Temperature and pressure dependence of the resistivity of β-(BEDT-TTF)2X (X = I3, I2Au) and αt-(BEDT-TTF)2I3

The temperature dependence of the resistivity of the organic metals and superconductors β-(BEDT-TTF)₂I₃, β-(BEDT-TTF)₂I₂Au and α_t(BEDT-TTF)₂I₃ was measured at ambient and at several isotropic pressures (up to 2.5 kbar). By the application of a relatively low pressure, it is possible to measure the term in the resistivity that is linear in temperature. This term is masked by the larger T² term at ambient pressure. It is shown that in the temperature range below 120 K, the external modes are mainly responsible for the resistivity, while above this temperature the flipping of the CH₂ groups becomes important. The linear electron-phonon coupling corresponds to a value of λ between 1 and 1.5.     

Microwave and d.c. conductivity of α-ET2I3 and βt-ET2I3 microcrystals in polymer films

Electrical properties of conducting polymer films containing an ET₂I₃ (ET=bis(ethylenedithiolo)tetrathiafulvalene) polyiodide crystalline network have been investigated. It is shown that the conditions of preparation of these films, i.e., time of exposition to solvent iodine vapours, concentration of iodine in solvent, time and temperature of annealing, have a very strong influence on the conducting properties of the films. By choosing proper preparation conditions one can obtain conducting composites showing the conductivity behaviour characteristic of α-ET₂I₃ or β_t-ET₂I₃ single crystals.     

Solubility of ammonium paratungstate in the system NH_3·H_2O·H_2O

The equilibrium solubilities of 5(NH4)O·12WO3·5H2O (APT·5H2O) were determined at the terminal ammonia concentration of 2 mol/L at 87-95℃. Experimental data were regressed. The linear functional relation between the solubility of APT- 5H2O and the temperature (t /℃) is given as y = - 588.08 + 7.28t. The solubility of the species as a function of the terminal ammonia concentration (x / mol · L-1) is also achieved: y = 36.76 + 18.86x. The solubility of APT · 5H2O produced by ion-exchange method in China is much lower, which is due to much lower silica, much higher NH4Cl, and a small amount of APT · 7H2O with low solubility in the APT crystals. APT · 7H2O forms because of a large amount of NH4Cl and the low activity of water in the crystallization.     

Mechanics of boring processes—Part I

Mechanics of boring operations are presented in the paper. The distribution of chip thickness along the cutting edge is modeled as a function of tool inclination angle, nose radius, depth of cut and feed rate. The cutting mechanics of the process is modeled using both mechanistic and orthogonal to oblique cutting transformation approaches. The forces are separated into tangential and friction directions. The friction force is further projected into the radial and feed directions. The cutting forces are correlated to chip area using mechanistic cutting force coefficients which are expressed as a function of chip-tool edge contact length, chip area and cutting speed. For tools which have uniform rake face, the cutting coefficients are predicted using shear stress, shear angle and friction coefficient of the material. Both approaches are experimentally verified and the cutting forces in three Cartesian directions are predicted satisfactorily. The mechanics model presented in this paper is used in predicting the cutting forces generated by inserted boring heads with runouts and presented in Part II of the article [1].     

Role of catastrophic oxidation in the embrittlement of steel ÉI395 and ÉI981A blooms

The causes of internal failures during the hot rolling of ingots formed from austenitic high-temperature steels are investigated.Physicotechnical Institute, Ural Branch, Russian Academy of Sciences. Production Union Izhstal. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 20–24, November, 1994.     

20CaO·13Al2O3·3MgO·3SiO2的合成与氧化铝的浸出性能

使用分析纯试剂配料,在1 500 ℃、保温1 h的条件下得到了四元化合物20CaO·13Al2O3·3MgO·3SiO2 (C20A13M3S3),研究了其氧化铝浸出性能,并通过XRD和SEM等分析了其在碳酸钠溶液中的作用机理.结果表明:C20A13M3S3具有一定的氧化铝浸出能力,其浸出率随着浸出时间的延长而提高,并在浸出2 h后达到最大值68.87%,低于同条件下12CaO·7Al2O3的氧化铝浸出率(92.78%);C20A13M3S3和Na2CO3反应的主要产物为NaAl(OH)4和CaCO3,并含有少量的Ca2SiO4和Mg(OH)2;生成的Ca2SiO4具有较高的活性,浸出2 h后,其分解率可达到19.35%.     

Microstructure and mechanical properties of spot welded Al–5·5Mg–0·3Cu alloy

Abstract

The influences of spot welding on the microstructure and mechanical properties of an Al–5·5Mg–O·3Cu alloy have been investigated. Results showed that dendrites were formed with porosity and cracks in the nugget. Grain boundary melting occurred in the heat affected zone and wide grain boundaries appeared. The alloy exhibited low hardness in the nugget centre. Tensile cracks propagated at the edge of the nugget and mixed rupture with dimples and intergranular fracture occurred. Fatigue fracture initiated at the edge of the nugget and propagated perpendicularly to the tensile axis. Transgranular fracture with striations was also observed.     

