Band 58, Heft 1

Cellulose nanocrystals (CNC) are a class of nanoscale biopolymers produced from cellulose sources. CNC materials have gained growing interests which can be attributed to their excellent properties such as excellent biocompatibility, good mechanical properties and high aspect ratio whilst also being an inexpensive material that can be produced from green and renewable sources. Due to the abundant hydroxyl functional groups, the surface of CNC materials are ready to be tuned and functionalized via chemical reactions allowing for many different applications, such as being a reinforcing agent to be incorporated into a hydrophobic polymer matrix. In this review paper,we firstly introduce the general methods for producing CNC from different sources. Different strategies used for surface modification ofCNCare then discussed. Finally, the recent progress on the applications of CNC and CNC composite materials are described in detail.

With the rapid development of nanotechnology during the past several years, attention has been focused on metallic nanomaterials, due to their specific physical and chemical characteristics. Zinc oxide nanoparticles (ZnO NPs) have numerous potential applications in industry, as a part of various consumer products, but also in medical research. Anticancer properties of ZnO NPs have been suggested in cell cultures, however, the precise mechanism responsible for their activity in these conditions remains elusive. Cytotoxicity and genotoxicity of ZnO NPs are also unclear. Apart from cancer research, ZnO NPs are today widely researched in almost all areas of fundamental medicine. In this short review, we discuss recently published articles on ZnO NPs applications in cellular physiology, pathology, neurosciences and oncology.

Here we analyze the microstructure and phase composition of a Ti alloy with 0.16Pd and 0.14Fe (wt%) alloy exposed to warm equal channel angular pressing (ECAP) at 648 K. The analysis shows that after four ECAP passes, the material assumes a submicrocrystalline structure with an average grain size of 0.28 μm, as against its initial value 10 μm, and that the α phase dominates in the alloy both before and after ECAP. The initial alloy reveals a high content of Fe and Pd atoms near grain boundaries compared to central grain regions. Such near-boundary zones contain orthorhombic α ′′ martensite in addition to the α phase, and β or α + β particles are found directly at the grain boundaries. These features of the phase composition are inherited after ECAP. The yield strength of the ECAP treated alloy is 500 MPa, being greater than the initial strength 350 MPa, and its margin of plasticity is rather high. The torsional strain up to fracture in the initial and in the ECAP treated alloy is 70% and 50%, respectively.

The change in demoulding strength of colloidal silica-bonded castables with and without magnesia is investigated with emphasis on the relationship between the demoulding strength and chemical bond changes. It was confirmed that the demoulding strength was raised with the presence of magnesia in colloidal silica-bonded castables because of the increased chemical bonding between the sol particles. The X-ray photoelectron spectroscopy (XPS) and the Fourier transformation infrared spectroscopy (FTIR) results indicate the formation of new Si–O–Mg chemical bond from the decreased O 1 s and Si 2 p binding energy, and the appearance of weak vibration peaks at 668 and 419 cm−1 in the spectrum of colloidal silica with the addition of MgO after curing at 30°C for 24 hours. The reaction between colloidal silica and magnesia could promote the formation of –Si–O–Mg–O–Si–bonds, which is the primary reason for the demoulding strength improvement.

Dissimilar welding offers exiting benefits for a wide range of engineering applications, such as automotive bodies, piping systems of nuclear power plants, health equipment. The main advantages of dissimilarwelding applications areweight reductions, lower costs, unique properties combinations, and improved energy-efficiency. The properties of dissimilar weld depend on the type of welding process used, the accuracy of the process parameters control, the characteristics of the base metal and the heat treatment procedures. The current study reviews the scientific literature on the topic of thermal analysis of dissimilar high-strength steels (HSS) welding. The review of experimental data was carried out to analyze the variable heat input effect on dissimilar welds. The results indicate the welds mechanical properties irregularity and reduction in toughness and tensile strength due to uneven changes in the microstructure. Furthermore, postweld heat treatment (PWHT) often resulted in the formation of intermetallic compounds whose properties are dependent on the duration of treatment. The research results can be used to optimize the heat input of the HSS welding process.

