In situ thermomechanical processing to avoid grain boundary precipitation and strength-ductility loss of age hardening alloys

To avoid grain boundary(GB) precipitation during aging, a new strategy of in situ thermomechanical processing for age hardening alloys was proposed. Specifically, high-density nanoscale precipitates were introduced into ultrafine grain(UFG) interiors of 7075 Al alloy by equal-channel-angular(ECAP) processing at 250 ℃ for 8 passes, thus avoiding GB precipitation. Tensile test results indicated that the UFG 7075 Al alloy exhibits superior mechanical properties(yield strength of 350 MPa, ultimate tensile strength of 500 MPa, uniform elongation of 18% and tensile ductility of 19%) compared with the UFG 1050 Al counterpart(yield strength of 170 MPa, ultimate tensile strength of 180 MPa, uniform elongation of 2.5% and tensile ductility of 7%). Fracture surface morphology studies revealed numerous homogeneous micro shear bands in necking shrinkage areas of both UFG 7075 Al and 1050 Al alloys, which are controlled by cooperative GB sliding. Moreover, the introduction of nanoscale precipitates in UFG 7075 Al matrix weakened the tendency of shear fracture, resulting in a higher tensile ductility and more homogeneous deformation. Different from the GB precipitation during postmortem aging, in situ thermomechanical treatment dynamically formed GBs after precipitation, thus avoiding precipitation on GBs.

Ammonium Metavanadate Fabricated by Selective Precipitation of Impurity Chemicals on Inorganic Flocculants

High purity ammonium metavanadate(NH_(4)VO_(3))is the most vital chemical to produce V2O5,VO2,VN alloy,VFe alloy and VOSO4,which have some prospective applications for high strength steel,smart window,infrared detector and imaging,large scale energy storage system.NH_(4)VO_(3)is usually produced by spontaneous crystallization from the aqueous solution due to its sharp dependence of solubility on the temperature.However,hazardous chemicals in industrial effluent,include phosphorate,silicate and arsenate,causing severe damage to the environment.In this work,these impurities are selectively precipitated onto inorganic flocculants,while the vanadate dissolved in an aqueous solution keeps almost undisturbed.Therefore,high purity NH_(4)VO_(3)is produced by the crystallization from the purified solution.By screening various flocculants and precipitating parameters,polyaluminum sulfate with an optimal amount of 50 g/L,is demonstrated to selectively remove phosphorate,silicate and arsenate,corresponding to the removing efficiency of 93.39%,97.11%and 88.31%,respectively.NH_(4)VO_(3)from the purified solution holds a purity of 99.21%,in comparison with 98.33%in the product from the crude solution.This purifying technology cannot only produce NH_(4)VO_(3)with high added value,but also reduce the environmental pollution of waste liquid.

Investigation of the Micro-Mechanics of an Extruded Precipitation-Strengthened Magnesium Alloy under Cyclic Loading

Precipitation strengthening is a crucial microscopic mechanism for enhancing the strength of magnesium alloys. In order to elucidate the influence of precipitation on the microscopic deformation mechanisms and macroscopic mechanical response of magnesium alloys under cyclic loading conditions, we employed a crystal plasticity model to analyze the stress-strain curves, specific crystal plane diffraction intensities, and the temporal evolution of various microscopic deformation mechanisms and twinning volume fractions for an extruded magnesium alloy, AXM10304, containing coherent precipitates. The research findings indicate that precipitation does not fundamentally alter the microscopic mechanisms of this alloy. However, it hinders twinning during the compression stage, mildly promotes detwinning during the tension stage, and enhances tension secondary hardening by elevating the difficulty of activation of the prismatic slip.

In-situ Observation of Dark Phase Precipitation during Heating and Soaking Process of a High Nickel Steel

In-situ observation of microstructural evolution during heating and soaking process was carded out for a high nickel steel using HTCLSM. Dark phases were observed when soaking at 900℃. Results showed that the number of the dark phases culminated in about 50 s during soaking at 900℃. With the increase of soaking time the area proportion of the dark phases increased and reached the maximum value in about 3 min, When temperature rose from 900 ℃, the dark phases remained steady initially, but started to dissolve into the matrix at about 1 060 ℃ and completely disappeared at 1 132℃. When the specimen soaked at 900 ℃ was cooled down to room temperature （RT）, the dark phases kept stable. Energy spectrum analysis results showed that the dark phases contained much more Cr and Mn elements than the matrix and,were also rich in V. Tensile test results showed that the dark phase strengthened the steel with the maximum tensile strength obtained after soaking at 900 ℃ for 3 minutes.

