The Hydration and Carbonation of Tricalcium Aluminate (C_3A) in the Presence of Heavy Metals

The hydration of tricalcium aluminate （ C3A ） has a significant effect on the effectiveness of cement-based systems. In addition, the carbonation of hydration products of C3A is particularly important in respect of durability performance. The present work investigates the hydration and carbonation reactions of C 3A and the changes induced by the presence of the heavy metal ions such as Zn^2＋ , Pb^2＋ , Cu^2＋ and Cr^3＋ by X-ray diffrac- tometry （ XRD ）. During hydration of C3A, gehlenite hydrate, hydrogarnet , calcium monoaluminate （ C4AHx ） and calcium carboaluminate were detected in C3A pastes except the Zn^2＋ doped paste, where hydrogarnet did not form. The examinations revealed that heavy metals coexisted with gehlenite hydrate, calcium monoaluminate （ C4AHx ） and calcium carboaluminate, inhibiting the formation of hydrogarnet. Hydrating C3A was liable to be carbonated on exposure to air and carbon dioxide, especially in the presence of heavy metals, resulting in the formation of carboaluminate and/or calcium carbonate. The presence of heavy metals in-fluenced the polymorphism of calcium carbonate, ndicating that heavy metals could co-precipitate with calcium to form a carbonate solid solution.

Transformation of alkali and alkaline-earth metals during coal oxy-fuel combustion in the presence of SO_2 and H_2O

The occurrence modes of alkali and alkaline-earth metals（AAEMs） in coal relate to their release behavior and ash formation during combustion. To better understand the transformation of AAEMs,the release behavior of water-soluble,HCl-soluble,HCl-insoluble AAEMs during Shenmu coal（SM coal） oxy-fuel combustion in the presence of SO2 and H2O in a drop-tube reactor was investigated through serial dissolution using H2O and HCl solutions. The results show that the release rates of AAEMs increase with an increase in temperature under the three atmospheres studied. The high release rates of Mg and Ca from SM coal are dependent on the high content of soluble Mg and Ca in SM coal. SO2 inhibits the release rates of AAEMs,while H2O promotes them. The effects of SO2 and H2O on the Na and K species are more evident than those on Mg and Ca species. All three types of AAEMs in coal can volatilize in the gas phase during coal combustion. The W-type AAEMs release excessively,whereas the release rates of I-type AAEMs are relatively lower. Different types of AAEM may interconvert through different pathways under certain conditions. Both SO2 and H2O promote the transformation reactions. The effect of SO2 was related to sulfate formation and the promotion by H2O occurs because of a decrease in the melting point of the solid as well as the reaction of H2O.

Additive effects of alkaline-earth metals and nickel on the performance of Co/γ-Al_2O_3 in methane catalytic partial oxidation

Nano-sized γ-alumina （γ-Al2O3） was first prepared by a precipitation method. Then, active component of cobalt and a series of alkaline- earth metal promoters or nickel （Ni） with different contents were loaded on the γ-Al2O3 support. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction （XRD） and thermogravimetry analysis （TGA）. The activity and selectivity of the catalysts in catalytic partial oxidation （CPO） of methane have been compared with Co/γ-Al2O3, and it is found that the catalytic activity, selectivity, and stability are enhanced by the addition of alkaline-earth metals and nickel. The optimal loadings of strontium （Sr） and Ni were 6 and 4 wt%, respectively. This finding will be helpful in designing the trimetallic Co-Ni-Sr/γ-Al2O3 catalysts with high performance in CPO of methane

Roles of crystal defects in the persistent luminescence of Eu^(2+), Dy^(3+) co-doped strontium aluminate based phosphors

The roles of different point defects in persistent luminescence of SrAl2O4：Eu,Dy phosphors were investigated. The research results showed that Dyer plays an important role in the persistent luminescence of SrA1EO4：Eu, Dy phosphors. It can serve as the electron trap of suitable depth for persistent luminescence. V~ does not serve as the electron trap of suitable depth, but its existence can increase the depth of electron traps. There is interaction between the Dy^3＋（ DySr ） and the Eu^2＋（Eu^x Sr ）, and only if the distance between the Dy^3＋（DySr） and the Eu^2＋ （Eu^x Sr） is close enough, the Dyer can work as an effective electron trap. The point defect of V＂ Sr can be hole trap, but the change of its density in crystal matrix does not arouse the obvious change of persistent luminescence.

