Quartz Holder Research Articles

Determination of Cl and S in crude oil by ICP-OES after sample digestion by microwave-induced combustion in disposable vessels

A simple, fast and promising sample preparation method based on microwave-induced combustion in disposable vessels (MIC-DV) was developed for Cl and S determination in crude oil by inductively coupled plasma optical emission spectrometry (ICP-OES). The MIC-DV consists of a new approach of conventional microwave-induced combustion (MIC). For the combustion, crude oil was pipetted on a disk of filter paper and placed on a quartz holder, followed by the addition of igniter solution (40 μL of 10 mol L−1 NH4NO3). The quartz holder was inserted into a commercial 50 mL disposable polypropylene vessel containing the absorbing solution, which was then inserted in an aluminium rotor. The combustion occurs under atmospheric pressure in a domestic microwave oven not compromising the operator's safety. The following parameters of combustion were evaluated: type, concentration and volume of absorbing solution, sample mass and the possibility of performing consecutive combustion cycles. Using MIC-DV, up to 10 mg of crude oil were efficiently digested, using 2.5 mL of ultrapure H2O as absorbing solution. Moreover, up to 5 consecutive combustion cycles were possible without analyte losses, reaching a total sample mass of 50 mg. The MIC-DV method was validated according to Eurachem Guide recommendations. Results obtained for Cl and S by MIC-DV were in agreement with those obtained using conventional MIC, as well as those obtained for S in a certified reference material of crude oil (NIST 2721). Analyte spike recovery experiments were performed and recoveries at three concentration levels ranged from 99 to 101% for Cl and from 95 to 97% for S, indicating a good accuracy. The limit of quantification achieved by ICP-OES after MIC-DV were 73 and 50 μg g−1 for Cl and S respectively, applying 5 consecutive combustion cycles.

Microwave-Induced Combustion in Disposable Vessels: A Novel Perspective for Sample Digestion.

A novel system for sample digestion was proposed based on microwave-induced combustion in disposable vessels (MIC-DV) for trace elements determination by inductively coupled plasma optical emission spectrometry (ICP-OES). As a proof of concept, botanical samples were digested by MIC-DV for further determination of Al, Cr, Cu, Fe, Mn, Sr, and Zn. The system consists of a quartz holder (a modified version of conventional MIC) placed inside disposable polypropylene (PP) vessels. The quartz holder was carefully designed to avoid excessive heating and damaging of the vessel walls. For the combustion, the PP vessels containing the quartz holder and sample were placed in a specially designed metallic rotor that prevents the heating of absorbing solution and allows the use of a domestic microwave oven for sample ignition. After combustion, the digestion vessel was shaken to ensure the analytes' absorption. The single-vessel principle was fulfilled, since no further dilution or liquid transfer was required and the same PP vessel used for digestion allowed solution storage until element determination. The influences of absorbing solution (diluted HNO3 and water) and sample mass (10 to 30 mg) were evaluated. By using the proposed MIC-DV system, low volumes of diluted absorbing solutions (5 mL of 1 mol L-1 HNO3) were possible, allowing the use of low reagent amounts and low energy consumption, since microwave irradiation is used only for sample ignition. The agreement with certified values ranged from 92 to 108% for all analytes, whereas the precision was below 15%. All of these advantages, combined with the use of low-cost disposable vessels and instrumentation, make MIC-DV suitable to be used for research and routine analysis.

