磷矿配炭球团高温固结工艺研究

为解决窑法磷酸工艺中回转窑结圈问题,提出一种球团高温固结工艺,考察了黏结剂种类、固结温度、固结时间对磷矿球团强度及其还原性的影响。结果表明,固结温度800℃以上,采用膨润土为黏结剂,球团抗压强度和落下强度明显高于腐殖酸钠为黏结剂的球团。在配碳量为理论用量的1.4倍、CaO与SiO_(2)物质的量比0.35、膨润土添加量为总物料量的1.5%、固结温度1000℃、固结时间30 min条件下,球团抗压强度和落下强度分别为345.36 N和33.50次。

淤泥高温固结模拟试验与分析

为了减少淤泥对施工、环境以及工程安全方面的危害,特进行淤泥高温固结的模拟试验,以探究淤泥在高温条件下的固结规律。试验通过控制加热管温度与淤泥的含水率,进行只含有1个变量的对比试验,通过整理、分析各温度仪读数来研究加热温度以及含水率对加热效率的影响,通过整理、分析电能表读数来研究能量消耗情况。结果表明:单热源系统中,淤泥升温过程可分为初始升温阶段、低温维持阶段、高温升温阶段、高温维持阶段;含水率相同时,热源温度越高,相同位置的淤泥升高相同温度消耗的能量越多;热源温度相同时,含水率越高,相同位置的淤泥升高相同温度消耗的能量越多;淤泥导热性较差,含水率越低,其导热性越差。试验结果与规律分析可为解决具体施工过程中的淤泥处理问题提供参考。

多热源情况下淤泥原位高温固结模拟分析

为探究多热源情况下淤泥原位高温固结地基处理方法的适用性,基于单热源情况下大连地区淤泥高温固结模型的试验数据,采用有限元软件COMSOL Multiphysics模拟了多热源情况下大体积淤泥原位高温固结的过程,研究了不同热源布置方式所形成温度场的分布规律,计算了不同布置方式、不同热源间距下地基承载力特征值达到1000kPa需要的加热时间和能量消耗。结果表明:两种布置方式的几何中心位置均为温度最低点;热源间距越小,所需加热时间越短,同热源间距等边三角形布置方式加热时间少于正方形布置方式;同热源间距下采用正方形布置方式能耗低于三角形布置方式;对模型的有效加热面积四周边界采取绝热措施,能耗降低20.81%~25.82%。

锡中矿高温氯化-氧化固结球团的研究

研究了添加剂对难选锡中矿高温氯化 氧化固结球团强度的影响 ,结果表明 ,在适当的原料配比和焙烧制度下 ,可获得理想的氧化焙球 ,其强度已达到高炉炼铁要求 。

混凝土降温收缩开裂机理分析

大体积、高强度等级以及炎热季节浇筑的混凝土散热能力差,水化产生的热量在内部积聚,硬化时,内部温度大幅度上升,高温固结将严重影响产物结构的综合性能。降温时,因冷缩和结构约束状态形成拉应力,产生收缩裂缝。目前,在配合比设计、材料选取和施工过程中采取了一些不当措施,增加了温升总量。预防降温收缩开裂,应从让混凝土结构少起热、多散热、降约束以及提高水化产物填充效率,改善界面过渡区,提高水泥浆和骨料变形协调能力入手。

Roles of Zr and Y in cast microstructure of M951 nickel-based superalloy

The influence of Zr and Y on the cast microstructure of a nickel-based superalloy was investigated by optical microscopy （OM）,scanning electron microscopy（SEM）,electron probe micro-analysis（EPMA）and X-ray diffraction（XRD）.Theγ＋γ′eutectic volume in the superalloy rises notably with the increase of Zr or Y content.Meanwhile,the morphologies of primary MC carbides change from needle and platelet-like to blocky shape with increasing Zr and Y doped.The XRD results show that the primary MC carbide lattice constant increases with Zr and Y additions,and EPMA investigation shows that the platelet-like MC carbides contain primarily Nb and C,while those carbides in blocky shape have 39.2%Zr and 39.6%Nb in average,.These influences on the cast microstructure can be attributed to the atomic size effects of Zr and Y.

