Addressing amorphization and transgranular fracture of B4C through Si doping and TiB2 microparticle reinforcing

Over the last two decades, many studies have contributed to improving our understanding of the brittle failure mechanisms of boron carbide and provided a road map for inhibiting the underlying mechanisms and improving the mechanical response of boron carbide. This paper provides a review of the design and processing approaches utilized to address the amorphization and transgranular fracture of boron carbide, which are mainly based on what we have found through 9 years of work in the field of boron carbides as armor ceramics.     

Carbon content-dependent microstructures,surface characteristics and thermal stability of mechanical alloying derived SiBCN powders

Three types of SiBCN: carbon-lean, -moderate and -rich powders with the same Si/B/N mole ratio were subjected to high-energy ball milling to yield an amorphous structure. The effects of carbon content on microstructures, solid-state amorphization, surface characteristics and thermal stability of the as-milled powders were studied in detail. Results showed that the increases in carbon content can drive solid-state amorphization accompanied by strain-induced, crystallite refinement-induced and/or chemical composition-induced nucleation of nano-SiC from an amorphous body. The specific surface area increases as carbon content increases. The amorphous networks of Si–C, C–B/C–C, C–N, B–N and C–B–N bonds that compose the amorphous nature, but the species and contents of the chemical bonds are carbon content-dependent. Carbon-moderate powders possess satisfying thermal stability while carbon-rich ones perform the worst. Mechanical alloying derived SiBCN powders have outstanding oxidation resistance below 800 °C; however only carbon-moderate powders show desirable anti-oxidation ability at higher temperatures. Thus, mechanical alloying of SiBCN appears a suitable technique for developing amorphous matrix materials for practical applications.     

Hydrogen-induced Amorphization in LaNi2.5M0.5 (M=Ni, Fe, Mn, Si) Alloys

采用XRD和电化学测试的方法研究了Fe、Mn、Si部分替代Ni对LaNi3型贮氢合金氢致非晶化的影响.结果表明:LaNi2.5M0.5(M=Ni,Fe,Mn,Si)贮氢合金的主相均为LaNi3相;在第一次充电后,合金均有一定程度的氢致非晶化现象;LaNi3和LaNi2.5Fe0.5合金的放电曲线没有放电平台,表明合金充电后为非晶态;LaNi2.5Mn0.5和LaNi2.5Si0.5合金的放电曲线有一个倾斜的平台,这表明少量的Mn和Si可以在一定程度上抑制LaNi3型贮氢合金的氢致非晶反应.     

Performance of (1 1 0) p-channel SOI-MOSFETs fabricated by deep-amorphization and solid-phase epitaxial regrowth processes

The impact of local deep-amorphization (DA) and subsequent solid-phase epitaxial regrowth (SPER) are studied for the co-integration of devices with hybrid surface orientation. Thin-body p-channel transistors with 20 nm thick film and HfO₂ gate insulator/metal gate along several directions on a (1 1 0) substrate were fabricated and characterized. No deterioration of transconductance or threshold voltage was induced by DA/SPER process. Device co-integration using DA/SPER process is therefore a realistic option. 〈1 1 0〉 channel on (1 1 0) SOI film yields a 200% gain on the current for the (1 0 0) surface orientation. However, the benefit of it decreases with the channel length.     

Formulation of tablets containing an ‘in-process’ amorphized active pharmaceutical ingredient

The aim of this work was a preliminary study of the “in-process” amorphization of clopidogrel hydrogensulfate (CLP) as model drug during the production of tablets as dosage form. A solvent method was used for amorphization and the crystalline phase of CLP was detected by differential scanning calorimetry; the physical parameters of fresh and stored tablets were investigated. For the amorphous form, Aerosil 200 was selected as crystallization inhibitor as the most suitable of eight auxiliary agents. The optimum composition of the product for amorphization in the scaling-up process (100-fold) was 7 parts of CLP to 3 parts of Aerosil 200. In this scaled-up product, the amorphous CLP was fixed on the surface of microcrystalline cellulose. The tablet form further stabilized the amorphous form. Finally, the steps of an “in-process” amorphization are given as a protocol, which can promote stabilization of an amorphized active pharmaceutical ingredient.     

Investigation of the phase formation wave in the model of solid state amorphization

Computation results of the model of solid state amorphization (SSA) based on a general approach to non-equilibrium phase transitions are reported. The model takes into account the mutual interaction of the structural elements of the amorphous phase via a deformation field. For the experimental parameters, corresponding to semiconductors undergoing amorphization by high-pressure treatment, a family of self-sustaining autowave solutions in the form of a traveling front, a traveling pulse and a series of pulses associated with the traveling front was obtained. The relation of these solutions with the expected morphology of amorphous samples produced by SSA is discussed.     

Amorphization of Fe38Ni30Si16B14V2 surface layers by laser cladding

Fe38Ni30Si16B14V2 amorphous composite coatings were fabricated by laser cladding on AISI 1045 steel in order to increase the wear resistance. The phase and microstructure of the coatings were analyzed by X-ray diffractometry and transmission electron microscopy. The wear properties of the coatings were also investigated by means of sliding wear test. The results show that the coating consists of amorphous phase in majority and nanocrystalline phase in minority. The amorphous coatings can be obtained while the scanning speed is 3 500 mm/min and the laser power is 4.8 kW. With increase of the laser power, the amorphous phase in the coating increases when it is lower than 4.8 kW. A gradient distribution of the microhardness ranges from Hv0.2 1 208 to Hv0.2 891 in the coating from top surface of the coating to the substrate. The amorphous coating is found to possess better property of wear than AISI 1045 steel substrate.     

Defect-induced amorphization of crystalline silicon as a mechanism of disordered-region formation during ion implantation

An atomic-scale simulation study is presented which demonstrates that siliconamorphization during ion implantation can be caused by defect-induced collapseof the crystalline lattice. The amorphization threshold is calculated in termsof critical defect concentrations required to induce the amorphizationtransition at room temperature. These concentrations are found to be about28%, 20%, and 25% of self-interstitials, vacancies, or Frenkel pairs,respectively. These high defect densities are consistent with experimentalmeasurements in silicon self-implanted with high-energy ions. The structureof the defect-induced amorphous phases is similar to that of the bulkamorphous phase produced by rapid quenching of liquid silicon.     

AMORPHIZATION TRANSFORMATION BY MECHANICAL ALLOYING IN THE Mo-Si SYSTEM

1.IntroductionInrecelltyears,MoSiZhasattractedconsiderableattentionasapotentialhigh-temperaturestructuralmaterial.Thecombinationofhighmeltingpoint(2030"C),moderatedensity(6.24gcm--'),excellentoxidationresistance,andhighmodulusatelevatedtemperaturemakesMoSiZoneofthemostpromisingmatrixphasetobeusedattemperaturesupto1600oC[l].Anothermolybdenumsilicide,Mo5Si3,hasbeenproposedasapotentialreinforcementforMoSt,[1,2].AmongawidevarietyofprocessingtechniquesutilizedtosynthesizeMoSt2,mechanicalalloy…