Properties of Cd-Based Binary Quasicrystals and Their 1/1 Approximants

Electronic and structural properties of Cd-based binary quasicrystals (QCs) and their 1/1 approximants (APs) without chemical disorder are overviewed in terms of electronic states, electronic transport, and phase transitions. A pseudogap in the electronic density of states (DOS) as well as hybridization effect between sp and d states are discussed for both the QCs and their 1/1 APs in comparison with theoretical calculations. In contrast with the cases of ternary stable QCs, the resistivity of the Cd_5.7Yb QC exhibits a positive temperature coefficient at low temperatures, which is regarded as an indication of an intrinsic metallic nature of the QC. A unique structural phase transition has been observed at low temperatures (LT) for a series of 1/1 Cd₆M APs, which is interpreted as an orientational transition of a tetrahedron residing at the center of the Tsai-type icosahedral cluster. In most of the cases, the LT superstructure is understood as an “antiferromagnetic” ordering of the tetrahedra along a <110> direction of the high-temperature bcc phase. The transition is classified as a non-diffusive order–disorder transition, which has not been observed in metallic alloys before.     

Metadislocations in Complex Metallic Alloys and their Relation to Dislocations in Icosahedral Quasicrystals

Complex metallic alloys and quasicrystals are closely related. Both possess icosahedral local order, but while in quasicrystals the long-range order and hence the macroscopic structure is also icosahedral, in complex metallic alloys a periodic structure with large lattice parameters is formed. Metadislocations are novel and highly complex structural defects in complex metallic alloys. Focusing on metadislocations in ε-type phases, we will review the basic geometric concepts of metadislocations and the relation between the number of phason planes, Burgers vector, and the elastic energy. The properties of dislocations in icosahedral Al-Pd-Mn will briefly be recalled and discussed in relation to metadislocations.     

SbSn金属间化合物的制备及其脱硫性能

以Sb、Sn为原料,用机械合金化法制备了SbSn金属间化合物,用X射线衍射仪和透射电镜对其进行了表征。实验考察了球料比、球磨时间、球磨转速、原料比以及使用后的清洗方式对SbSn金属间化合物性能的影响;并考察了2种不同性质的乳状液对脱硫的影响。结果表明球料比10∶1、转速270r/min、球磨时间8h为最佳合成条件。在常温常压下对于油品中的噻吩,单程脱除率在9.7%左右,3次循环实验后脱硫率可以达到23%。     

SbSn金属间化合物的机械合金化制备及其脱硫性能的研究

使用机械合金化法合成金属间化合物SbSn颗粒,并在合成的过程中添加适当助剂。考察了不同质量分数的助剂和不同球磨时间对金属间化合物SbSn颗粒比表面积大小的影响。在常温常压条件下,使用SbSn金属间化合物对汽油进行静态脱硫试验,考察了不同质量分数的助剂、球磨时间、处理时间及剂油比对脱硫率的影响。在施加直流电场的条件下,进行了动态脱硫试验,考察了电场的方向与大小对脱硫效率的影响。结果表明,动态操作时的脱硫率远高于静态操作时的脱硫率;电场的方向与大小对脱硫效率有显著影响;配以1.5 V的正电场对汽油中硫的单程脱除率最大可达38.9%。     

蒙脱石的湿法机械球磨剥离

以内蒙古钙基蒙脱石为原料,通过湿法改型、改性制备了钠基蒙脱石和有机蒙脱石.分别以钙基蒙脱石、钠基蒙脱石和有机蒙脱石为对象,在乙醇中湿法机械球磨、超声处理蒙脱石,利用XRD、TEM、AFM等手段研究了机械球磨法对不同层间离子的蒙脱石剥离效果.结果表明,内蒙古钙基蒙脱石湿法钠化及有机化效果良好,机械球磨法剥离钠基蒙脱石效果最佳,剥离型蒙脱石片层尺寸小于200 nm,其平均厚度约为15 nm;有机蒙脱石层间有机物具有稳定蒙脱石片层的作用,有机改性不能促进机械球磨法对蒙脱石片层的剥离.     

Formation of a Highly Protective Amorphous Aluminum Silicate Layer on Steel during Granite–Dry Steam Interaction

Formation of an amorphous Al₂Si₂O₅ layer on a steel pipe surface, after granite–dry steam interaction in the presence of copper, has been determined by XRD analysis and SEM (with energy dispersive X-ray microanalysis). Kinetic data indicate high-protective properties of the Al₂Si₂O₅ layer, which formed a three-dimension substrate ∼5 μm thick, after 100 h exposure.     

