Green synthesis of ZSM-5 using silica fume and catalytic co-cracking of lignin and plastics for production of monocyclic aromatics

ZSM-5 with hierarchical pore structure was synthesized by a simple two-step hydrothermal crystallization from silica fume without using any organic ammonium templates.The synthesized ZSM-5 were oval shaped particles with a particle size about 2.0 μm and weak acid-dominated with proper Brønsted(B)and Lewis(L)acid sites.The ZSM-5 was used for catalytic co-cracking of n-octane and guaiacol,lowdensity polyethylene(LDPE)and alkali lignin(AL)to enhance the production of benzene,toluene,ethylbenzene and xylene(BTEX).The most significant synergistic effect occurred at n-octane/guaiacol at 1:1 and LDPE/AL at 1:3,under the condition,the achieved BTEX selectivity were 24%and 33%(mass)higher than the calculated values(weighted average).The highest BTEX selectivity reached 88.5%,which was 3.7%and 54.2%higher than those from individual cracking LDPE and AL.The synthesized ZSM-5 exhibited superior catalytic performance compared to the commercial ZSM-5,indicating potential application prospect.

Effect of Sodium Tripolyphosphate and Silica Fume on Hydration of High Alumina Cement

It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry,inhibit CAH_(10),promote the generation of C_(3)AH_(6)and strätlingite C_(2)ASH_(8),or promote the conversion of CAH_(10)to C_(3)AH_(6).Sodium tripolyphosphate can retard the early hydration of cement,have a slight effect on 1 d hydration products of cement and inhibit the generation hydration products.Sodium tripolyphosphate and silica fume can promote the early hydration of cement,advance the formation of C_(2)ASH_(8)or the conversion from CAH_(10)to C_(3)AH_(6)at 1 d.

Effect of silica fume and glass powder for enhanced impact resistance in GGBFS-based ultra high-performance geopolymer fibrous concrete:An experimental and statistical analysis

Solid waste recycling is an economically sound strategy for preserving the environment,safeguarding natural resources,and diminishing the reliance on raw material consumption.Geopolymer technology offers a significant advantage by enabling the reuse and recycling of diverse materials.This research assesses how including silica fume and glass powder enhances the impact resistance of ultra-high-performance geopolymer concrete(UHPGC).In total,18 distinct mixtures were formulated by substituting ground granulated blast furnace slag with varying proportions of silica fume and glass powder,ranging from 10%to 40%.Similarly,for each of the mixtures above,steel fibre was added at a dosage of 1.5%to address the inherent brittleness of UHPGC.The mixtures were activated by combining sodium hydroxide and sodium silicate solution to generate geopolymer binders.The specimens were subjected to drop-weight impact testing,wherein an examination was carried out to evaluate various parameters,including flowability,density at fresh and hardened state,compressive strength,impact numbers indicative of cracking and failure occurrences,ductility index,and analysis of failure modes.Additionally,the variations in the impact test outcomes were analyzed using the Weibull distribution,and the findings corresponding to survival probability were offered.Furthermore,the microstructure of UHPGC was scrutinized through scanning electron microscopy.Findings reveal that the specimens incorporating glass powder exhibited lower cracking impact number values than those utilizing silica fume,with reductions ranging from 18.63%to 34.31%.Similarly,failure impact number values decreased from 8.26%to 28.46%across glass powder contents.The maximum compressive and impact strength was recorded in UHPGC,comprising 10%silica fume with fibres.

Thickening progression mechanism of silica fume-oil well cement composite system at high temperatures

This work studied the thickening progression mechanism of the silica fume-oil well cement composite system at high temperatures(110-180.C)in order to provide a theoretical guidance for the rational application of silica fume in the cementing engineering.Results showed that silica fume seldom affected the thickening progression of oil well cement slurry at 110-120.C,but when temperature reached above130.C,it would aggravate the bulging degree of thickening curves and significantly extend the thickening time,meanwhile causing the abnormal“temperature-based thickening time reversal”and“dosage-based thickening time reversal”phenomena in the range of 130-160.C and 170-180.C respectively.At 130-160.C,the thickening time of oil well cement slurry was mainly associated with the generation rate of calcium hydroxide(CH)crystal.The introduced silica fume would be attracted to the cement minerals'surface that were hydrating to produce CH and agglomerate together to form an“adsorptive barrier”to hinder further hydration of the inner cement minerals.This“adsorptive barrier”effect strengthened with the rising temperature which extended the thickening time and caused the occurrence of the“temperature-based thickening time reversal”phenomenon.At 170-180.C,the pozzolanic activity of silica fume significantly enhanced and considerable amount of C-S-H was generated,thus the“temperature-based thickening time reversal”vanished and the“dosage-based thickening time reversal”was presented.

