Extrusion behavior of micro-nanostructured Al-18%Si alloy powders

The extrusion of Al-Si alloy powders with different particle sizes allows manufacture of different products with unique microstructures and therefore with unique mechanical properties. The effects of powder size on the extrusion behavior and process defect of Al-18%Si alloy were studied by means of microscopy (optical, scanning electron) and density determination. The main objective of the work is to demonstrate the influence of the powder material characteristics on final density and quality of bar. The results show that the bigger the powder particles, the better the performance of cold compacting. The surface of alloy bar extruded from big particles has good quality without cracking. While the smaller the powder particles, the higher the density and the better the microstructure and mechanical properties. For practice application, the mixed powders are better than single powder.

MICROSTRUCTURES OF ULTRAFINE WC POWDERS

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Engineering properties and microstructure of expansive soil treated with nanographite powder

To reduce geological disasters caused by expansive soil,it is crucial to use a new type of modified material to rapidly improve soil strength instead of traditional soil improvement materials such as lime and cement.Nanographite powder(NGP)has excellent properties,such as high adsorption,conductivity,and lubrication,since it has the characteristics of small size,large specific surface area,and high surface energy.However,previous studies on the improvement of expansive soil with NGP are not processed enough.To study the improvement effect of NGP on expansive soil,non-load swelling ratio tests,consolidation tests,unconfined compressive strength tests,mercury injection tests,and micro-CT tests on expansive soil mixed with different NGP contents were performed.The results show that the non-load swelling ratio,mechanical properties,and porosity of expansive soil show some increasement after adding NGP.The strength of expansive soil reaches the maximum when the NGP content is 1.450%.The cumulative mercury volume and compressive strain of expansive soil reach the maximum with the 2.0%NGP content.Finally,the modification mechanism of swelling,compressibility,microstructure,and compressive strength of expansive soil by NGP is revealed.

PREPARATION AND PROPERTIES OF THE MICRO-POWDER PHASE AND A NEW PHASE OF AMMONIUM TETRAMOLYBDATES

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Structure Characterization and Dephosphorization Effect Analysis of Oyster Shell-silica Micropowder Waste Water Dephosphorization Materials

In this work,the effects of pH value of waste water and initial concentration of phosphorus on dephosphorization materials were investigated.The materials were prepared by shaping,sintering and hydrothermal reshaping oyster shell and silica micro-powder.Different concentrations of phosphorus-contained waste water were simulated with potassium dihydrogen phosphate solution,the effect of dephosphorization was tested with phosphomolybdenum blue spectrophotometer method,and the crystal phase and microstructure of materials were characterized by XRD and SEM methods. It was indicated that dephosphorization was completed in 6 h when the initial phosphorus concentration in waste water was lower than 15 mg/L, and the dephosphorization time prolonged as the increase of phosphorus concentration. It was observed that the pH value of waste water influenced dephosphorization significantly, and neutral subalkalic environment favored dephosphorization. When the pH value was 11, the efficiency of dephosphozation was the greatest. For waste water with an initial concentration of 20 mg/L, the dephosphozation rate is close to 100% in8 h.

Effects of Zhenren Yangzang Decoction Combined with Modified Shenling Baizhu Powder on Immune Function and Intestinal Microecology of Diarrhea Patients with Deficiency and Cold Syndrome

OBJECTIVE: To observe the effects of Zhenren Yangzang Decoction combined with modified Shenling Baizhu Powder on the immune function and intestinal microecology of diarrhea patients with deficiency and cold syndrome. METHODS: A total of 60 diarrhea patients with deficiency and cold syndrome were randomly divided into observation group and control group, with 30 cases in each group. The control group was treated with conventional western medicine. The observation group was given the treatment of Zhenren Yangzang Decoction combined with modified Shenling Baizhu Powder on the basis of the same treatment for 4 weeks. The clinical symptoms, fecal flora and immunoglobulin content of the 2 groups were observed and the clinical efficacy was evaluated. RESULTS: After treatment, the symptoms scores of fecal diarrhea, aversion to cold, cold limbs, loss of appetite, cold and painful waist and knee, abdominal fullness, abdominal distension and abdominal pain, and intestinal bacilli contents were significantly decreased(P < 0.05). The contents of lactobacillus, bifidus bacilli, IgG, IgM and IgA were significantly increased(P < 0.05), and the improvement of the above indexes in the observation group was significantly better than that in the control group(P < 0.05). The total effective rate after treatment in the observation group was 93.3%, which was significantly higher than 73.3% of the control group(P < 0.05). CONCLUSION: The treatment of diarrhea patients with deficiency and cold syndrome with Zhenren Yangzang Decoction and modified Shenling Baizhu Powder can effectively improve the intestinal micro-ecological environment, improve the immune function of patients and promote the rapid recovery of patients.