Relaxation Behavior of Magnetization for Electrochemically Lithium Inserted Gamma-Fe2O3

Introduction From the gradual potential change of γ-Fe2O3 after the termination of electrochemical lithium insertion, we have found that structural change occurs in the electrode material from the kinetically favorable to thermodynamically stable states. X-ray diffraction experiment coupled with the Rietveld structure refinement revealed not only the structure relaxation process after the termination of lithium insertion but also electrochemical lithium insertion mechanism. We named this technique as “Relaxation analysis” and applied on various electrode materials, such as γ-Fe2O3 [1,2], LiMn2O4 [3], LiFePO4 [4], LiCoO2 [5], or graphite [6]. γ-Fe2O3 possesses spinel-type structure with the space group , where iron ions essentially occupy 8a and 16d sites with a small amount of vacancy and the 16c site is vacant. In the previous study [1,2], it has been found that occupation factor of 8a site decreases and that of 16c site increases at the lithium insertion process. In addition, after the insertion termination, 8a site occupancy increases while 16c site declines during relaxation time as shown in Fig. 1. Therefore, we concluded that lithium ions at first insert into preferred 8a site pushing iron ions out to 16c site, thereafter iron ions return to 8a site after the termination of lithium insertion. According to the above model, magnetic moment should vary during the relaxation process, since the site movement of iron is involved in the model. In the present study, we measured the magnetization of lithium inserted γ-Fe2O3 during relaxation process to consider from the viewpoint of magnetic properties. Experiment Electrochemical lithium insertion into γ-Fe2O3 has been made by using an Ar-sealed glass beaker cell. The mixture of γ-Fe2O3 powder (AlfaAesar, >99%), Acetylene Black (AB) and PTFE powder with the weight ratio of 70:30:5 was employed for cathode material, which was spread onto a Ni mesh as a current collector. Lithium foil was used as the reference and counter electrodes, and 1 mol∙dm-3 LiPF6 in EC/DMC (2:1 v/v%, Kishida chemical Co., Ltd) was used as the electrolyte. Lithium ion has been electrochemically inserted into the sample to obtain LixFe2O3 (x = 1.5) at a constant current of 0.01 Ag-1. After the termination of lithium insertion, sample was scraped immediately out of the Ni mesh and set into a quartz holder for SQUID. Magnetization has been measured by using an MPMS SQUID magnetometer under an external field of 103 Oe at 300K. Magnetization of the sample was monitored for 70 hours. Results and discussion Fig. 2 shows the measured magnetization of Li-inserted γ-Fe2O3 (Li1.5Fe2O3). It was found that the magnetization gradually increases with relaxation time after the termination of lithium insertion. This is the first observation of the relaxation in the magnetization. The magnetization of γ-Fe2O3 comes from the superexchange interaction of iron via oxygen and it is well known that the change of crystal site of iron changes the superexchange interaction. Then it is considered that the change of the magnetization comes from the change of the superexchange interaction due to the change of occupation site of iron at the relaxation time.

Structural Analysis of Vertically-Aligned Single Crystalline ZnO Nanorods Grown on Different Seed Layers with Chemical Solution Deposition

We report the structural properties of the vertically-oriented ZnO nanorods fabricated on various ZnO seed layers with chemical solution deposition (CSD) technique. The ZnO nanorods were prepared using an aqueous solution with Zinc nitrate (Zn(NO3)2 x 6H2O, Aldrich) and hexamethylenetetramine (HMT, Aldrich) in a convection oven. A-plane sapphire substrates with a deposited ZnO thin film were placed upside down in a quartz holder to avoid any micro-crystalline contamination. Especially, our hydro-thermal syntheses are automatically processed on precision pump drive systems (Masterflex) to accurately control the pH of the aqueous solution. The [002] crystal orientation of the ZnO seed layer was observed by the X-ray diffraction pattern. Structural features of ZnO nanorods were systematically analyzed by scanning electron microscopy and tunneling electron microscopy, together with selective area electron diffraction patterns. Experimental observations clearly demonstrated the dependence of the growth direction of the ZnO nanorods on the crystal structures of the ZnO seed layers.

