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1.
制备了3种不同质量浓度的充填体试件,进行了单轴压缩声发射试验,分析了不同浓度的充填体力学特性,重点研究了试件破坏过程中的声发射振铃计数、声发射累计撞击数与声发射累计能量的比值(r值)、主频及其相对高频信号激增响应系数特征。研究表明:随着浓度的增加,充填体的峰值强度与弹性模量呈增大趋势,充填体中出现的声发射累计振铃计数越多;r值先升高再持续减小到一个较低值,随着外载荷的增加,进入缓慢升高阶段,峰值前均保持在该阶段。充填体破裂前兆信息在声发射信号主频分布中呈现主频段增多现象,表现为由加载初期的1~2个主频段,在临界主破裂时增多到3~5个主频段;且随着浓度的增加,声发射信号主频频段分布越宽,声发射相对高频信号(160~180 kHz)的激增响应系数呈递减趋势。以上特征可为不同浓度的尾砂胶结充填体稳定性监测、预测提供依据。  相似文献   
2.
试验采用磁化焙烧-磁选的方法来回收包头稀土尾矿中的Fe。考察了还原球团的粒径、焙烧温度、还原气体的成分、还原气气体流量、焙烧时间对于磁化焙烧回收Fe的影响。在焙烧温度为580℃,CO与CO2的浓度比为40∶60,还原气体气流量为1.2 L·min-1,焙烧时间为60 min的条件下对球团进行磁化焙烧,并将焙烧后的球团进行磨矿,使得-200目的物料占物料总重量的95%。将磨矿后的物料置于磁场强度为233 k A·m-1的磁选管中进行磁选,可以得到品位为60%左右的铁精矿,其铁回收率达到70%左右。  相似文献   
3.
In this study, ZSM-5, which is a Mobil-type five-type zeolite with well-defined crystal morphology, is successfully synthesized via a seed-assisted, liquid-free method that uses iron ore tailings as a silica source. The ZSM-5 crystallization kinetics at 423, 433, and 443 K and different synthesis times are investigated to identify the nucleation and crystallization mechanisms of the synthesized ZSM-5 zeolites, and results suggest that the crystallization kinetics follow a Kolmogorov-Johnson-Mehl-Avrami-type behavior. The activation energies for the induction and transition periods are 112.38 and 58.35 kJ mol−1, respectively. Furthermore, the Avrami exponent indicates three-dimensional crystal growth from both sporadic and instantaneous nucleation mechanisms. A comparison of our results with previous reports of the ZSM-5 crystallization mechanism demonstrates that the seed crystals play a significant role in nucleation and crystal growth. Finally, seed surface crystallization and new nuclei crystallization dual mechanism has been proposed to describe the crystallization process of ZSM-5.  相似文献   
4.
徐众  李军  吴恩辉  蒋燕 《应用化学》2022,39(3):461-469
以不同膨胀石墨(EG-300、EG-350和EG-400)为支撑材料,石蜡(PW)为相变主材,提钒尾渣(VT)为导电强化剂,采用熔融共混法制备复合相变材料,并对复合材料的稳定性和导电性进行测试分析。结果表明,进行60次热循环,EG/PW复合材料质量损失率小于0.03%,VT/EG/PW复合材料质量损失率小于0.08%,添加VT对材料热稳定性影响较小;直线拟合表明质量损失率与循环次数存在线性关系(R2范围在0.06143~0.85924之间);EG/PW复合相变材料的电阻率会随成型压力增加而减小,添加微米级VT之后规律一致,仅EG-300/PW电阻率随VT添加量增加而减小,添加量应该控制在2%以内,添加VT可以增强复合材料的导电性能;压力从2 MPa变到8 MPa时,电阻率下降率在49%以下,添加VT后复合材料电阻率下降率变大,添加VT可以使复合材料电阻率的压敏性提高;指数拟合显示复合相变材料电阻率与压力之间的指数相关性较高。  相似文献   
5.
We study the mechanical failure of cemented granular materials (e.g., sandstones) using a constitutive model based on breakage mechanics for grain crushing and damage mechanics for cement fracture. The theoretical aspects of this model are presented in Part I: Tengattini et al. (2014), A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables, Part I – Theory (Journal of the Mechanics and Physics of Solids, 10.1016/j.jmps.2014.05.021). In this Part II we investigate the constitutive and structural responses of cemented granular materials through analyses of Boundary Value Problems (BVPs).The multiple failure mechanisms captured by the proposed model enable the behavior of cemented granular rocks to be well reproduced for a wide range of confining pressures. Furthermore, through comparison of the model predictions and experimental data, the micromechanical basis of the model provides improved understanding of failure mechanisms of cemented granular materials. In particular, we show that grain crushing is the predominant inelastic deformation mechanism under high pressures while cement failure is the relevant mechanism at low pressures. Over an intermediate pressure regime a mixed mode of failure mechanisms is observed. Furthermore, the micromechanical roots of the model allow the effects on localized deformation modes of various initial microstructures to be studied. The results obtained from both the constitutive responses and BVP solutions indicate that the proposed approach and model provide a promising basis for future theoretical studies on cemented granular materials.  相似文献   
6.
