Abstract:When a concrete structure is exposed to fire, its structural safety is significantly compromised due to the spalling of members and scaling of concrete. In addition, its durability is substantially reduced due to certain chemical changes such as the dehydration of Ca(OH)2, the main hydration product of concrete, and the rehydration of CaO. Therefore, when fire damage occurs to a reinforced concrete (RC) building, rapid diagnosis and evaluation techniques are required for immediate repair and reinforcement, req… Show more
“…Consequently, this mixture change, even in the hydrogen-balanced condition, impacts the rate of axial growth. While the growth rate decreases, the fiber-to-fiber growth rate variation did reduce, albeit a modest decrease in Titanium oxide is known to exhibit a bronze color at low temperatures and a white color at higher temperatures [34]. The hydrogen-balanced (1:1) fibers exhibited a varying temperature gradient as it deposited, which was visible in Figure 7a, and where such thermal gradients would have created convective motion of the gases around the fiber that would lead to the oxidization of titanium.…”
In this study, the hyperbaric (2 bar) laser chemical vapor deposition of TiC fibers grown under various percent pressures of hydrogen and ratios of ethylene and titanium tetrachloride (2:1 or 1:1) are reported. In the hydrogen-rich (85%) condition, sequential fiber depositions became stunted as a result of a loss of hydrogen, which served as a reducing agent for the metal halide as hydrogen evolved with the hydrocarbon gas in the reaction zone because of the Le Chatelier principle. For the hydrogen-lean (25%) condition, the intrinsic fiber growth rate was invariant, but gas phase nucleation resulted in the hydrocarbon forming carbon soot in the chamber which subsequently deposited and coated on the fibers. In the hydrogen-balanced composition (50%), the 2:1 precursor ratio resulted in inconsistent intrinsic growth rates which ranged from approximately 30 μm/s to 44 μm/s. However, for the hydrogen-balanced (50%) 1:1 condition, the intrinsic growth rate variation was reduced to approximately 12 μm/s. The differences in fiber uniformity, composition, and structure under these process conditions are discussed in terms of hydrogen’s ability to serve as a reducing agent, a fluid to transport heat from the deposition zone, and alter the structure of the fiber through thermophoresis.
“…Consequently, this mixture change, even in the hydrogen-balanced condition, impacts the rate of axial growth. While the growth rate decreases, the fiber-to-fiber growth rate variation did reduce, albeit a modest decrease in Titanium oxide is known to exhibit a bronze color at low temperatures and a white color at higher temperatures [34]. The hydrogen-balanced (1:1) fibers exhibited a varying temperature gradient as it deposited, which was visible in Figure 7a, and where such thermal gradients would have created convective motion of the gases around the fiber that would lead to the oxidization of titanium.…”
In this study, the hyperbaric (2 bar) laser chemical vapor deposition of TiC fibers grown under various percent pressures of hydrogen and ratios of ethylene and titanium tetrachloride (2:1 or 1:1) are reported. In the hydrogen-rich (85%) condition, sequential fiber depositions became stunted as a result of a loss of hydrogen, which served as a reducing agent for the metal halide as hydrogen evolved with the hydrocarbon gas in the reaction zone because of the Le Chatelier principle. For the hydrogen-lean (25%) condition, the intrinsic fiber growth rate was invariant, but gas phase nucleation resulted in the hydrocarbon forming carbon soot in the chamber which subsequently deposited and coated on the fibers. In the hydrogen-balanced composition (50%), the 2:1 precursor ratio resulted in inconsistent intrinsic growth rates which ranged from approximately 30 μm/s to 44 μm/s. However, for the hydrogen-balanced (50%) 1:1 condition, the intrinsic growth rate variation was reduced to approximately 12 μm/s. The differences in fiber uniformity, composition, and structure under these process conditions are discussed in terms of hydrogen’s ability to serve as a reducing agent, a fluid to transport heat from the deposition zone, and alter the structure of the fiber through thermophoresis.
“…We set the time for plasma application to 30 s, which seems appropriate for the chair side of clinical dental treatment. Ti shows discoloration owing to the formation of an oxide film on the surface at high temperature [ 35 ], which suggests that a handheld plasma device is a useful tool for adding hydrophilization on Ti disks without discoloration. Our results showed that the handheld plasma device had no effect on the roughness of the Ti surface.…”
Purpose
This study aimed to clarify the effects of surface modification of titanium (Ti) implants by low-temperature atmospheric pressure plasma treatment on wound healing and cell attachment for biological sealing in peri-implant soft tissue.
Methods
Hydrophilization to a Ti disk using a handheld low-temperature atmospheric pressure plasma device was evaluated by a contact angle test and compared with an untreated group. In in vivo experiments, plasma-treated pure Ti implants using a handheld plasma device (experimental group: PL) and untreated implants (control group: Cont) were placed into the rat upper molar socket, and samples were harvested at 3, 7 and 14 days after surgery. Histological evaluation was performed to assess biological sealing, collagen- and cell adhesion-related gene expression by reverse transcription quantitative polymerase chain reaction, collagen fiber detection by Picrosirius Red staining, and immunohistochemistry for integrins.
Results
In in vivo experiments, increased width of the peri-implant connective tissue (PICT) and suppression of epithelial down growth was observed in PL compared with Cont. In addition, high gene expression of types I and XII collagen at 7 days and acceleration of collagen maturation was recognized in PL. Strong immunoreaction of integrin α2, α5, and β1 was observed at the implant contact area of PICT in PL.
Conclusions
The handheld low-temperature atmospheric pressure plasma device provided hydrophilicity on the Ti surface and maintained the width of the contact area of PICT to the implant surface as a result of accelerated collagen maturation and fibroblast adhesion, compared to no plasma application.
“…The compressive strength of concrete can decrease by up to 50 percent if the concrete is exposed to 600 °C. When concrete is exposed to fire for a long period, the concrete strength is reduced [2,3]. Also, the reinforcement steel strength inside the concrete was reduced [4].…”
When concrete structures are exposed to elevated temperatures or fire, their strength begins to degrade. The major problem is that the structure induces cracks, which let the aggressive material enter the concrete and the steel reinforcement corrosion. Therefore, the damaged member should have been strengthened or repaired; sometimes, the repair is chosen over demolition because it is more economical. Researchers used materials to repair heat-damaged concrete, such as fiber-reinforced polymer (FRP) composites, shotcrete, ferrocement, epoxy resin mortar, and fiber-reinforced concrete. The compatibility of these materials should be investigated, for example, the bond strength between repair material and substrate. Ferrocement can restore stiffness and toughness, while a structure with FRP jacketing cannot regain stiffness. Reviewing post-fire strength and repairing materials has not been done; therefore, this study highlights the strength loss of fire-damaged concrete and the repaired structure's confinement.
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