Pub Date : 2018-11-05DOI: 10.21741/9781945291999-25
D. Benea, R. Gavrea, M. Coldea, L. Barbu-Tudoran, O. Isnard, V. Pop
We report on the preparation and the atomic disorder reduction by annealing in Mn2xCoxVAl Heusler alloys. The degrees of the B2 and L21 atomic ordering for the as-cast samples, obtained from intensity ratios of (200) and (111) peaks respectively related to (220) peak of the Xray patterns, are significantly improved after annealing at 700 800 °C for 72 h. The diminution of the substitutional disorder is essential in these types of compounds, as the half-metallic character and the magnetic properties are primarily influenced by this factor. Introduction Heusler alloys are ternary intermetallic compounds of the L21 structure with stoichiometric composition X2YZ, where X and Y are usually two different transition metals and Z is a nonmagnetic element [1]. Earlier studies have shown that Mn2VAl Heusler alloy is a half-metallic ferrimagnet [2-5]. This compound is characterized by an antiparallel coupling between the Mn and V magnetic moments, the total spin moment being 2 μB per formula unit [2, 3]. The high Curie temperature of 760 K [3] makes it interesting for spintronic applications. The spin compensation in Mn2−xCoxVAl alloy was induced by progressive substitution of Co for Mn and a fully compensated ferrimagnetic behavior has been experimentally obtained for the MnCoVAl alloy [4]. The presence of a considerable atomic disorder in the Mn2VAl compound due to the intermixing of the V and Al atoms has been reported [5]. Previous studies have shown that the magnetic properties and the half-metallic character of these Heusler alloys are strongly influenced by the crystallographic disorder [1, 3, 6, 7]. The aim of the present work is to reduce the substitutional disorder by heat treatments in Mn2−xCoxVAl Heusler alloys. For the evaluation of the atomic ordering in the full Heusler alloys, the Takamura’s model has been used [8]. In order to determine and to adjust the ordering parameters defined in this model, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and neutron diffraction studies have been performed. Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 219-227 doi: http://dx.doi.org/10.21741/9781945291999-25 220 Experimental details The Mn2−xCoxVAl (x= 0, 0.2, 0.6, 1) ingots were prepared by induction melting under a purified Ar atmosphere of the starting components Mn (99.95 wt %), Al (99.999 wt %), V (99.99 wt %) and Co (99.99 wt %). An excess of 3 wt % of manganese was added to the stoichiometric mixture in order to compensate for preferential Mn evaporation during the melting processes. The samples were turned and remelted repeatedly in order to ensure homogeneity. The water-cooled copper crucible ensured a rapid cooling of the alloys after melting. The samples were wrapped in tantalum foil, sealed in quartz tubes and subsequently annealed in an Ar atmosphere for 72 hours. The stoichiometry of our as-cast samples was investigated using the energy dispers
Heusler合金的X2YZ - l21型晶体结构。图3所示。铸态Mn2-xCoxVAl样品的室温x射线衍射图。数据被归一化为(220)反射的强度。粉末冶金与先进材料- RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 211 -227 doi: http://dx.doi.org/10.21741/9781945291999-25 222铸态Mn2−xCoxVAl (x = 0,0.2, 0.6和1)合金的室温x射线衍射图如图3所示。XRD分析结果表明，铸态合金为单相结晶，属于X2YZ Heusler型结构，立方空间群Fm3 μ m(空间群no.;225)，其中Mn和Co原子占据8c Wyckoff位(X)，而V和Al原子分别位于4a (Y)和4b (Z)晶体位(见图2)。XRD谱图的(111)和(200)超晶格衍射线证明，Mn2-xCoxVAl合金均表现出完整Heusler合金的稳定L21结构。从(111)面反射的消光表明V原子和Al原子之间的混合。同样，如果所有Mn、V和Al原子混合，则超晶格反射(111)和(200)都将消失[1,4,8]。我们采用Takamura的模型来研究我们的Mn2−xCoxVAl (x = 0,0.2, 0.6和1)合金中的取代无序。在该模型中，定义了两种排序参数来描述原子位置之间的混合。SB2阶参数描述了Mn原子在X2YZ全Heusler合金中占据X位(8c)的概率，定义为:SB2 = MMM oM X - MMM oM X rrMror MMM oM X ffff - MMM oM X rrMror(1);二级参数SL21描述了V原子在X2YZ全Heusler合金中占据Y位的概率:SL21 = MVoM Y - MVoM Y rrMror MVoM Y ffff - MVoM Y rrMror(2)。铸态Mn2−xCoxVAl样品的结构参数包括SB2和SL21排序参数、单元常数和位点占用。Co含量(x)原子数x位Y位Z位SB2 SL21 alat (nm)
{"title":"Reduction of the substitutional disorder by heat treatments in Mn2-xCoxVAl Heusler alloys","authors":"D. Benea, R. Gavrea, M. Coldea, L. Barbu-Tudoran, O. Isnard, V. Pop","doi":"10.21741/9781945291999-25","DOIUrl":"https://doi.org/10.21741/9781945291999-25","url":null,"abstract":"We report on the preparation and the atomic disorder reduction by annealing in Mn2xCoxVAl Heusler alloys. The degrees of the B2 and L21 atomic ordering for the as-cast samples, obtained from intensity ratios of (200) and (111) peaks respectively related to (220) peak of the Xray patterns, are significantly improved after annealing at 700 800 °C for 72 h. The diminution of the substitutional disorder is essential in these types of compounds, as the half-metallic character and the magnetic properties are primarily influenced by this factor. Introduction Heusler alloys are ternary intermetallic compounds of the L21 structure with stoichiometric composition X2YZ, where X and Y are usually two different transition metals and Z is a nonmagnetic element [1]. Earlier studies have shown that Mn2VAl Heusler alloy is a half-metallic ferrimagnet [2-5]. This compound is characterized by an antiparallel coupling between the Mn and V magnetic moments, the total spin moment being 2 μB per formula unit [2, 3]. The high Curie temperature of 760 K [3] makes it interesting for spintronic applications. The spin compensation in Mn2−xCoxVAl alloy was induced by progressive substitution of Co for Mn and a fully compensated ferrimagnetic behavior has been experimentally obtained for the MnCoVAl alloy [4]. The presence of a considerable atomic disorder in the Mn2VAl compound due to the intermixing of the V and Al atoms has been reported [5]. Previous studies have shown that the magnetic properties and the half-metallic character of these Heusler alloys are strongly influenced by the crystallographic disorder [1, 3, 6, 7]. The aim of the present work is to reduce the substitutional disorder by heat treatments in Mn2−xCoxVAl Heusler alloys. For the evaluation of the atomic ordering in the full Heusler alloys, the Takamura’s model has been used [8]. In order to determine and to adjust the ordering parameters defined in this model, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and neutron diffraction studies have been performed. Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 219-227 doi: http://dx.doi.org/10.21741/9781945291999-25 220 Experimental details The Mn2−xCoxVAl (x= 0, 0.2, 0.6, 1) ingots were prepared by induction melting under a purified Ar atmosphere of the starting components Mn (99.95 wt %), Al (99.999 wt %), V (99.99 wt %) and Co (99.99 wt %). An excess of 3 wt % of manganese was added to the stoichiometric mixture in order to compensate for preferential Mn evaporation during the melting processes. The samples were turned and remelted repeatedly in order to ensure homogeneity. The water-cooled copper crucible ensured a rapid cooling of the alloys after melting. The samples were wrapped in tantalum foil, sealed in quartz tubes and subsequently annealed in an Ar atmosphere for 72 hours. The stoichiometry of our as-cast samples was investigated using the energy dispers","PeriodicalId":20390,"journal":{"name":"Powder Metallurgy and Advanced Materials","volume":"254 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73196697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-11-05DOI: 10.21741/9781945291999-6
B. Bita, V. Ţucureanu, I. Cernica, M. Popescu, A. Matei, C. Romanițan
In the present work, CuO nanoparticles were successfully prepared by the coprecipitation method using copper acetate (Cu(CH3COO)2) as a basic precursor, sodium hydroxide (NaOH) as a precipitator material, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) as anionic and cationic surfactants, respectively. The synthesized powders samples were characterized by Fourier transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The investigation showed that the added types of surfactants have effects on the decrease of the crystallite size, on the CuO particles morphology, shape and uniform distribution as it is noticed in the XRD and SEM characterizations. Additionally, the FTIR spectra for all the powders samples showed the same Cu-O stretching vibration mode which indicates the presence of a crystalline CuO monoclinic structure. The obtained results create premises for further advanced the applications of CuO powders in various domains. Introduction Over the years, the interests in developing nanoparticles metal oxides have considerably increased due to the necessity of obtaining materials with outstanding physical and chemical properties. Various methods of metal oxide synthesis have been know so far, researches continue to development a new approaches with a strict control over nanoparticles morphology, size and composition for several technological applications. Copper oxide (CuO), belonging to the nanomaterials class, which has attracted recent research because of its excellent properties, cost effectiveness and wide spectrum of practical applications (solar and electrochemical cells, gas sensors, field emitters, active catalyst and antimicrobial activity, etc.). Also, CuO as nanostructured oxide being classified as a p-type monoclinically structured semiconductor material with a direct band-gap value of 1.85 eV presents a particular attention. This type of material has a special concern because it extends the use in a board range of applications, such as electronics and optoelectronics, catalysts, sensors and biosensors, chemical sensing devices, nanofluids and field emitters, desinfection, cosmetic pigments, antibacterial agent, etc. [1–4]. In order for this material to exhibit viable properties in the desired field of applicability, it is intended to establish its method of obtaining and its synthesis parameters; there Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 52-60 doi: http://dx.doi.org/10.21741/9781945291999-6 53 have been elaborated and known various physical and chemical methods so far, such as sol-gel, coprecipitation, hydrothermal synthesis, mechanical mixing, solid state reaction, thermal descomposition of precursors, microemulsion, microwave irraditiaon, physical vapor deposition, ablation, etc. [3, 5, 6]. From the bottom-up type methods, precipitation is a cheap one, w
