Coupled effects of saline solutions and temperature on the swelling deformation property of GMZ bentonite-sand mixtures

Based on the results of one-dimensional free swelling tests, the coupled effects of NaCl-Na₂SO₄ solutions and temperature on the swelling deformation property of compacted GMZ bentonite-sand mixtures were analyzed. The concentrations of the NaCl-Na₂SO₄ solutions were 0, 0.008, 0.04, 0.08 and 0.16 mol/L, the temperatures were 20 °C, 40 °C, 60 °C, 80 °C and 90 °C and the sand contents were 0, 30 and 50%. X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) tests were also performed to find the influences of the temperature, solution concentration and sand content on the mineral composition and microstructure. The results showed that the maximum swelling strain of the specimens increased with an elevated temperature, while it decreased with increases in the solution concentration and sand content. The swelling process was accelerated by the rising temperature. The XRD tests indicated that the combined effect of a high temperature and a high solution concentration may have caused more Na⁺ from the saline solutions to enter the interlayer, partly displacing the divalent cations. The MIP tests demonstrated that adding sand to the bentonite could reduce the amount of inter-granular pores and increase the intra-aggregate pores. These findings are advantageous to the transfer of heat and pour fluid in the specimens; and thus, the swelling deformation capacity of the bentonite-sand mixtures was higher than that of pure bentonite under the same conditions.     

-180℃深冷处理对7A99铝合金峰值时效强韧性能与析出行为的影响

对7A99超高强铝合金反向挤压板材采用T6峰值时效处理与-180℃冷热循环时效热处理(简称T6-DCT),通过XRD、TEM、HRTEM与3DAP研究-180℃深冷处理对7A99铝合金反向挤压板材强韧性能以及析出行为的影响。结果表明,-180℃冷热循环时效处理使得铝基体的晶格常数由由0.40551 nm 增至0.40626 nm,起到了一定的固溶强化作用;-180℃冷热循环时效处理后晶粒内部生成大量与基体非共格的η相,晶界处η相呈现断续分布并形成晶界无析出带,降低材料的拉伸强度;-180℃冷热循环时效处理促进基体中Zn和Mg元素原子的微观偏聚,导致了Zn和Mg元素的非均匀析出;-180℃深冷处理可以减小时效终态析出相的平均等效半径与析出密度,将等效半径由1.2 nm减小至1.14 nm,将析出密度由4.53×10₂₄/m₃降低至3.87×10₂₄ /m₃,削弱析出强化效果; -180℃冷热循环时效处理后合金的强韧匹配性能得到显著改善,强度略有降低,韧性显著提高。     

席夫碱与硝酸铈复配物对1060纯铝的缓蚀作用

采用极化曲线、电化学阻抗谱、扫描电镜和能谱分析,研究合成的3-吡啶-4-氨基-1,2,4-三唑-5-硫酮席夫碱及其复配物硝酸铈在质量分数为3.5%NaCl溶液中对1060纯铝的缓蚀作用。结果表明：在293 K时席夫碱可有效抑制纯铝在3.5%NaCl溶液中的腐蚀,当席夫碱浓度为0.4 g.L_-1时缓蚀率最高,可达76.0%。席夫碱为混合型缓蚀剂,其在1060纯铝表面的吸附符合Langmuir吸附模型,且同时存在物理吸附和化学吸附。0.2 g.L_-1席夫碱与0.03 g.L_-1硝酸铈复配缓蚀率可达88.2%,二者具有协同缓蚀作用。     

Zn基钎料钎焊烧结NdFeB与DP1180钢接头微观组织及性能

采用Zn-5Sn-2Cu-1.5Bi(ZSCB)钎料实现了烧结NdFeB永磁材料(NdFeB)与DP1180钢的钎焊连接。在惰性气氛控制的高频感应炉中进行钎焊,采用OM、SEM、EDS、微区XRD和NIM-2000H磁性测试仪等手段分析了接头界面的微观组织结构、NdFeB的磁性能和接头剪切强度。结果表明,NdFeB与ZSCB钎料形成Nd-Fe-Zn和Fe-Zn冶金结合,FeZn13和Fe3Zn10相在DP1180钢侧的界面处形成。焊接温度对NdFeB的磁性能影响较小。与传统方法的粘接相比,接头的剪切强度从32.50MPa提高到44.00MPa,提高了35.38%。由于NdFeB和ZSCB钎料之间的热膨胀系数差异很大,在接近NdFeB的反应层处产生较高的残余应力,导致接头从NdFeB界面处断裂。     

A brief review of brazing diamond in cutting tools

Diamond has high hardness and good wear resistance. It is widely used in cutting tools and workpieces. Brazing is an effective method to realize high quality cemented carbide joints in various materials connection technologies. This paper analyzes the research status of diamond brazing in detail. The materials used as brazing filler in diamond brazing are reviewed. Copper base filler and nickel base filler are the most commonly used brazing filler in diamond brazing. The advantages and disadvantages of diamond grinding tools under different production methods are analyzed. In addition, a series of new brazing alloys such as amorphous Ni based brazing filler metals are analyzed. Finally, the development trend of diamond brazing is pointed out.     

