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Spark plasma sintering (SPS) technique was used to consolidate spray dried (SD) powder of TiC (T-SD), TiC-3.5 wt% WC (TW-SD) and TiC-3.5 wt% WC-2 wt% CNT (TWC-SD) at 1600 °C and 50 MPa pressure. Another, similar composition of ball milled (BM) powder of TiC-3.5 wt% WC-2 wt% CNT (TWC-BM) was consolidated by SPS technique at similar parameters, in which in-situ formation of 2-D graphene nanoribbons (GNR) was observed. High temperature plastic deformation (HTPD) behaviours of these four pellets were characterized by in-situ high temperature nanoindentation technique from RT to 650 °C in controlled atmosphere. Occurrence of HTPD was confirmed by analyzing the mechanical properties, plasticity index and plastic deformation zone radius of all four pellets from RT to 650 °C. The structural stability of 1-D CNTs in TWC-SD and 2-D in-situ formed GNRs in TWC-BM pellets was examined by Raman spectra after the HTPD at 650 °C. HR-TEM micrograph has inferred the collapse of CNT edges in TWC-SD pellet and the peeling of GNR layers in TWC-BM pellet after HTPD. However, the CNTs in TWC-SD pellet was able to lower down the plastic deformation zone radius formed due to HTPD by ~60%, while it was only ~20% by in-situ formed GNR in TWC-BM pellet. This was majorly attributed to the difference in stress dissipation mechanisms between CNTs and GNRs. The 1-D CNTs in TWC-SD was found to have axial stress dissipation, while the in-situ formed GNRs in TWC-BM pellet has dissipated the stresses in axial as well as transverse directions because of its 2-D nature.

Expansive soils are those soils which pose a very serious problem when they are subjected to moisture variation. Phosphogypsum is one of the industrial waste by-products that can be utilized for the purpose of soil stabilization. In this study, the strength of lime stabilized soil added with phosphogypsum for immediate 7 and 14 days of curing periods is compared with the strength of phosphogypsum amended black cotton soil for immediate 7 and 14 days of curing. From unconfined compressive strength test, it was found that 6% of phosphogypsum is the optimum content, that imparts the maximum strength to the soil that when it is used alone. The combination of 3% of lime and 6% of phosphogypsum gives the maximum strength, and the strength obtained is relatively higher than the strength of the black cotton soil stabilized with phosphogypsum alone.

We employ in situ nanoindentation method to measure spontaneous strain during thermally induced structural phase transition in VO 2 crystals. Large tip displacement of ~ 520 nm is observed normal to (011) facet of VO 2 crystals during phase transition. The captured actuation signals in the form of tip displacement from VO 2 indicate 0.53% of spontaneous strain normal to (011) facet during phase transition. Spontaneous strain across phase transition is found to be reversible over thermal cycles with different heating rates. The investigated aspects demonstrate the application of nanoindentation in quantifying actuation of VO 2 micro crystals towards highly efficient thermal actuators.

We report the effect of magnetic field (H) on the insulator-metal (IM) transition in VO2 microcrystals. We observed that the temperature coefficient of resistance (TCR) in the monoclinic phase (T < 338 K) varies from negative to positive values on the application of external magnetic field, and follows ∼H2 behavior. The magneto-resistance (MR) of VO2 microcrystals also varies from small negative to positive value across the transition temperature. The presented aspects are relevant for understanding the influence of magnetic field on the electrical resistance of functional oxides across phase transition.

The research area “Cryogenic Treatment of Materials” has been the subject of a multitude of research studies and therefore needs a proper review article to highlight the present state of understanding and to define the future research direction. Though reviews on cryogenic processing of tool steels are available, there has not been a review that attempts to systematically discourse the effect of cryogenic treatment on the metallurgy of various ferrous alloys. While previous reviews address transformation of retained austenite and the formation of fine precipitated carbides as the major phenomena of cryogenic treatment, developments such as the refinement of pearlite matrix, formation of fine martensite, and enhancement of properties in low carbon steel and cast iron are discussed in detail in this article. In addition, the influence of individual treatment parameters, their sequence, and the effect of room temperature stabilization on the metallurgical changes are extensively addressed. Moreover, ...