Treatment of Wastewater in Chemistry Laboratory through Flocculent Settling and Constructed Wetlands

The basic chemistry laboratories of three colleges and universities in Guizhou Province were investigated completely,especially the pollution situations of the basic chemistry projects were counted,and the discharge amounts of the poisonous and harmful pollutants in the waste liquid from laboratories were monitored and analyzed.On the basis of the summing-up and analysis of the current research findings,a simple and feasible treatment scheme through flocculating,precipitating and constructed wetlands was designed to control the three kinds of excessive pollutants.

铝离子絮凝剂对微生物加固砂土效果的影响试验研究

灌注次数过多制约了微生物诱导碳酸钙沉积(MICP)在实际工程中的应用。为了减少灌注次数、提高胶结效率,提出一种MICP加固强化方法,即在胶结液中添加铝离子絮凝剂,以提高MICP加固速率和增强加固效果。开展MICP砂柱试验,在胶结液中加入不同浓度AlCl3·6H2O进行灌注试验,然后测试加固砂柱碳酸钙含量及无侧限抗压强度(UCS)。在水溶液试验中,观察不同溶液条件下沉积物生成情况及溶液的pH值变化,并通过XRD、SEM试验研究铝离子絮凝剂对沉积碳酸钙的成分及形态的影响。结果表明:与常规方法的对照组比较,胶结液中加入适量铝离子絮凝剂,灌注3次后砂柱即可形成有强度的固结体,灌注5次后砂柱无侧限抗压强度可达到1.7MPa,而常规对照组达到相同的强度需要灌注9次。铝离子絮凝剂的掺入有效减少了MICP灌注处理次数,对实际应用有重要意义。

Effect of aging time on discontinuous precipitates,continuous precipitates and mechanical properties of AZ80A magnesium alloy

The evolution of precipitates and mechanical properties of AZ80A magnesium alloy with aging time was studied by in situ observation with SEM,TEM and tensile testing.The results show that the continuous precipitation(CP)phases near the reaction front(RF)are replaced by the discontinuous precipitation(DP)phases at the early aging stage.In DP regions,the elliptical phases coarsen obviously with the increase of aging time,which results in a slightly slow reduction of the intracrystalline hardness of DP regions.In CP regions,some small plate phases reprecipitate simultaneously with the growth of the initial precipitates,which contributes to a slight increase in the intracrystalline hardness in CP regions at the later aging stage.The aging hardening of DP regions is faster and stronger than that of CP regions.However,the age strengthening of CP regions not only compensates for the overaging softening of DP regions but also improves the strength of the alloy.

Effect of alloying elements on mechanical properties in Cu-15%Cr in-situ composites

The effects of alloying elements on the mechanical properties as well as electrical conductivity in Cu-15%Cr(mass fraction) in-situ composites were systematically studied and high strength and high electrical conductive Cu base in-situ composites have been developed. The best combination is the addition of 0.1% to 0.2% Zr, Ti, or Sn in Cu-15%Cr in-situ composite, thermomechanical treatment to refine the microstructure and optimizing the precipitation of second phase. The strength is controlled by high density of dislocations in the Cu matrix, the lamellar spacing of the second phase, and the fine Cr precipitates. The aging treatment to reduce solute atoms has a beneficial effect on the increase of electrical conductivity. The addition of Zr, or Ti of about 0.15% to 0.2% promotes the precipitation of Cr particles.

Effect of fine precipitates on initiation and propagation of micro-cracks in low alloy Cr-Mo-V steel

The effect of fine precipitates on the initiation and propagation of micro cracks and the length of dislocation free zone (DFZ) in a low alloy Cr Mo V steel was studied by in situ TEM observation for the specimens both in embrittled and toughened conditions. The results show that in the embrittled specimen, dislocations emitted from the crack tip can easily slip by cutting through the precipitates and move away from the crack tip region, so that a long DFZ forms and the brittle fracture occurs via cleavage cracks initiating and propagating. The size of DFZ mainly depends upon the diameter and the interparticle distance of the precipitates in the matrix. In the toughened specimens, the size of DFZ extremely changes with the interparticle distance. Mobile dislocations are emitted from the crack tip and bypassing the particles. The interaction between the dislocations and the particles results in the dislocation pile up and tangle, leading to diminishing of the DFZ. The crack tip is easy to blunt or chang the propagating direction and the crack propagation shows a jagged path.

<i>In Situ</i>Hydroxyapatite Synthesis: Influence of Collagen on Its Structural and Morphological Characteristic

Hydroxyapatite (HA) was synthesized in situ by the precipitation method, with and without the presence of collagen (COLL), to study its influence on HA’s structural and morphological characteristics. The material was characterized by energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TG) and scanning electron microscopy (SEM). The Ca/P molar ratio was influenced by collagen addition—1.89 and 2.38 for samples without and with collagen, respectively. The WAXD pattern revealed better resolution and intensity besides higher crystallinity degree of the HA in the presence of collagen. The photomicrographs showed a strong influence of collagen on the HA morphology.