Metals determination in milk powder samples for adult and infant nutrition after focused-microwave induced combustion

In this study, a recently sample preparation method based on focused microwave-induced combustion (FMIC) is proposed for milk powder digestion (for adult and infant nutrition) for subsequent determination of Ba, Ca, Co, Cr, Cu, Fe, Mg, Mn, Sr, V and Zn by inductively coupled plasma optical emission spectrometry (ICP OES). Combustion was carried out under oxygen flow rate (2 to 15lmin−1) using ammonium nitrate (50μl of 6moll−1 solution) as ignition aid. Samples were pressed as pellets (up to 3g) and placed on a quartz holder positioned inside the glass vessel. The concentration of the absorbing solution was investigated using nitric acid in the range of 2 to 14moll−1. Sample digestion was also performed by microwave-assisted wet digestion (MAWD) and by microwave-induced combustion (MIC). Agreement higher than 95% was obtained for all analytes by comparison with certified reference materials of milk powder after FMIC using diluted nitric acid (2moll−1) and by comparison of the results obtained by MAWD and MIC. The main advantage of FMIC when compared to MAWD and MIC is the possibility to digest higher sample masses (up to 3g) achieving better limits of detection. It was possible to use diluted nitric acid solution for analytes absorption and digests were suitable for determination of metals by ICP OES avoiding the use of more expensive instrumentation as inductively coupled plasma mass spectrometry.

Heavy crude oil sample preparation by pyrohydrolysis for further determination.

In this work, a method for chlorine determination in heavy crude oil using pyrohydrolysis for sample decomposition was developed. Chlorine was determined using ion chromatography (IC), inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry. In this case an ICP-MS spectrometer equipped with a dynamic reaction cell (DRC-ICP-MS) was used. Heavy crude oil samples were homogenized and placed on a quartz holder, which was then introduced into the pyrohydrolysis apparatus. Nitric acid (0.2 mL) was used to assist the decomposition of the sample. Solutions with different concentrations of ammonium hydroxide were evaluated to collect the volatile chloride produced using pyrohydrolysis. A 0.75 mol L-1 ammonium hydroxide solution was chosen in view of the better accuracy achieved. Best precision and accuracy were obtained by heating the sample for 10 min up to 1000 °C. The limits of quantification (LOQs, 10σ) of chlorine measured by IC, ICP OES and DRC-ICP-MS were 4.5, 48 and 3.6 µg g-1, respectively. A sample amount of 300 mg and final volume of 20 mL were taken into account to calculate the LOQs. The relative standard deviation (RSD) was lower than 5% (4 replicates). Accuracy was evaluated by analysis of certified reference material (NIST 1634c) and comparison with the results obtained using the ASTM D6470 method. In both cases the results obtained using pyrohydrolysis were in agreement. The proposed method was suitable for heavy crude oil decomposition and chlorine determination by IC, ICP OES and DRC-ICP-MS. Three samples per hour can be processed using a simple and low-cost pyrohydrolysis apparatus. The pyrohydrolysis procedure is easy to perform, which is very attractive for routine analysis of crude oil, a very complex matrix. According to the authors' knowledge this is the first application of pyrohydrolysis for heavy crude oil sample preparation.

Focused Microwave-Induced Combustion: A New Technique for Sample Digestion

A procedure for sample digestion based on focused microwave-induced combustion (FMIC) is proposed. This system was developed using a commercial focused microwave oven with a lab-made quartz sample holder and a modified glass vessel. Oxygen flow was used to start and support the combustion. A botanical sample was used to evaluate the operational conditions for further Al, Ba, Ca, Fe, Mg, Mn, Sr, and Zn determination by inductively coupled plasma optical emission spectrometry. Pelletized samples were positioned on the quartz holder, and 50 microL of 6 mol L(-1) NH(4)NO(3) solution was added as igniter. Combustion was completed in less than 2 min, and the temperature was higher than 950 degrees C. The use of a reflux step, the position of sample holder inside the vessel, sample mass, ignition and combustion time, oxygen flow rate, and condenser type were evaluated. Results were compared with those obtained by focused microwave-assisted wet digestion and by high pressure microwave-assisted wet digestion. Agreement of 95-103% was obtained for certified reference materials digested by FMIC (reflux step with 10 mL of 4 mol L(-1) HNO(3)). With the proposed procedure, a complete sample decomposition (residual carbon content lower than 0.5%) was achieved with low consumption of reagents as only 10 mL of diluted nitric acid was necessary. Low relative standard deviation (lower than 3.8%) was observed and high amount of sample (up to 1500 mg) could be digested that allowed lower limits of detection.

