bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the Hydration of Portland Cement Modified with Polyvinyl Alcohol and Nano Clay
Authors: Piqué Teresa María , Balzamo Humberto , Vázquez Analía
Published: January 2011

Polyvinylalcohol (PVA) is a polymer soluble in hot water, it has the property of film formation and it can improve the concrete performance. The effects of PVA modified with nano clay on the cement hydration reaction have been investigated by means of semiadiabatic calorimeter, FTIR spectroscopy and SEM. FTIR spectroscopy was employed to monitor chemical transformation of cement. The morphology of the different samples was compared by means of SEM micrographs. With the semiadiabatic calorimeter the hydration kinetic was measured to compare the heat rate of the admixtures materials. Fixing the water–cement ratio, w/c, in 0,45, the ratio of polymer to cement (p/c) was 2 wt% and the ratio of clay to polymer was 4 wt% (0.8wt.% related to cement). The polymer and modified polymer admixtures produced a retardation effect on the kinetic of cement hydration, but the clay acts as nucleating agent. The increase of the temperature with time was measured and a new model with four parameters was employed and the kinetic parameters were determined for each sample.
Hydration of Cement in the Presence of SBR Dispersion and Powder
Authors: Wang Ru , Wang Pei Ming
Published: January 2011

Hydration of cement in the presence of SBR dispersion and powder respectively was investigated using the methods of ITC, XRD and ESEM. The results show that both the dispersion and powder of SBR facilitate the formation, enhance the stability of AFt and inhibit the formation of C4AH13 in cement paste; the effect of the powder is more evident than the dispersion. Both the dispersion and powder of SBR delay the formation of C-S-H and Ca(OH)2 in cement paste, and the effect of the dispersion is more evident. Up to 3 days, the structure of the SBR dispersion – or powder – modified cement pastes has no significant difference with that of control paste except due to a thin polymer film on the surface. The two polymers delay the early cement hydration, but have no significant effect after 3 days.
Review on Gallium Zinc Oxide Films: Material Properties and Preparation Techniques
Authors: Nagarani S. , Jayachandran M. , Sanjeeviraja C.
Published: January 2011

Thin films continue to become more and more integral to numerous applications in today's advancing technologies. In recent years, thin film science has grown world-wide into a major research area. The importance of coatings and the synthesis of new materials for industry have resulted in a tremendous increase of innovative thin film processing technologies. Thin film properties are strongly dependent on the method of deposition, the substrate temperature, the rate of deposition, the background pressure etc. Hardness, adhesion, non porosity, high mobility of charge carriers / insulating properties and chemical inertness, which are possible with a selection of suitable functional materials and deposition techniques. There are number of different techniques that facilitate the deposition of stable thin films of oxide materials on suitable substrates. Material properties of gallium zinc oxide thin films and all the techniques used to deposit thin films are summarized with an elaborative account along with our results.
Nanomaterial Preparations by Microwave-Assisted Solution Combustion Method and Material Properties of SnO2 Powder - A Status Review
Authors: Nehru L.C. , Swaminathan V. , Jayachandran M. , Sanjeeviraja C.
Published: January 2011

A nanocrystalline tin oxide (SnO2) powders have been prepared by a simple, low-temperature initiated, self-propagating and gas producing by microwave-assisted solution combustion process. The effects of temperature on crystalline phase formation and particle size of nanocrystalline SnO2 and its structure have been investigated. It is observed that heat-treated upto 800°C shows tetragonal phase SnO2. It was observed that the average crystallite size of the annealed SnO2 samples is in the range 9 - 43 nm through controlled heat treatment process. The crystal density of the as-prepared powder is 5.850g cm-3 where as the bulk density is 6.998 g cm−3. The microstructure and morphology were studied by scanning electron microscope (SEM) and HRTEM it is interesting to note that as-prepared SnO2 sample are almost spherical in shape and average agglomerate crystal size of 0.2 – 0.4 μm with increase in calcination temperature, the samples become better morphology than the as-prepared sample. The crystallographic parameters were refined by XRD pattern and Rietveld refinement using TOPAS-3 and Diamond software was used to construct the structural parameters.
Inductive Sensor with Sintered Magnetic Core to Evaluate the Performances of the Table Tennis Players
Authors: Mangra Gabriel Ioan , Savu Sorin Vasile , Savu Danut
Published: January 2011

The reaction speed of the tennis player and the speed of the ball after the impact to the tennis blade, they both are important elements of the performance evaluation of a tennis player. The determination of those parameters is possible by using specialized contact sensors. Permanent ceramic magnets can be used to process such sensors and the paper presents the experimental results concerning the processing of such magnets of barium hexaferritte powders
CdS Powders Obtained by Chemical Bath Deposition
Authors: Popescu Violeta , Popescu George Liviu , Indrea Emil , Silipas Dan Teofil
Published: January 2011

We studied the influence of the mixing on the properties of CdS powders obtained by Chemical Bath Deposition. The powders were obtained from baths containing cadmium chloride, thiourea, and ammonia. The obtained powders were characterized using FT-IR, in order to evaluate the purity of the obtained powder. Granulometric studies were made in order to establish the grain size distribution of the particles, and X ray diffraction in order to determine the structure of nanostructured CdS.
An Electrochemical Machining Device for Residual Stresses Measurement in PM Parts by Layer Removal Method
Authors: Sahin Fatih , Kafkas Fırat , Karatas Cetin
Published: January 2011