The demand for metallic materials of exceptional tribological performance is rapidly growing due to constant development of automotive, tool or implant industry. As great attention nowadays is being paid to the surfacemodified materials, there is a need of establishing reliable methods for evaluation of coated metallic alloys. In this paper, methods for thickness, adhesion and mechanical properties measurement of anti-wear coatings are considered. The importance of altering the mechanical properties of the coating with regards to its expected wear performance is also discussed. According to the numerous findings, it is reasonable to pay attention to the hardness and Young’s modulus of the developed coating, as well as on the mismatch between its Young’s modulus and the elastic modulus of the substrate material. Information provided in this paper has been thoroughly illustrated and enriched with our own experience in the field.

This paper describes a study of the effect of partial replacement of ordinary Portland cement (OPC) by various mineral additives in the screed mixtures. Ceramic powder, blast furnace slag and fly ash were gradually employed in increments of 12.5 wt.% up to 50 wt.% to replace OPC. The mixtures were designed to a constant consistency. The influence of mineral additives was evaluated in terms of the air content in the fresh mixtures, the compressive strength, the flexural strength and the freeze-thaw resistance and using non-destructive measurements after 28 and 90 days. The accompanied paste sampleswere analysed using thermogravimetry to monitor the hydration process by means of total bound water content. The decrease in the mechanical properties and the frost resistance of the mixtures with the mineral additives were recorded, because of the necessity for a larger addition of water. According to the valid standards for concrete screed related to the frost resistance, it could be concluded that maximal suitable cement replacement contents are 12.5, 37.5 and 50 wt.% for ceramic powder, fly ash and blast furnace slag, respectively. The freeze-thaw resistance of the studied materials was found to be strongly related to the content of CSH and CAH hydrates.

In this paper, structural and mechanical properties of APS - atmospheric plasma spray coating Al-12Si are presented. The aim of the research was the optimisation of the flow of powder to produce layers with optimal mechanical and structural properties that will be applied to the worn out parts of airplanes. Three groups of samples were produced, by utilising three powder feed rates: 30 g/min, 45 g/min and 60 g/min. Evaluation of layers’ microhardness was done using HV 0.3 method and the bond strengthwas determined by testing of tensile strength. Surface morphology of the deposited powder particles was examined on SEM (Scanning Electron Microscope). The microstructure of the coating with the best measured mechanical properties was subsequently examined in etched condition on optical microscope and SEM (in accordance with the standard PN 585005, Pratt & Whitney). Also, fracture morphology of this coating in deposited state was examined using SEM. It was found that powder feed control with atmospheric plasma spraying can produce dense layers of Al-12Si coating with good bond strength.

The drug delivery system (DDS) is a hot spot in the field of medicine due to their favorable characteristics, such as the realizability of targeted therapy, sustained and controlled release of drug. Ceramic materials have abundant desirable properties, such as simple preparation, adjustable size and structure, surface area to volume ratio, desirable stability under physiological conditions and excellent biocompatibility, etc. Hence they have been successfully applied in the field of DDS considerably in decades, acting as drug carriers. Traditional ceramic materials refer to inorganic solid compound. They are mainly composed of carbides, oxides such as hydroxyapatite, tricalcium phosphate, silica, zeolite, and zirconia, etc. This review summarized the applications of the ceramic materials in the field of DDS in recent years, meanwhile the outlooks of future development were also proposed.

