Non-Traditional Cement and Concrete
Special Concrete and Composites 2017
Functional Materials and Application
Green Convergence on Materials Frontiers
Manufacturing Technologies: Materials, Operation and Applications
Structural and Mechanical Engineering for Security and Prevention
Advances in Fracture and Damage Mechanics XVI
International Symposium on Advanced Material Research
Materials Science and Technology IX
Materials Research and Application II
Recent Development in Machining, Materials and Mechanical Technologies II
Functional Materials and Application
摘要: The progress in the world industrial sector, together with new technologies increases solid waste generation and the consequent concern with the correct management of them. One of the biggest problems in the foundry sector is the generation of solid waste, consisting mainly of waste sands or discarded sand castings (ADF). Proper waste disposal is a challenge for industries, which are increasingly concerned about the need to preserve the environment and seeking for sustainable development. In Brazil, fused production in 2008 exceeded three million tons, generating approximately one ton of waste for each ton of metal produced. The main destination of this waste is industrial disposal landfills, which have high cost and is an increasing environmental concern for companies. Therefore, the aim of this research was to solve this problem, that is, it was proposed a methodology to reuse these solid wastes, testing our methodology by using concrete slabs with incorporation of foundry sand in different concentrations, in an increasing order of 5%, where natural sand was replaced by founding sand. The viability for the use of casting sand in relation to the resistance was significant in the traces 30% and 35%.
摘要: Due to the increasing concern about the environment and depleting conventional materials, a lot of research is going on in the field of material science to develop environment friendly materials, and to improve the recycling and reusing of waste materials. Composites are material providing possibilities to reach these targets. In this experimental study, the possibilities and potential in the utilization of mixed waste from recycling in the manufacturing of epoxy composites are studied. The studied properties are flexural properties, i.e. flexural strength and flexural modulus, and hardness as mechanical properties, and water absorption and thickness swelling as physical properties. Element analysis was used to determine the composition of construction and demolition waste used in manufacturing. The analysis revealed a large proportion of mineral elements with high hardness. Consequently, this had a clear impact on the hardness of the composite. The flexural properties were found to be on a reasonable level. The waste-epoxy composite showed a low uptake of water due to the minor content of hydrophilic materials present in the composite.
摘要: The centrifugal casting method was adopted to fabricate Al-25Si-8Mg functional composites tubes reinforced with in-situ particles to acquire the Al-Si-Mg composites cylinder liner which was used to produce 600 cc aluminum alloy engine cylinder for the first time through the low pressure die casting. The inner layer of the cylinder was corroded and a bench test was carried out to test the performance of the engine assembled with the cylinder. It is found that a large number of primary Si/Mg2Si particles are segregated in the inner layer of Al-25Si-8Mg tubes in the centrifugal filed, forming the particle reinforcement layer. During die-casting process, the cylinder bore needs to be filled with refractory cotton to avoid the running-out of liquid aluminum alloy. Using the Al-Si-Mg composites cylinder, the measured maximum output power and output torque of the 600 cc water-cooled engine reach 22.66 KW and 44.37 N·m, respectively. Temperature monitoring shows a reduction of 5~8 degrees than usual.
摘要: Recently lot of research is going on for different type of properties of composites and polymers.Fly ash is one source which is available abundantly and is considered an industrial waste. Fly ash can be used in huge amount in polymers.However there will be some problems with adhesion of the polymer matrix and fly ash. The matrix polymer chosen is Polypropylene and the flyash was treated with different material and composites were made . An effect of content of fly ash and study of effect of treatment on mechanical properties of the PP/fly ash composites was done. XRF studies were carried out to study the composition of fly ash.
摘要: Au-20Sn (mass fraction) eutectic alloy is a key lead-free solder material for high reliability microelectronics and optoelectronics packaging. The refinement of initial solidification structure can improved the processing performance of Au-20Sn alloy. This paper reported the research progresses on refining solidification structure of Au-20Sn alloy in our research group. The results indicated that the solidification structure of alloy can be effectively refined by rapid solidification with the increasing of cooling rate. The solidification structure can also be refined by incubated nucleation treatment with Au or Sn or by proper melt temperature treatment. The refinement mechanisms of solidification structure by the three types of solidification methods were thoroughly discussed.
摘要: The work was dealing with direct soldering of Al2O3 ceramics and a metal/ceramic composite (MMC) with Al matrix. The joints were fabricated by application of flux-less process by use of a hot plate at the assistance of ultrasound with frequency of 40 kHz. The experiments were performed by use of Zn6Al6Ag solder. Wetting was attained on both substrates. The joints of a good quality were fabricated. The soldering temperature was 420 °C. The microstructural studies of interface have revealed a transient zone of Al dissolving on the side of MMC and formation of Zn oxides on the side of ceramics, which were responsible for bond formation.
摘要: In this study, microstructural and mechanical properties of a Al-5 wt.% Si/2 wt% (NbB2, NbC) composite synthesized by sequentially milling (mechanical alloying (MA) and/or cryogenic milling (CM)) were investigated. Nb2O5, B2O3 and C powder blends were milled using high energy milling for 5 h and annealed at 1400 oC for 12 h to produce NbB2-NbC hybrid powders. The NbB2-NbC hybrid powders were mixed with the matrix Al-5 wt.% Si powders to constitute the Al-5 wt.% Si/2 wt.% (NbB2-NbC) powders blends which were mechanically alloyed (MA'd) for 4 h using SpexTM Mixer/Mill, cryo-milled for 10 min in a SpexTM 6870 Freezer/Mill and finally MA’d for 1h in SpexTM Mixer/Mill again. As-blended, MA’d and cryomilled powders were compacted in a hydraulic press with a uniaxial pressure of 450 MPa. Compacted samples were sintered at 570°C for 2 h under Ar gas atmosphere. Microstructural characterizations of the as-blended/MA'd powders and the sintered composites were performed using X-ray diffractometry (XRD) and scanning electron microscopy (SEM) techniques. Density and microhardness measurements and sliding wear tests were performed on the sintered composite samples. Sequentially milled and sintered Al-5 wt.% Si-2 wt.% (NbB2-NbC) samples had the highest mean microhardness value (2.29 ± 24.98 GPa) and the lowest wear volume loss (0.038 mm3).
摘要: The computational prediction of the surface adsorption in atomic layer deposition of gallium oxide by using trimethylgallium (TMG) is investigated. One dimer of Si (100)(2×1) is used as the substrate. The hydroxyl radicals are used to produce the absorption sites for the TMG adsorbed surface as OH–Si–Si–OH surface species. Two sites adsorption of the TMG on the surface are predicted. The geometry, vibrational frequency, and free energy of –OH adsorption sites and TMG adsorption are calculated by Gaussian 09 package by using standard B3LYP method. The results showed that TMG is possible to adsorb on silicon dimer with two sites adsorption. The geometry and vibrational frequencies are also reported in this paper.
摘要: Interaction of high energy electrons with spacecraft materials, such as polyimide (PI, Kapton-H®), is known to cause their physical degradation. However, understanding of the chemical nature of this damage and the effect on the electrical and optical properties of PI is still limited. This lack of understanding limits predictive spacecraft models (charging, thermal, etc) as only pristine material properties are used for calculation. This is a major source of error in spacecraft construction and anomaly resolution, since PI properties change after exposure to the space environment. In the presented study, we analyze the chemical, electrical, and optical changes to polyimide after exposure to 90 keV electrons.