Residual stresses play an important role in the performance of materials and the components produced from them. All manufacturing processes introduce residual stresses. These stresses can have a positive effect, for example by increasing the fatigue limit in the case of compressive surface residual stresses. Layer removal by electrochemical machining (ECM) can be used for measurement of the residual stresses in the PM parts. The device removed the layers by aid of electrochemical machining for this purpose is designed and developed. The device setup for residual stress measurement is based to the changes on deformation quantity. Since ECM is a non-mechanical metal removal process, ECM is capable of machining any electrically-conductive material with attendant high removal rates, regardless of mechanical properties. In particular, the removal rate in ECM is independent of the hardness, the porosity and toughness of the PM parts being machined. The micro constituents in PM steels resulting from different processing routes exhibit different thermal and mechanical behavior. This will lead to the formation of residual stresses around these micro constituents. Here we give the results of the first work carried out on PM steels in relation to residual stress measurements by the electro-chemical layer removal technique. The device works as follows. As a layer of thickness is removed, a certain amount of stress is removed from the sample. Equilibrium is violated and the sample deforms elastically to compensate for the stress removed. This elastic deformation in the sample is measured by the linear displacement gauge. This gauge pushes on the end of sample and deformation is recorded by this gage. The linear gauge send a signal to a display and then to the data converter. As simultaneous, this signal sent to the computer from the data converter for further calculations by RS 232.
Research on the Intermetallic Compounds Formation in a Ni-Ti Alloy Obtained through Powder Metallurgy Specific Methods
Authors: Cândea Viorel , Arghir George , Popa Catalin , Gligor Ionuţ , Popa Angela , Batin Gabriel
Published: January 2011

NiTi alloys, due to the special properties they posses, good corrosion resistance, biocompatibility, and shape memory, are used successfully in the medical field. The paper presents research concerning the elaboration of the NiTi alloy in the form of spherical shape powder with hollow particles. This type of powder would be the raw material for fabricating light weight products like prosthesis or surgical implants. The aim of the research was to elaborate this type of powder and determine the alloy’s phases in correlation with the need of obtaining a specific particle shape. Along with these aspects it was attempted to form different testing samples through sintering operations.
Nickel Ferrite Powder Obtained by High Energy Reactive Ball Milling
Authors: Marinca Traian Florin , Chicinaş Ionel , Prică Virgiliu Călin , Popa Florin
Published: January 2011

Nanocrystalline nickel ferrite powder was obtained using high energy reactive ball milling technique. Nickel oxide (NiO) and iron oxide (Fe2O3) powders were used as starting material. Milling was performed in air atmosphere using a planetary ball mill. Milling time was up to 30 hours. The product of milling was annealed at 350 oC for 4 hours in order to eliminate the internal stresses and finish the solid state reaction. X-ray diffraction analysis was used to study the nickel ferrite formation. A nanocrystallite mean size of 10 nm was found after 24 hours of milling. Using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDX) the particle morphology and the chemical homogeneity were studied. It was found that the obtained product has particle size in range of micron and submicron.
Obtaining of the Ir-Al Nanocrystalline Powders by Mechanical Alloying
Authors: Chicinaş Ionel , Cârlan P. , Popa Florin , Prică Virgiliu Călin , Sorcoi Lidia Adriana
Published: January 2011

The Ir-Al powder in the 1:1 atomic ratio was obtained by high energy mechanical alloying in a Pulverisette 4 Fritch planetary mill. The final product was obtained after 28 h of milling in argon atmosphere. Alloy formation was investigated by X-ray diffraction. After 4 h of milling the new structure of IrAl compound is found in the diffraction patterns. The obtained powders are nanocrystalline with a mean crystallite size of 11 nm after 28 h of milling. The particle morphology and the chemical homogeneity were studied using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDX). It was found that the obtained compound present large particles composed by smaller one.
SHS Processing of NiTi-Nb Smart Alloys
Authors: Orban Radu Liviu , Lucaci Mariana , Salomie Dana , Jumate Nicolaie , Brânduşan Liviu
Published: January 2011

Nb additions to NiTi smart alloys are known to lead to the PTT-hysteresis broadening and transformation temperatures raising – required in numerous applications. As Nb has a high affinity for oxygen, NiTi-Nb alloys processing by powder metallurgy, via SHS, from elemental Ni-Ti-Nb powder mixtures, seems to be more advantageous and cost-effective than by classical one. However, its application encounters difficulties determined by the NiTi higher Gibbs Free Energy of Formation than of Ni3Ti and NiTi2, possible Ni-Nb compounds formation, Nb acting as diluent in SHS. This research proved the possibility to overcome these difficulties and of NiTi-Nb alloys obtaining by SHS using energetically activated powder mixture by controlled Mechanical Alloying. Also, it was proved the possibility to reduce Nb content from the common one of 9 at.% to 5 at.% without a significant effect of transformation temperatures and hysteresis decreasing.
The Thermomechanical Modeling for Shape Memory Alloys
Authors: Cirstea Diana C. , Lucaci Mariana , Raducanu Doina , Tsakiris Violeta
Published: January 2011

