Non-metallic Constituents Research Articles

The effects of prenatal PM2.5 oxidative potential exposure on feto-placental vascular resistance and fetal weight: A repeated-measures study

BackgroundFeto-placental hemodynamic deterioration is a critical contributing factor to fetal growth restriction. Whether PM2.5 oxidative potential (OP) affects feto-placental hemodynamics and what impact is on estimated fetal weight (EFW) have not been fully elucidated. We sought to evaluate the association of PM2.5 OP with EFW and to explore whether feto-placental vascular impedance hemodynamic change is a possible mediator in this association. MethodsA repeated-measures study was conducted involving sixty pregnant women with at least 26 weeks of follow-up during pregnancy in Guangzhou, China, from September 2017 to October 2018. Daily filter-based PM2.5 samples were prospectively collected from ground monitors, and estimates of OP for PM2.5 and its metallic (OPv-metal) and non-metallic constituents (OPv-nonmental) were determined by dithiothreitol assay. Ultrasound data of fetal growth and umbilical arterial resistance, including estimated fetal weight (EFW), pulsatility index, resistance index, and systolic-to-diastolic ratio, were also obtained during gestation. Generalized estimating equations and polynomial distribution lag models were applied to analyze the associations of maternal exposure to PM2.5 OP with EFW and umbilical artery indices. Causal mediation analysis was used to evaluate the mediating role of umbilical arterial resistance. ResultsPrenatal exposure to ambient PM2.5 OP was significantly inversely associated with EFW. The magnitudes of effects of OPv-nonmetal on EFW were larger than those of OPv-metal. Significant mediation for the relationship between PM2.5-related OP and EFW by increased impedance in the umbilical artery was observed, with the estimated percent mediated ranging from 31% to 61%. The estimated percent mediated for OPv-nonmetal was higher than those for OPv-metal. ConclusionsFindings suggest that increased impedance in the umbilical artery may be one of the potential mediators of the relationship between PM2.5 oxidative potential exposure and low fetal weight.

Composite cellulose/Fe3O4/Cu for effective X-ray radiation shielding

In this study, a cellulose/Fe3O4/Cu composite was synthesized by the blending method and applied as an X-ray radiation apron. The content of Fe3O4 in each sample was 94 wt%, and the varying levels of cellulose and Cu were 1, 2, 3, 4, and 5 wt%. The crystal phase formed in the sample was observed using X-ray diffraction, and the functional group formed was examined using Fourier transform infrared spectroscopy. The performance of the sample as a radiation shield was analyzed using X-ray mobile with energies of 50, 60, 70, 81, and 90 keV at 10 mAs applied to the sample. The results showed that the samples with composition of 2 wt% cellulose and 4 wt% Cu exhibited the best values for the average size of the smallest crystallite size (12.21 nm), low transmittance, linear attenuation coefficient (μ), mass attenuation coefficient (μm), atomic cross-section (σa), electronic cross-section (σel), half value layer, and mean free path. Alterations observed on the surface of the composite material suggested the impact of incorporating metallic components into nonmetallic constituents. Surface analysis was conducted using scanning electron microscope and revealed that the surface model resembled Brassica oleracea. This feature is advantageous due to the large surface area and absorbent properties associated with such leaves.

Processing of Discarded Printed Circuit Board Fines via Flotation

The recovery of metals from discarded printed circuit boards using environmentally-friendly physical routes is gaining importance. Physical separation of metal values from non-metallic constituents exploits various characteristics of crushed powder such as density, liberation, shape, size, and wettability. However, the generation of fines during grinding/crushing of the printed circuit boards is an unavoidable but essential by-product. The fine fractions are discarded due to the higher amounts of non-metallic fraction and poor separation of metallic values. In this study, the flotation process was studied to separate metallic and non-metallic values without the addition of external additives from the fine fraction of printed circuit boards (< 212 µm). The natural hydrophobic response of plastic and organic matter in fines stabilized the froth without additional reagents. The difference in tapped density for tailing (~ 0.5 g/cm3) and concentrate (~ 2.7 g/cm3) fraction ensures good separation. The metallic fraction increases from 14.3% in the feed to 91.7% in the concentrate. Recovery for metallic values was observed as ~ 72.3% with a purity of ~ 92% and comprised 77.9% Cu, 8.3% Sn, and 5.5% Pb.

