Early Stage Hydration Mechanism of Cellulose Ether Modified Thin Layer Cement Pastes

The early stage hydration mechanism of cellulose ether modified thin layer cement pastes was studied, using brick as the matrix. Samples of 6 h, 24 h, and 3 d and 7 d hydration time were analyzed to study the hydration law on the surface of high water-absorbing matrix. Hydration products were qualitatively and semi-quantitatively analyzed using XRD, TG-DSC-DTG, FTIR and SEM. The experimental results show that there is no enough water for 2 mm thick cement pastes to hydrate, because of rapid water absorption of matrix. Trace amounts of Ca （OH）2 was detected after three days hydration. With the prolongation of hydration time, the category and concentration of hydration products do not change. Compared with 2 mm thick cement pastes, 6 mm thick cement pastes and 10 mm thick cement pastes have lower dehydration rate and water loss. The humidity field of the cement paste show different changes within the same time. 6 mm thick cement paste and 10 mm thick cement pastes have longer time and more water to hydrate. Ca（OH）2 and ettringite were detected after 6 hours hydration and the concentrations of hydration products increased from 24 hours to 7 days.

Analysis of Air Voids Evolution in Cement Pastes Admixed with Non-ionic Cellulose Ethers

Four cellulose ethers（CEs） were compared for their effects on the pore structure of cement paste using mercury intrusion porosimetry. The experimental results show that the total pore volume and porosity of cement pastes containing the four cellulose ethers are significantly higher than that of the pure cement pastes and the total pore volume and porosity of cement pastes containing HEC（hydroxyethyl cellulose ether） or low viscosity cellulose ethers are low in four CEs. By changing the surface tension and viscosity of liquid phase and the strengthening of liquid film between air voids in cement pastes, CEs affect the formation, diameter evolution and upward movement of air voids and the pore structure of hardening cement paste. For the four CEs, the pore volume of cement pastes containing HEC or low viscosity cellulose ethers is higher with the diameter of 30-70 nm while lower with the diameter larger than 70 nm. CEs affect the pore structure of cement paste mainly through their effects on the evolvement of the small air voids into bigger ones when the pore diameter is below 70 nm and their effects on the entrainment and stabilization of air voids when the pore diameter is above 70 nm.

Hydration Heat Effect of Cement Pastes Modified with Hydroxypropyl Methyl Cellulose Ether and Expanded Perlite

Hydration heat effect of cement pastes and mechanism of hydroxypropyl methyl cellulose ether （HPMC） and expanded perlite in cement pastes were studied by means of hydration exothermic rate, hydration heat amount, FTIR and TG-DTG. The results show that HPMC can significantly delay the hydration induction period and acceleration period of cement pastes. As mixing amount increased, hydration induction period of cement pastes enlarged and accelerated period gradually went back. At the same time, the amount of hydration heat gradually decreased. Expanded perlite had worse delay effects and less change of hydration heat amount of cement pastes than HPMC. HPMC changed the structure of C-S-H during cement hydration. The more amount of HPMC, the more obvious effect. However, EXP had little influence on the structure of C-S-H. At the same age, the content of Ca （OH）2 in cement pastes gradually decreased as the mixing amount increase of HPMC and expanded perlite, and had better delay effect than that single-doped with HPMC or expanded perlite when HPMC and expanded nerlite were both dooed in cement pastes.

Thermal Behavior and Thermal Safety of Nitrate Glycerol Ether Cellulose

The thermal behavior, nonisothermal decomposition reaction kinetics and specific heat capacity of nitrate glycerol ether cellulose（NGEC） were determined by thermogravimetric analysis（TGA）, differential scanning calori- metry（DSC） and microcalorimetry. The apparent activity energy（Ea）, reaction mechanism function, quadratic equa- tion of specific heat capacity（Cp） with temperature were obtained. The kinetic parameters of the decomposition reac- tion are Ea=170.2 kJ/mol and lg（A/s^-l）=16.3. The kinetic equation isf（α）=（4/3）（1-α）[-ln（1-α）]^1/4. The specific heat capacity equation is Cp=1.285-6.276×10^-3T＋1.581×10^-5T^2（283 K〈T〈353 K）. With these parameters, the thermal safety properties of NGEC were studied, such as the self-accelerating decomposition temperature（TSADT）, critical temperature of thermal explosion（Tb） and adiabatic time-to-explosion（tTlad）. The results of the thermal safety evalua- tion of NGEC are： TSADV=459.6 K, Tb=492.8 K, tTlad=0.8 S.