湿法研磨制备改性HMX及其机械感度研究

通过湿法研磨制备出不同粒度的改性HMX晶体,采用折光匹配法对其形貌进行表征,并测试了改性HMX的机械感度。讨论了研磨速率对HMX粒径的影响,以及改性前后HMX的机械感度,分析了湿法研磨对HMX机械感度的影响机理。结果表明,研磨速率为0.524m/s时得到的HMX粒度最小,为43.1μm,改性后的HMX摩擦感度降低60%,撞击感度降低68%,且研磨晶体粒度越小,晶体特性落高数值越大。晶体粒度及内部缺陷对机械感度的影响机制主要是研磨后晶体粒度减小且晶体内部缺陷减少,受到外力作用时,晶体内部热点产生和传播的概率降低。     

球磨时间对Ti-Al-C系机械合金化粉体相组成和形貌的影响

采用Ti,Al和C元素粉体为反应原料,通过机械合金化方法制备出高纯度Ti3AlC2陶瓷粉体.研究球磨时间对Ti-Al-C系混合粉体相组成和形貌的影响,探讨合成Ti3AlC2的反应机理.研究表明:当机械合金化的其它参数不变,球磨时间4h时,原料粉体仍以单质形式存在;将球磨时间延长至4.5h时,此时混合粉体中Ti3AlC2含量提升到86wt％(质量分数,下同);4.5 h后,混合粉体中Ti3AlC2含量开始下降;通过对实验机理进行分析,单质粉体发生机械诱发自蔓延反应合成Ti3AlC2.     

HRTEM and EELS Studies on the Amorphization of Hexagonal Boron Nitride Induced by Ball Milling

We present a new approach, namely ball milling, to synthesize amorphous boron nitride ( a -BN). The amorphization kinetics are revealed by X-ray diffractometry (XRD), high-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS). HRTEM investigations indicate that, in the early stage of milling, the thick sp ² layers are sliced into many thinner sheets because of cleavage along the basal planes. In the intermediate stage of milling, deformation is accommodated primarily by simultaneous shearing along the basal planes. As a result of sustained shearing, a number of defects, such as stacking faults, (0002) [11¯20] twinning, simultaneous shearing of lattice planes, and half Frank loops with Burgers vectors of 1/2[0001], are introduced in the hexagonal BN ( h -BN) grains. Simultaneous shearing also causes significant change in the lattice symmetry of most grains. In the final stage of milling, the fiberlike tightly bonded sp ² sheets are broken and refined further, until a nanocrystalline and amorphous mixture is formed. XRD of the sample milled for 180 h exhibits an amorphous halo pattern; nevertheless, HRTEM demonstrates that the end product is essentially a nanocrystalline and amorphous mixture. The grain sizes of the nano-crystals are <3 nm, and their stacking is turbostratic. EELS investigations of the a -BN indicate that bonding is primarily sp ², but a small fraction of sp ³ a -BN is also found, which is assumed to be the nuclei of the cubic phase ( c -BN) in the high-pressure and high-temperature experiments and thus facilitates the hexagonal to cubic transition. The present a -BN fabrication method can provide an effective way to facilitate the synthesis of sintered bulk c -BN materials.     

Characterization and Mechanical Properties of Flexible Dimethylsiloxane-Based Inorganic/Organic Hybrid Sheets

Flexible large sheets of dimethylsiloxane-based inorganic/organic hybrids with sizes of ∼200 mm × 290 mm and ∼1.5 mm thickness have been fabricated from poly(dimethylsiloxane) (PDMS) and metal alkoxides of Zr and Ta. The hybrid sheets were characterized by XPS, EXAFS, FT-IR, HRTEM, and SAXS. The inorganic components derived from metal alkoxides in the dimethylsiloxane-based hybrid sheets were found to be present as oxide-like clusters with sizes of 2–3 nm or below, which were chemically attached to PDMS via M–O–Si bonds. The hybrid sheets showed high elongation, strength, and thermal stability. A high elongation of about 100% was observed in the hybrid sheets fabricated in Zr(OBuⁿ)₄/PDMS = 2 at 180°C and a high tensile strength of about 3.0 MPa was observed in those fabricated in Zr(OBuⁿ)₄/PDMS = 4 at 180°C. The flexibility of the hybrid sheets was kept at least to 200°C for 100 h in N₂. These features are thought to come from the inorganic components derived from metal alkoxides, which are close to the molecular-level size and behave as a strong cross-linking agent of PDMS chains.     

