动态条件下PCC/PEG分散体系的剪切增稠及耗能行为

采用AR2000ex流变仪对沉淀碳酸钙(PCC)在聚乙二醇(PEG200,平均相对分子质量为200)分散体系中进行动态扫描实验,研究不同固定频率条件下该分散体系的应变剪切增稠及耗能行为。应力—应变曲线(LISSAJOUS曲线)及其归一化曲线表明,在固定频率下随着应变增大,LISSAJOUS曲线围成的面积增大,即体系消耗的能量增大,同时分散体系由线性粘弹性体系转变非线性粘弹性体系。分散体系消耗的能量Ed与应变幅度(γmax)满足以下关系:Ed=K(γmax)α,在剪切变稀区内α≈2,在剪切增稠区内α远大于2。另外还研究了频率(ω)对体系消耗能量Ed的影响,并确立了剪切增稠区的耗能指数(α)与频率(ω)的关系为α∝ω0.23±0.01。这种临时的,亚稳定的"粒子簇"导致可逆的剪切增稠,而这种长大的"粒子簇"阻碍体系的流动,从而使之需要额外的能量。     

矿物原料对保护渣物理化学性能的影响

实验室内通过配比不同矿物原料的保护渣系（/%:29~39水泥熟料,8硼砂,16~24石英,11~19硅灰石,8~16萤石,10~18纯碱）研究石英、硅灰石、萤石、纯碱对保护渣熔点、黏度、结晶温度、临界冷却速度的影响。试验结果表明,随着基料矿物石英、硅灰石含量增加,保护渣熔点、黏度增加,石英对熔点和黏度的影响明显大于硅灰石;随熔剂矿物萤石、纯碱含量增加,保护渣的熔点和黏度降低,萤石对降低黏度的作用显著,纯碱对降低熔点的作用相对较大;石英、硅灰石、纯碱含量增加,保护渣临界冷却速度减小,结晶温度降低,结晶能力减弱;相反,萤石含量增加,保护渣临界冷却速度却增大,结晶温度升高,说明萤石具有促进保护渣结晶的作用。最终得出包晶钢板坯连铸最佳保护渣配比为（/%）:37水泥熟料,8硼砂,20石英砂,15硅灰石,10萤石和10纯碱。     

TA17钛合金热力学行为及加工特性研究

为了研究TA17钛合金热轧条件下的高温变形行为及热加工特性,在热模拟机上开展变形温度为700~1100℃、应变速率为1~40 s~(-1)条件下的热压缩实验,建立基于Arrhenius模型的本构方程,以及应变分别为0.3和0.6时的热加工图,结合热变形显微组织分析,研究该合金的热塑性变形机制。结果表明:TA17钛合金流变应力随着变形温度的升高而降低,随着应变速率的升高而升高。在温度为800~1000℃、应变速率为1~10 s~(-1)时,材料的变形机制主要为动态再结晶;温度为1000~1100℃、应变速率为1~10 s~(-1)时,材料发生动态回复;温度为700~800℃或1000~1100℃、应变速率大于20 s~(-1)时,材料产生绝热剪切带;温度为700~800℃,应变速率为1~5 s~(-1)时,材料易产生裂纹。得出该合金较优的热轧工艺参数为:变形温度800~1000℃,应变速率1~10 s~(-1)。     

刚果(金)某氧化铜精矿还原熔炼渣物化性能研究

针对刚果(金)某氧化铜精矿中高硅、低铁的特性,通过高温马弗炉还原熔炼试验,考察了碱度和FeO对熔渣形貌、熔点、密度、黏度及电导率的影响。结果表明,该体系熔渣主要以硅酸钙的玻璃相存在,Mg、Al及Fe分散在其中。随着碱度从0.2增加到0.6,熔渣熔点先降低后升高,黏度先增大后减小,密度先减少后增大,电导率呈上升趋势;随着FeO含量从6%增加到10%,熔渣熔点和黏度呈下降趋势,密度和电导率呈上升趋势。适合本体系熔渣的碱度为0.5左右,FeO加入量6%,则熔渣熔化温度1 250℃,黏度2Pa·s(1 400℃),密度2.6～3.0g/cm~3。此时,粗铜品位达到96.5%,铜收得率超过98%。     

