High Temperature Rheological Performance of Graphene Modified Rubber Asphalt

To elucidate the high temperature rheological capability of graphene modified rubber asphalt,three contents of graphene and crumb rubber were prepared by a combination of mechanical agitation and high speed shearing machine,then used dynamic shear rheological test(DSR)and multiple stress creep recovery(MSCR)tests to evaluate.The hardness and softening point with rotational viscosity of samples raised with the addition of graphene,especially the addition of 0.04%.Dynamic shear rheological test revealedthat the dynamic shear modulus G*,rutting factor G*/Sin δ,and zero shear viscosity(ZSV)of graphene-modified rubber asphalt were greatly influenced along with graphene-increased,on the contrary,phase angle δ which characterize the viscoelastic ratio of asphalt decreased.Multiple stress creep recovery(MSCR)tests showed that the graphene-enhanced rubber asphalt had high-temperature stability through non-recoverable creep compliance(Jnr).Based on these findings,graphene-modified rubber asphalt binders with the addition of 0.04% graphene had good viscoelastic properties as well as high temperature rutting resistance performance.In the meantime,G*/Sin δ,ZSV,and Jnr100,Jnr3200 have good correlation,which can reveal the excellent high-temperature stability performance of asphalt.

Rheological properties of oil-based drilling fluids at high temperature and high pressure

The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 ℃ using the RheoChan 7400 Rheometer.The experimental results show that the apparent viscosity,plastic viscosity and yield point decrease with the increase of temperature,and increase with the increase of pressure.The effect of pressure on the apparent viscosity,plastic viscosity and yield point is considerable at ambient temperature.However,this effect gradually reduces with the increase of temperature.The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells.On the basis of numerous experiments,the model for predict the apparent viscosity,plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis.It is confirmed that the calculated data are in good agreement with the measured data,and the correlation coefficients are more than 0.98.The model is convenient for use and suitable for the application in drilling operations.

Experimental evaluation on high temperature rheological properties of various fiber modified asphalt binders

High temperature rheological properties of fiber modified asphalt binders and impact of the type and content on such properties were studied.Three types of fiber,including polyester(PET),polyacrylonitrile(PAN) and cellulose(CEL),a control content(0%) and four levels of fiber content(2%,4%,6% and 8% by total asphalt binder mass) were used with asphalt binders.The high temperature rheological properties,consisting of complex modulus(G*) and phase angle δ,were measured using SHRP's dynamic shear rheometer(DSR) between 46-82 ℃.Experimental results indicate that the changes of G* and tan δ of fiber modified asphalt binders with the increase of test temperature tend to slow down,and the temperature susceptibility is improved obviously compared to that of original asphalt binder.Fiber modification results in the increase of rutting parameter(G*/sin δ) at high temperatures,the decrease of temperature susceptibility,and further improved high temperature performance of asphalt binder.An excellent correlation exhibits between fiber content and high temperature performance of asphalt binder.Moreover,fiber type also has different influences on the improvement of G*/sin δ,G*/sin δ of PET and PAN fiber asphalt binders are both higher than that of CEL fiber,but G*/sin δ of CEL fiber is still higher than that of original asphalt.However,there is a critical fiber content when fibers start to interact with each other.Therefore,based on the critical fiber content and economic consideration,the optimum fiber contents for various fiber-modified asphalt binders are obtained.

Research on deepwater synthetic drilling fluid and its low temperature rheological properties

With the rapid development of deepwater drilling operations,more and more complex technical challenges have to be faced due to the rigorous conditions encountered.One of these challenges is that the drilling fluid used must had good rheological properties at low temperatures and high ability to inhibit hydrate formation.Synthetic drilling fluid has been widely applied to deepwater drilling operations due to its high penetration rate,excellent rheological properties,good ability to prevent hydrate formation,and high biodegradability.A synthetic drilling fluid formulation was developed in our laboratory.The rheological properties of this drilling fluid at low temperatures （0-20 °C） were tested with a 6-speed viscometer and its ability to inhibit hydrate formation was evaluated at 20 MPa CH 4 gas and 0 °C by differential scanning calorimetry （DSC）.Several factors influencing the low temperature rheological properties of this synthetic drilling fluid were studied in this paper.These included the viscosity of the base fluid,the amount of CEMU and organic clay,and the water volume fraction.

