A model of splats deposition state and wear resistance of WC-10Co4Cr coating

In this research both low temperature high velocity oxygen-fuel flame (LT-HVOF) and high velocity oxygen-fuel flame (HVOF) techniques were employed to prepare WC-10Co4Cr splats and coatings. In situ cutting of WC-10Co-4Cr splats was carried out with focused ion beam (FIB), and a model was proposed to describe how the wear resistance of WC-10Co4Cr coatings was correlated with its residual stress state and the splats deposition state. It was observed that in LT-HVOF spraying process, WC-10Co4Cr splats were slightly melted showing "hill" shape, while in HVOF spraying process, the splats were half melted having the appearance of "concavity". The residual stress of WC-10Co4Cr coatings is determined by the size, melting state, flight speed and temperature gradient of splats. In this paper, the quantitative function formula involving heating temperature and the flight speed of the powder is put forward for the first time to predict the wear resistance of the WC-10Co4Cr coatings. This will provide a theoretical basis for engineering practice and an effective way to save costs.     

Facile fabrication of graphene oxide-polyethylenimine composite and its application for the Cr(VI) removal

A binary composite consisting of graphene oxide (GO) and polyethylenimine (PEI) was fabricated by a facile physical mixing. Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), thermo-gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Zeta potential were used to characterize the prepared graphene oxide-polyethylenimine composite (GOPC). A series of experiments were carried out to investigate the effects of some important parameters, such as molecular weight of PEI, pH, time and temperature, on the adsorption efficiency of GOPC. Due to the high amine density of GOPC, its adsorption for Cr(VI) occurred more easily at lower pH mainly via electrostatic interaction. The adsorption process matched well with the Langmuir isotherm model and the pseudo-second-order kinetic model. The maximum adsorption capacity from the Langmuir model was 370.37 mg/g at pH 2.0 and 45°C for GOPC. Thermodynamic parameters revealed spontaneous and endothermic nature of the Cr(VI) adsorption onto GOPC. The main adsorption mechanism of GOPC toward Cr(VI) was electrostatic interaction. The adsorption-desorption experiments suggested GOPC was easily recycled and its stable adsorption capacity endowed it great potential as an adsorbent of Cr(VI) from wastewater.     

The effect of humidity and oxygen partial pressure on degradation of Pt/C catalyst in PEM fuel cell

Durability of Pt/C oxygen reduction reaction (ORR) catalyst remains one of the primary limitations for practical application of proton exchange membrane (PEM) fuel cells. In this work, the effects of relative humidity and oxygen partial pressure on platinum catalyst degradation were explored under potential cycling. At 60 °C, the loss rates of Pt mass and catalyst active surface area were reduced by about three and two times respectively when the relative humidity was lowered from 100% to 50%. The effects of oxygen partial pressure on cathode degradation were found to be insignificant. Cyclic voltammetry studies showed a slight increase in Pt electrochemical oxidation by water when the humidity increased from 50% RH to 100% RH. The rates of Pt dissolution were only slightly affected by change in humidity, and the accelerated catalyst degradation was ascribed to the increased Pt ion transport in the more abundant and larger water channel networks within the polymer electrolyte. Based on the parametric study results from our previous cathode degradation model, it was estimated that the diffusivity of Pt ions at fully humidified conditions was three times that of the value at 50% RH and 60 °C.     

Isolation of Solid Solution Phases in Size‐Controlled LixFePO4 at Room Temperature

State‐of‐the‐art LiFePO₄ technology has now opened the door for lithium ion batteries to take their place in large‐scale applications such as plug‐in hybrid vehicles. A high level of safety, significant cost reduction, and huge power generation are on the verge of being guaranteed for the most advanced energy storage system. The room‐temperature phase diagram is essential to understand the facile electrode reaction of Li_xFePO₄ (0 < x < 1), but it has not been fully understood. Here, intermediate solid solution phases close to x = 0 and x = 1 have been isolated at room temperature. Size‐dependent modification of the phase diagram, as well as the systematic variation of lattice parameters inside the solid‐solution compositional domain closely related to the electrochemical redox potential, are demonstrated. These experimental results reveal that the excess capacity that has been observed above and below the two‐phase equilibrium potential is largely due to the bulk solid solution, and thus support the size‐dependent miscibility gap model.     

湿法磷酸脱氟研究

本文用二次回归正交组合设计法,对用硫酸钠从湿法磷酸中脱氟生成氟硅酸钠过程中,MgO、Al_2O_3和Fe_1O_3等杂质及Na_2O对脱氟率的影响进行了研究.通过方差分析,得出数学模型.用文献数据和粗磷酸脱氟的实测数据对此模型进行了检验,脱氟率的计算值与实测值相对误差小于10％。用放置较长时间的湿法磷酸脱氟,可获得结晶粗大、便于过滤、洗涤的滤饼。用5％Na_2SO_4溶液充分洗涤后,所得氟硅酸钠符合二级品要求.     

THERMODYNAMIC PROPERTIES OF AQUEOUS ALUMINATE ION, Al (OH)_4~- (aq)

ＴＨＥＲＭＯＤＹＮＡＭＩＣＰＲＯＰＥＲＴＩＥＳＯＦＡＱＵＥＯＵＳＡＬＵＭＩＮＡＴＥＩＯＮ，Ａｌ（ＯＨ）＿４￣－（ａｑ）ＴＨＥＲＭＯＤＹＮＡＭＩＣＰＲＯＰＥＲＴＩＥＳＯＦＡＱＵＥＯＵＳＡＬＵＭＩＮＡＴＥＩＯＮ，Ａｌ（ＯＨ）＿４￣－（ａｑ）￥ＣｈｅｎＱｉ...     

锌锰干电池两种代汞缓蚀剂

通过浸泡实验,极化测量考察了在26％NH_4Cl溶液中BiCl_3、有机复合物MA对锌的缓蚀性能,并与HgCl_2的情况进行了对比。结果表明铋类似于汞同为阴极型缓蚀剂,但其适用的浓度范围较窄,在有氧存在时失去缓蚀作用。MA则为阳极型缓蚀剂,有较宽的浓度适用范围,在有氧存在的条件下,仍表现较好的缓蚀作用。     

钾钠氟在烧结过程中的行为

通过烧结中断试验，研究了包钢烧结过程中钾、钠、氟的行为：原矿中的微斜长石，霓石和萤石分别形成了钾霞石、三斜霞石和枪晶石，并存于烧结矿中；同时还发现烧结过程中产生了少量钾、钠、氟的挥发物，并为湿料带所吸附，而在烧结饼上部产生了区域净化现象。因此，为减少钾、钠、氟对高炉冶炼的危害，需要把烧结矿烧好烧透。     

水泥酸蚀过程的定量研究

本文研究了砂浆受酸液侵蚀的过程,并在数学上加以描述,建立了包括砂浆碱密度、侵蚀作用时间、氢离子浓度以及氢离子扩散系数等因素在内的砂浆酸蚀深度预测定量式.实验结果证实该定量式的计算值能较好地与实验值相吻合;同时表明,当侵蚀介质的酸度为pH2.0和pH3.0时,氢离子在砂浆酸化层中的扩散系数是在水溶液(9.1×10~(-9)m~2/s)中的8.9%和25.6%.