水硬性石灰合成及拉破坏特性试验研究

水硬性石灰在欧洲石质文物修复和加固中获得了很大成功。我国的石质文物主要是砂岩,水硬性石灰的修复效果不好。为满足我国石质文物修复和加固的需求,本文以石灰石和黏土为原料,在950℃煅烧不同时间,制备出水硬性石,对试样的成分、微观形貌、收缩率、抗拉强度和拉破坏过程等进行了研究。结果表明:(1)试样中含有水硬性成分2CaO·SiO2(C2S);煅烧8h时,成分与欧洲水硬性石灰NHL5接近;1.5CaO·SiO2·xH2O(C-S-H)和CaCO3的含量随龄期的增加逐渐增加。(2)龄期1~3d,收缩率较小;龄期4~6d,收缩率以线性规律增加;7d以后,收缩率趋于稳定。(3)局部变形区随拉应力的增加而变大,邻近局部变形区逐渐合并,形成面积更大的应变局部化带;载荷超过峰值后,产生微裂隙;随载荷进一步增加,微裂隙扩展,贯穿整个试件,发展成宏观裂隙,使试件破坏。(4)抗拉强度随龄期的增加而增加,水硬性石灰中C-S-H、CaCO3等相互交织,构成空间致密体,使试件力学强度提高。合成的水硬性石灰物理力学性能与欧洲水硬性石灰NHL5相近,并且成分均匀、可控,在石质文物修复和加固工程中具有良好应用前景。     

Effectively promoted catalytic activity by adjusting calcination temperature of Ce-Fe-Ox catalyst for NH3-SCR

A series of Ce-Fe-O_x catalysts prepared by the different calcination temperatures (marked as CF-X, where X represented calcination temperature) were used to the selectivity catalytic reduction of NO_x by NH₃. The results explained the relationship between calcination temperature and the sulfate species over Ce-Fe-O_x, and then investigated the surface acidity and catalytic performance. The large amounts of sulfate species were formed over CF-450 and CF-550 while it was decomposed with further the increasing of calcination temperature, which resulted in the loss of surface acidity, causing a decrease in the catalytic activity over Ce-Fe-O_x. Thereby, the CF-450 catalyst showed the best catalytic activity and over 90% NO_x conversion was obtained at 244–450 °C. Besides, the favored pore structure, more Fe³⁺ active species, higher Ce³⁺ concentration and the abundance of chemical adsorbed oxygen species, as well as the surface acid sites, would together contribute to the excellent catalytic activity of CF-450 catalyst.     

焙烧温度对LaSrFeMo0.9Co0.1O6催化剂催化甲烷燃烧性能的影响

采用溶胶凝胶法制备LaSrFeMo0.9Co0.1O6,以催化甲烷燃烧为目标反应,研究不同焙烧温度(600、700、800、900℃)对其催化甲烷燃烧性能的影响.通过XRD、BET、H2-TPR及SEM技术对其结构进行表征.结果表明,在不同的焙烧温度下均可形成完整的双钙钛矿晶型,且焙烧温度不同其催化活性不同,随着焙烧温度的升高其催化活性先升高后逐渐降低.当焙烧温度为800℃,样品比表面积为14 m2/g,起燃温度T10％为428℃,T90％为640℃.     

焙烧温度对K改性Ag-Fe/ZnO-ZrO2催化剂结构和CO加氢合成低碳混合醇醚性能的影响

采用并流共沉淀法在不同焙烧温度下制备K改性Ag-Fe/ZnO-ZrO₂催化剂,考察不同焙烧温度对催化剂CO加氢合成低碳混合醇醚反应性能的影响。通过N₂物理吸附(N₂-adsorption)、X射线衍射(XRD)、氢气程序升温还原(H₂-TPR)、一氧化碳程序升温脱附(CO-TPD)等手段对催化剂进行表征。结果表明,250 ℃焙烧的催化剂,由于焙烧温度较低,表面尚未形成足够多的活性位,未能达到最佳的催化性能;300 ℃焙烧的催化剂,其CO转化率最高、醇醚选择性较高,醇醚时空产率达到最大值。随着焙烧温度进一步升高,CO转化率逐渐降低,醇选择性先降低后增大,二甲醚(DME)选择性逐渐增大,醇醚时空产率逐渐降低。催化剂性能主要与其比表面积、还原性能、所含银铁复合物分散度及CO吸脱附性能有关,即比表面积较大、易于被还原、银铁复合物分散度较高以及较多的CO吸脱附活性位,有利于催化剂CO加氢转化。催化剂表面活性位对CO的非解离吸附强度降低,有利于醇醚产物的生成;而对CO的解离吸附强度增强,则不利于烃类产物的生成。     

