Effect of oil shale on Na+ solidification of red mud-fly ash cementitious material

Red mud-fly ash based cementitious material mixed with different contents of oil shale calcined at 700°C is investigated in this paper. The effect of active Si and Al content on the solidification of Na⁺ during the hydration process is determined by using X-ray diffraction (XRD), ²⁷Al and ²⁹Si magic-angle-spinning nuclear magnetic resonance (MAS-NMR), infrared (IR), scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It is shown that the content of oil shale has a remarkable effect on the solidified content of Na⁺. The hydration process generates a highly reactive intermediate gel phase formed by co-polymerisation of individual alumina and silicate species. This kind of gel is primarily considered as 3D framework of SiO₄ and AlO₄ tetrahedra interlinked by the shared oxygen atoms randomly. The negative charges and four-coordinated Al inside the network are mainly charge-balanced by Na⁺. The solidifying mechanism of Na⁺ is greatly attributed to the forming of this kind of gel.     

Synthesis of sub-micrometer lithium iron phosphate particles using supercritical hydrothermal method for lithium ion batteries

In this study, sub-micrometer LiFePO₄ particles with high purity and crystallinity were synthesized using supercritical hydrothermal method as the cathode material for lithium ion batteries. Experimental results show that templates and calcination time have significant impacts on the purity, particle size and morphology of LiFePO₄ particles. The as-prepared LiFePO₄ particles using polyvinyl pyrrolidone (PVP) template with additional one hour calcination at 700°C exhibit characteristics of good crystallinity, uniform size distribution, high capacity and cycling performance. The specific discharge capacities of 141.2 and 114.0mA·h/g were obtained at the charge/discharge rates of 0.1 and 1.0 C, respectively. It retained 96.0% of an initial capacity after 100 cycles at 1.0 C rate. The good electrochemical performance of the as-synthesized material is attributed to the synergistic factors of its reasonable particle size and surface areas and high crystallinity.     

水泥稳定废砖集料的强度特性研究

将废砖集料按0、30%、60%和100%的比例替代天然碎石配制4种水泥稳定废砖混合料级配,并按4%和5%水泥剂量拌和成型试件,测试水泥稳定废砖的击实特性、抗压强度、劈裂强度和抗压回弹模量。结果表明：CBA存在大量的孔隙与微裂缝,导致其强度低、吸水率大;由于CBA的密度小、吸水率大,导致水泥稳定废砖的最大干密度随着CBA含量的增加而增大,最佳含水量则逐渐减小;当水泥剂量相同时,各龄期水泥稳定废砖的无侧限抗压强度和回弹模量均随CBA含量的增加而降低,劈裂强度则随CBA含量的增加而增加;水泥稳定废砖的抗压回弹模量与无侧限抗压强度存在良好的线性关系。     

Effects of cooling rates on microstructures and mechanical properties of Nb-Ti microalloyed steel

The mechanical properties and microstructure of as-cast Nb-Ti microalloyed steel at different temperatures and cooling rates are investigated in this paper. The III brittle zone (700?C900°C) is revealed. The reduction of the hot ductility is due to the film-like proeutectoid ferrite or the Nb(C, N) precipitates along the austenitic grain boundaries. In the temperature range of 850?C1 000°C, with the increase of the cooling rate, the hot ductility decreases. However, in the range of 650?C850°C, the appearance of large volume fractions of ferrite on austenite grain boundaries minimizes the effect of cooling rate on hot ductility. When the cooling rate is 10°C/s, austenite transforms more quickly to ferrite and at a lower temperature a larger amount of ferrite nucleates and precipitates in the grain, which leads to a sharper improvement in the hot ductility at 650°C.     

Direct electrochemical extraction of Ti5Si3 from Ti/Si-containing metal oxide compounds in molten CaCl2

Direct electrochemical extraction of Ti₅Si₃ from pressed cathode pellets comprising of powdered Ti/Sicontaining metal oxide compounds was investigated by using molten salt electro-deoxidation technology.Three groups of mixtures including TiO₂ mixed with SiO₂,Ti-bearing blast furnace slag（TBFS） mixed with TiO₂, and TBFS mixed with high-titanium slag（HTS） were prepared at the same stoichiometric ratio（Ti:Si=5:3） corresponding to the target composition of Ti₅Si₃,and used as the starting materials in this experiment,respectively. The pressed porous cylindrical pellet of the Ti/Si-containing compounds served as a cathode,and two different anode systems,i.e.,the inert solid oxide oxygen-ion-conducting membrane（SOM） based anode system and graphite-based anode system were used contrastively.The electrochemical experiment was carried out at 900-1050℃and 3.0-4.0 V in molten CaCl₂ electrolyte.The results show that the oxide components were electro-deoxidized effectively and Ti₅Si₃ could be directly extracted from these complex Ti/Si-containing metal oxide compounds.     