The shape memory alloys are materials that can change their shape by applying thermomechanical treatments. In order to design SMA materials, the stress-strain-temperature relationship is necessary. Modeling the constitute behavior of these materials supposes a few phenomenological models that can provide a quick and reasonable approach to assess the behavior of SMA. The proposed constitutive equation expresses well the properties of the shape memory effect, pseudoelasticity and recovery stress.
Material Data for Modelling Density Distributions in Green Parts
Authors: Shang C. , Sinka I. Csaba , Pan J.
Published: January 2011

Die compaction of powders is a process which involves filling a die with powder, compaction using rigid punches to form a dense compact and ejection from the die. The process can be treated as a large deformation plasticity problem. The challenge is to develop and implement appropriate constitutive models that capture the evolution of the powder from a loose state into a dense compact. In this paper we describe data analysis procedures and calibrate classic incremental plasticity models, such as Cam-Clay, Drucker-Prager cap models. The complexity of the models is increased from models with a hardening law to more complex constitutive models using density as state variable. The compaction behaviour of a range of powder materials is characterized experimentally. Numerical simulation of the compaction of simple parts and complex parts is demonstrated. The merits of various models are evaluated in terms of the balance between complexity and practicality. The discussion is illustrated with case studies exploring the applicability of the models specific to various powder pressing scenarios.
NdFeB/αFe Nanocomposite Permanent Magnets with Enhanced Properties Prepared by Spark Plasma Sintering
Authors: Grigoraş Marian , Lostun M. , Lupu Nicoleta , Chiriac Horia
Published: January 2011

Nanocomposite NdFeB/αFe magnets were obtained by spark plasma sintering technique using high energy ball-milled Nd-Fe-B melt-spun ribbons mixed in different weight ratios with Fe commercial powders. The remanence of SPS nanocomposite magnets increases with the Fe powders content from 6.1 for 4 wt.% Fe to 6.4 kG for 5 wt.% Fe, while the estimated maximum energy product is also increased from 9.0 to 10.6 MGOe.
A Study on the Effect of Manufacturing Conditions on Surface Roughness during Machining of Cu/Al2O3 Composites
Authors: Mîtcă Luisa N. , Günay Mustafa , Orban Radu Liviu , Şeker Ulvi
Published: January 2011

In this study, the machinability of the Cu matrix composites reinforced with 5, 10, 15 and 20 vol.% of Al2O3 particulates produced by powder metallurgy have been investigated. The effects of compaction pressure, sintering duration and volume fraction of reinforcing component on the surface roughness during machining of the considered composites, obtained by the appropriate Cu-Al2O3 powder mixtures cool die pressing at 500, respectively 700 MPa, and sintered at 800 °C for durations of 45 and 60 minutes in an argon atmosphere were determined. The machining tests were performed on a CNC machining centre, by means of samples face milling in dry conditions, at two different feed rates and four different cutting speeds, while the depth of cut was kept constant. As cutting tools have been adopted commercial grade (H13A) uncoated cemented carbide inserts manufactured by Sandvik Coromant with the geometry of TPKN1603 PP-R. After the machining tests, the surface roughness measurements clearly showed an increasing trend in surface roughness when the feed rate is increased from 300 mm/min to 400 mm/min for both sintering durations. Surface damages created on the machined surface through release from the matrix of particles negatively impact surface roughness. The most stable results in terms of surface roughness were obtained at 20% reinforcing ratio for 700 MPa compacting pressure and 60 minutes sintering duration.
Effect of Different Vacuum Heat Treatments on the Microstructure of a Low Alloyed Sintered Steel
Authors: Bidulský Róbert , Grande Marco Actis , Brytan Zbigniew , Rosso Mario
Published: January 2011

The main aim of the present contribution is to show how different heat treatment conditions influence the microstructure of a Fe - [1.5Cr - 0.2Mo] - 0.6C powder system. In vacuum furnaces, the cooling rate is generally determined by the pressure of the gas (basically N2) introduced into the chamber. Different gas pressures have been applied, from 0 to 6 bars. The average cooling rates were calculated in the range of 1180 °C to 400 °C and were varying from 0.1 to 6 °C/s, according to the gas pressure. Considering the cooling rates, increasing the nitrogen pressure resulted in an increased amount of bainite/martensite microstructure. The microstructure constituents ranged from 97% pearlite + 3% ferrite in the system treated at 0 bar to 82 % martensite + 18 % bainite (with small amount of tempered martensite) in the system cooled applying N2 at 6 bars. Mechanical properties have been evaluated in terms of toughness, TRS and hardness for all processing conditions; the analysis of the properties allowed to plot graphs correlating the different properties as function of the characteristic microstructures.
PM Titanium – Based Composites with Improved Biocompatibility
Authors: Popa Catalin , Simon Viorica , Batin Gabriel , Pavel Codruta , Gligor Ionuţ , Conţ Liana , Cândea Viorel
Published: January 2011