This review focuses on grain growth behaviors and the underlying mechanisms of bulk electrodeposited nanocrystalline nickel and nickel-iron alloys. Effects of some important factors on grain growth are described. During thermal-induced grain growth process, grain boundary migration plays a key role. For similar thermal conditions, due to grain boundary mobility with solute drag, limited grain growth occurs in nanocrystalline alloys, as compared to pure metals. Nonetheless, in the case of stress-induced grain growth process, there are a variety of mechanisms in samples having various deformation histories. As an example the grain growth of nanocrystalline nickel and Ni-20%Fe alloy with nearly the same grain-size distribution and average grain size is compared in this paper. Thermal analysis indicates nanocrystalline nickel is much more prone to rapid grain growth than nanocrystalline Ni-20%Fe alloy. Nevertheless, grain growth of nanocrystalline Ni-20%Fe is found to be more pronounced than nanocrystalline nickel during rolling deformation.

TiO 2 is the most promising oxide semiconductor extensively used as photocatalyst in solar energy conversion into hydrogen and electric energy as well as in degradation of contaminants in water. To increase its efficiency, carbon dopants are applied. A series of TiO 2 /graphitic carbon nanocomposites with enhanced photocatalytic performance was synthesized at different temperatures in the 300 – 850°C range in the presence of benzene vapours. To investigate the magnetic properties of these nanocomposites, the dc magnetic susceptibility and electron paramagnetic resonance (EPR) measurementswere carried out. Magnetometry revealed the presence of three very different components: a temperature independent and easily recognized in the high-temperature range, another one in 20 – 100 K range displaying a slow increase with temperature decrease and saturation at low temperatures, and the third one observed at T < 20 K showing a sharp increase with decreasing temperature. Five types of EPR spectra were detected in the investigated samples and attributed to various paramagnetic centres. The role of TiO 2 phase composition, nanocrystalline sizes, carbon content in its different forms in establishing static and dynamic magnetic response of our samples will be discussed.

2 mm-thick LA141 plates were successfully friction stir lap welded (FSLW). The similar FSLWLA141Mg-Li alloy joint appeared a downward hook on the advanced side and an upward cold lap on the retreating side. The load of lap-shear tensile testing reached 2.8 kN, and the joints failed in the interface defects. The interface migration of LA141/LA141 lap joint during FSLW process was driven by forces at interface, such as a frictional force paralleled to the thread, a downward pressure perpendicular to the surface of the thread, the resistance from unsoftened metal and its own gravity. Moreover, the FSLWof AZ31/LA141 and LA141/AZ31 furtherly verified that forces at the interface were critical factors in determining the interface migration during FSLW process.

Titanium (Ti) and its alloys have been extensively applied in various fields of chemical industry, marine, aerospace and biomedical devices because of a specific combination of properties such as high strength to weight ratio, exceptional corrosion resistance and excellent biocompatibility. However, friction and wear, corrosion which usually occur on the surfaces of Ti-base components can lead to degradation in both properties and performance. Thermal oxidation (TO) of titanium and its alloys under certain conditions can accomplish significant improvements both in wear resistance and corrosion resistance, without special requirements for substrate geometries. In this review, the studies and applications of TO process in surface damage mitigation titanium and its alloys were reviewed and summarized.

A review on the characterization of mechanical, metallurgical, porosity, tribological and corrosion properties of spray deposited Al-alloys are presented in this paper. Al-alloys are potentially used in various applications specifically in bearing materials, aerospace due to low weight to high strength, proper lubrication, excellent wear and corrosion resistance. Al alloys being processed through spray forming technology, which possesses lower processing steps than the other conventional methods like ingot and powder metallurgy. Characterization of Al alloys spray deposits is carried out before and after mechanical processes to know their behaviour. Reviewed the characterization deportment of Al-alloys before and after spray deposition, effect of mechanical process like cold rolling, extrusion, aging, hot rolling, hot extrusion etc. and porosity on the metallurgical, hardness, tensile strength, elongation, tribological and corrosion properties.

