Super-tough poly(butylene terephthalate) based blends by modification with core-shell structured polyacrylic nanoparticles

Core-shell structured polyacrylic nanoparticles (named CSPN) impact modifiers consisting of a rubbery poly(n-butyl acrylate) core and a rigid poly(methyl methacrylate) shell with a size of about 352 nm were synthesized by seed emulsion polymerization. The CSPN modifier with core-shell weight ratio 80/20 was used to toughen poly(butylene terephthalate) (PBT) by melt blending. With an increase in CSPN content, the impact strength and the elongation at break of PBT/CSPN blends increased significantly compared with those of PBT; however, the tensile strength decreased. It was found that the polymerization had a very high instantaneous conversion (> 93%) and overall conversion (99%). The core-shell structure of CSPN was examined by means of transmission electron microscope. Scanning electron microscope was used to observe the morphology of CSPN particle and fractured surfaces of the blends. The dynamic mechanical analyses of PBT/CSPN blends showed two merged transition peaks of PBT matrix, with the presence of CSPN modifier, which was responsible for the improvement of PBT toughness. The results indicated that the notched impact strength of PBT/CSPN blend with a weight ratio of 80/20 was 8.61 times greater than that of pure PBT where the brittle-ductile transition point appeared.     

Development of electric resistance sintering process for the fabrication of hard metals: Processing,microstructure and mechanical properties

This work presents the development of the Electrical Resistance Sintering (ERS) process for the fabrication of hard metals. The compositions of the materials produced were WC with 6 and 10 wt% of Co. In addition to the specific characteristics of the technology, the characterization of the produced parts is presented and compared to materials obtained by conventional processes.The parts produced by ERS present densities comparable to the ones obtained by conventional methods. The microstructural comparison shows a considerable grain size reduction in the ERS materials which consequently brings a hardness increase. ERS materials show similar fracture toughness to conventional ones.The very fast sintering allows performing the process without any protective atmosphere, therefore making this process very attractive for the production of materials that need to be sintered under non-oxidising environments. The total duration of the cycle, including heating, holding time and cooling is few seconds.Finally, some considerations about the scale up and possible industrialization of the technology are explained.     

Hydrothermal-assisted synthesis of surface aluminum-doped LiCoO2 nanobricks for high-rate lithium-ion batteries

LiCoO₂ nano-particles precursor was synthesized through a mixed-alkalis (LiOH-NaOH) hydrothermal reaction, and finally sintered into LiCoO₂ nanobricks with a sickness of ~300?nm. This LiCoO₂ nanobrick cathode delivered a specific capacity of 131.8 mAh g^?1 at 1?C between 3.0 and 4.2?V and 90% capacity retention after 100 cycles. Those synthesized LiCoO₂ nanobricks were further treated by surface Al³⁺ doping to achieve much enhanced 4.5?V lithium storage capability and cycling stability. EIS results showed the surface Al³⁺ doping operation can signification decrease the charge-transfer resistances of the LiCoO₂ cathodes for both before and after cyclings.     

香炉山钨矿特大采空区地压微震监测技术应用研究

香炉山钨矿东区形成了形状复杂、体积巨大的采空区,地压灾害问题突出。为了确保矿山生产安全,该矿成功地建立了国内属先进的48通道全数字型微震监测系统。本文简要介绍了多通道微震监测系统的组成及技术特点,重点分析了微震监测技术在地压灾害预警、应力集中危险区域圈定、指导采矿设计、矿区整体地压活跃程度评价与监控民采盗矿等方面的成功应用实例,证明了微震监测技术已经成为该矿山残采区地压监测、生产安全预警的基本手段。     

Effects of sustained axial load and cooling phase on post-fire behaviour of reinforced concrete stub columns

In this paper is presented an experimental investigation of the effects of preload and cooling phase on the residual strength, stiffness and ductility of reinforced concrete stub columns which were heated and cooled down to room temperature under sustained axial load. Reinforced concrete stub columns were axially loaded and heated to designed temperatures in a specially built electrical furnace. After the specimens cooled down to ambient temperature with the axial loads kept constant, the stub columns were loaded to failure. The sustained preload led to significant residual deformations of reinforced concrete stub columns during the cooling phase. The test results showed that the mechanical behaviour of the fire-damaged reinforced concrete stub columns with preload was remarkably different from those without preload. The sustained axial loads resulted in obviously increased strength and stiffness during the loading phase, but reduced stiffness and deteriorated ductility in the unloading phase. Based on the test results, it is recommended that the effects of sustained axial loads during the fire and cooling phase should be taken into consideration in assessing the fire-damaged reinforced concrete columns.     