Effect of Zn,Cu,Cr and Pb Chlorides on the Formation of Tricalcium Aluminate Trisulfate Hydrate

The effect of addition of Zn, Cu, Pb and Cr chlorides as admixtures on the hydration reaction of the system 3CaO·Al2O3-gypsum with molar ratio 1：3 was studied. Different ratios of each salt were used, namely 0.5%, 2% and 4% by weight of the solid mixture. Hydration reaction was carried out at 35℃ for various time intervals from 0.5 h to up to 7 d. Hydration rate of the system 3CaO·Al2O3-CaSO4·2H2O in absence and presence of different salts was studied via the determination of the combined water contents. X-ray diffraction analysis showed that the ettringite was the only hydration product formed in the different mixes. The hydration products were investigated by scanning electron microscopy （SEM） and thermal gravimetric analysis. The results indicated that the rate of formation of ettringite and its microstructure depend on the admixture and its dosage.

Blue-emissions Modulated by Packing Forces in Alkaline-earth Metal OrganicFrameworks Based on Thiophene-2,5-dicarboxylic: Structures and Theoretical Calculations

Solvothermal reactions of Ca(NO), Sr(NO)with thiophene-2,5-dicarboxylic in DMF afforded two new inorganic-organic hybrid frameworks, [M(TDC)(DMF)]n(M = Ca(1), Sr(2), TDC = thiophene-2,5-dicarboxylic, DMF = N,N?-dimethylformamide), which have been characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analysis and IR spectra. Both compounds feature three-dimensional(3D) frameworks based on the versatile coordinated modes(μ-η~2:η~2, μ-η~2:η~1, μ-η~2:η~1) of carboxylic groups in tdc ligands. C–H···S hydrogen bonds and C–H···π interactions contribute to the stabilization of the structures. They exhibit weaker packing force compared with their literature isomers. Consequently, blue and blue/green luminescence of two compounds has been observed. Their luminescence mechanism can be ascribed to ligand-to-metal charge transfer(LMCT) compared with the ligand-centered luminescence in their isomers. Electronic structural calculations illustrate that under the condition of weaker packing forces, larger gaps can be achieved, which facilitate the LMCT. This work suggests that the introduction of S-heteroatom can result in more electrons rich in the metal centers, thus giving rise to metal-involved luminescence.

Geochemical Mobility Associated to Gold and Base Metal Occurrences of Mangodara Sector, in Southern Burkina Faso, Banfora Greenstone Belts (West African Craton)

In the Mangodara area within the Banfora greenstone belts (Baoulé-Mossi domain of the West African Craton), our study focused on geochemical assessment of the mobility of major and trace elements. Gold and base metal occurrences are hosted in highly metamorphic felsic (metarhyolite) and intermediate (metadacite and metaandesite) formations. Common mineral assemblages made up of staurolite - kyanite - pyrophyllite are interpreted to represent the metamorphosed equivalent of aluminous hydrothermal alteration. Associated felsic and intermediate volcanic rocks are enriched in Fe2O3, K2O (metaandesite, metarhyolite) and depleted in MgO, Al2O3, CaO, P2O5, Na2O (metarhyolite) and Fe2O3, MgO, CaO (metaandesite). Al2O3 depletion in mineralized kyanite-staurotide bearing metarhyolites suggests corroded minerals. Mineralized metarhyolites show enrichment in Au, Ag, Ba, Bi, Cr, Cu, Eu, La, Mo, Ni, Pb, S, Sc, V and depletion in As Sb Co, Sn, Zn while mineralized metaandesites show enrichment in Au, Ag, As, Mo, S, Sb and depletion in Co, Sn, Zn, Bi, Cr, Cu, Eu, Ni, Pb, Sc. Ba, La, V are immobile in metaandesites. Finally, Ag, As, Sn appear as geochemical vectors for gold exploration in the study area since gold mineralization is characterized by Au + Ba + Cu + Eu + La + Mo + Ni + S association in metarhyolites and Au + S + Sb + As + Ag + Bi in metaandesites.