Although titanium is considered to be the most successful metal for uncemented endosseous implants, its biocompatibility may be unsatisfactory in certain clinical cases. As an early osseointegration is essential in order to reduce the implant failure risk, the bioactive fixation becomes the appropriate solution for bone applications. The method requires bioactive materials such as hydroxyapatite (HA) to facilitate the chemical bonding to tissue. The present work refers to Ti-HA composites designed for endosseous implants and obtained through the classic PM route. Grade 1 c.p. Ti powder obtained through the hydriding – milling – dehydriding process, 63 - 100 μm grain size, was used. Sol-gel HA powder, grain size of less than 100 μm, was obtained through the sol-gel method. Blends of Ti and 5 to 50% HA were compacted in a rigid die (0.5 cm2), without the use of any lubricant, with 400, 500 and 600 MPa, then vacuum sintered (10-6 torr) at 1160°C for 60 minutes. Samples are well sintered with a compactness that increases with the applied compaction pressure. A transition layer can be seen in the EDX at the interface between the Ti matrix and the HA particles and is expected to increase the overall mechanical stability of compacts. The pores, essential for osseointegration, are interconnected, with irregular shapes and sizes that reach 100 μm, the critical size needed for the formation of a vital new bone. The HA content has to be limited to 30%, not to lead to an excessive brittleness. The biologic viability of compacts was assessed by immersion for 7 days into a simulated body fluid (SBF). The subsequent XRD analyses have proven that a new HA layer is formed on the surface of samples. This layer is essential for accelerating the cellular response of osteoblasts in the body.
Research on the Manufacture of some Tungsten-Copper Composite after Vacuum Sintering
Authors: Pascu Cristina Ileana , Stanimir Alexandru , Vida-Simiti Ioan
Published: January 2011

The paper presents the results of the experimental research carried out in order to obtain pseudoalloys WNiCu used in electrical industry, for the electrical apparatus of high tension and great power. As a result it was compulsory to study the parameters that influence the densification process and the sintered properties, depending on the grain-size distribution of tungsten powder, compaction pressure and sintering temperature in vacuum. Therefore, it has been studied the influence of these parameters on the density, hardness and microstructures changes for the composites with 78%W-2%Ni-20%Cu, (% wt). The better results were obtained for the value of 1350 0C for the copper infiltration temperature.
Behaviour of Some Unalloyed and Alloyed Sintered Steels at Static and Dynamic Loads
Authors: Brânduşan Liviu
Published: January 2011

The behaviour of alloyed and unalloyed sintered steels in static and dynamic loading is influenced by their macro and microstructure. The characteristics of the used powder, their chemical composition, the conditions of shaping by pressing, and the parameters of the sintering process are some factors determining the structure of the steels [1, 2]. Under the same technological conditions, sintered materials were produced using iron powder of different particle size or in different powder mixtures for establishing the structure influence on some mechanical properties, The results obtained shows that the sintered materials present a higher sensitivity towards the dynamic and variable loads [2]. In the same time, it was shown that a material made from a fine powder fraction behaves, at mechanical loads, almost in the same way as an elaborated material from the same powder but with a wider particle size distribution or particles size. Using of the different powder mixtures lead to some microstructures with better mechanical properties at the intergranulars necks. Using the copper powder or the low or high alloyed iron powder in a mixture with the basic iron powder determines an improvement of the mechanical properties by changing the materials microstructure. It was found that the addition of high alloyed steel powder has the strongest effect on the fatigue resistance.
Evaluation of Surface Integrity during Machining with Different Tool Grades of Sicp/Al-Si Composites Produced by Powder Metallurgy
Authors: Günay Mustafa , Şeker Ulvi
Published: January 2011

MMCs components are mostly produced using near net shape manufacturing methods and are subsequently machined to the final dimensions and surface finishes. The MMCs consist of extremely hard reinforcing particles and pose considerable challenges due to the poor machinability and severe wear of the cutting tool. In this study, cutting performance of WC, CBN and PCD cutting tools were investigated with respect to surface roughness during machining of 10 wt % SiCp reinforced Al-Si alloy matrix composites produced by powder metallurgy (PM) method. Average surface roughness (Ra) corresponding to each machining condition was measured. After the machining process the worn insert tips were examined under the scanning electron microscope (SEM). Chip geometry and machined surface photographs have been taken by optical microscopy. The experimental results showed that surface roughness decreased with increasing cutting speed for all of cutting tool materials. The best surface integrity was occurred after the machining with PCD insert at the highest cutting speed employed.
Analysis of Functional Properties of Cu-Al2O3 Particulate Reinforced Composites. A First Assessment: Elaboration
Authors: Mîtcă Luisa N. , Orban Radu Liviu , Kurt Adem , Brânduşan Liviu , Jumate Nicolaie
Published: January 2011

The possibilities of Cu-Al2O3 particulate reinforced composites, of competitive functional properties, processing by the classical powder metallurgy route have been investigated taking into consideration its known technical and economical advantages in respect to the known worldwide investigated technological routes of their processing. The adopted compositions, of (5.0÷20.0) [vol.%] Al2O3, were selected in agreement with published data for a large range of applications. Pharmaceutical homogenization method applied for powder mixtures preparation proved to assure a high homogeneity, evidenced by SEM and EDS analyses. Their determined compressibility has shown that, for all compositions, the obtainable compactness is very close to that of pure Cu (even over 94 %). Cold uniaxial compaction at 500 and 700 MPa, and subsequent sintering in argon of high purity at 800 °C for 45 and 60 min have been adopted for composites realization. The performed analysis of the compacting pressure and sintering time influence on the composite compactness proved that, beside the above specified values obtaining for 700 MPa and 60 minute processing parameters, high enough values, acceptable for numerous applications, can be also obtained at 500 MPa and 60 or even 45 minutes. Finally, microstructural analysis highlighted that, by the adopted processing conditions, a high uniformity of Al2O3 particles distribution in the Cu matrix can been assured, both creating premises for obtaining good functional properties of Cu-Al2O3 composites, proving the competitiveness of the investigated PM route for their elaboration.
The Beginnings of Romanian Research in the Field of Powder Metallurgy
Authors: Colan Horia
Published: January 2011