含钛高炉渣黏度和熔化性能

 基于混料试验中单纯形质心法建立了CaO-SiO₂-Al₂O₃-MgO-2%TiO₂渣黏度和熔化性能预测模型,利用预测模型、FactSage和X射线衍射(XRD)研究了不同w(Al₂O₃)含钛炉渣的冶金性能,并探讨了高Al₂O₃炉渣中w(MgO)/w(Al₂O₃)对黏度和熔化性能的影响。结果表明,炉渣黏度和熔化性能预测模型具有较高的精度,误差分别小于5%和2%。随着Al₂O₃质量分数由10%增加至18%,黏度(η)、熔化性温度(t_M)和液相线温度(t_L)均升高;低熔点相黄长石(Melilite)开始析出温度和析出量逐渐增大,高熔点相钙钛矿(CaTiO₃)和低熔点相硅灰石(CaSiO₃)开始析出温度先增大后减小,还析出了少量高熔点相尖晶石。当Al₂O₃质量分数小于15%、温度为1 450～1 525 ℃时,炉渣黏度均小于0.55 Pa·s,且温度为1 500 ℃时黏度为0.32～0.39 Pa·s,t_M和t_L分别为1 370 ℃和1 330 ℃;Al₂O₃质量分数为15%～18%,炉渣析出的高熔点相CaTiO₃和尖晶石较多,黏度对温度较为敏感,1 525 ℃时黏度为0.3 Pa·s左右,1 450 ℃时黏度增加至0.8 Pa·s。随着w(MgO)/w(Al₂O₃)由0.24增加至0.72,炉渣黏度降低,t_M和t_L增大;Melilite开始析出温度约为1 425 ℃,CaTiO₃开始析出温度由1 310 ℃大幅增加至1 394 ℃,CaSiO₃析出量降低,尖晶石析出量明显增加。此外,不同w(Al₂O₃)和w(MgO)/w(Al₂O₃)炉渣基础相均为Melilite,其开始析出温度高于CaTiO₃;w(Al₂O₃)对t_M和Melilite开始析出温度影响显著,w(MgO)/w(Al₂O₃) 对t_L和CaTiO₃开始析出温度影响显著。当碱度为1.21时,高Al₂O₃炉渣适宜w(MgO)/w(Al₂O₃)为0.48～0.60,t_M和t_L分别为1 400 ℃和1 340 ℃左右,炉渣流动性和稳定性较好。     

Ti-6Al-4V粉末注射成形喂料流变主曲线的生成

从流变学基本理论出发,讨论剪切速率、温度与Ti-6Al-4V粉末注射成形喂料的剪切粘度的关系。结果表明:随剪切速率增加,喂料的粘度降低;随温度升高,喂料的粘度下降;且喂料在不同温度下的粘度曲线形状相似,只是位置因温度不同而发生相对位移。在此基础上应用由"时温等效原理"发展而来的(0/??~???0)主曲线生成方法获得Ti-6Al-4V合金粉末喂料的流动主曲线。借助该主曲线,对于进一步研究金属粉末注射成形(MIM)喂料的其它特性以及生产实践大有益处。     

Custom 450高强度不锈钢的动态再结晶行为

为了探究Custom 450钢的动态再结晶行为,采用Gleeble-3800热模拟试验机,在变形温度为1 050～1 200℃和应变速率为0.01～10 s~(-1)的变形条件下开展了单道次等温压缩试验。研究结果显示,在变形温度为1 050～1 200℃和应变速率为1.0～10 s~(-1)的变形范围内,钢虽发生了完全的动态再结晶,但应力应变曲线未表现出明显的应力峰值;钢的动态再结晶的晶粒尺寸随着变形温度的升高和应变速率的降低逐渐增大,当应变速率为0.01 s~(-1)时,动态再结晶晶粒发生长大。采用双曲正弦函数构建了Cutom 450钢的热变形方程,并建立了钢的动态再结晶动力学、临界应变、峰值应变及动态再结晶晶粒尺寸与Zener-Holloman参数的定量关系。     

甘油溶液的泡沫化行为

采用常温甘油溶液体系模拟高钛型高炉渣,通过系统的实验研究了黏度、表面张力和固体颗粒掺杂对泡沫化行为的影响。实验结果表明:随黏度的增加,溶液泡沫化指数先增加后减小,也即涨泡性能先增强后减弱,黏度为93.6mPa·s时达到最大。相同的气体表观速率下,泡沫高度随表面张力的减小而增加;表面张力相同时,泡沫高度随表观速率的增加而增加。表观速率一定时,泡沫高度随固体颗粒PPS含量的增加而增增加,随固体颗粒PPS粒径的减小而增大。同一表观速率下,随着滤板孔径的增大,泡沫高度显著降低。     

中高密度系列钨镍合金粉末注射成形喂料的流变性能研究

利用XLY-Ⅱ型毛细管流变仪研究3种不同密度(分别为10g/cm3、14 g/cm3、17g/cm3)的钨镍合金粉末注射成形喂料的流变行为,分析了剪切速率、温度以及钨镍成分配比对喂料流变性能的影响。实验结果表明,钨镍合金喂料是一种假塑性流体,其表观粘度随剪切速率的增大、温度的升高而减小;非牛顿指数随温度的升高而增大;钨在合金中所占比重越大,喂料对剪切速率的变化及温度的变化越敏感。     

