Microscopy of electrical treeing behavior

The microstructural sequence of electrical treeing behavior has been presented from a study of electric breakdown lifetime and microscopy. The effect of absorbed moisture on the electric lifetime has been explained by means of the electric lifetime equation.     

A Raman microprobe study of a magnesia partially stabilized zirconia fracture surface

Raman microprobe analysis has been used to determine the extent of phase transformation on the fracture surface of a magnesia partially stabilized zirconia test bar. This has been found to vary across the fracture face and is considered to be related to the amount of microcracking which occurs in the sample during fracture.     

Acrylamide polymerization kinetics in gel electrophoresis capillaries. A Raman microprobe study.

The formation of 3.5% T, 3.3% C cross-linked polyacrylamide is monitored in 75-microns-i.d. electrophoresis capillaries by Raman microprobe spectroscopy. The disappearance of the acrylamide 1292-cm-1 band is followed with 60-s time resolution for 30 min, and 2-4 min resolution for up to 10 h. Polymerization is 98% complete in 1.5 h and greater than 99% complete after 2 h. In the 900-1700-cm-1 region no bands attributable to cross-linking are observable. Reaction in the capillary follows second-order kinetics. The reaction is faster in the bulk system because heat dissipation is not sufficient to maintain a constant temperature.     

Lamellar structure in heat-treated polyethylene. A Raman spectroscopic study

Measurement of the low frequency Raman spectrum of polyethylene affords a method of following the effects of sample deformation on lamellar structure and of the process of annealing on lamellar thickness.     

纳米SiO2对交联聚乙烯交/直流击穿强度和耐电树枝性能影响

为系统地研究纳米SiO₂对交联聚乙烯（XLPE）交/直流击穿强度和交/直流耐电树枝特性的影响,使用平行双螺杆分别制备了含0.5wt%和1wt%纳米SiO₂的纳米SiO₂/XLPE复合材料,以商用直流电缆料和普通XLPE作为参照,测试了掺杂纳米SiO₂对XLPE交流电树枝和直流接地电树枝的引发和生长特性及交/直流击穿强度的影响。实验结果表明,商用直流电缆料的直流击穿强度与普通XLPE相近,但其直流接地电树枝的引发更困难,树枝生长也更缓慢;随着纳米SiO₂添加量增大,纳米SiO₂/XLPE复合材料交/直流击穿强度的作用增强,对交/直流电树枝引发的抑制作用也增强,1wt%纳米SiO₂/XLPE复合材料具有显著抑制直流接地电树枝生长的效果,其直流接地电树枝引发和生长特性均优于商用电缆料;1wt%纳米SiO₂/XLPE复合材料的交流击穿强度和交流电树枝起始电压均高于普通XLPE,但其对交流电树枝的生长抑制作用仅局限在电树枝生长初期,电树枝生长达到一定阶段后,1wt%纳米SiO₂/XLPE复合材料中的电树枝生长速度超过普通XLPE。      

Raman microprobe analysis of preforms and optical fibers

The concentration profile of various dopants (germanium, phosphorus, and fluorine) in preforms and optical fibers has been obtained with a Raman microprobe. A 2-microm spatial resolution was achieved. In the case of germanium and phosphorus, the results agree quite well with those obtained with an electron microprobe. Raman spectroscopy easily detects fluorine. From measurements of various F-doped samples, diffusion of fluorine in undoped and doped silica is suggested.     

The structure of crystalline polyethylene sulphide — a laser Raman study

That polyethylene sulphide crystallizes in lamellar units within spherulites, has been presumed. In this paper further evidence for lamellae from Raman spectroscopy is presented and discussed. Thickening of the lamellae betweenT _M-90 andT _M-15 is also demonstrated.     

A study of twinning in polyethylene

Both {1 1 0} and {3 1 0} deformation twinning modes have been predicted for polyethylene. The existence of the former twinning mode has been confirmed in this work by non-photographic X-ray methods. When comparing and explaining bulk and single crystal twinning behaviour in terms of the influence of fold surface geometry, certain discrepancies arise. These may be resolved by noting that {1 1 0} twins occur at relatively low stresses and that {3 1 0} twins are formed under conditions of high strain during which the crystalline morphology is changed from lamellar to microfibrillar.     