The paper presents the main stages of the development of Romanian international relations in powder metallurgy, especially regarding its beginnings at the Technical University of Cluj-Napoca, with a tradition of almos51t 60 years.
Mechanical and Tribological Characteristics of Sintered Manganese Steels
Authors: Selecká Marcela , Šalak Andrej , Jakubéczyová Dagmar
Published: January 2011

The effect of three iron powder grades and three manganese carrier types on mechanical and tribological characteristics of sintered 1 -5% Mn steels was investigated. The different effect of iron powder grades in dependence on manganese addition expressed oneself in strength and in wear. The highest strength and highest wear attained the steels with 3% Mn added as high carbon ferromanganese. The components – rollers - prepared from manganese steel exhibited lower wear than that from Fe-4Ni-1.5Cu-0.5Mo powder. The gears for hydrogenerator prepared from Fe-3.5Mn-0.5Mo-0.3C steel exhibited longer life time at increased oil pressure compared with that from through hardened sintered Fe-4Ni-1C steel.
Formation of the Hipernik Alloy by Mechanical Alloying
Authors: Chicinaş Ionel , Pop Viorel , Popa Florin , Prică Virgiliu Călin , Marinca Traian Florin , Neamţu Bogdan Viorel , Sorcoi Lidia Adriana
Published: January 2011

The Hipernik alloy (50Ni50Fe wt. %) was obtained by mechanical alloying. The milling was performed in argon atmosphere, with a ball/powder mass ration of 8:1 for times ranging from 2 up to 20h. The alloy formation was studied by X-ray diffraction. The obtained structure is face cantered cubic, indicating the extension of the γ domain for the Ni-Fe alloys by mechanical alloying. The mean crystallite size was calculated with the Williamson – Hall method. Using scanning electron microscopy (SEM) the morphology and the chemical homogeneity of the powders was analysed. The technological properties of the powders as particle size distribution and flowability are determined as a function of the milling time. The magnetic behaviour of the samples was studied by magnetic measurements under high magnetic fields.
The Improving of the Process of the Iron, the Cast Iron and the Copper Powder Mixing
Authors: Ciupitu Ion , Benga Gabriel , Ionescu Adela , Savu Danut
Published: January 2011

This paper presents the experimental results concerning the compacting process of some iron, cast iron and copper mixtures. In these mixtures the participation of the cast iron powder to the chemical composition of the mixtures was 5%, 10% and 15% and the participation of the copper powder was 2% and 5%. The paper emphasizes the influence of the carbon content, the cast iron hardness and the cast iron powder content on the mixtures compaction ability at different compacting pressures.
Modeling of Droplet Dynamic and Thermal Behavior during Gas Atomization Process
Authors: Bodea Marius , Mureşan Radu , Prică Virgiliu Călin
Published: January 2011

The paper is focused on the physical phenomena that occurs during gas atomization process, like fragmentation mechanism of the molten stream, the secondary breakup mechanism, droplets velocities and particles temperature history. The modeling of droplet dynamic and thermal history was achieved by using a software program realized by authors, called MetLAB, using the heat balance equations between the cooling gas and the molten metal droplets.
Wear Resistant In Situ MMC Sintered with FeBC Liquid Phase
Authors: Saltykova Anastasia , Berns Hans
Published: January 2011

Powder metallurgy represents a good alternative to a conventional casting process to produce wear resistant materials. MMC (metal matrix composite) of a hardenable steel matrix and hard phases compacted by hot isostatic pressing (HIP) are highly wear resistant but high in price. In the present study liquid phase sintering was preferred to HIP and expensive hard phases as tungsten carbides were replaced by ferrotitanium particles (FeTi) to reduce costs. A mixture of gas atomized hot work steel powder of < 150 µm in size, hypereutectic FeBC powder of < 36 µm in size as liquid phase donor (LPD) and ferrotitanium particles (100-150 µm in size) with about 70 mass% of Ti was sintered in vacuum to give a wear resistant MMC of full density. However, the elements B and C from LPD diffused to the steel powder before the liquid phase appeared. Therefore these two powders merged into a near-eutectic or hypoeutectic constitution. The LPD was diluted by the steel. During sintering the ferrotitanium particles are transformed in situ into hard phases (in situ HP) with a Fe-rich core surrounded by a hard TiC case to withstand abrasive wear. Numerous investigations by LOM, SEM with EDX, WDX and DTA were realized step by step for a deeper understanding of what happens in the initial three-component mixture during liquid phase sintering and how the in situ MMC forms. The resistance to wear was measured by pin-on-plate tests against abrasive paper of different hardness and mesh size and compared with HIP-MMC and SLPS-MMC.
Shape Memory NiTi Alloys Obtained by Powder Metallurgy Route
Authors: Lucaci Mariana , Valeanu M. , Orban Radu L. , Tsakiris Violeta , Cirstea Diana C. , Leonat Lucia
Published: January 2011

