Effect of preferential dissolution on erosion-corrosion for chromium steel in alkali slurry

An investigation was carried out concerning the effect of preferential dissolution on the erosion-corrosion for a chromium steel in 1 mol/L NaOH. Preliminary tests using a potentiodynamic technique were performed in order to establish the presence of preferential dissolution in the alkali solution with and without the alumina particles at different rotation speeds. For purposes of quantifying the observed phenomena a potentiostatic mass loss method was also used. The results show that the active peaks occur at potential between +0.4 and +0.5 V on the polarization curves, which indicates that there is a preferential dissolution for chromium steel under erosion-corrosion conditions and the ferrite phase acts as a sacrificial anode in favor of (Fe,Cr) 7C 3 phase. Addition of particles can promote the preferential dissolution at different rotation speeds. The combined effects of erosion-corrosion results in total mass loss rates to be greater than the sum effects of each process taken alone, thus showing a strong synergism between erosion and corrosion due to preferential dissolution.

The preferential growth and related textural evolution during static recrystallization in a cold-rolled Mg-Zn-Gd alloy

The grain growth process plays an important role in the texture formation in magnesium alloys.The microstructural and micro-textural evolution of a cold-rolled Mg-Zn-Gd alloy during annealing at 350℃for 60-190 min were tracked by quasi-in-situ electron backscatter diffraction method.The results show that grain growth takes place gradually with the annealing time increasing.Moreover,the TD-split texture maintains the texture type but alters in three aspects-the increased tilting angle,the decreased pole intensity and the widened distribution of high-intensity area.Grains with their c-axis tilting 45-70°from normal direction show preferential growth which is closely associated with the texture changes.The original grain size advantage is one of the important factors leading to the growth advantage,some grain boundaries,such as 50-60°[1^(-)21^(-)0],50-60°[2750],60-70°[1^(-)21^(-)0](18b),and 70-80°[1^(-)01^(-)0](10)are also considered to be related to this preferential growth.

Stability of Crystal Growth Face and Dissolution Face in Crystallization from Solution under Microgravity

The stability of the shapes of crystal growth face and dissolution face in a two-dimensional mathematical model of crystal growth from solution under microgravity is studied. It is proved that the stable shapes of crystal growth face and dissolution face do exist, which are suitably shaped curves with their upper parts inclined backward properly.The stable shapes of crystal growth faces and dissolution faces are calculated for various values of parameters, Ra, Pr and Sc. It is shown that the stronger the convection relative to the diffusion in solution is, the more backward the upperparts of the stable crystal growth face and dissolution face are inclined. The orientation and the shape of dissolution face hardly affect the stable shape of crystal growth face and vice versa.

Crystals of suspended marine barite in the eastern equatorial Pacific:processes of dissolution and effects on crystal morphology

Suspended particulate substances were sampled in the eastem equatorial Pacific in water column from surface to near bottom in five stations in 2005, from which 868 barite crystals were recovered. The barite crystals were examined under scanning electron microscopy. About 61% of the total barites crystals contained detectable Sr by energy dispersive X-ray spectrometry. Barite crystals could be classified into four groups based on their morphology： 1） bladed; 2） ovoid or rounded; 3） arrow-like; and 4） irregularly shaped. The arrow-like barite crystals in natural environment has never been reported before. In addition, about a half of the studied crystals showed features of dissolution as cavities or holes inside of the crystals or around their edges. We found that differential dissolution of barite crystals is consequence of heterogeneous Sr distribution in barite crystals. Our results would help in understanding the biogeochemical processes of marine barite formation and preservation in seawater and marine sediments.

