Microstructural Modifications Research Articles

Enhanced adhesion strength between electroplated Cu and ABF substrate with isothermal annealing treatment

This study aimed to enhance the adhesion strength between electroplated Cu and a low-profile Ajinomoto build-up film (ABF) substrate through isothermal annealing treatment. We examined the electroplated Cu microstructure evolution (including grain size, orientation, and texture) and elemental distribution at the Cu/ABF interface after annealing at 180 °C and 210 °C by means of electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and transmission electron microscopy (TEM) in conjunction with energy dispersive X-ray spectroscopy (EDS). Furthermore, the adhesion strength of the Cu/ABF structure after isothermal annealing for different times was investigated through a peeling test based on the IPC-TM-650 test methods. The chemical bond and atomic concentration depth profiles of the fracture surface (ABF side) after the peeling test were characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). These investigations demonstrated that the adhesion strength of the Cu/ABF structure can be greatly enhanced by the electroplated Cu microstructure modification and Cu/ABF interdiffusion through appropriate isothermal annealing treatment.

High-temperature effect on the mechanical behavior of recycled fiber-reinforced concrete containing volcanic pumice powder: An experimental assessment combined with machine learning (ML)-based prediction

The increasing volume of waste generated by various activities has increased interest in using waste to create sustainable construction materials to achieve possible benefits. In addition, using recycled materials to produce fresh concrete is a desirable option because of its low cost, lower landfill space requirement, and the completed concrete quality. Therefore, an experimental inquiry is undertaken to ascertain the impacts of up to 20 wt% cement displaced by Volcanic Pumice Powder (VPP) with the incorporation of 1% and 2% Recycled Nylon Fiber (RNF) on the mechanical properties of concrete composites following room temperature to high-temperature (600 °C) exposure. Fresh concrete characteristics tests were performed, including slump, compacting factor, Kelly ball penetration, and density. The heat resistance of the concrete was then measured by calculating the percentage decrease in weight, the splitting tensile strength, and the compressive strength of the specimens. Heating mainly raised VPP's pozzolanic reactivity and lowered high vapor pressure through melting RNF. Therefore, VPP and RNF-treated concrete had superior mechanical performance than control concrete even when exposed to elevated temperatures. Further, the microstructural modifications brought on by RNF and VPP additions were also explored by deploying Scanning Electron Microscopy (SEM). The use of VPP in concrete led to an improvement in fresh properties, while RNF demonstrated deterioration in the same qualities. Despite this, supervised machine learning techniques are a central focus of this investigation because of their potential to predict concrete characteristics accurately. To predict the fresh and mechanical characteristics of concrete, both the Random Forest (RF) and the K-Nearest Neighbors (KNN) algorithm, along with their ensemble model counterparts, were explored. The outcomes revealed that RNF and VPP considerably improved the concrete's heat resilience and mechanical characteristics and halted the concrete composites' explosive spalling behavior at 600 °C temperatures. To prevent strength loss at high temperatures, it was discovered that adding 1% RNF content to concrete with 10% VPP was the best combination. In addition, the high coefficient correlation (R2) value of the RF and the ensemble model indicates great accuracy in outcome prediction, while the low R2 value of the KNN model indicates that the KNN model is less accurate.

Ion-exchange induced mechanical properties enhancement and microstructural modifications of transparent lithium aluminosilicate glass-ceramics

Alkali-aluminosilicate glass and glass-ceramics can be effectively strengthened by ion-exchange if compression is introduced into the surface, which have been widely used in many electronic devices, especially for mobile phones. In this work, the transparent lithium aluminosilicate glass-ceramics with eucryptite crystalline phase were ion-exchanged in the mixed x NaNO3 + (100－x) KNO3 (wt%, x = 60, 70, 80, 90, 100) molten salts at 420 °C for 4 h. With the increase of NaNO3 concentration in the molten salts from 60 to 100 wt%, the depth of stress layer increase from 98 to 104 μm, and the surface compressive stress increase to the maximum ∼500 MPa at x = 80 and then decrease. In addition, there is also a K+-rich layer observed with the depth of ∼25 μm. The ion-exchange takes place in both crystalline and residual glassy phases, and thus leads to the microstructural modifications, including the amorphization of eucryptite and the presence of lithium phosphate. Upon ion-exchange, the Vickers hardness of glass-ceramics increase from 7.03 GPa to the maximum ∼7.62 GPa (x = 80), and the bending strength from 198 MPa to the maximum ∼510 MPa (x = 90). The improvement in mechanical properties is mainly related to the generation of surface compressive stress layer. Meanwhile, the amorphization and transformation of crystalline phase during the ion-exchange process are probably conductive for the reduction of surface cracks and defects, leading to the enhancement of mechanical properties, especially for the bending strength.