The effect of Fe, respective Cu, additions as substitute for Ni in NiTi shape memory alloys (SMAs) on the delaying of its phase transition and narrowing hysteresis are well known, NiTi-Fe and NiTi-Cu SMAs having applications especially to the actuators that require such properties. These SMAs are currently produced by conventional melting methods, which are energo-intensive and impose very severe processing conditions to avoid contamination. The results of researches presented in this paper prove the possibility of these SMAs obtaining by powder metallurgy via reactive sintering – more advantageous from both technical and economic point of view. A beneficial effect on both sintering and homogeneity of the obtained SMAs proved to have a controlled mechanical alloying applied to powder mixture before compacting and sintering.
Electromagnetic Bulging of Stainless Steel Sheet by Using Flat One-Turn Coil
Authors: Ishibashi Masaki , Okagawa Keigo , Aizawa Tomokatsu
Published: January 2011

In this paper, we describe an electromagnetic bulging for a SUS304-O stainless steel sheet (0.15 mm thick) and its experimental results. In the die forming, the flat one-turn coil is adopted for the bulging of the SUS304-O sheet, when an aluminum sheet (0.3 mm thick) as a driving plate (driver) is used together. When an impulse current from an energy-storing capacitor bank passes through the flat one-turn coil, a high-density magnetic flux is suddenly generated around the coil. Eddy currents are induced in the driver placed on the coil. The SUS304-O sheet is pressed by an electromagnetic force generated in the driver, leading to bulge into a meandering groove with small concave shape. The bank energy required for the bulging of 12mm wide, 60mm long and 0.43mm high is about 4.5 kJ, and the obtained workpiece does not almost have wrinkles and curves.
Numerical Simulation of the Shock Compaction of W/Cu Powders
Authors: Dai Kai Da , Chen Peng Wan
Published: January 2011

A numerical simulation approach is used to study the deformation and temperature distribution of W/Cu powders under shock compaction. A two-dimensional micromechanical model is employed where only a few particles are considered. The simulation is performed using plane strain element and Lagrange formulation. Shock compaction is achieved by bringing in the W/Cu powders an intense compression wave using a high-velocity rigid wall. The effects of compact velocity, particle size and friction on the particle deformation and temperature distribution are discussed based on the results of simulations. The study provides a detailed understanding of the micromechanical behavior of metal powders during shock compaction process.
Underwater Explosive Consolidation of Mechanically Milled Al/TiB2 Composites
Authors: Eskandari H. , Hokamoto Kazuyuki
Published: January 2011

Aluminum matrix composites containing10, 20 and 30vol%TiB2 particles were manufactured by underwater shock consolidation method. High energy ball milling was used to produce a homogenous Al matrix composite reinforced by TiB2 powders. Microstructures of recovered compacts were examined by optical microscope. Sintering of the compacts was carried out at 400 C for 70 minutes. Density, hardness and bending strength of the compacts were measured before and after sintering treatment. The sintered composite samples showed better improvement in the bending strength and deflection The sintered Al matrix samples with 20vol%TiB2 showed highest bending strength and high deflection. SEM fractography examination was used for analysis of fracture surfaces of the compacts.
Processing of Zinc Sulfide Based Electroluminescent Material Using TNT in a High Pressure Vessel
Authors: Kennedy Greg , Wada Naoyuki , Hayashi Y. , Kurihara M. , Hokamoto Kazuyuki , Itoh S.
Published: January 2011

Electroluminescent, EL, materials are of interest in providing high brightness for display screens found in portable electronic devices, where the battery life is limited. Currently organic luminescent materials are being used, but the lifetime is low due to the degradation of the organic material under electric field over time. Some recent work with inorganic material of zinc sulfide has indicated high brightness at very long life times. This work focuses on the thermal processing of the zinc sulfide based EL material with trinitrotoluene, TNT. The zinc sulfide based phosphor and TNT are placed in a stainless steel container that can withstand high pressure. After closing, the chamber was evacuated and subsequently heated to over 300°C. The ZnS based phosphor was heated to a high temperature as the TNT decomposed. The sample was recovered after cooling and separated by optical observation of photoluminescence with a ultraviolet lamp. X-ray diffraction analysis showed that some transformation to hexagonal wurtzite phase occurred and was retained after cooling. EL and photoluminescence, PL, measurements were performed to characterize the luminescent properties of the material. Results of SEM observations of the particle sizes are discussed. The most recent data shows that blue luminescence at 450nm can be obtained by the treatment of ZnS phosphor with TNT in this high pressure containment device.
Effects of Shock Doping on the Energy Gap of TiO2
Authors: Gao Xiang , Chen Peng Wan , Liu Jian Jun , Yin Hao , Huang Feng Lei
Published: January 2011

