural modifications of natural (-)-( Z)-β-santalol have shown that the sandalwood odor impression is highly sensitive, even to small structural changes. Particularly, the substitution of the quaternary carbon is of great influence on the scent. Epi-compounds with side chains in the endo-position possess sandalwood odor in only a few derivatives, whereas modifications at this side chain, as well as modification at the bicyclic ring systems mostly lead to a complete loss of sandalwood fragrance.

Structural changes induced by cation ordering in ferrotapiolite

2006 ◽  
Vol 70 (3) ◽  
pp. 319-328 ◽  
Author(s):  
M. Zema ◽  
S.C. Tarantino ◽  
A. Giorgiani
Keyword(s):  
Structural Changes ◽  
Rapid Determination ◽  
Linear Increase ◽  
X Ray Diffraction ◽  
Ionic Radii ◽  
Structural Modifications ◽  
Lattice Constants ◽  
Structure Factors ◽  
Polyhedral Volumes ◽  
Degree Of Order

AbstractStructural modifications as a function of the degree of order (Q) in FeTa2O6 ferrotapiolite have been characterized by means of single-crystal X-ray diffraction (SC-XRD). A total of 26 datasets covering the range of Q between 0.154 and 1 have been obtained by thermal treatments followed by quenching of natural tapiolite crystals. Ordering of Fe2+ at the A sites and of Ta5+ at the B sites causes a linear increase in the a/c lattice constants ratio, as a consequence of a linear decrease of the c dimension and only slight modifications of the a parameter. Calibration of a/c vs. Q represents a very useful tool for a rapid determination of the degree of order of tapiolite samples. Polyhedral volumes of the two octahedral sites vary linearly with Q as a consequence of the different ionic radii of the two species. Both the sites remain almost regular at all Q values but the B site shows an increasing off-centre displacement of the cation with increasing Q. Observed structure factors of supercell reflections, characterized by l ≠ 3n, increase linearly as a function of Q, thus representing a further tool for a quick evaluation of the degree of order.

Effect of carbon nanotubes modified with different concentrations of rare earth lanthanum on the mechanical and tribological properties of epoxy composites

2021 ◽  
pp. 002199832098764
Author(s):  
Mingren Jiang ◽  
Xianhua Cheng
Keyword(s):  
Carbon Nanotubes ◽  
Rare Earth ◽  
Polymer Matrix ◽  
Photoelectron Spectroscopy ◽  
Polymer Matrix Composites ◽  
Testing Machine ◽  
Matrix Composites ◽  
Mechanical And Tribological Properties ◽  
The Coefficient Of Friction ◽  
The Rare Earth

Rare earth modified acidified carbon nanotubes were prepared by functionalization of acidified carbon nanotubes with different concentrations of LaCl3. The modification results were characterized by Fourier-transform infrared and X-ray photoelectron spectroscopy. The rare earth successfully increases the surface activity of the acidified carbon nanotubes. Polymer matrix composites were prepared by using the rare earth modified acidified carbon nanotubes as the reinforcement in epoxy matrix. Mechanical properties were analyzed by Zwick Z100 testing machine and the tribological behaviors were test by multifunctional tribological tester. Compared with pure epoxy (epoxy resin), the mechanical strength of the best composite sample was increased by 50–120%, the coefficient of friction was reduced by 19.4% and the wear rate was reduced by approximately 40 times. The experimental results show that the RE concentration of 0.2–0.3 wt% has the most obvious influence on the properties of polymer composites. The mechanism of rare earth reinforcement in polymer matrix is analyzed and suggested.