Piezoelectric properties of low loss and high Curie temperature (Bi, La)FeO_3-Pb(Ti, Mn)O_3 ceramics with Mn doping

Piezoelectric ceramics of 0.6(Bi0.9La0.1)FeO3-0.4Pb(Ti1-xMnx)O3 (BLF-PTM) for x=0, 0.01, 0.02, and 0.03 were prepared by sol-gel process combined with a solid-state reaction method. The tan? for BLF-PTM of x=0.01 is just 0.006 at 1 kHz, drastically decreasing by using Mn dopants. The TC increases to 490 ℃ for BLF-PTM of x=0.02. Furthermore, Mn modification effectively enhances the poling state and the piezoelectric properties of BLF-PTM. The kp, Qm, d33, and g33 of 0.34, 403, and 124 pC1·N-1 and 37×10-3 Vm·N-1 are achieved for BLF-PTM of x=0.01. The results indicate that Mn modified BLF-PTM is a competitive high power and high temperature piezoelectric material with excellent piezoelectric properties.

Study on Low-Temperature Traction Behavior of a Space Lubricating Oil No.4116

The traction behavior of space lubricating oil No. 4116 was measured and analyzed at various oil inlet temperatures below 0 ℃ and various rolling speeds under normal loads by a test rig simulating the operating conditions of space bearings. A traction coefficient calculation model was presented. The rheological property and rheological parameters of the lubricant at a low oil inlet temperature were analyzed based on the Tevaarwerk-Johnson model. The results showed that the lubricating oil No. 4116 was sensitive to the rolling speed and had lower sensitivity to the normal load. This lubricating oil is more suitable for applications under high speed when it is used below 0 ℃. It behaves as an elastic-plastic fluid operating below 0 ℃. Both the average limiting shear stress and the average elastic shear modulus have a negative correlation with the rolling speed and oil inlet temperature and have a positive correlation with the normal load.

Microstructure and Electrical Properties of Er_2O_3-Doped ZnO-Based Varistor Ceramics Prepared by High-Energy Ball Milling

The microstructure, electrical properties and density of ZnO-based varistor ceramics with different Er2O3 content prepared by high-energy ball milling （HEBM） and sintered at 800℃ were investigated. With increasing Er2O3 content, the ZnO grain size decreases due to the Er-rich phases inhibiting grain growth ; and nonlinear coefficient （ α ） decreases because of the decrease of barrier height （φB） The breakdown voltage （Eb） and density increase, whereas leakage current （IL） decreases with increasing Er2O3 content. The barrier height （φB）, donor concentration （Nd）, density of interface states （Ns） decrease and barrier width （ω） increases with increasing Er2O3 content due to acceptor effect of Er2O3 in varistor ceramics.

Microstructure and electrical properties of Y_2O_3-doped ZnO-based varistor ceramics prepared by high-energy ball milling

Y2O3-doped ZnO-based varistor ceramics were prepared using high-energy ball milling （HEBM） and low-temperature sin- tering technique, with voltage-gradient of 1934-2197 V/mm, non-linear coefficients of 20.8-21.8, leakage currents of 0.59-1.04 μA, and densities of 5.46-5.57 g/cm3. With increasing Y2O3 content, the voltage-gradient increases because of the decrease of ZnO grain size; the non-linear coefficient and the leakage current improve but the density decreases because of more porosity; the donor con- centration and density of interface states decrease, whereas the barrier height and width increase because of the acceptor effect of Y2O3 in varistor ceramics.

Study on the Effect of Fibers on the Properties of Asphalt Mastics

To study the influence of fiber on the properties of asphalt mortar,the properties of lignin fiber,polyester fiber,and basalt fiber were summarized and analyzed respectively.The high-and low-temperature properties of fiber asphalt mortar were studied and analyzed by using three indexes,rutting factor and tensile fracture energy.The results showed that all three kinds of fibers could improve the performance of asphalt mortar to varying degrees,with lignin fiber demonstrating the best effect,followed by basalt fiber and polyester fiber.The type the fiber can be selected based on the required thermal stability and cost depending on the project type.