The method of testing of XLPE cable insulation resistance to partial discharges and electrical treeing

The paper gives a method of model XLPE medium voltage cable insulation testing for partial discharges and electrical treeing with a point to plane test geometry. Based on this method, a comparative estimate of insulation resistance to treeing and partial discharges have been made. XLPE crosslinked by different methods (steam medium and hot nitrogen medium) and with varying contents of inorganic filler kaolin were tested. The characteristics of partial discharges were measured by means of a pulse height analyser characterized with a microscope. The data have been analysed statistically.     

The Raman spectra of high modulus polyethylene fibres by Raman microscopy

Raman-microscopy has been used to analyse a series of high modulus polyethylene fibres. The high degree of orientation within the material means that upon 90° rotation of the samples and/or polarisation analyser, marked variations in band intensities occur throughout the spectra. Measurements of the 1131 : 1064 cm–1 band intensity ratio of the fibres are made and related to their Young's modulus. This relationship is useful in morphological studies of polyethylene fibres.     

Raman microprobe analysis of elastic strain and fracture in electrophoretically deposited CdSe nanocrystal films

The mechanical stability of nanocrystal films is critical for applications, yet largely unexplored. Raman microprobe analysis used here to probe the nanocrystal cores of thick, fractured electrophoretically deposited films of 3.2 nm diameter CdSe nanocrystals measures approximately 2.5% in-plane tensile strain in cores of unfractured films. The crack dimensions determine the overall in-plane film strain, approximately 11.7%, and the film biaxial modulus, approximately 13.8 GPa, from which the biaxial modulus of the trioctylphosphine oxide ligand matrix is inferred, approximately 5.1 GPa.     

Electrical treeing in solid polymeric insulation

Polymeric materials are gradually replacing naturally occurring substances for insulators. However their high electrical strength and good mechanical and thermal properties are degraded by the occurrence of water and electrical treeing. The article describes the nature of the forms of electrical treeing and reviews the theories of their formation, their inhibition and their detection     

Raman microprobe: a diagnostic tool for processed silicon. Analysis of microindented silicon

Laser-assisted processes are currently used in silicon technology. The response of the material to the laser beam depends strongly on its own physical properties and on the laser power density. The use of a microRaman system, allows the structural characteristics of the material to be analysed by varying the excitation laser power density on the sample over a large power range with a submicrometre lateral resolution. Results are reported on microindented crystalline silicon, showing that changes in the physical properties of the material, introducing grain boundaries, dislocations and cracking, result in a strong modification of the Raman spectrum. These spectral changes are enhanced for increasing laser power densities. Several mechanisms are pointed out as possible sources of the observed spectral modifications. These results show that Raman microprobe is a very promising technique for the diagnosis of technologically processed semiconductors and devices.     

Raman and electrical studies of multiferroic BiFeO3

Monophasic rhombohedral structure of BiFeO₃ electroceramic is successfully synthesized by conventional solid state reaction route followed by slow step sintering schedule. Effect of sintering temperature is found to greatly influence its structural, dielectric, ferroelectric, capacitance and leakage behavior of bulk ceramic. From XRD analysis it is seen that at lower sintering temperature (750 °C) bulk BiFeO₃ sample showed rhombohedral structure (R3c) along with few impurity phases, which become suppressed at higher sintering temperature and facilitates the compactness of grains and formation of dense microstructure. The leakage current and capacitive characteristic of the sample was improved significantly with increase in sintering temperature of BiFeO₃ (850 °C). At higher sintering temperature, ferroelectric behavior of the sample is found to change its shape from semi elliptical lossy P–E features to a typical ferroelectric loop with improvement of its remnant as well as saturation polarization value. Raman spectra over the frequency range of 100–700 cm^?1 have been systematically investigated. Besides the changes of the peak position and the line width of all modes, the prominent frequency shift, the line broadening and variation of the intensity were observed with increase in sintering temperature.     

Analysis of pigmentary materials on the vinland map and tartar relation by Raman microprobe spectroscopy

Studies by Raman microprobe spectroscopy have shown that the black ink defining each feature on the controversial Vinland Map consists of carbon that overlays a yellow line containing anatase. This material was not detected elsewhere on the map. Since anatase has not been found on medieval artifacts, and such yellow lines are only naturally produced by iron gallotannate inks, a modern (post 1923) origin for the Vinland Map is strongly indicated. The ink of the Tartar Relation is different and probably consists of an iron gallotannate mixed with a small proportion of carbon. The rubrication is established to be vermilion.