Joining of CBN abrasive grains to medium carbon steel with AgCu/Ti powder mixture as active brazing alloy

In order to develop new generation brazed CBN grinding wheels, the joining experiments of CBN abrasive grains and medium carbon steel using the powder mixture of AgCu alloy and pure Ti as active brazing alloy are carried out at elevated temperature under high vacuum condition. The relevant characteristics of the special powder mixture, the microstructure of the interfacial region, which are both the key factors for determining the joining behavior among the CBN grains, the filler layer and the steel substrate, are investigated extensively by means of differential thermal analysis (DTA), scanning electron microscope (SEM) and energy dispersion spectrometer (EDS), as well X-ray diffraction (XRD) analysis. The results show that, similar to AgCuTi filler alloy, AgCu/Ti powder mixture exhibits good soakage capability to CBN grains during brazing. Moreover, Ti in the powder mixture concentrates preferentially on the surface of the grains to form a layer of needlelike TiN and TiB compounds by chemical metallurgic interaction between Ti, N and B at high temperature. Additionally, based on the experimental results, the brazing and joining mechanism is deeply discussed in a view of thermodynamic criterion and phase diagram of TiBN ternary system.     

Cyclodextrin polyurethanes polymerized with multi-walled carbon nanotubes: Synthesis and characterization

Insoluble cyclodextrin polymers co-polymerized with multi-walled carbon nanotubes were synthesized by polymerizing β-cyclodextrin with acid-functionalized multi-walled carbon nanotubes and diisocyanate linkers; hexamethylene- and toluene-2,4-diisocyanate. The polymers are useful in removing some organic pollutants from water, and we now report the full characterization of these polymers using infrared spectroscopy (IR), Raman spectroscopy, scanning and transmission electron microscopy (SEM and TEM) and thermal techniques such as thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).The polymers could be synthesized as either powders or amorphous solids. Results of the IR analysis showed the presence of functional groups such as CO, CC, CH and CO, indicating that polymerization indeed took place. Characterization of the polymers by scanning electron microscopy and BET analysis showed that these polymers had a spongy appearance indicating a hierarchical pore structure. Incorporation of small amounts (<5%) of multi-walled nanotubes (MWNTs) improved the thermal stability of the polymers. This observation was further confirmed by differential scanning calorimetry (DSC) measurements.     

A high-energy X-ray diffraction, P and B solid-state NMR study of the structure of aged sodium borophosphate glasses

The structure of aged melt-quenched sodium borophosphate glasses of composition (P₂O₅)₄₀(B₂O₃)_x(Na₂O)_60−x (with x in the range 10–40) has been studied by high-energy X-ray diffraction (HEXRD), ³¹P and ¹¹B magic angle spinning (MAS) NMR. Similar to the fresh samples, both POP and POB linkages are found to be present in these glasses. All three techniques show that the cross-linking between borate and phosphate units increases with boron oxide content. Distinctively upon aging, the glass is found to hydrolyze causing the network to degrade. At the same time, crystalline phases are now also observed. XRD and DTA show that the samples have a higher tendency towards crystallization with increasing boron oxide content upon exposed to moisture. ³¹P and ¹¹B MAS NMR results are in agreement with these findings. TGA data show that samples with higher boron oxide content take up more moisture upon aging, suggesting that crystallization may be associated with glass hydrolysis. HEXRD results also suggest that sodium ions are preferentially associated with borate units with increasing boron oxide content.     

Preparation and characterization of ultrafine alumina via sol–gel polymeric route

Ultrafine alumina powder was prepared through resin formation between urea and formaldehyde. Aluminium stearate soap was introduced during resin preparation. Ethylene glycol was used to terminate the thermosetting reaction. Calcination of the product was carried out at 700, 1000, 1100, 1300 and 1400 °C to obtain aluminium oxide.IR and Raman spectroscopic analysis indicated the occupation of Al³⁺ at different sites in the polymer network (CO, NH₂, CO, NH, and CH₂OH).X-ray diffraction of powder calcined at 1000 °C revealed the presence of a mixture of α- and θ-alumina together, while a mixture of α- and β-alumina phases were obtained on calcination at 1400 °C. Transmission electron microscope (TEM) examination of the powder fired at 700 °C showed uniform grains in the form of clusters with average size between 22.02 and 30.5 nm. Clusters are multi-particles as evident from the electron diffraction pattern. Crystallite size of alumina powder calcined at 1000 °C was found to be ≈25.67 nm, while that of powder calcined at1400 °C was ≈30.52 nm. The calculated specific surface area of alumina powder calcined at 1000 °C was 59.17 m² g⁻¹, while that calcined at 1400 °C was 49.77 m² g⁻¹.     