Measuring the electrical and mechanical responses of coexisting phases at nanoscale provides a platform to engineer micro-/nanoscale pattern of metallic and insulating domains with control over properties to make novel devices. Here, we employ several in situ characterization techniques, namely Raman, optical imaging and electrical measurements, to identify the phase coexistence of metallic and insulating domains. Further, we performed site-specific in situ nanoindentation to address the spatial variation in nanomechanical properties in vanadium dioxide (VO2) single-crystal microbeams in proximity to metal–insulator transition temperature. We also investigated load or contact depth dependence on elastic modulus at various temperatures to avoid the interference of indentation size effect on nanomechanical properties across the phase transition. The obtained results confirm the abrupt increase in elastic modulus (~17 GPa) and nanohardness (1 GPa) across the transition from monoclinic (insulator) to rutile (metal) phase.

We report the chemical vapor deposition (CVD) based growth of aligned MoS2 two-dimensional (2D) nanostructures and their wetting and catalytic behaviors. Controlling the alignment of atomically thin MoS2 layers provides an excellent platform to tune the contact angle from ∼70° to ∼106°, leading to a transition from hydrophilic to hydrophobic surfaces. We also tested the catalytic performance of surface engineered MoS2 nanostructures and found that vertically aligned MoS2 with a hydrophobic surface shows a higher current density at lower potential for the hydrogen evolution reaction (HER). The observed unusual behavior of the hydrophobic surface showing better HER performance is further explained by the high electrochemical surface area of vertically aligned MoS2 nanostructures. Horizontal and vertical growth of MoS2 is achieved by tuning the supersaturation by varying the S : MoO3 ratio and the distance between them. Mechanistic understanding of MoS2 growth and alignment has been developed with the aid of detailed atomic force and electron microscopy observations. High resolution transmission electron microscopy (HRTEM) and Raman spectroscopy investigations of strained atomically thin layers in vertically aligned MoS2 revealed the role of strain variation in stabilizing the self-standing vertical alignment of 2D nanostructures. The presented results of tuning the wettability of semiconducting MoS2 by controlling the aligned growth of 2D materials and their electrochemical performance are relevant for smart surface, water splitting and energy storage applications.

We report the sulfur evaporation rate controlled screw dislocation driven growth of two-dimensional MoS2 that contains unprecedented atomic step density. Screw dislocation assisted growth of atomic thin MoS2 on amorphous SiO2 or a crystalline and conducting Si substrate paves the way to form spiral morphology of two-dimensional materials without the need for single crystalline miscut substrates to initiate the line defects. The unique spiral morphology promoted by screw dislocation is typically observed at a high nucleation rate induced by an abrupt increase in sulfur concentration. Screw dislocation assisted spiral MoS2 growth leads to a high step density with an ∼5 fold increase in the total edge length. Statistical analysis from detailed atomic force microscope phase imaging of flat and spiral MoS2 flakes reveals the linear increase in total edge length from ∼470 nm to ∼2325 nm with respect to variation in the number of steps available at the spiral structure in the range of 2–8. High resolution transm...

The marine environmental condition, especially NaCl, has been identified as one of the major sources of contamination on the performance of open cathode Proton Exchange Membrane Fuel Cells (PEMFC) system, when the power source is based on fuel cells for marine applications like submarines, navy ships etc., In the present paper, we have studied the performance of PEMFCs under the marine environment for a longer duration and also the recovery mechanism of the PEMFC power pack after contamination. It has been observed that the NaCl is a major contaminant for PEMFC, compared to NO x and SO x , which are major contaminants for fuel cells operating in the land regions. We have observed a performance loss of 60 % in PEMFC, when operated for 48 h, due to poisoning of PEMFC by NaCl vapours. The recovery of the stack is attempted by repeated water washing on the cathode side of the fuel cell, presuming that the salts get deposited only on the surface of the electrodes and the performance is easily recoverable. The recovery mechanisms are analysed by constant-current discharging operation and by modified experimental methods and are reported here. The performance vagaries in fuel cells due to sea water contamination is also analysed by linear fit and it is found that the rate of power increment after water wash is higher than the rate of power increment, around 11.5 W/10 h compared to normal environmental conditions, which is 4.1 W/10 h.

