DYNAMIC RHEOLOGICAL BEHAVIOR OF POLYPROPYLENE FILLED WITH ULTRA-FINE POWDERED RUBBER PARTICLES

Dynamic rheological characteristics of polypropylene (PP) filled with ultra-fine full-vulcanized powdered rubber (UFPR) composed of styrene-butadiene copolymer were studied through dynamic rheological measurements on an Advanced Rheometric Expansion System (ARES). A specific viscoelastic phenomenon, i.e. 'the second plateau', appeared at low frequencies, and exhibits a certain dependence on the amount of rubber particles and the dispersion state in the matrix. This phenomenon is attributed to the formation of aggregation structure of rubber particles. The analyses of Cole-Cole diagrams of the dynamic viscoelastic functions suggest that the heterogeneity of the composites is enhanced on increasing both particle content and temperature.

Comparison of rheological analytic model with numerical simulation in powder injection molding filling process

Mathematical model of filling disk-shaped mold cavity in steady state was studied.And the mathematical model under vibration field was developed from the model in steady state.According to the model of filling disk-shaped mold cavity in steady state,the filling time,the distribution of velocity field and the pressure field were obtained.The analysis results from rheological analytic model were compared with the numerical simulation results using Moldflow software in the powder injection molding filling process.Through the comparison,it is found that it is unreasonable to neglect the influence of temperature when calculated the pressure changing with the time at the cavity gate,while it can be neglected in other situations such as calculating the distribution of the velocity fields.This provides a theoretical reference for the establishment of correct model both in steady state and under vibration force field in the future.

Effect of Curing Procedure on the Properties of Copper-Powder-Filled Conductive Adhesives

By means of testing the shear strength with single lap joint, measuring electrical resistivity for cured products and the curing strain with strain gauges, the effect of cure parameters on the properties of HT1012 conductive adhesive filled with copper powder was investigated, and the residual stress in the conductive adhesives was also estimated. The experimental results show that the properties such as shear strength of the adhesives, electrical resistivity of products as well as the residual stress of cured HT 1012 copperfitted conductive adhesive were evidently affected by curing temperature and time. The diagrams of scanning electron microscopy （SEM） and Fourier transform infrared （FT-IR） were also used to determine the properties. The higher mechanical property was achieved under the condition of curing the adhesive 3 h at 60 ℃ as the density of the hydrogen links or linkages existed in the adhesive was relatively higher and the lower electrical resistivity occurred at 80 ℃.

Phase evolution of plasma sprayed Al_2O_3-13%TiO_2 coatings derived from nanocrystalline powders

Commercial nanosized alumina and titania particles were selected as raw materials to prepare the blended slurry with composition of A1203-13%TiO2 （mass fraction）, which were reconstituted into micrometer-sized granules by spray drying, subsequently sintering at different temperatures to form nanostructured feedstock for thermal spraying, and then A1203-13%TiO2 nanocoatings were deposited by plasma spraying. The evolution of morphology, microstructure, and phase transformation of the agglomerated powder and as-sprayed coatings were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that A1203 retains the same a phase as the raw material during sintering, while TiO2 changes from anatase to futile. During plasma spraying, some a-A1203 phases solidify to form metastable y-A1203, and the volume fraction of a-A1203 decreases as CPSP increases. However, peaks of the TiO2 phase are not observed from the as-sprayed coatings except for the coatings sprayed at the lower CPSP. As the CPSP increases, nanostructured TiO2 is dissolved easily in y-A1203 or z-A1203＇TiO2 phase. After heat treatment, y-A1203 in the coatings transforms to a-A1203, and rutile is precipitated.

Synthesis of (Ca, Mg)-α′-Sialon-AlN-BN powders from boron-rich blast furnace slag by microwave carbothermal reduction-nitridation

(Ca, Mg)-α′-Sialon-AlN-BN powders were synthesized by the carbothermal reduction and nitridation (CRN) method using boron-rich slag, one of the intermediate products from pyrometallurgy separation of pageit, as the staring material. The influences of synthesis temperature and holding time on the phase composition and microstructure during the microwave CRN were studied by XRD, SEM and EDS. The comparison between two heating techniques, conventional and microwave heating, on the synthesized powder was presented as well. The experimental results revealed that the phase compositions and microstructures of the synthesized products were greatly affected by the synthesis temperature and holding time. With an increase in the synthesis temperature or holding time, the relative amount of α′-Sialon increased and α′-Sialon became the main crystalline phase at 1400 °C for 6 h. The synthesized products also contained AlN, BN and a small amount of β-SiC. Elongated α′-Sialon grains, short rod AlN grains, aggregate nanoscale BN grains were observed in the synthesized powders. The reaction temperature of microwave heating method was reduced by 80 °C, the reaction time was shortened by 2 h, and more elongated α′-Sialon grains with large aspect ratio were observed.