Effect of High-Power Laser Cleaning for Surface Contaminants Removal on SS304L

In this study, artificially formed corrosion and paint layers on 304L stainless steel (SS304L) specimen were removed using a kilowatt level high-power Nd:YAG laser. A laser power of 1140 W and a pulse duration of 89 ns were used for the corrosion removal, and a laser power of 850 W and a pulse duration of 54 ns were adopted for the paint removal. Surface composition was analyzed via electron probe micro-analysis (EPMA) and x-ray diffraction (XRD) analysis before and after the laser cleaning process, confirming that the corrosion and paint layers were successfully removed from the SS304L surface by the laser cleaning process. The effect of the laser cleaning process on the mechanical properties of SS304L was investigated. The hardness and tensile strength of the laser-cleaned specimens were analyzed to determine their mechanical properties. After the laser cleaning process, the surface hardness was slightly increased up to depths of 250 µm for the corrosion removal and up to 50 µm for the paint removal. However, only marginal changes in tensile strength and elongation were detected after the laser cleaning process. These results confirmed that laser cleaning can effectively remove surface contaminants (i.e., corrosion and paint) on SS304L with only a minimum modification of microstructure and mechanical properties.

Modification of microstructure and mechanical properties for twin-wire directed energy deposition-arc fabricated Ti–48Al–2Cr–2Nb alloys via current regulation

Considering the advantages of low density and excellent high-temperature performance, titanium aluminide is identified as an ideal aerospace structural material. In recent years, twin-wire directed energy deposition-arc (TW-DED-arc), which possesses the characteristics of low cost but high deposition efficiency, has continuously attracted worldwide attention. However, obtaining equiaxed grains with small Al variation for titanium aluminide using TW-DED-arc method is still a key concern. In the present research, Ti–48Al–2Cr–2Nb alloy with equiaxed lamellar colonies and less than 1 at.% of Al content was successfully fabricated by regulating deposition current of TW-DED-arc. Also, the effect of deposition current on microstructure and mechanical properties was systematically investigated. The experimental results that focus on top and middle regions of as-fabricated TiAl-4822 alloys, indicate that increasing current favors in generation of equiaxed grains and γ lamellae, which leads to columnar to equiaxed transition and higher γ phase content, respectively. Also, elemental homogeneity can be significantly homogenized. As deposition current increases, tensile strength increases while degree of tensile anisotropy decreases significantly, benefiting from the equiaxed grains with satisfying size. Importantly, microstructure evolution, tensile anisotropy and fracture characteristics of TW-DED-arc fabricated TiAl-4822 alloys are discussed in detail. Generally, these findings provide an effective process method to optimize microstructure and mechanical properties of TW-DED-arc fabricated TiAl-4822 alloys.