核桃根际耐旱促生菌的分离筛选及其促生作用研究

为获得高效促生的核桃根际菌株,研制微生物菌肥,改善土壤肥力,促进植株生长发育,提升核桃品质奠定理论基础。以核桃根际土壤为材料,分离筛选具有固N、溶P、解K、分泌生长素和产胞外多糖能力的菌株,通过16S rDNA测序鉴定菌属。按照功能叠加增效、功能互补的原则,人工构建合成菌群,采用盆栽试验验证菌群对核桃幼苗的促生效果。结果表明,共筛选出9株耐旱促生菌株,其中5株具有溶P能力,溶P量为2.28~61.63μg·mL^(-1),4株具有分泌IAA能力,分泌IAA量为2.32~9.44μg·mL^(-1),4株具有产胞外多糖的能力,产胞外多糖量为37.69~112.84μg·mL^(-1)。经鉴定分别属于节杆菌属、肠杆菌属、剑菌属、中华根瘤菌属、假单胞菌属和鞘氨醇杆菌属。盆栽试验表明,4种菌群均能显著促进核桃幼苗的生长,株高、生物量和净光合速率,与对照相比,分别增加了32.3%~64.2%、37.6%~52.6%和47.4%~68.5%。此外,复合菌群的施用还显著提高了土壤β-葡萄糖苷酶(BG)、β-N-乙酰葡糖胺糖苷酶(NAG)和碱性磷酸酶(AP)活性,增加了速效P、硝态N及铵态N含量(P<0.05),其中以复合菌群T4效果最佳。研究结果可为研制适合干旱半干旱区的微生物肥料提供菌种资源。

Al-H_(2)O反应中催化剂对Al(OH)_(3)形貌演化的作用机理

研究不同催化剂在铝-水(Al-H_(2)O)反应中对Al(OH)_(3)晶体形貌及其生长机理的作用。采用NaOH、KOH、四甲基胍(TMG)和四甲基氢氧化铵(TMAH)作为催化剂进行反应,原位观察产物的演化过程。结果表明,反应120 min后得到的产物分别具有六棱柱形、六棱长柱状、长棒状和不规则棒状。在NaOH和KOH体系中,产物为三水铝石,三水铝石在NaOH体系中主要沿(110)、(001)和(100)晶面生长,而在KOH体系中主要沿(100)、(102)和(110)晶面生长。在TMG和TMAH体系中,产物是拜耳石,拜耳石在这两个体系中均沿(110)、(111)和(001)晶面生长。其中,三水铝石的Al—O键较多,有利于柱状晶体的形成。

ZnO纳米结构薄膜的构建及气敏传感性能研究

针对ZnO气敏传感器灵敏度较低和响应恢复时间长的问题,采用磁控溅射法,通过调控生长条件,构建了具有纳米结构的ZnO薄膜,研究了不同生长条件下ZnO纳米结构薄膜的形貌、结晶取向及其气敏传感性能。结果表明:高生长速度和高温条件下容易生长为柱状晶体且具有(103)晶面择优取向结构的薄膜,其对乙醇的灵敏度较好,达到81.7。

Temperature inversion enables superior stability for low-temperature Zn-ion batteries

It is challenging for aqueous Zn-ion batteries(ZIBs)to achieve comparable low-temperature(low-T)performance due to the easy-frozen electrolyte and severe Zn dendrites.Herein,an aqueous electrolyte with a low freezing point and high ionic conductivity is proposed.Combined with molecular dynamics simulation and multi-scale interface analysis(time of flight secondary ion mass spectrometry threedimensional mapping and in-situ electrochemical impedance spectroscopy method),the temperature independence of the V_(2)O_(5)cathode and Zn anode is observed to be opposite.Surprisingly,dominated by the solvent structure of the designed electrolyte at low temperatures,vanadium dissolution/shuttle is significantly inhibited,and the zinc dendrites caused by this electrochemical crosstalk are greatly relieved,thus showing an abnormal temperature inversion effect.Through the disclosure and improvement of the above phenomena,the designed Zn||V_(2)O_(5)full cell delivers superior low-T performance,maintaining almost 99%capacity retention after 9500 cycles(working more than 2500 h)at-20°C.This work proposes a kind of electrolyte suitable for low-T ZIBs and reveals the inverse temperature dependence of the Zn anode,which might offer a novel perspective for the investigation of low-T aqueous battery systems.