Thermal, structural and optical properties of new tungsten lead–pyrophosphate glasses

Crystalline lead–pyrophosphate precursor was prepared in aqueous solution from lead nitrate and phosphoric acid and characterized by X-ray diffraction, thermogravimetry and Raman scattering. This crystalline lead–phosphate was then used to prepare glass samples in the binary system Pb₂P₂O₇–WO₃. Dependence of WO₃ content on thermal, structural and optical properties were investigated by thermal analysis (DSC), Raman spectroscopy, UV–visible and near-infrared absorption and M-Line technique to access refractive index values. Incorporation of WO₃ in the lead–pyrophosphate matrix enhances the glass transition temperature and thermal stability against devitrification, favors formation of POW bonds and WO₆ clusters. In addition, optical properties are strongly modified with a redshift of the optical bandgap with WO₃ incorporation as well as an increase of the refractive index from 1.89 to 2.05 in the visible.     

Effect of the extrusion conditions on microstructure evolution of the extruded Al–Mg–Si–Cu alloy rods

Hot extrusion experiment was conducted using an Al–Mg–Si–Cu alloy and the effect of the extrusion conditions on microstructure and texture changes through the radial direction was investigated by using SEM/EBSP analysis method. In the surface layer where severe frictional shear deformation is predominant, the recrystallized 1 1 0//ED grains surrounded by high angle grain boundaries are formed in spite of the existence of some peripheral overcoarse grains. Strong 1 0 0//ED and 1 1 1//ED fiber textures evolve in the center where axisymmetric deformation along the extrusion direction is intensive. As the extrusion ratio increases, number of 1 1 1//ED grains remarkably decreases while the number of 1 0 0//ED grains apparently increases. It is also found that the 1 0 0//ED grains surrounded by low angle grain boundaries form orientation colonies in the center of the extruded rods.     

Preparation of novel transparent glass–ceramics containing fluoride crystals

Transparent glass–ceramics containing YLiF₄ nano-crystals were synthesized by controlled heat-treatments of LiFYF₃Al₂O₃SiO₂ glass. The crystallite size estimated to be about 8 nm was much less than the wavelength of the visible light. The transmittance of the glass–ceramic with a thickness of 2 mm was more than 85% at 400 nm and as high as 95% in the infrared region. The fluorescence centered around 1000 nm was hardly observed from Er³⁺-doped precursor glass under 800 nm excitation, while the emission with the Stark spitting was clearly observed for the Er³⁺-doped glass–ceramic. The phonon sideband of the ⁷F₀ → ⁵D₂ excitation spectra of Eu³⁺ reveals that Eu³⁺ doped in precursor glass is in silicate network while Eu³⁺ doped in the glass–ceramic is in not only silicate framework but also fluoride framework. These results indicate that rare-earth ions such as Er³⁺ and Eu³⁺ could be successfully incorporated into YLiF₄ nano-crystals in the glass–ceramics.     

Electrical characterization of CMOS transistors subject to externally applied mechanical stress

Hole and electron mobilities in CMOS structures are significantly influenced by a mechanical strain state. In the present work a new experimental device has been designed, able to apply a uniaxial in-plane strain along different crystallographic orientations. A hole mobility enhancement of +10% and an electron mobility decrease of −5% have been demonstrated with the application of a 0.05% compressive 1 1 0 strain; a hole mobility enhancement of +2% and an electron mobility decrease of −3% have been induced into the material with the application of a 0.05% compressive 1 0 0 strain.     