The Influence of Carbon Nanotubes and Nano-Silica Fume on Enhancing the Damping and Mechanical Properties of Cement-Based Materials

This paper conducted experimental studies on the damping and mechanical properties of carbon nanotube-nanosilica-cement composite materials with different carbon nanotube contents. The damping and mechanical properties enhancement mechanisms were analyzed and compared through the porosity structure test, XRD analysis, and scanning electron microscope observation. The results show that the introduction of nanosilica significantly improves the dispersion of carbon nanotubes in the cement matrix. At the same time, the addition of nanosilica not only effectively reduces the critical pore size and average pore size of the cement composite material, but also exhibits good synergistic effects with carbon nanotubes, which can significantly optimize the pore structure. Finally, a rationalization suggestion for the co-doping of nanosilica and carbon nanotubes was given to achieve a significant increase in the flexural strength, compressive strength and loss factor of cement-based materials.

Effect of Different Silica Fumes on Properties of Al_(2)O_(3)-SiC-C Castables for Iron Trough

In order to improve the performance of Al_(2)O_(3)-SiC-C castables for iron trough,samples were prepared using brown corundum,dense corundum,activated alumina micropowder,ball pitch,and silicon as main raw materials,calcium aluminate cement as the binder.Several kinds of silica fumes(93SiO_(2),96SiO_(2),and 99SiO_(2))with different particle size distributions and chemical composition were added to research the effects on the properties of castables.The results show that the sample with 99SiO_(2) fume has high water requirement for molding,but the bulk density is the lowest,the apparent porosity is the highest,the oxidation resistance is the worst,and the permanent linear change on heating is low after firing at 1 450 ℃ for 3 h.The bulk density and the apparent porosity of the sample with 93SiO_(2) fume or 96SiO_(2) fume are equivalent,the hot modulus of rupture of the sample with 93SiO_(2) fume is the lowest,and the slag resistance of the sample with 96SiO_(2) fume is the best.The comprehensive performance of the sample with 96SiO_(2) fume is the best.

On the Combination of Silica Fume and Ceramic Waste for the Sustainable Production of Mortar

The combined use of silica fume(SF)and ceramic waste(CW)for the production of mortar is studied.Sand is replaced by 5%,10%,15%and 20%of CW while a fixed 5%percentage(%wt of cement)of SF is used.The results show that the best results are obtained by using silica fume and ceramic waste sand with 15%weight of sand and 5%wt of cement.With the addition of sand ceramic waste(SCW),the mortar compressive strength and density increase,while the porosity displays an opposite trend.The experimental analysis is complemented with theoretical considerations on the matrix strength and related improvements in mechanical behavior.It is shown that the agreement between the experimental values and the estimated values is good.

Enhancing Concrete Properties Using Silica Fume:Optimized Mix Design

In the current work concrete mixes containing(7.0-33.11)weight%silica fume as fractional substitution of cement with water/cement ratio(0.42-0.48)were formulated conferring to an implemented two factorial central composite design.The samples were water cured for 7,28,56,and 90 days.The samples were tested for compressive strength and density.The experimental results approved that compressive strength and density increase with age and with rising silica fume content up to 11.9 wt.%.Response surface analysis results for samples cured for 28 days confirmed that silica fume concrete with developed compressive strength(53.42 MPa)could be prepared by incorporation of 11.9 wt.%silica fume as a substituent for cement using a 0.42 water/cement ratio.An intensification in compressive strength and density(up to 39.3%and 2.6%)respectively was recorded for silica fume concrete mixes in contrast to Portland cement concrete.Overall,the research findings revealed that silica fume concretes prepared with appropriate silica fume content and water/cement ratio exhibited superior strength and density features candidate them to be used effectively in civil engineering structural applications.

