Key Engineering Materials Vols. 575-576

Abstract: The fatigue strength of the newly developed β-type titanium alloy Ti-29Nb-13Ta-4.6Zr (referred to as TNTZ) is important for its applications in spinal fixation rods. Enhancements in the fatigue strength of TNTZ upon solution treatmnet and thermo-mechanical processing (aging after severe cold-caliber rolling or sever cold-swaging) have been investigated. Aging the rods at 723 K for 259.2 ks after cold-swaging is shown to be the optimal thermo-mechanical processing method for the TNTZ rod , yeilding a high 0.2% proof stress of about 1200 MPa, high elongation of 18%, and high fatigue strength of 950 MPa. High springback is undesirable for application of TNTZ spinal-fixation rods. To reduce springback, a High Youngs modulus is required; on the other hand, a low Youngs modulus is beneficial to reduce bone absorption and obtain good bone remodeling. To achieve a balance between these two factors, TNTZ has been modified by adding Cr to obtain an alloy with a high Youngs modulus at the deformed region and a low Youngs modulus throughout the undeformed region. TNTZ-8Ti-2Cr and TNTZ-16Ti-4Cr are novel alloys whose β phase is more stable than that of TNTZ. Only the β phase is present in these alloys, which exhibit relatively low Youngs moduli of <65 GPa after solution treatment, and higher Youngs moduli after cold rolling, owing to a deformation-induced ω-phase transformation. These modified TNTZ alloys show significantly less springback than the original TNTZ, based on tensile and loadingunloading bending tests.

Abstract: A novel β-type titanium alloy with a changeable Youngs modulus, that is, with a low Young's modulus to prevent the stress-shielding effect for patients and a high Young's modulus to suppress springback for surgeons, should be developed in order to satisfy the conflicting requirements of both the patients and surgeons in spinal fixation operations. In this study, the oxygen content in ternary Ti-11Cr-O alloys was optimized in order to achieve a large changeable Young's modulus with good mechanical properties for spinal fixation applications. The increase in Youngs moduli of all the examined alloys by cold rolling is attributed to the deformation-induced ω-phase transformation which is suppressed by oxygen. Among the examined alloys, the Ti-11Cr-0.2O alloy exhibits the largest changeable Youngs modulus and a high tensile strength with an acceptable plasticity under both solution-treated (ST) and cold-rolled (CR) conditions. Therefore, the Ti-11Cr-0.2O alloy, which shows a good balance among a changeable Youngs modulus, high tensile strength and good plasticity, is considered a potential candidate for spinal fixation applications.

Abstract: Dried Red mud slurry was ground to small powders. It was then mixed with waste glass and dolomite powders. The mixtures with different amounts of red mud and dolomite were pressed to form green bodies, which were foamed at high temperatures. To achieve a good foaming effect, the content of red mud is 35~45% in the batch and 10wt% of dolomite should be added as the foaming agent. It is found that the best foaming temperature is 1130°C, much higher than the decomposition temperature of the pure dolomite. The best obtained product has an apparent density, bending strength of 0.896g/cm³ and 9.7MPa, respectively. X-ray measurement results indicate that the red mud has reaction with the other raw materials used in the green body. The crystalline phase formed in the sample is augite. The present study provides a simple way to directly foam a mixture containing red mud to form useful glass-ceramics.

Abstract: The premise of the flexible multi-point die stamping processing is that each punch can be adjusted to required position. Using numerical control technique, punches can be adjusted by stepping motors through driving screw rods. But each punch requires a stepping motor in this equipment. This kind of equipment is much expensive. In addition, the distance between adjacent punches is much big. Thus, this kind of equipments is not suitable for processing some small and medium-sized sheet metal parts. A new kind of equipment for press forming sheet metal parts is presented. Only two DC motors are needed to adjust punches of male and female moulds in this kind of equipment. Punches can be arranged more closely. This kind of equipments can be used to process small and medium-sized sheet metal parts.