Stroke is an acute cerebrovascular disorder caused by sudden decrease or interruption of blood flow in brain arteries. Deficiency of timely and effective reperfusion of ischemic brain tissue can lead to irreversible brain injury and neurological dysfunction. Currently, recombinant tissue plasminogen activator (rt-PA) is the only appropriate thrombolytic agent which is approved by FDA for patients with acute ischemic stoke. However, due to the limitation of very narrow therapeutic time window and severe intracranial hemorrhagic complication, the outcome of stroke treatment mediated by rt-PA still remains unsatisfactory. Therefore, it is urgent to find new alternative drugs or develop novel drug delivery system to achieve better outcomes. In recent years, with the rapid development of nanotechonology, nanomaterials as a drug delivery system can provide new strategies and methods to carry t-PA specifically to the occlusion site and provide advanced treatment for stroke. In this review, we briefly introduced the physiopathologic mechanisms of thrombolysis and focused on the comparison of the t-PA mediated thrombolysis and t-PA conjugated nanomaterial mediated thrombolysis.

The manganese-doped polymorphs of bismuth orthoniobate were studied using thermal analysis, ESR, XPS and NEXAFS spectroscopy. It was shown that the phase transition from the orthorhombic ( α ) to the triclinic ( β ) modification can be reversible and it can be achieved by prolonged calcination of samples at 750°C. The DSC curves revealed no thermal effects associated with the phase transformation from the triclinic to the orthorhombic modification near 750°C. In the ESR spectra, the absorption band with g = 3.8 characterized by sextet structure disappeared during the phase transformation from the - to the -form and only the broad component with average intensity was observed at g = 2.2-2.0. According to NEXAFS spectroscopy data, the content of oxidized Mn(III) atoms increased and the content of Mn(II) decreased in the orthorhombic polymorph obtained at 750°C from the tri-clinic modification.

The effect of two different milling devices, namely attrition mill versus vibration mill, on the reactivity of fly ash was studied. High calcium fly ash from 4 th Thermal power station of Ulaanbaatar (Mongolia) was used for the experiments. The raw and processed samples were characterized by XRD, SEM, Particle size distribution, BET, Blaine surface area and density measurements. The efficiency of 1 hour milling was evaluated with the Blaine surface area set to be more than 5000 cm 2 /g. The physical and chemical properties of the attrition milled fly ash changed not much compared to the vibration milled samples. For example the d 50 particle size became reduced from 29 µm to 6 µm by attrition milling and in vibration milled fly ash it was reduced to 7 µm. The density increased from 2.44 g/cm 3 of raw fly ash to 2.84 g/cm 3 and 2.79 g/cm 3 in attrition and vibration milled samples, respectively. Mechanical milling revealed not only a particle size reduction but also the formation of a denser microstructure. As a result the vibration milled fly ash showed a weaker interaction with the alkaline solution (8 M NaOH used here) compared to the attrition milled fly ash. Consequently, compressive strength of the binder prepared using the attrition milled fly ash was higher, 61 MPa, while for vibration milled fly ash it was 49 MPa. For comparison unmilled fly ash, it was 21 MPa.

BACKGROUND : Zirconia is a commonly used ceramic for fixed full-ceramic restorations. Porcelain-fused-to-metal restorations applied for bruxers are often very quickly destroyed by this group of patients. OBJECTIVE : The aim of this study was to investigate the influence of accelerated aging tests on BruxZir HT 2.0 zirconia. METHODS : Zirconia samples were prepared with ISO 13356:2013 and ISO 14704:2008 protocol recommendations. The ageing conditions were times of 2.5, 5 and 10 hours, and pressure of 0.2 MPa and a temperature of 134°C. RESULTS : The correlation between ageing time and mechanical properties, particularly hardness, was difficult to find, while correlations between hardness and the surface topography and fracturing were clear. CONCLUSION : On the basis of the conducted research, it can be stated that BruxZir HT 2.0 zirconia meets the technical requirements for medical grade zirconia used in dental technology. Future investigations should include phase composition research.