TC27钛合金的热变形行为及加工图

通过Thermecmaster-Z热模拟试验机,对TC27钛合金在变形温度900～1 150℃和应变速率0. 01～10 s~(-1)范围内进行等温恒应变速率热压缩实验,压缩变形量为50%。结果表明,流变应力随应变的增加迅速增大,达到峰值后随应变的增加而减小,最后趋于相对稳定。流变应力随着温度的增加而减小,随着应变速率的增加而增大。TC27钛合金加工图有2个耗散效率峰值区,一个是900℃/0. 01 s~(-1),此区域变形时出现动态回复;另一个峰值区为1 050℃/0. 01 s~(-1),此区域变形时出现再结晶。     

Psychosocial rehabilitation for the mentally disabled: what have we learned?

To investigate the possibility of hemodilution with oxygen carrying fluid, we measured the viscosity effects of LEH which was suspended in different weight percentage of plasma expanders for different shear rates. All of LEH/Plasma expander suspensions show shear thinning flow behavior, and the viscosity of those suspensions increase with increased the weight percentage of each expander in suspensions for a fixed shear rate. Compared the viscosity data to those of human blood at 40% of hematocrit, LEH/albumin suspensions contained with 4% to 8% of albumin are the most suitable, whereas LEH/dextran (Dex) suspensions contained with 6% Dex70c is the least favorable suspension media for LEH. In point of viscosity effects, hemodilution with LEH/albumin or LEH/0.9% oxypolygelatin (Gel) may be valuable for further testing their efficacy in animal model.     

溶剂热法合成CoS纳米晶及其表征

以六水合硝酸钴(Co(NO3)2·6H2O)和硫脲为原料,采用混合溶剂热法制备硫化钴(COS)纳米晶.利用X射线衍射(XRD),扫描电镜(SEM)和透射电镜(TEM)对硫化钴纳米晶的组成、粒径及表面形貌进行表征.结果表明,在180℃恒温条件下所得粉末样品为六方相CoS纳米粉末,粉末粒径在40nim左右.粉末的产率随温度...     

On the Trail of Better Dispersion: Rheological Characterization of Moderately Loaded,Finely Balanced,Negatively Buoyant Ceramic Suspensions

This work aims at finding the best dispersion in a series of alumina suspensions stabilized with the help of different dosages of an electrosteric dispersant phosphate ester. Time dependent viscosities of these suspensions were measured with the help of a conventional Brookfield viscometer at low shear rate domain of 1–8 sec^–1. Sedimentation tests, microscopic observations and gloss value measurement show that some of these suspensions are well-dispersed and some of them are flocculated. Time dependent viscosity measurements for all the well-dispersed suspension and a flocculated suspension were carried out in a conventional Brookfield viscometer. Interestingly, all the well-dispersed suspensions show positive drifts in viscosity with time at a constant shear; however, the magnitude of drifts differed for these suspensions. Rheological measurements show strong evidences of shear induced hydrodynamic migration occurring under the action of the applied shear rates for the well-dispersed suspensions. On the other hand, the flocculated suspensions show just the reverse behavior. Application of short-time shear ramp and long-time shear ramp on the well-dispersed suspensions shows interesting variations. ESA studies conducted for these suspensions showed strong signatures of varying particle sizes for each of these suspensions. The present investigation shows strong indication that the physics behind shear induced diffusion may be utilized to characterize and identify the best dispersion in a series of finely balanced negatively buoyant particulate suspensions by studying the time-dependent viscosities of these suspensions under low shear conditions.     

The Influence of Surface Chemistry on the Rheology and Flow of Flocculated Particulate Suspensions

Abstract

The role of the surface chemistry of particles in controlling the rheology of flocculated particulate suspensions is discussed. The case is developed for the measurement of the shear yield stress of a suspension of alumina particles and a theoretical interpretation of the yield stress is presented which is able to describe the effect of particle size distribution, solid loading, pH and hence, electrokinetics of the suspension. Scaling of the data to the maximum yield stress at a given volume fraction provides a means of removing particle size and volume fraction related effects and gives information as to the mode of failure in yielding of suspensions and the mode of action of molecular additives.     

溶胶-凝胶法制备95多品氧化铝纤维

以结晶氯化铝、铝粉和硅溶胶为主要原料,用溶胶-凝胶法制备95多晶氧化铝纤维.研究了PEG的加入量和胶体黏度对纤维平均直径和单丝拉伸强度的影响,并对不同温度烧成的纤维单丝拉伸强度和比表面积进行了对比.结果表明:当PEG加入质量分数为4%、胶体黏度为30 Pa·s时,纤维平均直径为3.7 μm,且拥有较好的强度;纤维的比表...     