Photothermal effect for Fe3O4 nanoparticles contained in micelles induced by near-infrared light

Near infrared (NIR) light induced photothermal effect for Fe₃O₄ nanoparticles, contained in Pluronic F127 micelles, has been studied and it exhibits high photothermal converting efficiency. Heat is found to be rapidly generated in micelles containing Fe₃O₄ nanoparticles by NIR laser irradiation. Upon irradiation at 808 nm light and with mass concentration of Fe₃O₄ nanoparticles in 4 g/L, the micelle temperature increase is higher than 34°C for 10min irradiation. The maximum temperature of micelles containing Fe₃O₄ nanoparticles in 4 g/L reaches 62°C.     

气泡混合土抗冻融循环性能试验研究

为解决冻土地区普通路基由于保温性能差导致的路基病害问题,采用保温隔热性能好的气泡混合土作为路基填料,可起到保护冻土、减少病害的作用。为探讨气泡混合土的抗冻性能,选取了不同容重的气泡混合土试件进行冻融循环试验研究,研究气泡混合土质量及强度损失规律,从而获知气泡混合土的容重对其抗冻性能的影响;进而,向气泡混合土试件中掺入玻璃纤维,探讨其对气泡混合土抗冻性能的增强作用。结果表明：气泡混合土的抗冻性能随着容重的增大而提高,表现为容重越大,所能经受的冻融循环次数越多,抗压强度和质量损失率越低;容重为800kg/m3的气泡混合土试件经过15次冻融循环后抗压强度迅速降低,经过100次冻融循环后,试件的质量损失达到9.2%;而容重为1 200kg/m3的气泡混合土试件在经过50次冻融循环后,抗压强度才开始明显降低,经过100次冻融循环后,试件的质量损失只有4.5%。玻璃纤维能显著提高气泡混合土的抗冻性能,其抗压强度损失率和质量损失率明显较未掺纤维的普通气泡混合土要小,且抗压强度和质量损失的速率明显降低;不同容重的气泡混合土试件掺入纤维后,经过50次冻融循环后,试件的抗压强度损失减少50%以上,质量损失减少40%以上。     

大孔隙水泥稳定碎石(CTPB)排水基层性能的室内试验研究

通过室内试验,研究了用于路面排水结构层的大孔隙水泥稳定碎石(CTPB)的材料要求、配合比设计、压实成型方法、强度特性和抗压回弹模量等。得出了以下结论:集料颗粒的最大粒径选择应以排水层的厚度及该层的结构强度要求为基础;水泥含量、C/A及孔隙率Va是影响CTPB排水基层混合料抗压强度最显著的因素;施工中,CTPB排水基层混合料的成型应采用静压成型,不宜采用振动压实;要求集料具有较低的压碎值。     

水泥搅拌砂土强度特性及影响因素研究

兰州至中川机场铁路工程沿线大多地段为饱和黄土地基,设计采取水泥土搅拌桩复合地基加固;该线部分地段饱和黄土地基中含有呈透镜状分布的砂土.对水泥搅拌砂土在不同的水泥和粉煤灰(以下简称"二灰")掺合比、养护龄期、搅拌均匀程度下进行强度特性试验研究,分析了水泥搅拌砂土无侧限抗压强度的变化规律.试验表明:水泥搅拌砂土无侧限抗压强度随二灰掺量的增加而增加,二灰掺入量从7%增加到20%水泥搅拌砂土的无侧限抗压强度增长了160.1%;随养护龄期的增加而增大,7~28d增长较快,28d以后仍有较大程度的增长,龄期90d抗压强度与28d强度有较好的相关性,可以用28d强度预测90d强度,缩短试验周期;随着搅拌均匀程度的提高,水泥搅拌砂土的无侧限抗压强度显著增大,搅拌非常均匀的试件无侧限抗压强度比搅拌极不均匀的试件增长了238%~263%.     