盐酸溶解磷石膏重结晶制备石膏晶须

以工业磷石膏为原料,使用盐酸对其进行溶解,探索了单因素试验条件(盐酸浓度、液固比、反应温度、反应时间)对磷石膏溶解率的影响,得到了磷石膏最佳溶解条件:盐酸浓度4 mol/L、液固比20 mL/g、反应温度80℃、反应时间20 min,在此条件下溶解率为86.12%;探究了控温速率对石膏晶须析出率、产物组分、结晶程度和微观显微形貌的影响规律,结果表明:降温速率差异对石膏晶须析出程度几乎没有影响;4种降温速率(0.40、0.30、0.27、0.20℃/min)下的产物均为二水硫酸钙;石膏晶须的特征衍射峰均较尖锐,形成的晶粒较大,结晶程度较高;随着降温速率的减小,石膏晶须的长径比不断增大、形貌更加均匀。研究成果为工业磷石膏的高值高效利用提供了新思路。

三株单菌株及其复合菌剂对蕲艾的促生效应研究

本研究旨在筛选对蕲艾种子萌发和幼苗生长具有促进作用的蕲艾内生细菌,为开发蕲艾专用促生菌剂提供科学依据。通过采用钼蓝比色法、原子吸收分光光度计和Salkowski比色法,测定了菌株Acinetobacter pittii lzy1、Pseudomonas psychrotolerans lzy2、Curtobacterium luteum lzy9及其1∶1∶1复合菌剂在溶解有机磷、溶解无机磷、解钾和产IAA方面的能力,并评估了它们对基质养分的影响及对蕲艾种子萌发和幼苗生长的促进作用。研究结果显示,复合菌剂lzy129在这些方面相较于单一菌剂表现出显著优势,尤其在对蕲艾种子萌发和幼苗生长的促进作用上更为突出。此外,本研究首次利用植物源的Acinetobacter pittii成功制备了复合菌剂。这一研究为进一步研发蕲艾专用微生物菌肥,推动蕲艾产业的可持续发展奠定了坚实基础。

铸钢铸造中气孔缺陷的控制技术与工艺改进

以铸钢铸造气孔缺陷问题为研究对象,重点剖析气体在钢中的溶解行为、气孔形核、生长机制等,并结合某仪表有限公司的实践案例,具体分析铸钢件生产环境和样品制备过程对气孔缺陷造成的实际影响,同时进一步研究金属液体处理、浇铸温度速度控制等气孔缺陷控制技术应用方案,以期通过案例分析验证先进熔炼技术和新型铸造工艺方法的有效性,为铸钢铸造行业提升铸件质量提供参考。

Limited Contribution of Preferential Dissolution to Radiogenic Uranium Isotope Disequilibrium Observed in Weathered Moraines

Radiogenic uranium isotope disequilibrium(^(234)U/^(238)U) has been used to trace a variety of Earth surface processes,and is usually attributed to direct recoil of ^(234)Th and preferential dissolution of radioactively damaged lattices at the mineral surface.However,the relative contribution of these two mechanisms in the natural environment remains unresolved,making it hard to use the extent of disequilibrium to quantify processes such as weathering.This study tests the contribution of preferential dissolution using well-characterized weathered moraines and river sediments from the southeastern Tibetan Plateau.The observations show that weathering of recent moraines where the contribution from direct recoil is negligible and is not associated with depletion of ^(234)U at the mineral surface.It suggests a limited role for preferential dissolution in this setting.We attribute this lack of preferential dissolution to a near-to-equilibrium dissolution at the weathering interfaces,with little development of etch pits associated with radioactively damaged energetic sites.

A novel scale-free network model based on clique growth

A novel scale-flee network model based on clique （complete subgraph of random size） growth and preferential attachment was proposed. The simulations of this model were carried out. And the necessity of two evolving mechanisms of the model was verified. According to the mean-field theory, the degree distribution of this model was analyzed and computed. The degree distribution function of vertices of the generating network P（d） is 2m^2m1^-3（d-m1 ＋ 1）^-3, where m and m1 denote the number of the new adding edges and the vertex number of the cliques respectively, d is the degree of the vertex, while one of cliques P（k） is 2m^2Ek^-3, where k is the degree of the clique. The simulated and analytical results show that both the degree distributions of vertices and cliques follow the scale-flee power-law distribution. The scale-free property of this model disappears in the absence of any one of the evolving mechanisms. Moreover, the randomicity of this model increases with the increment of the vertex number of the cliques.