Analysis of Nonmetallic Constituents of Lubricating Oil Using Indirect Ablation Laser-Induced Breakdown Spectroscopy

Indirect ablation laser-induced breakdown spectroscopy (IA-LIBS) was applied to the analysis of the nonmetallic constituents of engine oil and considered as a feasible technique for the evaluation of the consumption and/or combustion of engine oil during routine engine operation. The evolution of CN emission and C2 emission was investigated for different driving time intervals of the motor. The exponentially decaying curve showed that the intensity of CN emission and C2 emission decayed at different driving time intervals. The evolution of total CN emission and C2 emission was analyzed, and the ratio of CN to C2 was calculated, which might be taken as an indicator to evaluate the performance of the used engine oils and/or to diagnose the conditions of the motor engine. Thus, it is shown that IA-LIBS is a potential method for analyzing the metallic and nonmetallic constituents of engine oil.

Examining the physicochemical and microbial qualities and mineral content of selected brands of bottled water marketed and consumed in Asaba, Delta State, Nigeria

The quality of bottled water sold in Asaba, Delta State, Nigeria, was investigated in this study. Six (6) brands of highly consumed bottled water were randomly selected for evaluation of physicochemical parameters, metallic and nonmetallic inorganic constituents, and microbial properties. The study revealed that physicochemical parameters such as pH, TDS and Chloride ranged between 6.63±0.03-7.54±0.02, 3.3±0.8-88.4±6.1 and 2.48±0.6-39.3±3.6 respectively, while the metal contents were highly variable amongst the bottled water examined. The study also showed from bacteriological analysis, that 5.2 % of tested samples had Klebsiella sp., Streptococcus faecalis and Pseudomonas aeruginosa . Values for the physicochemical and non-metal inorganic elements were below the prescribed maximum limits of the World Health Organization (WHO) and Standard Organization of Nigeria (SON). Generally, the bottled waters were found to be microbiologically safe, going by the results of total coliform and heterotrophic plate count and were also not contaminated by heavy metals. A direct comparison of the values obtained with the mineral water categorization system showed low mineral content and hence most suitable for low-sodium diets. The study recommends regular monitoring and analysis of bottled waters sold and consumed in Nigeria for quality assurance. Keywords: Bottled Water, Water Quality, Public Health, Regular Monitoring, Asaba

Copper/Iron Brake Friction for Military Aircraft Application

The present study assesses the infl uence of non-metallic constituents and manufacturing parameters, such as compaction pressure and sintering temperature, to produce a metal matrix composite (MMC) of copper/iron, based on the brake disc of aircraft AT-29 SuperTucano. The samples were produced with six different compositions, by varying the amount of abrasive particles (quartz and zirconia silicate) and the solid lubricant (graphite), with one of the compositions manufactured without the addition of graphite. The compaction pressures were 210 and 420 MPa, with sintering temperatures of 950°C and 1050°C in a furnace with controlled atmosphere of argon + 10% H2. After sintering, the effectiveness of the sintering process was evaluated through the apparent density (Archimedes’s method), Brinell and Vickers hardness, and the microstructure by Scanning Electron Microscopy (SEM). The sintering process was severely affected by the solid lubricant (graphite): its reduction resulted in a density increase near 18%, and the hardness of the compound up to 62%. The hardness values demonstrated significant variation with compaction pressure, with a pronounced effect on compounds with less non-metallic elements. SEM analysis demonstrated that not only graphite, but also the ceramic particles affected the sintering process through the agglomeration of inclusions into the metal-metal interface. The samples without graphite exhibited almost the same value of pores after sintering, regardless of the compaction pressure, indicating that the graphite content affects directly the sintering process, regardless of the compaction pressure.

Effect of chemical pretreatment on pyrolysis of non-metallic fraction recycled from waste printed circuit boards

The non-metallic fraction from waste printed circuit boards (NMF-WPCB) generally consists of plastics with high content of Br, glass fibers and metals (e.g. Cu), which are normally difficult to dispose. This work aims to study the chemical pretreatments by using alkalis, acids and alkali-earth-metal salts on pyrolysis of NMF-WPCB. Char (60–79%) and volatile matter (21–40%) can be produced via the pyrolysis process. In particular, the ash content can reach up to 42–56%, which was attributed to the high content of glass fibers and other minerals. Copper (Cu, 2.5%), calcium (Ca, 28.7%), and aluminum (Al, 6.9%) were the main metal constituents. Meanwhile, silicon (Si, 28.3%) and bromine (Br, 26.4%) were the predominant non-metallic constituents. The heavy metals such as Cu were significantly reduced by 92.4% with the acid (i.e. HCl) pretreatment. It has been proved that the organic Br in the plastics (e.g. BFR) can be transformed into HBr via the pyrolysis process at relatively high temperature. It was noteworthy that the alkali pretreatment was more benefit for the Br fixation in the solid char. Particularly, the Br fixation efficiency can reach up to 53.6% by the sodium hydroxide (NaOH) pretreatment with the pyrolysis process. The formed HBr can react with NaOH to generate NaBr.