Pilot Study on Powder Active Carbon / Flotation/Microflocculation / Ultrafiltration Combined Process for Treatment of Reservoir Water

[Objective] The study aimed to discover the effects of powder active carbon（ PAC） /flotation /micro-flocculation /ultrafiltration combined process on the treatment of reservoir water. [Method]Taken the water from a mountainous reservoir for the initial samples,the parameters such as turbidity,COD Mn,chlorophyll-a and methylisobormeol（ MIB） of water samples were monitored before and after treated with combined processes of micro-flocculation /ultrafiltration, flotation /micro-flocculation /ultrafiltration, PAC /flotation /micro-flocculation /ultrafiltration. [Result] The results showed that the removal rates of turbidity of water samples by the above three processes were 97. 5%,98. 0% and 98. 6%,respectively. The removal rates of COD Mn were 30. 9%,35. 0% and 52. 0%. The removal rates of chlorophyll-a were 80. 6%,91. 0% and 99. 0%. The removal rates of MIB were 17. 0%,34. 2% and 97. 0%. [Conclusion]The PAC /flotation /micro-flocculation ultrafiltration combined process can be flexibly combined based on the characteristics of algae and odor in water,and is suitable for water plant construction or reconstruction.

隧道超挖超耗管控措施研究

隧道的超挖超耗管控是绿色低碳时代背景下工程界最关心的难题,对施工企业的成本控制和效益提升具有重要意义。以武两高速XFS隧道为背景,系统总结了隧道超挖超耗的10类影响因素和常见对策,包括围岩条件、施工参数、测量放样、爆破方案、钻孔质量、喷射混凝土回弹率、预留变形量、物资设备性能、作业人员水平和现场施工管控。分析了XFS隧道超挖超耗的原因,并制定了加强地质预报和超前支护施作,减小开挖进尺;动态调整爆破方案,严格炮孔质量检查;引入超细改性硅微粉优化配合比,提高喷射工艺水平;加强现场施工管控,制定超挖超耗管控办法,落实作业人员的激励奖惩等措施。措施执行后,XFS隧道平均超挖由30.1 cm降低至16.6 cm,综合超耗由173.7%降低至100.7%。

Micro-FAST中升温速率和烧结温度对零件致密化的影响

采用Gleeble-1500D热模拟机对316L不锈钢粉末进行烧结,制备出尺寸为Φ1.0 mm×1.0 mm的微型零件,并研究了升温速率和烧结温度对微型零件微观组织及性能的影响。结果表明:随着升温速率和烧结温度的提高,烧结试样体系的孔隙数量减少,试样的相对密度增加;在升温速率为50℃/s、烧结温度为900℃时,得到了近全致密的试样,且烧结温度低于传统烧结方法的烧结温度;试样最大轴向尺寸变化出现在快速升温阶段,说明在多物理场活化烧结微成形中升温速率对致密化的贡献比烧结温度更大。

Sintering technology for micro heat pipe with sintered wick

In order to study reasonable sintering technological parameters and appropriate copper powder size range of micro heat pipe (MHP) with the sintered wick, the forming principle of copper powders in wicks and MHP's heat transfer capabilities were first analyzed, then copper powders with different cell sizes and dispersions were sintered in RXL-12-11 resistance furnace under the protection of the hydrogen at different sintering temperatures for different durations of sintering time, and finally the sintered wicks' scanning electron microscope (SEM) images and their heat transfer capabilities were analyzed. The results indicate that the wick sintered with copper powders of larger cell size or smaller size range has better sintering properties and larger heat transfer capabilities; and that the increase of either sintering temperatures or sintering time also helps to improve the wick's sintering properties and heat transfer capabilities, and the former affects more obviously than the latter. Considering both its manufacturing cost and performance requirements, it is recommended that copper powders with the size range of 140-170 μm are sintered at 900-950℃ for 30-60 min in practical manufacturing. In addition, two approaches to improve wick's porosity are also proposed through theoretical analysis, which suggests that the larger the wick's porosity, the better the heat transfer capabilities of the MHP.

An overview of laser-based multiple metallic material additive manufacturing: from macro- to micro-scales

Additive manufacturing(AM)is an emerging customized three-dimensional(3D)functional product fabrication technology.It provides a higher degree of design freedom,reduces manufacturing steps,cost and production cycles.However,existing metallic component 3D printing techniques are mainly for the manufacture of single material components.With the increasing commercial applications of AM technologies,the need for 3D printing of more than one type of dissimilar materials in a single component increases.Therefore,investigations on multi-material AM(MMAM)emerge over the past decade.Lasers are currently widely used for the AM of metallic components where high temperatures are involved.Here we report the progress and trend in laser-based macro-and micro-scale AM of multiple metallic components.The methods covered in this paper include laser powder bed fusion,laser powder directed energy deposition,and laser-induced forward transfer for MMAM applications.The principles and process/material characteristics are described.Potential applications and challenges are discussed.Finally,future research directions and prospects are proposed.

