Alkali-activated slag concrete: Fresh and hardened behaviour

The behaviour of fresh and hardened alkali-activated slag (AAS) and OPC concretes was compared and the effect of mixing time assessed. OPC and AAS concrete slump and rheological results proved to differ, particularly when the slag was activated with waterglass (WG). The nature of the alkaline activator was the key determinant in AAS concrete rheology. Bingham models afforded a good fit to all the OPC and AAS concretes. In OPC and NaOH-activated AAS concretes, longer mixing had an adverse effect on rheology while improving hardened performance only slightly. In WG-AAS concrete, longer mixing times, improved mechanical properties and also rheological behaviour was enhanced, in which those conditions were required to break down the microstructure. Longer mixing raised thixotropy in OPC and NaOH-activated AAS concretes, but lowered the value of this parameter in waterglass-activated slag concrete.     

Mechanism of mechanical–chemical synergistic activation for preparation of mullite ceramics from high-alumina coal fly ash

High-alumina coal fly ash (HAFA) is a special solid waste due to the existence of more than 45% alumina and 35% silica, which can be applied to prepare Al-Si series ceramics if the impurities can be removed and the Al/Si mass ratio can exceed 2.55 (Mullite: 3Al₂O₃.2SiO₂). In this work, a new mechanical–chemical synergistic activation–desilication process is proposed, and the contents of different impurities can be lowered up to less than 1%, and the Al/Si mass ratio can be elevated from 1.26 to 2.71. Especially, the mechanism of this process is investigated in detail. The analysis of the mechanism shows that the decrease of Q⁴(3Al) and the increase of Q⁴(0Al), Q⁴(1Al), and Q⁴(2Al) improve amorphous silicate reactivity through synergistic activation, and the exposed amorphous Si-O-/Si-O-Si can be removed by OH- during the desilication process (desilicated ratio>55%), which help the fine mullite to exhibit excellent properties (bulk density > 2.85 g/cm³, apparent porosity < 0.5%) during the sintering process. Finally, this process not only decreases the pollution but also alleviates the shortage of Al/Si resources and promotes the clean development of coal-fired power generation.     

Rare-earth mediated dihydrogen activation and catalytic hydrogenation

This review covers H-H bond cleavage of dihydrogen(H_2) mediated by structurally well-defined rareearth metal(scandium,yttrium and lanthanides) complexes,and their applications in homogenous catalysis,such as catalytic hydrogenation of unsaturated organic molecules.Depending on the mechanism of the H-H bond cleavage,this review is organized in two parts:(1) σ-bond metathesis,and(2)non-σ-metathesis H_2 activation.The latter is a new trend in this research field and is the emphasis of this review.Converting H_2 into inorganic rare-earth polyhydride complexes,albeit their potential applications as hydrogen-storage materiel,is not in the scope of this review.     

热处理对C-276合金无缝管晶粒长大行为的影响

研究了不同的热处理工艺对C-276合金冷轧无缝管晶粒长大行为的影响。结果表明:在同一保温时间下,随热处理温度的升高,C-276合金的晶粒尺寸逐渐增大,且不同保温时间下的晶粒长大趋势相同。当热处理温度为1040～1080 ℃时,晶粒长大较快;在1080～1160 ℃时放缓;在1160～1200 ℃时又加快。在1040～1200 ℃下保温10 min后C-276合金的晶界迁移表观激活能为313.77 kJ/mol。当热处理温度为1040～1080 ℃时,随保温时间的延长晶粒长大较为缓慢;温度为1120～1160 ℃时,当保温时间在10 min内,晶粒长大较快,当保温时间大于10 min后晶粒长大减慢;温度升高到1200 ℃时,随保温时间的延长晶粒长大趋势较为平缓。热处理温度在1040～1200 ℃范围内,随温度的升高,C-276合金的晶粒长大动力学时间指数η先增大后减小。     

最低点火温度条件下煤粉自燃特性试验研究

火电厂及煤化工行业中需要将原煤加工成煤粉,煤粉在制备及输送过程中具有粒度小、环境温度高和供氧条件充分等特点,易发生自燃现象。最低点火温度Tm指在一定条件下煤粉能够发生自燃的最低环境温度,是衡量煤粉自燃危险性的重要参数。因此,研究煤粉在最低点火温度下的自燃特性参数及热动力学行为,对了解在最低点火温度时煤粉自燃行为、建立相应的预警机制具有重要意义。以3种不同变质程度的煤粉(张家卯弱黏煤ZJM、兖州气煤YZ和长治贫瘦煤CZ)为研究对象,采用油浴程序控温试验装置对煤样自燃特性进行测试,确定了3种煤粉的Tm和延迟点火时间ti;得出最低点火温度下各煤样耗氧速率、CO及C2H4产生量的变化规律;采用热动力学分析方法计算了3种煤粉的表观活化能。试验结果表明:①ZJM、YZ和CZ煤粉的最低点火温度分别为120、130、164℃,随变质程度的增加而增加;煤的变质程度越高,内部活性基团数量越少,自燃需要热量更多,导致高变质程度煤的最低点火温度较高;3种煤粉在最低点火温度处的延迟点火时间均约为20 min。②耗氧速率呈现出先增加后缓慢减少的趋势,在试验后期由于氧气浓度较低,引起煤粉氧化反应强度降低,最终导致耗氧速率出现缓慢下降;最低点火温度处的CO产生量随时间呈现出先升高后降低趋势,当煤粉温度约120℃时,产生C2H4。③最低点火温度处ZJM、YZ和CZ煤粉的表观活化能分别为24.33、29.50和18.67 kJ/mol,其中变质程度最高的CZ煤粉的表观活化能低于另外2个煤样,这表明高变质程度煤样的最低点火温度高,初期氧化反应速率较高。     