引进I·S机大口轻量瓶初型设计

<正> 0 前言 行列式制瓶机在国外简称为I·S机,在引进I·S机上生产大口轻量瓶时,玻璃模具中的初型设计是整个模具设计的重要环节,它包括初型模的雏型设计和冲头参与成型部分设计,合理的初型设计能有效地改善玻璃瓶罐的质量,生产出理想的薄壁轻量瓶罐。本文的工作企图是以经验方法为主。分     

Effect of velocity and elevated temperature on pitting of Al 6013-20SiCp composite in 3·5 wt-%NaCl

Abstract

This paper presents new data on the effect of temperature and velocity on the pitting potential E_p, corrosion potential E_corr, and pitting morphology of O, F, and T4 tempers of alloy 6013-20SiC_p in 3·5 wt-%NaCl in the temperature range 30–130°C and at velocities of 0·5–1·0 m S_?1. The pitting potential of tempers T4 and O tended to increase with increasing temperature and flow velocity, but the pitting potential of temper F showed the opposite behaviour. Temper T4 of the alloy showed the best resistance to pitting. Alloy 6013-20SiC_p in temper T4 is therefore considered to be suitable for application in chloride containing environments.     

Influence of chromium additions on corrosion resistance of Co75·5Si13·5B9 Nb3Cu1 metallic glass in marine environment

Abstract

This study addressed the influence of Cr concentration on the corrosion resistance of Co_73·5Si_{13 ·5}B₉Nb₃Cu₁ metallic glass in simulated marine atmospheres with 1000 ppm of chlorides. Anodic and cyclic polarisation measurements were carried out to study the susceptibility to passivation and localised corrosion. The corrosion kinetics were analysed using dc electrochemical techniques. Every test was conducted using the same material in different states: amorphous, nanocrystalline and crystalline. The study also focused on changes in the magnetic properties of the material as a result of Cr addition and exposure to an aggressive medium. These properties depend mainly on the Cr concentration and the material state (amorphous, crystalline or nanocrystalline).     

Thermodynamic properties of LaCrO3

1. Introduction It is known that a lanthanum chromate with perovskite structure with high melting point and chemical stability [1] is a promising candidate base material for solid oxide fuel cells interconnects [2-3] and electrode materials [4]. In order to evaluate the chemical compatibility between a lanthanum chro- mate and other ceramic materials, it is necessary to study the thermodynamic properties of LaCrO3. Na- tsuko Sakai and Svein St?len [5] studied the heat capacity and thermodyna…     

Post-weld heat treatment influence on galvanic corrosion of GTAW of 17-4PH stainless steel in 3·5%NaCl

Abstract

The influence of post-weld heat treatment (PWHT), solution annealing followed by aging at 480, 550 and 620°C on the galvanic corrosion in 17-4PH stainless steel weldment in 3·5%NaCl was studied. Potentiodynamic polarisation revealed that all PWHTs improve the passivity of weld region by increasing the pitting potential. Heat affected zone disappears, and base and weld regions act as the anode and the cathode respectively. Zero resistance ammetry measurement for 42 h showed that PWHTs improve the galvanic corrosion resistance by decreasing the galvanic current density to a few to tenths of nanoampere per square centimetre. Aging at 620°C has the highest risk of galvanic corrosion among the three PWHTs. Difference in corrosion characteristic of base and weld were addressed to microstructure variations including ferrite, copper rich precipitates and reverted austenite.     

Al2O3��������ײ���۳�����ֵģ���·���

基于分形理论,建立了Al2O3凝聚态夹杂物分形碰撞凝聚长大新数学模型,并利用Fluent软件将此新数学模型应用于某钢铁公司冶炼铝镇静钢的中间包中,从夹杂物的分布特征角度比较了新数学模型与传统等体积球状数学模型的差异。结果表明:与传统等体积球状数学模型相比,Al2O3凝聚态夹杂物分形碰撞凝聚长大新数学模型的计算结果数值较大,且夹杂物粒子分布特征复杂;新数学模型显示出了夹杂物粒子容易在出水口和入水口富集的特征,这与实际生产中Al2O3夹杂物容易堵塞水口现象一致;实际生产中很难找到球形Al2O3夹杂物,大多是簇群状形貌夹杂物,分形维数在1.78~1.85,表明Al2O3夹杂物分形碰撞凝聚长大新数学模型具有一定的现实意义。     

矿业更应重视3·15

<正>3·15是"国际消费者权益日",目的在于扩大消费者权益保护的宣传,使之在世界范围内得到重视,促进各国和地区消费者组织之间的合作与交往,在国际范围内更好地保护消费者权益。作为消费者,有"四项权利",即:有权获得安全保障;有权获得正确资资料呢?地质报告有多少水分?在笔者的工作经历中,感觉有大约80%以上不可靠,只是虚的大小而已。尤其提交到政府的资料,有多少是应付?有多少真实可靠?有多少企业从买矿第一步就失败?再比如环评报告,有多少企业是为了办证而办证,有几个企业从内心为了     

On microstructure and mechanical properties of linear friction welded dissimilar Ti–6Al–4V and Ti–6·5Al–3·5Mo–1·5Zr–0·3Si joint