玄武岩纤维水泥砂浆的力学性能研究

以有机聚丙烯纤维为对比,进行了无机玄武岩纤维水泥砂浆的抗压、抗折、抗拉伸及抗弯系列力学性能试验研究。研究结果表明：在最佳掺量下,玄武岩纤维水泥砂浆的各种力学性能优于聚丙烯纤维水泥砂浆;玄武岩纤维对水泥浆体早期具有显著的增强作用,但降低了水泥砂浆的28d强度;掺入玄武岩纤维可以增加砂浆的韧性,对砂浆的抗拉强度改善起到了一定作用;玄武岩纤维对砂浆的抗弯破坏强度改善不显著,但明显增大了相同荷载下试件的挠度。     

废旧塑料颗粒水泥混凝土力学性能研究

从改善混凝土性能以及研究绿色环保材料的角度出发,将废旧ABS／PC塑料颗粒作为一种添加成分,采用体积替代细骨料的方法对水泥混凝土进行改性研究。以C30普通混凝土为基础,研究了水泥混凝土在不同废旧塑料颗粒掺量下的立方体抗压强度、劈裂强度、抗折强度等力学指标的变化规律。研究结果表明：废旧塑料颗粒的掺加能较好地改善水泥混凝土的力学性能,在四种掺量（2％、5％、8％、11％）下,当掺量为5％时,水泥混凝土的立方体抗压强度、劈裂强度和抗弯拉强度均达到最大值。     

水泥低活性粉煤灰钢渣路用性能试验研究

为研究水泥低活性粉煤灰钢渣路用性能,对其抗压强度、干缩性能、冲刷性能、抗疲劳性能进行了室内试验研究,数据分析表明水泥低活性粉煤灰钢渣路用性能优越于水泥钢渣和粉煤灰,因此,建议有条件的地区,道路基层施工可采用水泥低活性粉煤灰钢渣。     

Study on Oxidation Activity of CuCeZrO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Doped with K for Diesel Engine Particles in NO/O<Subscript>2</Subscript>

CuCeZrO_x and KCuCeZrO_x catalysts were synthesized and coated on the blank diesel particulate filter (DPF) substrate and a particulate matter (PM) loading apparatus was used for soot loading. The catalytic performances of soot oxidation were evaluated by temperature programmed combustion (TPC) test and characterization tests were conducted to investigate the physicochemical properties of the catalysts. The reaction mechanism in the oxidation process was analyzed with diffuse reflectance infrared Fourier transform spectroscopy. The results demonstrated that CuCeZrO_x catalyst exhibited high activities of soot oxidation at low temperature and the best results have been attained with Cu_0.9Ce_0.05Zr_0.05O_x over which the maximum soot oxidation rate decreased to 410 °C. Characterization tests have shown that catalysts containing 90% Cu have uniformly distributed grains and small particle sizes, which provide excellent oxidation activity by providing more active sites and forming a good bond between the catalyst and the soot. The low-temperature oxidation activity of soot could be further optimized due to the excellent elevated NO’s conversion rate by partially substituting Cu with K. The maximum particle oxidation rate can be easily realized at such a low temperature as 347°C.     

低温条件下水泥搅拌饱和黄土的强度特性研究

兰州至中川机场铁路工程沿线大多地段为饱和黄土地基,设计采取水泥土搅拌桩复合地基加固.由于该地区冬季气温较低,需要探究温度对水泥搅拌饱和黄土强度的影响,以便确定在冬季温度较低的情况下能否施工以及低温环境下水泥搅拌饱和黄土的强度增长规律.通过室内试验研究低温条件下水泥搅拌饱和黄土无侧限抗压强度随水泥和粉煤灰(以下简称"二灰")掺入比、养护龄期、养护方式的变化规律.试验表明:低温条件下水泥搅拌饱和黄土的无侧限抗压强度也随二灰掺入比增加、养护龄期的增长而增大;低温水中养护条件下水泥搅拌饱和黄土的无侧限抗压强度较标准水中养护(20±1℃)的强度低,龄期为28d、掺入比为12%的抗压强度为标准水中养护条件下的36%,掺入比20%的抗压强度为标准水中养护条件下的33%;随着养护龄期的增大,低温水中养护条件下抗压强度与标准水中养护条件下的差距逐渐增大,龄期为60d、掺入比为12%的抗压强度是标准水中养护条件下的26%.     

纳米水泥混凝土力学特性研究

纳米SiO2是一种新兴的材料,用途非常广泛。水泥混凝土路面存在刚性过大、抗弯拉强度不足的问题。通过在普通水泥混凝土中掺加不同量的SiO2纳米材料,测试纳米水泥混凝土的抗压强度和抗弯拉强度。研究表明:纳米SiO2的掺加能改善水泥混凝土的抗压强度和抗弯拉性能,纳米水泥混凝土抗弯拉强度的改善优于抗压强度。     

Effect of Needle Coke on Gas Permeability of Ceramic Casting Molds

The permeability of a new investment casting mold system prepared by adding needle cokes has been investigated in this work. The permeability tests of the molds were carried out at the temperature of 25–1200 °C. The results showed that the addition of needle cork could significally increase the permeability of the molds by a factor of about 4 because the burning of needle cokes increased the porosities of the molds. Meanwhile, the needle coke modified molds exhibited higher green strength and greater thickness both on flat section and at sharp edges compared with the full fused silica mold. Taking account of the mold thickness, the needle coke modified molds had increased adjusted fracture load (AFL) by a factor of about 2 at the test temperature of 25–1200 °C. The addition of needle coke significally improved the permeability of the molds during both autoclaving and casting, and optimized the correlation between the permeability and green strength of the molds.     