{"title":"Synthesis and characterization of various surfactants for stabilized CuO powder","authors":"B. Bita, V. Ţucureanu, I. Cernica, M. Popescu, A. Matei, C. Romanițan","doi":"10.21741/9781945291999-6","DOIUrl":"https://doi.org/10.21741/9781945291999-6","url":null,"abstract":"In the present work, CuO nanoparticles were successfully prepared by the coprecipitation method using copper acetate (Cu(CH3COO)2) as a basic precursor, sodium hydroxide (NaOH) as a precipitator material, sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) as anionic and cationic surfactants, respectively. The synthesized powders samples were characterized by Fourier transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The investigation showed that the added types of surfactants have effects on the decrease of the crystallite size, on the CuO particles morphology, shape and uniform distribution as it is noticed in the XRD and SEM characterizations. Additionally, the FTIR spectra for all the powders samples showed the same Cu-O stretching vibration mode which indicates the presence of a crystalline CuO monoclinic structure. The obtained results create premises for further advanced the applications of CuO powders in various domains. Introduction Over the years, the interests in developing nanoparticles metal oxides have considerably increased due to the necessity of obtaining materials with outstanding physical and chemical properties. Various methods of metal oxide synthesis have been know so far, researches continue to development a new approaches with a strict control over nanoparticles morphology, size and composition for several technological applications. Copper oxide (CuO), belonging to the nanomaterials class, which has attracted recent research because of its excellent properties, cost effectiveness and wide spectrum of practical applications (solar and electrochemical cells, gas sensors, field emitters, active catalyst and antimicrobial activity, etc.). Also, CuO as nanostructured oxide being classified as a p-type monoclinically structured semiconductor material with a direct band-gap value of 1.85 eV presents a particular attention. This type of material has a special concern because it extends the use in a board range of applications, such as electronics and optoelectronics, catalysts, sensors and biosensors, chemical sensing devices, nanofluids and field emitters, desinfection, cosmetic pigments, antibacterial agent, etc. [1–4]. In order for this material to exhibit viable properties in the desired field of applicability, it is intended to establish its method of obtaining and its synthesis parameters; there Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 52-60 doi: http://dx.doi.org/10.21741/9781945291999-6 53 have been elaborated and known various physical and chemical methods so far, such as sol-gel, coprecipitation, hydrothermal synthesis, mechanical mixing, solid state reaction, thermal descomposition of precursors, microemulsion, microwave irraditiaon, physical vapor deposition, ablation, etc. [3, 5, 6]. From the bottom-up type methods, precipitation is a cheap one, w","PeriodicalId":20390,"journal":{"name":"Powder Metallurgy and Advanced Materials","volume":"81 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79776638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-11-05DOI: 10.21741/9781945291999-18
B. Neamțu, T. Marinca, H. Chicinaş, F. Popa, I. Chicinaș, O. Isnard, G. Ababei, M. Gabor
{"title":"A comparative study of the Co-based amorphous alloy prepared by mechanical alloying and rapid quenching","authors":"B. Neamțu, T. Marinca, H. Chicinaş, F. Popa, I. Chicinaș, O. Isnard, G. Ababei, M. Gabor","doi":"10.21741/9781945291999-18","DOIUrl":"https://doi.org/10.21741/9781945291999-18","url":null,"abstract":"","PeriodicalId":20390,"journal":{"name":"Powder Metallurgy and Advanced Materials","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73366797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-11-05DOI: 10.21741/9781945291999-16
F. Mindivan, M. Goktas
{"title":"Green synthesis of Reduced Graphene Oxide (RGNO) / Polyvinylchloride (PVC) composites and their structural characterization","authors":"F. Mindivan, M. Goktas","doi":"10.21741/9781945291999-16","DOIUrl":"https://doi.org/10.21741/9781945291999-16","url":null,"abstract":"","PeriodicalId":20390,"journal":{"name":"Powder Metallurgy and Advanced Materials","volume":"421 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84922543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-11-05DOI: 10.21741/9781945291999-23
C. Pascu, Ș. Gheorghe, C. Nicolicescu, D. Tărâţă
Because of their great properties titanium and titanium alloys have been used in automotive industry, biomedical applications, aerospace industry, computer components, emerging applications, architecture of buildings, etc. In the last decade there has been revived interest in the utilization of the Powder Metallurgy (PM) route as a low-cost way for obtaining components from this alloys. This research presents the experimental results concerning the processing of Ti based alloy by Two-Steps Sintering and Multiple-Steps Sintering, techniques belonging to PM technology. The initial powder mixture consists in TiH2 powder particles that have been combined with some metallic powders (Al, Mn, Sn, Zr) for improving the final mechanic-chemicals and functional properties for using in the automotive industry. As a result it was studied the physical-mechanical properties after sintering, the influence of the sintering temperature and time on the microstructural changes of the composite material based on titanium. Introduction Titanium alloys have multiple applications in diverse fields such as industrial and medical fields [1-4]. This is due to their excellent performances such as: low density, good corrosion resistance, non-magnetic properties, high specific strength, high chemical stability, resistant to high temperatures, etc. [5, 6]. The basic advantages of titanium alloys in terms of the automotive industry are the high strength to density, their