This study aims to determine the characteristics of oil palm boiler ash (OPBA) after processing with ball mill and coprecipitation methods. The method used is OPBA from a palm oil mill, processed using a ball mill for 1 hour at a speed of 250 rpm. Then prepared with the coprecipitation method by dissolving it in 2M HCl solution and NaOH solution with variations (2; 2.5; 3) M. Particles were characterized by XRD, SEM, XRF, and FTIR. XRD characterization shows the size of each crystal (83,79; 72,30 and 56,31) nm, with trigonal crystal structure with the SiO 2 phase. SEM shows a homogeneous mixture. EDX shows the biggest elements are Si, O and C content. XRF shows the amount of silica is 31.45%. FTIR shows absorption peaks which are the characters of molecular vibrations of the sample.

Copper is an essential trace element and is an integral part of many metabolic and other chemical processes in cells and tissues. Copper-based nanoparticles (CuNPs) have wide industrial and engineering applications, as catalysts, sensing materials, part of superconductors, storage systems, and phototermal / thermoelectric materials. In recent years, their potential use in biology and medicine has also contributed to the increased interest by scientific community. Unfortunately, many aspects of CuNP interactions with cells and tissues remain unknown. It is unclear if, in a living organism, CuNPs behave the same way as conventional metallic copper. Possible impact of CuNPs on the functioning of organs such as liver, kidney and brain is of particular concern. This concise review aims to cover recent research on potential CuNP toxicity, with the emphasis on neurotoxocity, nephrotoxicity and hepatotoxicity. Also, potential implications of CuNPs toxicity in fundamental and clinical medicine are discussed.

The microstructural characterizations and partitioning of carbon element in the weld heat affected zones of a commercial API 5L X60 line pipe steel were studied by applying a high speed heating and cooling dilatometry technique in the present research work. The hollow cylindrical specimens were quickly heated to 1000°C, soaked for only 5 s followed by continuous cooling to ambient temperature. Besides the construction of CCT diagram of this high strength low alloy steel using the dilatation data, the hardening response, microstructural features and carbon partitioning of weld simulated specimens were investigated. The obtained results showed that the hardening response of samples increased from 142 to 261 HV 10 kg with increasing cooling rates. These hardening variations were attributed to the changes in microstructural features and carbon partitioning that occurred between the microconstituents present in the microstructures of weld simulated samples.

Purpose: This part of the study focuses on the influence of zirconia heat treatment for surface morphology, phase composition and mechanical properties Methods: Zirconia samples was prepared with ISO 13356:2013 and ISO 14704:2008 recommendations. X-ray diffraction, observations (SEM) and (AFM), microhardness ( Olivera & Phara method ), and static bending test (4PBT) were taken. Results: characterization of YSZ and high temperature heat treatment has clearly shown that the aging process influences the change in phase composition of the material, significantly worsening the topography. In turn, re-treatment of the high temperature made after the artificial aging process results in reverse transformation of the desired tetragonal phase, but does not affect the improvement of surface morphology. Conclusions: The research made it possible to assess the negative impact of the zirconium oxide aging simulation process. Because of the failure to achieve the intended results, it was also proved that the high-temperature re-processing was not appropriate.

Solar steam generation with low-cost and excellent energy efficiency is of great significance for alleviating an energy crisis, reducing water pollution and promoting seawater desalination. However, there are still numerous challenges for solar steam generation system to practical energy utilization. In this review, based on our previous research, we summarize various methods of solar steam generation, photothermal conversion mechanism and efficiency. We studied a series of effecting factors for solar steam generation. Our systematic investigation provided a clearer understanding of how to design and optimize the photothermal conversion system to improve the steam generation rate and energy conversion rate, including improving light absorption, reducing heat loss, and optimizing water supply. This article aims to make a comprehensive review of present solar steam technology, so that people can better apply photothermal conversion technology. Meanwhile, it also provides a route for the selection of photothermal materials, the design and optimization of the photothermal conversion system.