In this paper, nitrogen-doped titania was achieved by detonation-driven flyer impacting on the mixtures of TiO2 and different nitrogen precursors. XRD、UV-Vis and XPS spectra were employed to characterize the phase composition, N doping concentration and energy gap of recovered samples. N doping concentration can be effectively regulated by choosing different doping nitrogen resources, changing initial content of doping nitrogen resources and flyer velocity in order to regulate the energy gap of TiO2. The maximum concentration of nitrogen of doped TiO2 by shock loading at 3.37 km/s is 13.45 at%. The results show that anatase transforms to rutile and srilankite appears at a higher flyer velocity (1.9-2.52km/s), the concentration of doped nitrogen in the recovered samples increases with increasing flyer velocity, the maximum concentration of nitrogen is 13.45 at%. The edge adsorption wavelength of nitrogen-doped titania induced by shock wave is shifted from 435nm to 730 nm and the corresponding energy gap is reduced from 2.85 eV to 1.73 eV.
Synthesis and Characterization of Graphite-Encapsulated Metal (Fe,Co,Ni) Nanoparticles by a Detonation Method
Authors: Li Xiao Jie , Luo Ning , Bai Min Li
Published: January 2011

A method for synthesizing carbon-encapsulated metal nanoparticles(CEMNPs) is reported. In the proposed method, a composite precursors containing various nitrate dissolved in absolute ethanol is ignited by a nonelectric detonator in nitrogen gas in an explosion vessel. Upon the completion of detonation reaction, CEMNPs (Fe@C, Ni@C, Co@C) with diameters ranging from a few nanometers to about 20 nm are produced in the explosion vessel.The material characteristics of these nanoparticles are then examined with the XRD, TEM, EDX and VSM, which characterize the feature of morphology, components, phases and magnetism of nano-composite particles. The composite particles whose coating shell were graphite carbon could be dispersed finely. The core of nanoparticles were composed of iron,cobalt and nickel crystal to that of the above explosive precursors.The magnetic analysis indicated that the different composite nanoparticles have good ferromagnetism and superparamagetism in room temperature.
Study of Corrosion Behavior of Conventional and Nanostructured WC-Ni High Velocity Oxy Fuel (HVOF) Sprayed Coatings
Authors: Khameneh Asl Shahin , Saghi Beyragh Mohammad Reza , Noori Neda Faale
Published: January 2011

The current study is focused on WC-Ni cermet coatings, materials that are extensively used in applications requiring wear resistance. In this work, WC-10%Ni powder was thermally sprayed onto mild steel using High Velocity Oxy Fuel (HVOF) spray technique. The nanostructured specimen was produced from sprayed samples by heat-treating at 1100°C in a vacuum chamber. Their structures were studied by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Polarization and electrochemical impedance spectroscopy (EIS) tests were performed on both types of coated samples in 3.5% NaCl solution. The amorphous phase in WC-10%Ni coating was transformed to crystalline phases by heat treatment at high temperatures. Heat treatment of these coatings at high temperature also resulted in partially dissolution of WC particles and formation of new crystalline phases. Generation of these phases produced the nanostructured coating with better mechanical properties. Comparative electro chemical test results showed that, the heat treatment could improve corrosion resistance of the nanostructured WC-10%Ni coating than the as sprayed coatings.
A Numerical Research on the Penetration into a Semi-Infinite Rolled Homogeneous Armor by a Medium-Caliber Kinetic Energy Projectile
Authors: Joo Jae Hyun , Lee Chang Hyun , Choi Joon Hong
Published: January 2011

This paper presents numerical analysis on the penetration into a semi-infinite Rolled Homogeneous Armor(RHA) steel target by a medium-caliber projectile at the velocity range from 900m/s to 1000m/s. The projectile was made of a 93% tungsten heavy alloy(WHA) having a diameter of 18mm. LS-DYNA, an explicit non-linear finite element analysis code, was used for the numerical analysis. This kind of penetration problem is generally accompanied by large deformation, high strain rate and thermal softening, accordingly the Johnson-Cook constitutive models combined with Johnson-Cook fracture model and Mie-Gruneisen equation of state were employed to describe the RHA target and the WHA projectile, respectively. Due to the lack of the parameters of the Johnson-Cook failure model of RHA, the corresponding data of 4340 steel were applied for RHA inevitably. Here, two different failure strains for 4340 steel from the literatures were substituted in for RHA and their effects on the numerical analysis results were discussed and compared to the test results in terms of penetration efficiency(P/L) and crater hole shape. A quarter parts of the semi-infinite RHA target and the WHA projectile were only modeled considering the symmetric configuration of the problem for the analysis.
Experimental and Numerical Study on Liner Shaped Charge
Authors: Tanaka Shigeru , Kennedy Greg , Hokamoto Kazuyuki , Itoh Shigeru
Published: January 2011

There are few research papers of liner shaped charge (LSC). In this time simplified LSC was made from an explosive and vertically-folded copper plate. In order to confirm a performance of the simplified LSC, steel cutting experiments were conducted by changing distance from the simplified LSC to target steel. Numerical analysis was also conducted by using Ls-dyna. Penetration depth was measured after experiments. Collision velocity of copper was calculated by using Gurnney equation. Numerical simulation model was made by SPH, because large deformation was occurred during collision of copper and steel penetration process. Results from numerical analysis were good correspondence with experimental results. Details are reported on this paper.
A Framework for Analyzing the Microstructure Level Thermomechanical Response Polymer Bonded Explosives
Authors: Barua Ananda , Zhou Min
Published: January 2011

