EFFECT OF PAN-MILLING ON RHEOLOGICAL PROPERTIES OF HIGH DENSITY POLYETHYLENE*

The effect of pan-milling on the rheological properties of high density polyethylene (HDPE) was studied. Aninnovative milling apparatus, viz. an inlaid pan-mill, was used. Melt indexer, capillary rheometer, Haake Rheocord 90 single-screw extruder and Brabender rheometer were used to evaluate the rheologieal properties of HDPE. HDPE with higher initialmolecular weight and larger particle size was easier to degrade under pan-milling stress, as indicated by the melt index.Pressure oscillation in capillary flow occurred at significantly higher shear stress and shear rate for milled HDPE than forunmilled HDPE. The apparent shear viscosity of HDPE decreased with increasing times of milling. After milling, the flowactivation energy decreased and thus the sensitivity of viscosity to temperature was reduced. Die pressure and torque duringsingle screw extrusion were reduced significantly after milling. Plasticizing time as measured in a Brabander mixer decreasedmarkedly with increasing milling times.     

Improvement of Li+ conductivity in ball-milled LiI and the local structure analysis by pair distribution function based on X-ray total scattering

Journal of Solid State Electrochemistry - The effects of ball milling on the ionic conduction properties of LiI are investigated. It is found that ball milling drastically increased the...     

Catalytic effect of nanoparticle 3d-transition metals on hydrogen storage properties in magnesium hydride MgH2 prepared by mechanical milling

We examined the catalytic effect of nanoparticle 3d-transition metals on hydrogen desorption (HD) properties of MgH(2) prepared by mechanical ball milling method. All the MgH(2) composites prepared by adding a small amount of nanoparticle Fe(nano), Co(nano), Ni(nano), and Cu(nano) metals and by ball milling for 2 h showed much better HD properties than the pure ball-milled MgH(2) itself. In particular, the 2 mol % Ni(nano)-doped MgH(2) composite prepared by soft milling for a short milling time of 15 min under a slow milling revolution speed of 200 rpm shows the most superior hydrogen storage properties: A large amount of hydrogen ( approximately 6.5 wt %) is desorbed in the temperature range from 150 to 250 degrees C at a heating rate of 5 degrees C/min under He gas flow with no partial pressure of hydrogen. The EDX micrographs corresponding to Mg and Ni elemental profiles indicated that nanoparticle Ni metals as catalyst homogeneously dispersed on the surface of MgH(2). In addition, it was confirmed that the product revealed good reversible hydriding/dehydriding cycles even at 150 degrees C. The hydrogen desorption kinetics of catalyzed and noncatalyzed MgH(2) could be understood by a modified first-order reaction model, in which the surface condition was taken into account.     

An environmental friendly approach for recycling of post‐vulcanized fluoroelastomer scraps through high‐shear mechanical milling

An environmental friendly approach for partial de‐crosslinking of post‐vulcanized fluoroelastomer (FKM) scraps through high‐shear mechanical milling has been developed for recycling of the FKM. The method not only overcomes the expensive use and recovery of organic solvents but also gives rise to reclaimed rubbers with superior mechanical properties. After 32 cycles of milling, the gel fraction of FKM decreased from its original 97.8% to 79.7%. The appearance of the –CF₂‐associated peaks C1s spectra after mechanical milling confirmed the partial de‐crosslinking of FKM. The structure change of FKM sol part before and after mechanical milling was also investigated by Fourier transform infrared (FTIR) analysis and gel permeation chromatography (GPC) measurements. The reclaimed FKM exhibited excellent mechanical and thermal properties, indicating a strong potential for future applications. The tensile strength of FKM re‐vulcanizates is 6.6 MPa, retaining about 84% properties of virgin FKM vulcanizates (7.9 MPa), and the elongation at break was increased from 337.1% to 368.7%. Copyright © 2010 John Wiley & Sons, Ltd.     

CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles structural and magnetic stability relative to ball milling

The combustion method has been utilized to generate cobalt spinel ferrite nanoparticles. The generated nanoparticles were ball milled for different times. Physical and chemical properties of the nanoparticles were characterized by X- ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). Crystalline structure of the nanoparticles was stable after ball milling. FTIR showed that oxygen-metal bonding was stronger after ball milling. Moreover, the ball milled nanoparticles magnetically were harder than the nanoparticle without ball milling.     

