Applied Rheology as Tool for the Assessment of Chitosan Hydrogels for Regenerative Medicine

The regeneration of soft tissues that connect, support or surround other tissues is of great interest. In this sense, hydrogels have great potential as scaffolds for their regeneration. Among the different raw materials, chitosan stands out for being highly biocompatible, which, together with its biodegradability and structure, makes it a great alternative for the manufacture of hydrogels. Therefore, the aim of this work was to develop and characterize chitosan hydrogels. To this end, the most important parameters of their processing, i.e., agitation time, pH, gelation temperature and concentration of the biopolymer used were rheologically evaluated. The results show that the agitation time does not have a significant influence on hydrogels, whereas a change in pH (from 3.2 to 7) is a key factor for their formation. Furthermore, a low gelation temperature (4 °C) favors the formation of the hydrogel, showing better mechanical properties. Finally, there is a percentage of biopolymer saturation, from which the properties of the hydrogels are not further improved (1.5 wt.%). This work addresses the development of hydrogels with high thermal resistance, which allows their use as scaffolds without damaging their mechanical properties.

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Impact of Flax Fiber Reinforcement on Mechanical Properties of Solid and Foamed Geopolymer Concrete

Advances in Technology Innovation ◽

10.46604/aiti.2021.5294 ◽

2020 ◽

Author(s):

Kinga Korniejenko ◽

Michał Łach ◽

Maria Hebdowska-Krupa ◽

Janusz Mikuła

Keyword(s):

Mechanical Properties ◽

Significant Influence ◽

Energy Demand ◽

Raw Materials ◽

Previous Treatment ◽

Strength Properties ◽

Flax Fiber ◽

Building Industry ◽

Geopolymer Concrete ◽

Advanced Composites

The main objective of this study is to develop the advanced composites for civil engineering applications as material for the building industry, especially for an insulation purpose. The research processes include several steps. Firstly, the prototype elements, such as bricks and elevation elements were performed from eco-friendly composite -flax fiber reinforced geopolymer. The elements were designed to take into consideration for environment. Geopolymers are environmentally friendly, sustainable, and resource efficient, including energy demand. Next, the wall was built from these elements and exposed during the three months in a relevant environment. The main conclusion of the research is that the kind of fibers is important for the mechanical properties of the composite, including the fact that for those different fibers could be more beneficial for different raw materials, giving higher strength properties. The significant influence on the mechanical properties of the composites has the adhesion between fiber and material used as a matrix. The adhesion depends among others on the previous treatment of the fibers.

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The Sintering Behaviour and Mechanical Properties of Hydroxyapatite - Based Composites for Bone Tissue Regeneration

Revista de Chimie ◽

10.37358/rc.18.5.6306 ◽

2018 ◽

Vol 69 (5) ◽

pp. 1272-1275 ◽

Cited By ~ 1

Author(s):

Camelia Tecu ◽

Aurora Antoniac ◽

Gultekin Goller ◽

Mustafa Guven Gok ◽

Marius Manole ◽

...

Keyword(s):

Mechanical Properties ◽

Tricalcium Phosphate ◽

Cosmetic Surgery ◽

Mechanical Stability ◽

Raw Materials ◽

Oyster Shell ◽

Bone Tissue Regeneration ◽

Sintering Behavior ◽

Bovine Bone ◽

Human Teeth

Bone reconstruction is a complex process which involves an osteoconductive matrix, osteoinductive signaling, osteogenic cells, vascularization and mechanical stability. Lately, to improve the healing of the bone defects and to accelerate the bone fusion and bone augmentation, bioceramic composite materials have been used as bone substitutes in the field of orthopedics and dentistry, as well as in cosmetic surgery. Of all types of bioceramics, the most used is hydroxyapatite, because of its similar properties to those of the human bone and better mechanical properties compared to b-tricalcium phosphate [1]. Currently, the most used raw materials sources for obtaining the hydroxyapatite are: bovine bone, seashells, corals, oyster shell, eggshells and human teeth. There are two common ways to obtain hydroxyapatite: synthetically and naturally. Generally, for the improvement of the mechanical properties and the structural one, hydroxyapatite is subjected to the sintering process. Considering the disadvantages of hydroxyapatite such as poor biodegradation rate, b-TCP has been developed, which has some disadvantages too, such as brittleness. For this reason, the aim of this study is to look into the effect of adding magnesium oxide on the sintering behavior, the structure and the mechanical properties of the hydroxyapatite-tricalcium phosphate composites.