High hysteresis-free dielectric tunability in silver niobate-based ceramics

Moderate dielectric constant, low dielectric loss, and high dielectric tunability around or above Curie temperature are essential characteristics of dielectric tunable devices. Silver niobate (AgNbO3), known for its antiferroelectric (AFE) and weak ferroelectric (FE) nature, offers a natural “composite” system combining AFE and FE attributes, making it an attractive candidate for tunable device materials. Microstructural modification through chemical methods can enhance its dielectric tunability. To this end, we propose and prepare a doped AgNbO3 ceramic system, denoted as (1-x) AgNbO3-xLiTaO3 (ANLT100x, x ≤ 3.8 mol%). Structural analysis reveals that all samples maintain an average AFE-like polar structure. The introduction of dopants disrupts the ordered AFE-like structure, altering the proportion of AFE and FE states. This disruption leads to a notably improved relaxor dielectric response and an FE transition around room temperature. Consequently, we achieve a ceramic material (x = 3.8 %) with a moderate dielectric constant (εr = 520) and low dielectric loss (tanδ = 0.008), accompanied by a hysteresis-free dielectric tunability (nr = 37.2 %) under an applied bias electric field of 40 kV cm−1, which is four times larger than that in AgNbO3 (nr = 8 %) ceramic. These findings open new possibilities for developing dielectric tunable materials in device design.

A comparative study of the activation energy and shielding properties of some binary and ternary echo-friendly alloys reinforced by Bi substitutes Zn particles for radiation protection

The thermal and mechanical stability besides environmentally friendly of some low-melting binary systems dopant with third element such as Bi started to gain much attention. This study provides the synthesized, effects of rapid solidification processing (RSP) and Bi doping on the microstructural, mechanical performance and gamma radiation shielding of various lead-free binary and ternary alloys have compositions Sn-(50-x)Zn-xBi (where x = 0, 10, 20, 30 and 40 wt.%) using high cooling rate. Microstructure modifications, elastic and plastic behavior were investigated. As well as the gamma-ray shielding performance of all as-prepared melt-spun process alloys was examined experimentally using FH 40G dose rate measuring unit. Phy-X/PSD software was used to compute the μ m values across a large energy range of 0.015 MeV–15 MeV. To clearly understand the gamma radiation shielding capability of the melt-spun process alloys, different shielding parameters includes linear attenuation coefficients, LAC, mass attenuation coefficient, MAC, mean free path, MFP, half value layer (HVL) and tenth value layer (TVL) were calculated and compared to other commonly shielding materials. X-ray diffraction (XRD) analysis confirms the presence of different phases such as β-Sn, Bi, Zn as well as two IMCs Sn0.95Bi0.05 and Sn0.85Zn0.15. The morphology features of the samples using scanning electron microscopy (SEM) revealed that Bi particles dopant the matrix led to refine the microstructures as well as forming a uniform and homogeneous distribution of IMCs. It is also, reported that the increase of Bi dopant led to enhancing the Bi segregation in the matrix in addition to decreasing the crystallite size which reinforces the mechanical strength and radiation shielding properties. The elastic modulus and Vickers microhardness increase with increasing Bi additions to about 35% and 27%, respectively. The results showed that correlation between activation energy and shielding properties of as-prepared alloys. The mass and linear attenuation coefficient for all prepared samples increases as Bi increases from 10 to 40 wt.%. On the other hand, low activation energies indicate easier formation and growth of IMCs. The results also show that the Sn-10Zn-40Bi alloy has the highest mechanical and shielding attenuation properties. It may be attributed to promoting the brittleness of Bi, refinement of crystallite size, extended the solid solubility and microstructure features accompanying Bi content using rapid cooling. As a result, Sn-10Zn-40Bi alloy may be recommended as a preferable alloy for radiation shielding performance to be used for medical, industrial and nuclear waste storage fields. In the current work, an attempt has been made not only to summarize the various investigations made so far on visualizing the feasibility of alloys as radiation shielding material; but also, to provide a comparative study for further consideration to be used in other fields.

Fabrication, Processing, Properties, and Applications of Closed-Cell Aluminum Foams: A Review.

Closed-cell aluminum foams have many excellent properties, such as low density, high specific strength, great energy absorption, good sound absorption, electromagnetic shielding, heat and flame insulation, etc. As a new kind of material, closed-cell aluminum foams have been used in lightweight structures, traffic collision protections, sound absorption walls, building decorations, and many other places. In this paper, the recent progress of closed-cell aluminum foams, on fabrication techniques, including the melt foaming method, gas injection foaming method, and powder metallurgy foaming method, and on processing techniques, including powder metallurgy foaming process, two-step foaming process, cast foaming process, gas injection foaming process, mold pressing process, and integral foaming process, are summarized. Properties and applications of closed-cell aluminum foams are discussed based on the mechanical properties and physical properties separately. Special focuses are made on the newly developed cast-forming process for complex 3D parts and the improvement of mechanical properties by the development of small pore size foam fabrication and modification of cell wall microstructures.