It is well-known that carbon nanotubes (CNTs) can be grown directly on the surface of stainless steel (SS) alloys, because the native composition of SS contains elements that seed CNT growth upon hydrocarbon exposure at elevated temperature. Often such methods use acid immersion or oxidation in air to treat the surface prior to hydrocarbon exposure for CNT growth. However, there lacks a general understanding of how the surface chemistry and morphology influences the nucleation and growth of CNTs. Using environmental transmission electron microscopy, we observe that CNT growth is enabled by surface reconstruction of SS upon oxygen exposure at elevated temperature, followed by further breakup of the surface upon reduction, and subsequent CNT nucleation and growth upon hydrocarbon exposure. Using electron energy loss spectroscopy, we find that catalyst particles consist of both pure iron as well as iron alloys such as Fe–Cr and Fe–Ni. We use these insights to study the synthesis of CNTs on bulk net-shaped po...

As technology progresses, understanding online learner's behavior is the key for successful implementation of digital learning. The more we know about learners, the more tailored learning experiences will be. Analyzing the learner's preferences will help to predict the behavior of learner's so that required support and guidance can be provided on time. For achieving this much more efficient systems are required to process all types of the learner interactions with the learning management system during their each learning activity. This paper discusses the importance of learning analytics, and presents its usage in eLearning. It describes how learning analytics can help the learners, instructors and institutions to look into ongoing learning processes and how the online educational processes can be improved. It also depicts about the proposed system how the learning styles can be used for improving learning experience.

The constantly increasing urbanization of the metropolises requires more and more realization of a fast and efficient transportation network. Underground transport lines often constitute an ideal solution in term of efficiency and low nuisance for the environment. The technical advancements brought to the underground excavation methods allow the achievement of projects in difficult environmental conditions, especially in urban areas. Providing space for parking, public amenities, etc in multi-storey buildings at town centers has created a need to go deep excavations into ground. The construction of deep excavations in the urban environment is a technically challenging problem. Underground construction may be in the vicinity of already existing tunnels. Deep excavations may have impact on the adjacent tunnels. Such excavation will impose significant influence on the tunnel linings, including changes of stress and deformation. Such effects are observed due to the “space effect” of excavation. The study involves the analysis of influence of deep excavation on the existing tunnel, structural impact on the tunnel lining and measures for controlling the soil and tunnel deformation using finite element software Plaxis (2D). In this study the influence of deep excavation on the existing tunnel with varying position is analyzed. Analysis is carried out by considering tunnel just below the excavation and just beside the excavation. Effect of excavation on tunnel lining and displacement of tunnel due to excavation is observed. Also Analysis involves soil improvement technique to reduce impacts of excavation on tunnel. Grouting method is adopted for the analysis and its role in controlling the effects on tunnel is analyzed.

Cr(VI) adsorption experiments were carried out using activated carbon obtained from a waste weed Salvinia cucullata. The adsorbent was characterized using SEM, BET, EDAX, FT-IR, etc. Matrix method was used to develop an empirical mathematical model. Factorial design of experiments was used to minimize the number of experiments required to develop an empirical model. In the mathematical model, percentage adsorption of Cr(VI) was represented as a function of process variables like contact time, initial pH of the solution, and temperature. pH had the most influential effect on the adsorption process followed by contact time and temperature. The significance of different adsorption parameters and their combined effect on the adsorption process was established. The empirical model was simulated and solved using MATLAB and LabVIEW. The goodness of fit of the developed mathematical models to the experimental values was examined using different error analysis methods such as SSE, SAE, ARE, and ARS.

The hydrothermal reaction of a mixture of a colloidal dispersion of graphite oxide and ammonium vanadate yielded a hybrid made of graphene and a nanotubular metastable monoclinic polymorph of VO2, known as VO2(B). The formation of VO2(B) nanotubes is accompanied by the reduction of graphite oxide. Initially the partially scrolled graphite oxide layers act as templates for the crystallization of VO2(B) in the tubular morphology. This is followed by the reduction of graphite oxide to graphene resulting in a hybrid in which VO2(B) nanotubes are dispersed in graphene. Electron microscopic studies of the hybrid reveal that the VO2(B) nanotubes are wrapped by and trapped between graphene sheets. The hybrid shows potential to be a high capacity cathode material for lithium ion batteries. It exhibits a high capacity (similar to 450 mAh/g) and cycling stability. The high capacity of the hybrid is attributed to the interaction between the graphene sheets and the VO2(B) tubes which improves the charge-transfer. The graphene matrix prevents the aggregation of the VO2(B) nanotubes leading to high cycling stability. (C) 2012 Elsevier Ltd. All rights reserved.

