maryam mohri
Semnan University, Metallurgical and Materials Science Faculty, Faculty Member
Research Interests:
Abstract Diffusion annealing of palladium into two Ti-rich alloys of Ti-47 at.% Ni and Ti-49.8 at.% Ni were performed to produce a compositionally graded high-temperature Ti-Ni-Pd shape memory alloy (SMA). A (Ni + Pd)-rich layer was... more
Abstract Diffusion annealing of palladium into two Ti-rich alloys of Ti-47 at.% Ni and Ti-49.8 at.% Ni were performed to produce a compositionally graded high-temperature Ti-Ni-Pd shape memory alloy (SMA). A (Ni + Pd)-rich layer was observed throughout the diffusion zone in both alloys. The Ti-47 at.% Ni/Pd alloy failed to show high-temperature characteristics. However, high-temperature peaks with wide transformation temperature intervals were observed on DSC curves of the Ti-49.8 at.% Ni/Pd alloy, which confirmed the success of the method to obtain a graded high-temperature SMA. This was attributed to the formation of Ni-rich precipitates within the diffusion zone of this alloy. The shape recovery studies were performed by micro-hardness, nano-indentation and tension tests. It was shown that, Ti-49.8 at.% Ni/Pd alloy exhibits the higher shape recovery ability than Ti-47 at.% Ni/Pd alloy on both macroscopic and microscopic scales. Furthermore, despite the reports on destructive effect of Pd addition on shape recovery properties of NiTi alloys, Pd diffusion led to an improved shape recovery in Ti-47 at.% Ni/Pd system.
Research Interests:
In the present work, high energy ball milling of binary ( Mg 2 Ni ) and ternary powder mixtures ( Mg 1.75 Nb 0.25 Ni and Mg 2 Ni 0.75 Nb 0.25, i.e., substitution of Nb for Mg and Ni , respectively) was carried out. The effects of milling... more
In the present work, high energy ball milling of binary ( Mg 2 Ni ) and ternary powder mixtures ( Mg 1.75 Nb 0.25 Ni and Mg 2 Ni 0.75 Nb 0.25, i.e., substitution of Nb for Mg and Ni , respectively) was carried out. The effects of milling process parameters on the microstructure of binary and ternary milled products were studied. Also, electrochemical properties of the nano-structured electrodes made from the milled products were measured. It was found that Nb substitution for Mg ( Mg 1.75 Nb 0.25 Ni ) has beneficial effect on the formation kinetic of Mg 2 Ni -based nano-crystallites. Electrode made from the 20h milled product using initial composition of Mg 1.75 Nb 0.25 Ni exhibited a high discharge capacity of ~600mAhg-1 and relatively longer discharge life. Such electrode showed a microstructure consisting of an amorphous core surrounded by nano-crystallites.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
In this study, lemon juice at different concentrations as a new additive was poured into the bath of the anodizing process to enhance the mechanical properties of the manufactured aluminum oxide layers. X-ray diffraction (XRD) and... more
In this study, lemon juice at different concentrations as a new additive was poured into the bath of the anodizing process to enhance the mechanical properties of the manufactured aluminum oxide layers. X-ray diffraction (XRD) and field-emission scanning electron microscopy were utilized to detect formed phases and microstructure, respectively. To investigate mechanical properties, microhardness, indentation toughness, and wear tests of various aluminum oxide layers were performed. The XRD patterns showed a crystalline phase of [Formula: see text]-Al2O3 for all oxide layers. The microhardness of modified layers increased up to 62.2% compared to the unmodified layer. However, by increasing the additive concentration to 2.5 vol%, the hardness decreased. This was based on increasing the pore size of layers. The lowest friction coefficient with a value of 0.53, the lowest wear rate, and the highest indentation toughness was also related to the modified aluminum oxide layer when the conc...