A low-dimensional crystal growth model on an isotropic and quasi-free sustained substrate

A new crystal growth theoretical model is established for the low-dimensional nanocrystals on an isotropic and quasifree sustained substrate. The driven mechanism of the model is based on the competitive growth among the preferential growth directions of the crystals possessing anisotropic crystal structures, such as the hexagonal close-packed and wurtzite structures. The calculation results are in good agreement with the experimental findings in the growth process of the lowdimensional Zn nanocrystals on silicone oil surfaces. Our model shows a growth mechanism of various low-dimensional crystals on/in the isotropic substrates.

浅析影响方解石生长和溶解的动力学因素及机制

碳酸盐岩约占显生宙沉积岩的20%,全球至少有60%已探明的石油储量赋存于碳酸盐岩储层中。方解石是普遍的碳酸盐矿物,其溶蚀对于地壳浅部次生孔隙的形成具有重要的意义。综述结果表明:方解石的生长主要受控于温度、压力、过饱和度、离子的种类及半径等因素;压力的降低、离子强度和过饱和度的增大有利于方解石的生长。方解石的溶蚀主要受温度、压力、p(CO_(2))分压、离子的种类和强度、盐度、pH值、介质流体组分、方解石表面Zeta电位及溶液相对于方解石的饱和程度等因素的影响;介质流体中的离子种类对方解石溶解所起的促进或抑制作用主要受控于方解石表面的Zeta电位。此外,本文还发现在方解石生长和溶蚀过程中,不同溶剂类型、离子的种类及浓度形成具有显著不同的微形貌,这使得通过对矿物微形貌的观察可以用来反演古介质流体的组分。本文以独特的视角对当前有关实验取得的不一致结果进行了深入剖析并提出了新的观点,着重对影响碳酸盐岩溶蚀的因素进行调研,寻找有利于碳酸盐岩溶蚀的最优解,进而为圈定优质储层提供可靠的理论依据。本文的另一个意义是便于后续相关研究能够悉知该领域的前沿热点及最新进展。

酸法浸铀过程中Fe^(3+)与浸出铀之间关系的数值模拟

为探究酸法地浸过程中Fe^(3+)作为氧化剂时铀的浸出情况,通过使用模拟软件PHREEQE建立模型,观察浸出液各组分的浓度及迁移变化,揭示氧化剂Fe^(3+)与浸出铀之间的关系。结果表明:作为氧化剂的Fe^(3+)促使铀矿的溶解及Fe^(2+)的出现,随着铀的浸出结束,Fe^(3+)的浓度趋于稳定;且铀矿的溶解速率与Fe^(3+)、Fe^(2+)的增长速率密切相关。Fe^(3+)的浓度增长变快时,Fe^(2+)的浓度增长及铀矿的溶解也加快;随着铀矿的溶解速率降为零后,Fe^(2+)的增长速率也趋近于零,氧化剂Fe^(3+)的增长速率也降为零。

经济增长目标、税收特惠政策与资源配置

现有研究表明,经济增长目标既可引领经济增长,又会加剧资源错配。对此,本文提出一个逻辑自洽的解释:特惠政策。在理论上,本文证明当政府资源有限时,为了最大化辖区产出,政府采取偏向大企业的税收特惠政策来吸引流动性要素,从而增加辖区产出并加剧要素错配。在实证上,本文利用1998—2013年中国工业企业数据库和省级增长目标数据,实证发现:增长目标每增加1个百分点,税收减免特惠程度显著提高3.2%;税收特惠政策偏向大企业,而不是偏向中小企业;在增长目标激励下,税收特惠政策加剧地区内的资本和劳动力错配。本文揭示了地方政府为达成经济增长目标而实施特惠政策的普遍做法,表明新时代发展需要转向普惠政策,提高发展质量。