Thermal neutron activation analysis, a high-resolution Ge(Li) gamma-ray spectrometer, and an IBM 360/67 digital computer were used to determine the concentration of Na, K, Sc, Cr, Mn, Fe, Co, Cu, Zn, Se, Br, Rb, Sb, Cs, and Hg in ground coffee and tea. This nondestructive multielement technique requires neither pre- nor postirradiation chemistry and eliminates problems of reagent contamination. The method is simple, precise and sensitive to 15 elements. Interferences from fast neutron (n, p) and (n, α) reactions are small and, if necessary, corrections may be applied easily. This technique can be applied to percolated tea and coffee.  相似文献   
7.
以铁尾矿和金尾矿为主要原料,采用熔融法制备了添加0~20wt%Fe_2O_3的CaO-MgO-Al_2O_3-SiO_2(CMAS)系纳米晶尾矿微晶玻璃,利用差示扫描量热分析(DSC)、X射线衍射分析(XRD)、红外光谱(IR)、扫描电镜(SEM)和综合力学性能仪等测试手段,研究了Fe_2O_3含量对该体系微晶玻璃显微结构及性能的影响。实验结果表明:随着Fe_2O_3含量的增加,样品的晶化温度和玻璃化转变温度逐渐降低;且Fe_2O_3可促进主晶相透辉石相(Mg_(0.6)Fe_(0.2)Al_(0.2))Ca(Si_(1.5)Al_(1.5))O_6的形成;同时Fe_2O_3能够有效减小透辉石相平均晶粒尺寸;另外,微晶玻璃的密度、显微硬度和耐碱性随晶粒尺寸的减小而增加,而抗折强度和耐酸性随晶粒尺寸的减小而降低。  相似文献   
8.
Iron ore tailings have become one kind of the most hazardous solid waste. Beneficiation of iron ore tailings is a significant issue in the world steel industries, from the point of view of both pollution control and secondary resources. This investigation addressed the processing of tailings with high sulphur content from an iron ore concentrator to produce pellet feed fines and to prevent acid mine drainage. This study was the lab-scale testing of an integrated method consisting of froth flotation combined with gravity and magnetic separation. Reverse flotation located at the end of the primary treatment circuit (high- and low-intensity magnetic separation) will lower a large amount of the sulphur from magnetic separator concentrate. The effects of various operating parameters such as concentrations of collector, frother, depressant and activator, pH, solid-in-pulp concentration have been studied on the sulphur removal using reverse flotation. According to the data presented in this study, the maximum recovery of total sulphur was obtained when the operational parameters were set to the PAX dosage160?gr/t, MIBC dosage 140?gr/t, CuSo4 100?gr/t, air flow rate 10?l/min, pH 8.5, and pulp density 30%. With these optimum parameters, final concentrate with the grade of 63.7% Fe and 0.085% S was obtained. The results of this study indicated that, with this method, a great amount of iron concentrate is produced and, simultaneously, the sulphidic fraction is separated that can later be managed more easily owing to the reduced volume.  相似文献   
9.
Diamond films deposited on tungsten carbide can lead to major improvements in the life and performance of cutting tools. However, deposition of diamond onto cemented tungsten carbide (WC-Co) is problematic due to the cobalt binder in the WC. This binder provides additional toughness to the tool but results in poor adhesion and low nucleation density of any diamond film. A two-step chemical etching pretreatment (Murakami reagent and Caro acid, (MC)-pretreatment) and a boronization pretreatment have both been used extensively to improve adhesion of CVD diamond film on WC-Co substrates. Here we discuss the applicability of MC-pretreatment for a range of Co-containing WC-Co substrates, and demonstrate a controlled synthesis process based on liquid boronizing pretreatment for obtaining smooth and dense micro- or nano-crystalline diamond films on high Co-containing WC-Co substrates. Substrate treatments and deposition parameters were found to have major influences on the smoothness, structure and quality of the diamond films. The best quality diamond films were achieved under conditions of relatively high substrate temperature (Ts) and the best adhesion was achieved at Ts = 800 °C.  相似文献   
10.
针对矿山尾矿中微量银元素测定的技术难题,提出了一种基于超短光路原理的能量色散X荧光能谱快速检测的方法。提高元素测量分辨率,提高样品分析效率,降低光管功率,延长仪器使用寿命。能谱系统优化了滤片以及探测器屏蔽物等设计,准直器采用对X射线基本无散射的聚四氟乙烯,达到微量银元素的检测要求。实际尾矿测试中,银的检出限达到0.1mg·kg~(-1),RSD在0.1%~2.6%之间,准确度在87%~115%之间。对比尾矿、原矿及精矿的检测实验,证明了在能量色散X荧光能谱中引入超短光路设计方法,能够提升系统峰/本底比,满足微量银元素的检测要求。  相似文献   
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