Are Microstructures in Plutonic Rocks Primary or Secondary? A Re-examination of the Metasomatism Hypothesis for the Roof-Sourced Autoliths in the Skaergaard Intrusion

Abstract The roof-derived autoliths in the floor cumulates of the Skaergaard Intrusion have been argued to have been extensively metasomatised and recrystallised, forming the foundation of the hypothesis that microstructures in plutonic rocks are essentially metamorphic. However, the augite–plagioclase–plagioclase dihedral angles and plagioclase core composition of the autoliths match with those of the roof rocks, demonstrating that they were generally solid on arrival at the floor, with no subsequent microstructural or compositional modification. Many autoliths have mafic rinds, which were used as evidence of metasomatism: these rinds fall into two groups. The rarely developed rind rock of Irvine et al. (1998) is most likely chilled magma infiltrating along fractures in the roof rocks, either associated directly with detachment of roof material, or occurring before final detachment. Thin mafic rims are widespread in LZc and MZ, present at the tops of the more elongate autoliths, with a corresponding felsic rim at the base of the most elongate autoliths. The close correspondence of thin rim development with autolith shape, rather than composition, is argued to be evidence that they formed as a result of differential migration of immiscible conjugate interstitial liquids: the dense Fe-rich liquid flowed downwards and ponded on the tops of impermeable autoliths, whereas its buoyant Si-rich conjugate flowed upwards and was trapped underneath. Any differences in microstructure and bulk composition of the autoliths compared with the remaining exposures of the roof sequence reflect the wider range of lithologies in the now-eroded regions of the roof.

Improved strength in nickel‑aluminum bronze/steel bimetallic component fabricated using arcing-wire arc additive manufacturing with alternating deposition strategy

To enhance microstructure and mechanical properties, arcing-wire arc additive manufacturing (AWAAM) with alternating deposition strategy was firstly employed to produce nickel‑aluminum bronze (NAB)-steel components. The implementation of alternating deposition strategy fostered the creation of interlocked microstructures, establishing robust bonds at the interface. Moreover, the convection within the melt pool during alternating deposition induced the formation of numerous precipitates, serving as a precipitation reinforcement. Simultaneously, these precipitates served as heterogeneous nucleation sites, facilitating the formation of substantial fine equiaxed crystals, resulting in grain boundary strengthening. A comprehensive examination of microstructure and mechanical properties was conducted using a variety of microscopy techniques and mechanical testing for components with and without arcing-wire. After applying arcing-wire, precise control was exerted over the melting of both matrix and wire, effectively preventing interface cracking caused by excessive melting. Moreover, with the arc heat input diminished, the temperature gradient in the melt pool decreased, leading to grain and precipitate refinement, consequently enhancing their strength. Owing to microstructural modifications, AWAAM demonstrated enhancements in ultimate tensile strength and yield strength by up to 20.1 % and 21.1 %, respectively, when compared to WAAM.

THE EFFECT OF HARDENING TECHNIQUES ON WEAR RESISTANCE AND FATIGUE LIFE OF DUCTILE CAST IRON

Many hardening methods have been developed and proposed as an effective technology to produce microstructural modification and improvement of mechanical properties of variety metallic materials. In this experimental study, the effects of applying laser peening (LP) and friction stir processing (FSP) methods on wear resistance and fatigue properties of selected cast iron ASTM A536, grade (80-55-06) with ferrite/pearlite microstructure were investigated. Microscopic study revealed evident refinement and crashing of graphite nodules as 50% of the basic size with FSP and 32% with LP within the processed surfaces hence improving average microhardness by 100% and 48% respectively. The wear resistance and fatigue life were increased by 33% and 122% after FSP whereas, the corresponding increments were 15% and 22% after LP in comparison with the basic ductile iron. These improvements were linked to surface hardening, compressive stresses and structural modification by the employed processes.

