Mechanical wet-milling and subsequent consolidation of ultra-fine Al_2O_3-(ZrO_2+3%Y_2O_3) bioceramics by using high-frequency induction heat sintering

Alumina/zirconia composites were synthesized by wet-milling technique and rapid consolidation with high frequency induction heat sintering(HFIHS). The starting materials were a mixture of alumina micro-powder (80%, volume fraction) and 3YSZ nano-powders (20%). The mixtures were optimized for good sintering behaviors and mechanical properties. Nano-crystalline grains are obtained after 24 h milling. The nano-structured powder compacts are then processed to full density at different temperatures by HFIHS. Effects of temperature on the mechanical and microstructure properties were studied. Al2O3-3YSZ composites with higher mechanical properties and small grain size are successfully developed at relatively low temperatures through this technique.

Growth of BaTiO_3-Ag hybrid composite films at room temperature by aerosol deposition

Barium titanate (BaTiO3) and silver (Ag) composite film with high dielectric constant was grown at room temperature by an aerosol deposition method.The dielectric constant increases by 0.5 times after adding Ag to the BaTiO3 matrix,compared with pure BaTiO3.The high dielectric constant can be attributed to the percolation effect of Ag inclusions in the BaTiO3 matrix.The Ag was present in the form of discrete layer in the BaTiO3 film.The dielectric properties of BaTiO3 Ag were discussed in detail taking into account the changes in microstructures.

低温烧结原位合成微米级Al_2O_3颗粒强化Al基复合材料

以Al-10wt%SiO2粉末为研究体系,对比机械混合与球磨的粉末,研究了球磨粉末的相组成和微结构,用差热分析的方法确定了两种粉末体系中的置换反应发生的温度,以此为据,优化了烧结两种粉末压坯的工艺。结果表明,4h球磨的粉末颗粒明显细化,部分SiO2颗粒嵌入Al基体,形成反应扩散耦Al/SiO2;混合粉末中置换反应不能发生,球磨粉末中置换反应的温度区间为560-680℃;球磨粉末的压坯在640℃烧结2h,可形成组织均匀的微米级Al2O3颗粒强化Al基复合材料。

Interface properties and phase formation between surface coated SKD61 and aluminum alloys

The intermediate phase formation and surface protection effects between SKD61 die mold alloys and aluminum alloys were investigated during a simulated die-casting process.The surface coatings of SKD61 alloy were carried out via Si pack cementation coatings at 900 ℃ for 10 h and the ε-FeSi phase formed.When the coated SKD61 alloy was dipped in the liquid aluminum alloy(ALDC12),the surface coated SKD61 alloys showed better surface properties compared with uncoated SKD61 alloys,i.e.,the intermediate phases(FeSiAl compound) were not produced for the coated SKD61 alloy.The coating layer of ε-FeSi served as a diffusion barrier for the formation of FeSiAl compounds.

喷墨印刷／软光刻技术结合气相聚合法制备聚3，4-乙撑二氧噻吩图像

采用气相聚合,以咪唑衍生物为辅助料可以成功制备高导电透明的聚3,4-乙撑二氧噻吩(PEDOT)薄膜。带有1～2个烷基官能团的咪唑衍生物的加入可以显著提高PEDOT的电导率。为了研制一种易于实现的PEDOT成像法,本文采用了喷墨印刷或软光刻技术结合气相聚合法,并以带取代基的对甲苯磺酸铁为氧化剂,3,4-乙撑二氧噻吩为聚合单体来制备PEDOT图像。这种新型方法的实现将为制得本征导电高分子材料图像提供一个高效便捷的方法。

铸造Mg-2%Ca合金的拉伸蠕变和抗腐蚀性能(英文)

对分别添加Zn和Al的Mg-2%Ca合金的拉伸蠕变和抗腐蚀性能进行比较。结果表明:添加Zn比添加Al能更加显著地提高Mg-2%Ca合金在170°C下的蠕变性能。然而,添加Al对提高合金的耐腐蚀性能更为有效。由于添加Zn的合金的凝固区间更为宽大,因此,为了生产高质量的铸件产品,对铸造工艺的控制要求更加严格。

Functionally Graded Ti-50.5Ni Alloy

Transformation behavior and shape memory characteristics of a temperature gradient annealing(TGA)treated Ti-50.5Ni(at%)alloy have been investigated by means of differential scanning calorimetry(DSC)and thermal cycling tests under constant load.By annealing the specimen under the temperature gradient from 823 K to 658 K after solution treatment,the B19' martensitic transformation start temperature changed by 60 K along the length of sample(150mm).Temperature dependence of transformation elongation(dε/dT)of the TGA treated wire was found to be 0.16 %/K.By annealing the specimen under the temperature gradient from 823 K to 658 K after 47 % cold working without solution treatment,the B19' martensitic transformation start temperature changed by 61K along the length of sample(150mm).Temperature dependence of transformation elongation(dε/dT)of the TGA treated wire was found to be 0.04 %/K.The large decrease in dε/dT by cold working effect suggested that an introduction of dislocation was more effective than precipitates for lowering dε/dT.