Effect of texture and testing conditions on strain localization during cyclic deformation of copper polycrystals

Fatigue tests were performed on pure copper polycrystals with a crystallographic texture different from that produced by ‘standard’ thermomechanical treatments, which emphasize multi-slip 111–100 textures. The texture along the loading axis deviated by 10–15° from these two poles for the samples used here. The experiments were initiated by ramp loading as a mechanical pretreatment and the cyclic stress–strain curve (CSSC) was established by step tests using enough cycles at each step to insure saturation. Under these conditions, a plateau was observed in the CSSC at an appropriate stress level and in a reproducible fashion.     

Dependencies of grain refinement on processing route and die angle in equal channel angular extrusion of bcc materials

The efficiency of grain refinement in equal channel angular extrusion of body-centered cubic (bcc) materials is investigated based on slip activities from crystal plasticity simulations, which account for both the macroscopic and crystallographic features of deformation. It is shown that the characteristics of slip activities, especially the relative contributions of slip systems newly activated or reversed at the transitions between successive passes, vary significantly with the processing routes (A, B and C) and die angles ( = 90° and 120°). The simulations assuming {1 1 0}111 slip suggest that routes B and A lead to the most significant contributions of newly activated slip systems and hence are most efficient for grain refinement with  = 90° and 120°, respectively. Further incorporation of {1 1 2}111 slip systems leads to the highest efficiency by route B for both die angles. These predictions are in partial agreement with experimental observations in the literature. Comparison of these results with those of face-centered cubic materials reveals the relevance of crystal structure and deformation mechanism during grain refinement.     

Magnetron sputtering of Zr-Si-C thin films

The phase composition and chemical bonding of ZrC and ZrSiC films deposited by magnetron sputtering has been studied. The results show that the binary Zr-C films at higher carbon contents form nanocrystallites of ZrC in an amorphous carbon matrix. The addition of Si induces a complete amorphization of the films above a critical concentration of about 15 at.%. X-ray diffraction and transmission electron microscopy confirm that the amorphous films contain no nanocrystallites and therefore can be described as truly amorphous carbides. The amorphous films are thermally stable but start to crystallize above 500 °C. Analysis of the chemical bonding with X-ray photoelectron spectroscopy suggests that the amorphous films exhibit a mixture of different chemical bonds such as ZrC, ZrSi and SiC and that the electrical and mechanical properties are dependent on the distribution of these bonds. For higher carbon contents, strong SiC bonds are formed in the amorphous Zr-Si-C films making them harder than the corresponding binary Zr-C films.     

Fluorescence and phosphorescence behavior of TPD doped and TPD neat films

Photoluminescence spectra of N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine (TPD) are studied in a temperature range from 10 K to room temperature using a neat TPD film, and 5 wt.% TPD doped films with polystyrene (PS), 4,4′-N,N′-dicarbazole-biphenyl (CBP), and polycarbonate (PC) as hosts. The photo-excitation occurred in the singlet absorption region of TPD. The blue fluorescence and green phosphorescence quantum yields, _F and _P, of TPD are determined from their quantum distributions, E_F(λ) and E_P(λ). The yields are found to be _F = 0.39 and _P = 0.012 for neat films at room temperature, while _F = 0.78 and _P = 0.026 are measured for a TPD doped PS film. The lower luminescence quantum yield in the neat film is caused by self-quenching.     

Microstructure and mechanical properties of nanocrystalline high strength Al–Mg–Si (AA6061) alloy by high energy ball milling and spark plasma sintering

In the present paper, the microstructure and mechanical properties of nanostructured Al–Mg–Si based AA6061 alloy obtained by high energy ball milling and spark plasma sintering were reported. Gas atomized microcrystalline powder of AA6061 alloy was ball milled under wet condition at room temperature to obtain nanocrystalline powder with grain size of 30 nm. The nanocrystalline powder was consolidated to fully dense compacts by spark plasma sintering (SPS) at 500 °C. The grain size after SPS consolidation was found to be 85 nm. The resultant SPS compacts exhibited microhardness of 190–200 HV_100 g, compressive strength of 800 MPa and strain to fracture of 15%.     