Effects of Dissimilar Alumina Particulates on Microstructure and Properties of Cold-Sprayed Alumina/A380 Composite Coatings

In this study,alumina/A380 composite coatings were fabricated by cold spray.The influence of alumina particulates' morphology(spherical and irregular) and content on the deposition behavior of the coatings(including surface roughness,surface residual stress,cross-sectional microstructure and microhardness) was investigated.Results revealed that the spherical alumina mainly shows micro-tamping effect during deposition,which result in remarkable low surface roughness and porosity of the coatings.In addition,very low deposition efficiency and good interfacial bonding between the coating and the substrate were achieved.For irregular alumina particles,the embedding of ceramic particulates in the coating was dominant during deposition process,resulting in high retention in the final deposit.However,it showed limited influence on porosity,surface roughness and interfacial bonding of the deposit.The coatings containing irregular alumina particulates exhibited much higher microhardness than those containing spherical alumina due to the higher load-bearing capacity of deposited alumina.     

Soldering of Zr-based bulk metallic glass and copper by Au-12Ge eutectic alloy

Zr-based bulk metallic glass and copper with different surface roughness were soldered using low temperature eutectic Au-12 Ge(wt%) solder on a thermomechanical simulator. The cross-sectional microstructures of the brazed joints were analyzed by scanning electron microscopy(SEM) and transmission electron microscope(TEM) in detail, and the compositional distribution along the interface was analyzed by energy-dispersive spectrometer(EDS). Results show that the surface roughness of base metals plays an important role in the quality of the brazed joint because the surface roughness can enlarge the effective contact area, which can improve the brazing surface quality between two materials. A moderate roughness of treated Zr-based metallic glass of 18 μm is shown to be the best for the soldering, while the surface roughness has a weak effect on the soldering behavior of Au-12 Ge solder on copper. After soldering, long-range diffusion of atoms occurs between the base metal and solder, and five distinct regions are formed at the joint region.     

青海交通社矿区碱长花岗岩锆石U-Pb年龄、岩石地球化学特征及成因探讨

交通社铌钽矿床位于阿尔金造山带,是该带近年来新发现的一个铌钽矿床。论文以该矿床为研究对象,通过开展矿床地质特征调查,利用锆石U-Pb年代学、岩石地球化学特征,探讨了与成矿密切相关的碱长花岗岩岩石成因类型及成岩成矿构造背景,探讨矿床成因。锆石LA-ICP-MS U-Pb同位素定年龄结果显示,碱长花岗岩为(453±4) Ma,属于高钾钙碱性系列,岩浆演化程度高;碱长花岗岩构造背景为后碰撞构造环境。微量元素表现为轻重稀土分馏不明显,稀土元素配分图显示,轻重稀土均相对平坦,具有明显Eu/Eu~*负异常。结合主量元素判别,同位素分析得出成岩、成矿物质为壳幔混合源。通过对比研究,结合矿床大地构造环境、成矿条件,认为交通社铌钽矿床形成于晚奥陶世,碱长花岗岩的侵入导致矿床的形成。矿床类型初步定为碱性花岗岩型铌钽矿床。     

装配式建筑工程总承包管理的探索与实践

中建科技在 EPC 管理模式基础上,结合装配式建筑的产业特点,创新提出并推广“研发+设计+制造+采购+施工装配”REMPC 五位一体工程总承包建造模式。在 REMPC 模式的指导思想下,结合裕璟幸福家园项目实践,创新提出“11231”的工程总承包管理方法并全面应用于深圳坪山高新区综合服务中心项目,效果显著。     

ICP-AES测定酸泥中硒碲含量

研究建立了王水溶样—电感耦合等离子体原子发射光谱测定酸泥中硒、碲含量的分析方法,通过实验对仪器工作参数、分析线的选择等进行了研究,确定了合适的分析线和仪器分析条件,并对本方法进行了精密度和准确度实验。实验结果显示,硒的相对标准偏差(RSD,n=7)为1.40%~1.67%,加标回收率为99.4%~107.7%,碲的相对标准偏差(RSD,n=7)为1.82%~2.44%,加标回收率为95.0%~104.0%,满足样品中硒、碲分析测定要求。