机械球磨固相化学反应制备AlH3及其放氢性能

以LiAlH4和AlCl3为原料, 采用机械球磨固相化学反应方法制备了铝氢化合物, 通过X射线衍射(XRD)、热分析(TG-DSC)和质谱(MS)分析等方法对反应产物进行分析和表征, 研究了不同球磨时间(4、8、15和20 h)对LiAlH4+AlCl体系的固相反应转变规律﹑合成产物和放氢性能的影响. 研究结果表明, 随球磨时间的增加, 球磨固相反应按3LiAlH4+AlCl3→4AlH3+3LiCl方向进行, 形成了非晶态铝氢化合物AlH3, 球磨20 h时反应基本完全. 球磨产物的放氢动力学特性随球磨时间增加而改善, 其放氢起始温度均低于100 ℃, 最大放氢量达到2.6%-3.6%(H2)(w), 接近反应体系的理论储氢量4.85%(H2)(w). 球磨过程中反应产物形成LiCl·H2O以及少量AlH3发生分解是影响球磨产物最大放氢量的主要因素.     

二种或多种添加元素及机械球磨对钒磷氧化物的性能调变

钒磷氧化物（VPO）是目前由正丁烷选择氧化制顺酐的最为有效的催化剂体系犤１，２犦。这是极为复杂的一类催化剂体系，虽然对其进行过较多研究，但对反应活性位等问题尚未有很好的认识犤３，４犦。VPO催化剂的一个重要特点是不同制备条件对催化剂的结构及反应性能有很大的影响，而其它元素的引入可以提高丁烷的转化率或马来酐的选择性，但对引入组份的确切作用尚不清楚犤５犦。Hutchings等曾对不同种类的单一添加元素进行过系统的比较研究犤６犦，但对二组份及二组份以上添加组份的研究鲜有报道。在实用VPO催化剂中常含有二种以上的添加…     

Influence of Homogenizing Methodology on Mechanical and Tribological Performance of Powder Metallurgy Processed Titanium Composites Reinforced by Graphene Nanoplatelets

In the present work, 0.25 wt%GNP-Ti composites were prepared through powder metallurgy route by adopting three types of mixing modes to investigate the extent of mixing on the mechanical and tribological properties. Dry ball milling, wet ball milling, and rotator mixing were independently employed to homogenize the composite constituents. Three types of composite powders obtained were subsequently sintered into composite pellets by cold compaction followed by vacuum sintering. Morphological investigation of composite powders performed by SEM revealed better homogenization of GNPs in Ti matrix for dry ball milled composite powder, whereas wet ball milled and rotator mixed composite powders showed aggregation and bundling of GNPs. Micro Vickers hardness of composites produced via dry ball milling is 4.56% and 15.7% higher than wet ball milled and rotator mixed samples, respectively. Wear test performed by pin-on-disk tribometer showed higher wear loss for wet ball milled and rotator mixed composites in comparison to dry ball milled.     

分级过程对LiFePO4/C电池性能的影响

本文采用磷酸铁工艺路线制备碳包覆的磷酸铁锂（LiFePO₄/C）复合正极材料,系统考察气流粉碎分级过程对LiFePO₄/C正极材料及全电池性能的影响. 研究表明：分级前磷酸铁锂颗粒粒度较大,中值粒径为17.37μm,呈规整球形形貌,具有较高的振实密度和碳含量;分级后球形被打碎,振实减小. 全电池测试结果显示：分级过程对全电池的容量、交流内阻、直流内阻、功率密度的影响较小;但分级前电芯的低温放电容量保持率和550周的高温循环保持率分别60.1%和87.5%,明显优于分级后的49.5%和84.7%. 分级前碳层能均匀包覆在磷酸铁锂表面形成均匀导电网络,而分级过程将磷酸铁锂的碳层有一定的剥离和破坏导致性能下降.     