Influences of ZrO_2-SiC Composite Powder and Commercial SiC on Properties of Al_2O_3-C Refractories

In order to improve oxidation resistance and ther- mal shock resistance of Al2O3-C refractories, two groups of specimens were prepared with phenolic resin as binder, adding 0, 2 wt% , 4 wt% and 6 wt% commercial SiC or ZrO2-SiC composite powder synthesized from zircon respectively to Al2O3- C refractories, pressing at 200 MPa, drying fully at 250℃, and then carbon embedded firing at 1400℃ for 2 h. Oxidation resistance and thermal shock resistance were researched, phase composition was analyzed by XRD. The results showed that the oxidation of SiC in additives could protect carbon in specimens effectively and thus decreased the mass loss ratio and oxidation area, and improved the oxidation resistance of the specimen. Thermal shock resistance was improved owing to the micro crack toughening of ZrO2 and grain toughening of SiC. In this experiment, the specimens with 6 wt% ZrO2 -SiC composite powder or 6 wt% SiC powder had the best oxidation resistance and thermal shock resistance.

超细镁渣微粉-水泥复合胶凝材料的性能及水化机理

镁合金被誉为“21世纪绿色工程金属结构材料”,我国皮江法炼镁所得镁渣规模庞大、亟待解决,制备建筑材料是消纳镁渣的重要渠道,但国内外相关研究屈指可数,且普遍以镁渣耦合其他固废及水泥制备复合胶凝材料为主,鲜有针对镁渣-水泥简单体系的细致研究,故镁渣水化及其对水泥水化的影响机制尚未明确。本工作通过探究超细镁渣微粉-水泥复合胶凝材料(MS-C)新拌浆体和硬化浆体的性能、组成及结构演化规律,分析超细镁渣微粉对MS-C水化进程的影响机制,进一步揭示镁渣-水泥的协同水化机理。镁渣中的硅酸二钙以低活性γ-C_(2)S为主,超细粉磨是发挥其填充效应的关键途径,掺入30%的超细镁渣粉使水泥中1000 nm以上孔含量由7.98%降低至6.83%。在减水剂作用下,MS-C浆体的流动性随超细镁渣微粉掺量的增大而增大,在无减水剂时其作用相反。低掺量超细镁渣微粉的水化及弱胶凝作用可增大其填充效应对强度的贡献,并促进Ca(OH)_(2)和C-S-H凝胶的生成,使得低超细镁渣微粉掺量的MS-C获得优于纯水泥的28 d力学性能。本研究获得了超细镁渣微粉-水泥水化特性的基础结论,为提高镁渣资源化利用价值及利用率提供理论依据。

A New Combustion Process for Nanosized BaCe_(0.95)Y_(0.05)O_(3-δ) Powders

Nanosized BaCe_(0.95)Y_(0.05)O_(3-δ) powders with the homogeneous composition were synthesized by a new combustion process based on the Pechini method. A polymeric precursor sol was formed by use of citric acid and ethylene glycol as the chelating agents of metal ions. The perovskite-type BaCe_(0.95)Y_(0.05)O_(3-δ) powders with uniform shape and smaller than 40 nm in sized were obtained through the combustion of the polymeric precursor sol at the existence of nitric acid and ammonium hydroxide. It was found the particle size could be controlled by modulating the quantities of nitric acid and ammonium hydroxide, the quantities of the residue, carbonate ions were also affected by the quantities of the citric acid and ethylene glycol.

Synthesis of La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(3-δ) Powder for Solid Oxide Fuel Cell by a Nitrate-Citrate Combustion Route

A nitrate-citrate combustion route to synthesize La0.9Sr0.1Ga0.8Mg0.2O3-σ powder for solid oxide fuel cell application was presented. This route is based on the gelling of nitrate solutions by the addition of citric acid and ammonium hydroxide, followed by an intense combustion process due to an exothermic redox reaction between nitrate and citrate ions. The optimum technical parameters are that the pH value is 5, and the molar ratio of citric acid to the total metallic ion is 1.5:1. X-ray diffraction characterization of calcined gel shows that pure phase was synthesized after calcination at 1400℃for 10 h, and the TEM result shovvs the calcined powder with average particle size is about 150 nm. The grain resistance contributes to the total resistance of sintered peliet below 500℃. The conductivity of the sintered peliet at 800℃ was 0.07 S-1·cm-1 higher than the conductivity of YSZ (0.05 S-1·cm-1 at 800℃)