Research Interests:
Research Interests:
Research Interests:
This study reviews the recent works on the development and application of iron‐based shape memory alloy (Fe‐SMA), the so‐called memory‐steel, for steel structures. First, the studies on the material properties of Fe‐SMA in terms of shape... more
This study reviews the recent works on the development and application of iron‐based shape memory alloy (Fe‐SMA), the so‐called memory‐steel, for steel structures. First, the studies on the material properties of Fe‐SMA in terms of shape memory effect and superelasticity are discussed. Next, the use of Fe‐SMA in prestressed strengthening of steel structures is explained, including the applications in strengthening of steel girders, connections, and fatigue crack repairs. Various strengthening solutions such as using mechanically anchored or adhesively‐bonded Fe‐SMA, as well as the studies on the behavior of the Fe‐SMA‐to‐steel bonded joints, are discussed. The use and application of Fe‐SMA for strengthening of a 113‐years steel bridge has been explained. In addition, studies on the innovative application of the Fe‐SMA as pipe couplers are presented. At the end, innovative ongoing research on the additive manufacturing of architected Fe‐SMA (4D‐printing) are discussed.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
The challenge of anodizing processes is to decrease the chromate compounds or other poisonous materials from the anodizing bath in a way that the performance of oxide layers does not change. Therefore, in this study, a new anodizing bath... more
The challenge of anodizing processes is to decrease the chromate compounds or other poisonous materials from the anodizing bath in a way that the performance of oxide layers does not change. Therefore, in this study, a new anodizing bath was developed to create the alumina layers. The new bath contained an H2SO4 solution with an eco-friendly additive. This additive was lemon juice (which contained natural citric acid) at various concentrations (0.3 to 2.5 vol%). Field-emission scanning electron microscopy (FESEM) was used to investigate the microstructural evaluations. Tafel polarization and electrochemical impedance spectroscopy (EIS) were also utilized to study the corrosion behavior of the alumina layers on aluminum substrates. The obtained results depicted that the presence of the bio-additive in the anodizing bath caused a reduction in corrosion rates of alumina layers by approximately 90.2 to 100% compared to the layer manufactured without additive. EIS measurements showed an ...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
One bi-layer Ni-Ti thin films with chemical compositions of Ni45TiCu5 /Ni50.8Ti (numbers indicate at.%) determined by energy dispersive X-ray spectroscopy was deposited on Si substrates using RF magnetron sputtering. The structures and... more
One bi-layer Ni-Ti thin films with chemical compositions of Ni45TiCu5 /Ni50.8Ti (numbers indicate at.%) determined by energy dispersive X-ray spectroscopy was deposited on Si substrates using RF magnetron sputtering. The structures and transformation temperatures of annealed thin films at 773 K for 1h were studied using grazing incidence X-ray diffraction (GIXRD) and differential scanning calorimetry (DSC), respectively. Nanoindentation was used to characterize the mechanical properties. The DSC and X-ray diffraction results indicated the bi-layer was composed of austenitic and martensitic thin films. The bi-layer thin film exhibited a combined pseudo elastic behavior and shape memory effect at the same time similar to the austenitic and martensitic thin films, respectively. The combination of pseudo elastic with shape memory effect produces a two-way shape memory effect with a reduced hysteresis in the bilayers.
Research Interests:
Research Interests:
Research Interests:
In this research, glassy Ni–Ti thin films were sputtered on a flexible substrate (Kapton) using direct current (DC) magnetron sputtering system at ambient temperature. The influence of the sputtering pressure on the microstructure,... more
In this research, glassy Ni–Ti thin films were sputtered on a flexible substrate (Kapton) using direct current (DC) magnetron sputtering system at ambient temperature. The influence of the sputtering pressure on the microstructure, chemical composition, thickness, mechanical properties and the ability to form nano-glass structure was investigated. Micro-structural characterizations of the thin films by x-ray diffraction, scanning and transmission electron microscopy (SEM and TEM) indicate that the sputtered thin films at a minimum pressure of 0.3 Pa have an amorphous structure consisting of nano-glassy grains. Furthermore, as the pressure increasing from 0.1 up to 0.8 Pa, the difference between the chemical composition of the thin films and the target increases. This difference is due to increasing of interatomic collisions between Ar and sputtered atoms that reduces the kinetic energy of sputtered atoms and rises to the scatter of atoms. In addition, the formation of micro-cracks in the films is also encouraged by increasing the sputtering pressure. For evaluation of the mechanical properties of the crystallized Ni–Ti/Kapton composite thin films, the tensile test was used and the results show that the partially crystallized Ni–Ti thin film sputtered at 0.3 Pa has the optimum ultimate tensile strength and toughness due to its composite (amorphous/nano-crystalline) structure.
