Specific Features of Glass Damage and Fracture Resistance under the Rockwell Indenter Scratching of the Specimen Surface until the Edge Chipping Appearance

Strength of Materials - The paper presents the experimental results of investigations using different types of glass by the Rockwell indenter scratching of the specimen surface till its edge...     

Formation of a Network Structure in the Gaseous Reduction of Magnetite Doped with Alumina

Reduction of un-doped magnetite is developed topochemically with the formation of a dense iron shell. However, the reduction of alumina-doped magnetite to wüstite proceeds with the formation of a network-like structure which consists of criss-crossed horizontal and vertical plates of wüstite. Reduction of magnetite includes the conversion of Fe³⁺ to Fe²⁺ and the movement of iron cations from the tetrahedral sites on the {400} and {220} planes of magnetite to the octahedral sites on the {200} planes of wüstite. Alumina has a negligibly small solubility in wüstite. In the reduction of magnetite doped with Al₂O₃, rejected Al³⁺ cations from wüstite diffuse to the magnetite–hercynite solid solution. Enrichment of the Fe₃O₄–FeAl₂O₄ solution with alumina in the vicinity of the reduction interface restricts the growth of {220} planes of wüstite and nucleation of {220} planes adjusted to the existing planes, preventing the merging of wüstite plates during the reduction process. Reduction of magnetite from the magnetite–hercynite solid solution practically stops when the Al³⁺ content at the interface approaches the solubility limit. Wüstite in the separated plates is reduced further to iron.     

The effect of SiO2 on high-temperature deformation and strength of zirconia-toughened alumina

At room temperature, SiO₂ additions may increase the fracture toughness, K _IC, by diminishing the tetragonal phase contents to about 50%, but with ground surfaces the influence on strength is small. A pronounced decrease in strength is observed with rising temperature in the high toughness region from 20°C to M _s, the starting temperature for martensitic transformation. Beyond M _s at lower toughness, the strength behaviour is very similar to nontransforming alumina ceramics, and an even modest increase of the silicate concentration intensively promotes propagation-controlled failure in the brittle creep region (> 900°C) and inelastic deformation. With less than 1% amorphous grain boundary phases, damage-free superplasticity is restricted to small strains of less than 10%. The significance of high-temperature data for tool applications is considered by cutting tests with high feeding rates.     

Additive-Free Aqueous MXene Inks for Thermal Inkjet Printing on Textiles

Direct printing of functional inks onto flexible substrates allows for scalable fabrication of wearable electronics. However, existing ink formulations for inkjet printing require toxic solvents and additives, which make device fabrication more complex, limit substrate compatibility, and hinder device performance. Even water-based carbon or metal nanoparticle inks require supplemental surfactants, binders, and cosolvents to produce jettable colloidal suspensions. Here, a general approach is demonstrated for formulating conductive inkjet printable, additive-free aqueous Ti₃C₂T_x MXene inks for direct printing on various substrates. The rheological properties of the MXene inks are tuned by controlling the Ti₃C₂T_x flake size and concentration. Ti₃C₂T_x-based electrical conduits and microsupercapacitors (MSCs) are printed on textile and paper substrates by optimizing the nozzle geometry for high-resolution inkjet printing. The chemical stability and electrical properties of the printed devices are also studied after storing the devices for six months under ambient conditions. Current collector-free, textile-based MSCs show areal capacitance values up to 294 mF cm⁻² (2 mV s⁻¹) in poly(vinyl alcohol)/sulfuric acid gel electrolyte, surpassing reported printed MXene-based MSCs and inkjet-printed MSCs using other 2D nanomaterials. This work is an important step toward increasing the functional capacity of conductive inks and simplifying the fabrication of wearable textile-based electronics.     

用于蛋白快速分离的1-mm内径的高效聚合物整体材料

多年来,整体技术已经成功地从概念阶段发展到表征良好且可重复的商用阶段。不同的整体柱化学材料,包括阴离子交换剂、阳离子交换剂和在ProSwift线性整体柱的反相功能基团,均可用于多种蛋白质的分离。与更大尺寸的色谱柱相比,1-mm内径的色谱柱在灵敏度提高和使用方便二者间达到了很好的协调。由于背压较小,这些整体柱可以在高动力学流速下运行,从而可以在标准的分析型色谱仪器上使用,而不需要微柱或者毛细管柱高效液相色谱系统。     

Strength and crack resistance of zirconium dioxide crystals containing yttrium and terbium oxides

Conclusions We studied the mechanical behavior of the partially stabilized (with yttrium oxide) zirconium dioxide crystals in which a small quantity of terbium oxide was introduced as an additive. The obtained data indicate the suitability of this material for practical applications. The effect of heat treatment on the physical and mechanical properties of such materials was revealed. It was established that on cooling up to –150°C, their strength and thermal shock resistance are improved.The lack of correspondence between the values of the crack resistance determined according to the methods of bend testing and indentation was established. The existence of a significant barrier to fracture was observed. The two possible types of surfaces of the crystals under consideration were revealed and the relationship between the structure of these surfaces (and, also, the near-surface layers adjoining them) and the resistance to fracture was established.Translated from Ogneupory, No. 6, pp. 2–8, June, 1993.     

Synthesis of Boron Nitride Coating on Carbon Nanotubes

A method to synthesize boron nitride coating on the surface of carbon nanotubes (nanofibers) without damaging the tube walls has been developed. A reaction between boric acid and ammonia was performed at moderate temperatures on the surface of carbon nanotubes to form boron nitride (BN) coatings. The surface structure of the carbon nanotubes significantly influences the morphology of the boron nitride coating. If the surface of the tubes is free of defects, highly crystallized insulating BN nanotubes can encapsulate carbon nanotubes. On the surface of carbon nanotubes with disordered wall structure, a polycrystalline BN sheath was produced.