轴压作用下CFRP约束钢管-活性粉末混凝土短柱承载力计算模型

通过碳纤维增强树脂复合材料(CFRP)约束钢管-活性粉末混凝土(CFRP约束钢管-RPC)和钢管-RPC轴压短柱破坏过程的异同比较,探讨了CFRP套箍系数和钢管套箍系数对CFRP约束钢管-RPC和钢管-RPC的影响及内在联系,为CFRP约束钢管-RPC短柱承载力的理论分析奠定了基础。基于双剪强度理论,提出了简易的计算模型,基于叠加理论,通过分析核心RPC、钢管和CFRP的应力-应变方程,推导得出了CFRP约束钢管-RPC轴压短柱的理论计算模型,将两类计算模型结果分别与试验实测值相比较,验证了理论式的可取性。

Influences of Al and Si Powders on Microstructure and Hot Mechanical Properties of Al_2O_3-C Slide Plates

The basic formulation of Al2O3- C slide plates was65%（ in mass,the same hereinafter） white fused corundum particles,25% white fused corundum fines,6% active α-Al2O3 micropowder,4% carbon black and flake graphite, and additional 4% phenolic resin.Based on this formulation,3% Al powder,3% Si powder,and 3% Al ＋ 3% Si powder were used to substitute equivalent white corundum fines to improve the hot mechanical properties of Al2O3- C slide plates. The specimens with dimensions of 140 mm × 25 mm × 25 mm were pressed at 150 MPa,dried at 200 ℃ for 24 h,and hot treated at 1 400 ℃ for 3 h in carbon embedded condition. Then hot modulus of rupture and thermal shock resistance of the specimens were tested and the phase compositions and microstructure were analyzed. The results show that specimen with 3% Al powder has the higher hot modulus of rupture but lower residual modulus of rupture after thermal shock than the specimen with3% Si powder; the specimen with 3% Al ＋ 3% Si powders exhibits the highest hot modulus of rupture and the best thermal shock resistance; the change of mechanical property is closely related with the in-situ formed nonoxides： AlN in the form of bars is formed in specimens with Al powder; fibrous SiC whiskers are formed in specimens with Si powder; in the specimens with both Al and Sipowders,besides AlN and SiC whiskers,hexagonal tabular SiAlON is in-situ synthesized,which interlocks with each other.

Effect of Al_2O_3-ZrO_2 Composite Powder on Thermal Shock Resistance of ZrO_2 Sizing Nozzles

ZrO2 sizing nozzles with a basic Jormulation were prepared using 45% （by mass, the same hereinafter ） （ Mg, Y） - PSZ aggregate, 55% （ Mg, Y） - PSZ fines and 5% PVA binder. Al2O3 - ZrO2 composite powders （ 3%, 6%, 9% and 12% ） prepared by sol - gel method were added to replace the equal amount of （ Mg, Y） - PSZfines. Effects of Al2O3 - ZrO2 composite powders on physical properties, phase composition and microstructure of the ZrO2 sizing nozzles were studied. The results show that： the performances of the modified sizing nozzles with 3% Al2O3 - ZrO2 composite powder are better than those of the nobles without composite powder used in current production process, and the thermal shock resistance of the ,former nozzles is six times of that of the latter one.

RPC外包方钢管混凝土柱轴压受力性能研究

为了研究活性粉末混凝土(Reactive powder concrete,RPC)外包方钢管混凝土柱的轴压受力性能,以RPC厚度和长细比为参数,对6根构件开展轴压试验研究,探讨该类组合柱的破坏模式、受力机理、套箍效应和承载力。试验结果表明:外层RPC可为内部方钢管混凝土柱提供较强的约束力,在受力后期套箍效应凸显。随着RPC厚度的增加,组合柱的承载力逐渐提高;随着组合柱长细比的增大,虽然其弹性刚度和承载力逐渐降低,但延性改善。采用ABAQUS软件建立RPC外包方钢管混凝土柱的有限元模型,分析RPC强度、RPC厚度、钢管强度等级、含钢率、内部混凝土强度和长细比等参数对组合柱承载力的影响规律,可得方钢管混凝土柱发挥系数的变化幅值为0.78~1.01。在试验研究、有限元参数分析和理论探讨的基础上,借鉴钢管混凝土结构技术规范,提出了RPC外包方钢管混凝土轴压短柱和长柱的承载力简化计算方法,公式计算值与已有数据样本吻合良好。

Development of Technology and Equipment for Non-destructive Testing of Defects in Sewing Mandrels of a Three-roll Screw Mill 30-80

The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established that multiple cycles of heating up to 600℃ and cooling with water up to 80℃ for about 7 seconds/1 cycle lead to the formation of ridges,shells and cracks on the surface and in the volume of the tool.The loss of structural strength of the material leads to the breakdown of the mandrel during the stitching process.The technique and equipment of magnetic powder control have been developed to establish the dynamics of the growth of internal and external defects of mandrels.An equation is obtained that allows determining the increase in the number of defects in the sewing tool of a screw rolling mill.The technology of non-destructive testing made it possible to develop a rational plan for replacing the sewing mandrels,which allows for predicting the appearance of defects leading to a complex breakdown of the deforming tool at the NPO Pribor machine-building enterprise.