High Coercivity Induced in Nickel Ferrite Nanoparticles by Mechanical Milling

This work reports a study of the structure and magnetic behavior of NiFe₂O₄ ferromagnetic oxide nanoparticles synthesized by the combustion method. The structural and magnetic properties of nanoparticles after mechanical milling are investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, transmission electron microscope. Their structural properties and magnetic behavior are characterized by a vibrating sample magnetometer (VSM). The non-milled sample presents a coercivity of 89 Oe, a saturation magnetization of 69 emu/g, and a remanence of 13 emu/g. After milling, the sample attains the coercivity, the saturation magnetization, and the remanence of 160.7 Oe, 56 emu/g, and 12.8 emu/g respectively. The porosity estimated from the X-ray density and bulk density is about 35%. The XRD analysis by Stokes–Wilson, Williamson-Hall, and dislocation density equations are used to estimate strain and the dislocation density induced by mechanical milling in the sample.     

Systematic investigation of mechanically alloyed Ti-Mg-Ni used as negative electrode in Ni-MH battery

In this study, a series of Ti-Mg-Ni alloys have been synthesized by mechanical alloying using a planetary high-energy ball mill. The effect of varied composition on the microstructure and electrochemical hydrogenation properties of Ti-Mg-Ni system have been investigated through the compared analysis of Ti_1-xMgNi_x and TiMg_1-xNi_x alloys. The structural transformation and discharge capacities were characterized by XRD and electrochemical measurements at galvanostatic conditions, respectively. Additionally, a separate milling process has been employed for improving the electrochemical properties of Ti-Mg-Ni alloys. It is shown that the separated milling process can extremely enhance the discharge capacities of Ti-Mg-Ni composite materials.     

Thermal Properties of Mechanochemically Pretreated Precursors of BaTiO3 Synthesis

The changes of physico-chemical properties of mechanochemically pretreated (BaCO₃ +TiO₂ +PbO) powders were investigated. The values of apparent activation energy of BaTiO₃ formation calculated by the Freeman and Carroll method decrease with milling time. The changes of precursors density may be interpreted as a consequence of mechanochemical reactions during milling. This revised version was published online in July 2006 with corrections to the Cover Date.     

The electrical properties of chemically obtained barium titanate improved by attrition milling

Barium titanate ceramics were prepared using the nanopowder resulting from a polymeric precursor method, a type of modified Pechini process. The obtained nanopowder was observed to agglomerate and in order to de-agglomerate the powder and enhance the properties of the barium titanate the material was attrition milled. The impact of this attrition milling on the electrical properties of the barium titanate was analysed. The temperature dependence of the relative dielectric permittivity showed three structural phase transitions that are characteristic for ferroelectric barium titanate ceramics. The relative dielectric permittivity at the Curie temperature was higher for the attrition-treated sample than for the non-treated barium titanate. The dielectric losses were below 0.04 in both barium titanate ceramics. The grain and grain-boundary contributions to the total resistivity were observed using impedance analyses for both ceramics. A well-defined ferroelectric hysteresis loop and piezoelectric coefficient d₃₃ = 150 pC/N were obtained for the ceramics prepared from the de-agglomerated powder. In this way we were able to demonstrate that by attrition milling of chemically obtained powders the ferroelectric and piezoelectric properties of the ceramics could be enhanced.     

Probing the effect of high energy ball milling on PVC through a multitechnique approach

The effects induced by ball milling treatment on PVC features and properties were deeply investigated through a multitechnique approach. SEM analysis showed a drastic change in PVC morphology; the hierarchical structure of PVC grains was partially destroyed as well as the domain size strongly reduced. A X-ray diffraction and DSC comparative study proved a structural modification in the PVC crystalline phase. Moreover, it was found that these morphological and structural changes strongly affected the gelation behavior, the microstructure and the mechanical parameters of PVC. In particular, the gelation time increased with increasing the ball milling time; the residual primary crystallite content doubled with respect to neat PVC and the toughness improved up to 25% as a function of the resulting microstructure.     

Influence of machining process on the mechanical behaviour of injection-moulded specimens of talc-filled Polypropylene

The mechanical properties of injection-moulded components are usually obtained by conducting uniaxial tensile tests on dog bone specimens. Current standards do not regulate the machining process used to make the coupons and do not quantify an acceptance limit of the surface roughness. The surface qualities of milling, laser cutting and water jet cutting were examined in this study for 18% talc-filled Polypropylene using optical measurements. It shows that the machining processes influence the surface roughness of the specimen, leading to different strengths at failure of the same thermoplastic material. The specimens machined by the water jet technology produced the roughest sample edges and exhibited the lowest resistance to failure in tensile tests. On the contrary, the milling process generated the best edge quality, which showed repeatable testing results.     