Survey of the 1997, 1998 and 1999 annual technical reports on patent information activities (part II: I to Z)

The activities of 59 intellectual property offices and organisations worldwide in the field of patent information are summarised for the period 1997–1999. The summary is presented under eight standard headings, as far as relevant, for each country. Activity varies enormously from just a handful of applications through to RU (24K), GB (30K), DE (58K), KR (80K), EP (121K), US (270K utility patents), and Japan (405K); the numbers are continuing to increase significantly in most countries. This part (second of two) covers 35 countries and organisations, with WIPO codes starting I to Z.The author concludes, inter alia, that

(i) the number of patent applications is increasing at such a rate that the granting or registration activities of many IP Offices are unable to keep up;

(ii) the development of electronic filing systems is proceeding apace;

(iii) the IPC, or derivatives such as ECLA, continue to be the primary tools for allocation, classification, and search in all IP Offices, except US and GB;

(iv) automated search systems continue to be developed and are used in tandem with manual search files, commercial and free Internet online databases; and

(v) the use of complex jukebox systems to handle the vast numbers of patent specifications on CD-ROM continues to increase.

Influence of additives on the impact toughness of Al–10.8% Si near-eutectic cast alloys

This article investigates the effects of melt treatment and addition of alloying elements on the impact toughness of as-cast and heat-treated Al–10.8% Si near-eutectic alloys. Increasingly precise impact behaviors are discussed in the context of differentiating between initiation and propagation energies, including the ductility index, which is the ratio of the propagation to initiation energies; total energy as a useful measure is also discussed. Details concerning the evaluation of tensile properties are reported in a separate article [Mohamed AMA, Samuel FH, Samuel AM, Doty HW. Influence of additives on the microstructure and tensile properties of near-eutectic Al–10.8%Si cast alloy. Mater Des, in press]. The concentration of elements in the alloys was changed to the following range: Fe 0.5–1 wt%, Mn 0.5–1 wt%, Cu 2.25–3.25 wt%, and Mg 0.3–0.5 wt%, while the impact toughness upon artificial aging in a temperature range of 155–240 °C for 5 h was also investigated. The results indicate that the morphology of fibrous Si in Sr-modified alloys enhances toughness because of its profound effect on crack initiation and crack propagation resistance. The combined addition of modifier and grain refiner leads to a 33% increase in the impact strength compared to the untreated alloy. In alloys containing high levels of iron, such as the RF2 (1% Fe, 1% Mn) and RF4 (1% Fe, 0.5% Mn) alloys, the addition of iron leads to an increased precipitation of sludge or β-Fe platelets, respectively; these particles also act as crack initiation sites and reduce the impact properties noticeably. In alloys already containing high levels of copper, such as the RC2 (3.25% Cu, 0.3% Mg) and RC5(0.3.25% Cu, 0.5% Mg) alloys, increasing the copper level lowers the impact properties significantly, in view of the fact that the fracture behavior is now predominantly influenced by the Al₂Cu phase rather than by the Si particles. The average crack propagation speed of impact-tested samples shows a good inverse relationship to impact energy. Crack propagation speed can thus provide a qualitative estimation of the impact energy expected for special alloy conditions.     

Grain boundary plane distributions and single-step versus multiple-step grain boundary engineering

The ‘five-parameter’ (i.e. both misorientation and grain boundary plane) distribution in type 304 austenitic stainless steel has been measured and evaluated for an ‘as-received’ (AR) specimen and specimens undergoing both single-step grain boundary engineering processing (SSGBE) and multiple-step grain boundary engineering processing (MSGBE) comprising three iterations. The results showed that the fundamental requirement for twinning-related GBE is to maximise concomitantly the proportion of both Σ3 and Σ9 boundaries, which in turn supports the development of special planes in the grain boundary network. 1 1 0 and 1 1 1 tilt and twist boundaries play a key role in the formation of ‘special’ grain boundary planes. MSGBE added increased proportions of Σ3 boundaries and resulted in development of different characteristics in the planes distribution compared to SSGBE. These modifications are likely to result in improved grain boundary properties after MSGBE compared to SSGBE.     