聚丙烯还原氧化镍制备Ni-C微粉催化电极材料的研究

利用聚丙烯(PP)与氧化镍(NiO)粉末混合物(质量比1∶2.3~1∶2.7)在氩气气氛下加热制备Ni-C微粉析氢电极催化材料。重点探究质量比对Ni-C微粉制备过程及其催化性能的影响。采用同步热分析仪(TG-DSC)监测反应过程,利用XRD和SEM-EDS确定反应固相产物的物相组成及微观形貌,析氢催化性能及稳定性由电化学工作站(Parstat 3000A)测试获得。结果表明,混合粉末在加热过程中PP发生熔化和裂解反应,其裂解产物还原NiO。当温度高于1073K时,固相产物由镍、碳单质组成。固相产物中镍单质的含量随初始NiO含量的增加而增大。由PP∶NiO=1∶2.6及1∶2.7两样品制备的Ni-C微粉在高过电位下以及低过电位下均拥有较好的析氢效果及稳定性,1000次循环伏安测试后仍保持了良好的析氢催化效果。

Synthesis of Y_2O_3 Nano-Powder from Yttrium Oxalate under Ambient Temperature

High purity Y_2O_3 nano-powders was synthesized directly from solution ofindustrial YCl_3 by method of oxalate precipitation through super-micro-reactors made by complexnon-ionic surfactant. The purity and diameter of Y_2O_3 particles were controlled by such processingparameters as concentration of YCl_3 and oxalic acid and complex non-ionic surfactant etc. TEMphotomicrographs show that Y_2O_3 particles are spherical in shape, with an average diameter of lessthan 30 nm. Test results certify that the purity and particle diameter as well as the dispersion ofY_2O_3 nano-powder depend on the concentrations of YCl_3, oxalic acid and complex non-ionicsurfactant. The optimum ranges of the concentrations for YCl_3 and complex non-ionic surfactant whenthe diameter of Y_2O_3 particles is smaller than 100 nm are 0.43 ～1.4 mol ? L^(-1) and0.031～0.112 mol·L^(-1) respectively, while the mass fraction range of oxalic acid is 10% ～18% .The purity of Y_2O_3 nano-powder tested by ICP-AES analysis is 99.99% .

葛根全粉添加对重组米蒸煮特性的影响

为实现葛根的全质化利用,将葛根制成全粉并用于重组米的制备,评价葛根全粉对重组米蒸煮特性、质构特性和微观结构的影响。研究发现,随着葛根全粉添加量的增加重组米的L~*值降低,而ΔE值增加。重组米在葛根全粉添加量为0%时糊化度最低,为69.27%,但随着添加量的增加糊化度无显著性差异(p>0.05);而碘蓝值随着葛根全粉添加量的增加而呈减小的趋势,20%时最低,为15.55。不同葛根全粉添加量下重组米蒸煮吸水率无显著性差异,蒸煮吸水率范围为217.84%~235.17%,高于市售原米,但是低于市售重组米;蒸煮损失率和膨胀率都随着添加量的增加呈先减小后增加趋势。葛根全粉的添加显著增加重组米的黄酮和多酚含量,添加量20%时分别为3.80 mg/g和2.42 mg/g,相对于原米其含量增加2.62倍和3.56倍。与市售重组米和原米相比,添加葛根全粉后的重组米截面呈蜂窝状,有密集的微孔,重组米的硬度、黏性、弹性和咀嚼性增加。

轻质高强蒸压加气混凝土的制备及性能研究

本文利用新疆地区粉煤灰和微硅粉等典型固废资源为原料,开展轻质高强蒸压加气混凝土制备技术研究,分析了原料配比、水料比和发气剂掺量对制品绝干密度和抗压强度的影响。结果表明,当m(粉煤灰)∶m(微硅粉)∶m(石英砂)∶m(生石灰)∶m(水泥)∶m(石膏)=30∶25∶10∶25∶8∶2、铝粉量为总物料质量的0.10%、水料比为0.58、蒸压温度为195℃、蒸压压力为1.2 MPa、蒸压时间为8 h时,轻质高强蒸压加气混凝土的绝干密度为568.70 kg/m^(3),抗压强度为5.4 MPa,导热系数为0.140 W/(m·K),达到了A5.0、B06等级。