low density, the outstanding corrosion resistance [7, 8]. In the automotive field, one of the greatest applications of titanium-based materials is for components of the internal combustion engine area that equip the vehicle (pistons, valves, connecting rod, crank caps, bolts, etc.) [9, 10]. Also, for modern jet turbine engines titanium alloys usually represent approximately 30% of the used materials, especially in the forward zone of the engine [11]. However, compared to other traditional materials, the major impediment represents the high cost of titanium [12]. Another disadvantage of titanium for applications in the automotive industry is its low tribological properties because of poor plastic shearing resistance and work hardening ability [13, 14]. Using inexpensive alloying elements (such as Sn, Mn, Fe, Cr, etc.) instead of expensive alloying metals (V, Nb, Mo, Zr, etc.) to improve the strengthen alloys is one of the methods to reduce the cost of manufacturing titanium alloys [15]. Due to the properties they possess, by alloying Ti with small amounts of aluminium percentage a Ti-Al (γ Ti-Al) alloy is obtained with excellent mechanical properties and corrosion resistance at Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 200-211 doi: http://dx.doi.org/10.21741/9781945291999-23 201 temperatures above 700°C, which allows the replacement for traditional Ni based superalloy for turbine engine components [16]. Due to the very good wear b
{"title":"Composite material obtained by powder metallurgy with applications in the automotive industry","authors":"C. Pascu, Ș. Gheorghe, C. Nicolicescu, D. Tărâţă","doi":"10.21741/9781945291999-23","DOIUrl":"https://doi.org/10.21741/9781945291999-23","url":null,"abstract":"Because of their great properties titanium and titanium alloys have been used in automotive industry, biomedical applications, aerospace industry, computer components, emerging applications, architecture of buildings, etc. In the last decade there has been revived interest in the utilization of the Powder Metallurgy (PM) route as a low-cost way for obtaining components from this alloys. This research presents the experimental results concerning the processing of Ti based alloy by Two-Steps Sintering and Multiple-Steps Sintering, techniques belonging to PM technology. The initial powder mixture consists in TiH2 powder particles that have been combined with some metallic powders (Al, Mn, Sn, Zr) for improving the final mechanic-chemicals and functional properties for using in the automotive industry. As a result it was studied the physical-mechanical properties after sintering, the influence of the sintering temperature and time on the microstructural changes of the composite material based on titanium. Introduction Titanium alloys have multiple applications in diverse fields such as industrial and medical fields [1-4]. This is due to their excellent performances such as: low density, good corrosion resistance, non-magnetic properties, high specific strength, high chemical stability, resistant to high temperatures, etc. [5, 6]. The basic advantages of titanium alloys in terms of the automotive industry are the high strength to density, their low density, the outstanding corrosion resistance [7, 8]. In the automotive field, one of the greatest applications of titanium-based materials is for components of the internal combustion engine area that equip the vehicle (pistons, valves, connecting rod, crank caps, bolts, etc.) [9, 10]. Also, for modern jet turbine engines titanium alloys usually represent approximately 30% of the used materials, especially in the forward zone of the engine [11]. However, compared to other traditional materials, the major impediment represents the high cost of titanium [12]. Another disadvantage of titanium for applications in the automotive industry is its low tribological properties because of poor plastic shearing resistance and work hardening ability [13, 14]. Using inexpensive alloying elements (such as Sn, Mn, Fe, Cr, etc.) instead of expensive alloying metals (V, Nb, Mo, Zr, etc.) to improve the strengthen alloys is one of the methods to reduce the cost of manufacturing titanium alloys [15]. Due to the properties they possess, by alloying Ti with small amounts of aluminium percentage a Ti-Al (γ Ti-Al) alloy is obtained with excellent mechanical properties and corrosion resistance at Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 200-211 doi: http://dx.doi.org/10.21741/9781945291999-23 201 temperatures above 700°C, which allows the replacement for traditional Ni based superalloy for turbine engine components [16]. Due to the very good wear b","PeriodicalId":20390,"journal":{"name":"Powder Metallurgy and Advanced Materials","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90563427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-11-05DOI: 10.21741/9781945291999-1
I. Zapodeanu, M. Codescu, M. Burlacu, V. Midoni, R. Erdei, D. Pătroi, E. Patroi, E. Manta, K. Kappel
