An electron microscopic study on MnBi thin films

The structure and orientation of MnBi thin films prepared by sequential evaporation of bismuth and manganese on glass substrates were studied by transmission electron microscopy and electron diffraction. Results indicate that these films develop a preferred orientation with thec-axis perpendicular to the film plane. This preferred orientation is due to the formation of MnBi from a highly oriented bismuth layer, i.e., a layer with thec-axis perpendicular to the film plane. Trace amounts of elemental bismuth, manganese and MnO are found in these MnBi films. There is evidence of close parallel alignment between the MnBi and the bismuth lattices.     

An electron microscopic study of the morphology of cured epoxy resin

An electron microscropic study of fracture surfaces and microtomed sections of a cured epoxy resin based on a difunctional bisphenol A type resin cured with different amounts ofm-phenylenediamine is presented. Heterogeneities in the range 5 to 100 nm are seen to be present and have relatively higher crosslink density compared to the surrounding matrix. It is observed that the fracture path is around the heterogeneity and not through it. The size of the heterogeneity is a function of curing agent concentration and also of cure cycle. The stoichiometric sample, which has the highest crosslink density and the highest glass transition temperature, has the smallest heterogeneities. On either side of stoichiometry, the heterogeneity size increases. Samples subjected to a more severe post-curing cycle have much larger heterogeneities. The possible physical basis for these differences is discussed.On leave from the Indian Institute of Technology, New Delhi 110016, India.     

Improved mechanical property of foam glass composites toughened by glass fiber

The mechanically improved foam glass composite toughened by glass fiber was prepared by sintering technique, using waste sodium-calcium silicon flat glass powder as main raw materials. In this study, the preparation and properties of the samples were characterized by differential thermal analysis (DTA), field-emission scanning electron microscopy (FESEM) and mechanical property test. The specific strength of the composite was defined for the first time, and applied into the investigation of mechanical property. The results show that the specific improved bending strength of 10.45-22.26 MPa/(g cm^− 3), and the specific compressive strength of 30.45-34.34 MPa/(g cm^− 3) can be displayed when sintered at 790-815 °C with the addition of 5-25 wt.% glass fiber. Good correlations between the microstructure (in particular the fiber distribution), the high specific strength and the high modulus of elasticity of glass fibers.     

硫化钠沉淀法处理含镍废水

采用化学沉淀法处理含镍废水,以硫化钠为沉淀剂,将废水中的镍离子以某种含镍沉淀的形式析出,从而达到净化废水的目的,考察硫化钠的投加量、反应速率、搅拌时间和pH值对废水中镍离子的去除率的影响。结果表明,在pH=6.0,硫化钠投加质量为4.0 g,即为理论值的1.1倍时,以30 r/min的转速搅拌反应30 min的条件下,模拟含镍废水的处理效果最佳,去除率达到95.2%,所得的沉淀物经X射线衍射仪检测显示为氢氧化镍沉淀,中间过程生成的硫化氢气体可继续对废水进行处理。     

Transmission electron microscopic study of multiwalled carbon nanotubes

Multiwalled carbon nanotubes have been studied by transmission electron microscopy, selectedarea electron diffraction, and transmission electron energy loss spectroscopy (EELS). The results demonstrate that the walls of carbon nanotubes consist of graphite-like layers with an increased interlayer spacing compared to graphite. The local density distribution in the CNTs has been evaluated from EELS scans over the nanotubes.     

An X-ray diffraction and electron spectroscopic study of metallic glass In20Te80

Results of X-ray diffraction and X-ray photoelectron spectroscopy investigations on the crystallization behaviour of an amorphous In₂₀Te₈₀ system and the effects of crystallization on the electronic core levels of In and Te atoms are presented. During controlled heat treatments three crystalline phases, Te, -In₂Te₃, and In₂Te₅-I, were observed in this system. In addition, a few splat-cooled samples were found to exhibit a new metastable crystalline phase. Photoelectron measurements revealed that the Te 3d and 4d core levels of amorphous In₂₀Te₈₀ were shifted downwards in energy from their characteristic values of pure Te metal. The In 3d and 4d levels experienced large energy shifts due to alloying, but remained unaffected by heating at temperatures below 520 K.     

Microstructure and fracture toughness of nickel particle toughened alumina matrix composites

Al₂O₃-Ni composite materials have been made by a hot pressing technique. Two composite microstructures, i.e. a dispersive distribution of nickel particles and a network distribution of nickel particles in an alumina matrix, have been produced. The fracture toughness of the composite materials has been measured by a double cantilever beam method. Both composites are tougher than the virgin alumina matrix. The fracture toughness of the composite with a network microstructure is much higher and has a more desirable R-curve behaviour than the composite with a microstructure of dispersed particles. For the particulate dispersion microstructure, the main limitation to toughening is the lack of plastic deformation of the ductile nickel due to the pull out of nickel particles, indicating weak bonding at the Al₂O₃/Ni interface. For the network microstructure composite, the gauge length of the ductile phase is much larger, allowing the ductile nickel to stretch to failure between the crack faces. A large extent of nickel plastic deformation has been observed, and the weak bonding at the Al₂O₃/Ni interface can promote partial debonding and contribute further to toughening.     