Lattice distortion and magnetic property of high entropy alloys at low temperatures

Deformation mechanisms and magnetic properties of medium and high entropy alloys(MEA/HEAs)closely relate to lattice distortion and are strongly temperature-dependent,in particular,at low temperature ranges.However,little attention has been paid to the evolution of lattice distortion with temperature decreasing and its effects on deformation behavior and magnetic state transition.In this work,we carry out in situ synchrotron radiation based X-ray powder diffraction(SR-XRD)experiments from 293 to 123 K aiming for determining lattice distortion evolutions of Cr Co Ni MEA,Cr Fe Co Ni and Cr Mn Fe Co Ni HEAs.Magnetic measurements at corresponding low temperatures and cryogenic ranges are further conducted.The in situ SR-XRD results demonstrate a general reduction of lattice distortion magnitude with temperature decreasing,which shows a similar tendency with that of reported stacking fault energy(SFE)values.It is thus suggested that lattice distortion reduction possibly makes a critical contribution to deformation mechanism transition.The magnetic measurement results show a clear ferromagnetic transition of Cr Fe Co Ni HEA when temperature is below 173 K.While,no obvious magnetic state transition is observed for Cr Co Ni MEA and Cr Mn Fe Co Ni HEA.The present findings on lattice distortion evolutions will pave the way for designing targeted HEAs with particular properties.

Improvement of High-Temperature Mechanical Properties of Low-Carbon RAFM Steel by MX Precipitates

To investigate the influence of tantalum content on high-temperature mechanical properties of low-carbon reduced acti- vation ferritic/martensitic （RAFM） steels, RAFM steels containing different tantalum contents （0 and 0.073%） were fabricated, and the tensile tests at room temperature and high temperature were performed, as well as the creep tests were conducted at 550 ~C with the applied stress of 180 and 220 MPa. It was found that 0.073% tantalum addition results in the increase in amount of stable carbonitrides （MX）, and the creep rupture time of the steel under 180 MPa is obviously increased. In addition, the increase in MX caused by tantalum addition also leads to the improvement of high-temperature tensile strength. The improvement of high-temperature mechanical properties of RAFM steels is primarily related to the evolution of precipitates.

Low-temperature combined with high-humidity thawing improves the water-holding capacity and biochemical properties of Portunus trituberculatus protein

This study compared the effects of conventional thawing methods(water immersion thawing(WIT,(25±1)℃),natural air thawing(AT,(25±1)℃,relative humidity(RH(65±2)per cent),refrigerator thawing(RT,4℃,RH(80±2)per cent)and low-temperature(LT)combined with high-humidity thawing LT,-1℃to 1℃(LT-1-1),2-4℃(LT2-4),5-7℃(LT5-7)and 8-10℃(LT8-10),RH>95 per cent)on the water-holding capacity,lipid oxidation and biochemical properties of Portunus trituberculatus(P.trituberculatus)myofibrillar protein.The results showed that WIT and AT significantly decreased the water-holding capacity while dramatically increasing lipid oxidation,protein oxidation and degeneration,resulting in serious P.trituberculatus quality deterioration.High humidity was beneficial for P.trituberculatus\.ha\A/\ng.The thawing time of P.trituberculatus under the conditions of LT2-4 was only 39.39 per cent of that of conventional air thawing at 4℃(RT),and the LT2-4 samples not only maintained better water-holding capacity but also had an obviously reduced degree of lipid oxidation,protein oxidation and denaturation.Thawed samples LT2-4 and LT5-7 provided better maintenance of P.trituberculatus quality than the LT-1-1 and LT8-10 samples.The best quality was exhibited after thawing at 2-4℃.The levels of thiobarbituric acid reacting substances,carbonyl content and surface hydrophobicity observably decreased in these samples,while the total sulfhydryl contents dramatically increased compared to those of conventionally thawed samples,indicating lower lipid oxidation and protein oxidation.Moreover,the Ca2+-ATPase activity of the sample thawed at 2-4℃(2.06 μmol Pi/mg prot/h)was markedly higher than that of samples subjected to WIT and AT.The product qualities observed after thawing at-1℃to 1℃,5-7℃and 8-10℃under LT were comparable to that observed by RT.Considering its thawing efficiency and product quality,LT is a suitable method for the thawing of P.trituberculatus,and the ideal thawing conditions were LT at 2-4℃.