The Characteristics of Green Calcium Oxide Derived from Aquatic Materials

Thermogravimetric Analysis of three aquatic materials, i.e. cuttlebone, mussel shell and oyster shell, and other physicochemical characteristics were investigated. The highest decomposition rates of aquatic materials under two surrounding gases, i.e. oxygen and nitrogen, exhibited no significant difference for cuttlebone (3.6×10^-5-4.8×10^-5 mg s^-1 mg_initial^-1 at heating rate 5 °C/min and 11.8 ×10^-5 -12.5×10^-5 mg s^-1 mg_initial^-1 at heating rate 15 °C/min) and mussel shell (3.4×10^-5- 5.2×10^-5 mg s^-1 mg_initial^-1 at heating rate 5 °C/min and 11.9×10^-5 – 12.4×10^-5 mg s^-1 mg_initial^-1 at heating rate 15 °C/min), while oyster shell provided the higher decomposition rate under nitrogen surrounding gas (7.6×10^-4 mg s^-1 mg_initial^-1 at heat rate 5 °C/min and 21.53×10^-4 mg s^-1 mg_initial^-1 at heating rate 15 °C/min). This is probably because of the difference in their starting crystalline structures, i.e. aragonite (cuttlebone and mussel shell) and calcite (oyster shell). The cubic calcium oxides were prepared by calcination of three aquatic materials under oxygen and nitrogen surrounding gases at 5 °C/min ramping to 850 °C for 2 hours. All resulting calcium oxides obtained from oxygen atmosphere provided only cubic crystalline phases and the adsorption-desorption isotherms (IUPAC Type III), whereas the calcinations under nitrogen surrounding gas gave a presence of calcium hydroxide crystalline or hydroxyl- contaminate existing with cubic calcium oxide that influences on the strength and the number of carbon dioxide adsorption sites. The specific surface area of all resulting calcium oxides ranged from 0.1 – 1.5 m²/g and the average pore diameter was found in the range of 40-60 nm. The the number of basic sites belonging to CaO derived from Oyster shell or Cuttlebone were improved while firing under oxygen atmosphere. The suitable firing condition is at the low heating rate to develop porous materials.     

Nanoporous polyimide film from poly(ethylene glycol-co-imide) using a one-step heat calcination process

Polyamic acid (PAA) made from 3,3, 4,4-biphenyltetracarboxylic dianhydride and 4,4-diaminodiphenyl ether was synthesized and used as the backbone of nanoporous polyimide. Thermally labile polyethylene glycol (PEG) at 10, 20 or 30 wt% was introduced to the end group of PAA. Self-assembled PAA-b-PEG micelle-like nanoparticles could be formed as a result of amphiphilic characteristics of hydrophobic PAA and hydrophilic PEG. Thermal imidization and degradation of spin-coated amphiphilic PAA-b-PEG film were performed sequentially through one-step heat treatment to obtain polyimide film with nanopores. Pore sizes decreased with increasing amount of PEG block and their dielectric constants decreased from 2.71 ± 0.13 to 2.38 ± 0.11.     

六钛酸钾晶须的制备及生长机理的研究

通过KDC方法成功制备了六钛酸钾(K_2Ti_6O_(13))晶须,并进行了热重分析和差热分析,研究烧结时间和烧结温度对K_2Ti_6O_(13)晶须结晶过程的影响,通过X射线衍射分析了K_2Ti_6O_(13)晶须的相组成和晶体指数。此外,通过扫描电子显微镜和透射电子显微镜研究晶须的微观结构,揭示了K_2Ti_6O_(13)晶须的生长机理。     

菱镁矿悬浮态与堆积态煅烧对产物特性的影响

利用实验室自制小型模拟悬浮态煅烧装置和马弗炉,对菱镁矿进行快速煅烧试验制备轻烧氧化镁,分别对悬浮态和堆积态的煅烧产物进行分解率、XRD、SEM、活性等分析,探讨两种煅烧方式对轻烧氧化镁特性的影响。结果表明:相对于堆积态煅烧,菱镁矿经悬浮态煅烧1 min后分解率即可达到98%以上,得到的轻烧氧化镁晶粒尺寸小、结晶度低,比表面积大、表现出很高的活性;悬浮态煅烧显著强化了热传递过程,加快了反应速度,生产效率成倍提高,产品性能好、质量稳定,可应用于大规模生产高活性轻烧氧化镁。     

焙烧温度对1,4-丁烯二醇加氢Cu/Raney-Ni催化剂结构和性能影响

在Ni-Al合金粉上浸渍硝酸铜溶液,经不同温度焙烧得到Cu改性Ni-Al合金粉,采用质量分数10%NaOH溶液浸渍上述改性合金粉得Cu/Raney-Ni催化剂。采用EDX、XRD、N_2吸附-脱附、TEM和NH_3-TPD等手段表征了Ni-Al合金粉及相应Raney-Ni催化剂的元素含量、晶体结构、孔结构特征、表面形貌和表面酸碱性,并以1,4-丁烯二醇加氢制1,4-丁二醇为探针反应,考察了焙烧温度对Raney-Ni催化剂加氢性能的影响。表征分析表明,焙烧温度500℃所制备的CRT500催化剂比表面积较大,为64.96m~2/g;弱酸中心比例较高,达81.2%。结果表明,焙烧温度升高,BED可实现完全转化,BDO选择性和收率均先升高后降低。其中,CRT500加氢性能较好,BED转化率为100.00%,BDO选择性为61.88%。进一步升高焙烧温度,催化剂RCT550和RCT600的BDO选择性和收率反而降低,这是由于高温下催化剂易发生团聚或烧结。结合催化剂表征可知,CRT500具有较好的加氢性能,这与该催化剂具有合适的Ni/Al物质的量比(3.84)、弱酸中心所占比例较大和活性组分Ni分散性好等因素有较大关联。     

焙烧温度对ZnO粉体结晶及光学性能的影响

以草酸铵和醋酸锌为原料,采用直接沉淀法制备ZnO粉体,考察了焙烧温度对粉体结晶和光学性能的影响。 采用热重分析（TGA-DTA）、X射线衍射、紫外-可见漫反射（UV-Vis）、荧光分光光度计（FS）和扫描电子显微镜（SEM）等方法对样品进行了分析。 结果表明,制备的前驱物为C2O4Zn·2H2O,最低焙烧温度400 ℃,随着焙烧温度的提高,粉体结晶度提高,一次粒径增大;600 ℃焙烧后有较强紫外发光峰,粉体由200 nm的粒子排列成层叠状;900 ℃焙烧后有较强可见发光峰,粉体粒子大于500 nm,团聚严重;粉体有较强的紫外吸收,吸收峰有蓝移。