Advanced Materials Research Vols. 295-297

Abstract: Molecular dynamics simulations are carried out to investigate the effect of the occupation of the cages on the stability of sI CO₂ hydrates. Three types of cage occupations are concerned. The TIP4P/EPM2/DUAN potential models are used for the water-water, CO₂-CO₂, water-CO₂ intermolecular interactions. The simulation results show that the occupation of the large cage is preferable compared to the occupation of the small cage. It may be induced that the hydration number of sI CO₂ hydrates is mostly to be 9.

Abstract: Taking Attapulgite Clay(ATP) as a carrier, TiO₂/ATP precursor was prepared by acid sol-gel method, and then made its composite under different heat-treatment conditions. The structures, dimensions, compositions of the composite are characterized by X-Ray diffraction, transmission electron microscope, thermogravimetric-differential thermal analysis and spectroscopic analysis measurements, respectively. the results show that TiO₂/ATP composite increase the crystal transition temperature of TiO₂, rutile TiO₂ emerge in the composite until 800°C, ATP lost its layer constructure and collapse at 850°C.

Abstract: This paper presents a review of current research, both theoretical predictions and experimental measurements, on the mechanical properties of carbon nanotubes (CNTs). The emphasis has been given to the tensile strength and Young’s modulus. Deformabilities including buckling, bending, and twisting are also examined. The predicted and measured values of mechanical behaviors of CNTs are compared and an analysis on the variation of the values is made. The challenges facing the research of mechanical properties of CNTs are stated. CNT reinforced composites are involved as well in the paper. A thorough understanding of the properties of CNTs helps exploring full applications of this unique group of materials.

Abstract: Electroless nickel plating on magnesium alloy was studied when NiSO₄ as the main salt in the solution. The influence of the composition of the solution and process parameters on the coating appearance, the plating rate and bath stability was studied too. As a result, the optimum conditions of electroless nickel are: The main salt and reducing agent molar ratio between 0.3 and 0.45, mixed complexion agents was used, temperature 90°C, pH value 6.5.

Abstract: In recent years, chalcopyrite semiconductor thin films are being intensively investigated for low-cost terrestrial phovoltaic applications. One prerequisite for solid state solar cells is the strong interface to allow the intimate contact between semiconductors. The paper studied the possibilities of CuInS₂ thin film surface control by using sodium dodecyl sulfate as additive in precursors’ solution in concentration below and above the critical micelle concentration of the surfactant in solution. The sample with the amount of surfactant lower than the critical micelle concentration in precursors’ solution has the highest surface energy value. The use of surfactant conducted to increased preference for formation of thin films with peaks, the higher peaks being obtained for the thin films obtained from solutions with surfactant concentration higher than critical micelle concentration.

Abstract: In this paper, the effect of die-swell ratio on the microstructure and properties of as-spun fibers was systematically analyzed by electron microprobe analysis (EMPA) and the measurement of die-swell ratio, boiling-water shrinkage, porosity and mechanical properties. The formation mechanism of the spin orientation and skin-core structure were revealed. It was shown that with different die-swell ratio, the spinodal decomposition speed and the orientation degree between the outer and inner of as-spun fibers is different, which leads to a difference of denseness and hardness between the outer and inner, thus the skin-core and porous structures are formed. A small die-swell ratio leads to an enhanced spin orientation, a reduced skin-core difference and a more compact and homogeneous microstructure. As a result, the breaking tenacity of as-spun fibers and resultant precursors all increased.

Abstract: A theoretical study has been made on the cam-clamping device. In this article, we consider specifically the calculations of cam geometry, calculations of clamping force and clamping torque, conditions for self-locking, and conditions for contact strength. Machine fixtures are essential in the process of mechanical manufacturing. There are many different types of fixtures, such as manual jig, pneumatic clamps, hydraulic fixtures, electric fixtures, etc. There are also many ways of clamping, such as incline clamp, screw clamp, eccentric circle clamp, hinge clamp [1], among which the eccentric circle clamp finds wide applications, especially in fast-clamping devices. Although the circular eccentric fixture possesses the advantages of simple structure, convenient manufacturing, and low cost, it suffers the drawbacks of small clamping force, short clamping-surface travel distance, and unreliable self-locking mechanism. The cam-clamping device discussesed in this article involves replaceing the eccentric circle with a cam, as shown in Fig. 1. The cam profile curve can be designed according to any requirements. The advantages of this replacement are obvious, in addition to preserving the advantages of the circular eccentric fixture, the cam-clamping can be designed according to the actual needs of clamping paths and selection of the appropriate cam profile to improve the self-locking.

Abstract: In this study W was found to have strong effects on solidification structure of the binary alloy. Based 0.5 W₀、W₀ and 1.5W₀ base W₀, three conditions with free energy base W equal to 0.5 W₀, W₀ and 1.5W₀ respectively were computed. The results showed that the variation of energy base contributed a lot to the development of side branches of equiaxed dendrite structures, the lower W, the more developed side branches, the higher W, the more restrained side branches. Furthermore, the effects of boundary layer thickness δ on solidification structures were also studied. It is found that when the layer thickness δ is as small as Δx/0.94, computational errors occurred at the base of the dendrite and when the layer thickness δ is as big as Δx/0.54, some irreal phenomena, such as coarsened dendrite trunks and maladjusted side branches, could be caused. Further study on space step Δx showed that bigger space steps made higher computational errors. It is given that the relationships among phase-field perturbation, space step and solidification structure.

Abstract: Fault detection during dynamic loading conditions of rotational machineries unlike the traditional diagnosis method, the use of contactless, non-destructive infrared thermographic method is proposed. In this paper, by using a rotating deep-grooved ball bearing, passive thermographic experiment was performed as an alternative to proceeding the traditional fault monitoring. In addition, the thermographic experiment was compared with the traditional vibration spectrum analysis to evaluate the efficiency of the proposed method. Based on the results, the temperature characteristics of the ball bearing under dynamic loading conditions were analyzed thoroughly.

Abstract: The single-crystalline nanobelts of monoclinic Ni(SO₄)_0.3(OH)_1.4 have been synthesized on a large scale through a convenient, low-temperature hydrothermal method. The influences of reaction time, pH value, concentration of ammonia on the phase and shape evolution of nanobelts were systematically investigated. It was found that the initial layered Ni(OH)2 thin films as intermediates could be split and converted into the monoclinic Ni(SO₄)_0.3(OH)_1.4 nanobelts through SO₄^2- ions inserting process. The formation mechanism of nanobelts involved in the inserting process and the corresponding drive force have been investigated in detail by means of X-ray diffraction (XRD), and scanning electron microscopy (SEM), FT-IR spectra and pH value analyses. In addition to, we have also found that the ammonia molecules acted as both weak base and ligand agent was crucial to the controlling nucleation and inserting process in the formation process of nanobelts.