再生复合微粉混凝土界面过渡区性能研究

为研究再生复合微粉复掺比对混凝土界面过渡区性能的影响机理,用宏微观试验相结合的方法,分析不同复掺比对混凝土劈裂抗拉强度和显微硬度的影响规律,并利用灰色关联法探究力学性能与微观结构的关系。结果表明:再生砖粉对混凝土的改善效果优于再生混凝土粉,且掺入合理的再生复合微粉会改善混凝土界面过渡区的微观结构;再生复合微粉混凝土各组相显微硬度关系为:骨料相>砂浆相>界面过渡区相,且界面过渡区厚度随养护龄期的增加而逐渐减小;界面过渡区厚度与劈裂抗拉强度关系显著,呈线性负相关,所建立的模型拟合度较高。界面过渡区厚度能准确地表征再生复合微粉混凝土宏观性能变化规律,当再生混凝土粉/再生砖粉为2∶8时,可制备出性能良好的C30混凝土,具有良好的推广应用价值。

融合石膏组分和微纳米结构“双基因”调控的铁尾矿粉无熟料固结体力学性能

为了探究超细铁尾矿粉颗粒表面非晶态SiO_(2)和Al_(2)O_(3)在石灰-石膏体系中的水化固化机理及调控因素,本工作考察了石膏掺量和铁尾矿粉中微纳米级颗粒含量之间的匹配对固结体强度的影响,利用XRD、TG-DSC、SEM和化学滴定法测试分析了固结体试样中水化产物的种类、形貌及含量的变化,研究了这些变化对固结体强度的影响及作用机理。结果表明,超细铁尾矿粉中小于1.096μm的微纳米颗粒含量显著影响着铁尾矿粉在碱溶液中Si和Al元素的溶出行为,固结体强度随着这些微纳米颗粒含量的增加而提高。固结体中的主要水化产物是铝掺杂的水化硅酸钙(C-(A)-S-H)和钙矾石(AFt)。石膏掺量与铁尾矿粉中微纳米颗粒含量的最佳匹配值对固结体的强度具有显著影响,并且微纳米颗粒含量越高,对应的石膏最佳掺量越大。石膏组分保证了AFt的生成和稳定,同时也加速了铁尾矿粉颗粒表面非晶态成分的水化。本工作探明了固结材料中最佳石膏掺量与微纳米铁尾矿粉颗粒含量的关联关系及其机理,证实了微纳米级颗粒是无熟料固结体结构中的基本活性单元,石膏的掺入对微纳米颗粒的水化起到调控作用,水化后的微纳米颗粒演变为固结体的基本结构单元,这种组分和结构的“双基因”调控机制影响着固结体的力学性能。

早强型钢渣基胶凝材料的制备及其水化机理研究

钢渣是炼钢过程中产生的主要废弃物,具有用途单一、产生量大、污染环境等特点。本文使用钢渣微粉、42.5普通硅酸盐水泥分别与增强剂Ⅰ、增强剂Ⅱ混合制备早强型钢渣基胶凝材料,通过测定原料化学成分、矿物组成,测试胶凝材料的力学性能,分析其热稳定性、微观形貌来揭示胶凝材料的水化机理。研究结果表明:胶凝材料的早期抗压强度大幅提高,后期抗压强度良好;这是因为增强剂能促进Ca(OH)2消耗并提高水化反应速率,Ca(OH)2水解出的OH-能促进钢渣微粉中玻璃体溶出硅酸盐,与Ca^(2+)生成C-S-H凝胶;增强剂含有的硫酸盐能与胶凝材料生成钙矾石AFt,并填充于凝胶孔隙中,增强了材料的密实度。早强型钢渣基胶凝材料的最优配比为钢渣微粉125 g、增强剂Ⅱ用量10 g。研究成果为早强型钢渣基胶凝材料的制备提供了新思路,也可为钢渣综合利用研究提供借鉴。

矿渣微粉改良红层填料的力学特性及其机理分析

为研究矿渣微粉改良红层填料的力学特性及其作用机理,通过无侧限抗压强度、直剪等试验,对不同矿渣微粉掺量下的红层填料进行了强度特性分析,并采用X衍射、热重分析、红外光谱、激光粒度、核磁共振和扫描电镜等微观分析方法,围绕矿渣微粉改良土体的作用机理进行了研究。试验结果表明,矿渣微粉对红层填料的力学强度和水稳定性具有较好的改良作用,改良填料的无侧限抗压强度由0.76 MPa逐渐增大至3.10 MPa;黏聚力与内摩擦角也得到了显著提高。通过红外光谱、激光粒度和核磁共振分析发现,改良填料颗粒间Al^(3+)阳离子配位的振动峰增强,降低了黏土矿物的双电层厚度,土颗粒团聚性显著增强,孔隙分布得到优化;通过X射线衍射和热重分析证明了水化产物的生成过程;扫描电镜观测到改良填料的具体作用机理:主要为填充效应和胶凝效应,其胶凝效应包括水化作用和离子交换作用。对微观扫描图的定量化分析进一步表明土体结构复杂程度增大,颗粒粗糙程度及骨架性增强。