基于加速老化试验的铝酸钙水泥基复合材料固化飞灰长期稳定性研究

酸雨淋滤是影响飞灰固化体长期稳定性的重要因素。在铝酸钙水泥(CAC)中加入磷酸二氢钠(NaH_(2)PO_(4))和二乙基二硫代氨基甲酸钠(DDTC)得到CAC基飞灰固化/稳定化复合材料,基于加速老化试验研究了飞灰固化体的长期稳定性,通过浸出试验研究了重金属Cd、Pb、Zn的浸出毒性,进行连续提取试验研究了重金属化学形态变化,通过X射线衍射和扫描电镜分析揭示了相关机理。结果表明,固化体中Cd和Pb的浸出质量浓度在模拟老化的第26年达到最低,之后浸出浓度随时间增加,到第78年超出了限值;在模拟的104 a中Zn的浸出质量浓度一直增大。经CAC基复合材料固化/稳定化后,飞灰中Cd、Pb和Zn的有机结合态和残渣态占比增加,铁锰氧化物结合态占比减小;随着老化进行,铁锰氧化物结合态逐渐增多而残渣态减少,导致浸出浓度逐渐增加。CAC的水化产物、磷酸盐沉淀以及络合物使飞灰中团聚体增多、孔隙减小,从而减少了重金属浸出;加速老化试验之后,这些成分减少甚至消失,对重金属的封固效果减弱。本文可为飞灰长期安全处置提供理论依据和技术参考。

Alkali/alkaline-earth metal-modified MnO_(x) supported on three-dimensionally ordered macroporous–mesoporous Ti_(x)Si+(1-x)O_(2) catalysts:Preparation and catalytic performance for soot combustion

The performance of catalysts used in after-treatment systems is the key factor for the removal of diesel soot,which is an important component of atmosphericfine particle emissions.Herein,three-dimensionally ordered macroporous–mesoporous Ti_(x)Si+(1-x)O_(2)(3DOM-m Ti_(x)Si+(1-x)O_(2)) and its supported MnO_(x)catalysts doped with different alkali/alkaline-earth metals (AMnO_(x)/3 DOM-m Ti_(0.7)Si_(0.3)O_(2)(A:Li,Na,K,Ru,Cs,Mg,Ca,Sr,Ba)) were prepared by mesoporous template (P123)-assisted colloidal crystal template (CCT) and incipient wetness impregnation methods,respectively.Physicochemical characterizations of the catalysts were performed using scanning electron microscopy,X-ray diffraction,N_(2)adsorption–desorption,H_(2)temperature-programmed reduction,O_(2)temperature-programmed desorption,NO temperature-programmed oxidation,and Raman spectroscopy techniques;then,we evaluated their catalytic performances for the removal of diesel soot particles.The results show that the 3DOM-m Ti_(0.7)Si_(0.3)O_(2)supports exhibited a well-defined 3DOM-m nanostructure,and AMnO_(x)nanoparticles with 10–50 nm were evenly dispersed on the inner walls of the uniform macropores.In addition,the as-prepared catalysts exhibited good catalytic performance for soot combustion.Among the prepared catalysts,CsMnO_(x)/3DOM-m Ti_(0.7)Si_(0.3)O_(2)had the highest catalytic activity for soot combustion,with T10,T50,and T90(the temperatures corresponding to soot conversion rates of 10%,50%,and 90%) values of 285,355,and 393℃,respectively.The high catalytic activity of the CsMnO_(x)/3 DOM-m Ti_(0.7)Si_(0.3)O_(2)catalysts was attributed to their excellent low-temperature reducibility and homogeneous macroporous–mesoporous structure,as well as to the synergistic effects between Cs and Mn species and between CsMnO_(x)and the Ti_(0.7)Si_(0.3)O_(2)support.