Effects of cooling rate on the microstructure and electrical properties of Dy_2O_3-doped ZnO-based varistor ceramics

The microstructure, electrical properties, and density of Dy2O3-doped ZnO-based varistor ceramics, prepared using high-energy ball milling （HEBM） and sintered at 800℃, were investigated by increasing the cooling rate in the order of H （slow cooling in furnace） → L （cooling in furnace） → K （cooling in air）. With the increase in cooling rate, the grain size and density decreased, the breakdown voltage （VImA/mm） increased, and the nonlinear coefficient （α） and leakage current （IL） exhibited extremum. The sample with the cooling type L showed the best properties with the breakdown voltage of 2650 V/ram, o：of 20.3, IL of 5.2 laA, and density of 5.42 g/cm^3. The barrier height （ФB）, donor concentration （Nd）, density of the interface states （Nd）, and barrier width （ω） all exhibited extremum during the alteration in cooling rate. The different relative amount of Bi-rich phase and its distribution as well as the characteristic parameters of grain boundary, resulting from the alteration of cooling rate, led to the changes in the properties of varistor ceramics.

极端环境温度对硅橡胶材料性能的影响研究进展

硅橡胶材料具有优异的机电性能以及出色的耐高低温性能,在电气绝缘领域具有广泛运用。本文综述了低温、高温对硅橡胶(SR)材料力学性能、电气性能的影响,同时介绍了硅橡胶在低温下的结晶行为以及提高硅橡胶材料热稳定性的方法,最后对硅橡胶材料的未来发展应用趋势进行了展望。

基于PG分级的高寒高海拔地区沥青结合料性能与适应性

为解决高寒高海拔地区沥青结合料性能不足的问题,结合京藏高速公路格尔木至那曲段地形地貌与气候变化特点,依托沿线多个气象观测站的30 a气象资料,对所处地貌、气候特征、海拔、交通荷载量等相关数据进行统计学分析、计算,探索高海拔大温差地区沥青胶结料PG分级方法的适应性。结果表明:基于青藏地区现场监测结果对LTPP高温温度计算模型进行修正,提出了更适合高寒高海拔地区沥青结合料高温温度计算公式,提高了沥青高温性能指标计算公式的可靠性;在京藏高速公路格拉段对沥青胶结料的PG分级建议值最高达到PG76-22,在高寒高海拔地区应充分考虑海拔增高对沥青低温抗裂性能的影响,将低温等级提高1~2级;在那曲地区建议使用SBRⅡ-A改性沥青,在格尔木地区建议使用SBS改性沥青;在沱沱河、五道梁地区,建议开发抗紫外温拌改性沥青,采用更高标号的基质沥青对沥青进行SBS/SBR复合改性,并进行适用性研究。本次研究成果为高寒高海拔地区沥青结合料的材料开发技术、施工工艺提升及工程化应用提供一定参考,有利于提高沥青路面修建质量,延长使用寿命。

共混GAP基含能热塑性弹性体的氢键行为与力学性能

为了改善GAP热塑性弹性体的力学性能,采用了DSC、低场核磁测试、静态力学测试和动态力学测试的方法对两种异氰酸酯固化的弹性体共混体系的氢键行为和力学性能进行分析,建立微观结构与宏观性能的关系。结果表明,由于分子结构原因,HMDI固化的GAP热塑性弹性体和IPDI固化的弹性体显示出不同的氢键行为和力学性能,通过物理共混得到了兼具抗拉强度及断裂延伸率的弹性体,50℃下抗拉强度高于1.5MPa,-40℃下延伸率不低于300%,相较于纯HMDI固化的弹性体,低温延伸率提升了约150%,IPDI固化的弹性体高温抗拉强度提升了约1.4MPa,说明通过共混可得到性能更为均衡的含能热塑性弹性体。