Understanding microstructure and mechanical properties of(AlTa(0.76))xCoCrFeNi(2.1) eutectic high entropy alloys via thermo-physical parameters

(AlTa(0.76))xCoCrFeNi(2.1)(x values in molar ratio,x=0.1,0.3,0.5,0.7,1.0,and 1.5) alloys were designed to investigate the microstructure and mechanical properties of the eutectic high entropy alloys(EHEAs)consisting of FCC,B2,and Laves phases.Depending on the compositional variatio,clear microstructural variation was observed,as follows:(1) Group 1:FCC dendrite+Laves interdendrite(x=0.1),(2) Group 2:FCC dendrite+fine-eutectic structure consisting of FCC and Laves phases(x=0.3,0.5 and 0.7),(3) Group 3:B2 dendrite+bimodal eutectic structure [FCC/B2+Laves](x=1.0),(4) Group 4:Laves dendrite+eutectic structure consisting of B2 and Laves phases(x=1.5).As the fraction of Laves or B2 phases increases,yield stress increases from 293 to 2336 MPa,while the plastic strain decreases from 50 % to 2%.Thermo-physical parameters,such as mixing entropy(△S(mix)),mixing enthalpy(△H(mix)),valence electron concentration(VEC),and atomic size difference(δr),were calculated to understand the microstructural variation.Two criteria(δr-VEC and δr-△H(mix)) were utilized to elucidate the formation of the eutectic structures in the present EHEAs,revealing the usefulness of the thermo-physical parameters in the development of EHEAs.

Substrate Temperature Dependent Properties of Cu Doped NiO Films Deposited by DC Reactive Magnetron Sputtering

The NiO-Cu composite films were deposited on a glass substrate at various substrate temperatures by DC reactive magnetron sputtering technique. The effect of substrate temperature on the structural, optical, morphological and electrical properties of the films was mainly investigated. X-ray diffraction studies revealed that when the substrate temperature increased to above 200 ℃, the preferred orientation tended to move to another preferred site from （220） to （111） and had a band gap values increased with increasing substrate observed that the grain size and root mean square stable cubic structure. The optical transmittance and temperature. From the morphological studies, it was roughness were increased with increasing substrate temperature. The electrical resistivity of the film decreased to 0.017 Ωcm at high substrate temperature of 400 ℃.

Prediction of Nitrogen Diffusivity in α-ferrite Based on Thermodynamics

A thermodynamic based equation to predict the diffusivity of nitrogen in α-ferrite was investigated in consideration of the equilibrium nitrogen concentration. The temperature-dependent jump distance calculated from the lattice parameter of ferrite was used to derive the frequency factor as a function of temperature. The calculation accuracy for nitrogen diffusivity using the proposed thermodynamic based equation was improved by comparing the calculation results using previous empirical equations based on Arrhenius type relationship with measured diffusivity of nitrogen for α-ferrite at different temperatures.

“One stone,two birds”solvent system to fabricate microcrystalline cellulose–Ti_(3)C_(2)T_(x)nanocomposite film as a flexible dielectric and thermally conductive material

A strategy for fabricating microcrystalline cellulose–Ti_(3)C_(2)T_(x)(MCC–MXene)nanocomposite films with high relative permittivity,high thermal conductivity,and excellent mechanical properties was developed.The MCC–MXene nanocomposite film was fabricated by casting a solution containing N,N-dimethylacetamide/lithium chloride(DMAc/LiCl)-soluble MCC and DMAcdispersible MXene nanosheets,followed by humidity control drying.The MXene nanosheets greatly enhanced the permittivity of the nanocomposite films owing to interfacial polarization.Thus,the nanocomposite film with 20 wt.%MXene content achieved a desirable permittivity of 71.4 at 102 Hz(a 770%improvement against that of neat cellulose),while the dielectric loss only increased by 1.8 times(from 0.39 to 0.70).The obtained nanocomposite films with 20 wt.%and 30 wt.%MXene exhibited remarkable in-plane thermal conductivities of 8.523 and 9.668 W∙m^(−1)∙K^(−1),respectively,owing to the uniform dispersion and selfalignment of the MXene layered structure.Additionally,the uniformly dispersed MXene nanosheets in the MCC network with interfacial interaction(hydrogen bonding)and mechanical entanglement endowed the nanocomposite films with excellent mechanical properties and flexibility.Furthermore,the thermal stability,water resistance,and antibacterial properties of the nanocomposite films were effectively improved with the introduction of MXene.Moreover,using DMAc/LiCl as the solvent system not only improves the compatibility between MCC and MXene but also avoids the problem of easy oxidation of MXene in aqueous systems.With the high stability of the MCC–MXene solution and enhanced properties of the MCC–MXene films,the proposed strategy manifests great potential for fabricating natural biomass-based dielectric materials.