Influence of Cellulose Ethers on Hydration Products of Portland Cement

Cellulose ethers are widely used to mortar formulations,and it is significant to understand the interaction between cellulose ethers and cement pastes.FT-IR spectra,thermal analysis and SEM are used to investigate hydration products in the cement pastes modified by HEMC and HPMC in this article.The results show that the hydration products in modified cement pastes were finally identical with those in the unmodified cement paste,but the major hydration products,such as CH（calcium hydroxide）,ettringite and C-S-H,appeared later in the modified cement pastes than in the unmodified cement paste.The cellulose ethers decrease the outer products and increase inner products of C-S-H gels.Compared to unmodified cement pastes,no new products are found in the modified cement pastes in the present experiment.The HEMC and HPMC investigation shows almost the same influence on the hydration products of Portland cement.

A Review on the Structure and Biodegradation of Cellulose-Lignin Complexes

Cellulose is the most abundant organic macromolecule in nature and is renewable,degradable,and biocompatible.The structure of native cellulose has not yet been completely elucidated.Part of cellulose is tightly combined with lignin macromolecules through chemical bonds to form cellulose-lignin complexes(CLC).The existence of the CLC structure inhibits the complete separation of cellulose from lignocellulosic material,which not only increases the consumption of chemicals in the cooking process and causes environmental pollution,but also makes the cellulose subject to certain degradation during the deep delignification process.Therefore,elucidation of the relationship between the cellulose-lignin connection structure and performance is of great significance for efficient separation of cellulose.This article reviews the current research status of CLC and discusses the research progress regarding its biodegradation characteristics.

Preparation of Carboxymethylcellulose from Waste Paper

We aimed at producing sodium carboxymethylcellulose (CMC) from waste paper cellulose.For this etherification,the raw material was waste paper,the cellulose was initially alkalized with NaOH,the etherifying agent was sodium chloroacetate,and the reaction medium was water or ethanol.The method provided by us,i e,a method for preparing CMC from waste paper,was environment-friendly,could be easily implemented,and could be conveniently applied to make waste paper efficiently used with high profit,and to expand the range of usable raw materials for CMC production.We successfully synthesized CMC and prepared CMC plastic membrane.This practice changes waste into valuables,which is beneficial to our living environment.For preparation of CMC,one of the crucial factors is appropriate pretreatment of the cellulose from waste paper.The pretreatment was done with a self-built hydrolysis method.We experimentally examined the effects of the mass ratios of reactants,reaction temperature,time,and reaction environment of homogeneous or heterogeneous on CMC yield.The innovative points of this research could be stated as follows:the reaction activity of cellulose was improved by pre-hydrolysis;synthesizing CMC with cellulose from waste paper changes waste into valuables is beneficial to our living environment;and a freezing treatment for the cellulose-alkali mixture was innovatively added.The effects were exhibited by a desired final conversion efficiency.

THE MORPHOLOGY AND STRUCTURE OF ETHYLCYANOETHYL CELLULOSE IN STYRENE AND POLYSTYRENE

Ethyl-cyanoethyl cellulose ((E-CE)C)/styrene solution could form anisotropic system when the concentration was high enough. The (E-CE)C/polystyrene(PS)multiphase polymer could be obtained by radical polymerization of the styrene in the solution. The (E-CE)C/PS multiphase polymer maintained both the crystalline structure of the (E-CE)C and the amorphous structure of the PS. In the multiphase polymer produced from the isotropic solution, however, the (E-CE)C formed spherulites and spread in the PS amorphous phase. While, in the multiphase polymer produced from the anisotropic solution, the (E-CE)formed cylinderic crystalline aggregates. Moreover, the ordered lamellar texture was also observed in the multiphase polymer produced from the anisotropic solution.