We investigate structure and stress relaxation in situ across the metal–insulator transition in SmNiO3 thin films. An epitaxial thin film of SmNiO3 grown on LaAlO3 single crystal shows a metal–insulator transition at 155 °C based on electrical measurements. In situ electron diffraction experiments do not show any noticeable change with temperature. SmNiO3 thin films grown on silicon show a smoothly varying compressive stress across the transition boundary. The experimental observation of a metal–insulator transition without sharp stress changes is an encouraging preliminary result towards switching device applications.

Thermal barrier coating of mullite was plasma sprayed on cast aluminum A 356.0, in the T6 condition (solution treated, quenched and artificially aged) for use in internal combustion engine applications. This study pertains to the mechanical, thermal, wear, corrosion and micro structural characterization of the coating. An average coating tensile strength of 50 MPa and average adhesive bond strength of 20 MPa was measured in the mechanical tests. A wear factor of 0.7 × 10−3 mg/Nm was measured in the wear studies using a pin on disk apparatus. An average value of 0.151 W/m K was measured in the thermal conductivity test. The coating withstood 100 cycles in the thermal shock test, without any sign of spallation. Corrosion tests showed no signs of corrosion even after 500 h. The microstructural and porosity studies were conducted using an optical microscope and scanning electron microscope with an energy dispersive spectroscopy (EDS) attachment. The studies revealed a crystalline microstructure of the substrate, which correspond to the splat structure of the coating. The porosity of the coated layers ranged from 6 to 21% by volume, at an average of 12-16%. EDS studies showed the elements present in the coating. X-ray diffraction patterns taken on coated specimens, showed the phases present in the coating, and indicated a crystalline structure of the coating along with some amorphous matter.

Microstructure evolution along with crystallographic orientation change as a function of film thickness was investigated in Ni thin films grown on (100) yttria-stabilized zirconia (YSZ) single crystal substrates. Texture development with two different orientation relationships, OR1: Ni {111}//YSZ {100} and OR2: Ni {100}//YSZ {100}, cube on cube orientation were identified by X-ray diffraction and transmission electron microscopy depending on the film thickness. The observed orientation transition reveals the existence of a critical thickness (∼320 nm) favoring two different orientations in sputtered Ni films on YSZ (100) substrate.

Reversible stress switching across the thermally triggered phase transition in vanadium dioxide thin films grown on silicon has been investigated using in situ wafer curvature measurements. Stability of the recoverable stress, hysteresis width and the transition temperature over 100 cycles are studied. Fine control over the recoverable stress has been demonstrated by thermal arrest across the phase boundary, exploiting the incomplete martensitic transition. Stability of the fractional stress changes across the martensitic transition is reported at various temperatures.

We present a simple template-free method for the synthesis of interconnected hierarchical porous palladium nanostructures by controlling the aggregation of nanoparticles in organic media. The interaction between the nanoparticles is tuned by varying the dielectric constant of the medium consistent with DLVO calculations. The reaction products range from discrete nanoparticles to compact porous clusters with large specific surface areas. The nanoclusters exhibit hierarchical porosity and are found to exhibit excellent activity towards the reduction of 4-nitrophenol into 4-aminophenol and hydrogen oxidation. The method opens up possibilities for synthesizing porous clusters of other functional inorganics in organic media.

p-Aminobenzoate ion intercalated alpha-hydroxides of nickel/cobalt were synthesized by precipitation using ammonia (pH = similar to 12). Aqueous colloidal suspension of alpha-hydroxide of nickel/cobalt was obtained on washing the precipitate as the pH was reduced to similar to 7. The development of partial positive charge on the amine end of the intercalated anion causes repulsion between the layers leading to exfoliation and colloidal suspension of monolayers in water. While theb layers could be restacked from the colloidal suspension in the presenceof other anions in the case of alpha-cobalt hydroxide, the exfoliation could not be reversed easily in the case of the nickel analog. (C) 2010 Elsevier Inc. All rights reserved.

The control of shapes of nanocrystals is crucial for using them as building blocks for various applications. In this paper, we present a critical overview of the issues involved in shape-controlled...