Thermochemical treatment of non-metallic residues from waste printed circuit board: Pyrolysis vs. combustion

The non-metallic fraction of waste printed circuit board (NMF-WPCB) mainly consists of plastics with high content of Br, glass fibers and metals (e.g., Cu). This work studied the pyrolysis and combustion of NMF-WPCB pretreated by alkalis, acids and alkali-salts. Copper (Cu, 2.5%), calcium (Ca, 28.7%), and aluminum (Al, 6.9%) were the main metal constituents. Meanwhile, the silicon (Si, 28.3%) and the bromine (Br, 26.4%) were the predominant non-metallic constituents. The heavy metal such as Cu was significantly reduced by 92.4% with the acid (e.g., HCl) pretreatment. The organic Br in the plastics can be converted to HBr via the pyrolysis process. The alkali pretreatment was benefit for the Br fixation in the char. In particular, the Br fixation efficiency can reach up to 53.6% by the NaOH pretreatment combined with the pyrolysis process, since the formed HBr reacted with NaOH to generate NaBr. Compared with the pyrolysis process, most of Br in the solid phase can be transferred to the liquid and gas phase in the combustion process. The gaseous organic-Br can cause serious environmental pollution. Furthermore, the ecological risk assessment analysis showed that the HCl leaching combined with the NaOH pretreatment has a high potential to be used for the pyrolysis disposal of NMF-WPCB environmentally friendly.

Printed circuit board waste as a source for high purity porous silica

The electronic waste stream is one of the fastest growing streams of waste in the world. Printed circuit boards which are found in all electronic equipment are composed of a mixture of various metallic and non-metallic constituents. In this manuscript, the nonmetallics have been treated with acids followed by thermal treatment aiming at the production of high purity porous silica. The results show the possibility of obtaining SiO2 with a specific surface area (BET) as high as 300m2/g and purity higher than 99% (X-ray fluorescence, molar%). The as-prepared silica is comparable to industrially sold samples. The study has successfully demonstrated the possibility of using these unwanted electronic wastes for the synthesis of materials with higher value and utility.

Enrichment implication of froth flotation kinetics in the separation and recovery of metal values from printed circuit boards

The e-waste printed circuit boards (PCBs) are rich in metal content and processing these wastes for extracting the metal values and removing the non-metallic constituents is a prospective proposition. Froth flotation methodology was observed to be a promising technique for rejecting plastics from the comminution product. It has been shown that nearly reagent-free flotation of relatively coarse size (−1.0mm) pulverized e-waste is feasible with a reasonably good product at a high yield and excellent recovery. In the present research work, enrichment of ground 1.0mm PCB powder was investigated through flotation route by varying the operating variables such as frother dosage, pulp density, air flow rate and rotational speed of impeller. The liberation studies accomplish that liberation of metal value from non-metallic constituents at −1.0mm size is excellent and the particulate system is significantly rich in metal value, containing around 23% metal. In-depth study of froth flotation kinetics is primarily focused on high rejection of plastics and also identification of optimum operating conditions for the same. Single-stage flotation enhances metal content from 23% to over 37%, contributing a mass yield of around 75% with recovery of nearly 95% metal values, suffering nominal loss of around 4% metal value only, while effectively rejecting 32% of the materials in feed through float fraction. The interdependence of kinetics and process variables has been discussed and it has been concluded that a high rotor speed aids efficient rejection of the plastics. However, addition of frother is essential to help stabilize the froth and enhance the kinetics, while efficient pre-concentration is facilitated through a combination of moderate air flow with low pulp density. Generation of pre-concentration through flotation route from the entire −1.0mm comminution product stands accomplished.

Novel physical separation process for eco-friendly recycling of rare and valuable metals from end-of-life DVD-PCBs

Present paper reports a simple and eco-friendly physical separation process for the recycling of metallic values from PCBs. The separation of material is based on distribution of metallic and non-metallic constituents in different size fractions depending on their liberation size due to their malleable or ductile nature. The studies showed the enrichment of metals in coarser particles (−1000+150μm) and non-metals in the finer particles −150μm following pneumatic separation and froth flotation process. A grade of 88% with 75% recovery was achieved by froth flotation, but lower grade of ∼75% with ∼65% recovery were obtained by pneumatic separation with −1500μm powder. Overall grade of metals was achieved up to 88% by controlling the feed and air flow rates during pneumatic separation. Using this beneficiation technique, the concentration of rare metals in the different fractions varying from 1.88% to 4.18% was enriched up to 9%.