铁载体在环境污染与资源利用中的应用研究进展

Fe在地表环境中的生物利用率极低,为了适应低铁环境,微生物和植物会分泌一种低分子量有机化合物--铁载体来螯合环境中的Fe(Ⅲ),以满足自身生命活动需求。铁载体在地表环境中普遍存在,并广泛参与微生物、植物和环境中Fe的迁移和转化。系统总结了铁载体的类型、检测方法以及其在矿物溶解、污染修复、植物促生和生物防治等领域的作用研究进展。结果表明:细菌、真菌、蓝细菌和植物均能产生不同类型铁载体,通过螯合作用从环境中摄取和竞争Fe;依据铁载体中特定的官能团,可采用生物方法和化学方法对其进行定性和定量检测;铁载体可以加速铁硅酸盐矿物和铁氧化物/氢氧化物矿物溶解,推动地表环境中不同相态Fe的生物地球化学循环;铁载体能够螯合多种重金属离子并促进有机污染物降解,修复重金属和有机物污染的土壤,维持土壤良好的生态功能和农业生产能力;铁载体还可以捕获植物所需的营养元素并抑制植物病原菌的繁殖,促进植物生长与产量提高,有效进行生物防治。最后,在综述研究的基础上展望了铁载体的未来研究方向,以期为推动铁载体在环境地学领域的研究发挥积极作用。

Prediction model for austenite grains growth during reheating process in Ti micro-alloyed cast steel by coupling precipitates dissolution and coarsening behavior

A combined model to predict austenite grains growth of titanium micro-alloyed as-cast steel during reheating process was established.The model invoIves the behaviors of austenite grains growth in continuous heating process and isothermal soaking process,and the variation of boundary pinning efficiency caused by the dissolution and coarsening kinetics of sec on d-phase particles was also con sidered into the model.Furthermore,the experimental verificatio ns were performed to examine the prediction power of the model.The results revealed that the mean austenite grains size increased with the increase in reheating temperature and soaking time,and the coarsening temperature of austenite grains growth was 1423 K under the current titanium content.In addition,the reliability of the predicted results in continuous heating process was validated by continuous heating experimenls.Moreover,an optimal regression expression of austenite grains growth in isothermal soaking process was obtained based on the experimental results.The compared results indicated that the combined model in conjunction with precipitates dissolution and coarsening kinetics had good reliability and accuracy to predict the austenite grains growth of titanium micro-alloyed casting steel during reheating process.

重组人表皮生长因子凝胶在激光祛斑祛痣术后创面修复的应用价值

目的探讨重组人表皮生长因子凝胶在激光祛斑祛痣术后创面修复的应用价值。方法选取2020年1月—12月酒钢医院收治的564例激光祛斑祛痣术患者作为研究对象,按照随机数字表法分为两组,各282例。对照组给予红霉素软膏治疗,观察组在对照组基础上加用重组人表皮生长因子凝胶治疗,比较两组临床疗效、创面愈合时间与完全溶痂时间及治疗前后炎症因子[降钙素原(PCT)、超敏C反应蛋白(hs-CRP)]水平、蛋白酶[基质金属蛋白酶-1(MMP-1)、基质金属蛋白酶-2(MMP-2)]水平与并发症发生情况。结果观察组治疗总有效率为93.62%,高于对照组的80.14%,差异有统计学意义(P<0.05)。观察组创面愈合时间为(10.01±3.22)d、完全溶痂时间为(12.85±3.72)d,均短于对照组的[(12.36±4.25)d、(15.80±3.68)d],差异有统计学意义(P<0.05)。治疗前,两组PCT与hs-CRP水平比较差异无统计学意义;治疗后,两组PCT与hs-CRP水平低于治疗前,且观察组低于对照组,差异有统计学意义(P<0.05)。治疗前,两组MMP-1与MMP-2水平比较差异无统计学意义;治疗后,两组MMP-1与MMP-2水平低于治疗前,且观察组低于对照组,差异有统计学意义(P<0.05)。观察组并发症发生率为4.61%,低于对照组的19.86%,差异有统计学意义(P<0.05)。结论重组人表皮生长因子凝胶用于激光祛斑祛痣术后创面修复效果确切,可加快创面修复速度,减少并发症发生,值得临床推广应用。