Layers from delaminated colloidal dispersions of two structurally different layered solids-octylamine-intercalated graphite oxide and cetyltrimethylammonium-intercalated smectite – could be costacked to obtain smectite clay/graphite oxide composites. The layers of the two parent solids were randomly stacked together in these composites. On thermal decomposition the graphite oxide sheets in the composites are reduced to graphene sheets resulting in clay/graphene composites. The composition is not uniform in these composites, which have many smectite-rich and carbon-rich regions. The clay component of the clay/graphene composites could be leached out to obtain exfoliated graphite.

The catalysts, Ti0.9M0.1O2-δ (M = Cr, Mn, Fe, Co, Cu), were synthesized in anatase phase by solution combustion. Selective catalytic reduction (SCR) of NO with NH3 was investigated over these catalysts. The reaction occurred at the lowest temperature over Ti0.9Mn0.1O2-δ, but the selectivity for N2 was highest over Ti0.9Fe0.1O2-δ. Therefore, both Mn and Fe were substituted in TiO2 (Ti0.9Mn0.05Fe0.05O2-δ). The reaction occurred at low temperature with a high selectivity over this catalyst. In order to understand the reaction mechanism and the nature of the active sites, temperature programmed desorption (TPD) of NH3 and hydrogen uptake studies were carried out. The relation between the Lewis acid sites and SCR window and the relation between Bronsted acid sites and low temperature was established. The order of the SCR reaction with respect to NO, NH3, and O2 was also investigated. It was also shown that the N2 selectivity of the SCR reaction has a strong inverse correlation with the oxidation of ammonia.

Organic versus Inorganic Manures in Land Improvement and Crop Production

We present the design of a concentric tube (CT) reactor for roll-to-roll chemical vapor deposition (CVD) on flexible substrates, and its application to continuous production of graphene on copper foil. In the CTCVD reactor, the thin foil substrate is helically wrapped around the inner tube, and translates through the gap between the concentric tubes. We use a bench-scale prototype machine to synthesize graphene on copper substrates at translation speeds varying from 25 mm/min to 500 mm/min, and investigate the influence of process parameters on the uniformity and coverage of graphene on a continuously moving foil. At lower speeds, high-quality monolayer graphene is formed; at higher speeds, rapid nucleation of small graphene domains is observed, yet coalescence is prevented by the limited residence time in the CTCVD system. We show that a smooth isothermal transition between the reducing and carbon-containing atmospheres, enabled by injection of the carbon feedstock via radial holes in the inner tube, is essential to high-quality roll-to-roll graphene CVD. We discuss how the foil quality and microstructure limit the uniformity of graphene over macroscopic dimensions. We conclude by discussing means of scaling and reconfiguring the CTCVD design based on general requirements for 2-D materials manufacturing., National Science Foundation (U.S.). Science, Engineering, and Education for Sustainability (Postdoctoral Fellowship Award 1415129)

The integrity of composites is determined by the interfacial reactions that take place during processing. The interfacial reaction between hydroxyapatite and alumina has been studied. It was found that alumina completely reacted with hydroxyapatite and formed alumina-rich calcium aluminates at relatively low temperatures. This has been attributed to the diffusion of Ca2+ from hydroxyapatite into the alumina matrix. The depletion of Ca2+ from hydroxyapatite leads to the decomposition of hydroxyapatite in to tricalcium phosphate at lower temperatures.

Singapore has been using dual membrane technology (MF/UF RO) to produce high-grade water (NEWater) from secondary treated sewage. Membrane bioreactor (MBR) has very high potential and will lead to the further improvement of the productivity and quality of high-grade water. This study was focused on the technical feasibility of MBR system for water reclamation in Singapore, making a comparison between various membrane systems available and to get operational experience in terms of membrane cleaning and other issues. Three MBR plants were built at Bedok Water Reclamation Plant with a design flow of 300 m3/day each. They were commissioned in March 2003. Three different types of submerged membranes were tested. They are Membrane A, plate sheet membrane with pore size of 0.4 μm; Membrane B, hollow fibre membrane with pore size of 0.4 μm; and Membrane C, hollow fibre membrane with pore size of 0.035 μm. The permeate quality of all the three MBR Systems were found equivalent to or better than that of the conventional tertiary treatment by ultrafiltration. MBR permeate TOC was about 2 mg/l lower than UF permeate TOC. GC-MS, GC-ECD and HPLC scan results show that trace organic contaminants in MBR permeate and UF permeate were in the same range. MBR power consumption can be less than 1 kwh/m3. Gel layer or dynamic membrane generated on the submerged membrane surface played an important role for the lower MBR permeate TOC than the supernatant TOC in the membrane tank. Intensive chemical cleaning can temporarily remove this layer. During normal operation conditions, the formation of dynamic membrane may need one day to obtain the steady low TOC levels in MBR permeate.