Effect of formulation on the rheology of theophylline compound suspensions in Gelucires

The theophylline derivatives, etofylline, diprophylline and proxyphylline, which exhibit increasing aqueous solubility, were used to prepare suspensions in seven saturated polyglycolyzed glycerides (Gelucires) characterized by their rising hydrophilic-lipophilic balance (HLB). Drug concentration was set at 25% w/w and the production temperature was set at the Gelucire melting point plus 30 degrees C in order to obtain suitable suspensions. Various formulation factors were studied. Ostwald flow indices revealed that the suspensions had a thixotropic shear-thinning behaviour and a relative viscosity which increased as drug aqueous solubility rose and Gelucire HLB decreased. These rheological properties could be explained by the chemical composition of Gelucires and drugs used. A microstructure was proposed for the liquid suspension such that colloidal particles and aggregates formed in these suspensions directly influenced the observed rheological properties. Observation of solidified suspensions by scanning electron microscopy confirmed this hypothesis. Moreover, a correlation between the relative viscosity of drug suspensions on the one hand and drug concentration, drug solubility and Gelucire HLB on the other allowed for the calculation of the required concentration of each theophylline derivative in each Gelucire to obtain a given viscosity.     

CCT and TTT Diagrams to Characterize Crystallization Behavior of Mold Fluxes

The isothermal and non-isothermal experiments were performed to construct the continuous cooling transformation （CCT） and temperature time transformation （TTT） diagrams of four industrial mold fluxes through visual observations in an experimental apparatus based on the single hot thermocouple technique （SHTT）. The results of the CCT diagrams indicate that ① the crystallization temperature of mold fluxes lowers as the cooling rate increases, ② the mold fluxes have larger critical cooling rate, higher crystallization temperature, and less onset time of crystallization when the basicity increases or the viscosity decreases, ③ the influences of the melting points of the mold fluxes on their crystallization tendency are not significant. Isothermal tests show that the onset time of crystallization decreases at first, and then increases, and finally represents a ＂C＂ shape with increasing isothermal temperature. The TTT diagrams of four industrial mold fluxes were divided into two separate ＂C＂ shape regions. The crystal phase of C20A selected was analyzed by X-ray diffraction, which is cuspidine （Ca4 Si2 O7F2 ） over I 100 ℃ and calcium silicon oxide fluoride （Ca2SiO2F2） below 1 100℃. When compared with the TTT diagram, the CCT diagram can provide a more realistic estimate of the critical cooling rate of the mold fluxes. Thus, both the CCT and TTT diagrams can unambiguously describe the crystallization phenomena of the mold fluxes.     

活性填料对聚碳硅烷基悬浮液直写成形3D碳化硅的影响

分别采用纳米钛粉(Ti)和氧化亚镍粉(NiO)为活性填料,聚碳硅烷(polycarbosilane,PCS)为碳化硅(SiC)陶瓷先驱体,以正己烷作为溶剂制备浆料,然后通过3D直写成形和高温裂解制备SiC陶瓷基复合材料,对浆料的流变性能以及SiC陶瓷基复合材料的物相和微观形貌进行表征,研究活性填料纳米Ti粉和纳米NiO粉对3D-SiC陶瓷基复合材料的物相与微观形貌的影响。结果表明,浆料的黏度与PCS的质量分数成正比,具有剪切变稀现象,w(PCS)为75%的浆料具有稳定的打印性能。纳米Ti粉可有效降低成形坯体热处理过程中的质量损失率和线收缩率。随m(Ti)/m(PCS)的值从0增加到1.0,1 450℃高温裂解后陶瓷的质量损失率和线收缩率分别由18.29%和24.38%降低至14.05%和12.13%,所得陶瓷包含Ti C和SiC两相,相比于Ti粉,NiO可作为SiC的表面修饰催化剂,并通过气-液-固(V-L-S)生长机制使SiC陶瓷表面原位生长SiC晶须团簇。     

ZrO2悬浮液性能研究

采用乙醇为溶剂，PVB为分散剂和粘结剂，对固相的质量分数为55％的ZrO2悬浮液的制备和性能进行了研究。通过测定悬浮液的粘度和最终沉降体积，确定最佳分散剂含量。悬浮液的制备分两个阶段：第一阶段，悬浮液由ZrO2粉、乙醇和质量分数为0．7％的PVB(分散剂)组成，球磨24h，目的是打开颗粒团聚体和润湿粉料；第二阶段，主要是使悬浮液与粘结剂的混合，分别加入不同量的PⅦ(粘结剂)，球磨24h。结果表明，分散剂含量为粉体质量的0．7％时，能使ZrO2粉末得到良好的分散；当粘结剂含量少于6％时，在涂层坯体过程中容易出现裂纹；而粘结剂含量高于6％时，悬浮液中含有较多的气泡。加入0．7％分散剂和6％粘结剂，可以获得粘度适中、悬浮稳定的ZrO2悬浮液。