Prepared by the Taylor – Ulitovsky technique, the glass-coated microwires are formed from a metallic core, with the diameter 3 to 50 μm, surrounded by an insulating layer from glass, with the thickness of 1 to 20 μm. Embedded in the cellulose matrix, the ferromagnetic glasscoated microwires allow their use as security element for the authentication of valuable papers in the electronic validation process. The authentication of the security paper is realised with a special detector, by “YES” or “NO” answer. This paper can be used as anti-shoplifting or validating elements to identify the counterfeit products. The paper presents the experimental results related to the retention of ferromagnetic microwires in the cellulose matrix, a complex process characterised by specific features, primarily due to the shape and diameter/length ratio of the microwires. The ferromagnetic retention yield was η = 65 – 90%, for the prepared papers with basis weight more than 50 g/m. Introduction Faced with increasing of goods counterfeiting, a wide range of methods are currently used to protect consumer goods, bank, state and commercial documents. Thanks to impossibility to produce security elements without proper equipment and under special conditions imposed by the very high degree of accuracy, the advanced technologies offer the solution, ensuring a high degree of protection against falsification. Investment and research efforts are being made to diversify the field of high security elements. The moment of launching the technology for glass-coated microwires (GMW) fabrication [1,2] has become revolutionary on the high-tech technology market, opening up the gates of a large variety of technological benefits for the existing applications and also setting the foundation for new applications [3-9]. The advantages of ferromagnetic GMWs securing [10] were: possibility of identifying at distance; stable magnetic properties even at high temperatures and corrosive media; wide range of functional temperatures; stability at shielding – the codes shielded by metallic panels can be read; stability at the mechanical action; small sizes and low consumption and, for the microfibbers from the last generation, with special properties, allowing the possibility to the information magnetic encoding): very large amount of the generated codes; the information can be read both from a stationary source and from a source in motion; the encoding is impossible to destroy, both in the Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 1-10 doi: http://dx.doi.org/10.21741/9781945291999-1 2 continuously and in variable magnetic field, (reliable encoding); possibility to read the information from any code randomly oriented in space. The structure of the paper consists of vegetable fibers (wood or non-wood), in which auxiliary materials, such as fillers, gluing agents, pigments, additives etc. are incorporated. Depending on t
{"title":"A study of the ferromagnetic microwires retention in cellulose matrix in the security papers","authors":"I. Zapodeanu, M. Codescu, M. Burlacu, V. Midoni, R. Erdei, D. Pătroi, E. Patroi, E. Manta, K. Kappel","doi":"10.21741/9781945291999-1","DOIUrl":"https://doi.org/10.21741/9781945291999-1","url":null,"abstract":"Prepared by the Taylor – Ulitovsky technique, the glass-coated microwires are formed from a metallic core, with the diameter 3 to 50 μm, surrounded by an insulating layer from glass, with the thickness of 1 to 20 μm. Embedded in the cellulose matrix, the ferromagnetic glasscoated microwires allow their use as security element for the authentication of valuable papers in the electronic validation process. The authentication of the security paper is realised with a special detector, by “YES” or “NO” answer. This paper can be used as anti-shoplifting or validating elements to identify the counterfeit products. The paper presents the experimental results related to the retention of ferromagnetic microwires in the cellulose matrix, a complex process characterised by specific features, primarily due to the shape and diameter/length ratio of the microwires. The ferromagnetic retention yield was η = 65 – 90%, for the prepared papers with basis weight more than 50 g/m. Introduction Faced with increasing of goods counterfeiting, a wide range of methods are currently used to protect consumer goods, bank, state and commercial documents. Thanks to impossibility to produce security elements without proper equipment and under special conditions imposed by the very high degree of accuracy, the advanced technologies offer the solution, ensuring a high degree of protection against falsification. Investment and research efforts are being made to diversify the field of high security elements. The moment of launching the technology for glass-coated microwires (GMW) fabrication [1,2] has become revolutionary on the high-tech technology market, opening up the gates of a large variety of technological benefits for the existing applications and also setting the foundation for new applications [3-9]. The advantages of ferromagnetic GMWs securing [10] were: possibility of identifying at distance; stable magnetic properties even at high temperatures and corrosive media; wide range of functional temperatures; stability at shielding – the codes shielded by metallic panels can be read; stability at the mechanical action; small sizes and low consumption and, for the microfibbers from the last generation, with special properties, allowing the possibility to the information magnetic encoding): very large amount of the generated codes; the information can be read both from a stationary source and from a source in motion; the encoding is impossible to destroy, both in the Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 1-10 doi: http://dx.doi.org/10.21741/9781945291999-1 2 continuously and in variable magnetic field, (reliable encoding); possibility to read the information from any code randomly oriented in space. The structure of the paper consists of vegetable fibers (wood or non-wood), in which auxiliary materials, such as fillers, gluing agents, pigments, additives etc. are incorporated. Depending on t","PeriodicalId":20390,"journal":{"name":"Powder Metallurgy and Advanced Materials","volume":"94 9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91085757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-11-05DOI: 10.21741/9781945291999-20