Scanning electron microscopic study of acacia and eucalyptus wood chars

SEM studies of acacia and eucalyptus wood chars, prepared under different carbonization conditions, were undertaken to provide information on what happens in the transformation of wood to chars. The material normally lost as volatiles contributes totally to the formation of pores, cracks and pyrolytic carbon. Both woods exhibited similar devolatilization behaviour in pore structure development, crack formation and pyrolytic carbon deposition, showing a decrease in pore size with an increase in carbonization temperature and cracks/voids formation during rapid carbonization at higher temperatures (i.e. 800–1050 °C). Slow carbonization led to pyrolytic carbon deposition in resulting wood char structures and did not disturb the fibrous nature and cell structures of the wood, even at a high carbonization temperature of 1200 °C. Prolonged heating at carbonization (slow) temperatures of 800 and 1000 °C caused sintering of the adjacent fibres resulting in the formation of compacted mass.     

A scanning electron microscopic study of hybrid composite impact response

Scanning electron micrographs of fracture surfaces of various hybrid composite materials subjected to Charpy impact tests are presented. Macrophotographs of the failed specimens which indicate the gross failure modes, and actual impact load-time traces obtained using an instrumented tup impact test technique are also included. These data permit a direct comparison between observed microfailure modes and the gross response of each composite to failure. An all-graphite/epoxy control configuration and three hybrid configurations are considered. The third-phase fibre additions in these hybrids include glass, Kevlar 49, and Nomex nylon. Longitudinal and transverse impact tests of both notched and unnotched standard Charpy specimens are included, for both a basic unidirectional graphite/epoxy composite and a quasi-isotropic laminate orientation.     

A transmission electron microscopic study of the Bethany iron meteorite

The Bethany iron meteorite which is a part of the Gibeon shower is a fine octahedrite with zoned plessite fields of various sizes. The optically irresolvable microstructural details inside the plessitic fields have been studied by transmission electron microscopy, and the crystallographic relationships between the primary kamacite () and the parent taenite (), and between the and particles in the coarse plessite, have been examined using electron diffraction. In the case of primary kamacite the orientation-relationship with was close to the Nishiyama-Wasserman relationship, whereas, for the plessitic , the orientation-relationship with was close to Kurdjumov-Sachs. It was also found that the (111) and (110) planes were not strictly parallel. Additionally, measurements of the composition profile through the zoned plessite have been made using STEM microanalysis technique, and related to microstructure.     

Transmission electron microscopy of a transformation toughened white cast iron

Transmission electron microscopy has been used to study the microstructure of an experimental white cast iron, in which a combination of modified alloy composition and unconventional heat treatment has resulted in a fracture toughness of 40 MPa m-1/2. Microstructural features of the alloy that contribute to the toughness improvement and hence distinguish it from conventional white irons have been investigated. In the as-cast condition the dendrites are fully austenitic and the eutectic consists of M7C3 carbides and martensite. During heat treatment at 1130 °C the austenite is partially destabilized by precipitation of chromium-rich M7C3 carbides. This results in a dendritic microconstituent consisting of bulk retained austenite and secondary carbides which are sheathed with martensite. The martensite sheaths, which contain interlath films of retained austenite, are irregular in shape with some laths extending into the bulk retained austenite. Emphasis has been placed on the morphology, distribution, and stability of the retained austenite and its transformation products in the dendrites. The implications of these findings on the transformation toughening mechanism in this alloy are discussed.     

A transmission electron microscope study of the structure of electrolytic nickel

Conclusions In conclusion, during the electrolysis of nickel from acid sulphate solutions, the coverage of the cathode by a possible colloidal film of nickel hydroxide is the decisive factor. In its presence, the cathode exhibits a very fine-grained, randomly oriented structure. If the film is removed, the structure consists at these current densities of relatively large grains with a very strong texture [100] perpendicular to cathode. The large grains are often twinned, but no individual stacking faults are found.The inhibitive action of the hydroxide film can be eliminated by chloride ions [2], or it can be replaced by an organic additive [3].     

Adhesion of glassy arsenic sulfide to quartz glass

Adhesion between As₂S₃ glass and quartz glass has been studied by a uniform pull-off method. The pull-off stress for the adhesion of glassy As₂S₃ to quartz glass has been determined as a function of temperature in the temperature range 110–190°C. The results demonstrate that, in the case of As₂S₃ glass, the adhesion strength increases exponentially with increasing test temperature and exceeds 2500 kPa at the glass transition temperature. We have studied how the adhesion strength is influenced by the contact temperature and time, tension test temperature, and quartz glass surface roughness.     

An investigation of nickel cobalt oxide nanorings using transmission electron, scanning electron and helium ion microscopy

Nickel cobalt oxide alloy nanorings have been synthesized using a wet chemistry method. Standard characterization techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been used to characterize the nanorings. We, however, also examined the nanostructures in the helium ion microscope (HIM) and employed backscattered ion spectroscopy to determine thickness and composition of the nanostructure. The HIM provides complementary information of the nanostructures and the viability of using it as a tool for magnetic nanoparticle characterization was demonstrated by comparing the results from all three microscopes.     

Transmission electron microscopic study of three-dimensional polyacrylonitrile fibre-mesophase pitch matrix carbon-carbon composite

Conventional and high resolution transmission electron microscopy performed in this study provides some detailed microstructural information of a polyacrylonitrile (PAN) fibremesophase pitch matrix carbon-carbon composite which has not been published in open literature. The PAN fibre in this composite possesses a turbostratic structure throughout the fibre. The structure of the mesophase pitch matrix is graphitic and anisotropic. Near-fibre matrix crystallites are aligned roughly parallel to the fibre surface, exhibiting a flow-type morphology. The fibre-matrix interface in this composite is microfissured. Numerous microcracks exist both within the matrix and along partially bonded interfaces. The irregularly shaped interfacial microcracks readily expose the fibre surface topography. Microcracks within the matrix are formed between, and parallel to, the basal planes of the graphitic platelets. Such submicron-sized matrix cracks appear smaller and denser near the fibre-matrix interface.