硅灰及矿渣粉对大掺量粉煤灰砂浆力学性能的影响及机理研究

以硅灰和矿渣粉(GGBS)为辅助胶凝材料,使用聚羧酸高性能减水剂,分别研究了硅灰和GGBS对大掺量粉煤灰砂浆抗压强度的影响。通过压汞测试(MIP)、扫描电子显微镜(SEM)以及X射线衍射(XRD)等方法对制备试件的孔结构、微观产物、物相组成进行分析,得到了硅灰和GGBS影响大掺量粉煤灰砂浆强度的机理。结果表明:单掺硅灰的大掺量粉煤灰砂浆的抗压强度随着硅灰含量增加先增大后减小,单掺GGBS的规律与硅灰类似;复掺硅灰和矿渣时,砂浆的强度较其他同龄期组均有一定的提高,二者表现出良好的协同作用;无论是单掺还是复掺,硅灰和GGBS都对大掺量粉煤灰砂浆强度有良好的提升作用。砂浆试件总孔隙率和大孔占比与抗压强度总体呈负相关,强度越高的砂浆试件微观结构越致密,但相比于总孔隙率,毛细孔和大孔占比表现出与抗压强度更好的相关性。当硅灰和GGBS质量分数分别为8%和6%时,砂浆28 d强度最大,为88.05 MPa。

空心微珠低密度水泥浆在高温下的水化特性

空心微珠主要是硼硅酸盐玻璃材质制成,内部富含SiO2组分,在120℃、150℃下,对不同龄期微珠低密度水泥浆抗压强度、渗透率、微观分析、稠化可调性进行了测试,确认了空心微珠对高温水化特性的影响。研究结果表明,120、150℃下,空心微珠中的硅质组分均参与了水泥水化,对水泥石强度起到了抑制或补偿抑制作用,其中120℃时仅16%空心微珠可以在28 d之内起到抑制抗压强度衰退作用,150℃时抑制衰退则需要内掺一定的硅粉,确保硅粉含量与空心微珠含量之和达到40%以上;高温下微珠因参与反应表面形成显著的孔隙轮廓,随着养护龄期延长,水泥石总孔隙增多,无硅粉配方增加的孔径以50~100 nm的毛细孔居多,渗透率随着养护龄期的延长逐步增大,由最初的0.003 mD增加至0.011 mD,增幅较为明显,但渗透率净值并不大;内掺硅粉增加的孔径以小于50 nm的凝胶孔居多,渗透率随养护龄期延长基本变化不大;在没有硅粉情况下,14 d时水泥石中Ca(OH)2相消失,与玻璃微珠反应生成C—S—H凝胶,添加硅粉配方水化产物中未见Ca(OH)2相,反应迅速,生成具有良好抗衰退作用的托博莫来石相,起到较好的防止衰退作用;稠化时间具有可调性,硅粉和空心微珠都不会对水泥浆高温早期水化规律性造成不良影响。

硅粉和活化煤矸石粉改性透水混凝土强度和耐久性研究

为研究硅粉和活化煤矸石粉对透水混凝土强度和耐久性的影响规律,分别利用硅粉和活化煤矸石粉代替0%、5%、10%、15%、20%、25%的水泥进行透水混凝土试样制备,对新拌混凝土的流动性以及硬化混凝土强度、耐久性进行了测试分析,研究了硅粉和活化煤矸石粉对透水混凝土基本特性的影响规律,以及2种材料的掺量范围和适用性。结果表明:①掺入10%~15%的硅粉和10%的活化煤矸石粉可以有效提高混凝土强度,且硅粉对强度的提升效果更为明显,但对混凝土流动性和透水性会有不利影响;②随着硫酸溶液侵蚀时间和冻融循环次数增加,混凝土抗压强度和质量比均不断下降。根据上述分析可知:①掺入5%~10%的硅粉和5%的活化煤矸石粉对混凝土的抗H_(2)SO_(4)溶液长期侵蚀性有利;②掺入5%~20%的硅粉和10%~15%的活化煤矸石粉对混凝土的抗酸雨—冻融循环侵蚀性有利;相比之下,硅粉对混凝土的长期冻融耐久性更有利。