Optical properties and scanning probe microscopy study of some AgAsSSe amorphous films

Doping of AsSSe amorphous films by silver photo-dissolution leads to a decrease of the optical gap and to an increase of the refractive index in forming AgAsSSe films. The difference of the optical gap and refractive index between undoped and doped films has been found in case of Ag₁₅As₂₆S₂₉Se₃₀ film up to 0.37 eV and 0.26, respectively. Transreflectance in far infrared spectral region indicates formation of AgAsS₂ and AgAsSe₂ entities in Ag₁₅As₂₆S₂₉Se₃₀ film. Scanning probe microscopy, namely atomic force microscopy, atomic force acoustic microscopy (AFAM) and Kelvin probe force microscopy (KPFM) was used for studying AgAsSSe films. It was found that silver growth is rather three dimensional and it is reminiscent of the Stranski-Krastanov growth mode. Observed silver protuberances represent silver reservoirs responsible for a local increase of silver content. Hence, the silver growth mode enhances formation of nano/meso inhomogeneities of the surface and near surface density/stiffness, seen in AFAM, and in the surface electric potential, seen in KPFM.     

Targets emitting transition radiation for performing X-ray lithography by the tabletop synchrotron MIRRORCLE-20SX

The tabletop storage ring synchrotron (SRS) MIRRORCLE-20SX is a powerful source of soft X-rays emitted from transition radiation (TR) targets. SRS can be used as a source for performing X-ray lithography (XRL) when it emits TR power P_XRL50–100 mW of photons having energy in the range 490–1860 eV. One-foil targets in SRS can emit a high TR power, and the electron beam geometry of MIRRORCLE-20SX requires using TR strip targets with a width 3 mm. P_XRL emitted by one-foil strip TR targets is estimated for several foil materials, and varying foil thickness d. These results show that a target containing one C foil with d260 nm can be used for performing XRL. Target made of one collodion foil with d290 nm, and target of one Al foil with d200 nm emit less, but could also be used for XRL. We manufactured such targets by depositing layers of these materials on slide glass, using Teepol as a releasing agent, and subsequently floating them on a water surface. The C layer is prepared by a horizontal resistance thermal evaporation, and supported by a 270–300 nm thick collodion layer, formed onto the Teepol film. The Al layer is thermally evaporated.     

Thin films deposition with ECR planar plasma source

The results of film deposition of pure tungsten as well as intermetallic compound of NdFeB type on various substrates using planar ECR plasma source (with multipole magnetic field) developed in our laboratory are presented. The frequency of 2.45 GHz was generated within the magnetic system by two-slot antenna. The ions of ECR argon plasma are used for target sputtering. The main plasma parameters are density 10¹⁰ cm⁻³, T_e15 eV, ions energy 20 eV, ion current density 3.5 mA/cm² at the ultimate magnetron power. Under sputtering of Nd₈Fe₈₆B₆ target the amorphous films with high adherence and thickness of 5 μm were formed on the substrate. The deposition rate of tungsten films (target biasing 900 V) was 0.59 nm/s. The fine-grained films with high adhesion were obtained. They were tested against heat loads up to 100 J/cm² produced under irradiation of coatings with plasma streams.     

A vapor phase deposition of self-assembled monolayers: Vinyl-terminated films of volatile silanes on silicon oxide substrates

Vinyl-terminated self-assembled monolayers (SAMs) offer significant flexibility for further chemical modification and can serve as a versatile starting point for a tailoring of surface properties. A vapor phase deposition of such films would offer advantages in cases where the preparation from solution is not an option or not desired, for example in connection with silicon microstructures such as micro-electromechanical systems. We show that SAMs of 9-decenyltrichlorosilane (CH₂CH(CH₂)₈SiCl₃), 10-undecenyltrichlorosilane (CH₂CH(CH₂)₉SiCl₃), 14-pentadecenyltrichlorosilane (CH₂CH(CH₂)₁₃SiCl₃), decyltrichlorosilane (CH₃(CH₂)₉SiCl₃), and octadecanetrichlorosilane (CH₃(CH₂)₁₇SiCl₃) can be prepared both from solution and from the vapor phase. The resulting layers were compared by static contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy to determine their surface wettability, the film thickness, the smoothness and homogeneity of the respective films, and their chemical composition and each method gave films of comparable quality. Deposition of functionalized SAMs from the vapor phase is rare. Here we report the parameters for the preparation of well-ordered vinyl-terminated SAMs from the vapor phase.