Method development for arsenic analysis by modification in spectrophotometric technique

Abstract. Arsenic is a non-metallic constituent, present naturally in groundwater due to some minerals and rocks. Arsenic is not geologically uncommon and occurs in natural water as arsenate and arsenite. Additionally, arsenic may occur from industrial discharges or insecticide application. World Health Organization (WHO) and Pakistan Standard Quality Control Authority have recommended a permissible limit of 10 ppb for arsenic in drinking water. Arsenic at lower concentrations can be determined in water by using high tech instruments like the Atomic Absorption Spectrometer (hydride generation). Because arsenic concentration at low limits of 1 ppb can not be determined easily with simple spectrophotometric technique, the spectrophotometric technique using silver diethyldithiocarbamate was modified to achieve better results, up to the extent of 1 ppb arsenic concentration.

Manufacturing Brake Pads by Using Hot Powder Preform Forging for Low Duty Applications

To develop a high density brake pad for low duty application, a P/M route based on ‘Hot Powder Preform Forging’ was developed, which is not possible by sintering route. The mechanical properties of these materials were characterized using ASTM standards. The limitations of the conventional technique i.e. Compacting and Sintering for the manufacture of brake pads were tried to remove by adopting this technology. It offers better opportunity for pore free materials with better bonding between metallic and non-metallic constituents. Fade and Recovery test were done by using a Krauss Tester. μfade, μrecoveryand μperformancelie within the range of friction materials used for low duty applications.

Development of Iron Based Brake Friction MMC Used for Military Aircraft Application by A New P/M Route

A new P/M route based hot powder pre-form forging process has been evolved to develop high density brake materials for heavy duty applications. Number of iron based MMC’s so developed offer better characteristics for braking applications in comparison to the materials developed through conventional P/M route based on high pressure compaction and pressure sintering. The process so developed in the present investigations is much simpler and easy to adopt by existing P/M industries. Hot powder pre-form forging technique for making heavy duty brake pads offers better opportunity for pore free material with better bonding between various metallic and non-metallic constituents. After conducting an initial characterization such as hardness, density and Pin-on Disc tests, the samples were tested for high energy (32,933kgfm) on Sub-scale dynamometer under Rejected Take Off conditions. The results have also been compared with respect to brake pads employed in heavy duty Military aircraft tested under identical laboratory conditions. The present work indicates that the newly developed materials compare better than the one being currently employed in heavy duty aircraft. The reasons for better performance are improved processing technique and resulting higher levels of density and improved binding of the product.

Impact of urbanization on the quality of water in a natural reservoir: a case study with the Deepor Beel in Guwahati city, India

The Deepor Beel is a natural, freshwater wetland in the south-west corner of Guwahati, India. The Beel harbours a large number of migratory aquatic birds, especially in winter, and is a Ramsar site since 2002. The wetland provides livelihood to the people of the surrounding villages through collection and sale of fish, nymphaea nuts and flower, ornamental fish, orchids, medicinal plants, etc. The water quality of the Beel is threatened by excessive fishing, hunting of water birds, pollution from pesticides and fertilizers and infestation by water hyacinth. The present work reports on the water quality of the wetland by continuous monitoring from February to July, covering the dry, temperate period and the wet, hot and humid period. Sampling was carried out at 10 sites for physical and aggregate properties, metallic and nonmetallic constituents, organic contaminants and microbiological parameters.

A novel flowsheet for the recovery of metal values from waste printed circuit boards

Recovery of metal values from waste printed circuit boards using physical beneficiation techniques was studied. A novel flowsheet using a combination of wet and dry unit operations was developed to achieve the separation of metals from non-metallic constituents. The wet concentration circuit consisted of flowing film concentration in tabling, flotation of plastics and enhanced gravity separation in multi-gravity separator. The dry purification circuit consisted of electrodynamic and electrostatic separation. Substantial enrichment of the ground powder with good recovery of metals was achieved using the flowsheet. The starting PCB powder, ground to −0.5 mm size, had about 23% total metal. Complete liberation of metals from plastics was achieved below 100 μm size. Metal values were found to be more abundant in the coarser sizes. A concentrate grade of over 93% total metal at a recovery of over 54% or a grade of 66% total metal at 95% recovery could be achieved using this flowsheet. Recovery of small and flat metal pieces was problematic in conventional gravity separation. Using gravity separation as a pre-concentration operation followed by flotation and enhanced gravity separation, these problems could be solved to a great extent and good recoveries could be achieved. The circuit has great potential to recover metal values from waste printed circuit boards in an industrial scale.