Determination of Cd in blood by microwave-induced combustion coupled to flame furnace atomic absorption spectrometry

Microwave-induced combustion system was coupled to a metallic flame furnace (FF) atomic absorption spectrometer and applied for cadmium determination in blood. Lyophilized blood samples were prepared as pellets, positioned on a quartz holder and introduced into a glass chamber used for the combustion step. The glass chamber was coupled to the metallic flame furnace by using polytetrafluoroethylene and quartz tubes. Ignition was performed by microwave radiation using ammonium nitrate solution added to a small piece of previously cleaned paper. Oxygen was used to assist the sample combustion and also to transport combustion products up to the FF heated by an air/acetylene flame. High purity graphite powder was mixed with samples before pellets preparation. The volume of NH4NO3 solution, oxygen flow-rate, flame stoichiometry, sample holder type and the sample mass range were evaluated. Calibration step was feasible using adsorbed reference solution in pelletized high purity graphite avoiding the use of certified reference material (CRM). Sample masses up to 56 µg could be used allowing quantification limit of 0.018 µg g-1 and characteristic mass of 50 pg Cd. Low values for blanks were obtained (integrated absorbance lower than 0.01 s) and results were considered satisfactory regarding to both accuracy (agreement with results using CRMs between 95 to 99%), and precision (relative standard deviation < 12%). Up to 15 determinations can be performed per hour including the weighing step.

Chlorine and sulfur determination in extra-heavy crude oil by inductively coupled plasma optical emission spectrometry after microwave-induced combustion

In this study, microwave-induced combustion (MIC) of extra-heavy crude oil is proposed for further chlorine and sulfur determination by inductively coupled plasma optical emission spectrometry (ICP OES). Combustion was carried out under oxygen pressure (20 bar) in quartz vessels using ammonium nitrate (50 µl of 6 mol l − 1 solution) as ignition aid. Samples were wrapped with polyethylene film and placed on a quartz holder positioned inside the quartz vessels. The need for an additional reflux step after combustion and the type and concentration of absorbing solution (water, 0.02 to 0.9 mmol l − 1 H 2O 2, 10 to 100 mmol l − 1 (NH 4) 2CO 3 or 0.1 to 14 mol l − 1 HNO 3) were studied. The influence of sample mass, O 2 pressure and maximum pressure attained during the combustion process were investigated. Recoveries from 92 to 102% were obtained for Cl and S for all absorbing solutions. For comparison, Cl and S determination was also performed by ion chromatography (IC) using 25 mmol l − 1 (NH 4) 2CO 3 as absorbing solution. Using MIC with a reflux step the agreement was better than 95% for certified reference materials of similar composition (crude oil, petroleum coke, coal and residual fuel oil). Microwave-assisted digestion and water extraction in high pressure closed vessels were also evaluated. Using these procedures the maximum recoveries were 30 and 98% for Cl and S, respectively, using microwave-assisted digestion and 70% for Cl and less than 1% for S by water extraction procedure. Limits of detection by ICP OES were 12 and 5 µg g − 1 for Cl and S, respectively, and the corresponding values by IC were 1.2 and 8 µg g − 1 . Using MIC it was possible to digest simultaneously up to eight samples resulting in a solution suitable for the determination of both analytes with a single combustion step.