Abstract: The effects of different negative voltages on micro-arc oxidation coating fabricated on ZK60 Mg alloy were investigated under two steps increasing mode of 280-360V. The microstructure, coating thickness and corrosion resistance of coatings were evaluated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), microscope with super-depth of field and electrochemical impedance spectroscopy (EIS). Current-time responses during MAO process were also analyzed combined with coating characteristic. The results reveal that higher negative voltage helped to develop a compact, smooth, thicker and better corrosion-resistant coating. The coating with maximum thickness of about 20.2μm formed under negative voltage of 20V exhibits higher impedance value and the best corrosion resistance.

Abstract: Formaldehyde (HCHO) gas sensors based on pentacene active layer and low cost poly (merthyl methacrylate) (PMMA) insulator were fabricated with a structure of bottom contact organic thin-film transistor (OTFT). The OTFT sensor not only presented a remarkable response characteristic in the absence and the presence of HCHO gas with different concentrations, but also exhibited a good repeatability for sensing the HCHO gas. Meanwhile, compared to the device operated in nitrogen circumstance, obvious changes in saturation drain-source current (I_DS) and off-state current were observed when the device exposed to HCHO gas. Also the device performance and sensing mechanisms were discussed.

Abstract: This article describes a new and efficient type spraying equipment with core technology of controlled droplet (centrifugal atomization), and describes the overall design of the equipment, technical characteristics and innovation. The test results show that the equipment has the following characteristics: precisely controlled droplet diameter, real-time, precisely adjusted spray flow, three-dimensional space evenly spray, and the operating status could be remotely controlled by automation. It is new type spray equipment for facility agriculture applicable for different crop varieties, crop growth period, control objects, pesticide formulations, as well as operating environment inside the green house.

Abstract: The quality and safety of agricultural products is a concern for the entire world. The main focus is pesticide residues, which is especially typical in process of tea production. The technology of Using Light to Trap is the best way to solve the problem, because it is to induce and kill pests with physical means of light, electricity, color and etc. Over the past decade, pilot demonstration and applications of insecticidal lamps applied in tea plantation have been conducted in more than a dozen provinces all over China, which achieved remarkable results. This article aims to conduct the work of conclusion and analysis on the basis of test results from fields over the years and the work of comprehensive analysis and accession with the consideration of current development status of the technology of Using Light to Trap, and thus provides scientific basis for ecological control of pests and diseases in tea plantation, reduction on volume of chemical pesticides, decrease of pesticide residues in tea, maintenance of ecological balance and protection for agricultural ecological environment.

Abstract: Lead-free Sr-and Mn-doped Ca_1-xSr_xBi₄Ti₄O₁₅, Ca_1-yMn_yBi₄Ti₄O₁₅ bismuth layer piezoelectric ceramics have been prepared. The microstructure and electrical properties of the products were studied by XRD, SEM and Broadband LRC digital bridge. The obtained ceramics have Bi-layer perovskite phase. The dopings do not change the crystal phase of CaBi₄Ti₄O₁₅. However, the doping amounts affect the size of crystal grain and porosity of the final products. The appropriate amounts of dopings for obtaining the highest dielectric constant and the lowest dielectric loss are determined. The prepared ceramics show the largest piezoelectric constant of 5.2~5.3 pC/N with the optimal Sr-and Mn-dopings.

Abstract: Mn, Co, and Ni-doped La_0.5Sr_0.5FeO₃ thin films were prepared by the sol-gel technique. The structure and dielectric properties of the films were studied by XRD, SEM, and electrical measurements. The morphology observation demonstrated these films had uniform grain size and smooth surface. The dielectric properties of La_0.5Sr_0.5FeO₃ films were improved by the replacement of Fe with Mn, Co, and Ni. The doping amount of Mn, Co, and Ni for the optimal dielectric properties of La_0.5Sr_0.5FeO₃ films is 5%, 2%, and 3%, respectively. The observed pure perovskite phase of the doped films suggested the dissolution of Mn, Co, and Ni in La_0.5Sr_0.5FeO₃ crystal lattice.