Papers by Keyword: Interface Characteristics

Abstract: Copper/diamond composites show promise as potential thermal management materials for electronic devices due to their excellent thermophysical properties. In this study, copper/55vol%Ti-coated diamond composites were fabricated by hot pressing at 800oC and varying pressures of 300MPa, 400MPa, 500MPa, and 685MPa. The results illustrated that the thermal conductivity of the copper/Ti-coated diamond composites initially increased and then decreased as the pressing pressure increased. Among these hot-pressed composites, the composite hot-pressed at 500MPa exhibits the highest thermal conductivity of 466W/mK. This is attributed to the uniform diamond distribution, highly covered TiC interface on the diamond, and the strong interfacial bonding between the copper and the diamond. Hot pressing is a feasible alternative to fabricate copper/diamond composites with high relative density and high thermal conductivity, the pressing pressure plays a vital role in the microstructure and the final properties of the copper/Ti-coated diamond composites.

Abstract: The Cu/55vol.%diamond (Ti) composites were fabricated by hot forging of the cold-pressed powder preforms, consisted of elemental copper powders and Ti-coated diamond particles, at 800 °C (800C-Cu/55Dia composite) and 1050 °C (1050C-Cu55Dia composite), respectively. Well bonded interface was achieved between the diamond and the copper matrix for the 800C-Cu/55Dia composite, and the coverage of diamond by interface was about 96%, attributed to homogeneously distributed nanospherical TiC interface formed on the diamond surface. However, obvious coarse TiC particle size and spallation of the formed interface were observed in the 1050C-Cu55Dia composite, implying that the composite had a relatively low bonding strength. The formed chemical bonding, good wettability and strong mechanical interlocking between the diamond and the copper matrix enable the 800C-Cu/55Dia composite having a high tensile strength of 145 MPa and a strain at fracture of 0.35%, which are about 260% and 170% higher than those of the 1050C-Cu55Dia composite, suggesting that the 800C-Cu/55Dia composite has the potential to have a high thermal conductivity and use as high-performance heat sink materials.

Abstract: With the rapid development of reinforced earth technology, different reinforced materials are also gradually applied to Reinforced earth. In this paper, we focus on the need for the study of interface characteristics between different reinforced materials and clay, by making indoor drawing test with two kinds of reinforced materials commonly used in engineering and the same clay. The test results show that: the drawing strength between the two reinforced materials and clay both increase with the normal stress increasing, both of their strength envelopes are straight lines; In the drawing test between the warp knitted geogrid and clay, the cohesive strength is 6.65kPa, the friction angle is 21.03°; while the drawing test between the geonet and clay, the cohesive strength is 2.9kPa, the friction angle is 10.96°; The average tensile strength of warp knitted geogrid is 26.4% of genet's, while the drawing strength of warp knitted geogrid in the test is about 48.1% of genet's, so when chosing reinforced materials in some engineerings, it is an important factor that we must consider the particle size and gradation of the filled reinforced materials, selecting the most appropriate size effect.

Abstract: The ways of chemical component analysis, chemical analysis photoelectron energy spectrum (ESCA) analysis and X ray diffraction were used to research and analyze the variation law of material (wood) chemical component, functional groups and cellulose crystallinity in the process of making board. The results showed that：(1) The maximum contents of holocellulose and pentosan were wood, in the next place were fiberboard, and the minimum one were binderless fiberboard. The maximum contents of α-cellulose were woodfiber, in the next place were wood, and the minimum one were binderless fiberboard. The minimum contents of xylogen were wood, in the next place were woodfiber, and the maximum one were binderless fiberboard. (2) The C1and C3 functional groups relative contents of woodfiber and binderless fiberboard were higher than wood. The C2 functional groups relative contents of wood were higher than woodfiber and binderless fiberboard. The C4 functional groups relative contents of woodfiber were zero, and the binderless fiberboards were higher than wood. (3)The maximum cellulose relative crystallinity was binderless fiberboard, in the next place was fiberboard, and the minimum one was wood.

Abstract: Fiber reinforced metal matrix composites (MMCs) are recently used in automobile, ship, aerospace and manufacturing industry because they have high stiffness and strength. The effective utilization of the strength and stiffness of the fiber reinforced MMCs depends on efficient load transfers from the matrix to fibers through the interfacial region. However, during the fabrication and afterward utilization of composites, so many numbers of micro crack may extend, especially at the interface, even before any load has been applied. Thus, in this study, the interfacial stress state and behavior of the interfacial perpendicular crack for transversely loaded unidirectional fiber reinforced MMCs investigated by using the elastic-plastic finite element analysis.

Abstract: Magnesium alloys show promise in meeting the demand for materials of lighter weight and higher rigidity. Mg alloys are hard to process and normally require grain refining for improved formability and mechanical properties. To process these fine-grained Mg alloys effectively, it is important to relate their load stress and mechanical properties to changes in their microstructures. Using a biaxial tensile machine and cruciform specimens, to evaluate the mechanical properties, microstructure, and plasticity, in a high temperature biaxial stress state, used of AZ31 Mg alloy sheet. With biaxial deformation, grain boundary slide occurred more frequently than with uniaxial deformation, causing grain boundary separation and formation of micro-voids between the grains. In the vicinity of the cracks and at the locations of grain boundary separation, although deformation temperature at higher than the recrystallization temperature, fine grains (about 2 μm) showing in duplex grain structures were formed locally. The formation of duplex grain structures as a result of local formation of fine grains during the deformation process is a major issue to be solved from the viewpoint of plasticity processing.