Research Interests:
The effects of mechanical alloying on the microstructure of binary and ternary powder mixtures with stoichiometric compositions of Mg 2 Ni and Mg 2 Ni 0.75 Nb 0.25 were studied, respectively. Also, the electrode properties of the milled... more
The effects of mechanical alloying on the microstructure of binary and ternary powder mixtures with stoichiometric compositions of Mg 2 Ni and Mg 2 Ni 0.75 Nb 0.25 were studied, respectively. Also, the electrode properties of the milled products were investigated in 6M KOH solution. X-ray diffraction and scanning electron microscopy of the milled products showed the formation of Mg 2 Ni -based nanocrystallites after 15 and 10h of milling using the initial binary and ternary mixtures, respectively. It was found that partial substitution of Nb for Ni has beneficial effect on the formation kinetic of nanocrystalline Mg 2 Ni . Longer milling times resulted in the formation of an amorphous phase. A relatively high discharge capacity of 350mAhg-1 was measured for the electrode made up of the ternary milled product after 20h. Also, the ternary milled product showed longer discharge life. This ternary electrode showed a microstructure consisting of Mg 2 Ni nanocrystallites and an amorphous ...
Research Interests:
Research Interests:
Research Interests:
Nb addition was found to be beneficial to the electrode properties of mechanically alloyed Mg2Ni-based product in 6M KOH solution. Formation of Mg2Ni-based nanocrystalites occurred after 15 and 5h of milling using the initial binary and... more
Nb addition was found to be beneficial to the electrode properties of mechanically alloyed Mg2Ni-based product in 6M KOH solution. Formation of Mg2Ni-based nanocrystalites occurred after 15 and 5h of milling using the initial binary and ternary powder mixtures with stoichiometric compositions of Mg2Ni and Mg1.75Nb0.25Ni, respectively. Further milling of the ternary mixture resulted in the formation of an amorphous phase which became dominant after 30h. Negative electrode made from ternary product after 20h of milling exhibited the highest initial discharge capacity and the longest discharge life. This electrode showed to have a microstructure consisting of nanocrystalline Mg2Ni and an amorphous phase.
Research Interests:
ABSTRACT
Research Interests:
Shape memory thin films are candidates for micro-electro-mechanical-systems because of their strong recovery force and large deformation. In the present study Ni-Ti thin films have been deposited on Si (111) substrates by RF magnetron... more
Shape memory thin films are candidates for micro-electro-mechanical-systems because of their strong recovery force and large deformation. In the present study Ni-Ti thin films have been deposited on Si (111) substrates by RF magnetron sputtering. The two targets (NiTi and Ti) were prepared by vacuum arc re-melting (VAR), used for co-sputtering. In this study, two mono Ni-rich and Ti-rich and two bi-layers (Ni-rich/Ti-rich and Ti-rich/Ni-rich) thin films have been deposited on Si (111) substrates. The as-deposited Ni-Ti thin films were annealed to transform the amorphous to a nano-structured material. Subsequently, shape memory and super elastic behavior were characterized. The compositions of the films were determined by energy dispersive X-ray spectroscopy. Crystallization and transformation temperatures were studied using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and electrical resistance. Nanoindentation was used to characterize the mechanical properties. T...