A Polysiloxide Complex with two Chromium(III) η2-Superoxo Moieties

The isolation and identification of intermediates formed in the course of the activation of dioxygen at transition metal centers reveals important mechanistic insights concerning such processes. We previously reported the reaction of the dinuclear Cr^II complex [L₂Cr₂(MeCN)₂][Li(MeCN)]₂ (L=PhSi(OSiPh₂O⁻)₃) ( 5 ) with dioxygen, which resulted in the formation of the Cr^IV oxo complex [L₂Cr₂O₂][Li(THF)₂]₂ ( 6 ), as the final room temperature stable product. Here we now report the isolation and characterization of an intermediate en route to 6 , namely the dinuclear Cr^III superoxo complex [L₂Cr₂(O₂)₂][Li(MeCN)]₂ ( 7 ). 7 is the first example of a structurally characterized dinuclear Cr^III superoxo complex with two independent side-on bound superoxo ligands. Reactivity studies outline the capability of this superoxo complex to activate weak O−H bonds.     

微波加热CO2活化法制备生物质活性炭及其脱硫性能研究

以富含含氮官能团的大豆秸秆为原料前体，结合微波加热的特殊优势，将微波加热技术应用于大豆秸秆热解和活化工艺。以热解固体产物为活化原料，以CO₂为活化剂进行活性炭制备研究，以期制备出高脱硫性能的生物质活性炭。首先通过正交实验设计及极差分析得出最优活化水平，再通过单因素实验法考察微波功率、CO₂流量和活化时间对活性炭产率、孔隙结构以及脱硫性能的影响。对比分析选出最佳活化条件为微波功率900 W，CO₂流量0.10 L/min，活化时间20 min。在此条件下活性炭产率为76.3%（质量），SO₂饱和吸附容量为112.56 mg/g，比表面积为466.28 m²/g。相比热解炭，活性炭的比表面积更大，孔隙更加丰富，脱硫性能显著提高。     

超声促进Ni/Sn固-液溶解行为

钎焊接头的可靠性主要由界面金属间化合物的形貌及接头微观组织决定,超声辅助钎焊过程中母材溶解行为直接影响接头可靠性。为进一步探明超声对Ni-Sn溶解行为的影响,本文采用浸入实验法对比研究了加载超声和无超声辅助下Ni在Sn中的溶解动力学,通过模拟探明了熔池中声压分布规律,观察了Ni-Sn界面微观组织。上述研究表明,超声作用10 s Ni丝的溶解量与不加超声保温5 min的溶解量相当,表明超声能促进Ni在熔融Sn钎料中的溶解。无超声辅助时,随着保温时间的增加,Ni-Sn界面金属间化合物逐渐增厚,阻碍了Ni与Sn 之间的相互扩散；而在超声空化作用下,Ni-Sn界面处于动态非平衡状态,能促进Ni在液态Sn中不断溶解；同时,在声流作用下界面Ni原子快速迁移至Sn中,在随后的冷却过程中析出大量细长棒状的Ni₃Sn₄金属间化合物。     

重组人淋巴细胞活化基因-3蛋白胞外段的真核表达及鉴定

目的真核表达重组人淋巴细胞活化基因-3(lymphocyte activation gene-3,LAG-3)蛋白胞外段,并进行鉴定。方法用植物血球凝集素(phytohaemagg lutinin,PHA)刺激Jurkat细胞,流式细胞术检测Jurkat细胞中LAG-3蛋白的表达;提取Jurkat细胞总mRNA,RT-PCR法扩增人LAG-3蛋白胞外段基因片段,同时在蛋白C-末端引入His标签,将其克隆入载体pcDNA3. 1+,构建重组质粒,转染Expi293F真核细胞,当细胞活率低于50%时收获细胞上清,经镍柱亲合层析纯化。纯化产物进行4%~20%SDS-PAGE、HPLC及Western blot分析,BCA法测定浓度。结果经菌液PCR、双酶切及测序鉴定,表明质粒构建正确。重组表达蛋白的相对分子质量约60 000,纯化后纯度达95%以上,与鼠抗LAG-3单克隆抗体可发生特异性结合,浓度为2. 4 mg/mL。结论成功构建了重组真核表达质粒LAG-3/pcDNA3. 1+,并于Expi293F细胞中表达,纯化获得了纯度较高的LAG-3蛋白,为后期LAG-3蛋白的相关研究及其单抗的制备奠定了基础。     

彩色纳米碳酸钙的研制

以纳米碳酸钙中试装置为平台,通过控温碳化、加热湿法染色、加热湿法改性和分散处理,制得了具有良好一次粒子形态的彩色纳米碳酸钙产品。激光粒度仪测试表明,彩色纳米碳酸钙产品的D₅₀约为350 nm,具有粒度分布均匀、分布范围窄等特点。产品在空气中长期放置不氧化、不褪色,说明具有良好的化学稳定性。亲水性实验表明,彩色纳米碳酸钙产品在水中长时间放置、反复搅拌,仍然不沉降、不掉色,说明染色和活化都是牢固的。以酸性媒染蓝黑B染料和硬酯酸为例,分析了纳米碳酸钙的湿法染色和湿法活化机理,并且探讨了硬酯酸分子、染色剂分子和碳酸钙颗粒之间的化学交联作用。