Use of solid state ionic conductors the so-called Solid Electrolytes has brought new impetus to the field of solid state memories namely resistive random access memory (Re-RAM). In this review article, to begin we present the detailed understanding on the basics of solid electrolytes. Later, the same has been reviewed focusing on its application in novel solid state memory applications. Few examples of solid electrolytes are considered and their impact on the state-of-art research in this domain is discussed in detail. An in-depth analysis on the fundamentals of Resistive switching mechanism involved in various classes of Memristive devices viz., Electrochemical Metallization Memories (ECM) and Valence change Memories (VCM). A few important applications of Memristors such as Neuristor and artificial synapse in neuromorphic computing are reviewed as well. Finally, the most anticipated energy efficient battery-like cells as artificial synapse in brain-inspired computing is also covered.

CrN/CrCN/TaN multilayer films were deposited onto the CoCrMo alloy substrates at different number layers as two, four and 8 layers by close-field unbalanced magnetron sputtering method. Microstructure and the tribo-logical properties of the films were characterized by XRD, SEM, pin-on-disk wear test, scratch test, micro hardness. CrN/CrCN/TaN multilayer coatings exhibited good adhesion properties on the CoCrMo alloy substrate. A very high hardness value of 60 GPa was obtained for 8 multilayered coating. As a result of the pin-on-disc wear tests, it was found that the tribological properties of the CoCrMo alloy were enhanced by coating its surface with this architecture by using close-field unbalanced magnetron system with used parameters.

This review manuscript highlights the effects of various ceramic particulates on different aspects like tribo-logical (sliding wear), mechanical and thermal behaviour etc. of aluminium alloy composites, across various operating parameters like normal load (N), sliding velocity (m/s), sliding distance (m), temperature (°C), reinforcement weight percentage. It also discusses different fabrication techniques of such composites as reported by various scholars. Such advanced alloyed-composites find frequent applications in automotives, military, marine, structural, etc. applications, where tribo-logical phenomenon plays a dominant role. The material scientists world-wide are actively engage in improving life of such components by enhancing their mechanical, physical, chemical etc. properties along with improvement in wear resistance in a cost-effective manner. This overall enhances the working efficiency of the component in required applications. Single or binary or hybrid ceramic reinforcement with varying content is explored by scholars and has ample scope of further exploration. It has been concluded from the literature review that ceramic reinforcement lead to significant enhancement in mechanical, tribological and thermal characteristics of Al alloy based MMCs. Further, the micro-sized ceramic particulates increase the interfacial bond strength between the matrix-reinforcement that enhances effective load transfer and sustain it at various tribological operating parameters, that further validated by surface morphology studies.

Recent developments in the field of carbon nanotube (CNT) have attracted attentions on a new development of aluminum matrix composite (AMC). Homogenous dispersion and interfacial bonding of CNT/metal matrix are the two main problems yet to have sound solutions. In general, to ensure uniform dispersion, the overall process can be divided into three steps: preprocessing, mixing and post processing. This paper summarizes previous works on solid and liquid processing techniques which some are more successful than others by looking at the improvement of the composite tensile strengths. On the other hand the interfacial bonding depends on the existance of Al 4 C 3 phase and physical conditions of CNT. Both elements must be controlled for the optimized results. The review presented here would be used as references in the future works to fabricate higher strength CNT/aluminum composites.

Bulk metallic glass of Cu 60 Zr 20 Ti 20 composition has been synthesized by copper mold casting. Slices of the as-cast glass has been subjected to severe plastic deformation by high-pressure torsion for different whole turns. The microstructure and the thermal behavior of the deformed disks have been investigated by X-ray diffraction and differential scanning calorimetry. It was confirmed that the initial compression preceding the high pressure torsion induces crystallized structure, which shows only minor further changes upon the severe plastic shear deformation achieved by twisting the sample. The X-ray line profiles have been evaluated by the Convolutional Whole Profile Fitting algorithm in order to determine the evolution of the microstructural parameters, such as the median and variance of the crystallite size distribution, average crystallite size and dislocation density as a function of the number of revolutions. Hardness measurements by nanoindentation have also been carried out on the as-cast alloys and the deformed disks.