Investigation of the effect of mineralogy as rate-limiting factors in large particle leaching

Although heap leaching is by now well established in the mining industry, the process remains limited by low recoveries with different rate-limiting factors that are not clearly understood. In this study, three large particle size classes (+19/−25, +9.5/−16, +4.75/−5 mm) were prepared from a sphalerite ore by two different methods of comminution (HPGR and cone crusher). The particles were then packed into leach reactors that were operated continuously for 11 months with well-mixed internal circulation of the leach solution. Characterization of the residue of the leach reactors indicated that there are areas within the ore particles where although sphalerite grains are accessible to the solution, they remain unreacted. X-ray tomography and QEMSCAN® analysis of the selected samples before, during and after leaching, showed increased leaching of sphalerite grains associated with pyrite due to galvanic interactions. Mineral chemistry (Fe, Mn content of sphalerite) and jarosite precipitation were also investigated as factors influencing sphalerite leaching.     

石煤钒矿富氧焙烧试验研究

研究了石煤钒矿在富氧条件下的焙烧试验,考察了氧浓度、焙烧温度、焙烧时间等因素对钒浸出率的影响。结果表明,在氧浓度65%、焙烧温度860℃、焙烧时间210min的条件下,平均钒浸出率可达到84.5%,且生产五氧化二钒全流程总钒回收率为80.28%。     

Slag resistance mechanism of MgO–Mg2SiO4–SiC–C refractories containing porous multiphase aggregates

The slag resistance of MgO–SiC–C (MSC) refractories should be improved because of the mismatch in the thermal expansion coefficient between the aggregates and matrix, as well as the defects caused by the affinity between periclase and slag. In this study, MgO–Mg₂SiO₄–SiC–C (MMSC) refractories were prepared using porous multiphase MgO–Mg₂SiO₄ (M-M₂S) aggregates to replace dense fused magnesia aggregates. Compared to MSC, the slag penetration index of MMSC decreased by 43.5%. The structure of the porous aggregates increased the surface roughness, and the multiphase composition of the aggregates decreased the mismatch of the thermal expansion coefficient with the matrix, thus reducing debonding between the aggregates and matrix. The aggregates and matrix in the MMSC formed an interlocking structure, which bound them more tightly to improve the slag resistance. The slag viscosity at different depths from the initial slag/refractory interface was calculated using the Ribond model. The M-M₂S aggregates increased Si_xO_y^z− in the slag, which increased the slag polymerization and slag viscosity. The aggregates and matrix in the MMSC reacted with the slag to form high melting point phases, which reduced the channel of the slag. In addition, the penetration depth and velocity derived from the Washburn Equation were modified for the CaO–SiO₂–Al₂O₃–MgO–FeO slag and magnesia based refractory to accurately evaluate slag penetration.     

Improved dielectric energy storage performance of Na0.5Bi0.5TiO3-based lead-free relaxation ferroelectric ceramics achieved by domain structural regulation and enhanced densification

There is still a problem of low energy storage density in dielectric capacitors which is a core component of power systems. For the improvement of the energy storage density, the linear dielectric material CaTiO₃ (CT) was introduced in Na_0.5Bi_0.5TiO₃ (NBT) ceramics in this paper. By modifying the A site, a new relaxor ferroelectric ceramic was successfully synthesized and attained a recoverable density (W_rec) of 2.34 J/cm³ at x = 0.18. Moreover, the preparation process was optimized in this paper. Through the viscous polymer process (VPP) route, the energy density (W_A) of 82NBT-18CT_VPP ceramic further reaches 6.45 J/cm³ at 340 kV/cm, with efficiency (η) up to 75% and a W_rec of 4.82 J/cm³. At the same time, the change of W_rec is small at temperature (30–150 °C) and frequency (1 Hz–300 Hz), which demonstrates its excellent stability. The discharge power density reaches about 180 MW/cm³ and the discharge time is 0.117 μs, which indicates its excellent pulse discharge performance. The results show that 82NBT-18CT lead-free relaxation ferroelectric material is expected to become ideal for high-energy storage applications.