低温冲击磨处理对银耳及其多糖性质的影响

【目的】探究低温冲击磨超微粉碎处理对银耳及其多糖性质的影响,以期为银耳的精深加工及活性成分提取提供理论依据。【方法】利用低温冲击磨的不同分级机频率(10、20、30和40 Hz)粉碎干燥银耳,并通过水提醇沉法提取银耳多糖,对不同银耳粉的基本营养成分、物理性质及银耳多糖的基本理化性质、流变特性、结构等进行测定,探究分级机频率对银耳粉及其多糖的影响。【结果】随着分级机频率的增加,银耳粉的水分含量(10.41%~12.18%)逐渐降低,而蛋白质和灰分含量无显著差异(P>0.05);银耳粉颜色由黄色逐渐变为白色,表现为L^(*)增加、a^(*)和b^(*)均降低;平均粒径D_(50)(47.7~389.0μm)显著降低(P<0.05),持水力(2.90~3.63 g/g)增加,持油力(2.67~3.36 g/g)增加,粉末流动性降低。与未经低温冲击磨处理银耳粉提取多糖的性质相比,低温冲击磨处理后银耳粉提取多糖的得率(5.23%~13.88%)及中性糖(63.71%~74.12%)、糖醛酸(24.17%~28.60%)含量增加,蛋白质含量(0.29~0.65 g/g)降低。此外,分级机频率为30 Hz时,多糖的分子量最低,为15400 kD;不同银耳多糖均以甘露糖为主要单糖,其余由核糖、鼠李糖、葡萄糖醛酸、半乳糖醛酸、葡萄糖、半乳糖、木糖、岩藻糖组成。多糖Zeta电位绝对值随分级机频率增加整体呈增加趋势。流变特性测定结果表明,不同银耳多糖溶液均属于非牛顿流体,且分级机频率为20 Hz时,溶液的黏度最高。红外光谱及X射线衍射结果表明,不同分级机频率银耳粉提取的多糖均不会产生新官能团,为无定型结构。【结论】低温冲击磨粉碎能改善银耳粉色泽,改变银耳粉粒径及流动性,提高多糖得率,也影响银耳多糖的流变性质,但不会改变多糖的单糖组成和基本结构。

青川岩沥青/SBS复合改性沥青流变性能及疲劳特性研究

为探究青川岩沥青(Qingchuan rock asphalt,QRA)和SBS在桥面铺装中的应用,以2%,3%SBS和5%,10%,15%QRA为改性剂,制备得到6组QRA/SBS复合改性沥青(QRA/SBS composite modified asphalt,QSMA),综合研究QSMA基本路用性能、微观改性机理、高温流变性能和疲劳特性。结果表明,QRA能够提高QSMA软化点并降低针入度,SBS对提升QSMA的5℃延度有利。特征官能团显示QSMA与基质沥青含有相同烃类化合物,QSMA改性机理为物理改性。QRA和SBS掺量的增大能提高沥青的变形阻力,抑制沥青不可恢复形变的产生,进而提升QSMA抵抗高温车辙变形的能力。QRA和SBS的加入可提高沥青的劲度和弹性。QRA和SBS能提升沥青基体抵抗疲劳断裂的能力,表现出更小的应变依赖性和更好的抗疲劳性。综合三大指标、高温流变实验与疲劳实验结果,推荐最优掺量组合为3%SBS+15%QRA。

小麦低温制粉系统各粉路小麦粉品质特性差异性研究

通过对小麦低温制粉系统各粉路小麦粉品质特性的研究,可为开发不同专用小麦粉提供参考。以低温制粉系统的4个皮磨粉、6个心磨粉、1个渣磨粉和1个尾磨粉共12个粉路样品和通路粉(该批次市场产品)面粉为研究对象,通过测定小麦粉品质和面团流变学特性,比较分析不同粉路小麦粉品质差异。结果表明,心磨粉路1M、2M、3M和渣磨粉路的小麦粉光泽度高;心磨粉路蛋白质含量、湿面筋含量、面筋指数普遍低于皮磨粉路;皮磨和心磨粉路的靠前粉路小麦粉灰分和损伤淀粉低于靠后粉路,峰值粘度高于靠后粉路。皮磨和心磨的靠后路粉的吸水量(500 FU)高于靠前路粉;皮磨粉路小麦粉的P值、W值、L值、G值、能量和最大拉伸阻力普遍高于心磨粉路,但延伸度普遍低于心磨粉路。

PPA对基质沥青及SBS改性沥青流变特性影响研究

为了研究PPA对基质沥青及SBS改性沥青流变性能的影响规律及差异性,借助动态剪切流变仪(DSR)及弯曲梁流变仪对PPA改性沥青及PPA/SBS复合改性沥青在高温和低温下的流变性能进行研究,将PPA改性沥青及PPA/SBS复合改性沥青的试验结果进行对比分析。试验结果表明:PPA使沥青的相位角减小,车辙因子显著提高,可改善沥青的高温性能且对SBS改性沥青的影响更显著;PPA提高了沥青蠕变恢复率,降低了沥青的不可恢复蠕变柔量,但提高了沥青的应力敏感性;PPA提高了沥青的劲度模量、降低了蠕变速率,会对沥青的低温性能产生不利影响且对SBS改性沥青的影响更明显。