Papers by Keyword: Thermal Stability

Abstract: A novel poly (methyl methacrylate) (PMMA) based copolymer was synthesized by bulk copolymerization of methyl methacrylate (MMA) and a phosphorus-containing monomer, acryloxyethyl phenoxy phosphorodiethyl amidate (AEPPA). The chemical structure of AEPPA was confirmed by FTIR, ¹H NMR and ³¹P NMR. The structure of copolymers was characterized using FTIR. TGA results indicate that the thermal stability of copolymers was remarkably enhanced with the addition of APEEA. LOI and MCC results suggest that the flame retardancy of copolymers was also improved. Detailed flame-retardant mechanism is proposed. The char formation during degradation caused by APEEA plays a key role in the property improvements.

Abstract: Resin concrete generally has good mechanical properties, excellent thermal stability and great vibration resistance, the model of the ultra-precision machining center bed is established to study the thermal stability of the resin concrete using virtual reality and collaborative simulation technology based on Pro/E and ANSYS Workbench. The main factors that affect the machine tool bed thermal deformation were found through analyzing the deformation results and the materials and restrain conditions were optimized. The results proved that the optimized machine tool bed has good thermal stability and theoretical basis was provided to improve the thermal stability of the ultra-precision machining centers.

Abstract: β-Tricalcium phosphate bioceramics with small, close to bone-like amounts of Mg were obtained by modified precipitation method and following sintering. The effect of small amounts of Mg on the thermal stability, microstructure and sintering behavior of β-tricalcium phosphate bioceramics was evaluated. Addition of small amounts of Mg, can induce a remarkable effect on the physic-chemical properties of β-TCP and therefore the chemical composition of the starting materials should be controlled.

Abstract: The yttria-doped mesoporous zirconia was successfully synthesized by evaporation induced self-assembly (EISA) method, and the microstructure and textural properties of the as-made product were studied extensively. The results showed that the as-made product possessed crystallized framework walls and a worm-like mesopore with a narrow pore distribution. The BET specific surface area and pore volume of the as-made product calcined at 500°C are 111 m²/g and 0.16 cm³/g respectively, and the corresponding data changed to 73 m²/g and 0.052 cm³/g after calcined at 700°C, which indicated that the as-made yttria-doped mesoporous zirconia possess a higher thermal stability.

Abstract: Polyester resins has found a wide spread in many applications. Filler materials are used extensively with polyester resin for a variety of reasons like cost reduction, and more importantly to enhance some physical and/or mechanical properties. Through the present work several types of inorganic fillers (cement, silica fume, and sand) were incorporated into the polyester resin. Their effects on the mechanical and the thermal properties were investigated. Quantitative measurements and qualitative observations were made to recognize the different aspects related to their employment in attempt to find an appropriate means to enhance a prescribed property. Test results revealed that although a pronounced enhancement of the mechanical properties was achieved, but a specific filler type may not has the same effect on each mechanical property. Therefore, in real applications where only some of the properties are of concern, the proper filler type and content should be specified accordingly. Anyhow, employing a combination of filler types (mixed fillers) is an efficient way to utilize the benefits of each of the employed fillers.

Abstract: (Ti,Al)N coatings possess superior hardness, good thermal and chemical stability. To further study the oxidation resistance, the arc-deposited AlTiN bulk material was collected from the substrate shutter of a commercial coating system deposited for over 100 batches. The thermal behaviour of the materials was studied by TGA/DSC with different annealing temperature or different atmospheres. The results show that AlTiN bulk material annealed in nitrogen exhibits the denser structure and thermal stability up to 1000°C. The oxidation resistance of the AlTiN can reach to 800°C. Annealed at 600 ~ 700°C proceed the recrystallization process which denser the structure. New phase of TiO₂ is formed by incorporate oxygen in exchange of nitrogen. nanoscaled 1D wire formation occurred at the 1000°C for 3 hours in air.

Abstract: ZrB₂ thin films were prepared by DC magnetron sputtering technique. The microstructure, thermal stability and optical properties of thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and spectrophotometer. The compactness of ZrB₂ thin films was studied to improve the thermal stability by optimizing the deposition parameters. The compactness and thermal stability of the coatings were improved with the increase of substrate temperature. However, these properties of the coatings were enhanced firstly and then weakened with the increase of substrate bias voltage. The selectivity of sample deposited at high substrate temperature and suitable bias voltage degraded slightly after annealing at 500 °C/100 h in air. This provided a new way to improve the thermal stability of high-temperature solar selective absorber.

Abstract: A thermal study (using TGA) was carried out on polyurethane (PU) paint modified with layered silicate (organoclay) nanocomposites. The result showed that by adding clay, the PU paint/organoclaynanocomposites demonstrated better thermal stability than the virgin polyurethanepaint. The PU paint was synthesized with polyol prepared from palm oil i.e. a renewable resource.Whilst polyurethane modified with layered silicate (organoclay) nanocomposite is considered a new class of material. A tremendous improvement of the nanocompositecompared to pure polymers, although the filler content is just 2-5 wt%.The unmodified layered silicate (kunipia-F) was treated with cetyltrimethyl ammonium bromide (CTAB-mont) and octadodecylamine (ODA-mont) were used as swelling agents to treat Na⁺-montmorillonite and forming organoclay through ion exchange.The morphology of the nanocomposites was characterized by X-ray diffraction (X-RD) and transmission electron microscopic (TEM) and the pattern showed that all of the nanocomposites produced from this work are intercalated type.

Abstract: Rosin based polyether polyols were synthesized from rosin formaldehyde adduct, propylene epoxide and ethylene epoxide in the presence of catalyst. Rigid polyurethane foams (PUFs) were prepared with these rosin-based polyols and compared with foam made with an industrial polyether polyol (TC-4110) and rosin-based polyester polyols. The mechanical and thermal properties of foams were analyzed by some methods. The experimental results show that the foaming behavior for the foams prepared from such rosin based polyether polyols is similar to that of industrial products, but the reaction activities were higher, the viscosities are much lower. Furthermore, their 10% compression strength and thermal stability were higher and the dimensional stability is similar or somewhat better than that of TC-4110 system. All these unique properties of rigid PUFs made with rosin based polyether polyols were more suitable for as industrial production.

Abstract: To analyze the thermal effect of the pile foundation of permafrost, a two-dimensional transient finite element model of the thermal fields with phase change were established. The developments of heat influence limit and maximum thawed depth with and without climate warming were predicted and analyzed. Results indicate that (1) the heat influence limit and maximum thaw depth in permafrost regions enlarge with time elapse, while the global climate warming will have a greater influence to full-space pile foundation compared with the cone-cylinder pile foundation; (2) Considering the global climate warming, heat influence limit (L_max) and maximum thaw depth (H_max) in 50^th year for full-space pile foundation, cone-cylinder pile foundation are 10.1m, 5.2m, 4.1m, 3.7m, respectively; the maximum thaw depth of full-space pile foundation during the operation will have exceeded the depth of structure (2.5m), which might put the structure at risk; (3) the structure of cone-cylinder pile foundation could effectively preserve permafrost and avoid pile foundations failure; (4) the spacing of cone-cylinder pile foundations is reasonable and the interaction of temperature distribution among cone-cylinder pile foundations can be negligible.