Analyzing the impact of interlocking on non-oriented electrical steel (NOES) laminations: A microstructural and mechanical property perspective

Non-oriented electrical steel laminations are widely used in electric motor cores and are manufactured using various techniques such as cutting, punching, interlocking, and welding. These manufacturing processes can have a detrimental effect on the performance of the electric motor. Thus, in order to enhance the performance of the electric motor, it is essential to comprehend the microstructural, mechanical, and magnetic property changes resulting from manufacturing. The current study focuses on the microstructural modifications caused by interlocking, which is known to impact the core magnetic properties of motors, and its relation to mechanical properties like hardness. Six interlocked non-oriented electrical steel samples were prepared by incomplete punching at different loads from 500 N to 4000 N. Scanning Electron Microscopy (SEM) and Electron backscattered diffraction (EBSD) analysis was performed on the interlocked samples to study the microstructure and crystallographic texture near the edge whereas nanoindentation was used to determine the hardness profile. Pop-in analysis was done to study the extent of work hardening due to punching and its effect on hardness. The hardness change due to residual stress was determined, which was used to estimate the induced residual stress near the edge. It ranged from 0.04 GPa at 550 N load to 11 GPa at 4000 N load near the punched edge.

Experimental evaluation of cement integrity on exposure to supercritical CO2 using NMR: Application to geostorage

Carbon sequestration is one approach to achieve carbon dioxide reduction in the atmosphere. Underground storage of CO2 requires an understanding of geochemical and geomechanical alteration on the integrity of the injection wellbore. In this study, we investigate the reactivity of supercritical CO2 (scCO2) at 65 °C and 20.7 MPa on Portland class G cement plugs used for oil and gas well completion, for exposure of up to 5 weeks.For nanoporous media, such as cement, diffusion is believed to be the major mass transport mechanism (Perkins and Johnston, 1963) [1]. To quantify the extent of the alteration (mineralization/dissolution) on fluid diffusivity through the cement matrix, a novel approach based on Nuclear Magnetic Resonance (NMR) is employed to derive diffusional tortuosity. Comparing pre- and post-scCO2 exposure, deuterium oxide (D2O) intrusion profiles allow us to determine flow path alteration in the cement plugs. Additional characterizations include Fourier Transform Infrared Spectroscopy (FTIR) to observe the change in cement composition, micro X-ray Computed Tomography (μXCT), along with Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to determine invasion extent and microstructure modifications, Mercury Injection Capillary Pressure (MICP) for pore throat size distribution and BET N2 isothermal adsorption for surface area and pore size distribution.The results show that exposure to scCO2 promotes both calcium carbonate precipitation and dissolution simultaneously. However, the alteration is pore size dependent. After 5 weeks of exposure, there is evidence of carbonate dissolution in smaller pores (<30 nm) and both precipitation and dissolution in larger pores (30–200 nm). The alteration of the cement plugs leads to a decrease in the storage and connectivity of the cement. The porosity decreased from 37 to 33 % in 5 weeks, while the matrix tortuosity increased by 6 and 3 times after 2 and 5 weeks of exposure, respectively. The experimental results imply that the cement carbonate precipitation can limit the migration of scCO2 through the cement matrix.This work also highlights an alternative laboratory approach to quantify the risk associated with scCO2 exposure on Portland cement using NMR-derived tortuosity.

Advancements in Zinc Oxide (ZnO) thin films for photonic and optoelectronic applications: A focus on doping and annealing processes

This study focuses on the potential of Zinc oxide (ZnO) as a versatile material for photonic and optoelectronic applications, owing to its direct wide bandgap (Eg ≈ 3.175 eV) and significant excitonic energy. ZnO, both in pure and doped forms, exhibits promise in various domains, including solar cells, photoelectrochemical cells, thin film transistors, gas sensors, and nanogenerators. The manuscript delves into the methodologies for producing ZnO:B films, including reactive evaporation, evaporation from two sources, and flash evaporation, each addressing the challenges of achieving the desired film composition and structure. The investigation reveals that the optimized ZnO:B films possess crystalline phases with hexagonal lattice structures, demonstrating significant enhancements in electrical conductivity upon specific annealing treatments. The research underscores the impact of doping and microstructure modifications on the optoelectronic properties of ZnO films, contributing to advancements in semiconductor-based thin films and powders.