倾斜隧道双火源双竖井对自然通风隧道火灾烟气流动特征的影响

为研究城市倾斜隧道发生火灾后的烟气流动特征,通过FDS数值模拟仿真软件模拟了自然通风状态下不同坡度与垂直多竖井耦合作用时的温度分布及烟气运动,分析了由隧道及竖井温度场表现的烟气层吸穿现象、竖井上部开口处烟气速率及质量流率变化。结果表明,水平隧道中,隧道下游处竖井发生烟气层吸穿现象,隧道坡度增大,烟气聚集于下游,隧道下游处竖井内烟气层吸穿现象的消失对竖井排烟效率起正向影响;坡度是自然通风状态下影响竖井排烟效率的主要因素;竖井内烟气流动特征主要由坡度决定,存在临界坡度使竖井内发生边界层分离现象且该现象不会随坡度增大而消失;固定长度段隧道中多竖井的存在一定程度上延缓了由坡度导致的排烟效率下降的过程。

基于流变特性的压浆料稳定性评价方法研究

文中设计了一种基于同轴圆筒流变仪的压浆料稳定性测试程序,定义了剪切稳定度量化不同配比浆体的稳定性.通过粘度改性剂设计了两种不同稳定性的浆体,验证了剪切稳定度的可靠性.应用剪切稳定度测试,研究了超塑化剂和硅灰对压浆料浆体稳定性的影响.结果表明:超塑化剂的掺入降低了浆体的稳定性,硅灰能够提高浆体的稳定性,剪切稳定度0.9以上的浆体稳定性和均匀性较好.

抑烟沥青复掺配比优化及抑烟效果评价

为抑制沥青在高温下烟气的产生,降低环境污染及对作业人员健康的影响程度,本文进行了抑烟沥青复掺配比优化研究。基于单掺抑烟沥青的针入度、延度及软化点及自制沥青烟生成富集装置的沥青产烟结果,结合熵权法与遗传算法进行抑烟沥青复掺配比优化,并分析优化复掺抑烟剂在沥青中的分散均匀性、储存稳定性及其对沥青特征官能团的影响;基于优化复掺配比的抑烟沥青高、中、低温性能测试,并对其抑烟效果进行评价,验证优化复掺配比方法的有效性。研究表明:抑烟剂均匀分散于沥青中,且未对沥青特征官能团产生改变,优化复掺抑烟沥青满足储存稳定性要求。优化复掺抑烟剂对沥青高、低温性能具有改善作用,并提升了沥青中温抗疲劳性能。沥青烟收集前后滤管颜色变化表明该沥青烟富集方式具有较高的可靠性,且优化复掺抑烟沥青具有显著抑烟效果,最大抑烟率为99.7%。优化复掺配比下的指标预测值与实测值差异较小,证明了该优化复掺配比方法的可靠性。

PET复合纤维的制备及其隔热性能

为改善聚对苯二甲酸乙二醇酯(PET)纤维的保温隔热性能,使用熔融纺丝工艺制备具有保温隔热性能的PET/二氧化硅气凝胶(SA)/气相SiO2(FS)复合纤维,并用NaOH溶液对纤维进行碱处理,以在纤维表面形成孔隙;采用SEM、XRD、TG、DSC和导热系数仪等表征技术对复合纤维进行了表征,探究了碱处理时间对纤维表面形貌、拉伸强度、导热系数等物化性质的影响。结果表明:碱处理之后的PET/SA/FS复合纤维表面出现孔隙,断裂强度降低24.5%;热导率从纯PET纤维的0.0894 W/(m·K)最低降低到PET/SA/FS复合纤维的0.0400 W/(m·K),降低了55.3%,从而显著提高了纤维的保温隔热性能。

外掺料对珊瑚混凝土的力学性能及耐久性能的影响

为了探明外掺料对珊瑚混凝土综合性能的影响,利用粉煤灰和硅灰部分取代水泥,试配C30和C50珊瑚混凝土,对珊瑚混凝土的力学性能和耐久性能进行了试验,并对试验结果及影响规律进行了分析。研究结果显示,在珊瑚混凝土中同时掺入粉煤灰和硅灰,可以显著提高其抗压强度、劈裂抗拉强度及抗硫酸盐侵蚀能力和抗Cl-渗透性能,当两种材料的掺入比例都为10%时效果最好。