赤泥用于酸性含锰废水中锰的净化研究

采用还原焙烧-磁选预处理赤泥,得到非磁性物;非磁性物经煅烧、盐酸溶出后加入饱和偏铝酸钠聚合剂聚合后过滤、熟化制备聚合氯化铝(PAC)基液;使用该PAC基液,在沉降时间5 h、PAC基液与废水体积比1∶120、搅拌转速140 r/min、pH值8、反应温度30℃、聚丙烯酰胺(PAM)投加量20 mg/L条件下处理含锰酸性废水,处理后液中锰质量浓度由325.3 mg/L降至1.5 mg/L,锰去除率达99.5%,净化后液中锰质量浓度达到国家一级排放标准。

新型有机絮凝剂处理磷酸铁母液试验研究

针对加氨水后的磷酸铁生产母液在处理过程中生成沉淀颗粒小且长时间难以沉淀的问题,采用絮凝沉淀法提高沉淀效率。通过对PFS+APAM和GFL49+GFA98共2种絮凝剂组合进行对比,选出最优组合,并在最优药剂组合条件下确定絮凝剂投加量、搅拌转速和搅拌时间。结果表明:GFL49+GFA98为最优絮凝剂组合,GFL49和GFA98的最佳投加量分别为280、2.2mg/L。当水温25℃、搅拌转速100r/min、搅拌时间90s、沉淀1min后母液上清液浊度为2.1NTU,浊度去除率为99.475%。实验证明:相较于传统絮凝剂PFS+APAM,GFL49+GFA98具有生成絮体更大、投加量小、产生污泥量少的优点。

化学氧化-絮凝工艺在压裂返排液除硼中的应用

为降低压裂返排液中的硼含量,满足水样回用配液或外排标准,以5口水平井压裂后的返排液为研究对象,考察了氧化剂类型、投加量、预处理条件、沉淀剂类型、投加量对化学氧化工艺的影响;在化学氧化工艺出水的基础上,考察了絮凝剂投加量、搅拌速度和加药时间间隔对絮凝工艺的影响,并监测了两者耦合联用后的效果。结果表明,H_(2)O_(2)和BaCl_(2)分别作为氧化剂和沉淀剂时,除硼效果较好,建立了最佳投加量与返排液中初始硼浓度相关的线性方程,便于现场快速选定加药浓度;当PAC浓度为80 mg/L、PAM浓度为5 mg/L、搅拌速度30 r/min、加药时间间隔30 s时,絮凝工艺的处理效果最优;将化学氧化-絮凝工艺耦合后,在氧化反应pH值为9、氧化反应时间为30 min,沉淀反应pH值为9和最佳絮凝工艺的条件下,可保证滤液中硼质量浓度小于5 mg/L,满足回用配液的要求。研究结果可为压裂返排液的高效、清洁处理提供实际参考。

Fe_(3)O_(4)纳米颗粒的共沉淀法制备及其性能研究

目的:开发高效、清洁、经济的磁性纳米颗粒,进一步推动磁絮凝法在污水处理中的应用。方法:采用共沉淀法制备了四氧化三铁(Fe_(3)O_(4))纳米颗粒,研究了n(Fe^(3+))∶n(Fe^(2+))配比及反应温度对颗粒形貌、粒径、结构、表面官能团、Zeta电位等的影响,并测试了样品的磁性能。结果:n(Fe^(3+))∶n(Fe^(2+))配比为1.75∶1,反应温度为50℃时,共沉淀法制备Fe_(3)O_(4)纳米颗粒粒径为10~80 nm,晶型稳定,表面基团-OH较多,Zeta电位绝对值小;其饱和磁化强度为67.18 emu·g^(-1),矫顽力为3242.00 A·m^(-1),剩余磁化强度为4.47 emu·g^(-1)。结论:采用共沉淀法制备获得Fe_(3)O_(4)纳米颗粒,可作为优良的磁絮凝材料促进水中的絮凝反应。

水厂排泥水固体通量及微砂增效絮凝沉淀试验

城市水厂在净水过程中产生的大量排泥废水,不仅影响水厂的正常运行,还会对生态环境卫生造成较大威胁。为探索一种经济高效的排泥水絮凝沉降技术,试验取上海市某水厂沉淀池排泥水进行自然沉降试验,探究微砂增效阳离子型聚丙烯酰胺(CPAM)絮凝处理对排泥水沉降性能及其固体通量的影响规律。结果表明:低浓度排泥水的自然沉降速率较大,静沉固体通量高,当到达压密点后沉降速率变小,沉降曲线发生明显变化;随着排泥水浓度增加,自然沉降速率减小,但具有较大的向下流排泥固体通量。单独投加CPAM对于高浓度排泥水沉降性的改善作用有限,而采用60%微砂增效1.0 mg CPAM/g絮凝处理对低、高浓度排泥水的沉降性均具有良好的促进效果,并产生较高的总固体通量,是一种高效的絮凝浓缩技术。该试验结果为水厂排泥水的高效絮凝处理提供了重要参考。