Desulphurization of Hot Metal and Ferronickel With Calcium Aluminate Fluxes

Traditionally, fluxes containing calcium fluoride and other additives are used for the treatment of hot metal and molten steel. Recently, magnesium powder or lime-Mg mixture is used more popularly in hot metal desulphurization. However, the use of calcium fluoride has been restricted due to environmental concerns, and the supply of magnesium is uncertain for the countries, which are short of magnesium resource. For those reasons, calcium aluminate fluxes are a possible alternative to replace slags containing calcium fluoride or magnesium. Calcium aluminate fluxes can be produced from three different raw materials: (1) high-quality bauxite, (2) residuals from aluminum dross treatment processes and (3) waste products from alumina production. Due to the limited amount and high cost associated with high-quality bauxite, the other two sources are preferred based on both economic and environmental considerations. The objective of this paper is to examine the use of waste slags and by-products from the aluminum industry as potential refining fluxes for the steel industry so that waste disposal from the aluminum industry can be reduced with economical and environmental benefits for both industrial sectors.

DNTF基熔铸炸药的金属加速作功能力

用圆筒试验获得含铝和不含铝两种配方的DNTF基熔铸炸药的筒壁膨胀速度、比动能和格尼系数的变化规律,研究了其金属加速作功能力,并与Octol炸药进行了对比。结果表明,DNTF可显著提高混合炸药的金属加速作功能力;加入少量铝粉虽然会降低初始筒壁速度,但在圆筒膨胀后期,筒壁速度可超过不含铝配方,且提高了DNTF基熔铸炸药的持续金属加速作功能力;与Octol炸药相比,含铝DNTF基熔铸炸药的格尼系数提高了6.2%。

Al粉对炸药爆炸加速能力的影响

采用电探针法测量了RDX基含铝炸药爆炸驱动金属薄片的速度变化,分析了铝粉含量对炸药爆炸加速能力的影响。结果表明,炸药爆炸对金属薄片的加速能力受配方中铝粉的反应比例影响;金属薄片的加速过程分速度增长和速度减小两个阶段;金属薄片达到最大速度的距离与铝粉的含量有关,随着铝粉含量的增加,达到最大速度的距离有所增加,该距离在40～60mm。铝粉含量对炸药爆炸加速能力的贡献有一最佳值,对于RDX基含铝炸药,其值约为15%。

硝酸酯对RDX基含铝炸药驱动能力的影响

为了研究硝酸酯对RDX基含铝炸药驱动能力的影响,采用圆筒试验研究了含硝酸酯的RDX基含铝炸药加速圆筒壁膨胀速度和格尼能的变化过程,并与不含硝酸酯的RDX基含铝炸药进行了对比,分析了硝酸酯对炸药能量释放特性及金属驱动能力的影响。结果表明,硝酸酯可改善RDX基含铝炸药的铝氧比,改变其反应速率;在反应初期,含硝酸酯的RDX基炸药加速筒壁的速度低于不含硝酸酯的炸药,而在爆炸反应中后期,含硝酸酯的RDX基炸药加速筒壁的速度以及格尼能均高于不含硝酸酯的炸药;含硝酸酯的RDX基含铝炸药的能量释放特性使其适合用于破片战斗部中,可提高其金属驱动能力。

碱土金属铝酸盐系列长余辉磷光体的制备研究

研究了MAl2O4∶Eu2+(M=Ca,Sr,Ba)磷光体的制备过程,通过向磷光体中引入微量Dy3+,B3+等添加剂离子,得到了发绿色光的超长余辉磷光体,余辉发光初始亮度达4.8cd·m-2,激发停止50h后,其余辉发光仍清晰可见。制备出发紫色光、蓝色光及黄色光的碱土金属铝酸盐系列长余辉磷光体。分析了各磷光体发射光谱、激发光谱及余辉发光,讨论了磷光体的光谱移动以及Eu2+在碱土金属铝酸盐中的发光。