改性硫铝酸盐水泥砂浆力学性能及耐久性能研究

过快的流动度损失和后期不稳定的强度发展限制了硫铝酸盐水泥工程中的进一步应用。因此以葡萄糖酸钠作为缓凝剂,掺入硅灰制备成改性硫铝酸盐水泥砂浆,并对其工作性能、力学性能和抗氯离子渗透性能开展了系统研究。研究结果表明:葡萄糖酸钠掺量0.4%可有效延长硫铝酸盐水泥砂浆凝结时间,提高砂浆流动性和抗氯离子渗透性能;硫铝酸盐砂浆工作性能、力学性能和抗氯离子渗透性能均随硅灰掺量的增加先提高后降低,硅灰最优掺量为20%。

基于乳化的智能型高效油烟废气净化装置研究

餐饮业产生的油烟废气蕴含大量有害气体,而传统抽油烟废气设备将没有经过任何去污染净化处理的油烟废气直接排放到空中,严重污染生活环境,危害人体健康,急需治理;针对治理餐饮业油烟废气污染环境难题,提出一种以提高油烟废气净化效率为目标进行优化控制的智能装置设计;装置实时监测油烟废气浓度和电解液pH值大小,通过控制超声波雾化强度喷射适量碱性水雾促进油烟废气乳化,又不会过量喷射碱性水雾造成二次环境污染;同时监测环境污染物颗粒浓度,开启负离子发生器,产生适量负离子与油烟废气颗粒结合使油烟废气颗粒变大更容易沉积,提高油烟废气净化效率;沉积的油烟废气沿着管道下流不但自动清洗黏附油垢,而且方便收集循环再利用;实验结果表明,装置不仅净化油烟废气控制有效,而且提升环境空气质量,既节能又环保,特别适合在食堂、街头地摊等规模使用排油烟废气地方,具有较好的实用性和广泛的应用前景。

茶树新品系‘福茗2号’区域试验报告

【目的】选育早生、高产、高香茶树新品种,满足消费需求的多样化。【方法】以‘黄棪’为对照,在福建福安、松溪、福州3个区试点对‘福茗2号’新品系的种植成活率、物候期(一芽一叶、一芽二叶和一芽三叶期)、鲜叶产量、制茶品质、抗性等方面进行为期6年(2016—2021年)的茶树品种区域试验。【结果】‘福茗2号’新品系种植成活率高,达89%以上;物候期比对照早1~2 d;鲜叶产量比对照高5%左右;制乌龙茶品质比对照高出0.5~1.1分;耐寒、耐旱性强,茶炭疽病和茶小绿叶蝉抗性均表现为抗。【结论】‘福茗2号’是一个早生、高产、优质、高抗的乌龙茶新品种,适宜在福建福安、松溪、福州及相似乌龙茶地区种植和推广应用。

热硫化硅橡胶耐高温性能的影响因素探讨

以甲基乙烯基硅橡胶生胶为主要原料,添加白炭黑、结构化控制剂、脱模剂及耐热助剂等制备了耐高温硅橡胶,并研究了生胶种类、白炭黑种类及用量、结构化控制剂种类、脱模剂及耐热剂种类等对硅橡胶耐高温性能的影响。结果表明,对白炭黑进行疏水处理及耐热剂复配有利于抑制硅橡胶老化。以乙烯基封端的甲基乙烯基硅橡胶为生胶、添加51份比表面积为200 m^(2)/g的气相白炭黑为补强填料、甲基苯基二甲氧基硅烷为结构化控制剂、氧化铈/二氧化钛为复配耐热剂,并加入苯基乙烯基硅树脂,对硅橡胶进行二次硫化后,硅橡胶性能最佳。此时其邵氏A硬度为65、拉伸强度9.6 MPa、断裂伸长率640%,经280℃×72 h老化后邵氏A硬度为68、拉伸强度4.9 MPa、断裂伸长率280%。