High conductive graphite additives for magnesium catalyzed cast PA6 polymer matrix

2010 ◽  
Vol 1 (1) ◽  
pp. 86-89
Author(s):  
Matyas Ando ◽  
Gabor Kalacska ◽  
T. Czigany
Keyword(s):  
Polymer Matrix ◽  
Tribological Properties ◽  
Surface Resistance ◽  
Polyamide 6 ◽  
Mechanical And Tribological Properties ◽  
Base Matrix ◽  
Cast Polyamide

At this article we give a brief review about the additives effects for cast polyamide 6engineering plastics. The natural grade Magnesium catalyzed polyamide 6 has unique mechanicalproperties. Our target is to keep the mechanical and tribological properties with the development ofantistatic and ESD composite version. High conductive very effective to improve the electricalconductivity of magnezium catalized cast PA 6. Only few amount, 0,5% can result good antistaticproperty for the base matrix. Over 3% of additive the surface resistance of the material – performing107 Ω - can reach the ESD (Electrostatic Dissipative) category.

scholarly journals Pathological transitions in myelin membranes driven by environmental and multiple sclerosis conditions

2018 ◽  
Vol 115 (44) ◽  
pp. 11156-11161 ◽  
Author(s):  
Rona Shaharabani ◽  
Maor Ram-On ◽  
Yeshayahu Talmon ◽  
Roy Beck
Keyword(s):  
Multiple Sclerosis ◽  
Phase Transition ◽  
Lipid Composition ◽  
Environmental Conditions ◽  
Structural Changes ◽  
Environmental Changes ◽  
Hexagonal Phase ◽  
Structural Phase ◽  
Structural Modifications ◽  
Transition Points

Multiple sclerosis (MS) is an autoimmune disease, leading to the destruction of the myelin sheaths, the protective layers surrounding the axons. The etiology of the disease is unknown, although there are several postulated environmental factors that may contribute to it. Recently, myelin damage was correlated to structural phase transition from a healthy stack of lamellas to a diseased inverted hexagonal phase as a result of the altered lipid stoichiometry and low myelin basic protein (MBP) content. In this work, we show that environmental conditions, such as buffer salinity and temperature, induce the same pathological phase transition as in the case of the lipid composition in the absence of MBP. These phase transitions have different transition points, which depend on the lipid’s compositions, and are ion specific. In extreme environmental conditions, we find an additional dense lamellar phase and that the native lipid composition results in similar pathology as the diseased composition. These findings demonstrate that several local environmental changes can trigger pathological structural changes. We postulate that these structural modifications result in myelin membrane vulnerability to the immune system attacks and thus can help explain MS etiology.

Investigation of Heat Treated Electrodeposited CoNiFe on Microstructure and Hardness

2015 ◽  
Vol 1113 ◽  
pp. 56-61
Author(s):  
Nor Azrina Resali ◽  
Koay Mei Hyie ◽  
M.N. Berhan ◽  
C.M. Mardziah
Keyword(s):  
Heat Treatment ◽  
Heat Treatment Temperature ◽  
Treatment Temperature ◽  
Crystallographic Structure ◽  
Face Centered Cubic ◽  
Heat Treated ◽  
Hardness Property ◽  
Finishing Process ◽  
The Face ◽  
Face Centered

In this research, heat treatment is the final finishing process applied on nanocrystalline CoNiFe to improve microstructure for good hardness property. Nanocrystalline CoNiFe has been synthesized using the electrodeposition method. This study investigated the effect of heat treatment at 500°C, 600°C, 700°C and 800°C on electrodeposited nanocrystalline CoNiFe. The heat treatment process was performed in the tube furnace with flowing Argon gas. By changing the heat treatment temperature, physical properties such as phase and crystallographic structure, surface morphology, grain size and hardness of nanocrystalline CoNiFe was studied. The nanocrystalline CoNiFe phase revealed the Face Centered Cubic (FCC) and Body Centered Cubic (BCC) crystal structure. FESEM micrographs showed that the grain sizes of the coatings were in the range of 78.76 nm to 132 nm. Dendrite shape was found in the microstructure of nanocrystalline CoNiFe. The nanocrystalline CoNiFe prepared in heat treatment temperature of 700°C, achieved the highest hardness of 449 HVN. The surface roughness of nanocrystalline CoNiFe heated at 700°C was found to be smaller than other temperatures.

scholarly journals The Loop of the TPR1 Subdomain of Phi29 DNA Polymerase Plays a Pivotal Role in Primer-Terminus Stabilization at the Polymerization Active Site

Biomolecules ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 648
Author(s):  
del Prado ◽  
Santos ◽  
Lázaro ◽  
Salas ◽  
de Vega
Keyword(s):  
Dna Polymerase ◽  
Active Site ◽  
Structural Changes ◽  
Binding Capacity ◽  
Dna Polymerases ◽  
Crystallographic Structure ◽  
Genome Replication ◽  
Terminal Protein ◽  
Phi29 Dna Polymerase