Solid-Solution Effects of a Small Amount of Nickel Oxide Addition on Phase Stability and Mechanical Properties of Yttria-Stabilized Tetragonal Zirconia Polycrystals

Stability and mechanical properties of the tetragonal phase were investigated for NiO-doped yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) systems. Only 0.3 mol% of NiO in solid solution could be added to the Y-TZP while maintaining the tetragonal phase. Fracture toughness improved remarkably on addition of a small amount of NiO. Raman spectroscopy analysis around cracks introduced by Vickers indentation revealed that the amount of monoclinic phase transformed from tetragonal phase was increased. It was confirmed that fracture toughness improvement was due not only to increased grain size, but also to Y-TZP destabilization by solid solution of NiO.     

Mechanical properties study of VO2 micro-beam according to metal-insulator transition

Many attempts have been made to develop applications using the metal-insulator transition (MIT) phenomenon of VO₂. However, the difference in the densities of the two phases poses serious obstacle for those applications, as it can destroy or disable during the phase transformations. For microsized or nanosized devices, this aspect can be critical. We attempted to measure the mechanical properties when the two phases co-exist, as well as for an individual phase, via in-situ control of the temperature of plate-shaped VO₂. The lamella structure is formed during MIT. At this time, the stress is applied by the gradient of density, and the residual strain can easily occur at the interface of each phase. Therefore, the co-exist state was judged to be the most vulnerable during the MIT. The change in mechanical properties of VO₂ during phase transition was also simulated by finite element method.     

Some Aspects of Bond Formation and Failure in Adhesive Wood Joints

An investigation has been made of the effect of varying glue-spread on the bond strength of holly (Ilex aquifolium) using three adhesives and three different wood sections. The glue-spreads are lower than those normally used, and it has been found with edge-grain joints that 100% cohesive wood failure can occur with a glue-spread as low as 2.7mg/cm². Scanning electron microscopy shows that interlocking between adhesive and adherend does not occur. Factors leading to delamination and joint failure are discussed.

Lignin, without further addition, has been shown to be a useful wood adhesive. It has also been shown that it is possible to make end-grain joints without the use of an adhesive; the lignin present in the wood specimens is considered to be responsible for such joints.     

Evolution of Microstructures and Nitrogen Sorption during High-Energy Milling of Silicon in Ammonia

The structural transformation, microstructural changes, and nitrogen sorption of crystalline Si induced by high-energy ball milling in ammonia have been investigated. It is found that significant refinement of particles and crystallites occurs at the early stage of milling (within ∼10 h of milling), after which the average particle size and crystallite size decrease gradually and approach a lower limit of ∼100 and 6.0 nm, respectively. It is proposed that refinement of particle sizes is dominated by the fragmentation process, whereas refinement of crystallite sizes is dictated by plastic deformation. Substantial amorphization does not occur until most of the crystallites have reached the average size of 6.5–6.0 nm. The crystallite-refinement-induced amorphization has been identified as the major mechanism for the nanocrystalline-to-amorphous transformation. A substantial amount of nitrogen is sorbed by Si powders and primarily dissolved in the amorphous Si phase.     

Unusual Elastic and Mechanical Behaviors of Copper Phosphate Glasses with Different Copper Valence States

Elastic and mechanical properties such as Young's modulus E, Poisson's ratio ν, Debye temperature θ_D, Vickers hardness H_v, fracture toughness K_c, and fracture surface energies γ_f of yCuO_x·(100−y)P₂O₅ glasses (y= 45, 50, 55) with different copper valence states, i.e., R(Cu⁺) = Cu⁺/(Cu⁺+ Cu²⁺), at room temperature (humidity 64%) have been examined. The following features have been found: (1) the glass transition temperature (218–434°C), H_v (2.7–4.4 GPa), E (50.6–78.2 GPa), and θ_D (358–434 K) decrease largely with increasing R(Cu⁺); (2) the mean atomic volume, K_c (0.56–1.14 MPa·m^1/2), and γ_f (1.9–11.2 J·m⁻²) tend to increase with increasing R(Cu⁺); (3) 50CuO_x·50P₂O₅ glasses with R(Cu⁺) = 0.42 and 0.55 have a high resistance against crack formation in Vickers indentation tests and no crack is observed in the 45CuO_x·55P₂O₅ glass with R(Cu⁺) = 0.57 under an applied load of about 98 N. The results demonstrate that elastic and mechanical properties of yCuO_x·(100−y)P₂O₅ glasses depend strongly on the copper valence state and the CuO_x/P₂O₅ ratio. The unusal mechanical and elastic properties of copper phosphate glasses are well explained qualitatively by considering unique oxygen coordination and bonding states of Cu⁺ ions, i.e., lower coordination number and more covalent bonding compared with Cu²⁺ ions.     