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Influence of Gating System Parameters of Die-Cast Molds on Properties of Al-Si Castings

Materials ◽

10.3390/ma14133755 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3755

Author(s):

Štefan Gašpár ◽

Tomáš Coranič ◽

Ján Majerník ◽

Jozef Husár ◽

Lucia Knapčíková ◽

...

Keyword(s):

Mechanical Properties ◽

Computer Modelling ◽

Permanent Deformation ◽

Surface Hardness ◽

Technological Parameters ◽

Inlet System ◽

Die Cast ◽

Key Factor ◽

Fine Grained Structure ◽

Design Solutions

The resulting quality of castings indicates the correlation of the design of the mold inlet system and the setting of technological parameters of casting. In this study, the influence of design solutions of the inlet system in a pressure mold on the properties of Al-Si castings was analyzed by computer modelling and subsequently verified experimentally. In the process of computer simulation, the design solutions of the inlet system, the mode of filling the mold depending on the formation of the casting and the homogeneity of the casting represented by the formation of shrinkages were assessed. In the experimental part, homogeneity was monitored by X-ray analysis by evaluating the integrity of the casting and the presence of pores. Mechanical properties such as permanent deformation and surface hardness of castings were determined experimentally, depending on the height of the inlet notch. The height of the inlet notch has been shown to be a key factor, significantly influencing the properties of the die-cast parts and influencing the speed and filling mode of the mold cavity. At the same time, a significant correlation between porosity and mechanical properties of castings is demonstrated. With the increasing share of porosity, the values of permanent deformation of castings increased. It is shown that the surface hardness of castings does not depend on the integrity of the castings but on the degree of subcooling of the melt in contact with the mold and the formation of a fine-grained structure in the peripheral zones of the casting.

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Effect of Water Ingress on the Mechanical and Chemical Properties of Polybutylene Terephthalate Reinforced with Glass Fibers

Materials ◽

10.3390/ma14051261 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1261

Author(s):

Catarina S. P. Borges ◽

Alireza Akhavan-Safar ◽

Eduardo A. S. Marques ◽

Ricardo J. C. Carbas ◽

Christoph Ueffing ◽

...

Keyword(s):

Mechanical Properties ◽

Water Absorption ◽

Water Uptake ◽

Significant Influence ◽

Water Immersion ◽

Water Diffusion ◽

Polybutylene Terephthalate ◽

Chemical Changes ◽

Water Ingress ◽

Effect Of Water

Short fiber reinforced polymers are widely used in the construction of electronic housings, where they are often exposed to harsh environmental conditions. The main purpose of this work is the in-depth study and characterization of the water uptake behavior of PBT-GF30 (polybutylene terephthalate with 30% of short glass fiber)as well as its consequent effect on the mechanical properties of the material. Further analysis was conducted to determine at which temperature range PBT-GF30 starts experiencing chemical changes. The influence of testing procedures and conditions on the evaluation of these effects was analyzed, also drawing comparisons with previous studies. The water absorption behavior was studied through gravimetric tests at 35, 70, and 130 °C. Fiber-free PBT was also studied at 35 °C for comparison purposes. The effect of water and temperature on the mechanical properties was analyzed through bulk tensile tests. The material was tested for the three temperatures in the as-supplied state (without drying or aging). Afterwards, PBT-GF30 was tested at room temperature following water immersion at the three temperatures. Chemical changes in the material were also analyzed through Fourier-transform infrared spectroscopy (FTIR). It was concluded that the water diffusion behavior is Fickian and that PBT absorbs more water than PBT-GF30 but at a slightly higher rate. However, temperature was found to have a more significant influence on the rate of water diffusion of PBT-GF30 than fiber content did. Temperature has a significant influence on the mechanical properties of the material. Humidity contributes to a slight drop in stiffness and strength, not showing a clear dependence on water uptake. This decrease in mechanical properties occurs due to the relaxation of the polymeric chain promoted by water ingress. Between 80 and 85 °C, after water immersion, the FTIR profile of the material changes, which suggests chemical changes in the PBT. The water absorption was simulated through heat transfer analogy with good results. From the developed numerical simulation, the minimum plate size to maintain the water ingress unidirectional was 30 mm, which was validated experimentally.