Microwave-Induced Combustion Coupled to Flame Furnace Atomic Absorption Spectrometry for Determination of Cadmium and Lead in Botanical Samples

A procedure based on microwave-induced combustion coupled to flame furnace (FF) atomic absorption spectrometry (FF-AAS) was used for analysis of solid samples. Botanical samples were prepared as pellets and introduced into a quartz holder device. This device was fitted to a glass chamber that was used for the combustion step. The complete device was coupled to the flame furnace by using poly(tetrafluoroethylene) and quartz tubes. The glass chamber was placed inside a microwave oven in a position previously set to receive the higher power of microwave radiation. Ignition was performed by microwave radiation using a small piece of paper wetted with NH4NO3 solution. An oxygen flow was used to assist the sample combustion and also to transport the combustion products up to the heated FF positioned above an air/ acetylene burner. Flame furnace temperature, oxygen flow rate, flame stoichiometry, and sample mass range were evaluated. Cadmium and lead were determined in botanical samples as examples to demonstrate the potential of the proposed procedure for trace analysis. Sample masses up to 60 mg could be used, allowing a limit of detection as low as 0.003 and 0.24 microg g(-1) for Cd and Pb, respectively. Integrated absorbance was used with an integration time of 30 s. Background signals were always low, and relative standard deviation (n = 5) was below 9% for Cd and 11% for Pb. The throughput was 20 determinations/h, including the weighing step. Accuracy was between 94 and 105%, and calibration was performed using standard solutions. The combustion device could be easily adapted to conventional atomic absorption spectrometers.

Chloride determination by ion chromatography in petroleum coke after digestion by microwave-induced combustion

Microwave-induced combustion was applied to petroleum coke digestion in closed vessels for further chloride determination by ion chromatography. Samples were pressed as pellets and placed on a quartz holder. Combustion was performed using oxygen pressure of 2 MPa and 50 μl of 6 mol l −1 NH 4NO 3 as aid for ignition. Recoveries from 97 to 102% were obtained for all studied absorbing solutions (water, H 2O 2, Na 2CO 3 or (NH 4) 2CO 3). Accuracy was evaluated using certified reference materials with agreement better than 98% using water as absorbing solution with reflux step. The limit of quantification was 3.8 μg g −1.

Active Regeneration of Diesel Particulate Filter Employing Microwave Heating

Wall-flow diesel particulate filters (DPFs) are considered the most effective devices for the control of diesel particulate emissions. A requirement for the reliable operation of the DPFs, however, is the periodic and/or continuous regeneration of the filters. While microwave heating has been considered a potential active regeneration method for the DPFs, past studies on the technology have identified several technical problems leading to filter failure. The problems are mainly associated with the use of inappropriate filter materials for the microwave system and the generation of local hotspots due to uneven microwave heating, resulting in the physical damage to the filters. The objective of this study was to develop and demonstrate the technology employing a microwave-absorbing filter material coupled with an effective waveguide design for the reliable regeneration of DPFs. In this study, a well-equipped diesel emission control laboratory was established to conduct the experiments. The experimental facilities included a 6-kWe diesel generator, an exhaust flow control system, a diesel particulate filter system, a microwave energy supply system, a soot sampling system, a differential-pressure measurement system, and a temperature measurement system. The DPF was a silicone carbide wall-flow monolith filter enclosed in a quartz filter holder. A commercial 1.4-kWe microwave oven was modified to accommodate the quartz holder and a waveguide was engineered to evenly supply the microwave energy to the enclosed filter to achieve filter regeneration. In the experiments, the diesel engine exhaust was lined up to flow through the filter with a fixed flow rate. The microwave regeneration was triggered after a specific amount of soot loading was reached based on the differential pressure drop reading. The results have indicated that the designed system has been able to achieve uniform temperature profiles both in the radial and the vertical DPF positions. The off-line regeneration of DPF by microwave energy has been observed to be highly efficient in terms of energy consumption and regeneration efficiency. The DPM filtration efficiency has remained comparably high after 150 cycles of filtration/regeneration with no apparent physical damage to the DPF being observed. The on-line microwave regeneration of the DPF, however, is not as efficient as the off-line regeneration due to the insufficient oxygen concentration in the engine exhaust stream.