This work looks at the dynamic behavior of laminated carbon-epoxy (C-E) composites with inserted interleaf polytetrafluoroethylene (PTFE)-coated material. Instrumented impact tests performed on the interleaved test samples showed significant differences in the energy absorption characteristics that could be correlated with the failure mode. It was inferred that with the introduction of small amounts of less adherent layers of material at specific locations, the load-carrying ability decreased while the energy-absorbing capability was found to improve considerably. These and other experimental observations are discussed in this article.

We demonstrate direct production of graphene on SiO2 by CVD growth of graphene at the interface between a Ni film and the SiO2 substrate, followed by dry mechanical delamination of the Ni using adhesive tape. This result is enabled by understanding of the competition between stress evolution and microstructure development upon annealing of the Ni prior to the graphene growth step. When the Ni film remains adherent after graphene growth, the balance between residual stress and adhesion governs the ability to mechanically remove the Ni after the CVD process. In this study the graphene on SiO2 comprises micron-scale domains, ranging from monolayer to multilayer. The graphene has >90% coverage across centimeter-scale dimensions, limited by the size of our CVD chamber. Further engineering of the Ni film microstructure and stress state could enable manufacturing of highly uniform interfacial graphene followed by clean mechanical delamination over practically indefinite dimensions. Moreover, our findings suggest that preferential adhesion can enable production of 2-D materials directly on application-relevant substrates. This is attractive compared to transfer methods, which can cause mechanical damage and leave residues behind.

This work looks at the compression behavior of laminated carbon–epoxy (C–E) composites with inserted interleaved polytetrafluoroethylene-coated fabric material at different locations either continuously or discontinuously within the specimen. Also, the effect of water ingress in these specimens on the strength values is reported. Although significant differences were noticed in the trend of the strengths for different architectural arrangements in dry and water-immersed samples, significant differences for the modulus was less perceptible. The introduction of small amounts of less-adherent layers of material at specific locations causes a decrement in the load-carrying capability of the C–E system. It is further observed that with an increase in the number of buffer/delaminating strips insertions, the water ingress increases and the compressive strength values decrease. Examination of the samples, noting macroscopic features including the interfacial regions, assisted in observing a correlation between the observed strength values, architecture, and the failure mode. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 408–416, 2002

Instrumented impact testing has been used to evaluate the influence of moisture on the impact resistance of Carbon-Epoxy (C-E) system with buffer strips (BS) incorporated into the laminated composite. Impact tests were done with BS bearing strips posited within the lay-up right below the loading point in one case and away from it in the other. The extent of water ingress was found to increase with increase in the number of BS insertions. While the energy absorption values in plain samples subjected to impact after immersion in water were higher than the corresponding tests on dry samples that for the BS bearing gave varied results depending on the number of BS and their location vis-à-vis the loading point during impact event. The maximum load recorded by various samples, on the other hand, show a general decrease for the water ingressed test coupons. As regards the ductility index values for different set of samples, generally stating, the water immersed BS bearing samples tended to yield lower values.

The work looks at the dynamic behaviour of laminated carbon-epoxy (C-E) composites with inserted interleaf material. Instrumented impact tests were performed to study the impact response of C-E system containing the interleaved PTFE-coated fabric material. Significant differences were noticed in the trend of the load-time plots. It was inferred that the introduction of small amounts of less adherent layers of material at specific locations causes a decrement in the load carrying capability of this material. An attempt to correlate these trends with the post impact observed failure features has been made in this work.

The ability to predict the morphology of crystals formed by chemical reactions is of fundamental importance for the shape-controlled synthesis of nanostructures. Based on the atomistic mechanism for crystal growth under different driving forces, we have developed morphology diagrams to predict regimes for the growth of two-dimensional crystals. By using controlled reactions for crystal growth in the absence of surfactants/capping agents, we demonstrate the validity of this approach for the formation of 2-D structures of Au, Ag, Pt, Pd and hydroxyapatite., Comment: 31 pages, 10 figures