蒸压轻质混凝土板专用粘结砂浆的制备与性能研究

采用P·O42.5水泥、粉煤灰、石灰石超细粉、矿粉以及外加剂为原料制备水泥基粘结砂浆。采用正交试验确定水泥基胶凝材料的最优配合比,研究淀粉醚对纤维素醚取代率和膨胀剂对水泥基粘结砂浆的性能影响,并利用XRD和SEM分析水化产物和微观形貌,研究外加剂的作用机理。结果表明,m(水泥)∶m(粉煤灰)∶m(矿粉)∶m(石灰石超细粉)=22∶4∶4∶5时,水泥基胶凝材料的性能最优;淀粉醚适量取代纤维素醚可以增强砂浆保水性,提高砂浆强度,减少收缩;少量膨胀剂可以提高砂浆的早期强度,增加掺量则降低早期强度,提高砂浆后期强度。制备的水泥基粘结砂浆符合JC/T 890—2017《蒸压加气混凝土墙体专用砂浆》的要求。

Ce掺杂的OMS-2催化剂上二甲醚催化燃烧性能的研究

通过氧化还原法合成了氧化锰八面体分子筛(OMS-2),而后浸渍负载一定量的Ce。采用TG-DSC、XRD、低温氮气吸附-脱附、TEM、FT-IR、Uv-vis、O2-TPD、H2-TPR以及XPS等技术对制备材料的结构和氧化还原性能进行了表征,考察了催化剂的二甲醚催化燃烧反应性能。结果表明,低掺杂量的Ce高度分散在OMS-2中;高含量时存在独立的CeO2。光谱测试结果表明,Ce的掺杂并未对OMS-2的晶型产生影响。XPS结果表明,Ce的掺杂会提高OMS-2中晶格氧的量。O2-TPD和H2-TPR结果表明,制备的催化剂具有比较丰富的氧物种,低温下易还原,因而在二甲醚催化燃烧中表现出了良好的催化活性和热稳定性。起燃温度在160℃左右,完全燃烧温度在170℃左右,反应产物仅有二氧化碳和水,并且反应后催化剂晶型保持不变,没有积炭产生。

Ce助剂对CuO-ZnO-Al_2O_3/HZSM-5在CO_2加氢合成二甲醚中的性能影响

采用凝胶网格共沉淀法制备二甲醚的催化剂CuO-ZnO-Al2O3/HZSM-5,考察不同助剂La、Ce、Co、Zr对其性能的影响。结果表明,加入助剂后,CO2转化率和二甲醚的选择性都有不同程度的提高,进行比较后发现尤其是加入Ce助剂后,二甲醚的选择性达到61.5%,CO2的转化率达到40%。利用BET、XRD、SEM、H2-TPR、H2-TPD等表征方法对其物化性质进行表征。

纤维素醚结构对CSA水泥砂浆拉伸黏结强度的影响

研究了固定水灰比条件下具有不同取代度和取代基团的5种纤维素醚在0.3%和0.6%掺量时对硫铝酸盐(CSA)水泥砂浆拉伸黏结强度的影响,并结合保水率测试及压汞法对砂浆孔结构进行分析,探讨了纤维素醚结构对其拉伸黏结强度的影响机制.结果表明:对于同类纤维素醚,高取代度的引气多,改性砂浆孔隙率大、拉伸黏结强度低;对于不同类纤维素醚,羟乙基甲基纤维素醚改性砂浆的孔隙率较羟丙基甲基纤维素醚改性砂浆的要小,拉伸黏结强度更高.基于测试结果提出了CSA水泥砂浆拉伸黏结强度影响因子模型.

纤维素发酵中间体选择性制备轻质烯烃

定向合成生物基轻烯烃对促进化学工业的可持续发展具有重要意义.本文探究了利用纤维素发酵中间体(丙酮-丁醇-乙醇)选择性地制备轻烯烃的催化过程.该制备包括两步:生物质发酵制备丙酮-丁醇-乙醇和丙酮-丁醇-乙醇在Ce/SAPO-34催化剂表面选择性脱水获取轻烯烃.本文研究了催化剂活性中心和催化剂的稳定性,获得了高的丙酮-丁醇-乙醇转化率(91.9%)和高的烯烃选择性(86.1%).通过对丙酮-丁醇-乙醇中各组分的催化研究,提出了丙酮-丁醇-乙醇合成轻烯烃的反应路径.