V. Nicoară, F. Popa, T. Marinca, C. Nicolicescu
The morphology of the particles is important in the process of obtaining alloys based on W/Cu, thus this investigation is focused on the influence of the copper content on the properties of W/Cu nanocomposites powders obtained after 20 hours of high energy ball milling. The experimental results regarding the obtaining of W100-x/Cux nanocomposites (x between 20 and 45 wt. %) are presented. Composition of the mixtures influenced the particle size distribution namely, the higher is Cu content the larger dimensions of the particles will be attained. After 20 hours of high energy ball milling the crystallites size was about 30 nm for copper respectively 12 nm for tungsten and Cu atoms entered in the W structure. Introduction One of the specific classes of materials which are suitable for elaboration by Powder Metallurgy (PM) consists in pseudo-alloys based on W-Cu due to their mutual insolubility. These materials are very important due to their wide field of applicability such as: welding electrodes, nozzle liners for rockets and missiles, heat sink materials, high power electrical contacts, fission reactors and so on, applications that require high mechanical properties conferred, in this case by tungsten, combined with high electrical and thermal conductivity which are conferred by copper [1-6]. The properties of these materials are in correlation with their composition and morphology and because of that is very important to choose the right composition function of the application [7]. In the field of high power electrical contacts, W-Cu materials must have high arc erosion resistance high temperature strength and high tribological properties to ensure an as long as possible lifetime [8, 9]. Particle size of the component elements plays an important role in the final properties of WCu alloys [10]. One of the techniques used for fabrication of the W-Cu materials is the infiltration one, which consists in the formation of a porous skeleton by tungsten which will be filled with molten copper. Vacuum pulse carburisation was reported [11] to be an infiltration method that leads to the formation of W-30wt.%Cu material with core-shell structure which presents high electrical conductivity (46.55%IACS) compared to the national standard (GB/T8320-2003 – 42%IACS) and a friction coefficient μ=0.64. To improve the sinter ability of W-Cu materials it can be introduced some activators such as Ni, Fe or Co which can be grain growth inhibitors [12]. Using of this activators can lead to a decreasing of electrical and thermal conductivity of W-Cu Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 173-181 doi: http://dx.doi.org/10.21741/9781945291999-20 174 materials [13, 14]. A technique used for mass production which is suitable to produce W-Cu complex shape parts is Metal Injection Moulding (MIM) [15]. Another method to produce W-Cu materials is Mechanical Alloying (MA) which ensures obtaining
(2)给出了10分钟MM(休息2分钟)温度和压力的演变。粉末冶金与先进材料- RoPM&AM材料研究论坛有限责任公司2017材料研究论文集8 (2018)173-181 doi: http://dx.doi.org/10.21741/9781945291999-20 175从(图2)可以看出，由于为干磨型，温度不超过50℃，压力基本恒定。这些参数必须控制，因为如果温度过高，可能会损坏碗和设备。粉末混合物的形态学方面使用JEOL显微镜JSM-5600 LV。采用美国Brookhaven Instruments公司的90Plus粒度分析仪，配备波长为660 nm的35 mW固体激光器，采用动态激光散射(DLS)技术研究了粒径分布和多分散性的演变。温度为25℃，散射角为90°。在水中稀释粉末混合物，每个样品的溶液进行超声波处理5分钟，以避免颗粒絮凝。x射线衍射的研究是用Inel衍射仪进行的，型号为Equinox 3000，工作在反射和Co辐射中。2的研究间隔是20-110度。结果和讨论在(图3)中分别给出了初始均质混合物和研磨20小时样品的形貌。从(图3 a, c, e, g, i, k)可以明显看出，初始均质混合物中钨颗粒的粒径(纳米级)低于铜颗粒。此外，在(图3k)中可以观察到钨纳米粉对铜颗粒的覆盖程度较高，这与混合物的组成(80W/Cu)相一致。经过20小时的MM处理(图3 b, d, f, h, j, l)，所有样品的元素个体形态都变为均匀状态。很可能实现了不同粒子的混合和焊接。而且粉末容易结块。图4为不同阶段混合物的XRD谱图。图中给出了未铣削样品和铣削5、10、15和20 h样品的W-Cu混合物的x射线衍射图。除了这些衍射图外，在同一图中还给出了W和Cu的平均晶粒尺寸随铣削时间的变化。粉末冶金与先进材料- RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 173-181 doi: http://dx.doi.org/10.21741/9781945291999-20 176来自Im-3m空间组，根据JCPDS文件04-0806和04-0836，在未研磨样品的x射线衍射图中可以观察到W - bcc结构的峰特征。图3所示。a) 55W/Cu均质混合物的SEM图像;b) MM 20小时后55W/Cu;c) 60W/Cu均质混合物;d) MM 20h后60W/Cu;e) 65W/Cu均质混合物;f) MM 20h后65W/Cu;g) 70W/Cu均质混合物;h) MM 20小时后70W/Cu;i) 75W/Cu均质混合物;j) MM 20h后75W/Cu;k) 80W/Cu均质混合物;l) MM 20h后80W/Cu;W和Cu峰强度的比值随着混合物中W和Cu含量的变化而变化，正如预期的那样。还可以观察到钨衍射峰的展宽，这是由于混合物中使用的钨粉的纳米晶状态。钨粉的平均晶粒尺寸(用Scherrer法计算)为12±2 nm。研磨5 h后，铜的衍射峰也变宽，表明铜的晶体减少。进一步增加铣削时间也会导致铜的衍射峰增大，直到铣削时间结束，在所有W和Cu之比的衍射图中都没有发现其他的衍射峰。可以观察到，与材料中Cu的含量无关，在衍射图中可以观察到其峰。研磨20 h后，材料中出现fcc铜基结构。已知在平衡条件下W和Cu之间没有溶解度，也知道通过机械铣削可以得到不混相元素之间的固溶体，可以假设经过20次铣削后，一些Cu原子进入了W结构。x射线研究表明，在铣削结束时，材料是由W-Cu固溶体和Cu纳米晶组成的纳米复合材料。可以注意到钨晶在与铜一起研磨时没有明显的变化。它保持在12±2 nm左右。 平均粉末冶金和先进材料- RoPM&AM 2017材料研究论坛LLC材料研究论文集8 (2018)173-181 doi: http://dx.doi.org/10.21
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Pub Date : 2018-11-05DOI: 10.21741/9781945291999-14
V. Merie, M. Pustan, G. Negrea, C. Bîrleanu