铝粒表面微凸起对凝聚产生的影响

为进一步研究非球形铝粒表面微凸起对含铝推进剂凝聚燃烧的影响,用Young Laplace公式和化学势的微分式,推出非球形铝粉凝聚起始温度下降公式。发现铝粒表面微小凸起的平均半径越小,则铝粉凝聚起始温度就越低,其影响不容忽视。用电化学微电池理论,阐明了铝粉与NaOH溶液的反应机理。铝粒与NaOH溶液构成局部腐蚀电池,金属铝在阳极上失去三个电子,发生氧化反应。由于非球形铝粒组织和物理状态的均匀性比球形铝粒的差,表面的微电池数目比球形铝粒的多,因此有较大的反应速率。

Pd对K17合金低压固体粉末包埋渗铝工艺的影响

研究了在高温合金K17表面上低压固体粉末包埋(LPPC)渗铝工艺。实验结果表明:在合金表面电镀Pd-20wt%Ni合金后,在950℃和1050℃渗铝制备铝化物涂层,与未经过电镀处理的样品相比,其渗铝速度得到提高,形成铝化物涂层的动力学在950℃和1050℃时符合抛物线规律。在950℃时,“S”渗铝量占总渗铝量的比例略大于18%,在1050℃时该比例为44.2%～47%,和渗铝温度有关,与样品预处理状态无关;提高渗铝温度,“S”渗铝比例提高。Pd元素加快了元素的扩散速度,促进了涂层的生长。

Eu^(2+)激活的碱土金属铝酸盐磷光体的研究进展

主要概述了Eu^(2+)激活的碱土金属铝酸盐磷光体的光谱特性,总结了近年来在铝酸盐基质研究以及长余辉机理研究等方面所取得的进展,同时对今后的研究提出了展望。

X80管线钢LF-RH二次精炼过程夹杂物行为及控制

研究了210 t BOF-LF-RH-CC工艺流程生产X80管线钢(%:0.041～0.044C、0.15Si、1.78～1.80Mn、0.007～0.010P、0.000 8～0.001 2S、0.039～0.047[Al]s)时精炼过程中夹杂物的变化。在BOF出钢阶段采用加Al强脱氧(0.01%～0.02%[Al]s),LF精炼过程采用高碱度、强还原性精炼渣(精炼渣成分%:50～58CaO、7～10MgO、20～25Al_2O_3、4～7SiO_2、0.5～1.4TFe),炉渣和钢液反应活跃,使得钢中Al_2O_3夹杂物很快向液态钙铝酸盐和部分液态CaO-MgO-Al_2O_3复合夹杂物转变。液态夹杂物通过碰撞、聚合、长大及上浮去除,提高了钢液的洁净度。浇铸前T[O]降到(7～10)×10^(-6),钢中夹杂物尺寸在3～5μm,试验炉次的热轧板内未发现大尺寸的低熔点钙铝酸盐类长条夹杂物。

金属柱壳约束对非理想炸药驱动效率的影响

通过分析金属柱壳在内部炸药滑移爆轰作用下的动力学响应,建立了爆轰产物压力与壳体径向膨胀位移、材料动态屈服强度之间的关系式。基于Taylor假定确定了壳体完全破裂时爆轰产物压力的阈值。以两种具有相近格尼系数的RDX基含铝炸药为例,对该模型的适用性进行了验证。结果表明,相同壳体下,与无硝酸酯的RDX基含铝炸药相比,含硝酸酯的RDX基含铝炸药的驱动能量利用率具有明显优势。当壳体材料动态屈服强度从0.2GPa增至0.8GPa时,其有效作功能的相对增量约从7.5%迅速增大至15.2%,符合战斗部实际应用中的趋势,表明该分析模型可用于非理想炸药驱动作功性能的综合评价。

固体推进剂中铝颗粒结团过程研究进展

推进剂燃烧环境中金属颗粒的结团现象对固体火箭发动机性能有重大影响.本文对双基推进剂结团的表面反应层模型及复合推进剂结团的口袋模型进行了述评.鉴于实验中发现的某些燃速和压强效应的异常,本文还对新近提出的亚口袋机理和口袋间机理进行了述评.