粉剂固定式灌装机机械结构设计

通过对江、浙部分软包装企业的调研发现,便携尿袋里面的吸水防臭粉目前均由人工灌装,灌装次品率高、生产效率低。针对这一现象,提出了一种粉剂固定式自动灌装机。首先确定了灌装机技术方案,接着分别对进给组件、移动组件、尿袋撑口组件、料斗装料组件进行了机械结构设计,并且研制了粉末材料自动灌装机的样机。样机实际使用表明,该设备运行性能稳定,可显著提高生产效率,降低人工成本,提升企业经济效益。

大掺量石灰石粉泡沫轻质土的制备及其性能研究

利用石灰石粉替代部分水泥制备的泡沫轻质土可用作路基的填充材料,达到减小地基的沉降量和附加应力的目的。研究表明:在普通泡沫轻质土体系中,随着石灰石粉掺量增加,泡沫轻质土的流值和强度均逐渐降低,配制设计强度为1.0 MPa的泡沫轻质土,石灰石粉掺量不宜超过20%;而在高性能泡沫轻质土体系中,采用水固比为0.4,减水剂掺量0.2%,且减水剂与泡沫剂具有良好的相容性,石灰石粉的掺量可以达到40%。泡沫轻质土中掺入石灰石粉有利于泡沫的分散,不易形成大孔,大于0.5 mm大孔少,多数孔径在0.2 mm以下,孔径大小不均;孔形呈球状,连通孔少,多为单独的孔。大掺量石灰石粉泡沫轻质土样品的水化产物中C-S-H、CH、AFt和单碳水化铝酸钙C_(3)A·CaCO_(3)·11H_(2)O特征峰明显,石灰石粉具有早期加速水泥水化的作用。

注射成形参数对PEG-PMMAFe-2Ni喂料充模性能的影响

采用自行开发的水溶性PEG PMMA粘结剂 ,讨论了该粘结剂与Fe 2Ni混合的喂料在注射成形阶段各注射参数对成形性的影响。发现参数设定后需注射 5次以上注射过程才趋于稳定 ,注射坯质量密度在各参数下是不变的。注射温度、注射压力、保压压力、注射速度均对注射坯质量或尺寸有影响 ,其中注射压力影响最大 ,注射温度和保压压力影响次之 ,注射速度影响最小。

铝酸酯DL-411与硅烷KH-570偶联剂复合改性粉石英研究

选择适合粉石英矿物特点的铝酸酯DL-411偶联剂和硅烷KH-570偶联剂作为改性剂,利用干法机械力化学改性,通过两种偶联剂之间相互缠绕和交联作用对粉石英进行复合改性,制备高品质的功能填料活性粉石英。复合改性后粉石英产品填充制品的力学性能,有很大的提高。当复合偶联剂用量为0.7%时[硅烷KH-570(g)∶铝酸酯DL-411(g)=1∶1],粉石英改性效果最好。

Bio-oss骨粉在根管充填中的应用研究

目的评价B io-oss骨粉在根尖吸收、根尖区溢脓患牙病例的根管充填中应用的效果。方法选取80例根尖吸收、根尖区溢脓的患牙,根管预备后拍X线片,分别用传统根管填材料以及用B io-oss骨粉糊剂进行根管充填,观察其疗效,随访。结果应用B io-oss骨粉糊剂作为根管充填材料的患者X线片示根尖有新生骨样组织生长,根尖区阴影减少,临床症状消失;传统材料充填的患者X线片示根尖区阴影无明显改变,治疗后复发率高。结论B io-oss骨粉在根尖吸收、根尖区溢脓患牙病例根管充填中应用,可取得较好的临床效果。

Effect of Heat Treatment on Gradient Microstructure and Tensile Property of Laser Powder Bed Fusion Fabricated 15-5 Precipitation Hardening Stainless Steel

This work investigated the gradient microstructure evolution and tensile property of LPBF fabricated 15-5 precipitation hardening stainless steel in post-process direct ageing(DA)and solution treating&ageing(STA).The varied microstructures for austenite and small-sized oxide inclusions at different sample heights in the as-built(AB)condition was generally preserved after DA treatment.However,austenite was almost disappeared,and oxide particle grew significantly after the STA treatment.As a result,the tensile property differences in sample top and bottom for AB and DA conditions did not occur in the STA samples.For the influence of post-process heat treatment,the STA condition had the highest yield strength due to the highest volume fraction of nano-sized Cu precipitates.However,the DA specimen had the highest ultimate tensile strength and elongation owing to the considerable amount of austenite phase and associated transformation induced plasticity effect.