Bacteriophage Phi29 DNA polymerase belongs to the protein-primed subgroup of family B DNA polymerases that use a terminal protein (TP) as a primer to initiate genome replication. The resolution of the crystallographic structure showed that it consists of an N-terminal domain with the exonuclease activity and a C-terminal polymerization domain. It also has two subdomains specific of the protein-primed DNA polymerases; the TP Regions 1 (TPR1) that interacts with TP and DNA, and 2 (TPR2), that couples both processivity and strand displacement to the enzyme. The superimposition of the structures of the apo polymerase and the polymerase in the polymerase/TP heterodimer shows that the structural changes are restricted almost to the TPR1 loop (residues 304–314). In order to study the role of this loop in binding the DNA and the TP, we changed the residues Arg306, Arg308, Phe309, Tyr310, and Lys311 into alanine, and also made the deletion mutant Δ6 lacking residues Arg306–Lys311. The results show a defective TP binding capacity in mutants R306A, F309A, Y310A, and Δ6. The additional impaired primer-terminus stabilization at the polymerization active site in mutants Y310A and Δ6 allows us to propose a role for the Phi29 DNA polymerase TPR1 loop in the proper positioning of the DNA and TP-priming 3’-OH termini at the preinsertion site of the polymerase to enable efficient initiation and further elongation steps during Phi29 TP-DNA replication.

scholarly journals Isolation of Candida species in children and their biofilm-forming ability on nano-composite surfaces

2020 ◽  
Vol 1 (1) ◽  
pp. 40-52
Author(s):  
Harina Akila Che Hussin ◽  
Nadiah Arshad ◽  
Siti Nor Humaira Nor Azemi ◽  
Raja Izzatun Nisa Raja Sahrul Hishan ◽  
Wan Nur Fatihah Wan Mohd Kamaluddin ◽  
...  
Keyword(s):  
Dental Caries ◽  
Oral Cavity ◽  
Buccal Mucosa ◽  
Candida Species ◽  
Soft Tissues ◽  
Tooth Surface ◽  
Nano Composites ◽  
Candida Spp ◽  
Nano Composite ◽  
Tooth Surfaces

Candida species including Candida albicans, Candida krusei and Candida glabrata are opportunistic microorganisms that inhabit oral cavity. The objective of this study is to determine the effect of dental caries on Candida spp. biofilm-forming ability on nano- composite with the hypothesis that dental caries enhances the colonization of Candida spp. To assess Candida spp. colonisation in the oral cavity of the paediatric patient, samples were obtained from 30 subjects aged five to six years old from Kuantan, Pahang, Malaysia. The samples were collected from buccal mucosa, palate and tooth surfaces using sterile swabs. 10 mL of patient’s saliva suspension was also collected. Following that, the samples were inoculated on CHROMagar and incubated for 24 h at 37 ºC. Candida biofilm of caries isolate C. albicans (HNFC2), and C. albicans ATCC 32354 were developed on three different types of nano-composites. The study showed that no C. albicans was isolated from the caries-free oral cavity while 76% of children with caries possessed Candida spp. 65% of the yeasts were isolated from the tooth surface. Only 35% of the total isolates were obtained from soft tissues, including palatal and buccal mucosa. C. albicans is the most isolated Candida spp. with 82% and 67% of the yeast were obtained from the tooth surface and buccal mucosa, respectively. Besides, HNFC2 significantly colonised the nano- composites more than the ATCC (P < 0.05). In the comparison of the three types of nano- composites, nano-hybrid-based containing pre-polymerised filler (cB) exhibited the least C. albicans HNFC2 cells colonisation with 7.7 x 10³ cells mL-1. In contrast, the nano-composite that contained bulk-filled nanohybrid (cC) was the most colonised with 14.3 x 10³ cells mL-1. In conclusion, dental caries enhances the colonization of Candida spp. in children's oral cavity, and that caries isolate form more biofilm on nano-composites compared to the lab strain C. albicans.

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