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Effect of Sintering Temperature on Microstructure and Mechanical Properties of Hot-Pressed Fe/FeAl2O4 Composite

Crystals ◽

10.3390/cryst11040422 ◽

2021 ◽

Vol 11 (4) ◽

pp. 422

Author(s):

Kuai Zhang ◽

Yungang Li ◽

Hongyan Yan ◽

Chuang Wang ◽

Hui Li ◽

...

Keyword(s):

Mechanical Properties ◽

Bending Strength ◽

Sintering Temperature ◽

Raw Materials ◽

Hot Press ◽

Microstructure And Mechanical Properties ◽

Powder Particles ◽

Hot Press Sintering ◽

Sintering Method

An Fe/FeAl2O4 composite was prepared with Fe-Fe2O3-Al2O3 powder by a hot press sintering method. The mass ratio was 6:1:2, sintering pressure was 30 MPa, and holding time was 120 min. The raw materials for the powder particles were respectively 1 µm (Fe), 0.5 µm (Fe2O3), and 1 µm (Al2O3) in diameter. The effect of sintering temperature on the microstructure and mechanical properties of Fe/FeAl2O4 composite was studied. The results showed that Fe/FeAl2O4 composite was formed by in situ reaction at 1300 °C–1500 °C. With the increased sintering temperature, the microstructure and mechanical properties of the Fe/FeAl2O4 composite showed a change law that initially became better and then became worse. The best microstructure and optimal mechanical properties were obtained at 1400 °C. At this temperature, the grain size of Fe and FeAl2O4 phases in Fe/FeAl2O4 composite was uniform, the relative density was 96.7%, and the Vickers hardness and bending strength were 1.88 GPa and 280.0 MPa, respectively. The wettability between Fe and FeAl2O4 was enhanced with increased sintering temperature. And then the densification process was accelerated. Finally, the microstructure and mechanical properties of the Fe/FeAl2O4 composite were improved.

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Comparative Study of High-Performance Concrete Characteristics and Loading Test of Pretensioned Experimental Beams

Crystals ◽

10.3390/cryst11040427 ◽

2021 ◽

Vol 11 (4) ◽

pp. 427

Author(s):

Pavlina Mateckova ◽

Vlastimil Bilek ◽

Oldrich Sucharda

Keyword(s):

Mechanical Properties ◽

High Performance ◽

High Performance Concrete ◽

Raw Materials ◽

Load Capacity ◽

Materials Testing ◽

Loading Test ◽

Conventional Concrete ◽

Concrete Mechanical Properties ◽

Normal Strength

High-performance concrete (HPC) is subjected to wide attention in current research. Many research tasks are focused on laboratory testing of concrete mechanical properties with specific raw materials, where a mixture is prepared in a relatively small amount in ideal conditions. The wider utilization of HPC is connected, among other things, with its utilization in the construction industry. The paper presents two variants of HPC which were developed by modification of ordinary concrete used by a precast company for pretensioned bridge beams. The presented variants were produced in industrial conditions using common raw materials. Testing and comparison of basic mechanical properties are complemented with specialized tests of the resistance to chloride penetration. Tentative expenses for normal strength concrete (NSC) and HPC are compared. The research program was accomplished with a loading test of model experimental pretensioned beams with a length of 7 m made of ordinarily used concrete and one variant of HPC. The aim of the loading test was to determine the load–deformation diagrams and verify the design code load capacity calculation method. Overall, the article summarizes the possible benefits of using HPC compared to conventional concrete.

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Microstructure and Mechanical Properties of ZrB2/h-BN Multiphase Ceramics by Low-Temperature Reactive Sintering

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.697.510 ◽

2016 ◽

Vol 697 ◽

pp. 510-514 ◽

Cited By ~ 1

Author(s):

Feng Rui Zhai ◽

Ke Shan ◽

Ruo Meng Xu ◽

Min Lu ◽

Zhong Zhou Yi ◽

...