Phase Formation and Dielectric Characterization of the Bi2O3–TeO2 System Prepared in an Oxygen Atmosphere

Solid-state synthesis of compositions from the Bi₂O₃–TeO₂ system show that, under an oxygen atmosphere, Te⁴⁺ oxidizes to Te⁶⁺ and yields four room-temperature stable compounds: Bi₂Te₂O₈, Bi₂TeO₆, Bi₆Te₂O₁₅, and new a compound with the nominal composition 7Bi₂O₃·2TeO₂. Dense ceramics can be prepared from all these compounds by sintering between 650° and 800°C under an oxygen atmosphere. The permittivity of these compounds varies from ∼30 to ∼54, the Q × f value from 1.100 to 41.000 GHz (∼5 GHz), and the temperature coefficient of resonant frequency from −43 to −144 ppm/K. Bi₆Te₂O₁₅ and 7Bi₂O₃·2TeO₂ do not react with silver, and, therefore, they have the potential to be used for applications in low-temperature cofired ceramic (LTCC) technology.     

壳牌气化炉磨煤及干燥系统常见问题分析

介绍了壳牌粉煤气化装置磨煤干燥系统的工艺流程;分析了称重给煤机、磨煤机和循环风机出现问题的原因;提出了相应的处理措施。     

Aliphatic polyesters as models for relaxation processes in crystalline polymers: 3. Mechanical relaxation in copolymers of adipic acid with 1,6 and 2,5-hexanediols

The shear moduli of a series of the title polyesters spanning a crystallinity range of 0–60% have been measured as a function of temperature at ≈1 Hz using a torsion pendulum. The experimental isochronal temperature scans of G′ and G″ are fitted to phenomenological equations. With only minor adjustments, the same relaxation spectrum parameters as found dielectrically for these polymers (relaxation shape, central relaxation times) fit the mechanical data. Thus, for the β (glass—rubber) relaxation in the amorphous fraction the broadness is very sensitive to the presence of the crystal fraction and becomes increasingly broad as the degree of crystallinity increases. In contrast, the γ process dynamic behaviour is insensitive to the presence of and degree of crystallinity. Unrelaxed and relaxed moduli values are determined for the γ and β processes. A composite model approach is used to determine bounds on the amorphous-phase unrelaxed and relaxed γ and β moduli from the bulk specimen values. As was the case dielectrically, the γ process, in addition to being assigned to the amorphous fraction, has a strength that depends on the diol composition also. The relaxed (γ + β) amorphous-phase rubbery shear modulus is bound reasonably well from application of the composite model to the bulk specimen values and is assigned the value 100 ± 20 MPa at 250 K. It decreases relatively strongly with increasing temperature.     

Mechanical Properties of CoAl Materials with the Combined Additions of ZrO2(3Y) and Al2O3

Intermetallic CoAl powder has been prepared via self-propagating high-temperature synthesis (SHS). Dense CoAl materials (99.6% of theoretical) with the combined additions of ZrO₂(3Y) and Al₂O₃ have been fabricated via spark plasma sintering (SPS) for 10 min at 1300°C and 30 MPa. The microstructures are such that tetragonal ZrO₂ (0.3 μm) and Al₂O₃ (0.5 μm) particles are located at the grain boundaries of the CoAl (8.5 μm) matrix. Improved mechanical properties are obtained; especially the fracture toughness and the bending strength of the materials with ZrO₂(3Y)/Al₂O₃= 16/4 mol% are 3.87 MPa·m^1/2 and 1080 MPa, respectively, and high strength (>600 MPa) can be retained up to 1000°C.     

Structure Changes and Thermal Behaviors of Polymer in PP/BaTiO3 Nanocomposites during Solid State Shear Milling

Polypropylene/barium titanate (PP/BaTiO₃) nanocomposites were prepared by a novel method—solid state shear milling (S³M). The effects of S³M on the structure changes and thermal behaviors of PP were investigated by X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC) study. The results showed that PP underwent significant amorphization. The crystallinity of PP decreased from 50.29% to 35.65% after 20 cycles of milling. During the subsequent heating process, the destroyed crystalline structure of PP can readily be recovered, though incompletely. Double melting characteristics were detected by DSC in the milled samples. It was inferred that the milling process resulted in enhanced intimacy between PP and BaTiO₃, which would significantly influence the melting behavior of the polymer phase. The abnormal thermal behaviors can be interpreted using an inferred nanocrystalline morphology, during which residual lamellae fragments randomly distribute in the amorphous bulk PP. The conclusions were also strongly supported by quantitative analysis of the XRD.