This paper is a study on three metallic thin films usable for manufacturing optical MEMS. The films were deposited by thermal evaporation on glass substrates. They were characterized from the topographical, tribological and mechanical point of view at nanoscale. The results pointed out that the silver thin films present higher values of the tribological and mechanical properties than the other two films when testing at room temperature. Increasing the testing temperature from 20 to 100 °C caused a decreased of both hardness and Young’s modulus with about 30 up to 55 %. Introduction The optical microelectromechanical systems (MEMS) are formed in general by multi-layers of metallic thin films characterized by good optical properties. Over the last decades, the attention of the researchers was focused on developing different devices known as microelectromechanical systems (MEMS) that are satisfying the demands of the customers. The properties of the materials employed for manufacturing such devices determine its properties and its performance [1]. The optical MEMS are a category of MEMS devices that are combining the optical, mechanical, and electronic properties in a single device. They are used in the manufacture of optical sensors, attenuators, micro-lenses, micro-mirrors, displays and so on [2-5]. Aluminum [6, 7], gold [8, 9] and silver [10, 11] are one of the most used materials for manufacturing optical MEMS due to their physical, chemical, mechanical, and optical properties. These materials can be obtained as thin films by different methods such as thermal evaporation [6], magnetron sputtering [7-9], electron beam deposition [12], and so on. Arrazat and his colleagues reported their results concerning the evolution of gold thin films deposited by sputtering on silicon substrates. They investigated the deposited films by electron back scatter diffraction analyses that allowed them to study the reliability of micro-switches manufactured using gold thin films [13]. The growth of aluminum thin films and the interfacial precipitation between such films and the silicon substrates were studied by Dutta and his coworkers. They pointed out that at the interface between the aluminum thin films and the silicon substrate during the heat treatment, some silicon precipitates are formed. According to them, these precipitates are supplying the driving force necessary for the deposit of the aluminum thin films [14]. Hojabri and his team worked on determining the influence of substrate temperature on the morphological and structural characteristics of silver thin films deposited by direct current magnetron sputtering on silicon substrates. Their results showed that the substrate temperature Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 125-133 doi: http://dx.doi.org/10.21741/9781945291999-14 126 strongly influence the growth of the silver thin films, their surface roughness, as well
{"title":"Atomic force microscopy analyses on metallic thin films for optical MEMS","authors":"V. Merie, M. Pustan, G. Negrea, C. Bîrleanu","doi":"10.21741/9781945291999-14","DOIUrl":"https://doi.org/10.21741/9781945291999-14","url":null,"abstract":"This paper is a study on three metallic thin films usable for manufacturing optical MEMS. The films were deposited by thermal evaporation on glass substrates. They were characterized from the topographical, tribological and mechanical point of view at nanoscale. The results pointed out that the silver thin films present higher values of the tribological and mechanical properties than the other two films when testing at room temperature. Increasing the testing temperature from 20 to 100 °C caused a decreased of both hardness and Young’s modulus with about 30 up to 55 %. Introduction The optical microelectromechanical systems (MEMS) are formed in general by multi-layers of metallic thin films characterized by good optical properties. Over the last decades, the attention of the researchers was focused on developing different devices known as microelectromechanical systems (MEMS) that are satisfying the demands of the customers. The properties of the materials employed for manufacturing such devices determine its properties and its performance [1]. The optical MEMS are a category of MEMS devices that are combining the optical, mechanical, and electronic properties in a single device. They are used in the manufacture of optical sensors, attenuators, micro-lenses, micro-mirrors, displays and so on [2-5]. Aluminum [6, 7], gold [8, 9] and silver [10, 11] are one of the most used materials for manufacturing optical MEMS due to their physical, chemical, mechanical, and optical properties. These materials can be obtained as thin films by different methods such as thermal evaporation [6], magnetron sputtering [7-9], electron beam deposition [12], and so on. Arrazat and his colleagues reported their results concerning the evolution of gold thin films deposited by sputtering on silicon substrates. They investigated the deposited films by electron back scatter diffraction analyses that allowed them to study the reliability of micro-switches manufactured using gold thin films [13]. The growth of aluminum thin films and the interfacial precipitation between such films and the silicon substrates were studied by Dutta and his coworkers. They pointed out that at the interface between the aluminum thin films and the silicon substrate during the heat treatment, some silicon precipitates are formed. According to them, these precipitates are supplying the driving force necessary for the deposit of the aluminum thin films [14]. Hojabri and his team worked on determining the influence of substrate temperature on the morphological and structural characteristics of silver thin films deposited by direct current magnetron sputtering on silicon substrates. Their results showed that the substrate temperature Powder Metallurgy and Advanced Materials – RoPM&AM 2017 Materials Research Forum LLC Materials Research Proceedings 8 (2018) 125-133 doi: http://dx.doi.org/10.21741/9781945291999-14 126 strongly influence the growth of the silver thin films, their surface roughness, as well","PeriodicalId":20390,"journal":{"name":"Powder Metallurgy and Advanced Materials","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89658023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-11-05DOI: 10.21741/9781945291999-3