Deposition Uniformity Control in a Commercial Scale HTO-CVD Reactor

AbstractHigh-temperature silicon dioxide chemical vapor deposition (HTOCVD), using SiH2Cl2 and N2O, can realize dense and conformal oxide film, not only on large size silicon wafers, but even inside of microscopic silicon trenches, at high-temperature around 800°C.In this work, we investigated the kinetics of HTOCVD using a commercial scale low pressure (LP) CVD reactor, focusing on the correlation between deposition rate and surface-to-volume ratio (S/V ratio), which is a specific surface area of substrate wafer divided by the space volume between two adjacent wafers. We also investigated the deposition rate profile on wafers, and along the axial direction of the reactor near the region where one, two or three substrate wafers are extracted from the quartz holder. The deposition rate profiles on wafer characteristically change from skillet-like to pancake-like, according to the increase of wafer spacing. The influence on the deposition rate of wafer spacing spreads to ranges not only downstream, but also upstream in the gas flow. These experimental results strongly suggest that in the HTOCVD gas-phase reactions through intermediate states of active species contribute to deposition reaction as well as direct deposition reaction of source gases on Si surface.

Microwave-assisted sample combustion: a technique for sample preparation in trace element determination.

A novel digestion procedure based on sample combustion ignited by microwave radiation is proposed for organic samples. Certified samples of bovine liver, pig kidney, and skim milk were used as examples to demonstrate the performance of the proposed procedure. Cadmium and copper were determined in these samples by electrothermal atomic absorption spectrometry. Samples (between 50 and 250 mg) were wrapped with paper and placed on a homemade quartz holder that was positioned inside to quartz vessels used in a commercial microwave oven. Ammonium nitrate solution was added to the paper, and vessels were pressurized with oxygen to 15 bar. The rotor containing four vessels was placed inside the oven, and microwave radiation was applied for 20 s at 1400 W. Combustion was complete in few seconds, and an additional reflux step, which was optional, was applied. The agreement to the certified values was between 96 and 105% for both analytes. Only with the combustion step, the residual carbon (RC) was below 1.3%. The RC decreased to less than 0.4% when an additional reflux step with concentrated nitric acid was applied.

Thermal stress at wafer contact points in rapid thermal processing investigated by repeated spike treatment before oxidation

Repeated spike treatment (RST), which was characterized by setting the temperature to ramp up and down repeatedly, was employed to study the stress effect on wafers by annealing the silicon wafers in ambient N2, followed by oxidation in O2. These RST+O samples had three apparent local thick oxide regions that adjoined the contacts of the three-pin quartz holder, as opposed to the typical+O samples annealed with a conventional temperature profile before the same oxidation process. It was observed that defects could be created on the silicon surface due to the high thermal stress at contacts during RST, and that the oxidation rate of these damaged zones was greatly increased. I–V data show that for a similar oxide thickness, the leakage currents in RST+O samples are higher and more scattered than those in typical+O samples. C–V measurements illustrate that RST+O samples have higher interface state densities than typical+O samples. These enhanced degradation phenomena could be caused by the RST, which resulted in a rough Si/SiO2 interface and nonuniform oxide thickness.

Characterization of the tetramethylammonium hydroxide thermochemolysis products of carbohydrates