非晶Mg-Fe复合物的机械球磨制备及其电化学储氢特性

研究了机械球磨制备的(2Mg+Fe)+x%Ni(x=0, 50, 100, 200)复合物的微结构和电化学储氢性能. 结果表明, 不加镍粉时, 镁粉与铁粉混合物经120 h球磨后仍然为纯镁与纯铁两相组织, 其电化学放电容量不到20 mA·h/g. 而加入镍粉和提高球磨强度有助于Mg-Fe非晶的形成, 并使颗粒尺寸减小, 添加镍粉越多, Mg-Fe非晶化程度越高, 放电容量越大, 而组合钢球混合球磨的粉末比等径钢球球磨的非晶化程度更高, 颗粒也更加细小均匀. 在x=100时, 不同尺寸和等径钢球球磨120 h合成的Mg₂Fe非晶复合物的最大放电容量分别达到542.0和455.3 mA·h/g.     

Zr,Mo,Zn添加剂及机械球磨对钒—磷—氧催化剂性质的影响

利用X射线衍射（XRD）,X射线光电子能谱（XPS）及傅利叶红外光谱（FT－IR）等手段考察了添加剂Zr,Mo,Zn和机械球磨对VPO催化剂结构与性质的影响,采用了正丁烷选择氧化反应评价催化剂的催化性能,实验表明,添加Mo,Zn,会减少（200）面的相对暴露,但是可以增大表面＋4价钒的相对比较,因此反应活性提高,助剂Zr可能会取代表面＋4价的,明显增大催化剂的表面P／V比,因此没有明显的助催化作用,机械球磨可以明显增大VPO催化剂活性组分（VO）2P2O7晶相（200面的相对暴露,导致催化剂的反应活性上升。     

高能机械球磨法制备V-Ti-O超细微粒催化剂

负载型V2O5/TiO2氧化物催化剂因具有优良的催化性能而广泛地用于烃类选择性氧化[1,2]和氮氧化物选择性催化还原(SCR)[3]. 迄今,所研究的负载型V2O5/TiO2氧化物催化剂大多是采用浸渍法制备的[2,4～6],通过调整催化剂的组成[2,5]、引入适当的助剂组分[2,6]和选择适宜的反应操作条件[2,5]可进一步优化其催化性能.     

Electrochemical Performance of LiMn2O4/LiFePO4 Blend Cathodes for Lithium Ion Batteries

A series of LiMn₂O₄/LiFePO₄ blend cathodes was prepared by hand milling and ball milling in order to compensate the disadvantage of spinel LiMn₂O₄ and olivine LiFePO₄. The morphologies of the blends were studied by scanning electron microscopy, and their electrochemical properties were studied by charge-discharge cycling, cyclic voltammetry and electrochemical impedance spectroscopy. It is easy to obtain uniform LiMn₂O₄/LiFePO₄ blends by the hand milling technique, while significant particle agglomeration is caused by the ball milling technique. When the LiMn₂O₄:LiFePO₄ mass ratio is 1:1, the nano-sized LiFePO₄ powders not only uniformly cover the micron-sized LiMn₂O₄ particles but also effectively fill in the cavities of the LiMn₂O₄ space. Such morphology offers a good electrical contact and a high tap density, which leads to a high discharge capacity and good cycle stability.     

Real dispersion of isolated fumed silica nanoparticles in highly filled PMMA prepared by high energy ball milling

Fumed silica nanoparticles with 14 nm of diameter were blended with poly(methylmethacrylate), PMMA, by means of a high energy ball milling process. AFM analysis revealed how this process of blending allows obtaining a very homogeneous dispersion of the nanoparticles within the PMMA. Furthermore, it was observed that the properties of the composite are highly dependent on the active milling time: (i) SEM inspection showed that the particle size of the silica-PMMA nanocomposite decreases and (ii) DSC analysis demonstrated that the Tg also decreases due to a reduction in the molecular weight of the PMMA caused by chain scission during the high energy blending process. Two Tg's were obtained in the case of the nanocomposite when milling times were higher than 6 h, one of them being even higher than that of the PMMA without being subjected to the HEBM process. This result was assigned to surface-induced molecular weight segregation near the nanoparticles surface. It has been demonstrated the possibility of preparing transparent nanocomposites with excellent moldability.