Mitigating hydrogen embrittlement of advanced high-strength steel by controlling carbides (cementite and alloy carbides) and microstructural modification

This work aims to demonstrate that the resistance to hydrogen embrittlement of conventional advanced high-strength steel (AHSS) with a bainitic ferrite structure can be significantly enhanced through two metallurgical strategies. Firstly, a smaller fraction of cementite in a mixture of bainitic ferrite and lath-martensite structures is realized by an intercritical annealing process with rapid cooling. Secondly, a higher fraction of alloy carbides (MC) with a mean size of less than 30 nm is formed through the combined addition of Ti, Mo, and V as micro-alloying elements. The reduction of cementite precipitation in the matrix leads to an increased resistance to hydrogen evolution/adsorption on the surface under cathodic polarization. Moreover, a large number of V-bearing nanoprecipitates ((Ti,Mo,V)-carbides and V-carbides) provides intermediate trapping for hydrogen atoms, effectively delaying the diffusion kinetics of hydrogen towards potential crack-forming areas in the matrix. Consequently, the lower strain reduction during slow strain rate test and the higher resistance to cracking during the four-point bending test in acidic aqueous solutions are manifested in the newly designed AHSS.

Nano-rods in Ni-rich layered cathodes for practical batteries.

Lithium transition metal oxide layers, Li[Ni1-x-yCox(Mn and/or Al)y]O2, are widely used and mass-produced for current rechargeable battery cathodes. Development of cathode materials has focused on increasing the Ni content by simply controlling the chemical composition, but as the Ni content has almost reached its limit, a new breakthrough is required. In this regard, microstructural modification is rapidly emerging as a prospective approach, namely in the production of nano-rod layered cathode materials. A comprehensive review of the physicochemical properties and electrochemical performances of cathodes bearing the nano-rod microstructure is provided herein. A detailed discussion is regarding the structural stability of the cathode, which should be maximized to suppress microcrack formation, the main cause of capacity fading in Ni-rich cathode materials. In addition, the morphological features required to achieve optimal performance are examined. Following a discussion of the initial nano-rod cathodes, which were based on compositional concentration gradients, the preparation of nano-rod cathodes without the inclusion of a concentration gradient is reviewed, highlighting the importance of the precursor. Subsequently, the challenges and advances associated with the nano-rod structure are discussed, including considerations for synthesizing nano-rod cathodes and surface shielding of the nano-rod structure. It goes on to cover nano-rod cathode materials for next-generation batteries (e.g., all-solid-state, lithium-metal, and sodium-ion batteries), inspiring the battery community and other materials scientists looking for clues to the solution of the challenges that they encounter.

Fatigue life analysis of deep rolled bearing inner rings

The deep rolling process can influence the surface and subsurface of hardened steels, such as the bearing steel AISI 52100, due to mechanical loading and elastoplastic deformation. By intentionally adjusting the surface and subsurface properties, the fatigue life of bearing inner rings can be increased. This is among others attributed to the strengthening of surface and subsurface. Residual stresses induced by deep rolling and modifications of the material microstructure also contribute to this effect. In the investigations presented the deep rolling process parameters of rolling pressure, overlap ratio, and ball diameter were specifically selected based on previous works. Fatigue life investigations were conducted on honed and deep rolled bearing inner rings to enhance the understanding of failure mechanisms and to quantify the influence of the deep rolling process on fatigue life. It was found that the deep rolled bearing inner rings exhibit higher compressive residual stresses in the subsurface than honed rings and also showed longer fatigue life under rolling loads. Optical analyses of bearing rings that failed due to fatigue were performed to detect the failure mechanisms. The tested bearings showed classical fatigue, where cracking is initiated below the surface and propagates to the surface under further stress. Residual stresses can influence both the crack initiation and propagation.

Permissible domain walls in monoclinic MAB ferroelectric phases.