Synthesis and electrochemical performance of Li_2Mg_(0.15)Mn_(0.4)Co_(0.45)SiO_4/C cathode material for lithium ion batteries

The synthesis, structure and performance of Li2Mg0.15Mn0.4Co0.45SiO4/C cathode material were studied. The Li2Mg0.15Mn0.4Co0.45SiO4/C solid solution with orthorhombic unit cell （space group Pmn21） was synthesized successfully by combination of wet process and solid-state reaction at high temperature, and its electrochemical performance was investigated primarily. Li2Mg0.15Mn0.4Co0.45SiO4/C composite materials deliver a charge capacity of 302 mA-h/g and a discharge capacity of 171 mA.h/g in the first cycle. The discharge capacity is stabilized at about 100 mA-h/g after 10 cycles at a current density of 10 mA/g in the voltage of 1.5-4.8 V vs Li/Li^＋. The results show that Mg-substitution for the Co ions in Li2Mn0.4Co0.6SiO4 improves the stabilization of initial structure and the electrochemical nerformance.

UH model considering temperature effects

The influences of temperature on the mechanical behavior of saturated clays are discussed first. Based on the concept of true strength and the revised calculation method of the potential failure stress ratio, the equation of the critical state stress ratio for saturated clays under different temperatures is deduced. Temperature is introduced as a variable into the UH model （3-dimensional elastoplastic model for overconsolidated clays adopting unified hardening parameter） proposed by Yao et al. and then the UH model considering temperature effects is proposed. By means of the transformed stress method proposed by Yao et al., the proposed model can be applied conveniently to 3-dimensional stress states. The strain-hardening, softening and dilatancy behavior of overconsolidated clays at a given temperature can be described using the proposed model, and the volume change behavior caused by heating can also be predicted. Compared with the modified Cam-clay model, the proposed model requires only one additional parameter to consider the behavior of the decrease of preconsolidation pressure with an increase of temperature. At room temperature, the proposed model can be changed into the original UH model and the modified Cam-clay model for overconsolidated clays and normally consolidated clays, respectively. The considered temperature range here is from the melting point to the boiling point of the pore water （e.g. the experimental temperatures （20℃-95℃） mentioned in this paper are within this range）. Comparison with existing test results shows that the model can reasonably describe the basic mechanical behavior of overconsolidated clays under various temperature paths.

Composition dependence of phase structure and electrical properties of(1-y)Bi_(1-x)Nd_xFeO_(3-y)BiScO_3 ceramics

In this work, we have studied a new lead-free ceramic of（1-y）Bi1-xNdxFeO3-yBiScO3（0.05≤x≤0.15 and 0.05≤y≤0.15） prepared by a conventional solid-state method, and the influences of Nd and Sc content on their phase structure and electrical properties were investigated in detail. The ceramics with 0.05≤x≤0.10 and 0.05≤y≤0.15 belong to an R3 c phase, and the rhombohedral-like and orthorhombic multiphase coexistence is established in the composition range of 0.125≤x≤0.15 and y=0. The electrical properties of the ceramics can be enhanced by modifying x and y values. The highest piezoelectric coefficient（d33～51 p C/N） is obtained in the ceramics with x=0.075 and y=0.125, which is superior to that of a pure BiFeO3 ceramic. In addition, a lowest dielectric loss（tan δ～0.095%, f=100 k Hz） is shown in the ceramics with x=0.15 and y=0 due to the involvement of low defect concentrations, and the improved thermal stability of piezoelectricity at 20–600℃ is possessed in the ceramics. We believe that the ceramics can play a meaningful role in the high-temperature lead-free piezoelectric applications.