Keyword(s):

Mechanical Properties ◽

Relative Density ◽

Fracture Strength ◽

Solid Phase ◽

Raw Materials ◽

Solid Phase Reaction ◽

Phase Reaction ◽

Microstructure And Mechanical Properties ◽

Multiphase Ceramics ◽

Strength And Toughness

In the present paper, the ZrB2/h-BN multiphase ceramics were fabricated by SPS (spark plasma sintering) technology at lower sintering temperature using h-BN, ZrO2, AlN and Si as raw materials and B2O3 as a sintering aid. The phase constitution and microstructure of specimens were analyzed by XRD and SEM. Moreover, the effects of different sintering pressures on the densification, microstructure and mechanical properties of ZrB2/h-BN multiphase ceramics were also systematically investigated. The results show that the ZrB2 was obtained through solid phase reaction at different sintering pressures, and increasing sintering pressure could accelerate the formation of ZrB2 phase. As the sintering pressure increasing, the fracture strength and toughness of the sintered samples had a similar increasing tendency as the relative density. The better comprehensive properties were obtained at given sintering pressure of 50MPa, and the relative density, fracture strength and toughness reached about 93.4%, 321MPa and 3.3MPa·m1/2, respectively. The SEM analysis shows that the h-BN grains were fine and uniform, and the effect of sintering pressure on grain size was inconspicuous. The distribution of grain is random cross array, and the fracture texture was more obvious with the increase of sintering pressure. The fracture mode of sintered samples remained intergranular fracture mechanism as sintering pressure changed, and the grain refinement, grain pullout and crack deflection helped to increase the mechanical properties.

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Atomistic insights into the structure and elasticity of densified 45S5 bioactive glasses

Physical Chemistry Chemical Physics ◽

10.1039/d1cp02192c ◽

2021 ◽

Author(s):

Youssef Ouldhnini ◽

Achraf Atila ◽

Said Ouaskit ◽

abdellatif hasnaoui

Keyword(s):

Regenerative Medicine ◽

Soft Tissues ◽

Soda Lime ◽

Model System ◽

Bioactive Glasses

Glasses have applications in regenerative medicine due to their bioactivity, enabling interactions with hard and soft tissues. Soda-lime phosphosilicate glasses, such as 45S5, represent a model system of bioactive glasses....

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In Situ Preparation and Mechanical Properties of (ZrB2+ZrC)/Zr3[Al(Si)]4C6 Composites

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.602-603.438 ◽

2014 ◽

Vol 602-603 ◽

pp. 438-442

Author(s):

Lei Yu ◽

Jian Yang ◽

Tai Qiu

Keyword(s):

Mechanical Properties ◽

Fracture Toughness ◽

Bending Strength ◽

Coefficient Of Thermal Expansion ◽

Raw Materials ◽

Linear Increase ◽

Fine Grain ◽

Fine Grain Strengthening ◽

Uniform Microstructure

Fully dense (ZrB2+ZrC)/Zr3[Al (Si)]4C6 composites with ZrB2 content varying from 0 to 15 vol.% and fixed ZrC content of 10 vol.% were successfully prepared by in situ hot-pressing in Ar atmosphere using ZrH2, Al, Si, C and B4C as raw materials. With the increase of ZrB2 content, both the bending strength and fracture toughness of the composites increase and then decrease. The synergistic action of ZrB2 and ZrC as reinforcements shows significant strengthening and toughing effect to the Zr3[Al (Si)]4C6 matrix. The composite with 10 vol.% ZrB2 shows the optimal mechanical properties: 516 MPa for bending strength and 6.52 MPa·m1/2 for fracture toughness. With the increase of ZrB2 content, the Vickers hardness of the composites shows a near-linear increase from 15.3 GPa to 16.7 GPa. The strengthening and toughening effect can be ascribed to the unique mechanical properties of ZrB2 and ZrC reinforcements, the differences in coefficient of thermal expansion and modulus between them and Zr3[Al (Si)]4C6 matrix, fine grain strengthening and uniform microstructure derived by the in situ synthesis reaction.

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