The concept of monoclinic ferroelectric phases has been extensively used over recent decades for the understanding of crystallographic structures of ferroelectric materials. Monoclinic phases have been actively invoked to describe the phase boundaries such as the so-called morphotropic phase boundary in functional perovskite oxides. These phases are believed to play a major role in the enhancement of such functional properties as dielectricity and electromechanical coupling through rotation of spontaneous polarization and/or modification of the rich domain microstructures. Unfortunately, such microstructures remain poorly understood due to the complexity of the subject. The goal of this work is to formulate the geometrical laws behind the monoclinic domain microstructures. Specifically, the result of previous work [Gorfman et al. (2022). Acta Cryst. A78, 158-171] is implemented to catalog and outline some properties of permissible domain walls that connect `strain' domains with monoclinic (MA/MB type) symmetry, occurring in ferroelectric perovskite oxides. The term `permissible' [Fousek & Janovec (1969). J. Appl. Phys. 40, 135-142] pertains to the domain walls connecting a pair of `strain' domains without a lattice mismatch. It was found that 12 monoclinic domains may form pairs connected along 84 types of permissible domain walls. These contain 48 domain walls with fixed Miller indices (known as W-walls) and 36 domain walls whose Miller indices may change when free lattice parameters change as well (known as S-walls). Simple and intuitive analytical expressions are provided that describe the orientation of these domain walls, the matrices of transformation between crystallographic basis vectors and, most importantly, the separation between Bragg peaks, diffracted from each of the 84 pairs of domains, connected along a permissible domain wall. It is shown that the orientation of a domain wall may be described by the specific combination of the monoclinic distortion parameters r = [2/(γ - α)][(c/a) - 1], f = (π - 2γ)/(π - 2α) and p = [2/(π - α - γ)] [(c/a) - 1]. The results of this work will enhance understanding and facilitate investigation (e.g. using single-crystal X-ray diffraction) of complex monoclinic domain microstructures in both crystals and thin films.

PVA/CdS-Ag Nanocomposites: Effect of Composition and UV Radiation on Optical, Electrical and Structural Properties

PVA incorporated with different content of CdS-Ag nanostructures are prepared using chemical reduction technique. Along with this these nanocomposites are exposed to UV radiated for different times. The X-ray spectraof PVA /CdS-Ag nanocomposites indicatethe formation of CdS and Ag nanostructures within PVA.Changes in the band structure of nanocomposites with and without UV exposure are studied by UV-Visible spectroscopy. Absorbance and refractive index are noticed to show increment with the concentration of nanostructures and time of exposure. Along with this, the behaviour of different optical parameters such as E0 and Ed is investigated. FE-SEM and EDX analysis exhibit microstructural modification occurring in nanocomposites due to changes in the concentration of incorporated nanostructures and UV radiation. Influence of concentration and UV exposure on conductivity and dielectric parameters on PVA/CdS-Ag nanocomposites are studied.

A Review of Friction Welding Research Addressing the Influence, Development, Similar &amp; Dissimilar Welding

This review paper discusses the recent research work carried out in the frictional joining of dissimilar and similar alloys through the friction welding (FW) process with various parameters and modifications. It includes further the latest developments and advances in the research on FW and the influences of FW’s process parameters on the quality of joints and their properties. The specimens’ faying surfaces can also influence the joint properties as the surface modifications stimulate or change the metal joints’ bonding according to the welding parameters selected during FW. Though the rise of friction pressure (FP) during FW improves the strength of the joints, the improper selection of parameters leads to metal damage. It feels better if the axial shortening is less than 30 mm for FW of soft metals. The axial shortening values are less than 25 mm for the hemispherical bowl-type faying surfaces under 18 bar FP and it is noted that the bevel-type tapered faying surfaces increase the shortening. FW provided very narrow weld interfaces with around 5-10 µm width. With a low FP, it was possible to obtain a maximum of 100 % efficiency by modifying their faying surfaces. The small-diameter soft material needs less FP and friction time. The microstructure modification is possible and the weld joint is shown as U and V shapes for the bowl and tapered faying surfaces. It further increases the contact area and thus increases strength.