T. Marinca, N. Sechel, I. Chicinaș, F. Popa, H. Chicinaş, B. Neamțu
{"title":"Reactive mechanical milling of Fe-Ni-Fe2O3 mixtures","authors":"T. Marinca, N. Sechel, I. Chicinaș, F. Popa, H. Chicinaş, B. Neamțu","doi":"10.21741/9781945291999-3","DOIUrl":"https://doi.org/10.21741/9781945291999-3","url":null,"abstract":"","PeriodicalId":20390,"journal":{"name":"Powder Metallurgy and Advanced Materials","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82149251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-11-05DOI: 10.21741/9781945291999-8
E. Manta, B. Cekić, V. Ivanovski, A. Umićević, Katarina Ćirić
In this paper, it is reported the structural and magnetic properties of Nd13.7Pr0.7Dy0.2Fe73.1Co6.3Ga0.4B5.6 and Nd7.7Pr0.7Dy0.2Fe79.1Co6.3Ga0.4B5.6 magnetic nanocomposites, synthesized by melt-spinning and annealing methods. The Nd-Fe-B ribbons are melt-spun at v=30 m/s in high vacuum and annealed at 715C for 4 min. in argon. Furthermore, Xray diffraction and transmission Fe Mössbauer spectra at RT are used to investigate the effects of substituent elements: Dy, Pr, Co, Ga on the hard magnetic properties and microstructure of both nanocomposites. Analysis of Mössbauer spectra for Nd13.7Pr0.7Dy0.2Fe73.1Co6.3Ga0.4B5.6 is done in terms of ten Zeeman sextets, one paramagnetic doublet related to Nd1.1Fe4B4 phase and two hyperfine magnetic fields distributions extracted from spectrum. Similar result of analysis of the second nanocomposite is obtained with eleven sextets, one doublet and one distribution. One sextet corresponds to α-Fe phase, while we have identified six iron sextets corresponding to the six distinct iron sites in the Nd2Fe14B structure: 16k1, 16k2, 8j1, 8j2, 4c and 4e. The three remaining sextets belong to Fe3B structure with three inequivalent Fe sites: FeI(8g), FeII(8g) and FeIII(8g). The eleventh sextet of Nd7.7Pr0.7Dy0.2Fe79.1Co6.3Ga0.4B5.6 belongs to FeB. All relevant parameters for both nanocomposites: magnetic hyperfine field, isomer shift and quadrupole splitting are determined for each of these sites. To highlight the thermally induced structural transformations, the quenched samples have been analysed by differential scanning calorimetry and thermomagnetic measurements. The magnetic properties, measured at RT on the quenched and annealed ribbons, revealed the relationship between the alloy chemical composition and processing.
{"title":"Mössbauer spectroscopic analysis of (Nd,Pr,Dy)2(Fe,Co,Ga)14B/α-Fe permanent magnetic nanocomposites","authors":"E. Manta, B. Cekić, V. Ivanovski, A. Umićević, Katarina Ćirić","doi":"10.21741/9781945291999-8","DOIUrl":"https://doi.org/10.21741/9781945291999-8","url":null,"abstract":"In this paper, it is reported the structural and magnetic properties of Nd13.7Pr0.7Dy0.2Fe73.1Co6.3Ga0.4B5.6 and Nd7.7Pr0.7Dy0.2Fe79.1Co6.3Ga0.4B5.6 magnetic nanocomposites, synthesized by melt-spinning and annealing methods. The Nd-Fe-B ribbons are melt-spun at v=30 m/s in high vacuum and annealed at 715C for 4 min. in argon. Furthermore, Xray diffraction and transmission Fe Mössbauer spectra at RT are used to investigate the effects of substituent elements: Dy, Pr, Co, Ga on the hard magnetic properties and microstructure of both nanocomposites. Analysis of Mössbauer spectra for Nd13.7Pr0.7Dy0.2Fe73.1Co6.3Ga0.4B5.6 is done in terms of ten Zeeman sextets, one paramagnetic doublet related to Nd1.1Fe4B4 phase and two hyperfine magnetic fields distributions extracted from spectrum. Similar result of analysis of the second nanocomposite is obtained with eleven sextets, one doublet and one distribution. One sextet corresponds to α-Fe phase, while we have identified six iron sextets corresponding to the six distinct iron sites in the Nd2Fe14B structure: 16k1, 16k2, 8j1, 8j2, 4c and 4e. The three remaining sextets belong to Fe3B structure with three inequivalent Fe sites: FeI(8g), FeII(8g) and FeIII(8g). The eleventh sextet of Nd7.7Pr0.7Dy0.2Fe79.1Co6.3Ga0.4B5.6 belongs to FeB. All relevant parameters for both nanocomposites: magnetic hyperfine field, isomer shift and quadrupole splitting are determined for each of these sites. To highlight the thermally induced structural transformations, the quenched samples have been analysed by differential scanning calorimetry and thermomagnetic measurements. The magnetic properties, measured at RT on the quenched and annealed ribbons, revealed the relationship between the alloy chemical composition and processing.","PeriodicalId":20390,"journal":{"name":"Powder Metallurgy and Advanced Materials","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89806474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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