Abstract

Linear friction welding of dissimilar titanium alloys Ti–6Al–4V (TC4) and Ti–6·5Al–3·5Mo–1·5Zr–0·3Si (TC11) was achieved. Microstructural examination showed that the joint has a clearly identified weld zone and a thermomechanically affected zone on both TC4 and TC11 sides with a clearly identified weld line. In the weld zone of TC4, superfine α grains are dispersed in the β matrix, while in that of TC11, a few recrystallised α grains are observed along the β boundaries. In the thermomechanically affected zone of TC4, both deformed and recrystallised grains exist in the same area, while that of TC11 has a deformed α+β structure. The tensile strength of the joint is comparable to that of the parent TC4 where fracture occurs. The joint microhardness is well related to its microstructure.     

Preparation,crystal structures and electrical conducting properties of new charge-transfer salts: (ET)2·SO3CF3 and (ET)·ClO4

Two new charge-transfer (CT) salts: (ET)₂·SO₃CF₃ and (ET)·ClO₄ were prepared by chemical oxidation of ET with AgSO₃CF₃ and AgClO₄, respectively. Their crystal structures were determined: monoclinic system, Cc, a=35.239(7) Å, b=6.5440(13) Å, c=14.646(3) Å, β=110.26(3)°, V=3168.5(11) Å³ for (ET)₂·SO₃CF₃; monoclinic system, C2/c, a=15.981(3) Å, b=10.627(2) Å, c=11.495(2) Å, β=120.61(3)°, V=1680.2(6) Å³ for (ET)·ClO₄. Electrical conductivity measurements indicate that (ET)₂·SO₃CF₃ shows semi-conducting behaviour with room temperature conductivity of 0.29 S cm⁻¹, while (ET)·ClO₄ is an insulator.     

Why superconducting transition of polycrystalline β-ET2I3 in surface conducting films is observed below 8 K?

An onset of the superconducting transition in surface conducting films of polycarbonate with β-ET₂I₃ (ET: bis (ethylenodithio)tetrathiafulvalene) is observed at temperature(5–6 K) lower than that for single crystals (8 K). It is shown using X-ray diffraction technique that the interlayer spacing d in β-ET₂I₃ microcrystals in polymer film decreases stronger with temperature than in crystals without polymer. This is considered as an important factor suppressing the transition to superconductivity. It is assumed that stronger dependence d(T) in β-ET₂I₃ in polymer films is related to the stress induced by the shrinkage of the polymer matrix.     

Effect of the Mass Ratio of CaCO3 to CaHPO4·2H2O on in Situ Synthesis of Hydroxyapatite Coating by Laser Cladding

Hydroxyapatite coatings were fabricated on Ti substrates by laser cladding (LC) using mixed powders of CaCO3 and dicalcium phosphate dihydrate (DCPD, CaHPO4·2H2O). The effect of the mass ratio of CaCO3 to DCPD on phase and microstructure formation of the coatings was investigated. The reactions between CaCO3 and DCPD can produce high crystallized hydroxyapatite (HA, Ca5(PO4)3(OH)) in the coatings as well as tetracalcium phosphate (TTCP, Ca4P2O9), α-tricalcium phosphate (α-TCP, α-Ca3(PO4)2), β-tricalcium phosphate (β-TCP, β-Ca3(PO4)2) and Ca2P2O7. The Ca/P molar ratio (CMR) of the mixed powders (CMRP) has a great influence on the contents of the phases in the coating. HA can be produced in the coating only when the CMRP is higher than 1.54, and its content increases slowly as the CMRP increases. The coating contains only about 25wt% HA when CMRP reaches 2.00, and there exists large amount of TTCP in the coating. So a post heat treatment with furnace cooling is recommended to increase the amount of HA in the coating. All the coatings have porous structures because the reactions between the powders produce lots of gases during LC. The pore size in the coating fabricated by the powders with CMR equal to 2.00 is about 100-300 mm. CMRP also has a great influence on the bond strength, porosity and cracks of the coatings. Along with the increase of the CMRP, the bond strength and porosity decrease, whereas the number of cracks increases     

Influence of AlF3 and hydrothermal conditions on morphologies of α-Al2O3

Homogeneous α-Al2O3 platelets were synthesized by introducing AlF3 to alumina precursor.The effects of AlF3 additive on the phase transformation and morphology of the prepared α-Al2O3 platelets were investigated.The results show that a single phase of α-Al2O3 with an average particle size of 8μm can be obtained at 900℃ with 2% AlF3 additive.The transformation temperature decreasing IS attributed to introduction of Al3 vacancy and to the formation of intermediate compound of AlOF,which is considered to accelerate the mass transportation from transitional Al2O3 to α-Al2O3.AlF3 concentration and hydrothermal temperature can also affect the morphology of α-Al2O3.When hydrothermal temperature is 120℃,the morphology of α-Al2O3 transforms from irregular to flat hexangular platelet with increasing AlF3 concentration.As hydrothermal temperature increases,the morphology of α-Al2O3 with 2% AlF3 additive changes from polyhedron to hexangular platelet and then to vermicular.