纤维素醚基传感器的研究进展

随着柔性可穿戴设备的快速发展,传统的半导体、陶瓷等材料难以广泛地单独应用于柔性传感器领域。天然纤维素来源广泛,是一种良好的柔性材料,但存在不能熔融、难溶于常规溶剂、理化性能差等问题,而纤维素醚能有效改善天然纤维素的上述问题,因此在传感、储能、产能和柔性器件等领域作为绿色基材得到了初步开发。基于纤维素醚基材料在便携化、多功能化、生物相容性等方面的良好性能,及其应用于柔性传感领域的巨大潜力,本文综述了纤维素醚的制备及纤维素醚基材料在应力应变传感、温/湿度检测、气体传感、离子检测等领域的最新研究进展,分析了纤维素醚基传感器应用前景和未来发展面临的挑战。

CE和LP对水泥体系保水性能的影响研究

从两方面对CE(纤维素醚)和LP(乳胶粉)改性水泥浆体体系性能进行了分析探讨:①通过失水量和保水率分析,对CE和LP共同作用下,水泥体系保水性能的变化规律进行观察,LP对体系保水性能的影响较小,保水率CE则对体系保水性能的影响起主要作用;②通过XRD分析,CE掺量在1.0%时,对CE和LP改性水泥浆体体系的水化有一定的促进作用,但掺量在2.0%时,会抑制水泥的水化,并从聚合物膜锁水机理分析了抑制水化的原因。对实际应用CE和LP对水泥浆体改性的作用,提供了理论指导。

纤维素醚在聚合物水泥防水浆料中的应用研究

研究了纤维素醚MFS6003对聚合物水泥防水浆料性能的影响。结果表明,随着MFS6003用量的增加,聚合物水泥防水浆料的施工性能、抗流挂性和憎水能力显著提高,对聚合物水泥防水浆料的抗压、抗折强度,横向变形能力及抗渗性能几乎没有影响。当MFS6003用量为0.07%时,制得的防水浆料抗渗压力大于0.5 MPa,横向变形能力为2.5 mm,28 d收缩率为0.28%,符合JC/T2090—2011《聚合物水泥防水浆料》中I型产品的要求。

刨花板纹清水混凝土研究与应用

为制备优质刨花板纹清水混凝土,研究了纤维素醚、水胶比、粉煤灰微珠以及引气剂+消泡剂对刨花板纹清水混凝土的影响。发现纤维素醚能提高保水性和工作性能,但若过量会使和易性变差;降低水胶比可提高保水性,但减少用水量会使流动性变差;粉煤灰微珠能更有效地减水润滑、提高抗氯离子渗透性,但降低保水性;引气剂+消泡剂可改善混凝土外观质量。

预分散高活性硅灰浆体的试验研究

本文通过配合使用几种无机、有机悬浮剂,探究不同悬浮剂对硅灰浆体的性能影响,并尝试制备悬浮稳定性、粘度、活性各项性能良好的预分散高活性硅灰浆体。实验结果表明:有机悬浮剂提供良好的悬浮性能并在一定程度上提高浆体的粘度和活性,无机悬浮剂A及膨润土具有提高浆体触变性,静置时稳定浆体的作用;纤维素醚则会极大地的增加浆体的粘度,不利于浆体的使用。

Ce-N共掺杂TiO_2/纤维素气凝胶的制备及光催化性能

以微晶纤维素为原料,NaOH/尿素体系为溶剂,制备纤维素水凝胶。以钛酸四丁酯、硝酸铈等为原料,与纤维素水凝胶复合,制备Ce及Ce-N共掺杂TiO_2/纤维素复合气凝胶。采用扫描电子显微镜(SEM)、X-射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)对其进行表征,并采用吸附亚甲基蓝的方法对其光催化性能进行测试。研究结果表明Ce-N共掺杂TiO_2/纤维素复合气凝胶为白色固体。XRD和FT-IR分析结果表明复合气凝胶内含有钛元素。SEM分析结果表明复合气凝胶仍具备纤维素气凝胶的三维网状结构,孔隙变小。光催化及紫外分析结果表明掺铈提高了纤维素气凝胶原有的光催化性能,且Ce/Ti质量比为4%时光催化效果最好。

PEMFC用Ce-MCM-41/SPEES复合膜的研究

室温下,通过非水热合成法制备了Ce-MCM-41淬灭剂,通过XRF、FT-IR、XRD等表征显示了Ce4+很好地插入到MCM-41骨架中,TEM表征了Ce-MCM-41的多孔结构,利用二甲基亚砜(DMSO)作为捕获剂通过UV-VIS光谱方法表征了Ce-MCM-41淬灭剂捕获自由基的能力。为了降低燃料电池条件下自由基(HO.)对膜的降解制备了Ce-MCM-41/SPEES复合膜,通过离线Fenton实验和在线加速开路降解实验观察了膜的稳定性,结果显示了Ce-MCM-41/SPEES复合膜的稳定性得到了提高。