Inverse Perovskites (RE3N)Sn with RE = La, Ce, Pr, Nd, Sm: Preparation, Crystal Structures and Physical Properties

The ternary compounds (RE3N)Sn with RE = La, Ce, Pr, Nd, Sm were prepared starting from the elements. The compounds with RE = La, Ce, Pr were obtained as single phase materials according to X-ray powder diffraction patterns, which also indicate the cubic inverse perovskite crystal structure (space group Pm3̄m, La: a = 509.48(2) pm, Ce: a = 501.59(2) pm, Pr: a = 497.53(2) pm, Nd: a = 494.70(5) pm, Sm: a =488.35(9) pm). Chemical analyses proof the correct composition and particularly the absence of nonmetallic constituents next to nitrogen. All studied compounds show metallic characteristics in the electrical resistivity. Magnetic susceptibility measurements indicate (La3N)Sn to be a Pauli-paramagnet. Initially observed superconductivity was traced down to be due to thin La films on the surface of the grains. The Ce and Pr containing compounds show the behavior of 4f1 ions and 4f2 ions, and order antiferromagnetically at 6.8(2) K and 48(1) K, respectively.

The Influence of Material Properties and Spreading Resistance in the Thermal Design of Plate Fin Heat Sinks

The thermal design of plate fin heat sinks can benefit from optimization procedures where all design variables are simultaneously prescribed, ensuring the best thermodynamic and air flow characteristic possible. While a cursory review of the thermal network established between heat sources and sinks in typical plate fin heat sinks would indicate that the film resistance at the fluid-solid boundary dominates, it is shown that the effects of other resistance elements, such as the spreading resistance and the material resistance, although of lesser magnitude, play an important role in the optimization and selection of heat sink design conditions. An analytical model is presented for calculating the best possible design parameters for plate fin heat sinks using an entropy generation minimization procedure with constrained variable optimization. The method characterizes the contribution to entropy production of all relevant thermal resistances in the path between source and sink as well as the contribution to viscous dissipation associated with fluid flow at the boundaries of the heat sink. The minimization procedure provides a fast, convenient method for establishing the “best case” design characteristics of plate fin heat sinks given a set of prescribed boundary conditions. It is shown that heat sinks made of composite materials containing nonmetallic constituents, with a thermal conductivity as much as an order of magnitude less that typical metallic heat sinks, can provide an effective alternative where performance, cost, and manufacturability are of importance. It is also shown that the spreading resistance encountered when heat flows from a heat source to the base plate of a heat sink, while significant, can be compensated for by making appropriate design modifications to the heat sink.

Analytical challenges in characterization of high purity materials

Available analytical literature reveals that it is possible to identify a lot of procedures to carry out any determination using a plethora of analytical techniques. The fundamental analytical requirements for realizing the desired and acceptable information from a chemical analysis are representative nature of the sample, precision, accuracy, selectivity and sensitivity. These decide, to a larger extent, the selection of the most appropriate methodology in order to obtain chemical information from a system. A number of analytical methodologies are being used in the author’s laboratory for carrying out trace elemental analysis as a part of chemical quality control. Quite a good number of analytical challenges with specific reference to the characterization of high purity materials of relevance to nuclear technology were addressed and methodologies were developed for trace elemental analysis of both metallic and non-metallic constituents. A brief review of these analytical challenges and the analytical methodologies developed and also the future needs of analytical chemist are presented in this paper.

Metallurgical coke microconstituents: their transformation and separation during heat treatment to 2400°C

The metallic and non-metallic constituents present in metallurgical coke are important indicators of coke quality and possible application as a feedstock for more valuable carbon materials. High-temperature production of these materials affects the qualitative and quantitative content of the ingredients as well as their separation during heat treatment. Changes in S, Ca, Si, Fe and Ni contents before and after temperature treatment of coke samples at 1200, 1600, 2000 and 2400°C were examined. Samples were heated at 10 and 30 K min −1. The heating time was 2 and 4 h. The metallic and non-metallic microconstituents in metallurgical coke were mainly present in the form of oxides, silicates and sulfides. The results obtained suggested that the separation during high-temperature treatment was partial and different for each element.