The identification of the thermochemolysis products (in the presence of tetramethylammonium hydroxide, TMAH) of carbohydrates is presented. Analysis was carried out using on-line flash pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and off-line flash (vacuum) pyrolysis followed by GC/MS. Standard samples of hexoses, pentoses, deoxyhexoses, lactose, cellulose and starch were treated with 25% aqueous TMAH (100 times excess by weight). Approximately 50 μg (for on-line analysis) or 250 μg (for off-line analysis) of the carbohydrate/TMAH mixture was heated to 700°C (10 s) using a quartz holder and a CDS pyroprobe. From electron and chemical impact mass spectral data, and, from literature on alkaline decomposition of carbohydrates, tentative structures of unique products and the mechanisms of their formation are proposed. A series of permethylated deoxy aldonic acids are tentatively identified as key products. It is postulated that these ‘saccharinic acids’ are initially formed from the action of alkali on reducing sugars which are then subsequently methylated. In addition, thermochemolytic analysis of lactose, cellulose and starch afforded their own unique permethylated deoxy aldonic acids as well producing methoxy benzene products, i.e. 1,2,4-trimethoxybenzene, 2,4-dimethoxyphenol. It is believed that glycosidically-linked saccharides initially degrade under alkaline conditions similar to the so-called ‘peeling reaction’ observed for cellulose under alkaline pulping conditions and then are finally methylated. An algal sample has been analyzed for its carbohydrate composition. The observation of hexose, pentose and polysaccharide thermochemolysis products illustrate the potential of the method to characterize the saccharide composition of more complex biomaterials.

Analysis of Polystyrene in Polluted Sediments by Pyrolysis--Gas Chromatography--Mass Spectrometry

The use of pyrolysis combined with gas chromatography and mass spectrometry for the analysis of polystyrene in sediments is described. The method is applied to a sediment core of the Lagoon of Ravenna (Pialassa Baiona); in these sediments, polystyrene is detected at mg/g levels in surface layers. Dried sediment samples are directly pyrolyzed in a quartz tube holder, the peak area of the evolved styrene is determined in the single ion monitoring mode, and polystyrene concentration is calculated from the appropriate calibration curve. Linear plots of styrene peak area versus polystyrene content are obtained by pyrolyzing the polymer in the presence of various matrices: calcite, quartz, kaolinite, montmorillonite, and whole sediment. The pyrolytic behavior of polystyrene is strongly affected by the presence of clay minerals, whereas calcite and quartz exhibit a lower influence. The effect of other organic constituents, such as humic substances and styrene-butadiene rubbers, is discussed.

Progress towards an alanine/ESR therapy level reference dosimetry service at NPL

This paper describes work being carried out at the National Physical Laboratory towards the establishment of an alanine reference dosimetry service for radiotherapy applications. A precision fused quartz holder has been constructed to allow precise positioning of alanine dosimeters in the ESR cavity. A novel method of signal analysis based on spectrum fitting has been developed to minimize the effect of baseline distrotions. Data are also presented on the relative response of alanine to 60Co gamma rays and high energy photons (4–12 MeV).

RF Induction‐Heated Hot‐Wall Type Reactor for High‐Volume, Low‐Cost Si Epitaxy

A prototype epitaxy reactor capable of processing a high volume of wafers has been designed and constructed. Wafers are in parallel, stacked on a vertical‐type rotating quartz holder, with a wafer‐to‐wafer spacing of about 10 mm, and are RF induction‐heated by a hot‐wall susceptor. The nutrient gaseous mixture is injected into all wafer spacings by multiple quartz gas distributor tubes. Hydrogen chloride gas is added to nutrient gas to prevent silicon deposition on the quartz parts in the reactor. This new type of reactor is found capable of producing at least 20 5‐inch‐diameter wafers per 100 mm of stack length, with thickness variations of less than ±5% within a wafer, as well as between wafers, both at atmospheric and reduced pressure growth.

Quartz single crystal sample holder for ESR

During an ESR experiment in metal powder heat is supplied to the sample by an RF power and therefore its temperature may be higher than that of the surrounding coolant. In order to minimise this effect the authors have built a single quartz crystal sample holder. In addition, they have mixed the metal powder with quartz powder obtained by grinding a monocrystal and pressed the mixture into the holder. This has largely increased the heat flow from the sample and reduced the temperature difference between the sample and the surrounding coolant, compared with the usual procedure where fused silica glass tube is used as a sample holder and the metal powder is mixed with paraffin. This improvement can be particularly important when using high RF power. The effectiveness of the quartz holder was demonstrated in the measurement of the ESR of TiBe2 at liquid He temperature range as compared with a conventional holder.