A framework for quantifying the thermomechanical response of polymer bonded explosives (PBX) at the microstructural level is developed using a cohesive finite element method (CFEM). This framework allows the contributions of individual constituents, fracture and frictional contact along failed crack surfaces to heating to be analyzed and tracked. Digitized micrographs of actual PBX materials and idealized microstructures with various distributions of grain sizes are used in the analysis. The analysis concerns impact loading of HMX/Estane with strain rates on the order of 104 – 105 s-1. Issues studied include large deformation, thermomechanical coupling, failure in the forms of microcracks in both bulk constituents and along grain/matrix interfaces, and frictional heating. The Estane matrix is described by a thermo-elasto-viscoelastic constitutive formulation, accounting for temperature dependence, strain rate sensitivity and strain hardening. The HMX crystals are assumed to be elastic under the conditions analyzed. Energy localization leading to formation of local hot spots as potential ignition sites is primarily due to the viscoelastic dissipation in the matrix in early stages of deformation and frictional heating along crack surfaces in later stages of deformation. Microstructure-response relations that can be used in the design of soft energetic composites are established.
Comparative Study of Al/TiB2 Composites Manufactured by Underwater and Direct Shock Wave Consolidation
Authors: Eskandari H. , Ghasemi H.M. , Emamy M. , Hokamoto Kazuyuki
Published: January 2011

Aluminum matrix composites containing of 10, 20 and 30 vol% TiB2 particles were compacted by underwater and direct shock wave consolidation methods. SEM and Optical Microscopic examination, hardness and bending strength measurements were used to characterize the samples. It is observed that there were different distributions of TiB2 particles in recovered compacts by each method. In the direct method, the distribution of TiB2 particles at the center and at the periphery of the sample was different whereas in the underwater method there was a uniform microstructure in the sample. The microhardness of the compacts increased with increasing TiB2 particle volume fraction in both methods. The results showed highest bending strength for the composite containing 20 vol% TiB2 particles.
Trial Computation of Dynamic Axial Compression of Adhesive-Bonded Tubular Structure
Authors: Yamashita Minoru , Kien Nguyen Trung , Hattori Toshio
Published: January 2011

The dynamic axial compression of adhesive-bonded tubular structures with hat-shaped cross-section was numerically investigated using dynamic explicit finite element method. The numerically modeled Type I tubular structure consisted of a hat-shaped part and a flat plate. Type II consisted of two hat-shaped parts. The hat flange portion was assumed to be joined by adhesive bonding. The impact velocity of 10 m/s was given. Parametric computation was performed, where thicknesses of the plate and adhesive layer, and mechanical properties of the plate material were varied. As the result of computation, separation behavior of the hat flange portion was almost avoided for the case where the strength of plate material was lower. However, it was clearly observed for the higher strength material, though the plate was thin. The separation of the flange portion in Type I structure was more remarkable in comparison with that in Type II. The crush strength increased as the thickness of the adhesive layer thickened, when the plate thickness was thin and the strength was low. The Type II structure exhibited larger crush strength than that of Type I.
Improvement of Drop-Hammer Compression Test for Rubber Material
Authors: Yamashita Minoru , Sato Yasuhisa
Published: January 2011

The drop-hammer compression testing method where the stroke is calculated by solving the equation of motions of the drop-hammer and anvil was improved in order to determine the strain-rate dependence of the elastic modulus of rubber material. An additional tool for interrupting the compression was embedded in the apparatus. The tool was a thick washer which informed the time when the prescribed compressive strain was achieved by the sharp increase of compression force. The oscillatory stress-time curve obtained by the load cell was appropriately smoothed employing the method of moving average. The effect of the friction at the interface between the rubber specimen and the tools was properly eliminated by the extrapolating method using the specimens with several variations in heights. The stress-strain relationship was obtained under the dynamic condition. The numerical simulation of impact compression disclosed that the effect of inertia on the deformation pattern was practically small under the experimental condition adopted. Conducting the low-speed compression tests, the dependence in elastic modulus of rubber material on the strain-rate was appropriately determined.
Explosive Welding Using Underwater Shock Wave Generated by the Detonation of the Detonating Code
Authors: Mori Akihisa , Ruan Li Qun , Shiramoto Kazumasa , Fujita Masahiro
Published: January 2011

Detonating code is a flexible code with an explosive core. It is used to transmit the ignition of explosives with high detonation velocity in the range of 5.5 to 7 km/s. However, it is difficult to use detonating code for the explosive welding of common metals since the horizontal point velocity usually exceeds the sound velocity. Hence, in the present work, a new method using underwater shock wave generated by the detonation of detonating code was tried. The details of the experimental parameters and the results are presented. From the results it is observed that the above technique is suitable to weld thin metal plates with relatively less explosives.
Eccentric Spherical Forming of Metal Plate by Underwater Shock Loading
Authors: Iyama Hirofumi , Itoh Shigeru
Published: January 2011

Explosive forming is one of the effective metal forming methods using underwater shock wave generated by the detonation of an explosive. We have done the experiment of eccentric spherical free metal forming by this method. This free metal forming process does not use require expensive metal die. We used simple metal die with only circular edges and considered the metal plate formed to required shape using this method. It was possible to change the pressure distribution applied on the metal plate by changing the set-up position of explosive and the shape of the device. We have considered this method to cause lessen cost in the small production by various types of metal forming process. In this paper, we introduce the method of eccentric spherical free metal forming using underwater shock wave and present the experimental results.