Microwave hydrothermal synthesis and characterization of ZnO nanostructures in aqueous solution

ZnO nanostructures were prepared in aqueous solution by microwave hydrothermal synthesis. Xray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were used to characterize ZnO nanostructures (ZNs). The effects of pH, reaction temperature and reaction time on yield of ZnO were investigated. The yield of ZnO increased significantly with the increase of pH value, reaction temperature and reaction time. High yield and well crystallinity of ZNs could be obtained at 120°C for 60min by microwave hydrothermal synthesis. The spherical and rugby-like ZNs were obtained at 120°C without triethanolamine (TEA) and with TEA (mass ratio, $r = m_{Zn^{2 + } }$ : m _TEA = 1: 1), respectively. The concentration of Zn(OH) ₄ ^?2 ions in the reaction solution and TEA had an important effect on the nucleation and morphology of ZnO nanostructures. Mechanism for the formation of ZnO nanostructures was proposed.     

Catalytic Combustion of Lean Methane Assisted by Electric Field over Pd/Co<Subscript>3</Subscript>O<Subscript>4</Subscript> Catalysts at Low Temperature

A series of Pd/Co₃O₄ catalysts were prepared by Self-Propagating High-Temperature Synthesis (SHS) method in this study, and electric field was applied for catalytic combustion of lean methane over Pd/Co₃O₄ catalysts at low temperature. When electric field was applied, the catalytic combustion performance of Pd/Co₃O₄ catalysts was greatly improved, and the application of electric field could reduce the load of active element Pd to some extent while maintaining the same efficiency. Based on experimental tests and the analysis results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H₂-temperature-programmed reduction (H₂-TPR) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS), the mechanism of catalytic oxidation of CH₄ over Pd/Co₃O₄ catalysts in electric field was proposed. The catalytic combustion of CH₄ occurs only when the temperature is higher than 250 °C normally, but when electric field was applied, the whole process of CH₄ oxidation was promoted significantly and the reaction temperature was reduced. Electric field could promote the reduction of the support Co₃O₄ to release the lattice oxygen, resulting in the increase of PdO_x and the surface chemisorbed oxygen, which could provide more active sites for the low-temperature oxidation of CH₄. Furthermore, electric field could accelerate the dehydroxylation of CoOOH to further enhance the activity of the catalysts.     

多因素对氯氧镁水泥混凝土抗压强度的影响

为了解西部地区氯氧镁水泥混凝土的抗压强度以及田口方法在混凝土配合比中的适应性,针对活性MgO与MgCl₂摩尔比、粉煤灰、耐水性改性剂和减水剂对氯氧镁水泥混凝土抗压强度的影响进行了研究,确定了各因素对氯氧镁水泥混凝土抗压强度的影响程度,并量化表征,提出了多因素共同作用氯氧镁水泥混凝土抗压强度信噪比的多元非线性回归模型. 研究结果表明,最优氯氧镁水泥混凝土28 d抗压强度设计组合为:摩尔比为5.4,不掺粉煤灰,耐水性改性剂为1%磷酸,减水剂为1%,各因素影响程度从大到小的顺序为:减水剂、粉煤灰、摩尔比、耐水性改性剂. 最优氯氧镁水泥混凝土长期抗压强度设计组合为:摩尔比为5.4,不掺粉煤灰,耐水性改性剂为2%磷肥,减水剂为1%,各因素影响程度从大到小的顺序为:摩尔比、粉煤灰、耐水性改性剂、减水剂.      

混凝土复合掺合料火山灰活性与形貌研究

用锂盐渣、粉煤灰按比例复合作为一种新型的混凝土活性掺合料，对该复合掺合料的试验研究表明：锂盐渣掺量对复合掺合料的火山灰活性影响差别较大；对混凝土7d，28d和60d各龄期强度影响也较大。研究中采用了扫描电镜及X衍射等现代测试技术，并对该复合掺合料火山灰活性及复合掺合料水泥浆体水化初期和后期形貌特征进行了深入研究，得出复合掺合料中锂盐渣存在较佳掺量。