Research Interests:
Research Interests:
The present investigation is focused on the electrode properties of various nanocrystalline Mg2Ni -based powders synthesized using high energy ball milling technique. The chemical composition was modified by the ternary (Nb) and... more
The present investigation is focused on the electrode properties of various nanocrystalline Mg2Ni -based powders synthesized using high energy ball milling technique. The chemical composition was modified by the ternary (Nb) and quaternary ( Al and Nb ) additives. The process parameters were adjusted to achieve nanocrystalline based products. Characterization of the ternary and quaternary milled products using scanning and transmission electron microscopy and X-ray diffraction showed a composite microstructure of an amorphous core surrounded by nanocrystalline Mg2Ni . Electrode made from the quaternary milled product showed superior initial charge density and longer discharge duration.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Shape memory thin films deposited by sputtering are attractive candidates for micro-electro-mechanical-system (MEMS) because of their large deformation and strong recovery force. In the present study Ni-Ti thin films have been deposited... more
Shape memory thin films deposited by sputtering are attractive candidates for micro-electro-mechanical-system (MEMS) because of their large deformation and strong recovery force. In the present study Ni-Ti thin films have been deposited on NaCl substrates by DC magnetron sputtering source fitted with an 80mm diameter alloy target. In order to obtain a variety of film compositions, several discs of alloy target, which prepared in vacuum arc remelting (VAR), were used. Three types of thin films have been deposited; Ti and Ni-rich thin films were separately deposited on NaCl substrate and also a composite layer of Ni45Ti50Cu5 and Ni-rich. The as deposited Ni-Ti thin films were crystallized to change the amorphous structure to a nanostructured material to characterize shape memory and superelastic behaviors. The effect of composition on film structure and mechanical behavior was studied by using X-ray diffraction (XRD) and nanoindentation. The results of thin films behavior were used to calculate the thickness ratio of be-layer composite NiTi to obtain enhanced shape memory behavior.
Research Interests:
ABSTRACT Ni–Ti thin film shape memory alloys (SMAs) have become a promising material for micro-actuators because of their excellent mechanical properties and biocompatibility. Films with composition gradient have the added feature of an... more
ABSTRACT Ni–Ti thin film shape memory alloys (SMAs) have become a promising material for micro-actuators because of their excellent mechanical properties and biocompatibility. Films with composition gradient have the added feature of an intrinsic two-way shape memory effect. In this study two kinds of the Ni–Ti bi-layer thin films (Ni50.8Ti/Ni45TiCu5 and Ni50.8Ti/Ni49Ti) were developed. The thin films were deposited onto Si (1 1 1) substrates by RF magnetron sputter deposition from separate alloy targets. The three targets with atomic compositions of Ni45Ti, Ni47Ti and Ni42TiCu5 were prepared by vacuum arc re-melting (VAR). For crystallization, the as-deposited amorphous thin films were annealed at 773 K for 1 h. The annealed bi-layer thin films formed compositional gradients at the interface of the films through diffusion. The effect of the composition on film structure, surface morphology, transformation temperatures and mechanical properties was studied using grazing incidence X-ray diffraction, transmission electron microscopy, atomic force microscopy, electrical resistivity and nano-indentation. The chemical and stress gradient in the bi-layers affects the structure, phase transformation and shape memory effect. Thin films exhibit multi-step phase transformation. Also, the bi-layer presented pseudo elastic and shape memory effect, simultaneously. The depth recovery ratio due to pseudo elastic in the Ni50.8Ti/Ni45TiCu5 compared with the Ni50.8Ti/Ni49Ti bi-layer is higher while the recovery ratio due to shape memory in the Ni50.8Ti/Ni49Ti bi-layer is higher. The combination of pseudo elastic with shape memory effect produces a two-way shape memory effect with a reduced hysteresis in the bi-layers.
Research Interests:
Research Interests:
In this study, functionally graded NiTi multilayer thin films were created by radio frequency magnetrun sputtering and subsequent annealing. The chemical compositions of the multilayer thin films which determined by energy-dispersive... more
In this study, functionally graded NiTi multilayer thin films were created by radio frequency magnetrun sputtering and subsequent annealing. The chemical compositions of the multilayer thin films which determined by energy-dispersive x-ray spectroscopy are about Ni51Ti/Ni49Ti (numbers indicate at.%). The structures, surface morphology, and transformation temperatures of annealed thin films at 500°C for 1 h were studied using grazing incidence x-ray diffraction, atomic force microscopy, and differential scanning calorimetry (DSC), respectively. Moreover, a coupled nanoindentation/atomic force microscopy technique is employed to characterize both the superelastic and shape memory effects. Specifically, an analysis of recoverable energy through the stress-induced phase transformation and recoverable strain through de-twinning and the subsequent thermally induced phase transformation were performed. The DSC and x-ray diffraction results indicated the multilayer was composed of austeniti...