深度净化含高氮、磷、化学需氧量污水的方法探究

城镇生活污水中总磷(total phosphorus,TP)、总氮(total nitrogen,TN)、氨氮(ammonia nitrogen,NH 3-N)含量及化学需氧量(chemical oxygen demand,COD)值较高,需经过处理来降低水质参数值。文中比较了不同絮凝剂、吸附剂对污水中氮和磷的去除能力,比较了臭氧氧化法和芬顿法降低污水COD值的效果,通过化学沉淀法降低TP含量,最后采用多步联用处理技术对污水进行深度处理。结果表明:污水中TP、NH 3-N的去除率及COD值下降率均高于88.7%,其中COD值及NH 3-N浓度达到了国标一级A标准,而TP和TN浓度基本达到了的一级B标准。

微电解-絮凝沉淀协同处理氰化提金废水的研究

采用微电解-絮凝沉淀技术处理高浓度氰化提金废水,主要研究了电压、电解时间、极板间距、温度、聚合氯化铁(PFC)添加量对CNT、CN-、Cu和Zn离子去除率的影响及过程反应机制。结果表明:室温条件下,以钛板为阴极、石墨板为阳极,采用一阴两阳电解体系处理氰化提金废水,当PFC添加量为750mg·L^(-1),电压4.5V,时间3h,极板间距10mm时,废水中CNT、CN-、Cu和Zn离子的去除率分别为97.29%、97.83%、99.36%和98.74%,处理后废水可直接返回浸出系统。电场作用下废水中原有的Cl-及PFC解离产生的Cl-定向迁移至阳极发生氧化反应,产生的Cl2及ClO-将阳极附近的游离氰、金属氰络合离子间接氧化生成N2和CO_(2),释放出的重金属离子部分在阴极电沉积析出,部分Cu^(2+)会以Cu(OH)2沉淀形式被去除,Zn^(2+)与Cu(CN)32-发生共沉淀以Zn(CN)2及CuCN沉淀形式被去除。同时,微电解-絮凝与PFC水解互相促进,水解产生的氢氧化物与多核羟基络合物通过吸附、絮凝作用有助于沉淀物的快速沉降。采用该技术可达到快速高效去除氰化物及综合利用有价金属的目的,为氰化提金废水的无害化处理与资源综合利用提供了新的途径。

Fabrication and Characterization of Chitosan-Silk Fibroin/Hydroxyapatite Composites via in situ Precipitation for Bone Tissue Engineering

Homogeneous chitosan-silk fibroin/hydroxyapatite （CS-SF/HA） composites were prepared by in situ precipitation method driven by a multiple-order template. The morphology of the composites was investigated by scanning electron microscope （SEM） and transmission electron microscope （TEM）. The compositional analysis was carried out by X-ray diffraction analysis （XRD） and Fourier transformed infrared spectroscopy （FTIR）. The mechanical properties and biocompatibility of the composites were also determined. The results indicated that the inorganic particles of uniform size （50 nm） were well-dispersed among the CS-SF matrices. The compressive modulus of the CS-SF/HA composites was enhanced with the increasing amount of SF. The in vitro results suggested that the MC3T3-E1 osteoblast-like cells on CS-SF/HA composite disks displayed strong bonding and spreading, and the cell proliferation cultured on each composite disk increased throughout the culture period for up to 7 days. Especially, the samples with higher content of SF had much better biological properties. The evidences proved that the CS-SF/HA composites possessed excellent biocompatibility. By using the freeze-drying technique, hierarchical porous scaffolds with pores ranging from 50 μm to 200 μm were obtained. This work presented the advantages of in situ precipitation method to prepare the organic/inorganic composites, and a multiple-order template was introduced in the system to improve the properties of the composites by combining the merits of each organic template.

反应沉淀一体式生物反应器在水质净化厂应急处理中的应用

为解决滨河水质净化厂提标扩建实施阶段服务片区内污水处理缺口,设计采用反应沉淀一体式生物反应器,将该工艺模块安装在水质净化厂的原有池体内,进行原位改造。在调试运行过程中,发现该工艺具有占地省、投资较低、改造时间较短等优点,同时在设计和运行中需着重考虑选用合适的气水比、停留时间和污泥负荷,以最大限度发挥该工艺的优势。